Soft magnetic metal powder, molded body thereof, and sintered body thereof

Abstract

The present invention provides a soft magnetic metal powder that allows for a reduction in the energy load associated with sintering, with excellent magnetic properties and sintered body strength.　Provided is a soft magnetic metal powder containing one or more metal elements selected from Fe, Ni, and Co. After this soft magnetic metal powder is heat-treated at 450 °C, the specific surface area thereof is 90% or less of the specific surface area before the heat treatment. Also provided is a soft magnetic metal powder that contains one or more metal elements selected from Fe, Ni, and Co, has an average primary particle diameter between 0.05 μm and 2.0 μm inclusive, and further contains 1.0 wt% or more of O.

Description

Soft magnetic metal powder, its compact, and its sintered body

[0001] The present disclosure relates to a soft magnetic metal powder, a molded body thereof, and a sintered body thereof.

[0002] In recent years, there has been a demand for miniaturization and high integration of electronic components such as inductors, magnetic cores, and magnetic heads in order to improve device performance. In particular, soft magnetic metal powder materials are characterized by their high saturation magnetic flux density. Therefore, demand for soft magnetic metal powder materials is expected to continue to grow in the future.

[0003] Generally, these soft magnetic metal powder materials are molded and mounted on electronic components, and therefore, if the molded body has low strength, there is a risk that the molded body will break when subjected to impact.

[0004] To improve the strength of a compact, a method of sintering powders by heat treatment is known. Typically, in the case of soft magnetic metal powder materials, sintering proceeds by heat treatment at a high temperature of about 1000°C.

[0005] However, heat treatment at high temperatures requires a lot of energy, can place a large load on components such as coils, and requires expensive, specialized equipment, such as a baking furnace, that can withstand high temperatures.

[0006] Increasing the packing density of soft magnetic metal powder is also effective in improving the strength of sintered bodies. Generally, soft magnetic metal powders used in electronic components have particle sizes ranging from several μm to several tens of μm. For high-density packing, it is considered ideal to combine powders with submicron-sized particle sizes that can fill the gaps between the powders.

[0007] Japanese Patent Application Laid-Open No. 2000-223308

[0008] Patent Document 1 discloses a technique for obtaining a magnetic core with high mechanical strength by heat treating a compact of soft magnetic material powder at a high temperature of 700° C. or higher. However, the energy load during sintering is large, and sufficient mechanical strength cannot be obtained.

[0009] In order to address the technical challenge of resolving the above-mentioned problems, the developers conducted numerous prototypes and experiments through trial and error. As a result, they achieved the remarkable result of being able to reduce the energy load associated with sintering and prepare soft magnetic metal powder that has excellent magnetic properties and sintered body strength. This solved the above-mentioned technical challenges.

[0010] The above technical problem can be solved by the example of the present embodiment described below.

[0011] The soft magnetic metal powder according to this embodiment is a soft magnetic metal powder containing one or more metal elements selected from Fe, Ni, and Co. Here, the specific surface area of ​​the soft magnetic metal powder heat-treated at 450°C is 90% or less of the specific surface area of ​​the soft magnetic metal powder before heat treatment. (Embodiment 1)

[0012] The soft magnetic metal powder according to the first embodiment may have an average primary particle size of 0.05 μm or more and 2.0 μm or less.

[0013] The soft magnetic metal powder according to this embodiment may contain one or more metal elements selected from Fe, Ni, and Co, have an average primary particle size of 0.05 μm or more and 2.0 μm or less, and may further contain 1.0 wt % or more of O. (Embodiment 3)

[0014] The molded body according to this embodiment is a molded body containing the soft magnetic metal powder according to the first or third embodiment. (Embodiment 4)

[0015] The sintered body according to this embodiment is a sintered body containing the soft magnetic metal powder according to the first or third embodiment. (Embodiment 5)

[0016] The soft magnetic metal powder according to this embodiment contains one or more metal elements selected from Fe, Ni, and Co. Furthermore, after the soft magnetic metal powder is heat-treated at 450°C, its specific surface area is 90% or less of the specific surface area before the heat treatment. In other words, the soft magnetic metal powder can be sintered at a low temperature. Furthermore, the soft magnetic metal powder has excellent magnetic properties. Furthermore, a sintered body with excellent strength can be obtained from the soft magnetic metal powder.

