Aluminum Alloy Melt Ultrasonic Degassing Mechanism And Experimental Study

In the process of semi-continuous casting of aluminum alloy, as the amount of the gas absorbed by the melt exceeded the allowance limit, the mechanical strength and performance of the materials were greatly weakened. In order to guarantee the quality of the product, it was necessary to degas the excessive gas by taking certain technics measures.Ultrasonic degassing, which is fresh, environment-preserved and clean, is the international research hotspot nowadays and a new direction of future casting technique. This paper took aluminum ultrasonic degassing as penetration point and the main study was shown as follows:1、The source of the gas in the aluminum alloy melt was expatiated and the kinetics process of the formation of the gas in the melt was analyzed based on a serial of "adsorption-diffusion-solution". The energy transmission property of ultrasonic in treating metal melt was described, which provided a academic basis for the theoretical analysis of ultrasonic degassing and the proceeding of experiments.2、According to the theory of quasi-crystalline model, the consolidated effect of ultrasonic field on the diffusion of hydrogen atom was analyzed from the point of view atomy kinetics. The functionary mechanisms of ultrasonic cavitation effect and cavity bubble’s pulse on the degassing of the 7050 aluminum alloy melt were studied in view of concentration gradient, temperature gradient, and pressure gradient respectively.3、A serial of experiments were performed based on different ultrasonic parameters applied to 7050 aluminum alloy. Experimental results showed that:the hydrogen content of the melt was gradually reduced as the ultrasonic power increased within a certain range (105W～240W); the degassing effect in the resonance condition was much better than that was in the non-resonance condition; the efficiency of degassing between 700℃to 720℃was much greater than that was between 640℃to 660℃; with the increase of the vibration depth, the vibration strength and vibration amplitude decreased within a certain range, which lead to the weak of the efficiency of ultrasonic degassing; the degassing effect under dynamic intermittent vibration was much better than that under static continuous vibration, and the effect of the shifting of the power from large to small on the ultrasonic degassing was much better than that was shifted from small to large under the dynamic intermittent condition.