A method for forming small-diameter, thick-walled tubular circumferential welds

Abstract

This invention provides a method for forming a small-diameter, large-walled tubular circumferential weld, comprising the following steps: clamping and positioning two conduit segments to be welded, ensuring that the axial clearance and radial misalignment at the joint meet welding requirements; introducing argon gas for protection, and performing root pass welding on the bottom of the joint using automatic pulsed TIG welding; lowering the weld temperature below a set temperature, and performing fill pass welding using automatic DC TIG welding, oscillating along the weld width direction; lowering the weld temperature below a set temperature, and performing cap pass welding using automatic DC TIG welding or automatic pulsed TIG welding, oscillating along the weld width direction during cap pass welding; and completing the welding of all conduit segments according to a preset welding sequence. This invention effectively improves the welding efficiency of liquid rocket engine ignition conduits, reduces deformation, and enhances welding quality and consistency.

Description

Technical Field

[0001] This invention belongs to the field of rocket engine manufacturing technology, and specifically relates to a method for forming a small-diameter, large-walled tubular circumferential weld, used for the assembly and welding of ignition conduits for liquid rocket engine ignition devices. Background Technology

[0002] For liquid rocket engines using non-self-igniting bicomponent propellants such as liquid oxygen / hydrocarbon or liquid oxygen / liquid hydrogen, an ignition device (also called an igniter) is required to provide the initial ignition heat source to ignite the non-self-igniting propellant. Common igniter types include chemical igniters, solid propellant igniters, and electric igniters. Chemical igniters use less igniter propellant, are reliable initiation, and can ensure multiple engine restarts during flight. Chemical ignition has been used in various liquid oxygen / kerosene engines, such as the Soviet RD-120, RD-170, RD-180, and RD-190, and the F-1 engine of the American Saturn V launch vehicle.

[0003] The commonly used ignition technology for liquid rocket engines using liquid oxygen and kerosene as propellants involves using starting fuel that can spontaneously combust with gaseous oxygen. Under a certain pressure, the starting fuel first enters the combustion chamber and ignites with the incoming gaseous oxygen, subsequently igniting the kerosene and liquid oxygen that follow. This technology can be used to start the first and second stages of rocket engines. The starting fuel can be stored in a sealed container (ignition conduit) on the fuel line before the combustion chamber, sealed by two diaphragms. When the main fuel valve is opened, the main fuel flows along the line to fill the chamber. Under a certain pressure, the two diaphragms in the ignition conduit rupture sequentially, allowing the starting fuel to enter the combustion chamber first and spontaneously combust with the oxidizer. The combustion products of the starting fuel and oxidizer then ignite the subsequently entering main fuel and oxidizer. The igniter consists of 85% triethylboron (C2H5)3B and 15% triethylaluminum (C2H5)3Al, which are flammable and explosive hazardous chemicals. Therefore, the welds in the ignition conduit require high pressure resistance and sealing performance.

[0004] After the ignition conduit is filled with ignition flux, it needs to be stored for a long time. It adopts a fully welded structure. The quality of each weld in the ignition conduit is evaluated according to the Class I standard requirements of QJ1842-95 "Technical Conditions for Fusion Welding of Structural Steel and Stainless Steel". X-ray inspection of the weld quality should meet Class I requirements. Helium mass spectrometry leak testing of each weld should show a leakage rate value not exceeding 5×10⁻⁸ Pa·m³ / s. The weld must withstand a working fluid pressure of 65 MPa, and the hydraulic failure fluid pressure under extreme conditions should not be less than 90 MPa. During engine assembly, the ignition conduit is assembled at the pre-reserved positions of ignition conduit samples. Typically, a single test engine will undergo multiple ignition tests, requiring good consistency in the ignition conduit's shape and dimensions, good interchangeability, easy replacement, and reduced engine structural deformation caused by assembly stress. The required dimensions for the ignition conduit are 629±1 mm and 103±0.5 mm.

