DE60317460T2 - RARE TERMINAL PERMANENT MAGNET ON R-T-B BASE - Google Patents

Description

Technical area

The The present invention relates to a rare earth permanent magnet of the R-T-B system which is referred to as Main components R (where R represents one or more rare earth elements, under the condition that the rare earth elements include Y), T (where T is at least one transition metal element representing essentially Fe or Fe and Co) and B contains (boron).

State of the art

Under The rare earth permanent magnet has a need for a rare earth permanent magnet from the R-T-B system due to its magnetic properties excellent and its main component Nd abound as a source is available and relatively inexpensive, year by year gone up.

Research and development focused on improving the magnetic properties of the RTB system rare earth permanent magnet are well advanced. For example, the Japanese Patent Laid-Open Publication No. 1-219143 in that the addition of 0.02 to 0.5% by weight of Cu as well as the heat treatment conditions improves the magnetic properties of the RTB system rare earth permanent magnet. That in the Japanese Patent Laid-Open Publication No. 1-219143 However, described method is not sufficient to first-class magnetic properties that are required for a high-performance magnet, such. As a high coercive force (HcJ) and a high remanent magnetic flux density (Br) to obtain.

The obtained by sintering magnetic properties of a rare earth permanent magnet from the R-T-B system from the sintering temperature. On the other hand, it is difficult to Heating temperature over to match all parts of a sintering furnace on an industrial scale. For one Rare earth permanent magnet of the R-T-B system, it is therefore necessary the desired get magnetic properties, even if the sintering temperature changes. One Temperature range in which the desired magnetic properties can be obtained is referred to herein as a suitable sintering temperature range.

Around a high performance rare earth permanent magnet from the R-T-B system It is necessary to obtain those contained in the alloys To reduce the amount of oxygen. If the ones contained in the alloys Oxygen level is reduced, but is likely to occur abnormal grain size growth in the sintering process, resulting in a reduction of the rectangular behavior (squareness) leads. This one touches therefore, that oxides by that contained in the alloys Oxygen are formed which inhibit grain size growth.

As a means for improving the magnetic properties, therefore, a method of adding a new element to a RTB rare earth permanent magnet containing Cu was investigated. The Japanese Patent Laid-Open Publication No. 2000-234151 discloses the addition of Zr and / or Cr to obtain a high coercive force and a high residual magnetic flux density.

Also the Japanese Patent Laid-Open Publication No. 2002-75717 discloses a method for uniformly dispersing a ZrB fine compound, NbB compound or HfB compound (hereinafter referred to as MB compound) into an RTB system rare earth permanent magnet containing Zr, Nb or Hf and Co, Al and Cu followed by precipitation so that grain size growth is inhibited in a sintering process and the magnetic properties and the suitable sintering temperature range are improved.

According to the Japanese Patent Laid-Open Publication No. 2002-75717 For example, the appropriate sintering temperature range is extended by dispersion and precipitation of the MB compound. However, in Example 3-1 described in the above publication, the suitable sintering temperature range is narrow, namely, approximately 20 ° C. Accordingly, in order to obtain first-class magnetic properties using a mass-production furnace or the like, it is desirable to further expand the suitable sintering temperature range. Moreover, in order to obtain a sufficiently wide suitable sintering temperature range, it is effective to increase the addition amount of Zr. However, as the addition amount of Zr increases, the remanent magnetic flux density decreases, so that first-class magnetic properties of interest can not be obtained.

Kim A.S. et al. (IEE Trans. On Magnetics, US, Vol. 33, No. 5, Part 2, P. 3823/5) discusses the microstructure of Zr-containing Nd (Dy) FeB alloys. Of the Effect of different Zr contents on the coercive force was examined to determine the optimal Zr level.

Pollard R.J. et al. (IEEE Trans On Magnetics, US, Vol. 24, No. 2, p. 1626/8) refers to the effect of Zr additions on the microstructural and magnetic properties of NdFeB-based magnets.

Benesicar et al. (Journal of magnetism and magnetic materials, Elsevier Sc. Publ., NL, Vol. 104-107, Part 2, pp. 1175/8) discusses the influence of ZrO ₂ addition on the microstructure and magnetic properties of NdDyFeB magnets ,

It is therefore an object of the invention, a Rare earth permanent magnet from the R-T-B system, which inhibits grain size growth allows while the decline the magnetic properties is kept to a minimum, and it too allows to further improve the suitable sintering temperature range.

