Iron-based soft magnetic alloy and its manufacturing method

Abstract

The present invention provides an iron-based soft magnetic alloy that can achieve a Bs of 1.55T to 1.75T inexpensively without adding expensive Co and Cu, has low core loss performance, and can be made into a laminated core. [Solution] Composition formula Fe 100-x-y-z Ni z Si x (B 1-m C m ) y The iron-based soft magnetic alloy is expressed as follows: where the composition ratios x, y, z, and m satisfy 1.0≦x≦2.2 atomic %, 11.0≦y≦14.0 atomic %, 0.0≦z≦15.0 atomic %, and 0.0≦m≦0.3, respectively; it has a metal structure consisting of an α-Fe phase; it has a saturation magnetic flux density of 1.55 T or more and 1.75 T or less; it has an iron loss of 50 W / kg or less at a magnetic flux density of 1.0 T and a frequency of 2 kHz; it has a thickness of 18 μm or more and less than 40 μm; and it does not contain Co or Cu.

Description

[Technical Field]

[0001] The present invention relates to an iron-based soft magnetic alloy and a method for manufacturing the same, and more particularly to an iron-based soft magnetic alloy applicable to various brushless DC motors and a method for manufacturing the same. [Background technology]

[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 in the power electronics field, such as inductors and reactors used as electronic components. Demand is increasing for iron-based amorphous materials, which are soft magnetic materials with high magnetic permeability and low iron loss, and Fe-Si-B rapidly solidified alloy ribbons with a thickness of approximately 17 μm to 25 μm, which are made by rapidly solidifying a molten metal made primarily of iron (Fe), silicon (Si), and boron (B), such as iron-based nanocrystalline materials, as low iron loss soft magnetic materials to replace conventional silicon steel sheets (Fe-Si), for use in large transformers and inductors.

[0003] In addition, the Fe-Si-B rapidly solidified alloys mentioned above have been considered for use in the stator cores of brushless direct current (BLDC) motors, taking advantage of their lower iron loss compared to silicon steel sheets. By applying them to the stator cores of brushless direct current (BLDC) motors, researchers are studying how to improve the motor's efficiency by reducing iron loss. In particular, for high-speed motors exceeding 10,000 or 20,000 rpm, the operating range of soft magnetic materials is a high-frequency band of 1 kHz or higher, which has been confirmed to reduce iron loss in the stator core and achieve unprecedented efficiency. Furthermore, with motors now accounting for approximately 60% of the world's electricity, improving motor efficiency is expected to be a direct means of achieving a carbon-free society, leading to expectations for their application in electric vehicles, white goods such as air conditioners, and factory automation motors.

[0004] However, Fe-Si-B amorphous alloys have a saturation magnetic flux density Bs of 1.6 T or less, which is lower than the 1.8 T of electromagnetic steel sheets, which are currently used as motor core materials. Therefore, while they can ensure the necessary motor output for high-speed motors of 10,000 rpm or more, they are difficult to apply to motors that require high torque at low speeds, such as those used in factory automation and air mobility.

[0005] On the other hand, motors other than those requiring high torque even at low rotation speeds (e.g., compressor motors used in air conditioners and refrigerators, and fan motors used in data centers, etc.) operate at a constant speed and torque for long periods of time, so a high Bs of around 1.8 T is not necessarily required. High efficiency, i.e., power savings, can be achieved by suppressing the iron loss in the motor core that accompanies high-speed rotation of the motor. Therefore, a low-iron-loss soft magnetic material is sufficient. However, a certain amount of torque is required when the motor starts operating or when using an air conditioner that rapidly lowers the room temperature. Therefore, the market demand for iron-based soft magnetic materials that have low iron loss equivalent to that of existing iron-based amorphous alloys, but are inexpensive, and can achieve a Bs of 1.55 T to 1.75 T equivalent to or higher than that of iron-based amorphous alloys, is extremely high in order to realize a decarbonized society, just as it is for low-iron-loss soft magnetic materials with a high Bs of around 1.8 T.

[0006] Adding Co (cobalt) to iron-based amorphous alloys is effective in increasing Bs, but adding Co, an expensive rare metal, increases the alloy price by 1.5 to 2 times. Therefore, there are extremely high expectations in the motor market worldwide for soft magnetic materials for motor cores that can achieve Bs of 1.55T to 1.75T without adding Co, while maintaining low iron loss performance on par with Fe-Si-B amorphous alloys.

[0007] However, it has traditionally been difficult to achieve a Bs of 1.55 T or more with iron-based amorphous alloys without the addition of Co, and there have been no examples of Co-free iron-based soft magnetic materials being brought to market as materials for air conditioner compressors or motors for data centers.

[0008] For this reason, motors for air conditioner compressors and fan motors for data centers have traditionally been made highly efficient by combining magnetic steel sheet core materials with anisotropic rare-earth iron-boron sintered magnets, which exhibit excellent permanent magnetic properties, and utilizing magnetic torque. However, with magnetic steel sheets, which have high iron loss, the input power is lost through iron loss generated in the stator core, making it impossible to achieve the energy savings in motors required as a decarbonization measure, i.e., improvements in power efficiency.

