Method for producing alloy ribbon sheet

Abstract

The present invention is a method for manufacturing an alloy ribbon sheet. Provided is a method for manufacturing an alloy ribbon sheet, whereby it is possible to easily manufacture an alloy ribbon sheet by punching an alloy ribbon. A method for producing an alloy ribbon sheet containing a nanocrystalline alloy, the method being characterized by comprising: a preparation step for preparing an alloy ribbon containing a FeNiB-based amorphous alloy; a heat treatment step in which alpha Fe crystal grains and Fe2B crystal grains are precipitated by heating a part to be processed around a part to be crystallized, said part being a region in which the alloy ribbon piece is punched, to a first temperature region in which the alpha Fe crystal grains and the Fe2B crystal grains are precipitated; heating the predetermined crystallization part to a second temperature range which is higher than the crystallization start temperature and lower than the first temperature range to crystallize the predetermined crystallization part; and a punching step in which the alloy ribbon sheet is formed by punching a region including the predetermined crystallization part from the alloy ribbon by cutting the predetermined processing part of the alloy ribbon after the heat treatment step.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an alloy thin ribbon containing a nanocrystalline alloy. Background Art

[0002] Soft magnetic materials have been used in the cores of electric motors for hybrid electric vehicles (HEV) and electric vehicles (BEV). Soft magnetic materials are required to have high magnetization (high torque) and low coercivity (low loss). Electromagnetic steel sheets are generally used as soft magnetic materials, but electromagnetic steel sheets have a limit in reducing losses. Generally, for Fe (iron)-based soft magnetic materials such as electromagnetic steel sheets, the smaller the thickness of the sheet and / or the smaller the particle size of the αFe grains in the material, the lower the loss. Therefore, in recent years, thin amorphous alloy ribbons (alloy ribbons containing amorphous alloys) have been manufactured by liquid rapid cooling, and nanocrystalline alloy ribbons (alloy ribbons containing nanocrystalline alloys) in which nanocrystalline grains of αFe are precipitated by crystallizing the amorphous alloy ribbons through rapid heat treatment have been expected to be soft magnetic materials that can simultaneously achieve high magnetization and low coercivity.

[0003] On the other hand, when using a soft magnetic material in an electric motor core, a plate of the soft magnetic material is punched out to produce a plate of the desired shape, and a plurality of these plates are stacked and fixed to obtain a laminate, which is then used to form an iron core. As a technique related to a method for producing a plate of the desired shape of a soft magnetic material comprising an amorphous alloy ribbon, a nanocrystalline alloy ribbon, etc., for example, a method is known in which, after preparing a laminate by stacking a plurality of core metal plates (plates of soft magnetic material), a temperature gradient is imparted to the laminate, the laminate is pressed, and the temperature gradient of the laminate is removed after the pressing (Patent Document 1). Furthermore, a composite magnetic ribbon (plate of soft magnetic material) having excellent pressing properties such as punching and a method for producing the same are known (Patent Document 2).

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-47831

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-163486 Summary of the Invention

[0007] Nanocrystalline alloy ribbons, due to the fragile interface between the nanocrystalline grains of αFe and the amorphous alloy phase, may crack like thin glass, making it difficult to perform processes such as punching that involve material deformation. Therefore, it is difficult to produce nanocrystalline alloy ribbon sheets (alloy ribbon sheets containing nanocrystalline alloys) by punching nanocrystalline alloy ribbons into sheets of the desired shape of soft magnetic material. On the other hand, although amorphous alloy ribbons before crystallization of the nanocrystalline alloy ribbons can be punched out one by one, the thickness of each sheet is extremely thin, around 20μm. Therefore, the clearance between the punch and die used as the mold for punching needs to be reduced to about 1μm to 2μm, resulting in increased wear on the punch and die. In addition, since amorphous alloy ribbons have no crystallization interface that serves as the starting point for material deformation and have high hardness, they are subject to increased wear on the punch and die. Therefore, even in the method of producing nanocrystalline alloy ribbon sheets by punching an amorphous alloy ribbon to form alloy ribbon sheets and then crystallizing the resulting sheets, production is not easy, and the punch and die wear out quickly. As a result, productivity is lower than when using electromagnetic steel sheets.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing an alloy ribbon sheet containing a nanocrystalline alloy, wherein the alloy ribbon sheet can be easily produced by punching an alloy ribbon.

[0009] In order to solve the above-mentioned problems, the method for producing an alloy ribbon sheet of the present invention is a method for producing an alloy ribbon sheet containing a nanocrystalline alloy, characterized by comprising a preparation step, a heat treatment step, and a punching step.

