Property that permits magnetism

[Nellysdad]

I believe the property required in a material that permits a desired level of magnetism is called "permeability", but I have also heard "permittivity" used.
Is there a way to measure a raw material to define if it is suitable for magnetizing to a certain Gauss level.
We have some magnets that are not reaching our desired 13000 gauss but stop short at 9000. there are others in the same batch that are fine and we have tested our equipment so we suspect the material. If it is possible, we would like to test some of the rogue parts for this property.
Any feedback is welcome.
Regards

 

[EdStainless]

What material?
It may be composition, or heat treatment, or fabircation.

There is no test to tell you if a material can be made into a 'good' magnet, only the testing of the magnet will tell you.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[IRstuff]

permittivity:

Etymology: 1permit + -ivity (as in selectivity)
: the ability of a dielectric to store electrical potential energy under the influence of an electric field measured by the ratio of the capacitance of a condenser with the material as dielectric to its capacitance with vacuum as dielectric -- called also dielectric constant

from

http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=permittivity

TTFN

 

[Nellysdad]

Sorry,
sorry, the material is neodymium.
I cannot believe that there is no test whatsoever. There must be a some way of measuring whatever property it is that Magnetism has an affinity for.
I agree, the processing of the magnet shape and form is critical but there has to be a method of testing pre-magnetize. Thankyou for the feedback though,
regards

 

[MagMike]

Permeability is a measurement of how much a magnetic material will respond to an applied magnetic field. Sometimes people use the term "permittivity" in place of "permeability" but that is not accurate.

For all Neodymium-Iron-Boron magnets, the permeability is very close to 1 under most operating conditions.

The most effective way to check the quality of a given batch of magnetic material is to magnetize it. I realize you are looking for some kind of secondary test, but so many variables play a role (chemical composition, chemical distribution, powder particle size, porosity, grain structure, alignment field during processing, dimensions of the part, etc.)in determining magnetic behavior, the only certain method is to magnetize.

Have you checked with your supplier about this? Could you return some of the magnets that produce 9000 Gauss? If you can't or don't want to have them tested by your supplier, there are independent testing houses that you can send them to.

 

[sreid]

I would change suppliers or demand that your current supplier ship material from a qualified, reliable source. I believe there is still some real junk comming out of China (but there are some excellent suppliers in China).

 

[EdStainless]

Each lot of raw material is quailified by making magnets out of it. There is no magic test.
But, finished magnets should always meet the expected quality. There is no excuse for that.

Are you sure that you are fully saturating these at magnetization?

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[Clyde38]

Magnetic material analysis can be obtained from companies such as Walker Scientific Inc. I have not used there services for quite some time, but they would provide Magnetic Hysteresisgraphs for the material you provide. This is basically a four quadrant hysteresis curve for the material supplied. The also sell the equipment to do this in house. Somewhat expensive though. Another method for cheking is the Helmholtz coil after magnetizing your material. I'm not sure this is what your after so I hope it helps.

 

[MagMike]

Hello Nellysdad,

Just been wondering: Has there been any clarification (either from your supplier or from further testing) about why some of the magnets in your batch were only producing 9000 Gauss?

 

[RHMagster]

Hello Nellysdad,

MM brings forth a good point, material alignment maybe the culprit here. I have experienced similar and found with testing that the alignment of the material was skewed.

You can check for this with a 3 point Helmholtz coil measurement if design of cicuit allows. Of course saturation, if your system cannot deliver enough energy to the coil (or mag fixture).

Then also, it maybe a matter of receiving different grades of material. The Hci of NdFeB will determine its ease of saturation and generally, is converse of the level of Hci the material exhibits. ex. 30 K Oe material is easier to saturate vs. 14 k Oe material, if of the same geometry.

You may have enough energy to saturate the higher Hci material, only borderline, but not enough to saturate the lower Hci material.

Also, alternatively, if you are receiving two different grades of material ( an assumption brought to light in an earlier post) this of course would also give lower flux as Br and Hci are inversely proportional. To find this one would saturate samples, apply a knockdown field of such for the desired material, then measure the after effect level of flux from the samples. If there is considerable difference between the samples, say > 10% as an example, I would insist on an outside test of material properties such as mentioned by Clyde38.

Hope this helps