Method of producing seamless steel tube by using mandrel mill

摘要

A mandrel mill for rolling seamless steel tubes includes a plurality of roll stands each having a pair of rolls defining a roll groove therebetween, an axis of the rolls of each roll stand being orthogonal to the axis of the rolls of the adjacent roll stands. The mandrel mill further includes a mandrel bar disposed in the roll grooves configured by the roll stands. The ratio between the radius of curvature of a groove bottom of the groove and a distance between the groove bottom of the roll groove of the first stand ranges from 0.46 to 0.54, and that of the second stand ranges from 0.48 to 0.52.