WO2025023038A1 - Iron-based crystal alloy production method - Google Patents

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 (Fe_1-yCo_y)_100-x(B_1-zC_z)_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

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

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, such as inductors and reactors used as electronic components. Such materials include iron-based amorphous materials and iron-based nanocrystalline materials, whose main raw materials are iron (Fe), silicon (Si), and boron (B). Demand for Fe-Si-B amorphous alloy ribbons with a thickness of about 17 to 25 μm, which are produced using such soft magnetic materials by the molten metal rapid solidification method, is growing as an alternative to conventional silicon steel sheets, mainly for use in large transformers and inductors.

In addition, since the Fe-Si-B amorphous alloy ribbons mentioned above have lower core loss than silicon steel sheets, it is being considered to take advantage of this feature and apply them to the rotor and stator cores of brushless direct current (BLDC) motors to improve motor efficiency. In particular, when used in high-speed BLDC motors that exceed 20,000 rpm, high motor efficiency can be obtained as the operating range of the soft magnetic material is in the high-frequency band of around 2 kHz, so it is expected that they will be used in white goods such as vacuum cleaners and auxiliary motors for electrical equipment, which require high-speed motor rotation.

On the other hand, drive motors for EVs, which require even higher efficiency than motors for white goods, cannot obtain the necessary output unless they have a saturation magnetic flux density (Bs) equivalent to that of silicon steel sheet. However, the maximum Bs of Fe-Si-B amorphous alloys is around 1.6 T, making it difficult to replace silicon steel sheets, which have 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 introduced to the market.

　In the past, BLDC motors for driving EVs in the tens of kW class or more have been made more efficient by combining silicon steel core material with anisotropic rare earth iron boron sintered magnets, which have excellent permanent magnetic properties, and utilizing magnet torque. However, silicon steel, 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.

Fe-Si-B amorphous alloys have a higher magnetic permeability than silicon steel sheets and can reduce iron loss to about one-tenth of that of silicon steel sheets, so they are being considered as a replacement for silicon steel sheets as a core material for BLDC motors for driving EVs. However, because of the low saturation magnetic flux density (Bs) mentioned above, they are mainly used in high-speed BLDC motors of 15,000 rpm or more, where the effects of iron loss become significant, and it is difficult to apply them to EV drive motors with rotation speeds of less than 15,000 rpm. In addition, Fe-Si-B amorphous alloy ribbons are thin, at about 25 μm, and it is difficult to perform punching press processing to manufacture laminated cores for rotor cores and stator cores of BLDC motors, so their use is limited mainly to wound cores, making it difficult to replace silicon steel sheets in motor applications.

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 pressed powder cores, and like Fe-Si-B amorphous alloys, they are difficult to use as laminated cores.

In order to obtain an Fe-Si-B system amorphous structure or nanocrystalline structure, it is necessary to add Si and B, and to obtain 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 ≧ 1.7T. For this reason, no iron-based alloy has been found to date that can be easily made into a laminated core and that can ensure Bs ≧ 1.7T.

For example, Non-Patent Document 1 discloses that the addition of phosphorus (P) reduces the rapid solidification rate, and an iron-based amorphous alloy ribbon with a thickness of 50 μm or more can be obtained. However, phosphorus-added alloys not only cause a decrease in Bs due to the addition of phosphorus, but also have the risk of serious contamination inside and outside the molten metal rapid cooling equipment due to the volatilization of phosphorus components during alloy melting, and are also flammable, so there are still few examples of their application in the industrial field.

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

Patent Document 4 discloses a method for manufacturing a metal ribbon that uses a multi-hole nozzle to prevent the thickness of the metal ribbon from becoming uneven when producing a wide quenched ribbon. The invention in Patent Document 4 is characterized by the shape of the nozzle opening, but there is a problem that the nozzle processing costs rise due to the difficulty of processing, making it difficult to use on a mass production level.

Patent Document 5 discloses a method for manufacturing an iron-based silicon boron amorphous alloy using a discharge nozzle with a staggered multi-orifice to produce thicker plates, but compared to silicon steel plates, it is difficult to ensure a high Bs and sufficient thickness.

Patent Document 6 discloses an Fe-Si-B rapidly solidified alloy that can be made into a laminated core and is characterized by a high Bs of Bs ≧ 1.7T and a thickness of ≧ 40μm. The invention in 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 laminated cores from the resulting alloy ribbon is inferior to that of silicon steel sheet, leaving room for further improvement in the manufacture of laminated cores at low cost.

