JP7645127B2 - Magnetic material, its manufacturing method and iron core - Google Patents

Description

The present invention relates to a magnetic material in which a cobalt concentration gradient is formed in an iron-cobalt alloy, its manufacturing method, and an iron core.

The material with the highest saturation magnetic flux density Bs among bulk alloys is an iron-cobalt alloy. For example, Fe-49Co-2V permendur has a bulk Bs of 2.3 T and is widely used in motor cores and other applications as a soft magnetic material with a high Bs. However, iron-cobalt alloys have issues with mass production and cost because they contain cobalt, which is more expensive than iron.

In recent years, iron nitride α″-Fe ₁₆ N ₂ has attracted attention as a magnetic material that is less expensive than iron-cobalt alloys and that, in the form of a thin film, exhibits a high saturation magnetic flux density Bs equivalent to that of iron-cobalt alloys. α″-Fe ₁₆ N ₂ is a body-centered tetragonal (bct) iron-based martensite, and has a crystal structure in which N penetrates α-Fe and the lattice spacing is expanded in the c-axis direction. The Bs of a thin film of α″-Fe ₁₆ N ₂ is known to exceed 2.4 T.

Iron nitride α″-Fe ₁₆ N ₂ is a metastable phase, has low thermal stability, and is known to be difficult to grow. Conventionally, various research and development efforts have been conducted on α″-Fe ₁₆ N ₂ , including manufacturing methods. Patent Document 1 describes a soft magnetic material containing martensite containing carbon and nitrogen, and a manufacturing method thereof.

JP 2020-132894 A

In various applications such as rotating electrical machines and transformers, there is a demand for soft magnetic materials that are inexpensive yet have a high saturation magnetic flux density Bs. Conventional iron-cobalt alloys such as permendur contain nearly 50 atomic % Co, so it is desirable to reduce the amount of Co. However, when part of the Co is replaced with another element, the saturation magnetic flux density Bs decreases, the magnetic permeability μ decreases, and the iron loss Pi increases.

Iron nitride α″-Fe ₁₆ N ₂ is also an inexpensive magnetic material that exhibits a high saturation magnetic flux density Bs, but its low thermal stability prevents its industrial production. It is expected that Bs will be further improved if nitrogen atoms are substituted into an iron-cobalt alloy with a high Bs, such as iron nitride α″-Fe ₁₆ N ₂ .

However, nitrogen atoms have difficulty diffusing within the alloy phase of iron-cobalt alloys, and it is not easy to form nitrogen-substituted martensite. It is possible to add Al, Cr, Mo, Nb, V, etc. to iron-cobalt alloys along with nitrogen, but this reduces Fe and Co, lowering the saturation magnetic flux density Bs and the magnetic permeability μ, which increases the iron loss Pi.

In addition, in applications of soft magnetic materials such as iron cores, not only is it necessary to suppress iron loss Pi, but mechanical properties such as strength and toughness are also required. Mechanical properties must be obtained in a material form that provides appropriate magnetic properties. Regardless of whether or not nitrogen substitution is introduced, there is a demand for soft magnetic materials that are inexpensive and reduce material costs, yet can achieve high saturation magnetic flux density Bs and low iron loss Pi, and that have a basic composition and structure that allows for the introduction of nitrogen substitution and improved mechanical properties.

The present invention aims to provide a magnetic material that can achieve both high saturation magnetic flux density and low iron loss while reducing material costs, a manufacturing method for the same, and an iron core using the same.

In order to solve the above problems, the magnetic material according to the present invention is a magnetic material containing Fe and Co in a total amount of 90 mass % or more, the magnetic material being in the form of a foil or plate, containing 5 mass % or more and 40 mass % or less of Co and 0.1 mass % or more and 4.0 mass % or less of N , and containing an ordered phase α″-Fe ₁₆ N ₂ and an irregular phase α′-Fe ₈ N 2 in which the N is dissolved. The core according to the present invention includes at least one of N and a high concentration region having a cobalt concentration of 20 mass% or more in the thickness direction of the foil or plate, a low concentration region having a cobalt concentration of more than 0 mass% and not more than 10 mass%, and a concentration transition region connecting the cobalt concentration of the high concentration region and the cobalt concentration of the low concentration region. The iron core according to the present invention is an iron core in which soft magnetic steel plates are laminated, and a part or all of the soft magnetic steel plates are formed from the magnetic material. The manufacturing method of the magnetic material according to the present invention is a manufacturing method of a magnetic material containing Fe and Co, the magnetic material is a foil or plate, and includes a precursor formed from an iron-based material having a cobalt concentration of 20 mass% or more, and an iron-based material or cobalt-based material having a cobalt concentration of more than 0 mass% and not more than 10 mass%. and a precursor having a cobalt concentration of 20% by mass or more, a low concentration region having a cobalt concentration of more than 0% by mass and not more than 10% by mass, and a concentration transition region connecting the cobalt concentrations of the high concentration region and the low concentration region, in the thickness direction of the foil or plate, to obtain a magnetic material, and then the precursor or the magnetic material is subjected to a nitrous heat treatment in which a nitrous gas is brought into contact with the precursor or the magnetic material under heat treatment to allow nitrogen to penetrate and diffuse, and the precursor or the magnetic material that has been nitrous heat treated is subjected to a cooling step in which the precursor or the magnetic material is quenched to transform the precursor or the magnetic material into a martensite structure, thereby producing a magnetic material containing 5% by mass or more and 40% by mass or less of Co and 0.1% by mass or more and 4.0% by mass or less of N, and containing at least one of an ordered phase α″-Fe ₁₆ N ₂ and an irregular phase α′-Fe ₈ N in which the N is dissolved.

The present invention provides a magnetic material that can achieve both high saturation magnetic flux density and low iron loss while reducing material costs, a manufacturing method for the same, and an iron core using the same.

FIG. 1 is a diagram illustrating an example of a magnetic material according to an embodiment of the present invention. FIG. 1 is a diagram illustrating an example of a magnetic material according to an embodiment of the present invention. FIG. 1 is a diagram illustrating an example of a magnetic material according to an embodiment of the present invention. 1A to 1C are diagrams illustrating an example of a method for producing a magnetic material according to an embodiment of the present invention. FIG. 1 is a perspective view illustrating an example of a stator of a rotating electric machine. FIG. 2 is an enlarged schematic cross-sectional view of a slot region of the stator. 1 is an image showing a backscattered electron image by a scanning electron microscope and the results of composition analysis of a magnetic material according to an example. 1 is an image showing a backscattered electron image by a scanning electron microscope and the results of composition analysis of a magnetic material according to an example.

The following describes a magnetic material according to one embodiment of the present invention, its manufacturing method, and an iron core and a rotating electric machine using the same, with reference to the drawings. Note that in the following drawings, common configurations are given the same reference numerals and duplicated descriptions are omitted.

