Brinell Testing

Another common hardness test type, the Brinell test, consists of applying a constant load or force, usually between 500 and 3000 Kgf, for a specified time (from 10 - 30 seconds) using a 5 or 10 mm diameter tungsten carbide ball. The load time period is required to ensure that plastic flow of the metal has ceased. Lower forces and smaller diameter balls are sometimes used in specific applications. Similar to Knoop and Vickers testing, the Brinell test applies only a single test force. After removal of the load, the resultant recovered round impression is measured across diagonals at right angles and is usually recorded millimeters using a low-power microscope or an automatic measuring device.

The actual Brinell hardness (BHN) is calculated by factoring the indent size and the test force however it is not necessary to make the actual calculation for each test. Calculations have already been made and are available in tabular form for various combinations of diameters of impressions and load. In addition various forms of automatic Brinell reading devices are available to perform these tasks.

Brinell testing is typically used in testing aluminum and copper alloys (at lower forces) and steels and cast irons at the higher force ranges. Highly hardened steel or other materials are usually not tested by the Brinell method, but the Brinell test is particularly useful in certain material finishes as it is more tolerant of surface conditions due to the indenter size and heavy applied force. Brinell testers are often manufactured to accommodate large parts such as engine castings and large diameter piping.