Introduction To Welding PDF

## SECTION 1 ### INTRODUCTION TO WELDING 1. Welding and Cutting Processes. 9 2. The Physics of Welding. 15 3. Weld Joints and Positions. 23 ### Chapter 1 ### Welding and Cutting Processes After studying this chapter, you will be able to: - Cite advantages of welding over other joining processes....

## SECTION 1 ### INTRODUCTION TO WELDING 1. Welding and Cutting Processes. 9 2. The Physics of Welding. 15 3. Weld Joints and Positions. 23 ### Chapter 1 ### Welding and Cutting Processes After studying this chapter, you will be able to: - Cite advantages of welding over other joining processes. - List the significant developments in the history of welding. - Identify recent developments in welding and cutting processes. - Identify several occupations in the welding industry and list the recommended amount of education for each. ### TECHNICAL TERMS Force welding, fushion welding, occupation, process, prototype parts, weld, welding, weldment. ### THE WELDING PROCESS A process is an operation used to produce a product. Riveting, forging, cutting, turning, bending, and welding are processes used in industry. Metalworking processes have been used for thousands of years. Metals have been joined by riveting and welding for thousands of years. Blacksmiths used their skills and knowledge of metalworking processes to work metal into many desired products. Hinges, nails, cooking pots, farm implements, wagon wheels, and swords were produced by forging and forge welding. Blacksmiths are employed today to make prototype parts for cars, airplanes, and other equipment. Prototype parts are the first models of parts that later may be mass produced. Prototype parts are generally handcrafted. After the prototype parts are approved, machines and equipment are designed to mass produce the parts. ### Forge welding is a process used by blacksmiths to produce welded metal parts. In forge welding, the parts are heated until they are very hot and in a softened state. The heated ends are then placed together on an anvil and struck repeatedly with a hammer. See Fig. 1-1. This hammering creates a weld by forcing the hot softened metal from the pieces to intermix and form a single unit. If the welding process is performed properly, the weld is stronger than the original metal. Welding is defined as a process of "[j]oining metallic or nonmetallic material in a relatively small area by heating the area to the welding temperature. Pressure may or may not be applied; welds may be made by applying pressure only. Welds may be made with or without the addition of filler material." Not all materials can be welded, but most metals and plastics are weldable. ### Welding Technology Fundamentals Most welding processes require the addition of heat to the weld area. In fusion welding, heat is applied to a small area until it becomes molten (liquid). The molten areas of the weld joint then flow together, forming a single until after they cool. Welds are also made with the metal at or near room temperature. Cold welding and explosion welding are examples of welding processes that are performed at room temperature. Extremely high pressure is applied to the area to be welded. Metal at the surface of one part is driven into the surface of the adjoining part by high pressure. The pieces are thus joined or welded at the surface. ## ADVANTAGES OF WELDING AND CUTTING PROCESSES Welding and cutting processes offer a number of advantages over other joining and cutting methods. Most welding and cutting equipment is portable. It can be operated inside boilers, furnaces, large containers, or pipes to make repairs. Welding and cutting can be done under water to repair ships or to cut up and remove water hazards. Welding and cutting equipment can be transported into the field to repair farm machinery, trucks, and earth-moving equipment. See Fig. 1-2. Welding is used to construct pipelines, buildings, and ships. Because of modern welding techniques, engineers are able be design strong parts that are lightweight, complex, and often less expensive. As late as 1920, many steel structures were built using rivets. Automobile and truck chassis also were constructed using rivets. Handles were attached to cooking pots using rivets. Holes are drilled into parts to be riveted. This weakens the parts in that area. Thicker and heavier metal is used to compensate for the weakness. See Fig. 1-3. Today, many parts are designed for welding. The welded parts are lighter and generally cheaper to produce than riveted parts. Parts joined by welding are known as weldments. Many complex shapes are cast or forged and then machined into their final shape. Cast or forged parts are heavy and require large, costly equipment to produce them. A large amount of equipment and machining would be required to produce the part in Fig. 1-4A from 3" (76 mm) solid stock. The same part can be produced from 3" (76 mm) and 1 1/2" (38 mm) stock by cutting the stock to length and welding it at both ends. See Fig. 1-4B. The weldment would be generally faster, use less material, and be cheaper to produce. Applications of welding and cutting processes are unlimited. For example, stones can be welded together to build or repair a statue. A layer of weldable metal can be added to the stone surfaces by thermal spraying. The metal can then be welded to join the stones together. Fig. 1-5 shows a layer of harder material being applied to a soft metal shaft using the thermal spraying process. ## HISTORY OF WELDING The use of welding dates back to 2000 B.C., but the development of modern forms of welding began in 1881. Some of the major dates and developments are as follows: - 2000 B.C.