JP6330907B2 - Method for producing rare earth magnet compact - Google Patents

Description

  The present invention relates to a method for manufacturing a magnet molded body, and more particularly to a method for manufacturing a rare earth magnet molded body with high productivity and improved magnetic force.

  Rare earth magnets composed of rare earth elements and transition metals are promising for various applications as permanent magnets because of their large magnetocrystalline anisotropy and saturation magnetization. Among them, rare earth-transition metal-nitrogen based magnets represented by Sm—Fe—N based magnets are known to exhibit excellent magnetic properties without using expensive raw materials.

  Moreover, there are mainly two types of rare earth magnets that are currently used: sintered magnets and bonded magnets. Sintered magnets are sintered at a high temperature to be formed as represented by Nd—Fe—B magnets. In the case of a sintered magnet, the magnetic raw material powder has poor magnetic properties, and excellent magnetic properties are exhibited by heating to a high temperature at which a liquid phase is generated. On the other hand, bond magnets are used by solidifying and molding magnet raw material powder having excellent magnetic properties with a resin at room temperature.

  While Sm—Fe—N magnets are promising as permanent magnets, they have a drawback of lacking thermal stability. When a Sm—Fe—N magnet is heated to 600 ° C. or higher, it is decomposed into a rare earth nitride and α-Fe, so that a magnet compact cannot be produced by a sintering method as in the conventional powder metallurgy method. For this reason, it has been used as a magnet powder for bonded magnets. In this case, since the volume of the resin as a binder occupies about 30% of the whole, a sufficient magnetic force cannot be obtained.

  Therefore, in the production of an Sm—Fe—N-based magnet molded body, there is a demand for a solidified molding method that can provide a magnet molded body that contains as little substance as possible other than magnet powder. As such a solidification molding method, a powder impact molding method using explosives described in JP-A-6-77027 has been studied so far.

  However, the method described in the above prior art has problems in quality stability (magnetic characteristic variation), productivity (mass production cycle time), and processing yield (whether near net shape molding is possible). The powder impact molding method using an explosive can obtain an Sm-Fe-N bulk magnet having a relative density exceeding 90%. However, since it is a method using an explosive, there is a limitation as a mass production method. Further, since the impact force is too great, the Sm—Fe—N magnet is decomposed into rare earth nitride and α-Fe, and the magnetic properties are deteriorated.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a method for producing a rare earth magnet suitable for mass production with improved quality stability, productivity and processing yield. To do. Furthermore, it aims at providing the manufacturing method of the rare earth magnet by which the fall of the magnetic characteristic was suppressed.

  The present inventors have intensively studied to solve the above problems. As a result, the method for producing a rare earth magnet compact of the present invention comprises compacting Sm—Fe—N magnet powder having a temperature of 600 ° C. or lower in a mold at a molding surface pressure of 1 to 5 GPa. It has a warm compacting step to obtain an Sm-Fe-N magnet molded body of 80% or more.

It is a flowchart for demonstrating the manufacturing method of 1st embodiment. It is a flowchart for demonstrating the manufacturing method of 2nd embodiment. It is a flowchart for demonstrating the manufacturing method of 3rd embodiment. It is a flowchart for demonstrating the manufacturing method of 4th embodiment. (A) is a schematic diagram which shows a preferable example of a shaping | molding die, (b) is sectional drawing of the shaping | molding die of (a).

  Hereinafter, embodiments of the present invention will be described in detail.

<First embodiment>
The manufacturing method of 1st embodiment has a preparatory process (S11), a warm compaction process (S12), and a heat treatment process (S13), as shown in FIG. The preparation step (S11) is a step of preparing Sm—Fe—N magnet powder, and is optional. In the warm compacting step (S12), Sm—Fe—N magnet powder having a temperature of 600 ° C. or lower is compacted at a molding surface pressure of 1 to 5 GPa in a mold, and Sm having a relative density of 80% or more. A -Fe-N magnet molded body is obtained. In the heat treatment step (S13), the molded body obtained in the warm compaction step (S12) is heated at a temperature of 350 to 600 ° C. for 1 to 120 minutes. However, the preparation step (S11) and the heat treatment step (S13) are optional steps. In this way, a magnet molded body as a product is obtained.

(Preparation process (S11))
The rare earth magnet compact of the present embodiment is molded using Sm—Fe—N based magnet powder. The Sm—Fe—N-based magnet powder contains a magnet phase mainly composed of Sm—Fe—N. As described above, the Sm—Fe—N magnet powder is promising as a permanent magnet because of its excellent magnetic properties. A commercially available product may be used for the Sm—Fe—N magnet powder as a raw material, or it may be prepared by itself. Further, it is also preferable to use a metal binder blended with the Sm—Fe—N magnet powder. When using a commercial product of Sm-Fe-N magnet powder, a preparation step is not particularly required. However, when preparing an Sm—Fe—N magnet powder as a raw material by itself and using a blend powder with a metal binder, a preparation step of preparing a raw material powder for a magnet compact is performed. The blended powder may also be referred to as Sm—Fe—N magnet powder.

(Step of obtaining Sm—Fe—N magnet powder by fine grinding)
When preparing Sm-Fe-N magnet powder, Sm-Fe-N magnet powder can be pulverized to obtain Sm-Fe-N magnet powder. The size (average particle diameter) of the Sm—Fe—N-based magnet powder may be within a range in which the effects of the present embodiment can be effectively expressed. However, the smaller the value, the higher the coercive force, so that it is 10 μm or less. It is preferable to finely pulverize. More preferably, it is 0.1-8 micrometers, More preferably, it is the range of 0.5-6 micrometers. When the average particle diameter of the rare earth magnet powder is 10 μm or less, a magnet molded body having excellent coercive force can be obtained. In addition, also when using a commercial item as a Sm-Fe-N type magnet powder, the average particle diameter of powder is 10 micrometers or less, More preferably, it is 0.1-8 micrometers, More preferably, it is 0.5-6 micrometers.

  Here, the average particle diameter of the magnet powder can be subjected to particle size analysis (measurement) by, for example, SEM (scanning electron microscope) observation or TEM (transmission electron microscope) observation. In some cases, the magnet powder or its cross-section may include a powder having an irregular shape with a different aspect ratio (aspect ratio) rather than a spherical or circular shape (cross-sectional shape). Therefore, the average particle diameter mentioned above is expressed by the average value of the absolute maximum length of the cut surface shape of each magnet powder in the observation image because the shape of the magnet powder (or its cross-sectional shape) is not uniform. . The absolute maximum length means the maximum length among the distances between any two points on the contour line of the magnet powder (or its cross-sectional shape). In addition to this, for example, by obtaining the crystallite diameter obtained from the half-value width of the diffraction peak of the rare earth magnet phase in X-ray diffraction or the average value of the particle diameter of the magnet powder obtained from the transmission electron microscope image. You can also. In addition, it can obtain | require similarly about the measuring method of another average particle diameter.

A commercially available product may be used for the Sm-Fe-N magnet coarse powder, or it may be prepared by itself. The Sm-Fe-N magnet coarse powder is produced, for example, by producing a SmFe alloy powder from a samarium oxide or iron powder by a reduction diffusion method, and a mixed gas of N ₂ gas, NH ₃ gas, N ₂ gas and H ₂ gas. For example, SmFeN can be used by performing heat treatment at 600 ° C. or lower in an atmosphere such as the above. Moreover, you may use what nitrided the powder obtained by manufacturing a SmFe alloy by the melt | dissolution method and carrying out the coarse grinding | pulverization.

  There is no restriction | limiting in particular as a method of grind | pulverizing a Sm-Fe-N type magnet coarse powder until it becomes a desired average particle diameter, A well-known grinder can be used. Preferably, a dry jet mill or a wet bead mill can be used. Although it is technically difficult to finely pulverize the dry jet mill until the average particle size becomes 2 μm or less, it is advantageous in that the finely pulverized magnet powder hardly contains impurities. On the other hand, the wet bead mill is preferable because the magnetic powder can be finely pulverized to an average particle diameter of 2 μm or less, and the coercive force of the obtained molded body is increased. However, since the magnetic powder is pulverized in an organic solvent, there is a demerit that the amount of impurities in the magnetic powder obtained is larger than that of a dry jet mill.

