| 摘要 |
PURPOSE:To eliminate deviation in strength over whole length of steel strip to improve the yield, by hot rolling steel having a specified compsn., then winding said strip at a specified temp., and fitting heat insulator cover thereto at heat insulating temp. and time indicated by a specified formula. CONSTITUTION:Steel contg. by weight, 0.10-0.60% C, <=0.6% Si, 0.8-2.0% Mn, <=0.030% P, <=0.030% S, 0.005-0.080% Al, <=0.015% N as basic components, if necessary, each <=0.100% one or >=2 kinds among Cr, Mo, Ni, Nb, V, Ti is hot rolled. The steel is wound at >=450 deg.C, then heat insulating cover is fitted under conditions of heat insulating temp. and time satisfying P=T(20+logt), 16X10<3=P<=20X10<3> [P: tempering parameter, T: heat insulating temp. ( deg.K), t: heat insulating time (hr)]. By this way, material qualities of top and rear ends of steel strip are ensured to the same level as that at center part in longitudinal direction thereof.
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