Brinell test is a method used to determine the hardness of metals in forming operations using a spherical indenter. It mostly tests materials with coarse structures or those with rough surfaces that cannot be tested using any other method. This testing method leverages high test loads of about 3000 kgf and a diameter indenter of 10mm. This ensures that the indentation averages both the sub-surface and surface inconsistencies of Brinell hardness (HBW). The selection of the ball diameter has to be done in a way that allows the indent to cover the largest portion of the working area as defined by ISO 6506 and ASTM E10 standards. Resulting impressions from the application of the encoded test load to fixed measurements of carbide ball is measured with an optical system of a Brinell microscope.
The Test Method
Most errors in a Brinell test result from indentation measurements. This is due to operator disparities, meaning that results can still vary even in the most suitable situations. In worse cases, the variations can be more pronounced. Most times, when getting the testing surface ready, a grinder is used to get rid of the surface conditions. It has serrated edges, which can create ambiguous indentation when interpreting. In the past years, two technologies have been developed to help in countering errors in Brinell measurements. One of them is the B.O.S.S system, which uses image analysis to interpret indentations consistently. The other is Brinell units, which rely on ASTM E103 in measurements. This one gives repeatable outcomes. The only drawback of this testing method is that the indent size must be measured optically, meaning that the test point has to be completed well for accurate measurements.