JP2021070851A - Method for producing powdered metal - Google Patents

Abstract

To provide a method for producing powdered metal that can improve production efficiency of powdered metal by utilizing disproportionation reaction.SOLUTION: A method for producing powdered metal includes a preparation step S11 of preparing a mixture containing a bulk metal including 95 mass% or more of one or more selected from a group consisting of iron, chromium, titanium, aluminum, vanadium and rare earth metals, a molten salt and a metal ion source and a formation step S21 of forming powdered metal by agitating the mixture by means of an agitation blade while heating and holding the mixture after the preparation step S11 in which in the formation step S21, an equilibrium constant K for forming powdered metal in the mixture is 10-2 to 102.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a powdered metal.

Titanium has characteristics such as low density, high mechanical strength, and excellent corrosion resistance. On the other hand, titanium is also known as an active and difficult-to-process material, and its manufacturing cost and processing cost tend to be high. Therefore, although titanium is a promising metal material, it has not yet been widely applied in terms of cost such as manufacturing.

Conventionally, in the production of titanium or titanium alloy powder, an atomizing method, a plasma treatment method, a hydrogenation dehydrogenation method, or the like has been used (for example, Patent Documents 1 to 3). However, all of the above methods tend to have high manufacturing costs. Therefore, from the viewpoint of reducing the production cost, it is known to produce titanium powder by a disproportionation reaction as a method for easily producing titanium powder without going through multiple steps.

For example, in Non-Patent Document 1, titanium sponge, titanium chloride, and an equimolar ratio of NaCl-KCl molten salt are added to heat and hold the molten salt at an appropriate temperature, and the molten salt is bubbling with argon gas. , It is described that the disproportionation reaction represented by the following chemical formula (1) occurs in the molten salt to produce titanium powder.

Japanese Unexamined Patent Publication No. 08-199207 Japanese Unexamined Patent Publication No. 03-173704 Japanese Unexamined Patent Publication No. 05-163508

QIUYU WANG et al., “The Equilibrium Between Titanium Ions Titanium Matel in NaCl-KCl Equimolar Molten Salt”, 44B, 2013, 906-913.

When the present inventors produced titanium powder based on the known technique described in Non-Patent Document 1, they were able to produce fine titanium powder. However, in the known technique described in Non-Patent Document 1, it takes a very long time to produce titanium powder, so that the temperature in the crucible must be controlled during that time, and the production efficiency of titanium powder is improved. It was hard to say that it was expensive. Therefore, it is considered that there is still room for improvement in the technique of Non-Patent Document 1.

Therefore, in one embodiment of the present invention, it is an object of the present invention to provide a method for producing a powder metal capable of improving the production efficiency.

That is, in one aspect, the present invention comprises a mixture containing a bulk metal, a molten salt, and a metal ion source containing 95% by mass or more of one or more selected from the group consisting of iron, chromium, titanium, aluminum, vanadium and rare earth metals. A preparatory step for preparing and a production step for producing powder metal by stirring the mixture with a stirring blade while heating and holding the mixture after the preparatory step are included. In the production step, the powder metal in the mixture is produced. It is a method for producing a powdered metal, in which the equilibrium constant K for producing is 10 ^-2 to 10 ^2.

In one embodiment of the method for producing powdered metal according to the present invention, the ratio of the volume of the molten salt to the volume of the bulk metal is 10 or more.

In one embodiment of the method for producing a powder metal according to the present invention, after the production step, a particle size control step of recovering the powder metal and heating the powder metal to adjust the particle size of the powder metal is further performed. Including.

In one embodiment of the method for producing a powder metal according to the present invention, the bulk metal contains 95% by mass or more of titanium.

In one embodiment of the powder metal production method according to the present invention, the mass concentration ratio based on the following formula (3) is 0.01 to 10.
Mass concentration ratio = (mass of metal ion source / (mass of molten salt + mass of metal ion source)) × 100 ... Equation (3)

In one embodiment of the method for producing powdered metal according to the present invention, the metal ion source contains at least TiCl _x (X = 2 to 3).

In one embodiment of the method for producing powdered metal according to the present invention, the metal ion source further comprises _{AlCl 3} or VCl _3.

According to one embodiment of the present invention, the disproportionation reaction can be utilized to improve the production efficiency of powdered metal.

