High-strength jointing method for tantalum and copper alloy dissimilar materials and welding assembly

Abstract

The invention provides a high-strength joint method of tantalum and copper alloy and a welding assembly, and relates to the technical field of metal welding. Comprising the steps that a to-be-welded surface of tantalum is subjected to single-direction grinding treatment, and the surface roughness Ra is 0.6-1.3 microns; carrying out concentric circle grinding treatment on the to-be-welded surface of the copper alloy; the treated tantalum to-be-welded surface and the copper alloy to-be-welded surface are directly contacted and combined, and the edge interval between the tantalum and the copper alloy is 0.5-1mm; the assembly is placed in a sheath, and degassing treatment is conducted at the temperature of 450-550 DEG C; and hot isostatic pressing welding is conducted under the conditions that the temperature ranges from 810 DEG C to 860 DEG C and the pressure is not lower than 100 MPa. According to the method, a middle transition layer does not need to be introduced, the tensile strength of an obtained welding joint is not lower than 275 MPa and the shear strength is not lower than 175 MPa by optimizing a grinding mode and welding process parameters, tantalum grains are fine and uniform after welding, and the average grain size is smaller than 55 microns.

Description

Technical Field

[0001] The present invention relates to the technical field of metal welding, and particularly relates to a high-strength joining method for dissimilar materials of tantalum and copper alloy and a welding assembly. Background Art

[0002] Tantalum and its alloys are widely used in the fields of semiconductors, chemical engineering, etc. due to their excellent corrosion resistance and high-temperature performance. Copper alloys have good electrical and thermal conductivity and are commonly used as key functional materials for electronic components. Due to the large differences in the physical and chemical properties of tantalum and copper alloys, the reliable connection of the two materials has always been a technical difficulty in engineering applications.

[0003] At present, the hot isostatic pressing (HIP) welding technology has become an important technical means for connecting tantalum and copper alloys because it can achieve solid-phase diffusion bonding of metal materials under high temperature and high pressure conditions. However, the existing HIP welding processes generally have the following problems: First of all, in order to improve the bonding performance of tantalum and copper alloys, the prior art usually needs to form an intermediate layer between the two surfaces to be welded. The formation of such an intermediate layer requires special processes such as spraying, thermal spraying or electroplating, which not only increases the complexity of the process, but also greatly increases the production cost, and is not conducive to industrial production.

[0004] Secondly, there are many deficiencies in the pretreatment methods of the surfaces to be welded in the prior art. Some technologies use pickling treatment, which involves the use and treatment of hazardous chemicals, increasing the environmental protection treatment cost; some technologies require surface polishing and ultrasonic cleaning, with cumbersome processes and the need to invest in special polishing and cleaning equipment; and some technologies require threading the surface to be welded of tantalum to a depth of 2 mm - 4 mm, greatly increasing the raw material cost.

[0005] In addition, there are also problems with the selection of welding temperature in the prior art. If too low a welding temperature is used, such as described in the Chinese patent with publication number CN101733544A that "the temperature is 8% - 10% of the melting point of copper, aluminum or titanium welded to tantalum", the melting point of copper is 1083 °C, so the disclosed welding temperature is actually 80 °C - 100 °C, and it is difficult to achieve effective welding bonding at this temperature; on the other hand, if too high a welding temperature is used, not only does the copper-zinc alloy undergo liquefaction, but also the tantalum grains are significantly coarsened, which is not conducive to obtaining an ideal microstructure. These factors result in generally low strengths of the welded joints obtained by the prior art, with the highest only reaching about 200 MPa, far from reaching the strength level of the copper alloy base material. Summary of the Invention

[0006] The object of the present invention is to provide a high-strength joining method and a welding assembly for dissimilar materials of tantalum and copper alloy, which can avoid using an intermediate transition layer, simplify the surface treatment process, and obtain higher welding strength by optimizing the welding process parameters, so as to meet the requirements of industrial applications.

