WO2023119896A1

WO2023119896A1 - Production method for water-atomized metal powder, and production device for water-atomized metal powder

Info

Publication number: WO2023119896A1
Application number: PCT/JP2022/040910
Authority: WO
Inventors: 誠中世古; 繁宇波; 拓也高下; 尚貴山本
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2021-12-21
Filing date: 2022-11-01
Publication date: 2023-06-29

Abstract

Provided are a production method and a production device for producing a water-atomized metal powder, whereby a metal powder having a degree of amorphization and having high apparent density and high circularity can be produced through a low cost, high-productivity water-atomizing method.　In the method for producing a water-atomized metal powder, cooling water is jetted against a falling molten metal flow such that the molten metal flow and the cooling water collide, thereby dividing the molten metal flow into parts to form a metal powder. The cooling water is jetted downward from the perimeter of the molten metal flow and toward the falling molten metal flow so as to gather at a center point. The molten metal flow contacts the cooling water at a position separated at a horizontal distance from the center point by an eccentricity amount E. In the relationship between the eccentricity amount E and the vertical distance L from a leading end of a cooling water nozzle to the center point, the value of E/L is in the range of 0.05-0.20.

Description

Method for producing water-atomized metal powder and apparatus for producing water-atomized metal powder

The present invention relates to a method for producing water-atomized metal powder and an apparatus for producing water-atomized metal powder. In the method for producing a water-atomized metal powder and the apparatus for producing a water-atomized metal powder according to the present invention, the total content of Fe, Ni and Co is 76.0 atomic % or more and 86.0 atomic % or less. It is suitable for producing soft magnetic metal powders with high loading density, high degree of circularity, and high degree of amorphization.

The production volume of hybrid vehicles (HV), electric vehicles (EV) and fuel cell vehicles (FCV) is increasing, and the reactors and motor cores used in these vehicles are required to have low iron loss, high efficiency and miniaturization. is requested.

Until now, these reactors and motor cores have been manufactured by laminating thin magnetic steel sheets. Recently, attention has been paid to motor cores manufactured by compression-molding metal powder, which has a high degree of freedom in shape design.

　In order to reduce the iron loss of reactors and motor cores, it is considered effective to make the metal powder used as a raw material amorphous.

Furthermore, it is necessary to increase the magnetic flux density of the metal powder used as raw materials in order to make reactors and motors smaller, lighter, and more powerful. For this purpose, it is important to increase the total content of Fe, Ni and Co, and there is an increasing demand for an amorphous soft magnetic metal powder in which the total content is 76.0 atomic % or more in terms of atomic fraction. ing.

In addition, when atomized metal powder (metal powder produced by the atomization method) is used as a reactor or motor core by compression molding as the metal powder, the low core loss contributes to the low loss and high efficiency of the reactor or motor core. It is also important for For this purpose, it is important that the atomized metal powder has a high degree of amorphization. Furthermore, the core loss is often affected by the shape of the atomized metal powder. That is, the core loss tends to decrease as the shape of the atomized metal powder becomes more spherical. Furthermore, there is a close relationship between spheroidization and apparent density, and the higher the apparent density, the more spherical the shape of the metal powder. In recent years, atomized metal powders used as raw materials for reactors and motor cores are required to have an apparent density of 3.5 g/cm ³ or more.

From the above, the following two points are required as characteristics of the atomized metal powder used as a raw material for reactors and motor cores.
1) Fe, Ni, and Co should be contained at high concentrations for miniaturization and high performance of motors. Due to the high density and circularity, as well as the increasing demand for atomized metal powders due to the increase in HV, EV and FCV of automobiles, the following are required.
3) Low cost and high productivity

JP-A-2001-64704 JP 2012-111993 A

The method shown in Patent Document 1 has been proposed as a means of amorphizing metal powder and controlling the shape by atomization.

In Patent Document 1, a molten metal flow is divided by a gas jet with an injection pressure of 15 to 70 kg/cm ² , and diffused while being dropped over a distance of 10 mm or more and 200 mm or less, and plunged into a water flow at an incident angle of 30 to 90°. discloses a method of obtaining metal powders. In addition, in Patent Document 1, an amorphous powder cannot be obtained at an incident angle of less than 30°, and when the incident angle exceeds 90°, powder particles tend to have a low circularity shape such as an oblate ellipsoid.

