Magnetostrictive materials for power generation and magnetostrictive vibration power generation devices

Abstract

To provide a magnetostrictive material for power generation, which is used for magnetostrictive power generation, has a high power generation output, and can be stably mass-produced.SOLUTION: In a magnetostrictive material for power generation, on the surface layer of a base material made of a grain-oriented electrical steel sheet containing Si, there are a high Al region with an Al concentration of 0.1 mass% or more and a high Si region with a Si concentration higher than the average Si concentration of the grain-oriented electrical steel sheet, the high Al region is in the range from the boundary surface of the base material to a depth of 0.1 mm, the position indicating the maximum Si concentration in the surface layer is on the side of the center of the sheet thickness than the position indicating the maximum Al concentration.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a magnetostrictive material for power generation and a magnetostrictive vibration power generation device. [Background technology]

[0002] In the use of the Internet of Things (IoT), which has been developing in recent years, wireless sensor modules that integrate sensors, power sources, wireless communication devices, etc. are used to connect things to the Internet. There is a demand for the development of power generation devices that can generate electricity from energy generated in the environment where they are installed, as the power source for such wireless sensor modules, without the need for regular manual maintenance such as battery replacement or charging.

[0003] One example of such a power generation device is a magnetostrictive vibration power generation device that uses inverse magnetostriction, which is the opposite effect of magnetostriction. Inverse magnetostriction is a phenomenon in which the magnetization of a magnetostrictive material changes when stress such as vibration is applied to the material. Magnetostrictive vibration power generation applies stress to the magnetostrictive material through vibration, and the change in magnetization caused by the inverse magnetostriction effect generates an electromotive force in a coil wound around the magnetostrictive material according to the law of electromagnetic induction.

[0004] In the past, attempts have been made to increase the amount of magnetostriction in order to improve the power generation performance of magnetostrictive materials. This is because the larger the amount of magnetostriction, the larger the change in magnetic flux density (ΔB) due to inverse magnetostriction when tensile stress and compressive stress are alternately applied to the magnetostrictive material, and the larger the power generation output. One method for increasing the amount of magnetostriction in magnetostrictive materials is to control the crystal structure of the magnetostrictive material. The basic lattice structure of previously developed Fe-Co alloys and Fe-Ga alloys is the bcc structure, <001> Therefore, the magnetostriction in the GOSS orientation {110} is the largest. <001> How to align the texture of single crystals <001> A method of cutting out the data along the direction is being implemented.

[0005] For example, Patent Document 1 describes a method for forming an Fe-Ga alloy sheet, which is a magnetostrictive material, by adding one or more additional elements selected from Al, Be, B, etc. In this method, a {110} Fe alloy having a large magnetostriction is formed by pack rolling. <001> It is said to produce a texture with a GOSS orientation.

[0006] Patent Document 2 describes a magnetostrictive material in which carbide (Nb2C) is finely dispersed in an Fe-Ga alloy to refine the crystal structure and improve rolling workability.

[0007] Patent Document 3 describes Fe-Co alloys as magnetostrictive materials, including massive bulk, thin plate, and thin ribbon alloys of Fe-Co alloys with a Co atomic percentage of 56 to 80% and a magnetostriction of 60 ppm or more.

[0008] Patent Document 4 describes a method for producing an Fe-Co alloy, which includes melting and solidifying 67 to 87 mass % of Co and 1 mass % or less of one or more selected from Nb, Mo, V, Ti, and Cr, followed by hot rolling, cold rolling, and heat treatment.

[0009] Patent Document 5 describes a plate-shaped magnetostrictive material made by forming recesses or residual stress portions on the surface of a magnetostrictive material made of an Fe-Ga alloy, an Fe-Co alloy, or an Fe-Al alloy.

[0010] Patent Document 6 describes a magnetostrictive material in which Ga or Ga-Sn is infiltrated into an Fe-Si alloy from the surface. Patent Document 6 describes a method of infiltrating Ga or Ga-Sn into an Fe-Si alloy, in which the heat treatment temperature when heat treating a Ga-plated Fe-Si-based alloy is preferably 900°C or higher, within the range of 300°C to 1400°C, from the viewpoint of increasing the permeability of Ga into the Fe-Si alloy.

[0011] Patent Document 7 describes a non-oriented electrical steel sheet having an aluminum concentration gradient in the thickness direction for the purpose of reducing eddy current loss.

[0012] Non-Patent Document 1 describes an Fe—Al alloy as a magnetic material with large magnetostriction. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] US Patent Application Publication No. 2008 / 0115864 [Patent Document 2] US Patent Application Publication No. 2015 / 0028724 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-177664 [Patent Document 4] International Publication No. 2015 / 083821 [Patent Document 5] Japanese Patent Publication No. 2020-107715 [Patent Document 6] Japanese Patent Application Publication No. 2020-041192 [Patent Document 7] International Publication No. 2009 / 072394 [Non-patent literature]

[0014] [Non-Patent Document 1] "On the Dynamic Characteristics of the Magnetostrictive Alloy "Alfer", Journal of the Japan Institute of Metals, Vol. 13, No. 1 (1949), pp. 1-4 Summary of the Invention [Problem to be solved by the invention]

[0015] The Fe—Ga alloys described in Patent Documents 1 and 2 are brittle and therefore have poor workability. Furthermore, they are difficult to manufacture by conventional hot rolling or cold rolling, making them unsuitable for mass production. Furthermore, Ga is more expensive than Co, which increases the cost of raw materials and the resulting high material price.

[0016] On the other hand, the Fe-Co alloys described in Patent Documents 3 and 4 can be processed by ordinary hot rolling and cold rolling, and therefore are more suitable for mass production than Fe-Ga alloys, and the material price is also lower than that of Fe-Ga alloys. However, the amount of magnetostriction is small, and when used as a power generation element, there is a problem that the power generation output is low.

[0017] Patent Document 5 discloses that the amount of power generation is improved by forming recesses or residual stress on the surface of a magnetostrictive material such as an Fe-Ga alloy, an Fe-Co alloy, or an Fe-Al alloy, thereby controlling the magnetic domain structure. <001> If the texture is not controlled in the orientation, the amount of magnetostriction is small, which leads to problems such as low power generation output.

[0018] In this regard, the magnetostrictive material described in Patent Document 6, in which Ga or Ga-Sn is infiltrated into an Fe-Si alloy, uses a grain-oriented electrical steel sheet as the base material, so texture control is not necessary. However, since the Ga element is expensive, there is a problem that the raw material cost is high and the material price is also high.

[0019] Patent Document 7 increases the electrical resistance of the surface layer by concentrating Al on the surface of non-oriented electrical steel sheet in order to reduce eddy current loss during high-frequency operation. Electrical steel sheets contain Si in addition to Fe to increase electrical resistance throughout the sheet thickness and reduce eddy current loss. However, because eddy currents flow in large amounts in the surface layer due to the skin effect in the high-frequency range, Al, which has the same effect of increasing electrical resistance as Si, is concentrated in the surface layer. Reducing iron loss is essential for electrical steel sheets. Iron loss is the sum of hysteresis loss and eddy current loss. Since increasing magnetostriction increases hysteresis loss, there is no concept of increasing magnetostriction in electrical steel sheets. Furthermore, there is no concept of adding Al to grain-oriented electrical steel sheets for the purpose of increasing magnetostriction in order to increase magnetostriction in power transformers used in the commercial frequency range, where reducing hysteresis loss is important.

[0020] Non-Patent Document 1 describes that the Fe-Al alloy exhibits increased magnetostriction as the Al content increases, but also describes the problem that Fe-Al alloys cannot be processed at room temperature.

[0021] Thus, in the alloy design of conventional magnetostrictive materials, it is necessary to improve the magnetostriction in order to increase the power generation output, but alloys with high magnetostriction, such as Fe-Ga alloys, are brittle and therefore difficult to process, making mass production difficult and expensive. Furthermore, if mass production and price are prioritized, the magnetostriction will be low, making it difficult to improve the power generation output.

[0022] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a magnetostrictive material for power generation that has a high power generation output for use in magnetostrictive power generation, and a magnetostrictive vibration power generation device that uses the magnetostrictive material for power generation. [Means for solving the problem]

[0023] In order to solve the above problems, the present invention employs the following configuration. [1] The surface layer of the base material made of Si-containing grain-oriented electrical steel sheet, a high Al region having an Al concentration of 0.1 mass% or more and a high Si region having a Si concentration higher than the average Si concentration of the grain-oriented electrical steel sheet, the high Al region is in a range from the boundary surface of the base material to a depth of 0.100 mm, The magnetostrictive material for power generation, wherein the position showing the maximum Si concentration in the surface layer is closer to the center of the plate thickness than the position showing the maximum Al concentration. [2] The magnetostrictive material for power generation according to [1], characterized in that the Al concentration at the position showing the maximum Si concentration is 1.0 mass % or more and 12 mass % or less. [3] The magnetostrictive material for power generation according to [2], characterized in that the Al concentration in the high Al region at a position on the boundary surface side of the base material is 6.0 mass % or more. [4] The magnetostrictive material for power generation according to [2], wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less. [5] The magnetostrictive material for power generation according to [3], wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less. [6] The magnetostrictive material for power generation according to [1], characterized in that the Al concentration in the high Al region at a position on the boundary surface side of the base material is 6.0 mass % or more. [7] The magnetostrictive material for power generation according to [6], wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less. [8] The magnetostrictive material for power generation according to [1], wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less. [9] The magnetostrictive material for power generation described in [1], characterized in that the position showing the maximum value of the Si concentration in the surface layer is located at a depth of less than 0.07 mm from the boundary surface side of the high Al region.

[10] The magnetostrictive material for power generation according to [1], characterized in that the ratio of the change in magnetic flux density ΔB during dynamic measurement at a vibration frequency of 150 Hz to the change in magnetic flux density ΔB during quasi-static measurement is 95% or more.

