使用积分球系统测量了1.319μm处45#钢反射率随温度的变化规律，通过对实验后钢片表面的能谱分析，揭示了反射率发生变化的原因。测量结果表明，钢片温度从常温升高至325℃时，表面反射率不会发生显著变化；在325℃到395℃之间，反射率从0.64降低到约0.15；在395℃与440℃之间，反射率不再发生明显变化；钢片降温过程中反射率不再发生明显变化，其值与最高温度处的数值基本相同。反射率的变化主要源于钢片表面发生的氧化反应，温度越高，氧化反应越剧烈，表面氧元素的含量就越高，反射率也就越低。

Temperature dependence of reflectivity of 45# steel at the wavelength of 1.319μm was measured by using an integrating sphere system. The change of the reflectivity was explained by analyzing the surface energy spectrum of steel plates, which was heated. Reflectivity didn’t change remarkably in the range of room temperature to 325℃, and it decreased from 0.64 at 325℃ to 0.15 at 395℃. As the temperature kept on increasing, the reflectivity didn’t change obviously. In the cooling process, reflectivity held as a nearly constant value, which was the same as the value at the highest temperature. The change of reflectivity is mainly due to the oxidation of surface. As the temperature rises, oxidation reaction becomes severe and the atom percentage of oxygen in the surface increases, so the reflectivity decreases.