Mechanism Of Vibration Style Ladle Slag Carry-over Detection Method And Its Key Technologies

Ladle slag carry-over detection technology (SCDT) is of important practical significance to steel continuous casting production (CCP), it can effectively improve the casting blank quality, increase molten steel yield ratio, and protract the service life of tundish. Aiming at the problems of current SCDTs, such as low detection success rate, short working life, inconvenient installation and maintenance, a kind of SCDT based on vibration signal measurement was put forward. Mechanism of vibration detection method and its key technologies were discussed deeply, and the industrial application system oriented to actual CCP was successfully designed and implemented.According to the shock vibration difference created by molten steel and the slag because of their different density when they flow through the nozzle shroud, vibration signal was looked upon the main detecting signal. Based on fluid similarity principle, water model experimental platform for ladle slag detection was established by using vibration sensors, which could simulate the evolution process of slag carry-over and its dynamical characters under laboratory conditions.Physical process of slag carry-over in terminal phase of ladle pouring was studied, it was found that sink vortex was the most important reason of slag carry-over. Combined viscous fluid stability theory, fluid kinetic model of ladle internal flow field was set up based on Rankine vortex model. The critical values of all orders for vortex occurrence were obtained, and shock vibration phenomenon was proved to be existed when vortex penetrated by strict mathematic deduction.In allusion to the direct target detected-nozzle shroud, the nozzle dynamical model was set up based on Flugge cylindrical shell vibration equation According to fluid-solid coupling theory, the model was revised to get the eigenequation of coupling system corresponding to axial wave number. The displacement response generated by vortex shock vibration of cylindrical shell was obtained at every circumferential modal by wave propagation method.In view of the characteristics of vortex shock in pouring terminal phase, vibration signal time series of nozzle shroud was divided into three typical sections:no-slag, mixing slag and full slag. The character data was extracted from pre-processed field vibration signal by using vector quantization (VQ), and codebook was trained to recognize the pouring status and finish relative automatic control tasks for slag detection.Ladle slag detection system was developed grounded on above research results. Industrial experiments prove that this system has long working life, can be installed and repaired easily; it can increase molten steel yield ration and slag thickness of tundish effectively, and its slag detection success rate is above 95%.