CN114570923A

CN114570923A - Superfine spherical alloy powder and preparation method thereof

Info

Publication number: CN114570923A
Application number: CN202210272855.4A
Authority: CN
Inventors: 席生岐; 谷臻
Original assignee: Shaanxi Zhiqi Kaiwu New Material Co ltd
Current assignee: Shaanxi Zhiqi Kaiwu New Material Co ltd
Priority date: 2022-03-18
Filing date: 2022-03-18
Publication date: 2022-06-03
Anticipated expiration: 2042-03-18
Also published as: CN114570923B

Abstract

The invention discloses superfine spherical alloy powder and a preparation method thereof, belonging to the technical field of metal materials and comprising the following steps: (1) weighing metal powder, carrying out wet grinding, drying at 60 ℃ for 24h, carrying out dry high-energy grinding, uniformly mixing absolute ethyl alcohol and the dry high-energy grinding metal powder in a grinding container, taking out, precipitating, and carrying out vacuum drying to obtain mechanical alloy powder; (2) and placing the mechanical alloying powder in a spiral powder feeding system, then dropping the powder in a drop tube fusing device under a high-temperature heating environment under the condition of inert gas, and cooling to room temperature to obtain the superfine spherical alloy powder. The invention realizes the preparation of the spherical alloy powder by the powder single-particle containerless melting, the thorough alloying and the liquid drop spheroidization of the uniformly mixed elements, can flexibly design new alloy, prepare the superfine spherical alloy powder, has simple and easy operation of tool equipment, short and easy control of process flow and can reduce the preparation cost of the superfine spherical alloy powder.

Description

Superfine spherical alloy powder and preparation method thereof

Technical Field

The invention relates to the technical field of metal materials, in particular to superfine spherical alloy powder and a preparation method thereof.

Background

The spherical alloy powder is the basis of 3D printing no matter the metal is directly deposited or the metal is selected to be sintered in a region by a metal cladding 3D process. High-quality spherical alloy powder is needed for 3D printing of parts, the internal components of the alloy powder are uniform, the granularity of the spherical alloy powder is as fine as possible (<105um) for improving the surface quality of the printed parts, and the granularity of the powder is required to be ultrafine (<25um) for printing fine parts such as vascular stents, so that stent parts with the rod diameter of 50-100 um can be printed.

At present, two methods for producing spherical alloy powder mainly comprise gas atomization powder preparation and plasma rotating electrode atomization powder preparation. The quality of the spherical powder prepared by gas atomization is influenced by a plurality of process conditions, the problems of segregation of hollow powder, satellite powder, alloy components and the like are easily caused, the particle size distribution is wide, and the control is difficult.

The plasma rotating electrode atomization powder preparation technology (PREP) has the advantages of high powder sphericity, high purity, few hollow powder and satellite powder and the like, and is one of the technologies for preparing high-quality spherical metal powder. However, this process requires the preparation of consumable electrodes for different alloys, is not friendly to the development of novel spherical alloy materials, and cannot solve the problem of component segregation in the alloys. The method is subject to the technical bottlenecks of equipment working speed, electrode bar diameter and the like, and the particle size of metal powder produced by the powder preparation of a common rotating electrode is concentrated at 20-250 mu m. Taking titanium alloy TC4 powder as an example, the yield of powder with the particle size of less than 100 μm is less than 40%, and the application of PREP technology in the field of 3D printing technology (the particle size of powder is concentrated in 10-105 μm) formed by powder melting is limited by the thicker powder particle size.

Therefore, how to provide a method for preparing spherical alloy powder with fine particle size is a problem that needs to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present invention provides an ultrafine spherical alloy powder and a preparation method thereof, which can solve the problems of segregation of element components, hollowing, satellite powder, purification (inclusion) and the like in the conventional preparation of spherical alloy powder by melting and atomization,

in order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of superfine spherical alloy powder comprises the following steps:

(1) weighing metal powder, carrying out wet grinding, drying at 60 ℃ for 24h, carrying out dry high-energy grinding, uniformly mixing absolute ethyl alcohol and the metal powder obtained by the dry high-energy grinding in a grinding container, taking out, precipitating, and carrying out vacuum drying to obtain mechanical alloying prealloy powder;

(2) and placing the short-time mechanical alloying prealloying powder into a spiral powder feeding system, then, dropping the powder in a high-temperature heating environment in a drop tube fusing device under the protection of inert gas, and cooling to room temperature to obtain the superfine spherical alloy powder.

