Preparation method of cobalt-free high-temperature-resistant iron-based rare earth permanent magnet material

Abstract

The invention relates to a preparation method of a cobalt-free high-temperature-resistant iron-based rare earth permanent magnet material, and aims to provide a novel permanent magnet material which is low in cost and can keep excellent magnetic performance in a high-temperature environment. The method comprises the steps of alloy smelting, powder preparation, powder pressing, high-temperature sintering, heat treatment and the like. In combination with a surface treatment technology, through specific alloy design and process parameters, the material shows excellent magnetic performance and stability at high temperature, and is particularly suitable for high-end application fields such as high-temperature motors.

Description

Technical Field

[0001] This invention belongs to the field of high-performance permanent magnet materials technology, specifically referring to a cobalt-free iron-based rare earth permanent magnet material suitable for high-temperature environments and its preparation method. Background Technology

[0002] Permanent magnet materials are a class of magnetic materials with high remanence and high energy product, widely used in many fields such as electric motors, generators, sensors, and hard disk drives. Currently, the mainstream permanent magnet materials on the market mainly include ferrite, AlNiCo, and rare-earth permanent magnet materials. Among them, rare-earth permanent magnet materials stand out due to their superior magnetic properties, especially neodymium iron boron (NdFeB) permanent magnet materials, which are highly favored for their high energy product and high coercivity.

[0003] However, the application of rare-earth permanent magnet materials in high-temperature environments is limited. This is because cobalt, a key element in traditional rare-earth permanent magnet materials, is easily oxidized at high temperatures, leading to a decrease in the material's magnetic properties. Furthermore, the scarcity and price volatility of cobalt also present cost challenges for the large-scale production and application of permanent magnet materials.

[0004] To overcome these problems, researchers have been exploring cobalt-free permanent magnet materials. Iron-based rare-earth permanent magnet materials have become a research hotspot due to their lower raw material costs and abundant resources. However, the magnetic stability of cobalt-free iron-based rare-earth permanent magnet materials at high temperatures remains a technical challenge.

[0005] Those skilled in the art have explored ways to improve the high-temperature performance of iron-based rare-earth permanent magnet materials by adding other elements, such as zirconium (Zr) and molybdenum (Mo), to enhance the material's oxidation resistance and mechanical strength. Furthermore, surface coating techniques have also been used to improve the material's high-temperature resistance, for example, by applying coatings with high-temperature resistant materials such as alumina (Al2O3) or silicon nitride (Si3N4).

[0006] Nevertheless, the magnetic properties of existing cobalt-free iron-based rare-earth permanent magnet materials at high temperatures still cannot meet the requirements of certain high-end applications, especially in fields such as high-temperature motors. Therefore, developing an iron-based rare-earth permanent magnet material that is both cobalt-free and possesses excellent high-temperature stability is of great significance for promoting the development of permanent magnet material technology and expanding its application areas. Summary of the Invention

[0007] To address the problems existing in the aforementioned background technology, this invention provides a method for preparing cobalt-free, high-temperature resistant iron-based rare-earth permanent magnet materials. Through specific alloy design and process flow, the preparation method of this invention successfully produces iron-based rare-earth permanent magnet materials that maintain excellent magnetic properties even at high temperatures. The permanent magnet materials of this invention are not only low-cost but also possess high remanence, energy product, and coercivity, making them particularly suitable for high-end applications such as high-temperature motors.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] The alloy composition of iron-based rare earth permanent magnet materials includes iron (Fe), neodymium (Nd), dysprosium (Dy), zirconium (Zr), and molybdenum (Mo), but does not contain cobalt. The specific alloy composition ratio is: Fe 85-92%, Nd 5-10%, Dy 1-5%, Zr 0.5-2%, and Mo 0.5-2%.

[0010] Alloy smelting: under a vacuum degree range of 1×10 -5 Up to 1×10 -1 Under an inert atmosphere (argon or helium), the above alloy components are melted in a high-temperature furnace at 1400 to 1600°C for 6-10 hours to ensure uniform mixing of the alloy components.

[0011] Powder preparation: The molten alloy is pulverized by passing it through an inert gas stream at a pressure of 5-10 bar, and the powder particle size is controlled within the range of 10-50 micrometers.

[0012] Powder pressing: Alloy powder is pressed into shape under high pressure of 700 to 900 MPa to form a preform with a certain shape.

