Construction And Realization Of Ultrasonic Function In New Type Hot-pressing Sintering Furnace

In order to improve the sintering property of the hot press sintering furnace,solve the problems of long sintering time,high sintering temperature,low density and coarse grains of the prepared material,the ultrasonic function is introduced into the hot press sintering,based on the powder metallurgy,thermodynamics,power ultrasonics and other related theories have constructed the key components in the ultrasonic-assisted hot press sintering furnace: ultrasonic vibration components;simulated the effects of component materials and structure on vibration characteristics,and revealed the changes of various parameters on resonance frequency,the structural parameters of the component were obtained;the influence of the components on the ultrasonic vibration characteristics of the components is experimentally studied,and the structure of the components is further optimized to make the vacuum hot-pressing sinter have the ultrasonic function.The main research conclusions are as follows:(1)According to the structure of the vacuum hot-pressing sinter,combined with the characteristics of power ultrasonic,the structure of the power ultrasonic component matching the hot press sintering furnace is constructed;in the hot pressing sintering process,because the ultrasonic system cannot withstand large pressure,a protective device for the transducer is constructed(2)According to the high temperature characteristics of the hot press sintering furnace during the working process,the cooling amplitude transformer of "blind hole" and "singleshaped" were constructed respectively,and the size of the amplitude transformer was obtained by the four-terminal network method;the finite element method was ued to simulate and study the influence of the size of the horn on the ultrasonic frequency,and found that as the temperature increases,the resonance frequency of the amplitude transformer gradually increases;at the same time,with the 20 k Hz ultrasonic frequency as the target,a multi-objective optimization method is adopted.The size of these two amplitude transformers has been optimized.(3)Experimental study of the frequencies of these two amplitude transformers shows that the frequency of the "blind hole" horn is 19.9k Hz,but its large impedance is not conducive to the transmission of ultrasound,while the frequency of the "single-shaped" horn is 19.2k Hz,its impedance is small,suitable for power ultrasound,but the ultrasound efficiency is low,and there is a ultrasonic wave leakage at the flange.(4)According to the design theory of the amplitude transformer,a double-node amplitude transformer is constructed to reduce the thickness of the flange.The size of the horn is obtained by the four-terminal network method,and a simulation study is carried out.The results show that the resonant frequency of the dual-node amplitude transformer is 19.8k Hz;the experiment obtained the frequency of the amplitude transformer,and its value is 19.5k Hz,which is close to the target frequency,which improves the ultrasonic efficiency,but there is still a ultrasonic wave leakage at the flange.Based on this,a looper flange structure is constructed,and the resonance frequency of the amplitude transformer is obtained by experiment,its value is19.6k Hz,and there is no leakage at the flange.(5)According to the high temperature characteristics of the hot press sintering furnace,the ultrasonic tool head used in the sintering furnace was developed.Graphite and molybdenumzirconium-titanium alloy were used as tool materials.The dimensions of the two tool heads were obtained by using the wave equation and carried out.The simulation research shows that the resonance frequency of the graphite tool head is 19.4k Hz,and the resonance frequency of the molybdenum-zirconium-titanium alloy tool head is 19.9k Hz.At the same time,the frequency characteristics of the two tool heads are simulated and studied under high temperature load.As it rises,the resonant frequency of the tool head gradually increases.At the same time,the experiment obtained the resonant frequencies of the two tool heads,their values were 20.5k Hz and 19.6k Hz,but due to the poor tensile property of graphite,the tool head was broken and ultrasonic failure occurred,while the molybdenum-zirconium-titanium alloy has good ultrasound function.(6)In a normal temperature environment,the vibration performance of the ultrasonic component and the cooling reliability of the component structure have been experimentally studied.When no pressure is applied,the maximum amplitude of the ultrasonic component is16?m;after the high-pressure cooling water is passed through,the test is accumulated for 100 hours,no leakage occurred in the joints and welds.At the same time,a set of ultrasonic-pressure test equipment was developed to use the influence of pressure and ultrasonic time on the density of alumina powder.It was found that when the pressure is less than 20 MPa and is constant,the density of the material continues to increase with the extension of the ultrasonic time.When the pressure is greater than 20 MPa and is constant,the density of the material does not change much with the prolongation of the ultrasonic time.