Welding process of nickel-based alloy pipe HT700P

Abstract

The present application relates to the technical field of welding process, in particular to a welding process of nickel-based alloy pipe HT700P, comprising the following steps: preparing a groove: the mechanical tungsten electrode argon arc welding groove is processed into a U type, and the groove gap is 0-1.0 mm, the land length of the root face is 0.5-1.5 mm, and the thickness of the root face is 1.5-3.0 mm; welding preparation and assembly preparation: the groove and the inner and outer walls on both sides thereof are cleaned by alcohol or acetone to remove water, oil and other dirt, two HT700P pipes to be welded are assembled in alignment, the gap of the assembly is 0-1.0 mm, the misalignment of the assembly is 0-0.5 mm, the assembly is fixed by manual tungsten electrode argon arc welding after assembly, the current of the assembly positioning welding is 90-140 A, and the voltage is 9-14 V; the welding joint with excellent mechanical properties and good appearance is formed, and the welding process is original and is for the large-diameter nickel-based pipe HT700P.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to a welding process for a nickel-based alloy tube HT700P. Background Technology

[0002] HT700P is an age-hardening nickel-based alloy with a chemical composition of 33Ni-42Fe-16Cr-2Co-Al-Ti. Due to its excellent high-temperature mechanical properties, ease of processing, and high economic efficiency, it has become a candidate material for advanced ultra-supercritical boilers with a temperature range of 650℃ and above. However, during welding, HT700P is prone to hot cracking under welding stress due to the segregation of trace elements and the formation of low-melting-point eutectics. Furthermore, the poor fluidity of the weld metal during welding of nickel-based alloys makes it highly susceptible to defects such as incomplete fusion and incomplete penetration.

[0003] Secondly, the existing tungsten inert gas welding process for circumferential welds of large-diameter pipes mostly involves fixing the welding torch on a robotic arm or gantry while the pipe rotates on a roller frame. The drawback of this process is that due to the bending deformation of the pipe during the incoming process, the welding position relative to the welding torch will have a large vertical and horizontal movement during the rotation process. This results in low welding stability and greatly affects the welding quality of the product. The longer the pipe, the greater the movement and the lower the stability.

[0004] Furthermore, if the heat treatment process of age-hardened nickel-based alloys is not well controlled, the thermal stress generated during the heat treatment process will cause the product to crack and fail. At the same time, the inability to effectively eliminate welding residual stress will increase the risk of product cracking and failure during operation. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problems of hot cracking, poor fusion and inclusion in the existing HT700P large-diameter nickel-based alloy pipe, thereby providing a welding process for HT700P nickel-based alloy pipe.

[0006] To solve the above-mentioned technical problems, this invention provides a welding process for HT700P nickel-based alloy pipes, comprising the following steps: Beveling preparation: For mechanical tungsten inert gas (TIG) welding, the beveling is machined into a U-shape, with a beveling gap of 0-1.0 mm, a blunt edge platform length of 0.5-1.5 mm, and a blunt edge thickness of 1.5-3.0 mm; Pre-welding cleaning and assembly preparation: The beveling and its inner and outer walls are cleaned with alcohol or acetone to remove water, oil, and other contaminants. Two HT700P pipes to be welded are then assembled, with an assembly gap of 0-1.0 mm and an assembly misalignment of 0-0.5 mm. After assembly, manual TIG welding is used for spot welding to fix the pipes, with a tack welding current of 90 Ω. -140A, voltage 9-14V; Pre-welding material preparation: When using mechanical argon arc welding, select AWSERNiCrCoMo-1 nickel-based alloy coiled welding wire with a diameter of φ1.0mm; Pre-welding equipment arrangement: Before welding, fix the rail to the pipe with legs, adjust the height of the legs, and adjust the distance between the legs and the edge of the bevel; Preheating temperature: No preheating is required before each layer of welding, but when the room temperature is low, below 5℃, preheat the area on both sides of the weld joint to at least 150mm to 15-20℃; Backside argon protection: Before welding layers 1-4, the inside of the HT700P pipe is protected with 100% argon gas at a flow rate of 10-25L / m. The groove is sealed on both sides. After argon gas is introduced for a certain period of time, an oxygen content analyzer is used for testing. Welding can only proceed when the reading reaches below 0.1%. During welding: Place the tungsten electrode in the welding torch in the groove, adjust the position and angle of the welding torch and tungsten electrode, start the welding power supply to form an arc for 5-10 seconds, then start the roller frame. Stop welding after the welding carriage has traveled 365°. The overlap length between the arc start and end positions should be 10-20mm, and the arc start positions between each layer or pass should be staggered by ≥20mm. Welding pass requirements: When welding 1-2 layers, no weld pass is required. When welding the filler layer from the 3rd layer to the cover layer, each layer needs to be welded in a pass. Next; If the pressure of the second pass can be ≥5mm, then each layer is welded in 2 passes, provided that the sidewall fusion is good. If the pressure of the second pass is <5mm, then each layer needs to be welded in 3 passes to ensure that the pressure is ≥5mm and that the interpass fusion is good. The cover layer welding can be done in 4-5 passes, with the pressure between weld passes ≥5mm, and ensuring that the two sides of the cover weld cover the bevel edge ≥5mm. Non-destructive testing: After the first layer welding is completed, after passing the penetrant test, subsequent welding is carried out. After the cover layer welding is completed, radiographic testing, ultrasonic testing, and penetrant testing are carried out. After passing the tests, post-weld heat treatment is carried out. Post-weld heat treatment: After welding, the HT700P is subjected to stress-relieving heat treatment.

