Guided Tour 72 Modern Welding Copyright Goodheart-Willcox Co., Inc. coming into contact with the metal during the weld- ing process. Welders must wear an approved helmet with proper lenses for shielded metal arc welding, gloves, and protective clothing. The welding workstation must be well ventilated. Chapter 5, Shielded Metal Arc Welding Equipment and Supplies, and Chapter 6, Shielded Metal Arc Welding, pro- vide more detailed information about shielded metal arc welding. 4.1.2 Gas Metal Arc Welding (GMAW) In gas metal arc welding, an electric arc between a contin- uously fed metal electrode and the base metal produces heat. The heat melts the base metal and the electrode, creating the weld. The arc is shielded by a gas that is sup- plied through the welding gun. This process is popular in production, robotic welding, and repair shops. Nonstandard Terminology Gas metal arc welding is often referred to by the nonstan- dard term MIG (metal inert gas) welding. The heat of the electric arc can be controlled by the current setting and by the arc length. Electrode diame- ter and fl ux material determine the amount of welding current and the type current (AC or DC) required. The arc between the welding electrode and the base metal is struck (initiated) by the welder. The welder must keep the electrode positioned the proper distance from the workpiece (arc length) to maintain the arc. Some of the covering on the electrode burns off to form a protective gas shield that surrounds the arc as the electrode melts. Some of the covering melts to form a slag that covers the completed weld. The slag layer protects the hot metal from oxidizing (or rusting) while it cools. The term oxidation refers to oxygen chemically combining with a metal. The surface of metals that have joined with oxygen become oxidized. The new material that is formed through the chemical combi- nation of a metal and oxygen is called an oxide. Oxida- tion of metals containing iron results in an unwanted layer of oxide called rust. Rust is also known as iron oxide or ferrous oxide. Oxidation should be avoided in joining opera- tions. The unwanted layer of oxide changes the physi- cal properties of the metal, generally weakening it. Oxidation can be avoided by preventing oxygen from Employability the first impression about you. Fill out the form accurately, completely, and neatly. How well you accomplish this can determine whether you get the job. Many employers now request electronic applications, either through the employer’s website or an independent job-search website. When filling out an online applica- tion, it is extremely important to include key terms that the employer may search for. This will help you stand out from the many other applicants. When preparing your application, be sure to save it in the appropriate file format. If a preferred format is not given, it is best to save the application in Microsoft Word file format (.doc or .docx) or save it as a PDF file. This enables the employer to find specific search terms in your document. Be sure to complete all the fields of the applica- tion. Many job-search sites have sample forms on which you can practice before attempting to complete a real application. Searching for and finding welding-related jobs has never been easier because of the Internet. Today, the vast major- ity of welding jobs are advertised on company websites. Online applications can be completed and submitted by accessing the company’s website. Job leads can also be found by checking classified ads and school bulletin boards, networking, talking to friends and family, and attending job fairs hosted by techni- cal colleges and welding schools. School officials and gov- ernment agencies can also assist you in searching and applying for jobs. Once you find a job opening, you will generally be asked to fill out a job application. This can be done in per- son or online. You should also have a résumé and a port- folio prepared, as many employers will ask to see these along with the application. Employers often use these forms to screen applicants for the skills needed on the job. The appearance of the application form can give an employer Applying for a Job Nonstandard Terminology features diff erentiate between AWS standard terminology and nonstandard terms commonly used in the workplace. Safety Notes alert you to potentially dangerous materials and practices. 