JPH01219143A - Sintered permanent magnet material and its production - Google Patents

Abstract

PURPOSE:To obtain a permanent magnet having superior magnetic properties by incorporating Cu to a rare-earth sintered permanent magnet containing Fe-B-rare earths as a basic series and also containing Co and subjecting the above magnet to sintering and then to heat treatment under specific conditions. CONSTITUTION:Powdered raw materials are mixed so that they are formed into a composition consisting of, by atom., 12-17%, in total, of Nd and Pr, 5-14% B, <20% Co, 0.02-0.5% Cu, and the balance Fe, which is pulverized in an inert-gas atmosphere of Ar, etc. The above powdered raw materials are compacted in a magnetic field and the resulting green compact is sintered in a reducing or nonoxidizing atmosphere at 900-1,200 deg.C, and the sintered compact is subjected to heat treatment in vacuum, in an inert-gas atmosphere, or in a reducing atmosphere at 430-600 deg.C for about 5min-40hr. By this method, the sintered permanent magnet having high coercive force, and superior square characteristic in demagnetization curve can be obtained.

Description

[Detailed description of the invention] Industrial field of application The present invention relates to a rare earth sintered permanent magnet based on Fe-B-R and containing Co, and a method for manufacturing the same, in which the magnetic properties are significantly improved by containing Cu. The present invention relates to permanent magnets, sintered permanent magnet materials that have a wide optimum range of heat treatment conditions and extremely high manufacturability, and methods for manufacturing the same.

BACKGROUND TECHNOLOGY The present applicant has previously developed Nd, which does not require expensive Sm or Co.
By using light rare earths, which are rich in resources, mainly including and Pr,
, Fe is the main component, and is a new high 1↓ ability magnet that greatly exceeds the best characteristics of conventional rare earth cobalt magnets.
Special Publication No. 61-34242 to propose B-R series permanent magnets
issue).

In addition, in these magnet materials, a part of Fe was replaced with Co to raise the Curie temperature and to improve the temperature characteristics of the magnet.
No. 3).

Furthermore, in order to obtain stable coercive force in the harsh environments required of today's permanent magnets, such as when used in high-temperature atmospheres or when exposed to demagnetizing fields due to armature reaction when incorporated into motors, etc. Additive element M (=Nb,
(Cr, Mo, W, AI, etc.) (JP-A-59-64733, JP-A-59-132104), and in order to obtain a higher coercive force, some of the Nd and Pr are added with Tb, Dy, etc. (Japanese Unexamined Patent Publication No. 58-141850), permanent magnets whose coercive force is improved by aging treatment (Japanese Unexamined Patent Publication No. 59-21)
No. 7304 and Japanese Unexamined Patent Publication No. 59-218704).

In each of the above permanent magnets, Fe-Co-B containing Co
-R-based magnets improve the temperature characteristics and corrosion resistance of the magnet, but in order to obtain high coercive force, the optimum temperature range of heat treatment conditions is narrow and it is difficult to maintain this range, resulting in reduced coercive force and demagnetization. This had the effect of reducing curve squareness.

In addition, the additive element M and the heavy rare earth elements must be used in large quantities in order to obtain a high coercive force, and although the coercive force increases, the residual magnetic flux density Br decreases accordingly, and a high energy product is not obtained. There was a problem that could not be resolved.

Purpose of the Invention The present invention provides a permanent magnet material that exhibits high magnetic properties of 40MGOe class in Fe-Co-B-R permanent magnet materials containing Co, and has high coercive force and excellent squareness. The present invention aims to provide a manufacturing method for obtaining the permanent magnet with good productivity.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has made various studies on the composition of permanent magnet materials, and has found that Fe-Co-B-
Fe-Co- based on R system and containing a very small amount of Cu
Molding a B-R-Cu alloy powder with a certain composition range,
By sintering this and further heat-treating it at a specific temperature, it is possible to obtain a permanent magnet material with significantly improved coercive force and squareness of the demagnetization curve without any decrease in magnetic properties, especially residual magnetic flux density. This knowledge led to the completion of this invention.

