JP2000072429A - Vanadium carbide powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a uniform and fine vanadium carbide powder of high purity having good dispersibility in an alloy in order to improve the characteristics of a ultrafine sintered carbide alloy and to provide a producing method and a producing device of the powder. SOLUTION: This vanadium carbide powder has <=1.0 μm average particle size, >=15 wt.% of bonded carbon amt. and <=0.5 wt.% oxygen content. To produce the vanadium carbide powder, a producing device of the vanadium carbide powder is used and is equipped with a rotary furnace in which reduction carbonization is carried out in a hydrogen flow. The rotary furnace 10 is equipped with a cylindrical heater 3 in the center part and a two-layer cylinder consisting of first and second graphite cylinders 1, 2 is installed so as to surround the heater. The first cylinder 1 is arranged and fixed in the outside of the second cylinder 2 and the second cylinder 2 is rotatably provided. The material to be treated is heat-treated while the material continuously flows through the second cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vanadium carbide powder used for producing a cemented carbide used in a drill for drilling an IC print substrate, a cutting blade for cutting a magnetic tape, and the like, a method for producing the same, and an apparatus for producing the same. .

[0002]

2. Description of the Related Art In recent years, cemented carbides used for drills for drilling IC printed circuit boards, cutting knives for cutting magnetic tape, and the like are required to have high hardness and high strength. The cemented carbide satisfying such requirements uses ultra-fine tungsten carbide powder as a raw material, and a small amount of vanadium carbide powder, chromium carbide powder, tantalum carbide powder or the like is mainly added to suppress grain growth during sintering. You. Of these, vanadium carbide powder is the most effective.

[0003] As a conventional method for producing vanadium carbide powder, there is the following method.

First, a raw material mixed powder of a metal vanadium powder and a carbon powder or a raw material mixed powder of a vanadium oxide powder and a carbon powder is subjected to a pusher-type continuous process in a hydrogen stream at a temperature range of 1500 ° C. or more. This is a method of performing carbonization in a furnace or a batch type vacuum furnace.

A second method is to calcine a reaction product of a halide or alkoxide of vanadium with a carbohydrate to obtain a vanadium carbide powder (Japanese Patent Publication No. 58-5092).
No. 8).

[0006]

In the first method, since a pusher type continuous furnace or a batch type furnace is used for carbonization, heat is hardly transmitted uniformly, and quality such as carbon content and oxygen content is not improved. There is a disadvantage that the dispersion is large. Further, since the treatment is performed at a high temperature for a long time, the grain growth of the vanadium carbide powder is remarkable. Therefore, there are drawbacks that it takes a long time for the pulverization, impurities such as iron are mixed, the powder is oxidized during the pulverization, and the productivity is poor.

Here, when the vanadium carbide powder, which is a grain growth inhibitor, has a large number of coarse grains, it is difficult to uniformly disperse the powder during the production of the alloy, and the grain growth suppressing effect may not be sufficiently obtained. Further, it precipitates as a third phase in the alloy, which causes a decrease in alloy strength.

[0008] The above-mentioned second method can obtain fine vanadium carbide powder having a small amount of impurities, but has the disadvantage that the yield is poor, mass production is difficult, and the amount of oxygen is large. Further, there is a disadvantage that the halide is expensive and a large amount of chemicals is consumed, which is disadvantageous in cost.

Therefore, the general technical problems of the present invention are:
An object of the present invention is to provide a uniform and fine-grained high-purity vanadium carbide powder having good dispersibility in an alloy, a method for producing the same, and an apparatus for producing the same, in order to improve the properties of ultrafine-grained cemented carbide.

Another special technical object of the present invention is to provide a vanadium carbide powder which is not only advantageous in cost but also suitable for mass production, and a method and an apparatus for producing the same. is there.

Another special technical object of the present invention is to provide a vanadium carbide powder capable of obtaining a cemented carbide having a small WC grain growth with good reproducibility, a method for producing the same, and an apparatus for producing the same. is there.

[0012]

According to the present invention, the vanadium carbide powder has an average particle size of not more than 1.0 μm, an amount of bonded carbon of not less than 15 wt%, and an oxygen content of 0.5 wt%.
A vanadium carbide powder characterized by the following is obtained.

