Iron-based rare earth boron isotropic magnet alloy

Abstract

An iron base rare earth boron-based isotropic magnet alloy which is represented by the compositional formula T100-x-y-z(B1-nCn)xREyMz (where: T is one or more types of transition metal element selected from the group consisting of Fe, Co, and Ni, and necessarily includes Fe; RE is one or more types of rare earth element from among Nd and Pr, and necessarily includes Nd; and M is one or more types of metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), which has an alloy composition that has a composition such that the compositional ratios of x, y, and z satisfy 4.2 at%≤x≤5.6 at%, 11.5 at%≤y≤13.0 at%, and 0.0 at%≤z≤5.0 at% and such that 0.0≤n≤0.5 is satisfied, in which the B concentration is lower than the stoichiometric composition of an RE2Fe14B-type tetragonal compound, the main phase of which is an RE2Fe14B-type tetragonal compound having an average crystalline particle diameter of not less than 10 nm but less than 70 nm, and which has a metal structure having a grain boundary phase surrounding the main phase.

Description

[Technical Field]

[0001] The present invention relates to an iron-based rare earth boron isotropic magnet alloy, a method for producing an iron-based rare earth boron isotropic magnet alloy, and a method for producing a resin-bonded permanent magnet. [Background technology]

[0002] In recent years, microcrystalline isotropic magnets have been developed, consisting of hard magnetic phases such as Nd-Fe-B and Sm-Fe-N, which are made up of fine crystal grains on the order of nanometers to submicrometers, and nanocomposite isotropic magnets (hereinafter referred to as "nanocomposite magnets"), in which hard magnetic phases such as Nd-Fe-B and Sm-Fe-N, which are made up of fine crystal grains, exist in the same metal structure, along with soft magnetic phases such as Fe-B and α-Fe. Computer simulations using micromagnetics have revealed that these rare-earth iron-based isotropic magnets, consisting of crystal grains on the order of nanometers to submicrometers, exhibit excellent magnetic properties due to the fine crystal grains, which are magnetically coupled by exchange interactions in addition to magnetostatic interactions. These magnets are being put to practical use as high-performance permanent magnet materials.

[0003] Until now, fine-crystalline rare earth iron-based isotropic magnets have been utilized primarily in the electronics component industry, taking advantage of their isotropic properties. They have been crushed to an average particle size of between 50 μm and 200 μm, and then mixed with epoxy resin-based thermosetting resins or thermoplastic resins such as nylon and polyphenylene sulfide (PPS) to form resin-bonded magnets (commonly known as bonded magnets), which allow for a high degree of freedom in shape and are used as net-shape magnets, typically for optical drives and hard disk spindle motors, vibration motors (pager motors) for mobile phones, various sensors, etc. In recent years, the improved magnetic properties of fine-crystalline rare earth iron-based isotropic magnets have raised expectations for their use in brushless DC motors of around 1 horsepower (750 W) or less, for automobiles (including electric and hybrid vehicles) and white goods.

[0004] In particular, in order to achieve high performance and efficiency in small motors in the several hundred watt class, there is a shift from brushed motors using conventional ferrite magnets to brushless DC motors using bonded magnets, and there is a demand for magnetic materials for bonded magnets that have better residual magnetic flux density Br, intrinsic coercivity HcJ, and maximum energy product (BH)max than the bonded magnets using fine-crystalline rare earth iron-based isotropic magnetic materials that have been used in spindle motors, vibration motors, etc.

[0005] To meet these magnetic property requirements, it is necessary to maximize the volume ratio of the ferromagnetic phase, which exhibits hard or soft magnetism and is responsible for the magnetic properties, and minimize the volume ratio of the non-magnetic phase, which forms the grain boundary of the hard magnetic phase. For example, in an isotropic rare earth iron boron-based magnet material, the volume ratio of the hard magnetic phase, RE2Fe 14 The main phase is a B-type (RE is a rare earth element) compound, and the presence of a non-magnetic grain boundary phase containing boron surrounding the main phase adjusts the magnetic interaction between the main phase particles, resulting in the development of an intrinsic coercivity HcJ of 700 kA / m or more, which is applicable to various high-performance motors. 14 Increasing the volume ratio of B-type compounds requires reducing the boron content, but reducing the boron content too much reduces the squareness of the demagnetization curve, resulting in a decrease in the residual magnetic flux density Br and maximum energy product (BH)max. Therefore, there are no practical materials with a boron content of 0.9 mass% or less, and there is hope for an isotropic rare earth iron boron-based magnet material that can reduce the boron content and achieve excellent magnetic properties.

[0006] Nd2Fe with fine crystal grains is expected to have high magnetic properties. 14Although isotropic magnets with a B-type tetragonal compound as the main phase have a basic stoichiometric composition of Nd:Fe:B=11.76:balance:5.88, in order to achieve a residual magnetic flux density Br≧0.85 T that is applicable to various high-performance motors, it is necessary to make Nd≦11.76 atomic % and B≦5.88 atomic %. However, this composition range does not achieve an intrinsic coercivity HcJ of 700 kA / m or more, which is necessary for use in brushless DC motors of approximately 1 horsepower (750 W) or less for automobiles (including electric vehicles and hybrid vehicles) and white goods.

[0007] Also, Nd2Fe 14 In isotropic iron-based rare earth nanocomposite magnet alloys with B-type tetragonal compounds as the main phase, NdFe 14 The B phase and the α-Fe phase or the Fe-B phase are mixed in the same metal structure with nanometer-order crystal grain sizes, and the exchange interaction between the crystal grains causes them to behave as if they were a single magnet, resulting in excellent permanent magnet properties. 14 Because the proportion of B-type compounds cannot be increased, no RE-Fe-B isotropic permanent magnet material exhibiting sufficient magnetic properties has been found.

[0008] Patent Document 1 describes RE2Fe 14 The paper discloses an anisotropic sintered magnet with a B tetragonal crystal structure as the main phase, but the magnet is made of RE2Fe 14 It has a metal structure consisting of tetragonal crystal grains, and the magnetic moment is increased by magnetic orientation. 14 This magnet exhibits good magnetic properties by aligning the C-axis direction of the B tetragonal crystal, but as an isotropic magnet in which the magnetic moments are randomly arranged, good magnetic properties cannot be obtained and it cannot be used as a practical magnet.

[0009] Patent Document 2 discloses RE2Fe alloys containing at least 10 atomic % of rare earth elements, approximately 0.5 atomic % or more and approximately 10 atomic % or less of boron, and the remainder being iron. 14They have disclosed an isotropic permanent magnet with a hard magnetic phase having a B tetragonal crystal structure as the main phase, and have achieved a high intrinsic coercivity HcJ of up to 1460 kA / m. 14 The grain size of B-type crystal grains is 20 nm or more and 400 nm or less. 14 It contains crystal grains that exceed the single magnetic domain crystal grain size of B-type crystal grains. As a result, magnetization is reduced, and even in the example that obtained the best magnetic properties, the maximum residual magnetic flux density Br was 0.83 T and the maximum energy product (BH)max was 103 kJ / m. 3 Therefore, the magnetic properties required for use in automobiles (including electric vehicles and hybrid vehicles) and white goods as brushless DC motors of 1 horsepower (750 W) or less have not been achieved.

[0010] Patent Documents 3 and 4 disclose iron-based rare earth isotropic nanocomposite magnets. These iron-based rare earth isotropic nanocomposite magnets contain primarily α-Fe phase as the soft magnetic phase, and therefore may be able to achieve a high residual magnetic flux density Br of 0.9 T or more. However, they have poor squareness of the demagnetization curve and are inferior in demagnetization resistance and heat resistance, making them unsuitable as permanent magnet materials for use in automobiles and white goods.

[0011] On the other hand, Patent Document 5 describes that in an iron-based rare earth isotropic nanocomposite magnet containing mainly an iron-based boride phase as the soft magnetic phase, the addition of Ti suppresses the precipitation and growth of the α-Fe phase during the cooling process of the molten alloy, and NdFe 14 However, Ti easily combines with boron (B) and crystallizes into the TiB2 phase during the crystallization process, which means that the precipitation and growth of the main phase, Nd2Fe 14 The absolute amount of boron required for forming the B phase decreases, and the intrinsic coercivity HcJ expected from the concentration of the rare earth elements cannot be obtained.

