WO2013054778A1 - 希土類磁石前駆体の焼結体を形成する磁性粉体の製造方法 - Google Patents
希土類磁石前駆体の焼結体を形成する磁性粉体の製造方法 Download PDFInfo
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- WO2013054778A1 WO2013054778A1 PCT/JP2012/076065 JP2012076065W WO2013054778A1 WO 2013054778 A1 WO2013054778 A1 WO 2013054778A1 JP 2012076065 W JP2012076065 W JP 2012076065W WO 2013054778 A1 WO2013054778 A1 WO 2013054778A1
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- H—ELECTRICITY
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- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
- C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/048—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by pulverising a quenched ribbon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C2202/00—Physical properties
- C22C2202/02—Magnetic
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
Definitions
- the present invention relates to a method for producing a magnetic powder for forming a sintered body of a rare earth magnet precursor.
- Rare earth magnets using rare earth elements such as lanthanoids are also called permanent magnets, and their uses are used in motors for driving hard disks and MRIs, as well as drive motors for hybrid vehicles and electric vehicles.
- Residual magnetization residual magnetic flux density
- coercive force can be cited as indicators of the magnet performance of this rare earth magnet.
- rare earth magnets used also The demand for heat resistance is further increasing, and how to maintain the coercive force of a magnet under high temperature use is one of the important research subjects in the technical field.
- Nd-Fe-B magnets one of the rare-earth magnets frequently used in vehicle drive motors, to refine crystal grains, use a composition alloy with a large amount of Nd, Attempts have been made to increase the coercivity by adding heavy rare earth elements such as high Dy and Tb.
- rare earth magnets there are not only general sintered magnets whose crystal grains (main phase) constituting the structure have a scale of about 3 to 5 ⁇ m, but also nanocrystalline magnets whose crystal grains are refined to a nanoscale of about 50 nm to 300 nm. Among them, nanocrystal magnets that can reduce the amount of expensive heavy rare earth elements added (free) while miniaturizing the crystal grains described above are currently attracting attention.
- Dy which is the most used heavy rare earth element
- the production and export volume of rare metals such as Dy by China are regulated. Therefore, the resource price of Dy has risen sharply since the beginning of 2011. Therefore, the development of Dy-less magnets that guarantee coercive force performance while reducing the amount of Dy, and Dy-free magnets that guarantee coercive force performance without using any Dy is an important development issue. This is one of the major factors that have increased the attention of nanocrystalline magnets.
- the manufacturing method of the nanocrystal magnet is outlined.
- Nd-Fe-B-based molten metal is discharged onto a cooling roll and rapidly solidified, and the resulting rapid cooling ribbon (quenched ribbon) is pulverized to produce magnetic powder.
- hot plastic working when the degree of work (compression ratio) by hot plastic working is large, for example, when the compressibility is about 10% or more
- the sintered body can be referred to as hot strong processing or simply strong processing, and the sintered body can also be referred to as a strong processing precursor) to produce a molded body.
- Patent Document 1 discloses a method for producing a molded body by subjecting this sintered body to hot plastic working.
- a rare earth magnet made of a nanocrystalline magnet is manufactured by applying a heavy rare earth element having high coercive force performance or an alloy thereof to the formed body obtained by hot plastic working by various methods.
- the plastic grains typically Nd 2 Fe 14 B phase
- the crystal grains rotate (or rotate), and the easy magnetization axis (c-axis) is oriented in the processing direction (press direction) to obtain a compact with a high degree of orientation, and the residual magnetization can be increased. Is obtained.
- a crystal grain having a maximum grain size of 300 nm or more is defined as “coarse grain” in this specification.
- this coarse grain is present or the proportion thereof is increased, It has also been found that the rotation is suppressed and the degree of orientation described above tends to decrease.
- the present inventors precisely and efficiently select magnetic powder that does not contain coarse particles in the structure, and have a structure composed of optimal nano-sized crystal grains. It has come up with the idea of the manufacturing method of the magnetic powder which forms a sintered compact.
- the present invention has been made in view of the above-mentioned problems, and relates to a method for producing a magnetic powder for forming a sintered body of a rare earth magnet precursor. It is an object of the present invention to provide a method for producing a magnetic powder that forms a sintered body of a rare earth magnet precursor that can be selected and produced a magnetic powder having a structure composed of optimum nano-sized crystal grains.
