WO2012169256A1

WO2012169256A1 - Method for producing molybdenum granulated powder and molybdenum granulated powder

Info

Publication number: WO2012169256A1
Application number: PCT/JP2012/057347
Authority: WO
Inventors: 山口　悟; 勉森岡; 斉青山
Original assignee: 株式会社東芝; 東芝マテリアル株式会社
Priority date: 2011-06-08
Filing date: 2012-03-22
Publication date: 2012-12-13
Also published as: JPWO2012169256A1

Abstract

This method for producing a molybdenum granulated powder is characterized by comprising: a step in which an organic solvent is placed in a container; a step in which polyvinyl butyral is added to the organic solvent as a binder; a step in which a solution containing molybdenum is prepared by loading molybdenum powder with an average particle size of 1 to 10 μm, to which at least one of a potassium component, an aluminum component and a silicon component has been added, while stirring the organic solvent; and a step in which the solution containing molybdenum is loaded in a spray dryer in which, when the rotation speed of a rotator of the spray dryer in which the solution containing molybdenum is to be dispersed is regarded as A (rpm), and the average particle size of the granulated powder is regarded as B (μm), A/B ranges from 50 to 700, and the solution containing molybdenum is dispersed and dried to prepare the molybdenum granulated powder. The abovementioned method enables a molybdenum granulated powder having the intended average particle size to be efficiently produced at a high yield.

Description

Method for producing molybdenum granulated powder and molybdenum granulated powder

The present invention relates to a method for producing molybdenum granulated powder and molybdenum granulated powder.

Molybdenum (Mo) is used in various fields as a heat resistant material because it has a high melting point of 2620 ° C. For example, it is used as a constituent material for thermal spraying materials, sintering furnace plates, electrode parts, magnetron stems, sputtering targets, and the like. There is a method of supplying the thermal spray material with Mo powder or Mo rod. In addition, the plate material may be manufactured by sintering, or may be manufactured by combining rolling and forging. Moreover, an electrode component etc. may be manufactured by the case where a board | plate material is processed, the case where it draws and wire-processes, or a sintering method.
Thus, when using Mo, (1) The method of using Mo as a powder, (2) The method of using Mo as a sintered compact, (3) It is plate-like by rolling, forging, casting, etc. Examples thereof include a method of processing, and (4) a method of drawing and using as a wire.
Even if it is any usage method, Mo powder or Mo molten metal will be used as an initial raw material. The molten Mo is used by a method of melting and casting the Mo material and processing it into a desired shape. The method using the molten Mo is a method in which the molten metal is poured into a mold, so that it can be processed into a product having a relatively simple and large shape. On the other hand, since Mo is a high melting point material as described above, large equipment with high heat resistance is required to strictly manage the molten Mo. Moreover, since it is the method of pouring molten Mo into a type | mold, there exists a fault which cannot respond to a complicated shape.
For this reason, Mo powder is sintered and used as a Mo sintered body. With this sintering method, a product having a complicated shape can be produced by filling the mold with Mo powder. For example, Japanese Patent No. 4157369 (Patent Document 1) discloses a sintered electrode for a cold cathode tube having a U-shaped cross section (cup shape). In Patent Document 1, a cup-shaped electrode having a diameter of about 1 to 2 mm is manufactured using a sintering method.
When producing a sintered compact by a sintering method, a granulation process, a formation process, a degreasing process, a sintering process, etc. are implemented with respect to Mo powder. So far, in the sintering method, the improvement has been advanced mainly on the improvement of the degreasing process and the sintering process. In paragraph [0027] of Patent Document 1, it is disclosed that the degreasing step is performed in a wet hydrogen atmosphere while the sintering step is performed in a hydrogen atmosphere. As a result, the sinterability is increased and the yield is improved.
Further, a pamphlet (Patent Document 2) of International Publication WO2011 / 004887A1 discloses a method for producing high-purity molybdenum powder having an average particle size of 0.5 to 100 μm. Patent Document 2 discloses a molybdenum powder in which the proportion of primary particles is 50% or more.
In the conventional Mo sintering method, the improvement regarding Mo raw material powder, a degreasing process, and a sintering process has been advanced. However, the product yield has not necessarily reached 100%. Such a phenomenon also occurred in the same way for a Mo sintered body using Mo powder to which a dopant such as potassium was added.

