标准硬度块 meaning in English

hardness standard block
standard block of hardness

Metallic brinell hardness test - part 3 : calibration of hardness reference blocks
金属布氏硬度试验第3部分:标准硬度块的标定
The indirect verification is performed by comparing the values indicated by the hardness testing machine with values of the standard hardness blocks at three points within the working range of the hardness testing machine
间接校正是在其硬度机的工作范围，从硬度机测试三块不同硬度的标准硬度块的显视数值与标准硬度块的数值作出比对。