JP2021125678A - Rare earth cobalt permanent magnet, method for manufacturing the same, and device - Google Patents

Abstract

To provide a rare earth cobalt permanent magnet having a superior magnetic property, a manufacturing method thereof, and a device having such a rare earth cobalt permanent magnet.SOLUTION: A rare earth cobalt permanent magnet comprises 23-27 mass% of a rare earth element R, 1.0-5.0 mass% of Cu, 18-25 mass% of Fe, and 1.5-3.0 mass% of Zr with the balance consisting of Co and an inevitable impurity, where R represents a rare earth element including at least Sm. The rare earth cobalt permanent magnet has a plurality of crystal grains and grain boundaries. In the grain boundaries, a concentration of Cu is two or more times of a concentration of Zr.SELECTED DRAWING: Figure 3

Description

The present invention relates to a rare earth cobalt permanent magnet, a method for producing the same, and a device, which are particularly applicable to a variable field motor.

Variable magnetic field motors are attracting attention from the viewpoint of energy saving of motors. The variable magnetic field motor is a motor that changes the magnetic flux according to the rotation speed. Variable field motors generally generate high magnetic flux when torque is required at low speeds and low magnetic flux at high speeds, providing energy in any region from low to high speeds. Highly efficient products are required.

Examples of the method of changing the magnetic flux amount of the variable field motor include a variable magnetic force method, a magnetic field coil method, and a winding switching method.
For example, Patent Document 1 discloses a method of realizing a variable field by combining an NdFeB magnet having a high magnetization and a coercive force and an alnico magnet having a high magnetization but a low coercive force. However, the alnico magnet has a problem that it is difficult to use because the coercive force is too small.

Further, as a variable magnetic force method, a method using a samarium-cobalt magnet capable of changing the amount of magnetic flux is being studied. For example, Patent Document 2 proposes using a samarium-cobalt magnet as a magnet for a variable field magnet. However, the method of Patent Document 2 has a residual magnetization value of 80% or more in a magnetic field of 10 kOe, and cannot be said to be sufficiently compatible with high torque operation requiring a strong magnetic flux.

Patent No. 49655924 International Publication No. 2009/145229

From the viewpoint of improving the efficiency of the variable magnetic field motor, the permanent magnet preferably reaches saturation magnetization with a low magnetic field during remagnetization after demagnetization, and the ratio of the magnetic field (Hk) to the coercive force (Hcj) (Hk). A permanent magnet having a high square ratio represented by / Hcj) is required.

The present invention solves the above problems, and provides a rare earth cobalt permanent magnet having a high residual magnetic flux density, a low coercive force, and a high square ratio, a method for producing the same, and a device having the rare earth cobalt permanent magnet. The purpose.

In the rare earth cobalt permanent magnet of the present embodiment, when R is a rare earth element containing at least Sm,
By mass percentage, it contains rare earth elements R: 23-27%, Cu: 1.0-5.0%, Fe: 18-25%, Zr: 1.5-3.0%, and the balance is Co and unavoidable impurities. A rare earth cobalt permanent magnet consisting of
It has a plurality of crystal grains and grain boundaries,
At the grain boundary, the Cu concentration is at least twice the Zr concentration.

In one embodiment of the rare earth cobalt permanent magnet, the size of the cell structure constituting the crystal grains is 50 to 200 nm.

One embodiment of the rare earth cobalt permanent magnet has a saturation magnetization of 1.16 T or more and an intrinsic coercive force Hcj of 120 to 800 kA / m.

One embodiment of the rare earth cobalt permanent magnet has a saturation magnetization of 1.16 T or more and an intrinsic coercive force Hcj of 240 to 800 kA / m.

In one embodiment of the rare earth cobalt permanent magnet, in the demagnetization curve, the square ratio represented by the ratio (Hk / Hcj) of the magnetic field Hk at 90% magnetization of the residual magnetization and the intrinsic coercive force Hcj is 60% or more. Yes and
When remagnetized from a demagnetizing field that exceeds the knick point of the demagnetization curve, a magnetization of 95% or more of the saturation magnetization can be obtained with a magnetic field of 5 times or less the intrinsic coercive force Hcj.

In one embodiment of the rare earth cobalt permanent magnet, in the demagnetization curve, the square ratio represented by the ratio (Hk / Hcj) of the magnetic field Hk at 90% magnetization of the residual magnetization and the intrinsic coercive force Hcj is 60% or more. Yes and
When remagnetized from a demagnetizing field that exceeds the knick point of the demagnetization curve, a magnetization of 95% or more of the saturation magnetization can be obtained with a magnetic field of 3 times or less the intrinsic coercive force Hcj.

One embodiment of the rare earth cobalt permanent magnet is diffracted when the diffraction intensity I (006) on the (006) plane and the diffraction intensity I (303) on the (303) plane are measured by a powder X-ray diffraction method. The intensity ratio I (006) / I (303) is 0.225 to 0.4.

