1. Selection of Testing Instruments
Rockwell hardness tester (HRC): Suitable for testing the hardness of quenched steel (e.g., the hardness of 45# steel before heat treatment can reach HRC55~62).
Leeb hardness tester: Portable for on-site testing (e.g., LS252D model), supports rapid multi-point measurement, but attention should be paid to the influence of surface roughness.
Brinell hardness tester (HBW): For testing large-sized parts after tempering, the indentation diameter should be within the range of 2.5~3.0mm.
2. Operating Procedures
Surface treatment: Remove scale, decarburized layer, and burrs to ensure a smooth testing surface.
Measurement point distribution: Measure at least 3 points at each location, and the non-uniformity must meet the process requirements (e.g., HRC fluctuation ≤ ±2).
Calibration requirements: The hardness tester needs to be calibrated regularly to avoid overlapping indentations or edge effects.
3. Special Scenarios
Testing the core of thick-walled tubes: Use an ultrasonic thickness gauge (such as LS211) for auxiliary positioning; the core hardness may be 5-10 HRC lower than the surface.
Surface hardened layer: Vickers hardness method (HV) for layer-by-layer measurement; the critical value is usually 550HV.
