Study On The Investmend Casting Technology Of K424 Complex Thinwalled Parts

K424 complex thin wall plate is an important part of the tail nozzle of a new type aero engine.Its outline size is large,the wall is thin,the structure is complex,the dimension precision is high,the precision casting process is difficult,and the shrinkage defect is easily produced in the casting process,and the product qualification rate is low.In this paper,the effect of pouring system and pouring parameters on the shrinkage of the complex thin wall plate of K424 nickel base superalloy is studied.Through the study of the selection of the parameters of the wax mould manufacturing,the study of the shell process and the experiment of the melting process parameters,the optimum casting process of the plate is obtained.It has important application value and can provide technical support for the future development of large wall and thin nickel base superalloy precision castings.The main results of the paper are as follows:The research results of the pouring system show that the K424 complex thin-walled plate is prone to produce shrinkage defects at the intersection of the vertical and horizontal bars near the top of the gate cup,which increases the size of the runner and the inner gate.It can make the hot joints on both sides of the bar continuous to the metal liquid supplement and realize the casting casting system.In order to solidify in sequence,the tendencies of Pinus Pinus decreased significantly.Under the same shell preheating temperature,refining temperature and pouring time,decreasing casting temperature is beneficial to reduce shrinkage defects.The optimized wax mold preparation process is: the wax temperature(68~73),the pressure of the wax(1.5 to 2)MPa and the pressure holding time(25~35)s;by placing the "spiny" cold wax core which can be positioned in the thick lug,the shrinkage of the wax mould pressing can be eliminated.The composite shell was made of silica sol binder and coating agent with alternate coating of silicate ethyl ester.A silica sol coating with a layer of viscosity(25~30)s was pre coated with a layer of viscosity(25~30).The viscosity of the coating was(silica sol + corundum powder),the viscosity was(35~40),the sand material used corundum sand;the reinforcement coating was used alternately(the ethyl silicate hydrolysate + bauxite powder)and the(silica sol + bauxite powder)coating.10~20)s,sanding material using coal gangue sand,cooperating with 7 layers of coating,the shell made of high temperature performance and high dimensional accuracy.The optimized casting mold casting process: the shell preheating temperature(1100 ± 5)?,refining temperature(1590 ± 5)?,pouring temperature(1480 ±5)?,casting time(2-3)s.The qualified rate of castings with optimized casting process can reach 90%.