Brinell hardness test
Classification, process, differentiation and practical recommendations.Categorisation of the Brinell method
The Brinell method is a static hardness testing method, which can be characterised as follows:
- It is one of the standardised procedures (ISO 6506, ASTM E10).
- The Brinell method has a test load range of 1 to 3000 kgf, which means that this method can be used for hardness testing in the low-load and, above all, macro ranges (conventional range).
- It is an optical method. This means that the size of indentation left by the indenter is measured to determine the hardness value of a test specimen.
- Indenter shape and material: The indenter is a tungsten carbide metal ball, with a diameter of 1, 2.5, 5 or 10 mm, depending upon the specific Brinell method.
Advantages and disadvantages of the Brinell method
The Brinell method has the following advantages:
- The Brinell method can be used for testing non-homogeneous materials (e.g. castings), because the large ball comes into contact with many crystals (different metallographic constituents of the material), thereby forming a mechanical average value.
- A choice can be made between a large number of test forces and ball diameters for the widest variety of applications.
- Relatively large test indents that are easier to measure the rather small Vickers indentations.
- The specimen surface can be rough.
The Brinell method has the following disadvantages:
The surface quality of the specimen must be good, because the indent is measured optically. This means that the test location must be prepared.
High risk of deforming the material to be tested when testing in the macro range with high test loads (e.g. HBW 10/3000) and consequent risk of measuring errors due to wall formation. Therefore good illumination of the test indent is important for ensuring correct evaluation of the test indent (e.g. with the aid of a ring light).
Limitation in applying the method on thin specimens of very hard materials (see Brinell method, minimum specimen thickness).
The process is slow (by comparison with the Rockwell method). The test cycle takes somewhere between 30 and 60 seconds, not including the time taken to prepare the specimen.