What are the key points of hardness test of 45 Quenched And Tempered Steel

The hardness test of 45 quenched and tempered steel has the following points:

Test method selection: Commonly used tests include Rockwell hardness test, Brinell hardness test and Vickers hardness test. Rockwell hardness test is easy to operate and efficient, and is suitable for mass-produced parts; Brinell hardness test results are relatively accurate and can reflect the average hardness of the material, but the indentation after the test is large, and it is not suitable for thin parts or parts with high surface accuracy requirements; Vickers hardness test has high accuracy and can be used for various materials and parts of different sizes and shapes, especially for studying the relationship between material microstructure and hardness, but the test process is relatively complicated.
Sample preparation: The surface of the sample should be flat and smooth, without defects such as oxide scale, oil stains, cracks, etc. The roughness of the test surface should generally not be greater than Ra0.8μm to ensure the accuracy of the test results. At the same time, the thickness of the sample should meet the test requirements, generally not less than 10 times the indentation depth, otherwise the test results will be inaccurate due to the thin sample.
Test operation: During the test, the hardness tester should be placed vertically and stably on the sample surface to ensure that the indenter is perpendicular to the sample surface. The loading load should be accurate and stable, and the loading and unloading speeds should meet the standard requirements of the corresponding hardness test method. For Rockwell hardness testing, pay attention to the order of application and holding time of the initial load and the main load; for Brinell hardness testing, the appropriate indenter diameter and load should be selected according to the material hardness and sample thickness; for Vickers hardness testing, the load and loading time should be precisely controlled.
Data processing: Each sample should be tested at multiple points in different parts, generally not less than 3 points, and the average value should be taken as the test result. If the hardness value of the test point deviates too much, the cause should be analyzed and retested. At the same time, the hardness value and test position of each test point should be recorded to analyze and trace the test results.
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