Soft magnetic alloy plate, method for manufacturing the soft magnetic alloy plate, iron core and rotating electric machine using the soft magnetic alloy plate

Abstract

To provide a soft magnetic iron alloy plate which has magnetic properties higher than that of electromagnetic pure iron plate and can be made lower cost than permendur, and an iron core and a rotating electric machine each using the soft magnetic iron alloy plate.SOLUTION: A soft magnetic iron alloy plate according to the present invention has an average composition including 5 to 25 atomic % Co, 0 to 1 atomic % V, 0.2 to 5 atomic % N, and 0 to 5 atomic % C, and the balance being Fe and impurities, and has a first phase and a second phase having contents of Co and N different from each other, the first phase has a relatively higher Co content than that of the second phase, the second phase has a relatively higher N content than that of the first phase, and the soft magnetic iron alloy plate has a region in which a plurality of two-phase crystal grains are connected in the thickness direction, and the region is at least half the thickness of the soft magnetic iron alloy plate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to soft magnetic material technology, and more particularly to a soft magnetic alloy plate having magnetic properties higher than those of an electromagnetic pure iron plate, a method for manufacturing the soft magnetic alloy plate, and an iron core and a rotating electric machine using the soft magnetic alloy plate. [Background technology]

[0002] Laminated cores, made by laminating multiple sheets of soft magnetic material such as pure iron sheets or electromagnetic steel sheets (e.g., 0.01 to 3 mm thick), are widely used as cores for rotating electrical machines and transformers. In recent years, there has been a strong demand for miniaturization and higher output in these rotating electrical machines and transformers, and improving the magnetic properties of the cores is one of the urgent issues.

[0003] For iron cores, high conversion efficiency between electrical energy and magnetic energy is important, and high magnetic flux density and high magnetization are important magnetic properties. To increase the magnetic flux density / magnetization of an iron core, it is desirable for the material to have a high saturation magnetic flux density Bs / saturation magnetization Ms. Known iron-based materials with a high Bs / Ms include, for example, Fe-Co alloy materials and Fe-N martensitic materials.

[0004] Among Fe-Co alloy materials, Permendur (49Fe-49Co-2V mass% = 50Fe-48Co-2V atomic%) has the highest Ms (239 emu / g) of any currently commercially available soft magnetic bulk material. However, the material cost of Co, although it varies depending on market conditions, is 100 to 200 times higher than that of Fe, making Permendur a weak point in terms of material cost. Permendur also has some drawbacks in terms of workability, leading to high processing costs. Reducing the Co content reduces material costs and improves workability, but it also reduces Ms, its greatest feature.

[0005] Meanwhile, for Fe-N martensitic materials, for example, Patent Document 1 (JP 2020-132894 A) discloses a plate- or foil-shaped soft magnetic material with high saturation magnetic flux density, which contains iron, carbon, and nitrogen, and includes martensite containing carbon and nitrogen and γ-Fe, where the γ-Fe has a nitrogen-containing phase. According to Patent Document 1, a soft magnetic material with a saturation magnetic flux density exceeding that of pure iron and thermal stability can be manufactured at low cost, and this can be used to improve the characteristics of magnetic circuits in electric motors and the like, thereby enabling the miniaturization and high torque of electric motors and the like. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2020-132894 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to increase the electrical / magnetic energy conversion efficiency in an iron core, it is important to suppress iron loss Pi in addition to high Bs / high Ms. Pi is the sum of hysteresis loss and eddy current loss, and a small coercive force Hc is desirable to reduce hysteresis loss. The magnetic properties of commercially available electromagnetic pure iron sheets are said to be Bs ≒ 2.1 T, Ms ≒ 215 emu / g, and Hc ≒ 80 A / m. Iron cores using electromagnetic pure iron sheets have the advantages of high Bs, high Ms, and low material costs, but have the disadvantage of a relatively high Hc, which makes Pi easily large.

[0008] The currently widely used Fe-Si based electrical steel sheet has the advantage of having a smaller Pi than the pure iron sheet, but has the disadvantage that the Bs / Ms of the Fe-Si based electrical steel sheet is smaller than that of the pure iron sheet. Also, the soft magnetic material of Patent Document 1 has the advantage of having a higher Bs than the pure iron sheet, but has the disadvantage that Hc is easily increased.

[0009] In recent years, there has been a strong demand for high-torque / high-power designs in rotating electrical machines and transformers, and there is a strong demand for improvements in the Bs / Ms ratio of the core. In other words, improving the Bs / Ms ratio of the core is given priority, and if the improvement in Bs / Ms is large, a certain degree of increase in Pi tends to be tolerated.

[0010] On the other hand, reducing the cost of the iron core is naturally one of the important issues, and there is a demand for a soft magnetic material that can be manufactured stably and at a lower cost than permendur while still meeting the expected and required magnetic properties.

