Alloy and preparation method thereof, NdFeB magnet and preparation method thereof, diffusion coating

Abstract

The present invention provides an alloy and its preparation method, a neodymium iron boron magnet and its preparation method, and a diffusion coating; wherein, the chemical formula of the alloy is B x Ga y Ti z1 Zr z2 Fe 1‑x‑y‑z1‑z2 ; x, y, z1, and z2 are respectively valued as follows: 0.9% ≤ x ≤ 1.5%, 15% ≤ y ≤ 25%, 5% ≤ z1 ≤ 8%, 2% ≤ z2 ≤ 5%, and 7% ≤ z1 + z2 ≤ 10%. The alloy provided by the present invention can be applied to the preparation of neodymium iron boron magnets, while improving the relevant properties such as the remanence and coercivity of the neodymium iron boron magnets, reducing the addition amount of rare earth elements, and achieving the purpose of low cost and energy conservation.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic materials, and in particular to an alloy and a preparation method thereof, a neodymium iron boron magnet and a preparation method thereof, and a diffusion coating. Background Art

[0002] Rare earth permanent magnet materials have always played a very important role in today's era, and large-scale commercial production has been achieved. Since their discovery, rare earth permanent magnet materials have been widely used in many fields such as computers, hybrid vehicles, medical treatment, household appliances, and wind power generation. Their application scope and output are still increasing year by year, which is particularly evident in the field of new energy vehicles. In recent years, with the consumption of mineral fuels and a series of resource and environmental problems, green transportation tools such as hybrid vehicles and pure electric vehicles have received great attention. Among them, sintered NdFeB magnets play an irreplaceable role in energy conversion.

[0003] At present, many applications of NdFeB magnets are in high temperature environments. Researchers' research on the thermal stability of NdFeB magnets is mostly focused on adding appropriate elements or improving the magnet preparation process to improve the coercive force of the magnet. The high coercive force of the magnet is used to resist the decline in magnet performance caused by changes in the external environment. At present, there are two methods to improve the coercive force of NdFeB magnets. The first is to add appropriate trace elements, such as heavy rare earths (dysprosium, terbium, etc.), copper, aluminum, etc., during the preparation of NdFeB magnets. By adding trace elements, the anisotropy field of NdFeB magnets is increased, and the increase in the anisotropy field drives the increase in the coercive force of NdFeB magnets. The second type is to improve the microstructure of sintered NdFeB magnets, improve the microstructure of the grain boundaries and the internal crystals of sintered NdFeB magnets, reduce the presence of stray magnetic fields, and improve the coercive force of sintered NdFeB magnets. In order to ensure that NdFeB has a certain coercive force and significant effect, it is mainly necessary to add a certain amount of heavy rare earths such as dysprosium or terbium.

[0004] However, the current conventional process adds a relatively large amount of heavy rare earths, which not only wastes resources but also increases production costs. Summary of the invention

[0005] The present invention aims to solve at least one of the above technical problems.

[0006] To this end, a first object of the present invention is to provide an alloy.

[0007] The second object of the present invention is to provide a method for preparing the alloy.

[0008] The third object of the present invention is to provide a neodymium iron boron magnet.

[0009] The fourth object of the present invention is to provide a method for preparing a NdFeB magnet.

[0010] A fifth object of the present invention is to provide a diffusion coating.

[0011] To achieve the first object of the present invention, an embodiment of the present invention provides an alloy, the alloy is as shown in formula (I);

[0012] B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 (I);

[0013] Among them, x, y, z1 and z2 are respectively taken as follows: 0.9%≤x≤1.5%, 15%≤y≤25%, 5%≤z1≤8%, 2%≤z2≤5%, and 7%≤z1+z2≤10%.

[0014] In this embodiment, Ti and Zr increase the sintering temperature resistance of the magnet, and no abnormal grain growth occurs, and the change of the magnetic phase can be very effectively prevented; in the diffusion stage, Ti will form a dual alloy phase or a multi-alloy phase with Ga / B / Fe. In the process of further high-temperature densification, a hardened structure can be formed in the outer layer of the grain, which effectively prevents heavy rare earth from entering the main phase, thereby preventing the increase in coercive force from being affected. Ga can play a role in wetting the grain boundary by virtue of its low melting point; B can optimize the grain boundary and reduce grain boundary defects. Both can improve the efficiency of diffusion while improving performance. This embodiment effectively optimizes the distribution of the grain boundary structure of the magnet, and the effect is better than that of traditional grain boundary modification technology. Therefore, it is feasible to improve the wettability and fluidity of the grain boundary, open up the diffusion channel, and obtain a high-performance diffusion matrix with a continuous distribution of the grain boundary phase through composition design combined with dual alloy technology and grain boundary phase formation process regulation.