[0007] To achieve the above object, the present invention is realized through the following technical solutions: A high-strength joining method for tantalum and copper alloy, comprising the following steps: S1: Grind the surface to be welded of tantalum in a single direction to obtain a surface roughness Ra of 0.6 μm - 1.3 μm; S2: Grind the surface to be welded of copper alloy in a concentric circle to obtain a surface roughness Ra of 0.7 μm - 1.2 μm; S3: Directly contact and combine the treated surface to be welded of tantalum with the surface to be welded of copper alloy, and the edge interval between tantalum and copper alloy is 0.5 - 1 mm; S4: Place the combined component in a shroud, and perform degassing treatment for 3 h - 5 h under the conditions of a temperature of 450°C - 550°C and a vacuum degree higher than 2×10 -3 Pa; S5: Perform hot isostatic pressing welding for 2 h - 4 h at a temperature of 810°C - 860°C under the condition that the pressure is not less than 100 MPa.

[0008] Further: In the step S1, after the grinding treatment of the surface to be welded of tantalum, use a lint-free cloth to dip in an organic solvent and wipe and clean it along the grinding direction, and then use compressed air to dry it; the organic solvent is alcohol.

[0009] Further: In the step S2, before the grinding treatment of the surface to be welded of copper alloy, first use a lint-free cloth to dip in an organic solvent for cleaning and drying; after the grinding treatment, use a lint-free cloth to dip in an organic solvent and wipe and clean it along the grinding direction, and then use compressed air to dry it; the organic solvent is alcohol.

[0010] Further: In the step S3, the combination is carried out within 5 hours after the cleaning of the surface to be welded.

[0011] Further: The purity of the tantalum is higher than 99.995%, wherein Mo ≤ 1 ppm, Nb ≤ 5 ppm, and W ≤ 5 ppm.

[0012] Further: The copper alloy is HSn62-1 copper alloy, wherein the mass percentage content of zinc is 35.7% - 38.1%, the mass percentage content of copper is 61% - 63%, and the mass percentage content of tin is 0.7% - 1.1%.

[0013] Further: in the step S5, the tensile strength of the joint obtained after welding is not less than 275 MPa, and the shear strength is not less than 175 MPa.

[0014] The present invention also provides a welded component of tantalum and copper alloy prepared by the above method, and the component includes: A tantalum substrate, the welding surface of the tantalum substrate has grinding lines in a single direction, and the surface roughness Ra is 0.6 μm - 1.3 μm; A copper alloy substrate, the welding surface of the copper alloy substrate has concentric circular grinding lines, and the surface roughness Ra is 0.7 μm - 1.2 μm; The tantalum substrate and the copper alloy substrate are directly welded and connected through the welding surface.

[0015] Further: the purity of the tantalum substrate is higher than 99.995%, wherein Mo ≤ 1 ppm, Nb ≤ 5 ppm, and W ≤ 5 ppm.

[0016] Further: the copper alloy substrate is HSn62-1 copper alloy, wherein the mass percentage content of zinc is 35.7% - 38.1%, the mass percentage content of copper is 61% - 63%, and the mass percentage content of tin is 0.7% - 1.1%.

[0017] Further: the tensile strength of the welded joint of the welded component is not less than 275 MPa, and the shear strength is not less than 175 MPa.

[0018] Further: after welding, the tantalum grains on the welding surface of the tantalum substrate are fine and uniform, and the average grain size is less than 55 μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects: First, the present invention adopts a unique surface treatment method, that is, the tantalum surface to be welded is ground in a single direction to obtain a surface roughness of 0.6 μm - 1.3 μm, and the copper alloy surface to be welded is ground with concentric circles to obtain a surface roughness of 0.7 μm - 1.2 μm, and direct welding of tantalum and copper alloy can be realized without introducing an intermediate transition layer. Under the optimized HIP welding parameters (810 - 860 °C, pressure ≥ 100 MPa, holding for 2 - 4 h), the tensile strength of the obtained welded joint can reach 298 MPa (average value), and the highest can reach 318 MPa; the shear strength can reach 200 MPa (average value), and the highest can reach 228 MPa, far exceeding the joint strength level of 100 - 200 MPa in the prior art.