The wet grinding and the dry high-energy grinding are both carried out in a high-energy horizontal vibration rod mill, and the structure of the high-energy horizontal vibration grinding machine is shown in figures 2-3, and the structure specifically comprises the following steps:

a base;

an air spring; the air spring is fixed on the base, 4 air springs incline inwards to form a support, and a vibration rack is arranged on the support;

a vibration table frame; the vibration rack consists of a main shaft provided with an eccentric block and a bracket for supporting the grinding tank, and is driven by a motor to generate eccentric elliptical vibration;

specially manufacturing a grinding tank; the special grinding tank is of a cylinder structure and is horizontally and detachably connected to the air cushion spring, and the special grinding tank is used for placing grinding media and alloy powder to be prepared;

a motor; the motor is used for providing power for the vibration table frame, and the vibration table frame drives the grinding tank to realize vibration grinding;

a control system; the control system is used for controlling the rotating speed of the motor, monitoring the state of the special grinding tank in real time and transmitting the state to the mobile terminal.

The high-energy horizontal vibration grinding machine adopts an eccentric vibration mechanism system, a motor drives a main shaft of a vibration rack to rotate, an eccentric block capable of adjusting vibration energy is arranged on the rotating main shaft, the vibration rack is supported and balanced by an air bag soft spring, a grinding tank is arranged on the vibration rack, the rigidity coefficient of the system is adjusted by utilizing air bag pressure, and the stable work of the vibration system during high-energy grinding is ensured by matching with reasonable air bag pressure. The control system of the system can adjust the vibration state of the whole high-energy vibration rod mill on line by monitoring and regulating the rotating speed of the motor, the pressure of the air bag and the position of the eccentric block, wherein the vibration state comprises vibration frequency, amplitude and the like.

The inner wall of the grinding tank is provided with a water cooling system (i.e. a cooling device), so that the grinding instrument can continuously grind, and the continuous grinding time is usually not more than 20 h. One end of the grinding tank is closed, and a grinding cover at the other end is provided with an air inlet and outlet pipeline, a switching ball valve and a temperature measuring thermocouple, so that high-energy grinding and temperature monitoring under vacuum and atmosphere protection can be realized; the air inlet pipeline comprises a pressure transmitter monitoring system which can detect the pressure of the protective gas in the grinding tank and carry out overpressure safety protection; the control system is a microprocessor, and digital production is realized.

The spiral powder feeding system integrally belongs to a link of a drop tube fusing device. Mainly comprises a small stepping motor, a spiral powder feeder, a screen, a special metal funnel, a rotary driving rod, a rotary driving sheet and a screen. The special metal funnel is hourglass-shaped and comprises an upper funnel and a lower funnel, and two ends of the special metal funnel are provided with screens; the rotary poking rod penetrates through the specially-made metal funnel; one end of the rotary poking rod extends to the outside of the specially-made metal funnel and is provided with a small stepping motor, the other end of the rotary poking rod is positioned in the lower funnel, and a rotary poking sheet is fixedly arranged and is abutted against the screen mesh; the part of the rotary rod in the upper funnel is provided with a spiral powder feeder.

The small-sized stepping motor can drive the spiral powder feeder to rotate; the surface of the special metal funnel is smooth, and the powder flowability is improved; the rotary poking rod is connected with a rotary poking sheet, so that the powder can uniformly and dispersedly fall down before finally falling into the heating element; the screen can obstruct the powder with larger particle size, so that the size of the falling powder is uniform.

