THE MANUFACTURE OF ROCKWELL HARDNESS STANDARD BLOCKS IN BRAZIL

In the present work, the heat treatments used during production of national Rockwell hardness standard blocks, in the ranges of 60-80 HRB, 85-100 HRB, 20-30 HRC, 35-55 HRC and 60-70 HRC as well as their resulting microstructures are presented. Two kinds of steels with different contents of carbon and a very low level of impurities were used in the manufacturing process of the blocks. The microstructural changes were studied by means of optical microscopy analyses. The hardness measurements were carried out in hardness tester machines belonging to the Brazilians institutions involved in the present study. Preliminary results suggest that the heat treatment parameters influence directly on the microstructural homogeneity and stability and consequently on the uniformity of hardness values.