JP6677942B2 - Titanium joining method - Google Patents

Description

  The present invention relates to a method for joining titanium materials, which joins a plurality of titanium materials.

  Conventionally, brazing, laser welding, and solid phase diffusion bonding have been proposed as methods for bonding titanium materials.

  In the joining by brazing, since the joining is performed by melting the brazing material (600 to 1000 ° C.), there is a problem in positioning accuracy, and the application range is also limited. In addition, a flux containing a fluoride is used for brazing, and there is a problem of corrosion due to the flux residue and a problem that the flux is harmful to the human body.

In the joining by laser welding, the vicinity of the welded portion is softened by welding heat, and micro cracks occur. Also, micro-cracking and corrosion are problems due to the clearance at the joint.
Furthermore, since titanium is an active metal, there is a problem that it easily reacts with oxygen, nitrogen, hydrogen, and the like, and the welded portion is embrittled.

When titanium is exposed to the atmosphere, a strong natural oxide film, which is a bonding inhibitor, is formed.
Therefore, in order to obtain a high-strength joint in solid-state diffusion bonding, the oxide film must be mechanically destroyed by increasing the joining pressure and joining temperature, and the amount of deformation during joining naturally increases. There is a problem.

  Further, it has been proposed to perform a solid-phase diffusion bonding after treating a bonding surface of a metal material with an oxide film removing solution made of an organic acid (for example, see Patent Document 1).

JP 2006-334652 A

  However, in the case of titanium or the like, if solid phase diffusion bonding is performed only by treating the surface with an organic acid as in Patent Document 1, sufficient bonding strength cannot be obtained.

  In order to solve the above-described problems, the present invention provides a method for joining titanium materials that can be joined at a relatively low temperature and can suppress deformation during joining.

The method for bonding a titanium material according to the present invention includes a step of immersing an aluminum sheet in an alkali solution, or a step of subjecting the aluminum sheet subjected to the alkali treatment to exposure to a vapor containing an alkali, using an organic acid solution. A sheet in which an aluminum organic acid salt film is formed on the surface of an aluminum sheet by boiling in an air or being exposed to a vapor containing an organic acid, and the aluminum organic acid salt film is formed on the aluminum sheet surface And a step of heating and pressing a plurality of titanium materials with the sheet interposed between the bonding surfaces to bond the plurality of titanium materials, and each of the plurality of titanium materials is composed of only titanium. .

According to the present invention described above, a higher bonding strength can be obtained at a lower bonding temperature than in the related art.
This makes it possible to lower the joining temperature, reduce the energy required for heating, and reduce the amount of deformation during joining.

It is a flowchart of the procedure of the joining method of the titanium material of one Embodiment of this invention. It is a perspective view which shows the joining state in experiment 1. It is a figure which shows the relationship between joining temperature and tensile strength in each case of formic acid treatment, acetic acid treatment, and no organic acid treatment when the thickness of an aluminum sheet is 0.5 mm. It is a figure which shows the relationship between joining temperature and tensile strength in each case of formic acid treatment, acetic acid treatment, and no organic acid treatment when the thickness of an aluminum sheet is 1.0 mm.

Hereinafter, embodiments for carrying out the invention (hereinafter, referred to as “embodiments”) will be described.
The description will be made in the following order.
1. 1. Outline of the present invention Embodiment 3 FIG. Example

<1. Overview of the present invention>
First, the outline of the present invention will be described.
The method for joining titanium materials according to the present invention is a method for joining a plurality of titanium materials.
The present invention includes a step of joining a plurality of titanium materials by interposing a sheet having an aluminum salt coating formed on the surface of an aluminum sheet on a joining surface.

In the present invention, further, a step of immersing the aluminum sheet in an alkali solution, or performing an alkali treatment by exposing the aluminum sheet to a vapor containing an alkali, and boiling the alkali-treated aluminum sheet in an organic acid solution. Alternatively, it is possible to adopt a configuration including a step of forming an organic acid salt film of aluminum on the surface of an aluminum sheet by exposing to a vapor containing an organic acid to produce a sheet.
Thereby, the oxide film on the surface of the aluminum sheet is removed and the aluminum hydroxide is formed by the alkali treatment step, and an organic acid acid film can be formed on the surface of the aluminum sheet by the organic acid.

  In the present invention, since a sheet in which an organic acid salt film of aluminum is formed on the surface of an aluminum sheet is used, a separately prepared sheet may be used, or a sheet manufactured by another person may be used. It is also possible. In those cases, the above-described steps of alkali-treating the aluminum sheet and forming the sheet by forming an organic acid salt film of aluminum on the surface of the aluminum sheet are omitted.

