JP2017022192A - Manufacturing method for magnet and magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for magnet having a high residual magnetic flux, and to provide a magnet.SOLUTION: In a manufacturing method for magnet having a process for obtaining a molding by pressure molding magnetic powder, the magnetic powder 11 consists of a mixed powder of spherical magnetic powder of magnetic anisotropy having a ratio of long diameter and short diameter of less than 2, and flat magnetic powder 12 of magnetic isotropy having a ratio of long diameter and short diameter of 2 or more. Rearrangement of magnetic powder where the shape of particles is different is promoted, and a dense molding 6 with less voids is obtained.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a magnet manufacturing method and a magnet.

Japanese Patent Application Laid-Open No. 2005-272986 (Patent Document 1) includes rare earth metal (R), at least one transition metal (TM) selected from iron, cobalt, or nickel, and nitrogen as main components. R ₂ TM ₁₇ N _X type rare earth-transition metal-nitrogen based magnet alloy powder (magnetic powder) is described. The magnetic powder is described as a production method using an alloy powder obtained by pulverizing a mother alloy produced by a melt casting method, a liquid quenching method, a reduction diffusion method or the like as a raw material for the reduction diffusion method. The use of this magnetic powder in a bonded magnet is also described.

  JP-A-2015-8200 (Patent Document 2) uses R-Fe-N-based compounds containing rare earth elements as R or magnetic particles of a hard magnetic material formed from an Fe-N-based compound, A primary molded body is formed by pressurizing a plurality of times with a mold, and the primary molded body is heated at a temperature lower than the decomposition temperature of the magnetic powder to form a secondary molded body by bonding the surfaces of adjacent magnetic powders. Thus, it is described that a magnet is manufactured.

JP 2005-272986 A Japanese Patent Laying-Open No. 2015-8200

  The magnetic powder described in Patent Document 1 is used for bonded magnets and binds in a state where the magnetic powder is contained in the synthetic resin. In a normal bonded magnet, when the volume of magnetic powder is 100 vol%, synthetic resin is included at a ratio of 40 vol% or more. The magnetic properties of the bond magnet are determined by the ratio of the magnetic powder contained (the content ratio of the magnetic powder). When the content ratio of the magnetic powder is lowered, the magnetic properties of the bonded magnet are deteriorated. Further, when the content ratio of the magnetic powder becomes high, not only the moldability of the magnet (moldability of injection molding) is significantly lowered, but also the fixing of the magnetic powder particles becomes insufficient and the shape of the bonded magnet cannot be maintained. Therefore, the bond magnet has a limit in improving the magnetic characteristics (suppressing the decrease in residual magnetic flux density).

In Patent Document 2, which is a technique for such a problem, the magnetic characteristics are improved because no resin is used. However, in Patent Document 2, voids are likely to remain in the primary molded body formed by pressurizing magnetic powder, and it is difficult to increase the density of the manufactured magnet. That is, there is a limit to the improvement of the residual magnetic flux density of the manufactured magnet.
This invention is made | formed in view of such a situation, and it aims at providing the manufacturing method and magnet of a magnet which can obtain a high residual magnetic flux density.

  The magnet manufacturing method of the present invention that solves the above-mentioned problems is a method for manufacturing a magnet having a step of pressing a magnetic powder to obtain a molded body, and the magnetic powder is a sphere having a ratio of major axis to minor axis of less than 2 It is characterized by comprising a mixed powder of magnetic anisotropy magnetic powder and a flat magnetic isotropic magnetic powder having a major axis / minor axis ratio of 2 or more.

  In the magnet manufacturing method of the present invention, a compact is obtained by pressure molding a mixed powder of magnetic powder made of spherical particles and magnetic powder made of flat particles. In this case, rearrangement of magnetic powders having different particle shapes is promoted during pressurization, and a dense molded body with few voids can be obtained. Therefore, according to the manufacturing method of the present invention, a magnet having a high residual magnetic flux density can be manufactured.

The magnet of the present invention that solves the above problems is manufactured by the above-described magnet manufacturing method.
The magnet of the present invention is manufactured by the above-described manufacturing method, and becomes a magnet having a high residual magnetic flux density.

It is the figure which showed each process of the manufacturing method of the magnet of Embodiment 1. FIG. 2 is a photomicrograph of spherical magnetic anisotropic magnetic particles of Embodiment 1. 2 is a micrograph of a flat isotropic magnetic powder of Embodiment 1. FIG. It is a figure which shows the relationship between the ratio of the magnetic powder of the flat shape of the magnetic powder of Embodiment 1, and a magnetic characteristic. It is a schematic diagram which shows the process of mixing the magnetic powder and lubricant of Embodiment 1. It is a schematic diagram which shows the process of further mixing the magnetic powder and lubricant of Embodiment 1. It is sectional drawing which shows typically the state which the magnetic powder and binder of Embodiment 1 mixed. It is a schematic diagram which shows the state before the pressurization of the pressurization process of the magnetic powder of Embodiment 1. It is a schematic diagram which shows the state at the time of the pressurization of the pressurization process of the magnetic powder of Embodiment 1. It is an enlarged view which shows typically the arrangement | sequence state of the magnetic powder of Embodiment 1. FIG. FIG. 3 is an enlarged view schematically showing an arrangement state of magnetic powders of the molded body of Embodiment 1. It is an enlarged view which shows the structure of the magnet of Embodiment 1 typically. It is the figure which showed each process in the manufacturing method of the magnet of Embodiment 2. It is the figure which showed the temperature change of the heating process in the manufacturing method of the magnet of Embodiment 2.

