New investment casting process

Based on the development and improvement of conventional processes, new process methods have been developed to further improve the quality of castings, increase production efficiency, and expand the application range of investment casting. The sixth issue of "Die Casting" in 1978 reported that the Beijing Oil Pump Nozzle Plant adopted the cage-type combined large module process. The cage-shaped components ensure sufficient rigidity of the module and double as a pouring system, increasing the utilization rate of molten steel by about 10%.

Hebei Institute of Technology, etc., by controlling the solidification time of castings, inner runners, and gate rods, make M parts ≤ M inner ≤ M rods, and make solidification stop between the inner runner and the gate rod, and the liquid in the gate rod The metal is poured back into the hearth to achieve sprueless investment casting. The second issue of "Casting" in 1982 reported that Tsinghua University and others used vacuum suction casting to control the solidification time. When the sprue is solidified and the sprue is not solidified, the vacuum is released and the liquid alloy in the sprue is returned to the furnace. The process has strong filling performance, produces thin-walled castings, and has a high utilization rate of molten steel. The release of suctionchina die casting vacuum is determined according to the thermal conductivity of the mold shell and the solidification time of the suction casting. The third issue of "Casting" in 1984 published Ye Shengyong's article introducing the electrophoretic shell making process.

Dip the conductive coating on the wax module, and add a small amount of chain phosphate as electrolyte in the electrophoresis suspension to make the surface of the refractory material absorb cations. Under the action of the electric field, the refractory material will undergo electrophoresis and accumulate on the surface of the pattern. Electroosmosis occurs, forming a certain strength shell. The electrophoresis shell-making process is few and the production cycle is short. The fourth issue of "Casting" in 1984 reported that Northwestern University of Technology used semi-hydrated gypsum and added quartz powder, quartz glass, and clay as refractory fillers as a gypsum casting process to produce large complex aluminum alloy castings. 621 uses semi-hydrated gypsum and coal rock as the refractory filler to reduce the shrinkage of the gypsum shell and reduce cracking. Titanium and its alloys are important materials for aerospace and petrochemical use. Investment casting began to produce titanium alloy castings in the late 1970s. my country is one of the five largest investment casting titanium alloy producers in the world. The second issue of "Casting" in 1979 was published in the Shanghai Iron and Steel Research Institute using propane cracking under high temperature and vacuum, vapor-phase precipitation of graphite on the surface of corundum (ethyl silicate hydrolyzate shell), and the production process of titanium alloy investment casting. Beihang Materials The research institute uses phenolic resin as a binder and graphite powder (sand) as a refractory material to produce graphite shells, which are roasted in a vacuum resistance furnace to carbonize the resin binder to obtain a shell with good strength and air permeability to produce titanium alloys High-speed pressurized blades.

Shenyang Foundry Research Institute published an article in "Casting" in 1986 on the 3rd, introducing the use of ZTS-1 resin and toner to prepare coatings, p-toluenesulfonic acid as curing agent, and graphite sand and ethanol to prepare coated sand , The production of shells, the process of producing titanium alloy castings by high-temperature baking and vacuum treatment. "Casting" published an article by Li Bangsheng in the 7th issue of 1987, using zirconia ceramic powder, zirconium sol as a binder, and preparing coatings , Prepare the shell, and conduct research on the production of titanium alloy investment casting.