| 摘要 |
PURPOSE:To obtain a hot-rolled steel strip having excellent uniformity in the material quality in a thickness direction by limiting the components of the hot-rolled steel stirp and specifying the thickness of the sheet bars in the stage of finish rolling and the cooling rate and coiling temp. after the finish rolling. CONSTITUTION:A continuous casting material or ingot making material contg., by weight, 0.20-0.60% C, 0.05-0.50% Si, <=1.80% Mn, <=0.040% P, and <=0.020% S and consisting of the balance substantially Fe is preprd. The finish rolling of the continuous casting material or the like in hot finishing is started at <=30mm. thickness of the sheet bar to be rolled and the temp. differences in the thickness direction are reduced by accelerating the radiation of the heat retained by the steel material. After the rolled material after the finish rolling is cooled down to 530 deg.C at 70-120 deg.C/sec. cooling rate, the material is coiled at 480-530 deg.C, whereby the hot-rolled steel strip having excellent uniformity in material quality more particularly in the thickness direction is obtained. |