It is a flow figure for demonstrating one Embodiment of the powder metal manufacturing method which concerns on this invention. It is a front view which shows typically the internal structure of the crucible used in one Embodiment of the powder metal manufacturing method which concerns on this invention. (A) is a front view schematically showing the internal structure of the crucible in another embodiment of the method for producing powder metal according to the present invention, and (B) is a front view schematically showing the internal structure of the crucible, and (B) is a line III-III of FIG. 3 (A). It is a cross-sectional view of a part of the arrow. (A) is a front view schematically showing the internal structure of the crucible in another embodiment of the powder metal manufacturing method according to the present invention, and (B) is the IV-IV line of FIG. 4 (A). It is a cross-sectional view of a crucible. (A) is a front view schematically showing an internal structure of a crucible in another embodiment of the method for producing a powder metal according to the present invention, and (B) is a VV line of FIG. 5 (A). It is a cross-sectional view of a crucible. It is a front view which shows typically the internal structure of the crucible used in another embodiment of the powder metal manufacturing method which concerns on this invention. It is a front view which shows typically the internal structure of the crucible used in Comparative Example 1 and Reference Example 1 and 2.

Hereinafter, the present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the gist thereof. In addition, various inventions can be formed by appropriately combining the plurality of components disclosed in each embodiment. For example, the invention may be formed by deleting some components from all the components shown in the embodiment. Furthermore, the invention may be formed by appropriately combining the components of different embodiments. In addition, in this specification, a powder metal means a powder of a simple substance or an alloy.

[1. Overview of the process]
First, the present inventors put sponge titanium (not shown), LiCl-KCl molten salt, and TiCl ₂ placed on the bottom into a crucible 200 (see FIG. 7) to prepare a mixture of these raw materials. The molten salt in the crucible 200 was stirred by bubbling the mixture with argon gas through a tube 210 while holding the mixture to produce fine titanium powder. However, the reaction time until a predetermined amount of titanium powder was produced was very long, and the production efficiency was not high. It is considered that the reason for this is that the argon gas supplied to the molten salt only rises in the bubbling, and the stirring power of the molten salt is insufficient.

For example, if bulk titanium (sponge titanium, titanium scrap, etc.) is present in the molten salt, the leveling reaction represented by the following chemical formula (2) proceeds preferentially in the vicinity thereof, and Ti ²⁺ is generated. Are known. Therefore, in order to improve the production efficiency of powdered metal, the present inventors conceptually divide the molten salt into two layers, an upper layer and a lower layer, and grasp the molten salt, for example, in the upper layer, the disproportionation represented by the above chemical formula (1). It was noted that the chemical reaction was carried out and the leveling reaction represented by the following chemical formula (2) was carried out in the lower layer on which the bulk titanium was placed.

The present inventors considered to generate a swirling flow and a vertical circulation flow in the molten salt to separate the reaction fields of the leveling reaction and the disproportionation reaction in the mixture, and used a stirring blade as a stirring means for that purpose. .. In such a case, for example, as shown in FIG. 2, if bulk titanium BT is present in the lower layer of the molten salt M, the leveling reaction represented by the above chemical formula (2) is carried out in the lower layer. ^{Ti 2+} produced by the leveling reaction from the bulk titanium BT in the lower layer is transported to the upper layer by the vertical circulation flow ULF generated by the stirring of the stirring blade 130. In the upper layer, the disproportionation reaction represented by the above chemical formula (1) is carried out by ^{Ti 2+.} At that time, titanium produced by the disproportionation reaction is produced as a fine powder. ^{The Ti 3+} produced by the disproportionation reaction is transported to the lower layer by the vertical circulation flow ULF generated by the stirring of the stirring blade 130. Then, in the lower layer, Ti ^{3+ and bulk titanium BT form Ti 2+} in the molten salt by a leveling reaction. By repeating such a leveling reaction and a disproportionation reaction (hereinafter, also referred to as "shuttle reaction"), it is considered that a fine powder metal can be obtained.
Furthermore, since the equilibrium constant of the disproportionation reaction affects the dispersion rate of the powder metal, the particle size of the powder metal, etc., it is also necessary to control the temperature of the molten salt and the raw material composition so that the equilibrium constant is within an appropriate range. Is.

As described above, as a result of diligent studies, the present inventors have found that it is possible to improve the production efficiency when producing a fine powder metal.
Hereinafter, preferred embodiments will be described.

[2. Manufacturing method of powder metal]
As shown in FIG. 1, one embodiment of the method for producing a powder metal according to the present invention includes a preparation step S11, a production step S21, and a particle size control step S31. Hereinafter, preferred embodiments of each step will be described.

<Preparation process>
In the preparation step S11, for example, a mixture containing a metal, a molten salt, and a metal ion source is prepared in a vessel containing a molten salt such as a crucible.

