Studying On Dual-Ingot Low Frequency Electromagnetic Semi-Continuous Casting

This work is the part of Technology of multi-ingots casting under low frequency electromagnetic field, which is a industrialization project, is to study effects of the arrangement of the inductor coils, the direction of the coil current, the casting parameters and magnetic conditions on the structures of 7075 Al alloy ingots, the effects of the casting parameters, construction of the mold and the insulating hat on the surface quality of the ingots to force this technique used in industrialization.Three-dimensional finite element model of dual-ingot low frequency electromagnetic semi-continuous casting process was built. Numerical simulation on the effects of the current direction, the distance of coils, the current frequency, and the current intensity on the magnetic field distribution was carried out. The results shows that when the current direction is opposite, the magnetic intensity in ingots near each other is stronger than that in the same direction, and when increasing the distance between the coils, the magnetic induction intensity of the proximal ingots is gradually reduced in the dual-ingot low frequency electromagnetic semi-continuous casting process, Under the dual-ingot low frequency electromagnetic semi-continuous casting conditions, regardless of current direction is in the same direction or reverse, the remote magnetic field strength in the ingots is greater than the proximal magnetic field strength.The effect of different magnetic field conditions on the internal macrostructure of ingot is verified by experiment. The experimental results show that grains are refined and homogeneous when the frequency of coil current is at 15Hz-25Hz. As the current increases, grains become much smaller. The greater the current is, the finer the grains become. Under the same conditions, the macrostructure of the ingot under the opposite direction of coil current is slightly finer than that in the same direction.The influence of the construction of the insulation hat and the mold on the surface quality of ingots is studied. By inspections on the influence casting speed, the size of overhang, first cold intensity and the distance form the graphite ring to second water point on the surface quality, and the effects of triangular area composed of overhang and graphite ring on the surface quality of ingot, the optimum construction of insulation hat, the mold and process parameters have been obtained that casting speed is 105-115mm/min, the cooling water is 55-70L/min, the size of overhang is 4-6mm, the distance from bottom of graphite ring to the water point of second cooling water is about 23mm, the mixture of graphite powder and coconut oil is daubed in the triangular area composed of overhang and graphite ring.