| 摘要 |
PURPOSE: A hot-rolled steel sheet, a cold-rolled steel sheet with high carbon and a production method thereof are provided to have an excellent surface property which have high strength and high hardness simultaneously and to omit a heat treatment process. CONSTITUTION: A production method of a hot-rolled steel sheet and a cold-rolled steel sheet with high carbon executes the following steps. A high carbon rolled steel is prepared being composed of 0.9-1.2 weight% of C; less than 0.5 weight% of Si; 0.1-1.5 weight% of Mn; less than 0.05 weight% of P; less than 0.03 weight% of S; less than 1.5 weight% of one or more elements selected from Cr, Ni, Cu; a remaining weight% of Fe; and other inevitable impurities. A steel sheet is produced executing hot rolling in an austenite region. The steel sheet is rapidly cooled to 520-660 degreeC before starting a phase change in a run-out table[ROT]. A cooling temperature maintained is kept flat. The rolled shit is winded in the cooling temperature maintained. [Reference numerals] (AA) Hot-rolling(perlite); (BB) Souring; (CC) Annealing into spherical shape; (DD) First cold-rolling; (EE) Heat-processing(fine perlite); (FF, JJ) Grinding/Pickling; (GG) Second cold-rolling; (HH) Hot-rolling(fine perlite); (II) Removing post processes; (KK) Cold-rolling |
