Iron-based crystal alloy production method

Abstract

Provided is an iron-based crystal alloy production method comprising: a step for preparing an (Fe,Co)-B-based molten alloy 3 that has a composition represented by the empirical formula (Fe1-yCoy)100-x(B1-zCz)x, where x, y and z satisfy the conditions 10.0≤x≤18.0 at%, 0.05≤y≤0.5, and 0.0≤z≤0.3, respectively; and a rapid solidification step for rapidly solidifying the molten alloy 3 on a cooling roller 8, said rapid solidification step comprising a step for fabricating an iron-based crystal alloy 9 such that the proportion of an α-Fe phase is at least 50 vol% and less than 95 vol% and the remainder is composed of an Fe-B phase by jetting the molten alloy 3 from a tapping nozzle 6 onto the surface of the cooling roller 8 while rotating the cooling roller 8 at a roller surface speed of at least 15 m / sec and at most 40 m / sec. The iron-based crystal alloy is formed in a thin ribbon shape having a thickness of at most 50 µm, and has a saturation magnetic flux density of at least 1.7 T, an iron loss (W10 / 1k) at a magnetic flux of 1.0 T and a frequency of 1 kHz of at most 20 W / kg, and a magnetic permeability at 1 kHz of at least 1500. The arithmetic average roughness of the surface of the cooling roller 8 is at least 0.01 µm and at most 0.6 µm.

Description

Method for producing iron-based crystalline alloy

[0001] The present invention relates to a method for producing an iron-based crystalline alloy, and more particularly to a method for producing an iron-based crystalline alloy that can be suitably used as a core material for a DC motor.

[0002] In recent years, the market has been demanding materials with low iron loss and high saturation magnetic flux density for various passive elements and transformers used as electronic components, such as inductors and reactors. Iron-based amorphous materials and iron-based nanocrystalline materials, which are primarily made from iron (Fe), silicon (Si), and boron (B), are known as such materials. Demand for Fe-Si-B amorphous alloy ribbons with thicknesses of approximately 17 to 25 μm, which are produced using such soft magnetic materials by the molten metal rapid solidification method, is growing, primarily for use in large transformers and inductors, as an alternative to conventional silicon steel sheets.

[0003] Furthermore, because the Fe-Si-B amorphous alloy ribbons mentioned above have lower iron loss than silicon steel sheets, it is being considered to utilize this feature to apply them to the rotor cores and stator cores of brushless direct current (BLDC) motors to improve motor efficiency. In particular, when used in high-speed BLDC motors exceeding 20,000 rpm, high motor efficiency can be achieved because the operating range of soft magnetic materials is in the high-frequency band of around 2 kHz, so it is expected to be used in white goods such as vacuum cleaners and auxiliary motors for electrical equipment, which require high-speed motor rotation.

[0004] Meanwhile, drive motors for EVs, which require even higher efficiency than motors for white goods, cannot obtain the required output unless they can secure a saturation magnetic flux density (Bs) equivalent to that of silicon steel sheet, but the maximum Bs of Fe-Si-B amorphous alloys is around 1.6 T, making it difficult to replace silicon steel sheets with a Bs of 1.7 T or more. For this reason, there have been no examples to date of EV drive BLDC motors using Fe-Si-B amorphous alloys being brought to market.

[0005] BLDC motors for EV drives in the tens of kilowatts class or larger have traditionally been developed to achieve high efficiency by combining silicon steel sheet core material with anisotropic rare earth iron boron sintered magnets, which offer excellent permanent magnetic properties, to utilize magnet torque. However, silicon steel sheet, which has low magnetic permeability, cannot fully utilize the excellent magnetic properties of anisotropic rare earth iron boron sintered magnets, making it difficult to achieve a low iron loss core material. For this reason, there is extremely high market demand for high-output, high-efficiency BLDC motors that can contribute to energy savings in automobiles through the synergistic effect of effectively utilizing permanent magnet performance and reducing iron loss in the core material.

