JP2013112878A - Titanium composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide titanium powder in which fine particle properties and excellent fluidity are made consistent, and which can be used for powder metallurgy by metal injection molding, and to provide a titanium composition serving as a raw material thereof.SOLUTION: The titanium composition is obtained by contacting metallic titanium or a titanium alloy with hydrogen in the temperature range of 600 to 700°C, reducing the temperature and performing heating treatment in the temperature range of 500 to 580°C under the reduced pressure in an inert atmosphere. The titanium composition is characterized in that the diffraction peak Iappearing in the vicinity of 2θ=35° and the diffraction peak Iappearing in the vicinity of 2θ=38° in powder X-ray diffraction measurement satisfy I>I. Further, the titanium powder serving as the raw material of the titanium composition has the maximum particle diameter of ≤74 μm and also has a fluidity of <100 sec/50 g.

Description

  The present invention relates to a titanium or titanium alloy composition (hereinafter simply referred to as “titanium-based composition”) and alloy powder (hereinafter simply referred to as “titanium-based powder”) obtained by a hydrodehydrogenation method.

  Conventionally, as a means for producing a titanium-based powder, titanium tetrachloride is reduced with a reducing metal to form a titanium sponge lump, and the powder generated when the sponge titanium lump is crushed, or tetrachloride A method for obtaining titanium powder by reducing titanium with metallic sodium and smelting titanium is known.

  Among these, the former method uses titanium powder that is generated secondaryly during the titanium smelting process by the crawl method, and the production amount is restricted, and more impurities such as oxygen, nitrogen, or iron are included. There was a drawback that only low-quality products were obtained. Moreover, the particle size of the powder is as coarse as about 60 to 20 mesh (particle size 250 to 850 μm), and it is usually applicable only to uses such as fireworks and raw materials for welding rods.

  On the other hand, the latter method is generally called the Hunter method, and titanium powder can be obtained at a relatively low cost. However, since a large amount of sodium and chlorine components remain in the powder, high mechanical strength and reliability are obtained. Is not suitable for powder metallurgy raw materials for automobile parts and the like that require

  For these methods, utilizing the hydrogen embrittlement of titanium metal, the raw material titanium or titanium alloy is once hydrogenated and then crushed to an arbitrary particle size, and this is dehydrogenated by vacuum heating to obtain a titanium-based powder. The hydrodehydrogenation method can produce a titanium-based powder that has a very low chlorine content required for a sintered raw material for powder metallurgy.

  That is, the quality of the titanium-based powder obtained by this method mainly depends on the material of the titanium-based raw material, so that, for example, high quality with extremely low chlorine content by using ingot chips and scraps previously dissolved as raw materials. The titanium-based powder can be obtained, and the particle size of the powder can be adjusted relatively easily.

  Usually, the titanium-based powder production method by hydrodehydrogenation method includes a hydrogenation step in which a titanium-based raw material is hydrogenated in a hydrogen gas atmosphere at a high temperature, and the obtained titanium hydride lump or titanium hydride alloy lump is predetermined. Pulverization / classification process for pulverizing and classifying to the particle size of the powder, dehydrogenation process for dehydrogenating the pulverized titanium hydride-based powder in a high-temperature vacuum, and a process for pulverizing the titanium ingot sintered at the time of dehydrogenation It comprises a sieving step for classifying and adjusting the obtained titanium-based powder to a predetermined particle size.

  However, in the above production method, the powders are strongly sintered and agglomerated at the stage of the dehydrogenation process, and a phenomenon occurs in which it cannot be mechanically pulverized into a fine titanium-based powder in the subsequent pulverization process, This is a big problem as an industrial manufacturing technique.

  As a means for effectively mitigating and suppressing the sintering of powder in such a dehydrogenation step, the titanium hydride lump is preliminarily made into a particle size distribution with a particle size of particle size of 63 μm or less of 30% by weight or less after the hydrogenation step. There is known a method for producing titanium or titanium alloy powder, in which the titanium hydride-based powder pulverized as described above is dehydrogenated in this manner (see, for example, Patent Document 1).

