A method for automatically controlling the quality of ring seam welding of a stainless steel bulging curved workpiece

Abstract

The application discloses a kind of automatic composite welding quality control methods of stainless steel bulging curved surface workpiece ring seam, through the material of welding piece to be rolled into shape→cleaning→positioning welding welding piece→welding piece longitudinal butt joint→welding piece bulging and cleaning after welding→positioning welding→preheating→ring seam welding→welding annealing→detection etc., give full play to the advantages of plasma arc welding and TIG welding itself, realize the single-side welding of stainless steel double-side forming, the front and back weld forming is good, and no porosity, crack defects are found in weld and heat-affected zone, solve the porosity, un-melted welding defects such as butt joint ring seam of S30408 stainless steel bulging curved surface cylinder assembly, make the welding joint forming well, without welding defects, with good mechanical properties, meet the product design requirements.

Description

Technical Field

[0001] This invention relates to stainless steel welding, and more specifically to a method for quality control of automatic composite welding of circumferential seams in stainless steel bulging curved surface workpieces. Background Technology

[0002] Applying stainless steel to the manufacture of components such as the metal nose cone of weapons and equipment not only reduces production costs, but also leverages the superior corrosion resistance, oxidation resistance, high-temperature and low-temperature toughness, as well as good mechanical and processing properties of stainless steel to enable weapons and equipment to remain stable under extreme conditions, thereby improving their durability and reliability and ensuring their range and mobility.

[0003] In the research and development and production of weaponry, welding technology has become an important component of the weapon manufacturing field, and its role and status are increasingly prominent. With the rapid development of weaponry and the continuous improvement of equipment performance requirements, weaponry itself places higher demands on high-quality and high-efficiency welding methods. Typically, limitations in input energy, welding stability issues, and the need to increase welding efficiency often lead to a decrease in weld quality. However, the emergence of composite welding methods allows for the complementary advantages of multiple heat sources, significantly improving welding efficiency while improving weld quality, making it a research hotspot in the welding field in recent years.

[0004] Traditional stainless steel welding methods such as submerged arc welding, shielded metal arc welding, and tungsten inert gas welding (TIG) suffer from either low welding efficiency and high labor costs, or high heat input, poor weld joint quality, and significant workpiece deformation. In contrast, plasma arc welding utilizes a highly compressed arc, characterized by high energy density, strong penetration, a small heat-affected zone, high welding efficiency, and minimal weld deformation. TIG welding offers advantages such as stable welding process, high weld quality, and low cost.

[0005] Combining plasma arc welding and tungsten inert gas welding (TIG) not only allows the plasma arc to penetrate the weld joint and ensure the back side is formed, but also allows TIG welding to compensate for defects such as weld collapse and undercut on the front side, ensuring the front side is formed. This combination has the advantages of beautiful weld formation, high efficiency, small workpiece deformation, high joint quality, and low labor intensity for welders.

[0006] Currently, among the series of products, there is S30408 ​​stainless steel with a thickness of about 4.0mm, designed as a conical curved cylinder. The cylinder is welded via longitudinal welds at the butt joint and circumferential welds at the butt joints with flanges of different diameters at both ends. However, in actual production, the product also undergoes bulging processing of the conical cylinder's curved surface using a rigid mold. This places strict requirements on the overall shape accuracy, such as the scalloped curve, of the bulged product. In practice, problems such as workpiece deformation caused by longitudinal and circumferential welds often prevent the weaponry from meeting the product design requirements. The main reasons are deviations in bevel assembly, improper process control, and unreasonable weld joint design. Defects such as incomplete fusion and porosity also frequently occur. Among these, longitudinal welds are easier to assemble because the base materials on both sides are easier to control in terms of welding deformation. Furthermore, by welding arc-starting and arc-extinguishing plates at both ends, defects such as incomplete penetration, porosity, and burn-through caused by arc initiation and extinguishing can be effectively addressed. However, for circumferential welding, which is a closed weld, the constraint is relatively large. In addition, stainless steel has a large coefficient of thermal expansion, making it more prone to deformation during welding. Therefore, the assembly of welded joints must be more strictly controlled, and spot welding must be performed evenly along the circumference. Especially during arc initiation and arc extinguishing, defects are easily formed. In addition, when the welding ambient temperature is below 10℃, irregularities in the weld formation may occur on both sides.

