JP2022080585A - Rare-earth cobalt permanent magnet, manufacturing method for the same, and device - Google Patents

Abstract

To provide a rare-earth cobalt permanent magnet of excellent magnetic property.SOLUTION: A rare-earth cobalt permanent magnet is an intermetallic compound including rare-earth cobalt which has R:23 to 27% (R is a sum of rare-earth elements including at least Sm), Cu:4.0 to 5.0%, Fe:22 to 27%, Zr:1.7% to 2.5% in mass percentage composition and has a remaining part composed of Co and inevitable impurities. It has a plurality of crystal grains and grain boundaries and the maximum diameter of its pore is 40 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a rare earth cobalt permanent magnet, a method for producing the same, and a device.

Rare earth cobalt permanent magnets are known to contain, for example, Fe, Cu, Zr, etc. from various viewpoints such as improvement of magnetic properties.

Patent Document 1 describes rare earth elements R: 23 to 27%, Cu: 3.5 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to 3.0% in mass%. A rare earth cobalt permanent magnet is disclosed in which the balance is composed of Co and unavoidable impurities, and the content of Cu and Zr in the grain boundary portion is higher than that of the crystal grains.
Further, Patent Document 2 contains 25 to 40% by mass of Fe, an element selected from Zr, Ti and Hf, a rare earth element, Cu and Co in a specific ratio, and has a high Cu concentration. Permanent magnets with phases are disclosed.

International Publication No. 2017/061126 Japanese Unexamined Patent Publication No. 2014-103239

The present inventors have studied rare earth cobalt permanent magnets having a high Fe content concentration from the viewpoint of improving magnetic characteristics such as residual magnetic flux density Br and maximum magnetic energy product (BH) m of rare earth cobalt permanent magnets. The present inventors have found that when the sintering treatment is performed by increasing the proportion of Fe, pores (voids) may occur in the sintered body. The generation of large pores hindered the homogenization of the structure of the sintered body, and as a result, the influence of the demagnetic field was increased and the magnetic properties were sometimes deteriorated.

The present invention solves the above-mentioned problems, and provides a rare earth cobalt permanent magnet having excellent magnetic properties and a method for producing a rare earth cobalt permanent magnet capable of suppressing the generation and enlargement of pores.

The rare earth cobalt permanent magnet according to the present invention has a mass percentage composition of R: 23 to 27% (R is the total of rare earth elements including at least Sm), Cu: 4.0 to 5.0%, and Fe: 22 to 27. %, Zr: 1.7% to 2.5%, an intermetallic compound containing rare earth cobalt consisting of Co and unavoidable impurities in the balance, having a plurality of crystal grains and grain boundaries, and having a maximum pore diameter. It is 40 μm or less.

One embodiment of the rare earth cobalt permanent magnet includes a powder sintered body having a specific surface area of 0.30 m ² / g or more.

One embodiment of the rare earth cobalt permanent magnet has a sintered body density of 8.25 g / cm ³ or more, a maximum energy product of 260 kJ / m ³ or more, an intrinsic coercive force of 1600 kA / m or more, and 90% of Br. When the magnitude of the reverse magnetic field is Hk, Hk / Hcj is 65% or more.

The method for manufacturing a rare earth cobalt permanent magnet according to the present invention is as follows.
By mass percentage composition, R: 23 to 27% (R is the total of rare earth elements including at least Sm), Cu: 4.0 to 5.0%, Fe: 22 to 27%, Zr: 1.7% to 2 Step (I) of preparing an alloy consisting of 5.5%, the balance of Co and unavoidable impurities, and
In the pulverization step (II) in which the alloy is made into a powder having a specific surface area of 0.30 m ² / g or more,
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product and
The step (V) of solution-treating the sintered compact and
The step of quenching the molded product after the solution treatment (VI),
It has a step (VII) of heat-treating the molded product after the solution treatment.

The device according to the present invention is characterized by having the rare earth cobalt permanent magnet.

INDUSTRIAL APPLICABILITY The present invention provides a rare earth cobalt permanent magnet having excellent magnetic properties and a method for producing a rare earth cobalt permanent magnet capable of suppressing the generation and enlargement of pores.

It is an optical microscope image which shows the polished surface of the permanent magnet of Example 2. It is an optical microscope image which shows the polished surface of the permanent magnet of the comparative example 3. FIG. It is an optical microscope image which shows the polished surface of the permanent magnet of the comparative example 5.

Hereinafter, the rare earth cobalt permanent magnet according to the present invention will be described.
Unless otherwise specified, "-" indicating a numerical range includes the lower limit value and the upper limit value.

