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Calibration Steps for Hardness Testers


A hardness tester is a hardness testing instrument. The measurement of metal hardness was first proposed by Ray Omr to define hardness, which represents the ability of a material to resist the pressing of a hard object into its surface. It is one of the important performance indicators of metal materials. Generally, the higher the hardness, the better the wear resistance. The hardness tester calibration test block is mainly used to calibrate the hardness tester. The error and repeatability of the hardness tester shall be within the range defined in the table below.


Ⅰ. Preparation before calibration of hardness tester


1. Before calibration, the calibration personnel should read the entire calibration operation specification and the description of the parts to be calibrated.


2. The calibrator should confirm that the required standard parts hardness measuring tools are within the validity period before calibration.


Ⅱ. The hardness tester correction steps


1. Wipe the standard hardness sheet with alcohol, dry it gently, and place it on the loading table of the hardness tester of the hardness tester.


2. Turn on the power switch of the hardness tester and observe the hardness sample with a 40x objective lens. Adjust the lift handwheel until a clear surface of the hardness test sample is observed from the eyepiece.


3. Press the start button to load the hardness test piece.


4. After removing the durometer, measure the diameter of the prism with a 40x objective lens according to the operation specification of the digital durometer. Read test data from the hardness tester screen and record the results in detail.


5. Carry out three tests according to the above steps, and record the results in detail.


6. Judge whether it is qualified according to the calibration standard of the hardness tester. Attach the corresponding calibration label: If the calibration result is unqualified, an exception handling order will be set; the device using the calibration tool will issue a maintenance request form and send it to the calibration device to apply for maintenance. If the calibration is still unsatisfactory after repair, the application of the scrapped instrument should be cancelled.


Ⅲ. Calibration method of hardness test of hardness tester


1. The standard block used for calibrating the hardness tester cannot be used on both sides, because the hardness of the standard surface and the back may not be the same. It is generally stipulated that the standard block is valid for one year from the date of calibration.


2. When replacing the indenter or anvil, pay attention to cleaning the contact parts. After the replacement, use a steel sample with a certain hardness to test several times until the hardness value obtained twice in a row is the same. The purpose is to press the indenter or the anvil and the contact part of the testing machine tightly, so as to avoid affecting the accuracy of the test results.


3. After the hardness tester is adjusted, when starting to measure the hardness, the first test point is not used. For fear of poor contact between the sample and the anvil, the measured value is inaccurate. In particular, after the first test is completed, the hardness tester is in the normal operating mechanism state and then the sample is formally tested, and the measured hardness value is recorded.


4. When the test piece allows, generally choose different parts to test at least three hardness values, take the average value, and take the average value as the hardness value of the test piece.


5. For the specimen with complex shape, the corresponding shape of the spacer should be used, which can be tested after being fixed. The round specimens are generally placed in the V-groove for testing.


6. Before loading, check whether the loading handle is placed in the unloading position. When loading, the action should be light 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 in a loaded state for a long time, causing plastic deformation and affecting the measurement accuracy.


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