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| Microstructural Evolution and High-temperature Mechanical Properties of In-service Super304H Heat-resistant Steel Tube |
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| DOI：10.7643/issn.1672-9242.2022.12.017 |
| KeyWord:ultra-supercritical unit Super304h steel tube grain size secondary phase microstructural evolution high-temperature mechanical property |
| Author | Institution |
| LIU Run |
School of Materials Science and Engineering, Hefei University of Technology, Hefei , China |
| LIU Jun-jian |
Datang Boiler and Pressure Vessel Testing Center Co., Ltd., Hefei , China;Datang East China Electric Power Test and Research Institute, Hefei , China |
| WANG Wan-li |
Datang Boiler and Pressure Vessel Testing Center Co., Ltd., Hefei , China |
| WU Yue |
Datang Boiler and Pressure Vessel Testing Center Co., Ltd., Hefei , China;Datang East China Electric Power Test and Research Institute, Hefei , China |
| WANG Yan |
Datang Boiler and Pressure Vessel Testing Center Co., Ltd., Hefei , China |
| TANG Wen-ming |
School of Materials Science and Engineering, Hefei University of Technology, Hefei , China |
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| Abstract: |
| The work aims to explore the effects of microstructural evolution of outer-wall coarse grain zone of the in-service Super304H steel tube and the effects on its high-temperature mechanical properties, to provide technical support for operation management and safety assessment of the ultra-supercritical units. The microstructure and the tensile mechanical properties of the in-service Super304H heat resisting steel tube of different service duration were studied to discuss the austenite grain abnormal growth and secondary phase precipitation of the outer wall and its effects on the high-temperature mechanical properties of the steel tube. The results showed that the secondary phases in the in-service Super304H steel tube were mainly composed of the copper-rich phase, MX and M23C6. The austenite grains of the outer wall grew abnormally to form the coarse grain zone, while the grains near the inner wall of the steel tube grew slowly to form the fine grain zone. Compared with the fine grain zone, more secondary phases of a higher size and a lower dispersion degree were precipitated in the austenite grains and along the austenite grain boundaries in the coarse grain zone, leading to a significant decrease in the high-temperature tensile properties. Therefore, a strict metal supervision is required for Super304H heat resisting steel tube in long term operation at high temperature to eliminate the potential safety risk due to abnormal growth of the austenite grains in the outer wall. |
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