[Rare earth cobalt permanent magnet]
The rare earth cobalt permanent magnets of the present embodiment (hereinafter, also referred to as the permanent magnets) have a mass percentage composition of R: 23 to 27% (R is the total of rare earth elements including at least Sm) and Cu: 4.0 to 5. An intermetallic compound containing 0.0%, Fe: 22-27%, Zr: 1.7% -2.5%, and a rare earth cobalt composed of Co and unavoidable impurities, with a plurality of crystal grains and grain boundaries. The maximum diameter of the pore is 40 μm or less.

Residual magnetic flux density (Br) is one of the magnetic characteristics of permanent magnets. Br is defined as the amount of magnetic flux penetrating per unit area. The presence of pores in the permanent magnet means that the amount of magnetic material in the permanent magnet is reduced, and the amount of magnetic flux penetrating the entire permanent magnet is reduced. In addition, since the composition and the structure of the cell are disturbed around the pores, reverse magnetic domains are likely to occur. Therefore, it is important to prepare a high-density sample in order to increase the amount of magnetic flux as much as possible and to exhibit high-performance characteristics as a permanent magnet.
This permanent magnet contains a relatively large amount of Fe (22%), but the maximum diameter of the pores is suppressed to 40 μm or less. Therefore, magnetic characteristics such as maximum energy product (BH) m and square ratio (Hk / Hcj). Is excellent.

A method of observing pores will be described with reference to FIG. FIG. 1 is an optical microscope image showing a polished surface of the permanent magnet of Example 2. The microscope image is etched by mirror-polishing the permanent magnet (sintered body) to be measured and then impregnating it with an acid solvent. At this time, since the grain boundary portion is corroded faster than the crystal grain main body portion, the grain boundary appears clearly and each crystal grain can be clearly observed.
As shown in FIG. 1, the permanent magnet has a plurality of crystal grains 1 and a crystal grain boundary 2 that is a boundary between the crystal grains 1. The black part in FIG. 1 corresponds to the pore 4. The gray part shown by 3 in FIG. 1 is an oxide of a rare earth element and is different from Pore 4. For the maximum diameter of the pore 4 in this permanent magnet, the pore having the maximum diameter is determined from the optical microscope image, and the diameter of the pore is set as the maximum diameter. If the pore is not a circle and is an indefinite type, the longest width is the maximum diameter.
The size of crystal grains and the size of pores can be grasped more accurately by using image processing software.

The present inventors have found that the pores tend to increase when the concentration of Fe is high. Pore is considered to be generated by degassing or the like during the sintering process. The present inventors presume that when the concentration of Fe is high, the diffusion rate and the wettability are relatively low, and it is difficult for the pores to be filled during the sintering process. It is presumed that the permanent magnet can easily fill the pores with a metal component during the sintering process even if pores are generated by a manufacturing method described later, and a sintered body having a maximum diameter of 40 μm or less can be obtained.

The maximum diameter of the pore may be 40 μm or less. Above all, the maximum diameter of the pore is preferably 20 μm or less from the viewpoint of increasing the density of the permanent magnet and obtaining better magnetic characteristics. Further, the abundance ratio (area ratio) of the pores in the optical microscope image is preferably 10% or less, more preferably 5% or less, from the viewpoint of increasing the density of the permanent magnet and obtaining better magnetic characteristics.

The composition of this permanent magnet is mass percentage, rare earth element R including Sm: 23 to 27%, Cu: 4.0 to 5.0%, Fe: 22 to 27%, Zr: 1.7% to 2. 5%, the balance consists of Co and unavoidable impurities. By having such a composition, the permanent magnet shows the same composition fluctuation tendency in the cell structure, the desired magnetic domain structure and magnetic characteristics can be obtained, and the permanent magnet has excellent magnetic characteristics.

In the present embodiment, the rare earth element R is a general term for Sc, Y, and lanthanoids (elements having atomic numbers 57 to 71). This permanent magnet contains at least Sm as a rare earth element R. The rare earth element R may be used alone for Sm, or may be a combination of Sm and one or more other rare earth elements. As the other rare earth elements, Pr, Nd, Ce, and La are particularly preferable from the viewpoint of magnetic properties. Further, from the viewpoint of magnetic properties, Sm is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more with respect to the entire rare earth element R.
The permanent magnet contains 23 to 27% of the rare earth element R by mass percentage. By containing the magnet in the above ratio, a permanent magnet having high magnetic anisotropy and high coercive force can be obtained. Above all, 23.5 to 26.5% is preferable from the viewpoint of improving the magnetic characteristics.

