Vacuum electron beam welding method for oxygen-free copper high-pressure container

Abstract

The invention discloses a vacuum electron beam welding method for an oxygen-free copper high-pressure container. The vacuum electron beam welding method comprises the following steps: cleaning a welding seam of a cylinder of the high-pressure container; the high-pressure container barrel is fixed to a two-dimensional working platform of a vacuum electron beam welding machine, and the butt joint gap of welding seams is not larger than 0.1 mm; the high-pressure container barrel is fixed between the rotary positioner and the tail top; the two-dimensional working platform drives the high-pressure container barrel, the rotary positioner and the tail top to move into the vacuum chamber; electron beam welding is conducted after the vacuum chamber is vacuumized to the target vacuum degree; the electron beam welding process comprises electron beam scanning cleaning before welding, preheating before welding and formal welding. Good internal quality and appearance quality of the welding seam can be obtained, the welding seam joint is smooth and attractive, defects such as oxidation and cracks are avoided, the comprehensive performance of the welding seam is good, and the method is suitable for electron beam welding of high-pressure containers of spaceflight solid rocket engine products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding, and particularly relates to a vacuum electron beam welding method for oxygen-free copper high-pressure containers. BACKGROUND

[0002] With the development of aerospace technology, the aerospace product requires 100% qualified rate for each part to ensure high product quality. Oxygen-free copper has good corrosion resistance, oxidation resistance, wear resistance, and good processing performance and welding performance. Some key components combine the requirements of weight reduction and high thermal conductivity, and oxygen-free copper is more and more applied in the above-mentioned fields. If the material can be successfully applied to the manufacture of aerospace products, the structure weight of the product can be effectively reduced, and the flight performance of the product can be improved. However, during the actual engineering development of the product, different parts are often connected by welding to achieve the design requirements of the product. The welding quality and the welding difficulty directly affect the application of the material in the product, and therefore the metal welding method and the welding process need to be strictly controlled.

[0003] There are many welding methods for copper and copper alloy, such as diffusion welding, argon arc welding, electron beam welding, and laser welding. However, copper is difficult to fuse during welding, and the weld forming ability is poor. The thermal conductivity of copper is large, and the heat is quickly transmitted to the heating area during welding, which expands the heating range. The thicker the welding piece, the more serious the heat dissipation. Therefore, a high-power heat source needs to be used during welding, and preheating is often required before welding. When copper is at the melting temperature, the surface tension is one-third smaller than that of iron, and the flowability is 1-1.5 times larger than that of steel. The surface forming ability of copper is poor, and a forming device such as a backing plate needs to be used on the back during single-sided welding. Copper is prone to produce thermal cracks during welding, which is caused by the oxidation of liquid copper, impurities, and grain growth during the heating process.

[0004] Electron beam welding has the advantages of fast welding speed, concentrated welding heat input, and no oxidation of the weld, and can realize effective welding between metals and meet the needs of complex and diverse aerospace product structures in the future. However, electron beam welding of oxygen-free copper high-pressure containers is prone to produce internal pores, cracks and other defects. At present, there is a lack of related research on electron beam welding of oxygen-free copper used in high-pressure containers of solid rocket engines to ensure weld forming and control pores and cracks. SUMMARY

[0005] The purpose of the present application is to overcome the above-mentioned defects, and to provide a vacuum electron beam welding method for oxygen-free copper high-pressure containers, which solves the technical problem that electron beam welding of oxygen-free copper high-pressure containers is prone to produce internal pores, cracks and other defects. The present application can obtain good internal and external quality of the weld, and the weld joint is flat and beautiful, without oxidation, cracks and other defects. The comprehensive performance of the weld is good, and the present application is suitable for electron beam welding of high-pressure containers of aerospace solid rocket engine products.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] The present application discloses a kind of oxygen-free copper high-pressure container vacuum electron beam welding method.Oxygen-free copper high-pressure container vacuum electron beam welding method is disclosed in the present application.

[0008] The present application provides the following technical solutions.

[0009] (1) the high-pressure container cylinder weld is cleaned;

[0010] (2) the high-pressure container cylinder is fixed on the two-dimensional work platform of vacuum electron beam welding machine, so that the butt joint gap of weld is not more than 0.1mm;

[0011] (3) the high-pressure container cylinder is fixed between the rotary positioner and the tail top;

[0012] (4) the two-dimensional work platform drives the high-pressure container cylinder, the rotary positioner and the tail top to move into the vacuum chamber;

[0013] (5) vacuum electron beam welding is carried out after the vacuum chamber is pumped to the target vacuum degree;The electron beam welding process includes pre-welding electron beam scanning cleaning, pre-welding and formal welding.

