Soft magnetic iron alloy plate, iron core using said soft magnetic iron alloy plate, and rotating electric machine

Abstract

To provide a soft-magnetic iron alloy sheet capable of suppressing an excessive increase in Pi while showing higher Bs than an electromagnetic pure iron sheet, and achieving lower cost than permendur, to provide an iron core using the same, and to provide a rotary electric machine.SOLUTION: A soft-magnetic iron alloy sheet has a chemical composition which includes 1-30 atom% of Co, 0.2-10 atom% N and 0.5-5 atom% of M component capable of forming MN type nitride, and has the balance comprising Fe and impurities. When observing the cross section of the soft-magnetic iron alloy sheet, nitride particles of the M component are precipitated at an average particle diameter of 0.5 μm or less and a number density of 50 pieces / 100 μm2 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to soft magnetic material technology, and more particularly to a soft magnetic iron alloy plate having a higher saturation magnetic flux density than an electromagnetic pure iron plate, and an iron core and a rotating electric machine using the soft magnetic iron 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 (for example, 0.01 to 1 mm thick), are widely used as cores for rotating electrical machines and transformers. For iron cores, it is important that the conversion efficiency between electrical energy and magnetic energy is high, so high magnetic flux density and low iron loss are important.

[0003] On the other hand, in mechanical devices that use iron cores, reducing the cost of soft magnetic materials is naturally one of the most important issues, and technological development has been actively carried out for a long time to enable inexpensive and stable production while satisfying the required characteristics.

[0004] For example, Patent Document 1 (JP 2005-264315 A) discloses an electrical steel sheet containing, by mass%, C: 0.0400% or less, Si: 0.2 to 4.0%, Mn: 0.05 to 5.0%, P: 0.30% or less, S: 0.020% or less, Al: 8.0% or less, N: 0.0400% or less, with the remainder being Fe and unavoidable impurities, the structure being mainly composed of ferrite phase in a range that satisfies the volume fraction of ferrite phase: 50% or more and martensite phase: 50% or less, and the steel material containing intermetallic compounds with a diameter of 0.050 μm or less inside. The electrical steel sheet may also contain 70% by mass or more of Fe, and 10.0% by mass or less of one or more of Ni, Mo, Ti, Nb, Co, and W; 10.0% by mass or less of each of one or more of Zr, Cr, B, Cu, Zn, Mg, and Sn; and 5.0% by mass or less of each of one or more of Ag, Pt, Ga, Ge, In, V, Pd, Ir, Rh, Cd, and Ta.

[0005] According to Patent Document 1, the tensile strength during use is 60 kg / mm 2 It is said that this method makes it possible to stably produce high-strength non-oriented electrical steel sheets that have high strength, deformation resistance, fatigue resistance, wear resistance, etc., and that also have excellent magnetic properties equivalent to those of ordinary soft electrical steel sheets.

[0006] Patent Document 2 (WO 2007 / 069776 A1) discloses a high-strength non-oriented electrical steel sheet having a chemical composition that contains, by mass%, C: 0.010% or less, N: 0.010% or less, and C+N≦0.010%, Si: 1.5% to 5.0%, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less, and S: 0.01% or less, and further contains one or two of Ti and V in a total amount of 0.01% to 0.8% and in a range that satisfies the relationship (Ti+V) / (C+N)≧16, with the balance being Fe and unavoidable impurities, and wherein the area ratio of unrecrystallized recovered structures in the steel sheet is 50% or more. The high-strength non-oriented electrical steel sheet may further contain, in mass%, at least one selected from the group consisting of Ni: 0.1 to 5.0%, Sb: 0.002 to 0.1%, Sn: 0.002 to 0.1%, B: 0.001 to 0.01%, Ca: 0.001 to 0.01%, Rem: 0.001 to 0.01%, and Co: 0.2 to 5.0%.

[0007] According to Patent Document 2, it is possible to provide a non-oriented electrical steel sheet that is high in strength and has excellent sheet shape and magnetic properties, and a method for manufacturing the same, without substantially adding any restrictions or new processes to the manufacturing of ordinary non-oriented electrical steel sheets.

