KR100787928B1 - Method of joining of ti and dissimilar metal using ag diffusion control layer - Google Patents

Abstract

A method for preventing embrittlement of joints of Ti and dissimilar metal and improving inherent strength of the joints by using an Ag diffusion control layer is provided, wherein the method is usefully used in brazing of the Ti and dissimilar metal by suppressing the generation of an intermetallic compound with high brittleness on the joints, thereby preventing embrittlement of the joints and improving toughness of the joints. A method for preventing embrittlement of joints of Ti and dissimilar metal and improving adhesion of the joints by using an Ag diffusion control layer(B) comprises the steps of: forming an Ag diffusion control layer on a Ti base metal(A1); positioning an insert material between the Ti base metal having the Ag diffusion control layer formed thereon and a dissimilar metal; and heating the Ti base metal and the dissimilar metal to at least a melting temperature of the positioned insert material to bond the Ti base metal and the dissimilar metal. The Ag diffusion control layer is formed by a method selected from the group consisting of coating, deposition and cladding. The insert material is positioned by positioning the dissimilar metal on the insert material after placing the insert material on the Ti base metal having the Ag diffusion control layer formed thereon. The insert material is positioned by coating the insert material on the Ti base metal having the Ag diffusion control layer formed thereon, or on the dissimilar metal.

Description

Method of joining of Ti and dissimilar metal using Ag diffusion control layer}

1 is a state diagram between silver (Ag) and copper (Cu),

2 is a schematic diagram of a method of bonding a titanium base material and a dissimilar metal using a diffusion control layer according to the present invention;

3 is a photograph showing a microstructure of a junction after depositing a silver diffusion control layer on titanium and bonding with copper according to an embodiment of the present invention,

Figure 4 is a photograph showing the microstructure of the junction after bonding with copper without a silver diffusion control layer in accordance with a comparative example of the present invention.

<Short description of the major marks>

A1: titanium base material

A1-1: Titanium with Diffusion Control Layer

A2: copper

B: silver diffusion control layer

C: Insert

D1: heating means

D2: heating means

a: Ti S.S. (Ti-rich)

b: Ti ₂ Cu

c: TiCu

d: Ti ₃ Cu 4

e: TiCu ₂ (or Ti ₂ Cu ₃ )

f: TiCu ₄

g: Ag-rich

f: Cu (Ti, Ag)

i: Cu-rich

α: TiAg

β: Ag

γ: Cu S.S. (Cu-rich)

δ: Ag S.S. (Ag-rich)

The present invention relates to a method of preventing brittleness and bonding strength of titanium and dissimilar metal joints using a silver diffusion control layer.

Current architecture; Structures including transportation equipment such as automobiles, ships, airplanes, and trains; Various piping; And pipes, etc., there are many component parts that require joining between metals or alloys. Most of the welding between the metal and the alloy is a welding method using a high temperature melt bonding.

However, melt bonding and welding have a problem of deteriorating the mechanical properties by changing the structure of the surrounding base material such as grain coarsening due to the high working temperature, and stress corrosion cracking (SCC) due to internal stress formation by high temperature treatment. It is causing a problem. Considering this point, the research on low-temperature solid-state joining technology using a non-melting method that provides sufficient tensile strength and adhesive strength and excellent leak tight characteristics between metals and alloys of such structural parts and is applicable in the field Is actively underway. Brazing technology, one of these solid-state joining technologies, has been actively researched to be applied to new materials such as ceramics and high temperature materials. In terms of stress, a very desirable effect is shown.

However, when joining dissimilar metals and alloys which are not homogeneous by the brazing joining method, there is a problem in that an intermetallic phase between two base material components to be joined is generated at the joint, thereby lowering the toughness of the joint. This is because at the time of brazing bonding, two dissimilar metals or alloying components to be joined into the molten insert are dissolved in large quantities and an intermetallic compound between the two components is produced upon cooling. For example, when hetero-brazing bonding between titanium and copper using a silver-copper-titanium-based insert used for titanium brazing, Ti ₂ Cu, TiCu, Cu ₃ Cu ₄ , Ti ₂ Cu ₃ , TiCu ₂ , Since a titanium-copper intermetallic compound such as TiCu ₄ is formed at the junction, the toughness of the junction is lowered, causing a decrease in strength of the titanium-copper junction.

Accordingly, while the present inventors have studied to suppress the generation of intermetallic compounds during titanium dissimilar metal brazing bonding, the inventors have formed a silver (Ag) diffusion control layer on the titanium base metal to increase brittleness in the joints during titanium dissimilar metal brazing bonding. It was confirmed that the formation of a large intermetallic compound was suppressed to improve the brittleness and the toughness of the joint, and the present invention was completed.

