JP2002047501A - Titanium base powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide titanium hydride powder and titanium powder having the reduced content of oxygen and content of chlorine, combining excellent fluidity with compaction performance and suitable as the raw material for producing a sintered titanium or titanium alloy product by a powder metallurgy method. SOLUTION: In this titanium hydride powder produced by being subjected to a stage in which titanium or a titanium alloy is embrittled with hydrogen and having the maximum grain size of substantially <=150 μm, the ratio of the powder with a grain size of <=10 μm is <=8 wt.%, the content of oxygen is <=0.15 wt.%, and the content of chlorine is <=0.06 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a titanium-based powder comprising titanium hydride powder (including titanium hydride alloy powder, hereinafter the same) and titanium powder (including titanium alloy powder, hereinafter the same). The present invention relates to a titanium-based powder suitably used as a raw material for producing a sintered titanium product by a powder metallurgy method.

[0002]

2. Description of the Related Art Recently, sintered titanium or sintered titanium alloy products manufactured by powder metallurgy have been used in various fields such as heat-resistant members. I have. As a raw material, use of titanium powder and titanium hydride powder by a hydrodehydrogenation method, which is high in quality and excellent in moldability, has been attempted. Although excellent mechanical properties are required for the sintered titanium or sintered titanium alloy member, the strength is greatly affected by the oxygen content, and the oxygen content in the titanium-based sintered member is 0.3% by weight. %, Mechanical properties such as elongation are known to be significantly reduced (Toyota Central R & D Review, 26-1 (1991),
44.). In consideration of unavoidable oxygen contamination in the sintering process, it is desirable to maintain the oxygen content of the titanium-based powder as the raw material at 0.15% by weight or less.

[0003] Among the titanium hydride powder and the method for producing the titanium powder, the hydrogen embrittlement of titanium or titanium alloy is used to hydrogenate titanium or titanium alloy, and then pulverized to an arbitrary particle size to obtain titanium hydride powder. The hydrodehydrogenation method, in which this is dehydrogenated by vacuum heating to convert it to titanium powder, is capable of obtaining high-quality powder by improving the quality of the raw material, and easily reducing the powder particle size. Since it has an advantage that it can be adjusted, it is attracting attention as a method for producing titanium hydride powder and titanium powder.

[0004] Specifically, this method comprises a hydrogenation step of hydrogenating a titanium or titanium alloy raw material in a hydrogen gas atmosphere at a high temperature, and a pulverization step of pulverizing the obtained titanium hydride mass to a predetermined particle size. To produce titanium hydride powder,
The method comprises producing a titanium-based powder through a dehydrogenation step of dehydrogenating the pulverized titanium hydride powder in a vacuum at a high temperature and a pulverization step of pulverizing a sintered titanium mass at the time of dehydrogenation.

[0005] In the titanium-based powder, the oxygen content of the entire powder increases as the number of fine powders having a small particle diameter increases.
As a method for reducing the oxygen content in the powder, for example, the particle size distribution of the titanium hydride powder is adjusted by sieving and removing fine particles having a particle size of 63 μm or less in advance to a predetermined ratio or less, and then dehydration. A method for obtaining titanium powder by elementary treatment has been proposed. (JP-A-5-247503)
However, this method has a drawback that a large amount of fine powder is removed, so that the product yield is greatly reduced and the production cost is increased.

On the other hand, fluidity and formability are also important for titanium hydride powder and titanium powder for powder metallurgy raw materials. Therefore, these properties must be satisfied. As a titanium powder having both properties, the particle diameter range is 5 to 74 μm, the average particle diameter is 20 μm
The one having the following particle properties has been proposed (Japanese Unexamined Patent Publication No. 7-278601) .However, in this titanium powder, there is a limit in reducing the oxygen content because the particle size is fine,
For example, an oxygen content of 2000 to 3000 ppm (0.2 to 0.3 wt.
%).