  When the Sm—Fe—N magnet coarse powder is finely pulverized and prepared by itself, the steps after the preparatory step, that is, the preparatory step, the warm compaction step, and the heat treatment step may be performed in an inert atmosphere. preferable. Under an inert atmosphere means an atmosphere that does not substantially contain oxygen. Under an inert atmosphere, the performance of the magnet is related to the amount of impurities, so that it is possible to prevent the amount of impurities such as oxygen from increasing and magnetic properties from deteriorating. Furthermore, when heating the finely pulverized Sm—Fe—N magnet powder, it is possible to prevent the powder from combusting due to violent deterioration of magnetic properties due to oxidation.

  The inert atmosphere may be an inert gas atmosphere such as nitrogen or a rare gas. Under an inert atmosphere, the oxygen concentration is preferably 100 ppm by volume or less, more preferably 50 ppm by volume or less, and even more preferably 10 ppm by volume or less. In addition, when using a commercial item as Sm-Fe-N type | system | group magnetic powder, since the powder is surface-treated, it is not necessary to implement a subsequent process under inert atmosphere. When the Sm-Fe-N-based magnet coarse powder is finely pulverized to obtain the Sm-Fe-N-based magnet powder, a magnet compact with better magnetic properties can be obtained because the fine powder is not surface-treated.

  Hereinafter, the Sm—Fe—N magnet powder that can be used in the present embodiment will be described.

(Sm-Fe-N magnet powder)
More specifically, as a magnet powder containing Sm-Fe-N as a main component, for example, Sm ₂ Fe ₁₇ N _x (where x is preferably 1 to 6, more preferably 1 as follows) 0.1 to 5, more preferably 1.2 to 3.8, more preferably 1.7 to 3.3, particularly preferably 2.0 to 3.0), Sm ₂ Fe ₁₇ N ₃ , (Sm _{0. 75} Zr _0.25 ) (Fe _0.7 Co _0.3 ) N _x (where x is preferably 1-6), SmFe ₁₁ TiN _x (where x is preferably 1-6) And (Sm ₈ Zr ₃ Fe ₈₄ ) ₈₅ N ₁₅ , Sm ₇ Fe ₉₃ N _x (wherein x is preferably 1 to 20), etc., but are not limited thereto. Absent. More preferably, a magnet powder containing Sm ₂ Fe ₁₇ N _x (x = 1.7 to 3.3) as a main component, and more preferably Sm ₂ Fe ₁₇ N _x (x = 3.0) is desirable. This is because the anisotropic magnetic field and saturation magnetization are large and the magnetic characteristics are excellent. These Sm-Fe-N magnet powders may be used alone or in combination of two or more.

  As content of the main component (Sm-Fe-N) of the magnet powder of this embodiment, what is necessary is just to have Sm-Fe-N as a main component, and Sm-Fe-N is with respect to the whole magnet powder. It is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 90 to 99% by mass. The upper limit of the range is more preferably 99% by mass and not 100% by mass because it contains surface oxides and inevitable impurities. That is, in this embodiment, it may be 50% by mass or more, and it is possible to use 100% by mass. However, in practice, it is difficult, complicated, and high to remove surface oxides and inevitable impurities. Expensive refining (smelting) technology is required and is expensive.

  Further, the rare earth magnet phase mainly composed of Sm—Fe—N includes those containing other elements within the technical scope of the present embodiment. Examples of other elements that may be contained include, for example, Ga, Nd, Zr, Ti, Cr, Co, Zn, Mn, V, Mo, W, Si, Re, Cu, Al, Ca, B, Ni, C, La, Ce, Pr, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Th, MM, preferably B, C substituting for Co, Ni, N replacing Fe However, it is not limited to these. These may contain one kind alone or two or more kinds. These elements are introduced by replacing or inserting part of the phase structure of the magnet phase mainly composed of Sm—Fe—N.

Similarly, the rare earth magnet powder containing Sm—Fe—N as a main component may contain a rare earth magnet phase other than Sm—Fe—N. Examples of such other rare earth magnet phases include other existing rare earth magnet phases other than Sm—Fe—N. Such other existing rare earth magnet phases include, for example, Sm ₂ Fe ₁₄ B, Sm ₂ Co ₁₄ B, Sm ₂ (Fe _1-x Co _x ) ₁₄ B (where x is preferably 0 ≦ x ≦ 0). Sm ₁₅ Fe ₇₇ B ₅ , Sm ₁₅ Co ₇₇ B ₅ , Sm _11.77 Fe _82.35 B _5.88 , Sm _11.77 Co _82.35 B _5.88 , Sm _1.1 Fe ₄ B ₄ , Sm _1.1 Co ₄ B ₄ , Sm ₇ Fe ₃ B ₁₀ , Sm ₇ Co ₃ B ₁₀ , (Sm _1-x Dy _x ) ₁₅ Fe ₇₇ B ₈ (where x is preferably 0 ≦ x ≦ 0.4), (Sm _1-x Dy _x ) ₁₅ Co ₇₇ B ₈ (where x is preferably 0 ≦ x ≦ 0.4), Sm ₂ Co ₁₇ N _x (Where x is preferably 1 to 6), Sm _{1 5} (Fe _1-x Co _x ) ₇₇ B ₇ Al ₁ , Sm ₁₅ (Fe _0.80 Co _0.20 ) _77-y B ₈ Al _y (where y is preferably 0 ≦ y ≦ 5) ), (Sm _0.95 Dy _0.05 ) ₁₅ Fe _77.5 B ₇ Al _0.5 , (Sm _0.95 Dy _0.05 ) ₁₅ (Fe _0.95 Co _0.05 ) _77.5 B _{6 .5} Al _0.5 Cu _0.2 , Sm ₄ Fe ₈₀ B ₂₀ , Sm _4.5 Fe ₇₃ Co ₃ GaB _18.5 , Sm _5.5 Fe ₆₆ Cr ₅ Co ₅ B _18.5 , Sm ₁₀ Fe ₇₄ Co ₁₀ SiB ₅ , Sm _3.5 Fe ₇₈ B _18.5 , Sm ₄ Fe _76.5 B _18.5 , Sm ₄ Fe _77.5 B _18.5 , Sm _4.5 Fe ₇₇ B _18.5 , Sm _3.5 DyFe ₇₃ Co ₃ GaB _{8.5, Sm 4.5 Fe 72 Cr 2} Co 3 B 18.5, Sm 4.5 Fe 73 V 3 SiB 18.5, Sm 4.5 Fe 71 Cr 3 Co 3 B 18.5, Sm 5. Sm—Co alloy system such as ₅ Fe ₆₆ Cr ₅ Co ₅ B _18.5 , SmCo ₅ , Sm ₂ Co ₁₇ , Sm ₃ Co, Sm ₃ Co ₉ , SmCo ₂ , SmCo ₃ , Sm ₂ Co ₇ , Sm ₂ Fe ₁₇ , SmFe ₂ , SmFe _{3 and} other Sm—Fe alloy systems, CeCo ₅ , Ce ₂ Co ₁₇ , Ce ₂₄ Co ₁₁ , CeCo ₂ , CeCo ₃ , Ce ₂ Co ₇ , Ce ₅ Co _{19 and} other Ce—Co alloy systems Nd—Fe alloy systems such as Nd ₂ Fe ₁₇ , Ca—Cu alloy systems such as CaCu ₅ , Tb—Cu alloy systems such as TbCu ₇ , Sm—Fe—Ti alloys such as SmFe ₁₁ Ti Type, Th-Mn alloy type such as ThMn ₁₂ , Th-Zn alloy type such as Th ₂ Zn ₁₇ , Th-Ni alloy type such as Th ₂ Ni ₁₇ , La ₂ Fe ₁₄ B, CeFe ₁₄ B, Pr ₂ Fe ₁₄ B, Gd ₂ Fe ₁₄ B, Tb ₂ Fe ₁₄ B, Dy ₂ Fe ₁₄ B, Ho ₂ Fe ₁₄ B, Er ₂ Fe ₁₄ B, Tm ₂ Fe ₁₄ B, Yb ₂ Fe ₁₄ B, Y ₂ Fe ₁₄ B, Th ₂ Fe ₁₄ B, La ₂ Co ₁₄ B, CeCo ₁₄ B, Pr ₂ Co ₁₄ B, Gd ₂ Co ₁₄ B, Tb ₂ Co ₁₄ B, Dy ₂ Co ₁₄ B, Ho ₂ Co ₁₄ B, Er ₂ Co ₁₄ B, Tm ₂ Co ₁₄ B, Yb ₂ Co ₁₄ B, Y ₂ Co ₁₄ B, Th ₂ Co ₁₄ B, YCo ₅ , LaCo ₅ , PrCo ₅ , NdCo ₅ , GdCo ₅ , T bCo ₅ , DyCo ₅ , HoCo ₅ , ErCo ₅ , TmCo ₅ , MMCo ₅ , MM _0.8 Sm _0.2 Co ₅ , Sm _0.6 Gd _0.4 Co ₅ , YFe ₁₁ Ti, NdFe ₁₁ Ti, GdFe ₁₁ Ti, TbFe ₁₁ Ti, DyFe ₁₁ Ti, HoFe ₁₁ Ti, ErFe ₁₁ Ti, TmFe ₁₁ Ti, LuFe ₁₁ Ti, Pr _0.6S m _0.4 Co, Sm _0.6 Gd _0.4 Co ₅ , Ce (Co _0.72 Fe _0.14 Cu _0.14 ) _5.2 , Ce (Co _0.73 Fe _0.12 Cu _0.14 Ti _0.01 ) _6.5 , (Sm _0.7 Ce _0.3 ) ( _{Co 0.72 Fe 0.16 Cu 0.12) 7} , Sm (Co 0.69 Fe 0.20 Cu 0.10 Zr 0.01) 7.4, Sm (Co 0.6 Fe _0.21, such as Cu _0.05 Zr _{0.02) 7.67,} and the like, but not in any way be construed as being limited thereto. These may be used alone or in combination of two or more. In addition, rare earth magnet powders are inevitable components such as rare earth oxide phase (SmO ₂ phase), Fe / rare earth impurities, Fe rich phase, Fe poor phase and other inevitable components present at the boundary of rare earth magnet phase. Impurities, etc. may be included.