(crucible)
As shown in FIG. 2, the crucible 100, which is an instrument, can store the molten salt M. The crucible 100 includes a stirrer 110. The material of the body is not particularly limited, and the body may be made of, for example, metal, alumina, graphite, or the like. From the viewpoint of suppressing the elution of the metal component of the crucible 100 into the molten salt M in the production step S21, the body of the crucible 100 or the like may be made of alumina or graphite. In the following, an example of using the crucible 100 as the body will be described.

The ratio H / D of the height H of the bath surface S of the molten salt M to the inner diameter D of the crucible 100 is 1.0 from the viewpoint of providing a region in which the powder metal produced by the disproportionation reaction in the production step S21 can be dispersed. The above is sufficient. The ratio H / D may be typically 5.0 or less, or 2.0 or less, in consideration of the space for installing the crucible 100. Further, the height H of the bath surface S of the molten salt M means the distance from the inner surface 105 on the lower end side of the crucible 100 to the bath surface S of the molten salt M along the vertical direction V with respect to the inner diameter D of the crucible 100.

(mixer)
The stirrer 110 is installed so as not to come into contact with the inner surface 105 on the lower end side of the crucible 100, and includes a rotating shaft 120 and a stirring blade 130 attached to the lower end 125 side of the rotating shaft 120. The materials of the rotating shaft 120 and the stirring blade 130 are not particularly limited, but from the viewpoint that they have sufficient strength at 500 to 800 ° C. and are inactive without reacting with bath components, for example, they are made of stainless steel, carbon steel, or nickel. Examples include those made of a base alloy. The stirring blade 130 may be attached by providing a notch at the lower end 125 of the rotating shaft 120, fitting the notch into the notch, and welding.

(Stirring blade)
The shape of the stirring blade 130 is not particularly limited, and examples thereof include a paddle type, an inclined paddle type, a propeller type, and an edged turbine blade from the viewpoint of generating a swirling flow and a vertical circulation flow ULF in the molten salt M during stirring. ..

The ratio d / D of the length d of the stirring blade 130 arranged parallel to the inner surface 105 on the lower end side of the crucible 100 and the inner diameter D of the crucible 100 is Ti ^{2+ generated by the leveling reaction occurring on the lower layer side of the molten salt M.} Is preferably 0.6 or more from the viewpoint of improving the production efficiency of the powder metal by transporting the molten salt M to the upper layer side. The ratio d / D is typically 0.9 or less so that the stirring blade 130 does not come into contact with the inner surface 105 of the crucible 100.

Further, from the viewpoint of improving the production efficiency of powder metal by effectively utilizing the reaction field where the shuttle reaction is performed in the molten salt M, the stirring blade 130 of the crucible 100 is prevented from coming into contact with the inner surface 105 of the crucible 100. It is installed on the lower side. Further, the stirring blade 130 is preferably installed directly above the bulk metal so as not to come into contact with the bulk metal.

The stirring blade 130 has a viewpoint of improving the production efficiency of powder metal by efficiently transporting ^{Ti 2+} generated by the leveling reaction occurring on the lower layer side of the molten salt M to the upper layer side of the molten salt M, for example. Therefore, a plurality of them may be attached to the rotating shaft 120. For example, as shown in FIG. 3A, the two stirring blades 140 and 142 are attached to the lower end 125 side of the rotating shaft 120, respectively. At this time, as shown in FIG. 3B, the stirring blades 140 and 142 are attached to the rotating shaft 120 at equal intervals in the rotating direction. Further, for example, as shown in FIG. 4A, one of the two stirring blades 150 and 152 is attached to the lower end 125 side of the rotating shaft 120, and the remaining one stirring blade 152 Is attached to the rotating shaft 120 at a distance from the stirring blade 150. At this time, as shown in FIG. 4B, the stirring blades 150 and 152 are overlapped in the rotation direction and attached to the rotation shaft 120. Further, as shown in FIG. 5A, one of the four stirring blades 160, 162, 164, and 166 has one stirring blade 160 attached to the lower end 125 side of the rotating shaft 120, and the other one. The stirring blade 162 is attached to the rotating shaft 120 away from the stirring blade 160, and another stirring blade 164 is attached to the rotating shaft 120 away from the stirring blades 160 and 162, and the remaining one stirring blade is agitated. The blade 166 is attached to the rotating shaft 120 at a distance from the stirring blades 160, 162, 164. At this time, as shown in FIG. 5B, the stirring blades 160, 162, 164, and 166 are attached to the rotating shaft 120 at equal intervals in the rotating direction.
The stirring blades 140, 142, 150, 152, 160, 162, 164, and 166 shown in FIGS. 3 (A) to 5 (B) are not limited to the same shape, but have different shapes. It may be there. Further, the interval in the rotation direction of each stirring blade may be appropriately determined.

