One-step formed samarium-cobalt magnet and preparation method thereof

Abstract

The invention discloses a one-step formed samarium-cobalt magnet and a preparation method thereof, and belongs to the technical field of magnetic materials. The method solves at least one of the problems of tedious preparation process flow, low production efficiency, high cost and poor product consistency caused by the fact that an existing samarium-cobalt magnet preparation method needs a cold isostatic pressing process. The preparation method disclosed by the invention comprises the following steps: step 1, a smelting and powdering stage to obtain samarium-cobalt magnet powder; step 2, a powder mixing stage; adding a lubricant into the samarium-cobalt magnet powder and uniformly mixing; step 3, an orientation forming stage, wherein a samarium-cobalt magnet blank is finally obtained; 4, the samarium-cobalt magnet blank is sintered under inert gas; 5, the samarium-cobalt magnet blank is subjected to solution treatment under inert gas; and 6, aging treatment is conducted on the samarium-cobalt magnet blank after solution treatment, and finally the samarium-cobalt magnet is obtained. According to the method, isostatic cool pressing is not needed, and the maximum magnetic energy product of the prepared samarium-cobalt magnet is more than 29.05 MGOe.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of magnetic materials, in particular to a one-step forming samarium-cobalt magnet and a preparation method thereof. BACKGROUND

[0002] Sintered samarium-cobalt permanent magnet is a new type of functional material developed gradually since the 1960s. It has high magnetic energy product, high coercivity, low temperature coefficient, and excellent high-temperature resistance (more than 350℃), and also has excellent corrosion resistance and oxidation resistance. The material is widely used in motors, instruments and meters, sensors, detectors, engines, radar systems and other high-tech fields, and is one of the key functional materials indispensable in modern industry and technology.

[0003] In the existing production process of sintered samarium-cobalt permanent magnet, in order to effectively improve the density of the magnet, a cold isostatic pressing process is usually introduced after orientation forming. Before the implementation of this process, in order to prevent the magnet from being contaminated by oil or other media in a high-pressure environment, the blank must be tightly wrapped, bagged, and vacuum packaged. After the cold isostatic pressing process is completed, the packaging must be removed and the magnet must be cleaned. This series of auxiliary operations not only significantly increases the labor input and packaging material consumption, increasing production costs, but also prolongs the production cycle, resulting in a decline in overall efficiency. In addition, the multiple manual interventions and packaging processes may introduce mechanical damage and consistency fluctuations, which in turn adversely affect the performance uniformity and long-term stability of the final magnet product.

[0004] Therefore, it is necessary to develop a one-step forming samarium-cobalt magnet preparation method with good magnetic properties. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a one-step forming samarium-cobalt magnet and a preparation method thereof, while ensuring the magnetic properties of the samarium-cobalt magnet, to solve at least one problem of the prior art, such as the need for a cold isostatic pressing process in the preparation method of the samarium-cobalt magnet, resulting in a long preparation process, low production efficiency, high cost, and poor product consistency.

[0006] The purpose of the present application is mainly achieved by the following technical solutions:

[0007] On the one hand, the present application provides a preparation method of a one-step forming samarium-cobalt magnet, which comprises the following steps:

[0008] Step 1, smelting and powdering stage;

[0009] According to Sm(CoFeCuZr) zThe weight proportions of each element in the alloy are weighed and mixed, and after being mixed uniformly, vacuum induction melting is performed to obtain a samarium-cobalt magnet ingot; the samarium-cobalt magnet ingot is sequentially subjected to coarse crushing, medium crushing and airflow fine processing to obtain a samarium-cobalt magnet powder;

[0010] Step 2, powder mixing stage;

[0011] An additive is added to the samarium-cobalt magnet powder, and the two are mixed uniformly;

[0012] Step 3, orientation forming stage;

[0013] The uniformly mixed samarium-cobalt magnet powder is distributed in a forming mold, and then pressure is applied to the forming mold to form the samarium-cobalt magnet powder; during the forming process, an external magnetic field is applied to achieve orientation, and finally a samarium-cobalt magnet blank is obtained;

[0014] Step 4, sintering treatment of the samarium-cobalt magnet blank under an inert gas;

[0015] Step 5, solid solution treatment of the samarium-cobalt magnet blank after sintering treatment under an inert gas;

[0016] Step 6, aging treatment of the samarium-cobalt magnet blank after solid solution treatment, and finally a samarium-cobalt magnet is obtained.

