What is Chromite Sand for Foundry ?
Chromite sand for foundry (chromite ore sand)is a high-performance special refractory sand for steel& metal foundry, made from natural chromite (FeCr₂O₄, iron chromium oxide) via crushing, grinding, washing, magnetic separation and screening to controlled grain sizes and purity.
Basic Properties
Main composition: Cr₂O₃ ≥45%(better ≥46%); low silica (SiO₂ <1%).
Density: 4.0–4.8 g/cm³ (much higher than silica sand, ~2.65 g/cm³).
Refractoriness: ≥1900 °C, stable at extreme casting temperatures.
Hardness: Mohs 5.5–6.5, good abrasion resistance.
Thermal conductivity: 2–3× that of silica sand; low thermal expansion.
Chemistry: Near-neutral, resistant to alkaline slags; inert to iron oxides.
Key Functions & Benefits
1. High refractoriness & anti-penetration Withstands >1800 °C; resists molten metal penetration and burn-in, eliminating sand sticking on steel/iron surfaces.
2. Chilling effect & solidification control High thermal conductivity accelerates cooling, promotes directional solidification, reduces shrinkage/porosity, and improves casting density.
3. Low expansion & dimensional stability Minimal thermal expansion prevents mold cracking, scabbing, or deformation; ensures tight dimensional tolerance for precision parts.
4. Chemical inertness Does not react with Mn steel, Cr steel, or high‑Ni alloys; ideal for high‑alloy, stainless, and heavy‑section castings.
5. Safer & cleaner Low free silica reduces silicosis risk; less dust and better reusability than silica sand.
Main Applications
Facing sand (15–50 mm thick): On mold/core surfaces contacting molten metal (steel, stainless, Mn steel).
Core sand: For heavy or hot‑spot cores to prevent burn‑in and improve cooling.
Separator layer: Between silica sand mold and core to avoid fusion at high temperature.
Refractory filler: In coatings, ramming mixes, and as a chill substitute.
Processes: Green sand, resin‑bonded sand, lost foam, V‑process, and investment casting.
Typical Fineness (AFS)
AFS 25-30, AFS 30-35,AFS35–40, AFS40-45: For heavy steel castings, general facing sand.
AFS45-50,AFS 45-55: For precision parts and thin‑wall castings.
Chromite sand for foundry is the premium choice for high‑quality steel and alloy castings where surface finish, dimensional accuracy, and defect-free surfaces are critical. Though costlier than silica sand, it reduces cleaning, scrap, and rework lowering total production cost.