Disclosure of the invention

The present inventors have found that when a product rich in Zr is in an R ₂ T ₁₄ B phase constituting the main phase of an RTB system rare earth permanent magnet, the permanent magnet is suitable for increasing the grain size while minimizing the decrease in magnetic properties, and is capable of improving the proper sintering temperature range. That is, the present invention therefore provides an RTB system rare earth permanent magnet which is a sintered body composed of 28 to 33% by weight of R, 0.5 to 1.5% by weight of B, 0.03 to 0.3 wt.% Al, 0.03 to 0.3 wt.% Cu, 0.05 to 0.2 wt.% Zr, 0.1 to 4 wt.% Co, and balance Fe and unavoidable impurities, wherein the sintered body comprises:
a major phase consisting of an R ₂ T ₁₄ B phase, wherein R represents one or more rare earth element (s), with the condition that the rare earth elements include Y, and T represents one or more transition metal elements that are Fe or Fe and Co include; and a grain boundary phase containing a larger amount of R than the main phase, wherein in said R ₂ T ₁₄ B phase there is a Zr-rich product having a length of several hundred nm and a width between a few nm and 15 nm ,

In the rare earth permanent magnet according to the invention from the R-T-B system For example, the product rich in Zr has a flat or acicular shape on.

In the RTB system rare earth permanent magnet of the present invention, the amount of oxygen contained in the above sintered body is preferably 2000 ppm or less. This is because the effects obtained by the presence of the Zr-rich product in the R ₂ T ₁₄ B phase, such as. As the inhibition of the grain size growth or the extension of the suitable sintering temperature range, become significant when the amount of oxygen contained in the sintered body, 2000 ppm or less.

In the rare earth permanent magnet according to the invention of the R-T-B system, the sintered body preferably has a composition from 28 to 33% by weight R, from 0.5 to 1.5% by weight B, from 0.03 to 0.3% by weight Al, 0.03 to 0.3 wt% Cu, 0.05 to 0.2 wt% Zr, 0.1 to 4 wt% Co and the balance is essentially Fe.

In the rare earth permanent magnet according to the invention Of the R-T-B system, Zr is particularly preferable within a range between 0.1 and 0.15 wt .-% in the sintered body.

Brief description of the drawings

1 is a table showing the combinations of low R alloys and high R alloys used in Embodiment 1 and the compositions of the obtained permanent magnets;

2 Fig. 12 is a table showing the magnetic properties of the permanent magnets obtained in Embodiment 1;

3 Fig. 12 is a graph showing the relationship between the amount of the additive element M (Zr or Ti) and the residual magnetic flux density (Br) of the respective permanent magnets obtained in Embodiment 1;

4 Fig. 16 is a graph showing the relationship between the amount of the additive element M (Zr or Ti) and the coercive force (HcJ) of the respective permanent magnets obtained in Embodiment 1;

5 Fig. 12 is a graph showing the relationship between the amount of the additive element M (Zr or Ti) and the rectangular behavior (Hk / HcJ) of the respective permanent magnets obtained in Embodiment 1;

6 is a TEM (Transmission Electron Microscope) image of a sample (containing 0.10 wt% Zr) of Example 1;

7A Fig. 12 is a graph showing an EDS (Energy Dispersive X-ray Fluorescence Spectrometer) profile of a product existing in the sample (containing 0.10 wt% Zr) of Example 1;

7B Figure ₃ is a graph showing an EDS profile of the R ₂ T ₁₄ B phase of the sample (containing 0.10 wt% Zr) of Example 1;

8th is a high resolution TEM image of the sample (containing 0.10 wt% Zr) of Example 1;

9 is a TEM image of the sample (containing 0.10 wt% Zr) of Example 1;

10 is another TEM image of the sample (containing 0.10 wt% Zr) of Example 1;

11A is a photograph (lower) showing the Zr assignment results of the sample (containing 0.10 wt% Zr) of Example 1 by an EPMA (Electron Micro Analyzer) and a photograph (top) showing a composition image in the same region as the Zr Allocation results (lower) shows;

11B Fig. 15 is a photograph (lower) showing the Zr assignment results of a sample (containing 0.10 wt% Zr) of Comparative Example 2 by an EPMA, and a photograph (upper) showing a composition image of the same region as Zr; Assignment results (lower) shows;

12 Fig. 14 is a table showing the magnetic properties of the permanent magnets obtained in Embodiment 2;

13 Fig. 12 is a graph showing the relationship between the sintering temperature and the residual magnetic flux density (Br) in Embodiment 2;

14 Fig. 12 is a graph showing the relationship between the sintering temperature and the coercive force (HcJ) in Embodiment 2;

15 Fig. 12 is a graph showing the relationship between the sintering temperature and the rectangular behavior (Hk / HcJ) in Embodiment 2;

16 Fig. 12 is a graph showing the correspondence between the residual magnetic flux density (Br) and the rectangular behavior (Hk / HcJ) at the respective sintering temperatures in Embodiment 2;

17 Fig. 14 is a table showing the combinations of low R alloys and high R alloys used in Embodiment 3, showing the compositions for the obtained permanent magnets;

18 Fig. 10 is a table showing the magnetic properties of the permanent magnets obtained in Embodiment 3;

19 Fig. 12 is a table showing the combinations of low R alloys and high R alloys used in Embodiment 4 and the compositions of the obtained permanent magnets;

20 is a table showing the magnetic properties of the permanent magnets obtained in Embodiment 4.