Japanese Patent No. 4157369 Pamphlet of International Publication WO2011 / 004887A1

The inventors have investigated the reason why the yield of products using Mo powder as an initial raw material is not improved. As a result, it has been found that if there are large variations in the size, density, fluidity, etc. of the granulated powder, the raw powder filling density and supply amount in the molding process will vary, causing a decrease in product yield. Further, when Mo granulated powder is used as the thermal spray powder, the supply amount (supply speed) to the thermal spray flame varies, and there is a problem that the characteristics as the thermal spray film are not stabilized. As a result of pursuing this cause, it was found that there was a cause that the management according to the average particle size of the intended granulated powder was not performed in the granulation step.
The present invention is for solving such problems, and provides a method for efficiently producing molybdenum granulated powder, which can improve the quality and yield of Mo products (powder or sintered body). Is to do.

A method for producing a molybdenum granulated powder according to an embodiment of the present invention includes a step of putting an organic solvent in a container, a step of adding polyvinyl butyral as a binder to the organic solvent, and stirring the organic solvent while potassium component. A step of preparing a molybdenum-containing solution by adding molybdenum powder having an average particle diameter of 1 to 10 μm to which at least one of an aluminum component and a silicon component is added, and a rotary plate of a spray dryer for dispersing the molybdenum-containing solution When the rotational speed of A is set to A (rpm) and the average particle diameter of the granulated powder is set to B (μm), the molybdenum-containing solution is put into a spray dryer in which A / B is in the range of 50 to 700, And a step of dispersing molybdenum-containing solution and drying to prepare molybdenum granulated powder. It is.
Further, it is preferable to further carry out a sieving step of passing a sieve having a mesh diameter 2 to 3 times the average particle size B of the molybdenum granulated powder after completion of the granulation step by a spray dryer. The average particle diameter B of the molybdenum granulated powder is preferably 20 to 150 μm. Further, the rotational speed A of the rotating plate of the spray dryer is preferably 5000 to 16000 rpm. Moreover, it is preferable that an organic solvent is ethanol.
Further, the content (addition amount) of the potassium component is preferably in the range of 100 to 1000 ppm by mass in terms of potassium element alone. In addition, the content of the aluminum component is preferably in the range of 100 to 1000 ppm by mass in terms of a single aluminum element. Further, the content of the silicon component is preferably in the range of 100 to 1000 ppm by mass in terms of silicon element.
In addition, when the total amount of molybdenum powder to be added is 100 parts by volume, the volume of the binder is preferably 3 to 20 parts by volume. The apparent density of the resulting molybdenum granulated powder is preferably 1.3 to 3.0 g / cc. The molybdenum-containing solution preferably has an organic solvent amount of 0.2 to 1 liter when the molybdenum powder amount is 100 parts by mass.
The spray dryer preferably dries the molybdenum granulated powder while supplying hot air at 100 to 300 ° C. Moreover, it is preferable that the spray drier carries out the drying of the molybdenum granulated powder in a reduced-pressure atmosphere below atmospheric pressure. Moreover, it is preferable that the fluidity of the obtained granulated powder is 50 sec / 50 g or less.
The molybdenum granulated powder according to the present invention is characterized in that it contains at least one of a potassium component, an aluminum component, and a silicon component and has an apparent density of 1.3 to 3.0 g / cc.
The average particle diameter of the molybdenum granulated powder is preferably 20 to 150 μm. Further, when the total amount of molybdenum powder is 100 parts by volume, the volume of the binder is preferably 3 to 20 parts by volume. Further, the fluidity of the molybdenum granulated powder is preferably 50 sec / 50 g or less.

According to the method for producing molybdenum granulated powder according to the present invention, in the granulation step, while stirring the organic solvent, the dopant-added molybdenum powder and the binder are supplied, and the average particle diameter of the intended granulated powder is further increased. Since the rotation speed of the spray dryer is controlled within a predetermined range, molybdenum granulated powder having excellent average particle diameter, apparent density and fluidity can be efficiently produced with a high yield.

It is sectional drawing which shows an example of the process of preparing the molybdenum containing solution used with this invention method. It is sectional drawing which shows an example of the process of throwing a molybdenum containing solution into the spray dryer used by the method of this invention. It is a front view which shows the example of a shape of the molybdenum granulated powder which concerns on this invention.

