| 摘要 |
PURPOSE:To obtain the composite steel plate, as captioned above, suitable for weight reduction of a car body, by a procedure in which the steel composed of specific components, e.g. C, Mn, etc., is hot-rolled at a specific finish temperature, quickly cooled at a specific cooling rate, and then rolled up within a specific temperature range below 230 deg.C. CONSTITUTION:The steel, composed of 0.03-0.13% C, 0.8-1.7% Mn, 0.1% or less Al, 1-2% (excluding 1%) Si, 0.5% or less Cr as needed, and the balance Fe, is hot-rolled to raise its temperature to 780-850 deg.C as a finish temperature, quickly cooled to the temperature below 230 deg.C at an average cooling rate of 30 deg.C/s- 500 deg.C/s, and rolled up while regulating the rolling condition in such a way that the upper and lower limits of the rolling-up temperature is within a temperature width of 100 deg.C and the upper limit does not exceed 230 deg.C. Thus, a composite steel plate, whose yield strength after when being given a process strain will increase further by being heated at approx. 170-200 deg.C, can be obtained. |
