Welding is a vast topic in collision repair, and like many other segments in the industry, ever changing. I aim to address the most common types of welding in the shop, such as Gas Metal Arc Welding (GMAW) — the correct name for what most people call MIG welding (Fig 1).
We’ll take a look both shop and personal safety; power for the welder; weld testing; MIG steel, MIG Aluminum and MIG silicon bronze welding; and finally the types of metal transfer of MIG welding.
In the shop you are likely to be using either a 110v or a 220v welder. Because of that power and the arc that is generated to form the weld, welders must protect themselves and fellow workers from the dangers of the welding process. First, one must be sure that the area set up for the technician to weld in is safe. The welding technician should follow all equipment makers’ recommendations and also check that the cables and connections are in good condition. The welder also needs to know and follow the local electrical codes for extension cords (more on cords later). Workers should never weld in a wet area or while wearing wet clothing, and should not use the welder as storage or a workbench. In keeping with general workplace safety rules, keep the area clean from clutter and debris. Working with the welding helmet down restricts vision enough without being sidelined by a slip or stumble over items in the way.
Personal protective equipment (PPE) such as a welding helmet, respirator and spark protection are necessary to prevent injury. For eye protection, a helmet with at least a grade 9 filter should be used to protect your eyes from ultraviolet damage. If the welding is done at a current above 60 amps, the filter must be darker (a higher number). If the operator is sensitive to ultraviolet exposure (indicated if he or she sunburns easily), a darker shade should be used. Additionally, a safety lens cover should be used over the filter lens. Though not necessary, the auto-darkening helmets are very helpful, as they switch from a nearly clear lens to the proper darkening shade as the arc is struck.
Next is the respirator. Though you don't often think of a respirator in relation to welding, it is necessary in collision repair, where there are often fumes that burn off the vehicle. Even when the weld site is properly cleaned, fumes may be harmful, and in addition there may be natural fumes formed from the welding process. Wear an approved welding respirator, even in a well ventilated area. A welding fume extractor placed above the welding area is also a good idea, but it doesn't take the place of the respirator. Also, don't point a fan at the weld area because it may blow the shielding gas from the weld site and cause poor weld performance.
Your skin, like your eyes, can be damaged from the UV rays produced from the welding process. Protect yourself from these and from spark burns by covering your skin with heavy flame resistant cloth or leather. Use heavy welding gloves with a long cuff and safety glasses with side shields under the helmet. Fasten the top button of your shirt to keep your neck from being burned with UV; and never keep a plastic butane lighter in your pocket, where a stray spark may cause it to explode. Don't weld in an area where there are flammable materials, and always have a fire extinguisher at hand for emergencies.
Shop Safety: Either have a spark and UV shield around the area you are welding to protect your fellow workers, or signal them by saying "welding cover" before you strike an arc.
Vehicle Safety: When a vehicle is being welding, the vehicle must be protected as well. Precautions include covering all glass from sparks around the weld area, disconnecting and isolating the negative battery cable, having the ignition switch in the locked position, disarming the passive restraint system and following the vehicle maker’s recommendation for removal of computer modules when welding or heating within 12 inches of the modules.