Issue |
MATEC Web Conf.
Volume 269, 2019
IIW 2018 - International Conference on Advanced Welding and Smart Fabrication Technologies
|
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Article Number | 03012 | |
Number of page(s) | 5 | |
Section | Corrosion and Failure Analysis | |
DOI | https://doi.org/10.1051/matecconf/201926903012 | |
Published online | 22 February 2019 |
Effect of Long-term Service on Microstructure and Mechanical Properties of NiCrMoV Steel Welded Joint
1
Technology Development Department, Shanghai Electric Power Generation Equipment Co., Ltd.. Shanghai
2
Department of Mechanical Engineering, Tsinghua University, Beijing, China
Corresponding author: fanmj@shanghai-electric.com
The influences of prolonged service on microstructure evolution and mechanical properties of NiCrMoV steel welded joint in an ex-service welded steam turbine rotor were investigated. The welded rotor had been operated for 22 years since 1991. The specimens for the present study were taken from the location where the temperature was as high as 230°C. The optical microscope (OM) showed that even after long-term service, there were no obvious defects such as creep cavities, cracks found in the microstructure of the whole welded joint after such a long term service. The microstructure was uniform and no obvious grain coarsening was observed. However some black strip-shaped zones were found in base metal and heat affected zone (HAZ). The distribution of hardness across the welded joints showed no anomalies. The results of tensile strength and fracture toughness tests demonstrated that the welded joint still exhibited excellent. Mechanical performance after long-term service, indicating that the welding process of Shanghai Turbine Plant was reliable and stable. With the improvement of forging and welding qualities and improved heat treatment furnaces with more accurately controlled temperature, it is reasonable to assume that the current large low-pressure (LP) welded rotors are definitely safe to operate under similar service conditions for designed life.
© The Authors, published by EDP Sciences, 2019
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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