JPH04247604A - Rare earth-fe-co-b anisotropic magnet - Google Patents

Abstract

PURPOSE:To form an R-Fe-Co-B magnet which exhibits remarkable magnetic anisotropy and also has a small coercive force temperature coefficient by using hydrogen-treated powder containing one or two or more of specific elements together with Co. CONSTITUTION:This is an R-Fe-Co-B anisotropic magnet mainly containing at least a kind of rare earth elements (referred to R) including Y together with Fe, Co and B. The anisotropic magnet contains 10 to 20% of R, 0.1 to 50% of Co, 3 to 20% of B and 0.001 to 5.0% of a sum of one or two or more kinds of Ti, V, Nb, Ta, Al and Si by atomic percentage. The remaining comprises composition containing Fe and unavoidable impurities and a grain aggregate structure where crystal grains with an R2(Fe,Co)14B-type intermetallic compound phase showing a tetragonal structure as a main phase are crystallized. This is a hot-pressed mold or hotisostatic-pressed mold wherein a ratio of the shortest grain diameter to the longest grain diameter is less than 2 and an average crystal grain diameter is 0.05 to 20mum.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to at least one rare earth element containing Y (hereinafter referred to as R), Fe, Co, and B, which have excellent magnetic properties and a small coercive temperature coefficient.
The present invention relates to an R-Fe-Co-B anisotropic magnet whose main component is R-Fe-Co-B. More specifically, R made of hot press or hot isostatic press (hereinafter referred to as HIP) compact
-This relates to an anisotropic magnet based on Fe-Co-B.

0002

[Prior Art] Japanese Unexamined Patent Publication No. 1-132106 discloses that R
-Fe-Co-B based permanent magnet powder is described, and this R-Fe-Co-B based permanent magnet powder has a main phase of R2 (Fe, Co) 14B type intermetallic compound phase which is a ferromagnetic phase. An R-Fe-Co-B mother alloy is used as a raw material, and this mother alloy raw material is heat-treated in an H2 atmosphere at a predetermined temperature range to form phases of RHx, (Fe, Co)2 B, and the remainder Fe. After accelerating the transformation, H2 is removed from the raw material in a deH2 step, and the ferromagnetic phase R2 (Fe, C
o) The structure of the resulting R-Fe-Co-B permanent magnet powder is extremely fine R2 (Fe, Co) with an average particle size of 0.05-3 μm.
) The texture has a recrystallized structure of the 14B type phase as the main phase.

[0003] The above R-Fe-Co-B permanent magnet powder cannot obtain sufficient magnetic anisotropy just by hot-pressing it into a hot-press molded product, so it has been disclosed in Japanese Patent Laid-Open No. 2-3
As described in Japanese Patent No. 9503, the hot press molded body is further subjected to hot rolling such as hot rolling to orient the C axis of the crystal grains of the R2 (Fe, Co)14B phase. The structure improved the magnetic anisotropy.

0004

[Problems to be Solved by the Invention] However, the R-F obtained by further hot rolling the above-mentioned hot press molded product
Although e-Co-B rolled magnets have excellent magnetic anisotropy, the temperature coefficient of coercive force increases, and this R-Fe-C
When an o-B type rolled magnet is incorporated into a motor or the like, there are problems such as the performance of the motor changes due to changes in temperature and lacks stability.

[0005] Furthermore, the R-Fe-Co-B rolled magnet is
Variations in processing rate depending on location lead to variations in magnetic anisotropy, and in order to prevent this, the hot plastic working process had to become complicated.

[0006]

[Means for solving the problem] Therefore, the present inventors
The above increase in the temperature coefficient of coercive force is caused by hot rolling the hot press molded body, so if a magnet with excellent magnetic anisotropy can be obtained without the above hot rolling, the above As a result of research based on the recognition that no increase in the temperature coefficient of coercive force occurs, R: 10 to 20%, Co: 0.1 to 50%, B: 3 to 20%, Ti, V, Contains a total of 0.001 to 5.0% of one or more of Nb, Ta, Al and Si,
A composition in which the remainder is Fe and unavoidable impurities, a shape in which the ratio b/a of the shortest grain size a to the longest grain size b of each crystal grain is less than 2, and an average grain size of 0.05 to 20 μm
R2 (Fe, C
o) R-Fe-Co-B composed of a hot press molded body or a HIP molded body consisting of a crystal grain texture composed of crystal grains having a 14B type intermetallic compound phase as the main phase.
They found that the system magnet exhibits excellent magnetic anisotropy without increasing the temperature coefficient of coercive force.

[0007] The present invention was made based on this knowledge, and it is possible to obtain an R-Fe-Co- This is a characteristic of B-based anisotropic magnets.

