METHOD FOR MANUFACTURING ATOMIZED METAL POWDER

Abstract

[Object] Provided is a method for manufacturing atomized metal powder having a high amorphous material fraction by using a water atomizing method.

[Solution] A method for manufacturing atomized metal powder in which atomized metal powder having an amorphous material fraction of 90% or more is obtained, the method including ejecting high-pressure water so as to collide with a molten metal stream flowing vertically downward, separating the molten metal stream into metal powder, and cooling the metal powder, in which the high-pressure water collides with the molten metal with a collision pressure of 20 MPa or higher, and in which a temperature of the molten metal and/or a temperature of the high-pressure water are controlled so that the high-pressure water is in a subcritical state or a supercritical state on a collision surface with the molten metal.

Claims

1. A method for manufacturing atomized metal powder in which atomized metal powder having an amorphous material fraction of 90% or more is obtained, the method comprising ejecting high-pressure water so as to collide with a molten metal stream flowing vertically downward, separating the molten metal stream into metal powder, and cooling the metal powder, wherein the high-pressure water collides with the molten metal with a collision pressure of 20 MPa or higher, and wherein a temperature of the molten metal and/or a temperature of the high-pressure water are controlled so that the high-pressure water is in a subcritical state or a supercritical state on a collision surface with the molten metal.

2. The method for manufacturing atomized metal powder according to claim 1, wherein an average temperature of the molten metal and the high-pressure water is 374 C. or higher at a time of collision between the high-pressure water and the molten metal.

3. The method for manufacturing atomized metal powder according to claim 1, wherein, when a flow rate of the molten metal stream per unit time is defined as Qm (kg/min) and an ejection rate of the high-pressure water per unit time is defined as Qaq (kg/min), a mass ratio (Qaq/Qm) is 35 or more.

4. The method for manufacturing atomized metal powder according to claim 2 wherein, when a flow rate of the molten metal stream per unit time is defined as Qm (kg/min) and an ejection rate of the high-pressure water per unit time is defined as Qaq (kg/min), a mass ratio (Qaq/Qm) is 35 or more.

5. The method for manufacturing atomized metal powder according to claim 1, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction.

6. The method for manufacturing atomized metal powder according to claim 2, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction.

7. The method for manufacturing atomized metal powder according to claim 3, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction.

8. The method for manufacturing atomized metal powder according to claim 4, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2.0 at % or less in terms of atomic fraction.

9. The method for manufacturing atomized metal powder according to claim 1, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 m or more.

10. The method for manufacturing atomized metal powder according to claim 2, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 m or more.

11. The method for manufacturing atomized metal powder according to claim 3, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 m or more.

12. The method for manufacturing atomized metal powder according to claim 4, wherein the atomized metal powder contains iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and has an average particle size of 5 m or more.

13. The method for manufacturing atomized metal powder according to claim 1, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

14. The method for manufacturing atomized metal powder according to claim 2, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

15. The method for manufacturing atomized metal powder according to claim 3, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

16. The method for manufacturing atomized metal powder according to claim 4, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

17. The method for manufacturing atomized metal powder according to claim 5, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

18. The method for manufacturing atomized metal powder according to claim 6, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

19. The method for manufacturing atomized metal powder according to claim 9, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

20. The method for manufacturing atomized metal powder according to claim 10, wherein the subcritical state is represented by a pressure of 0.5 MPa to 22 MPa and a water temperature of higher than 150 C. and lower than 374 C., and wherein the supercritical state is represented by a pressure of 22 MPa or higher and a water temperature of 374 C. or higher.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG. 1 is a schematic diagram of an example of a manufacturing apparatus which can be used in a method for manufacturing atomized metal powder according to aspects of the present invention.

[0052] FIG. 2 is a schematic diagram illustrating an example of manufacturing equipment for implementing the manufacturing method according to aspects of the present invention.

[0053] FIG. 3 is a diagram illustrating the relationship between the pressure, temperature, and state of water.

[0054] FIG. 4 is a graph illustrating the relationship between an amorphous material fraction and a collision pressure.

