Simulation And Optimization Of Double Runner Process For Low Pressure Casting Of Large Aluminum Alloy Wheel Hub

Aluminum alloy hub has the advantages of light weight,strong impact resistance,good heat dissipation effect and so on.It occupies an important position in the process of automobile lightweight.Aluminum alloy hub is often formed by low pressure casting process,but for large aluminum alloy hub,its spoke plane is large,the use of single runner low pressure casting process,will lead to the spoke and the center of the wheel defects,product qualified rate is reduced.In order to reduce defects and improve the mechanical properties of spoke,this paper proposed a process scheme of double runner casting of large aluminum alloy hub.Procast software was used to simulate the filling and solidification process of the process,and the process parameters were optimized to produce qualified products.The main research contents and results are as follows:(1)The filling and solidification process of double runner casting process for large aluminum alloy wheel was studied under the condition of mold air cooling.According to the shrinkage and porosity defect existed in the spoke position of single runner casting process,the corresponding process s cheme of double runner casting system was proposed.In order to make the simulated situation conform to the actual working condition,the inverse module of Procast was used to reverse solve the heat transfer coefficient and optimize the heat transfer coeff icient between castings and molds.Moreover,Procast software was used to simulate and analyze the filling and solidification process of double runner process and the location of defects under the condition of mold air cooling.The results show that,in th e filling process of double runner,there is not one metal liquid filling cavity for each runner,but three metal liquid filling cavity for each runner.The solidification sequence of double runner process is different from that of single runner.The solid ification sequence is as follows: rim and spoke → junction of rim and spoke.The defects of the double runner process under the condition of mold air cooling mainly exist in two places: one is between the air hole and the air hole;The second is the place where the runner meets the rim,and the defect of the spoke part is basically eliminated.(2)In order to eliminate casting defects of the double runner process castings under the condition of mold air cooling,the runner structure,cooling position and cooling strategy of the double runner process for large aluminum alloy wheels were optimized step by step,and the simulation calculation and analysis were carried out.The results show that the defects can be reduced by 95% through the improvement of runner and the formulation of cooling scheme.Then,by adding water cooling and changing the cooling strategy,the whole solidification sequence of the hub is spokes,rims → the junction of spokes and rims → the runner on both sides,eliminating macroscopic shrinkage cavity and porosity,and obtaining the cooling process parameters of the double runner process.(3)The optimization measures of the above process plan were tested and the organization and performance of the product were analyzed.The results show tha t there are no obvious defects in the area between and above the air holes.Under the fatigue test conditions of radial load of 4125kg·m,cycle number of 3.35 million revolutions,bending moment of 2828kg·m and test revolution of 5 million revolutions;The hub performance is qualified.The size of cell crystals and the spacing between secondary dendrites in spokes were reduced significantly by the double-runner process,and the grain structure in spokes was improved effectively.The average mechanical properties of spoke parts were improved compared with that of single runner process.The yield strength,tensile strength,elongation and hardness were increased by 17.8%,9.8%,211.8% and 6.7%,respectively.(4)The mold temperature variation during the proces s from preheating temperature to mold heat balance was simulated,and the influence law of different blowing cooling time on mold and casting temperature field was analyzed,which provided relevant theoretical guidance for mass production of double runner process.