[0017] Therefore, the soft magnetic metal powder according to this embodiment can be suitably used in small inductors or noise suppression parts.

[0018] Fig. 1 is an SEM photograph (20,000 magnification) of the soft magnetic metal powder obtained in Example 1. Fig. 2 is an SEM photograph (20,000 magnification) of the soft magnetic metal powder obtained in Example 1 after heat treatment at 450°C. Fig. 3 is an SEM photograph (20,000 magnification) of the soft magnetic metal powder obtained in Comparative Example 1 after heat treatment at 450°C.

[0019] This embodiment will be described in detail below.

[0020] First, the soft magnetic metal powder according to this embodiment will be described.

[0021] The soft magnetic metal powder according to this embodiment contains one or more metal elements selected from Fe, Ni, and Co. After this soft magnetic metal powder is heat-treated at 450°C, its specific surface area is 90% or less of the specific surface area before the heat treatment.

[0022] The soft magnetic metal powder according to this embodiment contains one or more metal elements selected from Fe, Ni, and Co. This allows the soft magnetic metal powder to exhibit the magnetic properties required as a material for electronic components.

[0023] The content of one or more metal elements selected from Fe, Ni, and Co contained in the soft magnetic metal powder according to this embodiment is not particularly limited. A preferred content is 80% by weight or more. If the content is within the above range, the soft magnetic metal powder has sufficient magnetic properties (σs). A more preferred content is 85% by weight or more. An even more preferred content is 90% by weight or more.

[0024] Examples of metal compounds contained in the soft magnetic metal powder according to this embodiment include FeB, α-Fe, FeNi, FeCo, and FeCoNi.

[0025] The soft magnetic metal powder according to this embodiment may contain elements other than Fe, Ni, and Co, as long as the elements do not affect the magnetic properties. The elements are not particularly limited. Examples of such elements include boron (B), phosphorus (P), and oxygen (O).

[0026] In order to improve the electrical resistance value by the oxide coating, the O content of the soft magnetic metal powder according to the present disclosure is 1.0 wt % or more. The O content is preferably 1.5 wt % or more, and more preferably 2.5 wt % or more. Furthermore, in order to suppress a decrease in saturation magnetization, the O content is preferably 10.0 wt % or less, and more preferably 8.0 wt % or less.

[0027] The soft magnetic metal powder according to this embodiment may contain 0% by weight of B. When B is contained, the content thereof is preferably 10.0% by weight or less, more preferably 9.0% by weight or less, and even more preferably 8.0% by weight or less.

[0028] If the B content is more than 10.0 wt %, the proportion of magnetic elements will be reduced, resulting in a low σs value, which may make it difficult to obtain sufficient magnetic properties.

[0029] The shape of the soft magnetic metal powder according to this embodiment is not particularly limited. From the viewpoint of dispersibility in resins or solvents, or from the viewpoint of improving packing properties, a spherical shape is preferred.

[0030] The specific surface area change rate (%) of the soft magnetic metal powder according to this embodiment was calculated by the following (Equation 1). The specific surface area of ​​the soft magnetic metal powder after heat treatment at 450°C is defined as the specific surface area after heat treatment. The specific surface area before heat treatment is defined as the specific surface area before heat treatment. (Equation 1): Specific surface area change rate (%) = (specific surface area after heat treatment / specific surface area before heat treatment) x 100

[0031] The specific surface area change rate of the soft magnetic metal powder according to this embodiment is 90% or less. If the specific surface area change rate exceeds 90%, the soft magnetic metal powder will not exhibit sufficient low-temperature sintering properties. The specific surface area change rate is preferably 85% or less, more preferably 70% or less. The lower limit is not particularly limited. For example, the lower limit can be set to 5%.

[0032] The average primary particle diameter of the soft magnetic metal powder according to this embodiment is preferably 0.05 μm to 2.0 μm, more preferably 0.07 μm to 1.5 μm. If the average primary particle diameter is less than 0.05 μm, the proportion of oxide coating on the particle surface increases. As a result, the saturation magnetization of the soft magnetic metal powder decreases. Furthermore, an average primary particle diameter greater than 2.0 μm is not suitable as the particle diameter of auxiliary fine particles in a high-filling design.

