Definition value range of hardness of heat treatment workpiece

1. HRC means Rockwell hardness C scale,

2. HRC and Hb are widely used in production,

3. Application scope of HRC 20-67, equivalent to hb225-650

If the hardness is higher than this range, use the Rockwell a scale HRA.

If the hardness is lower than this range, use Rockwell hardness B scale HRB.

The upper limit value of cloth hardness hb650 can not be higher than this value.

4. The indenter of C scale of Rockwell hardness tester is a diamond cone with a top angle of 120 degrees. The test load is a certain value, and the Chinese standard is 150 kg force.

The indenter of Brinell hardness tester is hardened steel ball (HBS) or hard alloy ball (HBW). The test load varies with the ball diameter, from 3000 to 31.25 kg force.

5. The Rockwell hardness indentation is very small, and the measured value is local. It needs to measure several points to get the average value. It is suitable for finished products and thin sheets, and belongs to the category of non-destructive testing. The cloth hardness indentation is large, and the measured value is accurate. It is not suitable for finished products and thin sheets, and generally does not belong to the category of non-destructive testing.

6. The hardness value of Rockwell hardness is an unknown number without unit. (therefore, it is not correct to call the hardness of Rockwell quench) the hardness value of cloth hardness has units, and it has an approximate relationship with the tensile strength.

7. Rockwell hardness can be directly displayed on the dial or digital display, which is convenient, fast and intuitive, and suitable for mass production. The cloth hardness needs to measure the indentation diameter with a microscope, and then check the table or calculate, the operation is complicated.

8. Under the condition, Hb and HRC can be checked and exchanged. Its mental formula can be roughly recorded as: 1hrc ≈ 1 / 10hb.

Hardness test is a simple test method in mechanical property test. In order to replace some mechanical property tests with hardness tests, a more accurate conversion relationship between hardness and strength is needed in production.

It has been proved that there is an approximate relationship between the hardness values and the strength values of the metal materials. Because the hardness value is determined by the initial plastic deformation resistance and the continuous plastic deformation resistance, the higher the strength of the material, the higher the plastic deformation resistance, and the higher the hardness value.

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