Soft magnetic iron plate, method for producing the same, iron core using the same, and rotating electrical machine

Abstract

The present invention provides a soft magnetic iron plate exhibiting a higher saturation magnetic flux density and lower iron loss than an electromagnetic pure iron plate, a method for producing the soft magnetic iron plate, an iron core, and a rotating electrical machine using the soft magnetic iron plate. The soft magnetic iron plate of the present invention is a soft magnetic iron plate containing iron as a main component and nitrogen, characterized in that the soft magnetic iron plate comprises, along the thickness direction of the soft magnetic iron plate, a high nitrogen concentration layer having a nitrogen concentration of 2 to 11 atomic %, a low nitrogen concentration layer having a nitrogen concentration less than half that of the high nitrogen concentration layer, and a nitrogen concentration transition layer connecting the nitrogen concentrations of the high nitrogen concentration layer and the low nitrogen concentration layer, with the surface regions of at least two main surfaces of the soft magnetic iron plate constituting the low nitrogen concentration layer.

Description

Technical Field

[0001] The present invention relates to magnetic material technology, and in particular to a soft magnetic iron plate having both a higher saturation magnetic flux density and lower iron loss than an electromagnetic pure iron plate, a method for producing the soft magnetic iron plate, and an iron core and a rotating electric machine using the soft magnetic iron plate. Background Art

[0002] Electromagnetic steel sheets or electromagnetic pure iron sheets (e.g., 0.01 to 1 mm thick) are formed by laminating multiple sheets and used as the core material for rotating motors or transformers. In the core, high conversion efficiency between electrical energy and magnetic energy is very important, and high magnetic flux density and low iron loss are important. In order to increase the magnetic flux density, it is desirable that the material has a high saturation magnetic flux density Bs. As iron-based materials with high Bs, Fe-Co alloy materials and iron nitride materials (e.g., Fe-Co alloys) are known. 16 N2).

[0003] Furthermore, reducing the cost of the iron core is naturally one of the most important issues, and we have been actively developing technologies to stably and inexpensively produce materials having a high Bs.

[0004] For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-046074) discloses magnetic metal fine particles composed primarily of Fe, coated with graphite, and having a nitrogen content of 0.1 to 5% by weight, including at least one of Fe4N and Fe3N. Furthermore, a method for producing the magnetic metal fine particles is disclosed, comprising mixing iron oxide powder and carbon-containing powder, heat-treating the mixed powder in a non-oxidizing atmosphere to obtain metal fine particles composed primarily of Fe and coated with graphite, and then further nitriding the fine particles to obtain the magnetic metal fine particles.

[0005] According to Patent Document 1, magnetic metal fine particles having excellent corrosion resistance and a method for producing the same can be provided.

[0006] In addition, Patent Document 2 (re-publication WO2014 / 104393) discloses the following method for manufacturing a grain-oriented electrical steel sheet: a steel billet is used as a raw material, the steel billet containing, in terms of mass % or mass ppm, less than 0.08% C, 2.0 to 4.5% Si, and less than 0.5% Mn, and the S, Se, and O contents are each suppressed to less than 50 ppm, the sol.Al is suppressed to less than 100 ppm, and the N content is controlled to [sol.Al]×(14 / 27) ppm. The present invention relates to a composition having a nitrogen content within the range of ≤N≤80ppm, the remainder being Fe and inevitable impurities. In the manufacture of the grain-oriented electrical steel sheet, a nitriding treatment is performed after cold rolling and before the start of secondary recrystallization annealing to adjust the nitrogen content to 50 mass ppm or more and 1000 mass ppm or less. The annealing separator contains sulfides and / or sulfates in an amount of 0.2 to 15 mass % in total. During the temperature rise process of the secondary recrystallization annealing, the residence time in the temperature range of 300 to 800°C is ensured to be 5 hours or more.

[0007] According to Patent Document 2, by precipitating silicon nitride (Si3N4) and MnS and using them as a suppressing force for normal grain growth, the deviation of magnetic properties can be greatly reduced, and grain-oriented electromagnetic steel sheets with good magnetic properties can be stably manufactured industrially.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-046074

[0011] Patent Document 2: International Publication No. 2014 / 104393 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] While powder cores are suitable for smaller electrical components such as noise filters and reactors, larger electrical equipment such as rotating motors and transformers use cores formed by laminating electromagnetic steel sheets, which is advantageous from the perspective of mechanical strength.

[0014] Patent Document 1 is considered a technology suitable for powder cores, but it cannot be said to be suitable for the production and use of thin plate materials such as electromagnetic steel sheets. Furthermore, Patent Document 2 is a technology for electromagnetic steel sheets, but suffers from the disadvantage that the Bs of these electromagnetic steel sheets is lower than that of electromagnetic pure iron sheets. In other words, Patent Documents 1 and 2 do not reveal a method for producing thin plate materials that exhibit higher magnetic properties than electromagnetic pure iron sheets, or for producing such thin plate materials stably and inexpensively.

[0015] Furthermore, to improve the efficiency of electrical / magnetic energy conversion in the iron core, reducing iron loss, Pi, is also crucial. Pi is the sum of hysteresis loss and eddy current loss. To reduce hysteresis loss, a low coercive force, Hc, is desirable, and to reduce Hc, large grain sizes are desirable. Furthermore, to reduce eddy current loss, high resistivity and thin sheets are desirable. However, the technology for stably and cost-effectively producing electromagnetic steel sheets that exhibit a higher Bs than pure electromagnetic iron sheets and a lower Pi has yet to be established.

[0016] Therefore, an object of the present invention is to provide a soft magnetic iron plate showing a higher saturation magnetic flux density and lower iron loss than an electromagnetic pure iron plate, a method for producing the soft magnetic iron plate, and an iron core and a rotating electrical machine using the soft magnetic iron plate.

[0017] Technical solutions to solve problems

[0018] (I) One embodiment of the present invention provides a soft magnetic iron plate having iron as a main component and containing nitrogen, wherein:

[0019] The soft magnetic iron plate includes, in a thickness direction thereof, a high nitrogen concentration layer having a nitrogen concentration of not less than 2 atomic % and not more than 11 atomic %, a low nitrogen concentration layer having a nitrogen concentration of not more than half the nitrogen concentration of the high nitrogen concentration layer, and a nitrogen concentration transition layer that makes the nitrogen concentration of the high nitrogen concentration layer continuous with the nitrogen concentration of the low nitrogen concentration layer.

[0020] The surface regions of at least both main surfaces of the soft magnetic iron plate serve as the low nitrogen concentration layer.

[0021] The present invention can supplement the soft magnetic iron plate (I) of the present invention described above with the following improvements or changes.

[0022] (i) The average nitrogen concentration gradient of the nitrogen concentration transition layer is not less than 0.1 atomic % / μm and not more than 10 atomic % / μm.

[0023] (ii) The nitrogen concentration of the low nitrogen concentration layer is 1 atomic % or less.

