JPH0233647B2 - FUKUGOTANCHITSUKABUTSUKOYOTAIFUNMATSUNOSEIZOHO - Google Patents

Description

[Detailed description of the invention]

This invention is a titanium-based composite made of group 4a, 5a, and 6a elements, which has a low oxygen content and free carbon content, and a high nitrogen content and bonded carbon content, and is highly pure and has uniform grains. This invention relates to a method for producing carbonitrided complete solid solution powder. In recent years, in order to provide powder for powder metallurgy, abrasive materials, and other uses, titanium-based materials, as well as group 4a, 5a, and 6a elements, have been developed as hard powder members.
That is, the demand for a composite carbonitrided complete solid solution powder consisting of one or more elements selected from Zr, Hf, V, Nb, Ta, Cr, Mo, and W is increasing. Traditionally titanium-based 4a, 5a and 6a
The method for producing a composite carbonitride solid solution powder consisting of group elements is as follows: After blending titanium and single carbide powders and nitride powders of group 4a, 5a, and 6a elements to the desired composition, the mixture is heated at high temperature. A method of solid solution treatment by heating, or a method of solid solution treatment using composite carbide or nitride has been adopted. However, in such conventional methods,
As mentioned above, since carbide powder and nitride powder are used as raw materials, it is necessary to perform solid solution treatment at least once. Even when the powder is sufficiently mixed, heating to a high temperature (preferably 2000°C or higher) is required to promote solid solution formation, and in particular, if the particle size of the powder is coarse, heating to a higher temperature is required. Naturally, such high-temperature heating causes the problem that even if solid solution formation is completed, the powder particles grow, and the particles become coarse due to the progress of sintering between the particles. In addition, without going through the intermediate process of manufacturing carbides and nitrides of titanium and other elements,
Until now, there have been few notable reports on methods for directly producing composite carbonitride solid solution powders based on titanium and composed of group 4a, 5a, and 6a elements, much less using oxides as raw materials for titanium and other elements. At present, no interesting reports have yet been found regarding the method for producing composite carbonitride solid solution powder using . By the way, although it is different from the production of the composite carbonitride solid solution powder described above, titanium oxide is used as a raw material, carbon is added as a reducing agent and carbonizing agent, and carbonization is performed by heating it in a non-oxidizing atmosphere. Methods for producing titanium powder are already known;
On the other hand, it has been reported that titanium nitride powder can be produced by adding carbon as a reducing agent to titanium oxide and heating it in a nitrogen-containing atmosphere. Attempts have been made to produce titanium carbonitride solid solution powder by adding a carbonizing agent or a carbonizing agent and heating the mixture in a nitrogen-containing atmosphere. However, in the method of producing titanium carbide powder or titanium nitride powder from titanium oxide as described above, oxygen tends to dissolve into titanium carbide or titanium nitride, resulting in high oxygen content and residual free carbon content. Therefore, there is a problem in that it is extremely difficult to produce titanium carbide powder with a high amount of bonded carbon or titanium nitride powder with a high content of nitrogen. The conditions have to be complicated and strict, and as a result, not only is the process unsuitable for industrial production in terms of equipment and economy, but also another problem arises in that it is impossible to obtain a desirable fine powder. However, based on this, one or more of titanium oxides and metal powders of group 4a, 5a, and 6a elements, and one or more oxides of the above elements other than the metal powders are required. The same applies when attempting to directly produce a composite carbonitride solid solution powder by adding a reducing agent or a carbonizing agent to a mixture mixed according to the conditions and heating the mixture in a nitrogen-containing atmosphere. For these reasons, it is difficult to produce with high productivity a composite carbonitride solid solution powder with a low content of oxygen and residual free carbon, and a high content of nitrogen and bonded carbon, and which has uniform and fine grains. When producing titanium-based composite carbonitride solid solution powder containing group 4a, 5a and 6a elements, using oxides as all raw materials is more difficult as complex reactions proceed in parallel at once. It was accompanied by many difficulties. From the above-mentioned viewpoint, the inventors of the present invention have developed a method of producing high-gun strength, fine, uniform grains without going through complicated processing steps.
After repeated trial and error research to find a cost-effective way to produce titanium-based composite carbonitride solid solution powders containing group 4a, 5a, and 6a elements, we have discovered that their oxides can be used as a source of titanium and other elements. In addition, a metal powder is used as at least one of the other element sources, a carbon source is added as a reducing and carbonizing agent, and the material is heated in a nitrogen-containing atmosphere. By organically intertwining and managing the settings of raw material mixing conditions, heating conditions, etc., it is possible to carry out the solid solution reaction at the same time as reduction, carbonization, and nitridation, and also to achieve satisfactory purity and particle size. This led to the discovery that a composite carbonitride solid solution powder can be obtained. Therefore, this invention has been made based on the above findings, and uses anatase-type titanium oxide powder as a titanium raw material to obtain the composition of the target composite carbonitride solid solution powder, and uses group 4a (Cr,
As the raw materials for one or more elements selected from Mo, W), metal powder is used as the raw material for at least one element, and oxides are used as the raw materials for the other elements. Add an amount of amorphous carbon powder necessary to reduce the carbonitride and carbonize it to the composition of the target composite carbonitride solid solution,
After thoroughly grinding and mixing these in a wet process and drying, the resulting mixed powder is placed in a nitrogen-containing atmosphere.
Heating at a temperature of 1200-1400℃, then further
By heating to a temperature of 1,700 to 2,000℃, solid solution treatment is performed simultaneously with reduction, carbonization, and nitridation, and the amount of oxygen and residual free carbon is as low as 0.5% by weight or less, and the total amount of nitrogen and bound carbon is low. A titanium-based titanium-based material with high purity and an average grain size of 2 μm or less, essentially containing no coarse particles of 2 μm or more and having an average particle size of 2 μm or less.
The present invention is characterized in that it produces a composite carbonitride solid solution powder containing group 5a and 6a elements. In the method of this invention, as described above, anatase type titanium oxide is used and amorphous carbon powder is used as the carbon source. There are two types of commercially available titanium oxide powder: one with a rutile crystal structure and one with an anatase crystal structure. It is known that it converts to rutile form at around 800℃, even in the coexistence of a carbon source.On the other hand, as an industrial commercial product of high-purity carbon, graphite powder is There are two types of titanium oxide: anatase and amorphous carbon powder (e.g. carbon black), and it is known that amorphous carbon converts into graphite at temperatures above 1300°C when heated, but titanium oxide is anatase. type, other group 4a, 5a and 6a elements are used as oxides, metal powder is employed to supply at least one of the other elements, and carbon black is used as the carbon source. ,reduction,
