JPH01139706A - Manufacture of low chlorine titanium powder - Google Patents

Abstract

PURPOSE:To manufacture titanium powder having only a little impurities of chlorine, etc., by hydrogenizing raw material titanium, washing the powder with water after pulverizing and dehydrating and drying after removing chlorine content in the powder. CONSTITUTION:After hydrogenized-treating the metal titanium raw material of sponge titanium, etc., it is pulverized at about 0.2-200mum under inert gas atmosphere, etc. This powder is washed with water to dissolve and remove the chlorine content of compositions, such as NaCl, MgCl2, FeCl2, FeCl3. Successively, after dehydrating and filtering, it is vacuum- or hot-dried. The titanium obtd. by this method has only a little impurities of chlorine and Mg, etc., and a titanium alloy sintered product by using this titanium powder has excellent strength and fatigue characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is based on a hydrodehydrogenation method (
The present invention relates to a method for producing titanium powder by the HDH method (hereinafter referred to as HDH method).

[Conventional technology]

Nowadays, titanium alloys have high specific strength, excellent heat resistance, and corrosion resistance, making them ideal materials for aircraft equipment, etc. However, on the other hand, they have difficulties in processability such as melting, forging, and cutting.

Therefore, from the viewpoint of reducing processing costs and improving yield, powder metallurgy has become a promising technique for directly manufacturing semi-finished products with a shape close to the final shape.

When producing titanium alloys by powder metallurgy, there are two methods: one uses a mixed powder of pure titanium powder and titanium master alloy powder as a raw material. The former method is considered advantageous because alloys of various compositions can be manufactured at low cost by changing the mixing ratio of both powders.

One method for producing pure titanium is to mechanically crush titanium sponge, which is commonly obtained as metal titanium, into a powder, but since titanium sponge is highly malleable, even if it is directly crushed, it will still be a fine powder. That's difficult.

There is also a method (plasma rotating electrode method) in which titanium sponge is melted, formed into an electrode shape, and then melted using a plasma arc or the like while rotating as an electrode to obtain a fine powder.

According to this method, titanium powder with relatively high purity can be obtained, but there are drawbacks to the powder shape and the cost due to the melting process.

For this reason, titanium sponge is hydrogenated to form a brittle titanium hydride, which is then ground in a ball mill to form a fine powder of titanium hydride, and then dehydrogenated by vacuum heating to obtain titanium powder.Hydrodehydration A method based on the elementary method (HDH method) is generally employed.

[Problem that the invention seeks to solve]

However, titanium sponge, which is a raw material for powder, is produced by reducing titanium tetrachloride (TiCj4) with sodium and magnesium, and impurities such as chlorine, magnesium, and sodium are present in titanium sponge.

Such impurities are not removed in the conventional hydrodehydrogenation powder manufacturing process, but are introduced into the powder.

In other words, titanium powder obtained by the HDH method also contains 0.02%
Approximately 0.1% of chlorine remains, and sodium and magnesium are also included.

When producing sintered products etc. using this powder as an alloy raw material,
These impurities, especially chlorine, play the role of inclusions as chlorides and affect the material properties such as fatigue strength and life of the product.

[Means for solving problems]

The purpose of the present invention is to provide titanium powder with less impurities such as chlorine, and it is possible to improve the mechanical properties, particularly fatigue strength and life, of sintered parts using this powder as a starting material. This is what I am trying to do.

That is, the present invention provides a method for producing titanium powder by a hydrodehydrogenation method, in which raw material titanium is hydrogenated and pulverized, and then
The powder is washed with water to remove the chlorine content, then dehydrated and dried.

The present invention will be explained in detail below.

The production of titanium powder in the HDH method uses spongy or coarse powdered titanium metal, usually called sponge titanium, which is obtained by reducing 7iCJ 4 with metal Na or Mg in a high-temperature retort.

This titanium sponge is placed in a refractory container made of stainless steel or alumina, and charged into a heat treatment furnace, and hydrogen is supplied into the furnace to perform hydrogenation treatment. The hydrogenation reaction starts at around 520°C, but the temperature increase due to heat generated as the reaction progresses is controlled by the amount of hydrogen supplied or the hydrogen partial pressure. After the end of heat generation, it is cooled in hydrogen to complete the hydrogenation treatment.