[11] The magnetostrictive material for power generation according to [1], characterized in that the ratio of the change in magnetic flux density ΔB during dynamic measurement at a vibration frequency of 250 Hz to the change in magnetic flux density ΔB during quasi-static measurement is 90% or more.

[12] The high Al region, the high Si region, and the base material are all composed of {110} <001> The magnetostrictive material for power generation according to any one of [1] to

[11] , having an orientation texture.

[13] A magnetostrictive part including the magnetostrictive material for power generation according to any one of [1] to

[11] ; a support portion that supports the magnetostrictive portion in a vibrable state; a bias magnet that applies a bias magnetic field to the magnetostrictive portion; an induction coil disposed at a distance from the magnetostrictive portion.

[14] The high Al region, the high Si region, and the base material in the magnetostrictive material for power generation are all formed of {110} <001> The magnetostrictive vibration power generation device according to

[13] , having an orientation texture. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a magnetostrictive material for power generation that has a high power generation output and a magnetostrictive vibration power generation device that uses the magnetostrictive material for power generation. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view showing an example of a magnetostrictive material for power generation according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional view showing an example of a magnetostrictive material for power generation according to an embodiment of the present invention; [Figure 3] FIG. 2 is a diagram showing the concentration profile of the surface layer of the magnetostrictive material for power generation according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram showing an example of a magnetostrictive vibration power generation device according to an embodiment of the present invention; [Figure 5] FIG. 1 shows the results of EBSD measurement for Example 1. [Figure 6] FIG. 1 is a schematic diagram showing a measurement unit for measuring a magnetic flux density change ΔB. DETAILED DESCRIPTION OF THE INVENTION

[0026] In magnetostrictive vibration power generation devices, the greater the magnetostriction of the magnetostrictive material, the greater the change in magnetic flux density (ΔB) due to inverse magnetostriction when tensile stress and compressive stress are applied to the magnetostrictive material, and the greater the power generation output. Therefore, in order to improve the power generation performance of magnetostrictive materials, methods have been attempted to increase the magnetostriction. Specifically, technologies aimed at increasing ΔB by aligning the crystal orientation in a specific direction have been studied.

[0027] Known magnetostrictive materials are primarily those with large saturation magnetostriction, such as FeGa alloys with saturation magnetostriction levels of approximately 200 ppm, and FeCo and FeAl alloys with saturation magnetostriction levels of 80 ppm. The larger the saturation magnetostriction, the greater the magnetoelastic energy generated when strain is applied to the magnetostrictive material, and the easier it is for the magnetization direction within the magnetostrictive material to change in order to reduce this energy.

[0028] However, FeGa alloys, for example, are manufactured using single-crystal growth methods such as the Czochralski method and the Bridgman method to align the crystal orientation, which results in high manufacturing costs. Furthermore, Ga is an expensive raw material. Therefore, using FeGa alloys in magnetostrictive vibration power generation devices results in high prices.

[0029] Patent Document 6 describes a material in which Ga is plated on the surface of an FeSi-based grain-oriented electrical steel sheet, and then heat-treated at high temperature for a long period of time to diffuse Ga as uniformly as possible into the interior. Patent Document 6 aims to make the entire electrical steel sheet similar to an FeGa alloy, which has a high saturation magnetostriction, while utilizing the texture of the grain-oriented electrical steel sheet. Since FeAl alloys have long been known to have high saturation magnetostriction, it has been thought that, as with Ga, it would be possible to use grain-oriented electrical steel sheet as the raw material and increase the saturation magnetostriction by diffusing Al from the surface of the grain-oriented electrical steel sheet. However, it has been found that Al cannot increase power generation performance in the same way as Ga, and in fact, power generation performance is reduced.

[0030] By the way, grain-oriented electrical steel sheets have the GOSS texture {110} <001> This method is cost-effective compared to the FeGa alloy manufacturing method described above. However, the magnetostriction constant of grain-oriented electrical steel sheets is approximately 25 ppm, which is about one-tenth of that of Fe-Ga alloys, and the inverse magnetostriction effect of grain-oriented electrical steel sheets is smaller than that of Fe-Ga alloys. Therefore, grain-oriented electrical steel sheets, which have a small magnetostriction constant, do not reach the power generation performance level of FeGa alloys. Therefore, it is expected that by using grain-oriented electrical steel sheets as a material and making improvements that can be implemented at low cost, a performance level exceeding that of FeGa alloys can be achieved.

[0031] The inventors have found that by forming an Al layer of a predetermined thickness on the surface of grain-oriented electrical steel sheet and then heat treating it at a predetermined temperature for a predetermined time, Al is enriched in a predetermined distribution only in the surface layer of the grain-oriented electrical steel sheet, and the Si concentration distribution is controlled, thereby improving power generation performance. <001> Grain-oriented electrical steel sheet with GOSS texture <001> We have newly discovered that when compressive or tensile strain is applied while a magnetic field is applied in the direction, the magnetic flux density changes significantly.

[0032] The reason why Al was selected as the diffusing element is that it is an element that increases the magnetostriction constant of an Fe solid solution. While Co, Cr, Mo, V, Ge, and other elements can generally achieve this effect, the inventors chose Al because it is an inexpensive element. Furthermore, Al is easy to obtain and easily diffuses into grain-oriented electrical steel sheets, making it a good diffusing element. Examples of methods for forming an Al layer on a grain-oriented electrical steel sheet include plating, sputtering, and lamination of Al foil.

[0033] In order to improve power generation performance by diffusing Al from the surface of an electrical steel sheet, it is necessary to form a predetermined Al concentration distribution and a predetermined Si concentration distribution in the surface layer of the grain-oriented electrical steel sheet. The inventors discovered that power generation performance can be improved by using an electrical steel sheet with low saturation magnetostriction as the magnetostrictive material for a magnetostrictive vibration power generation device, and further by concentrating Al in a predetermined distribution only in the surface layer of the grain-oriented electrical steel sheet and controlling the predetermined Si concentration distribution, which led to the completion of the present invention.

[0034] Hereinafter, a magnetostrictive material for power generation and a magnetostrictive vibration power generation device according to embodiments of the present invention will be described with reference to the drawings.

[0035] The magnetostrictive material for power generation of this embodiment has, in the surface layer of a base material made of Si-containing grain-oriented electrical steel sheet, a high-Al region with an Al concentration of 0.1 mass% or more and a high-Si region with a Si concentration higher than the average Si concentration of the grain-oriented electrical steel sheet, the high-Al region being in the range from the boundary surface of the base material to a depth of 0.100 mm, and the position showing the maximum Si concentration in the surface layer being closer to the center of the sheet thickness than the position showing the maximum Al concentration. In the magnetostrictive material for power generation according to this embodiment, the high Al region, the high Si region, and the base material all have a {110} <001> It is preferable that the alloy has an orientation texture. In the magnetostrictive material for power generation of this embodiment, the Al concentration at the position showing the maximum Si concentration is preferably 1.0 mass % or more and 12 mass % or less. In the magnetostrictive material for power generation of this embodiment, the Al concentration in the high Al region at the position on the boundary surface side of the base material is preferably 6.0 mass % or more. In the magnetostrictive material for power generation of this embodiment, the maximum value of the Si concentration in the high Si region is preferably in the range of 3.6 mass % or more and 6.0 mass % or less. In the magnetostrictive material for power generation of this embodiment, the position showing the maximum Si concentration in the surface layer is preferably located at a depth of less than 0.07 mm from the boundary surface side of the high Al region. In the magnetostrictive material for power generation of this embodiment, it is preferable that Al contained in the high Al region is in solid solution in the surface layer of the base material.

[0036] Here, the Al concentration and Si concentration in the surface layer of the magnetostrictive material for power generation are determined by exposing a cross section of the surface layer of the magnetostrictive material for power generation and performing elemental analysis on the cross section of the surface layer at each predetermined measurement depth position along the depth direction. More specifically, elemental analysis is performed at each predetermined measurement depth position, and the Al content (mass%) and Si content (mass%) are determined for each measurement depth position, with the total of the detected elements being 100 mass%. Then, a concentration profile in the depth direction of the surface cross section is obtained. The Al content (mass%) and Si content (mass%) at each predetermined depth position in this concentration profile are defined as the Al concentration and Si concentration.

[0037] The average Si concentration of the grain-oriented electrical steel sheet is the Si content (mass%) in the base material of the magnetostrictive material for power generation, excluding the high Al and high Si regions. This Si content is the same as the Si content (mass%) in the steel of the grain-oriented electrical steel sheet, which is the raw material, and therefore is defined as the average Si concentration of the grain-oriented electrical steel sheet in this embodiment.

[0038] 1 and 2 show cross-sectional schematic diagrams of an example of the magnetostrictive material for power generation according to this embodiment. Each of FIGS. 1 and 2 also includes depth-direction concentration profiles of Al concentration, Si concentration, and Fe concentration. In FIGS. 1 and 2, the upper cross-sectional schematic diagram is an enlarged cross-sectional schematic diagram of the surface layer of the magnetostrictive material for power generation, with the thickness direction of the surface layer extending horizontally in the diagram. The horizontal axis of the lower concentration profile corresponds to the thickness direction of the upper cross-sectional schematic diagram. The concentration profiles of Al, Si, and Fe shown in FIGS. 1 and 2 are merely examples, and the distribution of Al concentration and Si concentration in the surface layer of the magnetostrictive material for power generation according to the present invention is not limited to the concentration profiles shown in FIGS. 1 and 2.

