JPH04216601A - Material of permanent magnet, manufacture thereof and bonded magnet - Google Patents

Abstract

PURPOSE:To raise the Curie temperature for securing the thermal stability by a method wherein an Sm-(Fe, Co) base magnet is composed of N and Cu as well as at least one element selected from Zr, Hf, Nb, Ta, W, Mo, Ti, V and Cr. CONSTITUTION:The title magnet is a two phase separation type precipitation hardening magnet composed of 5-15 atomic % of Sm, 1-17% of Cu, 0.1-10 atomic % of M (where M is at least one element selected from a group comprising Zr, Hf, Nb, Ta, W, Mo, Ti, V and Cr) and 0.5-25 atomic % of N and residual % of Fe or Fe and Co with residual Fe containing ratio exceeding 20 atomic %. Accordingly, the separated setting type magnet containing N can raise the Curie temperature thereby enabling the excellent thermal stability and high saturation magnetization to be secured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet material, a method for manufacturing the same, and a bonded magnet.

0002

[Prior Art] As a high-performance rare earth magnet, Sm-Co
Although Nd-Fe-B based magnets and Nd-Fe-B based magnets are known, new rare earth magnets have been actively developed in recent years.

For example, at a composition near Sm2Fe17N2.3, which is a compound of Sm2Fe17 and N, 4πIs=
The basic physical properties of 15.4kG, Tc=470℃, HA=14T can be obtained, and (BH)max of 10.5MGOe can be obtained as a metal bonded magnet using Zn as a binder. It has been reported that the Curie temperature was significantly increased and the thermal stability was improved by the introduction of N (Pape N
o. S1.3 at the Sixth I
international symposium
on Magnetic Anisotropy
An Coercivity in Rare
Earth-Transition Metal
Alloys, Pittsburgh, PA, Oc.
tober 25, 1990. (Proceedin
gs Book: Carnegie Mellon
University, Mellon Inst.
itute, ittsburgh, pa 15213
, USA)).

However, (BH)m of Sm2Fe17 magnet
The (BH)max of the bonded magnet predicted from the theoretical value of ax of about 59MGOe is about 40MGOe, whereas the (BH)max of the bonded magnet shown in the above report is about 40MGOe.
H) max is low. This is because the magnetic particles used in the ponded magnet reported above have a grain size that is almost single crystal grains, and the coercive force generation mechanism is a nucleation type, so the magnetic properties are This is thought to be because it is more susceptible to the influence of the surface condition of the particles.

In other words, defects occur on the surface of magnet particles due to mechanical impact during crushing, oxidation of particles, etc., and domain walls are generated due to these defects, but in nucleation type magnets, pinning sites for domain walls are formed within the crystal grains. Since there is no magnetic field, domain wall movement easily occurs, and the coercive force tends to deteriorate. For this reason, it is difficult to obtain high magnetic properties with the magnet shown in the above proposal. In addition, when the surface of the magnet particles is oxidized by heating, the coercive force is significantly deteriorated, so even though the Curie temperature is high, the stability against heating is low when actually used. Moreover, since deterioration of magnetic properties due to deterioration of particle surface conditions is irreversible, there is a risk of irreversible damage when used at high temperatures.

The bonded magnet shown in the above report is a metal bonded magnet using Zn as a binder. The surface of the magnetic particles of a metal bonded magnet melts when it comes into contact with high-temperature molten metal during molding, so it is thought that the particle surface is smoothed and the generation of domain walls is suppressed. It is presumed that magnets are used, but metal bonded magnets have poor formability and high specific gravity compared to resin bonded magnets, so their field of application is narrow. Further, even when metal is used as a binder, it is impossible to prevent defects on the surface of magnet particles that occur after forming a bonded magnet, such as deterioration of the surface condition due to oxidation, and deterioration of magnetic properties cannot be suppressed.

On the other hand, resin bonded magnets using resin as a binder have excellent moldability and low specific gravity, and are therefore widely used in various applications. However, in a resin-bonded type bonded magnet, the surface of the magnet particles cannot be smoothed due to the low temperature during molding, and a decrease in coercive force due to surface defects of the particles is unavoidable.