[0014] Further, in step (1), the method for cleaning the high-pressure container cylinder weld includes:

[0015] The oxide skin and oil stains within 20-50mm from the center of the weld are cleaned, the butt joint end surface of the weld is polished with sandpaper, and then wiped with acetone.

[0016] Further, in step (2), the vacuum electron beam welding machine uses an ion beam as an energy source, with a maximum voltage of 60KV and a maximum power of 30KW, and has an electron beam scanning function.

[0017] Further, in step (2), two inner support toolings are installed in the two high-pressure container cylinders respectively.

[0018] The inner support tooling includes a plurality of melon-seed structure.

[0019] All melon-seed structures are combined to form a cylindrical body, and the cylindrical body is matched with the inner cavity shape of the high-pressure container cylinder.

[0020] Each pumpkin piece is shaped by mechanical processing, a plurality of threaded holes are arranged on each pumpkin piece in the circumferential direction, the threaded holes of the pumpkin piece are screwed and fixed with bolts, the bolt head is spherical, the contact area and contact force of the pumpkin piece structure and the inner wall of the high-pressure container cylinder are adjusted by the bolts on the pumpkin piece structure, and the support of the high-pressure container cylinder is realized.

[0021] Further, in step (3), the high-pressure container cylinder is fixed between the rotary positioner and the tail top by the core rod and the end cap.

[0022] The core rod passes through the pumpkin piece structure in the axial direction, the pumpkin piece structure is fixed on the core rod by the sleeve and the bolt, and the two end caps are respectively assembled on the two ends of the high-pressure container cylinder and are screwed and relatively fixed by the threads at the end of the core rod; specifically, the pumpkin piece structure is located outside the sleeve, the sleeve is provided with a support rod connected with the pumpkin piece, the core rod passes through the sleeve and is fixed with the threaded holes on the core rod by the bolt, and the connection with the core rod and the relative position with the core rod are determined.

[0023] The rotary positioner and the tail top are respectively connected to the two ends of the core rod.

[0024] Further, in step (5), the target vacuum degree is 6.65*10 -5 mbar or more.

[0025] Further, in step (5), the process parameters of the electron beam scanning cleaning before welding include:

[0026] The voltage is 60KV, the focusing current is 515-535mA, the scanning current is 10-20mA, the welding speed is 5-10mm / s, the scanning pattern is circular, and the scanning radius is 0.5mm.

[0027] Further, in step (5), the process parameters of the preheating before welding include:

[0028] The voltage is 60KV, the focusing current is 515-535mA, the scanning current is 15-25mA, the welding speed is 8-12mm / s, the scanning pattern is circular, and the scanning radius is 0.5mm.

[0029] Further, in step (5), the process parameters of the formal welding include:

[0030] The focusing current is 530-550mA, the welding speed is 8-12mm / s, the welding current is 43mA-48mA, the scanning pattern is circular, and the scanning radius is 0.5mm.

[0031] The formal welding adopts a continuous attenuation positive rotary waveform output, so that the welding arc pit gradually shrinks and closes in the repeated melting and solidification process.

[0032] Further, in step (5), the high-pressure container cylinder is made of oxygen-free copper material, the purity of oxygen-free copper reaches 99.98%, and the oxygen content is less than 0.003%.

[0033] Compared with the prior art, the present application has at least one of the following beneficial effects:

[0034] (1) The present application creatively proposes a vacuum electron beam welding method for oxygen-free copper high-pressure container, which can effectively reduce the weld crack sensitivity, obtain good internal quality of the weld, and make the weld excessively smooth, meeting the I-class weld requirement of GJB1718A-2005 standard, and the comprehensive mechanical properties of the weld are excellent.

[0035] (2) The present application designs an inner support type tooling, which can effectively ensure the assembly precision of oxygen-free copper.

[0036] (3) The present application uses electron beam scanning preheating to effectively reduce the influence of fast copper heat conduction and fast heat dissipation during welding.

[0037] (4) The present application uses a pre-welding scanning cleaning process to further remove residual impurities and oxide scales, which is beneficial to improve the welding quality.

[0038] (5) The present application uses continuous attenuation sine-shaped energy output during arc collection to weaken the influence of arc collection. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a high-pressure container welding structure schematic diagram of the present application.

[0040] Figure 2 It is an inner support type tooling schematic diagram of the present application.

