Fracture causes of a tubing

A tubing fractured at about 211 mm away from the end thread of the pipe from the thick end of the pier. The fracture causes of tubing was analyzed by macroscopic observation, chemical composition analysis, fracture analysis and metallographic examination. The results show that there were H₂S and CO₂ in the operating environment, non-metallic inclusions in the microstructure of the tubing, mechanical damage caused by tools and fixtures on the tubing produces local hardening and stress concentration, resulting in stress corrosion cracking of the tubing under wet H₂S environment.