[0055] FIG. 5 is a schematic diagram illustrating a measurement configuration for determining the collision pressure of molten metal by using a collision pressure sensor.

[0056] FIG. 6 is a diagram illustrating a B-H diagram obtained by using a VSM.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0057] Hereafter, an embodiment of the present invention will be described. Here, the present invention is not limited to the embodiment below.

[0058] FIG. 1 schematically illustrates an example of a manufacturing apparatus which can be used in a method for manufacturing atomized metal powder according to aspects of the present invention. In FIG. 1, after molten metal 3 has been charged into a tundish 2, the molten metal 3 flows downward through a molten metal-injecting nozzle 4 due to the weight of the molten metal 3. In addition, cooling water 20 (corresponding to high-pressure water) fed into a nozzle header 5 is ejected through cooling nozzles 6. The cooling water 20 collides with the molten metal (molten metal stream flowing downward) and, as a result, the molten metal is atomized, that is, separated into metal powder 8.

[0059] FIG. 2 schematically illustrates an example of manufacturing equipment for implementing the manufacturing method according to aspects of the present invention. In the manufacturing equipment illustrated in FIG. 2, atomized metal powder is manufactured by controlling the temperature of cooling water in a cooling water tank 15 by using a cooling water-temperature controller 16, by transporting the cooling water, whose temperature has been controlled, to a high-pressure pump 17 for atomizing cooling water, by transporting the cooling water from the high-pressure pump 17 for atomizing cooling water through pipework 18 for atomizing cooling water to an atomizing apparatus 14 (corresponding to the manufacturing apparatus in FIG. 1), and by ejecting the high-pressure water, which collides with the molten metal stream flowing vertically downward, from this atomizing apparatus 14 to separate the molten metal stream into metal powder and to cool the metal powder.

[0060] First, one aspect of the present invention is characterized by controlling a collision pressure to be 20 MPa or higher when the cooling water 20 collides with the molten metal and the state of the water to be a subcritical state of water or a supercritical state of water on a collision surface. The expression supercritical state of water denotes a state which is represented by a temperature of 374 C. or higher and a pressure of 22 MPa or higher. The expression subcritical state of water denotes a high-temperature and high-pressure state which is close to a critical point and which is exemplified by, as illustrated in FIG. 3, a state which is represented by a temperature of higher than 150 C. and lower than 374 C. and a pressure of 0.1 MPa or higher and lower than 22 MPa, a state which is represented by a temperature of 374 C. or higher and a pressure of 2 MPa or higher and lower than 22 MPa, and a state which is represented by a temperature of 250 C. or higher and lower than 374 C. and a pressure of 22 MPa or higher.

[0061] In the manufacturing method according to aspects of the present invention, the collision pressure of the cooling water 20 at the time of collision with the molten metal is set to be 20 MPa or more. The collision pressure is determined by using a pressure sensor having a collision surface sensor whose diameter is 2 mm when atomizing is not performed. To control the collision pressure to be 20 MPa or more, it is necessary that the ejection pressure of the cooling water 20 be more than the collision pressure. To control the collision pressure so that the maximum ejection pressure is 98 MPa, it is preferable that the pressure control be performed by using an inverter high-pressure pump. In addition, since there is a decrease in ejection pressure in the case where the cooling water 20 is spread out in a fan-like form, it is preferable that solid stream-type nozzles be used. In addition, since there is a decrease in ejection pressure in the case where the distance between the cooling nozzles 6 and the molten metal is increased, it is preferable that the linear distance between the ejection ports of the cooling nozzles 6 for the cooling water 20 and the molten metal be 150 mm or less or more preferably 100 mm or less.

[0062] In addition, in accordance with aspects of the present invention, the temperature of the molten metal and/or the temperature of the cooling water are controlled so that the cooling water 20 is in a subcritical state or a supercritical state on a collision surface with the molten metal. It is possible to control the temperature of the molten metal by controlling the heating temperature of a melting furnace through high-frequency output. In addition, by holding the molten metal 3 in the melting furnace after heating has been performed, it is possible to control the temperature of the molten metal 3 which is fed into the tundish 2.

