JPH02298003A - Manufacture of rare-earth permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a permanent magnet which displays a high coercive force and a high energy product by a method wherein an R-Fe(Co)-B-based molten metal containing a specific amount of titanium is quenched and solidified and it is heat-treated in two stages. CONSTITUTION:An alloy which is expressed by a general formula of Rx(Fe1-wCow)1-x-y-zByTiz (where R represents one or two or more kinds of rare- earth elements including Y) and whose compositions are 6<=x<=16, 2<=y<=25, 0<=z<=12 and 0<=w<=1.0 is melted by using an arc; it is sprayed onto the surface of a turning roll through a quartz nozzle and is cooled at high speed; an amorphous or fine crystalline thin belt is obtained. A first-stage heat treatment is executed isothermally at 300 to 800 deg.C; then, a second-stage heat treatment is executed at 600 to 1000 deg.C and isothermally at a temperature higher than that at the first-stage heat treatment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a rare earth-cobalt-boron system (hereinafter referred to as r
Regarding permanent magnets (referred to as "R-Fe (Co)-B system"),
More specifically, R-Fe (Co)- containing titanium
The present invention relates to a method for producing a rare earth permanent magnet that exhibits high coercive force and high energy product even with a composition with a low rare earth content by rapidly solidifying a B-based molten alloy as a liquid and subjecting it to two-stage heat treatment.

[Prior art] Methods for producing R-Fe-B permanent magnets include a sintering method in which powder metallurgy is used, a casting method in which a cast alloy is heat-treated after hot working, and a method in which it is rapidly cooled from a molten state. There is a rapid cooling method that solidifies the material into an extremely fine structure.

Among these, the quenching method involves melting, high-speed quenching, coarse pulverization, and
(cold pressing) (warm pressing) - It is performed using a magnet process, and has the advantage of making the process smoother than other methods, and various research is underway.

[Problem to be solved by the invention] Permanent magnets obtained by the rapid cooling method are basically RI Fo.
The main phase is a zB compound. Rm of about 0.01 to 1 μm
Due to the extremely fine structure in which F41+4B fine particles are surrounded by an amorphous phase, it is a pinning type magnet in which the binding of the domain wall determines the coercive force.

Although the coercive force generation mechanism is different from that of sintered magnets and cast magnets, the rare earth content of the rapidly solidified magnets in practical use is R=13%, which is slightly higher than that of the main phase. When the R content is less than 12%, the coercive force iHc rapidly deteriorates. In Japanese Patent Publication No. 59-64739. RxCo
= 10%, it has been shown that iHc becomes 6 kOe or less. (In this specification, all "%" are "atomic %")
Regardless of the sintering method, casting method, or quenching method, in conventional R-Fe-B permanent magnet alloys, coercive force decreases when the rare earth element content is less than 12%. A phenomenon in which iHc rapidly decreases is observed.

In addition, attempts have been made to add various additives to the R-Fe-B system in order to improve the magnetic properties; for example, in JP-A-63
190138 describes that adding an appropriate amount of T1 can improve the temperature characteristics of coercive force.

The purpose of the present invention is to reduce the content of rare earth elements (12%
less than) & [l/i! The object of the present invention is to provide a method for producing a permanent magnet that is isotropic and exhibits high coercive force and high energy product even in the 6N region.

[Means for Solving the Problems] The present invention. RxCo11(F e +-1, lCOm
) +-*-y-mB, Ti, (wherein RxCo is one or more rare earth elements including Y), and is represented by the general formula: 6≦x≦16.2≦y≦25.0 <z≦12
゜0≦wfa1. A liquid quenched alloy that is O is used.

Then, the first stage heat treatment is performed isothermally at 300 to 800°C, and then the second stage heat treatment is performed isothermally at 600 to 1000°C and at a higher temperature than the first stage. As described above, the features of the present invention are that a material having a composition in which an appropriate amount of Ti (titanium) is added is liquid-quenched, and that the liquid-quenched alloy is subjected to a specific two-step heat treatment.

