Hard magnetic powder

Abstract

To provide powder for a magnetic member capable of absorbing an electromagnetic wave of extremely high frequency.SOLUTION: A material of hard magnetic powder is an alloy containing Nd: 10.8 atom% or more and 16.0 atom% or less, B: 1.2 atom% or more and 9.0 atom% or less, C: 0.3 atom% or more and 1.0 atom% or less, and O: 15.0 atom% or less. The alloy further contains one or two or more elements selected from a group consisting of Cu, Al, Co, Ga, Dy, and Tb. The balance is Fe and inevitable impurities. The metallographic structure of the alloy contains a Nd2Fe14B-type compound phase and an αFe phase. The intensity ratio (P2 / P1) of a diffraction peak P2 relating to a (110) plane of the αFe phase to a diffraction peak P1 relating to a (410) plane of the Nd2Fe14B-type compound phase is 1.0 or more and 10.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This specification discloses powders having hard magnetic properties. [Background technology]

[0002] Electronic devices such as personal computers and mobile phones have circuits. Radio wave noise emitted from electronic components installed in these circuits causes radio wave interference between electronic components and between electronic circuits. Radio wave interference can lead to malfunctions in electronic devices. To suppress malfunctions, electromagnetic wave absorbing sheets are inserted into electronic devices.

[0003] In recent years, there has been a growing demand for faster communication speeds in information and communication technologies. This high-speed communication utilizes high-frequency radio waves. Furthermore, high-frequency radio waves are also used in on-board radar systems for autonomous driving. Therefore, electromagnetic wave absorbing sheets suitable for use in the high-frequency range are in demand.

[0004] Japanese Patent Publication No. 2020-152979 discloses a magnetic sheet suitable for use in the high-frequency range. This magnetic sheet contains a powder, which consists of numerous flattened particles. The material of this powder is an Fe-Ni-Al-Co alloy.

[0005] Japanese Patent Publication No. 2002-161302 discloses an atomized powder with excellent coercivity. The material of this powder is an Nd-Fe-B alloy. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-152979 [Patent Document 2] Japanese Patent Publication No. 2002-161302 [Overview of the project] [Problems that the invention aims to solve]

[0007] The coercivity of the powder disclosed in Japanese Patent Publication No. 2020-152979 is 31 kA / m or less. This powder is not suitable for absorbing electromagnetic waves with extremely high frequencies.

[0008] The saturation magnetic flux density of the powder disclosed in Japanese Patent Publication No. 2002-161302 is low. This powder is not suitable for absorbing electromagnetic waves with extremely high frequencies.

[0009] The applicant's intention is to provide a powder for a magnetic material that can absorb electromagnetic waves of extremely high frequencies. [Means for solving the problem]

[0010] The hard magnetic powder disclosed herein consists of numerous particles. The material of these particles is Nd: 10.8 atomic% or more and 16.0 mass% or less, B: 1.2 atomic% or more and 9.0 atomic% or less, C: 0.3 atomic% or more and 1.0 atomic% or less, and O: 15.0 atomic% or less This alloy contains one or more elements selected from the group consisting of Cu, Al, Co, Ga, Dy, and Tb. The remainder is Fe and unavoidable impurities. In this alloy, The Cu content is 7.5 atomic percent or less. The Al content is 11.1 atomic percent or less. The Co content is 5.4 atomic percent or less. The Ga content is 4.6 atomic percent or less. The Dy content is 4.2 atomic percent or less. The Tb content is 4.3 atomic percent or less. The metallic structure of this alloy is Nd2Fe 14 It contains a type B compound phase and an αFe phase. Nd2Fe 14The intensity ratio (P2 / P1) of the diffraction peak P2 related to the (110) plane of the αFe phase to the diffraction peak P1 related to the (410) plane of the B-type compound phase is 1.0 or more and 10.0 or less.

[0011] Preferably, the coercive force iHc of the hard magnetic powder is 80 kA / m or more and 500 kA / m or less. Preferably, the saturation magnetic flux density Ms of the hard magnetic powder is 0.90 T or more.

Advantages of the Invention

[0012] In the magnetic member using this hard magnetic powder, electromagnetic waves at extremely high frequencies can be absorbed.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments will be described in detail while appropriately referring to the drawings.