Further, according to the present invention, there is provided a method for producing the above-mentioned vanadium carbide powder, comprising mixing a vanadium oxide powder and a carbon powder as starting materials, and mixing the raw material mixed powder with a diameter of 1.0 to 4.0 mm. After molding into a cylindrical shape with a length of 2 to 10 mm or a spherical shape with a diameter of 2.0 to 6.0 mm, and drying,
A method for producing vanadium carbide powder, characterized in that these raw material molded bodies are subjected to a reduction carbonization treatment in a hydrogen stream at 1300 ° C. to 1800 ° C.

Further, according to the present invention, in the method for producing a vanadium carbide powder, the raw material having an average particle diameter of 2.0 μm or less in the vanadium oxide powder and an average particle diameter of 1.0 μm or less in the carbon powder is used. A method for producing a vanadium carbide powder, characterized in that it is used, is obtained.

Further, according to the present invention, in any one of the above-mentioned methods for producing vanadium carbide powder, in the reduction carbonization treatment in the hydrogen stream, a cylindrical heater is installed at the center and the graphite is wrapped around the heater. Double cylinders are installed, the outer cylinder is fixed, the inner cylinder rotates, and heat treatment is performed using a rotary furnace in which the processed material flows continuously in the inner cylinder. Thus, a method for producing a vanadium carbide powder, characterized in that:

Further, according to the present invention, in the apparatus for producing vanadium carbide powder provided with a rotary furnace for performing reduction carbonization in a hydrogen stream, the rotary furnace is provided with a cylindrical heater at the center thereof, and the heater is used as the heater. A double cylinder composed of graphite first and second cylinders is installed so as to enclose the first cylinder, the first cylinder is fixedly disposed outside the second cylinder, and the second cylinder is disposed outside the second cylinder. Is provided so as to be rotatable, and has a configuration in which the heat treatment is performed while the processing object continuously flows in the second cylinder, thereby obtaining an apparatus for producing vanadium carbide powder.

Further, according to the present invention, a cemented carbide characterized by using the above-mentioned vanadium carbide powder can be obtained.

More specifically, the present invention will be described. As the raw materials, vanadium oxide powder having an average particle size of 2.0 μm or less (preferably 1.0 μm or less) and carbon powder having an average particle size of 1.0 μm or less are used. After thoroughly dry-mixing, the mixture is kneaded with various solvents, and has a diameter of 1.0 to 4.0 mm and a length of 2 to 10
It is molded into a cylindrical shape having a diameter of 2.0 mm or a spherical shape having a diameter of 2.0 to 6.0 mm, and dried.

The raw material compact was placed in a hydrogen stream at 1300-1.
In a temperature range of 800 ° C., the reduced carbonization treatment is performed while stirring the processed material using a rotary furnace capable of rapidly removing generated gas and uniformly supplying heat.

As a result, the average particle diameter was 1.0 μm or less, the carbon content was 15 wt% or more, and the oxygen content was 0.5 wt%.
A uniform and fine vanadium carbide powder characterized by the following is obtained.

When the vanadium carbide powder of the present invention is used for a cemented carbide, a cemented carbide having a large grain growth suppressing effect and a high alloy strength can be obtained with good reproducibility as compared with conventional ones.

Next, the reason why the manufacturing conditions in the present invention are limited as described above will be described.

The reason why the average particle size of the vanadium carbide powder used in the cemented carbide is set to 1.0 μm or less is that when a vanadium carbide powder exceeding 1.0 μm is added, a third phase which causes a reduction in strength is precipitated and the This is because the strength is reduced.

The vanadium carbide powder has a bound carbon content of 15 watts.
The reason why the content is set to t% or more is that it is difficult to control the amount of alloy carbon if the content is less than 15 wt%.

The oxygen content of the vanadium carbide powder is 0.5 wt.
The reason for the lower limit is that if the amount of vanadium carbide powder exceeds 0.5 wt%, pores due to the reaction gas remain in the cemented carbide and it becomes difficult to suppress the carbon content of the alloy.

