高含硫气田压力容器异种钢焊接接头失效泄漏原因分析

Cause analysis on failure and leakage of dissimilar steel welded joints at pressure vessels in high sulfur gas field

对国内某高含硫气田酸性湿气增压项目压缩机进气洗涤罐进行“酸敏试验”,试验过程中上封头与长高颈法兰连接角焊缝处即异种钢焊接部位连续出现了两次介质泄漏事故。通过宏观形貌观察、化学成分分析、金相组织分析、硬度测试、断口宏观与微观形貌分析等方法,对现场试样进行系统分析,再结合焊接冶金学机理分析,确定了异种钢焊接接头失效泄漏的原因。在硫化物应力腐蚀开裂敏感环境中,在残余应力与外加应力的共同作用下,裂纹沿最薄弱的熔合线分布,从内侧启裂,并向外侧扩展,最终穿透管壁,导致泄漏发生。

Acid sensitivity tests were carried out on the inlet washing tank of the compressor in a domestic wet gas pressurization project at high sulfur gas fields.During the experiment,two medium leakage accidents occurred at the fillet weld between the upper head and the long weld neck flange,that is,the welding site of dissimilar steel.Through macroscopic morphology observation,chemical composition analysis,metallographic structure evaluation,hardness testing,as well as macroscopic and microscopic morphology examination of the fracture surface,a systematic investigation of the on-site samples was conducted.Combined with welding metallurgy mechanism analysis,the reasons for the failure and leakage of welded joints at dissimilar steel were determined.In the environment susceptible to sulfide stress corrosion cracking,under the combined action of residual stress and external stress,cracks were distributed along the weakest fusion line,starting from the inside and expanding outward,ultimately penetrating the pipe wall and causing leakage.