JPWO2003085147A1 - Alloy for bond magnet, isotropic magnet powder, anisotropic magnet powder, production method thereof, and bond magnet - Google Patents

Abstract

The alloy for bonded magnets of the present invention includes iron (Fe) as a main component, a rare earth element (R) containing 12 to 16 atomic% (at%) yttrium (Y), and 10.8 to 15 at% boron. (B) is contained at least. When magnet powder obtained by d-HDDR treatment of this magnet alloy is used, pellets with excellent powder feeding properties to the molding die for bonded magnets can be obtained, and the cost of bonded magnets with excellent magnetic properties can be reduced. I can plan.

Description

【図面の簡単な説明】
図１は、磁石粉末から製造したボンド磁石用ペレットの流動度を対比した棒グラフである。
図２は、磁石粉末から製造したボンド磁石用ペレットの嵩密度を対比した棒グラフである。
図３は、ｄ−ＨＤＤＲ処理して製造した磁石粉末のコストパフォーマンスを対比した棒グラフである。Technical field
The present invention relates to an alloy for bonded magnets capable of producing a bonded magnet having excellent magnetic properties at low cost, an isotropic magnet powder and an anisotropic magnet powder obtained from the alloy, a production method thereof, and further, The present invention relates to a bonded magnet obtained from magnet powder.
Background art
Hard magnets (permanent magnets) are used in various devices such as motors. In particular, there is a strong demand for small and high-powered vehicle motors. Such hard magnets are required to be low cost in order to enhance the global competitiveness as well as high performance in terms of magnetic properties.
First, from the viewpoint of high performance, development of RFeB magnets (rare earth magnets) composed of rare earth elements (R), boron (B), and iron (Fe) has been actively conducted.
As such RFeB magnets, for example, US Pat. No. 4,851,058 (hereinafter referred to as “Prior Art 1”) and US Pat. No. 5,411,608 (hereinafter referred to as “Prior Art 2”) have magnetic isotropy. An RFeB-based magnet alloy (composition) is disclosed.
Specifically, Prior Art 1 includes a magnet alloy comprising about 10 to 40 at% Nd, Pr or Nd and Pr, about 50 to 90 at% Fe, and about 0.5 to 10 at% B. Is disclosed. Prior Art 2 discloses a magnet alloy comprising 12 to 40 at% Nd, Pr or Nd and Pr, 10 at% or less Co, 3 to 8 at% B, and the balance Fe. In the prior art 2, the heat resistance is improved by increasing the Curie temperature by adding Co. In both of these conventional techniques, a magnet powder having the above composition is obtained by a melt span method which is a kind of rapid solidification method.
This magnet powder (magnetic powder) is often used industrially as a raw material powder for a bonded magnet (hard magnet). The bonded magnet is obtained, for example, by first producing pellets from the magnetic powder and a resin as a binder, feeding the pellets to a molding die, and press-molding the pellets. Generally, when the pellets are powdered into the mold, if the fluidity is small, the powdering time is shortened and the productivity of the bonded magnet can be improved. Moreover, when the bulk density of a pellet is large, the uniform powder supply to a metal mold | die will be attained and the defect rate of a bonded magnet can be reduced. Therefore, the smaller the fluidity and the larger the bulk density, the lower the cost of the bonded magnet and the better the economy. The fluidity and bulk density depend on the particle shape of the magnetic powder, and the more suitable the fluidity and bulk density are as spherical.
However, since the particle shape of the magnetic powder produced from the prior arts 1 and 2 is a flake shape having a thickness of 20 to 50 μm, the fluidity is larger and the bulk density is smaller than the spherical shape. Of course, it is also conceivable to pulverize the flakes into a spherical shape, thereby reducing the fluidity and increasing the bulk density. However, the number of man-hours increases, and even if it is made spherical, it is actually difficult to effectively reduce the fluidity or increase the bulk density. This is because, when the original particle size is 50 μm at the maximum, powder of 50 μm or less generally tends to adhere and aggregate.
The situation is the same for SmFeN-based magnetic powders having different compositions. Even if the particle shape of the magnetic powder is close to a sphere, if the average particle diameter is 1 to 5 μm, it is easy to cause adhesion and aggregation, and the fluidity and bulk density deteriorate.
Therefore, as a method for producing magnetic powder in place of the melt span method, there is a method using a HDDR (hydration-deposition-desorption-recombination) treatment method or a d-HDDR treatment method. Since the magnetic powder obtained by these consists of substantially spherical particles, the fluidity and bulk density are superior to the magnetic powder obtained by the above-described conventional techniques 1 and 2.
The HDDR treatment method is used for producing RFeB-based isotropic magnet powder (isotropic magnetic powder) and RFeB-based anisotropic magnet powder (anisotropic magnetic powder), and mainly consists of two steps. That is, a first step (hydrogenation step) in which a hydrogen gas atmosphere of about 100 kPa (1 atm) is maintained at 773 to 1273 K to cause a three-phase decomposition disproportionation reaction, and then dehydrogenation is performed in a vacuum. Process (2nd process).
On the other hand, the d-HDDR treatment is a method mainly used for producing RFeB-based anisotropic magnetic powder. Controlling the reaction rate between RFeB yarn alloy and hydrogen from room temperature to high temperature, as reported in detail in a well-known document (Mishima et al .: Journal of Japan Society of Applied Magnetics, 24 (2000), p.407). Is made by Specifically, a low-temperature hydrogenation step (first step) in which hydrogen is sufficiently absorbed by the RFeB alloy at room temperature, and a high-temperature hydrogenation step (second step) in which a three-phase decomposition disproportionation reaction is caused under a low hydrogen pressure. Steps), an evacuation step for dissociating hydrogen under as high a hydrogen pressure as possible (third step), and a subsequent dehydrogenation step (fourth step) for removing hydrogen from the material. The difference from the HDDR treatment is that a plurality of processes with different temperatures and hydrogen pressures are provided, so that the reaction rate between the RFeB alloy and hydrogen is kept relatively moderate and a homogeneous anisotropic magnetic powder can be obtained. It is a point.
The following prior art can be mentioned as a manufacturing method of the magnet powder using each of these processes.
First, a method for producing an RFeB-based isotropic magnetic powder using HDDR processing is disclosed in Japanese Patent Publication No. 7-68561 (Patent No. 2041426: hereinafter referred to as “Prior Art 3”). According to this prior art 3, an alloy ingot containing R, Fe, and B as main components is subjected to a pulverization step and a homogenization heat treatment step, and then the HDDR treatment is performed to produce magnetic powder. Here, in this case, the two steps (grinding step, homogenization heat treatment step) before the HDDR treatment are indispensable for obtaining isotropic magnetic powder having a large magnetic property. As in the prior art 3, when these two steps are omitted and the magnetic powder is manufactured by directly HDDR processing on the cast body of the RFeB alloy, the coercive force (hereinafter referred to as the coercive force) of the bonded magnet manufactured using the obtained magnetic powder. , IHc) is at most 0.76 MAm ^-1 This is because it shows a very low value.
However, the two processes are both expensive and inferior in economic efficiency. In particular, the homogenization heat treatment process that performs high-temperature treatment at 873 to 1473K requires about twice the cost of HDDR treatment, and is very economical.
Next, a method for producing RFeB anisotropic magnetic powder using HDDR processing is disclosed in Japanese Patent No. 2576671 (hereinafter referred to as “Prior Art 4”) and Japanese Patent No. 2576672 (hereinafter referred to as “Prior Art 5”). No. 2586198 (hereinafter referred to as “Prior Art 6”) and Japanese Patent No. 2586199 (hereinafter referred to as “Prior Art 7”).
According to the examples described in these prior arts, an alloy ingot comprising about 10 to 20 at% R, about 5 to 20% B, the balance Fe, and various additive elements, a homogenization heat treatment step and a grinding step After that, the HDDR process is performed to manufacture the magnetic powder. However, the B content of the alloys disclosed in the examples is disclosed in detail when the content is 10.4 at% or less, but alloys whose B content exceeds 10.4 at% are alloys of 10.4 at% and 20 at%. Only. And (BH) max of the anisotropic bond magnet manufactured from the magnetic powder whose B amount is 10.4 at% is 83-112 kJ / m. ³ , IHc is 0.74 to 0.97 MA / m, and (BH) max of an anisotropic bonded magnet manufactured from magnetic particles having a B content of 20 at% is 80 to 93 kJ / m. ³ , IHc is 0.46 to 0.75 MA / m. All of these magnetic properties are inadequate. In particular, when the amount of B increases to 20 at%, iHc decreases remarkably.
And in the case of the said prior art, since the homogenization heat processing is performed at 1393K-1413K and high temperature, the manufacturing cost of a magnetic powder becomes higher and also economical efficiency worsens. Of course, in this case as well, although the cost can be reduced if the homogenization heat treatment is omitted, as in the case of the prior art 3, iHc deterioration is unavoidable.
Incidentally, it is actually difficult to industrially mass-produce anisotropic magnetic powder using methods such as the prior arts 4 to 7. This is because, in order to obtain magnetic powder with excellent anisotropy, it is necessary to strictly control the temperature during HDDR processing. Specifically, highly anisotropic magnetic powder cannot be obtained unless HDDR treatment is performed in a temperature range of about ± 20K with respect to the target temperature. Nevertheless, if the throughput per batch of HDDR treatment is increased, the amount of heat generated during the disproportionation reaction between hydrogen and the RFeB alloy and the endothermic amount during dehydrogenation increase rapidly, and the ambient temperature is desired. This is because it becomes out of bounds. As a result, the magnetic powder mass-produced by the methods of the conventional techniques 4 to 7 has a small magnetic property, particularly anisotropy.
Therefore, when mass production of RFeB-based anisotropic magnetic powder is performed, JP 2001-148306 A (hereinafter referred to as “Prior Art 8”) and JP 2001-76917 A (hereinafter “Prior Art 9”). It is recommended to use d-HDDR processing as disclosed in the above. According to this d-HDDR treatment, magnetic powder having high anisotropy can be obtained even if the amount of treatment per batch is increased. As described above, in the case of d-HDDR treatment, the reaction rate between the RFeB alloy and hydrogen can be controlled gently in each step, so the amount of heat generated during the disproportionation reaction between the RFeB alloy and hydrogen can be reduced. This is because the amount of heat absorbed can be suppressed.
However, even in the case of these conventional techniques 8 and 9, after applying a homogenization heat treatment step using an alloy ingot composed of about 12 to 15 at% R, about 6 to 9 at% B and the balance Fe, An anisotropic magnetic powder is manufactured by performing d-HDDR treatment. For this reason, it is the same in that the manufacturing cost is still high, as in the manufacturing method described above.
So far, we have mainly explained the cost reduction of high-performance hard magnets, but considering the practicality of hard magnets, it is also important that the hard magnets have excellent aging characteristics such as corrosion resistance. is there. In particular, hard magnets incorporated in household motors, automobile motors, and the like used in high temperature environments are required to have excellent heat resistance and the like from the viewpoint of ensuring the reliability of the motors.
However, the rare earth magnet described above is easily deteriorated by oxidation corrosion of Fe and R, which are the main components, and it is difficult to stably secure the high magnetic properties. In particular, when a rare earth magnet is used at room temperature or higher, its magnetic properties tend to deteriorate rapidly. Such a change with time of the magnet is usually quantitatively indicated by a permanent demagnetization rate (%). However, in the case of conventional rare earth magnets, most of the permanent demagnetization rate exceeds 10%. The permanent demagnetization rate is a reduction rate of magnetic flux that is not restored even after re-magnetization after a long time (1000 hours) at a predetermined high temperature.
Disclosure of the invention
The present invention has been made in view of such circumstances. That is, a low-cost and excellent magnetic property RFeB-based magnet powder obtained for HDDR treatment or d-HDDR treatment, which is obtained without performing a high-cost homogenization heat treatment step, and a method for producing the same, and further It aims at providing the bonded magnet which consists of magnet powder. Moreover, it aims at providing the RFeB type | system | group magnet alloy suitable for manufacture of the magnet powder.
In addition, it is possible to provide a bonded magnet that is not only excellent in magnetic properties at low cost but also has little deterioration over time, and further provides an RFeB-based magnet alloy, an RFeB yarn magnet powder, and a method for producing the same. Objective.
As a result of intensive studies to solve this problem and repeated various systematic experiments, the present inventor has developed a new magnet alloy having a B amount different from the conventional one, and has completed the following invention.
(Alloy for bonded magnet)
First, the alloy for bonded magnets of the present invention includes iron (Fe) as a main component and a rare earth element (hereinafter referred to as “R”) containing 12 to 16 atomic% (at%) yttrium (Y). It contains at least 10.8 to 15 at% boron (B).
In addition to such expressions, the present invention contains at least Fe as a main component, R containing 12 to 16 at% Y, and 10.8 to 15 at% B, and is a kind of hydrogenation treatment. It is good also as a magnet alloy characterized by using for the HDDR process or d-HDDR process which is.
The alloy for bonded magnets of the present invention (hereinafter simply referred to as “magnet alloy” as appropriate) has a B amount that is different from the RFeB-based magnet alloy that has been developed so far, and has a relatively large B amount. The present inventor has found that the magnet alloy having a large amount of B suppresses the precipitation of α-Fe which is the primary crystal. As a result of suppressing the precipitation of α-Fe, which leads to a decrease in magnetic properties, it is possible to omit the homogenization heat treatment step, which has been considered indispensable for improving the magnetic properties. It came to be obtained.
This reason can be considered as follows at present. By increasing B, the melting point is 10-30K lower than RFeB at the beginning of casting. ₁ Fe ₁ B ₄ A phase (hereinafter referred to as “B-rich phase”) is formed. And, since α-Fe which is the primary crystal is taken into the B-rich phase, it is considered that the precipitation of α-Fe is suppressed.
As a result of subjecting this magnet alloy (for example, its ingot) to the HDDR treatment or d-HDDR treatment described above, high iHc magnet powder was obtained. This can be thought of as follows. When hydrogen is absorbed into the magnet alloy of the present invention, the R that bears the B-rich phase and the magnet phase described above. ₂ Fe ₁₄ B phase reacts sufficiently with hydrogen, α-Fe, Fe ₂ B, R hydride. Next, when it is dehydrogenated, the B-rich phase precipitates finely and densely, and this is thought to be because the RFeB recrystallized grains became fine as a result of pinning the crystal growth of RFeB. In order to effectively obtain this pinning effect, for example, the hydrogen absorption time is preferably set to 360 minutes or more.
From such a viewpoint, B is set to 10.8 at% or more. Thereby, the homogenization heat treatment process which impairs economically can be omitted, and iHc can be increased. On the other hand, if B exceeds 15 at%, the volume fraction of the B-rich phase in the magnet powder is increased, and the maximum energy product (BH) max is lowered, which is not preferable.
In Examples of the prior arts 4, 5, 6, and 7, a magnet powder having a B content of 20 at% is disclosed, and its iHc is 0.46 to 0.75 MAm. ^-1 And low. This is presumably because the hydrogen absorption time was as short as 240 minutes, the reaction between the B-rich phase and hydrogen was insufficient, and the B-rich phase did not precipitate finely and densely during the subsequent dehydrogenation.
On the other hand, if R is less than 12 at%, primary crystal α-Fe is likely to be precipitated, leading to a decrease in iHc. On the other hand, when R exceeds 16%, (BH) max is lowered, which is not preferable.
Such R consists of scandium (Sc), yttrium (Y), and a lanthanoid. However, as an element having excellent magnetic properties, R is Y, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium. It is preferable to comprise at least one of (Dy), holmium (Ho), erbium (Er), thulium (Tm) and lutetium (Lu). Among these, R is preferably composed of one or more of Pr, Nd, and Dy from the viewpoint of cost and magnetic properties.
The magnet alloy of the present invention further preferably contains 0.1 to 6 at%, more preferably 1 to 6 at% of cobalt (Co) in addition to the above elements. This is because Co is an element that increases the Curie temperature of the magnet and improves the heat resistance. If Co is less than 0.1 at%, there is no substantial effect. On the other hand, since Co is expensive, it is preferably 6 at% or less from the viewpoint of industrial cost.
The magnet alloy of the present invention includes gallium (Ga), zirconium (Zr), vanadium (V), aluminum (Al), titanium (Ti), hafnium (Hf), and copper (Cu) (hereinafter referred to as “first element group”). A total of 0.1 to 2 at%. This is because these elements improve the coercive force iHc of the magnet.
The magnet alloy of the present invention contains 0.1 to 2 at% in total of at least one of niobium (Nb), tantalum (Ta) and nickel (Ni) (hereinafter referred to as “second element group”). May be. This is because these elements increase the residual magnetic flux density (Br) of the magnet.
When both the element in the first element group and the element in the second element group are included, the maximum energy product (BH) max can be improved. In any case, if the sum of them is less than 0.1 at%, there is no substantial effect, and if it exceeds 2 at%, iHc, Br or (BH) max is undesirably lowered. In consideration of cost and magnetic characteristics, Ga is 0.1 to 1.0 at%, more preferably 0.2 to 0.4 at% (about 0.3 at%), Nb is 0.1 to 1.0 at%, More desirably, the content is 0.1 to 0.4 at% (about 0.2 at%).
Needless to say, the alloy and powder according to the present invention may contain unavoidable impurities as appropriate. Their composition is balanced with Fe, but to put it simply, Fe is 59-77.2 at%.
Furthermore, it is preferable that the magnetic alloy of the present invention contains 0.001 to 1.0 at% La apart from R. Thereby, the aged deterioration of the magnet powder and hard magnet which consist of the magnet alloy can be suppressed.
This is because La is an element having the highest oxidation potential among rare earth elements (RE). For this reason, La acts as a so-called oxygen getter, La is selectively (preferentially) oxidized over R (Nd, Dy, etc.), and as a result, oxidation of magnet powder and hard magnets containing La is performed. It is suppressed. Although use of Dy, Tb, Nd, Pr, etc. can be considered instead of La, these elements cannot sufficiently suppress the oxidation of magnet powder and hard magnets. In view of cost, the use of La is preferable to these elements. At this time, R in the magnet alloy is a rare earth element other than La.
