The short answer

Permanent magnets are often manufactured with a process known as powder metallurgy, during which a powerful electromagnet realigns the atoms of the magnet using a high-voltage current.

The long answer

Let's start with the basics.

A magnet is an object wherein most or all of its electrons move in the same direction, creating a magnetic field with north and south ends. ​Click here to learn more about how magnets work.

What are the main types of magnets?

There are three main types of magnets:

Permanent: Permanent magnets, as the name suggests, retain their magnet properties. There are natural permanent magnets, but you can also make certain materials into permanent magnets by subjecting them to a magnetic force.

• Use cases: Fridge magnets, crafts & DIY, door catches, part in electromagnets, magnetic drive pumps, and many more.

Temporary: Temporary magnets only have magnetic properties when they are physically near a magnetic field. Once they are no longer attached to or close to the magnetic field, they stop behaving like magnets.

• Use cases: Not much, but you can create temporary magnets out of objects like paper clips and nails.

Electromagnet: Electromagnets are a type of temporary magnet that requires an electrical field to be magnetic. When the object no longer has electricity passing through it, it stops being magnetic. These types of magnets are able to be turned on and off and can be incredibly strong.

• Use cases: Industrial lifting, MRI machines, most electric appliances, telephones, ​power transformers​, high-speed trains, and many more.

Since permanent magnets are necessary to create electromagnets and ​temporary magnets can be made with a simple science experiment​, I'll dig into the process by which permanent magnets are manufactured.

How are permanent magnets manufactured?

There are many ways to make permanent magnets, but powder metallurgy is the most common method. Here is are the steps taken to make permanent magnets through powder metallurgy:

Step 1: Melting and powdering the metals

The journey begins with melting metals in a vacuum. The choice of metals depends on the desired type of magnet (e.g. flexible refrigerator magnets vs. heavy-duty magnets). Common materials include neodymium, iron, boron, and others.

Once the mixture is cooled, it's crushed into a fine powder. This powder is highly reactive and can spontaneously ignite in the presence of oxygen, so it's carefully handled in vacuum conditions to avoid this risk.

Steps 2 & 3: Aligning the magnetic fields & pressing them into shape

This powdered metal is then placed in a mold and compacted into shape. During this compression, an important process occurs: the alignment of the particles' magnetic fields. A low voltage, high current charge is passed through the powder, aligning the magnetic regions in a preferred direction. At this stage, the object is slightly magnetized.

Step 4: Heating

Next, the pressed shape is heated in a vacuum furnace to a sintering temperature, which is when it is hot enough to fuse the particles into a solid mass without melting it.

After it has cooled down, the magnet undergoes annealing, a heat treatment that removes any residual impurities and reinforces the metal's structure.

Step 5: Finishing and coating

The magnets are then precisely machined into their final shapes and sizes. This might involve grinding, slicing, or other methods. To protect against corrosion and enhance durability, magnets are often coated with materials like epoxy, nickel, or zinc.

Step 6: Magnetizing

The final step in the magnet-making process is magnetization. The magnets are exposed to a powerful magnetic field using a magnetizing coil or solenoid, which imparts a strong, permanent magnetic field. The electromagnetic process involves charging the metal with a high-voltage current, realigning the atoms to establish the desired magnetism permanently. Check out the video I linked on the image above to watch this in action.

Check out some other curious questions:

Sources

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