通过宏观检验、金相检验和断口分析等方法, 对F304不锈钢截止阀卸压杆断裂的原因进行了分析。结果表明: 卸压杆发生了应力腐蚀开裂, 裂纹起源于杆中心孔内壁并向材料中扩展;开裂的原因是卸压杆冷加工成形后未进行高温固溶处理, 奥氏体不锈钢中存在大量形变诱发马氏体组织, 同时天然气中存在硫等腐蚀性物质, 导致氢脆型应力腐蚀, 最终造成卸压杆断裂。

The fracture reason of pressure relief valve rod of F304 stainless steel was investigated by macroscopic inspection, metallographic examination, fracture analysis and so on. The results showed that the fracture of rod belonged to stress corrosion cracking. Cracks initiated from the inner surface of rod center hole and expanded to outer surface of rod. The cracking reason was that pressure relief valve rod had not been heat-treated for solid solution after cold working and led to a large number of strain induced martensite structure appeared in austenite stainless steel. There was corrosive substance including sulfur in natural gas. Hydrogen embrittlement stress corrosion cracking occurred in pressure relief valve rod.