CN111566766A - Method for producing rare earth metal bonded magnet and rare earth metal bonded magnet - Google Patents
Method for producing rare earth metal bonded magnet and rare earth metal bonded magnet Download PDFInfo
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- CN111566766A CN111566766A CN201880083626.XA CN201880083626A CN111566766A CN 111566766 A CN111566766 A CN 111566766A CN 201880083626 A CN201880083626 A CN 201880083626A CN 111566766 A CN111566766 A CN 111566766A
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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
- H01F1/059—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and Va elements, e.g. Sm2Fe17N2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
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Abstract
A method for manufacturing a rare earth metal bonded magnet, comprising the steps of: a step of preparing a composition for a magnet, the composition for a magnet including magnetic material particles for a rare earth magnet and metal particles having a Vickers hardness Hv of 200 or less; a step of molding the composition for a magnet to produce a molded body; and a step of heat-treating the molded body in the presence of oxygen.
Description
Technical Field
The present invention relates to a method for producing a rare earth metal bonded magnet and a rare earth metal bonded magnet.
Background
As rare earth magnets using a magnetic material containing a rare earth element, there are known: a rare earth sintered magnet obtained by sintering a magnetic material at a high temperature; and a rare earth bonded magnet obtained by molding a mixture of a magnetic material and a binder.
Since the rare earth sintered magnet has a large shrinkage due to sintering, the dimensional accuracy is low, and post-processing after sintering is required. On the other hand, since the rare earth bonded magnet is obtained by molding, the rare earth bonded magnet has an excellent degree of freedom in shape as compared with a rare earth sintered magnet. Further, since the rare earth bonded magnet is superior in dimensional accuracy to the rare earth sintered magnet, it can be produced inexpensively without requiring post-processing. Therefore, rare earth bonded magnets are widely used in automobiles, general household electric appliances, communication equipment, audio equipment, medical equipment, general industrial equipment, and the like.
As the binder of the rare earth bonded magnet, a resin material or a metal material is mainly used. As a resin material for a binder of a rare earth bonded magnet, for example, thermosetting resins as disclosed in patent document 1 and patent document 2 are known. As a metal material of a binder for a rare earth bonded magnet, for example, metal materials such as Zn are known as disclosed in patent document 3 and patent document 4 below.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. H08-273916
Patent document 2: japanese laid-open patent publication No. 10-275718
Patent document 3: japanese patent laid-open publication No. 2009-076631
Patent document 4: japanese patent laid-open publication No. 2017-010960
Disclosure of Invention
Problems to be solved by the invention
Rare earth bonded magnets are also used in applications requiring heat resistance. In applications requiring heat resistance, there is an increasing demand for a rare earth bonded magnet to improve mechanical strength (hereinafter, also referred to as high-temperature strength) that can withstand use in a high-temperature environment. A rare earth bonded magnet (rare earth metal bonded magnet) using a metal material as a binder tends to have excellent heat resistance as compared with a rare earth bonded magnet using a resin material as a binder, but it is desired to further improve the strength at higher temperatures.
The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a method for producing a rare earth metal bonded magnet having excellent strength at high temperatures, and a rare earth metal bonded magnet.
Means for solving the problems
The means for solving the above problems include the following aspects.
< 1 > a method for producing a rare earth metal bonded magnet, comprising the steps of:
a step of preparing a composition for a magnet, the composition for a magnet including magnetic material particles for a rare earth magnet and metal particles having a Vickers hardness Hv of 200 or less;
a step of molding the composition for a magnet to prepare a molded body; and
and a step of heat-treating the molded body in the presence of oxygen.
< 2 > according to the method for producing a rare earth metal bonded magnet < 1 >, the heat treatment is performed at a temperature of 500 ℃ or lower.
< 3 > the method for producing a rare earth metal bonded magnet according to < 1 > or < 2 >, wherein the heat treatment is performed at a temperature at which the magnetic material particles for the rare earth magnet do not sinter.
< 4 > the method for producing a rare-earth metal bonded magnet according to any one of < 1 > to < 3 >, wherein the heat treatment is performed at a temperature of 500 ℃ or lower, and the metal particles contain at least one of copper (Cu) and aluminum (Al).
< 5 > the method for producing a rare-earth metal bonded magnet according to any one of < 1 > to < 4 >, wherein the heat treatment is performed in an atmosphere containing water vapor.
