PREVENTION OF LAMELLAR TEAR TYPE WELDING CRACK AT BUTT WELD JOINT

摘要

PURPOSE:To enable to prevent lamellar tear welding cracks at butt weld joints, by removing deleterious inclusions by enlarging the boundary between inclusions and base metal by heating the groove face and detecting the location of inclusions with an inspection method. CONSTITUTION:Welding groove face 2 and its vicinity of rolled thick steel plate 1 are heated with burner 5 and rapidly quenched with water, etc., and thus a tensile thermal stress is generated in the direction of thickness of steel plate 1. In this way, the boundary between harmfull nonmetallic inclusion layer 3 and the base metal of steel plate 1 is enlarged at beveling surface 2. After that the existence of inclusion layer 3 is detected by a surface defect inspection method. In this case, since nondeleterious nonmetallic inclusions 4 does not open, they will not appear as a defect in the surface defect inspection method. Then the opening and its vicinity are shaved with grinder, etc., and a hole is bored. Then the bore 6 is filled by welding to mend and then butt weld is performed.