[0015] Furthermore, the above B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 In the alloy, the values ​​of x, y, z1 and z2 are as follows:

[0016] 0.9% ≤ x ≤ 1.2%, 15% ≤ y ≤ 22%, 5% ≤ z1 ≤ 7%, 3% ≤ z2 ≤ 5%; or

[0017] 1.0% ≤ x ≤ 1.5%, 18% ≤ y ≤ 25%, 6% ≤ z1 ≤ 8%, 2% ≤ z2 ≤ 4%; or

[0018] 1.1%≤x≤1.3%, 19%≤y≤21%, 6%≤z1≤7%, 3%≤z2≤4%.

[0019] In this embodiment, an alloy for catalyzing the diffusion effect of NdFeB magnets is provided through component optimization.

[0020] To achieve the second objective of the present invention, an embodiment of the present invention provides a method for preparing an alloy, comprising the following steps:

[0021] S11: mixing and smelting alloy raw materials to obtain alloy ingots;

[0022] S12: crushing the alloy ingot to obtain alloy powder.

[0023] In this embodiment, there is no particular restriction on the source of the alloy raw material, and conventional sources known to those skilled in the art can be used. Those skilled in the art can select and adjust according to actual production conditions, product requirements, quality control and other factors. For example, the alloy raw materials include pure boron, pure gallium, pure titanium, pure zirconium and pure iron, and the above alloy raw materials can be in powder, granular or block form, etc., which are not limited here. In some implementation methods of this embodiment, the alloy raw material can be added in the form of an alloy in addition to being added in the form of a single substance.

[0024] Furthermore, the crushing includes coarse crushing, disc milling crushing, ball milling crushing; and / or the average particle size of the alloy powder is 1.5-2.5 μm.

[0025] In this embodiment, the crushing involves coarse crushing by a crusher, disc grinding crushing by a disc mill, and ball milling crushing by a ball mill; more specific process details are not limited here, and the above technical solution is intended to crush the alloy ingot into alloy powder for easy addition to the NdFeB magnet. It is worth noting that the average particle size of the alloy powder is preferably 1.5-2.5μm, more preferably 1.5-2.2μm, and most preferably 1.5-2.0μm; specifically, it can also be 1.5μm, 1.6μm, 1.7μm, 1.8μm, and 1.9μm.

[0026] To achieve the third object of the present invention, an embodiment of the present invention provides a neodymium iron boron magnet, comprising the above-mentioned B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 alloy.

[0027] In this embodiment, adding alloy to the NdFeB magnet can polish and optimize the grain boundaries, inhibit grain expansion at high temperatures, increase ferromagnetism between grain boundaries, improve coupling, and help diffusion.

[0028] To achieve the fourth objective of the present invention, an embodiment of the present invention provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0029] S21: obtaining raw materials of NdFeB magnets, and smelting and powdering to obtain NdFeB powder;

[0030] S22: Orienting and molding the NdFeB powder and sintering it to obtain a NdFeB blank;

[0031] S23: coating a diffusion coating on the surface of the NdFeB blank, and performing heat treatment to obtain a NdFeB magnet;

[0032] Among them, the above-mentioned B is added to the NdFeB powder x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 Alloy; and / or

[0033] Add the above B to the diffusion coating x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 alloy.

[0034] In some implementations of this embodiment, raw materials for NdFeB magnets are obtained, and NdFeB powder is obtained by smelting and powdering; including: obtaining raw materials for NdFeB magnets according to the component ratio, smelting, hydrogen crushing, and air flow grinding to obtain NdFeB powder.

[0035] Furthermore, alloy is added to NdFeB powder, and the mass of the alloy added is 0.5-0.8% of the mass of NdFeB powder; alloy is added to diffusion coating, and the mass of the alloy added is 1.2-1.5% of the mass of diffusion coating.

[0036] In this embodiment, the amount of alloy added is small. Specifically, in NdFeB powder, the amount of alloy added is 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75% or 0.8%; in diffusion coating, the amount of alloy powder added is 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45% or 1.5%.

[0037] Furthermore, the sintering is low-temperature non-density sintering; wherein the sintering temperature of the low-temperature non-density sintering is 1020-1050°C; and / or the sintering time of the low-temperature non-density sintering is 3-5 hours; and / or the vacuum degree of the low-temperature non-density sintering is ≤0.02Pa; and / or the sintering density of the low-temperature non-densification sintering is 96-98% of the density.

