MIG Welding AluminiumMIG is the most commonly used process for welding aluminium and its alloys, and standard MIG welding equipment is suitable. When welding aluminium absolute cleanliness is essential. The tenacious surface oxide and all dirt, grease and other contaminants must be removed before welding. On sections above 10mm it may be necessary to pre-heat. When MIG welding aluminium a totally inert shielding gas must be used. Pure argon, helium or argon-helium mixtures are standard. Any active component (O2, CO2) will oxidise and ruin the weld. MIG consumables are solid wires based on pure Al, Al-Mg or Al-Si compositions. It is normal to try to use a filler material that is as close to the parent material as possible but this is not always possible. Aluminium MIG wires are soft and tend to buckle when being fed. To minimise this effect special liners and feed rolls are used and push/pull guns may be beneficial. The other main welding problems encountered in MIG welding aluminium are porosity and solidification or liquation cracking in sensitive alloys. Attention to joint design, cleaning procedures and use of preheat, correct filler, current, and heat input, are vital if these problems are to be avoided. MIG welding aluminium can produce particulate fume (aluminium oxide) and ozone gas in considerable amounts particularly at high currents in pure argon shielding gas.
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