< 6 > the method for producing a rare earth metal bonded magnet according to any one of < 1 > to < 5 >, wherein the heat treatment is performed at a temperature of 250 ℃ or lower.
< 7 > the method for producing a rare earth metal bonded magnet according to any one of < 1 > to < 6 >, wherein the magnetic material particles for a rare earth magnet contain samarium (Sm).
< 8 > the method for producing a rare earth metal bonded magnet according to any one of < 1 > to < 7 >, wherein a content of a metal having a Vickers hardness Hv of 200 or less in the rare earth metal bonded magnet is 1 to 60% by mass.
< 9 > the method for producing a rare earth metal bonded magnet according to any one of < 1 > to < 8 >, wherein the metal particles contain at least one of copper (Cu) and aluminum (Al).
< 10 > the method for producing a rare earth metal bonded magnet according to any one of < 1 > to < 9 >, wherein a ratio of a long diameter to a short diameter of the metal particles is 1 to 3.5.
< 11 > A rare earth metal bonded magnet which is obtained by heat-treating a molded body comprising magnetic material particles for a rare earth metal magnet and metal particles having a Vickers hardness Hv of 200 or less in the presence of oxygen.
< 12 > A rare earth metal bonded magnet which is a heat-treated product of a molded body comprising magnetic material particles for a rare earth magnet and metal particles having a Vickers hardness Hv of 200 or less, and which comprises at least one of an oxide and a hydroxide of a component contained in the magnetic material particles for a rare earth magnet.
Effects of the invention
According to the present disclosure, a method for producing a rare earth metal bonded magnet having excellent strength at high temperatures and a rare earth metal bonded magnet are provided.
Detailed Description
Hereinafter, one embodiment of the present invention will be described in detail.
However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps) are not essential unless otherwise explicitly stated. The same applies to values and ranges, without limiting the invention.
In the present disclosure, the term "step" includes a step that is independent from other steps, and also includes a step that can achieve the purpose of the step if the step cannot be clearly distinguished from other steps.
In the present disclosure, the numerical range expressed by "to" includes numerical values before and after "to" as the minimum value and the maximum value, respectively.
In the numerical ranges recited in the present disclosure in stages, the upper limit value or the lower limit value recited in one numerical range may be replaced with the upper limit value or the lower limit value recited in other numerical ranges recited in stages. In the numerical ranges disclosed in the present disclosure, the upper limit or the lower limit of the numerical range may be replaced with the values shown in the examples.
A variety of substances corresponding to the respective ingredients may be contained in the present disclosure. When a plurality of substances corresponding to each component are present in the composition, the content or content of each component means the total content or content of the plurality of substances present in the composition unless otherwise specified.
A plurality of particles corresponding to each component may be contained in the present disclosure. In the case where a plurality of particles corresponding to each component are present in the composition, the particle diameter of each component is a value indicating a mixture of the plurality of particles present in the composition unless otherwise specified.
< method for producing rare earth metal bonded magnet >
One embodiment of the disclosed method for producing a rare earth metal bonded magnet is a method for producing a rare earth metal bonded magnet, the method comprising: a step of preparing a composition for a magnet, the composition for a magnet including magnetic material particles for a rare earth magnet (hereinafter, also referred to as magnetic material particles) and metal particles having a vickers hardness Hv of 200 or less (hereinafter, also referred to as metal particles); a step of molding the composition for a magnet to prepare a molded body; and a step of heat-treating the molded body in the presence of oxygen.
Hereinafter, the step of preparing a magnet composition containing magnetic material particles and metal particles is referred to as a magnet composition preparation step. The step of molding the composition for a magnet to prepare a molded article is referred to as a molding step. The step of heat-treating the above-mentioned molded article in the presence of oxygen is referred to as a heat treatment step.
In the present disclosure, the treatment performed so that the maximum reaching temperature of the molded body of the magnet composition is 80 ℃ or higher is referred to as "heat treatment".
According to the method for producing a rare earth metal bonded magnet of the present disclosure, a rare earth metal bonded magnet having excellent strength at high temperatures can be obtained. The reason for this is not clear, but can be considered as follows.