The first method for producing the rare earth cobalt permanent magnet of the present embodiment is
When R is a rare earth element containing at least Sm, in terms of mass percentage, rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to Step (I) of preparing an alloy containing 3.0% and the balance consisting of Co and unavoidable impurities, and
The crushing step (II) in which the alloy is made into powder, and
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product at 1200 to 1250 ° C.
The step (V) of solution-treating the molded product after sintering, and
A step (VI) of heat-treating the molded product after the solution treatment at 600 to 850 ° C.
A step (VII) of cooling the molded product after the heat treatment at 0.2 to 10 ° C./min to 400 ° C. or lower, and
A step (VIII) of heat treatment at 700 to 900 ° C. and a temperature higher than that of the step (IV), and
It has a step (IX) of cooling the molded product after the heat treatment at 0.1 to 5 ° C./min to 400 ° C. or lower.

The second method for producing the rare earth cobalt permanent magnet of the present embodiment is
In the method for producing a rare earth cobalt permanent magnet according to the present invention, when R is a rare earth element containing at least Sm, the rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, in terms of mass percentage, The step (I) of preparing an alloy containing Fe: 18 to 25% and Zr: 1.5 to 3.0%, the balance of which is Co and unavoidable impurities.
The crushing step (II) in which the alloy is made into powder, and
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product at 1200 to 1250 ° C.
The step (V) of solution-treating the molded product after sintering, and
A step (VI-a) of heat-treating the molded product after the solution treatment at 750 to 850 ° C.
A step of cooling the molded product after the heat treatment at 0.5 to 10 ° C./min to 500 to 600 ° C. and maintaining it at an isothermal temperature (VII-a).
It has a step (VIII-a) of quenching the molded product after maintaining the isothermal temperature.

The present invention also provides a device having the rare earth cobalt permanent magnet.

INDUSTRIAL APPLICABILITY The present invention provides a rare earth cobalt permanent magnet having a high residual magnetic flux density, a low coercive force, and a high square ratio, a method for producing the same, and a device having the rare earth cobalt permanent magnet.

It is a schematic diagram for demonstrating the structure of this permanent magnet. It is a graph which shows the 1st quadrant and the 2nd quadrant of the hysteresis curve of the permanent magnet of Example 1. FIG. It is a dark field scanning transmission electron microscope (DF-STEM) image of the permanent magnet of Example 1. It is a graph which shows the composition analysis result including the grain boundary part of the permanent magnet of Example 1. 3 is a powder X-ray diffraction spectrum of the permanent magnets of Examples 3 and 4 and Reference Example 1.

Hereinafter, the rare earth cobalt permanent magnet according to the present invention, a method for producing the same, and a device will be described in order.
Unless otherwise specified, "~" indicating the numerical range shall include the lower limit value and the upper limit value.

<Rare earth cobalt permanent magnet>
The rare earth cobalt permanent magnet (hereinafter, also referred to as the present permanent magnet) according to the present invention has a mass percentage of rare earth element R: 23 to 27% including Sm, Cu: 1.0 to 5.0%, Fe: 18 to. A rare earth cobalt permanent magnet containing 25%, Zr: 1.5 to 3.0%, and the balance consisting of Co and unavoidable impurities.
It has a plurality of crystal grains and grain boundaries,
At the grain boundary, the Cu concentration is at least twice the Zr concentration.

Generally, in _{a rare earth cobalt permanent magnet having a Sm 2} CO _17- phase type crystal phase (hereinafter, also referred to as 2-17 phase), Cu increases the coercive force and Zr increases the amount of solid dissolved Fe and remains indirectly. It is believed to increase the magnetic flux density Br.
This permanent magnet has a high residual magnetic flux by controlling the diffusion of Cu and Zr by two kinds of manufacturing methods described later so that the Cu concentration at the grain boundary is twice or more, preferably three times or more the Zr concentration. A magnet with a high density and low coercive force and a high square ratio can be obtained.
Since this permanent magnet has magnetic characteristics suitable for a variable field motor in this way, it is possible to manufacture a variable magnetic field motor that realizes high efficiency from low speed to high speed by applying it to a variable magnetic field motor.

The rare earth element R is a general term for Sc, Y and lanthanoids, and in this permanent magnet, the R contains at least Sm. By containing the rare earth element in the above ratio, a permanent magnet having high magnetic anisotropy can be obtained. The rare earth element R may consist only of Sm, or may be a combination of Sm and other rare earth elements. As the other rare earth element R, one or more selected from Nd, Pr and Ce is preferable from the viewpoint of magnetic properties. From the viewpoint of magnetic properties, the rare earth element R preferably has an Sm of 70% by mass or more, more preferably 80% by mass or more, based on the total rare earth element.

