HOW IT'S MADE: Magnets

There are classic main shapes of magnets that are manufactured in the industry. These molds are filled with sand and smoothened out completely. Then gases are pumped into the furnace and this chemically alters the sand, hardening it completely. This would next be infused with metals like copper, cobalt, sulfur, pure iron, aluminum, and even titanium.

These metals are loaded into an induction furnace and are heated upto 3000 degrees Fahrenheit! This mixes with the sand in the mold and forms the metal mix. It is then cooled. The molds are shattered by the workers or the machines and we obtain a lot of metal pieces.
Step #2. Magnetizing the metal pieces

There would be a set of rings which is a really powerful electromagnet. The ring-covered pipe is placed in a tube with the silica sand hardened metal pieces and both ends of the tube are sealed with concrete.

It is then passed through an electric furnace which heats up the tube until it is red. This allows the rings inside to accept an electromagnetic field which will be delivered by this metal rod.

The rod slides down the center of the copper pipe and is clamped into place thoroughly. The water keeps the pipe from melting as a low-voltage high-current charge is delivered to the rings. Later, the seal is broken and the rings would be mildly magnetized. You may wonder why this isn’t very powerful, but it is only because the material is getting prepped for magnetization.

This step empowers them with a strong electromagnetic charge such that the establishment of that weak magnetic field earlier ensures that the magnetization is now properly oriented.

This is the basic overview, but how are the next few steps done in an industrial process?
Making magnets in the industry

There are various processes to make magnets but the most common method has to be Powder Metallurgy where a pre-decided metal mix is pulverized and heated to meld it all together in a liquid phase sintering. Most of the magnets you find are sintered magnets.

Ferrite, Samarium cobalt, and neodymium-iron-boron magnets are all made like this.
The SmCo and Neo magnets mentioned before are made first by melting them under a vacuum or some inert gas in an induction melting furnace.

This is poured into a mold or processed in a strip caster which forms thin strips. This is then pulverized to form a fine powder that can be from 3 upto 7 microns in diameter. This powder is highly chemically reactive and even capable of igniting spontaneously in the air, and thus must be protected from oxidation in the air.

The compacting of this powder is super important as aligning the particles so that in the finished piece all the magnetic regions should be pointing in a prescribed direction.
Step #3. Compacting or Pressing

This is done by axial or transverse pressing where the powder is placed in a cavity and just before the pressing, the magnetic field is applied. So, the compaction just fixes the particles in this alignment. This leads to a high-energy product that is very efficient.

There is even another compaction method called isostatic pressing where a flexible container is filled with powder and dunked into a fluid which could be hydraulic fluid or water which is used to compact it. The main advantages are that large blocks can be made where the powder stays in good alignment.
Step #4. Sintering

These are next directed through a vacuum sintering furnace where the particular temperatures and type of vacuum or inert gas would determine the type and grade of the magnet being produced. This has a well-studied list and following those conditions are very important. When it reaches room temperature, both materials are given a lower temperature heat treatment.

During sintering, the magnets actually reduce in size to about 15 to 20 percent of their original size. The finished magnets have a rough surface and irregular dimensions.
Step #5. Finishing

The finishing aspect gives shape to the magnets. This requires little diamond wheels for slicing or abrasive wheels for shaping. The magnet material is both brittle yet very hard. Slicing has to be performed with superb precision and it has to be monitored carefully to prevent cracks and slips.

When many pieces have to be manufactured, in bulk, about 5000 and more, tooling is preferred. When pressing to shape, all the material scrap would be minimized, thus avoiding wastage.

The order quantity, part shape, size, and complexity will all contribute to the decision of the method of manufacture. The delivery time will also affect all the decisions as making limited quantities from stock blocks is better than ordering tooling for press-to-shape parts.

Many specialized magnet shapes can be made from these alloys but the materials we’ve discussed above are best suited for simpler shapes. Machined magnets will have sharp edges that could be prone to chipping.
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