A samarium iron nitrogen motor magnetic strip and its preparation method

Abstract

This invention discloses a samarium iron nitrogen (SFeNi) motor magnetic strip and its preparation method, belonging to the field of magnetic materials technology. The SFeNi motor magnetic strip is made from the following raw materials in parts by weight: 88%–90% isotropic SFeNi magnetic powder, 9%–11% CPE130A powder, 0.3%–0.5% KH570 coupling agent, 0.1%–0.3% calcium stearate lubricant, and 0.1%–0.3% dioctyl terephthalate plasticizer. The isotropic SFeNi magnetic powder is Sm2Fe that has undergone passivation-coating treatment. 17 N3 magnetic powder; the first to propose and implement a dual protection strategy of chemical passivation-physical coating, using a mixing and gradient rolling process, avoids the high cost and easy decomposition of magnetic powder in high-temperature sintering process, and also solves the problem of low magnet density in conventional bonding process. The steps are simple and controllable, with conventional equipment requirements, and are suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials technology, specifically relating to a samarium iron nitrogen motor magnetic strip and its preparation method. Background Technology

[0002] The magnetic stripe of a motor is a core functional component for energy conversion, and its magnetic properties directly determine the motor's torque output, energy conversion efficiency, and long-term operational stability. Currently, most mainstream motor magnetic strips on the market are made by mixing ferrite magnetic powder with chlorinated polyethylene (CPE), which is then rolled into magnetic sheets and cut. However, ferrite magnetic powder itself has inherent limitations in magnetic properties, resulting in motor magnetic strips with low surface magnetic intensity and poor magnetic property uniformity. This leads to insufficient motor torque and poor dynamic balance during operation, failing to meet the actual needs of high-end motors. Patent application CN101000818A discloses a bonding motor magnetic strip and its preparation method, but it uses a combination of conventional magnetic powder and binder and does not involve the application of samarium iron nitrogen magnetic powder, so the magnetic performance improvement effect is limited. Patent application CN112053823A discloses a high-elasticity, aging-resistant motor magnetic strip and its preparation method. This application focuses on optimizing the elasticity and aging resistance of the magnetic strip and adopts a multi-component binder system. It does not focus on the core improvement requirements of magnetic performance and fails to solve the key technical problems of low surface magnetism and poor uniformity of the magnetic strip. Patent application CN103580302A discloses a halogen-free motor magnetic strip and its preparation method. This application mainly focuses on the halogen-free environmental protection performance, and its magnetic powder selection is still mainly based on traditional ferrite, which cannot break through the technical bottleneck of insufficient motor torque.

[0003] Patent application CN102360653A discloses a method for preparing a calendered anisotropic flexible rare-earth bonded magnet. The method involves mixing surface-treated anisotropic rare-earth composite permanent magnet powder, crushing and sieving it, then performing a single calendering process to form a magnetic sheet. This sheet is then stacked and rolled again to obtain the calendered anisotropic flexible rare-earth bonded magnet. Since the D50 particle size of anisotropic magnetic powder is generally between 1 and 3 μm, and it requires orientation to realize its performance advantages, smaller particle sizes require more binder to achieve the desired shape and strength, while orientation is a complex and difficult process to achieve.