[0011] Therefore, an object of the present invention is to provide a soft magnetic iron alloy plate that has higher magnetic properties than electromagnetic pure iron plate and can be made less expensive than permendur, a method for manufacturing the soft magnetic alloy plate, and an iron core and a rotating electric machine that use the soft magnetic iron alloy plate. [Means for solving the problem]

[0012] (I) One aspect of the present invention is a soft magnetic iron alloy plate, The average composition includes 5 atomic % or more and 25 atomic % or less of cobalt (Co), 0 atomic % or more and 1 atomic % or less of vanadium (V), 0.2 atomic % or more and 5 atomic % or less of nitrogen (N), and 0 atomic % or more and 5 atomic % or less of carbon (C), with the remainder being iron (Fe) and impurities; a first phase and a second phase having different contents of Co and N, The first phase has a relatively higher Co content than the second phase, The second phase has a relatively higher N content than the first phase, The present invention provides a soft magnetic iron alloy plate characterized in that the soft magnetic iron alloy plate has a region in which a plurality of crystal grains of the second phase are connected in the thickness direction of the soft magnetic iron alloy plate, and the region is at least half the thickness of the soft magnetic iron alloy plate.

[0013] In the present invention, the following improvements and modifications can be freely combined and added to the above-mentioned soft magnetic iron alloy plate (I). (i) The first phase contains more than 5 atomic % and not more than 40 atomic % Co and 0 atomic % or more and less than 0.2 atomic % N, and the second phase contains 0 atomic % or more and 5 atomic % or less Co and 0.5 atomic % or more and 10 atomic % or less N. (ii) The first phase and the second phase each have an average particle size of 45 μm or less. (iii) The volume fraction of the first phase is 50% by volume or more and 95% by volume or less, and the volume fraction of the second phase is 50% by volume or less and 5% by volume or more. (iv) The saturation magnetization is 222 emu / g or more.

[0014] In the present invention, the average grain size of the soft magnetic iron alloy plate is the average diameter of the equivalent area circle of the crystal grains observed by microstructural observation (e.g., scanning electron microscope observation). The average grain size of the powder is the volume-based average grain size (D50) measured using a laser diffraction / scattering particle size distribution analyzer or the like.

[0015] (II) Another aspect of the present invention is a method for producing the soft magnetic iron alloy plate described above, a starting material preparation step of preparing a starting material by mixing, in a predetermined ratio, a first powder made of an iron-cobalt alloy containing more than 5 atomic % and 40 atomic % or less of cobalt and 0 atomic % or more and 1.2 atomic % or less of vanadium, and a second powder made of an iron-based metal containing 0 atomic % or more and 5 atomic % or less of cobalt; a molding / sintering step of forming a sintered body by molding and sintering the starting material; a martensite phase generating step of subjecting the sintered body to a heat treatment for infiltrating and diffusing nitrogen atoms, followed by rapid cooling to generate a martensite phase; A sub-zero treatment step of further cooling the sintered body quenched in the martensite phase generation step to 0 ° C or less. The present invention provides a method for manufacturing a soft magnetic iron alloy plate, characterized by the above-mentioned.

[0016] In the present invention, the following improvements and modifications can be freely combined and added to the above-mentioned method (II) for producing a soft magnetic iron alloy plate. (v) The predetermined ratio in the starting material preparing step is such that the second powder is 5% by mass or more and 50% by mass or less. (vi) The first powder and the second powder in the starting material preparation step each have an average particle size of 1 μm or more and 45 μm or less, and the ratio of the average particle size of the first powder to the average particle size of the second powder is 1 or more and 10 or less. (vii) The heat treatment in the martensite phase formation step includes a process of adjusting the atmosphere to contain ammonia gas after the temperature reaches 500°C or higher, raising the temperature to a temperature range for austenite phase formation, and then alternately switching between an atmosphere containing ammonia gas and an atmosphere not containing ammonia gas.

[0017] (III) Another aspect of the present invention is an iron core made of a laminate of soft magnetic iron alloy plates, The present invention provides an iron core, wherein the soft magnetic iron alloy plate is the soft magnetic iron alloy plate according to the present invention.

