Metal treatment – Stock – Nickel base
Reexamination Certificate
2000-11-20
2003-02-18
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Nickel base
C148S427000, C420S442000
Reexamination Certificate
active
06521060
ABSTRACT:
BACKGROUND OF THE INVENTION
This Invention relates to a filler metal for use in the welding of Ni—Cr—W alloys that are excellent in high-temperature strength and corrosion resistance and which are used in the hot-zone structures of high-temperature gas-cooled reactors, gas turbines, etc.
Heretofore, Ni—Cr—W and Ni—Cr—W—Mo alloys have been developed as super-heat resistant materials for use in the hot-zone structures of high-temperature gas-cooled reactors, gas turbines, etc. These alloys are used at high temperatures near 1000° C. and required to be excellent in high-temperature creep strength and corrosion resistance.
To meet these requirements, Ni—Cr alloys strengthened with W or Mo have been proposed in Japanese Patent Public Disclosure Nos. 29316/1976, as well as Japanese Patent Publication Nos. 33212/1979 and 47612/1993. Welding is employed to fabricate structures with these alloys. Since the fabricated structures are put to prolonged service at high temperatures, the welded portions must also have high-temperature creep strength.
Japanese Patent Public Disclosure No. 29316/1976 teaches a heat-resistant alloy for use in the fabrication of welded structures with Ni—Cr—W and Ni—Cr—W—Mo alloys but the patent is limited to a compositional range of 3-20% W alloys that indicates low susceptibility to cracking in weldments. Ni—Cr—W alloys are so sensitive to weld cracking that if an alloy having an identical chemical composition to the base metal is used as a filler metal, weld cracking occurs, making it difficult to fabricate sound welded structures. In order to assure integrity of high-temperature structures, the welded portions must have a high-temperature creep strength comparable to that of the base metal. In the case of Ni—Cr—W alloys, no filler metal has yet been developed that can be worked Into a welding wire, that has good weldability and that produces welded portions having comparable high-temperature creep strength to the base metal.
SUMMARY OF THE INVENTION
An object, therefore, of the present invention is to provide a welding filler metal suitable for use with Ni—Cr—W alloys which have originally high susceptibility to cracking in weldments. The welding filler metal has enough hot workability Into a welding wire, excellent weldability and capability which produces welded portions having comparable high-temperature creep strength to the base metal.
This object of the invention can be attained by a filler metal for use in the welding of Ni—Cr—W alloys which comprises on a mass basis:
C≦0.05%
Mn≦0.1%
Si≦0.1% (Mn+Si≦0.1%)
Cr=17-20%
W=20-23% (Cr+W=39-43%)
Ti=0.02-0.1%
Zr≦0.03%
Y≦0.015%
B=0.0003-0.01%
Al≦0.1%
Mg≦0.05%
Nb≦0.06% (10Zr+10B+5Nb+2Y≦0.3%)
the balance being Ni and incidental impurities.
REFERENCES:
patent: 5449490 (1995-09-01), Kondo et al.
patent: 51-29316 (1976-03-01), None
patent: 54-33212 (1979-10-01), None
patent: 5-47612 (1988-12-01), None
Development of Ni-Cr-W Superalloys for High Temperature Components in High Temperature Gas-Cooled Reactors, 2: Examination of Effects of Minor Alloying Elements and Proposal of Optimum Chemical Composition, Report (1992), JAERI-M-92-137; Order No. DE93764469, 84pp. Avail.: NTIS From Energy Res. Abstr. 1993, 18(4), Abstr: No. 9473.
Kurata Yuji
Nakajima Hajime
Saito Teiichiro
Shindo Masami
Takatsu Tamao
Banner & Witcoff , Ltd.
Ip Sikyin
Japan Atomic Energy Research Institute
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