Stress corrosion cracking failure of 20 steel used for hot water pipe

The failure analysis for hot water pipes of 20 steel was performed by means of examinations of macro-morphology, metallograph and fractured surface, as well as chemical analysis and mechanical property measurement for the relevant materials. Results showed that the fracture occurred in the weld joints with obvious deterioration in weld area due to creep. The fracture initiated and propagated with typical brittle characteristics. The occurrence of corrosion products on cracking wall and in the cracking tip revealed that stress corrosion cracking (SCC) was the dominant factor of the pipe burst. Creep crack and fatigue characteristics were also found on the fracture, which accelerated the SCC and pipe burst.