[0007] Therefore, considering the welding production problems of stainless steel bulging curved surface products and the characteristics of product structure, plasma arc welding and tungsten inert gas welding, in order to improve the welding quality of products and enhance the reliability of weapon products, it is necessary and of practical significance to design an automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces. Summary of the Invention

[0008] The purpose of this invention is to provide an automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces, in order to solve the welding technical problems of welding defects such as porosity and lack of fusion in the circumferential seams of stainless steel bulging curved surface cylindrical components, poor weld joint formation, or even welding deformation, so that the weld joints are well formed, free of welding defects, have good mechanical properties, and meet product design requirements.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces. The welding method utilizes welding positioning and clamping fixtures to strictly control the pre-welding workpiece assembly gap and misalignment, and employs an incremental arc initiation and decremental arc termination plasma arc welding method. Automatic welding is achieved through preheating of the flange and cylinder circumferential butt joints, tack welding of the assembly joints, plasma arc root pass welding, and tungsten inert gas (TIG) cap weld. The specific steps are as follows: Step 1: Rolling the material to be welded into shape: The cut plate is rolled into a frustum shape by a plate rolling machine to form the weldment; Step 2 Cleaning: After the weldment is tapered, first wipe the welded area with industrial wiping paper dipped in anhydrous alcohol. Then, use a steel wool pad, scraper, and chemical treatment to clean the surface of all welded parts inside the bevel and within 30mm on both sides of the bevel, as well as the welding wire to remove oil and rust. Remove oil, rust, burrs, moisture, oxide scale and other debris until the metal luster is exposed. Then, wipe the welded area and within 30mm on both sides with industrial wiping paper dipped in anhydrous alcohol until there is no dirt on the wiping paper. Step (3) Positioning and Welding the Workpiece: Place the cleaned workpiece, ensuring the welding area remains horizontal on the roller support. The assembly gap should not exceed 0.5mm, and the misalignment should not exceed 1.5mm. Use manual pulse TIG welding, performing tack welding along the axial direction at the joint. The weld spots should be evenly distributed, with a length of 3mm–4mm. The weld spot surface should be flush with the base material. Use cerium tungsten electrodes with a diameter of 2.4mm. The pulse peak current should be 200A–220A, the pulse base current 70A, the pulse frequency 2Hz, and the duty cycle 50%. Use a 1.2mm diameter welding wire and a gas flow rate of 15L / min–18L / min. The argon purity should be no less than 99.99%. Confirm that the weld is free of cracks and the workpiece is free of deformation defects after welding. Step 4: Welding the longitudinal butt joint of the workpiece: Before welding, pre-weld the arc-starting plate and the arc-extinguishing plate to the starting section and the extinguishing end of the workpiece, respectively. Place the workpiece blank on the longitudinal seam welding fixture, always keeping the welding part in a horizontal position. Use a piano key clamp to press the workpiece firmly, starting the welding from the small diameter end of the frustum-shaped workpiece. A cerium tungsten electrode should be used, with a diameter of 3mm. The workpiece should be in a cold welding state at the beginning of the welding process. Preheat the workpiece first, using the left welding method, with the tungsten electrode perpendicular to the joint seam. The angle between the welding wire and the tungsten electrode is 75º~80º. After the arc is ignited on the arc-starting plate, it stays and then welds along the longitudinal weld joint to the arc-extinguishing plate. After the arc is started, the welding gun performs plasma arc root pass welding. Then, tungsten inert gas (TIG) cover pass welding is performed with a current of 230A, a shielding gas flow rate of 18L / min~20L / min, a wire feed speed of 1.5m / min, a welding speed of 600mm / min, and an argon purity of not less than 99.99%, ultimately forming a single-sided weld with double-sided forming. Step 5: Post-weld bulging and cleaning of the welded parts: The welded parts are bulged using a punch bulging fixture to form the curved surface of the generatrix; after bulging, the welded parts are wiped with industrial wiping paper dipped in anhydrous alcohol, and then all the areas to be welded and the surface within 30mm on both sides are cleaned with steel wool, scraper and chemical treatment to remove oil and rust from the welding wire, and remove oil, rust, burrs, moisture, oxide scale and other debris until the metal luster is exposed. Then the welded parts and the area within 30mm on both sides are wiped with industrial wiping paper dipped in anhydrous alcohol until there is no dirt on the wiping paper; Step 6: Tack welding: Tack weld the upper and lower flanges to be welded to the circumferential butt joint of the welded component evenly along the circumference with the center of the circle as the center of symmetry. The assembly gap should not exceed 0.5mm, and the misalignment should not exceed 0.2mm. The weld surface should smoothly transition to the welded component. The weld length should be 3mm to 4mm. A cerium tungsten electrode should be used, with a diameter of 2.4mm. The pulse peak current should be 200A to 220A, the pulse base current should be 70A, the pulse frequency should be 2Hz, the duty cycle should be 50%, the welding wire diameter should be 1.2mm, and the gas flow rate should be 15L / min to 18L / min. The argon purity should be not less than 99.99%. Confirm that the weld is free of cracks and the workpiece is free of deformation defects after welding. Step 7: Preheating: Locally preheat the welded joints of the assembled weldment, upper flange, and lower flange; Step (8) Circumferential Welding: Before welding, rotate the workpiece circumferentially to adjust the distance between the tungsten electrode and the workpiece, maintaining a distance of 3mm. The angle between the welding wire and the tungsten electrode should be 75º~80º, with the end of the welding wire 3mm away from the tip of the tungsten electrode. Weld using the method of feeding the wire first and the arc second. The circumferential weld is completed by passing the arc extinguishing end 10mm~15mm past the starting end, forming a single-sided weld with double-sided forming. The tungsten electrode should be a cerium tungsten electrode with a diameter of 3mm. The welding torch should not be oscillated and should be continuously welded without interruption. Plasma arc root pass welding and tungsten inert gas (TIG) argon arc cover pass welding should be performed. The welding environment temperature should not be lower than 10℃, the relative humidity should not be greater than 75%, and the air flow should not be greater than 2m / s. Step 9: Post-weld annealing: After welding, the welded components are allowed to cool naturally to room temperature. The post-weld annealing temperature is 200℃±5℃, and the holding time is 4h~5h. Then, the components are cooled in the furnace to 60℃ and then air-cooled to room temperature. Step 10: Inspection: The weld is inspected using X-ray flaw detection. Cracks and pores are not allowed on the weld surface; visual inspection is required to identify any pits or undercut defects.

