Study On Numerical Simulation And Process Optimization Of Die Casting Process For Automotive Ccb Of Magnesium Alloy

Automotive cross car beam(CCB)of magnesium alloy is mainly produced by die casting process.Because of unreasonable die design or die casting process,many die casting defects are easily produced,which seriously affects product quality.Combining the numerical simulation of die casting with the actual production,the numerical simulation of die casting process,the optimization of process parameters and the analysis of die casting defects can be better carried out,which has a certain guiding significance for die casting production.In this paper,the numerical simulation of die casting process,the optimization of process parameters and the analysis of die casting defects of automotive CCB of magnesium alloy were studied.The main work and conclusions are as follows:(1)Based on ProCAST software,die casting process of CCB was simulated.By solving the temperature field,velocity field and stress field,the defects such as air entrainment,misrun,shrinkages and hot tears were predicted.It is found that the liquid metal is filled in near and far order during filling process,but there are air entrainment and Misrun in the far-end area of CCB.It is found that the liquid metal solidifies in far and near order during solidification,but the thick wall region of CCB solidifies finally.There is an isolated liquid phase zone and the stress concentration is serious.There are many shrinkages in the thick wall region of CCB.The tendency of hot tearing in variable cross-section region and corner transition region of CCB is larger.(2)By means of orthogonal design,Taguchi design and RSM design,the effects of die casting process parameters on the quality of CCB were studied,including pouring temperature,die preheat temperature,injection speed.It is found that the injection speed has a significant effect on the filling time,while the pouring temperature and die preheating temperature have a limited effect on it.For the hot tearing tendency and the total shrinkage porosity,die preheating temperature and pouring temperature have a significant effect on them,while the injection speed has a limited effect on them.In addition,the optimal die casting process of CCB is obtained,in which the pouring temperature is 660?,the die preheating temperature is 220?,and the injection speed is 4 m/s.In this condition,the hot tearing tendency is 0.1822,the total shrinkage porosity is 1.4794 cc,and CCB has the best comprehensive quality.(3)Die casting production test of CCB was carried out,mechanical properties of qualified parts was tested,and defects of bad parts were analyzed.It is found that the yield stress of qualified parts is about 120 MPa,the tensile strength is about 230 MPa and the elongation is about 9%.Die casting defects are mainly located in the CCB middle bracket and high tower areas,mainly cold shuts and hot tears.Defects are analyzed from alloy,parts structure,die and casting system,die casting process and other aspects,and improvement countermeasures are given.It is found that the causes of hot tears are related to local stress concentration and internal defects such as oxide inclusions,shrinkages and microcracks.It is found that the causes of cold shuts are related to the lower temperature of liquid metal and its diversion phenomenon.