高载小幅波动对X80管线钢近中性pH土壤应力腐蚀开裂的影响研究

Study on Effect of High Load Fluctuation with Relatively Narrow Range on Stress Corrosion Cracking of X80 Pipeline Steel in the Soil with Near-neutral pH Value

在模拟近中性pH土壤腐蚀环境的NS4溶液中,通过高载小幅拉-拉交变载荷条件下的应力腐蚀开裂试验,研究了高载小幅波动载荷对X80钢管焊缝材料近中性pH土壤应力腐蚀开裂的影响。结果表明,载荷波动会促进应力腐蚀开裂裂纹扩展,最大应力给定时,应力比R越低,应力波动幅度越大,裂纹扩展速率越快。在应力水平较高时,应力比变化对应力腐蚀开裂速率的影响程度要明显大于应力改变带来的影响。故对在役X80高强度管道,要尽可能控制压力波动,以降低管道发生近中性土壤应力腐蚀开裂失效风险。

In NS4 solution simulating near-neutral pH soil environment,the effect of high load fluctuation with narrow range on stress corrosion cracking of X80 steel pipe weld material were studied by alternating tension-tension loading test.The results show that load fluctuation could substantially promote propagation of SCC of X80 steel pipe weld in near-neutral soil.For a given maximum stress,the lower the stress ratio R is,the bigger the fluctuation range is,and the faster the SCC propagation rate is.The impact degree of change in stress ratio R on the SCC rate is apparently big than the effect brought by change in stress under relatively high stress level.Therefore,for X80 high-strength pipeline in service,it is required to control the range of load fluctuation as much as possible in order to reduce SCC failure risk of the pipeline in near-neutral pH soil.