The method for producing molybdenum granulated powder according to an embodiment of the present invention includes a step of adding an organic solvent to a container, a step of adding polyvinyl butyral as a binder to the organic solvent, and stirring the organic solvent while potassium is added. A step of preparing a molybdenum-containing solution by introducing a molybdenum powder having an average particle diameter of 1 to 10 μm to which at least one of a component, an aluminum component and a silicon component is added, and rotation of a spray dryer for dispersing the molybdenum-containing solution When the rotational speed of the plate is A (rpm) and the average particle diameter of the granulated powder is B (μm), the molybdenum-containing solution is put into a spray dryer in which A / B is in the range of 50 to 700, And a step of dispersing the molybdenum-containing solution and drying to prepare a molybdenum granulated powder. It is.
FIG. 1 shows an example of a process for preparing a molybdenum-containing solution. In the figure, reference numeral 1 is a container (a container for preparing a molybdenum-containing solution), 2 is an organic solvent, 3 is a molybdenum powder (dope-containing molybdenum powder), 4 is a binder, and 5 is An organic solvent is charged again as necessary, and 6 is a molybdenum-containing solution.
First, the organic solvent 2 is injected into the container 1. Alcohol etc. can be used as this organic solvent. As the alcohol, ethanol (ethyl alcohol: C ₂ H ₅ OH) is preferable. Ethyl alcohol is preferable because it easily dissolves a binder (polyvinyl butyral) described later.
Moreover, after inject | pouring the organic solvent 2 into the container 1, you may implement the process heated to 50 degrees C or less as needed. Heating above 50 ° C. is not preferable because the organic solvent evaporates excessively. If it is a heating of 50 degrees C or less, a binder can be melt | dissolved efficiently.

Next, a step of adding the binder 4 to the organic solvent 2 is performed. Polyvinyl butyral (PVB) is used as the material of the binder. Polyvinyl butyral is readily soluble in organic solvents, especially ethanol. Moreover, in order to make it melt | dissolve in an organic solvent uniformly, it is preferable to add a binder, stirring an organic solvent.
Next, a step of preparing a molybdenum-containing solution is performed by adding molybdenum powder having an average particle diameter of 1 to 10 μm while stirring the organic solvent. The average particle size of the molybdenum powder is the average particle size of the primary particle size. Here, the value obtained by the FSSS method (Fischer method) is defined as the average particle size. If the average particle size is less than 1 μm, the Mo powder is too small and difficult to manufacture, which increases the cost.
On the other hand, if the average particle size exceeds 10 μm, the primary particle size becomes excessive, and it becomes difficult to stabilize the characteristics of the molybdenum granulated powder. Therefore, the average particle diameter of the molybdenum powder is 1 to 10 μm. Further, 2 to 5 μm is preferable. In addition, when a large amount of molybdenum powder is added at once, the molybdenum powder tends to aggregate more than necessary, so it is preferable to add a small amount, for example, 0.5 to 2 kg.

Moreover, it is preferable to add molybdenum powder after confirming that the entire amount of the binder is dissolved in the organic solvent. When the binder is added in a powder state, it can be visually discriminated whether or not it is dissolved. When polyvinyl butyral powder is used as the binder, when the polyvinyl butyral powder is completely dissolved in the organic solvent (ethanol), the organic solvent (ethanol) before adding the molybdenum powder becomes translucent. In order to make it easy to determine whether or not the binder is completely dissolved in the organic solvent (ethanol), it is preferable to add the molybdenum powder after the binder is added.
In preparing the molybdenum-containing solution 6 by adding the molybdenum powder 3 and the binder 4 to the organic solvent 2, when the total amount of the molybdenum powder to be added is 100 parts by volume, the volume of the binder is 3 to 20 parts by volume. It is preferable to do. The binder serves as an adhesive that bonds the molybdenum powders together when forming the molybdenum granulated powder. Therefore, when the total amount of molybdenum powder is 100 parts by volume, if the amount of binder added is less than 3 parts by volume, the amount of binder may be too small to obtain uniform granulated powder. Moreover, when the addition amount of a binder exceeds 20 volume part, a binder will enter too much into the clearance gap between molybdenum powders, and it will become a granulated powder with a large dispersion | variation in a density. Therefore, the addition amount of the binder is preferably 3 to 20 parts by volume, more preferably 5 to 15 parts by volume with respect to 100 parts by volume of the molybdenum powder.