  The plurality of titanium materials to be joined may be the same material or different materials within the range of titanium or a titanium alloy. Among these, examples of combinations of different materials include pure metals and alloys, alloys having different constituent elements other than titanium, alloys having different alloy compositions, and the like.

In the present invention, various alkalis can be used for the alkali solution or the vapor containing the alkali in the alkali treatment step.
For example, sodium hydroxide and sodium carbonate can be used. An aqueous solution of these alkalis or steam containing alkalis can be used.
When the aluminum sheet is immersed in an alkaline aqueous solution, the alkaline aqueous solution is more preferably boiled. By boiling the alkaline aqueous solution, it is possible to efficiently remove the oxide film on the surface of the metal member and form aluminum hydroxide.

In the present invention, various organic acids can be used as the organic acid.
For example, one or more selected from formic acid, acetic acid, and citric acid can be used.

In the present invention, the bonding strength can be increased by interposing a sheet in which an aluminum salt coating is formed on the surface of an aluminum sheet on the bonding surface of a plurality of titanium materials (titanium or titanium alloy).
Since a high bonding strength can be obtained in this manner, it is possible to obtain a high bonding strength at a lower temperature than before.

  The aluminum organic acid salt coating (coating such as aluminum formate) formed on the surface of the sheet undergoes a thermal decomposition reaction in the step of joining the titanium material by heating and pressing, and the aluminum and titanium material of the sheet are generated. Since the atomic surface of titanium is exposed, the adhesion is improved, and the metallic contact area between the titanium material and the sheet is increased, so that high bonding strength can be obtained.

As described above, according to the present invention, a sufficiently high bonding strength can be obtained at a lower temperature than in the past, so that bonding can be performed at a low temperature.
Then, from the same viewpoint as the temperature, a sufficiently high bonding strength can be obtained even if the pressure at the time of bonding is reduced.
Thereby, joining at a low pressure becomes possible, and the amount of deformation at the time of joining can be reduced, so that the positional accuracy of joining can be improved. By improving the positional accuracy of the joining, high positional accuracy can be maintained, and joining of a titanium material having a complicated shape, which has been difficult by welding, becomes possible.
In addition, since bonding can be performed at low temperature and low pressure, the configuration of the bonding apparatus can be simplified, energy required for heating can be reduced, and energy efficiency can be improved. For example, power consumption, heating fuel, time required for joining, and the like can be reduced.

Further, according to the present invention, since the sheet on which the organic acid salt coating of aluminum is formed is interposed on the bonding surface, the organic acid salt coating is formed on the sheet rather than forming the organic acid salt coating on a plurality of titanium materials to be joined. Can be easily formed.
Thereby, even with a titanium material having a complicated shape or a large-sized titanium material, it is possible to join with high positional accuracy.

Further, according to the present invention, it is possible to join titanium, which has been difficult in the conventional solid-state joining, so that high recyclability can be secured.
Furthermore, despite the fact that titanium has high strength and high corrosion resistance, it was difficult to join due to the formation of a strong oxide film, and thus the use of titanium was avoided. Bonding with the member for use.

<2. Embodiment>
FIG. 1 shows a flowchart of a procedure of a method of joining titanium materials according to an embodiment of the present invention.
As shown in FIG. 1, first, in step S11, the aluminum sheet is immersed in an alkaline solution or exposed to a vapor containing an alkali.
As a result, the oxide film on the surface of the aluminum sheet is removed, and aluminum hydroxide is formed.
When the aluminum sheet is immersed in an alkaline aqueous solution, the alkaline aqueous solution is more preferably boiled. By boiling the alkaline aqueous solution, it is possible to efficiently remove the oxide film on the surface of the metal member and form aluminum hydroxide.

Next, in step S12, the aluminum sheet is boiled in an organic acid solution or exposed to steam containing an organic acid.
Thereby, an organic acid salt film is formed on the surface of the aluminum sheet.

  The organic acid can be selected from those that produce an aluminum metal salt that thermally decomposes at low temperatures, and formic acid, acetic acid, citric acid, and other organic acids can be used. As the solvent, water and various polar solvents can be used.

