JPH09314357A - Insert member for titanium alloy joining and joining method of titanium alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the insert member to join titanium alloy with high applicability and high reliability and the joining method of titanium alloy. SOLUTION: The insert member 12 is provided with a base metal 24, which has <=200μm thickness and a pair of facing faces 30, is faced to end faces 14a, 14b of metals to be joined of cylindrical members 10a, 10b, etc., and is made of titanium, and a coated layer 26, which is made of a metal thin film and has malleability higher than titanium, corrosion resistance of titanium or more and about 0.1-10μm thickness. When joining the cylindrical members 10a, 10b with using the insert member 12, by pressing a pair of the cylindrical members 10a, 10b each other, the coated layer 26 interposed between the cylindrical members 10a, 10b and the base metal 24 is deformed in following the surface shape of the end faces 14a, 14b of cylindrical members 10a, 10b due to its high malleability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for joining members made of titanium alloy to each other, and an interposing member which is inserted at a joining interface when joining titanium alloys.

[0002]

2. Description of the Related Art Titanium alloys have high corrosion resistance and high mechanical strength. Therefore, titanium alloys are used as materials for components and devices used in a corrosive atmosphere and in an environment where high stress can occur. It is used instead.

By the way, in the case of producing a component having a complicated shape that is difficult to integrally form, or in the case of producing a long cylindrical or cylindrical component which is industrially difficult to integrally form, etc., it is generally produced separately. It has been practiced to join the formed members to each other to form a component having a predetermined shape or a cylindrical or cylindrical component having a predetermined length. Such joining work is often performed by, for example, general arc welding for steel materials, but the titanium alloy reacts with O ₂ , N ₂ , H _2, etc. when heated to a high temperature in the atmosphere. There is a problem. Therefore, when joining titanium alloys, the TI is welded in a state in which the portion that is heated to a high temperature is shielded from the atmosphere.
G welding (Tungsten Inert Gas welding), MIG welding (Metal Inert Gas welding), etc. were generally performed. However, with these welding methods, it has been difficult to stably obtain a high mechanical strength of the welded portion as the working time becomes long.

[0004]

Therefore, the present inventors have previously proposed that titanium (hereinafter, simply referred to as “titanium” in the present application, for example, has a purity of 99 [mass] at the bonding interface of a pair of materials to be bonded made of a titanium alloy. %] Or more of pure titanium), or each of the above elements capable of reacting with a titanium alloy by interposing a sheet-like interposing member or forming a joining layer made of titanium on at least one of the joining interfaces. In a non-oxidizing atmosphere in which there is no pressure, pressure is applied at a specified pressure so that the bonding interfaces are pressed against each other, and at a specified temperature lower than the α → β phase transformation temperature of the members to be bonded (for example, tens to hundreds of degrees Celsius). We proposed a joining method of joining by solid-phase diffusion reaction by heating to a predetermined temperature (somewhat low). For example, the titanium alloy joining method described in Japanese Patent Application No. 7-222333 (unpublished) is used.

Further, the present inventors have formed a joining layer made of a titanium alloy having a melting point lower than that of the members to be joined on at least one of the joining interfaces of a pair of members to be joined made of a titanium alloy. While applying pressure in a non-oxidizing atmosphere,
We proposed a joining method of joining by a liquid phase diffusion reaction by heating to a temperature lower than the α → β phase transformation temperature of the members to be joined and higher than the melting point of the joining layer. For example, a joining method of a titanium material or a titanium alloy described in Japanese Patent Application No. 7-44828 (unpublished) is that.

According to these techniques, it becomes possible to perform the joining work in a shorter time than in the case of TIG welding or the like, and at the same time, the titanium alloy or titanium constituting the interposing member, the joining layer or the material to be joined is mutually bonded. Since the pair of materials to be bonded are bonded to each other by the diffusion layer that is continuously formed between the pair of materials to be bonded by being diffused, the structure of the bonding part becomes uniform and A high mechanical strength similar to the value of is stably obtained.

