Problems related to magnets
Magnetic materials are closely related to our life. From the most ordinary refrigerator refrigeration to high-end magnetic levitation, they are all inseparable. So, let’s learn about this magical material.
1. Why is a magnet magnetic?
Table of Contents
- 1. Why is a magnet magnetic?
- 2. How to define the performance of magnets?
- 3. How to divide metal magnetic materials?
- 4. Comparison of magnetic force size of several kinds of commonly used magnets
- 5. Sex-price analogy of different magnetic materials?
- 6. Characteristics of NdFeB magnet
- 7. What is single-sided magnetic iron?
- 8. The use of single-sided magnetic iron?
- 9. What are the matters needing attention during the transportation of magnets?
- 10. How to be magnetic?
- 11. Which ferrite material can conduct electricity?
- 12. What is the temperature of Juli, a permanent magnet ferrite?
- 13. What are the effective parameters of magnetic core?
- 14. Why is the radius of the corner circle very important for winding?
- 15. Which type of magnetic core is suitable for making transformers?
- 16. What kind of magnetic core is the best?
- 17. What is an anti-interference magnetic ring?
- 18. How to demagnetize magnetic core?
- 19. What is magnetic elasticity (ASKs)?
- 20. What is magnetic mismatch?
- 1. What are the characteristics and processing techniques of ferrite magnets?
- 2. Characteristics and processing technology of aluminum nickel cobalt magnet
- 3. Characteristics and processing technology of samarium cobalt magnet?
- 4. Magnetic field orientation and voltage pattern
- 5. The orientation direction of the magnet?
- 6. How to judge the magnetizing direction of the magnet?
- 7. Which magnet can be used in water?
- 8. What is magnetic tile?
- 9. What is the production process of ferrite magnetic tile?
- 10. Production process of NdFeB magnetic tile
- 11. Choice of workpiece cleaning method?
- 12. What are the precautions during the transportation of magnets?
- 13. What is a strong magnet?
- 14. How to demagnetize strong magnets?
- 15. How to detect the quality of coating?
- 16. What should be paid attention to when measuring the particle size distribution of NdFeB powder by laser particle size meter?
- 17. Which motors will use NdFeB magnetic tiles?
- 18. How to apply NdFeB magnetic tile in brushless motor?
- 19. Performance comparison between ferrite and NdFeB?
- 20. How to preserve NdFeB magnetic materials?
Most substances are composed of molecules, which are composed of atoms, which are composed of nuclei and electrons. Inside the atom, the electron rotates around the nucleus without stopping. Both movements of the electron generate magnetism. However, in most substances, the movement directions of electrons are different and messy, and the magnetic effects offset each other. Therefore, most substances are not magnetic under normal circumstances.
Ferromagnetic substances such as iron, cobalt, nickel or ferrite are different, whose internal electron spin can be spontaneously arranged in a small range to form a spontaneous magnetization region, this spontaneous magnetization region is called a magnetic domain. After magnetizing ferromagnetic substances, the internal magnetic domains are arranged in order and in the same direction, which strengthens the magnetism and constitutes a magnet. The process of the magnet taking the iron is the process of magnetization. The attraction is generated between the magnetized iron and the different polarity of the magnet, and the iron firmly sticks to the magnet.
2. How to define the performance of magnets?
There are mainly the following three performance parameters to determine the performance of the magnet:
- Remanence Br: After the permanent magnet is magnetized until the technology is saturated and the external magnetic field is removed, the retained Br is called remanence magnetic induction.
- Coercive force Hc: reduce the B of the permanent magnet magnetized to technology saturation to zero, and the strength of the reverse magnetic field to be added is called magnetic coercive force, which is called coercive force for short.
- Magnetic energy product BH: it represents the magnetic energy density built by the magnet in the air gap space and the magnet’s two magnetic pole spaces), namely the quiet magnetic energy of the unit volume of the air gap.
3. How to divide metal magnetic materials?
Metal magnetic materials are divided into two categories: permanent magnetic materials and soft magnetic materials. Materials with internal coercive force greater than 0.8kA/ m are usually called permanent magnetic materials, and materials with internal coercive force less than 0.8kA/ m are called soft magnetic materials.
