MANUFACTURING METHOD OF ROLLED STEEL BLOCK FOR PREVENTING SURFACE DEFECT CAUSED DURING CONTINUOUS CASTING AND FOLLOWING BLOOM ROLLING

摘要

PROBLEM TO BE SOLVED: To provide a method which prevents occurrence of a surface crack on a rolled steel block manufactured through bloom rolling of a continuously cast bloom.;SOLUTION: The continuously cast bloom in a rectangular cross section is spray-cooled in a bloom cooler, and is bloom-rolled into the steel block after heated in a heating furnace. In the method, in relation to a time from a starting of continuous casting to arrival to the bloom cooler, management of a starting temperature of cooling and control of cooling speed in the bloom cooler, and management of heating temperature and retention time in the heating furnace to suit the bloom-rolling are conducted. A temperature difference between the bloom surface and center is controlled within a designated range at the time of extraction from the heating furnace and then the extracted bloom is subjected to bloom-rolling. Furthermore, in the cooling of the bloom in the bloom cooler from charging the bloom into the bloom cooler to starting of bloom-rolling, keeping a face on a short side of the rectangular cross section of the bloom upward, the side face of the bloom during cooling in the bloom cooler coincides with a side face of the bloom at the time of starting rolling reduction for bloom-rolling so that the cooling is applied from the side face of the bloom.;COPYRIGHT: (C)2005,JPO&NCIPI