[0009] The electromagnetic steel sheets used in the rotor and stator cores of BLDC motors are used as laminated cores, but existing Fe-Si-B amorphous alloys are difficult to punch due to their thin thickness of approximately 20 μm. In addition, due to the thin alloy thickness, the space factor when laminated into a core is low at less than 90%, compared to the 92% or more of electromagnetic steel sheets, making it difficult to obtain motor torque on a par with that of electromagnetic steel sheets.

[0010] In Non-Patent Document 1, Fe-Si-B amorphous alloys have been used for 10 4 ~10 6 It has been disclosed that an amorphous structure could only be obtained by rapidly solidifying alloy ribbons with a thickness of approximately 17 μm to 22 μm at an extremely fast rapid solidification rate of 1000 K / sec, but that the addition of phosphorus (P) can reduce the rapid solidification rate and obtain iron-based amorphous alloy ribbons with a thickness of 50 μm or more. However, the addition of P not only reduces the saturation magnetic flux density Bs, but also causes significant furnace contamination due to the volatilization of the P component during alloy melting, and therefore there are still few examples of application in the industrial field.

[0011] Non-Patent Document 2 discloses that the Fe-Si-B-P-Cu based iron-based nanocrystalline alloy "NANOMET (registered trademark)" is a soft magnetic material with a high saturation magnetic flux density Bs of 1.85 T and low iron loss performance comparable to that of an iron-based amorphous alloy. However, this iron-based nanocrystalline alloy is extremely brittle and difficult to form into laminated cores using a punching press process, making it difficult to apply to the rotor cores and stator cores of BLDC motors at the mass-production level, and there have been no examples of it being put into practical use as a core material for motors, except at the prototype level.

[0012] Patent Documents 1, 2, and 3 describe methods for producing rapidly solidified alloy ribbons with a thickness of 50 μm or more, but none of them have produced an Fe-Si-B amorphous alloy having Bs≧1.55T, and there have been no examples of iron-based amorphous alloys being used industrially as soft magnetic materials to replace silicon steel sheets.

[0013] Patent Document 4 discloses a method for producing a metal ribbon, in which molten metal is ejected onto a moving cooling substrate (a rotating cooling roll) from a plurality of openings (multi-hole nozzles) that are arranged substantially perpendicular to the direction of movement of the substrate and each of which has an angle of 10 to 80 degrees relative to the direction of movement, and then rapidly solidified. However, Patent Document 4 is an invention made with the aim of reducing the variation in thickness of a metal ribbon in the width direction when producing a wide rapidly spun ribbon. Furthermore, it is difficult to process a plurality of openings in the shape of an elongated parallelogram, trapezoid, or ellipse with angles of 10 to 80 degrees, and there is also the problem of high nozzle processing costs, making it difficult to use on an industrial mass production level.

[0014] Patent Document 5 discloses a method for producing an Fe-Si-B-based amorphous alloy with a thickness of 40 μm or more, but does not disclose an alloy composition that can ensure Bs≧1.55T, and the invention is not intended to provide a soft magnetic material for BLDC motors used to drive EVs.

[0015] Patent Document 6 describes an Fe-Si-B based rapidly solidified alloy having a thickness of 40 μm to 70 μm and a saturation magnetic flux density Bs≧1.7 T, a coercive force Hc≦200 A / m, and a method for producing the alloy. However, during the rapid solidification process, 0.1 vol % to 10 vol % of an α-Fe phase precipitates in the surface layer, and the remainder of the rapidly solidified alloy is an amorphous structure. This may make punching press processing difficult depending on the core shape.

[0016] Patent Documents 7, 8, and 9 describe methods for producing rapidly solidified (Fe,Co)-Si-B alloys that can obtain a high Bs of nearly 1.8 T, comparable to that of electrical steel sheets, while maintaining low iron loss comparable to that of Fe-Si-B amorphous alloys. However, the substitution rate of Co for Fe is between 5% and 50%, which requires the addition of expensive Co. This results in a material price that is at least as high as that of Co-added Fe-Si-B amorphous alloys, making it difficult to use the alloys as core materials for air conditioner compressors or fan motors for data centers. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] JP 5-329587 [Patent Document 2] Patent Publication No. 7-113151 [Patent Document 3] JP 8-124731 [Patent Document 4] Patent Publication No. 63-220950 [Patent Document 5] Patent Publication No. 2018-153828 [Patent Document 6] Patent Publication No. 2021-193199 [Patent Document 7] Patent No. 7627981 [Patent Document 8] Patent No. 7625198 [Patent Document 9] Patent No. 7656988 [Non-patent literature]