- a method for producing a magnetic powder for forming a sintered body of a rare earth magnet precursor comprises: a crystal grain that is a main phase of a Nd—Fe—B system having a nanocrystalline structure; Rare earth formed by a sintered body composed of a grain boundary phase around a phase, which is subjected to hot plastic working which gives anisotropy to the sintered body and further diffuses an alloy which improves coercive force
- the magnetic powder production method of the present invention adjusts the particle size range when the obtained quenched ribbon is pulverized to produce the magnetic powder, and the magnetic powder in this particle size range and having a mass within a predetermined range is magnetically
- This is a method for producing a magnetic powder in which only a magnetic powder containing no coarse particles or having a very small content is selected by applying a separation method and used as a magnetic powder for forming a sintered body.
- a low magnetic magnet having a surface magnetic flux density of 2 mT or less is used for a magnetic powder pulverized in a particle size range of 50 ⁇ m to 1000 ⁇ m and having a mass range of 0.0003 mg to 0.3 mg. It has been specified that a magnetic powder that does not contain coarse particles can be finely selected by examining whether or not it adsorbs on the surface.
- the magnetic powder to be inspected has a mass range of 0.0003 mg to 0.3 mg, so 2 mT, 1.5 mT, 1 mT depending on the mass within this mass range.
- a magnetic powder with a mass range of 0.0003 mg to 0.3 mg is adsorbed to a low magnetic magnet of 2 mT or less, and the magnetic powder adsorbed to the low magnetic magnet has coarse particles, so that the coercive force is low.
- the magnetic powder that is not adsorbed on the surface does not have coarse particles or has a very low content, so that the coercive force is high, and the magnetic powder that is not magnetically adsorbed is collected and used for the production of a sintered body.
- the particle size of the magnetic powder exceeds 1000 ⁇ m, it is difficult to apply this magnetic separation method, and if the particle size is smaller than 50 ⁇ m, the magnetic properties are significantly deteriorated due to strain introduced during pulverization.
- the particle size range is defined as 50 ⁇ m to 1000 ⁇ m.
- the magnet used when applying the magnetic attraction method may be either an electromagnet in which a coil is wound around a soft magnetic member and a magnetic field is generated by energizing the coil, or a low magnetic permanent magnet. Further, by applying a magnet having a shape that can generate a uniform magnetic field as widely as possible, the sorting efficiency of the magnetic powder can be increased. Examples of such a shape and form include a cylindrical shape, a plurality of rod-like shapes provided at intervals, and a plate-like shape.
- the region corresponding to the region on the cooling roll side of the quenching ribbon that is the precursor thereof is the region on the roll surface side of the magnetic powder
- the region corresponding to the region on the opposite side of the cooling roll of the quenching ribbon is the magnetic powder.
- the D free of the crystal grains in the free surface side area of the magnetic powder and the average particle diameter D roll of the crystal grains in the roll surface side area of the magnetic powder are used, the D free is 20 nm to It is preferable that the range is 200 nm, and D free / D roll is 1.1 or more and 10 or less.
- a sintered body formed from a magnetic powder that is not adsorbed to a magnet having a surface magnetic flux density of 2 mT or less is further subjected to hot plastic processing and adsorbed to the magnet.
- the former had a degree of orientation of 93-94% and a remanent magnetization of 1.42-1.44T, whereas the latter It has been confirmed that there is a large divergence in the remanent magnetization due to the difference in the degree of orientation, and the coercive force has a similar divergence as well.
- the particle size distribution in the sintered body before hot plastic working is in the range of 50 ⁇ m to 1000 ⁇ m as described above, D free is in the range of 20 nm to 200 nm, D free / D roll is 1.1 or more and 10
- D free is in the range of 20 nm to 200 nm
- D free / D roll is 1.1 or more and 10
- the rapid cooling ribbon (cooling roll) by the one-side cooling is used for the rapid cooling ribbon that is the precursor of the magnetic powder, so that the free surface side that is not in contact with the cooling roll has a reduced solidification rate and In contrast, grain growth is promoted, and an Nd-rich phase is precipitated by solidification of the residual liquid phase part.