[0024] (iii) The saturation magnetic flux density exceeds 2.14 T, and the iron loss at a magnetic flux density of 1.0 T and 400 Hz is less than 40 W / kg.

[0025] (iv) The thickness of the soft magnetic iron plate is not less than 0.01 mm and not more than 1 mm.

[0026] (v) It contains an α phase, an α′ phase, and an α″ phase, wherein the α phase is a main phase and the volume fraction of the α″ phase is 10% or more.

[0027] (vi) The α″ phase is a phase in which the ratio of the lattice constant of the c-axis to the a-axis is different from that of the stoichiometric composition Fe. 16 N2 has a crystalline phase at this ratio.

[0028] (vii) The total content of elements other than the above-mentioned iron and the above-mentioned nitrogen is less than 1 atomic %.

[0029] (viii) Contains cobalt in addition to the above-mentioned iron and nitrogen.

[0030] (ix) The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration is distributed along the thickness direction.

[0031] In the present invention, the surface region is defined as the outermost region including the main surface along the thickness direction of the iron plate, and the inner region is defined as the region excluding the nitrogen concentration transition layer within the region sandwiched by the surface region.

[0032] (II) Another aspect of the present invention provides a method for producing a soft magnetic iron plate, which is the above-mentioned method for producing a soft magnetic iron plate, characterized by comprising:

[0033] a starting material preparation step of preparing a starting material composed of a soft magnetic material having iron as a main component and having a thickness of not less than 0.01 mm and not more than 1 mm;

[0034] a nitrogen concentration distribution controlled heat treatment step of subjecting the starting material to a predetermined nitrogen concentration distribution controlled heat treatment to form a predetermined nitrogen concentration distribution along the thickness direction of the starting material; and

[0035] The phase transformation / iron nitride phase generation step causes the starting material having the above-mentioned nitrogen concentration distribution to undergo martensitic transformation and disperse the iron nitride phase.

[0036] The above-mentioned nitrogen concentration distribution control heat treatment is a heat treatment carried out within the austenite phase formation temperature range, and is a combination of nitriding heat treatment and denitriding heat treatment, wherein the above-mentioned nitriding heat treatment is a treatment in which nitrogen atoms invade and diffuse from the two main surfaces of the above-mentioned starting material to make the internal nitrogen concentration become greater than 2 atomic % and less than 11 atomic %, and the above-mentioned denitriding heat treatment is a treatment in which nitrogen is released from the two main surfaces of the starting material to form the above-mentioned low nitrogen concentration layer and the above-mentioned nitrogen concentration transition layer connected to it in the above-mentioned surface area.

[0037] The present invention can supplement the above-mentioned method (II) for producing a soft magnetic iron plate of the present invention with the following improvements or changes.

[0038] (x) The nitriding heat treatment is a heat treatment in which the ammonia partial pressure is controlled in an atmosphere containing ammonia gas to control the concentration of nitrogen that penetrates and diffuses. The denitriding heat treatment is a heat treatment in which the ammonia partial pressure is lowered and the temperature is increased compared to the nitriding heat treatment.

[0039] (xi) The temperature difference between the denitrification heat treatment and the nitriding heat treatment is 20° C. or more and 200° C. or less.

[0040] (xii) The above-mentioned phase transformation / iron nitride phase formation step includes quenching to below 100°C and low-temperature treatment to below 0°C.

[0041] (III) Another aspect of the present invention provides an iron core composed of a laminate of soft magnetic iron plates, wherein the soft magnetic iron plates are the soft magnetic iron plates of the present invention described above.

[0042] (IV) Another aspect of the present invention provides a rotating electrical machine having an iron core, wherein the iron core is the iron core of the present invention described above.

[0043] Effects of the Invention

[0044] The present invention provides a soft magnetic iron plate that exhibits a higher saturation magnetic flux density and lower iron loss than an electromagnetic pure iron plate, and a method for manufacturing the soft magnetic iron plate. Furthermore, by using the soft magnetic steel plate, an iron core and a rotating electrical machine can be provided that have improved electrical energy-magnetic energy conversion efficiency compared to an iron core using pure iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1A This is a graph showing an example of the relationship between the nitrogen concentration and the length in the thickness direction of the soft magnetic iron plate of the present invention.

[0046] Figure 1B This is a graph showing another example of the relationship between the nitrogen concentration and the length in the thickness direction of the soft magnetic iron plate of the present invention.

[0047] Figure 1C This is a graph showing another example of the relationship between the nitrogen concentration and the length in the thickness direction of the soft magnetic iron plate of the present invention.

[0048] Figure 2 This is a process diagram showing an example of a method for producing the soft magnetic iron plate of the present invention.

[0049] Figure 3A It is a perspective schematic diagram showing an example of a stator of a rotating electrical machine.

[0050] Figure 3B is an enlarged cross-sectional view of the slot area of ​​the stator.

[0051] Figure 4 This is a graph showing the nitrogen concentration distribution and the cobalt concentration distribution in the plate thickness direction of sample C-01 of the present invention. DETAILED DESCRIPTION

[0052] [Basic idea of ​​the present invention]

[0053] Pure iron has the advantages of being inexpensive and having a high saturation magnetic flux density, Bs (2.14 T). Fe-Si alloys containing approximately 1-3% silicon (Si) by mass can significantly reduce iron loss, Pi, compared to pure iron, but have the disadvantage of slightly lowering Bs (2.0 T). Furthermore, Fe-Co alloys containing approximately 50% cobalt (Co) by mass exhibit a sufficiently high Bs (2.4 T) and low Pi compared to pure iron, but suffer from the disadvantage of Co having a higher material cost than Fe.

[0054] On the other hand, as a soft magnetic material showing a higher Bs than pure iron, there is the above-mentioned Fe 16 The inventors of the present invention have focused on the possibility of generating Fe2 phase by adding N to a soft magnetic material mainly composed of Fe. 16 N2 phase, Bs may be increased. However, Fe 16 The N2 phase is a metastable compound phase. In the prior art, most of the research is focused on powder materials, and there is almost no knowledge related to the manufacturing technology of thin plate materials.

[0055] Therefore, the inventors of the present invention considered using it in the form of an electromagnetic iron plate (for example, a thickness of 0.01 to 1 mm) and conducted in-depth research on a process for stably manufacturing a nitrogen-containing soft magnetic iron plate that exhibits superior magnetic properties to those of an electromagnetic pure iron plate using inexpensive starting materials (for example, an electromagnetic pure iron plate or an electromagnetic steel plate).

[0056] As a result, they discovered that by subjecting the starting material to a predetermined nitrogen concentration distribution controlled heat treatment combining nitriding and denitriding heat treatments to achieve a predetermined nitrogen concentration distribution along the thickness direction, followed by a predetermined phase transformation / iron nitride phase formation treatment, it is possible to stably produce a soft magnetic iron plate exhibiting a higher Bs and lower Pi than pure iron. This discovery led to the completion of the present invention.