[0013] High-temperature sintering: In an inert atmosphere, the preform is sintered at 1100-1300℃ for 2-4 hours and then cooled to room temperature at a rate of 3-6℃ / min.

[0014] Heat treatment: The sintered permanent magnet material is heat-treated at 1000-1200℃ for 3-6 h, followed by water quenching to optimize its magnetic properties and microstructure.

[0015] High-temperature resistant material coatings, such as alumina (Al2O3) or silicon nitride (Si3N4), are applied to the surface of permanent magnet materials using chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques, with the coating thickness controlled within the range of 5-10 micrometers.

[0016] The prepared permanent magnet material was subjected to magnetic property tests, including remanence (Br), energy product (BHmax), and coercivity (Hcj). The magnetic stability of the permanent magnet material was tested at high temperatures, ranging from 200℃ to 600℃.

[0017] The cobalt-free iron-based rare-earth permanent magnet material prepared by this invention exhibits excellent high-temperature stability and magnetic properties, and is also low in cost. The addition of elements such as zirconium (Zr) and molybdenum (Mo) improves the material's corrosion resistance and mechanical strength. Surface coating treatment further enhances the material's stability and durability under high-temperature conditions. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are intended to further illustrate the content of the present invention and should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the embodiments are all disclosed in the prior art, such as those that can be directly purchased or prepared according to prior art methods. Example 1

[0019] Alloy smelting: The raw materials are smelted under a vacuum of 1×10⁻⁶ kg / cm² according to the weight percentage ratio of Fe 88%, Nd 8%, Dy 3%, Zr 1%, and Mo 1%. -2 The alloy was melted at 1600℃ for 8 h under an argon atmosphere to obtain a uniform alloy.

[0020] Powder preparation: The molten alloy was prepared into powder by argon gas atomization technology, and the atomization pressure was controlled at 7.5 bar to obtain powder with an average particle size of 30 micrometers.

[0021] Powder pressing: The powder is pressed into shape under a pressure of 800 MPa to form a preform with a density of more than 92% of the theoretical density.

[0022] High-temperature sintering: The preform is sintered at 1200℃ for 3 hours and then cooled to room temperature at a rate of 5℃ / min.

[0023] Heat treatment: The sintered body was heat treated at 1120℃ for 4 hours, followed by water quenching.

[0024] Surface coating: A 7-micron-thick Al2O3 coating is applied to the surface of the permanent magnet material using chemical vapor deposition technology.

[0025] Performance testing: At a high temperature of 500℃, the remanence (Br) of this material is 1.22 T, with a remanence retention rate of 90%, the magnetic energy product (BHmax) is 220 kJ / m³, with a magnetic energy product retention rate of 85%, and the coercivity (Hcj) is 778 kA / m, with a coercivity retention rate of 95%. Example 2

[0026] Alloy smelting: The raw materials are smelted under a vacuum of 1×10⁻⁶ kg / m³, according to the weight percentage ratio of Fe 90%, Nd 6%, Dy 4%, Zr 1.5%, and Mo 1.5%. -3 The alloy was melted at 1500℃ for 9 h under an argon atmosphere to obtain a uniform alloy.

[0027] Powder preparation: The molten alloy was prepared into powder by argon gas atomization technology, and the atomization pressure was controlled at 9.5 bar to obtain powder with an average particle size of 35 micrometers.

[0028] Powder pressing: The powder is pressed into shape under a pressure of 900 MPa to form a preform with a density of more than 93% of the theoretical density.

[0029] High-temperature sintering: The preform is sintered at 1300℃ for 2 hours and then cooled to room temperature at a rate of 3℃ / min.

[0030] Heat treatment: The sintered body was heat treated at 1200℃ for 5 hours, followed by water quenching.

[0031] Surface coating: A 5-micron-thick silicon nitride (Si3N4)3 coating is applied to the surface of the permanent magnet material using physical vapor deposition technology.

[0032] Performance testing: At a high temperature of 550℃, the remanence (Br) of this material is 1.18 T, with a remanence retention rate of 88%, the magnetic energy product (BHmax) is 200 kJ / m³, with a magnetic energy product retention rate of 82%, and the coercivity (Hcj) is 700 kA / m, with a coercivity retention rate of 92%. Example 3

[0033] Alloy smelting: The raw materials are smelted under a vacuum of 1×10⁻⁶ kg / m³ according to the following weight percentage ratios: Fe 87%, Nd 9%, Dy 2%, Zr 1.5%, and Mo 1.5%. -1 The alloy was melted at 1500℃ for 8 h under an argon atmosphere to obtain a uniform alloy.