[0020] Second, the present invention uses a simple mechanical grinding method to replace the complex processes such as spraying, thermal spraying, and electroplating required in the prior art, omits the process of preparing the intermediate transition layer, and simplifies the production process flow. At the same time, the use of dangerous chemicals such as pickling is avoided, and there is no need to invest in spraying equipment and polishing equipment, significantly reducing the production cost and achieving a more environmentally friendly production method.

[0021] Third, the HIP welding temperature window (810 - 860 °C) selected in the present invention is both higher than the low-temperature region (500 - 650 °C) where effective welding is difficult to achieve and lower than the high-temperature region (>900 °C) that causes the tantalum grains to become coarse. At the same time, it avoids the phase transition temperature of the copper-zinc alloy (above 890 °C), ensuring the welding quality while obtaining a fine and uniform tantalum grain structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow chart of the method for high-strength bonding of tantalum and copper alloy in an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a tantalum and copper alloy welding assembly prepared by applying the method for high-strength bonding of tantalum and copper alloy in an embodiment of the present invention; Figure 3 It is a surface effect diagram after single-direction grinding and cleaning treatment of the tantalum surface to be welded; Figure 4 It is a surface effect diagram after circumferential grinding and cleaning treatment of the copper alloy surface to be welded; Figure 5 It is a schematic example diagram after combining the tantalum surface to be welded and the copper alloy surface to be welded; Figure 6 It is a schematic example diagram after vacuum packaging of the assembly to be welded; Figure 7 It is a schematic diagram of the cladding and degassing structure; Figure 8 It is a curve graph for setting HIP welding process parameters; Figure 9 It is a schematic diagram for confirming non-bonding of tantalum and copper alloy at 500 °C in Comparative Example 1; Figure 10 It is a schematic diagram for confirming non-bonding of tantalum and the intermediate layer titanium at 650 °C in Comparative Example 2; Figure 11 It is a diagram of the sampling positions for the bonding strength in Comparative Example 4; Figure 12 It is a curve graph for tensile strength detection in Comparative Example 4; Figure 13 It is a curve graph for shear strength detection in Comparative Example 4; Figure 14 It is a diagram of the tantalum grain morphology under the welding condition of 500 °C; Figure 15It is a tantalum grain morphology diagram under the welding condition of 650°C; Figure 16 It is a tantalum grain morphology diagram under the welding condition of 830°C; Figure 17 It is a tantalum grain morphology diagram under the welding condition of 880°C; Figure 18 It is a diagram of the pre-welding state of tantalum grains under the welding condition of 830°C; Figure 19 It is a diagram of the post-welding state of tantalum grains under the welding condition of 830°C; In the figure: 1. Copper alloy matrix; 2. Tantalum matrix; 3. Sleeve body; 4. Steel sheet; 5. Degassing port. Specific implementation manners

[0023] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0025] In one embodiment, the method for high-strength bonding of tantalum and copper alloy of the present invention is as Figure 1 shown, and the specific implementation steps are as follows: S1: Grind the surface to be welded of tantalum in a single direction to obtain a surface roughness Ra of 0.6 μm - 1.3 μm; Specifically, use a target grinder to grind the tantalum surface in a single direction, as Figure 3 shown, to obtain regular unidirectional grinding lines, and control the surface roughness Ra within the range of 0.6 μm - 1.3 μm after grinding. After the grinding treatment, use a lint-free cloth dipped in alcohol to wipe and clean along the direction of the grinding lines until the lint-free cloth does not change color, and then use compressed air to dry for standby.