<Magnetic materials>
The magnetic material according to the present embodiment is ferromagnetic at room temperature and is provided in the form of a foil or plate. This magnetic material contains a total of 90% by mass or more of iron (Fe) and cobalt (Co) relative to 100% by mass of the material, and contains at least 5% by mass or more and 40% by mass or less of Co relative to 100% by mass of the material, and is a magnetic material that exhibits soft magnetism.

The magnetic material according to this embodiment has a cobalt concentration gradient formed in the thickness direction perpendicular to the main surface of the foil or plate. Along the thickness direction of the foil or plate, regions with different cobalt concentrations are formed, and cobalt atoms are diffused between these regions, forming a cobalt concentration gradient connecting these regions.

Specifically, the magnetic material according to this embodiment has, in the thickness direction of the foil or plate, a high concentration region where the cobalt concentration is relatively high, a low concentration region where the cobalt concentration is relatively low, and a concentration transition region interposed between these regions. The concentration transition region forms a concentration gradient connecting the cobalt concentration of the high concentration region and the cobalt concentration of the low concentration region, and is a region that exhibits a cobalt concentration intermediate between the cobalt concentration of the high concentration region and the cobalt concentration of the low concentration region.

Conventionally, electric motors such as motors use cores made of laminated foils or plates of soft magnetic materials, including electromagnetic steel sheets. The thickness of the foils or plates is about 10 μm to 1 mm. Conventional iron-cobalt alloys such as permendur are soft magnetic materials that exhibit high saturation magnetic flux density Bs, but because they contain expensive cobalt, it is desirable to achieve both low cost and good magnetic properties.

The magnetic material used in the core is required to exhibit soft magnetism, a saturation magnetic flux density Bs higher than that of pure iron, an iron loss Pi equal to or lower than that of electromagnetic steel sheet, high mechanical strength, good toughness, and the ability to be processed and laminated. Pure iron has a Bs of 2.14 T at 20°C, and it is desirable to be able to achieve a higher Bs at low cost.

When the amount of Co in an iron-cobalt alloy such as permendur is reduced, the amount of Co, which is expensive compared to Fe, is reduced, and it is possible to obtain a soft magnetic material that is suitable for mass production and cost-effective. However, when the amount of Co is reduced, the saturation magnetic flux density Bs decreases, and the magnetic permeability μ decreases and the iron loss Pi increases. Increasing the amount of other alloying elements such as Ni can improve the magnetic permeability μ and reduce the iron loss Pi, but this has the problem of lowering Bs and increasing material costs.

Additionally, iron nitride α″-Fe ₁₆ N ₂ is known as an inexpensive magnetic material that exhibits a high saturation magnetic flux density Bs. It has been discovered that α″-Fe ₁₆ N ₂ has the potential to achieve a high Bs of 2.1 to 2.8 T. When nitrogen is added to an iron-cobalt alloy, as in the case of iron nitride α″-Fe ₁₆ N ₂ , and the nitrogen atoms are made into a substitutional solid solution, there is a possibility that the Bs can be improved in the same way as with iron nitride.

However, compared to pure iron, nitrogen atoms are less likely to diffuse within the alloy phase of an iron-cobalt alloy, and it is not easy to dissolve the nitrogen atoms in a substitutional solid solution. It is possible to add Al, Cr, Mo, Nb, V, etc. along with nitrogen, but adding many elements reduces the amount of Fe and Co. As the saturation magnetic flux density Bs decreases, the magnetic permeability μ decreases and the iron loss Pi increases. If nitrogen atoms are dissolved in a substitutional solid solution, crystal distortion increases, which is also a problem as does Pi.

Under these circumstances, the inventors investigated and examined the interrelationships between various factors such as the form of cobalt concentration distribution, heat treatment time, and magnetic properties of magnetic materials based on iron-cobalt alloys, discovered the effectiveness of a cobalt concentration gradient, and completed the present invention. They discovered that by forming a cobalt concentration gradient and providing a high concentration region, a low concentration region, and a concentration transition region, it is possible to obtain the advantages of pure iron and permendur, which has a high Bs and low Pi, and to achieve both a high saturation magnetic flux density Bs and low iron loss Pi while suppressing material costs.

1, 2 and 3 are diagrams each showing a schematic diagram of an example of a magnetic material according to an embodiment of the present invention.
1, 2 and 3, the upper part of each figure shows an example of a layer structure of a magnetic material having a cobalt concentration gradient, and the lower part of each figure shows a rough concentration distribution of cobalt along the thickness direction of the magnetic material.

In each figure, the reference numerals 1, 2, and 3 indicate magnetic materials that form a cobalt concentration gradient. The reference numeral 100 indicates a high-concentration region where the cobalt concentration is relatively high. The reference numeral 200 indicates a low-concentration region where the cobalt concentration is relatively low. The reference numeral 300 indicates a concentration transition region that is interposed between the high-concentration region and the low-concentration region.

As shown in FIG. 1, the magnetic material according to this embodiment can be provided in a two-layer structure in which, for example, a high concentration region 100/(concentration transition region 300)/low concentration region 200 are laminated in this order. The high concentration region 100 and the low concentration region 200 have different magnetic properties. However, in applications in which foil or plate magnetic material is laminated, even with such a two-layer structure, the geometric magnetic anisotropy can be reduced.

As shown in FIG. 2, the magnetic material according to this embodiment can be provided in a three-layer structure in which low concentration region 200/(concentration transition region 300)/high concentration region 100/(concentration transition region 300)/low concentration region 200 are stacked in this order. Also, as shown in FIG. 3, the magnetic material can be provided in a three-layer structure in which high concentration region 100/(concentration transition region 300)/low concentration region 200/(concentration transition region 300)/high concentration region 100 are stacked in this order.

The high concentration region 100, low concentration region 200, and concentration transition region 300 are not particularly limited in thickness or volume ratio per magnetic material. The thickness of each region can be set to any thickness depending on the required performance, material cost, etc. From the viewpoint of manufacturability, it is preferable that the thickness of the high concentration region 100 and the low concentration region 200 is approximately 0.1 μm or more and 0.5 mm or less.

The cobalt concentration in each of the high concentration region 100, low concentration region 200, and concentration transition region 300 is not particularly limited. The cobalt concentration in the high concentration region 100 and low concentration region 200 can be set to any concentration within a predetermined range depending on the required performance, material costs, etc. The cobalt concentration in the high concentration region 100 and low concentration region 200 may be substantially uniform along the thickness direction in each region, or may form a concentration gradient.

In addition, in Figures 1, 2, and 3, the concentration transition region 300 is illustrated as an independent layer, but the concentration transition region 300 does not have to have a clear boundary with the high concentration region 100 or the low concentration region 200. As long as the concentration transition region 300 shows a cobalt concentration intermediate between the high concentration region 100 and the low concentration region 200 in elemental analysis, it does not have to show a linearly changing concentration distribution, and may show a curved or stepwise changing concentration distribution.