  For the same purpose, in the method for producing titanium powder by hydrodehydrogenation, titanium powder is pulverized with an average particle size of 10 μm or less, and the dehydrogenation temperature is 300 to 600 ° C. Has also been proposed (see, for example, Patent Document 2).

  By the way, titanium powder used for powder metallurgy by metal injection molding is considered to be a very important requirement characteristic that it is fine and has excellent fluidity. A homogeneous and high-density molded body cannot be obtained.

  Generally, the fluidity of powder has a close correlation with the particle size, and it is known that the fluidity decreases as the powder particle size becomes finer. For this reason, in titanium powder advantageous for applications such as metal injection molding, there is a tradeoff between refinement and good fluidity, and titanium powder with a fine particle size is simply suitable for this purpose. It had the problem of not becoming.

  In order to solve this fluidity problem, a technique has been examined in which the particle size range of titanium powder is 5 to 74 μm and the average particle size is 20 μm or less (for example, see Patent Document 3). However, in order to remove all fine powders of 5 μm or less, a new problem that the manufacturing cost is increased is required.

JP-A-5-247503 Japanese Patent Laid-Open No. 3-122205 JP 7-278601 A

  An object of the present invention is to provide titanium powder excellent in fluidity despite the fact that the average particle size is fine. In particular, the object is to provide titanium powder suitable for injection molding. is there.

  In view of the above situation, the present inventors have conducted extensive research on a technique for producing a titanium-based powder suitable for uses such as metal injection molding having a fine particle size and excellent fluidity. By performing hydrogenation and dehydrogenation under the conditions of the above, a titanium-based composition having a specific peak intensity ratio in powder X-ray diffraction measurement is obtained, and the above-mentioned characteristic requirements are obtained by using the titanium-based powder obtained using this composition. Has been found to be able to achieve both effectively, and the present invention has been completed.

That is, the titanium-based composition according to the present invention is a titanium or titanium alloy hydride obtained by contacting metal titanium or a titanium alloy with hydrogen in a temperature range of 600 to 700 ° C. under reduced pressure in an inert atmosphere. A titanium-based composition obtained by heat treatment in a temperature range of 580 ° C., and in powder X-ray diffraction measurement, a diffraction peak I ₁ that appears in the vicinity of 2θ = 35 ° and a diffraction peak I ₂ that appears in the vicinity of 2θ = 38 ° Is characterized in that I ₁ > I ₂ .

  In addition, the titanium-based composition according to the present invention preferably has a maximum particle diameter of 74 μm or less and a fluidity of less than 100 sec / 50 g.

  Titanium powder or titanium alloy powder having the characteristics described above has the effect of excellent fluidity despite being fine particles of 74 μm or less, and is particularly suitably used as titanium powder for injection molding. can do.

It is an XRD chart reported in JCPDS (44-1294) of hexagonal titanium. It is a schematic diagram which shows the lattice plane of hexagonal titanium. It is an XRD chart of an Example. It is an XRD chart of a comparative example.

  The titanium-based composition of the present invention is a preferred embodiment in which metal titanium or titanium alloy is hydrogenated / dehydrogenated under the following conditions.

  The hydrogenation reaction of titanium metal or titanium alloy is heated to 600 to 700 ° C. in a reduced pressure atmosphere and brought into contact with hydrogen gas in the temperature range of 600 to 700 ° C., and the furnace temperature rises due to heat generation due to hydrogenation. It is preferable that the temperature is controlled to not exceed 770 ° C. and the temperature is lowered to room temperature while maintaining the hydrogen gas pressure of 0.2 MPa.

  When the temperature of hydrogenation exceeds 770 ° C., titanium hydride produced by the hydrogenation reaction is thermally decomposed and tends to return to metallic titanium, which is not preferable.

  Moreover, it is preferable to perform the hydrogenation atmosphere pressure in a pressurized state. It is preferable to perform the hydrogenation reaction in a pressurized state because the hydrogenation reaction rate can be increased.