[0012] Patent Document 6 discloses an iron-based rare earth isotropic nanocomposite magnet that contains mainly an iron-based boride phase as the soft magnetic phase, and teaches that the addition of Ti and carbon (C) can provide the following effects:

[0013] 1. The liquidus temperature of the molten alloy is lowered by 5°C or more (for example, by approximately 10°C or more and approximately 40°C or less). When the liquidus temperature of the molten alloy is lowered by adding carbon, the precipitation of coarse TiB2 phases and other phases is suppressed, so even if the molten alloy temperature is lowered accordingly, the viscosity of the molten alloy hardly increases. As a result, it becomes possible to continuously form a stable molten alloy flow during the quenching process of the molten alloy.

[0014] 2. When the molten metal temperature is low, sufficient cooling can be achieved on the surface of the chill roll, preventing winding on the chill roll and making it possible to uniformly refine the rapidly solidified alloy structure.

[0015] 3. Because the (B+C) concentration is high and the amorphous formation ability is high, the molten metal cooling rate is set to 10 2 °C / sec or more, 10 4 Therefore, it is possible to obtain a fine metal structure even at a relatively low temperature of about °C / sec or less. 14 It is possible to produce a rapidly solidified alloy containing 60% or more of the B phase by volume.

[0016] As described above, the iron-based rare earth isotropic nanocomposite magnet described in Patent Document 6, which requires the addition of Ti, has a uniform fine NdFe 14 It is believed that excellent permanent magnet properties are obtained when a hard magnetic phase with a B-type crystal structure and a soft magnetic phase consisting of an Fe phase and an Fe-B phase coexist in the same metal structure. However, Ti, an essential element, is a non-magnetic element, and Nd2Fe 14 Since the atoms do not enter the B phase, the Fe phase, or the Fe-B phase as compounds but are scattered at the grain boundaries, this results in a decrease in magnetization and does not allow for the realization of sufficient magnetic properties. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Publication No. 59-46008 [Patent Document 2] Japanese Patent Application Publication No. 60-9852 [Patent Document 3] Japanese Patent Application Publication No. 8-162312 [Patent Document 4] Japanese Patent Application Publication No. 10-53844 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-175908 [Patent Document 6] Japanese Patent Application Laid-Open No. 2003-178908 Summary of the Invention [Problem to be solved by the invention]

[0018] To enable application to various high-performance motors, the intrinsic coercivity HcJ ≥ 700kA / m is a necessary condition, so the main phase, RE2Fe 14 The B phase must account for 70% or more by volume. At the same time, to obtain the desired residual magnetic flux density Br ≥ 0.85T, it is necessary to minimize the amount of non-magnetic additive elements such as Ti that do not form compounds, while minimizing the size of the crystal grains to an average grain size of 10 nm or more and less than 70 nm so that the exchange interaction can function effectively, in order to maximize the interaction between each particle.

[0019] In addition, there is a trade-off between the intrinsic coercivity HcJ and the residual magnetic flux density Br. 14 Increasing the volume ratio of the main phase consisting of B-type hard magnetic compounds leads to a decrease in remanence Br. Therefore, in order to suppress the decrease in remanence Br, it is necessary to make the grain boundary phase adjacent to the main phase a hard or semi-hard magnetic phase that has high magnetization and a certain degree of anisotropy field, in addition to increasing the exchange interaction acting between each grain by achieving the above-mentioned uniform and fine metallographic structure.

[0020] The inventors have developed RE2Fe 14It was thought that by making the grain boundary phase adjacent to the main phase consisting of the B-type hard magnetic compound hard or semi-hard, it might be possible to obtain a permanent magnet material with superior magnetic properties not previously available. However, as mentioned above, it was found that it is difficult to suppress the decrease in remanence Br while maintaining a high intrinsic coercivity HcJ with the addition of elements such as Ti.

[0021] The present invention has been made in view of the above circumstances, and its main object is to provide an iron-based rare earth boron-based isotropic magnet alloy that can improve the residual magnetic flux density, intrinsic coercivity HcJ, and maximum energy product (BH)max, which are magnetic properties required for application to brushless DC motors of approximately 1 horsepower (750 W) or less in automobiles (including electric vehicles and hybrid vehicles) and white goods, as well as a method for producing the iron-based rare earth boron-based isotropic magnet alloy, and a method for producing a resin-bonded permanent magnet containing the iron-based rare earth boron-based isotropic magnet alloy. [Means for solving the problem]

[0022] In a first embodiment, the iron-based rare earth boron isotropic magnet alloy of the present invention is represented by the composition formula T 100-x-y-z (B 1-n C n ) x RE y M z (T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element selected from the group consisting of Nd and Pr, and is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and has an alloy composition having a composition in which the compositional ratios x, y, and z satisfy the following, respectively: 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5; RE2Fe 14 RE2Fe has a lower B content than the stoichiometric composition of the B-type tetragonal compound, but has an average crystal grain size of 10 nm or more and less than 70 nm. 14RE2Fe, with B-type tetragonal compound as the main phase 14 It has a metal structure that is finer than the critical diameter of the single magnetic domain of B-type tetragonal compounds.

[0023] In a second embodiment, the iron-based rare earth boron isotropic magnet alloy of the present invention is represented by the composition formula T 100-x-y-z (B 1-n C n ) x RE y M z (T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element selected from the group consisting of Nd and Pr, and is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and has an alloy composition having a composition in which the compositional ratios x, y, and z satisfy the following, respectively: 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5; RE2Fe 14 RE2Fe has a lower B content than the stoichiometric composition of the B-type tetragonal compound, but has an average crystal grain size of 10 nm or more and less than 70 nm. 14 The metal structure has a B-type tetragonal compound as the main phase, and a grain boundary phase surrounding the main phase.

[0024] The method for producing an iron-based rare earth boron-based isotropic magnet alloy of the present invention is to 100-x-y-z (B 1-n C n ) x RE y M z(T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that necessarily contains Fe; RE is at least one rare earth element that does not substantially contain La and Ce; and M is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and the composition ratios x, y, and z are each 4.2 atomic %≦x≦ 5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5; and spraying the molten alloy onto the surface of a rotating roll whose main component is Cu, Mo, W, or an alloy containing at least one of these metals at an average pouring rate of 200 g / min or more and less than 2000 g / min per orifice provided at the tip of a nozzle, thereby producing RE2Fe. 14 and producing a rapidly solidified alloy having 1% by volume or more of either a crystalline phase including a B phase or an amorphous phase.

[0025] In a first aspect, the method for producing a resin-bonded permanent magnet of the present invention comprises the steps of: preparing an iron-based rare earth-boron-based isotropic magnet alloy powder produced by the above-mentioned method for producing an iron-based rare earth-boron-based isotropic magnet alloy; adding a thermosetting resin to the iron-based rare earth-boron-based isotropic magnet alloy powder; filling the mixture into a molding die; and compression-molding the mixture into a compact; and then heat-treating the compact at a temperature equal to or higher than the polymerization temperature of the thermosetting resin.

[0026] In a second aspect, the method for producing a resin-bonded permanent magnet of the present invention comprises the steps of: preparing an iron-based rare earth-boron-based isotropic magnet alloy powder produced by the above-mentioned method for producing an iron-based rare earth-boron-based isotropic magnet alloy; and adding a thermoplastic resin to the iron-based rare earth-boron-based isotropic magnet alloy powder to prepare an injection molding compound, and then injection molding the compound. [Effects of the Invention]

[0027] The present invention provides an iron-based rare earth boron isotropic magnet alloy that can improve the remanence Br, intrinsic coercivity HcJ, and maximum energy product (BH)max, which are magnetic properties required for application to brushless DC motors of approximately 1 horsepower (750 W) or less in automobiles (including electric vehicles and hybrid vehicles) and white goods. The present invention also provides a method for producing the iron-based rare earth boron isotropic magnet alloy. Furthermore, the present invention also provides a method for producing a resin-bonded permanent magnet containing the iron-based rare earth boron isotropic magnet alloy. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view schematically showing an example of an iron-based rare earth boron isotropic magnet alloy of the present invention. [Figure 2] (a) is a diagram showing the equipment configuration of a heat treatment furnace that realizes flash annealing, and (b) is a diagram showing the state of the rapidly solidified alloy moving inside the furnace tube. [Figure 3] FIG. 2 is a conceptual diagram of the thermal history of flash annealing performed in the present invention. [Figure 4] 1 shows a bright-field image and element mapping of the iron-based rare earth boron isotropic magnet alloy obtained in Example 13, observed with a transmission electron microscope. [Figure 5] 1 shows a bright-field image and element mapping of the iron-based rare earth boron isotropic magnet alloy obtained in Comparative Example 38, observed with a transmission electron microscope. [Figure 6] 1 shows a powder X-ray diffraction profile of the rapidly solidified alloy obtained in Example 13. [Figure 7] 1 shows a powder X-ray diffraction profile of the rapidly solidified alloy obtained in Example 13 after flash annealing (crystallization heat treatment). [Figure 8] 1 is a powder X-ray diffraction profile of the rapidly solidified alloy obtained in Comparative Example 38 after flash annealing (crystallization heat treatment). DETAILED DESCRIPTION OF THE INVENTION

[0029] The following describes the iron-based rare earth boron isotropic magnet alloy of the present invention, the method for producing the iron-based rare earth boron isotropic magnet alloy of the present invention, and the method for producing a resin-bonded permanent magnet of the present invention. Note that the present invention is not limited to the following configurations and may be modified as appropriate without departing from the gist of the present invention. Furthermore, a combination of multiple individual preferred configurations described below also constitutes the present invention.