[0005] The following problems exist in the current manufacturing process: The ignition conduit has eight circumferential welds on its outer wall. The base material at each connection point has a small diameter and a large wall thickness (3mm-6mm), using 1Cr21Ni5Ti and S-06 steel. Currently, manual TIG welding with multi-layer filler wire is used, resulting in low production efficiency and difficulty in achieving quantitative control of the welding process. Inconsistent welding techniques among operators cause significant differences in the heat input energy and thermal shrinkage at each weld point on the ignition conduit, leading to poor weld quality consistency, large variations in the post-weld ignition conduit length, and engine assembly stress issues. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for forming small-diameter, large-wall-thickness tubular circumferential welds, which can effectively improve the welding efficiency and welding quality of small-diameter, large-wall-thickness tubular components.

[0007] The technical solution of this invention is:

[0008] A method for forming small-diameter, large-walled tubular circumferential welds, used for welding multiple duct ring segments of rocket engine ignition ducts, includes the following steps:

[0009] (1) Clamp and position the two conduit ring segments to be welded so that the butt joint of the two conduit ring segments is in a horizontal welding position and the axial clearance, radial misalignment and radial runout of the butt joint meet the welding requirements.

[0010] (2) Determine the welding process and welding parameters based on the structural form of the butt joint, the material of the base material at both ends of the butt joint, and the outer diameter and wall thickness of the butt joint; if the butt joint is a butt structure, proceed to step (3); if the butt joint is a lock bottom butt structure, proceed to step (4).

[0011] (3) Use automatic hot wire pulse TIG argon arc welding to perform root welding on the bottom of the butt joint. After the root welding is completed, wait for the temperature of the weld to drop below the set temperature value, and then use automatic hot wire DC or pulse TIG argon arc welding to perform cover welding on the basis of the root weld. During the cover welding process, swing welding is performed along the width direction of the weld.

[0012] (4) The bottom of the butt joint is welded by automatic hot wire pulse TIG argon arc welding. After the root welding is completed, the temperature of the weld is lowered to below the set temperature value. The filler weld is then welded by automatic hot wire DC TIG argon arc welding on the basis of the root weld. During the filler weld, the welding is oscillating along the width of the weld. After the filler weld is completed, the temperature of the weld is lowered to below the set temperature value. The cover weld is then welded by automatic hot wire DC TIG argon arc welding on the basis of the filler weld. During the cover weld, the welding is oscillating along the width of the weld.

[0013] (5) Weld all catheter ring segments in sequence according to the preset welding sequence.

[0014] Preferably, in step (1), the axial gap welding requirements for the butt joint are as follows: the axial gap of the butt joint is evenly distributed; if the butt joint is a lock-bottom butt structure, the axial gap requirement is 1.6±0.3mm; if the butt joint is a butt structure, the axial gap is not greater than 0.2mm.

[0015] Preferably, in step (1), the radial misalignment of the butt joint is required to be: the radial misalignment of the butt joint is evenly distributed and the radial misalignment is not greater than 0.2 mm; the radial runout of the butt joint is required to be not greater than 0.8 mm.

[0016] Preferably, the set temperature value is 60°C.

[0017] Preferably, in step (3), if the wall thickness of the butt joint is less than or equal to 3 mm, the cover welding adopts automatic hot wire pulse TIG argon arc welding; if the wall thickness of the butt joint is greater than 3 mm, the cover welding adopts automatic hot wire DC TIG argon arc welding.

[0018] Preferably, for butt joints with S-06 steel as the base material at both ends, an outer diameter of 32mm and a wall thickness of 3mm, the root pass welding adopts automatic hot wire pulse TIG argon arc welding with the following process parameters: base current 50±5A, base time 0.2s, peak welding current 115±15A, peak time 0.2s, arc voltage 11±2V, arc voltage tracking current peak, welding speed 100±20mm / min, and hot wire current 30±10A during the filler wire process.