[0017] Further, in step 1, the heating temperature during vacuum induction melting is greater than 1550°C, and after all the metals are completely melted, cooling is performed to obtain a samarium-cobalt magnet ingot.

[0018] Further, in step 1, the particle size of the samarium-cobalt magnet powder is 3.5-4.5 μm.

[0019] Further, in step 2, the mixing time of the samarium-cobalt magnet powder and the additive is 2-2.5 h.

[0020] Further, in step 4, the heating temperature during sintering is 200-500°C, and the temperature is maintained for 0.5-2 h.

[0021] Further, in step 4, after maintaining the temperature, the temperature is raised to 1195-1220°C, and the temperature is maintained for 0.5-5 h.

[0022] Further, in step 5, the heating temperature during solid solution treatment is 1160-1190°C.

[0023] Further, in step 5, the temperature maintaining time during solid solution treatment is 2-12 h.

[0024] Further, in step 6, the aging treatment temperature is 800-900°C, and the temperature maintaining time is 4-24 h.

[0025] In another aspect, the application also provides a one-step forming samarium-cobalt magnet prepared by the above-mentioned method for preparing one-step forming samarium-cobalt magnet; the components of the samarium-cobalt magnet include, in percentage by weight, Sm 24-26 wt.%, Fe 15-20 wt.%, Cu 4-7 wt.%, Zr 2-3 wt.%, and the rest is Co.

[0026] Compared with the prior art, the application can achieve at least one of the following beneficial effects:

[0027] (1) The application improves the powder flowability by adding additives in the powder mixing stage, ensures the density distribution of the compact to be more uniform, reduces the pressure loss caused by friction of the powder, and reduces the density difference of the compact from top to bottom and from center to edge, greatly improving the consistency. The release agent is sprayed in the orientation forming stage to reduce the resistance between the powder and the forming mold during the release process, improve the service life of the forming mold, and improve the integrity of the compact.

[0028] (2) The application can obtain high-performance samarium-cobalt magnets without cold isostatic pressing process in the process of preparing samarium-cobalt magnets. The application adds lubricant in the powder mixing stage to ensure that the initial pressing density of the magnet is ≥4.9 g / cm 3 , effectively improves the initial pressing density of the magnet (the initial pressing density of the magnet before the existing cold isostatic pressing process is 4.2-4.4 g / cm3), and ensures that the magnet has sufficient density during the heat treatment process. The maximum magnetic energy product of the samarium-cobalt magnet obtained finally is above 29.05 MGOe, and the magnetic performance is not affected.

[0029] (3) The application can omit the cold isostatic pressing process and directly obtain high-performance samarium-cobalt magnets, thereby simplifying the production process, improving the production efficiency, reducing the cost, and ensuring the consistency and stability of the product.

[0030] In the application, the above technical solutions can be combined with each other to achieve more preferred combination solutions. Other features and advantages of the application will be described in the subsequent specification, and some advantages will become apparent from the specification or be understood by implementing the application. The purpose and other advantages of the application can be achieved and obtained from the content specifically indicated in the specification examples and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings are included to provide a further understanding of the application and are incorporated herein and constitute a part of the application. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. In the drawings:

[0032] Figure 1 The transmission electron microscope is for Example 1;

[0033] Figure 2The energy spectrum of Example 1;

[0034] Figure 3 This is a transmission electron microscope (TEM) of Example 2;

[0035] Figure 4 The energy spectrum of Example 2;

[0036] Figure 5 This is a transmission electron microscope (TEM) of Example 3;

[0037] Figure 6 The energy spectrum of Example 3;

[0038] Figure 7 This is a transmission electron microscope for Comparative Example 2;

[0039] Figure 8 This is the energy spectrum of Comparative Example 2. Detailed Implementation

[0040] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0041] On one hand, the present invention provides a method for preparing a one-piece molded samarium-cobalt magnet, the method comprising the following steps:

[0042] Step 1: Melting and powdering stage;

[0043] According to Sm(CoFeCuZr) z The weight ratio of each element in the alloy was determined, the raw materials were weighed and mixed, and then placed in a samarium-cobalt melting furnace for vacuum induction melting. During melting, the heating temperature was greater than 1550℃ (exceeding the melting point of all metals). After all metals were completely melted, water cooling or other cooling methods were used to obtain samarium-cobalt magnet ingots. Subsequently, the samarium-cobalt magnet ingots were subjected to coarse crushing, medium crushing, and air jet milling for fine processing, finally yielding samarium-cobalt magnet powder.