[0010] In the preparation step, an alloy ribbon containing a FeNiB-based amorphous alloy is prepared.

[0011] In the heat treatment step, a predetermined processed portion of the alloy strip surrounding a predetermined crystallization portion, which is a region from which the alloy strip piece is punched, is heated to a first temperature range in which αFe grains and Fe2B grains are precipitated, thereby causing αFe grains and Fe2B grains to precipitate. Simultaneously, the predetermined crystallization portion is heated to a second temperature range that is higher than a crystallization start temperature and lower than the first temperature range, thereby causing crystallization.

[0012] In the punching step, the alloy strip is sheared at the planned processing portion after the heat treatment step, thereby punching out a region including the planned crystallization portion from the alloy strip, thereby forming the alloy strip piece.

[0013] According to the present invention, alloy thin strip sheets can be easily produced by punching the alloy thin strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic perspective view showing the steps of a method for producing an alloy thin strip sheet according to one embodiment.

[0015] Figure 2 It is a schematic perspective view showing the steps of a method for producing an alloy thin strip sheet according to one embodiment.

[0016] Figure 3 The present invention is a perspective view schematically showing a method for manufacturing an alloy thin strip sheet and a method for manufacturing a stator core using the alloy thin strip sheet according to one embodiment.

[0017] Figure 4 This is a graph showing DSC curves of the FeNiB-based amorphous alloy contained in the alloy ribbons used in Reference Examples 1 and 2.

[0018] Figure 5 (a) and (b) are photographs showing punching tests of Reference Examples 1 and 2, respectively.

[0019] Figure 6 (a) is a diagram showing the X-ray diffraction pattern of the alloy strips after heat treatment of Reference Examples 1 and 2, (b) is a structural image of the alloy strip after heat treatment of Reference Example 1 observed using SEM at a magnification of 5000 to 20000 times, and (c) is a schematic diagram of the structure of the alloy strip after heat treatment of Reference Example 2.

[0020] Description of Reference Numerals

[0021] 1: Alloy thin strip sheet; 10: Alloy thin strip; 10a: Outer periphery planned processing portion; 10b: Inner periphery planned processing portion; 10c: Planned crystallization portion; U: Upper die for heat treatment; L: Lower die for heat treatment; P: Punch (upper die); D: Die (lower die). DETAILED DESCRIPTION

[0022] First, an embodiment is exemplified and a method for manufacturing an alloy ribbon sheet according to the embodiment is briefly described. The method for manufacturing an alloy ribbon sheet according to the embodiment is a method for manufacturing an annular alloy ribbon sheet constituting a laminated body used in a stator core of an electric motor. Figure 1 (a)~ Figure 3 (b) is a schematic perspective view showing a method for manufacturing an alloy thin strip sheet according to an embodiment and a method for manufacturing a stator core using the alloy thin strip sheet. Figure 2 (b) also shows a schematic cross-sectional view showing a cross section along the line AA' in the perspective view.

[0023] In the method for manufacturing an alloy thin strip according to one embodiment, first, Figure 1As shown in (a), an alloy strip 10 is prepared (preparation process). Then, the alloy strip 10 is arranged between the bottom surface (heating surface) Ub of the upper mold U for heat treatment and the upper surface (support surface) Lt of the lower mold L for heat treatment (first arrangement process). The alloy strip 10 is an alloy strip containing an FeNiB-based amorphous alloy. The upper mold U for heat treatment is a mold having a roughly cylindrical shape with a cylindrical through hole Uh in the center, and a bottom surface Ub having a circular ring shape. Inside the upper mold U for heat treatment, a heater (not shown) is provided that can set the heating temperature for each part of the bottom surface Ub. In the bottom surface Ub of the upper mold U for heat treatment, the outer edge Uba and the inner edge Ubb are preheated by the heater at a heating temperature of 650°C or more and 700°C or less, and the central portion Ubc (the portion of the bottom surface Ub excluding the outer edge Uba and the inner edge Ubb) is preheated by the heater at a heating temperature of 490°C or more and 520°C or less. Furthermore, the outer edge portion Uba, the inner edge portion Ubb, and the central portion Ubc of the bottom surface Ub of the upper heat treatment mold U have the same shape and dimensions as the outer peripheral planned processing portion 10a, the inner peripheral planned processing portion 10b, and the planned crystallization portion 10c, respectively, when viewed from the thickness direction of the alloy strip 10. On the other hand, the lower heat treatment mold L is a plate-shaped mold with the alloy strip 10 placed on its upper surface Lt.

