Design And Optimization Of Casting Process For A356 Aluminum Alloy Thin-wall Frame Casting

A356 aluminum alloy large thin-walled frame castings have a complex structure and thin walls.At the same time,because the castings change from liquid to solid during the casting process and release a large amount of heat,the chance of casting deformation and cracking is very large,which affects the subsequent processing of the casting and Usability,so hot deformation and cracking of casting is one of the important issues that determine the quality of castings.In order to avoid casting defects such as cracks,deformation,shrinkage and shrinkage in the sand casting,this article designs and optimizes the casting process for a company’s A356 aluminum alloy thin-walled frame castings to further improve the quality of castings.Shorten the design cycle and design cost of the new process,and provide guidance on the process and theoretical direction for actual production.The main work and conclusions carried out in this article are as follows:(1)Analyze the solidification process of castings,determine the constitutive equation as elasto-viscoplastic constitutive equation,combine with the stress model in Pro-CAST software,and determine to use Perzyna elasto-viscoplastic model as the stress simulation model.(2)Design the pouring system and the shrinkage system,and determine the first and second process plans.Comparing the flow field,temperature field and stress field of the two process schemes,the second scheme is more reasonable.(3)In the second scheme based on optimization,try to add reinforcement ribs,and use reinforcement ribs as a pouring system.Comparing the influence of the number of different gates on the flow field of the casting,it is finally concluded that when the five gates(scheme three)are filled,the casting is stable and the probability of gas entrainment is minimized.(4)The effects of pouring speed,pouring temperature and sand mold temperature on the final equivalent stress of castings using schemes 2 and 3 are studied.The pouring speed values are 1kg/s,1.5kg/s,1.82kg/s,the pouring temperature values are 680 ℃,730 ℃,750℃,and the sand mold temperature values are 50℃,100℃,180℃.It is concluded that when the casting speed is 1.5 kg/s,the casting temperature is 730 ℃,and the sand mold temperature is 180 ℃,the probability of deformation and cracking of the casting is small.Scheme 3 When the casting speed is 1.82kg/s,the pouring temperature is 680℃,and the sand mold temperature is 180℃,the chance of deformation and cracking of the casting is small.(5)The hot cracking tendency and cold cracking tendency of the optimized scheme were studied,and the second scheme was obtained as the final process scheme in this paper,in which the pouring speed was 1.5kg/s,the pouring temperature was 730℃,and the sand mold temperature was 180℃.Analyze the final displacement of the casting,and compare the structure of the whole casting before and after deformation,and get the final plan.The total deformation of the casting is within the controllable range,and does not affect the subsequent processing.(6)Calculate the growth kinetic parameters,and use the CAFé method to simulate the microstructure of the final casting process.Compared with the actual production castings,the metallographic and EBSD comparisons show that the overall microstructure of the castings is uniform.