JPS63313807A - Of highly efficient permanent magnet with high-anticorrosivity, and manufacture thereof - Google Patents

Abstract

PURPOSE:To increase the anticorrosivity of magnet by wrapping R2Fe14B main phase with a specific composition phase. CONSTITUTION:Based on atomic %, the main phase consists of 13-16% R (R=R1+R2. R1 is more than 50% of R and consists of one or two kinds of Nd or Pr. R is the remaining of R and consists of at least one kind of Dy, Tb or Ho.), 5-10% B, 15-25% Co and 51-77% Fe. Besides the main phase of R2Fe14 B tetragonal phase, the structure involves, as a grain boundary phase, B rich phase, R rich phase and R (Fe1-xCox)2 phase (X=0.5-0.75) and R3(Fe1-yCoy) phase (y=0.5-0.9) of non-magnetic phase and the R2Fe14B main phase is wrapped with R3(Fe1-yCoy) phase. High-efficient permanent magnet with high-anticorrositity can be thereby obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to the improvement of Fe-B-R permanent magnets.
The present invention relates to a Fe-B-R permanent magnet having excellent corrosion resistance and high coercive force, which prevents a decrease in iHc due to o content, and a method for manufacturing the same.

Background technology Previously, Fe-
As a B-R permanent magnet, a Co-containing Fe-B-R permanent magnet was proposed (Japanese Patent Application Laid-Open No. 59-64733.
132104) has been proposed.

By containing Co in the Fe-BR-based permanent magnet, it is possible to improve the temperature coefficient of magnetic properties by raising the Curie point by one point, and to improve corrosion resistance. There was a problem that the magnetic force iHc decreased.

Therefore, the iHc of Co-containing Fe-B-R permanent magnet
In order to prevent the decrease, it has been proposed to add AI as an additive element, but this is not preferable because it causes deterioration of the residual magnetic flux density Br.

In addition, coercive force iH of Co-containing Fe-B-R permanent magnet
The presence of a Co-rich soft magnetic phase is well known as a cause of the decrease in c. However, no means for suppressing the formation of such phases has been proposed.

Purpose of the Invention The present invention provides an improvement in the coercivity iHc of Fe-B-R permanent magnets without impairing the improvement of the temperature coefficient of magnetic properties due to an increase in Curie point and the improvement of corrosion resistance. The purpose is to provide a Fe-B-R permanent magnet that prevents the decrease in iHc, and also to provide a manufacturing method that can inexpensively provide a Fe-B-R permanent magnet that prevents such a decrease in iHc without changing the composition. .

Components of the Invention The inventor has discovered the cause of iHc reduction due to the inclusion of CO in Fe-B-R permanent magnets, and the iH
As a result of various investigations into measures to prevent the deterioration of C, when R is Nd, the inclusion of Co in the Fe-B-R permanent magnet has no effect on the deterioration of the magnetic properties of the main Nd2Fe14B tetragonal phase. Furthermore, although the B-rich phase and Nd-rich phase in the grain boundary phase do not have a negative effect on the deterioration of magnetic properties, the Co-rich soft magnetic phase generated in the grain boundary phase is the cause of the decrease in coercive force iHc. When this Co-rich soft magnetic phase was investigated by EPMA, thermal analysis, and X-ray diffraction, it was found that the Co-rich soft magnetic phase mainly consists of two Nd (Fe1-xCox) phases (where x = 0. 5
~0.75), and this Nd(Fe1-XCox
) The two phases are thermally decomposed by heating to 900°C or higher, and part of them becomes non-magnetic N, which is unrelated to the deterioration of magnetic properties.
d3 (Fe1-y Coy) phase (however, y = 0.5~
0.9. ).

Furthermore, detailed investigations such as EPMA revealed that this Nd5 (
It has become clear that the Fet-yCoy) phase forms a structure that envelops the R2Fe14B main phase, and that this enveloping structure is responsible for the excellent magnetic properties.

