Laser joining of steel-aluminum joints in T configuration

For the production of steel to aluminium transition joints a laser joining process with an Nd:YAG laser source and a cold wire feeder has been developed. For a good joint strength it is critical to minimize the intermetallic phase buildup during the joining. With careful manipulation of the laser power and the spot position the steel is kept in a solid state and the aluminium is molten, thus ensuring an intermetallic layer thickness of less then 5 µm. To further optimize the joint strength the wetting of the steel by the aluminium has been maximized to increase the load bearing surface. Optimal wetting has been achieved with a 12% aluminium silicon filler wire and zinc coated steel, where the zinc significantly improves the wetting. Because of this the use of flux was not needed. The research has concentrated on the joining of sheet materials in a T configuration. Breaking strengths of up to 150 MPa have been realized for a material thickness of 3 mm and 140 MPa for 5 mm.