Do you know about magnets? Do you want to know all kinds of information about magnets? The following article will tell you all the answers about magnets.
Magnet is a material that plays a vital role in modern technology. They are used in a wide range of fields, covering everything from electronic equipment to medical technology to aerospace. This article will take an in-depth look at the four main types of magnets: NdFeB magnets, Samarium Cobalt magnets, Alnico magnets, and ferrite magnets and provide you with key information about these materials.
4 Types of Permanent Magnets
There are many types of magnets, generally divided into two categories: permanent magnets and soft magnets. Permanent magnets are divided into two categories. The first category is metal alloy magnets, including neodymium iron boron magnets, samarium cobalt magnets, and alnico magnets. The second largest category is ferrite permanent magnets.
Magnet Type 1: Ferrite Magnet
Its main raw materials include BaFe12O19 and SrFe12O19. It is a brittle material with a hard texture. Ferrite magnets are widely used because of their good temperature resistance, low price, and moderate performance. Ferrite magnets have high magnetic properties, good time stability and low temperature coefficient.
Ferrite magnet applications: widely used in instruments, instruments, motors, automatic controls, microwave devices, radar and medical equipment, etc.
The magnetization direction of ferrite magnets can be axially and radially magnetized as needed.
Ferrite magnet shapes: cylindrical, round, rectangular, flat, tile-shaped, axe-shaped.
Magnet Type 2: NdFeB Magnet
NdFeB is currently the most commercialized type of magnet and is known as the magnet king. It has extremely high magnetic properties and its BHmax is more than 10 times higher than that of ferrite. Its mechanical properties are quite good. The operating temperature can reach 200 degrees Celsius. Moreover, its texture is hard, its performance is stable, and its cost performance is very good, so it is widely used. However, because of its strong chemical activity, its surface must be treated.
Characteristics: NdFeB permanent magnet is a permanent magnet material based on the intermetallic compound Nd2Fe14B. NdFeB permanent magnets have been widely used in modern industry and electronic technology due to their advantages such as high magnetic energy product, large rectifying force, and high energy density.
Material properties: Nd-Fe-B has the advantages of high cost performance and good mechanical properties; its disadvantages are low Curie temperature point, poor temperature characteristics, and easy to powder and corrode. It must be improved by adjusting its chemical composition and adopting surface treatment methods to meet the requirements of practical applications.
Manufacturing process: NdFeB is manufactured using powder metallurgy process.
Shape: Neodymium arc magnet, Neodymium cylindrical magnet, Neodymium block magnet, Neodymium ring magnet, Neodymium disc magnet, Neodymium countersunk head magnet.
Magnet Type 3: Samarium Cobalt Magnet
Samarium cobalt magnets are divided into SmCo5 and Sm2Co17 according to their composition. Due to the high price of samarium cobalt materials, the development of samarium cobalt is restricted. As a rare earth permanent magnet, samarium cobalt magnets not only have 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.
Samarium cobalt magnets are also called samarium cobalt permanent magnets, samarium cobalt permanent magnets, samarium cobalt powerful magnets, rare earth cobalt permanent magnets, etc. It is a magnetic material made by mixing Sm, Co and other rare earth metal materials, smelting them into alloys, and crushing, pressing, and sintering them. It has high magnetic energy product and extremely low temperature coefficient. The maximum working temperature can reach 350℃, and there is no limit to negative temperature. When the operating temperature is above 180°C, the maximum magnetic energy product, temperature stability and maximum magnetic energy product are obtained. The chemical stability is higher than that of NdFeB permanent magnets. Widely used in aerospace, national defense, military, microwave devices, communications, medical equipment, instrumentation, various magnetic transmission devices,
Typical shapes of samarium cobalt magnets: circular, ring, square, tile and other special shapes.
Magnet Type 4: Alnico Magnet
Alnico magnets are alloys composed of aluminum, nickel, cobalt, iron and other trace metal elements. The casting process can be made into different sizes and shapes with good processability. Cast AlNiCo permanent magnets have the lowest reversible temperature coefficient and can operate at temperatures up to 600 degrees Celsius. Alnico permanent magnet products are widely used in various instrumentation and other fields.
Classification of Alnico magnets: cast Alnico and sintered Alnico.
Application fields: Cast aluminum nickel cobalt products are mainly used in automotive parts, instrumentation, electroacoustics, motors, teaching and aerospace and military industries. They have the characteristics of low temperature coefficient, high temperature resistance, moisture resistance, not easy to oxidize, and good working performance. Stablize. Sintered alnico is produced using powder metallurgy. Suitable for producing complex, light, thin and small products. Widely used in instrumentation, communications, magnetoelectric switches and various sensors.
Shape: cylindrical, round, rectangular, flat, tile-shaped, horseshoe-shaped.
Magnet Strength
The strength of a magnet can be found in the magnet specifications, called BHmax, which is the maximum energy density of the magnet. This is defined in Megagauss Oersted (MGOe). On the magnetic demagnetization curve, this is the highest point of the magnet's strength, or the magnet's maximum magnetic energy product.
For neodymium (NdFeB) magnets, BHmax typically ranges from 30 MGOe to 55 MGOe. So when defining your magnet needs, remember that the higher the number, the stronger the magnet. Neodymium magnets produce the highest MGOe of all permanent magnet materials. The most common neodymium magnet grades are N35, N38, N40, N42, N45, N48, N50, N52, and N55.