Here, La exhibits an effect of improving corrosion resistance or the like as long as it is contained in a minute amount exceeding the level of inevitable impurities in the magnet alloy. And since the inevitable impurity level amount of La is less than 0.001 at%, in the present invention, the La amount is set to 0.001 at% or more. On the other hand, if La exceeds 1.0 at%, iHc is lowered, which is not preferable. Here, it is more preferable that the lower limit of the amount of La is 0.01 at%, 0.05 at%, and further 0.1 at% since sufficient effect of improving corrosion resistance and the like is exhibited. And from a viewpoint of improvement of corrosion resistance etc. and suppression of a fall of iHc, it is still more preferred in the amount of La being 0.01-0.7 at%.
The alloy composition containing La is R ₂ Fe ₁₄ B ₁ R is not an alloy composition that can exist as a single phase or nearly a single phase, but R ₂ Fe ₁₄ B ₁ It is an alloy composition consisting of a multiphase structure such as a phase and a B-rich phase.
(Magnet powder and its manufacturing method)
The magnet alloy referred to in the present invention may be in an ingot shape or a powder shape regardless of its form. Moreover, in the case of powder, the particle size, particle shape, etc. are not ask | required. Therefore, for example, the magnet alloy of the present invention can be grasped as isotropic magnet powder or anisotropic magnet powder.
For example, the isotropic magnet powder of the present invention is an alloy ingot containing at least 1023 to 1173K hydrogen containing Fe as a main component, R containing 12 to 16 at% Y and 10.8 to 15 at% B. It is obtained through a manufacturing method in which HDDR treatment is performed, which includes a hydrogenation step held in a gas atmosphere and a dehydrogenation step for removing hydrogen after the hydrogenation step.
Further, the anisotropic magnet powder of the present invention is an alloy ingot containing at least 873K or less hydrogen gas containing Fe as a main component, R containing 12 to 16 at% Y and 10.8 to 15 at% B. A low-temperature hydrogenation step maintained in an atmosphere; a high-temperature hydrogenation step maintained in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low-temperature hydrogenation step; and a 0.1 to 20 kPa after the high-temperature hydrogenation step. It is obtained through a manufacturing method in which a d-HDDR treatment including a first evacuation step maintained in a hydrogen gas atmosphere of 1023 to 1173K and a second evacuation step for removing hydrogen after the first evacuation step is performed.
(Bonded magnet)
Furthermore, when these magnet powders are used, a high-performance bonded magnet can be obtained at a low cost.
For example, when an isotropic magnet powder is used, the bonded magnet of the present invention is made of an alloy containing at least Fe as a main component, R containing 12 to 16 at% Y, and 10.8 to 15 at% B. A binder is mixed with an isotropic magnet powder obtained by HDDR treatment comprising a hydrogenation step of holding an ingot in a hydrogen gas atmosphere of 1023 to 1173K and a dehydrogenation step of removing hydrogen after the hydrogenation step. It is characterized by being molded.
When the anisotropic magnet powder is used, the bonded magnet of the present invention is made of an alloy containing at least Fe as a main component, R containing 12 to 16 at% Y, and 10.8 to 15 at% B. A low temperature hydrogenation step for holding an ingot in a hydrogen gas atmosphere of 873 K or less, a high temperature hydrogenation step for holding in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low temperature hydrogenation step, and the high temperature hydrogenation step The difference obtained by the d-HDDR treatment comprising a first exhaust process that is later maintained in a hydrogen gas atmosphere of 102 to 1173 K at 0.1 to 20 kPa, and a second exhaust process that removes hydrogen after the first exhaust process. It is characterized in that isotropic magnet powder and a binder are mixed and pressure-molded.
In addition, the content regarding R, Co, the first element group, or the second element group described above also applies to the isotropic magnet powder, the anisotropic magnet powder, the manufacturing method thereof, and the bonded magnet as appropriate. The same applies to the addition of La, details of which will be described later.
BEST MODE FOR CARRYING OUT THE INVENTION
A. Embodiment
Hereinafter, the present invention will be described in more detail with reference to embodiments.
(1) Magnet powder and manufacturing method thereof
The magnet powder of the present invention can be obtained by subjecting the ingot or coarse powder (particles) of the magnetic alloy to the HDDR treatment method or d-HDDR treatment method described above.
(A) HDDR processing method
As described above, the HDDR treatment according to the present invention is obtained by subjecting an alloy (ingot) having B in the composition of 10.8 to 15 at% to a hydrogenation step and a dehydrogenation step. The conditions for the hydrogenation step are as described above.
Specifically, in the dehydrogenation step, for example, a hydrogen pressure of 10 is used. ^-1 This is a step of creating an atmosphere of Pa or lower. Moreover, what is necessary is just to set the temperature in a dehydrogenation process to 1023-1173K, for example. In addition, unless otherwise indicated, the hydrogen pressure as used in this specification means the partial pressure of hydrogen. Therefore, as long as the hydrogen partial pressure in each step is within a predetermined value, a vacuum atmosphere or a mixed atmosphere such as an inert gas may be used.
The processing time for each of the above steps depends on the processing amount per batch. For example, when the processing amount per batch is 10 kg, the hydrogenation step may be performed for 360 to 1800 minutes and the dehydrogenation step for about 30 to 180 minutes. In addition, since the HDDR process itself is disclosed in detail in the above-described prior art 3 and the like, it may be referred to as appropriate.
The magnet powder obtained by this HDDR processing method has industrial significance as an isotropic magnet powder. The magnet powder has, for example, iHc of 0.8 to 1.7 (MA / m) and (BH) max of 60 to 120 (kJ / m). ³ ) Excellent magnetic properties.
Next, each step of the HDDR process and the relationship with the magnet alloy of the present invention having the above B-rich composition will be described.
In the hydrogenation process, which is the first process of the HDDR process, hydrogen and the RFeB alloy and hydrogen and the B-rich phase are sufficiently reacted. In the subsequent dehydrogenation step, which is the second step, the B-rich phase is finely and densely prayed. The finely precipitated B-rich phase pinches the RFeB crystal grain growth and makes the RFeB crystal grain fine. Thereby, a high coercive force (iHc) is obtained.
(B) d-HDDR processing method
As described above, the d-HDDR treatment according to the present invention is applied to an alloy (ingot) having B in the composition of 10.8 to 15 at% into the low temperature hydrogenation step, the high temperature hydrogenation step, the first exhaust step, and the second An exhaust process is performed.
The conditions for the high-temperature hydrogenation process and the first exhaust process are as described above. A low-temperature hydrogenation process is a process made into the atmosphere whose hydrogen pressure is 30-200 kPa, for example. In the second exhaust process, for example, the hydrogen pressure is set to 10 ^-1 In this step, the atmosphere is set to Pa or lower, and the temperature at that time is, for example, about 1023 to 1173K. The first evacuation process and the second evacuation process together constitute a dehydrogenation process.
The processing time for each of the above steps depends on the processing amount per batch. For example, if the processing amount per batch is 10 kg, the low temperature hydrogenation process is 30 minutes or more, the high temperature hydrogenation process is 360 to 1800 minutes, the first exhaust process is 10 to 240 minutes, and the second exhaust process is 10 to 10 minutes. It only takes about 120 minutes. Note that the d-HDDR processing method itself is disclosed in detail in the above-described prior art 9 and the like, and may be referred to as appropriate.
The magnet powder obtained by this d-HDDR treatment method is an anisotropic magnet powder that exhibits excellent magnetic properties. The magnetic properties are, for example, iHc of 0.8 to 1.7 (MA / m) and (BH) max of 190 to 290 (kJ / m). ³ ) Also.
Next, each step of the d-HDDR processing and the relationship with the magnet alloy of the present invention having the above B-rich composition will be described.
In the low-temperature hydrogenation step (hydrogen pressure: about 30 to 200 kPa), which is the first step of the d-HDDR treatment, hydrogen is rapidly increased to the RFeB-based alloy. In the subsequent high-temperature hydrogenation process (hydrogen pressure: about 20 to 100 kPa), hydrogen and the RFeB-based alloy are reacted slowly. At this time, Fe which becomes an anisotropic orientation transfer phase ₂ The crystal orientation of the B phase is precipitated in almost one direction, and hydrogen and the B rich phase are sufficiently reacted. Furthermore, in the first exhaust process, which is the third process, Fe ₂ While maintaining the crystal orientation of the B phase, the RFeB crystal is precipitated, and the B rich phase is finely and densely precipitated. RFeB crystal grain growth is pinned by the fine and densely precipitated B-rich phase, and the RFeB crystal grains become fine. Finally, hydrogen remaining in the alloy is removed in a second exhaust process, which is a fourth process.
Of particular importance here is the high-temperature hydrogenation process, ₂ In the first evacuation step, the B phase crystal orientation is precipitated in almost one direction, ₂ The RFeB crystal is finely precipitated by the pinning effect of the B-rich phase finely and densely precipitated while maintaining the crystal orientation of the B phase. Thereby, anisotropic magnet powder with high iHc is obtained.
Further, in any of the above treatments, the ingot can be used as a raw material alloy, but each treatment can be efficiently advanced by using a pulverized coarse powder. The pulverization of the ingot and the pulverization performed after the above treatment can be performed using dry or wet mechanical pulverization (a jaw crusher, a disk mill, a ball mill, a vibration mill, a jet mill, or the like).
(C) Fluidity and bulk density
The magnet powder obtained by subjecting the magnet alloy of the present invention to the HDDR treatment or d-HDDR treatment has a substantially spherical particle size. For this reason, unlike the flakes produced by the melt span method as in the prior arts 1 and 2, pellets produced using the magnet powder of the present invention have a low fluidity and a high bulk density. As a result, when producing a bonded magnet, which is the most important application of the magnet powder, it is possible to improve the powder feeding property of the pellets to the molding die. In addition, since the magnet powder of the present invention has an appropriate average particle size of about 50 to 200 μm, not only the fluidity and bulk density can be improved, but also adhesion and aggregation can be suppressed. Also excellent. As a result, productivity, quality, yield, etc. of bonded magnets can be improved, and the cost of various magnets can be reduced.
Specifically, the fluidity of pellets obtained by mixing the magnetic powder and the organic resin 10 to 45 mass% as a binder is 0.55 to 0.64 (s / g), and the bulk density is 3.25 to 3.5 (g / cm ³ ) Also. The amount of the organic resin mixed with the magnet powder is more preferably 10 to 25 mass% in the case of compression molding pellets, 30 to 45 mass% in the case of pellets for injection molding, and 20 to 35 mass% in the case of pellets for extrusion molding. .
By the way, the reason why the particle diameter of the magnet powder is substantially spherical is as follows. When magnet powder is produced by performing HDDR treatment or d-HDDR treatment, the resulting particle shape is greatly affected by the alloy structure before the treatment. This is because when the alloy occludes hydrogen in the initial stage of the hydrogenation process of the HDDR process or in the low-temperature hydrogenation process of the d-HDDR process, it causes volume expansion and breaks mainly at fragile grain boundaries.
Here, when the magnet alloy is made of a cast body such as an ingot, the crystal structure of the central part is equiaxed and the crystal structure of the end part is dendritic. In the present invention, the presence of the B-rich phase suppresses the crystallization or precipitation of α-Fe, which is the primary crystal, so that the dendritic crystal structure formed at the end also becomes fine. As a result, when HDDR treatment or d-HDDR treatment is performed on a cast body made of the magnet alloy of the present invention, one crystal grain is obtained as almost one substantially spherical particle from the center of the cast body. From the end, a plurality of dendritic crystals are obtained as one substantially spherical particle. In this way, the constituent particles of the magnet powder are much closer to a sphere than the magnet powder obtained by the conventional melt span method or the like.
(2) Bonded magnet and its manufacturing method
When the magnet powder obtained as described above is used, not only the magnetic properties are excellent, but also a bonded magnet can be produced at low cost because of its excellent powder feeding property.
This bonded magnet is obtained through a mixing step of mixing the aforementioned isotropic magnet powder or anisotropic magnet powder and a binder, and a forming step of forming the mixed powder obtained by this mixing step. In addition to the organic binder as described above, the binder includes a metal binder and the like. However, organic binders such as resin binders are common. The resin used for the resin binder may be a thermosetting resin or a thermoplastic resin. When such a resin binder is used, the mixing step may be a kneading step of kneading the magnet powder and the resin binder. The molding process includes compression molding, injection molding, extrusion molding and the like. When anisotropic magnetic powder is used as the magnet powder, the anisotropic magnetic powder is molded in a magnetic field. Further, when a thermosetting resin is used as the resin binder, a heating (curing) process is performed during or after the molding process.
(3) Addition of La material
As described above, since La has the highest oxidation potential among rare earth elements, La-containing magnet powders and hard magnets exhibit very excellent corrosion resistance and the like because their oxidation is suppressed. As the addition form of La, for example, the following three forms can be considered.
(1) When a La powder is added from the melting stage and a magnet powder or the like is produced using an RFeB magnet alloy (ingot) containing La,
(2) When a La material is mixed with RFeB magnet powder obtained by HDDR treatment or d-HDDR treatment and La is diffused or coated on the magnet powder,
(3) This is a case where a La-based material is mixed with RFeB-based hydride (RFeBHx) obtained during the production of magnet powder, and La is diffused or coated on the hydride.
In any case, as long as La exists separately from R, the corrosion resistance and the like of the magnet powder and the hard magnet can be improved. Therefore, in the present invention, the addition form of La is not particularly problematic.
However, from the viewpoint of suppressing the oxidation of the magnet powder and the like more effectively by giving the function of oxygen getter to La, it is preferable that La is present on the surface of the constituent particles of the magnet powder or the vicinity thereof. Therefore, it is more advantageous to mix La-based material after the magnet powder is produced or in the middle of production and to diffuse La on the surface or inside of the magnet powder, rather than including La from the beginning in the magnet alloy.
Therefore, for example, in the case of the above-described method for producing an isotropic magnet powder, the magnet powder obtained after the dehydrogenation step is mixed with a La-based material composed of at least one of La, La alloy, and La compound. When the La mixture is heated to 673 to 1123K and a diffusion heat treatment process for diffusing La into the surface and the inside of the magnet powder is performed, when the total isotropic magnet powder is 100 at%, La is set to 0. It is preferable to contain 001-1.0at%.
It is also conceivable that a La-based material is mixed with RFeBHx powder or the like, which is in the process of manufacturing magnet powder, and La is diffused on the surface and inside thereof. This RFeBHx powder or the like is in a state in which R and Fe are very difficult to be oxidized as compared to RFeB yarn powder and the like. For this reason, it is more preferable in that La is diffused or coated in a state where oxidation is suppressed, and magnet powder excellent in corrosion resistance and the like can be obtained with stable quality. By the way, this hydride (RFeBHx) is a three-phase decomposed RH in the hydrogenation process. ₂ Hydrogen is removed from the phase and Fe ₂ The polycrystal having the B phase crystal orientation transferred is recombined and obtained after the first evacuation step of the d-HDDR treatment.
Therefore, the method for producing anisotropic magnet powder of the present invention further comprises Lae simple substance, La alloy, La compound or one or more of those hydrides to the RFeB hydride obtained after the first exhaust step. A diffusion heat treatment step is performed in which a La mixture obtained by mixing La-based materials is heated to 673 to 1123 K to diffuse La into the surface and inside of the RFeB hydride, and the second exhaust step includes the diffusion heat treatment step. This is a process for removing hydrogen from the La-treated product later, or after the diffusion heat treatment process and the second exhaust process at the same time, or after the second exhaust process. It is preferable that the anisotropic magnet powder obtained by such a method contains 0.001 to 1.0 at% La when the whole is 100 at%.
Here, the diffusion heat treatment step is a step of diffusing (or coating) La on the surface and inside of the RFeB magnet powder or RFeB hydride. This diffusion heat treatment step may be performed after mixing the La-based material or simultaneously with the mixing. If this processing temperature is less than 673 K, the La-based material is unlikely to be in a liquid phase, and diffusion processing is difficult. On the other hand, if it exceeds 1123K, crystal growth of RFeB-based magnet powder or the like occurs, leading to a decrease in iHc, and improvement in corrosion resistance and the like (reduction in permanent demagnetization factor) cannot be sufficiently achieved. The treatment time is preferably 0.5 to 5 hours. If it is less than 0.5 hour, the diffusion of La becomes insufficient, and the corrosion resistance of the magnet powder does not improve so much. On the other hand, when it exceeds 5 hours, iHc falls. Needless to say, this diffusion heat treatment step is preferably performed in an oxidation-preventing atmosphere (for example, a vacuum atmosphere). The La-based material is as described above, but the form is not limited. However, from the viewpoint of efficiently and reliably performing the production process of the magnet powder, it is preferable that they are in powder form. The La alloy or La compound is preferably an alloy or compound (including an intermetallic compound) of La and a transition metal element (TM). For example, LaCo, LaNdCo, LaDyCo, etc. Co is particularly suitable for increasing the Curie point of the magnet powder.
