Method for improving mechanical properties of samarium-cobalt magnets and samarium-cobalt magnet

Abstract

The application discloses a method for improving mechanical properties of a samarium-cobalt magnet and the samarium-cobalt magnet, which comprises the following steps: placing the samarium-cobalt magnet into an inductive heating coil in a vacuum cavity, vacuumizing, inputting inert gas, starting the power supply of the inductive heating coil, heating and then heat preserving, and cooling to room temperature at a speed of 0.5-20 DEG C / min; wherein the heating temperature is 300 DEG C <= T < Curie temperature, and the heat preserving time is 1-120 min. The mechanical properties of the samarium-cobalt magnet are greatly improved; compared with traditional inductive heating, the cooling speed is controlled, and the synchronous improvement of the mechanical properties and the magnetic properties of the samarium-cobalt magnet is ensured.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet materials technology, specifically relating to a method for improving the mechanical properties of samarium cobalt magnets and samarium cobalt magnets. Background Technology

[0002] Samarium cobalt permanent magnets possess advantages such as high magnetic properties, high temperature resistance, corrosion resistance, and low temperature coefficient, making them widely used in defense, new energy vehicles, consumer electronics, rail transportation, wind power generation, and other fields. However, due to their inherent characteristics such as low slip systems, anisotropy, and porous sintering, samarium cobalt materials are prone to problems like chipping and breakage during product processing, handling, inspection, and magnetization. According to literature research, the bending strength of samarium cobalt magnets is only 80-140 MPa, and their fracture toughness is only 1.5-2.5 MPa. 1 / 2 Its brittleness leads to production losses of up to 20-30%, which severely restricts its application range and deep processing.

[0003] To improve the mechanical properties of samarium-cobalt permanent magnets, researchers have conducted numerous experiments. While coating / plating a protective layer on the surface of magnetic materials can improve mechanical properties, the improvement is limited. Some researchers have improved the strength and toughness of samarium-cobalt magnets through elemental doping, reducing anisotropy, and grain refinement, but these methods often result in a loss of magnetic properties. Induction heating technology offers advantages such as high efficiency, energy saving, and stable quality, making it an effective means of surface strengthening for metallic materials and capable of significantly improving their mechanical properties. However, induction heating often involves rapid quenching, which can easily cause fracture in brittle samarium-cobalt materials and leads to severe magnetic property attenuation, affecting the application of samarium-cobalt products. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the mechanical properties of samarium cobalt magnets and a samarium cobalt magnet.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for improving the mechanical properties of samarium cobalt magnets, comprising: placing the samarium cobalt magnet in an induction heating coil of a vacuum chamber and evacuating it; introducing an inert gas; turning on the power supply of the induction coil; heating and holding the magnet at that temperature; and then cooling it to room temperature at a rate of 0.5 to 20°C / min; wherein the heating temperature is 300°C ≤ T < the Curie temperature of the samarium cobalt magnet, and the holding time is 1 to 120 min.

[0008] In a preferred embodiment of the method described in this invention, the heating temperature is 500℃≤T≤700℃.

[0009] In a preferred embodiment of the method described in this invention, the heat preservation time is 10 to 60 minutes.

[0010] In a preferred embodiment of the method described in this invention, the cooling rate to room temperature is 1–5 °C / min.

[0011] In a preferred embodiment of the method described in this invention, the induction heating, heat preservation, and cooling to room temperature are performed once or multiple times.

[0012] In a preferred embodiment of the method described in this invention, the samarium-cobalt magnet is placed at the center of the magnetic field of the induction heating coil.

[0013] In a preferred embodiment of the method described in this invention, the inert gas is high-purity argon.

[0014] Another object of the present invention is to overcome the shortcomings of the prior art and provide a method for producing a samarium cobalt magnet.

[0015] As a preferred embodiment of the samarium cobalt magnet of the present invention, the bending strength of the samarium cobalt magnet is 116~300MPa.

[0016] As a preferred embodiment of the samarium cobalt magnet of the present invention, the maximum energy product (BH) of the samarium cobalt magnet is 29~33 MGOe.

