Method for manufacturing alloy ribbon piece

Abstract

To provide a method for manufacturing an alloy ribbon piece, capable of facilitating the manufacture of the alloy ribbon piece by punching work of an alloy ribbon.SOLUTION: A method for manufacturing an alloy ribbon piece containing a nanocrystalline alloy, includes: a preparation step of preparing an alloy ribbon containing an FeNiB-based amorphous alloy; a heat treatment step of heating a processing planned portion at a circumference of a crystallization planned portion that is an area in which the alloy ribbon piece is punched of the alloy ribbon to a first temperature range in which crystal grains of αFe and crystal grains of Fe2B deposit to cause the crystal grains of αFe and the crystal grains of Fe2B to deposit, and simultaneously heating the crystallization planned portion to a second temperature range of a crystallization starting temperature or higher and lower than the first temperature range to crystallize the crystallization planned portion; and a punching step of punching an area including the crystallization planned portion from the alloy ribbon by shearing the processing planned portion of the alloy ribbon after the heat treatment step thereby to form the alloy ribbon piece.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing alloy strips containing nanocrystalline alloys. [Background technology]

[0002] Soft magnetic materials have traditionally been used for motor cores (iron cores) in hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs). Soft magnetic materials are required to have high magnetization (high torque) and low coercive force (low loss). While electromagnetic steel sheets are commonly used as soft magnetic materials, there are limitations to the loss reduction they can achieve. Generally, for Fe (iron)-based soft magnetic materials such as electromagnetic steel sheets, the thinner the sheet and the smaller the grain size of the α-Fe crystal grains in the material, the lower the loss. For this reason, in recent years, thin amorphous alloy ribbons (alloy ribbons containing amorphous alloys) have been produced by a liquid quenching method, and then crystallized by rapid heat treatment to precipitate α-Fe nanocrystalline grains. Nanocrystalline alloy ribbons (alloy ribbons containing nanocrystalline alloys) are expected to be soft magnetic materials that can achieve both high magnetization and low coercive force.

[0003] On the other hand, when using a soft magnetic material for a motor core or the like, a plate of the soft magnetic material is manufactured into a desired shape by processing such as punching, and a plurality of the plates are stacked and fixed to form a laminate to form a core or the like. As a technique for manufacturing a plate of a soft magnetic material including an amorphous alloy ribbon, a nanocrystalline alloy ribbon, or the like into a desired shape, for example, a method is known in which a laminate is prepared by stacking a plurality of metal plates (plates of the soft magnetic material) for the core, a temperature gradient is applied to the laminate, the laminate is pressed, and the temperature gradient of the laminate is removed after pressing (Patent Document 1). Also known is a composite magnetic ribbon (plate of the soft magnetic material) that is excellent in press workability such as punching, and a manufacturing method thereof (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-47831 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-163486 Summary of the Invention [Problem to be solved by the invention]

[0005] Nanocrystalline alloy ribbons have a fragile interface between the α-Fe nanocrystalline grains and the amorphous alloy phase, which can crack like thin glass, making them difficult to process, such as punching, which involves deformation of the material. Therefore, it is difficult to produce nanocrystalline alloy ribbon flakes (alloy ribbon flakes containing a nanocrystalline alloy) as soft magnetic material sheets of a desired shape by punching the nanocrystalline alloy ribbon. Meanwhile, amorphous alloy ribbons before the crystallization of the nanocrystalline alloy ribbon can be punched one by one, but each sheet is extremely thin, with a thickness of about 20 μm. Therefore, the clearance of the punch and die, which are the dies used for punching, must be reduced to about 1 μm to 2 μm, resulting in significant wear of the punch and die. Furthermore, amorphous alloy ribbons have no crystal interfaces that can be the starting point for deformation of the material, and are therefore highly hard, resulting in significant wear of the punch and die. Therefore, even when an amorphous alloy ribbon is punched to form alloy ribbon pieces and then crystallized to produce nanocrystalline alloy ribbon pieces, the production is not easy and the punch and die wear out quickly, resulting in lower productivity compared to when an electrical steel sheet is used.

