How to Use Metallurgical Analysis for Fire Investigation: The Case of AISI 316 Stainless Steel

In this work, fire simulations were carried out on AISI 316 austenitic stainless steel sheets (similar to EN X5CrNiMo17-12-2), usually employed for the production of flue pipes. The thermal alteration induced by the fire was simulated by heating samples at different temperatures (from 20 degrees C to 1050 degrees C) and for different exposure times (1 h and 6 h) in a laboratory furnace. The metallurgical investigation concerned the surface coloring by photographic analysis; the morphology and chemical composition of the surface oxides by SEM and EDS; the microstructure as a function of temperature by LOM. The influence of the different parameters was discussed by a statistical ANOVA approach. The obtained results allowed to associate each temperature to one or more alterations in color, to the morphology and the chemical composition assumed by the surface oxides, as well as to the microstructure of the steel.