[Embodiment 1]
The manufacturing method of the magnet of this invention is concretely demonstrated as embodiment, referring FIGS. 1-12. FIG. 1 is a view showing each step of the magnet manufacturing method of the present embodiment.

(Step S1: Preparation of magnetic powder)
As shown in step S1 of FIG. 1, magnetic powder 1 is prepared as a magnet material.

  The magnetic powder 1 is a mixed powder of a spherical magnetic anisotropic magnetic powder 11 having a major axis / minor axis ratio of less than 2 and a flat magnetic isotropic magnetic powder 12 having a major axis / minor axis ratio of 2 or more. It becomes more. That is, magnetically anisotropic magnetic powder 11 and magnetically isotropic magnetic powder 12 are prepared and mixed to obtain magnetic powder 1.

  The magnetic powder 11 is composed of spherical particles having a major axis / minor axis ratio of less than two. Since the magnetic powder 11 is a magnetic powder excellent in magnetic anisotropy, an anisotropic magnet manufactured by magnetic field orientation molding using the magnetic powder 11 can obtain excellent magnetic characteristics. The magnetic powder 11 is shown in FIG. As shown in FIG. 2, the magnetic powder 11 consists of substantially spherical particles having no corners.

  The magnetic powder 11 is composed of spherical particles having a major axis / minor axis ratio of less than 2, so that rearrangement of the particles of the magnetic powder 11 is not hindered during pressure molding. Moreover, even if a pressure is applied between adjacent particles at the time of pressure molding, partial pressure concentration does not occur due to the spherical particles. For this reason, particle destruction due to partial concentration of stress does not occur. The ratio of the major axis to the minor axis of the particles of the magnetic powder 11 can be obtained by observing the outer shape of the particles of the magnetic powder 11. The ratio of the major axis to the minor axis of the particles of the magnetic powder 11 may be less than 2, preferably as close to 1.0, and most preferably 1.0.

  The magnetic powder 12 is made of flat particles having a major axis / minor axis ratio of 2 or more. Since the magnetic powder 12 is made of flat particles, the magnetically isotropic magnetic powder 12 is rearranged around the magnetic anisotropy magnetic powder 11 when pressure-molded, and the gap of the magnetic powder 1 is reduced and manufactured. The magnetic properties of the magnet to be increased. The magnetic powder 12 is shown in FIG. As shown in FIG. 3, the magnetic powder 12 consists of substantially flaky particles with many corners.

Since the magnetically isotropic magnetic powder 12 has a flat shape, the flat particles are broken into fine particles when pressed. These fine particles are rearranged around the magnetic powder 11 so that the voids of the magnetic powder 1 are further reduced, and a denser compact is produced.
The ratio of the major axis to the minor axis of the magnetic powder 12 may be 2 or more, and is preferably 3 or more.

  The magnetically isotropic magnet forming the magnetic powder 12 is inferior in magnetic properties as compared with the magnetic anisotropic magnet of the magnetic powder 11. However, in this embodiment, the magnetic powder 12 forms fine particles, and the fine particles can be rearranged around the magnetic anisotropic magnetic particles 11. That is, fine particles are arranged at positions that become voids in the molded body in the case of only the spherical magnetic powder 11. As a result, a denser molded body 6 is manufactured. And the magnetic characteristic of the molded object 6 and the magnet 8 improves by arranging the magnet (fine particle | grains) with a magnetic characteristic in the position used as a space | gap in the molded object in the case of only the spherical magnetic powder 11. FIG.

  In the magnetic powder 1, the ratio of the magnetic anisotropic magnetic powder 11 and the magnetically isotropic magnetic powder 12 is not limited. When the mass of the magnetic powder 1 is 100%, the ratio of the flat magnetic isotropic magnetic powder 12 is preferably 5 to 25%. When the ratio of the magnetic powder 12 falls within this range, the above-described magnetic characteristics are excellent, and a dense molded body 6 can be obtained. If the ratio of the magnetic powder 12 is less than 5 mass%, the effect of containing the magnetic powder 12 is not sufficiently exhibited. When it exceeds 25 mass%, the content ratio of the magnetically anisotropic magnetic powder 11 is reduced, and the magnetic properties of the molded body 6 are lowered. The ratio of the flat magnetic isotropic magnetic powder 12 is more preferably 10 to 20 mass%, and most preferably 15 mass%.

  FIG. 4 shows the relationship between the content ratio of the magnetic powder 12 and the magnetic characteristics of the magnet 8. In FIG. 8, the residual magnetic flux density ratio on the vertical axis is a ratio when the residual magnetic flux density of the magnet 8 when the content ratio is 0% is 1.0. As shown in FIG. 4, it can be confirmed that the residual magnetic flux density ratio exceeds 1.0 when the ratio of the magnetic powder 12 is in the range of 5 to 25%, and the highest value is about 15%. That is, the above-mentioned action / effect can be confirmed.