The specific reason why the carbonization and nitridation reactions are promoted as well as the solid solution reaction is still not clear. In particular, anatase-type titanium oxide crystallizes into the rutile type at about 800℃, which is before the temperature at which reduction by carbon starts. Carbon black, which is amorphous carbon, also begins to convert into graphite, although it is not completely converted into crystals, at temperatures above about 1,300°C, which is the temperature at which lower titanium oxide is formed during the reduction process and above the start of carbonization. Considering this fact, it can be assumed that the reaction promotion effect is produced by creating a mechanism that promotes the solid phase diffusion reaction during heating when such specific raw materials are mixed. This seems to be due to a mechanism other than the improvement of mixing due to simple particle size reduction, such as mechanochemical phenomena, which occurred to a greater extent than in the case of other combinations of raw materials. This can be understood from the fact that the mixing conditions have a large influence, but in this invention, the reaction acceleration effect was secured with this best combination of raw materials, and the mixing conditions of these raw materials also ensured that the effect of promoting the reaction was further improved. It is considered that the above effects were enhanced and the reaction was sufficiently promoted. Furthermore, in the method of the present invention, the heating conditions also have a great influence on the quality of the product. Of course, if you use anatase-type titanium oxide and amorphous carbon powder and add at least one metal powder and the other oxide as raw materials for group 4a, 5a, and 6a elements, you can heat it to 1700-2000℃ in a nitrogen-containing atmosphere. However, reduction, carbonization and nitridation reactions are accelerated,
Although it is possible to obtain a highly pure powder with low content of oxygen and free carbon, and high content of nitrogen and bound carbon, and even grain size, the solution reaction is incomplete and a higher temperature is required to complete the solution. When heat treatment is performed, a phenomenon occurs in which the powder particle size becomes coarser. However, by dividing this heating into two stages, first performing primary heating at a temperature of 1200 to 1400°C, and then performing secondary heating at a temperature of 1700 to 2000°C, the solid solution reaction can be prevented. It can be promoted and completed. The reason why the heating temperature was limited to the above value was 1.
The temperature in the next heating is less than 1200℃, or
This is because if the value exceeds 1400°C, the desired effect of promoting the solid solution reaction cannot be obtained in any case, and in secondary heating,
The lower the temperature, the finer the average particle size of the powder, but the higher the amount of oxygen and carbon contained.
If the temperature is lower than 1700℃, the oxygen content will be more than 0.5% by weight, making it impossible to obtain the desired quality.
On the other hand, if the temperature exceeds 2000°C, it becomes difficult to suppress the average particle size of the powder to 2 μm or less. In the method of this invention, the reason why solid solution formation is promoted by adding primary heating as described above has not been fully elucidated. However, when heated rapidly in a nitrogen-containing atmosphere and maintained at 1700°C or higher, the blended anatase-type titanium oxide and other elemental oxide powders undergo reduction, carbonization, and nitridation reactions with amorphous carbon. At the same time, the solid solution reaction proceeds, but the elements added in the form of metal powder seem to promote the carbonization reaction, but make the solid solution reaction incomplete.
When primary heating is performed in the temperature range of 1200 to 1400℃, the added metal powder remains as it is or is partially carbonized depending on the type of element and exists as a carbide in the temperature range below 1200℃. It is thought that a solid-phase diffusion reaction occurs with other blended oxides or reduced lower oxides, resulting in the effect of promoting solid solution formation. In addition, the primary heating is in the temperature range of 1200 to 1400℃.
However, as long as the temperature is kept at least within this temperature range for a certain period of time, the solution reaction will not occur under any heating conditions, such as by gradually increasing the temperature within this temperature range. It is promoted. And this one
The holding time for the secondary heating depends on various factors, such as the ratio of all metal powders added as raw materials for group 4a, 5a, and 6a elements, the relationship between the total amount of reactants and the heating method, and the heating conditions before and after the primary heating temperature range. Although it varies depending on the conditions and cannot necessarily be limited,
Heating for 10 minutes or more is preferable, and in particular, heating for 1 hour or more will give satisfactory results in most cases. The reason why we set the raw material grinding and mixing conditions to the wet method as described above is because, for example, a simple dry mixing method would
Although the oxygen and carbon content of the obtained powder becomes considerably high, and the average particle size also becomes coarse, the wet process and the presence of a mixing promoting medium yield a highly pure powder. It is. The gas for the nitriding reaction in the method of the present invention, that is, the atmosphere during heating, may be any atmosphere containing nitrogen as long as it does not inhibit the reduction, nitriding, and carbonization reactions, and the solid solution reaction. For example, it can be carried out in an atmosphere sufficiently supplied with a mixed gas of nitrogen and other gases or ammonia gas. In the method of this invention, when rutile type titanium oxide is used instead of anatase type as the raw material for titanium oxide, the content of oxygen and free carbon in the resulting composite carbonitride solid solution powder are both high, at 0.5% by weight or more, and at the same time, The average particle size also becomes coarse particles of 2 μm or more, and if graphite powder is used instead of amorphous carbon powder, the effect is less than changing the titanium oxide raw material, but the amount of contained carbon and free carbon in the resulting powder decreases. exceeds 0.5% by weight in all cases, and the average particle size also tends to become coarser. In addition, in the method of the present invention, 4a other than titanium,
Even if carbide powder is used instead of the metal powder used as a raw material for at least one element among Group 5a and 6a elements, equivalent results can be obtained by adjusting the amount of amorphous carbon added. Can be done. Regarding the composition range of each component in the method of this invention, particularly large effects can be obtained when the amount of titanium contained in the target composite carbonitride solid solution powder is approximately 70% by weight or less; Of course, the desired effect can be obtained as long as it is in the complete solution range, but even with component compositions outside this range, the theoretical amount can be almost completely dissolved, and at the same time, high purity, uniform grains, and fine particles can be obtained. A powder can be obtained and therefore the composition range of each component is not limited. Next, the present invention will be explained in more detail with reference to Examples. Example In order to produce a composite carbonitride solid solution powder in which the weight ratio of Ti, TiN, and WC is 35:30:35, anatase-type titanium oxide (TiO ₂ ) powder: 854 g and metallic tungsten (W) powder: Charge 329g and 345g of carbon black powder into a ball mill,
Furthermore, a carbide ball (5 times the amount) and acetone were added, and wet mixing was performed for 24 hours. This mixture was dried under reduced pressure, then pressure molded, heated in a nitrogen gas stream, held at a temperature of 1300°C for 1 hour, and then heated to 1800°C and held for 2 hours. The obtained heat-treated product was pulverized, and the analysis values and particle size of the powder are shown in Table 1 as Test No. 1 along with the manufacturing conditions. Table 1 also shows titanium-based
In order to produce composite carbonitride solid solution powders of various compositions containing elements of groups 4a, 5a and 6a, anatase titanium oxide and a metal powder of at least one of the elements of groups 4a, 5a and 6a are combined. , other oxide powders of the above elements, and carbon black powder were blended in a ratio corresponding to the component composition ratio of the target composite carbonitride solid solution powder, and treated in the same manner as Test No. 1. The analytical values and particle size of the powder obtained are also shown. However, the heating temperature was 1200 to 1400°C for primary heating and 1700 to 2000°C for secondary heating. moreover,
For test numbers 1 to 8, the obtained powders were subjected to X-ray diffraction, and it was confirmed that solid solution formation had been completed by basically showing only diffraction lines corresponding to titanium carbonitride, and this fact was also confirmed. displayed. In addition, the abbreviations in Table 1 are: T・C: total carbon content, F・C: free carbon content, C・
C: amount of bonded carbon (C・C=T・C−F・C),

