Welding device and welding method for rocket engine nozzle

Abstract

The present invention discloses a welding device and a welding method for a rocket engine nozzle, and belongs to the field of aerospace engine welding technology. The welding device for a rocket engine nozzle comprises: a first tool for clamping the melon slices to be welded of the engine nozzle, a second tool for clamping the cylinder to be welded, and a gas protection cover for performing inert gas protection on the front of the weld of the engine nozzle. The first tool comprises a first inner support member, a pressure plate is sleeved on the outside of the first inner support member, and a first clamping structure for clamping the edge of the melon slice is provided on the pressure plate; the second tool comprises a second inner support member and a third inner support member for supporting the cylinder, and a clamping mechanism for clamping the joints of adjacent cylinders is provided on the outside of the second inner support member or the third inner support member. The use of the welding device and the welding method for a rocket engine nozzle according to the present invention can solve the problems of the existing engine nozzle being easily oxidized and producing defects when welded in the atmosphere, and the high welding cost.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace engine welding, and in particular to a welding device and a welding method for a rocket engine nozzle. Background Art

[0002] With the rapid development of aerospace technology, performance requirements for key components such as liquid rocket engines are becoming increasingly stringent, with large-scale and lightweight components becoming a key trend. Niobium (Nb) and its alloys, due to their excellent high-temperature strength and corrosion resistance, are ideal materials for manufacturing high-temperature structural components such as large-scale nozzle extensions for liquid rocket engines. However, niobium alloys are high-temperature reactive metals, and their welding, especially in the manufacture of large, thin-walled components, presents significant challenges.

[0003] The primary challenge lies in the high chemical activity of niobium alloys, which react violently with oxygen during high-temperature welding. This leads to severe oxidation of the weld and heat-affected zone, increasing hardness while significantly decreasing plasticity and toughness. The interface between the resulting oxide layer and the substrate can easily become a source of stress concentration, inducing critical defects such as weld cracks. Furthermore, for large, thin-walled nozzle structures, controlling heat input and deformation during welding is crucial. Uneven heating and cooling can easily lead to unacceptable deformation or residual stress in the component.

[0004] Traditional welding methods have limitations. While vacuum electron beam welding can produce high-quality welds, it is expensive and complex, and the size of the vacuum chamber severely restricts the efficiency and cost of manufacturing large nozzles. Conventional atmospheric laser welding, while efficient and flexible, often employs standard shielding methods such as side-blowing or coaxial air blowing, which fail to provide sufficient and effective protection for niobium alloys. The welds are susceptible to oxidation, resulting in defects such as porosity, and thus failing to meet the high reliability requirements of aerospace products. Recent vacuum laser welding technologies (such as the vacuum oscillating laser welding disclosed in Chinese patent CN114985933A) combine the advantages of laser welding and address the oxidation issue using a vacuum environment. However, their fundamental limitation—reliance on large vacuum equipment—results in high costs and long production cycles, making it difficult to achieve low-cost, efficient, and scalable manufacturing of large-scale niobium alloy nozzles. Summary of the Invention

[0005] The purpose of the present invention is to provide a welding device and a welding method for a rocket engine nozzle, so as to solve the problems that the existing engine nozzle is easily oxidized and produces defects when welded in the atmosphere, and the welding cost is high.

[0006] To achieve the above-mentioned object, the present invention provides a welding device for a rocket engine nozzle, comprising:

[0007] The first tooling is used to clamp the melon segments to be welded on the engine nozzle and assemble the melon segments into a cylinder; the first tooling includes a first inner support member, a pressure plate is sleeved on the outside of the first inner support member, the melon segments are located between the first inner support member and the pressure plate, and the pressure plate is provided with a first pressing structure for pressing the edges of the melon segments;

[0008] The second tooling is used to clamp the cylinders to be welded and assemble the cylinders into the engine nozzle; the second tooling includes a second inner support member and a third inner support member for supporting the cylinders, and a clamping mechanism is provided on the outside of the second inner support member or the third inner support member for clamping the joints of adjacent cylinders;

[0009] A gas protection hood is provided on the welding head to provide inert gas protection to the front of the weld of the engine nozzle. The first tooling and the second tooling are provided with a back gas protection structure to provide inert gas protection to the back of the weld.

[0010] Preferably, the outer surface of the first inner support member is a contoured surface that fits the melon slices, the first protection structure of the back gas protection structure is arranged on the first inner support member, and the first inner support member is arranged on a rotating table; the first protection structure includes a first protection air duct, the first protection air duct is arranged on the outer surface of the first inner support member, the first protection air duct is located at the joint of two adjacent melon slices, and an air inlet is provided at one end of the first protection air duct, which is connected to the inert gas bottle through a connecting pipe.

[0011] Preferably, several adjusting members for adjusting the distance between the pressure plate and the first inner support member are provided between the pressure plate and the first inner support member. One end of the adjusting member is provided with a long strip adjusting hole for adjusting the installation position of the adjusting member on the pressure plate. The bolt passes through the adjusting hole to fix the adjusting member to the top end of the pressure plate, and the other end of the adjusting member is connected to the first inner support member through a top screw.

[0012] Preferably, the first clamping structure includes a first pressing claw, and an avoidance hole passing through the pressing plate is provided on the pressing plate, the avoidance hole is located at the connection between adjacent melon slices, and the first pressing claws are arranged in a linear array at the avoidance hole, and the first pressing claws on both sides of the avoidance hole respectively press and fix the edges of the two adjacent melon slices, and the pressing plate is provided with an installation hole for installing the first pressing claw.

[0013] Preferably, the side surfaces of the second inner support member and the third inner support member are contoured surfaces that fit the inner side surfaces of the cylinder body. The second inner support member and the third inner support member are arranged on a column. The outer surface of the column is provided with an external thread. The second inner support member and the third inner support member are connected to the column through a locking nut; the second protection structure of the back gas protection structure is arranged in the middle of the outer surface of the second inner support member and the third inner support member, the second protection structure includes a second protection gas duct, the second protection gas duct is located at the connection between the two adjacent cylinders, and the second protection gas duct is connected to the inert gas bottle through a connecting pipe.

