INFLUENCE OF METAL ALLOYS RADIATIVE CHARACTERISTICS ON METHODICAL ERRORS OF TWO-COLOR COMPENSATIVE AND CLASSICAL THERMOMETRY

Investigations of methodical errors of two-color compensative and classical energy and spectral ratio pyrometry are  performed  under  conditions  of  changeable  radiative  characteristics  of metal  alloys. To  quantitatively  estimate  the  radiative characteristics we  proposed  such  parameters  as  an  average  level  of  emissivity  and  selectivity  factor. As  average  (adjustment) values  of  these  parameters  we  chose  the  values,  which  correspond  to  tungsten  in  vacuum  with  temperature  1600  K  (for wavelengths  0.7  and  0.9 µm). The  ranges  of  changes  of  these  parameters  correspond  to metallurgical  furnaces  and  aggregates conditions  in  optimal  sighting  zones.  In  accordance  with  adjustment  values  of  radiative  characteristics  the  corrections  in mathematical models of classical and two-color compensative  thermometry were made. On the base of analysis of  thermometry methods mathematical models influence regularities of emissivity average level and selectivity coefficient on methodical errors are established. As distinct  from classical  thermometry, methodical errors of  two-color  compensative  thermometry practically don’t depend on selectivity factor. This fact is advantage of two-color compensative thermometry.  In such a way we can minimize the errors of contactless temperature measurements of metal alloys coated by transparent and semitransparent oxide films. These films cause significant changes in the selectivity factor. The deviations of average level of emissivity from adjustment value which cause methodical errors absolute values 1.0 % and 0.5 % are determined. They are ±0.042 and ±0.020, correspondingly. The complex influence of  radiative characteristics on methodical errors of optical  thermometry  is  the most widespread  in metallurgy. That  is why the ratio of investigated methods errors will change depending on ratio of radiative characteristics. The function between the selectivity factor and the average level of emissivity which demands the equality of methodical errors of all investigated methods is  determined.  Under  the  complex  influence  of  average  level  of  emissivity  and  selectivity  factor  the  errors  of  two-color compensative thermometry are lower than the errors of infrared classical energy and spectral ratio thermometry in 1.04–1.26 and 1.21–1.57 times, respectively.