There are multiple types of sand used in the sand-casting process. The sand chosen for your project can impact the performance and price of your casting. Here is a comparison of the sands typically used in sand-casting manufacturing.
TRADITIONAL SANDS
• Silica Sand, which consists of silicon dioxide, is the most common type of sand used in sand casting. It has been the go-to molding material for centuries. It is plentiful, inexpensive, and easy to use across multiple binder systems. Silica sand produces quality castings due in part to its good thermal properties.
The major downside to using silica sand is that exposure to silica in its crystalline form can cause health problems for individuals who work closely with it. As such, foundries are becoming more restrictive in their use.
Located in Milwaukee, WI, Badger Alloys is fortunate to have ready access to the best foundry sand in the world; extensive sandstone formations are located just hours away in east-central Wisconsin.
• Zircon Sand, or zirconium silicate, is an alternative sand with several key property differences from pure silica. It is rarely used to make entire molds or cores due to its cost. Instead, it is commonly used as a facing material to provide additional heat removal capacity when compared to silica or for castings where silica sand can cause adverse surface reactions. Because it offers superior refractoriness and minimal thermal expansion, Badger Alloys typically uses zircon sand for precision casting applications.
The major sources of zircon for foundry applications are Florida and South Africa, which contributes to the higher cost of the material.
• Chromite Sand, or chromium iron oxide, is another traditional industry sand. It is known for excellent thermal conductivity and high resistance to thermal shock, making it ideal for high-temperature alloys.
Because this sand’s properties are very similar to zircon’s, Badger Alloys doesn’t currently use chromite sand.
• Olivine, also known as magnesium iron silicate, is the most expensive sand in common foundry use. It has exceptional thermal characteristics and, for green sand molding, it requires less moisture content to maintain the shape of the molds. Aside from the cost, the chemistry of olivine makes it a challenge to use at most foundries: olivine’s magnesium content makes it basic rather than acidic, while the other major molding sands are acidic or neutral in nature. This can cause issues with chemical binder systems and can lead to unwanted mold-metal reactions. The high cost and the chemical issues with olivine sand restrict its use mostly to foundries that pour aluminum alloys or manganese steels.
NEW INNOVATIONS IN SAND
Advancements in material science have introduced innovative sand solutions that improve performance and sustainability.
• Ceramic Sands are engineered sands that provide excellent dimensional stability, high durability, and reduced dust, making them ideal for precision castings and high-temperature applications. Ceramic sand has become more popular with foundries in recent years because they are manufactured products that are largely based on aluminum oxide and are customarily sold as silica-free. Ceramic sands last longer through multiple rounds of thermal or mechanical reclamation as well. They can produce castings of exceptional quality. Badger Alloys uses ceramic sands for critical applications.
The key downside of ceramic sand blends is that they are often significantly more expensive than silica sands, leaving foundries to balance the higher initial cost against improved surface quality, improved dimensional stability, superior reusability and – most importantly – employee safety.
• Resin-Coated Sands are pre-coated with a binder and reduce the steps in core-making while offering excellent strength and surface finish.
• Green Sand Alternatives, modern formulations that use less clay and water, improve surface finish and reduce environmental impact.
• Hybrid Sands combine traditional silica or chromite with advanced binders. These sands offer the benefits of reduced defects, improved flowability, and higher reusability.
In short, silica sand is inexpensive and makes simple castings very well. Zircon is more expensive and helps foundries better make more challenging castings. Ceramic sand is high cost but makes superior castings in any size or complexity; it will likely become the standard sand of choice in the future due to safety concerns and environmental regulations. Badger Alloys works with all three of these sands to offer customers flexibility in performance and cost.
If you have questions about the sands used in our sand-casting process, please reach out to our sales engineer, Nick Hanson: nickh@badgeralloys.com or 414.258.8200.