[0030] In a first embodiment, the iron-based rare earth boron isotropic magnet alloy of the present invention is represented by the composition formula T 100-x-y-z (B 1-n C n ) x RE y M z (T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element selected from the group consisting of Nd and Pr, and is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and has an alloy composition having a composition in which the compositional ratios x, y, and z satisfy the following, respectively: 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5; RE2Fe 14 RE2Fe has a lower B content than the stoichiometric composition of the B-type tetragonal compound, but has an average crystal grain size of 10 nm or more and less than 70 nm. 14 RE2Fe, with B-type tetragonal compound as the main phase 14 It is characterized by having a metal structure that is finer than the critical diameter of the single magnetic domain of a B-type tetragonal compound.

[0031] In a second embodiment, the iron-based rare earth boron isotropic magnet alloy of the present invention is represented by the composition formula T 100-x-y-z (B 1-n C n ) x RE y M z(T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element selected from the group consisting of Nd and Pr, and is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and has an alloy composition having a composition in which the compositional ratios x, y, and z satisfy the following, respectively: 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5; RE2Fe 14 RE2Fe has a lower B content than the stoichiometric composition of the B-type tetragonal compound, but has an average crystal grain size of 10 nm or more and less than 70 nm. 14 The iron-based rare earth boron isotropic magnet alloy of the present invention is characterized by a metal structure in which a B-type tetragonal compound is the main phase and a grain boundary phase surrounds the main phase. An example of such an iron-based rare earth boron isotropic magnet alloy of the present invention is shown in Figure 1.

[0032] In a second aspect, the iron-based rare earth boron isotropic magnet alloy of the present invention is RE2Fe 14 It has a metal structure finer than the critical diameter of the single magnetic domain of B-type tetragonal compounds, and is 14 It is preferable that the grain boundary phase surrounding the main phase made of the B-type tetragonal compound contains RE and Fe as main components.

[0033] In the second aspect of the iron-based rare earth boron isotropic magnet alloy of the present invention, 14 The grain boundary phase containing RE and Fe as main components and surrounding the main phase made of the B-type tetragonal compound is preferably a ferromagnetic phase.

[0034] In the second aspect of the iron-based rare earth boron isotropic magnet alloy of the present invention, 14 The width of the grain boundary phase containing RE and Fe as main components and surrounding the main phase made of the B-type tetragonal compound is preferably 1 nm or more and less than 10 nm.

[0035] The iron-based rare earth boron isotropic magnet alloy of the present invention is characterized by a low boron content, and is represented by RE2Fe 14 The boron (B) content in the alloy composition range in which a magnet alloy with the B phase as the main phase can be obtained is defined as RE2Fe 14 The content of the rare earth element (RE) and iron (Fe) in the main phase of the iron-based rare earth boron isotropic magnet alloy of the present invention is in a surplus state, which is lower than the stoichiometric composition of the B phase. 14 The grain boundary phase is formed from the excess RE and Fe that are not required for the formation of the B phase. As a result, the iron-based rare earth boron isotropic magnet alloy of the present invention has an REFe alloy with an average grain size of 10 nm or more and less than 70 nm. 14 It has a unique fine metal structure with a grain boundary phase that surrounds the B phase and is composed mainly of RE and Fe and has a width of 1 nm or more and less than 10 nm.

[0036] By realizing the above-mentioned unique uniform and fine metal structure, the inventors have found that the main phase, RE2Fe 14 The B phase and the grain boundary phase, which is uniformly present around the main phase and is mainly composed of RE and Fe, are connected by strong exchange interactions in addition to magnetostatic interactions, and behave as if they are an integrated hard magnetic phase with the grain boundary phase (e.g., α-Fe phase) that has a saturation magnetization equal to or greater than that of the main phase, resulting in the formation of the RE2Fe 14 It was found that a high remanence Br and a high maximum energy product (BH)max can be obtained by improving the squareness of the demagnetization curve without compromising the intrinsic coercivity HcJ of the B phase. In particular, it is believed that the presence of the grain boundary phase described above contributes to the realization of a high intrinsic coercivity HcJ, and that the presence of a small average crystal grain size described above contributes to the realization of a high remanence Br and intrinsic coercivity HcJ.

[0037] When the boron content is less than 4.2 atomic %, the main phase, RE2Fe 14 Since the formation of the B phase is inhibited, both the intrinsic coercivity HcJ and the residual magnetic flux density Br are significantly reduced. 14 B single phase or RE2Fe14 Since the metal structure has a non-magnetic B-rich phase around the B phase, a high intrinsic coercivity HcJ can be maintained, but the remanence Br and maximum energy product (BH)max do not increase, resulting in insufficient magnetic properties, such as remanence Br: 0.85T or more, intrinsic coercivity HcJ: 700kA / m or more but less than 1400kA / m, maximum energy product (BH)max: 120kJ / m. 3 The above magnetic properties cannot be obtained.

[0038] On the other hand, when the boron concentration is 4.2 atomic % or more and 5.6 atomic % or less, the main phase, RE2Fe 14 It is believed that the above magnetic properties are obtained because the grain boundary phase, which is mainly composed of RE and Fe, is uniformly formed without impairing the formation of the B phase.

[0039] Patent Documents 2, 3, 4, 5 and 6 all use the intrinsic coercivity HcJ of RE2Fe 14 The present paper discloses a microcrystalline isotropic permanent magnet material made of B-type tetragonal compounds, and the magnitude of the intrinsic coercivity HcJ is mainly determined by the RE2Fe 14 It depends largely on the volume ratio of B-type tetragonal compounds, RE2Fe 14 If the volume ratio of the B phase is high, the intrinsic coercivity HcJ will be high, and RE2Fe 14 If the volume ratio of the B phase is low, the intrinsic coercivity HcJ will be low.

[0040] On the other hand, the anisotropic RE2Fe described in Patent Document 1 14 In B sintered magnets, heavy rare earth elements such as Dy and Tb are used in the main phase, RE2Fe 14 Included in B-type tetragonal compounds is RE2Fe 14 By increasing the anisotropy field of the B-type tetragonal compound, the intrinsic coercivity HcJ is improved. The above-mentioned fine isotropic permanent magnet material and anisotropic sintered magnet are both RE2Fe 14 Although the main phase of the anisotropic sintered magnet is a B-type tetragonal compound, the size of the main phase is approximately 1 μm or more and 10 μm or less. 14This is greater than the critical diameter for a single magnetic domain of a B-type tetragonal compound. Therefore, although an anisotropic sintered magnet is in a multi-domain state before magnetization, the magnetic moments are aligned in the magnetization direction (C-axis direction) upon magnetization, and the magnet exhibits permanent magnetic properties by becoming a single domain. Therefore, the intrinsic coercivity HcJ of an anisotropic sintered magnet represents the ability to maintain a state in which the magnetic moments are aligned in the same direction, and therefore RE2Fe 14 By increasing the anisotropy field of the B-type tetragonal compound, the intrinsic coercivity HcJ is improved.

[0041] The iron-based rare earth boron isotropic magnet alloy of the present invention, characterized by its low boron content, realizes a unique metal structure with a grain boundary phase mainly composed of RE and Fe. When a heavy rare earth element such as Dy is added to the alloy composition, the main phase, REFe, 14 The anisotropy field of not only the B-type tetragonal compound but also the grain boundary phase is improved. Therefore, it is possible to suppress the demagnetization of the magnetic moment of the main phase, which is smaller than the single-domain crystal grain size, by the grain boundary phase, and this is superior to the conventional fine-crystal isotropic RE2Fe 14 It has been found that the addition of heavy rare earth elements can improve the intrinsic coercivity HcJ, which was not effective in the case of B permanent magnet materials. Therefore, the iron-based rare earth boron-based isotropic magnet alloy of the present invention can produce an unprecedented high-performance isotropic RE2Fe alloy with high intrinsic coercivity HcJ without causing a significant decrease in remanence Br. 14 B permanent magnet is obtained.

