| 摘要 |
PURPOSE: A method of manufacturing a high strength hot-rolled steel sheet is provided to have tension strength of 70kg/mm2 and yield strength not less than 58kg/mm2 by using not more than 0.03wt% of Si. CONSTITUTION: A slab consists of Fe as a main element, 0.17-0.23wt% of C, not more than 0.03wt% of Si, 1.0-1.6wt% of Mn, not more than 0.04wt% of P, not more than 0.005wt% of S, 0.02-0.05wt% of so/-A/, 0.040-0.045wt% of Nb and 0.040-0.045wt% of V. In hot rolling a steel sheet having a thickness of 1.8-2.3mm with the slab, the rolling temperature is not less than Ar3 critical point. The coiling temperature is maintained 600-650°C after hot rolling, and the hot-rolled steel sheet with yield strength not less than 58kg/mm2 is manufactured.
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