By the way, there are water atomization method and gas atomization method for dividing the molten metal flow by the atomization method. The water atomization method is a method of injecting cooling water into the molten metal flow to divide the molten steel to obtain metal powder, and the gas atomization method is a method of injecting an inert gas into the molten metal flow. Patent Literature 1 discloses a gas atomization method in which a molten metal flow is first divided by gas.

In the water atomization method, the flow of molten steel is divided by a water jet injected from a nozzle or the like to make powdered metal (metal powder), and the water jet also cools the metal powder to obtain atomized metal powder. On the other hand, the gas atomization method uses an inert gas injected from a nozzle. In the case of the gas atomization method, since the ability to cool molten steel is low, equipment for separately cooling the molten steel after atomization may be provided.

Compared to the gas atomization method, the water atomization method uses only water to produce metal powder, and thus has a high production capacity and a low cost. However, the metal powder produced by the water atomization method (water-atomized metal powder) has an irregular shape. Since the molten steel solidifies as it is, the apparent density becomes less than 3.5 g/cm ³ .

On the other hand, the gas atomization method requires the use of a large amount of inert gas and is inferior to the water atomization method in the ability to divide the molten steel during atomization. However, the metal powder produced by the gas atomization method takes a longer time from division to cooling than by the water atomization method. Therefore, since it is cooled after it becomes spherical due to the surface tension of the molten steel before it solidifies after being cut, the shape tends to be closer to a sphere and the apparent density is higher than that of the water-atomized metal powder.

In the technique described in Patent Document 1, by adjusting the injection angle (incidence angle) of water in cooling after gas atomization, both spheroidization and amorphization of the metal powder are achieved. However, as described above, the gas atomization method has problems of low productivity and high production cost due to the use of a large amount of high-pressure inert gas. Furthermore, the metal powder produced by the gas atomization method generally tends to have a large average particle size (D ₅₀ ) of more than 50 μm because the breaking energy during gas atomization is smaller than that in water atomization.

In this regard, in Patent Document 2, water is sprayed obliquely downward from a spray nozzle in a V-shaped crossing, and molten steel is dropped in the center of the crossing to atomize and sphere the molten steel. disclosed. In the technique described in Patent Document 2, a water atomization method is adopted, water sprayed from a spray nozzle is crossed in a V-shape, and molten steel is dropped toward the intersection to obtain fine metal powder. there is This technique is a good means of obtaining fine metal powder, but since the water is dispersed rather than concentrated at the center point, part of the water does not contribute to the division or cooling of the molten steel at all. Therefore, this method is not suitable for increasing the cooling capacity. Therefore, the metal powder obtained by this method has a problem that it is difficult to make it amorphous.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a low-cost, high-productivity water atomization method in which the total content of Fe, Ni and Co is 76.0 at% or more, Provided is a method and apparatus for producing a water-atomized metal powder capable of producing a metal powder having an average particle diameter (D ₅₀ ) of 50 µm or less, a high degree of amorphousness, a high apparent density, and a high degree of circularity. to provide.

The inventors have conducted extensive research to solve the above problems.

Normally, in the water atomization method, the nozzle tip is arranged circumferentially and at a downward mounting angle so that the cooling water concentrates in the same place where the molten steel falls vertically.

Usually, the molten metal flow is dropped toward the center (central point) where the cooling water concentrates. It was found that it is effective to set the position away from the center (center point) where the

The inventors of the present invention have determined the horizontal distance E (hereinafter also referred to as the eccentricity E) between the position where the cooling water collides with the molten metal flow and the center point where the cooling water concentrates, and the injection distance of the cooling water. It has been found that it is effective to set the ratio (E/L) of the vertical component (the vertical distance from the tip of the cooling water nozzle to the center point) L to 0.05 to 0.20. The L is preferably 300 mm or less, more preferably 250 mm or less. In this specification, the term “perpendicular” means perpendicular to the horizontal plane (that is, vertical).

Furthermore, the present inventors have found that it is preferable to set the ratio of the amount of cooling water to the amount of falling molten metal flow (water/molten steel ratio) to 50 or more.