Next, in step S13, the two titanium materials are joined by heating and pressing with the sheet having the organic acid salt film formed on the surface of the aluminum sheet interposed between the joining surfaces.
With this, heating and pressurization are performed in a state where the surface contaminant layer is removed or replaced with the organic acid salt, and the organic acid salt undergoes a thermal decomposition reaction and is decomposed. The surface is exposed, and the bonding strength can be increased. Since a high bonding strength can be obtained, it is possible to obtain a high bonding strength at a lower temperature and a lower deformation amount than before.
That is, compared to a conventional joining method in which titanium materials are directly joined to each other without using an aluminum sheet, or a joining method using an aluminum sheet in which an organic acid salt film is not formed on the surface, It becomes possible to lower the heating temperature and pressure.

As the titanium material, titanium or a titanium alloy can be used.
The same material or different materials of titanium or titanium alloy can be used for the two metal members.

In the present embodiment, in the process of step S11, for example, sodium hydroxide or sodium carbonate can be used as the alkali. An aqueous solution of these alkalis or steam containing alkalis can be used.
By using these alkalis, the oxide film on the surface of the aluminum sheet can be removed to form aluminum hydroxide.
Further, after the step S11 and before the next step S12, a step of cleaning the aluminum sheet or a step of drying the aluminum sheet may be performed as necessary.

In the present embodiment, in the step S12, for example, formic acid, acetic acid, and citric acid can be used as the organic acid.
By using these organic acids, an organic acid salt film of aluminum can be formed on the surface of the aluminum sheet.
After that, if necessary, a step of washing the aluminum sheet with pure water or alcohol, or a step of drying the aluminum sheet may be performed.

According to the above-described embodiment, by immersing the aluminum sheet in an alkali solution or exposing the aluminum sheet to a vapor containing an alkali, the oxide film on the surface of the aluminum sheet is removed and aluminum hydroxide is formed. .
Subsequently, an organic acid salt film can be formed on the surface of the aluminum sheet by boiling the aluminum sheet in an organic acid solution or exposing the aluminum sheet to a vapor containing an organic acid.
Further, the sheet having the organic acid salt film formed on the surface of the aluminum sheet is interposed between the joining surfaces, and the two titanium materials are joined by heating and pressing, whereby the organic acid salt causes a thermal decomposition reaction. As a result, the atomic plane of the metal atom of the titanium material is exposed, and the bonding strength can be increased.
As a result, a high bonding strength can be obtained, so that a high bonding strength can be obtained at a low temperature. Compared with a conventional case where no sheet is used or a case where the aluminum sheet is not treated with an organic acid, the bonding is performed. In this case, the heating temperature can be reduced. That is, bonding in a solid state at a low temperature becomes possible.
Even if the pressure at the time of joining is reduced, sufficiently high joining strength can be obtained, and joining in a solid state at a low pressure becomes possible, so that the amount of deformation at the time of joining can be reduced. As a result, the positional accuracy of the joining can be improved. By improving the positional accuracy of the joining, high positional accuracy can be maintained, and joining of a titanium material having a complicated shape, which has been difficult by welding, becomes possible.
In addition, since bonding can be performed at low temperature and low pressure, energy efficiency can be improved. For example, power consumption, heating fuel, time required for joining, and the like can be reduced.

  In the case where a separately prepared sheet is used or the sheet manufactured by another person is used, steps S11 and S12 in the flowchart of FIG. 1 are omitted.

<3. Example>
Next, a titanium material was actually joined according to the present invention, and characteristics were examined.

(Experiment 1) Presence or absence of organic acid treatment, and relationship between joining temperature and tensile strength As two titanium materials to be joined, a plate-like titanium material made of pure titanium and having a width of 15 mm, a length of 12 mm, and a height of 5 mm was used. A titanium material having a diameter of 10 mm and a height of 15 mm was prepared.
Then, the joining surface of each titanium material was finished using # 4000 emery paper.

  As the aluminum sheet, a 12 mm × 12 mm × 0.5 mm thick sheet and a 12 mm × 12 mm × 1.0 mm thick sheet made of pure aluminum were prepared.

  Samples without formic acid treatment, acetic acid treatment, and no organic acid treatment were produced by the following production methods.

(Formic acid treatment)
A sample was prepared by subjecting an aluminum sheet to a formic acid treatment.
First, the aluminum sheet was boiled in a boiling 10% aqueous sodium hydroxide solution for 60 seconds, and then washed in methanol for 10 seconds.
Next, the aluminum sheet was boiled in boiling formic acid for 30 seconds.
Thereafter, the sheet was washed in pure water for 10 seconds to obtain a sheet obtained by treating an aluminum sheet with formic acid.

