Microstructure and mechanical properties of welded joint of nanostructured bainite steel with regeneration

Due to the poor weldability of nanostructured bainite steel,a method called welding with regeneration was proposed to obtain a welded joint with the same microstructure as the base metal,so the welded joint could possess the excellent mechanical properties. Regeneration treatment was used after tungsten inert gas (TIG) welding of nanostructured bainite steel. The microstructures of the welded joint were characterized by X-ray diffraction,scanning electron and transmission electron microscopes. The tensile and microhardness tests were carried out to evaluate the mechanical properties. The results show that nanostructured bainite was obtained in the fusion zone and quenched zone with 300 nm and 70 nm thick bainite plates,respectively. The tensile strength of the welded joint was 1 500 MPa,and the microhardness in the fusion zone was 7 000 MPa,which were almost equivalent to those of the base metal.