JP5267665B2 - Magnetic powder manufacturing method and manufacturing apparatus thereof - Google Patents

Description

  The present invention relates to a magnetic powder manufacturing method and a manufacturing apparatus therefor, and more particularly to a magnetic powder manufacturing method and a manufacturing apparatus suitable for manufacturing a sintered magnet having excellent magnetic properties.

Permanent magnets (rare earth magnets) obtained by sintering magnetic powders such as Nd—Fe—B have been used in recent years because of their excellent magnetic properties. Permanent magnets such as Nd ₂ Fe ₁₄ B system in which such powder is sintered as the range of application of magnets has expanded to respond to environmental problems, including home appliances, industrial equipment, electric vehicles, and wind power generation. There is a demand for higher performance.

As an index of the performance of the magnet, the magnitude of the residual magnetic flux density and the coercive force can be given. For example, increasing the residual magnetic flux density of a Nd—Fe—B based sintered magnet can be achieved by increasing the volume fraction of the Nd ₂ Fe ₁₄ B compound and improving the degree of crystal orientation. Various process improvements have been made to achieve this.

On the other hand, in order to increase the coercive force, it can be achieved by various approaches, such as a method of refining crystal grains, a method using a composition alloy with an increased amount of Nd, or a method of adding an effective element. Can do. In particular, among these approaches, the most common technique is to increase the coercive force by using a composition alloy in which a part of Nd is substituted with Dy or Tb. Specifically, by substituting these elements for Nd in the Nd ₂ Fe ₁₄ B compound, the anisotropic magnetic field of the compound increases, thereby increasing the coercive force.

  However, the amount of Dy used greatly exceeds the natural abundance ratio of rare earth elements, and the estimated burial amount of deposits that are currently being developed is small. Therefore, the necessity of element strategy has been recognized. Tb can be cited as a rare earth element that exhibits the same effect as Dy for the purpose of achieving a high coercive force, but the abundance of Tb is much lower than Dy. To date, the coercive force of Nd—Fe—B based sintered magnets has been remarkably improved as compared with the early stage of development by adding such a trace amount of elements and searching for heat treatment conditions. Accordingly, in view of such an improvement effect, it is unavoidable to reduce the amount of Dy or Tb added as a trace element.

  On the other hand, substitution with Dy or Tb reduces the saturation magnetic polarization of the compound. Therefore, as long as the holding force is increased by the above method, a decrease in the residual magnetic flux density cannot be avoided. Furthermore, since Dy and Tb are expensive and have a small reserve, there is a high risk of using them as resources. Therefore, it is desirable to reduce the amount used as much as possible.

From such a point of view, a technique is employed in which Dy and Tb are concentrated only at the grain boundaries of the magnet or in the vicinity thereof. For example, a two-alloy method is proposed in which a powder in which Dy and Tb are contained in a larger amount than the main phase (Nd ₂ Fe ₁₄ B) and a powder in which these elements are not mixed are sintered in advance (for example, a patent) Reference 1). As another method, a method is proposed in which a fluorine compound such as Dy or Tb is applied to the surface of a sintered magnet, and Dy or Tb is diffused and penetrated into grain boundaries near the surface by heat treatment (for example, Patent Documents). 2).

On the other hand, as a method of reducing the amount of use by concentrating Dy and Tb at the grain boundaries of the magnet and extending the region to the center of the formed magnet having a thickness of several millimeters, sintering powder is used. A method of coating with Dy or Tb in advance is also conceivable.
JP-A-6-207203 JP 2006-303433 A

  However, the particle size of the hard magnetic powder for sintering rare earth magnets is about 3 to 5 μm, and these transition elements (transition metals) and the like are magnetic powder having a thickness of several nm to several tens of nm. It is extremely difficult to uniformly coat around.

  For example, among transition metals, rare earth metals easily react with moisture, and basically, it is difficult to coat rare earth metals around powders in a wet environment. In addition, magnetic powders of about 3 to 5 μm tend to aggregate with each other, forming particles solidified by these tens of magnetic powders, and uniformly covering the surface of each magnetic powder with a transition element It's not easy.

  Considering this point, even if we try to coat this hard magnetic powder with a metal such as a transition metal in a dry manner, due to the nature of rare earth metal, it is a fine powder with a particle size of 3-5 μm. It is difficult to avoid surface oxidation of the powder. And when a sintered magnet is molded using magnetic powder whose surface has been oxidized, the magnetic properties are lowered. Moreover, even if it carries out by a dry type, the aggregation of the magnetic powder mentioned above cannot be avoided.

  The present invention has been made in view of the above-described problems, and the magnetic properties of a sintered magnet can be improved by uniformly coating the surface of a hard magnetic powder with a metal such as a transition metal. It aims at providing the manufacturing method of a powder, and the manufacturing apparatus of a magnetic powder.

  In order to achieve the above object, the inventors have made extensive studies and as a principle of attaching a metal such as a transition metal to the surface of the hard magnetic powder, pay attention to the thermophoresis phenomenon and use this phenomenon. As a result, a new finding has been obtained that a small amount of metal can be uniformly attached (coated) to the surface of the magnetic powder.

  The present invention is based on the inventors' new knowledge, and a method for producing a magnetic powder according to the present invention includes a step of aerosolizing a hard magnetic powder with an inert gas, and a metal under an inert gas atmosphere. Heating and vaporizing, and attaching the vaporized metal to the surface of the aerosolized hard magnetic powder.

