KR20200078630A - Method for manufacturing atomized metal powder - Google Patents

Abstract

(Task) A method for producing an atomized metal powder having a high amorphization rate by a water atomization method is provided.
(Solution) High-pressure water that collides with molten metal falling in the vertical direction is sprayed, the molten metal is divided into metal powder, and the metal powder is cooled to obtain atomized metal powder having an amorphization rate of 90% or more. As a manufacturing method, the impact pressure when the high pressure water collides with the molten metal is 20 MPa or more, and the high pressure water becomes a subcritical state or a supercritical state in a collision surface with the molten metal. A method for producing an atomized metal powder that adjusts the temperature and/or the temperature of the high pressure water.

Description

Method for manufacturing atomized metal powder

The present invention relates to a method for producing atomized metal powder. The present invention is particularly suitable for the production of atomized metal powder in which the total content of iron-based components (Fe, Ni, Co) is 76 at% or more in atomic fraction.

Conventionally, there is an atomizing method as a method for producing a metal powder. The atomizing method includes a water atomizing method in which a metal powder is obtained by spraying a high pressure water jet (high pressure water) to a flow of molten metal, and a gas atomizing method injecting an inert gas instead of the water jet.

In the water atomization method, the flow of molten metal is divided by a jet of water sprayed from a nozzle or the like to form a powdered metal (metal powder), and cooling of the powdered metal (metal powder) by water jet is also performed. A maize metal powder is obtained. On the other hand, in the gas atomizing method, the flow of molten metal is divided by an inert gas injected from a nozzle to form a powdery metal, and then, usually, the powdered metal is a water tank or a running water provided under the atomizing device. ) Is dropped in a drum, and the powdery metal (metal powder) is cooled to obtain an atomized metal powder.

In manufacturing the metal powder, the water atomization method has a higher production capacity and a lower cost than the gas atomization method. In the gas atomizing method, it is necessary to use an inert gas when atomizing, and the energy force when atomizing is also inferior to that of the water atomizing method. In addition, while the metal powder produced by the gas atomization method is substantially spherical, the metal powder produced by the water atomization method is in an irregular shape, and when the metal powder is compression molded to produce a motor core or the like, Compared to the spherical metal powder of the gas atomizing method, the metal powder having an indefinite shape of the water atomizing method has the advantage that the powders are easily entangled and the strength after compression is increased.

In recent years, from the viewpoint of energy saving, reduction in size and miniaturization of a motor core used in, for example, an electric vehicle or a hybrid vehicle has been desired. Conventionally, these motor cores have been produced by laminating and thinning electrical steel sheets. In recent years, a motor core produced using a metal powder having a high degree of freedom in shape design has attracted attention. It is considered that it is effective to amorphize (amorphize) the metal powder used to reduce the iron of the motor core. In order to obtain an amorphized metal powder, it is necessary to prevent crystallization by rapidly cooling the atomized metal powder with a cooling medium while atomizing from the high temperature in the molten state. In addition, it is necessary to increase the magnetic flux density for miniaturization and high output of the motor with low iron loss, and it is important to increase the Fe-based (including Ni, Co) concentration to increase the high magnetic flux density, and the Fe-based concentration Amorphous soft magnetic metal powder for a motor core, which is about 76 to 90 at%, is required. When the Fe concentration is 80 at% class, in order to amorphize, a cooling rate of 10 ⁶ K/s or more is required, and it is very difficult to achieve both low iron loss of the metal powder and improved magnetic flux density.

In particular, as a cause that prevents an increase in the cooling rate, when the hot molten metal is cooled with water, when the water comes into contact with the molten metal, the water evaporates in an instant to form a vapor film around the molten metal, and is cooled. It can be said that the state prevents direct contact between the surface and water (occurrence of film boiling), and the cooling rate does not increase.

In manufacturing amorphous iron powder, studies illustrated in Patent Literatures 1 to 11 have been made to solve the problem of suppressing cooling due to this vapor film/film boiling.

