In this test a hardened steel ball is pressed into the surface of the test material using a prescribed ball. The ball and load have to be selected to suit the material being tested.
The Brinell hardness test consists of indenting the test material with a 10 mm diameter hardened steel or carbide ball subjected to a load of 3000 kgf (29 430 N). For softer materials the load can be reduced to 1500 kgf (14 715 N) or 500 kgf (4 905 N ) to avoid excessive indentation. The full load is normally applied for 10 to 15 seconds for harder ferrous metals and for 30 seconds or more for other metals softer metals.
The diameter of the indentation left in the test material is measured with a microscope. The Brinell hardness number is calculated by dividing the load applied by the surface area of the indentation.
BHN = 2.F / (p.D .(D - √(D2-D1)
D = Diameter of Ball
D1 = Diameter of indentation
F = applied force