In the method for producing a rare earth metal bonded magnet according to the present disclosure, the molded body of the magnet composition is heat-treated in the presence of oxygen. Thus, the following tendency occurs: at the boundaries between the magnetic material particles and the metal particles, the amount of oxide and hydroxide of a component contained in the magnetic material particles (for example, Fe contained in Sm — Fe — N based magnetic material particles) relatively increases. This tendency does not occur in the heat treatment under an inert gas atmosphere. It is also presumed that the relatively increased oxides and hydroxides contribute to the improvement in the strength of the rare earth metal bonded magnet.
In the method of the present disclosure, the heat treatment is preferably performed at a temperature at which the magnetic material particles do not sinter. From the viewpoint of ensuring sufficient magnetic properties, the heat treatment is preferably performed at a temperature of 500 ℃ or lower. This suppresses the decomposition of the magnetic material particles (for example, Sm — Fe — N magnetic material particles), and tends to maintain good magnetic properties.
(1) Preparation process of composition for magnet
The method of the magnet composition preparation step is not particularly limited as long as the magnet composition containing the magnetic material particles and the metal particles can be prepared. For example, the magnetic material particles and the metal particles may be mixed to prepare a composition for a magnetic body.
When the composition for a magnet is prepared by mixing the magnetic material particles and the metal particles, the preparation of the composition for a magnet can be performed using a known mixing apparatus such as a mixing shaker, a tumbler mixer, a V-type mixer, a double cone mixer, a ribbon type mixer, a Nauta mixer (Nauta mixer), a henschel mixer, or a super mixer.
Magnetic material particles
The type of the magnetic material particle is not particularly limited as long as it is a magnetic material particle containing a rare earth element. Examples thereof include magnetic material particles containing Sm (samarium) as a rare earth element, and magnetic material particles containing Nd (neodymium) as a rare earth element. The magnetic material particles contained in the composition for a magnetic body may be only one type or may be a combination of two or more types.
Examples of the magnetic material particles containing Sm include Sm-Fe-N magnetic material particles (Sm)2Fe17N3、SmFe7NxEtc.), Sm-Fe-B magnetic material particles (Sm)2Fe14B、Sm15Fe77B5Etc.), Sm-Co magnetic particles (SmCo)5、Sm2Co17Etc.), Sm-Co-N magnetic material particles (Sm)2Co17NxEtc.), Sm-Co-B magnetic material particles (Sm)15Co77B5Etc.) and the like.
The magnetic material particles containing Nd include Nd-Fe-B magnetic material particles (Nd)2Fe14B, etc.), and the like.
Among the Sm-containing magnetic material particles, Sm — Fe — N magnetic material particles are preferred from the viewpoint of excellent balance between coercive force and magnetic flux density.
Here, the Sm — Fe — N magnetic material particles mean magnetic material particles containing Sm (samarium), Fe (iron), and N (nitrogen).
The Sm-Fe-N magnetic material particles may contain other elements in addition to Sm, Fe and N. Examples of the other elements include 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, and the like. These other elements may be used alone or in combination of two or more. The other elements may be introduced by substituting a part of the phase structure of the magnetic phase containing Sm, Fe, and N in an amount of 50 mass% or more, or may be introduced by insertion. When the Sm — Fe — N magnetic material particles contain an element other than Sm, Fe, and N, the total amount of Sm, Fe, and N is preferably 50% by mass or more of the whole.
The volume average particle diameter (D50) of the magnetic material particles is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 50 μm, and still more preferably 1 to 20 μm.
The volume average particle diameter (D50) of the magnetic material particles can be measured as follows: the volume-based particle size distribution measured by using a laser diffraction scattering particle size distribution measuring apparatus was measured as a particle size (D50) at which the cumulative particle size from the small diameter side reached 50%.
The shape of the magnetic material particles is not particularly limited, and examples thereof include irregular shapes. Since the magnetic material particles have irregular shapes, voids are reduced when a molded body described later is produced, and a rare earth metal bonded magnet having improved mechanical strength tends to be obtained. The ratio of the major axis to the minor axis (major axis/minor axis) of the magnetic material particles having irregular shapes is not particularly limited. From the viewpoint of easier improvement of mechanical strength, the lower limit of the ratio of the major axis/minor axis is preferably not less than 1, more preferably not less than 1.5, and still more preferably not less than 2. From the viewpoint of dispersibility in the magnet composition, the upper limit of the ratio of the major axis to the minor axis is preferably 3.5 or less, and more preferably 3 or less.