[0007] Furthermore, in the pre-welding cleaning and assembly preparation steps, the welding wire used for spot welding is AWSERNiCrCoMo-1 nickel-based alloy rod welding wire; the shielding gas used in the welding torch is 100% argon gas with a flow rate of 8-12 L / min.

[0008] Furthermore, in the pre-welding equipment arrangement step, the circumferential distance from the center of the rack on the track to the edge of the bevel is the same, and the center of the track coincides with the center of the HT700P pipe as much as possible.

[0009] Furthermore, during welding, the shielding gas used in the welding torch is 100% Ar, with a flow rate of 8-20 L / min.

[0010] Furthermore, the tungsten electrode position requirements are as follows: For the first layer of welding, place the tungsten electrode in the groove, aligning it with the center of the groove and keeping it 5-15mm from the root of the groove. During welding, the tip of the tungsten electrode should not move relative to the center line of the groove, or the movement angle should be ≤6°. For the second layer of welding, place the tungsten electrode in the groove, aligning it with the center of the weld and keeping it 5-15mm from the weld surface. During welding, the tip of the tungsten electrode should move relative to the center line of the groove at an angle Ф1 = 15-25°. °; When welding the filler layer in two passes, if welding the left side, shift the welding torch to the left until it is centered between the weld centerline and the bevel edge, and rotate the tungsten electrode to the left by Ф2 = 15-30° to use as the tungsten electrode rocking center, with a rocking angle of Ф1 = 15-25°; if welding the right side, shift the welding torch to the right until it is centered between the weld centerline and the bevel edge, and rotate the tungsten electrode to the right by Ф2 = 15-30° to use as the tungsten electrode rocking center, with a rocking angle of Ф1 = 15-25°. When welding the filler layer in three passes, it can be divided into left-side welding, middle welding, and right-side welding, and performed sequentially. For left-side welding, shift the welding torch to the left until it aligns with the center line of the weld and the edge of the bevel. Rotate the tungsten electrode to the left by Ф2 = 15-30° to use as the center of the electrode movement, with a movement angle of Ф1 = 15-25°. For middle welding, place the tungsten electrode in the bevel, aligning it with the center of the weld and keeping it 5-15mm away from the weld surface. During welding, the tungsten electrode... The tungsten electrode tip is oscillated at an angle Ф1 = 18-30° relative to the center line of the bevel. If welding the right side, shift the welding torch to the right until it is centered between the weld center line and the edge of the bevel. Rotate the tungsten electrode to the right by Ф2 = 15-30° to use as the center of tungsten electrode oscillation. The oscillation angle is Ф1 = 15-25°. When welding the cover layer, the welding torch position is shifted to the left or right, provided that the overlap and sidewall fusion are satisfied. The tungsten electrode does not need to be rotated. The tungsten electrode oscillation angle is Ф1 = 18-30°.

