JP6706502B2 - Centrifugal atomization powder production disk - Google Patents

Description

The present invention relates to a disk for producing a centrifugal atomizing powder suitable for producing a metal fine powder having a tapping temperature of 400° C. or higher by the centrifugal atomizing method.

In recent years, powders having high fluidity have been demanded in the fields of solder powder, filler powder, thermal spraying powder, additive manufacturing powder and the like. The powder having low fluidity causes deterioration of characteristics and defects of a product using the powder.

The fluidity of the powder changes depending on the sphericity of the powder, the width of the particle size distribution, and the presence or absence of satellites. A powder having a high sphericity, a narrow particle size distribution, and a small amount of satellites has high fluidity. Known methods of producing powders include a water atomizing method (water atomizing method), a gas atomizing method (gas atomizing method), and a centrifugal atomizing method (disk atomizing method). Among them, the centrifugal atomization method is characterized in that it has a high sphericity, a narrow particle size distribution, and a satellite-free powder. This method has an advantage in that a powder having high fluidity can be obtained as compared with other powder manufacturing methods.

In the production of powder by the centrifugal atomization method, the molten metal is dropped from the tapping nozzle onto the center of a centrifugal atomization powder production disk (referred to as a rotating disk) installed at the bottom. This melt forms a thin liquid film on the rotating disk. The thin film becomes thinner due to the centrifugal force due to the rotation of the disk, and fine droplets are scattered from the tip of the rotating disk. A powder is obtained by solidifying the scattered droplets.

The key to producing metal powder by the centrifugal atomization method is a rotating disk. Since the molten metal is dropped on the rotating disk, a base material that does not react with the molten metal and does not soften even at the temperature of the molten metal is used. Further, when the molten metal is dropped, thermal stress is generated in the rotating disk, so that a base material having a thermal shock resistance value higher than the temperature of the molten metal is used. Further, the rotating disk is required to have strength capable of withstanding high speed rotation.

Heretofore, the rotating disk has been generally applied when the melting point is low and the tapping temperature is low, specifically, when the tapping temperature is 300° C. or less and powder production is possible. Its application was mainly for the production of low melting point solder powder. This is because it is not easy to manufacture a rotating disk satisfying the above-mentioned characteristics for metal powder having a high melting point which requires a high tapping temperature. Therefore, various studies have been made on a rotating disk applicable to the production of metal powder having a high melting point.

Japanese Unexamined Patent Application Publication No. 2013-119663 discloses a study example of manufacturing silver (Ag) powder using a rotating disk made of a carbide-dispersed molybdenum alloy.

Japanese Unexamined Patent Application Publication No. 2005-298299 discloses a study example of manufacturing copper (Cu) powder using a silicon nitride rotary disk.

Japanese Unexamined Patent Application Publication No. 2009-62573 discloses a disk (referred to as a base disk) made of a base material having heat resistance and better thermal conductivity than ceramics, and ceramics for covering the upper surface of the base disk. A rotating disk comprising a thin film is disclosed.

Japanese Unexamined Patent Application Publication No. 2012-117115 discloses a rotating disk having a thermal shock resistance value of 710° C. or more and a thermal conductivity of 100 W/m·K or less.

Japanese Unexamined Patent Publication No. 59-133303 proposes a rotating disk capable of withstanding the melting point of pure iron up to 1535°C.

In the rotating disk described in Japanese Patent Application Laid-Open No. 07-145408, a thin metal plate having excellent heat resistance is used as a rotating disk. When installing this on the pedestal of the rotating disk, it is necessary to provide a space between this disk and the pedestal, or to interpose a substance with low thermal conductivity such as ceramics between this disk and the pedestal. ,Proposed.

JP, 2013-119663, A JP, 2005-298299, A JP, 2009-62573, A JP, 2012-117115, A JP-A-59-133303 JP, 07-145408, A

When the present inventor tried the rotating disk described in JP 2013-119663 A, it was possible to produce Ag powder. However, this rotating disk does not have sufficient softening resistance for powder production of an alloy having a higher melting point than Ag. When the present inventor tried to produce the powder of the Fe-based alloy with the rotating disk described in the above publication, the rotating disk was softened and the shape of the rotating disk could not be maintained. Further, also in the production of Ag powder, when raising the tapping temperature for the purpose of pulverization, the softening resistance may not be sufficient.

The rotary disk described in Japanese Unexamined Patent Application Publication No. 2005-298299 has an insufficient thermal shock resistance value. When the present inventors set the temperature of the molten metal at 1250° C. or higher for the purpose of pulverization, the rotary disk was damaged due to insufficient thermal shock resistance.

