18 Resistance spot welding of magnesium alloys

Resistance spot welding (RSW) of magnesium alloy is discussed in this chapter. Surface condition is important for RSW of magnesium due to the high chemical reactivity of magnesium and because oxides that form are hard, strong and electrically insulated. Expulsion, weld strength and electrode life are all related to surface conditions. Welding conditions (welding current, weld time, electrode force and weld spacing), nugget growth and dynamic resistance are discussed and compared with those of steel and aluminum alloys. Microstructure of the nugget and the influence of secondary particles are studied in detail. Technologies and mechanisms of dissimilar joining of magnesium alloy to steel and magnesium to aluminum alloys are also discussed.