Modified laser beam welding of aluminum-silicon coated 22MnB5

Press hardened 22MnB5 is an excellent structural material, but there are several issues when it comes to welding. Especially in the case of overlap joint laser welding, the most severe issue is precipitation of the aluminium silicon (AlSi) coating at the fusion line. If the coating remains on the sheets, an ultimate strength of 20 kN with a crack initiation at the fusion line is reached in tensile tests instead of 30 kN with a crack initiation in the heat affected zone (HAZ) when the coating is removed prior to welding. In the presented work, the influence of coating on the material properties as well as the structure of the precipitation at the fusion line are examined and discussed. It is stated that the precipitation does not consist of AlxFey intermetallic phases, but of an iron, aluminium and silicon solid solution. The fractured surfaces of tensile tests show brittle behavior for the precipitation and ductile behavior for areas where the crack propagated through the steel. A modified beam oscillation in the shape of a recumbent "8" in welding direction is introduced. It was possible to increase the ultimate strength by 10 kN and nearly double the possible elongation.