| 摘要 |
PURPOSE: A method of manufacturing a thin steel sheet with a structure of high strength is provided to have material characteristic in tension strength over 70kg/mm2 by applying hot direct rolling. CONSTITUTION: Aluminium killed steel consists of, by weight: 0.015-0.1% of C, not more than 0.015% of S, not more than 0.015% of N, 0.05-0.1% of P, Fe and incidental impurities. Alloy-added steel is continuously cast, and a high-temperature slab is kept for 10-30 minutes without passing through hot-rolling. The slab is hot-rolled and coiled at a temperature lower than 650°C. The slab is cold-rolled with steel forming a large amount of precipitates and then annealed at a temperature of 680-730°C.
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