[0024] Then, if Figure 1As shown in FIG. 2( b ), in a room temperature atmosphere, an alloy strip 10 is placed on the upper surface Lt of a heat treatment lower die L. In this state, a circular ring-shaped crystallization target portion 10c, which serves as the area where the alloy strip sheet is to be punched out, a circular ring-shaped outer peripheral processing target portion 10a surrounding the outer periphery of the crystallization target portion 10c, and a circular ring-shaped inner peripheral processing target portion 10b surrounding the inner periphery of the crystallization target portion 10c are clamped by the bottom surface Ub of the heat treatment upper die U and the upper surface Lt of the heat treatment lower die L. At this time, the outer edge portion Uba, the inner edge portion Ubb, and the center portion Ubc of the bottom surface Ub of the heat treatment upper die U are respectively pressed against the outer peripheral processing target portion 10a, the inner peripheral processing target portion 10b, and the crystallization target portion 10c of the alloy strip 10 for a predetermined period of time (e.g., 3 seconds). In this way, a rapid heat treatment (heat treatment process) is performed in which the outer peripheral predetermined processing portion 10a and the inner peripheral predetermined processing portion 10b in the alloy strip 10 are heated to a first temperature range of 600°C to 650°C (a first temperature range where αFe grains and Fe2B grains precipitate) and maintained, while the predetermined crystallization portion 10c is heated to a second temperature range of 470°C to 500°C (a second temperature range above the crystallization start temperature and below the first temperature range) and maintained. Thus, the crystallization of the outer peripheral predetermined processing portion 10a and the inner peripheral predetermined processing portion 10b of the alloy strip 10 is carried out, and the coarsened αFe grains and Fe2B grains are densely precipitated. At the same time, the predetermined crystallization portion 10c of the alloy strip 10 is crystallized, and nano-grains of αFe are precipitated, thereby generating a crystallization portion 10c' (at the time of the crystallization) in which the amorphous alloy of the predetermined crystallization portion 10c is modified into a nanocrystalline alloy. Figure 2 (shown in Figure 5a).

[0025] Then, if Figure 2As shown in (a), the alloy strip 10 after rapid heat treatment is arranged between the bottom surface (punch surface) Pb of the punch (upper die) P and the upper surface (support surface) Dt of the die (lower die) D (second arrangement step). The punch P is a die having a roughly cylindrical shape with a cylindrical through hole Ph in the center, and the bottom surface Pb has a circular ring shape. The die D is a die having a die hole Dh for the punch P to enter from the upper surface Dt side. The die hole Dh is a hole that penetrates in a direction perpendicular to the upper surface Dt of the die D. The die hole Dh has a circular ring shape that is roughly the same as the bottom surface Pb of the punch P, and its outer edge Dhp and inner edge Dhn are larger than the outer edge Pbp and inner edge Pbn of the bottom surface Pb of the punch P by the amount of the gap. Furthermore, the punch P and the die D have shapes and dimensions such that the outer edge Pbp of the bottom surface Pb of the punch P and the outer edge Dhp of the die hole Dh of the die D are located inside between the outer edge 10ap and the inner edge 10an of the outer circumference planned processing portion 10a of the alloy strip 10. Furthermore, the inner edge Pbn of the bottom surface Pb of the punch P and the inner edge Dhn of the die hole Dh of the die D are located inside between the outer edge 10bp and the inner edge 10bn of the inner circumference planned processing portion 10b of the alloy strip 10. In other words, the diameter of the outer edge Pbp of the bottom surface Pb of the punch P and the diameter of the outer edge Dhp of the die hole Dh of the die D are between the diameters of the outer edge 10ap and the inner edge 10an of the outer circumference planned processing portion 10a of the alloy strip 10. The diameter of the inner edge Pbn of the bottom surface Pb of the punch P and the diameter of the inner edge Dhn of the die hole Dh of the die D are the dimensions between the diameters of the outer edge 10bp and the inner edge 10bn of the inner peripheral portion to be processed 10b of the alloy strip 10.

