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Arc welding procedure for repairing wrought iron in historic bridges

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Title:
Arc welding procedure for repairing wrought iron in historic bridges
Creator:
Chomsrimake, Preeda
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
Publication Date:
Language:
English
Physical Description:
1 electronic file. : ;

Subjects

Subjects / Keywords:
Electric welding ( lcsh )
Historic bridges -- Maintenance and repair ( lcsh )
Electric welding ( fast )
Historic bridges -- Maintenance and repair ( fast )
Genre:
non-fiction ( marcgt )

Notes

Abstract:
Highway historic bridge maintenance projects have impact on the public, and many state DOTS have developed historic bridge programs. FWHA assists in the preservation of historic bridge programs and encourages state to incorporate the concepts of context sensitive design in the rehabilitation and reuse of historic bridges. After this research the use of proper shielded metal arc welding procedure is acceptable for repairing wrought iron members to restore historic bridges. There is currently no such available recognized welding procedure for the routine repairing of wrought iron members. This demand has been accompanied by a need for information on the qualities of the wrought iron materials and the current welding application to present day problems. The manufacture of wrought iron is an old branch of the ferrous metal industry, and until recent years the details concerning the methods employed were not generally known because a high degree of individual skill was required to produce good quality material. Thus, in many cases, users of wrought iron had available little reliable information on which to base their decisions. This theses is intended as a users procedure to assist owners, managers, and maintenance work forces effectively maintain the nation's remarkable assemblage of metal historic bridges. This thesis has been written top serve as a source of up-to-date information on wrought iron for all who are interested in maintenance procedure as well as material properties of wrought iron.
Thesis:
Thesis (M.S.)--University of Colorado Denver. Civil engineering
Bibliography:
Includes bibliographic references.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Preeda Chomsrimake.

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Source Institution:
|University of Colorado Denver
Holding Location:
|Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
861757908 ( OCLC )
ocn861757908

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ARC WELDING PROCEDURE FOR REPAIRING WROUGHT IRON IN HISTORIC BRIDGES by PREEDA CHOMSRIMAKE B.Eng., Khon Kaen University, Thailand, 1982 A thesis submitted to the College of Engineering and Applied Science of the University of Colorado Denver in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering 2012

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ii This thesis for the Master of Science degree by Preeda Chomsrimake has been approved for College of Engineering and Applied Science by Frederick R. Rutz, Chair Cheng Yu Li Yail Jimmy Kim November 16, 2012

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iii Chomsrimake, Preeda (M.S. Civil Engineering) Arc Welding Procedure for Repairing Wrought Iron in Historic Bridges Thesis directed by Assistant Professor Frederick R. Rut z ABSTRACT Highway historic bridge maintenance projects have impact on the public, and many State DOTs have developed historic bridge programs. FHWA assis ts in the preservation of historic bridge programs and encourages states to incorporate the con cepts of context sensitive design in the rehabilitation and reuse of historic bridges. After this research, the use of proper shielded metal arc welding procedure is acceptable for repairing wrough t iron members to restore historic bridges. There is currently no such available recognized welding proc edure for the routine repairing of wrought iron members. This demand has been accompanie d by a need for information on the qualities of the wrought iron material and the current we lding application to present day problems. The manufacture of wrought iron is an old bran ch of the ferrous metal industry, and until recent years the details concerning the methods empl oyed were not generally known because a high degree of individual skill was required to p roduce good quality material. Thus, in many cases, users of wrought iron had available very littl e reliable information on which to base their decisions. This thesis is intended as a “users’ procedure” to assist owners, managers, and maintenance work forces effectively maintain the nation’s remarkabl e assemblage of metal historic bridges. This thesis has been written to serve as a source of up -to-date information on wrought iron for all who are interested in maintenance procedure as well as m aterial properties of wrought iron.

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iv The basic Shielded Metal Arc Welding (SMAW) and American Welding Society (AWS) Codes were understood, and well defined by this research prior to “Butt Joint” welding performance. The material and mechanical testing compl eted after wrought iron samples made of base metal and welded metal with single V-groove welding in butt joints were prepared by SMAW. Final test data were evaluated and an arc welding pr ocedure was developed. The evaluation of the test results verifies that the use of SMAW procedure for repairing wrought iron is acceptable, which is meeting this research goal, to the public and historic structures. This welding procedure will satisfy and be useful for future historic bridge maintenance projects. This thesis also provides the additional knowledge of wrough t iron properties to a researcher and others who are interested in this historic iron. I t is very important to know the behavior and material properties of wrought iron before utilizing the current repair procedure or techniques to historic structures because it could be harmful to struct ures and unsafe to the public traffic. The form and content of this abstract are approved. I r ecommended its publication. Approved: Frederick R. Rutz

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v ACKNOWLEDGEMENTS This master thesis was supported by Dr. Frederick R. Rutz. His continual support is greatly appreciated. The experimental part of this resear ch could not be possible without the help of Paul Miller, Jac Corless and Thomas Thuis fro m the Civil Engineering Laboratory at University of Colorado Denver, and Ryan Thomas at Emily Griffith Technical Collage, Denver, Colorado. The research is based on the Master Thesis of Preeda Chomsrimake submitted in partial fulfillment of the requirements for the M.S. degree i n Civil Engineering at the University of Colorado Denver. This researcher would like to thank Dr. Frederick A. Rutz for his guidance and positive attitude throughout his study, and also Peter M arxhansen, Ryan Thomas, and Hamid C. Khan for providing him welding directions, procedure, guidelines techniques, trouble shooting, and helpful comments and suggestions. Working wi th them was a great pleasure and contributed a lot. This researcher would also like to tha nk the committee members, Dr. Cheng Yu Li and Dr. Yail Jimmy Kim at Department of Civil Eng ineering for their review and comments during his thesis defense process. The successful completion of this research has been ma de possible through the friendly cooperation of many individuals whose contributions, const ructive criticisms, and practical suggestions are acknowledged with thanks.

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vi TABLE OF CONTENTS CHAPTER I. INTRODUCTION ...................................... ................................................... ...................1 1.1 Research Interest ................................. ................................................... ..........................1 1.2 Objective .......................................... ................................................... .............................1 1.3 Thesis Overview .................................... ................................................... .......................1 1.4 Summary of Work .................................... ................................................... .....................2 II. HISTORIC BACKGROUND ............................... ................................................... .........3 2.1 Background ............................................ ................................................... .......................3 2.2 Definition ......................................... ................................................... .............................4 2.2.1 Wrought Iron Manufacture Prior to 1850 .................. ..................................................7 2.2.2 Modern Wrought Iron Manufacture ....................... ................................................... 15 2.2.3 Properties and Characteristics of Wrought Iron .... ................................................... .. 20 2.3 The Welding of Wrought Iron ........................... ................................................... .......... 23 2.3.1 Plastic Welding .................................... ................................................... ................. 24 2.3.2 Fusion Welding ...................................... ................................................... ............... 24 III. ARC WELDING PROCEDURE ............................. ................................................... .... 26 3.1 Welding Practice & Objective ......................... ................................................... ............ 27 3.2 SMAW Application and Materials....................... ................................................... ........ 27 3.3 Required Tools and Equipment ........................... ................................................... ........ 29 3.3.1 Electrode Selection ................................. ................................................... ............... 29 3.3.2 Power Supply .......................................... ................................................... .............. 33 3.3.3 Typical Stick Welding Set-up Techniques and Practices ..... ...................................... 38

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vii 3.3.4 Basic SMAW Techniques and Practices ................... ................................................ 39 3.3.5 Weld Flaws and Defects .............................. ................................................... .......... 45 3.4 Joint Welding Procedures and Techniques ................... ................................................... 46 3.4.1 Fillet Weld on Lap and T-Joint in Flat Welding Position .. ........................................ 47 3.4.2 Fillet Welding on Lap and T-Joints in Horizontal Positi on........................................ 48 3.4.3 Fillet Welding on Lap and T-Joints in Vertical-up Positio n ...................................... 50 3.4.4 Fillet Welding on Lap and T-Joints in Overhead Position ........................................ 51 3.4.5 V-Groove Welding in a Butt Joint in Flat Position ...... .............................................. 52 3.5 Shielded Metal Arc Welding Procedure ..................... ................................................... .. 55 3.5.1 Weld Qualifications.................................. ................................................... ............. 56 3.5.2 WPS Qualification ................................... ................................................... ............. 56 3.5.3 Types of Tests and Purpose ............................ ................................................... ....... 58 3.5.4 Approval of WPSÂ’s ................................... ................................................... ............ 58 3.5.5 Welder Qualification ................................. ................................................... ............ 59 3.6 SMAW for Wrought Iron ............................... ................................................... ............. 59 3.7 SMAW Procedures for Wrought Iron ...................... ................................................... .... 60 3.7.1 Preparation of Workpieces ........................... ................................................... ......... 60 3.7.2 SMAW Procedure for Wrought Iron ....................... .................................................. 61 IV. MATERIAL TESTING .................................. ................................................... ............. 63 4.1 Material Utilized in Testing ....................... ................................................... .................. 63 4.2 Type of Tests and Purpose ............................. ................................................... .............. 68 4.3 Test Locations ..................................... ................................................... ........................ 69 4.3.1 Spark Testing ....................................... ................................................... ................. 69

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viii 4.3.2 Mechanical Testing ................................. ................................................... .............. 70 4.4 Test Specimens – Number, Type and Preparation .......... ................................................. 70 4.4.1 Preparation of Base Metal Samples for Mechanical Testi ng...................................... 70 4.4.2 Preparation of Welded Samples for Mechanical Testing .......................................... 70 4.5 Spark Test Initial Wrought Iron Identification ......... ................................................... .. 74 4.5.1 Equipment ........................................... ................................................... .................. 74 4.5.2 Test Method ....................................... ................................................... ................... 74 4.5.3 Test Observation ................................... ................................................... ................ 75 4.6 Optional Visual Test Initial Wrought Iron Identificatio n............................................... 76 4.7 Mechanical Testing ................................. ................................................... .................... 77 4.7.1 Tension Testing ................................... ................................................... .................. 77 4.7.2 Guided Bend Testing .................................. ................................................... ........... 86 V. SUMMARY OF TEST RESULTS............................ ................................................... ... 94 5.1 Spark Test Results .................................. ................................................... ..................... 94 5.2 Tension Test Results .............................. ................................................... ..................... 96 5.2.1 Sample Measurement and Records ....................... ................................................... 96 5.2.2 Stress Strain Relationship ........................ ................................................... ............ 97 5.2.3 Additional Tensile Test Sample ...................... ................................................... ..... 101 5.3 Guided Bend Test Results ............................. ................................................... ............ 102 VI. SUMMARY AND CONCLUSIONS ........................... ................................................. 105 6.1 Evaluation and Discussion ............................ ................................................... ............. 105 6.1.1 Spark Test .......................................... ................................................... ................. 105 6.1.2 Tensile Test ...................................... ................................................... ................... 106

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ix 6.1.3 Guided Bend Test ..................................... ................................................... ........... 108 6.2 Conclusions ....................................... ................................................... ........................ 109 6.3 Recommendations for Future Research ................... ................................................... .. 110 REFERENCES ........................................ ................................................... ............................ 111 APPENDIX A. SMAW Procedure ................................... ................................................... ............. 113 B. Summary of Test Data............................. ................................................... ............. 116 C. Curves of Tension Test Results ...................... ................................................... ...... 119

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x LIST OF FIGURES FIGURE 2.1. Wrought Iron Slag Fibers...................... ................................................... ........................7 2.2. Cort’s Dry Puddling Process .................. ................................................... ..................... 12 2.3. Heating Cycle in Cort’s Dry Puddling Process .. ................................................... .......... 14 2.4. Typical Plot of Stress-Strain of Tensile Te st to Full Failure .................................. ......... 23 3.1. Basic Tools for SMAW ...................... ................................................... ........................ 29 3.2. High Output Welding Power Supply AC/DC for SMAW ............................................... 34 3.3. Stringer Bead Weld Practice with E7018 1/8” Dia. El ectrode......................................... 41 3.4. Fillet Weld Practice on a Lap Joint in Flat Position ........................................... ............. 48 3.5. Fillet Weld Practice on a T-Joint in Flat P osition ............................................. .............. 49 3.6. Fillet Weld Practice in Horizontal Position .................................................. .................. 49 3.7. Vertical-up Welding Position Practice ........ ................................................... ................ 51 3.8. Overhead Welding Position Practice .......... ................................................... ................. 52 3.9. Oxyacetylene Cutting (gas cutting) Bevel Edges of Steel Plate ...................................... 53 3.10. Multiple Pass Weld Practice in Butt Joint ... ................................................... .............. 54 3.11. Butt Joint Weld Practice in Flat Position .. ................................................... ................. 55 3.12. Multiple Pass V-Groove Welds in Butt Joint Sam ple in Flat Position ........................... 55 3.13. Groove Welding in Wrought Iron Butt Joint ...... ................................................... ....... 62 4.1. Donated Wrought Iron Members for Testing ....... ................................................... ....... 63 4.2. Kent Street Bridge ......................... ................................................... ............................. 65 4.3. Parshallburg Bridge ........................... ................................................... ......................... 66 4.4. State Street Bridge ........................ ................................................... .............................. 66 4.5. Cutting Wrought Iron Plates by Portable Circula r Saw.............................................. ..... 71

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xi 4.6. Single VGroove Weld in Butt Joint with Back ing Typical Section............................... 72 4.7. Visual Examination of V-Groove Weld in Butt Jo int of Bend Test Specimen ................ 73 4.8. Milling Machine for Sample Preparation in CE Lab ................................................... .... 73 4.9. Spark Test in CE Lab ....................... ................................................... ........................... 74 4.10. Spark Characteristics for Common Irons and S teels ............................................. ........ 75 4.11. Silica Slag in Test Sample Surface ......... ................................................... ................... 77 4.12. Test Specimen to Longitudinal Direction ..... ................................................... ............. 78 4.13. MTS – Tension Testing Machine ................ ................................................... .............. 79 4.14. INSTRON Tension Testing Machine ........... ................................................... ........... 80 4.15. Specimen Grips mounted in Tensile Testing Machi ne (MTS) ...................................... 81 4.16. Configurations of Test Specimens for Tension Tes ting .............................................. .. 83 4.17. Configuration of Welded Test Specimen for Tensi on Testing ...................................... 84 4.18. Fracture on a Wrought Iron Sample in CE Lab ................................................... ........ 85 4.19. Station Manager Program to Record Tensile Te sting Data ......................................... .. 86 4.20. Guided Bend Testing Machine, WATTS W-50 .......... .................................................. 88 4.21. Guided Bend Test Jig of WATTS W-50 Machine ........ ................................................ 89 4.22. Base Metal Specimen for Face-bend Test ..... ................................................... ............ 90 4.23. Welded Specimen for Face-Bend Test ........... ................................................... ........... 91 4.24. Welded Specimen for Root-Bend Test ............. ................................................... ......... 92 4.25. Schematic Fixture for the Guided-Bend Test.... ................................................... ......... 87 4.26. Bend Test Specimen in Guided-Bend Test Machine, W ATTS W-50 ............................ 93 5.1. Fitting Tension Test Specimens after Fracture ................................................... ............ 97 5.2. Stress-Strain Relationship of Tension Test ... ................................................... ............. 101

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xii 5.3. Shows Fractured Ends of Face Bend Test Sample .................................................. ...... 104

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xiii LIST OF TABLES TABLE 2.1. Pig Iron and Wrought Iron Components........... ................................................... ........... 14 2.2. Distribution of Non-ferrous Constituents (Chem ical Composition) ................................ 21 3.1. Last Digit Indication of Electrode Current C oding .............................................. ........... 32 3.2. Last Two Digit Codes of Electrode Composition .................................................. ......... 33 4.1. List of Donated Wrought Iron Members ........ ................................................... ............. 67 4.2. Table of Spark Test Characteristics of Common Irons and Steels .................................. 76 5.1. Spark Test Results ........................ ................................................... .............................. 94 5.2. Bend Test Results .......................... ................................................... ........................... 103

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1 CHAPTER IINTRODUCTION 1.1 Research Interest Highway historic bridge maintenance projects have c onsiderable impact on the public. Many State DOTs have developed historic bridge programs. These programs aim to preserve the historic and cultural value of long-standing bridge s where possible and expedite the consideration of historic bridges in project develo pment and environmental review. For example, Indiana's Historic Bridge Program helps pl anners prioritize a list of bridges for preservation, while providing bridge owners incenti ves for this preservation (M&H Architecture, 2007). FHWA assists in the preservation of histori c bridges and encourages states to incorporate the concepts of context-sensitive design in the reh abilitation and reuse of historic bridges. 1.2 Objective Wrought iron bridges and structures also need prope r repairing of their members, which may have some cracks due to fatigue or accident of vehi cle collision. However, a recognized welding procedure for the routine repairing of wrou ght iron members is unavailable. Our goal or objective is to study wrought iron properties and d etermine an acceptable welding procedure for repairs with common arc welding as used in the stee l fabrication industry. 1.3 Thesis Overview The basic shielded metal arc welding (SMAW) methods and American Welding Society (AWS) Codes for structural welds shall be understoo d by this researcher prior to “butt joint” welding performance testing. He was able to perfor m comprehensive welding as a skilled welder to ensure that quality of weld on specimens was acceptable prior to preparations of welded samples. Final test data was evaluated, an arc welding procedure was developed, and this research outcome is expected to be a guideline for State Departments of Transportation.