The ceramic thin film disclosed in JP 2009-62573 A is as thin as 1×10 ² μm or less and 1×10 ⁻¹ μm or more. The porosity of graphite or boron nitride, which is the substrate described in this publication, is generally 10 to 20% by volume. When these are used as a disk substrate, a thin film is not formed on the pores existing on the upper surface of the disk, so that a defect occurs in the coating film. When the base material and the molten metal react with each other, the molten metal and the base material may react with each other at the defective portion to damage the disk.

The rotating disk described in Japanese Unexamined Patent Application Publication No. 2012-117115 does not have sufficient strength against rotation. When the present inventor tried powder production with this rotating disk, the strength of the disk was insufficient and the disk was damaged when the rotation speed of the disk was higher than 60000 rpm. Further, due to the restriction that the thermal conductivity is 100 W/m·K or less, there is a concern that the usable material may be limited when trying to eliminate the insufficient strength of the rotating disk.

In the rotating disk disclosed in Japanese Patent Laid-Open No. 59-133303, the cooling fluid is circulated or collided into the cavity provided in the disk. Since this structure is complicated, it is difficult to miniaturize this disc. Therefore, this disk is not suitable for high-speed rotation for the purpose of pulverizing the powder. In fact, this publication states that the maximum rotation speed of this disk is 35,000 rpm. When the present inventor tried this disc, the rotation speed was limited to 35,000 rpm.

In the rotating disk described in JP-A-07-145408, when the molten metal temperature rises and the disk rotation speed increases, the difference in the coefficient of thermal expansion between ceramics and metal causes the durability of the disk and the characteristics at high speed rotation. It is feared that it will affect. However, with this rotating disk, no study has been made on atomization in which the melt temperature exceeds 1000° C. or atomization in which the disk rotation speed exceeds 18000 rpm.

An object of the present invention is to provide a rotating disk having a strength capable of withstanding high-speed rotation even in the production of metal powder having a high melting point.

A disk for producing a centrifugal atomized powder according to the present invention comprises a substrate made of an alloy containing carbide and the balance being molybdenum and inevitable impurities. The carbide is dispersed in the molybdenum matrix. The ratio (N1/N) of the number N1 of the carbides having an equivalent circle diameter of less than 1 μm to the total number N of the carbides is 90% or more.

Preferably, the ratio (N1/N) is 95% or more.

Preferably, the shortest distance L between the carbides having a circle equivalent diameter of 1 μm or more is 10 μm or more.

Preferably, the carbide includes at least one of Ti carbide, Zr carbide, and Hf carbide.

Preferably, the average crystal grain size Dave of the molybdenum is 50 μm or less.

The disk may further include a ceramic film that covers the upper surface of the substrate. Preferably, the thickness Ct of the ceramic film is 100 μm or more and 500 μm or less,
The ratio (Ct/Br) of the thickness Ct to the value Br of the surface roughness Rz of the upper surface of the substrate is larger than 1.0 and smaller than 10.

Preferably, the ratio (Ch/Bh) of the thermal conductivity Ch of the ceramic to the thermal conductivity Bh of the substrate is more than 0.001 and less than 1.0.

Preferably, the ratio (Ce/Be) of the coefficient of thermal expansion Ce of the ceramic to the coefficient of thermal expansion Be of the substrate is larger than 1.0 and smaller than 3.0.

In the substrate of the disk for producing the centrifugal atomized powder according to the present invention, the carbide is dispersed in the molybdenum matrix. Molybdenum has higher strength and toughness than other high melting point materials such as graphite. This rotating disk has the strength to withstand high-speed rotation. Further, in this substrate, the number N1 of carbides having an equivalent circle diameter of less than 1 μm in the dispersed carbides is 90.0% or more of the total number N of carbides. A carbide having an equivalent circle diameter of less than 1 μm effectively suppresses the growth of molybdenum crystals even in a high temperature state. In this rotating disk, recrystallization of molybdenum is effectively suppressed. Therefore, even during the atomization, the softening resistance of the rotating disk is prevented from decreasing. With this rotating disk, strength capable of withstanding high-speed rotation is maintained even in the production of metal powder having a high melting point. This rotating disk is suitable for producing fine metal powder having a melting point of 400° C. or higher.

FIG. 1 is a conceptual diagram showing a configuration of a centrifugal atomizing device using a disk for centrifugal atomizing powder production according to an embodiment of the present invention. FIG. 2 is an enlarged view showing the disc of FIG. FIG. 3 is an enlarged sectional view showing a disk for centrifugal atomization powder production according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

FIG. 1 is a conceptual diagram showing a configuration of a centrifugal spraying device 2 using a disk for centrifugal powdering method powder production according to an embodiment of the present invention. The centrifugal spraying device 2 is provided with a chamber 4, a crucible 6, a tapping nozzle 8, a stopper 9, a disk 10 (rotating disk 10) for powder production by centrifugal spraying method, a motor 12, a thermocouple 14, and a heating coil 15.