[0044] In step 1 above, the particle size of the samarium cobalt magnet powder is 3.5-4.5 μm. Strictly controlling the particle size of the samarium cobalt magnet powder within this range is to ensure that the samarium cobalt magnet possesses excellent magnetic properties.

[0045] In step 1 above, the components of the samarium cobalt magnet, by weight percentage, include: 24-26 wt.% Sm, 15-20 wt.% Fe, 4-7 wt.% Cu, 2-3 wt.% Zr, and the remainder is Co; after the ingredients are prepared, an additional 5 wt.% Sm is added to compensate for burn-off.

[0046] In step 1 above, the purity of Sm reaches 99.5 wt.% or higher, the purity of Co is not greater than or equal to 99.9 wt.%, and the melting vacuum degree is controlled at 10. -2 Within Pa.

[0047] It should be noted that the smelting vacuum degree should be controlled at 10. -2 Within the Pa range, the entry of impurity elements (mainly oxygen) into the magnet can be effectively reduced, thereby preventing the oxygen in the impurity elements from reacting with rare earth elements, which would lead to an increase in the final oxygen content of the samarium-cobalt magnet, thus affecting its performance and making it worse.

[0048] Preferably, the composition of the samarium cobalt magnet, by weight percentage, includes: 24.8 wt.% Sm, 18 wt.% Fe, 5.9 wt.% Cu, 2.7 wt.% Zr, with the remainder being Co.

[0049] Step 2, Mixing stage;

[0050] Additives were added to the prepared samarium cobalt magnet powder, and the two were mixed for 2-2.5 hours.

[0051] In step 2 above, the additive includes a lubricant.

[0052] The addition of lubricant during the powder mixing stage of this invention can improve powder flowability, ensure a more uniform density distribution of the pressed blank, reduce pressure loss caused by friction, and reduce density differences from top to bottom and from center to edge of the pressed blank, thereby improving consistency.

[0053] In step 2 above, the lubricant is added at a rate of 0.05 wt.% to 0.2 wt.%, for example, the weight percentage of the lubricant added is 0.06 wt.%, 0.09 wt.%, 0.10 wt.%, 0.13 wt.%, 0.15 wt.%, or 0.18 wt.%.

[0054] In this invention, the proportion of lubricant added must be strictly controlled. If the proportion of additive is too low, it will result in poor powder flowability, making it difficult to achieve an initial compressive density ≥4.9 g / cm² when the molding pressure is 0.7-0.85 t / cm². 3 If the proportion of additives is too high, lubricant will remain or partially remain in the powder. After heat treatment, a lot of carbon will remain in the magnet, which will significantly affect the coercivity and maximum energy product of the magnet.

[0055] In step 2 above, the lubricant comprises ethyl decanoate and dichloromethane. Ethyl decanoate primarily functions as a liquid-phase lubricant, effectively reducing friction and static electricity between powder particles. Dichloromethane, an organic solvent, is used to dissolve ethyl decanoate and exhibits good volatility, leaving virtually no residue.

[0056] In step 2, the mass ratio of ethyl decanoate to dichloromethane is 1:3-1:8.

[0057] The present application needs to strictly control the addition ratio of ethyl decanoate and dichloromethane, because ethyl decanoate has poor volatility and is easy to remain on the magnet, thereby affecting the performance of the samarium-cobalt magnet; in contrast, dichloromethane has good volatility and almost no residue, so its addition ratio needs to be strictly controlled.

