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Chapter 1 Introduction to Welding

Chapter 1 Introduction to Welding. Explain each welding process List factors affecting welding process selection Discuss the history of welding Describe various welding positions Define the terms: Weld, forge welding, resistance welding, fusion welding, coalescence, and certification.

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Chapter 1 Introduction to Welding

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  1. Chapter 1Introduction to Welding

  2. Explain each welding process List factors affecting welding process selection Discuss the history of welding Describe various welding positions Define the terms: Weld, forge welding, resistance welding, fusion welding, coalescence, and certification Objectives

  3. As civilization developed, materials, tools, and machinery improved Egyptians fastened stones with gypsum mortar In ancient times adhesives joined wood and stone Bronze and Iron Ages - forming, casting, and alloying metals Early metal-joining methods Sand molds for casting Pouring molten metal between two pieces of metal Introduction

  4. Figure 1-1 Direct casting using a sand mold

  5. Industrial Revolution (1750 – 1850) forge welding Also known as hammer welding A forge was used to heat metal The ends of the iron were hammered together Elihu Thomson - resistance welding (1886) Faster, more reliable Riveting was replaced by fusion welding Welding considered vital to military security Welding repairs to ships damaged during World War I were done in secrecy Introduction (continued)

  6. Weld: a localized coalescence Coalescence: the fusion of the grain structure of the materials being welded Produced by heating materials to required temperatures With or without pressure Can be created by applying pressure alone Filler added as needed to form a completed weld Can be made from plastic, glass and ceramic Welding Defined

  7. Ships, bridges, recreational rides, machines to manufacture new products Commercial and military aircraft The space program Modern techniques enabled space exploration The space shuttle's construction required the improvement of welding processes And more… Uses of Welding

  8. The number of welding processes has grown recently Processes differ in the manner in which heat, pressure, or both are applied Popular welding processes: Oxyacetylene welding (OAW) Shielded metal arc welding (SMAW) Gas metal arc welding (GMAW) Flux cored arc welding (FCAW) Torch brazing (TB) Welding Processes

  9. Shielded metal arc welding (SMAW) Makes high-quality welds rapidly Excellent uniformity Gas tungsten arc welding (GTAW) Provides high- quality welds Requires little or no postweld finishing Gas metal arc welding (GMAW) Easily used for thin-gauge metal and heavy plate Flux cored arc welding (FCAW) Does not use an external shielding gas GMAW and FCAW most commonly used Welding Processes (continued)

  10. Figure 1-7 Oxyfuel welding and cutting equipment.

  11. Figure 1-8 Shielded metal arc welding equipment.

  12. Figure 1-9 Gas tungsten arc welding equipment

  13. Figure 1-10 Gas metal arc welding equipment

  14. Skilled workers use regional terms Names used for oxyacetylene welding: Gas welding Torch welding Names used for shielded metal arc welding: Stick Welding Rod Welding Welding Welding Processes (continued)

  15. Selection depends upon many factors Availability of equipment Repetitiveness of the operation Quality requirements Location of work Materials to be joined Appearance of the finished product Size of the parts to be joined Time available for work Skill or experience of workers Cost of materials Code or specification requirements Selection of the joining Process

  16. The welder must also select the application method: Manual – the welder manipulates the process Semiautomatic – filler is added automatically Machine – done mechanically under observation Automatic – no interaction with the operator Automated – performed repeatedly by a robot programmed for multiple tasks Selection of the joining Process (continued)

  17. Welders perform the actual welding Tack welders make small welds to hold parts in place Welding operators operate automatic equipment Welders' helpers clean slag, position weldments Welder assemblers position the parts Interpret blueprints and welding procedures Knowledge contraction and expansion of metals Occupational Opportunities in Welding

  18. Inspectors hold a special certification Shop supervisors have good management skills Salespersons have understanding of welding and marketing skills Shop owners are often skilled welders with knowledge of small-business management The test for welding inspector certification covers: The welding process, blueprint reading Weld symbols, metallurgy Codes and standards, Inspection techniques Occupational Opportunities in Welding (continued)

  19. Both school and work experience are required An entry-level welder must have workplace skills Some welding jobs require theoretical knowledge Robotics and computer-aided manufacturing (CAM) require computer literacy Employers prefer high school or vocational training in welding processes Training for Welding Occupations

  20. A formal apprenticeship is usually not required The American Welding Society (AWS) Three levels of certification for welders Entry Level Welder ids for beginner welders Level II and Level III for more skilled welders SkillsUSA Sponsors welding skill competitions for students Emphasizes community service and citizenship Training for Welding Occupations (continued)

  21. Figure 1-13 Skills USA welding assembly. Courtesy of Larry Jeffus.

  22. Chapters contain both experiments and practices Intended to develop welding knowledge and skills Work in small groups as you try experiments Practices are designed to build welding skills Welding is developed in stages from basic to complex Each practice gives evaluation or acceptable limits Experiments and Practices

  23. Each of the four tape sets covers specific equipment setup and operation for: Welding Cutting Soldering Brazing Read the material, watch the video, and practice to develop your welding skills Welding Video Series

  24. FIGURE 1-14 Close-up of GMA welding. Courtesy of Larry Jeffus. View Welding Video

  25. Both standard and metric (SI) units are given SI units are in brackets () following the unit SI units rounded to the nearest whole number Rounded to agree with the standard value Whole numbers are easier to work with Rounding metric units makes the system easier Sometimes conversions must be exact Many calculators have standard-metric conversions Metric Units

  26. Welding is diverse, used in almost every manufacturing process Welded products range from small objects to buildings and space shuttles The art and science of joining metals has been around for centuries With minor changes it will be around through the 21st century Summary

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