The method for producing powder using the centrifugal atomizer 2 is as follows. The metal raw material is put into the crucible 6 with the tap nozzle 8 being closed. This metallic material is heated by high-frequency induction heating in the heating coil 15 and becomes a molten metal 16 which is a molten metal. The temperature of the molten metal 16 is measured by the thermocouple 14 so that it can be heated to an appropriate temperature. The motor 12 is operated and the rotating disk 10 rotates. By moving the stopper 9 upward, the molten metal 16 flows into the hot water discharge nozzle 8. As a result, the molten metal 16 is dripped onto the rotating disk 10. The dropped molten metal 16 forms a thin liquid film on the rotating disk 10. The thin film becomes thinner due to the centrifugal force of the rotating disk 10, and fine droplets are scattered from the tip of the rotating disk 10. The fine droplets are solidified to form spherical powder. The produced powder is collected from the chamber 4.

FIG. 2 is an enlarged view of the rotary disk 10 of FIG. The rotating disk 10 is T-shaped when viewed from the front. The rotating disk 10 includes a substrate 18 and a shaft 20. The substrate 18 has a disc shape. The molten metal 16 is dropped on the upper surface of the substrate 18. The shaft 20 is connected to the motor 12. The substrate 18 and the shaft 20 are made of the same material. The substrate 18 and the shaft 20 are integrally formed.

The substrate 18 includes carbide. The balance consists of alloys of molybdenum and unavoidable impurities. Molybdenum has a high melting point of 2623°C. This rotating disk 10 can be applied to the production of metal powder having a high melting point. Further, molybdenum has higher strength and higher toughness than graphite, which is also a material having a high melting point. The rotating disk 10 has strength enough to withstand high-speed rotation. The rotating disk 10 has strength enough to withstand use at a rotation speed of 150,000 rpm.

The temperature of the rotating disk 10 on which the molten metal 16 is dropped becomes high. When the temperature of the metal rises, recrystallization causes a significant decrease in strength. Even with the rotating disk 10 having high strength at a relatively low temperature, the strength may be insufficient at the time of manufacturing the metal powder having a high melting point.

In this rotating disk 10, carbides are dispersed in a molybdenum matrix. The ratio (N1/N) of the number N1 of carbides having an equivalent circle diameter of less than 1 μm to the total number N of carbides in the dispersed carbides is 90.0% or more. A carbide having an equivalent circle diameter of less than 1 μm effectively suppresses the growth of molybdenum crystals even in a high temperature state. By setting the ratio (N1/N) to 90.0% or more, recrystallization of molybdenum is effectively suppressed in the rotating disk 10. Specifically, in the rotating disk 10 of this embodiment, the recrystallization temperature is 1400° C. or higher. The rotating disk 10 has strength that can withstand use at a rotation speed of 150,000 rpm even at a high temperature of 1400°C.

Here, the equivalent circle diameter of the carbide, the number N1 and the total number N are measured in the cross section of the substrate 18. The substrate 18 is divided into two semi-disk-shaped portions by an arbitrary line passing through the center point of the substrate 18. In a cross section of one portion, a region of 30 μm in length and 40 μm in width is magnified and photographed at an arbitrary portion using a microscope. The equivalent circle diameter of the cross section of the carbide present in the photographed area is the equivalent circle diameter of the carbide. Here, the equivalent circle diameter of a cross section is the diameter of a circle having the same area as this cross section. The total number of cross-sections of the carbide existing in this region is the total number N. The number of cross sections having an equivalent circle diameter of less than 1 μm existing in this region is the number N1. The equivalent circle diameter, the number N1 and the total number N are calculated by magnifying and photographing the above cross section and analyzing this image with a computer.

The ratio (N1/N) is more preferably 95.0% or more. By setting the ratio (N1/N) to 95% or more, recrystallization of molybdenum is suppressed more effectively. From this viewpoint, the ratio (N1/N) is more preferably 97%, most preferably 100%.

The shortest distance (shortest distance) L among the distances between the carbides having a circle equivalent diameter of 1 μm or more is preferably 10 μm or more. If the distance between the carbides having a circle equivalent diameter of 1 μm or more is short, the effect of suppressing the crystal growth by the carbides becomes small. This causes a decrease in the recrystallization temperature. This causes a crack near the center of the rotating disk 10. By setting the shortest distance L to 10 μm or more, recrystallization of molybdenum can be effectively suppressed. From this viewpoint, the shortest distance L is more preferably 50 μm or more.

The shortest distance L is measured in the area where the equivalent circle diameter, the number N1 and the total number N are measured. In this area, the gap between the contours of the carbide cross section having a circle equivalent diameter of 1 μm or more is measured. This minimum value is the minimum distance L. This is calculated by enlarging the cross section of the substrate 18 and analyzing this image with a computer.