[0041] In the figure, 1 is a vacuum electron beam welding gun, 2 is a two-dimensional work platform, 3 is a rotary positioner, 4 is a tail top, and 5 is a high-pressure container. DETAILED DESCRIPTION

[0042] The characteristics and advantages of the present application will become more clear and explicit with the following detailed description of the present application.

[0043] The special word "exemplary" here means "serving as an example, embodiment or illustration". Any embodiment described as "exemplary" here is not necessarily to be interpreted as superior or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0044] The traditional manual electric arc welding has low welding efficiency and low first-pass rate, and the oxygen-free copper high-pressure container electronic beam welding method can improve the difficulty of the existing manual operation process, and provides a simple structure, easy operation, good internal and external quality of the weld, smooth and beautiful weld joint, no oxidation and crack, and good comprehensive performance of the weld, which is suitable for the electronic beam welding of the high-pressure container of the aerospace solid rocket engine product, and improves the welding quality and product performance.

[0045] As Figure 1 The oxygen-free copper high-pressure container vacuum electronic beam welding method comprises the following steps:

[0046] 1) The surface and the peripheral oxide skin, oil stains and impurities of the high-pressure container cylinder ring weld are cleaned;

[0047] 2) The cleaned high-pressure container cylinder is passed through the melon petal structure inner support tool to ensure that the weld assembly butt joint gap is not greater than 0.1mm;

[0048] 3) The assembled high-pressure container is connected to the rotary positioner and the tail top through the core rod;

[0049] 4) The high-pressure container is moved to the vacuum chamber through the two-dimensional working platform, and after the vacuum degree reaches 6.65*10 - 5 mbar or above, welding is started;

[0050] 5) The welding process comprises the following processes: electronic beam scanning cleaning before welding, preheating before welding, welding implementation process, and slow cooling after welding.

[0051] Preferably, in step 1), the oxide skin and oil stains within the range of 20mm-50mm from the center of the weld are cleaned, the butt joint end face of the weld is polished with sandpaper, and then cleaned with acetone.

[0052] Preferably, the vacuum electronic beam welding equipment adopted in the application adopts an ion beam as an energy source, has a maximum voltage of 60KV and a maximum power of 30KW, and has an electronic beam scanning function.

[0053] Preferably, the surface oil stains, impurities and the like are cleaned by electronic beam scanning before welding; the high-pressure container to-be-welded part is preheated before welding; and the welding process parameters are as follows: the focusing current I is 540mA, the focusing current is 15mA, the welding speed is 8-12mm / s, and the welding current is 43mA-48mA.

[0054] Preferably, the welding arc adopts a continuous attenuation positive rotating waveform output, so that the welding arc pit gradually shrinks and closes in the repeated melting and solidification process.

[0055] Preferably, the purity of the oxygen-free copper reaches 99.98%, and the oxygen content is less than 0.003%.

[0056] Preferably, the inner support type tool is used to ensure the butt joint quality of the welding seam.

[0057] Embodiment:

[0058] The present application provides a vacuum electron beam welding method for an oxygen-free copper high-pressure container, comprising the following steps:

[0059] 1) The surface and the periphery of the high-pressure container cylinder to be welded are cleaned of the oxide skin and oil stains by using sandpaper, acetone and the like;

[0060] 2) The cleaned high-pressure container to be welded is assembled, the sleeve of the inner support type tool is connected with the core rod, and the two sets of inner support type tools are respectively placed at a distance of 5mm from the welding position, the roundness and assembly gap are adjusted by the tightness of the screw holes and bolts on the melon, and the assembly gap of the two sets of inner support type tools is adjusted to ensure that the welding seam assembly butt joint gap is not greater than 0.1mm;

[0061] 3) The assembled high-pressure container is fixed on the rotary positioner and the tail top through the core rod and the end cover, and the clamping of the solid rocket engine high-pressure container is realized through the rotary positioner and the tail top; specifically, the diameter of the end cover is matched with the high-pressure container, and the end cover is assembled at the end away from the welding seam, the center of the end cover is provided with a hole matched with the core rod, the core rod is provided with threads at both ends, the core rod directly penetrates through the hole in the center of the end cover, and the connection between the core rod, the end cover and the cylinder is realized by tightening the nut.

[0062] 4) The fixed high-pressure container is moved into the vacuum chamber through the two-dimensional working platform, and the vacuum degree is extracted to be higher than 6.65*10 -5 mbar after the vacuum degree is extracted to be higher than 6.65*10

[0063] 5) When the vacuum chamber reaches the welding vacuum state, the high-pressure container is opened to start welding, and the welding process includes the welding pre-electron beam scanning cleaning, the welding preheating, the welding implementation process and the welding post-cooling process.

