JP3565513B2 - Alloy for bonded magnet, isotropic magnet powder and anisotropic magnet powder, their production method, and bonded magnet - Google Patents

Description

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【図面の簡単な説明】
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【図１】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】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】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】
[0001]
The present invention provides 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 method for producing the same, and furthermore, The present invention relates to a bonded magnet obtained from magnet powder.
[Background Art]
[0002]
Hard magnets (permanent magnets) are used in various devices such as motors. Above all, there is a strong demand for small size and high output vehicle motors. Such a hard magnet is required not only to have high performance in terms of magnetic properties but also to be low in cost in order to enhance global competitiveness.
[0003]
First, from the viewpoint of high performance, RFeB-based magnets (rare earth magnets) composed of a rare earth element (R), boron (B), and iron (Fe) have been actively developed. As such RFeB-based magnets, for example, U.S. Pat. No. 4,851,058 (hereinafter, referred to as "Patent Document 1") and U.S. Pat. No. 5,411,608 (hereinafter, referred to as "Patent Document 2") have magnetic isotropy. An RFeB-based magnet alloy (composition) having the same is disclosed.
[0004]
Specifically, Patent Document 1 discloses a magnetic alloy comprising about 10 to 40 at% of Nd, Pr or Nd and Pr, about 50 to 90 at% of Fe, and about 0.5 to 10 at% of B. Is disclosed. Patent Document 2 discloses a magnet alloy including 12 to 40 at% of Nd, Pr or Nd and Pr, 10 at% or less of Co, 3 to 8 at% of B, and the balance of Fe. In addition, Patent Literature 2 aims to improve heat resistance due to an increase in Curie temperature by adding Co. In both of these patent documents, a magnet powder having the above composition is obtained by a melt spun method which is a kind of rapid solidification method.
[0005]
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 preparing a pellet from the magnetic powder and a resin serving as a binder, supplying the pellet to a molding die, and performing pressure molding. Generally, when the pellets are fed into a mold, if the fluidity is small, the powder feeding time is also shortened, and the productivity of the bonded magnet can be improved. In addition, when the bulk density of the pellets is large, the powder can be uniformly supplied to the mold, and the defective rate of the bonded magnet can be reduced. Therefore, the lower the fluidity and the higher the bulk density, the lower the cost of the bonded magnet and the better the economic efficiency. The fluidity and bulk density depend on the particle shape of the magnetic powder, and the more spherical the powder, the more favorable the fluidity and bulk density.
[0006]
However, the particle shape of the magnetic powder produced according to Patent Documents 1 and 2 is a flake shape having a thickness of 20 to 50 μm, and therefore has a higher fluidity and a lower bulk density than a spherical case. Of course, it is also conceivable to pulverize the flakes into spheres to reduce the fluidity and increase 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, in the case where the size of the original particles is 50 μm at the maximum, powder having a size of 50 μm or less generally tends to cause adhesion and aggregation.
[0007]
The same applies to SmFeN-based magnetic powder having a different composition. Even if the particle shape of the magnetic powder is close to spherical, if the average particle size is made as fine as 1 to 5 μm, adhesion and agglomeration easily occur, and the fluidity and bulk density deteriorate.
[0008]
Therefore, as a method for producing magnetic powder instead of the above-mentioned melt-span method, there is a method using a HDDR (hydrogenation-diproporation-desorption-recombination) processing method or a d-HDDR processing method. Since the magnetic powder obtained by these methods is composed of substantially spherical particles, the magnetic powder has better fluidity and bulk density than the magnetic powder obtained according to Patent Documents 1 and 2.
[0009]
The HDDR processing method is used for producing an RFeB-based isotropic magnet powder (isotropic magnetic powder) and an RFeB-based anisotropic magnet powder (anisotropic magnetic powder), and mainly includes two steps. That is, the first step (hydrogenation step) of maintaining the temperature at 773 to 1273K in a hydrogen gas atmosphere of about 100 kPa (1 atm) to cause a three-phase decomposition disproportionation reaction, and then performing a dehydrogenation in a vacuum. Step (second step).
[0010]
On the other hand, d-HDDR processing is a method mainly used for producing RFeB-based anisotropic magnetic powder. As described in detail in a well-known document (Mishima et al .: Journal of the Japan Society of Applied Magnetics, 24 (2000), p. 407), controlling the reaction rate between an RFeB alloy and hydrogen from room temperature to high temperature. Made by Specifically, a low-temperature hydrogenation step (first step) in which the RFeB-based alloy sufficiently absorbs hydrogen at room temperature, and a high-temperature hydrogenation step (second step) in which a three-phase decomposition disproportionation reaction occurs under a low hydrogen pressure. Process), an evacuation process for dissociating hydrogen under the highest possible hydrogen pressure (third process), and a subsequent dehydrogenation process for removing hydrogen from the material (fourth process). The difference from the HDDR process is that by providing a plurality of steps with different temperatures and hydrogen pressures, the reaction rate between the RFeB-based alloy and hydrogen is kept relatively slow, and a homogeneous anisotropic magnetic powder is obtained. That is the point.
[0011]
The following patent documents can be cited as methods for producing 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. 7-68161 (Patent No. 2041426; hereinafter, referred to as “Patent Document 3”). According to Patent Document 3, a magnetic powder is manufactured by subjecting an alloy ingot containing R, Fe, and B as main components to a pulverizing step and a homogenizing heat treatment step, and then performing the HDDR processing. Here, in this case, two steps (a pulverizing step and a homogenizing heat treatment step) before the HDDR processing are indispensable for obtaining isotropic magnetic powder having large magnetic properties. As described in Patent Document 3, when these two steps are omitted and a magnetic powder is produced by directly performing an HDDR treatment on a casting of an RFeB-based alloy, the coercive force (hereinafter, referred to as a bond magnet) produced using the obtained magnetic powder. , IHc) is at most 0.76 MAm ^-1 This is because it shows a very low value.
[0012]
However, both of these two steps are expensive and economical. In particular, the homogenizing heat treatment step of performing a high-temperature treatment at 873 to 1473 K requires about twice the cost of the HDDR treatment, and is extremely inefficient.
[0013]
Next, a method for producing an 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”). ), Japanese Patent No. 2586198 (hereinafter referred to as “Patent Document 6”) and Japanese Patent No. 2586199 (hereinafter referred to as “Patent Document 7”).
[0014]
According to the examples described in these patent documents, an alloy ingot comprising about 10 to 20 at% of R, about 5 to 20% of B, the balance Fe and various additional elements is subjected to a homogenizing heat treatment step and a pulverizing step. And then subject to HDDR processing to produce magnetic powder. However, although the B content of the alloys disclosed in the examples is disclosed in detail at 10.4 at% or less, alloys having a B content exceeding 10.4 at% are alloys of 10.4 at% and 20 at%. Only. The (BH) max of the anisotropic bonded magnet manufactured from magnetic powder having a B content of 10.4 at% is 83 to 112 kJ / m. ^Three , IHc is 0.74 to 0.97 MA / m, and the (BH) max of an anisotropic bonded magnet manufactured from magnetic powder having a B content of 20 at% is 80 to 93 kJ / m. ^Three , IHc is 0.46 to 0.75 MA / m. All of these magnetic properties are inadequate. In particular, as the B content increases to 20 at%, the decrease in iHc becomes significant.