Cu is contained in an amount of 1.0 to 5.0% by mass. By setting the Cu content within this range, a high square ratio can be obtained while adjusting the coercive force within the appropriate range.
Fe is contained in an amount of 18 to 25% by mass. By setting the Fe content within this range, it is easy to achieve a high residual magnetic flux density. Further, the saturation magnetization is improved by containing 18% or more of Fe, and the coercive force is adjusted to an appropriate range by containing 25% or less of Fe.
Further, Zr is contained in an amount of 1.5 to 3.0% by mass. By setting the Zr content within the above range, it is easy to increase the solid solution amount of Fe and indirectly increase the residual magnetic flux density Br. In addition, the maximum energy product (BH) max, which is the maximum static energy that the magnet can hold, is improved.

Further, in this permanent magnet, the balance (that is, 40 to 56.5% by mass) is composed of Co and unavoidable impurities.
By containing Co, the thermal stability of the permanent magnet is improved. On the other hand, if the Co content is excessive, the Fe content ratio may be relatively lowered and the magnetization may be lowered. From these points, the content ratio of Co is preferably 40 to 56.5% by mass.

Next, the structure of the permanent magnet will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a part of a cross section of the permanent magnet. As shown in the example of FIG. 1, the permanent magnet 10 has a plurality of crystal grains 1 (region surrounded by a solid line in the figure), and a grain boundary portion 2 (solid line in the figure) is provided between the crystal grains 1. have. Each crystal grain 1 includes a cell phase 3 (in the figure, only a dotted line or a region surrounded by a dotted line and a solid line) including a crystal phase _{having a Th 2} Zn _{17-type structure (hereinafter, also referred to as a 2-17 phase).} (in the figure, dotted line) cell walls 4 comprising crystalline phases of RCo ₅ type structure surrounding the cell phase (hereinafter 1-5 phase also called) having a. In the present invention, the cell structure refers to a combination of one cell phase 3 and a cell wall 4 surrounding the cell phase 3, and is the smallest unit constituting a crystal grain.

As described above, this permanent magnet has a cell phase having a crystal phase having a _{Th 2} Zn _{17-type structure 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 portion is occupied by rare earth elements and Zr, and the Zn portion is occupied by Co, Cu, Fe, and Zr. There is. Also it has a cell wall containing a crystal phase of RCo ₅ type structure as described above. In _{the crystal phase of the RCo 5} type structure, the R moiety is occupied by rare earth elements and Zr, and the Co moiety is occupied by Co, Cu, and Fe. In the permanent magnet 10, the size of the cell structure represents the length of the cell wall 4 (the length of the crystal phase of the _{RCo 5 type structure).} In this permanent magnet, the cell size is preferably 50 to 200 nm from the viewpoint of low coercive force.

Next, the characteristics of the permanent magnet will be described with reference to FIG. FIG. 2 is a graph showing the first quadrant and the second quadrant (decay curve) of the hysteresis curve of the permanent magnet of the first embodiment described later. The vertical axis represents magnetization (magnetic polarization), and the horizontal axis represents the strength of the magnetic field. Positive values on the horizontal axis indicate the strength of the magnetic field applied in the direction of magnetizing the permanent magnet, and negative values indicate the strength of the magnetic field applied in the direction of demagnetizing the permanent magnet.
When a positive magnetic field is applied to a permanent magnet, magnetic polarization occurs according to the initial magnetization curve and reaches saturation magnetization. Next, when a negative magnetic field is applied to the permanent magnet in the saturated magnetization state, the magnet is rapidly demagnetized through the knick point. The strength of the magnetic field when the magnetic polarization becomes 0 is the intrinsic coercive force (Hcj).
In the present invention, the magnetic field at 90% magnetization of the residual magnetization is defined as Hk, and the ratio to the intrinsic coercive force Hcj (Hk / Hcj) is defined as the square ratio. The permanent magnet can achieve the square ratio of 60% or more, preferably 70% or more.
Furthermore, this permanent magnet has a magnetic field that is 5 times or less (absolute value) of the intrinsic coercive force Hcj when remagnetized from the demagnetizing magnetic field (point A) that exceeds the knick point of the demagnetization curve, and is 95 of the saturation magnetization. % Or more magnetization is obtained, and preferably, with a magnetic field of 3 times or less (absolute value) of the intrinsic coercive force Hcj, 95% or more of the saturation magnetization is obtained.
As described above, this permanent magnet is excellent in the responsiveness of magnetization to a magnetic field, and can be suitably used even in a variable magnetic field motor having a large change in rotation speed.

Further, the permanent magnet has, for example, a saturation magnetization of 1.16 T or more and a magnetic coercive force Hcj of 120 to 800 kA / m, preferably 200 to 800 kA / m, and more preferably 240 to 800 kA / m. It can be a permanent magnet.

<Manufacturing method of rare earth cobalt permanent magnet>
The rare earth cobalt permanent magnet can be manufactured by the following two manufacturing methods. The two manufacturing methods will be described.