Best embodiment of the invention

The Embodiments of the invention are described below.

microstructure

The RTB system rare earth permanent magnet according to the present invention comprises a sintered body composed of 28 to 33% by weight of R, 0.5 to 1.5% by weight of B, 0.03 to 0.3% by weight of Al, 0.03 to 0.3 wt .-% Cu, 0.05 to 0.2 wt .-% Zr, 0.1 to 4 wt .-% Co and the remainder substantially Fe and unavoidable impurities, wherein the sintered body comprising:
a major phase consisting of an R ₂ T ₁₄ B phase, wherein R represents one or more rare earth element (s), with the condition that the rare earth elements include Y, and T represents one or more transition metal elements which are Fe or Fe and Co include; and a grain boundary phase containing a larger amount of R than the main phase. The present invention is characterized in that a product rich in Zr and having a length of several hundreds nm and a width between several nm and 15 nm exists in the R ₂ T ₁₄ B phase.

The RTB system rare earth permanent magnet containing this product is capable of inhibiting grain size growth while minimizing a decrease in magnetic properties and extending the proper sintering temperature range. This product must be present in the R ₂ T ₁₄ B phase, but it is not required to be present in all R ₂ T ₁₄ B phases. This product may also be in the grain boundary phase. However, when the Zr-rich product is only in the grain boundary phase, the effects of the present invention are not obtained. In the RTB rare earth permanent magnet, Ti is conventionally known as an additive element which forms the product in the R ₂ T ₁₄ B phase (for example, Appl. Phys. 69 (1991), 6055). The present inventors have found that the formation of the product in the R ₂ T ₁₄ B phase is effective by the addition of Zr or Ti for the extension of a suitable sintering temperature range. When Zr is added, it causes almost no decrease in magnetic properties and, in particular, no decrease in remanent magnetic flux density (Br) even when Zr is added in an amount necessary for obtaining an effect such as the extension of a suitable sintering temperature range. On the other hand, when Ti is added, the remanent magnetic flux density (Br) is significantly reduced when this element is added in an amount necessary for obtaining an effect such as the extension of a suitable sintering temperature range, and it is therefore clear that the Addition of Ti is not preferred in practice. When the composition of the product is rich in Zr, it is possible to consistently produce permanent magnets having superior magnetic properties in a wide suitable sintering temperature range, as mentioned above.

The present inventors have confirmed that there are some requirements for the manufacturing process to enable the product rich in Zr to be in the R ₂ T ₁₄ B phase. The procedure of the manufacturing method of the permanent magnet of the invention will be described later. The requirements for the Zr-rich product to be in the R ₂ T ₁₄ B phase are described below.

There are two methods for producing an RTB system rare earth permanent magnet: a method using as the starting alloy a single alloy having a desired composition (hereinafter referred to as a single method) and a method using as starting alloys a variety of alloys having different compositions used (hereinafter referred to as mixing method). In the mixing method, alloys containing an R ₂ T ₁₄ B phase as a main component (low-R alloys) and alloys containing a larger amount of R than the low-R alloys (alloys having much R) are usually used as starting alloys used.

The present inventors have added Zr to either low R alloys or high R alloys to obtain a rare earth RTB system magnet. As a result, the present inventors confirmed that the product rich in Zr is in the R ₂ T ₁₄ B phase when Zr is added to low-R alloys to produce a permanent magnet. The present inventors also confirmed that the Zr rich product is not in the R ₂ T ₁₄ B phase when Zr is added to high R alloys.

Even in the case where Zr is added to low-R alloys, and when the Zr-rich product was in the R ₂ T ₁₄ B phase in the low-R alloy, it was not confirmed that the Zr-rich Product was present after a sintering step in the R ₂ T ₁₄ B phase although it existed in an R-rich phase (grain boundary phase) located at a triple point in the microstructure of the sintered bodies. Accordingly, in order to allow the Zr-rich product to be in the R ₂ T ₁₄ B phase of the RTB rare earth permanent magnet, it is important that the Zr-rich product not be in the R ₂ T ₁₄ B phase present in the mother alloy stage.

This finding should be taken into account in a process for producing mother alloys. If the low-R alloys are made by the strip casting method, the peripheral speed of the chill roll must be controlled. If the peripheral speed of the chill roll is too low, this results in precipitation of α-Fe, and the Zr-rich product is generated in the R ₂ T ₁₄ B phase of the low-R alloys. As a result of researches by the present inventors, it has been found that when the peripheral speed of the chill roll is within a range of 1.0 to 1.8 m / s, low R alloys can be obtained in which the Zr rich product is not in the R ₂ T ₁₄ B phase is present. By using the obtained low-R alloys, a permanent magnet having excellent magnetic properties can be obtained.

Even in the case where low R alloys are obtained in which the Zr rich product is not in the R ₂ T ₁₄ B phase, it is not desired in the present invention that the low R alloys obtained Heat treatment are subjected and then used as mother alloys. This is because the Zr-rich product is produced in the R ₂ T ₁₄ B phase of the low-R alloys as a result of the heat treatment in a temperature range (approximately 700 ° C. or higher) in which the microstructure of the low-alloy alloys R can be modified.