[0014] [Material] The hard magnetic powder according to this embodiment consists of a large number of particles. The material of these particles is an alloy. This alloy contains Nd, B, C, and O. This alloy further contains one or more elements selected from the group consisting of Cu, Al, Co, Ga, Dy, and Tb. Preferably, the balance is Fe and unavoidable impurities.

[0015] [Metallographic Structure] The metallographic structure of this alloy is Nd2Fe 14 contains a B-type compound phase. The powder containing this compound phase has a high coercive force. This metallographic structure further contains an αFe phase. The αFe phase can suppress the decrease in the saturation magnetic flux density caused by the elements added to the alloy.

[0016] [Neodymium (Nd)] Nd is an essential element for the formation of the intermetallic compound (Nd2Fe 14 B). Nd2Fe 14Powders having a B-type compound phase have a high coercive force. From this perspective, in the present embodiment, the Nd content is defined to be 10.8 atomic % or more. This content is more preferably 10.9 atomic % or more, and particularly preferably 11.1 atomic % or more. Excessive Nd precipitates excessive Nd2Fe 14 B-type compound phase. Excessive precipitation inhibits sufficient precipitation of the α-Fe phase and causes a shortage of saturation magnetic flux density. Excessive precipitation further impairs the ductility of the alloy. In the powders to be subjected to the flat rolling described later, excessive Nd2Fe 14 B-type compound phase inhibits processing into flat grains with a large aspect ratio. From the perspective of saturation magnetic flux density and ductility, in the present embodiment, the Nd content is defined to be 16.0 atomic % or less. This content is more preferably 15.0 atomic % or less, and particularly preferably 14.0 atomic % or less.

[0017] [Boron (B)] B is an essential element for the formation of the intermetallic compound (Nd2Fe 14 B). Powders having a Nd2Fe 14 B-type compound phase have a high coercive force. From this perspective, in the present embodiment, the B content is defined to be 1.2 atomic % or more. This content is more preferably 2.0 atomic % or more, and particularly preferably 3.0 atomic % or more. Excessive B precipitates excessive Nd2Fe 14 B-type compound phase. Excessive precipitation inhibits sufficient precipitation of the α-Fe phase and causes a shortage of saturation magnetic flux density. From this perspective, the B content is preferably 9.0 atomic % or less, more preferably 8.5 atomic % or less, and particularly preferably 7.9 atomic % or less.

[0018] [Carbon (C)] From the viewpoint of coercivity, carbon (C) is an essential element for the powder according to this embodiment. The compound obtained by the bonding of C with Nd is presumed to contribute to coercivity. From the viewpoint of coercivity, the C content in this embodiment is specified to be 0.3 atomic percent or more. This content is more preferably 0.4 atomic percent or more, and particularly preferably 0.5 atomic percent or more. Excessive C content leads to excessive precipitation of the compound obtained by the bonding of C with Nd, resulting in a deficiency in saturation magnetic flux density. From this viewpoint, the C content in this embodiment is specified to be 1.0 atomic percent or less. This content is more preferably 0.9 atomic percent or less, and particularly preferably 0.8 atomic percent or less.

[0019] [Oxygen (O)] O inevitably enters the alloy during atomization and flattening. O reacts with Nd to form oxides, such as Nd2O3. This oxide formation is Nd2Fe 14 This leads to a decrease in the amount of type B compound phase formed, which inhibits the coercivity of the powder. From the viewpoint of coercivity, in this embodiment, the O content is specified to be 15.0 atomic% or less. This content is more preferably 13.0 atomic% or less, and particularly preferably 11.0 atomic% or less.

[0020] [Copper (Cu)] In alloys containing Cu, an NdCu phase can precipitate. The NdCu phase is a nonmagnetic phase. On the other hand, Nd2Fe 14 The B-type compound phase and the αFe phase are ferromagnetic phases. Nd2Fe 14 In alloys where the NdCu phase is precipitated at the grain boundaries of the type B compound phase or the αFe phase, the propagation of magnetic moment reversal can be inhibited. This alloy exhibits excellent coercivity. From the viewpoint of coercivity, the Cu content is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. Excess Cu leads to excessive precipitation of the NdCu phase, resulting in a decrease in coercivity. From the viewpoint of coercivity, the Cu content is preferably 7.5 atomic% or less, more preferably 7.0 atomic% or less, and particularly preferably 6.5 atomic% or less. Cu is not an essential element. In other words, the Cu content may be below the detection limit.

