Method for welding dissimilar metal through electron beam composite ultrasonic vibration

Abstract

The invention relates to a method for welding dissimilar metal through electron beam composite ultrasonic vibration, in particular to an electron beam composite ultrasonic vibration welding method for Ti-6Al-4V and T2 pure copper. The method comprises the following specific steps: firstly, carrying out pre-welding pretreatment on a weldment; then the workpiece and the three-axis sliding rail are placed into a welding chamber; then, an ultrasonic device is assembled, and the distance between an ultrasonic rolling head ball and an electron beam and the pressure between the ultrasonic rolling head ball and the to-be-welded workpiece are adjusted; and then ultrasonic parameters and electron beam welding parameters are set. And finally, the welding chamber is vacuumized, double-electron-beam welding is conducted, the front electron beam is located on the copper side, the rear electron beam is located on the titanium side, and the two welding seams are adjacent but not overlapped. The welding method has the welding characteristics that aiming at the problems of coarse weld grains, larger post-welding residual stress and the like in the electron beam welding dissimilar metal process, an ultrasonic rolling head ball is adopted for vibrating a welding material, and sound streaming and cavitation effects are generated on a welding pool, so that the grains are refined, air holes are discharged, the welding residual stress is eliminated, and the mechanical property of a welding joint is further improved.

Description

Technical Field

[0001] The present invention relates to the field of welding of dissimilar metals with relatively large differences in physical and chemical properties, and is a method for welding dissimilar metals with electron beam composite ultrasonic vibration. Background Art

[0002] Dissimilar metal structural parts, as a composite structural part that can combine the excellent properties and advantages of different metals, have attracted widespread attention and application in various industrial fields in recent years due to their low cost, high efficiency and simple process. They meet the requirements of modern industrial fields for multifunctional, multi-layered, high-quality and low-cost materials. At the same time, due to their characteristics of combining the properties of multiple metals, they usually have high mechanical properties while ensuring that the materials have excellent physical properties such as corrosion resistance and high conductivity, which greatly improves the comprehensive value of industrial products and saves production costs. Welding, as a process that is efficient, low-cost and can achieve good connection of different metals, has received special attention, so the field of dissimilar metal welding has gradually become a research hotspot.

[0003] In recent years, titanium and its alloys have become a popular welding structural material and additive material, mainly due to its low density, high strength and other excellent properties. It still occupies an important application position in aerospace, automobile structure weight reduction, shipbuilding and other fields, especially when combined with other metals, it can achieve the effect of weight reduction. Copper and its alloys have excellent electrical and thermal conductivity, ductility and corrosion resistance. As one of the earliest metals discovered and used by humans, it is widely used in various fields. The disadvantages of the two metals are high cost and many welding defects, but the titanium-copper welding structure can not only maintain the high strength and toughness of titanium itself, but also take into account the excellent physical properties of copper. It has great application value in various fields with multiple performance requirements, and it has higher specific strength and environmental protection than traditional titanium steel structures. Therefore, it can be widely used in ships, aerospace, and even automation.

[0004] At present, the common problem in the field of dissimilar metal welding is that due to the large difference in physical and chemical properties between the two metals, high residual stress and deformation, alloy element loss caused by the large difference in thermal expansion coefficient, and large difference in wettability or fluidity make it impossible to fully mix the liquid metal, resulting in cracks and unfusion, residual gas cannot be discharged to form pores and many other problems; most of the dissimilar metals will form thicker intermetallic compounds, which usually grow in the form of columnar crystals to form needle-shaped or band-shaped intermetallic compounds, and their grain boundary strength is low. Therefore, the intermetallic compound layer will cause the mechanical properties of the welded joint to be seriously degraded.

