Sumitomo Metal Industries, Inc.

Tatsuro Kunitake

Yasutaka Okada

Hiroo Ohtani

Masaru Nishiguchi

Toshiji Takigawa

Yoshiro Matsumoto

Seiichi Watanabe

Kazuo Tsumura

Iwao Saito

Masahiro Nishio

A heavy thick steel casting having high mechanical strength with a tensile strength of 80 kg/mm.sup.2 or more, excellent impact properties with a vE.sub.O value of more than 8 kg-m/cm.sup.2 and improved weldability, and also a method of manufacturing the same. In the method, steel containing boron as an essential component and with a Ceq value corresponding to the maximum thickness of the product is cast. The casting is solidified in air, then heated to a temperature of 930.degree. to 1,050.degree. C. for one hour or more, followed by air cooling. Thereafter, the casting is quenched and tempered to thereby impart the casting with the desired characteristics.

Heavy thick high-strength casting having improved weldability and impact

A method of producing a tube with an ultra-high tensile strength over 255 kg/mm.sup.2 and remarkably improved ductility and toughness is provided, which comprises preparing a mother tube through hot extrusion of a steel consisting essentially of 15.0 - 18.5% by weight of Ni, 12.5 - 15.0% by weight of Co, 5.0 - 6.9% by weight of Mo, 1.00 - 1.28% by weight of Ti, 0.01 - 0.20% by weight of Al and the balance essentially iron, cold working the mother tube with a reduction in wall thickness of 5 - 25%, then raising the temperature of the resulting tube to a temperature of 800 - 950.degree. C in a period of from 20 minutes to 2 hours and maintaining the heated tube at this temperature for from 30 minutes to 3 hours, and, after cooling to or below room temperature, ageing the cooled tube at a temperature of 450.degree. - 550.degree. C for 1 - 10 hours.

Method of producing a tube of ultra-high strength steel having

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Toyonaka, Japan

Tatsuro Kunitake