PURPOSE: To obtain the high tensile strength steel for welded structure having excellent stress relief annealing embrittlement resistance by limiting each amt. of alloy elements to be added and limiting their total amt. to be added.
CONSTITUTION: The above high tensile strength steel for welded structure contains, by weight, ≤0.18% C, ≤0.70% Si, ≤2.0% Mo, ≤2.0% Mn, ≤0.020% P and 0.005 to 0.10% Al, according to the require for strength and toughness, furthermore contains one or more kinds among ≤0.7% Cu, ≤2.0% Ni, ≤1.0% Cr, ≤1.0% Mo, ≤0.2% V, ≤0.05% Nb, ≤0.03% Ti and ≤0.015% B, which has the strong point of satisfying the inequality. According to the fig., in the steel satisfying the limited componental area in the above-mentioned manner and having ≤2.0% Ceq (S) value, toughness of ≤-35°C vTr6 is secured even after subjected to heating treatment corresponding to stress relief annealing. Thus, it is clear that the steel has stress relief annealing resistance.
INOUE HISASHI
YAMATO KAZUNARI
