Numerical Simulation Of Liquid Forging Of Aluminum Alloy And Defects Prediction

Liquid forging is a technology combining forging process with casting process. So it has both the advantages of casting and forging. Since Liquid metal solidifies under high pressure condition, it can not only make the workpiece grain fined, microstructure compacted and lower liability to shrinkage, but also give a sound part with precise size and good composite mechanical properties. The liquid forging technique involves a series of complex processes, such as metallurgy, fluid flow, heat transfer and plastic deformation etc. So a proper liquid forging process is a pre-condition of getting a liquid forging part with high quality. With the rapid development of the computer techniques, numerical simulation technique has also been used in forging industry widely, such as it can be used to optimize the technological design, shorten the trial-production periods of the product, reduce the cost, and insure the product quality and properties. Therefore, it's significant to simulate liquid forging process.In this paper, a 2A50 aluminum alloy wheel of tank has been investigated, the solidification process and stress field of liquid forging are numerically simulated by the casting software of Pro-CAST. In addition, shrinkage and hot tearing defects in wheel are predicted. According to the predicted results: the solidification tendency of the wheel is from up to down, from surface to inside, the corner and bottom centers of the wheel are the last solidified parts; After the stage of solidification, the wheel suffered compressive stress on the surfaces and tensile stress in the bottom center because its shrinkage is hindered by pre-solidified parts; In addition, shrinkages and hot tearing are found in the last solidified part of the wheel, and tensile stress in the corner of the wheel makes the hot tearing possible.As for the shrinkages and hot tearing happened in the corner of the wheel, we have optimized our simulation technologies which are proved by experiments. In order to get a higher pressure in the corner of the wheel, make the solidification under pressure and eliminate the defects, two-way pressures have been applied instead of unidirectional pressure. As results show: solidification under two-way pressures totally reduces the defects, and the prediction results have a better agreement with experiment. Then, several numerical simulations of liquid forging have been taken, and the liquid forging parameters are optimized, as for aluminum alloy wheel, the pressure should be about 100MP, the pouring temperature should be about 720℃and the pre-heat temperature of mold should be about 300℃.