Manufacturing shell material and process

Manufacturing shell material can be divided into two types, one is used to directly form the model of the shell, such as refractory material, binder, etc; Another kind is to obtain high quality shell, simplify the operation, the improvement of technology with the material, such as fluxing agent, curing agent, surfactant, etc. 1) Refractory materials currently used in investment casting are mainly quartz and corundum refractory, and aluminum silicate refractory materials, such as refractory clay, aluminium vanadium and soil, the chamotte, and so on. Sometimes also with zircon, magnesia ( MgO） And so on. 2) Adhesive used in investment casting is the most common form of binder colloidal silicate solution ( Silica sol) Such as hydrolyzed ethyl silicate, sodium silicate and silica sol, etc. The substance of them, mainly silicate ( H2SiO3） And solvent, sometimes have stabilizing agent, such as NaOH in silica sol. Hydrolyzed ethyl silicate ethyl silicate is obtained after hydrolysis of silica sol casting in the earliest, the most common form of binder; Sodium silicate shell mold easy out of shape, craze, with its pouring casting dimension accuracy and surface finish is poor. But in our country, when production accuracy requirement is carbon steel castings and low melting point of nonferrous alloy casting, water glass is still widely used in production. Silica sol stability is good, can be stored for a long time, does not need special curing agent, when making a shell but silicon sol moudle of wetting is a bit poor, shell hardening process is a dry process, takes longer. The main working procedure in process of shell making and process as follows: 1) Module oil and removal moudle wax base model material is used in the system, in order to improve the coating wetting ability on the surface of the module, should be to get rid of oil pollution on the surface of the module. 2) Hang on module before coating and coating of sanding smearing, should mix coating evenly, minimize paint barrels of refractory precipitation, adjust good paint viscosity or density, so that the coating can pack well and wetting moudle, hanging coating, soak your module in the paint, or shake, can make the paint is very good wetting moudle, evenly covering the surface of the group. Paint coating, can be noisy. 3) Shell per Shanghai juji good drying and hardening layer shell, will be to drying and hardening it, make the paint of the adhesive from the sol to gel, gel, ties the refractory material. 4) Since the loss of molten model shell in the shell completely hardened, melt to module from the shell, because of the module commonly used material made from wax base model, so this process is called dewaxing. According to the heating method is different, there are a lot of, dewaxing method, use morer is hot water method and with the pressure steam method. 5) Roasting shell for modelling ( Sand filling) Before pouring in the roasting will release after the shell is buried in the sand, reload furnace roasting. Such as shell of high temperature strength, do not need to model casting, can send the shell directly after demoulding boiling roasting. Gradually increase when roasting furnace temperature, will be heated to 8000 - type shell 10000 c, thermal insulation for a period of time, can be cast.