[0019] The cover welding adopts automatic hot wire pulse TIG argon arc welding. The process parameters are as follows: welding current base value 55±5A, base value time 0.2s, welding current peak value 110±10A, peak value time 0.2s, arc voltage 11±2V, arc voltage tracks current peak value, welding speed 100±20mm / min, wire feed speed 400mm / min~450mm / min, hot wire current during the filler wire process 30±10A, oscillation width 1mm~2mm, single oscillation and dwell time on both sides are 0.2s.

[0020] Preferably, for butt joints with S-06 steel as the base material at both ends, an outer diameter of 70 mm, and a wall thickness of 4 mm, the root pass welding adopts automatic hot wire pulse TIG argon arc welding with the following process parameters: base current 100±10A, base time 0.2s, peak welding current 195±15A, peak time 0.2s, arc voltage 11±2V, arc voltage tracking current peak, welding speed 100±20mm / min, and hot wire current during the filler wire process 30±10A.

[0021] The cover welding adopts automatic hot wire DC TIG argon arc welding with the following process parameters: welding current 140±10A, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feed speed 800mm / min~1200mm / min, hot wire current during the filler wire process 30±10A, oscillation width 1.5mm~3mm, and single oscillation and dwell time on both sides are 0.2s.

[0022] Preferably, for butt joints with a lock-bottom butt structure where the base materials at both ends are S-06 steel and 1Cr21 Ni5Ti respectively, with an outer diameter of 78mm~82mm and a wall thickness of 5mm~6mm, the root pass welding adopts automatic hot wire pulse TIG argon arc welding, and the process parameters are: base current 100±10A, base time 0.2s, peak welding current 200±20A, peak time 0.2s, arc voltage 11±2V, arc voltage tracking current peak, welding speed 100±20mm / min, and hot wire current during the filler wire process 30±10A;

[0023] The filler welding adopts automatic hot wire DC TIG argon arc welding with the following process parameters: welding current 140±20A, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feed speed 800mm / min~1000mm / min, hot wire current during filler welding 30±10A, oscillation width 1mm~2mm, and single oscillation and dwell time on both sides are 0.2s.

[0024] The cover welding adopts automatic hot wire DC TIG argon arc welding with the following process parameters: welding current 140±20A, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feed speed 800mm / min~1500mm / min, hot wire current during the filler wire process 30±10A, oscillation width 2.5mm~5mm, and single oscillation and dwell time on both sides are 0.2s.

[0025] Preferably, before welding, the ignition conduit is cleaned with Freon to remove oil, then dried with compressed air and finally dried completely.

[0026] Preferably, when welding in steps (3) and (4), argon gas is first introduced into the weld area for protection before welding, and argon gas is continuously introduced during the welding process until the weld temperature drops to room temperature after welding is completed.

[0027] The advantages of this invention compared to the prior art are:

[0028] (1) The present invention adopts automatic hot wire TIG welding, and the welding method is applied according to the matching process parameters. The input energy is precisely controlled, which improves the consistency of welding quality, reduces welding deformation, effectively improves welding quality, and also improves welding efficiency.

[0029] (2) The present invention performs root welding, fill welding and cover welding on the weld in sequence. The root welding of the weld is performed by automatic pulse argon arc welding. Pulse argon arc welding can reduce the average current, reduce the heat input of the workpiece, and the arc has good stability and stiffness, making it easy to control the weld formation. The fill welding and cover welding of the weld are performed by DC argon arc welding to ensure the heat of the filler wire and achieve high-efficiency welding formation. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the process for forming a small-diameter, large-wall-thickness tubular circumferential weld seam according to the present invention;

[0031] Figure 2 This is a schematic diagram of the weld distribution of the ignition conduit in an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the clamping and positioning of the first weld in the embodiment of the present invention. Detailed Implementation

[0033] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0034] This invention provides a method for forming a small-diameter, large-wall-thickness tubular circumferential weld, such as... Figure 1 As shown, it includes the following steps:

[0035] S1 clamps and positions the two conduit ring segments to be welded, so that the axial clearance and radial misalignment at the joint of the two conduit ring segments meet the welding requirements.

