Sintering method and sintering device for permanent magnet material

Abstract

This invention relates to the field of permanent magnet materials technology, and discloses a method and apparatus for sintering permanent magnet materials. The method includes the following steps: a preparation stage: placing the permanent magnet blank into a sintering furnace; a preheating stage: heating the sintering furnace to a preheating temperature and maintaining it at a first temperature for a period of time; a vacuum heating stage: raising the temperature of the sintering furnace to a first sintering temperature, and then evacuating the sintering furnace to a preset pressure at the first sintering temperature; a gas filling stage: filling the sintering furnace with inert gas while simultaneously raising the temperature of the sintering furnace to a second sintering temperature until the inert gas reaches a high pressure state; a holding stage: after the sintering furnace reaches the second sintering temperature, holding the sintering furnace at this temperature; and a cooling stage: filling the sintering furnace with inert gas to cool it down until the permanent magnet material inside the sintering furnace reaches a preset cooling temperature. The permanent magnet sintering method of this application can improve the sintering consistency and density of the prepared permanent magnets.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet materials technology, specifically to a method for sintering permanent magnet materials, and also to a device for sintering permanent magnet materials. Background Technology

[0002] Currently, rare earth permanent magnet materials are widely used in industries such as aerospace, automotive, and medical devices, which places higher demands on the magnetic properties and consistency of rare earth permanent magnet materials.

[0003] In existing industrial production, products are heated by absorbing heat radiation from heating elements in a vacuum environment, which has problems such as low heat transfer efficiency and high energy consumption. At the same time, the sintering furnace has a large space, resulting in temperature differences in different directions. Furthermore, uneven heating of different positions of the same workpiece can also lead to temperature differences in the workpiece, affecting the consistency of performance.

[0004] Existing technologies typically employ methods such as adding air intake pipes to improve the temperature uniformity within the sintering furnace, and introducing low-melting-point metals into the permanent magnet blank to lower the melting point of the neodymium-rich grain boundary phase in the magnetic powder, in order to obtain neodymium-iron-nitrogen magnets with high density. Alternatively, low-pressure sintering and temperature control can be used to rapidly densify the magnets. However, the poor uniformity of densification still results in inconsistent performance of the prepared permanent magnets. Summary of the Invention

[0005] The first aspect of the present invention is to provide a sintering method for permanent magnet materials, which can improve the density and performance consistency of the prepared permanent magnets.

[0006] A second aspect of the present invention is to provide a permanent magnet material sintering apparatus that can improve the density and performance consistency of the prepared permanent magnets.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for sintering permanent magnet materials, comprising the following steps: Preparation stage: Place the permanent magnet blank into the sintering furnace; Preheating stage: The sintering furnace is heated to the preheating temperature and maintained at the first temperature until the holding time reaches the preset holding time; Vacuum heating stage: The sintering furnace is heated to the first sintering temperature, and the sintering furnace is evacuated to a preset pressure at the temperature of the first sintering temperature; Gas filling stage: Inert gas is filled into the sintering furnace, and the sintering furnace is heated to the second sintering temperature until the inert gas reaches a high pressure state.

[0008] Heat preservation stage: After the sintering furnace is heated to the second sintering temperature, the sintering furnace is subjected to heat preservation during sintering. Cooling stage: Inert gas is introduced into the sintering furnace to cool the furnace until the permanent magnet material inside the furnace reaches the preset cooling temperature.

[0009] Furthermore, the preheating temperature is 300℃-500℃.

[0010] Furthermore, the first sintering temperature is 700℃-900℃, and the preset gas pressure is 10. -3 -10 -2 Pa.

[0011] Furthermore, the second sintering temperature is 1000℃-1300℃, and the pressure of the inert gas under high pressure is 0.1×10⁻⁶. 6 Pa-10×10 6 Pa.

[0012] Furthermore, during the cooling stage, the temperature of the inert gas introduced into the sintering furnace is 20-100°C, and the flow rate is 10-100 m / s.

[0013] Furthermore, the inert gas includes at least one of helium, neon, argon, krypton, xenon, and radon.

