Research on CT90 Coiled Tubing Butt Welding Process and Joint Performance

The butt welding of the Φ60.3 mm×4.8 mm CT90 coiled tubing is conducted by means of the manual TIG process, and the strength, plasticity, toughness, hardness and fatigue life of the weld joint are tested. The test results show that the performance of the coiled tubing butt welding joint is good, and the hardness difference between the weld, the HAZ and the base metal is not obvious;no significant softening is found in the HAZ;the tensile property, bending deformation resistance, the collapse resistance, and the internal pressure resistance of the welding joint are all excellent;and its average fatigue life is up to 50% of that of the base tube, having been in full compliance with relevant oil field work requirements.