4. Comparison of magnetic force size of several kinds of commonly used magnets
5. Sex-price analogy of different magnetic materials?
- Ferrite: low performance and lowest price, good temperature characteristics, corrosion resistance, good performance price ratio.
- NdFeB: highest performance, medium price, good strength, no high temperature resistance and corrosion
- Samarium: high performance, highest price, brittle, excellent temperature characteristics, corrosion resistance
- Aluminum nickel cobalt: low performance and medium price, excellent temperature characteristics, corrosion resistance, poor interference resistance.
Samarium Cobalt, ferrite and neodymium iron boron can be manufactured by sintering and bonding methods, with high sintering magnetic properties, poor molding, good formability of bonded magnet and much lower performance. AlNiCo can be made by casting and sintering methods. The cast magnet has high performance, poor formability, low sintering magnet and good formability.
6. Characteristics of NdFeB magnet
Neodymium iron boron permanent magnet material is a permanent magnet material based on intermetallic compound Nd2Fe14B. ND-Fe-B has extremely high magnetic energy product and supple force. Meanwhile, the advantage of high energy density makes Nd-Fe-B permanent magnet material widely used in modern industry and electronic technology, thus making instrumentation, electro-acoustic motor, the miniaturization, lightweight and thinning of such equipment as magnetic separation and magnetization become possible.
Material characteristics: the advantages of NdFeB are high cost performance and good mechanical characteristics; The disadvantage is that the temperature point of the center is low, the temperature characteristics are poor, and it is easy to cause powder corrosion, it must be improved by adjusting its chemical composition and adopting surface treatment method to meet the requirements of practical application.
Manufacturing process: NdFeB is manufactured by powder metallurgy.
Process flow: Batching → smelting ingot → Milling → embossing → sintering tempering → magnetic detection → grinding processing → Pin cutting processing → electroplating → finished product.
7. What is single-sided magnetic iron?
Magnets have two poles, but in some working positions, a single-sided pole magnet is required, so a piece of iron is needed to wrap the magnet so that the side of the iron is shielded, the magnet reflected by the iron sheet on the other side enhances the magnetic force of the other side. Such magnets are collectively referred to as single-sided or single-sided magnets. There is no real single-sided magnetic iron.
The materials used by single-sided magnetic iron are generally curved iron sheet and NdFeB strong magnet, while the shapes of NdFeB strong magnet used by single-sided magnetic iron are generally in the shape of round sheet.
8. The use of single-sided magnetic iron?
- (1) the print industry is widely used, and there is single-sided magnetic iron in gift packaging boxes, mobile phone packaging boxes, alcohol and tobacco packaging boxes, mobile phone packaging boxes, MP3 packaging boxes, moon cake packaging boxes and other products.
- (2) leather goods are widely used in the industry. Single-sided magnetic iron exists in leather goods such as bags, briefcases, travel bags, mobile phone covers, wallets, etc.
- (3) stationery is widely used in the industry, notebooks, whiteboard buttons, folders, magnetic nameplates and so on all have single-sided magnetic iron.
9. What are the matters needing attention during the transportation of magnets?
To pay attention to the indoor humidity, must be maintained at a dry level. The temperature should not exceed room temperature; Products in black or blank state can be properly oiled (General oil is OK); Electroplating products should be sealed in vacuum or stored in air isolation to ensure the corrosion resistance of the coating; magnetized products should be sucked together, packed and stored to avoid absorbing other metal bodies; Magnetized products should be stored away from disks, magnetic cards, tapes, computer monitors, watches and other objects sensitive to magnetic field. When the magnet is in magnetized state, it should be shielded, especially when it is in air transportation.
10. How to be magnetic?
Only materials that can be adsorbed to the magnet can play the role of isolating the magnetic field, and the thicker the material, the better the effect of the magnetic insulation.
11. Which ferrite material can conduct electricity?
Ferrite made of soft magnetic material belongs to magnetic material, which has high permeability and high resistivity, and is generally used at high frequency, mainly for electronic communication. Like the computers and televisions we contact every day, there are applications in them.