[0042] In addition, it has been discovered that the iron-based rare earth-boron isotropic magnet alloy of the present invention, characterized by its low boron content, can achieve an improvement in intrinsic coercivity HcJ without a decrease in remanence Br by substituting a portion of the boron (B) with carbon (C). Furthermore, the improvement in intrinsic coercivity HcJ can be further enhanced by combining the carbon (C) substitution with the addition of a heavy rare earth element.

[0043] [Alloy composition] The alloy composition of the iron-based rare earth boron isotropic magnet alloy of the present invention is represented by the composition formula T 100-x-y-z (B 1-n C n ) x RE y Mz (T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element selected from the group consisting of Nd and Pr, and is at least one element that must include Nd; and M is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and has a composition in which the compositional ratios x, y, and z satisfy the following, respectively: 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5. The composition of the entire magnet alloy according to the present invention is analyzed by ICP mass spectrometry. Combustion-infrared absorption spectrometry may also be used in combination, if necessary.

[0044] The transition metal element T, which contains Fe as an essential element, accounts for the remainder of the above-mentioned elements. The desired hard magnetic properties can also be obtained by substituting a portion of the Fe with one or both of Co and Ni, which are also ferromagnetic elements like Fe. However, since a substitution amount of more than 30% of Fe results in a significant decrease in magnetic flux density, the substitution amount is preferably in the range of 0% to 30%. The addition of Co not only contributes to improving magnetization but also reduces the viscosity of the molten metal, thereby stabilizing the melt tapping rate from the nozzle during quenching. Therefore, the Co substitution amount is more preferably 0.5% to 30%. From the viewpoint of cost-effectiveness, the Co substitution amount is even more preferably 0.5% to 10%.

[0045] In the iron-based rare earth boron-based isotropic magnet alloy of the present invention, when the composition ratio x of B+C is less than 4.2 atomic %, RE2Fe 14If the amount of B+C necessary to form the B-type tetragonal compound cannot be secured, the magnetic properties and amorphous formation ability will be significantly reduced, resulting in the precipitation of an α-Fe phase during rapid solidification of the molten alloy, resulting in a loss of squareness in the demagnetization curve. Furthermore, if the B+C composition ratio x exceeds 5.6 atomic percent, a grain boundary phase primarily composed of RE and Fe will not be formed, potentially making it impossible to ensure the above-mentioned magnetic properties. Therefore, the composition ratio x is limited to a range of 4.2 atomic percent to 5.6 atomic percent. The composition ratio x is preferably 4.2 atomic percent to 5.2 atomic percent, and more preferably 4.4 atomic percent to 5.0 atomic percent.

[0046] In the iron-based rare earth-boron isotropic magnet alloy of the present invention, substituting a portion of B with C lowers the melting point of the molten alloy and reduces the amount of wear on the refractory used during rapid solidification, thereby reducing the process costs associated with rapid solidification and improving the intrinsic coercivity HcJ. However, if the substitution rate of C for B exceeds 50%, the amorphous formation ability decreases significantly, which is undesirable. Therefore, the substitution rate of C for B is limited to a range of 0% to 50%, i.e., 0.0≦n≦0.5. From the perspective of improving the intrinsic coercivity HcJ, the substitution rate of C for B is preferably 2% to 30%, and more preferably 3% to 15%.

[0047] In the iron-based rare earth boron isotropic magnet alloy of the present invention, if the composition ratio y of at least one rare earth element RE, which must contain at least Nd among Nd and Pr, is less than 11.5 atomic %, a grain boundary phase mainly composed of RE and Fe will not be generated, and the above-mentioned magnetic properties may not be ensured. Furthermore, if the composition ratio y exceeds 13.0 atomic %, the magnetization will decrease. Therefore, the composition ratio y is limited to a range of 11.5 atomic % or more and 13.0 atomic % or less. Furthermore, from the viewpoint of ensuring a stable intrinsic coercivity HcJ, the composition ratio y is set to RE2Fe 14 It is preferably 11.76 atomic % or more and 13.0 atomic % or less, which is the stoichiometric composition of a B-type tetragonal compound, and more preferably 11.76 atomic % or more and 12.5 atomic % or less from the viewpoint of ensuring a high residual magnetic flux density Br.

[0048] In addition, the rare earth REs mentioned above are used to obtain higher intrinsic coercivity HcJ. y =(Nd 1-l Pr l ) y In this case, l is limited to 0.05 or more and 0.7 or less. If the ratio l of Pr to Nd is too low, the effect of improving HcJ is small, and if l is too high, the absolute value of the temperature coefficient β related to the coercivity of the magnet alloy becomes small, raising concerns about a decrease in heat resistance. Therefore, l is preferably 0.15 or more and 0.6 or less, and more preferably 0.2 or more and 0.5 or less.

[0049] The iron-based rare earth-boron isotropic magnet alloy of the present invention may contain one or more metal elements M selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb. The addition of metal elements M improves the amorphous formation ability, the intrinsic coercivity HcJ by uniformly refining the metal structure after crystallization heat treatment, and the squareness of the demagnetization curve, thereby improving magnetic properties. However, since a composition ratio z of these metal elements M exceeding 5.0 atomic percent results in a decrease in magnetization, the composition ratio z is limited to a range of 0.0 atomic percent to 5.0 atomic percent. Furthermore, the composition ratio z is preferably 0.0 atomic percent to 4.0 atomic percent, and more preferably 0.0 atomic percent to 3.0 atomic percent.

[0050] [Metal structure] In the iron-based rare earth boron isotropic magnet alloy of the present invention, the main phase RE2Fe 14 If the average crystal grain size of a B-type tetragonal compound is less than 10 nm, the intrinsic coercivity HcJ decreases, and if it is 70 nm or more, the squareness of the demagnetization curve decreases due to the decrease in the exchange interaction between the crystal grains. Therefore, for example, the remanence Br: 0.85 T or more, the intrinsic coercivity HcJ: 700 kA / m or more but less than 1400 kA / m, and the maximum energy product (BH)max: 120 kJ / m 3 To achieve the above magnetic properties, RE2Fe 14The average crystal grain size of the B-type tetragonal compound is limited to the range of 10 nm or more and less than 70 nm. 14 The average crystal grain size of the B-type tetragonal compound is preferably 15 nm or more and 60 nm or less, and more preferably 15 nm or more and 50 nm or less.

[0051] RE2Fe 14 The average crystal grain size of a B-type tetragonal compound means the average value of the equivalent circle diameters of each particle present in the field of view when the particle size of each particle is measured at three or more points by the line segment method using a transmission electron microscope (TEM).

[0052] In addition, the above RE2Fe 14 When the width of the grain boundary phase, mainly composed of RE and Fe and surrounding the main phase of a B-type tetragonal compound, is less than 1 nm, the bonding force between the main phase particles increases, resulting in a decrease in the intrinsic coercivity HcJ. Conversely, when the width of the grain boundary phase is 10 nm or more, the interparticle bonding weakens, resulting in a decrease in the squareness of the demagnetization curve. Therefore, the width of the grain boundary phase is preferably 1 nm or more but less than 10 nm, more preferably 2 nm or more but 8 nm or less, and even more preferably 2 nm or more but 5 nm or less. The width of the grain boundary phase was determined by image analysis of bright-field images taken using a scanning transmission electron microscope at an accelerating voltage of 200 kV and a magnification of 900,000 times.

[0053] In the second aspect of the iron-based rare earth boron isotropic magnet alloy of the present invention, 14 In the composition ratio of the grain boundary phase mainly composed of RE and Fe surrounding the main phase made of a B-type tetragonal compound, it is preferable that the ratio of the main phase is 70% by volume or more but less than 99% by volume, and the ratio of the grain boundary phase is 1% by volume or more but less than 30% by volume. This results in, for example, a remanence Br of 0.85 T or more, an intrinsic coercivity HcJ of 700 kA / m or more but less than 1400 kA / m, and a maximum energy product (BH)max of 120 kJ / m. 3This makes it easier to achieve the above magnetic properties. The ratio of the main phase is preferably 80 volume % or more and less than 99 volume %, and more preferably 90 volume % or more and less than 98 volume %. The composition ratio of the main phase and grain boundary phase was determined by performing image analysis on bright-field images taken using a scanning transmission electron microscope under conditions of an accelerating voltage of 200 kV and an observation magnification of 900,000 times.

