Application of a new radiation thermometry method to galvannealed and cold-rolled steels

The authors describe an experimental and analytical study of a novel radiation thermometry method. The method uses a priori knowledge concerning the reciprocal relationship between two uniquely defined spectral emissivities, making quite accurate temperature measurement possible for materials to which conventional spectral and ratio methods are not applicable. The validity of the method is demonstrated by experimental results on galvannealed and cold-rolled steel specimens, whose emissivity changes by alloying and oxidation, respectively. Zinc film thickness, steel grade, and alloying temperature had little effect on the reciprocity function for the two emissivities. It is concluded that the use of two polarized spectral emissivities at the same wavelength can be advantageous in measuring the temperature and emissivities of cold-rolled steel in a continuous annealing furnace