[0004] To avoid issues related to particle size and orientation, patent application CN118609981A discloses a flexible samarium iron nitride (SMR) magnet, its preparation method, and its application. This method involves sequentially applying isotropic SMR magnetic powder through a first coating treatment and a second coating treatment. The resulting coated magnetic powder is then mixed with a binder, followed by mixing, crushing, and calendering to obtain SMR magnetic sheets. A sulfiding agent is added, and a sulfidation treatment is performed. The magnetization voltage is 2450-2550V. However, excessive surface treatment, the use of sulfiding agents, and high-temperature sulfidation ultimately lead to a significant decrease in magnetic properties, failing to meet the requirements of high-performance motors. Furthermore, the extremely high magnetization voltage is unsuitable for general equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a samarium iron nitrogen motor magnetic strip and its preparation method, so as to solve the problems of low surface magnetic intensity and poor uniformity of magnetic properties of motor magnetic strips.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a samarium iron nitrogen motor magnetic strip, made from the following raw materials in parts by weight: The magnetic powder composition comprises 88%–90% isotropic samarium iron nitrogen (SmFeNi) magnetic powder, 9%–11% CPE130A powder, 0.3%–0.5% KH570 coupling agent, 0.1%–0.3% lubricant, and 0.1%–0.3% plasticizer; the isotropic SmFeNi magnetic powder is Sm2Fe that has undergone passivation and coating treatment. 17 N3 magnetic powder.

[0007] Synergistic mechanism: KH570 forms a chemically bonded layer on the surface of the magnetic powder, enhancing the interfacial bonding force with CPE130A; the lubricant reduces the frictional resistance between the material and the equipment; and the plasticizer plasticizes the molecular chains of CPE130A. These synergistic effects result in more uniform dispersion of the magnetic powder in the binder, and a balance between material flowability and density is achieved during the molding process. In some possible implementations, the CPE130A powder is a highly elastic chlorinated polyethylene with a particle size of 100~150μm. It has excellent compatibility with samarium iron nitrogen magnetic powder, which can effectively improve the molding performance and mechanical strength of the magnetic strip, while avoiding problems such as magnetic powder shedding and magnetic performance attenuation caused by insufficient binder performance.

[0008] In some possible implementations, the Sm2Fe 17 N3 magnetic powder has a D50 particle size of 8~10μm, a Curie temperature ≥470℃, and a thermal weight loss ≤1% in air at 300℃. It has a remanence of 7000~7500 Gs, a coercivity of 13~17kOe, and a magnetic energy product of 10~12MGOe. Compared with traditional ferrite powders, it improves magnetic properties; compared with anisotropic samarium iron nitrogen powders, it reduces binder usage, increases the density of rolled magnetic strips, and requires no orientation, simplifying the process.

[0009] The magnetic powder is subjected to dual passivation treatment using methylene diphosphonic acid and nano-silica. Methylene diphosphonic acid forms an organophosphonate conversion film on the surface of the magnetic powder, which combines the barrier properties of inorganic passivation with the affinity of organic functional groups, thus improving the compatibility between the magnetic powder and the polymer binder. Nano-silica fills the pores of the phosphate passivation layer, further enhancing its temperature resistance and corrosion resistance.

[0010] Breaking through the limitations of existing technologies such as single coating or simple phosphating, this paper proposes and implements for the first time a dual protection strategy of chemical passivation and physical coating. Its synergistic mechanism lies in the following: the inner methylene diphosphonic acid passivation layer actively occupies the active sites on the magnetic powder surface through chemical bonding, inhibiting oxidation at a chemical level; the outer silica coating layer constructs a dense physical barrier, effectively isolating the penetration and diffusion of oxygen and moisture, and inhibiting the agglomeration and excessive growth of the magnetic powder during subsequent processing. The two layers complement each other, jointly achieving comprehensive protection for samarium iron nitride magnetic powder.

[0011] In some possible implementations, passivation-coating treatment of Sm2Fe 17 N3 magnetic powder is prepared through the following steps: (1) Passivation treatment: Sm2Fe 17 N3 magnetic powder and deionized water are mixed at a mass ratio of 1:3 to 1:4. The mixture is stirred at room temperature to form a uniform slurry. The slurry temperature is maintained at 45 to 50°C, and methylene diphosphonic acid is added to the slurry. The mixture is stirred for 5 to 10 minutes to allow the methylene diphosphonic acid to fully contact the surface of the magnetic powder and undergo a chemical bonding reaction, thus completing the phosphate passivation treatment.