[0021] [Aluminum (Al)] In alloys containing Al, the NdAl phase can precipitate. The NdAl phase is a nonmagnetic phase. Nd2Fe 14 In alloys where the NdAl phase is precipitated at the grain boundaries of the type B compound phase or the αFe phase, the propagation of magnetic moment reversal can be inhibited. This alloy exhibits excellent coercivity. From the viewpoint of coercivity, the Al content is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. Excess Al leads to excessive precipitation of the NdAl phase, resulting in a decrease in coercivity. From the viewpoint of coercivity, the Al content is preferably 11.1 atomic% or less, more preferably 9.5 atomic% or less, and particularly preferably 9.0 atomic% or less. Al is not an essential element. In other words, the Al content may be below the detection limit.

[0022] [Cobalt (Co)] Co can contribute to the coercivity of the powder. From the viewpoint of coercivity, the Co content is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. Excess Co leads to the excessive precipitation of Nd-rich phases, resulting in a decrease in coercivity. From the viewpoint of coercivity, the Co content is preferably 5.4 atomic% or less, more preferably 5.0 atomic% or less, and particularly preferably 4.5 atomic% or less. Co is not an essential element. In other words, the Co content may be below the detection limit.

[0023] [Gallium (Ga)] In alloys containing Ga, an NdGa phase may precipitate. The NdGa phase is a nonmagnetic phase. Nd2Fe 14In alloys where the NdGa phase is precipitated at the grain boundaries of the type B compound phase or the αFe phase, the propagation of magnetic moment reversal can be inhibited. This alloy exhibits excellent coercivity. From the viewpoint of coercivity, the Ga content is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. Excess Ga leads to excessive precipitation of the NdGa phase, resulting in a decrease in coercivity. From the viewpoint of coercivity, the Ga content is preferably 4.6 atomic% or less, more preferably 4.0 atomic% or less, and particularly preferably 3.5 atomic% or less. Ga is not an essential element. In other words, the Ga content may be below the detection limit.

[0024] [Dysprosium (Dy)] Dy is Nd2Fe 14 It contributes to the crystalline magnetic anisotropy of the type B compound phase. Alloys containing Dy exhibit excellent coercivity. From the viewpoint of coercivity, the Dy content is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. Excess Dy leads to a decrease in saturation magnetic flux density. From the viewpoint of saturation magnetic flux density, the Dy content is preferably 4.2 atomic% or less, more preferably 4.0 atomic% or less, and particularly preferably 3.8 atomic% or less. Dy is not an essential element. In other words, the Dy content may be below the detection limit.

[0025] [Terbium (Tb)] Tb is Nd2Fe 14 It contributes to the crystalline magnetic anisotropy of the type B compound phase. Alloys containing Tb exhibit excellent coercivity. From the viewpoint of coercivity, the Tb content is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. Excess Tb leads to a decrease in saturation magnetic flux density. From the viewpoint of saturation magnetic flux density, the Tb content is preferably 4.3 atomic% or less, more preferably 4.1 atomic% or less, and particularly preferably 3.9 atomic% or less. Tb is not an essential element. In other words, the Tb content may be below the detection limit.

[0026] [Cu, Al, Co, Ga, Dy and Tb] As mentioned above, Cu, Al, Co, Ga, Dy, and Tb are not essential elements. On the other hand, it is necessary for the alloy to contain one or more elements selected from the group consisting of Cu, Al, Co, Ga, Dy, and Tb. Alloys containing Cu, Al, Co, Ga, Dy, or Tb have high coercivity. From the viewpoint of coercivity, the total content of Cu, Al, Co, Ga, Dy, and Tb is preferably 0.1 atomic% or more, more preferably 0.3 atomic% or more, and particularly preferably 0.5 atomic% or more. The total content is preferably 15.0 atomic% or less, more preferably 13.0 atomic% or less, and particularly preferably 11.0 atomic% or less.

[0027] [Remainder] In this embodiment, the remainder of the alloy consists of Fe and unavoidable impurities. The Fe content is preferably 50 atomic% or more, more preferably 53 atomic% or more, and particularly preferably 55 atomic% or more.