[0006] Fe-Si-B amorphous alloys have higher magnetic permeability than silicon steel sheets and can reduce iron loss to approximately one-tenth of that of silicon steel sheets. Therefore, they are being considered as a potential replacement for silicon steel sheets as the core material for BLDC motors for electric vehicle (EV) drives. However, due to their low saturation magnetic flux density (Bs) as mentioned above, they are primarily used in high-speed BLDC motors (over 15,000 rpm), where the impact of iron loss is significant. Their application to EV drive motors (with rotational speeds of less than 15,000 rpm) is difficult. Furthermore, Fe-Si-B amorphous alloy ribbons are thin (approximately 25 μm), making it difficult to stamp them using a punch press to manufacture laminated cores for rotor and stator cores in BLDC motors. Therefore, their use is limited primarily to wound cores, making it difficult to replace silicon steel sheets in motor applications.

[0007] On the other hand, Fe-Si-B nanocrystalline materials are prone to cracking and chipping, so they can only be used as wound cores or crushed and then molded into powder cores, and like Fe-Si-B amorphous alloys, they are difficult to use as laminated cores.

[0008] To obtain an Fe-Si-B amorphous structure or nanocrystalline structure, it is necessary to add Si and B, and to form a nanocrystalline structure, additional elements such as Cu and Nb are required, which results in a decrease in the Fe composition ratio, making it impossible to obtain Bs ≥ 1.7 T. For this reason, no iron-based alloy has been found to date that can be easily fabricated into a laminated core and that can ensure Bs ≥ 1.7 T.

[0009] For example, Non-Patent Document 1 discloses that the addition of phosphorus (P) reduces the rapid solidification rate and allows the production of an iron-based amorphous alloy ribbon with a thickness of 50 μm or more. However, phosphorus-added alloys not only cause a decrease in Bs due to the addition of phosphorus, but also volatilize the phosphorus component during alloy melting, causing significant contamination inside and outside of a molten metal quenching device, and are also flammable, so there are still few examples of their application in the industrial field.

[0010] Patent Documents 1 to 3 disclose methods for producing amorphous alloy ribbons having a thickness (e.g., about 50 μm) that allows for punching by using a multiple-slit method in which molten alloy is poured from multiple slit nozzles onto a rotating chill roll. However, even with this technology, it is difficult to achieve Bs≧1.7T, making it difficult to apply this material as a soft magnetic material for laminated cores in BLDC motors for EV drives, replacing silicon steel sheets.

[0011] Patent Document 4 discloses a method for manufacturing a metal ribbon using a multi-hole nozzle to prevent the thickness of the metal ribbon from becoming non-uniform when a wide quenched ribbon is produced. The invention of Patent Document 4 is characterized by the shape of the nozzle opening, but there is a problem that the nozzle processing cost rises due to the difficulty of processing, and it is difficult to use on a mass production level.

[0012] Patent Document 5 discloses a method for producing an iron-based silicon-boron amorphous alloy using a discharge nozzle with a staggered multi-orifice arrangement to produce thick plates. However, compared to silicon steel plates, it is difficult to ensure a high Bs and a sufficient thickness.

[0013] Patent Document 6 discloses an Fe-Si-B based rapidly solidified alloy that can be made into a laminated core and that is characterized by a high Bs of Bs≧1.7T and a thickness of ≧40 μm. The invention of Patent Document 6 optimizes the compounding ratio of each element in the ternary composition of the essential elements iron, silicon, and boron, but the workability of the punching press used to manufacture a laminated core from the resulting alloy ribbon is inferior to that of silicon steel sheet, leaving room for further improvement in terms of manufacturing laminated cores at low cost.

