The Brinell hardness test is suitable for a range of materials hardness’. Brinell hardness testing involves forcing a hardened steel ball (or a tungsten carbide ball for extremely hard materials) into the surface of the specimen. The ball usually has a diameter of 10mm and is pressed into the sample using a predetermined load dependent on the relative hardness of the material e.g. 500kg for softer metals and 3000kg for hard metals.
The load is applied for a defined time, usually 10-15 seconds and the impression diameter measured using a low power microscope.
Calculating Brinell Hardness
The hardness is then calculated as a ratio of the load to the curved surface of the impression using the equation:
HB = Brinell hardness
F = load in kg
D = the diameter of the indenter in mm
Di = impression diameter in mm
Advantages of Brinell Hardness Measurements
Due to the size of the indenter and the impression, the Brinell system is more indicative of the bulk material hardness compared to other techniques which test over a much smaller area and may in fact be measuring impurities or inclusions.