[Table] shows the average particle size according to Fisher Co., Ltd.
This is the Sub-Sieve Sizer measurement value. In addition, the particle size of the composite carbonitride solid solution powder obtained in this way according to the present invention and the composite carbonitride solid solution powder obtained by solid solution treatment using solid solution powder of titanium carbide and tungsten carbide and titanium nitride powder as raw materials by the conventional method. In order to compare the grain shapes, scanning electron micrographs of each are shown in FIGS. 1 and 2. As is clear from the results shown in Table 1, anatase type titanium oxide is used as the raw material.
At least one of the elements of groups 4a, 5a and 6a is a metal powder, the other elements are an oxide powder, and carbon black is used as a carbon source, and a mixture is sufficiently pulverized and mixed by a wet method. By heating and holding at a temperature of 1200 to 1400°C in a nitrogen-containing atmosphere and then raising and holding the temperature to a temperature of 1700 to 2000°C, the content and free carbon content are as low as 0.5% by weight or less. It can be seen that a highly pure composite carbonitride solid solution powder in which the total amount of nitrogen and bound carbon is close to the theoretical value can be produced as a fine, uniform particle with an average particle size of 2.0 μm or less. Furthermore, from FIG. 1 and FIG. 2, it can be seen that the composite carbonitride solid solution powder produced by the method of the present invention has angular, large particles similar to the powder produced by the conventional method, in which various carbide powders and nitride powders are made into a solid solution by high-temperature heating. It can be seen that the particles do not have a wide particle size distribution including coarse particles, but have extremely uniform particle shapes and particle sizes. In addition, the amount of amorphous carbon added in the above example is based on the titanium nitride production reaction of the formula TiO ₂ + 2C + 1/2N ₂ →TiN + 2CO, and TiO ₂ , ZrO ₂ ,
Each oxide of HfO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , Cr ₂ O ₃ , MoO ₃ or WO ₃ or Zr, Hf, V, Nb,
From reaction systems of Ta, Cr, Mo or W metals and carbon, TiC, ZrC, HfC, VC, NbC, TaC,
Approximately 99% of the theoretical amount calculated by the reaction equation that produces Cr ₃ C, MoC or WC carbide, and a CO production system.
%, but the optimum amount to be added is determined by various factors, such as the amount of oxygen in the heating atmosphere and the rate of temperature increase at temperatures below about 1300°C. , it was not something that should be set at a constant value. As described above, according to the present invention, 4a, 5a, and 4a, 5a, and 4a, 5a, and A composite carbonitride solid solution powder containing Group 6a elements can be produced at a low cost, and its uses can be further expanded, providing industrially useful effects.