The titanium hydride thus hydrogenated is extremely brittle and can be ground to the desired particle size by various mechanical grinding methods such as a rotary ball mill or a bottle mill. The pulverization must be carried out in an inert gas atmosphere such as Ar, and sufficient measures must be taken to prevent oxidation. The average particle size and particle size distribution of the powder are controlled by the grinding method and grinding conditions.

The titanium powder is ground to about 0.2μ to 200μ.

The effect of removing impurities such as Cj by water washing is influenced by the ratio of the amount of powder to be treated and the amount of water, the pl+ of the water used, and the chlorine content 1 water washing method. The ratio of the amount of powder to be treated and the amount of water is 1:5 to 20, preferably 1:10 to 20, in order to ensure efficient contact between water and powder and elution of impurities.

The number of times of water washing is three or more times when the ratio between the amount of powder to be treated and the amount of water is small, and about two times when the ratio is large. Further, the water temperature may be room temperature, but warm water of 50 to 100°C is more efficient.

Adding ammonia or the like to the water used for washing to make it pH 9-10 on the alkaline side is also effective in terms of chlorine removal efficiency.

In the final stage of washing, it is preferable to use pure water from which CQ ions have been removed by ion exchange or the like. Note that the cleaning effect can be increased by adding agitation such as applying ultrasonic waves during washing with water.

If the powder particle size is fine, 20μ or less, the number of washings is 3 times or more, each washing time is 10 minutes or more, and if the particle size is 20μ or more, the number of washings is
Although the time can be simplified to 10 minutes or less twice, the final C1 etc. removal efficiency is more efficient as the powder is finer.

The cleaning described above is not limited to the above-mentioned punch processing, but can also be applied to continuous processing such as one-sided drinbu or overflow processing.

After washing with water, dehydration and drying are performed by filtration and vacuum or hot air drying. Vacuum drying is desirable from the viewpoint of oxidation prevention. Titanium powder is obtained by removing impurities by washing with water and removing hydrogen combined with titanium from the dried titanium hydride powder (dehydrogenation treatment). The dehydrogenation treatment may be carried out under the usual conditions, but preferably at 650 to 700°C for 30 minutes to
It is heated in a vacuum for about 2 hours. At temperatures below 650°C, dehydrogenation requires a long time, and at temperatures above 700"C, powder solidification becomes significant during the dehydrogenation process. In addition, this process prevents oxidation and nitridation of the titanium powder obtained.
At the same time, it is desirable to conduct the heat treatment under a vacuum of 10 -5 Torr or less in order to completely dehydrogenate. Titanium powder is often slightly consolidated due to dehydrogenation treatment, but these consolidated powders can be re-pulverized using a rotary ball mill, crusher mill, bottle mill, etc. to form the predetermined powder prepared by crushing after hydrogenation treatment. It can be returned to powder particle size. In this case, oxidation prevention is also necessary as in the case described above.

In this way, titanium powder containing less impurities such as chlorine can be obtained.

In addition, when removing these impurities by washing with water, titanium sponge may be hydrogenated and pulverized, and then washed with water after dehydrogenation treatment.However, heating after pulverization suppresses chloride elution through surface diffusion of titanium. Perhaps because of this, although chlorine can be removed, the removal efficiency decreases.

The mechanism by which chlorine is removed is Na in the titanium sponge.
These impurities captured as impurities in the form of Cj or Mgα, FeClg+ FeCl3 are exposed on the powder surface by powdering, and since these impurities are water-soluble, they are dissolved by washing with water.

This is because it will be removed.

〔Example〕

1 kg of titanium sponge produced by the Mg reduction method as shown in Table 1 A was placed in a stainless steel container without a lid (S
US304) and put it into a heat treatment furnace capable of vacuum and hydrogen annealing to reach a vacuum of 10-5 Torr, then raise the temperature to 600'C at a rate of 10°C/min and introduce hydrogen into the furnace. did.

Immediately, the titanium sponge started a hydrogenation reaction.

The temperature of the titanium sponge undergoing a hydrogenation reaction was checked using a thermocouple embedded in the titanium sponge in advance, and the amount of hydrogen gas supplied was controlled to suppress excessive heat generation. After the heat generation due to hydrogen absorption stopped, the furnace was cooled while flowing hydrogen gas. The titanium hydride was taken out from the container, firstly ground in a ball mill, and then secondarily ground in a bottle mill to obtain a titanium hydride powder with a particle size of 0.5 to 40μ, with an average size of 15μ.