[0038] In this embodiment, the sintering process selects low-temperature non-dense sintering, which plays a role in regulating the size of the pores between the grains. The density of the NdFeB blank obtained by non-dense sintering is smaller and the pores between the grains are larger, so that during the heat treatment diffusion process of the NdFeB blank, the alloy elements and heavy rare earth elements can flow more easily into the grain boundaries, thereby accelerating the diffusion rate.

[0039] Further, the heat treatment includes diffusion treatment and aging treatment, and the diffusion treatment includes a first-stage diffusion treatment and a second-stage diffusion treatment; wherein the temperature of the first-stage diffusion treatment is 880-920°C; and / or the time of the first-stage diffusion treatment is 10-20 hours; and / or the temperature of the second-stage diffusion treatment is 970-1010°C; and / or the time of the second-stage diffusion treatment is 5-10 hours; and / or the temperature of the aging treatment is 480-520°C; and / or the time of the aging treatment is 5-10 hours.

[0040] In this embodiment, the diffusion treatment is divided into two stages. The temperature of the first stage diffusion treatment is relatively low, which can make the alloy and rare earth elements flow into the grain boundaries. The second stage diffusion treatment is a high-temperature stage, which accelerates the flow, polishing and optimization of the alloy phase between the grain boundaries. Since the density of the NdFeB blank obtained by low-temperature non-dense sintering is relatively low, a high-temperature stage is designed to further densify the magnet, but it will not affect its performance.

[0041] To achieve the fifth object of the present invention, an embodiment of the present invention provides a diffusion coating, comprising the above-mentioned B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 alloy.

[0042] The diffusion coating provided in this embodiment can be coated on the surface of the NdFeB substrate and then subjected to heat treatment to obtain the NdFeB magnet, which is beneficial to the diffusion of the substrate. The coating method can be spraying. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Electron microscope images of magnets provided for some embodiments of the present invention. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the related art, in order to improve the coercivity of NdFeB, rare earth elements are generally added for diffusion. Specifically, a coating containing rare earth elements is coated on the surface of the NdFeB magnet. After heat treatment, the rare earth elements, as a diffusion source, diffuse and penetrate from the grain boundary to the main phase, improving problems such as grain unevenness, thereby improving the coercivity of the magnet. However, the effect of using rare earth alloys or rare earth diffusion is limited, the diffusion depth is not enough, and the coercivity increase is limited. If you want to forcibly increase the coating amount, it will cause a waste of materials.

[0046] Therefore, the present invention aims to provide an alloy that can be used to promote the diffusion effect of rare earth elements on NdFeB magnets. Specifically, the conventional diffusion method is to coat a diffusion source on a substrate, and the diffusion source generally includes rare earth elements, such as terbium, dysprosium, etc.; on this basis, adding the alloy provided by the embodiment of the present invention can promote the diffusion effect. That is, the above alloy is a catalyst that promotes the diffusion of the diffusion source. In terms of effect, under the condition that the coating amount of the diffusion source is the same, adding the alloy can increase the coercive force of the NdFeB magnet; under the premise of achieving the same coercive force, adding the alloy provided by the embodiment of the present invention can reduce the coating amount of the rare earth element.

[0047] Based on this, the alloy provided by the embodiment of the present invention is as shown in formula (I);

[0048] B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 (I);

[0049] Among them, x, y, z1 and z2 are respectively taken as follows: 0.9%≤x≤1.5%, 15%≤y≤25%, 5%≤z1≤8%, 2%≤z2≤5%, and 7%≤z1+z2≤10%.

[0050] In this embodiment, there is no particular limitation on the specific definition of formula (I), and it can be expressed in such a way that is familiar to those skilled in the art, and can be understood as a mass ratio. That is, the alloy provided in this embodiment includes 0.9-1.5% boron, 15-25% gallium, 5-8% titanium, 2-5% zirconium, and the remainder is iron, wherein the sum of the mass percentages of titanium and zirconium is 7-10%. In some implementations of this embodiment, the above alloy also includes unavoidable impurities.

[0051] Among them, Ti and Zr increase the sintering temperature resistance of the magnet, and do not cause abnormal grain growth, and can effectively prevent the change of magnetic phase; in the diffusion stage, Ti will form a dual alloy phase or a multi-alloy phase with Ga / B / Fe. In the process of further high-temperature densification, it can form a hardened structure on the outer edge of the grain, effectively preventing heavy rare earth from entering the main phase, thereby preventing the increase in coercivity from being affected. Ga can use its low melting point to wet the grain boundary; B can optimize the grain boundary and reduce grain boundary defects. Both can improve the efficiency of diffusion while improving performance.

