JPH10212165A - Composite carbide powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce composite carbide powder used for a cemented carbide hard to chip and having a long service life when it is used as a cutting edge. SOLUTION: This composite carbide powder contains tungsten carbide and metal chromium that forms a solid soln. or intermetallic compd. with a metal tungsten phase. When the metal chromium forms the carbonized product, tungsten carbide powder is remarkably finely crystallized by incorporating 0.5-2.0wt.% metal chromium to the amt. of the tungsten carbide. This composite carbide powder is obtd. as follows; tungsten oxide powder is mixed with at least one of chromium oxide powder and metal chromium powder and the resultant mixture is heated in an atmosphere of hydrogen at 700-1,100 deg.C and then the resultant solid soln. or intermetallic compd. is mixed with carbon powder and carbonized at 1,300-1,700 deg.C in an atmosphere of hydrogen or in vacuum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite carbide powder containing fine tungsten carbide particles and being a raw material of a fine-grained cemented carbide having excellent toughness and wear resistance, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, demands for drills made of cemented carbide, especially small-diameter drills have been increasing rapidly in recent years as electronic devices have become smaller and lighter. Cemented carbides used in small diameter drills are required to be used at high speeds and have high hardness, strength and toughness. In order to satisfy this requirement, a fine-grain cemented carbide is indispensable. An invention has been proposed in which fine WC powder is used as a starting material or various inhibitors are added to suppress grain growth in the sintering process. I have.

[0003] Japanese Patent Application Laid-Open No. 61-12847 (hereinafter referred to as "prior art 1") discloses a method of suppressing the grain growth of WC by adding V and Cr to a WC-Co alloy. Are disclosed.

[0004] Japanese Patent Application Laid-Open No. 4-257197 (hereinafter referred to as "prior art 2") discloses that W particles having an average particle size of 0.6 μm or less and a maximum particle size of 3.0 μm or less are dispersed.
In the base of C-base cemented carbide, the maximum grain size is 3.0 μm.
Carbide or carbonitride particles of one of V, Cr, Ta, Nb and Ti, or V, Cr, T
A WC-based cemented carbide having a structure in which solid solution particles of two or more of a, Nb, and Ti are dispersed.

Japanese Patent Application Laid-Open No. 61-76664 (hereinafter referred to as prior art 3) discloses that V, Cr, and T are added to a WC-Co alloy.
A method is disclosed in which the addition of a suppresses the grain growth of WC and produces a fine-grain cemented carbide.

[0006]

However, in the method of the prior art 1, since V and Cr are added at the time of forming an alloy, the dispersion is not uniform, and when a drill having a small diameter is formed, breakage is caused and the stability of the tool is reduced. There was a problem of lack of sex.

In the prior art 2, the solid solution particles of carbides or carbonitrides of V, Cr, Ta, Nb and Ti in the fine WC may function as coarse particles, thereby improving toughness, hardness and strength. There is a problem that does not work.

In the prior art 3, NaCl-type solid solution carbide is formed in the alloy to add Ta.
Since this NaCl-type solid solution carbide is coarser than WC particles, it has a problem that it acts as a defect in the alloy and lacks tool stability.

As described above, any of the inventions is a method for suppressing grain growth when sintering a cemented carbide. At present, these conventional methods cannot completely suppress grain growth in a cemented carbide. Therefore, although the above-mentioned WC-based cemented carbide has high hardness and excellent strength, when it is used as a small diameter drill, coarse particles in the cemented carbide are apt to cause chipping defects on the cutting edge, and are relatively short. The service life is reached in hours.

Accordingly, it is an object of the present invention to provide a composite carbide powder used for cemented carbide having a long service life without generating defects when used as a cutting edge, and a method for producing the same. is there.

[0011]

Means for Solving the Problems Therefore, the present inventors have proposed:
From the above viewpoints, research was conducted to provide a raw material for a fine-grained cemented carbide in order to solve the problems of the conventional WC-based cemented carbide.

As a result, if the chromium metal or carbide forms a solid solution or an intermetallic compound with the tungsten metal phase and contains 2% by weight or less of the tungsten carbide when the carbide is formed, the chromium carbide becomes
The carbides are present as inclusions at the grain boundaries of tungsten carbide, and the structure of the cemented carbide is similar to that of Co entering the grain boundaries in the WC grains during the sintering process and separating the polycrystalline WC grains. It was also found that a composite carbide formed by adding a carbide that inhibits the growth was also effective in refining and equalizing the WC grain size of the cemented carbide.