[0057] The following describes embodiments of the present invention in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and can be appropriately combined with or improved upon known technologies without departing from the technical spirit of the invention. Components with the same meaning are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0058] [Soft Magnetic Iron Plate of the Present Invention]

[0059] Figure 1A This is a graph showing an example of the relationship between the nitrogen concentration and the length in the thickness direction of the soft magnetic iron plate of the present invention. Figure 1B This is a graph showing another example of the relationship between the nitrogen concentration and the length in the thickness direction of the soft magnetic iron plate of the present invention. Figure 1C This is a graph showing another example of the relationship between the nitrogen concentration and the length in the thickness direction of the soft magnetic iron plate of the present invention.

[0060] The nitrogen concentrations shown in the figures were quantitatively analyzed using an electron probe microanalyzer (EPMA, manufactured by JEOL Ltd., JXA-8800RL) based on a spot diameter of 1 μm.

[0061] like Figures 1A to 1C As shown, the soft magnetic iron plate of the present invention includes, in its thickness direction, a high nitrogen concentration layer 10 having a nitrogen concentration of not less than 2 atomic % and not more than 11 atomic %, a low nitrogen concentration layer 20 having a nitrogen concentration of not more than half the nitrogen concentration of the high nitrogen concentration layer, and a nitrogen concentration transition layer 30 that makes the nitrogen concentration of the high nitrogen concentration layer continuous with the nitrogen concentration of the low nitrogen concentration layer, and the surface regions of at least two main surfaces of the soft magnetic iron plate serve as the low nitrogen concentration layer 20. Figure 1B and Figure 1C In addition to the low nitrogen concentration layer 20 in the surface region of both main surfaces, the soft magnetic iron plate also has a low nitrogen concentration layer 20 and a nitrogen concentration transition layer 30 inside. Figures 1A to 1C It is found that the nitrogen concentration distribution of the soft magnetic iron plate of the present invention is line-symmetrical about the center in the thickness direction.

[0062] The high nitrogen concentration layer 10 preferably has a nitrogen concentration of 2 atomic % or more and 11 atomic % or less, and more preferably 2 atomic % or more and 9 atomic % or less. It is believed that by containing 2 atomic % or more of nitrogen, the α″ phase (regular martensite phase, Fe 16 N2 phase, body-centered tetragonal phase) can be generated in an effective amount (e.g., 10% by volume or more), contributing to an increase in the Bs of the soft magnetic iron plate (Bs exceeding 2.14T). By controlling nitrogen to 11% or less, the formation of undesirable phases (e.g., Fe4N phase) can be suppressed, preventing a decrease in the Bs of the soft magnetic iron plate (Bs below 2.14T).

[0063] In addition, as will be described in detail later, based on the results of wide-angle X-ray diffraction (WAXD) measurements, it can be considered that the high nitrogen concentration layer 10 is not entirely in the α″ phase, but rather forms a state in which the α phase (ferrite phase, body-centered cubic crystal) is the main phase (the phase with the largest volume fraction), and the α″ phase and α′ phase (irregular martensite phase, Fe8N phase, body-centered tetragonal crystal) are dispersed.

[0064] In addition, the α" phase in the soft magnetic iron plate of the present invention preferably has a ratio "c / a" of the c-axis length to the a-axis length of the lattice constant measured by WAXD, and the "c / a" is different from the stoichiometric composition Fe 16 The crystal phase of N2 with "c / a=1.10" means that the lattice of the α" phase is deformed on average. The reason for this is that the stoichiometric composition of Fe 16 Compared with N2 crystal, N atoms are missing and the lattice is deformed, so compared with the lattice without deformation, it can be expected that the magnetic moment will be increased.

[0065] The volume fraction of the α' phase is not particularly limited, but since the α' phase may be generated as a precursor to the formation of the α" phase, the volume fraction of the α' phase is preferably 10% or greater. Furthermore, since the γ phase (austenite phase, face-centered cubic crystal) is nearly non-magnetic, if the volume fraction of the γ phase exceeds 5%, the volume fraction of the α phase decreases, making it difficult for the Bs of the soft magnetic iron plate to exceed the Bs of the electromagnetic pure iron plate. The volume fraction of the γ phase is more preferably 3% or less, and even more preferably 1% or less.

[0066] The inventors of the present invention have studied and found that if the entire soft magnetic iron plate is composed of a high nitrogen concentration layer 10, the Hc tends to increase due to the large magnetocrystalline anisotropy, and thus the Pi tends to increase. Therefore, in the soft magnetic iron plate of the present invention, by intentionally forming a low nitrogen concentration layer 20 with a low Hc and generating magnetic coupling between the high nitrogen concentration layer 10 and the low nitrogen concentration layer 20, the Pi of the entire soft magnetic iron plate can be reduced.

[0067] To clarify the Hc difference between the high nitrogen concentration layer 10 and the low nitrogen concentration layer 20 , the nitrogen concentration of the low nitrogen concentration layer 20 is preferably less than half the nitrogen concentration of the high nitrogen concentration layer 10 , more preferably less than 1 atomic %, and further preferably less than 0.5 atomic %.

[0068] It is also very important to form a nitrogen concentration transition layer 30 with a predetermined average concentration gradient between the high nitrogen concentration layer 10 and the low nitrogen concentration layer 20. Forming the nitrogen concentration transition layer 30 facilitates the transfer of the magnetization state of the low nitrogen concentration layer 20 to the high nitrogen concentration layer 10 (in other words, facilitates the transfer of the magnetic walls and magnetization of the high nitrogen concentration layer 10). As a result, Hc decreases, lowering the Pi of the entire soft magnetic iron plate.

[0069] The average nitrogen concentration gradient of the nitrogen concentration transition layer 30 is preferably not less than 0.1 atomic % / μm and not more than 10 atomic % / μm. If the average nitrogen concentration gradient is less than 0.1 atomic % / μm, it is difficult to overcome the potential for magnetization pinning caused by the large magnetocrystalline anisotropy of the high nitrogen concentration layer 10. On the other hand, if the average nitrogen concentration gradient exceeds 10 atomic % / μm, the concentration gradient is too steep, making magnetic coupling between the high nitrogen concentration layer 10 and the low nitrogen concentration layer 20 less likely to occur.

[0070] The composition of the soft magnetic iron sheet of the present invention is not particularly limited, except for nitrogen. Existing soft magnetic materials that are readily and inexpensively available industrially and commercially (e.g., electromagnetic pure iron, electromagnetic steel, Fe-Si alloy, Fe-Co alloy) can be appropriately utilized as the sheet material. In other words, by using these existing soft magnetic materials as a matrix and applying the nitrogen concentration profile specified in the present invention, a higher Bs and lower Pi can be achieved compared to the soft magnetic material used as the matrix. For example, using electromagnetic pure iron as the matrix can achieve a Bs exceeding 2.14 T and a Pi of less than 40 W / kg (under conditions of a magnetic flux density of 1.0 T and 400 Hz).