Furthermore, when titanium sponge produced by the Kroll method is used as the titanium material to be subjected to the hydrogenation step, it contains magnesium chloride by-produced in the step of producing titanium sponge, so that about 0.08% by weight of chlorine is usually used. It is included. This chlorine remains as an impurity element also in the titanium powder after hydrodehydrogenation, and is repelled as a cause of expanding and increasing the porosity of the sintered titanium member as a final product, leading to a decrease in fatigue strength. Accordingly, a low-chlorine titanium powder is desired, and as a means therefor, a method of removing residual chlorine by washing the titanium powder after hydrodehydrogenation with water has been proposed (JP-A-1-139706).

However, it is required that the water used for washing be ion-exchanged water which does not substantially contain chlorine, and further oxygen contamination during washing cannot be ignored, and a perfect drying means for avoiding such contamination. Is an essential requirement, which raises new issues in terms of resource and energy costs.

The present inventors have conducted various studies to solve the problems left in the above prior art, and as a result, by adjusting the powder ratio of fine powder having a particle size of 10 μm or less, the content in the titanium hydride powder was adjusted. In addition to finding that the amount of oxygen can be controlled to an allowable range of 0.15% by weight or less, it has been found that chlorine as an impurity is deflected in fine powder having a particle size of 10 μm or less. It was also confirmed that the chlorine content in the titanium-based powder was also reduced by this, and it was further confirmed that powder properties such as flowability and moldability of the titanium-based powder could be significantly improved, and the present invention was completed. .

[0010]

That is, an object of the present invention is to provide a raw material for producing a sintered titanium product by powder metallurgy, which has reduced oxygen content and chlorine content, has excellent fluidity and moldability. It is an object of the present invention to provide a titanium hydride powder and a titanium powder which can be suitably used as a powder.

[0011]

According to the present invention, there is provided a titanium hydride powder having a maximum particle size of substantially 150 μm or less produced through a step of hydrogen embrittlement of titanium or a titanium alloy. Wherein the proportion of powder having a particle size of less than 10 μm is 8% by weight or less.

The titanium powder according to the present invention is a titanium powder having a maximum particle size of substantially 150 μm or less obtained by dehydrogenating the above-mentioned titanium hydride powder, and having a particle size of 10 μm.
The compositional characteristic is that the proportion of powder of m or less is 5% by weight or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The titanium hydride powder according to the present invention has a maximum particle size of substantially 150 μm or less obtained through a hydrogenation step of hydrogen embrittlement of a titanium or titanium alloy raw material. Substantially 150 μm or less means that there may be some powder remaining on the 150 μm mesh at the time of sieving, but that is also less than 1% of the whole powder and 99%
Above means 150 μm or less. The average particle size of the titanium hydride powder is preferably 100 μm or less in order to maintain fluidity and moldability during powder molding.

The titanium hydride powder in the present invention has an oxygen content of 0.15% by weight or less and a chlorine content of 0.06% by weight or less by setting the proportion of powder having a particle size of 10 μm or less to 8% by weight or less. When used as a raw material for powder metallurgy, the oxygen content and the chlorine content of the titanium-based sintered member as the final product are sufficiently reduced. Also,
By setting the proportion of powder having a particle size of 10 μm or less to 8% by weight or less, the fluidity required in powder metallurgy is ensured, and the fine powder having a high oxygen content and poor compression moldability is removed. A titanium hydride powder that also satisfies the moldability can be obtained. If the proportion of powder having a particle size of less than 10 μm exceeds 8% by weight, the proportion of fine powder increases, the oxygen content and chlorine content relatively increase, and the fluidity and moldability also decrease. An oxygen content of 0.15% or less is an oxygen content in a range that can sufficiently satisfy mechanical properties such as elongation of a sintered titanium product or a sintered titanium alloy product manufactured by powder metallurgy using the powder as a raw material. And also
The chlorine content of 0.06% by weight or less is an allowable range for satisfying the fatigue strength of the titanium-based sintered member as the final product. In order to secure the desired oxygen content and chlorine content, the proportion of powder having a particle size of 10 μm or less should be 8% by weight or less depending on the powder properties required for the target sintered product and the set product cost. It is appropriately adjusted within the range, and for example, it is also preferable to set the content to 5% by weight or less.

