Method for producing multilayer material for magnetostrictive vibration power generation

Abstract

Provided is a method for producing a multilayer material for magnetostrictive vibration power generation.　Two kinds of metal strip sheets, which are an Fe-Co alloy material having a surface hardness of 250 HV or less and an Ni material having a surface hardness of 140 HV or less, are used as materials. The method includes: a compression bonding step in which the two kinds of metal strip sheets are superposed upon each other and compression bonded with each other at a draft of 45-90%; and a diffusion heat treatment step in which a diffusion heat treatment is performed at 730-1400°C. The method subsequently includes in the following order: a cold rolling step in which cold rolling is performed at a cumulative draft of 10-98%; and a finish heat treatment step in which a finish heat treatment is performed at a heating temperature of 730-1000°C. Consequently, a multilayer material which has a two-layer structure is obtained. As a result, embrittlement of the Fe-Co alloy material is suppressed, and a multilayer material having excellent magnetostrictive responsiveness and excellent bonding strength can be obtained with high productivity.

Description

Manufacturing method for laminated material for magnetostrictive vibration power generation

[0001] The present invention relates to a method for manufacturing a laminated material having a two-layer clad structure for use in magnetostrictive vibration power generation. Note that "magnetostrictive vibration power generation" as used herein refers to vibration power generation that utilizes the inverse magnetostriction characteristics caused by vibration of a magnetostrictive material.

[0002] Magnetostrictive vibration power generation is a method of generating electricity using stresses such as shocks and vibrations, using an energy conversion element that can utilize the change in shape caused by magnetization. The energy conversion element generates vibrations when an alternating magnetic field is applied.

[0003] The energy conversion element is generally constructed as a two-layer clad structure made up of a material that expands and a material that contracts when a magnetic field is applied. The material used for magnetostrictive vibration power generation is preferably a magnetic material with large magnetostriction and high saturation magnetic flux density.

[0004] Magnetostriction is a phenomenon in which dimensions change when a magnetic material is magnetized. In the case of Fe-Co alloys, the amount of change is relatively large, and the saturation magnetostriction (λs / 10 -６ ) is about 70. In the case of Ni material, the saturation magnetostriction (λs / 10 -６ ) is around -40.

[0005] Saturation magnetic flux density is the magnetic flux density when a magnetic material is magnetically saturated, and the higher the saturation magnetic flux density, the stronger the magnet. For example, an Fe50%-Co50% alloy is an alloy in which Co is added to Fe, a widely used magnetic material, to increase the saturation magnetic flux density, and is known as an alloy with extremely strong magnetic force, with the Bohr magneton number peaking on the Slater-Pauling curve.

[0006] For example, Patent Document 1 discloses an energy conversion member in which a magnetostrictive material and a soft magnetic material are joined together. The energy conversion member described in Patent Document 1 is described as comprising an Fe—Co alloy, an Fe—Al alloy, Ni, a Ni—Fe alloy, or a Ni—Co alloy as the magnetostrictive material, and a soft magnetic material having a coercive force of 3 A / cm or less and a magnetic material with a magnetostriction constant of a different sign from that of the magnetostrictive constant of the magnetostrictive material. Specific examples of combinations of these materials include an Fe—Co alloy or an Fe—Al alloy with a positive magnetostriction constant, and an Ni-0 to 20 mass % Fe alloy or an Ni—Co alloy with a negative magnetostriction constant.

[0007] In the technique described in Patent Document 1, a solid magnetostrictive material and a solid soft magnetic material are joined together by thermal diffusion bonding, hot rolling, and hot drawing.

[0008] International Publication No. WO2018 / 230154

[0009] However, Patent Document 1 does not describe specific conditions for the above-mentioned bonding process.

[0010] For example, Fe-Co alloys can become embrittled or exhibit reduced magnetostrictive response depending on manufacturing conditions such as heat treatment. Furthermore, in alloys with a body-centered cubic structure, domain walls are less likely to move under stress, so stress generated during joining and other processes must be removed by heat treatment. For these reasons, it is important to manufacture magnetic materials used in energy conversion elements under manufacturing conditions suited to the material.

