Instructor’s Guide Welding Processes and Fundamentals Series Gas Metal Arc Welding (GMAW) Introduction This guide provides information to help you get the most out of the Shopware Gas Metal Arc Welding program of the Welding Processes and Fundamentals series. As the title suggests, Gas Metal Arc Welding introduces this popular fabrication and repair process, covers the basic setup procedures involved, and illustrates basic welding techniques. This video program also describes the potential dangers that gas metal arc welding poses, along with the steps you should take to ensure welding safety. Learning Objectives After viewing the program, students will be able to: • Understand how gas metal arc welding (GMAW) systems work. • Identify the potential dangers welding presents to trade professionals. • Understand how a GMAW system is set up for use. • Understand how GMAW systems are used for repair and fabrication. Copyright © 2012 Films Media Group® • www.shopware-usa.com • 1-800-322-8755 1 43940 Gas Metal Arc Welding (GMAW) Instructor’s Guide Program Overview This program is designed to give viewers a foundation in gas metal arc welding (GMAW) systems, their setup, and their proper use. Sections 1 and 2 of this program introduce the GMAW process and examine the physical components of a typical GMAW system. After this, a comprehensive dis- cussion of the personal protective equipment (PPE), such as appropriate helmets, gloves, and cloth- ing, is undertaken. Section 4 introduces the often poorly understood concept of Metal Transfer and how this occurs when GMAW equipment is being operated. The remaining sections cover the setup of a typical GMAW system and proper usage. In particular, students are shown proper GMAW techniques and the attributes of high-quality welds. Also shown are several different arrangements of the base metals being joined. This includes different horizontal, vertical and other configurations and the types of welding beads and passes that are most appropriate for each. The gas metal arc welding program ends with a short conclusion and words of encouragement for student welders. Correlates to all National CTE Organizational Standards (including the provisions of the Perkins Act). Main Topics Section 1: Introduction to Gas Metal Arc Welding This section introduces the viewer to gas metal arc welding (GMAW) and explains how the electric arc between the electrode and base metal creates molten metal that the welder uses to join the base metals together. This segment also explains the value of using an inert shielding gas to protect the molten weld puddle from atmospheric contamination. Section 2: Components of a Gas Metal Arc Welding System Here, viewers learn about the technology and use of typical GMAW systems and practical consid- erations when using them. Students learn about the GMAW welder and DC power, details on the filler wire used, the shielding gases employed, grounding clamps and other components. Section 3: Safe Welding Environment and Protective Equipment This section covers the steps necessary to ensure that the welding environment is safe for the welder and others in the work area. This segment also introduces the student to the personal protective equipment (PPE) that should be worn whenever cutting or welding is practiced. Section 4: Types of Metal Transfer Section 4 explains that there are several distinct modes by which GMAW systems deposit metal to create welds. The two most common methods are short-circuit and globular transfer, both of which are explained in detail and illustrated via animations. Students are advised that both methods have particular applications as to where they are best used and each method has advantages and disadvan- tages that should be understood. Copyright © 2012 Films Media Group® • www.shopware-usa.com • 1-800-322-8755 2 43940 Gas Metal Arc Welding (GMAW) Instructor’s Guide Section 5: Setting Up GMAW for Use This section goes step-by-step through the process of setting up a GMAW system for use. Discussed is the careful examination of equipment before use, the proper settings on the GMAW welder, and the preparation of the welding tip on the electrode gun. Section 6: Laying a Bead Section 6 goes through the process of creating high-quality welds with GMAW equipment. In the trade, this is often referred to as “laying a bead.” The many details that student welders should know when welding and laying beads are covered. Special emphasis is paid to the best two-hand tech- niques to use when holding the welding gun and how the proper traveling motion of the gun and arc can be used to create high-quality beads. Section 7: Reading the Bead Good welders must be able to look at welds and beads and be able to judge their quality. When welds are created that are poor quality, welders must know the parameters that caused this, such as voltage, travel speed, gas of pressure, etc. This section covers these details and shows images of weld beads that are