Q235B 钢含硫污水罐的腐蚀开裂失效分析

目的对某炼油厂原料水罐Q235B钢腐蚀开裂失效原因进行分析。方法采用宏观形貌、金相组织和断口观察以及成分分析和力学性能测定等手段,分析Q235B钢腐蚀开裂失效的宏观和微观行为。结果 Q235B钢在污水罐罐顶形成的湿硫化氢环境中发生沿晶型应力腐蚀开裂。腐蚀过程中,电化学反应产生的氢渗入基体,导致微裂纹的萌生。腐蚀产物在基体表面积聚,其自身体积膨胀以及涂层的闭塞作用对基体形成非常大的拉应力。结论结合应力分析和环境分析,Q235B钢含硫污水罐的腐蚀开裂失效机制为硫化氢应力腐蚀开裂,应力来源于氢渗透和腐蚀产物膨胀。

Stress Corrosion Cracking Failure of Q235B Steel Used for Sulfur-containing Waste Water Tank

Objective Cause for corrosion crack failure of Q235B steel water tank served in a refinery was analyzed. Methods The macroscopic and microscopic behaviors of Q235B steel corrosion crack failure were characterized by means of macro-morphology, microstructure, fracture observation, chemical composition analysis and mechanical property analysis. Results In the humid atmosphere containing H2S formed at the top of the water tank, inter-granular stress corrosion cracks occurred for the Q235B steel. During the corrosion, micro-cracks were induced by permeation of the hydrogen generated by electrochemical reactions into the substrate. Meanwhile, the corrosion products accumulated on the surface of the substrate. Extremely large tensile stress was formed as a result of the combined effect of expansion of corrosion products and occlusion of the coating. Conclusion Combining stress analysis and environment analysis, the corrosion cracking failure mechanism of the Q235B steel sulfur-containing waste water tank was stress corrosion cracking induced by H2S, and the stress was derived from hydrogen permeation and the expansion of the corrosion products.