For example, Patent Document 1 discloses a method for producing a metal powder whose cooling rate until solidification is 10 ⁵ K/s or more when cooling and solidifying a molten metal while scattering it to obtain a metal powder. In the technique described in Patent Literature 1, it is said that the above-mentioned cooling rate is obtained by bringing the scattered molten metal into contact with the cooling liquid generated by turning the cooling liquid along the inner wall surface of the normal body. It is said that the flow rate of the coolant generated by turning the coolant is preferably 5 to 100 m/s.

In addition, Patent Document 2 describes a method for producing a rapid cooling solidification metal powder. In the technique described in Patent Document 2, the cooling liquid is supplied from the circumferential direction from the outer circumferential side of the upper end of the cylindrical portion of the cooling vessel whose inner circumferential surface is a cylindrical surface, and is dropped while turning along the inner circumferential surface of the cylindrical portion, and the centrifugal force caused by the vortex causes a cavity in the center A layered orbiting coolant layer having a void is formed, and a metal molten metal is supplied to the inner peripheral surface of the orbiting coolant layer to rapidly solidify. Thereby, it is said that cooling efficiency is good and a high-quality quench solidification powder is obtained.

In addition, Patent Document 3 includes a gas jet nozzle for jetting a jet of gas to molten metal to flow, and a gas jet nozzle for dividing into volumes, and a cooling cylinder having a cooling liquid layer that rotates and flows on an inner circumferential surface. An apparatus for manufacturing a metal powder by a maize method is described. In the technique described in Patent Document 3, it is said that molten metal is divided into two stages by a gas jet nozzle and a cooling liquid layer that rotates to obtain a finely quenched solidified metal powder.

In addition, in Patent Document 4, molten metal is supplied into a liquid refrigerant, a vapor film covering the molten metal is formed in the refrigerant, and the generated vapor film is collapsed to directly contact the molten metal and the refrigerant to cause boiling due to natural nuclear generation. A method for producing amorphous metal microparticles is described, wherein the molten metal is rapidly cooled and amorphized using the pressure wave to form amorphous metal microparticles. The collapse of the vapor film covering the molten metal is possible when the temperature of the molten metal supplied to the refrigerant is brought into direct contact with the refrigerant, the interface temperature is below the lower boiling temperature of the membrane, or above the spontaneous nucleation temperature, or by ultrasonic irradiation. Doing.

Moreover, in Patent Document 5, when the molten material is supplied as a droplet or jet stream in the liquid refrigerant, the temperature of the molten material is set to be in a molten state above the spontaneous nucleation temperature of the liquid refrigerant, and also enters the flow of the liquid refrigerant. When the relative velocity difference between the velocity of the molten material and the flow rate of the liquid refrigerant is 10 m/s or more, the vapor film formed around the molten material is forcibly collapsed, causing boiling due to spontaneous nucleation. A method for producing particulates that are allowed to cool, solidify while being atomized, is described. Thereby, it is said that even a material that has been difficult in the past can be micronized and amorphized.

Moreover, in Patent Document 6, a raw material in which a functional additive is added to a material serving as a base material is melted and supplied into a liquid refrigerant, thereby minimizing by vapor explosion and controlling the cooling rate when cooling and solidifying, thereby eliminating polycrystalline crystals without segregation or A method for producing a functional member comprising a step of obtaining an amorphous homogeneous functional fine particle and a step of solidifying the functional fine particle and the fine particle of the base material as a raw material to obtain a functional member is described.

In Patent Documents 7, 8, it is described that a suction tube is provided below the water atomize, and the vapor film around the powder can be destroyed by suctioning the powder after melt powdering.

Patent Document 9 discloses that a cooling block is provided below water atomization, 80 kgf/cm 2 or more of liquid is sprayed, the powder after melt-pulverization is hit by the cooling block, and the vapor film around the powder is destroyed.

In Patent Document 10, a device for dispensing a second liquid under an atomization is provided, and the spray pressure of the liquid is 5 to 20 kPa, forcibly changing the direction in which the dispersion liquid containing the molten metal moves, thereby covering the covered vapor film. Deletion is described.

In Patent Document 11, although it is a patent of an iron boron-based ferromagnetic material (permanent magnet) containing rare earths, the water pressure is 750 to 1200 kgf/cm 2 and the water temperature is 20° C. in fine powder and amorphization by water atomization. It is described that it is preferable to set the amount of water per 1 kg of iron to 25 to 45 L (liters) below.

