Magnetic material including spherical powder and method for fabricating magnet

Abstract

The disclosed magnetic material comprises spherical RE-Fe-B alloy powder containing rare earth elements (RE) and rare earth compound powder. In the RE-Fe-B alloy powder, RE represents one or more combinations of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y). The content of rare earth elements in the RE-Fe-B alloy powder is 10 at% or less, and the content of the rare earth compound powder is 7 weight% or more of the total magnetic material. The magnetic material is applicable to various additive manufacturing processes and can improve the performance of magnets.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a magnet, and more specifically, to a magnetic material comprising spherical powder and a method for manufacturing a magnet. Background Technology

[0002] Recently, the demand for high-performance motors is rapidly increasing due to the growth of next-generation mobility industries such as electric vehicles, drones, and robots. The driving principle of an electric motor involves a soft magnetic stator generating a rotating magnetic field to convert electrical energy into magnetic energy, and a hard magnetic rotor rotating along the magnetic field to convert the magnetic energy into mechanical energy, which serves as power.

[0003] To increase motor efficiency, technology is required to optimize the distribution of magnetic flux within the motor through shape control of the soft magnetic stator and permanent magnet rotor. In particular, for the permanent magnet components of the rotor, which are the core of motor performance, if the existing 2D shape is implemented into a 3D shape of the Ellipse / Helix type, it is possible to maximize motor performance by improving rotor rigidity and increasing motor efficiency through enhanced cooling effects.

[0004] However, since conventional powder metallurgy permanent magnet manufacturing technology can only produce simple shapes such as rectangular prisms and cylinders, a new manufacturing process with high design freedom and precision is required to manufacture permanent magnets with complex three-dimensional shapes.

[0005] 3D printing (3DP) technology is a bottom-up process that manufactures three-dimensional shapes by stacking layers one by one. It is called Additive Manufacturing (AM) technology and is receiving great interest in various industries because it enables the manufacturing of parts with complex shapes.

[0006] In particular, the laser powder bed fusion (LPBF) method, which is the most widely used method among various additive manufacturing technologies, is attracting attention as a new process for manufacturing three-dimensional permanent magnets because it has excellent design freedom and precision.

[0007] However, Nd-Fe-B permanent magnets exhibit strong brittleness, and due to the content of highly volatile rare earth elements, it is difficult to manufacture spherical powders; furthermore, their mechanical properties, which are susceptible to thermal stress, make them difficult to apply to additive manufacturing processes.

[0008] In particular, the powder composition of spherical permanent magnets (MQP-S) currently applicable to additive manufacturing processes has a rare earth element (RE element) content that is half the level of commercial Nd-Fe-B permanent magnets, making it suitable for Nd2Fe 14 There is a problem in that a compositional region is formed in which the formation of phase B is difficult and a large amount of soft magnetic ferrite phase is precipitated, which adversely affects permanent magnet performance. The problem to be solved

[0009] The technical problem of the present invention is conceived in this regard and is to provide a magnetic material that can be used to manufacture permanent magnets through an additive manufacturing method and can improve magnetic performance.

[0010] Another objective of the present invention is to provide a method for forming a magnet through additive manufacturing with the magnetic material.

[0011] However, the problem that the present invention aims to solve is not limited to the problem mentioned above, and may be expanded in various ways without departing from the spirit and scope of the present invention. means of solving the problem

[0012] A magnetic material for realizing the purpose of the present invention described above comprises spherical RE-Fe-B alloy powder containing rare earth elements (RE) and rare earth compound powder. In the RE-Fe-B alloy powder, RE represents one or more combinations of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y), and the content of rare earth elements in the RE-Fe-B alloy powder is 10 at% or less, and the content of the rare earth compound powder is 7 weight% or more of the total magnetic material.

[0013] According to one embodiment, the RE-Fe-B alloy powder contains 7 at% to 8 at% of Nd and 0.5 at% to 1 at% of Pr.

[0014] According to one embodiment, the RE-Fe-B alloy powder comprises 7 at% to 8 at% of Nd, 0.5 at% to 1 at% of Pr, 2 at% to 3 at% of cobalt (Co), 8 at% to 10 at% of B, 2 at% to 3 at% of zirconium (Zr), 2 at% to 3 at% of titanium (Ti), and the remainder being Fe.

[0015] According to one embodiment, the average particle size of the RE-Fe-B alloy powder is 30 μm to 40 μm, the average particle size of the rare earth compound powder is 30 μm to 40 μm, and the difference between the average particle size of the RE-Fe-B alloy powder and the average particle size of the rare earth compound powder is within 5 μm.

[0016] According to one embodiment, the rare earth compound powder comprises at least one selected from the group consisting of rare earth fluorides, rare earth hydrides, and rare earth nitrides.

