Specific differences and conversions of hardness such as Rockwell hardness (HRC) and Brinell hardness (HB)

Hardness is a performance index to measure the hardness of a material. There are many methods for hardness testing, and the principles are different. The measured hardness values ​​and meanings are not exactly the same. The most commonly used is the static load indentation hardness test, namely the Brinell hardness HB, Rockwell hardness HRA, HRB, HRC, Vickers hardness HV, rubber and plastic Shore hardness HA, HD and other hardness values. The value indicates the ability of the material surface to resist the indentation of hard objects. The Leeb hardness Hl and Shore hardness HS belong to the rebound hardness test, and their values ​​represent the magnitude of the work of metal elastic deformation. Therefore, hardness is not a simple physical quantity, but a comprehensive performance index that reflects the elasticity, plasticity, strength and toughness of the material.

1.HRC means Rockwell hardness C scale,

2.HRC and HB are widely used in production

3.HRC applicable range HRC 20-67, equivalent to HB225-650.
If the hardness is higher than this range, use Rockwell hardness A scale HRA.
If the hardness is lower than this range, use Rockwell hardness B scale HRB.

The upper limit of Brinell hardness is HB650, which cannot be higher than this value.

4. The indenter of Rockwell hardness tester C scale is a diamond cone with a vertex angle of 120 degrees. The test load is a fixed value, and the Chinese standard is 150 kgf.

The indenter of Brinell hardness tester is a hardened steel ball HBS or a carbide ball HBW. The test load varies with the diameter of the ball, ranging from 3000 to 31.25 kgf.

5. The indentation of Rockwell hardness is very small, and the measured value is localized. It is necessary to measure several points to find the average value. It is suitable for finished products and thin slices and is classified as non-destructive testing.

The indentation of Brinell hardness is large, and the measured value is accurate. It is not suitable for finished products and thin slices, and is generally not classified as non-destructive testing.

6. The hardness value of Rockwell hardness is an unnamed number without a unit. Therefore, it is incorrect to call Rockwell hardness as a certain degree.

The hardness value of Brinell hardness has a unit, and it has a certain approximate relationship with tensile strength.

7. Rockwell hardness is displayed directly on the dial or digitally. It is easy to operate, quick and intuitive, and suitable for mass production.

Brinell hardness requires the use of a microscope to measure the indentation diameter, and then look up the table or calculate, which is cumbersome to operate.

8. Under certain conditions, HB and HRC can be interchanged by looking up the table.

Hardness test is the simplest and most feasible test method in mechanical property tests. In order to be able to use hardness tests instead of certain mechanical property tests, a more accurate conversion relationship between hardness and strength is required in production.

Practice has shown that there is an approximate corresponding relationship between the various hardness values ​​of metal materials and between the hardness values ​​and strength values. Because the hardness value is determined by the initial plastic deformation resistance and the continued plastic deformation resistance, the higher the strength of the material, the higher the plastic deformation resistance, and the higher the hardness value. (end)