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Welding processes, protocols and certification

A look at MAG, STRSW, weld bonding, MIG brazing, MIG aluminum and more for steel and aluminum
Wednesday, September 30, 2015 - 07:00
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Welding has become a hot topic as of late. After structural repair procedures, welding is one of the most improperly performed procedures in collision repair. This can be due to a wide range of issues within the repair facility. Sometimes the equipment is outdated, damaged or simply not even in the shop, other times technician skill and training is lacking. Most often, it tends to be a combination of the two.

Here we are going to discuss the different types of welding methods used for steel and aluminum and the equipment and certifications required. Welding has become a big topic, with the 2015 Ford F-150, which is primarily aluminum, driving discussions, and because of the introduction of some new advanced high-strength steels (AHSS). Many OEMs have had to redesign their tool and equipment requirements, along with their training programs, because of these new substrates, or entirely make a new repair training program. Most of the aluminum collision repair certification programs require specific structural repair equipment and tools, welding equipment and certification to be on their program.        

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MAG (Metal Active Gas) welding steel
Only inert gases or gas mixtures are used for the shielding gas when MIG (Metal Inert Gas) welding. Typical inert gases used for MIG welding are argon and helium. These gases are usually used for MIG welding of aluminum and other non-ferrous metals.

MAG welding uses active gas mixtures that have been developed primarily for welding steels. Typical shielding gases are mixtures of argon, carbon dioxide and oxygen. Generally in collision repair the gas mixture is 75 percet Ar/25 percent CO2; 70 percent Ar/30 percent CO2; or 65 percent Ar/35 percent CO2.

The composition of the shielding gas has a substantial effect on the stability of the arc, metal transfer and the amount of spatter. The shielding gas also affects the behavior of the weld pool, particularly its penetration and the mechanical properties of the welded joint. At one time MAG welding was the only way to weld panels together in the collision repair field. Once Squeeze Type Resistance Spot Welders (STRSW) were developed for the collision industry, MAG was still preferred. But due to the development of AHSS and the heat affect on the these metals, AHSS welding manufactures were forced to produce more advanced STRSW. Although STRSW is the preferred method, MAG welding is still allowed by many OEMs for outer panel replacement.  MAG is even required in certain situations where the STRSW arms cannot reach both sides of the panel or for certain structural component replacement. Obviously, MAG is required for seam welding in sectioned areas.     

STRSW

Squeeze Type Resistance Spot Welding is the preferred method for replacing outer panel structural components, as per most OEM replacement procedures. In some cases, the OEM requires STRSW for replacement of their components, providing the arms can reach both sides of the flange. Some manufactures will allow STRSW on flanges and in areas accessible by the arms. Since no one allows single-sided welding, most OEMs will allow MAG plug welds and some limited OEMs require rivets in areas where there is no backside access. STRSW has advanced to meet AHSS needs and ensure a small heat affect zone (HAZ). To be current with the types of steel materials utilized in late-model vehicles, most of the STRSW equipment you should own should have been purchased within the past five years. STRSW is not used for aluminum repair.  

2mm to 2mm plate; 300mm long open butt weld 3mm plate to 3mm plate T weld 4mm cast to 2mm plate
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