[0012] (2) Coating treatment Ammonia (NH3·H2O) was then added to the passivated slurry to adjust the system to a weakly alkaline state. Tetraethyl orthosilicate (TEOS) was then slowly added dropwise to the slurry. The addition time was controlled at 10-30 min, the reaction temperature at 45-50℃, and the reaction time at 30-60 min. Under alkaline conditions, TEOS underwent hydrolysis. The resulting silicic acid monomers underwent a condensation reaction, losing water molecules to form oligomers linked by Si-O-Si bonds and a three-dimensional network structure.

[0013] In this process, the formed nano-silica preferentially fills the micropores on the surface of the methylene diphosphonic acid passivation layer, and then further cross-links and condenses under alkaline catalysis to form a continuous and uniform amorphous SiO2 shell. This shell is not only dense, but also minimizes the dilution of the magnetic properties of the magnetic powder.

[0014] After the reaction was completed, the powder was washed repeatedly with deionized water and ethanol 3-5 times to remove unreacted TEOS, ammonia, byproducts, and any free SiO2 nanoparticles that might be generated. After filtration, the samarium iron nitrogen magnetic powder was placed in a nitrogen atmosphere and dried at 80°C for 3 hours to obtain pretreated modified samarium iron nitrogen magnetic powder.

[0015] In some possible implementations, the amount of methylene diphosphonic acid used is Sm2Fe 17 1%–2% of the mass of N3 magnetic powder; The amount of tetraethyl orthosilicate used is Sm2Fe 17 The mass of N3 magnetic powder is 0.2%–0.6%; In some possible implementations, weak alkalinity corresponds to a pH value of 8.5-10.5.

[0016] A second aspect of this invention provides a method for preparing a samarium iron nitrogen (SFI) motor magnetic strip, comprising the following steps: Intensive mixing process: After the isotropic samarium iron nitrogen magnetic powder and KH570 coupling agent are mixed evenly, CPE130A powder is added and mixing is continued. The temperature is raised, and then lubricant and plasticizer are added. The mixture is heated and melted to complete the intensive mixing process. The mixture is then cooled and crushed. Gradient calendering: The roller temperature of the open mill is set to 65~70℃, the gap of the open mill is adjusted to 0.3-0.5mm, the gap is widened in a stepwise manner, the gap difference is 0.3-0.5mm, the sheet is repeatedly calendered under each gap, the magnetic particles are sheared by differential speed rollers, and the gradient calendering is carried out to the target thickness; cutting and assembly; high-pressure magnetization.

[0017] The raw sheet is put back into the open mill for further refining to improve the density and uniformity of the material, and the differential speed is adjusted to constant speed. Then, the gap of the open mill is gradually widened to 1mm, 1.5mm, 2mm and 2.5mm in steps. The sheet is repeatedly refined 3 times under each gap to ensure that the magnetic powder is evenly dispersed in the binder and there is no agglomeration. Finally, the sheet thickness is controlled at 2.5mm to obtain a uniform and dense magnetic sheet.

[0018] In some possible implementations, the differential speed ratio is 1:1.13~1.15, and the roller speed is 3~10 rpm; The constant speed roller has a speed of 3~10 rpm.

[0019] This step employs a gradient rolling forming process, which achieves uniform dispersion of samarium iron nitrogen magnetic powder and layer-by-layer densification of magnetic strips through a design of small initial rolling gap, stepped widening of gap, and variable temperature and roll speed rolling.

[0020] Initial rolling temperature: 65~70℃, roll speed: 3~4 rpm; as the gap widens to 1 / 1.5 / 2 / 2.5mm, temperature is controlled in stages: 70~73℃ for 1~1.5mm gap, 73~75℃ for 2~2.5mm gap, with gradual temperature increase and gradual small reduction of roll speed; the internal stress of the binder is released, and the uniformity of magnetic powder distribution is further improved.

