| 摘要 |
PURPOSE:To easily produce a high-strength steel sheet having good ductility by using low alloy components by coiling a specifically composed steel consisting of C, Si, Mn, Al, N and Fe at a low temp. after hot rolling and cooling the steel, then subjecting the steel sheet to a heat treatment under adequate conditions after cold rolling. CONSTITUTION:The steel contg. 0.10-0.45wt% C, 0.5-1.8% Si, 0.5-3.0% Mn, 0.01-0.07% SolAl, and <=0.02% total N, and consisting of the balance Fe and inevitable impurities is coiled at <=650 deg.C after hot rolling and is cooled. The hot rolled sheet is cold rolled directly or after pickling and is then annealed for 0.5-30min in the temp. region of Ac1-(3Ac3+2Ac1)/5. The steel sheet after annealing is cooled down to a temp. region of 350-500 deg.C at a cooling rate of 1-400 deg.C/sec and is subjected to an aging treatment for 1-30min in the above-mentioned temp. region; thereafter, the steel sheet is cooled down to a room temp. The steel sheet which has about >=80kgf/mm<2> strength and is well balanced in the strength and elongation is thus obtd.
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