L415+316L机械复合管焊接接头失效分析

为了减少油田L415+316L复合管环焊接头在水压、运行过程中的失效现象,利用硬度测试、组织分析、弯曲试验、断口形貌分析等方法对开裂的焊接接头进行试验研究。分析发现,由于封焊层、过渡层是高合金钢与碳钢之间的焊接,焊缝易因增碳造成硬度偏高,从而导致韧性降低;R309L封焊层、R309LMo过渡层焊缝的断口均呈现准解离状态,为脆性断裂,焊接接头的封焊层因承受较高应力集中而产生裂纹,且裂纹沿轴线方向扩展。分析得出的复合焊管焊接接头开裂原因,可为复合管设计者改进设计提供参考。

Failure Analysis on Welded Joint of L415+316L Mechanical Composite Pipe

In order to reduce the failure phenomenon occurred in hydraulic pressure and operation course of L415+316L composite pipe circumferential welded joint, the cracked welded joint was analyzed by hardness test, microstructure analysis, bending test and fracture morphology. The results showed that because of the sealing layer, transition layer are welded by high alloy steel and carbon steel, the weld recarburization easily causes high hardness, thus lead to lower toughness. The R309L sealing layer and the weld fracture of R309LMo transition layer show a quasi-dissociation state, it is brittle fracture. The sealing layer of welded joint generate cracks because of bearing high stress concentration, and extend along the axis direction. Finally, the cracking reasons of composite pipe welded joint were obtained, which can be used as the reference for the designer to improve design.