Mechanical properties of Q235 and 20# steel after CO2 fire extinguishing treatment

The carbon dioxide fire extinguishing process can produce temperatures as low as −80 °C. However, the effect of rapid cooling and ultralow temperatures on the properties of steel is not yet clear. To accurately evaluate the effect of CO2 fire extinguishing on the mechanical properties of crude oil tank walls (Q235-B) and accessory and pipe materials (20#), this study employs tensile, Charpy impact, and bending tests to analyze the changes in the primary mechanical properties of Q235-B and 20# steels after three pretreatments: high-temperature burning, CO2 spraying, and CO2 fire extinguishing. The results of the study show that 1) the high-temperature burning process and short-term spraying of CO2 after fire may damage the mechanical properties of steel; 2) the rapid use of CO2 spraying after fire does not damage the mechanical properties of Q235-B or 20#; and 3) the three pretreatments investigated have little effect on the bending properties of all the specimens.