Precise Control Of Shrinking Size Of ZL205A Alloy Complex Casting

Since the 1970 s,Near-Net Forming Technology has developed rapidly in the casting field.The invention and application of various special casting technologies have improved the forming quality and dimensional accuracy of castings.However,as an important part of dimensional control in casting production,the shrinkage rate of castings is rarely studied.Even the value of the shrinkage rate of castings in most manufacturing enterprises is still limited to the use of scales to assign values ??to castings.This traditional design scheme requires a lot of trial production to obtain a more accurate casting linear shrinkage,and this design scheme is not general,and different casting structures need to be repeated trial production.In view of the above actual situation,this article uses ANSYS simulation software to simulate the linear shrinkage behavior of castings with different structures,and finds that there is an obvious centripetal behavior during the shrinkage of the castings,and further compares the circumscribed circle center,the largest inscribed circle center and the geometric centroid.Based on the shrinkage center hypothesis,the shrinkage center representation node,that is,the geometric centroid of the casting,is determined based on the engineering reality.Then,the complex casting structure is divided based on the shrinkage center,and the casting shrinkage rate assignment scheme based on the local envelope density is designed and compared with traditional experience.Comparison between the casting shrinkage assignment scheme and the overall envelope density casting shrinkage assignment scheme,it is found that this design scheme has a better shrinkage dimension control accuracy.When the ZL205 A aluminum alloy material is selected for sand casting,the overall tolerance is CT4.Alloy castings.This article explores the effects of casting wall thickness,geometric symmetry and cooling rate on the shrinkage center of the casting.Through a single variable control study,a model with a wall thickness from 50 mm to 250 mm is selected for casting wall thickness comparison experiment,three-dimensional symmetry to one-dimensional symmetry Degree model for geometric symmetry comparison experiment and5?3000W/m2·K different degree of heat exchange coefficient for cooling rate comparison experiment,the study found that the thicker the wall thickness of the casting,the better the geometric symmetry,the local cooling rate and the overall cooling rate The smaller the difference,the easier the actual contraction center of the casting is to move closer to the geometric centroid.This paper also explores the effect of three structural division methods based on the shrinking center ray division method,shrinkage center curve division method andwall thickness symmetry center division method on the accuracy of the local envelope density assignment scheme.The experimental results show that the casting structure is divided based on the shrinkage center ray method The formed casting has the highest dimensional accuracy,and the dimensional accuracy of the casting obtained by the shrinking center curve division method is second,but it is not much different from the dimensional accuracy of the ray division method.When a complex casting is involved,a simple curve division can replace the ray Divide the way,simplify the process design process.Finally,based on the local envelope assignment method,the linear shrinkage value is assigned to the radial dimension of the thin-walled ring in actual production.Compared with actual production,the dimensional accuracy of the inner wall is controlled within ±0.4mm.