Although two-layer and three-layer structures are shown in Figures 1, 2, and 3, the high concentration regions 100 and low concentration regions 200 may be provided in a layer structure of four or more layers, as long as a concentration transition region 300 is interposed between the regions. Either the high concentration region 100 or the low concentration region 200 may be located on both main surfaces of the foil or plate of the magnetic material.

The high concentration region (100) is a region having a cobalt concentration of 20 mass% or more relative to 100 mass% of the magnetic material. By forming a high concentration region with a relatively high cobalt concentration, the saturation magnetic flux density Bs of the magnetic material can be improved compared to that of pure iron. In addition, since a high magnetic permeability μ can be obtained, the iron loss Pi of the magnetic material can be reduced.

The high concentration region can be configured to have a Co content of 20 mass% or more and optionally contain one or more of nitrogen (N), carbon (C), nickel (Ni), manganese (Mn), silicon (Si), chromium (Cr), titanium (Ti), niobium (Nb) and vanadium (V), with the balance being iron (Fe) and unavoidable impurities. A preferred form of the high concentration region is a composition that does not contain any of these elements, a composition that contains only N among these elements, or a composition that contains N and C.

The amount of Co in the high concentration region may be 25 mass% or more, 30 mass% or more, 35 mass% or more, 40 mass% or more, etc. With a large amount of Co, a high saturation magnetic flux density Bs is obtained. In addition, a high magnetic permeability μ is obtained, and therefore the iron loss Pi is reduced. The amount of Co in the high concentration region is preferably 40 mass% or less, more preferably 35 mass% or less, even more preferably 30 mass% or less, and even more preferably 25 mass% or less. The smaller the amount of Co, the cheaper the magnetic material is obtained.

The low concentration region (200) is a region having a cobalt concentration of more than 0% and not more than 10% by mass relative to 100% by mass of the magnetic material. By forming a low concentration region with a relatively low cobalt concentration, the magnetic material contains less cobalt, making it possible to obtain a magnetic material that is inexpensive and suitable for industrial production.

The low concentration region can be configured to have a Co content of more than 0 mass% and not more than 10 mass%, and optionally contain one or more of nitrogen (N), carbon (C), nickel (Ni), manganese (Mn), silicon (Si), chromium (Cr), titanium (Ti), niobium (Nb) and vanadium (V), with the balance being iron (Fe) and unavoidable impurities. A preferred form of the low concentration region is a composition that does not contain any of these elements, a composition that contains only N among these elements, or a composition that contains N and C.

The amount of Co in the low concentration region may be 8 mass% or less, 6 mass% or less, 4 mass% or less, 2 mass% or less, etc. The smaller the amount of Co, the cheaper the magnetic material will be. The amount of Co in the low concentration region may be 1 mass% or more, 3 mass% or more, 5 mass% or more, 7 mass% or more, etc. A large amount of Co will result in a high saturation magnetic flux density Bs. In addition, a high magnetic permeability μ will be obtained, thereby reducing iron loss Pi.

The concentration transition region (300) is a region that connects the cobalt concentration of the high concentration region and the cobalt concentration of the low concentration region. In other words, it is a region that has a cobalt concentration intermediate between the cobalt concentration of the high concentration region and the cobalt concentration of the low concentration region. The concentration transition region is formed by diffusing cobalt atoms between the precursor of the high concentration region and the precursor of the low concentration region, which have different cobalt concentrations. When the concentration transition region is formed, it becomes easier for magnetization states such as domain walls to propagate between the high concentration region and the low concentration region.

The concentration transition region has an intermediate chemical composition between the high concentration region and the low concentration region. The concentration transition region contains an amount of Co according to the chemical composition of the high concentration region and the low concentration region, and like the high concentration region and the low concentration region, optionally contains one or more of nitrogen (N), carbon (C), nickel (Ni), manganese (Mn), silicon (Si), chromium (Cr), titanium (Ti), niobium (Nb) and vanadium (V), with the remainder being iron (Fe) and unavoidable impurities.

With a magnetic material in which such a cobalt concentration gradient is formed, high concentration regions, low concentration regions, and concentration transition regions are formed, and the advantages of both pure iron and permendur are obtained, making it possible to suppress material costs and achieve both high saturation magnetic flux density Bs and low iron loss Pi. Since high magnetic permeability μ is ensured, it is useful as a soft magnetic material. In addition, since a low concentration region in which the cobalt concentration is relatively low is formed, nitrogen atoms are more likely to diffuse in the low concentration region. Therefore, when nitrogen atoms are made into a substitutional solid solution, Bs can be appropriately improved even if the added element that has an affinity for nitrogen is reduced or omitted.

The concentration gradient of the cobalt concentration in the concentration transition region is preferably 0.1 mass%/μm or more and 10 mass%/μm or less. If the concentration gradient is less than 0.1 mass%/μm, the difference in cobalt concentration between the high concentration region and the low concentration region is small, and material costs cannot be sufficiently reduced. On the other hand, if the concentration gradient exceeds 10 mass%/μm, the concentration gradient is too steep, making it difficult for magnetic coupling to occur between the high concentration region and the low concentration region.

Here, we will specifically explain the chemical composition of the entire material for the magnetic material in which a cobalt concentration gradient is formed. In the following explanation, "%" means mass %.

(Fe, Co: 90% or more)
Fe and Co are the main components of the magnetic material according to this embodiment, and contribute to improving the magnetic properties. If the total amount of Fe and Co is less than 90%, magnetic properties such as high saturation magnetic flux density Bs, high magnetic permeability μ, and small coercive force Hc cannot be obtained. On the other hand, if it is 90% or more, good magnetic properties required for soft magnetic materials can be obtained. Therefore, the total amount of Fe and Co is set to 90% or more in the entire magnetic material.

(Co: 5% or more and 40% or less)
Co is a main component of the magnetic material according to this embodiment, and forms a concentration gradient to contribute to improving the magnetic properties. If the amount of Co is less than 5%, the effect of adding Co cannot be obtained. If the amount of Co is 5% or more, a high saturation magnetic flux density Bs can be obtained. In addition, since a high magnetic permeability μ can be obtained, the iron loss Pi can be reduced. On the other hand, if the amount of Co exceeds 40%, the chemical composition becomes close to that of conventional permendur, so the material cost becomes high. If the amount of Co is 40% or less, the material cost can be reduced more than before. Therefore, the amount of Co is 5% or more and 40% or less in the entire magnetic material. The amount of Co is preferably 10% or more. In addition, the amount of Co is preferably 35% or less.