However, as a result of further research conducted by the present inventors, it became clear that the joining method utilizing the diffusion reaction as described above has the following problems. That is, first, in the joining method by the solid phase diffusion reaction, there is a problem that sufficiently high mechanical strength cannot always be obtained stably. Generally, on the bonding interface of a material to be bonded made of a titanium alloy and on the surface of an interposing member or a bonding layer made of titanium, there are fine irregularities generated at the time of manufacturing the material. In this case, since titanium forming the interposing member and the joining layer has a higher malleability than the titanium alloy, the surface shape is deformed in response to the joining interface of the joined materials by being pressed and heated. However, even if there are fine irregularities, it does not have the malleability enough to imitate the joint interface. Therefore, even after the deformation, a small amount of voids (internal defects) remain at the bonding interface, leading to a decrease in mechanical strength.

Further, in the joining method by the liquid phase diffusion reaction, since it is necessary to form a joining layer made of a titanium alloy having a low melting point at the joining interface of the materials to be joined, there is a problem that the applicable range is limited. is there. Generally, in order to sufficiently increase the mechanical strength of the joint, it is desired that the joint layer made of the titanium alloy be made as thin as possible. Therefore, it is difficult to produce and use a sheet-like interposing member having a similar composition in place of the bonding layer as in the case of solid phase diffusion reaction, and it is essential to form it at the bonding interface of the materials to be bonded. Become. In order to form a sufficiently thin and uniform bonding layer, it is desirable to use a vapor deposition method, an ion plating method, or the like. Therefore, the applicable range is limited to the materials to be bonded that can be used with those film forming apparatuses. Is done.

That is, in any of the methods, there is a problem that the high mechanical strength of the joint portion is stably obtained and the joint method is not versatile. The present invention has been made in view of the above circumstances, and an object of the present invention is to insert an interposing member for joining titanium alloys with high versatility and high reliability and a joining method for titanium alloys. To provide.

[0010]

[Means for Solving the Problem] The gist of a titanium alloy joining insertion member of the first invention for achieving the above object is to press a pair of joined materials made of titanium alloy against each other. In addition, the titanium alloy joining member that is interposed at the joining interface of the pair of materials to be joined when they are joined to each other based on the solid phase diffusion reaction by heating and (a) having a thickness of 200 (b) a substrate having a pair of facing surfaces facing each other at the bonding interface, and (b) having a malleability higher than that of titanium and a corrosion resistance equal to or higher than that of 0.1 (μm) and having a thickness of 0.1 ( μm) or more of the metal thin film, and a coating layer provided on each of the pair of opposing surfaces of the base material.

[0011]

[Effect of the first invention] With this configuration, the thickness is 200 (μm).
Below, a base material made of titanium having a pair of facing surfaces that are opposed to the bonding interface of the materials to be bonded, and a pair of facing surfaces of the base material, each of which has a malleability higher than that of titanium and corrosion resistance equal to or higher than titanium. And a coating layer made of a metal thin film having a thickness of 0.1 (μm) or more, and a titanium alloy joining member is formed. Therefore, when joining the materials to be joined using this interposing member, when a pair of materials to be joined are pressed against each other, the coating layer interposed between the material to be joined and the base material is
Due to its high malleability, it is deformed following the surface shape of the bonding interface of the materials to be bonded. Therefore, in the case of joining based on the solid phase diffusion reaction, generation of internal defects due to the unevenness of the joining interface is suppressed, and high mechanical strength can be obtained. Moreover, it is not necessary to provide any metal layer or the like corresponding to the interposing member on the material to be joined side. Therefore, it is possible to obtain an interposing member that can join titanium alloys with high versatility and high reliability.

The thickness of the base material made of titanium is 200 (μ
When it exceeds m), the layer made of titanium remains after the diffusion bonding and the mechanical strength after the bonding becomes low. Therefore, the thickness of the base material needs to be 200 (μm) or less. Further, in order to reliably suppress the occurrence of internal defects due to the unevenness of the bonding interface, the thickness of the coating layer is required to be 0.1 (μm) or more, the coating layer after diffusion bonding In order to suppress the residual and causing a decrease in mechanical strength, it is preferably 50 (μm) or less, particularly about 1 to 10 (μm),
Furthermore, it is more preferable that the thickness is about 1 to 5 (μm). The base material is made of titanium in order to increase the corrosion resistance and mechanical strength after joining as much as possible.
For the same reason, the coating layer is required to have corrosion resistance equal to or higher than that of titanium.

