Welding method for tungsten-based and copper-based dissimilar metal materials

Abstract

The invention belongs to the technical field of dissimilar metal welding, and particularly relates to a welding method for tungsten-based and copper-based dissimilar metal materials. According to the method, the middle layer is added before welding, the middle layer takes titanium (Ti) as a base body and is supplemented with elements such as Al, V and Fe, the physical performance differences (such as the linear expansion coefficient and the melting point) of tungsten and the chromium-zirconium-copper alloy can be effectively coordinated, and cracks, generated due to thermal stress, of a welding interface are reduced; by adding Al and V, an active intermediate phase can be formed, the atomic diffusion rate is increased, the welding time is shortened, and meanwhile the uniformity of interface metallurgical bonding is improved; oxygen content (O is less than 0.2%) and low carbon (C is 0.07-0.11%) are strictly controlled, so that formation of oxides and carbides in the welding process is avoided, and interface purity is ensured; the titanium-based alloy is excellent in high-temperature resistance, the structure can still be kept stable under the diffusion welding condition of 880-900 DEG C, and melting-through or deformation of the middle layer is prevented.

Description

Technical Field

[0001] The present invention belongs to the technical field of dissimilar metal welding, and particularly relates to a welding method for tungsten-based and copper-based dissimilar metal materials. Background Art

[0002] The advantage of tungsten as a high-temperature resistant material lies in its melting point as high as 3410 °C and excellent corrosion resistance, so it has special applications in the fields of aerospace, energy, and electronics, such as being used as the lining of fuel nozzles and the anode of vacuum electronic devices. Copper-chromium-zirconium alloy is often selected as a heat dissipation material due to its high thermal conductivity characteristics. Connecting tungsten and copper can not only maintain high-temperature resistance but also enhance heat dissipation efficiency.

[0003] However, the connection of the above heterogeneous materials faces double challenges: First, the significant differences in mechanical and physical properties between the two will cause serious residual stresses inside the joint, thus triggering the risk of fracture during the cooling process; Second, due to the large difference in melting points, it is impossible to directly form a metallurgical bond, and traditional diffusion bonding methods are difficult to apply.

[0004] In view of this, the inventor expects to design a new welding method suitable for welding tungsten-based and copper-based dissimilar metal materials. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above problems existing in the traditional technology and provide a welding method for tungsten-based and copper-based dissimilar metal materials.

[0006] To achieve the above technical purpose and reach the above technical effect, the present invention is realized through the following technical solutions:

[0007] The present invention provides a welding method for tungsten-based and copper-based dissimilar metal materials, including the following steps:

[0008] S1. Gradually grind and polish the tungsten base material and the chromium-zirconium copper base material with sandpaper, and perform ultrasonic cleaning to ensure the cleanliness of the surface of the base material;

[0009] S2. Prepare an intermediate layer, and the material of the intermediate layer is composed of the following components in mass percentage: Al: 5.5 - 6.75%, V: 3.5 - 4.5%, Fe: 0.3 - 0.4%, C: 0.07 - 0.11%, O < 0.2%, and Ti is the balance;

[0010] S3. Place the parts to be welded of the tungsten base material and the chromium-zirconium copper base material on both sides of the intermediate layer respectively, and use a pressing die to lock the positions of the three and press them to the set pressure;

[0011] S4. Use a vacuum melting furnace to perform vacuum diffusion welding on the overlapping base materials, with a welding current of 380 - 400 A, a heating time of 30 - 35 min, and a heating temperature of 880 - 900 °C;

[0012] S5. Grind and process the weld surface until it is flush with the base metal surface.

[0013] Further, in step S1, the tungsten base metal is pure tungsten, and the chromium zirconium copper base metal is a chromium zirconium copper alloy.

[0014] Further, in step S1, the sheet specifications of the tungsten base metal and the chromium zirconium copper base metal are 50 mm × 15 mm × 1.5 mm.

[0015] Further, in step S1, the surface of the base metal is successively polished with #240, #400, #800, #1000, and #1500 sandpapers, and then surface polishing treatment is carried out with diamond paste on a polishing cloth; finally, the base metal is ultrasonically cleaned successively with ethanol and deionized water.

[0016] Further, in step S2, the material of the intermediate layer is composed of the following components by mass percentage: Al: 6.25%, V: 3.9%, Fe: 0.35%, C: 0.08%, O < 0.2%, and Ti is the balance.