[0018] (IV) Yet another aspect of the present invention is a rotating electric machine having an iron core, The present invention also provides a rotating electric machine, wherein the iron core is the iron core according to the present invention. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a soft magnetic iron alloy plate that has higher magnetic properties than electromagnetic pure iron plate and can be made at a lower cost than permendur, a method for manufacturing the soft magnetic alloy plate, and an iron core and a rotating electric machine that use the soft magnetic iron alloy plate. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a process diagram showing an example of a method for manufacturing a soft magnetic iron alloy plate according to the present invention. [Figure 2A] FIG. 2 is a schematic perspective view showing an example of a stator of a rotating electric machine. [Figure 2B] FIG. 2 is an enlarged cross-sectional schematic view of a slot region of the stator. [Figure 3]1 shows an example of a component plane analysis in cross-sectional observation in Example 1, showing the results of (a) Fe component mapping and (b) Co component mapping. DETAILED DESCRIPTION OF THE INVENTION

[0021] [Basic concept of the present invention] To achieve the above-mentioned object, the inventors considered reducing the Co content compared to Permendur to reduce material costs, and compensating for the decrease in magnetic properties (Bs and / or Ms) due to the decrease in Co content by forming an Fe-N martensite phase. They also considered that by forming an Fe-C martensite phase, it would be possible to suppress the increase in Pi without decreasing Bs / Ms.

[0022] However, it is said that it is difficult for N and C atoms to penetrate and diffuse into Fe-Co alloy materials, making it difficult to form Fe-N martensite phases or Fe-C martensite phases. In other words, it is not easy to simply penetrate and diffuse N and C atoms into Fe-Co alloy materials.

[0023] On the other hand, simply adding elements that promote the penetration and diffusion of N and C atoms to an Fe-Co alloy material to form an Fe-N martensite phase makes it easier to form nonmagnetic, nonmetallic particles, which act as pinning points that prevent domain wall movement during magnetization reversal. The formation of nonmagnetic particles leads to a decrease in Bs and / or Ms, and the pinning points for domain walls lead to another problem: an increase in Pi.

[0024] Therefore, the present inventors conducted extensive research into a method for effectively penetrating and diffusing N and C atoms into the interior of a soft magnetic iron alloy sheet while maintaining the magnetic properties of the Fe-Co alloy material itself. As a result, they devised a method in which a first-phase powder made of an Fe-Co alloy, which has excellent magnetic properties, is mixed and sintered with a second-phase powder made of an Fe-based metal, through which N and C atoms can penetrate and diffuse relatively easily, followed by a nitriding heat treatment or a nitriding-carburizing heat treatment. The second phase serves as a penetration and diffusion path for N and C atoms, allowing them to penetrate and diffuse into the interior of the soft magnetic iron alloy sheet, effectively producing an Fe-N martensite phase, or an Fe-N and Fe-C martensite phase. The present invention was completed based on this finding.

[0025] Furthermore, numerous experiments by the present inventors have shown that a clear improvement in characteristics / significant difference can be achieved if a Bs improvement of 0.03 T or more or an Ms improvement of 3 emu / g or more is achieved compared to a comparative soft magnetic material. For this reason, the soft magnetic iron alloy sheet of the present invention must exhibit a Bs of at least 2.17 T or more or an Ms of 218 emu / g or more. From the perspective of recent demands for higher torque / higher output in rotating electrical machines, a Bs of 2.21 T or more or an Ms of 222 emu / g or more is more desirable.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described herein, and can be appropriately combined with or improved on known techniques without departing from the technical concept of the invention.

[0027] [Soft magnetic iron alloy plate] Fig. 1 is a process diagram showing an example of a method for producing a soft magnetic iron alloy sheet according to the present invention. As shown in Fig. 1, the method for producing a soft magnetic iron alloy sheet according to the present invention generally comprises a starting material preparation step S1, a compacting and sintering step S2, a martensite phase generation step S3, and a sub-zero treatment step S4. In the present invention, in order to obtain a soft magnetic iron alloy sheet that achieves the intended purpose, the structure of the sintered body obtained in the compacting and sintering step S2 is controlled, and the composition of the starting material prepared in the starting material preparation step S1 is controlled to control the structure of the sintered body.

[0028] Each step will be described in more detail below.

[0029] The starting material preparation step S1 is a step of preparing a starting material by mixing, in a predetermined ratio, a first powder made of an Fe-Co alloy containing more than 5 atomic % and 40 atomic % or less of Co and 0 atomic % or more and 1.2 atomic % or less of V, and a second powder made of an Fe-based metal containing 0 atomic % or more and 5 atomic % or less of Co. The V component contributes to improving formability in the subsequent compacting and sintering step S2, but is not an essential component (i.e., it may or may not be included).

[0030] The first powder and / or the second powder may contain 0 atomic % or more and 5 atomic % or less of the C component (in other words, the C component is not an essential component). Note that, after the subsequent compacting and sintering step S2, the C component can be added by performing a carburizing heat treatment to penetrate and diffuse the C component, if necessary.

[0031] It is preferable to control the mixing ratio of the first powder and the second powder so that the average composition of the entire starting material contains 5 atomic % or more and 25 atomic % or less of Co, 0 atomic % or more and 1 atomic % or less of V, and 0 atomic % or more and 5 atomic % or less of C, with the remainder being Fe and impurities.

