Preparation method of ceramic bond sintered samarium-iron-nitrogen permanent magnet

Abstract

The invention discloses a preparation method of a ceramic bond sintered samarium-iron-nitrogen permanent magnet, and belongs to the field of rare earth permanent magnet materials. Low-temperature ceramic is adopted as a binding agent, samarium-iron-nitrogen powder and low-temperature ceramic powder are mixed and then subjected to magnetic field orientation, preheating and prepressing, then hot pressed sintering is conducted at the temperature of 500-600 DEG C, and the sintered samarium-iron-nitrogen permanent magnet is prepared. The high-density and high-magnetic-performance samarium-iron-nitrogen permanent magnet is obtained by using the low-temperature ceramic binding agent to activate the sintering process, and the volume ratio of the binding agent is reduced, so that the magnetic performance advantage of samarium-iron-nitrogen is brought into full play, and a magnet piece in a thermal demagnetization state can be obtained according to requirements. The prepared sintered samarium-iron-nitrogen permanent magnet can be applied to the fields of new energy automobiles, industrial motors, robots, consumer electronics, medical equipment and the like, the cost can be reduced, the requirements for miniaturization and corrosion resistance can be met, and the sintered samarium-iron-nitrogen permanent magnet is adaptive to precise devices.

Description

Technical Field

[0001] This invention relates to rare earth permanent magnet materials, and more specifically to a method for manufacturing sintered samarium iron nitrogen permanent magnets using a low-temperature ceramic binder (glass). Background Technology

[0002] Since the discovery of the interstitial atom effect of nitrogen by Yang Yingchang's research team at Peking University in 1990, samarium iron nitride (SmFeN) permanent magnets have become a highly anticipated new generation of rare-earth permanent magnet materials in recent years, and are considered the fourth generation of rare-earth permanent magnet materials after neodymium iron boron (NdFeB). Samarium iron nitride permanent magnets are composed of... Formed through nitriding, it has the following core advantages: high magnetic properties and thermal stability, high Curie temperature (about 472℃), excellent temperature resistance and oxidation resistance; abundant raw material resources, high natural abundance, and stable price over a long period of time, only 1 / 16 to 1 / 6 of the price of metallic neodymium, resulting in low supply chain risk; corrosion resistance, which can resist humid and corrosive environments without the need for surface coating, reducing processing costs.

[0003] Although the theoretical magnetic energy product of samarium iron nitride (SFeNi) can reach over 60 MGOe, currently widely used magnets are all bonded magnets, such as those made from thermoplastic resins (PA and PPS) through injection molding, or flexible magnets made from nitrile rubber (NBR) or TPU / TPE through calendering and extrusion. Molded bonded magnets using thermosetting resins such as epoxy resin as binders are also possible. Because the binders are mostly organic matter present in a high volume percentage, the magnetic properties are diluted, resulting in SFeNi permanent magnets with relatively low magnetic performance. Furthermore, the organic binders limit the operating temperature of the magnets, thus restricting the application scenarios of SFeNi and failing to fully utilize its magnetic performance advantages. Currently, there is no effective method for preparing sintered SFeNi internationally. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a method for manufacturing sintered samarium iron nitrogen permanent magnets using a low-temperature ceramic binder, so as to fully utilize the magnetic performance advantages of samarium iron nitrogen.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution: A method for preparing a sintered samarium iron nitrogen permanent magnet involves using low-temperature ceramic as a binder, mixing samarium iron nitrogen powder and low-temperature ceramic powder, then subjecting the mixture to magnetic field orientation, preheating, pre-pressing, and finally hot-pressing and sintering at 500~600°C (pressurization is applied simultaneously with heating).

[0006] At high temperatures, the low-temperature ceramic binder forms a liquid phase. Combined with pressure, this facilitates the formation of sintering necks between samarium iron nitrogen (SFeNi) powder particles, effectively activating the sintering process and increasing the density of the sintered green body. This results in high-density, high-magnetic-performance SFeNi permanent magnets. Furthermore, because the sintering temperature is controlled above the Curie point but below the decomposition temperature of SFeNi, high-temperature demagnetization is achieved, eliminating residual magnetism caused by the orientation process. This facilitates remagnetization for subsequent applications and also ensures the stability of the magnet's chemical properties.

[0007] like Figure 1 As shown, the preparation method of the sintered samarium iron nitrogen permanent magnet provided by the present invention includes the following steps: 1) Mixing process: Mix the samarium iron nitrogen powder evenly, then add 0.5~2 wt% low-temperature ceramic powder and mix thoroughly. 2) Preheating and prepressing process under magnetic field: The mixed powder is loaded into the molding mold, an orientation magnetic field is applied, the direction of the magnetic field is perpendicular to the pressing direction, preheating and prepressing are performed, and the temperature and pressure are maintained for a period of time. 3) Hot pressing sintering process: Heat to 500~600°C, and after reaching the preset temperature, adjust the pressure to 30~50 MPa and maintain the temperature and pressure for a period of time; 4) Cooling and demolding: After the heat preservation and pressure holding process of sintering is completed, the pressure is unloaded, the magnet is cooled, and the sintered magnet is removed from the mold. 5) Machining and magnetization: Use diamond grinding wheels or wire cutting equipment to machine the magnet workpieces to meet the dimensional requirements, and perform secondary magnetization as needed.