  According to the present invention, an aerosol of hard magnetic powder is generated, and the aerosolized hard magnetic powder is dispersed in an inert gas (aerosol). Then, vaporized metal is attached to the surface of the dispersed magnetic powder in an inert gas atmosphere. At this time, the vaporized metal, that is, the vapor particles of the metal has a higher temperature than the hard magnetic powder. Since there is a large thermal gradient between the hard magnetic powder and the vapor particles, the vapor particles having a higher temperature than the hard magnetic powder exert a force (thermophoretic force) to be attracted to the hard magnetic powder having a lower temperature. . As a result, the vapor particles are densely and firmly adsorbed (coated) on the surface of the magnetic powder. In addition, since the vaporized metal (vapor particles) is several tens of nanometers and smaller than the hard magnetic powder, a small amount of vapor particles are uniformly distributed on the surface of the hard magnetic powder as compared with the conventional method. Can be attached.

  Here, “aerosol” as used in the present invention refers to a substance in which a large number of hard magnetic powders are floated in a gas, and aerosolization means that a number of hard magnetic powders are floated in a gas. The “hard magnetic powder” according to the present invention is a powder that does not retain magnetization when a magnetic field is removed after applying a magnetic field, and is a powder for producing a permanent magnet. On the other hand, after applying a magnetic field, the powder that remains magnetized even if the magnetic field is removed and the magnetized state is maintained is soft magnetic powder.

In addition, examples of the inert gas include He, N ₂ , and Ar gases, and are particularly limited as long as they do not oxidize the hard magnetic powder and the vaporized metal (vapor particles). is not.

  Moreover, the deposition method is not particularly limited as long as the vaporized metal can be adhered to the surface of the aerosolized hard magnetic powder. However, more preferably, in the attaching step, the aerosolized hard magnetic powder and the vaporized metal are carried in an air stream, and the vaporized metal is allowed to collide with the aerosolized hard magnetic powder. More preferably, the flow velocity of the vaporized metal air flow is more preferably equal to or higher than the flow velocity of the aerosolized hard magnetic powder.

  According to the present invention, as described above, the vaporized metal (vapor particles) is several tens of nanometers as described above, and when the vapor particles are carried in an air stream, compared to the hard magnetic powder. Easily accelerated. Thereby, the vaporized metal can be collided with the aerosolized hard magnetic powder with higher energy. In this way, the vapor particles can be more firmly and densely attached to the surface of the hard magnetic powder. In the present invention, “the aerosolized hard magnetic powder is placed on the airflow” means that the aerosol of the hard magnetic powder itself is transported.

  The metal deposited on the hard magnetic powder for use in the method for producing magnetic powder of the present invention is preferably a transition metal or an alloy metal thereof. A more preferable transition metal is a rare earth metal (third transition element (4f transition element)), and among these, Dy, Tb, or Pr is more preferable. Since these rare earth metals are elements having a higher anisotropic magnetic field than other metals, the magnets produced thereby can improve the magnetic properties. The metal to be deposited may be an alloy metal of Dy, Tb or Pr and Nd. These alloy metals are easy to dissolve into the grain boundaries as compared with Dy, Tb or Pr alone.

  In addition, other metals to be deposited include Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Co, Ga, Ge, Zr, Nb, Mo, Pd, Examples thereof include Ag, Cd, Sn, Sb, Hf, Ta, W, and alloy metals thereof. Among these, basically, a highly anisotropic metal or a nonmagnetic metal is desirable, and Al and Cu are more preferable. Both Al and Cu are easily melted into a magnet during sintering, and can form a Nd-rich phase and a low-melting eutectic alloy to improve the wettability at the grain boundary. Since it can be made discontinuous, the magnetic properties can be improved.

Here, the hard magnetic powder is not particularly limited as long as it can produce a permanent magnet by sintering. For example, R ₂ Tm ₁₄ (B, C) ₁ series Examples thereof include magnetic powder (R is a rare earth metal, Tm is a transition metal excluding the rare earth metal, etc.). Examples of the rare earth metal include Sc, Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Yb, and Lu. Moreover, as other transition metals excluding rare earth metals, Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Co, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, W, etc. can be mentioned. More preferably, the hard magnetic powder is an Nd—Fe—B based magnetic powder. According to the present invention, such a magnetic powder has a higher holding force and excellent magnetic properties than other combinations. The magnetic powder thus produced is suitable for use as a magnet by sintering.

  As the present invention, an apparatus for producing magnetic powder suitable for producing the above-described magnetic powder is disclosed below. An apparatus for producing a magnetic powder according to the present invention includes an aerosol chamber for aerosolizing a hard magnetic powder with an inert gas, a vapor generation chamber for heating and vaporizing a metal in an inert gas atmosphere, and the vaporized metal It is characterized by comprising: an attaching portion for attaching the metal to the surface of the aerosolized hard magnetic powder; and a discharge chamber for releasing the hard magnetic powder to which the metal is attached.

  According to the present invention, the hard magnetic powder can be aerosolized with an inert gas in the aerosol chamber, while the metal can be vaporized by heating in an inert gas atmosphere in the vapor generation chamber. Then, the vaporized metal can be adhered to the surface of the aerosolized hard magnetic powder at the adhesion portion, and the hard magnetic powder with the metal adhered can be discharged in the discharge chamber. At this time, the vaporized metal can be uniformly adsorbed on the surface of the hard magnetic powder dispersed in the aerosol by the thermophoretic phenomenon described above.

