氧化层厚度对铸坯表面偏振角发射率的影响

Influence of Oxide Skin Thickness on Photoemissivity of Polarizing Angle from Surface of Continuous Casting Billets

发射率是铸坯表面温度测量精度的一个重要影响因素，在连铸表面测温现场应用过程中氧化层又是影响发射率的主要因素，根据波传播理论建立了铸坯表面辐射的多层模型，研究铸坯氧化层厚度变化对其发射率的影响．推导了铸坯表面偏振角发射率的递推公式，根据文献资料确定各层物理参数，通过计算结果发现，铸坯在水平偏振方向上的角发射率在60°～80°之间明显增强；当氧化层增厚到一定程度后，发射率逐渐稳定．这两个结论为设计现场表面测温装置提供重要的理论依据．

Photoemissivity is an important factor to the measurement accuracy by optical thermometry for the surface of continuous casting billets, while the oxide skin thickness affects greatly the photoemissivity in the measuring process. According to the theory of electromagnetic wave propagation, a multitayer model was developed for the surface radiation of the billets to investigate how the oxide skin thickness affects the photoemissivity. A recursion formula was deduced for the photoemissivity of polarizing angle from billet surface, where the physic parameters of different layers were given as shown in relevant literature. The calculated results revealed that the photoemissivity is significantly increased when the horizontal polarizing angle is in the range from 60°to 80°. However, the photoemissivity comes to be stabilized after the oxide skin thickness increases to a certain extent. The two conclusions will benefit theoretically the instrument layout for surface thermometry in site.