[0054] [Magnetic properties] As will be described later, the iron-based rare earth boron isotropic magnet of the present invention has, for example, a residual magnetic flux density Br of 0.85 T or more, an intrinsic coercivity HcJ of 700 kA / m or more but less than 1200 kA / m, and a maximum energy product (BH)max of 120 kJ / m. 3 Although the above magnetic properties can be exhibited, when used in various rotating machines that are optimal for electrical equipment and home appliances of approximately 1 horsepower (750 W) or less, and in a magnetic circuit configuration in which a reverse magnetic field is easily applied to permanent magnets such as surface permanent magnet rotors (SPM rotors), the intrinsic coercivity HcJ is preferably 800 kA / m or more, and more preferably 950 kA / m or more. Note that, because magnetization significantly decreases when the intrinsic coercivity HcJ is 1400 kA / m or more, the intrinsic coercivity HcJ is preferably 1300 kA / m or less, and more preferably 1250 kA / m or less. Furthermore, when an embedded magnet rotor (IPM rotor) or the like is used, it becomes possible to drive the motor at a higher operating point (permeance) than with an SPM rotor, so it is better for the residual magnetic flux density Br to be as high as possible. However, when considering the balance with the intrinsic coercive force HcJ, the residual magnetic flux density Br is preferably 0.87 T or more, and more preferably 0.9 T or more.

[0055] The reason why the residual magnetic flux density Br is set to 0.85T or more is that when used as an isotropic bonded magnet in a DC brushless motor, the operating point (permeance Pc) of the magnet is between 3 and 10, so if the residual magnetic flux density Br is 0.85T or more, within this Pc range, the maximum energy product (BH)max is 300kJ / m 3This is because the effective magnetic flux Bm can be obtained at the same level as the anisotropic Nd-Fe-B sintered magnets described above. It is more preferable that the residual magnetic flux density Br is 0.86 T or more.

[0056] The reason why the intrinsic coercivity HcJ is set to 700kA / m or more is that if the intrinsic coercivity HcJ is less than 700kA / m and the magnet is applied as an isotropic bonded magnet to a DC brushless motor, the motor's heat resistance temperature cannot be guaranteed to 100°C, and there is a possibility that the desired motor characteristics will not be obtained due to thermal demagnetization. Additionally, the reason why the intrinsic coercivity HcJ is set to less than 1400kA / m is that if the intrinsic coercivity HcJ is 1400kA / m or more, magnetization becomes difficult, and multi-pole magnetization to ensure Pc: 3 or more and 10 or less becomes difficult.

[0057] Furthermore, the maximum energy product (BH)max is 120kJ / m 3 The reason for this is that the maximum energy product (BH) is 120kJ / m 3 Below this, the squareness ratio of the demagnetization curve (residual magnetization Jr / saturation magnetization Js) will be 0.8 or less, and if used as an isotropic bonded magnet in a DC brushless motor, the magnetic properties will deteriorate due to the reverse magnetic field generated during motor operation, and there is a possibility that the desired motor characteristics will not be obtained.

[0058] The method for producing an iron-based rare earth boron-based isotropic magnet alloy of the present invention is to 100-x-y-z (B 1-n C n ) x RE y M z(T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that necessarily contains Fe; RE is at least one rare earth element that does not substantially contain La and Ce; and M is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), and the composition ratios x, y, and z are each 4.2 atomic %≦x≦ 5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %, and 0.0≦n≦0.5; and spraying the molten alloy onto the surface of a rotating roll whose main component is Cu, Mo, W, or an alloy containing at least one of these metals at an average pouring rate of 200 g / min or more and less than 2000 g / min per orifice provided at the tip of a nozzle, thereby producing RE2Fe. 14 and producing a rapidly solidified alloy having 1% by volume or more of either a crystalline phase including a B phase or an amorphous phase. Note that RE is at least one rare earth element that does not substantially contain La and Ce, but as an example, as described above, it can be at least one rare earth element that necessarily contains at least Nd out of Nd and Pr. Details are as described above.

[0059] [Quenching of molten metal] In the method for producing an iron-based rare earth boron-based isotropic magnet alloy of the present invention, raw materials prepared to have a predetermined alloy composition are melted to produce a molten alloy, and then the molten alloy is sprayed onto the surface of a rotating roll whose main component is Cu, Mo, W, or an alloy containing at least one of these metals at an average pouring rate of 200 g / min or more and less than 2000 g / min per orifice provided at the tip of a nozzle. 14A rapidly solidified alloy containing at least 1% by volume of either a crystalline phase, including a B phase, or an amorphous phase is produced. However, if the average tapping rate is less than 200 g / min, productivity is poor, and if it is more than 2000 g / min, the rapidly solidified alloy structure will contain a coarse α-Fe phase, which may prevent the magnetic properties from being achieved even after crystallization heat treatment. Therefore, the average tapping rate per orifice located at the tip of the nozzle is limited to a range of 200 g / min or more and less than 2000 g / min. The average tapping rate is preferably 300 g / min or more and 1500 g / min or less, and more preferably 400 g / min or more and 1300 g / min or less.

[0060] The hole at the nozzle tip through which the molten metal is discharged does not have to be a circular orifice; it can be any shape, such as square, triangular, elliptical, etc., and a slit shape is also acceptable as long as it can ensure a predetermined dispensing rate. In addition, the nozzle material is acceptable as long as it is a refractory material that does not or is difficult to react with the molten alloy, but ceramic materials such as SiC, C, or BN are preferred, as they cause little wear to the nozzle orifice due to the molten metal during dispensing, and BN is more preferred, with hard BN containing an additive being even more preferred.

[0061] When producing the above-mentioned rapidly solidified alloy, an oxygen-free or low-oxygen atmosphere is preferred for rapid solidification, since this prevents oxidation of the molten alloy, suppresses an increase in the molten alloy viscosity, and maintains a stable melt tapping rate. To achieve this atmosphere, the rapid solidification apparatus must be evacuated to a vacuum of 20 Pa or less, preferably 10 Pa or less, and more preferably 1 Pa or less, and then an inert gas must be introduced into the rapid solidification apparatus to adjust the oxygen concentration within the apparatus to 500 ppm or less, preferably 200 ppm or less, and more preferably 100 ppm or less, before rapid solidification. As the inert gas, rare gases such as helium and argon, or nitrogen, can be used. However, because nitrogen is relatively reactive with rare earth elements and iron, rare gases such as helium and argon are preferred, and argon gas is more preferred from a cost perspective.

[0062] In the process of producing a rapidly solidified alloy, the rotating roll used to rapidly cool the molten alloy is primarily composed of Cu, Mo, W, or an alloy containing at least one of these metals. It is preferable for the rotating roll to have a base material containing such a primary component. This is because these base materials have excellent thermal conductivity and durability. Furthermore, plating the surface of the rotating roll base with Cr, Ni, or a combination thereof can enhance the heat resistance and hardness of the rotating roll base surface and suppress melting and deterioration of the rotating roll base surface during rapid solidification. The diameter of the rotating roll is, for example, Φ200 mm or more and Φ20,000 mm or less. If the rapid solidification time is short, 10 seconds or less, water cooling of the rotating roll is not necessary. However, if the rapid solidification time exceeds 10 seconds, it is preferable to flow cooling water inside the rotating roll to suppress temperature rise of the rotating roll base material. The water cooling capacity of the rotating roll is preferably calculated based on the latent heat of solidification per unit time and the melt tapping rate, and is optimally adjusted as appropriate.

[0063] [Flash Annealing] The method for producing an iron-based rare earth boron-based isotropic magnet alloy of the present invention further comprises a step of flash annealing the rapidly solidified alloy, in which the alloy is heated at a rate of 10°C / sec or more and less than 200°C / sec to a constant temperature range of not less than the crystallization temperature and not more than 850°C, and then rapidly cooled after a lapse of not less than 0.1 sec and not more than 7 min. 14 RE2Fe has a lower B content than the stoichiometric composition of the B-type tetragonal compound, but has an average crystal grain size of 10 nm or more and less than 70 nm. 14 RE2Fe has a B-type tetragonal compound as its main phase, and a grain boundary phase, mainly composed of RE and Fe, with a width of 1 nm or more and less than 10 nm, surrounding the main phase. 14 It is preferable to form a metal structure finer than the critical diameter of the single magnetic domain of a B-type tetragonal compound.