The gist of the present invention is as follows.
[1] A method for producing a water-atomized metal powder by injecting cooling water against a falling molten metal flow and causing the molten metal flow and the cooling water to collide to divide the molten metal flow into metal powder. hand,
the cooling water is jetted downward from the perimeter of the molten metal flow toward the molten metal flow so as to converge at a central point;
The molten metal flow contacts the cooling water at a position separated by an eccentricity E in the horizontal distance from the center point,
The amount of eccentricity E is in the relationship between the vertical distance L from the tip of the cooling water nozzle that injects the cooling water to the center point, and the value of E/L is in the range of 0.05 to 0.20. A method for producing atomized metal powder.
[2] The injection pressure of the cooling water is 10 MPa or more, and F/M, which is the ratio of the amount F (kg/min) of the cooling water to the falling amount M (kg/min) of the molten metal flow, is 50. The method for producing a water-atomized metal powder according to [1], which is the above.
[3] The metal powder has a total content of Fe, Ni and Co in an atomic fraction of 76.0 at % or more and 86.0 at % or less, an apparent density of 3.5 g/cm ³ or more, and a circular shape. The water-atomized metal powder according to [1] or [2], which has a degree of 0.90 or more, an average particle diameter (D ₅₀ ) of 50 μm or less, and an amorphous degree of 95% or more. Method.
[4] An apparatus for producing water-atomized metal powder by injecting cooling water against a falling molten metal flow and causing the molten metal flow and the cooling water to collide to divide the molten metal flow into metal powder. hand,
a plurality of cooling water nozzles for injecting the cooling water toward the molten metal flow downward from the periphery of the molten metal flow so as to converge at a central point;
a molten steel nozzle that supplies the molten metal flow so as to contact the cooling water at a position separated by an eccentricity E in the horizontal distance from the center point,
Manufacture of water-atomized metal powder, wherein the amount of eccentricity E is in a relationship between the vertical distance L from the tip of the cooling water nozzle to the center point, and the value of E/L is in the range of 0.05 to 0.20. Device.

According to the present invention, the total content of Fe, Ni and Co is 76.0 at% or more, the average particle diameter (D ₅₀ ) is 50 μm or less, the degree of amorphization is 95% or more, and the apparent density is of 3.5 g/cm ³ or more and a circularity of 0.90 or more can be produced by the water atomization method.

FIG. 1 is a diagram schematically showing a manufacturing apparatus for water-atomized metal powder according to an embodiment of the present invention, and is an example of a manufacturing apparatus in which the falling position of the molten metal stream is eccentric by shifting the molten steel nozzle in the horizontal direction. is shown. FIG. 2 is a diagram schematically showing a production apparatus for water-atomized metal powder according to another embodiment of the present invention, showing an example of an eccentric production apparatus in which the molten steel nozzle is arranged obliquely with respect to the vertical direction. It is a thing. FIG. 3 is a diagram schematically showing a configuration example of a production facility for water-atomized metal powder.

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

In the method for producing water-atomized metal powder according to the present embodiment, cooling water is jetted against a falling molten metal flow, and the molten metal flow collides with the cooling water to divide the molten metal flow into metal powder. It is a method for producing a water-atomized metal powder. Cooling water is jetted toward the falling molten metal stream from the perimeter of the molten metal stream downwards to converge at a central point.

The molten metal flow is supplied so as to come into contact with the cooling water at a position eccentric to the central point where the cooling water concentrates by the amount of eccentricity E. The eccentricity E is related to the vertical component of the cooling water injection distance (the vertical distance from the tip of the cooling water nozzle to the center point) L, and the value of E/L is in the range of 0.05 to 0.20. is set to be The value of E/L is preferably 0.07 or more. Also, the value of E/L is preferably 0.12 or less.

Further, the injection pressure of the cooling water to be injected is 10 MPa or more, and F/M, which is the ratio of the amount F (kg/min) of the cooling water to the falling amount M (kg/min) of the molten metal flow, is 50 or more. is preferable, and may be 60 or more.

In the metal powder obtained in the present embodiment, the total content of Fe, Ni and Co is 76.0 at% or more and 86.0 at% or less in terms of atomic fraction, and the apparent density is 3.5 g/cm ³ or more. , a circularity of 0.90 or more, an average particle diameter (D ₅₀ ) of 50 μm or less, and an amorphization degree of 95% or more.