Therefore, in the production of Co-containing Fe-B-R permanent magnets, without adding any additive components to the magnet composition, after sintering,
By adjusting the aging treatment under specific conditions and the subsequent cooling conditions, the coercive force i of the Co-containing Fe-B-R permanent magnet can be increased.
They discovered that Hc can be improved and completed this invention.

In other words, this invention is based on R in atomic % (however, R=R1+R2, R1 is N at 50% or more of R).
d or Pr, R2 is the remainder of R, and consists of at least one of Dy, Tb, and Ho)1
3-16%, 85-10%, Co15-25%, Fe5
The main component is 1 to 77%, and in addition to the main R2Fe14B tetragonal phase, the grain boundary phase includes a B-rich phase, an R-rich phase, and two R(Fei-xCox) phases (where x = 0.5 to 0). ．．
75) and the nonmagnetic phase R3 (Fe1 Coy) phase (
However, it is a high-performance permanent magnet with excellent corrosion resistance, which has a y = 0.5 to 0.9) and has a capsule-like structure in which the R2Fe14B main phase is surrounded by the R3 (Fe1-, Coy) phase. be.

Further, the permanent magnet of the present invention is produced by molding and sintering a raw material powder having the above composition as a main component,
It is obtained by a manufacturing method characterized by aging treatment at a temperature range of 00°C to lower than the sintering temperature, and further rapid cooling at a cooling rate of 100°C/min or more.

Preferred Embodiment of the Invention In this invention, the sintering conditions are preferably 950°C to 1100°C for 0.5 to 10 hours. If the sintering temperature is less than 950°C, it will take a long time for sintering, which is unfavorable in terms of production efficiency, and if it exceeds 1100°C, the iHc of the sintered magnet will drop significantly, which is undesirable.

If the sintering time is less than 0.5 hours, due to the structure of the continuous sintering furnace,
It is not practical, and if the time exceeds 10 hours, the sintering cost will increase, which is not preferable. More preferable sintering conditions are sintering at 1020° C. to 1080° C. for 1 hour to 3 hours.

Further, as the aging treatment conditions, aging treatment at 900° C. to 1000° C. for 5 minutes to 1 hour is preferable, and if the aging temperature is less than 900° C. and exceeds 1000° C., the effect of improving iHc is small and is not preferable.

If the aging treatment time is less than 5 minutes, the magnetic properties of the magnet will vary, making it impossible to obtain a magnet with homogeneous characteristics, and if it exceeds 1 hour, the effect will be saturated, so in order to reduce production costs,
The aging treatment time is preferably within 1 hour.

The cooling rate from the aging treatment temperature, which is a feature of this invention, is 10
If it is less than 0'C/min, the R3 (Fe1-, Co,) phase, which is the characteristic phase of this invention magnet, will be difficult to form and the iHc will drop significantly, which is undesirable. If it exceeds 2000C/min, the sintered body will This is undesirable because it causes cracks, deformation, and other external defects, and the cooling rate is 100°C/min to 20°C.
00°C/min. Furthermore, the cooling rate is preferably 300°C/min to 1500°C/min.

Reason for limiting the composition of permanent magnet The rare earth element R used in the permanent magnet of this invention has a composition of 1
It accounts for 3 at% to 16 at%, but more than 50% of R is N.
d or Pr (R1), and the remainder of R consists of at least one of Dy, Tb, and Ho (
R2).

Also, one type of ordinary is usually sufficient, but in practice two types are sufficient.
A mixture of more than one species (Mitushmetal, Didim, etc.) can be used for reasons such as availability.

Note that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in production within an industrially available range.

R is an essential element in Fe-B-R permanent magnets, and if it is less than 13 at%, a cubic crystal structure with the same crystal structure as α-iron will precipitate, resulting in high magnetic properties, especially high coercive force. If it is not obtained and exceeds 16 atom %, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, the rare earth element is in the range of 13 atomic % to 16 atomic %.

