Silica Sand AFS
Calculator
Calculate the AFS grain fineness number from sieve analysis results. Learn the classification and recommended use of your foundry sand.
AFS Grain Fineness Number
Enter Retained Percentages
Enter the percentage of sand retained on each sieve. Total should be 100%.
AFS Formula
Classification
- AFS < 40 → Coarse Sand
- AFS 40-60 → Medium Sand
- AFS > 60 → Fine Sand
Note
As the AFS number increases, sand becomes finer. Finer sands give better surface finish but reduce permeability.
Silica Sand Supply
High quality silica sand supply for the foundry sector. Stock available in various grain sizes, AFS 40-70.
Get a QuoteWhat is the AFS Grain Fineness Number (GFN)?
The AFS Grain Fineness Number (GFN) expresses the average grain size of foundry sand as a single number. It is computed from a sieve analysis: the percent retained on each sieve is multiplied by that sieve's multiplier, and the ratio of the sums is taken — GFN = Σ(retained % × multiplier) ÷ Σ(retained %). The higher the number, the finer the sand. Typical foundry sands are AFS 40–90: fine sand (high AFS) gives a smooth surface but low gas permeability.
AFS/GFN calculation and effect on casting
The AFS GFN is the key parameter standardizing sand quality in a foundry. The sand is passed through a standard sieve series (AFS/ASTM); the material retained on each sieve is weighed and its percentage found. Each sieve has a multiplier (fine sieves have high multipliers). Calculation: • For each sieve: percent retained × sieve multiplier = product • GFN = Σ(products) ÷ Σ(percent retained) The result is the theoretical sieve number the sand would match if all grains were the same size. Meaning: high AFS = fine sand → smoother cast surface but lower gas permeability (gas-defect risk). Low AFS = coarse sand → high permeability but rougher surface. AFS is chosen based on the casting's wall thickness and surface requirement. Aktif Çelik supplies foundry and industrial silica sand at controlled AFS values.
Standard Sieve Series for AFS-GFN Calculation
| Mesh No. | Opening (mm) | Multiplier |
|---|---|---|
| 6 | 3.35 | 3 |
| 12 | 1.70 | 5 |
| 20 | 0.85 | 10 |
| 30 | 0.60 | 20 |
| 40 | 0.425 | 30 |
| 50 | 0.30 | 40 |
| 70 | 0.212 | 50 |
| 100 | 0.15 | 70 |
| 140 | 0.106 | 100 |
| 200 | 0.075 | 140 |
| 270 | 0.053 | 200 |
| Pan | — | 300 |
The "Pan" row refers to the bottom collecting pan with no mesh. The dash "—" means no opening.
Frequently Asked Questions
How is AFS grain fineness calculated?+
From a sieve analysis: GFN = Σ(percent retained on each sieve × that sieve's multiplier) ÷ Σ(percent retained). Fine sieves have higher multipliers; the result gives the sand's average grain fineness as one number.
Is high AFS or low AFS better?+
It depends. High AFS (fine sand) gives a smoother surface but low gas permeability (gas-defect risk). Low AFS (coarse sand) is more permeable but rougher. Thin-wall / critical-surface parts favour high AFS, thick parts lower AFS.
What is the typical AFS range for foundry sand?+
Most foundry applications are AFS 40–90. Steel casting is usually 50–70, with higher values where a fine surface is needed.
What is the relationship between AFS and gas permeability?+
It is inverse: as AFS rises (sand gets finer), the voids between grains shrink and gas permeability drops. So a balance is struck between surface quality and gas venting.
What is the ideal AFS-GFN range for iron casting?+
For gray iron, 40–55 GFN is typical (finer sand gives better surface finish but reduces permeability); ductile iron uses 50–60 GFN; aluminum casting may go as fine as 60–80 GFN for surface quality.
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