[0017] Further, in step S2, the sheet specification size of the intermediate layer is 20 mm × 15 mm × 0.05 mm.

[0018] Further, in step S3, the pressure die includes two cover plates and four groups of bolts. Each cover plate is provided with four mounting holes for facilitating the installation of bolts. The two cover plates can clamp and apply pressure to the stacked tungsten base metal - intermediate layer - chromium zirconium copper base metal under the locking and pushing of the bolts. The cover plates are made of H13 die steel, and their specification size is 55 mm × 55 mm × 8 mm; the bolts are composed of 310S screws and 310S nuts.

[0019] Further, in step S4, the specific operating steps for vacuum diffusion welding with a vacuum melting furnace are as follows:

[0020] 1) Open the mechanical pump and the roughing valve, extract gas, and observe the air pressure display;

[0021] 2) When the air pressure is less than 10 Pa, open the lower valve;

[0022] 3) After the air pressure display is lower than 10 Pa, open the diffusion pump and wait for 40 - 50 min;

[0023] 4) Open the fine pumping valve, close the roughing valve, and start extracting high vacuum;

[0024] 5) When the barometer shows high vacuum, close the fine pumping valve, the diffusion pump, and the digital display vacuum gauge switch, and fill the furnace with a protective gas to reach the specified pressure;

[0025] 6) Turn on the heating power switch to make the welding current reach 380 - 400 A, with a heating time of 30 - 35 min and a heating temperature of 880 - 900 °C;

[0026] 7) After heating is completed, turn off the heating power switch. Wait for 1 h and then turn off the lower valve and the mechanical pump in sequence.

[0027] Further, in step S5, the grinding and machining is carried out using a metallographic grinding and polishing machine to grind and polish the weld surface flat.

[0028] Further, it also includes step S6: perform performance analysis on the weld by means of microstructure observation and mechanical property testing.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. The method of diffusion welding with an intermediate layer metal adopted by the present invention can avoid the melting of the base material and reduce the deformation of the base material during the welding process. At the same time, when the diffusion welding of the base material is carried out in a vacuum environment, the oxidation and nitridation of the base material can be effectively avoided, and the denaturation of the base material during the welding process is greatly reduced. Using vacuum diffusion welding to weld tungsten copper can effectively achieve the connection between tungsten and copper atoms, enhance the weld strength, reduce the deformation and denaturation of the base material, and improve the yield rate of welding.

[0031] 2. An intermediate layer is added before welding in the present invention. The intermediate layer is based on titanium (Ti) and supplemented with elements such as Al, V, and Fe, which can effectively coordinate the physical property differences (such as linear expansion coefficient and melting point) between tungsten and chromium zirconium copper alloy, and reduce the cracks generated at the welding interface due to thermal stress; the addition of Al and V can form an active intermediate phase, accelerate the atomic diffusion rate, shorten the welding time, and improve the uniformity of the interfacial metallurgical bond at the same time; strictly control the oxygen content (O < 0.2%) and low carbon (C: 0.07 - 0.11%) to avoid the formation of oxides and carbides during the welding process and ensure the purity of the interface; the titanium-based alloy has excellent high-temperature resistance and can still maintain a stable structure under the diffusion welding conditions of 880 - 900 °C, preventing the penetration or deformation of the intermediate layer.

[0032] Of course, it is not necessary for any product implementing the present invention to achieve all the above advantages simultaneously. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1Schematic diagram of the overall structure of the pressurizing die in the embodiment;

[0035] Figure 2 Schematic diagram of the cover plate of the pressurizing die in the embodiment;

[0036] Figure 3 Practical use diagram of the pressurizing die in the embodiment;

[0037] Figure 4 Exploded view of the physical object of the pressurizing die in the embodiment;

[0038] Figure 5 Schematic diagram of the internal structure of the sample in the embodiment;

[0039] Figure 6 Physical diagram of the sample in the embodiment;

[0040] In the drawings, the reference numerals of the various components are as follows:

[0041] 1 - Cover plate, 2 - Bolt, 3 - Mounting hole. Detailed implementation manners

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] Embodiment 1

[0044] This embodiment provides a welding method for tungsten-based and copper-based dissimilar metal materials, including the following steps:

[0045] S1. The tungsten base material is pure tungsten, and the chromium zirconium copper base material is a chromium zirconium copper alloy; the sheet specifications of the tungsten base material and the chromium zirconium copper base material are 50 mm × 15 mm × 1.5 mm; the surfaces of the base materials are successively polished with #240, #400, #800, #1000, and #1500 sandpapers, and then surface polishing treatment is carried out with diamond paste on a polishing cloth; finally, the base materials are ultrasonically cleaned with ethanol and deionized water in sequence to ensure the cleanliness of the surfaces of the base materials.

