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Bolts common hardness index

Bolt hardness indicates the ability of a material to resist the intrusion of a hard object into its surface. It is one of the important performance indicators of metal materials. The higher the general hardness, the better wear resistance. Commonly used hardness index Brinell hardness, Rockwell hardness and Vickers hardness.

  1. Brinell hardness (HB) to a certain load (usually 3000kg) to a certain size (diameter is generally 10mm) hardened steel ball pressed into the surface of the material, to maintain a period of time, to load, the load and its indentation area ratio , That is, Brinell hardness value (HB), in kg / mm2 (N / mm2).
  2. Rockwell Hardness (HR) When HB> 450 or the sample is too small, can not use the Brinell hardness test instead of Rockwell hardness measurement. It is a 120 ° angle of the diamond cone or a diameter of 1.59,3.18mm ball, under pressure in the measured material under pressure, the indentation from the depth of the hardness of the material. According to the hardness of the test material, divided into three different scales to represent:

HRA: hardness obtained with a 60 kg load and a diamond cone press, for very hard materials (eg cemented carbide, etc.).

HRB: is the use of 100kg load and diameter 1.58mm hardened steel ball, the hardness obtained for the hardness of the lower materials (such as annealing steel, cast iron, etc.).

HRC: 150kg load and the use of diamond cone press into the hardness obtained for a high hardness of the material (such as hardened steel, etc.).

3 Vickers hardness (HV) to 120kg within the load and the vertex angle of 136 ° diamond cone press into the material surface, with the material indentation surface area divided by the load value, that is, the value of Vickers hardness HV). From the above description shows, Vickers hardness is one of the surface hardness. It has a conversion relationship with other hardness units. Expansion bolt hardness refers to the surface hardness, the material is no hardness within the requirements. Only the mechanical properties (tensile strength, yield strength and impact toughness).

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