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多次热处理对超超临界锅炉用 P92 钢显微组织及 硬度的影响
Effect of the Tempering Times on the Microstructure and Hardness of P92 Steel for USC Boilers
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- DOI:
- 作者:
- 王 瑜 1 ， 2 ，坚永鑫 1 ， 3 ，胡鹏飞 2 ，王耿洁 3 ，皇志富 3
WANG Yu 1,2 , JIAN Yongxin 1,3 , HU Pengfei 2 , WANG Gengjie 3 , HUANG Zhifu 3
- 作者单位:
- 1. 西安交通大学 机械工程学院，陕西 西安 710049；2. 陕西省特种设备检验检测研究院，陕西 西安 710054；3. 西安交 通大学 材料科学与工程学院 金属材料强度国家重点实验室，陕西 西安 710049
1. School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China; 2. Shaanxi Special Equipment Inspection and Testing Institute, Xi'an 710054, China; 3. State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China
- 关键词:
- P92 钢；回火处理；显微组织；析出相；维氏硬度
P92 steel; tempering treatment; microstructure; precipitated phase; Vickers hardness
- 摘要:
- 在超超临界机组用 P92 钢管道现场安装过程中，为了满足硬度标准经常对接头部位进行多次回火处理，但当前关于多次热处理对 P92 钢显微组织及其硬度的影响规律尚不清楚。为此，本文对 P92 钢进行 1~4 次回火处理，借助OM 、 SEM 、 XRD 、 TEM 及硬度计等分析其显微组织特征及硬度变化规律。结果表明，多次回火处理后 P92 钢均主要由板条状回火马氏体、原奥氏体界面处的 M 23 C 6 相和马氏体内的 MX 相组成，其物相组成无明显差异。 随回火次数增加，马氏体板条宽度逐渐增加， 4 次热处理后提高约 52.2% ；界面处的 M 23 C 6 析出相发生明显粗化，但析出相数量有所减少，主要粗化机制为 Ostwald 熟化；基体中 Cr 、 Mo 和 W 合金元素的固溶含量下降，导致回火马氏体的固溶强化作用减弱， P92钢的硬度呈现降低现象。During the installation process of P92 steel pipes in the ultra-supercritical units, tempering treatment is a popular method to adjust the hardness of weld joints so that the hardness can meet the installation standard. However, it is still unclear how repeated heat treatments affect the microstructure and hardness of P92 steel. Thus, P92 steel was subjected to 1~4 times of tempering, and the microstructure and hardness evolution were analysed by utilizing OM, SEM, XRD, TEM and hardness testing. The results show that P92 steel is mainly composed of lath martensite, the M 23 C 6 phase and the MX phase. The M 23 C 6 phase mainly precipitates on the interface of the lath or original austenite boundaries, while the MX phase distributes inside martensite laths. The phase composition of P92 steel has little change after different tempering times. With increasing tempering times, the width of the martensitic lath gradually increases by approximately 52.2% after 4 times of tempering. The M 23 C 6 phase at the interface obviously coarsens, while the amount gradually decreases. The main coarsening mechanism of the M 23 C 6 phase is Ostwald ripening. In addition, the contents of Cr, Mo and W alloying elements decrease in the matrix, causing the weakening of the solid solution strengthening. Consequently, the Vickers hardness of P92 steel tends to decrease with increasing tempering times.