(Bulk metal)
The bulk metal shall contain 95% by mass or more of 1 or more selected from the group consisting of iron, chromium, titanium, aluminum, vanadium and rare earth metals in consideration of the composition of the powder metal produced. The bulk metal may include at least titanium. Further, as the bulk metal, one containing 95% by mass or more of titanium may be used. When titanium powder is produced as the powder metal, the bulk metal may be titanium sponge or titanium scrap. When Ti—Al alloy powder is produced as the powder metal, the bulk metal contains titanium and aluminum, and these may contain one or more selected from titanium scrap and aluminum scrap. When producing TiV alloy powder as a powder metal, the bulk metal contains titanium and vanadium, which may contain one or more selected from titanium scrap and vanadium scrap.

(Molten salt)
The molten salt M is a solid salt heated to a molten state. The molten salt M is not particularly limited, and examples thereof include simple salts and mixed salts of alkali halides from the viewpoint of high chemical stability and ease of handling. The molten salt M may be composed of, for example, one or more selected from _{LiCl, NaCl, KCl, and MgCl 2.} Specific examples of the mixed salt include LiCl-KCl, NaCl-KCl and the like.

(Metal ion source)
The metal ion source supplies metal ions that are the source of the powdered metal. Further, since the metal ion source is contained in the mixture of the raw materials at the start of the production of the powder metal, the shuttle reaction can be started at an early stage and the production efficiency of the powder metal is improved. From the viewpoint of precise control of powder metal formation in the shuttle reaction, the mass concentration ratio of the metal ion source to the molten salt M is preferably 0.01 to 10. The ratio is preferably 0.01 or more, and more preferably 0.05 or more on the lower limit side. Further, the above ratio is preferably 10 or less, more preferably 0.5 or less on the upper limit side.
The mass concentration ratio is calculated based on the following formula (3).
Mass concentration ratio = (mass of metal ion source / (mass of molten salt + mass of metal ion source)) × 100 ... Equation (3)

Since the metal ion source produces titanium powder in the production step S21, _{it is preferable that the metal ion source contains at least TiCl x} (X = 2 to 3). It is preferable that TiCl _x (X = 2 to 3) contains TiCl ₂ as a main component, and TiCl ₃ may be contained in an amount equal to or less than the molar amount of TiCl _2.

When the Ti—Al alloy powder is produced, the metal ion source preferably further contains _{AlCl 3} in order to efficiently ^{react with Ti 2+ in the disproportionation reaction.}
_{When AlCl 3} is used as the metal ion source to generate the Ti—Al alloy powder, Al as a bulk metal may be placed on the upper layer of the molten salt M, and may be placed on the lower layer together with titanium sponge or the like. It may be installed. Here, examples of the shape of Al as a bulk metal include plate-like, small pieces, sections, and powder.

Further, when producing a Ti-V alloy powder, it is more preferable that the _{metal ion source further contains VCl 3} in order to efficiently ^{react with Ti 2+ in the disproportionation reaction.}
_{When VCl 3} is used as the metal ion source to generate the Ti-V alloy powder, V as a bulk metal may be placed on the upper layer of the molten salt M, and may be placed on the lower layer together with titanium sponge or the like. It may be installed. Here, as the shape of V as a bulk metal, for example, a plate shape, a small piece, a section, a powder or the like can be mentioned.

In the preparation step S11, from the viewpoint of providing a reaction field for generating metal ions from the bulk metal by the disproportionation reaction and generating powder metal from the metal ions by the disproportionation reaction in the production step S21, the bulk metal The ratio B / A of the volume B of the molten salt M to the volume A is preferably 10 or more, and more preferably 20 or more. The ratio B / A is typically 50 or less from the viewpoint of reducing the manufacturing cost.

Further, in the preparation step S11, as an example of preparing the mixture, the molten salt and the metal ion source may be prepared in advance in the crucible, and then the bulk metal may be put into the crucible. Further, after the solid salt is charged into the crucible, the solid salt may be melted by heat to prepare a molten salt, and then the bulk metal and the metal ion source may be charged, respectively.