As the magnetic powder 1 (spherical magnetic anisotropic magnetic powder 11 and flat magnetic isotropic magnetic powder 12), a powder that is an aggregate of particles of a magnetic material is used. The magnetic material of the magnetic powder 1 is not limited, but is preferably made of a hard magnetic material. Examples of the hard magnetic material include ferrite magnets, Al—Ni—Co based magnets, rare earth magnets containing rare earth elements, and iron nitride magnets.
In the magnetic powder 1, the magnetic powder 11 and the magnetic powder 12 are preferably magnets having the same composition.

  As the magnetic powder 1 (magnetic powder 11, magnetic powder 12) of the hard magnetic material, it is preferable to use a compound composed of one or more of an Fe—N compound and an R—Fe—N compound (R: rare earth element). The rare earth element represented by R is an element known as a so-called rare earth element (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm. Yb, Lu, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr), and rare earth elements other than Dy (R: Dy) Rare earth elements excluded) are more preferable. Of these, light rare earth elements are more preferable, and Sm is most preferable among them. Here, the light rare earth element is an element having a smaller atomic weight than Gd among lanthanoids, that is, La to Eu. The Fe—N-based compound is included in the iron nitride magnet. R—Fe—N-based compounds are included in rare earth magnets.

The specific composition of the magnetic powder 1 (magnetic powder 11, magnetic powder 12) is not limited as long as it is an Fe—N compound or an R—Fe—N compound. The magnetic powder 1 (magnetic powder 11, magnetic powder 12) is most preferably a powder of Sm ₂ Fe ₁₇ N ₃ or Fe ₁₆ N ₂ .
The production method of the magnetic powder 1 (magnetic powder 11 and magnetic powder 12) is not limited, but is preferably produced by liquid phase synthesis.

  The particle diameter (average particle diameter) of the magnetic powder 1 (magnetic powder 11, magnetic powder 12) is not limited. The average particle diameter (D50) is preferably about 2 to 5 μm. In addition, as the magnetic powder 1, a powder in which an oxide film is not formed on the entire particle surface is used.

(Step S2: Preparation of lubricant)
As shown in step S2 of FIG. 1, the lubricant 2 is prepared. As the lubricant 2, a solid substance (solid lubricant) is used under normal conditions (atmosphere and room temperature). As the lubricant 2, a powdery lubricant is used.

  As the lubricant 2, a metal soap-based lubricant (solid lubricant powder) is used. As the lubricant 2, for example, a powder of stearic acid metal such as zinc stearate is used. The average particle diameter (D50) of the powder of the lubricant 2 is about 10 μm. Here, the average particle diameter of the lubricant 2 is preferably larger than the average particle diameter of the magnetic powder 1. The specific gravity of the lubricant 2 is smaller than the specific gravity of the magnetic powder 1. Therefore, the mass per one particle of the lubricant 2 can be increased by increasing the size of the initial state of the lubricant 2 to some extent, and the lubricant 2 dances when mixing in the step S3 described later. Scattering can be suppressed.

  The mixing ratio of the magnetic powder 1 and the lubricant 2 can be arbitrarily set. The mixing ratio of the magnetic powder 1 and the lubricant 2 is preferably a volume ratio of magnetic powder 1:80 to 90% by volume and lubricant 2: 5 to 15% by volume. In addition to the magnetic powder 1 and the lubricant 2, an additive may be added. As an additive, additives, such as an organic solvent which lose | disappears by subsequent heating, can be mentioned.

(Step S3: Production of mixed powder)
As shown in step S3 of FIG. 1, the magnetic powder 1 and the lubricant 2 prepared in the previous two steps are mixed to obtain a mixed powder.
The magnetic powder 1 and the lubricant 2 are mixed by mixing the powders 1 and 2 while grinding them. As shown in FIG. 5, the mixed powder is formed by mixing the magnetic powder 1 and the lubricant 2 while grinding them in the mixing container 4. By mixing while grinding, as shown in FIG. 6, the lubricant 2 having a low bond strength is subdivided, and the particle size of the lubricant 2 is reduced as a whole. At the end of this step, there are lubricants 2 having different particle sizes.

  Furthermore, the mixed powders 1 and 2 can reduce the lump part only by the magnetic powder 1 (crush the secondary particle of the magnetic powder 1), and can make the size of the lubricant 2 small. That is, the finely divided lubricant 2 can be present at a position close to each particle of the magnetic powder 1.

(Step S4: Formation of adsorption film)
Subsequently, as shown in step S <b> 4 of FIG. 1, the mixed powders 1 and 2 are heated to form the adsorption film 3 on the surface of the magnetic powder 1.
Previous step magnetic powder 1 and powder mixture 1,2 lubricant 2 was mixed with (step S3), and then heated at a heating temperature T _1, to form an adsorption film 3 of the lubricant 2 to the surface of the magnetic powder 1. The heating temperature T ₁ of the mixed powders 1 and 2 at this time is lower than the decomposition temperature T ₂ of the magnetic powder _{1 and} is equal to or higher than the melting point T ₃ of the lubricant 2 (T ₃ ≦ T ₁ <T ₂ ).

