Abstract
Stainless steels are in general materials with strong resistance to different corrosive agents. This resistance is mainly related to the presence of chromium as an alloyed element in the iron-carbon alloy. The stainless steels are, on the other hand, susceptible to intergranular corrosion particularly when the operating temperatures are in the range of 425 °C to 815 °C. This type of corrosion is mainly related to the precipitation of chromium carbides along the grain boundaries. This phenomenon gives rise to an appreciable diminution of chromium in the austenitic grains and consequently an inability to form the chromium oxide which is responsible for the corrosion resistance of the steels. In this work we present some cases of failures of stainless steel pipes used in a direct reduction mill of IMEXSA. The results presented indicated that the failures are mainly related to the sensitization phenomenon due to the precipitation of chromium carbides along the grain boundaries. Experimental results from stainless steel specimens which have been heat treated at high temperatures suggest that the sensitization phenomenon can be partially avoided using pipes with the appropiate heat treatment.
