Determination Of Metal-mold Heat Transfer Coefficient During Casting Solidification For Aluminum Alloys

With the rapid development of numerical simulation technology, thesolidification simulation of casting has been taken as an effective tool for designingthe casting process and improving the quality of casting. In the casting process, thesolidification simulation of casting is highly dependent on the heat transfer behaviorat the casting-mold interface. It is therefore believed that such heat transfer behaviorcould directly influence the growing and evolution of the microstructure, generationand distribution of the related defects and ultimately the mechanical properties of thecasting. During casting simulation, the numerical calculation of temperature field isone of the key contents. It may be taken as a foundation to predict the defects in thecasting process, such as shrinkage, crack and segregation. However, some accuratematerial properties and boundary conditions are essential for such simulationsaccepted as realistic descriptions of the process. Heat transfer at the casting-moldinterface can be characterized by a key parameter, namely the interfacial heat transfercoefficient (IHTC), which has been widely investigated nowadays due to its particularimportance and potential application value.In this paper, the IHTC between the casting and metal mold was identified byusing an inverse analysis method combined numerical simulation and optimizationtechnology based on the measured temperature. Then, by applying the identifiedIHTC in the microstructure simulation, the comparison between numerical calculatedand experimental results was made to verify the correctness of method. The resultshowed that the numerical calculated temperatures were in well agreement withexperimental ones. The research results in this thesis are summarized as following:1) A temperature measurement device in the solidification process of gravitycasting were designed and made. The temperature measurement tests on gravitycastings including five kinds of pouring temperature of620℃、650℃、680℃、700℃、720℃were carried out. The temperature evolution at different locations insidethe metal was obtained.2) Based on ProCAST software, the model had been designed for the calculationof the metal-mold interfacial heat transfer coefficients by a virtual test, the obtainedheat transfer coefficients were compared with the pre-setting ones. The resultindicated that the designed method is accurate and effective. 3) Three measured temperatures in the casting were employed as input data in theinverse model, and the others were only used to validate the process. Based on themeasured temperatures, IHTC were calculated by the designed inverse model. Theinfluences of the pouring temperature on the IHTC were investigated. It was foundthat the IHTC park increase with the increase of pouring temperature. The maximumvalue of IHTC was about4500W m~2K and the identified IHTC varied in the range ofabout550-750W m~2K after the solidifaction was completed.4) Through designing a complex interface model for an interfacial heat transfercoefficient, the temperature data at different positions in the casting and mold havebeen obtained. Based on the measured temperatures, IHTC was determined. Thecomparison between numerical calculated and experimental results was made toverify the correctness of method by applying the identified IHTC in themicrostructure simulation.