Research On Preparation Technology And Service Life Evaluation Of Rolled Alumina Ball

Alumina balls have been used as filler in due to the advantages of its roundness,good fluidity and high temperature resistance.the raw material should not be crushed by extrusion in the printing process.In addition,the packing density should be controlled to ensure the thermal insulation performance of the product.Finally,the lifespan of ceramic balls is related to the quality and life of downstream products.At present,there are few researches on the properties of alumina ball preparation process and evaluation of the service life of alumina ball.It is found that different sintering temperature and polishing time have great influence on the properties of rolling alumina ball,and the change of thermal conductivity can reflect the degree of damage failure of alumina ball under fatigue.Therefore,effects of sintering temperature and polishing time on the properties of rolling alumina spheres were investigated to analyze the optimum preparation process parameters.The thermal conductivity of alumina spheres was studied to evaluate their service life.The main contents are as follows:(1)The effects of sintering temperature on the shape and properties of rolled alumina spheres were studied.The results showed that: As the sintering temperature(1400-1600?)increases,the average particle size and angle of repose of 30-40 mesh,40-50 mesh and 50-60 mesh decrease,while the compressive strength and packing density increase with the sintering temperature;at the same sintering temperature,the larger the particle size is,the larger the average particle size is,angle of repose and compressive strength is and the smaller the packing density is;and the sintering temperature does not affect the roundness and sphericity of alumina sphere.This is mainly due to the internal sintering of the sphere at high temperature further strengthened,and the smaller the particle size is,the more uniform the temperature is,and the smaller the gap between the accumulated particles is,which makes the sintering condition of alumina ball better.In the process of compaction,the amount of grinding is insufficient,thus the surface is not smooth enough,and the roundness,sphericity and angle of repose need to be improved.(2)The effects of polishing time on the shape and properties of rolled alumina spheres were studied.The results showed that: for the 1400? and 1600? of sintered alumina,with the prolongation of polishing time(1-6 h),the average particle size and repose angle of 30-40 mesh,40-50 mesh and 50-60 mesh alumina ball decreased slightly,the compressive strength decreased obviously,while the roundness,sphericity and packing density increased.And the optimum polishing time of alumina ball was 4h.The average particle size decreases more obviously and the roundness and sphericity of the intermediate particle size samples increased greatly after 1600?of sintered alumina the same polishing time compared with 1400? sintered samples larger.The reduction rate of the angle of repose of large and medium particles is large,The packing density increases less and the compressive strength decreases less.This is mainly due to the fact that after high temperature sintering the sintered alumina ball is easily polished under the action of mutual impact force and friction force with the prolongation of polishing time,resulting in the reduction of particle size is.And the larger the particle size is,the larger the impact force and friction force is and the smaller the contact area is,so the self-grinding effect of medium particles is the best,while the strength of alumina after high temperature sintering,which is beneficial to improving the polishing effect of medium particles.There will be debris in the micropores on the polished surface,which is one of the reasons for the increase of packing density.When the polishing time is 4 h,the optimum polishing time of alumina ball is 4 h.because the polishing time has little effect on the average particle size,roundness,sphericity and fluidity of the sample.(3)In this work,the thermal conductivity of rolled alumina solid ball is studied,the results show that the thermal conductivity of bulk material increases linearly with temperature in the range of 200?-1500?,which can predict the value of thermal conductivity at a certain temperature point.When 30-40 mesh is mixed with 50-60 mesh,the mass ratio of the former is 75%,and the thermal conductivity is get the maximum value;the alumina ball with single particle size or mixed particle size in the experimental range is subjected to multiple thermal fatigue at 600?-1200?.the value of thermal conductivity of fatigue four times at each temperature point remains unchanged,and the experiment does not reach the service life limit.