An object of the present invention is to provide a method for preventing brittleness and improving bonding strength of titanium and dissimilar metal joints using a silver diffusion control layer.

In order to achieve the above object, the present invention

Forming a silver diffusion control layer on the titanium base material (step 1);

Placing the insert between the titanium base material and the dissimilar metal on which the silver diffusion control layer is formed in step 1 (step 2); And

It provides a method of preventing brittleness and bonding strength of a titanium heterojunction using a silver diffusion control layer comprising the step (step 3) of joining a titanium base material and a dissimilar metal by heating above the melting temperature of the insert inserted in step 2.

Hereinafter, the present invention will be described in detail.

When the titanium dissimilar metal brazing is bonded using Ag-Cu-Ti, a large amount of titanium and copper, which are the base metals, are dissolved in the molten insert, thereby forming a titanium-copper intermetallic compound at the joint. Thus, when the intermetallic compound is formed at the junction, the toughness of the junction is lowered and fracture occurs at low strength. Therefore, the formation of such an intermetallic compound should be prevented to improve the bonding strength of the joint and prevent brittleness of the joint.

In order to prevent the formation of intermetallic compounds at the joints, at least one of the two base materials to be joined must be prevented from being melted into the molten insert during brazing bonding.

In view of the above, the present invention has devised a method of forming a silver diffusion control layer on the titanium base material to prevent dissolution of titanium into a molten insert, thereby improving the toughness of the joint during brazing bonding. At this time, the silver (Ag) as a diffusion control layer has a research result that the titanium-silver phase generated between the titanium and silver is better than the other intermetallic compound, silver-copper state diagram ( Fig. 1 As shown in), since the complete process reaction generates only silver and copper solid solutions and no other intermetallic compounds, it can have a great effect on the toughness of the joint.

Hereinafter will be described in detail the present invention with reference to a step-by-step.

First, step 1 is a step of forming a silver diffusion control layer (B) in the titanium base material (A1).

In the present invention, the silver diffusion control layer (B) has better toughness than other intermetallic compounds, and when the silver diffusion control layer (B) is formed on the titanium base material (A1), the titanium (A1) is molten inserted. It prevents the melting of ashes and prevents the formation of other intermetallic compounds, which helps to improve the toughness of the joint.

In the present invention, the method for forming the silver diffusion control layer (B) can be used a variety of methods, such as coating, deposition and cladding is not particularly limited.

Next, step 2 is a step of placing the insert (C) between the titanium base material (A1-1) and the dissimilar metal (A2) on which the silver diffusion control layer is formed in step 1.

In the present invention, the insert (C) to be used may be generally used Ag-Cu-Ti-based, the insert (C) may be in the form of powder, ribbon, plate, etc., but is not limited thereto. Do not.

In the present invention, the method of positioning the insert (C) is not particularly limited. For example, after the insert (C) is placed on the titanium base material (A1-1) on which the silver diffusion control layer is formed, the type of the insert (C) is different. Various methods can be used, such as a method of placing the metal A2 thereon, a method of coating the insert C on the titanium base material A1-1 or the dissimilar metal A2 on which the silver diffusion control layer is formed.

Step 3 is a step of bonding the titanium base material (A1) and the dissimilar metal (A2) by heating above the melting temperature of the insert (C) inserted in the step 2.

After inserting the insert (C) between the titanium base material (A1-1) and the copper (A2) on which the silver diffusion control layer is formed, the insert (C) and the ambient temperature are adjusted using the heating means (D1, D2). When heated above the melting temperature of the insert (C) and maintained for a predetermined time, the composition component between the molten insert (C) and the silver diffusion control layer (B) and the dissimilar metal (A2) formed in the titanium (A1-1) Diffusion of alloying elements occurs due to the difference, and thus a strong bonding can be achieved between the insert (C) and titanium (A1-1) and the dissimilar metal (A2). In addition, diffusion of the same principle occurs between the titanium base material A1 and the silver diffusion control layer B, thereby forming a strong bond.

In the method according to the present invention, the bonding temperature is preferably 770 to 960 ° C because the melting point of the insert C is 770 ° C or lower and the melting point of silver, the diffusion control layer B, is 962 ° C.

In this way, since the titanium base material (A1) cannot be dissolved into the molten insert (C) due to the silver diffusion control layer (B), the junction part does not form a titanium-heterometal intermetallic compound. It can prevent brittleness and improve toughness.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only examples of the present invention, and the scope of the present invention is not limited to the following examples.

