Magnets are objects that have a magnetic field, which attracts certain metals and other magnets. There are four main types of magnets: permanent, temporary, electromagnets, and natural magnets.
Permanent magnets
Permanent magnets are the most common type of magnet. They can retain their magnetic properties indefinitely without any external source of energy. Examples include refrigerator magnets and ceramic magnets.
Permanent magnets, which can be natural products, also known as natural lodestones, or artificially made (the strongest magnets are neodymium magnets), have wide hysteresis loops, high coercivity, high remanence, and materials that can maintain constant magnetism once magnetized. In applications, permanent magnets work in deep magnetic saturation and the second quadrant demagnetization part of the magnetosphere loop after magnetization. Permanent magnets should have as high a coercivity Hc, remanence Br, and maximum magnetic energy product (BH) m as possible to ensure maximum magnetic energy storage and stable magnetism.
There Are Several Types Of Permanent Magnets
1. Neodymium Magnets
Neodymium magnets are permanent magnets of neodymium, iron, boron, and other elements. They have extremely high magnetic energy products and coercive force and are one of the strongest permanent magnet materials in the world.
2. SmCo Magnets
SmCo magnet is a type of rare earth permanent magnet material, made of samarium (Sm) and cobalt (Co) as the main components, through a powder metallurgy process. It has a high magnetic energy product, high coercive force, and good temperature stability, allowing it to maintain good magnetic properties in high-temperature environments.
3. AlNiCo Magnets
AlNiCo magnets are composed of spherical elements. This material is widely used as a permanent magnet due to its high coercive force and good magnetic properties. An iron alloy consisting mainly of aluminum (Al), nickel (Ni), cobalt (Co) iron, and other trace gold.
4. Sintered Ferrites
Sintered ferrites are a type of magnetic material made by sintering iron oxide (mainly Fe₂O₃) and other metal oxides (such as BaO, SrO, etc.) through a ceramic process. It belongs to hard magnetic material, has high magnetic energy product and coercive force, and can maintain magnetism after power failure.
5. Rubber Magnet
A rubber magnet is a soft, elastic, and twistable magnet made by mixing magnetic material powder (such as ferrite or NdFeB) with flexible materials such as rubber or plastic and then extruding, calendering, injection molding, and other processes. It allows it to be processed into various shapes and sizes and has a certain elasticity and softness.
Permanent magnet process classification
1. Bonded NdFeB
Bonded NdFeB is a magnet made by mixing NdFeB magnetic powder and a binder through compression molding or injection molding. Bonded magnets have high dimensional accuracy and can be made into magnetic components with relatively complex shapes. They also have the characteristics of one-time molding and multi-pole orientation.
2. Sintered NdFeB
Sintered NdFeB is a high-performance permanent magnet material, mainly composed of rare earth element Nd, transition metal iron, and non-metallic element boron. It is manufactured by powder metallurgy process, including the steps of mixing, melting, crushing, pressing, sintering, and heat treatment of these elements in a specific proportion. Sintered NdFeB has extremely high magnetic energy products, high remanence, and high coercivity, and is one of the strongest permanent magnet materials currently available.
3. Injection Molded NdFeB
Injection-molded NdFeB is a special NdFeB permanent magnet material that combines the advantages of injection molding technology and NdFeB magnetic materials. This material is made by mixing NdFeB magnetic powder with high molecular polymer and then making various complex-shaped magnetic parts through an injection molding process. Injection-molded NdFeB not only retains the high magnetic properties of NdFeB but also has good machining performance and corrosion resistance.
Permanent Magnet Application Field
Permanent magnets have a wide range of applications and have the characteristics of maintaining magnetism, so they are widely used in many fields, covering multiple industries and fields.
It is widely used in various fields such as electronics, electrical, machinery, transportation, medical, and daily necessities. Such as the permanent magnets of speakers and telephone receivers; the magnetic system of magnetoelectric meters; the magnetic poles in generators and permanent magnet motors; permanent magnetic devices used in the machinery manufacturing industry (such as permanent magnetic chucks for surface grinders, etc.) and magnetic suspension systems, magnetic bearings; magnetic separation systems, magnetic ore separation, magnetic water purification systems, magnetrons, magnetic systems of proton accelerators, etc.
