JPH02104632A - Manufacture of permanent magnetic alloy - Google Patents

Abstract

PURPOSE:To dissolve the compositional nonuniformity of the title permanent magnet and to improve its rectangular hysteresis properties in a secondary quardrant by melting a Co alloy contg. specific wt.% of rare earth elements, Fe, Cu, Zr, etc., subjecting it to rapid solidification into powder, converting the powder into fine powder, thereafter compacting it, sintering the green compact at a specific temp. and thereafter subjecting it to aging treatment. CONSTITUTION:A Co alloy constituted of, by weight, 20 to 30% R (rare earth elements), 10 to 25% Fe, M (at least one kind among Zr, Hf, Ti, Ta, Nb, Ni and V) and the balance Co is melted in an inert gas or in vacuum. The molten metal is subjected to rapid solidification in an inert gaseous flow into powder, which is furthermore pulverized into fine powder. The fine powder is compacted and is sintered at 1100 to 1250 deg.C in a nonoxidizing atmosphere. The sintered body is rapidly cooled to the starting temp. of aging treatment or below. Finally, the sintered body is subjected to aging treatment in which starting temp. is regulated to 600 to 900 deg.C and it is gradually cooled to <=400 deg.C. In this way, the compositional nonuniformity of the permanent magnet is dissolved and its rectangular hysteresis properties in a secondary quadrant can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the improvement of the magnetic properties of R1Co permanent magnets (where R is a rare earth element).

[Conventional technology]

Two-phase separation type RgCo,? system permanent magnet (where R is rare earth,
The coercive force generation mechanism of ferromagnetic elements) is due to the coexistence of two fine ferromagnetic phases, which prevents the movement of domain walls. In order for these two phases to coexist, C
Since the presence of u is indispensable and the addition of Fe is effective in increasing the residual magnetic flux density, -C is used for boat fishing.
One in which part of o is replaced with Cu and Fe has been put into practical use. In addition, in recent years, Zr (Japanese Unexamined Patent Publication No. 52-11
5000) or 11f (JP-A-53-106326
) by adding a small amount of transition elements such as
Magnet alloys with increased Hc and maximum energy product (BH)+s have been proposed.

In this two-phase separated R, Co, and permanent magnet, the state of the fine precipitated phase that precipitates in the matrix during aging treatment, which is heat treatment, greatly influences the level of coercive force and the squareness of the second quadrant. Therefore, it is important in manufacturing to carry out this aging treatment under optimal conditions. For this reason, RtCo
, 7 series permanent magnets have been improved mainly by aging treatment. For example, in JP-A-50-133106, 7
A method of multi-stage aging from 00 to 900 degrees Celsius to around 400 degrees Celsius is described in JP-A-53-106624.
A method of slowly cooling from a temperature of 0°C to a temperature around 400°C is shown. In addition, 40
Isothermal treatment at a temperature of 0-750 °C, then 600-10
A method of cooling from 300 to 600 degrees Celsius with a starting temperature of 00 degrees Celsius is disclosed in JP-A-59-153873.
℃ to 700℃ or less.As a result, today, by applying appropriate aging treatment according to the alloy composition, high A coercive force of 11c can be obtained.

[Problem that the invention seeks to solve]

However, there is a knick in the second quadrant of the magnetization curve of such R2Co, 7 series permanent magnet, and therefore the maximum energy product (Bll) m obtained from the value of residual magnetic flux density is The problem was that the standard had dropped considerably. This knick tends to become more pronounced as the coercive force 1Hc increases.

Therefore, this knick changes the aging conditions and increases the coercive force, llc
It is possible to reduce the extent of the problem by suppressing it. 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 R, Co, 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 R2Co1t-based permanent magnets, the present inventors discovered that the above object could be achieved by improving the manufacturing method of the raw material powder, and completed the present invention. This is what led to this.