[0033] The variation coefficient of the primary particle diameter (hereinafter referred to as variation coefficient) in this embodiment is calculated from the following (Equation 2): The variation coefficient is preferably 0.25 or less, more preferably 0.23 or less, and even more preferably 0.16 or less.

[0034] (Equation 2) Coefficient of variation = Standard deviation of primary particle diameter / Average primary particle diameter

[0035] If the coefficient of change of the soft magnetic metal powder according to this embodiment exceeds 0.25, when the sintered body is used in a small electronic component, sufficient strength may not be obtained.

[0036] The lower limit of the variation coefficient is, for example, 0.001.

[0037] The aggregation ratio in this embodiment is calculated from the following (Equation 3): The aggregation ratio is preferably 3.0 or less, more preferably 2.7 or less, and even more preferably 2.5 or less.

[0038] (Formula 3) Agglomeration ratio = median diameter / average primary particle diameter

[0039] If the agglomeration ratio exceeds 3.0, the sintered body may not have sufficient strength when used in small electronic components.

[0040] When the soft magnetic metal powder according to this embodiment contains fine particles with little aggregation, the aggregation ratio may be less than 1.0. The lower limit of the aggregation ratio in this embodiment is, for example, 0.3.

[0041] The median diameter of the soft magnetic metal powder according to this embodiment is preferably 0.02 to 6.0 μm, and more preferably 0.05 to 3.0 μm.

[0042] The median diameter change rate in this embodiment is calculated using Equation 4, which will be described later.

[0043] The median diameter change rate of the soft magnetic metal powder according to this embodiment is preferably 110% or more, more preferably 115% or more, and even more preferably 120% or more. If the median diameter change rate is less than 110%, the sintered body may not have sufficient strength. The upper limit of the median diameter change rate is not particularly limited. For example, the upper limit of the median diameter change rate can be set to 300%.

[0044] In order to obtain a sintered body having sufficient magnetic properties, the soft magnetic metal powder according to this embodiment preferably has a σs of 120 Wb m / kg or more, more preferably 130 Wb m / kg or more, and even more preferably 140 Wb m / kg or more.

[0045] The sintered body containing the soft magnetic metal powder according to this embodiment preferably has a crushing strength of 100 N or more. If the crushing strength of the sintered body is 100 N or more, the possibility of crushing is reduced. Therefore, the reliability of the component is improved. The crushing strength of the sintered body is more preferably 150 N or more, and even more preferably 200 N or more.

[0046] The soft magnetic metal powder according to this embodiment may be coated with a metal oxide, which is expected to improve the insulating effect.

[0047] Examples of the metal elements contained in the metal oxide include Al, Si, Zr, Ti, Y, P, Fe, Co, and Ni.

[0048] The content of the metal element in the metal oxide is preferably in the range of 2.0 to 10.0% by weight. If the content of the metal element is more than 10.0% by weight, the saturation magnetization may decrease.

[0049] Next, a method for producing the soft magnetic metal powder according to this embodiment will be described.

[0050] The soft magnetic metal powder according to this embodiment can be produced by a liquid-phase reduction method. In the liquid-phase reduction method according to this embodiment, an aqueous solution of a metal salt containing one or more metal elements selected from the group consisting of Fe, Ni, and Co is used. The aqueous solution of the metal salt is reduced by a reducing agent.

[0051] Examples of iron salts include iron(II) sulfate, iron(II) chloride, iron(II) acetate, iron(II) oxalate, iron(III) chloride, and iron(III) sulfate, but the iron salts that can be used are not limited to these examples.

[0052] Examples of nickel salts include nickel(II) chloride, nickel(II) sulfate, nickel(II) nitrate, and nickel(III) fluoride, but are not limited to these examples.

[0053] Examples of cobalt salts include cobalt(II) chloride, cobalt(II) sulfate, and cobalt(II) nitrate, although the usable cobalt salts are not limited to these examples.

[0054] The aqueous metal salt solution may contain one or more complexing agents or one or more reducing agents.

[0055] The complexing agent is not particularly limited, and examples of usable complexing agents include glycine, alanine, ammonium sulfate, ammonium chloride, and sodium citrate III.

[0056] The metal salt aqueous solution does not necessarily need to contain a reducing agent. However, the metal salt aqueous solution may contain a P-based reducing agent. Examples of P-based reducing agents include sodium hypophosphite and calcium hypophosphite. However, the P-based reducing agents that can be used are not limited to these examples.

