Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1994-05-04
1997-02-04
Yee, Deborah
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C21D 602
Patent
active
055994083
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of producing the a structural member, such as a hydrofoil of high-speed passenger craft and an offshore oil-related facility, which requires high strength, high toughness, and high corrosion resistance and involves welding work, and a method of producing the same.
BACKGROUND ART
Conventionally, the heat treatment of the above-described structural member is normally carried out by quench-and-temper. After welding is performed, re-solution treatment and aging treatment are carried out.
However, when the above-described re-solution treatment is done, the welded structural member is deformed by residual stress or gravitation. To prevent the deformation, considerably large-scale, firm constraint is required. Even a structural member which does not involve welding has far lower toughness as compared with a member heat-treated in accordance with the present invention.
The present invention was made in view of the above situation. Accordingly, an object of the present invention is to provide a method of producing a structural member in which the deformation occurring during heat treatment is prevented and the toughness is significantly improved.
DISCLOSURE OF THE INVENTION
The inventors eagerly carried out researches to solve the above problems. As a result, we invented a method of producing a new structural member in which the deformation occurring during heat treatment is prevented and the toughness is significantly improved.
Specifically, the present invention has features described in the following items (1) to (15).
(1) A structural member with high toughness and little distortion due to heat treatment, in which .epsilon. phase precipitates in the matrix having a composition of 0.07% or less carbon, 1% or less silicon, 1% or less manganese, 2.5 to 5% copper, 3 to 5.5% nickel, 14 to 17.5% chromium, 0.5% or less molybdenum, 0.15 to 0.45% niobium, by weight, and the balance composed substantially of iron, and comprising 6 to 30 vol % austenitic phase and the balance composed substantially of martensitic phase.
(2) A ship comprising a hull, propulsion equipment installed at the rear of the hull, and hydrofoils which are installed under the hull in the substantially horizontal direction and are made of a stainless steel with a structure in which .epsilon. phase precipitates in the matrix having a composition of 0.07% or less carbon, 1% or less silicon, 1% or less manganese, 2.5 to 5% copper, 3 to 5.5% nickel, 14 to 17.5% chromium, 0.5% or less molybdenum, 0.15 to 0.45% niobium, by weight, and the balance composed substantially of iron, and comprising 6 to 30 vol % austenitic phase and the balance composed substantially of martensitic phase.
(3) A method of producing a structural member comprising the steps of: performing first solution treatment at 1010.degree. to 1050.degree. C. on a stainless steel having a composition of 0.07% or less carbon, 1% or less silicon, 1% or less manganese, 2.5 to 5% copper, 3 to 5.5% nickel, 14 to 17.5% chromium, 0.5% or less molybdenum, 0.15 to 0.45% niobium, by weight, and the balance composed substantially of iron; performing first aging treatment at a temperature not lower than 520.degree. C. and not higher than 630.degree. C.; performing second solution treatment at 730.degree. to 840.degree. C.; and performing second aging treatment at a temperature not lower than 520.degree. C. and not higher than 630.degree. C.
(4) A method of producing a structural member comprising the steps of: performing first solution treatment at 1010.degree. to 1050.degree. C. on a stainless steel having a composition of 0.07% or less carbon, 1% or less silicon, 1% or less manganese, 2.5 to 5% copper, 3 to 5.5% nickel, 14 to 17.5% chromium, 0.5% or less molybdenum, 0.15 to 0.45% niobium, by weight, and the balance composed substantially of iron; performing first aging treatment at a temperature not lower than 520.degree. C. and not higher than 630.degree. C.; fabricating a structural member of any shape by means of welding work; performin
REFERENCES:
patent: 3871928 (1975-03-01), Smith, Jr. et al.
Fujita Akitsugu
Kawano Takayuki
Kimura Manabu
Matsumoto Tatsuki
Nakamura Makoto
Mitsubishi Jukogyo Kabushiki Kaisha
Yee Deborah
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