B is an essential element in Fe-B-R permanent magnets, and if it is less than 5 at%, the rhombohedral structure becomes the main phase and high coercive force (iHc) cannot be obtained, and if it exceeds 10 at%,
The amount of B-rich nonmagnetic phase increases, and the residual magnetic flux density (Br)
As a result, excellent permanent magnets cannot be obtained. Therefore, B is in the range of 5 atomic % to 10 atomic %.

Fe is an essential element in Fe-B-R permanent magnets, and if it is less than 51 at%, the residual magnetic flux density (Br) decreases, and if it exceeds 77 at%, high coercive force cannot be obtained. The content is 51 atomic % to 77 atomic %.

Further, in the permanent magnet of the present invention, containing Co is effective in improving the temperature characteristics and corrosion resistance of the magnetic properties, but if it is less than 15 at%, the effect of improving iHc is small; When exceeding Br, (BH
) The decrease in max is extremely undesirable.

In addition, the permanent magnet according to the present invention includes R, B, and Fe, as well as
The presence of impurities that are inevitable in industrial production can be tolerated.

In addition, at least one of the following additional elements is R-Co
It can be added to -B-Fe permanent magnets because it is effective in improving coercive force, manufacturability, and lowering costs.

9.5 atom% or less of AI, 4.5 atom% or less of Ti, 9
．． 5 at% or less V, 8.5 at% or less Cr, 8.0
Mn not more than 5.0 atom %, Bi not more than 5.0 atom %, Nb not more than 9.5 atom %, Ta not more than 9.5 atom %, Mo not more than 9.5 atom %, W not more than 9.5 atom % , sb of 2.5 atom% or less, Ge of 7 atom% or less, Sn of 3.5 atom% or less, Zr of 5.5 atom% or less, Mi of 9.0 atom% or less, 9.0 atom% or less of Si, 1.1 at% or less of Z
At least one of n, Hf of 9.0 atomic % or less is added. However, if two or more types are contained, the maximum content is the atomic % of the one with the maximum value among the added elements.
By containing the following, the above effects can be obtained.

A tetragonal crystal phase is essential for producing a sintered permanent magnet with superior magnetic properties than a fine and uniform alloy powder.

The permanent magnet according to this invention has a maximum energy product (BH)
In the composition range where max is preferable, (BH)max≧25M
GOe, and the maximum value reaches 30 MGOe or more.

The most preferable composition in this invention is R14 atomic % to
15.5 at%, B6.5 at% to 8.5 at%, Co
15 at% to 25 at%, Fe51 at% to 64 at%
It exhibits excellent magnetic properties of (BH)max=35MGOe or more in the composition range.

Examples Example 1 As a starting material, electrolytic iron with a purity of 99.9%, B19.3
% containing ferroporon alloy, 99.9% pure electrolytic Co
, Nd and Dy with a purity of 99.7% or more are used, and after mixing these, they are high-frequency melted, and then cast in a water-cooled copper mold.
An ingot having a composition of 13.5Nd 1.5Dy 7B22Co56Fe was obtained.

After that, this ingot is coarsely and finely crushed to obtain an average particle size of 3, Op.
A fine powder of m was obtained.

This fine powder was oriented in a magnetic field of 8 kOe and molded at a pressure of 1.5 ton/cm2 in a direction perpendicular to the magnetic field.

The obtained molded body was sintered at 1080° C. for 2 hours in an Ar atmosphere, and then cooled to room temperature to obtain a sintered magnet having dimensions of 10 mm in length, 8 mm in width, and 7 mm in thickness.

This sintered magnet body was heated to 960°C for 1 hour as aging treatment conditions.
After the time aging treatment, cooling was performed at a cooling rate of 800° C./min.

The demagnetization curve of the sintered magnet body (Example 1) after such heat treatment is shown in FIG. 1, and the magnetic properties are shown in Table 1.