Japanese Patent Application Publication No. 2010-150587 Japanese Patent Publication No. Hei 7-107167 Japanese Patent Publication No. 3932573 Japanese Patent Publication No.3461344 Japanese Patent Publication No. 4793872 Japanese Patent Publication No. 4784990 Japanese Patent Application Publication No. 60-24302 Japanese Patent Application Publication No. 61-204305 Japanese Patent Application Publication No. 60-24303 Japanese Patent Publication No. 2007-291454 Japanese Patent Application Publication No. 2004-349364

The techniques described in Patent Literatures 1 to 3 are intended to supply molten metal to a coolant layer formed by rotating the cooled metal particles by turning the coolant, and to remove the vapor film formed around the metal particles, but the temperature of the broken metal particles If is high, the film tends to boil in the coolant layer. Moreover, since the metal particles supplied in the coolant layer move together with the coolant layer, there is a small relative velocity difference with the coolant layer, so that it is difficult to avoid the film boiling state. .

In addition, in the techniques described in Patent Documents 1 to 6, metal powders are produced using the gas atomization method, but the gas atomization method requires a large amount of inert gas for atomization, thereby increasing manufacturing cost. There is a problem that causes.

The techniques described in Patent Documents 7 to 10 relate to the water atomization method. Although the technique described in Patent Documents 7 and 8 is said to be capable of removing a vapor film by sucking powder, if water is present around a hot object, water is continuously vaporized by heat from inside the object to form a vapor film. , It is difficult to remove the vapor film just by suctioning water and molten metal together.

In Patent Literature 9, it is said that it is possible to break the vapor film by providing a cooling block under the atomization and hitting the molten metal covered with the vapor film to the cooling block, but when the liquid is used for the separation, the temperature of the liquid increases. , As a result, the vapor film is easily formed, and since the injection pressure (pressure energy) of the liquid is used for the division, the amount of energy for breaking the vapor film is insufficient when it comes into contact with the cooling block. Even if the vapor film is collapsed, the vapor film is immediately revived as long as the molten metal (powder) is at a high temperature. For this reason, it is always necessary to continuously remove the vapor film.

Also in Patent Document 10, it is said that the vapor film can be removed by changing the traveling direction of a dispersion liquid containing molten metal that has become droplets after atomizing by liquid jet spraying. If the metal temperature is too high, there is a possibility that the vapor film is covered again due to the cooling water in the surroundings. On the other hand, if the temperature when it hits the cooling block is too low, the molten metal may solidify and crystallization may proceed. In particular, when the content of the iron-based element (Fe + Co + Ni) is large, the melting point increases, so the cooling start temperature is high, the film is easily boiled from the beginning of the cooling, and the liquid injection pressure cannot be said to be sufficient at about 5 to 20 MPa. .

In Patent Document 11, although it is a powder for permanent magnets, 750 to 1200 kgf/cm 2 to make the powder micronized and amorphized, the water temperature to 20° C. or less, and the water quantity per 1 kg of iron is 25 to 45 ℓ (liter ), and it is not shown to remove the film boiling or vapor film by these, but it is costly to the high pressure pump and high pressure piping to set the injection pressure to a high pressure of 60 MPa or higher, which means that the product price increases. do. Moreover, although the quantity of water per 1 kg of iron is 25 to 45 L, this is not enough for a soft magnetic material having a high iron-based element.

As described above, as described in the background art, the water atomization method is advantageous from the viewpoint of productivity and adhesion between mouths. Moreover, when quenching to amorphize, it is advantageous to amorphize to perform quenching with water after gas atomization as in Patent Documents 1 to 6. In the case of water atomization, since it is covered with a vapor film by cooling water subjected to atomization around the molten metal divided after atomization, it is necessary to add another means, and means such as Patent Documents 7 to 11 are used. have. In particular, each effect is insufficient for amorphization of the soft magnetic material having an iron-based element of 76 at% or more.

The present invention has been completed to solve the above problems, and an object of the present invention is to provide a method for producing an atomized metal powder having a high amorphization rate by a water atomization method.

