A method for improving the brittleness of high-coercivity blank material

Abstract

The application relates to the technical field of preparation of rare earth permanent magnet materials, in particular to a method for improving the brittleness of high-coercivity blank material, which comprises designing the matrix alloy component of a sintered neodymium-iron-boron magnet as follows: Nd a M b N c O d Fe 100‑a‑b‑c‑d‑e B e ; wherein Nd is a neodymium element; M is at least one of La, Ce and Pr elements; N is at least one of Dy, Tb and Gd elements; O is at least one of Co, Mn, Cu, Al, Ti, Ga, Zr, V, Hf, W and Nb elements; Fe is an iron element, and B is a boron element; a, b, c, d and e satisfy the following relations: 27.5 <= a <= 31, 8.5 <= b <= 12, 0.05 <= c <= 0.2, 0 <= d <= 5 and 0.9 <= e <= 1.2; wherein a, b, c, d and e all represent mass percentage contents; the matrix alloy component of the neodymium-iron-boron magnet provided by the application has good toughness of the blank obtained through powdering, forming and sintering, and can effectively avoid the problems of breakage such as edge chipping and corner chipping.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet material preparation technology, and in particular to a method for improving the brittleness of high coercivity billet materials. Background Technology

[0002] As a third-generation rare-earth permanent magnet material with excellent comprehensive performance, NdFeB magnets have received considerable attention since their inception. Sintered NdFeB magnets possess excellent magnetic properties and are widely used in aerospace, microwave communication technology, automotive industry, instrumentation, and medical devices. In recent years, the promotion and application scope of sintered NdFeB magnets in high-end fields such as wind power, variable frequency compressors, and hybrid power have expanded rapidly, leading to higher market demands for their performance.

[0003] Over the past decade, engineers have developed various production processes, continuously improving the performance of the magnets. Employing rapid solidification and hydrogenation processes, supplemented by other methods (powder particle size control, molding additives, etc.), mass production of magnets with a magnetic energy product exceeding 50 MGOe has been achieved. Furthermore, significant progress has been made in improving the operating temperature and corrosion resistance of NdFeB magnets. However, the inventors of this application have discovered that in the preparation process of sintered NdFeB magnets, the sintered billets suffer severe breakage such as chipping and corner chipping during subsequent processing and surface treatment, greatly affecting the material yield. Moreover, with the continuous expansion of the application fields of sintered NdFeB magnets, the magnets inevitably undergo environmental tests such as impact and vibration. Once the magnet breaks, it will cause huge losses to users. Therefore, it is necessary to improve the mechanical properties of sintered NdFeB magnets, increase their toughness, and reduce the risk of breakage during subsequent billet processing and in the operating environment. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the brittleness of high coercivity billet materials. This method improves the brittleness of sintered NdFeB billets and avoids the problem of low product yield caused by breakage such as chipping and corner chipping.

[0005] To achieve the above objectives, the present invention provides a method for improving the brittleness of high coercivity billet materials, the method comprising designing the matrix alloy composition of the sintered NdFeB magnet to be: Nd a M b N c O d Fe 100-a-b-c-d-e B e Wherein, Nd is neodymium; M is at least one of La, Ce, and Pr.

[0006] N is at least one of the elements Dy, Tb, and Gd;

[0007] O is at least one of the elements Co, Mn, Cu, Al, Ti, Ga, Zr, V, Hf, W, and Nb;

[0008] Fe is the element iron, and B is the element boron;

[0009] a, b, c, d, e satisfy the following relationships: 27.5≤a≤31, 8.5≤b≤12, 0.05≤c≤0.2, 0≤d≤5, 0.9≤e≤1.2; where a, b, c, d, e all represent mass percentages.

[0010] In a further technical solution, a, b, c, d, and e satisfy the following relationships: 29≤a≤30, 9≤b≤11, 0.1≤c≤0.15, 1≤d≤4, and 1≤e≤1.1.

[0011] In a further technical solution, the method further includes post-processing the sintered NdFeB billet by surface coating penetration.

[0012] In a further technical solution, the surface coating penetration method specifically involves: after attaching a diffusion source to the surface of a sintered NdFeB blank to form a coating, simultaneously applying laser shock and ultrasonic vibration to the coating.

[0013] In a further technical solution, the pulse width of the laser shock is 10-15 ns, and the energy of a single pulse is 5-20 J.

[0014] In a further technical solution, the frequency of the ultrasonic vibration is 100-150kHz, the amplitude is 10-50μm, and the ultrasonic vibration power is 500-3000W.