[0021] Repeated calendering with small gaps throughout the process can easily lead to decreased material flowability and thermal aging of the binder, affecting the mechanical strength of the magnetic strip and the dispersion effect of the magnetic powder. Conversely, direct calendering with large gaps can cause uneven stress on the mixture of magnetic powder and binder, resulting in agglomeration of the magnetic powder, low density, and poor uniformity of the magnetic strip's magnetic properties.

[0022] This invention employs a gradient calendering process, achieving uniform dispersion of samarium iron nitrogen magnetic powder and gradual densification of the magnetic strips through a design involving small initial rolling gaps, progressively widening gaps, and a fixed number of open rolling cycles. Repeated calendering with small gaps throughout the process reduces material flowability and causes thermal aging of the binder, affecting the mechanical strength of the magnetic strips and the dispersion of the magnetic powder. Direct calendering with large gaps results in uneven stress on the mixture of magnetic powder and binder, leading to powder agglomeration, low density, and poor uniformity of the magnetic properties of the magnetic strips.

[0023] In some possible implementations, passivated and coated samarium iron nitrogen magnetic powder and KH570 coupling agent are added to an internal mixer and mixed for 5-10 minutes at room temperature and a speed of 30-40 r / min to uniformly coat the surface of the magnetic powder with KH570 coupling agent, effectively improving the interfacial bonding force between the magnetic powder and the binder. Then, CPE130A powder is added and mixing continues for 5-10 minutes to achieve initial dispersion of the magnetic powder and the binder. Afterward, the temperature of the internal mixer is slowly increased to 65-70℃, lubricant and plasticizer are added, the speed is adjusted to 50-60 r / min, and mixing continues for 5-10 minutes, during which the temperature naturally rises to 120-125℃ to fully melt and uniformly disperse the raw materials, completing the internal mixing. The mixed material is cooled to room temperature and crushed into magnetic particles with a particle size of 3-5 mm for later use.

[0024] Cutting and Assembly: Based on the actual specifications of different motors, precision cutting equipment is used to cut the calendered magnetic strips. For example, motor magnetic strips of different sizes, such as 94×16×2.5mm and 80×15×2.5mm, can be obtained. The cutting accuracy is controlled within ±0.1mm to avoid dimensional deviations affecting the motor assembly accuracy and operational stability. The cut magnetic strips are then assembled into an iron shell to form the motor rotor.

[0025] In some possible implementations, high-voltage magnetization is used: the assembled rotor is placed in a magnetization fixture and saturated magnetization is performed using a pulsed high-voltage radial four-pole magnetization method. The magnetization voltage is controlled at 1200~1500V and the magnetization time is 0.5~1s.

[0026] The beneficial effects of this invention are: 1. Significantly improved magnetic properties, effectively addressing existing technical pain points: This invention abandons traditional ferrite magnetic powder and selects high-performance isotropic samarium iron nitrogen magnetic powder as the core raw material. Combined with an optimized formula system, after being magnetized at 1500V high voltage, the surface magnetic strength of the magnetic strip can reach about 1800Gs, which is more than 50% higher than that of traditional ferrite magnetic strips. This can effectively improve motor torque and meet the needs of high-end motors. At the same time, samarium iron nitrogen magnetic powder has excellent thermal stability and oxidation resistance, eliminating the need for additional surface coating for rust prevention. The magnetic strip has good temperature resistance, and the surface magnetic flux decreases slowly after long-term use at high temperatures.

[0027] 2. Excellent uniformity of magnetic properties, ensuring stable motor operation: By optimizing the mixing process parameters and adopting a step-by-step gradient rolling method, the magnetic particles are transformed into green sheets through small gaps in the initial rolling and differential speed rollers. The differential speed ratio is 1:1.13~1.15. The design of step-by-step widening of the gap and variable temperature and variable roller speed achieves uniform dispersion of samarium iron nitrogen magnetic powder and layer-by-layer densification of the magnetic strips. The final magnetic strips have good performance consistency and the waveform meets the requirements of high-end motors. This ensures uniform dispersion of samarium iron nitrogen magnetic powder in CPE binder without agglomeration. The surface magnetic difference of the three different parts of the magnetic strip is controlled within 20Gs, significantly improving the uniformity of magnetic properties. This effectively improves the consistency and dynamic balance of the motor during operation, reduces motor operating noise, and extends the motor's service life.

