Oscillated electron beam welding with cosmetic welding was applied to 5mm AF1410 steel. Microstructural features and tensile failure fractures of joints were examined by means of OM

SEM and microhardness tester. Results showed that the heat affected zone (HAZ) contains light etched zone and dark etched zone

which are composed of martensite (M)

M+ reverted austenite (Ar) respectively; the weld zone (WZ) is divided into 3 different zones

namely remelted zone

normalized zone and tempered zone

and occupied by columnar grains

besides martensite exists in intragranular areas and retained austenite (A) exists at intergranular areas. After post-weld heat treatment

microhardness and microstructure of joint are nearly the same as base metal. The room tensile strength of joint reaches 98% of base metal and all cracks initiate at HAZ and propagate through the whole WZ in60° direction.