Japanese Patent Application Publication No. 5-329587 Japanese Unexamined Patent Publication No. 7-113151 Japanese Patent Application Publication No. 8-124731 Japanese Unexamined Patent Publication No. 63-220950 JP 2018-153828 A JP 2021-193199 A

Creation of new bulk metallic glass/amorphous thick plates with high saturation magnetic flux density (Tohoku University, Metallic Glass Research Center) Akihiro Makino, Ken Kubota, Tono Chuntao

The present invention aims to provide a method for manufacturing an iron-based crystalline alloy that can be easily punched while ensuring low iron loss and high saturation magnetic flux density.

The object of the present invention is to provide a method for producing a molten alloy of an (Fe,Co)-B system, the molten alloy being expressed by a composition formula (Fe1 _{- yCoy} ) _100-x ( _{B1- zCz} ) _x , where x, y, and z satisfy 10.0≦x≦18.0 atomic %, 0.05≦y≦0.5, and 0.0≦z≦0.3, respectively, 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, so that the ratio of the α-Fe phase is 50 vol % or more and less than 95 vol %, and the balance being Fe-B and producing an iron-based crystalline alloy consisting of a ferromagnetic phase, the iron-based crystalline alloy being formed 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, a magnetic permeability of 1500 or more at 1 kHz, and an arithmetic mean roughness of the surface of the cooling roll being 0.01 μm or more and 0.6 μm or less.

In this method for producing an iron-based crystalline alloy, it is preferable that the slit width of the discharge nozzle is 0.2 mm or more and 0.7 mm or less.

It is also preferable that the distance from the molten metal nozzle to the surface of the cooling roll is 0.2 mm or more and 5.0 mm or less.

The present invention provides a method for producing an iron-based crystalline alloy that can be easily punched while ensuring low iron loss and high saturation magnetic flux density.

1 is a schematic diagram of an apparatus used in a method for producing a ribbon-shaped iron-based crystalline alloy according to an embodiment of the present invention. 2A and 2B are enlarged views showing the main parts of the device shown in FIG. 1, in which FIG. 1 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in one embodiment of the present invention. 1 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in another embodiment of the present invention. 1 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in still another example of the present invention. 1 is a powder X-ray diffraction profile of an iron-based crystalline alloy obtained in a comparative example of the present invention.

[Alloy composition]
To improve the punchability of iron-based alloys, it is necessary to make them crystalline rather than amorphous, which is hard and easily broken. The composition of the iron-based crystalline alloy of the present invention is based on a binary Fe-B alloy composition, with part of the Fe replaced by Co, which is a ferromagnetic element like Fe, and is expressed by the formula (Fe1 _{-yCoy ) 100-x} (B1 _{-zCz ) x} .

If the substitution rate of Co for Fe is too low, it becomes difficult to achieve Bs≧1.7T, so y in the above composition formula must be 0.05 or more. As the value of y increases, the Bs of the iron-based crystal alloy increases monotonically up to y=0.5, but when the value of y exceeds 0.5, Bs does not increase and only the manufacturing cost increases due to the use of Co, which is an expensive element. 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 preferable, and when considering manufacturing costs, 0.15≦y≦0.4 is even more preferable.

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, easing the rapid solidification conditions and making it easier to produce the iron-based crystalline alloy.

However, if the substitution rate of C for B is too high, Fe-C compounds are generated, making it difficult to obtain a uniform and fine crystal structure consisting of α-Fe phase and Fe-B phase. For this reason, 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 even more preferable.

If the proportions of B and C in the overall composition of the iron-based crystalline alloy are too low, coarse α-Fe phases that can become the starting points for cracks during punching presses are more likely to precipitate, while if the proportions of B and C in 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≧1.7T. 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 %.

[Metal structure]
The iron-based crystal alloy of the present invention is an (Fe,Co)-B-based iron-based crystal alloy having a composite structure of an α-Fe phase and an Fe-B phase, and has magnetic and mechanical properties that greatly contribute to improving the efficiency of a BLDC motor. If the abundance ratio of the α-Fe phase is too low, it becomes difficult to ensure Bs≧1.7T, while if it is too high, coarse α-Fe of about 10 μm or more is likely to precipitate, which may become the starting point of cracks during punching press, and furthermore, it is likely to cause an increase in iron loss and a decrease in magnetic permeability. Therefore, the abundance ratio of the α-Fe phase is 50 vol% or more and less than 95 vol%, preferably 60 vol% or more and less than 90 vol%, and more preferably 60 vol% or more and less than 85 vol%. The Fe-B phase is the remaining phase of the α-Fe phase, and is a phase mainly composed of FeB and Fe2B. As will be described later, the abundance ratio and crystal grain size of the α-Fe phase can be adjusted to a desired value by controlling the quenching speed 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) described later.

