How to choose permanent magnet?

Neodymium Magnets 07/23/2020

1. Decide the shape and size of magnets, which can server you applications best.

The properties of the magnet will differ greatly according to the size and shape (Disc, Cylinder, Block & Bar, Cube, Ring & Tube, Sphere & Ball, Arc & Wedge, Other). Take into consideration whether the magnet will fit in the object in which you wish to place it, whether the magnet is too thick or too thin, and then select the size which would be easiest to handle. For round neodymium magnets, we have a wide range of Dia.\Thick from 1/32inch to over 3inch in diameter.

2. Choose Permanent Magnet Materials

The major types of magnets are neodymium magnets, ferrite magnets, samarium cobalt magnets and alnico magnets. Each type has different characteristics. Please check the differences in properties in order to select a suitable magnet for your usage.

Permanent Magnet Material Comparison

Material Cost Index Maximum Energy Products
(BH)max(MGOe)
Coercivity 
Hci(Koe)
Maximum Working 
Temperature(°C)
Machinability
Nd-Fe-B(sintered) 65% Up to 45 Up to 30 180 Fair
Nd-Fe-B (bonded) 50% Up to 10 Up to 11 150 Good
Sm-Co (sintered) 100% Up to 30 Up to 25 350 Difficult
Sm-Co (bonded) 85% Up to 12 Up to 10 150 Fair
Alnico 30% Up to 10 Up to 2 550 Difficult
Hard Ferrite 5% Up to 4 Up to 3 300 Fair
Flexible 2% Up to 2 Up to 3 100 Excellent

TableNote: The data listed in the table are for reference only.

Material properties of neodymium magnet

Magnet Element symbol Name of element Advantages Disadvantages Usage
Neodymium NdFeB Neodymium
Iron
Boron
This is the strongest magnet that currently exists. It has high mechanical strength. Recently it is high in demand. We can make these magnets even in small lots It rusts easily so must be surface treated. Usually it is nickel plated. The price of rare earthes, the raw material used, is soaring. Hard disk, MRI, hybrid automobiles
Ferrite Fe2O3
BaCO3
or
SrCO3
Ferric oxide
barium carbonate
or
strontium carbonate
This low cost raw material is suitable for use in high volume production. Anisotropic ferrite is practical because it has relatively good adsorptive power. Not suitable for prototypes in small lots because a metal mold may be necessary. Speakers, monitors
Samarium cobalt SmCo Samarium
Cobalt
It has excellent coercivity and is suitable for use in high temperature environments. It is brittle and chips easily. The price of rare earthes, the raw material, is soaring. Motors
Alnico AlNiCo Aluminum
Nickel
Cobalt
It has excellent mechanical strength and is suitable for use in high temperature environments. Recently the demand is low and in most cases metal molds are required because they are manufactured through a casting process. It demagnetizes easily even when exposed to repelling magnetic fields. Precision machines
Horse shoe (U) shaped
compass
Rubber magnet sheets  CM Chlorinated Polyethylene It is made from a mixture of resin and ferrite magnet powder, is flexible and can easily be machined to your desired shape. It is made from a mixture of resin and ferrite magnet powder, is flexible and can easily be machined to your desired shape. Learner driver decals
Protection for elevators etc

3. Choose a Grade -> (Magnet Grade)

Selecting a grade is the next step, once you have decided which permanent magnet material is best for your application. Generally, a grade indicates the Maximum Energy Product of a magnet. For instance, Grade 32 implies the (BH)max is about 32 MGOe. A higher grade of permanent magnet has a better performance. However, higher grade is usually associated with a higher cost. Taking sintered Nd-Fe-B magnets as an example, the price of Grade 45 is twice and even more of that of Grade 33. Other property parameters, such as Br and Hci, also need to be considered in selecting a grade. One way to select the suitable grade for your application is 'trial and error'. You can purchase the several magnets with different grades (some suppliers have these magnets available on their shelves) and try each grade until you find one right for your application.

4. Submit your inquiry
After decide the magnet specification, you can submit the inquiry via Inquiry page or Custom Magnets page, we will receive your request and provide you with our price quotation. You can also email us at sales@albmagnets.com with your specifications and drawings directly.

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How to choose and buy a strong neodymium magnet? ALBMagnets is a professional company for strong magnet design and manufacturing,
providing you with reliable N35, N38, N42, N52, N42SH and other grade super neodymium magnets and SmCo rare earth magnets.

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