KR20260046292A - Method for manufacturing iron crystal alloy - Google Patents

Abstract

The method for manufacturing an iron-based crystal alloy comprises a process for preparing a (Fe,Co)-B alloy molten metal (3) having a composition expressed as (Fe1-yCoy)100-x(B1-zCz)x, wherein x, y, and z each satisfy 10.0≤x≤18.0 atomic%, 0.05≤y≤0.5, and 0.0≤z≤0.3, and a rapid solidification process for rapidly solidifying the alloy molten metal (3) on a cooling roll (8), wherein the rapid solidification process comprises a process for producing an iron-based crystal alloy (9) such that the presence ratio of the α-Fe phase is 50 volume% or more and less than 95 volume% and the remainder is composed of the Fe-B phase, by rotating the cooling roll (8) at a roll surface speed of 15 m/sec or more and 40 m/sec or less, and spraying the alloy molten metal (3) from a discharge nozzle (6) onto the surface of the cooling roll (8). The iron crystal alloy is formed in a thin strip shape with 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 permeability of 1500 or more at 1 kHz. The arithmetic mean roughness on the surface of the cooling roll (8) is 0.01 μm or more and 0.6 μm or less.

Description

Method for manufacturing iron crystal alloy

The present invention relates to a method for manufacturing an iron-based crystal alloy, and more specifically, to a method for manufacturing an iron-based crystal alloy suitable for use as a core material for a DC motor.

Recently, there has been a market demand for materials with low iron loss and high saturation magnetic flux density for various passive components, such as inductors and reactors, used as electronic parts, as well as for transformers. As such materials, iron-based amorphous materials or iron-based nanocrystalline materials with iron (Fe), silicon (Si), and boron (B) as main raw materials are known, and Fe-Si-B amorphous alloy thin strips with a thickness of about 17 μm to 25 μm, produced by the molten metal rapid solidification method using these soft magnetic materials, are replacing conventional silicon steel sheets and demand is increasing, mainly for large transformers and inductors.

In addition, since the aforementioned Fe-Si-B amorphous alloy thin strip has lower iron loss compared to silicon steel sheets, it is being considered to increase motor efficiency by utilizing this characteristic and applying it to the rotor core and stator core of brushless DC (BLDC) motors. In particular, when used in high-speed rotating BLDC motors such as those exceeding 20,000 rpm, the operating range of the soft magnetic material becomes a high-frequency band of around 2 kHz, so high motor efficiency is obtained. Therefore, it is expected to be applied to white goods such as vacuum cleaners that require high-speed motor rotation, as well as auxiliary machinery motors for electrical applications.

Meanwhile, for EV drive motors, which require higher efficiency than motors for white goods, the necessary output cannot be obtained unless a saturation magnetic flux density (Bs) equivalent to that of silicon steel sheets is secured; however, since the Bs of Fe-Si-B amorphous alloys is only about 1.6T at most, it is difficult to replace silicon steel sheets with a Bs of 1.7T or higher. For this reason, there have been no instances to date of EV drive BLDC motors using Fe-Si-B amorphous alloys being introduced to the market.

For EV drive BLDC motors of several tens of kW or higher, high efficiency has traditionally been achieved by combining silicon steel core materials with anisotropic rare-earth iron-boron sintered magnets that exhibit excellent permanent magnet characteristics and utilizing magnet torque; however, since silicon steel sheets have low permeability, it is difficult to realize low-iron-loss core materials because the excellent magnetic properties of anisotropic rare-earth iron-boron sintered magnets cannot be fully utilized. For this reason, there is very high market demand for high-output, high-efficiency BLDC motors that can contribute to energy saving 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 higher permeability than silicon steel sheets and can reduce iron loss by up to 1/10, so their replacement from silicon steel sheets as core materials for BLDC motors used for EV drives is being considered. However, as mentioned above, due to the low saturation magnetic flux density (Bs), their application has mainly been limited to high-speed rotating BLDC motors with rotational speeds of 15,000 rpm or higher, where the impact of iron loss becomes significant, making it difficult to apply them to EV drive motors with rotational speeds below 15,000 rpm. Furthermore, since Fe-Si-B amorphous alloy strips are thin, with a thickness of approximately 25 μm, punching press processing for manufacturing laminated cores for rotor and stator cores of BLDC motors is difficult; consequently, their use is mainly limited to wound cores, making it difficult to replace silicon steel sheets for motor applications.