[Brief explanation of drawings]

Figure 1 shows TiC:TiN:WC according to the method of the present invention.
Fig. 2 is a scanning electron micrograph of a composite carbonitride solid solution powder with a weight ratio of 35:30:35. Figure 2 is a scanning electron micrograph of a composite carbonitride powder obtained by a conventional method.

Claims (1)

[Scope of Claims] 1 Titanium oxide powder contains a predetermined amount of one or more metal powders from the group consisting of groups 4a, 5a, and 6a of the periodic table of elements excluding Ti, or one of the above groups. After blending one or more metal powders and one or more metal oxide powders from the above group with a predetermined amount of carbon powder, wet grinding and mixing, and drying,
Composite carbonitride solid solution powder is heated in a nitrogen-containing atmosphere to a temperature of 1200 to 1400°C, and further heated to a temperature of 1700 to 2000°C to perform reduction, carbonization, nitridation, and solid solution formation. In the manufacturing method, by using anatase-type titanium oxide powder and amorphous carbon powder as the titanium oxide powder and carbon powder, respectively, the amount of oxygen content and the amount of residual free carbon can be reduced, and the amount of nitrogen content and the amount of combined oxygen can be reduced. A method for producing a composite carbonitride solid solution powder of high-purity and uniformly fine-grained Ti and one or more metals from the above group, characterized by a high content.