The molybdenum-containing solution preferably has an organic solvent amount of 0.2 to 1 liter when the molybdenum powder amount is 100 parts by mass. The spray dryer is charged in a molybdenum-containing solution. At this time, if the amount of the organic solvent is less than 0.2 liter with respect to 100 parts by mass of the molybdenum powder, the amount of the organic solvent is too small and the viscosity of the molybdenum-containing solution increases, and it is difficult to stably supply it to the spray dryer.
On the other hand, when the amount of the organic solvent exceeds 1 liter, the amount of the organic solvent is too large and stable supply is difficult. When the amount of the organic solvent is large, there is also a method of stably supplying by supplying with stirring. The supply of the molybdenum-containing solution to the spray dryer can be mechanized and automated.
Moreover, you may add the organic solvent 5 further as needed. For example, since ethanol has a relatively low boiling point of 78.3 ° C., there is a possibility that the amount of solvent may change greatly due to evaporation of ethanol when a binder and molybdenum powder are added and mixed. When a large container having a volume of 20 liters or more is used as the container 1, the amount of the organic solvent is mixed with the binder and the molybdenum powder at 30 to 60% of the final amount, and then the remaining amount of the organic solvent. A method of adjusting the blending amount of molybdenum powder and the amount of organic solvent by additionally adding 70 to 40% is also possible. In order to make it easy to visually confirm whether or not the binder is completely dissolved in the organic solvent, it is effective to add the organic solvent.

The molybdenum powder of the present invention is a molybdenum powder to which at least one of a potassium component, an aluminum component, and a silicon component is added. As the potassium component, aluminum component, or silicon component, compounds such as simple elements, oxides, and complex oxides are used, respectively.
In addition, the content (addition amount) of the potassium component is preferably in the range of 100 to 1000 ppm by mass in terms of potassium element alone. The content of the aluminum component is preferably in the range of 100 to 1000 ppm by mass in terms of an aluminum element. Further, the content of the silicon component is preferably in the range of 100 to 1000 ppm by mass in terms of silicon element. If the amount is less than 100 ppm by mass, the effect of addition is small. Moreover, a dopant may be 1 type or may add 2 or more types.
Moreover, a potassium component, an aluminum component, and a silicon component are components called a dopant. By adding these dopants, the recrystallization temperature is increased and the high temperature strength is increased as compared with high purity molybdenum. Moreover, since ductility improves after recrystallization heat processing, secondary workability, such as a drawing process to a wire, improves. Secondary processing includes wire bending processing, wire bending processing, plate material (plate material made of Mo sintered body) rolling processing, bending processing, punching processing, and the like. Further, the wire characteristics can improve non-sag, high-temperature vibration resistance, and blackening resistance.
Moreover, although the manufacturing method of the molybdenum powder which added the dopant is not specifically limited, the following are illustrated.
First, ammonium dimolybdate ((NH ₄ ) ₂ .Mo ₂ O ₇ )) is prepared as a raw material for molybdenum powder, and heated at a temperature of 600 to 750 ° C. in a hydrogen stream to obtain Mo oxide. Potassium silicate is added to the Mo oxide so that the amount of elemental potassium element per elemental Mo is 100 to 1000 ppm by mass. At this time, pure water is added, kneaded, heated to 100-140 ° C. with stirring, and dried to obtain a dopant-added molybdenum oxide powder. The dopant-added molybdenum oxide powder can be obtained by heating and reducing the dopant-added molybdenum oxide powder at a temperature of 1000 to 1200 ° C. for 2 to 5 hours in a hydrogen atmosphere.
The above shows an example in which potassium is added as a dopant. When silicon or aluminum is added as a dopant, silicon alone or a silicon compound, and aluminum alone or an aluminum compound are added, respectively. Moreover, although potassium silicate was used as the potassium component, the invention is not limited to this, and other potassium compounds may be used.
Moreover, when adding 2 or more types of potassium, aluminum, and silicon, what is necessary is just to add each element or compound and to obtain a dopant addition molybdenum powder.
The purity of the dopant-added molybdenum powder is not particularly limited, but the total of Mo and the dopant is preferably 99% by mass or more, and more preferably 99.9% by mass or more. Main impurities of the molybdenum powder include Fe (iron), Ca (calcium), and Mg (magnesium). Other impurities include Ni (nickel), Na (sodium), Pb (lead), Bi (bismuth), Cd (cadmium), Cu (copper), Mn (manganese), and Sn (tin). It is done.
The measurement of the purity of molybdenum is Fe (iron), Ca (calcium), Mg (magnesium), Ni (nickel), Na (sodium), Pb (lead), Bi (bismuth), Cd (cadmium), Cu (copper) ), Mn (manganese) and Sn (tin) are subtracted from 100% by mass. Moreover, as each impurity amount, Fe (iron) is 10 mass ppm (wtppm) or less, Ca (calcium) is 30 mass ppm or less, Mg (magnesium) is 20 mass ppm or less, Ni (nickel) is 50 mass ppm. Hereinafter, Na (sodium) is 10 mass ppm or less, Pb (lead) is 70 mass ppm or less, Bi (bismuth) is 70 mass ppm or less, Cd (cadmium) is 70 mass ppm or less, and Cu (copper) is 70 mass ppm. Hereinafter, it is preferable that Mn (manganese) is 20 mass ppm or less and Sn (tin) is 30 mass ppm or less.
Moreover, gas components, such as oxygen, are mentioned as impurities other than the said metal impurity. While the amount of oxygen is 7% by mass or less, the amount of nitrogen is preferably 7% by mass or less.