[0034] Powder preparation: The molten alloy was prepared into powder by helium gas atomization technology, and the atomization pressure was controlled at 7 bar to obtain powder with an average particle size of 34 micrometers.

[0035] Powder pressing: The powder is pressed into shape under a pressure of 850 MPa to form a preform with a density of more than 91% of the theoretical density.

[0036] High-temperature sintering: The preform is sintered at 1250℃ for 5 hours and then cooled to room temperature at a rate of 4℃ / min.

[0037] Heat treatment: The sintered body was heat treated at 1150℃ for 4.5h, followed by water quenching.

[0038] Surface coating: An 8-micron-thick silicon nitride (Si3N4)3 coating is applied to the surface of the permanent magnet material using physical vapor deposition technology.

[0039] Performance testing: At a high temperature of 600℃, the remanence (Br) of this material is 1.20 T, with a remanence retention rate of 85%, the magnetic energy product (BHmax) is 210 kJ / m³, with a magnetic energy product retention rate of 80%, and the coercivity (Hcj) is 760 kA / m, with a coercivity retention rate of 90%.

Claims

1. A cobalt-free, high-temperature resistant iron-based rare earth permanent magnet material, characterized in that, The permanent magnet material is composed of the following components by weight percentage: iron (Fe) 85-92%, neodymium (Nd) 5-10%, dysprosium (Dy) 1-5%, zirconium (Zr) 0.5-2%, molybdenum (Mo) 0.5-2%, with the balance being unavoidable impurities.

2. The permanent magnet material according to claim 1, characterized in that, The method for preparing the permanent magnet material includes the following steps: (1) Alloy smelting: Under the protection of an inert atmosphere with a certain vacuum degree, iron, neodymium, dysprosium, zirconium and molybdenum are smelted and held at high temperature for a period of time to form an alloy; (2) Powder preparation: The molten alloy is pulverized into powder by airflow, and the powder particle size is controlled within the range of 10-50 micrometers; (3) Powder pressing: Alloy powder is pressed into shape under high pressure to form a preform with a certain shape; (4) High-temperature sintering: In an argon atmosphere, the preform is sintered at a certain temperature for a certain time and then cooled to room temperature at a certain rate. (5) Heat treatment: The sintered permanent magnet material is subjected to appropriate heat treatment for a certain period of time, followed by water quenching.

3. The permanent magnet material according to claim 2, characterized in that, The surface coating process employs chemical vapor deposition (CVD) or physical vapor deposition (PVD) techniques. The coating material is alumina (Al2O3) or silicon nitride (Si3N4), and the coating thickness is controlled within the range of 5-10 micrometers.

4. A method for preparing a cobalt-free, high-temperature resistant iron-based rare earth permanent magnet material according to claim 2, characterized in that... The vacuum level range is 1×10 -5 Up to 1×10 -1 Torr; the inert gas is argon or helium, the high-temperature treatment temperature is 1400 to 1600°C, and the heat preservation time is 6-10 h.

5. A method for preparing a cobalt-free, high-temperature resistant iron-based rare earth permanent magnet material according to claim 2, characterized in that, The pulverizing gas stream used is an inert gas, including but not limited to argon, with a gas pressure of 5-10 bar.

6. A method for preparing a cobalt-free, high-temperature resistant iron-based rare earth permanent magnet material according to claim 2, characterized in that, The powder molding pressure range is 700 to 900 MPa.

7. A method for preparing a cobalt-free, high-temperature resistant iron-based rare earth permanent magnet material according to claim 2, characterized in that, The high-temperature sintering atmosphere used is an inert atmosphere including but not limited to argon, the sintering temperature is 1100 to 1300℃, the holding time is 2-6h, and the cooling rate is 3-6℃ / min.

8. A method for preparing a cobalt-free, high-temperature resistant iron-based rare earth permanent magnet material according to claim 2, characterized in that, The sintered permanent magnet material is heat-treated at a temperature of 1000-1200℃ for 3-6 hours, followed by water quenching.