[0008] Patent Document 3 (JP 2020-132894 A) discloses a plate- or foil-shaped soft magnetic material having a high saturation magnetic flux density, which contains iron, carbon, and nitrogen, and includes martensite containing carbon and nitrogen and γ-Fe, in which a nitrogen-containing phase is formed in the γ-Fe.

[0009] According to Patent Document 3, a soft magnetic material having a saturation magnetic flux density exceeding that of pure iron and thermal stability can be manufactured at low cost, and by using this, the characteristics of the magnetic circuits of electric motors and the like can be improved, thereby realizing miniaturization of electric motors and the like, high torque, etc. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-264315 [Patent Document 2] International Publication No. 2007 / 69776 [Patent Document 3] Japanese Patent Publication No. 2020-132894 Summary of the Invention [Problem to be solved by the invention]

[0011] In rotating electrical machines, increasing the saturation magnetic flux density Bs of soft magnetic materials is important for achieving high output and torque, while suppressing loss (iron loss Pi) in soft magnetic materials is important for achieving high efficiency. Pi is the sum of hysteresis loss and eddy current loss, and a small coercive force Hc is desirable for reducing hysteresis loss, while increasing electrical resistance and using thinner plates are effective for reducing eddy current loss.

[0012] The magnetic properties of commercially available electromagnetic pure iron sheets are said to be Bs ≈ 2.1 T. Iron cores using electromagnetic pure iron sheets have the advantages of high Bs and low material costs, but a weakness in that Pi tends to be large due to a relatively high Hc. The electromagnetic steel sheets of Patent Documents 1 and 2 have the advantages of high mechanical strength and low Pi, but a weakness in that Bs is smaller than that of electromagnetic pure iron sheets, and therefore the Bs of the entire iron core does not exceed that of electromagnetic pure iron cores. Furthermore, the soft magnetic material of Patent Document 3 has the advantage of having a higher Bs than electromagnetic pure iron sheets, but is thought to have a weakness in that Hc is higher than that of electromagnetic pure iron sheets.

[0013] Known iron-based materials that have a higher Bs than electromagnetic pure iron sheets include Fe-Co-based materials and Fe-N-based martensitic materials.

[0014] Among Fe-Co based materials, permendur (49Fe-49Co-2V mass% = 50Fe-48Co-2V atomic%) has the highest Bs (approximately 2.4 T) of any currently commercially available soft magnetic 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 its high material cost. Permendur also has some drawbacks in terms of workability, which can lead to high processing costs. Lowering the Co content reduces material costs and improves workability, but unfortunately also reduces Bs, its greatest feature.

[0015] On the other hand, Fe-N martensitic materials (e.g., Fe8N phase (α' phase), Fe 16 The N2 phase (α″ phase) is an attractive material with a material cost that is significantly lower than permendur and a high Bs comparable to that of permendur. However, it has a weakness in that Hc and Pi tend to increase due to an increase in crystal lattice distortion caused by the intrusion of N atoms and differences in the local concentration of N atoms, which can lead to strain differences between crystal lattices.

[0016] 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 improved Bs in soft magnetic materials. In other words, improving the Bs of soft magnetic materials is given priority, and if the degree of improvement in Bs is large, a certain degree of increase in Pi tends to be tolerated. For example, if a Bs of over 2.20 T can be achieved, it is considered acceptable for a rotating electrical machine to have a Pi of up to 60 W / kg.

