A356 Alloy Melt Control On The Fluidity Of The Mechanism

Fluidity is one of important performances of casting alloy, but it is really complex because of the effect of solidify process, unstable flow and unstable heat transfer process etc. In order to make clear what will happen about fluidity with the change of elements, this article begin with a new fluidity measuring instrument design, based on experiment contrast, theoretical analysis and manufacture, and use this instrument to research the effect of viscosity, oxide, refine, modify and melt overheating treat on the fluidity on A356 alloy. Obtained the basic rule of the effect of elements variation on alloy fluidity, and mathematical formula of fluidity theoretical calculation also have been preliminary esTab.lished, it has reference value for manufacture and research.of aluminum alloy.After compared advantages and disadvantages of many traditional fluidity tester, this paper designs a new metal mould to test fluidity, use induction heating to heat preservation and it can also make melt uniform, then put forward new pouring cup structure, use feat coating and drying method, design filter at the entrance of pouring cup, remove inclusion, smooth flowing speed, this fluidity test mode is easy to make and results are repeatability. it can be used to fluidity test of all nonferrous metal, and this acticle is based on the datas obtained by this new fluidity measuring instrument.Melt viscosity is one of the important parameters of fluidity. During alloy solidification process, atoms change from the disordered movement to the fixed vibration around one crystal lattice point, atomic vibrations frequency reduce and atomic spacing curtail, in this process, the atomic force increase gradually, the macro is melt viscosity increased, the speed and scale of the increase of melt viscosity are relation with the measurement of diffusion activation energy. there is a relationship between viscosity and its components:This formula indicated a new thinking of fluidity calculation is twice revises on the base of pure Al viscosity. Melt viscosity is affect by vibration frequency, amplitude, radius, quality, diffusion activation energy, melt temperature, percentage of alloy elements, for Al-Si alloy melt, viscosity value abtained by calculation is basic agreement with the datas batained by experiment.Fluidity will be effected by serperheart treat or addition agent change, with the change of melt structure and oxide amount. With increased of oxide films the fluidity will increase a little bit, but the quality of casting will decrease severe; proper heat treatment will make quasicrystal cluster more thining, increasing surper-cooling ability of melt, then make fluidity invreasing. A new melt treat method which dicusse in this article with compined of heat treatment and electromagic mixing together has a good result in A356 alloy manufacture.Grain refinement and modification changed fluidity by change the nucleation and melt environment, silidoid rate and appearance. Grain refinement can increase fluidity with surpercooling incrasing and prolong dendritic contact point. But experiment find that increase addition of refiner continue, fluidity of melt will decrease. It suggest that with the incrase addition of refiner continue will lead to liquied temperature of melt acsend, which make viscosity increasing and fluidity reducing. Therefore, the influence of alloy refine and modify is a result decided by both positive effects of delay of dendrite contact and negative effects of increase viscous force with solid-phase increased.Numerical simulation found, a little addition of Si,Mg,Ti,Cu,Fe will change fluidity notability, but a little addition of Pb,Mn,Sn,Zn has little effect on fluidity.The change of fluidity with a little Si,Mg,Ti,Cu,Fe addition will abide by quadratic function principle. Bi-channel fluidity test modulus simulation suggests that different channel formed different length in a practical experiments, it also proved fluidity indexes should be an average value. And numerical simulation also found during A356 filling process, head of flow stops in a-Al nucleation process, a-Al nucleation ending when flow has stopped, therefore, at the time of Si separate out to form Al-Si eutectic structure flow had been stopped, this explanation that increasing Si addition in Al-Si alloy will lead to fluidity increase for the reason of latent need further discussion, because the Si phase formed when Al-Si eutectic, flow has stopped at this time. Numerical simulation also found quadratic function discipline and exponential function discipline of the influence of fluidity with ingredient change which are similar with experimental results.According to the research of this articl, there is a consuming relation between viscosity and melt fluidity,because on the viscosity caculating formulation, combine those factors obtained in experiments which effect on fluidity of casting alloy such as casting modulus, solidoid dispersion degree, filling pressure, degree of superheat etc, and fluidity change with quadratic functiondiscipline, exponential function discipline, a new formula to theory calculation of effects of alloy element on fluidity has been put forwarded:Although this formula needs to be completed, it also has reference value on fluidity control and inhance process.