The reason why the vanadium oxide powder having an average particle size of 2.0 μm or less and the carbon powder having an average particle size of 1.0 μm or less are used is to increase the contact area between the vanadium oxide powder and the carbon powder and to rapidly reduce and carbonize the fine particles. Was determined as described above to obtain vanadium carbide powder. 1.0-4.
0mm, 2-10mm long cylindrical or 2.0 ~ diameter
The molding into a spherical shape of 6.0 mm was carried out as described above in order to stir the raw material molded article and to allow the reduction carbonization reaction to proceed quickly and sufficiently. If it is larger than this, an unreacted portion is generated at the center of the raw material molded body. If the diameter is smaller than this, a problem such as clogging of the raw material in the rotary furnace occurs.

In the present invention, the rotary furnace is used for the reduction carbonization treatment because the heat is efficiently transmitted to the processed material by agitating the raw material molded body so that the solid phase (vanadium oxide particles) and the solid phase can be solidified. This is to increase the reactivity of the (carbon particles) and quickly remove the reaction product gas (CO, CO ₂ ) to quickly reduce and carbonize the raw material molded body, thereby suppressing the grain growth of the generated carbide. .

Further, in the present invention, the reduction and carbonization temperature is set to 1300 to 1800 ° C., because at a temperature lower than 1300 ° C., more than 0.5% by weight of oxygen remains, unreacted vanadium oxide remains, and the temperature decreases from 1800 ° C. At a high temperature, oxygen is sufficiently removed, but there is a disadvantage that the vanadium carbide powder causes grain growth and formed carbide becomes coarse.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a main part of a vanadium carbide producing apparatus according to an embodiment of the present invention. Referring to FIG. 1, a rotary furnace 10 includes a cylindrical heater 3 disposed at a position of a center axis, and first and second graphite heaters disposed so as to wrap around the cylindrical heater 3. Cylinder 1, 2
A gear 6 disposed at the downstream end of the second cylinder 2, a driving motor 4, and a gear 5 provided on the driving motor 4.
And an outer shell 11 made of a heat insulating material that covers the periphery thereof. The first cylinder 1 is fixed in the furnace,
The second cylinder 2 is configured to be rotated by a driving motor 4 via a gear 5 and a gear 6.

The rotary furnace 10 is configured such that the central axis thereof is lowered on the right side in the figure, and a hydrogen gas flow is introduced into the furnace. In the figure, the raw material is supplied from the upper left side, and by rotation of the second cylinder 2 and inclination of the central axis,
Move to the right side of the figure and take it out.

Next, a specific method for producing vanadium carbide according to the embodiment of the present invention will be described.

(First Embodiment) Average particle size 2.0 μm
Was mixed with a carbon powder having an average particle size of 1.0 μm so as to have a predetermined amount of bound carbon, and mixed with a high-speed rotary mixer to prepare a raw material mixed powder. Various solvents for facilitating molding are added to the raw material mixed powder, molded into a column having a diameter of 1.0 mm and a length of 2 mm, and dried.
A raw material molded body was produced. This raw material molded body was reacted at 1300 ° C. in a hydrogen stream using the rotary furnace 10 shown in FIG.
At this time, the rotary furnace 10 has an inner diameter of 85 mm and a length of 2400 m.
m inside a graphite cylinder, outer diameter 40mm, length 2620mm
The graphite cylinder heater 3 was installed, and the graphite cylinder was rotated at 1 rpm and used at an angle of about 6 degrees with respect to the horizontal. In the rotary furnace 10, hydrogen flowed 1.8 m ³ / h, and the graphite cylinder was maintained at 1300 ° C. by energizing and heating the graphite column heater 3. In this state, a raw material molded body was charged from the upper part of the rotary furnace 10 at a rate of 6 kg / h. The residence time of this raw material molded article in the furnace was about 30 minutes. The production conditions and analytical values of the product of the present invention thus obtained are shown in Table 1 of the present invention powder sample number 1.

