JPS59110706A - Preparation of powder - Google Patents

Abstract

PURPOSE:To prepare a fine WC-powder in which V is uniformly dispersed, by a method wherein molten WO3 is injected to be cooled at a specific speed and cooled WO3 is heated to a specific temp. under a reduced pressure atmosphere comprising a specific gaseous mixture consisting of H2, CH4 and VCl4. CONSTITUTION:In preparing a fine stock carbide powder as an ultra-hard phase, molten WO3 is injected to a cooling body to be quenched at a cooling speed of 10<4> deg.C/sec or more. Subsequently, this quenched WO3 is heated to 900 deg.C or more under a reduced pressure atmosphere comprising a gaseous mixture prepared by partially mixing VCl4 in a gaseous mixture of which the mixing ratio of H2 and CH4 is 1/10-100/1. By this method, WC in which V is mixed from the gas phase is formed and particle growth suppressing effect is developed by the uniform dispersion of V and a fine particulate powder hardly generating particle growth is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fine grain raw material carbide powder used as a hard phase in cemented carbides and cermets.

As general methods for producing carbides, the following methods are known: 1) In-phase reaction between metal powder and carbon, 2) Solid phase or gas phase reaction between metal powder and carbon, 2) Menstrum process, and 4) Reaction between halides and hydrocarbons. However, these conventional methods
For example, in method ① above, mechanical pulverization is performed to allow the reaction to occur at high humidity, but it is difficult to pulverize the material to a size of 1 micron or less without contaminating harmful impurities, and the particle size of the synthetic powder is There are difficulties in that it depends on the size of the solid carbon and that contamination with impurities from the solid carbon is unavoidable.

Method (2) is partially used, for example, when WC powder is synthesized by the reaction of W metal powder and CHa gas, but in addition to the slow carbonization rate, the particle size of the synthesized powder is determined by the size of the metal powder particles. It had the disadvantage of being Since the method (2) requires the reaction to be carried out at high temperatures, the resulting particles are coarse single crystals of around 100 μm, making it difficult to obtain fine powder. Further, in the method (2), a fine and highly pure powder of several hundred angstroms can be obtained. However, raw materials for cemented carbide with a practical microstructure include o, i-
A particle size of approximately 1,0 μm is preferable, and a powder of several hundred angstroms has a low industrial merit.

The present invention eliminates the drawbacks of the above-mentioned prior art, has excellent productivity,
Moreover, it is an object of the present invention to provide a new manufacturing method for obtaining fine particles of 1.0 μm or less.

In order to achieve the above object, the present invention is a method for obtaining fine powder by treating rapidly cooled oxide powder in a carbonizing atmosphere at the same time as reduction, and in particular, when reacting with a gas phase, V is mixed in from the gas phase. This is a novel method for synthesizing a powder that is fine and resistant to grain growth.

In the present invention, when synthesizing WC from WO2,
It is preferable to use H2 as the reducing gas, and CH4 is preferable as the carbonizing gas.

Also, the mixing ratio of H2 and CH4 is '1/10~100/
If it is within the range of 1, a sufficiently preferable synthetic powder can be obtained. When H2'/CH4''<' 1/10, sufficient reduction reaction does not proceed, and when H2/CH4>100/
On the contrary, carbonization rate becomes slow in case of No. 1, which is industrially unfavorable.

There is no particular restriction on the inclusion of VC+4 here. However, since V is mixed into the WC from the gas phase,
The discoverer has discovered that V is more uniformly dispersed than in conventional production methods, and as a result, a grain growth suppressing effect appears even in very small amounts, and this point is one of the advantages of the present invention.

In addition, the degree of g) must be 900°C or higher;
If the temperature is below ℃, the reduction will not proceed sufficiently.

Since the method according to the invention is entirely based on in-phase-gas-phase reactions, it has the advantage of obtaining very high purity.

Furthermore, when WC is synthesized by the method described above after cooling W Oa at a cooling rate of 104°C/' seconds or more, commercially available W Oa
This method has the advantage that the reaction with the gas phase is extremely active compared to the case where a powder is carbonized. This is probably because a large amount of strain energy stored during rapid cooling contributes to the reaction with the gas phase. Anyway, quenching W Oa
By using this method, it becomes possible to easily produce fine WC, which has been considered difficult in the past, and it becomes possible to produce particles with an average particle size of about 0.1 μm.

In addition, in the present invention, the cooling rate of W Oa is set to 10°C/
When the time is slower than seconds, the strain energy stored is small and the above-mentioned effect is small.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 WOa powder was put into a quartz tube with a nozzle-shaped tip,
This was placed in a furnace heated to 1480°C and held there for 5 minutes, then rapidly moved downwards to the outside of the furnace, and at the same time Ar gas of 2.5K(+/CIl+' was introduced into the quartz tube to melt the W). Oa was ejected from the tip of the quartz tube.At a distance of 2+ nm directly below the tip of the quartz tube, a circumferential velocity of 30If/See was preliminarily applied.
The uppermost part of a copper rotary cooling body with an outer diameter of 300 mm was placed at the top of the rotating body, and the jetted W Oa was collided with this rotary body to rapidly cool it, thereby obtaining flaky W Oa. Next, put this flaky quenched W Oa into a carbon container and mix H2/CH4/
It was installed in a mixed gas atmosphere of VCI a = 1/1/0.02. The pressure at this time was 100 Torr. After maintaining this state at 950° C. for 1 hour to sufficiently promote reduction and carbonization reactions, heating was terminated. The cooling bond synthetic powder was taken out.

This synthetic powder was confirmed to be WC by X-ray diffraction. In addition, as a result of C analysis, the bond CI was 6.13% by weight.
That is, S E M (S canningE
It was confirmed that the average particle size was 0.1 μm for IeCtrOn M 1crO8(iol)e ).

Furthermore, I CP (Inductively
CoupledP lasma S 11eCtrO
Microanalysis was performed using ph(itoIIlf3ter) in comparison with commercially available WC.

Table 1 shows some of the results of A's measurements.

As shown in Table 1, it can be seen that WC synthesized by gas phase reaction has extremely high purity. In particular, when used as a raw material for cemented carbide, S has a great negative effect on the WC according to the present invention.
It is a noteworthy effect that the content of ``r-'' is extremely small.

Agent Toku Kotobuki

Claims (1)

[Claims] Molten W Oa is injected into the cooling body at a cooling rate of 104°C/
After quenching for more than 10 seconds, this quenched W O3 is
Under a reduced pressure mixed gas atmosphere in which a part of VCI 4 was mixed into a mixed gas with a H4 mixing ratio of 1/10 to 100/1,
A method for producing WC powder in which V is dissolved in solid solution, the method comprising heating to 900°C or higher.