Numerical Simulation Of Hot-top Semi-continuous Casting Of7XXX Aluminum Alloy

Hot top casting has solved some defects which are caused by general casting, such as segregation, cold shut, pores, cracks, etc. However, the study on numerical simulation method is relatively less. This paper, with PROCAST and other assisted software, makes a further research on the temperature and stress field of the7050aluminum alloy during hot top casting and provides a better practice guide for the production of hot top casting.First,based on two group tests (test one and test two), the temperature curve of ingot is measured in first cooling water and the second one, which will be compared and checked with result from numerical simulation to obtain the most accurate results. How to use the numerical simulation method? At first, heat transfer coefficients of the two cooling water is evaluated by one-dimensional heat conduction equation. Then it is input ProCAST as a terminal condition to get the temperature curve of ingot. The Study proves that the heat transfer coefficient is not linear with temperature increment or decrement. As for the test one, heat transfer coefficient increases firstly and reduces afterward with maximum value2018W/(m-2k-1) at about300℃. As for test two, trend of heat transfer coefficient with the temperature is almost the same as the test one with maximum value14763W/(m-2k-1) at about220℃. In short, through simulation of temperature field, the error of the two results is below7%.Second,ProCAST software is used to simulate the casting speed and casting temperature on the ingot temperature field, stress field, Sump, and nucleation rate. The study found that the initial condensate point in the casting process, with the casting speed increases down. Initial condensate points is in the thermal hat when the casting speed is70mm/min; initialcondensate points is in the mold and along the18mm from the mold when the casting speed is85mm/min; casting speed of100mm/min, initial condensate point is in the mold and along the46mm from the mold surface. Sump depth increases with increasing casting speed.Sump depth are142mm,156mm and187mm when casting speed is70mm/min,85mm/min and100mm/min respectively. Nucleation rate arel.215× 1024,3.731×1023and6.043×1022, in the three casting speeds. The maximum stress location in the casting process took place in the surface of the ingot or the bottom of the ingot and the maximum stress values increase withthe increase of the casting speed, decreases with increasing casting temperature. Comprehensive analysis to consider the casting speed and casting temperature on the ingot stress field, has been effective in preventing the cracks of the casting process.