[0028] 3. Technological innovation for large-scale production: This invention employs a mixing and gradient rolling process, which avoids the high cost and easy decomposition of magnetic powder in high-temperature sintering processes, and also solves the problem of low magnet density in conventional bonding processes. The entire process is simple and controllable, requires conventional equipment, has low production costs, and can achieve large-scale production, making it suitable for industrial application.

[0029] 4. Formula optimization to improve overall product performance: Precise control of the weight percentage of each raw material, the addition of KH570 coupling agent can effectively improve the interfacial bonding force between magnetic powder and CPE binder, and the synergistic effect of calcium stearate and DOTP can improve the processing fluidity of materials and improve the calendering effect; the prepared magnetic strips not only have excellent magnetic properties, but also have good mechanical strength and elasticity, are not easy to break or fall off, and can adapt to the working conditions of long-term motor operation.

[0030] 5. Resource-friendly and cost-effective: Samarium iron nitrogen magnetic powder does not use heavy rare earth elements, which can effectively avoid the cost pressure and price fluctuations of heavy rare earth raw materials. Compared with neodymium iron boron magnets, it has better corrosion resistance and its resistivity is more than 1,000 times that of sintered magnets, which can effectively avoid eddy current losses and adapt to the development trend of high frequency and high speed motors. At the same time, through formula optimization, the amount of binder is reasonably controlled while ensuring high magnetic performance, balancing product performance and production costs, and the cost-effectiveness is significantly better than existing high-end magnetic strip products. Attached Figure Description

[0031] Figure 1 This is a waveform diagram of the rotor surface magnetic distribution in Embodiment 1 of the present invention. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] The following is a detailed description of a samarium iron nitrogen motor magnetic strip and its preparation method according to an embodiment of this application.

[0034] The following is a detailed description with reference to specific examples.

[0035] Example 1 This embodiment provides a samarium iron nitrogen (SMR) motor magnetic strip, prepared from the following raw materials by weight percentage: 88% isotropic SMR magnetic powder, 11% CPE130A powder, 0.5% KH570 coupling agent, 0.3% calcium stearate, and 0.2% DOTP; wherein the isotropic SMR magnetic powder is Sm2Fe2Fe2Fe2Fe2Fe2Fe2Fe2Fe2Fe2Fe3 ... 17 N3 magnetic powder has an average particle size of 8μm, a Curie temperature of 472℃, and a thermal weight loss of 0.5% in air at 300℃; CPE130A powder has a Shore A hardness of 130.

[0036] Its preparation method includes the following steps: 1. Magnetic powder modification treatment: (1) Passivation treatment: Sm2Fe 17 N3 magnetic powder and deionized water are mixed at a mass ratio of 1:3. The mixture is stirred at room temperature for 5 minutes to form a uniform slurry. The slurry temperature is maintained at 45°C, and 1.5% (by weight) of methylene diphosphonic acid (MDA) is added to the slurry. The mixture is stirred for 10 minutes to allow MDA to fully contact the surface of the magnetic powder and undergo a chemical bonding reaction, thus completing the phosphate passivation treatment.

[0037] (2) Coating treatment: A small amount of ammonia water (NH3·H2O) was then added to the passivated slurry to adjust the pH of the system to 9.5 (weakly alkaline); 0.4% of the magnetic powder mass of tetraethyl orthosilicate (TEOS) was slowly added dropwise to the slurry. The dropwise addition time was controlled at 30 min, the reaction temperature was 50℃, and the reaction time was 60 min.