[0032] Furthermore, in the subsequent compacting and sintering step S2, it is preferable to form a region where multiple crystal grains originating from the second powder are connected, and to control the length of this region (particularly the length in the thickness direction of the sintered body) to be at least half the thickness of the sintered body. To achieve this, the mixing ratio of the first powder to the second powder is preferably controlled so that the second powder is in the range of 5% by mass to 50% by mass (the first powder is in the range of 95% by mass to 50% by mass), and more preferably so that the second powder is in the range of 10% by mass to 50% by mass (the first powder is in the range of 90% by mass to 50% by mass).

[0033] There are no particular limitations on the average particle sizes of the first powder and the second powder, but from the viewpoint of shape controllability of the sintered body in the subsequent compacting and sintering step S2, it is preferable that each be 1 μm or more and 45 μm or less. There are also no particular limitations on the ratio of the average particle sizes of the first powder to the average particle sizes of the second powder, but it is preferable to control it within the range of, for example, 1 or more and 10 or less.

[0034] When two types of powders with different average particle sizes are mixed and molded, the powder with the larger average particle size generally tends to form the skeleton of the molded body, while the powder with the smaller average particle size tends to be arranged so as to fill the gaps in the skeleton. This tendency becomes stronger as the ratio of average particle sizes increases (for example, when it becomes 5 or more). In other words, when the ratio of average particle sizes is large, the powder with the smaller average particle size tends to form islands in a sea-island structure.

[0035] As mentioned above, it is preferable that the sintered body obtained in the subsequent compacting and sintering step S2 have a region where multiple crystal grains originating from the second powder are connected to each other, and that the length of this region (the length in the thickness direction of the sintered body) is at least half the thickness of the sintered body. There are several possible starting material configurations for achieving this structure. For example, "the ratio of the average particle sizes of the two powders is small (e.g., 2 or less)," "the average particle size of the second powder is larger than that of the first powder and the mixing ratio of the second powder is low (e.g., 20% by mass or less)," or "the average particle size of the second powder is smaller than that of the first powder and the mixing ratio of the second powder is high (e.g., 30% by mass or more)."

[0036] The molding and sintering step S2 is a step in which the starting material prepared in the previous step S1 is molded and sintered to form a sintered body. In the present invention, the order of molding and sintering in step S2 does not matter. That is, sintering may be performed after molding, or pre-molding and sintering may be performed before main molding, or molding and sintering may be performed simultaneously.

[0037] The molding and sintering methods are not particularly limited as long as they produce a dense sintered body, and conventional powder metallurgy techniques for metal materials can be used as appropriate. Suitable methods include cold isostatic pressing (CIP), hot isostatic pressing (HIP), hot pressing (HP), gas pressure sintering, millimeter wave sintering, microwave sintering, electric field assisted sintering, flash sintering, and spark plasma sintering (SPS). A dense sintered body preferably has a porosity of 7% or less by area, more preferably 5% or less by area, and even more preferably 3% or less by area, when observed through a cross section. For example, when spark plasma sintering is used, sintering is preferably performed at a heating temperature of 1100°C or less and a maximum surface pressure of 50 MPa.

[0038] The sintered body obtained by this step S2 has the structural characteristics of having a region of crystal grains based on the first powder and a region where multiple crystal grains based on the second powder are connected to each other, and the length of the region based on the second powder (the length in the thickness direction of the sintered body) is at least half the thickness of the sintered body.

[0039] The martensite phase generation step S3 is a step in which the sintered body formed in the previous step S2 is subjected to a nitriding heat treatment to penetrate and diffuse N atoms, followed by rapid cooling to generate a martensite phase. In the nitriding heat treatment, N atoms penetrate and diffuse preferentially into the crystal grains of the second powder. After nitriding to the desired N content, the martensite phase is generated by quenching, which involves rapid cooling to below 100°C.

[0040] Nitriding heat treatment involves infiltrating and diffusing N atoms from the surface of the sintered compact (particularly from the surface of the region where multiple crystal grains originating from the second powder are connected) at a temperature of 500°C or higher (for example, in the austenite (γ phase) formation temperature range) in a specified ammonia (NH3) gas atmosphere. As the NH3 gas atmosphere, in addition to NH3 gas alone, a mixed gas of NH3 gas and N2 gas, a mixed gas of NH3 gas and Ar gas, or a mixed gas of NH3 gas and H2 gas can be suitably used.

[0041] It is preferable to introduce NH3 gas after the temperature reaches 500°C or higher. This is because if NH3 gas is actively introduced in the stable temperature range of the ferrite phase (α phase), the desired tetragonal structure of the Fe-N phase (Fe8N phase (α' phase) and / or Fe 16 This is because undesired Fe-N phases (for example, FeN phase (γ' phase) and FeN phase (ε phase)) are more likely to form than undesired Fe-N phases (for example, FeN phase (γ' phase) and FeN phase (ε phase)).