[0011] Furthermore, the technology described in Patent Document 1 employs sheet-by-sheet processing using strip-shaped materials for bonding, but this results in poor yield and poor productivity, and each product is affected by factors such as materials / components, equipment / machines, workers, work methods, and inspection / measurement. This requires thorough quality control for each product, and there is a risk of quality variations occurring depending on the control method.

[0012] In view of the above circumstances, an object of the present invention is to provide a method for producing a magnetostrictive vibration power generation laminate that is highly productive, has little variation in quality, and has excellent vibration power generation characteristics.

[0013] To achieve the above-mentioned objectives, the inventors first came up with the idea of ​​using a coiled metal strip as the raw material (magnetic material) from the perspective of improving productivity and further reducing quality variation, etc. After examining various manufacturing conditions, they decided to stack, press, and bond two types of metal strips (Fe-Co alloy material and Ni material) to create a laminated material with a two-layer clad structure. This allows for consistent manufacturing conditions, improves productivity, and, from the perspective of quality control, allows for stable quality maintenance and reduces quality inspections. Furthermore, using a long coiled metal strip as the raw material makes it easier to obtain a laminated material with a uniform thickness ratio.

[0014] The present invention was completed based on the above findings and through further investigation. The gist of the invention is as follows: [1] A method for manufacturing a laminate for magnetostrictive vibration power generation having a two-layer clad structure, using two types of metal band plates as raw materials: an Fe-Co alloy material having a surface hardness of 250 HV or less and a Ni material having a surface hardness of 140 HV or less, the method comprising the steps of: a compression bonding process in which the two types of metal band plates are stacked and subjected to a compression bonding process at a rolling reduction of 45 to 90% to form a laminate having a two-layer clad structure; a diffusion heat treatment process in which diffusion heat treatment is performed at a heating temperature of 730 to 1400°C; a cold rolling process in which cold rolling is performed at a cumulative rolling reduction of 10 to 98%; and a finish heat treatment process in which finish heat treatment is performed at a heating temperature of 730 to 1000°C, in this order. [2] A method for manufacturing a magnetostrictive vibration power generator laminate according to [1], characterized in that the cold-rolled laminate is a cold-rolled metal strip with a thickness of 0.03 to 2.0 mm. [3] A method for manufacturing a magnetostrictive vibration power generator laminate according to [1] or [2], characterized in that the cold-rolled laminate contains an Fe-Co alloy layer at a thickness of 40 to 60% of the total thickness. [4] A method for manufacturing a magnetostrictive vibration power generator laminate according to any one of [1] to [3], characterized in that the pressure bonding treatment is performed at a processing temperature range of 20 to 720°C. [5] A method for manufacturing a magnetostrictive vibration power generator laminate according to any one of [1] to [4], characterized in that the diffusion heat treatment is performed for a holding time of 1 to 30 minutes, and the finish heat treatment is performed for a holding time of 2 hours or more. [6] A method for manufacturing a laminate for magnetostrictive vibration power generation according to any one of [1] to [5], characterized in that the Fe-Co alloy material has a composition, by mass%, of 40 to 60% Fe, or further 1 to 5% V, with the remainder being Co and unavoidable impurities, and the Ni material has a composition, by mass%, of 99.5% or more Ni, with the remainder being unavoidable impurities.

[0015] According to the present invention, embrittlement of Fe-Co alloy materials is suppressed, and laminated materials having excellent magnetostriction response and excellent bonding strength can be obtained with high industrial productivity, and this provides significant industrial benefits as laminated materials for vibration power generation.

[0016] It is an explanatory diagram showing the manufacturing process in the present invention. It is an explanatory diagram showing an outline of a pressure bonding treatment. It is an explanatory diagram showing an outline of a cold rolling. It is an explanatory diagram showing an outline of a power generation device used in the examples.

[0017] The present invention provides a method for producing a laminated material having a two-layer clad structure, which is useful for magnetostrictive vibration power generation. The laminated material obtained by the present invention has a two-layer clad structure of an Fe—Co alloy material and a Ni material.