[0071] [Method for producing soft magnetic iron plate of the present invention]

[0072] Figure 2 1 is a process diagram showing an example of a method for manufacturing a soft magnetic iron plate of the present invention. Figure 2 As shown, the method for producing a soft magnetic iron plate according to the present invention generally comprises a starting material preparation step S1, a nitrogen concentration distribution control heat treatment step S2, and a phase transformation / iron nitride phase formation step S3. A carburizing heat treatment step S4 may be performed between steps S2 and S3. Each step will be described in more detail below.

[0073] (Starting material preparation process)

[0074] This step S1 is a step of preparing a thin plate material (e.g., 0.01 to 1 mm thick) of a soft magnetic material that is easily and inexpensively available industrially and commercially as a starting material. There are no particular restrictions on the soft magnetic material, as long as it is iron as the main component, and existing materials (e.g., electromagnetic pure iron materials, electromagnetic steel sheets, Fe-Si alloy materials, Fe-Co alloy materials) can be used as appropriate. Since these soft magnetic materials have a low carbon (C) content, it is relatively easy to control the nitrogen concentration distribution in the iron plate and generate the α" phase in subsequent steps, which also helps to reduce process costs.

[0075] (Nitrogen Concentration Distribution Control Heat Treatment Process)

[0076] This step S2 is a step of subjecting the starting material to a predetermined nitrogen concentration distribution controlled heat treatment (a combined heat treatment of nitriding S2a and denitrification S2b) to form a predetermined nitrogen concentration distribution along the thickness direction of the starting material (soft magnetic iron plate). Step S2 of the manufacturing method of the present invention has an important feature.

[0077] Nitriding heat treatment S2a is a heat treatment that causes nitrogen atoms to infiltrate and diffuse from both main surfaces of the soft magnetic iron plate to a predetermined nitrogen concentration within the plate. It is performed in an atmosphere containing ammonia (NH3) gas, heating to a temperature within the γ phase formation temperature range in the Fe-N phase diagram (a temperature above the eutectoid transformation point (592°C), for example, 700-900°C). Because ammonia molecules decompose on the surface of the soft magnetic iron plate, allowing nitrogen atoms to infiltrate and diffuse, the introduction of ammonia gas is preferably performed after the temperature reaches approximately 500°C or higher.

[0078] The nitrogen concentration in the soft magnetic iron plate can be controlled primarily by controlling the ammonia partial pressure. This can be achieved, for example, by controlling the total pressure of the heat treatment environment and / or by mixing it with nitrogen (N2) gas. Furthermore, by intermittently controlling the supply of ammonia (controlling the times when it is supplied and the times when it is not supplied), the balance between the intrusion of nitrogen atoms into the soft magnetic iron plate and the diffusion of nitrogen atoms within the plate can be adjusted, thereby controlling the nitrogen concentration distribution through the plate thickness (particularly in the inner region).

[0079] Denitrification heat treatment S2b is a heat treatment that releases nitrogen from both main surfaces of the soft magnetic iron plate to form a low nitrogen concentration layer 20 in the surface region and a nitrogen concentration transition layer 30 connected thereto. Compared to the aforementioned nitriding heat treatment S2a, the ammonia partial pressure is lowered during the denitrification heat treatment S2b. To achieve greater denitrification efficiency, the treatment is preferably conducted at a higher temperature than that of the nitriding heat treatment S2a. The temperature difference between denitrification heat treatment S2b and nitriding heat treatment S2a is preferably 20°C to 200°C, and more preferably 50°C to 120°C.

[0080] The nitrogen concentration of the low nitrogen concentration layer 20 in the surface region can be controlled primarily by controlling the ammonia partial pressure. The thickness of the low nitrogen concentration layer 20 can be controlled primarily by controlling the heat treatment time. The average concentration gradient of the nitrogen concentration transition layer 30 can be controlled primarily by controlling the temperature.

[0081] (Carburizing heat treatment process)

[0082] This step S4 is a heat treatment to allow carbon to infiltrate the low nitrogen concentration layer 20 in the surface region formed by the denitrification heat treatment in step S2. Step S4 is not essential, but by infiltrating carbon into the low nitrogen concentration layer 20 in the surface region, Pi can be reduced without reducing the Bs of the soft magnetic iron plate.

[0083] The method of carburizing heat treatment is not particularly limited, and existing methods (such as heat treatment in an acetylene (C2H2) gas atmosphere) can be appropriately used. As an example, the denitrification heat treatment can be performed by changing the atmosphere gas to acetylene gas.

[0084] Through this step S2, the above-mentioned Figures 1A to 1CSuch a soft magnetic iron plate with a nitrogen concentration distribution. Figure 1A This is an example in which nitrogen is uniformly diffused to the center in the plate thickness direction during the nitriding heat treatment S2a. Figure 1B is with Figure 1A Compared to the example in which the nitrogen diffusion time of the nitriding heat treatment S2a is shortened and the low nitrogen concentration layer 20 and the nitrogen concentration transition layer 30 are formed in the central region in the plate thickness direction (remaining example), Figure 1C is with Figure 1B Compared with the further shortened nitrogen diffusion time of nitriding heat treatment S2a, a larger area than that of the plate in the central region in the thickness direction is formed. Figure 1B Examples of thick low nitrogen concentration layer 20 and nitrogen concentration transition layer 30 (remaining examples).

[0085] (Phase transformation / iron nitride phase formation process)

[0086] This step S3 is a step of rapidly cooling the soft magnetic iron plate, which has been formed into a predetermined nitrogen concentration distribution in step S2, to below 100°C by quenching, thereby transforming the γ phase into a martensite structure and dispersing and generating an iron nitride phase (particularly an α″ phase). The quenching method is not particularly limited, and existing methods (e.g., oil quenching) can be appropriately utilized.

[0087] In order to transform the retained γ phase in the soft magnetic iron plate into martensite, it is preferable to perform a low-temperature treatment to 0°C or below (e.g., conventional low-temperature treatment using dry ice or ultra-low-temperature treatment using liquid nitrogen). In addition, to impart toughness to the soft magnetic iron plate, tempering at 100°C to 210°C may be performed as needed.

[0088] [Iron Core and Rotating Electric Machine Using the Soft Magnetic Iron Plate of the Present Invention]

[0089] Figure 3A is a perspective schematic diagram showing an example of a stator of a rotating electrical machine, Figure 3B This is an enlarged cross-sectional view of the slot area of ​​the stator. The cross section refers to the section perpendicular to the direction of the rotating axis (the section with the normal line parallel to the axial direction). Figure 3A-3B A rotor (not shown) is arranged radially inside the stator.

