Classifications

• • 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
• • 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
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
  • B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
  • B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
• • 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
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • 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
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/14—Treatment of metallic powder
  • B22F1/145—Chemical treatment, e.g. passivation or decarburisation
• • 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
  • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
  • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
  • B22F9/10—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying using centrifugal force
• • 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
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
  • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
• • 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
  • C22C33/0235—Starting from compounds, e.g. oxides
• • 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
  • H01F1/06—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 in the form of particles, e.g. powder
  • H01F1/065—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 in the form of particles, e.g. powder obtained by a reduction
• • 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
  • B22F2304/00—Physical aspects of the powder
  • B22F2304/10—Micron size particles, i.e. above 1 micrometer up to 500 micrometer
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • 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
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
• • 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
  • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
• • 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

Definitions

• the present invention relates to a method for producing an anisotropic magnetic powder and an anisotropic magnetic powder.
• Patent Document 1 discloses a SmFeN-based sintered magnet, and discloses a magnetic powder having a small average particle diameter and a low oxygen content as a magnetic powder used for sintering.
• a magnetic powder having an average particle size of 20 ⁇ m or more is pulverized with a jet mill to produce a magnetic powder, and only a powder having a wide particle size distribution can be produced.
• Patent Document 2 discloses a method of washing a magnetic powder obtained by nitriding with an acid in order to remove calcium used in the reduction diffusion step.
• Patent Document 2 discloses a method of washing a magnetic powder obtained by nitriding with an acid in order to remove calcium used in the reduction diffusion step.
• the purpose of removing calcium at least in the examples, only magnetic powders having a high oxygen content are disclosed.
• An object of the present invention is to provide an anisotropic magnetic powder having a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high residual magnetic flux density, and a method for producing the same.
• the method for producing an anisotropic magnetic powder according to one aspect of the present invention is a pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere.
• the process of nitriding the alloy particles to obtain a nitride, and The step of alkali-treating the nitride to obtain a magnetic powder is included.
• the span defined by is 1.6 or less, includes Sm, Fe, N, and O, and the amount of O is 0.05% by mass or more and 0.65% by mass or less.
• an anisotropic magnetic powder of the present invention since the nitride is treated with an alkali, an anisotropic magnetic powder having a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high residual magnetic flux density is produced. be able to.
• the first method for producing the anisotropic magnetic powder of the present embodiment is a pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere, the partial oxide.
• Treatment of unreacted metallic calcium contained in nitrides and by-produced calcium nitride with water causes heat generation and oxidation due to heat generation, but treatment with an alkaline solution instead of water causes heat generation and heat generation. Since the accompanying oxidation can be suppressed, it is possible to obtain a magnetic powder having a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high residual magnetic flux density.
• the oxide containing Sm and Fe used in the pretreatment step may be obtained by, for example, mixing Sm oxide and Fe oxide, but a solution containing Sm and Fe and a precipitant are mixed to form Sm. It can be produced by a step of obtaining a precipitate containing Fe (precipitation step) and a step of obtaining an oxide containing Sm and Fe by firing the precipitate (oxidation step).
• the Sm raw material and the Fe raw material are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe.
• the molar ratio of Sm and Fe is preferably 1.5:17 to 3.0:17, and 2.0:17 to 2.5:17. Is more preferable.
• Ingredients such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, Lu may be added to the above solution.
• La In terms of residual magnetic flux density, it is preferable to include La.
• W in terms of holding power and square shape ratio.
• the Sm raw material and Fe raw material are not limited as long as they can be dissolved in a strongly acidic solution.
• samarium oxide can be mentioned as the Sm raw material
• FeSO 4 can be mentioned as the Fe raw material.
• the concentration of the solution containing Sm and Fe can be appropriately adjusted within a range in which the Sm raw material and the Fe raw material are substantially dissolved in the acidic solution.
• the acidic solution include sulfuric acid and the like in terms of solubility.
• the solution containing Sm and Fe may be a solution containing Sm and Fe at the time of reaction with the precipitating agent.
• the precipitating agent is not limited as long as it is an alkaline solution that reacts with a solution containing Sm and Fe to obtain a precipitate, and examples thereof include aqueous ammonia and caustic soda, and caustic soda is preferable.
• a method of dropping a solution containing Sm and Fe and a precipitating agent into a solvent such as water is preferable because the properties of the particles of the precipitate can be easily adjusted.