[0010] The stainless steel is S30408 ​​stainless steel.

[0011] In step (1), the thickness of the weldment is 4mm, the diameter of the small end of the frustum is 300mm to 500mm, the diameter of the large end of the frustum is 400mm to 700mm, and the total length of the assembly is 400mm to 2000mm.

[0012] In steps (4) and (7), the preheating temperature is 30℃~35℃.

[0013] In steps (4) and (8), plasma welding is used with incremental arc initiation and incremental arc termination. The welding speed is 220 mm / min, and the welding current gradually increases from 150 A to 200 A within 2.5 seconds. The wire diameter is 1.2 mm, and the wire feed speed increases to 350 mm / min within 4 seconds, then to 600 mm / min within 2 seconds. The plasma gas flow rate increases to 5.0 L / min within 2.5 seconds, the shielding gas flow rate is 18 L / min to 20 L / min, and the back shielding gas flow rate is 30 L / min to 35 L / min. When terminating the arc, the welding current gradually decreases to 135 A within 6 seconds, the wire feed speed gradually decreases to 1500 mm / min within 6 seconds, and the plasma gas flow rate gradually decreases to 1.5 L / min within 7 seconds.

[0014] In steps (4) and (8), tungsten inert gas (TIG) welding is used for cover welding. The welding wire diameter is 1.2 mm, the gas flow rate is 15 L / min to 18 L / min, the argon purity is not less than 99.99%, the current is 230 A, the shielding gas flow rate is 18 L / min to 20 L / min, the wire feed speed is 1.5 m / min, and the welding speed is 600 mm / min.

[0015] In steps (3), (4), (6), and (8), the welding wire grades are ER304, ER304L, ER308, and ER308L, respectively.

[0016] This invention discloses an automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces, designed using the aforementioned technical solution. The welding method is based on an automatic composite welding quality control method for longitudinal and circumferential seams of stainless steel bulging curved surface workpieces. Addressing issues such as circumferential seam porosity, incomplete fusion defects, and welding deformation, it utilizes welding positioning and clamping fixtures to strictly control the pre-welding workpiece assembly gap and misalignment, and employs a plasma arc welding method with incremental arc initiation and decremental arc termination. Automatic welding is achieved through preheating of the flange and cylinder circumferential butt joints, tack welding of the assembly joints, plasma arc root pass welding, and tungsten inert gas (TIG) cap pass welding. It has the following beneficial effects: 1. By fully leveraging the advantages of plasma arc welding and TIG welding, the penetration capability of the plasma arc itself can be fully utilized to ensure good fusion of the weld between stainless steels. It achieves double-sided forming of stainless steel single-sided welding, with good weld formation on both sides. X-ray inspection revealed no porosity or crack defects in the weld and heat-affected zone. 2. Reasonable energy input, joint assembly control, preheating before welding, and incremental arc initiation and decrementing arc termination methods solve welding problems such as weld porosity and lack of fusion, making workpiece deformation controllable and enabling high-quality welds to be obtained for the circumferential seams of frustoconical workpieces. 3. The method of the present invention is applicable to the quality control method of automatic composite welding of circumferential seams of stainless steel bulging curved surface workpieces, and can be extended to the automatic welding method of circumferential seams of thin-walled cylindrical stainless steel cylinders and flanges, automatic composite welding of circumferential seams of thin-walled frustoconical stainless steel cylinders and flanges, etc. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the welding process of the present invention.

[0018] In the diagram: 1-Welding component, 2-Upper flange, 3-Lower flange, 4-Weld, 5-Weld, 6-Weld. Detailed Implementation

[0019] The following description, in conjunction with the accompanying drawings, details an automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces according to the present invention.

[0020] This invention discloses an automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces. Based on the automatic composite welding quality control method for longitudinal and circumferential seams of stainless steel bulging curved surface workpieces, it addresses issues such as circumferential seam porosity, lack of fusion defects, and welding deformation. It utilizes welding positioning and clamping fixtures to strictly control the pre-welding workpiece assembly gap and misalignment, and employs a plasma arc welding method with incremental arc initiation and decremental arc termination. Automatic welding is achieved through preheating of the flange and cylinder circumferential butt joints, tack welding of the assembly joints, plasma arc root pass welding, and tungsten inert gas (TIG) cap weld.

