Brinell hardness (Brinell Hardness) measurement principle is to use a certain magnitude test force F(N) (force unit is usually kg force kgf, note: 1kgf=9.8N, kgf is the meaning of one Kilogram force), the diameter of D (mm) hardened steel ball or cemented carbide ball into the measured metal surface, maintain the specified time after unloading the test force, using a reading number microscope to measure the average diameter of indentation d (mm), Then calculate the Brinell hardnessHB value according to the formulas, or the radical data d from the prepared Brinell hardness table to find the HB value.

formulas ：

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