[0013]

[Other Embodiments of the First Aspect of the Invention] Preferably, the metal thin film has a melting point higher than the α → β phase transformation temperature of the titanium alloy. By doing so, when joining the titanium alloy based on the diffusion reaction, since it is heated at a temperature lower than the α → β phase transformation temperature of the titanium alloy, the coating layer composed of the metal thin film at the time of the joining. Does not melt. Therefore, the thickness of the melted coating layer is locally non-uniform due to non-uniform pressure applied to the bonding surface, and the bonding strength is not reduced.

Preferably, the metal thin film is gold (A
u), platinum (Pt), and palladium (Pd). If you do this,
Since these metals have corrosion resistance and melting point equal to or higher than titanium, and have extremely high malleability and easy forging, they are firmly bonded to the titanium alloy at the bonding interface, and after bonding, Higher mechanical strength can be obtained.

Further, preferably, the surface roughness of the bonding interface of the pair of materials to be bonded and the facing surface is the maximum height R _max.
And is less than 10 (μm). In this way, since both the bonding interface and the facing surface that faces the bonding interface are sufficiently smooth, the occurrence of internal defects at the bonding interface is further suppressed, and higher mechanical strength after bonding is achieved. Is obtained.

[0016]

A second aspect of the present invention for attaining the above-mentioned object is to provide a method for joining titanium alloys according to the first aspect of the present invention. A joining method for joining a pair of materials to be joined made of a titanium alloy to each other by using an insertion member, wherein (c) the titanium alloy joining interposing member is interposed at a joining interface of the pair of materials to be joined. By pressing the pair of bonding interfaces against each other with a predetermined pressure and heating them to a predetermined temperature, the pair of materials to be bonded is bonded by a solid phase diffusion reaction.

[0017]

[Effects of the Second Invention] With this configuration, the titanium alloy joining interposing member is interposed at the joining interface between the pair of materials to be joined,
By pressing the joint interfaces against each other and heating them,
The pair of materials to be joined are joined by a solid phase diffusion reaction. Therefore, when joining a pair of materials to be joined, there is no need to perform a conventional treatment for forming a joining layer at the joining interface. Further, when the coating layer provided on the interposing member is deformed according to the surface shape of the bonding interface when pressed and heated for bonding, the solid phase is solidified in a state where the unevenness of the bonding interface is filled. Since the diffusion reaction proceeds and the pair of materials to be joined are joined, internal defects due to the unevenness of the joining interface do not occur. Therefore, it becomes possible to join titanium alloys with high versatility and high reliability.

[0018]

[Other embodiment of the second invention] Preferably, the predetermined temperature is a temperature lower by a predetermined value than the α → β phase transformation temperature of the titanium alloy. With this configuration, the pair of materials to be bonded can be bonded by the solid phase diffusion reaction without deteriorating the materials to be bonded made of the titanium alloy and without melting the coating layer. The predetermined value is preferably, for example, about several tens to hundreds (° C.) in order to promote the diffusion reaction.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following examples, the dimensional ratios and the like of each part are not necessarily drawn accurately.

FIG. 1 (a) is a diagram schematically showing a joining apparatus to which the titanium alloy joining method of one embodiment of the present invention is applied. In the figure, for example, a pair of columnar members 10a and 10b made of titanium alloy (hereinafter, simply referred to as the columnar member 10 unless otherwise specified) has an insertion member 12 having end faces 14a and 14b (hereinafter not particularly distinguished). Are abutted against each other with being interposed between the end faces 14). These cylindrical members 10a, 10b
Are held by the fixed chuck 16a and the movable chuck 16b, respectively, and the movable chuck 16b is pressed toward the fixed chuck 16a in the direction of arrow A in the figure, so that the end surfaces 14a and 14b thereof are inserted. The members 12 are pressed against each other. This pressing force is controlled by the controller 18. In this embodiment,
The cylindrical member 10 corresponds to a member to be joined, and the end surface 14
Corresponds to the bonding interface.