Generally I? In the production of zCoIt-based permanent magnets, there are two methods: melting the raw metal by high-frequency induction melting to create an alloy ingot, and pulverizing it to obtain the raw material powder, and the other method by reducing the oxide raw material with a reducing agent to produce Co powder. ,? A so-called reduction diffusion method is used to obtain alloy raw material powder by diffusing it into powder or the like. In the course of research, the present inventors produced R, Co, and raw material powders using these conventional manufacturing methods and evaluated their magnetic properties. Figure 1 shows, as an example of experimental results, 5ra25.5wt%, Fe14.0wt%, Cu
The magnetization curve (4πI-H curve) in the second quadrant of a permanent magnet alloy containing 4.4 wt% Zr, 2.7 wt% Zr, and the balance Co is shown.

Although the level of coercive force changes depending on the aging treatment conditions, it can be seen that under all conditions, there is a knick in the magnetization curve and the squareness is poor. Also, when alloy raw material powders of the same composition prepared by the reduction diffusion method were used, almost the same results as in FIG. 1 were obtained.

From the magnetization curve in FIG. 1, it can be seen that the magnitude of pinning of the domain wall inside the magnet is not necessarily uniform, but is non-uniform. It can also be seen that the non-uniformity tends to expand as the coercive force increases with changes in the aging treatment conditions. In order to clarify the cause of the non-uniformity in the size of this pinning, the inventors once again applied the solution treatment to the sample shown in Figure 1 by heating it to a temperature 20°C lower than the sintering temperature and then rapidly cooling it to room temperature. After straining, SEM (Scannin
g Elect-ron Microanalyzer
), E P MA (Electron Prob
eMicroanalyzer LTEM (Anal
ytica'l Electron Microscope
The microcomposition was analyzed using a device such as e). As a result, it has been revealed that even within the same crystal grain, there is slight compositional non-uniformity among the constituent elements centered on Cu. Furthermore, as a result of aging the same sample and observing magnetic domains using the Kerr effect, we found that the generation of reversed magnetic domains in the second quadrant begins from a specific part of the grain boundary, and that there is no correspondence with the above microcomposition analysis. It has been found that the composition near this specific part is relatively slightly lower in Cu and Sm than other parts within the same crystal grain.

From the above study results, the non-uniformity of the microscopic composition inside the crystal grains of the permanent magnet induces the non-uniformity of the precipitation state of the SmCo5 phase due to aging treatment, and this causes the non-uniformity of the pinning of the domain wall. It is thought that this causes the formation of a knick in the second quadrant. Through subsequent research by the present inventors,
The non-uniformity of the composition inside the crystal grains of the above-mentioned permanent magnet originates from the non-uniformity of the composition inside the raw material powder, and in the melting method, it is also due to the non-uniformity of the cooling rate and phase separation during the cooling process of the alloy ingot. , it became clear that this is due to the non-uniformity of diffusion in the reduction-diffusion method. Therefore, the present inventors attempted to make the alloy ingot or permanent magnet sintered body uniform in composition by heat treatment and by examining the sintering conditions, but they were unable to obtain good results. . Figure 2 shows, as an example of experimental results, Sm25.0i, which was produced by the dissolution method.
yt%, Fe14.0-t%, Cu4.8ivt%, Z
r3. % Qwt%, the balance being Co, the magnetization curve (4πI-H curve) in the second quadrant after the aging treatment when the sintered body of the permanent magnet alloy was solution-treated under various conditions. A slight improvement in the knicks in the second quadrant was observed as the solution treatment time increased, and this confirms the validity of the above discussion of the cause of the knicks. On the other hand, even after long-term solution treatment, the nicks do not fundamentally disappear, and this shows that compositional non-uniformity once generated cannot be eliminated by the degree of atomic diffusion caused by heat treatment.

From the above research results, the present inventors have come to the conclusion that the use of a compositionally uniform raw material powder is the key to eliminating the second quadrant knick and improving the squareness of this permanent magnet. As a result of various studies, specifically, the molten metal having the composition shown in the claims is dropped into a high-speed stream of inert gas or blown out with a nozzle to rapidly solidify it into a powder, and this powder is used as a raw material to form a powder. It has been discovered that the above object can be achieved by forming a permanent magnet using a powder metallurgical method.

