Microstructure and Tensile Properties of a 1.25Cr-0.5Mo Main Steam Pipe After Long-Term Service

Volume 6B: Materials and Fabrication Pub Date : 2018-07-15 DOI:10.1115/PVP2018-84185

Bingxiu Yang, Wenchun Jiang, Wenjuan Sun, Yan-ling Zhao, Weiya Zhang

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引用次数: 1

Abstract

Metallographic tests, micro-hardness tests and tensile tests were conducted for a 1.25Cr-0.5Mo main steam pipe weldment served for more than 26 years. The results were compared with those for virgin material. Microstructural evolution of 1.25Cr-0.5Mo base metal was investigated. Degradation in micro-hardness and tensile properties were also studied. In addition, the tensile properties of subzones in the ex-service weldment were characterized by using miniature specimens. The results show that obvious microstructural changes including carbide coarsening, increasing inter lamella spacing and grain boundary precipitates take place after long-term service. Degradation in micro-hardness is not obvious. However, the effects of long term service on tensile deformation behavior, ultimate tensile strength and yield stress are remarkable. Based on the yield stress of micro-specimens, the order of different subzones is: WM > HAZ > BM, which is consistent with the order of different subzones based on micro-hardness. However, the ultimate tensile strength and fracture strain of HAZ are lower than BM. Brittle failures can happen more easily for HAZ due to its high yield ratio.

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1.25Cr-0.5Mo主蒸汽管长期使用后的组织与拉伸性能

对服役26年以上的1.25Cr-0.5Mo主蒸汽管焊件进行了金相试验、显微硬度试验和拉伸试验。并与未加工材料进行了比较。研究了1.25Cr-0.5Mo母材的显微组织演变。显微硬度和拉伸性能的退化也进行了研究。此外，利用微缩试样对退役焊件中各亚区拉伸性能进行了表征。结果表明:长期使用后，合金发生了碳化物粗化、片间间距增大、晶界析出等明显的组织变化。显微硬度退化不明显。然而，长期使用对拉伸变形行为、极限抗拉强度和屈服应力的影响是显著的。从微观试样的屈服应力来看，不同亚区顺序为:WM > HAZ > BM，这与显微硬度不同亚区顺序一致。然而，热影响区(HAZ)的极限抗拉强度和断裂应变均低于BM。热影响区由于其高屈服比，更容易发生脆性破坏。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Volume 6B: Materials and Fabrication

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