  Specifically, it is preferably performed in a pressure range of 100 kPa to 350 kPa (1 atm to 3.5 atm). If the pressure in the furnace is less than 100 kPa, the atmosphere may flow into the furnace and must be avoided for safety.

  On the other hand, when the furnace pressure exceeds 350 kPa, the improvement effect on the hydrogenation reaction rate shows a saturation tendency, and the effect of pressurization is diminished.

  Therefore, in the present invention, the furnace pressure is preferably in the range of 100 kPa to 350 kPa. Here, 100 kPa = 0.1 MPa = 1 atm.

  Next, the titanium hydride produced by the hydrogenation reaction of the titanium raw material is once cooled down and cooled, and then transferred to a pulverization / classification step. The pulverization is preferably performed in an inert gas atmosphere such as argon, and the pulverization and classification are preferably performed simultaneously.

  Classification of titanium hydride can be performed using means such as air classification, and management such as complete removal of fine powder of 5 μm or less, for example, is unnecessary. In order to completely remove fine powder by air classification, it is often necessary to select operating conditions that reduce the product rate. However, in this application, special fine powder removal is unnecessary and the production cost can be reduced. .

  The titanium hydride cooled to room temperature is preferably pulverized and classified in an inert atmosphere to obtain a titanium hydride powder having a maximum particle size of 74 μm or less.

  Here, when the maximum particle size is classified into a shape having a maximum particle size exceeding 74 μm, it is not preferable because titanium powder is used to cause a phenomenon that is difficult to be densified in the sintering process. Therefore, in the present invention, it is preferable to classify the maximum particle size to 74 μm or less.

The ground and classified titanium hydride powder is then transferred to the dehydrogenation process. The dehydrogenation step is performed by heating in a reaction furnace under an inert atmosphere and under a required reduced pressure (for example, 1 × 10 ⁻⁴ Torr) while evacuating. The heating temperature at this time is 500 to 580 ° C. It is necessary to set to the range. At this time, if the heating temperature is set to less than 500 ° C., the time required for dehydrogenation becomes remarkably long, so that productivity is lowered and oxygen content is also increased. On the other hand, when the temperature exceeds 580 ° C., the powders are sintered together during dehydrogenation and become agglomerated, making it difficult to disintegrate.

The titanium powder produced by the above method is a titanium-based material in which the diffraction peak I ₁ that appears in the vicinity of 2θ = 35 ° and the diffraction peak I ₂ that appears in the vicinity of 2θ = 38 ° in the powder X-ray diffraction measurement satisfy I ₁ > I _2. A composition can be suitably obtained. In addition, the titanium-based composition can be crushed and classified to obtain a titanium-based powder having a particle property with a maximum particle size of 74 μm or less.

Various data of X-ray diffraction of titanium powder have been reported. In the database JCPDS, which collects standard peaks of X-ray diffraction, hexagonal titanium is reported with the numbers 44-1294, and the peak in FIG. 1 is reported. Here, I ₁ / I ₂ = 0.83.

The diffraction peak I ₁ appearing near 2θ = 35 ° corresponds to the (100) plane, and the diffraction peak I ₂ appearing near 2θ = 38 ° corresponds to the (002) plane. The maximum peak is a diffraction peak that appears in the vicinity of 2θ = 40 °, and this peak corresponds to the (101) plane. The lattice plane corresponding to each peak is shown in FIG. Defined in I ₁ (100) plane has a low in-plane density of the titanium atom, atoms present covered within the lattice is large.

The (002) plane defined by I ₂ is the most dense surface of titanium, the atomic density in the plane is the highest, and the proportion of titanium atoms appearing on the surface is high. When considering the flowability of the powder, it is considered that if the ratio of atoms on the surface is high, the degree of interference between the powders is high and the flowability is low. On the other hand, when the ratio of titanium atoms covered inside is high, it is considered that the powder surface is smooth and exhibits high fluidity.