[0006] The present invention has been made in consideration of these points, and its object is to provide a method for manufacturing alloy strips containing nanocrystalline alloys, which can easily manufacture alloy strips by punching the alloy strips. [Means for solving the problem]

[0007] In order to solve the above problems, the manufacturing method of the alloy ribbon flakes of the present invention is a manufacturing method of an alloy ribbon flake containing a nanocrystalline alloy, and is characterized by comprising: a preparation step of preparing an alloy ribbon containing an FeNiB-based amorphous alloy; a heat treatment step of heating a portion to be processed around a portion to be crystallized in the alloy ribbon, which is the area where the alloy ribbon flakes will be punched, to a first temperature range in which αFe crystal grains and FeB crystal grains precipitate, thereby precipitating αFe crystal grains and FeB crystal grains, and simultaneously heating the portion to be crystallized to a second temperature range that is equal to or higher than a crystallization start temperature and lower than the first temperature range, thereby crystallizing the portion to be crystallized; and a punching step of, after the heat treatment step, shearing the portion to be processed of the alloy ribbon to punch out a region including the portion to be crystallized from the alloy ribbon, thereby forming the alloy ribbon flakes. [Effects of the Invention]

[0008] According to the present invention, alloy ribbon pieces can be easily produced by punching an alloy ribbon. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic perspective view showing a manufacturing method of an alloy thin strip according to one embodiment. [Figure 2] 1 is a schematic perspective view showing a manufacturing method of an alloy thin strip according to one embodiment. [Figure 3] 1 is a schematic perspective view showing a method for manufacturing an alloy strip according to one embodiment and a method for manufacturing a stator core using the alloy strip; [Figure 4] 1 is a graph showing DSC curves of FeNiB-based amorphous alloys contained in alloy ribbons used in Reference Examples 1 and 2. [Figure 5] Photographs (a) and (b) show the punching tests of Reference Examples 1 and 2, respectively. [Figure 6]1(a) is a graph showing X-ray diffraction patterns of the alloy ribbons after the heat treatments of Reference Examples 1 and 2. 1(b) is a structural image of the alloy ribbon after the heat treatment of Reference Example 1 observed with an SEM at a magnification of 5,000 to 20,000 times. 1(c) is a schematic diagram of the structure of the alloy ribbon after the heat treatment of Reference Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] First, an outline of a method for manufacturing alloy ribbon flakes according to an embodiment will be described by taking one embodiment as an example. The method for manufacturing alloy ribbon flakes according to one embodiment is a method for manufacturing annular alloy ribbon flakes that constitute a laminate used in a stator core of a motor. FIGS. 1(a) to 3(b) are schematic perspective views of the process illustrating a method for manufacturing alloy ribbon flakes according to one embodiment and a method for manufacturing a stator core using the alloy ribbon flakes, and FIG. 2(b) also shows a schematic cross-sectional view showing a cross section along line AA' in the perspective view.

[0011] In a manufacturing method of an alloy ribbon according to one embodiment, first, as shown in FIG. 1(a), an alloy ribbon 10 is prepared (preparation step). Then, the alloy ribbon 10 is placed between a bottom surface (heating surface) Ub of an upper mold for heat treatment U and an upper surface (support surface) Lt of a lower mold for heat treatment L (first placement step). The alloy ribbon 10 is an alloy ribbon containing an FeNiB-based amorphous alloy. The upper mold for heat treatment U 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. A heater (not shown) capable of setting a heating temperature for each portion of the bottom surface Ub is installed inside the upper mold for heat treatment U. On the bottom surface Ub of the upper mold for heat treatment U, the outer edge portion Uba and the inner edge portion Ubb are preheated by a heater at a temperature of 650°C to 700°C, and the central portion Ubc (the portion of the bottom surface Ub excluding the outer edge portion Uba and the inner edge portion Ubb) is preheated by a heater at a temperature of 490°C to 520°C. The outer edge portion Uba, the inner edge portion Ubb, and the central portion Ubc on the bottom surface Ub of the upper mold for heat treatment U have the same shapes and dimensions as the outer peripheral processing portion 10a, the inner peripheral processing portion 10b, and the crystallization portion 10c, respectively, when the alloy ribbon 10 is viewed in a plan view from the thickness direction. On the other hand, the lower mold for heat treatment L is a plate-shaped mold on whose upper surface Lt the alloy ribbon 10 is placed.

