新型铁素体耐热钢焊接接头的再热裂纹机制及多尺度预测模型

Due to the bursting and leakage caused by reheat cracking in the new ferrite heat-resistant steel welded joints of water wall used in Ultra Super Critical (USC) Power Plants, it is necessary to clarify the mechanism of reheat cracking under the influence of welding residual stress and microstructure in HAZ for the new ferritic heat resistant steel welded joints. In order to avoid reheat cracking in the field heat treatment or early high temperature and high pressure environment, it is urgent to establish a prediction model considering the welding residual stress and the microstructure in HAZ of the joints to realize the reheat crack prediction of the new ferrite heat-resistant steel welded joints. In this program, the modified T23 steel was selected. In order to clarify the effect of microstructure and residual stress on reheat cracking, a newly designed compact tension creep specimen with residual stress was developed for stress-relief cracking test. By combined 3D-Voronoi technology, peridynamic theory and finite element method, the multiple dimensioned dynamical propagation of crack was simulated to reveal the stress-relief cracking mechanism for the modified T23 steel welded joints. The evaluation and prediction of stress-relief crack susceptibility by means of the proposed model would provide a significant help to improve the saftey of power plants.

由于超超临界锅炉机组上使用的新型铁素体耐热钢水冷壁管焊接接头的再热裂纹导致的爆管和泄漏，因此急需建立基于焊接残余应力和接头粗晶区微观组织对再热裂纹形成的作用机理，建立考虑焊接残余应力和接头粗晶区微观组织的预测模型，实现新型铁素体耐热钢焊接接头再热裂纹预测，形成一种现场热处理或早期高温高压环境中避免再热裂纹的有效方法。本项目以新型铁素体耐热钢－改进的T23钢为研究对象，采用可预制三轴残余应力的预压缩－紧凑拉伸（CT）试样进行再热裂纹模拟试验，探讨再热裂纹与微观组织（晶界特征、析出相）和焊接残余应力间关系，全面掌握焊接残余应力对焊接结构再热裂纹的作用机制；基于有限元数值模拟方法、3D-Voronoi划分技术和近场动力学，建立多轴残余应力状态下焊接结构再热裂纹的本构描述和多尺度动态裂纹数值模型，实现新型铁素体耐热钢焊接接头再热裂纹的评估和预测，对提高超超临界电站运行安全有重要意义。

由于超超临界锅炉机组上使用的新型铁素体耐热钢水冷壁管焊接接头的再热裂纹导致的爆管和泄漏，本项目建立基于焊接残余应力和接头粗晶区微观组织对再热裂纹形成的作用机理，建立考虑焊接残余应力和接头粗晶区微观组织的预测模型，实现新型铁素体耐热钢焊接接头再热裂纹预测，形成一种现场热处理或早期高温高压环境中避免再热裂纹的有效方法。本项目以新型铁素体耐热钢－改进的T23钢为研究对象，采用可预制三轴残余应力的预压缩－紧凑拉伸（CT）试样进行再热裂纹模拟试验，探讨再热裂纹与微观组织（晶界特征、析出相）和焊接残余应力间关系，全面掌握焊接残余应力对焊接结构再热裂纹的作用机制；建立多轴残余应力状态下焊接结构再热裂纹的本构描述和多尺度动态裂纹数值模型，实现新型铁素体耐热钢焊接接头再热裂纹的评估和预测，对提高超超临界电站运行安全有重要意义。