- This Nd-rich grain boundary phase is necessary to enable low-temperature sintering, and the average grain size D free in the free surface side region of the magnetic powder and the average grain size in the roll surface side region of the magnetic powder
- the D free / D roll is adjusted to the range of 1.1 to 10 and the D free is adjusted to 20 nm to 200 nm, and the particle size is refined and homogenized. This is the reason why the degree of orientation is 93 to 94% and the remanent magnetization is 1.42 to 1.44T as described above when formed into a compact by hot plastic working. it is conceivable that.
- D free / D free is adjusted to a range of 1.1 or more and 10 or less, an Nd-rich phase with a low melting point and close to a liquid state is precipitated in the region of the free surface of the magnetic powder as described above. Therefore, sintering at a low temperature becomes possible, which leads to suppression of coarsening of crystal grains.
- the sintered body of the present invention is manufactured using the magnetic powder described above, and an anisotropic shaped body is manufactured by subjecting this sintered body to hot plastic processing (or strong processing).
- a rare earth magnet composed of a nanocrystalline magnet excellent in both magnetization and coercive force can be obtained.
- the particle size when producing the magnetic powder by pulverizing the obtained quenched ribbon Magnetic powder with a small particle content by adjusting the range and applying a magnetic separation method using a low magnetic magnet to a magnetic powder in this particle size range and in a predetermined range of mass The sintered body made of the selected magnetic powder is subjected to hot plastic processing, thereby forming a molded body having a very high degree of orientation and high remanence and coercive force, and thus a rare earth formed from this molded body. Magnets can be manufactured.
- FIG. 6C is a structure diagram of magnetic powder that is not magnetically attracted
- FIG. (A), (b), (c), (d) is a schematic diagram illustrating an embodiment of a low magnetic magnet applied by a magnetic separation method.
- (A) is a low magnification SEM image figure of the sintered compact which is the precursor of the molded object of Example 1 in the magnetic property evaluation test
- (b) is a magnetic powder forming the sintered body in (a). It is a high magnification TEM image figure regarding the roll surface side area
- (c) is a high magnification SEM image figure regarding the free surface side area
- (A) is a low magnification SEM image figure of the sintered compact which is the precursor of the compact
- (c) is a comparative example in a magnetic characteristic evaluation test, respectively.
- FIG. 3 is a low-magnification SEM image of a sintered body that is a precursor of the shaped bodies 1 and 2;
- (A) is the TEM image figure of the molded object of Example 1
- (b) is the TEM image figure of the molded object of the comparative example 1.
- FIG. It is a figure which shows the magnetic characteristic evaluation test result of the magnetic powder fractionated by the magnetic separation method. It is a figure which shows the result of orientation degree among the magnetic characteristic evaluation test results of the molded object of a rare earth magnet precursor. It is a figure which shows the result of a residual magnetization among the magnetic characteristic evaluation test results of the molded object of a rare earth magnet precursor. It is a figure which shows the result of a coercive force among the magnetic characteristic evaluation test results of the molded object of a rare earth magnet precursor.
- FIG. 1A is a diagram for explaining a method for producing a quenching ribbon
- FIG. 2A is a diagram for explaining a method for producing a magnetic powder following FIG. 1A, in which magnetic powder is separated by applying a magnetic separation method.
- FIG. 2b is a structure diagram of magnetic powder that is not magnetically adsorbed
- FIG. 2c is a structure diagram of magnetic powder that is magnetically adsorbed.
- a rapid cooling ribbon B (quenched ribbon) is produced by jetting onto a roll R, and this is coarsely pulverized.
- a region on the cooling roll R side (for example, a region having a half thickness on the cooling roll R side in the thickness of the quenching ribbon B) is referred to as a roll surface, and a region on the opposite side is referred to as a free surface. Since both regions have different distances from the cooling roll R, the speed of crystal grain growth is different.
- composition of the molten alloy is represented by a composition formula of (Rl) x (Rh) yTzBsMt, where Rl is one or more light rare earth elements including Y, Rh is one or more heavy metals composed of Dy and Tb.
- the method of coarsely pulverizing the quenching ribbon B is performed by using an apparatus capable of pulverizing with low energy such as a mortar, a cutter mill, a pot mill, a jaw crusher, and a jet mill.
