Inverse Calculation Of Cast-die Interfacial Heat Transfer Coefficient During Aluminum Alloy Gravity Casting And The Application In Simulation

As a characterization of the heat transfer behavior between cast and die, theinterfacial heat transfer coefficient is a typical boundary condition that is difficult tobe obtained directly. Its value is affected by a lot of factors. Currently, there is nomature theories or methods to analyze it quantitatively, and there is no equipment tomeasure it directly. So the accurate sloving and analysis for it become practicalsignificant.In the present study, the A356aluminum alloy is used in the gravity castingsolidification experiments under a variety of conditions as a material of cast. As aknown parameters, the temperature data collected from the experiments is used tofigure out the interfacial heat transfer coefficient through the inverse heat conductionprogram. The results show that changes of the interfacial heat transfer coefficient inthe solidification process can be divided into three stages: rapid increase stage, rapiddecline stage and maintain low stage. When the pouring complete, the interfacial heattransfer coefficient reach the maximum value rapidly. With the thickening of thesolidification layer and the shrinkage exacerbate, interfacial status become partialcontact from perfect contact gradually. The expansion of the air gap lead to a rapiddecline of the interfacial heat transfer coefficient. In the end of the solidification, thecontact status between cast and mold become stable, and the interfacial heat transfercoefficient become stable gradually.By comparing the interfacial heat transfer coefficients obtained from theexperiment without coating and the experiment with coating, it can be found that theuse of coating leads to a reduction in the interfacial heat transfer coefficient value anda lengthening in time for it to reach the maximum value. By comparing the interfacialheat transfer coefficients obtained from the experiments with different chill material,it can be found that copper chill yield highest interfacial heat transfer coefficientvalue, followed by brass chill and45steel, it is probably because of the differencethermal parameters. By comparing the interfacial heat transfer coefficients obtainedfrom the experiments with different vertical height of the cast:100mm,190mm, and230mm, it can be found that the interfacial heat transfer coefficient value increasewith the increasing of the vertical height of the cast, it is probably affected by thedifference in melt hydrostatic pressure and the heat storage of cast. A solidification experiment of the trapezoidal cast is conducted. And theinterfacial heat transfer coefficient obtained is applied in the simulation of thisprocess. It is obviously that the simulation temperature which set a constant as theinterfacial heat transfer coefficient have a relatively larger difference with theexperimental temperature. While the simulation temperature which set the curveobtained by the inverse heat conduction method as the interfacial heat transfercoefficient match the experimental temperature better. Such a result verify thecorrectness of inverse heat conduction method, and proved that a correct interfacialheat transfer coefficient can improve the accuracy of simulation.