[0021] like Figure 1 The specific steps of this invention are as follows: Step (1) The material of the part to be welded is S30408. Part 1 is rolled into shape: The cut plate is rolled into a frustum shape by a plate rolling machine; the small end diameter of the frustum is 330mm, the large end diameter of the frustum is 535mm, the length of the frustum is 467mm, and the total length of the assembly is 500mm. Step 2 Cleaning: After the cone is formed, first wipe the welding area with industrial wiping paper dipped in anhydrous alcohol. Then, use steel wool, scraper, and chemical treatment to clean the surface of all welded parts, including the inside of the bevel and the area within 30mm on both sides of the bevel, as well as the welding wire, to remove oil and rust. Remove oil, rust, burrs, moisture, oxide scale, and other impurities until the metal luster is exposed. Then, wipe the welding area and the area within 30mm on both sides with industrial wiping paper dipped in anhydrous alcohol until there is no dirt on the wiping paper. Step (3) Positioning and Welding Part 1: After cleaning, place the part to be welded horizontally on the roller support. The assembly gap should not exceed 0.5mm, and the misalignment should not exceed 1.5mm. Use manual pulse TIG welding to perform tack welding along the axial direction at the joint of part 1. The weld spots should be evenly distributed, with a weld length of 3mm to 4mm. The surface of the weld spot should be on the same plane as the base material. Cerium tungsten electrodes should be used, with a diameter of 2.4mm. The pulse peak current should be 200A to 220A, the pulse base current should be 70A, the pulse frequency should be 2Hz, and the duty cycle should be 50%. The welding wire type should be ER308L, with a diameter of 1.2mm. The gas flow rate should be 15L / min to 18L / min. The argon purity should be not less than 99.99%. Confirm that there are no cracks or deformation defects in the weld after welding. Step 4: Welding the longitudinal butt joint of workpiece 1: Before welding, pre-weld the arc-starting plate and the arc-extinguishing plate at the starting section and the extinguishing end of the workpiece, respectively. Place the workpiece blank on a special longitudinal seam welding fixture, always keeping the welding part in a horizontal position. Use a piano key clamp to press the workpiece tightly. The welding starts from the small diameter end of the frustum-shaped workpiece. The tungsten electrode should be a cerium tungsten electrode with a diameter of 3mm. The workpiece is initially in a cold welding state. Preheat the workpiece to be welded to 30℃~35℃. Use the left welding method, with the tungsten electrode perpendicular to the joint seam. The angle between the welding wire and the tungsten electrode should be 75º~80º. After igniting the arc on the arc-starting plate, continue welding along the longitudinal joint seam to the extinguishing plate. Use the incremental arc-starting and incremental arc-ending method for plasma welding, moving at a normal welding speed of 220mm / min. Gradually increase the welding current from 150A to the normal welding current of 200A within 2.5s. Use ER308L welding wire. The welding wire diameter is 1.2mm, and the wire feed speed increases to 350mm / min within 4s, then to 600mm / min within 2s. The plasma gas flow rate increases to 5.0L / min within 2.5s, the shielding gas flow rate is 18L / min~20L / min, and the back shielding gas flow rate is 30L / min~35L / min. When the arc is terminated, the welding current gradually decreases to 135A within 6s, the wire feed speed gradually decreases to 1500mm / min within 6s, and the plasma gas flow rate gradually decreases to 1.5L / min within 7s for plasma arc root pass welding. Then, tungsten inert gas (TIG) cap pass welding is performed with a current of 230A, a shielding gas flow rate of 18L / min~20L / min, a wire feed speed of 1.5m / min, a welding speed of 600mm / min, and an argon purity of not less than 99.99%, ultimately forming a single-sided weld with double-sided forming. Step 5: bulging and cleaning of post-weld part 1: The post-weld