[0039] The magnetostrictive material for power generation shown in FIG. 1 has a base material 1 made of grain-oriented electrical steel sheet and an Fe-Al alloy layer 5 laminated on the base material 1. The interface between the base material 1 and the Fe-Al alloy layer 5 is the boundary surface 1a of the base material 1. The base material 1 has a surface layer 2 on the boundary surface 1a side. The surface layer 2 has a high Al region 3 and a high Si region 4. The high Al region 3 is in the range from the boundary surface 1a of the base material 1 to a depth of 0.100 mm. The high Si region 4 is located deeper than the high Al region 3. The position M showing the maximum Si concentration in the surface layer 2 is Si is the position M where the Al concentration is maximum in the high Al region 3. Al It is located closer to the center of the plate thickness than the

[0040] The Fe—Al alloy layer 5 shown in FIG. 1 will now be described. The magnetostrictive material for power generation of this embodiment is manufactured by laminating an Al layer on a grain-oriented electrical steel sheet, which serves as a raw material, and then diffusing the Al in the Al layer into the grain-oriented electrical steel sheet by heat treatment. During this process, Fe contained in the grain-oriented electrical steel sheet diffuses into the Al layer. The Al layer with Fe diffused in this way is the Fe—Al alloy layer 5. In the magnetostrictive material for power generation of this embodiment, the Fe—Al alloy layer 5 does not contribute to power generation, so it may be left as is or may be removed. Alternatively, the amount of Al attached to the surface of the grain-oriented electrical steel sheet may be adjusted so that the Fe—Al layer 5 does not remain, and all of the Al in the Al layer may be diffused into the grain-oriented electrical steel sheet by heat treatment.

[0041] The magnetostrictive material for power generation shown in FIG. 2 is a magnetostrictive material for power generation that does not have the Fe—Al alloy layer 5 shown in FIG. 1. That is, the magnetostrictive material for power generation shown in FIG. 2 has a base material 1 made of grain-oriented electrical steel sheet. The base material 1 has a surface layer 2 on the central side of the boundary surface 1a in the sheet thickness direction. The surface layer 2 has a high Al region 3 and a high Si region 4. The high Al region 3 is located in the range from the boundary surface 1a of the base material 1 to a depth of 0.100 mm. The high Si region 4 is located deeper than the high Al region 3. Position M showing the maximum Si concentration in surface layer 2 Si is the position M where the Al concentration is maximum in the high Al region 3. Al 2. The boundary surface 1a in the case of FIG.

[0042] 1 and 2, the high Al region 3 is located closer to the boundary surface 1a of the base material 1 than the high Si region 4. Note that, as shown in FIGS. 1 and 2, the high Al region 3 and the high Si region 4 may partially overlap each other. That is, the region of the high Al region 3 on the center side of the base material 1 in the thickness direction and the region of the high Si region 4 on the boundary surface 1a side of the base material 1 may overlap each other.

[0043] It is believed that the presence of Fe and Al in the high Al region 3 provides the effect of a high magnetostrictive layer, while the presence of Fe and a higher concentration of Si than in grain-oriented electrical steel sheets in the high Si region 4 provides the function of a magnetic transmission layer.

[0044] In addition, the high Al region 3, the high Si region 4, and the base material all have a {110} <001> It is preferable that the magnetostriction has a texture of the crystal orientation, which allows compressive strain and tensile strain to be applied in the λ100 direction, where magnetostriction is at its maximum in terms of crystal orientation, thereby maximizing the inverse magnetostriction effect.

[0045] Furthermore, it is preferable that the Al contained in the high Al region 3 is in the form of a solid solution in the surface layer 2 of the base material, and it is desirable to prevent Al from being present as a non-solid solution as much as possible, which allows Al to further enhance the inverse magnetostriction effect.

[0046] FIG. 3 shows the depth profiles of the Al concentration, Si concentration, and Fe concentration in the magnetostrictive material for power generation of this embodiment. The concentration profile shown in FIG. 3 is the same as the concentration profile attached to FIG. 1. An electron probe microanalyzer (EPMA) was used to measure the concentration profile shown in FIG. 3. The concentration profile can be obtained by setting the electron beam spot diameter to 0.05 μm. As described above, a cross section of the surface layer of the magnetostrictive material for power generation is exposed, and elemental analysis is performed on the cross section of the surface layer at each predetermined measurement depth position along the depth direction. The Al content (mass %) and Si content (mass %) are determined for each measurement depth position, assuming the total of the detected elements to be 100 mass %. Then, a concentration profile in the depth direction of the surface cross section is obtained, as shown in FIG. 3. The Al content (mass %) and Si content (mass %) at each predetermined depth position in this concentration profile are defined as the Al concentration and Si concentration. It should be noted that the Al concentration and Si concentration may become extremely large due to edge effects during EPMA measurement, and when disturbances such as edge effects are recognized, the concentrations around the edge effects are used for interpolation. The concentration profiles of Al, Si, and Fe shown in Fig. 3 are merely examples, and the distribution of the Al concentration and Si concentration in the surface layer of the magnetostrictive material for power generation of the present invention is not limited to the concentration profiles shown in Fig. 3.

[0047] As shown in FIG. 1, when an Fe—Al alloy layer 5 is laminated on a base material 1, the position of the boundary surface 1a of the base material 1 is determined as follows. First, a cross section of the surface layer is exposed. This cross section is a cross section obtained by cutting the base material, a grain-oriented electrical steel sheet, so that a plane perpendicular to the rolling direction appears. The rolling direction of the grain-oriented electrical steel sheet is approximately parallel to the easy axis of magnetization of the grain-oriented electrical steel sheet. In this cross section, <001> A crystal structure with a vertical orientation appears. The crystal structure is then analyzed using Electron Backscatter Diffraction (EBSD). The crystal structure is the same as the crystal structure in the center of the sheet, where the crystalline structure of the grain-oriented electrical steel sheet remains intact. <001> The area where the deviation from the direction is within 10° is regarded as the same base material 1, and the area outside these conditions is regarded as the Fe—Al alloy layer 5, and the boundary between the base material 1 and the Fe—Al alloy layer 5 is regarded as the interface 1a. In other words, the interface 1a is the interface between the {110} <001> This is the surface of a crystal composed of a GOSS texture.

[0048] As explained above, confirmation that the Al contained in the high Al region 3 is solid-solved in the surface layer 2 of the base material is made by exposing a cross section of the surface layer of the magnetostrictive material for power generation and analyzing the crystal structure using the above-mentioned electron backscattering analysis, and identifying a region with the same crystal orientation in the surface layer 2. Next, an electron beam microanalyzer is used to measure the Al concentration in the identified region, and it is determined that Al is contained in a region with the same crystal orientation as the base material.

[0049] In this way, the position of the boundary surface 1a of the base material 1 is identified, and the Al concentration at the boundary surface 1a is set as the Al concentration at the position of the high Al region 3 on the boundary surface 1a side of the base material 1. In this embodiment, the Al concentration at the position of the high Al region 3 on the boundary surface 1a side of the base material 1 is the maximum Al concentration in the surface layer, and the position M where the boundary surface 1a of the base material 1 shows the maximum Al concentration Al This becomes:

[0050] In addition, the Si peak position M SiThe position where the Si concentration reaches its maximum in the Si concentration profile measured by EPMA is called the Si peak position M Si The Si peak position M Si The Al concentration is determined by the Si peak position M Si and the Al concentration at the same position.

[0051] These high Al regions 3 and high Si regions 4 are formed by diffusing Al into the surface layer of the grain-oriented electrical steel sheet by performing a heat treatment with Al disposed on the surface of the grain-oriented electrical steel sheet.

[0052] The magnetostrictive material for power generation of this embodiment has a high-Al region and a high-Si region in the surface layer of a Si-containing grain-oriented electrical steel sheet, and is made from grain-oriented electrical steel sheet. Therefore, the portion of the base material 1, excluding the surface layer 2, remains grain-oriented electrical steel sheet. Grain-oriented electrical steel sheet is a functional material, sometimes called a "silicon steel sheet," in which silicon (Si) is added to iron (Fe) to improve the magnetic properties of iron. The grain-oriented electrical steel sheet of this embodiment preferably has a silicon (Si) content (average Si concentration) of 0.5% or more and 4% or less. Grain-oriented electrical steel sheet may contain a trace amount of Al as an impurity element or inhibitor, with the upper limit being less than 0.1%, 0.050% or less, 0.030% or less, or 0.010% or less.

[0053] Generally, there are two types of electrical steel sheets: grain-oriented and non-oriented. Grain-oriented electrical steel sheets are steel sheets in which the crystal orientation of the metal crystals is aligned in the rolling direction of the steel sheet. <001> The direction was aligned, and the rolling surface was oriented in the (110) direction. <001> The material is an electrical steel sheet having a GOSS texture. On the other hand, a non-oriented electrical steel sheet has a relatively random crystal orientation, where the crystal orientation of the metal crystals is not aligned in a specific direction. In this embodiment, a grain-oriented silicon steel sheet is used as the material in order to utilize the crystal orientation with the highest magnetostriction constant.

[0054] The grain-oriented electrical steel sheet of this embodiment has a rolling direction <001> The direction was aligned, and the rolling surface was oriented in the (110) direction. <001> It has a GOSS texture. This is thought to be because, when a certain magnetic field is applied to a grain-oriented electrical steel sheet in the

[0100] direction, the ratio of 180° domains and 90° domains parallel to the

[0100] direction is such that they interact well with each other, and when strain is applied to the grain-oriented electrical steel sheet, the 180° domains are easily transformed into 90° domains, or vice versa. Specifically, when compressive strain is applied parallel to the magnetization direction of the 180° domains (i.e., in the

[0100] direction), the 180° domains decrease and the 90° domains increase, while when tensile strain is applied in the

[0100] direction, the 90° domains decrease and the 180° domains increase. Furthermore, when compressive strain is applied perpendicular to the magnetization direction of the 180° magnetic domains (i.e., in the

[0110] direction), the 90° magnetic domains decrease and the 180° magnetic domains increase, and when tensile strain is applied in the

[0110] direction, the 180° magnetic domains decrease and the 90° magnetic domains increase. These changes in magnetic domains change the magnetization of the grain-oriented electrical steel sheet, allowing it to function as a magnetostrictive material for power generation. In magnetostrictive vibration power generation devices, the above changes in magnetization induce a voltage in the detection coil wound around the magnetostrictive material.

