100 things about magnets：What's a magnet?

What is a magnet?

As the name suggests, a magnet is a magnet that attracts metals.

The components of magnets are atoms such as iron, cobalt, and nickel. The internal structure of the atoms is relatively special and they have magnetic moments themselves. Magnets can generate a magnetic field and have the property of attracting ferromagnetic substances such as iron, nickel, cobalt, and other metals.

Magnet type

Shape magnets: square magnets, tile-shaped magnets, special-shaped magnets, cylindrical magnets, ring magnets, disc magnets, bar magnets, and magnetic stand magnets.

Properties of magnets: samarium cobalt magnets, neodymium iron boron magnets (powerful magnets), ferrite magnets, alnico magnets, iron chromium cobalt magnets.

Industry magnets: magnetic components, motor magnets, rubber magnets, plastic magnets, etc.

Magnets are divided into permanent magnets and soft magnets. Permanent magnets are added with strong magnetism to align the spin of the magnetic material and the angular momentum of the electrons in a fixed direction. Soft magnets are added with electricity. (It is also a method of adding magnetism.) When the current is removed, the soft iron will slowly lose its magnetism.

Hang the midpoint of the bar magnet with a thin wire. When it is at rest, its two ends will point to the south and north of the earth. The end pointing north is called the north pole or N pole, and the end pointing south is the south pole or S. pole.

If you imagine the Earth as a big magnet, the Earth's magnetic north pole is the south pole, and the geomagnetic south pole is the north pole. Between magnets, magnetic poles with the same name repel, and magnetic poles with different names attract. So, the compass and the south pole repel, the north and north poles repel, and the compass and the north pole attract.

Classification: Magnets can be divided into "permanent magnets" and "non-permanent magnets". Permanent magnets can be natural products, also known as natural magnets, or they can be artificially manufactured. Non-permanent magnets, such as electromagnets, become magnetic only under certain conditions.

Magnets are mainly divided into two categories, one is a soft magnet and the other is a hard magnet.

Soft magnets include silicon steel sheets and soft magnetic cores. Hard magnets include alnico, samarium cobalt, ferrite, and neodymium iron boron. Among them, the most expensive is samarium cobalt magnets and the cheapest is ferrite magnets. The highest is the NdFeB magnet, but the one with the most stable performance and best temperature coefficient is the Alnico magnet. Users can choose different hard magnetic products according to different needs.

The magnets we refer to generally refer to permanent magnets.

Permanent magnets are divided into two categories.

The first category

Metal alloy magnets include neodymium iron boron magnet (Nd2Fe14B magnet), samarium cobalt magnet (SmCo magnet), alnico magnet (ALNiCO magnet), iron chromium cobalt magnet (FeCrCo magnet)

Sintered rubidium iron boron: It is a new type of permanent magnet material developed after 1983. It has extremely high magnetic properties and is widely used in various permanent magnet motors, engineering machinery, electroacoustics, electrical appliances, and medical equipment.

Sintered samarium cobalt permanent magnet is a superior permanent magnet material, which has high magnetic performance, strong anti-corrosion and oxidation resistance, low-temperature coefficient, high Curie temperature, and can operate in high environments. It is widely used in motors, sensors, detectors, radars, and other high-tech fields.

Alnico is suitable for producing complex shapes. Light, thin, and small products are widely used in instrumentation, communications, magnetoelectric switches, and various sensors.

FeCrCo magnet is a transformer among permanent magnets. Alloy permanent magnets are the most deformable and can be wire drawn (0.2-0.3mm), pipe drawn, rolled strip, and various mechanical processing. A.FeCrCo (iron-chromium-cobalt) deformed permanent magnet alloy has high magnetic properties, comparable to AlNiCo permanent magnet alloy, but its Co content is about 50% lower than AlNiCo. B. FeCrCo alloy has excellent plasticity and ductility and is easy to process. This is a characteristic that cast permanent magnet alloys cannot match. The alloy's higher operating temperature is around 400, which is inaccessible to NdFeB rare earth permanent magnets. C. FeCrCo alloy can be processed into wires, rods, tubes, strips, and forged materials. Through mechanical processing such as turning, milling, planing, drilling, and stamping, it can be made into various permanent magnetic components with complex shapes, especially for small ones. Long and thin components show unique characteristics. The thinnest strip can reach 0.05mm, and the finest wire can be processed to 0.1mm.

The second-largest category

Ferrite permanent magnet material (Ferrite)

1. NdFeB magnet is the magnet with the highest commercial performance currently found. It is known as the magnet king. It has extremely high magnetic properties and its maximum magnetic energy product (BHmax) is more than 10 times higher than that of ferrite. Its own machining performance is also quite good. The operating temperature can reach up to 200 degrees Celsius. Moreover, its texture is hard, its performance is stable, and it has good cost performance, so its application is extremely wide. However, because of its strong chemical activity, its surface must be treated with a coating. (Such as Zn, Ni plating, electrophoresis, passivation, etc.).

2. Ferrite magnet: Its main raw materials include BaFe12O19 and SrFe12O19. Made through ceramic technology, the texture is relatively hard and brittle. Because ferrite magnets have good temperature resistance, low price, and moderate performance, they have become the most widely used permanent magnets.