The present inventors have repeatedly studied in order to solve the above problems. As a result, when the high pressure water is injected into the molten metal, the molten metal is divided, cooled, and when obtaining atomized metal powder, pay attention to the collision pressure, not the injection pressure. By adjusting the state of the water on the collision surface, the above-mentioned problems have been solved. More specifically, the present invention provides the following.

[1] The molten metal falling in the vertical direction is collided by spraying high-pressure water, and the molten metal is divided into a metal powder, and the metal powder is cooled to produce an atomized metal powder having an amorphization rate of 90% or more. As a way to do,

The collision pressure when the high pressure water collides with the molten metal is 20 MPa or more,

A method for producing an atomized metal powder that adjusts the temperature of the molten metal and/or the temperature of the high pressure water so that the high pressure water becomes a subcritical state or a supercritical state in a collision surface with the molten metal.

[2] The method for producing the atomized metal powder according to [1], wherein in the collision of the high pressure water and the molten metal, the average temperature of the temperature of the molten metal and the temperature of the high pressure water is 374°C or higher.

[3] The mass ratio (Qaq/Qm) is 35 or more when the falling amount per unit time of the molten metal is Qm (kg/min) and the injection amount per unit time of the high pressure water is Qaq (kg/min) or more. The manufacturing method of the atomized metal powder as described in [2].

[4] The atomized metal powder has a total content of iron-based components (Fe, Ni, Co) of 76.0 at% or more in atomic fractions, and a content of Cu of 0.1 at% or more and 2.0 at% or less in atomic fractions [1] -The manufacturing method of the atomized metal powder in any one of [3].

[5] The atomized metal powder has a total content of iron-based components (Fe, Ni, Co) of more than 82.5 at% in atomic fractions and less than 86 at%, and at least two types selected from Si, P and B. The manufacturing method of the atomized metal powder in any one of [1]-[3] which contains Cu and has an average particle diameter of 5 micrometers or more.

[6] In the subcritical state, the pressure is 0.5 to 22 MPa, and the water temperature is 150 to 274°C, and in the supercritical state, the pressure is 22 MPa or more and the water temperature is 374°C or more [1] to [ The manufacturing method of the atomized metal powder in any one of 5].

Amorphization of the atomized metal powder by 90% or more was attained by the present invention. Thereby, when the atomized metal powder obtained in the present invention is subjected to an appropriate heat treatment after molding, nano-sized crystals are deposited. In particular, if it is a high Fe-based soft magnetic material (the total content of iron-based components (Fe, Ni, Co) is 76 at% or more in atomic fraction), proper heat treatment after molding of the present powder results in low loss and high magnetic flux density. It became possible to be compatible. As such, the present invention is suitable for the production of any conventionally used amorphous soft magnetic material.

In addition, recently, Materia Vol.41 No.6 P.392, Journal of Applied Physics 105, 013922 (2009), Japanese Patent Publication No. 4288687, Japanese Patent Publication No. 4310480, Japanese Patent Publication No. 4815014, WO2010- As shown in 084900, Japanese Patent Application Publication No. 2008-231534, Japanese Patent Application Publication No. 2008-231533, Japanese Patent Publication No. 2710938, heteromorphic materials having a high magnetic flux density or nanocrystalline materials have been developed. The present invention is very advantageously suitable for the production of soft magnetic materials of high concentration of these Fe-based components by water atomization. In particular, when the concentration of the Fe-based component exceeds 82.5% by at%, and furthermore, when it exceeds 83.5%, it has been difficult to increase the amorphization rate in the prior art. However, when the production method of the present invention is applied, the amorphization rate after atomization can be made 90% or more. Moreover, in the prior art, it has been very difficult to make the amorphization rate to be 90% or more and an average particle diameter of 5 µm or more. However, when the manufacturing method of the present invention is applied, the amorphization rate can be made 90% or more even if the average particle diameter is increased. Since the amorphization rate can be 90% or more and an average particle diameter of 5 µm or more, if a suitable heat treatment is performed after molding, the saturation magnetic flux density (Bs) value becomes very large.

