GB/T 24523-2020 in English

Test principles and technological changes

This method uses a tungsten carbide alloy ball indenter to press into the material surface under a specific test force, and measures the indentation depth to convert it into the Brinell hardness value. Compared with the 2009 version, the main technical changes include:

• Delete 7 old regulations such as initial test force and test temperature
• Add determination of hardness extreme value (Chapter 9)
• Add factors affecting measurement accuracy (Chapter 10)
• Optimize hardness tester calibration process (Appendix A)

Automotive gear heat treatment detection

A gearbox manufacturer uses a fast Brinell hardness tester with a 3000kgf test force to conduct furnace pre-inspection on 20CrMnTi gears:

1. Maintain the verticality of the pressure head ≤1° as required by Clause 8.3
2. Use the daily inspection procedure in Appendix A.5 and verify with HRC55-58 standard blocks every day
3. Determine the qualified range as 180-220HBWT according to the method in Chapter 9

After implementation, the detection efficiency increased by 300% and the misjudgment rate dropped to below 0.5%.

Main error sources and countermeasures

• Initial test force deviation: Use a hardness tester calibrated by A.3.2 (tolerance ±1%)
• Indentation depth error: Ensure that the accuracy of the measuring device reaches ±0.05% of the indenter diameter (A.3.3.2)
• Temperature influence: The test environment temperature is recorded to 1°C (A.2.2)

It is recommended to use standard hardness blocks regularly for indirect testing (cycle ≤12 months) to ensure the accuracy of the conversion formula.