The neodymium magnet production and special features of the super magnets

Leaving aside electromagnets, neodymium magnets are the strongest in the world. The holding power or adhesion is very high even with small versions and should never be underestimated. Ferrite magnets don't even come close to matching them in terms of magnet strength. But what are neodymium magnets and how exactly does magnet production work? We clarify that below.

How are neodymium magnets made?

The production of strong neodymium magnets takes place in several consecutive steps. As the name suggests, they consist of neodymium, among other things. This substance belongs to the so-called rare earths and is assigned to the lanthanides. In nature, the metal only occurs in chemical compounds – mostly together with minerals. To promote the substance during magnet production and to separate it from the other associated substances, extraction - for example in an electrolysis furnace - is necessary. The neodymium obtained is one of three basic materials for the manufacture of neodymium magnets.

The next step is to create an alloy of neodymium, iron and boron (chemical: NdFeB). The fabrics are weighed and then placed in a vacuum induction furnace. Every magnet manufacturer swears by their own recipe and adds other elements such as cobalt or copper to the basic materials. With these additions, the magnets can end up acquiring additional properties such as corrosion resistance. The mixed substances are fused together in the oven. The resulting alloy is then placed in molds. Depending on the composition, the quality of the neodymium magnets varies after manufacture.

The resulting shapes are then directly ground again or embrittled and brought to a grain size of approx. three micrometers. The fine powder has then already been pressed and compacted several times using different techniques. In the end, the so-called green body remains, which has only a slight magnetic effect and has a brittle consistency.

The final manufacturing step in magnet production is sintering. This part of the manufacturing process involves compacting and firing the alloy under both high pressure and high temperatures. This creates the final shape of the magnets. After this process, the blanks are finally slowly cooled. Various chemical reactions ensure that a special crystal structure is created in the magnet, which is particularly beneficial for subsequent magnetization.

How is a magnet made? The surface treatment determines the quality

The cooled magnets are technically finished after sintering, but they don't look high-quality yet. Two additional steps are therefore necessary to finish the surfaces of the neodymium magnets after manufacture. First, they are sanded to remove rough spots and bumps. According to the specified tolerances, the material can still be cut to the desired size.

If the magnet has the right dimensions, the surfaces must be sealed with a protective layer. For this step, the material must be thoroughly cleaned and dry. There are many different magnet coatings for neodymium magnet manufacture. The most used plating is a Ni-Cu-Ni plating, which is a nickel-copper-nickel composition.
Other possible coatings are:

• Gilding (Ni-Cu-Ni-Au)
• Chrome (Ni-Cu-Ni-Cr)
• Copper (Ni-Cu)
• Epoxy resin (Ni-Cu-Ni-Epoxy)
• Zinc (Zn)

Now only the actual magnetization process is missing. This process of neodymium magnet production is implemented with a magnetic coil whose magnetic force is at least three times as high as the desired strength of the new magnets. The charge with magnets must be fixed well before the process begins, otherwise they will immediately repel or attract each other after magnetization. The coil delivers a magnetizing pulse to the raw magnets, causing the crystals inside to realign. From this point on, the blanks are permanently magnetized - this is how permanent magnet production works.

Differences in magnet manufacture: Why are neodymium magnets so strong?

Neodymium magnets are also often referred to as super magnets. Compared to ferrite magnets, they are much more attractive. Some of them hold six hundred times their own weight. The energy density is given in kilojoules per cubic meter (kJ/m3). A numerical example can be used to show the difference between ferrite and neodymium magnets: Ferrite magnets normally have an energy density of approx. 30 kJ/m3. Neodymium magnets, on the other hand, have a maximum energy density that is almost twenty times higher, namely approx. 500 kJ/m3.

Magnet Type
	Ferrite	Neodymium
Energy density	30 kJ/m³	500 kJ/m³
Area of application	Private Area, Household	Industry

The latter are usually not used in the private sector, but preferably in industry or similar work areas. The reason for their enormous adhesive power lies in the chemical compound and the crystal structure. This has a large anisotropy and at the same time extremely high coercive field strengths.

How dangerous are neodymium super magnets?

The use of neodymium magnets should always be well thought out. Their extremely high adhesive force can lead to serious bruises or even broken bones if handled carelessly. The metals often have hard edges that can injure the skin if handled incorrectly. Therefore, you should wear padded gloves for all magnet applications.

When bringing two magnets together, you should also consider that they attract each other from a certain distance and unexpected dangerous situations can arise. The neodymium alloy is brittle in this state. Due to the high forces, metal chips can splinter off the magnets and injure the skin if the material impacts.

Make your own magnets: Here's how

If you want to make a magnet yourself at home, a simple experiment will help. All you need is an iron nail and an iron magnet to magnetize the former. First place the nail on a neutral surface - for example a wooden or plastic board. Then stroke the iron nail about 50 times with the magnet. Be sure to stick to one direction.
The nail is now magnetized! You can easily test this, for example, by placing the nail near a staple or something similar. The latter is now attracted to the iron nail.