JP5532745B2 - Magnetic anisotropic magnet and manufacturing method thereof - Google Patents

Description

The present invention relates to a magnetic anisotropic magnet obtained by performing hot plastic working and a manufacturing method thereof.

In recent years, magnets containing rare earth elements such as neodymium and samarium (rare earth magnets) have been actively used for applications such as motors and generators. The reason why rare earth magnets are used is that they are excellent in magnetic properties and relatively inexpensive. In this magnetic characteristic, coercive force (iHc) and residual magnetic flux density (Br) are important indicators.
The coercive force is the magnitude of a magnetic field necessary to make the magnetization zero. Generally, it is known that when this coercive force is large, the heat resistance is excellent.
The residual magnetic flux density indicates the magnitude of the maximum magnetic flux density (degree of magnetic field strength) in the magnet material. When this residual magnetic flux density is large (high), it is very advantageous because it is possible to reduce the size of a device such as a generator and reduce the cost of the magnet.
For this reason, Nd (neodymium) -Fe (iron) -B (boron) magnets having a high residual magnetic flux density are most frequently used as rare earth magnets.

  On the other hand, conventionally, a magnet alloy obtained by subjecting an R (rare earth element) -Fe-B magnet alloy to hot plastic working is known (see Patent Document 1). This Patent Document 1 describes that an anisotropic magnet having excellent magnetic properties can be obtained by optimizing the composition of R-Fe-B magnet alloys and the processing conditions thereof.

  Moreover, in order to improve a coercive force, the magnet which mainly uses Pr (praseodymium) is well-known (refer patent document 2). This Patent Document 2 describes a magnet in which the composition of Pr is limited to a range of 15 to 17 atomic% from the viewpoint of ensuring workability during casting and hot rolling and a high coercive force (paragraph “0014”). See). Further, it is known that a magnet having a high coercive force can be obtained by applying an appropriate heat treatment to a Pr—Fe—B based cast alloy (see [Operation] in Patent Document 3).

  However, conventional magnets have the following problems as applications for motors used in high-temperature environments.

Technically, the magnetic properties of rare earth magnets mainly composed of Pr and Nd are in a trade-off relationship that the coercive force decreases if the residual magnetic flux density improves, and the magnetic flux density decreases if the coercive force improves, It is difficult to improve both at the same time.
For this reason, the magnet alloy described in Patent Document 1 has a problem that a sufficient coercive force is not obtained although the maximum energy product ((BH) max) is improved by increasing the magnetic flux density. It was. The magnets described in Patent Documents 2 and 3 have a high coercive force, but have a problem that a sufficient residual magnetic flux density is not necessarily obtained.

Japanese Patent Laid-Open No. 11-329810 JP-A-8-273914 JP-A-2-3210

The problem to be solved by the present invention is to improve the coercive force without reducing the residual magnetic flux density in a magnetic anisotropic magnet mainly composed of Pr.

In order to solve the above problems, a magnetic anisotropic magnet according to the present invention has the following configuration.
(1) The magnetic anisotropic magnet includes Pr: 12.5 to 15.0 atomic%, B: 4.5 to 6.5 atomic%, and Ga: 0.1 to 0.7 atomic%. The remainder has a Pr—T—B—Ga-based component composition consisting of T and inevitable impurities.
However, T is obtained by replacing Fe or a part of Fe with Co.
(2) The magnetic anisotropic magnet has a degree of magnetic orientation defined by residual magnetic flux density (Br) / saturated magnetic flux density (Js) of 0.92 or more.
(3) The magnetic anisotropic magnet has a crystal grain size of 1 μm or less.
(4) The magnetic anisotropic magnet has a coercive force of 1600 kA / m or more and a residual magnetic flux density of 1.20 T or more, and is subjected to hot plastic working.

In the magnetic anisotropic magnet , part of Pr may be substituted with Nd. However, Pr is 50 atomic% or more of all the rare earth elements.
In the magnetic anisotropic magnet , a part of Pr (and Nd added as necessary) may be substituted with at least one selected from the group consisting of Dy and Tb.
Furthermore, the magnetic anisotropic magnet may further include at least one selected from the group consisting of Cu and Al.
The method for producing a magnetic anisotropic magnet according to the present invention includes:
A melting / quenching / crushing step of rapidly cooling a molten alloy of a component composition formulated so as to be a magnetic anisotropic magnet according to the present invention, and crushing a ribbon obtained by the rapid cooling;
A cold forming step of cold forming the alloy powder obtained by grinding,
A preheating step of preheating the cold formed body obtained in the cold forming step at a temperature of 500 ° C. or higher and 850 ° C. or lower;
A hot forming step of hot forming the preheated cold formed body;
E Bei hot plastic working step of performing hot plastic working to the obtained hot compact in the hot forming process
The magnetic anisotropic magnet has a magnetic orientation degree of 0.92 or more, a crystal grain size of 1 μm or less, a coercive force of 1600 kA / m or more, and a residual magnetic flux density of 1.2 T or more .

  Since the magnetic anisotropic magnet material according to the present invention contains Pr, which has a larger effect of increasing the coercive force than Nd, as a main component, a high coercive force can be obtained. In addition, since the amount of Pr is limited to 12.5 to 15.0 atomic%, coercive force is improved, and at the same time, there are practical problems such as increased difficulty in hot plastic working and seizure to the mold. Does not occur.