[0055] Specific examples of grain-oriented electrical steel sheets include Orient Core, Orient Core Hi-B (for example, 27ZH100), Orient Core Hi-B Laser, and Orient Core Hi-B Permanent, all manufactured by Nippon Steel Corporation.

[0056] Next, the high Al region 3 and the high Si region 4 will be described. The high Al region 3 is a region where the Al concentration is higher than the Al content already contained in the grain-oriented electrical steel sheet, and is a region where Al is contained in an amount of at least 0.1 mass % or more. The Al concentration in the high Al region 3 is not necessarily constant. That is, as shown in FIG. 3, the Al concentration in the high Al region 3 is high on the side of the boundary surface 1a of the base material 1 and decreases as it approaches the center of the sheet thickness of the base material 1. Therefore, in this embodiment, the boundary surface 1a of the base material 1 is at the position M where the Al concentration is maximum. AlThe position of the boundary surface 1a of the base material 1 coincides with the position of the surface of the grain-oriented electromagnetic steel sheet that is the raw material of the magnetostrictive material for power generation.

[0057] The high Al region 3 is preferably located within a range from the boundary surface 1a of the base material 1 to a depth of 0.100 mm toward the inside of the plate thickness. The reason for this is that if Al is diffused to a depth of more than 0.1 mass %, it becomes difficult to form the high Si region 4.

[0058] The Al concentration in the high Al region 3 at the position on the boundary surface 1a side of the base material 1 is preferably 6.0 mass% or more. If the Al concentration in the high Al region 3 at the position on the boundary surface 1a side of the base material 1 is less than 6.0 mass%, the power generation performance will decrease. It is believed that the presence of 6.0 mass% or more Al on the outermost layer side of the high Al region 3 more effectively exerts the effect of the high magnetostrictive layer existing in the region inside from that position.

[0059] On the other hand, the Al concentration in the high Al region 3 at the position on the boundary surface 1a side of the base material 1 is preferably 45% by mass or less. Increasing the Al concentration beyond 45% by mass is not only not very effective in improving power generation performance, but also requires diffusing a large amount of Al, which makes the process for diffusing Al complicated, which is not preferred.

[0060] The high Al region 3 may overlap with the high Si region 4 at the center of the thickness of the magnetostrictive material for power generation. In this overlapping region, there is a position M where the Si concentration is at its maximum. Si (Hereinafter, the peak position of Si concentration M Si The peak position of Si concentration M Si The Al concentration in the above ranges preferably from 1.0 mass % to 12 mass %.

[0061] Si concentration peak position M SiIf the Al concentration at the boundary surface 1a side of the high Al region 3 is 1.0 mass % or more, the Al concentration at the boundary surface 1a side of the high Al region 3 can be 6.0 mass % or more, and the high magnetostrictive layer can be sufficiently effective. Si If the Al concentration at the peak position M of the Si concentration is 12 mass % or less, the Al concentration at the position on the boundary surface 1a side of the high Al region 3 will be 45 mass % or less, the magnetostriction constant in the high Al region 3 will be high, and the power generation performance will be improved. Si The Al concentration in the alloy is preferably 1.0 mass % or more and 12 mass % or less.

[0062] Next, the high Si region 4 is a region where the Si concentration is higher than the average Si concentration of the grain-oriented electrical steel sheet that is the raw material. In the high Si region 4, the Si concentration is not constant within the region, and as mentioned above, there is a peak position M Si As shown in FIG. 3, the profile of the Si concentration is almost constant at the center of the thickness of the base material 1, but increases toward the boundary surface 1a of the base material 1, and reaches a peak position M Si The peak position M Si The Si concentration decreases toward the boundary surface 1a of the base material 1, and the Si concentration at the boundary surface 1a of the base material 1 becomes lower than the average Si concentration of the grain-oriented electrical steel sheet.

[0063] The maximum Si concentration is preferably 3.6 mass% or more and 6.0 mass% or less, and may be 3.6 mass% or more and 4.8 mass% or less. If the maximum Si concentration is in the range of 3.6 mass% or more and 6.0 mass% or less, power generation performance can be improved. If the maximum Si concentration is 3.6 mass% or more and 6.0 mass% or less, it is thought that the high Si region 4 more effectively exhibits its effect as a magnetic transmission layer.

[0064] Si concentration peak position M Si The peak position M of the Si concentration of the high Si region 4, which exerts the effect as a magnetic transmission layer, is preferably located at a depth of less than 0.07 mm from the boundary surface 1a side of the high Al region 3. Siis located closer than 0.07 mm from the boundary surface 1a side of the high Al region 3, the power generation performance can be improved compared to the grain-oriented electrical steel sheet that is the raw material.

[0065] As shown in Fig. 3, the Al concentration is increased at the Si peak position M Si The gradient of the Al concentration in this region is preferably 50 mass % / mm or more, and more preferably 100 mass % / mm or more.

[0066] Furthermore, as shown in Figure 3, the Al concentration profile is the concentration profile of normal diffusion that occurs when an Al layer is placed on a grain-oriented electrical steel sheet and then heat treated. On the other hand, for Si, the distribution is almost uniform along the depth direction before heat treatment, but after heat treatment, it becomes non-uniform with a peak in the Si concentration, and diffusion occurs in the opposite direction to normal diffusion. As a result, the Si concentration decreases on the side of the interface 1a, and the Si concentration peaks at a relatively deep position. With this Si distribution, the magnetostrictive material for power generation of this embodiment has a high Si region 4 where Si is concentrated and functions as a magnetic transmission layer, and a high Al region 3 where Al is concentrated and functions as a high magnetostrictive layer.

[0067] As explained above, the surface layer 2 has a high Al region 3 with an Al concentration of 0.1 mass % or more and a high Si region 4 with a Si concentration higher than the average Si concentration of the grain-oriented electrical steel sheet. The high Al region 3 is located in the range from the boundary surface 1a of the base material 1 to a depth of 0.100 mm, and the position M showing the maximum Si concentration in the surface layer 2 is Si is the position M where the Al concentration is at its maximum. AlIt was found that by locating the base material 1 closer to the center of the thickness than the center of the sheet, the interaction between the crystalline structure of the grain-oriented electrical steel sheet, the Si-enriched magnetic transmission layer (high Si region 4), and the Al-enriched high-magnetostrictive layer (high Al region 3) has the effect of improving power generation performance. Although the magnetostriction exhibited by the crystalline structure of grain-oriented electrical steel sheet is low, the saturation magnetic flux density is high. Because the saturation magnetic flux density is high at the center of the thickness of the base material 1, when a magnetization change in the base material 1 occurs in response to a magnetization change from the high-magnetostrictive layer (high Al region 3) through the magnetic transmission layer (high Si region 4), a larger change in magnetic flux density occurs, contributing to an improvement in power generation.

[0068] The functions of the high Al region 3 and the high Si region 4 in the magnetostrictive material for power generation of this embodiment are unclear, but are presumed to be as follows. Because the high Al region 3 is located at the boundary surface 1a, it undergoes large deformation when subjected to bending strain. Therefore, by applying a predetermined magnetic field (bias magnetic field) in the

[0100] direction of the magnetostrictive material for power generation, when strain is applied to the magnetostrictive material for power generation, a transformation from 180° magnetic domains to 90° magnetic domains, or a transformation from 90° magnetic domains to 180° magnetic domains, occurs first in the high Al region 3 (high magnetostrictive layer), where magnetostriction is presumed to be large. Subsequently, a magnetic domain transformation occurs in the matrix of the grain-oriented electrical steel sheet inside the surface layer 2 due to magnetic interaction. Furthermore, it is presumed that the high Si region 4 (magnetic transmission layer) formed between the high Al region 3 (high magnetostrictive layer) and the matrix of the grain-oriented electrical steel sheet has the effect of making this magnetic interaction more likely to occur.

[0069] The change in magnetic flux density ΔB that occurs when an external stress is applied to a magnetostrictive material for power generation can be used as an index for evaluating the performance of the material. ΔB (unit: mT or T) can be calculated using the following method.

[0070] A magnetostrictive material for power generation with a cross-sectional area of ​​S is inserted into a coil with N turns and an external stress is applied. When a change in magnetic flux density ΔB occurs over time Δt, a voltage V of V = -N(S·ΔB / Δt) is generated in the coil. Therefore, ΔB can be calculated as the time integral of the voltage signal generated in the coil. The performance index of a magnetostrictive material for power generation can be evaluated as the total voltage generated over Δt. In other words, it can be evaluated as the change in magnetic flux density ΔB, which is the time integral of the voltage. ΔB can be measured by connecting the voltage generated in the coil to a flux meter.

[0071] There are two methods for measuring ΔB: quasi-static and dynamic. Quasi-static measurements are performed by measuring the amount of change in magnetic flux density when an external stress is applied only once (bending strain is applied) using a state in which no external stress is applied to the magnetostrictive material for power generation (no bending strain) as a reference. In quasi-static measurements, the external stress is applied by, for example, fixing one end of a plate-shaped magnetostrictive material for power generation and pressing the other end in the thickness direction to a predetermined displacement, thereby elastically deforming the magnetostrictive material for power generation.

[0072] On the other hand, dynamic measurement is performed by measuring the change in magnetic flux density when an external stress is continuously applied (continuous bending strain is applied) to the magnetostrictive material for power generation, with a state in which no external stress is applied (no bending strain) as a reference. The external stress applied in dynamic measurement is, for example, performed by fixing one end of a plate-shaped magnetostrictive material for power generation and continuously vibrating the other end with the plate thickness direction as the amplitude direction. The vibration frequency and amplitude length may be set as appropriate, but the vibration frequency may be, for example, in the range of 500 Hz or less, 300 Hz or less, or 100 Hz or less. The amplitude length may be set as appropriate depending on the size of the magnetostrictive material for power generation. The detailed method and apparatus for measuring ΔB (unit: mT or T) will be explained in the examples below.