That is, chromium metal or carbide is
It has a catalytic effect of accelerating the carbonization reaction, and diffuses and dissolves in the W particles with the progress of the carbonization reaction. When WC is completely formed, the solubility is lost, and a phase considered as a composite compound is precipitated.

Due to this effect, the WC particles are refined, the precipitation phase suppresses the growth of crystal grains in the polycrystal, and the development of a composite carbide powder in which the tungsten carbide phase in the cemented carbide is remarkably finely crystallized. It was successful and led to the present invention.

That is, according to the present invention, there is provided a composite carbide powder containing tungsten carbide and chromium metal, wherein the chromium metal forms a solid solution or an intermetallic compound with a tungsten metal phase, and the chromium metal is added. By forming the tungsten carbide powder in an amount of 0.5 to 2.0% by weight with respect to the tungsten carbide during the formation of the carbide, a composite carbide powder characterized in that the tungsten carbide powder is remarkably finely crystallized can be obtained.

According to the present invention, the tungsten oxide powder is mixed with at least one of chromium oxide powder and metal chromium powder,
Obtaining a composite carbide powder by mixing a solid solution or an intermetallic compound obtained by heating in a hydrogen atmosphere of 0 ° C. or less with carbon powder and carbonizing at a temperature of 1300 ° C. to 1700 ° C. in a hydrogen and vacuum atmosphere. A method for producing a composite carbide powder characterized by the following.

Further, according to the present invention, a tungsten oxide powder, at least one powder of chromium oxide powder and metallic chromium powder, and carbon powder are mixed and mixed.
A method of producing a composite carbide powder characterized by obtaining a composite carbide powder by heating in a nitrogen atmosphere at 0 ° C. or higher and subsequently carbonizing in a hydrogen stream at 1300 to 1700 ° C.

Further, according to the present invention, tungsten powder, at least one of chromium oxide powder and metallic chromium powder, and carbon powder are mixed and mixed in a hydrogen and vacuum atmosphere at 1300 ° C. to 1700 ° C. A carbonized powder is obtained by carbonizing at a temperature of the above.

Next, the reason for limiting the present invention as described above will be described.

First, in the present invention, one that forms a solid solution or an intermetallic compound with a tungsten metal phase is used. The reason is that metals or carbides of Group IVa, Va, VIa which do not form a solid solution or an intermetallic compound with the tungsten metal phase do not exist as inclusions at the tungsten carbide grain boundaries when carbonizing the metal phase tungsten. This is because the effect of miniaturization is weakened.

In the present invention, the content of chromium metal is set to 0.5 to 0.5% with respect to tungsten carbide during carbide formation.
The reason why the content is limited to 2.0% by weight is that when the content exceeds 2% by weight, a solid solution or an intermetallic compound is formed, and the ratio of the composite carbide powder in the cemented carbide increases, and depending on the sintering conditions, Three phases precipitate. On the other hand, if it is less than 0.5% by weight, the proportion of the composite carbide powder in the cemented carbide becomes small, and the effect of atomization and uniformization cannot be obtained.

Further, in the present invention, the temperature when the tungsten oxide powder, the chromium oxide or the metal powder is heated in a hydrogen atmosphere, that is, the reduction temperature is set at 70 ° C.
The reason why the temperature is limited to 0 ° C or higher and 1100 ° C or lower is that
If the temperature is lower than 00 ° C., the progress of the reduction reaction is slow, and as a result, unreacted tungsten and chromium oxides are mixed in. On the other hand, if the temperature exceeds 1100 ° C., grain growth occurs, and fine grains are formed. This is because a uniform target powder cannot be obtained.

In the present invention, the carbonization temperature, that is, tungsten oxide powder and tungsten powder, and IVa,
Va, VIa oxide or metal powder at 1300 ° C
A solid solution or an intermetallic compound obtained by reduction in a hydrogen atmosphere at a temperature of 1300 ° C. or less is mixed with carbon powder, and the mixture is mixed with hydrogen at a temperature of 1300 ° C.
The reason why the carbonization is limited to the temperature of 00 ° C. is that if the temperature is lower than 1300 ° C., the progress of the carbonization reaction is slow, and as a result, intermetallic compounds of tungsten and chromium which are not carbonized become mixed. On the other hand, when the temperature exceeds 1700 ° C., grain growth occurs, and it is impossible to obtain a fine and uniform target powder.

[0024]

Embodiments of the present invention will be described below.

(First Embodiment) First, the first embodiment of the present invention will be described.
An embodiment will be described.