Further, the end faces 1 of the columnar members 10a and 10b.
A high frequency induction coil 20 is provided in the vicinity of 4 so as to cover the outer peripheral surface thereof, and the high frequency induction coil 2 is provided.
A radiation thermometer 22 for measuring the temperature of the end face 14, that is, the joint portion, is provided on the side of 0 through a through hole provided in the high-frequency induction coil 20, both of which are provided in the control device 18. It is connected. The high frequency power supplied to the high frequency induction coil 20 is the radiation thermometer 22.
Controller 1 based on the temperature of the joint measured by
The temperature of the joint is maintained at a desired value.

As shown in FIG. 1 (b), the interposing member 12 is made of titanium having a purity of about 99.5 (mass%) and a base material 24 having a thickness of about 50 to 200 (μm). The base material 24
On both surfaces, that is, the facing surfaces 30 and 30 facing the end surfaces 14a and 14b, respectively, and having a thickness of 0.1 to 10
(μm), for example, gold (Au), platinum (Pt), palladium (Pd) and the like, the coating layer 26, 26 made of a metal thin film having a malleability and corrosion resistance equal to or higher than titanium. ing. The coating layer 26 is formed on the base material 24 by, for example, sputtering or vapor deposition, and its melting point, that is, the melting point of each metal is 10
It is about 63 (℃), 1755 (℃), and 1555 (℃), which is higher than the α → β phase transformation temperature of titanium alloys (generally about 930 to 980 [℃]). The insertion member 12 has a similar shape so that the upper surface and the lower surface in the drawing are abutted against the pair of end surfaces 14a, 14b corresponding to the shape of the end surfaces 14a, 14b of the pair of columnar members 10a, 10b. Is formed in.

When joining the columnar members 10a and 10b using the joining apparatus configured as described above, first, the surface roughness of the columnar member 10 is set to, for example, the maximum height R _max.
And polish to about 10 (μm) or less. Then, FIG. 1 (a)
As shown in FIG. 5, the fixed chuck 16a and the movable chuck 16b hold the cylindrical members 10a and 10b, respectively, and the movable chuck 16b is moved to the end face 14a and 14b with the interposing member 12 interposed therebetween. Is applied with a predetermined pressure in the direction of. At this time, the pressing force on the end face 14 is about 5 to 15 (MPa). Further, with the high frequency induction coil 20 arranged near the end face 14 and the radiation thermometer 22 provided at a predetermined position, a non-oxidizing gas is introduced into the high frequency induction coil 20 using a gas supply device (not shown). By doing so, the vicinity of the end face 14 is made into a non-oxidizing atmosphere such as argon (Ar) or helium (He). Alternatively, the space between the high-frequency induction coil 20 and the cylindrical member 10 that is the material to be joined is sealed, for example, 10 ⁻⁴ (Torr)
Create a vacuum atmosphere.

Then, for example, by operating a start switch (not shown) provided in the control device 18, the high frequency power supply (not shown) provided in the control device 18 causes the high frequency induction coil 20 to have a frequency of, for example, 200 (kHz) or less. Is applied to heat the vicinity of the end face 14. At this time, the temperature in the vicinity of the end face 14 is measured by the radiation thermometer 22, and the control device 18 controls the high frequency power source based on the measured temperature, whereby the end face 1
The temperature in the vicinity of 4 is maintained at a predetermined joining temperature of, for example, about 900 to 950 (° C). As a result, a solid phase diffusion reaction occurs between the columnar member 10 and the insertion member 12, and, for example,
By holding the temperature at the above temperature for a predetermined time of about 1000 to 2000 seconds, a diffusion region 28 in which the composition of the titanium alloy is slightly changed is formed in the vicinity of the butted portion, and the cylindrical member 10 integrally joined is formed. You can get it. In addition,
The predetermined joining temperature is set to be several tens to hundreds (° C.) lower than the α → β phase transformation temperature of the titanium alloy forming the columnar member 10.