[0008]

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and provides a permanent magnet material with high magnetic properties and good thermal stability, a method for manufacturing the same, and a method using this permanent magnet material. The purpose of the present invention is to provide a bonded magnet.

[0009]

[Means for Solving the Problems] Such objects are achieved by the present invention as described in (1) to (5) below.

(1) 5 to 15 atomic % of Sm and 1 to 15 atomic % of Cu
17 atomic%, M (where M is Zr, Hf, Nb, T
It is at least one element selected from the group consisting of a, W, Mo, Ti, V, and Cr. ) from 0.1 to 10
atomic% and 0.5 to 25 atomic% of N, with the balance being F.
or Fe and Co, the content of Fe in the remainder is 20 atomic % or more, and the permanent magnet material is a two-phase separation type precipitation hardening magnet.

(2) A method for producing the permanent magnet material described in (1) above, wherein the master alloy is subjected to an aging treatment to form two-phase separated magnet particles, and the two-phase separated magnet particles are exposed to a nitrogen atmosphere. 1. A method for producing a permanent magnet material, comprising the step of performing heat treatment inside.

(3) A bonded magnet characterized by containing particles of the permanent magnet material described in (1) above and a binder.

(4) The above (3) wherein the binder is a resin.
) Bonded magnets described in ).

(5) The bonded magnet according to (3) or (4) above, wherein the particles of the permanent magnet material have an average particle diameter of 20 μm or more.

[0015]

[Function] The permanent magnet material of the present invention is Sm-(Fe, Co
) system magnets include N, Cu and M (where M is Zr, H
At least one element selected from the group consisting of f, Nb, Ta, W, Mo, Ti, V, and Cr. ).

Since this permanent magnet material contains N, it has a high Curie temperature and is excellent in thermal stability. Further, by containing N, high saturation magnetization can be obtained. The improvement in saturation magnetization is due to the formation of an interstitial solid solution by the addition of N,
This is thought to be because the distance between atoms is optimized.

Furthermore, since the inclusion of Cu and M results in a two-phase separated precipitation hardening magnet, pinning sites exist within the crystal grains. Therefore, when crushed into single crystal particles for use in bonded magnets, movement of domain walls within the grains caused by defects on the particle surfaces can be prevented. Therefore, deterioration of magnetic properties due to surface defects generated during crushing is suppressed, and high coercive force can be obtained even when applied to a resin-bonded type bonded magnet. Furthermore, since it is possible to suppress the deterioration of magnetic properties due to oxidation of the particle surface when used in a high temperature environment, it is possible to effectively utilize the improvement in the Curie temperature due to N addition.

Furthermore, since domain wall movement within the particles is suppressed, the particle diameter can be increased, and high oxidation resistance is thereby obtained, so from this point of view as well, thermal stability is high.

[0019] Furthermore, EP 0 369 097
Run No. of Example 36 of Al. 1
In No. 4, Sm2Fe17 alloy was annealed at 900°C for 7 days, coarsely pulverized, and then heat treated in a mixed gas of ammonia and hydrogen to form Sm2Fe17N4.0H0.
．． 5 and further mixed with 10 atomic % of Cu, pulverized to a particle size of 5 μm, molded in a magnetic field, and sintered. As typically shown in this Example 36, E
The manufacturing method disclosed in P 0 369 097 A1 adds Cu after annealing, and such a manufacturing method does not cause two-phase separation. Also, EP
0 369 097 A1 states that when the average grain size reaches about 20 to 30 μm, a large number of domain walls gather inside the grains and iHc is not improved. From this description, it is clear that the magnet is not a two-phase separation type magnet. Therefore, EP 0 369 097 A1
The described magnet does not achieve the effects of the present invention. In fact, the obtained magnet had a Br of 7.8 kG and an iHc of 3.8 kO.
e, (BH)max is 8.0 MGOe, which is significantly lower than the magnetic properties obtained in the examples of the present invention.

[0020]

[Specific Structure] Hereinafter, the specific structure of the present invention will be explained in detail.

