JP2007009287A - Method for producing titanium alloy material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a titanium alloy material, in which the titanium alloy material is obtained by a powder metallurgy method. <P>SOLUTION: A binder is added to titanium alloy powder so as to be mixed. The mixture is subjected to extrusion molding, and thereafter, the binder is removed therefrom. Subsequently, sintering is performed, so as to produce a titanium alloy material. If required, B and C, and, further, one or more selected from Ni, Fe and Co are incorporated into the titanium alloy powder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a titanium alloy material, and more particularly to a method for producing a titanium alloy material by a powder metallurgy technique.

Conventionally, iron-based materials have been widely manufactured by powder metallurgy.
In material production using this powder metallurgy technique, powder is filled into a press die and press-molded (compact molding), and the press-molded product is then sintered.
In manufacturing using such a powder metallurgy technique, it is possible to form a near net shape, that is, a shape close to the final shape, compared to the case of obtaining a raw material from a melted material, and therefore the subsequent machining amount is small. This has the advantage that the processing cost is low.

In addition, in the case of the material obtained from the melted material, there is an inherent problem that the structure is coarsened and the fine part is generated, and the structure is likely to be uneven. In the case of a material, there is also an advantage that a uniform structure can be obtained.
In producing a titanium alloy material, it is desirable to obtain the advantages as described above if a powder metallurgy technique can be used as in the case of iron-based materials.

However, in the case of a titanium alloy, unlike the iron-based material, it has the following specific problems, and it is difficult to use the usual powder metallurgy technique used in the iron-based material as it is.
In general, in the case of iron-based materials, a water spray method is used as a powder manufacturing method in which a molten metal is discharged from a nozzle, and a water jet is jetted into the powder to form powder.

  In the powder obtained by this water spraying method, the surface of each particle is uneven, and therefore when the powder is filled in a press mold and pressed (compacted), each particle is on the surface. Due to the unevenness, the molded product is intertwined with each other, and the required strength is imparted to the molded product.

On the other hand, in the case of a titanium alloy, since it is very easy to oxidize, it is difficult to produce powder by the water spray method as described above.
Therefore, in the case of a titanium alloy, a gas spraying method in which a high pressure gas is injected into a molten metal flow from a nozzle to be powdered must be used as a powder manufacturing method.

However, the powder obtained by such a gas spraying method has round particles that are close to a sphere with little unevenness on the surface, and therefore the powder obtained by such a gas spraying method is different from the conventional powder. Similarly, when press molding, the particles are not entangled with each other, so the strength of the molded product is weak and handling is difficult, and the powder constituting the molded product is missing from the molded product as “battered” during handling. Will come.
That is, in the case of titanium alloy powder, there is a problem that it cannot be formed into a predetermined shape by ordinary press forming.

In addition, there exists what was disclosed by the following patent document 1 as a prior art with respect to this invention.
However, since the titanium powder produced by the hydrodehydrogenation method disclosed in Patent Document 1 exhibits an irregular shape, it is excellent in moldability, but has a large specific surface area, so it contains a large amount of oxygen due to surface oxidation. , Has the disadvantage of reducing the toughness of the sintered body.

JP 7-278609 A

  The present invention has been made for the purpose of providing a method for producing a titanium alloy material, which can obtain a titanium alloy material by a powder metallurgy technique.

  Thus, according to the first aspect of the present invention, a binder is added to a spherical titanium alloy powder produced by a gas spraying method, and the mixture is extruded and then debindered, followed by sintering to obtain a titanium alloy material. It is characterized by manufacturing.

  A second aspect of the present invention is characterized in that, in the first aspect, the titanium alloy powder contains B and C.

  A third aspect of the present invention is characterized in that, in any one of the first and second aspects, the titanium alloy powder contains one or more of Ni, Fe, and Co.

Effects and effects of the invention

  As described above, the present invention adds a binder to a spherical titanium alloy powder produced by a gas spraying method, mixes the mixture, forms the mixture into a predetermined shape by extrusion molding, and then performs sintering to form a titanium alloy material. According to the present invention, even if the titanium alloy powder is a powder obtained by gas spraying, that is, even if each particle has a round spherical shape with no irregularities on the surface, it is formed without any trouble. Processing and subsequent handling can be performed, and further, sintering can be performed after forming to obtain a sintered body having a predetermined shape, that is, a titanium alloy material.

In the present invention, since extrusion molding is used as the molding method, it is particularly suitable as a method for obtaining a plate-like, rod-like or tubular material.
Alternatively, various shapes can be obtained by applying appropriate machining.

The present invention is particularly suitable as a method for producing a titanium alloy material containing B and C as alloy components (claim 2).
When titanium alloy materials containing these B and C are produced by ordinary melting, precipitates of B and C as alloy components grow coarsely during solidification, or segregate and precipitate uniformly. Therefore, the structure becomes non-uniform, and it is difficult to fully exhibit the effects of B and C as alloy components.

  However, when a titanium alloy powder containing B and C is manufactured in advance and a titanium alloy material is manufactured by subsequent molding and sintering using the powder, the above-described problems do not occur, and boride , Carbide is finely and uniformly dispersed in the material, the structure becomes uniform, and the effects of B and C as alloy components can be fully exerted to effectively increase the strength of the titanium alloy material. High hardness can be achieved.

