WO2012169259A1

WO2012169259A1 - Method for producing molybdenum carbide granulated powder and molybdenum carbide granulated powder

Info

Publication number: WO2012169259A1
Application number: PCT/JP2012/057362
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: WO2012169260A1; WO2012169257A1; WO2012169261A1; JPWO2012169257A1

Abstract

This method for producing a molybdenum carbide granulated powder is characterized by comprising: a step in which an organic solvent is injected into 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 carbide is prepared by loading molybdenum carbide powder with an average particle size of 1 to 10 μm while stirring the organic solvent; and a step in which the solution containing molybdenum carbide is loaded in a spray dryer in which, when the rotation speed of a rotator of the spray dryer is regarded as A (rpm), and the average particle size of the granulated powder to be prepared is regarded as B (μm), A/B ranges from 50 to 700, and the solution containing molybdenum carbide is dispersed by the rotor, and then dried to prepare molybdenum carbide granulated powder having a prescribed average particle size. The abovementioned method enables a molybdenum carbide granulated powder having the intended average particle size to be efficiently produced.

Description

Method for producing molybdenum carbide granulated powder and molybdenum carbide granulated powder

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

Molybdenum carbide (Mo ₂ C) has a high melting point of about 2687 ° C. and high hardness, and is therefore used in various fields as a heat-resistant material and a super hard material. For example, applications such as thermal spraying materials and carbide tools can be mentioned. As a thermal spraying material, there is a method of supplying molybdenum carbide powder. In addition, carbide tools and the like may be manufactured by a sintering method.
Thus, when using molybdenum carbide, (1) when using molybdenum carbide as a powder, (2) when using molybdenum carbide as a sintered body, (3) rolling, forging, casting, etc. For example, when processing into a plate shape. Whichever method is used, molybdenum carbide powder is used as an initial raw material (starting material).
In the case of the sintering method, it is possible to produce a component having a complicated shape by filling a mold with molybdenum carbide powder. When producing a sintered body by a sintering method, a granulation process, a forming process, a degreasing process, a sintering process, and the like are performed on the molybdenum carbide powder. Until now, the sintering method has been advanced mainly on the degreasing process and the improvement of the sintering process.
Japanese Patent Application Laid-Open No. 2002-4026 (Patent Document 1) discloses a thermal spraying powder using molybdenum carbide powder. Thermal spraying is a method in which a thermal spraying powder is supplied to a combustion flame, and the thermal spraying powder is melted and blown toward the base material to form a coating on the base material.
As described above, various products using molybdenum carbide have been put into practical use. However, in any case, there has been a problem that the yield cannot be improved.

Japanese Patent Laid-Open No. 2002-4026

The present inventors have investigated the reason why the yield of products using molybdenum carbide powder as an initial raw material is not improved. As a result, it was found that the variation in size, density, fluidity, etc. of the granulated powder is large, which causes variations in the packing density and supply amount in the molding process, which causes a decrease in product yield. In addition, when molybdenum carbide granulated powder is used as the thermal spraying powder, there are problems such as variations in the amount supplied to the combustion flame and unstable properties as the thermal spraying film.
As a result of pursuing this cause, it has been found that there is a cause that the management corresponding to the average particle size of the intended granulated powder is not performed in the granulation step.
The present invention has been made to solve such problems, and is capable of producing a molybdenum carbide granulated powder capable of stabilizing the quality and improving the yield of molybdenum carbide products (powder or sintered body). A method is provided.

The method for producing a molybdenum carbide granulated powder according to the present invention comprises a step of injecting an organic solvent into a container, a step of adding polyvinyl butyral as a binder to the organic solvent, an average particle size of 1 to 10 μm while stirring the organic solvent. When preparing the molybdenum carbide-containing solution by introducing molybdenum carbide powder, the rotational speed of the rotating plate of the spray dryer is A (rpm), and the average particle size of the granulated powder to be prepared is B (μm) Molybdenum carbide-containing powder having a predetermined average particle diameter is prepared by charging the molybdenum carbide-containing solution into a spray dryer having an A / B in the range of 50 to 700, dispersing the molybdenum carbide-containing solution with the rotating plate, and further drying the solution. And a step of preparing.
Further, the molybdenum carbide powder preferably has a carbon content of 11.0 to 11.3 wt% in the molybdenum carbide.
Further, it is preferable to carry out a sieving step in which the granulated powder after the spray dryer step is passed through a sieve having a mesh size 2 to 3 times the average particle size B. The average particle size B of the 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, when the total amount of the molybdenum carbide 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 carbide granulated powder is preferably 1.3 to 3.0 g / cc. The molybdenum carbide-containing solution preferably has an amount of organic solvent of 0.2 to 1 liter when the amount of molybdenum carbide powder is 100 parts by mass.
The spray dryer preferably dries the granulated powder while supplying hot air of 100 to 300 ° C. The spray dryer preferably dries the granulated powder in a reduced-pressure atmosphere at atmospheric pressure or lower. The obtained granulated powder preferably has a fluidity of 50 sec / 50 g or less.
The molybdenum carbide granulated powder of the present invention is characterized by an apparent density of 1.3 to 3.0 g / cc.
Further, the average particle diameter of the molybdenum carbide granulated powder is preferably 20 to 150 μm. Further, when the total amount of the molybdenum carbide powder is 100 parts by volume, the volume of the binder is preferably 3 to 20 parts by volume. Further, the fluidity is preferably 50 sec / 50 g or less.