[0014] Preferably, the clamping structure includes a second clamping structure and a third clamping structure, the third clamping structure is located above the second clamping structure, the second clamping structure is used to clamp and fix the top end of the lower cylinder on the second inner support or the third inner support, and the third clamping structure is used to clamp and fix the bottom end of the upper cylinder on the second inner support or the third inner support; the third clamping structure includes a top plate, the top plate is set on the column, a second pressure ring is set below the top plate, the second pressure ring is connected to the top plate through a number of second connecting rods, and the second pressure ring is provided with a number of third pressure claws that press the bottom end of the upper cylinder against the side wall of the second inner support or the third inner support, and the third pressure claws are connected to the second pressure ring through bolts.

[0015] Preferably, the second clamping structure includes a base plate, the base plate is arranged on the rotating table, the column is arranged on the base plate, a first pressure ring is arranged above the base plate, the first pressure ring is connected to the base plate through a plurality of first connecting rods, and the first pressure ring is provided with a plurality of second pressure claws for pressing the top end of the lower cylinder onto the side wall of the second inner support or the third inner support, and the second pressure claws are connected to the first pressure ring through bolts.

[0016] Preferably, the gas protection cover includes a shell, one end of which is provided with a clamping column, the shell is connected to the welding head through the clamping column and the universal meter seat, an air chamber is provided inside the shell, an air inlet communicating with the air chamber is provided on the shell, and the air inlet is connected to the inert gas bottle through a connecting pipe;

[0017] The middle part of the gas chamber is provided with a main protection gas channel, which is used to provide inert gas protection to the welding area; the front end of the gas chamber is provided with a front protection gas channel inclined forward, which is used to provide pre-welding protection to the welded area; the rear end of the gas chamber is provided with a rear protection gas channel inclined backward, which is used to purge the weld after welding;

[0018] The main protective air duct includes a first diffusion chamber and a second diffusion chamber. The first diffusion chamber is connected to the air chamber through a connecting hole. The first diffusion chamber and the second diffusion chamber are connected through several equalizing flow holes. The second diffusion chamber is provided with several air outlet holes; an oxygen content detection sensor is provided in the second diffusion chamber.

[0019] The welding method based on the welding device of the rocket engine nozzle comprises the following steps:

[0020] S1. Connect the gas shield to the welding head through the universal meter base, and adjust the angle and distance between the gas shield and the melon slice or cylinder through the universal meter base, so that the center of the gas shield is aligned with the center of the weld track.

[0021] S2. Assemble the melon segments using the first tool; fix the first inner support member on the rotating table, place the melon segments on the contoured surface of the outer surface of the first inner support member, adjust the distance between the first inner support member and the pressing plate according to the thickness of the melon segments using the adjusting member, lock the first inner support member and the pressing plate using the jackscrew, and clamp the melon segments between the first inner support member and the pressing plate;

[0022] S3. Install a first pressing jaw on the pressure plate using a wrench with a force sensor. The first pressing jaw uniformly presses the edge of the melon slice to be welded against the first inner support member.

[0023] S4. Inert gas in the inert gas bottle is introduced into the gas protection support cover and the first protective gas channel through the connecting pipe to pre-purge the melon segments to be welded. After the oxygen content detection sensor stabilizes, the laser welder is started and the longitudinal connecting seams between adjacent melon segments are welded using the laser welding head to weld the melon segments into a cylindrical body.

[0024] S5. Assemble the cylinders using the second tooling; adjust the distance between the second inner support and the third inner support using the locking nut according to the height of the cylinders to be welded; place the two cylinders to be welded outside the second inner support and the third inner support, respectively, and fit them to the contoured surfaces of the second inner support and the third inner support, with the second protective air duct located at the connection between the two adjacent cylinders;

[0025] S6. Install a first pressure ring on the outside of the third inner support member, and the first pressure ring is connected to the bottom plate through a first connecting rod; install a top plate on the column, and install a second pressure ring on the outside of the third inner support member, and the second pressure ring is connected to the top plate through a second connecting rod; install a second pressure claw and a third pressure claw on the outside of the first pressure ring and the second pressure ring respectively by bolts, and the second pressure claw and the third pressure claw respectively press the lower cylinder and the upper cylinder to the contoured surface of the third inner support member, and the upper cylinder is coaxial with the lower cylinder;

[0026] S7. Pass the inert gas in the inert gas bottle into the gas protection support cover and the second protection gas duct through the connecting pipe to pre-purge the cylinder to be welded. After the oxygen content detection sensor is stable, start the laser welder and weld the transverse connecting seams between adjacent cylinders through the laser welding head. Use a symmetrical welding method to weld the cylinders into the engine nozzle. The welding angle of each welding is 10°-15°.

[0027] Preferably,

[0028] In S4 and S7, the total flow rate of the inert gas in the gas protection cover is 15 L / min-25 L / min, and the total flow rate of the inert gas in the first protection gas duct and the second protection gas duct is 10 L / min-15 L / min;

[0029] In S4 and S7, the laser power is 2200W, the welding speed is 2m / min, the defocus amount is +2mm, the swing amplitude is 0.8mm, the swing frequency is 130Hz, and a circular swing mode is adopted.

[0030] The advantages and positive effects of the welding device and welding method of the rocket engine nozzle of the present invention are:

[0031] 1. The provision of the gas protection hood of the present invention avoids dependence on expensive and bulky vacuum systems, significantly reduces equipment investment and operating costs, and improves production flexibility and efficiency.

[0032] 2. The provision of the gas shield in the present invention significantly reduces oxidation and nitridation during welding. Combining the welding process with swing welding is beneficial to reducing pores, improving weld formation, reducing crack sensitivity, and effectively suppressing welding defects.