[0018] [Non-Patent Document 1] 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, Tono Haruta [Non-patent document 2] Latest research and development trends of "NANOMET", an ultra-low core loss, high iron content soft magnetic alloy, Journal of the Japan Society for Metals, Material, Vol. 55, No. 3 (2016) Summary of the Invention [Problem to be solved by the invention]

[0019] Rapidly solidified Fe-Si-B alloys are expected to have a saturation magnetic flux density Bs of 1.55 T to 1.75 T, which is suitable for use in air conditioner compressors, data center fan motors, and other BLDC motors, the demand of which is expected to rapidly increase in the future due to global warming. They also have low iron loss performance comparable to that of Fe-Si-B amorphous alloys, and can be stamped using a press like electrical steel sheets. They can ensure a core space factor of 90% or more, making them suitable for use in laminated motor cores. However, it is difficult to achieve a Bs of 1.55 T to 1.75 T with Fe-Si-B amorphous alloys without adding expensive Co. Meanwhile, the rapidly solidified Fe-Si-B alloy described in Patent Document 6, which contains a mixture of an amorphous structure and a crystalline phase consisting of α-Fe, can achieve a saturation magnetic flux density Bs of 1.55 T or more, but is difficult to stamp at press speeds comparable to those of electrical steel sheets. For this reason, it has previously been difficult to use it as a motor core capable of supporting the miniaturization and high output of air conditioner compressors and data center fan motors.

[0020] Therefore, the present invention aims to provide an iron-based soft magnetic alloy that can achieve a Bs of 1.55 T or more and 1.75 T at low cost without adding expensive Co and Cu, has low iron loss performance, and can be made into a laminated core, and a method for manufacturing the same. [Means for solving the problem]

[0021] The iron-based soft magnetic alloy according to the present invention has the composition formula Fe 100-x-y-z Ni z Si x (B 1-m C m ) y wherein the composition ratios x, y, z, and m satisfy 1.0≦x≦2.2 atomic %, 11.0≦y≦14.0 atomic %, 0.0≦z≦15.0 atomic %, and 0.0≦m≦0.3, respectively; the alloy has a metal structure consisting of an α-Fe phase, a saturation magnetic flux density of 1.55 T or more and 1.75 T or less, an iron loss at a magnetic flux density of 1.0 T and a frequency of 2 kHz of 50 W / kg or less, a thickness of 18 μm or more and less than 40 μm, and is free of Co and Cu.

[0022] Furthermore, the present invention The above The manufacturing method of the iron-based soft magnetic alloy is 100-x-y-z Ni z Si x (B 1-m C m ) y The present invention comprises the steps of: preparing a molten alloy having a composition in which the compositional ratios x, y, z, and m satisfy the following relations: 1.0≦x≦2.2 atomic %, 11.0≦y≦14.0 atomic %, 0.0≦z≦15.0 atomic %, and 0.0≦m≦0.3, respectively, and which does not contain Co and Cu; and rapidly solidifying the molten alloy on a chill roll whose main raw material is any of pure copper, a copper alloy, Mo, and W. The rapidly solidifying step involves rotating the chill roll at a roll surface speed of 20 m / sec or more and 55 m / sec or less, and spraying the molten alloy from a nozzle onto the surface of the chill roll to form a thick film. The method for producing an iron-based soft magnetic alloy includes a step of forming a ribbon of rapidly solidified alloy having a roughness of 18 μm or more and less than 40 μm, wherein the surface roughness of the chill roll is an arithmetic mean roughness (Ra) of 0.01 μm or more and 0.6 μm or less, the nozzle is made of a material containing as a main component any of quartz (SiO2), carbon (C), boron nitride (BN), silicon carbide (SiC), and alumina (Al2O3), and the molten alloy is poured at a pressure of 5 kPa or more and 50 kPa or less.

[0023] In this method for producing an iron-based soft magnetic alloy, the nozzle is preferably a single-slit nozzle, and is arranged so that the longitudinal direction of the slit is perpendicular to the rotation direction of the chill roll.The opening width of the slit is preferably 0.2 mm or more and 0.8 mm or less, and the distance from the nozzle to the chill roll is preferably 0.1 mm or more and 2.0 mm or less. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an iron-based soft magnetic alloy that exhibits a relatively high Bs of 1.55 T or more and 1.75 T or less, and at the same time has low iron loss performance equal to or greater than that of Fe-Si-B amorphous alloys, and that can be made into a laminated core, as well as a method for producing the same. [Brief explanation of the drawings]