[0058] In the process of mixing the lubricant with the samarium-cobalt magnet powder (main powder), the lubricant can reduce the friction and surface energy between the powders, and is adsorbed on the surface of the main powder particles by physical action such as van der Waals force, forming a uniform and smooth thin film coating. This not only can significantly improve the flowability of the powder and ensure that the density distribution of the green body is more uniform, but also can reduce the pressure loss caused by friction, so that the density difference of the green body from top to bottom and from center to edge is reduced, and the consistency is greatly improved.

[0059] Step 3, orientation forming stage;

[0060] The mixed samarium-cobalt magnet powder is uniformly distributed in the cavity of the forming mold, and then pressure is applied to the cavity of the forming mold to form the powder samarium-cobalt magnet, and the forming pressure is 0.7-0.85 t / cm 2 ; In addition, a strong magnetic field of 1.8T to 2.0T is applied during the forming process to align the magnetic domains in the same direction to achieve orientation, so as to obtain ideal magnetic properties during final magnetization.

[0061] It should be noted that during orientation forming, a mold release agent (such as zinc stearate or isopropyl alcohol) is first sprayed into the cavity of the forming mold, and then the samarium-cobalt magnet powder is placed in the cavity, so as to reduce the resistance between the powder and the mold during demolding, avoid the occurrence of drawing the mold, ensure that the initial pressure density is ≥4.9 g / cm3, and obtain a samarium-cobalt magnet blank with high integrity, while improving the service life of the mold.

[0062] Step 4, sintering treatment of the samarium-cobalt magnet blank under inert gas;

[0063] In the above step 4, the heating temperature during sintering is 200-500℃, the holding time is 0.5-2h, and then the temperature is raised to 1195-1220℃, and the holding time is 0.5-5h.

[0064] Step 5, solid solution treatment of the samarium-cobalt magnet blank after sintering treatment under inert gas;

[0065] In the above step 5, the heating temperature during solid solution treatment is 1160-1190℃, and the holding time is 2-12h.

[0066] The main purpose of the solution treatment is to improve the plasticity and toughness of the steel or alloy, while strengthening the solid solution, enhancing the toughness and corrosion resistance, eliminating stress and achieving softening, so as to facilitate subsequent processing or forming. For samarium-cobalt alloy, the solution treatment can further optimize the microstructure and performance. Specifically, the solution treatment can convert the 2:17R phase in the samarium-cobalt magnet blank into the 1:7H phase, while the magnet microstructure is converted into a cellular structure. Because only the samarium-cobalt magnet with such a structure can exhibit excellent magnetic performance, the samarium-cobalt magnet of the present application is also called a 2:17 type samarium-cobalt magnet, which has two key performance indicators of maximum magnetic energy product and coercive force.

[0067] Step 6, after the solution treatment, the samarium-cobalt magnet blank is subjected to aging treatment, and finally the samarium-cobalt magnet is obtained.

[0068] In the above step 6, the aging treatment temperature is 800-900℃, the holding time is 4-24h, and after the holding is completed, the temperature is lowered to 350-500℃ at a cooling rate of 0.5-2℃ / min, and the holding time is 2-15h.

[0069] It should be noted that in the samarium-cobalt alloy, the aging treatment can eliminate the residual stress generated during sintering and solution treatment, improve the toughness and heat resistance of the material, and also help to further improve the hardness and strength of the material. After sintering, solution treatment and aging treatment, the magnetic performance of the samarium-cobalt magnet can be ensured, and the maximum magnetic energy product of the samarium-cobalt magnet is above 29MGOe.

[0070] It should be particularly emphasized that in the existing production process of sintered samarium-cobalt permanent magnets, in order to improve the density of the magnet, a cold isostatic pressing process is usually introduced after orientation forming. This process requires the blank to be tightly wrapped, bagged and vacuum packaged to prevent the magnet from being contaminated in a high-pressure environment. After cold isostatic pressing, the packaging needs to be removed and the magnet needs to be cleaned. This series of auxiliary operations not only increases the labor input and packaging material consumption, but also increases the production cost, prolongs the production cycle and reduces the overall efficiency.

