GB/T 42670-2023 in English

1. Background and significance of the standard

GB/T 42670—2023 "Method for determination of Rockwell hardness of carbon materials" is an important standard for hardness testing of carbon materials. This standard specifies the principle, instrumentation, specimen preparation and test steps of Rockwell hardness determination, and is applicable to carbon materials with aggregate particles less than $0.8\mathrm{mm}$.

2. Principle of Rockwell hardness determination

The Rockwell hardness test characterizes the hardness of a material based on the change in indentation depth. The initial test force and the main test force are applied by a standard indenter, the residual indentation depth is measured, and the hardness value is calculated according to the formula:

Wherein, $N$ and $S$ are the full range constant and scale constant.

3. Instrument and Indenter Selection

Note: Different scales are suitable for different material hardness ranges. The specific selection should be determined according to actual needs.

4. Specimen preparation requirements

• Specimen thickness: The recommended size is $\phi35~\mathrm{mm}\times30~\mathrm{mm}$.
• Parallelism deviation: not more than $0.10\mathrm{mm}/100\mathrm{mm}$.
• Surface roughness: $R a\leqslant3.2\mu\mathrm{m}$.

5. Experimental steps and precautions

Before the test, ensure that the equipment is calibrated and the indenter is free of rust or scratches. During the test, the measurement should be repeated at least 5 times and the average value should be taken.

6. Implementation suggestions

To ensure the accuracy of the test, it is recommended that:

1. Strictly calibrate the equipment according to the standard.
2. Choose an appropriate Rockwell hardness scale.
3. Record the test conditions and result deviations.