[0026] S2: Grind the surface to be welded of the copper alloy in a concentric circle to obtain a surface roughness Ra of 0.7 μm - 1.2 μm; Specifically, first, dip a lint-free cloth in alcohol for preliminary cleaning and then dry it. Then use a scouring pad to perform grinding treatment along the circumferential direction, as Figure 4 shown to obtain concentric circular grinding lines. After grinding, the surface roughness Ra is controlled within the range of 0.7μm - 1.2μm. After grinding is completed, also use a lint-free cloth to dip in alcohol and wipe and clean along the grinding direction until the lint-free cloth does not change color, and finally dry it with compressed air for standby.

[0027] S3: Directly contact and combine the processed tantalum surface to be welded with the copper alloy surface to be welded, and the edge interval between tantalum and copper alloy is 0.5 - 1mm; Specifically, directly stack and combine the processed tantalum surface to be welded with the copper alloy surface to be welded, as Figure 5 shown. The edge interval between the two is controlled within 0.5μm - 1mm. It should be noted that after the surface to be welded is cleaned, the combination should be completed within 5 hours to prevent the surface from being contaminated. The combined parts can be vacuum-packed first, as Figure 6 shown, but this step can be omitted if subsequent degassing treatment can be directly carried out.

[0028] S4: Place the combined parts in a jacket, and carry out degassing treatment for 3h - 5h under the condition that the temperature is 450℃ - 550℃ and the vacuum degree is higher than 2×10 -3 Pa; Specifically, load the combined parts into a jacket made of low-carbon steel, as Figure 7 shown. The jacket includes a sleeve body 3, a degassing port 5 provided on the sleeve body 3, and a stainless steel sheet 4 laid on the combined installation side of tantalum and copper alloy. The material of the sleeve body 3 is carbon steel. Under the condition that the temperature is 450℃ - 550℃ and the vacuum degree is higher than 2×10 -3 Pa, carry out degassing treatment for 3 - 5 hours through the degassing port 5. After degassing is completed, seal the parts to be welded in the jacket by welding, and keep the vacuum degree in the jacket higher than 2×10 -3 Pa.

[0029] S5: Carry out hot isostatic pressing welding for 2h - 4h under the condition that the temperature is 810℃ - 860℃ and the pressure is not lower than 100MPa.

[0030] Specifically, place the sealed jacket assembly in a hot isostatic pressing furnace for welding. As Figure 8 shown in the process curve, at a temperature of 810℃ - 860℃, apply a pressure not lower than 100MPa and keep it for 2 - 4 hours. After welding is completed, cool it in the furnace to below 100℃ and then take it out. Finally, remove the external jacket by machining to obtain the welded assembly of tantalum and copper alloy.

[0031] In another embodiment, before step S1, it further includes: selecting tantalum and copper alloy raw materials. Preferably, tantalum materials with a purity higher than 99.995% are used, and the content of main impurity elements meets the requirements of Mo ≤ 1 ppm, Nb ≤ 5 ppm, and W ≤ 5 ppm. The copper alloy is preferably HSn62-1 copper alloy, and its main components by mass percentage are: zinc 35.7% - 38.1%, copper 61% - 63%, and tin 0.7% - 1.1%.

[0032] The present invention also conducted multiple groups of comparative experiments and comparative example verifications: Comparative Example 1: Using the above process, HIP welding was carried out at 500 °C. The results showed that effective welding between tantalum and HSn62-1 alloy could not be achieved, and the two directly separated after removing the cladding, as Figure 9 shown.

[0033] Comparative Example 2: A 2-mm-thick pure titanium transition layer was added between tantalum and HSn62-1 alloy, and HIP welding was carried out at 650 °C. Although welding between titanium and copper alloy was achieved, bonding between tantalum and titanium could not be achieved, as Figure 10 shown.

[0034] Comparative Example 3: Using the direct welding method, HIP welding was carried out at 650 °C, and the average tensile strength of the obtained joints was 226 MPa.

[0035] Comparative Example 4: According to the optimal process parameters of the present invention, HIP welding was carried out at 830 °C. Strength test sampling was carried out as Figure 11 shown, a total of 9 samples were taken, and the obtained welded joint performance was excellent: the average tensile strength reached 298 MPa, and the maximum could reach 318 MPa; the average shear strength was 200 MPa, and the maximum could reach 228 MPa. The specific test data are shown in Table 1.

