JPH0298105A - Permanent magnet - Google Patents

Abstract

PURPOSE:To stably manufacture a high-performance permanent magnet by mixing Co to specific principal constituent elements contained in specific weight percentages. CONSTITUTION:This permanent magnet contains 22-28wt.% R (R: rare earth elements), 10-25wt.% Fe, 1-10wt.% Cu, 0.2-5wt.% M1 (M1: one of Zr and Hf), and 0.05-5wt.% M2 (M2: at least one of W and Mo). When the adding quantity of W and Mo is more than 0.05wt.%, the break in the second quadrant disappears and the angularness is improved, but, when the quantity is more than 5wt.%, no merit can be expected from the addition, since the density of residual magnetic fluxes considerably drops and the coercive force also slightly decreases. By adding the high-melting point element of W or Mo by an appropriate quantity in such way, the angularness in the second quadrant of this R2Co17 permanent magnet is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to improving the magnetic properties of RzCo+ based permanent magnets (where R is a rare earth element).

[Prior art] The coercive force generation mechanism of a two-phase separated R, Co, 7-based permanent magnet (where R is a rare earth element) is that the movement of the domain wall is hindered by the coexistence of two fine ferromagnetic phases. This is caused by The presence of Cu is essential for the coexistence of these two phases, and addition of Pe is effective in increasing the residual magnetic flux density. The one replaced with is in practical use.

In addition, in recent years, Zr (Japanese Unexamined Patent Publication No. 52-1150
Coercive force, Hc can be improved by adding trace amounts of transition elements such as
Magnet alloys with increased maximum energy product (BH) m have been proposed.

In this two-phase separation type R2Co, 7-series permanent magnet, the state of the fine precipitated phase precipitated in the matrix by aging treatment, which is heat treatment, greatly influences the level of coercive force and the squareness of the second quadrant. A key point in manufacturing is to carry out this aging treatment under optimal conditions. For this reason, R2Co
Improvements in the magnetic properties of +□-based permanent magnets have been carried out mainly through aging treatment. For example, in JP-A-50-133106, 7
A method of multi-stage aging from 00 to 900°C to around 400°C is disclosed in JP-A-53-106624.
A method of slowly cooling from a temperature of 900°C to a temperature around 400°C is shown. Also, JP-A-57-161044
isothermal treatment at a temperature of 400-750 °C, followed by 6
300-600° with a starting temperature of 00-1000°C
JP-A-59-153873 discloses a method of cooling to a temperature of 750 to 950°C to a temperature of 700°C or less by repeating heat treatment two or more times. As a result, today, by applying appropriate aging treatment according to the alloy composition, high coercivity of 10 kOe or more can be achieved.
Hc can be obtained.

(Problem to be solved by the invention) However, there is a knick in the second quadrant of the magnetization curve of such R2Co, 7 series permanent magnets, and as a result, the residual magnetic flux density is lower than the level expected from the value of the residual magnetic flux density. There has been a problem that the level of the maximum energy product (Bt()n+) that can be obtained is considerably lowered. This knick tends to become more pronounced as the coercive force 1Hc increases.

Therefore, it is possible to reduce the extent of this knick by changing the aging conditions and suppressing the coercive force IHc.

However, changing the statute of limitations alone cannot completely resolve the issue.

An object of the present invention is to solve the above-mentioned problems and provide an R2C017 permanent magnet having high coercive force and energy product and good squareness in the second quadrant of the magnetization curve.

[Means for solving problems]

As a result of various studies on methods for improving the squareness of the second quadrant of R2C0I7-based permanent magnets, the present inventors have found that the above objective can be achieved by adding a specific amount of a specific high-melting point metal element to the present alloy. This is the heading that led to the completion of the present invention.

That is, first, in the course of research, the inventors of the present invention discovered that the magnetic properties of the present RZCoIt-based permanent magnet change greatly in response to slight changes in the sintering temperature, and drew attention to this fact. In Figure 1, as an example of experimental results, 5rr125.5ivt%
, Fe14. Owt%, Cu4.4wt%, Zr2.7
The relationship between the sintering temperature of a permanent magnet alloy with wt% and balance Co and the magnetization surface vA (4πI-H curve) in the second quadrant is shown.