Has the advantages that: the invention combines the short-time mechanical alloying process and the powder drop tube fusing spherical process, fully exerts the advantages of conveniently and flexibly preparing the superfine prealloying powder by the short-time mechanical alloying process, avoids the problems of low efficiency and medium pollution caused by long time of conventional mechanical alloying by the alloying action of the subsequent powder drop tube fusing spherical process, provides conditions and guarantees for preparing stable superfine spherical alloy powder by the subsequent prealloying powder through the drop tube fusing spherical process, and can obtain high-quality superfine spherical alloy powder.

The short-time mechanical alloying technology in the invention can realize uniform mixing of elements in single powder particles and proper deformation energy storage.

In the mechanical alloying process, the metal element powder is subjected to rapid flaking on the morphology within a short time to form fine polygonal particles, the components are repeatedly subjected to cold welding and fracture within a short grinding time, the powder size also reaches the limit particle size within the range of 0.5-20 um, the component layers in the powder are refined, the mechanical mixing of the components within the powder particles is realized, the principle of the method is shown in figure 5, the powder is repeatedly subjected to cold welding and fracture under the collision of a grinding rod to realize the mixing of the components, a multilayer film structure is formed (shown in figure 6), and the internal structure of a typical Ag-Cu mechanical alloying powder section is shown in figure 7.

The mechanical alloying powder single particle not only can realize the mechanical uniform mixing of the components, but also stores higher deformation energy in the repeated high-energy grinding process, and is very favorable for spheroidizing, especially alloying, of the alloy powder in the subsequent fusing. This key technology can be achieved by dedicated high energy mills.

Preferably, the metal powder in step (1) includes any of Ag, Fe, Cu, Ni, Ti, Cu, Cr and Mo.

Has the beneficial effects that: the mechanical alloying can realize solid-state alloying of immiscible elements which are difficult to alloy by the traditional smelting and rapid cooling technologies, breaks through the limitation of an equilibrium phase diagram, and is a typical non-equilibrium preparation method. Mechanical alloying is mainly achieved by high-energy milling, and commonly used apparatuses are a stirring mill, a vibration mill, a planetary mill, and the like. In the process of cold welding-crushing, no matter which system the elements are in, the dynamic balance of cold welding and crushing can be achieved after long-time grinding, and finally, a nano isometric crystal structure containing a large number of defects is formed. These ultra-fine structures and defects in the structures promote solid state diffusion and ultimately complete mechanical alloying. In addition, supersaturated solid solutions can be obtained by mechanical alloying, and these solid solutions are often formed in some immiscible or limited solid solubility alloy systems (e.g., Cu-Cr, Cu-Mo, Cu-Fe, Al-Pb, etc.). The metastable alloy powder obtained by mechanical alloying and the immiscible component are mechanically ground, so that solid alloying of an immiscible system is hopefully promoted, the solid solubility of the insoluble element in an immiscible matrix is further expanded, and the application of the alloy powder in the fields of additive manufacturing and aerospace is further promoted.

Preferably, the wet grinding aid in the step (1) is absolute ethyl alcohol, and the adding proportion of the metal powder to the absolute ethyl alcohol is 2 kg: 1L; the wet grinding rate is 1440r/min, and the time is 1-3 h.

Has the advantages that: the anhydrous ethanol has good wettability to the metal powder in the invention, and can fully diffuse the metal powder in the tank, thereby better performing cold welding and crushing processes with a grinding medium, improving the alloying efficiency and shortening the time.

Preferably, the dry high-energy grinding rate in the step (1) is 1440r/min, and the time is 3-8 h; the addition ratio of the anhydrous ethanol to the dry high-energy grinding metal powder is 0.6 g: 1 ml.

Preferably, the temperature of the wet grinding and the dry high-energy grinding in the step (1) is not higher than 300 ℃, and the wet grinding and the dry high-energy grinding are both carried out under the condition of inert gas; the inert gas is argon.

Preferably, the vacuum drying temperature in the step (1) is less than 40-60 ℃, the vacuum degree is less than 1Pa, and the vacuum drying time is 8 h.

Has the advantages that: the vacuum drying temperature is too low, so that the powder is not dried, and too high causes the surface to be dry, the inside to be wet and the drying to be uneven; drying time is a parameter obtained by long-term experiments.