In addition, as described above, the present invention is preferable for the production of atomized metal powder having a high Fe concentration, but the present invention is applied to a method for producing atomized metal powder other than atomized metal powder having a high Fe concentration. The lower surface has the effect that the amorphous powder can be stably obtained even with a large diameter powder more easily than before.

In addition, "amorphization rate", after removing the dust other than the metal powder for the obtained metal powder (soft magnetic iron powder), the halo peak from the amorphous (amorphous) and the diffraction peak from the crystal by an X-ray diffraction method. It is measured and calculated by the WPPD method. The "WPPD method" as used herein is an abbreviation for Whole-powder-pattern decomposition method. The WPPD method is described in detail by Hideya Toraya: Japanese Journal of Crystals, vol.30 (1988), No.4, P253 to 258.

1 is a view schematically showing an example of a manufacturing apparatus that can be used in the method for producing an atomized metal powder of the present invention.
2 is a diagram schematically showing an example of manufacturing equipment for carrying out the manufacturing method of the present invention.
3 is a view showing the relationship between pressure, water temperature, and water state.
4 is a graph showing the relationship between the amorphization rate and the collision pressure.
5 is a schematic view for explaining a state in which a collision pressure of a molten metal is measured by a collision pressure measurement pressure sensor.
It is a figure which shows the BH diagram obtained by VSM.

Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

1 schematically shows an example of a manufacturing apparatus that can be used in the method for producing an atomized metal powder of the present invention. In FIG. 1, in the state where the molten metal 3 is injected into the tundish 2, the molten metal 3 falls from the molten metal injection nozzle 4 by the self-weight of the molten metal 3. . Further, the cooling water supplied to the nozzle header 5 is sprayed with cooling water 20 (corresponding to high pressure water) from the cooling nozzle 6. The cooling water 20 collides with the molten metal (falling molten metal), is atomized, and becomes a metal powder 8 that is a divided molten metal.

2 schematically shows an example of manufacturing equipment for carrying out the manufacturing method of the present invention. The manufacturing equipment shown in FIG. 2 uses the temperature controller 16 for cooling water to adjust the temperature of the cooling water in the cooling water tank 15, sends the temperature-adjusted cooling water to the high pressure pump 17 for atomizing cooling water, and atto It is sent from the high pressure pump 17 for maize cooling water to the atomizing device 14 (equivalent to the manufacturing apparatus of FIG. 1) through the atomizing cooling water piping 18, and from the atomizing device 14 in the vertical direction. The atomized metal powder is produced by spraying high pressure water impinging on the falling molten metal, dividing the molten metal into a metal powder, and cooling the metal powder.

First, in the present invention, it is characterized in that the impact pressure when the cooling water 20 collides with the molten metal is adjusted to be 20 kPa or higher and water becomes a subcritical state or a supercritical state at the collision surface. The supercritical state of water is a region of 374°C or higher and 22 MPa or higher. The subcritical state of water is a high temperature and high pressure state close to the critical point. For example, as shown in FIG. 3, an area of 100°C or more and less than 374°C, and 0.1 MPa or more and less than 22 MPa, 374°C or more and 2 MPa or more and 22 MPa or more The area of less than 250°C or more and less than 374°C is also a region of 22 mm 2 or more.

In the manufacturing method of the present invention, the collision pressure when the cooling water 20 collides with the molten metal is 20 MPa or more. The collision pressure is measured by a pressure sensor having a collision surface sensor diameter of φ2 mm at the time of viatomization. In order to set the collision pressure to 20 MPa or more, the injection pressure of the cooling water 20 needs to be more than that. The injection pressure is up to 98 kPa, and it is preferable to perform pressure adjustment with an inverter-type high pressure pump to adjust the collision pressure. Moreover, since the injection pressure decreases when the cooling water 20 is spread in a fan shape, it is preferable to provide a straight type nozzle. Moreover, since the injection pressure decreases when the distance between the cooling nozzle 6 and the molten metal is increased, it is preferable that the linear distance from the injection port of the cooling water 20 of the cooling nozzle 6 to the molten metal is 150 mm or less. More preferably, it is 100 mm or less.