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

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) of silicon steel plate (JIS standard 35A360) of 96.6 W/kg. If the iron loss (W10/1k) exceeds 20 W/kg, the effect of improving motor efficiency decreases. To further improve motor efficiency, it is preferable that the iron loss (W10/1k) is ≦15 W/kg, and it is even more preferable that the iron loss (W10/1k) is ≦10 W/kg.

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 plate is reduced in terms of the amount of magnetic flux on the surface of the teeth in the stator core. To further increase the advantage over silicon steel plate, the magnetic permeability at 1 kHz is preferably 2000 or more, and more preferably 3000 or more.

[Method of manufacturing 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, the method including a step of preparing a molten alloy of an (Fe,Co)-B system having the above-mentioned composition, and a step of rapidly solidifying the prepared molten alloy.

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

The melting furnace 2 supplies the molten alloy 3, which is obtained by melting the raw materials by high-frequency induction heating, to a molten alloy storage container 5 by rotating a tilting shaft 4. The molten alloy storage container 5 is provided with a discharge nozzle 6 at the bottom, and the molten alloy 3 is further heated by a heating coil (not shown) and ejected from a slit 7 formed at the lower end of the discharge nozzle 6 onto the surface (outer circumferential surface) of a chill roll 8. The chill roll 8 quenches the molten alloy in contact with the surface by supplying cooling water to the inside, forming a thin ribbon-like rapidly solidified alloy 9 of (Fe,Co)-B system. The material of the discharge nozzle 6 can be appropriately selected from, for example, quartz (SiO ₂ ), boron nitride (BN), silicon carbide (SiC), and alumina (Al ₂ O ₃ ).

2 is an enlarged view of the discharge nozzle 6 of the device shown in FIG. 1, (a) being a cross-sectional view, and (b) being a bottom view. The discharge nozzle 6 shown in FIG. 2(a) is a single-slit nozzle with a single slit 7 formed therein. The width W1 of the slit 7 serves to adjust the discharge rate of the molten alloy 3 supplied to the chill roll 8. If the slit width W1 is too small, the slit processing is likely to become 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 discharge rate becomes too high, and the heat removal at the chill roll 8 is not kept up, and the rapidly solidified alloy sticks to the chill roll 8, making it difficult to continue stable molten rapid solidification. Therefore, the slit width W1 is 0.2 mm or more and 0.7 mm or less. The slit width W1 is preferably 0.3 mm or more and 0.6 mm or less, and more preferably 0.3 mm or more and 0.5 mm or less.

The molten metal supplied to the surface of the cooling roll 8 becomes a thin ribbon of rapidly solidified alloy 9 by the rotation of the cooling roll 8, and is peeled off from the cooling roll 8. If the surface speed of the cooling roll 8 is too low, the (Fe,Co)-B-based rapidly solidified alloy becomes excessively thick, exceeding 50 μm, and coarse α-Fe phases precipitate, which makes it easy for cracks to occur during punching press. On the other hand, if the surface speed of the cooling roll 8 is too high, the (Fe,Co)-B-based crystal alloy becomes too fine, and the proportion of α-Fe phase decreases, making it difficult to ensure Bs≧1.7T. For this reason, the surface speed of the cooling 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 cooling roll 8 is, for example, 200 to 20,000 mm. The cooling roll 8 does not necessarily need to be water-cooled if the quenching and solidification time is short, 10 seconds or less, but if the quenching and solidification time is 10 seconds or more, it is preferable to suppress the temperature rise on the surface of the cooling roll 8 by running cooling water inside the cooling roll 8. It is preferable to adjust the water-cooling capacity of the cooling roll 8 appropriately according to the latent heat of solidification and the molten metal pouring rate per unit time.

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 slip on the surface of the chill roll 8, making sufficient cooling difficult, whereas 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.

In FIG. 1, if the distance d from the tip of the discharge nozzle 6 to the surface of the chill roll 8 is too small, the quenched alloy may stick to the chill roll 8, making it difficult to continue stable quenching and solidification of the molten alloy 3. On the other hand, if the distance is too large, a puddle may not be formed on the surface of the chill roll 8, making it difficult to rapidly solidify 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.

