Indirect measurement of molten steel level in tundish based on laser triangulation

Abstract

For real-time and precise measurement of molten steel level in tundish during continuous casting, slag level and slag thickness are needed. Among which, the problem of slag thickness measurement has been solved in our previous work. In this paper, a systematic solution for slag level measurement based on laser triangulation is proposed. Being different from traditional laser triangulation, several aspects for measuring precision and robustness have been done. First, laser line is adopted for multi-position measurement to overcome the deficiency of single point laser range finder caused by the uneven surface of the slag. Second, the key parameters, such as installing angle and minimum requirement of the laser power, are analyzed and determined based on the gray-body radiation theory to fulfill the rigorous requirement of measurement accuracy. Third, two kinds of severe noises in the acquired images, which are, respectively, caused by heat radiation and Electro-Magnetic Interference (EMI), are cleaned via morphological characteristic of the liquid slag and color difference between EMI and the laser signals, respectively. Fourth, as false target created by stationary slag usually disorders the measurement, valid signals of the slag are distinguished from the false ones to calculate the slag level. Then, molten steel level is obtained by the slag level minus the slag thickness. The measuring error of this solution is verified by the applications in steel plants, which is ±2.5 mm during steady casting and ±3.2 mm at the end of casting.

Geometrical Model of Laser Triangulation System Based on Synchronized Scanners

“…The active source of laser triangulation technology [8,9] is one of the most common methods for 3D measurement, which generally includes point laser [10] and line laser [11,12]. There are two kinds of methods to obtain points cloud, such as probe movement and laser swing.…”

Molten Steel Level Measurement Based on Temperature Attenuation Characteristic

“…By analyzing the curvature of the vertical temperature distribution, this system precisely locates the molten steel level. Based on the above system, monocular vision 18) and laser device 19) plugins are introduced to acquire the slag level in real-time. Assuming the thickness of the slag is constant for 10 minutes, the system obtains the molten steel level in real time by the last molten steel level and the fluctuation of the slag level during the period.…”