[0028] [Diffraction peak] As mentioned above, in this powder, Nd2Fe 14 The B-type compound phase contributes to coercivity, and the αFe phase contributes to saturation magnetic flux density. From the viewpoint of achieving both coercivity and saturation magnetic flux density, the alloy is Nd2Fe. 14 It is preferable that the B-type compound phase and the αFe phase are contained in a well-balanced manner. Nd2Fe 14 The intensity ratio (P2 / P1) of the diffraction peak P2 of the αFe phase relative to the diffraction peak P1 of the type B compound phase relative to the (410) plane is preferably 1.0 or more and 10.0 or less. Powders with this intensity ratio (P2 / P1) of 1.0 or more have a large saturation magnetic flux density. From this viewpoint, this intensity ratio (P2 / P1) is more preferably 2.0 or more, and particularly preferably 3.0 or more. Powders with this intensity ratio (P2 / P1) of 10.0 or less have a large coercivity. From this viewpoint, this intensity ratio (P2 / P1) is more preferably 9.0 or less, and particularly preferably 8.0 or less.

[0029] Diffraction peaks P1 and P2 are measured using an X-ray diffractometer. The measurement conditions are as follows: X-ray source: CuKα ray Scan speed: 4° / min Amount of powder used for measurement: 1.0g

[0030] As a means of bringing the intensity ratio (P2 / P1) within the above range, the atomized powder is subjected to heat treatment. This heat treatment is preferably carried out in an argon gas atmosphere, with a heating rate of 1°C / min to 20°C / min, holding at 500°C to 800°C for 0.5 hours to 3 hours, and cooling at a rate of 0.1°C / min to 3°C / min.

[0031] [Particle shape] In this embodiment, each particle has a flattened shape. These particles can absorb high-frequency electromagnetic waves. The particles may also have a spherical shape. The powder may contain both flattened and spherical particles. The powder may also contain particles of other shapes.

[0032] [Coercivity iHc] Coercivity iHc is the strength of the external magnetic field required to return a magnetized magnetic material to an unmagnetized state. Powders with a high coercivity iHc can absorb high-frequency electromagnetic waves because the rise frequency of the imaginary permeability is increased. From this viewpoint, the coercivity iHc of the powder is preferably 80 kA / m or higher, more preferably 90 kA / m or higher, and particularly preferably 100 kA / m or higher. This powder is hard magnetic. Powders with excessively high coercivity iHc cannot react to weak external magnetic fields. From this viewpoint, the coercivity iHc of the powder is preferably 500 kA / m or less, more preferably 400 kA / m or less, and particularly preferably 300 kA / m or less.

[0033] The coercivity iHc is measured using a vibrating sample magnetometer (VSM). The measurement conditions are as follows: Maximum applied magnetic field: 1204kA / m Powder mass: approximately 70 mg

[0034] [Saturation magnetic flux density Ms] Saturated magnetic flux density (Ms) is the magnetic flux density when a magnetic field is applied to a powder that is in a state of zero magnetic flux density and it saturates to a certain value. Powders with a low saturated magnetic flux density (Ms) cannot respond to a weak external magnetic field. From this viewpoint, the saturated magnetic flux density (Ms) of the powder is preferably 0.90 T or higher, more preferably 0.95 T or higher, and particularly preferably 1.00 T or higher. The saturated magnetic flux density (Ms) is measured in the same way as the coercivity (iHc).

[0035] [Powder manufacturing] The powder according to this embodiment can be obtained by gas atomization, water atomization, disc atomization, grinding, etc. Gas atomization is preferred. In gas atomization, the cooling rate is relatively slow. In gas atomization, oxidation is minimal.

[0036] In the gas atomization method, the raw metal is heated and melted to obtain molten metal. This molten metal flows out of a nozzle. Gas (typically argon gas) is blown onto this molten metal. The energy of this gas causes the molten metal to pulverize into droplets, which are cooled as they fall. These droplets solidify, forming particles. In this gas atomization method, the molten metal instantly condenses into droplets and cools simultaneously, resulting in a uniform microstructure. Moreover, because droplets are formed continuously, the compositional differences between particles are extremely small.

[0037] This powder is subjected to classification and heat treatment as needed. The preferred heat treatment temperature is between 500°C and 800°C.

[0038] In the production of flattened powders, the raw material powder obtained by atomization is subjected to heat treatment and then flattened. Typical flattening is performed using an atomizer. Flattening aids such as stearic acid may be used in the flattening process. The heat treatment preceding the flattening process does not impair the coercivity iHc obtained by the flattening process. [Examples]

[0039] The effects of the powders described in the examples below will be revealed, but the scope disclosed herein should not be interpreted as limiting based on the description of these examples.

