Study On The Behavior Of Inclusions In Al Melt Under Rotating Magnetic Field

Oxide inclusion is a common defect in metals,which seriously affects the performance of metals.Using electromagnetic field to purify metal liquid is an effective method to remove inclusions,but since it is impossible to directly observe the flow field distribution inside the metal melt and the behavior of inclusion particles under the action of electromagnetic field,the separation mechanism of melt and particles under the action of magnetic field is not clear,which has also been a research difficulty in the field of electromagnetic purification.In this paper,the effects of the rotating magnetic field on the behavior of oxide particles in aluminum melt were studied by means of simulation and experiment.A mathematical model for the motion of oxide particles in aluminum melt under rotating magnetic field was established,the electromagnetic force,flow field distribution and movement behavior of Al₂O₃ particles in aluminum melt were simulated under different magnetic field intensity conditions.At the same time,the distribution of Al₂O₃ in aluminum melt under the action of rotating magnetic field was obtained under the same experimental conditions,which indirectly verified the accuracy of the model.The experimental results are as follows:ANSYS and CFX software were used to calculate the behavior of Al₂O₃ particles with a content of 1wt.%and a size of 10?m in molten aluminum under the coupling effect of magnetic flow field.Numerical simulation results show that the molten melt rotates and flows under the action of electromagnetic force when the rotating magnetic field is applied.On cross section,the electromagnetic force distribution is a rotating force field which gradually increases from the center to the edge,on the longitudinal section,the electromagnetic force decreases from the middle height of melt wall to both ends and the center axis,and the electromagnetic force increases with the current,the uneven distribution of electromagnetic force causes the secondary circulation in the melt.Due to the difference in density,the motion of melt and Al₂O₃ particles under centrifugal force has a velocity difference,which gradually increases with the current.When the magnetic field action time is 2min and the current intensity increases from 12A to 36A,the velocity difference between particle and melt increases from 1.299×10^-2m/s to 6.650×10^-2m/s.Under the action of velocity difference,centrifugal motion and secondary circulation,the Al₂O₃ particles tend to move towards the upper part of the melt and aggregate.Through the solidification experiment of 1wt.%Al₂O₃?diameter 10?m purity 99.7%?in aluminum melt under the action of rotating magnetic field,it was found that the Al₂O₃particles are uniformly distributed in the ingot after solidification of Al-1%Al₂O₃ melt without the application of rotating magnetic field.After applying the rotating magnetic field,under the combined action of centrifugal movement and secondary circulation,Al₂O₃ has obvious agglomeration on the upper part of the ingot,and the influence of current change on it is more significant than that of time.When the magnetic field was applied for 2min,and the current increased from 12A to 24A,the number of Al₂O₃ particles in the upper unit area of the ingot increased by 130%.When the current was 24A,and the action time of the rotating magnetic field increased from 1min to 2min,the increase rate of the upper particles of the ingot was10%.when I=36A,t=3min,the fluid movement was too violent,and it was easy to involve the gas and reabsorb the floating particles into the ingot,so the removal efficiency was poor under this condition.Under the conditions of this experiment,the optimal electromagnetic action parameter of Al₂O₃ particle removal is I=24A and t=2min.