Welding Considerations

Gas tungsten arc and gas metal arc welding are the most commonly used processes for welding magnesium alloys. Plasma arc welding is also suitable for magnesium alloys. Oxyfuel gas welding should be used only for temporary repair work, when suitable arc welding equipment is not available.

Magnesium alloys are welded by the gas tungsten arc welding (GTAW) process using techniques and equipment similar to those used for aluminum. Argon, helium, or mixtures of these gases are used for shielding. Alternating current is preferred because of a combination of good arc cleaning action and good joint penetration, although direct current is also used. Direct current with the electrode positive provides excellent cleaning action but is limited to thin base metal. Direct current with the electrode negative is sometimes used for mechanized welding with helium shielding gas to provide deep joint penetration. GTAW is generally recommended for the welding of magnesium alloy castings. Welding is usually limited to the repair of defects in clean castings.

The basic principles for gas metal arc welding (GMAW) of magnesium alloys are the same as for other base metals. The higher filler metal deposition rate of this process reduces the welding time, thereby reducing weld distortion and fabrication costs. Argon is generally used as a shielding gas; occasionally mixtures of argon and helium are used. Pulsed GMAW and short circuit GMAW are both used for magnesium alloys. Higher welding current, to produce spray transfer of the filler metal without pulsing, is also used. Globular transfer is not suitable.