The shape, the major axis, and the minor axis of the magnetic material particles can be measured by observation using a Scanning Electron Microscope (SEM), a Transmission Electron Microscope (TEM), or the like. Specifically, the magnetic material particles have a major axis of: when observing the captured image of the magnetic material particle, the length of the line segment having the longest distance from an arbitrary point a on the surface of the magnetic material particle to an arbitrary point b different from the point a. The short diameter of the magnetic material particle is: and a length of a line segment having the longest length among line segments perpendicular to the major axis and connecting two points on the surface of the magnetic material particle. Then, 100 particles are extracted from the captured image as to the ratio of the major axis to the minor axis, and the arithmetic mean of the major axis and the minor axis of each particle is calculated and found as the ratio of the arithmetic mean.
The content of the magnetic material particles in the composition for a magnetic body is not particularly limited. From the viewpoint of securing sufficient magnetic properties and improving the balance of strength at high temperatures, it is preferably 40 to 99 mass% or more of the entire magnet composition. From the viewpoint of strength, the content of the magnetic material particles is more preferably 90% by mass or less, still more preferably 85% by mass or less, and particularly preferably 80% by mass or less of the entire magnet composition. From the viewpoint of ensuring the magnetic properties of the rare earth metal bonded magnet, the content of the magnetic material particles is more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly preferably 70% by mass or more of the entire magnet composition.
Metal particles-
The type of the metal particles is not particularly limited as long as the metal particles have a vickers hardness Hv of 200 or less and function as a binder. If the vickers hardness Hv of the metal particles is 200 or less, the metal particles are sufficiently soft, and therefore a rare earth metal bonded magnet having excellent strength while ensuring magnetic properties tends to be easily obtained.
The lower limit of the vickers hardness Hv of the metal particles is not particularly limited. The lower limit of the vickers hardness Hv of the metal particles may be, for example, 10 or more, or 30 or more. From the viewpoint of adhesiveness to the magnetic material particles, the upper limit of the vickers hardness Hv is preferably 150 or less, and more preferably 100 or less.
The kind of the metal particles is not particularly limited. Examples of the metal particles include simple substance particles of metals such as copper (Cu), aluminum (Al), iron (Fe), titanium (Ti), tin (Sn), and indium (In), and alloy particles of these metals. These metal particles may be used alone or in combination of two or more. Of these, the metal particles preferably contain at least any one of copper (Cu) and aluminum (Al).
In the present disclosure, "metal particles" refer to particles of a metal or an alloy containing no rare earth element.
For the following reasons, the metal particles more preferably contain Cu.
(1) When a magnet of a target size is produced using metal particles having a specific gravity without changing the content (mass basis) of the metal particles, the ratio (volume ratio) of the magnetic material particles to the entire magnet can be increased. Therefore, when the metal particles having a large specific gravity are used without changing the content on a mass basis, the rare earth metal bonded magnet easily ensures magnetic properties.
(2) Since Cu has high ductility, if it is used as metal particles, the magnetic material particles and the metal particles in a compact obtained by molding the composition for a magnetic body are easily packed most closely, and the density of the compact is increased. Further, Cu is excellent in sliding property (low frictional resistance), and therefore, also contributes to a long life of a mold used for molding.
(3) If Cu is used as the metal particles, the thermal expansion coefficient of the resulting magnet approaches that of iron (Fe). Therefore, when an iron member is used in a portion to which the magnet is applied, the obtained thermal expansion coefficient becomes satisfactory.
The method for measuring the Vickers hardness Hv is as follows. The surface of the test piece was pressed with a predetermined test force using a micro Vickers hardness tester (HM-200B, manufactured by Sanfeng corporation) in accordance with JIS Z2244 (2009), and the hardness of the test piece was calculated from the length of the diagonal line of the depression formed at that time.
The metal component contained in the magnet composition to be used as a raw material may be determined from the metal component contained in the rare earth metal bonded magnet. For example, the vickers hardness Hv of metal particles contained in a magnet composition to be a raw material can be estimated by performing elemental analysis (EDS) on a rare earth metal bonded magnet to be measured by energy dispersive X-ray analysis (EDS) using a scanning electron microscope (JSM-IT 100, manufactured by japan electronics corporation) to specify the type of metal contained in the rare earth metal bonded magnet.
The volume average particle diameter (D50) of the metal particles is not particularly limited, but is preferably 1 to 100. mu.m, more preferably 10 to 80 μm, and still more preferably 20 to 70 μm.