• the reaction temperature can be 0 to 50 ° C, preferably 35 to 45 ° C.
• the total concentration of the metal ions in the reaction solution is preferably 0.65 mol / L to 0.85 mol / L, more preferably 0.7 mol / L to 0.85 mol / L.
• the reaction pH is preferably 5 to 9, more preferably 6.5 to 8.
• the solution containing Sm and Fe preferably further contains one or more metals selected from the group consisting of La, W, Co and Ti in terms of magnetic properties.
• La is preferably contained in terms of residual magnetic flux density
• W is preferably contained in terms of holding power and square ratio
• Co and Ti are preferably contained in terms of temperature characteristics.
• the La raw material is not limited as long as it can be dissolved in a strongly acidic solution, and examples thereof include La 2 O 3 and La Cl 3 in terms of availability.
• the La raw material, the W raw material, the Co raw material, and the Ti raw material are appropriately adjusted within a range in which they are substantially dissolved in an acidic solution, and examples of the acidic solution include sulfuric acid in terms of solubility.
• Examples of the W raw material include ammonium tungstate, examples of the Co raw material include cobalt sulfate, and examples of the titanium raw material include titania sulfate. It is preferable to adjust the solution separately from the solution containing Sm and Fe so as to be substantially soluble in water.
• the solution containing Sm and Fe further contains one or more metals selected from the group consisting of La, W, Co and Ti
• it is selected from the group consisting of Sm, Fe and La, W, Co and Ti1
• the solution may be at least one selected from the group consisting of La, W, Co and Ti at the time of reaction with the precipitant.
• each raw material is prepared as a separate solution, and each solution is prepared. May be dropped and reacted with a precipitating agent, or may be adjusted together with a solution containing Sm and Fe.
• the anisotropic magnetic powder particles obtained in the precipitation step roughly determine the powder particle size, powder shape, and particle size distribution of the finally obtained magnetic powder.
• the size and distribution of the total powder should be within the range of 0.05 to 20 ⁇ m, preferably 0.1 to 10 ⁇ m. preferable.
• the average particle size of the anisotropic magnetic powder particles is measured as a particle size corresponding to 50% of the cumulative volume from the small particle size side in the particle size distribution, and is preferably in the range of 0.1 to 10 ⁇ m.
• the precipitate After separating the precipitate, the precipitate is redissolved in the remaining solvent in the heat treatment of the subsequent oxidation step, and when the solvent evaporates, the precipitate aggregates and the particle size distribution, powder diameter, etc. change. It is preferable to desolvate the separated product in order to suppress this.
• Specific examples of the method for removing the solvent include, for example, when water is used as the solvent, a method of drying in an oven at 70 to 200 ° C. for 5 to 12 hours can be mentioned.
• a step of separating and washing the obtained precipitate may be included.
• the washing step is appropriately performed until the conductivity of the supernatant solution becomes 5 mS / m 2 or less.
• a step of separating the precipitate for example, a filtration method, a decantation method or the like can be used after adding a solvent (preferably water) to the obtained precipitate and mixing them.
• the oxidation step is a step of obtaining an oxide containing Sm and Fe by calcining the precipitate formed in the precipitation step.
• the precipitate can be converted into an oxide by heat treatment.
• the precipitate When the precipitate is heat-treated, it must be carried out in the presence of oxygen, for example, in the air atmosphere.
• the non-metal portion in the precipitate contains an oxygen atom.
• the heat treatment temperature (hereinafter referred to as the oxidation temperature) in the oxidation step is not particularly limited, but is preferably 700 to 1300 ° C, more preferably 900 to 1200 ° C. If the temperature is lower than 700 ° C., the oxidation becomes insufficient, and if the temperature exceeds 1300 ° C., the desired shape, average particle size and particle size distribution of the magnetic powder tend not to be obtained.
• the heat treatment time is not particularly limited, but 1 to 3 hours is preferable.
• the obtained oxide is an oxide particle in which R and iron are sufficiently microscopically mixed in the oxide particle, and the shape, particle size distribution, etc. of the precipitate are reflected.
• the pretreatment step is a step of heat-treating the above-mentioned oxide containing Sm and Fe in a reducing gas atmosphere to obtain a partially reduced oxide.
• the partial oxide means an oxide in which a part of the oxide is reduced.
