Study On The Heat Transfer Characteristics And Influence Of High Silicon Aluminum Alloy Electromagnetic Separation

The electrothermal reduction method is the main way for preparing Al-Si alloy today.However,the high-silicon coarse Al-Si alloy produced by electrothermal reduction can not be directly applied in industrial casting-unless mixed with pure aluminum.The energy consumption of pure aluminum preparation process is huge which makes a long process flow and h igh raw material costs of the electrothermal reduction method.In view of the problem of high silicon content in the coarse Al-Si alloy,the silicon in high-silicon Al-Si alloy??25 wt.%Si?was separated by electromagnetic directional solidification method.Using this method the silicon content in the high-silicon Al-Si alloy and the impurity in separated silicon can both be reduced.By the way,the separated s ilicon is a high-quality raw material for producing solar grade silicon in the photovoltaic industry.Electromagnetic directional solidification technology can also achieve the effect of refining the alloy grains and improving the quality of the alloy.The refore,it can be used as an electrothermal reduction process optimization technology.According to the electromagnetic directional solidification separation model of high-silicon-aluminum-silicon alloy,the parameters such as current frequency,holding temperature,and pull-down speed in the process of separating Al-45wt.%Si high-silicon Al-Si alloy are optimized.The mass fraction ratios of silicon to aluminum R_Si/Al?Si/Al ratio?in the remaining alloys separated under different conditions were calculated by Electron Probe Microscopic Analyzer?EPMA?test results,and the effects of different parameters on the separation of high-silicon Al-Si alloy were quantified.The results show that the distribution of the Si phase in the remaining alloy after separation is more uniform by electromagnetic stirring at 3 k Hz.There is a clear separation interface between the primary silicon-rich part and the alloy part.When the holding temperatu re is lowered,the silicon content in the alloy part also decreases,but the grain size of the silicon phase gradually increases.Decreasing the pull-down speed helps reduce the R_Si/Al,which also making the separation interface of the sample more flat.The separation of different initial concentrations of hypereutectic Al-Si alloy?15,25,35,45 wt.%Si content?revealed that the Si content of the alloy part in several samples were controlled between 15%to 18%.Based on the heat transfer characteristics,the numerical simulation and experimental research were applied to improve the he at transfer effect of the Al-45wt.%Si alloy electromagnetic directional solidification equipment by optimizing the structure size and cooling?heat preservation?conditions.And then strengthen the separation.The results show that the application of graphite crucibles with better thermal conductivity and magnetic permeability under the same conditions can reduce the R_Si/Al in the alloy part to 0.104,while the R_Si/Al in the alloy part in corundum crucibles with poor thermal conductivity and magnetic permeability is as high as 0.2232.Enhancing melt axial heat dissipation or reducing radial heat dissipation can enhance separation by controlling primary silicon growth direction.