Research On The Expendable Pattern Shell Casting Process Of Aluminum Alloy

With the development of the aerospace,electrical and automotive industries,the demand for“precision”and“lightweight”castings has become more prominent.Because of the process advantages of expendable pattern shell casting,it has gained a huge development space.In this paper,the combination of single factor test and orthogonal test was used to analyze the influence of the adding amount of each component on the performance of the coating,and the expendable pattern shell coating with excellent performance was prepared.Then,the shell was prepared by using shell coating.The effects of vibration frequency and pouring temperature on the microstructure and properties of ZL101 alloy were studied.The single factor experiment method was used to study the effect of the adding amount of various components in the coating on the performance.The results show that the shell with better comprehensive performance could be obtained when the amount of CMC added is 0.5%,the amount of lithium bentonite added is 1.5%,the range of pregelatinized starch added is 1.5%~2.5%,the range of silica sol added is 10%~20%,and the range of sodium hexametaphosphate added is 5%~9%,the range of polypropylene fiber added is 0.7%~1.1%.The orthogonal test method was used to optimize the proportion of expendable pattern shell coating.The optimum formula of shell coating is determined,which is aluminum bauxite 100%,CMC 0.5%,lithium bentonite 1.5%,pregelatinized starch 1.5%,silica sol 20%,sodium hexametaphosphate 9%,polypropylene fiber 1.1%,OP-10 0.2%,n-butanol 0.6%,appropriate amount of water.The performance of the shell is tested,the results show that normal temperature bending strength is 13.76MPa,high temperature bending strength is 23.21MPa,normal temperature surface strength is 0.113g,high temperature surface strength is 0.050g,normal temperature permeability is 24Pa,high temperature permeability is 33Pa.The shell was prepared by using the shell coating,and the ZL101 alloy was used as the research object,the influence of the vibration frequency from 0Hz to 40Hz on the microstructure and properties of the expendable pattern shell casting ZL101 was studied.With the increase of the vibration frequency,the microstructure of the ZL101 alloy gradually develops from the coarse dendritic shape to the finely dispersed equiaxed shape.When the vibration frequency is 40Hz,the grain size of ZL101 alloy is 231.37μm,the tensile strength is 158MPa,the elongation is 3.1%,the Brinell hardness is 57.3HBW,and the filling length and filling area are 29.5cm and 162.25cm~2,respectively.The effect of pouring temperature on the microstructure and properties of the expendable pattern shell casting ZL101 alloy was studied.When the pouring temperature increases from 690°C to 730°C,the structure of ZL101 becomes fine first,then develops to coarse dendrite.The grain size is the smallest at 700°C,which is 282.32μm.The tensile strength of ZL101 alloy is 136MPa,the elongation is 2.9%,and the Brinell hardness is56.1HBW.The filling length and filling area increase as the pouring temperature increases.When the pouring temperature is 730°C,they are 29.0cm and 150.65cm~2,respectively.