US4505232A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Boiler tube
Assignee: Hitachi Ltd
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Filing: 1984-03-27
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Granted: 1985-03-19
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Expires: 2004-03-27
Abstract
Abstract A boiler tube having a double-tube structure constituted by an inner tube and an outer tube integrated with each other. The inner tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.15% of C, 0.5 to 3.5% of Si, not greater than 2% of Mn, 25 to 40% of Ni, 20.5 to 27% of Cr, 0.5 to 3% of Mo, not greater than 1% of Nb and the balance Fe and having a substantially fully austenite structure. The outer tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.2% of C, not greater than 3.5% of Si, not greater than 2% of Mn, 33 to 45% of Ni, 30 to 40% of Cr and the balance Fe and having a substantially fully austenite structure. The inner tube made of the alloy having the composition specified above exhibits a high resistance to steam oxidation without any reduction in high-temperature strength even at elevated steam temperature, while the outer tube made of the alloy having the composition specified above exhibits a superior resistance to corrosion by coal combustion gas.
Inventors
- 👤 Kenichi Usami
- 👤 Seishin Kirihara
- 👤 Hiroyuki Doi
- 👤 Choichi Asano
- 👤 Masayuki Sukekawa
- 👤 Yasuhide Sakaguchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:59
CPC Classifications
B; B32; B32B; B32B15/00; B32B15/01; F; F22; F22B; F22B37/00; F22B37/02; F22B37/04; Y; Y10; Y10S; Y10S122/00; Y10S122/13; Y10S165/00; Y10S165/905; Y10T; Y10T428/00; Y10T428/12; Y10T428/12493; Y10T428/12771; Y10T428/12861; Y10T428/12951; Y10T428/12958; Y10T428/12965
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
136 words
A boiler tube having a double-tube structure constituted by an inner tube and an outer tube integrated with each other, characterized in that: said inner tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.15% of C, 0.5 to 3.5% of Si, not greater than 2% of Mn, 25 to 40% of Ni, 20.5 to 27% of Cr, 0.5 to 3% of Mo, not greater than 1% of Nb and the balance Fe and having a substantially fully austenite structure; and said outer tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.2% of C, not greater than 3.5% of Si, not greater than 2% of Mn, 33 to 45% of Ni, 30 to 40% of Cr and the balance Fe and having a substantially fully austenite structure.
Claim 2
Dependent Claim
136 words
A boiler tube having a double-tube structure constituted by an inner tube and an outer tube integrated with each other, characterized in that: said inner tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.15% of C, 0.5 to 3.5% of Si, not greater than 2% of Mn, 25 to 40% of Ni, 20.5 to 27% of Cr, 0.5 to 3% of Mo, not greater than 1% of Nb and the balance Fe and having a substantially fully austenite structure; and said outer tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.2% of C, not greater than 3.5% of Si, not greater than 2% of Mn, 33 to 45% of Ni, 30 to 40% of Cr and the balance Fe and having a substantially fully austenite structure.
Claim 3
Dependent Claim
150 words
A boiler tube having a double-tube structure constituted by an inner tube and an outer tube integrated with each other, characterized in that: said inner tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.15% of C, 0.5 to 3.5% of Si, not greater than 2% of Mn, 25 to 40% of Ni, 20.5 to 27% of Cr, 0.5 to 3% of Mo, not greater than 1% of Nb, each not greater than 0.5% of at least one of Ti, B and W and the balance Fe and having a substantially fully austenite structure; and said outer tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.2% of C, not greater than 3.5% of Si, not greater than 2% of Mn, 33 to 45% of Ni, 30 to 40% of Cr and the balance Fe and having a substantially fully austenite structure.
Claim 4
Dependent Claim
150 words
A boiler tube having a double-tube structure constituted by an inner tube and an outer tube integrated with each other, characterized in that: said inner tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.15% of C, 0.5 to 3.5% of Si, not greater than 2% of Mn, 25 to 40% of Ni, 20.5 to 27% of Cr, 0.5 to 3% of Mo, not greater than 1% of Nb, each not greater than 0.5% of at least one of Ti, B and W and the balance Fe and having a substantially fully austenite structure; and said outer tube is made of an alloy consisting essentially of, by weight, 0.02 to 0.2% of C, not greater than 3.5% of Si, not greater than 2% of Mn, 33 to 45% of Ni, 30 to 40% of Cr and the balance Fe and having a substantially fully austenite structure.
Claim 5
Dependent Claim
33 words
A boiler tube according to claim 1, wherein said alloy from which said outer tube is made further contains, by weight, 0.5 to 3% of Mo and not greater than 1% of Nb.
Claim 6
Dependent Claim
42 words
A boiler tube according to claim 1 or 3, wherein said alloy from which said outer tube is made further contains, by weight, not greater than 0.5% of W, not greater than 0.5% of Ti and not greater than 0.03% of B.
Claim 7
Dependent Claim
42 words
A boiler tube according to claim 1, wherein the Ni equivalent of said alloy from which said inner tube is made is at least 2 higher than the line marking the lower limit of the fully austenite region shown in FIG. 1.
Claim 8
Dependent Claim
66 words
A boiler tube according to any one of claims 1 to 3 or 5, wherein said alloy from which said inner tube is made has a Cr equivalent of 24 to 33 and an Ni equivalent of 21 to 38, while said alloy from which said outer tube is made has a Cr equivalent of 36 to 44 and an Ni equivalent of 35 to 50.
Claim 9
Dependent Claim
33 words
A boiler tube according to any one of claims 1 to 3 or 5, wherein the wall thickness of said outer tube ranges between 10 and 30% of that of said inner tube.
Claim 10
Dependent Claim
59 words
A boiler tube according to claim 4, wherein said alloy from which said inner tube is made has a Cr equivalent of 24 to 33 and an Ni equivalent of 21 to 38, while said alloy from which said outer tube is made has a Cr equivalent of 36 to 44 and an Ni equivalent of 35 to 50.
Claim 11
Dependent Claim
26 words
A boiler tube according to claim 4, wherein the wall thickness of said outer tube ranges between 10 and 30% of that of said inner tube.
Claim 12
Dependent Claim
26 words
A boiler tube according to claim 6, wherein the wall thickness of said outer tube ranges between 10 and 30% of that of said inner tube.
References Cited (Backward Citations)
US3366473A
Cited
US3859082A
Cited
US3856516A
Cited
US3969153A
Cited
US4054174A
Cited
US4026699A
Cited
US4346739A
Cited
JPS56163244A
Cited
JPS58110660A
Cited
US4463061A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-03-18 | 1988-09-17 | 1989-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-03-18 | 1992-09-17 | 1993-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-03-18 | 1996-09-17 | 1997-03-19 | $7700.00 | Window Closed / Lapsed |