Brinell Hardness Test in a Foundry

Hi,
I was asked a question in my materials testing class about why a
foundry making castings would prefer to use a Brinell Hardness test
rather than any of the Rockwell Hardness Tests. To me, it seems like a
foundry would rather use the Rockwell Hardness tests because they are
the most common and they require no special skill to perform. They are
also relatively simple and inexpensive. The only reason I could think
of is that the Brinell Hardness Test tests a wider range of materials
(softer and harder), whereas with the Rockwell tests, one would have to
switch scales depending on the hardness of the material.
Can anyone think of a reason a foundry making castings would rather use
the Brinell Test?
Maybe it has something to do with Heat?
Or how they make the castings?
Thanks!
--rikki
Reply to
Erica Moser
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Rikki,
Brinell is used in foundries for several reasons -
1. Portable indentors are readily available (Kings, Foundrax etc), 2. Brinell is more versatile, in that you can test a wide range of materials with the one scale, 3. Brinell tests a larger area, so a good average bulk hardness value is obtained (especially for irons with free graphite), 4. Less sensitive to surface preparation than Rockwell, 5. Brinell machines tend to be more robust in the rough & tumble of foundry life.
While Brinell does take a bit longer and requires a bit more skill than Rockwell, Rockwell does have issues of its own, especially if the test piece moves during preload. Whatever testing is done requires a certain amount of skill.
Hope this helps.
Simon
Reply to
Simon Kay
Not exactly correct!
Brinell is the *only* hardness test that is usable when measuring the hardness of materials with inhomogen or coarse structure, as for instance cast iron (and other cast materials).
Here you need bigger indenting areas, to get a representative "average value reading", which is what you're interested in. Rockwell measurements can give much different readings/results on the same specimen.
Med venlig hilsen / Best regards Martin Jørgensen
Reply to
Martin Jørgensen
In terms of ease of use Brinell has an advantage in portability. The comment on Brinell's suitability for coarse structures is also true.
However there is one simple reason why a foundry will use Brinell rather than Rockwell. The standard / customer tells them to do so. You can wish all you want, but if the order calls for Brinell you cant just go and use Equotip for instance.
Reply to
David Deuchar
I can see that it uses a steel ball, ø1/16" = 1.5875 mm (diameter) and that the main load should be 90 kp = 882,6 N. It can be used from 20-100 HRB.
Comparing HRB with Brinell:
Ball diameter can be 1, 2, 2.5, 5 or 10 mm, which is a lot more. So, the problem with Rockwell according to my information, is that you need the ball to be bigger. I have a book in danish with a chapter called "Brinell test". The first sentence is: "Brinell testing is the only hardness test that is applicable for materials with inhomogen or coarse structure as cast iron and other cast materials, where big indenting areas are required to get a representative average hardness value."
So I assume this explanation is correct unless somebody else has other information that says something else.
Med venlig hilsen / Best regards Martin Jørgensen
Reply to
Martin Jørgensen
Thanks for looking!
Fine. The standard in german foundries ist 2.5mm. That is considerably bigger than in HRB.
Michael Dahms
Reply to
Michael Dahms
Hey, -no fair- using the W word without an explaination. :/ (I might be wrong about that tho;)
Alvin in AZ
Reply to
alvinj
Very rude - why wrong? I've used both, and Rockwell is more sensitive. I find it needs a much finer ground finish to give representative results in a real world situation.
Reply to
Simon Kay
Perhaps he is only aware of the smaller diameter Brinell tests. While I have not used all the Rockwell tests, I am not aware of any that could be used on the surface preparation used for 10 mm Brinell. If any one knows better I would like to know.
Reply to
David Deuchar
Rockwell was invented in order to be able to test the hardness of a rough surface. For Brinell, the surface must at least be ground.
Michael Dahms
Reply to
Michael Dahms
Generally we use HRc for testing induction hardened case depths and when testing, the samples are milled parallel and the test area is surface ground. There are every few items I would Rockwell test without extensive surface preparation. One of the primary reasons for using Brinell is casting size. There is only a small number of castings that we purchase that would fit on a standard Rockwell machine. Thus the extensive use of King portable brinell testers as well as hydraulic brinell units mounted to old radial arm drill presses and such. Michael McKean
Michael Dahms wrote:
Reply to
Michael Mckean
I would disagree with that statement. From my experience hardness testing materials over the past 35 years, the preparation required for a surface to be tested using Rockwell B-scale hardness measurement procedures (1/16" diameter ball indenter) is much more extensive than that required for Brinell testing, using an applied load of 500, 1500 or 3000 Kg.
Regards,
Greg
Reply to
greg

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