The titanium powder of the present invention is subjected to dehydrogenation treatment by heating the above-mentioned titanium hydride powder of the present invention in a vacuum, then crushed, and then adjusted for particle size, whereby the maximum particle size is substantially reduced. 150μm or less, particle size 10μm
It is an essential requirement that the following powder ratio is 5% by weight or less.

The titanium powder of the present invention satisfying the above requirements is
Oxygen content is 0.15% by weight or less, chlorine content is 0.0
The content is limited to 4% by weight or less, and when used as a raw material for powder metallurgy, the content is reduced to a level that does not adversely affect the mechanical properties of the titanium-based sintered member as a final product. In addition, by reducing the content of the fine powder, the fluidity at the time of powder molding is maintained well, the oxygen content is high, by removing as much as possible fine powder having poor compression moldability, The formability when used for powder metallurgy is also effectively secured.

The titanium hydride powder of the present invention is prepared by charging raw materials such as titanium sponge lump, titanium or titanium alloy ingot cutting chips, scrap chips, and offcuts generated during the processing step into a hydrogenation furnace capable of vacuum replacement. Then, at a high temperature of 1000 ° C. or less, hydrogen embrittlement is performed in a hydrogen gas atmosphere and hydrogenation treatment is performed to obtain a block of titanium hydride containing 3.5 to 4.5% by weight of hydrogen. The body is pulverized by mechanical means to form a titanium hydride powder having a maximum particle size of substantially 150 μm or less, and then classified and sieved to remove fine powder, and to reduce the proportion of powder having a particle size of 10 μm or less to 8% by weight or less. Sizing.
For mechanical pulverization, a pulverizing device such as a ball mill or a vibration mill can be used, and for classification, a screening device such as a circular vibrating sieve or an airflow classifier is used. Oxygen contained in the obtained titanium hydride powder is limited to 0.15% by weight or less, and chlorine is limited to 0.06% by weight or less.

In the production of titanium powder, the above-mentioned titanium hydride powder is filled in a container, and charged into a vacuum-heating type dehydrogenation furnace, for example, in a vacuum of 10 ^-3 Torr or less, and 500 to 900 Torr.
It is carried out by heating to a temperature of about ° C to dehydrogenate, mechanically crushing the obtained titanium mass, and then adjusting the particle size. The resulting titanium powder has a maximum particle size of substantially 150 μm or less, a proportion of powder having a particle size of 10 μm or less of 5% by weight or less, and an oxygen content of 0.15% or less as in the case of titanium hydride powder. Chlorine content is 0.0
It is limited to 4% by weight or less.

The titanium hydride powder and the titanium powder according to the present invention can reduce the oxygen content and the chlorine content by adjusting the powder ratio in a specific particle size range with respect to the whole powder, and can improve the fluidity and the compactability. It has excellent properties and can function as a high-quality powder metallurgy raw material that is well balanced in terms of required characteristics and set costs.

[0020]

EXAMPLES The present invention will be described below with reference to examples. Examples 1-2 A titanium sponge having a particle size of 1/2 mesh or less was charged into a hydrogenation furnace and hydrogenated to produce a hydrogenated sponge titanium having a hydrogen content of 4%. Pulverized with a ball mill to a maximum particle size of 150
It was a titanium hydride powder of μm or less.

Then, using a gas classifier, the proportion of powder having a particle size of 10 μm or less contained in the titanium hydride powder was 1.6% by weight (Example 1) and 7.3% by weight (Example 2), respectively. The fine powder was removed so that Table 1 shows the evaluation results of the oxygen content, chlorine content, fluidity, and moldability of the obtained titanium hydride powder.