In the production method according to the present invention, the molybdenum carbide powder and the binder are supplied while stirring the organic solvent, and the average particle diameter of the intended granulated powder and the rotation speed of the spray dryer are controlled within a predetermined range. Thus, molybdenum carbide granulated powder having excellent average particle diameter, apparent density and fluidity can be produced.

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

A method for producing a molybdenum carbide granulated powder according to an embodiment of the present invention includes a step of injecting an organic solvent into a container, and adding molybdenum carbide powder having an average particle size of 1 to 10 μm while stirring the organic solvent. A / B is in the range of 50 to 700 when the step of preparing the solution and the rotation speed of the rotating plate for dispersing the molybdenum-containing solution is A (rpm) and the average particle size of the granulated powder is B (μm) And adding a molybdenum carbide-containing solution to the spray dryer.
FIG. 1 shows an example of a process for preparing a molybdenum carbide-containing solution. In the figure, reference numeral 1 is a container (a container for preparing a molybdenum carbide-containing solution), 2 is an organic solvent, 3 is a molybdenum carbide powder, 4 is a binder, and 5 is again as necessary. An organic solvent to be added, and 6 is a molybdenum carbide-containing solution.
First, an organic solvent is poured into the container. Examples of the organic solvent include alcohol. The alcohol is preferably ethanol (ethyl alcohol: C ₂ H ₅ OH). Ethyl alcohol is preferable because it easily dissolves a binder (polyvinyl butyral) described later.
In addition, an organic solvent is put into the container 1. Then, 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 too much. If it is a heating of 50 degrees C or less, a binder can be melt | dissolved efficiently.

Next, a step of adding a binder to the organic solvent is performed. Polyvinyl butyral (PVB) is used as the material of the binder. Polyvinyl butyral is easily soluble in organic solvents, particularly 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 carbide-containing solution is performed by adding molybdenum carbide powder having an average particle diameter of 1 to 10 μm while stirring the organic solvent. The average particle size of the molybdenum carbide 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 diameter of the molybdenum carbide powder is less than 1 μm, the molybdenum carbide powder is too small to be manufactured, which increases the cost.
On the other hand, when the average particle diameter of the molybdenum carbide powder exceeds 10 μm, the primary particle diameter is too large, and it becomes difficult to stabilize the characteristics of the granulated powder. Therefore, the average particle diameter of the molybdenum carbide powder is preferably in the range of 1 to 10 μm, more preferably 2 to 5 μm. Further, if a large amount of molybdenum carbide powder is added at once, the molybdenum carbide 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 the molybdenum carbide powder after confirming that the entire amount of the binder is dissolved in the organic solvent. If the binder is added as a powder, it can be visually discriminated whether or not it has melted. 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 carbide 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 carbide powder after adding the binder.
Here, when preparing the molybdenum carbide-containing solution 6 by adding the molybdenum carbide powder 3 and the binder 4 to the organic solvent 2, the total volume of the molybdenum carbide powder to be added is 100 parts by volume. It is preferably 3 to 20 parts by volume.
The binder serves as an adhesive that bonds the molybdenum carbide powders together when forming the molybdenum carbide granulated powder. Therefore, when the total amount of molybdenum carbide 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.
On the other hand, when the addition amount of the binder exceeds 20 parts by volume, the binder enters too much into the gap between the molybdenum carbide powders, resulting in a granulated powder having a large variation in density. Therefore, the added amount of the binder is 3 to 20 parts by volume, more preferably 5 to 15 parts by volume with respect to 100 parts by volume of the molybdenum carbide powder.