[0014] JP 5-329587, JP 7-113151, JP 8-124731, JP 63-220950, JP 2018-153828, JP 2021-193199

[0015] Creation of new bulk metallic glasses / amorphous thick plates with high saturation magnetic flux density (Tohoku University, Metallic Glass Research Center) Akihiro Makino, Ken Kubota, and Tono Haruta

[0016] An object of the present invention is to provide a method for producing an iron-based crystalline alloy that can be easily punched while ensuring low core loss and high saturation magnetic flux density.

[0017] The object of the present invention is to provide a compound having the composition formula (Fe 1-y Co y ) 100-x (B 1-z C z ) x and a rapid solidification step of rapidly solidifying the molten alloy on a chill roll, the rapid solidification step being performed by rotating the chill roll at a roll surface speed of 15 m / sec or more and 40 m / sec or less, and ejecting the molten alloy from a single-slit nozzle onto the surface of the chill roll, thereby producing a molten alloy having an α-Fe phase content of 50 vol % or more and less than 95 vol %, and the remainder being Fe-B. The present invention is achieved by a method for producing an iron-based crystalline alloy comprising a phase, the method comprising the steps of: preparing an iron-based crystalline alloy comprising a phase; and forming the iron-based crystalline alloy into a ribbon shape having a thickness of 50 μm or less, a saturation magnetic flux density of 1.7 T or more, an iron loss (W10 / 1k) of 20 W / kg or less at a magnetic flux of 1.0 T and a frequency of 1 kHz, and a magnetic permeability of 1500 or more at 1 kHz. The present invention is also achieved by a method for producing an iron-based crystalline alloy comprising a phase; the method comprising the steps of: preparing an iron-based crystalline alloy comprising a phase;

[0018] In this method for producing an iron-based crystalline alloy, the molten metal tapping nozzle preferably has a slit width of 0.2 mm or more and 0.7 mm or less.

[0019] It is also preferable that the distance from the melt discharge nozzle to the surface of the chill roll is 0.2 mm or more and 5.0 mm or less.

[0020] According to the present invention, it is possible to provide a method for producing an iron-based crystalline alloy that can easily be punched while ensuring low core loss and high saturation magnetic flux density.

[0021] 1 is a schematic diagram of an apparatus used in a method for producing a ribbon-shaped iron-based crystalline alloy according to one embodiment of the present invention. FIG. 2 is an enlarged view showing a main part of the apparatus shown in FIG. 1, where (a) is a cross-sectional view and (b) is a bottom view. FIG. 3 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in one example of the present invention. FIG. 4 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in another example of the present invention. FIG. 5 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in yet another example of the present invention. FIG. 6 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in a comparative example of the present invention.

[0022] [Alloy Composition] To improve the punching workability of an iron-based alloy, it is necessary to make it into a crystalline structure rather than an amorphous structure which is hard and easily broken. The iron-based crystalline alloy composition of the present invention is based on an Fe-B binary alloy composition, with part of the Fe replaced by Co, which is also a ferromagnetic element like Fe, and has the composition formula (Fe 1-y Co y ) 100-x (B 1-z C z ) x It is expressed as:

[0023] If the substitution ratio of Co for Fe is too low, it becomes difficult to achieve Bs≧1.7T, so the y in the above composition formula must be 0.05 or greater. As the value of y increases, the Bs of the iron-based crystalline alloy increases monotonically up to y=0.5. However, if the value of y exceeds 0.5, Bs does not increase and the use of Co, an expensive element, increases production costs. For this reason, 0.05≦y≦0.5 is required, and from the perspective of achieving a high Bs, 0.1≦y≦0.5 is preferred. Taking production costs into consideration, 0.15≦y≦0.4 is even more preferred.

[0024] In the iron-based crystalline alloy of the present invention, B is an essential element for obtaining low core loss and high magnetic permeability, and plays a role in forming a uniform fine structure consisting of the α-Fe phase and the Fe-B phase. A part of B may be replaced with C, which lowers the melting point of the molten alloy, thereby easing the rapid solidification conditions and facilitating the production of the iron-based crystalline alloy.

