Effect Of Different Proportion Of Composite Fiber Corundum Sand On Properties Of Silica Sol Shell

Investment casting technology is one of the main forming methods for aerospace complex parts with high precision.In order to comply with the national strategy and the high requirements of the investment casting Market on product performance,it is urgent to solve the problem of mutual restriction between the strength and permeability of investment casting shell.PA66 and Al₂O₃ composite fibers were mixed in corundum sand to reinforce the shell.PA66 fiber was used as room temperature reinforcement material and pore forming agent,Al₂O₃ fiber was used as high temperature reinforcement material to improve the permeability of the shell and enhance the shell strength and resistance to high temperature self-weight deformation.The influence of different proportion of composite fiber hybrid corundum sand on the properties of silica sol shell is studied,which has a certain guiding effect on the preparation of high quality shell.In this paper,PA66 and Al₂O₃ composite fibers were used to reinforce the mold shell,and PA66 fibers with different contents were mixed into corundum sand.The effect of PA66 content on the properties of silica sol mold shell was studied,and the optimum PA66 fiber mixing amount was obtained.Then PA66 fibers and Al₂O₃ fibers were mixed into corundum sand with different ratios,The influence of the ratio of composite fibers on the shell properties was discussed and the strengthening mechanism of the two fibers was analyzed.The results show that when the content of PA66 fiber is between 0.25%and 1.25%,the air permeability and bending strength of the shell increase gradually with the increase of the amount of PA66 fiber mixture.The bending strength of the shell increases slowly and then decreases rapidly after calcination.When the content of PA66 fiber is 0.75%,the bending strength of the shell after calcination is 7.941MPa,which is only 0.024MPa lower than that of the unmixed fiber,But the bending strength at room temperature,air permeability and porosity increased by 32.21%,90.91%and 13.35%respectively;When the proportion of Al₂O₃fiber in the composite fiber varies from 20%to 80%,the air permeability and bending strength of the shell decrease gradually,the bending strength increases first and then decreases sharply after calcination,and the deformation rate at high temperature decreases first and then increases.When the proportion of Al₂O₃ fibers in the composite fibers varied from 20%to 60%,the composite fibers mainly existed as monofilaments in corundum sand,the bending strength of the shell increased gradually to the maximum value of 10.542MPa after calcination,and the deformation rate of high temperature deadweight gradually decreased to the minimum value of 0.81%.The bending strength and air permeability of the shell decreased gradually at room temperature.However,the strength and air permeability of the composite fibers were higher than that of the unmixed fibers.When the proportion of Al₂O₃ fibers in the composite fibers was 80%,the composite fibers braided corundum sand into clusters,and the bending strength and air permeability of the shell decreased sharply after calcination,and the deformation rate of high temperature dead weight increased.The influence of PA66 fiber content and the proportion of Al₂O₃ fiber on the properties of silica sol shell was studied.The reasonable preparation process of high strength porous silica sol shell was optimized,which provided theoretical guidance and technical basis for the production of high quality and complex Superalloy Integral precision castings.