• the oxygen concentration of the oxide is not particularly limited, but is preferably 10% by mass or less, more preferably 8% by mass or less. If it exceeds 10% by mass, the reduction heat generation with Ca becomes large in the reduction step, and the firing temperature becomes high, so that particles with abnormal particle growth tend to be formed.
• the oxygen concentration of the partial oxide can be measured by the non-dispersed infrared absorption method (ND-IR).
• the reducing gas is appropriately selected from hydrocarbon gases such as hydrogen (H 2 ), carbon monoxide (CO), and methane (CH 4 ), but hydrogen gas is preferable in terms of cost, and the gas flow rate is oxidation. It is adjusted appropriately as long as the object does not scatter.
• the heat treatment temperature (hereinafter, pretreatment temperature) in the pretreatment step is preferably 300 ° C. or higher and 950 ° C. or lower, more preferably 400 ° C. or higher, and further preferably 750 ° C. or higher.
• the upper limit is more preferably less than 900 ° C.
• the pretreatment temperature is 300 ° C. or higher, the reduction of the oxide containing Sm and Fe proceeds efficiently. Further, when the temperature is 950 ° C.
• the oxide particles are suppressed from growing and segregating, and the desired particle size can be maintained.
• hydrogen is used as the reducing gas, it is preferable to adjust the thickness of the oxide layer to be used to 20 mm or less, and further adjust the dew point in the reaction furnace to ⁇ 10 ° C. or less.
• the reduction step is a step of obtaining alloy particles by heat-treating the partial oxide in the presence of a reducing agent.
• reduction is performed by contacting the partial oxide with a calcium melt or calcium vapor.
• the heat treatment temperature is preferably 920 ° C. or higher and 1200 ° C. or lower, more preferably 950 ° C. or higher and 1150 ° C. or lower, and further preferably 980 ° C. or higher and 1100 ° C. or lower.
• the heat treatment may be performed at a first temperature of 1000 ° C. or higher and 1090 ° C. or lower, and then at a second temperature of 980 ° C. or higher and 1070 ° C. or lower, which is lower than the first temperature. ..
• the first temperature is preferably 1010 ° C. or higher and 1080 ° C. or lower
• the second temperature is preferably 990 ° C. or higher and 1060 ° C. or lower.
• the temperature difference between the first temperature and the second temperature is preferably lower in the range of 15 ° C. or higher and 60 ° C. or lower than the first temperature, and more preferably lower in the range of 15 ° C.
• each heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes, and the lower limit of the heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more.
• Metallic calcium is used in the form of granules or powder, and the particle size thereof is preferably 10 mm or less. This makes it possible to more effectively suppress aggregation during the reduction reaction.
• metallic calcium is a reaction equivalent (a stoichiometric amount required to reduce a rare earth oxide, and if Fe is in the form of an oxide, it includes the amount required to reduce it). It is preferable to add in an amount of 1.1 to 3.0 times, more preferably 1.5 to 2.5 times.
• a disintegration accelerator can be used as needed together with the metallic calcium which is a reducing agent.
• This disintegration accelerator is appropriately used to promote disintegration and granulation of the product in the alkali treatment step described later.
• an alkaline earth metal salt such as calcium chloride and an alkali such as calcium oxide. Examples include earth oxides.
• These disintegration accelerators are used in a proportion of 1 to 30% by mass, preferably 5 to 30% by mass, per rare earth oxide used as a rare earth source.
• the nitriding step is a step of obtaining anisotropic magnetic particles by nitriding the alloy particles obtained in the reduction step. Since the particulate precipitate obtained in the above-mentioned precipitation step is used, porous lumpy alloy particles can be obtained in the reduction step. As a result, nitriding can be performed uniformly by heat treatment in a nitrogen atmosphere immediately without performing pulverization treatment.
• the heat treatment temperature (hereinafter referred to as nitriding temperature) in the nitriding treatment of the alloy particles is preferably a temperature of 300 to 600 ° C., particularly preferably 400 to 550 ° C., and is carried out by replacing the atmosphere with a nitrogen atmosphere in this temperature range.
• the heat treatment time may be set so that the nitriding of the alloy particles is sufficiently uniform.
• Examples of the alkaline solution used in the alkaline treatment step include an aqueous solution of calcium hydroxide, an aqueous solution of sodium hydroxide, and an aqueous solution of ammonia. Of these, an aqueous solution of calcium hydroxide and an aqueous solution of sodium hydroxide are preferable in terms of wastewater treatment and high pH.
