| 摘要 |
PURPOSE:To prevent surface cracking and to improve the yield of a product by cooling a continuously cast steel ingot in a cooling process at a specific cooling rate and starting hot rolling in a prescribed temp. range. CONSTITUTION:The steel ingot in the cooling process is cooled at a cooling rate of 1.0-10.0 deg.C/sec until the temp. for starting the hot rolling is attained and the hot rolling is started as it is at 1,050-950 deg.C at the time of subjecting the above-mentioned steel ingot to direct rolling. Since the cooling rate is controlled to the specific range, the remaining of the unsolidified part in the hot ingot fed to the rolling stage can be prevented. The surface cracking arising from the embrittlement of the liquid metal is, therefore, prevented and since the temp. for starting the hot rolling is controlled to the prescribed range, the deposition of sulfide from the liquid metal is prevented. The surface cracking of the steel ingot is prevented and the yield of the product is improved by such remedies in both ways.
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