[0026] Then, if Figure 2As shown in (b), the alloy strip 10 is punched by being clamped between the bottom surface Pb of the punch P and the upper surface Dt of the die D. At this time, the punch P and the die D are pressed against the alloy strip 10 from both sides so that the outer edge Pbp of the bottom surface Pb of the punch P and the outer edge Dhp of the die hole Dh of the die D are in contact within the range of the planned processing portion 10a of the outer periphery of the alloy strip 10, and the inner edge Pbn of the bottom surface Pb of the punch P and the inner edge Dhn of the die hole Dh of the die D are in contact within the range of the planned processing portion 10b of the inner periphery of the alloy strip 10. This causes the bottom surface Pb of the punch P to enter the die hole Dh of the die D. In this way, after the heat treatment step, the outer peripheral planned processing portion 10a and the inner peripheral planned processing portion 10b of the alloy thin strip 10 are sheared at a position away from the boundary with the planned crystallization portion 10c (the inner edge 10an of the outer peripheral planned processing portion 10a and the outer edge 10bp of the inner peripheral planned processing portion 10b), thereby punching out a region from the alloy thin strip 10 that includes the crystallized portion 10c′ (the planned crystallization portion 10c) and a portion of the outer peripheral planned processing portion 10a and the inner peripheral planned processing portion 10b on the crystallized portion 10c′ side. Figure 3 As shown in (a), an alloy thin strip sheet 1 including a crystallized portion 10c' containing a nanocrystalline alloy and a portion of the outer peripheral planned processing portion 10a and the inner peripheral planned processing portion 10b on the crystallized portion 10c' side is formed (punching process). The alloy thin strip sheet 1 containing a nanocrystalline alloy is manufactured by the above-mentioned method. In addition, in the manufacturing method of the stator core using the alloy thin strip sheet according to one embodiment, as shown in FIG. Figure 3 As shown in FIG. 2 , a plurality of alloy strip sheets 1 manufactured by the method for manufacturing alloy strip sheets according to one embodiment are stacked and fixed to each other via a bonding layer (not shown) made of a heat-resistant resin or the like. Thus, a stator core 2 including the stack of alloy strip sheets 1 is manufactured.

[0027] In a method for manufacturing an alloy ribbon sheet according to one embodiment, during a heat treatment step, crystallization of the outer and inner portions 10a, 10b of the alloy ribbon 10 is advanced, causing dense precipitation of coarsened αFe grains and Fe2B grains. Simultaneously, the intended crystallization portion 10c of the alloy ribbon 10 is crystallized, causing precipitation of nanocrystalline αFe grains. This results in a crystallized portion 10c', which is a nanocrystalline alloy modified from the amorphous alloy of the intended crystallization portion 10c. Consequently, during the blanking step following the heat treatment step, the grain interfaces in the structure of the outer and inner portions 10a, 10b of the alloy ribbon 10, where both coarsened αFe grains and Fe2B grains are densely precipitated, can serve as starting points for plastic deformation, unlike in amorphous and nanocrystalline alloy ribbons, thereby reducing hardness. Therefore, when punching out a region including a crystallized portion 10c' (predetermined crystallized portion 10c) from the alloy strip 10 by shearing the outer periphery predetermined processing portion 10a and the inner periphery predetermined processing portion 10b of the alloy strip 10, shearing can be easily performed. Moreover, an alloy strip sheet 1 including a crystallized portion 10c' containing a nanocrystalline alloy capable of simultaneously achieving high magnetization intensity and low coercivity can be formed. Therefore, according to the method for manufacturing an alloy strip sheet of one embodiment, an alloy strip sheet 1 containing a nanocrystalline alloy capable of simultaneously achieving high magnetization intensity and low coercivity can be easily manufactured by punching out the alloy strip 10. In addition, thereby, the consumption of the mold (punch and die) used for punching can be reduced, thereby improving the productivity of the alloy strip sheet 1.

[0028] Next, the configuration of the method for producing the alloy ribbon sheet according to the embodiment will be described in detail.

[0029] 1. Preparation process

[0030] In the preparation step, an alloy ribbon containing a FeNiB-based amorphous alloy is prepared.

[0031] The alloy ribbon is not particularly limited as long as it is an alloy ribbon containing an FeNiB-based amorphous alloy. For example, it can be a continuous sheet-shaped amorphous alloy ribbon produced by a general method such as a single-roll method or a double-roll method. The FeNiB-based amorphous alloy is not particularly limited as long as it is an amorphous alloy containing Fe (iron), Ni (nickel), and B (boron) as main components. As the composition of the FeNiB-based amorphous alloy, a composition further containing Si (silicon) is preferred. Specifically, a composition represented by the following general formula (1) is preferred.