[0025] [Figure 1] (a) is a schematic diagram of a manufacturing apparatus used in a method for manufacturing an iron-based soft magnetic alloy according to one embodiment of the present invention, (b) is an enlarged view of the main part thereof, and (c) is an enlarged view of the nozzle bottom surface. [Figure 2] 1 is a powder X-ray diffraction profile of the iron-based soft magnetic alloy obtained in Example 2. [Figure 3] 1 is a powder X-ray diffraction profile of the iron-based soft magnetic alloy obtained in Example 4. [Figure 4] 1 shows X-ray diffraction profiles of the free surface (opposite to the contact surface with the chill roll) and the chill roll surface of the Fe—Si—B based rapidly solidified alloy obtained in Comparative Example 12. [Figure 5] 1 shows X-ray diffraction profiles of the free surface (opposite to the contact surface with the chill roll) and the chill roll surface of the (Fe,Co)-Si-B based rapidly solidified alloy obtained in Comparative Example 13. [Figure 6] 1 is a plot of the relationship between magnetic flux density and iron loss for each operating frequency in the iron-based soft magnetic alloy obtained in Example 2. [Figure 7]10 is a plot of the relationship between magnetic flux density and iron loss for each operating frequency in the Fe—Si—B based rapidly solidified alloy obtained in Comparative Example 12. [Figure 8] 1 shows the frequency dependence of iron loss (core loss) at 1.5 T for Example 2, Comparative Example 12, and an electrical steel sheet (35A360). [Figure 9] 1 is a TEM photograph of the iron-based soft magnetic alloy of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0026] The iron-based soft magnetic alloy of the present invention has low iron loss performance that is equal to or better than that of Fe-Si-B amorphous alloys, with iron loss being 1 / 10 or less than that of electromagnetic steel sheets, while exhibiting a saturation magnetic flux density Bs of 1.55 T or more and 1.75 T, which can contribute to the miniaturization and high output of air conditioner compressor motors and fan motors for data centers.It can also be used to mass-produce laminated cores with press punching efficiency equivalent to that of electromagnetic steel sheets, and has an average thickness of 18 μm or more and less than 40 μm, and does not contain Co or Cu.

[0027] As described above, the present inventors have discovered that an iron-based soft magnetic alloy can be obtained that has low iron loss performance equal to or better than that of an Fe-Si-B amorphous alloy, and that can be used to mass-produce laminated cores with press punching efficiency equivalent to that of electrical steel sheet, by using a ternary composition range of the essential elements Fe, Si, and B, with the compounding ratios of each element being 1.0 atomic % to 2.2 atomic %, 11 atomic % to 14 atomic % of B, 0.0 atomic % to 15.0 atomic % of the additional element Ni, and the remainder being Fe, in which a portion of the B is replaced with C up to 30%, resulting in an inexpensive alloy composition that does not contain Co or Cu. The iron-based soft magnetic alloy has low iron loss performance equal to or better than that of an Fe-Si-B amorphous alloy, and a saturation magnetic flux density Bs of 1.55 T to 1.75 T that is applicable to air conditioner compressors, fan motors for data centers, and the like, while also ensuring a saturation magnetic flux density Bs of 1.55 T to 1.75 T. This saturation magnetic flux density Bs is 1.55 T to 1.75 T, which is applicable to air conditioner compressors, fan motors for data centers, and the like, and that can be used to mass-produce laminated cores with press punching efficiency equivalent to that of electrical steel sheet, and has thus arrived at the present invention.

[0028] [Alloy composition] The metallographic structure, in which Fe is an essential element and the remainder of the above-mentioned elements is a fine α-Fe phase with an average crystal grain size of 10 nm or less, contributes to achieving a saturation magnetic flux density Bs of 1.55 T to 1.75 T. The α-Fe phase is preferably the primary crystalline phase. The primary crystalline phase refers to the crystal when only one type of crystal is precipitated, or to the crystalline phase with the largest proportion of crystals when multiple crystals are precipitated. The alloy of the present invention may also contain a subphase, an Fe-B phase, particularly an Fe3B phase with a saturation magnetic flux density Bs of 1.5 T, in addition to the α-Fe phase. However, since the Bs of the Fe-B phase including the Fe3B phase is lower than that of the α-Fe phase, it is difficult to achieve a saturation magnetic flux density Bs of 1.55 T to 1.75 T if the primary crystalline phase is not the α-Fe phase.

[0029] In the present invention, Si is not only an essential element for obtaining a fine metal structure, but also plays an important role in developing soft magnetic properties such as magnetic permeability. If the Si composition ratio x is less than 1.0 atomic percent, not only will the magnetic permeability at an applied magnetic field of 10 A / m deteriorate to 1000 or less, but the core loss at 1.0 T and 2 kHz will exceed 50 W / kg, thereby diminishing the high magnetic permeability and low core loss characteristics of the iron-based soft magnetic alloy of the present invention compared to electrical steel sheets. Furthermore, if the Si composition ratio x exceeds 2.2 atomic percent, the abundance ratio of Fe, which is responsible for magnetization, decreases, making it impossible to achieve a saturation magnetic flux density Bs of 1.55 T or higher. For this reason, the Si composition ratio x is set to 1.0 atomic percent or more and 2.2 atomic percent or less. The Si composition ratio x is preferably 1.2 atomic percent or more and 2.0 atomic percent or less, and more preferably 1.2 atomic percent or more and 1.8 atomic percent or less.