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2 1.4 Summary of Work This research task consisted of a literature review of w rought iron and arc welding procedure as it relates to the project, developing proficiency in SMAW techniques, developing a test plan, obtaining historic wrought iron samples, and making welded re pairs using modern steel electrodes. The project goal is to develop a welding proce dure for repairing of wrought iron using modern SMAW methods. In addition, this researcher completed E7018 SMAW welding c lass and prepared mechanical test samples with V-grooved welds and flat position in b utt joints on mild steel specimens prior to welding of the wrought iron specimens.

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3 CHAPTER IIHISTORIC BACKGROUND 2.1 Background From early cast and wrought iron pony truss bridges that did so much to make the metal truss bridge one of the most important inventions of the early 19th century to those that reflect the state highway department bridge bureauÂ’s mid-20th c entury emphasis on aesthetics, historic bridges are located in all parts of the United Stat es (Transystems, 2010). Highway historic bridge maintenance projects have considered on the public impact because of their recognized significance and distinction, historic bridges are worthy for later generation to know our history as well as valued artifacts from our past so that t hey should be preserved. To encourage and be a proactive approach about routine maintenance, some of these bridges continue to be useful as transportation facilities. The historic bridge reh abilitation or replacement decision-making guidelines have been considered by state and local transportation agencies. While the National Historic Preservation Act of 196 6 (amended) and Section 4(f) U.S. Department of Transportation Act of 1966 specify na tionally applicable process for considering preservation or replacement of historic bridges, th ere is no corresponding protocol that ensure a nationally consistent approach to determining which bridges should be rehabilitated or replaced (AASHTO, 2008). Many State Departments of Transpor tation (DOTs) have developed historic bridge programs. These programs aim to preserve th e historic and cultural value of longstanding bridges where possible and expedite the co nsideration of historic bridges in project development and environmental review. Federal Hig hway Administration (FHWA) assists in the preservation of historic bridges and encourages states to incorporate the concepts of context sensitive design in the rehabilitation and reuse of historic bridges.

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4 Successful maintenance and conservation strategies of hi storic bridges include routine maintenance activities that are obvious, but sometimes are not performed well. The lack of proper maintenance results in more extensive and expensive rehabilitation work that could have been avoided. Fortunately there are many effective and o ften very economical procedures that when performed regularly or when problems are first notic ed, will prolong the service life of a bridge. The guidelines included identification of various approaches to bring historic ridges into conformance with current design and safety standards, and the effect or implications of remedial action on historic significance. However maintenance and preservation guidance for wrought iron bridges including a recognized welding procedure is not avai lable for the routine repairing of wrought iron members at this time. There are a few researches going on recently including this research that used the current welding standards and pro cedures to apply for repairing wrought iron members of historic bridges. Eventually these proper repair guidelines would be available for restoring those historic bridges in the st ates. 2.2 Definition Wrought iron was officially defined by the American Socie ty for Testing Materials in 1930 as (Bowman, 2004): “A ferrous material aggregated from a solidifying mass of pa sty particles of highly refined metallic iron, with which, without subsequent fusion, i s incorporated in a minutely and uniformly distributed quantity of slag.” The word “wrought” is a form of the verb “to work,” an d so “wrought iron” literally means “Worked iron”. Wrought iron is the only ferrous metal th at contains siliceous slag, and the addition of slag occurs during the manufacturing process (As ton, 1949). Wrought iron is

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5 described as a two-component metal consisting of low car bon iron which is high percentage of purity iron, and iron silicate known as a glass-like sla g. This is why it looks similar to wood gains. Before the model steel development, wrought iron was th e most commonly used form of malleable iron. Unlike cast iron, wrought iron is ductile and can be deformed, while cast iron is brittle which cannot be worked either hot or cold. Wro ught iron has a lower carbon content which makes it harder and stronger, and is also easier to weld. The slag which melts within the iron at forging temperature, acts as a lubricant reducin g internal friction and hence resisting to distortion under the hammer; therefore, wrought iron is tough (not brittle or tender), malleable, ductile and easily welded. At its high demand in the mid t o late 19 th century, wrought iron was used in the manufacturing of nearly everything metal in a ll over the world. Many different processes have been employed in the man ufactures of wrought iron during the thousands of years it has been made and used by man ( Aston, 1949). The major improvements have been made in manufacturing methods as well as in the quality of the finished wrought iron, but the characteristics of the material component principals used in producing it have remained unchanged. The initial product, which is subsequently squeezed and rolle d by methods of manufacturer, is always composed of a solidi fying mass of refined iron without subsequently fusion and uniformly distributed quantity of sla g. Until recently, the slag content of wrought iron was c onsidered as an undesirable impurity. During the final stages of the refining process, the slag wa s present because the required fusion temperature of the iron metal was equal to or higher tha n the temperature of the furnace, so wrought iron does not become molten, thus causing the refi ned iron to solidify and to entrain some of the molten siliceous slag in which it was parti ally immersed (Aston, 1949).

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6 The slag present in the structure of wrought iron inhibits corrosion in the number of ways (The Real Wrought Iron Company, 2012): 1. Siliceous slags themselves are non-corrodible and serve as an effective barrier against the progress of corrosion of iron metal. 2. The structure of wrought iron has a very rough surface te xture, which interlocks with the oxide layer, be it rust or mill scale, preventing it fro m flanking off the surface. The oxides therefore act as a protective coating preventing further c orrosion. The slag content in wrought iron varies from 1% to 3% by we ight, depending upon the amount of rolling necessary to produce the finished section (Aston, 1949). When the material is rolled, the slag is “squeezed” out. Rolling causes the pockets of slag to become elongated and dispersed throughout the material. These elongated deposi ts of slag influence the iron so that it exists in fibers along one direction of the material. It is distributed throughout the metal in the form of fibers which extend in the direction of rollin g. In well-made wrought iron, there may be more than 250,000 slag threads or fibers per one square inch of area (Bowman, 1949). This creates a fibrous material structure that is similar t o some types of wood, as can be seen in the fracture depicted in Figure 2.1. The slag fibers in a wrought iron sample are included in the highly refined base metal. These fibers give the metal a tough fibrous structure. Wrought i ron properties and quality seem to be inconsistent because the manufacturing process of historic wrought iron production was not quite capable to make the homogeneous material and the metal wa s never completely molten. The process was also dependent on the raw material quality s uch as iron ore. Therefore the performance of wrought iron may vary in nature and it is very difficult to specify the properties for the engineering calculations before the chemical a nd mechanical tests are performed.

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7 Figure 2.1 Wrought Iron Slag Fibers 2.2.1 Wrought Iron Manufacture Prior to 1850 Wrought iron was known and used quite long time ago in the Iron Age. There is evidence that wrought iron tools such as a sickle b lade and a 5000-year old blade were found beneath the base of a sphinx and pyramids in Egypt. The similar discoveries have been made in Europe, the Mediterranean countries and the Far East. In 8th century B.C., early civilizations such as the Hittites and the Mycenaea n Greeks equipped their armies with iron swords. The use of iron spread from the Middle Eas t to Greece and the Aegean region by 1000 B.C. and had reached western and central Europ e by 600 B.C. (Aston, 1949). 2.2.1.1 Primitive Methods The history of wrought iron began in the primitive years and our ancestors found the method to forge iron ore into tools and weapons whi ch were tougher and stronger than wood or stone. They later found the way to produce the metal more quickly by breaking up the ore

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8 and mixing it with the fuel. The first iron furnace to f ire the iron consisted merely of a hole in the ground with an opening at the bottom to provide natural draft (Aston, 1949). 2.2.1.2 Early Egyptian Methods Prior to about 1500 B.C., the Egyptians had developed a bellow s made of goat skins with a bamboo nozzle and air inlet valve (Aston, 1949). The ope rator stood on the skin bag of the bellows to expel the air and re-inflated it by pulling up on a string attached to the top. The Egyptians’ furnaces consisted of pits into which the ore an d fuel were placed, and the quality of the wrought iron produced in them is indicated by the exc ellent condition equipment found from explorations of ancient tombs. The use of this fo rced draft was one of the first major developments in wrought iron manufacturer. 2.2.1.3 Asiatic Improvements The early Asiatic furnace had a trough at the top from which the smelter raked the raw materials on the fire. The bellows design was impro ved to supply the forced draft (Aston, 1949). The Asians developed their original furnaces introduce d by the idea of adding layers of the ore and fuel mixture at the top of the fire as reduction took place. The refined iron collected at the bottom of the furnace in a spongy mas s which was taken out and forged after a sufficient amount had been obtained. 2.2.1.4 Furnaces used in the Direct Processes There were many design of the early furnaces used for w rought iron production in the world. Most of them were the “shaft” type and others w ere of “hearth” type. The “Catalan Forge”, an open hearth-type and major advan ce furnace in the manufacture of wrought iron direct from the ore was developed by the ir on workers of Catalonia in Spain in the early 13 th century (Bowman, 2004). This furnace consisted of a hear th or crucible in

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9 which the mixture of ore and fuel was placed. The 140 pound s of wrought iron were produced by this furnace in five hours which was considerably higher quantity than that of earlier furnaces. This furnace was very popular, and intr oduced into the American colonies and used principally in the South (Aston, 1949). After the development of the Catalan furnace, the shaf t furnaces known as the Osmund furnace were used mainly in India and Sweden. It was devel oped in the eighth century A.D. and the upper portion of the shaft was used both as a stack and as an opening for charging the fuel and iron ore. The iron was refined and had collected o n the bottom in a spongy mass. An opening would be made in one side of the furnace to permit removal of the “ball” (Aston, 1949). From the time of American Colonization to the early twentieth century, the most common furnace used in the United States was the American Bloom ery (Aston, 1949). This furnace was named after the large balls of iron, or blooms that would be produced in the furnace and then rolled into shapes. The American Bloomery was de veloped while America was still colonized by the British and came into existence as a res ult of the Catalan Forge. The hearth was rectangular in shape, with water-cooled metal sides. It was surmounted by a chimney for carrying off the waste gases. The bellows supplying th e forced hot-blast were driven by a water wheel or a steam engine. As in all of the othe r direct processes, charcoal was used as fuel. Great Britain passed the Iron Act of 1740, which helped erect ed many furnaces, forge, and mills in communities throughout the colonies. It was intended that these communities would then produce colonial pig iron that was to be shipped to Great Britain (Bowman, 2004).

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10 As a result of the Iron Act of 1750, the American coloni als were able to develop the knowledge and tools to manufacture iron independently of Gr eat Britain. This knowledge and manufacturing independence turned out to be invaluable during t he revolutionary war and it helped to facilitate industrial progress of the Unit ed States. In the mid of 18th century an industrial revolution was a lso occurring in Great Britain. The iron was needed more than ever to support the booming industr ial growth. Because of the rising need for wrought iron and the current processes for manufacture of iron being too labor-intensive, a more mechanical approach was needed fo r producing wrought iron. 2.2.1.5 Double-Stage Refining Process In the fourteenth century in Europe the direct method of producing wrought iron from the ore was considered a wasteful method and was replaced by a division of the operation into two stages. The single-stage reduction process had been w asteful of time and materials, and the quantity of final products was uncertain. To make a good quality iron, the manganese, sulfur, phosphor us and other impurities were easily eliminated from the iron, but the eliminat ion of the carbon in the iron was a difficult process because the charcoal used as fuel was a n energetic carburizing agent. When wrought iron was brought into contact with this fuel, it was prevented from re-carburizing to the point that it was no longer malleable and ductile. It was discovered that a second heating would help the oth er refining the metal and also had been so over-carburized. The wrought iron produced by thi s additional heating was more uniform and better than the product of the single reduct ion process.

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11 In this second operation, the iron was further refined a nd, in addition, a portion of the slag was removed. This double refined ball of wrought iron wa s called the “bloom” is derived (Aston, 1949). 2.2.1.6 Indirect Process-the Puddling Process The early manufacture methods of wrought iron were base d on producing the finished product in single operation, direct methods. During the four teenth century A.D., the blast furnace was only altered and the indirect methods were de veloped. The modern hot blast furnace of the development of the Catalan furnace, known as a “Stuckofen” was introduced and required the charcoal as fue l in the early1800’s. The product of blast furnace was not malleable and ductile, and c ould not be forged or welded like wrought iron. The metal of this product could be cast into useful shape and it was called “Cast Iron”. The principal product of the blast furnace became “pig iron” because it was cast in small molds or “pig” (Aston, 1949). The production of pig iron was used to the development of t he indirect processes for the manufacture of wrought iron. The early attempts produced w rought iron from pig iron rather than direct from the ore, and the first ones were ma de in Belgium using a hearth type furnace. The reverberatory furnace was invented about 1613, but it wa s not used for refining pig iron until 1766 (Aston, 1949). In 1784, Henry Cort, an Englishman utilized the reverbera tory furnace in the development of his revolutionary “Dry Puddling” process for wrought iron manufacture, and Joseph Hall modified Cort’s furnace in 1830 to improve the l oss of the iron (Gasparini, 2010).

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12 Henry Cort improved a previous hearth furnace and patented a new process called the “Dry Puddling” process for producing wrought iron. He made so me modification in the hearth furnace by using of a reverberatory or air furna ce in heating the iron ore. The bottom of the furnace was dished out like a bath tub and lined with sand to contain the molten iron, and the fuel was burned separately from the hearth (Bowman 2004). The hearth had a chimney on one side and two doors at the front, which one door was used for loading coal into the hearth and the other to loa d the charge of hot gases into the fire-bridge. The fire-bridge door had a small covered apert ure and the stirring pole was inserted. The cast or pig iron was used as the raw mater ial loaded into the fire-bridge. The hot gases passed over and fused the charge of the iron. Th e most of the metalloid impurities were removed by oxidation. After the refining operation, the puddle balls were transferred to the squeezer and rolled to desired shapes such as flat sectio ns. This furnace was able to produce 20 times the amount of wrought iron produced using older methods in the same amount of time. However Cort’s puddling process reduced 30% of the total charged metal because the iron ore would often oxidize with the sand a t the bottom creating extra ironsilicate slag (Aston, 1949). Figure 2.2 Cort’s Dry Puddling Process The heat cycle in the puddling furnace during the refining proce ss of wrought iron production comprised several steps and is described as the fo llowing process, Figure 2.3 (Aston, 1949): Puddling Furnace Squeezer Wrought iron Pig Iron Molten

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13 1. The pig iron was melted by heat, and then iron oxide in t he form of roll piece was added to the bath of molten metal, which was thoroughly agi tated by the puddler using a rabble. 2. The oxidation reaction with the effect of the lining ma terial in the bottom of the hearth furnace eliminated carbon, silica, sulfur, phospho rus and manganese originally present in the pig iron. The composition of the refin ed metal approached that of almost pure iron. The furnace temperature of about 2600F wa s insufficient to maintain the metal in a liquid state. The finishing oper ations, therefore, were carried out with the refined metal in a partially solidified or pasty condition. However, this temperature was high enough to keep the slag in a molten co ndition throughout the heat. The metal became a spongy ball and molten spun s lag, plastic mass impregnated with the liquid slag. The slag was immersed t hroughout the iron in small pockets at this step. 3. The sponge ball of iron saturated with slag was divided in t he furnace into two or three portions weighing 200 to 300 pounds each. The hot ball w as transported to a rotary squeezer. The squeezer ejected the surplus slag exis ting in the metal and formed the metal into compact blooms which were less th an the original size and immediately rolled into rough, flat sections called “muck bar.” 4. The bar was then cut to short lengths which were piled, r eheated to a welding temperature, and rolled to the desired shapes. The “piling” operation was desirable to obtain a more uniform finished material and to provide a ma ss of metal sufficiently large to work properly.