< Example > Diffusion Control layer  Titanium and Heterogeneous Intermetallic  join

A 100 μm silver diffusion layer was formed on the titanium metal plate having a melting temperature of 1160 ° C. by the sputter coating method. Thereafter, a 100 μm-thick ribbon made of 70% by weight of silver, 28% by weight of copper, and 2% by weight of titanium was inserted between the titanium on which the silver diffusion layer was formed and the copper metal plate having a melting temperature of 1083 ° C., Infrared brazing was performed while heating up at a rate of 100 ° C./min until the temperature became 810 ° C. in an argon atmosphere. The temperature was maintained at 810 ° C. for 6 minutes and then cooled at an average cooling rate of 50 ° C./minute to bond titanium and copper.

< Comparative example > diffusion Control layer  Unused Titanium and Heterogeneous Intermetallic  join

The same process as in Example 1 was performed except that the silver diffusion layer was formed on the titanium metal plate. However, the temperature was maintained for 10 minutes at 810 ℃ when bonding.

< Experimental Example  1> Bonding surface analysis

In order to check the state of the junction of the titanium-dissimilar metal junction bonded by the method according to the present invention was carried out the following experiment.

After microscopic observation of the microstructure of the titanium-copper junctions bonded according to Examples and Comparative Examples, the results are shown in FIGS . 3 and 4 .

3, the the joint portion of the titanium and copper formed in the diffusion control layer above the titanium base material is any of titanium, due to the presence of the diffusion control layer, it was confirmed that no metal-to-metal between the copper compound is not generated, while Figure 4 As shown in the figure, in the absence of a silver diffusion control layer, Ti ₂ Cu (b), TiCu (c), Ti ₃ Cu 4 (d), and TiCu ₂ are joined to the junction. Or Ti ₂ Cu ₃ (e), TiCu ₄ It was confirmed that a titanium-copper intermetallic compound such as (f) was produced.

Accordingly, it can be seen that the method according to the present invention prevents brittleness by inhibiting the production of titanium-heterometal intermetallic compounds.

< Experimental Example  2> tensile test

In order to determine the strength of the titanium-dissimilar metal joint bonded by the method according to the present invention, the following experiment was performed.

The yield strength, tensile strength and elongation of the titanium-copper joints bonded according to the examples and the comparative examples were measured by the tensile test and the results are shown in Table 1.

division Yield strength (MPa) Tensile Strength (MPa) Elongation (%) Example 107 200 27 Comparative example - 54 0

As shown in Table 1, the titanium-copper junction where the silver diffusion control layer was formed according to the present invention had no toughness because the titanium-copper-intermetallic compound was not produced, so that the toughness was improved compared to that without using the silver diffusion control layer. It can be confirmed that it exhibits high strength and elongation.

As described above, the method according to the present invention by forming a silver diffusion control layer on the titanium base material to suppress the formation of highly brittle intermetallic compound at the junction during the brazing of titanium and dissimilar metals to prevent brittleness and improve the toughness of the junction Since it can be used in the brazing of titanium and dissimilar metal can be useful.

Claims (6)

Forming a silver diffusion control layer on the titanium base material (step 1); Placing the insert between the titanium base material and the dissimilar metal on which the silver diffusion control layer is formed in step 1 (step 2); And Method for improving the brittleness and bonding strength of the titanium and dissimilar metal joint using a silver diffusion control layer comprising the step (step 3) of bonding the titanium base material and the dissimilar metal by heating above the melting temperature of the insert inserted in step 2. The method of claim 1, wherein the method for forming the silver diffusion control layer is any one selected from the group consisting of coating, deposition, and cladding. . The method of claim 1, wherein the insertion material is placed on the titanium base material on which the silver diffusion control layer is formed, and then the dissimilar metal is placed thereon. Method for preventing brittleness and improving bonding strength of dissimilar metal joints. The method of claim 1, wherein the insertion material is coated on the titanium base material or the dissimilar metal on which the silver diffusion control layer is formed by placing the insert. How to improve bonding. The method of claim 1, wherein the insert is formed of any one selected from the group consisting of a powder, a ribbon, and a sheet. The method for preventing brittleness and bonding strength of titanium and dissimilar metal joints using a silver diffusion control layer. The method of claim 1, wherein the bonding temperature is 770 ° C. to 960 ° C. The method for preventing brittleness and bonding strength of a titanium and dissimilar metal junction using a silver diffusion control layer.

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