GB/T 21838.3-2008 For the calibration of standard blocks in metal hardness of materials and parametric instrumentation indentation tests. In the test, the standard block is the key to ensure the accuracy of the test. The standard specifies the type of standard block applicable, and elaborates the calibration process in detail, including the selection of appropriate calibration equipment and environmental conditions. Specify the key links in the calibration process such as loading force and displacement measurement, and specify the requirements and data processing methods for multiple measurements. Through rigorous calibration, ensure the accuracy and traceability of the standard block Hardness and related parameters, provide a reliable reference for the determination of metal hardness of materials and other parameters, and improve the overall test accuracy and data credibility.