| 摘要 |
PURPOSE: To produce a thick high tensile strength steel plate excellent in weldability, at the time of subjecting a steel whose componental compsn. and Pcm value are prescribed to hot rolling, by satisfying the specified inequality by the effective Nb content, Ceq value, V content and steel plate thickness. CONSTITUTION: A steel having a compsn. contg., by weight, 0.06 to 0.1% C, 0. 01 to 0.4% Si, 0.5 to 1.6% Mn, <=0.5% Mo, 0.005 to 0.05% Nb, <=0.1% V, 0.005 to 0.1%. Al, 0.0005 to 0.008% N, <0.005% Ti and <0.003% B, and in which Pcm value defined by the formula I is regulated to <=0.2 is subjected to hot rolling in the temp. range of 1000 to 1250 deg.C. At this time, the amt. of solid solution Nb calculated by the formula II is defined as the effective Nb content and the Ceq value defined by the formula III, the effective Nb content and the steel plate thickness t(mm) are allowed to satisfy the inequality shown by 1500×effective Nb+800V+675×Ceq>=t+210. Thus, the 600N/mm<2> class thick high tensile strength steel plate excellent in weldability and mechanical properties in the center part of the plate thickness can be obtd.
|