[0090] like Figure 3A-3B As shown, stator 50 has stator coils 60 wound around a plurality of stator slots 52 formed on the inner circumference of an iron core 51. Stator slots 52 are arranged at predetermined intervals around the circumference of the iron core 51 and extend axially through the stator. Axially extending slits 53 are formed in the innermost portion of the stator slots 52. The area separating adjacent stator slots 52 is called a tooth 54 of the iron core 51, and the portion defining the slits 53 at the inner circumferential tip of each tooth 54 is called a claw portion 55.

[0091] The stator coil 60 is generally composed of a plurality of segmented conductors 61. For example, Figure 3A-3B In the embodiment, the stator coil 60 is composed of three segmented conductors 61 corresponding to the U phase, V phase, and W phase of the three-phase AC. Furthermore, to prevent partial discharge between the segmented conductors 61 and the iron core 51, and partial discharge between the phases (U phase, V phase, W phase), each segmented conductor 61 is typically covered with an electrical insulating material 62 (e.g., insulating paper or insulating varnish coating) on ​​its outer circumference.

[0092] The iron core and rotating electric machine using the soft magnetic iron plates of the present invention refer to an iron core 51 formed by forming the soft magnetic iron plates of the present invention into a predetermined shape and then laminating the resulting material in a plurality of layers in the axial direction, and a rotating electric machine using this iron core 51. As described above, the soft magnetic iron plates of the present invention exhibit magnetic properties that exhibit a higher Bs and lower Pi than those of electromagnetic pure iron plates. Therefore, it is possible to provide an iron core that improves the efficiency of converting electrical energy into magnetic energy compared to iron cores using conventional electromagnetic steel plates. This highly efficient iron core contributes to the miniaturization and higher torque of rotating electric machines.

[0093] Example

[0094] The present invention will be described in more detail below through various experiments, but the present invention is not limited to the structures and configurations described in these experiments.

[0095] [Experiment 1]

[0096] A commercially available electromagnetic pure iron plate (thickness = 0.1 mm) was prepared as a starting material. The starting material was subjected to an ammonia atmosphere (partial pressure = 1×10 5 Pa) was subjected to a nitriding heat treatment at 800°C for 2 hours. At this time, ammonia gas was introduced at the stage of reaching 500°C during the temperature rise process, and intermittent control (NH3 gas and N2 gas were alternately circulated) was performed 6 times to adjust the nitrogen concentration to 5 atomic % uniformly along the thickness direction of the plate. Following this nitriding heat treatment, the ammonia partial pressure was reduced to 1×10 4 Pa and heat up to 820℃ and keep it for 5 minutes for denitrification heat treatment.

[0097] Next, the electromagnetic pure iron plate after the denitrification heat treatment was oil quenched (60°C) to cause martensitic transformation, and then subjected to ultra-low temperature treatment to cause the retained γ phase to also undergo martensitic transformation, thereby producing sample A-03.

[0098] The nitrogen concentration distribution in the thickness direction of the obtained sample A-03 was investigated using EPMA, and the result was the above-mentioned Figure 1A. It shows that a low nitrogen concentration layer (N concentration ≈ 0 atomic %, thickness = 10 μm) is formed in the surface area of ​​both main surfaces of the sample, a high nitrogen concentration layer (N concentration ≈ 5 atomic %, thickness = 70 μm) is formed in the inner area, and a nitrogen concentration transition layer (average N concentration gradient ≈ 1 atomic % / μm, thickness = 5 μm) is formed to connect the low nitrogen concentration layer and the high nitrogen concentration layer.

[0099] [Experiment 2]

[0100] Commercially available electromagnetic pure iron plates (thickness = 0.1 mm) and commercially available electromagnetic steel plates (thickness = 0.1 mm, carbon concentration = 0.2 atomic %) were prepared as starting materials. Next, the same procedures as in Experiment 1 were followed, except for varying the ammonia partial pressure in the nitriding heat treatment and / or the holding temperature or holding time in the denitriding heat treatment during the nitrogen concentration distribution control heat treatment step. Samples A-01 to A-02 and A-04 to A-12 were prepared, differing from those in Experiment 1 in the nitrogen concentration in the high nitrogen concentration layer, the thickness of the low nitrogen concentration layer, and / or the average nitrogen concentration gradient in the nitrogen concentration transition layer. The phase transformation / iron nitride phase formation steps were performed in the same manner as in Experiment 1.

[0101] The nitrogen concentration distribution in the plate thickness direction of the obtained samples A-01 to A-02 and A-04 to A-12 was examined using EPMA in the same manner as in Experiment 1. The description of each sample of Experiments 1 and 2 is summarized in Table 1 described below.

[0102] [Experiment 3]

[0103] A commercially available electromagnetic pure iron plate (thickness = 0.1 mm) similar to that used in Experiment 1 was prepared as the starting material. This starting material was subjected to only a nitriding heat treatment (no denitrification heat treatment) under the same conditions as in Experiment 1, resulting in Sample A-C1 (a sample without a low nitrogen concentration layer or nitrogen concentration transition layer) with a high nitrogen concentration layer (N concentration ≈ 5 atomic %) throughout the thickness of the plate. The phase transformation / iron nitride phase formation process was performed in the same manner as in Experiment 1. Sample A-C1 serves as a comparative sample to verify the effects of the low nitrogen concentration layer and nitrogen concentration transition layer in the surface region.

[0104] Separately, the same starting material (a commercially available electromagnetic pure iron plate with a thickness of 0.1 mm) was subjected to a nitriding heat treatment under adjusted heat treatment conditions to achieve a nitrogen concentration distribution with a high nitrogen concentration layer (N concentration ≈ 5 atomic %) in the surface region (thickness = 10 μm), a nitrogen concentration transition layer (average N concentration gradient ≈ 1 atomic % / μm, thickness = 5 μm), and a low nitrogen concentration layer (N concentration ≈ 0 atomic %) in the interior region (thickness = 70 μm). Sample A-C2 was prepared. No denitrification heat treatment was performed. The phase transformation / iron nitride phase formation process was performed in the same manner as in Experiment 1. Sample A-C2 had a nitrogen concentration distribution that was the exact opposite of that of Sample A-03 and served as a comparative sample to verify the effectiveness of the low nitrogen concentration layer in the surface region.

[0105] Furthermore, a commercially available electromagnetic pure iron plate (thickness = 0.1 mm) was used as reference sample A-R1 as a benchmark for Experiments 1 and 2. The descriptions of comparative samples A-C1 and A-C2 prepared in Experiment 3 and reference sample A-R1 are also listed in Table 1.

[0106] [Experiment 4]

[0107] WAXD measurements using Mo-Kα radiation and Cu-Kα radiation were performed on the cross-sections of 100 overlapping samples. Peak shape fitting was used to determine whether the α phase, α′ phase, α″ phase, and γ phase were detected, and the integrated intensity of each diffraction peak was calculated. Next, integrated intensity correction was performed using the sensitivity coefficient recorded in the standard data, and the volume fractions of the α″ phase and the γ phase were calculated from the ratio of the integrated intensities. In addition, the ratio "c / a" of the c-axis length to the a-axis length of the lattice constant of the α″ phase was calculated based on the diffraction peak of the α″ phase.

