JPS61106405A - Preparation of titanium carbonitride powder - Google Patents

Abstract

PURPOSE:To prepare titanium carbonitride having desired compsn. and uniform fine particle size by heating a mixture of titanium oxide powder and carbon powder in a specified proportion in N2 stream under specified conditions to perform reduction and carbonitridation. CONSTITUTION:Necessary amt. of carbon powder required from reducing TiO2 powder to titanium carbonitride of a desired compsn. is added to TiO2 powder. After mixing thoroughly the mixture, the mixture is heated at 1,600-2,000K (1,327-1,727 deg.C) while flowing N2 with partial N2 pressure PN2 satisfying the equation wherein PN2 is partial pressure (atm) of N2, and x is C/(C+N) in TiCN, and 1,600K<=T<=2,000K, to perform reduction and carbonitridation. By this method TiCN having a uniform fine particle size with a compsn. deviated only slightly from a desired compsn. is obtd.

Description

Detailed Description of the Invention Technical Field The present invention is aimed at producing titanium carbonitride with uniform grains and fine grains that have little deviation from the desired composition when producing titanium carbonitride, which is a raw material for cutting tools such as cemented carbide and cermet. Relating to a method of manufacturing.

Prior art and its problems Methods for producing titanium carbonitride can be roughly divided into the following three methods. A method of heat-treating a mixture of titanium carbide powder and titanium nitride powder at high temperatures (referred to as method A), a method of heat-treating a mixture of titanium metal powder and carbon powder under a nitrogen atmosphere (referred to as method B), and titanium oxide powder A method of heat-treating a mixture of carbon powder and carbon powder in a nitrogen atmosphere (
(referred to as method C).

First, method A has the advantage that it is easy to control the ratio of carbon to nitrogen in titanium carbonitride, but it requires a method that allows sufficient solid solution of titanium carbide and titanium nitride.
requires a high temperature of 2000°C or higher, and at such high temperatures, the particles become coarse and at the same time, sintering progresses between the particles and solidifies, making it difficult to grind as a post-process.
There is a problem that ζ. If an attempt is made to process at a low temperature to avoid this, it will take a long time to complete the solid solution, which is impractical.

Furthermore, using titanium carbide or titanium nitride that has been carbonized and nitrided as a raw material is wasteful in terms of energy, resulting in an increase in cost.

Next, regarding method B, when trying to obtain fine powder,
Fine particles of titanium metal powder as a starting material must be used, which has a problem of increasing the amount of oxygen remaining in the powder due to the increased surface area.

In addition, metal titanium powder generally has a square shape,
The resulting powder also retains this shape and requires pulverization before use.

Finally, method C can use fine particles of 1 μm or less for both titanium oxide and carbon powders as starting materials, and the resulting powder not only has similar fineness, but also saves energy and costs. There is an advantage. Despite this, the reason why this method has not been put to practical use is because it uses oxides as starting materials, oxygen tends to remain in the resulting powder, and the added carbon powder does not completely dissolve in solid solution, leaving it as free carbon. There is a big reason why they remain. A method to solve this problem has also been proposed (Japanese Patent Application Laid-Open No. 58-213617).
The process is heated to 1,700 to 2,000° C. to remove residual oxygen, so grain growth is unavoidable to some extent, and carbonitrides with a high nitrogen content cannot be produced in principle (described later).

Another problem is that it is difficult to control the ratio of carbon and nitrogen in the carbonitrides produced.

Means for Solving the Problems In order to solve the above problems and obtain titanium carbonitride with uniform grains and fine particles with little deviation from the desired composition, it is necessary to control not only the temperature but also the nitrogen partial pressure. I thought it might be necessary.

When producing titanium carbonitride, titanium carbide is stable at high temperatures, but titanium nitride decomposes into metallic titanium and nitrogen at high temperatures, so nitrogen separates during heat treatment during production, resulting in a change in the desired carbon to nitrogen ratio. It tends to shift, and the powder tends to have a low ratio (binary value) of nonmetallic elements to titanium.

The pressure at which this decomposition occurs (equilibrium nitrogen partial pressure) can be uniquely determined by determining the composition and temperature of the carbonitride.

FIG. 1 is a diagram showing the equilibrium nitrogen partial pressure for each composition of titanium carbonitride using temperature as a parameter, and also shows the application area of the present invention.

For example, in the case of a composition of TiC:TiN=1:1,
At a temperature of 2000 K, it is stable at a pressure of 8 atm or higher, and decomposition progresses below that.

That is, in order to make a powder of TiC:TiN=1:1 at 2,000 yen, it is necessary to apply a nitrogen partial pressure of at least Batm.

Based on this fact, the present inventors mixed titanium oxide powder and carbon powder at a predetermined ratio and controlled the temperature and nitrogen partial pressure to achieve a desired ratio of carbon and nitrogen.
It has been found that titanium carbonitride powder having a quality of 2 close to 1 can be obtained.

The present invention has been made based on the above findings, and in producing titanium carbonitride powder, titanium oxide powder and the amount necessary to reduce the titanium oxide and carbonize it to titanium carbonitride with a desired composition. After adding carbon powder and mixing thoroughly logP at a temperature of 1600 to -2000°
N2 =-4x-1j5X104・1/r +(10~
11) By heating, reducing and carbonitriding while flowing nitrogen with a nitrogen partial pressure that satisfies the following, titanium carbide powder with uniform grains and fine particles with little deviation from the desired composition is obtained. It is.

