METHOD FOR CONTINUOUSLY CASTING BILLET

摘要

PROBLEM TO BE SOLVED: To economically reduce the segregation at the time of continuously casting a billet at a high casting speed by making the solid phase ratio in the center of the cast billet at the inlet side of a light rolling reduction zone to a specific value or lower and the solid phase ratio in the center of the cast billet at the outlet side of the light rolling reduction zone to a specific value or higher and performing the rolling reduction to the range of the light rolling reduction zone using the rolls. SOLUTION: A solid phase ratio in the center of a cast billet at the inlet side of a light rolling reduction zone is made to <=0.3 and the solid phase ratio in the center of the cast billet at the outlet side of the light rolling reduction zone is made to >=0.7. It is preferable to make the solid phase ratio in the center of the cast billet at the inlet side of the light rolling reduction zone to <=0.4, the solid phase ratio in the center of the cast billet at the outlet side of the light rolling reduction zone to >=0.6 and a standard deviation of variation in a casting speed to <=0.05 m/min. The cast billet having good quality can be produced while keeping the high productivity. A merit of energy reduction is obtd. because a blooming process can be omitted and the energy needed to the production is reduced in comparison with the production of the billet with the blooming process after producing the billet in the bloom.