This permanent magnet contains 22 to 27% of Fe. Saturation magnetization is improved by containing 22% or more of Fe. Further, when the Fe content is 27% or less, the permanent magnet has a high coercive force. In this permanent magnet, the enlargement of the pores is suppressed even if Fe is 22% or more by the manufacturing method described later, and the maximum diameter of the pores is 40 μm or less. The Fe content is preferably 22.5 to 26.5% from the viewpoint of improving the magnetic properties.

This permanent magnet contains 4.0 to 5.0% of Cu. By containing 4.0% or more of Cu, it becomes a permanent magnet having a high coercive force. Further, when the Cu content is 5.0% or less, the decrease in magnetization is suppressed. The Cu content is preferably 4.0 to 4.5% from the viewpoint of improving the magnetic properties.

This permanent magnet contains 1.7% to 2.5% of Zr. By containing Zr within the above range, a permanent magnet having a high maximum energy product (BH) m, which is the maximum static energy that the magnet can hold, can be obtained. The Zr content is preferably 1.7% to 2.3% from the viewpoint of improving the magnetic properties.

Further, in this permanent magnet, the balance (that is, 38.5% to 49.3%) is composed of Co (cobalt) and unavoidable impurities. By containing Co, the thermal stability of the permanent magnet is improved. On the other hand, when the Co content is excessive, the Fe content ratio is relatively low.
Inevitable impurities are elements that are inevitably mixed from raw materials and manufacturing processes, and specifically, for example, C, N, P, S, Al, Ti, Cr, Mn, Ni, Hf, Sn, W and the like. However, it is not limited to these. The content ratio of unavoidable impurities in the permanent magnet is preferably 5% by mass or less in total, more preferably 1% by mass or less, and 0.1% by mass, in terms of mass percentage with respect to the total amount of the permanent magnet. The following is more preferable.

The content ratio of each element in the permanent magnet can be measured by using, for example, energy dispersive X-ray spectroscopy (EDX).

This permanent magnet has a crystal phase having a Th ₂ Zn ₁₇ -type structure (crystal grain 1 in FIG. 1; hereinafter, may be referred to as 2-17 phase) as a main phase. The Th ₂ Zn ₁₇ -type structure is a crystal structure having an R-3m-type space group. In this permanent magnet, the Th site is usually occupied by rare earth elements and Zr, and the Zn site is Co, Cu, Fe, and Zr. Is occupied. Further, the permanent magnet has a crystal phase having an _RCo5 type structure (crystal grain boundary 2 in FIG. 1, hereinafter may be referred to as 1-5 phase). In the 1-5 phase, the R moiety is usually occupied by rare earth elements and Zr, and the Co moiety is occupied by Co, Cu, and Fe. Further, the permanent magnet may have a crystal phase having a TbCu ₇ type structure (hereinafter, may be referred to as 1-7 phase). In the 1-7 phase, the Tb moiety is usually occupied by rare earth elements and Zr, and the Cu moiety is occupied by Co, Cu, and Fe. The crystal structure can be determined by the X-ray diffraction method.
In the permanent magnet of the present invention, it is presumed that the coercive force is exhibited by pinning the domain wall between the two phases of 2-17 phase and 1-5 phase when the domain wall moves. In addition, when Fe and Cu are concentrated into 2-17 phase and 1-5 phase, respectively, during the two-phase separation, the squareness is improved and (BH) m becomes large, so that the magnetic properties and composition ratio are greatly involved. Is a feature. Further, the more the composition ratio of the 2-17 phase and the 1-5 phase is constant over the entire sample, the better the magnetic characteristics can be obtained, and further, the yield can be improved when finely processed.

The permanent magnet is preferably densified because it has excellent magnetic characteristics such as residual magnetic flux density and square shape. Specifically, the density of the permanent magnet (sintered body density) is 8.25 g / cm. It is preferably ³ or more. On the other hand, the upper limit of the density is not particularly limited, but is usually 8.40 g / cm ³ or less due to the composition of the permanent magnet. It is preferable that the density of the permanent magnet is increased by reducing the maximum diameter of the pores and the abundance ratio of the pores, and the permanent magnet has a high density even when the content ratio of Cu is low. The above density can be achieved.

As an example, this permanent magnet has a sintered body density of 8.25 g / cm ³ or more, a maximum energy product of 260 kJ / m ³ or more, an intrinsic coercive force of 1600 kA / m or more, and a reverse magnetic field showing 90% of Br. When the magnitude of Hk is Hk, excellent magnetic properties with Hk / Hcj of 65% or more can be achieved. Hcj indicates a coercive force.