[0030] If the B+C composition ratio y is less than 11.0 atomic percent, the iron-based soft magnetic alloy obtained by rapid solidification will have a coarse metal structure, making it impossible to produce a metal structure containing an ultrafine α-Fe phase with a grain size of 10 nm or less. This not only hinders the low iron loss performance of 50 W / kg or less at a magnetic flux density of 1.0 T and a frequency of 2 kHz, but also makes the iron-based soft magnetic alloy prone to cracking during the punching process, making it difficult to fabricate laminated cores. Furthermore, if the B+C composition ratio y exceeds 14.0 atomic percent, the abundance ratio of Fe, which is responsible for magnetization, will decrease, making it impossible to achieve Bs≧1.55 T. Therefore, the B+C composition ratio y is set to 11.0 atomic percent or more and 14.0 atomic percent or less. The B+C composition ratio y is preferably set to 12.0 atomic percent or more and 13.5 atomic percent or less, and more preferably 12.0 atomic percent or more and 13.0 atomic percent or less.

[0031] By substituting a portion of B with C, the melting point of the molten alloy is lowered, the rapid solidification conditions are relaxed, and the iron-based soft magnetic alloy of the present invention is easier to produce. However, if the substitution ratio m of C to B exceeds 30%, it is not possible to ensure a saturation magnetic flux density Bs of 1.55 T or more and 1.75 T or less, which is not preferable. For this reason, the substitution ratio m is limited to 30% or less. From the viewpoint of achieving both high Bs characteristics and low magnetic permeability, the substitution ratio m is preferably 20% or less, and more preferably 15% or less.

[0032] The addition of Ni makes it possible to obtain a relatively high saturation magnetic flux density compared to a Ni-free composition, but increasing the amount of Ni added promotes the precipitation of the Fe-B phase, which has lower magnetization than the α-Fe phase, resulting in a decrease in Bs. Therefore, to ensure a saturation magnetic flux density Bs of 1.55 T or more and 1.75 T or less, the Ni content z must be 15 atomic % or less. The Ni content z is preferably in the range of 0.5 atomic % to 10.0 atomic % and more preferably in the range of 1.0 atomic % to 6.0 atomic %.

[0033] In the iron-based soft magnetic alloy of the present invention, it is possible to add one or more additive elements selected from the group consisting of Al, Si, V, Ti, Mn, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb, but adding an additive concentration of more than 2.0 atomic % is not preferable because a saturation magnetic flux density Bs of 1.55 T or more and 1.75 T or less cannot be obtained, and the presence of 2.0 atomic % or less, including as an impurity, is acceptable. The iron-based soft magnetic alloy of the present invention does not contain Co or Cu.

[0034] [Metal structure] The iron-based soft magnetic alloy of the present invention can achieve a saturation magnetic flux density Bs of 1.55 T to 1.75 T by forming a metallographic structure mainly composed of a fine α-Fe phase with a crystal grain size of 10 nm or less, which is isotropically precipitated without any particular orientation. This metallographic structure may contain an Fe-B phase and an amorphous phase. The α-Fe and Fe-B phases may also contain an ultrafine crystalline structure called a crystalline precursor (cluster) with a crystal size of less than 1 nm. The α-Fe phase at the crystalline precursor level cannot be distinguished from an amorphous structure even when viewed with a transmission electron microscope (TEM), but can be distinguished using an X-ray diffractometer. It is preferable to use an X-ray diffractometer using synchrotron radiation, such as a synchrotron. The crystal sizes of the α-Fe and Fe-B phases can be roughly determined from the half-width of the X-ray diffraction peak in powder X-ray diffraction (XRD), or by observing the metallographic structure of the iron-based rapidly solidified alloy with a transmission electron microscope (TEM).

[0035] When the iron-based soft magnetic alloy of the present invention is mass-produced for use in laminated cores, it is necessary to continuously punch the iron-based soft magnetic alloy using a press to match the shape of a rotor core, stator core, etc. However, during the rapid solidification process in the production of the iron-based soft magnetic alloy, coarse α-Fe crystalline phases with an average grain size of 100 nm or more oriented in the α-Fe (200) direction (in-plane orientation) precipitated near the surface of the quench roll or free surface by heterogeneous nucleation during rapid solidification. This coarse α-Fe crystalline phase with an average grain size of 100 nm or more may become the starting point for cracks during punching, making punching difficult. For the reasons mentioned above, if the coarse α-Fe crystalline phase oriented in the α-Fe (200) direction exceeds 10.0 vol% of the entire metal structure, cracks and chips may occur in the iron-based soft magnetic alloy during punching. Therefore, the in-plane oriented α-Fe crystalline phase precipitated in the surface layer of the iron-based soft magnetic alloy is preferably 5.0 vol% or less, and from the viewpoint of stable punching workability, it is preferably 2.0 vol% or less, and more preferably less than 1.0 vol%. In the present invention, the surface layer refers to a depth from the surface of the iron-based soft magnetic alloy that is within a range of 10% of the thickness of the iron-based soft magnetic alloy.