(N: 0% or more and 4.0% or less)
N contributes to improving mechanical and magnetic properties, especially saturation magnetic flux density Bs. The iron nitride phase includes ordered phase α″-Fe ₁₆ N ₂ or irregular phase α′-Fe ₈ N, and γ′-Fe ₄ N. The former has a high Bs, while the latter has a low Bs. When the former is formed, a magnetic material exhibiting a high Bs is obtained. When the N content exceeds 4.0%, low magnetic γ′-Fe ₄ N and the like are easily formed, and good magnetic properties cannot be obtained. When the N content is 4.0 or less, good magnetic properties and mechanical properties can be obtained by α″-Fe ₁₆ N _2. Therefore, the N content is set to 0% or more and 4.0% or less in the whole magnetic material. The N content is preferably 0.1% or more. The N content is preferably 1.0% or less.

(C: 0% or more and 1.0% or less)
C contributes to improving mechanical and magnetic properties. When combined with N, C forms Fe-C-N iron nitrides, and acts to improve Bs in the same way as N. If the C content exceeds 1.0%, low magnetic carbides and the like are easily generated, and good magnetic properties cannot be obtained. If the C content is 1.0 or less, good magnetic properties can be obtained due to iron nitrides and the like in which C is dissolved. Therefore, the C content is set to 0% or more and 1.0% or less in the entire magnetic material. The C content is preferably 0.5% or less.

(Ni: 0% or more and 2.0% or less)
Ni contributes to improving corrosion resistance, mechanical properties, temperature properties, etc. Ni exhibits relatively high magnetic permeability μ and magnetic moment, but its magnetic properties are inferior to Fe and Co. In addition, Ni is relatively expensive, and when N is substituted into a solid solution, it reduces the amount of N in solid solution. Therefore, the amount of Ni is set to 0% or more and 2.0% or less in the entire magnetic material.

(Mn, Si, Cr, Ti, Nb, V: 0% or more and 0.2% or less)
Mn, Si, Cr, Ti, Nb, and V contribute to improving mechanical properties. These elements form precipitates to improve strength and toughness and reduce iron loss Pi. However, if added in large amounts, they reduce the amounts of Fe and Co, which are the main components. In addition, when combined with N and C, they form low-magnetic nitrides and carbides. Therefore, the amount of these elements is set to 0% or more and 0.2% or less in the entire magnetic material.

(Inevitable impurities)
Examples of the unavoidable impurities include hydrogen (H), phosphorus (P), sulfur (S), oxygen (O), magnesium (Mg), calcium (Ca), copper (Cu), zinc (Zn), tin (Sn), etc. The unavoidable impurities are preferably 0.01% by mass or less, and more preferably 0.001% by mass or less, for each element.

The chemical composition of magnetic materials can be confirmed using a scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDX) or an electron probe micro analyzer (EPMA). The crystal structure of magnetic materials can be confirmed by X-ray diffraction (XRD) measurements.

<Method of manufacturing magnetic material>
The magnetic material according to this embodiment can be manufactured by stacking a precursor of a high concentration region and a precursor of a low concentration region, and diffusing cobalt atoms between the precursors. A foil or a plate can be used as the precursor for each region. A thin film formed on the surface of a foil or a plate can also be used as the precursor.

FIG. 4 is a diagram showing an example of a method for manufacturing a magnetic material according to an embodiment of the present invention.
As shown in FIG. 4, the magnetic material having a cobalt concentration gradient can be produced by a production method including a raw material mixing and melting step S1, a casting step S2, an annealing step S3, a first rolling step S4, a first annealing step S5, a second rolling step S6, a second annealing step S7, a lamination step S8, and a diffusion layer forming step S9.

In FIG. 1, the raw material mixing and melting process S1 includes a raw alloy block forming element process S1a and a remelting element process S1b. The lamination process S8 can be selected from a cladding processing process S8a or a physicochemical lamination process S8b.

The steps from raw material mixing and melting step S1 to secondary annealing step S7 can be carried out to produce a foil or plate precursor. These steps can produce a high-concentration region precursor, a low-concentration region precursor, or both. However, these steps are merely examples, and not all of these steps are essential. It is also possible to omit some steps or combine multiple steps into a continuous process.

(Raw material mixing and dissolving process)
The raw material mixing and melting step S1 is a step of mixing and melting the raw materials of the magnetic material. The raw materials of the magnetic material, such as metals, are charged into a melting furnace so as to have a desired chemical composition, and are heated and mixed to form a molten metal 30. The method of melting the raw materials is not particularly limited. As the melting furnace for melting the raw materials, an appropriate furnace such as an induction furnace, an arc type electric furnace, or a resistance furnace can be used.

When preparing a precursor for the high concentration region, the raw material can be an iron-based material such as alloy steel, iron-cobalt alloy, etc., which is low carbon and has a low alloying element and contains 20 mass% Co or more, or a cobalt-based material such as pure cobalt. When preparing a precursor for the low concentration region, the raw material can be an iron-based material such as pure iron, which contains 10 mass% Co or less, or an iron-based material such as steel, alloy steel, electromagnetic steel, iron-cobalt alloy, etc., which is low carbon and has a low alloying element. When melting, refining such as melt refining or extra-furnace refining can be performed depending on the chemical composition.

The raw material mixing and melting process S1 preferably includes a raw material alloy ingot forming elemental process S1a and a re-melting elemental process S1b. The raw material alloy ingot forming elemental process S1a is a process in which the raw materials of the magnetic material are mixed and melted, and the molten metal 10 is solidified to produce the alloy ingot 11. The re-melting elemental process S1b is a process in which the alloy ingot 31 is re-melted.

By carrying out the raw alloy ingot formation elemental process S1a and the remelting elemental process S1b, the alloy ingot 11 that was once melted is remelted, so that it is possible to remove inclusions that float up during remelting, and the macrosegregation that occurs during solidification is also reduced. As a result, unavoidable impurities such as O, P, and S, as well as macrosegregation, are reduced, and a purified molten metal 32 with a high degree of cleanliness can be obtained.

The method for remelting the alloy ingot 31 is not particularly limited. From the standpoint of reducing costs and obtaining the required refining effect, it is preferable to remelt the alloy ingot 31 by the Vacuum Arc Remelting (VAR) method or the Electro Slag Remelting (ESR) method.

(Casting process)
The casting step S2 is a step in which the molten metal obtained by melting the raw materials is solidified to cast a material for rolling processing. The molten metal 30 is poured into a mold to form a slab-shaped cast body 50. When the remelting step S1b is performed, the purified molten metal 32 is poured into the mold to form a cast body 50 with a high degree of cleanliness.

The thickness of the cast body 50 and the casting method are not particularly limited. The thickness of the cast body 50 can be, for example, 1 to 3 mm. Casting can be performed by any suitable method, such as continuous casting, precision casting, sand casting, or metal mold casting. Continuous casting can be performed in a continuous manner integrated with the subsequent steps. Precision casting can be performed without using wax, as long as it forms a plate- or foil-shaped cast body 50 that is close to the shape of the final product.