  The apparatus for producing the magnetic powder according to the present invention is not particularly limited as long as the vaporized metal can be adhered to the surface of the aerosolized hard magnetic powder.

  However, more preferably, in the magnetic powder manufacturing apparatus according to the present invention, the adhering portion includes a main transfer pipe connected to the aerosol chamber, and a sub-transfer pipe connected to the vapor generation chamber, The sub-transport pipe is connected to the main transport pipe so that the vaporized metal can adhere to the hard magnetic powder.

  According to the present invention, the aerosolized hard magnetic powder is carried by the main carrier tube on the air stream and conveyed toward the discharge chamber (the aerosol itself is conveyed toward the discharge chamber), and the sub-carrier tube is used for vaporization. The converted metal (vapor particles) can be carried in an air stream and conveyed toward the discharge chamber. The sub-transport pipe is connected to the main transport pipe so that the vapor particles can adhere to the hard magnetic powder, so that the vapor particles can collide with the aerosolized hard magnetic powder. Furthermore, it is possible to set the flow velocity of the vapor particles to a flow velocity higher than that of the aerosolized hard magnetic powder. In this way, the vapor particles can be more firmly and densely attached to the surface of the hard magnetic powder.

  Further, the number of the steam generation chambers is not particularly limited, but more preferably, the magnetic powder manufacturing apparatus according to the present invention includes the steam generation chamber and the sub-transport pipe connected to the steam generation chamber. And the plurality of sub-transport pipes are connected to the outer periphery of the main transport pipe at equal intervals.

  According to the present invention, a plurality of pairs of steam generation chambers and sub-transport pipes are provided, and each sub-transport pipe is connected (flighted) to the outer circumference of the main transport pipe at equal intervals. Vapor particles can be uniformly and uniformly attached to the surface of the hard magnetic powder contained in the aerosol. Further, since different metals can be vaporized in the plurality of vapor generation chambers, a multifunctional magnetic powder can be produced.

  The magnetic powder manufacturing apparatus according to the present invention more preferably includes a tube heating unit that heats the sub-transport tube. According to the present invention, since the sub-transport pipe is heated by the pipe heating section, it is possible to prevent vapor particles from adhering to the inner wall surface of the transport pipe.

  Further, the aerosol chamber and the steam generation chamber of the manufacturing apparatus according to the present invention are provided with a supply pipe for supplying the inert gas, and the supply pipe removes oxygen contained in the inert gas. More preferably, an oxygen removing device is provided. According to the present invention, the oxidation of the hard magnetic powder and the vapor particles can be suppressed by reducing the oxygen concentration contained in the inert gas. In particular, vapor particles of rare earth metals are preferable because they are easily oxidized.

  According to the present invention, by uniformly coating the surface of the hard magnetic powder with a metal such as a transition metal, it is possible to improve the magnetic characteristics of the sintered magnet using this powder.

It is a whole block diagram of the manufacturing apparatus of the magnetic powder which concerns on 1st embodiment. It is a schematic diagram of the magnetic powder manufactured by the manufacturing method of the magnetic powder which concerns on 1st embodiment. The figure for demonstrating the thermophoresis phenomenon in the manufacturing method of the magnetic powder shown in FIG. It is a figure for demonstrating the manufacturing apparatus of the magnetic powder which concerns on 2nd embodiment, (a) is a whole block diagram of the manufacturing apparatus of magnetic powder, (b) is b part shown to (a). An enlarged view and (c) are AA 'sectional views of (b). The figure which showed the relationship between Dy content of Examples 1, 2 and Comparative Examples 1-3, and holding power. The figure which showed the relationship between Dy content of Examples 1, 2 and Comparative Examples 1-3, and the maximum energy product.

DESCRIPTION OF SYMBOLS 11 ... Hard magnetic powder supply source, 12 ... Powder supply piping, 13a ... Oxygen removal apparatus, 13b ... Oxygen removal apparatus, 16 ... Inert gas piping, 17 ... Inert gas piping, 18 ... Cooler, 20 ... Aerosol chamber, DESCRIPTION OF SYMBOLS 21 ... Aerosol production | generation part, 21a ... Release port, 25 ... Exhaust pipe, 30 ... Steam generation chamber, 32 ... Metal melting furnace, 33 ... Heating device, 40 ... Adhesion part, 40A ... Adhesion part, 41 ... Main conveyance pipe, 42 ... Sub-transport pipe, 44 ... Transport pipe heater, 45: Merge section, 45A ... Merge section, 48 ... Transport pipe, 49 ... Nozzle section, 50 ... Release chamber, 53: Receiving section, 58 ... Inert gas pipe, 100 ... Magnetic powder production equipment, 100A ... Magnetic powder production equipment, AG ... Aerosol, P ... Hard magnetic powder, PV ... Magnetic powder, V ... Vapor particles (vaporized metal)

  Below, with reference to drawings, the manufacturing device of magnetic powder concerning the present invention and the manufacturing method of magnetic powder using this manufacturing device are explained based on two embodiments.

  FIG. 1 is an overall configuration diagram of a magnetic powder manufacturing apparatus according to a first embodiment for suitably performing the magnetic powder manufacturing method according to the present invention. FIG. 2 is a schematic view of a magnetic powder produced by the magnetic powder production method according to the first embodiment.

  As shown in FIG. 1, the magnetic powder manufacturing apparatus 100 according to the present embodiment includes at least an aerosol chamber 20, a vapor generation chamber 30, an attachment portion 40, and a discharge chamber 50.