[0018] In the method for producing a laminated material of the present invention, two types of metal strips, an Fe—Co alloy material and a Ni material, are used as raw materials, and as shown in Figure 1, a laminated material (metal strip) having a two-layer clad structure is obtained by preferably including a pretreatment step, a pressure bonding step, a diffusion heat treatment step, a cold rolling step, and a finish heat treatment step in this order. Each step will be explained below.

[0019] [Materials] In the present invention, two types of metal strips are used as materials: an Fe—Co alloy material and an Ni material. Here, the Fe—Co alloy material has a composition, in mass %, of 40 to 60% Fe, the remainder being Co and unavoidable impurities. It may also have a composition that further contains 1 to 5% V.

[0020] If the composition of the Fe-Co alloy material is within the above range, the saturation magnetostriction (λs / 10 -６ ) is large at 50 to 70, and the saturation magnetic flux density is so strong that the Bohr magneton number exceeds 2.25 on the Slater-Pauling curve. Utilizing an Fe-Co alloy material with these properties makes it possible to obtain an energy conversion element with excellent vibration power generation characteristics. Furthermore, by further adding V within the above range, cold workability is improved, and magnetostriction and saturation magnetic flux density can be maintained at high levels.

[0021] Furthermore, it is preferable to use a Ni material with a composition in which the Ni content is 99.5% or more by mass, with the remainder being unavoidable impurities. If the Ni content is less than 99.5%, the softening temperature and work hardening characteristics will change, which may affect the uniformity of the thickness ratio after joining. In addition, with a Ni material of the above composition, the saturation magnetostriction (λs / 10 -６ ) is -40, which is a very large difference in magnetostriction compared to Fe-Co alloy materials.

[0022] The surface hardness of the metal strip material must be 250 HV or less on the Vickers hardness scale for Fe-Co alloys and 140 HV or less for Ni alloys. If the hardness exceeds the above limits, the bonding at the joining interface will be poor, resulting in reduced adhesion strength (also referred to as bond strength). During the joining (crimping) process, softer materials are easier to work with and allow for a larger reduction rate per press, improving both the degree of deformation at the joining interface and the adhesion strength. Furthermore, the joining at this stage is between newly formed surfaces at the joining interface. The higher the reduction rate, the greater the area of ​​the newly formed surface, resulting in improved adhesion strength. The surface hardness of the metal strip material is preferably adjusted by heating in an annealing furnace or the like.

[0023] Furthermore, the Fe-Co alloy material used as the base material has a higher surface hardness (deformation resistance) than the Ni material used in combination. Therefore, when a laminate is produced by crimping a metal strip (base material) of the same thickness as the Ni material, the Ni material will be thinner due to the difference in deformation resistance. Therefore, the thicknesses of the Fe-Co alloy material and the Ni material must be appropriately adjusted depending on the difference in surface hardness (deformation resistance) of the materials. In the present invention, the thickness of the Fe-Co alloy material is preferably 85 to 95% of the thickness of the Ni material. This allows the thickness of the Fe-Co alloy layer in the finished laminate material to be 40 to 60% of the total thickness of the laminate material. Preferably, it is 45 to 55%. By making the thickness of the Fe-Co alloy layer close to 50% of the total thickness of the laminate material, the offset between the magnetostrictive effect and the inverse magnetostrictive effect is prevented.

[0024] Instead of the Fe-Co alloy, an Fe-Ni alloy or an Fe-Al alloy, which are similar magnetic materials, may be used. Although these alloys have inferior saturation magnetostriction and saturation magnetic flux density to the Fe-Co alloy, by applying the manufacturing method of the present invention, they can be used as a laminate material for magnetostrictive vibration power generation.

[0025] In addition, instead of the Ni material of the above composition, Ni-Co alloys and soft magnetic materials (Fe materials) such as SPCC can be combined with Fe-Co alloys to maintain similar vibration power generation characteristics. By combining Ni-Co alloys or Fe materials with Fe-Co alloys and applying the manufacturing method of the present invention, it is possible to produce laminated materials for magnetostrictive vibration power generation that maintain similar vibration power generation characteristics, although the characteristics are inferior to those of the combination of Fe-Co alloys and Ni materials. It is preferable that the surface hardness of the Fe-Co alloys, Fe-Ni alloys, and Fe-Al alloys used as raw materials be 250 HV or less on the Vickers hardness scale, and that the surface hardness of the Ni material, Ni-Co alloys, and soft magnetic materials (Fe materials) be 140 HV or less on the Vickers hardness scale.