[0036] S2 uses automatic hot-wire pulse TIG argon arc welding to perform root pass welding on the bottom of the butt joint;

[0037] After the S3 completes the root pass welding, wait for the temperature of the weld to drop below the set temperature value, and then use an automatic hot wire DC TIG argon arc welder to perform fill welding on the basis of the root pass weld. During the fill welding process, oscillating welding is performed along the width direction of the weld.

[0038] After the filler weld is completed in S4, the temperature of the weld seam is lowered to below the set temperature value. Automatic hot wire DC TIG TIG welding or automatic hot wire pulse TIG TIG welding is used to perform cover welding on the filler weld seam. During the cover welding process, oscillating welding is performed along the width direction of the weld seam.

[0039] During the welding process in steps (2) to (4), S5 continuously introduces argon gas into the weld area for protection.

[0040] S6 Repeat steps (1) to (5) according to the preset welding sequence until all catheter ring segments are welded;

[0041] After each weld is completed, the quality of the weld is inspected to ensure that the quality of each weld meets the requirements and that the ignition conduit as a whole meets the dimensional requirements after welding.

[0042] The method of the present invention will be further described below with reference to specific embodiments:

[0043] The ignition conduit and weld distribution directly applied in this invention are as follows: Figure 2 As shown, there are 8 circumferential welds, and the parameters of each weld are shown in Table 1.

[0044] Table 1 Weld parameters of embodiments of the present invention

[0045]

[0046] Based on the parameters of each weld, the process parameters for automatic hot-wire TIG welding of each weld are determined, as shown in Table 2:

[0047] Table 2. Automatic hot-wire TIG welding process parameters for each weld seam in the embodiments of the present invention.

[0048]

[0049]

[0050] The specific welding process includes the following steps:

[0051] 1) Pre-welding preparation: Clean the product parts with Freon degreasing, blow off the surface with gas, dry, and wipe the tooling surface clean with alcohol.

[0052] Specifically, a clean three-layer silk cloth is used to filter out trichlorofluoroethane. The surfaces of each part are then cleaned by wiping with the silk cloth and brushing with a brush. After cleaning, the surfaces are wiped with a clean white silk cloth; the absence of oil stains indicates that the product is clean. After cleaning, the surfaces of the parts are dried with compressed air and placed in a drying oven. The temperature is slowly raised to 50℃~60℃ and maintained for 2 hours, then slowly cooled to room temperature. The parts are then removed. The surfaces of the parts are visually inspected under light, and areas that are not visible are checked endoscopically. If the product is found to be unclean, the cleaning, blowing, and drying process can be repeated multiple times until it is clean. The surface of the tooling is wiped clean with alcohol to ensure that the surface is clean and free of any residue.

[0053] 2) Assembly and Positioning: Welds 1 through 8 are performed sequentially. Tooling is used to ensure uniform axial clearance and radial misalignment at the welding positions, with a radial misalignment not exceeding 0.2mm. The axial clearance requirement is determined based on the butt joint type: for welds 2 through 4, 7, and 8 using a lock-bottom butt joint, the required axial clearance range is 1.6 ± 0.3mm. Each weld is positioned at 4 to 8 points using manual tungsten inert gas welding before automatic hot-wire TIG welding, with the positioning points evenly distributed. For welds 1, 5, and 6 using a butt joint, the axial clearance is not greater than 0.2mm. This ensures that after welding welds 5 through 8, the overall dimensions of the ignition conduit are within the required range.

[0054] Furthermore, the reference current for manual tungsten inert gas welding is 160±10A.

[0055] Furthermore, to ensure overall rigidity and minimal deformation during the clamping process, the positioning pins at both ends of the tooling lock the product's outlet and inlet, ensuring the overall length and height dimensions of the product. Support seats at various locations provide support, fixation, guidance, and height adjustment, while ensuring that the product's length direction remains within the same tangential plane as the tooling's axis throughout the clamping process.