Further, in the present invention, the temperature of the molten metal and/or the temperature of the cooling water is adjusted so that the cooling water 20 is in a subcritical state or a supercritical state in a collision surface with the molten metal. The temperature of the molten metal can be adjusted by adjusting the heating temperature by high-frequency output in the melting furnace. Moreover, the temperature of the molten metal 3 injected into the tundish 2 can be adjusted by holding the molten metal 3 in a melting furnace after heating.

In the manufacturing method of the present invention, the average temperature of the temperature of the molten metal and the temperature of the cooling water 20 ((melting metal temperature + cooling water temperature)/2) is taken as the temperature of the water at the collision surface. The molten metal temperature can be measured using a non-contact thermometer at the atomization point. The temperature of the cooling water can be confirmed by a thermometer (not shown) that measures the water temperature of the cooling water tank 15 in FIG. 2. Then, based on the relationship between pressure, water temperature, and water, shown in FIG. 3, the collision pressure, the molten metal temperature, and the cooling water 20 are set to be an average temperature and a collision pressure that become a subcritical state or a supercritical state. Adjust the temperature. In addition, since the temperature of the molten metal and the cooling water tends to fluctuate, the molten metal temperature may be adjusted in the range of ±50°, and the cooling water temperature may be adjusted in the range of ±5°C.

Next, the effects of the present invention will be described.

4 is a graph showing the relationship between the amorphization rate and the collision pressure. In the graph shown in FIG. 4, the total content of the iron-based components (Fe, Ni, Co) is 76.0 at% (water-melting metal ratio (mass ratio: Qaq/Qm) 20) in atomic fractions, and atomize containing 0.5 at% of Cu. When manufacturing a metal powder and when the total content of the iron-based components (Fe, Ni, Co) is 85.8 at% in atomic fractions (water-melting metal ratio 35), and when producing an atomized metal powder containing 0.5 at% Cu It is about. Moreover, in the graph of FIG. 4, about the case where the collision pressure is 20 kPa, it was adjusted so that the state of the water of the collision surface of a cooling water and molten metal became a subcritical state. In the case where the collision pressure on the high pressure side was 22 MPa or more than this 20 MPa example, the water state on the collision surface was adjusted to be a supercritical state. Moreover, in the example of the lower pressure side than the 20 kPa example, the water state of the collision surface was adjusted to be other than the subcritical state and the supercritical state.

4, if the collision pressure is 20 MPa or more, regardless of whether the composition of the obtained atomized metal powder is changed, the water molten metal ratio is changed, or the state of water on the collision surface is subcritical or supercritical, 90 % Or more.

Moreover, when carrying out the manufacturing method of this invention, it is preferable to make the average temperature of the temperature of a molten metal and the temperature of a cooling water into 374 degreeC or more at the time of collision of cooling water (high pressure water) and molten metal. By setting the average temperature to 374°C or higher, the critical state is attained, and the steam is also made dense.

When the falling amount per unit time of molten metal is Qm (kg/min) and the injection amount per unit time of cooling water (high pressure water) is Qaq (kg/min), the mass ratio (Qaq/Qm) is preferably 35 or more. This is because, when the mass ratio is large, the amorphization rate is likely to be high, and if it is 35 or more, it is easy to adjust, and a sufficiently high effect is obtained.

In the production method of the present invention, the total content of the iron-based components (Fe, Ni, Co) is 76 at% or more in atomic fraction, and the content of Cu is 0.1 at% or more and 2 at% or less in atomic fraction. Is suitable for When the content of the iron-based element (Fe + Co + Ni) is high, the melting point increases, so the cooling start temperature is high, and the film is easily boiled from the beginning of the cooling. In the conventional method, it has been difficult to increase the amorphization rate to 90% or more. According to the present invention, even when the content of the iron-based element (Fe + Co + Ni) is large, the amorphization rate can be increased. According to the manufacturing method of the present invention, since the amorphization rate can be increased while increasing the content of the iron-based element (Fe + Co + Ni), high magnetic flux density can be achieved. As a result, the manufacturing method of the present invention contributes to miniaturization and high output of the motor.

In addition, when the composition of the molten metal is adjusted within the above range, the composition of the atomized metal powder also falls within the above range.

