Numerical Simulation Technology Of Squeeze Casting Solidification Process

With the rapid development of casting CAE simulation technology, a variety of casting numerical simulation softwares for solidification process are widely used in large enterprises.A new product basically should be carried out numerical simulation, in order to reduce the trial period,lower the production cost,decrease the casting defects, and improve quality of castings. Through the establishment of the mathematical model for heat transfer process, this paper has developped the temperature field simulation program which owns independent computing functions,with the aim to predict defects types and locations of casting products that may arise in the actual production process,and to provide theoretical guidance for optimizing the process parameters.In this paper, on the basis of thoroughly understanding the theory of squeeze casting and casting solidification process of computer simulation techniques, the heat conduction differential equations for the temperature field of the solidification process have been deduced according to the numerical heat transfer law of heat conduction. In order to obtain a unique solution on solving actual heat transfer problems, a mathematical model on behalf of the composite thermal conductivity has been successfully established in the treatment of boundary conditions between castings and the mould, which can express the heat transfer law in different calculation grid units. The paper has managed to discretize the previously established heat conduction differential equations in time and space by using the explicit finite difference method on the condition of comprehensively comparing various numerical methods, and succeeded in setting up difference equations with definite solution conditions by selecting a reasonable time step. The latent heat release mode that the solid fraction shows a linear relationship with temperature changes in the solidification crystallization interval has been given priority to use on the issue of dealing with latent heat problems.In addition, basing on the in-depth research of three common latent heat treatment methods including the enthalpy method, the temperature rise method and the equivalent heat capacity method, the final treatment method has been chosen as follows:for alloys with narrow solidification crystallization intervals, the temperature rise method has been adopted, on the other hand, for alloys with wide solidification crystallization intervals, the equivalent heat capacity method has been adopted. The corresponding latent heat treatment method has been carried out to revise the temperature of each computing grid cell according to the law of conservation of energy, which has improved the accuracy of the solidification process temperature field simulation results.In the part of program design, this article takes advantage of the object-oriented programming method on the development platform of Microsoft VC++6.0,and makes full use of the C++class’s characteristics,such as encapsulation, data hiding, inheritance and ambiguity. Finally, the paper has independently developed the dynamic link library in which the temperature field calculation function is packaged. Through sharing the STL file interface programs and the mesh dessection modules developed by the pre-treatment group, the article has successfully added a dialogbox interface for setting thermophysical parameters of castings and moulds, a setup interface for defining various solidification simulation computational conditions, and a display module for showing solidification simulation results. Lastly, the entire numerical simulation process of the solidification temperature field has been achieved vividly as well as extensionally linking with the main program developed by the whole group.In order to test the practicality of the previously developed solidification temperature field calculation module, the paper has carried out the numerical simulation calculation of the temperature field on two typical aluminum casting products under the condition of squeeze casting process,and compared the calculated results with the results from the casting simulation software AnyCasting.Ultimately,it shows that both of the calculation results are in agreement basically, which validates the accuracy of the temperature field solver module developed in this paper.