Laser Welding of Two Super-fine Grain Steels

The strength and toughnessof super-fine grain steels are greatly increased because of its micrometer or sub-micrometer grade grain size.In this paper the weldability of super-fine gum steels and characteristics of laser welding are discussed, the experiments of laser welding of super-fine grain steels are carried out, and the results of laser welding are compared with those of MAG welding and plasma arc welding. The coarse grain zones of laser welded joint of super-fine grain steel show good toughness. The hardening tendency of coarse grain zones is reduced if a low laser power and a slow welding speed are adopted.The tensile strength of laser welded joint of SS400 steel, which was rolled at higher temperature, is higher than that of parent metal. The welded joint of deeply rolled steel, which was work-hardened, has softening zones of recrystallization. The tensile strength of the joint is not affected if the softening zones are narrow.The laser welded joints of both SS400 steel and workhardeened steel have good bending ductility.