B. Example
The present invention will be described more specifically with reference to the following examples.
(Example 1, Example 2)
(1) Manufacture of alloys, magnetic powder and bonded magnets
As examples of the magnet alloy according to the present invention, ingots (magnet alloys) having the compositions listed in Samples 1 to 10 in Table 1 or Table 2 were produced by melting and casting. Moreover, as a comparative example, it manufactured by melt | dissolving and casting the ingot of the composition quoted to the samples C1-C6 in each table | surface. The manufactured ingots are about 30 kg each.
The alloy compositions of the samples shown in Table 1 and Table 2 are the same. However, Table 1 and Table 2 differ in the treatment applied to each sample (ingot). That is, Table 1 shows a case where each sample was subjected to HDDR treatment, and the magnetic powder shown in Table 1 is an isotropic magnet powder obtained through the treatment. Moreover, the bonded magnet shown in Table 1 is manufactured from the isotropic magnet powder. These are hereinafter referred to as Example 1.
Table 2 shows a case where each sample was subjected to d-HDDR treatment. The magnetic powder shown in Table 2 is an anisotropic magnet powder obtained through the treatment. The bonded magnets shown in Table 2 are manufactured from the anisotropic magnet powder. These are hereinafter referred to as Example 2.
Next, specific manufacturing conditions for the magnetic powder and bonded magnet shown in Tables 1 and 2 will be described.
(1) The magnetic powder shown in Table 1 is sample No. The ingots having the alloy compositions of 1 to 10 and C1 to C6 were produced by subjecting them to HDDR treatment comprising a hydrogenation step and a dehydrogenation step without being subjected to a homogenization heat treatment. That is, a heat treatment was performed for 360 minutes in a hydrogen gas atmosphere having a temperature and a hydrogen pressure shown in Table 1 (hydrogenation step). This is followed by vacuuming with a rotary pump and a diffusion pump for 60 minutes, ^-1 It cooled in the vacuum atmosphere below Pa (dehydrogenation process). Thus, about 10 kg of magnetic powder was produced per batch.
(2) Magnetic powder shown in Table 2 is also sample No. D-HDDR consisting of a low temperature hydrogenation step, a high temperature hydrogenation step, a first exhaust step and a second exhaust step without subjecting the ingots having the alloy compositions of 1 to 10 and C1 to C6 to homogenization heat treatment. Produced by treatment. That is, hydrogen was sufficiently absorbed in each sample alloy in a hydrogen gas atmosphere at room temperature and a hydrogen pressure of 100 kPa (low temperature hydrogenation step). Next, heat treatment was performed for 480 minutes in a hydrogen gas atmosphere at the temperature and hydrogen pressure shown in Table 2 (high-temperature hydrogenation step). Subsequently, a heat treatment for 160 minutes was performed at the same temperature shown in Table 2 in a hydrogen gas atmosphere at a hydrogen pressure of 0.1 to 20 kPa (first exhaust process). Finally, evacuate with rotary pump and diffusion pump for 60 minutes to ^-1 It cooled in the vacuum atmosphere below Pa (2nd exhaustion process). Thus, about 10 kg of magnetic powder was produced per batch.
(3) Next, using the various isotropic magnetic powders shown in Table 1 and the anisotropic magnetic powders shown in Table 2 thus obtained, the following bonded magnets were produced.
First, an epoxy resin (3 wt%) previously dissolved in butanone was mixed with each magnetic powder. Then, butanone was volatilized while evacuating to produce a bonded magnet pellet. As a reference sample, a similar pellet was prepared using a flake-shaped MQP-B (manufactured by Magnequench International) produced by a melt spinning method as a raw material. And this pellet was press-molded into a 7 mm cubic shape while being oriented in a 2.5 T magnetic field to obtain a bonded magnet.
(2) Magnetic measurement of magnetic powder and bonded magnet
{Circle around (1)} Each magnetic powder obtained was subjected to magnetic measurement. Since iHc of magnetic powder cannot be used with a normal BH tracer, iHc was measured as follows.
First, the magnetic powder was classified to a particle size of 75 to 106 μm. Using the classified magnetic powder, the demagnetizing factor is shaped to 0.2, and after orientation in a magnetic field, 4.57 MAm _-1 And (BH) max and iHc were measured by VSM (Riken Electronics Sales Co., Ltd., BH-525H). The results are also shown in Table 1 and Table 2.
(2) Further, (BH) max and iHc of the obtained various bonded magnets were measured with a BH tracer (BHU-25, manufactured by Riken Electronics Sales Co., Ltd.). The results are also shown in Table 1 and Table 2.
Note that “-” in Tables 1 and 2 indicates that the measurement was not performed because the magnetic characteristics were low.
(3) Evaluation
(1) An overview of Table 1 and Table 2 shows that sample no. As in C1, C2, C4, and C5, when the amount of B is lower than 10.8 at%, (BH) max and iHc rapidly decrease. Sample No. As in C3 and C6, even when B was higher than 15 at%, (BH) max also decreased.
In addition, when B amount is lower than 10.8 at%, it is considered that iHc is decreased because α-Fe is precipitated. In addition, when B is higher than 15 at%, the reason why (BH) max decreases is considered to be that the B-rich phase has increased.
Therefore, in order to balance (BH) max and iHc in a high dimension, it can be said that the B content is preferably 10.8 to 15 at%, as in the present invention. Next, the isotropic magnetic powder and its bonded magnet in Table 1 and the anisotropic magnetic powder and its bonded magnet in Table 2 will be specifically examined.
(2) Isotropic magnetic powder and its bonded magnet
Regarding the ternary isotropic magnetic powder obtained by subjecting the alloy ingots having different compositions of B to the HDDR treatment under the same conditions, examples (sample Nos. 1 and 2) and comparative examples (sample No. C1) shown in Table 1 were used. The following can be understood by comparing with C3).
Even if the amount of B is small or large as in the comparative example, specifically, if the amount of B is outside the range of 10.8 to 15 at%, the maximum energy product (BH) max of the magnetic powder decreases. On the other hand, in the case of the embodiment having the B amount within the range, 70 kJm. ^-3 A large (BH) max as described above is obtained. Thus, the peak value of (BH) max exists in the range of B: 10.8-15at%.
The coercive force iHc of the magnetic powder tends to increase as the B amount increases. However, in the range where the B amount is 10.8 at% or more, the increasing tendency of iHc becomes very gradual, and sufficient iHc is obtained when the B amount is 10.8 to 15 at%.
Next, with respect to hexotropic isotropic magnetic powders obtained by subjecting alloy ingots having different compositions of B to HDDR treatment under the same conditions, examples (sample No. 5) and comparative examples (sample No. 5) shown in Table 1 were used. Even if C4 to C6) are compared, the same can be said. That is, the peak value of (BH) max is in the range of B: 10.8 to 15 at%, and iHc obtained at that time is also close to the peak value.
The same can be said for bonded magnets manufactured using these isotropic magnetic powders regardless of whether they are ternary or ternary.
Furthermore, from Table 1, although the bond magnet according to the present embodiment of the 6-component system or more has the same (BH) max as the bond magnet made of MQP-B, iHc is improved by about 50%. I also understood.
(3) Anisotropic magnetic powder and its bonded magnet
About the ternary anisotropic magnetic powder obtained by performing the d-HDDR treatment under the same conditions on the alloy ingots that differ only in the composition of B, the examples (sample Nos. 1 and 2) shown in Table 2 and the comparative examples (sample No. .C1-C3), the following can be understood.
Even if the amount of B is small or large as in the comparative example, specifically, if the amount of B is outside the range of 10.8 to 15 at%, the maximum energy product (BH) max of the magnetic powder decreases. On the other hand, in the case of the embodiment in which the B amount is in the range, 210 kJm ^-3 A large (BH) max as described above is obtained. Thus, the peak value of (BH) max exists in the range of B: 10.8-15at%.
The coercive force iHc of the magnetic powder tends to increase as the B amount increases. However, in the range where the B amount is 10.8 at% or more, the increasing tendency of iHc becomes very gradual, and sufficient iHc is obtained when the B amount is 10.8 to 15 at%.
Next, with respect to the 6-component anisotropic magnetic powder obtained by subjecting an alloy ingot having a different composition of B to d-HDDR treatment under the same conditions, Examples (Sample No. 5) shown in Table 2 and Comparative Examples (Samples) No. C4 to C6), the same as above can be said. That is, the peak value of (BH) max is in the range of B: 10.8 to 15 at%, and iHc obtained at that time is also close to the peak value.
The same applies to bonded magnets manufactured using these anisotropic magnetic powders, regardless of whether they are ternary or ternary.
(Example 3)
Sample No. shown in Table 1 The relationship between the intrinsic coercivity iHc of the isotropic magnetic powder obtained by subjecting the ingots 2 and 6 to the HDDR treatment and the time of the hydrogenation step of the HDDR treatment (180 to 1800 minutes) was investigated. Except for the time of the hydrogenation step, the production conditions of each magnetic powder are the same as those of the HDDR process described in the first embodiment. The method for measuring the magnetic characteristics is the same as in the first and second embodiments. The results thus obtained are shown in Table 3.
From Table 3, it was found that iHc increased with increasing time of the hydrogenation process, and the increase in iHc tended to be almost saturated when it exceeded 360 minutes.
(Example 4)
Sample No. shown in Table 2 Investigate the relationship between the intrinsic coercivity iHc of anisotropic magnetic powder obtained by subjecting the ingots 2 and 6 to d-HDDR treatment and the time (180 to 1800 minutes) of the d-HDDR treatment high-temperature hydrogenation process did.
Except for the time of the high-temperature hydrogenation process, the production conditions of each magnetic powder are the same as those in the d-HDDR process described in Example 2. The method for measuring the magnetic characteristics is the same as in the first and second embodiments. The results thus obtained are shown in Table 4.
From Table 4, it was found that, as in the case of Example 3, when the processing time of the high-temperature hydrogenation process exceeds 360 minutes, the coercive force obtained tends to be almost saturated.
(Example 5)
Sample No. shown in Table 1 5 to 8 isotropic magnet powder, sample No. shown in Table 2. The fluidity and bulk density of each were examined using bonded magnet pellets comprising the anisotropic magnet powders 1 to 4 and the reference sample (MQP-B). The measurement results are shown in FIG. 1 and FIG.
The fluidity and bulk density of the pellets were measured according to JIS Z8041 (JIS standard).
As can be seen from FIGS. 1 and 2, in this example, the fluidity is improved by about 20% and the bulk density is improved by about 10% compared to the reference sample. This is presumably because the particle shape of each magnetic powder of this example is close to a sphere.
(Example 6)
Sample No. in Table 2 The cost performance of anisotropic magnetic powder obtained by performing d-HDDR treatment on the alloy ingot No. 6 was examined.
First, sample no. 6 ingots (about 30 kg) were produced by melting and casting. This ingot was not subjected to a homogenization heat treatment, and the sample alloy was sufficiently absorbed with hydrogen in a hydrogen gas atmosphere at room temperature and a hydrogen pressure of 100 kPa (low temperature hydrogenation step). Next, heat treatment was performed for 480 minutes in a hydrogen gas atmosphere at a temperature of 1073 K and a hydrogen pressure of 45 kPa (high-temperature hydrogenation step). Subsequently, heat treatment was performed for 160 minutes in a hydrogen gas atmosphere at a temperature of 1073 K and a hydrogen pressure of 0.1 to 10 kPa (first exhaust process). Finally, evacuate with rotary pump and diffusion pump for 60 minutes to ^-1 It cooled in the vacuum atmosphere below Pa (2nd exhaustion process). Thus, about 10 kg of magnetic powder was produced per batch.
Using this magnetic powder, a bonded magnet was produced in the same manner as in Examples 1 and 2, and its (BH) max was measured. The value obtained by dividing the measured (BH) max by the raw material cost (raw material cost, melting / casting cost) used for the d-HDDR treatment is shown in FIG.
As a comparative sample, an alloy ingot (about 30 kg) of sample C1 in Table 2 was manufactured by melting and casting. The ingot was kept in an Ar gas atmosphere at a temperature of 1413 K for 40 hours to perform a homogenization heat treatment. Thereafter, the same d-HDDR treatment as that of Sample 6 was performed. Thus, about 10 kg of magnetic powder was produced per batch.
Also for this magnetic powder, a bonded magnet was prepared in the same manner as in Sample 6 above, and its (BH) max was measured. The value obtained by dividing the measured (BH) max by the raw material cost (raw material cost, melting / casting cost and homogenization heat treatment cost) used for the d-HDDR treatment is also shown in FIG. 3 as cost performance.
From FIG. 3, the cost performance of the sample 4 that was not subjected to the homogenization heat treatment was improved by about 30% compared to the sample C1 that was subjected to the homogenization heat treatment.
(Example 7)
(1) Sample No. in Table 1 1, no. The alloy ingot No. 6 was subjected to the same HDDR treatment as in Example 1 to produce an isotropic magnetic powder. In this isotropic magnetic powder, La80Co20 alloy powder (La-based material) is mixed (mixing step) and heated (diffusion heat treatment step). 11-15 and sample no. 16 and 17 magnetic powders were obtained. The composition of each sample shown in Table 5 and Table 6 is a value analyzed by an ICP (high frequency plasma emission analyzer) after the diffusion heat treatment step. Table 5 also shows the diffusion heat treatment conditions for each sample. The diffusion heat treatment conditions in Table 6 are all 1073 K × 1 hr. Note that all of the mixing step and the diffusion heat treatment step are 10 ^-2 It was performed in a vacuum atmosphere of Pa or less. In Table 6, as an example, Sample No. The magnetic properties of the 16 and 17 isotropic magnet powders and the bond magnets using them are also shown. The measuring method and the like are as described above.
Here, the La80Co20 alloy is an alloy of La: 80 at% and Co: 20 at%, and is melted in the same manner as in the case of the magnet alloy (ingot) of Example 1. The powder was obtained by pulverizing the ingot by a hydrogen pulverization method and pulverizing with a vibration mill, and the average particle size was 10 μm.
Using the isotropic magnetic powder after the diffusion heat treatment step, a 7 mm square isotropic bonded magnet was produced in the same manner as in Example 1. Using this bond magnet, the permanent demagnetization rate was measured.
Permanent demagnetization factor is the ratio of the decrease relative to the initial magnetic flux from the difference between the initial magnetic flux of the bond magnet and the magnetic flux obtained by re-magnetization after holding in an air atmosphere at 100 ° C or 80 ° C for 1000 hours. It is what I have sought. Magnetization at this time was performed in 1.1 MA / m (45 kOe). A flux meter was used to measure the magnetic flux. The permanent demagnetization factor thus obtained is also shown in Tables 5 and 6.
(2) Sample No. listed in Table 5 as a comparative example. Bond magnets according to C7 to C9 were prepared. Sample No. The bonded magnet of C7 has a La amount exceeding 1.0 at%. The C8 bonded magnet was not mixed with a La-based material. The C9 bonded magnet has a low heating temperature of less than 400 ° C. during the diffusion heat treatment process. The diffusion heat treatment conditions and the permanent demagnetization factor in each case are also shown in Table 5.
(3) From Tables 5 and 6, it can be seen that the isotropic bonded magnet according to the present invention has a small permanent demagnetization factor, excellent heat resistance and high practicality. A small permanent demagnetization factor also means excellent corrosion resistance and small deterioration over time.
In particular, even in the case of 100 ° C. × 1000 hours, the permanent demagnetization rate is as small as less than 10%. In the case of 80 ° C. × 1000 hours, the permanent demagnetization factor is as low as about 5%.
On the other hand, in the comparative example, the permanent demagnetization rate is as high as about 10% at 80 ° C. × 1000 hours, and the permanent demagnetization rate is as high as about 15% at 100 ° C. × 1000 hours. Yes. Incidentally, as a reference sample, the permanent demagnetization factor of an isotropic powder (MQP-B) produced by a rapid solidification method is also shown in Table 5.
In addition, the magnetic properties of the magnetic powder and the bonded magnet were the same as the results shown in Table 1 of the example, or the magnetic properties were reduced by about 7 to 8% at the maximum, and there were no practical problems.
(Example 8)
(1) Sample No. in Table 2 1, no. The alloy ingot of No. 6 was subjected to the same low temperature hydrogenation process, high temperature hydrogenation process and first exhaust process as in Example 2 to obtain NdFeBH _x A powder (RFeB hydride) was obtained. This NdFeBH _x The same La80Co20 alloy powder as in Example 7 was mixed with the powder (mixing step) and heated (diffusion heat treatment step). This was followed by a second exhaust process similar to that in Example 2.
Thus, the sample numbers shown in Tables 7 and 8 were used. 11-15 and sample no. 16 and 17 magnetic powders were obtained. The composition of each sample shown in Table 7 and Table 8 is a value analyzed by ICP after the second exhaust process as in Example 7. Table 7 also shows the diffusion heat treatment conditions for each sample. The diffusion heat treatment conditions in Table 8 are all 1073 K × 1 hr. Note that all of the mixing step and the diffusion heat treatment step are 10 ^-2 It was performed in a vacuum atmosphere of Pa or less. In Table 8, as an example, Sample No. The magnetic properties of the 16 and 17 anisotropic magnet powders and the bond magnet using the same were also shown. The measuring method and the like are as described above.
And the permanent demagnetization factor calculated | required similarly to Example 7 was combined with Table 7 and Table 8, and was shown.
(2) The bonded magnet prepared as a comparative example is the same as in the case of Example 7. Table 7 shows the diffusion heat treatment conditions and the permanent demagnetization factor in each case.
(3) From Table 7 and Table 8, the anisotropic bonded magnet according to the present invention has a small permanent demagnetization factor and high practicality. In particular, even in the case of 100 ° C. × 1000 hours, the permanent demagnetization rate is as small as less than 10%. In the case of 80 ° C. × 1000 hours, the permanent demagnetization factor is a small value of 5 to 7%. On the other hand, in the comparative example, the permanent demagnetization rate is as high as 10% or more even at 80 ° C. × 1000 hours, and the permanent demagnetization rate is as high as 15% or more at 100 ° C. × 1000 hours. .
In addition, the magnetic properties of the magnet powder and the bonded magnet were the same as the results shown in Table 2 of the example or the magnetic properties were reduced by about 7 to 8% at the maximum, and there was no problem in practical use.