3. Alnico magnet is an alloy composed of aluminum, nickel, cobalt, iron, and other trace metal elements. The casting process can be processed into different sizes and shapes, and the machinability is very good. Cast AlNiCo permanent magnets have the lowest reversible temperature coefficient and the operating temperature can be as high as over 600 degrees Celsius. Alnico permanent magnet products are widely used in various instrumentation and other application fields.

4. Samarium cobalt (SmCo) is divided into SmCo5 and Sm2Co17 according to different compositions. Its development is limited due to the high price of its materials. Samarium cobalt (SmCo), as a rare earth permanent magnet, not only has a high magnetic energy product (14-28MGOe), reliable coercive force, and good temperature characteristics. Compared with NdFeB magnets, SmCo magnets are more suitable for working in high-temperature environments.

Magnetic force size arrangement

NdFeB magnets, samarium cobalt magnets, alnico magnets, ferrite magnets.

Performance

Definition

There are three performance parameters as follows to determine the performance of magnets:

Residual magnetic Br: After the permanent magnet is magnetized to technical saturation and the external magnetic field is removed, the remaining Br is called the residual magnetic induction intensity.

Coercive force Hc: To reduce the B of a permanent magnet that is magnetized to technical saturation to zero, the reverse magnetic field intensity that needs to be added is called magnetic induction coercive force, referred to as coercive force.

Magnetic energy product BH: represents the magnetic energy density established by the magnet in the air gap space (the space between the two magnetic poles of the magnet), that is, the static magnetic energy per unit volume of the air gap. Since this energy is equal to the product of the magnet's Bm and Hm, it is called the magnetic energy product.

Magnetic field: The space that exerts a magnetic effect on the magnetic poles is the magnetic field.

Surface magnetic field: the magnetic induction intensity at a specified position on the surface of a permanent magnet.

Diamagnetic

Diamagnetism is a magnetic phenomenon in which some types of substances produce a weak repulsive force on the magnetic field when they are in an external magnetic field.

Paramagnetic

Paramagnetism refers to the magnetic state of a material. Some materials can be affected by external magnetic fields and produce characteristics that refer to magnetization vectors in the same direction. Such substances have positive magnetic susceptibility. The opposite phenomenon to paramagnetism is called diamagnetism.

Choose a magnet

Before deciding which magnet to choose, you should clearly understand what role the magnet is required to play? Main function: moving objects, fixing objects, or lifting objects.

The shape of the magnet required: disc shape, ring shape, square shape, tile shape, or special shape.

Required magnet dimensions: length, width, height, diameter tolerance, etc.

The required magnet's suction power, expected price, quantity, etc.

As a manufacturer of magnetic assembly, we suggest doing some tests if it's available.

1. Sample test: Test the samples before purchasing, check the size, appearance, force, and lead time

2. Order force inspection test: Ask for inspection test report for each order

Magnet Manufacturing

Some substances can be rubbed into magnets. The material is either iron or steel, but not all steel can be made into magnets because they contain their own substances. Stainless steel cannot act as a magnet.

Let's make a magnet. The magnet and a screwdriver are the materials you need. Use the magnet to rub the metal part of the screwdriver. From one end to the other, they rub repeatedly to create a magnetic screwdriver.

Orientation direction

Concept

Most magnetic materials can be magnetized to saturation in the same direction, which is called the "magnetization direction" (orientation direction). Magnets with no orientation direction (also called isotropic magnets) are much weaker than oriented magnets (also called anisotropic magnets).

Definition of the north and south poles of a magnet

The definition of "North Pole" is that the North Pole of a magnet points to the North Pole of the Earth after random rotation, referred to as "N". Likewise, the South Pole of the magnet also points to the Earth's south pole, or "S" for short. The geomagnetic poles do not coincide with the geographical poles, and there is a certain magnetic declination.

Safe handling of magnets

Always be very careful as the magnets will stick to themselves and may pinch your fingers. When magnets are attracted to each other, the magnets themselves may be damaged due to collision (corners knocked off or cracks caused).

Keep magnets away from items that are easily magnetized, such as floppy disks, credit cards, computer monitors, watches, mobile phones, medical equipment, etc.

The magnet should be kept 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.

Magnets should be stored in a dry, constant-temperature environment as much as possible.

Magnetic isolation

Only materials that can be adsorbed to magnets can block the magnetic field, and the thicker the material, the better the magnetic isolation effect.

The strongest magnet

At present, the highest-performance magnets are rare earth magnets, and among rare earth magnets, neodymium iron boron is the most powerful magnet. But in an environment above 200 degrees Celsius, samarium cobalt is the most powerful magnet.

Magnetic force

Why magnets have magnetic force because the earth's magnetic field and current will continue to combine strongly due to its rotation, and finally the entire earth will become a very large magnetic field. Minerals on the earth such as nickel, cobalt, iron, and other substances rotate due to the rotation of the earth, thus becoming natural magnets.

Everyone knows that there is a gravitational field between matter. Similar to a magnetic field, it is a field that fills the space around the magnetic poles. The size of the magnetic field can be expressed by the number of imaginary magnetic field lines. Where the magnetic field lines are denser, the magnetic field is stronger. On the contrary, where the magnetic field lines are sparse, the magnetic field is weaker.

Questions: Since magnets can attract iron, can they also attract other metals?

Is gold magnetic? Is stainless steel magnetic? Is aluminum magnetic? Is copper magnetic? Is silver magnetic?

Is titanium magnetic? How do magnets work? Is brass magnetic?

Leave your concerns in the comment area and we will discuss them together in the following articles.