[0052] This embodiment effectively optimizes the distribution of magnet grain boundary structure, and the effect is better than the traditional grain boundary modification technology. Therefore, it is feasible to improve the wettability and fluidity of the grain boundary, open up the diffusion channel, and obtain a high-performance diffusion matrix with continuous distribution of grain boundary phases through composition design combined with dual alloy technology and grain boundary phase formation process regulation.

[0053] Furthermore, the above B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 In the alloy, the values ​​of x, y, z1 and z2 are as follows:

[0054] 0.9% ≤ x ≤ 1.2%, 15% ≤ y ≤ 22%, 5% ≤ z1 ≤ 7%, 3% ≤ z2 ≤ 5%; or

[0055] 1.0% ≤ x ≤ 1.5%, 18% ≤ y ≤ 25%, 6% ≤ z1 ≤ 8%, 2% ≤ z2 ≤ 4%; or

[0056] 1.1%≤x≤1.3%, 19%≤y≤21%, 6%≤z1≤7%, 3%≤z2≤4%.

[0057] In this embodiment, an alloy for catalyzing the diffusion effect of NdFeB magnets is provided by optimizing the composition. Specifically, the mass percentage of boron is 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%; the mass percentage of gallium is 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25%; the mass percentage of titanium is 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%; the mass percentage of zirconium is 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%; the balance is iron.

[0058] An embodiment of the present invention also provides a method for preparing an alloy, comprising the following steps:

[0059] S11: mixing and smelting alloy raw materials to obtain alloy ingots;

[0060] S12: crushing the alloy ingot to obtain alloy powder.

[0061] In this embodiment, there is no particular restriction on the source of the alloy raw material, and conventional sources known to those skilled in the art can be used. Those skilled in the art can select and adjust according to actual production conditions, product requirements, quality control and other factors. For example, the alloy raw materials include pure boron, pure gallium, pure titanium, pure zirconium and pure iron, and the above alloy raw materials can be in powder, granular or block form, etc., which are not limited here. In some implementation methods of this embodiment, the alloy raw material can be added in the form of an alloy in addition to being added in the form of a single substance.

[0062] Furthermore, the crushing includes coarse crushing, disc milling crushing, ball milling crushing; and / or the average particle size of the alloy powder is 1.5-2.5 μm.

[0063] In this embodiment, the crushing involves coarse crushing by a crusher, disc grinding crushing by a disc mill, and ball milling crushing by a ball mill; more specific process details are not limited here, and the above technical solution is intended to crush the alloy ingot into alloy powder for easy addition to the NdFeB magnet. It is worth noting that the average particle size of the alloy powder is preferably 1.5-2.5μm, more preferably 1.5-2.2μm, and most preferably 1.5-2.0μm; specifically, it can also be 1.5μm, 1.6μm, 1.7μm, 1.8μm, and 1.9μm.

[0064] The present invention also provides a neodymium iron boron magnet, comprising the above-mentioned B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 alloy.

[0065] In this embodiment, adding alloy to the NdFeB magnet can polish and optimize the grain boundaries, inhibit grain expansion at high temperatures, increase ferromagnetism between grain boundaries, improve coupling, and help diffusion.

[0066] The present invention also provides a method for preparing a NdFeB magnet, comprising the following steps:

[0067] S21: obtaining raw materials of NdFeB magnets, and smelting and powdering to obtain NdFeB powder;

[0068] S22: Orienting and molding the NdFeB powder and sintering it to obtain a NdFeB blank;

[0069] S23: coating a diffusion coating on the surface of the NdFeB blank, and performing heat treatment to obtain a NdFeB magnet;

[0070] Among them, the above-mentioned B is added to the NdFeB powder x Gay Ti z1 Zr z2 Fe 1-x-y-z1-z2 Alloy; and / or

[0071] Add the above B to the diffusion coating x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 alloy.

[0072] In some implementations of this embodiment, the raw material of the NdFeB magnet is obtained, and the NdFeB powder is obtained by smelting and powdering; including: obtaining the raw material of the NdFeB magnet according to the composition ratio, smelting, hydrogen breaking, and air flow grinding to obtain the NdFeB powder. Further, the NdFeB powder is sequentially oriented and sintered to obtain the NdFeB blank; on this basis, a diffusion coating is applied, and heat treatment is performed to finally obtain the NdFeB magnet. In a specific embodiment, the diffusion coating is also a diffusion source, containing rare earth elements. In this embodiment, the source of the alloy raw material and the specific process steps and parameters are well known to those skilled in the art, so no special limitation is made, and those skilled in the art can select and adjust according to factors such as actual production conditions, product requirements, and quality control; for example, the NdFeB blank is pickled and phosphated before coating.

