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How to Select Material Grades for Neodymium Magnets?

Posted on April 27, 2017

Armstrong neodymium magnets 

When you are trying to figure out which neodymium magnets to select for your design needs, you would always see the term “grade” or “N rating” from any supplier or manufacturer. Besides a few other criteria, desired material grade must be defined for a neodymium magnet. So, what does it mean and how it would affect the result of your application?

The material grade is the Maximum Energy Product, (BH)max, or the maximum strength that such magnet material can be magnetized to. In other words, it correlates to the magnetic flux output per unit volume. It is measured in unit of million Gauss Oersted (MGOe), which is the product of attractive force (Gauss) and permanence of the force (Oersted) and is also equivalent to 7,958 kJ/m3. Generally bigger value indicates more powerful magnet. The grade is determined during the initial steps of neodymium magnet manufacturing. Based on the exact recipes of the rare-earth ingredients composition for each corresponding material grade, our factory precisely weigh, melt, crush, mill and thoroughly mix them.

The material grades begin with nomenclature “N” standing for neodymium magnets, and followed by a 2-digit value ranging between 24 and 52 with 52 being the most power magnetic strength option. (However, theoretically highest grade can go all the way to N64, but it is not yet achieved in production.) Sometimes it ends with letter(s) representing Intrinsic Coercivity (Hci) of the material which directly relates to its maximum working temperature. Available grades are grouped as: N35-N52 with no ending letter (80oC), N33M-N50M (100 oC), N35H-N48H (120oC), N30SH-N45SH (150oC), N30UH-N40SH (180oC), N28EH-N38EH (200oC) and N30AH-N33AH (220oC). (Degree Celsius) is the corresponding maximum working temperature each grade can withstand before the magnet irreversibly lose a fraction of its magnetic strength. For example, a N40SH neodymium magnet has 40MGOe and can tolerate working temperature up to 180 oC with Hci of >20KOe.

For all inquiries on custom magnets, we ask the customers to provide us the material grade they want. Higher grade and/or higher working temperature entail more costs in raw material and production, and buyers should take both the magnet cost and performance into consideration when placing their orders. Also keep in mind that the higher the grade the more brittle the magnet becomes, and the (BH)max is greatly dependent upon the magnet’s operational environment. For each set of custom neodymium magnets, we report their (BH)max value along with a set of tested parameters and confirm that all numbers are well within the ranges for its targeted grade. For chart detailing Neodymium magnet grades vs magnetic properties, please visit Neodymium Magnets Overview.