METHOD FOR PRODUCING CONTINUOUS CASTING ROUND SLAB FOR SEAMLESS STEEL PIPE PRODUCTION, AND METHOD FOR PRODUCING SEAMLESS STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To continuously cast a round slab of high Cr steel having a Cr content of 2.0-18.0 mass% while preventing an inner face flaw in time of pipe production.SOLUTION: A method for producing continuous casting round slab uses a sectional circular mold 4 having a diameter on the inner face side ≤400 mm. A casting speed is 0.6-2.4 m/min. After a round slab 9 is perfectly coagulated at a surface temperature of 800-1,100°C, depression wherein a slab depression ratio RED is 10.0-30.0% is applied by one or more pinch rolls, and the round slab 9 is flattened such that the width dimension in the depression direction becomes smaller than the width dimension on a free face side in a direction orthogonal to the depression direction. The flattened slab is vertically depressed from the direction orthogonal to the vertically depressed direction by one or more shaping rolls to shape a section of the slab to a circular section having a prescribed dimension without flattening the slab.