US4581202A
Expired / Lapsed
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Sintered stainless steel and production process therefor
Assignee: Nippon Steel Corp
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Filing: 1985-03-11
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Granted: 1986-04-08
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Expires: 2005-03-11
Abstract
Abstract A sintered stainless steel and sintered seamless steel pipe exhibiting improved resistance to stress corrosion cracking are disclosed. The metallurgical structure comprises a matrix phase and a dispersing phase, which are different from each other in their metallurgical structures, the matrix phase comprising a substantially single ferritic structure, and the dispersing phase comprising a structure selected from the group consisting of an austenitic structure, an austenitic+ferritic dual phase structure, an austenitic+martensitic dual phase structure, and an austenitic+ferritic+martensitic triple phase structure. The sintered seamless stainless steel pipes are useful as heat exchanging tubes and piping to which sea water or industrial water is fed.
Inventors
- 👤 Takeo Kudo
- 👤 Yoshio Tarutani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 09:38
CPC Classifications
F; F28; F28F; F28F21/00; F28F21/08; F28F21/081; F28F21/082; C; C22; C22C; C22C33/00; C22C33/02; C22C33/0207; C22C33/0257; C22C33/0278; C22C33/0285; F28F2255/00; F28F2255/18
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
110 words
A sintered stainless steel exhibiting improved resistance to stress corrosion cracking, which comprises a matrix phase and discrete islands of a dispersing phase, the metallurgical structures of which are different from each other, the matrix phase comprising a substantially single ferritic structure derived from a ferritic stainless steel powder, and the dispersing phase comprising a structure selected from the group consisting of an austenitic structure, an austenitic+ferritic dual phase structure, an austenitic+martensitic dual phase structure, and an austenitic+ferritic+martensitic triple phase structure, which are derived respectively from an austenitic stainless steel powder, an austenitic+ferritic duplex stainless steel powder, an austenitic+martensitic duplex stainless steel powder and a triple phase stainless steel powder.
Claim 2
Dependent Claim
110 words
A sintered stainless steel exhibiting improved resistance to stress corrosion cracking, which comprises a matrix phase and discrete islands of a dispersing phase, the metallurgical structures of which are different from each other, the matrix phase comprising a substantially single ferritic structure derived from a ferritic stainless steel powder, and the dispersing phase comprising a structure selected from the group consisting of an austenitic structure, an austenitic+ferritic dual phase structure, an austenitic+martensitic dual phase structure, and an austenitic+ferritic+martensitic triple phase structure, which are derived respectively from an austenitic stainless steel powder, an austenitic+ferritic duplex stainless steel powder, an austenitic+martensitic duplex stainless steel powder and a triple phase stainless steel powder.
Claim 3
Dependent Claim
18 words
A sintered stainless steel as defined in claim 1, in which the dispersing phase comprises an austenitic structure.
Claim 4
Dependent Claim
22 words
A sintered stainless steel as defined in claim 1, in which the dispersing phase comprises an austenitic+ferritic or austenitic+martensitic dual phase structure.
Claim 5
Dependent Claim
21 words
A sintered stainless steel as defined in claim 1, in which the dispersing phase comprises an austenitic+ferritic+ +martensitic triple phase structure.
Claim 6
Dependent Claim
24 words
A sintered stainless steel as defined in claim 1, in which the matrix phase comprises a ferritic structure containing a slight amount of martensite.
Claim 7
Dependent Claim
25 words
A sintered stainless steel as defined in claim 1, in which on an average the nickel content of the matrix phase is 1% or less.
Claim 8
Dependent Claim
29 words
A sintered stainless steel as defined in claim 1, in which the metallurgical structure comprises 20-80% by weight of a ferritic phase derived from a ferritic stainless steel powder.
Claim 9
Dependent Claim
20 words
A sintered stainless steel as defined in claim 1, in which the matrix phase contains a small amount of molybdenum.
Claim 10
Dependent Claim
20 words
A sintered stainless steel as defined in claim 1, in which the matrix phase contains 0.5% or more of molybdenum.
Claim 11
Dependent Claim
28 words
A sintered stainless steel as defined in claim 1, in which the dispersing phase comprises an austenitic structure and the matrix phase contains a small amount of molybdenum.
Claim 12
Dependent Claim
28 words
A sintered stainless steel as defined in claim 1, in which the dispersing phase comprises an austenitic structure and the matrix phase contains 0.5% or more of molybdenum.
