| Electrocmagnetic stiring (EMS) Technology refers to the controlling the flow of molten metal by electromagnetic force, which can break the dendrite, and increase the nucleation rates. The EMS process can improve the solidification structure and properties of materials, and it has been widely used in the steel industry, but in ferious alloy field its role needs to be further explored.After cooling, manganese alloys are easy to crack and hard to shape up. In the manganese pelletization process, it would emerge near to 15% manganese powder due to the fragility of manganese. The power-wasting recycling process does not meet the requirements of energy conservation. When the manganese alloys are in liquid and semi-solid conditions, imposing mechanical vibration, die casting and EMS can effectively change the casting macrostructure and microstructure. In this paper, based on the comparison of casting structure and microstructure, it is focused on the following aspects.Firstly, magnetic parameters of middle carbon manganese, low carbon manganese and pure manganese were measured by using the soft magnetic material DC meter. The results show that manganese alloys are soft magnetic material and the magnetic induction increases with a increase of the carbon content.Secondly, based on the electromagnetic field theory, two-dimensional simulation model of the electromagnetic stirrer was set up. Finite element analysis software Ansoft was used to calculate the strength and distribution of the magnetic field. According to the influence of two-dimensional model parameters on the magnetic strength and magnetic flux density, it has been concluded that the main factors on affecting the electromagnetic stirrer is the frequency and current. By using a self-regulating magnetic induction meter, the strength of the magnetic flux density in the cavity of the electromagnetic stirrer was measured. The results show that the model simulation was accordance with the measured values.Finally, by comparing the crack number, crack temperature and other macro indicators of the cast ingots, it has been found that:mechanical vibration can refine the grain, but the cast ingots can not be formed; Die casting can also refine the grain in a certain extent and change the shape of the grain boundaries, so that the basic shape of manganese alloy can be formed. By imposing EMS in the solidification process, the nucleation rate increases and some globular grains appear. Imposing EMS before the molten mangnese alloy flowing into the casting mould, the vortex motion is produced by the electromagnetic force. A large number of grains of spherical or arc boundaries can be also observed. The grains number also increases tremendously. By comparing the four forming processes, it has been concluded that imposing EMS before the molten mangnese alloy flowing into the casting mould is the most feasible one. The more increasing the input current, the stronger stiring effect be available, then the crystal structure of manganese alloy tends to be better. There is a suitable range between the frequency of power-output and effective power of the EMS. Compared with middle carbon manganese and pure mangaese, the suitable stirring frequency for is 50Hz, however, low-carbon manganese is 30Hz. By selecting electrify coil with less pole pairs the rotate speed of the magnetic field can be increased, and the magnetic field lines of the rotating magnetic field can better run through the center of the chamber. The optimal pole pairs number is one pole pairs. |
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