| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a billet in which surface flows of the billet are reduced in blooming a continuously cast steel slab, a micro-porosity at a center part of the billet is prevented without providing any special equipment. SOLUTION: A cast billet from a continuous casting apparatus 1 is soaked at high temperature in a heating furnace 2, and kept in a soaking furnace 3 at the temperature Tk: 1100±50 deg.C lower then the atmospheric temperature in the heating furnace 2, the temperature inside the cast billet is Tm: <=1150 deg.C, and kept in a control furnace 4 at the atmospheric temperature of Tt:1300±50 deg.C higher than the atmospheric temperature on the soaking furnace 3 to keep the temperature inside the cast billet at the temperature not exceeding Tm and to keep the temperature on the surface of the case billet at 1100 deg.C. Then, the case billet is sent to the blooming process from the control furnace 4 and rolled by a blooming mill 5. The surface temperature of the cast billet is Th at which no flaws are generated in the blooming, the temperature inside the case billet is Tm at which no micro-porosity is generated in the center part, surface flows of the billet can be reduced without degrading the productivity of the practical blooming method, and generation of micro-porosity at the center part of the billet can be prevented.
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