[0046] S2. Prepare an intermediate layer, and the material of the intermediate layer consists of the following components by mass percentage: Al: 6.25%, V: 3.9%, Fe: 0.35%, C: 0.08%, O < 0.2%, and Ti is the balance; the sheet specification size of the intermediate layer is 20 mm × 15 mm × 0.05 mm.

[0047] S3. Place the parts to be welded of the tungsten base material and the chromium zirconium copper base material on both sides of the intermediate layer respectively, and use a pressing die to lock the positions of the three and press them to the set pressure.

[0048] The pressing die is as Figure 1 and Figure 2 shown, and includes two cover plates 1 and four groups of bolts 2. Four mounting holes 3 for facilitating the installation of the bolts 2 are opened on each cover plate 1. The two cover plates 1 can clamp and press the laminated tungsten base material - intermediate layer - chromium zirconium copper base material under the locking and pushing of the bolts 2. The cover plate 1 is made of H13 die steel, and its specification size is 55mm×55mm×8mm; the bolt 2 is composed of a 310S screw and a 310S nut. The internal structure of the laminated tungsten base material - intermediate layer - chromium zirconium copper base material, that is, the sample, is as Figure 5 shown.

[0049] S4. Use a vacuum melting furnace to perform vacuum diffusion welding on the lap joint base materials; the specific operation steps are as follows:

[0050] 1) Open the mechanical pump and the rough pumping valve, extract gas, and observe the air pressure display;

[0051] 2) After the air pressure is less than 10 Pa, open the lower valve;

[0052] 3) After the air pressure display is lower than 10 Pa, open the diffusion pump and wait for 45 min;

[0053] 4) Open the fine pumping valve, close the rough pumping valve, and start extracting high vacuum;

[0054] 5) After the barometer shows high vacuum, close the fine pumping valve, the diffusion pump and the digital display vacuum gauge switch, and fill the furnace with a protective gas to reach the specified pressure;

[0055] 6) Open the heating power switch to make the welding current reach 390 A, the heating time is 32 min, and the heating temperature is 890 °C;

[0056] 7) After the heating is completed, close the heating power switch, wait for 1 h, and then close the lower valve and the mechanical pump in sequence.

[0057] S5. Use a metallographic grinding and polishing machine to polish the surface of the weld, polish the surface of the weld until it is flat and flush with the surface of the base material.

[0058] Step S6. The physical diagram of the sample after welding is as Figure 6 shown. Through microscopic structure observation and mechanical property testing, the performance of the weld is analyzed.

[0059] Example 2

[0060] This embodiment is basically the same as Embodiment 1, except that the material of the intermediate layer is composed of components with the following mass percentages: Al: 5.5%, V: 4.5%, Fe: 0.3%, C: 0.11%, O < 0.2%, and Ti is the balance.

[0061] Embodiment 3

[0062] This embodiment is basically the same as Embodiment 1, except that the material of the intermediate layer is composed of components with the following mass percentages: Al: 6.75%, V: 3.5%, Fe: 0.4%, C: 0.07%, O < 0.2%, and Ti is the balance.

[0063] Embodiment 4

[0064] This embodiment is basically the same as Embodiment 1, except that a vacuum melting furnace is used for vacuum diffusion welding of the lap joint base material. In step 6), the heating power supply switch is turned on to make the welding current reach 380 A, the heating time is 35 min, and the heating temperature is 880 °C.

[0065] Embodiment 5

[0066] This embodiment is basically the same as Embodiment 1, except that a vacuum melting furnace is used for vacuum diffusion welding of the lap joint base material. In step 6), the heating power supply switch is turned on to make the welding current reach 400 A, the heating time is 30 min, and the heating temperature is 900 °C.