[0057] The P content of the soft magnetic metal powder of this embodiment is preferably 2.0 wt % or less. If the P content exceeds 2.0 wt %, the proportion of magnetic elements decreases. As a result, σs decreases. As a result, sufficient magnetic properties may not be obtained.

[0058] The pH of the aqueous metal salt solution is adjusted with a pH adjuster, preferably to a range of pH 6.5 to 11.0.

[0059] The pH adjuster is not particularly limited, and examples of usable pH adjusters include sodium hydroxide, aqueous ammonia, and sodium bicarbonate.

[0060] The aqueous metal salt solution may optionally contain a dispersant, a catalyst, or an antifoaming agent.

[0061] The reducing agent used to reduce the metal salt aqueous solution is not particularly limited. Examples of reducing agents that can be used include B-type reducing agents and hydrazine. One or more of the exemplified reducing agents can be used.

[0062] Examples of B-type reducing agents include sodium borohydride, potassium borohydride, and dimethylaminoborane.

[0063] The amount of the reducing agent added is preferably in the range of 15% by weight to 100% by weight based on the metal salt.

[0064] The reduction temperature is preferably in the range of 10°C to 95°C.

[0065] If the reduction temperature is lower than 10°C, the particle size may become too large and the desired particle size may not be obtained. In addition, the cooling cost will be high. Therefore, a reduction temperature lower than 10°C is not industrially preferable. On the other hand, if the reduction temperature is higher than 95°C, the reducing agent will be deactivated early. Therefore, the soft magnetic metal powder according to this embodiment may not be obtained.

[0066] A molded body can be produced by molding the soft magnetic metal powder according to this embodiment. The molding conditions can be appropriately selected depending on, for example, the application of the molded body. Therefore, the molding conditions are not particularly limited. An example of a molding method is a powder compaction method. A solvent such as PVA can also be added during molding as appropriate.

[0067] The content of the soft magnetic metal powder contained in the molded body is not particularly limited. The content can be changed as appropriate depending on the desired magnetic properties. The content is preferably 40 vol% or more, more preferably 60 vol% or more, and even more preferably 70 vol% or more. As long as the content is within the above content range, good magnetic properties can be obtained. From the viewpoint of moldability and magnetic properties, the upper limit of the content is, for example, 95 vol%. In this case, the remainder is occupied by, for example, voids or resin.

[0068] Moreover, a sintered body can also be obtained by sintering a molded body of the soft magnetic metal powder according to this embodiment.

[0069] The sintering apparatus used in this embodiment is not particularly limited as long as it is an apparatus that can heat the powder compact to a desired temperature and produce a sintered body. The sintering apparatus can be appropriately selected depending on the application or the required heat resistance. An example of the sintering apparatus is a box-type electric furnace.

[0070] The sintering temperature in the production of a sintered body containing the soft magnetic metal powder according to this embodiment is preferably 400° C. to 600° C., more preferably 400 to 550° C. If the sintering temperature is within this temperature range, a sintered body can be obtained without requiring excessive energy.

[0071] The sintering reaction in the production of a sintered body containing the soft magnetic metal powder according to this embodiment is preferably carried out in a nitrogen atmosphere. Treatment in a nitrogen atmosphere can reduce oxidation reactions. As a result, a sintered body with excellent magnetic properties can be obtained.

[0072] The reason why the soft magnetic metal powder according to this embodiment exhibits low-temperature sintering properties has not yet been fully elucidated. However, the developers speculate that the reason is as follows: In atomization or spray pyrolysis, soft magnetic metal powder is prepared by applying high heat. On the other hand, the soft magnetic metal powder according to this embodiment does not undergo high-temperature heat treatment during its powder production process. Therefore, it is presumed that the surface of the soft magnetic metal powder is unstable and highly active. Therefore, even when heat treatment is performed at a temperature lower than the conventional heat treatment temperature of 450°C, it is considered that the surface of the soft magnetic metal powder changes so that the specific surface area of ​​the soft magnetic metal powder becomes smaller compared to before the heat treatment. In other words, it is thought that the change in specific surface area due to a more stable surface state promotes sintering of the soft magnetic metal powder particles.

[0073] Examples of this embodiment will be described below, but this embodiment is not limited to these examples.

