JP2668621B2 - Method for producing titanium-based composite powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a titanium-based composite powder useful as a powder metallurgy raw material.

[0002]

2. Description of the Related Art As a means for producing titanium powder, a method of collecting by-product powder when crushing titanium sponge titanium lumps obtained by reducing titanium tetrachloride with metallic magnesium, and reducing titanium tetrachloride with metallic sodium to produce titanium The refining method (hunter method) and the like are conventionally known. Among them, the former method uses the powder secondarily generated during the titanium refining process, so that the production amount is limited and also contains a large amount of impurity components such as oxygen, nitrogen, chlorine or iron. It has the drawback that only low-quality products can be obtained. Also,
Powder particle size is also 60-20 mesh (particle size 250-850μ
Since it is roughly m), it can usually only be applied to extremely limited applications such as fireworks and raw materials for welding rods. On the other hand, the latter method can obtain titanium powder at a relatively low cost, but it is used as a raw material for powder metallurgy that requires high material strength and reliability because of the large amount of sodium and chlorine components remaining in the powder. It is difficult. In addition, coarse particles of about 50 μm are mainly used.

In contrast to these methods, hydrodehydrogenation method (HD which utilizes the property that metallic titanium occludes hydrogen to embrittle it)
The method of producing titanium powder by the H method) is capable of producing ultra-low chlorine titanium powder required for high-performance powder metallurgical raw materials, and is also capable of producing fine titanium powder at a relatively low cost. Is being used on an industrial scale. The hydrodehydrogenation method basically includes a hydrogenation step of hydrogenating a titanium raw material in a hydrogen gas atmosphere, a pulverization step of pulverizing a hydrogenated titanium mass to a predetermined particle size in an inert atmosphere, It consists of each process of the dehydrogenation step of dehydrogenating the titanium nitride powder at a temperature of 500 to 800 ° C. under vacuum. However, during the heat treatment of the dehydrogenation step, a phenomenon occurs that the titanium hydride powders mutually sinter. Actually, the crushing operation for crushing the sintered titanium lump after dehydrogenation is an essential post-treatment step.

[0004] Usually, the crushing treatment of the sintered titanium lump is performed using a crushing device such as a cutter crusher, but when the sintering progresses remarkably, the crushing is performed to the same level as the titanium hydride powder. Especially with great difficulty. Although the degree of sintering can be suppressed to some extent by setting the processing temperature low, this treatment results in an increase in the processing time of dehydrogenation and, as a whole, decreases production efficiency. . For this reason, the crushing step is a factor that lowers productivity, and is a major bottleneck for obtaining homogeneous and fine titanium powder required for high-performance powder metallurgy.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present inventors have conducted various researches on methods and conditions for treating powder without causing sintering in the dehydrogenation step. As a result, if a specific powder component that prevents sintering is mixed in advance with the titanium hydride powder to be dehydrogenated, the sintering phenomenon is effectively suppressed, and by directly selecting the powder components to be mixed at the same time, It was confirmed that a titanium-based composite powder suitable as a powder metallurgy raw material for each application was obtained.

The present invention has been developed on the basis of the above findings, and has as its object to eliminate the need for crushing after the dehydrogenation step and to provide fine titanium powder which can be used directly as a raw material for various powder metallurgy. The present invention provides a method for producing a titanium-based composite powder mainly composed of

[0007]

In order to achieve the above object, a method for producing a titanium-based composite powder according to the present invention is provided. A structural feature is that the above refractory metal powders are mixed and the mixed powders are dehydrogenated.

The present invention basically utilizes a method for producing titanium powder by the hydrodehydrogenation method. Therefore, the prerequisite technology is a process consisting of a hydrogenation process of titanium raw material, a crushing process of titanium hydride lump, and a dehydrogenation process, but a specific hard-to-sinter powder is mixed with titanium hydride powder before the dehydrogenation process. There are improved components that differ from the prior art.

As the starting material, titanium sponge lump, cutting powder of titanium ingot, scrap material or rolled scrap material can be appropriately selected and applied. In the hydrogenation step, these raw materials are charged into a vacuum-replaceable hydrogenation furnace, heated to a temperature of 400 ° C. or higher, and hydrogenated while supplying hydrogen gas into the system.

[0010] The hydrogenated raw material is embrittled and can be easily made into a powder by pulverization with a hammer or the like. However, industrially, mechanically using a pulverizer such as a ball mill or a vibration mill is used. Crushed. In this pulverizing step, it is preferable to pulverize the titanium hydride powder so that the particle size is 150 μm or less.