[0063] In the manufacturing method according to aspects of the present invention, the temperature of the water on the collision surface is defined as the average temperature of the molten metal and the cooling water 20 (((molten metal temperature)+(cooling water temperature))/2). It is possible to determine the molten metal temperature by using a non-contact thermometer at an atomizing point. It is possible to determine the temperature of the cooling water by using a thermometer (not illustrated) for determining the water temperature in the cooling water tank 15 illustrated in FIG. 2. In addition, in accordance with the relationship between the pressure, the temperature, and the state of water illustrated in FIG. 3, the collision pressure, the temperature of the molten metal, and the temperature of the cooling water 20 are controlled to achieve the average temperature and the collision pressure with which the cooling water is in a subcritical state or a supercritical state. Here, since the temperatures of the molten metal and the cooling water tend to fluctuate, the molten metal temperature may be determined within the margin of error of plus or minus 50 C., and the cooling water temperature may be determined within the margin of error of plus or minus 5 C.

[0064] Hereafter, the effects according to aspects of the present invention will be described.

[0065] FIG. 4 is a graph illustrating the relationship between an amorphous material fraction and a collision pressure. The graph in FIG. 4 relates to a case where atomized metal powder containing iron-group constituents (Fe, Ni, and Co) in a total amount of 76.0 at % in terms of atomic fraction (water-molten metal ratio(mass ratio: Qaq/Qm): 20) and Cu in an amount of 0.5 at % is manufactured and a case where atomized metal powder containing iron-group constituents (Fe, Ni, and Co) in a total amount of 85.8 at % in terms of atomic fraction (water-molten metal ratio: 35) and Cu in an amount of 0.5 at % is manufactured. In addition, in the graph in FIG. 4, in the case of a collision pressure of 20 MPa, the state of water was controlled to be a subcritical state on the collision surface between the cooling water and the molten metal. In the case of a collision pressure of 22 MPa or higher, that is, in the case of a collision pressure of higher than 20 MPa, the state of water was controlled to be a supercritical state on the collision surface between the cooling water and the molten metal. In addition, in the case of a collision pressure of lower than 20 MPa, the state of water was controlled not to be either a subcritical state or a supercritical state on the collision surface between the cooling water and the molten metal.

[0066] As indicated in FIG. 4, in the case where the collision pressure is 20 MPa or higher, it is possible to achieve an amorphous material fraction of 90% or more regardless of a variation in the chemical composition of obtained atomized metal powder, a variation in water-molten metal ratio, or whether the state of the water is a subcritical state or a supercritical state on a collision surface.

[0067] In addition, when the manufacturing method according to aspects of the present invention is implemented, it is preferable that the average temperature of the molten metal and the cooling water be 374 C. or higher at the time of collision between the cooling water (high-pressure water) and the molten metal. By controlling the average temperature described above to be 374 C. or higher, there is an advantage in that the state of water is brought close to a critical state and that there is an increase in vapor density.

[0068] When the flow rate of the molten metal stream per unit time is defined as Qm (kg/min) and the ejection rate of the cooling water (high-pressure water) per unit time is defined as Qaq (kg/min), it is preferable that a mass ratio (Qaq/Qm) be 35 or more. This is because, since there is a tendency for an amorphous material fraction to increase in the case where such a mass ratio is large, and since it is easy to control the mass ratio in the case where the mass ratio is 35 or more, it is possible to achieve a sufficiently high level of effect.

[0069] The manufacturing method according to aspects of the present invention can preferably be used for manufacturing atomized metal powder containing iron-group constituents (Fe, Ni, and Co) in a total amount of 76 at % or more in terms of atomic fraction and Cu in an amount of 0.1 at % or more and 2 at % or less in terms of atomic fraction. In the case where the content of iron-group elements (Fe+Co+Ni) is large, since there is an increase in cooling start temperature due to an increase in melting point, film boiling tends to occur at the beginning of cooling, which makes it difficult to increase an amorphous material fraction to 90% or more by using conventional methods. According to aspects of the present invention, it is possible to increase an amorphous material fraction, even in the case where the content of iron-group elements (Fe+Co+Ni) is large. By using the manufacturing method according to aspects of the present invention, since it is possible to increase an amorphous material fraction while increasing the content of iron-group elements (Fe+Co+Ni), it is possible to increase magnetic flux density. As a result, the manufacturing method according to aspects of the present invention contributes to reducing the size of a motor and to increasing motor power.