[0025] However, if the substitution ratio of C to B is too high, Fe-C compounds are generated, making it difficult to obtain a uniform and fine crystalline structure consisting of an α-Fe phase and an Fe-B phase. Therefore, z in the above composition formula is 0.0≦z≦0.3, and from the viewpoint of maintaining high Bs characteristics, 0.0≦z≦0.2 is preferable, and 0.05≦z≦0.15 is more preferable.

[0026] If the proportions of B and C relative to the overall composition of the iron-based crystalline alloy are too low, coarse α-Fe phases that become crack initiation points during punching press are likely to precipitate, while if the proportions of B and C relative to the overall composition of the iron-based crystalline alloy are too high, the volume ratio of the Fe-B phase increases and the volume ratio of the α-Fe phase decreases, making it difficult to ensure Bs ≥ 1.7 T. For this reason, x in the above composition formula is 10.0 ≤ x ≤ 18.0 atomic %, preferably 11.0 ≤ x ≤ 17.0 atomic %, and more preferably 12.0 ≤ x ≤ 16.0 atomic %.

[0027] [Metal Structure] The iron-based crystalline alloy of the present invention is an (Fe,Co)-B-based iron-based crystalline alloy having a composite structure of α-Fe and Fe-B phases. Its magnetic and mechanical properties significantly contribute to improving the efficiency of BLDC motors. If the α-Fe phase content is too low, it becomes difficult to achieve Bs ≥ 1.7 T. On the other hand, if it is too high, coarse α-Fe particles of approximately 10 μm or larger are likely to precipitate, which may serve as the starting point for cracks during punching presses, and may also increase core loss and reduce magnetic permeability. Therefore, the α-Fe phase content is 50% by volume or more but less than 95% by volume, preferably 60% by volume or more but less than 90% by volume, and more preferably 60% by volume or more but less than 85% by volume. The Fe-B phase is the remainder of the α-Fe phase and is primarily composed of FeB and FeB. As described below, the content and grain size of the α-Fe phase can be adjusted to desired values ​​by controlling the quenching rate of the molten alloy. The average crystal grain size of the α-Fe phase is preferably 2 nm to 20 nm, and can be determined from the half-width of the X-ray diffraction peak by powder X-ray diffraction (XRD) as described below.

[0028] [Magnetic Properties] The saturation magnetic flux density of the iron-based crystalline alloy of the present invention is Bs≧1.7T, but when considering application to a BLDC motor for driving an EV of 30kW or more, Bs≧1.72T is preferable, and Bs≧1.75T is even more preferable.

[0029] Furthermore, the iron-based crystalline alloy of the present invention has an iron loss (W10 / 1k) of ≦20 W / kg at a magnetic flux of 1.0 T and a frequency of 1 kHz, which is significantly lower than the iron loss (W10 / 1k): 96.6 W / kg of silicon steel plate (JIS standard 35A360). If the iron loss (W10 / 1k) exceeds 20 W / kg, the improvement effect on motor efficiency decreases. To further enhance the improvement effect on motor efficiency, the iron loss (W10 / 1k) is preferably ≦15 W / kg, and more preferably ≦10 W / kg.

[0030] The iron-based crystalline alloy of the present invention has a magnetic permeability of 1500 or more at 1 kHz. If the magnetic permeability at 1 kHz is lower than 1500, the advantage over silicon steel sheet is reduced in terms of the amount of magnetic flux on the surface of the teeth in the stator core. To further enhance the advantage over silicon steel sheet, the magnetic permeability at 1 kHz is preferably 2000 or more, and more preferably 3000 or more.

[0031] [Method for producing iron-based crystalline alloy] The iron-based crystalline alloy of the present invention is produced by a method for producing an iron-based crystalline alloy, which includes a step of preparing a molten (Fe, Co)-B-based alloy having the above-described composition, and a step of rapidly solidifying the prepared molten alloy.