part 1 is formed into a curved surface using a punch bulging fixture; after bulging, the welded area is wiped with industrial wiping paper dipped in anhydrous alcohol, and then all areas to be welded and the surface within 30mm on both sides are cleaned with steel wool, scraper, and chemical treatment to remove oil and rust from the welding wire, and remove oil, rust, burrs, moisture, oxide scale and other debris until the metal luster is exposed. Then, the welded area and the area within 30mm on both sides are wiped with industrial wiping paper dipped in anhydrous alcohol until there is no dirt on the wiping paper. Step 6: Tack welding: Tack weld the circumferential butt joints of flange parts 2 and 3 to be welded with the welded part 1 evenly along the circumferential direction with the center of the circle as the center of symmetry. The assembly gap should not exceed 0.5mm, the misalignment should not exceed 0.2mm, the weld surface should smoothly transition with the welded parts, the weld length should be 3mm to 4mm, the tungsten electrode should be a cerium tungsten electrode with a diameter of 2.4mm, the pulse peak current should be 200A to 220A, the pulse base current should be 70A, the pulse frequency should be 2Hz, the duty cycle should be 50%, the welding wire diameter should be 1.2mm, the gas flow rate should be 15L / min to 18L / min, and the argon purity should be not less than 99.99%. Confirm that there are no cracks or deformation defects in the weld after welding. Step 7: Preheating: Locally preheat the welded joints of the assembled weldment 1, upper flange 2, and lower flange 3 at a temperature of 30℃~35℃. Step (8) Circumferential Welding: Before welding, rotate the workpiece circumferentially to adjust the distance between the tungsten electrode and the workpiece, maintaining a distance of 3mm. The angle between the welding wire and the tungsten electrode should be 75º~80º, with the end of the welding wire 3mm from the tip of the tungsten electrode. The preheating temperature should be 30℃~35℃. Welding should be performed with the wire feed in front and the arc behind, moving at a normal welding speed of 220mm / min. The welding current should gradually increase from 150A to 200A within 2.5s. The welding wire type is ER308L, and the wire diameter is 1.2mm. The wire feed speed should increase to 350mm / min within 4s, and then to 600mm / min within 2s. The plasma gas flow rate should increase to 5.0L / min within 2.5s, and the shielding gas flow rate should be 18L / min~20L / min. The back shielding gas flow rate should be 30L / min. The welding current should be gradually reduced to 135A within 6 seconds when the arc is extinguished, the wire feed speed should gradually reduce to 1500mm / min within 6 seconds, and the plasma gas flow rate should gradually reduce to 1.5L / min within 7 seconds. The circumferential weld should be completed 10mm-15mm past the starting end of the arc-extinguishing end, forming a single-sided weld with double-sided forming. A cerium tungsten electrode should be used, with a diameter of 3mm. The current should be 230A, the shielding gas flow rate should be 18L / min-20L / min, the wire feed speed should be 1.5m / min, the welding speed should be 600mm / min, the argon purity should be not less than 99.99%, the welding torch should not be oscillated, and the welding should be completed continuously without interruption. TIG welding should be used for the tungsten inert gas (TIG) capping. The welding environment temperature should be not lower than 10℃, the relative humidity should be not greater than 75%, and the air flow rate should not be greater than 2m / s. Step 9: Post-weld annealing: After welding, the welded components are allowed to cool naturally to room temperature. The post-weld annealing temperature is 200℃±5℃, and the holding time is 4h~5h. Then, the components are cooled in the furnace to 60℃ and then air-cooled to room temperature. Step 10: Inspection: The weld is inspected using X-ray flaw detection. Cracks and pores are not allowed on the weld surface; visual inspection is required to remove defects such as pits and undercut.