The carbide of the rotating disk 10 preferably contains at least one of Ti carbide, Zr carbide, and Hf carbide. The inventors have investigated in detail the relationship between the carbide-forming element and the recrystallization temperature. As a result, they have found that the inclusion of any one of Ti, Zr, and Hf carbides can enhance the effect of suppressing the decrease in recrystallization temperature. Recrystallization of molybdenum can be effectively suppressed by containing at least one of these carbides. In this rotating disk 10, high strength is maintained even if the disk 10 is in a high temperature state during atomization. The rotating disk 10 can withstand use at a rotation speed of 150,000 rpm even in a high temperature state.

Energy dispersive X-ray analysis is mentioned as a method of identifying the metal element which constitutes carbide. This is to analyze an X-ray generated when a carbide is irradiated with an electron beam by an energy dispersive analyzer. According to this method, carbon, Ti, Zr and Hf can be detected. You may identify the metal element which comprises a carbide using other analyzers.

In the rotary disk 10, the average crystal grain size Dave of molybdenum is preferably 50 μm or less. During mass production of metal powder, the molten metal 16 may be continuously dropped onto the rotating disk 10 for 15 minutes or longer. If the average crystal grain size Dave of molybdenum is large, a high temperature state continues for a long time, and thus cracks may occur at the center of the rotating disk 10 where the temperature becomes the highest. By setting the average crystal grain size Dave of molybdenum to 50 μm or less, damage to the rotary disk 10 can be prevented even when the metal powder is continuously produced for a long time.

The average crystal grain size Dave is measured in the region where the equivalent circle diameter, the number N1 and the total number N are measured. In this region, the equivalent circle diameter of the molybdenum crystal is measured. The average of these is defined as the average crystal grain size Dave. This is calculated by enlarging the cross section of the substrate 18 and analyzing this image with a computer.

The value Cr of the surface roughness Rz of the upper surface of the substrate 18 is preferably 1 μm or less. By setting the value Cr to 1 μm or less, the effect of the Wenzel can be suppressed. This suppresses the decrease in wettability.

The ratio of carbide to molybdenum is preferably 0.01% or more and 2.0% or less in terms of atomic number ratio. By setting this ratio to 0.01% or more and 2.0% or less, recrystallization of molybdenum can be effectively suppressed. From this viewpoint, this ratio is more preferably 0.05% or more and 1.5% or less.

FIG. 3 is an enlarged sectional view showing a rotating disk 22 according to another embodiment of the present invention. The rotating disk 22 further includes a ceramic film 28 in addition to the substrate 24 and the shaft 26. The substrate 24 and shaft 26 of this embodiment are the same as the substrate 18 and shaft 20 of the rotating disk 10 of FIG. 2, respectively.

The ceramic film 28 covers the upper surface of the substrate 24. The molten metal 16 is dropped on the ceramic film 28. By selecting as a material a ceramic having good wettability with respect to the metal for producing the powder, the rotary disk 22 having high wettability with the molten metal 16 can be realized. This makes it possible to manufacture a powder having a smaller particle size. Further, the ceramic film 28 protects the substrate 24. The ceramic film 28 prevents the substrate 24 and the molten metal 16 from touching each other. Even when the substrate 24 and the molten metal 16 react with each other, the metal powder can be manufactured.

Examples of the method for coating the ceramic film 28 include a plating method, a thermal spraying method, a physical vapor deposition method, a chemical vapor deposition method, a sol-gel method, a sol-gel electrophoretic electrodeposition method and the like. In addition, a film may be formed by sintering ceramic particles on the base disk 22. In this case, a sintering aid may be added to the ceramic particles.

The thickness Ct of the ceramic film 28 is preferably 100 μm or more, and preferably 500 μm or less. By setting the thickness Ct to 100 μm or more, it is possible to prevent defects from occurring in the ceramic film 28 even if the rotating disk 22 has pores. By setting the thickness Ct to 500 μm or less, it is possible to prevent the ceramic film 28 from being cracked by its own weight and the centrifugal force generated when the disk 22 rotates.

As shown in the enlarged view of FIG. 3, the upper surface of the substrate 24 on which the ceramic film 28 is covered is roughened. Here, the thickness Ct of the ceramic film 28 is the thickness from the highest position of the upper surface of the substrate 24 to the upper surface of the ceramic film 28. The thickness Ct of the ceramic film 28 is calculated by measuring the thickness of the disk 22 before and after the ceramic film 28 is formed.

Assuming that the value of the surface roughness Rz of the upper surface of the substrate 24 is Br, the ratio (Ct/Br) of the thickness Ct of the ceramic film 28 to this value Br is preferably larger than 1.0 in this rotating disk 22. It is preferably less than 10.

