Sintered aluminum-nickel-cobalt magnetic steel and preparation method thereof

Abstract

The invention relates to sintered aluminum-nickel-cobalt magnetic steel and a preparation method thereof. In an electron backscatter diffraction pole diagram of the sintered aluminum-nickel-cobalt magnetic steel, along lt; 100 gt; the direction orientation degree is greater than or equal to 2.5, and the density of the sintered aluminum-nickel-cobalt magnetic steel is greater than or equal to 7.00 g / cm < 3 >. According to the sintered aluminum-nickel-cobalt magnetic steel, the orientation degree is improved, meanwhile, the high densification degree is achieved, and therefore the hard magnetic performance of the sintered aluminum-nickel-cobalt magnetic steel is remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of permanent magnet alloy materials, and in particular to a sintered aluminum-nickel-cobalt magnetic steel and a preparation method thereof. Background Art

[0002] Sintered AlNiCo magnets have advantages such as small dimensional tolerance, few surface defects, and easy preparation of special-shaped structural components. They are widely used in magnetic products with high dimensional accuracy requirements, complex shapes, and high appearance requirements. However, traditional sintered AlNiCo magnets have the problem of low hard magnetic properties. In particular, for typical sintered AlNiCo 5 and 8 products, the maximum magnetic energy product is only 32kJ / m 3 and 36 kJ / m 3 about. Summary of the Invention

[0003] Based on this, it is necessary to provide a sintered AlNiCo magnet and a preparation method thereof to address the above problems; the sintered AlNiCo magnet has a high degree of densification and improves the <100> The orientation degree in the direction is improved, thereby significantly enhancing the hard magnetic properties of sintered AlNiCo magnets.

[0004] A sintered AlNiCo magnet, wherein in the electron backscatter diffraction pole figure of the sintered AlNiCo magnet, <100> The directional orientation degree is greater than or equal to 2.5, and the density of the sintered AlNiCo magnet is greater than or equal to 7.00 g / cm 3 .

[0005] In one embodiment, in the X-ray diffraction image of the sintered AlNiCo magnet, the intensity ratio of the (200) diffraction peak to the (110) diffraction peak is greater than or equal to 0.45.

[0006] In one embodiment, the oxygen content of the sintered AlNiCo magnet is less than or equal to 2500 ppm;

[0007] and / or, along <100> Directional orientation degree is greater than or equal to 3;

[0008] And / or, the density of the sintered AlNiCo magnet is 7.00 g / cm 3 -7.31g / cm 3 .

[0009] In one embodiment, the composition of the sintered AlNiCo magnet includes 6wt%-10wt% Al, 10%wt%-20wt% Ni, 20wt%-40wt% Co, 2wt%-5wt% Cu, less than 8.0wt% Ti, less than 1.5wt% Nb, less than 0.5wt% S, less than 0.3wt% C, less than 0.5wt% Si, and the balance Fe.

[0010] Compared with the traditional sintered AlNiCo magnet, the present invention adjusts the density of the sintered AlNiCo magnet to achieve a higher degree of densification. At the same time, it regulates the grain orientation of the sintered AlNiCo magnet. <100> The orientation degree in the direction is greater than or equal to 2.5. By increasing the orientation degree, the hard magnetic properties of sintered AlNiCo magnets are significantly enhanced. For typical sintered AlNiCo Class 5 and Class 8 products, the maximum magnetic energy product performance is improved by up to 20% and 82% respectively, breaking through the technical bottleneck of traditional sintered AlNiCo magnets that are difficult to improve their hard magnetic properties.

[0011] A method for preparing the sintered AlNiCo magnet as described above comprises the following steps:

[0012] The AlNiCo alloy obtained in the process of casting AlNiCo magnets is crushed and pulverized to obtain a powder raw material, wherein the AlNiCo alloy has <100> A columnar crystal structure formed by crystal orientation, wherein the powder raw material includes a first alloy powder and / or a second alloy powder, the coercive force of the first alloy powder is greater than or equal to 10 Oe, and the coercive force of the second alloy powder is less than 10 Oe;

[0013] The powder raw material is oriented and formed in a magnetic field to obtain a compact, wherein when the powder raw material is the first alloy powder, the density of the compact is greater than or equal to 3.5 g / cm 3 Alternatively, when the powder raw material contains at least the second alloy powder, the density of the compact is greater than or equal to 4.5 g / cm 3 ;

[0014] The compact is subjected to isostatic pressing and then sintered to obtain a sintered blank, the density of which is greater than or equal to 7.00 g / cm 3 ;

[0015] The sintered blank is subjected to magnetic field heat treatment and tempering to obtain a sintered magnet.