  The aerosol chamber 20 is a chamber for aerosolizing the hard magnetic powder with an inert gas. The aerosol chamber 20 is provided with a jet mill or the like via the powder supply pipe 12 to supply the hard magnetic powder P into the chamber. It is connected to a hard magnetic powder supply source 11 having both a pulverizer and an air classifier.

  Further, the aerosol chamber 20 is provided with an aerosol generating unit 21 that aerosolizes the hard magnetic powder P supplied into the chamber, that is, generates an aerosol of the hard magnetic powder P below the chamber. The aerosol generation unit 21 is connected to the inert gas pipe 16 and is disposed in the aerosol generation unit 21 so as to be able to release the inert gas G3 toward the bottom of the room in order to aerosolize the hard magnetic powder. A plurality of discharge ports 21a are formed. The aerosol generation unit 21 may be, for example, a mechanism used in the aerosol deposition technique. A mechanism for stirring the hard magnetic powder P with the inert gas G3 or a container containing the hard magnetic powder P may be used. A mechanism for swinging can be used.

  The inert gas pipe 16 is connected to an oxygen removing device 13a that removes oxygen gas contained in the inert gas G3 and a gas cooler 18 that cools the inert gas G3. Furthermore, the aerosol chamber 20 is connected to an inert gas pipe 17 that replaces the gas in the chamber with the inert gas G2, and the inert gas pipe 17 similarly contains oxygen gas contained in the inert gas G2. An oxygen removing device 13a for removal is connected.

In addition, the inside of the aerosol chamber 20 is set to be pressurized to a pressure (120,000 Pa or less) higher than that of the discharge chamber 50 described later by the inert gas G2, and the aerosol chamber 20 and the discharge chamber 50 are separated from each other. Due to the differential pressure, the aerosolized hard magnetic powder in the aerosol chamber 20 can be conveyed to the discharge chamber 50. Further, the inert gases G2, G3 supplied into the aerosol chamber 20 are gases such as He, N ₂ , or Ar, and it is desirable that these gases have a purity of 99.999% or more.

It is desirable that the oxygen concentration in the gas be at least 1.0 × 10 ⁻⁶ atmO ₂ or less in terms of partial pressure. This partial pressure is preferably as low as possible, and it is effective to set it to 1.0 × 10 ⁻⁷ atmO ₂ or less via the oxygen removing device 13a or 13b, and 1.0 × 10 ⁻³⁰ if necessary. atmO may reduce the oxygen concentration to _2.

  On the other hand, the upper part of the aerosol chamber 20 is connected to a main transport pipe 41 that constitutes an attaching portion 40 described later, and this main transport pipe 41 is a pipe that transports the aerosolized hard magnetic powder P.

  The steam generation chamber 30 is a chamber for heating and vaporizing rare earth metals such as Dy, Tb, or Pr, and other metals such as transition metals. Here, Dy is used as the rare earth metal. The steam generation chamber 30 includes a metal melting furnace 32 and a heating device 33 that heats and melts the metal in the metal melting furnace 32. The heating device 33 is not particularly limited as long as the metal in the metal melting furnace 32 can be melted. For example, examples of the heating method include heat ray melting, high frequency melting, arc melting, laser heating melting, and electron beam melting.

  Similarly to the aerosol chamber 20, the vapor generation chamber 30 is pressurized to a pressure higher than that of the discharge chamber 50, which will be described later, by the inert gas G 2, and is pressurized to a pressure equal to or higher than the pressure of the aerosol chamber 20. Is set to In order to maintain such a pressure, a shutter for making the inside of the aerosol chamber 20 a sealed space may be provided.

In this manner, the vaporized metal in the steam generation chamber 30 can be transferred to the discharge chamber 50 due to the differential pressure between the steam generation chamber 30 and the discharge chamber 50. In addition, since the pressure is higher than the aerosol chamber, the flight speed of the vaporized metal (evaporated particles) V flying in the sub-transport pipe 42 is higher than the flight speed of the hard magnetic powder P flying in the main transport pipe 41. Can also be faster. As a result, it is possible to coat the surface of the hard magnetic powder P with stronger vapor particles V by causing the vapor particles V to strongly collide with the hard magnetic powder P at the junction 45. The pressure of the steam generating chamber 30, the following inert gas atmosphere 120000Pa, the oxygen concentration of the gas, it is desirable to at least 1.0 × ¹⁰ -8 atm0 ₂ or less at a partial pressure.

  The aerosol chamber 20 and the vapor generation chamber 30 are connected to a vacuum exhaust system including a vacuum pump via an exhaust pipe 25. Thereby, the gas in the aerosol chamber 20 and the vapor generation chamber 30 can be easily replaced with the inert gas G2.

  The adhesion part 40 is a part which adheres the vaporized metal V to the surface of the aerosolized hard magnetic powder P. The attachment unit 40 includes a main transport pipe 41 connected to the upper part of the aerosol chamber 20 and a sub-transport pipe 42 connected to the upper part of the vapor generation chamber 30. Further, the adhering portion 40 forms a confluence portion 45 in which the sub conveying pipe 42 is connected to the main conveying pipe 41 so that the vaporized metal V can adhere to the hard magnetic powder P. Further, a nozzle portion 49 extending from below the discharge chamber 50 to the inside thereof is formed further downstream of the merge portion 45.