The mixed powder 1, when heated at a heating temperature T _1, without the magnetic powder 1 is decomposed, lubricant 2 is melted. The molten lubricant 2 flows along the surface of the particles of the magnetic powder 1. The surface layer of the magnetic powder 1 is called a physical adsorption film 3 in which the chemical adsorption film 3 in which the soap component of the lubricant 2 is chemically bonded and the lubricant 2 that melts the surface of the magnetic powder 1 is physically covered. A film is formed (generated). Thereafter, the physical adsorption film 3 is solidified by cooling at a temperature lower than the melting point T ₃ .

The heating time t at the heating temperature T ₁ is not limited because it depends on the amount of heat applied to the mixed powders 1 and 2. In other words, the heating temperature T ₁ is if a high temperature, the amount of heat per time given to the mixed powder 1 is increased, can be shortened heating time t. Further, when the heating temperature T ₁ is a relatively low temperature, it is preferable to lengthen the heating time t.

For the heating temperature T ₁ of the heating time t, the larger the amount of heat applied to the mixed powder 1, can generate adsorption film 3 aggregated on the surface of the magnetic powder 1, resulting a coating breakage in pressing step (step S6) Disappear. And the high-density molded object 6 and the magnet 8 can be manufactured.

(Step S5: Mixing of binder)
Subsequently, as shown in step S <b> 5 of FIG. 1, an uncured binder 5 is disposed on the surface of the magnetic powder 1 on which the adsorption film 3 is formed.
As the binder 5, an uncured binder made of a silicone composition is used. This binder 5 is gel-like or liquid at room temperature and has fluidity. By mixing the binder 5 with the magnetic powder 1, the binder 5 is arranged on the surface of the magnetic powder 1 (particles thereof). In this state, as shown in the schematic diagram of the cross section in FIG. 7, the binder 5 is interposed between the particles of the adjacent magnetic powder 1.

  As the silicone composition of the binder 5, a composition having a main skeleton with siloxane bonds is used. For example, a silicone resin is used as the silicone composition. When the silicone composition is disposed on the surface of the magnetic powder 1, it is uncured (gel-like to liquid), and is cured in a subsequent process (in this embodiment, a heat-curing process in step S <b> 7).

  The method for curing the binder 5 is not limited. For example, methods such as heating, irradiation with ultraviolet light, and contact with a reaction initiator such as water to start curing can be mentioned. In this embodiment, a thermosetting silicone composition that is cured by heating is used.

In the thermosetting silicone composition, the curing temperature (curing start temperature) T ₄ is lower than the decomposition temperature T ₂ of the magnetic powder 1. The curing temperature (curing start temperature) T ₄ is more preferably a temperature lower than the melting point T ₃ of the lubricant 2 (T ₄ <T ₃ <T ₂ ). By setting the curing temperature (curing start temperature) T ₄ within these ranges, it is possible to prevent the magnetic powder 1 from being exposed to a temperature higher than T ₄ and causing the decomposition of the magnetic powder 1 and the loss of the adsorption film 3.

  The mixing ratio of the binder 5 can be arbitrarily set. For example, when the volume of the magnetic powder 1 (the state where the adsorption film 3 is formed) is 100 vol%, it can be 5 to 15 vol%, and more preferably 8 to 12 vol%.

(Step S6: Pressure molding)
Subsequently, as shown in step S6 of FIG. 1, the magnetic powder 1 is pressurized to form the formed body 6 (FIGS. 8 to 9). In the magnetic powder 1 pressed in this step, the binder 5 is interposed between the particles.
In the pressurizing step, as shown in the schematic diagram of FIG. 8, the magnetic powder 1 is placed (injected) into the cavity of the pressurizing die 7 (pressurizing lower die 71 (mold)). The pressure die 7 is made of nonmagnetic steel. The pressurization with the pressurizing die 7 was performed under the condition that the magnetic lines of force penetrate the magnetic powder 1 (under the condition of magnetic field orientation).

  Subsequently, as shown in the schematic diagram of FIG. 9, the magnetic powder 1 is applied by the pressurizing die 7 (71, 72) by assembling the pressurizing upper die 72 (mold) to the pressurizing lower die 71 and moving it in the approaching direction. Is pressed (press-molded). At this time, the pressure applied by the pressurizing die 7 (71, 72) is a pressure equal to or higher than the breaking pressure at which the magnetic powder 1 breaks. In this embodiment, it is 1 to 3 GPa.

  In this embodiment, the pressurization with the pressurizing die 7 destroys the particles of the magnetic powder 12 which are flat particles in the magnetic powder 1. This is because when one particle of magnetic powder (magnetic anisotropic magnetic powder 11 and magnetic isotropic magnetic powder 12) constituting magnetic powder 1 transmits a load (pressing force) to another adjacent particle, spherical particles Is compared with flat particles, flat particles generate stress concentration and are preferentially broken by a load higher than the breaking pressure. The particles of the magnetic powder 12 form fine crushed grains. When the fine crushed particles of the magnetic powder 12 are further pressurized, they are displaced and rearranged.

  As described above, in this embodiment, the flat magnetic powder 12 in the magnetic powder 1 is destroyed and rearranged by being pressurized at a pressure equal to or higher than the breaking pressure at which the magnetic powder 1 breaks during pressure molding. A compact 6 is formed.