The Soft Magnetic Ferrite mainly includes Mn-Zn, Ni-Zn and so on, and the permeability of Mn-Zn ferrite is higher than that of Ni-Zn ferrite.
12. What is the temperature of Juli, a permanent magnet ferrite?
It is reported that the Curry temperature of ferrite is about 450 ℃, usually greater than or equal to 450 ℃. Hardness is about 480-580. The centered temperature of neodymium iron boron magnet is basically between 350-370℃. However, the use temperature of ND-Fe-B magnet can not reach the curry temperature. The magnetic performance has decreased much when the temperature exceeds 180-200 ℃, and the magnetic loss is also very large, which has lost its use value.
13. What are the effective parameters of magnetic core?
Magnetic cores, especially ferrite materials, have a variety of geometric sizes. In order to meet the requirements of various designs, the size of the magnetic core is also calculated to suit the optimization requirements. These existing magnetic core parameters include physical parameters such as magnetic path, effective area and effective volume, etc.
14. Why is the radius of the corner circle very important for winding?
The reason why the angle radius is important is that if the edge of the magnetic core is too sharp, it may cut the insulation of the wire during the precise and tight winding process. Pay attention to ensure that the edges of the magnetic core are smooth. Ferrite cores have a certain standard roundness radius, and these cores are polished and Burr-removed to reduce the sharpness of their edges. In addition, most of the magnetic cores are painted or covered to not only make their angles passive, but also make their winding surface smooth. The powder core has one side is the pressure radius, and the other side is the semicircle for Burr removal. For ferrite material, an additional edge coverage is provided.
15. Which type of magnetic core is suitable for making transformers?
The magnetic core that meets the need of the transformer should have high magnetic induction intensity on the one hand and keep its temperature rise within a certain limit on the other hand.
For inductance, the magnetic core should have a certain air gap to ensure a certain permeability level under high dc or ac drive conditions. Ferrite and tape cores can be handled with air gap, powder core has its own air gap.
16. What kind of magnetic core is the best?
It should be said that there is no answer to this question, because the choice of magnetic core is determined according to the application occasion and frequency, and the choice of any material is also considered by factors such as the market, for example, some materials can ensure that their temperature rise is small, but their prices are expensive. In this way, when materials are selected for higher temperature rise, it is possible to choose materials with larger sizes but lower prices to complete such work. Therefore, the so-called best materials should first be selected according to the application requirements of your inductance or transformer, from this point of view, its operating frequency and cost are important factors. The optimal selection of different materials is based on switching frequency, temperature rise and magnetic flux density.
17. What is an anti-interference magnetic ring?
Anti-interference magnetic ring is also called ferrite magnetic ring. The source of the anti-interference magnetic ring is that it can play an anti-interference effect. For example, electronic products are affected by external disorder signals, invade electronic products, and make electronic products receive external disorder signals and fail to operate normally, just can have this function, as long as the product has an anti-interference magnetic ring, it can prevent the external disorder signal from invading the electronic products, make the electronic products run normally, and play an anti-interference effect, so it is called an anti-interference magnetic ring.
Anti-interference magnetic ring is also called ferrite magnetic ring, because ferrite magnetic ring is made of ferrite materials such as iron oxide nickel oxide, zinc oxide and copper oxide, because these materials contain ferrite components, the product made of ferrite material looks like a ring, so it is called ferrite magnetic ring as time passes.
18. How to demagnetize magnetic core?
The method is to add 60hz alternating current to the magnetic core to make its initial driving current saturated both the positive and negative terminals, and then gradually and slowly reduce the driving level, repeat several times until it drops to 0. This will make it a bit restored back to the original initial state.
19. What is magnetic elasticity (ASKs)?
After the magnetic material is magnetized, a small geometric size change will occur. The size of this change should be at the level of parts per million, which is called asks for money. For some applications, such as the ultrasonic wave generator, it uses the advantage of this characteristic to obtain mechanical deformation through magnetic excited striction. However, in other problems, when it works on the Audible audio frequency range, there will be a kind of noise. Therefore, low magnetic shrinkage materials can be applied to this situation.