The volume average particle diameter (D50) of the metal particles can be measured in the same manner as the volume average particle diameter (D50) of the magnetic material particles.
The shape of the metal particles is not particularly limited, and examples thereof include irregular shapes. By forming the metal particles into irregular shapes, voids are reduced and a rare earth metal bonded magnet having excellent strength tends to be obtained when a molded body to be described later is produced. The ratio of the major axis to the minor axis (major axis/minor axis) of the metal particles having an irregular shape is not particularly limited. From the viewpoint of easier improvement of mechanical strength, the lower limit of the ratio of the major axis/minor axis is preferably not less than 1, more preferably not less than 1.5, and still more preferably not less than 2. From the viewpoint of dispersibility in the magnet composition, the upper limit of the ratio of the major axis to the minor axis is preferably 3.5 or less, and more preferably 3 or less. The shape, the major axis, the minor axis, and the ratio of the major axis to the minor axis of the metal particles can be measured by the same methods as those for measuring the shape, the major axis, the minor axis, and the ratio of the major axis to the minor axis of the magnetic material particles.
The content of the metal particles in the composition for a magnetic body is not particularly limited. From the viewpoint of securing the balance between the magnetic properties and improving the strength at high temperatures, the content of the metal particles is preferably 1 to 60 mass% of the entire magnet composition. From the viewpoint of obtaining a rare earth metal bonded magnet excellent in strength at high temperatures, the content of the metal particles is more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 20% by mass or more of the entire magnet composition. From the viewpoint of ensuring the magnetic properties of the rare earth metal bonded magnet, the content of the metal particles is more preferably 50% by mass or less, still more preferably 45% by mass or less, and particularly preferably 40% by mass or less of the entire magnet composition.
The volume average particle diameter (D50) of the specific metal particles can be measured in the same manner as the volume average particle diameter (D50) of the magnetic material particles.
(resin component)
The composition for a magnet may include a resin. Examples of the resin include thermosetting resins such as epoxy resin and phenol resin. From the viewpoint of heat resistance and oil resistance of the resulting rare earth metal bonded magnet, the magnet composition preferably contains no resin or a resin content of 10% by mass or less based on the entire magnet composition.
(2) Shaping step
The method of the molding step is not particularly limited as long as a desired molded body can be obtained. From the viewpoint of moldability, the molding method is preferably a compression molding method. The pressure during compression molding is not particularly limited, and as the pressure is increased, a rare earth metal bonded magnet having a high magnetic flux density and high strength tends to be obtained. On the other hand, from the viewpoint of productivity, the pressure at the time of compression molding is preferably low. Therefore, the pressure at the time of compression molding may be, for example, 500MPa to 2500 MPa. The pressure at the time of compression molding is more preferably 700 to 1500MPa from the viewpoint of mass productivity and die life.
The density of the molded body obtained in the molding step (density of the entire molded body) is not particularly limited, and is preferably 75% to 90%, more preferably 80% to 90%, with respect to the true density of the magnet composition to be a raw material. When the density of the compact is in the range of 75% to 90% of the true density of the magnet composition, a rare earth metal bonded magnet having good magnetic properties and excellent mechanical strength tends to be obtained.
When a mold is used in the molding step, the mold may be heated and molded, or the mold may be molded without heating. When the mold is heated and molded, the heating temperature of the mold is not particularly limited. For example, the heating temperature of the mold is preferably 100 to 300 ℃, more preferably 150 to 250 ℃. The heating of the mold is different from the "heat treatment" performed on the molded body obtained in the molding step.
(3) Heat treatment Process
In the heat treatment step, the molded body obtained in the molding step is subjected to heat treatment in the presence of oxygen (that is, heat treatment is performed in an atmosphere containing oxygen). The method of heat treatment is not particularly limited. For example, the reaction can be carried out using a known apparatus such as a heating furnace. The "atmosphere containing oxygen" in which the heat treatment is performed is not particularly limited as long as it is an atmosphere in which oxygen is present. For example, oxygen gas may be supplied, or the reaction may be performed in the atmosphere. From the viewpoint of economy, it is preferable to carry out the reaction in the atmosphere (generally, the oxygen concentration in the components other than moisture is about 23 mass%).
The oxygen concentration in the atmosphere in which oxygen is present (concentration in components other than moisture, the same shall apply hereinafter) is not particularly limited. The oxygen concentration may be, for example, 10% by mass or more from the viewpoint of promoting the formation of oxides and hydroxides by the heat treatment. The oxygen concentration may be, for example, 40% by mass or less from the viewpoint of suppressing excessive production of oxides and hydroxides.
