JP6987884B2 - Titanium powder and its manufacturing method - Google Patents

Description

The present invention relates to titanium powder obtained by a hydrogenation dehydrogenation method and a method for producing the same.

Titanium powder for powder metallurgy is produced by a so-called hydrodehydrogenation method in which raw materials such as titanium sponge, titanium scrap and chips of titanium are hydrogenated to be brittle, then crushed and then dehydrogenated.

Conventionally, it has been considered that there is no particular problem even if the titanium powder produced by the hydrogenation dehydrogenation method contains about several hundred ppm of hydrogen. Therefore, there has been almost no demand for reduction of the hydrogen concentration in the titanium powder by the hydrogenation dehydrogenation method. In fact, the minimum hydrogen concentration in a commercial product is about 200 ppm. Here, the hydrogen concentration means a mass fraction, and 1 ppm is 1 mg / kg.

Regarding the conditions of the dehydrogenation step in the prior art, for example, in Patent Document 1, a container is filled with titanium hydride powder and charged into a vacuum-heated dehydrogenation furnace, for example, ^10-3 Torr (1. It is disclosed that dehydrogenation is performed by heating to a temperature of about 500 ° C. or higher and 900 ° C. or lower in a vacuum of 32 × 10 ^{-1 Pa) or lower.} In addition, the meaning of the pressure (= degree of vacuum) described in the specification of the prior art 1 means the pressure at the time of stopping heating.

Further, in Patent Document 2, in the dehydrogenation step, a container is filled with titanium hydride powder, set in a vacuum heating type dehydrogenation furnace, and evacuated under the required depressurization (for example, ^10-2 Torr). It is performed by the operation of heating, and it is disclosed that the heating temperature at this time needs to be set in the range of 500 ° C. or higher and 580 ° C. or lower. Further, in the embodiment, there is a description that the heating is stopped when the ^{pressure in the system reaches 10-2 Torr.}

Japanese Unexamined Patent Publication No. 10-195504 Japanese Unexamined Patent Publication No. 7-278601

In recent years, due to the demand for improving the density of sintered bodies using titanium powder by the hydrogenation dehydrogenation method, the demand for reducing the hydrogen concentration in titanium powder produced by the hydrogenation dehydrogenation method has been increasing. There is no prior document that discloses the technical idea of measures to reduce the hydrogen concentration of titanium powder by the hydrogenation dehydrogenation method.

As a result of experiments conducted by the present inventors, the hydrogen concentration of the titanium powder produced under the production conditions of Patent Document 1 and Patent Document 2 has not been sufficiently reduced and there is room for improvement. Furthermore, the production conditions of Patent Document 1 and Patent Document 2 both avoid a decrease in productivity due to a long dehydrogenation time and a difficulty in crushing due to agglomeration due to the progress of sintering between powders. It is a condition set as a purpose, and does not pay attention to the hydrogen concentration in the titanium powder, much less the problem of reducing the hydrogen concentration is not recognized at all.

An object of the present invention is to solve the above-mentioned problems, that is, to provide titanium powder having a reduced hydrogen concentration and a method for producing the same.

In order to achieve the above object, the present invention focuses on the degree of vacuum at the end of the dehydrogenation step, ^{and by setting the degree of vacuum to 5 × 10 −2} Pa or less, the titanium powder produced by the hydride dehydrogenation method can be used. We have found that the hydrogen concentration can be reduced and completed the present invention.

One embodiment of the present disclosure is a titanium powder obtained by a hydrogenation dehydrogenation method, wherein the hydrogen concentration contained in the titanium powder is 150 ppm or less. The hydrogen concentration contained in the titanium powder obtained by the hydrogenation dehydrogenation method may be 50 ppm or less.

One embodiment of the present disclosure is a method for producing titanium powder by a hydrogenation dehydrogenation method, characterized in that the ^{degree of vacuum at the end of the dehydrogenation step is 5 × 10 −2 Pa or less.} The degree of vacuum at the end of the dehydrogenation step ^{may be 5 × 10 -3} Pa or less. The heating temperature in the dehydrogenation step may be 450 ° C. or higher and 900 ° C. or lower, and the heating holding time may be 5 hours or longer and 30 hours or lower. The heating temperature in the dehydrogenation step may be 590 ° C. or higher.