Next, as shown in a perspective view in FIG. 2, the sheet-like titanium material 1 and the columnar titanium material 2 were joined by heating and pressing with the sheet 21 interposed between the joining surfaces.
Then, in a nitrogen atmosphere, the bonding pressure was 12 MPa, the bonding time was constant at 15 minutes, and the bonding was performed while maintaining the bonding temperature at a predetermined temperature in the range of 440 to 500 ° C. to produce a joint.

(Acetic acid treatment)
A sample was prepared by subjecting an aluminum sheet to acetic acid treatment.
First, the aluminum sheet was boiled in a boiling 10% aqueous sodium hydroxide solution for 60 seconds, and then washed in methanol for 10 seconds.
Next, the aluminum sheet was boiled in boiling acetic acid for 90 seconds.
Thereafter, the sheet was washed in pure water for 10 seconds to obtain a sheet obtained by treating an aluminum sheet with acetic acid.

Next, as shown in a perspective view in FIG. 2, the sheet-like titanium material 1 and the columnar titanium material 2 were joined by heating and pressing with the sheet 21 interposed between the joining surfaces.
Then, in a nitrogen atmosphere, the bonding pressure was 12 MPa, the bonding time was constant at 15 minutes, and the bonding was performed while maintaining the bonding temperature at a predetermined temperature in the range of 440 to 500 ° C. to produce a joint.

(No organic acid treatment)
As a comparative control, a sample in which the aluminum sheet was not subjected to the organic acid treatment was prepared.
As shown in a perspective view of FIG. 2, a sheet-like titanium material 1 and a cylindrical titanium material 1 are interposed between bonding surfaces, as shown in a perspective view in FIG. The material 2 was joined by heating and pressing.
Then, in a nitrogen atmosphere, the bonding pressure was 12 MPa, the bonding time was constant at 15 minutes, and the bonding was performed while maintaining the bonding temperature at a predetermined temperature in the range of 440 to 500 ° C. to produce a joint.

(Tensile test)
Further, a gripping jig was attached to one of the metal members of the joint obtained by joining the two metal members, and a tensile test was performed.
The tensile tester used was 5567 manufactured by INSTRON.

  FIGS. 3 and 4 show the relationship between the joining temperature and the tensile strength in each case without the formic acid treatment, the acetic acid treatment, and the organic acid treatment. FIG. 3 shows the result when the thickness of the aluminum sheet is 0.5 mm, and FIG. 4 shows the result when the thickness of the aluminum sheet is 1.0 mm.

From FIG. 3, when the thickness of the sheet is set to 0.5 mm, the joint having the tensile strength of about 10 times is obtained by performing the organic acid treatment as compared with the case where the organic acid treatment is not performed. You can see that. From FIG. 4, when the thickness of the sheet is 1.0 mm, the joint having the tensile strength of about 12 times is obtained by performing the organic acid treatment as compared with the case where the organic acid treatment is not performed. You can see that.
Therefore, by performing the organic acid treatment, the tensile strength can be improved and the titanium material can be joined at a lower temperature as compared with the case where the organic acid treatment is not performed.

(Without sheet)
Further, as a comparative control, a joint was produced by solid-phase bonding of titanium materials without using a sheet. The joining conditions were the same as in the case where the sheet was used. That is, in a nitrogen atmosphere, the bonding pressure was 12 MPa, the bonding time was constant at 15 minutes, and the bonding was performed while maintaining the bonding temperature at a predetermined temperature to produce a joint.
However, when a tensile test was performed on the manufactured joint, the samples bonded in any of the bonding temperature ranges broke before being attached to the tensile tester.
Therefore, it was found that it was difficult to directly solid-phase join titanium.

1 plate-shaped titanium material, 2 cylindrical titanium materials, 21 sheets

Claims (2)

A step of immersing the aluminum sheet in an alkaline solution, or subjecting the aluminum sheet to an alkali treatment by exposing it to a vapor containing an alkali,
The alkali-treated aluminum sheet is boiled in an organic acid solution or exposed to a vapor containing an organic acid to form an organic acid salt film of aluminum on the surface of the aluminum sheet. A step of producing a sheet having an organic acid salt coating of aluminum formed on the surface of the sheet,
Said sheet by interposing the bonding surface, heating and pressurizing a plurality of titanium material, and a step of bonding the plurality of titanium material,
The method of joining titanium materials, wherein the plurality of titanium materials are each composed of only titanium. The method for joining titanium materials according to claim 1, wherein the thickness of the aluminum sheet is 0.5 to 1.0 mm.

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