The magnetic anisotropic magnet material according to the present invention is obtained by subjecting an alloy powder having a predetermined composition to cold forming, preheating, hot forming, and hot plastic working. That is, the magnetic anisotropic magnet material is made of a polycrystalline body having crystal grains and a grain boundary phase arranged so as to surround the crystal grains.
When preheating + hot forming is performed on the cold formed body, the grain boundary phase is liquefied and the magnet material is densified, and at the same time, the liquefied grain boundary phase surrounds the crystal grains. At this time, the easy axis of magnetization of the crystal grains remains in a random direction. Next, when hot plastic working is performed on the obtained hot-formed body, the crystal grains are compressed in the pressing direction and plastically deformed, and at the same time, the easy axis of magnetization of each crystal grain is oriented in the pressing direction. As a result, the degree of magnetic orientation defined by the residual magnetic flux density (Br) / saturated magnetic flux density (Js) becomes 0.92 or more. Further, when the manufacturing conditions are optimized, the degree of magnetic orientation becomes 0.95 or more.
In the present invention, the residual magnetic flux density can be increased as a result of the easy magnetization axis being easily oriented in a certain direction. This is considered to be because when Pr is used as the main component of the magnetic anisotropic magnet material, the melting point of the grain boundary phase becomes relatively low and the crystal grains can be smoothly rotated. That is, according to the present invention, the coercive force can be improved without reducing the residual magnetic flux density due to the elemental characteristics of Pr itself and the action of Pr's unique orientation mechanism during hot plastic working.

It is a graph which shows the relationship between Pr content and coercive force (iHc), and the relationship between Pr content and residual magnetic flux density (Br). It is a graph which shows the relationship of Pr content-coercive force (iHc)-residual magnetic flux density (Br). It is a graph which shows the relationship between content of Pr, and magnetic orientation degree Br / Js. It is a graph which shows the relationship between Ga content and coercive force (iHc). It is a figure which shows each process of the manufacturing method of a magnetic anisotropic magnet raw material. It is a schematic diagram which shows the state inside a hot compact. It is a schematic diagram which shows the state inside a cylindrical molded object. It is the SEM photograph of the Pr type magnet which made the preheating temperature at the time of a hot press 750 degreeC. It is the SEM photograph of the Pr type magnet which made the preheating temperature at the time of a hot press 820 degreeC.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Magnetic anisotropic magnet material]
The magnetic anisotropic magnet material according to the present invention has the following configuration.
[1.1 Component composition]
The magnetic anisotropic magnet material according to the present invention has a Pr—T—B—Ga based component composition. That is, the magnetic anisotropic magnet material according to the present invention contains a predetermined amount of Pr, B, and Ga, with the balance being T and inevitable impurities. The range of each element and the reason for limitation are as follows.

[1.1.1 Main constituent elements]
(1) Pr: 12.5 to 15.0 atomic%
When the content of Pr is small, the coercive force (iHc) is extremely lowered. Further, when hot plastic working is performed, sufficient fluidity of the workpiece is not obtained, so that plastic working becomes difficult. Further, if the Pr content is low, the degree of magnetic orientation (Br / Js) decreases. Therefore, the Pr content needs to be 12.5 atomic% or more. The Pr content is more preferably 13.0 atomic%, more preferably 13.5 atomic% or more.
On the other hand, when the Pr content is excessive, the residual magnetic flux density (Br) is extremely reduced. In addition, when hot plastic working is performed, seizure to the mold is likely to occur. Furthermore, when the Pr content becomes excessive, the degree of magnetic orientation (Br / Js) decreases. Therefore, the Pr content needs to be 15.0 atomic% or less. The Pr content is more preferably 14.5 atomic% or less, and further preferably 14.0 atomic% or less.

(2) B: 4.5 to 6.5 atomic%
When the B content is small, the crystal grains in the magnetic anisotropic magnet material are coarsened, and a good orientation state of the crystal grains cannot be obtained. Therefore, B content needs to be 4.5 atomic% or more. In order to improve the coercive force without reducing the residual magnetic flux density, the B content is preferably 5.0 atomic% or more.
On the other hand, when the B content is excessive, the amount of grain boundary phase decreases, a hard and brittle B-rich phase such as PrFeB ₄ is formed at the crystal grain boundary, and the state of crystal grains with incomplete orientation tends to be formed. . Therefore, the B content needs to be 6.5 atomic% or less. In order to improve the coercive force without reducing the residual magnetic flux density, the B content is preferably 6.0 atomic percent or less.

(3) Ga: 0.1 to 0.7 atomic%
When the Ga content is low, the coercive force (iHc) decreases. Therefore, the Ga content needs to be 0.1 atomic% or more. The Ga content is more preferably 0.15 atomic% or more, and further preferably 0.2 atomic% or more. In order to improve the coercive force, the Ga content is preferably 0.4 atomic% or more.
On the other hand, when the Ga content is excessive, the coercive force (iHc) is lowered. In addition, since Ga is expensive, adding more than necessary Ga causes an increase in cost. Therefore, the Ga content needs to be 0.7 atomic% or less. In order to improve the coercive force, the Ga content is preferably 0.5 atomic% or less.

(4) T and inevitable impurities The remainder other than Pr, B, and Ga consists of T and inevitable impurities.
T may be composed only of Fe, or a part of Fe may be substituted with Co.
When a part of Fe is replaced with Co, corrosion resistance and thermal stability are improved. However, when the substitution amount of Fe by Co becomes excessive, the saturation magnetic flux density and the coercive force are lowered. Therefore, the Co content with respect to the total amount of elements in the magnetic anisotropic magnet material is preferably 6.0 atomic percent or less.

[1.1.2 Sub-constituent elements]
(1) Nd
A part of Pr may be substituted with Nd. In this case, it is preferable to be used in an application where high temperature characteristics are required. However, when the Nd content is excessive, the coercive force is reduced. Therefore, when Nd is contained, in addition to the total amount of Pr and Nd being 12.5 to 15.0 atomic%, the Pr content is set so that the Pr content is 50 atomic% or more of the total rare earth elements. It is preferred to substitute part with Nd.
Specifically, the Nd content with respect to the total amount of elements in the magnetic anisotropic magnet material is preferably 6.0 atomic percent or less. The Nd content is more preferably 5.0 atomic percent or less, still more preferably 4.0 atomic percent or less, and still more preferably 2.0 atomic percent or less.