On the other hand, Fe-Si-B nanocrystalline materials are prone to breakage or detachment, so they can only be used as coiled cores or as compacted cores after crushing and molding, and it is difficult to use them as laminated cores, just like Fe-Si-B amorphous alloys.

To obtain amorphous or nanocrystalline structures in the Fe-Si-B system, it is necessary to add Si and B, and to form a nanocrystalline structure, additional elements such as Cu and Nb are required. Consequently, due to the resulting decrease in the compositional ratio of Fe, it is not possible to obtain Bs ≥ 1.7T. For this reason, conventionally, no iron-based alloy capable of easily forming a stacked core and securing Bs ≥ 1.7T has been found.

For example, Non-patent Literature 1 discloses that by adding phosphorus (P), the rapid solidification rate is reduced, and an iron-based amorphous alloy strip with a thickness of 50 μm or more is obtained. However, phosphorus-added alloys not only cause a decrease in Bs due to the addition of phosphorus, but also cause significant contamination inside and outside the molten metal rapid cooling device when the phosphorus component volatilizes during alloy melting, and there is a risk that the seam shear is prone to burning, so there are still few examples of applications in the industrial field.

Patent documents 1-3 disclose a method for manufacturing an amorphous alloy thin sheet having a thickness (e.g., about 50 μm) that allows for punching processing by a multi-slit method in which a molten alloy is discharged from a plurality of slit nozzles onto a rotating cooling roll. However, even with the use of this technology, it is difficult to achieve Bs≥1.7T, making it difficult to apply as a soft magnetic material for laminated cores for EV drive BLDC motors as a substitute for silicon steel sheets.

Patent Document 4 discloses a method for manufacturing a metal foil that suppresses the non-uniformity of the metal foil thickness when producing a wide rapid-cooled foil using a porous nozzle. Although the invention of Patent Document 4 is characterized by the shape of the nozzle opening, it is difficult to process, which leads to a problem where nozzle processing costs skyrocket, making it difficult to use at the mass production level.

Patent Document 5 discloses a method for manufacturing an iron-based silicon-boron amorphous alloy that achieves thick plate by using a tapping nozzle having a zigzag multi-orifice, but compared to silicon steel sheets, it was difficult to secure high Bs or sufficient thickness.

Patent Document 6 discloses an Fe-Si-B-based rapid solidification alloy capable of forming a laminated core, characterized by high Bs of Bs≥1.7T and thickness≥40μm. The invention of Patent Document 6 optimizes the mixing ratio of each element in the ternary composition of the essential elements iron, silicon, and boron, but the workability of the punching press when manufacturing a laminated core from the alloy sheet obtained by this is inferior to that of silicon steel sheets, so there is room for further improvement in producing the laminated core at low cost.

Patent Document 1: Japanese Patent Publication No. JP 5-329587 Patent Document 2: Japanese Patent Publication No. JP 7-113151 Patent Document 3: Japanese Patent Publication No. JP 8-124731 Patent Document 4: Japanese Patent Publication No. 63-220950 Patent Document 5: Japanese Patent Publication No. 2018-153828 Patent Document 6: Japanese Patent Publication No. 2021-193199

Non-patent Literature 1: Creation of a Novel Bulk Metal Glass/Amorphous Thick Plate with High Saturation Magnetic Flux Density (Tohoku University, Metal Glass Research Center) Akahiro Makino, Ken Kubota, Haruto Toshiyuki

The present invention aims to provide a method for manufacturing an iron-based crystal alloy that facilitates punching while securing low iron loss and high saturation magnetic flux density.

The above objective of the present invention comprises a process for preparing a (Fe,Co)-B alloy molten metal having a composition expressed by the formula (Fe _1-y Co _y ) _100-x (B _1-z C _z ) _x , wherein 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 process for rapidly cooling and solidifying the alloy molten metal on a cooling roll, wherein the rapid solidification process comprises rotating the cooling roll at a roll surface speed of 15 m/sec or more and 40 m/sec or less, and spraying the alloy molten metal onto the surface of the cooling roll from a tapping nozzle consisting of a single-slit nozzle, thereby producing an iron-based crystal alloy having an α-Fe phase presence ratio of 50 volume% or more and less than 95 volume%, with the remainder being the Fe-B phase, and wherein the iron-based crystal alloy has a thickness of 50 μm This is achieved by a method for manufacturing an iron-based crystal alloy that is formed into a flat shape, has a saturation magnetic flux density of 1.7 T or more, has an iron loss (W10/1k) at a magnetic flux of 1.0 T and a frequency of 1 kHz of 20 W/kg or less, has a permeability of 1500 or more at 1 kHz, and has an arithmetic mean roughness on the surface of the cooling roll of 0.01 μm or more and 0.6 μm or less.