The molybdenum carbide-containing solution preferably has an amount of organic solvent of 0.2 to 1 liter when the amount of molybdenum carbide powder is 100 parts by mass. The spray drier is charged in the form of a molybdenum carbide-containing solution. At this time, if the amount of the organic solvent is less than 0.2 liters with respect to 100 parts by mass of the molybdenum carbide powder, the amount of the organic solvent is too small and the viscosity of the molybdenum carbide-containing solution increases, making it difficult to stably supply the spray dryer. . On the other hand, when the amount of the organic solvent exceeds 1 liter, the amount of the organic solvent becomes excessive, and it is difficult to stably supply the organic solvent. 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 carbide-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., ethanol may evaporate and the amount of solvent may change greatly when a binder and molybdenum carbide powder are charged and mixed.
When the container 1 has a large volume of 20 liters or more, the amount of organic solvent is mixed with the binder and molybdenum carbide powder at 30 to 60% of the final amount, and then the remaining amount of organic solvent is 70 to 70%. A method of adjusting the amount of molybdenum carbide powder and the amount of organic solvent by additionally adding 40% is also possible. In order to make it easy to visually confirm whether the binder is completely dissolved in the organic solvent, a method of adding the organic solvent is also effective.

The purity of the molybdenum carbide powder is not particularly limited, but the purity of the molybdenum carbide is preferably 99% by mass or more, and more preferably 99.9% by mass or more. Main impurities of the molybdenum carbide powder include Fe (iron), Al (aluminum), Ca (calcium), Mg (magnesium), and Si (silicon). As other impurities, Ni (nickel), Na (sodium), K (potassium), Pb (lead), Bi (bismuth), Cd (cadmium), Cu (copper), Mn (manganese), Sn (Tin).
The molybdenum purity was measured using Fe (iron), Al (aluminum), Ca (calcium), Mg (magnesium), Si (silicon), Ni (nickel), Na (sodium), K (potassium), Pb ( The total amount of lead), Bi (bismuth), Cd (cadmium), Cu (copper), Mn (manganese), and Sn (tin) shall be subtracted from 100% by mass.
The amount of impurities is 10 wtppm or less for Fe (iron), 50 wtppm or less for Al (aluminum), 30 wtppm or less for Ca (calcium), 20 wtppm or less for Mg (magnesium), 50 wtppm or less for Si (silicon), Ni ( Nickel) 50 wtppm or less, Na (sodium) 10 wtppm or less, K (potassium) 20 wtppm or less, Pb (lead) 70 wtppm or less, Bi (bismuth) 70 wtppm or less, Cd (cadmium) 70 wtppm or less, Cu (copper) Is preferably 70 wtppm or less, Mn (manganese) is preferably 20 wtppm or less, and Sn (tin) is preferably 30 wtppm or less.
Further, examples of impurities other than the metal impurities include gas components such as oxygen. The amount of oxygen is preferably 7% by mass or less, and the amount of nitrogen is preferably 7% by mass or less.
Further, the molybdenum carbide powder preferably has a carbon content of 11.0 to 11.3 mass% in the molybdenum carbide. As the molybdenum carbide, there are carbides such as Mo ₂ C and MoC having a different atomic ratio between molybdenum and carbon. When used as a thermal spraying powder or a carbide tool, if the amount of carbon in the molybdenum carbide is 11.0 to 11.3 mass%, it is thermally stable and the life is improved.
Moreover, the following method is mentioned as a preparation method of molybdenum carbide powder. First, ammonium dimolybdate ((NH ₄ ) ₂ .Mo ₂ O ₇ ) is prepared as a raw material and heated at 500 to 800 ° C. in a hydrogen atmosphere to obtain molybdenum oxide powder. The obtained molybdenum oxide powder is heated and reduced in a hydrogen atmosphere at 1000 to 1200 ° C. for 2 to 5 hours to obtain a metal molybdenum powder. Carbon can be added to the obtained metal molybdenum powder, mixed uniformly using a vibration mill or the like, and then placed on a carbon boat and carbonized at 900 to 1200 ° C. in a hydrogen atmosphere to obtain molybdenum carbide powder. . At this time, the amount of carbon to be added is preferably 11.0 to 11.3 mass%. The carbon to be added is preferably a carbon black powder having a specific gravity of 1.65 to 1.70, a moisture content of 0.1% or less, and an average particle size of 1 μm or less.

