Gas metal arc welding (GMAW) is a metal joining process that plays a critical role in the manufacturing sector. The welding process uses a consumable wire electrode that feeds continuously through the contact tip and a power supply that creates an electrical arc between the metal electrode and workpiece. The arc heats the metals, allowing them to join, while shielding gas protects the weld from environmental contamination during the process.
GMAW operations use two types of gases—inert or active—each of which characterizes one of the process’s two forms: MIG and MAG. Metal inert gas (MIG) welding uses inert gas during the welding process, while metal active gas (MAG) welding uses active gas. In addition to being categorized based on the assist gas employed, GMAW operations can also be classified based on their modes of transfer.
Although GMAW typically uses a constant voltage and direct current power system, the process also employs alternating current systems with a range of different amps and voltages and varying electrode diameters. Additionally, depending on the requirements and restriction of the welding application, GMAW can be configured to be semi-automatic—i.e., require some human operator involvement—or fully automatic with mechanized control. These options make the process a viable solution for a wide range of fastening applications.
Transfer Modes of GMAW
As noted above, GMAW uses different metal transfer modes. Each mode offers distinct characteristics and best use cases and is largely dependent on the specific welding process, power supply, and consumable employed. A variety of factors influence which transfer mode should be used for a GMAW application, including the amount and type of current, electrode chemistry, surface, and diameter, type and delivery of shielding gas, and contact-to-workpiece distance. The choice of transfer mode affects which filler metal is ideal.
The four modes of GMAW transfer include:
- Globular. This mode uses CO2 shielding gas, which is less expensive than other shielding gases such as argon. Although it offers a higher deposition rate that allows for faster welding speeds, it generates more heat than other modes, resulting in uneven weld surfaces and greater spatter production. To combat these disadvantages, welding operations that use the globular metal transfer mode require thicker materials and entirely flat positioning.
- Short-Circuiting. Welding operations that use the short-circuiting metal transfer mode are also referred to as short arc GMAW or SCT. In this transfer mode, short-circuiting occurs as the electrode contacts the workpiece, providing transfer rates of between 20 and 200 times per second. It uses a mixture of 75% argon and 25% CO2 or three-part gas mixtures as its shielding gas and can be used for thin (less than ¼ inch) stock of ferrous metals and pipes without backing.
- Spray. In the spray transfer mode, molten droplets of material—usually smaller than the diameter of the electrode—spray across the workpiece. This mode uses a variety of mixtures from 80% to 98% argon with 2% to 20% CO2 and requires higher voltage or amperage, faster wire feed rates, thicker materials, and horizontal or flat positioning.
- Pulse-Spray. The main characteristic of this mode is an alternation between a high voltage spray current and a low background current. This quality enhances the spray transfer process by supercooling the weld pool during the low current cycle and reduces heat generation and distortion.
Advantages of GMAW
Each of the transfer modes provides its own advantages in specific applications. However, there are some general advantages associated with using gas metal arc welding, including:
- Ability to be configured for semi-automatic or fully automated operation
- Versatility regarding material and joint thickness
- Ease of cleanup and lack of chipping
- Welding position flexibility
- Process speed
- Environmental friendliness (minimal waste is produced as electrodes are fully consumed)
Applications of GMAW
GMAW arose as a solution for welding aluminum and other non-ferrous materials. However, due to its capacity to speed up the welding process, its use has spread to steel and stainless steel applications. Its versatility allows for its use in any industry and with a wide range of materials. Some of the most common applications for GMAW include:
- Automotive production and maintenance operations
- Robotic assembly lines
- Pipe fitting
- Track construction and maintenance operations in the railway industry
Contact G.E. Mathis for Your GMAW Needs
At G.E. Mathis, we offer precision arc and MIG welding services to customers across a broad range of industries, including agriculture, mining, aerospace, military, and construction. Armed with a state-of-the-art facility and years of industry experience, our team of highly skilled welders has the tools and expertise necessary to offer a variety of welding services. In addition to GMAW, we provide:
- Dual wire submerged arc/MIG Welding
- Flux core arc welding (FCAW)
- Gas tungsten arc welding (GTAW)
- Seam welding
- Shielded metal arc welding (SMAW)
- Submerged arc welding (SAW)
Located in Chicago, Illinois, our 135,000 square foot facility—equipped with fully automated, CNC-controlled welding equipment—allows us to meet virtually any customer specifications on high precision, large volume projects. Our capabilities include:
- Production capacities for large weldments up to 12 feet wide or 80 feet long with the tightest tolerances available in the industry
- Material capabilities for a wide range of metals, such as carbon steel, stainless steel, Hardox® wear plate, Strenx®, and other alloys
To ensure the quality of our products, both our personnel and facilities maintain compliance with the highest certification standards, such as AWS D1.1, D1.6, D9.1, and D10.9.
In understanding different types of welding, and which is best suited for a specific project, one must consider many properties, applications and more. Over the years, there have been many advances that have allowed welders to more easily join different metals and materials. As specialized welding techniques are developed to better suit the needs of specific industry challenges, it may become less clear which option will be best for the job at hand. G.E. Mathis Company’s team of experts are on hand to review projects with our customers in order to select the best option available.