[0016] In one embodiment, the process of casting aluminum nickel cobalt magnets includes: melting and directional solidification treatment of raw materials containing at least Al, Ni, and Co elements to obtain an ingot, and then sequentially subjecting the ingot to solution treatment, magnetic field heat treatment, and tempering treatment to obtain cast aluminum nickel cobalt magnets, wherein the aluminum nickel cobalt alloy includes alloys or scraps obtained in the directional solidification treatment, the solution treatment, the magnetic field heat treatment, or the tempering treatment steps.

[0017] In one embodiment, the first alloy powder comprises an alloy powder obtained by crushing and pulverizing the alloy or scrap obtained in the magnetic field heat treatment or the tempering treatment step;

[0018] Alternatively, the second alloy powder includes alloy powder obtained by crushing and pulverizing the alloy or scrap obtained in the directional solidification treatment or the solution treatment step.

[0019] In one embodiment, the particle size of the crushed aluminum nickel cobalt alloy is less than 5 mm;

[0020] And / or, the particle size of the first alloy powder is 3 μm-100 μm, and the particle size of the second alloy powder is 3 μm-100 μm;

[0021] And / or, the oxygen content of the first alloy powder is less than 2000 ppm, and the oxygen content of the second alloy powder is less than 2000 ppm.

[0022] In one embodiment, when the powder raw material is the first alloy powder, the density of the compact is 3.5 g / cm 3 -6.5g / cm 3 Alternatively, when the powder raw material contains at least the second alloy powder, the density of the compact is 4.5 g / cm 3 -6.5g / cm 3 .

[0023] In one embodiment, before orientation molding in a magnetic field, the powder raw material is mixed with a molding agent, wherein the molding agent includes at least one of graphite powder, aluminum stearate, zinc stearate, glycerin or paraffin;

[0024] And / or, the magnetic field intensity of the orientation molding is greater than 1T;

[0025] And / or, the isostatic pressing treatment is performed under a pressure of 150 MPa-280 MPa and for a time of 5 min-60 min.

[0026] The preparation method provided in this application uses the AlNiCo alloy produced in the process of casting AlNiCo magnets as the raw material for sintering AlNiCo magnets. On the one hand, AlNiCo alloy has the characteristics of <100> The columnar crystal structure formed by the crystal orientation is beneficial to improve the <100> On the other hand, in view of the difference in magnetic properties of AlNiCo alloy, different degrees of orientation molding are carried out, and the magnetic force between the first alloy powders is used to reduce the density of the compact to 3.5g / cm 3 High orientation can be achieved, and the oxidation degree of AlNiCo alloy is low, which is beneficial to reduce the internal defects of pores, oxidation inclusions, etc. in sintered AlNiCo magnets, so that the density of sintered AlNiCo magnets reaches 7.00g / cm 3 Furthermore, the AlNiCo alloy has strong oxidation resistance, which can avoid the use of high-temperature hydrogen reduction treatment, thereby reducing production risks and improving production efficiency.

[0027] Therefore, the preparation method described in the present application not only enables the sintered AlNiCo magnet to have excellent hard magnetic properties, but also improves material utilization and production efficiency, reduces production costs and risks, and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is the X-ray diffraction (XRD) pattern of the aluminum nickel cobalt ingot obtained in Example 1;

[0030] Figure 2 The X-ray diffraction (XRD) pattern of the sintered AlNiCo magnet prepared in Example 1;

[0031] Figure 3 The electron backscatter diffraction (EBSD) pole figure of the sintered AlNiCo magnet obtained in Example 1;

[0032] Figure 4 The X-ray diffraction (XRD) pattern of the sintered AlNiCo magnet prepared in Comparative Example 1;

[0033] Figure 5 This is the X-ray diffraction (XRD) pattern of the aluminum nickel cobalt ingot prepared in Comparative Example 2;

[0034] Figure 6 The X-ray diffraction (XRD) pattern of the sintered AlNiCo magnet prepared in Comparative Example 2;

[0035] Figure 7 This is the X-ray diffraction (XRD) pattern of the sintered AlNiCo magnet prepared in Comparative Example 3. DETAILED DESCRIPTION

[0036] To facilitate understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present application can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present application. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0038] The present application provides a sintered AlNiCo magnet. In the electron backscatter diffraction pole figure of the sintered AlNiCo magnet, <100> The directional orientation degree is greater than or equal to 2.5, and the density of the sintered AlNiCo magnet is greater than or equal to 7.00 g / cm 3 .