By setting the ratio (Ct/Br) to be less than 10, the unevenness of the substrate 24 prevents the ceramic film from peeling off. Even if the rotary disk 22 rotates at a high speed, the ceramic film 28 having the above film thickness is prevented from peeling off. The ceramic film 28 does not separate even when the rotary disk 22 rotates at high speed. Specifically, this film does not peel even when the rotary disk 22 rotates at 150,000 rpm. From the viewpoint of preventing peeling, the ratio (Ct/Br) is more preferably smaller than 8.0.

By setting the ratio (Ct/Br) to be greater than 1.0, it is possible to prevent defects in the ceramic film 28 due to the unevenness of the upper surface of the substrate 24. Even if the irregularities are thermally expanded, the entire upper surface of the substrate 24 is covered with the ceramic film 28. From the viewpoint of preventing defects, the ratio (Ct/Br) is more preferably greater than 2.0.

In the present invention, the surface roughness Rz means the maximum height roughness defined in JIS B 0601. The method for measuring the surface roughness Rz is as follows. A roughness curve is created by scanning a stylus with a sharp tip under the conditions according to JIS-B-0601. This scan is done over a length of 2 mm anywhere on the surface. Next, the maximum value and the minimum value of the roughness curve are read and the difference between them is used as the surface roughness Rz.

As described above, the rotating disk 22 becomes hot. The heat of the rotating disk 22 may flow into the motor 12 and damage the motor 12. In the rotating disk 22 described in Japanese Unexamined Patent Application Publication No. 2012-117115, the heat flowing into the motor 12 is suppressed by configuring the rotating disk 22 with a material having a thermal conductivity of 100 W/m·K or less. However, the material that can be used is limited by the restriction that the thermal conductivity is 100 W/m·K or less. When molybdenum alloy is selected as the material, it is difficult to achieve the thermal conductivity of 100 W/m·K or less. As another method of suppressing the heat flow into the motor 12, there is a method of cooling the upper surface of the rotating disk 22 with a cooling gas. However, cooling the rotating disk 22 with the cooling gas causes solidification of the molten metal 16 flowing on the upper surface of the rotating disk 22. This causes flake powder to be generated.

The inventors have found that the heat flowing into the motor 12 from the rotary disk 22 can be suppressed by appropriately adjusting the thermal conductivity Ch of the ceramic film. The ratio (Ch/Bh) of the thermal conductivity Ch of the ceramics to the thermal conductivity Bh of the rotating disk 22 is preferably more than 0.001 and less than 1. By setting the ratio (Ch/Bh) to be larger than 0.001 and smaller than 1, the inflow of heat into the motor 12 can be effectively suppressed. As a result, even in the rotating disk 22 made of a molybdenum alloy, damage to the motor 12 can be suppressed without using the cooling gas. From this viewpoint, the ratio (Ch/Bh) is more preferably larger than 0.01 and smaller than 0.5.

Here, the thermal conductivity is measured by the temperature gradient method. In the temperature gradient method, a steady-state temperature gradient is provided in the thickness direction of the sample plate by heating one surface of the sample plate and cooling the opposite surface, and the amount of heat carried by this temperature gradient and the temperature gradient This is a method of calculating the thermal conductivity from the ratio to the temperature difference.

Ceramics that can satisfy the constraint of the above ratio (Ch/Bh) are preferably selected as the material of the coating film. For the rotary disk 22 made of molybdenum alloy, suitable ceramics include alumina, silica, zirconia, magnesia, and the like. Moreover, ceramics in which two or more kinds of ceramics are mixed may be used, such as stabilized zirconia in which zirconia and yttria are mixed by 8 mol %. This ceramic may also be manufactured so as to satisfy the above constraint of the ratio (Ch/Bh). These ceramics can be preferably used for the rotary disk 22.

When the coefficient of thermal expansion of the rotating disk 22 substrate 24 is Be and the coefficient of thermal expansion of the ceramic film 28 is Ce, the ratio (Ce/Be) of the coefficient of thermal expansion Ce to the coefficient of thermal expansion Be is larger than 1.0. preferable. By setting the ratio (Ce/Be) to be greater than 1.0, it is possible to suppress the occurrence of extreme tensile stress in the ceramic film 28 due to thermal stress. Generation of cracks due to this tensile stress can be suppressed. As a result, it is possible to prevent the molten metal 16 from entering through the cracks and reacting with the base material, and the deterioration of the wettability due to the cracks.

The ratio (Ce/Be) is preferably less than 3.0. By setting the ratio (Ce/Be) to be less than 3.0, it is possible to suppress the occurrence of extreme compressive stress in the ceramic film 28 due to thermal stress. The peeling of the ceramic film 28 due to this compressive stress can be suppressed. As a result, it is possible to prevent the molten metal 16 from entering the peeled portion to react with the base material and to prevent the wettability from being reduced due to the peeling.