[0015] In a further technical solution, before surface coating penetration, the surface of the sintered NdFeB blank is polished, then sprayed with sodium chloride solution, left to stand for 30 minutes, and then rinsed clean.

[0016] In a further technical solution, the diffusion source is Tb. 0.3 Dy 0.7 (Fe 1-x Al x )2 alloy powder, wherein x takes the value of 0.05, 0.10 or 0.15;

[0017] The particle size of the alloy powder is 1-2 mm.

[0018] In a further technical solution, the thickness of the coating formed by the diffusion source on the sintered NdFeB surface is 1-5 μm.

[0019] In a further technical solution, the laser impact spot radius is 2-3mm, and the laser impact treatment is performed row by row on the sintered NdFeB magnet to be treated, with an overlap rate of 50% or more between each row.

[0020] Compared with the prior art, the matrix alloy composition of the neodymium iron boron magnet provided by the present invention has better toughness in the blank obtained by powdering, forming and sintering, which can effectively avoid the problem of breakage such as chipping and corner breaking.

[0021] Other features and advantages of the present invention will be described in detail in the following specific embodiments. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further explained below with reference to specific embodiments.

[0023] As previously stated, this invention provides a method for improving the brittleness of high coercivity billet materials, the method comprising designing the matrix alloy composition of the sintered NdFeB magnet to be: Nd a M b N c O d Fe 100-a-b-c-d-e B e Wherein, Nd is neodymium; M is at least one of La, Ce, and Pr.

[0024] N is at least one of the elements Dy, Tb, and Gd;

[0025] O is at least one of the elements Co, Mn, Cu, Al, Ti, Ga, Zr, V, Hf, W, and Nb;

[0026] Fe is the element iron, and B is the element boron;

[0027] a, b, c, d, e satisfy the following relationships: 27.5≤a≤31, 8.5≤b≤12, 0.05≤c≤0.2, 0≤d≤5, 0.9≤e≤1.2; where a, b, c, d, e all represent mass percentages.

[0028] The inventors of this application have discovered that by designing the matrix alloy composition of neodymium iron boron magnets according to the above formula, the blanks obtained after powdering, molding and sintering have good toughness and can effectively avoid breakage problems such as chipping and corner breaking.

[0029] More preferably, a, b, c, d, e satisfy the following relationships: 29≤a≤30, 9≤b≤11, 0.1≤c≤0.15, 1≤d≤4, 1≤e≤1.1.

[0030] The matrix alloy provided by this invention differs from existing matrix alloys in that it significantly reduces the amount of heavy rare earth elements added while significantly increasing the amount of light rare earth elements added. Simultaneously, it increases the amount of neodymium. The inventors of this application have found that through these improvements, the sintered billet achieves better toughness, thereby overcoming the defect of reduced yield caused by breakage. However, the coercivity of the neodymium iron boron magnet formed using the above-mentioned formula is relatively low. Therefore, the method provided in this application also includes post-treatment of the sintered neodymium iron boron billet through surface coating penetration.

[0031] Furthermore, the surface coating penetration method specifically involves: after attaching a diffusion source to the surface of a sintered NdFeB blank to form a coating, simultaneously applying laser shock and ultrasonic vibration to the coating.

[0032] In this invention, the laser shock generates heat, causing the diffusion source in the coating to melt and penetrate into the NdFeB magnet blank. Simultaneously, ultrasonic vibration induces the diffusion source alloy to penetrate to a deeper depth, improving the grain boundaries at deeper locations in the NdFeB magnet blank, thereby further ensuring its high coercivity. Furthermore, the ultra-strong shock wave generated by the laser shock alters the composition and structure of the grain boundary phase on the NdFeB magnet surface, improving the physicochemical properties of the grain boundary phase and increasing the density of the NdFeB magnet surface, thus enhancing the overall performance of the NdFeB magnet; that is, reducing the impact of this alloy introduction method on other properties of the NdFeB magnet, such as the magnetic energy product.

[0033] According to the method provided by the present invention, the parameters of the laser shock can be selected within a wide range. Preferably, the pulse width of the laser shock is 10-15 ns and the energy of a single pulse is 5-20 J.

[0034] In this invention, the purpose of ultrasonic vibration is to promote the penetration of the diffusion source alloy, after laser shock melting, into a deeper location within the NdFeB magnet, thereby ensuring an increase in the coercivity of the NdFeB magnet. The parameters of the ultrasonic vibration can be selected within a wide range; preferably, the ultrasonic vibration frequency is 100–150 kHz, the amplitude is 10–50 μm, and the ultrasonic vibration power is 500–3000 W.