[0033] 3. The segmented independent pressure-adjustable structure of the first and second fixtures of the present invention ensures the assembly accuracy of large thin-walled components and the structural stability during welding, and effectively controls welding deformation.

[0034] 4. The parameters in the preparation method of the present invention are adjustable over a wide range and are suitable for welding niobium alloy nozzles with different wall thicknesses and structures. The process is stable and reliable, and the weld quality meets the stringent requirements of aerospace.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the three-dimensional structure of the first tooling according to an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the three-dimensional structure of a pressing plate according to an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the three-dimensional structure of the first inner support member according to an embodiment of the present invention;

[0040] Figure 5 For attachment Figure 4 Middle A enlarged view;

[0041] Figure 6 This is a schematic diagram of the three-dimensional structure of the second tooling according to an embodiment of the present invention;

[0042] Figure 7 This is a schematic front view of the structure of the second tooling according to an embodiment of the present invention;

[0043] Figure 8This is a schematic diagram of the cross-sectional structure of a second tooling according to an embodiment of the present invention;

[0044] Figure 9 This is a schematic diagram of the three-dimensional structure of the third compression structure according to an embodiment of the present invention;

[0045] Figure 10 For attachment Figure 8 Middle B: Enlarged image;

[0046] Figure 11 A schematic diagram of the three-dimensional structure of a gas protection cover according to an embodiment of the present invention;

[0047] Figure 12 A schematic diagram of the cross-sectional structure of a gas protection cover according to an embodiment of the present invention;

[0048] Figure 13 This is a schematic diagram of the three-dimensional structure of an engine nozzle according to an embodiment of the present invention;

[0049] Figure 14 The macroscopic morphology of the engine nozzle weld of an embodiment of the present invention; (a) is the front of the weld; (b) is the back of the weld;

[0050] Figure 15 This is the macroscopic morphology of the engine nozzle weld when welding without a gas shield;

[0051] Figure 16 This is a macroscopic morphology diagram of the engine nozzle weld joint after tensile testing according to an embodiment of the present invention;

[0052] Figure 17 Schematic diagram of the circular swing mode of the laser welding head during the engine nozzle welding process according to an embodiment of the present invention.

[0053] Reference numerals

[0054] 1. First tooling; 11. First inner support; 12. Pressing plate; 13. Adjusting member; 14. First pressing claw; 15. Avoidance hole; 16. Mounting hole; 17. First protective airway; 18. Air inlet;

[0055] 2. Second tooling; 21. Column; 22. Second inner support member; 23. Third inner support member; 24. Bottom plate; 25. First connecting rod; 26. Second pressure claw; 27. Top plate; 28. Second connecting rod; 29. ​​Third pressure claw; 210. First pressure ring; 211. Second pressure ring; 212. Second protective air duct; 213. Lock nut;

[0056] 3. Gas protection cover; 31. Housing; 32. Air inlet; 33. Clamping column; 34. Oxygen content detection sensor; 35. Air chamber; 36. Connecting hole; 37. First diffusion chamber; 38. Flow balancing hole; 39. Second diffusion chamber; 310. Air outlet; 311. Front protection air duct; 312. Rear protection air duct;

[0057] 4. Engine nozzle; 41. First cylinder; 42. Second cylinder; 43. Third cylinder; 44. Melon slice; 45. Reinforcement rib;

[0058] 5. Welding head. DETAILED DESCRIPTION

[0059] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is usually placed when in use. These are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. In the description of the present invention, it should also be noted that, unless otherwise expressly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the internal parts of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. In the event of any inconsistency, the meaning described in this specification or the meaning derived from the contents recorded in this specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0061] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0062] like Figure 13 As shown, the engine nozzle 4 includes a first barrel 41, a second barrel 42, and a third barrel 43 connected in sequence. The first barrel 41, the second barrel 42, and the third barrel 43 each have a small end and a large end formed at both ends of the axial direction. The first barrel 41, the second barrel 42, and the third barrel 43 are welded together via a transverse circumferential weld to form the engine nozzle 4. Each barrel section is formed by welding multiple melon segments 44 via longitudinal welds.

[0063] like Figure 1A welding device for a rocket engine nozzle, comprising:

[0064] The first fixture is used to clamp the segments of the engine nozzle to be welded, assembling them into the first fixture 1. It is used to clamp the segments 44 of the engine nozzle 4 to be welded, assembling them into the cylinder. The second fixture 2 is used to clamp the cylinder to be welded, assembling the cylinder into the engine nozzle 4. The gas shield hood 3, mounted on the welding head 5, provides inert gas shielding to the front of the weld seam of the engine nozzle 4. The first and second fixtures 1 and 2 are equipped with a back-side gas shielding structure to provide inert gas shielding to the back of the weld seam.

[0065] like Figure 2 、 Figure 3 、 Figure 4 As shown, the first tooling 1 includes a first inner support member 11, the outer surface of which is a contoured surface that mates with the melon segments 44. A pressure plate 12 is sleeved on the outer surface of the first inner support member 11, with the melon segments 44 positioned between the first inner support member 11 and the pressure plate 12. The pressure plate 12 presses the melon segments 44 against the outer surface of the first inner support member 11. The first inner support member 11 is mounted on a rotating table.

[0066] Several adjusting members 13 for adjusting the distance between the pressing plate 12 and the first inner support member 11 are provided between the pressing plate 12 and the first inner support member 11. One end of the adjusting member 13 is provided with a long strip-shaped adjusting hole for adjusting the installation position of the adjusting member 13 on the pressing plate 12. A bolt passes through the adjusting hole to fix the adjusting member 13 to the top of the pressing plate 12. The length of the adjusting member 13 extending out of the pressing plate 12 can be adjusted through the long strip-shaped adjusting hole, thereby adjusting the distance between the pressing plate 12 and the first inner support member 11 as needed. The other end of the adjusting member 13 is connected to the first inner support member 11 through a top screw to achieve locking and fixation between the pressing plate 12 and the first inner support member 11.