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14 Figure 2.3 Heating Cycle in Cort’s Dry Puddling Process After the refining process of wrought iron, the finished m etal consisted of lower carbon iron than the pig iron by about 98%, see Table 2.1. The w rought iron manufactured from the puddling process still has some deposits of impurity elements and the majority of these impurities are slag. Table 2.1 Pig Iron and Wrought Iron Components (Gasparini, 2010) Material % Element C Si S P Mn Pig Iron 3.5 – 4.25 1.0 – 2.0 0.03-0.10 0.50 – 1.0 0.25 – 1.0 Wrought Iron 0.05 – 0.25 0.10 – 0.20 0.02-0.10 0.05 – 0.20 0.01 – 0.10 Joseph Hall modified Cort’s hearth furnace in his attempt s to reduce the iron loss in the process by replacing the older hearth material lining the bottom with iron silicate and thus introduced iron oxide. This improvement called “Wet Puddling Pr ocess” reduced the Pig Iron (Do a few hundred pounds per time) Melt Molten spun slag Squeeze Reheat Oxidation Heat Carbon and other impurities burned Wrought Iron shapes

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15 charged iron loss by about 10% and also the heating time took about one and a half hours to complete (Bowman, 2004). The most important of the puddling process was that the produc tion of wrought iron was increased greatly from ten tons per week produced by one pla nt to two hundred tons per week. Also, the handling of larger masses of iron and t he use of improved methods and equipment made available a wrought iron of better quality than that produced previously (Aston, 1949). The new method for manufacturing wrought iron grew and many manufacturing plants were built throughout the United States. Minor improvem ents of the puddling process were made from time to time, but the puddling process was conforme d to CortÂ’s and HallÂ’s original developments of more than a century ago (Bowma n, 2004). 2.2.2 Modern Wrought Iron Manufacture 2.2.2.1 Revolution of Wrought Iron Industry During the middle of the 19th century, the United States wo uld experience the civil war; therefore, the demand for the raw material of wrought i ron hit its peak as iron popularity rose and it was needed for the war and for rebuilding after th e war. The revolution of U.S. industry lately occurred because wrought iron was used quite e xtensively throughout the country as well as in the construction industry (Bowman, 2004). From the time when wrought iron was introduced until withi n the past decade, the handpuddling process had limitation in both quantity production and physical uniformity of the finished product. As a result, the manufacture of wrought i ron finally selected suitable equipment for carrying out each of the operations separat ely and subsequently combining the products of the various steps to produce the finished material Many mechanical processes

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16 were invented in the attempts to increase the production a nd quality of wrought iron. These mechanical processes were needed to increase production capac ity and reduce the amount of labor (Aston, 1949). One of the first of the mechanically operated furnaces was the “Danks Puddling Furnace”, which was used in the United States between 1868 and 1885. This furnace was cylindrical shape, and was rotated about horizontal axis. While this furnace embodied most of the features of some of the more successful effort s of later date, it was a failure for several reasons including the absence of suitable refractory mate rials, a lack of knowledge and facilities for control and study of products, and non-unif ormity of products (Aston, 1949). Many new mechanical furnaces were introduced, but none wer e very successful in their attempts and the product was not of a commercial order. T he failure or only partial success of the various mechanical puddling furnaces led to an entirel y new, but most logical approach to the problem of wrought iron was just as radica l a departure from the accepted principles as was Cort’s development of 1784 (Aston, 1949). In 1915, the research on the structural characteristics and chemical composition of good quality wrought iron formed the basis for the development of the present-day manufacturing process. The present-day methods, Byer Process by A.M. Byer Company in 1930 for manufacturing wrought iron conforms to the hand-puddling proces s in all of these three essential steps. 1. To melt and refine the base metal 2. To produce and keep molten a proper slag 3. To granulate, or disintegrate, the base metal and mechanic ally incorporate with it the desired amount of slag.

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17 Each step, however, is separated and carried out in indiv idual pieces of equipment best suited to that operation. The process was placed on a c ommercial basis October 8, 1930 when largest wrought iron mill in existence was formall y dedicated at Ambridge, Pennsylvania. The process has resulted in a magnitude of pro duction, control of operations, and assurance of uniformity (Aston, 1949). The manufacturer also started manufacturing standardize d shapes and sizes of iron to be used for construction purposes. Each iron company had a set of standardized shapes that were produced only by that company. The American Institute of Steel Construction (1953) compiled many of these standard shapes from larger companie s throughout the country from the years 1873 to 1952. Some of these companies included Carnegie Brothers & Company, Limited, A.M. Byers Company, The Passaic Rolling Mill Co mpany, and the Phoenix Iron Company (Bowman, 2004). In addition to producing standardized shapes for building con struction, many of the iron manufacturers designed and produced bridges. One popular bridge company was the Wrought Iron Bridge Company of Canton Ohio (Bowman, 2004). Thi s company designed, patented, manufactured and constructed bridges. Most of th e bridge companies published pamphlets describing the different types of bridges they bui lt and their uses. Entrepreneurial, industrial and professional context could also be seen in products of bridge companies, railroad bridge designs, and early designs of consulting b ridge engineers (Gasparini, 2010). In modern manufacturing processes, the wrought iron is ma de from a process similar to that of steel. The iron is superheated to be completel y fluid and the impurities rise to the surface and are separated. During the modern process, the slag was added after the iron

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18 become molten and impurities have been separated which cre ates a different microstructure in the iron from historic wrought iron (Bowman, 2004). 2.2.2.2 End of Wrought Iron Popularity Concurrent with the attempts to improve the mechanical m anufacture of wrought iron in 1855, Henry Bessemer, an Englishman developed a new process to convert molten iron or remelted pig iron into steel or malleable iron without the use of fuel for reheating or continuing to heat the crude molten metal. The furnace was called “Pneumatic Bessemer Converter” (Gasparini, 2010). The basic concept of the Bessemer process depends on th e successful rapid oxidation of the impurities by keeping the iron ore in a fluid molten ba th with extreme heat, thus forcing the slag to separate from the steel by floatation. Thi s was done by subjecting molten pig iron to a superheated pressured blast for about fifteen minutes (G asparini, 2010). After oxidizing all the impurities out of the molten iron an aluminum and manganese alloy carrying several percent carbon was added. In ear ly prior of steel development, the steel making methods were very complex; therefore, it w as rare and more expensive to use for any sort of building purposes. These processes are kno wn as the cementation and crucible processes developed many years. These steel-maki ng processes involved the addition of carbon to iron by soaking iron in carbon an d letting it set over time, or melting wrought iron and mixing it with a carbonaceous material (Bo wman, 2004). The introduction of this alloy resulted in the addition of carbon to the molten iron, making it steel. Then the molten steel is poured and solidified into ingots and cast ings which are then rolled into shapes (Bowman, 2004).

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19 The original Bessemer process created brittle steel t hat was not useful. Then in 1856, Robert Mushet, Englishman discovered that by adding a com pound containing manganese and iron to the molten iron in Bessemer’s process, the resulting steel could be made more ductile and have superior strength (Bowman, 2004). Bessemer a nd Mushet received many patents for their process and traveled the world promoting it and the manufacturing of steel. While the Bessemer process had been developing, William K elly from Kentucky, 1857 was developing an idea to use a blast of air to oxidize o ut the impurities of iron. After many years of development, he then created what is known a s the pneumatic process for making mild steel and obtained an American Patent for this con cept (Bowman, 2004). About ten years later, the Open Hearth process was developed. This process, like the Bessemer process, utilized a blast of air to oxidize out the impur ities in pig iron. By the end of the 19 th century, steel became popular in the industry. Once th e new processes for making steel were developed, wrought iron wa s not immediately neglected. Wrought iron was already being manufactured throughout the United States, so it was easier and cheaper to construct with wrought iron even though it w as found that steel was stronger (Bowman, 2004). Originally in Great Britain, the rails for trains wer e made of wrought iron, but needed to be “turned” or replaced every six months. In an effort to promote mass produced steel, Henry Bessemer convinced the local authorities to try st eel rails. The trial steel rails did not need to be replaced for two years and it was soon deter mined that steel was a stronger and more durable material (Bowman, 2004). This knowledge was spre ad to the United States and steel rails were slowly used throughout the populated east As steel manufacturing mills

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20 began growing around the country, rails were eventually conv erted to steel across the country. The transition from wrought iron to steel in the cons truction industry parallels that of the railroad industry. Just like any other structural building product, it took time to convince the design and construction community of the benefits from ut ilizing steel as a structural material and to build more manufacturing plants. Wrought iron was more familiar, cheaper, and more trusted from experience. Since the quality of wrought iron was variable, and the process to make wrought iron was so labor intensive and time consumi ng compared to steel, it soon fell behind in use for building purposes. 2.2.3 Properties and Characteristics of Wrought Iron 2.2.3.1 Chemical Composition Chemical compositions of wrought iron consist of mostly iron with the addition of some elements such as carbon, manganese, phosphorous, sulfur an d silicon. Chemical analysis of wrought iron shows that there is typically less than 0. 15% carbon found in the material (Bowman, 2004). Although a similar amount of carbon is c ommonly found in some steels, the other elements comprising wrought iron create the diff erence in the materials. Phosphorous and silicon are typically found in wrought ir on and steel, but these elements usually exist in excess than what is typically found in steel. An excess of the silicon element is especially characteristic of wrought iron since it i s the main constituent found in the slag which defines the metal. The iron silicate slag content in wrought iron may vary from about 1% to 3% by weight depending on the amount of rolling to pro duce the finished section (Aston, 1949).

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21 The consistency and quality of wrought iron is difficult to assess simply because the manufacturing process utilized to make historic wrought iron was not capable of making wrought iron entirely structurally homogeneous in nature. Because of these imperfections, the performance of the material will vary considerably. The properties of the material also depend on the iron ore it was manufactured from and the i ndividual manufacture that was manufacturing it. Since it is difficult to find consis tency in both of these dependencies, it is also extremely difficult to find consistency in the mate rial properties to define a specification for structural design and analysis purposes. A typical chemical analysis of wrought iron showing the distribution of metalloids in the two constituents is listed in Table 2.2: Table 2.2 Distribution of Non-ferrous Constituents (Chemical Composition) (Aston, 1949) Elements Combined Analysis Constituents Occurring in Base Metal Constituents Occurring in Slag Carbon 0.02% 0.02% Manganese 0.03% 0.01% 0.02% Phosphorus 0.12% 0.1% 0.02% Sulfur 0.02% 0.02% Silicon 0.15% 0.01% 0.14% Slag, by Weight 3.0% Total 0.16% 0.18% 2.2.3.2 Characteristics of Wrought Iron Wrought iron is refined from pig iron that has been manipul ated into a material in which carbon forms less than 0.1% and the total proportion of al l impurities is no more than 0.4% (Transystems, 2010). From the practical application and i nstallation, the important characteristics of wrought iron include ductility, resist ance to corrosion, resistance to fatigue

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22 failure, the ability to take on and hold protective metall ic and paint coatings, good machining and threading qualities, and good forming and welding qualities. To describe above properties, wrought iron is the oldest type of almost pure iron, and with much less carbon content than steel and high sili cate slag, has the highest resistance to corrosion of all ferrous metals other than special al loy steels. Wrought iron is ideal for rolling, impact shaping, and even splitting. Its long fiber structure and mechanical working give it a relatively high tensile strength and elastic ity; therefore, it is not brittle like cast iron. Because of its high ductility, wrought iron is known to b e relatively insensitive to notch effects and unusually resistant to overstress. The pr esence of slag fibers gives the material toughness and deflects slip planes that contribute to fati gue failure. The slag also tends to resist the formation of cracks because of its high duct ility which allows the metal deform and can be bent as same as steel. 2.2.3.3 Properties of Wrought Iron The physical properties of wrought iron are largely those o f almost pure iron. The strength “along grains” uniaxial tensile behavior, elastic ity, and ductility are affected to some degree by small variations in the metalloid content and in even greater degree by the amount of the incorporated slag and the character of its distr ibution. The ultimate tensile strength and the ductility of wrough t iron are greater in the longitudinal or rolling direction than in the direction transverse to rolling. This difference is due to the nature of the slag distribution throughout the m etal in the two directions. The properties of wrought iron “along grain” uniaxial tensile be havior are as the following data (Gasparini, 2010).

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23 Tensile strength (Ultimate) = 45 – 55 ksi Modulus of elasticity = 25,000 29,000 ksi (gene rally 27,000 ksi) Elongation (%) = 10 25% Figure 2.4 displays the typical plot of stress-stra in curve of tensile test of wrought iron sample. This plot shows that the wrought iron speci men has yield strength about 31 ksi and the ultimate strength reached approximately 49 ksi before it failed. Figure 2.4 Typical Plot of Stress-Strain of Tensile Test to Full Failure (Bowman, 2004) 2.3 The Welding of Wrought Iron Wrought iron can be welded easily by some of proper used processes, such as forge welding, electric resistance welding, electric metallic arc welding (shielded metal arc welding), and oxy-

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24 acetylene welding. The first two come under the classif ication of plastic welding, which the others are classed as fusing process (Aston, 1949). 2.3.1 Plastic Welding Plastic welding including forge and electric resistance we lding has been used for many years with wrought iron. In fact, all standard wrought iron pipe and a majority of the large wrought iron pipe are produced by forge welding which embraces both roll and hammer welding (Aston, 1949). Resistance welding has been employed in fabricating many wrought iron installations. When jointing lengths of wrought iron pipe using resistance butt-welds, the best results are obtained by forcing the member ends together with pressure t hat is just sufficient to produce a sound union. 1. Forge welding is a solid-state welding process that joins t wo pieces of metal by heating them to a high temperature and then hammering them together. 2. Electric resistance welding (ERW) refers to a group of welding processes such as spot and seam welding that produce coalescence of faying surface s where the heat is applied. The weld is generated by the electrical resista nce of material versus the time and the force used to hold the materials together during w elding. 2.3.2 Fusion Welding The term fusion welding includes several different proce sses, and the ones most commonly used in joining wrought iron sections are oxy-ace tylene welding, shielded metal arc welding and electric carbon arc welding. Oxy-Acetylene (OA) welding is one of the many types of w elding. The oxy-acetylene flame burns the metal at a temperature which is below t he fusion point, and heating should be

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25 continued until the iron is fully melted. Oxy-acetylen e welding is simple by jointing two pieces of metal together, and the touching edges are melte d by the flame with or without the addition of filler rod. The shielded metal arc welding method, which is commonly u sed in steel building and bridge construction industry, was discussed in the next ch apter and chosen to repair wrought iron samples of bridge members in this research. The appropriate welding procedure for repairing of damaged bridge members is our attempts to provide c orrect guidelines for the restoration of historic bridges. Carbon arc welding (CAW) is a process which produces coales cence of metals by heating them with an arc between a non-consumable carbon (gra phite) electrode and the work-piece. It was the first arc-welding process ever developed, but is not used for many applications today.

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26 CHAPTER IIIARC WELDING PROCEDURE This chapter describes the use of shielded metal ar c welding procedure to repair wrought iron members. To ensure the weld quality is acceptable, an approved welding procedure specification (WPS) is required by AWS code. The WPS qualificat ion tests required by the code are also designed to provide assurance that the weld metal o n wrought iron joints produced by the welding produces weld metal strength, ductility, an d toughness conforming to the code. In the current bridge design specifications, the we lded splice design and details are specified conforming to the requirements of the latest editio n of the AASHTO/AWS D1.5M/D1.5 Code. Tension and compression members are recommended to be spliced by full penetration butt welds (AASTHO, 2010). AASTHO also recommends that welded field splices should be arranged to minimize overhead welding to ensure the quality of weld metal be acceptable. All production welds are performed in conformance with the provisi ons of an approved WPS, which is based upon successful test results as recorded in a Proce dure Qualification Record (POQ) unless qualified in conformance with AWS1.3.1. All WPSÂ’s and SMAW meeting the requirements of AWS 5.11 were reviewed, and this researcher practiced arc welding by himself prior t o performing the repair of wrought iron samples and qualification testing. The recommended arc welding procedure for wrought i ron included in this chapter is intended to be useful for and guide others who are interested in this research, and use the procedure for their repair projects on wrought iron members of historic bridges or other structures.

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27 3.1 Welding Practice & Objective To accomplish the objective of using SMAW for repairing wro ught iron members, this researcher has reviewed welding procedure including AASHTO Br idge Design Specifications, AWS Code and the presentation of Annual Historic Bridge Pre servation Seminar organized by Lansing Community College in Lansing, Michigan. To ensure th at this researcher had enough skill for the preparation of welded wrought iron samples for this research, he became involved in learning the procedure and techniques of basic arc welding on a ll joints and welding positions. This practice provided him with the familiarity with how t o control welding gap, welding position, running speed of welds, and setting up correct current f or each joint and position. After this practice, he was able to make a good weld on a metal j oint. This researcher has practiced by starting from fillet we lding on lap and T-joints in all positions, and used two workpieces of mild steel, ” thick, 2” wide, and 6” long. DC Polarity Positive current for E7018 electrode 1/8” in diameter with the current setting between 110-160 Amps depending on welding positions, was selected. In the f inal, he completed single V-groove welding in butt joints in flat position. The welding s kill that he has learned was carried out to prepare welded wrought iron samples for the mechanical test ing. Therefore, the basic welding procedure and techniques were described in this chapter to be gui dance for a person who has never had an experience in arc welding. 3.2 SMAW Application and Materials The most frequently used welding process in the maintenance and repair industry in the construction of steel structures, and in industrial fabr ication is the shielded metal arc welding or “stick welding”. SMAW has been one of the most popular welding processes in the world for years because of its versatility and simplicity. In recent years the use of SMAW has declined

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28 because flux-cored arc welding has expanded in the constructi on industry, and gas metal arc welding has become more popular in industrial environments. However, because of the low equipment cost and wide applicability, the SMAW process w ill likely remain popular, especially among small businesses where specialized welding processe s are uneconomical and unnecessary (Lincoln, 1994). SMAW is often used to weld carbon steel, low and high a lloy steel, stainless steel, cast iron, and ductile iron. The material being welded primarily by t he skilled welders with proper joint preparation and use of multiple passes, materials of virt ually unlimited thicknesses can be joined. Furthermore, depending on the electrode used and the skill of the welder, SMAW can be used for welding in any position. SMAW is a process which melts and joins a metal by heati ng them with an arc between a coated metal electrode and a work piece. The electrode ou ter coating called “flux” assists in creating the arc and provides the shielding gas and slag cover ing to protect the weld from contamination. The electrode core provides most of the weld filler metal. When the electrode is moved along the work piece at the correct speed, the metal is deposited in a uniform layer called a bead. An electric current is used to form an electric arc bet ween the electrode and the metals to be joined. The stick welding power source provides constant c urrent (CC) and may be either alternating current (AC) or direct current (DC) power suppl y, depending on the electrode being used. The best welding characteristic are usually obtai ned using DC power sources because DC maintains a suitably steady current. Skilled welders who perform complicated welds can vary the arc length and this can result in constant heat an d make welding easier with good weld results (Miller, 2010).

