基于非线性超声的Super304H钢高温老化状态检测研究  

Assessment of high temperature aged super304H steel by nonlinear ultrasonic technology

作　　者：袁廷璧 张曰涛 王昉 YUAN Tingbi;ZHANG Yuetao;WANG Fang

机构地区：[1]国能锅炉压力容器检验有限公司,北京102209 [2]华能左权煤电有限责任公司,山西晋中032600

出　　处：《电力科技与环保》2021年第4期20-28,共9页Electric Power Technology and Environmental Protection

基　　金：国家能源集团科技项目(GJ2016Y01J)。

摘　　要：Super304H耐热钢被广泛地运用于超超临界机组的过热器和再热器管道,随着超超临界机组运行日久,Super304H耐热钢在高温载荷作用下发生的高温损伤、力学性能退化以及劣化失效问题也越来越显著,其高温老化过程和早期损伤快速检测研究对于机组安全运行具有重要意义。非线性超声信号对微纳米尺度的微小缺陷和微裂纹比较敏感,能够填补传统无损检测方法在微尺度检测领域的空白,在材料早期损伤检测方面具有极大的应用潜力。研究了Super304H耐热钢高温时效条件下微观组织形貌、析出相形态和成分的变化情况,利用非线性超声技术得到材料时效保持时间与超声非线性系数之间的关系曲线,并根据材料的显微组织演变特征进行了分析。试验结果显示,在700℃时效温度下,Super304H耐热钢析出相的数量和尺寸逐渐增加,并随时效保持时间依次在晶界和晶体内部富集,析出相成分主要为块状的Cr_(23)C_(6)和Nb(C,N)相;Super304H的超声非线性系数随时效时间的增加而单调增加。超声非线性系数变化曲线的斜率与共格应变的形成程度有关,共格应变状态取决于时效过程中的晶粒和析出相的相互作用。试验结果证明了非线性超声对于Super304H钢时效样品的热损伤程度评估的可行性,为高温工况下Super304H钢非线性超声检测提供了理论依据。Super304H heat-resistant steel was widely used in superheater and reheater pipes of ultra-supercritical units.The problems of high temperature damage,degradation of mechanical properties and deterioration of Super304H heat-resistant steel arose increasingly in power plant with the long-term operation of ultra-supercritical units.As a result,study of high temperature aging process and early damage was meaningful to Super304H steel.The nonlinear ultrasonic signal was sensitive to micro defects and micro cracks at the micro-nano scale,which can fill the blank of traditional nondestructive testing methods in the field of micro-scale detection.In this work,the microstructure and the precipitates of high temperature aging Super304H steels were studied,and the quantative analysis between aging time and nonlinear ultrasonic coefficient was described and the mechanism was discussed based on the microstructure characteristics of aging steel samples.The results showed that,the number and size of precipitates gradually increased at the aged temperature of 700℃,and successively enriched in the grain boundary and the crystal with the increasement of aged time,The main components of precipitated phase were bulk Cr_(23)C_(6) and Nb(C,N)phase.The Nonlinear ultrasonic increased monotonically as the aged time increased,and the slope of the variation curve could be due to degree of of coherency strain formation.The coherency strain state depends on the interaction of grains and precipitated phases during aged process.The results demonstrated the feasibility of non-linear ultrasonic evaluation of thermal damage of Super304H steel,and provided a theoretical basis for nonlinear ultrasonic detection of Super304H steel under high temperature conditions.

关 键 词：SUPER304H钢 非线性超声 高温老化 超超临界机组 

分 类 号：TG142[一般工业技术—材料科学与工程] TH212[金属学及工艺—金属材料]