How Are Neodymium Magnets Made?
Magnetism may interact with the Earth’s natural magnetic field, however, today’s magnets are not formed naturally. One of the only naturally occurring magnets is lodestone, but its magnet strength is too weak for use in practical applications. Modern magnets are much stronger, because they are created from alloys of ferromagnetic metals, which include: iron, nickel, cobalt and a few others. Ferromagnetism actually means the ability for certain materials to be magnetic or magnetized.
These ferromagnetic metals form alloys that then become the different types of permanent magnets. Four of the most common permanent magnets are:
- Neodymium (NdFeB:neodymium-iron-boron)
- Samarium-Cobalt (SmCo)
- Alnicos (aluminum-nickel-cobalt)
The magnet-making process may vary slightly depending on the type of permanent magnet. Neodymium magnets are the most common and generally strongest of the types, so for this blog, let’s focus on how they are made.
Of course the initial step in magnet creation involves getting all the right ingredients-elements like neodymium, iron and boron from the Earth.
Melting and Milling
Once all the ingredients are acquired, they are often melted with electric currents to form ingots. The alloy ingots are then milled or ground into a powder and mixed to prepare for pressing. The composition and mixture of the alloys determines a magnet’s strength, grade and other characteristics. Overall, the process is similar to baking cookies only with more detailed and scientific composition.
Pressing and Alignment
Now the magnets can be pressed from powder to a more solid form and given a preferred magnetization direction by applying a magnetic field. There are several methods to use to press a magnet. After pressing, magnet manufacturers end up with a block shape that is sintered to give it more acute magnetic properties.
After pressing, the magnets are not quite a solid yet, so that is where sintering comes in. Sintering helps lock the magnetic particles in place through heating. The alloy mixture is carefully heated to a point that is high enough for adherence but low enough to avoid liquefaction.
Sintering often shrinks magnets, which often need to be specific sizes and shapes for their respective applications, so a process called machining is used to define the details.
Neodymium can corrode, so to prevent corrosion coatings are applied to the magnets. Some of the plastic coated magnets are examples of the type of protection that is applied during this step.
Now the magnets are almost ready, but they're not quite magnetic yet. In other words, they have been assigned pole directions but magnetism hasn’t been activated yet, so they will not attract or repel to their full capabilities. In order to activate their magnetism, an industrial magnetizer is often used. The magnet slugs are placed into it and are exposed to a strong magnetic field. You can see how we do this in this video: http://youtu.be/t-UusxQ2v-Q.
The process of creating a permanent magnet is an intricate and interesting one. However, it is important that it is done with professional care, because how a magnet is formed will affect how it functions. If you have more questions about magnet-making or products, feel free to contact us!