| 摘要 |
PURPOSE:To produce a high-strength hot rolled steel sheet having good workability at a low cost by subjecting the high-temp. slab which has the spe cific compsn. consisting of C, Si, Mn, S, Al, B, Ti and Fe and which is subjected to quick cooling and continuous casting to high-temp. hot rolling under adequate conditions. CONSTITUTION:A steel contg. 0.03-0.2wt% C, 0.02-1.5% Si, 0.6-2.5% Mn, <=0.01% S, 0.01-0.6% solAl, 0.0005-0.01% B, and 0.01-0.1% Ti, added with 0.1-1.0% Cr according to need and consisting of the balance Fe and unavoidable impurities is continuously cast at a cooling rate of >=50 deg.C/min in the stage of solidification. The resulted high-temp. slab is held at >=500 deg.C according to need and the hot rolling thereof is started after heating in the case of <1,050 deg.C or as it is in the case of >=1,050 deg.C before the slab temp. falls down to 550 deg.C. Such hot rolling is ended at the temp. of the Ar3 point or above and thereafter the steel sheet is subjected to the prescribed controlled cooling. The transformation strengthened high-strength hot rolled steel sheet contg. bainite is thus obtd. at a low heating cost. |
