文献类型：会议论文

英文题名：Failure analysis of spiral water wall tube cracking in Ultrasupercritical power plant boiler

作者：Si, Jun[1]; Yan, Zhenrong[1]; Chen, Jianjun[2]

机构：[1] Shanghai Institute of Special Equipment, Inspection and Technical Research, Shanghai, 200333, China; [2] School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai, 200237, China

会议论文集：ASME 2016 Pressure Vessels and Piping Conference, PVP 2016

会议日期：July 17, 2016 - July 21, 2016

会议地点：Vancouver, BC, Canada

语种：英文

外文关键词：Cracks - Steam turbines - Welds - Chemical analysis - Failure analysis - Pressure vessels - Residual stresses - Finite element method - Mechanical testing - Tubes (components) - Steam power plants - Failure (mechanical) - Outages - Fossil fuel power plants - Steam

摘要：The efficiency of conventional boiler/steam turbine fossil power plants has strong relationship to the steam temperature and pressure. At present, steam temperatures of the most efficient fossil power plants are now in the 600°C range. Higher-strength materials are needed for upper water wall tube of boilers with steam pressure above 24 MPa. A high-strength 2.5%Cr steel recently approved by ASME code as T23 is the preferred candidate material for this application. Due to its superior properties, T23 steel is typically not post-weld heat treated. However, after several years running there are a lot of incident reports for T23 tubes especially the breakage of weldment in the ultra-supercritical power plant. This is cause for concern for T23 tubes weldment used under high temperature environments. Previous studies showed that the residual stress may play an important role to the performance of spiral water wall tube. In this paper, the distribution of residual stress in T23 tube weldment has been investigated in detail. Inner wall cracks were found at the butt-jointed seam region of spiral water wall tubes by radiographic testing after one year's operation. Failure analysis of the spiral water wall tube cracking was conducted by chemical composition analysis, mechanical testing and finite element analysis in this paper. It was found that localized residual stress after the weld process caused concentrated stress, which is the primary reason for failure. Our studies illustrate the necessity of post weld heat treatment for the T23 tubes used under high temperature. Copyright ? 2016 by ASME.