<Generation process>
In the production step S21, after the preparation step S11, the powder metal is produced by stirring the mixture with a stirring blade while heating and holding the mixture. Then, in the generation step S21, the equilibrium constant K for producing a powdered metal in the molten salt M is 10 ^-2 to 10 ^2. In the present specification, the equilibrium constant K means the concentration equilibrium constant and is a parameter that changes depending on the temperature of the raw material. Regarding the method for measuring the equilibrium constant, for example, when an equilibrium experiment is performed in the molten salt M of LiCl-KCl and the concentration of titanium ions equilibrium with the metallic titanium in the molten salt M is analyzed, the above chemical formula (1) is obtained. It is calculated by the following formula (4) on the assumption that a disproportionation reaction is occurring. When the target of formation is titanium alloy powder, the equilibrium constant K may be taken into consideration as in the case of titanium powder.
K = [Ti ³⁺ ] ² / [Ti ²⁺ ] ³ ... Equation (4)
K: Equilibrium constant [Ti ³⁺ ]: Ti ³⁺ concentration in ^{molten salt [Ti 2+} ]: Ti ²⁺ concentration in molten salt Generally, the equilibrium constant K becomes higher as the temperature rises. Regarding the reaction of titanium, it is known that the equilibrium constants in the LiCl-KCl mixed molten salt are 0.011 (773K), 0.034 (873K), and 0.070 (973K), and the NaCl-KCl mixed molten salt is mixed and melted. The equilibrium constants in salt are known to be 0.24 (973K), 1.55 (1023K) and 2.48 (1073K).

^{The equilibrium constant K is preferably 10-2} or more and preferably ^10-1 or more on the lower limit side from the viewpoint of improving the reaction rate of the bulk metal. Moreover, the equilibrium constant K, from the viewpoint of stability of TiCl ₃ and TiCl ₂ is not much large, the upper limit is 10 ² or less, it may be 10 ¹ or less.

During stirring by the stirring blades 130, 140, 142, 150, 152, 160, 162, 164, and 166, the heating temperature of the molten salt M is 400 ° C. from the viewpoint of adjusting the equilibrium constant K to a desired range. If it is above, it is good, and if it is 450 ° C. or more, it is better. The heating temperature is typically 1000 ° C. or lower from the viewpoint of reducing the manufacturing cost.

The stirring is preferably carried out in a non-oxidizing atmosphere from the viewpoint of continuously proceeding the shuttle reaction to suppress the formation of metal oxides and improve the production efficiency. As used herein, the non-oxidizing atmosphere means an atmosphere that does not substantially contain oxygen, that is, an atmosphere of an inert gas such as helium or argon.

In another embodiment, as shown in FIG. 6, a basket 170 made of Ni is further provided on the upper side of the crucible 100, a bulk metal BM is placed in the basket 170, and then the molten salt M is added to, for example, 400. Stir with the stirring blade 130 while heating and holding at ~ 1000 ° C. As a result, the shuttle reaction proceeds, and fine powder metal is generated on the bottom side of the crucible 100. The basket 170 has a plurality of holes 171. Therefore, the molten salt M can pass through the cage 170.
Further, the heating temperature of the molten salt M may be the same as that of the above-described embodiment.

<Diameter control process>
In the particle size control step S31, after the production step S21, the powder metal is recovered and the powder metal is heated to adjust the particle size of the powder metal. Here, as a method of recovering the powdered metal, an operation of extracting the molten salt M in the crucible 100 in a liquid phase state by a extraction pipe (not shown) is performed while heating and holding the molten salt M in the crucible 100. Next, the inside of the crucible 100 is evacuated to create a non-oxidizing atmosphere, and the powder metal is sintered at, for example, 900 to 1000 ° C. for 2 hours or more. By doing so, the amount of impurities contained in the powder metal is reduced, and the particles of the powder metal grow and the particle size can be controlled. In such an operation method, the step of washing the powder metal with water can be omitted in order to reduce the amount of impurities contained in the powder metal.

In another embodiment, the molten salt M containing the powder metal obtained in the production step S21 is pumped from the crucible 100 to another crucible through a pipe by a pressure pump or the like. At this time, before the molten salt M is pumped, the temperature inside the crucible may be heated and held in advance so that the temperature inside the crucible is, for example, 400 to 1000 ° C., and after the molten salt M is pumped, the temperature inside the crucible is, for example, 400 to 1000 ° C. It may be heated so as to become. Then, the molten salt M is filtered through a filter attached to the crucible to separate the powder metal and the molten salt. After separation, the obtained molten salt is pumped from the crucible through a pipe to the crucible 100 used in the production step by a pressure pump or the like to reuse the molten salt. Further, the recovery container is evacuated, the molten salt adhering to the powder metal on the filter is vaporized, and the gas is transferred to another crucible for separation and removal.
Then, as described above, the particle size can be controlled by vacuum sintering the powder metal.

(Particle size)
The primary particles remaining in the powder metal after the sintering treatment may have an average particle size of 1 μm or less. Further, the secondary particles of the powder metal after the sintering treatment may have an average particle size of 10 to 50 μm. In the present specification, the secondary particles are composed of agglomerates of a plurality of primary particles.
The average particle size is observed in a range of 100 to 500 times using a scanning electron microscope (SEM), 100 particles whose contours can be confirmed are selected, and the selected particles are used with image processing software. Calculate the sphere conversion diameter and obtain it as the arithmetic mean value of the obtained sphere conversion diameter.