In the method for manufacturing this iron-based crystal alloy, the tapping nozzle preferably has a slit width of 0.2 mm or more and 0.7 mm or less.

In addition, it is preferable that the distance from the above-mentioned tapping nozzle to the surface of the cooling roll is 0.2 mm or more and 5.0 mm or less.

According to the present invention, a method for manufacturing an iron-based crystal alloy that facilitates punching processing while securing low iron loss and high saturation magnetic flux density can be provided.

[Fig. 1] This is a schematic diagram of an apparatus used in a method for manufacturing a flat iron crystal alloy according to one embodiment of the present invention.
[Fig. 2] An enlarged view showing the main part of the device shown in Fig. 1, where (a) is a cross-sectional view and (b) is a bottom view.
[Fig. 3] Powder X-ray diffraction profile of an iron-based crystal alloy obtained in one embodiment of the present invention.
[Fig. 4] Powder X-ray diffraction profile of an iron-based crystal alloy obtained in another embodiment of the present invention.
[Fig. 5] Powder X-ray diffraction profile of an iron-based crystal alloy obtained in another embodiment of the present invention.
[Fig. 6] Powder X-ray diffraction profile of an iron-based crystal alloy obtained as a comparative example of the present invention.

[Alloy Composition]

In order to improve the punching processability of iron-based alloys, it is necessary to have a crystalline structure rather than an amorphous structure that is hard and brittle. The iron-based crystalline alloy composition of the present invention is based on a binary alloy composition of Fe-B, and a portion of Fe is substituted with Co, which is a ferromagnetic element like Fe, and is expressed by the compositional formula (Fe _1-y Co _y ) _100-x (B _1-z C _z ) _x .

If the substitution rate of Co for Fe is excessively low, it becomes difficult to achieve Bs ≥ 1.7T; therefore, it is necessary to ensure that y in the above compositional formula is 0.05 or higher. As the value of y increases, the Bs of the iron-based crystal alloy increases monotonically up to y = 0.5, but if the value of y exceeds 0.5, Bs does not increase, and only manufacturing costs increase due to the use of Co, an expensive element. For this reason, 0.05 ≤ y ≤ 0.5, and from the perspective of increasing Bs, 0.1 ≤ y ≤ 0.5 is desirable, and considering manufacturing costs, 0.15 ≤ y ≤ 0.4 is more desirable.

In the iron-based crystal alloy of the present invention, B is an essential element for obtaining low iron loss and high permeability, and plays a role in making the structure composed of α-Fe phase and Fe-B phase into a uniform microstructure. It is acceptable to substitute a portion of B with C, and as a result, the melting point of the molten alloy is lowered, thereby relaxing the rapid solidification conditions and making it easier to produce the iron-based crystal alloy.

However, if the substitution rate of C for B is excessively high, Fe-C compounds are formed, making it difficult to obtain a uniformly fine crystal structure consisting of α-Fe phase and Fe-B phase. For this reason, z in the above compositional formula is 0.0≤z≤0.3, and from the perspective of maintaining high Bs characteristics, 0.0≤z≤0.2 is preferable, and 0.05≤z≤0.15 is more preferable.

If the ratio of B and C to the total composition of the iron-based crystal alloy is excessively low, a rough and coarse α-Fe phase, which serves as a starting point for fracture during punching press, is prone to precipitation. On the other hand, if the ratio of B and C to the total composition of the iron-based crystal alloy is excessively high, it leads to an increase in the volume ratio of the Fe-B phase and a decrease in the volume ratio of the α-Fe phase, making it difficult to secure Bs≥1.7T. For this reason, x in the above compositional formula is 10.0≤x≤18.0 atomic%, 11.0≤x≤17.0 atomic% is preferable, and 12.0≤x≤16.0 atomic% is more preferable.