[0073] In different embodiments, the alloy is added in different ways. In some embodiments of the present embodiment, alloy powder is added to NdFeB powder, and then the process steps of orientation molding, sintering, diffusion coating and heat treatment are carried out in sequence. In some embodiments of the present embodiment, alloy powder is added to the diffusion coating and coated on the surface of the NdFeB blank, and then subsequent heat treatment is carried out to finally obtain the NdFeB magnet. Of course, in the specific implementation process, the above two addition methods can be combined, and alloy powder can be added to NdFeB powder and diffusion coating at the same time; considering the economic benefits and the purpose of simplifying the process flow, this method is not recommended, but it can also solve the problem that the present invention seeks to solve and achieve the corresponding effect.

[0074] Furthermore, alloy is added to NdFeB powder, and the mass of the alloy added is 0.5-0.8% of the mass of NdFeB powder; alloy is added to diffusion coating, and the mass of the alloy added is 1.2-1.5% of the mass of diffusion coating.

[0075] In this embodiment, the amount of alloy added is small. Specifically, in NdFeB powder, the amount of alloy added is 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75% or 0.8%; in diffusion coating, the amount of alloy powder added is 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45% or 1.5%.

[0076] Furthermore, the sintering is low-temperature non-density sintering; wherein the sintering temperature of the low-temperature non-density sintering is 1020-1050°C; and / or the sintering time of the low-temperature non-density sintering is 3-5 hours; and / or the vacuum degree of the low-temperature non-density sintering is ≤0.02Pa; and / or the sintering density of the low-temperature non-densification sintering is 96-98% of the density.

[0077] In this embodiment, the sintering process selects low-temperature non-dense sintering, which plays a role in regulating the size of the pores between the grains. The density of the NdFeB blank obtained by non-dense sintering is smaller, and the pores between the grains are larger, so that the alloy elements and heavy rare earth elements are more likely to flow into the grain boundaries during the heat treatment diffusion process of the NdFeB blank, thereby accelerating the diffusion rate. For example, for NdFeB 45H, the conventional sintering process is used, and the dense density is 7.55g / cm 3 However, it adopts low-temperature non-compact sintering, and the sintering density is 7.4g / cm 3 About. For different NdFeB magnets, different element ratios will also affect their density; generally speaking, the sintering density obtained by low-temperature non-compact sintering is between 96-98% of the compact density. The process parameters of the above-mentioned low-temperature non-compact sintering are as follows: the sintering temperature is 1020-1050°C, preferably 1020-1040°C, more preferably 1025-1035°C, and most preferably 1030°C; the sintering time can be 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours; the vacuum degree is preferably 0.015Pa, more preferably 0.01Pa.

[0078] Further, the heat treatment includes diffusion treatment and aging treatment, and the diffusion treatment includes a first-stage diffusion treatment and a second-stage diffusion treatment; wherein the temperature of the first-stage diffusion treatment is 880-920°C; and / or the time of the first-stage diffusion treatment is 10-20 hours; and / or the temperature of the second-stage diffusion treatment is 970-1010°C; and / or the time of the second-stage diffusion treatment is 5-10 hours; and / or the temperature of the aging treatment is 480-520°C; and / or the time of the aging treatment is 5-10 hours.

[0079] In this embodiment, the diffusion treatment is divided into two stages. The temperature of the first stage diffusion treatment is relatively low, which can make the alloy and rare earth elements flow into the grain boundaries; the temperature of this stage is preferably 890-910°C, more preferably 900°C; the treatment time is preferably 12-18 hours, more preferably 14-16 hours. The second stage diffusion treatment is a high-temperature stage, which accelerates the flow, polishing and optimization of the alloy phase between the grain boundaries. Since the density of the NdFeB blank obtained by low-temperature non-dense sintering is relatively low, a high-temperature stage is designed to further densify the magnet, but it will not affect its performance. In the second stage diffusion treatment, the temperature is preferably 980-1000°C, more preferably 990°C; the treatment time is preferably 6-9 hours, more preferably 7-8 hours. In some embodiments of this embodiment, aging treatment is further performed after the diffusion treatment is completed, and the temperature is preferably 490-510°C, more preferably 500°C; the treatment time is preferably 6-9 hours, more preferably 7-8 hours.