(First manufacturing method)
The first manufacturing method of this rare earth cobalt permanent magnet (hereinafter, also simply referred to as the first manufacturing method) is
When R is a rare earth element containing at least Sm, in terms of mass percentage, rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to Step (I) of preparing an alloy containing 3.0% and the balance consisting of Co and unavoidable impurities, and
The crushing step (II) in which the alloy is made into powder, and
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product at 1200 to 1250 ° C.
The step (V) of solution-treating the molded product after sintering, and
A step (VI) of heat-treating the molded product after the solution treatment at 600 to 850 ° C.
A step (VII) of cooling the molded product after the heat treatment at 0.2 to 10 ° C./min to 400 ° C. or lower, and
A step (VIII) of heat treatment at 700 to 900 ° C. and a temperature higher than that of the step (VI), and
It has a step (IX) of cooling the molded product after the heat treatment at 0.1 to 5 ° C./min to 400 ° C. or lower.

According to the first manufacturing method, a rare earth cobalt permanent magnet having a plurality of crystal grains and grain boundaries and having a Cu concentration of twice or more the Zr concentration at the grain boundaries is manufactured. Can be done.
According to the first manufacturing method, a rare earth cobalt permanent magnet having a cell size of 50 to 200 nm can be preferably manufactured.
According to the first manufacturing method, a rare earth cobalt permanent magnet having a saturation magnetization of 1.16 T or more and an intrinsic coercive force Hcj of 240 to 800 kA / m can be suitably manufactured.
According to the first manufacturing method, in the demagnetization curve, the square ratio represented by the ratio (Hk / Hcj) of the magnetic field Hk at 90% magnetization of the residual magnetization and the intrinsic coercive force Hcj is 60% or more. Moreover, a rare earth cobalt permanent magnet capable of obtaining a magnetization of 95% or more of the saturation magnetization with a magnetic field of 3 times or less of the intrinsic coercive force Hcj when remagnetized from a demagnetizing field exceeding the knick point of the demagnetization curve is preferably used. Can be manufactured.
Further, according to the first manufacturing method, when the diffraction intensity I (006) of the (006) plane and the diffraction intensity I (303) of the (303) plane are measured by the powder X-ray diffraction method, the diffraction is performed. A rare earth cobalt permanent magnet having an intensity ratio I (006) / I (303) of 0.225 to 0.4 can be suitably produced.
In the first manufacturing method, the steps (I) to (IX) are usually carried out in this order, and other steps may be provided as long as the effects of the present invention are not impaired. be. Each step will be described below.

First, in terms of mass percentage, rare earth element R including Sm: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to 3.0%, and the balance is Co. And an alloy composed of unavoidable impurities is prepared (step (I)). The method for preparing the alloy is not particularly limited, and 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. May be good.
Hereinafter, specific examples of blending each element will be described, but the present production method 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 a mother alloy having a composition having a low eutectic temperature from the viewpoint that it is easy to make the composition of the obtained alloy uniform. In this production method, it is preferable to select and use FeZr or CuZr as the mother alloy. As FeZr, as an example, FeZr of about 20% Zn80% is preferable. Further, as CuZr, as an example, CuZr of around 50% Zr50% is preferable.
Blended These raw materials so that the desired composition, put into a crucible of alumina, 1 × 10 In -2 ^torr or less vacuum or in an inert gas atmosphere to dissolve by high-frequency melting furnace, homogenized alloy Is obtained. Further, the present manufacturing method 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 casting method). In the present invention, a method of melting with a melting furnace is preferable from the viewpoint that a permanent magnet having a high residual magnetic flux density and a square ratio can be easily obtained.

When the alloy ingot is formed by the casting, it is preferable to have a step of heat-treating the alloy ingot at the solution temperature of 1 hour or more and 20 hours or less before the step (II) described later. By this step, the composition can be made more uniform. 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 crushed into a powder (step (II)). The method for pulverizing the alloy is not particularly limited, and a conventionally known method may be appropriately selected. As an example, a method in which an alloy ingot or a flake-shaped alloy is first roughly pulverized to a size of about 100 to 500 μm by a known pulverizer and then finely pulverized by a ball mill, a jet mill or the like is preferably mentioned. The average particle size of the powder is not particularly limited, but the average particle size is 1 μm or more and 10 μm or less from the viewpoint of shortening the sintering time in the sintering step described later and producing a uniform permanent magnet. The powder is preferably about 6 μm.

Next, the obtained powder is pressure-molded to obtain a molded product having a desired shape (step (III)). In this production method, 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 characteristics. 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. In other words the manufacturing method, from the viewpoint of magnetic properties, the powder in magnetic field above 15 kOe, vertically 0.5 ton / cm ² or more 2.0ton / cm ² to pressing at a pressure of less than the magnetic field Is particularly preferable.