(2) Dy and Tb
A part of Pr may be substituted with at least one selected from the group consisting of Dy and Tb. When both Pr and Nd are included, part of Pr and / or Nd may be substituted with at least one selected from the group consisting of Dy and Tb.
When a part of Pr (and Nd) is substituted with Dy and / or Tb, the magnetic anisotropy is increased and a high coercive force can be achieved. Therefore, a magnetic anisotropic magnet material containing Dy and / or Tb is suitable as a magnet material used at a high temperature.
In order to increase the coercive force, in addition to the total amount of Pr (and Nd), Dy, and Tb being 12.5 to 15.0 atomic%, Dy with respect to the total amount of elements in the magnetic anisotropic magnet material And Tb content is preferably 1.0 atomic% or more.
On the other hand, when the substitution amount of Dy and / or Tb becomes excessive, the residual magnetic flux density decreases. Therefore, in addition to the total amount of Pr (and Nd), Dy, and Tb being 12.5 to 15.0 atomic%, the contents of Dy and Tb with respect to the total amount of elements in the magnetic anisotropic magnet material are: Each is preferably 2.0 atomic percent or less.
In addition to or instead of substitution with Nd, the substitution of Dy and / or Tb also preferably gives a total amount of Pr of 50 atomic% or more of the total rare earth elements.

(3) Cu and Al
Instead of or in addition to substituting a part of Pr (and Nd) with any one or more of Dy and Tb, the magnetic anisotropic magnet material is at least selected from the group consisting of Cu and Al. One kind may be further included.
When Cu and / or Al is added to a magnetic anisotropic magnet material having a predetermined composition, the coercive force is improved. This is because the addition of Cu and / or Al lowers the melting point of the grain boundary phase, and the grain boundary phase is uniformly formed around the main phase, and this makes it difficult to receive an external magnetic field. ,it is conceivable that. When the contents of Cu and Al are very small, the addition of these does not impair the magnetic properties of the main phase.
On the other hand, when the contents of Cu and Al become excessive, the residual magnetic flux density decreases. Accordingly, when Cu is added alone, the Cu content is preferably 1.0 atomic% or less, and more preferably 0.5 atomic% or less. Similarly, when Al is added alone, the Al content is preferably 1.0 atomic percent or less, and more preferably 0.5 atomic percent or less.
Further, when Cu and Al are added simultaneously, the total content of Cu and Al is preferably 2.0 atomic percent or less, and more preferably 1.5 atomic percent or less.

[1.2 Organization]
The magnetic anisotropic magnet material according to the present invention rapidly cools the molten alloy having the above composition, pulverizes the ribbon obtained by the rapid cooling, cold-forms the alloy powder obtained by the pulverization, It is obtained by preheating the hot formed body, hot forming the preheated cold formed body, and subjecting the hot formed body to hot plastic working. As a result, the magnetic anisotropic magnet material is a polycrystal having a crystal grain composed of a main phase (R ₂ T ₁₄ B phase (R is a rare earth element)) and a grain boundary phase arranged so as to surround it. Become a body.
When the component composition and manufacturing conditions described later are optimized, the residual magnetic flux density can be improved while maintaining the coercive force high. This is presumably because the degree of orientation of the easy magnetization axis is improved without causing coarsening of crystal grains and an increase in oxygen content.

The crystal grain size of the main phase affects the coercive force. Generally, the coercive force increases as the crystal grain size of the main phase decreases. In order to obtain a high coercive force, the crystal grain size is preferably 1 μm or less. The crystal grain size is more preferably 500 nm or less, more preferably 300 nm or less, and still more preferably 200 nm or less.
Here, "crystal grain size"
(A) Photographing the ab plane of the crystal (a plane parallel to the pressing direction. For example, in the case of an extruded cylindrical magnet, a longitudinal section)
(B) Draw one or more straight lines across the total of 100 crystal grains in a direction perpendicular to the compression direction on the captured image;
(C) Divide the total length of straight lines across 100 crystal grains by 100,
The value obtained by this.

[1.3 Magnetic orientation]
The degree of magnetic orientation refers to a value defined by residual magnetic flux density (Br) / saturation magnetic flux density (Js). The saturation magnetic flux density (Js) refers to the strength of the spontaneous magnetization of the magnetic material, in other words, the value at which the magnetization does not increase when an external magnetic field is applied to the magnetic material.
In a sample in which the easy axis (c-axis) of the R ₂ Fe ₁₄ B crystal (R is a rare earth element) is completely oriented, even if the external magnetic field is removed after magnetization to the saturation magnetic flux density Js, the residual magnetic flux density Br is It is predicted that it will be almost the same as Js. In other words, the fully oriented sample has a magnetic orientation degree of 1.
On the other hand, in the sample with the easy axis tilted at an angle, even if the sample has the same saturation magnetic flux density as the fully oriented sample, a considerable amount of easy axis rotation occurs in the process of reducing the external magnetic field, resulting in a decrease in magnetization. Invite. As a result, Js> Br.

  The magnetic anisotropy magnet material according to the present invention has a magnetic orientation degree of 0.92 or more when the component composition and manufacturing conditions are optimized. Further, when the component composition and manufacturing conditions are further optimized, the magnetic orientation degree becomes 0.95 or more.

[1.4 Coercive force and residual magnetic flux density]
The magnetic anisotropic magnet material according to the present invention has a coercive force (iHc) of 1600 kA / m or more when the component composition and production conditions are optimized. Further, when the component composition and manufacturing conditions are further optimized, the coercive force (iHc) is 1700 kA / m or more, 1800 kA / m or more, 1900 kA / m or more, or 2000 kA / m or more.
Further, the magnetic anisotropic magnet material according to the present invention has a residual magnetic flux density (Br) of 1.20 T or more when the component composition and manufacturing conditions are optimized.