Here, Tables 1 to 3 below show the results of joining the cylindrical members 10 (that is, the materials to be joined) made of various materials by the above joining method together with the joining conditions. In the table below, the ones in the comprehensive evaluation column of “◯” are the present examples, and the ones of “x” are the comparative examples. Also, in the columns for the materials to be joined, select "Grade 5" and "Grade
"6" and "Grade 9" are titanium alloys specified in ASTM B265, and No. 10 "6-2-4-2" is a titanium alloy specified in AMS-4975. The α → β phase transformation temperatures of these titanium alloys are 993 (℃) and 1038 (℃), respectively.
, 935 (℃), 993 (℃). In addition, the cylindrical member 10
And the surface roughness of the substrate 24 is the maximum height R _max.
It is a value expressed in (μm). Further, the tensile strength ratio and the impact strength ratio are the ratios of the respective measured values when the measured value of the columnar member 10 that has not undergone the bonding treatment, that is, the titanium alloy base material is 1. Further, in the column of the fracture position, "base material" indicates that the fracture occurred at a portion other than the joint interface.

[0026]

[Table 1] No. 1 2 3 4 5 Materials to be bonded Grade 5 Grade 5 Grade 5 Grade 5 Grade 5 Surface roughness 2 2 2 2 2 Base material − Ni Ti Ti Ti Thickness (μm) − 200 200 200 100 Surface Roughness − 2 2 2 3 Coating layer − Au Pt Au Au + Pt Thickness (μm) − 1 0.05 0.1 0.5 Forming method − Spatterlink Spatterlink Spatterlink Spatterlink Heating method Vacuum furnace Vacuum furnace Vacuum furnace Vacuum furnace Vacuum furnace Bonding temperature (° C) 950 950 950 950 950 Holding time (s) 1000 1000 1000 1000 1000 Pressurizing force (MPa) 5 5 5 5 7 Atmosphere Vacuum Vacuum Vacuum Vacuum Vacuum Vacuum property Tensile strength ratio 0.7 0.8 0.9 1.0 1.0 Breaking position Bonding interface Bonding interface Bonding interface Base metal Base metal impact strength ratio 0.3 0.4 0.8 1.0 1.0 Overall evaluation × × × ○ ○

In Table 1 above, No. 1 is the insertion member 12
The end surfaces 14a and 14b are directly abutted and joined together without using. Therefore, the solid phase diffusion reaction does not proceed sufficiently, and an internal defect due to the unevenness of the end face 14 is generated in the joint, so that the joint has low strength. Also,
No. 2 uses nickel (Ni) as the base material 24. Since nickel has a lower strength than titanium, the joint portion also has a low strength in this case. Also, No.3
In the case where the base material 24 is joined by using the interposing member 12 made of titanium, the cylindrical member 10 made of titanium alloy is used because the thickness of the coating layer 26 is as thin as about 0.05 (μm).
The unevenness of the end face 14 was not sufficiently filled, and internal defects were generated in the joint portion, and similarly the strength became low.

On the other hand, in Nos. 4 and 5 of this embodiment, the base material 24 is made of titanium and the thickness of the coating layer 26 is 0.1 (μ).
m) or 0.5 (μm), which is sufficiently thick as the insertion member 12, the strength of the base material 24 is sufficiently high, and the unevenness formed on the end surface 14 of the cylindrical member 10 is sufficient. Since it is difficult to cause internal defects by joining in a buried state,
Both the tensile strength and the impact strength were as high as those of the titanium alloy base material not bonded. Therefore, the base material 2
For 4, it is necessary to use titanium, and the thickness of the coating layer is required to be 0.1 (μm) or more. The heating method may be induction heating as shown in FIG. 1 (a) or heating in a vacuum furnace as shown in Table 1 above.

[0029]

[Table 2] No. 6 7 8 9 Materials to be bonded Grade 5 Grade 9 Grade 6 6-2-4-2 Surface roughness 5 5 7 10 Base material Ti Ti Ti Ti Thickness (μm) 50 100 200 100 Surface roughness 5 5 3 5 Coating layer Au + Pt + Pd Pd Au + Pd Pt Thickness (μm) 2 5 7 10 Forming method Vapor deposition Vapor deposition Vapor deposition Vaporization heating method Vacuum furnace Induction heating Current heating Induction heating Bonding temperature (℃) 900 900 950 950 Holding time (s) 2000 1000 1000 1000 Pressure (MPa) 6 8 10 15 Atmosphere Vacuum Ar He Vacuum characteristics Tensile strength ratio 1.0 1.0 1.0 1.0 Break position Base metal Base metal Base metal Impact strength ratio 1.0 1.0 1.0 1.0 Overall Evaluation ○ ○ ○ ○