When casting, such as precision casting, a large alloy ingot may be cast first, the resulting alloy ingot may be divided into pieces of appropriate size, and the divided alloy pieces may be remelted and cast. When using such a casting method, it is preferable to have a faster solidification rate than in the case of general steel plates, etc., in order to prevent the crystal grains from becoming coarse. Cooling methods that can be used during the casting process include contact conduction cooling, water cooling, forced air cooling, etc.

(Annealing process)
The annealing step S3 is a step of fully annealing the cast compact. The cast compact 50 is heat-treated at a temperature higher than the eutectoid temperature (A1 transformation point) of the iron-cobalt system to homogenize the cast structure. The heat treatment temperature is preferably 1000° C. or higher.

(First rolling process)
The first rolling step S4 is a step of first rolling the cast compact. In the first rolling, the cast compact 50 is rolled to a predetermined intermediate rolling ratio (rolling reduction). The first rolling can be cold rolling. For example, a 1-3 mm compact can be cold rolled to 0.2 mm. The rolling load of the first rolling can be, for example, 1-10 kN.

(First annealing process)
The primary annealing step S5 is a step of intermediate annealing the primary rolled material. The primary rolled material 60 is heat treated to perform stress relief annealing, and the residual stress remaining after the primary rolling is alleviated. By removing the processing strain, the magnetic properties of the magnetic material, particularly the iron loss Pi, can be reduced. The heat treatment temperature is preferably 1000°C or higher.

(Secondary rolling process)
The secondary rolling step S6 is a step of secondary rolling the primary rolled material. In the secondary rolling, the primary rolled material 60 is rolled to a thickness required for the precursor of the high concentration region or the precursor of the low concentration region. For example, the primary rolled material 60 of 0.2 mm can be cold rolled to 0.1 mm. The rolling load of the secondary rolling can be, for example, 4 to 6 kN.

(Secondary annealing process)
The secondary annealing step S7 is a step of intermediate annealing the secondary rolled material. The secondary rolled material is heat treated to perform stress relief annealing, and the residual stress remaining after the secondary rolling is relaxed. By removing the processing strain, the magnetic properties of the magnetic material, particularly the iron loss Pi, can be reduced. The heat treatment temperature is preferably 1000°C or higher.

(Lamination process)
The lamination step S8 is a step of laminating a precursor of a high concentration region and a precursor of a low concentration region. In the lamination step S8, a rolled material rolled to a predetermined thickness can be used as the precursor of the high concentration region or the precursor of the low concentration region. In the lamination step S8, a cladding process step S8a or a chemical lamination step S8b is performed depending on the method of laminating the precursors.

The cladding process S8a is a process in which the precursor of the high concentration region and the precursor of the low concentration region are joined by mechanical processing. Depending on the layer structure of the magnetic material to be manufactured, the precursor of the high concentration region and the precursor of the low concentration region are overlapped and pressed or welded together. When the layer structure includes multiple regions of at least one of the high concentration region and the low concentration region, the precursor of the high concentration region and the precursor of the low concentration region are stacked alternately.

In the cladding process S8a, the precursor for the high concentration region can be a foil or plate made of an iron-based material with Co: 20% by mass or more or a cobalt-based material such as pure cobalt. The precursor for the low concentration region can be a foil or plate made of an iron-based material with Co: more than 0% by mass and 10% by mass or less.

As a method for joining the precursors together, an appropriate method such as hot welding (rolling), cold welding (rolling), friction welding, ultrasonic welding, etc. can be used. As a device for joining the precursors together, a rolling roll, a press machine, a friction welding machine, an ultrasonic metal welding machine, etc. can be used.

The bonding of the precursors does not need to involve diffusion of cobalt atoms as long as the precursors can be temporarily fixed to each other. If the precursors can be fixed to each other without being bonded by compression or welding, it is possible to omit the cladding process S8a.

The physicochemical lamination process S8b is a process in which the precursor of the high concentration region and the precursor of the low concentration region are laminated by a physical film formation method or a chemical film formation method. Depending on the layer structure of the magnetic material to be manufactured, a thin film is formed on one or both sides of either the precursor of the high concentration region or the precursor of the low concentration region as the precursor of the other.

In the physicochemical lamination step S8b, a foil or plate made of an iron-based material with Co: 20% by mass or more can be used as the precursor for the high concentration region, or a thin film made of an iron-based material with Co: 20% by mass or more or a thin film made of a cobalt-based material such as pure cobalt can be formed. A foil or plate made of an iron-based material with Co: more than 0% by mass and 10% by mass or less can be used as the precursor for the low concentration region, or a thin film made of an iron-based material with Co: more than 0% by mass and 10% by mass or less can be formed.

As the film formation method, physical film formation methods such as vacuum deposition, sputtering, and ion plating, and chemical film formation methods such as electroplating and electrolytic plating can be used. When using a chemical film formation method, it is preferable to use a foil or plate as the precursor for the low concentration region and to form a thin film as the precursor for the high concentration region. It is also preferable to form a pure cobalt film as the precursor for the high concentration region.

In the lamination step S8, either the cladding step S8a or the chemical lamination step S8b may be performed depending on the layer structure of the magnetic material to be manufactured, or a combination of both may be performed. As the precursor for the high concentration region and the precursor for the low concentration region, a foil or plate of an appropriate thickness may be used, or a thin film of an appropriate thickness may be formed, depending on the target thickness of each region that constitutes the magnetic material.

The diffusion layer formation process S9 is a process in which the precursors of the high concentration region and the precursors of the low concentration region are heat-treated to diffuse the atoms. The precursors of the high concentration region and the precursors of the low concentration region that are stacked on top of each other are heat-treated to diffuse cobalt atoms and the like between the precursors. When the precursors are cooled after the diffusion of the cobalt atoms, a concentration transition region is formed near the interface between the precursors of the high concentration region and the precursors of the low concentration region, and a magnetic material in which a concentration gradient of cobalt is formed is obtained.

The temperature of the heat treatment to diffuse the atoms is preferably 800°C or more and 1200°C or less. At 800°C or more, the atomic diffusion speed is sufficiently high, so that the concentration gradient of cobalt can be formed in a short time. At 1200°C or less, impurities are less likely to be mixed in, the precursor does not melt, and coarsening of crystal grains can be suppressed. The heat treatment time is preferably 0.1 hours or more and 12 hours or less. The heat treatment to diffuse the atoms is preferably performed in an inert gas atmosphere such as argon gas.