[0017] Therefore, the object of the present invention is to provide a soft magnetic iron alloy plate that exhibits a higher Bs than electromagnetic pure iron plate while suppressing an excessive increase in Pi, and that can be made less expensive than permendur, as well as an iron core and a rotating electric machine using the soft magnetic iron alloy plate. [Means for solving the problem]

[0018] (I) One aspect of the present invention is a soft magnetic iron alloy plate, It has a chemical composition containing Co (cobalt) in an amount of 1 atomic % or more and 30 atomic % or less, N (nitrogen) in an amount of 0.2 atomic % or more and 10 atomic % or less, an M component capable of forming an MN-type nitride in an amount of 0.5 atomic % or more and 5 atomic % or less, and the balance being Fe (iron) and impurities, When the cross section of the soft magnetic iron alloy plate is observed, the nitride particles of the M component have an average particle size of 0.5 μm or less and a number density of 50 particles / 100 μm. 2 The present invention provides a soft magnetic iron alloy plate characterized by being precipitated as follows:

[0019] In the present invention, the average particle size of nitride particles refers to the average diameter of the equivalent area circle of nitride particles observed by microstructural observation (e.g., scanning electron microscope observation), and the number density refers to the number of precipitated nitride particles per given area observed by microstructural observation.

[0020] In the present invention, the soft magnetic iron alloy plate (I) can be improved or modified as follows. (i) The M component is at least one of V, Cr, Ti, Al, Nb, and Mo. (ii) When the cross section of the soft magnetic iron alloy plate is observed, the area ratio of nitride particles of the M component is 10% or less. (iii) The saturation magnetic flux density is greater than 2.20 T and the core loss is 60 W / kg or less. (iv) Vickers hardness is 200 or more.

[0021] (II) 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.

[0022] (III) Yet another aspect of the present invention is a rotating electric machine having an iron core, The present invention provides a rotating electric machine, wherein the iron core is the iron core according to the present invention. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a soft magnetic iron alloy plate that exhibits a higher Bs than electromagnetic pure iron plate while suppressing an excessive increase in Pi, and that can be made less expensive than permendur, as well as an iron core and a rotating electric machine that use this soft magnetic iron alloy plate. [Brief explanation of the drawings]

[0024] [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 2] 1 is a scanning electron microscope (SEM) image of a cross section of an iron alloy plate 2. [Figure 3] 1 is an SEM observation image of a cross section of an iron alloy plate 3. [Figure 4A] FIG. 1 is a schematic perspective view showing an example of a stator of a rotating electric machine. [Figure 4B] FIG. 2 is an enlarged cross-sectional schematic view of a slot region of the stator. DETAILED DESCRIPTION OF THE INVENTION

[0025] The basic idea of ​​the present invention is to reduce material costs by reducing the Co content compared to Permendur, and to compensate for the decrease in Bs due to the reduced Co content by forming an Fe-N martensite phase. However, it has been thought that N atoms do not easily penetrate and diffuse into Fe-Co based materials, making it difficult to form an Fe-N martensite phase.

[0026] Simply adding elements that promote the penetration and diffusion of N atoms to an Fe-Co material to form an Fe-N martensite phase makes it easier to form nonmagnetic nitride 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 the pinning points for domain walls lead to an increase in Pi.

[0027] As mentioned above, one of the purposes of the soft magnetic iron alloy sheet of the present invention is to exhibit a Bs superior to that of electromagnetic pure iron sheets. Numerous experiments by the inventors have shown that an improvement in Bs of 0.03 T or more compared to a comparative soft magnetic material can be considered a clear improvement / significant difference in characteristics. 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. From the perspective of recent demands for higher torque / higher output in rotating electrical machines, a Bs of 2.21 T or more is more desirable, and a Bs of 2.24 T or more is even more desirable.

[0028] Therefore, the present inventors have conducted extensive research into methods for infiltrating and diffusing nitrogen atoms into Fe-Co alloy sheets and effectively generating an Fe-N martensite phase. As a result, they have found that by adding an element that promotes the infiltration and diffusion of N atoms (an M component that can form M-N nitrides) and by infiltrating and diffusing N atoms in a temperature range where the diffusion and rearrangement of the M component is difficult (a temperature range where the diffusion coefficient is sufficiently small), it is possible to generate an Fe-N martensite phase while suppressing the generation of nitride particles. The present invention was completed based on this finding.

[0029] Hereinafter, embodiments of the present invention will be described in detail along with the manufacturing procedure with reference to the drawings. However, the present invention is not limited to the embodiments described here, and can be appropriately combined with known techniques or improved based on known techniques within the scope of the technical idea of ​​the invention.

