BIZOMAT MAKEOS · Materials
Brinell Hardness from Indentation
What Brinell hardness does this indentation give, and is the test valid?
Brinell hardness number from test force, ball diameter and mean indentation diameter, with validity checks and an approximate tensile strength for steels.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Test force | kgf | Test force in kilograms-force (3000 kgf with a 10 mm ball for steels; 1 kgf = 9.80665 N). |
| Ball diameter | mm | Diameter of the carbide ball. |
| Mean indentation diameter | mm | Mean of two perpendicular indentation diameters measured with the microscope. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Test force
- What it is
- The test force applied to the ball by the hardness tester, as selected on the machine.
- Units and format
- Enter a number in kgf: kgf. The form accepts 0.000001 kgf to 100000 kgf. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3000 kgf as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- For the same indentation, hardness rises in direct proportion.
- Get it right
- Enter kilograms-force as set on the tester, not newtons; one kgf is 9.80665 N.
What this means: Ball diameter
- What it is
- The diameter of the tungsten carbide ball used as the indenter.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the ball actually fitted; the force to ball size combination must suit the material.
What this means: Mean indentation diameter
- What it is
- The average diameter of the round impression left in the surface, from two readings at right angles taken with the measuring microscope.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger impression means a softer material and a lower hardness number.
- Get it right
- Average two perpendicular readings; one reading on an oval impression gives the wrong hardness.
Method and formulas
- HBW = 2F ÷ (πD(D − √(D² − d²))), F in kgf (equivalently 0.102 × 2F_N ÷ …).
- Valid indentation: 0.24D ≤ d ≤ 0.6D (ISO 6506-1).
- Approximate tensile strength of carbon and low-alloy steels ≈ 3.45 × HBW (MPa).
- Example: 3000 kgf on a 10 mm ball leaving a 4 mm indent is 228.77 HBW.
Limitations
- The tensile strength estimate is approximate and applies to steels only; use measured tensile tests for acceptance.
- Specimen thickness must be at least about 8 × the indentation depth.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Calculate HBW from a measured indentation
- Check test validity (indent size, force ratio)
- Estimate steel tensile strength
Who it is for
- Quality inspectors
- Metallurgists
- Materials engineers
What you get
- Brinell hardness HBW
- Force–diameter ratio
- Indentation ratio d/D
- Approximate tensile strength (steels)
Interpreting the result
- Report as HBW with the ball and force, e.g. 229 HBW 10/3000.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1406–1412. Topic reference; no source tables or recommended settings are reproduced.
- ISO 6506-1 Metallic materials — Brinell hardness test — Part 1: Test method
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Hardness and grain size
In Yield and Plastic Flow by the Numbers
What it covers: What a hardness test measures and how far it predicts strength, how grain size raises yield strength by the Hall–Petch relation, and why a coarse-grained heat passed a hardness check.
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