[0070] Here, by controlling the chemical composition of the molten metal to be within the range described above, the chemical composition of the atomized metal powder is also within the range described above.

[0071] The manufacturing method according to aspects of the present invention can preferably be used for manufacturing atomized metal powder containing iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86.0 at % in terms of atomic fraction, at least two selected from Si, P, and B, and Cu and having an average particle size of 5 m or more. In the case where conventional techniques are used for manufacturing atomized metal powder containing iron-group constituents in significantly large amounts, specifically, containing iron-group constituents (Fe, Ni, and Co) in a total amount of more than 82.5 at % and less than 86 at % in terms of atomic fraction, when an average particle size is small, since it is easy to cool the particles, it is possible to achieve an amorphous material fraction larger than that achieved when the average particle size is large. However, when the average particle size is 5 m or more, it is very difficult to increase the amorphous material fraction to 90% or more. According to aspects of the present invention, even when the average particle size is 5 m or more, it is possible to increase the amorphous material fraction to 90% or more. In addition, the upper limit of the average grain diameter with which it is possible to increase the amorphous material fraction to 90% or more in accordance with aspects of the present invention is 75 m as a rough guide. Here, the particle size is determined by performing classification utilizing a sieve method, and the average particle size (D50) is calculated by using an integration method. In addition, a laser diffraction/scattering particle size distribution analyzer may also be used.

EXAMPLES

[0072] Examples and comparative examples were implemented by using the manufacturing equipment illustrated in FIG. 2 in which the apparatus for manufacturing water-atomized metal powder illustrated in FIG. 1 was installed.

[0073] Molten metal 3, which has been prepared by melting a raw material at a predetermined temperature by using a high-frequency melting furnace or the like, is fed into a tundish 2. A molten metal-injecting nozzle 4 having a predetermined molten metal-injecting nozzle diameter has been set in the tundish 2 in advance. When the molten metal 3 is fed into the tundish 2, the molten metal is extruded through the molten metal-injecting nozzle 4 due to free drop or back pressure and flows downward. Cooling water, which is ejected through cooling water nozzles 6 with a predetermined water pressure by using a high-pressure pump 17 for atomizing cooling water, collides with the molten metal, so that the molten metal is separated, pulverized, and cooled. There may be a case where the cooling water has been stored in a cooling water tank 15 in advance to control the water temperature by using a cooling water-temperature controller 16 as needed. As the cooling water ejecting nozzles, solid stream-type nozzles were used. A dozen cooling water nozzles were arranged around the molten metal flowing downward so as to make an angle of 30 with respect to the vertical direction. Here, it is possible to realize the effects according to aspects of the present invention, even in the case where the nozzles are arranged so as to make an angle of 5 to 60 with respect to the vertical direction. Before atomizing is started, the collision pressure of the molten metal is determined by using a collision pressure sensor 51 (refer to FIG. 5). The collision pressure sensor 51 is arranged in a direction perpendicular to the nozzle ejection direction to confirm whether a predetermined collision pressure is achieved. Here, although FIG. 5 illustrates not only a configuration in which the cooling water is ejected onto the molten metal but also a configuration in which the cooling water is ejected onto the collision pressure sensor 51, this is only for the purpose of description, and the collision pressure is determined by using the collision pressure sensor 51 before the molten metal is allowed to flow down. Iron powder manufactured from the molten metal is collected by using a hopper, dried, classified, and subjected to evaluation regarding an amorphous material fraction. In the case of an amorphous material fraction of 90% or more is judged as satisfactory.

[0074] When the manufacturing methods of the examples and the comparative examples were implemented, soft magnetic materials having the following chemical compositions were prepared. % means at %. (i) through (v) are Fe-based soft magnetic row materials. (vi) is an FeCo-based soft magnetic material. (vii) is an FeCoNi-based soft magnetic material.