[0073] The magnetostrictive material for power generation of this embodiment has a higher change in magnetic flux density ΔB than conventional magnetostrictive materials, so when the magnetostrictive material for power generation of this embodiment is applied to a power generation device, the amount of power generated by the power generation device can be increased. Note that the improvement in ΔB in the magnetostrictive material for power generation of this embodiment can be obtained in both quasi-static and dynamic measurements.

[0074] Furthermore, the magnetostrictive material for power generation of this embodiment can increase the ratio of ΔB during dynamic measurement to ΔB during quasi-static measurement. In particular, the ratio of ΔB during dynamic measurement at a vibration frequency of 150 Hz to ΔB during quasi-static measurement can be made 95% or more. Furthermore, the ratio of ΔB during dynamic measurement at a vibration frequency of 250 Hz to ΔB during quasi-static measurement can be made 90% or more. This means that a high amount of power can be generated even when the magnetostrictive material for power generation of this embodiment is continuously vibrated at a relatively high vibration frequency. The reason for this is presumed to be as follows.

[0075] Generally, when a magnetostrictive material made of a metal material is continuously vibrated, a change in magnetic flux density occurs, but at the same time, eddy currents are generated inside the magnetostrictive material, and the change in magnetic flux density is reduced due to eddy current loss. On the other hand, the magnetostrictive material for power generation of this embodiment is made of grain-oriented electromagnetic steel sheet, and when vibrated at a vibration frequency of 100 Hz or more, eddy current loss can occur, just like in general magnetostrictive materials. However, in the magnetostrictive material for power generation of this embodiment, the position M showing the maximum Si concentration in the surface layer 2 Si is the position M where the Al concentration is at its maximum. Al Since it is located closer to the center of the plate thickness than position M Si and position M Al In the region between these two, Al and Si, elements that increase electrical resistance, coexist, and the presence of Si further enhances the effect of the magnetic transmission layer. The presence of such a region makes it difficult for eddy currents to flow, reducing eddy current loss, and, combined with the effect of the magnetic transmission layer, is thought to suppress the decrease in ΔB.

[0076] In particular, in the magnetostrictive material for power generation of this embodiment, the position MSi The Al concentration at position M is 1.0 mass % or more and 12 mass % or less. Si However, in the magnetostrictive material for power generation located at a depth of less than 0.07 mm from the boundary surface side of the high Al region, the eddy current loss is further reduced, and the decrease in ΔB is suppressed, which is preferable. In particular, when vibrated at a relatively high vibration frequency, the decrease in ΔB is suppressed, which is preferable.

[0077] Next, a method for manufacturing the magnetostrictive material for power generation of this embodiment will be described. The magnetostrictive material for power generation of this embodiment is manufactured by disposing an Al layer on the surface of a grain-oriented electrical steel sheet and diffusing Al in the Al layer into the interior of the grain-oriented electrical steel sheet by heat treatment.

[0078] The details of the grain-oriented electrical steel sheet used as the material are as described above.

[0079] The Al layer disposed on the grain-oriented electrical steel sheet may be formed on the surface of the grain-oriented electrical steel sheet by hot-dip galvanization, electroplating, sputtering, vapor deposition, or the like. The thickness of the Al layer is preferably in the range of 0.1 to 3,000 μm, for example. A thinner Al layer makes the Al layer less susceptible to embrittlement even during long-term heat treatment, so the thickness is preferably 300 μm or less. Furthermore, the thickness is preferably 30 μm or less. Even when the Al layer is thick, the effects of the present invention can be achieved by shortening the heat treatment time, thereby allowing diffusion only to the surface, similar to when the Al layer is thin. The allowable impurities contained in the Al layer, such as Si, Fe, Cu, Mn, Mg, and Zn, are in the ranges of Si: 0.15 mass% or less, Fe: 1.7 mass% or less, Cu: 0.05 mass% or less, Mn: 0.05 mass% or less, Mg: 0.05 mass% or less, and Zn: 0.05 mass% or less.

[0080] Alternatively, an Al layer may be formed by laminating an Al foil made of aluminum or an aluminum alloy on the surface of a grain-oriented electrical steel sheet. The Al foil may be, for example, an Al foil of an aluminum alloy containing 0.15% by mass or less of Si, 1.2 to 1.7% by mass of Fe, 0.05% by mass or less of Mn, 0.05% by mass or less of Mg, and 0.05% by mass or less of Zn, with the remainder being Al and impurities, or an Al foil made of pure Al. The thickness of the Al foil is preferably in the range of 1 to 100 μm, for example. Thin Al foils can easily cause uneven Al concentration due to surface tension, so a thickness of 10 μm or more is preferred. Even thin Al foils can be produced stably without uneven concentration by heating them while applying a pressure of about 20 kPa using a weight or a vice.

[0081] The heat treatment for diffusing Al from the Al layer into the grain-oriented electrical steel sheet is performed under conditions that form high-Al and high-Si regions in the surface layer. For example, a first-stage heat treatment is performed at a heating rate of 10 to 100°C / min, a soaking temperature of 700 to 1000°C, and a soaking time of 0 to 35 minutes, and a second-stage heat treatment is performed at a soaking temperature of 600 to 1000°C and a soaking time of 0 to 200 minutes, preferably 0 to 100 minutes. The soaking temperatures in the first-stage heat treatment and the second-stage heat treatment are different. Furthermore, for temperature adjustment, the temperature is increased or decreased at a rate of 10 to 100°C / min between the first-stage and second-stage heat treatments. Furthermore, after the second-stage heat treatment is completed, the temperature is decreased at a rate of 0.5 to 100°C / min, preferably 10 to 100°C / min, until the temperature reaches 20°C or below. The reason for performing the two-stage heat treatment is to create a predetermined concentration profile of Al and Si by utilizing the difference in the diffusion coefficients of Al and Si. Either or both of the soaking times for the first stage heat treatment and the second stage heat treatment may be set to longer than 0 minutes.

[0082] The heat treatment is preferably performed in a non-oxidizing atmosphere, such as an argon atmosphere.

[0083] Furthermore, for example, when the Al layer is formed by a hot-dip galvanizing method, the grain-oriented electrical steel sheet is heated by the heat from the galvanizing bath, and thus the heat treatment is considered to have been performed, and therefore it is possible to omit an independent heat treatment step.

[0084] The magnetostrictive material for power generation of this embodiment is made from grain-oriented electrical steel sheet, which is relatively easy to obtain, and can be manufactured by laminating an Al layer on this grain-oriented electrical steel sheet and then heat treating it, so it has excellent productivity and is also suitable for mass production.

[0085] Next, we will explain the magnetostrictive vibration power generation device of this embodiment. The term "magnetostrictive vibration power generation device" refers to a device that has a magnetostrictive part formed from the magnetostrictive material for power generation of this embodiment, which exhibits magnetostrictive properties, i.e., shape change (i.e., distortion) due to the application of a magnetic field, and is capable of generating electricity based on the inverse magnetostriction of the magnetostrictive part. The magnetostrictive part may be composed only of the magnetostrictive material for power generation, or may be composed of the magnetostrictive material for power generation and a substrate.

[0086] An example of a magnetostrictive vibration power generation device 300 according to this embodiment is shown in Fig. 4. The magnetostrictive vibration power generation device 300 shown in Fig. 4 includes a magnetostrictive part 310 including the magnetostrictive material for power generation according to this embodiment, a support part 350 that supports the magnetostrictive part 310 in a vibrable state, a bias magnet 340 that applies a bias magnetic field to the magnetostrictive part 310, and an induction coil 330 that is arranged at a distance from the magnetostrictive part 310.

[0087] The support part 350 is a U-shaped member made of an elastic material. The magnetostrictive material for power generation 311 according to this embodiment is joined with an adhesive or the like to an attachment part 312 on one end side of the support part 350. The attachment part 312 of the support part 350 and the magnetostrictive material for power generation 311 form the magnetostrictive part 310.

[0088] The attachment portion 312 functions as a stress control portion. That is, the attachment portion 312 is a portion for controlling stress in order to achieve either a compressive or tensile stress load on the entire magnetostrictive material for power generation 311 when bending strain or the like is applied to the magnetostrictive material for power generation 311. The material for forming the stress control portion is not particularly limited as long as it is an elastic material that can achieve the above purpose, and both non-magnetic and magnetic materials can be used. In particular, if the elastic material is a non-magnetic material, the magnetic field flows preferentially only through the magnetostrictive material for power generation 311 of the magnetostrictive portion 310, making it easy to adjust the bias magnetic field of the magnetostrictive portion 310, which is preferable.

[0089] In the support part 350, it is preferable to make it easier to vibrate the magnetostrictive part 310 by making the thickness of the attachment part 312 thinner than the thickness of the parts other than the attachment part 312. Also, to prevent the magnetostrictive material for power generation 311 from falling off the support part 350 due to vibration, both ends of the magnetostrictive material for power generation 311 may be restrained by claw parts 312a, as shown in Fig. 4 .

[0090] An induction coil 330 is installed near the magnetostrictive portion 310. Furthermore, bias magnets 340 are attached to both ends of the magnetostrictive portion 310 so that a bias magnetic field can be applied to the magnetostrictive material for power generation 311. It is preferable to use a permanent magnet as the bias magnet 340 in order to generate the bias magnetic field. Permanent magnets can be made smaller and the bias magnetic field can be easily controlled. Furthermore, an NdFeB magnet (neodymium magnet) is preferable as the permanent magnet because it can generate a larger bias magnetic field.