20. What is magnetic mismatch?
This phenomenon occurs in ferrite, which is manifested by the decrease in permeability when the magnetic core is degaussed. This kind of demagnetization can appear after the operating temperature is higher than the temperature of the main point, and then it can be applied with the alternating current or mechanical vibration of which the magnitude is gradually reduced.
In this phenomenon, the permeability first increases to its original level, and then it rapidly decreases indexized. If there are no special conditions expected by the application, the change in permeability will be very small, because many changes will change within a few months after production. High temperature accelerates the decrease of this permeability. Magnetic discordance will appear repeatedly after each successful demagnetization, so it is different from aging.
1. What are the characteristics and processing techniques of ferrite magnets?
- Features: its main raw materials include KaFe12O19 and SrFe12O19. Manufactured by ceramic process, texture is relatively hard, a fragile material, because ferrite magnets have good temperature resistance, low price, moderate performance, has become the most widely used permanent magnet.
- Features: it has higher magnetic performance, better time stability and lower temperature coefficient.
- Ferrite magnets are widely used in electricity meters, instruments, motors, automatic control, microwave devices, radar and medical devices.
- Ferrite magnet magnetizing direction: Axial, radial or as required.
- Ferrite magnet shape: can produce cylindrical, circular, rectangular, flat, tile, axe shape.
2. Characteristics and processing technology of aluminum nickel cobalt magnet
Characteristics of aluminum nickel cobalt magnet: it 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 good. Cast alnico permanent magnet has the lowest reversible temperature coefficient and the working temperature can be as high as 600 ℃. Alnico permanent magnet products are widely used in various instrumentation and other applications.
Classification of aluminum-nickel-cobalt magnets: it can be divided into two categories: cast aluminum-nickel-cobalt and sintered aluminum-nickel-cobalt.
Aluminum nickel cobalt application places casting aluminum nickel cobalt products are mainly used in automobile parts, instruments and meters, electroacoustics, electrical machines, teaching, aerospace, military and other fields, with low temperature coefficient, high temperature resistance, moisture resistance, it is not easy to oxidize and has the advantages of good working stability. Sintered Alnico is produced by powder metallurgy, which is suitable for producing products with complex, light, thin and small shapes, which are widely used in instrumentation, communication, magnetic and electrical switches and various sensors.
Aluminum nickel cobalt magnet shape: can produce cylindrical, round ring, rectangular body shape, flat shape, tile shape, horseshoe shape.
3. Characteristics and processing technology of samarium cobalt magnet?
Samarium magnet is also called samarium magnet, samarium permanent magnet, samarium permanent magnet, samarium strong magnet, rare earth cobalt permanent magnet, etc. It is a kind of magnetic material made from samarium, cobalt and other rare earth metal materials through matching, melting into alloy, and after crushing, forming and sintering. It has high magnetic energy product and extremely low temperature coefficient. The maximum working temperature can reach 350℃, and the negative temperature is not limited. When the working temperature is above 180℃, its maximum magnetic energy product, temperature stability and chemical stability exceed those of nd-fe-B permanent magnet material. It has strong corrosion resistance and oxidation resistance. Therefore, it is widely used in aerospace, national defense, microwave devices, communications, medical equipment, instruments, meters, various magnetic transmission devices, sensors, magnetic processors, motor, magnetic crane, etc.
Production process of samarium cobalt magnet: ingredients → smelting ingot → milling → compression → sintering tempering → magnetic detection → grinding processing → cutting pin processing → finished product.
Samissue magnet shape: wafer, ring, square piece, square bar, tile shape, special shape can be processed according to requirements.