[0015]
In addition, in the case of the above-mentioned patent document, since the homogenizing heat treatment is performed at a high temperature of 1393K to 1413K, the production cost of the magnetic powder becomes higher and the economic efficiency is further reduced. Of course, also in this case, if the homogenizing heat treatment is omitted, the cost can be reduced, but the degradation of iHc is inevitable as in the case of Patent Document 3.
[0016]
Incidentally, it is actually difficult to industrially mass-produce anisotropic magnetic powders using the methods as described in Patent Documents 4 to 7. This is because temperature control during HDDR processing must be strictly performed in order to obtain magnetic powder having excellent anisotropy. Specifically, unless the HDDR treatment is performed in a temperature range of about ± 20 K with respect to the target temperature, highly anisotropic magnetic powder cannot be obtained. Nevertheless, when the processing amount per batch of the HDDR processing is increased, the amount of heat generated during the disproportionation reaction between hydrogen and the RFeB-based alloy and the amount of heat absorbed during dehydrogenation increase sharply, and the ambient temperature becomes higher. It is because it becomes outside the enclosure. As a result, the magnetic powder mass-produced by the methods described in Patent Documents 4 to 7 has magnetic characteristics, particularly small anisotropy.
[0017]
Therefore, when mass-producing the RFeB-based anisotropic magnetic powder, Japanese Patent Application Laid-Open No. 2001-148306 (hereinafter, referred to as “Patent Document 8”) and Japanese Patent Application Laid-Open No. 2001-76917 (hereinafter, “Patent Document 9”). It is recommended to use the d-HDDR processing as disclosed in US Pat. According to the d-HDDR processing, a magnetic powder having high anisotropy can be obtained even if the processing amount per batch is increased. As described above, in the case of the d-HDDR treatment, the reaction rate between the RFeB-based alloy and hydrogen can be gently controlled in each step, so that the amount of heat generated during the disproportionation reaction between the RFeB-based alloy and hydrogen and the dehydrogenation This is because the amount of heat absorbed can be suppressed.
[0018]
However, even in the case of Patent Documents 8 and 9, after a homogenizing heat treatment step is performed using an alloy ingot including R of about 12 to 15 at%, B of about 6 to 9 at%, and the balance Fe, The anisotropic magnetic powder is manufactured by performing d-HDDR processing. Therefore, similarly to the above-described manufacturing method, the manufacturing cost is the same.
[0019]
Until now, we have mainly described 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, a hard magnet incorporated in a home motor or an automobile motor used in a high-temperature environment is required to have excellent heat resistance and the like from the viewpoint of ensuring the reliability and the like of the motor.
[0020]
However, the above-mentioned rare earth magnets are liable to be deteriorated by oxidative corrosion of Fe and R, which are main components thereof, and it is difficult to stably secure high magnetic properties. In particular, when a rare-earth magnet is used at room temperature or higher, its magnetic properties tend to sharply decrease. Such a change over time of the magnet is usually quantitatively indexed by a permanent demagnetization rate (%). In the case of conventional rare-earth magnets, the permanent demagnetization rate of most magnets exceeds 10% in most cases. The permanent demagnetization rate is a reduction rate of the magnetic flux that does not recover even after re-magnetization after a long time (1000 hours) at a predetermined high temperature.
[Patent Document 1]
U.S. Pat.
[Patent Document 2]
U.S. Pat. No. 5,411,608
[Patent Document 3]
Japanese Patent Publication No. Hei 7-68561
[Patent Document 4]
Japanese Patent No. 2576671
[Patent Document 5]
Japanese Patent No. 2576672
[Patent Document 6]
Japanese Patent No. 2586198
[Patent Document 7]
Japanese Patent No. 2586199
[Patent Document 8]
JP 2001-148306 A
[Patent Document 9]
JP 2001-76917 A
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0021]
The present invention has been made in view of such circumstances. That is, an RFeB-based magnet powder which is obtained without performing a homogenizing heat treatment step which causes a high cost, has excellent magnetic properties at a low cost, and is subjected to HDDR processing or d-HDDR processing, and a method of manufacturing the same. An object of the present invention is to provide a bonded magnet made of magnet powder. It is another object of the present invention to provide an RFeB-based magnet alloy suitable for producing the magnet powder.
[0022]
In addition, the present invention also provides a bonded magnet which 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. Aim.
[Means for Solving the Problems]
[0023]
The inventor of the present invention has intensively studied to solve this problem, and as a result of various systematic experiments, have developed a novel magnet alloy or the like having a different B content from the conventional one, and have completed the following invention.
[0024]
(Alloy for bonded magnet)
First, the bonded magnet alloy of the present invention comprises iron (Fe) as a main component, 12 to 16 atomic% (at%) of a rare earth element (hereinafter, referred to as “R”), and 10.8 to 15. at% boron (B), so that the homogenizing heat treatment step can be omitted when producing the magnet powder.
[0025]
In addition to the above expressions, the present invention is a type of hydrogenation treatment that contains at least Fe as a main component, 12 to 16 at% of R, and 10.8 to 15 at% of B. A magnet alloy characterized by being subjected to HDDR processing or d-HDDR processing may be used.
[0026]
The alloy for bonded magnets of the present invention (hereinafter, simply referred to as “magnet alloy” as appropriate) has a different B content from the RFeB-based magnet alloy developed so far, and has a relatively large B content. The present inventor has found that in a magnet alloy containing a large amount of B, precipitation of α-Fe, which is a primary crystal, is suppressed. Then, as a result of suppressing the precipitation of α-Fe which causes a decrease in magnetic properties, it becomes possible to omit the homogenizing heat treatment step which was conventionally considered to be indispensable for improving the magnetic properties, and to reduce the magnet powder and the like at low cost. Can now be obtained.
[0027]
This reason can be considered as follows at present. By increasing B, R1Fe1B whose melting point is lower than RFeB by 10 to 30K in the early stage of casting. _Four A phase (hereinafter, referred to as “B-rich phase”) is formed. It is considered that the precipitation of α-Fe was suppressed because α-Fe as the primary crystal was taken into the B-rich phase.
[0028]
As a result of subjecting the magnet alloy (for example, its ingot or the like) to the above-described HDDR treatment or d-HDDR treatment, a magnet powder having a high iHc was obtained. This can be considered as follows. When hydrogen is absorbed by the magnetic alloy of the present invention, the above-described B-rich phase and R _Two Fe ₁₄ The phase B reacts sufficiently with hydrogen to form α-Fe, Fe _Two It becomes B and R hydride. Next, when dehydrogenation was performed, it is considered that the B-rich phase was finely and densely precipitated, which pinned the crystal grain growth of RFeB, and as a result, the recrystallized grains of RFeB became fine. In order to effectively obtain the pinning effect, for example, the hydrogen absorption time is preferably set to 360 minutes or more.
