Process method for welding titanium alloy guide pipe of liquid propelling system

Abstract

The invention discloses a process method for welding a titanium alloy guide pipe of a liquid propulsion system, which is characterized in that a fillet weld welding scheme is designed as follows: a fillet weld tungsten electrode clamping conversion tool is utilized, so that the distance between the fillet weld tungsten electrode clamping conversion tool and an electrode holder clamping block can be increased, abnormal arcing is effectively avoided, and normal welding can be carried out. The fillet weld can be welded through an automatic pipe welding machine, the welding quality of the part with the protruding structure is better than that of a welding flux ring, and fillet weld welding without filling materials is difficult to achieve. Automatic argon arc welding is adopted for welding titanium alloy pipeline fillet welds, it needs to be guaranteed that parts can be clamped in welding tongs, and the sealing performance can be guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of welding technology for liquid propulsion systems, and particularly to a process method for welding titanium alloy ducts in liquid propulsion systems. Background Art

[0002] Liquid rocket engines have numerous ducts, just like blood vessels in the body. Ducts play an extremely important role in rocket engines. These are the channels for transporting fuel, oxidizer, and gas, and undertake the important tasks of transporting engine propellants and pressurizing rocket tanks. Leakage of any duct will have a significant impact on the rocket and even lead to the failure of the entire launch mission. With the continuous development of welding technology, the application of automatic welding technology is becoming more and more extensive, and the requirements for the assembly accuracy before welding are getting higher and higher. And due to space limitations for some local ducts, the length of the straight section of the duct is short, making it difficult to accurately position and weld. At the same time, titanium alloy ducts are prone to oxidation, and it is necessary to ensure welding under a protective atmosphere with appropriate internal and external pressures. At the same time, there are many fillet welds in the system. In order to improve the welding quality and efficiency, the automatic welding of ducts is extended to the field of fillet welds.

[0003] At present, most manufacturers still use manual argon arc welding for welded duct structures, which can only weld butt welds with equal wall thickness, and are prone to problems such as oxidation, welding heads, undercutting, slag inclusions, and low weld strength, and the quality cannot be guaranteed. For pipeline systems with high quality requirements and compact structures, high-energy beam welding or brazing is generally used, and automatic welding of fillet welds cannot be achieved, and the welding cost, efficiency, and quality are not easy to guarantee. To solve the above problems, a set of process methods for automatic welding of ducts has been explored and summarized. Summary of the Invention

[0004] A process method for welding titanium alloy ducts in a liquid propulsion system according to the present invention includes the design of a duct welding locator for butt welds of ducts, the design of a clamping and welding scheme for short straight sections of ducts, oxidation control, and fillet weld welding, these 4 technical problems. The welded titanium alloy ducts meet the design specifications and relevant standard requirements and can adapt to the complex working environment of engine products.

[0005] The technical solution adopted by the present invention is a process method for welding titanium alloy ducts in a liquid propulsion system, including the following steps: a) First, process the duct ports to ensure that the perpendicularity between the port plane and the tube center line is less than 0.05 mm, and use a precision positioning tooling to position the pipeline to be welded to ensure the butt gap and misalignment; b) Select clamping blocks according to the characteristics of the pipeline to be welded. In the case where the straight sections on both sides are short and cannot be clamped and one side is a threaded structure, use an adapter for fixation; c) Install the tungsten electrode to ensure it is at the center position of the butt weld; d) Adjust the distance between the tungsten electrode and the catheter before welding. The distance is (1 - 3) mm. Pass the shielding gas through the catheter in advance. Use an oxygen analyzer to determine the purity of the shielding gas at the outlet to protect the inner surface of the weld. At the same time, ensure the gas pressure inside the catheter, which is (20 - 90) KPa, to prevent sinking or bulging. e) Fix the catheter using the corresponding clamp block, adjust and fix the relative position with the tungsten electrode. For the welding process of the catheter, use multi-pass welding with a small current according to the characteristics of the pipe. Judge the current and the number of turns based on the melting condition of the weld. It is most appropriate to select 2 turns, and the decay time is (5 - 9) s. f) When welding the pipeline, it is divided into (8 - 15) segments in the circumferential direction for welding. The angle of each segment is between 30° and 90°. The welding speed and time are slightly adjusted according to the different pipe diameters. The overall trend of the current is from large to small. g) After welding is completed, cool down. The shielding gas inside and outside the catheter is not interrupted until the temperature drops below 50°C. h) For the oxidation color on the outer surface, install a copper sleeve near the adjacent clamp block outside to conduct heat diffusion.

