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Neodymium magnets have had a huge impact on many different industries, from electronics and medical devices to cars and green energy, and they are one of the strongest magnets you can buy. At Najing Huajin Magnet, we are experts in designing and making these magnets to meet the high standards of our customers all over the world. In this blog, we'll look at how to read neodymium grade charts, compare magnet strength, and share tips for choosing the best supplier.   The Role of the Neodymium Grade Chart   The neodymium grade chart (e.g., N35, N42, N52) is a list that puts magnets into different groups based on how strong their magnetism is and how well they can resist high temperatures. Here is a quick reference:   Grade           BHmax (MGOe)         Max Operating Temperature (°C)               Common Applications N35                           35                                             80                                           Hobby projects, DIY N42                           42                                             80                                            Motors, sensors N52                           52                                             80                                   High-performance industrial systems     More detailed forms can be obtained by sending an email.   Decoding the Neodymium Magnets Strength Chart   Another very useful resource when choosing magnets is the neodymium magnets strength chart. This chart provides important information about the magnetic force of different magnet grades. It helps designers to compare the pull strength, energy density, and overall performance of magnets in different situations.   By referring to a neodymium magnets strength chart, you can make sure that your applications – from electric motors to advanced sensor systems – receive the precise magnetic force needed for them to work as well as possible. At Nanjing Huajin Magnet, we use these charts to check the quality of our magnets. This means that every magnet we deliver will be strong enough for use in industrial applications.    Choosing Wholesale Neodymium Magnets Manufacturers: 5 Key Factors   Partnering with the right manufacturers of neodymium magnets is important for consistency, cost, and compliance.Here's what to look for:   Certifications: Look for ISO 9001, RoHS, and REACH compliance.   Customisation: Can they make changes to sizes, coatings (Ni, epoxy, gold), and magnetization patterns?   Testing capabilities: Do they provide BH curves, flux reports, or salt spray test results?   Scalability: Make sure they can handle large orders without delaying the delivery times.   Technical Support: They should be experts in choosing the right materials and making sure you use them in the best way.   Neodymium magnets are at the heart of many modern technologies. Whether you’re consulting a neodymium grade chart to determine the best magnet for your application, or reviewing a neodymium magnet's strength chart to understand performance parameters, selecting the right magnet is critical. As a leading wholesale neodymium magnets manufacturer, Nanjing Huajin Magnet is dedicated to supporting your success with products that combine strength, quality, and precision.   For more information or to discuss your specific needs, please contact our team today. Let us help you harness the power of neodymium magnets to drive your innovations forward.  

Accurately measuring magnetic field strength is critical for industries relying on neodymium (NdFeB) magnets, from quality control in manufacturing to optimizing applications in motors, sensors, and medical devices. A Gauss meter (or Tesla meter) is the go-to tool for this task. In this guide, we’ll explain how to use a Gauss meter effectively and why precise measurements matter for NdFeB magnet performance.   The working principle of the Gauss meter is mainly based on the application of the Hall effect: when a current-carrying conductor is placed in a magnetic field, due to the action of the Lorentz force, a transverse potential difference will appear in the direction perpendicular to both the magnetic field and the current. The gaussmeter is an instrument for measuring the magnetic field based on the principle of the Hall effect. The Hall probe generates a Hall voltage in the magnetic field due to the Hall effect. The measuring instrument converts the magnetic field strength value based on the Hall voltage and the known Hall coefficient. The current Gauss meter is generally equipped with a unidirectional Hall probe, which can only measure the magnetic field strength in one direction, that is, it can only measure the magnetic field strength perpendicular to the direction of the Hall chip. In some high-end measurement fields, there are also Hall probes that can measure three-dimensional magnetic fields. Through the conversion of the measuring instrument, the magnetic field strength in the X, Y, and Z axis directions can be displayed at the same time, and the maximum magnetic field strength can be obtained through trigonometric conversion.   Notes on using Gauss meter: 1. Do not bend the probe excessively When using a Gauss meter to measure the meter. The Hall chip at the end should generally be lightly pressed against the surface of the magnet. This is to ensure that the measuring point is fixed, and on the other hand, it is to ensure that the probe is close to the measuring surface and is horizontal to the measuring surface, but do not press hard.   2. Both sides of the Hall chip can be sensed, but the values ​​and polarities are different. The scale surface is used for convenient point selection and cannot be used as a measuring surface. The non-scale surface is the measuring surface.   The Gauss meter measures the magnetic field strength Bz of the default vertical measurement surface. The magnetic field strength B will be stronger than the center, but Bz is not necessarily stronger than the center. It is just the area limitation of the Hall chip measurement. Generally, the measured magnetic field strength of the corner is stronger than the center, at least not lower than the center magnetic field.   It is important to note here that when the magnetization directions are different, the measurement values ​​will differ greatly even for the same measurement surface.  