The permanent magnet material of the present invention has an Sm of 5 to 15
atomic %, preferably 7 to 14 atomic %, Cu 1 to 17 atomic %, preferably 3 to 9.5 atomic %, M (however, M is Zr, Hf, Nb, Ta, W, Mo, Ti, at least one element selected from the group consisting of V and Cr) in an amount of 0.1 to 10 at%, preferably 0.5 to 5
atom%, and N from 0.5 to 25 atom%, preferably 5
Contains ~20 at%, with the remainder being substantially Fe or Fe
and Co, and the Fe content in the remainder is 20 atomic % or more, preferably 30 atomic % or more.

If the Sm content is less than the above range, the coercive force iHc will decrease, and if it exceeds the above range, the residual magnetic flux density B will decrease.
r will decrease. In addition, in the present invention, a part of Sm is Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy.
, Ho, Er, Tm, Yb, Lu, and the like. If the amount of substitution is too large, the magnetocrystalline anisotropy decreases, so the amount of substitution of these elements is preferably 70% or less of Sm.

[0023] If the Cu content is less than the above range, the coercive force will decrease, and if it exceeds the above range, Br will decrease.

[0024] When the content of M is out of the above range, iHc
And the maximum energy product (BH) max will decrease. In addition, in order to obtain high magnetic properties, it is necessary to use Zr as M.
It is preferable to use Nb and/or Nb.

If the N content is less than the above range, the increase in Curie temperature and saturation magnetization will be insufficient, and if it exceeds the above range, Br will decrease.

[0026]Also, the remainder after removing each of the above elements is Fe, or Fe and Co, but if Fe in the remainder is
When the content is less than the above range, Br decreases. There is no particular upper limit to the Fe content in the remainder, but if it exceeds 80 at %, Br tends to decrease.

[0027] The permanent magnet material of the present invention contains Si.
, A1, Mn, Ni, Zn, and other elements other than those mentioned above may be contained. The content of these elements is preferably 3% by weight or less. Also, C, B, O, P, S, G
Although elements such as a may be contained, the content of these elements is preferably 2% by weight or less.

The permanent magnet material of the present invention having such a composition is a so-called two-phase separation type precipitation hardening magnet,
It has a microstructure with a cellular structure. The cells act as pinning sites during domain wall movement. In this cell structure, the average intercell distance (distance between the centers of adjacent cells) is preferably about 500A or more, more preferably 700A or more, and particularly preferably 1000A or more. By setting the inter-cell distance within this range, a high coercive force can be obtained. Note that when the distance between cells is larger than 600A, the squareness of the demagnetization curve tends to decrease, so it is preferable that the distance between cells is 600OA or less. Note that the inter-cell distance can be adjusted by controlling various conditions in the aging treatment for precipitation hardening. In addition, the cell structure and its dimensions are
This can be confirmed using a transmission electron microscope or the like. In addition, if the cell boundary width in the cell structure is too small, the function as a pinning site will be insufficient, and if the cell boundary width is too large, the magnetic properties will deteriorate.
It is preferable that it is about 200A.

A method suitable for producing the permanent magnet material of the present invention will be explained below.

First, raw metals or alloys are mixed to obtain a desired composition, and then the mixture is melted and cast to produce a master alloy ingot. The crystal grain size of the master alloy ingot is preferably such that single crystal grains can be obtained by pulverization as described below.

Next, the master alloy ingot is subjected to a compacting treatment. The compacting treatment is performed to improve the homogeneity of the ingot, and the treatment temperature is 900 to 1230 °C, especially 10
It is preferable that the temperature is 00 to 1200°C and the treatment time is about 0.5 to 24 hours. The containerization treatment can be carried out in various atmospheres, but it is preferably carried out in a non-oxidizing atmosphere such as an inert gas atmosphere, a reducing atmosphere, a vacuum, or the like.

After the containerization treatment, the ingot is subjected to an aging treatment to form a two-phase separated alloy. In this case, the aging treatment preferably consists of an initial aging performed by heating and holding at a predetermined temperature for a predetermined time, and subsequent multi-stage aging or continuous cooling. In the first stage aging, it is preferable to maintain the temperature at 700 to 950°C for 0.5 hours or more, particularly for about 1 to 500 hours. As for the multi-stage aging to be performed after such first-stage aging, the heating temperature should be increased by 0.2-5°C/100-200°C until the temperature is lowered to at least 600°C or lower, especially 400°C or lower.
Preferably, the cooling is performed at a rate of min.