Next, a method for producing a water-atomized metal powder will be explained while explaining a preferred apparatus for producing a water-atomized metal powder according to the present embodiment.

FIG. 1 is a diagram schematically showing a water-atomized metal powder manufacturing apparatus (hereinafter also referred to as an atomizing apparatus) according to this embodiment. In the atomizer shown in FIG. 1, the molten metal stream is dropped at an eccentric position by horizontally shifting the molten steel nozzle with respect to the central point where the cooling water concentrates.

FIG. 2 is a diagram schematically showing an atomizing device according to another embodiment of the present invention. In the atomizer shown in FIG. 2, the molten steel nozzle is arranged obliquely with respect to the vertical direction, so that the drop position of the molten metal flow is eccentric with respect to the central point where the cooling water concentrates.

FIG. 3 is a diagram schematically showing the configuration of water-atomized metal powder production equipment including an atomizer.

The atomizing device 14 shown in FIG. 1 has a tundish 1, a molten steel nozzle 3, a nozzle header 4, cooling water nozzles (spray nozzles) 5A and 5B, a water pipe 18 from a high pressure pump, and a chamber 19.

The tundish 1 is a container-shaped member into which the molten steel 2 melted in the melting furnace is poured. As the tundish 1, a commonly known one may be used. As shown in FIG. 1, an opening for connecting a molten steel nozzle 3 is formed in the bottom of the tundish 1 .

By adjusting the composition of the molten steel 2, the composition of the manufactured metal powder 9 can be adjusted. In the production method of the present embodiment, the total content of Fe, Ni and Co is 76.0 at% or more and 86.0 at% or less in atomic fraction, and the average particle diameter (D ₅₀ ) is 50 μm or less. Suitable for powder production. Also, the metal powder 9 preferably contains at least one selected from Si, P and B. Alternatively, it is also preferable to further contain Cu. In order to produce the metal powder having the above composition, the composition of the molten steel 2 should be adjusted within the above range.

The molten steel nozzle 3 is a cylindrical body connected to the opening at the bottom of the tundish 1. Molten steel 2 passes through the inside of the molten steel nozzle 3 . If the length of the molten steel nozzle 3 is long, the temperature of the molten steel 2 drops while passing through it. Therefore, the melting temperature in the melting furnace must be determined in anticipation of the temperature drop at the molten steel nozzle 3 . The length of the molten steel nozzle 3 is determined according to the thickness of the nozzle header 4 . If the injection pressure of the cooling water is increased, the thickness of the nozzle header 4 must be increased in relation to the pressure resistance, so the length of the molten steel nozzle 3 must also be changed. The amount of molten steel that falls per unit time (the amount of molten metal flow that falls) M (kg/min) can be adjusted by the injection hole diameter of the molten steel nozzle 3 .

The

spray nozzles

5A and 5B are suitable nozzles for discharging the cooling water 7 to collide with the molten metal flow 6. The

spray nozzles

5A and 5B inject cooling water 7 against the molten metal flow 6 falling through the inside of the molten steel nozzle 3, causing the molten metal flow 6 and the cooling water 7 to collide with each other. As a result, the molten metal flow 6 is divided and the metal powder 9 is obtained. The

spray nozzles

5A, 5B spray cooling water 7 toward the molten metal flow 6 downward from the periphery of the molten metal flow 6 so as to converge at a central point 11 .

In the atomizer 14 shown in FIG. 1, the molten steel nozzle 3 is arranged so that its axial direction is along the vertical direction. The molten steel nozzle 3 supplies the molten metal stream 6 so as to contact the cooling water 7 at a position separated by the eccentricity E in the horizontal distance from the center point 11 . In the molten steel nozzle 3, the amount of eccentricity E is such that the value of E/L is in the range of 0.05 to 0.20 in relation to the vertical distance L from the tip of the cooling water nozzle (spray nozzle) to the center point 11. are arranged so that In addition, the plurality of cooling water nozzles (spray nozzles) are arranged so that the heights of the tips of the nozzles are the same.

The water/molten steel ratio (F/M) is the ratio of the amount F (kg/min) of the cooling water 7 discharged from the discharge ports of the

spray nozzles

5A and 5B to the amount M (kg/min) of the molten metal flow 6. and In this embodiment, it is preferable to adjust the water/molten steel ratio (F/M) to 50 or more. The amount F of cooling water is the total amount of cooling water discharged from all cooling water nozzles (spray nozzles).