[0056] Furthermore, the welding fixture ensures the continuous flow of argon gas to the weld during the welding process. After the welding fixture is fixed to the product, it is mounted on the equipment chuck. Before welding, the radial runout of the area to be welded is measured by a dial indicator and is no more than 0.8 mm. The welding fixture ensures that each weld is in a horizontal welding position before and during the welding process.

[0057] Furthermore, the clamping and positioning of the first weld will be used as an example for explanation. Figure 3As shown, during clamping, the inner expansion fixture is inserted into the product and tightened. The protective gas plug is inserted into the protective gas copper tube of the welding equipment head seat. The chuck clamps the inner expansion fixture, and the radial runout is no more than 0.8mm. The gas plug is then used to seal the end of the inner expansion fixture. The tailstock tip is then tightened, and the axial butt gap is no more than 0.2mm. Internal protective argon gas is introduced. The joint is first positioned by manual tungsten argon arc welding, and then automatic welding is prepared to begin.

[0058] 3) Welding: As shown in the figure, the product is clamped on the welding equipment. Argon gas is introduced into the inner cavity of the product and argon gas is used to protect the outer weld area. Automatic hot wire TIG welding is performed according to the process parameters in Table 2. Welding is carried out in the order of root pass welding, filler weld, and cover weld. After each layer of welding is completed, the weld temperature is allowed to drop below 60°C before the next layer of welding is carried out.

[0059] Specifically, during the welding process, the flow rate of protective argon gas is 10L / min to 15L / min. After pre-gasping for 3 minutes, the root pass welding begins, and the same flow rate of argon gas is maintained for at least 3 minutes after welding.

[0060] The welding process of welds 1, 5, and 2 will be used as examples for illustration:

[0061] Weld 1: The root pass is welded using pulsed TIG welding with a base welding current of 50A±5A for 0.2s, a peak welding current of 115A±15A for 0.2s, an arc voltage of 11V±2V (with peak arc voltage tracking), a welding speed of 100mm / min±20mm / min, and a welding angle of 362°. An infrared thermometer is used to measure the weld temperature. Argon gas is used for post-weld protection in the inner cavity until the temperature drops below 60°C before proceeding directly to the cover pass. The cover pass is welded using pulsed TIG welding with a base welding current of 55A±5A for 0.2s, a peak welding current of 110A±10A for 0.2s, an arc voltage of 11V±1V (with peak arc voltage tracking), a welding speed of 100mm / min±20mm / min, a wire feed speed of 400mm / min~450mm / min, and a welding angle of 363°. During the filler wire process, the hot wire current is 30±10A.

[0062] Section 5 Weld: The root pass weld uses pulsed TIG welding with a base welding current of 90A–110A for 0.2s, a peak welding current of 180A–210A for 0.2s, an arc voltage of 11V±2V (with peak arc voltage tracking), a welding speed of 100mm / min±20mm / min, and a welding angle of 362°. An infrared thermometer is used to measure the weld temperature. After welding, the inner cavity is protected with argon gas until the temperature drops below 60°C before proceeding directly to the filler weld. The cover pass weld uses DC TIG welding with an oscillation width of 1.5mm–3mm, a single oscillation and dwell time on both sides of 0.2s, a welding current of 130A–150A, an arc voltage of 11V±2V (with peak arc voltage tracking), a welding speed of 100mm / min±20mm / min, a wire feed speed of 800mm / min–1200mm / min, and a welding angle of 363°. During the filler wire process, the hot wire current is 30±10A. The sixth weld is the same as the fifth weld.

