| 摘要 |
PURPOSE:To obtain a steel sheet having high strength, excellent low-temp. toughness and excellent resistance to hydrogen induced cracking in sour environment by subjecting a steel which is decreased in the content of Mn, is added with Cu as a substitutive element thereof and is limited in contents of other components to hot rolling then to air cooling or cooling under specific conditions. CONSTITUTION:The steel essentially consisting of 0.01-0.15wt% C, 0.01-0.5% Si, <=0.3% Mn, 1.2-3.0% Cu, 0.005-0.1% Al, <=0.015% P, and <=0.010% S, contg. >=1 kind among the following elements and consisting of the balance iron and inevitable impurities is used: <=0.1% Nb, <=0.005% B, 0.005-0.025% Ti, and <=0.005% Ca. After such steel is subjected to hot rolling, the steel is subjected to air cooling or accelerated cooling down to <=600 deg.C at a cooling rate of <=100 deg.C/sec. The above-mentioned steel sheet is further reheated to a temp. range from a room temp. up to the Ac1 transformation point at need. The above-mentioned steel sheet is adequate as a transport line pipe for petroleum and natural gas.
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