[0011] Furthermore, the cleaning methods and requirements between layers are as follows: After each layer or pass of welding is completed, observe whether the weld protection is good. If oxidation is found on the weld surface, use a grinding wheel or other mechanical methods to remove the oxide film. At the same time, before welding the next layer or pass, the weld surface and the inside of the groove need to be cleaned with alcohol or acetone to remove water, oil and other contaminants before subsequent welding can be carried out.

[0012] Furthermore, the interlayer temperature control methods and requirements are as follows: After each layer or pass of welding is completed, the temperature of the weld can be reduced to ≤100℃ by spraying or wiping cooling water on the weld surface and the surrounding pipe before subsequent welding can be carried out. The chloride ion content in the cooling water is required to be ≤25mg / L.

[0013] Further, the specific steps for post-weld heat treatment are as follows: Place the workpiece containing the weld into the heat treatment furnace at room temperature and place it stably in the effective heating zone of the heat treatment furnace. The support height must be ≥500mm to prevent deformation during heat treatment. Heat it to 500-600℃ at a rate of ≤100℃ / hour and hold it at that temperature for 1 hour. The purpose of this slow heating rate and holding at 500-600℃ is to reduce the generation of thermal stress.

[0014] Furthermore, the specific steps of post-weld heat treatment also include: after the heat treatment is completed, heating to 980-1010℃ at a rate of ≥120℃ / hour and holding for 3 hours. The purpose of this rapid heating step is to reduce the generation of precipitated strengthening phases to reduce internal stress. The purpose of holding at 980-1010℃ for 3 hours is to eliminate residual stress generated during the welding process. After the heat treatment is completed at 980-1010℃, the heat treatment furnace door is opened and the furnace is cooled to room temperature in the air.

[0015] Furthermore, the required speeds for the roller frame and the trolley are set as follows: The welding trolley moves along the track via a gear meshing with a rack on the track. A welding head is connected to the welding trolley, and a welding torch is mounted on the welding head. The roller frame is driven by a motor, which rotates the rollers on the roller frame. After the rollers rotate, the pipe placed on the rollers rotates in the opposite direction to the rollers due to friction. By setting the travel speed of the welding trolley and the rotation speed of the rollers to be the same, and 80-120 mm / min, and by setting the rotation direction of the welding trolley and the rollers to be the same, while the rotation direction of the welding trolley and the pipe is opposite, the welding torch is kept relatively stationary with respect to the center of the pipe. At this time, the welding torch can be fixed at any position between -10° and 5° from the vertical centerline of the pipe.

[0016] The technical solution of this invention has the following advantages:

[0017] 1. This invention provides a welding process for HT700P nickel-based alloy pipes. The welding process for HT700P nickel-based alloy pipes includes the following steps: Beveling preparation: For mechanical tungsten inert gas (TIG) welding, the beveling is processed into a U-shape, with a beveling gap of 0-1.0 mm, a blunt edge platform length of 0.5-1.5 mm, and a blunt edge thickness of 1.5-3.0 mm; Pre-welding cleaning and assembly preparation: The beveling and its inner and outer walls are cleaned with alcohol or acetone to remove water, oil, and other contaminants. Two HT700P pipes to be welded are then assembled, with an assembly gap of 0-1.0 mm and an assembly misalignment of 0-0.5 mm. After assembly, manual TIG welding is used for spot welding to fix the pipes. The assembly tack welding current is 90-140 A, and the voltage is 9-14 V; Pre-welding material preparation: When using mechanical tungsten inert gas (GTAW), AWS type is selected. ERNiCrCoMo-1 nickel-based alloy coiled welding wire, wire diameter φ1.0mm; Pre-welding equipment setup: Before welding, fix the track to the pipe with support legs, adjust the height of the support legs, and adjust the distance between the support legs and the edge of the bevel; Preheating temperature: No preheating is required before each layer of welding, but when the room temperature is low, below 5℃, preheat the area on both sides of the weld joint to 15-20℃ for at least 150mm; Back argon protection setup: Before welding layers 1-4, the HT700P pipe is protected with 100% argon gas at a flow rate of 10-25L / min, and the sides of the bevel are sealed. After argon gas is passed for a certain period of time, use an oxygen content analyzer to check. Welding can only be carried out when the reading reaches below 0.1%; During welding: Place the tungsten electrode in the welding torch in the bevel, adjust the position and angle of the welding torch and tungsten electrode, start the welding power supply to form an arc for 5-10s, then start the roller frame. After the welding carriage moves 365°, stop welding to ensure the welding... The overlap length between the arc initiation and termination points should be 10-20mm, and the arc initiation points between each layer (pass) should be staggered by ≥20mm. Welding pass requirements: When welding 1-2 layers, no weld passes are required. From the 3rd layer to the filler layer before the capping weld, each layer requires pass welding. If the overlap of the 2nd pass is ≥5mm, and the sidewall fusion is good, then each layer should be welded in 2 passes. If the overlap of the 2nd pass is <5mm, then each layer should be welded in 3 passes. To ensure good inter-pass fusion, the overlap between weld passes must be ≥5mm. The cover layer welding can be carried out in 4-5 passes, with an overlap between weld passes ≥5mm, and the cover weld must cover the bevel edge on both sides ≥5mm. Non-destructive testing: After the first layer welding is completed, a penetrant test is performed. If the test is qualified, subsequent welding can proceed. After the cover layer welding is completed, radiographic testing, ultrasonic testing, and penetrant testing are performed. If the test is qualified, post-weld heat treatment is performed. Post-weld heat treatment: The HT700P is subjected to stress-relieving heat treatment after welding.