[0005] The above problems also exist in the field of titanium-copper dissimilar metal welding. The main solution at present is to reduce atomic diffusion through solid phase welding methods such as diffusion welding and friction welding, or to reduce or inhibit the generation of intermetallic compounds by adding a welding intermediate layer. However, such methods are costly and have low welding efficiency. They are not suitable for rapid process production, and do not solve problems such as cracks, pores, and large residual stress. Experiments have shown that electron beam time-sharing dual-beam welding can achieve in-situ remelting of the intermetallic compound layer, thereby reducing the thickness of the intermetallic compound layer and improving the mechanical properties of the welded joint. And as a fusion welding method, it has lower welding costs and higher welding efficiency. However, this method has defects such as large grains in the intermetallic compound layer, a small amount of unfused and high residual stress. In order to solve these problems, this method adopts ultrasonic composite welding, which increases the nucleation supercooling inside the molten pool through the ultrasonic cavitation effect and acoustic streaming effect, breaks the intermetallic compounds and coarse dendrites, thereby increasing the number of nucleations and achieving the purpose of grain refinement; in addition, the introduction of ultrasonic waves can also effectively promote the diffusion and flow of liquid metal, thereby reducing the porosity and residual stress after welding, and because the liquid metal has greater fluidity, the phenomenon of unfused will also be greatly reduced; finally, ultrasound can also enhance the wetting and spreading ability of liquid metal on the surface of the base material, thereby improving the weld morphology and reducing the possibility of stress concentration after welding. Summary of the invention

[0006] The object of the present invention is to provide a method for electron beam composite ultrasonic vibration welding of dissimilar metals. Electron beam composite ultrasonic vibration welding overcomes the problems of coarse grains of intermetallic compound layer, a small amount of unfused and high residual stress in double-beam electron beam welding of dissimilar metals, thereby achieving the effects of grain refinement, reduced pores and reduced residual stress, and ultimately solving the problem of low strength of Ti6Al4V and T2 pure copper dissimilar metal welded structural parts.

[0007] The ultrasonic composite time-sharing dual-beam electron beam welding method of the present invention is to enable the welding molten pool to effectively receive ultrasonic waves. First, it is necessary to ensure that there is sufficient pressure between the rolling head ball and the workpiece without damaging the workpiece to ensure the effective propagation of ultrasonic waves; secondly, since the ultrasonic wave will refract at the interface when it enters from one medium to another different medium, the propagation direction of the ultrasonic wave inside the workpiece changes. Therefore, in order to ensure that the ultrasonic wave propagates parallel to the workpiece, it is necessary to adjust the angle between the ultrasonic device and the workpiece according to the material properties, so that the ultrasonic wave energy can be effectively propagated to the molten pool. In this way, the ultrasonic wave can effectively promote the diffusion and flow of liquid metal, thereby giving the pores more time to overflow, increasing the wetting and spreading ability of wood metal, and improving the weld morphology. Since the density of copper is high and the attenuation of ultrasonic waves propagating inside it is large, the ultrasonic waves emitted from the copper side lose more energy when reaching the molten pool. Therefore, the ultrasonic rolling head ball on the copper side should be closer to the center of the electron beam spot, and in order to enhance the effect of ultrasonic waves on the molten pool, the ultrasonic wave wavelength should be calculated according to the material properties so that the ultrasonic wave peak occurs in the center of the molten pool. When the welding pool receives ultrasonic waves of sufficient energy, intermetallic compounds and coarse dendrites will be broken, increasing the number of nucleations, thereby refining the grains and reducing the tendency to crack.

[0008] An electron beam composite ultrasonic vibration welding method, the specific steps are as follows:

[0009] Step 1: Pre-treat the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate before welding, including removing impurities, grinding and polishing, etc.

[0010] Step 2: Place the pre-treated workpiece to be welded in the middle of the workbench in the electron beam welding chamber, and use a cylindrical clamping device to apply a pressure of 5 to 10 kN on the four corners of the plate.

[0011] Step 3: Place two sets of movable three-axis slide rails on both sides of the workpiece to be welded, and use 4 sets of threaded connections to fix each set of slide rails to the bottom workbench.