[0012] Next, as shown in FIG. 1(b), the alloy ribbon 10 is placed on the upper surface Lt of the lower mold for heat treatment L in the atmosphere at room temperature. In this state, the annular portion to be crystallized 10c of the alloy ribbon 10, which is the region where the alloy ribbon piece will be punched out, as well as the annular outer peripheral portion to be processed 10a around the outer periphery of the portion to be crystallized 10c and the annular inner peripheral portion to be processed 10b around the inner periphery of the portion to be crystallized 10c, are sandwiched between the bottom surface Ub of the upper mold for heat treatment U and the upper surface Lt of the lower mold for heat treatment L. At this time, the outer edge portion Uba, the inner edge portion Ubb, and the central portion Ubc of the bottom surface Ub of the upper mold for heat treatment U are pressed against the outer periphery portion to be processed 10a, the inner periphery portion to be processed 10b, and the portion to be crystallized 10c of the alloy ribbon 10, respectively, for a predetermined time (e.g., 3 seconds). In this way, the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b of the alloy ribbon 10 are heated and maintained in a first temperature range of 600°C to 650°C (first temperature range where αFe crystal grains and FeB crystal grains precipitate), while the crystallization planned portion 10c is heated and maintained in a second temperature range of 470°C to 500°C (second temperature range above the crystallization start temperature and below the first temperature range) (heat treatment step). This promotes crystallization of the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b of the alloy ribbon 10, causing coarse αFe crystal grains and FeB crystal grains to precipitate densely. At the same time, the portion 10c of the alloy ribbon 10 to be crystallized is crystallized, and nanocrystalline grains of αFe are precipitated, thereby generating a crystallized portion 10c' (shown in Figure 2(a)) in which the amorphous alloy of the portion 10c to be crystallized is transformed into a nanocrystalline alloy.

[0013] Next, as shown in FIG. 2(a), the alloy ribbon 10 after the rapid heat treatment is placed between the bottom surface (punch surface) Pb of a punch (upper die) P and the top surface (support surface) Dt of a die (lower die) D (second placement process). The punch P is a die having a roughly cylindrical shape with a cylindrical through-hole Ph in the center and a bottom surface Pb having a circular ring shape. The die D is a die having a die hole Dh through which the punch P enters from the top surface Dt side. The die hole Dh is a hole that penetrates in a direction perpendicular to the top 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, respectively, by a clearance. 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 fit inside the outer edge 10ap and inner edge 10an of the outer peripheral processing target portion 10a of the alloy ribbon 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 fit inside the outer edge 10bp and inner edge 10bn of the inner peripheral processing target portion 10b of the alloy ribbon 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 inner edge 10an of the outer peripheral processing target portion 10a of the alloy ribbon 10. In addition, 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 dimensions between the diameter of the outer edge 10bp of the inner peripheral processing target portion 10b of the alloy ribbon 10 and the diameter of the inner edge 10bn.

[0014] 2(b), the alloy ribbon 10 is sandwiched between the bottom surface Pb of the punch P and the top surface Dt of the die D and punched. At this time, the punch P and the die D are pressed against the alloy ribbon 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 come into contact with the outer peripheral portion 10a of the alloy ribbon 10 to be processed, 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 come into contact with the inner peripheral portion 10b of the alloy ribbon 10 to be processed. In this way, after the heat treatment step, the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b of the alloy ribbon 10 are sheared at a position away from the boundary with the crystallization planned portion 10c (the inner edge 10an of the outer peripheral processing planned portion 10a and the outer edge 10bp of the inner peripheral processing planned portion 10b), thereby punching out a region including the crystallized portion 10c' (the crystallization planned portion 10c) and parts of the crystallized portion 10c' side of the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b from the alloy ribbon 10. As a result, as shown in FIG. 3(a), an alloy ribbon piece 1 including the crystallized portion 10c' containing a nanocrystalline alloy and parts of the crystallized portion 10c' side of the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b is formed (punching step). In this way, an alloy ribbon piece 1 containing a nanocrystalline alloy is manufactured. In the manufacturing method of a stator core using alloy ribbon flakes according to one embodiment, a plurality of alloy ribbon flakes 1 manufactured by the manufacturing method of alloy ribbon flakes according to one embodiment are stacked and fixed together via an adhesive layer (not shown) made of heat-resistant resin or the like, as shown in Fig. 3(b). In this way, a stator core 2 including a stack of alloy ribbon flakes 1 is manufactured.