Before the pulverized titanium hydride powder is transferred to the dehydrogenation step, ceramic powder having a difficulty in sintering,
Mix the refractory metal powder or both powders. As the hardly-sinterable ceramic powder, for example, one or more kinds of oxides, carbides, borides or nitrides of silicon, boron, aluminum, transition metals or rare earth metals are preferably used. Here, the transition metal is titanium,
Tungsten, zirconium, molybdenum, tantalum and the like can be mentioned, and rare earth metals include yttrium and lanthanum. On the other hand, 2000 for refractory metal powder
Those having a melting point of not less than ° C. and high sintering resistance are selectively used, and one or more of molybdenum, niobium, tantalum or tungsten or an alloy comprising these is preferably applied. The ceramic powder and the refractory metal powder preferably have a particle size of 150 μm or less.

The type and amount of the ceramic powder, refractory metal powder and the like to be mixed are appropriately determined in consideration of the intended use of the titanium-based composite powder to be produced. The mixing operation of the titanium hydride powder and the ceramic powder and / or the refractory metal powder is performed using a mixing apparatus such as a V-blender until the components are sufficiently dispersed and mixed.

Then, the mixed powder is filled in a container and then set in a vacuum heating type dehydrogenation furnace, and under a reduced pressure (for example, 10 ⁻³ ), which is necessary to reach a target hydrogen content in a temperature range of 500 to 800 ° C. Vacuum is applied to the Torr) for dehydrogenation. In addition, in the dehydrogenation process, it is preferable to interpose a titanium-based getter material for absorbing and removing oxygen and nitrogen gas around the container.

The mixed powder produced by the dehydrogenation process in this manner is a titanium-based composite powder containing fine titanium powder as a main component, and since sintering is suppressed, it is the same as that at the time of mixing. It is in the powder state with the particle size maintained.

[0015]

The sintering phenomenon of the titanium powder in the dehydrogenation process proceeds through a mechanism in which the titanium hydride powder to be treated through the dehydrogenation step tries to reduce the surface energy at the mutual grain contact interface. Therefore, the titanium hydride powder has a particle size of 45.
When the size is as fine as μm or less, the surface energy becomes large and the progress of sintering increases. However,
In accordance with the present invention, when titanium hydride powder is previously mixed with ceramic powder and / or refractory metal powder having a melting point of 2000 ° C. or more, which is difficult to sinter, and then subjected to dehydrogenation treatment, the titanium hydride powder has intergranular particles. These intervening hard-to-sinter powders prevent the degree of contact between titanium hydrides, and at the same time, the hard-to-sinter properties function to effectively prevent sintering of the entire mixed powder. Combined with such actions, it is suitable for the dehydrogenation process.
Even in the temperature range of 00 to 800 ° C., the sintering phenomenon is effectively suppressed and suppressed, and a titanium-based composite powder having substantially the same particle size as that at the time of mixing can be obtained.

Further, by examining the types and amounts of the ceramic powder and the refractory metal powder to be mixed in the present invention, a titanium-based composite powder having a composition suitable for the intended purpose can be produced. For example, a mixed system of titanium powder and ceramic powder can be used as it is as a powder metallurgy raw material powder of a titanium-ceramic composite material, and a step of mixing and kneading these components before use can be omitted.

[0017]

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Example 1 Pure titanium (equivalent to JIS-2, oxygen content 0.04 wt.
%) Ingot was used for cutting and charged into a stainless steel container, and then stored in a vacuum heating furnace.
The temperature was raised to 0 ° C. in a vacuum atmosphere. Then, about 1 hour after supplying hydrogen gas to the container, when it was confirmed that the inside of the container system became atmospheric pressure, the heating furnace was removed and supply of hydrogen gas was continued. After about 12 hours, hydrogen equivalent to a theoretical amount (in terms of TiH ₂ ) was absorbed. Then, the hydrogenated raw material was mechanically pulverized and sieved to obtain a titanium hydride powder having a particle diameter of 45 μm or less. Chemical composition of the obtained titanium hydride powder (% by weight)
Are TiH ₂ : 99.6, Fe: 0.02, Si: 0.0
1, Mn: 0.01, Mg: 0.001, Cl: 0.0
02 or less, N: 0.03 and O: 0.29.

60 weight% of the above titanium hydride powder has a particle size of 4
20% by weight of titanium carbide powder of 5 μm or less and particle size of 45
20% by weight of molybdenum powder having a particle size of not more than μm was blended and thoroughly mixed using a V-type blender. Then
The mixed powder was filled in a stainless container, set in a high temperature vacuum furnace, and dehydrogenated. Dehydrogenation is carried out at a temperature of 7
The conditions were such that the temperature was maintained at 40 ° C., heating was stopped when the degree of vacuum became 10 ⁻³ Torr or less after about 5 hours, and cooling was performed in vacuum.