Pressurization by the pressurization mold 7 (71, 72) is performed a plurality of times (two times or more). After applying the pressing force to the pressurizing upper mold 72, the pressing force applied to the pressing upper mold 72 is loosened, and the pressing force is applied to the pressing upper mold 72 again. Then, this operation is repeated. When loosening the pressure applied to the pressure upper mold 72, the pressure upper mold 72 may be moved upward, or only the pressure is reduced without moving the pressure upper mold 72 upward. You may make it let it.
The number of pressurizations by the pressurizing die 7 (71, 72) can be set to the number of times that the effect of improving the density of the molded body 6 is saturated. For example, it can be performed 2 to 30 times.

Furthermore, when the adsorption film 3 is not a layer but a film, in the pressurizing step, the pressurizing mold 7 (71, 72) is heated from the outer surface by a heater (not shown) or the like, for example. The magnetic powder 1 in 7 (71, 72) is heated. Heating temperature T ₅ of the magnetic powder 1 at this time, the temperature (melting point T ₃ or more temperatures) for liquefied melted adsorbed film 3, which is below the curing temperature T ₄ of the binder 5. The heating temperature _{T 5} is also less than the decomposition temperature _{T 2} of the magnetic powder _{1 (T 3 <T 5 <} T 4 <T 2). Therefore, the magnetic powder 1 is not decomposed even when heated, and the binder 5 is not cured.

  When the pressurization with the pressurizing die 7 is repeated, the compact 6 in which the gap between the particles of the magnetic powder 1 is reduced is formed, as schematically shown in FIGS. FIG. 10 is a diagram schematically showing the magnetic powder 1 in a state where it is put into the pressing die 7, and FIG. 11 is a diagram schematically showing the configuration of the magnetic powder 1 in the molded body 6. As shown in the schematic diagrams in FIGS. 10 to 11, the compact 6 is pressed a plurality of times, so that the particles of the magnetic powder 1 are rearranged with respect to the arrangement state of the particles of the magnetic powder 1 at the time of the previous pressurization. Because.

  In the rearrangement of the particles of the magnetic powder 1, the particles of the magnetic powder 1 are very smooth because the adsorption film 3 of the lubricant 2 is interposed on the contact surface (sliding contact surface) between adjacent particles of the magnetic powder 1. Move to. Due to the synergistic action of the rearrangement of the particles of the magnetic powder 1 and the slippage by the adsorption film 3, the gap between the particles of the magnetic powder 1 in the compact 6 is reduced.

  Further, the binder 5 is interposed between the particles of the magnetic powder 1 in an uncured state. The binder 5 in an uncured state exhibits the characteristics of silicone oil and also exhibits lubricity. That is, the movement (rearrangement) of the particles of the magnetic powder 1 is promoted by interposing the adsorption film 3 and the uncured binder 5 between the adjacent particles of the magnetic powder 1. This action also reduces the gap between the particles of the magnetic powder 1 in the molded body 6. That is, the compact 6 having a small gap between the particles of the magnetic powder 1 is obtained.

(Step S7: Heat curing)
Subsequently, as shown in step S <b> 7 of FIG. 1, the molded body 6 is heated to cure the binder 5.
Heating temperature T ₆ of the shaped body 6 is curing temperature of the thermosetting silicone composition (curing initiation temperature) T ₄ or more and less than the decomposition temperature T ₂ of the magnetic powder 1. The heating temperature T ₆ is preferably a temperature equal to or higher than the melting point T ₃ of the lubricant 2 (T ₄ ≦ T ₃ <T ₆ <T ₂ ).

Heating of the step is performed by heating the molded body 6 at a heating temperature T _6. For example, it is possible to perform the molded body 6 is molded by the pressurizing die 7 of the preceding pressing process (step S6), and without removing the pressure type 7, the temperature of the pressurizing die 7 as a heating temperature T _6.

Alternatively, the molded body 6 can be taken out from the pressure mold 7 and placed in a microwave heating furnace, electric furnace, plasma heating furnace, induction hardening furnace, heating furnace using an infrared heater, or the like.
Heating at a heating temperature T ₆ is binder 5 is a time to complete curing.
By performing the above steps, the magnet 8 of this embodiment can be manufactured.

(magnet)
As shown in the schematic diagram of FIG. 12, the magnet 8 of this embodiment manufactured by the above manufacturing method binds the particles of the magnetic powder 1 (magnetic powder 11 and magnetic powder 12) to each other. To wear. The particles of the magnetic powder 1 are not directly joined to other particles.

  The binder 50 is interposed only in the vicinity of the contact portion of the particles of the magnetic powder 1. That is, a part of the surface of the particles of the magnetic powder 1 is exposed. Moreover, fine voids may remain between the particles. In this case, the magnetic powder 1 has an adsorption film 3 formed on the surface thereof, and the magnetic material is prevented from being exposed. That is, a decrease in magnetic properties of the magnetic powder 1 such as oxidation due to the atmosphere is suppressed.

