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Investment Casting Materials and Manufacturing Process
Mold material
The performance of the molding material should not only ensure the convenient production of investment molds with accurate dimensions and high surface finish, good strength and light weight, but also create conditions for the manufacture of mold shells and good castings. Molding materials are generally formulated with waxes, natural resins and plastics (synthetic resins). All mold materials mainly prepared with wax materials are called wax-based mold materials, and their melting point is low, 60~70 ° C; all mold materials mainly prepared with natural resins are called resin-based mold materials, with a slightly higher melting point, about 70 °C. ~120℃.
invest-casting.com Precision Investment Castings China prototype company service include : High Quality Investment Casting Parts Custom,Lost Wax Investment CastingSand Casting,Lost Foam Casting,Gravity Casting,Die Casting,Graphite Casting ,Casting Moldsmanufacturers.
Manufacture of Folding Investments
In the production, the method of pressing the paste mold material into the mold is mostly used to manufacture the investment mold. Before pressing the investment, a thin layer of release agent should be applied to the surface of the embossing so that the investment can be removed from the embossing. When pressing wax-based molding materials, the parting agent can be engine oil, turpentine, etc.; when pressing resin-based molding materials, a mixture of sesame oil and alcohol or silicone oil is often used as a parting agent. The thinner the parting agent layer, the better, so that the investment mold can better replicate the surface of the embossing and improve the surface finish of the investment mold. There are three methods of pressing investment, plunger pressurization method, air pressure method and piston pressurization method.
invest-casting.com Metal Casting Industries include : Automotive Casting ,Pump Casting ,Plumbing Sanitary Casting ,Lock Casting ,Medical Casting,Machinery Casting ,Marine Casting ,Food Machine Casting,LightingCasting.
Assembly of Folding Investments
The assembly of the investment mold is to combine the investment mold that forms the casting and the investment mold that forms the gating riser system. There are two main methods:
1. Welding method Use a thin soldering iron to melt the joints of the investment to weld the investment together. This method is more common.
2. Mechanical assembly method In the mass production of small investment castings, the mechanical assembly method has been widely adopted abroad to combine modules. The use of this module can greatly improve the combination and efficiency of the modules, and the working conditions have also been improved.
The main processes and processes in the shell making process are:
1) Degreasing and degreasing of modules
In order to improve the ability of the coating to wet the surface of the module, the oil stain on the surface of the module needs to be removed when the wax-based moulding material is used to make the investment mould.
2) Apply paint and sand on the module
Before painting and hanging the paint, the paint should be stirred evenly to reduce the precipitation of refractory materials in the paint bucket as much as possible, and the viscosity or specific gravity of the paint should be adjusted so that the paint can fill and wet the investment mold well. The module is immersed in the paint and shakes up and down, so that the paint can well wet the investment mold and evenly cover the surface of the module. After the paint is applied, sanding can be carried out.
3) Shell drying and hardening
After each layer of shell is coated, it must be dried and hardened, so that the binder in the coating changes from sol to jelly and gel, and connects the refractory materials together.
4) Loss of investment from the shell
After the shell is completely hardened, the module needs to be melted from the shell. Because the module is usually made of wax-based mold material, this process is also called dewaxing. According to the different heating methods, there are many dewaxing methods, the hot water method and the same pressure steam method are used more.
5) Roasted shell
If molding (sand filling) is required for pouring, before firing, the demolded shell should be buried in the sand in the box, and then fired in a furnace. If the high temperature strength of the shell is high and no casting is required, the demolded shell can be directly sent to the furnace for roasting. During roasting, the furnace temperature is gradually increased, and the shell is heated to 800-1000 ° C and kept for a period of time before pouring.
invest-casting.com Metal Casting Material include : Stainless Steel Casting，Aluminum Casting，Iron Casting，Brass Casting，Titanium Casting，Steel Casting。
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Method of pouring and cleaning of castings
Commonly used pouring methods in investment casting are:
1) There are the following types of thermal gravity casting methods.