[0006] Preferably, in step c), for the fillet weld and the butt weld that are not in the middle position clamped by the welding tongs, use a tungsten electrode converter to adjust the position of the tungsten electrode so that the tungsten electrode is at the center of the weld.

[0007] The beneficial effects of the present invention are as follows: Through the welding locator and the flatness of the catheter port, the present invention effectively ensures the coaxiality and deformation amount between the catheters, can perform positioning under a relatively narrow gap, is applicable to the butt joint positioning of pipes with different diameters, ensures the consistency of the circumferential step difference, uses a set of tooling for positioning during the pipeline configuration process and before welding, enables the welding to proceed smoothly, the entire device has a neat structure, strong feasibility, simple technical solutions, easy to manufacture and use, and low manufacturing and use costs; a real-time solution for shortening the clamping distance is proposed, which can adapt to most catheter docking structures. At the same time, the use of a tungsten electrode converter can be extended to the welding of fillet welds. Using this process method, the welding of most titanium alloy catheter butt joints and fillet welds can be completed well, and it is also applicable to stainless steel and carbon steel pipes. The welding process is reliable, the weld strength is high, the repeatability is good, and the applicability is strong. Description of the Drawings

[0008] Figure 1 It is a schematic diagram of the precision positioning tooling of the present invention.

[0009] Figure 2 It is a schematic diagram of the structure of the tungsten electrode converter of the present invention.

[0010] Figure 3 It is a schematic diagram of the threaded structure of the short-segment catheter of the present invention.

[0011] Markings in the figure: 1. Compression bolt Ⅰ, 2. Bolt Ⅰ, 3. Support plate, 4. V-groove seat, 5. Locking screw, 6. V-groove Ⅰ, 7. Bottom V-groove base, 8. V-groove Ⅱ, 9. L-shaped fixing block, 10. Limit post, 11. Bolt Ⅱ, 12. Compression bolt Ⅱ, 13. Main body, 14. Tungsten electrode clamping bolt, 15. Nut, 16. Connecting rod, 17. Jacket, 18. Ventilation expansion connector. Specific implementation mode

[0012] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0013] A process method for welding titanium alloy ducts in a liquid propulsion system requires the basic parameters of the welding equipment to be: rated current: 165A; minimum welding speed: 0.1 mm / min; pipe diameter: φ4 - φ76; regional segmentation accuracy: 1°; weldable materials: titanium alloy, stainless steel, etc.; welding thickness: 0.5 - 4, and the structure of the welding tongs is that the clamping blocks with holes on both side plates clamp, and the tungsten electrode welds at the center position of the weld seam.

[0014] The materials used in a process method for welding titanium alloy ducts in a liquid propulsion system are generally TA1, TA2, 1Cr18Ni9Ti, etc., with a pipe diameter of φ4 - φ38 and a wall thickness of 0.5 - 1.5.

[0015] The structure of the welding positioner used in a process method for welding titanium alloy ducts in a liquid propulsion system is shown in Figure 1 As shown, the ducts to be positioned are assembled on the entire positioning device with the help of parts such as compression bolt Ⅰ1, V-groove Ⅰ6, V-groove Ⅱ8, and compression bolt Ⅱ12 to limit the radial displacement. One of the fixed pipes is at one end of the V-groove base, and the other pipe is positioned on the other side. Near one side of the V-groove, by adjusting up and down, the coaxiality of the two pipes is ensured. Then the two pipes are brought close and compressed. If positioning spot welding is required, positioning spot welding can be carried out through the notch. The V-groove Ⅰ6 and V-groove Ⅱ8 can be replaced with V-grooves of different sizes according to different ducts, so as to realize the flexibility of the use of this device.

