1.Hardness is the ability of a material to resist hard objects pressing into its surface. It is one of the important performance indexes of metal materials. General hardness is taller, wear resistance had jumped over. Commonly used hardness indicators are Brinell hardness, Rockwell hardness and Vickers hardness.
Brinell hardness (HB) Pressing hardened steel balls of a certain size (diameter is generally 10mm) into the surface of the material with a certain load (generally 3000kg) for a period of time. After the load is removed, the ratio of the load and the indentation area is the Brinell hardness value (HB), the unit is kg force /mm2(N/mm2).
2. Rockwell hardness (HR) when HB> 450 or the sample is too small, the Brinell hardness test can not be used instead of Rockwell hardness measurement. It is to use a diamond cone with a top Angle of 120° or a steel ball with a diameter of 1.59 or 3.18mm to press into the surface of the measured material under a certain load, and the hardness of the material can be calculated by the depth of the indentation.
According to the hardness of the test material, it is divided into three different scales:
HRA: Hardness obtained with a 60kg load and a diamond cone press for extremely hard materials such as hard alloys.
HRB: the hardness is obtained by using 100kg load and 1.58mm diameter hardened steel ball, used for low hardness materials (such as annealed steel, cast iron, etc.).
HRC:Hardness obtained by 150kg and drill cone press for very hard materials such as hardened steel.
3 Vickers hardness (HV) With a load of less than 120kg and a tip Angle of 136° diamond square cone indenter pressed into the surface of the material, material indentation pit surface area divided by the load value, namely Vickers hardness HV value (KGF /mm2).