Further, Table 2 shows various changes in the material and surface roughness of the cylindrical member 10, the thickness of the base material 24, the material and thickness of the coating layer 26, etc. The same strength as that of the titanium alloy base metal which is not obtained is obtained. That is, the present embodiment can be applied to titanium alloys of various compositions, and the surface roughness of the cylindrical member 10 may be about R _max = 5 to 10 (μm). Further, the thickness of the base material 24 can be about 50 to 200 (μm).
Further, as the material forming the coating layer 26, gold, platinum,
Palladium or the like may be used, but these may be used alone, or two or three kinds may be mixed and used, and the thickness thereof may be increased to about 2 to 10 (μm). Further, as a forming method, an evaporation method may be used instead of sputtering. If the coating layer 26 becomes too thick, the coating layer 26 remains in the diffusion region 28 after bonding and causes a decrease in strength. Therefore, the thickness of the coating layer 26 is preferably 50 (μm) or less.

The joining temperature can be appropriately changed within a range lower than the α → β phase transformation temperature of the titanium alloy forming the columnar member 10, and as shown in No. 6, it is about 900 (° C.). May be However, when the temperature is lowered,
It is necessary to lengthen the holding time (about 2000 seconds under the condition of No.6).

The atmosphere during heating may be an Ar or He atmosphere as shown in Nos. 7 and 8. Also,
As a heating method, as shown in No. 8, a cylindrical member 1
It is also possible to use electric heating to heat the junction by passing an electric current between 0a and 10b.

The pressing force is 6 to 6 as shown in the table.
Although it may be about 15 (MPa), it is not preferable to make it higher than necessary because it causes the deformation of the cylindrical member 10. In Nos. 8 and 9 of the examples in Table 2 above, the joint portion is expanded and deformed in the radial direction, which indicates that the pressing force was excessive. Therefore, although depending on the thickness of the base material 24, the thickness of the coating layer 26, and the like, it is preferable that the pressing force be lower than 10 (MPa). The reason why the pressure is increased is that the coating layer 26 is made thicker so that the adhesion of the end face 14 is improved so that the coating layer 26 does not remain after joining. The thickness is 5 (μ
m) or less is preferable.

[0034]

[Table 3] No. 10 11 12 13 Materials to be joined Grade 5 Grade 5 Grade 5 Grade 5 Surface roughness 2 2 15 2 Base material Ti Ti Ti Ti Thickness (μm) 200 300 100 100 Surface roughness 2 2 2 15 Coating layer Pt + Pd Au + Pd Au Au Thickness (μm) 1 5 10 10 Forming method Deposition Deposition Deposition Deposition Deposition Heating method Vacuum furnace Vacuum furnace Vacuum furnace Vacuum furnace Bonding temperature (℃) 1100 950 950 950 Holding time (s) 1500 1000 1000 1000 Applied pressure (MPa) 6 15 15 15 Atmosphere Vacuum Vacuum Vacuum Vacuum characteristics Tensile strength ratio 1.0 0.9 0.8 0.9 Fracture position Base metal Bonding interface Bonding interface Bonding interface Impact strength ratio 0.8 0.8 0.7 0.8 Overall evaluation × × × ×

Further, Table 3 above shows comparative examples outside the scope of the present invention. In No. 10, since the joining temperature was set higher than the α → β phase transformation temperature of the columnar member 10, the titanium alloy forming the columnar member 10 was phase-transformed to have low strength. is there. Also, N
In No. 11, the base material 24 of the insertion member 12 is thickened to about 300 (μm). Therefore, the joining process was performed with a relatively high pressing force, but since the base material 24 is too thick,
The titanium layer remains in the diffusion region 28 after joining, resulting in low strength.