In the production method of the present invention, the total content of the iron-based components (Fe, Ni, Co) exceeds 82.5 at% in atomic fractions and is less than 86.0 at%, contains Cu, and is at least 2 selected from Si, P, and B It is suitable for the production of atomized metal powder containing species and having an average particle diameter of 5 µm or more. In the conventional method, in the case of a very high iron-based component content, specifically, the average particle diameter is fine when the total content of the iron-based components (Fe, Ni, Co) exceeds 82.5 at% in atomic fraction and less than 86 at%. This makes it easier to cool, and the amorphization rate can be made higher than that of a large average particle diameter. However, when the average particle diameter was 5 µm or more, it was very difficult to increase the amorphization rate to 90% or more. According to the present invention, even if the average particle diameter is 5 µm or more, the amorphization rate can be 90% or more. In addition, in the present invention, the criterion for the upper limit of the average particle diameter that allows the amorphization rate to be 90% or more is 75 µm. In addition, the particle diameter is classified and measured by a sieve method, and the average particle diameter (D50) is calculated by the integration method. In addition, laser diffraction/scattering type particle size distribution measurement may be used.

Example

The Examples and Comparative Examples were carried out by applying the water atomized metal powder production apparatus shown in FIG. 1 to the production facility shown in FIG. 2.

The molten metal 3 in which the raw material is dissolved at a predetermined temperature by a high-frequency melting furnace or the like is injected into the tundish 2. A molten metal injection nozzle 4 having a predetermined molten metal injection nozzle diameter is set in advance in the tundish 2. When the molten metal 3 enters the tundish 2, the molten metal is extruded from the molten metal injection nozzle 4 and falls by free fall or back pressure. Cooling water sprayed from the nozzle 6 for cooling water at a predetermined water pressure by the high-pressure pump 17 for atomizing cooling water collides with the molten metal, and the molten metal is pulverized and micronized and cooled. Cooling water is stored in the cooling water tank 15 in advance, and the cooling water temperature regulator 16 may adjust the water temperature as needed. The coolant spray nozzle was used as a straight type. Around 12 where the molten metal falls, the vertical direction and the angle of 30 degrees were set and installed. Moreover, the effect of this invention is obtained even if the installation angle of a nozzle is adjusted to 5-60 degrees. Before the atomization starts, the collision pressure of the molten metal is measured with a collision pressure measurement pressure sensor 51 (see FIG. 5). The collision pressure measurement pressure sensor 51 is set in the vertical direction with the injection angle of the nozzle to confirm that it is a predetermined collision pressure. Here, although FIG. 5 shows the state in which the cooling water is injected into the molten metal and the state in which it is injected toward the collision pressure measurement pressure sensor 51, this is for convenience, and the collision pressure of the collision pressure measurement pressure sensor 51 is shown. Measurement is performed before dropping a molten metal. The molten metal that has become iron powder is recovered by a hopper, and after drying and classification, the amorphization rate is evaluated. It is set as a pass at an amorphization rate of 90% or more.

In carrying out the production methods of Examples and Comparative Examples, soft magnetic materials of the following component systems were prepared. "%" means "at%". (I) to (i) are Fe-based soft magnetic raw materials. (Iii) is a Fe + Co-based soft magnetic material. (Iii) is a Fe + Co + Ni-based soft magnetic material.

(Iii) Fe 76%-Si 9%-B 10%-P 5%

(Ii) Fe 78%-Si 9%-B 9%-P 4%

(Iii) Fe 80%-Si 8%-B 8%-P 4%

(Iii) Fe 82.8%-B 11%-P 5%-Cu 1.2%

(iii) Fe 84.8%-Si 4%-B 10%-Cu 1.2%

(Iii) Fe 69.8%-Co 15%-B 10%-P 4%-Cu 1.2%

(Iii) Fe 69.8%-Ni 1.2%-Co 15%-B 9.4%-P 3.4%-Cu 1.2%

(I) to (i) were adjusted so as to be blended for each purpose, but for the actual composition, an error of about ±0.3 at% or other impurities may be included at the point of dissolution and completion of atomization. have. In addition, some composition changes may occur due to oxidation or the like during dissolution, atomization, or after atomization.

