PURPOSE: To prevent the eccenticity of a core material at the time of continuously casting a complex cast billet by executing the rolling reduction to the last solidified part in a specific condition of an unsolidified cast billet and forcedly forming the last solidified position.
CONSTITUTION: Molten metal 10 is poured around the core material while inserting the core material 2 into both end opening mold 1. By drawing out the solidified shell 11 while continuously solidifying the molten metal 10, the complex cast billet is produced. Then, by executing the rolling reduction to the last solidified part in the unsolidified cast billet satisfying the inequality I, the last solidified position is forcedly formed. In the inequality I S2/S1 ≤0.1, S1 is the cross sectional area of the cast billet before the rolling reduction and S2 is the cross sectional area of the core material. The rolling reduction of the unsolidified cast billet is made to the eccentric rate or more of the complex cast billet when the rolling reduction is not executed to the unsolidified part, and the timing of the rolling reduction to the unsolidified part is made to the time when the rolling reduction, to be aimed is equallized with the unsolidified zone. By this method, the casting length can be made to long.
YOSHIHARA MASAHIRO
KATO TORU
