Brinell Hardness Number (BHN)
Definition
The Brinell Hardness Number (BHN) is a value that quantifies the hardness of materials, particularly metals and alloys. It is derived from the Brinell hardness test, which measures the resistance of the material to indentation.
Test Method
The Brinell hardness test involves the following steps:
- Indentation: A round steel or carbide ball is forced into the surface of the material under a known load.
- Measurement: After the load is removed, the diameter of the indentation left on the material’s surface is measured.
- Calculation: The BHN is calculated using the following formula:
BHN = \frac{2P}{\pi D(D – \sqrt{D^2 – d^2})}
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Where:
- (P) is the applied load (in kilograms).
- (D) is the diameter of the indenter ball (in millimeters).
- (d) is the diameter of the indentation (in millimeters).
Preferred Term
The preferred term for referring to the Brinell hardness value is now “HB” followed by the hardness number. For example, a material with a Brinell hardness number of 200 would be denoted as “HB 200”.
Application
The Brinell hardness test is widely used for:
- Determining the hardness of castings and forgings.
- Assessing the strength and wear resistance of materials.
- Quality control in manufacturing processes.
Advantages and Limitations
- Advantages: The Brinell test is relatively simple and can be applied to a wide range of materials. It provides a single, easy-to-understand number that indicates hardness.
- Limitations: The test may not be suitable for very hard or very soft materials. Additionally, it can be less accurate for small or thin samples due to the size of the indentation.
The Brinell hardness test remains a crucial method in material science for assessing material properties and ensuring quality in manufacturing and engineering applications.
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