[0039] Compared with the traditional sintered AlNiCo magnet, the present invention adjusts the density of the sintered AlNiCo magnet to achieve a higher degree of densification. At the same time, it regulates the grain orientation of the sintered AlNiCo magnet. <100> The orientation degree in the direction is greater than or equal to 2.5. By increasing the orientation degree, the hard magnetic properties of sintered AlNiCo magnets are significantly enhanced. For typical sintered AlNiCo Class 5 and Class 8 products, the maximum magnetic energy product performance is improved by up to 20% and 82% respectively, breaking through the technical bottleneck of traditional sintered AlNiCo magnets that are difficult to improve their hard magnetic properties.

[0040] It should be noted that in the electron backscatter diffraction pole figure, <100> Directional orientation strength is used to characterize the <100> Directional orientation, e.g. Figure 3 The electron backscatter diffraction (EBSD) pole figure shown in the figure shows that according to the intensity test value on the right side of the figure, <100> The directional orientation strength value is 5.2, that is <100> The orientation degree of the direction is 5.2.

[0041] Preferably, in the EBSD pole figure of the sintered AlNiCo magnet, <100> The degree of directional orientation is 3 or more, more preferably 4 or more.

[0042] Preferably, the density of the sintered AlNiCo magnet is 7.00 g / cm 3 -7.31g / cm 3 .

[0043] In one embodiment, in the XRD diffraction pattern of the sintered AlNiCo magnet, the intensity ratio of the (200) diffraction peak to the (110) diffraction peak is greater than or equal to 0.45, preferably greater than or equal to 0.55, more preferably greater than or equal to 0.65, further improving the <100> The orientation degree in the direction can enhance the hard magnetic properties of sintered AlNiCo magnets.

[0044] In one embodiment, the oxygen content of the sintered AlNiCo magnet is less than or equal to 2500 ppm, preferably less than or equal to 2000 ppm, and more preferably less than or equal to 1800 ppm. By controlling the oxygen content of the sintered AlNiCo magnet, it is beneficial to reduce defects such as pores and oxide inclusions inside the sintered AlNiCo magnet, thereby increasing the density of the sintered AlNiCo magnet and further improving the hard magnetic properties.

[0045] In one embodiment, the composition of the sintered AlNiCo magnet includes 6wt%-10wt% Al, 10%wt%-20wt% Ni, 20wt%-40wt% Co, 2wt%-5wt% Cu, less than 8.0wt% Ti, less than 1.5wt% Nb, less than 0.5wt% S, less than 0.3wt% C, less than 0.5wt% Si, and the balance Fe.

[0046] Preferably, the components of the sintered AlNiCo magnet include 6wt%-10wt% Al, 10%wt%-20wt% Ni, 20wt%-40wt% Co, 2wt%-5wt% Cu, less than 8.0wt% Ti, less than 1.5wt% Nb, less than 0.5wt% S, less than 0.3wt% C, less than 0.5wt% Si and the balance Fe, and the oxygen content of the sintered AlNiCo magnet is less than 2500ppm.

[0047] The raw materials for traditional sintered AlNiCo magnets typically include high-purity micron-sized powders of elemental metals such as Ni, Co, Fe, and Cu. These are not only extremely susceptible to oxidation but also relatively expensive. Oxidation of the raw powder not only reduces magnet density but also creates internal and external macroscopic defects such as pores and oxide inclusions during sintering, heat treatment, and tempering, significantly weakening the magnet's hard magnetic properties. Therefore, to prevent oxidation of the raw powder, the elemental powder is typically pre-treated with high-temperature hydrogen reduction. This not only increases production costs and reduces efficiency, but also significantly increases production risk.

[0048] Based on this, the present application also provides a method for preparing the sintered AlNiCo magnet as described above, comprising the following steps:

[0049] S1, crushing and pulverizing the Al-Ni-Co alloy obtained in the process of casting Al-Ni-Co magnets to obtain a powder raw material, wherein the Al-Ni-Co alloy has <100> A columnar crystal structure formed by crystal orientation, wherein the powder raw material includes a first alloy powder and / or a second alloy powder, the coercive force of the first alloy powder is greater than or equal to 10 Oe, and the coercive force of the second alloy powder is less than 10 Oe;

[0050] S2, orienting the powder raw material in a magnetic field to obtain a compact, wherein when the powder raw material is the first alloy powder, the density of the compact is greater than or equal to 3.5 g / cm 3 Alternatively, when the powder raw material contains at least the second alloy powder, the density of the compact is greater than or equal to 4.5 g / cm 3 ;

[0051] S3, the green compact is subjected to isostatic pressing and then sintered to obtain a sintered green compact, the density of which is greater than or equal to 7.00 g / cm 3 ;

[0052] S4, performing magnetic field heat treatment and tempering on the sintered blank to obtain a sintered magnet.

