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Common classification and precautions for hardness testers
2024-05-23
Hardness tester classification
Leeb hardness tester, Rockwell hardness tester, Brinell hardness tester, Shore hardness tester, Shaw hardness tester, Babbitt hardness tester, microhardness tester, Mohs hardness tester, Vickers hardness tester, fruit hardness tester, cement hardness tester, etc.
Precautions for hardness tester
In addition to special precautions when using various hardness testers, there are also some common issues that should be noted, as listed below:
1. The hardness tester itself will produce two types of errors: one is the error caused by the deformation and movement of its parts; The second is the error caused by hardness parameters exceeding the specified standards. For the second type of error, the hardness tester needs to be calibrated with a standard block before measurement. The calibration results of the Rockwell hardness tester are qualified with a difference within ± 1. A stable value with a difference within ± 2 can provide a correction value. When the difference is outside the range of ± 2, it is necessary to calibrate and repair the hardness tester or replace it with another hardness testing method for measurement. The various scales of Rockwell hardness have a practical application range, and should 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 accuracy and sensitivity of the hardness tester are poor and the hardness value is inaccurate when it exceeds its specified testing range, it is not suitable for use. Other hardness testing methods also have corresponding calibration standards. The standard block used for calibrating the hardness tester cannot be used on both sides, as the hardness of the standard surface and the back may not be consistent. Generally, standard blocks are valid for one year from the date of calibration.
2. When replacing the pressure head or anvil, be sure to wipe the contact area clean. After replacement, it is necessary to test a steel sample with a certain hardness several times until the hardness values obtained are the same for two consecutive times. The purpose is to make the contact part between the indenter or anvil and the testing machine tightly pressed and in good contact, so as not to affect the accuracy of the test results.
3. After adjusting the hardness tester, the first test point is not used when starting to measure hardness. Due to concerns about poor contact between the sample and the anvil, the measured values may not be accurate. After the first point of testing is completed and the hardness tester is in normal operating mode, the sample will be formally tested and the measured hardness value will be recorded. Spot welding machine
4. If allowed by the test piece, at least three hardness values are generally tested on different parts, and the average value is taken as the hardness value of the test piece.
5. For specimens with complex shapes, corresponding shaped pads should be used and fixed before testing. Generally, circular specimens should be tested in a V-shaped groove.
6. Before loading, check if the loading handle is placed in the unloading position. When loading, the action should be gentle and stable, and not too forceful. 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 measurement accuracy.
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