TIG Welding AluminiumTIG welding is a high quality process widely used for welding aluminium, particularly in section size up to about 6mm. The process may be operated with or without filler. AC TIG welding equipment is frequently used to take advantage of the alternating heating and oxide cleaning cycles. Many electronic power sources allow the AC waveform to be adjusted, and provide facilities for pre- and post- gas flow and current slope-in and slope-out. DC equipment may also be suitable. When TIG welding aluminium a totally inert shielding gas must be used to protect the tungsten electrode and the weld pool. Pure argon and argon-helium mixtures are standard for use with AC TIG and helium is used with DCEP. Zirconiated tungsten electrodes are usually used for AC TIG welding. TIG fillers are cut lengths of solid wire 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. The TIG process gives high quality welds, normally with very low defect levels, but if the tungsten electrode is allowed to touch the weld pool tungsten particles can be melted off and give inclusions. Other welding problems that may be encountered in TIG welding aluminium are porosity and solidification or liquation cracking in sensitive alloys. The tenacious surface oxide and all dirt, grease and other contaminants must be removed before welding since with TIG welding there are no fluxes to cope with these impurities. TIG welding aluminium normally produces very little particulate fume but ozone gas may be generated at high currents in pure argon shielding gas.
|