[0015] In one embodiment of the method for manufacturing an alloy ribbon flake, in the heat treatment step, crystallization of the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b of the alloy ribbon 10 is advanced, causing coarse αFe crystal grains and FeB crystal grains to precipitate densely. At the same time, the crystallization planned portion 10c of the alloy ribbon 10 is crystallized, causing αFe nanocrystal grains to precipitate, thereby generating a crystallized portion 10c' in which the amorphous alloy of the crystallization planned portion 10c is transformed into a nanocrystalline alloy. As a result, in the punching step following the heat treatment step, unlike an amorphous alloy ribbon or a nanocrystalline alloy ribbon, interfaces between crystal grains in a structure in which both coarse αFe crystal grains and FeB crystal grains are densely precipitated can serve as starting points for plastic deformation in the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b of the alloy ribbon 10, and the hardness is low. Therefore, when punching out a region including the crystallized portion 10c' (the portion to be crystallized 10c) from the alloy ribbon 10 by shearing the outer peripheral processing planned portion 10a and the inner peripheral processing planned portion 10b of the alloy ribbon 10, shearing can be easily carried out. Furthermore, it is possible to form alloy ribbon flakes 1 including the crystallized portion 10c' containing a nanocrystalline alloy that can achieve both high magnetization and low coercivity. Therefore, according to the manufacturing method of alloy ribbon flakes of one embodiment, it is possible to easily manufacture alloy ribbon flakes 1 containing a nanocrystalline alloy that can achieve both high magnetization and low coercivity by punching the alloy ribbon 10. Furthermore, this can reduce wear on the molds (punch and die) used for punching, thereby improving the productivity of the alloy ribbon flakes 1.

[0016] Next, the configuration of the method for manufacturing alloy ribbon flakes according to the embodiment will be described in detail.

[0017] 1. Preparation process In the preparation step, an alloy ribbon containing an FeNiB-based amorphous alloy is prepared.

[0018] The alloy ribbon is not particularly limited as long as it contains an FeNiB-based amorphous alloy. For example, it is a continuous sheet-like amorphous alloy ribbon produced by a general method such as the single-roll method or the 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 preferable. Specifically, for example, a composition represented by the following general formula (1) and the like are preferable.

[0019] Fe 100-x-y-z-w B x Ni y Si z M w (1) (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 are in atomic %, satisfying the conditions of 12 ≤ x ≤ 17, 1 ≤ y ≤ 3, 0 < z ≤ 1, and 0 < w ≤ 0.1.)

[0020] The thickness of the alloy ribbon is not particularly limited. For example, it is within the range of 10 μm or more and 100 μm or less, and particularly preferably within the range of 20 μm or more and 50 μm or less.

[0021] 2. Heat treatment process In the heat treatment process, in the above alloy ribbon, the processing planned part around the crystallization planned part, which is the area where the above alloy ribbon piece is punched out, is heated to the first temperature range where crystal grains of αFe and crystal grains of Fe2B precipitate, so that crystal grains of αFe and crystal grains of Fe2B precipitate. At the same time, the crystallization planned part is heated to the second temperature range above the crystallization start temperature and below the above first temperature range to cause crystallization.