[0064] If the heating rate during flash annealing (crystallization heat treatment) is less than 10°C / sec, excessive grain growth will prevent the formation of a fine metal structure, resulting in a decrease in intrinsic coercivity HcJ and residual magnetic flux density Br. If the heating rate is 200°C / sec or more, grain growth will not occur in time, resulting in RE2Fe with an average grain size of 10nm or more and less than 70nm, which is necessary for the development of a permanent magnet. 14 RE2Fe has a B-type tetragonal compound as its main phase, and a grain boundary phase with a width of 1 nm or more and less than 10 nm, which is mainly composed of RE and Fe, surrounding the main phase. 14 The metal structure does not become finer than the critical diameter of the single magnetic domain of the B-type tetragonal compound, and the magnetic properties deteriorate as in the case of heating at a rate of less than 10°C / sec. Therefore, the heating rate is preferably 10°C / sec or more and less than 200°C / sec, more preferably 30°C / sec or more and 200°C / sec or less, and even more preferably 40°C / sec or more and 180°C / sec or less.

[0065] In the flash annealing (crystallization heat treatment) in the manufacturing method of the iron-based rare earth-boron isotropic magnet alloy of the present invention, in order to obtain good magnetic properties, it is preferable to immediately quench the alloy after reaching a crystallization heat treatment temperature (holding temperature) in a constant temperature range of above the crystallization temperature and below 850°C. More specifically, a holding time of substantially 0.1 seconds or more after reaching the crystallization heat treatment temperature and before quenching is sufficient; holding for 7 minutes or more is undesirable because it damages the uniform and fine metal structure and leads to a deterioration of various magnetic properties. Therefore, a holding time of 0.1 seconds or more but less than 7 minutes is preferable, more preferably 0.1 seconds or more but less than 2 minutes, and even more preferably 0.1 seconds or more but less than 30 seconds.

[0066] In the flash annealing (crystallization heat treatment) in the manufacturing method of the iron-based rare earth boron-based isotropic magnet alloy of the present invention, it is preferable to cool the rapidly solidified alloy to 400°C or less at a temperature drop rate of 2°C / sec or more and 200°C / sec or less. If the temperature drop rate is less than 2°C / sec, the crystalline structure will become coarse, and if it exceeds 200°C / sec, the alloy may oxidize. Therefore, the temperature drop rate is preferably 2°C / sec or more and 200°C / sec or less, more preferably 5°C / sec or more and 200°C / sec or less, and even more preferably 5°C / sec or more and 150°C / sec or less.

[0067] The flash annealing (crystallization heat treatment) is preferably performed in an inert gas atmosphere to prevent oxidation of the rapidly solidified alloy. As the inert gas, rare gases such as helium and argon, or nitrogen can be used. However, since nitrogen reacts relatively easily with rare earth elements and iron, rare gases such as helium and argon are preferred, and argon gas is more preferred from the viewpoint of cost.

[0068] [Crushing and molding] The method for producing an iron-based rare earth-boron-based isotropic magnet alloy of the present invention may further include a step of producing an iron-based rare earth-boron-based isotropic magnet alloy powder by pulverizing the rapidly solidified alloy or the rapidly solidified alloy that has been subjected to the flash annealing.

[0069] The rapidly solidified alloy obtained through the above process may be roughly cut or crushed into thin ribbons, for example, to 50 mm or less, before flash annealing (crystallization heat treatment).Furthermore, by crushing the magnetic alloy of the present invention after flash annealing (crystallization heat treatment) into magnetic alloy powder with an average powder particle size of 20 μm or more and 200 μm or less, various resin-bonded permanent magnets (commonly known as plastic magnets or bonded magnets) can be manufactured using the magnetic alloy powder by known processes.

[0070] In a first aspect, the method for producing a resin-bonded permanent magnet of the present invention comprises the steps of: preparing an iron-based rare earth-boron-based isotropic magnet alloy powder produced by the above-mentioned method for producing an iron-based rare earth-boron-based isotropic magnet alloy; adding a thermosetting resin to the iron-based rare earth-boron-based isotropic magnet alloy powder, filling the powder into a molding die, and compression-molding the resulting compact, followed by heat treatment at a temperature equal to or higher than the polymerization temperature of the thermosetting resin.

[0071] In a second aspect, the method for producing a resin-bonded permanent magnet of the present invention is characterized by comprising the steps of: preparing an iron-based rare earth-boron-based isotropic magnet alloy powder produced by the above-mentioned method for producing an iron-based rare earth-boron-based isotropic magnet alloy; and adding a thermoplastic resin to the iron-based rare earth-boron-based isotropic magnet alloy powder to prepare an injection molding compound, followed by injection molding.

[0072] When producing the resin-sintered permanent magnet, the iron-based rare earth nanocomposite magnet powder is mixed with epoxy, polyamide, polyphenylene sulfide (PPS), liquid crystal polymer, acrylic, polyether, etc., and molded into the desired shape. In this case, a hybrid magnet powder may be used, which is a mixture of permanent magnet powder such as SmFeN magnet powder or hard ferrite magnet powder.

[0073] Using the resin-bonded permanent magnets described above, it is possible to manufacture various rotating machines that can be used as brushless DC motors of approximately 1 horsepower (750 W) or less for automobiles (including electric vehicles and hybrid vehicles) and white goods, as well as various magnetic sensors.

[0074] When the magnet alloy powder of the present invention is used for injection-molded bonded magnets, it is preferably pulverized to an average particle size of 100 μm or less, more preferably an average crystal grain size of 20 μm to 100 μm. When it is used for compression-molded bonded magnets, it is preferably pulverized to an average particle size of 200 μm or less, more preferably an average crystal grain size of 50 μm to 150 μm. Even more preferably, the particle size distribution has two peaks, and the average crystal grain size is 80 μm to 130 μm.

[0075] By subjecting the surface of the magnet alloy powder of the present invention to surface treatments such as coupling treatment and chemical conversion treatment (including phosphate treatment and glass coating treatment), it is possible to improve the moldability during molding of the resin-bonded permanent magnet and the corrosion resistance and heat resistance of the resulting resin-bonded permanent magnet, regardless of the molding method. In addition, when the surface of the resin-bonded permanent magnet after molding is subjected to surface treatments such as resin painting, chemical conversion treatment and plating, it is also possible to improve the corrosion resistance and heat resistance of the resin-bonded permanent magnet, just like the surface treatment of the magnet alloy powder.

[0076] The method for producing the iron-based rare earth boron isotropic magnet alloy of the present invention is not limited to the above, and other methods can be adopted as long as they can produce an iron-based rare earth boron isotropic magnet alloy having the above-mentioned composition, average crystal grain size, etc. For example, by using flash annealing, it is possible to produce RE2Fe with an average crystal grain size of 10 nm or more and less than 70 nm. 14 It is possible to form a fine metal structure with a B-type tetragonal compound as the main phase, but the formation of such a fine metal structure is not limited to flash annealing, and other methods can also be used. For example, even when a normal annealing process is used instead of flash annealing, good magnetic properties can be obtained by adjusting the surface speed of the rotating roll that quenches the molten alloy to form a homogeneous fine metal structure with crystal grains that are 5% to 20% smaller than the alloy structure that provides optimal magnetic properties. [Example]

[0077] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0078] (Example) To achieve the alloy composition listed in Table 1, 100 g of raw materials containing the major elements Nd, Pr, Dy, B, C, and Fe with a purity of 99.5% or higher, as well as additive elements such as Co, Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb, was placed in an alumina melting crucible and then placed in the work coil of a vacuum melting furnace. The vacuum melting furnace was then evacuated to below 0.02 Pa, and argon gas was introduced to atmospheric pressure. The alloy was then molten by high-frequency induction heating. The molten alloy was then poured into a water-cooled copper mold to produce the master alloy.

[0079] The resulting master alloy was then divided into appropriate sizes and inserted into a transparent quartz nozzle with an orifice of varying diameter (0.7 mm or more, 1.2 mm or less) at the bottom to achieve the average melting rate listed in Table 1 (in Table 1, simply referred to as "melting rate"). The nozzle was then set into the work coil of a single-roll quenching apparatus. The vacuum melting furnace was then evacuated to 0.02 Pa or less, and argon gas was introduced until the quenching pressure reached the atmospheric pressure listed in Table 1. The master alloy was remelted by high-frequency induction heating. The molten alloy was then poured from the nozzle orifice at a pressure of 30 kPa onto the surface of a rotating roll rotating at the roll surface speed (Vs) listed in Table 1, producing a rapidly solidified alloy. The distance between the nozzle tip and the rotating roll surface was 0.8 mm. The main component of the rotating roll was copper. The resulting rapidly solidified alloy consisted of NdFe 14 The material contained 1% by volume or more of either a crystalline phase including phase B or an amorphous phase.