[0029]
From such a viewpoint, B is set to 10.8 at% or more. As a result, a homogenizing heat treatment step that significantly impairs economic efficiency can be omitted, and iHc can be increased. On the other hand, when B exceeds 15 at%, the volume fraction of the B-rich phase in the magnet powder becomes high, and the maximum energy product (BH) max is undesirably reduced.
[0030]
In Examples of Patent Documents 4, 5, 6, and 7, a magnet powder with a B content of 20 at% is disclosed, and its iHc is 0.46 to 0.75 MAm. ^-1 And low. This is probably 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.
[0031]
When R is less than 12 at%, primary crystals of α-Fe are easily precipitated, which causes a decrease in iHc. On the other hand, if R exceeds 16%, (BH) max decreases, which is not preferable.
[0032]
Such R includes scandium (Sc), yttrium (Y), and lanthanoid. However, as elements having excellent magnetic properties, R is Y, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium. (Dy), holmium (Ho), erbium (Er), thulium (Tm) and lutetium (Lu) are preferable. In particular, R is preferably composed of one or more of Pr, Nd, and Dy from the viewpoint of cost and magnetic characteristics.
[0033]
The magnetic alloy of the present invention preferably further contains 0.1 to 6 at%, more preferably 1 to 6 at%, of cobalt (Co) in addition to the above elements. Co is an element that increases the Curie temperature of the magnet and improves 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 at most 6 at% from the viewpoint of industrial cost.
[0034]
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”). ) May be contained in a total of 0.1 to 2 at%. This is because these elements are elements that improve the coercive force iHc of the magnet.
[0035]
Further, the magnetic alloy of the present invention contains at least one or more of niobium (Nb), tantalum (Ta) and nickel (Ni) (hereinafter, referred to as “second element group”) in a total amount of 0.1 to 2 at%. May be. This is because these elements increase the residual magnetic flux density (Br) of the magnet.
[0036]
When both the elements in the first element group and the elements in the second element group are included, the maximum energy product (BH) max can be improved. In any case, if the total is less than 0.1 at%, there is no substantial effect, and if it exceeds 2 at%, iHc, Br or (BH) max is undesirably reduced. In consideration of cost and magnetic properties, 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 preferably 0.1 to 0.4 at% (about 0.2 at%).
[0037]
Needless to say, the alloy, the powder, and the like according to the present invention may appropriately contain unavoidable impurities. Their composition is balanced by Fe, but to put it bluntly, Fe is 59-77.2 at%.
[0038]
Further, it is preferable that the magnet alloy of the present invention contains La in an amount of 0.001 to 1.0 at%, in addition to R. As a result, aging of the magnet powder and the hard magnet made of the magnet alloy can be suppressed.
[0039]
This is because La is the element having the highest oxidation potential among rare earth elements (RE). Therefore, La acts as a so-called oxygen getter, and La is selectively (preferably) oxidized over R (Nd, Dy, etc.), and as a result, oxidation of La-containing magnet powder or hard magnet is prevented. Be suppressed. Use of Dy, Tb, Nd, Pr, or the like may be considered instead of La, but these elements cannot sufficiently suppress the oxidation of the magnet powder and the hard magnet. Also, from the viewpoint of cost, the use of La is preferable to those elements. Note that R in the magnet alloy at this time is a rare earth element other than La.
[0040]
Here, La has an effect of improving corrosion resistance and the like to the extent that La is contained in a small amount exceeding the level of unavoidable impurities in the magnet alloy. Since the unavoidable impurity level of La is less than 0.001 at%, the La content is set to 0.001 at% or more in the present invention. On the other hand, if La exceeds 1.0 at%, iHc is undesirably reduced. Here, it is more preferable that the lower limit of the La content is 0.01 at%, 0.05 at%, and further 0.1 at%, since a sufficient improvement effect such as corrosion resistance is exhibited. And from a viewpoint of improvement of corrosion resistance etc. and suppression of iHc fall, it is more preferable that La content is 0.01-0.7at%.
[0041]
The alloy composition containing La is R _Two Fe ₁₄ B ₁ Instead of an alloy composition in which the phases can exist as a single phase or near single phase, R _Two Fe ₁₄ B ₁ It is an alloy composition comprising a phase and a multi-phase structure such as a B-rich phase.
[0042]
(Magnetic powder and its manufacturing method)
The magnetic alloy according to the present invention may be in an ingot or a powder regardless of its form. In the case of powder, the particle size, particle shape and the like are not limited. Therefore, for example, the magnet alloy of the present invention can be understood as isotropic magnet powder or anisotropic magnet powder.
[0043]
For example, the isotropic magnet powder of the present invention is made of an alloy that contains at least Fe, which is the main component, 12 to 16 at% of R, and 10.8 to 15 at% of B, and has not been subjected to the homogenizing heat treatment step. The ingot is obtained through a manufacturing method of performing a HDDR process including a hydrogenation step of maintaining the ingot in a hydrogen gas atmosphere of 1023 to 1173K and a dehydrogenation step of removing hydrogen after the hydrogenation step.
[0044]
Further, the anisotropic magnet powder of the present invention is made of an alloy containing at least Fe as a main component, 12 to 16 at% of R, and 10.8 to 15 at% of B and which has not been subjected to a homogenizing heat treatment step. A low-temperature hydrogenation step of holding the ingot in a hydrogen gas atmosphere of 873K or less, a high-temperature hydrogenation step of holding the ingot in a hydrogen gas atmosphere of 1023 to 1173K at 20 to 100 kPa after the low-temperature hydrogenation step, and the high-temperature hydrogenation step A manufacturing method of performing a d-HDDR process including a first exhaust step of maintaining a hydrogen gas atmosphere of 0.13 to 1173K at 0.1 to 20 kPa later and a second exhaust step of removing hydrogen after the first exhaust step is described. Obtained through
[0045]
(Bond magnet)
Furthermore, by using these magnet powders, a low-cost, high-performance bonded magnet can be obtained.
For example, when isotropic magnet powder is used, the bonded magnet of the present invention contains at least Fe, which is the main component, 12 to 16 at% of R, and 10.8 to 15 at% of B, and contains a homogenized heat treatment step. Isotropic magnet powder obtained by HDDR processing comprising a hydrogenation step of holding an ingot of an alloy not subjected to a hydrogen gas atmosphere at 1023 to 1173K and a dehydrogenation step of removing hydrogen after the hydrogenation step And a binder are mixed and molded.
[0046]
When the anisotropic magnet powder is used, the bonded magnet of the present invention contains at least Fe as a main component, 12 to 16 at% of R, and 10.8 to 15 at% of B, and includes a homogenizing heat treatment step. Low-temperature hydrogenation step of holding the ingot of the alloy not subjected to the above in a hydrogen gas atmosphere of 873K or lower, and high-temperature hydrogenation step of holding the alloy ingot in a hydrogen gas atmosphere of 1023 to 1173K at 20 to 100 kPa after the low-temperature hydrogenation step A first evacuation step of maintaining a hydrogen gas atmosphere of 0.12 to 1173 K at 0.1 to 20 kPa after the high-temperature hydrogenation step, and a second evacuation step of removing hydrogen after the first evacuation step. It is characterized in that the anisotropic magnet powder obtained by the HDDR process is mixed with a binder and pressed and molded.