When the water/molten steel ratio (F/M) is less than 50, the cooling rate is slow, and part or all of the metal powder tends to crystallize, so the desired degree of amorphization may not be obtained. . Also, the water/molten steel ratio (F/M) is preferably 80 or higher. The water/molten steel ratio (F/M) is more preferably 100 or more.

FIG. 2 is a diagram schematically showing an atomizing device according to another embodiment. The atomizing device shown in FIG. 2 is an example of an eccentric manufacturing device in which the molten steel nozzle 3 (the axial direction of the molten steel nozzle 3) is obliquely arranged with respect to the vertical direction. 1 and 2 differ only in the arrangement angle of the molten steel nozzle 3, and the basic configuration is the same, so descriptions other than the molten steel nozzle 3 will be omitted.

FIG. 2 shows the amount of eccentricity E and the vertical distance from the tip of the cooling water nozzle to the central point where the cooling water concentrates (perpendicular to the cooling water injection distance) when the molten steel nozzle 3 is arranged obliquely to the vertical direction. Component) L is shown. As also shown in FIG. 2, the eccentricity E is the horizontal distance between the position where the cooling water collides with the molten metal flow and the central point where the cooling water concentrates. The vertical component L of the cooling water injection distance is the vertical component of the distance from the tip of the cooling water nozzle 5 to the central point where the cooling water concentrates.

FIG. 3 is a schematic diagram showing a configuration example of a manufacturing facility for water-atomized metal powder. The water-atomized metal powder manufacturing facility shown in FIG. In the present invention, as the atomizer 14, an atomizer as shown in FIGS. 1 and 2 is used. As for the cooling water, the cooling water temperature controller 16 is used to adjust the temperature in the cooling water tank 15, which is then sent to the cooling water high pressure pump 17, and from the cooling water high pressure pump 17 to the cooling water pipe (high pressure It is sent to the atomizer 14 through a water pipe 18 from the pump. Further, in the atomizer 14, cooling water 7 is sprayed from cooling water nozzles (spray nozzles) 5 onto the falling molten metal flow 6 to divide the molten metal flow 6 into metal powder and cool the metal powder. to produce metal powder. Although only one cooling water high-pressure pump 17 is shown in FIG. 3, two or more cooling water nozzles (spray nozzles) may be provided for each cooling water nozzle (spray nozzle).

A plurality of cooling water nozzles (spray nozzles) 5 are arranged in a circle when viewed from above. Cooling water is sprayed toward it. The center point 11 is the position where the axial straight lines (axes) of the cooling water nozzles converge. 1 to 3, of the plurality of cooling water nozzles, only two cooling water nozzles (spray nozzles) in the 3 o'clock and 9 o'clock directions when viewed from above are illustrated.

In the present invention, the molten metal flow 6 is determined by the horizontal distance (eccentricity E) between the collision position of the molten metal flow 6 and the cooling water and the center point 11 where the cooling water concentrates, which is the injection distance of the cooling water. The position where the cooling water concentrates so that the value of E/L is in the range of 0.05 to 0.20 in relation to the vertical component (vertical distance from the tip of the cooling water nozzle to the center point) L , to a position shifted horizontally from the center point 11 .

Next, the methods for measuring the average particle size, apparent density, circularity, and degree of amorphization of the obtained metal powder will be described.

Apparent density is measured in accordance with JIS Z 2504:2012.

Circularity is obtained by taking approximately 5000 projected images of metal powder dispersed on a slide using a particle image analyzer (G3SE) manufactured by Morphologi, and binarizing each metal powder data of the projected image. The value of the volume average value (C ₅₀ ) obtained by image analysis was used. Specifically, the volume average value (C ₅₀ ) is obtained as follows. By the above image analysis, the projected area and peripheral length of each metal powder are measured. Then, the degree of circularity (=2(π×projected area of metal powder) ^1/2 /peripheral length) is calculated for each metal powder. The diameter of a circle having the same area as the projected area of each metal powder (equivalent circle diameter) is calculated, and the volume of a sphere having the same diameter as that diameter is calculated. As a result, the circularity and volume of each metal powder can be obtained, and the volume frequency at each circularity can be calculated. Then, the circularities of all the metal powders subjected to image analysis are arranged in ascending order, and the circularity of the metal powder corresponding to 50% of the total volume of all the metal powders is taken as the volume average value (C ₅₀ ).