- the magnetic particle size of the coarsely pulverized magnetic powder is adjusted to a range of about 50 ⁇ m to 1000 ⁇ m, and the magnetic adsorption separation method is applied as a measure for eliminating the magnetic powder having coarse particles.
- the magnetic powder is adsorbed on the low magnetic magnet, and the magnetic powder adsorbed on the low magnetic magnet has coarse particles, so the coercive force is low, and the magnetic powder not adsorbed on the low magnetic magnet has coarse particles. Since it does not have a high coercive force, for example, magnetic powder that has not been magnetically attracted can be collected and used for manufacturing a sintered body. At this time, if the particle size exceeds 1000 ⁇ m, it is difficult to apply this magnetic separation method, and if the particle size is less than 50 ⁇ m, the magnetic property range due to strain introduced at the time of pulverization becomes prominent. Is 50 ⁇ m to 1000 ⁇ m.
- the term “magnetic powder free of coarse particles” means that the magnetic powder does not contain coarse particles completely, and also includes a magnetic powder with a very low content (for example, about 1 to 10 mass% or less). .
- the illustrated magnetic separation device 10 includes a coil 2 arranged around a soft magnetic metal member 1 and a circuit including the coil 2 and a DC power source 3.
- the constituent material and current value of the soft magnetic metal member 1 are adjusted so that when the coil 2 is energized, an electromagnet having a surface magnetic flux density of 2 mT or less is formed. Can be confirmed with the gauss meter 4.
- the magnetic powder p containing no coarse particles can be precisely selected. .
- FIG. 2b is a structure diagram of magnetic powder that is not magnetically adsorbed
- FIG. 2c is a structure diagram of magnetic powder that is magnetically adsorbed.
- a magnetic powder having a mass range of 0.0003 mg to 0.3 mg is adsorbed to a low magnetic magnet of 2 mT or less, and the magnetic powder p ′ adsorbed to the low magnetic magnet 1 has coarse particles and therefore has a low coercive force.
- the magnetic powder p that is not attracted to the low magnetic magnet 1 does not have coarse particles, or has a very low coercive force because of its extremely low content, and the magnetic powder p that has not been magnetically attracted is selected and collected. This is used for the production of a sintered body. Up to this selection is the method for producing the magnetic powder of the present invention.
- the magnetic powder p shown in FIG. 2b is an isotropic crystal with no coarse particles having a particle size of 300 nm or more in the structure, a flat planar shape (including a rectangular shape in a plan view or a shape similar to this). It is comprised from the grain g.
- the magnetic powder p ′ shown in FIG. 2 c has a crystal structure having a large number of coarse grains g ′ having a grain size of 300 nm or more in the structure.
- a cylindrical soft magnetic metal member 1A as shown in FIG. 3a (the surface to which the magnetic powder is adsorbed is K area ), and a plurality of needle-like soft magnetic members as shown in FIG. 3b.
- a region corresponding to the region on the cooling roll side of the quenching ribbon B which is a precursor thereof, is a region corresponding to the roll surface side region of the magnetic powder, and a region opposite to the cooling roll of the quenching ribbon B.
- FIG. 1 b is a diagram illustrating a method for manufacturing a sintered body.
- the produced magnetic powder p is filled in a cavity defined by a carbide die D and a carbide punch P that slides inside this hollow as shown in FIG. Direction)
- the Nd-Fe-B main phase crystal grains with a particle size range of about 20 nm to 200 nm
- a sintered body S made of a grain boundary phase such as an Nd—X alloy (X: metal element) is produced.
- the heating temperature by electric heating is in the range of 550 to 700 ° C, which is a low temperature range that does not cause coarsening of crystal grains, and the pressure range is 40 to 500 MPa, which is a pressure range that can suppress coarsening. It is preferable to manufacture the sintered body in an inert gas atmosphere with a holding time of 60 minutes or less.
- FIG. 1c is a diagram illustrating a method for manufacturing a molded body.
- the manufactured sintered body S is brought into contact with the end face in the longitudinal direction (the horizontal direction is the longitudinal direction in FIG. 1b), and a cemented carbide punch P is brought into contact with the cemented carbide punch P while being pressed (X direction).
- X direction is the longitudinal direction in FIG. 1b
- strong processing a compact C having a crystal structure composed of nanocrystal grains having magnetic anisotropy is produced.