  The discharge chamber 50 is a chamber for discharging (jetting) hard magnetic powder (magnetic powder) PV to which metal is attached. Here, as described above, the discharge chamber 50 has such a size that the magnetic powder PV naturally falls without colliding with the indoor wall surface due to the differential pressure between the aerosol chamber 20 and the vapor generation chamber 30. The discharge chamber 50 is provided with a receiving portion 53 for receiving the dropped magnetic powder PV.

Further, the discharge chamber 50 is connected to the vacuum exhaust system via the exhaust pipe 25 in the same manner as the aerosol chamber 20 and the vapor generation chamber 30, whereby the discharge chamber 50 is connected to 1.0 × 10 ^−6. A vacuum of atm or less is desirable. Also, like the aerosol chamber 20 and the steam generating chamber 30, it may be a room in an inert gas atmosphere, in this case, an inert gas, to an oxygen concentration of 1.0 × 10 ^-7 atm0 ₂ below Is effective. Further, the discharge chamber 50 is connected to a gas circulation system via a gas circulation pipe 54 in order to reuse the inert gas.

A method for producing magnetic powder PV using such a magnetic powder production apparatus 100 will be described below. First, the aerosol chamber 20 and the vapor generation chamber 30 are evacuated, and an inert gas is introduced into these chambers via the oxygen removing device 13b, whereby these chambers are made an inert gas atmosphere. Here, the pressure in the aerosol chamber 20 and the vapor generation chamber 30 is 120,000 Pa or less, the oxygen concentration is 1.0 × 10 ⁻⁷ to 10 ⁻⁸ atmO ₂ or less, and the pressure in the vapor generation chamber 30 is the aerosol. The pressure in the chamber 20 is increased. On the other hand, the inside of the discharge chamber 50 is evacuated to a pressure lower than that of the aerosol chamber 20 and the vapor generation chamber 30. At this time, if there is a shutter in each chamber, this is used to achieve the set pressure.

Next, the Nd—Fe—B system (Nd ₂ Fe ₁₄ B) of which the average particle size is classified into a range of 1 to 10 μm from a hard magnetic powder supply source 11 such as a jet mill through a powder supply pipe 12. The hard magnetic powder P is supplied into the aerosol chamber 20. On the other hand, after the oxygen gas contained in the inert gas G3 is removed by the oxygen removing device 13a, the inert gas G3 is cooled by the gas cooler 18, cooled to a temperature of about 20 ° C., and the cooled inert gas G3 is removed. Introduced into the aerosol generator 21.

  As a result, the cooled inert gas G3 is discharged from the plurality of discharge ports 21a of the aerosol generating unit 21 toward the bottom of the aerosol chamber 20, and the hard magnetic powder P at the bottom is shaken and stirred, and the aerosol is discharged. Floating in the chamber 20, an aerosol of magnetic particles is generated (the hard magnetic powder P is aerosolized). On the other hand, the rare earth metal Dy disposed in the metal melting furnace 32 in the steam generation chamber 30 is heated by the heating device 33 to be vaporized.

  The aerosolized hard magnetic powder P is transported in the main transport pipe 41 toward the discharge chamber 50 due to a differential pressure with the discharge chamber 50. Similarly, the vaporized metal (vapor particles) V is also transported in the sub transport pipe 42 toward the discharge chamber 50.

  Specifically, the hard magnetic powder P that has been aerosolized by the main transport pipe 41 is carried on the airflow and transported toward the discharge chamber 50 (the aerosol itself is transported toward the discharge chamber 50), and the sub-transport pipe By 42, the vapor particles V are carried on the airflow and conveyed toward the discharge chamber 50. And since the sub conveyance pipe 42 is connected to the main conveyance pipe 41 so that the vapor particle V can adhere to the hard magnetic powder P, the vapor particle V is converted into the vapor particle V at the junction 45 of the adhesion part. Can collide with.

  Here, the aerosolized hard magnetic powder P is cooled by the cooler 18, while the vapor particles V are vaporized by heating, and therefore, as shown in the schematic diagram of FIG. Vapor particles V having a size of about 1 nm to 100 nm can be attached to the surface of the hard magnetic powder P classified in the range of 1 to 10 μm.

  Specifically, as shown in FIG. 3, the vapor particles V collide with the hard magnetic powder P due to its thermal motion under the condition that the hard magnetic powder P is suspended in the gas. In particular, since there is a large thermal gradient between the hard magnetic powder P and the vapor particles V, the vapor particles V having a higher temperature than the hard magnetic powder P have a force so as to be attracted to the hard magnetic powder P having a low temperature. (Thermophoretic force) is exerted. As a result, the vapor particles V are densely and firmly attached (coated) to the surface of the hard magnetic powder P.

  Further, since the aerosolized hard magnetic powder P has a particle size on the order of several μm, and the vapor particles V have a particle size on the order of several tens of nm, the vapor particles V are smaller than the hard magnetic powder P. Therefore, it is easy to get on the airflow and is accelerated. That is, the flight speed of the vapor particles V is faster than the flight speed of the hard magnetic powder P due to the above-described differential pressure in each chamber and the size of the particles. Thereby, the vapor particles V can be densely and firmly attached to the surface of the hard magnetic powder P. In this way, the vapor particles V adhere to the surface of the hard magnetic powder P as shown in FIG.

  Thus, the hard magnetic powder (hard magnetic powder coated with Dy particles) PV to which the vapor particles V adhere is discharged into the discharge chamber 50 through the nozzle portion 49, and the receiving portion 53 has a magnetic property. Powder PV and vapor particles V are deposited. And these can be classified using an airflow classifier, and only magnetic powder PV can be obtained.

