Precautions For Using Commonly Used Hardness Testers

Precautions for commonly used hardness testers are as follows:
1. The hardness tester itself will produce two kinds of errors: one is the error caused by the deformation and movement of its parts; the other is the error caused by the hardness parameters exceeding the prescribed standards. For the second type of error, the hardness tester needs to be calibrated with a standard block before measurement. For the Rockwell hardness tester calibration results, the difference is qualified within ±1. A stable value with a difference within ±2 can give a correction value. If the difference is outside the range of ±2, the hardness meter should be calibrated and repaired or other hardness testing methods should be used. Each Rockwell hardness scale has an applicable range and must be selected correctly according to regulations. For example, when the hardness is higher than HRB100, the HRC scale should be used for testing; when the hardness is lower than HRC20, the HRB scale should be used for testing. Because the hardness value of the hardness tester is inaccurate outside its specified testing range, it should not be used. Other hardness testing methods also have corresponding calibration standards. The standard block used to calibrate the hardness tester cannot be used on both sides, because the hardness of the standard side and the back side are not necessarily the same. It is generally stipulated that the standard block must be used within one year from the date of calibration.
2. When replacing the indenter or anvil, pay attention to wiping the contact parts clean. After replacement, use a steel sample of a certain hardness to test several times until the hardness values obtained are the same twice in a row. The purpose is to press the contact part between the indenter or anvil and the testing machine tightly and ensure good contact, so as not to affect the accuracy of the test results.
3. After the hardness meter is adjusted, when starting to measure the hardness, the first test point is not used. Because of fear of poor contact between the sample and the anvil, the measured value will be inaccurate. After the first point test is completed and the hardness tester is in the normal operating mechanism, the sample is formally tested and the measured hardness value is recorded.
4. When the test piece allows, it is generally recommended to test at least three hardness values in different parts and take the average value as the hardness value of the test piece.
5. For specimens with complex shapes, cushion blocks of corresponding shapes should be used and fixed before testing. Round specimens are generally placed in a V-shaped groove for testing.
6. Before loading, check whether the loading handle is in the unloading position. When loading, the movement should be gentle and steady, and do not use too much force. After loading, the loading handle should be placed in the unloading position to prevent the instrument from being under load for a long time, causing plastic deformation and affecting the measurement accuracy.