There are various types of liquid quenching methods, and any method may be adopted by taking advantage of its characteristics. In particular, the centrifugal method, single-roll method, and twin-roll method are suitable for industrial production because they can continuously produce a large amount of ribbons.

In all of the above methods, an alloy is melted in an electric furnace or a high-frequency furnace, and the molten alloy is ejected from a nozzle at the tip of a crucible using gas pressure, and is solidified by contact on the surface of a rotating cooling body. From the standpoint of mass production, in the case of the present invention, a single roll method, that is, a method in which molten alloy is jetted onto the circumferential surface of one rotating roll, is most suitable.

Of course, other methods may also be used.

The reasons for limiting each component in the present invention are as follows. These were determined from the results of many experiments as described in the Examples. When the ilx of R is less than 6%, the iHc is 5.
If the amount y of B is less than 2%, the maximum energy product (BH) will be 5MGOe, and if the amount y of B is less than 2%, the iHc will be 5kOe.
If it is less than 25%, it is small, and if it exceeds 25% (BH), □ decreases. It is necessary to add Ti to increase LHc,
The effect becomes significant when the NZ content is 0.1% or more, or 1% or more. However, when 2 exceeds 12%, both Br and iHc decrease.

Furthermore, by substituting Fe with Co, the Curie temperature is improved and the temperature characteristics are improved. A high coercive force can be obtained over the entire area of the device.

W-1, that is, even if all Fe is replaced with Co, a magnet having a coercive force of 8 kOe or more can be obtained.

Furthermore, it is also possible to replace a part of B with C, P, St, A1, etc., making it possible to improve manufacturability and reduce costs.

[Function] When a molten alloy is directly quenched and solidified, the structure after quenching will vary depending on the alloy composition and quenching conditions, but will generally be amorphous, microcrystalline, or a mixed structure thereof. By heat-treating this, the microcrystalline or Mi texture consisting of amorphous and microcrystals and the size can be further controlled.
0.01～! A very desirable structure for a permanent magnet is obtained in which R1F614B fine particles of about μm size are surrounded by an amorphous phase.

When examining the effects of various additive elements on R-Fe (Co)-B materials obtained by the rapid cooling method, we found that, in particular, when Ti was added. Composition with low RxCo content (less than 12%)
However, it was found that a high-performance magnet suitable for practical use could be manufactured by exhibiting a high n-force.

Furthermore, even when the R content was 12% or more, the coercive force could be improved by adding Ti.

However, although the addition of Ti contributes to improving the coercive force, the maximum energy product (BH) □8 is low because the squareness of the hysteresis loop is poor. Therefore, in the present invention, a material rapidly solidified by a liquid quenching method is subjected to two-step heat treatment in an inert atmosphere or in a vacuum. The first stage is 300
Isothermal treatment at ~800°C, second stage at 600-1000°C
It is an isothermal treatment at a temperature higher than that of the first stage.

This two-step heat treatment improves (B)i). In the first heat treatment, the main phase is nucleated (the number of nuclei is controlled). In addition, in the second stage heat treatment, the main phase is grown (the size is controlled). By performing the two-stage heat treatment in this way, the number and size of the main phases are optimized in terms of magnetic properties. This heat treatment effect is. R
It is particularly effective in compositions with a low xCo content (less than 12%). No effect is seen in compositions with high R content (over 16%).

[Example 1] N d* Fe*1-xBs T i h (6≦
An alloy having a composition (x≦20) was arc melted. This molten alloy was passed through a quartz nozzle with an inner diameter of 0.7 onto the surface of a roll rotating at 20 m/sec at an argon gas pressure of 1 kg/
cm" and was rapidly cooled to obtain an amorphous or microcrystalline ribbon.

This ribbon was heated in a vacuum at a temperature of 300 to 1000℃ for 1
The steps were heat treated. Figure 1 shows the highest coercive force I Hc and residual magnetic flux density Br obtained under each condition.
-xBs i 6≦x≦20), the same processing was performed and the highest coercive force obtained under each condition is also shown. All magnetic properties are determined by filling the capsule with magnetic powder and using V
Measured by SM.