[0074] Example 1: The above compounds, iron (II) sulfate heptahydrate, glycine, and sodium hypophosphite were added to a glass beaker together with 600 ml of distilled water so that the concentrations of the compounds were 0.20 mol / L, 0.10 mol / L, and 0.20 mol / L. The resulting mixture was stirred at room temperature at 100 to 300 rpm using a stirrer. During the stirring operation, the pH of the mixture was adjusted to a range of 7.5 to 9.5 using sodium hydroxide. In this way, an aqueous metal salt solution was prepared.

[0075] Sodium borohydride was mixed with 200 ml of distilled water so that the concentration of sodium borohydride was 0.50 mol / L. The resulting mixture was then stirred at room temperature with a stirrer at 100 to 300 rpm, thereby dissolving the sodium borohydride in the distilled water. In this way, a reduced solution was prepared. In a nitrogen atmosphere, the reduced solution was added dropwise to a metal salt aqueous solution at 50°C, which was being stirred at 100 to 300 rpm with a stirrer.

[0076] The point at which no more bubbles were observed from the metal salt aqueous solution was considered to be the end point of the reduction reaction. After the reduction reaction was completed, the reaction product was washed with distilled water. Next, the distilled water was replaced with alcohol. The reaction product was then dried in an inert atmosphere of nitrogen gas. This resulted in the production of a soft magnetic metal powder. The soft magnetic metal powder particles obtained in Example 1 were spherical. The variation coefficient of the primary particle size was 0.14. The median diameter of the powder was 0.14 μm.

[0077] Example 2 The above compounds were added to a glass beaker together with 600 ml of distilled water so that the concentrations of iron (II) sulfate heptahydrate, glycine, ammonium sulfate, and sodium hypophosphite were 0.20 mol / L, 0.10 mol / L, 0.20 mol / L, and 0.20 mol / L, respectively. The resulting mixture was stirred at room temperature at 100 to 300 rpm using a stirrer. The pH of the mixture was adjusted to a range of 9.0 to 11.0 using sodium hydroxide. In this manner, a metal salt aqueous solution was prepared.

[0078] Sodium borohydride was mixed with 200 ml of distilled water so that the concentration of sodium borohydride was 0.30 mol / L. The resulting mixture was then stirred at 100 to 300 rpm with a stirrer at room temperature, thereby dissolving the sodium borohydride in the distilled water. In this way, a reduced solution was prepared. In a nitrogen atmosphere, the reduced solution was added dropwise to a metal salt aqueous solution at 25°C, which was being stirred at 100 to 300 rpm with a stirrer.

[0079] The reduction reaction was considered to have ended when no more bubbles were observed from the metal salt aqueous solution. After the reduction reaction was completed, the reaction product was washed with distilled water. Next, the distilled water was replaced with alcohol. The reaction product was then dried in an inert atmosphere of nitrogen gas. This resulted in the production of a soft magnetic metal powder. The soft magnetic metal powder particles obtained in Example 2 were spherical. The variation coefficient of the primary particle size was 0.12. The median diameter of the powder was 1.18 μm.

[0080] Example 3: The above compounds were added to a glass beaker together with 1500 ml of distilled water so that the concentrations of iron (II) sulfate heptahydrate, glycine, and sodium hypophosphite were 0.2 mol / L, 0.08 mol / L, and 0.1 mol / L, respectively. The resulting mixture was stirred at room temperature at 100 to 300 rpm using a stirrer. During the stirring operation, the pH of the mixture was adjusted to a range of 7.0 to 8.5 using sodium hydroxide. In this manner, an aqueous metal salt solution was prepared. The prepared aqueous metal salt solution was stirred at 100 to 300 rpm using a stirrer. During the stirring operation, the inside of the beaker was filled with nitrogen gas to create an inert atmosphere, and the mixture was heated to 45°C in this state.

[0081] Sodium borohydride was mixed with 300 ml of distilled water so that the concentration of sodium borohydride was 0.25 mol / L. The resulting mixture was then stirred at 100 to 300 rpm at room temperature, thereby dissolving the sodium borohydride in the distilled water. In this way, a reducing solution was prepared. In a nitrogen atmosphere, the reducing agent was gradually added dropwise to a metal salt aqueous solution at 45°C, which was being stirred at 100 to 300 rpm with a stirrer.

[0082] The end point of the reduction reaction was determined to be the point at which no more bubbles were observed from the metal salt aqueous solution. After the reduction reaction was completed, the reaction product was washed with distilled water. Next, the distilled water was replaced with alcohol. The reaction product was then dried in an inert atmosphere of nitrogen gas. This resulted in the production of a soft magnetic metal powder. The soft magnetic metal powder particles obtained in Example 3 were spherical. The variation coefficient of the primary particle size was 0.17. The median diameter of the powder was 0.45 μm.

[0083] (Comparative Example 1) A soft magnetic metal powder (NiFe-GB0301) manufactured by Ningbo Guangxin Nanomaterials Co., Ltd. using a physical vapor deposition method was prepared. The soft magnetic metal powder of Comparative Example 1 was spherical. The median diameter of the powder was 1.28 μm.

[0084] (Comparative Example 2) A soft magnetic metal powder (AW2-08PF-3K) was prepared using an atomization method manufactured by Epson Atmix Corporation. The soft magnetic metal powder of Comparative Example 2 was spherical. The median diameter of the powder was 3.2 μm.

[0085] (Heat treatment conditions for soft magnetic metal powder) The soft magnetic metal powders obtained in the examples and comparative examples were heat treated according to the following procedure. 1 g of soft magnetic metal powder was placed in a crucible. The crucible was then placed in a heat treatment furnace. The interior of the heat treatment furnace was heated from room temperature to 450°C in a nitrogen atmosphere, with the temperature rising over a period of 2 hours and 15 minutes. The soft magnetic metal powder in the crucible was then held in the heat treatment furnace for 1 hour at 450°C in a nitrogen atmosphere for heat treatment. The temperature inside the heat treatment furnace was then allowed to naturally drop to room temperature. In this way, a heat-treated soft magnetic metal powder was obtained.

[0086] (Criteria for Determining Low-Temperature Sinterability) Low-temperature sinterability was determined by comparing the SEM image of the soft magnetic metal powder after the heat treatment at 450°C with the SEM image of the soft magnetic metal powder before the heat treatment. When a clear increase in interparticle fusion was confirmed by comparing the SEM images before and after the heat treatment at 450°C, it was determined that sintering was observed. The soft magnetic metal powder of the sample was then determined to have low-temperature sinterability. When a clear increase in interparticle fusion was not confirmed by comparing the SEM images before and after the heat treatment at 450°C, it was determined that the soft magnetic metal powder of the sample did not have low-temperature sinterability. In the soft magnetic metal powders obtained in Examples 1 to 3, a clear increase in interparticle fusion was confirmed after the heat treatment compared to before the heat treatment. Therefore, the soft magnetic metal powders of Examples 1 to 3 were determined to have low-temperature sinterability. On the other hand, in the soft magnetic metal powders of Comparative Examples 1 and 2, no clear increase in interparticle fusion was confirmed even after the heat treatment. Therefore, the soft magnetic metal powders of Comparative Examples 1 and 2 were determined to not have low-temperature sinterability.

[0087] (Method for preparing sintered body for crushing strength measurement) A sintered body for crushing strength measurement was prepared by the following procedure. A soft magnetic metal powder was placed in a cylindrical mold having a diameter of 8 mm and a depth of 12.5 mm, and a pressure of 1 kgf / cm was applied to the powder. ２A molded body was obtained by applying a pressure of 1000 kJ / cm. The entire mold was then placed in a heat treatment furnace under a nitrogen atmosphere. The interior of the heat treatment furnace was heated from room temperature to 500°C over a period of 2 hours and 30 minutes. The molded body in the mold was then held in the heat treatment furnace at 500°C for 1 hour for heat treatment. The temperature in the heat treatment furnace was then allowed to naturally decrease to room temperature. The molded body removed from the mold was used as a sintered body for measuring crushing strength.

[0088] (Method for measuring the crushing strength of sintered body) The crushing strength of the sintered body for crushing strength measurement obtained in the previous section was measured using an EMX-1000-FA / manufactured by Imada Co., Ltd. More specifically, the peak strength was measured at a measurement speed of 70 mm / min. The measured value was expressed in Newton (N) units. The measurement limit was 611 N.