[0080] As a representative example, Figure 6 shows the powder X-ray diffraction profile of the rapidly solidified alloy obtained in Example 13. As can be seen from Figure 6, the Nd2Fe 14 The presence of phase B was confirmed.

[0081] The rapidly solidified alloy obtained in the above process was coarsely pulverized to a size of a few millimeters or less to obtain rapidly solidified alloy powder. The rapidly solidified alloy coarse powder was then placed in a flash annealing furnace (crystallization heat treatment furnace; muffle tube: transparent quartz, outer diameter 15 mm, inner diameter 12.5 mm, length 1000 mm, heating zone 300 mm, cooling zone 500 mm with a cooling fan). The coarse powder was then placed in a raw material hopper and heat-treated at a workpiece cutting rate of 20 g / min. The muffle tube inclination angle, muffle tube rotation speed, and muffle tube vibration frequency were appropriately adjusted along with the heat treatment temperature and heat treatment time listed in Table 2 to achieve the heating rate listed in Table 2. As a result, the rapidly solidified alloy powder passed through the muffle tube while undergoing a combination of stirring due to the muffle tube rotation and hopping due to the muffle tube vibration. This resulted in unique heat treatment conditions in which the rapidly solidified alloy powder was subjected to thermal history individually, rather than as a single powder. An example of a heat treatment furnace and a thermal history in the flash annealing step are shown in FIGS. 2 and 3, respectively.

[0082] The constituent phases of the rapidly solidified alloy powder after flash annealing (crystallization heat treatment) were confirmed by powder X-ray diffraction. 14 The presence of B phase was confirmed. Figure 7 shows a powder X-ray diffraction profile of the rapidly solidified alloy obtained in Example 13 after flash annealing (crystallization heat treatment) as a representative example. In addition, the α-Fe peak, which was not observed in Figure 6, is observed in Figure 7 after flash annealing (crystallization heat treatment), and the NdFe 14 It was confirmed that the metal structure was a mixture of B phase and α-Fe phase.

[0083] As a representative example, Figure 4 shows a bright-field image and elemental mapping of the iron-based rare earth boron isotropic magnet alloy obtained in Example 13, observed with a transmission electron microscope. The bright-field image reveals NdFe 14 B phase and NdFe 14The presence of a clear grain boundary phase surrounding the B phase was confirmed. In addition, elemental mapping confirmed the presence of a grain boundary phase enriched in Nd and Fe at the grain boundaries of the main phase, which is composed of the main constituent elements Nd, Fe, and B. Based on the results of the powder X-ray diffraction described above, it was inferred that the Fe present at the grain boundaries exists as an α-Fe phase. The inventors have confirmed that the grain boundary phase shown in Figure 4 was formed in all examples.

[0084] The iron-based rare earth boron isotropic magnet alloy obtained by flash annealing (crystallization heat treatment) shown in Table 2 was cut into a sample for magnetic property evaluation, measuring approximately 7 mm in length, approximately 0.9 mm or more and 2.3 mm or less in width, and 18 μm or more and 25 μm or less in thickness. It was then magnetized in the longitudinal direction with a pulsed magnetic field of 3.2 MA / m. The sample for magnetic property evaluation was then set longitudinally to suppress the effects of the demagnetizing field, and the room temperature magnetic properties were measured using a vibrating sample magnetometer (VSM). The results are shown in Table 3. Table 3 shows the above-mentioned residual magnetic flux density Br: 0.85 T or more, intrinsic coercivity HcJ: 700 kA / m or more and less than 1400 kA / m, and maximum energy product (BH)max: 120 kJ / m. 3 It was found that the above magnetic properties were obtained by the alloy compositions and manufacturing methods described in Examples 1 to 39. In particular, it was found that Examples 32 to 39, which contain Pr, had higher intrinsic coercivity HcJ than Examples 1 to 31.

[0085] Next, the flash-annealed (crystallization heat-treated) magnetic powder obtained in Example 13 was pulverized in a pin-disk mill to an average particle size of 125 μm. 2 mass% of epoxy resin diluted with methyl ethyl ketone (MEK) was then added to this pulverized magnetic powder, and after mixing and kneading, 0.1 mass% of calcium stearate was added as a lubricant to prepare a compound for compression-molded bonded magnets.

[0086] The above compound for compression-molded bonded magnets was compressed at 1568 MPa (16 ton / cm 2The magnet was compressed at a pressure of 1000 kJ / cm² to obtain a compact measuring 10 mm in diameter and 7 mm in height. This compact was then subjected to a curing heat treatment (curing) at 180°C for 1 hour in an argon gas atmosphere to obtain an isotropic compression-molded bonded magnet. The density of the resulting isotropic compression-molded bonded magnet was 6.3 g / cm². 3 (The true specific gravity of the magnetic powder is 7.5 g / cm 3 ), the magnetic powder filling rate was 84% ​​by volume.

[0087] The magnetic properties of the isotropic compression molded bonded magnet obtained using the magnetic powder of Example 13 were measured using a BH tracer after magnetizing it in the longitudinal direction with a pulsed magnetic field of 3.2 MA / m. The results were a residual magnetic flux density Br of 0.74 T, an intrinsic coercive force HcJ of 1028 kA / m, and a maximum energy product (BH)max of 89.4 kJ / m. 3 It was found that the magnetic properties of

[0088] Next, the flash-annealed (crystallization heat-treated) magnetic powder obtained in Example 13 was pulverized in a pin-disk mill to an average particle size of 75 μm. Then, while heating and stirring this pulverized magnetic powder, 0.75 mass% of a titanate-based coupling agent was sprayed onto the powder to perform a coupling treatment. After that, 0.5 mass% of stearic acid amide and 4.75 mass% of nylon 12 resin powder were added and mixed as a lubricant, and a compound for injection-molded bonded magnets was produced using a continuous extrusion kneader at an extrusion temperature of 170°C.

[0089] The compound for injection-molded bonded magnets was injection-molded at an injection temperature of 250°C to produce isotropic injection-molded bonded magnets with a diameter of 10 mm and a height of 7 mm. The density of the resulting isotropic injection-molded bonded magnet was 4.6 g / cm. 3 (The true specific gravity of the magnetic powder is 7.5 g / cm 3 ), the magnetic powder filling rate was 61% by volume.

[0090] The magnetic properties of the isotropic injection molded bonded magnet obtained using the magnetic powder of Example 13 were measured using a BH tracer after being magnetized in the longitudinal direction with a pulsed magnetic field of 3.2 MA / m. The results were as follows: residual magnetic flux density Br: 0.54 T, intrinsic coercivity HcJ: 1014 kA / m, maximum energy product (BH)max: 63.4 kJ / m 3 It was found that, despite being injection molded, it was possible to obtain magnetic properties at the same level as general-purpose isotropic Nd-Fe-B compression molded bonded magnets.

[0091] (Comparative Example) To obtain the alloy composition listed in Table 1, 100 g of raw materials containing the main elements Nd, Dy, B, and Fe with a purity of 99.5% or higher, as well as additive elements such as Co, Si, Ti, and Zr, were placed in an alumina melting crucible and then placed in the work coil of a vacuum melting furnace. The vacuum melting furnace was then evacuated to a pressure of 0.02 Pa or less, and argon gas was introduced to atmospheric pressure, after which the alloy was molten by high-frequency induction heating. The molten alloy was then poured into a water-cooled copper mold to produce the master alloy.

[0092] The resulting master alloy was then divided into appropriate sizes and 40 g of each was inserted into a transparent quartz nozzle with an orifice of varying diameter (0.7 mm or more, 1.2 mm or less) at the bottom to achieve the average melt tapping rate listed in Table 1 (referred to simply as "tap rate" in Table 1). The nozzle was then placed in the work coil of a single-roll quenching apparatus. The vacuum melting furnace was then evacuated to 0.02 Pa or less, and argon gas was introduced until the quenching atmosphere pressure reached the pressure listed in Table 1. The master alloy was remelted by high-frequency induction heating, and the molten alloy was then tapped from the nozzle orifice at a spray pressure of 30 kPa onto the surface of a rotating roll rotating at the roll surface speed (Vs) listed in Table 1 to produce a rapidly solidified alloy. The distance between the nozzle tip and the rotating roll surface was 0.8 mm.