[Manufacturing method of rare earth cobalt permanent magnet]
The method for producing a rare earth cobalt permanent magnet of the present embodiment (hereinafter, also referred to as the present production method) has a mass percentage composition, R: 23 to 27% (R is the total of rare earth elements including at least Sm), Cu: 4. Step (I) of preparing an alloy consisting of 0 to 5.0%, Fe: 22 to 27%, Zr: 1.7% to 2.5%, and the balance of Co and unavoidable impurities.
In the pulverization step (II) in which the alloy is made into a powder having a specific surface area of 0.30 m ² / g or more,
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product and
The step (V) of solution-treating the sintered compact and
The step of quenching the molded product after the solution treatment (VI),
It has a step (VII) of heat-treating the molded product after the solution treatment.

By this manufacturing method, it is possible to suppress the generation of large pores, and it is possible to manufacture the above-mentioned rare earth cobalt permanent magnet having excellent magnetic properties.

First, in terms of mass percentage composition, R: 23 to 27% (R is the total of rare earth elements including at least Sm), Cu: 4.0 to 5.0%, Fe: 22 to 27%, Zr: 1.7%. Prepare an alloy of ~ 2.5%, the balance of which is Co and unavoidable impurities (step (I)). The method for preparing the alloy may be prepared by obtaining a commercially available alloy having a desired composition, or the alloy may be prepared by blending each element so as to have a desired composition.
Hereinafter, specific examples of blending each element will be described, but the present invention is not limited to this method.
First, as raw materials, a desired rare earth element, each metal element of Fe, Cu, and Co, and a mother alloy are prepared. Here, it is preferable to select an alloy having a composition having a low eutectic temperature as the mother alloy from the viewpoint that it is easy to make the composition of the obtained alloy uniform. In the present invention, it is preferable to select and use FeZr or CuZr as the mother alloy. As the FeZr, as an example, a FeZr of around 20% Zr80% is suitable. Further, as CuZr, as an example, CuZr of around 50% Zr50% is suitable.
A uniform alloy is prepared by blending these raw materials so as to have a desired composition, putting them in a crucible such as Al, and dissolving them in a vacuum of 1 × ^10-2 torr or less or in an inert gas atmosphere with a high-frequency melting furnace. Is obtained. Further, the present invention may include a step of casting the melted alloy with a mold to form an alloy ingot. Alternatively, an alloy on flakes having a thickness of about 1 mm may be produced by dropping the melted alloy onto a copper roll (strip cast method).
Further, when the alloy ingot is obtained by the casting, heat treatment may be performed at the solution temperature of the alloy ingot for 1 to 20 hours. By the heat treatment, the composition can be made more uniform and the variation in the Fe / Cu ratio of the final product can be further suppressed. The solution temperature of the alloy ingot may be appropriately adjusted according to the composition of the alloy and the like.

Next, the alloy is pulverized to obtain a powder having a specific surface area of 0.30 m ² / g or more (step (II)). By using a powder having a large specific surface area, the sintered body becomes densified during sintering, which will be described later, and the maximum diameter of the pores is suppressed to 40 μm or less.
In the present embodiment, the specific surface area represents the specific surface area per unit mass and can be expressed by the following formula (1).
Specific surface area = surface area (m ² ) / mass (g): equation (1)

It is preferable to increase the surface area of the powder so that the specific surface area is 0.30 m ² / g or more. As a method for setting the specific surface area to 0.30 m ² / g or more, any method can be adopted as long as it is a method for imparting a sufficient uneven shape to the powder. From the viewpoint of ease of production, it is preferable to increase the surface area at the time of pulverization by adjusting the pulverization conditions. As an example, first, an alloy ingot or a flake-shaped alloy is roughly pulverized to a size of about 100 to 500 μm by a known pulverizer, and then the specific surface area is increased when finely pulverized. In order to increase the specific surface area, it is preferable to use a wet grinding method. Examples of the wet pulverization method include a ball mill method, a jet mill method, a planetary mill method, an attritor method, and the like, and a ball mill method or a jet mill method is preferable.
In the wet pulverization method, a solvent is first added to the coarsely pulverized alloy to form a slurry. By adjusting the viscosity of the slurry to a low level, the specific surface area of the fine powder after wet pulverization tends to increase. When the ball mill method is used, it is preferable to adjust the amount of balls to be small. It is presumed that these adjustments increase the fluidity of the alloy powder, resulting in an increase in shearing force and an increase in specific surface area.
The average particle size of the powder after fine grinding makes it possible to shorten the sintering time in the sintering step described later, and the average particle size is preferably 1 to 10 μm from the viewpoint of producing a uniform permanent magnet. ..

The specific surface area of the powder is degassed by enclosing the powder to be measured in an instrument of the specific surface area measuring device and evacuating while heating. After degassing, the mixture is cooled to room temperature, and the container containing liquid nitrogen is impregnated with the instrument to further cool it. After cooling to the temperature of liquid nitrogen, the gas is sealed in the instrument while changing the pressure step by step. The nitrogen gas isotherm adsorption curve is measured, and the specific surface area is calculated from the isotherm adsorption curve using the BET equation (formula (2) below). For the measurement of the isotherm adsorption curve, for example, a fully automatic specific surface area measuring device can be used.

