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Classification and explanation of hardness of steel ball

1. Brinell hardness (HB)

With 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 for some time, to load, the load and its indentation area ratio, that is Brinell hardness value HB), in kilograms force / mm2 (N / mm2).

2 Rockwell hardness (HR)

When HB> 450 or the sample is too small, you can not use the Brinell hardness test instead Rockwell hardness measurement. It is a 120 ° angle diamond cone or 1.59,3.18 mm diameter steel ball, under certain load into the surface of the material under test, indentation depth obtained by the hardness of the material.

According to the test material hardness, divided into three different scales to represent: HRA: is the use of 60kg load and diamond conical indentation obtained hardness, for the hardness of the material (such as cemented carbide, etc.).

HRB: The hardness is determined by 100kg load and 1.58mm diameter hardened steel ball, which is used for the material with lower hardness (such as annealed steel, cast iron, etc.).

HRC: 150kg load and diamond cone press obtained hardness, for high hardness materials (such as hardened steel, etc.).

Vickers hardness (HV)

Vickers hardness (HV) (kgf / mm2) is measured by pressing the surface area of ​​the indentation of the material with a load of 120 kg and a diamond square cone press with a vertex angle of 136 °.

Rockwell hardness HRA, HRB, HRC, etc. A, B, C are three different standards, known as the ruler A, ruler B, ruler C.

Rockwell hardness test is one of several common indentation hardness tests used today, the initial pressure of the three scales are 98.07N (10kgf), and finally calculate the hardness value according to the indentation depth.

Gauge A is a ball-point diamond indenter, and then pressurized to 588.4N (60kgf);

Rod B used a steel ball of 1.588 mm (1/16 inch) in diameter as ram and then pressurized to 980.7 N (100 kgf);

While the scale C uses the same spherical cone diamond as the scale A as the indenter, but the force after pressing is 1471N (150 kgf). Therefore, the scale B for the relatively soft material, while the scale C for harder materials.

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