[0032] Fe 100-x-y-z-w B x Ni y Si z M w (1)

[0033] (In the formula, M is one or more inevitable elements selected from Nb (niobium), Mo (molybdenum), Ta (tantalum), W (tungsten), Co (cobalt), and Sn (tin), and x, y, z, and w satisfy the conditions of 12 ≤ x ≤ 17, 1 ≤ y ≤ 3, 0 < z ≤ 1, and 0 < w ≤ 0.1 in atomic %).)

[0034] The thickness of the alloy thin strip is not particularly limited. For example, it is in the range of 10 μm or more and 100 μm or less, and preferably in the range of 20 μm or more and 50 μm or less.

[0035] 2. Heat treatment process

[0036] In the heat treatment process, by heating a predetermined processing part around a predetermined crystallization part that becomes the area of the alloy thin strip from which the alloy thin strip piece is blanked to the first temperature range where the grains of αFe and the grains of Fe2B precipitate, the grains of αFe and the grains of Fe2B are precipitated. At the same time, by heating the predetermined crystallization part to the second temperature range that is above the crystallization start temperature and lower than the first temperature range, it is crystallized.

[0037] Here, the so-called "predetermined crystallization part" refers to the part that becomes the area (alloy thin strip piece) blanked from the alloy thin strip in the blanking process, and can also be a part included in the blanked area. In addition, the so-called "predetermined processing part" refers to the part around the predetermined crystallization part, which is the part that extends a predetermined width outward from the edge of the predetermined crystallization part. The width of the predetermined processing part is not particularly limited as long as there is no breakage such as cracking that causes quality problems during blanking in the blanking process. For example, it is preferably 1 mm or more. This is because by being above this lower limit, the occurrence of breakage such as cracking can be effectively suppressed. The width of the predetermined processing part is preferably as small as possible. This is because in the area blanked from the alloy thin strip in the blanking process, by increasing the proportion of the crystallized predetermined crystallization part, the magnetic properties of the alloy thin strip piece can be improved. Here, the so-called "width of the predetermined processing part" refers to the dimension in the direction perpendicular to the edge of the predetermined processing part.

[0038] The so-called "crystallization start temperature" refers to the temperature at which the alloy thin strip starts to crystallize when the alloy thin strip containing the FeNiB-based amorphous alloy is heated. The crystallization of the alloy thin strip means the precipitation of grains of αFe (ferrite phase). The crystallization start temperature varies depending on the composition of the FeNiB-based amorphous alloy. For example, when the composition of the FeNiB-based amorphous alloy is the above-mentioned preferred composition, it is 350 °C or more and 500 °C or less.

[0039] The first temperature range is not particularly limited as long as it is a temperature range in which both αFe grains and Fe2B grains precipitate. It varies depending on the composition of the FeNiB-based amorphous alloy, but for example, when the composition of the FeNiB-based amorphous alloy is the preferred composition described above, it is preferably 600°C or higher and 650°C or lower. This is because both αFe grains and Fe2B grains can be densely precipitated. Furthermore, the phrase "precipitating αFe grains and Fe2B grains by heating the predetermined processing portion to the first temperature range in which αFe grains and Fe2B grains precipitate" refers to heating the predetermined processing portion to the first temperature range and maintaining the time required for the precipitation of αFe grains and Fe2B grains in the first temperature range. The time for which the intended working portion is held in the first temperature range is not particularly limited as long as αFe and Fe2B grains can be precipitated in the intended working portion without causing damage such as cracking during punching. For example, it is preferably within a range of 2 seconds to 4 seconds. This is because a time above the lower limit of this range allows dense precipitation of αFe and Fe2B grains in the intended working portion, while a time below the upper limit of this range prevents coarsening of αFe grains.