  The magnetic powder (hard magnetic powder coated with Dy particles) PV thus obtained is molded at a predetermined pressure while being oriented in a magnetic field. Then, the compact can be sintered in a sintering furnace under an inert gas atmosphere, and then subjected to a predetermined heat treatment to produce a magnet. The magnet obtained in this way can obtain a holding force more than conventional magnets by using a rare earth metal such as Dy slightly compared to the conventional magnets.

  FIG. 4 is a diagram for explaining a magnetic powder production apparatus according to the second embodiment, (a) is an overall configuration diagram of the magnetic powder production apparatus, and (b) is a diagram of (a). The enlarged view of the b section shown, (c) is an AA ′ cross-sectional view of (b). The manufacturing apparatus according to the second embodiment is mainly different from the apparatus according to the first embodiment in that a plurality of steam generation chambers are provided and the configuration of the adhesion portion connected to these steam generation chambers. Is different. That is, the difference is that a plurality of sets of steam generation chambers and sub-transport pipes are provided. Only differences from the first embodiment will be described below.

  As shown in FIG. 4, the magnetic powder manufacturing apparatus 100 </ b> A according to the second embodiment includes three steam generation chambers 30, 30, 30. Each steam generation chamber 30 has the same configuration as the steam generation chamber shown in the first embodiment. And the sub conveyance pipe 42 of 40 A of adhesion parts is connected to the upper part of the steam generation chamber 30. As shown in FIG. Each sub-transport pipe 42 is connected to the main transport pipe 41 at the junction 45A so that the vaporized metal V can adhere to the hard magnetic powder P.

  Further, in the junction portion 45 </ b> A, the three sub transport pipes 42 are connected to the outer periphery of the main transport pipe 41 at equal intervals. As described above, in the junction 45A, the sub-transport pipes 42 are connected to the outer periphery of the main transport pipe 41 at equal intervals, so that the hard magnetic powder contained in the aerosol AG passing (flighting) the main transport pipe 41. Vapor particles V can be uniformly and uniformly attached to the surface of P.

  Further, the sub-transport pipe 42 that transports the vaporized metal (vapor particles V) of the adhering portion 40 and the transport pipe (a part of the main transport pipe) that transports the magnetic powder PV to which the vapor particles V are attached, A conveyance tube heater (tube heating unit) 44 is disposed. By heating these tubes with the transfer tube heater 44, it is possible to prevent the vapor particles V from adhering to the inner wall surfaces of these transfer tubes.

  In the present embodiment, the discharge chamber 50 is connected to an inert gas pipe 58 that replaces the room gas with the inert gas G2, and the inert gas pipe 17 is similarly included in the inert gas G2. An oxygen removing device 13b for removing the oxygen gas is connected. Thereby, the inert gas can be filled in the discharge chamber 50.

  Below, based on an Example, the manufacturing method of the magnetic powder of this invention is demonstrated. The following examples are examples in which magnetic powder was produced using the magnetic powder device shown in the first embodiment shown in FIG.

Example 1
Nd, Al, Fe, Cu having a purity of 99.5% or more and ferroboron are dissolved at high frequency in an Ar gas atmosphere, and then Nd is 13.5 atomic%, Al is 0.5 atomic%, and Cu is 0.3 A strip cast of an alloy consisting of atomic%, B of 5.8 atomic%, and the balance of Fe and inevitable impurities was manufactured. This alloy was occluded with hydrogen at 0.1 MPa, dehydrated at 520 ° C., and cooled and sieved to produce Nd—Fe—B magnetic coarse powder (hard magnetic coarse powder) of 50 mesh or less.

Thereafter, the average particle size was pulverized to 4.2 μm with a jet mill, and the hard magnetic coarse powder was fed into an aerosol chamber of 1.0 × 10 ⁻⁶ atm Ar gas. In addition, after exhausting the gas in the chamber of the aerosol chamber and making the chamber a vacuum degree of 1.0 × 10 ⁻¹¹ atm in advance, oxygen is increased to a concentration of 1.0 × 10 ⁻¹¹ atmO ₂ with a zirconia oxygen pump. The residual gas in the room was replaced with Ar gas having a reduced concentration. And Ar gas adjusted so that gas temperature might be set to 20 degreeC with the cooler was used as gas for aerosol, setting the pressure in this room to 1.0x10 < ^-6 > atm. Then, the Nd—Fe—B based magnetic powder in the room was rocked and stirred to aerosolize the Nd—Fe—B based magnetic powder (to produce an Nd—Fe—B based magnetic particle aerosol).

On the other hand, in the vapor generation chamber, similarly to the aerosol chamber, the inside of the chamber was evacuated to 1.0 × 10 ⁻¹¹ atm, and then the O ₂ concentration was reduced to a concentration of 1.0 × 10 ⁻¹¹ atmO ₂ with a zirconia oxygen pump. Was replaced with Ar gas with reduced pressure, and the pressure in the room was set to 1.0 × 10 ⁻⁵ atm.

And the purity 99.9% Dy put into the carbon crucible was melted at 1077 ° C. by high-frequency melting with a high-frequency heating device to generate Dy vapor (Dy nano-vapor particles: average particle size 20 nm). Here, Dy has a melting point of 844 ° C. under a pressure environment of 1.0 × 10 ⁻⁵ atm.