[0080] See also Figure 1 , which is a scanning electron microscope image of a magnet after diffusion treatment provided by some embodiments of the present invention, in which ① marked is the hardened structure of the grain epitaxial layer, ② is the hole, and ③ is the alloy phase and the diffusion coating; it can be seen that after two stages of diffusion treatment, the density of the magnet is further improved, and at the same time, the formation of the hardened structure can effectively prevent heavy rare earth elements from entering the main phase, avoiding the influence of heavy rare earth elements on the increase of the coercive force of the magnet, thereby further improving the performance of the magnet.

[0081] The present invention also provides a diffusion coating, comprising the above-mentioned B x Ga y Ti z1 Zr z2 Fe 1-x-y-z1-z2 alloy.

[0082] The diffusion coating provided in this embodiment can be coated on the surface of the NdFeB substrate and then subjected to heat treatment to obtain the NdFeB magnet, which is beneficial to the diffusion of the substrate. The coating method can be spraying.

[0083] The technical solution provided by the present invention will be described in detail below in conjunction with specific implementation methods.

[0084] Example 1

[0085] This embodiment provides an alloy A, which includes, in appropriate proportions: B 0.9%, Ga 25%, Ti 5%, Zr 2%, and the balance is Fe.

[0086] This embodiment also provides a method for preparing the above alloy, comprising the following steps:

[0087] S11: obtaining alloy raw materials according to the composition ratio, and mixing and smelting to obtain alloy ingots;

[0088] S12: The alloy ingot is coarsely crushed by a crusher, crushed by a disc mill, or crushed by a ball mill to obtain alloy powder.

[0089] The average particle size of the alloy powder is 1.5-2.5 μm.

[0090] Example 2

[0091] This embodiment provides an alloy B, which includes, in appropriate proportions: B 1.5%, Ga 15%, Ti 8%, Zr 2%, and the balance is Fe.

[0092] This embodiment also provides a method for preparing the above alloy, comprising the following steps:

[0093] S11: obtaining alloy raw materials according to the composition ratio, and mixing and smelting to obtain alloy ingots;

[0094] S12: The alloy ingot is coarsely crushed by a crusher, crushed by a disc mill, or crushed by a ball mill to obtain alloy powder.

[0095] The average particle size of the alloy powder is 1.5-2.5 μm.

[0096] Example 3

[0097] This embodiment provides an alloy C, which includes, in appropriate proportions: B 1.1%, Ga 20%, Ti 5%, Zr 4%, and the balance is Fe.

[0098] This embodiment also provides a method for preparing the above alloy, comprising the following steps:

[0099] S11: obtaining alloy raw materials according to the composition ratio, and mixing and smelting to obtain alloy ingots;

[0100] S12: The alloy ingot is coarsely crushed by a crusher, crushed by a disc mill, or crushed by a ball mill to obtain alloy powder.

[0101] The average particle size of the alloy powder is 1.5-2.5 μm.

[0102] Example 4

[0103] This embodiment provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0104] S21: obtaining raw materials of NdFeB magnets according to the composition ratio, smelting, hydrogen crushing and pulverizing to obtain NdFeB powder.

[0105] S22: Orienting and molding the NdFeB powder and sintering it to obtain a NdFeB blank.

[0106] S23: pickling and phosphating the NdFeB blank, coating the surface with diffusion coating, and heat treating to obtain a NdFeB magnet; wherein the diffusion coating is added with the alloy provided in some embodiments of the present invention, and the addition ratio is 1.5% of the mass of the diffusion coating.

[0107] In this embodiment, the specific process parameters are as follows:

[0108] The low temperature non-dense sintering process is 1020℃*3 hours; vacuum degree ≤0.02Pa. The density of the sintered NdFeB blank is 7.397g / cm 3 , (its conventional process density is 7.55g / cm 3 about).

[0109] Heat treatment includes diffusion treatment and aging treatment. Diffusion treatment includes first-stage diffusion treatment and second-stage diffusion treatment. The first-stage diffusion process is 910℃*10 hours, and the second-stage diffusion process is 1000℃*5 hours. It takes 30 minutes for the first-stage temperature to rise to the second-stage temperature. The aging treatment process is 510℃*8 hours. The density of the final NdFeB magnet is 7.6g / cm 3 .

[0110] Under the same other conditions, the performance of NdFeB magnets made with different coatings was tested. NdFeB 45H was selected as the diffusion substrate (mass percentage PrNd 31%, B 0.95%, Co 0.5%, Al 0.35%, Cu0.2%, Ti 0.25%, Fe balance); the diffusion coating was pure terbium; the variables included whether to add alloy, the coating spraying ratio and the alloy composition ratio; the experimental results are shown in Table 1.

