Failure Analysis on Fracture of P110S Steel Grade Tubing

A P110S steel grade oil tubing was found fractured completely along the transversal direction during acidification operation in an oilfield. The fracture reasons of the oil tubing were analyzed by means of macro observation, chemical composition analysis, metallographic examination, mechanical property test, scanning electron microscope, energy spectrum analysis and so on. The results show that the fracture of the tubing was caused by sulfide stress corrosion cracking. The cracks initiated from the bottom of the tooth mark in the clamping area of the oil tubing. The work stress and the stress concentration at the bottom of the tooth mark, the sulfur-containing corrosive medium and the high strength of the tubing, these three causes resulted in the sulfide stress corrosion cracking of the tubing.