[0040] The second temperature range is not particularly limited as long as it is above the crystallization start temperature and below the first temperature range, but is preferably above the crystallization start temperature and below the compound phase precipitation start temperature. This is because it can suppress the precipitation of the compound phase. Here, the so-called "compound phase precipitation start temperature" refers to the temperature at which the compound phase begins to precipitate when the alloy ribbon is further heated after crystallization has started. In addition, the so-called "compound phase" refers to, for example, a compound phase that precipitates and degrades the soft magnetic properties when the alloy ribbon is further heated after crystallization has started, and includes various phases in addition to the above-mentioned Fe2B. The temperature range as the second temperature range varies depending on the composition of the FeNiB-based amorphous alloy, but for example, when the composition of the FeNiB-based amorphous alloy is the preferred composition described above, it is preferably above 470°C and below 500°C. This is because it can stably precipitate αFe nanocrystals, suppressing the coarsening of the grains and the precipitation of the compound phase. Furthermore, the phrase "crystallizing the predetermined crystallization portion by heating it to a second temperature range that is higher than the crystallization start temperature and lower than the first temperature range" means crystallizing the predetermined crystallization portion by heating it to the second temperature range and maintaining it in the second temperature range for the time required for crystallization. The time for which the predetermined crystallization portion is maintained in the second temperature range is not particularly limited, as long as it allows the precipitation of αFe nanocrystals in the predetermined crystallization portion in a manner that simultaneously achieves high magnetization and low coercivity. For example, it is preferably the same time as the time for which the predetermined processing portion is maintained in the first temperature range. Specifically, it is preferably within a range of 2 seconds to 4 seconds. This is because by maintaining the temperature above the lower limit of this range, αFe nanocrystals can be stably precipitated in the predetermined crystallization portion, and by maintaining the temperature below the upper limit of this range, the coarsening of the αFe grains can be suppressed.

[0041] The method for heating the intended processing portion to a first temperature range to precipitate αFe and Fe2B grains, and simultaneously crystallizing the intended crystallization portion by heating it to a second temperature range, is not particularly limited. For example, one embodiment includes a method in which the intended processing portion and the intended crystallization portion of the alloy strip are clamped between the heated surface of an upper heat treatment die and the support surface of a lower heat treatment die in ambient air at room temperature. In this method, the edge and center portions of the heated surface of the upper heat treatment die are preheated without preheating the lower heat treatment die. After this, the intended processing portion and the intended crystallization portion of the alloy strip are clamped between the heated surface of the upper heat treatment die and the support surface of the lower heat treatment die, with the edge and center portions of the heated surface of the upper heat treatment die respectively contacting the intended processing portion and the intended crystallization portion of the alloy strip for a predetermined period of time. The term "ambient temperature" refers to, for example, the temperature specified in JIS Z 8703.

[0042] In the heat treatment process, the predetermined processing portion is heated to the first temperature range to precipitate αFe grains and Fe2B grains in the predetermined processing portion. At this time, the predetermined processing portion is preferably formed by densely precipitating the αFe grains and Fe2B grains so that the interface between the grains becomes the starting point of plastic deformation, thereby becoming a predetermined processing portion with low hardness. In addition, the predetermined crystallization portion is crystallized by heating it to the second temperature range, thereby forming a crystallization portion containing a nanocrystalline alloy. At this time, the crystallization portion is preferably formed by precipitating αFe nano-grains without substantially generating the precipitation of the compound phase and the coarsening of the grains, thereby becoming a crystallization portion with desired magnetic properties (high magnetization intensity and low coercive force). The particle size of the αFe grains in the crystallization portion is not particularly limited as long as the desired magnetic properties can be obtained, for example, it is preferably within the range of 25nm or less. This is because if the coercive force is deteriorated. In addition, the particle size of the crystal grains can be measured by direct observation using a scanning electron microscope (SEM), for example.

[0043] 3. Blanking process

[0044] In the punching step, the predetermined processing portion of the alloy strip is sheared after the heat treatment step to punch out a region containing the predetermined crystallized portion from the alloy strip, thereby forming the alloy strip sheet. The punching step is not particularly limited as long as it punches out the region containing the predetermined crystallized portion from the alloy strip by shearing the predetermined processing portion. For example, as in one embodiment, it is preferable to punch out a region containing both the predetermined crystallized portion and a portion of the predetermined processing portion on the predetermined crystallized portion side from the alloy strip by shearing the predetermined processing portion at a position separated from the boundary with the predetermined crystallized portion. This is because it can prevent damage such as cracking from occurring during punching.

[0045] The method for punching out the intended crystallized portion from the alloy strip is not particularly limited. For example, as in one embodiment, a punch and a die are used, and the alloy strip is clamped between the punch face of the punch and the support surface of the die to perform the punching process. The punch and die are not particularly limited as long as they can punch out a region of the desired shape including the intended crystallized portion. For example, as in one embodiment, a punch and die are preferably shaped and sized so that the edge of the punch face of the punch and the edge of the die hole of the die are located inside the edge of the intended processed portion of the alloy strip. Furthermore, as a method for performing the punching process, as in one embodiment, a method is preferably used, such as using such a preferred punch and die, and pressing the punch and die from both sides against the alloy strip so that the edge of the punch face of the punch and the edge of the die hole of the die contact within the range of the intended processed portion of the alloy strip, thereby causing the punch to enter the die hole of the die. This is because a region including the planned crystallization portion and a portion of the planned processing portion on the planned crystallization portion side can be punched out from the alloy strip, thereby suppressing the occurrence of damage such as cracks.

