Nippon Steel Corporation

Tetuo Takeda

Hajime Nakasugi

Hiroshi Tamehiro

Hiroaki Masui

Kunio Watanabe

Masatoki Nakayama

Yoshio Hashimoto

Kameo Matsukura

Seiji Eiro

The production process characterized in that a steel ingot or slab containing not less than 0.004% of TiN not larger than 0.02.mu. is heated to a temperature not higher than 1150.degree. C and rolled, and growth of the .gamma. grains during this heating and rolling step is prevented by TiN to improve the toughness, and the resultant steel product has an excellent low-temperature toughness with a yield point of 40 kg/mm.sup.2 or higher, and is useful as hot rolled or as heated at a temperature ranging from 300.degree. to 750.degree. C after the hot rolling.

Process for producing a high tension steel sheet product having an

A method for producing a high tensile strength steel plate which comprises subjecting to a low temperature rolling, a steel composition containing not more than 0.25% of carbon, not more than 0.5% of silicon, 0.5 to 2.0% of manganese, not more than 0.015% of sulfur, 0.005 to 0.1% of aluminum, one or more of niobium, vanadium and titanium in an amount not less than 0.01%, and REM in an amount not less than 1.3 times the amount of sulfur, with optionally one or more of nickel, chromium and copper, with the balance being iron and unavoidable impurities, which steel possesses a low notch toughness transition temperature and high absorbed energy in the notch-impact test, and is suitable in the as rolled condition for use as pipe lines in cold districts.

Method for producing a high toughness and high tensil steel

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Kimitsu, Japan

Tetuo Takeda