Base-Metal Preparation – If you want to weld aluminum, you must take a good care of the base material and clean it thoroughly. Remove any aluminum oxide and hydrocarbon contamination from cutting solvents or oils, so you can perform the aluminum fabrication well. To clean these oxides and other contaminants, use a stainless steel bristle wire brush, as it is the most efficient cleaning method. Another alternative cleaning method is using chemical etching solutions, which must be removed from the aluminum work before welding. While aluminum oxide on the material surface melts at 110°C, the base-material aluminum underneath melts at 650°C.
Preheating – To complete your aluminum fabrication job better and avoid weld cracking, you need to preheat the aluminum piece that you are going to work. When preheating the aluminum workpiece, make sure the temperature is not over 110°C. To avoid overheating, you can use a temperature indicator. At the start point and the end point of the area to be welded on the workpiece, place two tack welds.
Welding Guns – The best tool for welding aluminum fabrication is a welding gun liner. This tool is easy to use, but also very safe. Restrict both liner ends to prevent gaps appearances between the gas diffuser on the gun and the liner, as well as to prevent wire chaffing. To minimize the risk of abrasive aluminum oxide which commonly leads to wire-feeding problems, change the liners more often. If the welding current exceeds the limit of 200 Ampers, you can use a water-cooled gun to reduce the buildup of heat.
Push Technique – Did you know that pushing the welding gun away from the weld instead of pulling it provides better welding results? This so-called push technique provides a cleaner action, reduced weld contamination and an improved shielding-gas coverage.
Travel Speed – The best aluminum weld is performed quickly and hot. Unlike steel or other metals, the aluminum has a high thermal conductivity that requires use of hotter amperage/voltage and higher weld travel speeds. If the weld travel speed is not running at the right high speed, there is a big risk of creating a huge burn-through.
Reference: A Complete Guide To Aluminium Fabrication