[0018] This welding process for HT700P nickel-based alloy pipe addresses common problems such as hot cracking, poor fusion, and inclusions in HT700P nickel-based alloys through precise control of welding material selection, beveling, interpass temperature, and welding parameters. This ensures the formation of welded joints with excellent mechanical properties and aesthetically pleasing results, representing a unique welding process specifically for large-diameter HT700P nickel-based pipes. Furthermore, by maintaining the same travel speed of the welding carriage and the rotation speed of the rollers, and ensuring that the carriage and rollers rotate in the same direction (opposite to the pipe rotation), the welding torch remains relatively stationary relative to the pipe center, achieving flat welding. This minimizes torch movement within the bevel, stabilizing the welding process and guaranteeing weld quality. By controlling the heating rate, holding temperature and time, and cooling rate during heat treatment, thermal stress is reduced, residual welding stress is eliminated, and workpiece failure during heat treatment is prevented, while simultaneously ensuring the workpiece meets the required performance specifications for operation.

[0019] The summary section is provided to present the chosen concepts in a simplified form, which will be further described in the detailed description below. The summary section is not intended to identify essential or necessary features of this disclosure, nor is it intended to limit the scope of this disclosure. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the bevel structure for a welding process of a nickel-based alloy tube HT700P provided by the present invention;

[0022] Figure 2 A schematic diagram of the equipment layout used in the welding process of a nickel-based alloy tube HT700P provided by the present invention;

[0023] Figure 3 A cross-sectional view showing the relative position of the welding torch and the tube in a welding process for a nickel-based alloy tube HT700P provided by the present invention.

[0024] Figures 4 to 6 A cross-sectional view of the welding torch and tungsten electrode positions within the bevel of a welding process for a nickel-based alloy tube HT700P provided by the present invention.

[0025] Figure 7 The heat treatment temperature curve of the welding process of nickel-based alloy tube HT700P provided by the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Welding torch; 2. Tungsten electrode; 3. HT700P tube; 4. Roller frame; 5. Support leg; 6. Rack; 7. Track; 8. Roller; 9. Welding carriage; 10. Welding head. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this disclosure. Therefore, the drawings and description are to be considered exemplary in nature and not restrictive.