Preferably, the wet grinding and the dry high-energy grinding are carried out under the condition of inert gas, and the inert gas is argon.

Has the advantages that: the invention can prevent powder oxidation caused by residual air in the grinding tank by grinding under the condition of inert gas, and simultaneously balance the atmospheric pressure inside and outside the grinding tank.

Preferably, the high-temperature heating temperature in the step (2) is 1200-1700 ℃.

Has the advantages that: the temperature range is larger than the melting point of common pure metal or alloy powder, so that the powder is liquefied rapidly in the tube dropping process and can be spheroidized rapidly in the cooling process.

Preferably, the powder feeding rate of the spiral powder feeding system in the step (2) is 10 g/min.

Has the advantages that: the special spiral powder feeding system is a powder feeder with a double-funnel spiral matching and following dispersion mechanism. The design can prevent fine powder from being embedded into the card machine, so that the powder can be smoothly dispersed and enter a high-temperature area of the drop tube, the powder single particles are ensured to uniformly fall from the upper end of the drop tube, and the pre-alloyed powder single particles can be melted and spheroidized in the vertical tube furnace. Aiming at the characteristic of large accumulation angle of non-spherical pre-alloyed powder, the screw rod with the large-angle funnel is adopted to feed in the small-angle funnel material tank in a rotating manner, so that the phenomenon that the powder is stuck when the screw rod rotates can be structurally ensured, the powder can be smoothly sent into the vertical tubular furnace tube by the screw rod and the follow-up dispersion mechanism in a continuous dispersion manner, and the melting, spheroidizing and alloying of the single-particle powder are realized.

Preferably, the parameters of the powder falling device in the step (2) are the rotating speed 1440r/min of the motor, and the powder falling speed is 10 g/min.

Has the advantages that: the powder drop tube fusing process parameter control ensures the adjustable design of the temperature and the length of the high-temperature area of the drop tube and the powder settling velocity. For drop tube fusing and spheroidizing powder preparation, whether the mechanically alloyed powder can form a uniform liquid phase in a short-time drop tube heating and melting process is crucial, the process parameters can be regulated and controlled, and the single-particle powder is subjected to high-temperature zone melting and subsequent cooling processes, so that the uniform-component ultrafine spherical alloy powder can be obtained in the subsequent solidification process.

The superfine spherical alloy powder is prepared by the preparation method of the spherical alloy powder.

According to the technical scheme, compared with the prior art, the invention discloses and provides the superfine spherical alloy powder and the preparation method thereof, and the invention fully utilizes the characteristics of homogenization and densification of the components of the short-time mechanically-alloyed superfine particle powder and the full alloying and spheroidizing functions of the powder particle during drop tube fusion, so that the single-particle container-free melting, complete alloying and liquid drop spheroidizing of the powder are realized to prepare the superfine spherical alloy powder. The invention can flexibly design new alloy, has simple and easy operation of tooling equipment and short and easy control of process flow, and can reduce the preparation cost of high-quality superfine spherical alloy powder.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a top view of a high-energy horizontal vibrator mill used in example 1 of the present invention;

FIG. 3 is a side view of a high-energy horizontal vibrator mill used in example 1 of the present invention;

FIG. 4 is a schematic view showing the structure of a pipe dropping device used in embodiment 1 of the present invention;

FIG. 5 is a schematic view showing the structure of a screw powder feeding system used in embodiment 1 of the present invention;

FIG. 6 is a schematic view of the preparation of the mechanical alloying powder according to the present invention;

FIG. 7 is a sectional internal structure view of a mechanically alloyed Ag-Cu powder obtained in example 1 of the present invention;

FIG. 8 is an SEM photograph of the morphology of CuCrMo drop tube powder obtained in example 1 before and after fusing; wherein part a is the morphology of the powder before fusing, and part b is the morphology of the powder after fusing;

FIG. 9 is an SEM photograph of the powder morphology of a NiTi drop tube obtained in example 2 of the present invention before and after fusing; wherein part a is the morphology of the powder before fusing, and part b is the morphology of the powder after fusing;