[0036] [Magnetic properties] The saturation magnetic flux density Bs of the iron-based soft magnetic alloy of the present invention is 1.55 T or more and 1.75 T or less, either immediately after rapid solidification (as-spun) or after heat treatment from the as-spun state at a temperature of 180°C or more but less than 450°C for the purpose of distortion removal. If Bs exceeds 1.75 T, the iron loss at a magnetic flux density of 1.0 T and a frequency of 2 kHz exceeds 50 W / kg. Therefore, when applied to motor cores for air conditioner compressor motors, data center fan motors, and the like, no clear improvement in motor efficiency is achieved compared to cores made from electromagnetic steel sheets. From the viewpoint of achieving both sufficient motor torque and high efficiency in the low-speed rotation range, Bs is 1.55 T or more and 1.75 T or less, preferably 1.6 T or more and 1.73 T or more, and more preferably 1.6 T or more and 1.7 T or less.

[0037] In addition, while the iron loss values ​​of existing electromagnetic steel sheets, iron-based amorphous alloys, and iron-based nanocrystalline alloys tend to increase at each operating frequency as the magnetic flux density increases, the iron-based soft magnetic alloy of the present invention exhibits extremely unique magnetic properties in that the iron loss values ​​at each operating frequency show a clear tendency to saturate as the magnetic flux density increases. In order to make motor cores for air conditioner compressor motors and data center fan motors smaller and more powerful, it is necessary to increase the motor's rotation speed. However, since the normal rotation speed of air conditioner compressor motors is 8,000 to 10,000 rpm and that of data center fan motors is around 20,000 to 30,000 rpm, the operating frequency of the motor must be increased from the conventional 1 kHz or less to around 2 kHz. If the iron loss value at a magnetic flux density of 1.0 T at 2 kHz is too high (for example, 300 W / kg or more), the iron loss will be at the same level as that of iron-based amorphous alloys and iron-based nanocrystalline alloys. Therefore, the iron loss value at a magnetic flux density of 1.0 T at a frequency of 2 kHz should preferably be 50 W / kg or less, more preferably 30 W / kg or less, and even more preferably 25 W / kg or less.

[0038] [Method of manufacturing iron-based crystalline alloy] The iron-based soft magnetic 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 alloy having the above-described composition, and a step of rapidly solidifying the prepared molten alloy.

[0039] Fig. 1(a) is a schematic diagram of a single-roll molten metal quenching apparatus used in a method for producing an iron-based soft magnetic alloy according to one embodiment of the present invention, Fig. 1(b) is an enlarged view of the nozzle, and Fig. 1(c) is an enlarged view of the nozzle bottom. The single-roll molten metal quenching apparatus 1 shown in Fig. 1 comprises a melting furnace 2, a molten metal storage vessel 5, and a cooling roll 8.

[0040] The melting furnace 2 supplies molten alloy 3, obtained by melting raw materials using high-frequency induction heating, to a molten metal storage container 5 by rotating a tilting shaft 4. The molten metal storage container 5 is equipped with a nozzle 6 at its bottom, and further heats the molten alloy 3 using a heating coil (not shown). The molten alloy 3 is then ejected onto the surface (outer periphery) of a chill roll 8 through a slit 7 formed at the bottom end of the 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 alloy 9. The material of the nozzle 6 can be appropriately selected from materials containing, for example, quartz (SiO2), carbon (C), boron nitride (BN), silicon carbide (SiC), and alumina (Al2O3) as its main component.

[0041] The nozzle 6 is a single-slit nozzle with a single slit 7. The slit 7 is arranged so that its longitudinal direction is perpendicular to the rotation direction of the chill roll 8 (i.e., parallel to the rotation axis of the chill roll 8). The width W1 of the slit 7 serves to adjust the rate at which the molten alloy 3 is 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 molten alloy will be discharged at an excessively high rate, preventing heat removal by the chill roll 8 in time. This will cause 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 or more and 0.8 mm or less. The slit width W1 is preferably 0.3 mm or more and 0.7 mm or less, and more preferably 0.3 mm or more and 0.6 mm or less.

[0042] 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 less than 15 m / sec, the rapidly solidified alloy will have an excessive thickness of 40 μm or more. This may result in the iron-based soft magnetic alloy ribbon having an α-Fe crystalline phase oriented in the (200) direction and an average crystal grain size of 100 nm or more, which is precipitated by heterogeneous nucleation during rapid solidification, exceeding 10.0 volume % near the surface of the chill roll or free surface. This may make the iron-based soft magnetic alloy more susceptible to cracking or chipping during punching. On the other hand, if the surface speed of the chill roll 8 exceeds 55 m / sec, the thickness of the iron-based soft magnetic alloy ribbon will be 18 μm or less, making it difficult to ensure a core space factor of 90% or more when it is made into a laminated core. Therefore, the surface speed of the cooling roll 8 is 15 m / sec or more and 55 m / sec or less, preferably 20 m / sec or more and 50 m / sec or less, and more preferably 25 m / sec or more and 45 m / sec or less.