[0029] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or connections that allow for communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0031] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0032] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0033] The preferred embodiments of this disclosure are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0034] Please see Figures 1 to 7As shown, this invention provides a welding process for nickel-based alloy pipe HT700P, including the following steps: Beveling preparation: For mechanical tungsten inert gas (TIG) welding, the beveling is processed into a U-shape, with a beveling gap of 0-1.0 mm, a blunt edge platform length of 0.5-1.5 mm, and a blunt edge thickness of 1.5-3.0 mm; Pre-welding cleaning and assembly preparation: The beveling and its inner and outer walls are cleaned with alcohol or acetone to remove water, oil, and other contaminants. Two HT700P pipes 3 to be welded are then assembled, with an assembly gap of 0-1.0 mm and an assembly misalignment of 0-0.5 mm. After assembly, manual TIG welding is used for spot welding to fix the pipes. The assembly tack welding current is 90-140 A. The voltage is 9-14V; Pre-welding material preparation: When using mechanical argon arc welding, select AWSERNiCrCoMo-1 nickel-based alloy coiled welding wire with a diameter of φ1.0mm; Pre-welding equipment arrangement: Before welding, fix the track 7 to the pipe using legs 5, adjust the height of the legs 5, and adjust the distance between the legs 5 and the edge of the bevel; Preheating temperature: Preheating is not required before each layer of welding, but when the room temperature is low, below 5℃, preheat the area on both sides of the weld joint to at least 150mm to 15-20℃; Backside argon protection setting: Before welding layers 1-4, the inside of HT700P pipe 3 is protected with 100% argon gas at a flow rate of 10-25L / min, and The bevel is sealed on both sides. After argon gas is introduced for a certain period of time, an oxygen content analyzer is used for testing. Welding can only proceed when the reading reaches below 0.1%. During welding: Place the tungsten electrode 2 of the welding torch 1 in the bevel. After adjusting the position and angle of the welding torch 1 and the tungsten electrode 2, start the welding power supply to form an arc for 5-10 seconds, then start the roller 8 frame 4. After the welding carriage 9 moves 365°, stop welding. The overlap length between the arc start position and the arc end position should be 10-20mm, and the arc start positions between each layer or each pass should be staggered by ≥20mm. Welding pass setting requirements: When welding the first 1-2 layers, no weld pass is required. When welding the filler layer from the 3rd layer to the filler layer before the cover layer, each layer needs to be passed. Welding; If the pressure of the second pass can be ≥5mm, then each layer is welded in 2 passes, provided that the sidewall fusion is good. If the pressure of the second pass is <5mm, then each layer needs to be welded in 3 passes to ensure that the pressure is ≥5mm and that the interpass fusion is good. The cover layer welding can be done in 4-5 passes, with the pressure between weld passes ≥5mm, and ensuring that the cover weld covers the bevel edge on both sides ≥5mm. Non-destructive testing: After the first layer welding is completed, after passing the penetrant test, subsequent welding is carried out. After the cover layer welding is completed, radiographic testing, ultrasonic testing, and penetrant testing are carried out. After passing the tests, post-weld heat treatment is performed. Post-weld heat treatment: The HT700P is subjected to stress-relieving heat treatment after welding.

[0035] This welding process for HT700P nickel-based alloy pipe addresses common problems such as hot cracking, poor fusion, and inclusions in HT700P nickel-based alloys through careful control of welding material selection, bevel preparation, interpass temperature, and welding parameters. This ensures the formation of welded joints with excellent mechanical properties and aesthetically pleasing results, representing a unique welding process specifically for large-diameter HT700P nickel-based pipes. Furthermore, by setting the traveling speed of the welding carriage 9 and the rotation speed of the rollers 8 to be the same, and with the welding carriage 9 and rollers rotating in the same direction (i.e., opposite to the pipe's rotation), the welding torch 1 remains relatively stationary relative to the pipe's center, achieving flat welding. This minimizes the movement of the welding torch 1 within the bevel, stabilizing the welding process and ensuring weld quality. By controlling the heating rate, holding temperature and time, and cooling rate during heat treatment, thermal stress is reduced, residual welding stress is eliminated, and workpiece failure during heat treatment is avoided, while simultaneously ensuring the workpiece meets the required performance conditions.

[0036] The materials used for welding are: HT700P large-diameter nickel-based pipes in solution-treated and aged states are required to be supplied by steel mills in solution-treated state. The applicable pipe diameter range is Φ159-1500mm and the thickness range is 10-200mm.

[0037] The welding and heat treatment process sequence is as follows: bevel preparation - pre-weld cleaning and assembly, pre-weld material preparation, pre-weld equipment layout - preheating - first layer welding - interpass cleaning and interpass temperature control - filler welding - interpass cleaning and interpass temperature control - capping welding - non-destructive testing - post-weld heat treatment.