[Brief description of the drawings]
FIG. 1 is a bar graph comparing the flow rates of bonded magnet pellets produced from magnet powder.
FIG. 2 is a bar graph comparing the bulk density of pellets for bonded magnets manufactured from magnet powder.
FIG. 3 is a bar graph comparing the cost performance of magnet powders manufactured by d-HDDR processing.

  The present invention relates to an alloy for bonded magnets capable of producing a bonded magnet having excellent magnetic properties at low cost, an isotropic magnet powder and an anisotropic magnet powder obtained from the alloy, a production method thereof, and further, The present invention relates to a bonded magnet obtained from magnet powder.

  Hard magnets (permanent magnets) are used in various devices such as motors. In particular, there is a strong demand for small and high-powered vehicle motors. Such hard magnets are required to be low cost in order to enhance the global competitiveness as well as high performance in terms of magnetic properties.

  First, from the viewpoint of high performance, development of RFeB magnets (rare earth magnets) composed of rare earth elements (R), boron (B), and iron (Fe) has been actively conducted. Examples of such RFeB magnets include magnetic isotropy in US Pat. No. 4,851,058 (hereinafter referred to as “Patent Document 1”) and US Pat. No. 5,411,608 (hereinafter referred to as “Patent Document 2”). An RFeB-based magnet alloy (composition) is disclosed.

  Specifically, Patent Document 1 discloses a magnetic alloy comprising about 10 to 40 at% Nd, Pr or Nd and Pr, about 50 to 90 at% Fe, and about 0.5 to 10 at% B. Is disclosed. Patent Document 2 discloses a magnet alloy composed of 12 to 40 at% Nd, Pr, or Nd and Pr, 10 at% or less Co, 3 to 8 at% B, and the balance Fe. Note that Patent Document 2 is intended to improve heat resistance by increasing the Curie temperature by adding Co. In both of these patent documents, a magnet powder having the above composition is obtained by a melt span method which is a kind of rapid solidification method.

  This magnet powder (magnetic powder) is often used industrially as a raw material powder for a bonded magnet (hard magnet). The bonded magnet is obtained, for example, by first producing pellets from the magnetic powder and a resin as a binder, feeding the pellets to a molding die, and press-molding the pellets. Generally, when the pellets are powdered into the mold, if the fluidity is small, the powdering time is shortened and the productivity of the bonded magnet can be improved. Moreover, when the bulk density of a pellet is large, the uniform powder supply to a metal mold | die will be attained and the defect rate of a bonded magnet can be reduced. Therefore, the smaller the fluidity and the larger the bulk density, the lower the cost of the bonded magnet and the better the economy. The fluidity and bulk density depend on the particle shape of the magnetic powder, and the more suitable the fluidity and bulk density are as spherical.

