Post-fire recovery and residual mechanical properties of SS304 stainless steel sheet

Fire exposure can degrade steel mechanical properties, affecting structural integrity and serviceability; however, structural redundancy may allow steel systems to remain standing after fire. This study experimentally investigates residual mechanical properties of SS304 stainless steel (conforms to Indian Standard IS 6911:2026) sheet after exposed to elevated temperatures. Initially, coupons were heated to 200–1100 °C for 30 min and cooled by air or water spray. Reduction factors for elastic modulus, yield strength, tensile strength, and hardness were evaluated. Test results show that elastic modulus remained unaffected by heating, except at 1100 °C under water spray cooling, whereas yield strength decreased above 600 °C. Tensile strength showed an average reduction of 14% between 300 and 800 °C. Empirical correlations were developed between post-fire yield strength and tensile strength against Vickers hardness, although the relationship exhibited considerable scatter. A comparative study of the existing predicted equations with the present experimental results are conducted in this study. Following two sets of unified predictive equations are proposed separately for the present experimental results and also by considering the existing experimental dataset for the austenitic stainless steel available in the literatures. Reliability analysis demonstrated that these equations satisfied target reliability requirements and agreed well with experimental data.