In the diffusion layer formation process S9, atoms are diffused by heat treatment, so that a concentration transition region is formed near the interface between the precursor of the high concentration region and the precursor of the low concentration region. This makes it easier for the magnetization state to propagate between the regions. In addition, the mechanical properties of the magnetic material can be improved by diffusing cobalt atoms, etc. In addition, the processing distortion caused by cladding processing, etc. can be removed, so the magnetic properties of the magnetic material, especially the iron loss Pi, can be reduced.

In the above steps, the cast body is subjected to multiple cold rolling and intermediate annealing, but the methods for producing the high-concentration region precursor and the low-concentration region precursor are not limited to these methods. The high-concentration region precursor and the low-concentration region precursor may be produced using hot rolling or a combination of hot rolling and cold rolling. In addition, the raw material mixing and dissolving step S1 and the subsequent steps may be performed continuously and integrally by roll casting to form multiple layers.

<Elemental substitution in magnetic materials>
The magnetic material according to this embodiment may have a chemical composition of more than 0 mass % and not more than 4.0 mass % N in the entire material, and nitrogen atoms may be substitutionally dissolved. That is, the magnetic material according to this embodiment may be a magnetic material containing more than 0 mass % and not more than 4.0 mass % nitrogen (N) and containing at least one of an ordered phase α″-Fe ₁₆ N ₂ and an irregular phase α′-Fe ₈ N.

The ordered phase α″-Fe ₁₆ N ₂ has a crystal structure in which N penetrates α-Fe and the lattice spacing is expanded in the c-axis direction, is a body-centered tetragonal (bct) system, and exhibits a high saturation magnetic flux density Bs. The ordered phase α″-Fe ₁₆ N ₂ and the disordered phase α'-Fe ₈ N cannot always be clearly distinguished, but when these iron nitride phases are contained, a high Bs tends to be obtained.

The magnetic material according to this embodiment may be a magnetic material containing more than 0 mass % and not more than 4.0 mass % nitrogen (N), and in which part or all of the iron (Fe) contained in at least one of the ordered phase α″-Fe ₁₆ N ₂ and the disordered phase α′-Fe ₈ N is replaced with cobalt (Co).

The ordered phase α″-Fe ₁₆ N ₂ or the disordered phase α′-Fe ₈ N may be contained in any of the high concentration region, low concentration region, and concentration transition region, but it is preferable that they are contained at least in the low concentration region. These iron nitride phases are stably formed in the low concentration region due to atomic diffusivity, and therefore can improve the magnetic properties of a magnetic material in which a cobalt concentration gradient is formed.

As a method for synthesizing the iron nitride phase, a method can be used in which a precursor of a high concentration region or a precursor of a low concentration region is used as the treated material and a nitrogen immersion heat treatment is performed before the diffusion layer formation process S9. Also, a method can be used in which a magnetic material in which a cobalt concentration gradient has been formed is used as the treated material and a nitrogen immersion heat treatment is performed after the diffusion layer formation process S9.

Specifically, when synthesizing an iron nitride phase, a precursor of a high concentration region, a precursor of a low concentration region, or a magnetic material in which a cobalt concentration gradient is formed can be subjected to a nitrogen immersion heat treatment process and a cooling process. The thickness of the material to be treated is preferably, for example, 0.01 mm or more and 1 mm or less. In view of the diffusivity of atoms, it is preferable to process at least the precursor of the low concentration region out of the precursor of the high concentration region and the precursor of the low concentration region.

When a precursor of a high concentration region or a precursor of a low concentration region is used as the material to be treated, it is preferable to subject it to a homogenization heat treatment process in advance. The homogenization heat treatment process is a process in which the material to be treated is heated to the austenite formation temperature (Ac3 transformation point) or higher to homogenize it. The homogenization heat treatment is carried out in an inert gas atmosphere such as argon gas. For example, the material to be treated is heated to 900°C or higher to diffuse the chemical components in the material into a highly uniform state.

The nitrous heat treatment process is a process in which a nitrous gas is brought into contact with the material being treated during heat treatment, and nitrogen penetrates and diffuses into the material being treated. The nitrous heat treatment is preferably carried out at a temperature higher than the eutectoid temperature (A1 transformation point). This is because nitrogen is easily dissolved in the γ phase and the like. For example, the gas-cooled material is heated to 700-900°C, and nitrous gas adjusted to about 1 x 10 ⁵ Pa is supplied under an inert gas atmosphere. Ammonia or the like can be used as the nitrous gas.

The nitrous heat treatment process can also be performed during the diffusion layer formation process S9. If a nitrous gas is supplied while cobalt atoms, etc. are being diffused in an inert gas atmosphere, nitrogen can penetrate and diffuse into the parent phase of the magnetic material, forming a substitutional solid solution.

The cooling process is a process in which the material to be treated is rapidly cooled to below the martensite transformation temperature (Ms transformation point) to cause a phase transformation to a body-centered tetragonal (bct) martensite structure. Rapid cooling can be a process in which the material is cooled to below 100°C using a coolant such as oil or water, or preferably a sub-zero process in which the material is cooled to below 0°C using a coolant such as dry ice or liquid nitrogen.

When the material to be treated is quenched after the nitrous heat treatment, a magnetic material is obtained in which nitrogen atoms are dissolved in the matrix and an ordered phase of α″-Fe ₁₆ N ₂ or an irregular phase of α′-Fe ₈ N is formed. Nitrogen atoms diffuse more easily into the Fe phase than into the alloy phase, so that an iron nitride phase can be formed with a high volume fraction, particularly on the low concentration region side.

The magnetic material according to this embodiment may be a magnetic material containing more than 0 mass % and not more than 4.0 mass % nitrogen (N) and more than 0 mass % and not more than 1.0 mass % carbon (C), in which a part of the nitrogen (N) contained in at least one of the ordered phase α″-Fe ₁₆ N ₂ and the disordered phase α′-Fe ₈ N is substituted with carbon (C).

When replacing part of the nitrogen with carbon, the material is subjected to a carburizing treatment at a temperature higher than the eutectoid temperature (A1 transformation point) before the cooling process and before or after the nitrous heat treatment process. The carburizing treatment can be performed, for example, by gas carburizing. Examples of the carburizing gas that can be used include acetylene, methane, propane, butane, etc. The carburizing gas can be supplied continuously or intermittently under an inert gas atmosphere.

When replacing part of the nitrogen with carbon, it is preferable to carburize the material to be treated at a temperature higher than the eutectoid temperature (A1 transformation point) and then cool to around 200°C to generate carbides. Next, after generating the carbides, it is preferable to heat the material to around the eutectoid temperature (A1 transformation point) and hold it there, then rapidly heat it to or above the austenite formation temperature (Ac3 transformation point) and rapidly cool it.

For example, the material to be treated, which has been cooled after carburizing to generate carbides, is heated to and held at 700-900°C, and then rapidly heated to 900°C or higher. The heating rate of the rapid heating is preferably 100°C/sec or higher. The rapid heating is preferably a process in which the material is held at around 950°C for about 1 second.