  The shape of the magnet powder mainly composed of Sm—Fe—N of the present embodiment may be any shape. For example, a spherical shape, an elliptical shape (preferably a range in which the aspect ratio (aspect ratio) of the central section parallel to the major axis direction is more than 1.0 and 10 or less), a cylindrical shape, a polygonal column (for example, a triangular prism, four Prismatic, pentagonal, hexagonal, ..n prismatic (where m is an integer greater than or equal to 7) shape, needle or rod shape (aspect ratio of the central section parallel to the long axis direction) Is preferably in the range of more than 1.0 and 10 or less.), Plate shape, disk (disk) shape, flake shape, scale shape, indeterminate shape, etc., but are not limited thereto. . Note that the rare earth magnet phase of Sm—Fe—N has a crystal structure, and can be formed into a predetermined crystal shape by crystal growth.

(Metal binder)
The Sm—Fe—N magnet powder of this embodiment is preferably blended with a metal binder. By blending the metal binder, the moldability is improved by bonding of the metal binder components during warm compaction described later. Therefore, the obtained magnet molding is excellent in mechanical strength. Furthermore, since the internal stress which a metal binder generate | occur | produces at the time of shaping | molding can be relieved, a magnet molded object with few defects can be obtained. Furthermore, by using metal particles as a binder, a magnet molded body that can be used even in a high-temperature environment can be obtained. When the metal binder is blended, there is no particular limitation, and the Sm-Fe-N magnet powder and the metal binder powder may be mixed with a mixer or the like until they are uniform. In addition, since a metal binder should just use a considerable small amount compared with the polymer binder in a bond magnet, it does not have a possibility of affecting the magnetic characteristic and causing the fall.

  The metal binder is preferably contained in an amount of 30% by mass or less, more preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass with respect to the total mass of the Sm—Fe—N magnet powder. Can do. If the metal binder is 30% by mass or less, there is no fear of impairing the magnetic properties of the magnet molded body. Moreover, if it is 0.1 mass% or more, the effect as a binder will fully be exhibited.

  As the metal binder, nonmagnetic metal particles having an elastoplastic ratio of energy accompanying plastic deformation of the metal binder particles of 50% or less (hereinafter also abbreviated as nonmagnetic metal particles having an elastoplastic ratio of 50% or less) are preferable. This is because easily deformable particles having an elastoplastic ratio of 50% or less relieve stress in the magnet molded body and effectively function as a binder. If the metal binder is too soft, the adhesion strength will be too small. Therefore, it is preferable that the soft metal has an elastic-plastic ratio of about 2.5%. The elasto-plastic ratio is preferably 2.5 to 50%, more preferably 2.5 to 45%, and particularly preferably 2.5 to 40%. The elasto-plastic ratio of energy accompanying plastic deformation of the metal binder was defined as an index of ease of deformation using the nanoindentation method.

  In the nanoindentation method, a diamond trigonal pyramid indenter is pushed to the surface of the sample placed on the base of the experimental apparatus to a certain load (press-fit), and then the load (P) is removed until the indenter is removed (unload). ) And displacement (press-fit depth h) (press-fit (load) -unload curve). The indentation (load) curve reflects the elastic-plastic deformation behavior of the material, and the unloading curve is obtained by the elastic recovery behavior. The area surrounded by the load curve, the unload curve and the horizontal axis is the energy Ep consumed for plastic deformation. Further, the area surrounded by the perpendicular line extending from the maximum load point of the load curve to the horizontal axis (pressing depth h) and the unloading curve is the energy Ee absorbed by the elastic deformation. From the above, the elastic-plastic ratio of energy accompanying plastic deformation of particles = Ep / Ee × 100 (%). For example, the Zn particles used in the examples have an elastoplastic ratio of 50% or less.

  The non-magnetic metal particles having an elasto-plastic ratio of 50% or less that are easily deformed are metal elements other than Ni, Co, and Fe, and can be used as long as they are obtained as a powder. Specifically, at least one soft metal or alloy of Zn, Cu, Sn, Bi, In, and Al is preferably used. Of these, Zn is particularly preferable. However, the present embodiment is not limited to these.

  The shape of the metal binder may be any shape as long as it does not impair the effects of the present invention. For example, a spherical shape, an elliptical shape (preferably a range in which the aspect ratio (aspect ratio) of the central section parallel to the major axis direction is more than 1.0 and 10 or less), a cylindrical shape, a polygonal column (for example, a triangular prism, four Rectangular prism, pentagonal prism, hexagonal prism,... N prism (where N is an integer greater than or equal to 7)), needle-like or rod-like (the aspect ratio of the central section parallel to the long axis direction is 1. A range of 0 to 10 is desirable.), A plate shape, a disk (disk) shape, a flake shape, a scale shape, an indefinite shape, and the like, but are not limited thereto.

  The average particle diameter of the metal binder may be within a range in which the effects of the present embodiment can be effectively expressed, and is usually 0.01 to 10 μm, preferably 0.05 to 8 μm, more preferably 0.1 to 0.1 μm. The range is 7 μm. When the average particle diameter of the nonmagnetic metal particles is 0.01 to 10 μm, a desired magnet molded body excellent in magnet characteristics (coercive force, residual magnetic flux density, adhesion) can be obtained.