Figure 1 shows that the addition of T1 reduces the Nd content (12
%less than)! It can be seen that a high coercive force of 5 kOe or more can be obtained even with a composition with a high Nd content (12% or more), and that the coercive force is improved even with a composition with a high Nd content (12% or more).

Next, regarding the ribbon obtained by the liquid quenching method described above, in a vacuum,
(B I-(), . . . when subjected to normal one-stage heat treatment and when subjected to two-stage heat treatment according to the present invention.

Figure 2 shows the comparison results. The heat treatment pattern is as follows.

・1-stage heat treatment pattern: 700°C x 1 hour ・2-stage heat treatment pattern (invention) 1st stage: 500°C x 1 hour 2nd stage: 700°C x 1 hour 2-stage heat treatment butter This effect is particularly effective when the Nd amount xfJ<12%, and becomes ineffective when it exceeds 16%.

[Example 2] N d + *F @ , -, syT i h (2
Example 1 A liquid rapidly solidified alloy having a composition of ≦y≦25)
It was manufactured using the same procedure as above, and subjected to one stage of heat treatment in a temperature range of 300 to 1000 tons in vacuum. Br of the obtained material,
The lHc characteristics are shown in FIG. From the figure, it can be seen that the high magnetic properties are reduced by 1% when 2≦y≦25.

Next, we will compare the (BH) amx of the ribbons with the above composition obtained by the 1 & body quenching method when subjected to normal 1-stage heat treatment in vacuum and when subjected to 2-stage heat treatment of the present invention. Fourth
As shown in the figure. The heat treatment pattern is as follows.

・1-stage heat treatment pattern: 650°C x 1 hour ・2-stage heat treatment pattern (invention) 1st stage: 400°C x 1 hour 2nd stage: 650°C x 1 hour 2-stage heat treatment The squareness is improved (BH). 8 improves.

[Example 3] N(1+oF6oz-mBa"riffi (0≦
A liquid rapidly solidified alloy having a composition of 2≦12) was prepared in the same manner as in Example 1, and subjected to one stage of heat treatment in a temperature range of 300 to 1000° C. in vacuum. Br, L of the obtained material
The Hc characteristics are shown in FIG. 5. From the same figure, it can be seen that high magnetic characteristics are obtained when O<z≦12.

Next, we will compare the results of (B H')aax when a thin ribbon with the above composition obtained by the liquid quenching method was subjected to a normal one-stage heat treatment in vacuum and a two-stage heat treatment according to the present invention. is shown in Figure 6. The heat treatment pattern is as follows.

・1-stage heat treatment pattern: 750°C x 1 hour ・2-stage heat treatment pattern (invention) 1st stage: 600°C x 1 hour 2nd stage: 750°C x 1 hour 2-stage heat treatment (BH) □8 improves.

[Example 4] Nd+o (F @+-w COii) tx-, T
A liquid rapidly solidified alloy having a composition of lb (0≦W≦1) was prepared in the same manner as in Example 1, and was heated to 300 to 1 in vacuum.
One stage of heat treatment was performed in a temperature range of 000°C.

The Br, 1) (c characteristics of the obtained material are shown in FIG. 7. From the figure, it can be seen that high magnetic properties are obtained over the entire range of 0≦W≦1.

Next, we will compare the results of (BH) 1o obtained by applying the normal one-stage heat treatment in vacuum and the two-stage heat treatment of the present invention for the ribbons with the above composition obtained by the liquid quenching method. It is shown in Figure 8. The heat treatment pattern is as follows.

・1-stage heat treatment pattern...800°C x 1 hour ・2-stage heat treatment pattern (invention) 1st stage...550°C x 1 hour 2nd stage...800°C x 1 hour 2 of the present invention By performing the step heat treatment, the squareness of the hysterinous groove is improved (BH), and the squareness is improved.

