Brinell hardness test
The Brinell hardness test is a standardized method for determining the hardness of metallic materials. It is primarily used when soft to medium-hard materials, cast materials or materials with inhomogeneous structure, porosities or coarse structural components to be tested. The comparatively large indentation of the Brinell ball covers a larger material area than smaller, more pointed indenters and therefore provides representative hardness values, especially for coarse or inhomogeneous structures.
the essentials in brief
- The Brinell hardness test works with a carbide ball as an intruder.
- The hardness value is calculated from test force, ball diameter and indentation diameter.
- Brinell is particularly suitable for Cast materials, non-ferrous metals and softer to medium-hard metals.
- The procedure is part of the standard series. DIN EN ISO 6506 .
- The optical evaluation of the test impression requires a suitable surface and a reliable measuring system.
What is the Brinell hardness test?
The Brinell hardness test is an indentation test. A hard metal ball is pressed into the surface of the material with a defined test force. After the pressure is released, a spherical indentation (calotte) remains, the diameter of which is measured optically.
The method dates back to the Swedish engineer Johan August Brinell and remains one of the established methods for industrial hardness testing. The Brinell hardness value is used as HBW specified. The abbreviation stands for Härte Brinell with Wolefin carbide ball.
For which materials is the Brinell hardness test suitable?
The Brinell hardness test is particularly suitable for materials where a larger indentation is desirable. This is the case, for example, with coarse, porous, or inhomogeneous structures. The ball creates a comparatively large contact area and therefore tends to form a mechanical average across the tested area.
Typical materials and applications include:
- Cast iron and cast steel
- low-alloy steels and structural steels
- aluminum alloys
- Copper, brass and bronze
- other non-ferrous metals
- Sintered materials, depending on the condition and the testing task
- Materials with a coarse or inhomogeneous structure
Brinell is less suitable for very hard materials, small components, or thin layers. In such cases, other methods are often used. Vickers or Rockwell in question.
How does the Brinell hardness test work?
The testing procedure follows a clearly defined principle:
- A hard metal ball with a suitable diameter is selected for the required load level.
- The sample is prepared and securely positioned, partially clamped using a clamping cap.
- The ball is pressed into the surface with a defined test force.
- The test force is applied for a defined period of time (holding time).
- After the pressure is released, a spherical impression remains.
- The indentation diameter is measured optically in two directions.
- The Brinell hardness value is calculated from the test force, ball diameter and mean indentation diameter.
Adherence to the test force and load duration is important because softer materials in particular can deform further during the application of force (flow behavior). Therefore, test time, material behavior, and evaluation directly influence the measurement result.
Video: Animation of Brinell's Law of Operation
What does a specification like 246 HBW 10/3000 mean?
Brinell hardness values must be fully specified so that the result remains verifiable.
A typical figure is: 246 HBW 10/3000
The breakdown of this information:
- 246 is the determined hardness value.
- HBW stands for Brinell hardness with tungsten carbide ball
- 10 denotes the ball diameter in millimeters.
- 3000 denotes the test force in kgf.
- For longer periods of exertion, the duration is also specified, for example: 246 HBW 10/3000/60. In this case, the last number represents a duration of 60 seconds.
Ball diameter, test force and load level
The ball diameter and test force must be appropriate for the material. In the Brinell hardness test, the degree of stress is taken into account. This describes the ratio of test force to ball diameter.
Excessive testing force can cause the indentation to become too deep and therefore unusable for meaningful evaluation. Conversely, insufficient testing force can produce an indentation that is too small or difficult to measure.
For the Brinell hardness test, the formula for the test force is: F = K*D²
Examples: F = 30 * sphere diameter 10² = 3.000 kgf
F = Test force [kgf]
K = Load level (e.g. 30 for steel and iron)
D = Ball diameter [mm]
| degree of stress | Typical application | Example |
|---|---|---|
| HB 30 | Steel, cast steel, cast iron | HB 10/3000 |
| HB 10 | Aluminum alloys, copper alloys, non-ferrous metals | HBW 10/1000 |
| HB 5 | softer metals and selected non-ferrous materials | HBW 10/500 |
| HB 2,5 or lower | very soft materials, depending on the standard and testing task | HBW 10/250 |
Special features of optical evaluation
The Brinell hardness test produces significantly larger test impressions than Vickers or ButtonThis is advantageous for inhomogeneous materials, but places higher demands on optical evaluation.