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29 3.3 Required Tools and Equipment SMAW equipment typically consists of a constant cur rent welding power supply and an electrode. There are an electrode holder and a gro und clamp, and welding cables known as welding leads connecting both with a power supply, see Figure 3.2. The welders also need safety gear such as safety shoes, welding helmet an d leather gloves (Figure 3.1). The other common cleaning tools are a chipping hammer and a w ire brush. Figure 3.1 Basic Tools for SMAW 3.3.1 Electrode Selection The electrode is coated in a metal mixture called f lux, which gives off gases as it decomposes to prevent weld contamination, introduce s deoxidization to purify the weld, causes weld-protecting slag to form, improves the a rc stability, and provides alloying elements to improve the weld quality. The composit ion of the electrode core is generally similar and sometimes identical to that of the base material, but even though many feasible Electrodes Leather gloves Wire brush Chipping hammer Welding helmet

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30 electrode options are available in the market, a sligh t difference in alloy composition can strongly impact the properties of the resulting weld. However, it sometimes is desirable to use electrodes with core materials significantly diffe rent from the base material to gain higher tension strength. For example, stainless steel electrodes are sometimes used to weld two pieces of carbon steel, and are often utilized to wel d stainless steel workpieces with carbon steel workpieces (Lincoln, 1994). 3.3.1.1 Electrode Groups Electrodes are divided into three groups – the electrodes des igned to melt quickly are called “fast-fill” electrodes, those designed to solidif y quickly are called “fast-freeze” electrodes, and the intermediate electrodes go by the n ame “fill-freeze" or "fast-follow" electrodes (Lincoln, 2004). 1. Fast-fill electrodes are designed to melt quickly so tha t the welding speed can be maximized. 2. Fast-freeze electrodes supply filler metal that solidif ies quickly, which make welding in a variety of positions possible by preventing the weld pool from shifting significantly before solidifying. 3. Fill-freeze electrodes are the intermediate electrod e between the first two which melt quickly and supply filler metal that solidifies quickly. 3.3.1.2 Electrode Coating Materials Electrode coatings consist of a number of different c ompounds including rutile, calcium fluoride, cellulose, and iron powder (Lincoln, 2004).

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31 1. Rutile electrodes coated with 25%–45% Titanium Dioxide (TiO2), are characterized by ease of use and good appearance of the resulting weld. However, they create welds with high hydrogen content causing brittle and cracke d welds. 2. Calcium fluoride electrodes containing calcium fluoride (C aF2), sometimes known as basic or low-hydrogen electrodes, are hygroscopic and must be stored in dry conditions. They produce strong welds, but the welds ha ve a coarse and convexshaped joint surface. 3. Cellulose electrodes coated with cellulose, especiall y when combined with rutile, provide deep weld penetration, but they have high moisture co ntent and special procedures must be used to prevent excessive risk of cracki ng. 4. Iron electrodes containing iron powder, which is a common coating admixture. It improves the productivity of the electrode, sometimes as much as doubling the yield. Electrodes for SMAW should conform to the requirements o f the latest edition of AWS A5.1/A5.IM, Specification for Covered Carbon Steel Arc W elding electrodes, or to the requirements of AWS A5.1/A5.1M, Specification for Low-All oy Steel Covered Arc Welding Electrodes (AWS, 2010). 3.3.1.3 Electrode Identification To identify different electrodes for SMAW, the AWS est ablished a system that assigns electrodes with a four-digit number such as E6010 or E7028. Co vered electrodes carry the prefix E, R or ER. E designates an electrode, R designate s a rod and ER designates the electrode or rod usage. The numbers on the welding electr ode indicate the minimum tensile strength, welding position, current and composition.

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32 The first two digits stand for minimum tensile strength in 1,000 psi; therefore, the 60 digit in E6010 means 60,000 psi. The second digit from the last digit indicates the r ecommended welding position permissible with the electrode. Typically the value “ 1” is used fast-freeze electrodes, meaning all position welding; value “2” is normally fast-f ill electrodes, meaning horizontal welding only; value “3” is used for flat welding only; and va lue “4” is used for flat, horizontal, overhead, and vertical down only. The welding current and type of electrode covering are spec ified by the last digit, Table 3.1. When applicable, a suffix is used to denote the alloyi ng element being contributed by the electrode. To learn the current setting for the de sired welding electrode, the last digit in the following Table 3.1 should be read and identified. Table 3.1 Last Digit Indication of Electrode Current Coding (Althouse, 2004) Last digit Current 0 DCEP 1 AC or DCEP 2 AC or DCEN 3 AC or DC (either DCEP or DCEN) 4 AC or DC (either DCEP or DCEN) 5 DCEP 6 AC or DCEP 7 AC or DCEN 8 AC or DCEP The last two digits are combined together to identify the proper application and the covering composition for an electrode (Table 3.2). The o nly coating ingredient would be

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33 considered the most important to know are the welding ro ds with low hydrogen composition which are the numbers 5, 6, and 8. Table 3.2 Last Two Digit Codes of Electrode Composition (Althouse, 2004) Last Two Digits Covering Composition EXX10 High-cellulose, sodium EXX11 High-cellulose, potassium EXX12 High-titanium, sodium EXX13 High-titanium, potassium EXX14 Iron powder, titanium EXX15 Low-hydrogen, sodium EXX16 Low-hydrogen, potassium EXX18 Iron-powder, low-hydrogen, potassium EXX20 High-iron oxide EXX22 High-iron oxide EXX24 Iron powder, titanium EXX27 Iron powder, High-iron oxide EXX28 Iron powder, Low-hydrogen, potassium EXX48 Iron powder, low-hydrogen, potassium 3.3.2 Power Supply The power in a welding circuit is measured in voltage and current. The voltage (Volts) is governed by the arc length between the electrode and the workpiece, and is influenced by electrode diameter. Current is a more practical measure of the power in a weld circuit and is measured in amperes (Amps).

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34 The proper power supply used in SMAW process should have constant current output to ensure that the heat remains relatively constant, e ven if the arc distance and voltage change. This is very important because most applications of SMAW require that a welder holds the electrode holder manually. It is very difficult fo r a welder to maintain a suitably steady arc distance if a constant voltage power source is used instead, and this can cause varied heat and make welding more difficult with poor characteristi cs. However, because the current is not maintained absolutely constant, skilled welders who perform complicated welds can vary the arc length to cause minor fluctuations in the curre nt. Figure 3.2 High Output Welding Power Supply AC/DC f or SMAW Typically, the power supply equipment used for SMAW consists of a step-down transformer and for DC models a rectifier, which co nverts AC into DC. Because the power normally supplied to the welding machine is high-vo ltage AC, the welding transformer is used to reduce the voltage and increase the current As a result, instead of 220 V at 50 Amp,

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35 for example, the power supplied by the transformer is droppe d around 17–45 V at the currents up to 600 Amp. A number of different types of trans formers can be used to produce this effect, including multiple coil and inverter machines, with each using a different method to manipulate the welding current. The multiple coil type adjusts the current by either varying the number of turns in the coil (in tap-type trans formers) or by varying the distance between the primary and secondary coils (in movable coi l or movable core transformers). Inverters, which are smaller and thus more portable, use electronic components to change the current characteristics. 3.3.2.1 DCEN and DCEP Fundamentals In welding industrial practice, the choice of the electro de may be made by the welder or specified by the welding procedure specification and/or codes us ed. The decision to use the preferred polarity of the SMAW system often depends on suc h variables as: 1. The depth of penetration desired 2. The rate at which filler metal is deposited 3. The position of the joint 4. The thickness of the base metal 5. The type of base metal The welding direct current electrode negative (DCEN) cir cuit is defined by the AWS as direct current straight polarity. In this circuit, th e electrons are flowing from the negative pole of the machine to the electrode. The electrons con tinue to travel across the arc into the base metal and to the positive pole of the machine. It is sometimes desirable to reserve the direction of electron flow or polarity in the arc welding circuit. This may be done by disconnecting the ele ctrode and workpiece leads, and

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36 reversing their positions. When electrons flow from t he negative pole of the arc welding machine to base metal, this circuit is known as direct c urrent electrode positive (DCEP) circuit. In this circuit, the electrons flow from t he negative pole of the welding machine to the workpiece. Electrons travel across the arc to the electrode and then return to the positive pole of the machine. For the comparison, DCEP produces better penetration tha n DCEN. The SMAW electrodes that have the best penetrating abilities are E6010, E6011, and E7010. These electrodes use DCEP. There is a theory that with a D CEP covered electrode, there is a jet action and/or expansion of the molten metal to be propell ed with great speed across the arc. The molten metal impacts on the base metal with the greater force. This heavy impact on the base metal helps to produce deep, penetrating welds (Althouse 2004). When a high rate of filter metal deposit is required, a n EXX2X electrode is recommended. DCEN is usually recommended for the EXX2X el ectrodes. Examples of the EXX2X electrodes that deposit a high rate of filler met al are E6020, E6027or E7027 (Althouse, 2004). 3.3.2.2 Setting-Up Machine To set up all connections of power supply machine for SMAW proc ess, the preferred polarity of the SMAW system depends primarily upon the e lectrode being used and the desired properties of the weld. DC current with a DCEN c auses heat to build up on the electrode, to increase the electrode melting rate and to decrease the depth of the weld. On the other hand, reversing the polarity so that the electrode is DCEP and the workpiece is negatively charged which increases the weld penetration. With AC current the polarity

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37 changes over 100 times per second an even heat distribution is created, providing a balance between electrode melting rate and penetration. The amperage needed for welding a joint depends on the ele ctrode diameter, the size and thickness of the base metal pieces, and the position of the welding. Thin metals require less current than thick metal, and a small electrode requires less amperage than a large one. The welder should know setting up serial electrodes with the s uggested diameters and recommended current. If thicker electrodes are used, the higher current should be selected. For example, a welder uses E7018 1/8” diameter electrodes, an d the proper current can be set between 110 and 160 Amps. As described previously and per additional guidelines below, w hen the welder attempts to select an electrode for SMAW, the following must be co nsidered: 1. The grooved weld design 2. Tensile strength of the required weld 3. The base metal composition 4. The position of the weld joint 5. The rate of deposition of the weld metal 6. The polarity type of arc welding current used (DCEN or DCE P) 7. The penetration required 8. The metal thickness 9. The experience of the welder 10. The specifications for the weld to be made

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38 3.3.3 Typical Stick Welding Set-up Techniques and Practices To run the welding correctly with SMAW process, this rese archer has learned and practiced how to set-up the current and the polarity of po wer supply for desired electrodes, E6010 and E7018. It also is very important for the students, w ho have never had any experience in welding to practice how to strike electrode s on workpieces. The others influence weld quality are controlling arc length, which i s difficult and it may take time several months for some students to be familiar with i t, and controlling stability of holding the electrode. The practical arc welding set-up is liste d as the following list: 1. Workpiece The welder should make sure workpiece is clean before wel ding. 2. Work Clamp The work clamp for ground line is placed as close to the w eld as possible. 3. Electrode Before striking an arc, an electrode shall be inserted in the electrode holder. A small diameter electrode required less current than a large on e. Following recommendations of the electrode manufacturer when set ting weld amperage. 4. Insulated Electrode Holder The insulated handle that clamps onto the electrode. The welder holds this device during welding to control the arc. 5. Electrode Holder Position Stability also plays a role in how nice a welding surfa ce turns out. A practical electrode holding method is to use two hands, one holding the stinger and the other

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39 holding the electrode. It's possible to use one hand, but in certain situations two hands can make a better weld. 6. Arc Length Arc length is the distance from the electrode to the w orkpiece. A short arc with correct amperage will give a sharp crackling sound. Corre ct arc length is related to electrode diameter. The welder should examine the weld bead to determine if the arc length is correct. Arc length for 1/16 and 3/32 in. diamete r electrodes should be about 1/16 in. Arc length for 1/8 and 5/32 in. diameter ele ctrodes should be 1/8 in. 7. Slag Stick welding is really a simple process, the only negativ e part about it is having to chip off the slag after every weld, unless the right heat and perfect technique are set to make the slag peel itself off. After stopping arc welding, the chipping hammer and wire brush should be used to remove slag. Then the welde r should check that weld beads are clean before making another weld pass. 3.3.4 Basic SMAW Techniques and Practices 3.3.4.1 Striking an Arc Scratch Start Technique When learning how to weld SMAW on workpieces, this research er started off striking the arc on workpieces. In arc welding it is very important t o be able to control the arc strike to produce an arc between the metal electrode and the base metal. To strike a welding arc, the electrode must first touch the base metal and be dragged ac ross workpiece like striking a match, followed by lifting the electrode slightly after touching the workpiece. Welding current starts as soon as electrode touches the workpiec e.

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40 When the arc goes out, electrode was lifted too high. If the electrode sticks to the workpiece, use a quick twist to free it. The welder shou ld practice to be familiar to control holding the electrode in the right length form the workpi ece. The scratch-start technique is preferred for arc welding (Miller, 2004). 3.3.4.2 Striking an Arc Tapping Technique The second technique to strike an arc is to bring the elect rode straight down to workpiece, then lift slightly to start arc. If arc goes out, el ectrode was lifted too high. If electrode sticks to workpiece, do a quick twist to free it. 3.3.4.3 Electrode Movement during Welding When stick welding, always keep the weld puddle moving forward. There are a few stick welding techniques to make an u-path or circle path. Stick wel ding with the u technique will build a weld pool of rounded shape, on the other hand making a circle welding technique could bring the weld pool back over the slag and it may get slag included in the weld. It's also better to pull the weld when stick welding. This rese archer also likes keeping a short arc which it helps in penetration and maintaining a nice weld puddle. There are two types of beads used in stick welding. The w elder can control the bead movement by the following methods. 1. Stringer Bead The electrode is moved steady forward along seam when t he joint is narrow. The bead width will be 2 to 3 times the electrode diameter. To practice the stringer beads, this researcher has used bo th E6010 and E7018 1/8” dia. electrodes to run the stringer beads on workpieces of mile steel ” thick, 6” wide by 6” long, shown in Figure 3.3.

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41 Figure 3.3 Stringer Bead Weld Practice with E7018 1 /8” Dia. Electrode 2. Weave Bead The electrode is moved side-to-side along seam wher e the joint is wider gap. The bead width will be 2 to 3 times the electrode diame ter. 3. Weave Patterns Weave patterns will be used to cover a wide area in one pass of the electrode. Weave width will be limited to 2.5 times diameter of elec trode. To practice the stringer bead, use a piece of mild steel ” thick, 6” wide, and 6” long. Select a DCNP for electrode E7018 1/8” in diameter. The current is set a range of 110-160 Amps. A single stringer bead is satisfactory for m ost narrow groove weld joints; however, for wide groove weld joints or bridging across gaps a weave bead or multiple stringer beads would work better.

