不锈钢封头在低温临氢工况下的开裂分析

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Through the means of hardness testing, detection of the martensite content, metallographic analysis and the cracks observation, the causes of cracking on the convex head of austenitic stainless steel in hydrogen service at low temperature were analyzed. The results show that the reason of failure is hydrogen induced cracking （HIC）, including the interaction of cold deformation, hydrogen diffusion at different temperature. Martensitic phase transformation and dislocation density increasing caused by cold forming are the ultimate causation of HIC. The residual stress created favorable conditions for crack formation and propagation. -50 ~C to -100 ~C temperature changing is the direct factor in the cracking of the heads. Solution annealing of metastable austenite stainless steel components after cold forming is an effective mean to reduce the hydrogen embrittlement susceptibility.利用硬度检测和马氏体含量检测、金相组织及现场裂纹观察等手段，对某低温临氢奥氏体不锈铜凸形封头的开裂原因进行了分析并进行了理论研究。认为该封头的开裂属于氢致裂纹（HIC），缘于冷加工形变、氢在不同温度下的扩散以及低温等因素的交互作用。冷加工变形所造成的马氏体相变、位错密度的升高是造成氢致裂纹的主要原因；残余应力为裂纹的形成与扩展创造了有利条件；氢在马氏体中的溶解度随温度变化而不同，从-50℃至-100℃溶解度降低幅度较大，析出的氢是造成封头开裂的直接因素。亚稳定型奥氏体不锈钢元件在冷加工成形后进行固溶处理是降低其氢脆敏感度的有效手段。