Note that all the pulverization was performed in an Ar atmosphere. Thereafter, this powder was transferred to a washing container, and tap water at 70''C was added thereto for the first washing.

The amount of water was approximately 10 times the weight of titanium, and ultrasonic waves were applied from outside the container to vigorously stir the mixture. After stirring for 10 minutes, it was stopped and the supernatant water was drained. From the second time onwards, similar operations were carried out using chlorine-free ion-exchanged water, and the work was completed on the third time. Collect the cleaning solution after stirring after each cleaning, and check for chlorine and chlorine in the cleaning solution. Ig
Figure 1 shows the analysis of the concentration over time. As can be seen from FIG. 1, the concentrations of chlorine and magnesium in the cleaning solution were significantly reduced after three washings, and the elution and removal of chlorine and magnesium from the powder was almost completed.

After washing, the powder was subjected to first removal of water using a filter (filter paper) and then removed in a vacuum drying oven.

Thereafter, this powder was placed in the same container as used for hydrogenation treatment, placed in a vacuum heat treatment furnace, and after reaching a degree of vacuum of 10-'Torr or less, it was heated at 700°C for 2 hours to perform dehydrogenation treatment.

During this time, hydrogen release started from around 600°C and 650°C.
It became active at ~700°C. During the dehydrogenation reaction, the degree of vacuum deteriorated due to released hydrogen, but once the reaction was completed, it returned to 10
- Returned to the Torr stand and became a high vacuum. The dehydrogenation treatment was completed by cooling in the furnace. Since the pure titanium powder was slightly consolidated after the dehydrogenation treatment, it was again lightly ground coarsely in a ball mill sealed with Ar gas, and then finely ground in a bottle mill.

The components and particle sizes of the obtained sponge titanium powder and the titanium powder produced by the conventional HDH method for comparison are shown in Tables B and C.

As can be seen from Table 1, the chlorine content of the titanium powder obtained by the method of the present invention is 50 ppm or less, which is significantly lower than the raw material sponge titanium. It has extremely low impurities.

In order to confirm the characteristics when titanium powder with few impurities is used as a sintered alloy, titanium powder was used as a base powder, and a master alloy powder with a composition of 60% V40% was mixed with it. The alloy composition was adjusted to 4% V to residual titanium. After press-forming this mixed alloy powder in advance, Δr
900”C2 under pressure of 1 ton/cffl in gas
A titanium alloy rod was obtained by performing hot isostatic pressure sintering (HIP) for several hours. From this, various JIS-based test pieces were cut out and subjected to material and fatigue tests.

For comparison, sponge titanium powder manufactured by the conventional method was used as base powder and the composition was the same as above (6%A
I! , -4% - remaining titanium) and the sintered crystals obtained by molding and sintering the alloy powder produced by the plasma rotating electrode method from the alloy melted to the same composition as above, and the above. Similar tests were also conducted on cast products obtained by melting and hot casting with the same composition. The compositions and grain sizes of these alloys are shown in Table 2, the mechanical properties are shown in Table 3, and the results of fatigue tests are shown in FIG.

The material quality and fatigue properties of the sintered material using the titanium powder produced by the method of the present invention as the base powder are improved compared to those of the sintered material using the titanium powder as the base powder produced by the conventional HDH method, especially the fatigue properties. The improvement in properties was remarkable, and properties equivalent to those of a sintered material using alloy powder obtained by a rotating electrode material (REP method) or an alloy material produced by melting or hot casting were obtained.

〔Effect of the invention〕

The titanium powder obtained by hydrogenating, pulverizing, dechlorinating, and dehydrogenating titanium sponge by the method of the present invention has extremely less impurities such as chlorine and magnesium compared to conventional ones.As a result, the titanium powder obtained by the method of the present invention The titanium alloy sintered product used as the raw powder bundle has excellent strength and fatigue properties.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the concentration of chlorine and magnesium in the titanium hydride powder washing water and the number of washings, and Figure 2 shows the fatigue characteristics of sintered products using titanium alloy powder obtained by various manufacturing methods. It is a figure showing (relationship between number of repetitions and maximum stress). 1st paper sheet 1 bud 2" hand 3 times sink taku times huan

Claims (1)

[Claims] A method for producing titanium powder by a hydrodehydrogenation method, in which the raw material titanium is hydrogenated and pulverized, the powder is washed with water to remove the chlorine content in the powder, and then dehydrated and dried. Production method.