(Effect of this embodiment)
(First effect)
In the manufacturing method of the present embodiment, the magnetic powder 1 is composed of a mixed powder of a spherical magnetic anisotropic magnetic powder 11 and a flat magnetic isotropic magnetic powder 12. According to this configuration, the rearrangement of the particles of the magnetic powder 1 is promoted when performing pressure molding. And the compact molded object 6 with few space | gap can be shape | molded. As a result, according to the manufacturing method of the present embodiment, the magnet 8 having a high residual magnetic flux density can be manufactured.

(Second effect)
In the manufacturing method of this form, the average particle diameter (D50) of the magnetic powder 1 is 2-5 micrometers. According to this structure, the movement (rearrangement of the particles) of the particles of the magnetic powder 1 is promoted, and a dense molded body 6 with a reduced gap is obtained. A dense magnet 8 with a reduced clearance is obtained from the dense molded body 6.

(Third effect)
In the manufacturing method of this form, when the mass of the magnetic powder 1 is 100%, the proportion of the flat magnetic powder 12 is 5 to 25%. According to this configuration, movement of the flat magnetic powder 12 (rearrangement of particles) occurs in the gap between the particles of the magnetic powder 1, and a dense molded body 6 with a reduced gap is obtained.

(Fourth effect)
In the manufacturing method of this embodiment, the pressure molding is performed a plurality of times with a pressure equal to or higher than the breaking pressure at which the flat magnetic powder 12 breaks. According to this structure, when the magnetic powder 1 is pressure-molded to form the compact 6, the flat magnetic powder 12 is broken into fine particles. The fine particles move in the gaps between the spherical particles of the magnetic powder 11 (particle rearrangement occurs), and a dense molded body 6 with a reduced gap is obtained.

  Further, the destruction of the particles of the magnetic powder 12 is performed in the vicinity of the particles of the magnetic powder 11. In this configuration, even if crushed particles of the magnetic powder 12 are generated, they are immediately rearranged around the particles of the magnetic powder 1. That is, before the crushed particles of the magnetic powder 12 are agglomerated, the particles of the magnetic powder 1 are rearranged to obtain a dense formed body 6 with a reduced gap.

  Further, when the molded body 6 is formed by pressure molding, there may be a difference in density between the vicinity of the surface of the molded body 6 and the inside. Specifically, in the vicinity of the pressurizing die 71 (pressing jig), a pressurizing force is applied to promote the rearrangement of the particles, resulting in a dense compact. However, the pressing force is hardly transmitted to the central portion of the molded body 6 due to the rearrangement of particles near the surface. For this reason, the particles were not sufficiently rearranged in the center, and voids were likely to remain. In this embodiment, since the pulverized grains of the magnetic powder 12 are also present in the gap in the center, the particles are rearranged in the entire compact 6. As a result, the effect that the compact 6 becomes dense throughout the region is also exhibited.

(Fifth effect)
According to the manufacturing method of the present embodiment, a compound comprising at least one of an Fe—N compound and an R—Fe—N compound (R: rare earth element) is used as the magnetic powder 1 of the hard magnetic material. According to this structure, a magnet can be manufactured at low cost. In addition, in the manufacturing method of this embodiment, it is possible to prevent R from using dysprosium (Dy). That is, a magnet can be manufactured at low cost.

(Sixth effect)
In the manufacturing method of this embodiment, the magnetic powder 1 contains the lubricant 2. According to this structure, the movement (particle rearrangement) of the particles of the magnetic powder 1 is promoted, and a dense molded body 6 with a reduced gap is obtained. A dense magnet 8 with a reduced clearance is obtained from the dense molded body 6.

(Seventh effect)
The magnet 8 of this embodiment is manufactured by the above manufacturing method. According to this structure, it becomes a magnet provided with the above-mentioned 1st-6th effect.
The magnet 8 of this embodiment includes particles of the magnetic powder 1 and a cured binder 50 that binds the particles. According to this configuration, the binding material 50 binds the particles of the magnetic powder 1, and does not form the shape of the magnet 8. For this reason, the content rate of the hardened | cured binder 50 (uncured binder 5) can be reduced. As a result, the magnet 8 can reduce the volume occupied by the binder 50 that does not exhibit magnetic performance, and becomes a magnet excellent in residual magnetic flux density.

[Embodiment 2]
The manufacturing method of the magnet of the present invention will be specifically described as an embodiment with reference to FIG. FIG. 13 is a view showing each step of the magnet manufacturing method of the present embodiment. Configurations not particularly mentioned in the present embodiment are the same as those in the first embodiment.

(Step S1: Preparation of magnetic powder)
As shown in step S1 of FIG. 13, magnetic powder 1 is prepared as a magnet material. This step is the same as step S1 in the first embodiment.

  That is, the magnetic powder 1 includes a spherical magnetic anisotropic magnetic powder 11 having a major axis / minor axis ratio of less than 2, and a flat magnetic isotropic magnetic powder 12 having a major axis / minor axis ratio of 2 or more. It consists of mixed powder obtained by mixing.

  The magnetic anisotropic magnetic powder 11 is composed of spherical particles having a major axis / minor axis ratio of less than 2. The magnetic powder 11 is made of a magnetic anisotropic magnet. The magnet with magnetic anisotropy is a magnet having excellent magnetic properties, and the magnetic properties of the magnet to be manufactured are enhanced by using the magnetic powder 11.