ここで、Ｖｍは窒素ガスの単分子層吸着量（第１層に吸着した窒素ガスの容量）、Ｖは吸着した窒素ガスの容量、Ｐはサンプル内の圧力、Ｐｏは飽和蒸気圧、Ｃは吸着熱などに関する定数である。
横軸にＰ／Ｐｏ、縦軸にＰ／Ｖ（Ｐｏ－Ｐ）を取りプロットすると直線（ＢＥＴプロット）が得られる。この直線の切片と傾きからＶｍが求められ、比表面積Ｓは下式（３）にから計算する。
Ｓ＝Ｖｍ×Ｎ×Ａｍ
ここで、Ｓは比表面積、Ｎはアボガドロ数であり、Ａｍは窒素ガス１分子の占める面積（０．１６２ｎｍ²）である。

Here, Vm is the amount of nitrogen gas adsorbed in the single molecule layer (capacity of nitrogen gas adsorbed on the first layer), V is the capacity of adsorbed nitrogen gas, P is the pressure in the sample, Po is the saturated vapor pressure, and C is. It is a constant related to heat of adsorption.
A straight line (BET plot) can be obtained by plotting P / Po on the horizontal axis and P / V (Po-P) on the vertical axis. Vm is obtained from the intercept and slope of this straight line, and the specific surface area S is calculated from the following equation (3).
S = Vm x N x Am
Here, S is the specific surface area, N is the Avogadro's number, and Am is the area occupied by one molecule of nitrogen gas (0.162 nm ² ).

Next, the obtained powder is pressure-molded to obtain a molded product having a desired shape (step (III)). In the present invention, it is preferable to perform pressure molding in a constant magnetic field from the viewpoint of aligning the crystal orientations of the powders and improving the magnetic properties. The relationship between the direction of the magnetic field and the pressing direction is not particularly limited, and may be appropriately selected according to the shape of the product and the like. For example, in the case of manufacturing a ring magnet or a thin plate magnet, a parallel magnetic field press in which a magnetic field is applied in a direction parallel to the pressing direction can be used. On the other hand, from the viewpoint of excellent magnetic characteristics, it is preferable to use a right-angled magnetic field press in which a magnetic field is applied at right angles to the pressing direction.

The magnitude of the magnetic field is not particularly limited, and may be, for example, a magnetic field of 15 kOe or less, or a magnetic field of 15 kOe or more, depending on the intended use of the product. Above all, from the viewpoint of excellent magnetic characteristics, pressure molding in a magnetic field of 15 kOe or more is preferable. Further, the pressure at the time of pressure molding may be appropriately adjusted according to the size, shape and the like of the product. As an example, the pressure can be 0.5 to 2.0 ton / cm ² . That is, in the method for producing a rare earth cobalt permanent magnet of the present invention, from the viewpoint of magnetic properties, the powder is applied in a magnetic field of 15 kOe or more at a pressure of 0.5 to 2.0 ton / cm ² or less perpendicular to the magnetic field. Pressure molding is particularly preferred.

Next, the molded product is heated at 1180 to 1220 ° C. for 20 to 240 minutes to obtain a sintered body (step (IV)). Sintering at 1180 ° C. or higher for 20 minutes or longer sufficiently densifies the obtained sintered body. Further, by heating at 1220 ° C. or lower for 240 minutes or less, evaporation of rare earth elements, particularly Sm, is suppressed, and a permanent magnet having excellent magnetic properties can be manufactured. The sintering time is preferably 30 to 180 minutes. Further, from the viewpoint of suppressing oxidation, the sintering step is preferably performed in a vacuum of 1000 Pa or less or in an inert gas atmosphere, and further, from the viewpoint of increasing the density of the sintered body, 1000 Pa or less, preferably 100 Pa or less. It is preferable to sinter in the vacuum of.

Next, a solution treatment (step (V)) is performed in which the sintered body is heated at 1120 to 1170 ° C. for 5 to 120 hours. By heating at 1120 ° C. or higher, the composition in the molded body is made uniform, and a precursor for using the crystal phase of Th ₂ Zn ₁₇ type structure as the main phase during the heat treatment step (step (VII)) described later. The 1-7 phase can be formed. Further, by setting the heating temperature to 1170 ° C. or lower, evaporation of rare earth elements is suppressed. Above all, the solution temperature is preferably 1130 to 1160 ° C. The solutionization time is preferably 10 to 100 hours. Since the optimum solution temperature of the sintered body changes depending on the composition of the sintered body, it is preferable to appropriately adjust the temperature within the above temperature range.