Therefore, the titanium powder in which the X-ray diffraction intensity I ₁ appearing near 2θ = 35 ° and the X-ray diffraction intensity I ₂ appearing near 2θ = 38 ° satisfy the relationship of I ₁ > I ₂ has high fluidity. It is considered to be.

  The titanium-based powder according to the present invention has a particle property with a maximum particle size of 74 μm or less, and contains fine powder as compared with the particle size distribution of powder that is conventionally required for metal injection molding. It is suitable for exhibiting excellent fluidity and always obtaining a uniform and high-density molded body.

  Thus, according to the present invention, by performing the hydrogenation step and the dehydrogenation step under the specified conditions, it has fine particle properties and good fluidity suitable for powder metallurgy particularly by metal injection molding, etc., and It becomes possible to efficiently produce a high-quality titanium-based powder having a low oxygen content.

[Example 1]
Using pure titanium (corresponding to JIS-1 type, oxygen content 500ppm) cutting ingot of about 2mm in thickness and about 30mm in length, this was placed in a stainless steel container and stored in a vacuum heating furnace The temperature was raised to 650 ° C. in a vacuum atmosphere. Here, the heating furnace heater was turned off, and purified hydrogen gas was supplied into the furnace. The temperature in the furnace was raised by an exothermic reaction between titanium and hydrogen gas, while adjusting the furnace temperature so that it did not exceed 770 ° C. and maintaining the pressurized state where the hydrogen partial pressure in the furnace was 0.2 MPa. The furnace temperature was maintained. Since hydrogen absorption was completed after about 1 hour, the inside of the furnace was cooled to room temperature with a hydrogen pressure of 0.2 MPa. By this treatment, hydrogen corresponding to a theoretical amount (in terms of TiH ₂ ) was absorbed. The titanium hydride lump treated in this way was pulverized in an argon atmosphere, and airflow classification was performed so that the maximum particle size was 74 μm or less.

The titanium hydride powder was put in a container and heated to 550 ° C. in a vacuum heating furnace. Hydrogen gas was generated from about 500 ° C. due to hydride separation, but evacuation was continued until the vacuum was recovered to 1 × 10 ⁻⁴ Torr.

A dehydrogenated titanium lump was taken out from the dish-like container, and titanium powder having a maximum particle size of 74 μm or less was obtained by crushing and classification. This titanium powder was subjected to XRD measurement and fluidity measurement. XRD diffraction was performed using Rigaku RINT-2000. The fluidity was measured according to JIS Z 2502. The obtained XRD chart is shown in FIG. 3, which was a ratio I ₁ / I ₂ = 1.2 of the diffraction peak I ₁ appearing near 2θ = 35 ° and the diffraction peak I ₂ appearing near 2θ = 38 °. The fluidity was 85 sec / 50 g.

[Comparative Example 1]
Fine powder generated during the production of sponge titanium was collected, and titanium powder having a maximum particle size of 74 μm or less was obtained by air classification. Under the same conditions as in Example 1, XRD diffraction and fluidity measurement of the powder were performed. An XRD chart is shown in FIG. The ratio I ₁ / I ₂ = 0.9 between the diffraction peak I ₁ appearing near 2θ = 35 ° and the diffraction peak I ₂ appearing near 2θ = 38 °. The fluidity was not measurable because no powder flow occurred under the given conditions.

As described above, it is possible to industrially produce a high-grade titanium-based powder having a fine particle size and fluidity suitable for applications such as metal injection molding with high productivity.

Claims (2)

Obtained by heat-treating titanium or titanium alloy hydride obtained by contacting metal titanium or titanium alloy with hydrogen in a temperature range of 600 to 700 ° C. in a temperature range of 500 to 580 ° C. under reduced pressure of an inert atmosphere. A titanium-based composition,
In the powder X-ray diffraction measurement, a diffraction peak I ₁ appearing in the vicinity of 2θ = 35 ° and a diffraction peak I ₂ appearing in the vicinity of 2θ = 38 ° satisfy I ₁ > I ₂ . 2. The titanium-based composition according to claim 1, having a maximum particle size of 74 μm or less and a fluidity of less than 100 sec / 50 g.

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