The heat treatment step is preferably performed in an atmosphere containing water vapor (that is, in an atmosphere containing oxygen and water vapor).
As described above, if the heat treatment is performed in the atmosphere containing oxygen, it is considered that the moisture contained in the composition for a magnetic body reacts with the components of the magnetic material particles to generate hydroxides and oxides. Here, if the heat treatment is performed in an atmosphere further containing water vapor in addition to oxygen, it is considered that the moisture contained in the composition for a magnetic body reacts with the water vapor and the components of the magnetic material particles to further promote the generation of the hydroxide and the oxide. As a result, it is considered that the strength of the obtained rare earth metal bonded magnet is further improved.
The concentration of water vapor in the atmosphere containing water vapor is not particularly limited. From the viewpoint of promoting the generation of hydroxides and oxides in the rare earth metal bonded magnet, for example, it is preferably not less than 10% by relative humidity. On the other hand, the concentration of water vapor is preferably 80% or less, and more preferably 70% or less, on a relative humidity basis, for example, from the viewpoint of suppressing the decrease in strength of the rare earth metal bonded magnet due to the excessive production of hydroxides and oxides in the rare earth metal bonded magnet.
The heat treatment may be carried out under reduced pressure or under increased pressure, or may be carried out under atmospheric pressure. From the viewpoint of economy, it is preferably carried out under atmospheric pressure.
The temperature of the heat treatment is not particularly limited. The heat treatment temperature is preferably not too high from the viewpoint of avoiding thermal decomposition of the magnetic material particles or degradation of the magnetic properties due to melting and diffusion of the metal particles in the magnetic material particles. Therefore, the temperature of the heat treatment is preferably 500 ℃ or lower, more preferably 400 ℃ or lower, still more preferably 250 ℃ or lower, and particularly preferably 200 ℃ or lower, from the viewpoint of obtaining a rare earth metal bonded magnet which ensures magnetic properties and has excellent strength at high temperatures. In addition, from the viewpoint of further improving the effect of the heat treatment, the lower limit of the temperature of the heat treatment is preferably not less than 100 ℃, more preferably not less than 150 ℃, and still more preferably not less than 180 ℃. Note that the temperature of the heat treatment in the present disclosure means the maximum reaching temperature.
The time of the heat treatment (holding time at the maximum attainment temperature) is not particularly limited. From the viewpoint of obtaining a sufficient heat treatment effect, the time for the heat treatment is preferably not less than 10 minutes, more preferably not less than 30 minutes, and still more preferably not less than 1 hour. From the viewpoint of mass productivity, the time for the heat treatment is preferably 100 hours or less.
In the heat treatment step, the rate of temperature rise until the maximum temperature is reached is not particularly limited. The lower limit of the temperature increase rate may be, for example, 2 ℃/min or more, or 5 ℃/min or more. The upper limit of the temperature increase rate may be, for example, 20 ℃/min or less, or 15 ℃/min or less.
After the heat treatment is completed, the molded body is cooled until the temperature of the molded body becomes room temperature (e.g., 25 ℃). The cooling rate is not particularly limited. The lower limit of the cooling rate may be, for example, 2 ℃ per minute or more, or 5 ℃ per minute or more. The upper limit of the cooling rate may be, for example, 20 ℃/min or less, or 15 ℃/min or less.
Through the above steps, a rare earth metal bonded magnet having excellent strength at high temperatures can be obtained.
The content of the metal contained in the rare earth metal bonded magnet obtained by the above method is not particularly limited. From the viewpoint of securing a balance between magnetic properties and improving strength at high temperatures, it is preferably 1 to 60 mass% of the entire rare earth metal-bonded magnet. From the viewpoint of obtaining a rare earth metal bonded magnet excellent in strength at high temperatures, the metal content is more preferably 10% by mass or more, still more preferably 15% by mass or more, and particularly preferably 20% by mass or more of the entire rare earth metal bonded magnet. From the viewpoint of ensuring the magnetic properties of the rare earth metal bonded magnet, the content of the metal is more preferably 50% by mass or less, still more preferably 45% by mass or less, and particularly preferably 40% by mass or less of the entire rare earth metal bonded magnet.