When titanium alloy materials are used for machine parts, etc., wear resistance due to increased strength and hardness is required. Therefore, the present invention is applied to the manufacture of titanium alloy materials that require such high strength and hardness. And suitable.
In this case, it is desirable that B and C are contained in the ranges of B: 0.5 to 3.0% and C: 0.5 to 1.5%, respectively.

The present invention is also particularly suitable when applied to the production of a titanium alloy material containing one or more of Ni, Fe, and Co as alloy components (claim 3).
When a titanium alloy material is manufactured by a powder metallurgy technique, that is, when a powder compact is manufactured by sintering, the density is lower than that when manufactured using a molten material.

However, when Ni, Fe, Co is included as an alloy component in the titanium alloy material, that is, when these are included as a powder component, a relative density of about 90% or more when these components are not included. In contrast, the density can be increased.
When these components are contained, a liquid phase is liable to be generated during sintering, and for this reason, the sinterability is improved and the density of the sintered body can be effectively increased.
Thus, if the density of the sintered body increases, the mechanical strength can be increased accordingly.

That is, by containing these components, it is possible to effectively improve the low density and weakness that are the disadvantages of the titanium alloy material made of a sintered body.
Here, Ni, Fe, and Co are all mass% in the case of single addition, Ni: 2% or more, Fe: 7% or more, Co: 5% or more, Ni (%) / in the case of simultaneous addition of two or more. It is desirable that 2 + Fe (%) / 7 + Co (%) / 5 ≧ 1, more desirably 3% or more.
In addition, the upper limit value is Ni: 10%, Fe: 20%, Co: 10% in the case of single addition, Ni (%) / 10 + Fe (%) / 20 + Co (%) / in the case of simultaneous addition of two or more. It is desirable to set 10 = 1 (%).

As described above, when the titanium alloy material is used for a machine part or the like, it is desirable that the strength is high. For that purpose, it is desirable that the titanium alloy material has a high sintered density.
In this sense, it is desirable that the density of the titanium alloy material is 85% or more.

On the other hand, titanium alloy materials are excellent in corrosion resistance and are not harmful to the human body.
Therefore, for example, the titanium alloy material can be suitably used for applications such as a filtration filter for seawater or a filtration filter for food.
When used as such a filtration filter, the density of the sintered body is desirably 80% or less.

In the present invention, the functions of B, C, Ni, Fe, and Co and the reason for limiting the range of the amount added are as follows.
B and C: B and C are made of Ti and compound, and it is desirable to contain more to improve the strength, hardness and rigidity of the alloy material. However, borides and carbides crystallize during melting in powder production, and the operability is significantly reduced.
Ni, Fe, Co: If it is less than the lower limit, the solidus temperature of the alloy is not sufficiently lowered, so that a liquid phase is hardly generated during sintering, and as a result, the density does not increase.
If the upper limit is exceeded, too much liquid phase is formed, and the shape of the sintered body is deformed.

Next, embodiments of the present invention will be specifically described below.
After mixing -250 μm (250 μm under) titanium alloy powder having a chemical composition shown in Table 1 and a commercially available water-soluble cellulose binder at a mass ratio of 100: 7, 10% (mass%) of water was further added to the mixture. In addition, kneading.
The kneaded material was formed into a sheet shape with an extruder at 5 mm thickness and 50 mm width at room temperature, and then cut into a length of 200 mm.
This was degreased by holding at 500 ° C. for 1 hour in a vacuum furnace, and further heated up to 1250 ° C. and held for 1 hour to obtain a sintered body.
A JIS Z 2201 No. 6 test piece was processed from the sintered body and subjected to a tensile test.

The results are shown in Table 1 together with Reference Examples and Comparative Examples.
Here, both the reference examples and the comparative examples are for melted materials.

As can be seen from the results in Table 1, the sample of Example 2 containing 1% each of B and C as the alloy components is relatively in comparison with the sample of the reference example (melted material) not containing these components. Despite the low density of 92%, both tensile strength and Young's modulus are high.
In Comparative Example 2 containing B and C in the same melted material as in the reference example, the relative density is the same as in the reference example, but the tensile strength value is rather low (however, the Young's modulus is high). )

In other words, when a titanium alloy material is produced from melted material, the tensile strength is reduced by containing B and C, but in the case of Example 2 where the titanium alloy material is produced using a powder metallurgy technique, the tensile strength is reduced. Moreover, both Young's modulus is increasing.
Moreover, the relative density of Example 1 containing 5% Ni as an alloy component is effectively increased compared to that of Example 2, and the tensile strength is also increased accordingly. .

  As described above, the present invention provides an unprecedented method for producing a new titanium alloy material, and according to the production method of the present invention, the strength and hardness of the titanium alloy material is produced from a molten material. It is possible to increase effectively compared to the case.

Claims (3)

  Titanium alloy material characterized by adding a binder to spherical titanium alloy powder produced by gas spraying method, mixing, extruding the mixture, debinding, and then sintering to produce a titanium alloy material Manufacturing method.   The method for producing a titanium alloy material according to claim 1, wherein the titanium alloy powder contains B and C.   The method for producing a titanium alloy material according to any one of claims 1 and 2, wherein the titanium alloy powder contains one or more of Ni, Fe, and Co.