[0108] WAXD analysis revealed that only the α phase was detected in reference sample A-R1. Diffraction peaks for the α, α′, and α″ phases were detected in samples other than reference sample A-R1, but no γ phase was detected. The volume fraction of the α″ phase was greater than 10% by volume, and the c / a ratio of the α″ phase was within the range of 1.02 to 1.09.

[0109] Bs and Pi were measured as magnetic properties. The magnetization (unit: emu) of the sample was measured using a vibrating sample magnetometer (VSM, BHV-525H manufactured by Riken Electronics Co., Ltd.) at a magnetic field of 1.6 MA / m and a temperature of 20°C. Bs (unit: T) was calculated based on the sample volume and sample mass. In addition, the Pi of the sample was measured using the H coil method of a BH loop analyzer (manufactured by IFG Co., Ltd., IF-BH550) at a magnetic flux density of 1.0 T, 400 Hz, and a temperature of 20°C. -1.0 / 400 (Unit: W / kg) The results of the magnetic properties are also shown in Table 1.

[0110] [Table 1]

[0111] Table 1 Description of samples A-R1, A-C1 to A-C2, A-01 to A-12 and results of magnetic properties

[0112]

[0113] As mentioned above, sample A-R1 shown in Table 1 is the reference sample prepared in Experiment 3, samples A-C1 and A-C2 are the comparison samples prepared in Experiment 3, samples A-01 to A-02 and A-04 to A-12 are the samples made in Experiment 2, and sample A-03 is the sample made in Experiment 1.

[0114] As shown in Table 1, the comparative sample A-C1, which has a high nitrogen concentration layer in the entire thickness direction, has a higher Bs than the reference sample A-R1, but the Pi -1.0 / 400 It shows that the comparative sample A-C2 has a low nitrogen concentration layer formed in the inner region but not in the surface region. Although the low nitrogen concentration layer is not formed in the surface region, the comparative sample A-C2 has a low nitrogen concentration layer formed in the inner region but not in the surface region. -1.0 / 400 decreased, but compared with the reference sample A-R1, Pi -1.0 / 400 Increase.

[0115] In contrast, samples A-01 to A-12 of the present invention showed an increase in Bs and a decrease in Pi compared to the reference sample A-R1. These results confirm that the high nitrogen concentration layer (which causes the formation of α" phase) in the structure of the soft magnetic iron plate of the present invention contributes to the increase in Bs, while the low nitrogen concentration layer and nitrogen concentration transition layer contribute to the increase in Pi. -1.0 / 400 of reduction.

[0116] In addition, the comparison between the comparative sample A-C2 and the sample A-03 confirmed that the low nitrogen concentration layer in the surface region contributes to the Pi -1.0 / 400 It is believed that when there is a layer with low Hc in the surface area, the responsiveness of magnetization change to external magnetic field change is improved, and Pi -1.0 / 400 In other words, it is considered that if a layer with high Hc exists in the surface region, the surface region acts as a magnetic shield, hindering the response of the magnetization change in the internal region.

[0117] [Experiment 5]

[0118] Commercially available pure metal raw materials (Fe and Co, each with a purity of 99.9%) were mixed to form the desired alloy composition and then arc-melted on a water-cooled copper bed (manufactured by Taia Vacuum Co., Ltd., in an automatic arc melting furnace under a reduced pressure Ar atmosphere) to produce an alloy ingot. To homogenize the alloy ingot, the sample was inverted and remelted six times. The resulting alloy ingot was then pressed and rolled to prepare an Fe-Co alloy plate (thickness = 0.1 mm) as the starting material.

[0119] The starting materials were subjected to ammonia atmosphere (partial pressure = 1×10 5 Pa) was maintained at 700°C for 2 hours. At this time, ammonia gas was introduced at the stage of reaching 500°C during the temperature rise process, and intermittent control (NH3 gas and N2 gas were alternately circulated) was performed 6 times to adjust the nitrogen concentration to 5 atomic % uniformly along the thickness direction of the plate. Following this nitriding heat treatment, the ammonia partial pressure was reduced to 1×10 4 Pa and then heated to 750°C and held for 5 minutes for denitrification heat treatment. Thereafter, oil quenching (60°C) and cryogenic treatment were performed in the same manner as in Experiment 1 to produce Sample B-03 of the present invention.

[0120] The nitrogen concentration distribution in the thickness direction of the obtained sample B-03 was investigated using EPMA in the same manner as in Experiment 1, and it was confirmed that Figure 1A The same nitrogen concentration distribution.

[0121] [Experiment 6]

[0122] Commercially available pure metal raw materials (Fe, Co, V, each with a purity of 99.9%) were mixed and melted to produce an alloy ingot having the desired alloy composition in the same manner as in Experiment 5. The resulting alloy ingot was then subjected to press working and rolling to prepare an Fe-Co alloy plate (thickness = 0.1 mm) as the starting material.

[0123] Next, the same procedures as in Experiment 5 were followed, except that the ammonia partial pressure in the nitriding heat treatment and / or the holding temperature or holding time in the denitriding heat treatment during the nitrogen concentration distribution control heat treatment step were changed. Samples B-01 to B-02, and B-04 to B-15 were prepared, each having a different nitrogen concentration in the high nitrogen concentration layer, thickness in the low nitrogen concentration layer, and / or average nitrogen concentration gradient in the nitrogen concentration transition layer than that in Sample B-03 of Experiment 5. The phase transformation / iron nitride phase formation step was performed in the same manner as in Experiment 1.

[0124] The nitrogen concentration distribution in the plate thickness direction of the obtained samples B-01 to B-02 and B-04 to B-15 was examined using EPMA in the same manner as in Experiment 1. The description of each sample of Experiments 5 and 6 is summarized in Table 2 described below.

[0125] [Experiment 7]

[0126] The starting material prepared in Experiment 5 was subjected to nitriding heat treatment alone (without denitrification heat treatment) under the same conditions as in Experiment 5, resulting in a sample B-C1 having a high nitrogen concentration layer (N concentration ≈ 5 atomic %) throughout the thickness direction. The phase transformation / iron nitride phase formation process was performed in the same manner as in Experiment 1. This sample B-C1 served as a comparative sample for verifying the effects of the low nitrogen concentration layer and the nitrogen concentration transition layer. Furthermore, as a benchmark for Experiments 5 and 6, the starting material itself was used as reference sample B-R1. The descriptions of the comparative sample B-C1 and reference sample B-R1 prepared in Experiment 7 are summarized in Table 2.