[0047]
In addition, the contents regarding R, Co, the first element group, or the second element group described above also apply to the above-described isotropic magnet powder, anisotropic magnet powder, a method for producing them, and a bond magnet as appropriate. The same applies to the addition of La, which will be described later in detail.
BEST MODE FOR CARRYING OUT THE INVENTION
[0048]
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 the coarse powder (particles) of the magnet alloy to the above-mentioned HDDR treatment method or d-HDDR treatment method.
[0049]
(a) HDDR processing method
As described above, the HDDR treatment according to the present invention is performed by subjecting an alloy (ingot) having a composition of 10.8 to 15 at% of B to a hydrogenation step and a dehydrogenation step. The conditions for the hydrogenation step are as described above.
[0050]
In the dehydrogenation step, specifically, for example, a hydrogen pressure of 10 ^-1 This is a step of setting the atmosphere to Pa or less. The temperature during the dehydrogenation step may be, for example, 1023 to 1173K. In addition, the hydrogen pressure referred to in this specification means a partial pressure of hydrogen unless otherwise specified. Therefore, as long as the hydrogen partial pressure in each step is within a predetermined value, a vacuum atmosphere or a mixed atmosphere of an inert gas or the like may be used.
[0051]
The processing time of 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 may be performed for about 30 to 180 minutes. In addition, the HDDR processing itself is disclosed in detail in the above-mentioned Patent Document 3 and the like, and may be appropriately referred to.
[0052]
The magnet powder obtained by the HDDR treatment method is industrially meaningful as an isotropic magnet powder. The magnet powder has, for example, an iHc of 0.8 to 1.7 (MA / m) and a (BH) max of 60 to 120 (kJ / m). ^Three )).
[0053]
Next, the respective steps of the HDDR treatment and the relation with the magnet alloy of the present invention having the above B-rich composition will be described.
In the hydrogenation step, which is the first step of the HDDR treatment, hydrogen and the RFeB-based 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 fine B-rich phase precipitates the RFeB crystal grains and makes the RFeB crystal grains fine. Thereby, a high coercive force (iHc) is obtained.
[0054]
(b) d-HDDR processing
As described above, the d-HDDR processing according to the present invention is performed by adding a low-temperature hydrogenation step, a high-temperature hydrogenation step, a first exhaustion step, and a second exhaustion to an alloy (ingot) having a composition of B of 10.8 to 15 at%. An exhaust process is performed.
[0055]
The conditions of the high-temperature hydrogenation step and the first exhaust step are as described above. The low-temperature hydrogenation step is, for example, a step of setting an atmosphere at a hydrogen pressure of 30 to 200 kPa. In the second evacuation step, for example, the hydrogen pressure is set to 10 ^-1 This is a step of setting the atmosphere to Pa or less, and the temperature at that time is, for example, about 1023 to 1173K. Note that the first exhaust step and the second exhaust step together constitute a dehydrogenation step.
[0056]
The processing time of each of the above steps depends on the processing amount per batch. For example, if the throughput per batch is 10 kg, the low-temperature hydrogenation step is 30 minutes or more, the high-temperature hydrogenation step is 360 to 1800 minutes, the first exhaust step is 10 to 240 minutes, and the second exhaust step is 10 to 240 minutes. It may be performed for about 120 minutes. The d-HDDR processing method itself is disclosed in detail in the above-mentioned Patent Document 9 and the like, and may be appropriately referred to.
[0057]
The magnet powder obtained by this d-HDDR treatment is an anisotropic magnet powder exhibiting excellent magnetic properties. Its magnetic properties are, for example, iHc of 0.8 to 1.7 (MA / m) and (BH) max of 190 to 290 (kJ / m). ^Three ).
[0058]
Next, the relation between each step of the d-HDDR treatment and 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 process, hydrogen is rapidly increased to the RFeB-based alloy. In the second high-temperature hydrogenation step (hydrogen pressure: about 20 to 100 kPa), hydrogen and the RFeB-based alloy are gently reacted. At this time, the crystal orientation of the Fe2B phase serving as the anisotropic orientation transfer phase is precipitated in almost one direction, and hydrogen and the B-rich phase are sufficiently reacted. Further, in the first evacuation step, which is the third step, 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. By the fine and densely precipitated B-rich phase, the growth of the RFeB crystal grains is pinned, and the RFeB crystal grains become fine. Finally, in a fourth step, a second exhaust step, hydrogen remaining inside the alloy is removed.
[0059]
What is particularly important here is that the crystal orientation of the Fe2B phase is precipitated in almost one direction in the high-temperature hydrogenation step, and that the crystal orientation of the Fe2B phase is finely and densely maintained in the subsequent first exhaust step while maintaining the crystal orientation. The purpose is to finely precipitate the RFeB crystal by the pinning effect of the precipitated B-rich phase. Thereby, a high iHc anisotropic magnet powder is obtained.
[0060]
In addition, in any of the above-described processes, an ingot can be used as a raw material alloy. However, when a coarse powder that has been pulverized is used, each process can be efficiently performed. The pulverization of the ingot and the pulverization performed after the above treatment can be performed using dry or wet mechanical pulverization (such as a jaw crusher, a disk mill, a ball mill, a vibration mill, and a jet mill).
[0061]
(c) Flow rate and bulk density
The magnet powder obtained by subjecting the magnet alloy of the present invention to the above HDDR treatment or d-HDDR treatment has a substantially spherical particle diameter. For this reason, unlike the flakes manufactured by the melt-span method as in Patent Documents 1 and 2, the pellets manufactured using the magnet powder of the present invention have low fluidity and large bulk density. As a result, in producing a bonded magnet, which is the most important use of the magnet powder, it is possible to improve the powder feeding property of the pellet to the molding die. Further, since the magnet powder of the present invention has an appropriate average particle size of about 50 to 200 μm, it can not only improve the fluidity and bulk density, but also suppress adhesion and agglomeration. Also excellent. As a result, the productivity, quality, yield, and the like of the bonded magnet and the like are improved, and the cost of various magnets can be reduced.
[0062]
Specifically, the fluidity of the pellet obtained by mixing the magnet powder and 10 to 45 mass% of the organic resin as the binder is 0.55 to 0.64 (s / g), and the bulk density is 3.25 to 3.5 (g / cm ^Three ). The amount of the organic resin to be mixed with the magnet powder is more preferably 10 to 25 mass% for compression molding pellets, 30 to 45 mass% for injection molding pellets, and 20 to 35 mass% for extrusion molding pellets. .
[0063]
The magnet powder has a substantially spherical particle size for the following reason. When magnet powder is manufactured by performing the HDDR process or the d-HDDR process, the obtained particle shape is greatly affected by the alloy structure before the process. This is because in the early stage of the hydrogenation process of the HDDR process or the low-temperature hydrogenation process of the d-HDDR process, when the alloy absorbs hydrogen, it causes volume expansion and breaks mainly at fragile crystal grain boundaries.