The analytical values of the powder obtained by treating the above-mentioned raw material molded body in a rotary furnace at 1800 ° C. in a hydrogen stream of 1.8 m ³ / h are shown in Table 1 of the present invention powder sample number 2. The above used raw material mixed powder was prepared into a cylindrical shape having a diameter of 1.0 mm and a length of 10 mm, a cylindrical shape having a diameter of 4.0 mm and a length of 2 mm, a cylindrical shape having a diameter of 4.0 mm and a length of 10 mm, and a spherical shape and a diameter of 2.0 mm. The analytical values of the powders molded into spherical shapes of 6.0 mm and processed in a rotary furnace at 1300 ° C. and 1800 ° C. in a hydrogen gas flow of 1.8 m 3 / h are shown in Table 1 as powder samples Nos. 3, 4, 5, and 6 of the present invention. ,
7, 8, 9, 10, 11, and 12 are shown.

Vanadium oxide powder having an average particle size of 2.0 μm and carbon powder having an average particle size of 0.5 μm. Average particle size 1.0 μm
Vanadium oxide powder and carbon powder having an average particle size of 1.0 μm and vanadium oxide powder having an average particle size of 1.0 μm and carbon powder having an average particle size of 0.5 μm are each formed into a columnar shape having a diameter of 1.0 mm and a length of 2 mm. The analysis of the powders processed in a rotary furnace at 1300 ° C. in a hydrogen stream of 1.8 m ³ / h is shown in Table 1 as powder samples 13, 14 and 15 of the present invention.

A comparative example of the production conditions of the product of the present invention is shown below.

The raw material compact used for the powder sample No. 1 of the present invention shown in Table 1 was treated in a hydrogen stream at 1.8 m ³ / h in a rotary furnace at 1200 ° C. and 1900 ° C. Analytical plants of these powders are shown in Table 1 as comparative powder sample numbers 1 and 2.

Further, the raw material mixed powder used for the powder sample No. 1 of the present invention in Table 1 was prepared as a column having a diameter of 1.0 mm and a length of 1 mm, a column having a diameter of 1.0 mm and a column having a length of 15 mm and a diameter of 0.1 mm.
5mm, 2mm long column, 8.0mm diameter, 2 length
mm column, 1.0 mm diameter sphere and 8.0 mm diameter
mm, and each was processed in a rotary furnace at 1300 ° C. in a hydrogen stream of 1.8 m ³ / h. The division values of these powders were compared with the comparative powder sample numbers 3, 4, 5, 6, 7 and 8 in Table 1.
Shown in

In addition, a vanadium oxide powder having an average particle size of 2.0 μm, a carbon powder having an average particle size of 2.0 μm, a vanadium oxide powder having an average particle size of 3.0 μm, and an average particle size of 1.0 μm
m of carbon powder were each formed into a columnar shape having a diameter of 1.0 mm and a length of 2 mm, and processed in a rotary furnace at 1300 ° C. in a hydrogen stream of 1.8 m ³ / h. The analytical values of the powder are shown in Comparative Powder Sample Nos. 9 and 10 in Table 1. A comparative example according to the conventional method is shown below.

The raw material compact used for the powder sample No. 1 of the present invention shown in Table 1 was subjected to a conventional pusher type continuous furnace to obtain 1
Treated at 300 ° C and 1800 ° C. 300 m ³ / h of hydrogen gas was flowed into the furnace, and the length of the raw material molded body was 300 mm.
mm graphite ports were inserted into the furnace at 60 minute intervals. The analysis values of the powder thus obtained are shown in Table 1 as comparative powder sample numbers 11 and 12.

[0041]

[Table 1]

(Second Embodiment) Next, among the vanadium carbide powders obtained in the first embodiment, the cemented carbide using powder sample numbers 1 and 2 of the present invention and comparative powder sample numbers 1 and 2 was used. An example of an alloy will be described.

As raw material powders, ultrafine tungsten carbide powder having an average particle diameter of 0.2 μm, cobalt powder having an average particle diameter of 1.2 μm, and the above-mentioned vanadium carbide powder were prepared.

Using these raw material powders, 89.5 wt% of tungsten carbide powder and 0.5% of vanadium carbide powder were used.
wt% and cobalt powder at a ratio of 10.0 wt%, and wet-mixed in alcohol for 8 hours. After mixing
It was dried under reduced pressure and press-molded at a pressure of 1000 kg / cm ² . Thereafter, vacuum sintering was performed at 1380 ° C. for 1 hour. Subsequently, at 1350 ° C. for 1 hour in an argon atmosphere, 100
HIP processing of 0 kg / cm ² was performed. These sintered bodies were JI of 4 mm x 8 mm x 25 mm using a diamond grindstone.
Made in S piece, Rockwell hardness (HRA), flexural strength,
The coercive force was measured. The results are shown in Table 2.