The total of Nd and Pr in atomic ratio is 12 to 17 at%, B5 to
14at%, Co 20at% or less, Cu 0.02~
It is a sintered permanent magnet material characterized by consisting of 0.5 at%, balance Fe and unavoidable impurities, and an alloy powder having the above composition with an average particle size of 0.5 pm to 10 pm is molded, and non-oxidizing or This is a method for producing a sintered permanent magnet material, which is characterized by sintering at a temperature of 900 to 1200°C in a reducing atmosphere, and after sintering, heat treating at a temperature of 430 to 600°C.

Effects of the invention Fe-Co-B-R-Cu permanent magnets are Fe-B-R
As a system-based compound magnet, it exhibits a crystalline X-ray analysis pattern that is completely different from conventional amorphous thin films or ultra-quenched ribbons, and has a tetragonal crystal structure as its main phase.

The inclusion of a very small amount of Cu, which is a feature of this invention, eases the heat treatment conditions for the Fe-Co-B-R permanent magnet material containing Co, and allows it to reach 13k without reducing the residual magnetic flux density.
A high coercive force of Oe or more and excellent squareness of the demagnetization curve can be obtained, and as a result, a high maximum energy product of 25 MGOe or more can be obtained.

In this invention, Cu is a conventional Fe-containing Co-containing material.
It becomes possible to relax the severe heat treatment conditions required in the BR system, that is, the narrow optimum temperature range and fast cooling rate conditions, and to select a wide optimum temperature and free cooling rate.

These are extremely effective in heat treating large magnets and in preventing cracks in magnets during cooling after heat treatment.

Reason for limiting the permanent magnet composition The rare earth element R increases the coercive force of the permanent magnet to 12 kOe or more,
12 to make the maximum energy product more than 25MGOe
It is necessary to add more than 17 at%, and when it exceeds 17 at%, Br decreases and (BH) ma
In order to reduce
t%.

Note that in water-based permanent magnets, Nd and Pr have almost the same functions as elements, and either can be contained alone, but due to the raw materials, if Nd is added, Pr will always be contained at a few percent. , Pr may be appropriately added depending on the raw material.

In addition, a portion of Nd and Pr may be replaced with heavy rare earth elements such as Dy and Tb at 0.2 at% to 3. By replacing Oat%, even higher coercive force can be obtained.

Furthermore, among the impurities contained in rare earth elements, La<
Ce and the like may be contained in a small amount, for example, in a range of 5 at % or less based on the total rare earth elements.

In water-based permanent magnet materials, Co is effective in improving oxidation resistance even in a small amount of, for example, lat%, and is also effective in increasing Tc.
An alloy with an arbitrary Tc of .degree. C. is obtained.

Coff1 is added to increase the iHc of the permanent magnet to 12 kOe or more, but in consideration of Tc improvement effect and cost, the content is set to 20 at% or less. As the Co component, R-Co alloy or the like can also be added. The preferred range of Coi is 1 to 8 at%.

B needs to be added in an amount of 5 at% or more in order to make the coercive force of the permanent magnet 10 kOe or more, and as it is added, 1II
Although c increases, in order to make (BH)max 20 MGOe or more, it needs to be 14 at% or less.

In this invention, Cu allows relaxation of heat treatment conditions in Fe-Co-B-R permanent magnets without reducing other magnetic properties, such as residual magnetic flux density B and maximum energy product (BH) max. As a result, the coercive force is increased and the squareness of the demagnetization curve is improved, (BH
) It is added because it makes it possible to improve max.

As shown in Figure 1, the change in the amount of Cu and the obtained magnetic properties,
Even when added in a very small amount, Cu significantly improves the magnetic properties of a Fe-BR magnet containing CO.

In this invention, the amount of Cu needs to be added at least 0.01 at% to improve magnetic properties, but 0.5
If it exceeds at%, the sintered density will decrease, so the upper limit is 0.
It is set to 5at%. The preferred range is 0.03at% to 0.03at%.
It is 3at%. More preferably (BH)max(7)
It is 0.05 at% to 0.2 at% from fEl1 point.

The Cu used in this invention is a mixture with iron and ferroboron, which are used as raw materials.

Furthermore, small amounts of C, S, P, Ca, Mg, and O are contained in the raw materials used or mixed during the manufacturing process.

The presence of AI and Si does not impair the effects of this invention.

Manufacturing method First, an alloy powder having a composition of Fe-Co-BR-Cu is obtained as a starting material.

