Study On The Electromagnetic Separation Of Silicon And Iron Phases In Primary Aluminum-silicon Alloys

Based on the problem of high content of Si and Fe in coarse Al-Si alloy,this study utilizes electromagnetic directional solidification with Mn addition to separate both Si and iron-rich phases from Al-Si alloy in the same experimental process.On the one hand,Si and iron-rich phases can be successfully separated and accumulated at the bottom alloy.On the other,the radium iron-rich phases inside Al-Si alloy are mainly dendritic-like,Chinese script-like,skeletal-like and bulk-like,which reduces the detrimental influence of iron-rich phases on the properties of Al-Si alloy.This research studies four process parameters:Mn addition,holding temperature,iron removal temperature and pulling down velocity,so as to propose a reasonable growth model of primary silicon and migrating model of iron-rich phases in the electromagnetic field.Effects of different parameters on the separation results of silicon and iron-rich phases were measured by iron content via ICP,R_Si/Al via quantitative characterization of EPMA and the improved micro-morphology of silicon and iron-rich phases.Research results indicates that,without Mn addition,electromagnetic directional solidification alone could effectively separate primary silicon from coarse Al-Si alloy,meanwhile most iron-rich phases could be removed with the residual iron content decreased to 0.9%.However,iron-rich phases still had a acicular shape though refined;As Mn/Fe=1.2,iron content were decreased to 0.42%,and an iron removal efficiency of over 90%was obtained.A relatively low pulling down velocity was beneficial to the separation of primary silicon and iron-rich phases,with the bottom silicon and iron-rich phases more concentrated.When pulling down velocity was 5?m/s,it was beneficial to reduce the R_Si/Al of Al-Si alloy;Reducing the iron removal temperature was conductive to improve the forming degree of iron-rich phases during the cooling stage.When iron removal temperature was 600?,separation efficiency could be enhanced;High holding temperature brought higher energy consumption,when holding temperature was 1150?,silicon content in Al-Si alloy could be decreased.By adding Mn with the electromagnetic directional solidification process,the morphology of iron-rich phases could be improved,decreasing the harmful effects on the property of Al-Si alloy.Mn could combine with iron-rich phases to from some complex intermetallic compounds with larger density,volume and magnetic susceptibility,which on the one hand improved the separation efficiency of iron-rich phases,and on the other decreased Si content in Al-Si alloy.Electromagnetic directional solidification combined with Mn addition has the merits of favorable cost,little energy consumption and desirable impurity removal efficiency,which provides the reliable basis for the preparation of casting Al-Si alloy from coarse Al-Si alloy via electro-thermal method.Furthermore,since the bottom alloy contains high content of Si and Fe,it can be used for producing steel-making deoxidizer and magnesium-reducing agent after adding Si and Fe respectively,or be used for the preparation of solar-grade silicon after acid leaching,which considerably improves the resource utilization efficiency.