Chemical composition

When next will be the desired Composition of the rare earth permanent magnet according to the invention from the R-T-B system. The term chemical composition refers to a chemical Composition obtained after sintering.

Of the rare-earth permanent magnet according to the invention contains From 28 to 33% by weight of R.

The term R as used herein denotes one or more rare earth elements selected from a group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu and Y. When the amount of R is less than 28% by weight, be carries, the R ₂ T ₁₄ B ₁ phase is not sufficiently generated as the main phase of the rare earth permanent magnet. Consequently, α-Fe or the like is deposited with soft magnetism and the coercive force is significantly reduced. On the other hand, when the amount of R exceeds 35% by weight, the volume fraction of R ₂ T ₁₄ B phase as the main phase and the residual magnetic flux density decrease. In addition, R reacts with oxygen and the oxygen content thereby increases when the amount of R exceeds 33% by weight. As the oxygen content increases, the R-rich phase effective for generating the coercive force decreases, resulting in a decrease in coercive force. The amount of R is therefore set between 28 and 33 wt .-%. The amount of R is preferably between 29 and 32 wt .-%.

There Nd as source in abundance available and relatively inexpensive For example, it is preferable to use Nd as the main component of R. Since the presence of Dy increases the anisotropic magnetic field it about it in addition, effectively containing Dy for improving the coercive force is. As a result, it is desirable Nd and Dy for R and select to adjust the total amount of Nd and Dy between 28 and 33% by weight. Furthermore For example, the Dy amount in the above range is preferably between 0.1 and 8% by weight. It is desirable that the Dy amount, depending on whether the remanent magnetic flux density or the coercive force is more important, arbitrary within the above Range is set. That is, if a high remanent magnetic flux density is required, the Dy amount is preferably adjusted between 0.1 and 3.5 wt .-%. When a high coercive force is required, it is preferably adjusted between 3.5 and 8 wt .-%.

Of Further contains the rare earth permanent magnet 0.5 according to the invention to 1.5% by weight boron (B). When the amount of B is less than 0.5% by weight is, high coercive force can not be obtained. If the amount of B, however, exceeds 1.5% by weight, probably decreases the remanent magnetic flux density. consequently the upper limit is set at 1.5% by weight. The amount of boron is preferably between 0.8 and 1.2 wt .-%.

Of the rare-earth permanent magnet according to the invention From the R-T-B system, Al and Cu can be in a range between 0.03 and Contain 0.3 wt .-%. The content of Al and Cu in the above range may be the permanent magnet obtained a high coercive force, a strong Corrosion resistance and an improved temperature stability of the magnetic properties to lend. The additive amount of Al is preferably between 0.05 and 0.25% by weight. The amount of additive Cu is preferably between 0.03 and 0.15 wt .-% and particularly preferably between 0.03 and 0.08 Wt .-%.

In order to allow the Zr-rich product to be in the R ₂ T ₁₄ B phase, the RTB system rare earth permanent magnet of the present invention contains Zr within a range of 0.05 to 0.2 wt%. When the oxygen content is lowered to improve the magnetic properties of the RTB system rare earth permanent magnet, Zr exerts an inhibiting effect on the abnormal grain size growth in a sintering process, thereby making the microstructure of the sintered body uniform and fine. Thus, when the amount of oxygen is small, Zr completely exerts its effect. The Zr amount is preferably between 0.1 and 0.15 wt .-%.

Of the rare-earth permanent magnet according to the invention from the R-T-B system 2000 ppm or less oxygen. If he has a large amount of oxygen contains assumes the oxide phase, which is a non-magnetic component, whereby the magnetic properties decrease. The contained in the sintered body Oxygen amount is therefore in the present invention to 2000 ppm or less, preferably 1500 ppm or less, and especially preferably 1000 ppm or less. When the amount of oxygen while being simply reduced, the oxide phase takes an inhibitory action on the grain size growth so that the grain size growth in a method for obtaining a complete increase in density during the Sintering occurs in a simple manner. In the present invention contains Therefore, the rare earth permanent magnet of the R-T-B system has some Amount of Zr that has an inhibitory effect on the abnormal grain size growth in the sintering process.

Of the rare-earth permanent magnet according to the invention from the R-T-B system Co in an amount of 0.1 to 4 wt .-%, preferably between 0.1 and 2.0% by weight, and more preferably between 0.3 and 1.0% by weight. Co forms a phase similar to that of Fe. Co has an effect on the improvement of the Curie temperature and the corrosion resistance the grain boundary phase on.

production method

When next is a suitable method for producing the rare earth permanent magnet according to the invention from the R-T-B system.

Embodiments of the present invention show a method for producing a rare earth permanent magnet using alloys (low R alloys) containing an R ₂ T ₁₄ B phase as the main phase and other alloys (high R alloys) containing a higher amount R as the alloys with little R contain.