4. Magnetic field orientation and voltage pattern
Powder magnetic field orientation is one of the key technologies to manufacture high-performance sintered magnets. The purpose of magnetic field orientation is to make every powder particle’s easy magnetizing direction (c axis) orient along the same direction to make various special magnets, in that case, along the direction of the powder particle’s c-axis orientation, there will be the maximum remanence Br, so as to improve the maximum magnetic energy product of the magnet. The orientation of the powder has an important influence on the residual magnetic Br and maximum magnetic energy product (BH)max of the magnet. Powder compression has two purposes: one is to press the powder into a certain shape and size according to user requirements; The other is to maintain the crystal orientation obtained in the magnetic field orientation. At present, there are three commonly used compression methods: molding method, molding plus cold isostatic pressure and rubber molding (plus cold isostatic pressure). The molding process is the main process of magnetic powder oxygen absorption, so there are strict anti-oxidation measures in the molding process, and the magnetic powder weighing or pressing process is required to work under the protection of inert gas. The equipment used in this process is a molding press.
5. The orientation direction of the magnet?
Sintered NdFeB permanent magnet is an anisotropic magnet. Orientation direction: the direction in which an anisotropic magnet can obtain the best magnetic properties is called the orientation direction of a magnet, also known as the “axis of orientation”,”the axis of easy magnetization”.
6. How to judge the magnetizing direction of the magnet?
Available magnetic pole test pieces. The principle of the magnetic pole test piece is actually to put some iron powder in the compartment, and then clamp it with transparent things. When there is magnetic force, the mezzanine magnetic powder will be attracted there. In the non-magnetic region, there is no magnetic powder, thus the distribution of magnetic pole can be observed.
7. Which magnet can be used in water?
Depending on the material, not every magnet can be used in water. A rusty magnet may endanger aquatic life. Ferrite has strong corrosion resistance and oxidation resistance, and can be used normally in water.
8. What is magnetic tile?
Magnetic tile is a kind of tile magnet mainly used in permanent magnet motors.
9. What is the production process of ferrite magnetic tile?
Ferrite tiles are mainly sintered ferrite.
The production process of sintered ferrite magnetic tile is mainly divided into wet compression, dry compression, dry compression, and the difference between the homogeneity and the homogeneity lies in whether there is a oriented magnetic field during the press forming. This article mainly introduces the technology of the opposite sex by wet pressure.
The process flow of wet pressing is as follows: raw material→pre-burning →coarse crushing (one-time ball milling) →batching →two-time ball milling (wet grinding) →magnetic field shaping→sintering →grinding →cleaning →magnetizing.
Because the formed slurry contains water, particles formed in the magnetic field are easy to turn, so it can obtain a higher degree of orientation and higher performance than the dry compression.
10. Production process of NdFeB magnetic tile
Sintering neodymium iron boron magnetic tile ingredients → smelting → crushing → milling → magnetic field molding → isostatic holp→vacuum sintering and tempering → wire cutting and other processes → electroplating → magnetization.
11. Choice of workpiece cleaning method?
The placement of the workpiece in the cleaning tank has a great relationship with the cleaning quality, and its placement is related to the size, shape and structure of the workpiece. Generally speaking, overlapping stacking between workpieces or excessive stacking at one time will affect the cleaning effect.
Although neodymium iron boron magnetic materials have different shapes, they are mostly small parts. It can be placed on the nylon net, shaking and cleaning in the cleaning tank, which is conducive to the shedding of the dirt on the surface of the workpiece, and also conducive to the damage of the water film with the blind hole workpiece, so that the cavitation effect is easy to occur in the blind hole. Another way of decoration is to directly flatten the workpiece on the bottom plate of the cleaning tank (that is, the ultrasonic transducer radiation plate), so that the workpiece can withstand strong ultrasonic impact. Practice has proved that this method of directly putting the workpiece on the bottom plate for cleaning has the best cleaning effect and the highest efficiency.
12. What are the precautions during the transportation of magnets?
To pay attention to the indoor humidity, must be maintained at a dry level. The temperature should not exceed room temperature; Products in black or blank state can be properly oiled (general oil is OK); Electroplating products should be sealed in vacuum or stored in air isolation to ensure the corrosion resistance of the coating; magnetized products should be sucked together, packed and stored to avoid absorbing other metal bodies; Magnetized products should be stored away from disks, magnetic cards, tapes, computer monitors, watches and other objects sensitive to magnetic field. When the magnet is in magnetized state, it should be shielded, especially when it is in air transportation.