[0075] (i) Fe76%-Si9%-B10%-P5%

[0076] (ii) Fe78%-Si9%-B9%-P4%

[0077] (iii) Fe80%-Si8%-B8%-P4%

[0078] (iv) Fe82.8%-B11%-P5%-Cu1.2%

[0079] (v) Fe84.8%-Si4%-B10%-Cu1.2%

[0080] (vi) Fe69.8%-Co15%-B10%-P4%-Cu1.2%

[0081] (vii) Fe69.8%-Ni1.2%-Co15%-B9.4%-P3.4%-Cu1.2%

[0082] Although (i) through (vii) were prepared so that each of the materials had a corresponding one of the target chemical compositions, in actual chemical compositions, after having performed melting and atomizing, there were errors within the margin of about plus or minus 0.3 at % or impurities were contained in some cases. In addition, in some cases, there was some variation in chemical composition due to, for example, oxidation occurring in a melting process or an atomizing process or after an atomizing process.

[0083] Examples 1 through 4 and comparative examples 1 through 3 were implemented under the conditions given in Table 1. The average particle size and the amorphous material fraction were evaluated by using the method described above. From the results of the examples and the comparative examples, it was clarified that an amorphous material fraction of 90% or more was achieved in the case of all the examples, which were within the range of the present invention. In the case of the comparative examples, an amorphous material fraction of 90% or more was not achieved.

[0084] The atomized metal powder of examples 1 through 4 were subjected to an appropriate heat treatment after having been subjected to forming. With this, nanosized crystals were precipitated. In addition, it was clarified that both low iron loss and high magnetic flux density were achieved. Specifically, such results were clarified by using the following method.

[0085] The sizes of the nanosized crystals were derived by using the Scherrer equation after having performed determination utilizing an XRD (X-ray diffractometer). In the Scherrer equation, K denotes a shape factor (usually assigned a value of 0.9), denotes a full-width at half maximum (expressed in units of radian), is expressed by the equation 2=52.505 (Fe110-plane), and denotes a crystal size.

=K/ cos (Scherrer equation)

[0086] In addition, the magnetic properties of the obtained powder were investigated by using a VSM (vibrating sample magnetometer), and, from the B-H diagram (FIG. 6) obtained by using the VSM, the saturated magnetic flux density was determined from point C (point F), the retaining force was determined from point E, the magnetic permeability was determined from the maximum slope of B, and the iron loss was determined from the hysteresis area (C-D-F-G). Here, the diagram in FIG. 6 is opened to the public by Japan Science and Technology Agency (JST), which is one of the National Research and Development Agencies, (URL: https://www.jst.go.jp/pr/report/report27/grf2.html, as searched on 16 Nov. 2017)

