Computer Simulation Of Temperature Field In Semi-Continuous Casting Process And Its Application In The Prediction Of Solidification Structure

The casting is an important process in material preparation and forming, however, the preparation and research of new materials which are based on experiments will cost a great deal of manpower, materials and financial resources. Along with the development of computer technology, digitalized foundry which is based on computer numerical simulation as its core has been applied in a wide range, by the study of numerical simulation to temperature field, stress field, microstructure and so on, the analysis and optimizing of various quality problem and the prediction and control of structure property of the products in casting process can be achieved, and the resources can be saved effectively in this way.In this paper, Mg-Al alloy was as the object of study. The temperature field model for casting process was established concerning the characteristics of semi-continuous casting process, which was solved using the finite volume method, and then by altering the different casting process parameters—pouring temperature, casting velocity and cooling intensity, the impact of different parameters to temperature distribution was analyzed. Through the simulation under the conditions of pouring temperature 882K, casting velocity 1.0mm/s, and cooling intensity 1000W/(m2·K), we can see:the temperature decreased slowly in the center of the ingot, with close to the surface, the temperature drop become faster and faster. In the different cross section of the ingot, the more distant from the entrance, the faster the temperature decreased. Raising pouring temperature to 927K or the casting velocity to 2.0mm/s would make the temperature increasing in the same location of the same cross-section, and the temperature drop in the center of the ingot would be greatly affected than the surface, so that the temperature distribution become more non-uniform, and melt cave become deeper; when increasing the cooling intensity, the speed of temperature fall raised in both internal and border ingot, so that the temperature was relatively lower in the same location of a cross section. When the cooling intensity was continued to increase from 1000W/(m2·K) to 1500W/(m2·K), its impact on the temperature field was weakened.The temperature of casting process has a direct impact on the solidification structure of castings, so this article further applied the results of temperature field in solidification structure prediction and used cellular automaton method to simulate solidification microstructure under different casting conditions. On the conditions of same casting velocity and cooling intensity, the differences of structure between the center and border of the casting were smaller when pouring at 882K—a lower temperature above the liquidus, and the grain roundness is better; On the conditions of same pouring temperature and cooling intensity, both the grain size and the differences of the grain size between the center and the border is relatively smaller under the casting velocity of 1.0mm/s, however, when the velocity increased to 2.0mm/s, the differences of grain size between the center and border become large, the grain roundness is also decreased significantly. On the conditions of same pouring temperature and casting velocity, the structure of the ingot was obviously improved when the cooling intensity was increased from 500W/(m2·K) to 1200W/(m2·K), but when continued to be raised to 1500W/(m2·K), the change of the temperature field which was affected by the cooling water was not obvious, and therefore little change in the structure of ingots. The result of the study is that the microstructure of Mg-9.0wt% Al alloy would be better under the conditions of pouring temperature 882K, casting velocity 1.0mm/s, cooling intensity 1200W/(m2·K). The study of this paper shows that, the temperature field is the basis to determining process parameters and predicting solidification structure. The correct simulation of temperature field has an important meaning for improving the quality of castings by changing the process parameters to improve the solidification microstructure.