  However, since the particle shape of the magnetic powder produced from Patent Documents 1 and 2 is a flake shape having a thickness of 20 to 50 μm, the fluidity is larger and the bulk density is smaller than the spherical shape. Of course, it is also conceivable to pulverize the flakes into a spherical shape, thereby reducing the fluidity and increasing the bulk density. However, the number of man-hours increases, and even if it is made spherical, it is actually difficult to effectively reduce the fluidity or increase the bulk density. This is because, when the original particle size is 50 μm at the maximum, powder of 50 μm or less generally tends to adhere and aggregate.

  The situation is the same for SmFeN-based magnetic powders having different compositions. Even if the particle shape of the magnetic powder is close to a sphere, if the average particle diameter is 1 to 5 μm, it is easy to cause adhesion and aggregation, and the fluidity and bulk density deteriorate.

  Therefore, as a method for producing magnetic powder in place of the melt span method, there is a method using a HDDR (hydration-deposition-desorption-recombination) treatment method or a d-HDDR treatment method. Since the magnetic powder obtained by these consists of substantially spherical particles, the fluidity and bulk density are superior to the magnetic powder obtained by Patent Documents 1 and 2 above.

  The HDDR treatment method is used for producing RFeB-based isotropic magnet powder (isotropic magnetic powder) and RFeB-based anisotropic magnet powder (anisotropic magnetic powder), and mainly consists of two steps. That is, a first step (hydrogenation step) in which a hydrogen gas atmosphere of about 100 kPa (1 atm) is maintained at 773 to 1273 K to cause a three-phase decomposition disproportionation reaction, and then dehydrogenation is performed in a vacuum. Process (2nd process).

  On the other hand, the d-HDDR treatment is a method mainly used for producing RFeB-based anisotropic magnetic powder. Controlling the reaction rate between RFeB alloy and hydrogen from room temperature to high temperature, as reported in detail in a well-known document (Mishima et al .: Journal of Japan Society of Applied Magnetics, 24 (2000), p.407). Is made by Specifically, a low-temperature hydrogenation step (first step) in which hydrogen is sufficiently absorbed by the RFeB alloy at room temperature, and a high-temperature hydrogenation step (second step) in which a three-phase decomposition disproportionation reaction is caused under a low hydrogen pressure. Steps), an evacuation step for dissociating hydrogen under as high a hydrogen pressure as possible (third step), and a subsequent dehydrogenation step (fourth step) for removing hydrogen from the material. The difference from the HDDR treatment is that a plurality of processes with different temperatures and hydrogen pressures are provided, so that the reaction rate between the RFeB alloy and hydrogen is kept relatively moderate and a homogeneous anisotropic magnetic powder can be obtained. It is a point.

The following patent documents can be cited as a method for producing a magnet powder using each of these treatments.
First, a method for producing RFeB-based isotropic magnetic powder using HDDR processing is disclosed in Japanese Patent Publication No. 7-68561 (Patent No. 2041426: hereinafter referred to as “Patent Document 3”). According to Patent Document 3, an alloy ingot containing R, Fe, and B as main components is subjected to a pulverization step and a homogenization heat treatment step, and then the HDDR treatment is performed to produce magnetic powder. Here, in this case, the two steps (grinding step, homogenization heat treatment step) before the HDDR treatment are indispensable for obtaining isotropic magnetic powder having a large magnetic property. As described in Patent Document 3, when the two steps are omitted and the magnetic powder is manufactured by directly HDDR processing on the cast body of the RFeB-based alloy, the coercive force (hereinafter referred to as the coercive force) of the bonded magnet manufactured using the obtained magnetic powder. , IHc) shows a very low value of 0.76 MAm ⁻¹ at the maximum.

  However, the two processes are both expensive and inferior in economic efficiency. In particular, the homogenization heat treatment process that performs high-temperature treatment at 873 to 1473K requires about twice the cost of HDDR treatment, and is very economical.

  Next, a method for producing RFeB-based anisotropic magnetic powder using HDDR processing is disclosed in Japanese Patent No. 2576671 (hereinafter referred to as “Patent Document 4”) and Japanese Patent No. 2576672 (hereinafter referred to as “Patent Document 5”). No. 2586198 (hereinafter referred to as “Patent Document 6”) and Japanese Patent No. 2586199 (hereinafter referred to as “Patent Document 7”).

According to the embodiments described in these patent documents, an alloy ingot composed of about 10 to 20 at% R, about 5 to 20% B, the balance Fe, and various additive elements, a homogenization heat treatment step and a grinding step After that, the HDDR process is performed to manufacture the magnetic powder. However, the B content of the alloys disclosed in the examples is disclosed in detail when the content is 10.4 at% or less, but alloys whose B content exceeds 10.4 at% are alloys of 10.4 at% and 20 at%. Only. And (BH) max of the anisotropic bonded magnet manufactured from the magnetic powder whose B amount is 10.4 at% is 83-112 kJ / m < ³ >, iHc is 0.74-0.97 MA / m, B amount is An anisotropic bonded magnet manufactured from 20 at% magnetic powder has a (BH) max of 80 to 93 kJ / m ³ and an iHc of 0.46 to 0.75 MA / m. All of these magnetic properties are inadequate. In particular, when the amount of B increases to 20 at%, iHc decreases remarkably.

  And in the case of the said patent document, since the homogenization heat processing is performed at 1393K-1413K and high temperature, the manufacturing cost of a magnetic powder becomes higher and also economical efficiency is bad. Of course, in this case as well, although the cost can be reduced if the homogenization heat treatment is omitted, as in the case of Patent Document 3, the deterioration of iHc is unavoidable.

  Incidentally, it is actually difficult to industrially mass-produce anisotropic magnetic powder using methods such as Patent Documents 4 to 7. This is because, in order to obtain magnetic powder with excellent anisotropy, it is necessary to strictly control the temperature during HDDR processing. Specifically, highly anisotropic magnetic powder cannot be obtained unless HDDR treatment is performed in a temperature range of about ± 20K with respect to the target temperature. Nevertheless, if the throughput per batch of HDDR treatment is increased, the amount of heat generated during the disproportionation reaction between hydrogen and the RFeB alloy and the endothermic amount during dehydrogenation increase rapidly, and the ambient temperature is desired. This is because it becomes out of bounds. As a result, the magnetic powder mass-produced by the methods of Patent Documents 4 to 7 has a small magnetic property, particularly anisotropy.

  Therefore, when mass production of RFeB-based anisotropic magnetic powder is performed, JP 2001-148306 A (hereinafter referred to as “Patent Document 8”) and JP 2001-76917 A (hereinafter referred to as “Patent Document 9”). It is recommended to use d-HDDR processing as disclosed in the above. According to this d-HDDR treatment, magnetic powder having high anisotropy can be obtained even if the amount of treatment per batch is increased. As described above, in the case of d-HDDR treatment, the reaction rate between the RFeB alloy and hydrogen can be controlled gently in each step, so the amount of heat generated during the disproportionation reaction between the RFeB alloy and hydrogen can be reduced. This is because the amount of heat absorbed can be suppressed.

  However, even in these Patent Documents 8 and 9, the alloy ingot composed of about 12 to 15 at% R, about 6 to 9 at% B and the balance Fe is used, and then subjected to the homogenization heat treatment step. An anisotropic magnetic powder is manufactured by performing d-HDDR treatment. For this reason, it is the same in that the manufacturing cost is still high, as in the manufacturing method described above.

  So far, we have mainly explained the cost reduction of high-performance hard magnets, but considering the practicality of hard magnets, it is also important that the hard magnets have excellent aging characteristics such as corrosion resistance. is there. In particular, hard magnets incorporated in household motors, automobile motors, and the like used in high temperature environments are required to have excellent heat resistance and the like from the viewpoint of ensuring the reliability of the motors.

However, the rare earth magnet described above is easily deteriorated by oxidation corrosion of Fe and R, which are the main components, and it is difficult to stably secure the high magnetic properties. In particular, when a rare earth magnet is used at room temperature or higher, its magnetic properties tend to deteriorate rapidly. Such a change with time of the magnet is usually quantitatively indicated by a permanent demagnetization rate (%). However, in the case of conventional rare earth magnets, most of the permanent demagnetization rate exceeds 10%. The permanent demagnetization rate is a reduction rate of magnetic flux that is not restored even after re-magnetization after a long time (1000 hours) at a predetermined high temperature.
US Pat. No. 4,851,058 US Pat. No. 5,411,608 Japanese Patent Publication No. 7-68561 Japanese Patent No. 2576671 Japanese Patent No. 2576672 Japanese Patent No. 2586198 Japanese Patent No. 2586199 JP 2001-148306 A JP 2001-76917 A

  The present invention has been made in view of such circumstances. That is, a low-cost and excellent magnetic property RFeB-based magnet powder obtained for HDDR treatment or d-HDDR treatment, which is obtained without performing a high-cost homogenization heat treatment step, and a method for producing the same, and further It aims at providing the bonded magnet which consists of magnet powder. Moreover, it aims at providing the RFeB type | system | group magnet alloy suitable for manufacture of the magnet powder.

  In addition, it is possible to provide a bonded magnet that is not only excellent in magnetic properties at low cost but also has little deterioration over time, and further provides an RFeB-based magnet alloy, an RFeB-based magnet powder, and a method for producing the same, from which such a hard magnet can be obtained. Objective.

  As a result of intensive studies to solve this problem and repeated various systematic experiments, the present inventor has developed a new magnet alloy having a B amount different from the conventional one, and has completed the following invention.

(Alloy for bonded magnet)
First, the alloy for bonded magnets of the present invention includes iron (Fe) as a main component, 12 to 16 atomic% (at%) rare earth element (hereinafter referred to as “R”), and 10.8 to 15; It consists of at% boron (B) and is characterized in that the homogenization heat treatment step can be omitted in the production of the magnet powder.

  In addition to such expressions, the present invention contains at least Fe as a main component, 12 to 16 at% R, and 10.8 to 15 at% B, and is a kind of hydrogenation treatment. It is good also as a magnet alloy characterized by using for a HDDR process or d-HDDR process.

  The alloy for bonded magnets of the present invention (hereinafter simply referred to as “magnet alloy” as appropriate) has a B amount that is different from the RFeB-based magnet alloy that has been developed so far, and has a relatively large B amount. The present inventor has found that the magnet alloy having a large amount of B suppresses the precipitation of α-Fe which is the primary crystal. As a result of suppressing the precipitation of α-Fe, which leads to a decrease in magnetic properties, it is possible to omit the homogenization heat treatment step, which has been considered indispensable for improving the magnetic properties. It came to be obtained.

This reason can be considered as follows at present. By the large amount of B, the casting initial melting point than RFeB is 10~30K low R1Fe1B ₄ phase (hereinafter, referred to as "B-rich phase".) Is formed. And, since α-Fe which is the primary crystal is taken into the B-rich phase, it is considered that the precipitation of α-Fe is suppressed.

As a result of subjecting this magnet alloy (for example, its ingot) to the HDDR treatment or d-HDDR treatment described above, high iHc magnet powder was obtained. This can be thought of as follows. When hydrogen is absorbed into the magnet alloy of the present invention, the aforementioned B-rich phase and the R ₂ Fe ₁₄ B phase, which bears the magnet phase, react sufficiently with hydrogen to become α-Fe, Fe ₂ B, and R hydride. Next, when it is dehydrogenated, the B-rich phase precipitates finely and densely, and this is thought to be because the RFeB recrystallized grains became fine as a result of pinning the crystal growth of RFeB. In order to effectively obtain this pinning effect, for example, the hydrogen absorption time is preferably set to 360 minutes or more.

  From such a viewpoint, B is set to 10.8 at% or more. Thereby, the homogenization heat treatment process which impairs economically can be omitted, and iHc can be increased. On the other hand, if B exceeds 15 at%, the volume fraction of the B-rich phase in the magnet powder is increased, and the maximum energy product (BH) max is lowered, which is not preferable.

In Examples of Patent Documents 4, 5, 6, and 7, magnet powders with a B content of 20 at% are disclosed, but their iHc is as low as 0.46 to 0.75 MAm ⁻¹ . This is presumably because the hydrogen absorption time was as short as 240 minutes, the reaction between the B-rich phase and hydrogen was insufficient, and the B-rich phase did not precipitate finely and densely during the subsequent dehydrogenation.

  On the other hand, if R is less than 12 at%, primary crystal α-Fe is likely to be precipitated, leading to a decrease in iHc. On the other hand, when R exceeds 16%, (BH) max is lowered, which is not preferable.

  Such R includes scandium (Sc), yttrium (Y), and lanthanoids. However, as an element having excellent magnetic properties, R is Y, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium. It is preferable to comprise at least one of (Dy), holmium (Ho), erbium (Er), thulium (Tm) and lutetium (Lu). Among these, R is preferably composed of one or more of Pr, Nd, and Dy from the viewpoint of cost and magnetic properties.

  The magnet alloy of the present invention further preferably contains 0.1 to 6 at%, more preferably 1 to 6 at% of cobalt (Co) in addition to the above elements. This is because Co is an element that increases the Curie temperature of the magnet and improves the heat resistance. If Co is less than 0.1 at%, there is no substantial effect. On the other hand, since Co is expensive, it is preferably 6 at% or less from the viewpoint of industrial cost.

  The magnet alloy of the present invention includes gallium (Ga), zirconium (Zr), vanadium (V), aluminum (Al), titanium (Ti), hafnium (Hf), and copper (Cu) (hereinafter referred to as “first element group”). A total of 0.1 to 2 at%. This is because these elements improve the coercive force iHc of the magnet.

  The magnet alloy of the present invention contains 0.1 to 2 at% in total of at least one of niobium (Nb), tantalum (Ta) and nickel (Ni) (hereinafter referred to as “second element group”). May be. This is because these elements increase the residual magnetic flux density (Br) of the magnet.

  When both the element in the first element group and the element in the second element group are included, the maximum energy product (BH) max can be improved. In any case, if the sum of them is less than 0.1 at%, there is no substantial effect, and if it exceeds 2 at%, iHc, Br or (BH) max is undesirably lowered. In consideration of cost and magnetic characteristics, Ga is 0.1 to 1.0 at%, more preferably 0.2 to 0.4 at% (about 0.3 at%), Nb is 0.1 to 1.0 at%, More desirably, the content is 0.1 to 0.4 at% (about 0.2 at%).