A detailed explanation will be given later on the specific method for manufacturing the thcO+ based permanent magnet alloy of the present invention, but the experiment shown in FIG. 1 was conducted using the same manufacturing method. From FIG. 1, it can be seen that among the magnetic properties, in particular, the level of coercive force +)Ic and the squareness of the second quadrant change greatly in response to a slight change of 5'C in the sintering temperature. On the other hand, it can be seen that the knick in the second quadrant is not completely eliminated at any sintering temperature. By observing the structure of the permanent magnet sintered body using an optical microscope, it was confirmed that the crystal grain size of the sintered body increased and became coarser as the sintering temperature increased. The above experimental results show that the coercive force, Hc level, and squareness of the second quadrant of R2C0,7-based permanent magnets are not uniquely determined by the aging treatment, but are also closely related to the state of the crystal grains of the sintered body. It shows that there is a relationship. At present, it is not clear how the microscopic condition of crystal grains, including grain boundaries, changes due to changes in sintering conditions. However, it can be easily inferred from the previous experimental results that this greatly influences the state of formation of precipitates that precipitate during the aging treatment process.

Based on the above experimental results, the present inventors believe that the addition of additives changes the microscopic condition of crystal grains, which causes R
, Co, , based on the prospect that the squareness of the second quadrant of permanent magnets would change, research was conducted on various additives. As a result, it was found that addition of W and Mo among high melting point metal elements is effective in improving the squareness in the second quadrant.

That is, the R2Co, 7-based permanent magnet in the present invention has a weight percentage of R22 to 28% (R is one or more rare earth elements), FelO to 25%, Cu1
~10%, MIo, 2~5% (however, Ml is Z r +
At least one species in HfO) l M20.05-5%
(However, M2 is at least one of W and Mo), and the remainder is essentially Co. Figure 2 shows an example of the experimental results: Sm 25.5wt%, Fe 14.0
wt%, Cu4.4wt%, Zr2.7wt%, WO~
The magnetization curve in the second quadrant of a permanent magnet alloy with 0 wt% I and the balance Co is shown. In addition, Fig. 3 shows Sm25.5wt%, F
e14.0wt%, Cu4.4wt%, Zr2.7wt
%, MoO to 10 wt%, and the balance is Co. It can be seen from FIGS. 2 and 3 that the addition of W or Mo eliminates the knick in the second quadrant and improves the squareness. It is also seen that the improvement effect is remarkable when the amount of both W and Mo added is 0.05 wL% or more. On the other hand, if the amount of both W and Mo added is more than 54%, the residual magnetic flux density decreases greatly and the coercive force also slightly decreases, so that the merits of addition cannot be obtained. Therefore, the amount of W and base 0 added is limited to a range of 0.05 to 5 wt%. In addition, even when W and Mo are added simultaneously, the second
The same effect of improving the squareness of the second quadrant as shown in FIG. 3 or FIG. 3 can be obtained. In this case, for the same reason as above, W
The total amount of addition of Mo and Mo is limited to a range of 0.05 to 5 wt%. Figure 4 shows Sm25.5hL%, Fe14. O
wt%, Cu4.4wt%, Zr2.7wt%W1.0
The relationship between the sintering temperature and the magnetization curve in the second quadrant of a permanent magnet alloy with wt% and balance Co is shown. Also, in Figure 5, Sm25.5w
t%, Fe14. Owt%+Cu4.4wt%+Zr
The relationship between the sintering temperature and the magnetization curve in the second quadrant of a permanent magnet alloy of 2.7 wt %, Mo 1.0 wt %, and the balance co is shown. By comparing Figure 4 or Figure 5 with Figure 1,
It can be seen that the dependence of the magnetic properties on the sintering temperature is alleviated by adding W or Mo.

Here, the reason for limiting the composition of elements other than W and Mo will be explained. The rare earth element R is 22 to 28 wt%. If the rare earth element content is less than 22-t%, sufficient coercive force cannot be obtained. Moreover, when the content of rare earth elements is more than 28-t%, the residual magnetic flux density decreases. Fe is IO~25-
t%. If it is less than 10-tχ, the residual magnetic flux density decreases. When the amount is more than 25-t%, coercive force and squareness decrease. Cu is 1 to lowt%. 1-1%
If it is less than that, sufficient coercive force cannot be obtained. When the amount is more than 10-t%, the residual magnetic flux density decreases. M1 element (Zr,
At least one type of Hf) is 0.2 to 5 wt%. If it is less than 0.2wt%, sufficient coercive force cannot be obtained, and 5w
When the amount is more than t%, the residual magnetic flux density decreases.

