JPS6135129B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing carbide raw material powder used as the hard phase of cemented carbides and cermets. Common methods for producing carbides include solid-phase reaction between metal powder and carbon, solid-phase and gas-phase reaction between metal powder and carbon, menstrum process, and reaction between halides and hydrocarbons. However, in these conventional methods, for example, in the above method, mechanical pulverization is performed because the reaction is carried out at high temperatures, but it is difficult to do so without contaminating harmful impurities to a particle size of 1 μm or less, and the particle size of the synthetic powder is limited to solid carbon. There are some difficulties, such as the fact that it depends on the size of carbon and the unavoidable contamination of impurities from solid carbon. but,
WC, the main raw material for cemented carbide, is most commonly produced using this method. This is because the particle size of WC synthetic powder is easy to adjust and the bonded carbon content is high. This method is used in some cases, for example, when WC powder is synthesized by the reaction of W metal powder and CH ₄ gas, but in addition to the slow carbonization rate, the particle size of the synthesized particles is The disadvantage was that the Since the method requires a high temperature reaction, the resulting particles are coarse single crystals of around 100 μm, making it difficult to obtain fine powder. In addition, the method yields fine, highly pure powder of several hundred angstroms. However, as a raw material for practical cemented carbide, a particle size of about 0.1 to 10 μm is preferable, and a powder of several hundred angstroms has little industrial merit. An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques, provide a new manufacturing method that is excellent in mass productivity, and obtains stable fine particles of 1.0 μm or less. In order to achieve the above object, the present invention first melts WO ₃ , adds V therein and disperses it uniformly, and then rapidly cools it, and simultaneously reduces and treats the rapidly cooled oxide in a carbonizing atmosphere. This is a novel method for obtaining fine, stable carbide powder. In the present invention, when WC is synthesized from quenched oxide, it is preferable to use H ₂ as the reducing gas, and CH ₄ is preferable as the carbonizing gas. Moreover, if the mixing ratio of H ₂ and CH ₄ is in the range of 1/10 to 100/1, a sufficiently preferable synthetic powder can be obtained.
When H ₂ /CH ₄ <1/10, sufficient reduction reaction does not proceed,
On the other hand, when H ₂ /CH ₄ >100/1, the carbonization rate becomes slow, which is industrially unfavorable. Further, in the present invention, when turning into plasma, it is necessary to reduce the pressure to 0.1 to 20 Torr.
This is because it is difficult to generate plasma outside this pressure range. When WO ₃ contains V oxide, compound, or metal powder, the synthesis temperature is at least
It is desirable to set the temperature to 1100℃ or higher. Since the method according to the present invention is entirely based on a solid phase-gas phase reaction, it has the advantage that very high purity can be obtained in the synthesis of WC. Further, when the mixed gas for reduction and carbonization is contributed to the reaction in a plasma state, the carbonization reaction is greatly accelerated compared to the conventional method. Therefore, it has the advantage that it is easy to increase the carbon bonding rate of the synthetic powder, and as a result, it is possible to produce a powder that is homogeneous and has a fine particle size. In addition, when a molten oxide containing V in WO ₃ is cooled at a cooling rate of 10 ⁴ °C/sec or higher and a carbide is synthesized from the obtained quenched solid solution oxide by the method described above, commercially available WO ₃ This method has the advantage that the reaction with the gas phase is extremely active compared to the case where powder is carbonized. This is probably because a large amount of strain energy stored by rapid cooling contributes to the reaction with the gas phase. In any case, by using quenched oxide, it is possible to achieve an average particle size of 0.3 μm, which was previously considered difficult.
It becomes possible to easily manufacture a WC of about 100%. Furthermore, in the present invention, when the reaction atmosphere is turned into plasma, the reaction becomes more active, and particles with an average particle size of about 0.1 μm can be produced. In the present invention, the cooling rate of the molten oxide is set to 10 ⁴
If the speed is slower than °C/sec, the strain energy stored is small and the above-mentioned effect is less. In the case of the present invention, which produces carbide powder containing WC as a solid solution, the use of the melting-quenching method not only provides the above-mentioned quenching effect, but also has the additional effect of uniformly mixing the elements by melting. Example 1 WO ₃ and 0.3 in a quartz tube with a nozzle-shaped tip
Powder mixed with ₅ % _V2O by weight is added and this is
After being placed in a furnace heated to 1510°C and held there for 5 minutes, it was rapidly moved downward to the outside of the furnace, and at the same time, 2.5Kg/cm ² of Ar gas was introduced into the quartz tube to transfer the molten WO ₃ to the tip of the quartz tube. It erupted. 2mm directly below the tip of the quartz tube is an external shape that rotates at a circumferential speed of 30m/sec.
The top of a 300 mm copper rotary cooling body was placed, and the jetted WO ₃ was quenched by colliding with this rotary body to obtain a flaky quenched oxide. Next, this flaky quenched oxide was heated to 1100°C and heated to H ₂ /CH ₄ =1/
1 was placed in a mixed gas atmosphere, maintained for 1 hour, cooled, and the synthesized powder was taken out. This synthetic powder has been shown to have a crystal structure by X-ray analysis and by SEM (Scanning Electron
It was confirmed with a microscope that the average particle size was 0.3 μm. Furthermore, ICP (Inductively Coupled Plasma)
Commercially available trace analysis using spectrophotometer
I compared it with WC. In addition, in both cases, V is approximately
It contains 0.3%. Table 1 shows some of the measured values.

