| 摘要 |
PURPOSE:To produce a high-carbon steel strip having high strength and excellent ductility at a low cost by subjecting a cold rolled steel strip consisting of specifically composed of C, Si, Mn, P, S, Cr and Fe to a specific heat treatment. CONSTITUTION:The cold rolled steel strip consisting of 0.20-0.70wt% C, 0.5-3.0% Si, 0.5-2.0% Mn, <=0.010% P, <=0.010% S, <=0.5% Cr and the balance Fe and unavoidable impurities is heated for 1-10min to the temp. above Ac1 and below Ac3 to form austenite at >=50%. The above-mentioned steel strip is thereafter quickly cooled at a cooling rate of >=20 deg.C/sec by mist cooling, etc. down to 500 deg.C to prevent the precipitation of pearlite. The steel strip is then slowly cooled down to the holding temp. below 500 deg.C at <20 deg.C/sec and is held at 350-450 deg.C holding temp. for 1-15min to form bainite and to stabilize the austenite. The steel strip is thereafter cooled down to the room temp. by air cooling, etc., by which the high-carbon steel strip having about 80-140kg/mm<2> tensile strength and excellent ductility is obtd. |
