超超临界机组低温再热器导向管夹焊缝泄漏分析

Leakage Analysis on Low-temperature Reheater Guide Clamp Weld of Ultra-Supercritical Unit

某1 000 MW超超临界机组投运4年内,低温再热器12Cr1MoV材质段水平管组导向管夹焊缝多次发生泄漏。取泄漏和未泄漏管样进行宏观、金相、显微硬度、断口扫描等检验,结果发现:低温再热器导向管夹连续多次泄漏,主要是由于施焊环境温度过低、焊条尺寸选用不当、焊接电流偏大导致在角焊缝内侧熔合线区域形成焊接裂纹。原始焊接裂纹在应力作用下疲劳扩展,导致最终泄漏。

Leakage failure occurred frequently in the guide tube-clamp weld of low-temperature reheater in a4-year 1000 MW USC unit. Leaked and unleaked tube samples were taken for macroscopic, metallographic,microhardness, fracture scanning and other tests. It was found that the main reason for the continuous multiple leaks was that the welding problem is caused by low welding temperature, improperly selected electrode size and large welding current, resulting in the formation of welding cracks in the fusion line area inside the fillet weld. The original welding crack expanded under stress, resulting in a final leak.