Heat treatment of welded joints of steel 0.3С–1Cr–1Si produced by high-power fiber lasers

•Fiber laser welding of 10 mm thick medium-carbon steels without cracks.•The hardness of the weld is 8500–9000 MPa because of the high speeds of welding and high cooling rates.•Heat treatment was carried out on two levels: quenching+middle tempering and high tempering.•Evolution of the microstructure and mechanical properties before and after heat treatment of the welded joint.

The effect of heat treatment on the welded joints of steel grade 0.3С–1Cr–1Si produced by 30 kW power fiber lasers was investigated in the paper. The speed of the welding process was 20 mm/s. Heat treatment was carried out on two levels, quenching with subsequent middle tempering and high tempering. The samples were examined before and after heat treatment, macro- and microstructure were studied using SEM, UTS, three points bent test, microhardness. The effect of heat treatment was significant: it allowed reduction of the weld hardness of considerably and enhancement of its ductility.