[0042] The N content in the sintered body (particularly in the region where multiple crystal grains originating from the second powder are connected) can be controlled by controlling the heat treatment temperature, the NH3 gas partial pressure, and / or the NH3 gas supply time. The N content distribution in the thickness direction of the sintered body can be controlled by alternately switching between an atmosphere containing NH3 gas and an atmosphere not containing NH3 gas.

[0043] Rapid cooling after nitriding heat treatment can transform most of the austenite phase (γ phase) into martensite, but some γ phase may remain (residual γ phase). Because the γ phase is nonmagnetic, it is preferable to keep the volume fraction of the residual γ phase below 5% from the perspective of magnetic properties.

[0044] Although not an essential step, when performing carburizing heat treatment to add C component, carburizing heat treatment may be performed subsequent to the above-mentioned nitriding heat treatment (for example, after nitriding heat treatment and before quenching). There are no particular limitations on the method of carburizing heat treatment, and conventional methods can be used as appropriate. For example, subsequent to nitriding heat treatment, the atmospheric gas can be changed to acetylene (C2H2) gas or carbon monoxide (CO) gas.

[0045] The carburizing heat treatment may be performed simultaneously with the nitriding heat treatment. In this case, after the temperature reaches 500°C or higher, C2H2 gas or CO gas is introduced in addition to NH3 gas, and the temperature is raised to the γ-phase formation temperature range in this gas environment, causing N atoms and C atoms to penetrate and diffuse from the surface of the sintered body (especially from the surface of the region where multiple crystal grains based on the second powder are connected to each other).

[0046] The C content can be controlled by controlling the heat treatment temperature, gas partial pressure, and / or gas supply time, similar to the control of the N content. The C content distribution in the thickness direction of the sintered body can be controlled by alternately switching between an atmosphere containing C2H2 or CO gas and an atmosphere not containing these gases.

[0047] Following the martensite phase generation step S3, it is preferable to carry out a sub-zero treatment step S4 to transform the residual γ phase into a martensite structure. Sub-zero treatment is a process of cooling to below 0°C, and preferred methods include ordinary sub-zero treatment using dry ice and ultra-sub-zero treatment using liquid nitrogen.

[0048] The N content of the Fe-N martensite phase (referred to herein as the second phase) obtained in step S3 is preferably 0.5 atomic % or more and 10 atomic % or less. By setting the N content to 0.5 atomic % or more, a significant amount of Fe-N martensite phase is generated, contributing to improving Bs / Ms. By setting the N content to 10 atomic % or less, the generation of undesired Fe-N phase can be suppressed. The lower limit of the N content of the second phase is more preferably 1 atomic % or more, and even more preferably 1.5 atomic % or more. Furthermore, the upper limit of the N content is more preferably 8 atomic % or less, and even more preferably 6 atomic % or less. The region of crystal grains originating from the first powder becomes the first phase in this specification.

[0049] The average composition of the entire soft magnetic iron alloy plate includes 5 atomic % to 25 atomic % Co, 0 atomic % to 1 atomic % V, 0.2 atomic % to 5 atomic % N, and 0 atomic % to 5 atomic % C, with the remainder being Fe and impurities.

[0050] Although not an essential step, a tempering step S5 at 100°C or higher and 210°C or lower may be further carried out (not shown in Figure 1) in order to impart toughness to the sintered body (soft magnetic iron alloy plate) that has undergone the sub-zero treatment step S4.

[0051] By the above process, it is possible to obtain a soft magnetic iron alloy plate in which the Co content is reduced compared to Permendur, thereby reducing material costs, and the decrease in magnetic properties due to the reduced Co content is compensated for by the formation of an Fe-N martensite phase.

[0052] [Iron cores and rotating electrical machines] Fig. 2A is a schematic perspective view showing an example of a stator of a rotating electric machine, and Fig. 2B is an enlarged schematic cross-sectional view of a slot region of the stator. Note that the cross-sectional view refers to a cross section perpendicular to the direction of the rotation axis (a cross section whose normal is parallel to the axial direction). In a rotating electric machine, a rotor (not shown) is disposed radially inside the stator of Figs. 2A and 2B.

[0053] 2A and 2B, the stator 20 has stator coils 21 wound in a plurality of stator slots 11 formed on the inner periphery of the laminated core 10. The stator slots 11 are spaces that are arranged at a predetermined circumferential pitch around the circumferential direction of the laminated core 10 and penetrate the laminated core 10 in the axial direction, with slits 12 opening in the innermost periphery and extending in the axial direction. The areas separating adjacent stator slots 11 are called teeth 13 of the laminated core 10, and the parts of the inner periphery tip areas of the teeth 13 that define the slits 12 are called tooth claw portions 14.