[0067] The pressure plate 12 is provided with a first clamping structure for clamping the edges of the melon segments 44. The first clamping structure includes a first pressure claw 14. The pressure plate 12 is provided with an avoidance hole 15 that passes through the pressure plate 12. The avoidance hole 15 is located at the connection between adjacent melon segments 44. The first pressure claws 14 are arranged in a linear array at the avoidance holes 15, and the first pressure claws 14 are evenly spaced along the longitudinal direction. The first pressure claws 14 on both sides of the avoidance hole 15 respectively clamp and fix the edges of the two adjacent melon segments 44. The pressure plate 12 is provided with a mounting hole 16 for mounting the first pressure claw 14, and the first pressure claw 14 is fixed to the pressure plate 12 by bolts.

[0068] The first inner support member 11 and the pressure plate 12 have different sizes depending on the size of the melon slices 44. In this embodiment, the first inner support member 11 is mounted on a rotating table during use, with the inner surface of the melon slices 44 completely aligned with the contoured surface of the outer surface of the first inner support member 11. After the melon slices 44 are in place, the pressure plate 12 is installed. An adjustment member 13 is mounted on the pressure plate 12 to fine-tune the gap between the pressure plate 12 and the first inner support member 11, ensuring that the edges of the melon slices 44 are firmly pressed against the first inner support member 11.

[0069] The rocket engine nozzle 4 of this embodiment utilizes independently adjustable first pressure jaws 14 arranged in sections along both sides of the weld seam during the longitudinal welding process. By cooperating with the internal first inner support 11, the nozzle can precisely conform to the complex contours of the nozzle. By independently adjusting the pressure of each first pressure jaw 14, a uniform and controllable clamping force is applied, effectively ensuring weld gap and misalignment, significantly suppressing thermal deformation during welding, and maintaining the geometric accuracy of the component. The first pressure jaws 14 of this embodiment are located on either side of the longitudinal seam between the two melon segments 44 to be welded. When using the first pressure jaws 14 to compress the melon segments 44, a wrench with a pressure sensor is used to install the first pressure jaws 14. During installation, the bolts driving the first pressure jaws 14 are tightened gradually and alternately. During the tightening process, the wrench with the pressure sensor controls the uniform and appropriate pressure distribution of each first pressure jaw 14, ensuring that the edges of the melon segments 44 are firmly pressed against the first inner support 11. The gaps and misalignment of all melon segments 44 are less than 10% of the wall thickness.

[0070] like Figure 6 、 Figure 7 、 Figure 8 As shown, the second fixture 2 includes a second inner support member 22 and a third inner support member 23 that support the cylinder. The side surfaces of the second and third inner supports 22 and 23 are contoured surfaces that conform to the inner side surfaces of the cylinder. The second and third inner supports 22 and 23 are mounted on a column 21. The outer surface of the column 21 is provided with external threads. The second and third inner supports 22 and 23 are connected to the column 21 via a locking nut 213. The distance between the second and third inner supports 22 and 23 is adjusted by rotating the locking nut 213 on the column 21.

[0071] The exterior of the second or third inner support member 22, 23 is equipped with a clamping mechanism that compresses the joints of adjacent cylinders. The clamping structure comprises a second and a third clamping structure, with the third structure located above the second. The second clamping structure is used to clamp and secure the top end of the lower cylinder to the second or third inner support member 22, 23, while the third clamping structure is used to clamp and secure the bottom end of the upper cylinder to the second or third inner support member 22, 23.

[0072] like Figure 9 、 Figure 10 The third clamping structure includes a top plate 27, which is mounted on the column 21 via a locking nut 213. A second pressure ring 211 is disposed below the top plate 27 and is fixedly connected to the top plate 27 via a plurality of second connecting rods 28. The second pressure ring 211 is provided with a plurality of third pressure claws 29 that press the bottom end of the upper cylinder against the side wall of the second inner support member 22 or the third inner support member 23. The third pressure claws 29 are connected to the second pressure ring 211 via bolts.

[0073] The second clamping structure includes a base plate 24, which is arranged on a rotating table. The column 21 is connected to the base plate 24 by a locking nut 213. A first pressure ring 210 is arranged above the base plate 24. The first pressure ring 210 is fixedly connected to the base plate 24 by a plurality of first connecting rods 25. The first pressure ring 210 is provided with a plurality of second pressure claws 26 that press the top of the lower cylinder against the side wall of the second inner support 22 or the third inner support 23. The second pressure claws 26 are connected to the first pressure ring 210 by bolts. The pressure and position of the corresponding second pressure claws 26 and third pressure claws 29 are adjusted by bolts to ensure the coaxiality of the two cylinders to be welded, so that the butt end faces of the cylinders are parallel and tightly fitted, thereby adjusting the gap between adjacent cylinders and the amount of distortion to be less than 10% of the wall thickness.

[0074] During the welding process of the first and second cylinders 41, 42, the second and third pressing structures press the first and second cylinders 41, 42 against the exterior of the third inner support 23. After the first and second cylinders 41, 42, are connected to the third cylinder 43, the height of the second inner support 22 is adjusted, and the second and third pressing structures press the bottom end of the second cylinder 42 and the top end of the third cylinder 43 against the exterior of the second inner support 22. The second and third pressing structures need to be replaced to meet the compression requirements of the first, second, and third cylinders 41, 42, 43.

[0075] like Figure 11 、 Figure 12 As shown, the gas shield hood 3 includes a housing 31, one end of which is provided with a clamping post 33. The housing 31 is connected to the welding head 5 via the clamping post 33 and the universal joint. The welding head 5 is a conventional laser welding head 5, and the universal joint is a conventional structure. The universal joint enables multi-degree-of-freedom adjustment, allowing precise adjustment of the position and angle of the gas shield hood 3 in the X, Y, and Z directions. An air chamber 35 is provided within the housing 31, and an air inlet 32 ​​is provided on the housing 31, communicating with the air chamber 35. The air inlet 32 ​​is connected to the inert gas bottle via a connecting pipe.