[0071] Compared with the prior art, the present application can obtain high-performance samarium-cobalt magnets without the need for a cold isostatic pressing process during the preparation of samarium-cobalt magnets. This is because: by adding a lubricant during the powder mixing stage, the initial density of the magnet is ≥4.9g / cm3 (the initial density of the magnet before cold isostatic pressing is 4.2-4.4g / cm3), which effectively improves the initial density of the magnet. The present application using the lubricant can ensure that the magnet has sufficient density during heat treatment, and its magnetic performance is not significantly affected. Therefore, the present application can reduce labor input and packaging material consumption by omitting the cold isostatic pressing process, effectively reducing production costs, shortening the production cycle and significantly improving overall efficiency.

[0072] In addition, since the cold isostatic pressing process is omitted, the present application can effectively avoid the mechanical damage and consistency fluctuation possibly introduced by multiple manual intervention and packaging process, thereby preventing the adverse effects on the performance uniformity and long-term stability of the final magnet product, and thus the product of the present application has high consistency.

[0073] In another aspect, the present application also provides a one-step formed samarium-cobalt magnet prepared by the above-mentioned preparation method of one-step formed samarium-cobalt magnet, and the maximum magnetic energy product of the samarium-cobalt magnet is above 29 MGOe.

[0074] In order to more clearly describe the present application, the following examples and comparative examples are further illustrated.

[0075] Examples 1-5 and Comparative Examples 1-2 are prepared according to the following preparation process, and the specific preparation conditions are shown in Table 1; the preparation process of the samarium-cobalt magnet is as follows:

[0076] Step 1, smelting and powdering stage;

[0077] According to the weight ratio of each element in Sm(CoFeCuZr) z The raw materials are accurately weighed and mixed according to the weight ratio of each element in the Sm(CoFeCuZr) alloy, and then placed in a samarium-cobalt smelting furnace for vacuum induction smelting after uniform mixing. During smelting, the heating temperature is greater than 1550℃, and after all the metals are completely melted, water cooling or other rapid cooling methods are used for treatment, and a samarium-cobalt magnet ingot is obtained. Subsequently, the samarium-cobalt magnet ingot is sequentially subjected to coarse crushing, medium crushing and airflow fine processing, and finally a samarium-cobalt magnet powder is obtained.

[0078] Step 2, mixing powder stage;

[0079] A lubricant composed of ethyl caprylate and dichloromethane is added to the prepared samarium-cobalt magnet powder, and the two are mixed for a certain time.

[0080] Step 3, orientation forming stage;

[0081] The mixed samarium-cobalt magnet powder is uniformly distributed in the forming mold, and then pressure is applied to the forming mold to make the powder samarium-cobalt magnet powder; during the forming process, an external strong magnetic field is applied to uniformly arrange the magnetic domains in the same direction to achieve orientation, so that ideal magnetic properties are obtained during the final magnetization.

[0082] Step 4, sintering treatment of the samarium-cobalt magnet blank under inert gas

[0083] Step 5, solid solution treatment of the samarium-cobalt magnet blank under inert gas after sintering treatment;

[0084] Step 6, aging treatment of the samarium-cobalt magnet blank after solid solution treatment, and finally obtaining the samarium-cobalt magnet.

[0085] Table 1. Implementation conditions of Examples 1-5 and comparative examples

[0086]

[0087]

[0088] Table 2. Composition of samarium-cobalt magnets in Examples 1-5 and Comparative Examples 1-2

[0089]

[0090]

[0091] Table 1 Comparison of parameters in Examples 1-5 and Comparative Examples 1-3

[0092]

[0093] Performance testing

[0094] The above Examples 1-5 and Comparative Examples 1-2 were tested, mainly including the detection of density and magnetic properties. The specific test results are shown in Table 2.

[0095] Table 2 Detection Results

[0096]

[0097] By comparing and analyzing Examples 1-5, Comparative Examples 1-2, and Table 2, it can be seen that the samarium-cobalt magnets obtained by the preparation method provided in the embodiments of the present invention not only possess excellent crack resistance but also exhibit outstanding magnetic properties. Testing showed that the maximum magnetic energy product of the obtained samarium-cobalt magnets exceeded 29.05 MGOe; the density ranged from 8.30 to 8.35 g / cm³. 3 Between; remanence is above 11.021 kGs; intrinsic coercivity is also above 29.05 kOe.