[0064]
Here, when the magnet alloy is made of a cast such as an ingot, the crystal structure at the center becomes equiaxed granular and the crystal structure at the ends becomes dendritic. In the case of the present invention, the crystallization or precipitation of α-Fe, which is the primary crystal, is suppressed by the presence of the B-rich phase, so that the dendrite-like crystal structure formed at the end becomes fine. As a result, when the caster made of the magnet alloy of the present invention is subjected to the HDDR process or the d-HDDR process, one crystal grain is obtained as one substantially spherical particle from the center of the cast product. A plurality of dendritic crystals are obtained as one substantially spherical particle from the end. Thus, the constituent particles of the magnet powder are much more spherical than the magnet powder obtained by the conventional melt-span method or the like.
[0065]
(2) Bond magnet and manufacturing method thereof
When the magnet powder obtained as described above is used, not only the magnetic properties are excellent, but also the bond magnet can be produced at low cost due to its excellent powdering property.
[0066]
This bonded magnet is obtained through a mixing step of mixing the above-mentioned isotropic magnet powder or anisotropic magnet powder with a binder, and a molding step of molding the mixed powder obtained by this mixing step. The binder includes a metal binder and the like in addition to the organic binder described above. However, an organic binder such as a resin binder is generally used. 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 step includes compression molding, injection molding, extrusion molding and the like. When using an anisotropic magnetic powder as the magnet powder, the anisotropic magnetic powder is formed in a magnetic field. When a thermosetting resin is used as the resin binder, a heating (curing) treatment is performed during or after the molding step.
[0067]
(3) Addition of La-based material
As described above, La has the highest oxidation potential among rare earth elements, and therefore, La-containing magnet powder and hard magnets are suppressed from being oxidized and exhibit extremely excellent corrosion resistance and the like. As the addition form of La, for example, the following three forms can be considered.
[0068]
(A) When a La-based material is added from the smelting stage and a magnet powder or the like is manufactured using an RFeB-based magnet alloy (ingot) containing La,
(B) When a La-based material is mixed with the RFeB-based magnet powder obtained by the HDDR process or the d-HDDR process, 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 the magnet powder, and La is diffused or coated on the hydride.
[0069]
In any case, as long as La is present 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 form of addition of La is not particularly a problem.
[0070]
However, from the viewpoint that La has an oxygen getter function to more effectively suppress oxidation of the magnet powder and the like, it is preferable that La exists on the surface of the constituent particles of the magnet powder and the like or in the vicinity thereof. Therefore, it is more advantageous to mix a La-based material after or during the production of the magnet powder and to diffuse La or the like into the surface or inside of the magnet powder, rather than including La in the magnet alloy from the beginning.
[0071]
Therefore, for example, in the case of the above-mentioned 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 alone, a La alloy, and a La compound. The La mixture is subjected to a diffusion heat treatment step of heating the La mixture to 673 to 1123 K to diffuse La on the surface and inside of the magnet powder, and when the whole of the obtained isotropic magnet powder is 100 at%, La is set to 0.1%. It is preferable to contain 001 to 1.0 at%.
[0072]
It is also conceivable to mix a La-based material with RFeBHx powder or the like in the course of manufacturing the magnet powder, and to diffuse La into the surface and inside. The RFeBHx powder and the like are in a state where R and Fe are hardly oxidized as compared with the RFeB-based powder and the like. For this reason, La is diffused or coated in a state where oxidation is suppressed, and it is more preferable that a magnet powder having excellent corrosion resistance and the like can be obtained with stable quality. By the way, this hydride (RFeBHx) is RH _Two The hydrogen is removed from the phase and Fe _Two The polycrystal in which the crystal orientation of the B phase has been transferred is recombined, and is obtained after the first evacuation step of d-HDDR processing.
[0073]
Therefore, the method for producing an anisotropic magnet powder of the present invention further comprises adding one or more of La alone, a La alloy, a La compound, or a hydride thereof to the RFeB-based hydride obtained after the first evacuation step. A diffusion heat treatment step of heating the La mixture obtained by mixing the La-based material to 673 to 1123 K to diffuse La into and out of the RFeB-based hydride; This is a step of removing hydrogen from the La-processed material to be performed later, or the diffusion heat treatment step and the second evacuation step are performed simultaneously, or the diffusion heat treatment step is performed after the second evacuation step. It is preferable that the anisotropic magnet powder obtained by such a method contains La in an amount of 0.001 to 1.0 at% when the whole is 100 at%.
[0074]
Here, the diffusion heat treatment step is a step of diffusing (or coating) La on the surface and inside of the RFeB-based magnet powder or the RFeB-based hydride. This diffusion heat treatment step may be performed after mixing the La-based material, or may be performed simultaneously with the mixing. If the processing temperature is lower than 673K, the La-based material is unlikely to be in a liquid phase, and diffusion processing is difficult. On the other hand, when the temperature exceeds 1123 K, crystal grains of RFeB-based magnet powder and the like are grown, and iHc is reduced, so that improvement of corrosion resistance and the like (reduction of permanent demagnetization rate) cannot be sufficiently achieved. The processing time is preferably 0.5 to 5 hours. If the time is less than 0.5 hour, the diffusion of La becomes insufficient, and the corrosion resistance and the like of the magnet powder are not significantly improved. On the other hand, if it exceeds 5 hours, iHc will decrease. Needless to say, this diffusion heat treatment step is preferably performed in an antioxidant 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 manufacturing process of the magnet powder, it is preferable that they are in a powder form. The La alloy or the La compound is preferably an alloy or a compound of La and a transition metal element (TM) (including an intermetallic compound). For example, LaCo, LaNdCo, LaDyCo, etc. In particular, Co is suitable because it can also increase the Curie point of the magnet powder.
【Example】
[0075]
Hereinafter, the present invention will be described more specifically with reference to examples.
(Example 1, Example 2)
(1) Manufacture of alloys, magnetic powders and bonded magnets
Examples of magnet alloys according to the present invention were produced by melting and casting ingots (magnet alloys) having the compositions listed in Samples 1 to 10 in Table 1 or Table 2. In addition, as comparative examples, ingots having the compositions shown in Samples C1 to C6 in the respective tables were produced by melting and casting. Each of the manufactured ingots is about 30 kg.
[0076]
The alloy compositions of the samples shown in Tables 1 and 2 are the same. However, the processing applied to each sample (ingot) is different between Table 1 and Table 2. That is, Table 1 shows a case where each sample was subjected to the HDDR treatment. The magnetic powder shown in Table 1 is an isotropic magnet powder obtained through the treatment. The bonded magnets shown in Table 1 were produced from the isotropic magnet powder. Hereinafter, these are referred to as Example 1.
[0077]
Table 2 shows the case where each sample was subjected to the 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 were produced from the anisotropic magnet powder. Hereinafter, these are referred to as Example 2.
[0078]
Next, specific manufacturing conditions of the magnetic powder and the bonded magnet shown in Tables 1 and 2 will be described.
(A) The magnetic powders shown in Table 1 correspond to Sample No. Ingots having alloy compositions of 1 to 10 and C1 to C6 were produced by subjecting them to HDDR treatment including a hydrogenation step and a dehydrogenation step without performing any homogenization heat treatment. That is, heat treatment was performed for 360 minutes in a hydrogen gas atmosphere having the temperature and hydrogen pressure shown in Table 1 (hydrogenation step). This was followed by evacuation with a rotary pump and a diffusion pump for 60 minutes. ^-1 It was cooled under a vacuum atmosphere of Pa or less (dehydrogenation step). Thus, about 10 kg of magnetic powder was produced per batch.
