Numerical Simulation And Microstructure Analysis Of A356 Aluminum Alloy Thin-walled Complex Casting

As an excellent casting material,aluminum alloy is widely used in the fields of aerospace and railway locomotives.Compared with the traditional steel casting materials,it has the advantages of high specific strength and corrosion resistance.It not only has important applications in energy and environment,but also has obvious advantages in surface quality and dimensional accuracy.However,in the actual production,if the castings to be formed are thin-walled castings with complex shapes,more trial production is often needed to improve the casting process,resulting in prolonged casting production cycle and low yield.Therefore,it is an effective scientific method to apply computer numerical simulation technology to casting process design.In this paper,the casting process of A356 aluminum alloy thin-walled complex casting was simulated by computer simulation software.By analyzing the simulation results,the casting scheme was improved,the casting defects were reduced and the casting quality was improved.The simulation results were verified by actual casting,and the influence of solidification conditions on casting structure was analyzed.In this paper,the theoretical basis of numerical simulation technology of casting process is briefly introduced,the mathematical model of mold filling process and solidification process is briefly discussed,and the simulation software with mature technology is introduced,and the Pro CAST software adopted in this subject is briefly explained.It provides a theoretical basis for the following simulation and process optimization.After 3D modeling of the casting,the numerical simulation of the initial scheme was carried out.According to the analysis of the simulation results,the filling process of the initial scheme was stable and orderly on the whole,with only a small part of the metal liquid flowing back at the inner gate at the bottom.In the process of solidification,due to the uneven thickness of the casting,the thin position on the casting wall dissipates heat faster,and the solidification order takes precedence,which results in the failure of the convex position on the thin wall and the thicker position on the bottom to obtain the replenishment of the surrounding metal liquid during solidification,resulting in shrinkage cavity and porosity defects.Then,in order to improve the casting quality,the casting system was redesigned and optimized.Through the simulation of the new process plan,itcould be found that the casting defects were mainly concentrated in the location of the sprue and riser,and there were basically no obvious defects in the casting.The orthogonal test was conducted with casting temperature,mold temperature and casting speed as variables.The experimental results showed that the optimal parameter combination of the new process was casting temperature of 740℃,casting speed of 100mm/s and mold temperature of 200℃.Under the pouring parameters,the filling speed of aluminum alloy casting is stable,the solidification process is orderly,and there are no defects on the whole.After improving the casting process under the existing conditions,a more advanced low-pressure casting process was provided to improve the production efficiency.The low-pressure casting process of aluminum alloy thin-walled complex castings was simulated by Pro CAST software,and the simulation results of mold filling process and solidification process were analyzed to improve the low-pressure casting process and improve the yield of products.Finally,the simulation results of gravity sand mold casting by Pro CAST software were verified by experiments to verify the feasibility of the designed pouring scheme.The effects of solidification conditions on casting microstructure were summarized by analyzing the simulation results and experimental results.The above tests show that for aluminum alloy castings with complex structure and uneven wall thickness,optimization of process plan and process parameters by Pro CAST software during the casting process can effectively improve the casting quality.