  Needless to say, the alloy and powder according to the present invention may contain unavoidable impurities as appropriate. Their composition is balanced with Fe, but to put it simply, Fe is 59-77.2 at%.

  Furthermore, it is preferable that the magnetic alloy of the present invention contains 0.001 to 1.0 at% La apart from R. Thereby, the aged deterioration of the magnet powder and hard magnet which consist of the magnet alloy can be suppressed.

  This is because La is an element having the highest oxidation potential among rare earth elements (RE). For this reason, La acts as a so-called oxygen getter, La is selectively (preferentially) oxidized over R (Nd, Dy, etc.), and as a result, oxidation of magnet powder and hard magnets containing La is performed. It is suppressed. Although use of Dy, Tb, Nd, Pr, etc. can be considered instead of La, these elements cannot sufficiently suppress the oxidation of magnet powder and hard magnets. In view of cost, the use of La is preferable to these elements. At this time, R in the magnet alloy is a rare earth element other than La.

  Here, La exhibits an effect of improving corrosion resistance or the like as long as it is contained in a minute amount exceeding the level of inevitable impurities in the magnet alloy. And since the inevitable impurity level amount of La is less than 0.001 at%, in the present invention, the La amount is set to 0.001 at% or more. On the other hand, if La exceeds 1.0 at%, iHc is lowered, which is not preferable. Here, it is more preferable that the lower limit of the amount of La is 0.01 at%, 0.05 at%, and further 0.1 at% since sufficient effect of improving corrosion resistance and the like is exhibited. And from a viewpoint of improvement of corrosion resistance etc. and suppression of a fall of iHc, it is still more preferred in the amount of La being 0.01-0.7 at%.

The alloy composition containing La is not an alloy composition in which the R ₂ Fe ₁₄ B ₁ phase can exist as a single phase or almost a single phase, but a multiphase such as an R ₂ Fe ₁₄ B ₁ phase and a B-rich phase. It is an alloy composition consisting of a structure.

(Magnet powder and its manufacturing method)
The magnet alloy referred to in the present invention may be in an ingot shape or a powder shape regardless of its form. Moreover, in the case of powder, the particle size, particle shape, etc. are not ask | required. Therefore, for example, the magnet alloy of the present invention can be grasped as isotropic magnet powder or anisotropic magnet powder.

  For example, the isotropic magnet powder of the present invention is an alloy that contains at least Fe as a main component, 12 to 16 at% R, and 10.8 to 15 at% B and has not been subjected to a homogenization heat treatment step. It is obtained through a manufacturing method in which an HDDR process including a hydrogenation step of holding an ingot in a hydrogen gas atmosphere of 1023 to 1173K and a dehydrogenation step of removing hydrogen after the hydrogenation step is performed.

  The anisotropic magnet powder of the present invention is an alloy that contains at least Fe as a main component, 12 to 16 at% R, and 10.8 to 15 at% B and has not been subjected to a homogenization heat treatment step. A low temperature hydrogenation step for holding an ingot in a hydrogen gas atmosphere of 873 K or less, a high temperature hydrogenation step for holding in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low temperature hydrogenation step, and the high temperature hydrogenation step A manufacturing method for performing d-HDDR treatment comprising a first evacuation step that is later maintained in a hydrogen gas atmosphere at 102 to 1173 K at 0.1 to 20 kPa, and a second evacuation step that removes hydrogen after the first evacuation step. It is obtained through.

(Bonded magnet)
Furthermore, when these magnet powders are used, a high-performance bonded magnet can be obtained at a low cost.
For example, when an isotropic magnet powder is used, the bonded magnet of the present invention contains at least Fe as a main component, 12 to 16 at% R, and 10.8 to 15 at% B, and a homogenization heat treatment step. Isotropic magnet powder obtained by HDDR treatment comprising a hydrogenation step in which an ingot of an alloy not subjected to heat treatment is maintained in a hydrogen gas atmosphere of 1023 to 1173 K and a dehydrogenation step in which hydrogen is removed after the hydrogenation step And a binder are mixed and molded.

  Moreover, when anisotropic magnet powder is used, the bonded magnet of the present invention contains at least Fe as a main component, 12 to 16 at% R, and 10.8 to 15 at% B, and a homogenization heat treatment step. A low temperature hydrogenation step for holding an ingot of an alloy not subjected to heat treatment in a hydrogen gas atmosphere of 873 K or less, and a high temperature hydrogenation step for holding a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low temperature hydrogenation step A first evacuation step that is maintained in a hydrogen gas atmosphere of 1023 to 1173 K at 0.1 to 20 kPa after the high-temperature hydrogenation step, and a second evacuation step that removes hydrogen after the first evacuation step. The anisotropic magnetic powder obtained by the HDDR process and a binder are mixed and pressure-molded.

  In addition, the content regarding R, Co, the first element group, or the second element group described above also applies to the isotropic magnet powder, the anisotropic magnet powder, the manufacturing method thereof, and the bonded magnet as appropriate. The same applies to the addition of La, details of which will be described later.

Hereinafter, the present invention will be described in more detail with reference to embodiments.
(1) Magnet powder and production method thereof The magnet powder of the present invention is obtained by subjecting the ingot or coarse powder (particles) of the magnetic alloy to the HDDR treatment method or d-HDDR treatment method described above.

(a) HDDR Treatment Method As described above, the HDDR treatment according to the present invention is performed by subjecting an alloy (ingot) having B in the composition of 10.8 to 15 at% to a hydrogenation step and a dehydrogenation step. The conditions for the hydrogenation step are as described above.

Specifically, the dehydrogenation step is a step of bringing the hydrogen pressure into an atmosphere of 10 ⁻¹ Pa or less, for example. Moreover, what is necessary is just to set the temperature in a dehydrogenation process to 1023-1173K, for example. In addition, unless otherwise indicated, the hydrogen pressure as used in this specification means the partial pressure of hydrogen. Therefore, as long as the hydrogen partial pressure in each step is within a predetermined value, a vacuum atmosphere or a mixed atmosphere such as an inert gas may be used.

  The processing time for each of the above steps depends on the processing amount per batch. For example, when the processing amount per batch is 10 kg, the hydrogenation step may be performed for 360 to 1800 minutes and the dehydrogenation step for about 30 to 180 minutes. In addition, the HDDR process itself is disclosed in detail in the above-mentioned Patent Document 3 and the like, and may be referred to as appropriate.

The magnet powder obtained by this HDDR processing method has industrial significance as an isotropic magnet powder. The magnet powder exhibits excellent magnetic properties with, for example, iHc of 0.8 to 1.7 (MA / m) and (BH) max of 60 to 120 (kJ / m ³ ).

Next, each step of the HDDR process and the relationship with the magnet alloy of the present invention having the above B-rich composition will be described.
In the hydrogenation process, which is the first process of the HDDR process, hydrogen and the RFeB alloy and hydrogen and the B-rich phase are sufficiently reacted. In the subsequent dehydrogenation step, which is the second step, the B-rich phase is finely and densely precipitated. The finely precipitated B-rich phase pinches the RFeB crystal grain growth and makes the RFeB crystal grain fine. Thereby, a high coercive force (iHc) is obtained.

(b) d-HDDR treatment method The d-HDDR treatment according to the present invention is carried out in the low-temperature hydrogenation process and the high-temperature hydrogenation process, as described above, to an alloy (ingot) having B in the composition of 10.8 to 15 at%. The first exhaust process and the second exhaust process are performed.

The conditions for the high-temperature hydrogenation process and the first exhaust process are as described above. A low-temperature hydrogenation process is a process made into the atmosphere whose hydrogen pressure is 30-200 kPa, for example. The second exhaust process is, for example, a process in which the hydrogen pressure is set to an atmosphere of 10 ⁻¹ Pa or less, and the temperature at that time is, for example, about 1023 to 1173K. The first evacuation process and the second evacuation process together constitute a dehydrogenation process.

  The processing time for each of the above steps depends on the processing amount per batch. For example, if the processing amount per batch is 10 kg, the low temperature hydrogenation process is 30 minutes or more, the high temperature hydrogenation process is 360 to 1800 minutes, the first exhaust process is 10 to 240 minutes, and the second exhaust process is 10 to 10 minutes. It only takes about 120 minutes. Note that the d-HDDR processing method itself is disclosed in detail in the aforementioned Patent Document 9 and the like, and may be referred to as appropriate.

The magnet powder obtained by this d-HDDR treatment method is an anisotropic magnet powder that exhibits excellent magnetic properties. The magnetic properties are, for example, iHc of 0.8 to 1.7 (MA / m) and (BH) max of 190 to 290 (kJ / m ³ ).

Next, each step of the d-HDDR processing and the relationship with the magnet alloy of the present invention having the above B-rich composition will be described.
In the low-temperature hydrogenation step (hydrogen pressure: about 30 to 200 kPa), which is the first step of the d-HDDR treatment, hydrogen is rapidly increased to the RFeB-based alloy. In the subsequent high-temperature hydrogenation process (hydrogen pressure: about 20 to 100 kPa), hydrogen and the RFeB-based alloy are reacted slowly. At this time, the crystal orientation of the Fe2B phase, which becomes an anisotropic orientation transfer phase, is precipitated in almost one direction, and hydrogen and the B-rich phase are sufficiently reacted. Further, in the first exhaust process, which is the third process, the RFeB crystal is precipitated while the crystal orientation of the Fe2B phase is maintained, and the B-rich phase is finely and densely precipitated. RFeB crystal grain growth is pinned by the fine and densely precipitated B-rich phase, and the RFeB crystal grains become fine. Finally, hydrogen remaining in the alloy is removed in a second exhaust process, which is a fourth process.

  What is particularly important here is that the crystal orientation of the Fe2B phase is precipitated almost in one direction in the high-temperature hydrogenation step, and the crystal orientation of the Fe2B phase is maintained finely and densely in the subsequent first exhaust step. The RFeB crystal is finely precipitated by the pinning effect of the precipitated B-rich phase. Thereby, anisotropic magnet powder with high iHc is obtained.

  Further, in any of the above treatments, the ingot can be used as a raw material alloy, but each treatment can be efficiently advanced by using a pulverized coarse powder. The pulverization of the ingot and the pulverization performed after the above treatment can be performed using a dry or wet mechanical pulverization (a jaw crusher, a disk mill, a ball mill, a vibration mill, a jet mill, or the like).

(c) Fluidity and bulk density Magnet powder obtained by subjecting the magnet alloy of the present invention to the HDDR treatment or d-HDDR treatment has a substantially spherical particle size. For this reason, unlike the flakes manufactured by the melt span method as in Patent Documents 1 and 2, pellets manufactured using the magnet powder of the present invention have a low fluidity and a large bulk density. As a result, when producing a bonded magnet, which is the most important application of the magnet powder, it is possible to improve the powder feeding property of the pellets to the molding die. In addition, since the magnet powder of the present invention has an appropriate average particle size of about 50 to 200 μm, not only the fluidity and bulk density can be improved, but also adhesion and aggregation can be suppressed. Also excellent. As a result, productivity, quality, yield, etc. of bonded magnets can be improved, and the cost of various magnets can be reduced.

Specifically, the fluidity of pellets obtained by mixing the magnetic powder and the organic resin 10 to 45 mass% as a binder is 0.55 to 0.64 (s / g), and the bulk density is It is also 3.25 to 3.5 (g / cm ³ ). The amount of the organic resin mixed with the magnet powder is more preferably 10 to 25 mass% in the case of compression molding pellets, 30 to 45 mass% in the case of pellets for injection molding, and 20 to 35 mass% in the case of pellets for extrusion molding. .

  By the way, the reason why the particle diameter of the magnet powder is substantially spherical is as follows. When magnet powder is produced by performing HDDR treatment or d-HDDR treatment, the resulting particle shape is greatly affected by the alloy structure before the treatment. This is because when the alloy occludes hydrogen in the initial stage of the hydrogenation process of the HDDR process or in the low-temperature hydrogenation process of the d-HDDR process, it causes volume expansion and breaks mainly at fragile grain boundaries.

  Here, when the magnet alloy is made of a cast body such as an ingot, the crystal structure of the central part is equiaxed and the crystal structure of the end part is dendritic. In the present invention, the presence of the B-rich phase suppresses the crystallization or precipitation of α-Fe, which is the primary crystal, so that the dendritic crystal structure formed at the end also becomes fine. As a result, when HDDR treatment or d-HDDR treatment is performed on a cast body made of the magnet alloy of the present invention, one crystal grain is obtained as almost one substantially spherical particle from the center of the cast body. From the end, a plurality of dendritic crystals are obtained as one substantially spherical particle. In this way, the constituent particles of the magnet powder are much closer to a sphere than the magnet powder obtained by the conventional melt span method or the like.

(2) Bonded magnet and its manufacturing method When the magnet powder obtained as described above is used, not only the magnetic properties are excellent, but also the bonded magnet can be produced at low cost because of its excellent powder feeding property.

  This bonded magnet is obtained through a mixing step of mixing the aforementioned isotropic magnet powder or anisotropic magnet powder and a binder, and a forming step of forming the mixed powder obtained by this mixing step. In addition to the organic binder as described above, the binder includes a metal binder and the like. However, organic binders such as resin binders are common. The resin used for the resin binder may be a thermosetting resin or a thermoplastic resin. When such a resin binder is used, the mixing step may be a kneading step of kneading the magnet powder and the resin binder. The molding process includes compression molding, injection molding, extrusion molding and the like. When anisotropic magnetic powder is used as the magnet powder, the anisotropic magnetic powder is molded in a magnetic field. Further, when a thermosetting resin is used as the resin binder, a heating (curing) process is performed during or after the molding process.

(3) Addition of La-based material As described above, since La has the highest oxidation potential among rare earth elements, La-containing magnetic powders and hard magnets have extremely excellent corrosion resistance with their oxidation suppressed. And so on. As the addition form of La, for example, the following three forms can be considered.