[0127] [Experiment 8]

[0128] For each sample obtained, the identification of the detected phase by WAXD measurement, the volume ratio of the α" phase and the γ phase, and the ratio of the c-axis length to the a-axis length of the lattice constant of the α" phase "c / a" were determined in the same manner as in Experiment 4. As a result, only the α phase was detected in reference sample B-R1. Diffraction peaks of the α phase, α' phase, and α" phase were detected in samples other than reference sample B-R1, but the γ phase was not detected. The volume ratio of the α" phase was greater than 10% by volume, and the "c / a" of the α" phase was in the range of 1.02 to 1.09.

[0129] In addition, Bs and Pi were measured as magnetic properties in the same manner as in Experiment 4. -1.0 / 400 The results of magnetic properties are also recorded in Table 2.

[0130] [Table 2]

[0131] Table 2 Description of samples B-R1, B-C1, B-01 to B-15 and results of magnetic properties

[0132]

[0133] As mentioned above, sample B-R1 shown in Table 2 is the reference sample prepared in Experiment 7, sample B-C1 is the comparison sample prepared in Experiment 7, samples B-01 to B-02, B-04 to B-15 are samples made in Experiment 6, and sample B-03 is the sample made in Experiment 5.

[0134] As shown in Table 2, the comparative sample B-C1, which has a high nitrogen concentration layer in the entire thickness direction, has a higher Bs than the reference sample B-R1. -1.0 / 400 In contrast, it is shown that the samples B-01 to B-15 of the present invention have improved Bs and Pi compared with the reference samples B-R1 and A-R1. -1.0 / 400 Based on these results, it can be confirmed that the high nitrogen concentration layer (which causes the formation of α "phase) as the structure of the soft magnetic iron plate of the present invention contributes to the improvement of Bs, and the low nitrogen concentration layer and the nitrogen concentration transition layer contribute to the improvement of Pi -1.0 / 400 of reduction.

[0135] [Experiment 9]

[0136] A thin plate material was prepared in which a Co film (thickness = 0.01 mm) was deposited on both main surfaces of a commercially available electromagnetic pure iron plate (thickness = 0.08 mm). Next, the thin plate material was subjected to nitrogen atmosphere (partial pressure = 1×10 5 Pa) was subjected to heat treatment (cobalt diffusion heat treatment) at 1000° C. for 5 hours. The thin plate material subjected to the cobalt diffusion heat treatment was used as a starting material.

[0137] The starting materials were subjected to ammonia atmosphere (partial pressure = 1×10 5Pa) was subjected to a nitriding heat treatment at 700°C for 2 hours. At this time, ammonia gas was introduced at the stage of reaching 500°C during the temperature rise process, and intermittent control (NH3 gas and N2 gas were alternately circulated) was performed 6 times to adjust the nitrogen concentration to 5 atomic % uniformly along the thickness direction of the plate. Following this nitriding heat treatment, the ammonia partial pressure was reduced to 1×10 4 Pa and then heated to 800°C and held for 5 minutes for denitrification heat treatment. Thereafter, oil quenching (60°C) and cryogenic treatment were performed in the same manner as in Experiment 1 to produce Sample C-01 of the present invention.

[0138] The nitrogen concentration distribution in the thickness direction of the obtained sample was investigated using EPMA. Figure 4 The results are shown in . Figure 4 This is a graph showing the nitrogen concentration distribution and the cobalt concentration distribution in the plate thickness direction of sample C-01.

[0139] like Figure 4 As shown, regarding the nitrogen concentration distribution, it is shown that a low nitrogen concentration layer (N concentration ≈ 0 atomic %, thickness = 10 μm) is formed in the surface area of ​​the two main surfaces of the sample, a high nitrogen concentration layer (N concentration ≈ 5 atomic %, thickness = 70 μm) is formed in the internal area, and a nitrogen concentration transition layer (average N concentration gradient ≈ 1 atomic % / μm, thickness = 5 μm) is formed to make the low nitrogen concentration layer and the high nitrogen concentration layer continuous.

[0140] Furthermore, the cobalt concentration distribution shows that the surface regions (thickness = 10 μm) of both main surfaces of the sample have a relatively high cobalt concentration (approximately 30-55 atomic %), gradually decreasing toward the interior, and a relatively low cobalt concentration (approximately 20 atomic %) in the inner region (thickness = 40 μm). This confirms that the cobalt diffusion heat treatment can form a cobalt concentration distribution in the thickness direction of the soft magnetic iron plate.

[0141] Next, the magnetic properties (Bs, Pi, -1.0 / 400 ), and obtained Bs = 2.45T, Pi -1.0 / 400 =10W / kg. The magnetic properties of sample C-01 show a high Bs comparable to that of Permindur Fe-Co alloy (Fe-49 mass% -2 mass% V) and a lower Pi than that of Permindur Fe-Co alloy. -1.0 / 400 The surface area of ​​sample C-01 has a low nitrogen concentration and a high cobalt concentration, so it is believed that a Fe-Co alloy layer is formed. Therefore, it is believed that the low coercivity of the Fe-Co alloy contributes to the overall Pi -1.0 / 400 of reduction.

[0142] The results of sample C-01 show that in order to achieve high Bs and low Pi -1.0 / 400In addition to forming a low-nitrogen concentration layer in the surface region, a high-nitrogen concentration layer in the interior region, and a continuous nitrogen concentration transition layer, as in samples B-03 and B-06, it is effective to also create a concentration profile that increases the cobalt concentration in the surface region. Furthermore, since sample C-01 uses less Co overall than the Permindur iron-cobalt alloy, it also offers the advantage of reducing material costs.

[0143] [Experiment 10]

[0144] A thin plate material was prepared in which a Co film (each thickness = 0.01 mm) was deposited on both main surfaces of a commercially available electromagnetic pure iron plate (thickness = 0.08 mm). 5 Pa) was subjected to a cobalt diffusion heat treatment at 1000°C. The cobalt concentration distribution was adjusted by controlling the holding time at 1000°C. In Experiment 10, the thin plate material with the adjusted cobalt concentration distribution was used as a sample of the soft magnetic iron plate.

[0145] The cobalt concentration distribution of the prepared soft magnetic iron plate samples was investigated using EPMA, and the magnetic properties (Bs, Pi -1.0 / 400 ). As a result, the magnetic properties of the sample with a cobalt concentration of 5 to 70 atomic % in the surface region of 10 μm thickness and a cobalt concentration of 0 to 2 atomic % in the inner region of 40 μm thickness were Bs = 2.25 T, Pi -1.0 / 400 = 20W / kg. The magnetic properties of the sample with a cobalt concentration of 30 to 60 atomic % in the surface region of 10 μm thickness and 20 to 25 atomic % in the inner region of 40 μm thickness are Bs = 2.35 T, Pi -1.0 / 400 =15W / kg.

[0146] The above-described embodiments and experiments are provided to facilitate understanding of the present invention, and the present invention is not limited to the specific structures described. For example, portions of the structures of the embodiments may be replaced with structures that are within the technical knowledge of those skilled in the art, and further, portions of the structures of the embodiments may be supplemented with structures that are within the technical knowledge of those skilled in the art. That is, the present invention may delete portions of the structures of the embodiments or experiments described in this specification, replace them with other structures, or supplement them with other structures, without departing from the scope of the technical concept of the invention.

