23
The BHN can be converted into the ultimate tensile strength (UTS), although the relationship is
dependent on the material, and therefore determined empirically. The relationship is based on
Meyer's index (n) from Meyer's law. If Meyer's index is less than 2.2 then the ratio of UTS to
BHN is 0.36. If Meyer's index is greater than 2.2, then the ratio increases.
BHN is designated by the most commonly used test standards (ASTM E10-08[2] and ISO 6506–
1:2005[3]) as HBW (H for hardness, B for Brinell and W for the material of the indenter,
tungsten carbide. In former standards HB or HBS were used to refer to measurements made
with steel indenters. HBW is calculated in both standards using the SI units as
8. 1 Technical Data for Hardness Evaluation
8.1.1 The degree of loading 1.02F/D² is important because different results can be obtained
depending on which degree of loading was used.
For example: a Brinell hardness value determined with a 10 mm ball and 9,807N (degree of
loading 10) for a material is different from the hardness value determined with a 10 mm ball
and 4,903N (degree of loading 5).
However, if the same material is measured with a 2.5 mm ball and a total test load of 612,9N
(degree of loading 10) the resulting hardness value is the same as in the first measurement
because the degree of loading is the same (provided that the material is homogeneous and has
no layers of different hardness’).
0.24D
＜
d
＜
0.6D
(d - dent diameter, D – ball diameter)