The magnetism of sintered NdFeB materials mainly comes from their easily magnetized crystal structure. They can obtain extremely high neodymium magnet grades under the action of a strong external magnetic field, and their magnetism will not disappear after the external magnetic field disappears. Therefore, "magnetization" is a key step for sintered NdFeB materials to obtain magnetism. In the production and preparation process of sintered NdFeB materials, magnetization is the last step before the delivery of the finished product, but the magnetic field orientation of the NdFeB blank, that is, the future magnetization direction, has been determined when the magnetic powder is pressed into a blank.   Magnetic field orientation   Magnetic materials are divided into two categories: isotropic magnets and anisotropic magnets. Isotropic magnets have the same magnetic properties in any direction and can be attracted together at will; anisotropic magnets have different magnetic properties in different directions, and the direction that can obtain the best magnetic properties is called the orientation direction of the magnet. For a square sintered NdFeB magnet, only the magnetic field intensity in the orientation direction is the largest, and the magnetic field intensity in the other two directions is much smaller.   If the magnetic material has an orientation process during the production process, it is an anisotropic magnet. Sintered NdFeB is generally formed and pressed by magnetic field orientation, so it is anisotropic. Therefore, the orientation direction, that is, the future magnetization direction, needs to be determined before production. Powder magnetic field orientation is one of the key technologies for manufacturing high-performance NdFeB.   Magnetization direction and method   Magnetization is the process of applying a magnetic field to the sintered NdFeB permanent magnet along the magnetic field orientation direction and gradually increasing the magnetic field strength to reach the technical saturation state.   Sintered NdFeB generally has several shapes such as square, cylindrical, ring, tile, etc. It is generally divided into single-pole and multi-pole magnetization. After multi-pole magnetization, multiple N and S poles can be presented on one plane.

Sintered NdFeB magnets are core functional components and are widely used in instruments and equipment such as motors, electroacoustics, magnetic attraction, and sensors. The magnets are subject to environmental factors such as mechanical force, hot and cold changes, and alternating electromagnetic fields. If the working environment is over the standard, it will seriously affect the function of the equipment and cause huge losses. Therefore, in addition to magnetic performance, we also need to pay attention to the mechanical, thermal, and electrical properties of magnets, which will help us better design and use magnet, and is also of great significance for improving their service stability and reliability.   Mechanical Properties   The mechanical properties of magnets include hardness, compressive strength, bending strength, tensile strength, impact toughness, etc. NdFeB is a typical brittle material. The hardness and compressive strength of magnets are high, but the bending strength, tensile strength, and impact toughness are poor. This makes it easy for magnets to lose corners or even crack during processing, magnetization, and assembly. Magnets are usually fixed in components and equipment by means of slots or adhesives, and shock absorption and buffering protection are also provided.   The fracture surface of sintered NdFeB is a typical intergranular fracture. Its mechanical properties are mainly determined by its complex multiphase structure and are also related to the formula composition, process parameters, and structural defects (voids, large grains, dislocations, etc.). Generally speaking, the lower the total amount of rare earth, the worse the mechanical properties of the material. By adding low-melting-point metals such as Cu and Ga in appropriate amounts, the toughness of neodymium magnet can be enhanced by improving the distribution of grain boundary phases. Adding high-melting-point metals such as Zr, Nb, and Ti can form precipitation phases at the grain boundaries, which can refine the grains and inhibit crack extension, helping to improve strength and toughness; but excessive addition of high-melting-point metals will cause the hardness of the magnetic material to be too high, seriously affecting processing efficiency.   In the actual production process, it is difficult to take both the magnetic properties and mechanical properties of magnetic materials into account. Due to cost and performance requirements, it is often necessary to sacrifice their ease of processing and assembly.   Thermal Properties   The main thermal performance indicators of NdFeB magnets include thermal conductivity, specific heat capacity and thermal expansion coefficient.   The performance of neodymium magnet gradually decreases with the increase of temperature, so the temperature rise of permanent magnet motor becomes a key factor affecting whether the motor can run under load for a long time. Good heat conduction and heat dissipation can avoid overheating and maintain the normal operation of the equipment. Therefore, we hope that the magnetic steel has a higher thermal conductivity and specific heat capacity, so that the heat can be quickly conducted and dissipated, and at the same time, the temperature rise will be lower under the same heat.   Electrical Properties   In the alternating electromagnetic field environment of the permanent magnet motor, the magnetic steel will produce eddy current loss and cause temperature rise. Since the eddy current loss is inversely proportional to the resistivity, increasing the resistivity of the NdFeB permanent magnet will effectively reduce the eddy current loss and temperature rise of the magnet. The ideal high-resistivity magnetic steel structure is to form an isolation layer that can prevent electron transmission by increasing the electrode potential of the rare earth-rich phase, so as to achieve the wrapping and separation of the high-resistance grain boundary relative to the main phase grains, thereby improving the resistivity of the sintered NdFeB magnet. However, neither the doping of inorganic materials nor the layering technology can solve the problem of magnetic performance deterioration. At present, there is still no effective preparation of magnets with both high resistivity and high performance.        