[0022] This invention solves the welding technical problems of poor weld joint formation and even welding deformation in the circumferential seam of S30408 ​​stainless steel bulging curved cylindrical components, such as porosity and lack of fusion in the weld joint. It makes the weld joint well formed, free of welding defects, with good mechanical properties, and can meet the product design requirements.

[0023] This invention fully leverages the advantages of plasma arc welding and TIG welding, achieving single-sided welding and double-sided forming of stainless steel. The weld formation on both sides is excellent, and no porosity or crack defects were found in the weld or heat-affected zone. Reasonable energy input, joint assembly control, and incremental arc initiation and decremental arc termination methods allow for controllable workpiece deformation, resulting in high-quality welds on the circumferential seams of frustoconical workpieces. This welding method has reference and promotional value for applications such as automatic welding of circumferential seams between thin-walled cylindrical stainless steel cylinders and flanges, and automatic composite welding of circumferential seams between thin-walled frustoconical stainless steel cylinders and flanges.

Claims

1. A method for automatic composite welding quality control of circumferential seams in stainless steel bulging curved surface workpieces, characterized in that: The welding method utilizes welding positioning and clamping fixtures to strictly control the pre-weld workpiece assembly gap and misalignment. It employs a plasma arc welding method with incremental arc initiation and decremental arc termination. The welding process involves preheating of the flange and cylinder annular butt joints, tack welding of the assembled joints, plasma arc root pass welding, and tungsten inert gas (TIG) cap pass welding for automated welding. The specific steps are as follows: Step 1: Rolling the material to be welded into shape: The cut plate is rolled into a frustum shape by a plate rolling machine to form the weldment; Step 2 Cleaning: After the weldment is tapered, first wipe the welding area with industrial wiping paper dipped in anhydrous alcohol. Then, use a steel wool, scraper, and chemical treatment to clean the surface of all weldment parts inside the bevel and within 30mm on both sides of the bevel, as well as the welding wire to remove oil and rust, and remove oil, rust, burrs, moisture, oxide scale and other debris until the metal luster is exposed. Then, wipe the welding area and within 30mm on both sides with industrial wiping paper dipped in anhydrous alcohol until there is no dirt on the wiping paper. Step (3) Positioning and Welding the Workpiece: Place the cleaned workpiece, ensuring the welding area remains horizontal on the roller support. The assembly gap should not exceed 0.5mm, and the misalignment should not exceed 1.5mm. Use manual pulse TIG welding, performing tack welding along the axial direction at the joint. The weld spots should be evenly distributed, with a length of 3mm–4mm. The weld spot surface should be flush with the base material. Use cerium tungsten electrodes with a diameter of 2.4mm. The pulse peak current should be 200A–220A, the pulse base current 70A, the pulse frequency 2Hz, and the duty cycle 50%. Use a 1.2mm diameter welding wire and a gas flow rate of 15L / min–18L / min. The argon purity should be no less than 99.99%. Confirm that the weld is free of cracks and the workpiece is free of deformation defects after welding. Step 4: Welding the longitudinal butt joint of the workpiece: Before welding, pre-weld the arc-starting plate and the arc-extinguishing plate to the starting section and the extinguishing end of the workpiece, respectively. Place the workpiece blank on the longitudinal seam welding fixture, always keeping the welding part in a horizontal position. Use a piano key clamp to press the workpiece firmly, starting the welding from the small diameter end of the frustum-shaped workpiece. A cerium tungsten electrode should be used, with