[2. Manufacturing method of magnetic anisotropic magnet material]
The method for producing a magnetic anisotropic magnet material according to the present invention includes a melting / quenching / pulverizing step, a cold forming step, a preheating step, a hot forming step, and a hot plastic working step. .

[2.1 Dissolution / Quenching / Crushing Process]
The melting / quenching / pulverization step is a step of melting an alloy having a predetermined composition, rapidly cooling the molten metal to form a ribbon, and pulverizing the obtained ribbon.
The method for melting the raw material is not particularly limited as long as it is a method capable of obtaining a molten metal having a uniform component and fluidity that can be rapidly solidified. In the case of the magnetic anisotropic magnet material according to the present invention, the temperature of the molten metal is preferably 1000 ° C. or higher.
In general, the molten metal is rapidly cooled by dropping the molten metal onto a rotating roll (copper roll) having high heat removal properties. The cooling rate of the molten metal can be controlled by the peripheral speed of the rotating roll and the amount of molten metal dropped. The peripheral speed is usually about 10 to 30 m / sec.
When the ribbon obtained by the rapid cooling is pulverized, a flaky alloy powder composed of fine crystal grains of about 20 nm is obtained.

[2.2 Cold forming process]
The cold forming step is a step of cold forming an alloy powder obtained by rapid cooling and pulverization.
Cold forming is performed by filling a mold with alloy powder at room temperature and pressurizing with a punch.
In general, the higher the molding pressure, the higher the density of the cold formed body. On the other hand, when the molding pressure exceeds a certain value, the density of the cold formed body is saturated, so there is no practical advantage in pressing more than necessary. The molding pressure is preferably appropriately selected depending on the composition, the size of the powder, and the like.
Pressurization time should just be more than the time when the density of a cold fabrication object is saturated. Usually, 1 to 5 seconds.

[2.3 Preheating step]
The preheating step is a step of preheating the cold formed body obtained in the cold forming step at a temperature of 500 ° C. or higher and 850 ° C. or lower.
Combining preheating and hot forming, which will be described later, is suitable as an industrial mass production method because the cold formed body can be continuously heated and pressurized. Further, when the preheating conditions are optimized and hot forming is performed, a compact with a uniform and fine crystal structure can be obtained. When this molded body is hot plastic processed, there is an advantage that the degree of magnetic orientation is further improved.

When preheating and hot forming are combined, if the preheating temperature is too low, liquefaction of the grain boundary phase at the time of hot forming becomes insufficient. As a result, cracks may occur in the molded body during hot forming. Therefore, the preheating temperature is preferably 500 ° C. or higher. The preheating temperature is more preferably 600 ° C. or higher, more preferably 700 ° C. or higher.
In order to avoid the occurrence of cracks in the molded body during hot forming, holding the molded body in the mold until the molded body reaches a predetermined temperature causes a reduction in production efficiency.
On the other hand, if the preheating temperature is too high, the crystal grains become coarse. When preheating is performed in the atmosphere, the higher the preheating temperature, the more the material is oxidized and the oxygen content increases. Therefore, the preheating temperature is preferably 850 ° C. or less. The preheating temperature is more preferably 800 ° C. or lower, and further preferably 780 ° C. or lower.

The preheating time may be a time for the molded body to reach a predetermined temperature. If the preheating time is too short, the grain boundary phase is not liquefied, and cracks occur during hot forming. On the other hand, preheating more than necessary causes the crystal grains to become coarse. The optimum preheating time is preferably selected according to the size of the molded body and the preheating temperature. Generally, it is preferable to increase the preheating time as the size of the molded body increases. In addition, it is preferable to increase the preheating time as the preheating temperature becomes lower.
The atmosphere at the time of preheating may be any of an inert atmosphere, an oxidizing atmosphere, and a reducing atmosphere. However, an increase in oxygen content leads to a decrease in magnetic properties. Therefore, the atmosphere at the time of preheating is preferably an inert atmosphere or a reducing atmosphere.

[2.4 Hot forming process]
The hot forming step is a step in which the pre-heated cold formed body is hot pressed to densify the magnet material.
In the present invention, “hot forming” refers to a so-called hot press method in which a cold formed body heated in a mold is pressed with a punch. When the cold formed body is hot-pressed using a hot press method, the pores remaining in the cold formed body disappear and can be densified.
As a method of hot forming using a hot press method, specifically,
(1) Insert a cold-formed body into the mold, and apply a predetermined pressure to the cold-formed body for a predetermined time before or after the temperature of the cold-formed body and the mold reaches a predetermined temperature, or in the process of raising the temperature. The first method to apply,
(2) A second method in which the cold formed body is preheated, the preheated cold formed body is inserted into a mold heated to a predetermined temperature, and a predetermined pressure is applied to the cold formed body for a predetermined time. ,
and so on.
In the present invention, the second method is used.

The optimum hot pressing conditions are selected according to the component composition and required characteristics.
Generally, when the hot press temperature is too low, liquefaction of the grain boundary phase becomes insufficient. As a result, densification becomes insufficient, or cracks may occur in the molded body after hot forming. Accordingly, the hot press temperature is preferably 750 ° C. or higher.
On the other hand, if the hot press temperature is too high, the crystal grains become coarse and the magnetic properties are deteriorated. Accordingly, the hot press temperature is preferably 850 ° C. or lower.