Temporary Magnets
Temporary magnets, also known as soft magnetic materials or temporary magnets, temporary magnets are made of a ferromagnetic material that can be magnetized for a short period with an external magnetic field but will lose its magnetic properties when the external field is removed. Such materials are characterized by low coercivity (i.e., weak ability to resist demagnetization), so their magnetic state can easily change with changes in external conditions. Common temporary magnets include nails and paper clips, which can be picked up or moved with strong magnets.
Performance of Temporary Magnets
1. Low coercivity: easy to be magnetized and easily demagnetized.
2. High magnetic permeability: can effectively guide and concentrate the magnetic field.
3. Low remanence: When the external magnetic field is removed, the remanence (residual magnetism) is very low.
4. Good conductivity: Some temporary magnet materials also have good conductivity.
In what fields can temporary magnets be used
Temporary magnets have a wide range of applications in industry, technical equipment, and daily life, mainly used to manufacture electromagnets, transformers and inductors, sensors and measuring equipment, automobiles and aerospace, medical equipment, etc.
Electromagnet
Electromagnets are temporary magnets created by passing electricity through a coil of wire to create a strong magnetic field. This type of magnet is used in many consumer electronics, such as electric motors and speakers. It consists of a coil and an iron core. A conductive winding matching its power is wound around the outside of the iron core. This coil with current flowing through it is magnetic like a magnet. It is also called an electromagnet. When current passes through the coil, a magnetic field is generated around the iron core, making the electromagnet magnetic. We usually make it into a bar or hoof shape to make the iron core easier to magnetize. In addition, to make the electromagnet demagnetize immediately when the power is turned off, we often use soft iron or silicon steel materials with faster demagnetization to make it. Such an electromagnet is magnetic when the power is turned on, and the magnetism disappears after the power is turned off.
Working Principle of Electromagnet
Faraday's law of electromagnetic induction states that when a magnetic flux passes through a conductor loop, an induced electromotive force is generated in the loop. In an electromagnet, when current passes through a coil, it generates a magnetic field. This magnetic field interacts with the iron core, causing the iron core to be magnetized.
After the iron core is magnetized, it becomes a temporary magnet with a north pole and a south pole. The strength of the magnetic field depends on the magnitude of the current, the number of turns of the coil, and the material and shape of the core.
When the core of the electromagnet is magnetized, it attracts or repels other magnetic objects. The magnetism of the electromagnet can be controlled by controlling the on and off of the current. When the current stops, the magnetic field disappears and the core loses its magnetism.
The working principle of the electromagnet is based on the interaction between the current and the magnetic field. This interaction enables electromagnets to play an important role in many applications, such as electromagnetic cranes, motors, relays, solenoid valves, etc.
What Electromagnets Are There in Life?
There are many electromagnets in our lives, widely used in electromagnetic cranes, electromagnetic locks, electromagnetic relays, solenoid valves, speakers, electric toys, maglev trains, generators, telephones, automation control equipment, packaging machinery, medical equipment, food machinery, textile machinery, etc.
Electromagnets achieve various useful functions by controlling the intensity of the current and magnetic field, such as attracting and repelling iron objects, and realizing mechanical movements such as linear movement, rotation, and swinging, and play an indispensable role in modern industry and life.
Natural Magnets
Natural magnets are those that occur naturally in nature and can be found in iron ore deposits. They are also referred to as lodestones or magnetite. They can attract magnetic metals such as iron, nickel, and cobalt. They are found in the earth's nature and usually have strong magnetism. Natural magnets are one of the earliest magnetic materials discovered and used by humans.
Natural magnets were discovered and used by people in ancient times and have important applications in history, especially in the field of navigation. For example, the ancient Chinese compass used the magnetism of natural magnets to indicate direction.
Unlike artificial electromagnets, the magnetism of natural magnets is determined by their internal atomic structure and electronic arrangement, and no external power supply is required to maintain magnetism. However, the magnetism of natural magnets is relatively weak and is usually not as strong and adjustable as artificial electromagnets.
Although most magnets used in modern technology are artificial, natural magnets are still used in some fields, such as in some types of education and scientific research, crafts and decorations, magnetic therapy products, etc. to demonstrate the concept of the magnetic field.
As an ancient magnetic material, natural magnets not only have an important position in history but also still have certain application value in modern society. Although their magnetic strength is not as strong as modern synthetic permanent magnets, their natural beauty and unique historical significance have earned them a place in education, research, and art.
Conclusion
These four types of magnets all have unique properties and uses, allowing them to be utilized for a variety of different applications. Whether you are looking for a permanent magnet, temporary magnet, electromagnet, or natural magnet, there is sure to be one that meets your needs!