[0076] The central portion of the air chamber 35 is provided with a main shielding channel, which is used to provide inert gas shielding to the welding area. A forward-angled front shielding channel 311 is provided at the front end of the air chamber 35. This channel is used to provide pre-weld protection to the welded area. A backward-angled rear shielding channel 312 is provided at the rear end of the air chamber 35. This channel is used to purge the weld after welding. The front and rear shielding channels are narrow, long gaps located at the front and rear edges of the bottom of the shell 31, respectively. The gas entering through these channels is ejected obliquely, providing better pre-weld protection and post-weld cooling and purging.

[0077] Different protection requirements for different areas can be met by designing different sizes of the front protection channel, rear protection channel, and main protection airflow channel. For example, the size of the front protection channel, rear protection channel, or the size of the main protection airflow channel can be increased.

[0078] The primary protective airway includes a first diffusion chamber 37 and a second diffusion chamber 39. The first diffusion chamber 37 communicates with the air chamber 35 through a connecting hole 36. The first diffusion chamber 37 and the second diffusion chamber 39 communicate with each other through a plurality of equalizing holes 38. The second diffusion chamber 39 is provided with a plurality of air outlet holes 310.

[0079] During use, the inert shielding gas enters the interior through the air inlet 32 ​​provided at the top of the shell 31. The gas first enters the air chamber 35, which serves as the initial pressure stabilizing and distribution chamber. In order to achieve precise protection for different stages of welding, the gas shield 3 is divided into three functionally independent areas from the top air chamber 35 downwards through a partition structure. The two sides are respectively the front protection channel and the rear protection channel, which are used to guide part of the gas to the front and rear ends of the shell 31 to achieve pre-welding purge and post-welding tail cooling protection. The middle area is the main protective air flow channel. The gas enters the first diffusion chamber 37, the equalizing hole 38 and the second diffusion chamber 39 from the air chamber 35. The inert gas flowing out of the air outlet 310 forms a stable inert atmosphere layer in the welding area, which effectively isolates the air and inhibits oxidation during the welding process.

[0080] Because the quality of the primary shielding airflow is crucial to welding results, this embodiment employs a two-stage diffusion structure within the primary shielding airflow channel. Gas entering from chamber 35 initially diffuses downward through a first diffusion chamber 37 and through flow-equalizing holes 38. The gas then enters a separate, shallow, and wide second diffusion chamber 39, located directly below flow-equalizing holes 38. Within this chamber, the gas undergoes secondary mixing, deceleration, and pressure stabilization, resulting in a highly uniform, low-turbulence airflow that effectively isolates the air and inhibits oxidation, resulting in a high-quality weld joint.

[0081] An oxygen content sensor 34 is located within the second diffusion chamber 39. In this embodiment, the second diffusion chamber 39 is provided with a microchannel, within which the oxygen content sensor 34 is located. This design enables real-time monitoring of the actual oxygen content of the primary shielding gas about to be ejected. The monitoring signal can be used for process recording and alarming for excess oxygen, ensuring that shielding gas quality is always under control.

[0082] like Figure 5 As shown, the backside gas protection structure includes a first protection structure and a second protection structure. The first protection structure is disposed on the first inner support member 11 and includes a first protection gas duct 17, which is disposed on the outer surface of the first inner support member 11. The first protection gas duct 17 is located at the junction of two adjacent melon segments 44. An air inlet 18 is provided at one end of the first protection gas duct 17, which is connected to the inert gas bottle via a connecting pipe.

[0083] The second protection structure is provided at the middle of the outer surface of the second inner support 22 and the third inner support 23. The second protection structure includes a second protection gas channel 212, which is located at the connection between two adjacent cylinders and is connected to the inert gas bottle through a connecting pipe.

[0084] The inert gas is high-purity argon with a purity of 99.999%.

[0085] In this embodiment, the material of the engine nozzle 4 is a niobium alloy, such as a niobium-hafnium alloy, a niobium-tungsten alloy, or a niobium-zirconium alloy. Niobium alloy not only has high-temperature strength and oxidation resistance, but also has good processing properties. Of course, in other embodiments, the nozzle material can also be a tungsten alloy. The engine nozzle 4 is composed of a first barrel 41, a second barrel 42, and a third barrel 43 from the small end to the large end. The thickness of the first barrel 41, the second barrel 42, and the third barrel 43 is 1 mm. The number m of melon segments 44 divided by the first barrel 41, the second barrel 42, and the third barrel 43 is 6, 8, and 10, respectively.

[0086] In this embodiment, sheet metal forming is performed according to the number and characteristics of the divided melon segments 44. In this embodiment, the curvature of each nozzle section is different, and the melon segments 44 of each section have their own characteristics in shape. For example, the melon segments 44 of the first barrel 41, the second barrel 42, and the melon segments 44 of the third barrel 43 are all press-formed. After the melon segments 44 are formed, they are milled to ensure that there is enough margin for the tight docking of the longitudinal seam and the annular seam. Sandpaper of different mesh sizes is used to polish the surface to be welded to remove surface oxides and improve the flatness of the weld surface. Then, 75% ethanol is used to wipe the weld surface to remove granular impurities attached to the surface.

[0087] The welding method based on the welding device of the rocket engine nozzle 4 comprises the following steps:

[0088] S1. The gas protection cover 3 is connected to the laser welding head 5.

[0089] Connect the gas shield hood 3 to the welding head 5 through the universal base, and adjust the angle and distance between the gas shield hood 3 and the melon slice 44 or the cylinder through the universal base to ensure that the bottom of the shell 31 is parallel to the workpiece surface, maintain the optimal working distance of 5mm to 10mm, and align the center of the gas shield hood 3 with the center of the weld trajectory.

[0090] S2, using the first tool 1 to assemble the melon slices 44. Specifically:

[0091] The first inner support member 11 is fixed on a rotating table, and the melon slice 44 is placed on the contoured surface of the outer surface of the first inner support member 11 .