[0008] Further, in step 1) above, it is preferable to mix the samarium iron nitride powder uniformly with both fine and coarse particles to obtain a high filling density. The fine particle size of the samarium iron nitride powder refers to a D50 particle size of 1-10 μm, and the coarse particle size refers to a D50 particle size of 10-100 μm. In some embodiments of the present invention, the mixing mass ratio of the fine and coarse particles is 1:(2-5).

[0009] Furthermore, the low-temperature ceramic powder refers to ceramic powder with a melting temperature of 350~450°C, preferably ceramic powder with a particle size of nanometers. Preferably, the low-temperature ceramic includes, but is not limited to, boron-based silicates, bismuth-based silicates, lithium-based silicates, aluminum-based silicates, and other ceramic materials.

[0010] Furthermore, the magnetic field strength of the orientation magnetic field mentioned in step 2) above is above 7000 Oe. Preferably, after preheating to 400~450°C and holding for 1~5 minutes, pre-pressurize to 10~25 MPa, and then continue to hold the temperature and pressure for 3~5 minutes.

[0011] Further, after heating to the preset temperature in step 3), adjust the pressure to 30~50 MPa and maintain the temperature and pressure for 5~10 minutes. If a demagnetized magnet is required, remove the orientation magnetic field in step 3); otherwise, retain the orientation magnetic field.

[0012] Furthermore, in step 4) above, when the sintered magnet cools to below 200°C, it is ejected from the mold using the ejection device of the press.

[0013] The main application areas of the sintered samarium iron nitrogen permanent magnet prepared by this invention include, but are not limited to: (1) New energy vehicles: The high temperature resistance of the sintered samarium iron nitrogen permanent magnet is suitable for drive motors, and can replace some neodymium iron boron permanent magnets that require the addition of heavy rare earth elements (such as dysprosium and terbium), thereby reducing costs; (2) Industrial motors and robots: The demand for high efficiency and energy saving drives the growth in demand for high-performance permanent magnets; (3) Consumer electronics and medical equipment: The sintered samarium iron nitrogen permanent magnet of this invention can meet the requirements of miniaturization and corrosion resistance, and is suitable for precision devices.

[0014] In summary, this invention uses a low-temperature ceramic binder, which can activate the sintering process and thus obtain high-density, high-magnetic-performance samarium iron nitrogen permanent magnets. It reduces the volume ratio of the binder, fully utilizes the magnetic performance advantages of samarium iron nitrogen, and can also obtain magnets in a thermally demagnetized state as needed. Attached Figure Description

[0015] Figure 1 This is a process flow diagram for preparing sintered samarium iron nitrogen permanent magnets according to the present invention. Detailed Implementation

[0016] The present invention is further described below through embodiments to help those skilled in the art to further understand the invention, but these embodiments do not limit the scope of the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention.

[0017] Example 1 Samarium iron nitrogen powder with a D50 of 2.1 μm, samarium iron nitrogen powder with a D50 of 56.4 μm, and borosilicate with a D50 of 0.012 μm were mixed in a weight ratio of 30:78:2 using an ultrasonic mixer for 60 minutes.

[0018] The uniformly mixed powder is loaded into a 50 mm × 50 mm × 10 mm rectangular mold, which is then placed into a vertically oriented magnetic field hydraulic press. The hydraulic press mold is equipped with an electromagnetic orientation field of 10,000 Oe, with the orientation direction perpendicular to the pressing direction. The hydraulic press is equipped with an ejection device.

[0019] Preheat the mold to 400℃ and hold for 3 minutes, then pre-pressurize it to 10 MPa. After reaching the set pressure and temperature, maintain the temperature and pressure for 3 minutes.

[0020] Heat the mold to 500℃, adjust the pressure to 30 MPa, and after reaching the set pressure and temperature, maintain the temperature and pressure for 10 minutes.

[0021] After the pressure is released and the mold cools to 200°C, the magnet is ejected from the mold.

[0022] The magnet was cut into 10 mm × 10 mm × 10 mm cubes and magnetized using a magnetizer with a pulsed magnetic field of 4.5 T or higher.

[0023] Tests showed that the maximum energy product of the sintered samarium iron nitrogen magnet reached 34 MGOe, the remanence reached 1.2 T, the intrinsic coercivity reached 9.5 kOe, and the coercivity reached 7.0 kOe.

[0024] Example 2 Samarium iron nitrogen powder with a D50 of 6.5 μm, samarium iron nitrogen powder with a D50 of 78.5 μm, and lithium silicate with a D50 of 0.020 μm were mixed in a weight ratio of 25:79:1 using an ultrasonic mixer for 60 minutes.

[0025] The uniformly mixed powder is loaded into a cylindrical mold with a diameter of 50 mm (bottom diameter) and a height of 20 mm. The mold is then placed into a vertically oriented magnetic field hydraulic press. The hydraulic press mold is equipped with an electromagnetic orientation field of 9000 Oe, with the orientation direction perpendicular to the pressing direction. The hydraulic press is equipped with an ejection device.

