Method for brazing TC4 and GH4169 dissimilar metal through copper foil

Abstract

The invention provides a method for brazing TC4 and GH4169 dissimilar metals by using a copper foil, which comprises the following steps of: using the copper foil as a brazing filler metal, forming a sandwich structure by using a base metal and the copper foil, placing the sandwich structure in a vacuum furnace, vacuumizing until the vacuum degree is 5.0 * 10 <-3 > Pa, heating to 300 DEG C at the rate of 15 DEG C / min, and keeping the temperature for 30 minutes, so that a quick-drying adhesive is fully volatilized, thereby obtaining the TC4 and GH4169 dissimilar metals. Continuously raising the temperature to 800 DEG C at the rate of 15 DEG C / min, and preserving heat for 10 minutes, so that the temperature in the furnace and the temperature of the to-be-welded sample are uniform; and continuously heating to the brazing temperature of 920-1000 DEG C at the rate of 15 DEG C / min, preserving heat for 30 minutes, finishing heating, cooling to 500 DEG C at the rate of 10 DEG C / min, and cooling to room temperature along with the furnace, thereby finishing the connection of TC4 and GH4169. The copper foil is used as the brazing filler metal, and the brazing filler metal is convenient in source and lower in cost. And meanwhile, generation of Ti-Ni intermetallic compounds between TC4 and GH4169 dissimilar metals can be reduced, the brittleness problem of a brazed joint can be solved, and the strength of the joint brazed through Ni-based brazing filler metal and Ti-based brazing filler metal is achieved.

Description

Technical Field

[0001] The invention relates to the field of brazing between dissimilar metals, in particular to a method for brazing dissimilar metals TC4 and GH4169 by using copper foil. Background Art

[0002] The composition of titanium alloy TC4 material is Ti-6Al-4V, which belongs to (α+β) type titanium alloy, with low density, high specific strength and good comprehensive mechanical properties. GH4169 is a precipitation-strengthened nickel-based high-temperature alloy, which has good comprehensive properties in the temperature range of -253 to 650℃, and the yield strength below 650℃ ranks first among deformed high-temperature alloys, and has good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good processing performance and welding performance.

[0003] TC4 and GH4169 are both important structural metals, widely used in aerospace, industry, medical and other fields. In particular, their outstanding high-temperature performance makes them widely used in engines, missiles, fuselages and other parts. In recent years, in order to meet the development trend of lightweight, high performance and low cost, TC4 and GH4169 are connected to solve the problems of weight reduction and high temperature adaptability. However, due to the large difference in chemical composition and thermal expansion coefficients of TC4 and GH4169 dissimilar metals, it is very easy to form a relatively brittle Ti-Ni intermetallic compound between the two alloys, which induces cracks in the connection area.

[0004] The main methods of connection between TC4 and GH4169 are brazing, laser welding, diffusion welding, friction welding, etc. Brazing has less welding stress than melting welding because the base material does not melt. At the same time, by improving parameters such as the brazing material composition ratio and welding temperature, the formation of intermetallic compounds can be reduced, thereby achieving a more effective connection between TC4 and GH4169 dissimilar metals. At present, the commonly used brazing materials for brazing dissimilar metals between TC4 and GH4169 are Ni-based and Ti-based brazing materials, but the above two brazing materials cannot completely solve the impact of Ti-Ni intermetallic compounds, and the brazing material preparation process is complicated.

[0005] Therefore, how to use a fast and low-cost method to connect TC4 and GH4169 dissimilar metals is a key technology that needs to be broken through. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a method for brazing TC4 and GH4169 dissimilar metals using copper foil, using copper foil as brazing filler metal, which is convenient to source and has lower cost. At the same time, the generation of Ti-Ni intermetallic compounds between TC4 and GH4169 dissimilar metals can be reduced, the brittleness problem of TC4 and GH4169 brazed joints can be improved, and the joint strength of brazing using Ni-based brazing filler metal and Ti-based brazing filler metal can be achieved.

[0007] In order to achieve the above object, the specific scheme adopted by the present invention is: A method for brazing TC4 and GH4169 dissimilar metals using copper foil mainly comprises the following steps: S1. Pre-treat TC4 base material, GH4169 base material and copper foil respectively; S2. Place the copper foil between the TC4 base material and the GH4169 base material, and use a quick-drying adhesive to glue the base material and the copper foil together to form a sample to be welded; S3. Place the graphite block on the sample to be welded to keep the base material and copper foil in close contact. Place the whole in a vacuum furnace and evacuate to a vacuum degree of 5.0×10 -3 Pa, then heat up to 300℃ at a rate of 15℃ / min and keep warm for 30min to make the quick-drying adhesive fully volatilize, continue to heat up to 800℃ at a rate of 15℃ / min and keep warm for 10min to make the temperature in the furnace and the temperature of the sample to be welded uniform; continue to heat up to the brazing temperature of 920℃~1000℃ at a rate of 15℃ / min and keep warm for 30min, end heating, cool down to 500℃ at a rate of 10℃ / min, and then cool to room temperature with the furnace, thus completing the connection between TC4 and GH4169.