[Example 5] Table 1 shows the results of performing the same treatment as in Example 1 for various rare earth elements. However, in vacuum 300~1oo
One stage of heat treatment was carried out in the temperature range of 0°C.

From Table 1, it can be seen that a sufficiently high coercive force can be obtained by adding Ti even in a composition with a low content (10% or less) of various rare earth elements.

Table 1 Next, the results of (BH) - χ The comparison results are shown in Table 2, and the heat treatment patterns are as follows.

・1st stage heat treatment pattern...750t x 1 hour 2nd stage heat treatment badan (invention) 1st stage...600°C x 1 hour 2nd stage...750°C x 1 hour Table 2 2nd stage By applying heat treatment, (BH) is improved. As can be seen from the comparative example, in the composition in which 'rl was not added, even if two-stage heat treatment was performed (B H). No improvement in 4 was observed.

[Effect of the invention 1] Since the present invention adds an appropriate amount of Ti element to the R-Fe (Co) -B system composition as described above, it can be used even in areas where the content of rare earth elements is small (less than 12%). ,
A high coercive force i Hc comparable to that obtained with a large amount of rare earth elements can be obtained, and costs can be reduced. In the present invention, since such a material is subjected to a specific double heat treatment, the maximum energy product (B l(')□) is improved, and a practically excellent permanent magnet can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the i l-1c and Br characteristics of N dm F f3nb-1B6 Ti4, and FIG. 2 is a graph showing the (BH) characteristics due to differences in heat treatment conditions. Figure 3 shows N d +eFe an-yB, T i
Figure 4 is a graph showing the i Hc and Br characteristics of No. 6, and Figure 4 is a graph showing the characteristics of (B l() @aX) due to the difference in heat treatment conditions. Figure 5 is a graph showing the characteristics of N d + o F e 8!, B s T I
FIG. 6 is a graph showing the IHC and Br characteristics of x, and FIG. 6 is a graph showing the (BH) characteristics due to differences in heat treatment conditions. Figure 7 shows Nd+e (Fat-w Cow)van@
Figure 8 is a graph showing the (Hc and Br characteristics) of (BH) due to the difference in heat treatment conditions. Patent applicant Shigeru Tomito Electrochemical Co., Ltd. Agent See 1st I
! I Fig. 2 Fig. 3 Fig. 4 15i Nd,, Fs, -, B, Ti. y 5th rlA 6th cause 7th figure

Claims (3)

[Claims] 1. R_xFe_1_-_x_-_y_-_zB_yT
Represented by the general formula i_z (where R is one or more rare earth elements including Y), 6≦x≦16, 2≦
Using a liquid quenching alloy with y≦25,0<z≦12, the first stage heat treatment is performed isothermally at 300 to 800°C, then the second stage heat treatment is performed at 600 to 1000°C, and the first stage A method for producing rare earth permanent magnets characterized by isothermal production at temperatures higher than eye temperature. 2. R_x(Fe_1_-_wCo_w)_1_-_x
It is represented by the general formula _-_y_-_zB_yTi_z (where R is one or more rare earth elements including Y), 6≦x≦16, 2≦y≦25, 0<z≦12, 0 Using a liquid quenched alloy with <w<1, the first stage heat treatment is performed isothermally at 300 to 800 °C, and then the second stage heat treatment is performed at 600 to 1000 °C and at a higher temperature than the first stage. A method for producing a rare earth permanent magnet characterized by carrying out the production at an isothermal temperature. 3. R_xCo_1_-_x_-_y_-_zB_yT
Represented by the general formula i_z (where R is one or more rare earth elements including Y), 6≦x≦16, 2≦
Using a liquid quenching alloy with y≦25,0<z≦12, the first stage heat treatment is performed isothermally at 300 to 800°C, then the second stage heat treatment is performed at 600 to 1000°C, and the first stage A method for producing rare earth permanent magnets characterized by isothermal production at temperatures higher than eye temperature.