In general, as the pressure during hot pressing increases, densification of the molded body proceeds. On the other hand, pressurization more than necessary has no practical benefit because the effect is saturated. The hot press pressure is preferably selected as appropriate depending on the composition, the size of the powder, temperature conditions, and the like.
In general, the densification of the molded body proceeds as the pressing time becomes longer. On the other hand, holding more than necessary causes the crystal grains to become coarse and causes a decrease in magnetic properties. The pressing time is preferably selected as appropriate according to the composition, the size of the powder, temperature conditions, and the like.
The atmosphere during hot pressing may be any of an inert atmosphere, an oxidizing atmosphere, and a reducing atmosphere. However, an increase in oxygen content leads to a decrease in magnetic properties. Therefore, the atmosphere during hot pressing is preferably an inert atmosphere or a reducing atmosphere.

[2.5 Hot plastic working process]
The hot plastic working step is a step of plastically deforming the densified hot-formed body into a predetermined shape.
The hot plastic working method is not particularly limited, and various methods can be used depending on the purpose.
Specifically, as a hot plastic working method,
(1) Hot extrusion (including backward extrusion and forward extrusion),
(2) Hot upsetting,
and so on. As the hot plastic working method, hot extrusion is particularly suitable from the viewpoint of industrial productivity.

The processing temperature may be any temperature that allows plastic deformation without causing cracks in the molded body. In general, when the processing temperature is too low, liquefaction of the grain boundary phase becomes insufficient, and there is a possibility that cracks may occur in the molded body. Accordingly, the processing temperature is preferably 750 ° C. or higher.
On the other hand, if the processing temperature is too high, the crystal grains become coarse and the magnetic properties are degraded. Accordingly, the processing temperature is preferably 850 ° C. or lower.
The atmosphere during hot plastic working may be any of an inert atmosphere, an oxidizing atmosphere, and a reducing atmosphere. However, an increase in oxygen content leads to a decrease in magnetic properties. Therefore, the atmosphere during hot plastic working is preferably an inert atmosphere or a reducing atmosphere.
After hot plastic working, if necessary, the magnet material having the desired component composition and shape can be obtained.

[3. Operation of Magnetic Anisotropy Magnet Material and Manufacturing Method Thereof]
When the rapidly solidified and ground alloy powder is cold formed and the cold formed body is preheated and hot formed, a dense hot formed body can be obtained. FIG. 6 is a schematic view showing an internal state of the hot formed body. As well shown in FIG. 6, the inside of the hot formed body is composed of crystal grains 51 and grain boundary phases 52. When the temperature of the compact exceeds about 600 to 700 ° C. during hot forming, the grain boundary phase 52 begins to liquefy. And when heating temperature exceeds about 700-800 degreeC, the crystal grain 51 will be in the state enclosed by the liquefied grain boundary phase 52. FIG.
At this time, the crystal grains 51 can be rotated in the direction indicated by the black arrow A. However, since the amount of compressive deformation is small at the time of hot working, the easy magnetization axis 53 (open arrow) existing in each crystal grain 51 has the magnetization direction (that is, the direction of N pole and S pole). It remains in a disaggregated state (isotropic state), and usually does not become a state in which the easy magnetization axis 53 is aligned in a certain direction (anisotropic state).

Next, when hot plastic working is performed on the obtained hot formed body, the hot formed body is plastically deformed to obtain a magnet material having a desired shape.
When the hot formed body is heated, the grain boundary phase is liquefied and the crystal grains can be rotated. When hot plastic working is performed in such a state, the crystal grains are compressed in the pressing direction and plastically deformed, and at the same time, the easy axis of magnetization is oriented in the pressing direction.

For example, when a hot back extrusion process is performed on a hot formed body, a bottomed cylindrical formed body is obtained. FIG. 7 is a schematic view showing an internal state of such a cylindrical molded body. In FIG. 7, the right side direction is the radial direction of the cylindrical molded body.
When a cylindrical molded body is manufactured by hot back extrusion, the punch is inserted in the axial direction, but the pressing direction of the material is the radial direction. Therefore, the crystal grains 51 surrounded by the liquefied grain boundary phase 52 are compressed in the radial direction along with the backward extrusion. At the same time, the easy magnetization axis 53 rotates so as to align in the radial direction. As a result, as shown in FIG. 7, a cylindrical molded body having easy magnetization axes 53 aligned in the radial direction is obtained.

Since the magnetic anisotropic magnet material according to the present invention is mainly composed of Pr, it has a high magnetic orientation (easy alignment of the easy magnetization axis 53). It is assumed that the reason why the magnetic orientation becomes high is that when Pr is contained as a main component, the melting point of the grain boundary phase 52 becomes relatively low. In other words, it is considered that Pr has a unique orientation mechanism in which the crystal grains 51 are easily rotated by performing hot plastic working at a high temperature.
That is, the magnetic anisotropic magnet material according to the present invention can improve the coercive force without reducing the residual magnetic flux density due to the characteristics of the element of Pr itself and the orientation mechanism unique to Pr during hot plastic working. It has become possible.

Further, when hot forming is performed using a hot press method, if the manufacturing conditions are optimized, the residual magnetic flux density can be further improved while maintaining the coercive force high. In particular, when a method of pre-heating the compact at a predetermined temperature and then hot pressing the compact in a mold heated to a predetermined temperature, the magnet material after hot plastic working is not pre-heated. As a result, the coercive force is improved more than the case, and at the same time, a magnet material having a magnetic orientation degree of 0.92 or more, and further 0.95 or more is obtained.
this is,
(1) By preheating at a predetermined temperature, the cold formed body is uniformly heated to a temperature close to the temperature of the mold, and the temperature distribution of the magnet material during the hot forming becomes uniform, and the hot forming is performed. Time is shortened. As a result, a hot formed body having a uniform microstructure can be obtained, and
(2) By hot plastic forming a hot formed body in which crystal grains are refined and uniformized, the c axis (magnetization easy axis) of R ₂ Fe ₁₄ B is in the pressing direction while the crystal grains are refined. Because it became easier to align,
it is conceivable that.