[0092] The distance between the first inner support member 11 and the pressure plate 12 is adjusted according to the thickness of the melon slices 44 through the adjusting member 13, and the first inner support member 11 and the pressure plate 12 are locked by the top screw, and the melon slices 44 are clamped and fixed between the first inner support member 11 and the pressure plate 12 so that the upper and lower ends of two adjacent melon slices 44 are aligned.

[0093] S3. Use a wrench with a force sensor to install the first pressing claw 14 on the pressing plate 12. The first pressing claw 14 presses the edge of the melon slice 44 to be welded evenly onto the first inner support 11.

[0094] During installation, tighten the bolts driving the first pressure claws 14 step by step and alternately. During the tightening process, the wrench with the pressure sensor controls the pressure distribution of each first pressure claw 14 to be uniform and of moderate size. Secondarily, ensure that the edges of the melon segments 44 are compacted on the first inner support 11, and the gaps and distortions of all the melon segments 44 are less than 10% of the wall thickness.

[0095] S4 and melon segments 44 are welded to form a cylindrical body.

[0096] The inert gas in the inert gas bottle is introduced into the gas protection support cover 3 and the first protective gas duct 17 through the connecting pipe to pre-purge the melon segments 44 to be welded. After the oxygen content detection sensor 34 is stable, the laser welder is started and the longitudinal connecting seams between adjacent melon segments 44 are welded by the laser welding head 5 to weld the melon segments 44 into a cylindrical body.

[0097] After welding two adjacent melon segments 44, the rotary table rotates a certain angle and repeats S4 to complete the welding of all longitudinal welds on the first cylinder 41. Repeat S2, S3 and S4 to complete the welding of the second cylinder 42 and the third cylinder 43.

[0098] S5. Use the second tool 2 to assemble the cylinder. Specifically:

[0099] According to the height of the second cylinder 42 to be welded, the distance between the second inner support member 22 and the third inner support member 23 is adjusted by the locking nut 213 .

[0100] The first and second cylinders 41, 42 to be welded are placed outside the third and second inner supports 23, 22, respectively, and aligned with the contoured surfaces of the second and third inner supports 22, 23. The second and first cylinders 42, 41 are positioned using the oblique side surfaces of the second and third inner supports 22, 23, respectively. The second shielding gas channel 212 on the third inner support 23 is located at the junction of the first and second cylinders 41, 42.

[0101] S6. Install a first pressure ring 210 on the outside of the third inner support 23, and the first pressure ring 210 is connected to the bottom plate 24 through the first connecting rod 25. Install the top plate 27 on the column 21 through the locking nut 213, and install the second pressure ring 211 on the outside of the third inner support 23, and the second pressure ring 211 is connected to the top plate 27 through the second connecting rod 28. Install the second pressure claw 26 and the third pressure claw 29 on the outside of the first pressure ring 210 and the second pressure ring 211 respectively by bolts, and adjust the pressure of the second pressure claw 26 and the third pressure claw 29 by a wrench with a pressure sensor so that the second pressure claw 26 and the third pressure claw 29 are evenly pressed against the bottom end of the first cylinder 41 and the top end of the second cylinder 42. When installing the first pressure ring 210 and the second pressure ring 211, ensure the horizontality of the first pressure ring 210 and the second pressure ring 211 to prevent tilting, which is conducive to improving the adjustment accuracy of the cylinder.

[0102] The second pressing claw 26 and the third pressing claw 29 respectively press and fix the second cylinder 42 and the first cylinder 41 on the contoured surface of the third inner support 23, and the gap and distortion between the first cylinder 41 and the second cylinder 42 are less than 10% of the wall thickness.

[0103] S7. The inert gas in the inert gas bottle is introduced into the gas protection cover 3 and the second protective gas channel 212 through the connecting pipe to pre-purge the cylinder to be welded. After the oxygen content detection sensor 34 stabilizes, the laser welder is started and the laser welding head 5 is used to weld the transverse connecting seams between adjacent cylinders.

[0104] Before starting the laser, perform sufficient pre-purge and continue ventilation for 10 to 30 seconds or longer until the sensor readings are stable and meet the standards, ensuring that the air in the protection area is completely replaced and a reliable inert atmosphere environment is established.

[0105] The welding angle for each weld is 10°-15°. After each weld is completed, the welder returns to the starting point and rotates 180° for symmetrical welding. Before performing the laser automatic welding, manual spot welding is first performed, with spot welding every 20mm-30mm to achieve pre-welding of the first cylinder 41 and the second cylinder 42.

[0106] After completing the annular weld of the first cylinder 41 and the second cylinder 42, weld with the third cylinder 43. First, adjust the height of the second inner support 22 according to the height of the third cylinder 43, and sleeve the bottom end of the third cylinder 43 on the outer surface of the bottom plate 24. The outer side surface of the bottom plate 24 is the contour surface of the inner surface of the third cylinder 43. Sleeve the second cylinder 42 on the outside of the second inner support 22. Replace the first pressure ring 210, the second pressure ring 211, the first connecting rod 25 and the second connecting rod 28 so that the second pressure claw 26 and the third pressure claw 29 are pressed tightly on the outer surface of the second inner support 22. Use the same welding method as the first cylinder 41 and the second cylinder 42 to weld the second cylinder 42 and the third cylinder 43. Inert gas is provided from the back of the weld through the second protective gas channel 212 on the second inner support 22 for inert gas protection.

[0107] After the annular welds of the first cylinder 41, the second cylinder 42 and the third cylinder 43 are welded, the engine nozzle 4 is obtained. Reinforcement ribs 45 are welded to the middle and bottom of the engine nozzle 4 respectively. The reinforcement ribs 45 are annular structures formed by splicing sections of ribs.

[0108] In S4 and S7, the total flow rate of the inert gas in the gas protection cover 3 is 15 L / min-25 L / min, and the total flow rate of the inert gas in the first protection gas duct 17 and the second protection gas duct 212 is 10 L / min-15 L / min.

