| Electromagnetic casting (EMC) is an original material processing technology and a comprehensive subject based on magneto-hydrodynamics (MHD) and combined with metallurgical engineering. Owing to the outstanding merits of EMC in its high smooth surface, good mechanical properties and high production efficiency, which has become an important method to produce high quality aluminum alloys. With the increasingly development of EMC in aluminum alloys and the merits of EMC, more and more research and experiments have been carried out in the EMC for copper, steel and magnesium alloy.The key technique to EMC is the shaping of liquid column of metal under the pressure of magnetic field. Due to the distinct electromagnetic and physical parameters, the feasibility of the electromagnetic shaping under magnetic field is distinct to different metals. For the purpose of analyzing the feasibility of electromagnetic shaping of different metals, the dissertation has studied the feasibility of electromagnetic shaping of Aluminum, steel, copper and magnesium alloy by means of numerical simulation combined with experiment research.The main work for this dissertation is as follows:Based on the principle of electromagnetic casting-the Maxwell's equations, the electromagnetic force induced in molten metal of cylindrical ingot was analyzed and numerically simulated. Compared with the traditional expression of the electromagnetic forcePm=B2/2μ that simply considers the magnetic flux density in computed grids, themathematical model of electromagnetic force in this paper takes into account the effect of the grads of magnetic field on it. Based on the model of the coupled circuit model, the magnetic field in molten metal was numerically simulated; then the electromagnetic force and the electromagnetic pressure for aluminum, copper, steel and magnesium alloy were also numerically simulated. Meanwhile, the influence of the magnetic field under different inductor, current, frequency on the electromagnetic pressure was investigated. Considering the balance between the electromagnetic pressure on the surface of molten metal and the static pressure of liquid column, the experimental condition of EMC for aluminum, copper, steel and magnesium alloy was studied. As a result, the electric parameters and the minimum magnetic flux density for different metals were presented, which will contribute to the experiments of EMC of those metals.An Electromagnetic Dimensionless Number (EMDN), which can be used to analyze thefeasibility of different metal to achieve EMC, was presented in this paper. By the application of EMDN, the feasibility of electromagnetic shaping for some metals at different experimental conditions were analyzed, and the experimental parameters and the required magnetic flux density to achieve EMC were estimated. The validity of the EMDN was proved by the experiments of Aluminum and Sn-3%Pb alloy.As the results of the research for the feasibility of different meals by means of EMDN and the numerical simulation, the magnetic flux density for different metals is distinct: for aluminum the magnetic flux density required for EMC is about 0.04-0.045T, and for steel that is about 0.08~0.085T, and for copper that is 0.094~0.099T, and for magnesium alloy that is about 0.038~0.043T. Meanwhile, it can be concluded by the research that the magnetic flux density of EMC for some a metal lies on its density, and the conductivity of the metal confines the choice of the frequency in EMC.The establishment of EMDN and the programme of the electromagnetic force provide the guidance for the design of the inductor and the choice of experimental parameters of EMC for different metals.
|
PDF Full Text Request