[0053] In step S1, the AlNiCo alloy produced in the process of casting AlNiCo magnets is used as the raw material for sintering to prepare AlNiCo magnets. On the one hand, AlNiCo alloy has the characteristics of <100> The columnar crystal structure formed by the crystal orientation is beneficial to improve the <100> On the other hand, AlNiCo alloy has strong oxidation resistance, which can avoid the use of high-temperature hydrogen reduction treatment, thereby reducing production risks and improving production efficiency.

[0054] In one embodiment, the casting process of aluminum nickel cobalt magnets includes: melting and directional solidification treatment of raw materials containing at least Al, Ni, and Co elements to obtain ingots, and then sequentially subjecting the ingots to solid solution treatment, magnetic field heat treatment, and tempering treatment to obtain cast aluminum nickel cobalt magnets. It can be understood that the aluminum nickel cobalt alloy includes alloys or waste materials obtained in the steps of the directional solidification treatment, the solid solution treatment, the magnetic field heat treatment, or the tempering treatment, and fully utilizes the recycled materials in the production process of the cast aluminum nickel cobalt magnets, thereby improving material utilization, helping to reduce production costs, and being suitable for industrial production.

[0055] Specifically, the first alloy powder is preferably an alloy powder obtained by crushing and pulverizing the alloy or scrap obtained in the magnetic field heat treatment or the tempering treatment step. It can be understood that the first alloy powder has permanent magnetic properties.

[0056] The second alloy powder is preferably an alloy powder obtained by crushing and pulverizing the alloy or scrap obtained in the directional solidification treatment or the solution treatment step. It is understandable that the second alloy powder does not have permanent magnetic properties.

[0057] In one embodiment, the crushing method includes but is not limited to mechanical crushing, preferably mechanical crushing; the particle size of the crushed aluminum nickel cobalt alloy is less than 5 mm, preferably less than 3 mm.

[0058] In one embodiment, the pulverizing method includes but is not limited to at least one of ball milling and air flow milling, preferably ball milling. Specifically, the ball-to-material ratio of the ball milling is 3:1-20:1, the rotation speed is 30rpm-150rpm, and the time is 5h-50h.

[0059] In one embodiment, the particle size of the first alloy powder is 3 μm-100 μm, preferably 10 μm-60 μm; the particle size of the second alloy powder is 3 μm-100 μm, preferably 10 μm-60 μm.

[0060] In one embodiment, the oxygen content of the first alloy powder is less than 2000 ppm, preferably less than 1800 ppm; the oxygen content of the second alloy powder is less than 2000 ppm, preferably less than 1800 ppm.

[0061] In step S2, different degrees of orientation molding are performed to address the magnetic property differences of the AlNiCo alloy, and the magnetic force between the first alloy powders is used to reduce the density of the first compact to 3.5 g / cm 3 High orientation can be achieved, and the oxidation degree of AlNiCo alloy is low, which is beneficial to reduce the internal defects of pores, oxidation inclusions, etc. in sintered AlNiCo magnets, so that the density of sintered AlNiCo magnets reaches 7.00g / cm 3 The second alloy powder does not have permanent magnetic properties, but its magnetization direction is also <100> direction, thus increasing the green compact density to 4.5g / cm 3 As described above, the powder raw material containing at least the second alloy powder can also be made along <100> Directional alignment to achieve fixed orientation.

[0062] Preferably, when the powder raw material is the first alloy powder, the density of the compact is 3.5 g / cm 3 -6.5g / cm 3 Alternatively, when the powder raw material contains at least the second alloy powder, the density of the compact is 4.5 g / cm 3 -6.5g / cm 3 , more preferably 5.0 g / cm 3 -6.5g / cm3 .

[0063] In one embodiment, the powder raw material is mixed with a forming agent before orientation molding in a magnetic field, which is beneficial to further improve the first alloy powder at 3.5 g / cm 3 Molding effect under low density conditions.

[0064] Specifically, the forming agent includes but is not limited to at least one of graphite powder, aluminum stearate, zinc stearate, glycerol or paraffin, preferably aluminum stearate, and further preferably, the mass of aluminum stearate is 0.1wt%-0.8wt% of the mass of the first alloy powder.

[0065] In one embodiment, the magnetic field intensity of the orientation molding is greater than 1 T, preferably 1.8 T to 2.5 T, which is more conducive to achieving orientation molding.

