Induction assisted laser beam welding of HSLA steel sheets

The laser beam weldability of structural steels is limited by the hardness increase and the lost of toughness in the weld seam, depending on the metallurgical concepts of the steel grades. That's why, the laser welding behaviour of a Q + T HSLA steel (S690QL), two thermo mechanical treated HSLA steels (S500MC and S700MC) and a heat treatable steel (C45) were investigated in the thickness range of 3 up to 6.8 mm. In order to adjust the temperature time cycle during laser beam welding to the material requirements, an inductive heat source was integrated within the laser welding process. Several strategies of induction assisted laser beam welding processes have been tested and compared to each other regarding the applied temperature fields. The welding results were evaluated with respect to the metallurgical reaction and the resulting mechanical seam properties.