| 摘要 |
PURPOSE:To produce a high strength hot rolled steel sheet having good workability at a low cost by subjecting a continuously cast high-temp. slab which is made of the specific compsn. consisting of C, Si, Mn, Cr, S, Al, and Fe and is quickly cooled to high-temp. hot rolling under adequate conditions. CONSTITUTION:The steel consisting of 0.03-0.2wt% C, 0.2-1.5% Si, 0.6-2.5% Mn, 0.3-1.5% Cr, <=0.01% S, 0.01-0.06% solAl, and th balance Fe and inevitable impurities is continuously cast at a cooling rate of >=50 deg.C/min in the stage of solidification. The resultant high-temp. slab is subjected to holding as necessary and the hot rolling thereof is started before the temp. thereof falls to 550 deg.C after heating the above-mentioned slab if the slab temp. is <1.050 deg.C or without heating the slab if the temp. is >=1,050 deg.C. The hot rolling is ended at the temp. above the Ar3 point, then the steel sheet is subjected to the prescribed controlled cooling. The high strength hot rolled steel sheet of a transformation strengthened type contg. bainite is thus obtd. at a low heating cost. |