[0147] Description of Reference Numerals

[0148] 10: high nitrogen concentration layer; 20: low nitrogen concentration layer; 30: nitrogen concentration transition layer; 50: stator; 51: iron core; 52: stator slot; 53: slit; 54: tooth; 55: tooth claw portion; 60: stator coil; 61: segmented conductor; 62: electrical insulation material.

Claims

1. A soft magnetic iron plate having iron as a main component and containing nitrogen, wherein: The soft magnetic iron plate includes, in a thickness direction thereof, a high nitrogen concentration layer having a nitrogen concentration of not less than 2 atomic % and not more than 11 atomic %, a low nitrogen concentration layer having a nitrogen concentration of not more than half the nitrogen concentration of the high nitrogen concentration layer, and a nitrogen concentration transition layer that makes the nitrogen concentration of the high nitrogen concentration layer continuous with the nitrogen concentration of the low nitrogen concentration layer. The surface regions of at least two main surfaces of the soft magnetic iron plate serve as the low nitrogen concentration layer. The high nitrogen concentration layer includes an α phase, an α′ phase, and an α″ phase, The α phase is the main phase, the volume ratio of the α" phase is 10% or more, and the ratio of the c-axis length to the a-axis length of the lattice constant of the α" phase is different from that of the stoichiometric composition Fe 16 The ratio of N2 to the crystalline phase is The saturation magnetic flux density of the soft magnetic iron plate exceeds 2.14 T, and the iron loss under the conditions of a magnetic flux density of 1.0 T and 400 Hz is less than 40 W / kg.

2. The soft magnetic iron plate according to claim 1, characterized in that The average nitrogen concentration gradient of the nitrogen concentration transition layer is greater than or equal to 0.1 atomic % / μm and less than or equal to 10 atomic % / μm.

3. The soft magnetic iron plate according to claim 1 or 2, characterized in that The nitrogen concentration of the low nitrogen concentration layer is 1 atomic % or less.

4. The soft magnetic iron plate according to claim 1 or 2, characterized in that The thickness of the soft magnetic iron plate is not less than 0.01 mm and not more than 1 mm.

5. The soft magnetic iron plate according to claim 3, characterized in that The thickness of the soft magnetic iron plate is not less than 0.01 mm and not more than 1 mm.

6. The soft magnetic iron plate according to claim 1 or 2, characterized in that The total content of elements other than the iron and nitrogen is less than 1 atomic %.

7. The soft magnetic iron plate according to claim 3, characterized in that The total content of elements other than the iron and nitrogen is less than 1 atomic %.

8. The soft magnetic iron plate according to claim 4, characterized in that The total content of elements other than the iron and nitrogen is less than 1 atomic %.

9. The soft magnetic iron plate according to claim 5, characterized in that The total content of elements other than the iron and nitrogen is less than 1 atomic %.

10. The soft magnetic iron plate according to claim 1 or 2, characterized in that In addition to the iron and nitrogen, cobalt is also contained.

11. The soft magnetic iron plate according to claim 3, wherein In addition to the iron and nitrogen, cobalt is also contained.

12. The soft magnetic iron plate according to claim 4, characterized in that In addition to the iron and nitrogen, cobalt is also contained.

13. The soft magnetic iron plate according to claim 5, characterized in that In addition to the iron and nitrogen, cobalt is also contained.

14. The soft magnetic iron plate according to claim 6, wherein In addition to the iron and nitrogen, cobalt is also contained.

15. The soft magnetic iron plate according to claim 7, wherein In addition to the iron and nitrogen, cobalt is also contained.

16. The soft magnetic iron plate according to claim 8, characterized in that In addition to the iron and nitrogen, cobalt is also contained.

17. The soft magnetic iron plate according to claim 9, characterized in that In addition to the iron and nitrogen, cobalt is also contained.

18. The soft magnetic iron plate according to claim 10, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

19. The soft magnetic iron plate according to claim 11, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

20. The soft magnetic iron plate according to claim 12, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

21. The soft magnetic iron plate according to claim 13, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

22. The soft magnetic iron plate according to claim 14, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

23. The soft magnetic iron plate according to claim 15, characterized in that The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

24. The soft magnetic iron plate according to claim 16, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

25. The soft magnetic iron plate according to claim 17, wherein The cobalt concentration in the surface layer region is higher than that in the inner region, and the cobalt concentration distribution is present along the thickness direction.

26. A method for manufacturing a soft magnetic iron plate, for manufacturing the soft magnetic iron plate according to any one of claims 1 to 25, the method comprising: a starting material preparation step of preparing a starting material composed of a soft magnetic material having iron as a main component and having a thickness of not less than 0.01 mm and not more than 1 mm; a nitrogen concentration distribution controlled heat treatment step of subjecting the starting material to a predetermined nitrogen concentration distribution controlled heat treatment to form a predetermined nitrogen concentration distribution along the thickness direction of the starting material; and The phase transformation / iron nitride phase generation step transforms the starting material having the predetermined nitrogen concentration distribution into a martensite structure and disperses and generates an iron nitride phase. The prescribed nitrogen concentration distribution control heat treatment is a heat treatment carried out within the austenite phase formation temperature range, and is a combination of a nitriding heat treatment and a denitriding heat treatment, wherein the nitriding heat treatment is a treatment in which nitrogen atoms are allowed to intrude and diffuse from the two main surfaces of the starting material so that the internal nitrogen concentration becomes greater than 2 atomic % and less than 11 atomic %, and the denitriding heat treatment is a treatment in which nitrogen is released from the two main surfaces of the starting material so as to form the low nitrogen concentration layer and the nitrogen concentration transition layer connected thereto in the surface area.

27. The method for manufacturing a soft magnetic iron plate according to claim 26, wherein: The nitriding heat treatment is a heat treatment in which the partial pressure of ammonia is controlled in an atmosphere containing ammonia to control the concentration of nitrogen that invades and diffuses. The denitrification heat treatment is a heat treatment performed by lowering the ammonia partial pressure and increasing the temperature compared to the nitriding heat treatment.

28. The method for manufacturing a soft magnetic iron plate according to claim 27, wherein: The temperature difference between the denitrification heat treatment and the nitriding heat treatment is 20° C. or higher and 200° C. or lower.

29. The method for producing a soft magnetic iron plate according to any one of claims 26 to 28, wherein: The phase transformation / iron nitride phase generation process includes quenching to below 100° C. and low-temperature treatment to below 0° C.

30. An iron core composed of a laminate of soft magnetic iron plates, characterized in that: The soft magnetic iron plate is the soft magnetic iron plate according to any one of claims 1 to 25.

31. A rotating electric machine having an iron core, wherein: The iron core is the iron core according to claim 30.

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