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42 3.3.4.4 Positioning Electrode Holder Techniques After learning to start and hold an arc, this researcher practiced running beads of weld metal on flat plates using a full electrode. As mention ed previously, stability affects in how a nice weld puddle turns out when using two hands. Another fac tor is the electrode holding angle. The following describes the common positions o f electrode holding for basic joints. 1. Groove Welds To hold the electrode nearly perpendicular to the workpiec e and tilt it ahead about 10 to 30 in the direction of travel will be helpful to co mplete a stringer bead having straight edges, evenly spaced ripple, and uniform height. The skilled welder understands the welding techniques knows t hat the best groove weld results can be produced when holding a short arc, tra veling at a uniform speed, and feeding the electrode downward at a constant rate as it melts. 2. Fillet Welds For fillet welds, the electrode should be held 45 to the workpiece. It is tipped forward 10 to 30 in the direction of travel. It is kept in line with the weld line for a stringer bead. 3.3.4.5 Effects When Running a Bead Once the welding arc is struck and stabilizes, the weld poo l will begin to form. As the welder moves the electrode forward, the weld bead forms. To make a good weld on any joint in any position, the first skill which must be mastered is to form a bead. Running a good weld bead in SMAW, the following characteristic s must be controlled manually by the welder:

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43 1. Arc Gap Distance or Arc Length Effect The arc length must be varied slightly as different e lectrode diameters are used. However, for covered electrodes, the arc length will b e about 3/16” to ”. Shielded metal arc welding may be done with one hand and a welder may use the other hand at times to hold a part while tacking it in place. This hol ding position will stabilize arc length, and the weld width and height is built normal re sult. If the arc length is too short, the weld will be too tall. On the other hand if the arc length is too far, the arc width will be too wide and thin, and spatter will be creat ed near the weld pool. One way of checking if the arc length is proper is to lis ten to the sound of the arc. The proper arc length will produce a cracking or hissing sound similar to eggs frying. 2. Speed of Forward Motion Effect The welder should judge the proper travelling speed by observ e two factors while welding: a) Bead width. When the travel speed is normal, the weld will have a r ounded shape. If the electrode speed is too slow, the weld shape will be too thin an d wide. If the electrode speed is too fast, the weld will be too tall and narrow. b) Noise of weld. The noise of weld sounds like a bullet-noise and sharped appe arance of the ripples, similar to eggs frying, at the rear of the molt en weld pool when the good weld is produced in a joint. This proper welding sound may be performed by the skilled welders and the welders control steadily speed a nd gap of an electrode on workpieces.

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44 3. Bead Width effect There are two types of beads used in arc welding, stringer beads and waving beads. a) To make stringer bead, the only motion of the electrode i s forward. The bead width should be 2 to 3 times the diameter of the elect rode. b) When a weaving bead is made, the electrode is moved uniforml y back and forth across the weld line while also moving forward. With such a motion, the beads fill up the joint. 4. Electrode Angle or Position Effect The electrode angle is tipped forward 10-30 in the direction of travel. It is kept in line with the weld line for a stringer bead. 3.3.4.6 Cleaning a Bead When shielded metal electrodes are used, a brittle slag co ating which is cooled flux that forms on top of the bead and slag protects cooling metal, i s then chipped off. This slag covering must be removed prior to restarting a bead. If the slag is not removed before restarting or welding over a bead, some slag will be tra pped or included in the weld. This will cause weld failure with lower strength capacity of a joint. Slag is generally removed manually with a chipping hammer and a wire brush. The sla g may also be removed mechanically by grinding, wire brushing or chipping. 3.3.4.7 Restarting an Arc Weld When a SMAW bead is stopped prior to completion, a deep cr ater is left in the base metal. Restarting the arc and completing the bead must be done with care. If the restart is done correctly, the bead ripples will be uniformed.

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45 Before restarting the welding arc, the previous bead must be cleaned. Restrike the arc about 3/8” ahead of the forward edge of the crater. The arc is then moved backward rapidly until the new molten weld pool just touches the rear edge of the previous crater. As soon as the two edges touch, the electrode is moved forward to cont inue the weld. If this is done correctly, the ripples of the old and the new bead will match. 3.3.4.8 Finishing an Arc Weld There are two ways to finish a bead or weld without leavi ng a crater the base metal being welded. 1. Use a run-off tab. A piece of metal of the same type and thickness is tack welded to the end of the base metal being welded. The arc bead or weld is completed on the base metal and continued on the run-off tab. The run-off tab is cut of f, leaving a full-thickness bead at the end of the base metal. 2. Reverse the electrode direction. Another method used to finish a weld without leaving a crate r is to reverse the electrode direction as the end of the weld is reached. The electrode is moved to the trailing edge of the weld pool. When the weld pool is filled, the electrode is then lifted until the arc broken. 3.3.5 Weld Flaws and Defects Completed welds may have variety of flaws. A flaw is anything about a weld that is an imperfection. If a flaw is large, it is called a defec t. Many flaws and defects can be seen with the visual inspection. Others may be found only thro ugh the use of destructive testing

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46 or non-destructive evaluation. By means of a visual inspe ction, a welder may find the following weld flaws and defects: 1. Poor weld proportions 2. Undercutting of base metal 3. Lack of penetration 4. Surface flaws and defects The weld face should have relatively small, evenly spaced ripples. The weld face on a groove joint should be wide enough to span the complete groov e. A groove weld should have complete penetration. On the lap joint and the unprepared corner joint of fille t welds, the weld normally does not penetrate to the other side. On a groove-type corner joint or T-joint, the weld may penetrate to the metal face opposite the bevel. An undercut condition into the base metal caused by a lo ng arc length or too high current setting which the excessive penetration and spatter can be indicated. When weld has been made with a low current setting or short arc length, th e weld bead is too thick and is overlapped at the toe of the weld as a result, this weld has poor penetration. Additional surface flaws can be seen during a visual inspection. Thes e include spatter, slag inclusions, and cracks in the weld bead or weld crater. 3.4 Joint Welding Procedures and Techniques The actual welding techniques utilized depend on the electrode, the composition of the workpiece, and the position of the joint being welded. T he choice of electrode and welding position also determine the welding speed. The electrode w ire may be a ferrous or nonferrous metal. Constant current power sources are dropper type power sources. If the correct current

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47 flow and arc length are maintained, the welder can produces a good weld. To make a good weld, the welder must consider the following: 1. The current (Amp) output of the welding machine. 2. The diameter, polarity, and type of electrode. 3. The arc and its manipulation. 4. The preparation of the base metal. 5. The type of base metal Flat welding position requires the least skilled welder, and can be done with electrodes that melt quickly but solidify slowly. This welding position permits higher welding speeds. Sloped, vertical or upside-down welding requires more a higher skill ed operator, and it often necessitates the use of an electrode that solidifies quickly to preve nt the molten metal from flowing out of the weld pool. However, this generally means that the elec trode melts less quickly, thus increasing the time required to lay the weld (Lincoln, 1994). It is preferable to weld on workpieces in the flat or horiz ontal position to ensure the proper weld is applied on the joint. However, when the welder s are forced to weld in vertical or overhead positions, it is helpful to reduce the amperage f rom that used when welding horizontally. Best welding results are achieved by mai ntaining a short arc, moving the electrode at a uniform speed, and feeding the electrode downward at a constant speed as it melts (Miller, 2010). 3.4.1 Fillet Weld on Lap and T-Joint in Flat Welding Position Fillet welding on a lap joint is common and produces a tri angular weld shape as same as for a T-joint. The weld face may have a flat, convex or concave shape.

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48 The single pass welding uses a drag technique with the tip of the electrode touching both plates at a 45 angle from the lower plate. The el ectrode is tipped 10-30 in the travel direction, and aimed into the bottom of the joint. For a single pass, the electrode tip is pointed more toward the lower metal surface rather than the top plate. When welding multiple passes, the first pass weld should be clea ned and slag should be removed before making other passes on both sides of the joint fill ed to fill up the triangle shape. Figure 3.4 Fillet Weld Practice on a Lap Joint in F lat Position 3.4.2 Fillet Welding on Lap and T-Joints in Horizontal Po sition When welding fillet welds on a lap joint in the hor izontal position (Figure 3.6), the electrode should point more toward the metal surfac e of the lower plate than the edge of top plate. The electrode is tipped about 10-30 forwar d the travel direction and has at a 45 angle from the lower plate. It takes more heat to melt the surface of the metal than the edge metal so that the electrode motion should be longer on the lower metal surface than the edge of top plate. The electrode movement should have a slight backward slant. This backward slant movement will let the arc force push the weld metal up as it attempts to sag down with gravity. In proper fillet welding, the forward sla nt motion takes place and the electrode is maintained longer to deposit the weld pool on the s ide plate (vertical plate).

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49 Figure 3.5 Fillet Weld Practice on a T-Joint in Fla t Position Figure 3.6 Fillet Weld Practice in Horizontal Posit ion

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50 3.4.3 Fillet Welding on Lap and T-Joints in Vertical-up Position The welders may be forced to make welds in the vertical position which requires higher level skilled welders because it is difficult to control the metal in the weld pool than flat and horizontal positions. The vertical-up welding position is preferred because the w eld pool is prevented by below weld metal at a fast speed enough to stay ahead of th e slag. In the other hand if vertical-downward welding is used, it will cause the slag r unning into the molten of weld pool. If welding speed is too fast, the weld does not produce adequat e penetration. When welding speed is too slow, the molten pool becomes too hot, or the weld pool along the vertical joint will become too wide, and the molten meta l may drip down out of the weld. To control the weld pool heat, and allow the metal time to cool, the electrode is pointed upward at 20-45, and a flip or whip movement between the workpiec es is used. At the same time, the electrode tip is moved forward and up slightly to keep the weld pool from sagging, Figure 3.7. The electrode is then brought back to the lowe r weld pool to continue the weld. During the time that the electrode and arc are moved up, fo rward, and back again, the weld pool cools down slightly. When making the multiple passes of fillet welds in vert ical-up position, the following techniques can be performed: 1. Make the first pass root beads with a whipping technique in the middle of workpieces. 2. Thereafter, a box weave is often needed for the secon d pass to assure good fusion along the edge of the first bead. The box weave is sim ilar to the straight weave

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51 except a slight upward motion is made at both sides of the weld. Maintain a short arc with no whipping. 3. Make a straight weave for the final passes. Simply move the electrode tip back and forth across the surface of the weld pausing slight ly at both edges to insure penetration and wash-in without undercut. Figure 3.7 Vertical-up Welding Position Practice 3.4.4 Fillet Welding on Lap and T-Joints in Overhead Posi tion The overhead arc welding is the most difficult weld ing position for this researcher during SMAW welding practices. Overhead welding technique s are very important for the welders to understand how to run the beads without the molt en metal spilling and dripping because it could cause a danger for a welder who is not wearin g the proper protective gear. The welders should practice making beads in the overhea d welding position before attempting production welds seams.

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52 To weld workpieces in overhead, the electrode must be held at an angle as same as in the flat and horizontal welding positions. The series of root beads are used with a slight circulation motion in the weld pool and sometimes a ccompanied by a whip, Figure 3.8. Weave bead should not be used for this welding posi tion because it will produce too hot molten weld and spill from the joint since the weld requires slower traveling speed. Figure 3.8 Overhead Welding Position Practice 3.4.5 V-Groove Welding in a Butt Joint in Flat Position After learning and practicing basic fillet welding in all positions, this researcher started to practice on V-groove welding in butt joints with fl at position as the proposed goal of this research to prepare welded wrought iron samples for mechanical testing.

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53 Before making a production single V-groove welding in a butt joint, this researcher has practiced on preparing workpieces, two 3/8” thick, 6”x 6” steel plates with ” x 1” wide x 8”long backing plate, and then performed the follow ing procedure: 1. Cutting the bevel edge at 30-degree angle on each w orkpiece with automatic oxyacetylene cutting or gas cutting, see Figure 3.9 Figure 3.9 Oxyacetylene Cutting (gas cutting) Bevel Edges of Steel Plate 2. Removing and cleaning scale and debris from the joi nt after cutting. 3. Placing two workpieces on a level surface with the root faces are on top, and beveled edges faced each other with ” gap. 4. Placing ” backing plate over the gap and making ta ck welds on backing plate and back of workpieces to prevent butt joint distortion by the materials in position before final weld.

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54 5. Locking workpiece with clamps to prevent distortion from occurring when heat is applied locally to a joint prior to starting SMAW. 6. Making a stringer bead through the root with a 1/8” E7018 electrode. The weld current was adjusted to about 115 Amps, and constan t travel speed was maintained to obtain the desired weld without any porosity. The electrode end position is pointed at 90-degree to the workpiece surfaces and tilted 10-3 0 forward to the direction of travel. 7. Cleaning the weld metal between layers before conti nuing the next beads. Figure 3.10 Multiple Pass Weld Practice in Butt Joi nt 8. Continuing other pass welding in the joint until we ld completion, the beads are made on each side of the joint. Holding electrode in ti lted position and alternated angles between 30 and 45 degree from the metal surfaces, a nd fusing one to the other, see Figure 3.10.

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55 Figure 3.11 Butt Joint Weld Practice in Flat Positi on Figure 3.12 Multiple Pass V-Groove Welds in Butt Jo int Sample in Flat Position 3.5 Shielded Metal Arc Welding Procedure As a production welding is required to perform in c onformance with an approved welding procedure specification (WPS) as recorded in a Proc edure Qualification Record (PQR) (AWS, 2010). The following topics describe the use of sh ielded arc metal welding procedures.

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56 3.5.1 Weld Qualifications The most common quality problems associated with SMAW inc lude weld spatter, porosity, poor fusion, shallow penetration, and cracking. P oor fusion is often easily visible. It is caused by low current, contaminated joint surfaces, or the use of an improper electrode. Any of these weld-strength-related defects can make the w eld prone to cracking, but other factors are involved as well. High carbon, alloy, or sulfur content in the base material can lead to cracking, especially if low-hydrogen electrodes and pr eheating are not employed. Furthermore, the workpieces should not be excessively re strained, as this introduces residual stresses into the weld and can cause cracking as the wel d cools and contracts (Lincoln, 1994). To ensure the weld quality is acceptable to qualify or verify WPSÂ’s as required by AWS code, all production welding shall be performed in conformanc e with the provisions of an approved welding procedure specification (WPS), which is base d upon successful test results as recorded in a Procedure Qualification Record (PQR) unle ss qualified in conformance with AWS1.3.1 (AASHTO, 2010). 3.5.2 WPS Qualification All WPSÂ’s shall reference the PQR that is the basic for acceptance. A copy of the proposed WPS and referenced PQR shall be submitted by the fabricator to the Engineer for approval. Recommended forms for WPSÂ’s and PQRs are provi ded in Appendix A. WPSÂ’s for SMAW that meet the requirements of AWS shall be con sidered prequalified and exempt from qualification testing. A welding procedure specification (WPS) sets guidelines for t he shop and field welding practice of the fabricator for each anticipated combinat ion of essential variables. Welding

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57 parameters and ranges are specified and used to prepare the as sociated welding procedure data sheets. 3.5.2.1 Welding Procedure Preparation The WPS qualification tests required by AWS code are desig ned to provide assurance that the weld metal produced by welding in conformance with the provision of this code shall produce weld metal strength, ductility, and toughness conforming to the code. The fabricator shall have WPS’s for each welding proce ss in use, the outlines of the general welding procedure to be followed in the constructio n of weld material built in accordance with the weld design and/or manufacturing stan dard. WPS’s submitted for acceptance shall cover as a minimum the items such as the various base metals to be joined by welding, the filler material to be used, the range of pr eheat and post-weld heat treatment, and thickness and other variables described for each weldi ng process. 3.5.2.2 Qualification Requirements for WPS Each fabricator and contractor must qualify the WPS’s by conducting tests and welding test coupons to qualify or verify WPS’s as required by AWS code. AWS codes require that all welds which will be encountered in actual construction shall be classified a (1) flat, (2) horizontal, (3) vertical, or (4) overhead in conformanc e with the definitions of welding positions. “Each WPS shall be tested in the position in which welding will be performed in the work” (AWS, 2010). Flat and horizontal welding position s look similar, but the weld faces are different positions. The weld axis, and workpi ece or weld face of flat welding position (down hand) are horizontal. The weld axis of h orizontal welding position is horizontal, but the workpiece face is vertical.

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58 3.5.3 Types of Tests and Purpose Mechanical testing of welded joint shall verify that th e WPS produces the strength, ductility, and toughness required by AWS codes for the fille r metal tested (AWS, 2010). Soundness tests shall meet the requirements of AWS Subse ctions 5.19.2 and 5.19.3. The following shall be tests for groove welds made with mat ching or undermatching filler metal, or for groove welds joining base metals of two different s pecified strengths (AWS, 2010). The matching weld uses weld strength the same as base meta ls, but in the opposite, the undermatching weld uses weld strength less than base metals: 1. All weld-metal tension tests to measure tensile strengt h, yield strength, and ductility. 2. CVN test to measure relative fracture toughness. 3. Marcroetch tests to evaluate soundness, and to measure ef fective throat or weld size; also, used to gage the size and distribution of weld layers and passes. 4. Visual examination to evaluate weld soundness. 5. Radiographic Test (RT) test to evaluate weld soundness. In addition, the following tests shall be required for m atching weld strength groove welds: 6. Reduced section tensile test to measure tensile strength (ASTM, 2005). 7. Side-bend test to evaluate soundness and ductility (ASTM, 1997) 8. Root and face bend tests (used only for special applications of welder qualification.) (ASTM, 1997) 3.5.4 Approval of WPSÂ’s Approval of WPSÂ’s shall be based upon the results of mech anical tests that demonstrate that the process and WPS use will produce sound weld metal w ith required strength, ductility, and toughness.