TABLE-US-00001 TABLE 1 Temper- Ejection Molten Cooling Water- ature Pressure of Atomizing Judgement Metal Flow Water Molten of High- High- Start Average Iron-group Average Amorphous (A ratio Example/ (Downward) Flow Metal pressure pressure Collision Temper- Temper- Constituent Particle Material of 90% Comparative Rate Rate Ratio Water Water Pressure ature ature State of Chemical Composition Fe + Ni + Co Size Fraction or more is Example [kg/min] [kg/min] [] [ C.] [MPa] [MPa] [ C.] [ C.] Water [at %] [at %] [m] [%] satisfactory.) Example 1 15 300 20 10 90 20 1200 605 Subcritical (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 32 93 Satisfactory Example 2 15 420 28 10 90 20 1200 605 Subcritical (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 33 99 Satisfactory 10 90 605 Subcritical (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 33 97 Satisfactory 10 90 605 Subcritical (iii) Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 35 94 Satisfactory Example 3 12 420 35 10 100 23 1200 605 Supercritical (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 34 100 Satisfactory 10 100 605 Supercritical (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 29 99 Satisfactory 10 100 605 Supercritical (iii) Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 29 97 Satisfactory 10 100 605 Supercritical (iv) Fe.sub.82.8B.sub.11P.sub.5Cu.sub.1.2 82.8 35 95 Satisfactory 10 100 605 Supercritical (v) Fe.sub.84.8Si.sub.4B.sub.10Cu.sub.1.2 84.8 36 94 Satisfactory 10 100 605 Supercritical (vi) Fe.sub.69.8Co.sub.15B.sub.10P.sub.4Cu.sub.1.2 84.8 32 93 Satisfactory 10 100 605 Supercritical (vii) Fe.sub.69.8Ni.sub.1.2Co.sub.15B.sub.9.4P.sub.3.4Cu.sub.1.2 86.0 35 92 Satisfactory Comparative 12 120 8 10 55 12 1200 605 Vapor (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 43 83 Unsatisfactory Example 1 10 55 605 Vapor (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 44 62 Unsatisfactory 10 55 605 Vapor (iii) Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 43 45 Unsatisfactory 10 55 605 Vapor (iv) Fe.sub.82.8B.sub.11P.sub.5Cu.sub.1.2 82.8 44 40 Unsatisfactory 10 55 605 Vapor (v) Fe.sub.84.8Si.sub.4B.sub.10Cu.sub.1.2 84.8 45 38 Unsatisfactory 10 55 605 Vapor (vi) Fe.sub.69.8Co.sub.15B.sub.10P.sub.4Cu.sub.1.2 84.8 42 35 Unsatisfactory 10 55 605 Vapor (vii) Fe.sub.69.8Ni.sub.1.2Co.sub.15B.sub.9.4P.sub.3.4Cu.sub.1.2 86.0 39 32 Unsatisfactory Comparative 12 420 35 10 60 15 1200 605 Vapor (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 44 88 Unsatisfactory Example 2 10 60 605 Vapor (ii) Fe.sub.78Si.sub.9B.sub.9P.sub.4 78.0 42 73 Unsatisfactory 10 60 605 Vapor (iii) Fe.sub.80Si.sub.8B.sub.8P.sub.4 80.0 39 63 Unsatisfactory 10 60 605 Vapor (vi) Fe.sub.82.8B.sub.11P.sub.5Cu.sub.1.2 82.8 43 53 Unsatisfactory 10 60 605 Vapor (v) Fe.sub.84.8Si.sub.4B.sub.10Cu.sub.1.2 84.8 46 52 Unsatisfactory 10 60 605 Vapor (vi) Fe.sub.69.8Co.sub.15B.sub.10P.sub.4Cu.sub.1.2 84.8 43 46 Unsatisfactory 10 60 605 Vapor (vii) Fe.sub.69.8Ni.sub.1.2Co.sub.15B.sub.9.4P.sub.3.4Cu.sub.1.2 86.0 43 44 Unsatisfactory Comparative 10 350 35 10 15 5 1200 605 Vapor (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 38 5 Unsatisfactory Example 3 Example 4 12 480 40 10 90 20 1200 605 Subcritical (i) Fe.sub.76Si.sub.9B.sub.10P.sub.5 76.0 33 100 Satisfactory

[0087] In Table 1, the term Atomizing Start Temperature denotes the temperature of the molten metal at the atomizing point. The temperature of the molten metal at the atomizing point was determined by using a non-contact thermometer.

[0088] In Table 1, the term Average Temperature denotes a value obtained by using the formula ((molten metal temperature)+(cooling water temperature))/2. The molten metal temperature at the atomizing point was determined by using a non-contact thermometer at an atomizing point, and the cooling water temperature was defined as the temperature of water in the cooling water tank which was determined by using a thermometer.

[0089] In Table 1, the term Water-Molten Metal Ratio denotes the mass ratio Qaq/Qm.

REFERENCE SIGNS LIST

[0090] 2 tundish [0091] 3 molten metal [0092] 4 molten metal-injecting nozzle [0093] 5 nozzle header [0094] 6 cooling nozzle [0095] 8 metal powder [0096] 14 atomizing apparatus [0097] 15 cooling water tank [0098] 16 cooling water-temperature controller [0099] 17 high-pressure pump for atomizing cooling water [0100] 18 pipework for atomizing cooling water [0101] 20 cooling water [0102] 51 collision pressure sensor