Finally, the permanent magnet alloy having the composition shown in the claims, which characterizes the method for producing an R2Co permanent magnet of the present invention, can be produced by a normal melting method or a so-called reduction diffusion method.

This alloy is processed by jet mill, ball mill, etc.
The powder is pulverized to a particle size of μ, and the pulverized powder is molded in a magnetic field to form a compact. The molded body is heated in vacuum or in a non-oxidizing atmosphere.
Sinter at a temperature of 100-1250°C. Next, the sintered body is maintained at a temperature 10 to 50°C lower than the sintering temperature in a non-oxidizing atmosphere, and then rapidly cooled to a temperature below the aging treatment start temperature to perform solution treatment. Finally, add the sample to 650~9
After holding at a temperature of 00°C for a certain period of time, aging treatment is performed by cooling in multiple stages or continuously to a temperature of 400°C or less.

Examples and comparative examples of the present invention will be described below, but the scope of the present invention is not limited thereby.

〔Example〕

(Example 1) An alloy having the composition (weight percentage) shown in No. 1-Nα5 in Table 1 was produced by high-frequency induction melting. This was coarsely crushed using each show crusher, and then finely crushed using a die mill. The particle size of the fine powder is approximately 4.0 μ (F・S −S −S
)Met. Magnetic field strength for orienting fine powder is 1QkOe, molding pressure is 3
A molded article was obtained by molding under the following conditions. The molded body was sintered under conditions of 1180° CX2H in a II gas atmosphere. Next, the sintered body was solution-treated at 1160° CX4H and rapidly cooled in water. Finally 800°CX8H
After the isothermal treatment, an aging treatment was performed in which the alloy was slowly cooled to room temperature at a cooling rate of l''C/min.The permanent magnet alloy was made into a permanent magnet through the above treatment, and its magnetic properties were measured, as shown in Table 2. I got the result like this.Here, HK
is the value of H on the I-H curve at the point of BrX0.9.

Also, the squareness ratio, which indicates the degree of squareness, is HK/1lcX
100 (χ). Table 2 shows that a good squareness ratio of 60% or more can be obtained by adding W.

(Example 2) Compositions shown in No. 6 to Nα10 in Table 3 (weight percentage)
The alloy was prepared by high frequency induction melting. This was treated under the same conditions as in Example 1 to form a permanent magnet, and its magnetic properties were measured, and the results shown in Table 4 were obtained. Table 4 shows that a good squareness ratio of 60% or more can be obtained by adding MO.

(Example 3) Alloys having the compositions (weight percentages) shown in Nα11 to Nα13 in Table 5 were produced by high-frequency induction melting. Example 1
When treated under the same conditions as above to form a permanent magnet and its magnetic properties were measured, the results shown in Table 6 were obtained. From Table 6,
It can be seen that a good squareness ratio of 60% or more can be obtained by adding W and Mo in combination.

(Comparative Example 1) Alloys having the compositions (weight percentages) shown in Nα14 to Nα18 in Table 7 were produced by high frequency induction melting. Example 1
When treated under the same conditions as above to form a permanent magnet and its magnetic properties were measured, the results shown in Table 8 were obtained. By comparing the magnetic properties in Table 8 with the magnetic properties of alloys with corresponding compositions listed in Tables 21, 45, and 6, it was found that alloys without W or Mo added have a higher It can be seen that the squareness ratio is poor and the maximum energy product (B)l)m is small.

Table H (KOe) [Effect of the invention] As described above, by adding an appropriate amount of high-melting point metal elements such as W or Mo, the squareness of the second quadrant of R, Co, and permanent magnets can be improved. and the dependence of magnetic properties on sintering temperature is relaxed. This results in high performance R,C
It has now become possible to stably manufacture o, system permanent magnets.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between sintering temperature and magnetic properties in a conventional composition. FIG. 2 is a diagram showing the relationship between the amount of W added and magnetic properties. FIG. 3 is a diagram showing the relationship between the amount of Mo added and magnetic properties. FIG. 4 is a diagram showing the relationship between sintering temperature and magnetic properties in the composition of the present invention. FIG. 5 is a diagram showing the relationship between sintering temperature and magnetic properties in the composition of the present invention. Figure H (in Oe) Figure Figure

Claims (1)

[Claims] Weight percentage: R22-28% (R is a rare earth element), Fe10-25%, Cu1-10%, M_10.2
~5% (However, M_1 is at least one of Zr and Hf
species), M_20.05-5% (however, M_2 is W, Mo
A rare earth-containing permanent magnet consisting of at least one of the following: