Ultrasonic Sound Field Distribution In The Aluminum Melt And The Cavitation Effect And Its Effect On The Solidification Process

Semi-continuous Casting is one of the most important casting techniques in nonferrous-alloy production. It can make the production automatic; simplify the process flow, save energy and raise labor productivity, so it plays great role in modern metallurgy production and be seen important extensively. But at home, the cast ingot organizations of conventional Semi-continuous Casting are non-homogeneous casting stress, cracks and so on whatever internal or outside,specially for large Al alloy ingot. To refine the freezing organization, improve the temperature filed and stress field shape used by ultrasonic, which can optimize confentioning process and get the high performance casting products. This thesis enphasis on propagation characteristic, cavitation, energy propagation regularity and the effect on aluminous' freezing process of ultrasonic.This thesis includes the following main aspects:1. By the Huygens' Principle, to divide the terminal face of transducer into incalculable small surface elements, and adopt Rayleigh integral method, calculate the regular hexagon, square, circle terminal face of transducer sound field distribution and sound field directivty property functions. Calculating the sound field directive property of different terminal face shape of transducer under the different wave numbers through matlab, and getting the different wave numbers, different transducer's terminal face regularities of sound field directive property.2. Analyzing the correlation of mechanical quality factor with acoustic pressure and acoustic intensity, which is abased on the researchers of ultrasonic vibrating system admittance characteristic in aluminum molten. According to sonic refraction reflection principles, deducing acoustic pressure amplitude value when the ultrasonic transferred to aluminum molten contacting interface with amplitude tool bar from vibrating system. And found correlative mathematical models, discussing the distributions of the power ultrasonic at aluminum molten, presenting ultrasonic characteristic quantities at aluminum molten. 3. To research the rationale of ultrasonic cavitation at the high temperature aluminum melt, discuss how physical parameters' effect to ultrasonic cavitation, found correlative mathematical models. Through Rayleigh-Plesset's numerical calculation by Matlab, study the impacts of supersonic frequency,sound pressure and initial radius of catitation bubbles at the aluminum melt.4. To simulate liquid cavern curve ofφ300 mm aluminum round casting ingot D.C.casting by marc software, incorporate ultrasonic power and amplitude transformer, the correlative mathematical models of aluminum molten has been founded. Study and discuss the ultrasonic propagation characteristics and ultrasonic field regularities of distribution in aluminum molten, analyz the ultrasonic refraction and reflection when it propagat to liquid cavern curve, figure out ultrasonic sound pressure values at liquid cavern curve, discuss primary causes of ultrasonic cavitations effect in aluminum molten, according to ultrasonic field regularities of distribution, handle Matlab mathematical tool, utilize difference quotient iteration, and numerical calculated cavitation bubbles moving, summarize the range of occurring cavitation effect of aluminum ultrasonic D.C.casting and effect of ultrasonic to ally organization under different initial radius.5. The effect of power ultrasound on solidification process of high temperature aluminum molten has been investigated under routine. Though add the ultrasonic in high temperature aluminum molten, it can made the crystalline grain of aluminum ingot refinement, and the organization was homogenous, and the representation of microstructure were thin equiaxed grain, compared with no power ultrasound in aluminum whose microstructure were coarse columnar grain. Then emphasized on cavitation effect and it created high-temperature and pressure theory, then discussed the partial high-temperature and pressure initiated various dynamic problem. And discussed the acting mechanism to solidification process of solidification process though the cavitation effect, acoustic streaming effect, and mechanical effect. Summarized by analyzing the aluminum ingots organization, the effect of power ultrasound on solidification process are results of multiform synthesis effects; it will supply some theoretical bases for the application on foundry effectively...