After normal alloy melting, an alloy ingot obtained by cooling under conditions that do not result in an amorphous state, such as casting, may be crushed, classified, blended, etc. to form an alloy powder, or Fe,
An alloy powder obtained by a reduction method from a rare earth oxide using a reducing agent such as Ca together with Co, FeB powder, etc. can be used.

The average particle size of this alloy powder is 0.
If it is less than 5 pm, the oxidation of the powder will be significant during pulverization or in the subsequent manufacturing process, and the density after sintering will not increase, resulting in poor magnetic properties.If it exceeds 10 μm, excellent magnetic properties will be lost. Therefore, the average particle size is set in the range of 0.5 to 10 pm. In order to obtain excellent magnetic properties, an average particle size of 1, θ to 5 pm is most desirable.

Fine pulverization can be carried out either wet or dry, but it is preferable to carry out the dry process, and it is necessary to carry out the process in an inert gas atmosphere such as nitrogen or argon in order to prevent oxidation of the powder. Examples of dry pulverization methods include disk mills and jet mills.

Next, the alloy powder is molded, and the molding method can be the same as a normal powder metallurgy method, and pressure molding is preferable.In order to make the alloy powder anisotropic, for example, the alloy powder is placed in a magnetic field of 5 kOe or more. Pressure is applied at a pressure of 0.5 to 3.0 ton/cm2.

The molded body is preferably sintered in a normal reducing or non-oxidizing atmosphere at a predetermined degree) H and 900 to 1200°C.

For example, this molded body is baked for 0.5 to 4 hours at a temperature range of 900 to 1200°C in a vacuum of 10'Torr or less or in an inert gas or reducing gas atmosphere of 1 to 76 Torr and a purity of 99% or more. conclude.

Note that the sintering is performed by adjusting conditions such as temperature and time so that a predetermined crystal grain size and sintered density can be obtained.

The density of the sintered body is preferably 95% or more of the theoretical density (ratio) in terms of magnetic properties. For example, at a sintering temperature of 1040 to 1160°C, a density of 7.2 g/cm3 or more can be obtained, which is 95% of the theoretical density. This corresponds to the above. Furthermore, in sintering at 1060-1100°C, the theoretical density ratio is 99
% or more, which is particularly preferable.

After sintering, the cooling rate to room temperature is required to be 100°C/min or more in order to prevent variations in magnetic properties in conventional Fe-Co-B-R magnets that do not contain Cu. Ta.

However, in the case of the present invention containing Cu, as shown in the examples, very slow cooling, for example at 3° C./min or more, is sufficient. Under such slow cooling conditions, the above-mentioned 43
It can stay between 0 and 600°C for a sufficiently long time,
-With slow cooling after sintering without cooling to near room temperature,
It is also possible to obtain effects equivalent to those of this invention.

The aging treatment is performed in a vacuum, inert gas, or reducing gas atmosphere at a temperature range of 430° C. to 600° C. for about 5 minutes to 40 hours.

For slow cooling after aging treatment, a fast cooling rate of 200° C./min or more was required in the conventional case that does not contain Cu in order to prevent a decrease in coercive force.

However, the present invention is extremely advantageous in that it can be cooled at a wide range of cooling rates, from 3 to b, preventing deformation and cracking of the magnet, and also preventing damage to the heat treatment furnace.

In addition, as an aging treatment for this type of sintered magnet, after sintering - 65 days
A multi-stage aging treatment of two or more stages in which the material is maintained at a temperature of 0 to 900° C. for 5 minutes to 10 hours and then heat-treated at a predetermined temperature is also effective.

In addition, in order to further increase the coercive force and improve the oxidation resistance of the magnet and powder, Ti, V, and Nb of less than lat% are added.
, Cr, Mo, W, AI, Zr, Hf,
It may contain Zn1Ca and Si.

Examples Example 1 Electrolytic iron with a purity of 99.9 wt%, copper, Co with a purity of 99.7 wt% or more, ferroboron containing 19 wt% B, and Nd with a purity of 97 wt% or more were used as starting materials. Fe-4Co-14,5Nd-7B-xCu (x =
An ingot was obtained by melting an alloy having a composition of 0.01 to 0.4 at% in a vacuum and an argon atmosphere.

