The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in materials science.
Proposed by Swedish engineer Johan August Brinell in 1900, it was the first widely used and standardised hardness test in engineering and metallurgy. The large size of indentation and possible damage to test-piece limits its usefulness.
The typical test uses a 10 mm diameter steel ball as an indenter with a 3,000 kgf (29 kN) force. For softer materials, a smaller force is used; for harder materials, a tungsten carbide ball is substituted for the steel ball. The indentation is measured and hardness calculated as:
where:
- P = applied force (kgf)
- D = diameter of indenter (mm)
- d = diameter of indentation (mm)
The BHN can be converted into the ultimate tensile strength (UTS), although the relationship is dependent on the material, and therefore determined empirically. The relationship is based on Meyer's index (n) from Meyer's law. If Meyer's index is less than 2.2 then the ratio of UTS to BHN is 0.36. If Meyer's index is greater than the ratio increases.1
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Common values
When quoting a Brinell hardness number (BHN or more commonly HB), the conditions of the test used to obtain the number must be specified. The standard format for specifying tests can be seen in the example "HBW 10/3000". "HBW" means that a tungsten carbide (from the chemical symbol for tungsten) ball indenter was used, as opposed to "HBS", which means a hardened steel ball. The "10" is the ball diameter in millimeters. The "3000" is the force in kilograms force.
| Material | Hardness |
|---|---|
| Softwood (e.g., pine) | 1.6 HBS 10/100 |
| Hardwood | 2.6–7.0 HBS 1.6 10/100 |
| Aluminium | 15 HB |
| Copper | 35 HB |
| Mild steel | 120 HB |
| 18-8 (304) stainless steel | 1250 HB |
| Glass | 1550 HB |
| Hardened tool steel | 1500–1900 HB |
| Rhenium diboride | 4600 HB |
| Note: Standard test conditions unless otherwise stated | |
Standards
- International (ISO) and European (CEN) Standard
- EN ISO 6506-1: Metallic materials - Brinell hardness test - Part 1: test method
- EN ISO 6506-2: Metallic materials - Brinell hardness test - Part 2: verification and calibration of testing machine
- EN ISO 6506-3: Metallic materials - Brinell hardness test - Part 3: calibration of reference blocks
- US standard (ASTM International)
- ASTM E10: Standard method for Brinell hardness of metallic materials.
See also
References
Notes
- ^ Tabor, p. 17.
Bibliography
- Tabor, David (2000), The Hardness of Metals, Oxford University Press, ISBN 0198507763, http://books.google.com/books?id=b-9LdJ5FHXYC.
External links
- Rockwell to Brinell conversion chart
- Struers hardness conversion table
- Brinell Hardness HB conversion chart
Wikipedia content modification information:
- This page was last modified on 30 December 2008, at 07:24.
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