CONTINUOUS CASTING METHOD FOR ROUND SLAB FOR SEAMLESS STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a continuous casting method for a round slab for a seamless steel pipe.;SOLUTION: A round slab 9 during continuous casting by a circular mold is, before the completion of its solidification, subjected to rolling reduction with a pair of rolling reduction rolls 6a, to obtain a slab. At this time, as a pair of the rolling reduction rolls, saddle type rolls in which the opening angle δ of a caliber bottom is 75 to 105° and also having projections 13a at the parts in contact with the round slab are used. Regarding the projection, at least one projecting protrusion continuous to the roll circumferential direction or a plurality of projections at least in one line discretely distributed to the roll circumferential direction are preferably used. In this way, the generation of porosities of the axial center part and axial center cracks easy to occur in a Cr-containing steel or the like can be suppressed at a reduced rolling draft and also without damaging the cross-sectional shape of the round slab, and the method can contribute to the reduction of production cost, the improvement of the quality of a seamless steel pipe or the like.;COPYRIGHT: (C)2010,JPO&INPIT