[0026] Preheat the mold to 450℃ and hold for 1 minute, then pre-pressurize it to 15 MPa. After reaching the set pressure and temperature, maintain the temperature and pressure for 4 minutes.

[0027] Heat the mold to 550℃, adjust the pressure to 41 MPa, and after reaching the set pressure and temperature, maintain the temperature and pressure for 5 minutes.

[0028] After the pressure is released and the mold cools to 200°C, the magnet is ejected from the mold.

[0029] The magnet is magnetized using a magnetizer with a pulsed magnetic field of 4.5 T or higher.

[0030] Tests showed that the maximum energy product of the sintered samarium iron nitrogen magnet reached 36 MGOe, the remanence reached 1.3 T, the intrinsic coercivity reached 9.5 kOe, and the coercivity reached 7.5 kOe.

[0031] Example 3 Samarium iron nitrogen powder with a D50 of 9.2 μm, samarium iron nitrogen powder with a D50 of 94.7 μm, and aluminum silicate with a D50 of 0.015 μm were mixed in a weight ratio of 19.5:79:0.5 using an ultrasonic mixer for 60 minutes.

[0032] The uniformly mixed powder is loaded into a 50 mm × 50 mm × 20 mm rectangular mold, which is then placed into a vertically oriented magnetic field hydraulic press. The hydraulic press mold is equipped with an electromagnetic orientation field of 12000 Oe, with the orientation direction perpendicular to the pressing direction. The hydraulic press is equipped with an ejection device.

[0033] Preheat the mold to 430℃ and hold for 2 minutes, then pre-pressurize it to 25 MPa. After reaching the set pressure and temperature, maintain the temperature and pressure for 5 minutes.

[0034] Heat the mold to 600℃, adjust the pressure to 48 MPa, and after reaching the set pressure and temperature, maintain the temperature and pressure for 10 minutes.

[0035] After the pressure is released and the mold cools to 200°C, the magnet is ejected from the mold.

[0036] The magnet was cut into a cylindrical shape of φ10 mm × 20 mm and magnetized using a magnetizer with a pulse magnetic field of 4.5T or higher.

[0037] Tests showed that the maximum energy product of the sintered samarium iron nitrogen magnet reached 35 MGOe, the remanence reached 1.25 T, the intrinsic coercivity reached 9.0 kOe, and the coercivity reached 7.0 kOe.

Claims

1. A method for preparing a sintered samarium iron nitrogen permanent magnet, characterized in that, Using low-temperature ceramics as a binder, samarium iron nitrogen powder is mixed with low-temperature ceramic powder, then oriented under a magnetic field, preheated, pre-pressed, and then hot-pressed and sintered at 500~600°C.

2. The preparation method according to claim 1, characterized in that, The low-temperature ceramic is a ceramic material with a melting temperature of 350~450°C.

3. The preparation method according to claim 1, characterized in that, The low-temperature ceramic is selected from at least one ceramic material among boron silicates, bismuth silicates, lithium silicates, and aluminum silicates.

4. The preparation method according to claim 1, characterized in that, Includes the following steps: 1) Mix the samarium iron nitrogen powder evenly, then add 0.5~2 wt% of low-temperature ceramic powder and mix thoroughly. 2) Load the powder mixed in step 1) into the molding mold, apply an orientation magnetic field with the magnetic field direction perpendicular to the pressing direction, preheat and prepress, and keep warm and pressurized for a period of time. 3) Heat to 500~600°C, adjust the pressure to 30~50 MPa, and maintain the temperature and pressure for a period of time to carry out hot pressing sintering; 4) After the sintering process is completed, the pressure is released, the magnet is cooled, and the sintered magnet is removed from the mold; 5) Machin the magnets and re-magnetize them as needed.

5. The preparation method according to claim 4, characterized in that, Step 1) Mix samarium iron nitrogen powder with a fine particle size and coarse particle size ratio of 1:(2~5), wherein the fine particle size refers to a D50 particle size of 1~10 μm and the coarse particle size refers to a D50 particle size of 10~100 μm; the low-temperature ceramic powder refers to a ceramic powder with a melting temperature of 350~450°C and a particle size of nanoscale.

6. The preparation method according to claim 4, characterized in that, The magnetic field strength of the orientation magnetic field mentioned in step 2) is above 7000 Oe, and it is preheated to 400~450°C and then pre-pressurized to 10~25 MPa.

7. The preparation method according to claim 4, characterized in that, Step 2) The heat preservation and pressure holding time after pre-pressurization is 3-5 minutes; Step 3) The hot pressing and sintering time is 5-10 minutes.

8. The preparation method according to claim 4, characterized in that, In step 3), the orientation magnetic field is removed to obtain a demagnetized magnet.

9. The sintered samarium iron nitrogen permanent magnet obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the sintered samarium iron nitrogen permanent magnet as described in claim 9 in new energy vehicles, industrial motors, robots, consumer electronics products and medical devices.

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