< rare earth metal bonded magnet (1) >)
One embodiment of the rare earth metal bonded magnet of the present disclosure is a rare earth metal bonded magnet formed by heat-treating a molded body containing magnetic material particles for a rare earth magnet and metal particles having a vickers hardness Hv of 200 or less in the presence of oxygen.
< rare earth metal bonded magnet (2) >)
Another embodiment of the rare earth metal bonded magnet of the present disclosure is a rare earth metal bonded magnet which is a heat-treated product of a molded body containing magnetic material particles for a rare earth magnet and metal particles having a vickers hardness Hv of 200 or less, and which contains at least one of an oxide and a hydroxide of a component contained in the magnetic material particles for a rare earth magnet (for example, Fe contained in Sm — Fe — N-based magnetic material particles).
The rare earth metal bonded magnet of the above embodiment ensures magnetic properties and has excellent strength at high temperatures. The reason is not necessarily clear, but it is considered that at least either of an oxide and a hydroxide generated by heat treatment of a compact including magnetic material particles and metal particles contributes to improvement of the bonding strength of the magnetic material particles.
The magnetic material particles and the metal particles in the rare earth metal bonded magnet of the above embodiment, and the molded body including these, and the details and preferred forms of the heat treatment conditions can be applied to the contents described in the method for producing a rare earth metal bonded magnet of the above embodiment.
As described above, the rare earth metal bonded magnet of the present disclosure ensures magnetic properties and has excellent strength at high temperatures, and therefore can be preferably used for applications requiring heat resistance. In addition, since the rare earth metal bonded magnet of the present disclosure uses metal particles as a binder, the rare earth metal bonded magnet is also superior in heat resistance and oil resistance to a rare earth metal bonded magnet mainly using a resin as a binder. Therefore, the rare earth metal bonded magnet of the present disclosure can be preferably used for applications requiring heat resistance and oil resistance.
Examples
The embodiments of the present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "part" means "part by mass" and "%" means "% by mass".
(preparation of composition for magnet)
Sm-Fe-N magnetic particles (volume average particle diameter of 2 to 5 μm, manufactured by Sumitomo Metal mining Co., Ltd.) were prepared as magnetic particles; as the metal particles, metal particles shown in table 1 were prepared. Then, the Sm — Fe — N magnet particles and the metal particles were mixed in the mixing amounts (unit: parts by mass) shown in table 1 to prepare a magnet composition. The mixing of the Sm — Fe — N magnet particles and the copper particles was performed at about 50 rpm for 30 minutes using a stirring device.
The abbreviations in table 1 are as follows.
"Cu 1": copper particles (Cu-S-100, manufactured by Futian Metal foil powder industries Co., Ltd.; copper foil powder, long diameter/short diameter ratio: 2.3, Vickers hardness Hv: 100, volume average particle diameter: 45 μm)
"Cu 2": copper particles (Cu-325 manufactured by Nippon Atomized Metal powders corporation, Water Atomized powder, ratio of major axis/minor axis: 1.5, Vickers hardness Hv: 100, volume average particle diameter: 45 μm)
"Cu 3": copper particles (Cu-A manufactured by Japan atomized powder, Long diameter/short diameter ratio: 1.3, Vickers hardness Hv: 100, volume average particle diameter: 60 μm)
"Cu 4": copper particles (CE-15, manufactured by Futian Metal foil powder industries Co., Ltd.; ratio of major axis/minor axis: 3.5, Vickers hardness Hv: 100, volume average particle diameter: 45 μm)
"Fe": iron particles (Water atomized powder manufactured by HOGANAS corporation, long diameter/short diameter ratio: 1.3, Vickers hardness Hv: 200, volume average particle diameter: 100 μm)
(production of molded article)
The obtained composition for a magnet was compression-molded using a hydraulic press under a pressure of 2000MPa to prepare a compression-molded article having a cylindrical shape with an outer diameter of 11.3mm × a height of 10 mm.
(Heat treatment)
The obtained compression-molded body was heat-treated under atmospheric pressure and in the presence of oxygen (oxygen concentration 23 mass%, relative humidity 60%) and under the conditions shown in table 1, to obtain a rare earth metal bonded magnet. In the heat treatment shown in table 1, the composition for a magnet was not sintered.
The compression-molded article of sample No.1 was left at 25 ℃ for 1 hour without heat treatment. The compression-molded body of sample No.20 was heat-treated in a nitrogen atmosphere.