[0043] 1(a), if the distance d from the tip of the 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 0.1 mm or more and 2.0 mm or less, preferably 0.1 mm or more and 1.5 mm or less, and more preferably 0.15 mm or more and 1.0 mm or less.

[0044] 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.

[0045] The chill roll 8 is preferably formed from a material whose main ingredient is pure copper, copper alloy, molybdenum (Mo), or tungsten (W), thereby providing excellent thermal conductivity and durability. The main ingredient means that the main ingredient accounts for 50% or more by weight. The surface of the chill roll 8 may be plated with chromium, nickel, or an alloy of these, 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.

[0046] The diameter of the chill roll 8 is, for example, 200 to 20,000 mm. If the continuous rapid solidification time is short, such as 10 seconds or less, the chill roll 8 does not necessarily need to be water-cooled. However, if the continuous rapid solidification time is 10 seconds or longer, it is preferable to run cooling water through the inside of the chill roll 8 to suppress a temperature rise on the surface of 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.

[0047] [Heat treatment] In a preferred embodiment, the iron-based soft magnetic alloy is heat-treated at a constant temperature of 180°C to 450°C after rapid solidification or after punching press, thereby enabling strain removal in the iron-based soft magnetic alloy and further improving magnetic permeability. Heat treatment temperatures below 180°C reduce the effect of strain removal, while temperatures above 450°C tend to increase iron loss due to grain growth of the α-Fe that constitutes the iron-based soft magnetic alloy. The heat treatment temperature is preferably 200°C to 400°C, more preferably 200°C to 350°C. The heat treatment is preferably performed in a vacuum or inert gas atmosphere, but heat treatment in air is also acceptable as long as it is 350°C or less.

[0048] In addition, the heat treatment may be performed in a state where a plurality of iron-based soft magnetic alloy ribbons are superposed and adhered to each other. An adhesive resin may be applied to the adhesion surfaces of the plurality of superposed iron-based soft magnetic alloy ribbons, and a thermocompression bonding treatment may be performed within the above-mentioned heat treatment temperature range, thereby forming a multilayer bonded iron-based soft magnetic alloy simultaneously with the heat treatment.

[0049] 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.

[0050] 100 kg of raw materials containing B, C, Co, and Fe with a purity of 99.5% or higher 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 a height of 400 mm, equipped with a single-slit BN nozzle at the bottom. The nozzle slit width and length are shown in Table 1.

[0051] The 50 kg of molten alloy was then further heated by passing electricity through a high-frequency heating coil installed around the molten alloy storage vessel. After the temperature of the molten alloy reached a temperature approximately 100°C higher than the melting point of the alloy composition, the alumina molten alloy stopper located above the nozzle was removed, and the molten alloy was sprayed 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 is shown in Table 1. The spray pressure of the molten alloy from the nozzle, the roll surface speed of the chill roll, and the arithmetic mean roughness (Ra) of the chill roll surface are shown in Table 2.

[0052] 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, thereby obtaining a ribbon-shaped rapidly solidified alloy (in the examples, an iron-based soft magnetic alloy) having the average thickness and average width shown in Table 3. The obtained rapidly solidified alloy was subjected to a 10-time punching test using a 1 mm diameter punch, and it was confirmed whether or not cracks occurred in the iron-based soft magnetic alloy during the test. The results are shown in Table 3.

[0053] The rapidly solidified alloys were subjected to structural evaluation by powder X-ray diffraction (XRD), and it was confirmed that the α-Fe phase of each of the iron-based soft magnetic alloys of Examples 1-11 was isotropically precipitated without being oriented in a specific direction.

[0054] As representative examples, X-ray diffraction profiles evaluated from the free surface side of the iron-based soft magnetic alloy ribbon for Example 2 and Example 4 are shown in Figures 2 and 3, respectively. In both Figures 2 and 3, a diffraction peak of (110) near 44.5 degrees, which is the main peak of α-Fe, and a diffraction peak of (200) near 65.0 degrees, which is a secondary peak, are confirmed, and since both diffraction peaks have wide half-widths, it was confirmed that the result is a fine metal structure in which an isotropically precipitated α-Fe phase exists. Furthermore, in Example 2, in which Ni was added, an isotropically precipitated Fe-B phase (mostly FeB) exists together with the α-Fe.

[0055] Of the iron-based soft magnetic alloys of Examples 1-11, all except Example 10 were measured immediately after rapid solidification, and Example 10 was measured after heat treatment. Measurements of saturation magnetic flux density Bs, core loss (core loss) at a magnetic flux density of 1.0 T at 2 kHz, and magnetic permeability (μ), Bs were carried out using a vibration-type sample magnetometer manufactured by Toei Kogyo, and measurements of μ and core loss were carried out using an Iwasaki Electric BH analyzer equipped with an SST unit (single sheet magnetic property tester). As a representative example showing the relationship between magnetic flux density and core loss, Figure 6 shows a plot of the iron-based soft magnetic alloy of Example 2 at each operating frequency.