Next, a step of putting the obtained molybdenum carbide-containing solution into a spray dryer is performed. FIG. 2 shows an example of the spray dryer process. In the figure, reference numeral 1 is a container containing a molybdenum carbide-containing solution, 6 is a molybdenum carbide-containing solution, 7 is an inlet for a molybdenum carbide-containing aqueous solution, and 8 is a rotating plate for dispersing the molybdenum carbide-containing aqueous solution 6. 9 is a molybdenum carbide granulated powder, 10 is an outer wall of a spray dryer, and 11 is a recovery container for the molybdenum carbide granulated powder.
The molybdenum carbide-containing solution 6 adjusted 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 poor. On the other hand, if it exceeds 80 cc / min, there will be variations in the characteristics of the granulated powder obtained due to too much input.

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 carbide-containing solution is supplied to the rotating rotating plate, it is repelled by a certain amount and spherical granulated powder 9 is formed by surface tension. The granulated powder 9 is collected in a recovery container 11 for the molybdenum carbide granulated powder 9 along the outer wall 10 of the spray dryer.
The average particle diameter of the molybdenum carbide granulated powder is highly related to the rotation speed of the rotating plate. Therefore, the present invention is characterized in that the ratio A / B is controlled in the range of 50 to 700, where A (rpm) is the rotation speed of the rotating plate and B (μm) is the average particle size of the granulated powder. It is. When the molybdenum carbide-containing solution 6 is supplied to the rotating plate 8, the molybdenum carbide-containing solution 6 is repelled on the rotating plate 8 by a certain amount, and the repelled molybdenum carbide-containing solution 6 becomes spherical granulated powder 9 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, since the rotational speed A of the rotating plate is insufficient with respect to the average particle size B of the intended granulated powder, the average particle size B of the target granulated powder is I can't get it. 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. Moreover, when A / B exceeds 700, since the rotational speed A of the rotating plate is too high with respect to the average particle diameter B of the intended granulated powder, the average particle diameter B of the intended granulated powder is obtained. Absent. When A / B exceeds 700, the average particle size B becomes smaller than the average particle size B of the intended granulated powder.
By controlling 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 diameter B of the intended granulated powder is 50 μm, ± 50% means that an average particle diameter of 25 to 75 μm can be obtained from 50 × 0.5 = 25 μm. . 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 granulated powder is preferably 20 to 150 μm. If the average particle diameter of the granulated powder is in the range of 20 to 150 μm, it can be applied to various applications. The rotational speed A is preferably 5000 to 16000 rpm. When the rotational speed A is in the range of 5000 to 16000 rpm, the molybdenum carbide-containing solution is efficiently dispersed and repelled on the rotating plate, and a granulated powder having a target average particle diameter is easily obtained.

Moreover, it is preferable that the spray dryer dries the granulated powder while supplying hot air of 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 bonding strength between the molybdenum carbide powders by the binder can be enhanced. As a result, a molybdenum carbide granulated powder having a target average particle diameter can be produced. 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, it is possible to prevent moisture evaporated from the granulated powder from being taken into other granulated powder by always supplying fresh hot air. Note that when the supply temperature of hot air is less than 100 ° C., the evaporation rate of the organic solvent is slow, and when it exceeds 300 ° C., the organic solvent is momentarily evaporated to cause variation in the particle size of the granulated powder.

Moreover, it is preferable to perform drying of the granulated powder with a spray dryer 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. If the pressure exceeds 500 Pa, the burden of controlling the reduced pressure atmosphere is increased, which increases the cost.

According to the method for producing the molybdenum carbide granulated powder according to the present invention, the rotational speed of the rotating plate of the spray dryer is adjusted in accordance with the average particle diameter of the granulated powder. Uniform granulated powder in the range of ± 50% can be obtained.
The apparent density of the resulting molybdenum carbide 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 carbide granulated powder is obtained using an enlarged photograph. With this method, the average particle diameter on appearance can be determined. However, if granulated powder with large voids and small density is present inside the granulated powder, the ratio of the partial molybdenum carbide powder will vary when used in subsequent products (spraying powder and sintered body). Occurs. Variation in the existence ratio leads to variation in products.
For example, when granulated powder is used as a thermal spraying powder, the presence of granulated powder with significantly different densities causes variations in the amount of molybdenum carbide powder that is put into the thermal spray flame, resulting in variations in the thermal sprayed Mo film. It becomes. Moreover, when producing a sintered compact, the variation in the amount of molybdenum carbide inserted into a molding die arises, and there exists a possibility that the pore in a sintered compact may become larger than necessary.