For the degree of amorphization, after removing dust other than the metal powder from the obtained metal powder, the halo peak from the amorphous phase and the diffraction peak from the crystal are measured by the X-ray diffraction method, and the WPPD method is used. Calculated by The "WPPD method" here is an abbreviation for Whole-powder-pattern decomposition method, and is described in Hideho Toratani: Journal of the Crystallographic Society of Japan, vol. 30 (1988), No. There is a detailed explanation on pages 4, 253-258.

For the average particle size, the average particle size ( _D50 ) is calculated by an integration method. It is also possible to use laser diffraction/scattering particle size distribution measurement. The average particle size (D ₅₀ ) is the particle size (median size) of 50% cumulative volume-based particles in the particle size distribution.

According to the present invention, the total content of Fe, Ni and Co is 76.0 at% or more and 86.0 at% or less in terms of atomic fraction, the apparent density is 3.5 g/cm ³ or more, and the circularity is A metal powder having an average particle diameter (D ₅₀ ) of 0.90 or more, an average particle diameter (D 50 ) of 50 μm or less, and an amorphization degree of 95% or more can be obtained by a water atomization method.

In addition, nano-sized crystals precipitate when a member molded from the water-atomized metal powder obtained in the present invention is subjected to an appropriate heat treatment.

In particular, if the water-atomized metal powder having a large total content of Fe, Ni, and Co obtained in the present invention is used as a raw material, a reactor or motor molded from the metal powder as a raw material can be appropriately heat-treated, It is possible to achieve both low loss and high magnetic flux density.

In addition, in recent years, Materia Vol. 41 No. 6P. 392, Journal of Applied Physics 105, 013922 (2009), Patent No. 4288687, Patent No. 4310480, Patent No. 4815014, WO2010/084900, JP-A-2008-231534, JP-A-2008-231 533 As shown in Japanese Patent Publication No. 2710938, hetero-amorphous materials and nanocrystalline materials having high magnetic flux densities have been developed. The present invention is very advantageously applied to the production of metal powders containing a large amount of Fe, Ni and Co, which are used in these materials, by the water atomization method. In particular, when the Fe-based component concentration is 76.0% or more in terms of at % (atomic fraction), it has been very difficult to increase the degree of amorphization with conventional techniques.

However, if the manufacturing method of the present invention is applied, even if the Fe-based component concentration is 76.0 at % or more, the apparent density is 3.5 g/cm 3 or more and the circularity (C ₅₀ ) is 0.5 g/cm ³ or more. 90 or more, an average particle diameter (D ₅₀ ) of 50 μm or less, and a degree of amorphization of 95% or more.

In particular, if the metal powder having a large total content of Fe, Ni, and Co obtained in the present invention is used as a raw material, a reactor or motor molded from the metal powder as a raw material is subjected to an appropriate heat treatment to reduce loss. It is possible to achieve both high strength and high magnetic flux density.

Examples of the present invention will be described below. However, the present invention is not limited to the following examples. In this example, metal powder was produced using the atomizing apparatus shown in FIGS. 1 and 2 and the atomizing apparatus and manufacturing equipment having the same configuration as the water-atomized metal powder manufacturing equipment shown in FIG. At that time, the invention examples and comparative examples of the present invention were carried out by changing the atomization conditions.

The drop amount of the molten metal flow was set to 4-5 kg/min. The atomizer was equipped with 12 cooling water nozzles (spray nozzles). The cooling water nozzles are arranged on a plane perpendicular to the falling direction (vertical direction) of the molten metal flow at equal intervals in a circumferential manner when viewed from above, and the cooling water trajectory is discharged toward the molten metal flow. The formed convergence angle α was 24° (see angle α in Figure 1). All of the cooling water nozzles were flat spray nozzles in which the sprayed water spreads in a fan shape. The amount of cooling water (total amount of cooling water injected from 12 cooling water nozzles) F was set to 250 kg/min, and the injection pressure of cooling water injected from each cooling water nozzle was set to 15 MPa.