3 Chapter 1 Safety in the Welding Shop applicable safety standards. Before operating, install- ing, or servicing any tool or unit, consult and follow the directions in the owner’s manual. Also, carefully read the safety data sheets for all metals and materials used. Pro Tip To ensure safety in a welding environment, every welder needs to read and understand Safety in Welding, Cutting, and Allied Processes (ANSI Z49.1) and keep a copy on hand. 1.1 Accidents The American Heritage Dictionary defi nes accident as “an unexpected undesirable event.” Many of the experts who study accidents and encourage safe practices believe that some personal or physical fac- tor is responsible in every accident. The following are some personal factors that may cause or contrib- ute to accidents: • Stress. People who are under stress may be distracted from their work by worry, anger, sorrow, love, or hate. • Illness. When a person is ill, he or she may not be able to give all the attention necessary to a task. • Fatigue. If a person does not get suffi cient sleep, for whatever reason, he or she may be less alert to the requirements of the job. Wards elding poses a wide range of safety and health risks to welders. Welding health haz- include exposure to toxic fumes and ultraviolet rays. Potential safety hazards, such as burns, eye damage, and electrical shock can arise from the use of powerful welding equipment. Care- ful training in proper work practices and the use of quality personal protective equipment (PPE) helps to reduce these dangers. While many important safety procedures are out- lined in this chapter, always read and comply with owner’s manuals, safety labels on products, and all Nederman, Inc. Hobart Brothers Co. Learning Objectives After studying this chapter, you will be able to: • Identify common causes of accidents. • Recognize health and safety hazards in the welding shop or other work environments and take appropriate measures to prevent accidents and injuries. • Select and properly use safety equipment appropriate to working conditions, including the clothing items that should be worn during welding or cutting. • Explain where to fi nd information about welding on hazardous containers and disposing of hazardous waste legally and safely. • Explain the purpose of a safety data sheet (SDS). Learning Objectives clearly identify the knowledge and skills to be obtained when the chapter is completed. Introductions provide an overview and preview of the chapter content. Pro Tips provide helpful advice and guidance applicable to on-the-job tasks and situations. Chapter 13 Oxyfuel Gas Welding 359 Copyright Goodheart-Willcox Co., Inc. Before using an oxyfuel gas welding or cutting outfi t for the fi rst time, make sure you understand how to operate the equipment: 1. Learn the proper ways to assemble the outfi t and prepare the station for use. 2. Learn how to check the entire outfi t for any gas leaks. 3. Learn the proper method of turning on the oxyacetylene outfi t and lighting the torch. 4. Learn how to adjust gas fl ows to produce a neutral fl ame. 5. Learn the proper method of shutting down the equipment. The proper procedures for handling the torch and selecting the size tip to use depend on several factors. These factors are the type of weld desired, the kind of metal used, the thickness of the metal, and the shape and position of the metal. These topics will be covered later in this chapter. 13.2.1 Assembling an Oxyfuel Gas Welding Outfit Proper assembly, care, and security of the oxyfuel gas welding outfi t is necessary for its safe and effective use. Care must be taken when assembling the various threaded fi ttings. When tightened, the fi ttings must not leak. The fi ttings are generally made from soft metal, such as brass. Caution Do not overtighten fittings, or the threads may be damaged. Warning Petroleum-based oil, grease, and soap contain flammable material. Petroleum-based products must not be used to lu- bricate any part of a cutting or welding outfit. These materi- als could ignite and cause a fire. An oxyfuel gas cutting outfi t is assembled in the same manner as an oxyfuel gas welding outfi t, since oxyfuel gas cutting and welding equipment is essen- tially the same. The main differences between the cut- ting and welding outfi ts are in the oxygen regulator and the torch. Aside from the torch and the oxygen regulator, the assembly of the oxyfuel gas outfi t is the same for both cutting and welding. Fixture for vertical, horizontal, and overhead welding practice Bench top Stool Bench Goodheart-Willcox Publisher Figure 13-7. A well-planned welding table. Note the built-in stool and the fixture for holding work in various welding positions. A B Goodheart-Willcox Publisher Figure 13-8. A well-designed bench enables a person to practice welding in any position and at various heights. A—Clamp used for holding weldments in the flat, horizontal, vertical, and overhead positions. B—Height adjustment that enables positioning of a weldment at various heights above the bench. Employability features provide information about skills needed to obtain a job and to achieve success on the job. Warnings alert you to situations and actions that have the potential to cause bodily injury or death. Cautions alert you to practices that could potentially damage equipment or instruments.