In this way, when the material to be treated is heated to near the eutectoid temperature, the carbides can be dispersed in a phase that has a lower solubility limit for carbon than the gamma phase. When the material is then rapidly heated, the carbides dispersed in the matrix are rapidly decomposed, allowing the carbon atoms to be uniformly dissolved. Therefore, when the material is rapidly cooled, a material is obtained in which some of the nitrogen has been uniformly replaced with carbon.

<Soft magnetic steel plate>
The magnetic material according to the present embodiment can be used in the form of a foil or plate-shaped soft magnetic steel sheet. The soft magnetic steel sheet is a steel sheet formed of the magnetic material and exhibits soft magnetism, and has a cobalt concentration gradient, including a high concentration region, a low concentration region, and a concentration transition region. The thickness of the soft magnetic steel sheet is, for example, 1 μm or more and 1 mm or less.

The soft magnetic steel sheet may be in the form of a laminate of foil or plate magnetic material having a cobalt concentration gradient, a high concentration region, a low concentration region, and a concentration transition region. As long as the laminated soft magnetic steel sheet contains such magnetic material, it may contain low carbon steel sheet, electromagnetic pure iron sheet, electromagnetic steel sheet, iron-silicon alloy sheet, iron-cobalt alloy sheet, etc.

<Iron cores and rotating machines>
The soft magnetic steel plate using the magnetic material according to the present embodiment can be used as a material for an iron core. The iron core is formed by punching and laminating soft magnetic steel plates. Such an iron core can be used in the stator of a rotating electric machine. The iron core may include a low carbon steel plate, an electromagnetic pure iron plate, an electromagnetic steel plate, an iron-silicon alloy plate, an iron-cobalt alloy plate, etc., as long as the iron core uses a foil or plate magnetic material having a cobalt concentration gradient and a high concentration region, a low concentration region, and a concentration transition region.

Figure 5 is a perspective view showing an example of a stator of a rotating electric machine. Figure 6 is a cross-sectional view showing an enlarged schematic of the slot region of the stator. Note that a cross-sectional view means a cross section perpendicular to the direction of the rotation axis (a cross section whose normal is parallel to the direction of the rotation axis). In a rotating electric machine, a rotor (not shown) is disposed radially inside the stator shown in Figures 5 and 6.

As shown in Figures 5 and 6, the stator 10 has a stator coil 20 wound in multiple stator slots 12 formed on the inner periphery of the iron core 11. The stator slots 12 are arranged at a predetermined circumferential pitch around the circumferential direction of the iron core 11 and are spaces that penetrate in the axial direction, with slits 13 opening in the innermost periphery and extending in the axial direction. The areas separating adjacent stator slots 12 are called the teeth 14 of the iron core 11. The parts of the inner periphery tip areas of the teeth 14 that define the slits 13 are called the tooth claw portions 15.

The stator coil 20 is usually composed of multiple segment conductors 21. For example, in Figures 5 and 6, the stator coil 20 is composed of three segment conductors 21 corresponding to the U-phase, V-phase, and W-phase of three-phase AC. In order to prevent partial discharge between the segment conductors 21 and the iron core 11, and between each phase (U-phase, V-phase, W-phase), each segment conductor 21 is usually covered on its outer periphery with an electrical insulating material 22 (e.g., insulating paper, enamel coating).

The iron core and rotating electric machine using the soft magnetic steel plate according to this embodiment are an iron core 11 formed by laminating multiple soft magnetic steel plates according to this embodiment in the axial direction after forming them into a predetermined shape, and a rotating electric machine using this iron core 11. Soft magnetic steel plates exhibit magnetic properties such as a saturation magnetic flux density Bs that exceeds that of pure iron and a coercive force Hc that is equal to or less than that of pure iron, so that an iron core can be provided that has a higher conversion efficiency between electric energy and magnetic energy than an iron core using conventional electromagnetic steel plates. A highly efficient iron core can realize a smaller rotating electric machine and a higher torque.

In addition, the soft magnetic steel plate according to this embodiment can be made of low-carbon steel plate, electromagnetic pure iron plate, etc., which have lower material costs than Fe-Co steel plate, and therefore has the advantage of being able to provide highly efficient iron cores and rotating electric machines at low cost.

A rotating electric machine using the soft magnetic steel plate according to this embodiment as the iron core includes such a stator (core) 10, a stator coil 20, and a rotor. In the stator (core) 10, the teeth 14, tooth claws 15, and back yoke of the iron core 11 have a cobalt concentration gradient formed therein, and contain a foil or plate magnetic material having a high concentration region, a low concentration region, and a concentration transition region, so that a high saturation magnetic flux density Bs can be obtained while keeping material costs down.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the present invention. For example, the present invention is not necessarily limited to having all of the configurations of the above-described embodiments. It is possible to replace part of the configuration of an embodiment with another configuration, add part of the configuration of an embodiment to another form, or omit part of the configuration of an embodiment.

The present invention will be described in detail below with reference to examples, but the technical scope of the present invention is not limited to these examples.

(Example T-1)
A magnetic material having a cobalt concentration gradient was produced, and the saturation magnetic flux density Bs, iron loss Pi, metal structure, and chemical composition were evaluated. A foil material of Fe-50Co alloy was used as the precursor of the high concentration region. A foil material of pure Fe was used as the precursor of the low concentration region, which was half the thickness of the precursor of the high concentration region. The magnetic material had a three-layer structure in which a low concentration region/(concentration transition region)/high concentration region/(concentration transition region)/low concentration region were laminated in this order.

The precursor of the high concentration region was used as the core material, and the precursor of the low concentration region was used as the skin material, and the skin material was clad on both sides of the core material to obtain a laminate with the chemical composition shown in Table 1. This laminate was heat treated under the conditions shown in Table 1 to obtain the magnetic material of Example T-1, which has a three-layer structure with a cobalt concentration gradient. The thickness was approximately 200 μm. The obtained magnetic material was subjected to measurement of saturation magnetic flux density Bs, measurement of iron loss Pi, observation of metal structure, and composition analysis.

(Example T-2)
A magnetic material according to Example T-2 having a three-layer structure with a cobalt concentration gradient was prepared in the same manner as in Example T-1, except that the heat treatment conditions were changed as shown in Table 1. The magnetic material was subjected to measurement of saturation magnetic flux density Bs, measurement of iron loss Pi, observation of metal structure, and composition analysis.

(Comparative Example C-1)
The foil material according to Comparative Example C-1, which has the chemical composition shown in Table 1 and is a bulk (single-layer structure) having no concentration gradient of cobalt, was subjected to measurement of saturation magnetic flux density Bs and iron loss Pi. The thickness was about 200 μm.