The usage scenarios of NdFeB permanent magnets can be roughly divided into adsorption, repulsion, induction, electromagnetic conversion, etc. In different application scenarios, the requirements for magnetic fields are also different.   The spatial structure of 3C products is extremely limited, but at the same time requires a higher adsorption strength. The spatial structure does not allow the size of the magnet to increase, so the magnetic field strength needs to be improved through magnetic circuit design；   In situations where magnetic field sensing is required, overly divergent magnetic lines of force can cause false touches on the Hall element, and the magnetic field range needs to be controlled through magnetic circuit design;   When one side of the magnet needs high adsorption strength and the other side needs to shield the magnetic field, if the magnetic field strength of the shielding surface is too high, it will affect the use of electronic components. This problem also needs to be solved through magnetic circuit design.   Where precise positioning is required and where a uniform magnetic field is required, etc.   As in all the above cases, it is difficult to achieve the use requirements using a single magnet, and when the price of rare earth is high, the volume and amount of the magnet will seriously affect the cost price of the product. Therefore, we can modify the magnetic circuit structure of the magnet to meet different usage scenarios while meeting the adsorption conditions or normal use, while reducing the amount of magnet to reduce costs.   Common magnetic circuits are roughly divided into HALBACH ARRAY, multi-pole magnetic circuit, focused magnetic circuit, added magnetic conductive material, flexible transmission, single-sided magnetism, and magnetic focusing structure. The following introduces them one by one.   HALBACH ARRAY This is an engineering-approximate ideal structure, the goal is to use the least amount of magnets to generate the strongest magnetic field. Due to the special magnetic circuit structure of the Halbach array, most of the magnetic field loop can circulate inside the magnetic device, thereby reducing leakage magnetic field to achieve magnetic concentration and realize self-shielding effect in the non-working area. After the optimized annular Halbach magnetic circuit design, the non-working area can achieve at least 100% shielding. As can be seen in the figure, the magnetic lines of force of the conventional magnetic circuit are symmetrically divergent, while the magnetic lines of force of the Halbach array are mostly concentrated in the working area, thus improving the magnetic attraction.     Multi-pole magnetic circuit The multi-pole magnetic circuit mainly utilizes the characteristic that the magnetic lines of force preferentially select the nearest opposite pole to form a magnetic circuit. Compared with ordinary single-pole magnets, the magnetic lines of force (magnetic field) of the multi-pole magnetic circuit are more concentrated on the surface, especially the more poles there are, the more obvious it is. There are two types of multi-pole magnetic circuits, one is the multi-pole magnetization method of a magnet, and the other is the adsorption method of multiple single-pole magnets. The difference between these two methods lies in the cost, and the actual functions are the same. The advantage of multi-pole magnetic circuits in small-pole adsorption is very obvious.     Focusing magnetic circuit The focused magnetic circuit utilizes a special magnetic circuit direction to concentrate the magnetic field in a small area, making the magnetic field in that area very strong, even reaching 1T, which is very helpful for accurate positioning and local sensing.     Magnetic materials Magnetic conductive materials utilize the magnetic field loop to preferentially select the path with the smallest magnetic resistance. Using high magnetic conductive materials (SUS430, SPCC, DT4, etc.) in the magnetic circuit can well guide the direction of the magnetic field, thereby achieving the effect of local magnetic concentration and magnetic isolation.     Flexible transmission The characteristics of flexible transmission are that the attraction and repulsion formed by magnets achieve non-contact flexible transmission, small size, simple structure, torque can be changed according to the volume of the magnet and the size of the air gap, and the adjustable space is large.     Single-sided magnetic The characteristic of single-sided magnet is that it shields the polarity of one side of the magnet and retains the polarity of the other side. The direct adsorption force is large, but the magnetic force attenuates greatly as the distance increases.     Magnetic structure The characteristic of the form is that the magnet and iron are arranged relative to each other according to polarity. As the ratio of magnet thickness to iron thickness increases, the thicker the iron thickness, the smaller the divergence of magnetic lines of force. The magnetic concentrating structure can be flexibly designed according to the size of the air gap to achieve the best effect, which can effectively save magnets and evenly distribute the magnetic field along the iron. However, the disadvantage is that the assembly cost is relatively high. The magnetic circuit of a neodymium magnet rod is this structure.      