[0091] Since the magnetostrictive material for power generation 311 is formed from a grain-oriented electromagnetic steel sheet containing Al, a larger voltage can be obtained by configuring the device so that a bias magnetic field is applied in the

[0100] direction of the grain-oriented electromagnetic steel sheet.

[0092] Furthermore, a weight 320 for amplifying vibrations is placed on one end of the support portion 350 .

[0093] In the magnetostrictive vibration power generation device 300 of this embodiment shown in FIG. 4, the magnetostrictive part 310 includes a magnetostrictive material for power generation 311 and an attachment part 312 as a stress control part. An induction coil 330 is wound around the magnetostrictive part 310, and the device also includes a bias magnet 340, a support part 310, and a weight 320 attached to the support part 310. In this magnetostrictive vibration power generation device 300, the magnetic field lines of the bias magnet 340 pass through the magnetostrictive part 310 and apply a bias magnetic field to the magnetostrictive material for power generation 311. Vibration of the weight 320 causes the support part 350, including the attachment part 312, to vibrate, applying tensile and compressive forces to the magnetostrictive material for power generation 311. At this time, the direction in which strain is applied to the magnetostrictive material for power generation 311 and the direction in which the bias magnetic field is applied to the magnetostrictive material for power generation 311 are parallel, and the magnetization of the magnetostrictive material for power generation 311 is changed by the inverse magnetostriction effect, thereby generating an induced current (or an induced voltage) in the coil.

[0094] The size of the magnetostrictive material for power generation 311 is not particularly limited, as it also depends on the dimensions of the magnetostrictive vibration power generation device 300 that includes it. The larger the dimensions of the magnetostrictive part 310 that includes the magnetostrictive material for power generation 311, the more turns the induction coil 330 can have in the magnetostrictive vibration power generation device 300, and the greater the voltage that can be obtained, which is preferable.

[0095] There are also no particular limitations on the thickness of the magnetostrictive material for power generation 311 that constitutes the magnetostrictive portion 310, but it is usually between 0.2 mm and 2 mm. A thickness of 0.5 mm or less is more preferable in order to reduce the mechanical resonance frequency. A thickness of 0.2 mm or more of the magnetostrictive material for power generation 311 is advantageous because it allows for a large change in magnetic flux and therefore a large generated voltage, while a thickness of 0.5 mm or less is advantageous because it facilitates the design of rigidity suitable for vibration.

[0096] Regarding the material of the mounting portion 312 as a stress control portion, examples of non-magnetic elastic materials include, but are not limited to, fiber reinforced plastics (e.g., glass fiber reinforced plastic (GFRP), carbon fiber reinforced plastic (CFRP)), austenitic stainless steel (e.g., SUS304, SUS316, etc.), copper alloys (e.g., brass, phosphor bronze), aluminum alloys (e.g., duralumin), titanium alloys (e.g., Ti-6Al-4V), etc. Among these, fiber reinforced plastics and austenitic stainless steel are preferred because they have a relatively high Young's modulus and it is easy to position the neutral plane outside the magnetostrictive portion 310 when a bending strain is applied.

[0097] Furthermore, if the magnetostrictive material for power generation 311 is made of grain-oriented electromagnetic steel sheet and the mounting portion 312 is made of magnetic steel sheet, when a bias magnetic field is applied, the bias magnetic field will flow through both the magnetostrictive material for power generation 310 and the mounting portion 312. However, because the grain-oriented electromagnetic steel sheet from which the magnetostrictive material for power generation 311 is made is a material with high magnetic permeability, it is thought that a larger bias magnetic field will flow through the magnetostrictive material for power generation 310, resulting in a magnetic domain change sufficient for power generation. However, compared to when the mounting portion 312 is made of a non-magnetic material, the magnetic force applied to the magnetostrictive material for power generation 311 will be reduced by the amount of magnetic flux flowing through the mounting portion 312 made of a magnetic material. To compensate for this decrease in magnetic force, it is advisable to use a bias magnet 340 that can generate a stronger magnetic field.

[0098] Examples of elastic materials that are magnetic materials include, but are not limited to, general structural rolled steel (e.g., SS400), general structural carbon steel (e.g., S45C), high-tensile steel (e.g., HT80), ferritic stainless steel (e.g., SUS430), and martensitic stainless steel (e.g., SUS410).

[0099] The magnetostrictive part 310 is a laminate of a magnetostrictive material for power generation 311 and an attachment part 312 of the support part 350. Such a laminate can be formed by bonding the attachment part 312 and the magnetostrictive material for power generation 311. There are no particular limitations on the method of bonding, but typical examples include bonding using an adhesive or adhesive sheet, brazing bonding, and liquid phase diffusion bonding.

[0100] There are no particular limitations on the dimensions of the mounting portion 312, but from the viewpoint of achieving either a compressive or tensile stress load on the entire magnetostrictive material for power generation 311, it is desirable that the mounting portion 312 be the same as or larger than the magnetostrictive material for power generation 311. There are no particular limitations on the thickness of the elastic material forming the mounting portion 312, but it is usually 0.1 mm or more and 2.0 mm or less, preferably 0.2 mm or more and 1.0 mm or less, and more preferably 0.2 mm or more and 0.5 mm or less. A thickness of 0.1 mm or more of the mounting portion 312 is advantageous for achieving either a compressive or tensile stress load on the entire magnetostrictive material for power generation 311, and a thickness of 2.0 mm or less can suppress interference with the vibration of the magnetostrictive portion 310.

[0101] The magnetostrictive vibration power generation device 300 of this embodiment is not particularly limited in structure as long as the material forming the power generation magnetostrictive material 311 included in the magnetostrictive portion 310 is the power generation magnetostrictive material of this embodiment. Therefore, it can have the same structure as a power generation device using the inverse magnetostriction effect, in which a conventional magnetostrictive material (such as an FeGa alloy, an FeCo alloy, or an FeAl alloy) is used for the magnetostrictive portion. Although the magnetostrictive vibration power generation device 300 of this embodiment has been described with reference to FIG. 4, the magnetostrictive vibration power generation device according to the present invention is not limited to that shown in FIG.

[0102] As described above, according to this embodiment, it is possible to provide a magnetostrictive material for power generation that has high power generation output and can be mass-produced stably for use in magnetostrictive power generation, and a magnetostrictive vibration power generation device using the magnetostrictive material for power generation.

[0103] Furthermore, the magnetostrictive vibration power generation device of the present invention can exhibit excellent power generation performance in both environments where vibrations occur intermittently or singly, and in environments where vibrations can occur continuously. As described above in the explanation of the magnetostrictive material for power generation, the magnetostrictive material for power generation of the present invention can achieve an improvement in ΔB in both quasi-static and dynamic measurements. Here, as described above, quasi-static measurement is performed by measuring the change in magnetic flux density when an external stress is applied only once, based on a state where no external stress is applied to the magnetostrictive material for power generation. This is a measurement condition similar to an environment where vibrations occur intermittently or singly. On the other hand, dynamic measurement is a measurement condition similar to an environment where vibrations occur continuously. The magnetostrictive material for power generation of the present invention can achieve an improvement in ΔB in both measurements, so the magnetostrictive vibration power generation device of the present invention can achieve excellent power generation performance in both of the above environments.

[0104] Furthermore, the magnetostrictive vibration power generation device of the present invention is equipped with a magnetostrictive power generation material in which the ratio of ΔB during dynamic measurement at a vibration frequency of 150 Hz to ΔB during quasi-static measurement is 95% or more, or the ratio of ΔB during dynamic measurement at a vibration frequency of 250 Hz is 90% or more.Therefore, the range of vibration frequencies at which power can be generated is wide, and high power generation performance can be demonstrated in a variety of usage environments.

[0105] Furthermore, while the magnetostrictive vibration power generation device of the present invention may have different natural vibration frequencies depending on its structure, size, etc., the magnetostrictive material for power generation of the present invention has a wide range of vibration frequencies that can be used to generate power, and therefore can be applied to various types of magnetostrictive vibration power generation devices.

[0106] As mentioned above, the magnetostrictive vibration power generation device of the present invention can be used in environments where vibrations occur intermittently or singly, or in environments where vibrations occur continuously. Examples of applications to the former environment include power supplies for motion sensors installed on the floors or doors of passageways. Examples of applications to the latter environment include power supplies for monitoring devices for machine tools and the like that vibrate during operation, and power supplies for monitoring devices or location information communication devices for transport containers.

[0107] Furthermore, the magnetostrictive vibration power generation device of the present invention can be used in a wide range of vibrational frequencies, from low frequencies to relatively high frequencies, for example, 100 Hz or higher, preferably 150 Hz or higher, and more preferably 250 Hz or higher, and can therefore be used as a power source for switches and equipment diagnostic devices that may generate vibrations in which various vibration frequencies are superimposed. Note that the magnetostrictive vibration power generation device of this embodiment is not particularly limited in terms of the upper limit of the vibrational frequency, as long as it can generate the amount of power required for the application. [Example]

[0108] Next, examples of the present invention will be described, but these are examples of conditions implemented to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0109] Example 1 The magnetostrictive material for power generation was a grain-oriented electrical steel sheet (35ZH115, coated) manufactured by Nippon Steel Corporation. The thickness of this grain-oriented electrical steel sheet was 0.35 mm, and the structure was a {110} crystal orientation. <001> The alloy had a GOSS texture, and the Si content (average Si concentration) was 3.2%, and the Al content was less than 0.1%.

[0110] The electrical steel sheet with the coating removed was sheared to a length of 40 mm and a width of 6.1 mm. When cutting, the longitudinal direction of the magnetostrictive material for power generation was aligned with the rolling direction of the grain-oriented electrical steel sheet. To remove any residual stress or strain that may have occurred during cutting, the sheet was annealed in a vacuum at 800°C for 2 hours. An Al layer was formed on the surface of the annealed grain-oriented electrical steel sheet using a magnetron sputtering device to the thickness shown in Table 1, and the sheet was then subjected to the heat treatment shown in Table 1 to obtain a magnetostrictive material for power generation.