If the apparent density of the molybdenum carbide granulated powder is less than 1.3 g / cc, the amount of molybdenum carbide in the granulated powder becomes too small, causing a variation in quality in the subsequent commercialization. On the other hand, if the apparent density exceeds 3.0 g / cc, the molybdenum carbide powder is tightly packed, so that it is difficult to stably manufacture with a spray dryer. The apparent density is measured by a method according to JIS-Z-2504.
The obtained granulated powder preferably has a fluidity of 50 sec / 50 g or less. The fluidity is also measured by a method according to JIS-Z-2504. Here, the fluidity indicates how smoothly the granulated powder moves (flows). If the fluidity is good (fluidity 50 sec / 50 g or less), it can be smoothly supplied to the molding die when commercialized. That is, it is a granulated powder with good handleability.
Moreover, that fluidity | liquidity is good means that the shape of 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 the shape of the molybdenum carbide granulated powder. In the figure, reference numeral 3 denotes molybdenum powder, 9 denotes molybdenum carbide granulated powder, L1 denotes a short diameter, and L2 denotes a long diameter. The aspect ratio is obtained by “major axis L2 / minor axis L1”. An aspect ratio of 1.0 indicates a state close to a true sphere.

Thus, if it is a manufacturing method of molybdenum carbide granulated powder concerning the present invention, molybdenum carbide granulated powder excellent in average particle diameter, apparent density, and fluidity can be efficiently manufactured with high yield.
Further, as a control of the average particle size, particularly the particle size distribution, there is a method of performing a sieving step of passing the granulated powder after the spray dryer step through a sieve having a mesh size 2 to 3 times the average particle size B. By carrying out this sieving step, excessive granulated powder can be removed. Thereby, control of the average particle diameter of granulated powder becomes possible. It is also effective to remove excessive granulated powder by a sieving step.

As described above, according to the method for producing a molybdenum carbide granulated powder according to the present invention, a molybdenum carbide 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.
Examples of the use of the granulated powder include thermal spraying powder and raw powders of various sintered bodies. By using molybdenum carbide granulated powder having excellent average particle diameter, apparent density and fluidity as the thermal spraying powder, the supply amount 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 carbide granulated powder as a raw material powder for various sintered bodies, it is possible to reduce the filling amount in the molding die by using molybdenum carbide granulated powder with excellent average particle diameter, apparent density and fluidity. It can be made uniform. 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 size 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 size of the granulated powder is 50 μm, and in the case of a sintered body having a thickness of about 5 mm, the average particle size of the granulated powder is 100 μm. Can be implemented efficiently.

(Example)
(Examples 1 to 5 and Comparative Examples 1 and 2)
Molybdenum carbide powder (Mo ₂ C purity of 99.9% or more), polyvinyl butyral (PVB) powder and ethanol were prepared as binders. Ethanol was put into a stainless steel container, and polyvinyl butyral powder was added while stirring at room temperature, and all the added polyvinyl butyral powder was dissolved. When all the polyvinyl butyral powder was dissolved, it was confirmed that the solution was translucent. Thereafter, 40 kg of molybdenum carbide powder was added in an amount of 1-2 kg. In the stirring of the molybdenum carbide powder, the ethanol vaporization deficiency was added as needed to prepare a molybdenum carbide-containing solution for Examples 1 to 5.
The conditions for the preparation steps of the molybdenum carbide-containing solution so far are shown in Table 1 below.

Next, using the molybdenum carbide-containing solutions of Examples 1 to 5, a spray dryer process was performed to prepare molybdenum carbide granulated powder according to Examples 1A to 5B and Comparative Examples 1 and 2. The conditions for each of the spray dryer steps are shown in Table 2 below.

The average particle diameter, aspect ratio, apparent density, fluidity and yield of the molybdenum carbide granulated powder obtained by the production methods of Examples 1A to 5B and Comparative Examples 1 to 2 were investigated.
In addition, the average particle diameter of each granulated powder is obtained by extracting an arbitrary 100 grains of the obtained molybdenum carbide granulated powder, taking an enlarged photograph, obtaining the maximum diameter reflected therein, and setting the average value of 100 grains as the average grain diameter. . As for the aspect ratio, the same magnified photograph was used to determine the minor axis L1 and the major axis L2, and the average value of each L2 / L1 was used as the aspect ratio. The apparent density and fluidity were measured according to the measuring method specified in JIS-Z-2504. The yield was calculated from the ratio of the amount of molybdenum powder 40 kg added and the total amount of molybdenum carbide granulated powder “(total amount of granulated powder / 40 kg) × 100%”.
The measurement results are shown in Table 3 below.

