Microstructure and mechanical properties of laser welded dissimilar joints between QP and boron alloyed martensitic steels

The newly developed quenching and partitioning (QP) steel QP980 and boron alloyed martensitic steel B1500HS were butt-welded using fiber laser at a constant laser power 4.5 kW and various welding speeds of 4∼10 m/min. Retained austenite was measured in the super-critical HAZ of B1500HS (0.9%), inter-critical HAZ of B1500HS (3.4%) and inter-critical HAZ of QP980 (0.6%), while the sub-critical HAZ of QP980 witnessed decomposition of retained …