[0032] Fig. 1 is a schematic diagram of a single-roll molten metal quenching apparatus used in a manufacturing method of an iron-based crystalline alloy according to one embodiment of the present invention. The single-roll molten metal quenching apparatus 1 shown in Fig. 1 includes a melting furnace 2, a molten metal storage vessel 5, and a cooling roll 8.

[0033] The melting furnace 2 supplies molten alloy 3, obtained by melting raw materials using high-frequency induction heating, to a storage container 5 by rotating a tilting shaft 4. The storage container 5 is equipped with a tapping nozzle 6 at its bottom. The molten alloy 3 is further heated by a heating coil (not shown) and ejected onto the surface (outer periphery) of a chill roll 8 through a slit 7 formed at the bottom end of the tapping nozzle 6. Cooling water is supplied to the chill roll 8, which rapidly cools the molten alloy that comes into contact with its surface, forming a thin ribbon of rapidly solidified (Fe, Co)-B alloy 9. The material of the tapping nozzle 6 can be appropriately selected from quartz (SiO2), boron nitride (BN), silicon carbide (SiC), and alumina (Al2O3), for example.

[0034] FIG. 2 is an enlarged view of the tapping nozzle 6 of the apparatus shown in FIG. 1 , with (a) being a cross-sectional view and (b) being a bottom view. The tapping nozzle 6 shown in FIG. 2(a) is a single-slit nozzle with a single slit 7. The width W1 of the slit 7 serves to adjust the tapping rate of the molten alloy 3 supplied to the chill roll 8. If the slit width W1 is too small, slit processing becomes difficult and the slit 7 is likely to be blocked by the molten alloy. On the other hand, if the slit width W1 is too large, the tapping rate becomes too high, preventing heat removal by the chill roll 8 in time. This causes the rapidly solidified alloy to stick to the chill roll 8, making it difficult to maintain stable rapid solidification of the molten alloy. Therefore, the slit width W1 is 0.2 mm to 0.7 mm. The slit width W1 is preferably 0.3 mm to 0.6 mm, and more preferably 0.3 mm to 0.5 mm.

[0035] The molten metal supplied to the surface of the chill roll 8 becomes a thin ribbon of rapidly solidified alloy 9 as the chill roll 8 rotates, and is then peeled off from the chill roll 8. If the surface speed of the chill roll 8 is too low, the (Fe,Co)-B-based rapidly solidified alloy becomes excessively thick, exceeding 50 μm, resulting in the precipitation of a coarse α-Fe phase, which is prone to cracking during punching. On the other hand, if the surface speed of the chill roll 8 is too high, the (Fe,Co)-B-based crystalline alloy becomes too fine, reducing the proportion of the α-Fe phase, making it difficult to ensure Bs≧1.7T. For this reason, the surface speed of the chill roll 8 is 15 m / sec or more and 40 m / sec or less, preferably 15 m / sec or more and 35 m / sec or less, and more preferably 17 m / sec or more and 32 m / sec or less. The diameter of the chill roll 8 is, for example, 200 to 20,000 mm. The chill roll 8 does not necessarily need to be water-cooled if the rapid solidification time is short, 10 seconds or less, but if the rapid solidification time is 10 seconds or longer, it is preferable to suppress the temperature rise on the surface of the chill roll 8 by running cooling water inside the chill roll 8. It is preferable to adjust the water-cooling capacity of the chill roll 8 appropriately depending on the latent heat of solidification per unit time and the melt pouring rate.

[0036] In producing the ribbon-shaped rapidly solidified alloy 9, the adhesion of the molten alloy 3 to the outer surface of the chill roll 8 is important, but this adhesion of the molten alloy is largely dependent on the surface roughness of the chill roll 8. If the surface roughness of the chill roll 8 is too small, the molten alloy 3 will slide on the surface of the chill roll 8, making it difficult to cool it sufficiently, while if the surface roughness of the chill roll 8 is too large, the quenched alloy may stick to the chill roll 8. For this reason, the arithmetic mean roughness (Ra) of the surface of the chill roll 8 is 0.01 μm or more and 0.6 μm or less, preferably 0.05 μm or more and 0.55 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less.