The raw material powders were blended in the composition shown in Table 1 below and mixed for 1 hour with a Henschel mixer. Next, as shown in Table 2 below, carbon powder was added to the obtained powder, mixed with a Henschel mixer for 1 hour, press-molded to a diameter of 5 mm, and then placed in a hydrogen atmosphere at a carbonization temperature shown in Table 2 below. The method of the present invention and the conventional method were processed. Thereafter, the obtained powder was pulverized and sieved, and the particle size of the powder was measured by the BET method. The measurement results at that time are shown in Table 3 below.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

It is apparent from Table 3 that the composite carbide powder of the present invention is finer than that of the conventional method under any conditions.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described.

The raw material powders were blended in the composition shown in Table 4 below and mixed for 1 hour with a Henschel mixer. Thereafter, the mixed powder was press-formed to a diameter of 5 mm, and the method of the present invention and the conventional method were processed at the carbonization temperatures shown in Table 4 below. The powder obtained above is crushed and sieved, and the particle size of the powder is
S was measured. The measurement results at that time are shown in Table 5 below.

[0033]

[Table 4]

[0034]

[Table 5]

As is evident from Table 5, the composite carbide powder of the present invention is smaller than the conventional method under any conditions.

(Third Embodiment) Next, a third embodiment of the present invention will be described.
An embodiment will be described.

The raw material powder was blended in the composition shown in Table 6 below and mixed for 1 hour with a Henschel mixer. Thereafter, the mixed powder was press-molded to a diameter of 5 mm, and the method of the present invention and the conventional method were processed at the carbonization temperatures shown in Table 6 below. The powder obtained above is crushed and sieved, and the particle size of the powder is
S was measured. The measurement results at that time are shown in Table 7 below.

[0038]

[Table 6]

[0039]

[Table 7]

As can be seen from Table 7, the composite carbide powder of the present invention is finer than that of the conventional method under any conditions.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described.
An embodiment will be described. The composite carbide powder samples 4, 24, and 37 according to the present invention prepared in the first, second, and third embodiments and the composite carbide powder samples 16, 24, and 45 according to the conventional method were used. It was used and blended in the composition shown in Table 8 below. Next, wet mixing was performed for 6 hours using an attritor. Then, the obtained powder was press-molded and sintered at 1380 ° C. for 60 minutes. Then 13
HIP treatment was performed at 50 ° C. for 60 minutes. The sintered body was processed into a two-flute end mill having a diameter of 4 mm using a diamond grindstone to obtain a WC-based end mill of the present invention and a conventional WC-based end mill. Next, cutting tests of these WC-based end mills were performed. The cutting conditions at that time are shown in Table 9 below. The flank wear width: 0.3 mm
The cutting lengths up to the service life were compared. The results are shown in Table 10 below.

[0042]

[Table 8]

[0043]

[Table 9]

[0044]

[Table 10]

As is clear from the results shown in Table 10 above, the cemented carbide using the composite carbide powder according to the present invention has superior cutting performance as compared with the cemented carbide using the composite carbide powder according to the conventional method. It can be seen that it has.

[0046]

As described above, according to the present invention, when used as a cutting edge, no fracture occurs and a composite carbide used for a cemented carbide having a long service life and a method for producing the same. Can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiko Doi 5--24-8 Higashiueno, Taito-ku, Tokyo Inside Tokyo Tungsten Co., Ltd.

Claims (4)

[Claims] 1. A composite carbide powder containing tungsten carbide and chromium metal, wherein the chromium metal forms a solid solution or an intermetallic compound with a tungsten metal phase, and the chromium metal is added when forming an additive. A composite carbide powder characterized in that tungsten carbide powder is remarkably finely crystallized by containing 0.5 to 2.0% by weight based on tungsten. 2. A solid solution or metal obtained by mixing tungsten oxide powder, at least one powder of chromium oxide powder and metallic chromium powder, and heating the mixture in a hydrogen atmosphere at 700 ° C. to 1100 ° C. Inter-compound,
1300 ° C in hydrogen and vacuum atmosphere mixed with carbon powder
A method for producing a composite carbide powder, comprising obtaining a composite carbide powder by carbonizing at a temperature of from about 1700C to about 1700C. 3. A mixture of tungsten oxide powder, at least one powder of chromium oxide powder and metallic chromium powder, and carbon powder, and heating in a nitrogen atmosphere at 1000 ° C. or higher. 1300-1700 ° C in air stream
A method for producing a composite carbide powder, comprising obtaining a composite carbide powder by carbonizing the mixture. 4. Tungsten powder, at least one of chromium oxide powder and metallic chromium powder, and carbon powder are mixed, and the mixture is mixed at 1300 ° C. in a hydrogen and vacuum atmosphere.
A method for producing a composite carbide powder, characterized in that a carbide powder is obtained by carbonizing at a temperature of 1700C.