The present invention has a small temperature coefficient of coercive force R-
Compared to conventional rolled magnets, Fe-Co-B anisotropic magnets have almost no variation in magnetic anisotropy depending on location and have excellent corrosion resistance.

Furthermore, since the R-Fe-B anisotropic magnet of the present invention has a crystal grain texture, R2 (Fe,
Co) around the 14B type compound composition, that is, R11.8F
It has excellent magnetic anisotropy and high coercive force even at compositions near ebal B5.9.

Next, a method for manufacturing the R-Fe-Co-B anisotropic magnet of the present invention will be explained.

[0011] The R-Fe-Co-B permanent magnet powder for producing the R-Fe-Co-B anisotropic magnet of the present invention is melted and cast to form Ti, V, Nb, Ta, Al and S
An R-Fe-Co-B mother alloy containing one or more of i to have a predetermined composition is produced, and this R-Fe-Co-B mother alloy is heated in a hydrogen gas atmosphere. Heat treatment is performed at a temperature of 500 to 1000°C in a hydrogen gas atmosphere or a mixed gas atmosphere of hydrogen gas and inert gas, and then in a vacuum atmosphere at a temperature of 500 to 1000°C and a hydrogen gas pressure of 1 Torr or less. Or hydrogen gas partial pressure: 1
It is produced by dehydrogenating until it becomes an inert gas atmosphere of Torr or less, and then cooling it.

[0012] The above Ti, V, Nb, Ta, Al and S
R-Fe containing a predetermined amount of one or more of i
- A step of homogenizing the Co-B-based master alloy at a temperature of 600 to 1200°C and the above dehydrogenation treatment followed by a temperature of 3
R-F has even better magnetic anisotropy and corrosion resistance by adding a heat treatment process at 00 to 1000°C
An e-Co-B permanent magnet powder can be produced.

[0013] R-Fe-Co thus produced
-The structure of the B-based permanent magnet powder is composed of a recrystallized texture in which recrystallized grains of the R2 (Fe, Co) 14B type intermetallic compound phase are aggregated without impurities or distortion within the grains or at the grain boundaries. .

[0014] It is sufficient that the average recrystallized grain size of the recrystallized grains constituting this recrystallized texture is within the range of 0.05 to 20 μm; It is more preferable that it be within the range of 0.05 to 3 μm.

The individual recrystallized grains having the above dimensions preferably have a shape in which the ratio of the shortest grain diameter a to the longest grain diameter b is b/a<2, and the recrystallized grains having this shape are It is necessary that it exists in an amount of 50% or more by volume of the crystal grains. By having the shape of the recrystallized grains in which the ratio b/a of the shortest grain size a to the longest grain size b is smaller than 2, the coercive force of the R-Fe-Co-B permanent magnet powder is improved and the 100
Temperature coefficient αiHc of coercive force at °C is -0.6%/°C
become smaller.

Furthermore, the R-F produced in this way
The recrystallized structure of the e-Co-B permanent magnet powder is substantially R2 (Fe, Co)14 with almost no grain boundary phase.
Since it has a recrystallized texture composed only of B-type intermetallic compound phase, it is possible to increase the magnetization value due to the absence of grain boundary phase, and it also prevents corrosion that progresses through grain boundary phase. In addition, since there is no stress strain caused by hot plastic working, there is less possibility of stress corrosion, and corrosion resistance is improved.

[0017] R-Fe-Co thus produced
-B-based permanent magnet powder is molded in a magnetic field to form a green compact, and then this green compact is hot-pressed or HIPed at a temperature of 600 to 900°C to form the R-Fe-Co-B-based permanent magnet powder. It is possible to obtain the R-Fe-Co-B based anisotropic magnet of the present invention which maintains the structure and characteristics of the present invention and has a small coercive force temperature coefficient αiHc.

[0018] Furthermore, the coercive force can be improved by heat treatment at 300 to 1000°C, if necessary.

When the green compact is sintered at a normal temperature, the sintering temperature is generally high, so R-Fe-Co-B
The fine recrystallized grains of the system permanent magnet powder grow and become large crystal grains, which is undesirable because the magnetic properties, especially the coercive force, deteriorate.

Therefore, the R-Fe-Co-
As a method for manufacturing an anisotropic B-based magnet, it is necessary to employ a hot press method or a HIP method that allows sintering at a temperature lower than the normal sintering temperature to suppress the growth of crystal grains. Moreover, since magnetic anisotropy is imparted by forming in a magnetic field, there is no need to perform hot plastic working after hot pressing and HIP.

Next, the reason why the component composition, average crystal grain size and crystal grains of the R--Fe--Co--B anisotropic magnet having a small coercivity temperature coefficient of the present invention are limited as described above will be explained.