Next, the molded product is heated to obtain a sintered body (step (IV)). In the present production method, the sintering conditions can be set to known conditions as long as the obtained sintered body is sufficiently densified. From the viewpoint of densification of the sintered body, the sintering temperature is preferably 1200 to 1250 ° C. By setting the temperature to 1250 ° C. or lower, evaporation of rare earth elements, particularly Sm, is suppressed, and a permanent magnet having excellent magnetic characteristics can be produced.
As for the temperature rising condition in the sintering step, from the viewpoint of removing the adsorbed gas contained in the molded product, it is preferable to first start evacuation at room temperature and raise the temperature at 1 to 10 ° C./min. In the temperature raising process, a hydrogen atmosphere may be used instead of evacuation. Also in this case, it is preferable to switch to the vacuum atmosphere in the range of 1150 ° C. or lower.
The sintering time is preferably 20 to 240 minutes, more preferably 30 to 180 minutes, from the viewpoint of sufficiently densifying while suppressing evaporation of Sm. From the viewpoint of suppressing oxidation, the sintering step is ^{preferably performed in a vacuum of 1 × 10 −2} Torr or less or in an atmosphere of an inert gas, and is preferably performed in ^{a vacuum of 1 × 10 -4} Torr or less. More preferred.

Next, the obtained sintered body is slowly cooled at a temperature lowering rate of 0.2 to 5 ° C./min. Next, the sintered body after slow cooling is subjected to solution treatment (step (V)). The solution temperature may be appropriately adjusted from the viewpoint of the sintered body and the desired magnet characteristics, and the solution treatment is preferably performed at a temperature 20 to 50 ° C. lower than the sintered temperature. The solutionization time may be appropriately adjusted in the range of, for example, 2 to 20 hours.

After the solution treatment, it is preferable to quench to at least 400 ° C. or lower.
The sintered body is then heat treated at 600-850 ° C. (step (VI)). The heat treatment time may be appropriately adjusted from the viewpoint of desired magnet characteristics, and is preferably 0.5 to 3 hours, for example. The molded product after the heat treatment is cooled to 400 ° C. or lower at 0.2 to 10 ° C./min (step (VII)). Then, the heat treatment is performed at 700 to 900 ° C. and at a temperature higher than that of the step (VI) (step (VIII)). The heat treatment time can be, for example, 0.5 to 10 hours. Next, the permanent magnet is obtained by cooling the molded product after the heat treatment at 0.1 to 5 ° C./min to 400 ° C. or lower (step (IX)).
In the first production method, it is presumed that a cell structure is formed in the crystal grains during the isothermal maintenance in the steps (VI and VIII), but at this stage, the Cu concentration in the crystal grains is low and the grain boundaries are reached. It is presumed to be concentrated. On the other hand, Zr is presumed to be solid-solved in crystal grains in order to form a 2-17 phase with a high Fe content. In the first production method, a cell structure having a cell wall of 50 to 200 nm is formed in the crystal grains by two heat treatments (step (VI) to step (IX)), and Cu and Zr are appropriately diffused. It is estimated that the Cu concentration at the grain boundary is twice or more, preferably three times or more the Zr concentration.

Further, according to the first manufacturing method, when the diffraction intensity I (006) of the (006) plane and the diffraction intensity I (303) of the (303) plane are measured by the powder X-ray diffraction method, the diffraction is performed. A rare earth cobalt permanent magnet having an intensity ratio I (006) / I (303) of 0.225 to 0.4 can be suitably produced. FIG. 5 is a powder X-ray diffraction spectrum of the permanent magnets of Examples 3, 4 and Reference Example 1. It has been shown that the permanent magnet obtained by the first manufacturing method has a high peak intensity on the (006) plane, which is the easily magnetized axis (C axis). As described above, according to the first manufacturing method, the degree of orientation of the C-axis is improved, and as a result, the magnetism is improved.

(Second manufacturing method)
The second manufacturing method of this rare earth cobalt permanent magnet (hereinafter, also simply referred to as the second manufacturing method) is
When R is a rare earth element containing at least Sm, in terms of mass percentage, rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to Step (I) of preparing an alloy containing 3.0% and the balance consisting of Co and unavoidable impurities, and
The crushing step (II) in which the alloy is made into powder, and
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product at 1200 to 1250 ° C.
The step (V) of solution-treating the molded product after sintering, and
A step (VI-a) of heat-treating the molded product after the solution treatment at 750 to 850 ° C.
A step of cooling the molded product after the heat treatment at 0.5 to 10 ° C./min to 500 to 600 ° C. and maintaining it at an isothermal temperature (VII-a).
It has a step (VIII-a) of quenching the molded product after maintaining the isothermal temperature.