[Table] From the table, it can be seen that the V-containing WC synthesized by the gas phase reaction according to the method of the present invention has extremely high purity. In particular, S, which has a great negative effect when used as a raw material for cemented carbide, can be replaced with V-containing WC by the method of the present invention.
It has the remarkable advantage of having an extremely low content. Example 2 A quenched flaky oxide was prepared by mixing WO ₃ with 0.2% by weight of V ₂ O ₅ in the same manner as in Example 1. The flaky quenched oxide was reduced and carbonized in the same atmosphere as in Example 1. however,
The holding temperature was 1300°C. The obtained synthetic powder is
X-ray analysis and
Confirmed with ICP. Moreover, it was confirmed by SEM observation that the average particle size was 0.2 μm. Example 3 A quenched flaky oxide was prepared in the same manner as in Example 2. We attempted to reduce and carbonize this flaky quenched oxide using a mixed gas of H ₂ and CH ₄ that was turned into plasma using high frequency under low pressure of less than 5 Torr and microwave under reduced pressure of 5 Torr or more and less than 20 Torr. Experimental conditions and results are shown in Table 2.

【table】

[Table] In this way, the present invention involves adding V metal, V oxide, or other V compound to molten WO ₃ and then quenching the molten WO 3 and reducing and carbonizing the quenched oxide in a mixed gas of H ₂ and CH ₄ . This method has great industrial effects because it is possible to obtain fine WC powder with few impurities and extremely stable against grain growth.

Claims (1)

[Claims] 1. A molten oxide containing V in WO ₃ is injected into a cooling body and quenched at a cooling rate of 10 ⁴ °C/sec or more, and then the quenched solid solution oxide is mixed with H ₂ and CH ₄ The mixing ratio of
A method for producing solid solution carbide powder of tungsten and vanadium, the method comprising heating to 1100°C or higher under a mixed gas of 10 to 100/1. 2 A molten oxide containing V in WO ₃ is injected into a cooling body to form a cooled solid solution oxide with a mixing ratio of H ₂ and CH ₄ .
A solid solution carbide powder of tungsten and vanadium is heated to 1100℃ or more in a reduced pressure atmosphere of 0.1 to 20 Torr, which is made into plasma by applying external electric energy to a 1/10 to 100/1 mixed gas. Production method.