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The hardness of the bolt

Update:20 Jun 2017
Summary:

Hardness means the ability of the material to withstand […]

Hardness means the ability of the material to withstand the hard objects into its surface. It is one of the important performance indicators of metal materials. The higher the hardness, the better the wear resistance. Commonly used hardness indicators are Brinell hardness, Rockwell hardness and Vickers hardness.
1. Brinell hardness (HB)
With a certain load (usually 3000kg) to a certain size (diameter is generally 10mm) hardened steel ball into the material surface, to maintain a period of time, after loading, the load and its indentation area ratio, that is Brinell hardness ( HB) in kg / mm2 (N / mm2).
2. Rockwell hardness (HR)
When HB> 450 or the sample is too small, can not use Brinell hardness test and switch to Rockwell hardness measurement. It is a vertex angle of 120 ° diamond cone or diameter of 1.59,3.18mm ball, under a certain load into the surface of the measured material, the depth of indentation from the hardness of the material. According to the hardness of the test material, divided into three different scales to represent:
  HRA: is the use of 60kg load and diamond cone press the hardness obtained for high hardness materials (such as hard alloy, etc.).
  HRB: is the use of 100kg load and 1.58mm diameter hardened steel ball, the hardness obtained for low hardness materials (such as annealing steel, cast iron, etc.).
  HRC: is the use of 150kg load and diamond cone press the hardness obtained for high hardness materials (such as hardened steel, etc.).
3 .Vickers hardness (HV)
The surface area of the indentation pits is divided by the load value, that is, the Vickers hardness value (HV), by pressing the material with a load of less than 120 kg and a diamond square cone presser of 136 °.
As can be seen from the above, Vickers hardness is one of the surface hardness. It and other units of hardness between the conversion relationship.
Hardness refers to the surface hardness, the material is no hardness requirements inside. Only mechanical performance requirements (tensile strength, yield strength and impact toughness).log  on to our official website for more details :http://www.lwhardware.com/