Low pressure casting refers to a casting method in which a mold is generally placed above a sealed crucible, and compressed air is introduced into the crucible to create low pressure (0.06-0.15 MPa) on the surface of the molten metal, causing the metal liquid to rise from the riser and fill the mold, and controlling solidification. This casting method has good shrinkage compensation, dense casting structure, and is easy to cast large thin-walled complex castings without the need f
or risers, with a metal recovery rate of 95%. No pollution, easy to achieve automation. But the equipment cost is high and the production efficiency is low. Generally used for casting non-ferrous alloys.
Principle
Low pressure casting is a casting method in which liquid alloy is pressed into the mold cavity from bottom to top under pressure, and solidifies under pressure to obtain castings. The principle of low-pressure casting is shown in Figure 1 "Principle of Low Pressure Casting". Dry compressed air or inert gas is introduced into a sealed crucible, and with the help of the pressure acting on the metal liquid surface, the metal liquid is smoothly filled into the mold through the sprue from bottom to top along the riser. The filling pressure is generally 20-60kPa. After the casting is completely solidified, release the gas pressure on the liquid surface, so that the metal liquid that has not solidified in the riser and runner flows into the crucible by its own weight, and then open the mold to remove the casting.
Basic Processes:
1. Mold preparation
Firstly, it is necessary to create a mold that can be used for low-pressure casting. This mold must be able to withstand the high temperature and pressure of liquid metal, and have sufficient strength to ensure the quality of the parts. Usually, molds are made of refractory materials and coated with a special layer of material inside to prevent metal adhesion
2. Preparation of heating furnace
In order to heat the metal to a sufficiently high temperature so that it can flow, a heating furnace needs to be prepared. Heating furnaces typically use natural gas or electricity to provide heating energy. When heating metal in a furnace, it is necessary to ensure that it reaches a sufficient temperature to turn it into a liquid state.
3. Metal melting
Heat the metal in a furnace until it completely melts. During this process, it is necessary to constantly stir the metal to ensure that it is uniformly heated and melted.
4. Mold pretreatment
Before pouring metal into the mold, it is necessary to pre treat the mold. This process includes cleaning the mold and applying a layer of special material to prevent metal adhesion. Then place the mold into the low-pressure casting machine to prepare for metal injection.
5. Metal injection
When the metal is completely melted and the mold is ready, it is time to start injecting the metal. In low-pressure casting, a filling head is used to inject metal into the mold. The filling head is usually composed of some holes, through which the flow rate and speed can be controlled.
6. Component cooling
When the metal completely fills the mold and has cooled down, the casting can be removed. Usually, it is necessary to wait for a period of time to ensure that the casting has completely cooled and solidified. Then the casting can be removed from the mold.
7. Post processing of parts
Finally, post-processing is required for the castings. This process includes removing any excess materials and surface treatment. Usually, machines or manual tools are required to complete these tasks.
Application
Low pressure casting is the earliest anti gravity casting technology, which began to be used in industrial production in the 1940s. Nowadays, low-pressure casting is mainly used for the production of aluminum alloy and magnesium alloy parts, such as automobile wheels in the automotive industry, cylinder blocks, cylinder heads, pistons, missile casings, impellers, wind deflectors and other castings with complex shapes and high quality requirements for internal combustion engines. When low-pressure casting is used to produce cast steel, such as cast steel wheels, special refractory materials need to be used for the lifting pipe. Low pressure casting can also be applied to small copper alloy castings, such as pipe fittings, bathroom faucets, etc.
Automotive manufacturing industry: Automotive manufacturing is a major application area of low-pressure casting. By usingUsing low-pressure casting technology, automobile manufacturers can produce a range of complex parts, including engine components and transmission parts.
Aerospace industry: In the aerospace industry, it is necessary to produce a series of complex parts, including turbine blades and aircraft engine components. Low pressure casting technology can help manufacturers produce these high-quality parts.
3. Industrial machinery manufacturing industry: Industrial machinery manufacturing is another major application area of low-pressure casting domain. By using low-pressure casting technology, a range of high-quality industrial machinery components can be produced, including gears, reducers, and transmission systems.
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