在JCOE成型过程中一根X80输油钢管母材发生纵向开裂, 裂纹长度达到了700 mm。通过化学成分分析、力学性能测试、断口分析及金相检验等方法分析了钢管的开裂原因。结果表明: 大尺寸外来非金属夹杂物的存在导致了钢板在连铸或轧制过程中产生裂纹。而较低的断裂韧度为裂纹进一步扩展创造了条件, 在成型拉应力的作用下微裂纹扩展并延伸。

One X80 steel oil pipe experienced longitudinal cracking during JCOE forming, and the crack length was getting up to 700 mm. The cracking reason was analyzed by means of chemical composition analysis, mechanical properties testing, fracture analysis and metallographic examination. The results showed that the primal crack resulted in pipe cracking during forming, and steel plate near the crack possessed low fracture toughness, which accelerated crack propagating under tension stress of forming. The existence of non-metal inclusions of big size was responsible for the generation of primal crack.