新一代钢铁材料为晶粒尺寸在微米或亚微米级的铁素体钢,其强度比普通铁素体钢提高一倍,同时又具有较好的韧性.解决该钢的焊接问题,是新一代钢铁材料成功的关键.本文采用CO2激光进行SS400钢的不填丝焊接,获得了强韧性高于母材的接头.当焊缝和热影响区金属主要由下贝氏体组成时,冲击功最高.当出现侧板条铁素体或低碳马氏体含量较多,冲击功下降,但都高于母材.接头硬度值低于HV330,无软化区,具有良好的弯曲塑性,强度高于母材金属.

New generation steels have double strength and higher toughness than the normal ferrite steels because of their micrometer or sub-micrometer sized grains. The weldability of the steels is the key for the success of the steels. In this paper SS400 steel is welded by CO2 laser beam and welded joint with higher toughness and strength than the base metal is obtained. When the microstructures of weld metal and coarse-grained HAZ mainly consist of lower bainite the toughness is the highest. When ferrite side plates occur or the microstructures contain high percentage of martensite. the toughness decreases , but is still higher than that of base metal. The hardness of welded joint is lower than Hv330 and there is no softened zone. The welded joint has good bending ductility and its tensile strength is higher than that of base metal.