The magnetically isotropic magnetic powder 12 is made of flat particles having a major axis / minor axis ratio of 2 or more. Since the magnetic powder 12 is made of flat particles, the magnetically isotropic magnetic powder 12 is rearranged around the magnetic anisotropy magnetic powder 11 when pressure-molded, and the gap of the magnetic powder 1 is reduced and manufactured. The magnetic properties of the magnet to be increased.
Other configurations (material and average particle size) of the magnetic anisotropic magnetic powder 11 and the magnetically isotropic magnetic powder 12 are the same as those in the first embodiment.

(Step S2: Preparation of lubricant)
As shown in step S2 of FIG. 13, the lubricant 2 is prepared. This step is a step of preparing a metal soap-based lubricant 2 (solid lubricant powder) as in step S2 of the first embodiment.

(Step S3: Production of mixed powder)
As shown in step S3 of FIG. 13, the magnetic powder 1 prepared in the previous two steps and the lubricant 2 are mixed to obtain a mixed powder. This step is a step performed by mixing both powders 1 and 2 while grinding, as in step S2 of the first embodiment.

(Step S4: Formation of adsorption film)
As shown in step S <b> 4 of FIG. 13, the mixed powders 1 and 2 are heated to form the adsorption film 3 on the surface of the magnetic powder 1. This step is a step of forming the adsorption film 3 of the lubricant 2 on the surface of the magnetic powder 1 by heating at the heating temperature T ₁ as in Step S 4 of the first embodiment.

(Step S5: Pressure molding)
As shown in step S <b> 5 of FIG. 13, the magnetic powder 1 is pressed to form the formed body 6. This step is a step of forming the magnetic powder 1 with a pressing force equal to or higher than the breaking pressure using the pressurizing die 7 as in step S6 of the first embodiment.
Specifically, the magnetic powder 1 is disposed (injected) in the cavity of the pressurizing die 7 (71, 72), and is pressurized with a pressure (1 to 3 GPa) that is equal to or higher than the breakdown pressure at which the magnetic powder 1 breaks.

  By pressurization with the pressurizing die 7, the particles of the magnetic powder 12, which are flat particles, of the magnetic powder 1 are destroyed. This is because when one particle of magnetic powder (magnetic anisotropic magnetic powder 11 and magnetic isotropic magnetic powder 12) constituting magnetic powder 1 transmits a load (pressing force) to another adjacent particle, spherical particles Is compared with flat particles, flat particles generate stress concentration and are preferentially broken by a load higher than the breaking pressure. The particles of the magnetic powder 12 form fine crushed grains. When the fine crushed particles of the magnetic powder 12 are further pressurized, they are displaced and rearranged.

  Thus, also in this embodiment, the flat magnetic powder 12 of the magnetic powder 1 is destroyed and rearranged by being pressurized at a pressure equal to or higher than the breaking pressure at which the magnetic powder 1 breaks during pressure molding. A compact 6 is formed.

(Step S6: Heat treatment step)
As shown in step S6 of FIG. 13, the molded body 6 is heated in an oxidizing atmosphere to form a secondary molded body (heat treatment step).
By heat-treating (heating) the molded body 6 in an oxidizing atmosphere, the exposed surfaces of the particles of the magnetic powder 1 react with oxygen, and an oxide film is generated on the surface of the magnetic powder 1. The surfaces of the particles of the magnetic powder 1 adjacent to the oxide film are joined together. That is, the oxide film is formed in a portion of the magnetic powder 1 exposed in the gap, and the portion of the magnetic powder 1 that is not exposed in the gap (interface where the particles are pressed) becomes the base material itself. Therefore, no oxide film is formed on the entire surface of the magnetic powder 1.

The secondary molded body formed in this way can sufficiently ensure strength. Thereby, the bending strength of a secondary molded object can be made high. Furthermore, the residual magnetic flux density by the secondary molded object after a heat treatment process can be made high because the area | region where the magnetic powder 1 does not exist in the molded object 6 decreases in a pressurization process. In addition, the density of a secondary molded object is about 5-6 g / cm < ³ >.

  The heat treatment step is performed by placing the primary compact in a microwave heating furnace, an electric furnace, a plasma heating furnace, an induction hardening furnace, an infrared heater, or the like. The heating in the heat treatment step is not limited, but can be performed, for example, through a temperature change shown in FIG.

As shown in FIG. 14, the heating temperature T ₆ is set to be lower than the decomposition temperature T ₂ of the magnetic powder 1. For example, when Sm ₂ Fe ₁₇ N ₃ or Fe ₁₆ N ₂ is used as the magnetic powder 1, the heating temperature T ₆ is set to less than 500 ° C. because the decomposition temperature T ₂ is about 500 ° C. For example, the heat treatment temperature _{T 6} in this step is about 200 to 300 [° C..

Further, the oxygen concentration and the atmospheric pressure of the oxidizing atmosphere are sufficient if the magnetic powder 1 can be oxidized, and it is sufficient if it is about the oxygen concentration in the atmosphere and about the atmospheric pressure. Therefore, it is not necessary to specially manage the oxygen concentration or the atmospheric pressure. Therefore, it is good to heat in an air atmosphere. Then, by the heating temperature _{T 6} to about 200 to 300 [° _C., in each case a magnetic powder of Sm _{2 Fe} 17 _{N 3} or _Fe 16 _{N 2,} it is possible to form an oxide film.