[0026] [Pretreatment Process] First, to facilitate the crimping of the two materials, it is preferable to perform a surface activation process on the entire surfaces of the Fe-Co alloy material and Ni material prior to the crimping process. Brushing is a process in which the material surface is polished with a brush. Surface activation processes may include chemical processes such as pickling, mechanical processes such as polishing and grinding with a grinder or blasting, or ion etching. The surface roughness after activation is preferably at least twice that before activation, in terms of arithmetic mean roughness (Ra), with a value of 0.1 μm to 3.0 μm for Fe-Co alloy material and 0.1 μm to 4.0 μm for Ni material. Here, the surface roughness is measured in accordance with JIS B 0601.

[0027] [Bonding Process] In the bonding process, two types of materials (Fe-Co alloy material and Ni material) that have been subjected to surface activation treatment are stacked and subjected to a bonding process with a rolling reduction ratio of 45 to 90%, and the two materials are mechanically and physically adhered (bonded) to form a laminated material with a two-layer clad structure. In the bonding process, as shown in Figure 2, metal strips 1 and 2 are stacked and compressed by rolling using rolls 3.

[0028] If the rolling reduction is less than 45%, the joining (crimping) is not performed sufficiently. If the rolling reduction exceeds 90%, edge cracks occur during the crimping process, making the crimping difficult. Here, edge cracks refer to cracks that occur on the surface of the sheet material near the edge end in the sheet width direction of the crimped material. For these reasons, the rolling reduction in the crimping process is set to a range of 45 to 90%. It is also preferable to perform the crimping process once.

[0029] The type of cold rolling mill used in the pressure bonding process does not need to be particularly limited, and any commonly used rolling mill such as a two-high rolling mill or a four-high rolling mill can be used, but it is preferable to use a multi-high rolling mill that has a uniform rolling force distribution in the plate width direction and a uniform plate thickness profile.

[0030] Furthermore, the compression bonding process is carried out in a processing temperature range of 20 to 720°C. If the temperature is below 20°C, it is difficult to manufacture at a temperature lower than this temperature, taking into account the heat generated by plastic processing. Furthermore, if the temperature exceeds 720°C, the α' phase may become ordered and the material may become significantly brittle. Therefore, during the warm compression bonding process, it is preferable to adjust the temperature within the above-mentioned range using a temperature controller or the like.

[0031] The order-disorder transformation point of the body-centered cubic α phase in Fe-Co alloys is around 730°C, and in the temperature range below 700°C, the alloy becomes a mixed phase of the body-centered cubic α' ordered phase and the face-centered cubic γ phase. In particular, if the cooling rate from around the transformation point of 730°C is slow, embrittlement occurs due to the ordering of the α' phase.

[0032] If a surface activation treatment is performed as a pretreatment step, the pressure bonding treatment is preferably performed within 12 hours after the pretreatment step. If the pressure bonding treatment is performed after 12 hours, the bonding strength of the bonding interface in the resulting laminated material (clad material) may decrease.

[0033] Furthermore, the laminated material (also referred to as laminated material after pressure bonding), which is a two-layered metal strip plate joined (press bonded) in the pressure bonding process, is usually wound up by a winder (not shown).

[0034] [Diffusion heat treatment process] The laminate obtained through the bonding process (also called the laminate after bonding process) is subjected to a diffusion heat treatment aimed at mutual diffusion of metal atoms at the bonding interface of the laminate. The diffusion heat treatment is a process of heating in the temperature range of 730 to 1400°C.

[0035] If the heating temperature is below 730°C, interdiffusion at the bonding interface of the laminated materials is difficult to occur, and sufficient bonding strength may not be obtained. On the other hand, if the heating temperature exceeds 1400°C, there is a risk of melting because nickel has a melting point of 1453°C.