The starting material is first subjected to a strip casting in a vacuum or an inert gas atmosphere, or preferably an Ar atmosphere, so that the low R alloys and the high R alloys are obtained. As mentioned above, it is necessary to pay special attention to the ribbons obtained, particularly the ribbons of the low R alloys, such that a Zr rich product is not produced in the R ₂ T ₁₄ B phase. Specifically, the peripheral speed of the cooling roll is set within a range between 1.0 and 1.8 m / s. The preferred peripheral speed of the chill roll is between 1.2 and 1.5 m / s.

For the present invention, it is important that a Zr-rich product not in the R ₂ T ₁₄ B phase for the duration of obtaining the low R alloys with the R ₂ T ₁₄ B phase in which the Zr rich Product is not present until the sintering process described later. In other words, it is important in the present invention to maintain the shape of the above R ₂ T ₁₄ B phase. For example, it is preferable not to conduct a heat treatment in which the low-R alloys are heated and maintained at 700 ° C. or higher before the grinding processes that start with the hydrogen milling. This point will be further described later in Embodiment 1.

The feature of the invention is that Zr is added to low R alloys. As explained above under the section "Microstructure", the reason is that the Zr-rich product in the R ₂ T ₁₄ B phase of the rare earth permanent magnet of the RTB system can be allowed to be added by addition of Zr Low R alloys are present which do not contain Zr rich products in their R ₂ T ₁₄ B phase. The low-R alloys contain Cu and Al in addition to the rare earth elements Fe, Co, and B. In addition, the high-R alloys may also contain Cu and Al in addition to the rare earth elements Fe, Co, and B.

To the production of alloys with low R and alloys with a lot of R, these main alloys are separated or together ground. The milling step includes a milling process and a pulverization process. First For example, each of the main alloys will approximate to a particle size of approximately one hundred microns ground. The milling is preferably carried out in an inert gas atmosphere using a stamping plant, a jaw crusher, a brown mill, etc. carried out. To improve coarse grindability, it is effective to grind after the absorption of hydrogen. On the other hand it is too possible, Release hydrogen after it has been absorbed, and then to carry out the grinding.

To performing the grinding leads the Procedure for a pulverization process. In the pulverization process becomes mainly one jet mill used and the ground powder having a particle size of approximately several hundred microns to a mean particle size between 3 and 5 μm pulverized. The jet mill is a process that releases a high-pressure inert gas (eg, nitrogen gas) from a narrow nozzle, so that high velocity gas flow is generated, which accelerates the ground powder and she to do so brings to meet one another, to hit the target or the wall of the container, so that the powders are pulverized.

If the alloys with little R and the alloys with a lot of R in that The pulverization process will be pulverized separately Low R alloy powder with the powdered alloy powder mixed with a lot of R in a nitrogen atmosphere. The mixed weight ratio of Alloy powder with little R to the alloy powder with a lot of R can be approximate between 80:20 and 97: 3. Also in the case where the alloys powdered with little R together with the alloys with a lot of R can be, the mixing weight ratio is approximately between 80:20 and 97: 3 are. When about 0.01 to 0.3 wt .-% of additive, such as z. As zinc stearate, during the Pulverization process can be added, a fine powder while compacting, which is well oriented.

Then be the mixed powder containing the alloy powder with little R and the alloy powder with a lot of R, into a tool equipped with electromagnets filled and then compressed in a magnetic field in a state in which their crystallographic axes by applying a magnetic field are oriented.

This densification can be carried out by applying a pressure of about 0.7 to 1.5 t / cm ² in a magnetic field of 12.0 to 17.0 kOe.

After the mixed powders have been compacted in the magnetic field, the compacted body is sintered in a vacuum or an inert gas atmosphere. The sintering temperature must vary depending on various conditions, such. For example, the composition, the milling method, the difference between the particle size and the particle size distribution may be set, however, the sintering may be carried out at 1000 ° C to 1100 ° C for about 1 to 5 hours. In the present invention, the Zr-rich product is produced in the R ₂ T ₁₄ B phase in this sintering process. The production mechanism after sintering of the Zr-rich product, which is not present at the low-R alloy, is unknown, but there is the possibility that Zr in the R ₂ T ₁₄ B phase may be in the alloy state with little R is dissolved during the sintering process could be deposited therein.

To Completion of sintering, the obtained sintered body of a Be subjected to aging treatment. The aging treatment is for regulation the coercive force important. If the aging treatment in two Steps performed it is effective to keep the sintered body at about for a while 800 ° C and about 600 ° C to keep. If a heat treatment at about 800 ° C after completion of sintering, the coercive force decreases to. As a result, it is particularly effective in the mixing process. If a heat treatment at about 600 ° C carried out In addition, the coercive force increases significantly. If the aging treatment is performed in a single step, it is therefore appropriate to carry it out at about 600 ° C.

embodiments

embodiment 1

One Rare earth permanent magnet of the R-T-B system was replaced by the following Manufacturing process produced.