[0046] 4. Method for manufacturing alloy thin strip sheet and alloy thin strip sheet

[0047] The method for manufacturing an alloy ribbon sheet is not particularly limited as long as it includes a preparation step, a heat treatment step, and a punching step, and may include other steps. The alloy ribbon sheet manufactured using the method for manufacturing an alloy ribbon sheet is not particularly limited as long as it includes a crystallized predetermined crystallization portion (crystallized portion). For example, it is preferably an alloy ribbon sheet that includes both the predetermined crystallization portion and a portion of the predetermined processing portion on the predetermined crystallization portion side, as in the alloy ribbon sheet manufactured in one embodiment.

[0048] [Example]

[0049] Hereinafter, embodiments of the present invention will be described in more detail with reference to examples.

[0050] [DSC curve of FeNiB-based amorphous alloy]

[0051] The FeNiB-based amorphous alloy contained in the alloy ribbons used in Reference Examples 1 and 2 was measured using a differential scanning calorimeter (DSC) to obtain a DSC curve. The FeNiB-based amorphous alloy used had a composition of 83.7 atomic percent Fe, 2 atomic percent Ni, 13.5 atomic percent B, and 0.8 atomic percent Si, with the remainder being unavoidable impurities. The heating rate of the FeNiB-based amorphous alloy during the DSC curve measurement was 100°C / min. Figure 4 This is a diagram showing DSC curves of the FeNiB-based amorphous alloy contained in the alloy ribbons used in Reference Examples 1 and 2.

[0052] exist Figure 4 In the DSC curve shown, the peak near 450°C is considered to be the exothermic peak of the crystallization reaction that precipitates αFe nanoparticles. Furthermore, the peak near 520°C is considered to be the exothermic peak of the crystallization reaction that precipitates Fe2B grains. Therefore, in Reference Example 1, described below, a heating temperature of 600°C was selected to promote crystallization of the alloy ribbon and densely precipitate coarse αFe grains and Fe2B grains. Furthermore, in Reference Example 2, described below, a heating temperature of 500°C was selected to promote crystallization of the alloy ribbon and precipitate αFe nanoparticles.

[0053] [Reference Example 1]

[0054] The crystallization and punching test of the alloy strip was conducted. First, an alloy strip containing the above-mentioned FeNiB-based amorphous alloy was prepared. Then, in the atmosphere at room temperature, the surface of the alloy strip was placed against the surface of a heating plate that had been preheated at 650°C by a heater for 3 seconds, thereby performing a rapid heat treatment to heat the alloy strip and maintain it at 600°C. Figure 5 As shown in (a), a punch (not shown) with a bottom surface (punch face) and a die with a punch hole of approximately rectangular shape and a gap of 10 μm between them is used to punch out an approximately rectangular area from a heat-treated alloy strip. Figure 5 As shown in (a), the desired substantially rectangular metal strip piece can be punched out without any problem.

[0055] [Reference Example 2]

[0056] The crystallization and punching test of the alloy strip was conducted. First, the alloy strip containing the same FeNiB-based amorphous alloy as in Reference Example 1 was prepared. Then, in the atmosphere at room temperature, the surface of the alloy strip was placed against the surface of a heating plate that had been preheated at 520°C by a heater for 3 seconds, thereby performing a rapid heat treatment to heat the alloy strip and maintain it at 500°C. Then, as Figure 5 As shown in (b), a roughly rectangular area was punched out from the alloy strip after heat treatment using the same punch (not shown) and die as in Reference Example 1. Figure 5 As shown in (b), the alloy thin strip is cracked during punching, and the desired substantially rectangular metal thin strip piece cannot be punched out.

[0057] [evaluate]

[0058] X-ray diffraction (XRD) was performed on the alloy ribbons after the heat treatment of Reference Examples 1 and 2 to measure the X-ray diffraction patterns. Figure 6(a) is a diagram showing the X-ray diffraction patterns of the alloy strips after heat treatment of Reference Examples 1 and 2. Figure 6 As shown in (a), in the X-ray diffraction pattern of the alloy strip after heat treatment of Reference Example 1, in addition to the peak of the αFe phase, the peak of the Fe2B phase can also be confirmed. On the other hand, the halo peak originating from the amorphous alloy phase cannot be confirmed. In contrast, in the X-ray diffraction pattern of the alloy strip after heat treatment of Reference Example 2, the peak of the αFe phase can be confirmed, but the peak of the Fe2B phase cannot be confirmed. On the other hand, the halo peak originating from the amorphous alloy phase can be confirmed. Based on the contents of these X-ray diffraction patterns, it is believed that the structure of the alloy strip after heat treatment of Reference Example 1 does not have any residual amorphous alloy phase, and has become a mixed phase structure of the αFe phase and the Fe2B phase. In contrast, it is believed that the structure of the alloy strip after heat treatment of Reference Example 2 has become a mixed phase structure of the amorphous alloy phase and the αFe phase.