[Metal structure]

The iron-based crystal alloy of the present invention is a (Fe,Co)-B-based iron-based crystal alloy having a composite structure of α-Fe phase and Fe-B phase, and possesses magnetic and mechanical properties that significantly contribute to improving the efficiency of BLDC motors. If the abundance ratio of the α-Fe phase is excessively low, it becomes difficult to secure Bs ≥ 1.7T, whereas if it is excessively high, rough and coarse α-Fe of about 10 μm or more is prone to precipitation, which may become a starting point for breakage during punching press, and also may easily lead to an increase in iron loss and a decrease in permeability. Therefore, the abundance ratio of the α-Fe phase is 50 volume% or more and less than 95 volume%, preferably 60 volume% or more and less than 90 volume%, and more preferably 60 volume% or more and less than 85 volume%. The Fe-B phase is the residual phase of the α-Fe phase and is a phase mainly composed of FeB and Fe2B. As described below, the abundance ratio or crystal grain size of the α-Fe phase can be adjusted to a desired value by controlling the rapid cooling rate of the molten alloy. It is preferable that the average crystal grain size of the α-Fe phase be 2 nm to 20 nm. The average crystal grain size of the α-Fe phase can be determined by the full width at half maximum of the X-ray diffraction peaks obtained by powder X-ray diffraction (XRD) described below.

[Self-characteristics]

The saturation magnetic flux density of the iron-based crystal alloy of the present invention is Bs≥1.7T, but when considering the application of a BLDC motor for EV driving of 30kW or more, Bs≥1.72T is preferable, and Bs≥1.75T is more preferable.

In addition, the iron-based crystal alloy of the present invention has an iron loss (W10/1k) ≤ 20 W/kg at magnetic flux: 1.0 T and frequency: 1 kHz, and has significantly lower low iron loss performance compared to the iron loss (W10/1k) of silicon steel sheet (JIS standard 35A360): 96.6 W/kg. If the iron loss (W10/1k) exceeds 20 W/kg, the effect of improving motor efficiency decreases. To further increase the effect of improving motor efficiency, an iron loss (W10/1k) ≤ 15 W/kg is desirable, and an iron loss (W10/1k) ≤ 10 W/kg is more desirable.

The iron-based crystal alloy of the present invention has a permeability of 1500 or higher at 1 kHz. If the permeability at 1 kHz is lower than 1500, the superiority over silicon steel sheets in terms of magnetic flux quantity on the tooth surface of the stator core decreases. In order to increase the superiority over silicon steel sheets, the permeability at 1 kHz is preferably 2000 or higher, and more preferably 3000 or higher.

[Method for manufacturing iron-based crystal alloys]

The iron-based crystal alloy of the present invention is manufactured by a method for manufacturing an iron-based crystal alloy comprising a process of preparing a (Fe,Co)-B-based alloy molten metal having the composition described above, and a rapid solidification process for rapidly cooling and solidifying the prepared alloy molten metal.

FIG. 1 is a schematic diagram of a single-roll molten metal quenching apparatus used in a method for manufacturing an iron-based crystal alloy according to one embodiment of the present invention. The single-roll molten metal quenching apparatus (1) shown in FIG. 1 is equipped with a melting furnace (2), a storage container (5), and a cooling roll (8).

The melting furnace (2) supplies the molten alloy (3), in which the raw materials are melted by high-frequency induction heating, to the storage container (5) by the rotation of the tilting shaft (4). The storage container (5) is equipped with a discharge nozzle (6) at the bottom and further heats the molten alloy (3) by a heating coil (not shown) to discharge the molten alloy (3) onto the surface (outer surface) of the cooling roll (8) from the slit (7) formed at the bottom of the discharge nozzle (6). The cooling roll (8) rapidly cools the molten alloy in contact with its surface by supplying cooling water to the inside, and forms a (Fe,Co)-B type rapid-cooled solidified alloy (9). The material of the water discharge nozzle (6) can be appropriately selected from, for example, quartz ( _SiO2 ), boron nitride (BN), silicon carbide (SiC) and _alumina ( _Al2O3 ).

