JP-7856480-B2 - hard magnetic powder

Inventors

• 細見 凌平
• 澤田 俊之

Assignees

• 山陽特殊製鋼株式会社

Dates

Publication Date

20260511

Application Date

20220509

Claims (3)

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 at% or more and 1.0 at% or less, It contains O: 15.0 atomic% or less, and further 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 contains an Nd₂Fe₁₄B - type compound phase and an αFe phase. 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 Nd2Fe14 B-type 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 its saturation magnetic flux density Ms is 0.90 T or higher.

Description

This specification discloses powders having hard magnetic properties. 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. This interference can lead to malfunctions in electronic devices. To suppress these malfunctions, electromagnetic wave absorbing sheets are inserted into electronic devices. 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 high demand. 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. Japanese Patent Publication No. 2002-161302 discloses an atomized powder with excellent coercivity. The material of this powder is an Nd-Fe-B alloy. Japanese Patent Publication No. 2020-152979Japanese Patent Publication No. 2002-161302 The following describes preferred embodiments in detail, with reference to drawings as appropriate. [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 remainder is Fe and unavoidable impurities. [Metal structure] The microstructure of this alloy contains a Nd₂Fe₁₄B - type compound phase. Powder containing this compound phase exhibits high coercivity. This microstructure further contains an αFe phase. The αFe phase can suppress the decrease in saturation magnetic flux density caused by the elements added to the alloy. [Neodymium (Nd)] Nd is an essential element for the formation of intermetallic compounds ( Nd₂Fe₁₄B ). Powders having the Nd₂Fe₁₄B type compound phase have high coercivity. From this viewpoint, in this embodiment, the Nd content is specified 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. Excess Nd causes the precipitation of excess Nd₂Fe₁₄B type compound phase. Excessive precipitation inhibits the sufficient precipitation of the αFe phase, leading to insufficient saturation magnetic flux density. Excessive precipitation further impairs the ductility of the alloy. In powders subjected to flattening as described later, excess Nd₂Fe₁₄B type compound phase inhibits processing into flattened grains with a large aspect ratio. From the viewpoint of saturation magnetic flux density and ductility, in this embodiment, the Nd content is specified 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. [Boron (B)] B is an essential element for the formation of intermetallic compounds ( Nd₂Fe₁₄B ). Powders having an Nd₂Fe₁₄B - type compound phase have high coercivity. From this viewpoint, in this embodiment, the B content is specified to be 1.2 atomic percent or more. This content is more preferably 2.0 atomic percent or more, and particularly preferably 3.0 atomic percent or more. Excess B causes the precipitation of excess Nd₂Fe₁₄B - type compound phase. Excess precipitation inhibits the sufficient precipitation of the αFe phase and leads to a deficiency in saturation magnetic flux density. From this viewpoint, the B content is preferably 9.0 atomic percent or less, more preferably 8.5 atomic percent or less, and particularly preferably 7.9 atomic percent or less. [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. [Oxygen (O)] O inevitably becomes mixed into the alloy during atomization and flattening. O reacts with Nd to form oxides, typic