[0008] The present invention limits the brazing temperature to 920°C to 1000°C, which can fully diffuse the copper foil and increase the joint strength. If the brazing temperature is too low, the joint interface will not diffuse sufficiently and cracks will easily form. If the brazing temperature is too high, too many brittle intermetallic compounds will easily form at the joint interface, resulting in a decrease in joint strength.

[0009] Furthermore, in step S1, the TC4 base material is a rolled plate with a thickness of 5 mm.

[0010] Furthermore, in step S1, the GH4169 base material is a rolled plate with a thickness of 5 mm.

[0011] Furthermore, the copper foil adopts a 10 μm thick pure copper foil. The copper foil acts as an intermediate layer to participate in the diffusion between the base materials. The thickness should not be too large. The greater the thickness, the worse the brazing effect.

[0012] Furthermore, in step S1, the TC4 base material and the GH4169 base material are cut into required sizes using electric spark wire cutting, and then the surfaces to be welded of the two base materials are polished step by step with 400 mesh, 600 mesh and 1000 mesh sandpaper to remove rough scratches and impurity layers on the surface. Finally, the two base materials are ultrasonically cleaned in anhydrous ethanol to remove impurities on the surface, and then dried with a hair dryer for standby use.

[0013] Furthermore, in step S1, the copper foil is placed in anhydrous ethanol for ultrasonic cleaning to remove impurities on the surface.

[0014] Furthermore, in step S3, the brazing temperature is 940°C.

[0015] Beneficial effects:

[0016] Ti-Ni is very easy to form brittle phase intermetallic compounds such as Ti2Ni. The present invention adds copper foil between Ti and Ni to reduce the formation of brittle intermediate phase Ti2Ni. The present invention successfully connects TC4 and GH4169 dissimilar metals by brazing with copper foil at normal pressure and high temperature. The joint connection strength through Cu contact reaction brazing is high. When the brazing condition is kept at 940°C for 30 minutes, the room temperature shear strength can reach 174.1MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the microstructure diagram of the brazed joint obtained in Example 1.

[0018] Figure 2 This is the port morphology of the brazed joint obtained in Example 1. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] Example 1

[0021] This embodiment discloses a method for brazing TC4 and GH4169 dissimilar metals using copper foil, which is specifically carried out in the following steps: 1. Prepare materials: Use electric spark wire cutting to cut the base materials TC4 and GH4169 into sizes of 15mm*10mm*5mm and Φ5mm*5mm respectively, and then polish the surfaces to be welded of the two base materials with 400 mesh, 600 mesh and 1000 mesh sandpaper in turn to remove the oxide layer and rough scratches on the surface of the base materials; the middle layer uses 0.01mm thick pure copper foil, and uses scissors to cut the copper foil into 7mm*7mm sheets; 2. Material pretreatment: Place the above-mentioned base material and copper foil in anhydrous ethanol and perform ultrasonic cleaning for 15 minutes to remove impurities on the surface, and finally blow dry with a hair dryer for standby use; 3. Sample loading: The cleaned base material TC4, copper foil, and GH4169 in step 2 are sequentially arranged in a sandwich structure in the vertical direction, and the base material and copper foil are fixed together with a quick-drying adhesive, and a graphite block is placed on the sandwich structure to keep the base material and copper foil in close contact; the whole is placed in a vacuum furnace; 4. Brazing: vacuum furnace is evacuated to 5.0×10 -3 Pa, and then heat up to 300℃ at a rate of 15℃ / min and keep it warm for 30min to fully volatilize the quick-drying adhesive; continue to heat up to 800℃ at a rate of 15℃ / min and keep it warm for 10min to make the temperature in the furnace and the sample temperature uniform; continue to heat up to 940℃ brazing temperature at a rate of 15℃ / min and keep it warm for 30min; V. Cooling: After the heating in step 4 is completed, cool down to 500℃ at a rate of 10℃ / min to avoid brittle cracking of the joint due to too fast cooling rate; finally cool to room temperature with the furnace to obtain TC4 / 0.01mmCu foil / GH4169 brazing joint.

[0022] The microstructure of the brazed joint in this embodiment is as follows: Figure 1 As shown, the fracture morphology is Figure 2 As shown. Figure 1 and Figure 2 It can be seen that the method of brazing TC4 and GH4169 dissimilar metals with copper foil of the present invention has achieved successful connection.

[0023] Example 2

[0024] The difference between Example 2 and Example 1 is that in step 4, the brazing temperature is 920°C.

[0025] Example 3

[0026] The difference between Example 3 and Example 1 is that in step 4, the brazing temperature is 960°C.

