Learning about Magnet Grades and Magnet Tables

Each day, we field inquiries about magnetic materials and their variations. There are many different grades of magnets available, and picking the right one depends on the application. This is especially true for Neodymium Magnets, Samarium Cobalt (SmCo) Magnets, Ceramic Magnets, Alnico Magnets, Bonded Magnets, and Injection Molded Magnets.

The purpose of this page is to clarify the distinctions between magnet grades and to provide a streamlined explanation of how magnets are classified. Neodymium magnets (NdFeB) and samarium cobalt (SmCo) magnets, the two strongest rare earth magnets currently on the market, will be our main emphasis.

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First Things First – Filling Out The Application

When assisting customers in selecting a magnet, we will naturally inquire as to the intended use. This provides crucial context for assessing the magnet’s needs and operating conditions. Concerns over privacy and confidentiality prevent almost half of our clients from publicly announcing their use of our software. If that’s the case, we’ll have questions like, “At what temperature would the magnet operate at its peak performance?”

Will the magnet be located near any other materials, and if so, what kinds of materials are they?

If the magnet were to be placed there, how big would that region be?

How strict must the standards be?

Does the magnet work as part of a larger assembly or does it have its own mechanism?

Is there a certain type of coating that must be used?

These are just a few examples of the many possible inquiries we may make in regards to software configuration and available features.

There are a variety of quality levels of both neodymium magnets and samarium cobalt magnets. While there are many aspects and considerations that go into design, the focus of this post will be on magnets and how to choose the best magnet for your application.

The Force of a Magnet

The maximum energy density of a magnet, or BHmax, is a magnet specification that indicates the magnet’s strength. Measured in Mega Gauss Oersteds (MGOe). If you look at a graph of a magnet’s energy product vs its magnetic field strength, you’ll see that its greatest strength occurs at this position on the graph.

The maximum allowable BHmax for neodymium (NdFeB) magnets is typically between 30 and 55 MGOe. It is important to remember that the greater the number, the stronger the magnet, when defining your magnet requirements. MGOe produced by neodymium magnets is the highest of any permanent magnet material. N35, N38, N40, N42, N45, N48, N50, N52, and N55 are the most popular Neodymium magnet grades.

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The (BH)max for Samarium Cobalt (SmCo) Magnets is between 16 MGOe and 32 MGOe. Simply said, as with neodymium magnets, a greater value indicates a more powerful magnet. Samarium-cobalt magnets often come in grades 16, 18, 20, 22, 24, 26, 28, 30, and 32. The MGOe values for neodymium magnets are greater than those for samarium cobalt magnets, proving that the former are more powerful.

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Magnet Coercivity

Coercivity, or the “Hci” of a material, needs to be defined first. You can see what’s out there in terms of magnet-receptive materials by consulting a magnet table. Some of the grades are followed by letters other than those used for the others. These symbols stand for the magnet’s resistance to demagnetization brought on by temperature or other magnetic influences. We shall focus on the most common method, the writing system, through which makers and suppliers of permanent magnets specify the coercive force. After the grade, the next letters (M, H, SH, UH, EH, and TH) indicate the magnets’ specifications for resisting demagnetization forces.

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Use of a letter after a magnet grade implies that the material has a stronger resistance to demagnetizing forces. Since heat is the most prevalent force affecting a magnet, we will use it as the demagnetizing force for our purposes. the following examples are meant to illustrate “generic rules,” not “hard and fast” regulations. A more in-depth explanation can be found below. Considerations.

For example, if a neodymium magnet’s strength rating is N (for either N38 or N45) or N (for N52), but there is no letter after the grade number, then it can only be used in temperatures no higher than 80 degrees Celsius. If a magnet’s designation ends in “M” (as in N35M, N42M, etc.), it can often withstand temperatures up to 100 degrees Celsius. A material with a “H” rating can withstand temperatures up to 120 degrees Celsius, a “SH” up to 150 degrees Celsius, a “UH” up to 180 degrees Celsius, a “EH” up to 200 degrees Celsius, and a “TH” up to 220 degrees Celsius. Again, these are broad guidelines, and particular circumstances will always call for more or less force.

See also An Ultimate Guide To Neodymium Magnets

Powerful Factors to Think About

As a result, why not always aim for maximum potency? For the simple reason that having the most power isn’t always the best option. When employed as a sensor magnet, for instance, a magnet may need to generate a very certain magnetic field at a very particular distance. The specifications for the sensors will specify this area. If a neodymium N52 is used when a samarium cobalt 24 is required, the sensor may not function properly. Similarly, motors are a commonplace example. While windings made of N48 material may work great for a motor, those made of N55 may cause it to overheat. It’s also possible that a stronger magnet would suffice in a holding application where a lesser quality material would fail. When selecting a magnet, it is helpful to have a sense of the desired pull or holding strength, the required magnetic field strength, and the saturation point of the surrounding materials.

Cost

In most cases, the topic of cost will come up. It’s a rule of thumb that the higher the quality, the more you’ll have to pay. While factors such as size and shape also have a role in pricing, we can simplify things by saying that a higher quality item will cost more. Additionally, in accordance with this guideline, the greater the value of the letter after the grade. In this case, the N48H will be a little more expensive than the N48. The N48SH will cost more than the N48H, and so on. Finally, if a higher letter is chosen, even a poorer quality material will cost more. For comparison’s sake, a N42UH will probably cost more than a N45 or N52.

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Application

As was said in the introduction, it is possible that we will not always know the ultimate use. In some cases, a lower quality magnet may suffice because it can be used in conjunction with other materials or even additional magnets to better impact the field. Having a highly concentrated magnetic field is a different topic with a lot of nuance, but if you need one, get in touch with us and we’ll help you figure it out, even if we don’t know the specifics of the application.

Magnet Dimensions and Outline

We have employed “generic norms” of strength and coerciveness in the preceding cases. There are always recursive influences at work in any engineering notion. The role of the magnet is also affected by its size and shape. A very thin N45H, for instance, may be rated for use at temperatures up to 120 °C; but, if the magnet’s size or form is exceedingly small, it may be preferable to use an N45SH material. If the magnet’s size and shape are problematic, we can examine whether or not it is possible to use other materials in conjunction with it while maintaining its coercivity.

A Grade Is Not a Grade Is Not a Grade Equal

Considering the costs and benefits of using permanent magnets is a necessary step. The preceding data suggests that you may have to prioritize either strength or coercivity. Or, whether neodymium magnets are preferable to samarium cobalt magnets. The use of Br and the use of Hcj both have their costs and benefits. It’s possible that the coercive force (Hcj) in a magnet won’t be accessible as you increase your magnet grade. For instance, a magnet that operates at 180 degrees Celsius requires a UH material because of its high thermal resistance. You can consult with a technical magnet expert to find out which magnet will work best for your needs. 

What you need to know about Tengye Magnetic: Permanent magnets, magnetic design and optimization, engineering support, and production are all services offered by Tengye Magnetic, a Chinese leading neodymium magnet manufacturer.