• the pH of the alkaline solution used in the alkaline treatment step is not particularly limited, but is preferably 9 or more, and more preferably 10 or more.
• the pH is less than 9, the reaction rate at the time of calcium hydroxide formation is high and the heat generation is large, so that the oxygen concentration tends to be high.
• the magnetic powder obtained after the treatment with an alkali can reduce the water content by a method such as decantation, if necessary.
• [Acid treatment process] It is preferable to include an acid treatment step of further treating with an acid after the alkali treatment step.
• the calcium component is removed by the alkali treatment of the nitride described above, the Sm-rich layer containing a certain amount of oxygen remains and functions as a protective layer, so that it is oxidized and the oxygen concentration is suppressed from increasing. ..
• the Sm-rich layer is removed to reduce the oxygen concentration in the entire magnetic powder.
• the average particle size of the anisotropic magnetic powder is small, the particle size distribution is narrow, and fine powder is not contained, so that an increase in oxygen concentration is suppressed. Is possible.
• the acid used in the acid treatment step is not particularly limited, and examples thereof include hydrogen chloride, nitric acid, sulfuric acid, and acetic acid. Of these, hydrogen chloride and nitric acid are preferable because impurities do not remain.
• the amount of the acid used in the acid treatment step is preferably 3.5 parts by mass or more and 13.5 parts by mass or less, and more preferably 4 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the magnetic powder. If it is less than 3.5 parts by mass, the oxide on the surface of the magnetic powder remains and the oxygen concentration becomes high. If it exceeds 13.5 parts by mass, oxidation is likely to occur when it comes into contact with the atmosphere, and the magnetic powder is dissolved. Therefore, the cost tends to be high.
• the magnetic powder obtained after the treatment with an acid can also reduce the water content by a method such as decantation, if necessary.
• the dehydration treatment means a treatment of reducing the water content contained in the solid content before and after these treatments by applying pressure or centrifugal force, and does not include mere decantation, filtration or drying.
• the dehydration treatment method is not particularly limited, and examples thereof include squeezing and centrifugation.
• the amount of water contained in the magnetic powder after the dehydration treatment is not particularly limited, but is preferably 13% by mass or less, more preferably 10% by mass or less, from the viewpoint of suppressing the progress of oxidation.
• the magnetic powder obtained by acid treatment or the magnetic powder obtained by dehydration treatment after acid treatment is preferably vacuum dried.
• the drying temperature is not particularly limited, but is preferably 70 ° C. or higher, more preferably 80 ° C. or higher.
• the drying time is not particularly limited, but is preferably 1 hour or longer, and more preferably 3 hours or longer.
• the method for producing an anisotropic magnetic powder is a pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere.
• the amount of acid with respect to 100 parts by mass of the magnetic powder is 3.5 parts by mass or more and 13.5 parts by mass or less.
• the second method for producing the anisotropic magnetic powder of the present embodiment is a pretreatment step of obtaining a partial oxide by heat-treating an oxide containing Sm and Fe in a reducing gas atmosphere, the partial oxide. Is heat-treated at 920 ° C. or higher and 1200 ° C. or lower in the presence of a reducing agent to obtain alloy particles, a step of nitriding the alloy particles to obtain a nitride, and a step of cleaning the nitride to obtain a magnetic powder.
• the amount of acid with respect to 100 parts by mass of the magnetic powder is 3.5 parts by mass or more and 13.5 parts by mass or less. And.
• the acid treatment step by setting the amount of acid to 3.5 parts by mass or more and 13.5 parts by mass or less with respect to 100 parts by mass of the magnetic powder, it is oxidized to the extent that reoxidation is unlikely to occur when exposed to the atmosphere after the acid treatment.
• the Sm-rich layer can be made to cover the surface of the magnetic powder. Therefore, an anisotropic magnetic powder having a low oxygen concentration, a small average particle size, and a narrow particle size distribution can be obtained.
• the pretreatment step, the step of obtaining alloy particles, the step of obtaining a nitride, and the step of acid treatment are as described above.
• the dehydration treatment and the dispersion treatment may be performed in the same manner as in the first production method.
• D50 (Here, D10, D50, and D90 are particle sizes corresponding to the integrated values of the particle size distribution based on the volume of 10%, 50%, and 90%, respectively.)
• the span defined by is 1.6 or less, includes Sm, Fe, N, and O, and the amount of O is 0.05% by mass or more and 0.65% by mass or less.
