Magnets have played an important role for centuries since they have been used as a compass for Chinese acupuncture. But, it was the application in 1820, where the electric current exerted a magnetic force that led to the widespread application of magnets in the industry.
Many things have changed and magnets are indispensable to modern life. They are in virtually every electrical appliance. While the first magnets were magnetite, modern custom magnets are formed from a combination of ferromagnetic materials. Industrial magnetic materials include ferrite, alnico and rare earth magnets, such as neodymium magnets.
Applications of industrial magnets
We know that iron is a good magnet, but it has its limitations that include loss of magnetism, heating due to stray currents and low magnetic force. That’s why industrial magnets are made from materials that resist magnetism, are powerful and have high resistivity. This is how magnets are used in the industry.
Also known as ceramic magnets, ferrite magnets are a chemical compound of iron oxide and various metals. Soft ferrites, which contain nickel, zinc or manganese compounds, have low coercivity and are commonly used in high frequency transformers and inductors. Hard ferrites, using strontium, barium and cobalt, retain their magnetism and are used in radios, speakers, microwave relays, drives and permanent magnet motors. The magnetic tape uses iron oxides to store information. The latest generation of magnetic tape can store 330 TB of data.
Alnico magnets developed in the 1930s and quickly became commonplace. They offer good magnetic resistance and withstand temperatures up to 425 ° C. Aluminum, nickel and cobalt compounds are expensive. They must be melted, and the magnetic field is oriented during heat treatment. Alnico magnets are used in electric motors, electric guitar pads, magnetic bearings and couplings, ABS systems and in military and aerospace applications. Because of its sensitivity to demagnetization, shape and length are fundamental.
Rare earth magnets are very powerful and are replacing more and more of the previous types of magnets. Neodymium magnets are the most powerful permanent magnets currently available, allowing the use of very small magnets. These are suitable for small sensors, hard disks and miniature audio equipment. Other applications could be in speakers, medical imaging equipment, magnetic couplings, wireless tools and magnetic bearings. The main limitation is that they can not be used above 200ºC.
When it is necessary to control the magnetic force, electromagnets are used. By using low coercivity materials, electromagnets use electric coils to quickly change the magnetic field. This makes power transformers feasible, as well as the powerful superconducting magnets used in magnetic levitation, levitation trains and magnetic resonance imaging. AC motors are a type of electromagnet, in which the rotating magnetic fields rotate the rotors. Other applications include lifting custom magnets, solenoids and relays.
What are the best industrial magnets?
The wide variety of magnetic materials means that selecting the best magnet can be an overwhelming exercise. Factors to consider include:
- Magnetic flux
- Shape and size
- Operating temperature
- Corrosion and erosion