Particularly with soft materials, material displacement can lead to bulging at the edge of the indentation. Depending on the surface condition, lighting, and material, the exact boundary of the indentation may be more or less clearly visible.
Modern Brinell hardness testers therefore use hHigh-resolution camera systems with intelligent image analysisSuitable ring light illumination and a clean sample surface are prerequisites for the reliable determination of the indentation diameter.
Advantages and limitations of the Brinell hardness test
| Benefits | boundaries |
|---|---|
| Well suited for coarse and inhomogeneous structures | Not ideal for very hard materials |
| Suitable for cast materials and many non-ferrous metals | Requires a sufficiently large test area |
| Standardized and established procedure | The surface must be suitable for optical measurement. |
| More tolerant of structural inhomogeneity | Severe material displacement makes evaluation difficult. |
Standards for Brinell hardness testing
The Brinell hardness test is part of the standard series. DIN EN ISO 6506 regulated. For practical application, the following areas are particularly relevant:
- DIN EN ISO 6506-1 describes the testing procedure.
- DIN EN ISO 6506-2 It covers the verification and calibration of testing machines.
- DIN EN ISO 6506-3 This concerns the calibration of hardness comparison plates.
- DIN EN ISO 6506-4 Contains tables for determining Brinell hardness values.
- ASTM E10 is relevant for Brinell tests according to American standards.
The standard specifies, among other things, the test specimen, test force, test procedure, evaluation, and result reporting. Therefore, to ensure comparable results, you should clearly clarify the required standard before conducting the test!
Common mistakes in Brinell hardness testing
Errors in Brinell hardness testing often arise from an unsuitable combination of material, test force, ball diameter, and evaluation. Typical sources of error include:
- incorrect ball diameter
- unsuitable tester
- Test surface too small or uneven
- inadequate surface preparation
- unsuitable lighting during optical measurement
- Insufficient distance to edges or other test impressions
- incomplete result
- direct equation with hardness values from other procedures
What types of Brinell hardness testers are available?
Various equipment concepts are available for Brinell hardness testing. The selection depends on the testing task, component size, test force range, degree of automation, required documentation, and available budget.
Possible device types include:
- stationary pure Brinell hardness testers
- Universal hardness tester with Brinell function
- Automatic Brinell hardness testing machines with motorized XY table
- Radial machine frame with test head for workpieces that can only be handled by medium forklifts/cranes
- Almost all new hardness testing systems are equipped with a camera and image analysis. Alternatively, there are suppliers of simpler Brinell presses that only produce the indentation; the optical measurement is performed externally using an optical or video magnifying glass.
For high-volume testing, automatic measuring systems, including motorized XY tables, are advantageous because they can automatically capture, evaluate, and document the test impression. For varying materials or multiple testing procedures, a universal hardness tester with tool changer (turret head) may be a suitable solution.
When is the Brinell method the right one?
| Application | Suitable for Brinell? |
|---|---|
| Cast materials | Yes, often very suitable |
| Coarse or inhomogeneous structures | Ja |
| Soft to medium-hard metals | Ja |
| Very hard materials | Rather not |
| Small components or thin layers | Mostly not |
| Hardness gradients | More likely Vickers |
| Rapid serial testing without optical measurement | Rather Rockwell |
Frequently asked questions about the Brinell hardness test
What is the Brinell hardness test?
The Brinell hardness test is a standardized test. Hardness testing method, in which a hard metal ball is pressed into the material with a defined test force. The diameter of the ball indentation (calotte) is then measured optically.
For which materials is Brinell suitable?
Brinell is particularly suitable for softer to medium-hard metals, cast materials, non-ferrous metals and materials with a coarse or inhomogeneous structure.
What does HBW mean?
HBW stands for Brinell hardness with tungsten carbide ball. This designation identifies the Brinell test commonly used today, which employs a tungsten carbide ball.
What does 246 HBW 10/3000 mean?
246 is the hardness value. HBW refers to the Brinell method using a tungsten carbide ball. 10 represents the ball diameter in millimeters and 3000 the test force in kgf.
Which standard applies to the Brinell hardness test?
The Brinell hardness test is regulated in the DIN EN ISO 6506 series of standards. For American requirements, ASTM E10 is relevant.
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