The solution treatment time is set to 20 hours or more from the viewpoint of sufficiently forming the 1-7 phase and homogenizing each element. Further, the solution treatment time is preferably 100 hours or less from the viewpoint of suppressing evaporation of rare earth elements, particularly Sm. From the viewpoint of suppressing oxidation, the solution treatment is preferably carried out in a vacuum of 1 × ^10-2 torr or less or in an atmosphere of an inert gas.

Further, from the viewpoint of improving productivity, it is preferable that the sintering step (IV) and the solution treatment step (V) are a series of steps. That is, after heating the molded product at 1190 ° C. or higher and 1225 ° C. or lower for 0.5 hours or longer and 3.0 hours or lower, the temperature is adjusted to 1120 ° C. or higher and 1180 ° C. or lower without cooling to room temperature, and then preferably 30. It is preferable to carry out the solution treatment for about 100 hours, more preferably 50 to 100 hours. By setting the solution formation time to 30 hours or more, preferably 50 hours or more, more uniform structure can be achieved.

Next, in the cooling step after the solution treatment step (V), the cooling rate is rapidly cooled at 60 ° C./min or more from at least 1000 ° C. to 600 ° C. (step (VI)). The reason for quenching in this way is to maintain the crystal structure of the 1-7 phase obtained in the solution treatment step (V), and if the quenching is insufficient, the 1-7 phase changes. There is a risk of doing. In particular, by shortening the time from the solution temperature to 600 ° C., the crystal structure of the 1-7 phase can be maintained. Above all, the cooling rate is preferably 80 ° C./min or more. On the other hand, the upper limit of the cooling rate depends on the shape of the molded product, but is preferably 250 ° C./min or less as an example.

Next, the molded product after the quenching step is aged to form a 2-17 phase and a 1-5 phase (step (VII)). The aging temperature is not particularly limited, but in order to obtain a rare earth cobalt permanent magnet having 2-17 phase as the main phase and 2-17 phase and 1-5 phase homogeneously, 2 to 20 at a temperature of 700 to 900 ° C. It is preferable to use a method in which the cooling rate is set to 2 ° C./min or less until the temperature is maintained for a long time and then cooled to at least 400 ° C. By holding at a temperature of 700 ° C. to 900 ° C. for 2 to 20 hours, the 2-17 phase and the 1-5 phase can be uniformly formed. Above all, aging treatment is preferable in the temperature range of 800 to 850 ° C. Further, from the viewpoint of obtaining good magnetic characteristics, the cooling rate is preferably 2 ° C./min or less, and more preferably 0.5 ° C./min or less. If the cooling rate is too fast, the elements will not be concentrated in the 2-17 phase and the 1-5 phase, and good magnetic properties cannot be obtained.

[device]
The present invention can further provide a device having the present permanent magnet. Specific examples of such devices include watches, electric motors, various instruments, communication devices, computer terminals, speakers, video discs, sensors, and the like. Further, since the rare earth cobalt permanent magnet of the present invention does not easily deteriorate its magnetic force even in a high environmental temperature, an angle sensor, an ignition coil, a drive motor such as an HEV (Hybrid electric vehicle) used in an automobile engine room, etc. Can also be suitably used.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. It should be noted that these descriptions do not limit the present invention.

(Examples 1 to 4)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Examples 1 to 4 in Table 1, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.30 m ² / g, 0.40 m ² in the inert gas using a ball mill. Fine pulverization was performed so as to be / g and 0.50 m ² / g, respectively.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered at 1210 ° C. for 80 minutes in a vacuum of 0.001 Pa, solutioned at 1145 ° C. for 50 hours, and rapidly cooled from 1000 to 600 ° C. at a cooling rate of 80 ° C./min. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 1 to 4. The magnetic properties of the obtained permanent magnets were measured, and then the structure was observed. Table 1 shows the evaluation results of the density of the obtained permanent magnets, (BH) m, Hcj, Hk / Hcj, and the maximum diameter of the pores. Further, FIG. 1 shows an optical microscope image used for observing the structure of the permanent magnet of Example 2.

<Evaluation criteria for maximum pore diameter>
⊚: It was less than 20 μm.
〇: It was 20 to 40 μm.
X: It was over 40 μm.

(Comparative Examples 1 to 4)
In Examples 1 to 4, the same as in Examples 1 to 4 except that fine pulverization was performed so that the specific surface areas were 0.10 m ² / g, 0.20 m ² / g, and 0.25 m ² / g. Then, the permanent magnets of Comparative Examples 1 to 4 were obtained. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 1. Further, FIG. 2 shows an optical microscope image used for observing the structure of the permanent magnet of Comparative Example 3.

