通过化学成分分析、力学性能测试、金相检验以及扫描电镜分析等方法对某规格为457 mm×7.1 mm的X65级高频焊(HFW)钢管水压试验时发生爆裂的原因进行了分析。结果表明: 钢管爆裂失效是由于其直焊缝上存在冷焊缺陷以及焊缝冲击韧度不合格所致; 焊缝中存在冷焊缺陷使其有效承载面积减小, 原始裂纹在冷焊缺陷处萌生并扩展, 加之焊缝冲击韧度低, 抗裂纹扩展能力差, 在水压试验压力作用下最终导致该钢管于焊缝处失稳爆裂。

Bursting reasons for the 457 mm×7.1 mm X65 grade high frequency welded (HFW) pipeline was analyzed by means of chemical compositions analysis, mechanical properties test, metallographic examination and scanning electron microscope analysis. The results show that existing cold welding defects in the welding line and disqualification of impact ductility of the welding line were main reasons for the bursting. The effective bearing area reduced because of the cold welding defects and the original cracks initiated and expanded in the welding line. At the same time the ability of resistance the crack spreading was worsened because of low impact ductility of the welding line. So the X65 grade pipeline burst at the welding line under the force of hydraulic pressure test.