Claims
- 1. In the method for making an apparatus for the exchange of heat in which a plurality of thin walled tubular metal members are formed, finned and welded to tube sheets in an array with gaps between said members, the improvement of using as the metal for the walls of said members a zirconium stabilized corrosion resistant ferritic stainless steel consisting essentially of, in weight percent:
- Carbon=0.025% max
- Nitrogen=0.025% max
- Carbon+Nitrogen=0.045% max
- Silicon=1.0% max
- Manganese=1.0% max
- Phosphorous=0.04% max
- Sulfur=0.03% max
- Chromium=18-20%
- Molybdenum=1.75-2.25%
- (Zirconium/Carbon).gtoreq.18
- the balance being iron and incidental impurities.
- 2. In the method for making moisture separator reheater and feedwater preheater apparatus for the exchange of heat in which a plurality of thin-walled tubular metal members are formed, finned and welded to tube sheets in an array with gaps between said members, the improvement of using as the metal for the walls of said members a zirconium stabilized and corrosion resistant ferritic stainless steel resistant to sensitization during long-term operation at intermediate temperatures in said apparatus for the exchange of heat and consisting essentially of, in weight percent:
- Carbon=0.025% max
- Nitrogen=0.025% max
- Carbon+Nitrogen=0.045% max
- Silicon=1.0% max
- Manganese=1.0% max
- Phosphorous=0.04% max
- Sulfur=0.03% max
- Chromium=17-20%
- [Zirconium/(Carbon+Nitrogen)].gtoreq.16
- the balance being iron and incidental impurities.
- 3. In the method for making moisture separator reheater and feedwater preheater apparatus for the exchange of heat in which a plurality of thin-walled tubular metal members are formed, finned and welded to tube sheets in an array with gaps between said members, the improvement of using as the metal for the walls of said members a zirconium stabilized corrosion resistant ferritic stainless steel consisting essentially of, in weight percent:
- ______________________________________Carbon 0.025% maxNitrogen = 0.025% maxCarbon + Nitrogen = 0.045% maxSilicon = 1.0% maxManganese = 1.0% maxPhosphorous = 0.04% maxSulfur = 0.03% maxChromium = 11-13% the larger percentage of zirconium satisfying theZirconium = criteria: (1) Zr/C .gtoreq. 20 or (2) Zr/(C + N) .gtoreq. 15______________________________________
- the balance being iron and incidental impurities, said thin-walled members being resistant to sensitization during long-term operation at intermediate temperatures.
CROSS-REFERENCE TO RELATED PATENT APPLICATION
This application is a continuation of application Ser. No. 268,458, filed May 29, 1981, now abandoned; the entirety of which is incorporated herein by reference.
US Referenced Citations (4)
Foreign Referenced Citations (2)
Number |
Date |
Country |
47-16319 |
Sep 1972 |
JPX |
55-24901 |
Feb 1980 |
JPX |
Non-Patent Literature Citations (2)
Entry |
Moroishi et al., "The Effect of Zr on the Oxidation Resistance of Chromium Stainless Steel", Sumitomo Metal Industries Report, May 20, 1978, pp. 1-23. |
Metals Abstracts, Nov. 1979, vol. 12, No. 31-2691, p. 52. |
Continuations (1)
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Number |
Date |
Country |
Parent |
268458 |
May 1981 |
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