[0109] In S4 and S7, the laser power was 2200W, the welding speed was 2m / min, the defocus was +2mm, the oscillation amplitude was 0.8mm, and the oscillation frequency was 130Hz, using a circular oscillation pattern. After the welding process was initiated, the laser welding head 5 and the gas shield hood 3 were moved synchronously along the weld trajectory, with the laser beam oscillating to perform welding. Stable gas shielding was maintained throughout the process, and process parameters and the reading of the oxygen content sensor 34 were monitored. After welding was completed, the shielding gas was maintained for 20 seconds. After sufficient cooling, the gas was turned off, and the workpiece was released and removed.

[0110] By properly setting the laser power, welding speed, and defocusing amount, and selecting the appropriate laser beam oscillation mode, amplitude, and frequency, this embodiment achieves effective stirring of the molten pool while ensuring sufficient penetration and welding efficiency. This stirring helps to promote the upward escape of tiny bubbles that may have formed within the molten pool, reducing porosity defects. Simultaneously, the oscillation expands the effective range of the laser, helping to create a weld with a smooth transition and more uniform stress distribution, and can also refine the weld structure to a certain extent.

[0111] After welding the longitudinal seams between the melon segments 44 and the circumferential seams between the barrels, the weld seams on the inner wall of the nozzle must be polished. Heat treatment is then performed to eliminate welding stress, and the nozzle outlet roundness is also corrected. This weld polishing is performed manually using a precision angle grinder, rotary file, straight grinder, or other equipment to ensure that the weld height is approximately the same as the parent material, and the polished surface is required to achieve a smooth transition.

[0112] During the welding process of the embodiment, under the atmospheric protection and tooling support provided by the gas shield hood 3, the optimized swing welding can significantly improve the stability of the molten pool, promote the escape of bubbles, optimize the weld formation, and reduce the defect sensitivity compared to non-swing welding, thereby obtaining a more reliable and higher-quality weld joint. Figure 17 Schematic diagram of the circular oscillation of the laser welding head during the welding of the rocket engine nozzle 4 according to an embodiment of the present invention. The laser welding head is used in the longitudinal welding of the melon segments 44 to form the barrel and the circumferential welding of adjacent barrels to form the nozzle.

[0113] Figure 14 FIG. 4 is a macroscopic morphology diagram of the weld seam of the engine nozzle 4 according to an embodiment of the present invention. Figure 14 As shown, in this embodiment, a gas shield is used during the longitudinal welding of the melon segments 44 to form the barrel and the circumferential welding of adjacent barrel segments to form the nozzle. The welds are well-formed, with a smooth and bright surface, free of oxidation discoloration, spatter, or other defects such as undercutting. In mechanical tensile testing, the tensile strength reached 480 MPa.

[0114] In the process of longitudinally welding the melon segments 44 to obtain the cylinder and circumferentially welding the adjacent cylinders to obtain the nozzle, the gas protection hood 3 is not used, and only the conventional side blowing protection method is adopted. Figure 15 This is the macroscopic surface morphology of the weld seam of the rocket engine nozzle 4 when the gas shield 3 is not used for welding. Figure 7 It can be seen that oxidation and through-crack defects appear on the weld surface, and the weld is poorly formed. The engine nozzle 4 obtained without the swing welding method has a tensile strength of 447 MPa in the mechanical properties tensile test. Figure 16The macroscopic morphology of the welded joint of the rocket engine nozzle 4 after the tensile test provided in the embodiment of the present invention shows that the tensile specimens of all embodiments show similar fracture characteristics, and the fracture positions are all located in the base material.

[0115] Therefore, the use of the rocket engine nozzle welding device and welding method described in the present invention can solve the problems of the existing engine nozzle being easily oxidized and defective when welded in the atmosphere, and the high welding cost.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A welding device for a rocket engine nozzle, characterized in that: include: A first tooling is used to clamp the melon segments to be welded on the engine nozzle and assemble the melon segments into a cylinder; the first tooling includes a first inner support member for providing internal support, a pressure plate is sleeved on the outside of the first inner support member, the melon segments are located between the first inner support member and the pressure plate, and a first pressing structure is provided on the pressure plate to press the edges of the melon segments; The second tooling is used to clamp the cylinders to be welded and assemble the cylinders into the engine nozzle; the second tooling includes a second inner support member and a third inner support member for supporting the cylinders to be welded, and the outside of the second inner support member or the third inner support member is provided with a clamping mechanism for clamping the joints of adjacent cylinders; A gas protection hood is provided on the welding head to provide inert gas protection to the front of the weld of the engine nozzle. A back gas protection structure is provided on the first fixture and the second fixture to provide inert gas protection to the back of the weld. The side surfaces of the second inner support member and the third inner support member are contoured surfaces that fit the inner side surfaces of the cylinder. The second inner support member and the third inner support member are arranged on the column. The outer surface of the column is provided with an external thread. The second inner support member and the third inner support member are connected to the column through a locking nut. The second protection structure of the back gas protection structure is arranged in the middle of the outer surface of the second inner support member and the third inner support member. The second protection structure includes a second protection gas duct. The second protection gas duct is located at the connection between the two adjacent cylinders. The second protection gas duct is connected to the inert gas bottle through a connecting pipe. The clamping structure includes a second clamping structure and a third clamping structure, the third clamping structure is located above the second clamping structure, the second clamping structure is used to clamp and fix the top end of the lower cylinder on the second inner support or the third inner support, and the third clamping structure is used to clamp and fix the bottom end of the upper cylinder on the second inner support or the third inner support; the third clamping structure includes a top plate, the top plate is arranged on the column, a second pressure ring is arranged below the top plate, the second pressure ring is connected to the top plate through a plurality of second connecting rods, and a plurality of third pressure claws are arranged on the second pressure ring to clamp the bottom end of the upper cylinder on the side wall of the second inner support or the third inner support, and the third pressure claws are connected to the second pressure ring through bolts; The second clamping structure includes a base plate, the base plate is arranged on the rotating table, the column is arranged on the base plate, a first pressure ring is arranged above the base plate, the first pressure ring is connected to the base plate through a plurality of first connecting rods, and the first pressure ring is provided with a plurality of second pressure claws for pressing the top end of the lower cylinder against the side wall of the second inner support or the third inner support, and the second pressure claws are connected to the first pressure ring through bolts.

