EXPERIMENTAL DETERMINATION OF EMISSIVITY MODELS OF STEEL 201 AT 800-1100 K DURING OXIDE LAYER GROWTH

This work investigated the variation in the spectral emissivity with wavelength and temperature during the growth of an oxide layer on the surface of steel 201 specimens. The measurements were performed at the wavelengths 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and 2.1 µm over a temperature range from 800 to 1100 K in steps of 20 K. During the experiment, the specimen was kept at a certain temperature in air for 6 h. Multispectral radiation thermometry was used to measure the radiances stemming from the specimen surface and the spectral emissivity at a certain temperature. Two thermocouples were symmetrically welded on the front surface of specimens near the measuring area for accurate monitoring of the surface temperature. The average of their readings was regarded as the true temperature of specimens. With the spectral emissivity measured, the variation of it with wavelength was studied at different temperatures and at different heating times. Similar variation in the spectral emissivity with wavelength at different temperatures and different heating times showed that it was governed by the same emissivity models. Ten emissivity models were ex− the thermometry. The experiments proved that both the five-parameter LLWE and LWE models can generate the best overall temperature predictions during 6 h of heating. As a conclusion, we confirm that the five-parameter LLWE and LWE models could be employed to accurately predict the surface temperature of steel 201 over the present wavelength and temperature ranges regardless of surface oxidization.