Abstract：The fracture of stop valves was observed in batches after use for one year. The fractured stop valves were comprehensively analyzed by means of chemical composition, hardness, microstructure and fracture appearance. The results showed that the chemical composition of the stop valves could meet the requirements of national standards (the mass fraction of Zn exceeds 38% of the total mass fraction). There was no abnormality for the hardness and microstructure. The fracture appearance indicated that the stress corrosion was the main reason to cause the failure of stop valves. The combined effect of three factors, i.e., no stress relief annealing was conducted for this batch of stop valves, the tightening force was larger, and the environment humidity was high, caused stress corrosion of stop valves which had strong tendency to stress corrosion. As a result, the early fracture occurred.
2023, Vol. 41 