[0022] Here, the "portion to be crystallized" refers to a portion that will become the region (alloy ribbon piece) that will be punched out of the alloy ribbon in the punching process, and may be a portion included in the punched region. Furthermore, the "portion to be processed" refers to a portion surrounding the portion to be crystallized, extending a predetermined width outward from the edge of the portion to be crystallized. The width of the portion to be processed is not particularly limited as long as no damage such as cracks that would cause quality problems occurs during punching in the punching process, but a width of 1 mm or more is preferable, for example. This is because having a width equal to or greater than this lower limit can effectively prevent damage such as cracks. The width of the portion to be processed is preferably as small as possible. This is because increasing the proportion of the portion to be crystallized that will be crystallized in the region that will be punched out of the alloy ribbon in the punching process can improve the magnetic properties of the alloy ribbon piece. Here, the "width of the portion to be processed" refers to the dimension in the direction perpendicular to the edge of the portion to be processed.

[0023] The "crystallization onset temperature" refers to the temperature at which crystallization of an alloy ribbon containing an FeNiB-based amorphous alloy starts when the alloy ribbon is heated. The crystallization of the alloy ribbon means the precipitation of crystal grains of αFe (ferrite phase). The crystallization onset 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, the crystallization onset temperature is 350°C or higher and 500°C or lower.

[0024] The first temperature range is not particularly limited as long as it is a temperature range in which both αFe crystal grains and Fe2B crystal grains are precipitated, and 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, a temperature range of 600°C or higher and 650°C or lower is preferable. This is because both αFe crystal grains and Fe2B crystal grains can be densely precipitated. Note that "precipitating αFe crystal grains and Fe2B crystal grains by heating the portion to be processed to the first temperature range in which αFe crystal grains and Fe2B crystal grains are precipitated" refers to heating the portion to be processed to the first temperature range and holding it in the first temperature range for the time required for precipitation of αFe crystal grains and Fe2B crystal grains. The time for which the portion to be processed is held in the first temperature range is not particularly limited as long as it allows αFe crystal grains and FeB crystal grains to precipitate in the portion to be processed so as not to cause damage such as cracking during punching, but is preferably, for example, in the range of 2 seconds to 4 seconds. This is because, by being above the lower limit of these ranges, αFe crystal grains and FeB crystal grains can be densely precipitated in the portion to be processed. This is because, by being below the upper limit of these ranges, coarsening of αFe crystal grains can be suppressed.

[0025] The second temperature range is not particularly limited as long as it is a temperature range equal to or higher than the crystallization onset temperature and lower than the first temperature range. However, a temperature range equal to or higher than the crystallization onset temperature and lower than the compound phase precipitation onset temperature is preferred. This is because compound phase precipitation can be suppressed. Here, the "compound phase precipitation onset temperature" refers to the temperature at which compound phase precipitation starts when the alloy ribbon is further heated after the start of crystallization. Furthermore, the "compound phase" refers to, for example, a compound phase that precipitates when the alloy ribbon is further heated after the start of crystallization and deteriorates the soft magnetic properties, and includes various phases in addition to the above-mentioned Fe2B. The temperature range of the second temperature range varies depending on the composition of the FeNiB-based amorphous alloy. For example, when the composition of the FeNiB-based amorphous alloy is the preferred composition described above, a temperature range of 470°C to 500°C is preferred. This is because αFe nanocrystalline grains can be stably precipitated, and coarsening of crystal grains and precipitation of compound phases can be suppressed. The phrase "crystallizing the portion to be crystallized by heating it to a second temperature range equal to or higher than the crystallization onset temperature but lower than the first temperature range" refers to crystallizing the portion to be crystallized by heating it to the second temperature range and holding it there for the time required for crystallization. The time for holding the portion to be crystallized in the second temperature range is not particularly limited as long as it allows αFe nanocrystal grains to precipitate in the portion to be crystallized so as to achieve both high magnetization and low coercivity. However, for example, a time similar to the time for holding the portion to be processed in the first temperature range is preferred, specifically, a time in the range of 2 to 4 seconds is preferred. By holding the time at or above the lower limit of these ranges, αFe nanocrystal grains can be stably precipitated in the portion to be crystallized. By holding the time at or below the upper limit of these ranges, coarsening of αFe crystal grains can be suppressed.

