Abstract：The mechanical properties and microstructure of 304 stainless steel under different heat input conditions in power fire scenes were studied, and the relationship between mechanical properties and microstructure evolution of 304 stainless steel under maximum fire temperature and different cooling conditions was analyzed. The results show that: At the same temperature, the holding time has little effect on the mechanical properties of 304 stainless steel. With the increase of temperature, the flow stress of the material decreases significantly. The tensile strength and yield strength of 304 stainless steel linearly decrease to 34.5MPa and 13MPa respectively at 1100℃, and the elongation after breaking increases linearly, increasing to 132% at 1100℃. At 1100℃, when the holding time is less than 30min, the grains gradually grow in the form of multiple grains merging into a large grain. When the holding time is more than 30min, annealing twins begin to appear inside the large grains, and the grain and structure no longer change. Cooling conditions have little effect on the overall mechanical properties of 304 stainless steel, tensile strength under different fire conditions compared with room temperature change rate is not more than 5%, yield strength at room temperature ~1000℃ change rate is not more than 10%, 1100℃, air cooling and water cooling conditions yield strength decreased to 81% and 86%, mainly due to the rapid growth of grains at 1100℃. The average grain diameter is 74.2μm.
2024, Vol. 31 