The inert gas pressure is not particularly limited, as it is necessary to select an appropriate value depending on the amount of dripping and blowing of the molten metal, but for example, when molten wood is 30 kg/kg from a φ5 nozzle hole,
When blowing out at a speed of 1 minute, the pressure in the inert gas line is 3
A suitable value is 0 aLm or more, preferably about 50 to 1100 at. The diameter of the molten metal dripping hole or nozzle hole needs to be determined appropriately depending on the amount of molten metal and the dropping and blowing speed.
When blowing at a speed of kg/min, the diameter of the nozzle hole is φ3.
~10 is appropriate. In addition, the material of the crucible for melting the molten metal is AlzOs and Mg.

etc. are used. It is preferable that the nozzle is made of the same material as the crucible. The powder produced by rapid solidification using this method is ultimately finely pulverized by mechanical pulverization, so its particle size is not particularly limited, but particles of 300μ or less account for 70-t% or more of the total powder. It is desirable that there be. This is because powder with a large particle size reduces the quenching rate and makes it difficult to achieve compositional uniformity, which is the object of the present invention. The particle size is controlled by appropriately combining the dropping or blowing rate of the molten metal and the pressure and flow rate of the inert gas. It is also possible to control the particle size distribution to a narrower range by installing a vibration device near the molten metal dripping hole or nozzle hole so that the molten metal is dripped or blown out while being vibrated.

Furthermore, as is clear from the comparison between the examples of the present invention and comparative examples described later, it is clear that the powder produced by rapid solidification by this method has a zero
□Amount is 0 of coarse powder produced by conventional dissolution method or reduction diffusion method.
Since the amount of residual magnetic flux is lower than that of 2, higher residual magnetic flux density can be obtained in alloys with the same composition.

FIG. 3 shows, as an example of experimental results, Sm25.5iyt%, Fe14. Owt%
.

The magnetization curve in the second quadrant (4
πI-H curve). R2GO+ of the present invention? A detailed explanation will be given later in Examples regarding a specific manufacturing method of the permanent magnet alloy, but the same manufacturing method was used in the experiment shown in FIG. Comparing FIG. 3 with FIG. 1 above, it can be seen that when a powder produced by rapid solidification is used and made into a permanent magnet, a magnetization curve with excellent squareness and no nicks can be obtained.

The sample shown in Figure 3 was subjected to solution treatment again, and first
Microcompositional analysis was carried out using the same method as for the sample shown in the figure, but unlike in the previous case, no compositional inhomogeneity within the same grain was detected.

Finally, the reasons for limiting the composition of the R, Go, 7-based permanent magnet alloy of the present invention will be explained. The rare earth element R is 22 to 30 wtX. If the rare earth element content is less than 22-t%, sufficient coercive force cannot be obtained. In addition, the content of rare earth elements is 304
%, the residual magnetic flux density decreases. Fe is 1
It is considered to be 0 to 25-1%. If it is less than 10 wt%, the residual magnetic flux density decreases. When the amount is more than 25 wt%, coercive force and squareness decrease.

Cu is assumed to be 1=lOwt%. If it is less than 1 wt%, sufficient coercive force cannot be obtained. When the amount is more than 10 wt%, the residual magnetic flux density decreases. M elements (Zr, elbow, Ti.

The amount of at least one of Ta, Nb, Ni, and V is 0.2 to 5 wt%. If it is less than 0.24%, sufficient coercive force cannot be obtained, and if it is more than 5wt%, the residual magnetic flux density decreases.

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) A total of 10 kg of raw materials were charged into an alumina crucible and melted by high frequency induction melting in a substantial vacuum. Next, the molten metal was passed through a φ4 nozzle hole provided at the bottom of the crucible.
kg was blown into a flow of Af gas at a pressure of 80 atm at a speed of 715 seconds to powder. By repeating this process, the compositions shown in Table 1 No. 1- No. 5 and 0□
Five types of powder were made with different amounts.

