In sand casting, the rate at which metal cools determines its internal soundness. Uneven cooling creates shrinkage porosity, hot spots, and weak zones. To control this, foundries use chills—metal inserts placed in the mold to accelerate cooling in specific areas. At Juize Machinery, we strategically apply chills to produce castings that are dense, sound, and free from internal voids. As a Gold Verified Supplier on Alibaba, our castings benefit from targeted thermal management.
What Are Chills?
Chills are blocks of metal (typically cast iron, steel, or copper) placed in the mold cavity or embedded in the sand. They absorb heat rapidly from the molten metal, creating localized rapid solidification. Common types include:
Internal Chills: Placed within the mold cavity, becoming part of the casting
External Chills: Placed against the mold surface, removable after casting
Why Use Chills?
Without chills, thick sections of a casting cool slowly while thin sections cool quickly. This differential creates:
Shrinkage Porosity: Slow-cooling areas lack feeding metal as they contract
Hot Tears: Stresses from uneven contraction cause cracks
Coarse Grain Structure: Slow cooling produces large, weak grains
Chills solve these problems by:
Equalizing Cooling Rates: Thick sections chill faster, matching thinner neighbors
Promoting Directional Solidification: Metal freezes progressively from chilled areas toward risers
Refining Grain Structure: Rapid cooling creates fine, strong grains
How We Apply Chills
Our foundry engineers determine chill placement based on casting geometry:
At heavy sections that would otherwise stay hot too long
Near bosses and pads that connect thick to thin walls
Around cored holes to prevent localized shrinkage
At thermal centers where heat concentrates
Design Considerations
Chills work best when integrated into casting design:
Accessible locations for chill placement during molding
Sufficient chill mass for required cooling effect
Compatibility with casting alloy (chill material affects cooling rate)
Verification
We verify chill effectiveness through:
Sectioning sample castings to inspect internal soundness
Radiographic inspection (X-ray) confirming porosity elimination
Mechanical testing validating property improvements