About Examples 1-4 and Comparative Examples 1-3, it implemented on the conditions shown in Table 1. The average particle diameter and the amorphization rate were evaluated by the methods described above. As a result of carrying out each Example and Comparative Example, in all of the Examples within the scope of the present invention, an amorphization rate of 90% or more was obtained. In the comparative example, an amorphization rate of 90% or more could not be obtained.

After forming the atomized metal powders of Examples 1 to 4, appropriate heat treatment was performed. Thereby, nano-sized crystals were deposited. Moreover, it was confirmed that both low loss and high magnetic flux density were compatible. Specifically, it confirmed by the following method.

The nanocrystal size was measured by XRD (X-ray diffraction apparatus), and then determined using a Scherrer equation. In this Scherrer equation, K is a shape factor (usually 0.9 is used), β is a peak half-value full width (however, radians), θ is 2θ = 52.505° (Fe 110 plane), and τ is a crystal size.

τ = Kλ/βcosθ (Sherer's expression)

Further, the magnetic properties of the obtained powder were investigated by a VSM (vibration magnetometer), and from the BH diagram (FIG. 6) obtained by the VSM, the saturation magnetic flux density was C point (F point), the holding force was E point, and the magnetic permeability was the maximum of B. The slope and loss were determined by the area of hysteresis (CDFG). In addition, FIG. 6 is publicly released from the National Research and Development Corporation Science and Technology Promotion Organization (JST) (Internet URL: https: //www.jst.go.jp/pr/report/report27/grf2.html Search date 2017 November 16).

In Table 1, "the atomization start temperature" is the temperature of the molten metal at the atomization point. The molten metal temperature at the atomization point was measured by a non-contact thermometer.

In Table 1, "average temperature" is represented by ((melting metal temperature + cooling water temperature)/2). The molten metal temperature at the atomization point was measured with a non-contact thermometer, and the cooling water temperature was measured with a thermometer of the water temperature of the cooling water tank.

In Table 1, "water molten metal ratio" is mass ratio Qaq/Qm.

2: tundish
3: molten metal
4: molten metal injection nozzle
5: nozzle header
6: Cooling nozzle
8: Metal powder
14: atomizing device
15: coolant tank
16: Temperature controller for coolant
17: high pressure pump for atomized cooling water
18: Atomized cooling water piping
20: cooling water
51: collision pressure measurement pressure sensor

Claims (6)

As a method of producing atomized metal powder having an amorphization rate of 90% or more by colliding with a molten metal falling in a vertical direction by spraying high-pressure water to collide, dividing the molten metal into a metal powder, and cooling the metal powder. ,
The collision pressure when the high pressure water collides with the molten metal is 20 MPa or more,
A method for producing an atomized metal powder that adjusts the temperature of the molten metal and/or the temperature of the high pressure water so that the high pressure water becomes a subcritical state or a supercritical state in a collision surface with the molten metal. According to claim 1,
At the time of the collision of the high pressure water and the molten metal, a method of manufacturing an atomized metal powder having an average temperature of the temperature of the molten metal and the temperature of the high pressure water being 374°C or higher. The method according to claim 1 or 2,
Method for manufacturing atomized metal powder having a mass ratio (Qaq/Qm) of 35 or more, when the amount of falling of the molten metal per unit time is Qm (kg/min) and the amount of injection of the high pressure water per unit time is Qaq (kg/min) . The method according to any one of claims 1 to 3,
The atomized metal powder has an iron content (Fe, Ni, Co) of which the total content is 76.0 at% or more in atomic fraction, and the content of Cu is 0.1 at% or more and 2.0 at% or less in atomic fraction. Way. The method according to any one of claims 1 to 3,
The atomized metal powder has a total content of iron-based components (Fe, Ni, Co) of more than 82.5 at% in atomic fractions and less than 86.0 at%, and contains at least two types selected from Si, P and B and Cu And a method for producing an atomized metal powder having an average particle diameter of 5 µm or more. The method according to any one of claims 1 to 5,
In the subcritical state, the pressure is 0.5 to 22 MPa, and the water temperature is 150 to 274°C,
The supercritical state is a method for producing an atomized metal powder having a pressure of 22 MPa or higher and a water temperature of 374°C or higher.

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