[0037] 1 , if the distance d from the tip of the molten alloy discharge nozzle 6 to the surface of the chill roll 8 is too small, the quenched alloy may stick to the chill roll 8, preventing stable rapid solidification of the molten alloy 3. If the distance d is too large, a puddle may not form on the surface of the chill roll 8, preventing rapid solidification of the molten alloy 3. For this reason, the distance d is 0.2 mm or more and 5.0 mm or less, preferably 0.3 mm or more and 3.0 mm or less, and more preferably 0.3 mm or more and 2.0 mm or less.

[0038] The chill roll 8 is preferably formed from a material whose main ingredient is pure copper, a copper alloy, molybdenum (Mo), or tungsten (W), thereby providing excellent thermal conductivity and durability. The term "main ingredient" refers to a material that accounts for 50% or more by weight. The surface of the chill roll 8 may be plated with chromium, nickel, or an alloy thereof, which increases the heat resistance and hardness of the chill roll 8 surface and prevents melting or deterioration of the roll surface during rapid solidification.

[0039] [Heat Treatment] In a preferred embodiment, heat treatment of a rapidly solidified (Fe,Co)-B alloy at a constant temperature of 200°C to 700°C enables strain removal in the rapidly solidified alloy, resulting in further reduction of iron loss. Heat treatment temperatures below 200°C are ineffective at removing strain, while temperatures above 700°C cause the α-Fe phase to coarsen, increasing the brittleness of the rapidly solidified alloy and making it more susceptible to cracking during punching. The heat treatment temperature is preferably 300°C to 700°C, more preferably 400°C to 680°C. The heat treatment time depends on the shape of the soaking zone of the heat treatment device, but an optimal heat treatment time is selected within a range of 3 minutes to less than 2 hours. The heat treatment is preferably performed in a vacuum or inert gas atmosphere, although heat treatment in air is also acceptable.

[0040] [Examples] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0041] 100 kg of raw materials containing B, C, Co, and Fe with a purity of 99.5% or higher were placed in an alumina crucible (melting furnace) and melted by high-frequency induction heating to form a molten alloy, so as to obtain the alloy compositions shown in Examples 1-11 and Comparative Examples 12-17 in Table 1 below. 50 kg of this molten alloy was poured into an alumina storage vessel with an inner diameter of 200 mm and a height of 400 mm, equipped at the bottom with a BN discharge nozzle having a slit as shown in Table 1. The slit width and length of the discharge nozzle are as shown in Table 1.

[0042] After this, 50 kg of molten alloy was further heated by passing electricity through the high-frequency heating coil installed around the molten alloy storage vessel. After the temperature of the molten alloy reached a temperature 100°C or higher than the melting point of the alloy composition, the alumina molten alloy stopper placed above the nozzle was removed. This caused the molten alloy to be ejected from the nozzle onto the surface of the chill roll directly below. The chill roll was made of chromium zirconium copper and had an outer diameter of 600 mm and a width of 200 mm. The gap between the nozzle and the chill roll surface was as shown in Table 1. The ejection pressure of the molten alloy from the nozzle, the surface speed of the chill roll, and the arithmetic mean roughness (Ra) of the chill roll surface were as shown in Table 2.

[0043] The molten alloy ejected onto the surface of the chill roll formed a puddle on the surface of the chill roll and was rapidly solidified at the interface between the puddle and the chill roll, yielding a ribbon-shaped rapidly solidified alloy having the average thickness and width shown in Table 3. For Example 3, the rapidly solidified alloy was subjected to a heat treatment at 650°C for 10 minutes in a flow of Ar. A punching test was conducted on the rapidly solidified alloy thus obtained, yielding the results shown in Table 3.

