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SECTION 8. BRINELL TESTING BASICS
Hardness Testing provides useful information, which can be correlated to tensile strength, wear
resistance, ductility, and other physical characteristics of the material. Hardness testing is
therefore useful for monitoring quality control and for aiding in the materials selection process.
BRINELL HARDNESS (ASTM E10, ISO 6506)
To determine a Brinell hardness number (BHN), a 10 mm diameter steel ball is typically used as
an indenter with a 3,000 kgf (29 kN) force. For softer materials, a smaller force is used; for
harder materials, a tungsten carbide ball is used. The BHN can also be converted into the
ultimate tensile strength (UTS), although the relationship is dependent on the material, and
therefore is only an empirically based value.
Hardness testing is accomplished with a ball of specified diameter (D) being pressed by a
specified force (F) into surface of the object to be tested (see figure below). The test force is
removed after holding for a specific period of time (dwell time). The indent diameter (d) is
measured with an optical manual microscope and the average pressure (N/mm2) acted on
spherical surface can be calculated as a hardness value.
The indentation is measured and hardness calculated as:
F
D
d
h
where:
HB – HBW (kgf/mm2)
P = applied force (kgf)
D = diameter of indenter (mm)
d = diameter of indentation (mm)
