The Performance And Fracture Characteristics Of Air-flow Coverage Cattail Fiber Reinforced Silica Sol Shell

Investment casting is a near net shape forming technology for liquid metal.The resulting castings generally have a high dimensional accuracy and surface quality.Silica sol is widely used in shell-making for investment casting process as an excellent water-binder.The advantages of shell-making: the high temperature strength is better,and the high temperature resistance to deformation is stronger,stable performance and shell-making process easily.But the prominent defect of the process of the silica sol shell-making is that the green strength and the permeability of shell are lower,long period of shell-making,casting cleaning difficulty.Therefore,it is of great significance and practical value to find a new technology of shell-making process.The methods of covering cattail fiber by air-flow to reinforce the comprehensive performance of silica sol shell,in this work.The cattail fiber cover on the back coating,the amount of fiber to be covered that is based on the 0.2wt.%~1.0wt.% change of the quality of the refractory power in the backing coating applied to the shell sample.The main research and analysis on the effects of different overlay amount on the strength of fiber reinforced shell,the detail roasting process was developed,the characteristic of the permeability and deformation under elevated temperature of fiber reinforced silica sol shell were measure.In order to improve the strength and deformation under elevated temperature of silicon sol shell for investment casting,the paper uses the cattail fiber as the reinforced phase.The results show that the amount of fiber paving in the device is about 6%.When the airflow covering,the fibers are well suspended and dispersed in the container,so that the uniformity of the fiber overlay on the back coating is improved,and the airflow time should not more than 30 s.Otherwise,the coating will appear a layer of dry film,which reduced fiber adhesion properties.The found in the experiment process,when the amount of fiber covered is 1.0wt.%,the fiber almost covers the surface layer of slurry,resulting in reduced adhesion properties of sand to back coating,uneven sanding,and influence the strength of composite shell.The result of researching show that the content of covering cattail fiber is 0.4wt.%,the green strength of the shell is up to 3.24 MPa increased obviously by about 11.62% than the ordinary shell.As the amount of cover fibers continues to increase that the phenomenon of fibers knot,winding,the effect of fiber reinforced shell decreased,even split the matrix.The result of researching the fiber effects on the fired strength of the silica sol shellshows that as covering fibers increased to the fired strength of the composite shell increased first and then decreased.When the covering fiber is 0.4wt.%,the silica sol shell has the best green strength,and the fired strength of shell also reaches the maximum value of 5.91 MPa,which increase by about 16.8% compare with the ordinary shell.When the amount of covering fiber is 0.4wt.%,the deformation of the shell specimen is 0.54%,which satisfies the requirement of the deformation of the shell.The permeability of the high strength composite shell is better than that of the free shell,about 32.5%,which is beneficial to improve the surface quality of the casting.