Effects of alloying elements and temperature on thermal conductivity of ferrite

Abstract

The thermal conductivity of steel and cast iron is often much lower than that of pure ferrite. One of the main reasons is the addition of alloying elements, which reduces the thermal conductivity of ferrite. Based on the theory of metal heat conduction, relationships between the thermal conductivity of ferrite and contents of alloying elements as well as temperature are established. Then, the effects of alloying elements and temperature on the thermal conductivity of ferrite are quantitatively and qualitatively analyzed, respectively. At 300 K, the effects of Si and Al on the thermal conductivity of ferrite are significant, while the effects of Mn, Cr, and Mo are relatively small and that of W is the weakest. However, the superposition of another element may change the influence of an alloying element on the thermal conductivity of ferrite. Within 300–800 K, the temperature dependence of electrical resistivity for alloyed ferrite is much weaker than that of pure ferrite. Although the phonon thermal conductivity of ferrite decreases monotonously with temperature, the electron thermal conductivity of ferrite changes from monotonic decreasing to monotonic increasing with the addition of alloying elements. The overall impact will make the thermal conductivity of alloyed ferrite with temperature decrease monotonously at low alloying content, and the latter increase first then decrease at medium alloying content, and finally increase monotonously at high alloying content.