The present invention will be specifically described with reference to Examples and Comparative Examples. The following examples and comparative examples are merely specific examples for facilitating the understanding of the technical contents of the present invention, and the technical scope of the present invention is not limited by these specific examples. Table 1 shows the production conditions and reaction rates of Example 1, Comparative Example 1, and Reference Examples 1 and 2, respectively. Further, the equilibrium constant K shown in Table 1 below shall be calculated based on the above formula (4) in both the production of titanium powder and titanium alloy powder.

[ _{Preparation of TiCl 2-} containing salt]
Titanium sponge and Titanium ₄ gas were reacted in the following procedure to synthesize _{Titanium 2.} First, LiCl (purity of more than 99.5% by mass) and KCl (purity of more than 99.5% by mass) were charged into an alumina crucible at a molar ratio of LiCl: KCl = 59.5: 40.5 having a eutectic composition. .. Then, LiCl and KCl in the crucible were dried in an oven at 200 ° C. for 24 hours and then mixed to obtain a LiCl-KCl mixed salt. Next, LiCl-KCl mixed salt and titanium sponge (purity of more than 99.0% by mass) were charged into a quartz tube with a quartz filter, and then the mixed salt was heated and melted at 750 ° C. under an argon atmosphere. A LiCl-KCl molten salt containing titanium sponge was obtained. _{Titanium 4} gas was aerated through a filter in the molten salt at 750 ° C. for 3 hours to bring it into contact with titanium sponge. After the reaction, the mixture was cooled to remove titanium sponge, and the _{concentration of TiCl 2} in the LiCl-KCl mixed salt was 9.8% by mass.

[Example 1]
An alumina crucible (outer diameter φ50 mm, inner diameter φ40 mm, height 100 mm) 100 shown in FIG. 2 was prepared. 30 g of LiCl-KCl mixed salt ( _{including a TiCl 2-} containing salt) and 0.5 g of titanium sponge were put into the pit 100 (the volume of mixed salt with respect to the volume of titanium sponge was 10 or more). ^{The Ti 2+} concentration in the LiCl-KCl mixed salt was adjusted to 0.43% by mass. The molten salt M in a molten state was obtained by heating and melting the raw material mixture containing titanium sponge to 500 ° C. in an argon atmosphere. The stirring blade 130 provided in the stirrer 110 was immersed in the molten salt M, and the stirring blade 130 was lowered to just above the titanium sponge and rotated so that the stirring blade 130 did not come into contact with the titanium sponge. The rotation speed was set to 100 rpm. The molten salt M in the molten state was heated and held at 500 ° C. while rotating the stirring blade 130, reacted for 360 minutes, and then stirring was stopped. Next, the stirrer 110 was pulled out from the molten salt M, and the molten salt M was naturally cooled. After the molten salt M solidified, the coagulated body was recovered from the crucible 100, and the coagulated body was dissolved and removed with deionized water. The residue, which is the undissolved portion of the coagulated product, was filtered off and dried in an oven at 50 ° C. to recover the powder. When the powder was measured by the X-ray diffraction method, it was confirmed that it was a titanium powder based on the database JCPDS, which collects the standard peaks of X-ray diffraction from the diffraction peaks appearing at 2θ = 35, 38, 40 °. did.
<Measurement conditions>
XRD diffractometer: ULTIMA (manufactured by RIGAKU)
Type of tube: Cu
X-ray type: K _α
Tube voltage: 40kV
Tube current: 40mA
Measurement range: 2θ = 10 ° to 100 °
Scan axis: 2θ / θ,
Scan speed: 3 ° / min
Step width: 0.02 °

The amount of titanium powder recovered was 0.45 g. Further, the reaction rate was 90% as shown in Table 1. This reaction rate was determined by the following method.
<Reaction rate>
The reaction rate α was calculated based on the following formula (5) for the amount of titanium sponge and the amount of recovered titanium.
α (%) = (ST _W / T _W ) × 100 ... (5)
α: Reaction rate (%)
T _W : Amount of titanium sponge ST _W : Amount of recovered titanium

The obtained titanium powder was put into an alumina crucible and sintered at 900 ° C. for 1 hour in an argon atmosphere to adjust the particle size of the titanium. Then, the average particle size of the primary particles of titanium and the average particle size of the secondary particles of titanium were measured under the following measurement conditions, respectively. As a result, the average particle size of the titanium primary particles was 1 μm or less, and the average particle size of the titanium secondary particles was 10 to 50 μm.
<Measurement method of particle size>
The average secondary particle size is observed using a scanning electron microscope (SEM) at an acceleration voltage of 15 kV and a magnification of 100 times. 100 particles whose contours can be confirmed are selected, and image processing software is used for the selected particles. The sphere conversion diameter was calculated using the wear, and was obtained as the arithmetic mean value of the obtained sphere conversion diameter.