[0036] The holding time for the diffusion heat treatment is preferably in the range of 1 to 30 minutes. If the holding time is less than 1 minute, interdiffusion at the bonding interface of the laminated materials is difficult to occur, and sufficient bonding strength cannot be obtained. On the other hand, if the holding time exceeds 30 minutes, productivity will decrease significantly.

[0037] The diffusion heat treatment described above strengthens the bonding interface, improving the bonding strength of the laminate. The bond at the bonding interface after the interdiffusion of metal atoms is so strong that no delamination of the bond was observed even in repeated 90-degree bending tests.

[0038] The above-mentioned diffusion heat treatment is preferably carried out using a continuous heat treatment furnace. When using a continuous heat treatment furnace, the maximum thickness of the material to be heat treated (the laminated material after the pressure bonding treatment) is preferably 5.0 mm or less. If the maximum thickness exceeds 5.0 mm, the heat treatment cannot be completed within 30 minutes.

[0039] In order to prevent embrittlement due to ordering of the α' phase at around the transformation point of 730°C in Fe-Co alloy materials, it is necessary to increase the cooling rate after the diffusion heat treatment, preferably to 300°C / min or more. In addition, the diffusion heat treatment is preferably carried out in an inert gas atmosphere such as Ar or N or a reducing atmosphere of hydrogen gas.

[0040] [Cold rolling process] In the cold rolling process, the diffusion heat-treated laminate (pressed laminate) is cold-rolled while still in the metal strip state at a rolling reduction rate selected so that the cumulative rolling reduction is 1 to 98%, to produce a laminate with a predetermined product thickness (laminate after cold rolling).

[0041] If the cumulative reduction is less than 1%, the tension between the front and rear of the winder will be stronger than the rolling force, causing the rolled material to slip and making cold rolling difficult. Furthermore, if the cumulative reduction exceeds 98%, the work hardening of the rolled material will cause it to reach its rolling limit, necessitating additional softening heat treatment, resulting in reduced productivity. Considering productivity, a cumulative reduction of 5 to 90% is preferable. The cumulative reduction can be calculated using the following formula: Cumulative reduction (%) = {(thickness before cold rolling) - (thickness after cold rolling)} ÷ (thickness before cold rolling) × 100. Cold rolling is a repeated rolling process in which multiple rolls are performed. The number of repetitions is preferably 5 to 10. After each roll, the material is wound into a coil by a coil winder (not shown). However, if the number of rolls is large, a reverse winding system is preferable, allowing for winding in both directions. As the rolling mill used for cold rolling, any of the conventional two-high rolling mills, four-high rolling mills, and multi-high rolling mills such as Sendzimir rolling mills and Lorne rolling mills are suitable, but it is preferable to select a rolling mill that provides a uniform rolling force distribution and thickness profile in the plate width direction, for example, a multi-high rolling mill. This is because, after the final finish heat treatment step, the plate may be slit (not shown) as needed and cut into sections in the width direction for shipment. Figure 3 shows an outline of cold rolling using a four-high rolling mill.

[0042] During cold rolling, the material to be rolled is cooled with rolling oil, but since heat generated by plastic working is unavoidable, cold rolling is preferably carried out at a working temperature range of room temperature to 200°C, and more preferably at a temperature range of room temperature to 100°C.

[0043] Furthermore, it is preferable that the thickness of the laminated material after cold rolling is 0.03 to 2.0 mm, which is the specified product thickness. If the thickness is less than 0.03 mm, the flatness will be poor and it will be difficult to correct the shape using a tension leveler. The flatness should be 100 mm or less from the viewpoint of vibration power generation characteristics. 2 It is preferable that the warpage or waviness is 1 mm or less within this area. The flatness is measured on a surface plate using a thickness gauge or a dial gauge. If the thickness of the cold-rolled laminate exceeds 2.0 mm, the holding time in the diffusion heat treatment process exceeds 30 minutes, which reduces productivity.

[0044] In the laminated material after cold rolling, the thickness of the Fe-Co alloy layer in the laminated material is set to 40 to 60% of the total thickness. If the thickness of the Fe-Co alloy layer is less than 40% or more than 60% of the total thickness, the magnetostrictive effect / inverse magnetostrictive effect of the Fe-Co alloy material and the Ni material will cancel each other out, resulting in reduced vibration power generation characteristics. Preferably, it is set to 45 to 55% of the total thickness. This thickness of the Fe-Co alloy layer in the laminated material after cold rolling can be achieved by adjusting the thickness of each material.