FIG. 2 is an enlarged view showing the tapping nozzle (6) of the device shown in FIG. 1, where (a) is a cross-sectional view and (b) is a bottom view. The tapping 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 tapping rate of the molten alloy (3) supplied to the cooling roll (8). If the slit width (W1) is too small, it is easy to make the slit processing difficult and easy for the slit (7) to be closed by the molten metal. On the other hand, if the slit width (W1) is too large, the tapping rate becomes too high, and the heat dissipation from the cooling roll (8) does not occur in time, causing the rapid solidification alloy to adhere to the cooling roll (8), making it difficult to continue stable rapid solidification of the molten metal. 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 strip-shaped rapid solidification 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 excessively low, the (Fe,Co)-B system rapid solidification alloy becomes excessively thick with a thickness exceeding 50 μm, so a rough and coarse α-Fe phase is precipitated, making it prone to cracking during punching press. On the other hand, if the surface speed of the cooling roll (8) is excessively high, the refinement of the (Fe,Co)-B system crystal alloy proceeds excessively, causing the proportion of the α-Fe phase to decrease, making it difficult to secure 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. Water cooling is not strictly necessary for the cooling roll (8) if the rapid solidification time is short, such as 10 seconds or less, but if the rapid solidification time is 10 seconds or longer, it is desirable to suppress the rise in temperature of the surface of the cooling roll (8) by flowing cooling water inside the cooling roll (8). It is desirable to appropriately adjust the water cooling capacity of the cooling roll (8) according to the latent heat of solidification per unit time and the tapping rate.

In the production of a flat-shaped rapid solidification alloy (9), the adhesion of the molten alloy (3) to the outer surface of the cooling roll (8) is important, but this adhesion of the molten alloy depends greatly on the surface roughness of the cooling roll (8). If the surface roughness of the cooling roll (8) is too small, the molten alloy (3) slides on the surface of the cooling roll (8), making it difficult to achieve sufficient cooling, whereas if the surface roughness of the cooling roll (8) is too large, there is a risk that the rapid solidification alloy will stick to the cooling roll (8). For this reason, the arithmetic mean roughness (Ra) on the surface of the cooling roll (8) is 0.01 μm or more and 0.6 μm or less, and is preferably 0.05 μm or more and 0.55 μm or less, and is 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 tapping nozzle (6) to the surface of the cooling roll (8) is too small, there is a concern that the rapid cooling alloy may stick to the cooling roll (8) and that the stable rapid cooling solidification of the molten alloy (3) cannot be continued, whereas if it is too large, there is a concern that the molten alloy may not be able to be rapidly cooled and solidified because no lump of molten alloy is formed on the surface of the cooling roll (8). For this reason, the above 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.

It is preferable that the cooling roll (8) be formed from a material having one of pure copper, a copper alloy, molybdenum (Mo), and tungsten (W) as the main raw material, so that it has excellent thermal conductivity and durability. The term "main raw material" refers to one that accounts for 50% or more of the weight ratio. The surface of the cooling roll (8) may be plated with chromium, nickel, or an alloy thereof, and accordingly, the heat resistance and hardness of the surface of the cooling roll (8) are increased, thereby suppressing melting or deterioration of the roll surface during rapid cooling solidification.

[Heat Treatment]

In a preferred embodiment, by heat-treating a (Fe,Co)-B-based quenched solidification alloy at a constant temperature of 200°C or higher and 700°C or lower (unless otherwise specified in the present invention, the unit of temperature is Celsius), distortion within the quenched solidification alloy can be eliminated, thereby realizing a new low iron loss. If the heat treatment temperature is below 200°C, the effect of eliminating distortion is small, and if it exceeds 700°C, the coarsening of the α-Fe phase proceeds, which increases the brittleness of the quenched solidification alloy, making the quenched solidification alloy prone to breakage during punching. The above-mentioned heat treatment temperature is preferably 300°C or higher and 700°C or lower, and more preferably 400°C or higher and 680°C or lower. The heat treatment time of the above heat treatment depends on the shape of the heat zone of the heat treatment device, but an appropriately suitable heat treatment time is selected within a time range of 3 minutes or more and less than 2 hours. In addition, the above heat treatment is preferably carried out in a vacuum or an inert gas atmosphere, but heat treatment in the atmosphere is also permitted.

[Example]

The present invention will be described in more detail below in the embodiments. However, the present invention is not limited to the following embodiments.

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

After that, 50 kg of molten alloy was further heated by energizing a high-frequency heating coil installed around the storage container, and 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 metal stopper placed above the tapping nozzle was pulled out. Accordingly, the molten alloy was ejected from the tapping nozzle onto the surface of the cooling roll directly below. The cooling roll is made of chrome zircon copper, with an outer diameter of 600 mm and a width of 200 mm. In addition, the gap between the tapping nozzle and the surface of the cooling roll is as shown in Table 1. Furthermore, the injection pressure of the molten alloy from the tapping nozzle, the roll surface speed of the cooling roll, and the arithmetic mean roughness (Ra) of the roll surface of the cooling roll are as shown in Table 2.

