12Cr1MoVG高温管道中异种钢焊缝引起的局部热应力

Local Thermal Stresses Induced by a Dissimilar Weld in a 12Cr1MoVG High Temperature Piping System

某12Cr1MoVG蒸汽管道非正常地采用了奥氏体不锈钢焊缝,高温工作条件下此焊缝局部区域可能存在较高的热应力,为管道安全运行带来隐患。分别采用弹性和弹塑性有限元方法,对局部热应力进行了分析。分析发现仅局部热应力就会引起整个焊缝和母材上的邻近带状区域发生屈服,且不能满足静载强度条件。简化的热循环计算表明,焊接接头会存在热棘轮现象。以弹性安定性为判据得到的管道使用温度上限为250℃,而标准中对异种钢之间焊接接头370℃的使用温度限制并不适用于本文同材质钢管之间的异种焊缝。

Austenitic stainless steel weld was abnormally adopted in a 12 Cr1 MoVG steam piping system;additional high level thermal stress may exist in the local areas of the weld under high temperature working conditions,a potential factor that may cause failure. Local thermal stresses were analyzed using elastic and elastic-plastic finite element method,respectively. It is found through analysis that the local thermal stress itself can yield the whole weld and a band-like adjacent area in the base metal,and cannot satisfy the statistic strength criteria. Thermal ratcheting will occur in the weld according to the simplified thermal cycling calculation. The upper operating temperature of the weld joint was 250 ℃ obtained according to elastic shakedown criterion,and the temperature limitation of 370 ℃ on weld of dissimilar steels in the standard is not suitable for dissimilar weld between pipes made of the same type of steel.