  The heater shown in FIG. 1 is set so that the temperature of at least the inner wall of the sub-transport pipe from the steam generation chamber shown in FIG. 1 to the adhering portion (region until the vapor metal is covered) becomes 844 ° C. or higher. And heated. This is to prevent the Dy nano vapor particles from adhering and laminating on the inner wall surfaces of the sub-transport pipe and the merging portion.

Further, the vacuum chamber was similarly evacuated to 1.0 × 10 ⁻¹¹ atm, and then Ar ₂ was reduced to a concentration of 1.0 × 10 ⁻¹¹ atmO ₂ with a zirconia oxygen pump. The interior of the room was replaced with gas, and the internal pressure was set to 1.0 × 10 ⁻⁷ atm.

  In such a state, the shutter that shuts off the communication between the aerosol chamber, the vapor chamber, and the discharge chamber is opened. At this time, the hard magnetic powder in the aerosol chamber flies through the main conveyance pipe and travels toward the discharge chamber due to the differential pressure between the aerosol chamber and the discharge chamber. On the other hand, the Dy nano vapor particles in the vapor generation chamber also fly in the sub-transport pipe due to the differential pressure between the vapor generation chamber and the discharge chamber, and go to the discharge chamber.

  At this time, due to the thermophoresis phenomenon, the Dy nano vapor particles collide or adsorb with the hard magnetic powder having a temperature lower than that, and adhere to cover the surface of the hard magnetic powder.

  Furthermore, as described in the description of FIG. 2 above, the Nd—Fe—B based magnetic powder has an average particle diameter of 4.2 μm in this example, and the Dy nano vapor particles have a diameter of about 20 nm. Since the diameter is about 200 times larger, the vapor particles are easier to ride on the airflow and are more easily accelerated. And when the differential pressure of each chamber mentioned above is provided and the size of the particle is taken into consideration, the flight speed of the Dy nano vapor particles at the time of collision and reaching the discharge chamber is the flight speed of the Nd-Fe-B magnetic powder. The relative speed is estimated to be 100 m / s or higher. Due to such a relative speed, the Dy nano vapor particles are densely attached and coated on the surface of the Nd—Fe—B based magnetic powder.

  The hard magnetic powder (magnetic powder) to which the Dy nano vapor particles are attached in this manner is discharged into the discharge chamber through the nozzle portion and allowed to cool, so that the Dy nano vapor particles attached to the hard magnetic powder are converted into the Dy nano particles. It was. The magnetic powder and the Dy nanoparticles that did not adhere to the magnetic powder were deposited on the receiving part in the discharge chamber, and these were classified by an airflow classifier to obtain only the magnetic powder.

The hard magnetic powder coated with the Dy nanoparticles thus obtained was molded at a pressure of 100 MPa while being oriented in a magnetic field of 15 kOe in an Ar gas atmosphere of 1.0 × 10 ⁻¹¹ atmO _2. It compacted in the mold. Next, this compact was put into a sintering furnace under an Ar gas atmosphere of 1.0 × 10 ⁻¹¹ atmO ₂ and sintered at 1067 ° C. for 2 hours. Furthermore, a heat treatment was performed under the treatment conditions of 820 ° C. for 5 hours, and subsequently, a heat treatment was performed for 520 ° C. for 1.5 hours to produce a magnet block.

  The magnet block was processed to a size of 5 × 5 × 2 mm with a diamond cutter, and then magnetic measurement was performed with a BH tracer (VSM (Lakeshore 7400)). The measurement contents are residual magnetization Br, coercive force Hcj, and maximum energy product (BH) max. The results are shown in Table 1 and FIGS.

(Example 2)
A magnet block was manufactured in the same manner as in Example 1. The difference from Example 1 is that Nd, Al, Fe, Cu, Dy having a purity of 99.5% or more and ferroboron are dissolved at high frequency in an Ar gas atmosphere, and then Nd is 11.5 atomic% and Dy is , 5.0 atomic%, Al 0.5 atomic%, Cu 0.3 atomic%, B 5.8 atomic%, the balance being the only alloy strip cast made of Fe and inevitable impurities It is. Then, as in Example 1, the remanent magnetization Br, the coercive force Hcj, and the maximum energy product (BH) max of the manufactured magnetic block were measured. The results are shown in Table 1 and FIGS.

(Comparative Example 1)
A magnetic block was manufactured in the same manner as in Example 1. The difference from Example 1 is that the Dy vapor particles were not adhered. Specifically, the average particle size was pulverized to 4.2 μm with a jet mill, and the same conditions as in Example 1 were applied. A magnetic block was manufactured by sintering the magnetic powder after molding. Then, as in Example 1, the remanent magnetization Br, the coercive force Hcj, and the maximum energy product (BH) max of the manufactured magnetic block were measured. The results are shown in Table 1 and FIGS.

(Comparative Example 2)
A magnetic block was produced in the same manner as in Example 2. The difference from Example 2 is that Dy vapor particles were not adhered. Specifically, the average particle size was pulverized to 4.2 μm with a jet mill, and the hard particles were subjected to the same conditions as in Example 2. A magnetic block was manufactured by sintering the magnetic powder after molding. Then, as in Example 1, the produced magnetic remanent magnetization Br, coercive force Hcj, and maximum energy product (BH) max were measured. The results are shown in Table 1 and FIGS.

(Comparative Example 3)
A magnetic block was manufactured in the same manner as in Example 1. The difference from Example 1 is that Dy vapor particles are not adhered, and instead, the following Dy surface diffusion method is used. Specifically, the average particle size was pulverized to 4.2 μm with a jet mill, and this hard magnetic powder was molded under the same conditions as in Example 1.