[0066] The isostatic pressing and sintering in step S3 and the magnetic field heat treatment and tempering in step S4 can adopt existing preparation methods and conditions, and this application does not limit this.

[0067] In one embodiment, the isostatic pressing treatment is performed at a pressure of 150 MPa to 280 MPa and for a time of 5 min to 60 min.

[0068] In one embodiment, multi-stage vacuum sintering is preferred. Specifically, the multi-stage vacuum sintering includes: -2 Pa, heat from room temperature to 400℃-500℃ at 0.5℃ / min-10℃ / min and keep warm for 0.5h-2h, then heat to 700℃-800℃ and keep warm for 1h-3h, continue to heat to 1100℃-1200℃ and keep warm for 1h-3h, further heat to 1260℃-1340℃ and keep warm for 0.3h-1h, finally heat to 1280℃-1360℃ and keep warm for 2h-6h, cool to below 300℃, take out of the furnace and air cool to room temperature to obtain a sintered blank.

[0069] It is understandable that the purpose of sintering is to achieve densification, and subsequent heat treatment and tempering have little effect on the density of the sintered blank. Therefore, the density of the sintered blank is the density of the final magnetic steel.

[0070] In one embodiment, the magnetic field heat treatment preferably includes: cooling to 820°C-950°C at a rate of 1°C / s-30°C / s, then slowly cooling to below 500°C or isothermally treating at 780°C-860°C for 5min-40min in a magnetic field greater than 0.25T, and finally air cooling to room temperature in a magnetic field.

[0071] In one embodiment, a three-stage tempering treatment is preferably adopted, specifically comprising: heating from room temperature to 620°C-660°C at 0.5°C / min-15°C / min and keeping warm for 3h-10h under the condition of gas pressure less than or equal to 10Pa, then cooling to 560°C-600°C and keeping warm for 10h-15h, further cooling to 530°C-570°C and keeping warm for 12h-20h, and finally cooling to below 150°C before being taken out of the furnace.

[0072] It is understandable that after magnetic field heat treatment and tempering, post-processing such as metal processing may be performed, and this application does not limit this.

[0073] Therefore, the preparation method described in the present application not only enables the sintered AlNiCo magnet to have excellent hard magnetic properties, but also improves material utilization and production efficiency, reduces production costs and risks, and is conducive to industrial production.

[0074] The sintered aluminum-nickel-cobalt magnet and its preparation method are further described below through the following specific examples. However, those skilled in the art will understand that the following examples are merely illustrative of the present application and should not be construed as limiting the scope of the present application. Where specific conditions are not specified in the examples, conventional conditions or those recommended by the manufacturer were followed. Reagents and instruments used, for which the manufacturer is not specified, are commercially available conventional products.

[0075] It should be noted that the raw materials used in the following examples and comparative examples are derived from the following process steps:

[0076] (1) Prepare the raw metal, place it in a crucible, melt the raw metal into molten steel through induction melting, stir and remove the slag, and then pour it into a high-temperature mold that has been preheated to about 1500℃. The bottom of the mold is placed on a cooling plate with circulating water cooling. After pouring, a layer of insulation cotton is wrapped around the outer surface of the mold to achieve directional solidification, and a product with <100> Oriented ingots;

[0077] (2) The ingots are placed in a sample box, arranged parallel and neatly along the pulling direction and fixed tightly. Then, the sample after the box is preheated at about 800℃ for 20min, then solution treated at about 1250℃ for 20min, and then cooled to about 900℃ at a rate of 5℃ / s. Then, it is placed in a 0.35T magnetic field (the growth direction of the columnar crystal of the sample is consistent with the direction of the magnetic field), isothermally treated at about 820℃ for 20min, and finally air-cooled to room temperature in the magnetic field to obtain Alnico 8 blanks; or slowly cooled to below 300℃ at a rate of 10℃ / min in a 0.35T magnetic field, and then air-cooled to room temperature to obtain Alnico 5 blanks.

[0078] (3) Place the blank in the tempering furnace and vacuum it to 1.0×10-2 After Pa, heat from room temperature to 650℃ at 5℃ / min and keep warm for 6h, then cool to 580℃ within 15min and keep warm for 12h, further cool to 550℃ and keep warm for 12h, and finally cool to below 150℃ and take out of the furnace to produce Alnico 8 type cast magnetic steel or Alnico 5 type cast magnetic steel.