[0098] The results of transmission electron microscopy observations of Examples 1-3 and Comparative Example 2 are as follows: Figures 1-8 As shown. (Through) Figures 1-8 Analysis shows that no carbon aggregation was found in the samarium-cobalt magnets obtained using the preparation conditions of Examples 1-3, thus exhibiting excellent magnetic properties. Figure 7 and Figure 8 The results show that the samarium-cobalt magnets obtained using the preparation method of Comparative Example 2 exhibit significant carbon aggregation, resulting in relatively poor magnetic properties.

[0099] Comparative Example 1 shows that insufficient use of additive lubricant resulted in the magnet's initial compressive density failing to reach 4.9 g / cm³. 3, and further affect the final density of the magnet, so that the magnetic properties are significantly reduced. Comparative Example 2 shows that too much lubricant is used, resulting in too much additive remaining in the magnet, which has a greater negative impact on the magnetic properties.

[0100] The above description is merely preferred specific embodiments of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method of producing a one-piece samarium-cobalt magnet, characterized by, The method comprises the following steps: Step 1, smelting and powdering; According to the weight proportions of each element in Sm(CoFeCuZr) z alloy, raw materials are weighed and mixed, and after being uniformly mixed, vacuum induction melting is performed to obtain a samarium-cobalt magnet ingot; the samarium-cobalt magnet ingot is subjected to crushing treatment to obtain a samarium-cobalt magnet powder; Step 2, powder mixing; An additive is added to the samarium-cobalt magnet powder, and the two are mixed evenly; Step 3, orientation molding; The mixed samarium-cobalt magnet powder is distributed in a molding mold, and then pressure is applied to the molding mold to mold the samarium-cobalt magnet powder; during the molding process, an external magnetic field is applied to achieve orientation, and finally a samarium-cobalt magnet blank is obtained; Step 4, sintering treatment of the samarium-cobalt magnet blank under an inert gas; Step 5, solid solution treatment of the sintered samarium-cobalt magnet blank under an inert gas; Step 6, aging treatment of the samarium-cobalt magnet blank after solid solution treatment, and finally a samarium-cobalt magnet is obtained.

2. The method for preparing a one-piece molded samarium-cobalt magnet according to claim 1, characterized in that, In the step 1, the heating temperature during vacuum induction smelting is greater than 1550℃, and after all the metals are completely melted, cooling is performed to obtain a samarium-cobalt magnet ingot.

3. The method of claim 2, wherein the one-step forming of the SmCo magnet is performed by a powder metallurgy process. In the step 1, the particle size of the samarium-cobalt magnet powder is 3.5-4.5μm.

4. The method for preparing a one-piece molded samarium-cobalt magnet according to claim 1, characterized in that, In the step 2, the mixing time of the samarium-cobalt magnet powder and the additive is 2-2.5h.

5. The method for preparing a one-piece molded samarium-cobalt magnet according to claim 1, characterized in that, In the step 4, the heating temperature during sintering is 200℃-500℃, and the temperature is kept for 0.5-2h.

6. The method of claim 5, wherein the one-step forming of the SmCo magnet is performed by a powder metallurgy process. In the step 4, after keeping the temperature, the temperature is raised to 1195-1220℃, and the temperature is kept for 0.5-5h.

7. The method for preparing a one-piece molded samarium-cobalt magnet according to claim 1, characterized in that, In the step 5, the heating temperature during solid solution treatment is 1160-1190℃.

8. The method of claim 7, wherein the one-step forming of the SmCo magnet is performed by a powder metallurgy process. In the step 5, the keeping time during solid solution treatment is 2-12h.

9. The method of producing a one-press samarium-cobalt magnet according to any one of claims 1 to 8, characterized by, In the step 6, the aging treatment temperature is 800-900℃, and the keeping time is 4-24h.

10. A one-piece samarium-cobalt magnet, characterized by, The method is prepared by the method for preparing a one-step molding samarium-cobalt magnet according to any one of claims 1-9; The components of the samarium-cobalt magnet include, in terms of weight percentage, Sm content 24-26wt.%, Fe content 15-20wt.%, Cu content 4-7wt.%, Zr content 2-3wt.%, and the rest is Co.

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