Hitachi, Ltd.

Hidehiko Sumitomo

Yasuhisa Aono

Masami Taguchi

Ryo Ishibashi

Masakuni Fujikura

Hiroki Masumoto

A high-strength and high-toughness ferritic steel having a tensile strength of not less than 1,000 MPA and a Charpy impact value of not less than 1 MJ/m is provided. A ferritic steel comprising, by weight, not more than 1% Si, not more than 1.25% Mn, 8 to 30% Cr, not more than 0.2% C, not more than 0.2% N, not more than 0.4% O, a total amount of not more than 12% of at least one compound-forming element selected from the group of Ti, Zr, Hf, V and Nb in amounts of not more than 3% Ti, not more than 6% Zr, not more than 10% Hf, not more than 1.0% V and not more than 2.0% Nb, also containing where necessary not more than 0.3% Mo, not more than 4% W and not more than 1.6% Ni, and the balance consisting of Fe and unavoidable impurities, and having an average crystal grain size of not more than 1 &mgr;m, can be obtained by a method comprising encapsulating a steel powder produced by mechanical alloying, and subjecting the encapsulated steel powder to plastic deformation.

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Ube, Japan

Hidehiko Sumitomo