[0030] 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 nitriding heat treatment step S2, and a sub-zero treatment step S3. Each step will be described in more detail below.

[0031] In the starting material preparation step S1, a plate material (thickness 0.01 mm to 1 mm) is prepared as a starting material, which contains Fe as the main component (the component with the highest content), Co at 1 atomic % to 30 atomic %, and M components capable of forming M-type nitrides at 0.5 atomic % to 5 atomic %.

[0032] By setting the Co content to 30 atomic % or less, material costs can be significantly reduced compared to permendur. From the viewpoint of ensuring an excellent Bs, the lower limit of the Co content is more preferably 5 atomic % or more, and even more preferably 10 atomic % or more. Furthermore, from the viewpoint of reducing material costs, the upper limit of the Co content is more preferably 25 atomic % or less, and even more preferably 20 atomic % or less.

[0033] As the M component capable of forming the MN-type nitride, one or more of V, Cr, Ti, Al, Nb, and Mo can be preferably used, and the content is preferably 0.5 atomic % or more and 5 atomic % or less. From the viewpoint of promoting the penetration and diffusion of N atoms, the lower limit of the M component content is more preferably 1 atomic % or more, and even more preferably 1.5 atomic % or more. Furthermore, from the viewpoint of suppressing the generation of nitride particles, the upper limit of the M component content is more preferably 4 atomic % or less, and even more preferably 3.5 atomic % or less.

[0034] The term "MN-type nitride" refers to a nitride in which M atoms and nitrogen atoms combine in a 1:1 ratio. Impurities (impurities that may be contained in the starting material, such as H (hydrogen), B (boron), C (carbon), Si (silicon), phosphorus (P), sulfur (S), manganese (Mn), nickel (Ni), and copper (Cu)) are permitted within a range that does not significantly affect the Bs of the soft magnetic iron alloy sheet (for example, a total concentration of 2 atomic % or less).

[0035] Next, in the nitrogen immersion heat treatment step S2, nitrogen immersion heat treatment is performed to infiltrate and diffuse N atoms into the prepared starting material sheet. After nitrogen immersion is performed until the desired N content is reached, the sheet is rapidly cooled to generate a martensite phase. The greatest feature of the method for producing a soft magnetic iron alloy sheet according to the present invention is this nitrogen immersion heat treatment step S2.

[0036] The N content in step S2 (average content in the entire iron alloy sheet) is preferably 0.2 atomic % or more and 10 atomic % or less. By making the N content 0.2 atomic % or more, a significant amount of Fe-N martensite phase (FeN phase (α' phase) and / or Fe 16 N phase (α″ phase)) is generated, which contributes to improving Bs. By setting the N content to 10 atomic % or less, it is possible to suppress the generation of undesired iron nitride phases (for example, FeN phase (γ′ phase) and FeN phase (ε phase)). The lower limit of the N content is more preferably 0.3 atomic % or more, and even more preferably 0.4 atomic % or more. The upper limit of the N content is more preferably 5 atomic % or less, and even more preferably 3 atomic % or less.

[0037] The nitrous heat treatment is preferably carried out in a predetermined NH3 (ammonia) gas atmosphere at a temperature range where the decomposition reaction of NH3 occurs, allowing N atoms to penetrate into the starting material, and where the diffusion and rearrangement of the M component is difficult (a temperature range where the diffusion coefficient is sufficiently small). Specifically, a temperature range of 450°C to 700°C is preferred, 480°C to 650°C is more preferred, and 500°C to 600°C is even more preferred.

[0038] 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 (argon) gas, or a mixed gas of NH3 gas and H2 gas can be suitably used. NH3 gas is preferably introduced after the temperature reaches 450°C or higher. This is because if NH3 gas is actively introduced from a low temperature range below 450°C, undesired iron nitride phases (γ' phase and ε phase) are more likely to form than the desirable tetragonal Fe-N martensite phase (α' phase and / or α" phase).