-Forge welding used to join copper and bronze. - 1881-Electric arc welding performed by Auguste de Meritens. A carbon electrode was used. - 1883-1885-Electric resistance welding developed by Elihu Thomson. It was used to weld the ends of wires together. - 1894-Carbon arc welding used commercially to produce steel barrels. - 1902-Arc cutting demonstrated. - 1903-Oxyfuel gas welding and cutting torches developed by Fouché and Picard. - 1907-Covered steel electrode developed by Kjellborg in Sweden. - 1917-Strength of welded joints was first tested by the British and United States governments and by Lloyd's of London (a ship insurance company). Test results proved that welded joints were as strong as riveted joints. - Welding became an accepted practice for repair and construction. When the U.S. entered World War I, the Germans severely damaged 105 of their own ships that were in U.S. ports. This was done to prevent their use by the United States. Repairs to boilers and pumps were performed using welding, saving $20,000,000. - 1918-First all-welded ship was launched. - 1920-First all-welded building was constructed. Built by Electric Welding Company of America, it measured 40'x 60′. - 1940-Submerged arc welding process developed in Russia. - 1942-Gas tungsten arc welding (GTAW) developed, using two tungsten electrodes and helium as a shielding gas. Also known as heliarc welding. - 1948-Gas metal arc welding (GMAW) developed. - 1990s-A total of 94 welding and cutting processes are in use with a variety of energy sources and shielding gases. American Welding Society (AWS) approved names and abbreviations are shown in Fig. 1-6. ## MASTER CHART OF WELDING AND ALLIED PROCESSES | ARC WELDING (AW) | SOLID-STATE WELDING (SSW) | BRAZING (B) | WELDING PROCESSES | OTHER WELDING PROCESSES | GAS WELDING (OFW) | |---|---|---|---|---|---| | Atomic hydrogen welding...AHW | | | | Block brazing..BB | - Oxyfuel | | Gas metal arc welding | | | | Diffusion brazing CAB | | | -pulsed arc.. GMAW-P | | | | Exothermic brazing..EXB | | | -short circuiting arc GMAW-S | | | | Flow brazing..FLOW | | | Gas tungsten arc welding | | | | Furnace brazing..FB | | | -pulsed arc GTAW-P | | | | Induction brazing..IB | | | Bare metal arc welding..BMAW | | | | Infrared brazing..IRB | | | Carbon arc welding CAW | | | | Resistance brazing..RB | | | -gas.. CAW-G | | | | Torch brazing..TB | | | -shielded .. CAW-S | | | | Twin carbon arc brazing TCAB | | | -twin CAW-T | | | | | | | Coextrusion welding..CEW | SOLID-STATE WELDING (B) | | | | | | Cold welding..CW | | | | | | | Diffusion welding..DFW | | | | | | | Explosion welding..EXW | | | | | | | Forge welding..FOW | | | | | | | Friction welding..FRW | | | | | | | Hot pressure welding..HPW | | | | | | | Roll welding...ROW | | | | | | | Ultrasonic welding..USW | | | | | | | - high vacuum..EBW-HV | | | | | | | | | | | | | | | | | RESISTANCE WELDING (RW) | | | | | | | - medium vacuum..EBW-MV | | | | | | | -nonvacuum..EBW-NV | | | | | | | - Flash welding..FW | | | | | | | - Electroslag welding..ESW | | | | | | | - Projection welding..PW | | | | | | | - Resistance seam welding..RSEW | | | | | | | - Flow welding..FLOW | | | | | | | - Induction welding..IW | | | | | | | - High frequency..RSEW-HF | | | | | | | - Induction..RSEW I | | | | | | | - Resistance spot welding..RSW | | | | | | | - Upset welding..UW | | | | | | | - High frequency..UW-HF | | | | | | | - Induction..UW-1 | | | | | | | - Arc spraying..ASP | | | | | | | - Flame spraying..FLSP | | | | | | | - Plasma spraying..........PSP | | | | | | | | | | | | | | | | - Oxyacetylene cutting..OFC-A | | | | | | | - Oxyhydrogen cutting..OFC-H | | | | | | | - Oxynatural gas cutting. OFC-N | | | | | | | - Oxypropane cutting...OFC-P | | | SOLDERING (S) | | | | | | | - Dip soldering..DS | | | | | | | - Furnace soldering..FS | | | | | | | - Induction soldering..IS | | | | - Oxygen arc cutting..AOC | | | - Infrared soldering..IAS | | | | - Oxygen lance cutting LOC | | | - Iron soldering..INS | | OTHER CUTTING | | | | | - Resistance soldering..RS | | | | | | | - Torch soldering..TS | | - Air carbon arc cutting CAC-A | | | | | - Ultrasonic soldering..USS | | | | - Carbon arc cutting CAC | | | | | | | | | - Gas metal arc cutting GMAC | | | | | | | | | - Gas tungsten arc cutting GTAC | | | | | | | | | - Plasma arc cutting PAC | | | | | | | | | - Shielded metal arc cutting..SMAC | | | | | | | | | - Electron beam cutting..EBC | | | | | | | | | - Laser beam cutting..LBC | | | | | | | | | - Air, evap., inert gas, oxygen LBC-A, EV, IG, 0 | | | | | WESISTANCE WELDING (RW) | | | | | | | - Wave soldering..WS | | | | | | | | | | | | ## RECENT DEVELOPMENTS IN WELDING AND CUTTING PROCESSES Engineers have developed new welding and cutting processes in recent years. New processes were developed because new metals and alloys were being used in newly developed products such as supersonic aircraft, nuclear plants, submarines, and spacecraft. Welding and cutting processes which have been recently developed include: - Plasma arc welding and cutting - Electron beam welding and cutting - Electroslag welding - Electrogas welding - Laser beam welding and cutting - Plasma spraying - Electric arc spraying - Flame