Example 1.1
[1. Preparation of sample]
The molten alloy having a predetermined composition was quenched. The obtained ribbon was pulverized to obtain an alloy powder. The alloy powder was cold formed, and the cold formed body was hot formed. Furthermore, hot plastic working was performed on this hot formed body to obtain a magnetic anisotropic magnet material.
The alloy composition is Pr _x Fe _94.05-x B _5.5 Ga _0.45 (x = 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16 0.0. Inevitable impurities included).
In addition, preheating conditions and hot forming conditions are:
(1) Preheating at 750 ° C. × 10 min + hot pressing at 815 ° C. (mold temperature) (with preheating), or
(2) Hot press (no preheating) at 850 ° C (mold temperature)
It was.

[2. Test method]
[2.1 Magnetic properties]
A magnetic anisotropic magnet material was magnetized, and its magnetic characteristics were measured with a DC BH tracer.
[2.2 Magnetic orientation]
A magnetic anisotropic magnet material was magnetized, and the degree of magnetic orientation was measured with a pulse type high magnetic field measuring device (magnetic field: 3988 kA / m).

[3. result]
FIG. 1 shows the relationship between the Pr content and the coercive force (iHc), and the relationship between the Pr content and the residual magnetic flux density (Br).
From FIG.
(1) In the absence of preheating, when the Pr content is less than 13 atomic%, the coercive force (iHc) is extremely reduced, and plastic working becomes difficult.
(2) In the absence of preheating, when the Pr content exceeds 15 atomic%, the residual magnetic flux density (Br) is extremely reduced, and seizure to the mold is likely to occur.
(3) In the case where there is preheating, when the content of Pr is 12.5 atomic% or more, the coercive force (iHc) is higher than that without preheating, and plastic working is also possible.
(4) When preheating is performed, the residual magnetic flux density (Br) is improved as compared to the case without preheating.
I understand that.

FIG. 2 shows the relationship of Pr content-coercive force (iHc) -residual magnetic flux density (Br). In FIG. 2, the closer to the upper right, the better the magnetic properties.
From FIG.
(1) When there is no preheating, the Pr content in which both the coercive force and the residual magnetic flux density are excellent is 13.0 to 14.5 atomic%, more preferably 13.5 to 14.0 atomic%. ,
(2) When preheating is performed, the range of Pr content in which both the coercive force and the residual magnetic flux density are excellent is expanded to 12.5 to 15.0 atomic%.
I understand that.

FIG. 3 shows the relationship between the Pr content and the degree of magnetic orientation Br / Js.
From FIG.
(1) When there is no preheating, the degree of magnetic orientation decreases when the Pr content is less than 13 atomic% and when the Pr content exceeds 15 atomic%.
(2) In the case where there is preheating, a magnetic orientation degree of 0.92 or more is obtained when the Pr content is in the range of 12.5 to 15 atomic%.
I understand that.

(Example 1.2)
[1. Preparation of sample]
The alloy composition is Pr _13.09 Fe _81.51-y B _5.4 Ga _y (y = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 A magnetic anisotropic magnet material was produced in the same manner as in Example 1.1 except that inevitable impurities were included.
[2. Test method]
A magnetic anisotropic magnet material was magnetized, and its magnetic characteristics were measured with a DC BH tracer.

[3. result]
FIG. 4 shows the relationship between the Ga content and the coercive force (iHc).
From FIG.
(1) When the Ga content is less than 0.1 atomic%, the coercive force (iHc) is extremely reduced.
(2) When the Ga content exceeds 0.7 atomic%, the coercive force (iHc) decreases.
(3) In order to obtain a high coercive force, the Ga content is preferably 0.2 to 0.7 atomic%, more preferably 0.4 to 0.5 atomic%.
(4) When preheating is performed, a higher coercive force can be obtained than when preheating is not performed.
I understand that.

(Examples 2.1 to 2.21, Comparative Examples 2.1 to 2.5)
[1. Preparation of sample]
With respect to the alloy compositions (Examples 2.1 to 2.21, Comparative Examples 2.1 to 2.5) shown in Table 1, magnetic anisotropic magnet materials were produced by the production methods shown below. In FIG. 5, each process of the manufacturing method of a magnetic anisotropic magnet raw material is shown.

[1.1 Dissolution / Quenching / Crushing Process]
Various predetermined amounts of alloy raw materials were blended and dissolved at 1000 ° C. or higher. The molten metal 11 was dropped from an orifice 12 onto a rotary roll 13 having high heat removal properties and rapidly cooled to produce a ribbon 14. The peripheral speed of the rotary roll 13 was 18 to 20 m / sec. The ribbon 14 was pulverized to obtain a flaky alloy powder 10 composed of fine crystal grains of 0.02 μm (20 nm).
[1.2 Cold forming process]
56 g of alloy powder 10 was set in the cold press machine 21. A pressure of about 5.1 t / cm ² (5.0 × 10 ² MPa) was molded into a cylindrical shape over a period of 1 to 5 seconds, and the cold-formed body 20 (outer diameter: 22.8 mm, height 30 mm) A cylindrical molded body) was obtained.

[1.3 Hot forming process]
The cold-formed body 20 was preheated at 750 ° C. for 10 minutes in an argon atmosphere. Next, the preheated cold formed body 20 was set in a hot press machine 31. This was molded into a cylindrical shape under a condition of 815 ° C. (mold temperature) in an argon atmosphere at a pressure of about 4 t / cm ² (3.92 MPa) for about 20 seconds, and the hot molded body 30 (outer diameter) 22.8 mm and a 20 mm-high columnar molded body) were obtained.
[1.4 Backward extrusion]
The hot formed body 30 is set in the backward extrusion device 41, and backward extrusion is performed in the atmosphere under the condition of 860 ° C. (die temperature), and the magnetic anisotropic magnet material 40 (outer diameter 22.8 mm, inner diameter 18. A cylindrical molded body having a height of 8 mm and a height of 40 mm was obtained.
When the hot molded body 30 is inserted into the mold 43 and extruded backward (upward in FIG. 5) with a punch 42 having a smaller diameter than the hot molded body 30, the hot molded body 30 is moved to the punch 42 and the mold. The punch 42 is pushed out in the direction opposite to the traveling direction of the punch 42. As a result, a bottomed cylindrical molded body 40 is obtained.
The bottom portion of the obtained cylindrical molded body 40 was cut off, and then magnetized in the radial direction to obtain a ring magnet.