[0039] The N content in the iron alloy sheet 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 iron alloy sheet (sheet thickness direction) can be controlled by alternately switching between an atmosphere containing NH3 gas and an atmosphere not containing NH3 gas.

[0040] Although the rapid cooling in the nitrous immersion heat treatment step S2 can transform most of the austenite phase (γ phase) into martensite, some γ phase may remain (residual γ phase). Because the γ phase is nonmagnetic, it is preferable that the volume fraction of the residual γ phase be 5% or less from the perspective of magnetic properties.

[0041] Therefore, it is preferable to carry out a sub-zero treatment step S3 following the nitrogen immersion heat treatment step S2 in order to transform the residual γ phase into a martensite structure. Sub-zero treatment is a process of cooling the material to below 0°C, and it is preferable to use ordinary sub-zero treatment using dry ice or ultra-sub-zero treatment using liquid nitrogen.

[0042] Although not an essential step, a tempering step S4 at 100°C or higher and 210°C or lower may be further carried out after the subzero treatment step S3 in order to impart toughness to the soft magnetic iron alloy plate (not shown in Figure 1).

[0043] As explained above, in a sheet material containing Fe as the main component, 1 to 30 atomic % Co, and 0.5 to 5 atomic % M component capable of forming M-N nitrides, 0.2 atomic % to 10 atomic % N atoms are introduced and diffused into the sheet material in a temperature range where the diffusion and rearrangement of the M component is difficult (a temperature range where the diffusion coefficient is sufficiently small), followed by rapid cooling. This makes it possible to generate an Fe-N martensite phase while suppressing the generation of nitride particles.

[0044] In other words, by including the M component, it is possible to penetrate and diffuse N atoms at a desired content throughout the entire sheet material, and by keeping the penetration and diffusion temperature of N atoms low, it is possible to suppress the precipitation of nitride particles of the M component to an average particle size of 0.5 μm or less and a number density of 50 particles / 100 μm. 2 The average particle size, number density and occupancy of nitride particles can be suppressed to 0.4 μm or less, and the occupancy of nitride particles can be suppressed to 10% by area or less. 2 More preferably, 0.3 μm or less and 5% by area or less, 30 / 100 μm 2 It is more preferably 2% by area or less.

[0045] As a result, the soft magnetic iron alloy sheet of the present invention can achieve a higher Bs than electromagnetic pure iron sheets while suppressing an increase in Pi due to the generation of nitride particles. Specifically, Bs exceeds 2.20 T and Pi can be suppressed to 60 W / kg or less.

[0046] [Iron cores and rotating electrical machines] Fig. 4A is a schematic perspective view showing an example of a stator of a rotating electric machine, and Fig. 4B 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 rotation axis direction (a cross section whose normal is parallel to the axial direction). In the rotating electric machine, a rotor (not shown) is disposed radially inside the stator of Figs. 4A and 4B.

[0047] 4A and 4B, stator 20 has stator coils 21 wound in a plurality of stator slots 11 formed on the inner periphery of core 10. Stator slots 11 are spaces that are arranged at a predetermined circumferential pitch around the circumferential direction of core 10 and penetrate the core 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 core 10, and the parts of the inner periphery tip areas of teeth 13 that define slits 12 are called tooth claw portions 14.

[0048] The stator coil 21 is usually made up of a plurality of segment conductors 22. For example, in Fig. 4A and Fig. 4B, 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. Furthermore, from the viewpoint of preventing partial discharge between the segment conductors 22 and the iron core 10 and partial discharge 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).

[0049] The rotating electric machine according to the present invention is a rotating electric machine that uses the iron core 10 according to the present invention. The iron core 10 according to the present invention has a higher Bs than conventional iron cores made of pure electromagnetic iron sheets or electromagnetic steel sheets, which leads to higher torque and higher output of the rotating electric machine. Furthermore, the iron core 10 according to the present invention can be manufactured at a lower cost than iron cores made of permendur sheets, which can prevent excessive cost increases in the rotating electric machine. [Example]

[0050] 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.