(Comparative Example C-2)
The foil material according to Comparative Example C-2, which has the chemical composition shown in Table 1 and has no concentration gradient of cobalt (one-layer structure), was subjected to measurement of saturation magnetic flux density Bs and iron loss Pi. The thickness was about 200 μm.

(Comparative Example C-3)
The foil material according to Comparative Example C-3, which has the chemical composition shown in Table 1 and has no concentration gradient of cobalt (one-layer structure), was subjected to measurement of saturation magnetic flux density Bs and iron loss Pi. The thickness was about 200 μm.

(Reference Example R-1)
A magnetic material according to Reference Example R-1 having a three-layer structure with no cobalt concentration gradient and a chemical composition shown in Table 1 was produced and subjected to measurement of saturation magnetic flux density Bs and iron loss Pi. This magnetic material was obtained by simply laminating a foil material of Fe-50Co alloy and a foil material of pure Fe having a thickness half that of the foil material in the same arrangement as in Example T-1, without carrying out heat treatment. The thickness was about 200 μm.

[Iron loss measurement]
The iron loss was measured by the following procedure. A test piece of 4 cm x 10 cm was taken from each of the prepared magnetic materials. The iron loss Pi (unit: W/kg) of the test piece was measured by the H coil method using a BH loop analyzer (IFG, IF-BH550) and a vertical yoke single plate tester under the conditions of a magnetic flux density of 1.0 T, 400 Hz, and a temperature of 20°C.

[Measurement of saturation magnetic flux density]
The saturation magnetic flux density was measured by the following procedure. A test piece measuring 4 cm x 10 cm was taken from each of the prepared magnetic materials. The magnetization (unit: emu) of the test piece was measured at an applied magnetic field of 1.6 MA/m and a temperature of 20°C using a vibrating sample magnetometer (VSM, manufactured by Riken Denshi Co., Ltd., BHV-525H), and the saturation magnetic flux density Bs (unit: T) was calculated from the volume and mass of the test piece.

[Structural observation and composition analysis]
The observation of the alloy structure and the analysis of the chemical composition were carried out according to the following procedure. A test piece measuring 4 cm x 10 cm was taken from each of the prepared magnetic materials. Using a scanning electron microscope (SEM, Hitachi High-Technologies Corporation, S-3400N), the backscattered electron images in the cross-sectional direction of the test piece were observed at 15 kV, and the components were analyzed by SEM-EDX.

Table 1 shows the chemical composition of each magnetic material, heat treatment conditions, and the measurement results of iron loss and saturation magnetic flux density.

As shown in Table 1, Examples T-1 and T-2, which have a cobalt concentration gradient, exhibited a similarly high saturation magnetic flux density Bs compared to Comparative Example C-3, which has the same overall chemical composition. Examples T-1 and T-2 had reduced iron loss Pi compared to Comparative Example C-3. It was confirmed that forming a cobalt concentration gradient makes it possible to achieve both a high saturation magnetic flux density Bs and low iron loss Pi.

7 and 8 are images showing a backscattered electron image by a scanning electron microscope of the magnetic material according to the example and the results of composition analysis.
7 and 8 show a backscattered electron (BSE) image of a cross section of a magnetic material taken with a scanning electron microscope (SEM) and a combined SEM-EDX spectrum of a cross section of the magnetic material. Fig. 7 shows the results of Example T-1. Fig. 8 shows the results of Example T-2.

As shown in Figures 7 and 8, when the laminate of the precursors was heat-treated to diffuse the cobalt atoms, a high-concentration region, a low-concentration region, and a concentration transition region were formed. Compared to Example T-1, Example T-2 had a longer heat treatment time, and it was confirmed that the thickness of the concentration transition region was enlarged and the thickness of the high-concentration region and low-concentration region were thinner.

1, 2, 3...magnetic material, 10...stator, 11...iron core, 12...stator slot, 13...slit, 14...teeth, 15...teeth claw portion, 20...stator coil, 21...segment conductor, 22...electrical insulation material, 100...high concentration region, 200...low concentration region, 300...concentration transition region

Claims (7)

A magnetic material containing Fe and Co in a total amount of 90 mass% or more,
The magnetic material is a foil or plate and contains 5% by mass or more and 40% by mass or less of Co and 0.1% by mass or more and 4.0% by mass or less of N ;
The steel contains at least one of an ordered phase α″-Fe ₁₆ N ₂ and a disordered phase α′-Fe ₈ N in which N is dissolved ,
In the thickness direction of the foil or plate,
A high concentration region having a cobalt concentration of 20 mass% or more;
A low concentration region having a cobalt concentration of more than 0 mass% and not more than 10 mass%;
a concentration transition region connecting the cobalt concentration of the high concentration region and the cobalt concentration of the low concentration region. The magnetic material according to claim 1 ,
A magnetic material containing more than 0 mass% and 1.0 mass% or less of C. The magnetic material according to claim 1 ,
Contains more than 0 mass% and not more than 1.0 mass% C,
The magnetic material has N contained in at least one of the ordered phase α″-Fe ₁₆ N ₂ and the disordered phase α′-Fe ₈ N substituted with C. The magnetic material according to claim 1 ,
A magnetic material in which the concentration gradient of cobalt in the concentration transition region is 0.1 mass %/μm or more and 10 mass %/μm or less. The magnetic material according to claim 1 ,
A magnetic material including a plurality of at least one of the high concentration regions and the low concentration regions. 6. An iron core in which soft magnetic steel plates are laminated, the soft magnetic steel plates being partly or entirely formed of the magnetic material according to claim 1 . A method for producing a magnetic material containing Fe and Co, comprising the steps of:
the magnetic material is a foil or a plate;
A precursor formed of an iron-based material having a cobalt concentration of 20 mass% or more and a precursor formed of an iron-based material or a cobalt-based material having a cobalt concentration of more than 0 mass% and not more than 10 mass% are laminated together;
heat-treating the precursors stacked on top of each other to diffuse atoms, thereby forming, in a thickness direction of the foil or plate, a high-concentration region having a cobalt concentration of 20 mass% or more, a low-concentration region having a cobalt concentration of more than 0 mass% and not more than 10 mass%, and a concentration transition region connecting the cobalt concentration of the high-concentration region and the cobalt concentration of the low-concentration region, thereby obtaining a magnetic material;
The precursor or the magnetic material is subjected to a nitrous heat treatment in which a nitrous gas is brought into contact with the precursor or the magnetic material under heat treatment to cause nitrogen to penetrate and diffuse, and the precursor or the magnetic material that has been subjected to the nitrous heat treatment is rapidly cooled to cause a phase transformation into a martensite structure,
A method for producing a magnetic material comprising: 5% by mass or more and 40% by mass or less of Co; and 0.1% by mass or more and 4.0% by mass or less of N; and comprising at least one of an ordered phase α″-Fe ₁₆ N ₂ and an irregular phase α′-Fe ₈ N in which the N is dissolved.

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