[0045] [Finishing Heat Treatment Step] In the finishing heat treatment step, the laminated material (laminated material after cold rolling) is subjected to finishing heat treatment at a heating temperature of 730 to 1000° C. to produce a product.

[0046] If the heating temperature is below 730°C, the stress in the Fe-Co alloy material cannot be removed. In BCC structure alloys, residual stress makes it difficult for the domain walls to move, resulting in a decrease in vibration power generation characteristics. Furthermore, if the heating temperature exceeds 1000°C, the γ phase begins to precipitate, reducing the function as a magnetic material and decreasing the magnetostriction and saturation magnetic flux density. A heating temperature of 900°C or less is preferable. When using Fe-Ni alloy material or Fe-Al alloy material as the raw material, the heating temperature is preferably 370 to 1200°C for Fe-Ni alloy material and 700 to 1200°C for Fe-Al alloy material.

[0047] The heat treatment furnace used for the finish heat treatment is preferably a batch type heat treatment furnace, since the cooling after the finish heat treatment must be slow. The finish heat treatment process is the final process, and it is important to increase the magnetostriction without considering embrittlement. The α' phase of Fe-Co alloy material becomes brittle due to ordering, but on the other hand, it has a high saturation magnetostriction (λs / 10 -６ Since the α' phase has a melting point of 70, which is higher than the α and γ phases, it is appropriate to make the structure after the finish heat treatment the α' phase. Therefore, it is preferable to cool slowly after the finish heat treatment at a cooling rate of 300°C / hour or less.

[0048] Furthermore, the holding time for the finish heat treatment is preferably 2 hours or more. If the holding time is less than 2 hours, the α phase cannot be sufficiently precipitated in the heating temperature range of 730 to 1000°C, and after cooling, a mixed phase of α' phase and γ phase will be formed, resulting in small magnetostriction. The atmosphere for the finish heat treatment is preferably a reducing atmosphere of hydrogen gas. During cooling, an inert gas atmosphere such as Ar or N is preferably used.

[0049] The laminated material manufactured by the manufacturing method including the above-mentioned steps can be used as an energy conversion member to improve the power generation efficiency of vibration power generation utilizing inverse magnetostriction. For example, when the laminated material of the present invention is used as a reciprocating beam and vibrated in reverse, repeated tensile and compressive deformation occurs in the Fe-Co alloy layer and the Ni layer, generating electricity. Moreover, since the direction of voltage is always the same in both layers, high power generation efficiency can be achieved. Furthermore, the use of the laminated material of the present invention can also improve the vibration efficiency of the vibrating part utilizing magnetostriction.

[0050] The present invention will be further described below with reference to examples.

[0051] The raw materials prepared were Fe-Co alloy materials (types: F1 to F9) with the compositions shown in Table 1 and Ni materials (types: N1 to N3) with the compositions shown in Table 2. The raw materials were both in the form of coiled metal strips (unit weight: 1.0 kg) with dimensions of 0.2 to 4.8 mm thick, 40 to 150 mm wide, and 20 to 100 m long.

[0052] The hardness of the Fe-Co alloy and Ni alloy materials prepared as raw materials was varied by annealing, as shown in Table 3. Furthermore, depending on the hardness of the Ni alloy, the thickness of the Fe-Co alloy was adjusted by cold rolling so that it was within 85–95% of the Ni alloy thickness. Some Fe-Co alloy materials were also prepared with thicknesses outside this range. Furthermore, as a pretreatment step, the entire surface of the metal strip material was subjected to a surface activation treatment, in which brushing was performed. After activation, the surface roughness (Ra) measured according to JIS B 0601 was 0.1–3.0 μm for the Fe-Co alloy material and 0.1–4.0 μm for the Ni material.

[0053] Two types of materials (metal strips) whose hardness and thickness had been adjusted as described above were combined as shown in Table 3, and a two-layer laminate was produced using a manufacturing method that included a pressure bonding process, a diffusion heat treatment process, a cold rolling process, and a finish heat treatment process in this order.

