Design And Experimental Research On Ladle Slag Detection Sensor Based On Electromagnetic Induction

During the continuous casting production,the protection slag plays an important part in preventing the oxidation of molten steel and keeping the temperature of liquid steel.But in the late casting stage,the confluence vortex is formed when the liquid level of the ladle falls.The slag that makes damage to the subsequent iron and steel production may flow from the ladle into the tundish along the long nozzle with the molten steel.Mainly on basis of the electromagnetic induction principle,a combined method of the theoretical analysis and experimental was adopted to determine the electromagnetic slag detection(ESD)sensor parameters in the thesis.The preliminary design of the sensor coil was completed after obtaining sensor coil wire material,wire diameter,parametric excitation.Then different slag distribution samples were measured by using the sensor coil.The thesis mainly included:(1)The principle analysis of the ESD.The magnetic field distribution in the space generated by the alternating current on spiral wire was calculated theoretically.On comparing with the single coil and double coil,the later one was determined.Based on the analysis of the casting process from the ladle into the tundish,the installation position of the slag sensor is determined.(2)Determination of the parameters of the ESD sensor coil.Through the calculation of characteristic frequency of molten steel and theoretical research of its skin effect and the penetration depth and the experimental study on the influence between the excitation frequency and the induction signal,the optimum frequency of the sensor coil was determine.The optimal diameter of the coil wire is calculated by calculating the minimum of the alternating resistance of the coil.Based on the principle of equal magnetic flux passing through different diameter coils,the signal base value zero was set through reverse concatenated between two coils.Through a series of experiments,the material of the sensor,the material of the coil,the insulation of the coils and the thermal shock protective measures of coil were determined.(3)Experimental data and analysis.Different slag distribution samples were measured by using of the handmade coil.The influence of adding different structure of reinforcing steel shell and aluminum carbon conductive refractory material on induction signal were also concerned.The comparison of current excitation and voltage excitation was carried out in condition of high temperature.The study showed that:The double coil structure was preferred.The coil could effectively distinguish the 25%center slag content and the slag signal sensitivity reached 14%by using of the coil parameters as follow,wire diameter was 0.5mm and excitation frequency was about 500 Hz.