[0036] Table 1. Strength of welded joints obtained according to Comparative Example 4

[0037] The stress-strain curves and fracture morphologies of the tensile and shear strengths are respectively as Figure 12 , 13 shown. The fracture position of all specimens was located on the side of the weld near the copper alloy.

[0038] It should be particularly noted that the welding temperature range of 810 °C - 860 °C determined by the present invention is the best process window verified through experiments. Within this temperature range, the tantalum grain structure remains stable and no significant changes occur. The following microstructural comparison diagrams Figures 14 - 17 confirm this conclusion: Figure 14 shows the tantalum grain morphology under welding conditions of 500 °C, Figure 15shows the tantalum grain morphology under welding conditions of 650 °C, Figure 16 shows the tantalum grain morphology under welding conditions of 830 °C. Comparative analysis shows that although the welding temperature is increased from 500 °C to 830 °C, the grain size, morphology and microstructure of tantalum do not show obvious degradation characteristics and maintain a good tissue state.

[0039] In contrast, Figure 17 shows the tantalum grain morphology under welding conditions of 880 °C. At this time, it can be clearly observed that the tantalum grain size increases significantly, the grain boundary morphology changes, and the microstructure characteristics are significantly degraded. This phenomenon indicates that when the welding temperature exceeds 860 °C, the tantalum material begins to show grain coarsening, verifying the rationality of the temperature upper limit determined by the present invention.

[0040] To further prove the scientificity of the temperature parameters of the present invention, Figure 18 and Figure 19 respectively show the comparison states of tantalum grains before and after welding under welding conditions of 830 °C. Comparative analysis of the two figures shows that after a complete hot isostatic pressing welding process at 830 °C, the tantalum grain characteristics are highly consistent compared with those before welding. After welding, the tantalum grains on the welding surface of the tantalum matrix are fine and uniform, and the average grain size is less than 55 μm, and no microstructural changes that are unfavorable to the material properties are generated.

[0041] The above results of microstructure analysis fully prove that the temperature range of 810 °C - 860 °C determined by the present invention can not only effectively promote the diffusion connection of the interface between tantalum and copper alloy, but also avoid the significant coarsening of tantalum grains, which is the key process parameter for achieving high-strength bonding. This temperature parameter is determined based on rigorous experimental research and has reliable repeatability and stability in practical engineering applications.

[0042] In another embodiment, the present invention also provides a welded component of tantalum and copper alloy prepared by the above method. As Figure 2 shown, the welded component of tantalum and copper alloy prepared by the above method includes a tantalum matrix 2 and a copper alloy matrix 1, which are directly connected together through a welding surface. Among them, the welding surface of the tantalum matrix 2 has grinding lines in a single direction, and the surface roughness Ra is 0.6 μm - 1.3 μm; the welding surface of the copper alloy matrix 1 has concentric circular grinding lines, and the surface roughness Ra is 0.7 μm - 1.2 μm. The purity of the tantalum matrix 2 is higher than 99.995%, and the contents of main impurity elements meet the requirements of Mo ≤ 1 ppm, Nb ≤ 5 ppm, and W ≤ 5 ppm; the copper alloy matrix 1 uses HSn62-1 copper alloy, and its main components by mass percentage are: zinc 35.7% - 38.1%, copper 61% - 63%, and tin 0.7% - 1.1%.

[0043] The welded component prepared by the above method has excellent performance of the welded joint, with a tensile strength of not less than 275 MPa and a shear strength of not less than 175 MPa. As Figure 12 and Figure 13 shown, during the tensile and shear strength tests, the specimens all fractured on the side of the weld near the copper alloy, indicating that the welded joint has good mechanical properties. While meeting the usage requirements, the overall structure of the welded component is simpler and more compact due to the omission of the intermediate transition layer, which is beneficial for saving space in practical applications. This high-strength direct welding structure makes the component particularly suitable for application scenarios with high requirements for both joint strength and structural compactness.