[0012] Step 4, assembling the ultrasonic device; assemble the ultrasonic generator-rotating plate-fixed plate-three-axis slide rail in sequence by tightening screws, wherein the rotating plate and the fixed plate use steel clamps; install a copper heat conducting strip on the clamp between the fixed plate and the slide rail; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator; the copper side rolling header ball is made of TC4 material and has a diameter of 8-10mm, and the titanium side rolling header ball is made of hardened steel and has a diameter of 6-8mm; according to Snell's law n1 sinθ i =n2 sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, and θ i and θ tThe incident angle and refraction angle are respectively adjusted to adjust the incident angle of the ultrasonic device; the ultrasonic parameters are adjusted, the power of the ultrasonic generating device on the copper side is set to 180-220W, and the ultrasonic frequency is set to 8-12kHz; the power of the ultrasonic generating device on the titanium side is set to 120-180W, and the ultrasonic frequency is set to 12-18kHz.

[0013] Step 5: Adjust the distance between the rolling head ball and the center of the electron beam spot according to the formula Where λ is the wavelength, v is the speed of sound, and f is the frequency. Where E is Young's modulus and ρ is material density. Set the distance between the rolling head ball and the center of the electron beam spot to an integer multiple of the wavelength. Adjust the pressing force between the rolling head ball at the bottom of the ultrasonic generator and the workpiece to 15-20MPa.

[0014] Step 6: Vacuum before welding, then open the electron beam gun for welding, the electron beam welding speed v: 8-12mm / s, the front electron beam welding trajectory is a1: 1.5mm from the center line of the butt joint to the copper side, the welding power P1: 25-40KW, and the weld width is recorded as C1; the rear electron beam welding trajectory is a2: 3mm from the center line of the butt joint to the titanium side, the welding power P2: 15-30KW, and the weld width is recorded as C2, wherein the two welds do not cross. The distance difference D between the rear electron beam and the front electron beam along the butt joint center line direction is 8-12mm.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] The present invention adopts ultrasonic vibration composite electron beam for welding in the titanium-copper dissimilar metal welding process. On the one hand, mechanical vibration effect can be generated in the molten pool, thereby promoting the diffusion of copper atoms and inhibiting the generation of titanium-rich phase intermetallic compounds. On the other hand, cavitation effect and acoustic streaming effect can make the nucleated crystals move randomly in the molten pool and cannot grow fixedly, thereby reducing the grain size of the growing intermetallic compound, and finally reducing the influence of the intermetallic compound layer on the mechanical properties of the welded joint; at the same time, ultrasonic composite welding can also play a stirring role to reduce the porosity of the weld, and ultrasound can enhance the wetting and spreading ability of liquid metal on the surface of the parent material, thereby improving the weld morphology, reducing the possibility of stress concentration after welding, thereby improving the tensile strength and other mechanical properties of the welded joint. Therefore, the electron beam composite ultrasonic vibration welding method of Ti6Al4V and T2 pure copper is expected to solve the disadvantages of low strength of titanium-copper dissimilar metal welding, promote the lightweight and multifunctional process in the industrial field, and take into account the concepts of green manufacturing and economical practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of electron beam composite ultrasonic vibration welding equipment.

[0018] Figure 2It is a schematic diagram of the weld formation of the workpiece to be welded.

[0019] 1. Workbench, 2. Movable three-axis slide rail, 3. Copper plate, 4. Titanium plate, 5. Ultrasonic transmitting device, 6. Power supply, 7. Deflection coil, 8. Focusing coil, 9. Anode, 10. Electron beam cathode, 11. Time-sharing dual-beam control system, 12. Ultrasonic device control system, 13. Rotating plate, 14. Fixed plate, 15. Titanium side weld, 16. Copper side weld, 17. Titanium side molten pool, 18. Copper side molten pool. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] An electron beam composite ultrasonic vibration welding method, the specific steps are as follows:

[0022] Step 1: Pre-treat the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate before welding, including removing impurities, grinding and polishing, etc.