[0017] Beneficial effects of this invention: Compared with the original sample, the mechanical properties of the samarium cobalt magnet of the present invention are significantly improved; compared with traditional induction heating, the cooling rate is controlled, ensuring that the mechanical properties and magnetic properties of the samarium cobalt magnet are improved simultaneously. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a stress-strain diagram of the bending strength of the samarium-cobalt magnet in Embodiment 3 of the present invention; Figure 2 This is a stress-strain diagram of the bending strength of a samarium cobalt magnet, Comparative Example 1 of the present invention. Figure 3 This is a Vickers hardness distribution diagram of the samarium-cobalt magnet in Embodiment 3 of the present invention; Figure 4 Magnetic performance curves of samarium-cobalt magnets in Embodiment 3 of the present invention; Figure 5 This is a graph showing the magnetic properties of the samarium cobalt magnet in Comparative Example 1 of the present invention. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0022] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available.

[0023] Example 1 This embodiment provides a method for improving the mechanical properties of samarium-cobalt magnets, including the following steps: First, the samarium cobalt magnets are processed into two specifications, 5×6×20mm and φ10×10mm, according to national standards. The processed samples are then placed inside the induction coil of a vacuum heating furnace.

[0024] Next, begin evacuation, raising the vacuum level inside the furnace to 3×10⁻⁶. -2The sample was charged with high-purity argon gas, and the intermediate frequency power supply of the coil was turned on. The sample was heated to 300℃ and held at that temperature for 60 minutes. Then, it was slowly cooled to room temperature at a rate of 1℃ / min according to the set program. Finally, the gas valve and power switch were turned off, the sample was removed, and the entire experiment was completed.

[0025] Example 2 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 500°C, held at that temperature for 60 minutes, and then slowly cooled to room temperature at a rate of 1°C / min according to the set program.

[0026] Example 3 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 700°C, held at that temperature for 60 minutes, and then slowly cooled to room temperature at a rate of 1°C / min according to the set program.

[0027] Figure 1 This is a stress-strain diagram of the bending strength of the samarium-cobalt magnet in Embodiment 3 of the present invention; Figure 3 This is a Vickers hardness distribution diagram of the samarium-cobalt magnet in Embodiment 3 of the present invention; Figure 4 This is a graph showing the magnetic properties of the samarium cobalt magnet in Embodiment 3 of the present invention.

[0028] Example 4 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 300°C, held for 10 minutes, and then slowly cooled to room temperature at a rate of 1°C / min according to the set program.

[0029] Example 5 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 500°C, held for 10 minutes, and then slowly cooled to room temperature at a rate of 1°C / min according to the set program.

[0030] Example 6 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 700°C, held for 10 minutes, and then slowly cooled to room temperature at a rate of 1°C / min according to the set program.

[0031] Example 7 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 300°C, held at that temperature for 60 minutes, and then slowly cooled to room temperature at a rate of 5°C / min according to the set program.

[0032] Example 8 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 500°C, held at that temperature for 60 minutes, and then slowly cooled to room temperature at a rate of 5°C / min according to the set program.

[0033] Example 9 The only difference between this embodiment and Embodiment 1 is that the sample is heated to 700°C, held at that temperature for 60 minutes, and then slowly cooled to room temperature at a rate of 5°C / min according to the set program.

[0034] Example 10 This embodiment is a traditional induction heating and rapid cooling method. The only difference from Embodiment 1 is that the sample is heated to 700°C, held at that temperature for 60 minutes, the coil power is turned off, and the sample is rapidly cooled to room temperature.

[0035] Comparative Example 1 The only difference between this comparative example and Example 1 is that the samarium cobalt magnet is the original sample and has not undergone any processing.

[0036] Figure 2 This is a stress-strain diagram of the bending strength of a samarium cobalt magnet, Comparative Example 1 of the present invention. Figure 5 This is a graph showing the magnetic properties of the samarium cobalt magnet in Comparative Example 1 of the present invention.

[0037] The samarium cobalt permanent magnet materials obtained in the above embodiments and comparative examples were characterized for room temperature magnetic and mechanical properties. The tests were conducted according to GB / T31967.2-2015 standard, and the samples were processed into 5×6×20mm samples for bending strength testing. The tests were conducted according to GB / T3217-2013 standard, and the samples were processed into φ10×10mm samples for room temperature magnetic property testing. The results are shown in Table 1.