[0079] Example 1

[0080] The raw metals are configured according to the mass percentage of 7% Al, 13% Ni, 35% Co, 3% Cu, 5% Ti, 0.5% Nb, 0.3% S, 0.2% C, 0.2% Si and the balance Fe. The Alnico 8 type cast magnetic steel is obtained by the above process. The X-ray diffraction of the cast magnetic steel is as follows: Figure 1 As shown, it proves that it has obvious <100> After cleaning the surface of the cast magnetic steel, it was mechanically crushed into a coarse powder with a particle size of less than 5 mm. Subsequently, an alloy powder with an average particle size of about 28 μm was prepared by mechanical ball milling with a ball-to-material ratio of 5:1, a ball milling time of 35 hours, and a rotation speed of 100 rpm / min.

[0081] The alloy powder was oriented and formed in a 2T magnetic field to obtain a density of 3.8g / cm 3 of the compact.

[0082] The compact was isostatically pressed at 250 MPa for 20 min and then vacuum sintered. The sintering furnace pressure was controlled to be lower than 1.0×10 -2 Pa, first heat from room temperature to 450℃ at 10℃ / min and keep warm for 0.5h, then heat to 700℃ at 5℃ / min and keep warm for 2h, continue to heat to 1100℃ at 4℃ / min and keep warm for 1h, further heat to 1300℃ at 1.5℃ / min and keep warm for 0.5h, finally heat to 1320℃ at 1℃ / min and keep warm for 3h, cool to below 300℃, take out of the furnace and air cool to room temperature to obtain a sintered blank.

[0083] The sintered blank was preheated at 800℃ for 20min, then solution treated at 1250℃ for 30min, then air-cooled to about 900℃ for 30s, and then isothermally treated at 820℃ for 20min in a magnetic field of about 0.3T. Finally, it was air-cooled to room temperature in the magnetic field to complete the magnetic field heat treatment. The gas pressure was controlled to be less than 1.0×10 -1Pa, heated from room temperature to 650℃ at 11℃ / min and kept at this temperature for 5h, then cooled to 600℃ at 2℃ / min and kept at this temperature for 10h, further cooled to 550℃ at 2℃ / min and kept at this temperature for 18h, then cooled to below 150℃ and taken out of the furnace. After gold processing, Alnico 8 type sintered magnetic steel was obtained. The X-ray diffraction of the sintered magnetic steel along the orientation direction is tested as follows Figure 2 As shown, the intensity ratio of the diffraction peak (200) to (110) is 0.58, which has a high degree of orientation. The electron backscatter diffraction test of the sintered magnetic steel is carried out, and the results are as follows Figure 3 As shown in the polar diagram <100> The orientation strength value is 5.2, that is, along <100> The degree of directional orientation is 5.2.

[0084] Example 2

[0085] The raw metals were prepared by mixing 8% Al, 15% Ni, 24% Co, 2.8% Cu, 0.2% Ti, 0.2% Nb, 0.3% S, 0.1% C, 0.2% Si, and the balance Fe by mass. Alnico Class 5 cast magnets were obtained using the above process. After cleaning the surface of the cast magnets, they were mechanically crushed into a coarse powder with a particle size of less than 5 mm. Subsequently, alloy powder with an average particle size of approximately 45 μm was prepared using a mechanical ball-to-material ratio of 10:1, a ball milling time of 24 hours, and a rotation speed of 120 rpm / min.

[0086] The alloy powder was oriented and formed in a magnetic field of 2.5 T to obtain a density of 4.8 g / cm 3 of the compact.

[0087] The compact was isostatically pressed at 180 MPa for 45 min and then vacuum sintered. The sintering furnace pressure was controlled to be lower than 1.0×10 -2 Pa, first heat from room temperature to 500℃ at 15℃ / min and keep warm for 0.5h, then heat to 750℃ at 5℃ / min and keep warm for 2h, continue to heat to 1200℃ at 5℃ / min and keep warm for 0.8h, further heat to 1310℃ at 1.5℃ / min and keep warm for 0.5h, finally heat to 1330℃ at 1℃ / min and keep warm for 2.5h, cool to below 300℃, take out of the furnace and air cool to room temperature to obtain a sintered blank.

[0088] The sintered blank was preheated at 850℃ for 20min and then solution treated at 1260℃ for 30min. It was then air-cooled for 30s to about 880℃. It was then slowly cooled to below 500℃ in a magnetic field of about 0.35T and finally air-cooled to room temperature in a magnetic field to complete the magnetic field heat treatment. The gas pressure was controlled to be less than 1.0×10 -1Pa, heated from room temperature to 635℃ at 11℃ / min and kept warm for 5h, then cooled to 585℃ at 2℃ / min and kept warm for 10h, further cooled to 550℃ at 2℃ / min and kept warm for 18h, cooled to below 150℃ and taken out of the furnace, and Alnico 5 type sintered magnet was obtained after gold processing.