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59 3.5.5 Welder Qualification Welders, welding operators, and tack welders using SMAW weld ing process shall be qualified by the tests described in AWS to make sure the we lder’s ability to produce sound welds (AWS, 2010). 3.5.5.1 Qualification Tests Required The welder qualification test for manual and semiautomat ic welding shall conform to the ASW Section 5.23 (AWS, 2010). 3.5.5.2 Method of Testing Specimens Welders shall submit test specimens: number, type and prepar ation to test to qualify a welder by mechanical testing as required per AWS Section 5. 25 and 5.26 (AWS, 2010). 3.6 SMAW for Wrought Iron SMAW welding to wrought iron has been done since 19 th century and studied by many researches. The recommendations of arc welding procedur e for repairing of the wrought iron members of historic bridges have been utilized (Bowman, 2004), however those procedures provided for the different joint types and repair details. In this research, the tensile testing was emphasized for repairing wrought iron bridge members with Vgroove welding in a butt joint by SMAW process with using 1/8” E7018 electrodes which were in conf ormance with AWS 5.1. It is also recommended that the best welds are produced whe n the welding speed is slightly decreased below that used for the same thickness of soft steel. This procedure seems to be reasonable because with reduced speed of welding the pool of m olten metal immediately following the arc is kept molten for a longer period of t ime, thus gases are allowed to release and the entrained slag is afforded to float out of the weld me tal (Aston, 1949).

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60 The wrought iron plates were recommended to be preheated up to 300F before SMAW process to prevent cracks (Yost, 2010). If a section of the wrought iron is heated too quickly, the surrounding area does not have ample time to absorb enough heat to allow the wrought iron to have a uniform temperature. This causes restricted expan sion and contraction. It occurs when the weld affected area is contained by cooler iron. This will always result in some stress, and often it is enough stress to cause additional cracking at the interface of weld metal and base metal. 3.7 SMAW Procedure for Wrought Iron 3.7.1 Preparation of Workpieces Before making single V-groove welding in a butt joint, the standard test samples were prepared with ” x 1” wide backing plates, and it is longer than the sample width by one inch on each side for later cutting after milling compl etions. 1. Cut a bevel edge at 22.5 angle on each workpiece with a utomatic gas cutting for 45 included angle open joint (minimum 40 and maximum 55). 2. Remove scale from material after cutting. A grinder ca n also be used to prepare bevels. 3. Place two workpieces on level with the root faces up, and b eveled edges faced to each other with ” opening. 4. Place ” backing plate over the gap, and lock the workpiece s on a working table by clamps to prevent the movement. Then carefully make ta ck welds to join the backing plate and workpieces to ensure they are in position befor e final SMAW welding. To prevent distortion of samples when heat is applied locall y to a joint, use clamps to lock each end of workpieces on a level plate or a workin g table, Figure 3.13.

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61 3.7.2 SMAW Procedure for Wrought Iron 1. Prior to welding in V-groove opening, the wrought iron plate s are recommended to be preheated up to 300F by applying the heat of oxyacetylene gas on t he workpieces to prevent cracks which the contraction may occur when coo l welds. Then an infrared thermometer (Ryobi model IR001) is used to measure the temper ature of the workpieces during preheating. 2. 1/8” diameter E7018 electrodes are selected. 3. Flat position welding is recommended. 4. Single V-Groove Joint Designation, ” thick plate (maxi mum 1”), ” root opening, and a 1/4"x1” backing plate. 5. Set current of a power supply between 110 and 165 Amps with DC positive polarity and the desirable current may be adjusted about 115 Amps. 6. Make a stringer bead through the root (gap) with an E7018 electr ode and travel speed should be maintained constantly to obtain the desired wel d in the root without porosity. The electrode end is pointed at 90-degree to the metal surfaces and tilted 10-30 forward to the direction of travel. The weld metal must be sure to penetrate about 1/32 in. beyond the bottom of the root. A single s tringer bead is always satisfactory for most narrow groove weld joints; howeve r, for wider groove weld joints or bridging across gaps, a weave bead would work bett er. On thick plates, it may be necessary to weave the top layers to fill the groove joint (Miller, 2010). 7. Clean each weld pool layer before moving on the next weld ing pass.

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62 8. Continue other welding passes in the joint until fi lling full joint opening, the beads are made on each side of the joint with the electro de tilted at alternate angles between 30 and 45 degrees from the metal surfaces, and fusi ng one to the other, see Figures 3.10 and 3.13. Figure 3.13 Groove Welding in Wrought Iron Butt Joi nt

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63 CHAPTER IVMATERIAL TESTING This chapter describes the materials utilized, spec imen descriptions, procedures followed, and data collected for all tests that were complete d during this research. The samples of wrought iron members as shown in Figure 4.1 were donated by Lansing Community College, Lansing, Michigan. To verify the properties of base and wel ded wrought iron members, extensive material and mechanical tests were completed in thi s research. Figure 4.1 Donated Wrought Iron Members for Testing 4.1 Material Utilized in Testing The physical properties of wrought iron are not tho se of pure iron because it has carbon content more than 0.008% by weight (ASM, 1985). Th e strength, elasticity, and ductility are affected by small variations of the metalloid conte nt, but to a greater degree by incorporated slag

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64 and the character of its distribution. The ultimate t ensile strength and ductility of wrought iron are greater in the rolling direction than in the trans verse direction to rolling. This difference is due to the nature of slag distribution throughout the metal in the two directions of wrought iron. Therefore, the material and structural differences in each historic bridge member make it necessary for the donated wrought iron members to be test ed and evaluated to ascertain the mechanical properties. Let us understand the character and properties of wrought i ron members before and after they were repaired by SMAW procedure. This repair was ass umed to be a welded splice connection of restored wrought iron members. To identify wrought iron samples prior to repairing them with SMAW, a chemical analysis to determine the chemical composition of each sample was desirable. A chemical analysis would provide the concentration of Carbon, Phosphorus, Manganes e, Silicon and Sulfur. However this research did not have enough funds for sending the sample s to an outside laboratory for conducting the chemical analysis, so the spark test was s elected to identify these samples instead. Then both original base metal and welded wrought iron samp les were prepared for mechanical testing. These wrought iron samples, which were cut from truss ey ebars, originated from the following historic bridges in Michigan: 1. Kent Street Bridge over Grand River (member pieces marked as “A”) was a pedestrian bridge in Portland, Ionia County, Michigan (Figure 4.2). It w as built in 1907 and is a single 224ft span metal pinned parker through-truss bridge. It is one o f only three Parker through trusses identified in the Michigan Historic Bridge Inventory. The term Parker refers to the use of a

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65 polygonal top chord on what is essentially a Pratt truss. The top chord gives the bridge an arched appearance (Holth, 2012). Figure 4.2 Kent Street Bridge (Photograph by Histor icBridges.org. Used with permission) (Holth, 2012) 2. Parshallburg Bridge over Shiawassee River (member p ieces marked as “B”) in Parshallburg, Saginaw County, Michigan (Figure 4.3) It was a single 140-ft span Thacher Metal Through-Truss bridge and was built in 1889. It had been the oldest surviving Thacher truss in the United States until it was destroyed from an ic y flood on December 28, 2008 (Holth, 2012). 3. State Street (Fort Road) over Cass River Bridge (me mber pieces marked as “C”) in Bridgeport, Saginaw County, Michigan (Figure 4.4). It was built in 1906 and was a two 126-ft span Metal Pinned Pratt Through-Truss bridge (Holth 2012).

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66 Figure 4.3 Parshallburg Bridge (Photograph by Histo ricBridges.org. Used with permission) (Holth, 2012) Figure 4.4 State Street Bridge (Photograph by Histo ricBridges.org. Used with permission) (Holth, 2012)

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67 The following list in Table 4.1 shows the shapes an d dimensions of donated wrought iron members of the historic bridges: Table 4.1 List of Donated Wrought Iron Members Mark Member Average Width or Diameter Thickness or Diameter Length* Shape A1 Bar 4” 7/8” 9” Eyebar 2 5/8” 7/8” 2’-10” A2 Bar 4” 7/8” 9” Eyebar 2 ” 7/8” 2’-10” B1 Bar 2 5/8” 5/8” 3’-3 3/8” Eyebar 1 3/8” 5/8” 2’-1” B2 Bar 2 ” 5/8” 3’-2 7/8” B3 Bar 3 ” 1” 4’-2 ”

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68 B4 Bar 3 ” 1” 3’-8” C1 Bar 2” 5/8” 5’-5 7/8” Eyebar 1 ” 5/8” 1’-1” C2 Bar 2” 5/8” 3’-8 ” Eyebar 1 ” 5/8” 1’-1” C3 Bar 2” 5/8” 5’-9 5/8” Note: Length along members. 4.2 Type of Tests and Purpose As mentioned above, the spark test was selected rat her than the chemical analysis to classify the metal samples. This test is a simple and quick method to identify the category of metal samples in a few minutes. AWS codes call for welds which are encountered in a ctual construction shall be classified a (1) flat, (2) horizontal, (3) vertical, or (4) over head in conformance with the definitions of welding positions. “Each WPS shall be tested in th e position in which welding will be

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69 performed in the work” (AWS, 2010). Therefore, the use of proposed flat welding position (1G) was conducted for single bevel-groove or Vgroove weld in butt joints of test specimens. This research concentrated on the mechanical properties of wrought iron samples after they were repaired by SMAW procedures, and some tests of AWS re quirements were not included. They may be performed in the future research study; ther efore, the tests conducted during this research are listed below: 1. Spark test for base wrought iron specimens 2. Reduced section tensile test for base wrought iron specim ens 3. Face-bend test for base wrought iron specimens 4. Reduced section tensile test for welded wrought iron speci mens 5. Face-bend test for welded wrought iron specimens 6. Root-bend test for welded wrought iron specimens 7. Visual examination of welds Due to inconsistent properties of wrought iron samples, fo ur specimens of each base metal and welded specimens were used for tension testing. One spec imen was used for each bend test to study the properties of wrought iron in bending condition 4.3 Test Locations 4.3.1 Spark Testing This test can be done by using a power grinder which most of ten is used in tool rooms and machine shops. All wrought iron samples of this research were identified by the spark test at the Civil Engineering Laboratory (CE Lab).

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70 4.3.2 Mechanical Testing The testing apparatus most often used for tension testing is the universal testing machine. A tension-compression testing machine, MTS Model 976.04-26 (hydrau lic loading system), which has maximum loading capacity of 20 kips and is housed in CE Lab. If it is necessary, there is the other option of testing machine, INSTRON M odel 5569 (screw power loading system) which is has maximum loading capacity of 10 kips an d located in Mechanical Engineering Laboratory (ME Lab). This machine has an ex tensometer (maximum 1-inch gage length) to attach on a test specimen for accurate def ormation measurement. All specimens for bend testing were tested in the welding shop at the Emily Griffith Technical College, Denver, CO by this researcher. 4.4 Test Specimens – Number, Type and Preparation 4.4.1 Preparation of Base Metal Samples for Mechanical Testing To prepare base wrought iron specimens for the mechanical te sting, the donated wrought iron plates were selected and cut using a portable circula r saw, see Figure 4.5. This cutting method would not build up significant heat or cause heat ef fects on the samples. The dimensions of specimens were laid out on the wrought iron members as the following: 1. Four tension test specimens: 1” or 2” wide and 13” long per pi ece. 2. One bend test specimen: minimum 2” wide and 9” long per pi ece. 4.4.2 Preparation of Welded Samples for Mechanical Testing The welded wrought iron specimens were prepared for the me chanical testing by cutting the selected wrought iron plates with the portable circu lar saw. The dimensions of specimens were laid out on the wrought iron members as the follow ing:

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71 1. Four tension test specimens: minimum 1” or 2” wide and minimum 7” long per piece and two pieces were required for each welded sample 2. Two bend test specimens: minimum 2” wide and minimu m 5” long per piece and two pieces were required for each welded sample. These samples were cut for some extra length to acc ommodate the bevel edge cutting for butt joints. Another benefit of the extra sample l ength is that the specimens would be mounted with a template at each end before the mach ining. The tensile test coupon for test specimens was a V-groove welding with a 45-degree i ncluded angle open joint. Figure 4.5 Cutting Wrought Iron Plates by Portable Circular Saw For Groove Weld Qualification Test of the sample pl ates which have varied thickness, the joint detail should have 1” maximum thickness with single V-groove, ” root opening and ” backing plate attached to the back faces of the pla tes by track welding as per AWS 5.23.1.2 requirements. If the sample plates are thicker tha n 1 inch, the tips of bevel edges must be cut off

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72 in vertical to make ” root opening (AWS, 2010). T his would allow weld metal filling in the root and penetrating into the base metal without me lting the tips of bevel edges. After the specimens were cut into the desired dimen sions, they were oriented on a working table or level plates for flat welding position as shown in Figure 4.6. Clamps were used to lock the specimens on a working table or level plates to prevent the distortion during welding. Prior to welding wrought iron specimens, the sample plate s were recommended to be preheated up to 300F (Yost, 2010). The infrared thermometer (Ryob i, Model IR001) was used to measure the temperature during preheating. Then 1/8” diameter E7018 electrodes were used to ma ke multiple pass welds in flat welding position (1G) in accordance with SMAW procedure des cribed in Chapter 3. Weld passes were alternated on either side to ensure that heat distr ibution in the piece was minimized. Figure 4.6 Single VGroove Weld in Butt Joint with Backing Typical Section

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73 Figure 4.7 Visual Examination of V-Groove Weld in B utt Joint of Bend Test Specimen Once the welding in butt joints was complete and ex amined (Figure 4.7), the welded specimens were then milled flush by a milling machi ne, Bridgeport Series I 2HP, Model 2J (Figure 4.8) at CE Lab until they met the required dimensions of the reduced-section tension test samples and the dimensions were in conformance with Figure 4.16. All welded specimens of bend test samples were cut and grinded until they met the desired dimensions for the face bend test and root bend test specimens. The dimensions were conformance with Figures 4.24 and 4.25. Figure 4.8 Milling Machine for Sample Preparation i n CE Lab

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74 4.5 Spark Test Initial Wrought Iron Identification A spark test is a method of determining the general classification of metals. This test is quick and easy, and the test was done in CE Lab within a few minutes. Also test samples did not have to be prepared in any way, and a piece of scraps ar e often used. This test is extensively used by welders to identify irons or steels (Althouse, 2004 ). Because welding procedures of iron or carbon steel members may be different, it is import ant to identify the base material prior to weld procedure. Figure 4.9 Spark Test in CE Lab 4.5.1 Equipment 1. A power grinder 2. Safety gear such as goggles and leather grooves 4.5.2 Test Method 1. Start with known pieces of mild steel and/or carbon tool steel to do spark test for a comparison basis, and follow by the wrought iron sa mples.

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75 2. The pieces of metal were placed in contact with a g rinding wheel in order to observe the sparks emitted. These spark characteristics ca n be compared with a chart, Figure 4.10, or to spark from a known test sample as menti oned in step 1 to determine the classification. 3. Repeat applying the rest of wrought iron samplers t o a grinder and record their spark characteristics. Figure 4.10 Spark Characteristics for Common Irons and Steels (Althouse, 2004) 4.5.3 Test Observation The samples can be quickly and easily determined by simple noticing the following spark characteristic list (Table 4.2) to identify which m aterials are which spark figure (Althouse, 2004): 1. Length of spark the longer the spark, the lower t he amount of carbon. 2. Color of spark the lighter the spark, the lower t he amount of carbon

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76 3. Spark volume more alloy results in a larger spark volu me. 4. Forks or bursts indicate alloys present in the mater ial. Forks are where one spark splits into two or three. Bursts are where one spark sp lits off into many. 5. Repeating, or ending forks or bursts notice if the forks o r bursts occur at the end of the spark or repeat along the spark stream. To quantify above characteristics, compare the spark char acteristics of all samples with Table 4.2 and Figure 4.10, and record the test data. Table 4.2 Table of Spark Test Characteristics of Common Irons an d Steels (Althouse, 2004) Metal Volume of Stream Relative Length of Stream Color of Stream Close to Wheel Color of Streaks near End of Stream Quantity of Spurts Nature of Spurts Wrought iron Large 65” Straw White Very few Forked Mild steel Large 70” White White Few Forked Carbon tool steel Moderately large 55” White White Very many Fine, Burst, and Repeating Grey cast iron Small 25” Red Straw Many Fine, Repeating White cast iron Very small 20” Red Straw Few Fine, Repeating Annealed mall, iron Moderate 30” Red Straw Many Fine, Repeating 4.6 Optional Visual Test Initial Wrought Iron Identification Wrought iron can also be identified by simple inspecting t he surface of test samples with a magnifying glass after they are machined or cut. Wrought i ron is identified if inclusions of silica slag exist in a sample with some slag pockets (Figure 4.11)

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77 Figure 4.11 Silica Slag in Test Sample Surface 4.7 Mechanical Testing Tension testing and bend testing were performed aft er the specimens were identified by the spark test. The elastic limit, the yield strength, and the modulus of elasticity were determined. 4.7.1 Tension Testing The tension test is a common stress-strain test and can be used to determine the mechanical properties of metals. The tension test related to the mechanical testing of steel products subjects a machined reduced-section or ful l-section specimen of the material under examination to a measured load sufficient to cause rupture. AWS codes call for test specimens to be tested conf ormance with ASTM A 370, “ Mechanical Testing of Steel Products” or the latest edition of AWS B4.0/B4.0M, “ Standard Methods for Mechanical Testing of Weld s.” (AWS, 2010). These test methods cover procedures and definition s for the mechanical testing of wrought iron.