According to the second manufacturing method, a rare earth cobalt permanent magnet having a plurality of crystal grains and grain boundaries and having a Cu concentration of twice or more the Zr concentration at the grain boundaries is manufactured. Can be done.
According to the second production method, a rare earth cobalt permanent magnet having a cell size of 50 to 200 nm can be preferably produced.
Further, according to the second manufacturing method, a rare earth cobalt permanent magnet having a saturation magnetization of 1.16 T or more and an intrinsic coercive force Hcj of 120 to 800 kA / m can be suitably manufactured.
According to the first manufacturing method, in the demagnetization curve, the square ratio represented by the ratio (Hk / Hcj) of the magnetic field Hk at 90% magnetization of the residual magnetization and the intrinsic coercive force Hcj is 60% or more. A rare earth cobalt permanent magnet capable of obtaining a magnetization of 95% or more of the saturation magnetization with a magnetic field of 5 times or less of the intrinsic coercive force Hcj when remagnetized from a demagnetizing field exceeding the knick point of the demagnetization curve is preferable. Can be manufactured.
In the second production method, the steps (I) to (VIII-a) are usually carried out in this order, and other steps may be provided as long as the effects of the present invention are not impaired. It is a thing.
In the second manufacturing method, steps (I) to (V) are the same as those in the first manufacturing method, and preferable manufacturing conditions are also common. Therefore, duplicate description will be omitted.

The molded product after the solution treatment (step (V)) is preferably rapidly cooled to at least 400 ° C. or lower.
Then, the sintered body is heat-treated at 750 to 850 ° C. (step (VI-a)). The heat treatment time may be appropriately adjusted from the viewpoint of desired magnet characteristics, and is preferably 0.5 to 10 hours, for example. By this step, a cell structure having a cell wall of 50 to 200 nm is formed in the crystal grains, and Cu and Zr are appropriately diffused, and the Cu concentration at the grain boundary is twice or more the Zr concentration, preferably. It will be more than 3 times.
The molded product after the heat treatment is cooled to 500 to 600 ° C. at 0.5 to 10 ° C./min and maintained at an isothermal temperature (step (VII-a)). The isothermal holding time may be appropriately adjusted in the range of, for example, 0.5 to 10 hours. The permanent magnet is obtained by quenching the molded product after maintaining the isothermal temperature (step (VIII-a)).
In the second production method, a cell structure is formed in the crystal grains by maintaining an isothermal temperature in the step (VI-a), but at this stage, the Cu concentration in the crystal grains is low and concentrated at the grain boundaries. It is estimated to be. On the other hand, Zr is presumed to be solid-solved in crystal grains in order to form a 2-17 phase with a high Fe content. When the process (VI-a) shifts from isothermal maintenance to slow cooling, it is estimated that Cu and Zr diffuse with each other and Cu concentrates in the cell walls that form the cell structure in the crystal grains, and as a result, the coercive force is retained. Will increase.

<Device>
The present invention further provides a device having the present permanent magnet. Specific examples of such devices include clocks, electric motors, various instruments, communication devices, computer terminals, speakers, video discs, sensors, and the like. As described above, the rare earth cobalt permanent magnet of the present invention has a high residual magnetic flux density, a low coercive force, and a high angular ratio. A variable magnetic field motor that achieves efficiency can be obtained.

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.

<Example 1: Second manufacturing method>
Raw materials containing 20% Fe, 80% Zr, and various elements are ^{melted in a vacuum of 1 × 10 -2} Torr or less by a high-frequency melting furnace, and Sm25.0 wt%, Cu4.0 wt%, Fe21.0 wt. An alloy ingot having a composition of%, Zr2.2 wt%, and the balance Co was obtained.
Next, the obtained alloy ingot was heat-treated at 1170 ° C. for 15 hours, roughly pulverized, and further pulverized in an inert atmosphere using a jet mill to obtain a powder having an average particle size of 6 μm. Next, this powder was subjected to ^{a pressing force of 1.0 ton / cm 2} in a magnetic field of 15 kOe to obtain a molded product having a shape of 100 mm in length × 50 mm in width × 50 mm in height by mold molding.
The obtained compact is ^{sintered in a vacuum of 1 × 10-2} Torr or less at a temperature of 1200 ° C., then lowered to 1170 ° C. at a rate of 1 ° C./min and held for 4 hours for solution treatment. Was given. Immediately after that, quenching was performed at a cooling rate of 100 ° C./min.
The sintered body after quenching is heated and held at a temperature of 800 ° C. for 1 hour in an inert atmosphere for isothermal aging treatment, and then continuously slowly cooled to 550 ° C. or lower at a cooling rate of 2 ° C./min at 550 ° C. The permanent magnet of Example 1 was obtained by quenching after holding for 5 hours.

<Example 2: Second manufacturing method>
A permanent magnet of Example 2 was obtained in the same manner as in Example 1 except that the isothermal aging treatment was changed to heat holding at a temperature of 800 ° C. for 5 hours.

<Comparative example 1>
In the first embodiment
The isothermal aging treatment was changed to heat retention at a temperature of 850 ° C. for 10 hours.
A permanent magnet of Comparative Example 1 was obtained in the same manner as in Example 1 except that the subsequent continuous slow cooling was performed at a cooling rate of 0.25 ° C./min to 350 ° C. or lower.

[evaluation]
From the permanent magnets of Examples 1 and 2 and Comparative Example 1, each processed into a shape of 10 × 10 × 7 mm was prepared as a measurement sample. The thickness of 7 mm is the direction of magnetic field orientation (C-axis orientation).