(1) nut alloys

Nut alloys (tapes) with the in 1 The compositions and thicknesses shown were made by the strip casting process. The roll peripheral speed for the low R alloys was set to 1.5 m / s and for the high R alloys to 0.6 m / s. The roller peripheral speed for the in 1 However, low R alloys shown in Comparative Example 3 were set at 0.6 m / s. The thickness of the alloys was an average obtained by measuring the thicknesses of 50 tapes. It was confirmed that a Zr-rich product (hereinafter referred to as intraphase product) does not exist in the R ₂ T ₁₄ B phase of the in 1 However, the intraphase product was found in the R ₂ T ₁₄ B phase of the low R alloys of Comparative Example 3 shown in the same figure.

(2) Hydrogen Milling Process

One Hydrogen grinding was carried out in which after absorption hydrogen at room temperature dehydration at 600 ° C for 1 hour in an Ar atmosphere was carried out.

to Control of in the sintered body contained oxygen amount to 2000 ppm or less, to first-class To obtain magnetic properties, the atmosphere in the present experiments at an oxygen concentration of less than 100 ppm in all processes of hydrotreating (recovery after the grinding process) until sintering (previously in the sintering furnace) controlled.

(3) mixing and milling process

in the Generally, a two-stage grinding is performed a grinding method and a pulverization method. In the however, the grinding process is omitted here.

Before the pulverization process was carried out, 0.05% by weight of zinc stearate was added. Thereafter, using a Nauta mixer, the low-R alloys with the high-R alloys of Example 1 and Comparative Examples 1 to 3 described in U.S. Pat 1 are shown, stirred for 30 minutes. In Example 1 and Comparative Examples 1 to 3, the mixing ratio of the low R alloys to the high R alloys was 90:10.

Subsequently was the mixture of a pulverization with a jet mill on a mean particle size of 4.8 to 5.1 μm subjected.

(4) Compaction process

The obtained fine powders were compacted in a magnetic field of 15.0 kOe by applying a pressure of 1.2 t / cm ² , so that a compacted body was obtained.

(5) sintering and aging processes

Of the obtained compacted body was at 1070 ° C for 4 hours followed in a vacuum atmosphere sintered by quenching. Subsequently, the obtained sintered body was a subjected to two-stage aging treatment, resulting from treatments at 800 ° C for 1 hour and 550 ° C for 2.5 hours (each in an Ar atmosphere) duration.

The magnetic properties of the resulting permanent magnets were measured with a BH tracer. The results are in 2 to 5 shown. In 2 to 5 Br represents the remanent magnetic flux density, HcJ represents the coercive force, and "Hk / HcJ" denotes the rectangular behavior. The rectangular behavior (Hk / HcJ) is an index of magnetic performance and represents the angular degree in the second quadrant of the magnetic hysteresis loop. Further, Hk denotes the external magnetic field strength obtained when the magnetic flux density is 90 ° C of the remanent magnetic flux density in the second quadrant of the magnetic hysteresis loop. In 2 to 5 For example, a permanent magnet in which an intraphase product was found has a circle (O), and a permanent magnet in which the product was not found is marked with a cross (X). The presence or absence of an intraphase product was confirmed on the basis of a study with a TEM (Transmission Electron Microscope, JEM-3010, manufactured by Japan Electron Optics Laboratory Co., Ld.). The sample for examination was obtained by an ion milling method, and the C plane of the R ₂ T ₁₄ B phase was examined. It is mentioned that the chemical compositions of the obtained sintered bodies in the column "Composition of the sintered body" in FIG 1 are shown. Further, no intrafase products were found in Comparative Example 3, but a Zr-rich product was found in the grain boundary phase.

Out 2 and 5 It can be seen that in rare earth permanent magnets of the RTB system in which an intraphase product was found (Example 1 and Comparative Example 1), the abnormal grain growth was inhibited and the rectangular behavior (Hk / HcJ) by adding only a small amount of an additive element M (Zr or Ti) was improved. When Ti has been selected as additive element M, as in 3 However, the remanent magnetic flux density (Br) decreased significantly. Even in the case where no intraprospase products were found in the rare earth permanent magnets of the RTB system (Comparative Examples 2 and 3), the rectangular behavior (Hk / HcJ) was increased by adding a large amount of Zr, such as 0.2 wt. %, improved (s. 5 ). However, a decrease in the remanent magnetic flux density (Br) was still significant (s. 3 ). As described above, a rare-earth permanent magnet of the RTB system in which the presence of an intraphase product has been detected enables high rectangular performance (Hk / HcJ) to be obtained while inhibiting the increase in the residual magnetic flux density (Br).

In Comparative Example 3, in which an intraphase product was found in the R ₂ T ₁₄ B phase at the low-R alloy stage, the reason why no intraphase product was present in the RTB rare earth permanent magnet is presumably the following: A Zr-rich product produced in the R ₂ T ₁₄ B phase (intraphase product) at the stage of low R alloys has grown and become extremely large. It is believed that although this product has been subjected to the hydrogen milling process, this has not led to volume expansion. This is explained by the fact that a crack is generated at the interface between the R ₂ T ₁₄ B phase and the product during the hydrogen grinding process. When the alloys are subjected to a grinding process in this state, the product is separated from the R ₂ T ₁₄ B phase. As a consequence, the product is not contained in the R ₂ T ₁₄ B phase but is present independently of the R ₂ T ₁₄ B phase. Accordingly, in the rare earth permanent magnet of the RTB system of Comparative Example 3, it is considered that the Zr-rich product is only in the grain boundary phase even after the sintering process.