  In the present embodiment, it is preferable not to use a binder made of a polymer, particularly an organic polymer. This is because the organic polymer binder occupies a large proportion of about 30% of the bonded magnet molded body, but does not function as a magnet, so that the magnetic properties of the magnet molded body deteriorate. The present embodiment is excellent in that it can prevent a decrease in magnetic properties due to an organic polymer binder because a magnet compact can be obtained by warm compaction without including a polymer binder. Moreover, the magnet which can be used also in a higher temperature environment can be obtained by not using the polymer binder with a low melting point. Moreover, the magnet formation body of this embodiment does not need such resin with respect to a bond magnet, and can be reduced in weight. However, the present embodiment includes a case where the polymer binder is contained in a very small amount so that the magnetic properties are not deteriorated.

(Warm compaction forming step (S12))
In the warm compacting step (S12), Sm—Fe—N magnet powder having a temperature of 600 ° C. or lower is compacted at a molding surface pressure of 1 to 5 GPa in a mold, and Sm having a relative density of 80% or more. This is a step of obtaining a -Fe-N magnet molded body. In this embodiment, since the magnet molded body is manufactured by compacting the Sm—Fe—N-based magnet powder at a high surface pressure, the deterioration of the magnetic characteristics that occurs when sintering is not caused. Therefore, a magnet compact can be obtained while maintaining the excellent magnetic properties of the Sm—Fe—N magnet powder, and an Sm—Fe—N magnet compact with improved magnetic properties can be obtained.

  In the present embodiment, the Sm—Fe—N magnet powder is compacted in a state where it is heated to a temperature at which the magnetic properties of 600 ° C. or lower do not change significantly. Therefore, in order to obtain a molded body having a relative density of 80% or more, for example, it is possible to obtain a molded body with a reduced molding surface pressure as compared with the case of compacting at normal temperature (not heated). Therefore, this embodiment can dramatically extend the life of the mold (molding die), has higher productivity and is suitable for industrial production. Furthermore, the density of the obtained magnet molding can be improved compared with the case where it compacts by the same molding surface pressure at normal temperature. The temperature of the Sm-Fe-N magnet powder at the time of compaction molding can extend the mold life while obtaining a molded article having a desired relative density, and can further prevent deterioration of magnetic properties due to decomposition. From this viewpoint, the temperature is more preferably 50 to 500 ° C, and further preferably 100 to 450 ° C.

  In the present embodiment, a magnet molded body having a relative density of 80% is obtained. This is because if the relative density is 80% or more, a magnet molded body having a sufficient bending strength for applications such as automobile motors can be obtained. The relative density is affected by the composition of the magnet and the pressure during compaction molding. Preferably the relative density is 85% or more, more preferably 90% or more. The relative density is obtained by using the true density obtained by calculation and the actual density obtained by measuring the size and weight of the magnet compact. The relative density is the ratio (%) of the actual density to the true density, and is calculated by dividing the actual density value by the theoretical density value and multiplying by 100.

  Moreover, according to this embodiment, the shaping | molding die suitable for a use can be selected. Therefore, if a mold having a desired magnet shape is used, it can be used in the next process almost as it is, and so-called near net shape molding with a very small processing margin becomes possible. Therefore, the processing yield is good, the manufacturing process is simplified, and this embodiment is suitable for mass production from these points. Furthermore, what is obtained in this embodiment is an Sm-Fe-N-based magnet molded body produced only by compaction molding, with less variation in magnetic properties than the conventional manufacturing method, and thus excellent quality stability. Yes.

  There is no particular limitation on heating the Sm—Fe—N magnet powder to 600 ° C. or lower. The Sm—Fe—N-based magnet powder may be heated before being charged into the mold, or may be heated together with the mold after the magnet powder has been charged into the mold. In the present embodiment, the compacting may be performed in a state where the Sm—Fe—N magnet powder is heated to 600 ° C. or less. Preferably, the cartridge heater is inserted and installed in the mold, so that the magnet powder can be heated together with the mold after the Sm—Fe—N magnet powder is charged into the mold. As a method for measuring the temperature of the magnet powder, a temperature sensor is installed in the mold, and the following method can be implemented. That is, after the mold reaches a predetermined temperature, the mold temperature is maintained for about 10 minutes until the entire magnet powder reaches the same temperature, and the temperature of the mold is regarded as the temperature of the magnet powder. In addition, heating by high frequency or the like is also possible. When magnet powder is heated together with the mold, it is preferable that the powder is not cooled and the manufacturing process is simplified. In addition, when only the Sm—Fe—N magnet powder is heated in advance, the magnet powder is heated to a predetermined temperature in an oven or the like and is put into a mold. This is preferable because the production lead time is reduced. It is only necessary that the Sm—Fe—N magnet powder is heated to a temperature of 600 ° C. or lower while being put in the mold.

  Consolidation molding is to form Sm—Fe—N magnet powder at a high surface pressure of 1 to 5 GPa. If the molding surface pressure is less than 1 GPa, it becomes difficult to obtain a high-density magnet molded body having a relative density of 80% or more. If the molding surface pressure exceeds 5 GPa, the life of the mold may be shortened. The molding surface pressure is more preferably 1.5 to 3.5 GPa from the viewpoint of further extending the mold life while obtaining a molded article having a desired relative density and magnetic characteristics. There is no restriction | limiting in particular as a method of compacting, What is necessary is just the method which can apply said high surface pressure to the wide area which covers the metal mold | die of the magnet formation body of a desired magnitude | size. Preferably, a high-output press used for forging can be used, and a hydraulic press, an electric press, an impact press, or the like is used.

  The mold is not particularly limited as long as it can withstand a temperature of 600 ° C. or lower and a high surface pressure of 1 to 5 GPa, and any mold can be used. Fig.5 (a) is the top view which showed the example of the preferable shaping | molding die typically, FIG.5 (b) is sectional drawing of the AA direction of Fig.5 (a). As shown in FIG. 5 (a), the molding die 10 is formed of a cemented carbide capable of withstanding high surface pressure, and the cylindrical inner die 11 whose outer shape is a cylindrical (upper ring shape) circular shape. 12 is made of softer metal. Further, as shown in FIG. 5 (b), magnet powder 14 is put on the lower mold 15 having a quadrangular prism shape in the central space of the inner mold 11, and an upper portion having a quadrangular prism shape is placed on the upper portion thereof. A mold 16 is inserted. The upper part of the upper mold 16 protrudes from the upper surfaces of the molds 11 and 12, and when the mold 10 is pressed (pressed) from the upper part by a hydraulic press, the protruding part of the upper mold 16 is pressed, By compacting the lower magnet powder, a quadrangular prism-shaped magnet compact can be formed. That is, by changing the space shape of the inner mold 11, a magnet molded body having a cylindrical shape, a polygonal column shape, or the like can be formed. Further, as shown in FIGS. 5A and 5B, the mold is provided with through holes 13a and 13b for passing the cartridge heater. The entire mold is heated by a cartridge heater (not shown) in the through holes 13a and 13b, and the magnet powder 14 in the molding space is maintained at 600 ° C. or lower and pressurized from above with a hydraulic press or the like. Further, as shown in FIG. 5A, the outer mold 12 is provided with a temperature sensor hole 17, and the temperature sensor (not shown) in the temperature sensor hole 17 causes the temperature of the outer mold 12. Measure. As shown in FIG. 5B, the temperature sensor hole 17 is provided at a height close to the upper surface of the magnet powder 14. Accordingly, after the heated outer mold 12 and the inner mold 11, the lower mold 15, the upper mold 16, and the magnet powder 14 are allowed to stand for a predetermined time until they are in a thermal equilibrium state, The temperature indicated by the temperature sensor in the sensor hole 17 can be regarded as the temperature of the magnet powder 14.

(Heat treatment step (S13))
In the heat treatment step, after the warm compaction step, the formed magnet powder is heated at a temperature of 350 to 600 ° C. for 1 to 120 minutes. Although the heat treatment step is not essential, it is preferable to carry out the heat treatment step because it can bring out magnetic properties close to the maximum. In addition, when a metal binder is used, the soft magnetic layer and defects on the surface of the Sm—Fe—N-based magnet powder are reduced, so that it is preferable to implement. Thereby, the further improvement of the magnetic characteristic of a Sm-Fe-N type magnet molded object can be performed.