In the method for producing titanium powder by the hydrogenation dehydrogenation method, the hydrogen concentration of the titanium powder can be reduced by paying attention to the degree of vacuum at the end of the dehydrogenation step and lowering the degree of vacuum as compared with the conventional method.

<Explanation of hydrogenation dehydrogenation method>
The hydrogenation dehydrogenation method is a method for producing titanium powder by the steps of hydrogenation, crushing, dehydrogenation, and crushing. At this time, it may be charged into a hydrogenation furnace capable of vacuum replacement in the hydrogenation step, and hydrogen embrittled in a hydrogen gas atmosphere at a high temperature of 100 ° C. or higher and 1000 ° C. or lower for hydrogenation treatment. This makes it possible to obtain a mass of titanium hydride.

In the pulverization step, it is preferable that after mechanical pulverization, fine powder is removed by classification and / or sieving, and the particle size is adjusted so that the powder ratio having an average particle size of 100 μm or less and a particle size of 5 μm or less is 10% by weight or less. A crushing device such as a ball mill or a vibration mill can be used for mechanical crushing, and a sieve classification device such as a circular vibration sieve or an air flow classifier may be used for particle size adjustment. In the present invention, the average particle size refers to a particle size in which the cumulative distribution on a volume basis is 50% in the particle size distribution measurement obtained by the laser diffraction / scattering method. That is, the measurement is performed based on JIS Z8825: 2013.

In the dehydrogenation step, the pulverized titanium hydride powder is filled in a container and charged into a vacuum heating type dehydrogenation furnace. For example, in a vacuum degree of less than 0.1 Pa, 450 ° C. or higher and 900 ° C. or lower. It may be heated to a certain temperature and dehydrogenated for 5 hours or more and 30 hours or less. The dehydrogenation step is preferably performed in a vacuum degree of, for example, 5 × 10 ^{−2 Pa or less.} It is more preferable that the dehydrogenation step is in a vacuum degree of, for example, 5 × 10 ^{-3 Pa or less.} In the dehydrogenation step, it is more preferable to dehydrogenate by heating to a temperature of, for example, 590 ° C. or higher. In the dehydrogenation step, for example, the heating and holding time is preferably 15 hours or more. The dehydrogenation step is more preferably heated to a temperature of, for example, 590 ° C. or higher, and the heating holding time is 15 hours or longer. In the dehydrogenation step, for example, the heating and holding time is more preferably 25 hours or more.

The obtained titanium agglomerates may be mechanically crushed in the crushing step. The titanium powder obtained as a result preferably has an average particle size of 100 μm or less and a powder ratio of 5 μm or less is preferably 10% by weight or less.

In the dehydrogenation step, a titanium powder having a hydrogen concentration of 150 ppm or less can be obtained by combining the temperature, time, and degree of vacuum limited to the above range. The titanium powder obtained by the hydrogenation dehydrogenation method according to the present embodiment preferably has a hydrogen concentration of 50 ppm or less, more preferably 30 ppm or less, and even more preferably 20 ppm or less. The hydrogen concentration means a mass fraction, and 1 ppm is 1 mg / kg.

<Explanation of hydrogen concentration analysis method>
The hydrogen concentration in the titanium powder is analyzed by an analysis method called a gas chromatograph method. Specifically, the sample is melted in a vacuum or an inert gas, or heated at a temperature below the melting point to extract _{hydrogen as H 2.} The extracted hydrogen (H ₂ ) is quantified by gas chromatography.

[Example 1]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 26.4 kg of hydride powder obtained by crushing with a crushing mill and removing fine powder of 10 μm or less is put into a furnace, evacuated and heated at 620 ° C. (at the start of heating in the dehydrogenation step. The same applies hereinafter). When the pressure (vacuum degree) reached 10 Pa, dehydrogenation was performed for a total of 6.0 hours until the furnace pressure (vacuum degree) reached 5 × 10 ^{-3 Pa using an oil diffusion pump.} The hydrogen concentration of the obtained titanium powder was 0.003% (30 ppm, n = 21). The average particle size of the obtained powder was 25 μm.

[Example 2]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 26.4 kg of hydride powder obtained by crushing with a crushing mill and removing fine powder of 10 μm or less is put into a furnace, evacuated and heated at 640 ° C., and oil diffusion is performed when the furnace pressure (vacuum degree) reaches 10 Pa. Using a pump, dehydrogenation was performed for a total of 5.5 hours until the furnace pressure (vacuum degree) reached 4 × 10 ^{-3 Pa.} The hydrogen concentration of the obtained titanium powder was 0.003% (30 ppm, n = 1). The average particle size of the obtained powder was 25 μm.

