Kawasaki Steel Corporation

Sakai Chemical Industry Co., Ltd.

Hiromu Oka

Tsutomu Nozaki

Yasuhiro Habu

Hakaru Nakato

Takao Koshikawa

Toshio Imae

Tsunehiro Ueda

Fumitaka Shimokawa

Hideaki Kishimoto

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.

Method of producing seamless steel tube by using mandrel mill

A mold additive for use in continuous casting, which includes a base material having a chemical composition of CaO--BaO--SiO.sub.2 --F system, and contains 2-15% by weight in total of at least one carbonate of alkali and alkaline earth metals, 2-30% by weight in total of at least one fluoride of alkali and alkaline earth metals and 0.2-10% by weight of carbon, and, if necessary, 2-10% by weight in total of at least one oxide of Fe, Mn and Ni, and has a solidification temperature of not more than 900.degree. C. and a viscosity at 1,300.degree. C. of not more than 3 poises. The base material has a weight ratio of (CaO+BaO)/SiO.sub.2 of 0.6-2.5 and contains not less than 2% by weight of BaO and 2-15% by weight of F.

Mold additives for use in continuous casting

Growing community of inventors

Chiba, Japan

Hiromu Oka