Sumitomo Metal Industries, Inc.

Akiyoshi Mori

Hajime Nashiwa

Makoto Tokuda

Yoshiyasu Kitagawa

A high strength steel plate of improved low temperature toughness useful for making an arctic grade line pipe is provided with the addition of 0.8 - 2.0% by weight of Ni and 0.0005 - 0.0040% by weight of Ca, which may be used in the as-rolled state and manufactured through two step controlled rolling the secondary step rolling of which is carried out at a temperature lower than a conventional rolling temperature.

As-rolled steel plate having improved low temperature toughness and

Herein disclosed is a process for the addition of calcium to a molten steel which achieves an excellent yield and effect. The process is applied to molten steels having a chemical composition of carbon 0.02 to 0.55%, Silicon less than 0.50%, Manganese 0.20 to 2.50%, sulfur less than 0.010%, total oxygen content less than 100 ppm, quantities of other standard alloying elements and the balance being iron, and being maintained at a temperature of 1480.degree. to 1800.degree. C. The process is conducted either by shooting projectiles which include calcium into the molten steel or by continuously feeding a wire of a calcium containing material into the molten steel in an amount of 0.1 to 2.0 kg per ton of molten steel calculated on the basis of pure calcium so that the calcium content of the resulting steel becomes 0.05 to 0.8 times the sulfur content. The resulting steel has excellent low temperature impact characteristics.

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Wakayama, Japan

Akiyoshi Mori