(a) R R is Nd, Pr, Tb, Dy, La, Ce, Ho, E
One or more of r, Eu, Sm, Gd, Tm, Yb, Lu and Y, generally mainly composed of Nd,
Other rare earth elements are added to this and used, but Tb, Dy and Pr in particular have the effect of improving the coercive force iHc, and even if the R content is lower than 10%, the
Even if it is higher than %, the coercive force of the anisotropic magnet decreases and excellent magnetic properties cannot be obtained. Therefore, the content of R is 10~
It was set at 20%.

(b) B Even if the B content is lower than 3% or higher than 20%, the coercive force of the anisotropic magnet decreases and excellent magnetic properties cannot be obtained. was set at 3-20%. Also, B
may be partially replaced with C, N, O, or F.

(c) Co The addition of Co improves the coercive force and magnetic temperature characteristics (for example, Curie point) of the anisotropic magnet, and also has the effect of improving corrosion resistance. .1
If the content is less than 50%, the desired effect cannot be obtained, while if the content exceeds 50%, the magnetic properties will deteriorate, which is not preferable. Therefore, the Co content was set at 0.1 to 50%. Since the coercive force is highest when the Co content is between 0.1 and 20%, it is more preferable that the Co content is between 0.1 and 20%.

(d) Ti, V, Nb, Ta, Al and Si These components are contained as components of the R-Fe-Co-B anisotropic magnet, and improve the coercive force and provide excellent magnetic properties. It has the effect of stably imparting anisotropy and corrosion resistance, but if its content is less than 0.001%, the desired effect cannot be obtained, while if it is contained in excess of 5.0%, magnetic properties will deteriorate. . Therefore, Ti, V, Nb, Ta, Al
The sum of one or more of Si and Si is 0.00
It was set at 1 to 5.0%.

Furthermore, Ni, Cu, Zn, Ga,
At least one of Ge, Zr, Mo, Hf, and W is 0
．． Even if the content is 0.001 to 5.0%, an anisotropic R-Fe-Co-B magnet having excellent magnetic anisotropy and corrosion resistance can be obtained.

(e) Average grain size R-R2 constituting the structure of the Fe-Co-B anisotropic magnet
(Fe, Co) The average crystal grain size of the 14B type phase crystal grains is 0
．． If it is smaller than 0.05 μm, magnetization becomes difficult, which is undesirable. On the other hand, if it is larger than 20 μm, coercive force and squareness will decrease, making it impossible to obtain high magnetic properties, which is not preferable.

[0028] Therefore, the average crystal grain size is 0.05 to 2
It was set at 0 μm. In this case, it is more preferable that the average crystal grain size is 0.05 to 3 μm, which is close to the single magnetic domain grain size (0.3 μm).

(f) Shape of crystal grains It is preferable that the shape of the crystal grains having the above-mentioned dimensions has a shape in which the ratio b/a of the shortest grain diameter a to the longest grain diameter b is smaller than 2. Grains account for 50% by volume of all grains
It is necessary for the above to exist. This is because by satisfying the above condition b/a<2, the coercive force of the R-Fe-Co-B anisotropic magnet is improved, the corrosion resistance is also improved, and the temperature coefficient of the coercive force is also reduced.

[0030]

[Examples] The present invention will be explained in detail based on Examples and Comparative Examples.

[0031] Various R-Fe-Co-B alloy ingots containing Co and one or more of Ti, V, Nb, Ta, Al and Si obtained by plasma melting and casting; Ti, V, Nb, Ta, Al, S
Prepare R-Fe-Co-B alloy ingots that do not contain any of i, and homogenize these alloy ingots in an argon gas atmosphere at a temperature of 1130°C for 20 hours. The homogenized ingot was crushed into approximately 15 mm square pieces to obtain a raw material alloy. This raw material alloy was heated from room temperature to 830°C in a hydrogen atmosphere of 1 atm, heat-treated in a hydrogen atmosphere for 1 hour at 830°C, and then heated at 830°C and vacuum degree: 1 x 10-1 Torr.
After dehydrogenation was carried out until the temperature was below r, argon gas was immediately introduced to rapidly cool the reactor. After completing the hydrogen treatment, heat treatment was performed at 630° C. for 2 hours in vacuum.

[0032] The obtained raw material alloy was lightly ground in a mortar,
R-Fe-Co-B permanent magnet powder having an average particle size of 40 μm was obtained.