[0056] On the other hand, powder X-ray diffraction (XRD) analysis of the Fe-Si-B rapidly solidified alloys of Comparative Examples 12-17 revealed that the amorphous phase was dominant. As representative examples, X-ray diffraction profiles evaluated from the free surface side of the rapidly solidified alloy ribbons for Comparative Examples 12 and 13 are shown in Figures 4 and 5, respectively. As shown in Figure 4, Comparative Example 12 had an amorphous single-phase structure. Furthermore, as shown in Figure 5, Comparative Example 13 was found to have a structure in which the amorphous phase, which was the main phase, and an α-Fe phase with in-plane orientation due to heterogeneous nucleation were mixed in the surface layer. The constituent phases of the rapidly solidified alloys estimated from the powder X-ray diffraction results are shown in Table 3.

[0057] For Examples 1-11 and Comparative Examples 12-17, the core loss and magnetic permeability (μ) were measured at a saturation magnetic flux density Bs and a magnetic flux density of 1.0 T at 2 kHz, and the results are shown in Table 4. As a representative example of a comparative example showing the relationship between magnetic flux density and core loss, a plot of the iron-based soft magnetic alloy of Comparative Example 12 at each operating frequency is shown in FIG.

[0058] The rapidly solidified alloy of Comparative Example 16 had a Si-free composition and a slow roll surface speed of 10 m / sec, resulting in a coarse metal structure with an average crystal grain size of 100 nm, making it impossible to punch. In Comparative Example 17, the slit width was as wide as 0.9 mm, which increased the rate at which the molten metal was supplied from the single slit to the surface of the rapidly solidified roll, resulting in an average thickness of 40 μm or more, as shown in Table 3, and the punching test results were unacceptable.

[0059] The relationship between the operating frequency and the iron loss at a magnetic flux density of 1.5 T for each of Example 2, Comparative Example 12, and a commercially available electrical steel sheet (35A360 manufactured by JFE Corporation) is shown in Figure 8. Also, a TEM observation photograph of the iron-based soft magnetic alloy of Example 2 is shown in Figure 9.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Table 4] [Explanation of symbols]

[0064] l Single roll molten metal quenching equipment 2 Melting furnace 3 Molten alloy 4 Tilt axis 5 Hot water container 6 nozzles 7 Slit 8. Cooling roll 9 Rapidly solidified alloys

Claims

1. Composition formula Fe 100-x-y-z Ni z Si x (B 1-m C m ) y where the composition ratios x, y, z, and m are expressed as follows: 1.0≦x≦2.2 atomic%, 11.0≦y≦14.0 atomic%, 0.0≦z≦15.0 atomic%, 0.0≦m≦0.3 Satisfied, It has a metal structure consisting of an α-Fe phase, The saturation magnetic flux density is 1.55T or more and 1.75T or less, The iron loss at a magnetic flux density of 1.0T and a frequency of 2kHz is 50W / kg or less. The thickness is 18 μm or more and less than 40 μm, An iron-based soft magnetic alloy that does not contain Co or Cu.

2. A method for producing the iron-based soft magnetic alloy according to claim 1, comprising: Composition formula Fe 100-x-y-z Ni z Si x (B 1-m C m ) y where the composition ratios x, y, z, and m are expressed as follows: 1.0≦x≦2.2 atomic%, 11.0≦y≦14.0 atomic%, 0.0≦z≦15.0 atomic%, 0.0≦m≦0.3 preparing a molten alloy having a composition that satisfies the above and does not contain Co and Cu; a rapid solidification step of rapidly solidifying the molten alloy on a chill roll whose main raw material is any one of pure copper, copper alloy, Mo, and W, the rapidly solidifying step includes a step of spraying the molten alloy from a nozzle onto the surface of the chill roll while rotating the chill roll at a roll surface speed of 20 m / sec or more and 55 m / sec or less, thereby forming a thin ribbon of rapidly solidified alloy having a thickness of 18 μm or more and less than 40 μm, The surface roughness of the cooling roll is an arithmetic mean roughness (Ra) of 0.01 μm or more and 0.6 μm or less, A method for producing an iron-based soft magnetic alloy, in which the nozzle is made of a material whose main component is one of quartz (SiO2), carbon (C), boron nitride (BN), silicon carbide (SiC) and alumina (Al2O3), and the molten alloy is poured at a pressure of 5 kPa or more and 50 kPa or less.

3. the nozzle is a single-slit nozzle, and is arranged so that the longitudinal direction of the slit is perpendicular to the rotation direction of the cooling roll; The opening width of the slit is 0.2 mm or more and 0.8 mm or less, 3. The method for producing an iron-based soft magnetic alloy according to claim 2, wherein the distance from the nozzle to the chill roll is 0.1 mm or more and 2.0 mm or less.

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