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78 4.7.1.1 Orientation of Test Specimens The terms “longitudinal test” and “transverse test” are applicable only in material specifications for wrought products. The test coup on of longitudinal test was used for this research. The lengthwise axis of the specimen is parallel to the direction of the greatest extension of the wrought iron during rolling or for ging. Therefore the greatest stress applied to a longitudinal tension test specimen is in the p arallel direction to rolling or grain direction (Figure 4.12). Figure 4.12 Test Specimen to Longitudinal Direction 4.7.1.2 Testing Apparatus and Operations 1. Loading Systems There are two general types of loading systems, mec hanical (screw power) and hydraulic. These differ mainly in the variability of the rate of load application. The apparatus normally include a tension test machine a nd a data acquisition system. For testing rectangular type specimens a variety of mec hanical wedge action grips are used, including manual, pneumatic and hydraulic wit h flat faces. The MTS testing machine (Figure 4.13) housed in the CE Lab is a hydraulic testing machine which allows stepless variation throughout the range of testing speeds. The

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79 MTS testing machine has maximum loading capacity of 20 kips, been maintained in good operating condition, and calibrated periodical ly in accordance with the latest revision of ASTM E-8 This machine is equipped with load-displacement rec orders (Station Manager Program) calibrated separately for plotting of load-displacement curves. Its recorders have a load measuring compon ent entirely separate from the load indicator of the testing machine. Due to miss ing of an attachment accessory for an extensometer, this research did not use an exten someter installed on the test samples. Figure 4.13 MTS – Tension Testing Machine The other option of tension testing machine, INSTRO N Model 5569, is mounted in ME Lab, Figure 4.14. It has an extensometer (1-inc h gage length) attached on the test

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80 specimens and maximum loading capacity of 10 kips. The test specimen is required to cut smaller width than MTS test samples by half because the machine has 10-kip loading capacity and the maximum grip width is one inch. With an extensometer for deformation reading, the displacement of test sampl es will be more precise than the measurement from MTS without an extensometer. Figure 4.14 INSTRON Tension Testing Machine 2. Loading It is the function of the gripping or holding devic e (Figure 4.15) mounted in the loading heads of the tensile testing machine to tra nsmit the load from the heads of the machine to the specimen under test. The load is tr ansmitted axially in which the centers of action of the grips are in alignment wit h the axis of the specimen at the

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81 beginning and during the test. For specimens with a reduced section used in this research, gripping of the specimen is restricted to the grip section. Figure 4.15 Specimen Grips mounted in Tensile Testi ng Machine (MTS) 3. Speed of Testing The speed of tension testing should not be greater than that at which load and strain readings can be made accurately. The speed of test ing is commonly expressed in terms of free-running crosshead speed (rate of move ment of the crosshead of the testing machine when not under load), in terms of r ate of separation of the two heads of the testing machine under load, in terms of rate of stressing the specimen, or in terms of rate of straining the specimen.

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82 The following limitations of the speed of testing are re commended as adequate for most steel products (ASTM, 2005): Any convenient speed of testing, maximum speed may be used up to 50% of the specified yield point or yield strength. After this point i s reached, the free running rate of separation of the crossheads should be adjust ed so as not to exceed 1/16 in. per min per inch of reduced section length or distance between the grips. In any event, the minimum speed of testing should not be less than 1/10 the specified maximum rates for determining yield point or yield strength. 4.7.1.3 Test Specimens 1. Specimen Types Improper preparation of specimens is often the reason fo r unsatisfactory test results. In order to ensure accurate and precise test results, spec imens should be machined carefully. a) Base Metal Test Specimens The preparation of base wrought iron specimens for the re duced-section tension testing was performed at the CE Lab. The cut samples h ad thickness varying from 5/8” to 1”. They were machined to meet the required di mensions. After a machined milling, the specimens finally have a section of 3” long and 2-inch wide at both ends, and a reduced section in the middle-length of 6” long with ” or 1 “ wide, usually machined in order to obtain uniform distrib ution of the stress over the cross section and to localize the zone of fr acture. It is desirable to have the cross-sectional area of the smallest specimen wi th thickness of 3/16” or more

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83 at the center of the gage length to ensure fracture within the gage length, see Figure 4.16 for the sections. Figure 4.16 Configurations of Test Specimens for Te nsion Testing b) Welded Test Specimens The preparation of welded wrought iron specimens fo r the reduced-section tension testing was the same as the base wrought ir on specimens. After welding the wrought iron samples with the single V-groove w eld in butt joint, test coupons for longitudinal tensile testing were prepared. A ll excessive metals of welded samples were removed by machining. The cut samples had varied thick plates, and were machined until meeting the dimensions as s hown in Figure 4.16 or 4.17.

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84 Figure 4.17 Configuration of Welded Test Specimen f or Tension Testing 2. Gage Marks The specimens shown in Figures 4.16 md 4.17 were ga ge-marked at the middle length in reduced-section. These marks are used to determine the percent elongation of specimens. Punch marks were made a minimum of 4. 0 inch gage length. 3. Measurement of Test Specimens To determine the cross-sectional area, the center w idth and thickness dimensions were measured to the nearest 0.001 in. 4. Test Procedure The standard testing method was applied for all ten sion tests (ASTM, 2005): a) Prepare the test machine by starting up the machine to warm it up to normal operating temperature about 30 minutes. b) Measure and record the dimensions of the reduced se ctions of all test specimens to the nearest 0.001 in. and determine the cross-se ctional area. c) Measure and record the gauge length to the nearest 0.001 in. prior to the testing.

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85 d) Mount a specimen in the grips of the testing machin e. e) Set up the testing machine using the Station Manage r program and verify that all readings of the recorders are at zero. f) Apply the tensile load at the desired loading rate. The loading was applied to a specimen until failure. g) After specimen failure, fit the fractured ends toge ther carefully and measure both the distance between the gauge marks of the specime n to the nearest 0.01 in. h) Repeat steps a through g for each remaining tensile specimen. 5. Record Test Data Upon completion of the testing, collect all laborat ory data and enter them into a single spreadsheet. Figure 4.18 Fracture on a Wrought Iron Sample in CE Lab

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86 Figure 4.19 Station Manager Program to Record Tensi le Testing Data 4.7.2 Guided Bend Testing The guided bend test is one method for evaluating d uctility of metal specimens, but it cannot be considered as a quantitative mean of pred icting service performance in bending operations. The severity of the bend test is prima rily a function of the angle of bend to which the specimen is subjected to, and of the cross sect ion of the specimen. These conditions are varied according to location and orientation of the test specimen and the chemical composition, tensile properties, hardness, type, an d quality of the steel specified. To accomplish the research objective, the standard test methods were conducted for the determination of soundness and ductility of wrought iron products as the following:

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87 1. ASTM E 190-92, “Standard Test Method for Guided Ben d Test for Ductility of Welds” 2. ASTM E 290-97, “Standard Test Method for Bend Testi ng of Material for Ductility” Both test methods were performed to determine and c onfirm ductility of base and welded wrought iron samples. After the tests, all results were evaluated for wrought iron properties. 4.7.2.1 Direction of Test for Wrought Iron In tests of longitudinal specimens, the axis of the bend shall be 90 to the direction of rolling, as shown in Figure 4.20. For transverse f ace bend test, the face surface of the flat specimen contains the greater width of the weld mat erial, while the opposite side is called the root surface. Figure 4.20 Schematic Fixture for the Guided-Bend T est (ASTM, 1997)

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88 When performing face bend test, the flat face of th e specimen with wide weld material was placed toward the opposite side of the guided j ig. The loading was applied on the root surface. For root bend test, the flat face of the specimen w ith small weld material was turned the other side of the guided jig. 4.7.2.2 Testing Apparatus and Operation 1. Loading System All face-bend tests were performed at Emily Griffit h Technical CollegeÂ’s welding shop by this researcher. WATTS (Model W-50) testin g machine is a combined tensile and bent tester as shown in Figure 4.21 con sisting of tensile testing assembly on the right end and bend testing assembly on the o ther end. This machine is equipped with a pressure gauge calibrated for deter mining the test loading. Figure 4.21 Guided Bend Testing Machine, WATTS W -50 This guided bend testing machine is customarily use d by the students in the welding classes to evaluate the quality of their welds as a function of ductility evidenced by

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89 their ability to resist cracking during bending. T he guided bend test jig assembly is shown in Figure 4.22. For this research, it was not only used for metal d uctility test of welded specimens, but also base metal specimens. The test results we re evaluated and compared the ductility of wrought iron specimens. Figure 4.22 Guided Bend Test Jig of WATTS W -50 Machine 2. Speed of Testing The speed of bending is ordinarily not an important factor because this test method does not provide numerical results. Therefore, an appropriate low speed of loading was applied on the test samples. 4.7.2.3 Test Specimens 1. Specimen Type The types of specimens used for a guided bend testi ng were rectangular ones cut from wrought iron samples. The test specimens for facebend tests had sufficient length to ensure free bending of the welded materials, and AS TM E190-92 and E 290-97 have

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90 specified the minimum length of 6 inches for each t est specimen. The test specimens for this research were prepared to have the total l ength of 8 inches to ensure that the specimens were long enough for 180 bending. The t wo types of test specimens were prepared as the following: a) Base Metal Test Specimens The preparation of base wrought iron specimens was done at Emily Griffith Technical College. At least one specimen is requir ed for this test to determine and compare the result with welded bend test specim ens. The cut samples had varied thickness from 5/8” to 1”, and then were gri nded to meet the required dimensions, conformance with Figure 4.23. The spec imens finally had the rectangular section of 3/8” thick, 1 inch wide an d total length of 8 inches. Figure 4.23 Base Metal Specimen for Face-bend Test b) Welded Test Specimens The preparation of welded wrought iron specimens fo r the bend testing was the same as the base metal specimens. After welding th e wrought iron samples with

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91 single V-groove weld, they were grinded to the same dimensions as the base metal specimens. The cut samples were grinded to m eet the dimensions of Figures 4.24 and 4.25. The face surface of the flat specimen contains the 1 ” width of the weld material, while the opposite side is the root surfa ce. Figure 4.24 Welded Specimen for Face-Bend Test The face-bend and root-bend test were done for this research. Face-bend test used two specimens and root-bend test used one welded sp ecimen to determine the weld quality. 2. Test Procedure a) Measure the dimensions of test specimens.

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92 b) Place the specimen over two rounded supports of the jig with the middle of specimen or the weld at mid span as shown in Figure 4.20. The face of the transverse, or welded, side is directed toward the gap, c. Figure 4.25 Welded Specimen for Root-Bend Test c) Apply a force to move the plunger in contact with t he specimen at the mid length. Then apply the bending force smoothly and steadily without shock until the specimen conforms to a U-shape, not to exceed 180, unless the specimen fails earlier, Figure 4.26. 3. Record Test Data After the bending, examine the convex surface of th e bent specimen for cracks or other defects.

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93 Figure 4.26 Bend Test Specimen in Guided-Bend Test Machine, WATTS W -50

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94 CHAPTER VSUMMARY OF TEST RESULTS The testing involved three testing procedures: spar k, tensile and bend tests that were used to verify the characteristics of the wrought iron, and to determine the material properties. From these test results, the mechanical properties of hi storic wrought iron were evaluated and compared with historic data in Chapter 6. 5.1 Spark Test Results Several iron and steel samples were subjected to th e spark test. They were mild steel, high carbon tool steel, and wrought iron members fr om the Michigan historic bridges marked as A, B and C as described in Chapter 4. The test ing results were compared with Figure 4.10 and Table 4.2 to quantify the spark characteristics and pictures are presented in Table 5.1. Table 5.1 Spark Test Results Mark or Metal Spark Characteristics Spark Photos Mild Steel White-red at wheel, white at end with large stream and few forks at the spurts.

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95 Carbon Tool Steel White-red at wheel, white at end with moderately large stream and very many fine repeating spurts. Wrought iron, A Straw (light yellow) at wheel, white at end with large stream and very few forked spurts. Wrought iron, B Straw (light yellow) at wheel, white at end with large stream and very few forked spurts. Wrought iron, C Straw (light yellow) at wheel, white at end with large stream and very few forked spurts.

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96 5.2 Tension Test Results This test is to determine the following properties of two different groups of wrought iron specimens, base metal and welded metal samples. Tensile stress (ultimate stress) Strain Yield stress (used 0.2% offset method, ASTM A370-05) % Elongation Modulus of elasticity 5.2.1 Sample Measurement and Records The wrought iron samples used for this test were selecte d from eyebar members marked B2, B3, B4 and C3 of the historic bridge members. The tensi on test samples were prepared in two specimen groups, base metal and welded metal sample s marked as BT and WT respectively. The specimen dimensions were measured and r ecorded before performing the test such as width, thickness, length gage length as shown in Table B-1, Appendix B. After specimen failure, the fractured ends were fit together ca refully (Figure 5.1) and then the distance between the gage marks and sample lengths were m easured. When tension testing was completed, the raw data of th e test results were collected from the computer program. Load-deformation data acquired from co mputer program were combined into spreadsheet format for later use in data an alysis and calculation of material properties. The results of the mechanical properties of both base metal and welded samples were recorded in Tables B-2 and B-3, Appendix B. The load-def ormation curves of all tension test samples were plotted and shown in Append ix C for further evaluation in Chapter 6.

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97 Figure 5.1 Fitting Tension Test Specimens after Fra cture 5.2.2 Stress Strain Relationship When a specimen is subjected to an external tensile loading, the metal will undergo elastic and plastic deformation. The properties of the test material can be determined and evaluated from the test data as the following metho ds. 1. Elastic Deformation Zone Initially, the metal will elastically deform giving a linear relationship of load and displacement to give as illustrated in Figure 5.2. If the applied load is released, the material will return to its original shape. These two parameters are then used for the calculation of the engineering stress and engineeri ng strain relationship. a) Engineering Stress A tensile stress is applied to a test sample by uti lizing loads (P) on a sample and it is extended until failure. The engineering stress is calculated by dividing the load by the initial (middle) section area (A) of the sam ple.

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98 b) Engineering Strain The engineering strain is calculated by dividing the change in measured displacement length for each applied load by the original measured length of the sample. It is recommended that an extensometer should be used to measure accurate deformation at a gage length in the middle of a test sample because it is much more realistic to measure the displacement of a sa mple in the reduced section portion than the total length of a sample which includes all extension along the sample in every section. The calculations of the engineering stress and strain are shown in equations 5.1 and 5.2 as follows: = P/A (5.1) = (L – L 0 )/L 0 (5.2) where is the engineering stress (psi) is the engineering strain (in/in) P is the external tensile load (lb) A is the original sectional area of a sample at middl e length (in^2) L 0 is the initial length of specimen or gage length (in) L is the deformed length of specimen or gage length at an applied stress (in) c) % Elongation (Ductility) Tensile ductility of the specimen can be represented as % elongation. It is a measure of how much a material deforms. It can be obta ined by fitting the ends of the fractured specimens together carefully, measuring t he final gage length of

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99 the sample, then dividing total elongation of a test s ample by the initial gage length and multiplied by 100%. % = 100x(L f – L 0 )/L 0 (5.3) Where L0 is the initial gage length (in) L f is the final gage length (in) d) Modulus of Elasticity The modulus of elasticity (E) is a measure of the stif fness of the material, and obtained by elastic slope calculation in a linear region of the stress-strain curve dividing the engineering stress by the strain. After plott ing an engineering stressstrain curve for each test result, most tensile testi ng curves show two portions of material behavior. In the initial test portion, the r elationship between applied load and the elongation of the specimen are linear in which the slope is a constant, or the ratio of stress is proportional to strain. This r elationship is defined as “Hooke’s Law” and E can be computed by using equation 5.4. E = / (5.4) 2. Plastic Deformation Zone By considering the stress-strain curve beyond the elas tic zone, the tensile loading continues, and yielding occurs at the beginning of plastic deformation. This yield point elongation shows the upper yield point followed by a sudden reduction in the stress or load till reaching the lower yield point. At the yield point elongation, a specimen continues to extend without a significant chan ge in the stress level. Load increment is then followed with increasing strain until the stress drops and the

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100 specimen fails. The maximum stress or ultimate strengt h of a specimen will be indicated before the fractured point of the specimen. a) Yield Stress ( y) The yield stress or strength, which indicates the onse t of plastic deformation, is considered to be the important values for engineering or s tructural designs. The yield strength values can be obtained at 0.5 and 1.0% strai n; however the most common method to determine the yield strength at 0.2% offse t. This can be carried out by drawing straight line parallel to the slope o f the stress-strain curve in the linear portion, having an intersection on the str ess-strain curve in plastic zone at a strain equal to 0.002 in/in. b) Ultimate Tensile Stress ( u) Beyond yield point, continuous loading leads to an increase in the stress required to permanently deform the specimen. This stage requires hi gher stress to uniformly and plastically deform the specimen; therefore, resulting in strain hardening. When the loading is continuously applied, the stress-str ain curve will reach the maximum point, which is the ultimate tensile strength. At this point the specimen can withstand the highest stress before necking takes pl ace. After necking, plastic deformation is not uniform and the stress decreased accor dingly until the fracture.