[0051] [Experiment 1] (Preparation of Starting Material 1, Reference Sample 1, and Reference Sample 2) Commercially available pure metal raw materials (Fe, Co, V, Cr, each with a purity of 99.9%) were mixed and an alloy ingot was produced by arc melting on a water-cooled copper hearth (Daia Vacuum Co., Ltd., automatic arc melting furnace, reduced-pressure Ar atmosphere). To homogenize the alloy ingot, the sample was remelted six times while being inverted. The resulting alloy ingot was then pressed and rolled to prepare a 0.1 mm thick Fe-18.5 at% Co-2.2 at% V-1.1 at% Cr alloy plate, which served as starting material 1.

[0052] Starting material 1 was dissolved in Ar gas (0.8 × 10 5 The specimen was subjected to strain removal annealing at 500°C under a pressure of 100 Pa to prepare Reference Sample 1. A commercially available electrical steel sheet (thickness = 0.35 mm, manufactured by Nippon Steel Corporation, 35H300) was also prepared as Reference Sample 2.

[0053] [Experiment 2] (Preparation of iron alloy plate 1) For the starting material 1 prepared in Experiment 1, a nitrogen immersion heat treatment process was carried out in a N2 gas atmosphere (0.8 × 10 5 The temperature was raised to 500°C under a pressure of 0.8×10 Pa and held for 30 minutes. 5 Pa, 1 min) and N2 gas atmosphere (0.8 × 105 The specimen was then subjected to an ultra-subzero treatment in which it was immersed in liquid nitrogen within 5 minutes to produce iron alloy plate 1.

[0054] [Experiment 3] (Production of iron alloy plate 2) For the starting material 1 prepared in Experiment 1, a nitrogen immersion heat treatment process was carried out in a N2 gas atmosphere (0.8 × 10 5 The temperature was raised to 600°C under a pressure of 0.8×10 Pa and held for 30 minutes. 5 Pa, 10 min) and N2 gas atmosphere (0.8 × 10 5 The specimen was then subjected to an ultra-subzero treatment in which it was immersed in liquid nitrogen within 5 minutes to produce iron alloy plate 2.

[0055] [Experiment 4] (Production of iron alloy plate 3) For the starting material 1 prepared in Experiment 1, a nitrogen immersion heat treatment process was carried out in a N2 gas atmosphere (0.8 × 10 5 The temperature was raised to 900°C under a pressure of 0.8×10 Pa and held for 30 minutes. 5 Pa, 1 min) and N2 gas atmosphere (0.8 × 10 5 The specimen was then subjected to an ultra-subzero treatment in which it was immersed in liquid nitrogen within 5 minutes to produce iron alloy plate 3.

[0056] [Experiment 5] (Production of iron alloy plate 4) For the starting material 1 prepared in Experiment 1, a nitrogen immersion heat treatment process was carried out in a N2 gas atmosphere (0.8 × 10 5 The temperature was raised to 900°C under a pressure of 0.8×10 Pa and held for 30 minutes. 5Pa, 10 min) and N2 gas atmosphere (0.8 × 10 5 The specimen was then subjected to an ultra-subzero treatment in which it was immersed in liquid nitrogen within 5 minutes to produce iron alloy plate 4.

[0057] As explained above, iron alloy sheets 1 and 2 were subjected to a relatively low temperature in the nitrous oxide heat treatment process and are samples of iron alloy sheets serving as examples of the present invention. Iron alloy sheets 3 and 4 were subjected to a relatively high temperature in the nitrous oxide heat treatment process and are samples serving as comparative examples of the present invention.

[0058] [Experiment 6] (Property and magnetic property investigation of iron alloy plates 1-4, reference sample 1 and reference sample 2) First, the crystal phase was identified by wide-angle X-ray diffraction (WAXD) measurement using Cu-Kα radiation on the surface of each sample using an X-ray diffractometer (Rigaku Corporation, Rint-Ultima III).