[0064] 6) The continuous attenuation sine-shaped energy output is used when the welding arc is received, and the influence of the arc receiving is weakened.

[0065] In a specific embodiment, the present application provides an inner support type tool for satisfying the girth seam welding of the high-pressure container, ensuring the welding seam butt joint quality and the deformation of the welding process, and fixing the high-pressure container between the three-jaw chuck rotary positioner and the tail top through the core rod, the end cover and other tools.

[0066] The inner support tool is composed of eight melon pieces, each melon piece is shaped by machining, and the eight melon pieces can be spliced into a complete high-pressure container inner cavity, the contact area and contact force with the high-pressure container inner cavity are adjusted through the bolts on each melon piece, so that the support inside the high-pressure container is achieved, the butt joint assembly condition between the high-pressure containers to be welded is adjusted, and then positioning and pressing are completed.

[0067] The inner support tool is connected with the welding mandrel through the center hole reserved in the center, the relative position of the inner support tool with the mandrel and the high-pressure container is determined by the tightness of the bolts, and the installation and disassembly of the inner support tool are completed.

[0068] The end cover and the mandrel are used to fix a certain high-pressure container of a solid rocket engine, and the high-pressure container is fixed between the rotary positioner and the tail top through the mandrel and the end cover, so that the rotation of the high-pressure container is driven to complete the welding in the vacuum chamber.

[0069] The end cover is provided with an exhaust hole to ensure that the internal and external pressures are the same in the vacuum environment.

[0070] In a specific embodiment, in step 1), before welding, the scale, oil stains and the like within a range of 20mm-50mm around the center of the weld are cleaned, the butt joint end face of the weld is polished with sandpaper, and then cleaned with acetone.

[0071] In a specific embodiment, the vacuum electron beam welding machine used in the application has a high pressure of 60KV and a maximum output power of 30KW, and has an electron beam scanning function.

[0072] In a specific embodiment, in step 5), before welding, the surface to be welded is scanned within a range of 20mm-50mm around the center of the weld using an electron beam scanning program to remove residual impurities and scale.

[0073] In a specific embodiment, in step 5), after scanning and cleaning before welding, the surface to be welded is preheated using the electron beam scanning function to reduce the influence of fast copper heat conduction and fast heat dissipation, and to further promote the formation of the weld.

[0074] In a specific embodiment, in step 5), the welding process parameters are as follows: the focusing current is 540mA, the focusing is 15mA, the welding speed is 8-12mm / s, and the welding current is 43mA-48mA.

[0075] In a specific embodiment, the welding arc distance is 5-10mm, and a continuous attenuating sinusoidal energy output is used when the arc is collected, so that the welding crater gradually shrinks and closes in the repeated melting and solidification process.

[0076] Example 1:

[0077] AsFigure 1 In the embodiment, the material of the solid rocket engine high-pressure container shell part is oxygen-free copper, the purity of the oxygen-free copper reaches 99.98%, the oxygen content is less than 0.003%, the diameter is 200 mm, the wall thickness is 1.5 mm, the weld is butt joint, and there is no gap and no filler wire.

[0078] To realize the vacuum electron beam welding of the 200 mm oxygen-free copper, the specific steps are as follows:

[0079] 1) The surface and the surrounding oxide skin and oil stains of the high-pressure container cylinder to be welded are cleaned by sandpaper, acetone and the like;

[0080] 2) The cleaned high-pressure container to be welded is assembled on a two-dimensional work platform 2 of a vacuum electron beam welding machine, as shown in Figure 2 The inner support tool is connected with the mandrel, and is placed at a position 5 mm away from the welding position. The roundness is adjusted by the tightness of the bolt on the melon, and the two inner support tools are adjusted to ensure that the assembly butt joint gap is not greater than 0.1 mm;

[0081] 3) The assembled high-pressure container 5 is connected and fixed on a rotary positioner 3 and a tail top 4 through the mandrel and the end cover, and the clamping of the solid rocket engine high-pressure container is realized through the rotary positioner and the tail top;

[0082] 4) The fixed high-pressure container is moved into the vacuum chamber through the two-dimensional work platform, and after the vacuum degree reaches 6.65*10 -5 mbar or above, welding is started;

[0083] 5) When the welding vacuum state is reached, the high-pressure vacuum electron beam welding gun 1 is opened to start welding. The welding process includes pre-welding electron beam scanning cleaning, pre-welding preheating, welding implementation process, and post-welding slow cooling process;

[0084] 6) The continuous attenuation sinusoidal energy output is adopted during the arc striking to weaken the influence of the arc striking.

