Sand casting is a casting method that uses silica sand as the molding material and is suitable for casting various metal materials. The advantages of sand casting are low cost, reusable molds, and the ability to produce castings with varying thicknesses and complex shapes. The manufacturing process is as follows:
Mold Making → Sand Mold Formation → Mold Assembly and Pouring → Casting Desanding → Post-Casting Processing (removal of sprues, grinding, polishing) →Casting Dimension and Appearance Inspection.
Overview of Sand Casting
1. Making the Sand Mold: A sand mold is created by filling a mold with sand containing a binder, shaped to match the desired part, and then removing the mold, leaving behind a hollow sand mold.
2. Pouring the Metal: Molten metal is poured into the sand mold, filling the cavity, and waiting for the metal to solidify.
3. Finishing the Part: The cast part is removed from the sand mold, excess metal and sand are removed, and then it undergoes grinding and surface treatment to achieve the desired size and quality.
The advantages of sand casting include low cost and suitability for producing large quantities or complex-shaped parts. However, it has lower precision and rough surfaces, requiring additional processing to remove gates, risers, sand cores, followed by cleaning, finishing, and surface treatment. The purpose of these finishing steps is to improve the quality and appearance of the castings.
Casting Alloy Materials
High-Chromium Cast Iron
This is a wear-resistant material with excellent wear resistance, suitable toughness, and corrosion resistance. It is widely used in steel metallurgy, power generation, mining (stone), cement, crushers, sand pumps, incinerators, pulp knives, sandblasting machines, and other industrial equipment components.
This high-alloy cast steel material has excellent heat resistance (~1,200°C), high-temperature strength, resistance to high-temperature oxidation, and corrosion resistance. It is widely used in steel, petrochemicals, cement, heat treatment, automotive (exhaust manifold turbocharger housing), and incinerator equipment components.
This alloy material offers excellent corrosion resistance, temperature resistance (~650°C), and oxidation resistance. It is commonly used in equipment components for food processing, chemicals, pharmaceuticals, and (sea) water treatment.
A high-alloy cast steel that combines high impact resistance, wear resistance, and toughness, and is non-magnetic. Widely used in steel, cement, crushers (mining, automotive), rails and their turntables, excavators (bucket teeth, ring gears), and sandblasting machines, among other equipment components.
Carbon Steel and Low-Alloy Steel
These materials have good castability and machinability and can be tailored to different environments, temperatures, and performance requirements. They can be further strengthened through heat treatment and are widely used in various industries for equipment and their components.
Nickel-Resistant Cast Iron (Ni-resist)
Can be divided into flake graphite and nodular graphite types, with excellent corrosion resistance, heat resistance, and dimensional stability, while retaining the characteristics of cast iron. Widely used in seawater pumps and impellers, turbine housings for power generation, automotive wear rings, and automotive (exhaust manifold turbocharger housings), among other equipment components.
Gray Cast Iron
A cast iron material with lamellar graphite, offering good castability, damping properties, heat conductivity, and machinability. It is commonly used in the production of various types of machinery base and components, automotive (engine cylinder blocks, brake discs), and coupling blocks, among other applications.
Also known as ductile cast iron, it features spherical graphite. It has good ductility, high strength, and machinability and is commonly used in flat-bottomed pans, water pipes and fittings, various manhole covers and bases, check valves, automotive (crankshafts, brake calipers brake master cylinders), hydraulic cylinders and bodies, and precision equipment and components for metal stamping.
Low-Expansion Cast Iron
With an extremely low coefficient of thermal expansion (<4.5x10-6/°C, ~100°C) and non-magnetic properties, it is used in precision equipment and components such as vacuum pump rotors, wafer grinding disks, extension arms for EDM machines, bases for semiconductor exposure equipment, ultra-precision grinding machine tables, and molds for precision carbon fiber/glass fiber molding.
Sand Casting Process
Design and draw the part based on its requirements and specifications.
Prepare sand molds according to the shape and size of the part. Typically, special casting sand (such as silica sand) mixed with binders is used to create the molds. The mold can be a single piece or split into upper and lower molds.
Place the mold material into the mold and use mold compaction tools to shape the internal and external contours of the sand mold. Ensure the compactness and accuracy of the sand mold during molding.
Casting System Design
Design the casting system, including runners, sprues, and gates, based on the shape and casting requirements of the part. The design of the casting system should allow the molten metal to smoothly flow into the mold and fill the entire cavity.
Pour the metal material (such as molten cast iron or aluminum alloy) into the mold's sprue, allowing the molten metal to fill the entire sand mold cavity. Once the metal cools and solidifies, the molded part is obtained.
After waiting for the metal to cool and solidify sufficiently, the mold is disassembled to remove the finished part. Care must be taken during mold disassembly to avoid damaging the part.
The extracted casting may require further post-processing, such as polishing , sand shells, and sand cores, as well as cutting, trimming, grinding, heat treatment, and other operations to achieve the final precision and surface finish.
Inspection and Quality Control
The castings are inspected, including dimensional measurements, material testing, and surface quality checks, to ensure they meet specifications and quality requirements.
Castings that pass inspection can be assembled into final components.