All five types of powder contain 30% or more of 80wt% of their total weight.
It had a particle size of 0μ or less. Each powder was then finely ground using a jet mill. The particle size of fine powder is approximately 4.0
It was μ (F-3-3-3).

Magnetic field strength for orienting fine powder: 10 kOe, molding pressure: 3 ton/c
A molded article was obtained by molding under +fl conditions. The molded body is 11
□Sintering was carried out in a gas atmosphere at 1180°C x 2 H. Next, the sintered body was subjected to solution treatment at 1160°C x 4 H and rapidly cooled in water. Finally, after performing isothermal treatment at 800°C for 8 hours, aging treatment was performed by slowly cooling to room temperature at a cooling rate of 1° (:/min). Through the above treatment, the permanent magnet alloy was turned into a permanent magnet, and its magnetic properties were measured. As a result, the results shown in Table 2 were obtained.

Here, IIK is H on the I-H curve at the point BrX0,9
is the value of In addition, the squareness ratio, which indicates the degree of squareness, is H1l
/+IIcX 100 (%). Table 2 shows that the permanent magnet alloy according to the present invention has a good squareness ratio of 60% or more.

(Comparative Example 1) A total of 10 kg of raw materials were charged into an alumina crucible and melted by high frequency induction melting in a substantial vacuum to produce an alloy ingot. Next, the alloy ingot was crushed using a show crusher to obtain a coarse powder of 300 μm or less. Repeat this process to get No. 6 to No. 6 in Table 3.
Five types of coarse powder having the composition shown in 10 and the amount of 0□ were prepared. From a comparison of Tables 1 and 3, it can be seen that there is a difference in the amount of 02 between the powder produced by the rapid solidification method and the coarse powder produced by the conventional melting method, with the former being smaller. Each coarse powder in Table 3 was treated under the same conditions as in Example 1 to become a permanent magnet, and its magnetic properties were measured, and the results shown in Table 4 were obtained. By comparing the magnetic properties in Table 4 with the magnetic properties of the alloys with the corresponding compositions listed in Table 2, the magnetic properties of the permanent magnet alloy using conventional melting raw materials can be compared to the magnetic properties of the permanent magnet alloy according to the present invention. It can be seen that the squareness is poor compared to the characteristics, and the residual magnetic flux density 4πIr and maximum energy product (BH) m are also small.

Table 1 Table 3 [Effect of the invention] As described above, by using the powder produced by the rapid solidification method as a raw material, the compositional non-uniformity of the RZCoI7 permanent magnet is eliminated, and as a result, the second quadrant The squareness has been improved. At the same time, a higher residual magnetic flux density than before can be obtained due to the secondary effect of lowering the level of the at content of the raw material.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between aging treatment conditions and magnetic properties in a conventional method. FIG. 2 is a diagram showing the relationship between solution treatment conditions and magnetic properties in a conventional method. FIG. 3 is a diagram showing the relationship between aging treatment conditions and magnetic properties in the present invention. Figure 1 H (to Oe) Figure 2 jI3 Figure H (to Oe)

Claims (1)

[Claims] Weight percentage: R22-30% (R is a rare earth element), Fe10-25%, Cu1-10%, M0.2-5
% (where M is Zr, Hf, Ti, Ta, Nb, Ni,
(V), the remainder of which is essentially Co, is melted into a molten metal in an inert gas atmosphere or in a substantial vacuum, and the molten metal is placed in a high-velocity stream of inert gas. Drop it or blow it out with a nozzle to rapidly solidify it into a powder, then mechanically grind it into a fine powder,
The fine powder is molded and the molded body is sintered at a temperature range of 1100 to 1250°C in a non-oxidizing atmosphere or in a substantial vacuum, and the sintered body is heated to a temperature 10 to 80°C lower than the sintering temperature. Rapid cooling to a temperature below the aging treatment start temperature, and finally 600~
A method for producing a permanent magnet alloy, which comprises performing an aging treatment with a starting temperature of 900°C and gradual cooling to a temperature of 400°C or less.