Nonaqueous cold die production manner of the X70 class steel sheet below board thickness 15mm which possesses high bombardment absorbed energy.

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a steel sheet with a sheet thickness of ≤15 mm which has strength in an X70 class and vE_-20 of ≥250J as it is cold-rolled without water.;SOLUTION: In the method for producing an X70 class steel sheet with a sheet thickness of ≤15 mm which has high impact absorbed energy, a slab having chemical components containing, by mass, 0.03 to 0.06% C, 1.4 to 2.0% Mn, 0.05 to 0.5% Mo, 0.01 to 0.1% Nb, ≤0.01% P, ≤0.003% S and ≤0.005% O, and further containing one or more metals selected from 0.05 to 0.5% Si, 0.001 to 0.05% Al and 0.005 to 0.05% Ti, and the balance iron with inevitable impurities is subjected to hot rolling so as to control the thickness of the slab before the rolling to ≥10 times that of the steel sheet after the rolling, and to be heated to ≥1,000°C. In this case, the rolling is finished so that the cumulative draft is controlled to 20 to 60% in the temperature range of Ar₃ to Ar₃+100°C, and, after that, air cooling is applied therefor.;COPYRIGHT: (C)2003,JPO