As is apparent from the results shown in Table 3 above, the molybdenum carbide granulated powder produced by the method for producing molybdenum carbide granulated powder according to this example has a small deviation from the target average particle diameter B, and the aspect ratio. The apparent density and fluidity were excellent. Moreover, it can be said that this is an efficient manufacturing method with a high yield. On the other hand, Comparative Example 1 and Comparative Example 2 in which A / B is outside the range of the present invention showed characteristics in which both parameters deteriorated.

1 ... Container (Container for preparing molybdenum carbide-containing solution)
DESCRIPTION OF SYMBOLS 2 ... Organic solvent 3 ... Molybdenum carbide powder 4 ... Binder 5 ... Organic solvent 6 thrown in again as needed ... Molybdenum carbide containing solution 7 ... Molybdenum carbide containing solution inlet 8 ... Rotary plate 9 ... Molybdenum carbide granulated powder 10 ... Outer wall 11 of spray dryer ... Molybdenum carbide granulated powder collection container

Claims

Injecting an organic solvent into the container;
Adding polyvinyl butyral as a binder to an organic solvent;
Preparing a molybdenum carbide-containing solution by adding a molybdenum carbide powder having an average particle size of 1 to 10 μm while stirring an organic solvent;
Molybdenum carbide-containing solution in a spray dryer in which 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 and B (μm) is the average particle size of the granulated powder to be prepared A step of dispersing the molybdenum carbide-containing solution with the rotating plate and further drying to prepare a molybdenum carbide granulated powder having a predetermined average particle size;
A method for producing a molybdenum carbide granulated powder characterized by comprising:
The method for producing granulated molybdenum carbide powder according to claim 1, wherein the molybdenum carbide powder has a carbon content of 11.0 to 11.3 mass% in molybdenum carbide.
3. The sieving step of passing the granulated powder after completion of the spray dryer step through a sieve having a mesh size 2 to 3 times the average particle size B is performed. A method for producing molybdenum carbide granulated powder.
The method for producing a molybdenum carbide granulated powder according to any one of claims 1 to 3, wherein the molybdenum carbide granulated powder has an average particle diameter B of 20 to 150 µm.
The method for producing a molybdenum carbide granulated powder according to any one of claims 1 and 4, wherein the rotational speed A of the rotating plate of the spray dryer is 5000 to 16000 rpm.
The method for producing a molybdenum carbide granulated powder according to any one of claims 1 to 5, wherein the organic solvent is ethanol.
The binder according to any one of claims 1 to 6, wherein when the total amount of the molybdenum carbide powder charged into the container is 100 parts by volume, the volume of the binder is 3 to 20 parts by volume. A method for producing molybdenum carbide granulated powder.
The method for producing a molybdenum carbide granulated powder according to any one of claims 1 to 7, wherein an apparent density of the obtained molybdenum carbide granulated powder is 1.3 to 3.0 g / cc. .
9. The molybdenum carbide-containing solution according to claim 1, wherein the amount of the organic solvent is 0.2 to 1 liter when the molybdenum carbide powder amount is 100 parts by mass. Method for producing molybdenum carbide granulated powder.
The method for producing a granulated molybdenum carbide powder according to any one of claims 1 to 9, wherein the spray dryer dries the granulated powder while supplying hot air of 100 to 300 ° C. .
The method for producing a molybdenum carbide granulated powder according to any one of claims 1 to 10, wherein the spray dryer dries the granulated powder in a reduced-pressure atmosphere of atmospheric pressure or less.
The method for producing a molybdenum carbide granulated powder according to any one of claims 1 to 11, wherein the obtained granulated powder has a fluidity of 50 sec / 50 g or less.
Molybdenum carbide granulated powder characterized by an apparent density of 1.3 to 3.0 g / cc.
The molybdenum carbide granulated powder according to claim 13, wherein the molybdenum carbide granulated powder has an average particle diameter of 20 to 150 µm.
15. The molybdenum carbide granulation according to claim 13, wherein the volume of the binder is 3 to 20 parts by volume when the total amount of the molybdenum carbide powder is 100 parts by volume. powder.
The molybdenum granulated powder according to any one of claims 13 to 15, wherein the flowability of the molybdenum carbide powder is 50 sec / 50 g or less.