[0063] The second weld: pulsed TIG welding is used, with a welding current base value of 90A to 110A, base value time of 0.2s, welding current peak value of 180A to 220A, peak value time of 0.2s, arc voltage of 11V ± 2V, arc voltage tracking peak value, welding speed of 100mm / min ± 20mm / min, welding angle of 362°, infrared thermometer to measure the temperature of the weld, argon gas protection is purged through the inner cavity after welding, and the temperature drops below 60° before direct filling welding. For filler welding, the oscillation width is 1mm–2mm, with a single oscillation and lateral dwell time of 0.2s. The welding current is 120A–160A, the arc voltage is 11V±1V, and the arc voltage is tracked at its peak value. The welding speed is 100mm / min±20mm / min, the wire feed speed is 800mm / min–1000mm / min, and the welding angle is 364°. An infrared thermometer is used to measure the weld temperature. After welding, the inner cavity is protected with argon gas until the temperature drops below 60°C before proceeding directly to capping welding. For capping welding, the oscillation width is 2.5mm–5mm, with a single oscillation and lateral dwell time of 0.2s. The welding current is 120A–160A, the arc voltage is 11V±2V, and the arc voltage is tracked at its peak value. The welding speed is 100mm / min±20mm / min, the wire feed speed is 800mm / min–1000mm / min, and the welding angle is 363°. During filler wire welding, the hot wire current is 30±10A. Welds 3, 4, 7, and 8 are similar to weld 2.

[0064] 4) Weld quality inspection: After each weld is completed, a quality inspection is carried out to ensure that the weld quality meets the Class I standard requirements of QJ1842-95 "Technical Conditions for Fusion Welding of Structural Steel and Stainless Steel".

[0065] Specifically, X-ray inspection of welds shows that the weld quality meets the Class I standard requirements, and helium mass spectrometry inspection of each weld shows a leak rate value of no more than 5 × 10⁻⁶.-8 Pa·m 3 / s, the weld liquid strength test of each ignition conduit product meets the requirement of no leakage under the 65MPa test, and 10% of each batch, no less than two pieces, are sampled for the 90MPa hydraulic strength test. There should be no leakage at the weld. The actual measured values ​​of the three coordinate measuring machine meet the requirements of 629±1mm and 103±0.5mm.

[0066] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0067] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method of forming a small diameter, large wall thickness tubular girth weld, characterized by, The application relates to a welding method for multiple pipe ring segments of a rocket engine ignition guide pipe. (1) two pipe ring segments to be welded are clamped and positioned so that the butt joint of the two pipe ring segments is in a horizontal welding position, and the axial gap, radial misalignment and radial runout of the butt joint meet the welding requirements; (2) according to the structure of the butt joint, the material of the base metal at both ends of the butt joint and the outer diameter and wall thickness of the butt joint, welding procedures and welding process parameters are determined; if the butt joint is a butt joint structure, step (3) is entered; if the butt joint is a lock-bottom butt joint structure, step (4) is entered; (3) the bottom of the butt joint is welded by automatic hot-wire pulse TIG argon arc welding, after the backing welding is completed, the temperature of the weld seam is lowered to below a set temperature value, and the backing weld seam is covered by automatic hot-wire direct-current or pulse TIG argon arc welding, and in the covering welding process, swing welding is performed along the width direction of the weld seam; (4) the bottom of the butt joint is welded by automatic hot-wire pulse TIG argon arc welding, after the backing welding is completed, the temperature of the weld seam is lowered to below a set temperature value, and the backing weld seam is filled by automatic hot-wire direct-current TIG argon arc welding, in the filling welding process, swing welding is performed along the width direction of the weld seam; after the filling welding is completed, the temperature of the weld seam is lowered to below a set temperature value, and the filling weld seam is covered by automatic hot-wire direct-current TIG argon arc welding, and in the covering welding process, swing welding is performed along the width direction of the weld seam; (5) according to a preset welding sequence, the welding of all pipe ring segments is sequentially completed.

2. The method of claim 1, wherein, In the step (1), the axial gap welding requirement of the butt joint is that the axial gap of the butt joint is uniformly distributed, and if the butt joint is a lock-bottom butt joint structure, the axial gap is 1.6+ / -0.3 mm; if the butt joint is a butt joint structure, the axial gap is not greater than 0.2 mm.