• the anisotropic magnetic powder in the present embodiment can be produced, for example, by the above-mentioned production method, but since the magnetic powder is not mechanically crushed by crushing or the like, the oxygen concentration is low and the average particle size is small.
• the anisotropic magnetic powder has a narrow particle size distribution (small span) and a high residual magnetic flux density.
• the anisotropic magnetic powder in the present embodiment typically has the following general formula Sm v Fe (100-v-w-x-y-z-u) N w La x W y Co z Ti u. (In the formula, 3 ⁇ v ⁇ 30, 5 ⁇ w ⁇ 15, 0 ⁇ x ⁇ 0.3, 0 ⁇ y ⁇ 2.5, 0 ⁇ z ⁇ 2.5, 0 ⁇ u ⁇ 2.5. ) It is represented by.
• v is defined as 3 or more and 30 or less because if it is less than 3, the unreacted portion ( ⁇ -Fe phase) of the iron component is separated and the coercive force of the nitride is lowered, so that it is not a practical magnet. If it exceeds 30, the element of Sm is precipitated, the magnetic powder becomes unstable in the atmosphere, and the residual magnetic flux density decreases. Further, the reason why w is defined as 5 or more and 15 or less is that when it is less than 5, coercive force can hardly be exhibited, and when it exceeds 15, Sm elements and nitrides of iron itself are generated.
• the average particle size of the anisotropic magnetic powder is 1.5 ⁇ m or more and 7 ⁇ m or less, preferably 3 ⁇ m or more and 7 ⁇ m or less, and more preferably 4 ⁇ m or more and 6.5 ⁇ m or less. If it is less than 1.5 ⁇ m, oxidation is likely to occur because the surface area is large, and if it exceeds 7 ⁇ m, the magnetic powder has a multimagnetic domain structure, and the magnetic properties tend to deteriorate.
• the average particle size means the particle size measured under dry conditions using a laser diffraction type particle size distribution measuring device.
• the following equation span of anisotropic magnetic powder (D90-D10) / D50 (Here, D10, D50, and D90 are particle sizes corresponding to the integrated values of the particle size distribution based on the volume of 10%, 50%, and 90%, respectively.)
• the span calculated in is 1.6 or less, but 1.3 or less is preferable. If it exceeds 1.6, large particles are present and the magnetic properties tend to deteriorate.
• the anisotropic magnetic powder contains oxygen, and the content thereof may be 0.05% by mass or more and 0.65% by mass or less, preferably 0.3% by mass or less. If it is less than 0.05% by mass, oxidation is likely to occur when exposed to the atmosphere, and if it exceeds 0.65% by mass, the magnetic properties tend to deteriorate.
• the oxygen content can be measured by the non-dispersed infrared absorption method (ND-IR).
• the average value of the circularity of the magnetic powder is preferably 0.50 or more, more preferably 0.70 or more, and particularly preferably 0.75 or more.
• the circularity is less than 0.50, the fluidity is deteriorated, and stress is applied between the particles during magnetic field forming, so that the magnetic properties are deteriorated.
• a scanning electron microscope was used to measure the circularity, and Sumitomo Metals Technology's particle analysis Ver. 3 is used as image analysis software.
• the SEM image taken at 3000 times is binarized by image processing, and the circularity is obtained for one particle.
• the circularity defined in the present invention means an average value of circularity obtained by measuring about 1000 to 10000 particles. Generally, the larger the number of particles having a small particle size, the higher the circularity.
• circularity (4 ⁇ S / L2) is used.
• S is the two-dimensional projected area of the particle
• L is the two-dimensional projected perimeter.
• the anisotropic magnetic powder of the present embodiment has a low oxygen concentration, it can be used as, for example, a sintered magnet or a bonded magnet.
• the bonded magnet is made of the anisotropic magnetic powder of the present embodiment and a resin. By including this anisotropic magnetic powder, a composite material having high magnetic properties can be formed.
• the resin contained in the composite material may be a thermosetting resin or a thermoplastic resin, but is preferably a thermoplastic resin.
• the thermoplastic resin include polyphenylene sulfide resin (PPS), polyetheretherketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), polyethylene (PE) and the like. can.
• the weight ratio (resin / magnetic powder) of the anisotropic magnetic powder to the resin when obtaining the composite material is preferably 0.10 to 0.15, more preferably 0.11 to 0.14. ..
