GT90连续油管对接焊接头的组织和性能分析

Microstructure and Mechanical Properties of Butt Welding Joint of GT90 Coiled Tubing

对GT90连续油管进行焊接工艺试验,分析其焊接接头组织及力学性能。分析认为:GT90连续油管焊接接头的焊缝组织为粒状贝氏体;由于焊接热循环的作用,焊接接头的热影响区出现软化,导致硬度、强度降低,在疲劳弯曲变形过程中,应变集中于软化区并发生断裂,使得接头疲劳寿命低于母材。对于连续油管,应采用较小的线能量进行焊接,以减少软化现象,改善接头力学性能不均,从而提高焊接接头的疲劳寿命。

Welding procedure test is conducted on the GT90 coiled tubing to analyze the structure and mechnical properties of its weld joint. It is concluded that the weld joint is of granular bainite structure; and due to the effect of welding thermal cycle, the butt welding weld joint HAZ shows softening that will result in decreased hardness and strength. During the process of fatigue bending deformation, strain will concentrate at the soften area and lead to fracture, which will make the fatigue life of the joint lower than that of the parent metal. So, in order to reduce softening phenomenon, improve mechanical properties and increase fatigue life of a weld joint, it is recommended to use smaller linear energy input to weld a coiled tubing.