[0033] These R-Fe-Co-B permanent magnet powders were press-molded in a magnetic field of 25 KOe to produce green compacts, and these green compacts were heated at a temperature of 720°C and a pressure of 1
．． 5Ton/cm2 hot press or temperature: 7
Sintered magnets 1 to 45 of the present invention and comparative sintered magnets 1 to 14 were manufactured by performing HIP at 10°C and pressure: 1.5 Ton/cm2, and further heat treatment at 620°C and holding in vacuum for 2 hours. did. Note that hot pressing was performed by arranging the green compact formed in a magnetic field so that the orientation direction coincided with the pressing direction during hot pressing. The above-mentioned sintered magnets 1 to 25 of the present invention and comparative sintered magnets 1 to 7 were manufactured by the above-mentioned hot pressing method, and the above-mentioned sintered magnets 26 to 45 of the present invention and comparative sintered magnets 8 to 14 were manufactured by the above-mentioned HIP method. Manufactured by law. In addition, all the densities were 7.5 to 7.6 g/cm 3 and were sufficiently dense.

For further comparison, Ti, V, Nb, T
a, R-Fe-Co-B permanent magnet powder manufactured from an alloy ingot containing neither Al nor Si was filled and sealed in a copper can in vacuum, and heated to 720°C to achieve a rolling ratio of 80%. A conventional anisotropic magnet was produced by rolling several times until it became .

The component compositions of the anisotropic magnets 1 to 45 of the present invention, comparative anisotropic magnets 1 to 14, and conventional anisotropic magnets manufactured in this manner are shown in Tables 1 to 6. The average crystal grain size of the magnet, the amount of crystal grains with a shape where the value of longest grain size / shortest grain size of individual crystal grains is smaller than 2 (volume %)
, coercive force temperature coefficient αiHc, and magnetic properties of an R-Fe-Co-B anisotropic magnet obtained by hot pressing or HIPing a compact obtained by press-molding in a magnetic field, These measured values are shown in Tables 7-11.

The coercive force temperature coefficient αiHc is determined by measuring the coercive force iHc25 at 25°C and the coercive force αiHc100 at 100°C, and calculating the ratio of the difference in coercive force (i
Hc100 -iHc25)/iHc25 with a temperature difference of 75
It is the value divided by °C.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

[0044]

[Table 8]

[0045]

[Table 9]

[0046]

[Table 10]

[0047]

[Table 11]

From the results in Tables 1 to 11, it can be seen that Ti,
One or two of V, Nb, Ta, Al and Si
The anisotropic magnets 1 to 45 of the present invention containing at least one of these elements have almost the same magnetic properties as conventional anisotropic magnets that are rolled magnets that do not contain any of these elements, but the temperature coefficient of coercive force is much smaller. , Comparative anisotropic magnets 1 to 1 in which the contents of Ti, V, Nb, Ta, Al, and Si deviate from the conditions of the present invention.
No. 4 has a decreased magnetic anisotropy, and it can be seen that the size and shape of the crystal grains also have a large influence on the magnetic properties.

[0049]

[Effect of the invention] This invention provides Ti, V, and N in addition to Co.
By using a hydrogen-treated powder containing one or more of Ta, Al, and Si, it exhibits remarkable magnetic anisotropy without hot plastic working, and at the same time, the temperature coefficient of coercive force can be reduced. A small R-Fe-Co-B magnet can be obtained, which has an excellent effect on improving the performance and stability of electric equipment such as motors.

Claims (3)

[Claims] Claim 1: An R-Fe-Co-B anisotropic magnet containing at least one rare earth element including Y (hereinafter referred to as R), Fe, Co, and B as main components, The anisotropic magnet has, in atomic percentage, R: 10-20%, Co: 0.1-5
0%, B: 3 to 20%, total of one or more of Ti, V, Nb, Ta, Al and Si: 0.001 to 5.0%,
It has a composition in which the remainder consists of Fe and unavoidable impurities, and a crystal grain texture in which crystal grains whose main phase is an R2 (Fe, Co) 14B type intermetallic compound phase having a tetragonal structure are aggregated, and the above crystal grains Texture is defined by the shortest grain size a of individual grains.
50% by volume or more of all crystal grains exist in which the ratio b/a of the longest grain size b is less than 2, and the average crystal grain size of the crystal grains constituting the crystal grain texture is 0.05~
R-Fe- characterized in that it is a hot press molded product or a hot isostatic press molded product having a dimension of 20 μm.
Co-B anisotropic magnet. 2. The R- according to claim 1, wherein the crystal grain texture in which the crystal grains are aggregated consists essentially of an R2 (Fe, Co) 14B type intermetallic compound phase.
Fe-Co-B anisotropic magnet. 3. The average crystal grain size is 0.05 to 3μ.
R- according to claim 1 or 2, characterized in that it is m.
Fe-Co-B anisotropic magnet.