Experimental determination of the normal spectral emissivity of titanium at the melting point by the infinitely thin plate method
Alexander V. Kostanovskiy, Dmitry V. Presnyakov and Margarita E. Kostanovskaya
The Infinitely Thin Plate (ITP) method is used to determine experimentally the normal spectral emissivity εnλ=650 nm of titanium at the melting point. The measurement of temperature with ITP method required the sample in the form of a thin plate with thickness H = 60μm, the laser with beam radius r1 = 1.5 mm, and the pyrometer with the radius of the sighting spot r2 = 0.45mm, such that it has H ≪ r2 ≪ r1. The determination the normal spectral emissivity εnλ=650 nm is based on the Planck’s law and on the known true melting temperature of the material. The value of normal spectral emissivity of titanium at Tmelt = 1944 K equals εnλ=0.65 μm = 0.44 ± 0.02. In work the substantiation of reliability of measurement of radiance temperature of melting for the given experimental conditions is provided. The substantiation is made on the basis of the numerical solution of the non-stationary equation of heat conductivity. The heat flux depends on radius of a spot of heating and describes by Gauss law.