• the composite material can be obtained, for example, by mixing the anisotropic magnetic powder and the resin at 280 to 330 ° C. using a kneader.
• a bonded magnet By using a composite material, a bonded magnet can be manufactured. Specifically, for example, a bonded magnet can be obtained by aligning magnetic domains that are easily magnetized with an alignment magnetic field (alignment step) while heat-treating the composite material, and then pulse magnetizing with a magnetizing magnetic field (magnetization step).
• the heat treatment temperature in the alignment step is preferably, for example, 90 to 200 ° C, more preferably 100 to 150 ° C.
• the magnitude of the alignment magnetic field in the alignment step can be, for example, 720 kA / m. Further, the magnitude of the magnetizing magnetic field in the magnetizing step can be, for example, 1500 to 2500 kA / m.
• the sintered magnet is manufactured by molding and sintering the anisotropic magnetic powder of the present embodiment.
• the anisotropic magnetic powder of the present embodiment is suitable for a sintered magnet because it has a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high residual magnetic flux density.
• the sintered magnet is a magnetic powder having an oxygen concentration of 0.5 volume ppm or less, a temperature higher than 300 ° C. and lower than 600 ° C., and a pressure of 1000 MPa or more and 1500 MPa or less. It is made by sintering below.
• the sintered magnet is, for example, as shown in International Publication 2015/199096, after the magnetic powder is pre-compressed in a magnetic field of 6 kOe or more, and then warm-consolidated at a temperature of 600 ° C. or lower and a molding surface pressure of 1 to 5 GPa. It is produced by.
• the sintered magnet is obtained by cold-consolidating a mixture containing a magnetic powder and a metal binder at a molding surface pressure of 1 to 5 GPa and then cold-consolidating at a temperature of 350 to 600 ° C. It is produced by heating for 1 to 120 minutes.
• the oxygen content was measured by a non-dispersive infrared absorption method (EMGA-820 manufactured by HORIBA, Ltd.).
• ⁇ Nitrogen content> The nitrogen content was measured by the thermal conductivity method (EMGA-820 manufactured by HORIBA, Ltd.).
• the particle size distribution was measured by a laser diffraction type particle size distribution measuring device (HELOS & RODOS manufactured by Nippon Laser Co., Ltd.).
• Production Example 1 (Preparation of medium particle size SmFe oxide) It was mixed and dissolved FeSO 4 ⁇ 7H 2 O 5.0kg of pure water 2.0 kg. Further, 0.49 kg of Sm 2 O 3 and 0.035 kg of La 2 O 3 and 0.74 kg of 70% sulfuric acid were added and stirred well to completely dissolve them. Next, pure water was added to the obtained solution to adjust the Fe concentration to 0.726 mol / l and the Sm concentration to 0.112 mol / l to obtain a SmFeLa sulfuric acid solution.
• Production Example 2 (Preparation of SmFe oxide with large particle size)
• 0.035 kg of La 2 O 3 was added, and the operation was the same as in Production Example 1 except that the atmospheric temperature was changed to 900 ° C. in the oxidation step to obtain a medium particle size SmFe oxide. ..
• Production Example 3 (Preparation of Small Particle Size SmFe Oxide)
• the operation was the same as in Production Example 1 except that 0.14 kg of 18% ammonium tungstate was dropped at the same time as the 15% ammonia solution and the firing temperature was changed to 900 ° C. in the oxidation step. A diameter of SmFe oxide was obtained.
• Example 1 (medium particle size magnetic powder) [Pretreatment process] 100 g of SmFeLa oxide obtained in Production Example 1 was placed in a steel container so as to have a bulk thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature was raised to the pretreatment temperature of 850 ° C. while introducing hydrogen gas, and the mixture was kept as it was for 15 hours. The oxygen concentration was measured by the non-dispersed infrared absorption method (ND-IR) (EMGA-820 manufactured by HORIBA, Ltd.) and found to be 5% by mass. As a result, it was found that the oxygen bound to Sm was not reduced, and 95% of the oxygen bound to Fe was reduced to obtain a black partial oxide.
• ND-IR non-dispersed infrared absorption method
• Example 2 (medium particle size magnetic powder) A magnetic powder was prepared by operating in the same manner as in Example 1 except that the 10 wt% calcium hydroxide aqueous solution was changed to a 10 wt% sodium hydroxide aqueous solution (pH 13.0) in the washing step of Example 1.