[0035] According to the method provided by the present invention, in order to improve the surface coating penetration effect, the method further includes grinding the surface of the sintered NdFeB blank before surface coating penetration, then spraying sodium chloride solution, letting it stand for 30 minutes, and then rinsing it clean.

[0036] More specifically, the surface of the NdFeB magnet blank is ground and polished using 1000# to 2000# SiC sandpaper, and then placed in an ultrasonic cleaner with a 2.5% (v / v) ethanol solution to remove dust and oil stains. The purpose of spraying sodium chloride solution is to create a weak corrosion on the surface of the NdFeB magnet blank, resulting in atomic vacancies or gaps at the surface grain boundaries. This allows the diffusion source alloy to more easily penetrate into the interior of the NdFeB magnet blank under laser shock and ultrasonic vibration conditions. This invention does not specifically limit the concentration of the sodium chloride solution; a 5% (v / v) sodium chloride solution is acceptable.

[0037] In this invention, the diffusion source is Tb. 0.3 Dy 0.7 (Fe 1-x Al x The alloy powder has a particle size of 1-2 mm, where x is 0.05, 0.10, or 0.15. This alloy component penetrates to the grain boundaries within the NdFeB magnet, effectively improving its coercivity. Simultaneously, while the inclusion of Al in the alloy component reduces anisotropy, the substitution of some Fe by Al improves the resistivity and compressive strength of the alloy. Furthermore, the inclusion of Al promotes deeper penetration of the diffusion source, thereby enhancing the coercivity of the NdFeB magnet.

[0038] In this invention, the thickness of the coating formed by the diffusion source on the surface of the sintered NdFeB magnet should not be too thick. If it is too thick, it will easily lead to a waste of heavy rare earth elements, while if it is too thin, it will not be able to provide a sufficient amount of heavy rare earth elements to improve the NdFeB magnet. Preferably, in this invention, the thickness of the coating formed by the diffusion source on the surface of the sintered NdFeB magnet is 1 to 5 μm.

[0039] According to the method provided by the present invention, the laser impact spot radius is 2-3 mm, and laser impact treatment is performed row by row on the sintered NdFeB magnet to be treated, with an overlap rate of 50% or more between rows. In specific implementation, the center of the laser beam spot is aligned with the upper left corner of the surface of the NdFeB magnet to be treated as the starting position of the laser impact. In this way, the surface of the NdFeB magnet is impacted row by row. Furthermore, in order to obtain a better impact effect, the impact is overlapped between rows, that is, when impacting the next row, the area already impacted in the previous row is impacted again, with an overlap rate of 50% or more, to ensure a good impact effect.

[0040] The following specific embodiments further illustrate the method for improving high coercivity billet materials provided by the present invention.

[0041] In the following embodiments, the diffusion source is prepared by formulating raw materials Tb, Dy, Fe, and Al (Tb: 99.99%, Dy: 99.9%, Fe: 99.98%, Al: 99.9%) into a solution with the target composition Tb. 0.3 Dy 0.7 (Fe 1-x Al x The alloy is 2; where x takes the value of 0.05, 0.10 or 0.15; in the specific preparation method, excess Tb and Dy are added at 5% burn loss to compensate for positive loss. The sample is melted and cast into an alloy under the protection of high-purity argon gas using a high-vacuum non-consumable arc melting equipment. The alloy is then crushed to obtain alloy powder with a particle size of 1-2 mm. Then, it is prepared into a slurry using an ethanol solution, wherein each 1 g of alloy powder is mixed with 10 mL of ethanol solution (95 wt%).

[0042] Example 1

[0043] The sintered NdFeB magnet blank provided in this embodiment is prepared using conventional rapid solidification casting, hydrogen crushing, air jet milling, forming, and sintering processes in the NdFeB production field. The matrix alloy composition is: Nd 29 Pr9Tb 0.1 Al3Fe 57.9 B1.

[0044] Post-processing steps:

[0045] Prepare diffusion source slurry, and add Tb 0.3 Dy 0.7 (Fe 0.95 Al 0.05 )2. Alloy powder is crushed to a particle size of 1.5 mm and mixed with ethanol solution (95 wt%) at a ratio of 1 g: 10 mL to form a slurry;

[0046] The slurry was coated on the surface of the aforementioned sintered NdFeB magnet blank to form a coating with a thickness of 3 μm. After the coating solidified, laser shock and ultrasonic vibration were applied to the coating simultaneously. The pulse width of the laser shock was 12 ns and the energy of a single pulse was 10 J. The frequency of the ultrasonic vibration was 120 kHz, the amplitude was 20 μm, and the ultrasonic vibration power was 2000 W.