[0040] [Example 1] The raw material powder was obtained by gas atomization. This raw material powder was subjected to classification to remove particles with a particle size of 106 μm or larger. This raw material powder was held in an argon gas atmosphere at 600°C for 1 hour and slowly cooled to obtain the powder of Example 1. The composition of this powder is shown in Table 1 below.

[0041] [Examples 2-9 and Comparative Examples 1-7] Powders for Example 2-9 and Comparative Example 1-7 were obtained in the same manner as in Example 1, except that the composition was as shown in Tables 1 and 2 below.

[0042] [Example 10] The raw material powder was obtained by gas atomization. This raw material powder was classified to remove particles with a particle size of 106 μm or larger. This raw material powder was held in an argon gas atmosphere at 600°C for 1 hour and then slowly cooled. 500 g of this raw material powder was placed in an attritor. 1.4 kg of naphthenic solvent was also placed in the attritor. 4.8 mm SUJ2 was used as the powder media. The powder was flattened using this attritor to obtain the powder of Example 10, which consists of flattened particles. The composition of this powder is shown in Table 1 below.

[0043] [Examples 11-19 and Comparative Examples 8-14] Powders for Examples 11-19 and Comparative Examples 8-14 were obtained in the same manner as in Example 10, except that the composition was as shown in Tables 1 and 2 below.

[0044] [Analysis of ingredients] The alloy's composition was analyzed. The timing of the analysis is as follows: Content of elements excluding C and O Spherical particles: Measured using powder after heat treatment. Flattened particles: Measured using powder after heat treatment but before flattening. C and O content Spherical particles: Measured using powder after heat treatment. Flattened particles: Measured using powder after heat treatment and flattening. The content of elements other than C and O was measured using an ICP (Inductive Coupled Plasma) emission spectrometer. The content of C was measured by combustion-infrared absorption spectroscopy. The content of O was measured by inert gas transport fusion-infrared absorption spectroscopy. These results are shown in Tables 1 and 2 below.

[0045] [Coercivity and saturation magnetic flux density] The coercivity iHc of each powder was measured using the method described above. Furthermore, the saturation magnetic flux density Ms of each powder was measured using the method described above. These results are shown in Tables 1 and 2 below.

[0046] [Table 1]

[0047] [Table 2]

[0048] As shown in Tables 1 and 2, the coercivity iHc and saturation magnetic flux density Ms of the powders in each example are high. This evaluation clearly demonstrates the superiority of this hard magnetic powder. [Industrial applicability]

[0049] The hard magnetic powder described above is suitable for various magnetic components.

Claims

1. A hard magnetic powder consisting of numerous particles, The material of these particles is Nd: 10.8 at% or more and 16.0 at% or less, B: 1.2 at% or more and 9.0 at% or less, C: 0.3 atomic% or more and 1.0 atomic% or less, and O: 15.0 atomic% or less It contains, and further It contains one or more elements selected from the group consisting of Cu, Al, Co, Ga, Dy, and Tb. The remainder is an alloy consisting of Fe and unavoidable impurities. In the above alloy, The Cu content is 7.5 atomic percent or less. The Al content is 11.1 atomic percent or less. The Co content is 5.4 atomic percent or less. The Ga content is 4.6 atomic percent or less. The Dy content is 4.2 atomic percent or less. The Tb content is 4.3 atomic percent or less. The total content of Cu, Al, Co, Ga, Dy, and Tb is between 0.1 atomic% and 15.0 atomic%. The metallic structure of the above alloy is Nd ２ Fe １４ It contains a type B compound phase and an αFe phase. The above Nd ２ Fe １４ A hard magnetic powder in which the intensity ratio (P2 / P1) of the diffraction peak P2 of the αFe phase relating to the (110) plane to the diffraction peak P1 relating to the (410) plane of the type B compound phase is 1.0 or more and 10.0 or less.

2. The hard magnetic powder according to claim 1, wherein its coercivity iHc is 80 kA / m or more and 500 kA / m or less.

3. The hard magnetic powder according to claim 1 or 2, wherein the saturation magnetic flux density Ms is 0.90 T or higher.

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