[0045]

[Table 2]

As is clear from Table 2 above, the alloy using the vanadium carbide powder of the present invention powder has higher hardness and higher strength than the alloy using the comparative powder, and the vanadium carbide powder of the present invention powder is superior. It turns out that there is.

[0047]

As described above, the vanadium carbide powder produced according to the present invention has high purity (the amount of bound carbon is 1).
5 wt% or more, oxygen content 0.5 wt% or less) and fine particles (average particle size 1.0 μm or less) and were uniform.

In the case of the cemented carbide using the vanadium carbide powder according to the present invention, a cemented carbide with small grain growth of WC particles was obtained with good reproducibility.

Further, the manufacturing method of the present invention is not only advantageous in cost, but also suitable for mass production.

According to the present invention, the average particle size is 2.0 μm.
The contact area between the vanadium oxide powder and the carbon powder is increased by using vanadium oxide powder of m or less (preferably 1.0 μm or less) and carbon powder having an average particle diameter of 1.0 μm or less as raw materials. By using a rotary furnace as the reduction carbonization treatment, the reaction gas is quickly discharged to the outside of the furnace, and the reduction and carbonization reaction is rapidly performed by efficiently and uniformly heating. As a result, the average particle size is 1.0 μm or less, the amount of bonded carbon is 15 wt% or more, and the oxygen content is 0.5 wt
% And a fine high-purity vanadium carbide powder having a uniform grain size of not more than%.

Further, according to the present invention, it is possible to provide an apparatus for producing vanadium powder which can be easily produced by using a rotary furnace.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of an apparatus for producing vanadium carbide powder according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st cylinder 2 2nd cylinder 3 Cylindrical heater 4 Motor 5, 6 Gear 10 Rotary furnace 11 Outer shell

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G046 MA06 MB02 MC04 MC06 MC07 MC08 4K017 AA04 BA07 BB13 CA07 DA06 EH01 EH18 FB03 FB06 FB09

Claims (6)

[Claims] 1. A vanadium carbide powder having an average particle size of 1.0 μm or less, a bound carbon content of 15 wt% or more, and an oxygen content of 0.5 wt% or less. 2. The method for producing a vanadium carbide powder according to claim 1, wherein the vanadium oxide powder and the carbon powder are mixed as starting materials, and the raw material mixed powder has a diameter of 1.0%.
After molding into a columnar shape having a length of 2 to 10 mm or a spherical shape having a diameter of 2.0 to 6.0 mm and drying, these raw material molded bodies are subjected to a reduction carbonization treatment in a hydrogen stream at 1300 ° C to 1800 ° C. A method for producing vanadium carbide powder. 3. The method for producing a vanadium carbide powder according to claim 2, wherein a material having an average particle diameter of 2.0 μm or less in the vanadium oxide powder and an average particle diameter of 1.0 μm or less in the carbon powder is used. A method for producing a vanadium carbide powder, comprising: 4. The method for producing a vanadium carbide powder according to claim 2, wherein in the reduction and carbonization treatment in the hydrogen stream, a cylindrical heater is provided at a central portion, and the graphite heater is wrapped around the heater. Heavy cylinders are installed, the outer cylinder is fixed, the inner cylinder rotates,
A method for producing a vanadium carbide powder, wherein a heat treatment is performed using a rotary furnace in which a processing object flows continuously in an inner cylinder. 5. A vanadium carbide powder producing apparatus provided with a rotary furnace for performing a reduction carbonization treatment in a hydrogen gas stream, wherein said rotary furnace is provided with a cylindrical heater at a central portion thereof and is made of graphite so as to surround the heater. A double cylinder consisting of a first and a second cylinder is installed, wherein the first cylinder is
The second cylinder is fixedly disposed outside the second cylinder, the second cylinder is rotatably provided, and has a configuration in which a heat treatment is performed while a processing object continuously flows in the second cylinder. An apparatus for producing vanadium carbide powder, characterized in that: 6. A cemented carbide using the vanadium carbide powder according to claim 1.