[0026] The method for heating the portion to be processed to a first temperature range to precipitate αFe grains and FeB grains while simultaneously heating the portion to be crystallized to a second temperature range to crystallize the portion to be crystallized is not particularly limited. For example, as in one embodiment, the portion to be processed and the portion to be crystallized in the alloy ribbon are sandwiched between the heating surface of an upper heat treatment mold and the support surface of a lower heat treatment mold in air at room temperature. In this method, the lower heat treatment mold is not preheated, but the edge and center of the heating surface of the upper heat treatment mold are preheated. Then, the portion to be processed and the portion to be crystallized in the alloy ribbon are sandwiched between the heating surface of the upper heat treatment mold and the support surface of the lower heat treatment mold, and the edge and center of the heating surface of the upper heat treatment mold are pressed against the portion to be processed and the portion to be crystallized in the alloy ribbon, respectively, for a predetermined time. Note that "room temperature" refers to, for example, a temperature specified in JIS Z 8703.

[0027] In the heat treatment process, the portion to be processed is heated to a first temperature range to precipitate αFe crystal grains and FeB crystal grains in the portion to be processed. In this case, the portion to be processed preferably has low hardness because dense precipitation of αFe crystal grains and FeB crystal grains allows the interfaces between the crystal grains to serve as the starting points for plastic deformation. Furthermore, the portion to be crystallized is heated to a second temperature range to crystallize the portion to be crystallized, resulting in a crystallized portion containing a nanocrystalline alloy. In this case, the crystallized portion preferably has desired magnetic properties (high magnetization and low coercivity) by precipitating αFe nanocrystal grains without substantially causing precipitation of compound phases or coarsening of the crystal grains. The grain size of the αFe crystal grains in the crystallized portion is not particularly limited as long as the desired magnetic properties are obtained, but is preferably within the range of 25 nm or less. This is because coarsening leads to a deterioration in coercivity. The grain size of the crystal grains can be measured, for example, by direct observation using a scanning electron microscope (SEM).

[0028] 3. Punching process In the punching step, after the heat treatment step, the portion to be processed of the alloy ribbon is sheared to punch out a region including the portion to be crystallized from the alloy ribbon, thereby forming the alloy ribbon piece. The punching step is not particularly limited as long as it is a step of shearing the portion to be processed to punch out a region including the portion to be crystallized from the alloy ribbon. For example, as in one embodiment, a step of shearing the portion to be processed at a position away from the boundary with the portion to be crystallized to punch out a region including the portion to be crystallized and a part of the portion to be processed on the side of the portion to be crystallized from the alloy ribbon is preferred. This is because damage such as cracking can be suppressed during punching.

[0029] The method for punching the planned crystallization portion from the alloy ribbon is not particularly limited, and examples thereof include a method of punching the alloy ribbon by sandwiching it between the punch face of the punch and the support face of the die, as in one embodiment. The punch and die are not particularly limited as long as they can punch out a region of the desired shape including the planned crystallization portion. However, as in one embodiment, for example, those having a shape and dimensions such that the edge of the punch face of the punch and the edge of the die hole of the die fit within the edge of the planned processing portion of the alloy ribbon are preferred. A preferred method of punching is, for example, as in one embodiment, to use such a preferred punch and die, and to press the punch and die against the alloy ribbon from both sides so that the edge of the punch face of the punch and the edge of the die hole contact the area of ​​the planned processing portion of the alloy ribbon, and then insert the punch into the die hole. This is because it is possible to punch out the planned crystallization portion and a region including a part of the planned processing portion side of the planned crystallization portion from the alloy ribbon, thereby suppressing damage such as cracking.

[0030] 4. Alloy ribbon manufacturing method and alloy ribbon The manufacturing method of the alloy ribbon flakes 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 flakes manufactured by the manufacturing method of the alloy ribbon flakes are not particularly limited as long as they include a crystallized portion to be crystallized (crystallized portion), but for example, like the alloy ribbon flakes manufactured in one embodiment, it is preferable that they include a part of the portion to be processed on the side of the portion to be crystallized together with the portion to be crystallized. [Example]

[0031] Hereinafter, the embodiments of the present invention will be described more specifically with reference to reference examples.

