BHN is designated by the most commonly used test standards (ASTM E10-14 and ISO 6506–1:2005) as HBW (H from hardness, B from brinell and W from the material of the indenter, tungsten (wolfram) carbide). Brinell Hardness: Now abbreviated HBW. HBW Conversion Chart, Brinell Hardness, HRC, Rockwell Hardness. This chart shows you the approximate hardness conversion numbers for non- austenitic steels. Steel hardness conversion chart: Shows equivalents using Brinell, Rockwell B and C and Vickers scales. Now if you wonder why there is this W and what difference it makes in hardness value then lets explain it as below.