Mathematical Modeling, Simulation And Experiment Study On Multi-field Coupling Of7050Aluminum Alloy DC Continuous Casting Of Large Scale Ingots With Ultrasonic Treatment

Casting of Large Scale Ingots with Ultrasonic Treatment Abstract:With the introduction of ultrasonic treatment in aluminum alloy DC casting of large scale ingots, grains can be refined, macro and micro structures can be improved, casting defects can be reduced and material properties can be upgraded. Such a casting method is a research focus and a development direction. In this paper, mathematical modeling and simulation are established as to describe macro physical fields’ interaction such as the coupling of acoustic, flow and thermal fields in the aluminum alloy DC casting process with ultrasonic treatment (UST). The main research work and conclusions are as follows:Firstly, mathematical modeling describing macro fields’interaction and coupling in aluminum alloy ingots’DC casting progress with UST is established. Acoustic, flow and thermal fields have been associated together by the introduction of the turbulence model of low Reynolds number form and the acoustic streaming driving force model.Secondly, a dynamic analysis of acoustic vibration system which consists of piezoelectric and structure coupling, structure and acoustic fluid coupling is conducted. Furthermore, the acoustic field distribution of the sump of round ingot with a diameter of300mm is settled as the acoustic pressure boundary conditions determined based on the conversion relationship of vibration amplitude and acoustic pressure.Thirdly, the macro coupling fields3D calculation model of aluminum alloy flat ingot DC continuous casting with UST based on FLUENT software is proposed. Acoustic, flow and thermal fields’ distributions are calculated based on the features of FLUNET software’s numerical simulation abilities. Simulation results show that, the suitable frequencies vary from15kHz to20kHz, when the vibration amplitude of radiator equals10μm. When the frequency equals20kHz, the suitable vibration amplitude of radiator varies from10μm to15μm.Finally, the experiment study on7050aluminum alloy1320x500mm flat ingot DC casting with UST is executed. Experiment study shows that ingot’s grain size is significantly reduced with the introduction of acoustic field and the distribution of grain size is becoming more uniform. The transition from dendrites to equiaxed grains is promoted. The reason can be explained in two aspects:aluminum melts’flow becomes stronger and the gradient of aluminum melts temperature becomes smaller with UST.