Stress Corrosion Cracking of A723 Steel Pressure Vessels: Two Case Studies

摘要

Two separate investigations of apparent stress corrosion cracking of cannon tubes under field service conditions are described. The first investigation involved several tubes in which cracking initiated at the inner diameter surface due to the combination of cannon firing products and tensile residual stresses. Results of metallographic and fracture surface studies; residual stress measurements; fatigue life and material mechanical tests; and stress corrosion simulation tests of tube sections are presented and discussed. The second investigation involved two tubes in which apparent stress corrosion cracking occurred on the outer diameter surface due to the combination of an unknown substance, presumed to be a cleaning product, and tensile residual stress due to autofrettage of the tube. The critical requirements for stress corrosion cracking are discussed in general and in relation to the pressure vessels of the two investigations. Conclusions are drawn regarding design and service conditions for pressure vessels which will help prevent the occurrence of stress corrosion cracking.