a diameter of 3mm. The workpiece should be in a cold welding state at the beginning of the welding process. Preheat the workpiece first, using the left welding method, with the tungsten electrode perpendicular to the joint seam. The angle between the welding wire and the tungsten electrode is 75º~80º. After the arc is ignited on the arc-starting plate, it stays and then welds along the longitudinal weld joint to the arc-extinguishing plate. After the arc is started, the welding gun performs plasma arc root pass welding. Then, tungsten inert gas (TIG) cover pass welding is performed with a current of 230A, a shielding gas flow rate of 18L / min~20L / min, a wire feed speed of 1.5m / min, a welding speed of 600mm / min, and an argon purity of not less than 99.99%, ultimately forming a single-sided weld with double-sided forming. Step 5: Post-weld bulging and cleaning of the welded parts: The welded parts are bulged using a punch bulging fixture to form the curved surface of the generatrix; after bulging, the welded parts are wiped with industrial wiping paper dipped in anhydrous alcohol, and then all the areas to be welded and the surface within 30mm on both sides are cleaned with steel wool, scraper, and chemical treatment to ensure that the welding wire is free of oil and rust, and to remove oil, rust, burrs, moisture, oxide scale and other debris until the metal luster is exposed. Then, the welded parts and the area within 30mm on both sides are wiped with industrial wiping paper dipped in anhydrous alcohol until there is no dirt on the wiping paper; Step 6: Tack welding: Tack weld the upper and lower flanges to be welded to the circumferential butt joint of the welded component evenly along the circumference with the center of the circle as the center of symmetry. The assembly gap should not exceed 0.5mm, and the misalignment should not exceed 0.2mm. The weld surface should smoothly transition to the welded component. The weld length should be 3mm to 4mm. A cerium tungsten electrode should be used, with a diameter of 2.4mm. The pulse peak current should be 200A to 220A, the pulse base current should be 70A, the pulse frequency should be 2Hz, the duty cycle should be 50%, the welding wire diameter should be 1.2mm, and the gas flow rate should be 15L / min to 18L / min. The argon purity should be not less than 99.99%. Confirm that the weld is free of cracks and the workpiece is free of deformation defects after welding. Step 7: Preheating: Locally preheat the welded joints of the assembled weldment, upper flange, and lower flange; Step (8) Circumferential Welding: Before welding, rotate the workpiece circumferentially to adjust the distance between the tungsten electrode and the workpiece, maintaining a distance of 3mm. The angle between the welding wire and the tungsten electrode should be 75º~80º, with the end of the welding wire 3mm away from the tip of the tungsten electrode. Weld using the method of feeding the wire first and the arc second. The circumferential weld is completed by passing the arc extinguishing end 10mm~15mm past the starting end, forming a single-sided weld with double-sided forming. The tungsten electrode should be a cerium tungsten electrode with a diameter of 3mm. The welding torch should not be oscillated and should be continuously welded without interruption. Plasma arc root pass welding and tungsten inert gas (TIG) argon arc cover pass welding should be performed. The welding environment temperature should not be lower than 10℃, the relative humidity should not be greater than 75%, and the air flow should not be greater than 2m / s. Step 9: Post-weld annealing: After welding, the welded components are allowed to cool naturally to room temperature. The post-weld annealing temperature is 200℃±5℃, and the holding time is 4h~5h. Then, the components are cooled in the furnace to 60℃ and then air-cooled to room temperature. Step 10: Inspection: The weld is inspected using X-ray flaw detection. Cracks and pores are not allowed on the weld surface; visual inspection is required to identify any pits or undercut defects.