spraying - Explosion welding Although the future of the welding industry is unknown, it is certain that it will continue to grow. New welding and cutting processes will have to be developed as new metals, alloys, plastics, and ceramics are created. ## OBTAINING AND HOLDING A JOB IN THE WELDING INDUSTRY There are, and will be, many jobs available in the welding industry. Most of these jobs will require a high school education or an apprenticeship. Other jobs may require a junior college (associates), four-year (bachelors) or advanced degree. A number of welding and welding-related jobs, together with the educational level usually required and where this education may be obtained, are listed below: **High School or Technical School** - Gas welder - Assembler brazer - Gun welder - Arc welder - Fitter welder - Tack welder - Resistance welder - Assembler welder - Combination welder - Solderer **Technical School or Community College** - Ultrasonic welding machine operator - Welding inspector - Laser beam machine operator - Welding supervisor - Experimental welder - Welding machine repair person - Robotic welding machine programmer - Tool-and-die welder **Military Training Schools** - Combination welder - Diver/welder - Repair welder - Specialty welder **Trade Apprenticeship** - Sheet metal worker - Pipe and steam fitter - Structural iron worker - Ornamental iron worker - Blacksmith for experimental parts **College or University** - Welding engineer - Metallurgist - Metallurgical engineer Getting a job is sometimes difficult, but often, the job seeker has control over the reasons for that difficulty. To get the job you want, you must take the required courses in school. You must have and demonstrate the personal traits that employers are looking for in an employee. ## SUGGESTED SCHOOL SUBJECTS FOR SUCCESS Welding is a technical trade, but to succeed an employee should know more than how to weld. Some of the school subjects suggested for greater success in finding and holding a job in the welding industry are: Print Reading, Mechanical Drafting, Electricity, Electronics, Metals, Physics, Math, Algebra, Geometry, Trigonometry, Calculus, and Welding. ## PERSONAL TRAITS SOUGHT BY EMPLOYERS Employers want the following personal traits in an employee: - Dependability. - The ability to follow directions. - The ability to get along with peers. - Thoroughness. - Self-confidence. - An ability to accept responsibility. - Initiative. - An ability to get along with supervisors. - The ability to communicate written ideas. - An ability to communicate ideas orally. Since school is a student's first job, you should learn and demonstrate the traits required by a future employer while still in school. All of the traits can be demonstrated in class, by participating in school sports and clubs, and by doing good work in a timely manner. ## ACADEMIC SKILLS SOUGHT BY EMPLOYERS The academic skills which employers are seeking include the ability to: - Read and understand written materials. - Write and understand the technical terms and language of the trade or business in which you desire to work. - Read and understand graphs and charts. - Understand basic math. - Use mathematics to solve problems. - Use research and library skills. - Use the tools and equipment involved in the business. - Speak the technical language in which the business is conducted. - Use the scientific method of solving problems. ## FACTORS THAT CAN LEAD TO REJECTION FOR EMPLOYMENT Employers have identified several personal factors or traits which would cause a person to be rejected for a job. These factors include: - A poor scholastic record. - Inadequate personality. - Lack of goals. - Lack of enthusiasm. - Inability to express yourself. - Unrealistic salary demands. - Poor personal appearance. - Lack of maturity. - Excessive interest in security and benefits. - A poorly completed job application. ## FACTORS THAT MAY LEAD TO TERMINATION FROM A JOB Employers have also identified several reasons for a person being overlooked for promotion or even being terminated. These reasons include: - Poor attendance without cause. - Habitually coming in late. - Alcoholism. - Illegal drug use. - Inability to perform the tasks assigned. - Inability to work as a team member. - Fighting and threats to peers. - Insubordination to directions from a supervisor. - Talking with others too much and too often. - Lack of respect for others. - Lack of respect for others' property. - Always making excuses. - Constant complaining. ## REVIEW QUESTIONS Write your answers on a separate sheet of paper. 1. Welding has been performed for _______ years. 2. Parts are heated until they are molten when for ______ welding. True or False? 3. Most welding and cutting equipment is portable. True or False? 4. Thicker metal is used for riveted parts to compensate for strength lost due to rivet holes. True or False? 5. Welding is performed on metallic and nonmetallic material. True or False? 6. In what year did welding become an accepted practice for repair and construction? 7. In what year were the first oxyfuel gas welding and cutting torches developed? 8. Refer to Fig. 1-6. Give the correct name for the SMAW process. 9. Refer to Fig. 1-6. What AWS abbreviation is used for oxyacetylene welding? 10. Identify one welding occupation that you would like to pursue at each educational level. Discuss your choices with a career counselor. Write a brief summary of each.