The cooling roll 8 is preferably made of a material whose main raw material is either pure copper, copper alloy, molybdenum (Mo) or tungsten (W), which provides excellent thermal conductivity and durability. The main raw material means that it accounts for 50% or more by weight. The surface of the cooling roll 8 may be plated with chromium, nickel or an alloy of these, which increases the heat resistance and hardness of the surface of the cooling roll 8 and prevents melting or deterioration of the roll surface during rapid solidification.

[Heat treatment]
In a preferred embodiment, the (Fe,Co)-B based rapidly solidified alloy is heat-treated at a constant temperature of 200°C to 700°C, which allows the removal of strain in the rapidly solidified alloy and further reduces iron loss. If the heat treatment temperature is less than 200°C, the effect of removing strain is small, and if it exceeds 700°C, the α-Fe phase becomes coarse, which increases the brittleness of the rapidly solidified alloy and makes the rapidly solidified alloy more likely to crack during punching. The heat treatment temperature is preferably 300°C to 700°C, more preferably 400°C to 680°C. The heat treatment time of the heat treatment depends on the shape of the soaking zone of the heat treatment device, but an optimal heat treatment time is appropriately selected within a time range of 3 minutes to less than 2 hours. The heat treatment is preferably performed in a vacuum or inert gas atmosphere, but heat treatment in the air is also acceptable.

[Example]
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.

100 kg of raw materials containing B, C, Co, and Fe with a purity of 99.5% or more was 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 height of 400 mm, equipped at the bottom with a BN discharge nozzle with a slit as shown in Table 1. The slit width and length of the discharge nozzle are as shown in Table 1.

After this, 50 kg of the 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 higher than the melting point of the alloy composition, the alumina molten alloy stopper placed on the top of the discharge nozzle was removed. This caused the molten alloy to be ejected from the discharge nozzle onto the surface of the chill roll directly below. The chill roll was made of chrome zircon copper and had an outer diameter of 600 mm and a width of 200 mm. The gap between the discharge nozzle and the chill roll surface is as shown in Table 1. The ejection pressure of the molten alloy from the discharge nozzle, the roll surface speed of the chill roll, and the arithmetic mean roughness (Ra) of the chill roll surface are as shown in Table 2.

The molten alloy sprayed 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 paddle and the chill roll, resulting in a ribbon-shaped rapidly solidified alloy with the average thickness and average 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 performed on the rapidly solidified alloy thus obtained, with the results shown in Table 3.

The rapidly solidified alloys obtained were subjected to a structural evaluation by powder X-ray diffraction (XRD), and all of the rapidly solidified alloys of Examples 1-11 were crystalline alloys consisting of α-Fe and Fe-B type compounds. The volume percentage of α-Fe precipitated in the rapidly solidified alloys (the α-Fe abundance ratio was determined by X-ray diffraction) is shown in Table 3. Quantitative analysis of the constituent phases by powder X-ray diffraction is a common evaluation method, and can be incorporated into the analysis software of the X-ray diffraction device to grasp the composition ratio of each phase. Representative examples of the 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 structures of the rapidly solidified alloys of Examples 4 and 9 were composite structures consisting of α-Fe and Fe-B phases.

Table 4 shows the Bs, core loss and magnetic permeability of the as-spun (immediately after rapid solidification) or 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 core loss and magnetic permeability were measured using a B-H analyzer manufactured by Iwasaki Electric Co., Ltd. As mentioned above, only the rapidly solidified alloy of Example 3 was subjected to heat treatment, but 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 α-Fe phase and Fe-B phase.

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

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

Claims (3)

preparing a molten (Fe,Co)-B alloy having a composition represented by the formula ( _{Fe1-yCoy ) 100-x} (B1 _{-zCz ) x} , where x, y, and z satisfy 10.0≦x≦18.0 atomic %, 0.05≦y≦0.5, and 0.0≦z≦0.3, respectively;
a rapid solidification step of rapidly solidifying the molten alloy on a cooling roll,
the rapid solidification step includes a step of spraying the molten alloy from a single-slit nozzle onto the surface of the chill roll 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 is 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, has 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 has a magnetic permeability of 1500 or more at 1 kHz;
The method for producing an iron-based crystalline alloy, wherein the arithmetic mean roughness of the surface of the chill roll is 0.01 μm or more and 0.6 μm or less. The method for producing an iron-based crystalline alloy according to claim 1, wherein the slit width of the discharge nozzle is 0.2 mm or more and 0.7 mm or less. The method for producing an iron-based crystalline alloy according to claim 1 or 2, wherein the distance from the discharge nozzle to the surface of the cooling roll is 0.2 mm or more and 5.0 mm or less.