Nippon Steel Corporation

Kawasaki Steel Corporation

Japan Casting & Forging Corporation

Yoshihiro Okamura

Ryota Yamaba

Seinosuke Yano

Tomoya Koseki

Junichi Kobayashi

Katsuo Kaku

Hirohide Muraoka

Yasushi Wakeshima

Ichiro Nakagawa

Hidetaka Chiba

In a journal part of a 9 to 12 wt % Cr steel turbine rotor, a groove face is formed, and on the groove face, a lower build-up layer is formed by using a first welding material containing C: 0.10 to 0.25 wt %, Si: 0.20 to 0.80 wt %, Mn: 1.0 to 2.5 wt %, Ni: 0.4 to 1.0 wt %, Cr: 1.0 to 3.0 wt %, Mo: 0.2 to 1.5 wt %, V: 0.03 to 0.10 wt %, and a remainder composed of Fe and inevitable impurities, and further on this lower build-up layer, an upper build-up layer is formed using a second welding material containing C: 0.10 to 0.25 wt %, Si: 0.20 to 0.80 wt %, Mn: 1.0 to 2.5 wt %, Ni: 0.4 to 1.0 wt %, Cr: 1.0 to 3.0 wt %, Mo: 0.2 to 1.5 wt %, and a remainder consisting of Fe and inevitable impurities.

Method for producing journal part of 9 to 12% Cr steel turbine rotor, and journal part produced by the method

An extra high tensile steel having an excellent stress corrosion cracking resistance in sea water and a yield strength of 1080 MPa or more is provided. A slab comprising, in terms of % by weight, 0.04 to 0.09% of C, 0.01 to 0.10% of Si, 0.05 to 0.65% of Mn, 8.0 to 11.0% of Ni, 0.5 to 1.5% of Mo, 0.2 to 1.5% of Cr, 0.02 to 0.20% of V and 0.01 to 0.08% of Al with the balance consisting of iron and unavoidable impurities is heated to a temperature between 1000.degree. C. and 1250.degree. C., hot rolled at a temperature of Ar' point or above, air-cooled, reheated at a rate of 120.degree. C./min or less to a temperature region of from (A.sub.C3 point--40.degree. C.) to (A.sub.C3 point+40.degree. C.), quenched and subsequently tempered at a temperature of the A.sub.C1 point or below.

Process for producing extra high tensile steel having excellent stress

An extra high tensile steel having an excellent stress corrosion cracking resistance and a yield strength of 1080 MPa or more is provided. A slab comprising, in terms of % by weight, 0.03 to 0.08% of C, 0.01 to 0.10% of Si, 0.05 to 0.65% of Mn, 8.0 to 11.0% of Ni, 0.5 to 1.5% of Mo, 0.2 to 1.5% of Cr, 0.02 to 0.20% of V and 0.01 to 0.08% of Al with the balance consisting of iron and unavoidable impurities is heated to a temperature between 1000.degree. C. and 1250.degree. C., hot-rolled in an austenite recrystallization temperature region with a reduction ratio of 30 to 70%, subsequently rolled in an austenite nonrecrystallization temperature region with a reduction ratio of 20 to 60%, subjected to roll finishing, water-cooled from a temperature of 600.degree. C. or above, reheated to so as to have an area ratio of non-diffusion type reverse transformed austenite grains of 40 to 80% and an area ratio of diffusion type reverse transformed austenite grains of 20 to 60%, quenched and then tempered at a temperature of A.sub.c1 point or below.

Process for producing extra high tensile steel in 1080 MPa yield

A method of high tension steel having superior weldability and low temperature toughness, comprises the steps of preparing a steel billet having a composition consisting, by weight, of 0.02 to 0.05% C, 0.02 to 0.5% Si, 0.4 to 1.5% Mn, 0.5 to 4.0% Ni, 0.20 to 1.5% Mo, 0.005 to 0.03% Ti, 0.01 to 0.08% Al, not more than 0.0002% B, 0.5 to 2.0% Cu, not more than 0.01% N, and the balance Fe and incidental impurities; heating said steel billet to a temperature of 900.degree. C. to 1000.degree. C.; hot-rolling the heated steel billet first at a rolling reduction of 30 to 70% in a temperature range in which austenite recrystallizes and then at a rolling reduction of 20 to 60% in another temperature range in which austenite does not recrystallize; hardening the hot-rolled billet by water-cooling from a temperature not lower than the Ar.sub.3 transformation point and terminating the cooling at a temperature not higher than 250.degree. C.; and tempering the hardened billet at a temperature which is not higher than the Ac.sub.1 transformation point.

Method of producing high tension steel superior in weldability and

A process for producing steel possessing a high level of toughness and strength free of anisotropy and having good resistance to stress corrosion cracking in seawater conditions comprises the steps of:

Process for producing high toughness, high strength steel having

A process for producing a high toughness, high strength steel having excellent resistance to stress corrosion cracking including the steps of: preparing a steel slab including 0.02 to 0.10 wt % of C, 0.50 wt % or less Si, 0.4 to 1.5 wt % Mn, 1.0 to 7.5 wt % Ni, more than 1.0 wt % up to 1.5 wt % Mo, 0.80 wt % or less Cr, 0.01 to 0.08 wt % sol. Al, and the balance of Fe and unavoidable impurities; heating the steel slab to a temperature of from 1000.degree. C. to 1250.degree. C.; hot rolling the heated steel slab at a finishing nip temperature of from 700.degree. C. to 880.degree. C., at a total reduction rate of 40% or more effected at the finishing nip temperature or lower, and at a finishing temperature of 650.degree. C. or higher, to provide a steel plate; then quenching the steel plate by initiating water cooling at a temperature of the A.sub.r3 point thereof or higher and by terminating the water cooling at a temperature of 150.degree. C. or lower; and tempering the quenched steel plate at a temperature of the A.sub.c1 point thereof or lower.

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Tokai, Japan

Yoshihiro Okamura