[0047] The laser impact spot radius is 2mm. Laser impact treatment is performed row by row on the sintered NdFeB magnet to be treated, with an overlap rate of 50% between rows. After the treatment is completed, the treated NdFeB magnet is obtained.

[0048] Example 2

[0049] The sintered NdFeB magnet blank provided in this embodiment is prepared using conventional rapid solidification casting, hydrogen crushing, air jet milling, forming, and sintering processes in the NdFeB production field. The post-processing steps are the same as in Example 1, except that:

[0050] The matrix alloy composition is: Nd 27.5 Pr 8.5 Tb 0.05 Al1Fe 62.05 B 0.9 .

[0051] Example 3

[0052] The sintered NdFeB magnet blank provided in this embodiment is prepared using conventional rapid solidification casting, hydrogen crushing, air jet milling, forming, and sintering processes in the NdFeB production field. The post-processing steps are the same as in Example 1, except that:

[0053] The matrix alloy composition is: Nd 31 Pr 12 Tb 0.2 Al5Fe 50.6 B 1.2 .

[0054] The coercivity of the neodymium iron boron magnets in Examples 1-3 above was tested according to GB / T 3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnet) Materials". At the same time, their impact toughness was tested. The test results are summarized in Table 1.

[0055] Table 1:

[0056]

[0057] Based on the above test data, it can be seen that the matrix alloy composition provided by the present invention ensures that the sintered NdFeB magnet blank has good impact toughness, thereby overcoming the defects of breakage such as chipping and corner chipping of the blank. At the same time, the post-processing process provided by the present invention can significantly improve its coercivity.

[0058] The foregoing has shown and described the basic principles, main features, and characteristics of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method of improving the brittleness of a high-coercivity blank material, characterized by, The method comprises designing the base alloy component of the sintered neodymium-iron-boron magnet as: Nd a M b N c O d Fe 100-a-b-c-d-e B e ; wherein Nd is a neodymium element; M is at least one of La, Ce, Pr elements; N is at least one of the elements Dy, Tb, and Gd; O is at least one of the elements Co, Mn, Cu, Al, Ti, Ga, Zr, V, Hf, W, and Nb; Fe is the element iron, and B is the element boron; a, b, c, d, e satisfy the following relationships: 27.5≤a≤31, 8.5≤b≤12, 0.05≤c≤0.2, 0≤d≤5, 0.9≤e≤1.2; where a, b, c, d, e all represent mass percentages.

2. The method of claim 1, wherein, a, b, c, d, e satisfy the following relations: 29≤a≤30, 9≤b≤11, 0.1≤c≤0.15, 1≤d≤4, 1≤e≤1.

1.

3. The method of claim 1, wherein, It also includes post-treatment of sintered NdFeB blanks by surface coating penetration.

4. The method according to claim 3, characterized in that, The surface coating penetration method specifically involves attaching a diffusion source to the surface of a sintered NdFeB blank to form a coating, and then simultaneously applying laser shock and ultrasonic vibration to the coating.

5. The method of claim 4, wherein, The pulse width of the laser shock is 10-15 ns, and the energy of a single pulse is 5-20 J.

6. The method of claim 4, wherein, The ultrasonic vibration frequency is 100-150kHz, the amplitude is 10-50μm, and the ultrasonic vibration power is 500-3000W.

7. The method of claim 4, wherein, Before surface coating penetration, the surface of the sintered NdFeB blank is polished, then sprayed with sodium chloride solution, left to stand for 30 minutes, and then rinsed clean.

8. The method of claim 4, wherein, The diffusion source is Tb 0.3 Dy 0.7 (Fe 1-x Al x )2 alloy powder, wherein x has a value of 0.05, 0.10 or 0.

15. The particle size of the alloy powder is 1-2 mm.

9. The method of claim 4, wherein, The diffusion source forms a coating with a thickness of 1-5 μm on the surface of the sintered NdFeB.

10. The method of claim 4, wherein, The laser impact spot radius is 2-3 mm, and the laser impact treatment is performed row by row on the sintered NdFeB magnet to be treated, with an overlap rate of 50% or more between each row.

Images