[Example 3]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 69.6 kg of hydride powder, which was crushed with a crushing mill to remove fine powder of 10 μm or less, was put into a furnace, evacuated and heated at 595 ° C., and oil diffused when the furnace pressure (vacuum degree) reached 10 Pa. Using a pump, dehydrogenation was performed for a total of 18 hours until the furnace pressure (vacuum degree) reached 5 × 10 ^{-3 Pa.} The hydrogen concentration of the obtained titanium powder was 26.5 ppm (n = 9). The average particle size of the obtained powder was 25 μm.

[Example 4]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 63.8 kg of hydride powder, which was crushed with a crushing mill to remove fine powder of 10 μm or less, was put into a furnace, evacuated and heated at 590 ° C., and oil diffused when the furnace pressure (vacuum degree) reached 10 Pa. Using a pump, dehydrogenation was performed for a total of 30 hours until the furnace pressure (vacuum degree) reached 5 × 10 ^{-3 Pa.} The hydrogen concentration of the obtained titanium powder was 19 ppm (n = 21). The average particle size of the obtained powder was 25 μm.

[Example 5]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 26.4 kg of hydride powder obtained by crushing with a crushing mill and removing fine powder of 10 μm or less is put into a furnace, evacuated and heated at 560 ° C., and oil is diffused when the furnace pressure (vacuum degree) reaches 10 Pa. Using a pump, dehydrogenation was performed for a total of 8.0 hours until the furnace pressure (vacuum degree) reached 5 × 10 ^{-3 Pa.} The hydrogen concentration of the obtained titanium powder was 0.0145% (145 ppm, n = 1). The average particle size of the obtained powder was 70 μm.

[Comparative Example 1]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 92.4 kg of hydrogenated powder crushed with a crushing mill to remove fine powder of 10 μm or less is put into a furnace, evacuated and heated at 580 ° C. for 17 hours, and dehydrated until the furnace pressure (vacuum degree) reaches 15 Pa. I went straight. The hydrogen concentration of the obtained titanium powder was 380 ppm (n = 91). The average particle size of the obtained powder was 25 μm.

[Comparative Example 2]
After putting the cut pieces of the ingot into the furnace and evacuating the furnace pressure (vacuum degree) to 5 Pa or less, the atmosphere is heated to 650 ° C and held for 30 minutes, then hydrogen is introduced into the furnace and hydrogen is stored in the hydrogen storage reaction. It became. After that, 26.4 kg of hydride powder obtained by crushing with a crushing mill and removing fine powder of 10 μm or less is put into a furnace, evacuated and heated at 580 ° C., and oil is diffused when the furnace pressure (vacuum degree) reaches 10 Pa. Using a pump, dehydrogenation was performed for a total of 6.0 hours until the furnace pressure (vacuum degree) reached 1 × 10 ^{-1 Pa.} The hydrogen concentration of the obtained titanium powder was 0.0719% (719 ppm, n = 1). The average particle size of the obtained powder was 25 μm.

As summarized in the above table, according to the present invention, it is possible to obtain a titanium powder obtained by a hydrogenation dehydrogenation method and having a hydrogen concentration of 150 ppm or less.

Claims (3)

It is a method for producing titanium powder by the hydrogenation dehydrogenation method. Titanium hydride is crushed, fine powder of 10 μm or less is removed from the obtained titanium hydride powder, and the heating temperature of the titanium hydride powder from which the fine powder has been removed is high. A titanium powder characterized by dehydrogenating at 450 ° C. or higher and 900 ° C. or lower and a heating holding time of 5 hours or longer and 30 hours or lower, and having a vacuum degree at the end of the dehydrogenation step of 5 × 10 ^{−2 Pa or lower.} Manufacturing method. A method of manufacturing a titanium powder by hydrogenation dehydrogenation method of producing titanium powder according to claim 1, characterized in that the end of the degree of vacuum dehydrogenation step and 5 × 10 ^-3 Pa or less .. The method for producing titanium powder according to claim 1 or 2 , wherein the heating temperature in the dehydrogenation step is 590 ° C. or higher.