(A) When a La-based material is added from the melting stage and a magnet powder or the like is manufactured using an RFeB-based magnet alloy (ingot) containing La,
(B) When a La material is mixed with RFeB magnet powder obtained by HDDR treatment or d-HDDR treatment, and La is diffused or coated on the magnet powder,
(C) A case where a La-based material is mixed with an RFeB-based hydride (RFeBHx) obtained during the production of a magnet powder, and La is diffused or coated on the hydride.

  In any case, as long as La exists separately from R, the corrosion resistance and the like of the magnet powder and the hard magnet can be improved. Therefore, in the present invention, the addition form of La is not particularly problematic.

  However, from the viewpoint of suppressing the oxidation of the magnet powder and the like more effectively by giving the function of oxygen getter to La, it is preferable that La is present on the surface of the constituent particles of the magnet powder or the vicinity thereof. Therefore, it is more advantageous to mix La-based material after the magnet powder is produced or in the middle of production and to diffuse La on the surface or inside of the magnet powder, rather than including La from the beginning in the magnet alloy.

  Therefore, for example, in the case of the above-described method for producing an isotropic magnet powder, the magnet powder obtained after the dehydrogenation step is mixed with a La-based material composed of at least one of La, La alloy, and La compound. When the La mixture is heated to 673 to 1123K and a diffusion heat treatment process for diffusing La into the surface and the inside of the magnet powder is performed, when the total isotropic magnet powder is 100 at%, La is set to 0. It is preferable to contain 001-1.0at%.

It is also conceivable that a La-based material is mixed with RFeBHx powder or the like, which is in the process of manufacturing magnet powder, and La is diffused on the surface and inside thereof. This RFeBHx powder and the like are in a state in which R and Fe are very difficult to oxidize compared to RFeB-based powder and the like. For this reason, it is more preferable in that La is diffused or coated in a state where oxidation is suppressed, and magnet powder excellent in corrosion resistance and the like can be obtained with stable quality. By the way, this hydride (RFeBHx) is obtained by removing hydrogen from the RH ₂ phase that has undergone the three-phase decomposition in the hydrogenation process and recombining the polycrystals to which the crystal orientation of the Fe ₂ B phase is transferred. Obtained after the first evacuation step of the treatment.

  Therefore, the method for producing anisotropic magnet powder of the present invention further comprises Lae simple substance, La alloy, La compound or one or more of those hydrides to the RFeB hydride obtained after the first exhaust step. A diffusion heat treatment step is performed in which a La mixture obtained by mixing La-based materials is heated to 673 to 1123 K to diffuse La into the surface and inside of the RFeB hydride, and the second exhaust step includes the diffusion heat treatment step. This is a process for removing hydrogen from the La-treated product later, or after the diffusion heat treatment process and the second exhaust process at the same time, or after the second exhaust process. It is preferable that the anisotropic magnet powder obtained by such a method contains 0.001 to 1.0 at% La when the whole is 100 at%.

  Here, the diffusion heat treatment step is a step of diffusing (or coating) La on the surface and inside of the RFeB magnet powder or RFeB hydride. This diffusion heat treatment step may be performed after mixing the La-based material or simultaneously with the mixing. If this processing temperature is less than 673 K, the La-based material is unlikely to be in a liquid phase, and diffusion processing is difficult. On the other hand, if it exceeds 1123K, crystal growth of RFeB-based magnet powder or the like occurs, leading to a decrease in iHc, and improvement in corrosion resistance and the like (reduction in permanent demagnetization factor) cannot be sufficiently achieved. The treatment time is preferably 0.5 to 5 hours. If it is less than 0.5 hour, the diffusion of La becomes insufficient, and the corrosion resistance of the magnet powder does not improve so much. On the other hand, when it exceeds 5 hours, iHc falls. Needless to say, this diffusion heat treatment step is preferably performed in an oxidation-preventing atmosphere (for example, a vacuum atmosphere). The La-based material is as described above, but the form is not limited. However, from the viewpoint of efficiently and reliably performing the production process of the magnet powder, it is preferable that they are in powder form. The La alloy or La compound is preferably an alloy or compound (including an intermetallic compound) of La and a transition metal element (TM). For example, LaCo, LaNdCo, LaDyCo, etc. Co is particularly suitable for increasing the Curie point of the magnet powder.

The present invention will be described more specifically with reference to the following examples.
(Example 1, Example 2)
(1) Manufacture of alloy, magnetic powder and bonded magnet As an example of a magnet alloy according to the present invention, an ingot (magnet alloy) having the composition listed in Samples 1 to 10 in Table 1 or Table 2 is melted and cast. Manufactured. Moreover, as a comparative example, it manufactured by melt | dissolving and casting the ingot of the composition quoted to the samples C1-C6 in each table | surface. The manufactured ingots are about 30 kg each.

  The alloy compositions of the samples shown in Table 1 and Table 2 are the same. However, Table 1 and Table 2 differ in the treatment applied to each sample (ingot). That is, Table 1 shows a case where each sample was subjected to HDDR treatment, and the magnetic powder shown in Table 1 is an isotropic magnet powder obtained through the treatment. Moreover, the bonded magnet shown in Table 1 is manufactured from the isotropic magnet powder. These are hereinafter referred to as Example 1.

  Table 2 shows a case where each sample was subjected to d-HDDR treatment. The magnetic powder shown in Table 2 is an anisotropic magnet powder obtained through the treatment. The bonded magnets shown in Table 2 are manufactured from the anisotropic magnet powder. These are hereinafter referred to as Example 2.

Next, specific manufacturing conditions for the magnetic powder and bonded magnet shown in Tables 1 and 2 will be described.
(A) The magnetic powder shown in Table 1 is sample No. The ingots having the alloy compositions of 1 to 10 and C1 to C6 were produced by subjecting them to HDDR treatment comprising a hydrogenation step and a dehydrogenation step without being subjected to a homogenization heat treatment. That is, a heat treatment was performed for 360 minutes in a hydrogen gas atmosphere having a temperature and a hydrogen pressure shown in Table 1 (hydrogenation step). This was followed by evacuation with a rotary pump and a diffusion pump for 60 minutes and cooling in a vacuum atmosphere of 10 ⁻¹ Pa or less (dehydrogenation step). Thus, about 10 kg of magnetic powder was produced per batch.

(B) The magnetic powder shown in Table 2 is also sample No. D-HDDR consisting of a low temperature hydrogenation step, a high temperature hydrogenation step, a first exhaust step and a second exhaust step without subjecting the ingots having the alloy compositions of 1 to 10 and C1 to C6 to homogenization heat treatment. Produced by treatment. That is, hydrogen was sufficiently absorbed in each sample alloy in a hydrogen gas atmosphere at room temperature and a hydrogen pressure of 100 kPa (low temperature hydrogenation step). Next, heat treatment was performed for 480 minutes in a hydrogen gas atmosphere at the temperature and hydrogen pressure shown in Table 2 (high-temperature hydrogenation step). Subsequently, a heat treatment for 160 minutes was performed at the same temperature shown in Table 2 in a hydrogen gas atmosphere at a hydrogen pressure of 0.1 to 20 kPa (first exhaust process). Finally, it was evacuated with a rotary pump and a diffusion pump for 60 minutes and cooled in a vacuum atmosphere of 10 ⁻¹ Pa or less (second exhaust process). Thus, about 10 kg of magnetic powder was produced per batch.

(C) Next, using the various isotropic magnetic powders shown in Table 1 and the various anisotropic magnetic powders shown in Table 2 thus obtained, the following bonded magnets were produced.

  First, an epoxy resin (3 wt%) previously dissolved in butanone was mixed with each magnetic powder. Then, butanone was volatilized while evacuating to produce a bonded magnet pellet. As a reference sample, a similar pellet was prepared using a flake-shaped MQP-B (manufactured by Magnequench International) produced by a melt spinning method as a raw material. And this pellet was press-molded into a 7 mm cubic shape while being oriented in a 2.5 T magnetic field to obtain a bonded magnet.

(2) Magnetic measurement of magnetic powder and bonded magnet (a) Magnetic measurement of each obtained magnetic powder was performed. Since iHc of magnetic powder cannot be used with a normal BH tracer, iHc was measured as follows.

  First, the magnetic powder was classified to a particle size of 75 to 106 μm. Using the classified magnetic powder, it was molded so that the demagnetizing factor was 0.2, and after orientation in a magnetic field, it was magnetized with 4.57 MAm-1, and VSM (BH-525H, manufactured by Riken Electronics Sales Co., Ltd.) (BH) max and iHc were measured at The results are also shown in Table 1 and Table 2.

(B) Moreover, (BH) max and iHc of the obtained various bonded magnets were measured with a BH tracer (BHU-25, manufactured by Riken Electronics Sales Co., Ltd.). The results are also shown in Table 1 and Table 2.
Note that “-” in Tables 1 and 2 indicates that the measurement was not performed because the magnetic characteristics were low.

(3) Evaluation (a) When Table 1 and Table 2 are overviewed, Sample No. As in C1, C2, C4, and C5, when the amount of B is lower than 10.8 at%, (BH) max and iHc rapidly decrease. Sample No. As in C3 and C6, even when B was higher than 15 at%, (BH) max also decreased.

  In addition, when B amount is lower than 10.8 at%, it is considered that iHc is decreased because α-Fe is precipitated. In addition, when B is higher than 15 at%, the reason why (BH) max decreases is considered to be that the B-rich phase has increased.

  Therefore, in order to balance (BH) max and iHc in a high dimension, it can be said that the B content is preferably 10.8 to 15 at%, as in the present invention. Next, the isotropic magnetic powder and its bonded magnet in Table 1 and the anisotropic magnetic powder and its bonded magnet in Table 2 will be specifically examined.

(B) Isotropic Magnetic Powder and Bonded Magnets The ternary isotropic magnetic powder obtained by subjecting the alloy ingots different only in the composition of B to the HDDR treatment under the same conditions, are shown in Examples (Sample No. 1) shown in Table 1. 1 and 2) and the comparative example (sample Nos. C1 to C3) are understood as follows.

Even if the amount of B is small or large as in the comparative example, specifically, if the amount of B is outside the range of 10.8 to 15 at%, the maximum energy product (BH) max of the magnetic powder decreases. On the other hand, in the example in which the B amount is within the range, a large (BH) max of 70 kJm ⁻³ or more is obtained. Thus, the peak value of (BH) max exists in the range of B: 10.8-15at%.

  The coercive force iHc of the magnetic powder tends to increase as the B amount increases. However, in the range where the B amount is 10.8 at% or more, the increasing tendency of iHc becomes very gradual, and sufficient iHc is obtained when the B amount is 10.8 to 15 at%.

Next, with respect to hexotropic isotropic magnetic powders obtained by subjecting alloy ingots having different compositions of B to HDDR treatment under the same conditions, examples (sample No. 5) and comparative examples (sample No. 5) shown in Table 1 were used. Even if C4 to C6) are compared, the same can be said. That is, the peak value of (BH) max is in the range of B: 10.8 to 15 at%, and iHc obtained at that time is also close to the peak value.
The same can be said for bonded magnets manufactured using these isotropic magnetic powders regardless of whether they are ternary or ternary.

  Furthermore, from Table 1, although the bond magnet according to the present embodiment of the 6-component system or more has the same (BH) max as the bond magnet made of MQP-B, iHc is improved by about 50%. I also understood.

(C) Anisotropic Magnetic Powder and Bonded Magnet Thereof Examples (samples) shown in Table 2 for ternary anisotropic magnetic powder obtained by subjecting alloy ingots having different compositions of B to d-HDDR treatment under the same conditions. No. 1 and 2) and the comparative example (sample Nos. C1 to C3) are understood as follows.

Even if the amount of B is small or large as in the comparative example, specifically, if the amount of B is outside the range of 10.8 to 15 at%, the maximum energy product (BH) max of the magnetic powder decreases. On the other hand, in the example in which the B amount is within the range, a large (BH) max of 210 kJm ⁻³ or more is obtained. Thus, the peak value of (BH) max exists in the range of B: 10.8-15at%.

  The coercive force iHc of the magnetic powder tends to increase as the B amount increases. However, in the range where the B amount is 10.8 at% or more, the increasing tendency of iHc becomes very gradual, and sufficient iHc is obtained when the B amount is 10.8 to 15 at%.

  Next, with respect to the 6-component anisotropic magnetic powder obtained by subjecting an alloy ingot having a different composition of B to d-HDDR treatment under the same conditions, Examples (Sample No. 5) shown in Table 2 and Comparative Examples (Samples) No. C4 to C6), the same as above can be said. That is, the peak value of (BH) max is in the range of B: 10.8 to 15 at%, and iHc obtained at that time is also close to the peak value.

  The same applies to bonded magnets manufactured using these anisotropic magnetic powders, regardless of whether they are ternary or ternary.

(Example 3)
Sample No. shown in Table 1 The relationship between the intrinsic coercivity iHc of the isotropic magnetic powder obtained by subjecting the ingots 2 and 6 to the HDDR treatment and the time of the hydrogenation step of the HDDR treatment (180 to 1800 minutes) was investigated. Except for the time of the hydrogenation step, the production conditions of each magnetic powder are the same as those of the HDDR process described in the first embodiment. The method for measuring the magnetic characteristics is the same as in the first and second embodiments. The results thus obtained are shown in Table 3.

  From Table 3, it was found that iHc increased with increasing time of the hydrogenation process, and the increase in iHc tended to be almost saturated when it exceeded 360 minutes.

(Example 4)
Sample No. shown in Table 2 Investigate the relationship between the intrinsic coercivity iHc of anisotropic magnetic powder obtained by subjecting the ingots 2 and 6 to d-HDDR treatment and the time (180 to 1800 minutes) of the d-HDDR treatment high-temperature hydrogenation process did.

Except for the time of the high-temperature hydrogenation process, the production conditions of each magnetic powder are the same as those in the d-HDDR process described in Example 2. The method for measuring the magnetic characteristics is the same as in the first and second embodiments. The results thus obtained are shown in Table 4.
From Table 4, it was found that, as in the case of Example 3, when the processing time of the high-temperature hydrogenation process exceeds 360 minutes, the coercive force obtained tends to be almost saturated.

