Research And Application Of Interfacial Heat-Transfer Coefficients In Metal-Mold Castings

An air-gap could be generated at the interfaces between the solidifying metal and surrounding mould during casting solidification.The air-gap produces a heat resistance which is traditionally described by an interfacial heat transfer coefficient.It varies with time and space and takes important part in the thermal transfer.The effect of heat transfer is described by an interfacial heat transfer coefficient.The interfacial heat transfer coefficient is the key parameter in the simulation of temperature field.As finite element software, ANSYS is used to analyze the solidification of metal casting in the paper.The interfacial heat transfer coefficient is determined using the inverse method.The correctness and convenience of this method is proved using experiments.The main tasks of this paper are as follows:1,ANSYS is used to simulate the temperature fields of the same casting solidification under two kinds of condition of considering the effect of heat resistance or ignoring its effect,and to analyze the influence of the heat resistant on the temperature distribution.Under the condition of considering the heat resistant, all of the simulated results with varying interfacial transfer coefficients are compared with the experimental results.Then the effect of the interfacial heat transfer coefficient on the temperature fields of solidification is received.2,Owing to the effect of gravity and the mold-environment heat transfer, the air-gap at the vertical interface is larger than that at the horizontal.Considering all above factors, the values of the interfacial heat transfer coefficients vary with the different locations of the boundary between the metal and mould.After simulation, the recorded cooling curves are compared with the simulated cooling curves.3,The interfacial heat transfer coefficient is determined using the Inverse Method by means of two transient techniques, which includes mathematically solving the interfacial heat transfer coefficient by thermocouple measurements and using 0.618 method to search the best fitting interfacial heat transfer coefficient directly.By applying ANSYS software, 0.618 method and the least-squares method, the rule and the mathematical model of the interfacial heat transfer coefficient with time can be made up.Based on all the methods and conclusions above, the model of the interfacial heat transfer with the contacting pressure, the thickness and the times or temperatures can be made up when it is extended to consider the respective factors.