[0054] The stator coil 21 is usually made up of a plurality of segment conductors 22. For example, in Figures 2A and 2B, the stator coil 21 is made up of three segment conductors 22 corresponding to the U-phase, V-phase, and W-phase of a three-phase AC. In order to prevent partial discharge between the segment conductors 22 and the laminated core 10 and between the phases (U-phase, V-phase, W-phase), the outer periphery of each segment conductor 22 is usually covered with an electrical insulating material 23 (for example, insulating paper or enamel coating).

[0055] The rotating electric machine according to the present invention is a rotating electric machine that uses the laminated core 10 of the present invention. The laminated core 10 of the present invention has a higher Bs / higher Ms than conventional laminated cores made of pure electromagnetic iron sheets or electromagnetic steel sheets, which leads to higher torque / higher output of the rotating electric machine. Furthermore, the laminated core 10 of the present invention can be made at a lower cost than laminated cores made of permendur sheets, which prevents excessive cost increases in the rotating electric machine. [Example]

[0056] The present invention will be explained in more detail below with reference to various experiments, however, the present invention is not limited to the configurations and structures described in these experiments.

[0057] [Experiment 1] (Preparation of Starting Materials 1 to 3 and Reference Material 1 by Starting Material Preparation Step) First, Fe-30 atomic % Co powder (raw material A) with an average particle size of approximately 30 μm, Fe-25 atomic % Co powder (raw material B) with an average particle size of approximately 30 μm, Fe-20 atomic % Co powder (raw material C) with an average particle size of approximately 30 μm, Fe-5 atomic % Co powder (raw material D) with an average particle size of approximately 30 μm, pure Fe powder (raw material E) with an average particle size of approximately 30 μm, and pure Fe powder (raw material F) with an average particle size of approximately 4 μm were prepared.

[0058] Starting material 1 was prepared by thoroughly mixing raw material A as the first powder and raw material F as the second powder so that the ratio of raw material A to raw material F was 67% by mass:33% by mass. Starting material 2 was prepared by thoroughly mixing raw material A as the first powder and raw material E as the second powder so that the ratio of raw material A to raw material E was 67% by mass:33% by mass. Starting material 3 was prepared by thoroughly mixing raw material B as the first powder and raw material D as the second powder so that the ratio of raw material B to raw material D was 67% by mass:33% by mass.

[0059] Starting materials 1 to 3 have an average Co content of approximately 20 atomic % throughout the starting materials, which means that the material cost can be significantly reduced compared to commercially available permendur.

[0060] In contrast, Reference Material 1 was prepared using only Raw Material C.

[0061] [Experiment 2] (Formation of Inventive Sintered Body 1 to 3 and Reference Sintered Body 1 by Compaction and Sintering Process) Appropriate amounts were sampled from each of the starting materials 1 to 3 and reference material 1 prepared in experiment 1, and the invention sintered bodies 1 to 3 and reference sintered body 1 (each 20 mm diameter x 0.1 mm thickness) were formed using the spark plasma sintering (SPS) method. The sintering conditions were vacuum: 10 Pa, sintering temperature: 1000°C, and holding time: 5 minutes. Multiple sintered body samples were produced for each.

[0062] [Experiment 3] (Production of Examples 1 to 3 and Reference Example 1 by Martensite Phase Generation Step and Subzero Treatment Step) Test pieces (10 mm×9.5 mm×0.1 mm) were cut out from each of the samples of the invention sintered bodies 1 to 3 and the reference sintered body 1 formed in Experiment 2, and subjected to a martensite phase generation process.

[0063] Nitriding heat treatment is carried out in a N2 gas atmosphere (0.8 × 10 5 After heating to 500°C under a pressure of 1×10 Pa, 5 The temperature was raised to 1000°C, and the temperature was maintained at 1000°C while the NH3 gas atmosphere (0.5×10 5 Pa) and N2 gas atmosphere (0.4 × 10 5 The nitrogen immersion temperature was alternately switched between 0.01 Pa and 0.02 Pa to control the amount of N atoms penetrating (N content) and the distribution of N content in the thickness direction of the sintered body. After the desired amount of nitrogen immersion was completed, the sintered body was oil quenched (60°C) to cause martensitic transformation.

[0064] Immediately after oil quenching, an ultra-subzero treatment was carried out to transform the residual γ phase into martensitic phase. In this manner, samples of Examples 1 to 3 and Reference Example 1 of soft magnetic iron alloy plates were produced.

[0065] [Experiment 4] (Property Investigation of Examples 1 to 3 and Reference Example 1) The surface of each sample was subjected to wide-angle X-ray diffraction (WAXD) using Cu-Kα radiation with an X-ray diffractometer (Rigaku Corporation, Rint-Ultima III) to identify the crystalline phase.