[0111] Electron Backscatter Diffraction (EBSD) was used to measure the position of the boundary surface of the base material of the magnetostrictive material for power generation (the surface position of the grain-oriented electrical steel sheet before Al diffusion). The cross section of the surface layer of the magnetostrictive material for power generation was exposed using the cross-section polisher method. The cross section was taken as a cross section of the grain-oriented electrical steel sheet, the base material, cut so that a plane perpendicular to the rolling direction was revealed. The rolling direction of the grain-oriented electrical steel sheet is approximately parallel to the easy axis of magnetization of the grain-oriented electrical steel sheet. The spot diameter of the electron beam for electron backscatter diffraction was 0.5 μm, and the step width was 0.10 μm. EBSD measurement was performed on the cross section, <001> The region where the deviation from the direction is within 10° was considered to be the base material, and the region outside these conditions was considered to be the Al layer (Fe-Al alloy layer) remaining on the grain-oriented electrical steel sheet, and the interface between the base material and the Al layer (Fe-Al alloy layer) was considered to be the boundary surface. Figure 5 shows the EBSD measurement results for the surface cross section of Example 1. As shown in Figure 5, the EBSD patterns are significantly different between the base material region and the Fe-Al alloy layer region, indicating that they have different crystal structures. Therefore, the position of the boundary surface in the base material can be easily identified using EBSD.

[0112] An electron probe microanalyzer (EPMA) was used to measure the concentration profiles of Al and Si in the thickness direction of the magnetostrictive material for power generation. The measurement surface of the magnetostrictive material for power generation was measured in the same field of view as the cross section measured by EBSD described above. The spot diameter of the electron beam was 0.05 μm. The concentration profiles of Examples 1 to 15 were similar to the concentration profile shown in FIG. 3. The Si peak position M in the high Si region Si The position where the maximum value is reached in the Si concentration profile measured by EPMA is called the Si peak position M Si The Si peak position M in the high Si region Si The Al concentration is determined by the Si peak position M SiThe Al concentration at the same position as the Al concentration at the boundary surface of the base material was taken as the Al concentration at the boundary surface side of the high Al region. This Al concentration was the maximum value. The thickness of the high Al region was taken as the width of the region from the boundary surface of the base material where the Al concentration was 0.1 mass% or more.

[0113] As explained above, the confirmation that the Al contained in the high Al region is solid-solubilized in the surface layer 2 of the base material was made by exposing a cross section of the surface layer of the magnetostrictive material for power generation and analyzing the crystal structure using the above-mentioned electron backscattering analysis, and identifying a region in the surface layer that has the same crystal orientation. Next, by measuring the Al concentration in the identified region using an electron probe microanalyzer, it was determined that the Al contained in the region that has the same crystal orientation as the base material is solid-solubilized.

[0114] The change in magnetic flux density ΔB was measured by the following method.

[0115] A 0.5 mm thick austenitic stainless steel plate (SUS304) was used as the non-magnetic material for the stress control section, which was then cut into pieces 40 mm long and 6.5 mm long to form the non-magnetic material for the stress control section.

[0116] As shown in FIG. 6, the magnetostrictive material for power generation 111 and a SUS304 steel plate 112 serving as a stress control section were bonded together at room temperature using an epoxy adhesive to obtain a magnetostrictive section 110. The obtained magnetostrictive portion 110 was incorporated into the measurement unit 100 shown in Fig. 6, and a change in magnetic flux density ΔB was measured when a bending strain was applied to the magnetostrictive portion 110. The measurement of ΔB was a quasi-static measurement.

[0117] Specifically, the magnetostrictive material 111 for power generation of the magnetostrictive portion 110 was placed on the bottom side, and its left end was fixed by the fixing block 150, so that compressive stress was applied to the magnetostrictive material 111 when the right end was pressed down. Furthermore, in contrast to the case of FIG. 6, the magnetostrictive material 111 for power generation of the magnetostrictive portion 110 was placed on the top side, and its left end was fixed by the fixing block 150, so that tensile stress was applied to the magnetostrictive material 111 when the right end was pressed down. For each measurement, the depth Δh (mm) to which the magnetostrictive material 111 for power generation was pressed down was used as the reference, i.e., the state without bending strain, and the magnetic flux density change ΔB at this time was measured. The change in magnetic flux density ΔB was calculated as the sum of the magnetic flux density change ΔB when compressive stress was applied and the magnetic flux density change ΔB when tensile stress was applied. Δh was set to 0.3 mm. Furthermore, the deformation of the magnetostrictive material for power generation 111 when compressive stress and tensile stress were applied was 0.6 mm (= 0.3 mm × 2). The measured magnetic flux density change ΔB is shown in Table 1. The power generation output is proportional to the magnetic flux density change ΔB. Note that since the magnitude of the applied bias magnetic field can be varied using Helmholtz coils, the magnetic fields that give the optimal values ​​for the magnetic flux density change ΔB shown in Tables 1 to 5 were applied.

[0118] More specifically, in the measurement unit 100, a downward pressure 170 was applied (i.e., pressed) to the right end of the magnetostrictive portion 110. At this time, a compressive strain was applied to the magnetostrictive material for power generation 111, and the longer the moving distance 171 of the magnetostrictive material for power generation 111 when pressed, the greater the compressive strain. Pressing was performed using a micrometer cylinder head, and the pressing depth was adjusted by the stroke of the cylinder head.

[0119] Furthermore, in the measurement unit 100 shown in FIG. 6, a Helmholtz-type coil was used as the bias magnetic field coil 120, and a current was passed through it to apply a magnetic field to the magnetostrictive portion 110. The magnitude of the magnetic field was adjusted by the magnitude of the DC power supply 140, and the magnitude of the magnetic field was previously calibrated using a Gauss meter. At this time, the magnetic field applied to the magnetostrictive portion 110 was changed from approximately 0 to 500 e, and the magnetic field at which the magnetic flux density change was maximized was evaluated. The magnetic flux change in the magnetostrictive portion 110 was detected as an induced voltage by the detection coil 130 (number of turns: 3500), and this induced voltage was measured as a change in magnetic flux by the flux meter 160. Furthermore, the magnetic flux density change ΔB was calculated by dividing the change in magnetic flux by the number of turns of the detection coil and the cross-sectional area of ​​the magnetostrictive material based on the following equation 1.

[0120]

number

[0121] (In the formula, V is the generated voltage, N is the number of turns in the coil, and S is the cross-sectional area of ​​the magnetostrictive part.)

[0122] The magnetic flux density change ΔB obtained by this measurement method is the time integral of the voltage change, and therefore does not depend on the speed at which the strain is applied.

[0123] The results are shown in Table 1. In Table 1, "depth of high-Al region (mm)" refers to the depth from the boundary surface of the base material. Regarding "GOSS orientation," EBSD measurements were performed on the high-Al region and high-Si region. When the crystal orientation in the high-Al region and high-Si region was the same as the GOSS orientation of the grain-oriented electrical steel sheet, a "○" was indicated, and when it was different, a "×" was indicated. The "Si concentration (mass%) in the high-Si region" refers to the maximum Si concentration (mass%) in the high-Si region. The "position showing the maximum Si concentration (mm)" refers to the depth position from the boundary surface of the base material. The Al concentration measured by EPMA at the boundary surface of the base material was taken as the Al concentration at the position on the boundary surface side of the high-Al region. This Al concentration was the maximum Al concentration. Furthermore, the concentration profiles of Examples 1 to 15 in Table 1 were similar to the concentration profile shown in Figure 3. This revealed that, in Examples 1 to 15, the position showing the maximum Si concentration in the surface layer was closer to the center of the sheet thickness than the position showing the maximum Al concentration. Furthermore, it was confirmed that in Examples 1 to 15, Al contained in the high Al region was dissolved in the surface layer of the base material.

[0124] [Table 1]

[0125] In Table 1, Comparative Example 1 is a grain-oriented electrical steel sheet as is, and Comparative Example 2 is an example in which an Al layer was formed on the surface of a grain-oriented electrical steel sheet but no heat treatment was performed. As is clear from the results of ΔB for each of Comparative Examples 1 and 2, when Al was not diffused into the grain-oriented electrical steel sheet, the effect of improving the generated voltage was not obtained.

[0126] Inventive Examples 1 to 15, an Al layer was formed on the surface of a grain-oriented electrical steel sheet, followed by heat treatment. As is clear from Table 1, inventive Examples 1 to 15, the magnetic flux density change ΔB exceeded 0.145, demonstrating an improved magnetic flux density change ΔB compared to comparative examples 1 and 2. Therefore, when used in a power generation device, it can be expected that the power generation output will be increased.

[0127] In Comparative Example 3, the holding time of the first heat treatment was long, so the high Al region extended to a depth of 0.12 mm from the boundary surface of the base material, and the magnetic flux density change ΔB was lower than in Invention Examples 1-15.

[0128] In Comparative Example 4, the holding time of the first heat treatment was long, so the high Al region extended to a depth of 0.15 mm from the boundary surface of the base material, and the magnetic flux density change ΔB was lower than in Invention Examples 1-15.

[0129] In Comparative Example 5, the temperature reached in the first heat treatment and the holding time were long, which caused excessive Al to diffuse into the grain-oriented electrical steel sheet, disrupting the GOSS orientation and resulting in a significant decrease in magnetic flux density change ΔB compared to Invention Examples 1 to 15.

[0130] (Power generation performance evaluation 1) Next, the power generation performance was confirmed using a measuring unit 100 incorporating the magnetostrictive materials for power generation of Examples 1 to 15 and Comparative Examples 1 to 5.

