The chemical properties of aluminium die casting must be taken into account for welding. Some of the important factors include the melting temperature, colour change, nonmagnetic characteristics, electrical properties and thermal properties. One of the main issues with welding aluminium die casting is that internal gas in the die casting makes both the weld and the metal next to the weld very porous. This produces a weaker weld then when joining other types of metal. Die-casting contains copper which makes welding aluminium more difficult because the aluminium is more susceptible to heat cracking.
Choose an appropriate environment for aluminium die cast welding. You want to weld indoors in a dry area free of drafts. Any humidity or moisture in the air can cause problems with the weld. Try to avoid welding when the air humidity is high if welding outside. However, it is best to avoid any moisture altogether in a dedicated room designed specifically for this type of welding.
Wipe the welding joint with acetone-soaked cloth to remove any grease or oil. Do not use water to clean the joint. Make sure you clean the joint and the surrounding area. Extend this cleaning to 25 millimetres on either side of the joint.
Remove the thin layer of oxide found on the aluminium die casting with a stainless steel brush that has only been used on aluminium. Do not use a grinding disk as this will deposit bits of dust and particles on the welding surface. It is best to start welding directly after cleaning though you can wait as long as three hours after cleaning.
Check that the welding materials are correct, as aluminium die casting uses a mixture of argon and helium that is 99.99 per cent pure. Clean the welding wire and filler rods that will be used if they are dirty. Clean the filler rods with stainless steel wool right before using.
Preheat the die casting before welding. The necessary preheating temperature depends on the size and type of die casting. Aluminium die casting that is 8 millimetres thick will require a starting temperature of 100 degrees Celsius. Larger die casting and those that are very complex require preheating temperatures of 350-400 degrees Celsius.
Choose the welding filler material based on the type of welding you are doing. Repairing welds, repairing cracks, cosmetic repairs and joining of multiple castings require different filling material. For aluminium welding any type of welding can be used though MIG, metal inert gas, and TIG, tungsten inert gas, welding are recommended for durable and high-quality welds. TIG is recommended for light gauge work and MIG for thicker welds.
Things you need
- Dry, moisture-free room for welding
- Stainless steel, wire brush
- Argona nd helium welding gas, 99.9 per cent pure
- Filler wire
- Filler rod
- MIG or TIG welder