[0111] Table 1 Comparison of NdFeB performance under different experimental conditions

[0112] serial number Alloy Type Spraying amount Br HkDJ Hk / Hcj 1 / 0.6％ 13.28 24.56 0.98 2 Alloy A 0.6％ 13.31 26.04 0.98 3 Alloy B 0.6％ 13.3 25.92 0.98 4 Alloy C 0.6％ 13.33 26.32 0.98 5 Alloy A 0.4％ 13.34 24.60 0.98 6 Alloy B 0.4％ 13.35 24.51 0.98 7 Alloy C 0.4％ 13.36 24.66 0.98

[0113] The spraying amount is the weight increase ratio of the diffusion coating before and after spraying.

[0114] The properties of NdFeB 45H substrate before diffusion are as follows: Br: 13.5 kGs, Hcj: 17 kOe.

[0115] Under the same conditions of heavy rare earth alloy diffusion, the coercivity increase was 1.0-2.0kOe, and the residual magnetism decrease was correspondingly reduced.

[0116] Example 5

[0117] This embodiment provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0118] S21: obtaining raw materials of NdFeB magnets according to the composition ratio, smelting, hydrogen crushing and pulverizing to obtain NdFeB powder.

[0119] S22: adding the alloy provided in some embodiments of the present invention to the NdFeB powder, performing orientation molding and sintering to obtain a NdFeB blank; wherein the addition ratio of the alloy is 0.5% of the mass of the NdFeB powder.

[0120] S23: pickling and phosphating the NdFeB blank, coating the surface with diffusion coating, and heat treating to obtain a NdFeB magnet.

[0121] In this embodiment, the specific process parameters are as follows:

[0122] The low temperature non-dense sintering process is 1050℃*5 hours; vacuum degree ≤0.02Pa. The density of the sintered NdFeB blank is 7.371g / cm 3 , (its conventional process density is 7.55g / cm 3 about).

[0123] Heat treatment includes diffusion treatment and aging treatment. Diffusion treatment includes first-stage diffusion treatment and second-stage diffusion treatment. The first-stage diffusion process is 910℃*10 hours, and the second-stage diffusion process is 1020℃*5 hours. It takes 30 minutes for the first-stage temperature to rise to the second-stage temperature. The aging treatment process is 510℃*8 hours. The density of the final NdFeB magnet is 7.6g / cm 3 .

[0124] Under the same other conditions, the performance of NdFeB magnets made with different coatings was tested. NdFeB 45H was selected as the diffusion substrate (mass percentage PrNd 31%, B 0.95%, Co 0.5%, Al 0.35%, Cu0.2%, Ti 0.25%, Fe balance); the diffusion coating was pure terbium; the variables included whether to add alloys and the composition ratio of the alloys; the experimental results are shown in Table 2.

[0125] Table 2 Comparison of NdFeB performance under different experimental conditions

[0126] serial number Alloy Type Spraying amount Br HkDJ Hk / Hcj 1 / 0.6％ 13.28 24.56 0.98 2 Alloy A 0.6％ 13.28 25.67 0.98 3 Alloy B 0.6％ 13.31 25.51 0.98 4 Alloy C 0.6％ 13.30 25.96 0.98

[0127] The spraying amount is the weight increase ratio of the diffusion coating before and after spraying.

[0128] The properties of NdFeB 45H substrate before diffusion are as follows: Br: 13.5 kGs, Hcj: 17 kOe.

[0129] Under the same conditions of heavy rare earth alloy diffusion, the coercivity increase was 1.0-2.0kOe, and the residual magnetism decrease was correspondingly reduced.

[0130] Example 6

[0131] This embodiment provides a method for preparing a NdFeB magnet, and the steps are the same as those in Embodiment 4. For specific process parameters, see Table 3. The alloy provided in some embodiments of the present invention is added to the diffusion coating, and the addition ratio is 1.2% of the mass of the diffusion coating.

[0132] Example 7

[0133] This embodiment provides a method for preparing a NdFeB magnet, and the steps are the same as those in Embodiment 4. For specific process parameters, see Table 3. The alloy provided in some embodiments of the present invention is added to the diffusion coating, and the addition ratio is 1.3% of the mass of the diffusion coating.

