JJG 147 - 2017 is a standard metal Brinell hardness block verification specification. It specifies the scope of application, and describes various technical requirements of standard metal Brinell hardness blocks, such as hardness uniformity, stability and other indicators. Specifies the standard equipment, environmental conditions and other elements required for verification in detail. Specifies the specific items, operation steps and methods of verification, including the measurement and calculation of hardness value. At the same time, the processing of verification results, uncertainty evaluation, etc. are stipulated to ensure the accuracy and reliability of the Brinell hardness block value of standard metal, and provide a solid traceability basis for metal Brinell hardness measurement.