连铸坯表面高温场极化辐射测温方法研究

The essence of continuous casting production is the solidification process of liquid steel by temperature control, and the solidification speed is the most important factor in determining surface and internal quality of billets. Therefore, controlling billets to have a good solidification speed by online monitoring surface temperature distribution of billets is an important way to stabilize and improve the quality of billets. However, because of randomly scattered iron oxide scale on surface of billets and uncertain emissivity of billets, online surface temperature measurement accurately for billets still remains an academic difficulty which has not been well solved yet in metallurgical field. Concerning this issue, an online temperature measurement approach based on heterogeneous multi-source information fusion for billets is proposed in this project, and these information is provided by a CCD camera with high resolution, a solidification and heat transfer model for billets and a polarized radiation thermometer. In this approach, the analysis of the inherent features in temperature field for billets based on the solidification and heat transfer model could offer a new train of thought and tactics for eliminating the influences of iron oxide scale on temperature measurement for billets. Moreover, in order to find the pseudo-Brewster angle in which P-polarized radiation can be considered as a black-body radiation approximately, this project studies the characteristics of polarized emissivity for billets with multiple rough surface, and analyze the influence of thickness of oxidized layer and surface roughness on P-polarized emissivity, and these works would establish the theoretical foundation for polarized radiation thermometry for billets with uncertain emissivity.

连铸本质是通过温度控制实现从钢水到钢坯的凝固，钢水凝固速度决定了铸坯表面及内部质量，因此通过对铸坯表面温度场在线测量，实现合适的液态钢水凝固速度是稳定和提高铸坯质量的重要手段。然而由于铸坯表面随机分布的氧化铁皮以及发射率不确定等因素的影响,铸坯表面温度场在线准确测量至今仍是冶金测温领域未能得到很好解决的一项难题。针对这一问题，本项目提出一种基于高分辨率CCD、铸坯凝固传热模型以及单点红外极化辐射测温仪的异类多信息融合的铸坯表面温度场在线测量方法。该方法基于铸坯凝固传热模型分析铸坯表面温度场分布固有特征，为消除氧化铁皮对温度测量稳定性的影响提供一种新的研究思路。此外，对具有多层介质的铸坯表面极化辐射特性进行系统深入研究，分析氧化层厚度、表面粗糙度等因素对P极化发射率变化规律的影响，寻找P极化辐射近似黑体辐射的伪Brewster角，为解决发射率不确定的铸坯表面极化辐射测温奠定理论基础。

本项目以铸坯表面温度场在线测量为应用背景，对金属表面发射率特性以及面阵CCD高温计开发等相关工作进行了较系统的研究。建立了分层随机粗糙表面极化发射率模型，并构建了发射率测量实验装置。在此基础上，研究了金属表面法向光谱带发射率与温度、表面粗糙度以及氧化时间等因素之间的关系，并基于实验数据建立了发射率与温度之间的非线性模型。此外，基于等效中心波长的宽波段CCD高温计数学模型，开发了面阵CCD高温计，研究了波长、增益、光圈等参数对高温计温度测量灵敏度以及温度测量范围的影响，并对高温计光学系统中因渐晕的存在而引起温度场测量畸变这一问题，提出了一种简单有效的渐晕系数估计方法。本项目的上述研究结果对金属表面温度场在线测量提供了理论指导。