[0032] [DSC curve of FeNiB amorphous alloy] The FeNiB-based amorphous alloy contained in the alloy ribbon used in Reference Examples 1 and 2 was measured for its DSC curve using a differential scanning calorimeter (DSC). The FeNiB-based amorphous alloy used had a composition containing 83.7 atomic % Fe, 2 atomic % Ni, 13.5 atomic % B, and 0.8 atomic % Si, with the remainder being unavoidable impurities. The heating rate of the FeNiB-based amorphous alloy during measurement of the DSC curve was 100°C / min. Figure 4 is a graph showing the DSC curve of the FeNiB-based amorphous alloy contained in the alloy ribbon used in Reference Examples 1 and 2.

[0033] In the DSC curve shown in Fig. 4, the peak near 450°C is considered to be an exothermic peak of a crystallization reaction that precipitates nanocrystalline grains of αFe. Furthermore, the peak near 520°C is considered to be an exothermic peak of a crystallization reaction that precipitates FeB crystal grains. Therefore, in Reference Example 1 described later, 600°C was selected as the heating temperature at which the crystallization of the alloy ribbon was advanced to densely precipitate coarse αFe crystal grains and FeB crystal grains. Furthermore, in Reference Example 2 described later, 500°C was selected as the heating temperature at which the alloy ribbon was crystallized to precipitate nanocrystalline grains of αFe.

[0034] [Reference example 1] Crystallization and punching tests were conducted on the alloy ribbon. First, an alloy ribbon containing the FeNiB-based amorphous alloy described above was prepared. Next, in the atmosphere at room temperature, the surface of the alloy ribbon was pressed against the surface of a heating plate preheated to 650°C by a heater for 3 seconds, thereby performing rapid heat treatment to heat the alloy ribbon to 600°C and maintain the temperature. Next, as shown in FIG. 5(a), a punch (not shown) with a bottom surface (punch surface) and a die hole in a roughly rectangular shape with a clearance of 10 μm was used to punch out a roughly rectangular region from the heat-treated alloy ribbon. As a result, as shown in FIG. 5(a), a desired roughly rectangular metal ribbon piece was successfully punched out.

[0035] [Reference example 2] Crystallization and punching tests were conducted on the alloy ribbon. First, an alloy ribbon containing the same FeNiB-based amorphous alloy as in Reference Example 1 was prepared. Next, in the atmosphere at room temperature, the surface of the alloy ribbon was pressed against the surface of a heating plate preheated to 520°C by a heater for 3 seconds, thereby heating the alloy ribbon to 500°C and maintaining the temperature. Next, as shown in FIG. 5(b), a roughly rectangular region was punched out of the heat-treated alloy ribbon using the same punch (not shown) and die as in Reference Example 1. As a result, as shown in FIG. 5(b), the alloy ribbon cracked during punching, and the desired roughly rectangular metal ribbon piece could not be punched out.

[0036] [evaluation] X-ray diffraction measurements (XRD) were performed on the alloy ribbons after the heat treatments of Reference Examples 1 and 2, and the X-ray diffraction patterns were measured. FIG. 6(a) is a graph showing the X-ray diffraction patterns of the alloy ribbons after the heat treatments of Reference Examples 1 and 2. As shown in FIG. 6(a), in the X-ray diffraction pattern of the alloy ribbon after the heat treatment of Reference Example 1, peaks of the FeB phase can be confirmed in addition to peaks of the αFe phase. On the other hand, halo peaks derived from the amorphous alloy phase cannot be confirmed. In contrast, in the X-ray diffraction pattern of the alloy ribbon after the heat treatment of Reference Example 2, peaks of the αFe phase can be confirmed, but peaks of the FeB phase cannot be confirmed. On the other hand, halo peaks derived from the amorphous alloy phase can be confirmed. From the contents of these X-ray diffraction patterns, it is considered that the structure of the alloy ribbon after the heat treatment of Reference Example 1 is a mixed phase structure of the αFe phase and the FeB phase, with no amorphous alloy phase remaining. In contrast, it is believed that the structure of the alloy ribbon after the heat treatment in Reference Example 2 was a mixed phase structure of an amorphous alloy phase and an α-Fe phase.

