| 摘要 |
PURPOSE:To obtain a high yield point high tensile steel having excellent weldability and a light degree of anisotropy by ending the rolling of a steel contg. C, Mn and Si in a prescribed temp. range, starting force cooling in succession before the temp. falls down to a specific temp., ceasing the cooling in a specific temp. range and further holding the steel at the prescribed temp. range below said range. CONSTITUTION:A steel contg., by weight, 0.03-0.12% C, 0.60-2.00% Mn and 0.15-0.50% Si is rolled and the rolling is ended at the temp. in an (Ar3+10 deg.C)- (Ar3-20 deg.C) range to accelerate the formation of fine alpha grains. Force cooling is started in succession at 5-20 deg.C/sec. cooling rate before the temp. drop of the steel after the end of the rolling attains <=50 deg.C, and the force cooling is ceased at 500-350 deg.C. The steel which is ceased of the force cooling is maintained at 300-350 deg.C for >=90min to avert the phenomenon of losing the high yield point. As a result, a high yield point high tensile steel, more particularly, a thick steel plate for ship building are advantageously produced. |
