Failure Analysis of the Openings of Copper Converter in Sarcheshmeh Complex after Service Exposure

In the present study, the austenitic heat resistant cast steel was investigated in as-cast conditions and after being used in copper converter parts. Specimens were cut from an ex-service failed converter part which has been aged for 1900 h. The openings of copper converter in Sarchashmeh Copper Complex in Iran are made of a heat resisting austenitic steel Fe-25Cr-15Ni. Microstructural changes after working period were studied via optical microscopy and scanning electron microscopy equipped with energy dispersive spectrum. The effect of temperature and carbon diffusion on the microstructure, chromium-rich carbides, the chromium carbides transformation to sigma phase and other precipitates during service condition were discussed. The diffusion of SO2 and copper and formation of sub layer decrease the mechanical properties. The formation of sigma phase can be lead to degrade the ductility and toughness.