[2. Test method]
[2.1 Composition analysis]
The composition of the alloy powder was measured by ICP analysis.
[2.2 Magnetic orientation]
The magnetic orientation degree Br / Js of the obtained ring-shaped magnet was measured using a pulse type high magnetic field measuring device (magnetic field: 3988 kA / m). This measurement was performed using a disk-shaped test piece having a diameter of about 5 mm cut from the side surface of the magnetized ring-shaped magnet.
[2.3 Magnetic properties]
The coercive force (iHc) and residual magnetic flux density (Br) of the obtained ring-shaped magnet were measured with a direct current BH tracer. Similar to the measurement of the degree of magnetic orientation, this measurement was performed using a disk-shaped test piece having a diameter of about 5 mm cut from the side surface of the magnetized ring-shaped magnet.
Table 1 shows the measurement results.

[3. Verification]
As shown well in Table 1, the magnetic orientation degrees Br / Js of Examples 2.1 to 2.21 are all high values of 0.92 or more, whereas Comparative Examples 2.1 to The degree of magnetic orientation Br / Js of 2.5 is less than 0.92. Further, the residual magnetic flux density (Br) of Examples 2.1 to 2.21 is equal to or higher than the residual magnetic flux density (Br) of Comparative Examples 2.1 to 2.5. .
This is presumably because the degree of magnetic orientation was improved by Pr's unique orientation mechanism and appropriate preheating during hot plastic working.

The coercive force (iHc) of Examples 2.1 to 2.21 containing Pr as the main component is 1600 kA / m or more. On the other hand, the coercive force (iHc) of Comparative Examples 2.1 to 2.5 containing Nd as the main component is less than 1600 kA / m. This is because the Pr ₂ Fe ₁₄ B type composition has an anisotropic magnetic field larger than that of the Nd ₂ Fe ₁₄ B type composition.

In Examples 2.15 to 2.19, since the substitution amount of Dy or Tb is 1 atomic% or more, the coercive force (iHc) is 2000 kA / m or more. Among these, especially in Example 2.16, since Cu was added, the coercive force (iHc) was satisfactory.
From this result, it can be seen that for applications with higher heat resistance requirements such as automobile motors used in high temperature environments, it is sufficient to use a Dy or Tb substitution amount of 1 atomic% or more. However, if it is replaced more than necessary, it can be considered that the degree of magnetic orientation during hot plastic working is adversely affected. Therefore, the substitution amount is preferably set to 2.0 atomic% or less.
Therefore, when the coercive force is particularly required in use, the substitution amount of Dy or Tb is preferably 1.0 to 2.0 atomic%.

Further, when Examples 2.2 to 2.4, which are substantially the same except for the composition of Cu and Al, are compared, Examples 2.3 and 2.4 to which Cu and Al are added have a coercive force (iHc). Good results. Similarly, when Examples 2.10 to 2.13, which are substantially the same except for the composition of Cu and Al, are compared, Examples 2.10, 2.11, and 2.13 to which Cu and Al are added have a coercive force ( iHc) is a good result.
From this result, it was confirmed that the coercive force was increased by adding Cu and Al.

Further, Examples 2.20 and 2.21 in which a part of Pr was substituted with Nd had magnetic characteristics equivalent to or higher than those of Example 2.18, in which the total amount of rare earth elements was almost the same as these.
From the above results, it was confirmed that the magnetic anisotropy magnet material according to Examples 2.1 to 2.21 can improve the coercive force without reducing the residual magnetic flux density. In addition, it was confirmed that the magnetic anisotropic magnet material according to the present invention can be expected particularly as a motor application requiring high magnetic force and heat resistance.

(Examples 3.1 to 3.9, Comparative examples 3.1 to 3.15)
[1. Preparation of sample]
Pr-based (Examples 3.1 to 3.9, Comparative Examples 3.10 to 3.15) and Nd-based (Comparative Examples 3.1 to 3.9) alloy powders were prepared by a rapid solidification / pulverization method. . The composition of the Pr-based alloy powder was 12.85Pr-5.36B-0.42Ga-bal. Fe (atomic%) was used. The composition of the Nd-based alloy powder was 12.87Nd-5.38B-0.44Ga-bal. Fe (atomic%) was used.
Using this alloy powder, cold forming, hot forming, and hot plastic working were performed to obtain a cylindrical formed body. The hot forming was performed by preheating the cold formed body at 500 to 820 ° C. in an Ar atmosphere, and pressurizing the preheated formed body in a mold heated to 815 to 850 ° C. However, no preheating was performed for Comparative Examples 3.10 to 3.15. The conditions for cold forming and hot plastic working were the same as in Examples 2.1 to 2.21.
The bottom portion of the obtained cylindrical molded body was cut off, and then magnetized in the radial direction to obtain a ring magnet.