[0037] Further, the alloy ribbon after the heat treatment of Reference Example 1 was subjected to microstructural observation by SEM. FIG. 6(b) shows microstructural images of the alloy ribbon after the heat treatment of Reference Example 1 observed by SEM at magnifications of 5,000 to 20,000. From the microstructural images at each magnification in FIG. 6(b), it can be confirmed that both coarse α-Fe crystal grains (white crystal grains) and FeB crystal grains (black crystal grains) are densely precipitated in the structure of the alloy ribbon after the heat treatment of Reference Example 1. On the other hand, although the alloy ribbon after the heat treatment of Reference Example 2 was not subjected to microstructural observation by SEM, it is considered from conventional knowledge that the structure is a mixed phase structure in which α-Fe nanocrystal grains are dispersed and precipitated in an amorphous alloy phase, as shown in FIG. 6(c).

[0038] Furthermore, 10 test pieces were cut out according to JIS Z2241 No. 13B standard from the alloy ribbons after the heat treatments of Reference Examples 1 and 2, and tensile tests were performed on the 10 test pieces to determine the average value of the upper yield point [MPa]. As a result, the average value (N=10) of the upper yield point determined for the test pieces of the alloy ribbon after the heat treatment of Reference Example 1 was 515.1 MPa. In contrast, the average value (N=10) of the upper yield point determined for the test pieces of the alloy ribbon after the heat treatment of Reference Example 2 was 907.8 MPa. From this, it is considered that the alloy ribbon after the heat treatment of Reference Example 1 is more susceptible to plastic deformation than the alloy ribbon after the heat treatment of Reference Example 2.

[0039] From the above results, it is believed that in the alloy ribbon after the heat treatment of Reference Example 1, as shown in the structural image of FIG. 6(b), the interfaces between the crystal grains in the structure in which both coarse α-Fe crystal grains and FeB crystal grains were densely precipitated served as the initiation points of plastic deformation, facilitating shearing along the edge of the bottom surface of the punch. As a result, it is believed that the desired approximately rectangular metal ribbon could be punched out without any problems. Furthermore, it is believed that such an alloy ribbon after the heat treatment can reduce wear on the punch and die. On the other hand, in the alloy ribbon after the heat treatment of Reference Example 2, as shown in FIG. 6(c), in the mixed-phase structure in which α-Fe nanocrystal grains were dispersed and precipitated in the amorphous alloy phase, the interfaces between the α-Fe nanocrystal grains and the amorphous alloy phase were dispersed and irregularly arranged. Therefore, it is believed that shearing along the edge of the bottom surface of the punch was difficult, even though the interfaces between the α-Fe nanocrystal grains and the amorphous alloy phase served as the initiation points of plastic deformation. It is believed that as a result, the alloy ribbon cracked during punching.

[0040] The above has described in detail the embodiments of the method for manufacturing alloy strip flakes of the present invention, but the present invention is not limited to the embodiments described above, and various design modifications can be made within the scope of the spirit of the present invention described in the claims. [Explanation of symbols]

[0041] 1: alloy strip, 10: alloy strip, 10a: outer peripheral processing target portion, 10b: inner peripheral processing target portion, 10c: crystallization target portion, U: heat treatment upper mold, L: heat treatment lower mold, P: punch (upper mold), D: die (lower mold)

Claims

1. A method for producing an alloy strip containing a nanocrystalline alloy, comprising: a preparation step of preparing an alloy ribbon containing an FeNiB-based amorphous alloy; In the alloy ribbon, a processing target portion around a crystallization target portion, which is a region where the alloy ribbon piece is punched, is formed by crystallizing αFe grains and Fe ２ By heating to the first temperature range where B crystal grains precipitate, αFe crystal grains and Fe ２ a heat treatment step of precipitating crystal grains of B and simultaneously crystallizing the portion to be crystallized by heating the portion to be crystallized to a second temperature range that is equal to or higher than the crystallization start temperature and lower than the first temperature range; a punching step, after the heat treatment step, of punching out a region including the portion to be crystallized from the alloy ribbon by shearing the portion to be processed of the alloy ribbon, thereby forming the alloy ribbon piece; A method for manufacturing an alloy strip, comprising:

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

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