[0085] The pre-welding scanning cleaning process is shown in Table 1:

[0086] Table 1: Pre-welding scanning cleaning process parameters

[0087]

[0088] The pre-welding preheating process is shown in Table 2:

[0089] Table 2: Pre-welding preheating process parameters

[0090]

[0091] The welding process is shown in Table 3:

[0092] Table 3: Welding process parameters

[0093]

[0094] According to the standard GJB1187A-2001, each weld is detected, and the defects such as excessive pores, cracks, and incomplete fusion and positions are identified. If there is a defect, the specific defect position is repaired, and the defect is eliminated to ensure that each weld meets the quality standard requirements. After detection, the surface of the welded weld is well shaped, free of pores, cracks, and other defects. The average tensile strength of the weld at room temperature can reach 165Mpa, and the fracture is at the base material.

[0095] The welding process of the present application is simple to operate, reduces the requirements for welding operators, and almost does not produce splashes during the welding process. The weld quality is good, free of defects such as pores and cracks, and the weld forming is beautiful.

[0096] The present application is described in detail above in combination with specific embodiments and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that the technical solutions and embodiments of the present application can be variously replaced, modified, or improved without deviating from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

[0097] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

Claims

1. A vacuum electron beam welding method for oxygen-free copper high-pressure vessels, characterized in that, include: (1) Clean the weld seams of the high-pressure vessel shell; (2) Fix the high-pressure vessel cylinder onto the two-dimensional working platform of the vacuum electron beam welding machine so that the butt gap of the weld is no more than 0.1 mm; (3) Fix the high-pressure vessel cylinder between the rotary positioner and the tail top; (4) The two-dimensional working platform drives the high-pressure vessel cylinder, rotary positioner and tail top to move into the vacuum chamber; (5) After the vacuum chamber is evacuated to the target vacuum level, electron beam welding is performed; the electron beam welding process includes pre-welding electron beam scanning and cleaning, pre-welding preheating and formal welding.

2. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (1), the method for cleaning the weld seams of the high-pressure vessel shell includes: Clean the oxide scale and oil stains within 20mm-50mm of the weld center, grind the weld joint surface with sandpaper, and then wipe with acetone.

3. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (2), the vacuum electron beam welding machine uses an ion beam as an energy source with a maximum voltage of 60KV and a maximum power of 30KW, and has an electron beam scanning function.

4. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (2), two internal support fixtures are installed inside the two sections of the high-pressure vessel cylinder respectively; The internal support fixture includes several melon-shaped structures; All the melon-shaped structures are combined to form a cylinder, which matches the shape of the inner cavity of the high-pressure vessel. Each segment is machined and formed, with several threaded holes along the circumference of each segment. Bolts are tightened into the threaded holes of the segment and fixed in place. The bolt heads are spherical. The contact area and contact force between the segment structure and the inner wall of the high-pressure vessel are adjusted by the bolts on each segment structure to achieve support for the high-pressure vessel.

5. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (3), the high-pressure vessel body is fixed between the rotary positioner and the tail top by means of the mandrel and end cap; The mandrel passes through the melon-shaped structure along the axial direction. The melon-shaped structure is fixed to the mandrel by a sleeve and bolts. The two end caps are respectively assembled at both ends of the high-pressure vessel body and are tightened and relatively fixed by the threads at the ends of the mandrel. The rotary positioner and the tail tip are respectively connected to both ends of the mandrel.

6. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (5), the target vacuum level is 6.65 × 10⁻⁶. -5 mbar or above.

7. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (5), the process parameters for pre-welding electron beam scanning cleaning include: Voltage 60KV, focusing current 515~535mA, scanning current 10~20mA, welding speed 5~10mm / s, scanning morphology is circular, scanning radius 0.5mm.

8. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (5), the preheating process parameters include: Voltage 60KV, focusing current 515~535mA, scanning current 15~25mA, welding speed 8~12mm / s, scanning morphology is circular, scanning radius 0.5mm.

9. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (5), the process parameters for the formal welding include: The focusing current is 530-550mA, with a lower focusing current of 15mA. The welding speed is 8-12mm / s, the welding current is 43mA-48mA, the scanning morphology is circular, and the scanning radius is 0.5mm. The formal welding arc termination uses a continuously decaying positive spiral waveform output, which causes the welding arc crater to gradually shrink and close during the repeated melting and solidification process.

10. The vacuum electron beam welding method for oxygen-free copper high-pressure vessels according to claim 1, characterized in that, In step (5), the high-pressure vessel cylinder is made of oxygen-free copper, with a purity of 99.98% and an oxygen content of less than 0.003%.

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