(Example 5)
Sample No. shown in Table 1 5 to 8 isotropic magnet powder, sample No. shown in Table 2. The fluidity and bulk density of each were examined using bonded magnet pellets comprising the anisotropic magnet powders 1 to 4 and the reference sample (MQP-B). The measurement results are shown in FIG. 1 and FIG.

The fluidity and bulk density of the pellets were measured according to JIS Z8041 (JIS standard).
As can be seen from FIGS. 1 and 2, in this example, the fluidity is improved by about 20% and the bulk density is improved by about 10% compared to the reference sample. This is presumably because the particle shape of each magnetic powder of this example is close to a sphere.

(Example 6)
Sample No. in Table 2 The cost performance of anisotropic magnetic powder obtained by performing d-HDDR treatment on the alloy ingot No. 6 was examined.

First, sample no. 6 ingots (about 30 kg) were produced by melting and casting. This ingot was not subjected to a homogenization heat treatment, and the sample alloy was sufficiently absorbed with hydrogen in a hydrogen gas atmosphere at room temperature and a hydrogen pressure of 100 kPa (low temperature hydrogenation step). Next, heat treatment was performed for 480 minutes in a hydrogen gas atmosphere at a temperature of 1073 K and a hydrogen pressure of 45 kPa (high-temperature hydrogenation step). Subsequently, heat treatment was performed for 160 minutes in a hydrogen gas atmosphere at a temperature of 1073 K and a hydrogen pressure of 0.1 to 10 kPa (first exhaust process). Finally, it was evacuated with a rotary pump and a diffusion pump for 60 minutes and cooled in a vacuum atmosphere of 10 ⁻¹ Pa or less (second exhaust process). Thus, about 10 kg of magnetic powder was produced per batch.

  Using this magnetic powder, a bonded magnet was produced in the same manner as in Examples 1 and 2, and its (BH) max was measured. The value obtained by dividing the measured (BH) max by the raw material cost (raw material cost, melting / casting cost) used for the d-HDDR treatment is shown in FIG.

  As a comparative sample, an alloy ingot (about 30 kg) of sample C1 in Table 2 was manufactured by melting and casting. The ingot was kept in an Ar gas atmosphere at a temperature of 1413 K for 40 hours to perform a homogenization heat treatment. Thereafter, the same d-HDDR treatment as that of Sample 6 was performed. Thus, about 10 kg of magnetic powder was produced per batch.

For this magnetic powder, a bonded magnet was prepared in the same manner as in Sample 6 above, and its (BH) max was measured. The value obtained by dividing the measured (BH) max by the raw material cost (raw material cost, melting / casting cost and homogenization heat treatment cost) used for the d-HDDR treatment is also shown in FIG. 3 as cost performance.
From FIG. 3, the cost performance of the sample 4 that was not subjected to the homogenization heat treatment was improved by about 30% compared to the sample C1 that was subjected to the homogenization heat treatment.

(Example 7)
(1) Sample No. in Table 1 1, no. The alloy ingot No. 6 was subjected to the same HDDR treatment as in Example 1 to produce an isotropic magnetic powder. In this isotropic magnetic powder, La80Co20 alloy powder (La-based material) is mixed (mixing step) and heated (diffusion heat treatment step). 11-15 and sample no. 16 and 17 magnetic powders were obtained. The composition of each sample shown in Table 5 and Table 6 is a value analyzed by an ICP (high frequency plasma emission analyzer) after the diffusion heat treatment step. Table 5 also shows the diffusion heat treatment conditions for each sample. The diffusion heat treatment conditions in Table 6 are all 1073 K × 1 hr. The mixing step and the diffusion heat treatment step were all performed in a vacuum atmosphere of 10 ⁻² Pa or less. In Table 6, as an example, Sample No. The magnetic properties of the 16 and 17 isotropic magnet powders and the bond magnets using them are also shown. The measuring method and the like are as described above.

  Here, the La80Co20 alloy is an alloy of La: 80 at% and Co: 20 at%, and is melted in the same manner as in the case of the magnet alloy (ingot) of Example 1. The powder was obtained by pulverizing the ingot by a hydrogen pulverization method and pulverizing with a vibration mill, and the average particle size was 10 μm.

  Using the isotropic magnetic powder after the diffusion heat treatment step, a 7 mm square isotropic bonded magnet was produced in the same manner as in Example 1. Using this bond magnet, the permanent demagnetization rate was measured.

  Permanent demagnetization factor is the ratio of the decrease relative to the initial magnetic flux from the difference between the initial magnetic flux of the bond magnet and the magnetic flux obtained by re-magnetization after holding in an air atmosphere at 100 ° C or 80 ° C for 1000 hours. It is what I have sought. Magnetization at this time was performed in 1.1 MA / m (45 kOe). A flux meter was used to measure the magnetic flux. The permanent demagnetization factor thus obtained is also shown in Tables 5 and 6.

(2) Sample No. listed in Table 5 as a comparative example. Bond magnets according to C7 to C9 were prepared. Sample No. The bonded magnet of C7 has a La amount exceeding 1.0 at%. The C8 bonded magnet was not mixed with a La-based material. The C9 bonded magnet has a low heating temperature of less than 400 ° C. during the diffusion heat treatment process. The diffusion heat treatment conditions and the permanent demagnetization factor in each case are also shown in Table 5.

(3) From Tables 5 and 6, it can be seen that the isotropic bonded magnet according to the present invention has a small permanent demagnetization factor, excellent heat resistance and high practicality. A small permanent demagnetization factor also means excellent corrosion resistance and small deterioration over time.

  In particular, even in the case of 100 ° C. × 1000 hours, the permanent demagnetization rate is as small as less than 10%. In the case of 80 ° C. × 1000 hours, the permanent demagnetization factor is as low as about 5%.

  On the other hand, in the comparative example, the permanent demagnetization rate is as high as about 10% at 80 ° C. × 1000 hours, and the permanent demagnetization rate is as high as about 15% at 100 ° C. × 1000 hours. . Incidentally, as a reference sample, the permanent demagnetization factor of an isotropic powder (MQP-B) produced by a rapid solidification method is also shown in Table 5.

  In addition, the magnetic properties of the magnetic powder and the bonded magnet were the same as the results shown in Table 1 of the example, or the magnetic properties were reduced by about 7 to 8% at the maximum, and there were no practical problems.

(Example 8)
(1) Sample No. in Table 2 1, no. The alloy ingot of No. 6 was subjected to the same low temperature hydrogenation step, high temperature hydrogenation step and first exhaust step as in Example 2 to obtain NdFeBH _X powder (RFeB hydride). This NdFeBH _X powder was mixed with La80Co20 alloy powder as in Example 7 (mixing step), and heated (diffusion heat treatment step). This was followed by a second exhaust process similar to that in Example 2.

Thus, the sample numbers shown in Tables 7 and 8 were used. 11-15 and sample no. 16 and 17 magnetic powders were obtained. The composition of each sample shown in Table 7 and Table 8 is a value analyzed by ICP after the second exhaust process as in Example 7. Table 7 also shows the diffusion heat treatment conditions for each sample. The diffusion heat treatment conditions in Table 8 are all 1073 K × 1 hr. The mixing step and the diffusion heat treatment step were all performed in a vacuum atmosphere of 10 ⁻² Pa or less. In Table 8, as an example, Sample No. The magnetic properties of the 16 and 17 anisotropic magnet powders and the bond magnet using the same were also shown. The measuring method and the like are as described above. And the permanent demagnetization factor calculated | required similarly to Example 7 was combined with Table 7 and Table 8, and was shown.

(2) The bonded magnet prepared as a comparative example is the same as in the case of Example 7. Table 7 shows the diffusion heat treatment conditions and the permanent demagnetization factor in each case.

(3) From Table 7 and Table 8, the anisotropic bonded magnet according to the present invention has a small permanent demagnetization factor and high practicality. In particular, even in the case of 100 ° C. × 1000 hours, the permanent demagnetization rate is as small as less than 10%. In the case of 80 ° C. × 1000 hours, the permanent demagnetization factor is a small value of 5 to 7%. On the other hand, in the comparative example, the permanent demagnetization rate is as high as 10% or more even at 80 ° C. × 1000 hours, and the permanent demagnetization rate is as high as 15% or more at 100 ° C. × 1000 hours. .

  In addition, the magnetic properties of the magnet powder and the bonded magnet were the same as the results shown in Table 2 of the example or the magnetic properties were reduced by about 7 to 8% at the maximum, and there was no problem in practical use.

It is the bar graph which contrasted the flow rate of the pellet for bond magnets manufactured from the magnet powder. It is the bar graph which contrasted the bulk density of the pellet for bond magnets manufactured from magnet powder. It is the bar graph which contrasted the cost performance of the magnet powder manufactured by d-HDDR processing.

Claims (17)

Iron (Fe) as the main component;
A rare earth element (hereinafter referred to as “R”) containing 12 to 16 atomic% (at%) of yttrium (Y);
A bonded magnet alloy containing at least 10.8 to 15 at% boron (B). The bonded magnet alloy according to claim 1, wherein R is one or more of Pr, Nd, and Dy. Furthermore, the alloy for bonded magnets of Claim 1 or 2 containing 0.1 to 6 at% of cobalt (Co). Furthermore, it contains 0.1 to 2 at% in total of at least one of gallium (Ga), zirconium (Zr), vanadium (V), aluminum (Al), titanium (Ti), hafnium (Hf) and copper (Cu). With
The alloy for bonded magnets according to any one of claims 1 to 3, comprising 0.1 to 2 at% in total of at least one of niobium (Nb), tantalum (Ta), and nickel (Ni). Furthermore, the alloy for bonded magnets in any one of the Claims 1-4 containing 0.001-1.0at% lanthanum (La). A hydrogenation step in which an ingot of an alloy containing at least Fe containing R as a main component, R containing 12 to 16 at% Y, and 10.8 to 15 at% B is held in a hydrogen gas atmosphere of 1023 to 1173 K;
An isotropic magnet powder obtained by HDDR treatment comprising a dehydrogenation step for removing hydrogen after the hydrogenation step. The isotropic magnet powder according to claim 6, further comprising 0.001 to 1.0 at% La. A low-temperature hydrogenation step of maintaining an ingot of an alloy containing at least Fe containing R as a main component and R containing 12 to 16 at% Y and 10.8 to 15 at% B in a hydrogen gas atmosphere of 873 K or less;
A high temperature hydrogenation step of holding in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low temperature hydrogenation step;
A first evacuation step of holding in a hydrogen gas atmosphere of 1023-1173 K at 0.1-20 kPa after the high-temperature hydrogenation step;
An anisotropic magnet powder obtained by d-HDDR treatment comprising a second exhaust step for removing hydrogen after the first exhaust step. The anisotropic magnet powder according to claim 8, further comprising 0.001 to 1.0 at% La. A hydrogenation step for holding an ingot of an alloy containing at least Fe containing R, which contains 12 to 16 at% Y, and 10.8 to 15 at% B in a hydrogen gas atmosphere of 1023 to 1173 K, and the hydrogen A bonded magnet obtained by mixing an isotropic magnet powder obtained by HDDR treatment including a dehydrogenation step for removing hydrogen after the forming step and a binder, followed by pressure molding. The bonded magnet according to claim 10, wherein the isotropic magnet powder further contains 0.001 to 1.0 at% La. A low-temperature hydrogenation step in which an ingot of an alloy containing at least Fe containing R as a main component and R containing 12 to 16 at% Y and 10.8 to 15 at% B is maintained in a hydrogen gas atmosphere of 873 K or less, A high-temperature hydrogenation step of holding in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low-temperature hydrogenation step, and a first step of holding in a hydrogen gas atmosphere of 1023 to 1173 K at 0.1 to 20 kPa after the high-temperature hydrogenation step. An anisotropic magnet powder obtained by d-HDDR treatment comprising a first exhausting step and a second exhausting step for removing hydrogen after the first exhausting step, and a binder are mixed and pressure-molded. Bond magnet characterized by. The bonded magnet according to claim 12, wherein the anisotropic magnet powder further contains 0.001 to 1.0 at% La. A hydrogenation step in which an ingot of an alloy containing at least Fe containing R as a main component, R containing 12 to 16 at% Y, and 10.8 to 15 at% B is held in a hydrogen gas atmosphere of 1023 to 1173 K;
A method for producing an isotropic magnet powder comprising performing an HDDR treatment comprising a dehydrogenation step of removing hydrogen after the hydrogenation step. Furthermore, the magnetic powder obtained after the dehydrogenation step is heated to 673 to 1123K with a La mixture obtained by mixing a La-based material composed of at least one of La, La alloy, and La compound. A diffusion heat treatment step of diffusing La on the surface and inside,
The method for producing an isotropic magnet powder according to claim 14, wherein the obtained isotropic magnet powder contains 0.001 to 1.0 at% La when the whole is 100 at%. A low-temperature hydrogenation step of maintaining an ingot of an alloy containing at least Fe containing R as a main component and R containing 12 to 16 at% Y and 10.8 to 15 at% B in a hydrogen gas atmosphere of 873 K or less;
A high temperature hydrogenation step of holding in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa after the low temperature hydrogenation step;
A first evacuation step of holding in a hydrogen gas atmosphere of 1023-1173 K at 0.1-20 kPa after the high-temperature hydrogenation step;
A d-HDDR treatment comprising a second evacuation step for removing hydrogen after the first evacuation step is performed. Further, the RFeB powder obtained after the first evacuation step or after the second evacuation step is a kind of La simple substance, La alloy, La compound or hydride thereof (La simple substance, alloy or hydride of compound). A diffusion heat treatment step of heating the La mixture formed by mixing the La-based material composed of the above to 673 to 1123K and diffusing at least La on the surface and inside of the RFeB-based powder;
The method for producing anisotropic magnet powder according to claim 16, wherein the obtained anisotropic magnet powder contains 0.001 to 1.0 at% La when the whole is 100 at%.

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