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101 Figure 5.2 Load-Deformation Relationship of Tension Test 5.2.3 Additional Tensile Test Sample After plotting the engineering stress-strain curves of a ll tensile test results from MTS testing machine, the E values of Modulus of Elasticity in the initial elastic zone seemed too low and unreasonable as compared with the predicted value o f about 27,000 ksi; even though, the stress values were quite correct and close to the historic test results. To verify the mechanical property of wrought iron samples ; therefore, the additional tensile test specimen marked 0BT-1-C3 was prepared and the te nsion testing was conducted by using INSTRON test machine in ME Lab. This machine has a n extensometer attached on the specimen which can read the displacement very precis ely, to measure the deformation in the reduced section during tensile loading. The test speci men was required to reduce half nr nrn r !"

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102 size of MTS test specimens to fit in smaller grips of I NSTRON machine. As a result the specimen had the reduced section width of ” for 3/16” plate thickness and 1” grip width at the ends. The load-deformation data of the 0BT-1-C3 specimen was input in the spreadsheet, and calculated the engineering stress and strain. The resul t was plotted as shown in Appendix C. The test result in Table B-2, Appendix B shows that the modulus of elasticity (E) was 28,400 ksi. 5.3 Guided Bend Test Results The guided bend test was conducted to determine the ductility o f wrought iron samples and welds on wrought iron samples. Three samples from me mbers marked A1 and C2 were selected to demonstrate the ductility property of wrought iron. The pictures of test results shown in Table 5.2 include the initial shapes and final conditions of the samples after the base metal face bend test, welded face bend test and welded root bend test. The convex surfaces of the bent specimens were examined cracks or other open defects. Both base metal (BB-A1) and welded root bend (RB-A1) test spe cimens were bent 180 without breaking apart, but there were a few minor cra cked lines on the welded root bend test sample near the weld. On the other hand, the welded fa ce bend test specimen (FB-C2) was broken near the butt joint, and the fractured ends seem to be jagged and uneven surfaces, clearly showing the “grain-like” characteristic of wrought iron, Figure 5.3.

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103 Table 5.2 Bend Test Results Mark Initial Shapes Final Conditions BB-A1 (Base Wrought Iron) FB-C2 (Welded 1G Butt Joint) RB-A1 (Welded 1G Butt Joint)

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104 Figure 5.3 Shows Fractured Ends of Face Bend Test S ample

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105 CHAPTER VISUMMARY AND CONCLUSIONS The material and mechanical testing completed after wrought iron samples made of both base metal and welded metal with V-groove welding i n butt joints were prepared by using the SMAW procedure for wrought iron in conformance with AWS codes. Since the wrought iron manufacturing processes were slightly different, it was decided to test material that was produced for each member. 6.1 Evaluation and Discussion The material testing completed in this research con sisted of spark test, tensile test, and bend tests. Their test results were corrected and anal yzed as shown in Appendix B. The evaluation has been performed and discussed in the following i tems. 6.1.1 Spark Test When the high carbon content metal touches the grin der, and is heated, the part of the metal oxidizes at high rate and high ignition tempe rature, and sparks are white color. On the other hand, lower carbon content metal or pure iron when heated by the grinding wheel, does not oxide as quickly. The sparks have a long strea m are “teardrop” shape, with light-yellow or straw color, and fade out on cooling. The spark tests of three wrought iron members, whic h were shipped from Michigan historic bridges had a large volume of spark stream with straw color near the grinding wheel, but there was a very low quantity of forked spurts, see Table 5.1. When their sparks were compared with of those of mi ld steel and carbon tool steel, these high carbon steel members produced a white-red spar k stream with much more quantity of forked spurts than all three wrought iron samples. Thus we conclude that all three historic bridge members were wrought iron.

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106 6.1.2 Tensile Test The tensile test results are very important for this research and discussed below because the repair them with current SMAW process will be useful for the future rehabilitation projects to restore historic bridges. 6.1.2.1 Ultimate Strength Ultimate strength is the point when fracture occurs bef ore the samples fail. The data in Tables B-2 in Appendix B shows that the average ultimate strength of base metal samples was 47.51 ksi with the standard deviation of 1.667% of this avera ge value. The data in Table B-3 shows that the average ultimate s trength of welded metal samples is 46.63 ksi and the standard deviation is 0.574% of this average va lue. The ultimate strengths of both test sample groups seem to be slightly different. However these values fall in the previous test data range of 45 – 55 ksi. This means that welded test samples had ultimate strengths which are at least equal to, and usually greater than, those of base metal. Using SMAW to make V-groove welding in a butt joint of the sample members still maintains the ultimate tension capacity of the historic wrought iron members. 6.1.2.2 Yield Strength Because of the error deformation reading of MTS machine, the yield strength at 0.2% offset could not be determined. The value of yield stren gth is expected to be about 0.60 times of the ultimate strength (AASHTO, 2010). The data in Table B-2 shows that the average yield strength at 60% of the ultimate strength of b ase metal samples is 28.5 ksi. Also the data in Table B-3 shows that the average yield strengt h of welded metal samples is 27.98 ksi.

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107 The yield strengths of both test sample groups appear sim ilar, and these values are slightly lower than the historic test data range of 30 – 38 ksi. The welded metal samples were expected to gain yield strengths which are at least equa l to, and usually greater than, those base metal after repaired with SMAW welding proce dure. 6.1.2.3 Modulus of Elasticity During the evaluation of the test results, the modulus of elasticity (E) of base metal and welded metal samples were investigated, and the average E v alues of test samples by MTS machine seemed very low compared with the historic data (27, 000 ksi). The test samples obtained average E values of 1,500 ksi. This could tell us th at the displacement reading from the tensile test data were in error. For further investigation, the additional base metal samp le (0BT-1-C3) was used to conduct the other tension testing by INSTRON with an ext ensometer. The test result in Table B-2 shows that the modulus of elasticity was 28,400 ksi as predicted. This could confirm us that the test data was correct; even though, t he engineering stress-strain curve had some variance and was not smooth as usual, which might be caused by the resistance of screw power system in the INSTRON and the loud noise th at was happening during the test. This test result confirmed that wrought iron sample has t he stiffness as same as the previous test. 6.1.2.4 Elongation The percent elongation (% ) of a metal is used to evaluate ductility, and the higher percent elongation is obtained, a metal can deform longe r before failure. When the percent elongation is lower, a metal be more brittle easier. The percent elongation of base metal and welded metal samples in this research were obtained from total deformations of test samples

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108 divided by the original gage lengths. The average percent elo ngation of base metal and welded metal are 17.07% and 9.85% respectively. Both percent e longations were about the same as the historic test data range of 10-25%. The average percent elongation of welded samples seems lo wer than base metal samples by 7.22%. This means that the welded samples were deforme d less than base metal samples because the weld material in butt joints has higher yield st rength and stiffness than base metal, and this is as expected. 6.1.3 Guided Bend Test The bend test is used to determine ductility of test sample s. The test results show that wrought iron base metal sample can be bent 180 without a crack as well as welded root bend test sample. However the welded face bend test sample w as broken in the base metal near the welded joint. The convex surfaces of the bent specimens were examined f or cracks or other open defects. Both base metal sample and root bend test sampl e had smooth surfaces, and there are very tiny edge cracks on the welds of the root bend t est sample. This explains that the welded face bend test sample, whic h had wider weld surface than the root bend test sample, has higher yield strength and st iffness than base metal. When concentrated loading was applied at the midpoint, the wel d tended to deform less than the base metal next to it until reaching the yield point of w rought iron, the base metal failed before the weld metal. As a result, this test tells us that wrought iron base metal has less stiffness than the weld metal and is more brittle, as expected.

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109 6.2 Conclusions To identify wrought iron with the spark test is simple an d can be done in a few minutes. The visual inspection and observation along with surface exam ination can determine the type of ferrous metal samples, and whether they are carbon ste el or wrought iron before making a decision what repair procedure would be used. The average ultimate strength of welded metal samples is 46.63 ksi. The comparison of ultimate strengths of welded and base metal samples see m to be slightly different, but they are considered to be realistic since these values fall in t he historic test data range of 45 – 55 ksi. The average yield strength of welded metal samples is 27.98 ksi which is about 0.6 times of ultimate strength. The yield strengths of both base a nd welded metal samples also seem to be close, but they are slightly lower than the historic test data range of 30 – 38 ksi. The modulus of elasticity of the additional test sampl e was 28,400 ksi as expected. The use of the extensometer for the deformation measurement i s useful and precise. Without an extensometer for the tension test can cause an unrelia ble test result. The evaluation of the test results verifies that the use of SMAW procedure for repairing wrought iron is acceptable in that tensile capacity is n ot reduced. Ductility is brought into question by the fractures of the face bend tests and future research is needed in this area. This research also provides the additional knowledge of wr ought iron properties to this researcher and others. It is very important to know th e properties of wrought iron before utilizing the current repair procedure or techniques to the his toric wrought iron bridges and structures.

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110 6.3 Recommendations for Future Research This research objective was satisfactory after the com pletion in developing proficiency arc welding with SMAW procedure and techniques for repairing of wro ught iron. This research was emphasized on repairing wrought iron br idge members with single Vgroove welding in a butt joint by the SMAW process by using 1/ 8” E7018 electrodes which is in conformance with AWS 5.1. The procedure requires preheating a wrought iron member up to 300F prior to SMAW welding; however a future research may utilize a higher preheating temperature such as 500F, and determine an effect on the wel d quality and mechanical properties of a welded sample. There are many kinds of welding joints to splice wrought ir on members when performing in maintenance projects. Double V-groove welding in a butt jo int is one of the recommended studies for the future research. However making a good wel ding bead is satisfactory for repairing wrought iron if a researcher has an experience in basic SMAW procedure.

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111 REFERENCES Althouse, Andrew D. Turnuist, Carl H. Bowditch, Wi lliam A., Bowditch, Kevin E. and Bowditch, Mark A. (2004). “Modern Welding”, 2004 Edition, the Goodh eart-Willcox Company, Inc., Tinley Park, IL. American Association of State Highway Transportation Offices (AASHTO) (2010). “LRFD Bridge Design Specifications”, 5 th Edition, Washington DC. American Association of State Highway Transportation Offices (AASHTO) (2008), “Guidelines for Historic Bridge Rehabilitation and Replacement”, Washi ngton, DC. American Society for Metals (ASM) (1985). “Metals Handb ook”, 9 th Edition, Volume 8, Mechanical Testing, Metals Park, OH. American Welding Society (AWS) (2010). “Bridge Welding Code”, 6 th Edition, AASHTO/AWS D1.5M/D1.5 An American National Standard, A joint Publicat ion of American Association of State Highway and Transportation Offic es, Washington, DC and American Welding Society, Miami, FL. ASTM A370-05 (2005). “Standard Test Methods for Tension Testing of Metallic Materials”, West Conshohocken, PA. ASTM E8-03 (2003). ”Standard Test Methods for Tension Testin g of Metallic Materials”, West Conshohocken, PA. ASTM E190-92 (Reapproved 1997). “Standard Test Method for Guided Bend Test for Ductility of Welds”, West Conshohocken, PA. ASTM E290-97a (1997). “Standard Test Method for Bend Testing of Material for Ductility”, West Conshohocken, PA. ASTM E 350-95 (Reapproved 2000). “Standard Test Methods for Chemic al Analysis of Carbon Steel, Low-Alloy Steel, Silicon Electrical Steel, I ngot Iron, and Wrought Iron”, West Conshohocken, PA. Aston, James and Story, Edward B (1949). “Wrought Iron-Its Manufacture, Characteristics and Applications”, Second Edition, A.M. Byers Company, Pitt sburg, PA Bowman, Mar D. and Piskorowski, Amy M (2004). “Evaluation a nd Repair of Wrought Iron and Steel Structures in Indiana”, Publication FHWA/IN/JTRP2004/04. Joint Transportation Research Program. Indiana Department of Transportation and Purdue University, West Lafayette, IN. Emily Griffith Technical School (2011). “Emily Griffith O pportunity School for All Who Wish to Learn, Catalog 2011-2012”, Denver, CO.

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112 Gasparini, Darino, Case Western Reserve University (2010). “Wrought Iron and Historic Steel”, Preservation of Historic Iron and Steel in Bridges and Other Metal Structures (DVD), National Center for Preservation Technology and Traini ng at Lansing Community College, Lansing, MI. Holth, Nathan (2012). “A Leading Historic Bridge Resource”, the HistoricBridges.org, MI, < http://www.historicbridges.org >. Lincoln Electric Company (1994). “The Procedure Handbook of Arc Welding”, 13 th Edition, the Lincoln Electric Company, Cleveland, OH. Lincoln Electric Company (2004). “Stick Electrode Product Cat alog for Mild and Low Alloy Steels”, the Lincoln Electric Company, Cleveland, OH. M&H Architecture, Inc. (2007). “Indiana Bridges Historic C ontext Study, 1830s-1965”, Indiana Department of Transportation, IN. Miller Electric Manufacturing (2010). “Guidelines for Shiel ded Metal Arc Welding (SMAW).” Miller Electric Manufacturing, Appleton, WI. Transystems (2010). “Ohio Historic Bridge Maintenance & Pr eservation Guidance”, Ohio Department of Transportation, Office of Environmental Se rvices, OH The Real Wrought Iron Company (2012). “The Sold World Supplier of Genuine Wrought Iron”, North Yorkshire, UK, < www.realwroughtiron.com >. Yost L., Lincoln Electric Company (2010). “Arc Welding Fund amental for Historic Bridges”, Preservation of Historic Iron and Steel in Bridges and Other Metal Structures (DVD), National Center for Preservation Technology and Traini ng at Lansing Community College, Lansing, MI.

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113 APPENDIX A SMAW PROCEDURE

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114 Form N-2 (AWS, 2010)

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115 Form N-3 PQR (AWS, 2010)

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116 APPENDIX B SUMMARY OF TEST DATA

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117 Table B-1 Specimen Dimensions Coupon ID Width, W f (in) Thickness, t f (in) Sample Length (in) Gage Length (in) Remark Initial, S 0 Final, S f Initial, L 0 Final, L f 0BT-1-C3 0.753 0.181 10.000 10.500 1.000 1.064 Base Metal 1BT-1-B2 1.505 0.190 12.000 12.907 3.996 4.690 Base Metal 2BT-1-B3 0.500 0.500 12.000 12.595 4.023 4.571 Base Metal 3BT-1-B4 0.503 0.501 12.000 12.840 4.025 4.696 Base Metal 4BT-1-B3 0.505 0.505 12.000 12.913 3.989 4.811 Base Metal 1WT-1-B4 0.505 0.501 12.000 12.478 3.988 4.385 Welded Metal 2WT-1-B3 0.504 0.505 12.000 12.475 4.021 4.430 Welded Metal 3WT-1-C3 0.505 0.503 13.000 13.585 3.979 4.455 Welded Metal 4WT-1-B3 0.503 0.500 12.000 12.356 3.960 4.250 Welded Metal

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118 Table B-2 Tension Test Results of Base Metal Samples Coupon ID Average Area (Sq.in.) Tensile Load E (ksi) Yield Strength (ksi) Tensile Strength % Elongation Remark (kips) (ksi) 0BT-1-C3 0.136 28,400 Base Metal 1BT-1-B2 0.286 14.33 30.07 50.11 17.37 Base Metal 2BT-1-B3 0.250 11.37 27.29 45.48 13.62 Base Metal 3BT-1-B4 0.252 11.85 28.22 47.04 16.67 Base Metal 4BT-1-B3 0.255 12.09 28.44 47.39 20.61 Base Metal Average 0.261 12.41 28.50 47.51 17.07 Base Metal Standard Deviation 0.015 1.138 1.000 1.667 2.482 Table B-3 Tension Test Results of Welded Samples Coupon ID Average Area (Sq.in.) Tensile Load (ksi) E (ksi) Yield Stre ngth (ksi) Tensile Strength % Elongation Remark (ksi) 1WT-1-B4 0.253 11.78 27.93 46.55 9.95 Welded Metal 2WT-1-B3 0.255 11.91 28.08 46.80 10.17 Welded Metal 3WT-1-C3 0.254 12.03 28.43 47.38 11.96 Welded Metal 4WT-1-B3 0.252 11.51 27.47 45.78 7.32 Welded Metal Average 0.253 11.81 27.98 46.63 9.85 Welded Metal Standard Deviation 0.001 0.194 0.345 0.574 1.656

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119 APPENDIX C CURVES OF TENSION TEST RESULTS

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