[0023] Step 2: Place the pre-treated workpiece to be welded in the middle of the workbench in the electron beam welding chamber, and use a cylindrical clamping device to apply a pressure of 5 to 10 kN on the four corners of the plate.

[0024] Step 3: Place two sets of movable three-axis slide rails on both sides of the workpiece to be welded, and use 4 sets of threaded connections to fix each set of slide rails to the bottom workbench.

[0025] Step 4, assembling the ultrasonic device; assemble the ultrasonic generator-rotating plate-fixed plate-three-axis slide rail in sequence by tightening screws, wherein the rotating plate and the fixed plate use steel clamps; install a copper heat conducting strip on the clamp between the fixed plate and the slide rail; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator; the copper side rolling header ball is made of TC4 material and has a diameter of 8-10mm, and the titanium side rolling header ball is made of hardened steel and has a diameter of 6-8mm; according to Snell's law n1 sinθ i =n2 sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, and θ i and θ t The incident angle and refraction angle are respectively adjusted to adjust the incident angle of the ultrasonic device; the ultrasonic parameters are adjusted, the power of the ultrasonic generating device on the copper side is set to 180-220W, and the ultrasonic frequency is set to 8-12kHz; the power of the ultrasonic generating device on the titanium side is set to 120-180W, and the ultrasonic frequency is set to 12-18kHz.

[0026] Step 5: Adjust the distance between the rolling head ball and the center of the electron beam spot according to the formula Where λ is the wavelength, v is the speed of sound, and f is the frequency. Where E is Young's modulus and ρ is material density. Set the distance between the rolling head ball and the center of the electron beam spot to an integer multiple of the wavelength. Adjust the pressing force between the rolling head ball at the bottom of the ultrasonic generator and the workpiece to 15-20MPa.

[0027] Step 6: Vacuum before welding, then open the electron beam gun for welding, the electron beam welding speed v: 8-12mm / s, the front electron beam welding trajectory is a1: 1.5mm from the center line of the butt joint to the copper side, the welding power P1: 25-40KW, and the weld width is recorded as C1; the rear electron beam welding trajectory is a2: 3mm from the center line of the butt joint to the titanium side, the welding power P2: 15-30KW, and the weld width is recorded as C2, wherein the two welds do not cross. The distance difference D between the rear electron beam and the front electron beam along the butt joint center line direction is 8-12mm.

[0028] Further, in step 1, the pre-welding preparation step is that the Ti-6Al-4V titanium alloy plate and the T2 pure copper alloy plate are not grooved, the surface of the to-be-welded position and the adjacent 30 mm area are mechanically polished with a grinding wheel and a wire brush, and after the metallic luster is exposed, 240#, 400#, and 600# sandpapers are used for fine polishing, and finally acetone is used to clean the surface oil stains; the mass percentage of the Ti-6Al-4V titanium alloy used in step 1 is as follows: Ti: 87.65-88.83%, Al: 5.51-6.75%, V: 3.51-4.5%, Fe: 0-0.3%, C: 0-0.08%; the mass percentage of T2 pure copper is as follows: Cu: 99.9%, Fe: 0-0.05%, Si: 0-0.05%.

[0029] Furthermore, in step 2, the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate are placed in a butt joint on a stainless steel pad with a circular hole groove to form a butt joint. The workpiece assembly gap is n: 0-0.1mm, and a cylindrical clamping device with a diameter of 10mm is used to apply a vertical pressure of 5 to 10kN to the four corners of the workpiece to make it tightly combined with the stainless steel pad.

[0030] Furthermore, in step 3, the movable three-axis slide rails are placed on both sides of the workpiece to be welded and kept parallel to the weld bead, and finally the two sets of slide rails are fixed on the workbench using four sets of threaded connections respectively.