Next, the obtained molybdenum-containing solution is put into a spray dryer and granulated. FIG. 2 shows an example of a granulation process using a spray dryer. In the figure, reference numeral 1 is a container containing a molybdenum-containing solution, 6 is a molybdenum-containing solution, 7 is an inlet for a molybdenum-containing aqueous solution, 8 is a rotating plate, and 9 is a molybdenum granulated powder. Reference numeral 10 denotes an outer wall of the spray dryer, and reference numeral 11 denotes a molybdenum granulated powder collection container.
The molybdenum-containing solution 6 prepared in the above process is poured into the charging port 7. The charging speed to the charging port 7 is preferably 10 to 80 cc / min. When the input speed is less than 10 cc / min, the input amount is too small and the mass productivity is deteriorated. On the other hand, when the charging speed exceeds 80 cc / min, the charging amount becomes excessive and the characteristics of the resulting granulated powder vary.

Next, the charged molybdenum-containing solution 6 is supplied onto the rotating plate 8. The rotating plate 8 rotates at a constant rotational speed. When the molybdenum-containing solution 6 is supplied to the rotating rotating plate 8, it is repelled by a certain amount, and spherical molybdenum granulated powder 9 is formed by surface tension. The molybdenum granulated powder 9 falls along the outer wall 10 of the spray dryer and is collected in a molybdenum granulated powder collection container 11.
The average particle diameter of the molybdenum granulated powder is highly related to the rotation speed of the rotating plate 8. Therefore, in the present invention, when the rotational speed of the rotating plate of the spray dryer is A (rpm) and the average particle diameter of the granulated powder is B (μm), A / B is controlled in the range of 50 to 700. It is characterized by.
When the molybdenum-containing solution 6 is supplied to the rotating plate 8, the molybdenum-containing solution 6 is repelled by a certain amount on the rotating plate 8, and the repelled molybdenum-containing solution 6 becomes spherical molybdenum granulated powder due to surface tension. Moreover, uniform granulated powder can be manufactured also from having added the binder.

When the ratio A / B is less than 50, the rotational speed of the rotating plate is insufficient with respect to the average particle diameter of the intended granulated powder, and thus the average particle diameter B of the intended granulated powder is obtained. Absent. Moreover, when A / B is less than 50, it becomes a granulated powder having a larger average particle diameter than the average particle diameter B of the intended granulated powder.
On the other hand, when A / B exceeds 700, the rotation speed of the rotating plate is too high with respect to the average particle diameter of the intended granulated powder, and thus the average particle diameter B of the intended granulated powder cannot be obtained. Moreover, when A / B exceeds 700, it becomes a small average particle diameter with respect to the average particle diameter B of the intended granulated powder.
By controlling the ratio A / B in the range of 50 to 700, a granulated powder having an average particle diameter in the range of ± 50% with respect to the average particle diameter B of the intended granulated powder can be obtained. For example, when the average particle size B of the intended granulated powder is 50 μm, the ± 50% width is 50 × 0.5 = 25 μm, so that a granulated powder having an average particle size of 25 to 75 μm can be obtained. Means. In addition, the average particle diameter of granulated powder uses an enlarged photograph, and makes the maximum diameter of the granulated powder reflected there the particle diameter, and the average value of 100 granulated powder is the average particle diameter of the granulated powder.

