Standard Neodymium Magnets
Neodymium magnets are technological marvels and the process for creating them is sophisticated and delicate. The main ingredients of a neodymium magnet are neodymium itself, iron, and boron; the chemical compound known as NdFeB. The exact ingredients depend on the grade or strength of the magnet being produced.
Sintered NIB magnets have the highest strength but are limited to relatively simple geometries and can be brittle. They are made by pressure forming the raw materials into blocks, which then go through a complex heating process. The block is then cut to shape and coated to prevent corrosion. Sintered magnets are typically anisotropic, which means they have a preference for the direction of their magnetic field. Magnetizing a magnet against the “grain” will reduce the strength of the magnet by up to 50%. Commercially available magnets are always magnetized in the preferred direction of magnetization.
Bonded NIB magnets are typically about half as strong as sintered magnets but are less expensive and can be made into almost any size and shape. Raw materials are mixed with epoxy as a binder, pressed into a die cavity, and heat cured. Bonded magnets are isotropic, which means they don’t have a “grain” or a natural preference for the direction of their magnetic field.
The basic compound for most Neodymium magnets is Nd2Fe14B. In practice, the actual chemical reaction used can be more complicated. A commonly used reaction is:
57 Fe + 8 B + 10 Fe2O3 + 7.5 Nd2O3 + 52.5 Ca -> Nd15Fe77B8 + 52.5 CaO
Note that the powder formed by this reaction is slightly different than the Nd2Fe14B ratio. Magnets are often made both Nd-rich and B-rich, where finished magnets typically contain non-magnetic bits of Nd and B in the grain, within which are highly magnetic Nd2Fe14B grains.
For higher temperature magnet grades, additional elements are added. When small amounts of Iron (Fe) are replaced with Cobalt (Co), the properties improve at elevated temperatures, but the intrinsic coercivity decreases. If small portions of Neodymium (Nd) are replaced with Dysprosium (Dy), the intrinsic coercivity is improved, but the maximum energy product (BHmax, a good measure of a magnet's strength) decreases. It is common to use both Co and Dy together.
First of all, all the elements to make the chosen grade of the magnet are placed into a vacuum cleaner induction furnace, heated and melted to create the alloy material.
This mix is then cooled to form ingots before being ground into tiny grains in a jet mill. Each grain is generally only three microns in dimension, smaller sized than a red cell.
The super-fine powder is then pressed in a mold as well as at the same time magnetic power is put on the mold.
Magnetism comes from a coil of wire that imitates a magnet when an electrical present is traveled through it.
As the combination is pressed, the direction of magnetism is secured! When the particle structure of the magnet matches the instructions of magnetism, this is called an anisotropic magnet.
This isn't completion of the procedure, rather, now the magnetized product is demagnetized and will be re-magnetized later while doing so.
At this stage, the product would be far too soft as well as brittle to be helpful.
The next action is for the product to be heated, almost until the melting point in a process called sintering which makes standard neodymium magnet bits fuse with each other.
This procedure occurs in oxygen totally free, inert atmosphere.
Neodymium Magnets
Nearly there, the warmed product obtains rapidly cooled down making use of a technique called quenching.
This fast air conditioning procedure reduces locations of poor magnetism as well as increases performance.
This is the stage when the raw magnets are machined into their preferred form, nevertheless, due to the fact that they are so hard diamond plated cutting tools are required!
>> Shop for a Neodymium Magnets here
The last action prior to the product being re-magnetized is important. Since neodymium magnets are so hard, making them vulnerable to breaking and also cracking, they need to be coated, cleansed, dried, and plated.
There are various sorts of coating that are utilized with neodymium magnets, the most common being a nickel-copper-nickel mix however they can be coated in various other metals as well as also rubber or PTFE.
Once plated, the ended up product is re-magnetized by putting it inside a coil, which, when electric existing is gone through it produces an electromagnetic field three times more powerful than the needed stamina of the magnet.
This is such an effective procedure that if the magnet is not held in place it can be flung from the coil like a bullet.
The quality of the resulting magnets is inspected for a variety of properties. A digital measuring projector verifies the dimensions. A coating thickness measurement system using x-ray fluorescence technology verifies the thickness of the plating. Periodic testing in salt-spray and pressure-cooker tests also verify the performance of coatings. A hysteresigraph measures the BH Curve of magnets, which confirms that they are fully magnetized as expected for the magnet's grade.
AH Magnet is a rare earth magnet supplier specialized in researching, developing, manufacturing, and exporting high-performance sintered neodymium iron boron magnets, 47 grades of standard neodymium magnets, from N33 to 35AH, and GBD Series from 48SH to 45AH are available. All magnets are widely applied to electric motors such as servo motors, stepper motors, brushless motors, linear motors, permanent magnet synchronous motors, etc.
top