[0038] After the reaction was completed, the powder was washed five times with deionized water and ethanol to remove unreacted TEOS, ammonia, byproducts, and any free SiO2 nanoparticles that might be generated. After filtration, the samarium iron nitrogen magnetic powder was placed in a nitrogen atmosphere and dried at 80°C for 3 hours to obtain pretreated modified samarium iron nitrogen magnetic powder.

[0039] 2. Internal mixing treatment: Add samarium iron nitrogen magnetic powder and KH570 coupling agent to the internal mixer and mix for 5 minutes at room temperature and a speed of 30 r / min; add CPE130A powder and continue mixing for 5 minutes; raise the temperature to 65℃, add calcium stearate and DOTP (dioctyl terephthalate), adjust the speed to 50 r / min, and mix for 10 minutes until the temperature reaches 120℃ to complete the internal mixing; after cooling the internally mixed material to room temperature, crush it into magnetic particles with a particle size of 3 mm.

[0040] 3. Calendering: Set the temperature of the open mill rollers to 65℃, preheat for 30 minutes, adjust the gap to 0.3mm, and add the magnetic particles prepared in step 2 evenly and slowly into the open mill. Use differential speed rollers to shear and soften the magnetic particles, and produce a sheet in one pass to obtain a preliminarily formed green sheet. The differential speed ratio is 1:1.13 and the roller speed is 4:4.52rpm.

[0041] The raw sheet was put back into the open mill for three rounds of milling to further improve the density and uniformity of the material. The differential speed was adjusted to constant speed, with a roller speed of 4 rpm. Then, the gap of the open mill was gradually widened to 1 mm, 1.5 mm, 2 mm, and 2.5 mm in stages, corresponding to temperatures of 70℃, 70℃, 75℃, and 75℃, and rotation speeds of 4 rpm, 3.5 rpm, 3.5 rpm, and 3 rpm, respectively. The sheet was repeatedly milled three times under each gap to ensure that the magnetic powder was evenly dispersed in the binder without agglomeration. The final sheet thickness was controlled at 2.5 mm to obtain a uniform and dense magnetic sheet.

[0042] 4. Cutting and Assembly: The magnetic sheet is cut into magnetic strips of 94×16×2.5mm using precision cutting equipment, with the cutting accuracy controlled within ±0.1mm. The cut magnetic strips are then assembled into the iron shell to form the motor rotor.

[0043] 5. High-voltage magnetization: A magnetization voltage of 1500V was used, and the magnetization time was 0.5s. Then, the rotor was placed in an environment of 120℃ for 300 hours, and the surface magnetic distribution was tested. The waveform of the surface magnetic distribution is shown in the figure. Figure 1 As shown.

[0044] Example 2 Compared with Example 1, the isotropic samarium iron nitrogen magnetic powder accounts for 89%, and the rest is the same as in Example 1.

[0045] Example 3 Compared with Example 1, the isotropic samarium iron nitrogen magnetic powder accounts for 90%, and the rest is the same as in Example 1.

[0046] Example 4 Compared to Example 1, 1% methylene diphosphonic acid was added during the passivation treatment in step 1, while the rest remained the same as in Example 1. Example 5 Compared with Example 1, 2% methylene diphosphonic acid was added during the passivation treatment in step 1, and the rest was the same as in Example 1.

[0047] Example 6 Compared with Example 1, 0.2% tetraethyl orthosilicate was added during the coating process in step 1, and the rest was the same as in Example 1.

[0048] Example 7 Compared with Example 1, 0.6% tetraethyl orthosilicate was added during the coating process in step 1, and the rest was the same as in Example 1.

[0049] Example 8 Compared with Example 1, the magnetization voltage in step 5 is 1200V, and the rest is the same as in Example 1.

[0050] Example 9 Compared with Example 1, the magnetization voltage in step 5 is 1350V, and the rest is the same as in Example 1.

[0051] Example 10 Compared with Example 1, the proportion of coupling agent was 0.3%, and the rest were the same as in Example 1. Example 11 Compared with Example 1, the DOTP ratio is 0.1%, and the rest is the same as in Example 1.