[0017] According to one embodiment, the rare earth compound powder is spherical and contains a rare earth fluoride.

[0018] According to one embodiment, the content of the rare earth compound is 7% to 8% by weight of the total magnetic material.

[0019] A method for manufacturing a magnet according to one embodiment of the present invention comprises the steps of: providing a magnetic material comprising a spherical RE-Fe-B alloy powder containing rare earth elements (RE) and a rare earth compound powder onto a substrate to form a powder layer; and melting the powder layer to form a rapidly solidified magnetic body. In the RE-Fe-B alloy powder, RE represents one or more combinations of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y), wherein the content of the rare earth element in the RE-Fe-B alloy powder is 10 at% or less, and the content of the rare earth compound is 7 weight% or more of the total magnetic material. The magnetic body is a spherical RE-Fe-B alloy powder with a higher content of RE2Fe. 14 Includes B. Effects of the invention

[0020] According to embodiments of the present invention, by adding a rare earth compound to spherical magnetic powder, the magnetic material has a fluidity suitable for additive manufacturing, and RE2Fe 14 Magnetic performance can be improved by increasing the content of the B phase and suppressing the α-Fe phase.

[0021] The magnetic material according to the embodiments of the present invention can be applied to various additive manufacturing processes and can be utilized for forming high-density molded bodies having complex shapes or free-form shapes and for manufacturing high-performance permanent magnets.

[0022] Accordingly, by bringing flexibility to the shape design, it is possible to miniaturize and lighten magnetic components such as permanent magnets, and improve the efficiency of electric systems such as motors through magnetic circuit optimization. Brief explanation of the drawing

[0023] FIG. 1 is a flowchart illustrating a method for manufacturing a magnet according to one embodiment of the present invention. FIG. 2 is a schematic diagram illustrating the composition of a magnetic material according to one embodiment of the present invention. FIG. 3 is a side view illustrating a laser powder stacking melting system used in a method for manufacturing a magnet according to one embodiment of the present invention. Figure 4 is a graph showing the residual magnetism (Br), coercivity (Hcj), and maximum magnetic energy ((BH)max) of a molded body (Nd-Fe-B-based permanent magnet) fabricated by additive manufacturing (L-PBF) using the mixed powder of Example 1 of the present invention (laser power: 125W). Specific details for implementing the invention

[0024] Hereinafter, a method for manufacturing a magnetic material and a magnet according to embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. In the attached drawings, the dimensions of the structures are shown enlarged compared to the actual dimensions for the clarity of the present invention.

[0025] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0027] FIG. 1 is a flowchart illustrating a method for manufacturing a magnet according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating the composition of a magnetic material according to an embodiment of the present invention. FIG. 3 is a side view illustrating a laser powder stacking melting system used in a method for manufacturing a magnet according to an embodiment of the present invention.

[0028] According to one embodiment, the method for manufacturing a magnet of the present invention is performed by an additive manufacturing method. An additive manufacturing method may mean a method of forming a layer by placing a printing material and then melting and solidifying (rapid solidification) a predetermined area according to a design, and then forming a layered structure of layers by placing a printing material again on the layer and melting and solidifying according to a design.

[0029] Referring to FIG. 1, a powder layer is formed by providing a powdered magnetic material on a substrate such as a bed (S10). Next, the powder layer is melted to form a magnetic body (magnet) (S20). By repeating the formation of the powder layer and the melting of the powder layer, the height of the magnetic body in the vertical direction can be increased. In addition, a three-dimensional magnet with a complex shape can be formed by adjusting the melting area during each powder layer melting.

[0030] The magnetic material comprises spherical powder. According to one embodiment, the magnetic material may comprise spherical RE-Fe-B alloy powder (10) and rare earth compound powder (20). RE represents one or more combinations of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y). According to one embodiment, RE may include Nd.

[0031] For example, the rare earth compound may include a fluoride of any one of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y), or a combination of two or more fluorides. However, embodiments of the present invention are not limited thereto, and the rare earth compound may include a rare earth hydride or a rare earth nitride. For example, the rare earth compound may include a hydride of any one of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y), or a combination of two or more hydrides. In addition, the rare earth compound may include any one of the nitrides of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y), or a combination of two or more nitrides.

[0032] Preferably, the rare earth compound powder may have a spherical shape. According to one embodiment, the rare earth compound may include yttrium fluoride (YF3), which is easy to manufacture into a spherical powder.