[0089] Example 3

[0090] Recycling of products with <100> Columnar crystal structure of cast aluminum nickel cobalt alloy with directionally grown columnar structure was prepared. After cleaning the surface of the scrap, it was mechanically crushed into coarse powder with a particle size of less than 5 mm. Then, alloy powder with an average particle size of 50 μm was prepared by mechanical ball milling with a ball-to-powder ratio of 10:1, a ball milling time of 24 hours, and a rotation speed of 120 rpm / min. The alloy powder composition was determined to be 7.3% Al, 13.8% Ni, 36.2% Co, 2.9% Cu, 6.1% Ti, 0.7% Nb, 0.27% S, 0.16% C, 0.22% Si, and the balance Fe.

[0091] The alloy powder was oriented and formed in a 2T magnetic field to obtain a density of 4.7 g / cm 3 of the compact.

[0092] The green compact was isostatically pressed at 200 MPa for 45 min and then vacuum sintered. The sintering furnace pressure was controlled to be lower than 1.0×10 -2 Pa, first heat from room temperature to 450℃ at 15℃ / min and keep warm for 0.5h, then heat to 750℃ at 5℃ / min and keep warm for 2h, continue to heat to 1200℃ at 5℃ / min and keep warm for 0.8h, further heat to 1290℃ at 1.5℃ / min and keep warm for 0.5h, finally heat to 1310℃ at 1℃ / min and keep warm for 2.5h, cool to below 300℃, take out of the furnace and air cool to room temperature to obtain a sintered blank.

[0093] The sintered blank was preheated at 800℃ for 30min, then solution treated at 1260℃ for 30min, then air-cooled to about 900℃ for 30s, and then isothermally treated at 820℃ for 25min in a magnetic field of about 0.35T, and finally air-cooled to room temperature in the magnetic field to complete the magnetic field heat treatment. The gas pressure was controlled to be less than 1.0×10 -1 Pa, heated from room temperature to 640℃ at 15℃ / min and kept warm for 5h, then cooled to 585℃ at 2℃ / min and kept warm for 10h, further cooled to 555℃ at 2℃ / min and kept warm for 18h, cooled to below 150℃ and taken out of the furnace, and Alnico 8 type sintered magnet was obtained after gold processing.

[0094] Example 4

[0095] The difference between Example 4 and Example 1 is that the ingot alloy scrap produced in the directional solidification process is used as a raw material to prepare the alloy powder, and the alloy powder is oriented and formed in a 2T magnetic field to obtain a density of 5.2 g / cm 3 of the compact.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 1 is that no magnetic field orientation molding treatment is performed.

[0098] The X-ray diffraction of the sintered magnetic steel obtained in this comparative example is as follows: Figure 4 shown.

[0099] Comparative Example 2

[0100] The difference between Comparative Example 2 and Example 1 is that the cast magnetic steel is prepared without directional solidification, and the crystal structure of the magnetic steel does not follow the <100> Direction orientation.

[0101] The X-ray diffraction patterns of the ingot and sintered magnetic steel obtained in this comparative example are shown in Figure 2. Figure 5 、 Figure 6 shown.

[0102] Comparative Example 3

[0103] The difference between Comparative Example 3 and Example 1 is that a traditional sintered aluminum nickel cobalt preparation process is adopted. The specific method is: Fe, Co, Ni, Cu and other elemental metal powders are mixed with CoAl, FeAl, NbFe, TiFe and other alloy powders. The alloy ratio is the same as that in Example 1. In order to reduce the degree of oxidation, the elemental metal powder is treated with high-temperature hydrogen to make the oxygen content of the powder raw material 2963ppm. The rest of the preparation method and conditions are the same as those in Example 1 to prepare sintered magnetic steel.

[0104] The X-ray diffraction of the sintered magnetic steel obtained in this comparative example is as follows: Figure 7 shown.

[0105] The alloy powders, compacts and sintered magnetic steels prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were characterized and tested, and the results are shown in Table 1.

[0106] Table 1

[0107]

[0108] The sintered magnetic steels prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to performance tests, and the results are shown in Table 2.

[0109] Table 2

[0110]

[0111] As shown in Tables 1 and 2, the sintered magnetic steels produced in Examples 1 to 4 achieve a high degree of densification while improving the degree of orientation, thereby significantly improving the hard magnetic properties of the sintered AlNiCo magnetic steels. Comparative Examples 1 and 2, while achieving a high degree of densification, have poorer degrees of orientation, resulting in lower hard magnetic properties than Example 1.

