The principle of Brinell Hardness measurement is to use a certain test force F (N) (the unit of force is usually kilogram-force kgf, note: 1kgf=9.8N, kgf means one kilogram of force), press a hardened steel ball or carbide ball with a diameter of D (mm) into the surface of the metal to be tested, keep the test force for a specified time and then remove it. Use a reading microscope to measure the average diameter of the indentation d (mm), and then calculate the Brinell hardness HB value according to the formula, or find the HB value from the prepared Brinell hardness table based on d.

formula:

BHN = (2*P) / [ (pi*D)(D - sqrt(D²-d²)) ]