After that, this ingot was coarsely crushed with a show crusher, further finely crushed with a jet mill using a N2 gas stream, and the finely crushed powder with an average particle size of 3.5 pm was charged into a mold of a press machine and placed in a magnetic field of 10 kOe. Orientation, 15t perpendicular to the magnetic field
Molding was carried out at a pressure of on/cm2.

The obtained molded body was heated at 1060 to 1100"C for 12 hours,
It was sintered in an Ar atmosphere, further heat treated at 500 to 600''C in an Ar atmosphere, and then cooled at a rate of about 30C/min.

The coercive force and maximum energy product of the various permanent magnets obtained,
The sintered density was measured and its relationship with changes in the amount of Cu added is shown in FIG. The highest value obtained for each composition is plotted in the figure.

In addition, a case in which no Cu was produced using the same method as in the example of the present invention, and a comparative example in which AI was added, which is known to increase the coercive force with the addition of a small amount, were as follows:
Similarly, the coercive force and maximum energy product of the comparative permanent magnet were measured, and the relationship with changes in AI addition level is shown in FIG.

As is clear from Figure 1, when AI of the comparative example is added, the coercive force increases as the amount of AI added increases, but if the addition is sufficient to obtain a sufficient increase in coercive force, the maximum energy product increases. It is declining.

On the other hand, in the case of adding Cu according to the present invention, Cu
It can be seen that the coercive force and maximum energy product increase significantly with the addition of a very small amount.

Example 2 Using the present invention sample containing 0.1 at% Cu and the comparative example sample containing no Cu, obtained in Example 1,
After sintering, heat treatment at various temperatures from 430 to 620°C for 1 hour, followed by cooling at a rate of 80°C/min, changes in the coercive force of each magnet are shown in Figure 2 as a relationship with the heat treatment temperature. show.

In the case of the comparative example, a high coercive force can be obtained only in an extremely narrow range of optimal heat treatment temperatures, whereas in the case of the magnet according to the present invention containing Cu, a high coercive force can be obtained over a wide temperature range. I know what I can get.

Example 3 Using the same manufacturing method as Example 1, the atomic ratio of Fe-2Co
-13,5Nd-1,5Dy-7B, 0.1at%C
A sample of the present invention containing u and a sample not containing Cu were prepared as a comparative example.

During production, after sintering, heat treatment was performed at various temperatures of 430 to 620°C for 1 hour, and the cooling rate after heat treatment was varied, and the coercive force of each obtained permanent magnet was measured, and the heat treatment temperature was determined. The relationship between cooling rate and coercive force is shown in FIG. 3 for the present invention and FIG. 4 for a comparative example. Note that the numbers in the figure indicate a coercive force of 1Hc (koe).

As is clear from FIGS. 3 and 4, conventionally, in order to obtain a high coercive force, the cooling rate after heat treatment must be maintained within a required range.

In addition, in the case of the present invention containing Cu, any cooling rate from extremely slow cooling to rapid cooling can be used, and a permanent magnet with an extremely high coercive force can be obtained regardless of manufacturing conditions. I understand.

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in coercive force, maximum energy product, and density of a permanent magnet with respect to changes in the amount of Cu (Al) added. FIG. 2 is a graph showing the relationship between heat treatment temperature and coercive force iHc. FIGS. 3 and 4 are graphs showing the relationship between heat treatment temperature, cooling rate, and coercive force; FIG. 3 shows the case of the present invention, and FIG. 4 shows the case of a comparative example.

Claims (1)

[Claims] 1 The total of Nd and Pr in atomic ratio is 12 to 17 at%, B5 to
A sintered permanent magnet material comprising 14 at% of Co, 20 at% or less of Co, 0.02 to 0.5 at% of Cu, and the remainder Fe and unavoidable impurities. 2 The total of Nd and Pr in atomic ratio is 12 to 17 at%, B5 to
An alloy powder consisting of 14 at% Co, 20 at% or less Co, 0.02 to 0.5 at% Cu, the balance Fe and unavoidable impurities is formed, sintered at 900 to 1200°C, and heat treated at a temperature of 430 to 600°C after sintering. A method for manufacturing a sintered permanent magnet material, characterized by: