BNS酸性管线管氢致开裂试验不合格原因分析

Analysis of HIC Test Failure of BNS Sour Linepipe

通过对原材料理化、金相、能谱分析及氢致开裂(HIC)试样的相关分析来验证HIC试验不合格的原因。结果表明:原材料本身存在带状组织和变形的非金属夹杂物是HIC试验不合格的原因。带状组织具有较好的输氢通道,轧制后形成的高位错密度加速氢原子扩散;变形的A类非金属夹杂物周围应力集中,使氢原子更容易聚集形成局部富集。处于H2S环境下的试样在带状组织和变形的非金属夹杂物共同作用下,引起氢原子聚集,当富集区氢压超过材料抗拉强度时引起氢致开裂。

Through mechanical and chemical analysis,metallographic analysis,energy spectrum analysis on raw material and analysis of hydrogen-induced cracking(HIC)specimens to verify the reason of HIC test failure.Analysis results show the reason for the failure is caused by the raw material with band structure and deformed non-metallic inclusions.Band structure has a good hydrogen transport channel.High density dislocations formed after rolling accelerate hydrogen atoms diffusion.The concentration of stress around deformed Class A nonmetallic inclusions makes it easier for hydrogen atoms aggregation and form local enrichment.When samples are exposed to H,S environment,band structure and deformed non-metallic inclusions cause hydrogen atoms aggregation.Hydrogen-induced cracking occurs when the hydrogen pressure in the enriched area exceeds the tensile strength of the material.