In the present invention, the coefficient of thermal expansion is measured by the method described in JIS-Z-2285.

The porosity of the ceramic film 28 is preferably 20% by volume or less. By setting the porosity to 20% by volume or less, the effect of the Cassie-Baxter can be suppressed. This suppresses the decrease in wettability.

The porosity of the ceramic film 28 is calculated from the area of the pores present in the film obtained by taking 10 view images of the cross section of the manufactured rotating disk 22.

The value Cr of the surface roughness Rz of the upper surface of the ceramic film 28 is preferably 1 μm or less. By setting the value Cr to 1 μm or less, the effect of the Wenzel can be suppressed. This suppresses the decrease in wettability.

The metal powder produced by the rotary disk 22 according to the present invention can be used in the fields of solder powder, filler powder, thermal spraying powder, shot powder, additive manufacturing powder, and the like. Specific metals include Sn-50Cu (mass%), Sn-80Ag-0.5In (mass%), Au-50Sn (mass%), Fe-8Cr-6.5B (mass%), Ag, Cu, SUS304L, SUS316L, AlloyC276, etc. are mentioned. Ceramics with good wettability are selected for each metal. By using the rotary disk 22 which is coated so as to satisfy the above-mentioned conditions, powders of these metals can be manufactured.

Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be limitedly interpreted based on the description of the examples.

[Experiment 1]
Metal powder was produced using the rotating disk of the embodiment of FIG.

[Preparation of molybdenum alloy]
A molybdenum powder having a controlled particle size and a carbide having a controlled particle size were mixed, and a columnar molybdenum alloy was produced by a hot isostatic pressing method (HIP). Multiple alloys were made with varying carbide composition, grain size and molybdenum grain size.

[Production of rotating disk]
A rotating disk having a substrate diameter of 60 mm and a thickness of 2 mm was produced from the above molybdenum alloy. The surface of the substrate was polished. The specifications of the manufactured rotating disk are shown in Tables 1 and 2.

[Metal for making powder]
By the disk atomization method, Sn-50 mass% Cu (melting point=690° C.), Sn-80 mass% Ag-0.5 mass% In (melting point=730° C.) pure Ag (melting point=960° C.), pure Cu (melting point=1083° C.) ), Ag-28 mass% Cu (melting point 780° C.), and Ag-30 mass% Zn (melting point=940° C.) powders were tried. In producing these powders, each metal was heated to a temperature 300° C. higher than its melting point. That is, Sn-50 mass% Cu at 990° C., Sn-80Ag-0.5In at 1030° C., pure Ag at 1260° C., pure Cu at 1383° C., Ag-28 mass% Cu at 1080° C., Cu-30 mass% Zn at 1240° C. The temperature was raised to °C.

[Evaluation methods]
[Rotating disk damage]
An attempt was made to make a powder by centrifugal atomization using a rotating disk. The tapping nozzle has a diameter of 4 mm. The amount of molten metal was 50 kg, the disk rotation speed was 130000 rpm, and the tapping temperature was 300° C. higher than the melting point for each of the metals used to form the powder. During the production of the powder, it was confirmed whether or not the rotating disk was damaged.

[Average particle size]
In the rotating disk breakage test, the rotating disk breakage did not occur and powder was obtained, and the average particle size of the powder was evaluated. A laser diffraction method was used as a method for measuring the average particle size of the powder.

[Comprehensive evaluation]
Based on the powder production results, the rotating disk was rated as follows.
A1: A powder can be produced, and the average particle size of the powder is 30 μm or less.
B1: A powder can be produced, and the average particle size of the powder is larger than 30 μm.
C1: Powder could be produced, but it was judged that the disk had cracks and continued use was difficult.
F1: The disc was damaged during atomization and the experiment was stopped.
The order of A1, B1, C1, and F1 is good.

[Evaluation results]
[Example 6-15]
In Examples 6-15, the rotating disk under the following conditions was used.
(1) Ratio (N1/N): 95.0% or more (2) Shortest distance L: 10 μm or more (3) Carbide composition: At least one of Ti, Zr, and Hf carbides is included.
(4) Average crystal grain size Dave: 50 μm or less The results are shown in Table 1. In the table, N12 is the number of carbides having a circle equivalent diameter of 1 μm or more. The same applies to the tables below.

[Example 1-5]
In Examples 1-5, the rotating disk under the following conditions was used.
(1) Ratio (N1/N): 90.0% or more and less than 95.0% Other conditions are the same as in Example 6-15 above. The results are shown in Table 1.