[0089] (Specific Surface Area) The specific surface area of ​​the soft magnetic metal powder was measured using a Macsorb HM Model-1201 (manufactured by Mountec Co., Ltd.) The rate of change in the specific surface area of ​​the soft magnetic metal powder before and after the heat treatment was calculated using the above-mentioned (Equation 1).

[0090] (Measurement of average primary particle diameter) The average primary particle diameter of the soft magnetic metal powder was measured using a scanning electron microscope at a magnification of 2000 to 10000. The longest diameter of all particles within the photographed field of view was measured using image analysis software A-zo-kun (manufactured by Asahi Kasei Engineering Co., Ltd.), and the average primary particle diameter and the standard deviation of the primary particle diameters were calculated.

[0091] (Measurement of Median Diameter) The median diameter of the soft magnetic metal powder was measured using a particle size distribution analyzer (Microtrac MT3300EXII / manufactured by Microtrac Bell Co., Ltd.). The measurement range was 0.02 μm to 2000 μm. Ethanol was used as the solvent. Before the measurement, the soft magnetic metal powder in ethanol was irradiated with ultrasound for 3 minutes. Thereafter, the median diameter was measured. The value of the volume cumulative particle size D50 at 50% cumulative volume obtained in the measurement was evaluated as the median diameter.

[0092] (Median Diameter Change Rate) The median diameter change rate of the soft magnetic metal powder before and after the 450°C heat treatment was calculated using the following (Equation 4): (Equation 4): Median diameter change rate = (Median diameter of soft magnetic metal powder after heat treatment / Median diameter of soft magnetic metal powder before heat treatment) x 100

[0093] (Identification of Compounds) The soft magnetic metal powders (compounds) obtained in the examples and comparative examples were identified by Rietveld analysis using an X-ray diffractometer (D8 ADVANCE, manufactured by Bruker Japan KK).

[0094] (Composition Analysis of Fe, Ni, Co, and P Elements) Composition analysis of the Fe, Ni, Co, and P elements contained in the soft magnetic metal powder was performed using a fluorescent X-ray diffractometer (ZSX Primus II / manufactured by Rigaku Corporation) in accordance with JIS K0119 "General Rules for Fluorescent X-ray Analysis."

[0095] (Composition Analysis of B Element) The composition analysis of the B element contained in the soft magnetic metal powder was carried out using an inductively coupled plasma (ICP) optical emission spectrometer (iCAP6500, manufactured by Thermo Fisher Scientific Co., Ltd.).

[0096] (Composition Analysis of O Element) The composition analysis of the O element contained in the soft magnetic metal powder was carried out using an oxygen / nitrogen / hydrogen analyzer (EMGA-930, manufactured by Horiba Ltd.).

[0097] (Magnetic Properties (Saturation Magnetization (σs))) The saturation magnetization (σs) of the soft magnetic metal powders of the Examples and Comparative Examples was measured using a vibrating sample magnetometer (VSM) (TM-VSM2130MRHL model, manufactured by Tamagawa Seisakusho Co., Ltd.).

[0098] Table 1 shows the properties of the soft magnetic metal powders obtained in the examples and comparative examples, and the crushing strength of the sintered bodies.

[0099]

[0100] The soft magnetic metal powder according to this embodiment has low-temperature sintering properties. Therefore, the soft magnetic metal powder according to this embodiment can be suitably applied to electronic components such as inductors with excellent magnetic properties. Furthermore, sintered bodies formed using the soft magnetic metal powder according to this embodiment have high strength. Therefore, they can be suitably mounted in devices as electronic components or elements. Therefore, the soft magnetic metal powder according to this embodiment has high industrial applicability.

Claims

1. A soft magnetic metal powder containing one or more metal elements selected from Fe, Ni, and Co, wherein the specific surface area of ​​the soft magnetic metal powder heat-treated at 450°C is 90% or less of the specific surface area of ​​the soft magnetic metal powder before heat treatment.

2. The soft magnetic metal powder according to claim 1, having an average primary particle size of 0.05 μm or more and 2.0 μm or less.

3. A soft magnetic metal powder containing one or more metal elements selected from Fe, Ni, and Co, having an average primary particle size of 0.05 μm or more and 2.0 μm or less, and containing 1.0 wt % or more of O.

4. A molded body containing the soft magnetic metal powder according to claim 1 or 3.

5. A sintered body containing the soft magnetic metal powder according to claim 1 or 3.

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