What Kind of Sand for Casting?

For casting metals, specific types of sand are used, primarily green sand, water glass or sodium silicate, and resin sand.

Sand casting, a technique dating back over 6,000 years, remains a popular method, especially for creating non-ferrous alloy casts. While the process has evolved, the core material—sand—remains central. However, not just any sand will do. Specialized sands with specific properties are required to create the mold that molten metal is poured into.

Based on the reference provided, there are three main types of sand utilized in this historical yet modern process:

Types of Sand Used in Metal Casting

The choice of sand depends on factors such as the type of metal being cast, the complexity of the shape, the desired surface finish, and production volume. Here are the principal types mentioned:

• Green Sand: This is the most common and economical type. It's a mixture of silica sand, clay (usually bentonite), water, and sometimes other additives. "Green" refers to its moist state when the molten metal is poured. It's highly recyclable.
• Water Glass or Sodium Silicate Sand: This type uses sodium silicate as a binder. The mold hardens when carbon dioxide gas is passed through it, reacting with the sodium silicate. This method, often called the CO₂ process, creates a stronger mold than green sand.
• Resin Sand: In this process, synthetic resins are used as binders. The sand can be mixed with a furan or phenolic resin and a catalyst. When heated or left to cure, the resin hardens, creating a very strong and dimensionally stable mold. This is often used for more complex shapes or when a better surface finish is required.

These specific sand types allow foundries to create molds with the necessary strength, permeability, collapsibility (ability to break down after casting), and thermal stability to withstand the high temperatures of molten metals.