[0031] Furthermore, in step 4, the ultrasonic device assembly steps are as follows:

[0032] 4.1, connect the ultrasonic generator to the fixed plate. A cylindrical boss with a radius of 12mm and a height of 8mm is opened on the contact surface between the rotating plate and the fixed plate, and a dial is set on the upper half. A countersunk hole with a radius of 10mm and a depth of 10mm is opened in the center of the fixed plate, so that the two can be matched. In addition, a 1 / 2 countersunk annular groove is set on the other side of the rotating plate, i.e. the non-contact surface, and corresponding threaded holes are opened on both sides of the fixed plate; according to the formula n1 sinθ i =n2 sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, and θ i and θ t are the incident angle and refraction angle respectively. After adjusting the inclination angle of the ultrasonic device on the copper side to 46±2° and the inclination angle of the ultrasonic device on the titanium side to 66±2°, ensure that the ultrasonic wave propagates parallelly inside the workpiece. Finally, use two fastening screws to fix the fixed plate and the rotating plate.

[0033] 4.2. Considering that the working environment of the ultrasonic system is a high-temperature vacuum environment, the rotating plate and the fixed plate use steel fixtures, and copper heat-conducting strips are installed on the fixtures between the fixed plate and the slide rail to ensure its heat dissipation;

[0034] 4.3. In order to isolate the splashing impact of the high heat of the electron beam on the ultrasonic device, a double-layer aluminum sheet is set between the electron beam device and the ultrasonic device;

[0035] 4.4, due to the different hardness of the two materials, the diameter of the copper side rolling ball is set to 10mm, and the diameter of the titanium side rolling ball is set to 8mm;

[0036] 4.5. The power of the ultrasonic generator on the copper side is set to 180-220W, and the ultrasonic frequency is set to 8-12kHz; the power of the ultrasonic generator on the titanium side is set to 120-180W, and the ultrasonic frequency is set to 12-18kHz;

[0037] Furthermore, in step 5, according to the Young's modulus, density and working temperature of the two different materials, the copper side rolling header ball is set to be 40 mm away from the center of the electron beam spot and the line connecting the two points is perpendicular to the welding direction, and the titanium side rolling header ball is set to be 70 mm away from the center of the electron beam spot and the line connecting the two points is perpendicular to the welding direction; according to the different hardness and elastic modulus of the two materials, the pressure between the rolling header ball and the workpiece to be welded is adjusted, and the clamping force between the copper side rolling header ball and the workpiece is set to 15 MPa, and the clamping force between the titanium side rolling header ball and the workpiece is set to 20 MPa.

[0038] Furthermore, in step 6, the welding area is evacuated to 2.0×10 -2 -4.0×10 -2Pa, in order to reduce the deformation degree of the base material during welding, a defocused electron beam is used to preheat the environment and the base material. The parameters are: electron beam current 15-20mA, electron beam focus diameter 3-4mm, preheating speed 20-30mm / s; the set welding parameters are electron beam acceleration voltage: 60-150kV, welding height: 250-300mm, focusing current: 650-750mA.

[0039] Furthermore, in step 6, the signal power supply of the ultrasonic generating device is connected to the power supply of the welding equipment. During the electron beam composite ultrasonic vibration welding process, the ultrasonic composite welding equipment will be turned on and off as the welding starts and ends, ensuring that the ultrasonic composite welding acts on the entire welding process.

[0040] Furthermore, the power distribution of the electron beam in step 6 is achieved by adjusting the duty cycle of the deflection current, which satisfies: 2≤(P1*V1 / P2*D)≤2.5; and the current frequency in the deflection coil that forms the time-sharing dual-beam electron beam is 15kHz.

[0041] Furthermore, in step 6, in order to suppress the growth of intermetallic compounds at the interface, the electron beam on the copper side first scans 10 mm, and then the electron beam on the titanium side begins scanning, so that the metal is remelted in situ at the interface.

[0042] The present invention provides specific embodiments as follows

[0043] Example 1

[0044] In this embodiment, the electron beam composite ultrasonic vibration welding method for Ti6Al4V and T2 pure copper is carried out in the following steps:

[0045] Step 1: Prepare Ti6Al4V titanium alloy plates and T2 pure copper plate samples with specifications of 300mm*100mm*4mm, and mechanically grind the surface of the welding position and the adjacent 30mm area with a grinding wheel and a wire brush. After the metallic luster is exposed, use 240#, 400#, and 600# sandpaper for fine grinding to remove the oxide layer on the surface to be welded, and finally use acetone to clean the surface oil.