[0016] The specific structures of the welding positioner and the converter are as follows: The main body 13 serves as the basic framework to support the entire connection structure. The connecting rod 16 is directly connected to the main body 13 and may be used to transfer force or fix other components. The jacket 17 wraps or clamps the workpiece and is fastened by the tungsten electrode clamping bolt 14 and the nut 15. The V-groove seats 4, 6, 7, 8 include the bottom V-groove base 7, the V-groove I 6, and the V-groove II 8, which are used to position cylindrical workpieces. In cooperation with the pressing bolt I 1, the pressing bolt II 12, the bolt I 2, and the bolt II 11, the clamping force is adjusted. The L-shaped fixing block 9 and the support plate 3 provide lateral support to enhance the structural stability. The limit post 10 restricts the movement range of the workpiece or the jacket. The locking screw 5 fixes the positions of the V-groove seats 4, 6, 7, 8 or the support plate 3 to prevent loosening. The ventilation expansion connector 18 is used to connect the cooling gas path (such as the shielding gas of the welding equipment) and is integrated near the jacket 17.

[0017] The clamping and welding scheme design for the short straight section of the conduit used in a welding process method for titanium alloy conduits in a liquid propulsion system: The ball-headed parts include the outer sleeve nut and the ball head. Since most of the ball-headed parts have a small outer diameter and can be covered within the clamping block, and the clamping block can be replaced and manufactured, a tooling is designed for the compensation of the welding straight line. The jacket 17 can insert the outer sleeve nut of the product into the part 18, increasing the clamping length. See Figure 3 , after compensation, as long as the protruding end of the ball head welding end meets the weld width, generally 3.5 mm is taken. The nozzle inside the clamping sleeve can be replaced according to different product interfaces, increasing its scope of application. This method has a wide scope of application; two-way and three-way parts can be transferred to a cylinder for clamping.

[0018] The anti-oxidation measures adopted in a welding process method for titanium alloy conduits in a liquid propulsion system: During the welding process, a copper alloy material ventilation tooling is made. According to different pipe diameters, different diameter ventilation toolings are selected. One end is used to connect the air pipe, and the other side is inserted into the product conduit. During use, it is wrapped with art paper (compared with the commonly used white adhesive tape, it can withstand high temperatures and has less residue after disassembly), and the open pipe port is also sealed with art paper to ensure tightness. At the same time, the pre-welding ventilation time is increased to not less than 1 minute, and the post-welding ventilation time is not less than 3 minutes, so as to ensure that the oxidation color on the inner surface meets the requirements. For longer or more important pipelines, first use an oxygen analyzer to ensure the purity of the shielding gas near the weld. After reaching the target value, adjust the pressure of the internal pressure gauge and perform welding. The reading of the oxygen analyzer should be less than 30 ppm, and there is basically no oxidation phenomenon on the inner wall, which fully meets the standard requirements. In addition, on the outside of one end of the welding torch, a copper sleeve is used for heat dissipation on the pipeline, and the heat dissipation is relatively fast, and the oxidation color at the clamping position of the welding torch is significantly improved.