To determine which type of welding is best suited for a specific project, welders must consider the physical properties of the work-piece and filler material, desired product specifications, and the necessary equipment and power supplies.
Let’s look at some of today’s most widely used welding methods and how they differ:
Submerged Arc Welding (SAW)
Requiring a continuous electrode feed to create an arc between a welding rod and the workpiece, this type of welding adds a thick granular flux to form a shield. The result is a flux blanket, under which the arc is submerged to protect the weld zone from atmospheric contamination. This process can be automated, mechanized, or semi-automated through the use of hand-held guns.
Shielded Metal Arc Welding (SMAW)
Commonly referred to as “stick” welding, shielded metal arc welding (SMAW) is a manual process requiring a welding rod coated in flux, which carries a high-power electric current. During welding, the electrode’s flux coating breaks down, creating a layer of slag as well as a gas shield to protect the weld until it cools. Final products may require finishing services, however, as molten splatter is a common occurrence.
Gas Metal Arc Welding (GMAW)
Gas metal arc welding, also called MIG (metal inert gas) welding, is distinct in its use of an adjustable, continuous solid wire electrode feed. Versatile and easily automated, GMAW only requires that the welder guides the welding gun in the proper position and orientation along the fusion point. The electric arc formed between the electrode and the workpiece heats and melts the metals to join them.
Flux Core Arc Welding (FCAW)
Similar to MIG welding, flux core arc welding uses a tubular wire filled with flux in place of a solid wire. Dual-shielded FCAW uses the flux with an external shielding gas for protection, while self-shielded FCAW relies only on flux to protect the molten weld puddle, making this an ideal option for outdoor applications. As an automated process, FCAW is also popular for projects requiring quick turnaround times.
Gas Tungsten Arc Welding (GTAW)
Gas tungsten arc welding, more commonly referred to as TIG (tungsten inert gas) welding, uses a non-consumable tungsten welding rod (or electrode) to apply intense heat to the base metal. This produces an autogenous weld by melting two pieces of metal directly together without a filler. TIG welds are also protected by an external shielding gas — usually argon. This method produces strong, high-quality welds, though the process can be painstaking, requiring extreme focus and precision to weld the small space between the arc and the work-piece.
Specialty Welding at G.E. Mathis Company
At G.E. Mathis Company, our experienced, skilled team of welders is certified to AWS D1.1, D1.6, D9.1, and D10.9 standards. We work regularly with HARDOX wear plate, high-strength steels such as STRENX, carbon steel, stainless steel, as well as other alloys.
To learn more about specialty welding, or to discuss how our team of experts can help with your next project, contact us today.
Welding is instrumental to the success of a construction project. Not only is it a handy repair tool for broken and damaged machine parts, it is the mainstay of production supplying any construction endeavor with the required raw materials to progress at the desired pace.
It is undertaken by skilled operators and has to be performed according to pre-defined mandates and a set of compliance rules in order to ensure that the joints are strong and immune to jostling and rust.
WELDING, ITS IMPORTANCE AND IMPERATIVE IN CONSTRUCTION
All kinds of welding rely on generating an arc that is capable of raising the temperature of the parent material to the melting point. It is then fused with a filler metal which by rule of thumb is chosen to be structurally
stronger than the original base. Ranging from sub-merged arc to metal active gas to manual metal arc, different welding processes are leveraged at construction sites around the world to serve unique needs. Special ventures in the aerospace and naval industries have progressed to laser arc hybrid welding and electron beam technology.
An operation team manipulating welding equipment must be knowledgeable of the nuances of this technique in order to ensure the integrity of welded joints and thus by association created products. A large scale construction project is only as durable as the quality of its individual components.
Also according to the Consumer Justice Group report, welding tasked to untrained labor is an extremely hazardous proposition. Thousands of injuries occur right on-site because of careless handling of equipment or experimentation by unskilled staff.
SOME BEST PRACTICES TO KEEP IN MIND
As far as possible, complicated welding responsibilities must be left to professionals. Construction projects call for the employment of AWS (American Welding Society) certified welders who are cognizant of the involved risks and capable of handling them expertly.
Especially for the frequently used MIG (Metal Inert Gas) welding:
- Care should be taken to ensure that welders wear protective gear (including an auto-darkening face shield) to eliminate the riskofcontact burns and blisters
- Cotton is the chosen material because it doesn’t melt like polyester
- Be on the look-out for splatters of molten metal and grinding sparks which can cause a fire
- Avoid using galvanized steel as the parent material since it gives off carcinogenic vapors
G.E. MATHIS COMPANY AND ITS HISTORY OF EXCELLENCE:
G.E. Mathis Company has been an industry renowned name in the field of precision arc and MIG welding. We have perfected our craft over 100 years of rigorous practice assisting construction companies, OEMs, independent projects and manufacturers with their welding and rolling needs. ISO 9001:2015 certified, we are the gold standard in the welding and precision services domain.
Contact us today at 773.586.3800 and we will be glad to discuss how our fabrication and welding capabilities may help with your next project