The hard magnetic powder coated with the Dy nanoparticles thus obtained was molded at a pressure of 100 MPa while being oriented in a magnetic field of 15 kOe in an Ar gas atmosphere of 1.0 × 10 ⁻¹¹ atmO _2. It compacted in the mold. Next, this compact was put into a sintering furnace under an Ar gas atmosphere of 1.0 × 10 ⁻¹¹ atmO ₂ and sintered at 1067 ° C. for 2 hours, and the magnet block was dimensioned by a diamond cutter to 5 × 5 × 2 mm. Processed into a magnet.

Subsequently, the magnet was immersed for 30 seconds while applying ultrasonic waves to a turbid liquid in which dysprosium fluoride with an average particle size of 10 μm was mixed with ethanol at a mass fraction of 50%, and placed in a vacuum desiccator. And dried for 30 minutes in an exhaust atmosphere. Further, the magnet covered with dysprosium fluoride was heat-treated at 800 ° C. for 10 hours in an Ar gas atmosphere, and further subjected to aging treatment at 510 ° C. for 1 hour to rapidly cool the magnet. Then, as in Example 1, the produced magnetic remanent magnetization Br, coercive force Hcj, and maximum energy product (BH) max were measured. The results are shown in Table 1 and FIGS.

(Results and discussion)
The magnets of Example 1 and Example 2 had higher coercive force and larger maximum energy product than those of Comparative Examples 1 to 3. This is considered due to the fact that Dy is uniformly and densely arranged at the grain boundaries of the particles made of magnetic powder. In addition, the magnet of Comparative Example 2 has a low coercive force and a small maximum energy product in spite of having a large Dy content as compared with the magnet of Example 1, because Dy does not exist at the grain boundaries. It is thought that. Further, in the magnet of Comparative Example 3, since Dy is not sufficiently diffused to the inside, it is considered that the coercive force is lower and the maximum energy product is smaller than that of the magnet of Example 1.

  As mentioned above, although embodiment of this invention has been explained in full detail using drawing, a concrete structure is not limited to this embodiment, Even if there is a design change in the range which does not deviate from the gist of the present invention. These are included in the present invention.

Claims (12)

Aerosolizing the hard magnetic powder with an inert gas;
A step of generating vapor particles vaporized from a part of the molten metal by heating and melting the metal in an inert gas atmosphere in a melting furnace;
A step of the vapor particles are deposited on the surface of the hard magnetic powder the aerosolized, only including,
In the adhering step, the aerosolized hard magnetic powder is transported in an air stream, and the vapor particles are transported in an air stream at a higher speed than the hard magnetic powder in the air stream, and the hard magnetic powder A method for producing a magnetic powder, characterized in that the vapor particles are adhered to the surface of the aerosolized hard magnetic powder by combining the vapor particles with the air flow . In the adhering step, the vapor particles are merged with the air flow of the hard magnetic powder by joining the air flow of the vapor particles to the air flow of the hard magnetic powder at equally spaced positions around the air flow on which the aerosolized hard magnetic powder is placed. The method for producing a magnetic powder according to claim 1, wherein the magnetic powder is adhered to the surface of an aerosolized hard magnetic powder .   The method for producing a magnetic powder according to claim 1, wherein the metal is a transition metal or an alloy metal thereof.   The method for producing a magnetic powder according to claim 3, wherein the transition metal is a rare earth metal.   The method for producing a magnetic powder according to claim 4, wherein the rare earth metal is Dy, Tb, or Pr.   The method for producing a magnetic powder according to claim 1, wherein the metal is Al or Cu.   The said hard magnetic powder is a Nd-Fe-B type magnetic powder, The manufacturing method of the magnetic powder in any one of Claims 1-6 characterized by the above-mentioned.   The magnet which sintered the magnetic powder manufactured by the manufacturing method in any one of Claims 1-7. An aerosol chamber for aerosolizing the hard magnetic powder with an inert gas;
A melting furnace for melting a metal by heating in an inert gas atmosphere, and generating a vapor particle vaporized from a part of the dissolved metal by melting the metal in the melting furnace ;
An attachment part for attaching the vapor particles to the surface of the aerosolized hard magnetic powder;
A discharge chamber for discharging the hard magnetic powder to which the vapor particles are attached , and
The adhering portion places the vapor particles on the airflow at a faster speed than the main conveyance pipe connected to the aerosol chamber so as to convey the hard magnetic powder on the airflow, and the hard magnetic powder on the airflow. A sub-transport pipe connected to the steam generation chamber so as to be transported, and the sub-transport pipe is connected to the main transport pipe so that the air flow of the vapor particles merges with the air flow of the hard magnetic powder. An apparatus for producing magnetic powder, wherein the magnetic powder is connected . The manufacturing apparatus includes a plurality of the steam generation chamber and the sub transport pipe connected to the steam generation chamber, and the plurality of sub transport pipes are connected to the outer periphery of the main transport pipe at equal intervals. The apparatus for producing a magnetic powder according to claim 9 . The apparatus for producing a magnetic powder according to claim 9 or 10 , further comprising a tube heating unit that heats the sub-transport tube. The aerosol chamber and the vapor generation chamber are provided with a supply pipe for supplying the inert gas, and an oxygen removing device for removing oxygen contained in the inert gas is provided in the supply pipe. The apparatus for producing magnetic powder according to any one of claims 9 to 11 .

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