2. The welding device for a rocket engine nozzle according to claim 1, characterized in that: The outer surface of the first inner support member is a contoured surface that fits the melon slices. The first protection structure of the back gas protection structure is arranged on the first inner support member, and the first inner support member is arranged on a rotating table; the first protection structure includes a first protection air duct, and the first protection air duct is arranged on the outer surface of the first inner support member. The first protection air duct is located at the joint of two adjacent melon slices. An air inlet is provided at one end of the first protection air duct, and the air inlet is connected to the inert gas bottle through a connecting pipe.

3. The welding device for a rocket engine nozzle according to claim 2, characterized in that: Several adjusting members for adjusting the distance between the pressing plate and the first inner support member are arranged between the pressing plate and the first inner support member. A long strip adjusting hole for installing the adjusting member on the pressing plate is provided at one end of the adjusting member. The bolt passes through the adjusting hole to fix the adjusting member to the top end of the pressing plate. The other end of the adjusting member is connected to the first inner support member through a top screw.

4. The welding device for a rocket engine nozzle according to claim 3, characterized in that: The first clamping structure includes a first pressing claw, and a pressure plate is provided with an avoidance hole that passes through the pressure plate. The avoidance hole is located at the connection between adjacent melon slices. The first pressing claws are arranged in a linear array at the avoidance hole. The first pressing claws on both sides of the avoidance hole respectively press and fix the edges of the two adjacent melon slices. The pressure plate is provided with an installation hole for installing the first pressing claw.

5. The welding device for a rocket engine nozzle according to claim 4, characterized in that: The gas protection cover includes a shell, one end of which is provided with a clamping column, the shell is connected to the welding head through the clamping column and the universal meter seat, an air chamber is provided inside the shell, and an air inlet connected to the air chamber is provided on the shell, and the air inlet is connected to the inert gas bottle through a connecting pipe; The middle part of the gas chamber is provided with a main protective gas channel, which is used to provide inert gas protection to the welding area; the front end of the gas chamber is provided with a front protective gas channel inclined forward, which is used to provide pre-welding protection to the welded area; the rear end of the gas chamber is provided with a rear protective gas channel inclined backward, which is used to provide post-weld cooling protection to the weld after welding; The main protective air duct includes a first diffusion chamber and a second diffusion chamber. The first diffusion chamber is connected to the air chamber through a connecting hole. The first diffusion chamber and the second diffusion chamber are connected through a number of equal flow holes. The second diffusion chamber is provided with a number of air outlet holes; a sensor interface is provided on the side wall of the shell, and the sensor interface is connected to the inside of the second diffusion chamber for installing an oxygen content detection sensor.

6. A welding method for a rocket engine nozzle welding device according to claim 5, characterized in that: The following steps are involved: S1. Connect the gas shield to the welding head through the universal meter base, and adjust the angle and distance between the gas shield and the melon slice or cylinder through the universal meter base, so that the center of the gas shield is aligned with the center of the weld track. S2. Assemble the melon segments using the first tool; fix the first inner support member on the rotating table, place the melon segments on the contoured surface of the outer surface of the first inner support member, adjust the distance between the first inner support member and the pressing plate according to the thickness of the melon segments using the adjusting member, lock the first inner support member and the pressing plate using the jackscrew, and clamp the melon segments between the first inner support member and the pressing plate; S3. Install a first pressing jaw on the pressure plate using a wrench with a force sensor. The first pressing jaw uniformly presses the edge of the melon slice to be welded against the first inner support member. S4. Inert gas in the inert gas bottle is introduced into the gas protection support cover and the first protective gas channel through the connecting pipe to pre-purge the melon segments to be welded. After the oxygen content detection sensor stabilizes, the laser welder is started and the longitudinal connecting seams between adjacent melon segments are welded using the laser welding head to weld the melon segments into a cylindrical body. S5. Assemble the cylinders using the second tooling; adjust the distance between the second inner support and the third inner support using the locking nut according to the height of the cylinders to be welded; place the two cylinders to be welded outside the second inner support and the third inner support, respectively, and fit them to the contoured surfaces of the second inner support and the third inner support, with the second protective air duct located at the connection between the two adjacent cylinders; S6. Install a first pressure ring on the outside of the third inner support member, and the first pressure ring is connected to the bottom plate through a first connecting rod; install a top plate on the column, and install a second pressure ring on the outside of the third inner support member, and the second pressure ring is connected to the top plate through a second connecting rod; install a second pressure claw and a third pressure claw on the outside of the first pressure ring and the second pressure ring respectively by bolts, and the second pressure claw and the third pressure claw respectively press the lower cylinder and the upper cylinder to the contoured surface of the third inner support member, and the upper cylinder is coaxial with the lower cylinder; S7. Pass the inert gas in the inert gas bottle into the gas protection support cover and the second protection gas duct through the connecting pipe to pre-purge the cylinder to be welded. After the oxygen content detection sensor is stable, start the laser welder and weld the transverse connecting seams between adjacent cylinders through the laser welding head. Use a symmetrical welding method to weld the cylinders into the engine nozzle. The welding angle of each welding is 10°-15°.

7. The welding method according to claim 6, wherein: In S4 and S7, the total flow rate of the inert gas in the gas protection cover is 15 L / min-25 L / min, and the total flow rate of the inert gas in the first protection gas duct and the second protection gas duct is 10 L / min-15 L / min; In S4 and S7, the laser power is 2200W, the welding speed is 2m / min, the defocus amount is +2mm, the swing amplitude is 0.8mm, the swing frequency is 130Hz, and a circular swing mode is adopted.

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