The hardness of the material to resist a hard object represents pressed into the surface of its capabilities. It is one of the important performance indicators of metallic materials. The higher general hardness, wear resistance, the better. Common indicators hardness Brinell hardness, Rockwell hardness and Vickers hardness.
1. Brinell hardness (HB)
To a certain load (usually 3000kg) to a certain size (diameter typically 10mm) hardened steel ball pressed into the surface of the material, for a period of time to go after load, the ratio of the area of the load and its indentation, that is Brinell hardness value (HB), units of kgf / mm2 (N / mm2).
2. Rockwell hardness (HR)
When HB> 450 or the sample is too small, can not be used Brinell hardness test and switched to a Rockwell hardness measurement. It is the apex angle of 120 ° with a cone or a diamond 1.59,3.18mm diameter steel ball pressed into a load at a certain surface of the material, determined by the depth of the indentation in the material hardness. Depending on the hardness of the test material, three different sub-scale is expressed: HRA: 60kg load and the use of the diamond is pressed into the filter cone hardness obtained high hardness material (such as cemented carbide, etc.) is used. HRB: is the use of 100kg load and 1.58mm diameter hardened steel ball, hardness obtained for the lower hardness of the material (e.g. anneal steel, cast iron, etc.). HRC: is the use of a diamond cone and a 150kg load hardness obtained is pressed into the high hardness material (such as hardened steel, etc.) is used.
3. Vickers hardness (HV) with 120kg load, and an apex angle of less than 136 ° square cone diamond is pressed into the material is pressed into the surface of the material divided by the surface area of ??the indentation load value with the pits, i.e. Vickers hardness HV value (kgf / mm2).
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