[Comparative Example 1]
An alumina crucible (outer diameter φ50 mm, inner diameter φ40 mm, height 100 mm) 200 shown in FIG. 7 was prepared. 30 g of LiCl-KCl mixed salt ( _{including a TiCl 2-} containing salt) and 0.5 g of titanium sponge were put into the crucible 200. ^{The Ti 2+} concentration in the LiCl-KCl mixed salt was set to 0.43% by mass. The raw material mixture containing titanium sponge was heated and melted to 500 ° C. in an argon atmosphere to obtain LiCl-KCl molten salt M containing titanium sponge. Next, the molten salt M was stirred by passing an alumina pipe 210 through the molten salt M to just above the titanium sponge and bubbling with argon gas supplied from above the pipe 210. The flow rate of argon gas was set to 20 mL / min (CCM). The molten salt M was heated and held at 500 ° C. while bubbling with argon gas, and after reacting for 360 minutes, bubbling was stopped and the molten salt M was naturally cooled. After the molten salt M solidified, the coagulated body was recovered from the crucible 200, and the coagulated body was dissolved and removed with deionized water. The residue, which is the undissolved portion of the coagulated product, was filtered off and dried in an oven at 50 ° C. to recover the powder. The powder was measured by the X-ray diffraction method in the same manner as in Example 1, and based on the database JCPDS, which collects standard peaks of X-ray diffraction from the diffraction peaks appearing at 2θ = 35, 38, and 40 °. It was confirmed that it was a titanium powder.

The amount of titanium powder recovered was 0.2 g. As a result, as shown in Table 1, the reaction rate was 40%. Further, the obtained titanium alloy was sintered in the same manner as in Example 1. As a result, the primary particle size of the titanium alloy was 5 μm or less, and the secondary particle size of the titanium alloy was 100 μm.

[Reference example 1]
A graphite crucible (outer diameter φ50 mm, inner diameter φ40 mm, height 50 mm) 200 shown in FIG. 7 was prepared. 35 g of LiCl-KCl mixed salt ( _{including a TiCl 2-} containing salt), 1 g of titanium sponge and 1.4 g of aluminum particles were put into the crucible 200. ^{The Ti 2+} concentration in the LiCl-KCl mixed salt was set to 0.43% by mass. The raw material mixture of titanium sponge and LiCl-KCl mixed salt was heated and melted to 550 ° C. under an argon atmosphere to obtain LiCl-KCl molten salt M containing titanium sponge. Next, the molten salt M was stirred by passing an alumina pipe 210 through the molten salt M to just above the titanium sponge and bubbling with argon gas supplied from above the pipe 210. The flow rate of argon gas was set to 20 mL / min (CCM). The molten salt M was heated and held at 550 ° C. while bubbling with argon gas, and after reacting for 300 minutes, the bubbling was stopped and the molten salt M was naturally cooled. After the molten salt M solidified, the coagulated body was recovered from the crucible 200, and the coagulated body was dissolved and removed with deionized water. The residue, which is the undissolved portion of the coagulated product, was filtered off and dried in an oven at 50 ° C. to recover the powder. The powder was measured by the powder X-ray diffraction method in the same manner as in Example 1, and based on the database JCPDS, which collects standard peaks of X-ray diffraction from the diffraction peaks appearing at 2θ = 39, 44, 46 °. , Ti ₂ Al ₅ It was confirmed that it was composed only of the intermetallic compound phase.

The recovered amount of the Ti—Al alloy powder was 1 g (titanium content 0.4 g). As a result, as shown in Table 1, the reaction rate was 40% (titanium equivalent). Further, the obtained Ti—Al alloy was sintered in the same manner as in Example 1. As a result, the primary particle size of the Ti-Al alloy was 1 μm or less, and the secondary particle size of the Ti-Al alloy was 10 to 50 μm.