Claim 13
Dependent Claim
89 words
A process for producing a sintered stainless steel exhibiting improved resistance to stress corrosion cracking, which comprises a matrix phase and discrete islands of a dispersing phase, the metallurgical structures of which are different from each other, comprising the steps of mixing a ferritic stainless steel powder with a powder selected from the group consisting of an austenitic stainless steel powder, an austenitic+ferritic duplex stainless steel powder, an austenitic+martensitic duplex stainless steel powder, and an austenitic+ferritic+martensitic triple phase stainless steel powder, and compacting and sintering the resulting powder mixture.
Claim 14
Dependent Claim
89 words
A process for producing a sintered stainless steel exhibiting improved resistance to stress corrosion cracking, which comprises a matrix phase and discrete islands of a dispersing phase, the metallurgical structures of which are different from each other, comprising the steps of mixing a ferritic stainless steel powder with a powder selected from the group consisting of an austenitic stainless steel powder, an austenitic+ferritic duplex stainless steel powder, an austenitic+martensitic duplex stainless steel powder, and an austenitic+ferritic+martensitic triple phase stainless steel powder, and compacting and sintering the resulting powder mixture.
Claim 15
Dependent Claim
27 words
A process for producing a sintered stainless steel as defined in claim 12, in which the compacting and sintering are simultaneously carried out using hot isostatic pressing.
Claim 16
Dependent Claim
32 words
A process for producing a sintered stainless steel as defined in claim 12, in which the compacting is carried out using cold isostatic pressing, and after compacting the sintering is carried out.
Claim 17
Dependent Claim
28 words
A process for producing a sintered stainless steel as defined in claim 12, in which the sintering is carried out at a temperature of 1100° C. or lower.
Claim 18
Dependent Claim
113 words
A sintered seamless stainless steel pipe exhibiting improved resistance to stress corrosion cracking which comprises a matrix phase and discrete islands of a dispersing phase, the metallurgical structures of which are different from each other, the matrix phase comprising a substantially single ferritic structure derived from a ferritic stainless steel powder, and the dispersing phase comprising a structure selected from the group consisting of an austenitic structure, an austenitic+ferritic dual phase structure, an austenitic+martensitic dual phase structure, and an austenitic+ferritic+martensitic triple phase structure, which are derived respectively from an austenitic stainless steel powder, an austenitic+ferritic duplex stainless steel powder, an austenitic+martensitic duplex stainless steel powder and an austenitic+ferritic+martensitic triple phase stainless steel powder.
Claim 19
Dependent Claim
113 words
A sintered seamless stainless steel pipe exhibiting improved resistance to stress corrosion cracking which comprises a matrix phase and discrete islands of a dispersing phase, the metallurgical structures of which are different from each other, the matrix phase comprising a substantially single ferritic structure derived from a ferritic stainless steel powder, and the dispersing phase comprising a structure selected from the group consisting of an austenitic structure, an austenitic+ferritic dual phase structure, an austenitic+martensitic dual phase structure, and an austenitic+ferritic+martensitic triple phase structure, which are derived respectively from an austenitic stainless steel powder, an austenitic+ferritic duplex stainless steel powder, an austenitic+martensitic duplex stainless steel powder and an austenitic+ferritic+martensitic triple phase stainless steel powder.
Claim 20
Dependent Claim
20 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the dispersing phase comprises an austenitic structure.
Claim 21
Dependent Claim
24 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the dispersing phase comprises an austenitic+ferritic or austenitic+martensitic dual phase structure.
Claim 22
Dependent Claim
22 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the dispersing phase comprises an austenitic+ferritic+artensitic triple phase structure.
Claim 23
Dependent Claim
26 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the matrix phase comprises a ferritic structure containing a slight amount of martensite.
Claim 24
Dependent Claim
27 words
A sintered seamless stainless steel pipe as defined in claim 16, in which on an average the nickel content of the matrix phase is 1% or less.
Claim 25
Dependent Claim
31 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the metallurgical structure comprises 20-80% by weight of a ferritic phase derived from a ferritic stainless steel powder.
Claim 26
Dependent Claim
22 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the matrix phase contains a small amount of molybdenum.
Claim 27
Dependent Claim
22 words
A sintered seamless stainless steel pipe as defined in claim 16, in which the matrix phase contains 0.5% or more of molybdenum.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-04-07 | 1989-10-07 | 1990-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-04-07 | 1993-10-07 | 1994-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-04-07 | 1997-10-07 | 1998-04-08 | $7700.00 | Window Closed / Lapsed |