[0014] Furthermore, it also includes: Tempering stage: The temperature inside the sintering furnace is maintained at the first tempering temperature and the second tempering temperature for a period of time, with the first tempering temperature being higher than the second tempering temperature.

[0015] Furthermore, the first tempering temperature is 900℃-950℃, and the second tempering temperature is 600℃-680℃.

[0016] A second aspect of the present invention provides a permanent magnet material sintering apparatus, comprising: Sintering furnace, used to hold permanent magnet blanks; Heater for heating the permanent magnet blank in the sintering furnace; A gas supply device is connected to the sintering furnace to supply inert gas to the sintering furnace, and a first heat exchanger is connected in series on the gas supply device to cool the inert gas via the first heat exchanger. A negative pressure pump is connected to the sintering furnace to draw gas from inside the sintering furnace.

[0017] Furthermore, a second heat exchanger is connected in series with the gas supply device to heat the inert gas via the second heat exchanger.

[0018] Through the above technical solution, the permanent magnet sintering method provided by the first aspect of the present invention can effectively remove organic additives in the permanent magnet blank by preheating the sintering furnace, thereby improving the quality of the prepared permanent magnet; evacuating the sintering furnace to a preset pressure at the first sintering temperature can ensure that gaseous impurities in the sintering furnace are basically removed; simultaneously filling the sintering furnace with inert gas and heating the sintering furnace to a second sintering temperature can make the temperature of the inert gas in various parts of the sintering furnace tend to be uniform, thereby using the inert gas as a heat conduction medium to ensure that the permanent magnet blank is heated uniformly in various parts of the sintering furnace, thereby improving the sintering consistency of the prepared permanent magnet; and by heating the inert gas to a high pressure state, the pressure can be applied to the permanent magnet blank by the inert gas, thereby increasing its density after sintering, thus improving the quality of the prepared permanent magnet.

[0019] The permanent magnet material sintering apparatus provided in the first aspect of the present invention, because it adopts the above-mentioned permanent magnet material sintering method, also has the technical effects brought about by the above-mentioned permanent magnet material sintering method.

[0020] Other advantages of the present invention and the technical effects of preferred embodiments will be further described in the following detailed description. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the permanent magnet material sintering method in this invention; Figure 2 This is a schematic diagram illustrating the principle of improving the density of permanent magnets in the sintering method of permanent magnet materials in this invention. The upper part shows a schematic diagram of the crystal phase structure of the permanent magnet blank before sintering, and the lower part shows a schematic diagram of the crystal phase structure of the permanent magnet blank after sintering. The blank hexagonal portion refers to Nd₂Fe. 14 The B main phase, the part between the hexagons is the Nd-rich phase, and the arrows around the crystal structure below indicate the pressure exerted by the high-temperature and high-pressure inert gas on the permanent magnet blank. Figure 3 This is a schematic diagram showing the difference between the permanent magnet material sintering device of the present invention and the existing sintering device for heating permanent magnet blanks. The upper diagram is a schematic diagram of the existing sintering device for heating permanent magnet blanks, in which the permanent magnet blank 1 is surrounded by a vacuum environment. The lower diagram is a schematic diagram of the permanent magnet material sintering device of the present invention for heating permanent magnet blanks, in which the permanent magnet blank 1 is surrounded by a high-temperature and high-pressure inert gas.

[0022] Explanation of reference numerals in the attached figures 1. Permanent magnet blank; 2. Heater. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to abutment; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features.

[0026] In a basic embodiment of the permanent magnet material sintering method provided in the first aspect of the present invention, see [link to relevant documentation]. Figures 1-3 The sintering method for permanent magnet materials includes the following steps: Preparation stage: Place the permanent magnet blank into the sintering furnace; Preheating stage: Heat the sintering furnace to the preheating temperature and maintain the sintering furnace at the first temperature until the preset holding time is reached; Vacuum heating stage: The sintering furnace is heated to the first sintering temperature, and then the sintering furnace is evacuated to the preset pressure at the temperature of the first sintering temperature. Gas filling stage: Inert gas is introduced into the sintering furnace, and the furnace is heated to the second sintering temperature until the inert gas reaches a high pressure state. Heat preservation stage: After the sintering furnace is heated to the second sintering temperature, the sintering furnace is heat preserved during sintering. Cooling stage: Inert gas is introduced into the sintering furnace to cool the furnace until the permanent magnet material inside reaches the preset cooling temperature.