[0052] Comparative Example 1 Compared with Example 1, the magnetic powder used is conventional isotropic ferrite powder, and the rest is the same as in Example 1.

[0053] Comparative Example 2 Compared with Example 1, the magnetic powder used is conventional anisotropic samarium iron nitrogen powder, and the rest is the same as in Example 1.

[0054] Comparative Example 3 Compared to Example 1, step 1 does not involve methylene diphosphonic acid passivation treatment; the rest is the same as in Example 1.

[0055] Comparative Example 4 Compared with Example 1, step 1 does not involve tetraethyl orthosilicate coating treatment; the rest is the same as in Example 1.

[0056] Comparative Example 5 Compared with Example 1, step 3 does not use gradient calendering process, but instead increases the thickness to 2.5 mm in one step, while the rest is the same as in Example 1.

[0057] Comparative Example 6 Compared with Example 1, the magnetization voltage in step 5 is 1000V, and the rest is the same as in Example 1.

[0058] The specific values ​​of the raw material ratios and magnetization voltages in Examples 1-11 and Comparative Examples 1-6 are shown in Table 1 below: Table 1

[0059] Test case The performance of the test samples prepared in Examples 1-11 and Comparative Examples 1-6 was tested. The surface magnetic distribution of the rotor was measured using a multipole magnetic ring measuring instrument, and the hardness and elongation at break of the magnetic strip were also measured. Then, the rotor was placed in an environment of 120°C for 300 hours, and the surface magnetic distribution was measured again. The surface magnetic decay rate was calculated using the average value. The results are shown in Table 2. Table 2

[0060] Compared with Examples 1, 2, and 3 and Comparative Examples 1 and 2, the use of isotropic samarium iron nitrogen (SMR) magnetic powder can significantly improve the surface magnetism and uniformity of the motor magnetic strip. Furthermore, the higher the SMR content, the higher the surface magnetism. The surface magnetism differences between different parts of the SMR magnetic strip are much smaller than those of ferrite magnetic strips. While ferrite powder and anisotropic SMR powder can be formed into sheets due to their excessively fine particle size, they have poor toughness and low elongation at break, failing to meet the requirements for motor applications. Comparative Examples 1, 4, 5 and 3, and Comparative Examples 1, 6, 7 and 4, the temperature resistance of the magnetic strip can be improved by methylene diphosphonic acid passivation treatment and tetraethyl orthosilicate coating treatment, which reduces the loss of magnetic surface magnetism at high temperatures. However, with the increase of the amount added, the initial magnetic surface magnetism at room temperature will decrease slightly.

[0061] Compared with Example 1 and Comparative Example 5, the gradient calendering process can effectively improve the uniformity of various parts of the magnetic strip. Without the gradient process, magnetic powder agglomeration and uneven dispersion will occur, resulting in local surface magnetic intensity increase and other surface magnetic intensity decrease, making the surface magnetic intensity very uneven.

[0062] Comparing Examples 1, 8, and 9 with Comparative Example 6, the higher the magnetization voltage, the closer the magnetic strip is to saturation, the higher the surface magnetism, and the better the uniformity of the surface magnetism. If the magnetization voltage is too low, the magnetic strip is not saturated, resulting in not only low surface magnetism but also significant differences between different parts, leading to poor uniformity.

[0063] Compared with Examples 1 and 10, the coupling agent can effectively improve the bonding between magnetic powder and CPE, thereby increasing the strength and toughness of the magnetic strip. Compared with Examples 1 and 11, the plasticizer can improve the toughness of the magnetic strip and increase the elongation at break, preventing cracks and other performance-affecting phenomena from occurring during bending and assembly of the magnetic strip.