The molten alloy ejected onto the surface of the cooling roll formed a molten pool (puddle) on the surface of the cooling roll, and by rapidly solidifying at the interface between the puddle and the cooling roll, a strip-shaped rapidly solidified alloy having the average thickness and average width shown in Table 3 was obtained. For Example 3, the rapidly solidified alloy was subjected to heat treatment at 650°C for 10 minutes in an Ar-flowing gas. A punching test was performed on the rapidly solidified alloy obtained in this way, and the results shown in Table 3 were obtained.

The obtained quenched solidification alloys were subjected to an evaluation of their microstructure by powder X-ray diffraction (XRD). As a result, the quenched solidification alloys of Examples 1-11 were all crystalline alloys composed of compounds of the α-Fe phase and the Fe-B phase. The volume percentage of α-Fe precipitated in the quenched solidification alloys (determined by the α-Fe presence ratio via X-ray diffraction) is shown in Table 3. Quantitative analysis of constituent phases by powder X-ray diffraction is a general evaluation method and can be included in the analysis software of an X-ray diffraction device to determine the composition ratio of each phase. As representative examples of the powder X-ray diffraction profiles of the quenched solidification alloys of the examples, Example 4 is shown in Fig. 3 and Example 9 in Fig. 4. As shown in Figs. 3 and 4, the microstructure of the quenched solidification alloys of Examples 4 and 9 was a composite microstructure composed of the α-Fe phase and the Fe-B phase.

Table 4 shows the Bs, iron loss, and permeability of the quenched solidification alloys of Examples 1-11 and Comparative Examples 12-17 as-spun (immediately after quenched solidification) or after heat treatment. Bs was measured using a vibrating sample magnetometer manufactured by Toei Industry Co., Ltd., and iron loss and permeability were measured using a B-H analyzer manufactured by Iwatsu Electric Co., Ltd. As mentioned above, only the quenched solidification alloy of Example 3 underwent heat treatment, but as shown in FIG. 5, the powder X-ray diffraction profile of the quenched solidification alloy of Example 3 also showed a composite structure consisting of α-Fe phase and Fe-B phase.

The quenched solidification alloys of Comparative Examples 12-17 were an amorphous single-phase metallographic structure as evaluated by powder X-ray diffraction (XRD). Table 3 shows the volume percentage of α-Fe (the ratio of α-Fe presence determined by X-ray diffraction). Comparative Example 12 is shown in Fig. 6 as a representative example of the powder X-ray diffraction profile of the quenched solidification alloys of the comparative examples. As shown in Fig. 6, the structure of the quenched solidification alloy of Comparative Example 12 was an amorphous single-phase structure.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

l Single-roll molten metal quenching device, 2 Melting furnace, 3 Molten alloy
4 Tilting shaft, 5 Hot water container, 6 Hot water outlet nozzle, 7 Slit
8 Cooling roll, 9 Rapid solidification alloy

Claims (3)

A process for preparing a (Fe,Co)-B alloy molten metal having a composition expressed by the formula (Fe _1-y Co _y ) _100-x (B _1-z C _z ) _x , wherein 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 process for rapidly cooling and solidifying the molten alloy on a cooling roll
Equipped,
The above rapid solidification process comprises a process for producing an iron-based crystal alloy in which the presence ratio of the α-Fe phase is 50 volume% or more and less than 95 volume%, and the remainder is the Fe-B phase, by rotating the cooling roll at a roll surface speed of 15 m/sec or more and 40 m/sec or less, and spraying the molten alloy onto the surface of the cooling roll from a tapping nozzle consisting of a single slit nozzle.
The above iron-based crystal alloy is formed in a thin strip shape with 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 permeability of 1500 or more at 1 kHz.
A method for manufacturing an iron-based crystal alloy having an arithmetic mean roughness of 0.01 μm or more and 0.6 μm or less on the surface of the cooling roll. The above-mentioned hot water nozzle has a slit width of 0.2 mm or more and 0.7 mm or less,
A method for manufacturing an iron-based crystal alloy as described in claim 1. The distance from the above-mentioned tapping nozzle to the surface of the above-mentioned cooling roll is 0.2 mm or more and 5.0 mm or less,
A method for manufacturing an iron-based crystal alloy as described in claim 1 or claim 2.