3. The method of claim 1, wherein, In the step (1), the radial misalignment requirement of the butt joint is that the radial misalignment of the butt joint is uniformly distributed, and the radial misalignment is not greater than 0.2 mm; the radial runout requirement of the butt joint is not greater than 0.8 mm.

4. The method of claim 1, wherein, The set temperature value is 60 DEG C.

5. The method of claim 1, wherein, In the step (3), if the wall thickness of the butt joint is less than or equal to 3 mm, the covering welding adopts automatic hot-wire pulse TIG argon arc welding; if the wall thickness of the butt joint is greater than 3 mm, the covering welding adopts automatic hot-wire direct-current TIG argon arc welding.

6. The method of claim 1, wherein, For a butt joint structure with S-06 steel and S-06 steel as the base metal materials at both ends, an outer diameter of 32 mm and a wall thickness of 3 mm, the backing welding adopts automatic hot-wire pulse TIG argon arc welding, and the process parameters are as follows: a current base value of 50+ / -5 A, a base value time of 0.2 s, a welding current peak value of 115+ / -15 A, a peak value time of 0.2 s, an arc voltage of 11+ / -2 V, an arc voltage tracking current peak value, a welding speed of 100+ / -20 mm / min and a hot-wire current of 30+ / -10 A in the wire filling process. The cap welding adopts automatic hot-wire pulse TIG argon arc welding, and the process parameters are as follows: welding current base value 55±5A, base value time 0.2s, welding current peak value 110±10A, peak value time 0.2s, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feeding speed 400mm / min-450mm / min, hot-wire current in the process of filling 30±10A, swing width 1mm-2mm, single swing and both sides stay time 0.2s.

7. The method of claim 1, wherein, For the butt joint of butt joint structure with S-06 steel and S-06 steel as the base material at both ends, an outer diameter of 70mm and a wall thickness of 4mm, the backing welding adopts automatic hot-wire pulse TIG argon arc welding, and the process parameters are as follows: current base value 100±10A, base value time 0.2s, welding current peak value 195±15A, peak value time 0.2s, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, hot-wire current in the process of filling 30±10A; The cap welding adopts automatic hot-wire direct current TIG argon arc welding, and the process parameters are as follows: welding current 140±10A, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feeding speed 800mm / min-1200mm / min, hot-wire current in the process of filling 30±10A, swing width 1.5mm-3mm, single swing and both sides stay time 0.2s.

8. The method of claim 1, wherein, For the butt joint of butt joint structure with S-06 steel and 1Cr21Ni5Ti as the base material at both ends, an outer diameter of 78mm-82mm and a wall thickness of 5mm-6mm, the backing welding adopts automatic hot-wire pulse TIG argon arc welding, and the process parameters are as follows: current base value 100±10A, base value time 0.2s, welding current peak value 200±20A, peak value time 0.2s, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, hot-wire current in the process of filling 30±10A; The filling welding adopts automatic hot-wire direct current TIG argon arc welding, and the process parameters are as follows: welding current 140±20A, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feeding speed 800mm / min-1000mm / min, hot-wire current in the process of filling 30±10A, swing width 1mm-2mm, single swing and both sides stay time 0.2s; The cap welding adopts automatic hot-wire direct current TIG argon arc welding, and the process parameters are as follows: welding current 140±20A, arc voltage 11±2V, arc voltage tracking current peak value, welding speed 100±20mm / min, wire feeding speed 800mm / min-1500mm / min, hot-wire current in the process of filling 30±10A, swing width 2.5mm-5mm, single swing and both sides stay time 0.2s.

9. The method of claim 1 to 8, wherein Before welding, the ignition guide pipe is cleaned by Freon, and then dried by compressed air and baked.

10. The method of claim 1-8, wherein In the welding of the steps (3) and (4), argon is first introduced into the welding area for protection, and then welding is performed, and the argon is continuously introduced during the welding until the welding is completed and the welding temperature is reduced to room temperature.

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