[0079]
(B) The magnetic powders shown in Table 2 were also used for Sample No. A d-HDDR comprising a low-temperature hydrogenation step, a high-temperature hydrogenation step, a first exhaustion step and a second exhaustion step without subjecting any ingots having alloy compositions of 1 to 10 and C1 to C6 to homogenizing heat treatment. Manufactured by processing. That is, in a hydrogen gas atmosphere at room temperature and a hydrogen pressure of 100 kPa, hydrogen was sufficiently absorbed by each sample alloy (low-temperature hydrogenation step). Next, heat treatment was performed for 480 minutes in a hydrogen gas atmosphere at the temperature and the hydrogen pressure shown in Table 2 (high-temperature hydrogenation step). Subsequently, a heat treatment was performed at the same temperature shown in Table 2 under a hydrogen gas atmosphere at a hydrogen pressure of 0.1 to 20 kPa for 160 minutes (first evacuation step). Finally, vacuum was applied for 60 minutes with a rotary pump and a diffusion pump to ^-1 Cooling was performed in a vacuum atmosphere of Pa or less (second evacuation step). Thus, about 10 kg of magnetic powder was produced per batch.
[0080]
(C) Next, using the obtained various isotropic magnetic powders shown in Table 1 and the various anisotropic magnetic powders shown in Table 2, the following bonded magnets were produced.
[0081]
First, an epoxy resin (3 wt%) previously dissolved in butanone was mixed with each magnetic powder. Then, the butanone was volatilized while evacuating to produce pellets for a bonded magnet. As a reference sample, a similar pellet made from a flaky MQP-B (manufactured by Magnequench International) manufactured by melt spinning was also prepared. Then, the pellet was pressure-molded into a 7 mm cubic shape while being oriented in a magnetic field of 2.5 T to obtain a bonded magnet.
[0082]
(2) Magnetic measurement of magnetic powder and bonded magnet
(A) The magnetic measurement of each obtained magnetic powder was performed. Since a normal BH tracer cannot be used for measuring iHc of the magnetic powder, iHc was measured as follows.
[0083]
First, the magnetic powder was classified to a particle size of 75 to 106 μm. Using the classified magnetic powder, the magnetic powder was molded so that the demagnetizing coefficient was 0.2, and after orientation in a magnetic field, it was magnetized at 4.57 MAm-1 and VSM (manufactured by Riken Electronics Sales Co., Ltd., BH-525H). The (BH) max and iHc were measured with a. The results are shown in Tables 1 and 2.
[0084]
(B) In addition, (BH) max and iHc of the obtained various bond magnets were measured with a BH tracer (BHU-25, manufactured by Riken Electronics Sales Co., Ltd.). The results are also shown in Tables 1 and 2.
Note that “-” in Tables 1 and 2 indicates that the measurement was not performed because the magnetic properties were low.
[0085]
(3) Evaluation
(A) An overview of Tables 1 and 2 shows that sample no. When the amount of B is lower than 10.8 at% as in C1, C2, C4, and C5, (BH) max and iHc sharply decrease. Further, the sample No. As in C3 and C6, (BH) max also decreased when B was higher than 15 at%.
[0086]
The reason why the iHc decreased when the B amount was lower than 10.8 at% is considered to be that α-Fe was precipitated. The reason why (BH) max decreases when B is higher than 15 at% is considered to be that the B-rich phase has increased.
[0087]
Therefore, in order to balance (BH) max and iHc in a high dimension, it can be said that the B amount is preferably 10.8 to 15 at% as described 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 are specifically examined.
[0088]
(B) Isotropic magnetic powder and its bonded magnet
Examples of ternary isotropic magnetic powder obtained by subjecting an alloy ingot having only the composition of B to HDDR treatment under the same conditions are the examples shown in Table 1 (Sample Nos. 1 and 2) and Comparative Examples (Sample No. C1). -C3), the following can be understood.
[0089]
Even if the B amount is small or large as in the comparative example, specifically, if the B amount is out of 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 amount of B is within the range, 70 kJm ^-3 As described above, a large (BH) max is obtained. As described above, the peak value of (BH) max exists in the range of B: 10.8 to 15 at%.
[0090]
The coercive force iHc of the magnetic powder shows a tendency 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 slow, and sufficient iHc is obtained when the B amount is 10.8 to 15 at%.
[0091]
Next, with respect to hexagonal isotropic magnetic powder obtained by subjecting an alloy ingot having only the composition of B to HDDR treatment under the same conditions, the examples shown in Table 1 (sample No. 5) and the comparative examples (sample No. 5). Even when C4 to C6) are compared, the same can be said as above. That is, the peak value of (BH) max is in the range of B: 10.8 to 15 at%, and the iHc obtained at that time is close to the peak value.
The same can be said for bond magnets manufactured using these isotropic magnetic powders, regardless of whether they are ternary or hexagonal.
[0092]
Furthermore, from Table 1, the bond magnet according to the present example of the six-element system or higher has the same (BH) max as the bond magnet made of MQP-B, but has about 50% improvement in iHc. I understand that
[0093]
(C) Anisotropic magnetic powder and its bonded magnet
Examples of ternary anisotropic magnetic powders obtained by subjecting alloy ingots differing only in the composition of B to d-HDDR treatment under the same conditions and Examples (Sample Nos. 1 and 2) shown in Table 2 and Comparative Examples (Sample Nos. .C1 to C3), the following can be understood.
[0094]
The maximum energy product (BH) max of the magnetic powder decreases when the B amount is outside the range of 10.8 to 15 at% even if the B amount is small or large as in the comparative example. On the other hand, in the case of the embodiment in which the amount of B is within the range, 210 kJm ^-3 As described above, a large (BH) max is obtained. As described above, the peak value of (BH) max exists in the range of B: 10.8 to 15 at%.
[0095]
The coercive force iHc of the magnetic powder shows a tendency 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 slow, and sufficient iHc is obtained when the B amount is 10.8 to 15 at%.
[0096]
Next, with respect to hexagonal anisotropic magnetic powders obtained by subjecting alloy ingots differing only in the composition of B to d-HDDR treatment under the same conditions, the examples shown in Table 2 (sample No. 5) and the comparative examples (samples) No. C4 to No. C6), the same can be said as above. That is, the peak value of (BH) max is in the range of B: 10.8 to 15 at%, and the iHc obtained at that time is close to the peak value.
[0097]
The same applies to bonded magnets manufactured using these anisotropic magnetic powders, regardless of whether they are ternary or hexagonal.
[0098]
(Example 3)
Sample No. shown in Table 1 was used. The relationship between the specific coercive force iHc of the isotropic magnetic powder obtained by subjecting the ingots Nos. 2 and 6 to the HDDR process and the time (180 to 1800 minutes) of the hydrogenation step of the HDDR process were investigated. Except for the time of the hydrogenation step, the production conditions of each magnetic powder are the same as in 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. Table 3 shows the results thus obtained.