An RTB system rare earth permanent magnet containing 0.10 wt% Zr in Example 1 was examined by TEM in the same manner as described above. The examination results are in 6 to 8th shown. 6 is a TEM image of a sample containing 0.10 wt% Zr. 7 is a set of EDS (Energy Dispersive X-ray Fluorescence Spectrometer) profiles of a product present in the sample and in the R ₂ T ₁₄ B phase of the sample. 8th is a high-resolution TEM image of the sample.

As in 6 is shown, an intraphase product with a large axial ratio can be found in the R ₂ T ₁₄ B phase. This product has a flat or acicular shape. 6 is a photograph obtained by examining the cross section of the sample, and it is therefore difficult to determine from such an examination whether the shape is flat or needle-shaped. Taking into account the results from the study of the other samples and 8th For example, the intraphase product has a length of several hundred nm and a width between a few nm and 15 nm. The detailed chemical composition of this intraphase product is not certain, however 7A it can be confirmed that the intraphase product is at least rich in Zr. Moreover, as a result of examining other samples that differ from the large aspect ratio intraphase product, undefined or round products of intrafase can be found, as in 9 and 10 will be shown. As a result of examination of 20 crystal grains (R ₂ T ₁₄ B phase) of Example 1, intraphase products were found in 6 crystal grains thereof. In contrast, in Comparative Example 2, no intrapatase products were found in any of the 20 crystal grains (R ₂ T ₁₄ B phase).

The bottom picture of 11A show the Zr assignment results of the sample of Example 1 containing 0.10% by weight of Zr by an EPMA (electron beam microanalyzer). The upper picture of 11A shows a composition image in the same area as in the lower image of FIG 11A Zr assignment results shown. In addition, the lower figure shows 11B the Zr assignment results of a sample of Comparative Example 2 containing 0.10 wt% Zr by an EPMA. The upper picture of 11B shows a composition image in the same area as that in the lower image of FIG 11B Zr assignment results shown.

As can be seen from the results obtained by examination by means of TEM, too 11A It can be seen that an R ₂ T ₁₄ B phase rich in Zr is present in the permanent magnet of Example 1 and that Zr also exists in its grain boundary phase. In contrast, can out 11B It can be understood that such a Zr-rich R ₂ T ₁₄ B phase is not found in the permanent magnet of Comparative Example 2 and that Zr exists only in its grain boundary phase.

embodiment 2

RTB system rare earth permanent magnets were obtained in the same manner as in Embodiment 1 except that the samples each containing 0.10% by weight of the additive element M (Zr or Ti) of the composition of the sintered body were for 4 Hours were sintered within a temperature range between 1010 and 1090 ° C. The magnetic properties of the obtained permanent magnets were measured in the same manner as in Embodiment 1. The results are in 12 shown. In addition, the changes in the magnetic properties due to the changes in the sintering temperature in 13 to 15 shown. In addition, the magnetic properties at each sintering temperature, expressed as a rectangular behavior (Hk / HcJ) to the residual magnetic flux density (Br), are 16 shown.

As in 12 to 16 10, it has been found that first-class magnetic properties are stably obtained in a wide sintering temperature range when an intraphase product is obtained by adding Zr as an additive element M. Specifically, in Example 2 of the present invention, a residual magnetic flux density (Br) of 13.9 kG or greater, a coercive force (HcJ) of 13.0 kOe or greater, and a squareness (Hk / HcJ) of 95% or more in the sintering temperature range be obtained between 1030 and 1090 ° C. When Ti is added as the additive element M, the residual magnetic flux density (Br) decreases (Comparative Example 4). Moreover, when there is no intraphase product, the rectangular behavior (Hk / HcJ) is weak and the suitable sintering temperature range is narrow (Comparative Example 5).

embodiment 3

When setting a roll peripheral speed of 0.6 to 1.8 m / s, four types of low R alloys and two types of R high alloy alloys were used 17 illustrated compositions and thicknesses produced by the strip casting process. Subsequently, four types of RTB system rare earth permanent magnets were used with the in 17 obtained combinations shown. In all Samples A to D, the mixing ratio of the low R alloys to the high R alloys was 90:10. In the 17 Low R alloys and high R alloys were subjected to a hydrogen milling process in the same manner as in Embodiment 1. After completion of the hydrogen milling process, 0.05% by weight of butyl oleate was added. Subsequently, the low R alloys with the high R alloys were placed in the in 17 mixed combinations shown. Thereafter, the mixture was subjected to pulverization by a jet mill to a mean particle size of 4.1 μm. The resulting fine powders were compacted in a magnetic field under the same conditions as in Embodiment 1 followed by sintering at 1010 to 1090 ° C for 4 hours. Subsequently, the obtained sintered body was subjected to a two-stage aging treatment consisting of treatments at 800 ° C for 1 hour and 550 ° C for 2.5 hours. The composition, the amount of oxygen and the amount of nitrogen of the sintered bodies obtained are in 17 shown. In addition, their magnetic properties in 18 shown.

