Welding and performance of advanced high temperature alloys
- Welding Research Council Inc., New York, NY (United States)
- Mitsubishi Heavy Industries, Ltd., Nagasaki (Japan)
The last decade has witnessed the development of many new alloys for elevated temperature service and recognition of a large number of them in the form of allowable stresses by the ASME Boiler and Pressure Vessel Code. These alloys offer considerable advantages in terms of higher tensile and stress rupture strengths, lower thermal stresses, superior corrosion resistance and, in one case, weldability. The improvements are obtained through additions of tungsten, vanadium, columbium, copper, nitrogen and other elements which significantly affect microstructure and weldability. The paper will discuss where introduction of these advanced materials may be warranted, the properties to be expected in comparison to conventional alloys, PWHT requirements and concerns regarding weld failure modes. Higher performance in operation of power plants is achieved by use of tungsten alloyed advanced 9--12%Cr ferritic steels, NF616 (9Cr-0.5 Mo-1.8W-V-Nb) and HCM12A (12Cr-0.4Mo-2W-1 Cu-V-Nb), which exhibit over 30% higher creep strength than T91/P91 (Mod. 9Cr-1 Mo) at 600 C. Thick-walled and large-diameter pipes of NF616 and HCM12A were subjected to fabrication tests such as joint welding and induction bending, and it was shown that the properties of the fabricated parts were satisfactory for the practical application of those steels. HCM2S, a newly developed low alloy steel (0.06C-2.25Cr-1.6W-0.25V0.05Nb) is approximately 1.8 times stronger than conventional T22 (2.25Cr-1 Mo) at around 600 C. The weldability of this low carbon content steel is much improved, as it needs no pre-weld nor postweld heat treatment. HCM2S was installed in a large capacity utility boiler.
- OSTI ID:
- 234152
- Report Number(s):
- CONF-9411168-; ISBN 0-87171-444-2; TRN: IM9624%%193
- Resource Relation:
- Conference: Maintenance and repair welding in power plants V, Orlando, FL (United States), 30 Nov - 2 Dec 1994; Other Information: PBD: 1995; Related Information: Is Part Of Maintenance and repair welding in power plants 5: Proceedings; PB: 269 p.
- Country of Publication:
- United States
- Language:
- English
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