[0059] In addition, the microstructure of the alloy ribbon after the heat treatment of Reference Example 1 was observed using SEM. Figure 6 (b) is a microstructure image of the alloy ribbon after heat treatment of Reference Example 1 observed by SEM at a magnification of 5000 to 20000 times. Figure 6 The microstructure images at various magnifications in (b) show that in the microstructure of the alloy strip after heat treatment in Reference Example 1, both coarsened αFe grains (white grains) and Fe2B grains (black grains) are densely precipitated. On the other hand, although the microstructure of the alloy strip after heat treatment in Reference Example 2 was not observed using SEM, it is believed based on conventional knowledge that the microstructure is as follows: Figure 6 As shown in (c), a mixed phase structure is shown in which nanocrystalline grains of αFe are dispersedly precipitated in an amorphous alloy phase.

[0060] Furthermore, 10 specimens were cut from the heat-treated alloy strips of Reference Examples 1 and 2 according to JIS Z2241 13B specifications. Tension tests were performed on these 10 specimens, and the average upper yield point (MPa) was determined. The results showed that the average upper yield point (N = 10) for the specimens of the heat-treated alloy strip of Reference Example 1 was 515.1 MPa. In contrast, the average upper yield point (N = 10) for the specimens of the heat-treated alloy strip of Reference Example 2 was 907.8 MPa. This suggests that the heat-treated alloy strip of Reference Example 1 is more susceptible to plastic deformation than the heat-treated alloy strip of Reference Example 2.

[0061] From the above results, it is believed that in the alloy strip after heat treatment in Reference Example 1, Figure 6As shown in the microstructure image (b), the interface between the grains in the microstructure where both the coarsened αFe grains and the Fe2B grains are densely precipitated becomes the starting point of plastic deformation, thereby making it easy to shear along the edge of the bottom surface of the punch. As a result, it is believed that the desired roughly rectangular metal strip sheet can be punched out without any problem. In addition, it is believed that if the alloy strip is subjected to such heat treatment, the consumption of the punch and the die can be reduced. On the other hand, it is believed that in the alloy strip subjected to heat treatment in Reference Example 2, as Figure 6 As shown in (c), in a mixed-phase structure with dispersed αFe nanocrystals precipitated within the amorphous alloy phase, the interface between the αFe nanocrystals and the amorphous alloy phase is scattered and irregularly arranged. Therefore, it is believed that although the interface between the αFe nanocrystals and the amorphous alloy phase serves as the starting point of plastic deformation, shearing along the edge of the punch's bottom surface becomes difficult. As a result, the alloy strip cracks during punching.

[0062] While the embodiments of the method for producing an alloy ribbon sheet of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design changes can be made without departing from the spirit of the present invention as described in the claims.

Claims

1. A method for manufacturing an alloy ribbon sheet, which is a method for manufacturing an alloy ribbon sheet containing a nanocrystalline alloy, characterized in that: It has preparation process, heat treatment process and blanking process. In the preparation step, an alloy ribbon containing a FeNiB-based amorphous alloy is prepared. In the heat treatment step, a predetermined processed portion of the alloy strip surrounding a predetermined crystallization portion, which will become a region from which the alloy strip piece is punched, is heated to a first temperature range in which αFe grains and Fe2B grains are precipitated, thereby causing αFe grains and Fe2B grains to precipitate. Simultaneously, the predetermined crystallization portion is heated to a second temperature range that is higher than a crystallization start temperature and lower than the first temperature range, thereby causing the portion to crystallize. In the punching step, the alloy ribbon piece is formed by shearing the planned processed portion of the alloy ribbon after the heat treatment step, thereby punching out a region including the planned crystallization portion from the alloy ribbon.

2. The method for manufacturing an alloy thin strip according to claim 1, wherein: In the heat treatment step, the first temperature range is 600° C. or higher and 650° C. or lower, and the second temperature range is 470° C. or higher and 500° C. or lower.

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