To make a true Brinell test using a floor-standing or bench-mounted Brinell hardness tester, according to the requirements of ISO 6506 or ASTM E10-18:
Setting up equipment for Brinell hardness testing
Make sure the equipment is properly set up. In most instances this involves keeping the test machine serviced and calibrated in accordance with the Standards and the manufacturer’s instructions (whichever are the stricter) along with mounting it on a level, vibration-free surface. It is worth noting that, for tests made using portable Brinell hardness testers that apply the full test load, (albeit without the ability to maintain it uninterrupted for the full ten seconds), whilst it is not necessarily possible to mount the machine on a sold and level surface, the rest of the advice still applies.
If the anvil is attached to a column, ensure that it is screwed tight / secured. Similarly, jigs should be in good condition, properly mounted and hold the test piece securely. It is easy to become blasé about the amount of energy that goes in to applying 3000 Kg to a 10mm ball, but if the component shatters under load the results can be dramatic and, potentially, very dangerous.
Of course, before handling heavy samples, ensure you are wearing safety boots!
Use the correct force-diameter index (F/D²) for the material being tested:
MATERIAL HARDNESS LEVEL F/D²
Steel, nickel alloys, titanium alloys 30
Cast iron <140 10
>140 30
Copper and copper alloys <35 5
35-200 10
>200 30
<35 2.5
5
Light metals and their alloys 35 – 80 10
15
>80 10
15
Lead tin 1
Sintered metal ACCORDING TO ISO 4498
Preparing material for Brinell hardness testing
The area of the component where the test is to be carried out must be prepared in order that the indenter will come into direct contact with the core material. For this the skin must be removed and so must any de-carburised layer. This can be done using a hand grinder with 60 grit abrasive (or finer if appropriate) in 3-5 seconds if a good, automatic Brinell microscope is going to be used to measure the indentation or 10-15 seconds if a good manual microscope will be used. This time differential is on the basis that a good automatic system will measure hundreds of diameters and ignore grinding “noise” when defining the true edge of the indentation, whereas an operator is limited to the number they can reasonably measure in the time available and with the equipment to hand, but in both cases, the better the surface, the better the result.
Place the material on the test machine’s table or anvil and ensure that it is stable and cannot move under the test load (ideally, machines with an integral clamp are preferable from this point of view). Moreover, the clamp must hold the material in such a position that the line of operation of the indenter is as perpendicular to the test surface as possible.
Carrying out the Brinell hardness test itself
Apply the test force in accordance with BS EN ISO 6506-1. While the indenter is in downward motion and in contact with the material, avoid doing anything that might create vibrations that could reach the machine. When the indenter has withdrawn, measure the resulting indentation in a minimum of two diameters perpendicular to each other and convert the mean measurement into an HBW number (note: if using a portable Brinell hardness tester, caution should be exercised when removing the machine from the component so that the edge of the indentation is not accidentally damaged when the machine is released). There is a diameter to hardness conversion chart here.
Important: Before performing a Brinell hardness test make sure both the test area and the indenter ball are clean and, in particular, free of all lubricants. Any lubrication of the test surface or indenter will invalidate the test because it can lubricate the path of the indenter and therefore make a very significant difference to the apparent hardness level. For example at 300 HBW the material may appear around 20 HBW softer than it actually is.
If you have any questions about performing the Brinell test, or if we can help in any further way, please contact sales@foundrax.co.uk or call +44 1458 274888.
