Semi-continuous Casting Mold Molten Pool Of Aluminum Alloy Ultrasonic Flow Numerical Simulation And Experiment Study

Treating aluminum melt by ultrasonic field is an effective method of improving casting ingot solidification structure and material mechanical properties. It is the international research hotspot nowadays and a new direction of future casting technique. Starting at ultrasonic casting of 7050 aluminum alloy, main study was done as follows:1. Based on the theory of acoustic transmission in multi-media, the sound pressure distribution in the melts was calculated. Based on the analysis of the effects of cavitation theory and cavitation threshold, the cavitating regions in the melts under different powers were analyzed, combining with the sound pressure distribution. By using heterogeneous nucleation model, the nucleation parameters of 7050 aluminum alloy melts were analyzed and calculated, which showed that the nucleation rate was obviously improved. The higher the power was, the higher the nucleation got. As the distance to the tool rod increasing, the nucleation rate dropped.2. By using CFD software Fluent, the molten pool flow field in the ultrasonic semi-continuous process was simulated. The streaming driving force in the experiment conditions was obtained by analysis and calculation. The driving force was introduced into the model by use of UDF. The results showed that the melts flowed in the liquid cave, which was by the effect of sprue gate flow field.2 vortexes that arranged symmetrically on both sides of the sprue gate axis formed in the mould; as the casting speed increasing, the flow speed of the melts obviously increased, but there was no significant change in the basic characteristics of the flow field; the ultrasonic flow field had much smaller influence on the flow speed than the sprue gate field, even could be ignored. According to the stimulation results of calculations show that the numbers of nucleations form in cavitation region is transferred into the other areas on the effect of molten pool flow field, and improves the nucleation rate in the molten pool. Along with the increase of casting speed, the nucleation rate near the center axis increase and the side decrease. 3. The result of aluminum alloy ultrasonic semi-continuous casting experiment shows that the grains are refined across the cross-section and presented equiaxed grains uniformly. And the grains decrease in center and increase in side along with the casting speed increase, which is same as the stimulation result and prove the reliability of stimulation.