[0027] Example 4

[0028] The difference between Example 4 and Example 1 is that in step 4, the brazing temperature is 980°C.

[0029] Example 5

[0030] The difference between Example 5 and Example 1 is that in step 4, the brazing temperature is 1000°C.

[0031] Comparative Example 1

[0032] The difference between Comparative Example 1 and Example 1 is that in steps 1 to 3, the copper foil is replaced with a 0.01 mm thick copper foil and a 0.05 mm thick titanium foil.

[0033] Comparative Example 2

[0034] The difference between Comparative Example 1 and Example 1 is that in step 1, the middle layer is made of pure copper foil with a thickness of 0.05 mm.

[0035] After the test, the mechanical properties of the brazed joints obtained in Examples 1-5 and Comparative Examples 1-2 were evaluated using tensile shear strength. The results are shown in Table 1 below.

[0036] Table 1 Shear strength of brazed joints obtained in Examples 1-5 and Comparative Examples 1-2 Shear strength / MPa Example 1 174.1 Example 2 131.46 Example 3 150.38 Example 4 143.47 Example 5 129.98 Comparative Example 1 21.05 Comparative Example 2 182.47

[0037] As can be seen from Table 1, the shear strength of the brazed joints obtained by the brazing method of the present invention exceeds 120 MPa, especially when the brazing temperature is kept at 940° C. for 30 minutes, the highest shear strength of the brazed joint is 174.1 MPa.

[0038] In Comparative Example 1, after brazing with 0.01 mm copper foil and 0.05 mm titanium foil as brazing materials in the middle layer, the shear strength of the obtained joint is very low. The applicant speculates that the reason is: the titanium content is high and the copper content is low, and the titanium in TC4 and the middle layer reacts less with the copper to generate Ti (Ni, Cu) intermetallic compounds, which react with the nickel in the GH4169 base material to generate a large amount of brittle intermetallic compounds such as Ti2Ni and TiNi, so the shear strength is very low. Comparative Example 2 uses 0.05 mm copper foil. Compared with the 0.01 mm thick copper foil used in Example 1, the copper foil thickness is much increased, and the cost is significantly increased, but the difference in shear strength is not very large, which shows the feasibility of the brazing method of the present invention, and shows that the method is low in cost and has a good brazing effect.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any equivalent changes or modifications made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for brazing TC4 and GH4169 dissimilar metals using copper foil, characterized in that: The main steps are as follows: S1. Pre-treat TC4 base material, GH4169 base material and copper foil respectively; S2. Place the copper foil between the TC4 base material and the GH4169 base material, and use a quick-drying adhesive to glue the base material and the copper foil together to form a sample to be welded; S3. Place the graphite block on the sample to be welded to keep the base material and copper foil in close contact. Place the whole in a vacuum furnace and evacuate to a vacuum degree of 5.0×10 -3 Pa, then heat up to 300℃ at a rate of 15℃ / min and keep warm for 30min to make the quick-drying adhesive fully volatilize, continue to heat up to 800℃ at a rate of 15℃ / min and keep warm for 10min to make the temperature in the furnace and the temperature of the sample to be welded uniform; continue to heat up to the brazing temperature of 920℃~1000℃ at a rate of 15℃ / min and keep warm for 30min, end heating, cool down to 500℃ at a rate of 10℃ / min, and then cool to room temperature with the furnace, thus completing the connection between TC4 and GH4169.

2. The method for brazing dissimilar metals of TC4 and GH4169 using copper foil according to claim 1, characterized in that: In step S1, the TC4 base material is a rolled plate with a thickness of 5 mm.

3. The method for brazing dissimilar metals of TC4 and GH4169 using copper foil according to claim 1, characterized in that: In step S1, the GH4169 base material is a rolled plate with a thickness of 5 mm.

4. The method for brazing dissimilar metals of TC4 and GH4169 using copper foil according to claim 1, characterized in that: In step S1, the copper foil is a pure copper foil with a thickness of 0.01 mm.

5. The method for brazing TC4 and GH4169 dissimilar metals using copper foil according to claim 1, characterized in that: In step S1, the TC4 base material and the GH4169 base material are cut into the required size by wire electric discharge cutting, and then the surfaces to be welded of the two base materials are polished step by step with 400 mesh, 600 mesh and 1000 mesh sandpaper to remove the rough scratches and impurity layers on the surface. Finally, the two base materials are ultrasonically cleaned in anhydrous ethanol to remove impurities on the surface, and then dried with a hair dryer for standby use.

6. The method for brazing TC4 and GH4169 dissimilar metals using copper foil according to claim 1, characterized in that: In step S1, the copper foil is placed in anhydrous ethanol for ultrasonic cleaning to remove impurities on the surface.

7. The method for brazing dissimilar metals of TC4 and GH4169 using copper foil according to claim 1, characterized in that: In step S3, the brazing temperature is 940°C.

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