NdFeB magnets are produced by powder metallurgy process. They are a kind of powder material with strong chemical activity. There are tiny pores and cavities inside them, which are easily corroded and oxidized in the air. After the material is corroded or the components are damaged, the magnetic properties will be attenuated or even lost over time, thus affecting the performance and life of the whole machine. Therefore, strict anti-corrosion treatment must be carried out before use.   At present, the anti-corrosion treatment of NdFeB generally adopts electroplating, chemical plating, electrophoresis, phosphating and other methods. Among them, electroplating is the most widely used as a mature metal surface treatment method.   NdFeB electroplating uses different electroplating processes according to the different product use environments, and the surface coatings are also different, such as zinc plating, nickel plating, copper plating, tin plating, precious metal plating, etc. Generally, zinc plating, nickel plating + copper + nickel plating, nickel plating + copper + chemical nickel plating are the mainstream processes. Only zinc and nickel are suitable for direct plating on the surface of NdFeB magnets, so multi-layer electroplating technology is generally implemented after nickel plating. Now the technical difficulties of direct copper plating of NdFeB have been broken through, and direct copper plating and then nickel plating is the development trend. Such a coating design is more conducive to the thermal demagnetization index of NdFeB components to meet customer needs. The most commonly used coatings for NdFeB strong magnets are zinc plating and nickel plating. They have obvious differences in appearance, corrosion resistance, service life, price, etc.:   Polishing difference: Nickel plating is superior to zinc plating in polishing, and the appearance is brighter. Those who have high requirements for product appearance generally choose nickel plating, while some magnets are not exposed and the requirements for product appearance are relatively low. Generally, zinc plating is used.       Difference in corrosion resistance: Zinc is an active metal that can react with acid, so its corrosion resistance is poor; after nickel plating surface treatment, its corrosion resistance is higher.   Difference in service life: Due to different corrosion resistance, the service life of zinc plating is lower than that of nickel plating. This is mainly reflected in the fact that the surface coating easily falls off after a long time of use, causing oxidation of the magnet and thus affecting the magnetic properties.   Hardness difference: Nickel plating is harder than zinc plating. During use, it can greatly avoid collisions and other situations that may cause corner loss and cracking of NdFeB strong magnets.   Price difference: Zinc plating is extremely advantageous in this regard, and the prices are arranged from low to high as zinc plating, nickel plating, epoxy resin, etc.   When choosing NdFeB strong magnets, it is necessary to consider the use temperature, environmental impact, corrosion resistance, product appearance, coating bonding, adhesive effect, and other factors when choosing the coating.    