(Examples 5 to 8)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Examples 5 to 8 in Table 2, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.30 m ² / g and 0.35 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered in a vacuum of 0.01 Pa at 1180 ° C., 1200 ° C., or 1220 ° C. for 120 minutes, and then solution-dissolved at 1130 ° C. for 90 hours, and the temperature was 80 ° C./min from 1000 to 600 ° C. It was rapidly cooled at the cooling rate of. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 5 to 8. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 2.

(Comparative Examples 5 to 7)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Comparative Examples 5 to 7 in Table 2, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas so as to have an average of about 100 to 500 μm, and then using a ball mill, the powder has a specific surface area of 0.25 m ² / g in the inert gas. Fine grinding was performed.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered in a vacuum of 0.01 Pa at 1180 ° C., 1200 ° C., or 1220 ° C. for 120 minutes, and then solution-dissolved at 1130 ° C. for 90 hours, and the temperature was 80 ° C./min from 1000 to 600 ° C. It was rapidly cooled at the cooling rate of. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Comparative Examples 5 to 7. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 2. Further, FIG. 3 shows an optical microscope image used for observing the structure of the permanent magnet of Comparative Example 5.

(Examples 9 to 13)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Examples 9 to 13 in Table 3, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.30 m ² / g and 0.45 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered in a vacuum of 0.1 Pa at 1215 ° C. for 20 minutes, 130 minutes, or 240 minutes, respectively, and then solutioned at 1160 ° C. for 70 hours, and the temperature was 1000 to 600 ° C. at 80 ° C./. It was rapidly cooled at a cooling rate of min. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 9 to 13. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 3.

(Comparative Examples 8 to 10)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Comparative Examples 8 to 10 in Table 3, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas so as to have an average of about 100 to 500 μm, and then using a ball mill, the powder has a specific surface area of 0.25 m ² / g in the inert gas. Fine grinding was performed.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered in a vacuum of 0.1 Pa at 1215 ° C. for 20 minutes, 130 minutes, or 240 minutes, respectively, and then solutioned at 1160 ° C. for 70 hours, and the temperature was 1000 to 600 ° C. at 80 ° C./. It was rapidly cooled at a cooling rate of min. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Comparative Examples 8 to 10. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 3.

(Examples 14 to 17)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Examples 14 to 17 in Table 4, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.30 m ² / g and 0.60 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered in a vacuum of 1 Pa at 1190 ° C. for 200 minutes, then solutioned at 1120 ° C., 1155 ° C. and 1180 ° C. for 40 hours, respectively, and cooled at a cooling rate of 80 ° C./min from 1000 to 600 ° C. It was cooled rapidly. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 14 to 17. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 4.

(Comparative Examples 11 to 13)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Comparative Examples 11 to 13 in Table 4, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.20 m ² / g and 0.25 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered at 1190 ° C. for 200 minutes in a vacuum of 1 Pa, then solutioned at 1120 ° C. and 1180 ° C. for 40 hours, and rapidly cooled from 1000 to 600 ° C. at a cooling rate of 80 ° C./min. did. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Comparative Examples 11 to 13. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 4.

(Examples 18 to 21)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Examples 18 to 21 in Table 5, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.30 m ² / g and 0.55 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered at 1205 ° C. for 150 minutes in a vacuum of 50 Pa, and then solutioned at 1150 ° C. for 5 hours, 65 hours or 120 hours, respectively, and cooled at a cooling rate of 80 ° C./min from 1000 to 600 ° C. It was cooled rapidly. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 18 to 21. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 5.

(Comparative Examples 14 to 16)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Comparative Examples 14 to 16 in Table 5, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.15 m ² / g and 0.25 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product is sintered at 1205 ° C. for 150 minutes in a vacuum of 50 Pa, then melted at 1150 ° C. for 5 hours or 120 hours, and rapidly cooled from 1000 to 600 ° C. at a cooling rate of 80 ° C./min. did. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 14 to 16. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 5.

(Examples 22 to 25)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Examples 22 to 25 in Table 6, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas to an average of about 100 to 500 μm, and then the specific surface area of the powder is 0.30 m ² / g and 0.70 m in the inert gas using a ball mill. Each was finely pulverized to ² / g.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered at 1185 ° C. for 210 minutes in a vacuum of 0.001 Pa, 1 Pa, or 1000 Pa, respectively, and then melted at 1140 ° C. for 100 hours, and cooled to 80 ° C./min at 1000 to 600 ° C. Quenched at speed. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Examples 22 to 25. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 6.