[0027] The permanent magnet sintering method provided by the above-described basic embodiment of the present invention, by preheating the sintering furnace and holding it for a period of time, can effectively remove organic additives from the permanent magnet blank, thereby improving the quality of the prepared permanent magnet. Specifically, taking Nd as an example... 15 Fe 78Taking B7 permanent magnets as an example, during their preparation, relevant additives, such as paraffin wax, are usually added to the powder materials required for preparing permanent magnets to act as a binder, making it easier to form the powder materials into permanent magnet blanks of the required shape. By preheating the sintering furnace, the paraffin wax can be effectively heated into a gas phase so that it can be removed later, ensuring the quality of the prepared permanent magnets.

[0028] The sintering furnace is then heated to the first sintering temperature, and the furnace is evacuated to a preset pressure while at the first sintering temperature. This ensures that gaseous impurities in the furnace are basically removed, including the aforementioned gaseous paraffin and air, thereby preventing the powder material from oxidizing.

[0029] Simultaneously introducing inert gas into the sintering furnace and raising the furnace to the second sintering temperature ensures that the temperature of the inert gas throughout the furnace is uniform. This allows the inert gas to act as a heat conduction medium, ensuring uniform heating of the permanent magnet blank throughout the furnace and improving the sintering consistency of the prepared permanent magnet. Furthermore, heating the inert gas to a high pressure state applies pressure to the permanent magnet blank, increasing its density after sintering and thus improving the quality of the prepared permanent magnet.

[0030] Finally, the high-temperature inert gas in the sintering furnace is discharged, and at the same time, room temperature or relatively low temperature inert gas can be introduced into the sintering furnace to gradually cool the permanent magnet material in the sintering furnace to the preset cooling temperature.

[0031] In one specific embodiment of the present invention, the preheating temperature is 300℃-500℃. The specific temperature can be set based on the gas phase temperature of the additives in the powder material. For example, when paraffin is used as a binder, the preheating temperature can be set to 320℃-350℃.

[0032] In one specific embodiment of the present invention, the first sintering temperature is 700℃-900℃, and the preset gas pressure is 10. -3 -10 -2 Pa, under the temperature condition of the first sintering temperature, the gas pressure in the sintering furnace is evacuated to 10 Pa. -3 -10 -2 Pa ensures that the air and additives that have turned into gaseous phase in the sintering furnace are removed from the furnace, so as to prevent the prepared permanent magnets from being oxidized or mixed with impurities, which would affect the quality.

[0033] In one specific embodiment of the present invention, the second sintering temperature is 1000℃-1300℃, and the pressure of the inert gas under high pressure is 0.1×10⁻⁶. 6 Pa-10×10 6At high temperatures (Pa), the inert gas used as a protective gas will expand upon heating until it reaches 0.1 × 10⁻⁶ Pa. 6 Pa-10×10 6 The pressure of Pa allows the inert gas to be applied to the permanent magnet blank, making the neodymium-rich phase in the permanent magnet blank more compact, thereby increasing the sintering density of the permanent magnet and thus increasing the magnetic energy product.

[0034] In one specific embodiment of the present invention, the temperature of the inert gas introduced into the sintering furnace during the cooling stage is 20-100°C, and the flow rate is 10-100 m / s. Specifically, the temperature of the inert gas introduced into the sintering furnace during the cooling stage can be gradually changed from high to low to prevent the permanent magnet structure from being damaged by a sudden drop in temperature. The inert gas introduced into the sintering furnace can be circulated to save the amount of inert gas used. The flow rate of the inert gas can also be adjusted according to the temperature when it circulates out of the sintering furnace. The greater the temperature difference between the inert gas entering the sintering furnace and the inert gas flowing out of the sintering furnace, the greater the flow rate of the inert gas introduced into the sintering furnace. Conversely, the smaller the temperature difference between the inert gas entering the sintering furnace and the inert gas flowing out of the sintering furnace, the smaller the flow rate of the inert gas introduced into the sintering furnace.

