Brinell hardness test method was proposed by J.A.Brinell when examining the implications of heat treatment on the structure of rolling in 1899 to 1900. This hardness test method, which is the earliest used one, is still widely used until now. Because the indentation of Brinell hardness test method is larger and the test samples have a small impact on its hardness. It has small detection results dispersion and good reproducibility, which can well reflect the real hardness value of the material.
1. The principle of Brinell hardness test and calculating formula
Pressing the specimen surface under the specified test force F by a cemented carbide ball with a specific diameter. unloaded after a period of maintaining test force. The Indentation Diameter on the specimen surface by testing is d. The test force divided by the indentation surface area’s is Brinell hardness. The calculating formula is as follows:
2.The application ranges of Brinell hardness test method
Brinell hardness test uses larger pressure and pressure head diameter and gets a larger indentation diameter, that determines this kin of hardness text method is suitable for detecting metals with large grains such as castings, forgings, steel, quenching, tempering, annealing, positive heat treatment parts and non-ferrous metals and their alloys, especially for some soft metal with accurate detection performance like aluminum, copper, lead, tin, zinc and their alloys.
Brinell hardness test method also has a limitation in practical application. This kind of test method first should put certain test force on the tested sample, then get the indentation by specialized optics, and finally look-up table to find the material Brinell hardness. Long-time operation and more steps are required to the detection process. What’s more, the indentation would be larger for the larger test force and the choice of larger indentation diameter, which belongs to destructive detection method.
3.Considerations of using Brinell hardness test
a.Relevant national standard (The specific standard number is GB/T 231.1-2009 Metallic Materials-Brinell Hardness Test and can be downloaded for free on the Shenyang Tianxing test instrument website)shall be strictly performed for measuring Brinell hardness numbers of the artifact in industry production.
b.Generally, the ambient temperature of the test should be between 10 and 35℃.
c.The choice of the test force and pressure head diameter in Brinell hardness tester
should meet the national standards.
d.The surface of the specimen should be ensured flat and smooth before testing, without any oxide or other contaminants.