The hysteresis curve of the first embodiment will be described with reference to FIG. The hysteresis curve is measured by sandwiching the measurement sample between the pole pieces of an electromagnet called a DC magnetization characteristic analyzer, and it is not necessary to correct the demagnetic field. At magnetic fields above, the apparent magnetization is reduced. However, in reality, the magnetization curve is such that it is magnetized to saturation magnetization. As shown in FIG. 2, it can be seen that in Example 1, the rise of the initial magnetization curve is steep and the saturation magnetization is reached in a low magnetic field of about 10 kOe. Similarly, the measurement results of the minor loop are also shown (dotted line). In Example 1, a magnetization curve that matches the initial magnetization curve was shown at 8 to 10 kOe, and when the magnetic susceptibility was compared at 10 kOe, the example was almost 100%. The measurement was performed in the same manner in Example 2 and Comparative Example 1. The results are shown in Table 1.
Table 1 also shows the measurement results of the residual magnetic flux density.

Next, FIG. 3 shows a DF-STEM image of Example 1. The left side of FIG. 3 is a DF-STEM image, and the right side of FIG. 3 is a Cu composition image obtained by extracting Cu. A unique cell structure formed by heat treatment of the Sm ₂ Co _{17 alloy is observed.} The inside of the cell is a 2-17 crystal phase composed of a ferromagnetic phase, and the cell wall between cells is a 1-5 crystal phase containing non-magnetic Cu. Therefore, the cell size can be measured from the Cu composition image. When the cell size of this alloy is measured by this method, it is found to be 50 to 200 nm.
Further, FIG. 4 shows the results of composition analysis by observing the grain boundary phase existing between the crystal grains and the grains. The “position” in the graph of FIG. 4 indicates the distance from the upper end to the measurement point with the upper end of the straight line LG4 in the DF-STEM image shown on the left of FIG. 4 as 0. As shown in FIG. 4, it can be seen that Cu and Zr are concentrated in the grain boundary phase. The ratio of Cu and Zr is shown in Table 1. It can be seen that in Example 1, the ratio of Cu is larger than the ratio of Zr.

<Example 3: First manufacturing method>
In Example 1, the alloy ingot having a composition of Fe21.55 wt%, Sm25.65 wt%, Cu4.5 wt%, Zr2.20 wt%, and the balance Co is the same as in Example 1 except for the amount of the raw material added. A molded product was obtained.
The obtained molded product was ^{sintered in a vacuum of 1 × 10-2} Torr or less at a temperature of 1210 ° C. for 1 hour, then solution-treated at 1155 ° C. for 15 hours, and then immediately cooled at 100 ° C./min. Quenched at speed. The sintered body after quenching was heated and held at a temperature of 750 ° C. for 2 hours in an inert atmosphere for isothermal aging treatment, and then slowly cooled to 400 ° C. or lower at a cooling rate of 2 ° C./min. Further, the product is subjected to isothermal aging treatment by heating and holding at a temperature of 765 ° C. for 5.5 hours in an inert atmosphere, and the cooling rate is 0.5 ° C./min to 700 ° C. and a cooling rate of 0.25 ° C./min. The permanent magnet of Example 3 was obtained by continuously slowly cooling to 500 ° C. and a cooling rate of 0.5 ° C./min to 400 ° C. or lower.

<Example 4: Second manufacturing method>
A molded ingot was obtained in the same manner as in Example 3 and subjected to sintering, solution formation, and quenching. The sintered body after quenching is heated and held at a temperature of 815 ° C. for 5.5 hours in an inert atmosphere for isothermal aging treatment, and then continuously slowly cooled to 550 ° C. at a cooling rate of 2 ° C./min to 550 ° C. The permanent magnet of Example 4 was obtained by holding at ° C. for 5 hours and then quenching.

<Reference example 1>
A permanent magnet of Reference Example 1 was obtained in the same manner as in Example 3 except that the steps after the aging treatment at 750 ° C. were not performed in Example 3.

[evaluation]
Examples 3 and 4 were evaluated in the same manner as in Examples 1 and 2. The results are shown in Table 2.
Further, the spectra of the permanent magnets of Examples 3 to 4 and Reference Example 1 measured by the powder X-ray diffraction method are shown in FIG. The peaks related to _{Sm 2} Co ₁₇ in Reference Example 1 are marked. The diffraction intensity ratio I (006) / I (303) of the diffraction intensity I (006) on the surface (006) and the diffraction intensity I (303) on the surface (303) was 0.138 in Reference Example 1 and 0.138 in Example 3. Was 0.270, and Example 4 was 0.197. It has been shown that the permanent magnet obtained by the first manufacturing method as in Example 3 has a high peak intensity on the (006) plane, which is the easily magnetized axis (C axis). As described above, it was shown that according to the first manufacturing method, the degree of orientation of the C-axis is improved, and as a result, the magnetism is improved.

