EFFECT OF SONOTRODE DESIGN ON SIMULTANEOUS GRAIN REFINEMENT AND DEGASSING OF Al ALLOYS BY ULTRASOUND

摘要

Grain refinement and degassing of Al alloys are the fatal processes to keep the high quality castings. The most widely used process for the grain refinement and the degassing is the addition of inoculants and the rotary degassing, respectively. However, these processes affect each other and make low efficiency of each process, in addition, these increase the cost. The application of the ultrasound for grain refinement and degassing has been studied to modify the processes, but the ultrasound could be only applied in special casting condition, such as solidification or in the semiliquid state, and the effect of ultrasound in this state seriously decreases because the fluidity of melt extremely dropped. In this study, new process using ultrasound, named as NUMT(Nucleation Ultrasonic Melt Treatment), is suggested as the melt treatment for grain refinement and degassing simultaneously in melt. NUMT process could be established by the special design of the sonotrode made by Ti, and it makes supply the nuclei in Al alloys melt continuously and efficiently. The grain size and the content of hydrogen drop extremely by NUMT.