[0033] The two-phase separated magnet obtained by such aging treatment is composed of R (T, Cu) with a high Cu content, where Fe and Co are represented by T and the rare earth metal element is represented by R.
5-based phase and an R2(T,Cu)17-based phase with a low Cu content, the R2(T,Cu)17-based phase is a matrix phase, and the R(T,Cu)5-based phase is a pinning phase. It has a structure that is a site.

[0034] The above-mentioned mother alloy ingot was coarsely crushed, further finely pulverized using a jet mill, etc., and then sintered in a magnetic field to produce a base metal ingot, which was used as the base metal ingot described above. Such aging treatment and aging treatment may also be performed. In this case, it becomes easy to set the crystal grain size of the master alloy ingot to an optimum size.

Furthermore, in the present invention, a high-speed rapidly solidified alloy can also be used as the master alloy. In this case, first, a molten alloy is rapidly cooled by a high speed quenching method such as a single roll method or a twin roll method to produce a high speed quenched alloy in the form of a ribbon, flake or granules. This high-speed rapidly solidified alloy is subjected to the above-mentioned compacting treatment as required, and further subjected to the above-mentioned aging treatment for precipitation hardening to produce a two-phase separation type permanent magnet material.

After the aging treatment, the permanent magnet material is pulverized into magnet particles. Although the average particle size of the magnet particles is not particularly limited, it is usually preferably about 2 to 200 μm. The pulverizing means is not particularly limited, and various ordinary pulverizers may be used, but a means for pulverizing hydrogen gas by occluding hydrogen gas in a permanent magnet material may also be used.

[0037] Note that it is not necessarily necessary to pulverize after the aging treatment, and the aging treatment may be performed after pulverization.
Thereafter, it may be further pulverized if necessary.

Next, the magnet particles are subjected to a nitriding treatment. In this nitriding treatment, alloy particles are heat-treated in a nitrogen atmosphere, and as a result, nitrogen is absorbed into the magnet particles. The holding temperature during the nitriding treatment is preferably about 400 to 700°C, particularly about 450 to 650°C. Further, the temperature holding time is preferably about 0.5 to 200 hours, particularly about 2 to 100 hours.

[0039] The amount of N in the magnet particles can be measured by gas analysis.

[0040] Furthermore, by absorbing hydrogen and pulverizing the magnet particles, and then subjecting them to the nitriding process without exposing them to the atmosphere, it is possible to suppress the formation of an oxide film on the surface of the particles.
High reactivity can be obtained during nitriding treatment. Further, in order to obtain sufficient oxidation resistance, the average particle diameter of the magnet particles is preferably 20 μm or more, more preferably more than 30 μm, and still more preferably 35 μm or more. In the present invention, since domain wall motion within the grain is pinned, a high coercive force can be obtained even when the single crystal grain has such a relatively large diameter. Moreover, by setting the particle size to such a value, a high-density bonded magnet can be obtained. There is no particular upper limit to the average particle diameter, but it is usually 1000 μm.
It is preferable to keep it to a certain extent or less.

In the present invention, the average particle size means the weight average particle size D50 determined by sieving. The weight average particle diameter D50 is the particle diameter when the weight is added starting from the particle with the smallest diameter and the total weight becomes 50% of the total weight of all particles.

The magnet particles after the nitriding treatment are usually combined with a binder to form a bonded magnet. The bonded magnet may be either a compression bonded magnet using press molding or an injection bonded magnet using injection molding.

The binder used in the production of bonded magnets may be any of various resins, various metals, etc., but the permanent magnet material of the present invention exhibits particularly high effects when combined with a resin binder. do. The type of resin binder is not particularly limited, and may be appropriately selected from various thermosetting resins such as epoxy resin and nylon, and various thermoplastic resins depending on the purpose. Further, various conditions such as the content ratio of the binder to the alloy particles and the pressure during molding are not particularly limited, and may be appropriately selected from a normal range.

[0044]

EXAMPLES Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Bonded magnet samples containing magnet particles having the composition shown in Table 1 below were produced by the method shown below.

[0046] First, master alloy ingots were prepared by high-frequency induction heating, and these master alloy ingots were subjected to a container treatment. The curing treatment was carried out at 114° C. in an Ar gas atmosphere.
It was carried out at 0 to 1180°C for 2 to 4 hours.