[0093] The rapidly solidified alloy obtained in the above process was coarsely pulverized to a size of a few millimeters or less to obtain rapidly solidified alloy powder. The rapidly solidified alloy coarse powder was then placed in a flash annealing furnace (crystallization heat treatment furnace, furnace tube: transparent quartz, outer diameter 15 mm, inner diameter 12.5 mm, length 1000 mm, heating zone 300 mm, cooling zone by cooling fan 500 mm) and heat treated at a workpiece cutting rate of 20 g / min. The furnace tube tilt angle, furnace tube rotation speed, and furnace tube vibration frequency were appropriately adjusted along with the heat treatment temperature and heat treatment time listed in Table 2 to achieve the heating rate listed in Table 2.

[0094] The constituent phases of the rapidly solidified alloy powder after flash annealing (crystallization heat treatment) were confirmed by powder X-ray diffraction. 14 The presence of B phase was confirmed. As a representative example, Fig. 8 shows the powder X-ray diffraction profile of the rapidly solidified alloy obtained in Comparative Example 7 after flash annealing (crystallization heat treatment). As can be seen from Fig. 8, Comparative Example 7 is NdFe 14 It was confirmed that the metal structure was a single phase with phase B as the main phase.

[0095] As a representative example, Figure 5 shows a bright-field image and elemental mapping of the iron-based rare earth boron isotropic magnet alloy obtained in Comparative Example 7, observed with a transmission electron microscope. The bright-field image shows NdFe with an average crystal grain size of 50 nm or less. 14 Although the B phase was confirmed, no clear grain boundary phase was confirmed. In addition, elemental mapping also revealed that the grain boundary phase where Nd and Fe were concentrated, as seen in Example 13, was not present at the crystal grain boundaries of the main phase consisting of the main constituent elements Nd, Fe, and B. This was also the case in the other comparative examples.

[0096] The iron-based rare earth boron isotropic magnet alloy obtained by flash annealing (crystallization heat treatment) shown in Table 2 was cut into a sample for magnetic property evaluation, measuring approximately 7 mm in length, approximately 0.9 mm or more and 2.3 mm or less in width, and 18 μm or more and 25 μm or less in thickness. It was then magnetized in the longitudinal direction with a pulsed magnetic field of 3.2 MA / m. The sample for magnetic property evaluation was then set longitudinally to suppress the effects of the demagnetizing field, and the room temperature magnetic properties were measured using a vibrating sample magnetometer (VSM). The results are shown in Table 3. Table 3 shows the above-mentioned residual magnetic flux density Br: 0.85 T or more, intrinsic coercivity HcJ: 700 kA / m or more and less than 1400 kA / m, and maximum energy product (BH)max: 120 kJ / m. 3 It was found that the above magnetic properties could not be obtained with the alloy compositions and manufacturing methods described in Comparative Examples 1-12.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3] [Explanation of symbols]

[0100] 1 Raw material hopper 2. Raw material supply feeder 3. Furnace tube 3a Enlarged view of the furnace tube 3b Enlarged cross section of the furnace tube 4 tube furnace 5 cooling tower 6 Collection Hopper 7. Oscillators 8. Furnace tube rotation motor 9. Core tube rotation axis 10. Device stand 11. Furnace tube tilt angle 12 Cooling fan wind 13 Rapidly solidified alloy powder (workpiece) 14 Workpiece movement direction 15 Workpiece hopping phenomenon 16 Heating rate 17 Holding temperature 18 Cooling rate 21 Main phase 22 Grain boundary phase

Claims

1. Composition formula T 100-x-y-z (B 1-n C n ) x RE y M z (T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element selected from Nd and Pr, and is at least one element that must include Nd; M is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), The composition ratios x, y, and z are 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %; and 0.0≦n≦0.5 The alloy composition has a composition that satisfies RE 2 Fe 14 RE having a B content lower than that of the stoichiometric composition of a B-type tetragonal compound and an average crystal grain size of 10 nm or more and less than 70 nm. 2 Fe 14 The alloy has a metal structure in which a B-type tetragonal compound is a main phase and a grain boundary phase surrounding the main phase is present, The grain boundary phase surrounding the main phase made of RE 2 Fe 14 B type tetragonal compound is Main components are RE and Fe, It is a ferromagnetic phase, The width is 1 nm or more and less than 10 nm, In the composition ratio of the grain boundary phase mainly composed of RE and Fe, the ratio of the main phase is 70 vol% or more and less than 99 vol%, and the ratio of the grain boundary phase is 1 vol% or more and less than 30 vol%. Iron-based rare earth boron isotropic magnet alloy.

2. RE 2 Fe 14 It has a metal structure finer than the single magnetic domain critical diameter of a B-type tetragonal compound.

2. The iron-based rare earth boron isotropic magnet alloy according to claim 1.

3. Residual magnetic flux density Br is 0.85T or more, intrinsic coercivity HcJ is 700kA / m or more but less than 1400kA / m, and maximum energy product (BH)max is 120kJ / m 3 The above magnetic properties are exhibited.

3. The iron-based rare earth boron isotropic magnet alloy according to claim 1 or 2.

4. Composition formula T 100-x-y-z (B 1-n C n ) x RE y M z (T is at least one element selected from the group consisting of Fe, Co, and Ni, and is a transition metal element that must include Fe; RE is at least one rare earth element that must include at least Nd among Nd and Pr; and M is at least one metal element selected from the group consisting of Al, Si, V, Cr, Ti, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), The composition ratios x, y, and z are 4.2 atomic %≦x≦5.6 atomic %, 11.5 atomic %≦y≦13.0 atomic %, 0.0 atomic %≦z≦5.0 atomic %; and 0.0≦n≦0.5 preparing a molten alloy having a composition that satisfies the above; The molten alloy is sprayed onto the surface of a rotating roll mainly composed of Cu, Mo, W or an alloy containing at least one of these metals at an average rate of 200 g / min or more and less than 2000 g / min per orifice provided at the tip of the nozzle, thereby producing RE. 2 Fe 14 preparing a rapidly solidified alloy having 1% by volume or more of either a crystalline phase including a B phase or an amorphous phase; a step of flash annealing the rapidly solidified alloy by heating it at a temperature rising rate of 10°C / sec or more and less than 200°C / sec to a constant temperature range of not less than the crystallization temperature and not more than 850°C, and then rapidly cooling it after a lapse of not less than 0.1 sec and not more than 7 min; Equipped with The flash annealing step forms a metal structure that is finer than the single magnetic domain critical diameter of an RE2Fe14B type tetragonal compound, in which the main phase is an RE2Fe14B type tetragonal compound having an average crystal grain size of 10 nm or more and less than 70 nm, while having a lower B content than the stoichiometric composition of the RE2Fe14B type tetragonal compound, and in which a ferromagnetic grain boundary phase having a width of 1 nm or more and less than 10 nm and mainly composed of RE and Fe surrounds the main phase. A method for producing an iron-based rare earth boron isotropic magnet alloy.

5. The method further comprises a step of producing an iron-based rare earth-boron-based isotropic magnet alloy powder by pulverizing the rapidly solidified alloy or the rapidly solidified alloy that has been subjected to the flash annealing.

5. A method for producing the iron-based rare earth boron isotropic magnet alloy according to claim 4.

6. a step of preparing an iron-based rare earth boron isotropic magnet alloy powder produced by the method of producing an iron-based rare earth boron isotropic magnet alloy according to claim 5; a step of adding a thermosetting resin to the iron-based rare earth boron isotropic magnet alloy powder, filling the powder into a molding die, and then compressing the powder to form a compact, followed by heat treatment at a temperature equal to or higher than the polymerization temperature of the thermosetting resin; Manufacturing method for resin-bonded permanent magnets.

7. a step of preparing an iron-based rare earth boron isotropic magnet alloy powder produced by the method of producing an iron-based rare earth boron isotropic magnet alloy according to claim 5; and adding a thermoplastic resin to the iron-based rare earth-boron isotropic magnet alloy powder to prepare an injection molding compound, and then injection molding the compound. Manufacturing method for resin-bonded permanent magnets.

8. The RE of the main phase and the grain boundary phase contains at least Nd and Pr, A method for producing the iron-based rare earth boron isotropic magnet alloy according to any one of claims 1 to 7.

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