- strain rate of 0.01-30 / s for a short time that can suppress the coarsening at a low temperature range of about 600-800 ° C where plastic deformation is possible and coarsening of the crystal grains is difficult to occur. It is preferable to carry out plastic working at a degree, and it is desirable to carry out in an inert gas atmosphere in order to prevent the molded body from being oxidized.
- the structure of the sintered body S which is a precursor thereof does not contain coarse particles, or the content thereof is extremely small, and the planar shape is flat in a particle size range of about 20 nm to 200 nm.
- the crystal grains are easily rotated during hot plastic working (strong processing), and thus a molded body having anisotropy in which the crystal grains are arranged in a high degree of orientation.
- FIG. 8 shows the results regarding the degree of orientation
- FIG. 9 shows the results regarding the remanent magnetization
- FIG. FIG. 10 shows the results
- Table 1 summarizes the results.
- FIG. 4a shows a low-magnification SEM image of the sintered body, which is a precursor of the molded body of Example 1
- FIG. 4b shows a high level related to the roll surface side region of the magnetic powder forming the sintered body in FIG. 4a.
- Fig. 4c shows a TEM image of magnification
- FIG. 4c shows a high magnification SEM image of the free surface side region of the magnetic powder forming the sintered body in Fig. 4a.
- Fig. 5a shows an example in a magnetic property evaluation test.
- Low-magnification SEM image diagrams of the sintered compact that is the precursor of the compact 2 are shown in FIGS. 5b and 5c, respectively.
- FIG. 6A shows a TEM image of the molded body of Example 1
- FIG. 6B shows a TEM image of the molded body of Comparative Example 1.
- Example 1 Quenched ribbon with Nd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6 (mass%) composition that does not contain coarse particles by one-side cooling, pulverized to produce magnetic powder, 400MPa applied, 600 ° C
- the sintered body was manufactured by holding for 10 minutes. After observing the structure of the sintered body with SEM and TEM, the plastic body of Example 1 was manufactured by performing hot plastic working at a temperature of 750 ° C. and a strain rate of 7 / s. The tissue observation was conducted.
- Example 2 Quenched ribbon with Nd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6 (mass%) composition that does not contain coarse particles by one-side cooling, pulverized to produce magnetic powder, applied with 100 MPa, 650 ° C
- the sintered body was manufactured by holding for 10 minutes. After the structure of the sintered body was observed by SEM, the molded body of Example 2 was manufactured by performing hot plastic working at a temperature of 750 ° C. and a strain rate of 7 / s.
- Comparative Example 1 By one-side cooling, a rapidly cooled ribbon with a composition of Nd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6 (mass%) containing coarse particles is manufactured, pulverized to produce a magnetic powder, and this is applied at 400 MPa, 600 A sintered body was produced by holding at 10 ° C. for 10 minutes. After observing the structure of the sintered body with SEM, the molded body of Comparative Example 1 was manufactured by performing hot plastic working at a temperature of 750 ° C. and a strain rate of 7 / s. Observations were made.
- Comparative Example 2 By one side cooling, a rapidly cooled ribbon with a composition of Nd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6 (mass%) containing coarse particles is manufactured, pulverized to produce a magnetic powder, and this is applied at 100 MPa, 650 A sintered body was manufactured by holding at 10 ° C. for 1010 minutes. After the structure of the sintered body was observed by SEM, the molded body of Comparative Example 2 was manufactured by performing hot plastic working at a temperature of 750 ° C. and a strain rate of 7 / s.
- the crystal grains constituting the molded body of Example 1 have a flat shape (square, rhombus, etc.) and their long sides are both 200 nm or less (the short sides are naturally natural). 200 nm or less).
- the compact of Comparative Example 1 contains a large number of coarse grains of 300 nm or more in the structure.
- FIG. 7 shows that the magnetic properties of both the magnetic powder that is not adsorbed by the low magnetic magnet and the magnetic powder that is adsorbed are compared with respect to the gradient that the graph crosses the vertical axis of coercive force of 0 (kOe) compared to the magnetic powder that is not adsorbed.
- the gradient of the magnetic powder that is adsorbed drops sharply (the gradient rises), which indicates that the residual magnetization is low.
- the unit kOe on the horizontal axis is converted to kA / m in SI units by multiplying it by 79.6.
