Effects of tempering temperature on temperature-dependent thermal properties of 1045 steel

The 1045 steel is extensively heat treated because its mechanical properties can be easily improved by thermal processes. Reliable knowledge of the relationship between microscopic structure and thermal properties is essential for the thermal design of parts and tools. This paper reports on coupling microstructural aspects with the effects of tempering temperature on the temperature-dependent thermal properties of 1045 steel. Thermal conductivity (k) and specific heat (c(p)) were simultaneously estimated using inverse heat conduction analysis. The thermal characterization technique handled a simple and low-cost experimental setup, based on transient one-dimensional heat transfer on samples subjected to different heat-treatment conditions. The results, which were discussed in connection with the resulting microstructures, demonstrated that all quenching and tempering (Q & T) conditions led to lower values of both thermal properties throughout the temperature domain. The tempering temperature was found to impact k more substantially. The robustness of the results was ascertained by recovering the applied heat flux based on linear regression equations for k and c(p) and temperature measurements. Accuracy analysis indicated that the inverse approach provides estimates with an uncertainty close to 4%.