In carrying out the manufacturing methods of invention examples and comparative examples, raw materials (molten steel) adjusted to have the following composition system were prepared.

Specifically, a soft magnetic material having the following composition was prepared. In addition, "%" means "at %" (atomic fraction). (i) to (v) are Fe-based soft magnetic raw materials, (vi) is an Fe+Co-based soft magnetic material, and (vii) is an Fe+Co+Ni-based soft magnetic material.
(i) Fe76.0%-Si9.0%-B10.0%-P5.0%
(ii) Fe78.0%-Si9.0%-B9.0%-P4.0%
(iii) Fe80.0%-Si8.0%-B8.0%-P4.0%
(iv) Fe82.8%-B11.0%-P5.0%-Cu1.2%
(v) Fe84.8%-Si4.0%-B10.0%-Cu1.2%
(vi) Fe69.8%-Co15.0%-B10.0%-P4.0%-Cu1.2%
(vii) Fe69.8%-Ni1.2%-Co15.0%-B9.4%-P3.4%-Cu1.2%

Tables 1 and 2 show raw material conditions, atomization conditions, and evaluation results of the produced metal powders of invention examples and comparative examples.

In the examples and comparative examples, raw materials such as iron were placed in a high-frequency melting furnace and melted by applying high frequency to each component (i) to (vii). At that time, the melting temperature before atomization was in the range of 1500 to 1650°C. The higher the iron content, the higher the melting point and therefore the higher the melting temperature. When the target melting temperature was reached, the high-frequency melting furnace was tilted to pour the molten steel into the tundish. A molten steel nozzle with a predetermined hole diameter was installed at the bottom of the tundish, and the drop amount of the molten metal flow was adjusted to be in the range of 4 to 5 kg/min. As shown in Table 1, the atomization conditions in each example are the convergence angle α, the type and number of cooling water nozzles, the injection pressure of cooling water (injection pressure of cooling water injected from each cooling water nozzle), and the amount of cooling water. (Total amount of cooling water injected from 12 cooling water nozzles) was adjusted. As a type of nozzle, a fan-shaped 15° spray is a cooling water nozzle (flat spray nozzle) in which the sprayed water spreads in a fan shape, and a flat spray in which the central angle (spread angle) of the fan shape is 15 °. It refers to using a nozzle. In addition, when the horizontally spreading flat spray was installed in the nozzle, the nozzle was installed so that the width spreading direction of the nozzle was horizontal.

In the present invention, the molten steel is dropped eccentrically (shifted) from the center of the atomized water sprayed in a downward cone (that is, the apex of the cone).

In the invention example, the eccentricity E (mm), which is the horizontal distance between the contact position of the molten metal flow and the cooling water and the center point where the cooling water concentrates, is the vertical component of the cooling water injection distance (cooling water nozzle In relation to the vertical distance L (mm) from the tip to the center point, the eccentricity was set so that E/L was in the range of 0.05 to 0.20. In invention examples 1 to 4, the molten steel nozzle was arranged vertically as shown in FIG. 1. In invention examples 5 and 6, since the amount of eccentricity E was large, the molten steel nozzle was arranged obliquely as shown in FIG. .

On the other hand, in Comparative Example 1, the contact position between the molten metal flow and the cooling water is not eccentric from the center point where the cooling water concentrates (eccentricity E=0, E/L=0). In Comparative Example 2, the amount of eccentricity was increased, and the relationship between the amount of eccentricity E and the vertical component L of the cooling water injection distance was set to E/L=0.25.

In the evaluation of the produced metal powder, circularity ( _C50 ), average particle size ( _D50 ), apparent density, and degree of amorphization were measured by the following methods (details are as described above).

The apparent density was measured according to JIS Z 2504:2012.

Circularity is obtained by taking approximately 5,000 projection images of powder particles dispersed on a slide using a particle image analyzer (G3SE) manufactured by Morphologi, and binarizing each metal powder data of the projection images. The value of the volume average value (C ₅₀ ) obtained by image analysis was used.

For the degree of amorphization, after removing dust other than the metal powder from the obtained metal powder, the halo peak from the amorphous phase and the diffraction peak from the crystal are measured by the X-ray diffraction method, and the WPPD method is used. Calculated by

As for the average particle size, the average particle size (D ₅₀ ) was calculated by the integration method. Laser diffraction/scattering particle size distribution measurements were used.

