The neodymium magnet production and special features of super magnets

Apart from electromagnets, neodymium magnets are the strongest in the world. The holding force or adhesion is very high even in small versions and should never be underestimated. Ferrite magnets do not come anywhere close to them in terms of magnetic strength. But what are neodymium magnets and how exactly does magnet production work? We will clarify this below.

How are neodymium magnets manufactured and magnetized?

The manufacture of strong magnets from neodymium takes place in several consecutive steps. As the name suggests, they consist of neodymium, among other things. This substance is one of the so-called rare earths and is classified as a lanthanide. The metal only occurs in nature in chemical compounds - usually together with minerals. In order to extract the substance during magnet production and to separate it from the other combined substances, extraction is required. for example in an electrolysis furnace. The neodymium obtained is one of three basic materials for neodymium magnet production.

In the next step, an alloy of neodymium, iron and boron must be produced (chemically: NdFeB). The materials are weighed and then placed in a vacuum induction furnace. Every magnet manufacturer swears by their own recipe and mixes other elements such as cobalt or copper into the basic materials. With these additions, the magnets can ultimately take on additional properties such as corrosion resistance. The mixed materials are melted together in the furnace. The resulting alloy is then put into molds. Depending on the composition, the quality of the neodymium magnets varies after production.
The resulting shapes are then immediately ground up again or embrittled and brought to a grain size of around three micrometers. The fine powder has then already been pressed and compacted several times using various techniques. At the end, what remains is the so-called green part, which has only a slight magnetic effect and a brittle consistency.

The last step in magnet production is sintering. During this part of the manufacturing process, the alloy is compressed and fired under high pressure and at high temperatures. This creates the final shape of the magnet. 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 conducive to later magnetization.

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

After being sintered, the cooled magnets are technically finished, but they do not yet look particularly high-quality. Two further steps are therefore necessary to prepare the surfaces of the neodymium magnets after production they are refined. First they are sanded to remove rough spots and unevenness. The material can then be cut to the desired size according to the specified tolerances.
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 production. The most commonly used coating is a Ni-Cu-Ni coating, i.e. a composition of nickel-copper-nickel.

Other possible coatings are:

• Gold plating (Ni-Cu-Ni-Au)
• Chromium (Ni-Cu-Ni-Cr)
• Copper (Ni-Cu)
• Epoxy resin (Ni-Cu-Ni-Epoxy)
• Zinc (Zn)

Now all that is missing is the actual magnetization process. This process of neodymium magnet production is with a magnetic coil whose magnetic force is at least three times as high as the desired strength of the new magnets. The batch of magnets must be well fixed before the process begins, because otherwise they will immediately repel or attract each other after magnetization. The coil emits a magnetization pulse to the raw magnets, which causes a realignment of the crystals inside them. From this point on, the blanks are permanently magnetized– this is how the production of a permanent magnet works.

Differences in magnet production: why are neodymium magnets so strong?

Neodymium magnets are also often referred to as super magnets. Compared to ferrite magnets, they have a significantly stronger magnetic field and therefore a higher performance. The larger ones can hold six hundred times their own weight. The energy density is given in kilojoules per cubic meter (kJ/m3). To illustrate the difference between ferrite and neodymium magnets, a numerical example is useful: Ferrite magnets normally have an energy density of around 30 kJ/m3. Neodymium magnets, on the other hand, have a maximum energy density that is almost twenty times higher, namely around 500 kJ/m3.

Type of magnet
	Ferrite	Neodymium
Energy density	30 kJ/m³	500 kJ/m³
Application	Private area, household	Industry

Ferrite-Magnets are often used in the private sector. For example, for hanging pictures on the refrigerator or for notice boards. The production of permanent magnets made of neodymium, on the other hand, is aimed at the industrial sector or similar work areas. The reason for their enormous adhesive force lies in the chemical compound and the crystal structure. This has a large anisotropy and extremely high coercive field strengths.

Info:
Unlike neodymium magnets, ferrite magnets are made from iron oxide and barium or strontium carbonate. These are ground, granulated, then pressed in a magnetic field and sintered. Coatings are rather unusual for these.

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 severe bruising, contusions or even broken bones if handled carelessly. The metals often have hard edges that can injure the skin if handled incorrectly. Magnet manufacturers therefore recommend that you wear padded gloves when using magnets.

When bringing two magnets together, you should also remember that they will attract each other from a certain distance away and that 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 when the material hits something and injure the skin.

Make your own magnets: here's how to do it

If you want to make your own magnet at home, a simple experiment will help. All you need is an iron nail and an iron magnet to magnetize the iron nail. First, place the nail on a neutral surface - for example, a wooden or plastic plate. 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 test this by simply placing the nail near a staple or something similar. The latter will now be attracted to the iron nail. Can you also make permanent magnets yourself? Unfortunately, the production of permanent magnets is more complex than described, which is why you cannot make them yourself at home.