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How It Works
The Brinell test presses a hard steel or tungsten-carbide ball into a material under a known load and measures the diameter of the resulting indentation. The BHN is the applied load divided by the curved surface area of the impression. Higher numbers mean harder material.
Example Problem
A 10 mm ball indenter at 3,000 kgf leaves a 5 mm impression. What is the BHN?
- Numerator: 2 × 3,000 = 6,000
- Denominator: π × 10 × (10 − √(100 − 25)) ≈ 42.1
- BHN = 6,000 / 42.1 ≈ 142.6
This falls in the mild-steel range (120–180 BHN).
Frequently Asked Questions
What is the difference between Brinell and Rockwell hardness?
Brinell measures the area of a spherical indentation, while Rockwell measures the depth of penetration from a cone or small ball. Brinell is preferred for coarse-grained metals; Rockwell is faster and better suited for production-line testing.
What is a typical BHN for mild steel?
Mild steel generally falls between 120 and 180 BHN. Tool steels can reach 600+, while soft metals like lead are around 5 BHN. Aluminum alloys range from 15 (pure) to about 150.
Is the Brinell test destructive?
Yes. It leaves a permanent indentation, so it is not suitable for finished surfaces. In practice, tests are performed on sample coupons or in non-critical areas of a workpiece.
Can BHN be converted to other hardness scales?
Approximate conversion tables exist (ASTM E140), but conversions between Brinell, Rockwell, and Vickers are not exact because each test measures a different physical property.
Related Calculators
- Percent Error Calculator — evaluate measurement accuracy against a known standard.
- Percent Difference Calculator — compare two hardness readings from different samples.
- Stress & Strain Calculator — analyze material deformation related to hardness testing.
- Force Equation Calculator — calculate the applied force used in Brinell hardness tests.
- Force Unit Converter — convert between newtons, kilogram-force, and other force units.