continuous casting method of 13Cr seamless steel pipe pipe round slab

摘要

PROBLEM TO BE SOLVED: To provide a continuous casting method of round cast slab for manufacturing 13Cr seamless steel tube by which the occurrence of shrinkage hole formed in a last stage of solidification, and A-type cracks attributable thereto are sufficiently suppressed on the practical level together with C-type cracks.;SOLUTION: When performing forcible cooling in the last stage of solidification during the continuously casting of a round cast slab for a 13Cr seamless steel tube, as a point at which the core part stress of a strand subjected to continuous casting is converted from the compression side to the tension side, a time point is obtained at which the sign of an integrated value of SR=(dT_s/dt)-(dT_c/dt) is converted form negative to positive, the integrated value of SR being derived from a drop rates (dT_s/dt) and (dT_c/dt) per unit time of the strand surface temperature T_s and the core part temperature T_c, and the condition for forcible cooling in the last stage of solidification is controlled so that the temperature of the strand core part at the sign conversion point is below 1,100°C, that is the temperature at which the hot ductility of molten steel is caused.;COPYRIGHT: (C)2013,JPO&INPIT