For comparison, a sintered magnet having the same composition as in Example 1 was aged at 630°C for 1 hour, and then cooled at a cooling rate of 50'C/min. Sintered magnet obtained under the same manufacturing conditions as (Comparative Example 1)
The demagnetization curve is shown in Figure 1, and the magnetic properties are shown in Table 1.

Next, when the magnet material according to the present invention was subjected to X-ray diffraction, it was found that R(Fet-x
The diffraction peak of the Cox)2 phase becomes weaker, and the diffraction peak of the R3(Fet-
It was confirmed that a diffraction peak of the yCo, ) phase appeared.

Furthermore, EPMA investigation revealed that this R3 (Fe1-y
It was confirmed that a enveloping structure of Coy ) phase was formed.

Table 1 Example 2 As a starting material, electrolytic iron with a purity of 99.9%, B20.1
% containing ferroboron alloy, 99.9% purity electrolytic co
, Nd and Dy with a purity of 99.5% or higher are used, and these are high-frequency melted after being blended, and then cast in a water-cooled copper mold.
Nd13. Dy 1. B 7.5. Co22.5. Fe
An ingot having a composition of 56 atomic ratios was obtained.

Then, this ingot was coarsely and finely pulverized to an average particle size of 2.7 pm.
A fine powder was obtained.

This fine powder was oriented in a magnetic field of 8 kOe and molded in the vertical direction under a pressure of 2.0 ton/cm2.

The obtained molded body was heated to 1070"C in an Ar atmosphere for 1.
After sintering for 5 hours, it was cooled to room temperature and subjected to the treatment according to the present invention, i.e., aged at 960'C in Ar for 1 hour, followed by cooling at a cooling rate of 500'C/min. went.

The demagnetization curve of the obtained sintered magnet body (Example 2) is shown in FIG. 2, and the magnetic properties are shown in Table 2.

For comparison, a sintered body with the same composition as in Example 2 was aged at 650°C x IHr under aging conditions.
It was manufactured under the same conditions except for cooling.

The demagnetization curve of the obtained comparative sintered magnet body (comparative example 2) was
The magnetic properties are shown in the figure and Table 2.

Furthermore, the results of X-ray diffraction of the magnet material according to this invention show that
As in Example 1, it was confirmed that the diffraction peak of the R3 (Fe1-XCox) phase appeared.

Furthermore, EPMA investigation revealed that R3(Fe1-y Co
It was confirmed that a enveloping structure of the y) phase was formed.

Table 2

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing demagnetization curves of sintered bodies in Examples.

Claims (1)

[Claims] R in atomic % (where R=R_1+R_2, R_1 is R
50% or more of the material consists of one or two of Nd or Pr,
R_2 is the remainder of R, and at least one of Dy, Tb, and Ho
Consisting of seeds) 13-16%, B5-10%, Co15-
In addition to the main R_2Fe_1_4B tetragonal phase, grain boundary phases include a B-rich phase, an R-rich phase, and an R(Fe_1_-_xCo_x)_2 phase (where x=0.
5 to 0.75) and the non-magnetic phase R_3(Fe_1_
-_yCo_y) phase (however, y=0.5 to 0.9), and R_2F due to the R_3(Fe_1_-_yCo_y) phase.
e_1_4B A high-performance permanent magnet with excellent corrosion resistance characterized by a enveloping structure in which the main phase is wrapped. R in atomic % (however, R=R_1+R_2, R_1 is R
50% or more of the material consists of one or two of Nd or Pr,
R_2 is the remainder of R, and at least one of Dy, Tb, and Ho
Consisting of seeds) 13-16%, B5-10%, Co15-
25%, Fe51~77% as main components,
After molding and sintering, it is aged at a temperature range of 900°C to lower than the sintering temperature, and then rapidly cooled at a cooling rate of 100°C/min or more. Production method.