Corrosion-resistant alloy heat transfer tubes for heat-recovery boilers

• US 5,378,427 A
• Filed: 11/05/1993
• Issued: 01/03/1995
• Est. Priority Date: 03/13/1991
• Status: Expired due to Term

• Current Assignee: Sumitomo Metal Industries Limited (Nippon Steel Corporation)
• Original Assignee: Sumitomo Metal Industries Limited (Nippon Steel Corporation)
• Inventors: Kudo, Takeo, Otsuka, Nobuo
• Primary Examiner(s): Yee, Deborah
• Application Number:
  US08/147,441
• Time in Patent Office: 424 Days
• Field of Search: 420/40, 420/586.1, 420/585, 420/586, 148/909
• US Class Current: 420/586.1
• CPC Class Codes: C22C 30/00 Alloys containing less than 50% by weight of each constituent
• CPC Class Codes: Y10S 148/909 Tube

Abstract

A corrosion-resistant austenitic alloy suitable for use in heat transfer tubes for heat-recovery boilers which withstands uniform corrosion, intergranular corrosion, and stress corrosion cracking in refuse-fired boilers and black-liquor combustion boilers. The alloy consists essentially, on a weight basis, of C: not more than 0.05%, Si: not more than 4%, Mn: not more than 7.5%, Ni: 25-55%, Cr: more than 20% and not more than 35%, Mo: an amount satisfying the following inequality (1) when Mn(%)≦2.5 or inequality (2) when 2.5≦Mn(%)≦7.5,

Mo(%)≦5.8--[Ni(%)/10]                               (1)

Mo(%)≦7.5--[Ni(%)/10]                               (2)

optionally one or more of Nb, Ti, Zr, and V: 0.1-3% in total, one or more of Cu, Co, and W: 0.1-5% in total, N: 0.1-0.3%, Al: not more than 0.5%, and at least one rare earth metal: 0.01-0.1% in total, and the balance of Fe and incidental impurities in which the content of P is not more than 0.030% and that of S is not more than 0.010%.

Claims

1. A corrosion-resistant heat transfer tube of a heat-recovery boiler which is made of an alloy consisting essentially, on a weight basis, of

View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 26, 27, 28)

2. The corrosion-resistant tube of claim 1, wherein one or more of Nb, Ti, Zr, and V are added in an amount of 0.1-3% in total.

3. The corrosion-resistant tube of claim 1, wherein one or more of Cu, Co, and W are added in an amount of 0.1-5% in total.

4. The corrosion-resistant tube of claim 1, wherein N is added in an amount of 0.1-0.3%.

5. The corrosion-resistant tube of claim 1, wherein at least one rare earth metal is added in an amount of 0.01-0.1% in total.

6. The corrosion-resistant tube of claim 1, wherein A1 is added in an amount of not more than 0.5%.

7. The corrosion-resistant tube of claim 1, wherein the alloy has a grain size equal to or less than ASTM grain size No. 7.

8. The corrosion-resistant tube of claim 1, wherein the Mo content satisfies inequality (1) with an Mn content of not more than 2.5%.

9. The corrosion-resistant tube of claim 1, wherein the Mo content satisfies inequality (2) with an Mn content of more than 2.5% and not more than 7.5%.

10. The corrosion-resistant tube of claim 1, wherein the Mo content is 0.5% or more.

11. The corrosion-resistant tube of claim 1, wherein the Si content is not more than 2%.

12. The corrosion-resistant tube of claim 1, wherein the Si content is not more than 0.3%.

13. The corrosion-resistant tube of claim 1, wherein the P content as an incidental purity is not more than 0.015%.

14. The corrosion-resistant tube of claim 1, wherein Si:

not more than 2%, Mn;

more than 2.5% and not more than 7.5%, and Mo;

0.5% or more with satisfying inequality (2).

15. The corrosion-resistant tube of claim 1, wherein Si:

not more than 0.3%, Mo;

0.3% or more, and the content of P as an incidental impurities is not more than 0.015%.

16. The corrosion-resistant tube of claim 1, wherein Si:

not more than 2%, Mn;

not more than 2.5%, Mo;

0.3% or more with satisfying inequality (1), one or more of Nb, Ti, Zr, and V;

0.1-3% in total.

17. The corrosion-resistant tube of claim 16, wherein the alloy has a grain size equal to or less than ASTM grain size No. 7.

26. The corrosion-resistant tube of claim 1, wherein an outer surface of the tube is exposed to a high-temperature corrosive environment in a heat-recovery boiler.

27. The corrosion-resistant tube of claim 1, wherein an outer surface of the tube includes chloride-containing fused salts deposited thereon, the fused salts comprising chloride-rich condensates produced in a high-temperature corrosive environment in a heat-recovery boiler in which the tube is located.

28. The corrosion-resistant tube of claim 1, wherein the tube is a superheater tube in a heat-recovery boiler.

18. A corrosion-resistant heat transfer tube of a heat-recovery boiler which is made of an alloy consisting essentially, on a weight basis, of

View Dependent Claims (21)

21. The corrosion-resistant tube of claim 18, wherein one or more of Cu, Co, and W are added in an amount of 0.1-5% in total.

19. a balance of Fe and incidental impurities in which the content of P is not more than 0.030% and that of S is not more than 0.010%.

22. The corrosion-resistant tube of claim 19, wherein at least one rare earth metal is added in an amount of 0.01-0.1% in total.

24. The corrosion-resistant tube of claim 19, wherein N is added in an amount of 0.1-0.3%.

25. The corrosion-resistant tube of claim 19, wherein A1 is added in an amount of not more than 0.5%.

20. A corrosion-resistant heat transfer tube of a heat-recovery boiler which is made of an alloy consisting essentially, on a weight basis, of

View Dependent Claims (23)

23. The corrosion-resistant tube of claim 20, wherein at least one rare earth metal is added in an amount of 0.01-0.1% in total.