HIGH HEAT INPUT BUTT WELDING JOINT EXHIBITING EXCELLENT CHARACTERISTICS IN RESISTANCE TO OCCURRENCE OF BRITTLE FRACTURE

摘要

A high heat input butt welding joint exhibiting excellent characteristics in the resistance to the occurrence of brittle fracture which is a butt welding joint in a welded structure, characterized in that (a1) a weld metal has a hardness being 110 % or less relative to that of a base material, or (a2) a weld metal has a hardness being 70 to 110 % relative to that of a base material, and optionally, (b) a weld metal has a width being 70 % or less relative to the thickness of a base plate, (c) the region of a weld heat affected zone being so softened as to have a hardness being 95 % or less relative to that of the base material zone not affected by heat has a width of 5 mm or more, and/or (d) the weld-affected zone (HAZ) adjacent to a weld melt line has an old austenite grain diameter of 200 mum or less.