[0054] [Bonding process] Two types of materials (Fe-Co alloy material and Ni material) were stacked and subjected to a single bonding process in the form of a metal strip using a multi-stage rolling mill at the temperature and reduction shown in Table 3, thereby bonding the two types of materials together to obtain a two-layer laminate. After the bonding process, the material was wound into a coil using a winder. If the material was not bonded, subsequent processing was stopped. Table 3 also lists the thickness of the laminate obtained by the bonding process.

[0055] "Diffusion Heat Treatment Step" The obtained laminated material after the pressure bonding process was subjected to a diffusion heat treatment using a continuous heat treatment furnace at the temperature and holding time shown in Table 3. The diffusion heat treatment was carried out in a hydrogen gas atmosphere. After the diffusion heat treatment, cooling was carried out by indirect water cooling. The cooling rate was in the range of 300 to 350°C / min.

[0056] The laminated material after the diffusion heat treatment was used as a test piece to evaluate the bond strength. The bond strength was evaluated by a bending test in accordance with the provisions of JIS Z 2248. The bending test was performed by bending at 90° using a metal pusher (tip radius R: 0.4 mm). After repeated bending until fracture, the fracture surface was observed under a stereomicroscope (x20). The fracture surface was evaluated as "Good" if there was no peeling at the joint, and "Poor" if there was peeling (fracture) at the joint. The results are also shown in Table 3. Note that specimens rated "Poor" did not undergo further treatment.

[0057] [Cold rolling process] The laminated material after the diffusion heat treatment was repeatedly cold rolled using a multi-stage rolling mill at the temperature and cumulative reduction shown in Table 3 to obtain a laminated material (laminated material after cold rolling) with a predetermined product thickness. After cold rolling, the laminated material was wound into a coil using a winder. The thickness of the obtained laminated material is also shown in Table 3.

[0058] Furthermore, when the laminated material after the diffusion heat treatment was cold-rolled, the presence or absence of fracture during the first cold rolling was observed. The embrittlement of the laminated material (laminated material after the diffusion heat treatment) was evaluated by marking "x" if fracture occurred during the first cold rolling and "o" if no fracture occurred. The obtained results are also shown in Table 3. Note that no further treatment was performed on the samples that fractured during cold rolling.

[0059] [Finishing heat treatment process] The resulting cold-rolled laminate was subjected to finishing heat treatment in a batch-type heat treatment furnace at the heating temperature and holding time shown in Table 3 to obtain a product (laminate). The finishing heat treatment was performed in a reducing atmosphere of hydrogen gas. After finishing heat treatment, the laminate was slowly cooled. The cooling rate was within the range of 250 to 300°C / hour.

[0060] The power generation capacity (mW) of the obtained product (laminate material) was measured using the power generation device shown in Figure 4. The obtained power generation capacity (mW) was compared with the power generation capacity (mW) when using a single Fe-Co alloy (type: 60Fe5VCo) to evaluate the power generation vibration characteristics. The power generation capacity was evaluated as ◯ when it was three times or more the power generation capacity when using a single Fe-Co alloy, and × when it was less than three times the power generation capacity.

[0061] As shown in Figure 4, the power generation device is composed of a yoke 9, a permanent magnet 8, a power generation coil 6, a vibration source 7, and a weight 10. The measurement specimen, a laminated material (two-layer structure consisting of an Fe-Co alloy layer 5 and a Ni layer 4), had a thickness equal to the product plate thickness, a width of 5 mm, and a length of 50 mm. The weight of the weight was adjusted so that the resonant frequency would be approximately 70 Hz.

[0062] The cross section of the obtained product (laminate) in the thickness direction was polished and photographed using an optical microscope (magnification: 100x), the thickness of each layer (Fe-Co alloy layer 5 and Ni layer 4) was measured, and the thickness ratio of each layer was calculated. The results are shown in Table 3.

[0063]

[0064]

[0065]

[0066] It was confirmed that all of the examples of the present invention had high bonding strength at the bonding interface, suppressed embrittlement of the laminate, and had excellent vibration power generation characteristics.On the other hand, the comparative examples outside the scope of the present invention either could not be crimped, or could be crimped but the bonding strength was insufficient, embrittlement had progressed, or the vibration power generation characteristics were reduced.