13. What is a strong magnet?
Strong magnet refers to NdFeB magnet. Its magnetic property greatly surpasses that of ferrite magnet, alnico, samarium cobalt. Ndfeb magnets can absorb 640 times the weight of its own weight, so NdFeB is often called a strong magnet by people outside the industry.
14. How to demagnetize strong magnets?
According to the use of strong magnets, certain methods can be formulated for demagnetization.
1) high temperature demagnetization method:
The main operation of the high temperature demagnetization method is to throw the magnet into the high temperature furnace for heating, after high-temperature processing, the magnetism of the magnet will be removed. But during the heating process, the structure of the object inside the magnet will change dramatically because of the high temperature, therefore, this demagnetization method is generally used for scrap and recycling magnets.
2) vibration demagnetization method:
The operation of this method is very simple that the strong magnet is vibrated strongly, and the internal structure of the magnet is changed after the vibration operation, so as to change the physical properties of the magnet this way is generally not effective using this kind of demagnetization method, only a small amount of demagnetization can be used temporarily.
3) magnet ac demagnetization method:
This way of demagnetization is to put the magnet into the space that can generate an alternating magnetic field. After the interference of the alternating magnetic field, the internal structure of the magnet will be disrupted, thus achieving the effect of demagnetization, this method is a more common demagnetization method.
The above three methods are effective for strong magnet demagnetization, but we usually prefer ac demagnetization method, which has better demagnetization effect than high temperature demagnetization method and vibration demagnetization method and higher efficiency, it is the most widely used method in industrial production at present.
15. How to detect the quality of coating?
The quality of the coating directly affects the service life of NdFeB. The main methods for testing the quality of NdFeB coatings are:
- 1. Visual appearance: the appearance is mainly observed by naked eyes, and it is the best under natural light (sunlight, not direct) or under fluorescent lamps with an illuminance equivalent to 40w. There should be no foaming, peeling, partial plating and uneven color, stains, water stains, etc.
- 2. Measurement of coating thickness.
- 3. Drop test (mainly for galvanized products).
- 4. Scribing test (generally used for nickel-plated products).
- 5. Exciting cold and exciting heat test.
- 6. PCT pressure test.
- 7. SST salt spray test.
- 8. Constant temperature and humidity test, etc.
16. What should be paid attention to when measuring the particle size distribution of NdFeB powder by laser particle size meter?
Neodymium iron boron particles have strong magnetism. Generally, the average particle size is measured by breathable method. At present, it is mainly used to measure particle size distribution by dry laser particle size meter. Neodymium iron boron powder has the characteristic of spontaneous combustion in the air. When the ambient temperature is slightly higher and its concentration reaches a certain level, it will cause spontaneous combustion. It often ignites the vacuum cleaner pipeline and the filter screen and burns the vacuum cleaner. The following measures to prevent spontaneous combustion should be adopted:
- (1) use inert gases such as high-pressure nitrogen as the gas source;
- (2) replace the vacuum cleaner pipe with smooth polyethylene pipe, so that the particles are not deposited in the pipeline;
- (3) choose a water-filtered vacuum cleaner.
17. Which motors will use NdFeB magnetic tiles?
Neodymium iron boron is a permanent magnet material and an indispensable part of permanent magnet motor. Rare earth permanent magnet motor is the largest application field of neodymium iron boron magnet, accounting for about 70% of the total magnet. It accounts for 40% ~ 50%, so the computer industry is the largest user of permanent magnetic motors.
Common permanent magnet motors are: permanent magnet dc motor and permanent magnet ac motor.
Permanent magnet dc motors include: brush dc motor, brushless motor, stepper motor, etc.
Permanent magnet ac motors include synchronous permanent magnet motor, permanent magnet servo motor, etc.
18. How to apply NdFeB magnetic tile in brushless motor?
As we all know, NdFeB magnetic tile or NdFeB radial magnetic ring is as important as human heart in motor products. The magnetic field generated by the coil after the current is powered up drives NdFeB magnetic tile or NdFeB radial magnetic ring magnetic field. Therefore, it is very important that the magnetic field strength of the radial magnetic ring of NdFeB and the motor operation efficiency are multiple. Let’s first look at the advantages of brushless motors:
- 1. No brush, low interference brushless motor in addition to the brush, the most direct change is no electric spark generated when the brush motor is running, which greatly reduces the interference of electric spark to remote control radio equipment.
