Brinell Hardness Test
Dr. J. A. Brinell invented the Brinell test in Sweden in
1900. The oldest of the hardness test methods in common use today, the Brinell
test is frequently used to determine the hardness of forgings and castings that
have a grain structure too course for Rockwell or Vickers testing. Therefore,
Brinell tests are frequently done on large parts. By varying the test force and
ball size, nearly all metals can be tested using a Brinell test. Brinell values
are considered test force independent as long as the ball size/test force
relationship is the same.
In the USA, Brinell testing is typically done on iron and
steel castings using a 3000Kg test force and a 10mm diameter carbide ball.
Aluminum and other softer alloys are frequently tested using a 500Kg test force
and a 10 or 5mm carbide ball. Therefore the typical range of Brinell testing in
this country is 500 to 3000kg with 5 or 10mm carbide balls. In Europe Brinell
testing is done using a much wider range of forces and ball sizes. It's common
in Europe to perform Brinell tests on small parts using a 1mm carbide ball and
a test force as low as 1kg. These low load tests are commonly referred to as
baby Brinell tests.
STANDARDS
Brinell Test methods are defined in the following standards:
ASTM E10
9SO 6506
BRINELL TEST METHOD
All Brinell tests use a carbide ball indenter. The test
procedure is as follows:
- The indenter is pressed into the sample by an accurately controlled test force.
- The force is maintained for a specific dwell time, normally 10-15 seconds.
- After the dwell time is complete, the indenter is removed leaving a round indent in the sample.
- The size of the indent is determined optically by measuring two diagonals of the round indent using either a portable microscope or one that is integrated with the load application device.
- The Brinell hardness number is a function of the test force divided by the curved surface area of the indent. The indentation is considered to be spherical with a radius equal to half the diameter of the ball. The average of the two diagonals is used in the following formula to calculate the Brinell hardness.
Brinell Formula
The Brinell number, which normally ranges from HB 50 to HB
750 for metals, will increase as the sample gets harder. Tables are available
to make the calculation simple. A typical Brinell hardness is specified as
follows:
356HBW
Where 356 is the calculated hardness and the W indicates
that a carbide ball was used. Note- Previous standards allowed a steel ball and
had an S designation. Steel balls are no longer allowed.
APPLICATIONS
Because of the wide test force range the Brinell test can be
used on almost any metallic material. The part size is only limited by the
testing instrument's capacity.
Strengths
One scale covers the entire hardness range, although
comparable results can only be obtained if the ball size and test force
relationship is the same
A wide range of test forces and b all sizes to suit every
application
Nondestructive, sample can normally be reused
Weaknesses
The main drawback of the Brinell test is the need to
optically measure the indent size. This requires that the test point be
finished well enough to make an accurate measurement
Slow. Testing can take 30 seconds not counting the sample
preparation time
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