[0035] In one specific embodiment of the present invention, the inert gas includes at least one of helium, neon, argon, krypton, xenon and radon, so that the inert gas does not easily react chemically with the permanent magnet blank, and can serve as both a protective gas for preparation and a heat conduction medium to improve the consistency of sintering.

[0036] In one specific embodiment of the present invention, the permanent magnet material sintering method of the present invention further includes: Tempering stage: The temperature inside the sintering furnace is maintained at the first tempering temperature and the second tempering temperature for a period of time. The first tempering temperature is higher than the second tempering temperature. The tempering stage can effectively eliminate the internal stress of the prepared permanent magnet, making the permanent magnet less susceptible to damage when subjected to external impacts during subsequent use.

[0037] In one specific embodiment of the present invention, the first tempering temperature is 900℃-950℃ and the second tempering temperature is 600℃-680℃. The gradient tempering can ensure that the prepared permanent magnet is not too brittle and is not easily damaged when subjected to external impacts during subsequent use.

[0038] In a specific embodiment of the permanent magnet material sintering apparatus provided in the second aspect of the present invention, the permanent magnet material sintering apparatus is used to implement the above-described permanent magnet material sintering method, and includes: The sintering furnace, used to hold the permanent magnet blank 1, is existing technology and will not be described in detail here; Heater 2 is used to heat the permanent magnet blank 1 in the sintering furnace. Specifically, infrared or microwave devices can be used to radiate and heat the permanent magnet blank 1, thereby reducing the introduction of impurities during the sintering process and preventing the oxidation of the permanent magnet blank 1. A gas supply device is connected to a sintering furnace to supply inert gas to the sintering furnace, and can be configured to circulate the inert gas in the sintering furnace (this is prior art and will not be described in detail here). A first heat exchanger is connected in series on the gas supply device to cool the inert gas through the first heat exchanger, thereby facilitating the control and adjustment of the temperature of the inert gas during the cooling stage. A negative pressure pump is connected to the sintering furnace to draw gas from inside the furnace.

[0039] In one specific embodiment of the present invention, a second heat exchanger is connected in series on the gas supply device to heat the inert gas, so that the temperature of the inert gas charged into the sintering furnace during the gas charging stage is higher, reducing the temperature difference between it and the second sintering temperature. This avoids the problem of poor sintering consistency of permanent magnet blanks caused by excessive temperature difference in different areas within the sintering furnace during the inert gas charging process.

[0040] The following are three examples of Nd magnets sintered using the permanent magnet sintering method described in this application. 15 Fe 78 B7 permanent magnet and an example of Nd magnet sintered using existing sintering methods. 15 Fe 78 An example of the B7 permanent magnet is shown to compare the differences between the two: Example 1 of the permanent magnet material sintering method of this application: Preparation stage: Preparation of Nd 15 Fe 78 B7 permanent magnet blank, particle size 3-4μm, powder loose density 1.5g / cm³ 3 Sintered NdFeB magnetic powder is oriented and formed under a magnetic field of 1.5T-2T, and then made into a blank under cold forging and static pressing of 200MPa. The permanent magnet blank is then placed into a sintering furnace. Preheating stage: The sintering furnace is heated to 300°C and held for a period of time, such as 30 minutes, to volatilize the organic additive paraffin in the green body; Vacuum heating stage: The sintering furnace is heated to 700℃ and held for 60 minutes. During the holding period, vacuum is continuously applied until the pressure inside the furnace reaches 10. -3 Continue heating after Pa; Gas charging stage: The gas is charged into the sintering furnace at a pressure of 0.1 × 10⁻⁶. 6 Pa, high-temperature and high-pressure argon gas at 1000℃, simultaneously heating the sintering furnace to 1000℃ until the inert gas reaches a high-pressure state. Heat preservation stage: After the sintering furnace is heated to 1000℃, the sintering furnace is heat preserved for 10 hours. Cooling stage: Turn on the gas supply device to circulate the argon gas in the furnace. During circulation, ensure that the argon gas flow rate in the furnace is 10m / s, and gradually cool down the high temperature and high pressure argon gas until the permanent magnet in the furnace reaches 20℃. Tempering stage: High-temperature argon gas at atmospheric pressure is introduced into the furnace for two tempering processes. The first tempering temperature is 900℃ and the tempering time is 4 hours. The second tempering temperature is 600℃ and the tempering time is 1 hour.