As described above, the rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to 3.0% are contained in a mass percentage, and the balance is The rare earth cobalt permanent magnet of the present invention, which is composed of Co and unavoidable impurities, has a plurality of crystal grains and a grain boundary portion, and has a Cu concentration of twice or more the Zr concentration at the grain boundary portion, has a high residual magnetic flux density. It has been clarified that it has a low coercive force, a high square ratio, and magnetic characteristics suitable for a variable field motor.

Although the present invention has been described above in accordance with the above-described embodiment, the present invention is not limited to the configuration of the above-described embodiment, and is within the scope of the claimed invention within the scope of the claims of the present application. Of course, it includes various modifications, modifications, and combinations that can be made by a person skilled in the art.

1 Crystal grain 2 Grain boundary 3 Cell phase 4 Cell wall 10 Rare earth cobalt permanent magnet

Claims (10)

When R is a rare earth element containing at least Sm,
By mass percentage, it contains rare earth elements R: 23-27%, Cu: 1.0-5.0%, Fe: 18-25%, Zr: 1.5-3.0%, and the balance is Co and unavoidable impurities. A rare earth cobalt permanent magnet consisting of
It has a plurality of crystal grains and grain boundaries,
A rare earth cobalt permanent magnet having a Cu concentration at least twice the Zr concentration at the grain boundary. The rare earth cobalt permanent magnet according to claim 1, wherein the size of the cell structure constituting the crystal grains is 50 to 200 nm. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the saturation magnetization is 1.16 T or more and the intrinsic coercive force Hcj is 120 to 800 kA / m. The rare earth cobalt permanent magnet according to claim 1 or 2, wherein the saturation magnetization is 1.16 T or more and the intrinsic coercive force Hcj is 240 to 800 kA / m. In the demagnetization curve, the square ratio represented by the ratio (Hk / Hcj) of the magnetic field Hk at 90% magnetization of the residual magnetization and the intrinsic coercive force Hcj is 60% or more, and
Any of claims 1 to 4, wherein when remagnetized from a demagnetizing field exceeding the knick point of the demagnetization curve, a magnetization of 95% or more of the saturation magnetization can be obtained with a magnetic field of 5 times or less of the intrinsic coercive force Hcj. The rare earth cobalt permanent magnet described in item 1. In the demagnetization curve, the square ratio represented by the ratio (Hk / Hcj) of the magnetic field Hk at 90% magnetization of the residual magnetization and the intrinsic coercive force Hcj is 60% or more, and
Any of claims 1 to 4, wherein when remagnetized from a demagnetizing field exceeding the knick point of the demagnetization curve, a magnetization of 95% or more of the saturation magnetization can be obtained with a magnetic field of 3 times or less of the intrinsic coercive force Hcj. The rare earth cobalt permanent magnet described in item 1. When the diffraction intensity I (006) on the (006) plane and the diffraction intensity I (303) on the (303) plane are measured by the powder X-ray diffraction method, the diffraction intensity ratio I (006) / I (303) The rare earth cobalt permanent magnet according to any one of claims 1 to 6, wherein the amount is 0.225 to 0.4. When R is a rare earth element containing at least Sm, in terms of mass percentage, rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to Step (I) of preparing an alloy containing 3.0% and the balance consisting of Co and unavoidable impurities, and
The crushing step (II) in which the alloy is made into powder, and
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product at 1200 to 1250 ° C.
The step (V) of solution-treating the molded product after sintering, and
A step (VI) of heat-treating the molded product after the solution treatment at 600 to 850 ° C.
A step (VII) of cooling the molded product after the heat treatment at 0.2 to 10 ° C./min to 400 ° C. or lower, and
A step (VIII) of heat treatment at 700 to 900 ° C. and a temperature higher than that of the step (VI), and
It has a step (IX) of cooling the molded product after heat treatment at 0.1 to 5 ° C./min to 400 ° C. or lower.
A method for manufacturing rare earth cobalt permanent magnets. When R is a rare earth element containing at least Sm, in terms of mass percentage, rare earth element R: 23 to 27%, Cu: 1.0 to 5.0%, Fe: 18 to 25%, Zr: 1.5 to Step (I) of preparing an alloy containing 3.0% and the balance consisting of Co and unavoidable impurities, and
The crushing step (II) in which the alloy is made into powder, and
The pressure molding step (III) using the powder as a molded body and
The step (IV) of sintering the molded product at 1200 to 1250 ° C.
The step (V) of solution-treating the molded product after sintering, and
A step (VI-a) of heat-treating the molded product after the solution treatment at 750 to 850 ° C.
A step of cooling the molded product after the heat treatment at 0.5 to 10 ° C./min to 500 to 600 ° C. and maintaining it at an isothermal temperature (VII-a).
It has a step (VIII-a) of quenching the molded product after maintaining the isothermal temperature.
A method for manufacturing rare earth cobalt permanent magnets. A device comprising the rare earth cobalt permanent magnet according to any one of claims 1 to 7.

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