[Examples 16-20]
In Examples 16-20, rotating disks under the following conditions were used.
(2) Shortest distance L: less than 10 μm Other conditions are the same as in Example 6-15 above. The results are shown in Table 1.

[Examples 21-25]
In Examples 21-25, rotating disks under the following conditions were used.
(3) Carbide composition: Does not include any of Ti, Zr, and Hf carbides.
Other conditions are the same as in Example 6-15 above. The results are shown in Table 1.

[Examples 25-30]
In Examples 21-25, rotating disks under the following conditions were used.
(4) Average crystal grain size Dave: Greater than 50 μm Other conditions are the same as in Example 6-15 above. The results are shown in Table 1.

[Comparative Example 1-5]
In Comparative Example 1-5, the rotating disk under the following conditions was used.
(1) Ratio (N1/N): less than 90.0% Other conditions are the same as in Example 6-15 above. The results are shown in Table 2.

[Experiment 2]
Metal powder was produced using the rotating disk of the embodiment of FIG.

[Preparation of molybdenum alloy]
A molybdenum powder having a controlled particle size and a carbide having a controlled particle size were mixed, and a columnar molybdenum alloy was produced by a hot isostatic pressing method (HIP). Multiple alloys were made with varying carbide composition, grain size and molybdenum grain size.

[Production of rotating disk]
From the above molybdenum alloy, a substrate disk having a substrate and a shaft having a diameter of 60 mm and a thickness of 2 mm was prepared. The upper surface of this substrate was roughened, and the upper surface was covered with a ceramic film to manufacture a rotary disk. The ceramics film was formed by applying ceramics and a sintering additive to the top surface of the substrate and sintering. After forming the ceramic film, the upper surface thereof was subjected to polishing treatment. Polishing treatment was performed so that the surface roughness Rz of the upper surface of the ceramic film, Cr, was 1 μm or less. The specifications of the manufactured rotating disk are shown in Table 3-8.

[Metal for making powder]
The metal used to form the powder is iron-based SUS316L (melting point=1396° C.), maraging steel (melting point=1430° C.), Ni-based AlloyC276 (melting point=1390° C.), Alloy718 (melting point=1400° C.), Co-based Co-28 mass% Cr-6 mass% Mo alloy (melting point=1440° C.) and Alloy No. 6 (melting point=1290° C.). Each alloy was heated to a temperature 50°C higher than its melting point. That is, SUS316L was 1446°C, maraging steel was 1480°C, AlloyC276 was 1440°C, Alloy718 was 1450°C, Co-28mass%Cr-6mass%Mo alloy was 1490°C, AlloyNo. Heated to 1340° C. at 6. The ceramic material is selected to have a good leak property with respect to the above metals.

[Evaluation methods]
[Peeling off film]
The manufactured rotating disk was installed in the motor as it was, and was rotated at a rotation speed of 150,000 rpm for 10 minutes. After that, the rotation was stopped and the presence or absence of peeling of the ceramic film was visually confirmed. The case where the peeling of the ceramic film did not occur was "OK", and the other cases were "NG".

[Rotating disk damage]
An attempt was made to prepare a powder by the centrifugal atomization method using a rotating disk that had no problem in the film peeling test. The tapping nozzle has a diameter of 4 mm. The amount of molten metal was 50 kg, the disk rotation speed was 150,000 rpm, and the tapping temperature was 50° C. higher than the melting point for each of the metals forming the powder. During the production of the powder, it was confirmed whether or not the rotating disk was damaged. If there was no damage to the rotating disk, the result was "OK", and the others were "NG".

[Motor temperature rise]
A thermocouple was brought into contact with the shaft of the motor of the centrifugal spraying device, and heat flow into the motor was confirmed. When the softening temperature of the metal used for the motor shaft was kept at 500° C. or lower, the result was “OK”, otherwise the powder production was stopped halfway and the result was “NG”.

[Average particle size]
In the above rotary disc breakage test, the average particle size of the powder was evaluated for the powders obtained without causing the rotary disc breakage. A laser diffraction method was used as a method for measuring the average particle size of the powder.

[Comprehensive evaluation]
Based on the above evaluation results, the following ratings were given to the rotating disk.
A2: A powder can be produced, and the average particle size of the powder is 30 μm or less.
B2: A powder can be produced, and the average particle size of the powder is larger than 30 μm.
C2: Powder was produced, but it was judged that the disk had cracks and it was difficult to continue using it.
D2: The temperature of the motor shaft rose during atomization and was discontinued.
E2: The coverage of the ceramics film on the substrate was 100%, but the film peeled off at 150,000 rpm, and the experiment by centrifugal spraying was stopped.
F2: The disc was damaged immediately after the atomization started, and it was canceled.
A2, B2, C2, D2, E2, and F2 are good in this order.

