Mold Design And Numerical Simulation Of Aluminum Impeller By Low Pressure Casting

In modern society, aluminum impeller is widely applied due to its light weight and good performance. In combination of factory practice, this project aims at studying how to get the aluminum impellors which have tight organization and good performance by the way of low pressure die casting production. Relative to other forms of casting, low pressure die casting is one of precision casting forms. By imposing relatively low pressure on liquid metal, the liquid metal will fill metal mould and solidifies under pressure,so as to get tight organized and high-performance casting.This subject uses metal mould and gypsum core to produce impellers. Relative to traditional sand mould, metal mould has the main advantages as follows. The first advantage is that metal mould can form clear-shape casting. The second is that metal mould has better heat conducting performance, and the impellors will cool faster, so the impellers will have tight organization and good performance. The last is that mental mould can be used repeatedly. Compared to sand core, gypsum core can shape blades which have smooth surface and clarity outline, so the casting has high dimensional accuracy and low surface roughness.Gypsum core is made by Rapid Prototype Manufacturing Technology. First produce the prototype of gypsum core by Rapid Prototype Manufacturing Technology. Second form silicon rubber mould using prototype. Third prepare gypsum mixed slurry. Fourth assemble silicon rubber mould and metal mould. And then pour the gypsum mixed slurry into the mould. When the gypsum mixed slurry solidifies, open the mold and get the gypsum core out. The gypsum core can be used into practice after being dried and roasted.Pro/Engineer Software can be used into designing mental mould, and MAGMASOFT Software can be used into simulating liquid metal filling mould and solidifying process. Casting defects can be predicted during simulating. Mould plans and pressure-time plans can also be optimized during simulating. First optimize mould plans. Set up two mould plans. Mould Plan Ⅰ is to impose cooling unit on the top of impeller cover. Mould Plan Ⅱ is to impose cooling unit on the top of impeller cover and top of impeller hub. After MAGMASOFT simulation. Mould Plan Ⅰ can not make casting solidify from top to bottom. Mould Plan Ⅱ can do it. So this project choose Mould Plan Ⅱ. Second optimize pressure-time plans. Set up four pressure-time plans according to filling pressure-adding velocity. The four plans are0.0015MPa/s,0.0020MPa/s,0.0025MPa/s,0.0030MPa/s. After MAGMASOFT simulation, the plan0.0030MPa/s get the least defects. So this project choose0.0030MPa/s plan. Third investigate the influence of filling time on casting quality. Set up three filling time plans on the basis of chose mould plan and pressure-time plan. After MAGMASOFT simulation, the conclusion is that the less filling time, the less defects on top of impeller cover and the more defects on impeller blades.According to simulation results, casting specimens are manufactured in factory. After T61heat treatment, microstructure of casting samples is observed and the organization is tight. The mechanical properties are tested. It is found that the tensile strength is no less than270MPa, the yield strength is no less than220MPa, and the elongation is no less than3%. And it meet the application requirements.