温度对Super304H焊缝金属再热裂纹敏感性的影响

Effect of Temperature on Reheat Cracking Susceptibility of Super304H Austenitic Stainless Steel Weld Metal

Super304H奥氏体不锈钢是超超临界火电机组中过热器与再热器管道的重要材料,在高温长期服役条件下,管道焊接接头的装配处易产生再热裂纹。本研究使用预压缩CT试样的方法系统研究了温度对Super304H奥氏体不锈钢焊缝金属再热裂纹敏感性的影响。结果表明,650℃时效温度下的焊缝金属产生裂纹所需的时间比600℃时效温度下所需时间更短,具有更高的再热裂纹敏感性。导致该现象的主要原因在于,650℃时效温度下晶界强度随时间延长退化更快,应力松弛速率更高,而不同温度下晶内强化差异带来的影响较小。

Super304H austenitic stainless steel has been widely used in superheater and reheater pipes of the ultra-supercritical thermal power unit boilers.During long-term thermal exposure,reheat cracking is prone to occur at the assembly sites of the pipeline weld joint.This study systematically studied the effect of temperature on the reheat cracking susceptibility of Super304H austenitic stainless steel weld metal by a pre-compressed CT specimen method.The results show that the time required for the weld metal to generate cracks at 650 °C is shorter than that of the weld metal at 600 °C,leading to a higher reheat cracking susceptibility.The main reason for this phenomenon is that the grain boundary strength decays faster with time and the stress relaxation rate is higher at 650 °C,while the effect of intragranular strengthening difference at different temperatures is negligible.