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Basic Knowledge Of Magnets

- Jul 26, 2018 -

The ancient Greeks and Chinese discovered that there is a natural magnetized stone in nature, called "the magnet." This stone can magically pick up small pieces of iron and always point in the same direction after swinging at will. 


Early voyagers used this magnet as their earliest compass to discern the direction at sea. After thousands of years of development, today's magnets have become a powerful material in our lives. The same effect as the magnetite can be achieved by synthesizing alloys of different materials, and the magnetic force can also be increased. Man-made magnets appeared in the 18th century, but the process of making stronger magnetic materials was very slow until the 1920s when Alnico was made. Subsequently, Ferrite was fabricated in the 1950s, and rare earth magnets were produced in the 1970s [Rare Earth magnets including NdFeB and SmCo). At this point, magnetic technology has developed rapidly, and magnetic materials have also made components more compact. What is the magnetization (orientation) direction? Most magnetic materials can be magnetized to saturation in the same direction, a direction called "magnetization direction" (orientation direction). 


A magnet that has no orientation direction (also called an isotropic magnet) is much weaker than an orientation magnet (also called an anisotropic magnet). What is the standard “North-Arctic” industrial definition? "Arctic" is defined as the north pole of the earth pointing to the north pole of the earth after the magnet rotates freely. Similarly, the south pole of the magnet also points to the south pole of the earth. How to identify the north pole of the magnet without marking? Obviously it is impossible to distinguish only by the eyes. You can use the compass to stick to the magnet, and the pointer to the north pole of the Earth points to the south pole of the magnet. How to handle and store magnets safely? Always be very careful, as the magnets will stick together and may pinch your fingers. When the magnets are attracted to each other, the magnet itself may be damaged by the collision (the corners are knocked off or the cracks are knocked out). Keep magnets away from items that are easily magnetized, such as floppy disks, credit cards, computer monitors, watches, mobile phones, medical devices, etc. Keep the magnet away from the pacemaker.


 For larger magnets, plastic or cardboard spacers should be placed between each piece to ensure that the magnets can be easily separated. The magnet should be stored in a dry, constant temperature environment as much as possible. How to achieve magnetic separation? Only materials that can be attracted to the magnet can function to block the magnetic field, and the thicker the material, the better the magnetic separation effect. What is the strongest magnet?


 At present, the highest performance magnet is a rare earth magnet, and in the rare earth magnet, neodymium iron boron is the most powerful magnet. However, in the environment above 200 degrees Celsius, samarium cobalt is the most powerful magnet. The type of magnet: magnet, should be called magnetic steel, English Magnet, magnetic steel is now divided into two major categories, one is soft magnetic, one is hard magnetic; soft magnetic includes silicon steel and soft magnetic core; hard magnetic including aluminum nickel Cobalt, samarium cobalt, ferrite and neodymium iron boron, among which the most expensive is samarium cobalt magnet, the cheapest is ferrite magnet, the highest performance is NdFeB magnet, but the performance is the most stable, The best temperature coefficient is AlNiCo magnet, users can choose different hard magnetic products according to different needs.


 How to define the performance of the magnet? There are mainly three performance parameters to determine the performance of the magnet: Remanent Br: The permanent magnet is magnetized to the technical saturation, and after the external magnetic field is removed, the retained Br is called the residual magnetic induction. Coercive force Hc: The B of the permanent magnet magnetized to the technical saturation is reduced to zero. The required reverse magnetic field strength is called the magnetic coercive force, which is simply referred to as the coercive force energy product BH: represents the magnet in the air gap. The magnetic energy density established by the space (the two magnetic pole spaces of the magnet), that is, the magnetostatic energy per unit volume of the air gap. Since this energy is equal to the product of the Bm and Hm of the magnet, it is called the magnetic energy product. Magnetic field: The space that magnetically acts on the magnetic pole is the magnetic field. 


The magnetic field: How does the magnetic induction of a certain position on the surface of the permanent magnet select the magnet? Before deciding which magnet to choose, what role does the magnet need to play? Main role: moving objects, fixing objects or lifting objects. The shape of the required magnet: a disk shape, a circular shape, a square shape, a tile shape or a special shape. The size of the required magnet: length, width, height, diameter and tolerance, etc. The suction of the required magnet, the expected price and quantity, etc.

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