[0046] Among them, the mass percentage composition of the Ti-6Al-4V titanium alloy used is: Ti: 87.65-88.83%, Al: 5.51-6.75%, V: 3.51-4.5%, Fe: 0-0.3%, C: 0-0.08%; the mass percentage composition of T2 pure copper is: Cu: 99.9%, Fe: 0-0.05%, Si: 0-0.05%.

[0047] Step 2: Assemble the ungrooved Ti6Al4V titanium alloy plate and the T2 pure copper plate to form a butt joint. The workpiece assembly gap is n: 0.1mm. Place the sample plate on a stainless steel pad with multiple circular heat dissipation holes. Use four cylindrical clamping devices with a diameter of 10mm to place them in the holes of the stainless steel pad so that the weldment is tightly combined with the stainless steel pad.

[0048] Step 3: Place the movable three-axis slide rails on both sides of the workpiece to be welded and keep them parallel to the weld bead. Finally, use four sets of threaded connections to fix the two sets of slide rails on the workbench.

[0049] Step 4: Adjust the angles between the copper side and titanium side ultrasonic generator and the workpiece to be welded to 45° and 65° respectively, and use two fastening screws to fix the fixed plate and the rotating plate; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator to prevent splashing; install a copper heat conducting strip between the fixed plate and the slide rail; set the diameter of the copper side rolling head ball to 10mm, and the diameter of the titanium side rolling head ball to 8mm; set the power of the copper side ultrasonic generator to 200W, and the ultrasonic frequency to 10kHz; set the power of the titanium side ultrasonic generator to 150W, and the ultrasonic frequency to 15kHz;

[0050] Step 5: Set the copper side rolling header to be 40mm away from the center of the electron beam spot and the line connecting the two points is perpendicular to the welding direction, and the titanium side rolling header to be 70mm away from the center of the electron beam spot and the line connecting the two points is perpendicular to the welding direction. Set the clamping force between the copper side rolling header and the workpiece to 15MPa, and the clamping force between the titanium side rolling header and the workpiece to 20MPa.

[0051] Step 6: Vacuum the welding area to 2.0×10 -2 -4.0×10 -2 Pa, in order to reduce the deformation degree of the base material during welding, a defocused electron beam is used to preheat the environment and the base material. The parameters are: electron beam current 15mA, electron beam focus diameter 3.5mm, and preheating speed 25mm / s.

[0052] Modify the parameters of the electron beam emission equipment and compile the electron beam welding work path. The set welding parameters are electron beam acceleration voltage: 80kV, welding height: 270mm, focusing current: 700mA; welding speed v1: 10mm / s, beam rise and fall time 1s.

[0053] Plan the distribution state and beam size of the dual electron beams. Start the deflection coil, pass a high-frequency current into the deflection coil, control its frequency to 20kHz, form a time-sharing dual electron beam, adjust the electron beam focus position, so that the two electron beams form a front and rear dual electron beam with a spot center distance of 10mm along the weld direction. At the same time, the front electron beam is offset to the copper plate side, and the spot center is offset from the center line of the butt joint by a1: 1.5mm. The rear electron beam is offset to the titanium plate side, and the offset distance from the center line is a2: 3mm. Adjust the duty cycle so that the output power of the front electron beam is 30000W and the output power of the rear electron beam is 15000W.

[0054] Start the servo enable of the vacuum chamber motion system, move the electron beam emitting device to the starting vertical welding surface position, start the welding program and the power supply of the ultrasonic generator, and after the rear beam forms a complete molten pool, move in a direction parallel to the center line of the butt joint to complete the welding. After completing two offset welds, turn off the equipment and the power supply of the ultrasonic generator to complete the entire welding.

