| The flow of molten steel in the mold of continuous casting is an extremely complicated transmission process.The variation of meniscus velocity of molten steel in actual production is directly related to many important defects in continuous casting products.Therefore,monitoring the speed,flow direction and variation of meniscus velocity is an important link in adjusting process parameters and controlling quality of products.However,in the face of opaque,high-temperature and highly corrosive molten metal fluid,accurately measuring the velocity yield poses a challenge for researchers and engineers.Lorentz force velocimetry based on electromagnetic induction principle is a kind of velocity measurement method which can be used in metallurgical industry.It yields the characteristics of non-contact and on-line measurement,and has attracted the attention of researchers at home and abroad since it was put forward.However,in the face of severe test environment such as electromagnetism,vibration and high temperature in industry,the mechanical structure and function realization of Lorentz force velocimetry still need further exploration and research under laboratory conditions.In order to verify the accurate measurement of open flow by velocimetry,this paper makes an experimental study on the test performance of velocimetry by combining numerical simulation with experiment.The main research contents of this paper are as follows:(1)Based on the principle of electromagnetic induction,the Lorentz force velocimetry is designed and developed,and an experimental platform for liquid calibration is set up,which realizes the on-line,real-time and in-situ measurement of force signals of the velocimetry under different flow speeds,different measurement environments and different flow forms,and on this basis,the measurement and calibration of molten metal speed are completed.(2)The main application range of the velocimetry in molten metal is theoretically analyzed by numerical simulation method,the size and shape of the electromagnetic sensitive area in actual molten metal measurement are determined,when the size of the magnet is 30 mm×30 mm×50 mm,its action range is concentrated below the projection of the magnet,its shape is close to a circle,and its diameter changes in the range of 23 ~ 34 mm.The variation law of the electromagnetic sensitive area in molten metal with measuring height and flow rate is explored.The experimental results are compared with the simulation results,and good consistency is obtained,which provides a theoretical basis for the effectiveness of flow rate measurement in the actual velocimetry system.(3)With the help of the liquid metal loop platform,several groups of test experiments of the velocimetry in the open channel were carried out,and the influence of the measurement position and flow structure on the magnetic field action area and measurement results of Lorentz force device was explored.The Lorentz force velocimetry was compared and verified by Ultrasonic doppler velocimetry(UDV).The results show that the velocimetry can accurately measure the horizontal velocity component in the area with a depth of 0 ~ 4 mm near the surface of the open flow.Compared with the Ultrasonic doppler velocimetry,the relative error is less than 8%,and the fixed-point measurement can be achieved for more than 20 minutes,and the measurement accuracy requirement can be reached with a repeatability error of ≤ 5%,which proves the accuracy and industrial applicability of Lorentz velocimetry in measuring the local velocity of the upper surface flow field in the mold. |
PDF Full Text Request