Research On The Purification Technique Of Molten Melt Under Alternating Combined Magnetic Field

A kind of A390aluminum alloy (Al-16.72wt%Si-4.57wt%Cu) was used asexperimental material in the thesis. Primary silicon particles precipitating fromthe solidification process of A390aluminum alloy were viewed as non-metallicinclusions. The movement behavior of non-metallic inclusions in molten metalunder alternating combined magnetic field is investigated. Alternating combinedmagnetic field is inducted by simultaneous imposition of traveling magneticfield (TMF) and alternating rotating magnetic field which is a special kind ofrotating magnetic field (RMF) by reversing rotation direction. A best pattern ofelectromagnet field for the purification of molten metal is proposed, and thepurification mechanism of this magnetic technique is investigated.The research discovers that:1. Alternating traveling magnetic field cancause a unsteady-state flow field in the molten metal. It cannot serve to makeprimary silicon particles to migrate to a particular part of the sample, however,it can promote primary silicon particles to collide and agglomerate. On thecondition of the same electromagnetic parameter, compared with TMF,alternating traveling magnetic field has a worse effect on migration of primarysilicon particles but a better effect on collision and agglomeration of that.2.Alternating rotating magnetic field can generate a time-dependent flow field inthe molten metal, which causes silicon particles to collide and agglomerate, andmigrate to the upper part of the sample quickly. Alternating rotating magneticfield has a better effect on agglomeration and migration of primary siliconparticles with the same electromagnetic parameter.3. Alternating combinedmagnetic field has higher purification efficiency than any single traveling oralternating rotating magnetic field. Alternating combined magnetic field has abetter effect than normal combined magnetic field induced by simultaneousimposition of TMF and RMF on separating non-metallic inclusion from moltenmetal. The purification efficiency of alternating combined magnetic field getswell as the efficiency of any single traveling or alternating rotating magnetic field increases.4. When alternating rotating magnetic field is more advancedapplied than TMF, this magnetic has a worse purification effect than that thesetwo magnetic was imposed simultaneously.The result indicates that:1. Alternating traveling magnetic field andalternating rotating magnetic field can generate unsteady flow in the moltenmelt, which promote inclusions to collide and agglomerate obviously. However,only alternating rotating magnetic field can cause inclusions to migrate mainly.2. In the present experimental conditions, on the condition of the sameelectromagnetic parameter, alternating combined magnetic field has the mostpurification efficiency of all the electromagnetic fields on the research.3. Onthe condition that the current of the traveling wave magnetic field increases, thecurrent or the frequency of alternating rotating magnetic field increases, and thealternate time of alternating rotating magnetic field is10seconds, thepurification efficiency of alternating combined magnetic field has improvedsignificantly.