of poor quality. Special emphasis is paid to monitoring the welding process and what steps to take if anomalies affecting the weld occur. Examples of this include too much spatter, poros- ity, poor penetration, and wavy beads. Section 8: Advanced Welding Techniques Welders must join pieces of metal in many different configurations and alignments. Each of these generally requires a specific approach for high-quality welds. Topics such as root passes, fill passes, and horizontal, vertical, and overhead locations are covered. Section 9: Conclusion This closing section shares safety tips for all trade professionals involved in GMAW along with wishes for continued success in the subject area. Fast Facts • GMAW is the most common industrial welding process, particularly in automotive manufacturing, because of its versatility, speed, and the relative ease of adapting to robotic automation. • GMAW was originally developed for welding aluminum and other nonferrous materials in the 1940s. • For production environments, GMAW is quicker than stick welding techniques. This makes it well suited for softer metals like aluminum. Copyright © 2012 Films Media Group® • www.shopware-usa.com • 1-800-322-8755 3 43940 Gas Metal Arc Welding (GMAW) Instructor’s Guide • One of the best practices to prevent injuries is to wear personal protective equipment (PPE) whenever welding or cutting. Those who disregard this practice subject themselves to unnec- essary risk. The Occupational Safety and Health Administration (OSHA), of the U.S. Department of Labor, states that welding, cutting, and brazing are hazardous activities posing safety and health risks to more than 500,000 workers in a wide variety of industries. • Mild steel melts at about 2750 degrees F, depending on the carbon content. • There are four primary methods of metal transfer in GMAW, called globular, short-circuit, spray, and pulsed-spray, each of which has distinct properties and corresponding advantages and limitations. • Butane lighters can explode in welders’ pockets. If molten spatter from welding lands on a plastic lighter, it can instantly melt and penetrate the butane container, causing the butane gas to explode with the force of a small stick of dynamite. • The brightness and danger of the light emitted during welding and cutting varies with the type of metal being welded and the welding process utilized. If skin is exposed to intense ra- diation energy, such as that from an electric arc, it can result in skin burns, premature aging, and ultimately skin cancer. • Many cutting and welding processes produce toxic fumes: gases and airborne particulates that can be harmful if inhaled. Welders and cutters should not disregard the danger of these fumes. • The presence of oily rags in the welding environment is a hazard. Sparks can travel 20–30 feet and smolder in oily rags for hours before actual combustion (flames) occurs. Vocabulary Terms Amperage–The amount of current flowing in a circuit, which is measured in amperes. Argon–An inactive gas commonly used as shielding. Argon is much heavier than air, so it effectively shields the weld area. Backhand Technique–Moving the electrode along the workpiece opposite the direction of the welding bead. Copyright © 2012 Films Media Group® • www.shopware-usa.com • 1-800-322-8755 4 43940 Gas Metal Arc Welding (GMAW) Instructor’s Guide Bird’s Nest–The jumble of filler wire that occurs when the filler wire gets jammed in the electrode channel and the wire spool continues to turn. Combustible–A substance that readily ignites and burns when exposed to flames and sparks. Confined Space Permit–A special permit issued by safety organizations such as OSHA that specify the requirements that must be met in order for welding or other processes to be executed in a “con- fined space.” Constant Voltage–Welding using a voltage that varies slightly with changes in current. Constant voltage (CV) is often used for gas metal arc welding (GMAW). DCEP–An abbreviation for direct current electrode positive. DCEP is another way of expressing direct current reverse polarity (DCRP). DCRP–Acronym for direct current reverse polarity. Duty Cycle–The term duty cycle refers to the amount of time during a 10-minute period that a piece of welding equipment can be used. For example, the Miller Thunderbolt XL creates a 200 amp DC output at 20 percent duty cycle. This means it can weld continuously at 200 amps for two minutes, and then must cool for eight minutes to prevent overheating. Electrode Gun–The handpiece used in GMAW systems. Also referred to as the MIG gun, MIG torch, and GMAW torch, among other names. FCAW–An abbreviation for flux-cored arc welding. An arc welding process that uses a continuously fed consumable electrode that contains flux in a hollowed-out center. Filler Wire–The wire electrode that is used with GMAW and FCAW systems. Flux–A nonmetallic material used to protect the weld puddle and solid metal from atmospheric contamination.