P91管接头重复回火后的显微硬度与力学性能

Microhardness and mechanical properties in re-tempered weld zone of P91 pipeline

对经焊接、焊后热处理的P91无缝管接头分别进行1~4次回火处理,利用化学成分分析、常温和高温拉伸试验、显微硬度及金相检验等,研究了回火次数对焊接区域力学性能及显微组织的影响,并探索焊接区域在不同热处理次数下显微硬度与常温及高温力学性能的对应关系。结果表明,P91管焊接区域在多次回火热处理后,其显微组织为回火索氏体,但析出碳化物有增多的趋势;参比样的显微硬度与室温抗拉强度相关系数最大,即3.69,而回火一次后,试样的显微硬度与高温抗拉强度间相关系数达到最大值,即1.48。

The P91 weld joint was tempered for 1-4 times respectively after welding and postweld heat treatment. On the basis of chemical composition analysis,room temperature and high temperature tensile test,microhardness test and metallographic test,the effect of tempering times on the mechanical properties and microstructure of its welding zone was investigated and the relationship between microhardness and mechanical properties under different heat treatment conditions of the local regions was obtained. The results indicate that its microstructure is tempered sorbite after high temperature re-tempering,but there is a growing trend in the precipitation of carbides,and the correlation coefficient between microhardness and room temperature tensile strength of the reference sample reaches maximum（ 3. 69）,while when retempering once,its maximum correlation coefficient between microhardness and high temperature tensile strength reaches to 1. 48.