[0059] As a result, diffraction peaks of only the α phase (ferrite phase) were confirmed in Reference Sample 1 and Reference Sample 2. In contrast, while the α phase was the main phase in Iron Alloy Sheets 1 to 4, diffraction peaks of the α' phase (Fe8N phase), VN phase (vanadium nitride phase), and CrN phase (chromium nitride phase) were confirmed. In addition, a diffraction peak of the ε phase (Fe3N phase) was also confirmed in Iron Alloy Sheet 4.

[0060] These results confirm that the nitrous immersion heat treatment and subzero treatment processes produce the α' phase of the Fe-N martensite phase and the VN and CrN phases of the MN-type nitride phases. The results are summarized in Table 1 below.

[0061] Test pieces for microstructural observation were taken from each sample, and the cross sections of the test pieces were mirror-polished and etched with a picric acid aqueous solution. The cross sections were subjected to microstructural observation using a scanning electron microscope (SEM, Hitachi High-Technologies Corporation, S4800). Furthermore, image analysis was performed on the obtained SEM observation images to determine the area of ​​100 μm 2 The number density was calculated from the number of precipitated particles observed within the square. 2 The occupancy rate (area %) of precipitated particles within the square of 100 μm was calculated. 2 The average particle size of the precipitated particles observed within the square (average diameter of the circle with equivalent area of ​​each precipitated particle) was calculated. The results are shown in Table 1.

[0062] Figure 2 is a cross-sectional SEM image of iron alloy plate 2, and Figure 3 is a cross-sectional SEM image of iron alloy plate 3. As shown in Figures 2 and 3, it can be seen that precipitate particles 2 are scattered throughout the matrix 1. Furthermore, when comparing iron alloy plate 2 and iron alloy plate 3, it is easily confirmed that the number density and occupancy of precipitate particles 2 are significantly different. Taking into account the WAXD results, it is believed that precipitate particles 2 are particles of the VN phase and CrN phase (i.e., MN-type nitride particles).

[0063] Quantitative analysis of the N concentration was performed on the cross-section of the test specimen for microstructural observation using an electron probe microanalyzer (EPMA, manufactured by JEOL Ltd., JXA-8530F). Specifically, spot measurements were performed at 200 equally spaced points along the thickness direction (plate thickness direction) of the test specimen cross-section, and the average value was taken as the N content. In addition, the average of the measurements for only the matrix region (region not containing precipitate particles) out of the 200 spot measurements was calculated as the matrix N concentration. The results are also shown in Table 1.

[0064] Next, as a mechanical property, the Vickers hardness (Hv) of the cross section of the test piece for microstructure observation was measured using a micro Vickers hardness tester (Matsuzawa Corporation, AMT-X7AFS) (load: 100 gf, holding time: 15 seconds, average of 10 measurements). The results are also shown in Table 1.

[0065] The magnetic properties (Bs, Hc, Pi) of each sample were investigated. The magnetization (unit: emu) of the sample was measured using a vibrating sample magnetometer (Riken Denshi Co., Ltd., BHV-525H) under conditions of a magnetic field of 1.6 MA / m and a temperature of 20°C. The saturation magnetic flux density Bs (unit: T) and coercive force Hc (unit: A / m) were calculated from the sample volume and 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 a BH loop analyzer (IFG Co., Ltd., IF-BH550) and the H coil method (compliant with JIS C 2556:2015) using a vertical yoke single sheet tester. -1.0 / 400 The results are shown in Table 2.

[0066] [Table 1]

[0067] [Table 2]

[0068] The results in Table 1 show that the N content increases from iron alloy sheets 1 to 4, and that an Fe-N martensite phase (α' phase) and an MN-type nitride phase (VN phase, CrN phase) are formed. Considering the manufacturing process of iron alloy sheets 1 to 4 (nitrogen immersion heat treatment process in Experiments 2 to 5), it is confirmed that the N content increases when the heat treatment temperature is increased or the NH3 gas supply time is extended.