[Evaluation results]
Tables 3 and 4 show the production results of SUS316L powder and maraging steel powder. In the "alloy" column of the table, "SUS" represents SUS316L. "MA" stands for maraging steel. Tables 5 and 6 show the production results of Alloy C276 powder and Alloy 718 powder. In the "alloy" column of the table, "AC276" represents Alloy C276. "A718" represents Alloy718. Tables 7 and 8 show Co-28 mass% Cr-6 mass% Mo alloy powder and Alloy No. It is a production result of 6 powders. In the column of "alloy" in the table, "CCrMo" represents Co-28 mass% Cr-6 mass% Mo. “A6” is Alloy No. Represents 6.

[Examples 41-54, 79-92 and 117-130]
In Examples 41-54, 79-92 and 117-130, rotating disks under the following conditions were used.
(1) Ratio (N1/N): 95.0% or more (2) Shortest distance L: 10 μm or more (3) Carbide composition: At least one of Ti, Zr, and Hf carbides is included.
(4) Average crystal grain size Dave: 50 μm or less The results are shown in Tables 3, 5 and 7.

[Examples 31-40, 69-78 and 107-116]
In Examples 31-40, 69-78 and 107-116, rotating disks under the following conditions were used.
(1) Ratio (N1/N): 90.0% or more and less than 95.0% Other conditions are the same as in Examples 41-54, 79-92, and 117-130.
The results are shown in Tables 3, 5 and 7.

[Examples 55-58, 93-96 and 131-134]
In Examples 55-58, 93-96 and 131-134, rotating disks under the following conditions were used.
(2) Shortest distance L: less than 10 μm Other conditions are the same as in the above-mentioned Examples 41-54, 79-92 and 117-130. The results are shown in Tables 3, 5 and 7.

[Examples 59-60, 97-98 and 135-136]
In Examples 59-60, 97-98 and 135-136, rotating disks under the following conditions were used.
(3) Carbide composition: Does not include any of Ti, Zr, and Hf carbides.
The other conditions are the same as those of the above-mentioned Examples 41-54, 79-92 and 117-130. The results are shown in Tables 3, 5 and 7.

[Examples 61-68, 99-106 and 137-144]
In Examples 61-68, 99-106 and 137-144, rotating disks under the following conditions were used.
(4) Average crystal grain size Dave: Greater than 50 μm Other conditions are the same as those in Examples 41-54, 79-92 and 117-130. The results are shown in Tables 4 and 5-8.

[Comparative Example 6-20]
In Comparative Example 6-20, the rotating disk under the following conditions was used.
(1) Ratio (N1/N): less than 90.0% Other conditions are the same as those in Examples 41-54, 79-92 and 117-130. The evaluation results are shown in Tables 4, 6 and 8.

The superiority of the present invention is clear from the evaluation results shown in Table 1-8.

The rotating disk described above can be applied to various powder production by the centrifugal atomization method.

2... Centrifugal spraying device 4... Chamber 6... Crucible 8... Hot water nozzle 9... Stopper 10, 22... Rotating disk 12... Motor 14... Thermocouple 15...・Heating coil 16... Molten metal 18, 24... Substrate 20, 26... Shaft 28... Ceramics film

Claims (7)

The substrate is made of an alloy containing carbide and the balance being molybdenum and inevitable impurities.
The carbide is dispersed in the molybdenum matrix,
To the total number N of the carbide, the ratio of the number of the carbide circle equivalent diameter of less than 1μm N1 (N1 / N) is state, and are 90% or more,
Further comprising a ceramic film covering the upper surface of the substrate,
The thickness Ct of the ceramic film is 100 μm or more and 500 μm or less,
A disk for producing a centrifugal atomization powder, wherein the ratio (Ct/Br) of the thickness Ct to the value Br of the surface roughness Rz of the upper surface of the substrate is larger than 1.0 and smaller than 10 . The disk according to claim 1, wherein the ratio (N1/N) is 95% or more. The disk according to claim 1 or 2, wherein the shortest distance L between the carbides having a circle equivalent diameter of 1 µm or more is 10 µm or more. The disk according to any one of claims 1 to 3, wherein the carbide contains at least one of Ti carbide, Zr carbide, and Hf carbide. The disk according to any one of claims 1 to 4, wherein the molybdenum has an average grain size Dave of 50 µm or less. The disk according to any one of claims 1 to 5 , wherein a ratio (Ch/Bh) of the thermal conductivity Ch of the ceramic to the thermal conductivity Bh of the substrate is larger than 0.001 and smaller than 1.0. Disk according to any one of the ratio (Ce / Be) is larger less than 3.0 according to claim 1 from 1.0 thermal expansion coefficient Ce of the ceramic to thermal expansion coefficient Be of the substrate 6.

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