This is the most widely used form of casting, that is, after the shell is removed from the roaster, it is cast at high temperature. At this time, the metal cools slowly in the mold shell, and the mold can be filled with high fluidity, so the casting can well replicate the shape of the cavity and improve the accuracy of the casting. However, the slow cooling of the casting in the hot mold will cause coarse grains, which reduces the mechanical properties of the casting. When casting carbon steel castings, the surface of the casting that cools more slowly is also prone to oxidation and decarburization, which reduces the surface hardness, finish and dimensional accuracy of the casting.invest-casting.com Precision Investment Castings China prototype company service include : High Quality Investment Casting Parts Custom,Lost Wax Investment CastingSand Casting,Lost Foam Casting,Gravity Casting,Die Casting,Graphite Casting ,Casting Moldsmanufacturers.
2) Vacuum suction casting
Put the mold shell in the vacuum casting box, and suck the gas in the mold cavity through the tiny pores in the mold shell, so that the liquid metal can better fill the mold cavity, copy the shape of the mold cavity, improve the casting accuracy, prevent pores, pouring Insufficient defects. This law has been applied abroad.
3) Crystallization under pressure
Put the shell in the pressure tank for pouring. After the end, the pressure tank is closed immediately, and high-pressure air or inert gas is introduced into the tank to solidify the casting under pressure to increase the density of the casting. The maximum pressure abroad has reached 150atm.
4) Directional crystallization (directional solidification)
Some investment castings such as turbine blades, magnetic steel, etc., if their crystalline structure is columnar crystals arranged in a certain direction, their working performance can be greatly improved, so the directional crystallization technology of investment casting is rapidly developed.
Casting cleaning
The main contents of investment casting cleaning are as follows:
(1) Remove the mold shell from the casting;
(2) Remove the casting from the pouring system;
(3) Remove the shell refractory adhering to the casting;
(4) Cleaning after heat treatment of castings, such as descaling, edge and cutting gate residues, etc.invest-casting.com Metal Casting Material include : Stainless Steel Casting，Aluminum Casting，Iron Casting，Brass Casting，Titanium Casting，Steel Casting。
The task of investment casting process design is
(1) Analyze the manufacturability of the casting structure;
(2) Select a reasonable process plan, determine the relevant casting process parameters, and draw the casting diagram on the basis of the above;
(3) Design the pouring system and determine the module structure.
It should be noted here that when considering the above three aspects, the main basis is still the basic principles of the general casting process, especially when determining the process plan and process parameters (such as casting fillet, machining allowance, process ribs, etc.) , except that the specific data is slightly different due to the technological characteristics of investment casting, the design principle is exactly the same as that of sand casting.
The task and importance of investment casting process design
Investment casting is a casting process with less or no cutting. It was also called lost wax casting in the past. Because the castings produced by the investment casting process are better than other casting methods in terms of dimensional accuracy and surface quality In addition, the investment casting method can complete the production of some complex and difficult to process castings, so it is deeply loved by enterprises.
Regarding the investment casting process, the investment casting process design is one of the most important links in the entire investment casting process. This link has a large technical difficulty factor and plays a very important role in the entire investment casting process. This link is mostly due to some professional and technical people.
Like other casting process designs, the design tasks of the investment casting process are: a. According to specific requirements, analyze the craftsmanship of the casting structure; b. Plan a reasonable process plan, determine the relevant casting process parameters, and draw the casting diagram on this basis. ;c. Design the pouring system and determine the module structure. Except for the specific data due to the slightly different process characteristics of investment casting, the design principle is exactly the same as that of sand casting.
Since the investment casting process design link is of great significance to the entire casting process, and this link has very high requirements on the quality of the designers themselves, enterprises should pay considerable attention to this link.
invest-casting.com Metal Casting Industries include : Automotive Casting ,Pump Casting ,Plumbing Sanitary Casting ,Lock Casting ,Medical Casting,Machinery Casting ,Marine Casting ,Food Machine Casting,LightingCasting.
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