Research On The Key Technology Of Batch Microwave Sintering Of Superhard Tool Materials

Based on the microwave sintering technology,this article studies the key technology of batch microwave sintering of superhard tool materials,aiming at the technical bottleneck of unstable heating process and uneven temperature field distribution in the process of batch microwave sintering of superhard tool materials.The thesis studies the heating characteristics of microwave sintered Al₂O₃-based tool materials,including the influence of dielectric parameters,thermal conductivity,microwave power,and microwave frequency on the heating characteristics of the tool materials,and simulates the influence of the amount of auxiliary heating material and the composition ratio on the temperature uniformity of Al₂O₃-based tool materials.The structure design of the batch microwave sintering equipment was carried out,and the three-dimensional size of the resonant cavity and the distribution position of the feed ports were determined.According to this,the auxiliary heating device for batch microwave sintering tool materials was designed specifically,and three auxiliary heating devices were studied for the heating of Al₂O₃-based tool materials by buried powder heating,setter plate heating,and setter plate small unit heating.Finally,the best structural parameters of the auxiliary heating device were determined.In order to improve the temperature uniformity of batch sintered tool samples,a moving heating method was proposed.The influence of the moving distance and moving period of the tool sample on the temperature uniformity of the tool sample was studied,and the best moving method was determined.The simulation researched the heating characteristics of Al₂O₃-based ceramic tools,and found that increasing the?'of the sample,the electric field distribution in the cavity does not change,and the electric field intensity at the position of the tool sample decreases slightly with the increase of?'the average temperature rise and temperature difference of the sample decrease with the increase of?'when?'changes,the electric field in the cavity and the sample does not change significantly the sample heating rate and temperature difference increase with the increase of?'under the same energy input condition,when the microwave power increases,the average temperature of the sample does not increase with the increase of the power increasing the thermal conductivity can significantly reduce the temperature difference of the sample the microwave frequency change will cause a huge change in the heating rate of the tool sample.Under the condition of batch sintering 50 pieces of tool materials,with the help of COMSOL Multiphysics simulation,the three-dimensional size of the batch microwave sintering equipment is determined as 650mm×400mm×420mm.The layout of 6 feed ports is adopted,the distance between the feed ports in the x direction is 130mm,the distance between the feed ports in the y direction and the cavity wall is 130mm,and the waveguide adopts the BJ26 type waveguide,which is arranged orthogonally.The simulation study of the Al₂O₃-based tool sample batch microwave sintering auxiliary heating device,it is found that when Si C powder is used for heating,the heating rate of the Al2O3-based tool sample is the highest when the Si C powder is 678g,and the final temperature is also the highest.When the Si C setter plate is used for heating,the microwave heating efficiency is the highest and the temperature uniformity is better when the setter plate thickness is 4mm.Using Si C setter plate small unit to assist heating,when the setter plate three-dimensional size is 218mm×114mm×8mm and the small unit size is 41mm×9mm×6mm,the tool sample heating rate is the highest,and the temperature uniformity is the best.Under the temperature change condition of material parameters,the best heat-assisting form is determined to be the heating of Si C setter plate,and the fillet diameter of the setter plate is 50mm after optimization.The effect of moving heating on the temperature uniformity of the tool sample is studied.Compared with the static heating,the temperature uniformity of the tool can be increased by17.5%when the maximum moving distance of the tool sample is 76.25mm and the movement period is 15s,the tool sample heating rate is 109.9?/min and the temperature unevenness coefficient is 0.0093,the heating rate is higher,and the temperature uniformity is the best.