Effect Of Compound Magnetic Field On Solidification Structure And Segregation Of Al-Si Alloy

As the Chinese economy enters a stage of high-quality development,people demand for high-quality metal materials is growing with each passing day,and the shortcomings of traditional production processes in quality and production efficiency have become increasingly prominent.In recent decades,electromagnetic metallurgy technology has been favoured by domestic and foreign steel producers.Electromagnetic stirring has significant effects of improving the ratio of equiaxed grains,refining grains,and decreasing segregation of the cast slab.In this paper,the important point is both simulation experiment of Ga In Sn flow field and solidification experiment of Al-7%Si alloy under compound magnetic field(static magnetic field and rotating magnetic field)to study magnetic induction distribution of the compound magnetic field platform,the flow characteristics of molten metal,the changes of alloy solidification curves and the quality of solidification structure:1.The gauss meter is used to measure the magnetic induction intensity distribution of the compound magnetic field platform in the laboratory,the results show that the magnetic induction intensity increases of static magnetic field with the increase of exciting voltage,and the magnetic induction intensity of rotating magnetic field increases with the increase of exciting current.When the current is changed from 50 A to 200 A,the magnetic induction intensity increases first and then decreases with the increase of frequency.When the frequency f=4 Hz,the magnetic induction intensity appears extreme value.2.The flow characteristics of Ga In Sn in a cylindrical container under the action of a compound magnetic field are measured by a Doppler ultrasonic speedometer.The results show that the flow characteristics of the liquid metal Ga In Sn in the cylindrical container under the compound magnetic field are that the liquid metal flows upward along the side wall as a whole and downward along the central region after reaching the top lunar surface.When the exciting voltage of static magnetic field increases from 50 V to 150 V,the fluid velocity will downs and the downward flow area will expand.When the rotating magnetic field exciting current increases from 50 A to 100 A,the flow inside the fluid becomes more intense and the area of secondary flow became large.When the frequency increases from 4 Hz to 8 Hz,the range of downward flow decrease first and then increases,and the axial velocity on both sides increases gradually.In this experiment,the axial flow velocity of liquid metal on both sides is the fastest under the parameters of f=8 Hz.In the range of Z/H=0.36 ? 0.68,the stirring effect of magnetic field is the strongest and the flow is the most intense.3.Taking Al-7%Si alloy as the research object,the effect of the compound magnetic field on the solidification curve,solidification structure and segregation of Al-Si alloy are studied.The result shows that compound magnetic field can shorten the solidification time of alloy effectively and the eutectic reaction temperature decreased by 3?5 ?.The solidification time increases with the increase of exciting voltage,decreases first and then remains unchanged with the increase of exciting current.With the increase of frequency,it is shortened first and then slightly prolonged.Under the conditions of the compound magnetic field,microstructure of Al-Si alloy is refined obviously.When other parameters are constant.The grain sizes are proportional to the increased exciting voltages and inversely proportional to the increased exciting currents.When I=100A,the average of the grain size is down to 190.40 ?m.The effect of frequency change in grain size is that there is an optimum refinement level.In this experiment,the average of the grain size is smallest at the f=6 Hz,which is down to186.05 ?m.The grain refinement effect of the solidification structure of the middle part of the alloy is better than that in the upper part and it is more sensitive to the change of magnetic field parameters.After applying the magnetic field,the shrinkage cavity and shrinkage porosity in the center of the ingot are reduced to one certain extent,and the cracks basically disappear.With the increasing of exciting voltage,the degree of segregation increases first and then decreases.When the exciting current and frequency increases,the degree of segregation increases gradually.In this experiment,100 V-50A-4 Hz scheme can improve the segregation effect best.