2. The automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces according to claim 1, characterized in that: The stainless steel is S30408 ​​stainless steel.

3. The automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces according to claim 2, characterized in that in step (1), the thickness of the weldment is 4mm, the diameter of the small end of the truncated cone is 300mm to 500mm, the diameter of the large end of the truncated cone is 400mm to 700mm, and the total length of the assembly is 400mm to 2000mm.

4. The automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces according to claim 2, characterized in that... In steps (4) and (7), the preheating temperature is 30℃~35℃.

5. A method for automatic composite welding quality control of circumferential seams in stainless steel bulging curved workpieces according to claim 2, characterized in that in steps (4) and (8), plasma welding is used with incremental arc initiation and incremental arc termination. The welding speed is 220 mm / min, the welding current gradually increases from 150 A to 200 A within 2.5 seconds, the wire diameter is 1.2 mm, the wire feed speed increases to 350 mm / min within 4 seconds, then to 600 mm / min within 2 seconds, the plasma gas flow rate increases to 5.0 L / min within 2.5 seconds, the shielding gas flow rate is 18 L / min to 20 L / min, and the back shielding gas flow rate is 30 L / min to 35 L / min. During arc termination, the welding current gradually decreases to 135 A within 6 seconds, the wire feed speed gradually decreases to 1500 mm / min within 6 seconds, and the plasma gas flow rate gradually decreases to 1.5 L / min within 7 seconds.

6. The automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces according to claim 2, characterized in that in steps (4) and (8), tungsten inert gas (TIG) welding is used for cover welding, the welding wire diameter is 1.2 mm, the gas flow rate is 15 L / min to 18 L / min, the argon purity is not less than 99.99%; the current is 230 A, the shielding gas flow rate is 18 L / min to 20 L / min, the wire feeding speed is 1.5 m / min, and the welding speed is 600 mm / min.

7. The automatic composite welding quality control method for circumferential seams of stainless steel bulging curved surface workpieces according to claim 2, characterized in that in steps (3), (4), (6), and (8), the welding wire grades are ER304, ER304L, ER308, and ER308L, respectively.

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