There are many types of foundry sand, which can be categorized as follows based on their mineral composition, source, and properties. Each type of sand has its own unique advantages and applications.
The following are commonly used foundry sands and detailed descriptions:
1. Silica Sand – The Most Common and Basic
• Composition: The primary component is silicon dioxide (SiO₂). The higher the SiO₂ content, the better the refractoriness.
It can serve as a base aggregate in various binder systems, including clay sand (green sand), resin sand, and water glass sand.
2. Chromite Sand – High-End Surface Sand
• Composition: Primarily composed of FeCr₂O₄, rich in Cr₂O₃.
• Advantages:
• Extremely high refractoriness (>1900°C)
• Good thermal stability (low coefficient of expansion)
• Strong slag resistance
• Rapid cooling, which helps refine grain size.
Disadvantages:
Expensive
Environmental Risks: High temperatures in alkaline environments may produce toxic hexavalent chromium, and waste sand must be disposed of as hazardous waste. Applications: Primarily used for surface grinding or coating of steel castings (especially large carbon steel and alloy steel parts) to prevent sand sticking.
3. Zircon Sand – Best Performance
Composition: Primarily composed of zirconium silicate (ZrSiO₄).
Advantages:
Extremely high refractoriness (>2400°C)
Extremely low thermal expansion coefficient (almost the lowest of all sand molds), resulting in extremely high dimensional accuracy in castings.
High thermal conductivity and rapid cooling of castings.
Fine, rounded particles, resulting in extremely smooth casting surfaces.
Disadvantages:
Extremely expensive. Global reserves are limited, and supply is affected by geopolitical factors.
Applications: Precision castings requiring extremely high surface quality and dimensional accuracy, such as topcoats and sanding materials for investment castings; face sand for large, thick-walled steel castings.
4. Olivine Sand – An Environmentally Friendly Alternative
Composition: Primarily composed of (Mg, Fe)₂SiO₄.
Advantages:
Low thermal expansion coefficient, between that of silica sand and chrome sand.
High refractoriness (approximately 1750-1850°C).
Chemically neutral, particularly suitable for high-manganese steel casting (does not react with MnO).
No silica dust hazards, environmentally friendly and non-toxic.
Disadvantages:
High hardness, causing severe wear on equipment.
Susceptible to iron oxide corrosion at high temperatures. • Applications: High-manganese steel components (such as turnouts and track shoes), alloy steel components, and cast iron components. It is an environmentally friendly alternative to silica sand and chrome sand.
Applications: A versatile alternative sand with excellent performance suitable for a variety of processes, including 3D printing sand molding, resin sand, and coated sand. Suitable for casting iron, steel, and non-ferrous alloys.