| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot-rolled steel sheet having a fine structure superior in workability, which has stably improved workability (hole expandability and press formability) by controlling a diameter of aγparticle to 10μm or smaller. SOLUTION: The method for manufacturing the hot-rolled steel sheet superior in the workability comprises the steps of: when rough-rolling a slab into a rough bar with a roughing mill and finish-rolling the rough bar with a finish rolling mill, cooling the roughing-rolled rough bar so that the temperature T<SB>2</SB>of the whole cross section of the rough bar can be an Ar<SB>3</SB>transformation temperature or lower; then heating it so that the temperature of the whole cross section can be the Ac<SB>3</SB>transformation temperature or higher with an induction heating device; cooling the surface of the rough bar to the temperature corresponding to the Ar<SB>3</SB>transformation temperature or lower which has been determined when a cooling rate measured with the high-frequency heating type fully-automatic transformation recording measurement instrument is 80 to 100°C/s, with the use of a high-pressure spraying device; recuperating it to the Ar<SB>3</SB>transformation temperature or higher; and finish-rolling it. COPYRIGHT: (C)2005,JPO&NCIPI
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