Dispersions of Optical Constants and Emissivities of Iron and Steel in the Temperature Range up to the Curie Point

Reflectivities of iron, mild steel, hard steel and stainless steel (SUS304) are measured in the wavelength region from 0.34 to 25μm and at the temperatures up to 900°K. The optimum values are obtained from the experimental data for the model parameters of the two-electron-type dispersion formula of optical constants. The dependence of the parameters on temperature and impurity concentration is examined by the theory of electric conductivity. The dependence is applied to express the optical properties of metals at the temperatures up to the Curie point for iron and carbon steel, and up to 900°K for stainless steel. Spectral and total emissivities are calculated for the iron and steel, which show a large dependence of emissivities on wavelength, temperature and impurity concentration.