Metal casting is a common and important casting method that uses metal molds and molten metal to produce metal components with complex shapes and high precision requirements.
Mold Preparation
The first step in metal casting is mold preparation. Metal molds are typically made of casting alloys and possess high temperature resistance and wear resistance. Mold preparation involves detailed design, machining, and precision inspection using CNC machines. The process also includes mold dewaxing, trimming, and post-processing of machined surfaces.
Dewaxing and Drying
Dewaxing is a crucial step in metal casting. Liquid wax is injected into the mold and allowed to cool and solidify for a certain period, forming wax patterns. Once the mold is removed, hollow shapes are obtained, representing the desired external shape of the final product. The wax patterns are then subject to drying to evaporate any residual moisture and ensure dryness.
Slurry Coating
A special coating called slurry is applied to the surface of the wax pattern. The primary purpose of the slurry coating is to create a barrier layer that prevents direct contact between the metal melt and the wax pattern, reducing adhesion between the two.
Shell Molding
After the slurry coating, the wax patterns are placed in a sand bed and surrounded by sand to create a shell. During the shell molding process, close attention is paid to the particle size, humidity, and compaction of the sand to ensure accuracy and precision of the final product.
Metal Melting
In metal casting, an appropriate metal alloy is selected and melted into a liquid state. This is typically achieved by placing the metal feedstock into a furnace for high-temperature melting. During the melting process, strict control of furnace temperature and metal alloy composition is necessary to ensure the quality and purity of the molten metal.
Pouring
Once the metal alloy has melted into a liquid state, it is poured into the shell mold. Pouring involves controlling the speed and pressure to ensure complete filling of every detail in the mold, avoiding the formation of voids or defects.
Solidification and Cooling
After pouring, the molten metal gradually cools and solidifies. The solidification process involves the formation of grain structures inside the metal, which ultimately affects the mechanical properties and microstructure of the product. Solidification speed and cooling control are critical factors determining the final product quality. During cooling, attention is also given to metal shrinkage and deformation to ensure dimensional accuracy of the castings.
Shell Removal and Wax Burnout
Once fully solidified and cooled, the molds are removed from the sand bed, and the shells are stripped. At this stage, the wax patterns have been completely transformed into solid metal castings. The next step is to burn out the remaining wax from the castings. Castings are placed in a high-temperature furnace and heated to completely eliminate the wax, leaving only the metal castings themselves.
Deflashing and Surface Treatment
After obtaining the metal castings, deflashing and surface treatment are conducted. This typically involves operations such as cutting, grinding, polishing, and cleaning to ensure smooth surfaces and accurate dimensions. Depending on the product requirements, additional surface treatments like heat treatment, coating, or plating may be performed to enhance the product’s performance and corrosion resistance.
Metal casting is a complex process that is commonly used to manufacture metal components with complex shapes and high precision requirements. The process involves mold preparation, dewaxing and drying, slurry coating, shell molding, metal melting, pouring, solidification and cooling, shell removal and wax burnout, as well as deflashing and surface treatment. By carefully controlling each step, metal casting enables the production of high-quality and precision metal components, providing essential support and development for various industries’ manufacturing sectors.
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