[0066] As a result, in Examples 1 to 3, the α phase (ferrite phase) was the main phase, and the generation of α' phase and / or α" phase (Fe-N phase with a tetragonal crystal structure) was confirmed, but the γ phase (austenite phase) and γ' phase (FeN phase) were not confirmed. On the other hand, in Reference Example 1, only the α phase was confirmed. The results of Reference Example 1 mean that the α' phase and / or α" phase were not generated at a level / amount that could be detected by WAXD measurement.

[0067] The cross section of each sample was subjected to microstructural observation using an electron probe microanalyzer (EPMA, manufactured by JEOL Ltd., JXA-8530F), and the porosity was investigated and the components were analyzed.

[0068] In the investigation of the porosity, the area ratio of pores was determined by image analysis of microstructure photographs, and it was confirmed that in all of Examples 1 to 3 and Reference Example 1, the porosity was 3 area % or less.

[0069] 3 shows an example of a component plane analysis in a cross-sectional observation of Example 1, showing (a) the results of Fe component mapping and (b) the results of Co component mapping. Example 1 is a sample obtained by mixing and sintering raw material A (Fe-30 atomic % Co powder, average particle size approximately 30 μm) and raw material F (pure Fe powder, average particle size approximately 4 μm).

[0070] The Fe component is uniformly distributed across the entire observation field (see Figure 3(a)). On the other hand, the Co component is clearly unevenly distributed (see Figure 3(b)). From these results, it can be seen that raw material A forms the skeleton, and raw material B fills the gaps in the skeleton and connects them in a network-like manner.

[0071] Quantitative analysis was performed by spot measuring the N concentration at 50 points each in the region based on raw material A and the region based on raw material B. As a result, the N concentration measured in the region based on raw material B was 1.2 to 1.5 atomic %. On the other hand, the N concentration measured in the region based on raw material A was 0 to 0.1 atomic %.

[0072] These findings confirm that the region based on raw material B (Fe-based metal region) acts as a pathway for the penetration and diffusion of N atoms, generating an Fe-N martensite phase and constituting a second phase region, and that the region based on raw material A (Fe-Co alloy region) is difficult for N atoms to penetrate and diffuse, making it difficult to generate an Fe-N martensite phase.

[0073] Furthermore, although not shown in the figure, the results of observing the element distribution using EPMA confirmed that there is an area in which multiple second-phase crystal grains are connected in the thickness direction of the soft magnetic iron alloy plate, and that this area occupies more than half the thickness of the soft magnetic iron alloy plate.

[0074] Furthermore, although not shown in the figures, it was confirmed that the same results as in Example 1 were obtained in Examples 2 and 3. It was confirmed that in Reference Example 1, the entire sample was in the region of an Fe-Co alloy, which made it difficult for N atoms to penetrate and diffuse, making it difficult to form an Fe-N martensite phase.

[0075] The magnetic properties of each sample were investigated using a vibrating sample magnetometer (Riken Denshi Co., Ltd., BHV-525H). The magnetization (unit: emu) of the sample was measured under conditions of a magnetic field of 1.6 MA / m and a temperature of 20°C, and the saturation magnetization Ms (unit: emu / g) was calculated from the sample mass. In addition, the iron loss Pi of the sample was measured under conditions of a magnetic flux density of 1.0 T, 400 Hz, and a temperature of 20°C using the H coil method (compliant with JIS C 2556:2015) using a BH loop analyzer (IFG Co., Ltd., IF-BH550) and a vertical yoke single sheet tester. -1.0 / 400 The results are shown in Table 1.

[0076] [Table 1]

[0077] As shown in Table 1, Examples 1 to 3 were confirmed to have a 5 to 7% improvement in saturation magnetization Ms compared to Reference Example 1, which has the same Co content as the average composition. -1.0 / 400 = 25 W / kg is a sufficiently low iron loss comparable to that of electromagnetic steel sheets.

[0078] The above-described embodiments and experiments have been described to aid in understanding the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace part of the configuration of the embodiments with configurations within the technical common sense of those skilled in the art, and it is also possible to add configurations within the technical common sense of those skilled in the art to the configuration of the embodiments. In other words, it is possible to delete, replace, or add part of the configurations of the embodiments and experiments in this specification without departing from the technical spirit of the invention. [Explanation of symbols]

[0079] 10... laminated core, 11... stator slot, 12... slit, 13... teeth, 14... teeth claw portion, 20...stator, 21...stator coil, 22...segment conductor, 23...electrical insulating material.