[0044] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-strength bonding method for tantalum and copper alloy, characterized in that: The following steps are involved: S1: The surface of the tantalum to be welded is ground in a single direction to obtain a surface roughness Ra of 0.6μm-1.3μm; S2: The surface of the copper alloy to be welded is subjected to concentric grinding to obtain a surface roughness Ra of 0.7 μm-1.2 μm; S3: directly contact and assemble the treated tantalum surface to be welded with the copper alloy surface to be welded, with the edge spacing between the tantalum and the copper alloy being 0.5 mm to 1 mm; S4: placing the assembly in a package at a temperature of 450°C-550°C with a vacuum degree higher than 2×10 -3 Degassing treatment was performed for 3h-5h under Pa conditions; S5: Hot isostatic pressing welding is performed for 2h-4h at a temperature of 810-860℃ and a pressure of not less than 100MPa.

2. The high-strength bonding method of tantalum and copper alloy according to claim 1, characterized in that: In the step S1, after the surface of the tantalum to be welded is ground, a dust-free cloth is dipped in an organic solvent to wipe and clean it along the grinding direction, and then compressed air is used to blow it dry; the organic solvent is alcohol.

3. The high-strength bonding method of tantalum and copper alloy according to claim 1, characterized in that: In the step S2, before the surface of the copper alloy to be welded is ground, it is first cleaned with a dust-free cloth dipped in an organic solvent and then blown dry; After the grinding process, wipe and clean the surface with a dust-free cloth dipped in an organic solvent in the grinding direction, and then blow dry with compressed air; the organic solvent is alcohol.

4. The high-strength bonding method of tantalum and copper alloy according to claim 1, characterized in that: In step S3, the welding surface is assembled within 5 hours after being cleaned.

5. The high-strength bonding method of tantalum and copper alloy according to claim 1, characterized in that: The purity of the tantalum is higher than 99.995%, wherein Mo≤1ppm, Nb≤5ppm, and W≤5ppm.

6. The high-strength bonding method of tantalum and copper alloy according to claim 1, characterized in that: The copper alloy is HSn62-1 copper alloy, in which the mass percentage of zinc is 35.7%-38.1%, the mass percentage of copper is 61%-63%, and the mass percentage of tin is 0.7%-1.1%.

7. A high-strength bonding method for tantalum and copper alloy according to any one of claims 1 to 6, characterized in that: In step S5, the tensile strength of the joint obtained after welding is not less than 275 MPa, and the shear strength is not less than 175 MPa.

8. A tantalum and copper alloy welding assembly prepared by the method according to any one of claims 1 to 7, characterized in that: The components include: A tantalum substrate, wherein the welding surface of the tantalum substrate has a grinding pattern in a single direction, and the surface roughness Ra is 0.6 μm-1.3 μm; the purity of the tantalum substrate is higher than 99.995%, wherein Mo≤1ppm, Nb≤5ppm, and W≤5ppm; A copper alloy substrate, wherein the welding surface of the copper alloy substrate has concentric grinding lines, and the surface roughness Ra is 0.7 μm-1.2 μm; the copper alloy substrate is HSn62-1 copper alloy, wherein the mass percentage of zinc is 35.7%-38.1%, the mass percentage of copper is 61%-63%, and the mass percentage of tin is 0.7%-1.1%; The tantalum substrate and the copper alloy substrate are directly connected by welding through the welding surface.

9. The tantalum and copper alloy welding assembly according to claim 8, characterized in that: The tensile strength of the welded joint of the welded assembly is not less than 275 MPa, and the shear strength is not less than 175 MPa.

10. The tantalum and copper alloy welding assembly according to claim 9, characterized in that: After welding, the tantalum grains on the welding surface of the tantalum matrix are small and uniform, and the average grain size is less than 55μm.

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