[0131] The measuring unit 100 incorporating the magnetostrictive materials for power generation of Examples 1 to 15 and Comparative Examples 1 to 5 was placed on an aluminum stand, and the aluminum stand was then placed on a vibrating device with the measuring unit 100 still on it. Then, the vibrating device was used to apply dynamic strain to the magnetostrictive portion 110. In other words, the power generation performance was measured by dynamic measurement. A tungsten weight was fixed to the end of the magnetostrictive part 110 opposite to the fixing block 150. A neodymium magnet was attached as a bias magnet to the surface of the magnetostrictive part 110 opposite to the surface to which the tungsten weight was attached.

[0132] The distance Δh from the position of the weight before vibrating the measurement unit 100 to the lowest position of the weight after vibration was measured using a laser distance meter. The weight of the weight was adjusted so that Δh was within the range of 0.5 to 1.0 mm. The vibration device was vibrated at 30 Hz and an acceleration of 1 G. Furthermore, the AC voltage induced in the detection coil 130 was captured using a digital oscilloscope, and the peak voltage of the waveform was measured. The measurement results are shown in Table 2.

[0133] [Table 2]

[0134] As is clear from the results in Table 2, Examples 1 to 15 of the invention vibrated in a bending mode in response to external vibrations and exhibited a power generation performance of 33 mV or more.

[0135] (Power generation performance evaluation 2) The magnetostrictive portion prepared above was incorporated into the magnetostrictive power generation device 300 shown in Fig. 4, and the generated voltage was measured. The magnetostrictive portion used was made by bonding the magnetostrictive material for power generation of Example 1 to a SUS304 steel plate.

[0136] A magnetostrictive part was incorporated into the support part 350 of the magnetostrictive vibration device 300 in Figure 4, and the lower part of the U-shaped support part 350 was fixed onto a vibration exciter. CFRP with a thickness of 2 mm was used for the U-shaped support part 350 in Figure 4. The thickness of the CFRP in the part corresponding to the stress control part where the magnetostrictive part was attached was set to 0.5 mm. The weight 320 was a 7 g weight made of tungsten. The magnetostrictive part was fixed with a claw made of CFRP. The bias magnet 340 was a neodymium magnet.

[0137] Then, the power generation performance was confirmed using the magnetostrictive vibration device 300 of FIG. 4. The power generation performance was measured by dynamic measurement. That is, the power generation performance was confirmed by vibrating the magnetostrictive vibration device 300 at 0.5 G using a vibration exciter and measuring the peak voltage at the resonance frequency with an oscilloscope. The resonance frequency was in the range of 150 to 250 Hz. The results are shown in Table 3.

[0138] [Table 3]

[0139] As is clear from the results in Table 3, the magnetostrictive vibration device 300 using the magnetostrictive material for power generation of Example 1 of the present invention exhibited greater power generation performance in response to external vibrations than the grain-oriented electrical steel sheet itself. Furthermore, since Inventive Examples 2 to 15 have a high ΔB like Inventive Example 1, they can be expected to exhibit superior power generation performance compared to Comparative Example 1, like Inventive Example 1.

[0140] (Example 2: Power generation performance when vibration frequency is changed) As in Example 1, as shown in Fig. 6, magnetostrictive materials for power generation 111 of Examples 1 to 15 and Comparative Examples 1 to 5 were bonded to SUS304 steel plates 112, which were stress control sections, using an epoxy adhesive at room temperature to obtain magnetostrictive sections 110. These magnetostrictive sections 110 were incorporated into the measurement unit 100 shown in Fig. 6, and the change in magnetic flux density ΔB when bending strain was applied to the magnetostrictive section 110 was measured.

[0141] In this example, ΔB was measured by both quasi-static and dynamic measurements.

[0142] The quasi-static measurement was performed in the same manner as in Example 1. The magnetostrictive material for power generation 111 was pressed to a depth Δh (mm) using a state without bending strain as a reference, and the magnetic flux density change ΔB at this time was measured. The change in magnetic flux density change ΔB was the sum of the magnetic flux density change ΔB when compressive stress was applied and the magnetic flux density change ΔB when tensile stress was applied. Δh was set to 0.3 mm. Δh was measured at a position 28 mm away from the end of the fixing block 150 that fixes the magnetostrictive portion 110. The deformation amount of the magnetostrictive material for power generation 111 when compressive stress and tensile stress were applied was 0.6 mm (= 0.3 mm × 2). The measured magnetic flux density change ΔB is shown in Table 4.

[0143] For the dynamic measurements, a measurement unit 100 incorporating the magnetostrictive materials for power generation of Examples 1 to 15 and Comparative Examples 1 to 5 was placed on an aluminum stand, and the aluminum stand was then placed on a vibrating device with the measurement unit 100 still on it. Dynamic strain was then applied to the magnetostrictive portion 110 by the vibrating device. A tungsten weight was fixed to the end of the magnetostrictive portion 110 opposite the fixing block 150. A neodymium magnet was attached as a bias magnet to the surface of the magnetostrictive portion 110 opposite the surface to which the tungsten weight was attached.

[0144] The distance Δh from the position of the weight before vibration of the measurement unit 100 to the position of the lowest point of the weight after vibration was measured using a laser distance meter. The weight of the weight was adjusted so that Δh was 0.3 mm, the same as in the static measurement. The vibration conditions of the vibration device were vibration frequencies of 50 Hz, 90 Hz, 150 Hz, 200 Hz, and 250 Hz. The magnetic flux density change ΔB was then measured while applying vibration. The change in magnetic flux density ΔB was taken as the sum of the magnetic flux density change ΔB when compressive stress was applied to the magnetostrictive material for power generation and the magnetic flux density change ΔB when tensile stress was applied. The measured magnetic flux density change ΔB is shown in Table 4. Table 5 also shows the ratio of the magnetic flux density change ΔB during dynamic measurement to the magnetic flux density change ΔB during quasi-static measurement.

[0145] As shown in Tables 4 and 5, the magnetostrictive materials for power generation of Examples 1 to 15 had a ratio of ΔB during dynamic measurement at a vibration frequency of 150 Hz to ΔB during quasi-static measurement of 95% or more, showing excellent ΔB even at high vibration frequencies. Furthermore, the magnetostrictive materials for power generation of Examples 1 to 15 had a ratio of ΔB during dynamic measurement at a vibration frequency of 250 Hz of 90% or more, showing sufficient ΔB.

[0146] In particular, in Examples 1 to 5, the position M Si The Al concentration at position M is 1.0 to 12 mass %. Si These magnetostrictive materials for power generation were located at a depth of less than 0.07 mm from the boundary surface of the high Al region, and showed superior characteristics, with a ΔB ratio of 98% or more during dynamic measurement at a vibration frequency of 150 Hz and a ΔB ratio of 92% or more during dynamic measurement at a vibration frequency of 250 Hz. In addition, Example 15 of the present invention had a ΔB ratio of 94.2% during dynamic measurement at a vibration frequency of 250 Hz, but the ΔB at 0 Hz (static measurement) was slightly lower.

[0147] [Table 4]

[0148] [Table 5]

Claims

1. The surface layer of a base material made of a grain-oriented electrical steel sheet containing Si and having a texture of {110}<001> orientation is a high Al region having an Al concentration of 0.1 mass % or more and a high Si region having a Si concentration higher than the average Si concentration of the grain-oriented electrical steel sheet, the high Al region is in a range from the boundary surface of the base material to a depth of 0.100 mm, A magnetostrictive material for power generation, wherein the position showing the maximum Si concentration in the surface layer is closer to the center of the plate thickness than the position showing the maximum Al concentration.

2. 2. The magnetostrictive material for power generation according to claim 1, wherein the Al concentration at the position showing the maximum Si concentration is 1.0 mass % or more and 12 mass % or less.

3. 3. The magnetostrictive material for power generation according to claim 2, wherein the Al concentration in the high Al region at a position on the boundary surface side of the base material is 6.0 mass % or more.

4. 3. The magnetostrictive material for power generation according to claim 2, wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less.

5. 4. The magnetostrictive material for power generation according to claim 3, wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less.

6. 2. The magnetostrictive material for power generation according to claim 1, wherein the Al concentration in the high Al region at a position on the boundary surface side of the base material is 6.0 mass % or more.

7. 7. The magnetostrictive material for power generation according to claim 6, wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less.

8. 2. The magnetostrictive material for power generation according to claim 1, wherein the maximum value of the Si concentration in the high Si region is in the range of 3.6 mass % or more and 6.0 mass % or less.

9. 2. The magnetostrictive material for power generation according to claim 1, wherein the position showing the maximum value of the Si concentration in the surface layer is located at a depth of less than 0.07 mm from the boundary surface side of the high Al region.

10. 2. The magnetostrictive material for power generation according to claim 1, wherein the ratio of the change in magnetic flux density ΔB during dynamic measurement at a vibration frequency of 150 Hz to the change in magnetic flux density ΔB during quasi-static measurement is 95% or more.

11. 2. The magnetostrictive material for power generation according to claim 1, wherein the ratio of the change in magnetic flux density ΔB during dynamic measurement at a vibration frequency of 250 Hz to the change in magnetic flux density ΔB during quasi-static measurement is 90% or more.

12. 12. The magnetostrictive material for power generation according to claim 1, wherein the high Al region, the high Si region, and the base material all have a texture of {110}<001> orientation.

13. A magnetostrictive part including the magnetostrictive material for power generation according to any one of claims 1 to 11; a support portion that supports the magnetostrictive portion in a vibrable state; a bias magnet that applies a bias magnetic field to the magnetostrictive portion; an induction coil disposed at a distance from the magnetostrictive portion.

14. 14. The magnetostrictive vibration power generation device according to claim 13, wherein the high Al region, the high Si region, and the base material in the magnetostrictive material for power generation all have a texture in the {110}<001> orientation.

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