[Reference example 2]
A graphite crucible (outer diameter φ50 mm, inner diameter φ40 mm, height 50 mm) 200 shown in FIG. 7 was prepared. 50 g of LiCl-KCl mixed salt ( _{including a TiCl 2-} containing salt), 1 g of titanium sponge and 2.4 g of NaCl-30 mol% VCl ₃ were added to the crucible 200. ^{The Ti 2+} concentration in the LiCl-KCl mixed salt was set to 0.43% by mass. LiCl-KCl molten salt M containing titanium sponge was obtained by heating and melting the mixed salt of titanium sponge and LiCl-KCl to 500 ° C. in an argon atmosphere. Next, the molten salt M was stirred by passing an alumina pipe 210 through the molten salt M to just above the titanium sponge and bubbling with argon gas supplied from above the pipe 210. The flow rate of argon gas was set to 20 mL / min (CCM). The molten salt M was heated and held at 500 ° C. while bubbling with argon gas, reacted for 60 minutes, then bubbling was stopped and naturally cooled. After the molten salt M solidified, the coagulated body was recovered from the crucible 200, and the coagulated body was dissolved and removed with deionized water. The residue, which is the undissolved portion of the coagulated product, was filtered off and dried in an oven at 50 ° C. to recover the powder. When the powder was measured by the X-ray diffraction measurement method in the same manner as in Example 1, the standard peaks of X-ray diffraction were collected from the diffraction peaks appearing at 2θ = 40 ° (titanium) and 42 ° (vanadium). Based on the database JCPDS, it was confirmed that the alloy was a solid solution alloy of Ti-56 mass% V. That is, the metals of Ti and V were fused with each other, and the whole became a uniform solid phase.

The recovered amount of the Ti-V alloy powder was 0.2 g (titanium content 0.088 g). As a result, as shown in Table 1, the reaction rate was 8.8% (titanium equivalent). Further, the obtained Ti-V alloy was sintered in the same manner as in Example 1. As a result, the primary particle size of the Ti-V alloy was 1 μm or less, and the secondary particle size of the Ti-V alloy was 10 to 50 μm.

In Example 1, the reaction rate from titanium sponge to titanium powder could be improved as compared with Comparative Example 1. ^{The reason for this is that in the stirring blade as a stirring means, Ti 2+} produced by the leveling reaction in the vicinity of titanium sponge in the lower layer of the molten salt is transported to the upper layer of the molten salt in the lower layer of the molten salt, and the disproportionation reaction proceeds. It is thought to be promoted. Therefore, in Example 1, it was confirmed that it is useful to adjust the equilibrium constant and stir the molten salt with a stirring blade.

In Reference Example 1, a Ti—Al alloy powder could be produced. Considering Example 1 and Comparative Example 1, it is considered that the production efficiency of the Ti—Al alloy is further improved when the stirring means is changed from bubbling to stirring blades.

In Reference Example 2, a solid solution alloy of TiV could be produced. Considering Example 1 and Comparative Example 1, it is considered that the production efficiency of the TiV alloy is further improved when the stirring means is changed from bubbling to stirring blades.

100, 200 Crucible 105 Inner surface 110 Stirrer 120 Rotating shaft 125 Lower end 130, 140, 142, 150, 152, 160, 162, 164, 166 Stirring blade 170 Basket 171 Hole 210 Tube BM Bulk metal BT Bulk titanium D Crucible inner diameter d Length of stirring blade H Height of molten salt bath surface M Molten salt S Bath surface S11 Preparation step S21 Generation step S31 Particle size control step ULF Vertical circulation flow V Vertical direction

Claims (7)

A preparatory step for preparing a mixture containing a bulk metal containing 95% by mass or more of 1 or more selected from the group consisting of iron, chromium, titanium, aluminum, vanadium and rare earth metals, a molten salt, and a metal ion source.
After the preparatory step, a production step of producing powdered metal by stirring the mixture with a stirring blade while heating and holding the mixture is included.
Wherein in the generating step, the equilibrium constant K for generating the powder metal in the mixture is 10 ^-2 to 10 ^2, a manufacturing method of the powder metal. The method for producing a powder metal according to claim 1, wherein the ratio of the volume of the molten salt to the volume of the bulk metal is 10 or more. The method for producing a powder metal according to claim 1 or 2, further comprising a particle size control step of recovering the powder metal and heating the powder metal to adjust the particle size of the powder metal after the production step. The method for producing a powder metal according to any one of claims 1 to 3, wherein the bulk metal contains 95% by mass or more of titanium. The method for producing a powder metal according to any one of claims 1 to 4, wherein the mass concentration ratio based on the following formula (3) is 0.01 to 10.
Mass concentration ratio = (mass of metal ion source / (mass of molten salt + mass of metal ion source)) × 100 ... Equation (3) The method for producing a powdered metal according to any one of claims 1 to 5, wherein the metal ion source contains at least TiCl _{x (X = 2 to 3).} The method for producing a powdered metal according to claim 6, wherein the metal ion source _{further contains AlCl 3} or VCl _3.

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