Post-Fire Response of Miilux 450 Wear-Resistant Steel Under Different Cooling Methods

Abstract The post-fire performance of Miilux 450 wear-resistant steel has been examined in detail. Three cooling methods including air cooling (AC), water cooling (WC), and CO₂ fire extinguisher cooling (CFE), were employed after the samples had been exposed to elevated temperatures ranging from 400 °C to 1000 °C. Next, tensile tests were carried out on the samples to determine the key mechanical parameters, specifically the yield strength and ultimate tensile strength. The findings showed that yield and ultimate tensile strengths decreased by up to 60% and 55%, respectively, up to 700 °C, and only minor differences among cooling methods were detected up to 700 °C. Above 700 °C, WC notably increased the strength and hardness compared to AC and CFE, which is attributable to martensitic transformation, though at the expense of ductility. The modulus of elasticity exhibited minimal reduction (< 12%) until 1000 °C and cooling methods thus have almost no effect on the modulus of elasticity. On the other hand, hardness trends paralleled strength variations. These changes were explained in terms of microstructural alterations that occurred due to the heat treatments employed. Predictive equations have been proposed to estimate post-fire mechanical properties as a function of temperature and the cooling method.