The average particle size B of the molybdenum granulated powder is preferably 20 to 150 μm. If the average particle diameter of the molybdenum granulated powder is in the range of 20 to 150 μm, it can be applied to various applications. Further, the rotational speed A of the rotary plate 8 of the spray dryer is preferably 5000 to 16000 rpm. When the rotational speed A is in the range of 5000 to 16000 rpm, the molybdenum-containing solution is efficiently repelled on the rotating plate, and molybdenum granulated powder having a target average particle diameter can be easily obtained.

The spray dryer preferably dries the molybdenum granulated powder while supplying hot air at 100 to 300 ° C. By supplying hot air of 100 to 300 ° C. into the outer wall of the spray dryer, the organic solvent in the granulated powder can be evaporated, and the binding force between the molybdenum powders by the binder can be enhanced. As a result, molybdenum granulated powder having a target average particle diameter and high structural strength can be produced.
Here, the hot air is supplied into the outer wall 10 of the spray dryer from a hot air supply port (not shown) and exhausted from an exhaust port (not shown). By supplying hot air while exhausting it from the supply port to the exhaust port, fresh hot air can always be supplied, and moisture evaporated from the granulated powder can be prevented from being taken into other granulated powder. . When the supply temperature of hot air is less than 100 ° C., the evaporation rate of the organic solvent is slow. On the other hand, when it exceeds 300 ° C., the organic solvent evaporates momentarily, causing the variation in the particle size of the granulated powder. Become.

Moreover, it is preferable that the spray dryer performs drying of the molybdenum granulated powder in a reduced-pressure atmosphere of atmospheric pressure or lower. By setting the inside of the outer wall 10 of the spray dryer to a reduced-pressure atmosphere of atmospheric pressure or less, the organic solvent in the granulated powder can be easily evaporated. The reduced-pressure atmosphere is preferably a reduced-pressure atmosphere that is 100 to 500 Pa lower than atmospheric pressure (1 atm = 1.01 × 10 ⁵ Pa). If the pressure is less than 100 Pa, the effect of reducing the reduced pressure atmosphere is not sufficient, and if the pressure exceeds 500 Pa, the burden of controlling the reduced pressure atmosphere increases, resulting in a cost increase.

According to the method for producing molybdenum granulated powder according to the present invention, since the rotation speed of the rotating plate of the spray dryer is adjusted in accordance with the average particle diameter of the granulated powder, ± A molybdenum granulated powder having a particle size in the range of 50% can be obtained.
The apparent density of the resulting molybdenum granulated powder is preferably 1.3 to 3.0 g / cc. As described above, in the present invention, the average particle diameter of the molybdenum granulated powder is measured using an enlarged photograph. If it is this measuring method, the average particle diameter on an external appearance can be judged.
However, if granulated powder with many voids and low density is present inside the granulated powder, when it is used for subsequent products (spraying powder or sintered body), the abundance ratio of the molybdenum powder partially varies. Arise. Variation in the existence ratio leads to variation in the product. For example, when granulated powder is used for the thermal spraying powder, if there are granulated powders with significantly different densities, the amount of molybdenum powder introduced into the flame flame flame will vary, resulting in variations in the characteristics of the thermal sprayed Mo film. Cause. Moreover, when producing a sintered compact, the amount of molybdenum with which a molding die is filled varies and the pores in the sintered compact may become larger than necessary.

If the apparent density of the molybdenum granulated powder is less than 1.3 g / cc, the amount of molybdenum in the granulated powder is too small, which causes variations in quality in subsequent product production. On the other hand, when the apparent density exceeds 3.0 g / cc, the molybdenum powder is tightly packed, so that it is difficult to stably manufacture with a spray dryer. The apparent density is measured by a measuring method based on JIS-Z-2504.
Moreover, it is preferable that the fluidity | liquidity of the obtained molybdenum granulated powder is 50 sec / 50g or less. This fluidity measurement is also performed by a measuring method based on JIS-Z-2504. The fluidity is an index indicating how smoothly and quickly the granulated powder moves (flows). When the fluidity is good (fluidity 50 sec / 50 g or less), the supply and filling into the molding die when commercialized can be carried out smoothly and rapidly.
In other words, it can be said that the granulated powder has good handleability. Moreover, that fluidity | liquidity is good means that the shape of molybdenum granulated powder is close to a sphere. When the granulated powder is close to a sphere, the aspect ratio is 1.5 or less. FIG. 3 shows an example of molybdenum granulated powder. In the figure, reference numeral 3 denotes a molybdenum powder, 9 denotes a molybdenum granulated powder, L1 denotes a short diameter of the molybdenum granulated powder 9, and L2 denotes a long diameter. The aspect ratio is calculated by “major axis L2 / minor axis L1”. An aspect ratio of 1.0 indicates a state close to a true sphere.