FIG. 10 is a graph showing the morphology and size of the spherical powder of the alloy in comparative example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

(1) powder preparation and wet grinding: cleaning the cylindrical grinding tank and grinding media (round thin stainless steel rods), weighing the mixture of Cu, Cr and Mo metal powders on an electronic scale, then loading into the cylindrical grinding tank, and then loading the grinding media into the cylindrical grinding tank. Adding absolute alcohol (1/3 volume of grinding tank is proper in principle, and adding ratio of the absolute alcohol to metal powder is 1L: 2kg), closing end cover of grinding tank, then installing the grinding tank on a high-energy horizontal grinding machine, starting cooling water circulation system and opening switch, grinding at 1440r/min for 1-3h, stopping machine operation, closing cooling water system and unloading the grinding tank. And (3) pouring out the metal powder cleaned in the grinding tank, and drying at 60 ℃ for 24 hours to obtain the wet-ground metal mixed powder.

And then cleaning the grinding equipment, firstly cleaning the tank and the grinding medium by using clear water, then repeating the steps by using industrial alcohol to clean the tank, the grinding medium and the grinding medium, and finally blowing the grinding medium, the grinding tank and the grinding tank end cover by using a blower.

(2) The charging process comprises the following steps: the method comprises the steps of putting a round fine stainless steel bar into a grinding tank, putting dried wet grinding metal mixed powder into the grinding tank, sealing a grinding tank end cover, pumping and filling inert protective gas (high-purity argon) into the sealed grinding tank for three times by using a vacuum pump, ensuring that impurity gases such as air and the like are discharged, and finally filling argon into the grinding tank to ensure that the grinding tank is filled with the inert gas and the indication of the vacuum pump is positive pressure, wherein the process can effectively avoid oxidation in the process of high-energy bar grinding. And finally, mounting the grinding tank filled with the powder on a vibration table frame of a high-energy horizontal vibrating rod mill.

(3) Dry high-energy grinding: firstly, checking whether a grinding tank is in positive pressure, ensuring that inert Ar gas exists in the grinding tank, checking whether a circulating cooling pump (or cooling water) leaks, and starting a cooling circulating system after the situation that no fault exists is determined; controlling the temperature of a cooling pump or the flow of cooling water to be a proper value (the adjusting process can be adjusted by a person skilled in the art according to common knowledge and actual needs), then turning on a power supply of the high-energy horizontal vibration rod mill, setting the rotating speed to 1440r/min, setting the grinding time to 2h, and starting up to run; whether the instrument normally operates is checked every half hour in the operation process of the high-energy horizontal vibrating rod mill, and meanwhile, the monitoring camera is connected through a mobile phone to check and guarantee the safety of a laboratory at any time.

(4) Shutting down and taking materials: stopping the operation of the high-energy horizontal vibration rod mill, and turning off the power supply; adding a certain amount of absolute ethyl alcohol into the grinding tank through a vacuum pump, starting the grinding tank again and running for 20min, washing most of powder cold-welded on the pipe wall of the grinding tank and a grinding medium in the process, then shutting down the high-energy horizontal vibrating rod mill, closing a circulating water cooling pump (or cooling water), unloading the grinding tank, pouring out a mixture of the grinding powder and alcohol, and naturally settling in a large beaker for a certain time.

(5) Protection drying and obtaining ground powder: after full natural precipitation, most of the ground particles are precipitated at the bottom of the beaker, after supernatant liquid in the beaker is filtered, the precipitated metal powder is put in a drying box for medium-low temperature vacuum drying, wherein the vacuum drying temperature is 40-60 ℃, the vacuum degree of the drying box is lower than 1Pa, and the vacuum drying time is 8 hours; and finally, taking out the dried powder, putting the powder into a sample bag, and quickly vacuumizing the sample bag for sealed storage to obtain the short-time mechanical alloying prealloying powder of Cu-Cr-Mo, wherein the microstructure of the powder is shown as part a in figure 8. Such a method of extraction avoids direct contact of the milled powder with air (mainly oxygen), thereby minimizing oxidation of the milled powder.

