Study On Furan Resin Sand For 3D Sand Printing

3D sand printing is a kind of Additive Manufacturing（AM）technology of indirect forming,which can directly manufacture the complex sand mold and core used in sand casting.In recent years,researchers at home and abroad are increasingly interested in this kind of incremental manufacturing technology for indirect production of metal parts,which is not only attributed to its ability to quickly produce molds（that are cores and molds）for complex metal castings,but also its possibility to make such complex metal castings when compared with traditional technology.In addition,this technology plays an irreplaceable auxiliary role in the design,development,manufacturing and molding of complex parts or products.Furan resin sand is a kind of mold（core）sand which is mixed with furan resin as adhesive and curing agent.Furan resin sand has the advantages of good self-hardening,collapsibility and high dimensional accuracy of castings,so it has been widely used in 3D sand printing technology.However,there are some problems in 3D printing furan resin sand,such as low core strength,high resin content,large mold gas evolution and so on.In order to solve the above problems,based on the 3D sand printing technology,the process parameters of furan resin sand are designed and optimized through the central composite experiment in the response surface method,and then the particle gradation of silica sand in furan resin sand is studied.Finally,the feasibility of the optimized process parameters applied to 3D sand printing technology is verified by experiments.The main conclusions of this paper are as follows:（1）The furan resin content,curing agent content,curing temperature and curing time are selected as investigation factors,and the tensile strength and gas evolution of furan resin sand are taken as indexes.The optimum process parameters of furan resin sand are determined by single factor experiment and response surface method（CCD）experimental design.Through calculation and comparative analysis,the optimum process parameters of resin sand are determined as follows:the amount of resin added is 2.13%of the weight of silica sand,the amount of curing agent is 17.8%of the weight of resin,the curing temperature is 112℃and the curing time is 88 min.The experimental results show that under these conditions,the tensile strength of resin sand is 1.57 MPa,and the gas evolution is 15.43 m L/g.（2）The optimum particle gradation of silica sand is analyzed by mixing design and three-dimensional simulation of particle flow program.Finally,the proportion of silica sand with each particle size is X₁（0.202 mm）:X₂（0.15 mm）:X₃（0.106 mm）=0.38:0.33:0.29.Under this gradation,the porosity of silica sand system is the smallest,which is 38.5%,which is 11.09%lower than that before screening.Under the same process,the average tensile strength of graded resin sand is 1.71 MPa,and the average gas evolution is 15.47 m L/g.Compared with the properties of resin sand before gradation,the gas evolution is the same,and the tensile strength is increased by 8.92%.（3）Using the optimized process parameters of resin sand and graded silica sand,the sand mold was printed by 3D printing equipment（PCM800）,and then poured,and the castings with good surface quality were obtained.The test results of mechanical properties of the castings show that the yield strength,tensile strength,elongation and hardness of the castings are 83 MPa,142 MPa,3.22%and 54.5 HB,respectively.The tensile specimens of castings show quasi-cleavage fracture.Compared with the castings obtained by the existing standard process parameters,the microstructure and fracture failure mechanism of the castings have not changed.There is no significant difference in hardness and yield strength,while the tensile strength is increased by 9.23%.the elongation is obviously increased,which is about13%higher than that of the standard process.