- 2. Low noise, smooth operation brushless motor without brush, the friction during operation is greatly reduced, the operation is smooth, the noise will be much lower, this advantage is a huge support for the stability of the model operation.
- 3. Long life, low maintenance cost less brush, brushless motor wear mainly on the bearing, from a mechanical point of view, brushless motor is almost a maintenance-free motor, when necessary, just do some dust removal maintenance.
Brushless motor, as the name implies, certainly does not need carbon brush original, forming a magnetic field around the winding coil, which rotates fully around the geometric axis of the motor, and this magnetic field drives the rotation of the permanent magnet magnetic steel on the rotor, the motor turns up. The performance of the motor is related to the number of NdFeB magnetic tiles, the radial magnetic flux intensity of NdFeB, the input voltage of the motor, etc, the electronic governor that really determines its performance is a good electronic governor without a brush, which requires the overall control of the single chip microcomputer control program design, circuit design, complex processing technology and other processes, so the price is much higher than that of a brush motor.
- Appearance: ferrite is loose and has no metallic luster. Generally, it is not electroplated, usually black. Neodymium iron boron is basically electroplated, otherwise it is easy to rust. The surface has silver metallic luster.
- Magnetic: according to the data, the magnetic force of ferrite is usually 800-1000 gauss and the density is 5(g/cm3). In the state of bare magnet, the magnetic force of NdFeB can reach about 3500 gauss. Density is 7.5(g/cm3).
- Performance: ferrite has good temperature resistance and stability, compared with ordinary NdFeB temperature resistance of only 80 degrees. And the price is also cheap. Ndfeb; Ndfeb has the characteristics of small volume, light weight and strong magnetism. It is completely different from ferrite in magnetism.
- Price: ferrite is usually cheap, and many of them are calculated on a piece-by-piece basis. The price has an impact on the shape, size and processing difficulty of ferrite. Ndfeb: now the price of NdFeB changes almost every day, depending on the brand and special requirements you need to use.
20. How to preserve NdFeB magnetic materials?
- 1. Ndfeb magnets should not be close to electronic equipment, because the magnet itself has positive and negative poles, and there is a circuit loop. If it is close, it will affect the electronic equipment and control circuits and affect the use.
- 2. Do not store the magnet in a humid environment to avoid its oxidation, resulting in changes in appearance, physical characteristics and magnetic properties.
- 3. People who are sensitive to metal objects will have rough skin and red if they get close to magnets. If the above reaction occurs, please do not touch the magnet.
- 4. Do not approach the magnet to floppy disk, hard disk drive, credit card, tape, credit card, TV picture tube, etc. If the magnet is close to the magnetic recorder and other devices, the recorded data will be affected or even destroyed.
Pay attention to the following aspects:
- 1. Never put magnets around strong current;
- 2. The magnet cannot be baked on the fire, after high temperature;
- 3. Magnets cannot be knocked and vibrated violently;
- 4. Small magnets cannot be put together with large magnets;
- 5. Shoe-shaped magnets should also be added with a soft iron on the two poles to connect the two poles, and put the south and north poles of adjacent magnets upside down;
- 6. Small magnets (such as magnetic needles) cannot be put together with large magnets.
When preserving NdFeB magnets, the environmental requirements are dry, and the chemicals such as acid and alkali are not allowed to be encountered by NdFeB magnets, so as not to affect NdFeB magnets and cause corrosion, rust and other phenomena. Therefore, placing NdFeB magnetic material on a layer of wooden board has a good effect on avoiding moisture. Always be very careful when storing magnets, because the magnets will be adsorbed together and may hurt your fingers. When magnets adsorb each other, they may also damage the magnet itself due to collision (hitting corners or hitting cracks).
Source: China Permanent Magnet Manufacturer – www.ymagnet.com