  There is no restriction | limiting in particular in heat-processing a molded object, What kind of method may be used if it can heat at said temperature. Preferably, the molded body can be heated by the same method as in the warm compaction process. For example, in the warm compaction process, when the mold and the Sm-Fe-N magnet powder are both heated with a heater installed in the mold, the same heater can be used after the compaction. Alternatively, the Sm—Fe—N-based magnet molded body can be taken out of the mold and separately placed in an oven for heat treatment. More preferably, the heat treatment step can be performed at 380 to 480 ° C. for 10 to 60 minutes. In addition, in order to acquire the high effect of a heat treatment process, it is preferable to make heat processing temperature higher than the heating temperature at the time of compaction molding.

  According to this embodiment, the Sm—Fe—N-based magnet compact can be obtained with a residual magnetic flux density Br of 0.75 T or more and a coercive force of 900 kA / m or more. More preferably, the residual magnetic flux density is 0.80 T or more and the coercive force is 1100 kA / m or more. The measuring method of the residual magnetic flux density and the coercive force is measured according to the method described in the examples.

<Second embodiment>
The manufacturing method of 2nd embodiment has the warm compaction process (S22) in a magnetic field instead of the warm compaction process (S12) of 1st embodiment. That is, as shown in FIG. 2, a magnet molded body as a product is obtained by the preparation step (S21), the warm compaction in magnetic field step (S22), and the heat treatment step (S23). The preparation step (S21) and the heat treatment step (S23) of the Sm—Fe—N magnet powder are the same as the preparation steps (S11) and (S13) of the first embodiment, respectively, and are optional steps.

(Warm compaction process in magnetic field (S22))
In the warm compaction step (S22), the Sm—Fe—N magnet powder having a temperature of 600 ° C. or less is compacted in a mold at a molding surface pressure of 1 to 5 GPa in a magnetic field of 6 kOe or more. An Sm—Fe—N-based magnet molded body having a relative density of 80% or more is obtained. The warm compaction step (S22) is the same as the warm compaction step (S12) of the first embodiment except that the warm compaction step is performed in a magnetic field.

  The Sm-Fe-N magnet powder used in the second embodiment is preferably anisotropic. By performing warm compaction molding in a magnetic field using anisotropic Sm-Fe-N magnet powder, the magnet powder is molded in a state where the easy magnetization axes are aligned in the magnetic field direction. Therefore, the obtained Sm—Fe—N-based magnet compact is an anisotropic magnet compact having a higher residual magnetic flux density. The applied magnetic field is more preferably 17 kOe or more.

  In order to perform the warm compaction process in a magnetic field, there is no particular limitation as long as a magnetic field of 6 kOe or more can be provided. For example, a known magnetic field orientation device can be installed around the mold, and compaction molding can be performed with a magnetic field applied. As the magnetic field orientation device, a suitable one from known magnetic field orientation devices can be selected from the shape, dimensions, etc. of the desired magnet compact. As a magnetic field application method, either a method of applying a static magnetic field like an electromagnet arranged in a normal magnetic field forming apparatus or a method of applying a pulsed magnetic field using alternating current may be adopted.

  As described above, the Sm—Fe—N-based magnet molded body of the present embodiment is obtained. Alternatively, an Sm—Fe—N-based magnet molded body can be obtained by performing the heat treatment step (S23) as necessary.

<Third embodiment>
The manufacturing method of the third embodiment includes a pre-compression molding step (S32) and a warm compaction step (S33) in a magnetic field instead of the warm compaction step (S12) of the first embodiment. The preparation step (S31) and the heat treatment step (S34) of the Sm—Fe—N magnet powder are the same as the preparation steps (S11) and (S13) of the first embodiment, respectively, and are optional steps. That is, as shown in FIG. 3, a magnet molded body as a product is obtained by the preparation step (S31), the pre-compression molding step in a magnetic field (S32), the warm compaction step (S33), and the heat treatment step (S34). .

(Preliminary compression molding step in magnetic field (S32))
In this embodiment, before the warm compaction step (S33), Sm—Fe—N magnet powder is compression molded in a magnetic field of 6 kOe or more, and a Sm—Fe—N system preliminary having a relative density of 30% or more. It further has a preliminary compression molding step (S32) for obtaining a compression molded body. The warm compaction uses a high surface pressure press. Therefore, attaching a magnetic field orientation device to such a large device requires a wide space and may be difficult in actual use. Therefore, a magnetic orientation machine is attached to the low surface pressure press and a pre-compression molded body having a relative density of 30% or more is produced in advance. Thereafter, the pre-compression molded body is heated and warm compacted with a high surface pressure press. This is because although the number of steps increases, it may be preferable to provide a preliminary compression molding step in consideration of mass production. By performing the pre-compression molding step, the Sm—Fe—N-based magnet powder having anisotropy in the pre-compression molded body is in a state in which easy axes of magnetization are aligned. Therefore, the magnet molded body obtained through the subsequent compacting process is also a magnet molded body having an easy magnetization axis and a higher residual magnetic flux density.

  In the pre-compression molding step (S32) in the magnetic field, it is only necessary to obtain a pre-compression compact having a relative density that does not damage the pre-compression compact during transportation and transportation. Preferably formed. Furthermore, from the viewpoint of preventing oxidation during warm compaction, it is more preferable to form a pre-compression molded body having a relative density of 60% or more. In the case of a pre-compression molded body having a relative density of 30% or more, preferably 60% or more, the Sm—Fe—N magnet powder having the easy magnetization axis aligned in the magnetic field direction does not move and the easy magnetization axis is aligned. It is maintained in the state. The upper limit of the relative density of the pre-compression molded body is not particularly limited, and the relative density may be 80% or more (see Table 4). As described above, in this embodiment, the pre-compression molding step (S32) in the magnetic field as the cold compaction step is inserted before the warm compaction step (S33), so that a relatively high density in the magnetic field (that is, It is preferable to prepare a pre-compression molded body having a relative density of 30% or more, preferably 60% or more. By heating and warm compacting the pre-compression molded body, an increase in oxygen amount due to heating in the warm compaction step (S33) (and further heat treatment step (S34)) is prevented, and high magnetic properties are obtained. An SmFeN bulk magnet compact can be produced. That is, a warm compression molding step (S33) is obtained by obtaining a preliminary compression molded body having a relatively high density and a reduced surface area ratio in a magnetic field preliminary compression molding step (S32) as a cold consolidation molding step. Thus, it is possible to effectively suppress oxidation due to heating until sufficient consolidation (high density, low surface area) is achieved. As a result, a magnet compact having high magnetic properties can be obtained. Further, an SmFeN bulk magnet compact having high magnetic properties can be produced without using a high purity inert gas atmosphere. Therefore, highly airtight equipment for installing (storing) a large press used in the pre-compression molding step (S32) in the magnetic field and the warm compaction step (S33), the supply of high purity inert gas, the exhaust system, etc. This equipment is unnecessary. Thereby, the process from the preparation of the Sm—Fe—N-based magnet powder to the production of the magnet compact can be continuously performed in an air atmosphere (in the air), which is suitable for mass production.

  Further, in the present embodiment, the same high surface pressure press machine is used in the compression (consolidation) molding in the preliminary compression molding process (S32) in the magnetic field as the cold compaction process and the compression molding in the warm compaction process (S43). Is excellent in that it can be shared. That is, the Sm—Fe—N magnet powder is filled in a die set (die) of a high surface pressure press machine, and after sufficiently reaching the (cold) forming temperature, using a hydraulic press in a magnetic field. Compression molding is performed by applying a desired molding surface pressure (cold) to obtain a pre-compression molded body having a desired relative density. Next, using a press machine with the same high surface pressure, after reaching the warm molding temperature sufficiently for the pre-compression molded body formed in the mold, a desired molding surface pressure is applied using a hydraulic press. It is possible to obtain a magnet compact having a desired high relative density by applying warm compaction under load.