[2. Test method]
The magnetic properties and the degree of magnetic orientation were measured according to the same procedure as in Examples 2.1 to 2.21.
Table 2 shows the results. Table 2 also shows preheating conditions and hot forming conditions.
In addition, the characteristic evaluation of the molded object in Table 2 was performed on the following reference | standard.
◎ = Extrusion time 15 seconds or less ○ = Extrusion time 16 to 20 seconds △ = Extrusion time 21 seconds or more

[3. result]
Table 2 shows the following.
(1) In the Pr-based magnet, the maximum energy product (BH) _max becomes maximum when the preheating temperature is 750 ° C. and the mold temperature is 815 ° C., and the degree of magnetic orientation exceeds 0.95. Also, very good moldability can be obtained.
(2) The degree of magnetic orientation of the Nd-based magnet is less than 0.90. Formability is relatively good, but not as good as Pr-based magnets with preheating.
(3) Even if it is a Pr-based magnet, if preheating is not performed, the formability of hot forming is reduced and a compact having a uniform microstructure cannot be obtained. take time. As a result, the coercive force is reduced due to the coarsening of the crystal grains, and the residual magnetic flux density is also reduced because it is difficult to orient. In other words, when preheating is performed, hot working and hot plastic working can be performed smoothly, and a magnet material having good magnetic properties can be obtained. In addition, in the Pr magnet, when the preheating temperature is too high, the maximum energy product decreases because of a decrease in coercive force due to coarsening of crystal grains and a decrease in residual magnetic flux density due to difficulty in crystal orientation. it is conceivable that.

(4) On the other hand, Nd-based magnets have a higher melting point of grain boundary phase than Pr-based magnets, so in order to make a hot compact compact and uniform structure, preheating at a higher temperature than Pr-based magnets. There is a need to. That is, in the case of an Nd-based magnet, an appropriate preheating temperature for producing a hot-formed body having a dense and uniform structure is shifted to a higher temperature range than that of a Pr-based magnet. For this reason, the maximum energy product (BH) _max of the Nd-based magnet is not significantly affected by the preheating temperature.
(5) When the preheating temperature is less than 500 ° C. for both Pd magnets and Nd magnets, the grain boundary phase does not liquefy and cracks occur in the work after hot forming, making magnet forming difficult. There were many.

8 and 9 show SEM photographs of Pr-based magnets preheated at 750 ° C. and 820 ° C., respectively. When the preheating temperature was 820 ° C., coarse particles were included, and the crystal grain size was 700 nm or more. On the other hand, when the preheating temperature was 750 ° C., coarse particles were not included and the crystal grain size was about 200 nm. The reason why high magnetic characteristics can be obtained by setting the preheating temperature to 750 ° C. is considered to be because the crystal grains are uniform and refined.
From the above results, it was found that a Pr-based magnet having a grain boundary phase melting point lower than that of an Nd-based magnet can be magnet-molded and has an appropriate preheating temperature with a small decrease in magnetic properties.

  The magnetic anisotropic magnet material according to the present invention is intended to improve the coercive force without reducing the residual magnetic flux density. For this reason, it is suitably used for an automobile-mounted motor that requires a particularly high coercive force and residual magnetic flux density. This is because such a motor is used in a high heat environment, and thus the magnetic anisotropic magnet material is required to have heat resistance. Furthermore, high rotational force (magnetic force) is required for miniaturization of automobile parts.

10 Alloy powder 20 Cold formed body 30 Hot formed body 40 Cylindrical formed body (magnetic anisotropic magnet material)
51 crystal grain 52 grain boundary phase 53 easy axis of magnetization

Claims (7)

A magnetic anisotropic magnet having the following configuration .
(1) The magnetic anisotropic magnet includes Pr: 12.5 to 15.0 atomic%, B: 4.5 to 6.5 atomic%, and Ga: 0.1 to 0.7 atomic%. The remainder has a Pr—T—B—Ga-based component composition consisting of T and inevitable impurities.
However, T is obtained by replacing Fe or a part of Fe with Co.
(2) The magnetic anisotropic magnet has a degree of magnetic orientation defined by residual magnetic flux density (Br) / saturated magnetic flux density (Js) of 0.92 or more.
(3) The magnetic anisotropic magnet has a crystal grain size of 1 μm or less.
(4) The magnetic anisotropic magnet has a coercive force of 1600 kA / m or more and a residual magnetic flux density of 1.20 T or more, and is subjected to hot plastic working. The magnetic anisotropic magnet according to claim 1, wherein a part of the Pr is substituted with Nd.
However, the Pr is 50 atomic% or more of the total rare earth elements. A part of the Pr and / or the Nd is substituted with at least one selected from the group consisting of Dy and Tb ;
The magnetic anisotropic magnet according to claim 1 or 2, wherein the contents of Dy and Tb are each 2.0 atom% or less . Further seen contains at least one selected from the group consisting of Cu and Al,
The content of Cu and Al, respectively, anisotropic magnet according to any one of 請 Motomeko 1 is 1.0 at% to 3. A melting, quenching, and pulverizing step of rapidly cooling a molten alloy having a component composition blended so as to be a magnetic anisotropic magnet according to any one of claims 1 to 4, and pulverizing a ribbon obtained by the rapid cooling ,
A cold forming step of cold forming the alloy powder obtained by grinding,
A preheating step of preheating the cold formed body obtained in the cold forming step at a temperature of 500 ° C. or higher and 850 ° C. or lower;
A hot forming step of hot forming the preheated cold formed body;
E Bei the hot plastic working step of performing hot plastic working to the obtained hot compact in the hot forming process
The magnetic anisotropic magnet has a magnetic orientation degree of 0.92 or more, a crystal grain size of 1 μm or less, a coercive force of 1600 kA / m or more, and a residual magnetic flux density of 1.2 T or more.
Manufacturing method of magnetic anisotropic magnet .   6. The method for producing a magnetic anisotropic magnet according to claim 5, wherein the hot forming step inserts the cold formed body into a mold heated to a predetermined temperature and applies a predetermined pressure.   The method for producing a magnetic anisotropic magnet according to claim 5 or 6, wherein in the preheating step, the cold formed body is preheated at a temperature of 500 ° C or higher and 750 ° C or lower.

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