| 摘要 |
To manufacture the titled steel sheet as rolled excellent in the toughness of the base body itself and toughness along its thickness, by uniformly strain-hardening austenitic grains before being transformed so as to obtain the tough structure composed of uniform fine grains after being transformed by rolling with relatively small reduction in an unrecrystallization zone. ! Steel contg. by wt%, 0.01W0.2% C, Si<=1.5% and 0.5W3% Mn is hot-rolled as follows. It is rolled with accumulated reduction ratio of 20W70% in the temp. zone where austenite is partially recrystallized during a rolling pass, to introduce prestrain into the specified austenitic grais. In succession, it is rolled with accumulated reduction ratio >=30% in the temp. zone where austenite is not recrystallized yet, to uniformly strain-harden the whole of austenitic grains. In addition, the ratio of accumulated reduction below Ar3 transformation point (the dual phase zone) is made below 40% when the rolling is finished, so as to obtain the tough structure composed of uniform fine grains after being transformed. ! (C)1983,JPO&Japio |