For comparison, titanium hydride powder from which fine powder having a particle size of 10 μm or less was not removed (Comparative Example 1),
With respect to titanium hydride powder (Reference Example) in which the ratio of powder having a particle diameter of 10 μm or less was further reduced, the oxygen content and the chlorine content were measured, and the fluidity and moldability were evaluated. Table 1 also shows the results.

The ratio of powder having a particle size of 10 μm or less was measured by a laser diffraction method, the fluidity was measured in accordance with JIS Z 2505, and a needle was used as necessary. Formability is JS
According to PM4-69 (Rutler test), the powder was 3 ton / cm ²
Was evaluated by the weight reduction rate of the pellet-shaped molded body pressed at the molding pressure of

As shown in Table 1, it has been proved that the titanium hydride powder according to the present invention has a low oxygen content, is excellent in fluidity, and has excellent moldability in a moldability test by a Rutler test. I have. On the other hand, the powder of Comparative Example 1 containing fine powder has an oxygen content exceeding 0.15% by weight, a chlorine content as high as 0.08% by weight, and a fluidity that is not practical. It is. In the reference example, the oxygen content was further lower, the fluidity and the moldability were good, but the product yield of the titanium hydride powder according to the present invention (Examples 1 and 2) was 90% or more. As a result, the product yield of the titanium hydride powder of the reference example was 60% or less, and the raw material basic unit increased 1.5 times.

[0025]

[Table 1]

Examples 3 and 4 The titanium hydride powders of Examples 1 and 2 were charged into a dehydrogenation furnace and heated to 500 to 900 ° C. under a vacuum of 10 ⁻³ Torr or less to dehydrogenate. The titanium mass produced by the above method was pulverized with a ball mill to obtain a titanium powder having a maximum particle size of 150 μm or less. Example 1 about the obtained titanium powder
The oxygen content was measured in the same manner as described above. The results are summarized in Table 2. Here, Examples 3 and 4 mean titanium powder obtained using the titanium hydride powder obtained in Examples 1 and 2 in Table 1 as a raw material. Comparative Example 2 means titanium powder obtained using the titanium hydride powder obtained in Comparative Example 1 in Table 1 as a raw material. The oxygen contents of Examples 3 and 4, in which the proportion of the powder having a particle size of 10 μm or less was adjusted to 5% by weight or less, were 0.12% by weight and 0.15% by weight, respectively. % By weight). On the other hand, in Comparative Example 2 in which the proportion of powder having a particle size of 10 μm or less exceeded 5% by weight, the oxygen content was 0.15% by weight.
And is not suitable as a raw material for powder metallurgy.

[0027]

[Table 2]

[0028]

According to the present invention, a titanium hydride powder and a titanium powder having reduced oxygen content and chlorine content and having both excellent fluidity and moldability can be provided at a low cost by a simple operation. The powder can be suitably used as a powder raw material for producing a sintered titanium or titanium alloy product by a powder metallurgy method.

Claims (6)

[Claims] The maximum particle size produced through the step of hydrogen embrittlement of titanium or a titanium alloy is substantially 150 μm.
Not more than 8% by weight of powder having a particle size of 10 μm or less
A titanium hydride powder or a titanium hydride alloy powder characterized by the following. 2. The titanium hydride powder or titanium hydride alloy powder according to claim 1, wherein the oxygen content is 0.15% by weight or less. 3. The titanium hydride powder or hydrogen titanium alloy powder according to claim 1, wherein the chlorine content is 0.06% by weight or less. 4. The titanium hydride powder or titanium hydride alloy powder according to claim 1, wherein the average particle diameter is 100 μm or less. 5. The titanium hydride powder or titanium hydride alloy powder according to claim 1, which is obtained by dehydrogenation, has a maximum particle size of substantially 150 μm or less, and a particle size of 10 μm or less. A titanium powder or a titanium alloy powder, wherein a powder ratio of the titanium powder is 5% by weight or less. 6. The titanium powder or titanium alloy powder according to claim 5, wherein the oxygen content is 0.15% by weight or less and the chlorine content is 0.04% by weight or less.