[0033] For example, the content of rare earth elements in the RE-Fe-B alloy powder may be 10 at% or less, or 9 at% or less. If the content of rare earth elements is high, it is difficult to obtain spherical RE-Fe-B alloy powder. For example, the content of rare earth elements in the RE-Fe-B alloy powder may be 9 at% or more and 10 at% or less. According to one embodiment, the RE-Fe-B alloy powder may contain 7 at% to 8 at% of Nd and 0.5 at% to 1 at% of Pr. More specifically, the RE-Fe-B alloy powder may contain 7 at% to 8 at% of Nd, 0.5 at% to 1 at% of Pr, 2 at% to 3 at% of cobalt (Co), 8 at% to 10 at% of B, 2 at% to 3 at% of zirconium (Zr), 2 at% to 3 at% of titanium (Ti), and the remainder being Fe.

[0034] For example, the average particle size of the RE-Fe-B-based powder may be 10 µm to 60 µm, 20 µm to 50 µm, or 30 µm to 40 µm. According to one embodiment, the average particle size of the RE-Fe-B-based powder is 30 µm to 40 µm, the average particle size of the rare earth compound is 30 µm to 40 µm, and the difference between the average particle size of the RE-Fe-B-based powder and the average particle size of the rare earth compound may be within 5 µm. If the difference between the average particle size of the RE-Fe-B-based powder and the average particle size of the rare earth compound is large, the fluidity of the entire powder may decrease.

[0035] According to one embodiment, in order to increase the uniformity of the entire powder, the RE-Fe-B-based powder and the rare earth compound can be mixed by a ball milling method.

[0036] The composition of the magnetic material as described above can have excellent spreadability and flowability, and accordingly, a three-dimensional magnet can be stably formed through an additive manufacturing process. According to one embodiment, the Hausner ratio of the entire magnetic material may be 1.0 to 1.26, and the flowability measured by a hall flowmeter may be 5 sec / 50g or less, or 3 sec / 50g or less.

[0037] According to one embodiment, the content of the rare earth compound powder may be 7 weight percent or more of the total magnetic material. If the content of the rare earth compound powder is 7 weight percent or less, an α-Fe (ferrite) phase is formed, and RE2Fe 14 The magnetic properties may be degraded as the content of phase B decreases. If the content of the rare earth compound powder is excessive, the amount of non-metallic elements (e.g., fluorine) volatilized during the melting process increases, which may increase the voids within the magnet and thus degrade the magnetic properties. For example, the content of the rare earth compound powder may be 7% to 10% by weight, or 7% to 8% by weight.

[0038] According to one embodiment, the method for manufacturing the magnet may utilize a laser powder bed fusion (L-PBF) method.

[0039] Referring to FIG. 3, the L-PBF system includes a bed (120) on which a powder magnetic material (110) is placed, a powder supply unit for providing the powder magnetic material, and a heating device for melting the magnetic material.

[0040] For example, the powder supply unit includes a supply piston (132) for raising the magnetic material (110). When the supply piston (132) raises the magnetic material (110), a roller (134) supplies the magnetic material (110) to the bed (120) to form a powder layer. The heating device may include a laser generating unit (142) and a scanning unit (144). The scanning unit (144) selectively provides a laser generated from the laser generating unit (142) to the powder layer to melt a predetermined area, and a magnetic layer rapidly solidified by cooling is formed.

[0041] When the magnetic layer is formed, the bed (120) is lowered to a certain depth, and a powder layer is formed on the magnetic layer by the operation of the powder supply unit.

[0042] By repeating the above operation, a three-dimensional magnet (200) can be formed.

[0043] Although a method using laser powder melting (LPBF) has been described above, the embodiments of the present invention are not limited thereto, and various known additive manufacturing methods such as electron beam melting (EBM), direct energy deposition (DED), and binder jetting may be used.

[0044] According to embodiments of the present invention, by adding a rare earth compound to spherical magnetic powder, the magnetic material has a fluidity suitable for additive manufacturing, and RE2Fe 14 Magnetic performance can be improved by increasing the content of the B phase and suppressing the α-Fe phase.

[0045] For example, a magnet obtained from the above magnetic material has a higher RE2Fe than spherical magnetic powder. 14The content of phase B may be (e.g., 60% or more or 70% or more), and the formation of the α-Fe phase may be suppressed (e.g., 1% or less).

[0046] The magnetic material according to the embodiments of the present invention can be applied to various additive manufacturing processes and can be utilized for forming high-density molded bodies having complex shapes or free-form shapes and for manufacturing high-performance permanent magnets.

[0047] Accordingly, by bringing flexibility to the shape design, it is possible to miniaturize and lighten magnetic components such as permanent magnets, and improve the efficiency of electric systems such as motors through magnetic circuit optimization.

[0048] Below, we will examine the fabrication and effects according to the embodiments of the present invention through specific experimental examples.