That is, as shown in FIG. 3, the tensile strength of the columnar member 10 after joining is such that when the thickness d of the base material 24 is within a predetermined critical thickness dc, the strength of the base metal (that is, before joining). Strength), but tends to gradually decrease when the critical thickness dc is exceeded. As described above, in the solid phase diffusion bonding, the diffusion region 28 in which the composition of the titanium alloy is changed is formed in a predetermined range near the base material 24. In this case, when the thickness of the base material 24 is relatively thin, the diffusion region 28 is formed over the entire base material 24, so that the tensile strength of the joint is almost the same as the base material strength. After that, the titanium layer constituting the base material 24 remains in the diffusion region 28. Therefore, mechanical strength such as tensile strength and impact strength is reduced. The critical thickness dc varies depending on the composition of the titanium alloy constituting the columnar member 10 (that is, the mechanical strength determined by the composition), but in the titanium alloy shown in this embodiment, it is 200 ( Therefore, the strength is reduced when the thickness is about 300 (μm) as described above.

Nos. 12 and 13 are end faces 1 of the cylindrical member 10.
4 or the surface roughness of the facing surface 30 of the base material 24 is R _max = 15.
Although it was about (μm), in both cases, internal defects occurred in the joints, resulting in low strength. These were also treated by increasing the pressing force at the time of joining to about 15 (MPa), but nevertheless, sufficient strength was not obtained. That is,
In order not to generate internal defects, it is desirable that the surface roughness of each of these is R _max ≦ 10 (μm).

In short, in this embodiment, the thickness is 20
A base material 24 made of titanium having a pair of facing surfaces 30 and 30 facing the end surface 14 of a material to be bonded such as a cylindrical member 10 having a size of 0 (μm) or less, and the pair of facing surfaces 30 of the base material 24. The interposing member 12 is formed of a metal thin film having a malleability higher than that of titanium and a corrosion resistance equal to or higher than that of titanium and a thickness of about 0.1 to 10 (μm). Therefore, when the pair of columnar members 10 are pressed against each other when the columnar members 10 are joined by using the interposing member 12, the coating layer 26 interposed between the columnar member 10 and the base material 24. However, due to its high malleability, it is deformed following the surface shape of the end surface 14 of the cylindrical member 10. Therefore, in the case of joining based on the solid phase diffusion reaction, the occurrence of internal defects due to the unevenness of the end face 14 is suppressed, and high mechanical strength can be obtained.
Moreover, it is not necessary to provide the coating layer 26 or the titanium layer on the end surface 14 of the columnar member 10. Therefore, it is possible to obtain the interposing member 12 capable of joining the titanium alloy with high versatility and high reliability.

Moreover, in this embodiment, the coating layer 26
As described above, the metal thin film forming the
→ β phase transformation temperature (in this example, 935-1038
It has a melting point higher than [° C]. Therefore, at the time of joining at a temperature lower than the α → β phase transformation temperature of the titanium alloy, the coating layer 26 made of a metal thin film is formed.
Does not melt. Therefore, the thickness of the melted coating layer 26 is locally nonuniform due to nonuniform pressure applied to the end surface 14 which is the bonding surface, and the bonding strength is not reduced.

Further, in this embodiment, the metal thin film forming the coating layer 26 is made of at least one of gold (Au), platinum (Pt) and palladium (Pd). Since these metals have corrosion resistance and melting point equal to or higher than titanium, and have extremely high malleability and easy forging, they are firmly bonded to the end face 14 of the columnar member 10. Higher mechanical strength is obtained after joining.

In this embodiment, the cylindrical member 1
The surface roughness of the end surface 14 of 0 and the facing surface 30 of the interposing member 12 that is opposed to the end surface 14 is the maximum height R _max .
It is 10 (μm) or less. Therefore, since both the end surface 14 and the facing surface 30 that faces the end surface 14 are sufficiently smooth, the occurrence of internal defects at the bonding interface is further suppressed, and higher mechanical strength is obtained after bonding. .

Further, in this embodiment, the interposing member 1 is attached to the end surfaces 14a and 14b of the pair of cylindrical members 10a and 10b.
2, the end surfaces 14a and 14b are pressed against each other and heated, so that the pair of cylindrical members 1
0a and 10b are joined by a solid phase diffusion reaction. Therefore, when joining the pair of cylindrical members 10a and 10b, there is no need to perform a process of forming a joining layer, that is, a layer corresponding to the interposing member 12, on the end faces 14 of the pair of cylindrical members 10a and 10b. In addition, when pressed and heated for joining, the covering layer 26 provided on the insertion member 12 is deformed according to the surface shape of the end face 14 to fill the irregularities of the end face 14, The solid-phase diffusion reaction proceeds and the pair of cylindrical members 10
Since the a and 10b are joined together, no internal defect due to the unevenness of the end face 14 occurs. Therefore, the columnar member 1 made of titanium alloy has high versatility and high reliability.
0 can be joined.