For samarium cobalt (SmCo) magnets, BHmax ranges from 16 MGOe to 32 MGOe. Again, just like neodymium magnets, the higher the number, the stronger the magnet. Common grades of samarium cobalt magnets are 16, 18, 20, 22, 24, 26, 28, 30 and 32. As you can see, neodymium magnets have a higher MGOe value than samarium cobalt magnets, which means: neodymium magnets are stronger than samarium cobalt magnets.
Magnet Coercivity
First, let's define coercivity, the "Hci" of a material. When you look at the magnet chart for available materials, some grades will have different letters after them. These letters represent the magnet's ability to withstand demagnetizing forces, which can be temperature or other magnetic forces acting on the magnet. In the field of permanent magnets, manufacturers or suppliers have several ways of defining coercivity, but we will focus on the most widely used one, the lettering system. This lettering system uses the following letters after the grade to define magnet specifications for resistance to demagnetizing forces: M, H, SH, UH, EH, and TH.
When a letter is used after a magnet grade, it indicates that that particular material has a greater ability to resist demagnetizing forces. For our purposes, we will use heat as the demagnetizing force since it is the most common force that affects magnets. Also, the following examples are "general rules," not "hard and fast rules." We explain further in the "Do's and Don'ts" section below.
There are no letters after the strength grade of NdFeB magnets, namely N38, N45, N52, which indicates that it can work in an environment where the maximum operating temperature does not exceed 80°C. Magnets with "M" (i.e. N35M, N42M, etc.) generally indicate that the magnet can be used in working environments up to 100C. The "H" material is suitable for up to 120°C, the "SH" material is suitable for up to 150°C, the "UH" material is suitable for up to 180°C, the "EH" material is suitable for up to 200°C, the "TH" material is suitable for up to 220°C. Again, these are general specifications and other factors do play a role in coercivity decisions.
The Difference Between the Four Types of Magnets
Below is a tabular summary of the differences between NdFeB magnets, SmCo magnets, Alnico magnets and ferrite magnets:
| Characteristic | NdFeB Magnet | Samarium Cobalt Magnet | Alnico Magnet | Ferrite Magnet |
|---|---|---|---|---|
| Main ingredients | NdFeB alloy | SmCo alloy | AlNiCo alloy | Ferrite material |
| Magnetic properties | High magnetic induction intensity | High remanence and coercivity | Low magnetic induction intensity | Low magnetic induction intensity |
| Temperature stability | Medium | High | High | Low |
| Corrosion resistance | Low | Low | good | Good |
| Cost | Medium | High | Low | Low |
| Environmental factors | High in rare earth elements, mining and refining processes may have negative environmental impacts | High in rare earth elements, mining and refining processes may have negative environmental impacts | Does not rely on rare earth elements and is environmentally friendly | Does not rely on rare earth elements and is environmentally friendly |
| Main application areas | Motors, magnets, sound equipment, power supplies | Motors, magnets, sound equipment, power supplies | Sensors, medical equipment, automotive industry | Electromagnets, transformers, microwave equipment |
Precautions
Strength
So why not get the highest possible power every time? The reason is simply that the highest intensity is not always the right choice. For example, a magnet used as a sensor magnet may need to produce a specific magnetic field at a certain distance. This field will be defined in the sensor requirements. A suitable magnet would probably be Samarium Cobalt 24, so if Neodymium N52 is used it may cause the sensor to not work properly. Another example we often encounter is motors. Motor windings may be fine using N48 material, but may overheat using N55 material. Alternatively, in a holding application, a stronger magnet may be sufficient and a lower grade material may not be sufficient for holding. Additionally, defining the pull or holding strength, magnetic field requirements, or saturation point of the surrounding materials will aid in magnet selection.
Cost
Cost considerations are often part of the discussion. Generally speaking, the higher the grade, the higher the price. There are other variables, including shape and size, but for this purpose we'll use the general rule that higher grade = higher price. And, according to this rule, the higher the letter after the grade, the higher the price. For example, the N48H will be more expensive than the N48. The N48SH will cost more than the N48H, and so on. Finally, even lower grade materials may be more expensive than higher grade materials if you choose a higher letter. For example, the N35SH will most likely cost more than the N38 or even the N40.
Magnet Size and Shape
In the above example we used the "general rules" related to strength and coercivity. In any engineering concept, there are some factors that in turn influence other factors. The size and shape of the magnet also play a role. For example, very thin N45H may be listed as being able to handle an operating temperature of 120°C, however, if the size of the magnet is very thin, or the shape is very tiny, then it may be better to choose the N45SH material. And if shape and size are indeed up for discussion, we could see if there is a solution using other materials and magnets to keep the coercive force intact.
Not All Grades are Created Equal
Using permanent magnets can mean there are trade-offs. As you can see from the above information, you may need to determine whether strength or coercivity is more important. Alternatively, are neodymium magnets a better choice than samarium cobalt magnets or vice versa. There is a trade-off between strength and coercivity. As the magnet grade becomes stronger, the coercive force in the magnet may become unavailable. For example, if you need a magnet that can withstand temperatures of 180°C, you'll need UH materials. A magnet technician can work with you to determine the best magnet for your application. If you would like to learn more about past projects that XHMAG engineers have worked with our clients, please jump to our Design Assistance page.
About XHMAG
Thank you for reading our article, we hope it helps you better understand the four types of magnets. If you want to know more about permanent magnets, we recommend you visit XHMAG for more information. The world's leading magnet supplier, has been engaged in the R&D, manufacturing and sales of magnets since 2011. XHMAG provides customers with high-quality rare earth permanent magnet products and other non-rare earth permanent magnet products at very competitive prices. If you have any further concerns about magnets, please feel free to contact us.
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