(6) Charging: putting the short-time mechanical alloying prealloying powder into a powder feeder shown in figure 4, opening a controller, introducing protective gas argon, and controlling a heating element to be maintained at 1200-1700 ℃;

(7) dropping the tube for dissolving and condensing: turning on the motor to enable the stirrer to rotate, enabling the powder to fall into the collecting device through the vertical long pipe, continuing introducing protective gas argon and starting the cooling circulation device after the powder completely falls into the collecting device, finally cooling to room temperature to take the powder and sealing, and enabling the shape of the fused powder of the dropping pipe of the finally obtained superfine CuCrMo spherical alloy powder to be as shown in part b in fig. 8. The average particle size after dropping the tube was 27.3 μm, and the alloy powder was ultrafine spherical alloy powder.

Example 2

A method for preparing an ultra-fine spherical alloy powder, which is different from the method of example 1 only in that:

in the step (1), the metal powder raw materials are Ni and Ti, and the grinding time is 4 h.

The morphology of the powder before and after the superfine NiTi spherical alloy powder is dropped into the tube and fused is shown in figure 9, and the average particle size after tube dropping is 22.7 mu m, and the powder is the superfine spherical alloy powder.

Comparative example 1

A method for preparing a spherical alloy powder, which is different from example 1 only in that: TC4 powder was milled directly using a Sailong Metal materials, LLC, model SLPA-D, tabletop PREP device. The morphology and particle size of the resultant TC4 powder are shown in fig. 10.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed in the embodiment corresponds to the method disclosed in the embodiment, so that the description is simple, and the relevant points can be referred to the description of the method part.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The preparation method of the superfine spherical alloy powder is characterized by comprising the following steps:

(1) weighing metal powder, carrying out wet grinding, drying at 60 ℃ for 24h, carrying out dry high-energy grinding, uniformly mixing absolute ethyl alcohol and the metal powder obtained by the dry high-energy grinding in a grinding container, taking out, precipitating, and carrying out vacuum drying to obtain short-time mechanical alloying prealloying powder;

(2) and placing the short-time mechanical alloying prealloying powder in a spiral powder feeding system, then, dropping the powder in a dropping pipe fusing device in a high-temperature heating environment under the condition of inert gas, and cooling to room temperature to obtain the superfine spherical alloy powder.

2. The method of claim 1, wherein the metal powder in step (1) comprises any one of Ag, Cu, Ni, Ti, Cu, Cr and Mo.

3. The method for preparing the ultrafine spherical alloy powder according to claim 1, wherein the wet grinding aid in the step (1) is absolute ethyl alcohol, and the addition ratio of the metal powder to the absolute ethyl alcohol is 2 kg: 1L; the wet grinding rate is 1440r/min, and the time is 1-3 h.

4. The method for preparing ultrafine spherical alloy powder according to claim 1, wherein the dry high-energy milling rate in step (1) is 1440r/min for 3-8 h; the addition ratio of the anhydrous ethanol to the dry high-energy grinding metal powder is 0.6 g: 1 ml.

5. The method for preparing an ultrafine spherical alloy powder according to any one of claims 1 to 4, wherein the wet grinding and the dry high-energy grinding in step (1) are carried out at a temperature of not higher than 300 ℃ and are both carried out under inert gas conditions; the inert gas is argon.

6. The method for preparing ultrafine spherical alloy powder according to claim 5, wherein the vacuum drying temperature in step (1) is less than 40-60 ℃, the degree of vacuum is less than 1Pa, and the vacuum drying time is 8 h.

7. The method as claimed in claim 1, wherein the high temperature heating temperature in step (2) is 1200-1700 ℃.

8. The method for preparing an ultrafine spherical alloy powder according to claim 1, wherein the powder feeding rate of the screw powder feeding system in the step (2) is 10 g/min.

9. The method for preparing ultrafine spherical alloy powder according to claim 1, wherein the powder falling device in step (2) has a motor rotation speed of 1440r/min and a powder falling speed of 10 g/min.

10. A spherical alloy powder produced by the method for producing an ultrafine spherical alloy powder according to any one of claims 1 to 9.