  The temperature of the magnet (magnet powder → pre-compression molded body) in the pre-compression molding step (S32) in a magnetic field is at least a temperature lower than that of the warm compaction molding step (S33), preferably 50 ° C. or less, most preferably room temperature. It is preferable to set it to (temperature without heating). By performing pre-compression (consolidation) molding in the above-mentioned relatively low temperature range (cold), it is possible to obtain a pre-compression molding with a relatively high density and high compression and a low surface area ratio while effectively preventing oxidation. Can do.

  In the pre-compression molding step (S32) in the magnetic field, there is no particular limitation on the application of the magnetic field, and a press machine can be installed in the magnetic field orientation machine. As the magnetic field orientation machine, the same magnetic field orientation machine as in the second embodiment can be used. Also, the press machine is not particularly limited, and any press machine can be used as long as it can obtain a pre-compression molded body having a relative density of 30% or more, preferably 60% or more from the Sm-Fe-N magnet powder. Things can also be used. For example, as described above, a high surface pressure (high output) press machine such as a hydraulic press machine, an electric press machine, or an impact press machine can be used. Further, when a pre-compression molded body having a relative density of about 30 to 50% is used, it is possible to use a press machine with a low surface pressure rather than a press machine with a high surface pressure used in the warm compacting step (S33). it can.

  Compression molding in the pre-compression molding step (S32) in a magnetic field is to form Sm—Fe—N magnet powder with a relatively high surface pressure in the range of 0.1 to 5 GPa. If the molding surface pressure during pre-compression molding in a magnetic field is less than 0.1 GPa, it becomes difficult to obtain a relatively high-density pre-compression molded body having a relative density of 30% or more, preferably 60% or more. On the other hand, if the molding surface pressure at the time of preliminary compression molding in a magnetic field exceeds 5 GPa, the life of the press mold (mold) may be shortened. The molding surface pressure at the time of preliminary compression molding in a magnetic field is more preferably 1 to 3.5 GPa from the viewpoint of preventing oxidation at the time of warm consolidation molding.

  The obtained preliminary compression-molded body is compacted in the next warm compacting step (S33) in the same manner as the warm compacting step (S12) of the first embodiment. Further, a heat treatment step (S34) is performed as necessary. Thereby, an increase in the amount of oxygen due to heating in the warm compaction step (S33) and further in the heat treatment step (S34) can be prevented, and an Sm—Fe—N bulk magnet compact having high magnetic properties can be obtained. .

<Fourth embodiment>
In the manufacturing method of the fourth embodiment, instead of the warm compacting step (S12) or (S22) of the first embodiment or the second embodiment, a preliminary compression molding step (S42) and a warm compacting step ( S43) or a warm compaction step in a magnetic field (S43 ′). Hereinafter, the warm compaction step (S43) or the magnetic field warm compaction step (S43 ') is also referred to as (in the magnetic field) warm compaction step (S43 or S43'). Moreover, the preparation process (S41) of the Sm—Fe—N-based magnet powder is the same as the preparation process (S11) of the first embodiment or the preparation process (S21) of the second embodiment. is there. Furthermore, the heat treatment step (S44) of the Sm—Fe—N-based magnet powder is the same as the heat treatment step (S13) of the first embodiment or the heat treatment step (S23) of the second embodiment, and is optional. is there. The preparation step (S21) and the heat treatment step (S23) of the second embodiment are the same as the preparation step (S11) and the heat treatment step (S13) of the first embodiment, respectively. That is, as shown in FIG. 4, it is a product by a preparation process (S41), a pre-compression molding process (S42), a (in a magnetic field) warm compaction process (S43 or S43 ′), and a heat treatment process (S44). A magnet compact is obtained.

(Preliminary compression molding step (S42))
In the present embodiment, before the warm compacting step (S43 or S43 ′) (in a magnetic field), the Sm—Fe—N magnet powder is compression-molded, and the Sm—Fe—N system having a relative density of 30% or more is used. It further has a preliminary compression molding step (S42) for obtaining a preliminary compression molded body. This embodiment is a technique for countermeasures against oxidation at the time of warm compaction (in a magnetic field). (In a magnetic field) Prior to the warm compaction step (S43 or S43 ′), a pre-compression molding step (S42) as a cold compaction step is inserted, and a relatively high density (that is, a relative density of 30% or more, A pre-compression molded body (preferably 60% or more) is produced. By heating and preliminarily compacting this pre-compressed compact (in a magnetic field or in a magnetic field of 6 kOe or more) and performing warm compaction (in a magnetic field), the warm compaction process (S43 or S43 ') (and further heat treatment process) An increase in the amount of oxygen due to heating in (S44) can be prevented, and an SmFeN bulk magnet molded body having high magnetic properties can be produced. That is, a warm compression molding step (S43 or S43 ′) is obtained by obtaining a preliminary compression molded body having a relatively high density and a reduced surface area ratio in the preliminary compression molding step (S42) as a cold compaction step. ) Can be effectively suppressed from being heated until it is sufficiently consolidated (high density, low surface area). As a result, a magnet compact having high magnetic properties can be obtained. Further, an SmFeN bulk magnet compact having high magnetic properties can be produced without using a high purity inert gas atmosphere. Therefore, highly airtight equipment and high-purity inert gas for installing (storing) a large press used in the pre-compression molding step (S42) and the warm compaction step (S43 or S43 ') (in a magnetic field) Equipment such as supply and exhaust systems are not required. Thereby, the process from the preparation of the Sm—Fe—N-based magnet powder to the production of the magnet compact can be continuously performed in an air atmosphere (in the air), which is suitable for mass production.

  In the present embodiment, the compression (consolidation) molding in the preliminary compression molding process (S42) as the cold compaction process and the compression molding in the warm compaction process (S43 or S43 ') (in a magnetic field) are the same. It is excellent in that it can share a surface pressure press. That is, the Sm-Fe-N magnet powder is filled in a die set (die) of a high surface pressure press machine, and after a sufficient (cold) molding temperature is reached, a desired molding surface is obtained using a hydraulic press. Compression molding is performed under pressure (cold) to obtain a pre-compression molded body having a desired relative density. Next, using a press machine with the same high surface pressure, the pre-compression molded body formed in the mold is sufficiently heated (in a magnetic field) to reach a warm molding temperature, and then a hydraulic press is used. A magnet compact having a desired high relative density can be obtained by applying a desired compacting surface pressure (in a magnetic field) and performing warm compaction.

  About the temperature of the magnet (magnet powder → pre-compression molded body) in the pre-compression molding step (S42), at least a temperature lower than the (heating) temperature in the warm compaction step (S43 or S43 ′) (in the magnetic field) The temperature is preferably set to 50 ° C. or less, and most preferably set to room temperature (temperature without heating). By performing pre-compression (consolidation) molding in the above-mentioned relatively low temperature range (cold), it is possible to obtain a pre-compression molding with a relatively high density and high compression and a low surface area ratio while effectively preventing oxidation. Can do.

  In the pre-compression molding step (S42), as a countermeasure against oxidation at the time of (in a magnetic field) warm compaction, as a cold compaction step before (in a magnetic field) warm compaction step (S43 or S43 '). The pre-compression molding step is inserted to produce a relatively high-density pre-compression molded body. From this viewpoint, a pre-compression molded body having a relatively high density (= surface area ratio decreased) having a relative density of 30% or more, preferably 60% or more is formed. In the case of a pre-compression molded body having a relative density of 30% or more, preferably 60% or more and a relatively high density and a low surface area ratio, the pre-compression molding is heated and subjected to warm compaction to obtain a temperature (in a magnetic field). It is possible to prevent an increase in the amount of oxygen due to heating in the intermediate compaction forming step (S43 or S43 ′). As a result, an SmFeN bulk magnet compact having high magnetic properties can be produced. The upper limit of the relative density of the magnet compact is not particularly limited, and the relative density may be 80% or more (see Table 4).