As can be seen in FIG. 1, if the treatment is carried out at a low temperature, a powder with a high nitrogen content can be obtained with the same nitrogen partial pressure. However, this is a consequence of equilibrium theory; when considering industrial production, it is also necessary to consider reaction kinetics. According to experiments conducted by the present inventors, it has been found that at temperatures below 1600 ℃, it takes more than 100 hours to complete the reaction, which is not practical.

On the other hand, when the molecular weight exceeds 2000, the reaction rate increases, but it is not particularly advantageous, and on the contrary, there is a problem that sintering and coarsening of the powder occur, which complicates the post-treatment process.

Moreover, from the viewpoint of energy saving, a high temperature of 2000 or higher is disadvantageous.

From these points, the temperature range was set at 1600-2000. Next, regarding the nitrogen partial pressure, once the composition and temperature are determined, the equilibrium nitrogen partial pressure is determined. However, this is often calculated using thermodynamic data, and there are few examples of measuring the true partial pressure. Figure 1 was also obtained through calculation.

Therefore, in implementing the present invention, it is not necessarily appropriate to strictly apply the determined equilibrium nitrogen partial pressure, and reduction and carbonitriding may be carried out under a nitrogen partial pressure within a certain allowable range. Appropriate.

For this reason, it is necessary to have a certain range of nitrogen partial pressure settings, and FIG. 1 shows, as an example, the range of nitrogen partial pressures in the case of 2,000 degrees.

If it is higher than this nitrogen partial pressure, nitriding progresses and the composition deviates from the desired composition, and free carbon tends to come out. If it is lower than this nitrogen partial pressure, nitriding does not progress sufficiently and oxygen tends to remain, which is undesirable. .

Examples will be explained below.

For production, titanium oxide powder 76.096, carbon powder 2
After dry mixing to a ratio of 4.096 mm, the powder was
, 5 inm s, cylindrical shape with a length lO~15+u, and carbonitrided at a temperature of 16.00 to -1700 for 1 hour. At that time, the nitrogen partial pressure is changed to Ti(C(BN
Production was carried out using both the method according to the present invention in which N2 is flowed while maintaining the equilibrium nitrogen partial pressure ((1,6)) ζ and the conventional method in which the equilibrium nitrogen partial pressure tζ is maintained at 1 atm. The analytical results, particle size and calculated composition of the powder produced are shown in Table 1.

Table 1 Example 2 To produce titanium carbonitride with a molar ratio of TiC and TiN of 3, titanium oxide powder was 74.3%; carbon powder was 25.7%.
After dry mixing at a ratio of 1,700 to 1,900 %, the powder was granulated into a cylinder with a diameter of 10 to 15 + u and a length of 1,700 to 1,900 yen.
Carbonitriding was carried out for 1 hour at a temperature of . At this time, both the method according to the present invention in which N2 is flowed while maintaining the nitrogen partial pressure at the equilibrium nitrogen partial pressure t of Ti (C0,3NO,7) at the relevant temperature, and the conventional method in which N2 is flowed at 1 atm. Manufactured. The analytical results and particle size of the powder produced and the calculated composition are shown in Table 2.

Table 2 Example 3 In order to produce titanium carbonitride with a molar ratio of TiC and TiN of 5:5, titanium oxide powder 72. '1% carbon powder 2
After dry mixing at a ratio of 7.396%, this powder was granulated into a cylindrical shape with a diameter of 1.5 liters and a length of 10 to 15 mm.
800-200. Carbonitriding was carried out at a temperature of OK for 1 hour. At that time, the nitrogen partial pressure is changed to Ti (CG, 5N0
．． Table 3 Example 4 Acid f titanium powder 70.5) for producing titanium carbonitride with a molar ratio of TiC and TiN of 8:2. 49/;, carbon powder 2
After dry mixing to a ratio of 9.696, the powder was
．． 5 yix and cylindrical shape with a length of 10 to 151 m, and carbonitrided at a temperature of 1800 to 2000 K for 1 hour.

At that time, the nitrogen partial pressure is changed to Ti (CG, 8N0.2
Production was carried out using both the method according to the present invention in which N2 is flowed while maintaining the equilibrium nitrogen partial pressure of 1 atm, and the conventional method in which N2 is flowed at 1 atm. Table 4 shows the analysis results and particle sizes of the powders produced, as well as the calculated compositions.

Table 4 Effects of the Invention As described above, titanium carbonitride having a desired composition and having a uniform grain size can be obtained by the method of the present invention.

[Brief explanation of the drawing]

Figure 1 shows the equilibrium nitrogen partial pressure for each titanium carbonitride composition.
FIG. 3 is a diagram showing temperature as a parameter.

Claims (1)

[Claims] 1) Add titanium oxide powder and carbon powder in an amount necessary to reduce the titanium oxide powder and carbonize it to titanium carbonitride of the desired composition, mix thoroughly, and then heat to 1600 ml.
At a temperature of ~2000K (1327℃~1727℃) logP_N_2=-4x-1.6×10^4・1/T
+(10~11) (1600≦T≦2000) [P_N_2: Nitrogen partial pressure ^(^a^t^m^)x: Ti
A method for producing titanium carbonitride powder, which comprises heating while flowing nitrogen at a nitrogen partial pressure that satisfies the following: C/C+N in CN, T: temperature (K)] to perform reduction and carbonitriding.