(Comparative Examples 17-18)
A mother alloy of 20% Fe and 80% Zr and each raw material were prepared so as to have the compositions of Comparative Examples 17 to 18 in Table 6, melted in a high-frequency melting furnace, and cast to obtain an alloy ingot.
The obtained mother alloy is coarsely pulverized in an inert gas so as to have an average of about 100 to 500 μm, and then using a ball mill, the powder has a specific surface area of 0.25 m ² / g in the inert gas. Fine grinding was performed.
Each of these powders was pressed in a magnetic field of 15 kOe at a pressure of 1 ton / cm ² to obtain a molded product.
This molded product was sintered at 1185 ° C. for 210 minutes in a vacuum of 0.001 Pa or 1000 Pa, respectively, then solution-dissolved at 1140 ° C. for 100 hours, and rapidly cooled from 1000 to 600 ° C. at a cooling rate of 80 ° C./min. did. After quenching, the magnets were kept at 850 ° C. for 12 hours, and then aged under the condition of slowly cooling to 350 ° C. at a cooling rate of 0.5 ° C./min to obtain permanent magnets of Comparative Examples 17 to 18. The obtained permanent magnets were measured in the same manner as in Examples 1 to 4. The results are shown in Table 6.

As shown in Tables 1 to 5, the permanent magnets of Examples 1 to 21 produced by using a powder having a specific surface area of 0.30 m ² / g or more and under predetermined heat treatment conditions have a density ≧ 8. All the conditions of 25 g / cm ³ , (BH) m ≧ 260 kJ / m ³ , Hcj ≧ 1600 A / m, and Hk / Hcj ≧ 65% were satisfied, and the maximum diameter of the pore was less than 40 μm.
On the other hand, the permanent magnets of Comparative Examples 1 to 16 using the powder having a specific surface area of less than 0.30 m ² / g of the fine powder have a density ≧ 8.25 g / cm ³ , even under the same heat treatment conditions as those of the examples. BH) m ≧ 260 kJ / m ³ , Hcj ≧ 1600 A / m, Hk / Hcj ≧ 65% did not satisfy all the conditions, and the maximum diameter of the pore was 40 μm or more.

As shown in Table 6, the permanent magnets of Examples 22 to 25 produced by using a powder having a specific surface area of 0.30 m ² / g or more and having a vacuum degree of 1000 Pa or less under predetermined heat treatment conditions are used. , Density ≧ 8.25 g / cm ³ , (BH) m ≧ 260 kJ / m ³ , Hcj ≧ 1600 A / m, Hk / Hcj ≧ 65%, and the maximum pore diameter was less than 40 μm.
On the other hand, the permanent magnets of Comparative Examples 17 to 18 using the powder having a specific surface area of less than 0.30 m ² / g of the fine powder have a density ≧ 8.25 g / cm ³ , (BH) even under the same heat treatment conditions as those of the examples. ) M ≧ 260 kJ / m ³ , Hcj ≧ 1600 A / m, Hk / Hcj ≧ 65% did not satisfy all the conditions, and the maximum diameter of the pore was 40 μm or more.

1 Crystal grain 2 Grain boundary 3 Oxide 4 Pore

Claims (5)

By mass percentage composition, R: 23 to 27% (R is the total of rare earth elements including at least Sm), Cu: 4.0 to 5.0%, Fe: 22 to 27%, Zr: 1.7% to 2 An intermetallic compound containing 5.5%, a rare earth cobalt consisting of Co and unavoidable impurities in the balance.
A rare earth cobalt permanent magnet having a plurality of crystal grains and grain boundaries and having a maximum pore diameter of 40 μm or less. The rare earth cobalt permanent magnet according to claim 1, which comprises a powder sintered body having a specific surface area of 0.3 m ² / g or more. When the size of the reverse magnetic field when the sintered body density is 8.25 g / cm ³ or more, the maximum energy product is 260 kJ / m ³ or more, the intrinsic coercive force is 1600 kA / m or more, and 90% of Br is shown, is Hk. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein Hk / Hcj is 65% or more. By mass percentage composition, R: 23 to 27% (R is the total of rare earth elements including at least Sm), Cu: 4.0 to 5.0%, Fe: 22 to 27%, Zr: 1.7% to 2 Step (I) of preparing an alloy consisting of 5.5%, the balance of Co and unavoidable impurities, and
In the pulverization step (II) in which the alloy is made into a powder having a specific surface area of 0.3 m ² / g or more,
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product and
The step (V) of solution-treating the sintered compact and
The step of quenching the molded product after the solution treatment (VI),
It has a step (VII) of heat-treating a molded product after a solution treatment.
A method for manufacturing rare earth cobalt permanent magnets. A device having the rare earth cobalt permanent magnet according to any one of claims 1 to 3.

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