[0134] Example 8

[0135] This embodiment provides a method for preparing a NdFeB magnet, and the steps are the same as those in Embodiment 4. For specific process parameters, see Table 3. The alloy provided in some embodiments of the present invention is added to the diffusion coating, and the addition ratio is 1.4% of the mass of the diffusion coating.

[0136] Example 9

[0137] This embodiment provides a method for preparing a NdFeB magnet, and the steps are the same as those in Embodiment 5. For specific process parameters, see Table 3. Among them, the addition ratio of the alloy is 0.6% of the mass of the NdFeB powder.

[0138] Example 10

[0139] This embodiment provides a method for preparing a NdFeB magnet, and the steps are the same as those in Embodiment 5. For specific process parameters, see Table 3. Among them, the addition ratio of the alloy is 0.7% of the mass of the NdFeB powder.

[0140] Embodiment 11

[0141] This embodiment provides a method for preparing a NdFeB magnet, and the steps are the same as those in Embodiment 5. For specific process parameters, see Table 3. Among them, the addition ratio of the alloy is 0.8% of the mass of the NdFeB powder.

[0142] Table 3 Process parameters of Examples 6-11

[0143]

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An alloy, characterized in that: The alloy is as shown in formula (I); B x Him y You z1 Zr z2 Fe 1-x-y-z1-z2 (Ⅰ); Among them, x, y, z1 and z2 are as follows: 0.9％≤x≤1.5％， 15％≤y≤25％， 5％≤z1≤8％， 2％≤z2≤5％， And 7%≤z1+z2≤10%.

2. The alloy according to claim 1, characterized in that The values ​​of x, y, z1 and z2 are as follows: 0.9% ≤ x ≤ 1.2%, 15% ≤ y ≤ 22%, 5% ≤ z1 ≤ 7%, 3% ≤ z2 ≤ 5%; or 1.0% ≤ x ≤ 1.5%, 18% ≤ y ≤ 25%, 6% ≤ z1 ≤ 8%, 2% ≤ z2 ≤ 4%; or 1.1%≤x≤1.3%, 19%≤y≤21%, 6%≤z1≤7%, 3%≤z2≤4%.

3. A method for preparing the alloy according to claim 1 or 2, characterized in that: The following steps are involved: S11: mixing and smelting alloy raw materials to obtain alloy ingots; S12: crushing the alloy ingot to obtain alloy powder.

4. The preparation method according to claim 3, characterized in that: The crushing includes coarse crushing, disc milling crushing, ball milling crushing; and / or The average particle size of the alloy powder is 1.5-2.5 μm.

5. A neodymium iron boron magnet, characterized in that: Comprising the alloy as claimed in claim 1 or 2.

6. A method for preparing a neodymium iron boron magnet, characterized in that: The following steps are involved: S21: obtaining the raw material of the NdFeB magnet, and smelting and powdering to obtain NdFeB powder; S22: Orienting and molding the NdFeB powder and sintering it to obtain a NdFeB blank; S23: coating a diffusion coating on the surface of the NdFeB blank, and heat treating the blank to obtain the NdFeB magnet; Wherein, the alloy as claimed in claim 1 or 2 is added to the NdFeB powder; and / or The alloy as claimed in claim 1 or 2 is added to the diffusion paint.

7. The preparation method according to claim 6, characterized in that: Adding the alloy to the NdFeB powder, wherein the mass of the alloy added is 0.5-0.8% of the mass of the NdFeB powder; The alloy is added to the diffusion coating, and the mass of the alloy added is 1.2-1.5% of the mass of the diffusion coating.

8. The preparation method according to claim 6, characterized in that: The sintering is low-temperature non-dense sintering; Wherein, the sintering temperature of the low-temperature non-compact sintering is 1020-1050°C; and / or The sintering time of the low-temperature non-compact sintering is 3-5 hours; and / or The vacuum degree of the low-temperature non-compact sintering is ≤0.02Pa; and / or The sintering density of the low-temperature non-densification sintering is 96-98% of the densification density.

9. The preparation method according to claim 6, characterized in that: The heat treatment includes diffusion treatment and aging treatment, and the diffusion treatment includes first-stage diffusion treatment and second-stage diffusion treatment; Wherein, the temperature of the first stage diffusion treatment is 880-920°C; and / or The duration of the first stage diffusion treatment is 10-20 hours; and / or The temperature of the second stage diffusion treatment is 970-1010°C; and / or The duration of the second stage diffusion treatment is 5-10 hours; and / or The aging treatment temperature is 480-520°C; and / or The time of the aging treatment is 5-10 hours.

10. A diffusion coating, characterized in that: Comprising the alloy as claimed in claim 1 or 2.

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