Many customers may have a question: do magnets of the same performance and volume have the same suction force? It is said on the Internet that the suction force of NdFeB magnets is 640 times its own weight. Is this credible?   First of all, it should be made clear that magnets only have adsorption force on ferromagnetic materials. At room temperature, there are only three types of ferromagnetic materials, they're iron, cobalt, nickel, and their alloys. They have no adsorption force on non-ferromagnetic materials.   There are also many formulas on the Internet for calculating suction. The results of these formulas may not be accurate, but the trend is correct. The strength of the magnetic suction is related to the magnetic field strength and the adsorption area. The greater the magnetic field strength, the larger the adsorption area and the greater the suction.   The next question is, if the magnets are flat, cylindrical, or elongated, will they have the same suction force? If not, which one has the greatest suction force?       First of all, it is certain that the suction force is not the same. To determine which suction force is the greatest, we need to refer to the definition of the maximum magnetic energy product. When the working point of the magnet is near the maximum magnetic energy product, the magnet has the greatest work energy. The adsorption force of the magnet is also a manifestation of work, so the corresponding suction force is also the greatest. It should be noted here that the object to be sucked needs to be large enough to completely cover the size of the magnetic pole so that the material, size, shape, and other factors of the object to be sucked can be ignored.   How to judge whether the working point of the magnet is at the point of maximum magnetic energy product? When the magnet is in a state of direct adsorption with the material being adsorbed, its adsorption force is determined by the size of the air gap magnetic field and the adsorption area.    Taking a cylindrical magnet as an example, when H/D≈0.6, its center Pc≈1, and when it is near the working point of maximum magnetic energy product, the suction force is the largest. This is also in line with the rule that magnets are usually designed to be relatively flat as adsorbents. Taking the N35 D10*6mm magnet as an example, through FEA simulation, it can be calculated that the suction force of the adsorbed iron plate is about 27N, which almost reaches the maximum value of magnets of the same volume and is 780 times its own weight.   The above is only the adsorption state of a single pole of the magnet. If it is multi-pole magnetization, the suction force will be completely different. The suction force of multi-pole magnetization will be much greater than that of single-pole magnetization (under the premise of a small distance from the adsorbed object).     Why does the suction force of a magnet of the same volume change so much after being magnetized with multiple poles? The reason is that the adsorption area S remains unchanged, while the magnetic flux density B value through the adsorbed object increases a lot. From the magnetic force line diagram below, it can be seen that the density of magnetic force lines passing through the iron sheet of a multi-pole magnetized magnet is significantly increased. Taking the N35 D10*6mm magnet as an example, it is made into a bipolar magnetization. The suction force of the FEA simulation adsorbing the iron plate is about 1100 times its own weight.     Since the magnet is made into a multi-pole magnet, each pole is equivalent to a thinner and longer magnet. The specific size is related to the multi-pole magnetization method and the number of poles.        

The main reasons why magnetic materials are magnetic can be attributed to the following points: Magnetic materials, the raw materials used in neodymium magnet production, exhibit magnetism due to the alignment of their atomic structure. At the core of their behavior are electrons, which act as tiny magnetic dipoles. In other materials, these dipoles cancel each other out. However, in neodymium magnetic materials, a significant number of these dipoles align in the same direction, creating a unified magnetic field.   Neodymium magnets, the strongest type of permanent magnets, have exceptional magnetism due to their unique composition and density of neodymium magnet material. They are made from a blend of neodymium, iron, and boron, which, when processed and magnetized, form a crystal structure capable of sustaining a strong magnetic force. This structure allows for the concentration of a magnetic field in a compact area, resulting in the remarkable neodymium magnet force observed in various applications.     The production process further enhances this magnetic capability. During neodymium magnet production, the material is sintered and aligned in a magnetic field to ensure maximum dipole alignment. This precise manufacturing process contributes to the magnet's high coercivity and strength.   These characteristics make neodymium magnets essential for applications ranging from electric motors to renewable energy devices. Their great magnetic properties originate from the atomic level, amplified by advanced production techniques and material density, ensuring reliable and powerful performance.  

Correct selection of permanent magnet motor power   Demagnetization is related to the power selection of the permanent magnet motor. Correctly selecting the power of the permanent magnet motor can prevent or delay demagnetization. The main reason for the demagnetization of the permanent magnet synchronous motor is excessive temperature, and overload is the main reason for excessive temperature.   Therefore, when selecting the power of the permanent magnet motor, a certain margin should be left. According to the actual load situation, about 20% is generally more appropriate.     Avoid heavy load starting and frequent starting   Cage-type asynchronous starting synchronous permanent magnet motors should avoid heavy-load direct starting or frequent starting.   During the asynchronous starting process, the starting torque is oscillating. In the starting torque trough section, the stator magnetic field has a demagnetizing effect on the rotor poles. Therefore, try to avoid heavy-load and frequent starting of asynchronous permanent magnet synchronous motors.   Improved design   1. Properly increase the thickness of the permanent magnet   From the perspective of permanent magnet synchronous motor design and manufacturing, the relationship between armature reaction, electromagnetic torque and permanent magnet demagnetization should be considered.   Under the combined effect of the magnetic flux generated by the torque winding current and the magnetic flux generated by the radial force winding, the permanent magnet on the rotor surface is prone to demagnetization.   In the case of the motor air gap remaining unchanged, the most effective way to ensure that the permanent magnet does not demagnetize is to appropriately increase the thickness of the permanent magnet.   2. There is a ventilation slot circuit inside the rotor to reduce the rotor temperature rise   If the rotor temperature rises too high, the permanent magnet will lose its magnetism irreversibly. When designing the structure, a ventilation circuit can be designed inside the rotor to directly cool the magnetic steel. This not only reduces the magnetic steel temperature, but also improves efficiency.

