KEVOS® MAKEOS · Materials
ASTM Grain Size Number
What ASTM grain size number does this count or intercept measurement give?
ASTM E112 grain size number G from grains per square inch at 100×, grains per mm² at 1×, or the mean lineal intercept length, with the equivalent values.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Measurement | choice | Which measurement you made. |
| Measured value | The measured number: grains per in² at 100×, grains per mm², or mean intercept length in micrometres. |
Method and formulas
- From a 100× count: G = 1 + log₂(n).
- From grains per mm² at 1×: G = 3.321928 log₁₀(N_A) − 2.954.
- From mean intercept ℓ (mm): G = −6.643856 log₁₀(ℓ) − 3.288.
- Example: 64 grains per in² at 100× is ASTM G 7.
Limitations
- The planimetric and intercept relations agree only approximately; report the method used.
- Assumes equiaxed grains; elongated or duplex structures need the standard’s special procedures.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Report grain size from a micrograph count
- Convert between grain size measures
- Check a material certificate requirement
Who it is for
- Metallurgists
- Quality inspectors
- Materials engineers
What you get
- ASTM grain size number G
- Grains per mm² and per in² at 100×
- Mean lineal intercept
Interpreting the result
- A larger G means finer grains.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 369–380. Topic reference; no source tables or recommended settings are reproduced.
- ASTM E112 Standard Test Methods for Determining Average Grain Size
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