Thus, according to the manufacturing method of the molybdenum granulated powder which concerns on this invention, the molybdenum granulated powder excellent in average particle diameter, apparent density, and fluidity | liquidity can be efficiently manufactured with a sufficient yield.
In addition, as a means for controlling the average particle diameter of the molybdenum granulated powder, particularly the particle size distribution, the mesh diameter is 2 to 3 times the average particle diameter B of the granulated powder after completion of the granulation process by a spray dryer. There is also a method of further carrying out a sieving step through a sieve having the same. By carrying out this sieving step, excessive granulated powder can be removed. Thereby, the stricter control of the average particle diameter becomes possible. It is also effective to remove excessive granulated powder by a sieving step.

As described above, according to the method for producing molybdenum granulated powder according to the embodiment of the present invention, molybdenum granulated powder having excellent average particle diameter, apparent density, and fluidity can be efficiently produced with a high yield. Therefore, the granulated powder according to each product can be manufactured with a good yield.
Applications of these molybdenum granulated powders include powders for thermal spraying and raw material powders for various sintered bodies. By using molybdenum granulated powder with excellent average particle diameter, apparent density and fluidity as the powder for thermal spraying, the supply amount (feed speed) of the molybdenum granulated powder to the thermal spray flame can be stabilized. . As a result, the quality of the sprayed film can be made uniform. In addition, when using molybdenum granulated powder as a raw material powder for various sintered bodies, molybdenum granulated powder for molding molds can be obtained by using molybdenum granulated powder with excellent average particle diameter, apparent density and fluidity. Can be homogenized. As a result, the density of the sintered body can be stabilized. In particular, the yield can be further improved by changing the average particle diameter according to the shape of the molding die. For example, in the case of a sintered body having a thickness of 1 mm or less, the average particle diameter of the granulated powder is set to about 50 μm, whereas in the sintered body having a thickness of about 5 mm, the average particle diameter of the granulated powder is set to about 100 μm. As a result, it is possible to efficiently fill the molding die.

(Example)
(Examples 1 to 5 and Comparative Examples 1 and 2)
A dopant-added molybdenum powder shown in Table 1 and polyvinyl butyral (PVB) powder and ethanol were prepared as binders. Ethanol was poured into a stainless steel container and the polyvinyl butyral powder was added while stirring at room temperature to dissolve all the added polyvinyl butyral powder. When all the polyvinyl butyral powder was dissolved, it was confirmed that the solution was a translucent solution. Thereafter, a total of 40 kg of molybdenum powder was added in an amount of 1-2 kg. When the molybdenum powder was agitated, ethanol was additionally added as needed for the shortage of ethanol evaporation. Examples 1 to 5 were molybdenum-containing solutions using polyvinyl alcohol powder as a binder.
The conditions for the preparation steps of the molybdenum-containing solution so far are shown in Tables 1 and 2 below.

Next, using each of the molybdenum-containing solutions according to Examples 1 to 5 prepared as described above, a granulation step using a spray dryer was performed. The conditions of the granulation process with a spray dryer are shown in Table 3 below.

The average particle diameter, aspect ratio, apparent density, fluidity and product yield of the granulated molybdenum powder obtained by the production methods of Examples 1A-5B and Comparative Examples 1-2 were investigated.
The average particle size was obtained by extracting 100 arbitrary particles of the obtained molybdenum granulated powder, taking an enlarged photograph, obtaining the maximum diameter reflected therein, and taking the average value of 100 particles as the average particle size. Moreover, the aspect ratio used the same enlarged photograph, calculated | required the short diameter L1 and the long diameter L2 of the molybdenum granulated powder, and made each average value of L2 / L1 the aspect ratio. The apparent density and fluidity were measured by a measuring method based on JIS-Z-2504. The product yield was calculated from the ratio of the amount of molybdenum powder charged to 40 kg and the total amount of recovered molybdenum granulated powder ((total amount of granulated powder / 40 kg) × 100%).
The measurement results are shown in Table 4 below.

As is clear from the results shown in Table 4 above, the molybdenum granulated powder produced by the method for producing molybdenum granulated powder according to each example has a small deviation from the target average particle diameter B, and has an aspect ratio and an apparent appearance. The density and fluidity were excellent. In addition, it was confirmed that the production method was high in yield and efficient. On the other hand, in Comparative Example 1 and Comparative Example 2 where A / B is outside the specified range in the present invention, both parameters showed a deteriorated characteristic.