[0069] Here, iron alloy sheets 3 and 4, which were subjected to a relatively high temperature in the nitrous heat treatment process, exhibited a large amount of precipitation of MN-type nitride particles, and the matrix N concentration was lower than the N content of the entire iron alloy sheet. In contrast, iron alloy sheets 1 and 2, which were subjected to a relatively low temperature in the nitrous heat treatment process, exhibited a small amount of precipitation of MN-type nitride particles, and the N content of the entire iron alloy sheet and the matrix N concentration were the same. These findings confirm that the formation and precipitation of MN-type nitride particles can be suppressed by setting the temperature in the nitrous heat treatment process lower (to a temperature range where the diffusion and rearrangement of the M component are difficult).

[0070] Furthermore, it was confirmed that the Vickers hardness increased as the matrix N concentration increased (and as a result, the amount of α' phase formed increased). Because Vickers hardness is positively correlated with mechanical strength such as tensile strength, it is expected that increasing the matrix N concentration and increasing the amount of α' phase formed will also increase mechanical strength.

[0071] Looking at the results in Tables 1 and 2 together, it can be seen that Reference Sample 2, a commercially available electrical steel sheet, has sufficiently low Hc and Pi. -1.0 / 400 However, the Bs does not reach that of the electromagnetic pure iron sheet (approximately 2.1 T). Reference sample 1, which does not allow the N component to penetrate or diffuse and does not form the α' phase, has a higher Bs than the electromagnetic pure iron sheet, but is significantly lower than the Bs of permendur (approximately 2.4 T).

[0072] In contrast, in the iron alloy sheets 1 and 2 according to the present invention, the N component penetrates and diffuses to form the α' phase, which clearly improves Bs compared to the reference sample 1, and Pi -1.0 / 400 indicates 60 W / kg or less.

[0073] On the other hand, in the comparative iron alloy sheets 3 and 4, the N concentration in the matrix is ​​not so high (clearly lower than the N content), so it is thought that the amount of α' phase generated is not so large, and Bs is about the same as that of iron alloy sheet 1. In addition, since a large amount of nitride particles are generated and precipitated, Hc and Pi -1.0 / 400 is extremely high.

[0074] From the above experiments, it was confirmed and demonstrated that in Fe-Co-M alloy sheets (M is an element capable of forming M-N nitrides), N atoms can penetrate and diffuse into the sheet in a temperature range where the diffusion and rearrangement of the M component is difficult (a temperature range where the diffusion coefficient is sufficiently small), generating the α' and / or α" phases, and by suppressing the precipitation of nitride particles of the M component to a predetermined level or below, it is possible to suppress an excessive increase in Pi while maintaining an excellent Bs.

[0075] 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]

[0076] 1...mother phase, 2...precipitated particles, 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, A chemical composition comprising Co in an amount of 10 atomic % or more and 20 atomic % or less, N in an amount of 0.2 atomic % or more and 3 atomic % or less, an M component capable of forming an MN-type nitride in an amount of 0.5 atomic % or more and 5 atomic % or less, and the balance being Fe and impurities; the M component is one or more of V, Cr, Ti, Al, Nb, and Mo; The soft magnetic iron alloy plate has an Fe—N martensite phase and an austenite phase volume fraction of 5% or less, When the cross section of the soft magnetic iron alloy plate is observed, the nitride particles of the M component have an average particle size of 0.5 μm or less and a number density of 30 particles / 100 μm. 2 A soft magnetic iron alloy plate characterized by being precipitated as follows:

2. The soft magnetic iron alloy plate according to claim 1, A soft magnetic iron alloy plate, characterized in that when a cross section of the soft magnetic iron alloy plate is observed, the occupancy rate of nitride particles of the M component is 2 area % or less.

3. The soft magnetic iron alloy plate according to claim 1 or 2, A soft magnetic iron alloy plate characterized by a saturation magnetic flux density exceeding 2.20 T and an iron loss of 60 W / kg or less.

4. The soft magnetic iron alloy plate according to any one of claims 1 to 3, A soft magnetic iron alloy plate having a Vickers hardness of 200 or more.

5. 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 4.

6. A rotating electric machine having an iron core, A rotating electric machine, wherein the iron core is the iron core according to claim 5.

Images