[0047] Next, in an Ar gas atmosphere, the temperature was 850°C.
The initial aging was carried out for 10 hours at
Multi-stage aging was performed by cooling to 0° C. and holding for 10 hours, and precipitation hardening was performed to obtain a permanent magnet material.

Next, the permanent magnet material was subjected to hydrogen absorption pulverization to obtain substantially single-crystal magnet particles. Note that the average particle diameter of the magnet particles is that of sample No. For samples No. 1 to 6, the diameter was 37 μm, and for sample No. 7, it was set to 50 μm.

Next, the magnet particles were subjected to nitriding treatment. The nitriding treatment was performed by heat treatment at 500° C. for 40 hours in a nitrogen gas atmosphere.

For comparison, magnet particles without nitriding were also produced.

For comparison, magnet particles without aging treatment were also produced.

[0052] These magnet particles were mixed with an epoxy resin, press-molded, and further heat-treated to obtain a compression bonded magnet sample.
The epoxy resin was used in an amount of 2 parts by weight based on 100 parts by weight of the magnet particles. The pressure holding time during press molding was 1 second, and the applied pressure was 8000 kgf/cm2. In addition, heat treatment
The test was carried out at 150°C for 1 hour.

For each bonded magnet sample thus obtained, coercive force iHc, residual magnetic flux density Br,
Maximum energy product (BH) max and Curie temperature T
c was measured.

[0054] In addition, each sample was heated at 85°C and 90% RH.
After being left in the air for 500 hours, the temperature was lowered to room temperature,
iHc was measured. The results are shown in Table 1 as iHc after storage.

[0055]

[Table 1]

Note that as a result of observing the samples shown in Table 1 with a transmission electron microscope, sample No. Two-phase separation occurs in 1 to 5 and 7, and the cell boundary width is 50 to 200A.
The distance between cells was about 500 to 1500A.

The effects of the present invention are clear from the above examples. That is, by containing N, the magnetic properties are improved and the Curie temperature is increased. In addition, there is little irreversible iHc decrease after high temperature storage.

Although Zr was used in the samples shown in Table 1, Hf, N
Even when using at least one element selected from the group consisting of b, Ta, W, Mo, Ti, V and Cr,
Results similar to the samples shown in Table 1 were obtained.

[0059]

[Effects of the Invention] The permanent magnet material of the present invention has a high Curie temperature because it contains N, has excellent thermal stability, and can obtain high saturation magnetization.

[0060] Since the inclusion of Cu and M creates a two-phase separated precipitation hardening magnet, pinning sites exist within the crystal grains, suppressing deterioration of magnetic properties due to surface defects generated during pulverization. It will be done. Therefore, a high coercive force can be obtained even when applied to a resin-bonded type bonded magnet in which surface defects of magnet particles cannot be improved.

Furthermore, since it is possible to suppress deterioration of magnetic properties due to oxidation of the particle surface when used in a high temperature environment, it is possible to effectively utilize the improvement in the Curie temperature due to N addition.

Furthermore, since it is a pinning type magnet,
Even if the diameter of the magnet particles is increased in order to obtain high oxidation resistance, the coercive force does not decrease.

Claims (5)

[Claims] Claim 1: Sm: 5 to 15 atomic %, Cu: 1 to 1 atomic %
7 atomic%, M (where M is Zr, Hf, Nb, Ta
, W, Mo, Ti, V and Cr. ) and 0.5 to 25 at% of N, with the balance being Fe.
, or Fe and Co, with F in the remainder
A permanent magnet material having an e content of 20 at % or more and being a two-phase separation precipitation hardening magnet. 2. A method for producing the permanent magnet material according to claim 1, wherein the base metal is subjected to an aging treatment to obtain two-phase separated magnet particles, and the two-phase separated magnet particles are subjected to an aging treatment in a nitrogen atmosphere. 1. A method for producing a permanent magnet material, comprising the step of heat-treating the material. 3. A bonded magnet comprising particles of the permanent magnet material according to claim 1 and a binder. 4. The bonded magnet according to claim 3, wherein the binder is a resin. 5. The bonded magnet according to claim 3, wherein the particles of the permanent magnet material have an average particle diameter of 20 μm or more.