[0044] The rapidly solidified alloys obtained were subjected to structural evaluation using powder X-ray diffraction (XRD). The rapidly solidified alloys of Examples 1-11 were all crystalline alloys composed of α-Fe and Fe-B compounds. The volume percentage of α-Fe precipitated in the rapidly solidified alloys (determined by X-ray diffraction) is shown in Table 3. Quantitative analysis of the constituent phases using powder X-ray diffraction is a common evaluation method, and can be incorporated into the analysis software of an X-ray diffractometer to determine the composition ratio of each phase. Representative examples of powder X-ray diffraction profiles of the rapidly solidified alloys of the examples are shown in Figure 3 for Example 4 and Figure 4 for Example 9, respectively. As shown in Figures 3 and 4, the rapidly solidified alloys of Examples 4 and 9 had composite structures composed of α-Fe and Fe-B phases.

[0045] Table 4 shows the Bs, iron loss, and magnetic permeability of the as-spun (immediately after rapid solidification) and heat-treated rapidly solidified alloys of Examples 1-11 and Comparative Examples 12-17. Bs was measured using a vibrating sample magnetometer manufactured by Toei Kogyo Co., Ltd., and iron loss and magnetic permeability were measured using a BH analyzer manufactured by Iwasaki Electric Co., Ltd. As described above, only the rapidly solidified alloy of Example 3 was subjected to heat treatment. However, as shown in Figure 5, the powder X-ray diffraction profile of the rapidly solidified alloy of Example 3 also showed a composite structure consisting of an α-Fe phase and an Fe-B phase.

[0046] The rapidly solidified alloys of Comparative Examples 12-17 were evaluated by powder X-ray diffraction (XRD) to have an amorphous single-phase metal structure. Table 3 shows the volume percentage of α-Fe (the α-Fe abundance ratio determined by X-ray diffraction). Figure 6 shows a representative example of the powder X-ray diffraction profile of the rapidly solidified alloy of Comparative Example 12. As shown in Figure 6, the structure of the rapidly solidified alloy of Comparative Example 12 was an amorphous single-phase structure.

[0047]

[0048]

[0049]

[0050]

[0051] 1. Single roll molten metal quenching device 2. Melting furnace 3. Molten alloy 4. Tilting shaft 5. Melt storage container 6. Melt outlet nozzle 7. Slit 8. Cooling roll 9. Rapidly solidified alloy

Claims

1. Composition formula (Fe 1-y Co y ) 100-x (B 1-z C z ) x and a rapid solidification step of rapidly solidifying the molten alloy on a chill roll, the rapid solidification step including a step of spraying the molten alloy onto the surface of the chill roll from a single slit nozzle while rotating the chill roll at a roll surface speed of 15 m / sec or more and 40 m / sec or less, thereby producing an iron-based crystalline alloy in which the abundance ratio of α-Fe phase is 50 volume % or more and less than 95 volume %, and the remainder being Fe-B phase, The iron-based crystalline alloy is formed into a ribbon shape having a thickness of 50 μm or less, has a saturation magnetic flux density of 1.7 T or more, an iron loss (W10 / 1k) of 20 W / kg or less at a magnetic flux of 1.0 T and a frequency of 1 kHz, and a magnetic permeability of 1500 or more at 1 kHz, and the arithmetic mean roughness of the surface of the cooling roll is 0.01 μm or more and 0.6 μm or less.

2. The method for producing an iron-based crystalline alloy according to claim 1, wherein the molten metal outlet nozzle has a slit width of 0.2 mm or more and 0.7 mm or less.

3. The method for producing an iron-based crystalline alloy according to claim 1 or 2, wherein the distance from the molten metal discharge nozzle to the surface of the chill roll is 0.2 mm or more and 5.0 mm or less.

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