The food processing industry is a rigorous and high-quality field, and ensuring food safety and quality is very important. Neodymium rod magnets are widely used in food processing as a key tool to remove possible ferromagnetic impurities such as metal fragments, iron filings, and magnetic particles. The following are the applications and advantages of neodymium rod magnets in the food processing industry:   Food production line   Neodymium rod magnets are usually installed in food production lines, in the flow of raw materials, or finished products. These production lines include bakeries, confectionery factories, meat processing plants, beverage production, etc. Neodymium rod magnets are able to capture metal impurities such as nails, screws, iron filings, etc., ensuring that these impurities do not enter the final product.   Raw material handling   In the food manufacturing process, raw materials may include iron ore, grains, spices, etc. Neodymium rod magnets are used to remove ferromagnetic impurities from these raw materials to ensure the composition and quality of the food.     One of the most important advantages of using neodymium rod magnets is ensuring food safety. By removing metal impurities, neodymium rod magnets help prevent metal fragments from entering food products, reducing potential hazards in food.     In addition to protecting food quality, neodymium rod magnets also help protect production equipment. Preventing metal impurities from entering equipment can reduce maintenance and repair costs and extend the life of equipment.  

The biggest risk in the use of permanent magnet motors is demagnetization caused by high temperature. As we all know, the key component of permanent magnet motors is neodymium magnet, and neodymium magnet is most afraid of high temperature. It will gradually demagnetize under high temperature for a long time. The higher the temperature, the greater the risk of demagnetization.   Once a permanent magnet motor loses its magnetism, you basically have no choice but to replace the motor, and the cost of repair is huge. How do you determine whether a permanent magnet motor has lost its magnetism?   1. When the machine starts running, the current is normal. After a period of time, the current becomes larger. After a long time, the inverter will be reported to be overloaded.   First, you need to make sure that the inverter selected by the air compressor manufacturer is correct, and then confirm whether the parameters in the inverter have been changed. If there are no problems with both, you need to judge by back electromotive force, disconnect the head from the motor, perform no-load identification, and run no-load to the rated frequency. At this time, the output voltage is the back electromotive force. If it is lower than the back electromotive force on the motor nameplate by more than 50V, it can be determined that the motor is demagnetized.     2. After demagnetization, the running current of permanent magnet motor will generally exceed the rated value.   Those situations where overload is reported only at low or high speed or occasionally reported, are generally not caused by demagnetization.   3. It takes a certain amount of time for a permanent magnet motor to demagnetize, sometimes several months or even one or two years.   If the manufacturer selects the wrong model and causes current overload, it does not belong to motor demagnetization.   An important indicator of permanent magnet motor performance is the high temperature resistance level. If the temperature resistance level is exceeded, the magnetic flux density will drop sharply. The high temperature resistance level can be divided into: N series, resistant to more than 80℃; H series, resistant to 120℃; SH series, resistant to more than 150℃. The motor's cooling fan is abnormal, causing the motor to overheat. The motor is not equipped with a temperature protection device. Ambient temperature is too high. Improper motor design.

Demagnetization may be caused by a variety of factors, including: high temperature, physical shock or long-term time-induced natural decline in magnetism.   Specifically, when a permanent magnet is subjected to high temperatures, the magnetic dipoles inside it lose their ordered arrangement, causing the magnetism to weaken or disappear.   For example, the Curie temperature of permanent magnets is relatively low, and once their maximum operating temperature is exceeded, the magnets will gradually demagnetize.     In addition, physical shock may also cause demagnetization of permanent magnets because the shock may change the arrangement of magnetic dipoles, destroying the magnetic domain structure and thus affecting the magnetic properties.   Over time, even if a permanent magnet is not subjected to significant physical shock or high temperatures, its magnetism may naturally decay, because the arrangement of the magnetic dipoles may gradually become disordered, resulting in a weakening of the magnetism.   This depends on the external conditions the magnet encounters and the properties of the permanent magnet itself.