• Example 3 (medium particle size magnetic powder) Up to the nitriding step, the same operation as in Example 1 was carried out to obtain a lumpy product which is a nitride.
• a 6% aqueous hydrochloric acid solution was added to 100 parts by mass of the magnetic powder obtained in the above step so as to have 10 parts by mass of hydrogen chloride, and the mixture was stirred for 1 minute. After standing still, the supernatant was drained by decantation. Addition to pure water, stirring and decantation were repeated twice. After solid-liquid separation, vacuum drying was performed at 80 ° C. for 3 hours to obtain a magnetic powder.
• Example 4 (medium particle size magnetic powder) A magnetic powder was prepared by operating in the same manner as in Example 1 except that the calcium hydroxide aqueous solution was changed to a 10 wt% sodium hydroxide aqueous solution (pH 13.0) in the washing step of Example 3.
• Comparative Example 1 Magnetic powder with medium particle size
• a magnetic powder was prepared by operating in the same manner as in Example 1 except that the calcium hydroxide solution was changed to pure water in the washing step of Example 1.
• Example 5 (medium particle size magnetic powder) [Pretreatment process] 100 g of the SmFe oxide obtained in Production Example 1 was placed in a steel container so as to have a bulk thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature was raised to the pretreatment temperature of 850 ° C. while introducing hydrogen gas, and the mixture was kept as it was for 15 hours. The oxygen concentration was measured by the non-dispersed infrared absorption method (ND-IR) (EMGA-820 manufactured by HORIBA, Ltd.) and found to be 5% by mass. As a result, it was found that the oxygen bound to Sm was not reduced, and 95% of the oxygen bound to Fe was reduced to obtain a black partial oxide.
• ND-IR non-dispersed infrared absorption method
• a 6% aqueous hydrochloric acid solution was added to 100 parts by mass of the powder obtained in the nitriding step so that the amount of hydrogen chloride was 4.3 parts by mass, and the mixture was stirred for 1 minute. After standing still, the supernatant was drained by decantation. Addition to pure water, stirring and decantation were repeated twice. After solid-liquid separation, vacuum drying was performed at 80 ° C. for 3 hours to obtain a magnetic powder.
• Examples 6 to 8 and Comparative Examples 2 to 5 (medium particle size magnetic powder) A magnetic powder was prepared by operating in the same manner as in Example 5 except that the amount of acid used was changed to that shown in Table 3.
• Examples 9 to 10 (magnetic powder having a large particle diameter) A magnetic powder having a large particle size was prepared by operating in the same manner as in Example 5 except that the SmFe oxide prepared in Production Example 2 was used and the amount of acid used was changed to that shown in Table 4. Using the magnetic powder obtained in each example, the oxygen content, the nitrogen content, and the particle size distribution were measured by the above-mentioned method. The evaluation results are shown in Table 4.
• Examples 11 to 13 and Comparative Example 6 (magnetic powder having a small particle size) A magnetic powder having a small particle size was prepared by operating in the same manner as in Example 5 except that the SmFe oxide prepared in Production Example 3 was used and the amount of acid used was changed to that shown in Table 5. Using the magnetic powders obtained in each Example and Comparative Example, the oxygen content, nitrogen content, and particle size distribution were measured by the above-mentioned methods. The evaluation results are shown in Table 5.
• Examples 14 to 15 the solid content after solid-liquid separation obtained in the acid treatment step was dehydrated by pressing and then vacuum-dried at 80 ° C. for 3 hours, respectively.
• the same procedure as in Examples 9 and 11 was carried out to prepare a magnetic powder.
• the water content of the solid content after dehydration treatment, the oxygen content, the nitrogen content, and the particle size distribution of the obtained magnetic powder were measured by the above-mentioned method.
• the evaluation results are shown in Table 6 together with the evaluation results of the magnetic powders prepared in Examples 9 and 11.
• Example 14 From the results in Table 6, in Example 14, the water content could be significantly reduced by performing the dehydration treatment, and the oxygen content in the obtained magnetic powder could be further reduced as compared with Example 9. Further, also in Example 15, the water content could be significantly reduced, and the oxygen content in the obtained magnetic powder could be further reduced as compared with Example 11.
• the anisotropic magnetic powder obtained by the production method of the present invention is an anisotropic magnetic powder having a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high residual magnetic flux density. Can be suitably applied to.

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