Further, in this embodiment, the predetermined temperature, that is, the joining temperature is only a predetermined temperature of several tens to hundreds (° C.) higher than the α → β phase transformation temperature of the titanium alloy forming the columnar member 10. It is set low. Therefore, the pair of columnar members 10a and 10b can be formed by the solid phase diffusion reaction without deteriorating (phase transformation) the titanium alloy forming the columnar member 10 and without melting the coating layer 26.
Can be joined.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be carried out in still another mode.

For example, in the embodiment, the insertion member 12
Although the thickness of the base material 24 was about 50 to 200 (μm),
It can be made thinner. However, the thinner the film, the more difficult it is to handle. Therefore, the thickness is preferably about 50 (μm) or more.

Further, in the embodiment, the surface roughness of the base material 24 is set to R _max = 2 to 5 (μm), but it may be further smoothed, and it may be about 10 (μm). The surface roughness of and may be removed.

In the embodiment, the coating layer 26 is formed by the sputtering or vapor deposition method.
It may be provided by another film forming technique such as an ion plating method.

Further, in the embodiment, the cylindrical member 10
The case where the present invention is applied to the joining of
The present invention applies to joining titanium alloys of various other shapes as well. For example, the same applies to the joining of cylindrical members and the joining of plate members. In these cases, the shape of the end surface of the insertion member 12, that is, the shape of the facing surface 30 is appropriately changed according to the shape of the end surface 14.

Although not illustrated one by one, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 (a) is a schematic view showing a configuration of a joining apparatus to which a joining method according to an embodiment of the present invention is applied, and FIG. 1 (b) is an enlarged view of an insertion member applied to the joining method. FIG.

FIG. 2 is a view showing a columnar member after being joined by the joining device of FIG.

FIG. 3 is a diagram showing the relationship between the thickness of the base material of the interposing member and the tensile strength of the columnar member after joining.

[Explanation of symbols]

 10: Cylindrical member 12: Interposition member 14: End face (joining interface) 24: Base material 26: Coating layer 30: Opposing surface

Claims (6)

[Claims] 1. When a pair of materials to be joined made of a titanium alloy are pressed against each other and heated to be bonded to each other based on a solid phase diffusion reaction, titanium is present at the bonding interface between the pair of materials to be bonded. An interposition member for alloy joining, which is made of titanium having a thickness of 200 (μm) or less, and a base material having a pair of opposing surfaces facing each other at the joint interface, and a material having a malleability equal to or higher than that of titanium. An interposer for joining titanium alloy, comprising a metal thin film having corrosion resistance and a thickness of 0.1 (μm) or more, and a coating layer provided on each of the pair of opposing surfaces of the base material. Element. 2. The metal thin film is formed of the titanium alloy α →
The titanium alloy joining member according to claim 1, which has a melting point higher than the β phase transformation temperature. 3. The metal thin film is gold (Au), platinum (P)
The titanium alloy joining member according to claim 1, which is composed of at least one of t) and palladium (Pd). 4. The titanium alloy for joining titanium alloy according to claim 1, wherein the surface roughness of the joining interface of the pair of materials to be joined and the facing surface is 10 (μm) or less in maximum height R _max . Insertion member. 5. A joining method for joining a pair of members to be joined made of a titanium alloy to each other by using the titanium alloy joining member according to claim 1, wherein the pair of members to be joined are joined together. By interposing the titanium alloy joining interposing member at the joining interface of, by pressing the pair of joining interfaces against each other with a predetermined pressure and heating to a predetermined temperature,
A method for joining titanium alloys, wherein the pair of materials to be joined are joined by a solid phase diffusion reaction. 6. The predetermined temperature is α →
The method for joining titanium alloys according to claim 5, wherein the temperature is lower than the β phase transformation temperature by a predetermined value.