Pressure casting (abbreviated as die casting) is a metal casting process characterized by filling the mold cavity with molten alloy under high pressure and high speed conditions, and cooling and molding under high pressure, with process features such as high productivity, short production process, higher casting finish and strength, less machining allowance, and saving metal materials.
Die casting is used in a wide range of applications, involving a considerable number of product areas and industrial categories, the main role is to help metal die casting products can be removed from the mold, and to maintain the integrity of the product and post-processing. In the die-casting process, the release agent plays three roles.
1, Before the metal is hydraulically injected, it is evenly distributed on the surface of the cavity, thus forming an isolation film between the mold and the metal liquid, which protects the cavity from direct scouring by the molten metal liquid.
2, In the process of die-casting, it helps the metal liquid to enter the cavity and make the filling intact.
3, After the casting is formed, it can make it easy to take off the mold.
Mechanism of action
Mold release agent and mold surface can produce non-polar or polar physical adsorption film, chemical adsorption film and chemical reaction film. When there is no polar molecule in the release agent, the release agent can only produce non-polar physical adsorption film on the surface of the mold; conversely, it produces polar physical adsorption film.
When the atoms in the release agent component and the atoms on the mold surface can use common electrons, a chemisorption film will be produced on the mold surface. Its strength is again higher than that of the polar physisorption film. At a certain contact pressure and temperature, the polar pressure agent in the release agent may also react chemically with the mold surface to produce a chemisorbed film. Its strength is again greater than that of chemisorption film.
Generally speaking, the higher the strength of the adsorption film of the mold release agent, the better the effect of preventing sticking to the mold. Therefore, according to different die castings, it is very important to choose the appropriate release agent to form a high strength adsorption film.
Die casting release agent classification and composition
Die casting release agent according to its performance characteristics can be divided into oil-based, powder-based and water-based release agent. From the initial development of oil-based release agent to water-based release agent, and then to the powder release agent has gone through a fairly long process. The basic components of oil-based mold release agents are oil and graphite, which have good lubricity. But the use of fumes, pollution of the environment, health hazards of workers, but also the fire aspect of the hidden danger, now has been gradually eliminated. Powder-based mold release agent is mainly wax as raw material, attached to the pressure chamber and the surface of the cavity, due to the temperature of the mold and make it dissolve, producing lubrication. The basic components are zircon, mica, talcum powder and graphite, microcrystalline wax, etc.
Water-based mold release agent currently occupies an important position in the die casting release agent market, and its composition should at least be composed of base material, emulsifier and water. The base material is oil, grease, wax, silicone and polymer, which are considered as the active ingredients and ultimately play the role of lubrication and mold release. Water is the carrier, which can be diluted with water by a factor of ten to a hundred, generally accounting for more than 95 %. The emulsifier will be the active ingredients in a very fine particle uniformly dispersed in the water phase, forming a stable emulsion. In addition, there are extreme pressure additives, mold inhibitors, rust inhibitors and other components.
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