Sintering of the dehydrogenated mixed powder was remarkably suppressed, and the same powder state as that at the time of filling was exhibited. Further, the titanium hydride powder was converted into titanium powder, and the residual hydrogen in the mixed powder was measured and found to be 0.01% by weight.

Next, the following measurements were made to investigate the degree of sintering during the dehydrogenation treatment. First, the mixed powder before the dehydrogenation treatment was press-molded at a pressure of 3 ton / cm ² to obtain a columnar molded body having a diameter of 11.3 mm and a height of 11.3 mm, and this molded body was placed in a high-purity alumina crucible. It was set and placed in a titanium container. The getter material of titanium chips was filled in the gap part and the upper part of the vessel, and the vessel was set in a high-temperature vacuum furnace, and heated to 800 ° C. while evacuating the system. The degree of vacuum is 1
After confirming that the pressure became 0 ^-3 Torr or less, the heating was stopped and the system was cooled. The shape and dimension of the molded body dehydrogenated in this manner were measured to determine the volumetric shrinkage ratio before dehydrogenation. The degree of sintering at the time of dehydrogenation is evaluated as showing that the smaller the shrinkage rate of the molded body is, the more the sintering is suppressed.
Table 1 shows the obtained measurement results.

Example 2 The same titanium hydride powder as in Example 1 was added to 80% by weight and the particle size was 45%.
20% by weight of titanium carbide powder having a particle size of not more than μm was mixed. This mixture was subjected to dehydrogenation treatment under the same conditions as in Example 1, and Ti
A titanium-based composite powder having a Ti-TiC composition containing as a main component was produced. The state of the mixture after dehydrogenation was in a state where it could be easily disintegrated although sintering was in progress, as compared with Example 1. Then, the volumetric shrinkage of the molded product was measured in the same manner as in Example 1 for the above mixture. Table 1 shows the results.
It was also attached to.

Comparative Example The titanium hydride powder of Example 1 was directly subjected to dehydrogenation treatment under the same conditions. In this case, sintering remarkably progressed in the dehydrogenation stage, and even if the crushing treatment was performed, the particle size distribution was not the same as that of the titanium hydride powder, and generation of coarse particles was inevitable. Then, the shrinkage of the compact was measured for the titanium hydride powder in the same manner as in Example 1, and the results are shown in Table 1.

[0024]

[Table 1]

From the results shown in Table 1, the volume shrinkage ratio is clearly reduced in Example 1 by mixing the titanium carbide powder and the molybdenum powder, and in Example 2 by mixing the titanium carbide powder, as compared with the comparative example. . Therefore, it was confirmed that sintering was effectively relaxed and suppressed.

[0026]

As described above, according to the present invention, in the process of producing titanium powder by the hydrodehydrogenation method, the ceramic powder having a low sintering property and / or the melting point of the titanium hydride powder before the dehydrogenation is 2,000. By mixing a refractory metal powder at a temperature of at least ℃, it is possible to effectively reduce and suppress the powder sintering phenomenon during the dehydrogenation treatment. Therefore,
Since the disintegration process after the dehydrogenation step required in the prior art can be remarkably simplified, the productivity and the production cost are reduced, and the product yield is also improved. further,
By examining the type and amount of the ceramic powder and / or refractory metal powder to be mixed, the resulting titanium-based composite powder can be used as it is as a powder metallurgy raw material powder for each application, and therefore excellent usefulness can be expected. .

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Nishi Nishi 64, Nishimukaishima-cho, Amagasaki City, Hyogo Prefecture Kubota Amagasaki Plant Co., Ltd. 56) References JP-A-3-122205 (JP, A) JP-A-56-13401 (JP, A) JP-A-59-190303 (JP, A)

Claims (3)

(57) [Claims] 1. A titanium-based material, characterized in that titanium hydride powder is mixed with ceramic powder having a difficulty in sintering and / or refractory metal powder having a melting point of 2000 ° C. or higher, and the mixed powder is subjected to dehydrogenation treatment. A method for producing a composite powder. 2. The method according to claim 1, wherein one or more of oxides, carbides, borides or nitrides of silicon, boron, aluminum, transition metal or rare earth metal are used as the ceramic powder having sintering resistance. Of the titanium-based composite powder according to claim 1. 3. The method for producing a titanium-based composite powder according to claim 1, wherein one or more of molybdenum, niobium, tantalum, and tungsten or an alloy thereof is used as the refractory metal powder.