1 ... container (container for preparing molybdenum-containing solution)
2 ... Organic solvent 3 ... Molybdenum powder (dope-added molybdenum powder)
4 ... Binder 5 ... Organic solvent 6 to be added again as required 6 ... Molybdenum-containing solution 7 ... Molybdenum-containing solution inlet 8 ... Rotary plate 9 ... Molybdenum granulated powder 10 ... Outer wall 11 of spray dryer ... Molybdenum granulated powder Collection container

Claims

Adding an organic solvent to the container;
Adding polyvinyl butyral as a binder to the organic solvent;
Preparing a molybdenum-containing solution by adding molybdenum powder having an average particle size of 1 to 10 μm to which at least one of a potassium component, an aluminum component and a silicon component is added while stirring the organic solvent;
A / B is in the range of 50 to 700, where A (rpm) is the rotational speed of the rotating plate of the spray dryer for dispersing the molybdenum-containing solution and B (μm) is the average particle size of the granulated powder. Adding a molybdenum-containing solution to a spray dryer, dispersing the molybdenum-containing solution and drying to prepare molybdenum granulated powder; and
A method for producing molybdenum granulated powder, comprising:
The granulated powder after completion of the granulation process by the spray dryer is further subjected to a sieving process through a sieve having a mesh diameter 2 to 3 times the average particle diameter B of the granulated powder. The manufacturing method of the molybdenum granulated powder of Claim 1.
3. The method for producing a molybdenum granulated powder according to claim 1, wherein the average particle diameter B of the molybdenum granulated powder is 20 to 150 μm.
The method for producing a molybdenum granulated powder according to claim 1 or 3, wherein the rotational speed A of the rotating plate of the spray dryer is 5000 to 16000 rpm.
The method for producing a molybdenum granulated powder according to any one of claims 1 to 4, wherein the organic solvent is ethanol.
The method for producing a granulated molybdenum powder according to any one of claims 1 to 5, wherein a content of the potassium component is in a range of 100 to 1000 ppm by mass in terms of a potassium element simple substance.
The method for producing a molybdenum granulated powder according to any one of claims 1 to 6, wherein the content of the aluminum component is in the range of 100 to 1000 ppm by mass in terms of a single aluminum element.
The method for producing a molybdenum granulated powder according to any one of claims 1 to 7, wherein a content of the silicon component is in a range of 100 to 1000 ppm by mass in terms of a silicon element.
The molybdenum structure according to any one of claims 1 to 8, wherein the volume of the binder is 3 to 20 parts by volume when the total amount of the molybdenum powder to be added is 100 parts by volume. A method for producing grain flour.
The method for producing molybdenum granulated powder according to any one of claims 1 to 9, wherein an apparent density of the obtained molybdenum granulated powder is 1.3 to 3.0 g / cc.
The molybdenum according to any one of claims 1 to 10, wherein the molybdenum-containing solution has an organic solvent amount of 0.2 to 1 liter when a molybdenum powder amount is 100 parts by mass. A method for producing granulated powder.
The molybdenum granulated powder production according to any one of claims 1 to 11, wherein the spray dryer dries the molybdenum granulated powder while supplying hot air of 100 to 300 ° C. Method.
The method for producing a molybdenum granulated powder according to any one of claims 1 to 12, wherein the spray dryer performs drying of the molybdenum granulated powder in a reduced pressure atmosphere at atmospheric pressure or lower.
The fluidity of the obtained molybdenum granulated powder is 50 sec / 50g or less, The manufacturing method of the molybdenum granulated powder of any one of Claim 1 thru | or 13 characterized by the above-mentioned.
A molybdenum granulated powder comprising at least one of a potassium component, an aluminum component, and a silicon component and having an apparent density of 1.3 to 3.0 g / cc.
The molybdenum granulated powder according to claim 15, wherein the average particle diameter of the molybdenum granulated powder is 20 to 150 µm.
The molybdenum granulated powder according to claim 15 or 16, wherein the volume of the binder is 3 to 20 parts by volume when the total amount of the molybdenum powder is 100 parts by volume.
The molybdenum granulated powder according to any one of claims 15 to 17, wherein the fluidity of the molybdenum powder is 50 sec / 50 g or less.