[0049] Example 1

[0050] Nd 7.5 Pr 0.7 Fe 75.4 Co 2.5 B 8.8 Zr 2.6 Ti 2.5 Spherical Nd-Fe-B permanent magnet powder (MQP-S-11-9, average particle size D50 (median diameter) approximately 33.3 μm, Hall flowability 2.29 sec / 50 g) having a composition of (unit: at%) was mixed with spherical YF3 powder (average particle size D50 approximately 35 μm) (so that the YF3 powder was 7 wt% of the total powder weight).

[0051] Mixing was performed using a rotary 3D mixing machine, with the mixing time set to 90 minutes and the mixing speed to 100 rpm. The mixed powder exhibited an average particle size D50 of approximately 34.4 μm and flow characteristics of 2.91 sec / 50 g, confirming that composite powder characteristics suitable for additive manufacturing processes were secured.

[0052] Magnet production

[0053] Nd-Fe-B permanent magnets were fabricated using the additive manufacturing method (L-PBF) with the mixed powder of Example 1. The fabricated bodies were designed in a cylindrical shape with a diameter of 10 mm and a height of 6.5 mm. A total of 24 specimens were arranged on a build plate, with a spacing of 3 mm between each specimen. The laser output was set to 125 W, 135 W, and 140 W, and the scan speed was varied to four values ​​(475, 550, 625, and 775 mm / s) to implement various heat input conditions. The layer thickness per layer was fixed at 50 μm, and the hatching spacing at 60 μm; for each layer, the laser scanning direction was rotated by 90°.

[0054] FIG. 4 is a graph showing the residual magnetism (Br), coercivity (Hcj), and maximum magnetic energy ((BH)max) of a molded body (Nd-Fe-B-based permanent magnet) fabricated by additive manufacturing (L-PBF) using the mixed powder of Example 1 of the present invention (laser power: 125W). In FIG. 4, the residual magnetism, coercivity, and maximum magnetic energy of a molded body obtained using commercial powder (MQP-S-11-9) as a comparative example are shown.

[0055] Referring to Fig. 4, it was confirmed that Nd-Fe-B permanent magnets can be manufactured using an additive manufacturing method (L-PBF) with the sealing of the present invention, and that the coercivity is significantly improved.

[0056] Although the invention has been described above with reference to embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims. Industrial applicability

[0057] The present invention can be utilized in the production of various magnets, and, for example, in the production of permanent magnets for electric motors such as motors. Explanation of the symbols

[0058] 10: RE-Fe-B alloy powder 20: Rare earth compound powder 110: Magnetic materials 120: Bed 132: Supply Piston 134: Roller 142: Laser generator 144: Scanning section 200: Magnet

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 The method comprises the steps of: providing a magnetic material comprising spherical RE-Fe-B alloy powder containing rare earth elements (RE) and spherical rare earth fluoride powder onto a bed to form a powder layer; and melting the powder layer to form a rapidly solidified magnetic body, wherein in the RE-Fe-B alloy powder, RE represents one or more combinations of neodymium (Nd), cerium (Ce), lanthanum (La), dysprosium (Dy), terbium (Tb), praseodymium (Pr), and yttrium (Y), wherein the content of rare earth elements in the RE-Fe-B alloy powder is 10 at% or less, the content of the rare earth fluoride powder is 7% to 8% by weight of the total magnetic material, and the RE2Fe of the rapidly solidified magnetic body 14 The content of phase B is RE2Fe of the spherical RE-Fe-B alloy powder. 14 A method for manufacturing a magnet with a content greater than that of phase B. Claim 9 A method for manufacturing a magnet according to claim 8, wherein a laser is irradiated to melt the powder layer. Claim 10 A method for manufacturing a magnet according to claim 8, wherein the RE-Fe-B alloy powder and the rare earth fluoride powder are mixed through ball milling. Claim 11 A method for manufacturing a magnet according to claim 8, wherein the step of forming the powder layer and the step of forming the magnetic body are repeated to form a magnet of a three-dimensional shape. Claim 12 A method for manufacturing a magnet according to claim 8, wherein the RE-Fe-B alloy powder comprises 7 at% to 8 at% Nd, 0.5 at% to 1 at% Pr, 2 at% to 3 at% cobalt (Co), 8 at% to 10 at% B, 2 at% to 3 at% zirconium (Zr), 2 at% to 3 at% titanium (Ti), and the remainder being Fe. Claim 13 A method for manufacturing a magnet according to claim 8, wherein the average particle size of the RE-Fe-B alloy powder is 30㎛ to 40㎛, the average particle size of the rare earth fluoride powder is 30㎛ to 40㎛, and the difference between the average particle size of the RE-Fe-B alloy powder and the average particle size of the rare earth fluoride powder is within 5㎛. Claim 14 delete

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