| Aluminum alloy has the advantages of low density,excellent electrical and thermal conductivity,good corrosion resistance,and easy for plastic processing.It is widely used in various fields such as aerospace transportation and home improvement,etc.In recent years,with the rapid development of modern aerospace technology and equipment industry,the requirements for the comprehensive performance of aluminum alloys have become higher and higher,hence the microstructural morphology finer.To obtain the slab with fine equiaxed grains,uniform structure,and better mechanical properties,electromagnetic casting has become a popular method of producing aluminum alloy.In this thesis,the finite element simulation method was used to model the coupling field of the flow field and temperature field in the solidification process under the action of external magnetic field.The boundary of two contact parts of different properties was treated by assigning certain values.And a new method was proposed for the calculation of the latent heat during the solidification of the metal.The open source software FreeFEM++ was applied for encoding program.It can be derived from this work some interesting results as follows:The electromagnetic field promotes the melt flow and makes the temperature distribution uniform.The greater the current intensity,the greater the effect of stirring on the melt flow field and temperature field,which makes the depth of the solidification liquid pool.It is benefit to the improvement of quality of aluminum alloy.The lower the frequency of the electromagnetic field,the better the effect of stirring on the flow field and temperature field.Then the stirring effect of the magnetic field reduces the difference between the depth of the solidification liquid pool at the edge of the melt and the center,which is helpful to the simultaneous solidification of the metal and the optimization of the internal microstructural grains.In this thesis,the best process parameters are taken when the magnetic field current is 50 A and the frequency is 10 Hz.This thesis also contemplates a new electromagnetic field application method,which is,based on the original parallel magnetic field coil,set a certain degree of inclination angle between the magnetic field coil plane and axial direction,and then the coil is tilted to a certain degree,on this basis,furthermore,make the coil deflect with its center point at the same horizontal plane with the center axis of the melt as the axial direction.The secondary deflection to the left or right directions can further change the direction of the magnetic field,then perform a more complicated stirring behavior.After simulation analysis,it was found that sending the magnetic field slightly obliquely upward,and then deflect the coil to the right can further optimize the distribution of the flow field and temperature field,strengthen the stirring effect,make the temperature field distribution more uniform,and reduce the depth of the solidification liquid pool,make benefit to uniform and stable microstructure properties after metal solidification.Under these conditions,it is found that the casting speed is 2 mm/s and the casting temperature is 660? through comparative simulation experiments,.In this thesis,the simulation method used can simulate the solidification process of various alloys,can also provide certain guidance for actual producing,optimize process parameters,and improve quality of product.In addition,the time when the magnetic field tilting method described in this thesis can be applied,it can further optimize the production process,improve the quality of aluminum alloy products,and provide a wider development space for electromagnetic semi-continuous casting of aluminum alloys. |
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