[0041] The performance parameters of the prepared permanent magnet include: remanence 1.374T, coercivity 902.8kA / m, magnetic energy product 354.8kJ / m³, and density 7.526g / cm³.

[0042] Example 2 of the permanent magnet material sintering method of this application: Preparation stage: Preparation of Nd 15 Fe 78 B7 permanent magnet blank, particle size 3-4μm, powder loose density 1.5g / cm³ 3 Sintered NdFeB magnetic powder is oriented and formed under a magnetic field of 1.5T-2T, and then made into a blank under cold forging and static pressing of 200MPa. The permanent magnet blank is then placed into a sintering furnace. Preheating stage: The sintering furnace is heated to 320℃ and held for a period of time, such as 30 minutes, to volatilize the organic additive paraffin in the green body; Vacuum heating stage: The sintering furnace is heated to 800℃ and held for 45 minutes. During the holding period, vacuum is continuously applied until the pressure inside the furnace reaches 5×10⁻⁶. -3 Continue heating after Pa; Gas charging stage: The gas is charged into the sintering furnace at a pressure of 0.5 × 10⁻⁶. 6 Pa, high-temperature and high-pressure argon gas at 1000℃, simultaneously raises the temperature of the sintering furnace to 1040℃ until the inert gas reaches a high-pressure state. Heat preservation stage: After the sintering furnace is heated to 1040℃, the sintering furnace is heat preserved for 9 hours. Cooling stage: Turn on the gas supply device to circulate the argon gas in the furnace. During circulation, ensure that the argon gas flow rate in the furnace is 20m / s, and gradually cool down the high temperature and high pressure argon gas until the permanent magnet in the furnace reaches 20℃. Tempering stage: High-temperature argon gas at atmospheric pressure is introduced into the furnace for two tempering processes. The first tempering temperature is 900℃ and the tempering time is 4 hours. The second tempering temperature is 600℃ and the tempering time is 1 hour. The performance parameters of the prepared permanent magnet include: remanence 1.369T, coercivity 850.2kA / m, magnetic energy product 355kJ / m³, and density 7.554kJ / cm³.

[0043] Example 3 of the permanent magnet material sintering method of this application: Preparation stage: Preparation of Nd 15 Fe 78 B7 permanent magnet blank, particle size 2.5-4μm, powder loose density 1.6g / cm³ 3 Sintered NdFeB magnetic powder is oriented and formed under a magnetic field of 1T-2T, and then made into a blank under cold forging and static pressing of 250MPa. The permanent magnet blank is then placed into a sintering furnace. Preheating stage: The sintering furnace is heated to 500℃ and held for a period of time, such as 30 minutes, to volatilize the organic additive paraffin in the green body; Vacuum heating stage: The sintering furnace is heated to 900℃ and held for 30 minutes. During the holding period, vacuum is continuously applied until the pressure inside the furnace reaches 10. -2 Continue heating after Pa; Gas charging stage: The sintering furnace is charged at a pressure of 1.5 × 10⁻⁶. 6 Pa, high-temperature and high-pressure argon gas at 1000℃, simultaneously raises the temperature of the sintering furnace to 1080℃ until the inert gas reaches a high-pressure state. Heat preservation stage: After the sintering furnace is heated to 1080℃, the sintering furnace is heat preserved for 8 hours. Cooling stage: Turn on the gas supply device to circulate the argon gas in the furnace. During circulation, ensure that the argon gas flow rate in the furnace is 30m / s, and gradually cool down the high temperature and high pressure argon gas until the permanent magnet in the furnace reaches 20℃. Tempering stage: High-temperature argon gas at atmospheric pressure is introduced into the furnace for two tempering processes. The first tempering temperature is 900℃ and the tempering time is 4 hours. The second tempering temperature is 600℃ and the tempering time is 1 hour.