[0019] Design of fillet weld welding scheme for a process method used in the welding of titanium alloy conduits in a liquid propulsion system: A fillet weld tungsten electrode clamping conversion tooling. Using this tooling can increase the distance from the welding clamp block, effectively avoiding abnormal arc starting and enabling normal welding. Achieving fillet weld welding with an automatic pipe welding machine, the welding quality of parts with a self - contained convex structure is superior to that of solder rings. Fillet weld welding without filler materials is difficult to achieve. When using automatic argon arc welding to weld the fillet welds of titanium alloy pipelines, it is necessary to ensure that the parts can be clamped in the welding pliers and the sealing performance can be guaranteed; A process method for welding titanium alloy conduits in a liquid propulsion system, including the following steps: i) First, process the conduit port to ensure that the perpendicularity between the port plane and the pipe center line is less than 0.05 mm. Use a precision positioning tooling to position the pipeline to be welded and ensure the butt gap and misalignment; j) Select the clamp block according to the characteristics of the pipeline to be welded. In the case where the straight - line segments for clamping on both sides are short and cannot be clamped and one side is a threaded structure, use an adapter for fixation; k) Install the tungsten electrode to ensure it is at the center position of the butt weld. For fillet welds and butt welds that are not in the middle position clamped by the welding pliers, use a tungsten electrode converter to adjust the position of the tungsten electrode so that the tungsten electrode is at the center of the weld; l) Adjust the distance between the tungsten electrode and the conduit before welding, generally (1 - 3) mm. Pass the protective gas through the conduit in advance. Use an oxygen analyzer to determine the purity of the outlet protective gas to protect the inner surface of the weld. At the same time, ensure the gas pressure inside the conduit, generally (20 - 90) KPa, to prevent sagging or bulging; m) Fix the conduit using the corresponding clamp block, adjust and fix the relative position with the tungsten electrode. The welding process of the conduit generally uses small - current multi - pass welding according to the characteristics of the pipe, which is particularly important for the weld formation of the pipe. Judge the current and the number of passes according to the melting condition of the weld. Small current and multiple passes input less heat to the pipeline per unit time. On the one hand, it can reduce welding deformation. On the other hand, the processes of heat absorption, melting, flow, and solidification of the weld metal are gentle and sufficient. However, the number of passes should not be too many, which may cause ablation of the base metal and coarse grains. Through exploration, about 2 passes are most appropriate. Under the good protection of argon, the weld formation is similar inside and outside, and the welded joint is neat and beautiful. The decay time is generally (5 - 9) s. Too short decay time is likely to produce arc pits and cracks at the arc end; n) When welding the pipeline, it is generally divided into about (8 - 15) segments in the circumferential direction for welding. The angle of each segment is between 30° and 90°. The welding speed and time are slightly adjusted according to the different pipe diameters. The overall trend of the current is from large to small. Since there are many welding setting parameters, the welding process parameters are not unique. On this basis, when the structure of the part changes, etc., the current at each position can be adjusted according to the correction factor; o) After welding is completed, cooling is carried out, and the protective gas inside and outside the conduit is not interrupted until the temperature drops below 50°C; p) Regarding the problem of the oxidation color on the outer surface, by installing a copper sleeve at the position adjacent to the external clamping block for heat diffusion, the external oxidation color can be indirectly reduced, achieving good results and ensuring that the external oxidation color is effectively reduced.

[0020] The welding process of the present invention uses the above device for positioning the conduit structure, which can ensure the assembly accuracy and stability of the conduit structure. It can perform positioning under a relatively narrow gap. A set of tooling is used for positioning during the conduit configuration process and before welding, and it can also be positioned in the system and complete tack welding without disassembling the conduit, realizing multiple functions with one piece. It is applicable to the butt joint positioning of pipes with different diameters, ensuring the consistency of the circumferential step difference. The entire device has a neat structure, strong feasibility, a simple technical solution, is easy to manufacture and use, and has low manufacturing and usage costs.

[0021] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for welding titanium alloy conduits for liquid propulsion systems, characterized in that: The steps include: First, the catheter port is processed to ensure that the verticality between the port plane and the center line of the pipe is less than 0.05mm. The pipeline to be welded is positioned using a precision positioning tool to ensure the butt clearance and misalignment. Select the clamp block according to the characteristics of the pipe to be welded. If the straight line sections on both sides are too short to clamp and one side is a threaded structure, use an adapter to fix it; Install the tungsten electrode to ensure it is in the center of the butt weld; Before welding, adjust the distance between the tungsten electrode and the conduit to (1-3) mm, pass the shielding gas into the conduit in advance, use the oxygen analyzer to determine the purity of the shielding gas at the outlet, protect the inner surface of the weld, and ensure the gas pressure inside the conduit to be (20-90) KPa to prevent sinking or bulging; Use the corresponding clamp to fix the catheter, adjust the relative position with the tungsten electrode and fix it. The welding process of the catheter adopts small current multi-pass welding according to the characteristics of the pipe. The current and number of turns are determined according to the melting condition of the weld. 2 turns are the most suitable, and the decay time is (5-9) s. When welding the pipeline, the circumferential direction is divided into (8 to 15) sections for welding, and the angle of each section is between 30° and 90°. The welding speed and time are slightly adjusted according to the different pipe diameters, and the overall trend of the current is from large to small; After welding is completed, the protective gas inside and outside the pipe should be kept on cooling until the temperature drops below 50℃; For the outer surface oxidation color, the heat is diffused by installing a copper sleeve close to the clamp block on the outside.

2. A process for welding a titanium alloy conduit for a liquid propulsion system according to claim 1, characterized in that: In the step c), for fillet welds and butt welds that are not in the middle of the welding clamp, a tungsten electrode converter is used to adjust the position of the tungsten electrode so that the tungsten electrode is in the center of the weld.

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