  There is no restriction | limiting in particular as a press machine which can be used for the compression molding in a precompression molding process (S42), From the Sm-Fe-N type | system | group magnetic powder, the relative density of 30% or more, Preferably it is 60% or more of precompression. Any press can be used as long as it can obtain a molded body. For example, high surface pressure (high output) presses such as hydraulic presses, electric presses, impact presses, etc., as well as the presses used in the warm compaction (in a magnetic field) of the first or second embodiment Can be used. Further, when a pre-compression molded body having a relative density of about 30 to 50% is used, it has a lower surface pressure than a high surface pressure press used in the warm compaction process (in a magnetic field) (S43 or S43 ′). A press can be used.

  The compression molding in the pre-compression molding step (S42) is to form Sm—Fe—N magnet powder with a relatively high surface pressure in the range of 0.1 to 5 GPa. When the molding surface pressure at the time of preliminary compression molding is less than 0.1 GPa, it becomes difficult to obtain a comparatively high-density preliminary compression molded body having a relative density of 30% or more, preferably 60% or more. On the other hand, if the molding surface pressure at the time of preliminary compression molding exceeds 5 GPa, the life of the molding die (die) of the press machine may be shortened. The molding surface pressure during preliminary compression molding is more preferably 1 to 3.5 GPa from the viewpoint of preventing oxidation during warm compaction.

  In the next (in a magnetic field) warm compaction step (S43 or S43 ′), the obtained pre-compression molded body is the warm compaction step (S12) of the first embodiment or the warm in the magnetic field of the second embodiment. Consolidation molding is performed in the same manner as in the consolidation molding step (S22). Furthermore, if necessary, heat treatment is performed as the heat treatment step (S44) in the same manner as the heat treatment step (S13) of the first embodiment or the heat treatment step (S23) of the second embodiment. This prevents an increase in the amount of oxygen due to heating in the warm compaction step (S43 or S43 ′) and further in the heat treatment step (S44) (in a magnetic field), and has high magnetic properties. A molded body can be produced.

  Hereinafter, although this embodiment is concretely demonstrated through an Example, this embodiment is not limited to the following Examples.

<Examples 1-7>
(Preparation process)
As the Sm—Fe—N-based powder, Sm ₂ Fe ₁₇ N _x (x≈3) (manufactured by Nichia Corporation) having an average particle diameter D ₅₀ = 3 μm was used. As the metal binder, zinc (Zn) powder (High Purity Chemical Laboratory Co., Ltd.) and copper (Cu) powder (manufactured by Nippon Atomizing Co., Ltd.) were used. Zn powder, the average particle diameter _{D 50} of the Cu powder each 7 [mu] m, was 1 [mu] m. The Sm—Fe—N powder and the metal binder powder were mixed at a ratio (mass ratio) of Sm—Fe—N powder: Zn powder: Cu powder = 80: 15: 5 to prepare a blend powder A.

(Warm compaction process)
8 g of the blended powder A was weighed and filled in a die set (cylindrical mold) having a diameter of 15 mm, and each of Examples 1 to 7 was held at a predetermined temperature shown in Table 1 for 10 minutes. After the powder A reached the molding temperature sufficiently, it was compacted by applying a molding surface pressure shown in Table 1 and holding it for 30 seconds using a hydraulic press. The magnet molded body of Examples 1-7 was obtained in the above processes.

(Evaluation)
By using the same molds as described above, the manufacture of the magnet molded bodies of Examples 1 to 7 was continued, and the mold lifespan was determined. Table 1 shows that the number of molds is 1000 or more, and ○ is less than 1000. The relative densities of the magnet compacts of Examples 1 to 7 were determined using the true density obtained by calculation and the actual density obtained from the dimensions and weight measurements of the magnet compact. The relative density is a ratio (%) of the actual density with respect to the true density, and is calculated by dividing the actual density value by the theoretical density value and multiplying by 100 (the same applies hereinafter). The relative density obtained is shown in Table 1.

<Comparative Examples 1-3>
In Comparative Examples 1 to 3, magnet compacts were produced in the same manner as in Example 1 except that the molding temperature was room temperature (non-heated state; cold compaction molding). The molding surface pressure was set to the molding surface pressure shown in Table 1, respectively. In addition, in Comparative Examples 1 to 3, the die number was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. The relative density of the obtained magnet compact was determined in the same manner as in Example 1. The relative density obtained is shown in Table 1.

  From the data in Table 1, by using the warm compaction of Examples 1 to 7, it is possible to reduce the molding surface pressure necessary to obtain a magnet molded body having the same relative density as compared with Comparative Examples 1 to 3. I understand. Furthermore, when Examples 1, 3 and 6 are compared with Comparative Example 2, it can be seen that the relative density of the magnet molded body can be improved in the example when molding is performed with the same molding surface pressure.

<Examples 8 to 14>
(Preparation process)
As the Sm—Fe—N-based powder, Sm ₂ Fe ₁₇ N _x (x≈3) (manufactured by Sumitomo Metal Mining Co., Ltd.) having an average particle diameter D ₅₀ = 2.4 μm was used. As the metal binder, zinc (Zn) powder (manufactured by Sakai Chemical Industry Co., Ltd.) having an average particle diameter D ₅₀ = 3 μm was used. Sm—Fe—N-based powder and Zn powder were mixed at a mass ratio of 80:20 to prepare blend powder B.

(Warm compaction process)
2.6 g from the blended powder B was weighed and filled in a 7 × 7 mm cemented carbide die set (square column mold) and held at a predetermined temperature for 10 minutes. After the powder B sufficiently reached the molding temperature, it was compacted by applying a molding surface pressure of 1 to 4 GPa using a hydraulic press and holding it for 60 seconds. The magnet moldings of Examples 8 to 14 were produced through the above-described steps (Table 2).

(Evaluation)
By using the same molds as described above, the manufacture of the magnet molded bodies of Examples 8 to 14 was continued, and the mold life was determined. Table 2 shows that the number of molds is 1000 or more, and x is less than 1000. The relative density of the obtained magnet compact was determined in the same manner as in Example 1. The relative density obtained is shown in Table 2.

<Comparative Examples 4-5>
In Comparative Examples 4 to 5, magnet compacts were produced in the same manner as in Example 8, except that the molding temperature was room temperature (not heated; cold compaction molding). The molding surface pressure was set to the molding surface pressure shown in Table 2, respectively. Moreover, also about Comparative Examples 4-5, what evaluated the metal mold life number similarly to Example 8 is shown in Table 2. The relative density of the obtained magnet compact was determined in the same manner as in Example 1. The relative density obtained is shown in Table 2.

  From the data in Table 2, it is possible to reduce the molding surface pressure necessary to obtain a magnet molded body having the same relative density by using warm compaction (Example), and when molding with the same molding surface pressure, It can be seen that the relative density of the magnet compact can be improved.

<Examples 15 to 22>
(Preparation process (S21))
As the Sm—Fe—N coarse powder, Sm ₂ Fe ₁₇ N _x (x≈3) (manufactured by Sumitomo Metal Mining Co., Ltd.) having an average particle diameter D ₅₀ ≈20 μm was used. Three types of powders prepared by finely pulverizing Sm—Fe—N-based coarse powder using a wet bead mill LMZ2 manufactured by Ashizawa Finetech Co., Ltd. were prepared. The average particle diameter _{D 50} of the milling powder A powder: 1.7 [mu] m, B powder: 1.6 [mu] m, C powder: at 1.4 [mu] m, the amount of oxygen magnetic powder was about 1% by weight.

  Sm—Fe—N-based fine powder and Zn powder as metal binder powder were mixed in the ratio shown in Table 3 below to prepare a blend powder. The zinc (Zn) powder was manufactured by Kojundo Chemical Laboratory Co., Ltd., and the average particle size was 3 μm.

