Effect of niobium and grain boundary density on the fire resistance of Fe–C–Mn steel

We show that the addition of 0.10 wt.% Nb to Fe–C–Mn steel increases the failure temperature of the steel by 92 °C during a fire-resistance test. Moreover, we demonstrate that increasing the grain boundary density of the steel with NbC precipitates from 0.06 to 0.64 μm−1 by increasing the cooling rate during the austenite-to-ferrite phase transformation from 0.17 to 100 °C s−1 increases the failure temperature linearly by an additional 45 °C.

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