[0099]
From Table 3, it was found that the iHc increased with an increase in the duration of the hydrogenation step, and that the increase in iHc tended to be substantially saturated after 360 minutes.
[0100]
(Example 4)
Sample No. shown in Table 2 The relationship between the specific coercive force iHc of the anisotropic magnetic powder obtained by subjecting the ingots of Nos. 2 and 6 to d-HDDR treatment and the time (180-1800 minutes) of the high-temperature hydrogenation step of the d-HDDR treatment was investigated. did.
[0101]
Except for the time of the high-temperature hydrogenation step, the production conditions of each magnetic powder are the same as in the d-HDDR treatment described in the second embodiment. The method for measuring the magnetic characteristics is the same as in the first and second embodiments. Table 4 shows the results thus obtained.
From Table 4, it was found that, as in the case of Example 3, when the processing time of the high-temperature hydrogenation step exceeds 360 minutes, the obtained coercive force tends to be almost saturated.
[0102]
(Example 5)
Sample No. shown in Table 1 The isotropic magnet powders according to Sample Nos. 5 to 8 and the sample Nos. The fluidity and bulk density of each of the anisotropic magnet powders according to Examples 1 to 4 and the bonded magnet pellets composed of the reference sample (MQP-B) were examined. The measurement results are shown in FIG. 1 and FIG.
[0103]
The fluidity and bulk density of the pellet were measured according to JIS Z8041 (JIS standard).
As can be seen from FIGS. 1 and 2, in the case of the present embodiment, the fluidity is improved by about 20% and the bulk density is improved by about 10% as compared with the case of the reference sample. It is considered that this is because the particle shape of each magnetic powder of the present embodiment is nearly spherical.
[0104]
(Example 6)
Sample No. of Table 2 The cost performance of the anisotropic magnetic powder obtained by subjecting the alloy ingot of No. 6 to d-HDDR treatment was examined.
[0105]
First, the sample No. Ingot 6 (about 30 kg) was melted and cast. The ingot was not subjected to the heat treatment for homogenization, and hydrogen was sufficiently absorbed by the 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 a temperature of 1073 K and a hydrogen pressure of 45 kPa (high-temperature hydrogenation step). Subsequently, a 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 evacuation step). Finally, vacuum was applied for 60 minutes with a rotary pump and a diffusion pump to ^-1 Cooling was performed in a vacuum atmosphere of Pa or less (second evacuation step). Thus, about 10 kg of magnetic powder was produced per batch.
[0106]
Bond magnets were prepared using the magnetic powder in the same manner as in Examples 1 and 2, and the (BH) max was measured. FIG. 3 shows a value obtained by dividing the measured (BH) max by the raw material cost (raw material cost, melting / casting cost) used in the d-HDDR process, as cost performance.
[0107]
As a comparative sample, an alloy ingot (about 30 kg) of sample C1 in Table 2 was produced 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 homogenizing 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.
[0108]
For this magnetic powder, a bonded magnet was prepared in the same manner as in Sample 6, and the (BH) max was measured. Then, the value obtained by dividing the measured (BH) max by the raw material cost (raw material cost, melting / casting cost, and homogenizing heat treatment cost) subjected to the d-HDDR process is also shown in FIG. 3 as cost performance.
As shown in FIG. 3, the cost performance of Sample 4 not subjected to the homogenization heat treatment was improved by about 30% as compared with Sample C1 subjected to the homogenization heat treatment.
[0109]
(Example 7)
(1) Sample No. of Table 1 1, No. Alloy ingot No. 6 was subjected to the same HDDR treatment as in Example 1 to produce isotropic magnetic powder. To this isotropic magnetic powder, La80Co20 alloy powder (La-based material) was mixed (mixing step) and heated (diffusion heat treatment step). 11 to 15 and sample Nos. 16 and 17 magnetic powders were obtained. The composition of each sample shown in Tables 5 and 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 are all performed in 10 steps. ^-2 The test was performed in a vacuum atmosphere of Pa or less. Table 6 shows, as an example, Sample No. The magnetic properties of the isotropic magnet powders 16 and 17 and the bonded magnets using the same are also shown. The measuring method and the like are as described above.
[0110]
Here, the La80Co20 alloy is an alloy of La: 80 at% and Co: 20 at%, and is produced as in the case of the magnet alloy (ingot) of the first embodiment. The powder was obtained by crushing the ingot by a hydrogen crushing method and pulverizing the powder by a vibration mill, and had an average particle diameter of 10 μm.
[0111]
A 7 mm square isotropic bonded magnet was produced in the same manner as in Example 1 using the isotropic magnetic powder after the diffusion heat treatment step. Using this bonded magnet, the permanent demagnetization rate was measured.
[0112]
Permanent demagnetization rate is calculated from the difference between the initial magnetic flux of the bonded magnet and the magnetic flux obtained by re-magnetizing after holding in an air atmosphere at 100 ° C. or 80 ° C. for 1000 hours, and calculating the ratio of the decrease to the initial magnetic flux. It is what I sought. The magnetization at this time was performed at 1.1 MA / m (45 kOe). A flux meter was used for measuring the magnetic flux. The permanent demagnetization rates thus obtained are shown in Tables 5 and 6.
[0113]
(2) Sample No. shown in Table 5 as a comparative example. Bond magnets for C7 to C9 were prepared. Sample No. The bonded magnet of C7 has a La content of more than 1.0 at%, and the sample No. The bonded magnet of C8 was obtained by mixing no La-based material. The heating temperature during the diffusion heat treatment step of the bonded magnet of C9 is as low as less than 400 ° C. Table 5 also shows the diffusion heat treatment conditions and the permanent demagnetization rate in each case.
[0114]
(3) From Tables 5 and 6, it can be seen that the isotropic bonded magnets according to the present invention have low permanent demagnetization rate, excellent heat resistance, and high practicality. Note that a small permanent demagnetization rate also means that it has excellent corrosion resistance and has little deterioration over time.
[0115]
In particular, even at 100 ° C. for 1000 hours, the permanent demagnetization rate is as small as less than 10%. Further, in the case of 80 ° C. × 1000 hours, the permanent demagnetization rate is reduced to about 5%.
[0116]
On the other hand, in the comparative example, the permanent demagnetization rate is as high as about 10% at 80 ° C. for 1000 hours, and is extremely high at about 15% at 100 ° C. for 1000 hours. . As a reference sample, Table 5 also shows the permanent demagnetization rate of the isotropic powder (MQP-B) produced by the rapid solidification method.
[0117]
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 examples, or were reduced by about 7 to 8% at the maximum, and were at a level having no practical problem.
[0118]
(Example 8)
(1) Sample No. of Table 2 1, 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 A powder (RFeB-based 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). Subsequently, a second evacuation step similar to that in Example 2 was performed.
[0119]
Thus, the sample No. shown in Tables 7 and 8 was used. 11 to 15 and sample Nos. 16 and 17 magnetic powders were obtained. The composition of each sample shown in Tables 7 and 8 is a value analyzed by ICP after the second evacuation step, 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 are all performed in 10 steps. ^-2 The test was performed in a vacuum atmosphere of Pa or less. Table 8 shows, as an example, Sample No. The magnetic properties of the anisotropic magnet powders Nos. 16 and 17 and the bonded magnets using the same were also shown. The measuring method and the like are as described above. Tables 7 and 8 also show the permanent demagnetization rates obtained in the same manner as in Example 7.