(Warm compaction step in magnetic field (S22) and heat treatment step (23))
2.6 g of the blended powder was weighed and filled in a 7 × 7 mm size cemented carbide die set (square column mold) and heated at the temperature shown in Table 3 below. Thereafter, a molding pressure of 3 to 4 GPa was applied using a hydraulic press while an external magnetic field of 21 kOe was applied, and warm compaction was performed by holding for 30 seconds. Thereafter, heat treatment was performed at 420 ° C. for 30 minutes. In addition, all the processes after pulverization were performed in a low oxygen atmosphere of 100 ppm or less.

(Evaluation)
The residual magnetic flux density Br and the coercive force Hcj of the obtained magnet compact were measured using a pulse-type automatic magnetization characteristic measuring apparatus (PBH-1000 manufactured by Nippon Electromagnetic Sokki Co., Ltd.). Table 3 shows the measurement results of the residual magnetic flux density Br and the coercive force Hcj of the obtained magnet compact. The relative density of the magnet compact was determined in the same manner as in Example 1. The obtained relative density is shown in Table 3.

  Moreover, also about Examples 15-22, the mold number was evaluated similarly to Example 1. FIG. The evaluation results are shown in Table 3.

  As can be seen from the results in Table 3, in Examples 15 to 22 according to the second embodiment, as a warm compaction process in a magnetic field, warm compaction is performed at 600 ° C. or less and 1 to 5 GPa with an external magnetic field of 21 kOe applied. Thus, a magnet molded body having a relative density of 80% or more was obtained. Further, these magnet compacts were found to have excellent magnetic properties such as a residual magnetic flux density Br of 0.75 T or more and a coercive force Hcj of 900 kA / m or more.

<Examples 23 to 27>
(Preparation process (S41))
As the Sm—Fe—N coarse powder, Sm ₂ Fe ₁₇ N _x (x≈3) (manufactured by Sumitomo Metal Mining Co., Ltd.) having an average particle diameter D ₅₀ ≈20 μm was used. The Sm—Fe—N-based coarse powder was finely pulverized using a wet bead mill LMZ2 from Ashizawa Finetech Co., Ltd. The average particle diameter _{D 50} of fine pulverized powder was 1.7 [mu] m.

  Blend powder C was prepared by mixing Sm—Fe—N fine powder and Zn powder as a metal binder powder in a ratio (mass ratio) of 93: 7. The zinc (Zn) powder was manufactured by Kojundo Chemical Laboratory Co., Ltd., and the average particle size was 3 μm.

(Preliminary compression molding step (S42))
2.56 g of the blended powder C was weighed and filled in a die set (cylindrical mold) having a diameter of about 7 mm, and each of Examples 23 to 27 was hydraulically pressed so as to have the relative density shown in Table 4 below. Was pre-compressed cold (room temperature) to obtain a pre-compression molded body.

(Warm compaction process (S43))
The pre-compressed bodies obtained thereafter were each held at 200 ° C. for 10 minutes. After the preliminary compression molded body sufficiently reached the molding temperature (200 ° C.), a compacting pressure of 3.5 GPa was applied at 200 ° C. using a hydraulic press, and the compact was warm compacted by holding for 30 seconds. The magnet moldings of Examples 23 to 27 were obtained through the steps as described above.

<Example 28>
In Example 28, blend powder C was prepared in the same manner as in Example 23, 2.56 g of this blend powder C was weighed without performing the pre-compression molding step (S42), and a die set having a diameter of about 7 mm ( A cylindrical mold) was filled and held at 200 ° C. for 10 minutes. After the blended powder C sufficiently reached the molding temperature (200 ° C.), using a hydraulic press, a molding surface pressure of 3.5 GPa was applied at 200 ° C. and held for 30 seconds to perform warm compaction. The magnet molded body of Example 28 was obtained through the process as described above.

(Evaluation)
The residual magnetic flux density Br of the magnet moldings of Examples 23 to 28 was measured using a DC BH tracer (TRF-5AH manufactured by Toei Kogyo Co., Ltd.). The oxygen content of the magnet molded bodies of Examples 23 to 28 was measured with an oxygen-nitrogen analyzer EMGA-920 type manufactured by Horiba, Ltd. Table 4 shows the measurement results of the residual magnetic flux density Br and the oxygen content. Further, the relative density of the precompression molded bodies of Examples 23 to 27 is the same as the relative density of the magnet molded body, the true density obtained by calculation, and the actual density obtained from the dimension and weight measurement of the precompression molded body. Was determined using. The relative density of the pre-compressed compact is the ratio (%) of the actual density to the true density, and is calculated by dividing the actual density value by the theoretical density value and multiplying by 100. Table 4 shows the relative density of the obtained pre-compression molded body.

  In addition, the relative density of the magnet moldings of Examples 23 to 28 was determined in the same manner as in Example 1. The relative densities of the warm compacted bodies (magnet shaped bodies) of Examples 23 to 28 were all 88%. Moreover, also about Examples 23-28, the mold number was evaluated similarly to Example 1. As a result, all were evaluated as “◯”.

  From the results of Table 4, in Examples 23 to 27 in which a preliminary compression molded body having a relative density of 60% or more was molded and the preliminary compression molded body was warm compacted, warm compaction was not performed without forming the preliminary compression molded body. Compared with the molded Example 28, the amount of oxidation in the magnet molded body can be suppressed. As a result, it was found that Examples 23 to 27 can produce SmFeN bulk magnet compacts having a high residual magnetic flux density Br as compared with Example 28.

  Further, in Examples 23 to 27 in which the amount of oxidation in the magnet compact was suppressed, the amount of oxidation in the magnet compact could be suppressed by warm compacting a precompression compact with a higher relative density. It was found that a magnet molded body having a higher residual magnetic flux density Br can be produced.

10 Mold,
11 Inner mold,
12 Outer mold,
13a, 13b through holes,
14 Magnet powder,
15 Lower mold,
16 Upper mold,
17 Temperature sensor hole,
S11, S21, S31 preparation steps,
S12, S33 Warm compacting process,
S13, S23, S34 heat treatment step,
S22 warm compaction process in a magnetic field,
S32 Pre-compression molding process.

Claims (11)

A warm compacting step of compacting Sm—Fe—N magnet powder having a temperature of 600 ° C. or less at a molding surface pressure of 1 to 5 GPa to obtain an Sm—Fe—N magnet compact having a relative density of 80% or more. When,
Before the warm compacting step, compression molding the Sm-Fe-N magnet powder to obtain a Sm-Fe-N magnet compact having a relative density of 30% or more, ,
In the preliminary compression molding step, the Sm-Fe-N magnet molded body is produced by performing the compression molding in a magnetic field of 6 kOe or more . The manufacturing method according to claim 1 , wherein in the preliminary compression molding step, an Sm-Fe-N magnet molded body having a relative density of 60% or more is obtained. The manufacturing method according to claim 1 or 2 , further comprising a preparatory step of pulverizing SmFe-N-based magnet coarse powder to obtain the Sm-Fe-N-based magnet powder before the preliminary compression molding step. The manufacturing method according to claim 3 , wherein the fine pulverization is performed using a dry jet mill. The manufacturing method according to claim 3 , wherein the fine pulverization is performed using a wet bead mill. The process according to any one of claims 3-5, wherein the preparation step subsequent steps are performed in an inert atmosphere. The manufacturing method according to any one of claims 1 to 6 , wherein the temperature of the Sm-Fe-N magnet powder in the warm compacting step is 50 to 500 ° C. The manufacturing method according to any one of claims 1 to 7 , wherein the molding surface pressure in the warm compaction step is 1.5 to 3.5 GPa. The manufacturing method according to any one of claims 1 to 8 , further comprising a heat treatment step of heating at a temperature of 350 to 600 ° C for 1 to 120 minutes after the warm compaction step. The manufacturing method according to any one of claims 1 to 9 , wherein the Sm-Fe-N magnet powder includes a metal binder. The manufacturing method according to any one of claims 1 to 10 , wherein an average particle diameter of the Sm-Fe-N magnet powder is 10 m or less.