🔩 Brinell Hardness
Hardness measurement of metals by indentation of cemented carbide ball with specified force. HBW designation — universal method for steel, cast iron and non-ferrous metals.
Overview
The Brinell method is one of the oldest and most widely used methods for measuring metal hardness, developed by Swedish engineer Johan August Brinell in 1900. It involves indenting a cemented carbide ball (designation HBW) of diameter D (1; 2.5; 5 or 10 mm) into the test material surface under a standardized force F, then measuring the diameter of the resulting indentation.
Brinell hardness is particularly useful for testing materials with coarse or non-uniform structure, such as cast irons, castings, forgings and low-alloy steels. The large ball leaves a relatively large indentation, which averages local hardness differences in the material (e.g., graphite in cast iron). The method is not suitable for very hard materials (>650 HBW) — then Vickers or Rockwell methods are used.
Standard PN-EN ISO 6506-1 specifies test conditions: the ratio of force to square of ball diameter (0.102 × F/D²) must correspond to one of the standardized values (1; 2.5; 5; 10; 15; 30). For steel, F/D² = 30 is standard (i.e., 10 mm ball, force 29.42 kN = 3000 kgf). Load application time is 10–15 s for steel.
Brinell hardness result is written in format: e.g., 200 HBW 10/3000/15, where 200 is hardness, 10 — ball diameter [mm], 3000 — force [kgf], 15 — application time [s].
Method principle
A cemented carbide ball (HBW) of diameter D is indented into the test material surface under force F for a specified time. Force is increased to final value in 2–8 s and maintained for 10–15 s (for steel). After unloading, indentation diameter d is measured in two perpendicular directions using a measuring microscope. Brinell hardness is calculated from formula: HBW = 0.102 × 2F / (πD(D - √(D² - d²))), or read from tables in standard PN-EN ISO 6506-4 based on measured indentation diameter.
Applications
- Quality control of structural and engineering steel
- Testing of gray, spheroidal and malleable cast iron
- Acceptance control of forgings and castings
- Testing of non-ferrous metals (aluminum, copper, bronze)
- Assessment of material condition after heat treatment
- Correlation of hardness with tensile strength (Rm ≈ 3.5 × HBW)
- Failure analysis — assessment of material degradation
Key parameters
| Parameter | Value |
|---|---|
| Ball diameters | 1; 2.5; 5; 10 mm (cemented carbide HBW) |
| Test forces | 9.807 N to 29 420 N (1 kgf to 3000 kgf) |
| F/D² ratio | 1; 2.5; 5; 10; 15; 30 (standardized) |
| Application time | 10–15 s (steel), 10–180 s (non-ferrous metals) |
| Hardness range | ≤650 HBW (above — Vickers method) |
| Measurement accuracy of d | ±0.5% of indentation diameter |
Standard
- Standard number
- PN-EN ISO 6506-1:2014
- Title (PL)
- Metale — Pomiar twardości sposobem Brinella — Część 1: Metoda badań
- Title (EN)
- Metallic materials — Brinell hardness test — Part 1: Test method
Step-by-step procedure
1. Specimen surface preparation
Test surface must be smooth (Ra ≤ 1.6 µm), flat and free from oxides. Grind with P240–P600 paper if necessary. Degrease.
2. Test parameter selection
Select ball diameter D and force F based on material and specimen thickness. For steel: D = 10 mm, F = 29 420 N (F/D² = 30). Specimen thickness ≥ 8d.
3. Hardness tester verification
Perform measurement on certified reference block. Result must be within certificate uncertainty range. If not — calibration.
4. Specimen placement
Place specimen on hardness tester table. Ensure stable support (must not move or deform). Level.
5. Indentation execution
Apply preload. Increase to final force F in 2–8 s. Maintain for 10–15 s. Release load.
6. Indentation diameter measurement
Measure indentation diameter d in two perpendicular directions using microscope. Calculate average. Diameter must satisfy: 0.24D ≤ d ≤ 0.6D.
7. Hardness calculation
Calculate HBW from formula or read from tables in PN-EN ISO 6506-4. Record result in full form (e.g., 185 HBW 10/3000/15).
8. Additional indentations
Make minimum 3 indentations. Distance between indentation centers ≥ 3d, distance from edge ≥ 2.5d.
9. Final result calculation
Result = arithmetic mean of minimum 3 measurements. Assess scatter — if >5% from mean, investigate cause.
10. Documentation
Prepare report: material, dimensions, test conditions (D, F, t), individual indentation results, average, reference standard.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Stationary Brinell hardness tester | EMCO DuraVision G5, Wolpert/Wilson UH4000, Zwick/Roell ZHU | 30 000–120 000 PLN |
| Set of cemented carbide balls | HBW balls: Ø1, 2.5, 5, 10 mm — certified per ISO 6506-3 | 200–800 PLN/set |
| Measuring microscope for indentations | Integrated with hardness tester or external, magnification 20×–50× | 3 000–15 000 PLN |
| Hardness reference blocks | Certified CRM per ISO 6506-3, e.g., 200 HBW, 400 HBW | 500–2 000 PLN/pc |
| Table and anvil for specimen mounting | Adjustable, with V-blocks for cylindrical specimens | 1 000–5 000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Hardness reference blocks | — | Certified reference materials CRM for hardness tester calibration, 2–3 ranges |
| Abrasive paper (surface preparation) | — | Grit P120–P600 for grinding specimen surface (Ra ≤ 1.6 µm) |
| Isopropyl alcohol | 67-63-0 | For degreasing specimen surface before testing |
Health and safety (OHS)
- Hardness tester — finger crushing risk when lowering indenter, do not hold specimen by hand
- Heavy metal specimens — injury risk when handling
- Metal filings during grinding — safety glasses mandatory
- Isopropyl alcohol — flammable, use away from ignition sources