- the degree of orientation in Examples 1 and 2 is significantly higher than 90% and is 93 and 94% as compared with the degree of orientation in Comparative Examples 1 and 2, and as a result, the residual It can be confirmed that the magnetization is remarkably high, about 0.15T. Furthermore, the coercive force is also increased by about 1 kOe. Therefore, it can be confirmed that the maximum energy product BHmax is greatly improved.
- both the sintered bodies which are the precursors of Comparative Examples 1 and 2 have a structure containing a large number of coarse grains of 300 nm or more, so the coarse grains are not oriented at all. As a result of lowering the degree of orientation of the entire structure, the remanent magnetization is greatly reduced.
- the sintered bodies that are the precursors of Examples 1 and 2 do not contain coarse particles, and have a planar shape with a size of 200 nm or less. Is composed of flat crystal grains, each crystal grain is easily rotated at the time of strong processing, and it is considered that a molded body having a high degree of orientation is easily obtained.
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Abstract
Description
図1a、1b、1cはこの順に、急冷リボンの製造、次いでこの急冷リボンを粉砕してなる磁性粉末を用いた焼結体の製造、次いでこの焼結体に熱間塑性加工を施してなる成形体の製造というフロー図になっている。図1aは急冷リボンの製造方法を説明する図であり、図2aは図1aに続いて磁性粉末の製造方法を説明した図であって磁気分離法を適用して磁性粉末の餞別をおこなっていることを説明した図であり、図2bは磁気吸着されない磁性粉末の組織図、図2cは磁気吸着された磁性粉末の組織図である。
図1bは焼結体の製造方法を説明した図である。製造された磁性粉末pを図1bで示すように超硬ダイスDとこの中空内を摺動する超硬パンチPで画成されたキャビティ内に充填し、超硬パンチPで加圧しながら(X方向)加圧方向に電流を流して通電加熱することにより、ナノ結晶組織のNd-Fe-B系の主相(20nm~200nm程度の粒径範囲の結晶粒)と、主相の周りにあるNd-X合金(X:金属元素)等の粒界相からなる焼結体Sが製造される。
図1cは成形体の製造方法を説明した図である。製造された焼結体Sをその長手方向(図1bでは水平方向が長手方向)の端面に超硬パンチPを当接させ、超硬パンチPで加圧しながら(X方向)熱間塑性加工(強加工)を施すことにより、磁気的異方性を有するナノ結晶粒からなる結晶組織の成形体Cが製造される。
本発明者等は、以下の方法で実施例1,2の成形体と比較例1,2の成形体を製作し、各成形体の磁気特性である配向度、残留磁化および保磁力を測定する実験をおこなった。以下、実施例1、2と比較例1、2の製造方法を示す。なお、実施例1と比較例1の成形体を成形する過程で使用される磁性粉末に関し、それらの配向度(残留磁化(Mr)/飽和磁化(Ms))と保磁力の関係グラフを求め、図7に示している。また、実施例1,2の成形体と比較例1,2の成形体の磁気特性評価試験結果に関し、配向度に関する結果を図8に、残留磁化に関する結果を図9に、保磁力に関する結果を図10にそれぞれ示し、表1にそれらの結果をまとめている。さらに、図4aに実施例1の成形体の前駆体である焼結体の低倍率のSEM画像図を、図4bに図4a中の焼結体を形成する磁性粉末のロール面側領域に関する高倍率のTEM画像図を、図4cに図4a中の焼結体を形成する磁性粉末のフリー面側領域に関する高倍率のSEM画像図をそれぞれ示しており、図5aに磁気特性評価試験における実施例2の成形体の前駆体である焼結体の低倍率のSEM画像図を、図5b、図5cにそれぞれ、磁気特性評価試験における比較例1、2の成形体の前駆体である焼結体の低倍率のSEM画像図を示しており、図6aに実施例1の成形体のTEM画像図を、図6bに比較例1の成形体のTEM画像図をそれぞれ示している。