The target values are an apparent density of 3.5 g/cm ³ or more, a circularity (C ₅₀ ) of 0.90 or more, an average particle diameter (D ₅₀ ) of 50 μm or less, and an amorphization degree of 95% or more. If all of the bulk density, circularity, average particle size and degree of amorphization reach the target values, it will be passed (○), and any of the apparent density, circularity, average particle size and degree of amorphization failed (x) if the target value was not reached.

All of Invention Examples 1 to 6 have an E/L in the range of 0.05 to 0.20, and the metal powder produced under these conditions has an apparent density, circularity, average particle size, and amorphization degree. All targets were exceeded and passed.

Comparative Example 1 is a case where the contact position of the molten metal flow and cooling water is not eccentric from the center point where the cooling water concentrates (eccentricity E = 0, E / L = 0), but the apparent density, Circularity did not reach the target value for all compositions.

In Comparative Example 2, E/L exceeded 0.20 and was set to 0.25, but the apparent density did not reach the target value for all compositions. Furthermore, the circularity did not reach the target value in some compositions.

As described above, all the metal powders produced in Invention Examples 1 to 6, which are conditions within the scope of the present invention, passed the test. On the other hand, all of the metal powders produced in Comparative Examples 1 and 2 under conditions outside the scope of the present invention were rejected.

From the above, E / L is in the range of 0.05 to 0.20, the total content of Fe, Ni and Co is 76.0 at% or more and 86.0 at% or less in atomic fraction, and the apparent density is 3 .5 g/cm ³ or more, a circularity of 0.90 or more, an average particle diameter (D ₅₀ ) of 50 μm or less, and an amorphization degree of 95% or more. rice field.

1 tundish 2 molten steel 3 molten steel nozzle 4

nozzle header

5, 5A, 5B cooling water nozzle (spray nozzle)
6 Molten metal flow 7 Cooling water 9 Metal powder 10 Convergence angle (mounting angle of two nozzles facing each other: vertical angle) α
11 Position where cooling water concentrates (central point)
14 Atomizing device 15 Cooling water tank 16 Cooling water temperature controller 17 Cooling water high pressure pump 18 Cooling water pipe (water pipe from high pressure pump)
19 Chamber

Claims

A method for producing water-atomized metal powder, in which cooling water is jetted against a falling molten metal flow, and the molten metal flow collides with the cooling water to divide the molten metal flow into metal powder,
the cooling water is jetted downward from the perimeter of the molten metal flow toward the molten metal flow so as to converge at a central point;
The molten metal flow contacts the cooling water at a position separated by an eccentricity E in the horizontal distance from the center point,
The amount of eccentricity E is in the relationship between the vertical distance L from the tip of the cooling water nozzle that injects the cooling water to the center point, and the value of E/L is in the range of 0.05 to 0.20. A method for producing atomized metal powder.
The injection pressure of the cooling water is 10 MPa or more, and F/M, which is a ratio of the amount F (kg/min) of the cooling water to the falling amount M (kg/min) of the molten metal flow, is 50 or more. A method for producing a water-atomized metal powder according to claim 1.
The metal powder has a total content of Fe, Ni and Co in an atomic fraction of 76.0 at% or more and 86.0 at% or less, an apparent density of 3.5 g/cm 3 or more, and a circularity of 0. 90 or more, an average particle diameter (D 50 ) of 50 μm or less, and an amorphization degree of 95% or more.
An apparatus for producing water-atomized metal powder in which cooling water is jetted against a falling molten metal flow, and the molten metal flow collides with the cooling water to divide the molten metal flow into metal powder,
a plurality of cooling water nozzles for injecting the cooling water toward the molten metal flow downward from the periphery of the molten metal flow so as to converge at a central point;
a molten steel nozzle that supplies the molten metal flow so as to contact the cooling water at a position separated by an eccentricity E in the horizontal distance from the center point,
Manufacture of water-atomized metal powder, wherein the eccentricity E is in a relationship between the vertical distance L from the tip of the cooling water nozzle to the center point, and the value of E/L is in the range of 0.05 to 0.20. Device.