[0120]
(2) The bond magnet prepared as a comparative example is the same as in the case of the seventh embodiment. Table 7 also shows the conditions of the diffusion heat treatment and the permanent demagnetization rate in each case.
[0121]
(3) From Tables 7 and 8, all of the anisotropic bonded magnets according to the present invention have a small permanent demagnetization rate and are highly practical. In particular, even at 100 ° C. for 1000 hours, the permanent demagnetization rate is as small as less than 10%. In the case of 80 ° C. × 1000 hours, the permanent demagnetization rate is a small value of 5 to 7%. On the other hand, in the comparative examples, the permanent demagnetization rate is as high as 10% or more even at 80 ° C. for 1000 hours, and the permanent demagnetization rate is as high as 15% or more at 100 ° C. for 1000 hours. .
[0122]
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 examples, or were reduced by about 7 to 8% at the maximum, and were at a level having no practical problem.
[0123]
[Table 1]

[0124]
[Table 2]

[0125]
[Table 3]

[0126]
[Table 4]

[0127]
[Table 5]

[0128]
[Table 6]

[0129]
[Table 7]

[0130]
[Table 8]

[Brief description of the drawings]
[0131]
FIG. 1 is a bar graph comparing the fluidity of pellets for bonded magnets manufactured 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 cost performance of a magnet powder produced by d-HDDR processing.

Claims (17)

Iron (Fe) as a main component;
12 to 16 atomic% (at%) of a rare earth element (hereinafter referred to as “R”);
Consisting of 10.8-15 at% boron (B),
An alloy for bonded magnets, wherein a homogenizing heat treatment step can be omitted in the production of magnet powder. The alloy for a bonded magnet according to claim 1, wherein the R is at least one of Pr, Nd, and Dy. The alloy for bonded magnets according to claim 1, further comprising 0.1 to 6 at% of cobalt (Co). Furthermore, at least one of gallium (Ga), zirconium (Zr), vanadium (V), aluminum (Al), titanium (Ti), hafnium (Hf) and copper (Cu) is contained in a total amount of 0.1 to 2 at%. Along with
The alloy for a bonded magnet according to any one of claims 1 to 3, wherein the alloy contains at least one of niobium (Nb), tantalum (Ta), and nickel (Ni) in a total amount of 0.1 to 2 at%. The alloy for bonded magnets according to any one of claims 1 to 4, further comprising 0.001 to 1.0 at% of lanthanum (La). An ingot of an alloy containing at least the main component Fe, R of 12 to 16 at%, and B of 10.8 to 15 at% and not subjected to the homogenizing heat treatment step is kept in a hydrogen gas atmosphere of 1023 to 1173 K. Hydrogenation process,
An isotropic magnet powder obtained by an HDDR treatment comprising a dehydrogenation step of removing hydrogen after the hydrogenation step. 7. The isotropic magnet powder according to claim 6, further comprising 0.001 to 1.0 at% La. An ingot of an alloy containing at least Fe, which is the main component, 12 to 16 at% of R, and 10.8 to 15 at% of B and not subjected to the homogenizing heat treatment step is kept in a hydrogen gas atmosphere of 873 K or less. A low-temperature hydrogenation process;
After the low-temperature hydrogenation step, a high-temperature hydrogenation step of maintaining in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa,
A first evacuation step of maintaining the hydrogen gas atmosphere at 102 to 1173 K at 0.1 to 20 kPa after the high-temperature hydrogenation step;
An anisotropic magnet powder obtained by d-HDDR processing comprising a second evacuation step of removing hydrogen after the first evacuation step. The anisotropic magnet powder according to claim 8, further comprising 0.001 to 1.0 at% of La. An ingot of an alloy containing at least Fe, which is the main component, 12 to 16 at% of R, and 10.8 to 15 at% of B and not subjected to the homogenizing heat treatment step is kept in a hydrogen gas atmosphere of 1023 to 1173 K. Isotropic magnet powder obtained by HDDR processing comprising a hydrogenation step of performing a hydrogenation step and a dehydrogenation step of removing hydrogen after the hydrogenation step, and a binder, and the mixture is subjected to pressure molding. Bond magnet. The bonded magnet according to claim 10, wherein the isotropic magnet powder further contains La of 0.001 to 1.0 at%. An ingot of an alloy containing at least Fe, which is the main component, 12 to 16 at% of R, and 10.8 to 15 at% of B and not subjected to the homogenizing heat treatment step is kept in a hydrogen gas atmosphere of 873 K or less. A low-temperature hydrogenation step, a high-temperature hydrogenation step in which the low-temperature hydrogenation step is performed in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa, and a hydrogen gas of 0.12 to 1173 K at 0.1 to 20 kPa after the high-temperature hydrogenation step Mixing a binder with an anisotropic magnet powder obtained by d-HDDR processing comprising a first evacuation step of keeping in a gas atmosphere and a second evacuation step of removing hydrogen after the first evacuation step; A bonded magnet characterized by being formed by pressure. The bonded magnet according to claim 12, wherein the anisotropic magnet powder further contains La of 0.001 to 1.0 at%. An ingot of an alloy containing at least the main component Fe, R of 12 to 16 at%, and B of 10.8 to 15 at% and not subjected to the homogenizing heat treatment step is kept in a hydrogen gas atmosphere of 1023 to 1173 K. Hydrogenation process,
A method for producing isotropic magnet powder, comprising performing an HDDR treatment comprising a dehydrogenation step of removing hydrogen after the hydrogenation step. Further, the magnet powder obtained after the dehydrogenation step is mixed with a La-based material composed of at least one of La alone, a La alloy, and a La compound, and heated to 673 to 1123 K to obtain a La powder. A diffusion heat treatment step for diffusing La into 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% of La when the whole is 100 at%. An ingot of an alloy containing at least Fe, which is the main component, 12 to 16 at% of R, and 10.8 to 15 at% of B and not subjected to the homogenizing heat treatment step is kept in a hydrogen gas atmosphere of 873 K or less. A low-temperature hydrogenation process;
After the low-temperature hydrogenation step, a high-temperature hydrogenation step of maintaining in a hydrogen gas atmosphere of 1023 to 1173 K at 20 to 100 kPa,
A first evacuation step of maintaining the hydrogen gas atmosphere at 102 to 1173 K at 0.1 to 20 kPa after the high-temperature hydrogenation step;
A method for producing anisotropic magnet powder, comprising performing d-HDDR processing comprising a second evacuation step of removing hydrogen after the first evacuation step. Further, a kind of La alone, a La alloy, a La compound, or a hydride thereof (a simple substance of La, an alloy or a hydride of a compound) is added to the RFeB-based powder obtained after the first evacuation step or the second evacuation step. A diffusion heat treatment step of heating the La mixture obtained by mixing the La-based material composed as described above to 673 to 1123 K to diffuse at least La into the surface and the 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% of La when the whole is 100 at%.

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