片側冷却により粗大粒を含有しないNd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6(mass%)組成の急冷リボンを製作し、粉砕して磁性粉末を製作し、これを400MPa印加し、600℃、10分間保持して焼結体を製作した。SEM、TEMにて焼結体の組織観察を実施した後に、温度750℃、歪速度:7/sで熱間塑性加工を実施して実施例1の成形体を製作し、TEMにて成形体の組織観察を実施した。
片側冷却により粗大粒を含有しないNd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6(mass%)組成の急冷リボンを製作し、粉砕して磁性粉末を製作し、これを100MPa印加し、650℃、10分間保持して焼結体を製作した。SEMにて焼結体の組織観察を実施した後に、温度750℃、歪速度:7/sで熱間塑性加工を実施して実施例2の成形体を製作した。
片側冷却により、粗大粒を含有するNd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6(mass%)組成の急冷リボンを製作し、粉砕して磁性粉末を製作し、これを400MPa印加し、600℃、10分間保持して焼結体を製作した。SEMにて焼結体の組織観察を実施した後に、温度750℃、歪速度:7/sで熱間塑性加工を実施して比較例1の成形体を製作し、TEMにて成形体の組織観察を実施した。
片側冷却により、粗大粒を含有するNd29.9Pr0.4Fe64.2Co4.0B0.9Ga0.6(mass%)組成の急冷リボンを製作し、粉砕して磁性粉末を製作し、これを100MPa印加し、650℃、1010分間保持して焼結体を製作した。SEMにて焼結体の組織観察を実施した後に、温度750℃、歪速度:7/sで熱間塑性加工を実施して比較例2の成形体を製作した。
Claims (2)
- ナノ結晶組織のNd-Fe-B系の主相である結晶粒と、該主相の周りにある粒界相からなる焼結体であって、該焼結体に異方性を与える熱間塑性加工が施され、さらに保磁力を向上させる合金が拡散されて形成される希土類磁石の前駆体である焼結体を形成する磁性粉体の製造方法であって、
前記組成を有する金属溶湯を冷却ロール上に吐出して急冷リボンを製作し、これを50μm~1000μmの粒度範囲内に粉砕して0.0003mg~0.3mgの質量範囲の磁性粉体を製作し、
前記質量範囲の磁性粉体が2mT以下の表面磁束密度を有する磁石に吸着するか否かを検査し、吸着しない磁性粉体を選別して焼結体を形成する磁性粉体とする希土類磁石前駆体の焼結体を形成する磁性粉体の製造方法。 - 磁性粉末のうち、その前駆体である急冷リボンの冷却ロール側の領域に対応する領域を磁性粉末のロール面側領域、急冷リボンの冷却ロールと反対側の領域に対応する領域を磁性粉末のフリー面側領域とし、磁性粉末のフリー面側領域における結晶粒の平均粒径Dfree、磁性粉末のロール面側領域における結晶粒の平均粒径Drollとした際に、Dfreeが20nm~200nmの範囲、Dfree/Dfollが1.1以上で10以下の範囲となっている請求項1に記載の希土類磁石前駆体の焼結体を形成する磁性粉体の製造方法。
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US14/350,447 US20140260800A1 (en) | 2011-10-11 | 2012-10-09 | Method for producing magnetic powder for forming sintered body that is precursor of rare-earth magnet |
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JP5640946B2 (ja) * | 2011-10-11 | 2014-12-17 | トヨタ自動車株式会社 | 希土類磁石前駆体である焼結体の製造方法 |
US10464132B2 (en) | 2013-05-24 | 2019-11-05 | Toyota Jidosha Kabushiki Kaisha | Permanent magnet source powder fabrication method, permanent magnet fabrication method, and permanent magnet raw material powder inspection method |
CN104240887B (zh) * | 2014-09-12 | 2017-01-11 | 沈阳中北通磁科技股份有限公司 | 一种低锰含量钕铁硼永磁铁及制造方法 |
CN104347217B (zh) * | 2014-10-16 | 2017-05-10 | 宁波金鸡强磁股份有限公司 | 一种矫顽力增强的钕铁硼系热变形磁体、制备方法及其应用 |
JP2017098454A (ja) * | 2015-11-26 | 2017-06-01 | トヨタ自動車株式会社 | 磁性粉末の磁気選別方法 |
CN105575576A (zh) * | 2016-02-03 | 2016-05-11 | 宁波韵升股份有限公司 | 一种NdFeB纳米双相复合永磁材料及其制备方法 |
JP7167484B2 (ja) * | 2018-05-17 | 2022-11-09 | Tdk株式会社 | R-t-b系希土類焼結磁石用鋳造合金薄片 |
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