Nippon Steel Corporation

Tadashi Koseki

Tadashi Ishikawa

Takehiro Inoue

Hiroshi Shimanuki

Masanori Minagawa

Akihiko Kojima

Jun Otani

A large-heat-input butt-welded joint of welded structures prepared by butt-welding high-strength steel plates over 50 mm in thickness, having excellent brittle fracture resistance, is characterized by: (a1) the hardness of the weld metal is not more than 110% of the hardness of the base metal or (a2) the hardness of the weld metal is not less than 70% and not more than 110% of the hardness of the base metal, and, as required, (b) the width of the weld metal is not more than 70% of the plate thickness of the base metal, (c) the width of the region affected by welding whose hardness is softened to not more than 95% of the hardness of the non-heat-affected base metal has a width not less than 5 mm, and/or (d) the prior austenite grain size in the heat-affected zone (HAZ) contacting the welding fusion line is not more than 200 &#x3bc;m.

Large-heat-input butt welded joints having excellent brittle fracture resistance

A welding method for manufacturing welded structures having excellent properties to prevent the propagation of brittle fracture occurring in welded joints, characterized by the step of forming a repair weld having a greater toughness than that of a butt weld and an outer edge whose angle &#x3c6; with respect to the longitudinal direction of the butt weld is not less than 10 degrees and not more than 60 degrees, by applying repair welding to a region to arrest a brittle crack in a butt-welded joint where a brittle crack is likely to propagate after removing part of the butt-welded joint, in said region, by gouging or machining.

Welded structure having excellent resistance to brittle crack propagation and welding method therefor

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Futtsu, Japan

Tadashi Koseki