[0112] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A sintered AlNiCo magnet, characterized in that: In the electron backscatter diffraction pole figure of the sintered AlNiCo magnet, along <100> The directional orientation degree is greater than or equal to 2.5, and the density of the sintered AlNiCo magnet is greater than or equal to 7.00 g / cm 3 .

2. The sintered AlNiCo magnet according to claim 1, characterized in that: In the X-ray diffraction image of the sintered AlNiCo magnet, the intensity ratio of the (200) diffraction peak to the (110) diffraction peak is greater than or equal to 0.

45.

3. The sintered AlNiCo magnet according to claim 1, characterized in that: The oxygen content of the sintered AlNiCo magnet is less than or equal to 2500 ppm; and / or, along <100> Directional orientation degree is greater than or equal to 3; And / or, the density of the sintered AlNiCo magnet is 7.00 g / cm 3 -7.31g / cm 3 .

4. The sintered AlNiCo magnet according to any one of claims 1 to 3, characterized in that: The components of the sintered AlNiCo magnet include 6wt%-10wt% Al, 10%wt%-20wt% Ni, 20wt%-40wt% Co, 2wt%-5wt% Cu, less than 8.0wt% Ti, less than 1.5wt% Nb, less than 0.5wt% S, less than 0.3wt% C, less than 0.5wt% Si, and the balance Fe.

5. A method for preparing a sintered AlNiCo magnetic steel according to any one of claims 1 to 4, characterized in that: The steps include: The AlNiCo alloy obtained in the process of casting AlNiCo magnets is crushed and pulverized to obtain a powder raw material, wherein the AlNiCo alloy has <100> A columnar crystal structure formed by crystal orientation, wherein the powder raw material includes a first alloy powder and / or a second alloy powder, the coercive force of the first alloy powder is greater than or equal to 10 Oe, and the coercive force of the second alloy powder is less than 10 Oe; The powder raw material is oriented and formed in a magnetic field to obtain a compact, wherein when the powder raw material is the first alloy powder, the density of the compact is greater than or equal to 3.5 g / cm 3 Alternatively, when the powder raw material contains at least the second alloy powder, the density of the compact is greater than or equal to 4.5 g / cm 3 ; The compact is subjected to isostatic pressing and then sintered to obtain a sintered blank, the density of which is greater than or equal to 7.00 g / cm 3 ; The sintered blank is subjected to magnetic field heat treatment and tempering to obtain a sintered magnet.

6. The method for preparing sintered AlNiCo magnetic steel according to claim 5, characterized in that: The casting process of aluminum nickel cobalt magnets includes: melting and directional solidification treatment of raw materials containing at least Al, Ni, and Co elements to obtain an ingot, and then sequentially subjecting the ingot to solid solution treatment, magnetic field heat treatment, and tempering treatment to obtain the cast aluminum nickel cobalt magnets. The aluminum nickel cobalt alloy includes alloys or scraps obtained in the directional solidification treatment, the solid solution treatment, the magnetic field heat treatment, or the tempering treatment steps.

7. The method for preparing sintered AlNiCo magnet according to claim 6, characterized in that: The first alloy powder includes an alloy powder obtained by crushing and pulverizing the alloy or scrap obtained in the magnetic field heat treatment or the tempering treatment step; Alternatively, the second alloy powder includes alloy powder obtained by crushing and pulverizing the alloy or scrap obtained in the directional solidification treatment or the solution treatment step.

8. The method for preparing sintered AlNiCo magnetic steel according to claim 5, characterized in that: The particle size of the crushed AlNiCo alloy is less than 5mm; And / or, the particle size of the first alloy powder is 3 μm-100 μm, and the particle size of the second alloy powder is 3 μm-100 μm; And / or, the oxygen content of the first alloy powder is less than 2000 ppm, and the oxygen content of the second alloy powder is less than 2000 ppm.

9. The method for preparing sintered AlNiCo magnetic steel according to claim 5, characterized in that: When the powder raw material is the first alloy powder, the density of the compact is 3.5 g / cm 3 -6.5g / cm 3 Alternatively, when the powder raw material contains at least the second alloy powder, the density of the compact is 4.5 g / cm 3 -6.5g / cm 3 .

10. The method for preparing sintered AlNiCo magnetic steel according to claim 5, characterized in that: Before orientation molding in a magnetic field, the powder raw material is mixed with a molding agent, wherein the molding agent includes at least one of graphite powder, aluminum stearate, zinc stearate, glycerin or paraffin; And / or, the magnetic field intensity of the orientation molding is greater than 1T; And / or, the isostatic pressing treatment is performed under a pressure of 150 MPa-280 MPa and for a time of 5 min-60 min.

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