Study Of Numerical Simulation About Vacuum And Low-Pressure Lost Foam Casting For Magnesium Alloy

Magnesium alloy is applied in the automotive industry,aerospace industry and the electronics industry increasingly with the time going.Vacuum and low-pressure lost foam casting(LFC)for magnesium alloy combines with the advantages of vacuum lost foam casting and low-pressure casting which makes the liquid magnesium alloy fill LFC mold with anti-gravity under the condition of low pressure,which has obvious advantages over the existing magnesium alloy forming process.The use of computer numerical simulation technology can study the filling process of metal liquid,the influencing of kinds of factors and predicting the casting defects quantitatively,which is an important mean to study the LFC process.This paper designs the LFC process of automobile intake manifold based on the characteristics,experience and actual production conditions of LFC process.The influence of pouring system,pouring temperature,mold-filling pressure and vacuum degree on the casting of vacuum and low pressure LFC for magnesium alloy was studied by numeral simulation software for obtaining the optimum parameters of high quality castings,and we also cast magnesium alloy intake manifold practically under the optimum parameters for verifying the simulation results.The study finds that the filling process of the pouring system of four in gate is more stable than that of two in gate by numeral simulation software and the solidification of various parts is more uniform,which obtains a better quality of casting.The simulation results of the influence of casting parameters on vacuum and low pressure LFC indicates that casting temperature,mold-filling pressure and vacuum degree have a great impact on the quality of castings.Regardless of the pouring temperature,when the filling pressure is 0.01 MPa will lead to a phenomenon of short run.However,the filling pressure can not be too high.When the filling pressure is too high,the filling process of the liquid metal is unstable which prunes to cause volume of gas phenomenon,non-uniform solidification,shrink shrinkage and sinkhole.When the pouring temperature is too low,it is necessary to improve the filling pressure in order to improve the liquid metal filling capacity properly.And when the pouring temperature is too high,it should reduce the filling pressure appropriately so as to improve the quality of castings.While the vacuum degree is also an important factor that affects the quality of castings.When the vacuum degree is 0.01 MPa the quality of the casting is worst.However,when the vacuum degree is 0.03 MPa and 0.05 MPa the defects of the casting are relatively small,but the higher the vacuum is,the sticky sand,roll gas is more serious,so the best vacuum degree is 0.03 MPa.Filling pressure,vacuum degree and pouring temperature are affected mutually,so we must consider all of the three parameters.The highest quality castings were obtained with a casting temperature of 730°C,a filling pressure of 0.03 Mpa and a vacuum degree of 0.03 MPa.The result of the actual casting shows the magnesium alloy intake manifolds obtained under the optimum parameters has no obvious defects and the quality of casting is high,which is in accordance with the simulation results.There also are many other parameters having a significant impact on vacuum and low pressure LFC for magnesium alloy intake manifold such as foam density,paint permeability,filling speed,so the following study is still very important.