As in 18 is shown, sample A has a remanent magnetic flux density (Br) of 14.0 kG or greater, a coercive force (HcJ) of 13.0 kOe or greater, and a squareness (Hk / HcJ) of 95% or more in the sintering temperature range 1030 and 1070 ° C on.

The Samples B and C, each containing a lower amount of Nd as the sample A, have a remanent magnetic flux density (Br) of 14.0 kG or greater, one Coercive force (HcJ) of 13.5 kOe or greater and a rectangular behavior (Hk / HcJ) of 95% or more in the sintering temperature range between 1030 and 1090 ° C.

The sample D containing a larger amount of Dy than the sample A has a residual magnetic flux density (Br) of 13.5 kG or greater, a Coercive force (HcJ) of 15.5 kOe or greater and a rectangular behavior (Hk / HcJ) of 95% or more in the sintering temperature range between 1030 and 1070 ° C.

When Result of examination of samples sintered at 1050 ° C by TEM Intraphase products were found in all samples. From the above Results can be interpreted that, first-class magnetic Properties consistent in a wide suitable sintering temperature range of 40 ° C or more can be obtained if an intraphase product is present.

embodiment 4

Two types of low R and two types of high R alloys were made by the thin strip casting process. Thereafter, two types of RTB system rare earth permanent magnets having the in 19 obtained combinations shown. In Sample E, the mixing ratio of the low R alloys to the high R alloys was 90:10. On the other hand, the mixing ratio of the low R alloys to the high R alloys in the sample F was 80:20. In the 19 Low R alloys and high R alloys were subjected to a hydrogen milling process in the same manner as in Embodiment 1. After completion of the hydrogen milling process, 0.05% by weight of butyl oleate was added. Thereafter, the low R alloys with the high R alloys using a Nauta mixer were placed in the 19 mixed combinations shown. Subsequently, the mixture was subjected to pulverization with a jet mill to a mean particle size of 4.0 μm. The obtained fine powders were compacted in a magnetic field under the same conditions as in Embodiment 1. Subsequently, in the case of Sample E, the compacted body was sintered at 1070 ° C for 4 hours and in the case of Sample F at 1020 ° C for 4 hours. Thereafter, the obtained sintered bodies of samples E and F were subjected to a two-stage aging treatment consisting of treatments at 800 ° C for 1 hour and 500 ° C for 2.5 hours. The composition, the amount of oxygen and the amount of nitrogen of the respective sintered bodies obtained are in 19 shown. In addition, their magnetic properties in 20 shown. In order to simplify the comparison, the magnetic properties produced in Embodiment 3 are also shown in FIGS 20 shown.

Although the constituent elements fluctuated as in Samples A to F shown, a remanent magnetic flux density (Br) of 13.8 kG or larger, one Coercive force (HcJ) of 13.0 kOe or greater and a rectangular behavior (Hk / HcJ) of 95% or more received.

Industrial Applicability

As described in detail above, there is a Zr-rich product in the R ₂ T ₁₄ B phase, which is the main phase of an RTB rare earth permanent magnet, so that grain size growth can be inhibited while decreasing the magnetic properties a minimum is kept. Since a suitable sintering temperature range of 40 ° C or more can be maintained even by using a large sintering furnace which usually results in unevenness of the heating temperature, according to the present invention, a RTB system rare earth permanent magnet consistent with first-class magnetic properties can be easily obtained.

Claims (4)

RTB system rare earth permanent magnet comprising a sintered body consisting of 28 to 33% by weight of R, 0.5 to 1.5% by weight of B, 0.03 to 0.3% by weight of Al, O. , 03 to 0.3 wt.% Cu, 0.05 to 0.2 wt.% Zr, 0.1 to 4 wt.% Co, and the remainder being substantially Fe and unavoidable impurities, the sintered body having the following comprising: a major phase consisting of an R ₂ T ₁₄ B phase, wherein R represents one or more rare earth elements, with the proviso that the rare earth elements include Y, and T represents one or more transition metal elements, the Fe or Fe and Co include; and a grain boundary phase containing a larger amount of R than the main phase, wherein in said R ₂ T ₁₄ B phase there is a Zr-rich product having a length of several hundred nm and a width between a few nm and 15 nm , Rare earth permanent magnet of R-T-B system according to claim 1, wherein said product has a flat or acicular shape. Rare earth permanent magnet of R-T-B system according to claim 1, wherein the amount of oxygen contained in said sintered body is 2000 ppm or less. Rare earth permanent magnet of R-T-B system according to claim 3, wherein in said sintered body 0.1 to 0.15 wt .-% Zr is included.