[0055] After the surface is cleaned, the tensile test and microscopic joint interface observation are performed, and the weld is well formed, the intermetallic compound layer is partially remelted, and the thickness of the layer is reduced.

[0056] The tensile strength of the joint is 249MPa, the elongation is 27.6%, and the strength is as strong as the parent material. The fracture occurs in the heat-affected zone on the copper side, showing obvious ductile fracture.

Claims

1. A method for electron beam composite ultrasonic vibration welding of dissimilar metals, characterized in that: The specific steps are as follows: Step 1, pre-treating the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate before welding, including removing impurities and grinding and polishing; Step 2, placing the pre-treated workpiece to be welded in the middle of the workbench in the electron beam welding chamber, and applying pressure to the four corners of the plate using a cylindrical clamping device; Step 3, place two sets of movable three-axis slide rails on both sides of the workpiece to be welded, and use 4 sets of threaded connections to fix each set of slide rails to the bottom workbench; Step 4, assembling the ultrasonic device; assemble the ultrasonic generator-rotating plate-fixed plate-three-axis slide rail in sequence by tightening screws, wherein the rotating plate and the fixed plate use steel clamps; install a copper heat conducting strip on the clamp between the fixed plate and the slide rail; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator; the copper side rolling header ball is made of TC4 material and has a diameter of 8-10mm, and the titanium side rolling header ball is made of hardened steel material and has a diameter of 6-8mm; according to Snell's law n1sinθ i =n2sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, and θ i and θ t The incident angle and refraction angle are respectively adjusted to adjust the incident angle of the ultrasonic device; the ultrasonic parameters are adjusted, the power of the ultrasonic generator on the copper side is set to 180-220W, and the ultrasonic frequency is set to 8-12kHz; the power of the ultrasonic generator on the titanium side is set to 120-180W, and the ultrasonic frequency is set to 12-18kHz; Step 5: Adjust the distance between the rolling head ball and the electron beam according to the formula Where λ is the wavelength, v is the speed of sound, and f is the frequency. Where E is Young's modulus, ρ is material density, and the spacing is set to an integer multiple of the wavelength; adjust the pressing force between the rolling head ball at the bottom of the ultrasonic generator and the workpiece to 15-20MPa; Step 6, evacuate before welding, then turn on the electron beam gun for welding, the electron beam welding speed V1: 8-12mm / s, the front electron beam welding trajectory is a1: 1.5mm from the center line of the butt joint to the copper side, the welding power P1: 25-40KW, and the weld width is recorded as C1; the rear electron beam welding trajectory is a2: 3mm from the center line of the butt joint to the titanium side, the welding power P2: 15-30KW, and the weld width is recorded as C2, wherein the two welds do not cross, and the distance difference D between the rear electron beam and the front electron beam along the butt joint center line direction is 8-12mm.

2. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 1, the pre-welding preparation step is that the Ti-6Al-4V titanium alloy plate and the T2 pure copper alloy plate are not grooved, the surface of the to-be-welded position and the adjacent 30 mm area are mechanically polished with a grinding wheel and a wire brush, and after the metallic luster is exposed, 240#, 400#, and 600# sandpapers are used for fine polishing, and finally acetone is used to clean the surface oil stains; the mass percentage of the Ti-6Al-4V titanium alloy used in step 1 is as follows: Ti: 87.65-88.83%, Al: 5.51-6.75%, V: 3.51-4.5%, Fe: 0-0.3%, C: 0-0.08%; the mass percentage of T2 pure copper is as follows: Cu: 99.9%, Fe: 0-0.05%, Si: 0-0.05%.

3. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 2, the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate are placed in a butt joint on a stainless steel pad with a circular hole groove to form a butt joint. The workpiece assembly gap is n: 0~0.1mm, and a cylindrical clamping device with a diameter of 10mm is used to apply a vertical pressure of 5~10kN to the four corners of the workpiece to make it tightly combined with the stainless steel pad.

4. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 3, the movable three-axis slide rails are placed on both sides of the workpiece to be welded and kept parallel to the weld bead. Finally, the two sets of slide rails are fixed on the workbench using four sets of threaded connections.

5. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 4, the ultrasonic device assembly steps are as follows: Step 4.1, connect the ultrasonic generator to the fixed plate; a cylindrical boss with a radius of 12mm and a height of 8mm is opened on the contact surface between the rotating plate and the fixed plate, and a dial is set on the upper half, and a countersunk hole with a radius of 10mm and a depth of 10mm is opened in the center of the fixed plate, so that the two form a match; in addition, a 1 / 2 countersunk annular groove is provided on the other side of the rotating plate, i.e., the non-contact surface, and corresponding threaded holes are opened on both horizontal sides of the fixed plate; according to the formula n1sinθ i =n2sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, and θ i and θ t are the incident angle and refraction angle respectively. After adjusting the inclination angle of the ultrasonic device on the copper side to 46±2° and the inclination angle of the ultrasonic device on the titanium side to 66±2°, ensure that the ultrasonic wave propagates parallelly inside the workpiece. Finally, use two fastening screws to fix the fixed plate and the rotating plate. Step 4.2, considering that the working environment of the ultrasonic system is a high-temperature vacuum environment, the rotating plate and the fixed plate use steel fixtures, and copper heat-conducting strips are installed on the fixtures between the fixed plate and the slide rail to ensure its heat dissipation; Step 4.3, in order to isolate the splashing impact of the electron beam on the ultrasonic device, a double-layer aluminum sheet is set between the electron beam device and the ultrasonic device; Step 4.4, due to the different hardness of the two materials, the diameter of the copper side rolling ball is set to 10mm, and the diameter of the titanium side rolling ball is set to 8mm; In step 4.5, the power of the ultrasonic generator on the copper side is set to 180-220 W, and the ultrasonic frequency is set to 8-12 kHz; the power of the ultrasonic generator on the titanium side is set to 120-180 W, and the ultrasonic frequency is set to 12-18 kHz.

6. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 5, according to the Young's modulus, density and working temperature of the two different materials, the copper side rolling header ball is set to be 40 mm away from the center of the copper side electron beam spot and the line connecting the two points is perpendicular to the welding direction, and the titanium side rolling header ball is set to be 70 mm away from the center of the titanium side electron beam spot and the line connecting the two points is perpendicular to the welding direction; in step 5, according to the different hardness and elastic modulus of the two materials, the pressure between the rolling header ball and the workpiece to be welded is adjusted, and the clamping force between the copper side rolling header ball and the workpiece is set to 15 MPa, and the clamping force between the titanium side rolling header ball and the workpiece is set to 20 MPa.

7. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, the welding area is evacuated to 2.0×10 -2 -4.0×10 -2 Pa, in order to reduce the deformation degree of the base material during welding, a defocused electron beam is used to preheat the environment and the base material, and the parameters are: electron beam current 15-20mA, electron beam focus diameter 3-4mm, preheating speed 20-30mm / s; in step 6, the set welding parameters are electron beam acceleration voltage: 60-150kV, welding height: 250-300mm, focusing current: 650-750mA.

8. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, the signal power supply of the ultrasonic generating device is connected to the power supply of the welding equipment. During the electron beam composite ultrasonic vibration welding process, the ultrasonic composite welding equipment will be turned on and off as the welding starts and ends, ensuring that the ultrasonic composite welding acts on the entire welding process.

9. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, the power distribution of the electron beam is achieved by adjusting the duty cycle of the deflection current, which satisfies: 2≤(P1*V1 / P2*D)≤2.5; in step 6, the current frequency in the deflection coil that forms the time-sharing dual-beam electron beam is 15kHz.

10. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, in order to suppress the growth of intermetallic compounds at the interface, the electron beam on the copper side first scans 10 mm, and then the electron beam on the titanium side starts scanning, so that the metal is remelted in situ at the interface.

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