[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A samarium iron nitrogen (SFI) motor magnetic strip, characterized in that, It is made from the following raw materials in parts by weight: 88%–90% isotropic samarium iron nitrogen magnetic powder, 9%–11% CPE130A powder, 0.3%–0.5% KH570 coupling agent, 0.1%–0.3% lubricant, and 0.1%–0.3% plasticizer; wherein the isotropic samarium iron nitrogen magnetic powder is Sm2Fe that has undergone passivation-coating treatment. 17 N3 magnetic powder.

2. The samarium iron nitrogen motor magnetic strip according to claim 1, characterized in that, The CPE130A powder is a highly elastic chlorinated polyethylene with a particle size of 100~150μm.

3. The samarium iron nitrogen motor magnetic strip according to claim 1, characterized in that, The Sm2Fe 17 N3 magnetic powder D50 has a particle size of 8~10μm, a Curie temperature ≥470℃, and a thermal weight loss ≤1% in air at 300℃.

4. The samarium iron nitrogen motor magnetic strip according to claim 1, characterized in that, Passivation-coating treatment of Sm2Fe 17 N3 magnetic powder is prepared through the following steps: Methylene diphosphonic acid for Sm2Fe 17 N3 magnetic powder is passivated; the passivated magnetic powder is then coated with tetraethyl orthosilicate.

5. A samarium iron nitrogen motor magnetic strip according to claim 4, characterized in that, The amount of methylene diphosphonic acid used is Sm2Fe 17 1%–2% of the mass of N3 magnetic powder; The amount of tetraethyl orthosilicate used is Sm2Fe 17 The mass of N3 magnetic powder is 0.2%–0.6%.

6. A samarium iron nitrogen motor magnetic strip according to claim 4, characterized in that, The coating treatment was carried out under conditions of pH 8.5-10.

5.

7. A method for preparing a samarium iron nitrogen (SFI) motor magnetic strip, used to prepare the SFI motor magnetic strip according to any one of claims 1-6, characterized in that, Includes the following steps: Intensive mixing process: After the isotropic samarium iron nitrogen magnetic powder and KH570 coupling agent are mixed evenly, CPE130A powder is added and mixing is continued. The temperature is raised, and then lubricant and plasticizer are added. The mixture is heated and melted to complete the intensive mixing process. The mixture is then cooled and crushed. Gradient calendering: The roller temperature of the open mill is set to 65~70℃, the gap of the open mill is adjusted to 0.3-0.5mm, and the gap is widened in a stepwise manner with a gap difference of 0.3-0.5mm. The sheet is repeatedly calendered under each gap, and the magnetic particles are sheared by differential speed rollers. The green sheet is put back into the open mill for 3 calendering cycles, and the magnetic particles are sheared by constant speed rollers. The gap of the open mill is widened to the target thickness; cutting and assembly; high-pressure magnetization.

8. The method for preparing a samarium iron nitrogen motor magnetic strip according to claim 7, characterized in that, The differential speed ratio is 1:1.13~1.15, and the roller speed is 3~10 rpm; The constant speed roller has a speed of 3~10 rpm.

9. The method for preparing a samarium iron nitrogen motor magnetic strip according to claim 7, characterized in that, Passivated and coated samarium iron nitrogen magnetic powder and KH570 coupling agent are added to an internal mixer and mixed for 5-10 minutes at room temperature and a speed of 30-40 r / min. Then, CPE130A powder is added and mixing continues for 5-10 minutes. After that, the temperature of the internal mixer is slowly increased to 65-70℃, lubricant and plasticizer are added, the speed is adjusted to 50-60 r / min, and mixing continues for 5-10 minutes. During this period, the temperature naturally rises to 120-125℃ to complete the mixing. The mixed material is cooled to room temperature and crushed into magnetic particles with a particle size of 3-5 mm for later use.

10. A method for preparing a samarium iron nitrogen motor magnetic strip according to claim 7, characterized in that, High-voltage magnetization: The magnetization voltage is controlled at 1200~1500V, and the magnetization time is 0.5~1s.

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