[0067] Laminate No. 25 (Comparative Example) had a high surface hardness of over 140 HV for the Ni material used as the base material, resulting in low adhesion strength during crimping, and thus failure to bond (failed bonding). Laminate No. 26 had a high surface hardness of over 250 HV for the Fe-Co alloy material used as the base material, resulting in low bonding strength during crimping, and thus failure to bond (failed bonding). Laminate No. 27 had a low rolling reduction of less than 45% during crimping, resulting in failure to bond (failed bonding). Laminate No. 28 fractured during the first cold rolling because the processing temperature during crimping exceeded 720°C, which led to embrittlement due to ordering of the α' phase. Laminate No. 29 had a diffusion heat treatment temperature of less than 730°C, which prevented interdiffusion at the bonding interface, resulting in insufficient bonding strength. In addition, the diffusion heat treatment holding time for Laminate No. 30 was less than 1 minute, which prevented interdiffusion at the bond interface and resulted in insufficient bond strength. In Laminate No. 31, the final heat treatment temperature was less than 730°C, which prevented stress removal in the Fe-Co alloy, resulting in reduced vibration power generation characteristics. In Laminate No. 32, the final heat treatment holding time was less than 2 hours, resulting in a mixed phase of α' and γ phases after cooling, resulting in reduced vibration power generation characteristics. In Laminates No. 33 and No. 34, the thickness of the Fe-Co alloy layer after cold rolling was outside the range of 40–60% of the total thickness of the laminate (cold-rolled laminate), which resulted in the offset of the magnetostrictive and inverse magnetostrictive effects of the Fe-Co alloy and Ni, resulting in reduced vibration power generation characteristics.

[0068] REFERENCE SIGNS LIST 1 Fe-Co alloy material 2 Ni material 3 Roll 4 Ni layer 5 Fe-Co alloy layer 6 Power generating coil 7 Vibration source 8 Permanent magnet 9 Yoke 10 Weight

Claims

1. A method for manufacturing a laminated material for magnetostrictive vibration power generation having a two-layer clad structure, comprising: using two metal strip plates, namely an Fe-Co alloy material having a surface hardness of 250 HV or less and a Ni material having a surface hardness of 140 HV or less, as raw materials; stacking the two metal strip plates and performing a crimping process with a reduction ratio of 45 to 90% to obtain a laminated material having a two-layer clad structure; a diffusion heat treatment process of performing a diffusion heat treatment at a heating temperature of 730 to 1400 °C; a cold rolling process of performing cold rolling with a cumulative reduction ratio of 10 to 98%; and a finish heat treatment process of performing a finish heat treatment at a heating temperature of 730 to 1000 °C, in this order. The method for manufacturing a laminated material for magnetostrictive vibration power generation is characterized by this.

2. The method for manufacturing a laminated material for magnetostrictive vibration power generation according to claim 1, wherein the laminated material after cold rolling is a cold-rolled metal strip having a thickness of 0.03 to 2.0 mm.

3. The method for manufacturing a laminated material for magnetostrictive vibration power generation according to claim 2, wherein the laminated material after cold rolling contains an Fe-Co alloy layer with a thickness of 40 to 60% of the total plate thickness.

4. The method for manufacturing a laminated material for magnetostrictive vibration power generation according to claim 1, wherein the crimping process is performed in a processing temperature range of 20 to 720 °C.

5. The method for manufacturing a laminated material for magnetostrictive vibration power generation according to claim 1, wherein the diffusion heat treatment has a holding time of 1 to 30 minutes, and the finish heat treatment has a holding time of 2 hours or more.

6. The Fe-Co alloy material has a composition consisting of, by mass%, Fe: 40 to 60%, or further V: 1 to 5%, with the balance being Co and unavoidable impurities, and the Ni material has a composition consisting of, by mass%, Ni: 99.5% or more, with the balance being unavoidable impurities. The method for manufacturing a laminated material for magnetostrictive vibration power generation according to claim 1 is characterized by this.

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