Claims

1. A soft magnetic iron alloy plate, an average composition comprising 5 atomic % or more and 25 atomic % or less of cobalt, 0 atomic % or more and 1 atomic % or less of vanadium, 0.2 atomic % or more and 5 atomic % or less of nitrogen, and 0 atomic % or more and 5 atomic % or less of carbon, with the remainder being iron and impurities; a first phase and a second phase having different contents of cobalt and nitrogen, the first phase has a relatively higher cobalt content than the second phase; the second phase has a relatively higher nitrogen content than the first phase, A soft magnetic iron alloy plate characterized in that the second phase crystal grains have a region in which multiple crystal grains are connected in the thickness direction of the soft magnetic iron alloy plate, and the region is at least half the thickness of the soft magnetic iron alloy plate.

2. The soft magnetic iron alloy plate according to claim 1, the first phase contains more than 5 atomic % and not more than 40 atomic % cobalt and 0 atomic % or more and less than 0.2 atomic % nitrogen; The soft magnetic iron alloy plate, characterized in that the second phase contains 0 atomic % or more and 5 atomic % or less of cobalt and 0.5 atomic % or more and 10 atomic % or less of nitrogen.

3. The soft magnetic iron alloy plate according to claim 1, A soft magnetic iron alloy plate, characterized in that the first phase and the second phase each have an average grain size of 45 μm or less.

4. The soft magnetic iron alloy plate according to claim 2, A soft magnetic iron alloy plate, characterized in that the first phase and the second phase each have an average grain size of 45 μm or less.

5. The soft magnetic iron alloy plate according to claim 1, The volume fraction of the first phase is 50% by volume or more and 95% by volume or less, A soft magnetic iron alloy plate characterized in that the volume fraction of the second phase is 50% by volume or less and 5% by volume or more.

6. The soft magnetic iron alloy plate according to claim 2, The volume fraction of the first phase is 50% by volume or more and 95% by volume or less, A soft magnetic iron alloy plate characterized in that the volume fraction of the second phase is 50% by volume or less and 5% by volume or more.

7. The soft magnetic iron alloy plate according to claim 3, The volume fraction of the first phase is 50% by volume or more and 95% by volume or less, A soft magnetic iron alloy plate characterized in that the volume fraction of the second phase is 50% by volume or less and 5% by volume or more.

8. The soft magnetic iron alloy plate according to claim 4, The volume fraction of the first phase is 50% by volume or more and 95% by volume or less, A soft magnetic iron alloy plate characterized in that the volume fraction of the second phase is 50% by volume or less and 5% by volume or more.

9. The soft magnetic iron alloy plate according to any one of claims 1 to 8, A soft magnetic iron alloy plate having a saturation magnetization of 222 emu / g or more.

10. A method for manufacturing a soft magnetic iron alloy plate according to any one of claims 1 to 8, a starting material preparation step of preparing a starting material by mixing, in a predetermined ratio, a first powder made of an iron-cobalt alloy containing more than 5 atomic % and 40 atomic % or less of cobalt and 0 atomic % or more and 1.2 atomic % or less of vanadium, and a second powder made of an iron-based metal containing 0 atomic % or more and 5 atomic % or less of cobalt; a molding / sintering step of forming a sintered body by molding and sintering the starting material; a martensite phase generation step of performing a heat treatment on the sintered body to infiltrate and diffuse nitrogen atoms, and then rapidly cooling the sintered body to generate a martensite phase; A sub-zero treatment step of further cooling the sintered body quenched in the martensite phase generation step to 0 ° C or less. A method for manufacturing a soft magnetic iron alloy plate.

11. The method for manufacturing a soft magnetic iron alloy plate according to claim 10, A method for manufacturing a soft magnetic iron alloy plate, characterized in that the specified ratio in the starting material preparation process is 5 mass% or more and 50 mass% or less of the second powder.

12. The method for manufacturing a soft magnetic iron alloy plate according to claim 11, the first powder and the second powder in the starting material preparing step each have an average particle size of 1 μm or more and 45 μm or less; A method for producing a soft magnetic iron alloy plate, wherein the ratio of the average particle size of the first powder to the average particle size of the second powder is 1 or more and 10 or less.

13. The method for manufacturing a soft magnetic iron alloy plate according to claim 12, a process for producing a soft magnetic iron alloy sheet, characterized in that the heat treatment in the martensite phase generation step includes a process of adjusting the atmosphere to contain ammonia gas after the temperature reaches 500°C or higher, raising the temperature to a temperature range for generating an austenite phase, and then alternately switching between the atmosphere containing ammonia gas and the atmosphere not containing ammonia gas.

14. An iron core made of a laminate of soft magnetic iron alloy plates, An iron core, wherein the soft magnetic iron alloy plate is the soft magnetic iron alloy plate according to any one of claims 1 to 8.

15. A rotating electric machine having an iron core, A rotating electric machine, wherein the iron core is the iron core according to claim 14.

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