Comparison research on spectral emissivity of three copper alloys during oxidation

•The emissivity of three copper alloys was investigated contrastively.•The emissivity discrepancies were explained from composition's perspective.•The thicknesses of oxide film calculated by two methods were analyzed. Accurate temperature measurement plays an important role in improving quality, saving energy and reducing consumption in the hot rolling. The crucial part of temperature measurement is the reliable data of spectral emissivity whose precise measurement can improve the accuracy of the radiation temperature measurement. In this work, the spectral emissivity of red copper, brass and cupronickel alloy at four oxidation temperatures (673, 773, 873 and 973 K) heating for 120 min is measured in the wavelength range of 2–20 μm. The dependency on wavelength, temperature, composition and oxidation of the emissivity for three copper alloy samples is investigated contrastively. The results show that the oscillation phenomenon exists in the emissivity distributions of three copper alloy samples, but the temperature at which the most violent oscillation occurs is different. The perspective of sample composition is accounted for the discrepancies in oxidation progress and degree of three copper alloy samples at the same temperature. Finally, the thickness of oxide film calculated based on the principle of thin film interference is compared with that measured by observing the cross-section of sample using scanning electron microscope (SEM), which is in accordance with the experimental results.