[0044] The performance parameters of the prepared permanent magnet include: remanence 1.372T, coercivity 867.4kA / m, magnetic energy product 354.9kJ / m³, and density 7.562 / cm³.

[0045] Existing sintering methods: Preparation of Nd 15 Fe 78 B7 permanent magnet blank, particle size 3-4μm, powder loose density 1.5g / cm³ 3Sintered NdFeB magnetic powder is oriented and shaped under a magnetic field of 1.5T-2T, and then formed into a blank under cold forging static pressure of 150MPa-200MPa. The permanent magnet blank is then placed in a sintering furnace for low-pressure sintering (sintering pressure of 10... -4 Pa-10 -2 Pa), tempering, and cooling.

[0046] The performance parameters of the prepared permanent magnet include: remanence 1.362T, coercivity 808.8kA / m, magnetic energy product 349.8kJ / m³, and density 7.387 / cm³.

[0047] As can be seen from the performance parameters of the permanent magnets obtained by the four embodiments described above, the permanent magnets sintered by the permanent magnet material sintering method of this application have higher density, higher remanence and magnetic energy product, and significantly improved coercivity compared with permanent magnets obtained by existing sintering methods. Therefore, the quality of permanent magnets sintered by existing methods is significantly improved.

[0048] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, and should also be regarded as the content disclosed by the present invention.

Claims

1. A method of sintering a permanent magnetic material, characterized by, Includes the following steps: Preparation stage: Place the permanent magnet blank into the sintering furnace; Preheating stage: The sintering furnace is heated to the preheating temperature and maintained at the first temperature until the holding time reaches the preset holding time; Vacuum heating stage: The sintering furnace is heated to the first sintering temperature, and the sintering furnace is evacuated to a preset pressure at the temperature of the first sintering temperature; Gas filling stage: Inert gas is filled into the sintering furnace, and the sintering furnace is heated to the second sintering temperature until the inert gas reaches a high pressure state. Heat preservation stage: After the sintering furnace is heated to the second sintering temperature, the sintering furnace is subjected to heat preservation during sintering. Cooling stage: Inert gas is introduced into the sintering furnace to cool the furnace until the permanent magnet material inside the furnace reaches the preset cooling temperature.

2. The sintering method of a permanent magnet material according to claim 1, wherein The preheating temperature is 300℃-500℃.

3. The sintering method of a permanent magnet material according to claim 1, wherein The first sintering temperature is 700℃-900℃, and the preset gas pressure is 10. -3 -10 -2 Pa.

4. The sintering method of a permanent magnet material according to claim 1, wherein The second sintering temperature is 1000℃-1300℃, and the pressure of the inert gas under high pressure is 0.1×10⁻⁶. 6 Pa-10×10 6 Pa.

5. The sintering method of a permanent magnet material according to claim 1, wherein During the cooling stage, the inert gas introduced into the sintering furnace is at a temperature of 20-100°C and a flow rate of 10-100 m / s.

6. The sintering method of a permanent magnet material according to any one of claims 1 to 5, characterized by, The inert gas includes at least one of helium, neon, argon, krypton, xenon, and radon.

7. The sintering method of a permanent magnet material according to claim 6, wherein Also includes: Tempering stage: The temperature inside the sintering furnace is maintained at the first tempering temperature and the second tempering temperature for a period of time, with the first tempering temperature being higher than the second tempering temperature.

8. The sintering method for permanent magnet materials according to claim 7, characterized in that, The first tempering temperature is 900℃-950℃, and the second tempering temperature is 600℃-680℃.

9. A permanent magnet material sintering apparatus for implementing the permanent magnet material sintering method according to any one of claims 1-8, characterized in that, include: Sintering furnace, used to hold permanent magnet blanks (1); Heater (2) is used to heat the permanent magnet blank (1) in the sintering furnace; A gas supply device is connected to the sintering furnace to supply inert gas to the sintering furnace, and a first heat exchanger is connected in series on the gas supply device to cool the inert gas via the first heat exchanger. A negative pressure pump is connected to the sintering furnace to draw gas from inside the sintering furnace.

10. The apparatus according to claim 9, wherein The gas supply device is also connected in series with a second heat exchanger to heat the inert gas.

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