HT590MPa CLASS REFRACTORY STEEL FOR WELDED STRUCTURE HAVING EXCELLENT GALVANIZING CRACK RESISTANCE IN WELD ZONE AND ITS PRODUCTION METHOD

溶接部の耐亜鉛めっき割れ性に優れたHT590MPa級溶接構造用耐火鋼とその製造方法

Abstract

PROBLEM TO BE SOLVED: To provide a HT590MPa class refractory steel for welded structure having excellent galvanizing crack resistance in the weld zone. SOLUTION: The HT590MPa class refractory steel for welded structure having excellent galvanizing crack resistance contains, by weight, 0.01 to 0.12% C, 0.02 to 0.5% Si, 0.8 to 3% Mn, ≤0.03% P, 0.0005 to 0.03% S, 0.001 to 0.2% Nb, 0.6 to 1.2% Mo, 0.0005 to 0.05% Al, 0.003 to 0.05% Ti, 0.0001 to 0.01% Mg and 0.0001 to 0.01% Ca, further satisfying the relation of free[Mg]=Total[Mg]-[Mg] contained in the total oxide≥5 ppm, and the balance iron with inevitable impurities, and in which old austenite grain sizes in the weld HAZ structure are ≤200 μm, and also, the grain boundary part includes grain boundary ferrite. COPYRIGHT: (C)2006,JPO&NCIPI
【課題】 溶接部の耐亜鉛めっき割れ特性に優れたHT590MPa級溶接構造用耐火鋼を提供する。 【解決手段】 重量%で、C:0.01〜0.12%、Si:0.02〜0.5%、Mn:0.8〜3%、P:≦0.03%、S:0.0005〜0.03%、Nb:0.001〜0.2%、Mo:0.6〜1.2%、Al:0.0005〜0.05%、Ti:0.003〜0.05%、Mg:0.0001〜0.01%、Ca:0.0001〜0.01%を含み、さらに free[Mg]=Total[Mg]− 全酸化物中の含有[Mg]≧5ppm なる関係を満足し、残部が鉄および不可避的不純物からなり、溶接部HAZ組織の旧オーステナイト粒径が200μm以下でかつ粒界部に粒界フェライトを有することを特徴とする耐亜鉛めっき割れ性に優れたHT590MPa級溶接構造用耐火鋼。 【選択図】 なし

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