(Step S7: Coating process)
As shown in step S7 of FIG. 13, the surface of the secondary molded body formed in the heat treatment step is treated with a coating film to obtain the magnet 8 of the present embodiment.
The coating film is a plating film formed by electroplating such as Cr, Zn, Ni, Ag, or Cu, a plating film formed by electroless plating, a resin film formed by resin coating, or a glass formed by glass coating. Examples of the coating include Ti, diamond-like carbon (DLC), and the like. Examples of electroless plating include electroless plating using Ni, Au, Ag, Cu, Sn, Co, alloys or mixtures thereof. Examples of the resin coating include coating with silicone resin, fluorine resin, urethane resin, and the like.

  That is, the coating film functions like an egg shell. Therefore, the magnet 8 can increase the bending strength when the oxide film and the coating film exert a bonding force. In particular, by applying electroless plating, the surface hardness and adhesion can be increased, and the bonding force of the magnetic powder 1 can be further strengthened. In addition, for example, electroless nickel phosphorus plating has good corrosion resistance.

  Furthermore, as described above, the oxide film joins the particles of the magnetic powder 1 not only on the surface of the secondary molded body but also inside. Therefore, inside the magnet 8, the particles of the magnetic powder 1 are restricted from freely operating by the bonding force of the oxide film. Therefore, it can suppress that a magnetic pole reverses when the magnetic powder 1 rotates. That is, a high residual magnetic flux density can be obtained.

  Here, when applying electroplating in a coating process, since the secondary compact before plating acts as an electrode, it is necessary to increase the joint strength of the secondary compact. However, in the coating process, when electroless plating, resin coating, or glass coating is applied, it is not necessary to increase the bonding strength of the secondary molded body as compared with electroplating. That is, the bonding force by the oxide film is sufficient. Therefore, a coating film can be reliably formed on the surface of the secondary molded body by the coating process as described above.

  Moreover, when performing electroless plating in a coating process, a secondary compact is impregnated with a plating solution. At this time, the plating solution tends to enter the inside of the secondary molded body, but since the oxide film is formed, the oxide film exhibits an effect of suppressing the ingress of the plating solution. That is, it can be expected to suppress the occurrence of corrosion or the like due to the plating solution entering the inside.

(Effect of this embodiment)
Also in this embodiment, as in the case of the first embodiment, the magnetic powder 12 is rearranged around the magnetic powder 11, so that a dense molded body 6 with a reduced gap can be obtained. A dense magnet 8 is obtained from the dense molded body 6.

  That is, the magnet 8 manufactured by the manufacturing method that does not use the binder 5 as in the present embodiment exhibits the effect of obtaining the dense magnet 8 as in the first embodiment. That is, in the manufacturing method in which the magnetic powder 1 is pressed to form the compact 6, the use of the mixed powder composed of the spherical magnetic powder 11 and the flat magnetic powder 12 enables the dense compact 6 and the magnet 8 to be obtained. Can be confirmed.

  1: Magnetic powder, 2: Lubricant, 3: Adsorption film, 4: Container for mixing, 5: Binder, 6: Molded body, 7: Pressurization type, 8: Magnet

The mixed powder 1, when heated at a heating temperature T _1, without the magnetic powder 1 is decomposed, lubricant 2 is melted. The molten lubricant 2 flows along the surface of the particles of the magnetic powder 1. The surface layer of the magnetic powder 1 forms a layer called a chemical adsorption film 3 in which the soap component of the lubricant 2 is chemically bonded . Further, the surface layer of the magnetic powder 1 forms (generates) a film called a physical adsorption film 3 in which the lubricant 2 that melts the surface of the magnetic powder 1 is physically covered. Thereafter, the physical adsorption film 3 is solidified by cooling at a temperature lower than the melting point T ₃ .

Claims (7)

A method for producing a magnet having a step of pressing a magnetic powder to obtain a molded body,
The magnetic powder is composed of a mixed powder of a spherical magnetic anisotropic magnetic powder having a major axis / minor axis ratio of less than 2 and a flat magnetic isotropic magnetic powder having a major axis / minor axis ratio of 2 or more. A method for producing a magnet.   The method for producing a magnet according to claim 1, wherein an average particle diameter (D50) of the flat magnetic particles and the spherical magnetic particles is 2 to 5 μm.   The method for manufacturing a magnet according to any one of claims 1 to 2, wherein a ratio of the flat magnetic powder is 5 to 25% when a mass of the magnetic powder is 100%.   The said press molding is a manufacturing method of the magnet of any one of Claims 1-3 which pressurize several times with the pressure more than the destructive pressure which the said flat magnetic powder destroys.   The magnet according to any one of claims 1 to 4, wherein the magnetic powder is made of a hard magnetic material selected from one or more of an Fe-N compound and an R-Fe-N compound (R: rare earth element). Method.   The said magnetic powder is a manufacturing method of the magnet of any one of Claims 1-5 containing a lubricant.   The magnet manufactured by the manufacturing method of the magnet of any one of Claims 1-6.