[0038] Table 1. Performance List of Samarium Cobalt Magnets

[0039] Compared to Comparative Example 1 using the traditional process, the flexural strength of the samarium cobalt magnets in Examples 1-10 was improved, with the highest value being Example 10, reaching 379.57 MPa. However, the magnetic energy product was severely reduced to only 1.68 MGOe, mainly due to the excessively rapid cooling rate. The cellular structure did not have enough time to redistribute at high temperatures, resulting in extremely low coercivity. Examples 1-3 involved changing the induction heating temperature while maintaining the same holding time and cooling rate. As the heating temperature increased, the mechanical properties gradually improved, with Example 3 exhibiting the highest flexural strength at 299.59 MPa and a magnetic energy product of 32.58 MGOe. Examples 4-6, compared to Examples 1-3, had a corresponding holding time adjusted to 10 min. With a shorter holding time, the flexural strength decreased accordingly, and the magnetic energy product slightly decreased. Examples 7-9, compared to Examples 1-3, had a cooling rate of 5 °C / min. With an increased cooling rate, the flexural strength did not change significantly.

[0040] In addition, the hardness of Example 3 was tested and analyzed, such as... Figure 3As shown, the results revealed that the Vickers hardness gradually decreased with increasing distance from the surface to the core. In the near-surface region, the hardness of the samarium-cobalt magnet was 858.2 HV0.025, while in the internal region, the average hardness was 651.5 HV0.025, representing a 31.7% increase in surface hardness. This is because induction heating forms a hardened layer on the surface, enhancing its surface hardness.

[0041] The above analysis shows that as the induction heating temperature increases, the bending strength gradually increases; as the holding time decreases, the mechanical properties decrease; as the cooling rate increases, the bending strength does not change much, but the magnetic energy product decreases significantly, especially at very high cooling rates, where the samarium-cobalt magnet has virtually no magnetic properties. Compared to the original sample in Comparative Example 1, the bending strength of each embodiment is improved, mainly due to the induced magnetic field generated by the induction coil, which induces eddy currents on the surface of the samarium-cobalt magnet, forming a harder hardened layer and improving the mechanical properties of the samarium-cobalt material. Suitable heating temperature, holding time, and cooling rate are key to the synergistic improvement of mechanical and magnetic properties. Furthermore, this invention can also be used for solution treatment of 1:5 and 2:17 type samarium-cobalt magnets, multi-stage / multi-stage aging treatments, and other heat treatment processes for samarium-cobalt magnets. This invention utilizes the principle of induction heating, combining induction coil heating technology with controlled cooling rate to obtain high-performance samarium-cobalt magnets, thereby overcoming the problem of the difficulty in synergistic improvement of force and magnetism in existing technologies.

[0042] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for improving the mechanical properties of samarium-cobalt magnets, characterized in that: The samarium cobalt magnet is placed inside the induction heating coil of the vacuum chamber and evacuated. An inert gas is introduced, the power supply to the induction coil is turned on, and the magnet is heated and held at that temperature. Then it is cooled to room temperature at a rate of 0.5 to 20°C / min. The heating temperature is 300℃≤T<Curie temperature, and the holding time is 1~120min.

2. The method as described in claim 1, characterized in that: The heating temperature is 500℃≤T≤700℃.

3. The method as described in claim 1, characterized in that: The heat preservation time is 10 to 60 minutes.

4. The method as described in claim 1, characterized in that: The cooling rate to room temperature is 1–5 °C / min.

5. The method as described in claim 1, characterized in that: The number of times the induction heating, heat preservation, and cooling to room temperature is performed is one or more.

6. The method as described in claim 1, characterized in that: The samarium-cobalt magnet is placed at the center of the magnetic field of the induction heating coil.

7. The method as described in claim 1, characterized in that: The inert gas is high-purity argon.

8. A samarium-cobalt magnet prepared by the method according to any one of claims 1 to 7.

9. The samarium-cobalt magnet as described in claim 8, characterized in that: The flexural strength of the samarium cobalt magnet is 116~300MPa.

10. The samarium-cobalt magnet as claimed in claim 8, characterized in that: The maximum energy product (BH) of the samarium cobalt magnet is 29~33 MGOe.

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