(evaluation)
Residual magnetic flux density Br-
The residual magnetic flux density Br was evaluated as follows.
The test piece of the rare earth metal bonded magnet prepared above was applied with a magnetic field from the height direction at room temperature (25 ℃) by an electromagnet using a magnetization characteristic measuring apparatus (BHU-60S, manufactured by seiko electronics corporation). Then, the value (Br) of the residual magnetic flux density when the magnetic force was detected by using the test coil was calculated, and the residual magnetic flux density was evaluated.
Compressive strength at-200-
The compressive strength at 200 ℃ was evaluated in the following manner.
The test piece of the rare earth metal bonded magnet prepared above was heated to 200 ℃ and compressed in the height direction using a universal compression tester (AG-10 TBR, manufactured by Shimadzu corporation). Then, the compressive strength (MPa) was calculated from the maximum value of the compressive pressure at which the test piece was broken by the compressive pressure, and the compressive strength was evaluated.
[ Table 1]
[ Table 2]
As shown in table 2, the rare earth metal bonded magnets of examples obtained by heat-treating the molded body including the magnetic material particles and the metal particles having the vickers hardness Hv of 200 or less in the presence of oxygen have superior strength at high temperatures as compared with the rare earth metal bonded magnet of comparative example (sample No.1) in which heat treatment was not performed and the rare earth metal bonded magnet of comparative example (sample No.22) in which heat treatment was performed in a nitrogen atmosphere.
All documents, patent applications, and technical standards described in the present specification are incorporated by reference into the present specification to the same extent as if each document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.
Claims (12)
1. A method for manufacturing a rare earth metal bonded magnet, comprising the steps of:
a step of preparing a composition for a magnet, the composition for a magnet including magnetic material particles for a rare earth magnet and metal particles having a Vickers hardness Hv of 200 or less;
a step of molding the composition for a magnet to produce a molded body; and
and a step of heat-treating the molded body in the presence of oxygen.
2. The method for producing a rare-earth metal bonded magnet according to claim 1, wherein the heat treatment is performed at a temperature of 500 ℃ or lower.
3. The method for producing a rare-earth metal bonded magnet according to claim 1 or 2, wherein the heat treatment is performed at a temperature at which the magnetic material particles for a rare-earth magnet do not sinter.
4. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 3, wherein the heat treatment is performed at a temperature of 500 ℃ or lower, and the metal particles contain at least any one of copper (Cu) and aluminum (Al).
5. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 4, wherein the heat treatment is performed in an atmosphere containing water vapor.
6. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 5, wherein the temperature of the heat treatment is 250 ℃ or lower.
7. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 6, wherein the magnetic material particles for a rare-earth metal magnet contain samarium (Sm).
8. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 7, wherein the content of the metal having a Vickers hardness Hv of 200 or less in the rare-earth metal bonded magnet is 1 to 60% by mass.
9. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 8, wherein the metal particles contain at least any one of copper (Cu) and aluminum (Al).
10. The method for producing a rare-earth metal bonded magnet according to any one of claims 1 to 9, wherein the ratio of the long diameter to the short diameter of the metal particles is 1 to 3.5.
11. A rare earth metal bonded magnet is formed by heat-treating a compact containing magnetic material particles for a rare earth metal magnet and metal particles having a Vickers hardness Hv of 200 or less in the presence of oxygen.
12. A rare earth metal bonded magnet which is a heat-treated product of a molded body comprising magnetic material particles for a rare earth magnet and metal particles having a Vickers hardness Hv of 200 or less, and which comprises at least one of an oxide and a hydroxide of a component contained in the magnetic material particles for a rare earth magnet.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| JPPCT/JP2017/047378 | 2017-12-28 | ||
| JP2017047378 | 2017-12-28 | ||
| PCT/JP2018/047641 WO2019131668A1 (en) | 2017-12-28 | 2018-12-25 | Method for manufacturing rare-earth metal bond magnet, and rare-earth metal bond magnet |
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| CN111566766A true CN111566766A (en) | 2020-08-21 |
| CN111566766B CN111566766B (en) | 2022-11-15 |
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| JP (1) | JP7180615B2 (en) |
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| WO2019131668A1 (en) | 2019-07-04 |
| JP7180615B2 (en) | 2022-11-30 |
| JPWO2019131668A1 (en) | 2020-12-10 |
| CN111566766B (en) | 2022-11-15 |
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