[0067] In the present invention, the intermediate layer is based on titanium (Ti) and supplemented with elements such as Al, V, and Fe, which can effectively coordinate the physical property differences (such as linear expansion coefficient, melting point) between tungsten and chromium zirconium copper alloy, and reduce the cracks generated at the welding interface due to thermal stress; the addition of Al and V can form an active intermediate phase, accelerate the atomic diffusion rate, shorten the welding time, and improve the uniformity of interfacial metallurgical bonding at the same time; strictly control the oxygen content (O < 0.2%) and low carbon (C: 0.07 - 0.11%) to avoid the formation of oxides and carbides during the welding process and ensure the purity of the interface; the titanium-based alloy has excellent high-temperature resistance and can still maintain structural stability under the diffusion welding conditions of 880 - 900 °C, preventing the intermediate layer from melting through or deforming.

[0068] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to only the specific implementation manners. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for welding tungsten-based and copper-based dissimilar metal materials, characterized in that: The steps include: S1. Use sandpaper to grind, polish and ultrasonically clean the tungsten and chromium-zirconium-copper base materials step by step to ensure the surface of the base materials is clean; S2. Prepare the middle layer. The material of the middle layer consists of the following components in percentage by weight: Composition: Al: 5.5-6.75%, V: 3.5-4.5%, Fe: 0.3-0.4%, C: 0.07-0.11%, O < 0.2%, Ti is the balance; S3, placing the parts to be welded of the tungsten base metal and the chromium-zirconium-copper base metal on both sides of the middle layer respectively, locking the positions of the three using a pressurizing mold and pressurizing them to a set pressure; S4. Use a vacuum melting furnace to perform vacuum diffusion welding on the overlapping parent materials, with a welding current of 380-400A, a heating time of 30-35min, and a heating temperature of 880-900℃; S5. Grind the weld surface until it is flush with the parent material surface.

2. The welding method according to claim 1, characterized in that: In step S1, the tungsten matrix is ​​pure tungsten, and the chromium-zirconium-copper matrix is ​​a chromium-zirconium-copper alloy.

3. The welding method according to claim 1, characterized in that: In step S1, the plate specifications of the tungsten mother material and the chromium-zirconium-copper mother material are 50 mm×15 mm×1.5 mm.

4. The welding method according to claim 1, characterized in that: In step S1, the surface of the base material is polished step by step using sandpapers of #240, #400, #800, #1000 and #1500 in sequence, and then the surface is polished on a polishing cloth using diamond paste; finally, the base material is ultrasonically cleaned using ethanol and deionized water in sequence.

5. The welding method according to claim 1, characterized in that: In step S2, the material of the intermediate layer is composed of the following components in mass percentage: composition: Al: 6.25%, V: 3.9%, Fe: 0.35%, C: 0.08%, O<0.2%, and Ti is the balance.

6. The welding method according to claim 1, characterized in that: In step S2, the specification size of the plate material of the middle layer is 20mm×15mm×0.05mm.

7. The welding method according to claim 1, characterized in that: In step S3, the pressurizing mold includes two cover plates and four groups of bolts. Each cover plate is provided with four mounting holes for installing bolts. The two cover plates can clamp and pressurize the stacked tungsten matrix-intermediate layer-chromium zirconium-copper matrix under the locking push of the bolts. The cover plates are made of H13 mold steel with a specification size of 55mm×55mm×8mm; the bolts are composed of 310S screws and 310S nuts.

8. The welding method according to claim 1, characterized in that: In step S4, the specific operation steps of performing vacuum diffusion welding using a vacuum melting furnace are as follows: 1) Open the mechanical pump and roughing valve, extract gas, and observe the air pressure display; 2) When the air pressure is less than 10Pa, open the lower valve; 3) After the air pressure display is lower than 10Pa, turn on the diffusion pump and wait for 40 to 50 minutes; 4) Open the fine pumping valve, close the rough pumping valve, and start to draw high vacuum; 5) When the barometer shows high vacuum, close the fine pumping valve, diffusion pump and digital vacuum gauge switch, and fill the furnace with protective gas to reach the specified pressure; 6) Turn on the heating power switch, make the welding current reach 380-400A, the heating time is 30-35min, and the heating temperature is 880-900℃; 7) After heating is completed, turn off the heating power switch, wait for 1 hour, and then close the lower valve and mechanical pump in turn.

9. The welding method according to claim 1, characterized in that: In step S5, the grinding process is performed using a metallographic grinding and polishing machine to grind the weld surface flat and polish it.

10. The welding method according to claim 1, characterized in that: The method further includes step S6, analyzing the performance of the weld by microstructure observation and mechanical property testing.

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