Laser beam welding of magnesium to coated high-strength steel 22MnB5

Magnesium alloy AZ31 was laser-welded to AlSi10Fe3-coated high-strength steel 22MnB5. The surface of the 22MnB5 steel sheet was treated by sandblasting before welding. Laser welding of magnesium with steel was found to be a welding-brazing process, due to the large difference in the melting temperatures of steel and magnesium. The liquid magnesium was wetted on the solid steel surface, which thus was a brazing process on the steel side. AZ61 magnesium welding filler was used to improve adhesion of the liquid magnesium to the steel surface. Furthermore, the suitability of using a flux was determined. Welded steel/magnesium joints with a high tensile strength of 2680–3090 N (178–213 MPa) were produced using a flux and inductive preheating of the conditioned steel surface. Under tensile loading, the welded joints did not fail at the steel/magnesium interface, but in the AZ61 magnesium welding filler. Metallurgical bonding at the magnesium/steel interface was attributed to the formation of a thin Al-Fe-rich layer, which is due to the alloyed aluminum (6 mass%) in the magnesium welding filler.