| 摘要 |
PURPOSE: To produce a steel for low temp. use excellent in the toughness of the weld heat affected zone by specifying the comps. constituted of C, Si, Mn, P, S, Al, Ti, N, Mg and Fe and uniformly and finely dispersing Al-Ti-Mg mutiple oxide therein. CONSTITUTION: A steel for low temp. use having a compsn. contg., by weight, 0.03 to 0.09% C, <=0.50% Si, 0.50 to 1.8% Mn, <=0.02% P, 0.002 to 0.010% S, 0.005 to 0.020% Al, 0.005 to 0.020% Ti, 0.0020 to 0.0006% N and <=0.0010% Mg, furthermore contg., at need, prescribed amounts of Cu, Ni, Nb, V, Cr, Mo and B, and the balance Fe with inevitable impurities is obtd. Moreover, a multiple oxide consisting essentially of Al-Ti-Mg is allowed to contain in the base metal of the same steel. This multiple oxide is dispersed in such a manner that the grain size is regulated to 0.01 to 1.0μm and the number of the grains is regulated to 1×10<4> to 2×10<5> pieces/mm<2> .
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