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针对国内油气田较多应用的L415QB/UNS S31603双金属复合管环焊缝失效原因,采用金相显微镜、显微硬度计、扫描电镜和能谱仪对失效裂纹进行了形态、组织、成分分布和断口分析。研究发现,焊缝不同焊层间的组织差异,是焊缝开裂的组织因素;内衬与基管间贴合性能差造成的径向应力和焊缝横向应力,是焊缝开裂的力学因素。L415QB/UNS S31603复合管环焊缝焊接应采用ER309Mo L或E309Mo L填充材料,不应采用低合金E71T8-Ni1J焊材作为填充材料;焊接应选用较低热输入量的脉冲焊接工艺方法,以降低熔合比。
Aiming at the failure reasons of L415QB / UNS S31603 bimetallic composite ring girth welds with more applications in domestic oil and gas fields, the morphology, structure, composition distribution and fracture of the failure cracks were investigated by metallographic microscope, microhardness tester, scanning electron microscope and energy dispersive spectrometer analysis. It is found that the difference of microstructure between weld layers is the organizational factor of weld cracking. The radial stress and the transverse stress caused by poor bonding between liner and base pipe are the mechanical factors of weld cracking. L415QB / UNS S31603 composite pipe ring weld welding should be ER309Mo L or E309Mo L filler material, low alloy E71T8-Ni1J welding consumables should not be used as filler material; welding should use a lower heat input pulse welding process to reduce Fusion ratio.