[0038] Among them, for mechanical tungsten inert gas (TIG) welding, the bevel is processed into a U-shape, such as... Figure 1 As shown in the figure, the bevel gap is 0-1.0mm, the blunt edge platform length is 0.5-1.5mm, and the blunt edge thickness is 1.5-3.0mm;

[0039] This setup effectively ensures complete weld penetration, achieving a single-sided weld with double-sided forming effect, and avoiding defects such as burn-through or incomplete weld penetration.

[0040] The meaning of "penetration" is that the root of the weld joint is completely melted through.

[0041] The effect of single-sided welding with double-sided forming is that when welding on one side, the weld on the other side can also be well formed;

[0042] Before welding the first to fourth layers of argon protection on the back side, the inside of the tube is protected with 100% argon gas at a flow rate of 10-25 L / min, and the sides of the bevel are sealed to effectively prevent argon gas from escaping.

[0043] After argon gas has been passed through for a certain period of time, an oxygen content analyzer is used to check the oxygen content. Welding can only proceed when the reading reaches below 0.1% to prevent oxidation and embrittlement of the weld seam at high temperatures after welding.

[0044] In some embodiments, in the pre-welding cleaning and assembly preparation steps, the welding wire used for spot welding is AWSERNiCrCoMo-1 nickel-based alloy rod welding wire; the shielding gas used in welding torch 1 is 100% argon gas with a flow rate of 8-12 L / min.

[0045] In some embodiments, during the pre-welding equipment arrangement step, the circumferential distance from the center of the rack 6 on the track 7 to the edge of the bevel is the same, and the center of the track 7 coincides as much as possible with the center of the HT700P pipe 3. This adjustment aims to minimize the lateral and vertical movement of the welding torch 1 within the bevel during welding, and to minimize arc fluctuations during welding. Specifically, during welding, the shielding gas used for the welding torch is 100% Ar, with a flow rate of 8-20 L / min.

[0046] In some embodiments, the position of the tungsten electrode 2 requires the following: During the first layer of welding, the tungsten electrode 2 in the welding torch is placed in the groove, aligning the tungsten electrode 2 with the center of the groove, and the tungsten electrode 2 is 5-15mm away from the root of the groove. During welding, the tip of the tungsten electrode 2 should not be moved relative to the center line of the groove, or the moving angle should be ≤6° (e.g., ...). Figure 4 (As shown); During the second layer welding, place the tungsten electrode 2 in the groove of the welding torch, aligning it with the center of the weld, and keeping it 5-15mm away from the weld surface. During welding, the tip of the tungsten electrode 2 should be tilted relative to the center line of the groove at an angle Ф1 = 15-25° (reference). Figure 4 (As shown); When welding the filler layer in two passes, if welding the left side, shift the welding torch to the left until it is centered between the weld centerline and the bevel edge. Rotate the tungsten electrode 2 to the left by Ф2 = 15-30° to use as the center of rotation for the tungsten electrode 2. The rotation angle is Ф1 = 15-25° (as shown). Figure 5 (As shown); If welding the right side, shift the welding torch to the right until it is centered between the weld centerline and the bevel edge, and rotate the tungsten electrode 2 to the right by Ф2 = 15-30° to use as the center of rotation for the tungsten electrode 2. Rotate the electrode around this center by Ф1 = 15-25° (as shown). Figure 6 (As shown); When welding the filler layer in 3 passes, it can be divided into left-side welding, middle welding, and right-side welding, and the welding should be carried out in sequence; When welding the left side, shift the welding torch to the left to the center of the weld centerline and the edge of the bevel, and rotate the tungsten electrode 2 to the left by Ф2 = 15-30° to use as the center of the tungsten electrode 2, with a shaking angle of Ф1 = 15-25° (as shown); Figure 5(As shown); During intermediate welding, place the tungsten electrode 2 in the groove of the welding torch, aligning it with the center of the weld, and keeping it 5-15mm away from the weld surface. During welding, the tip of the tungsten electrode 2 should be tilted relative to the center line of the groove at an angle Ф1 = 18-30° (as shown). Figure 4 (As shown); If welding the right side, shift the welding torch to the right until it is centered between the weld centerline and the bevel edge, and rotate the tungsten electrode 2 to the right by Ф2 = 15-30° to use as the center of rotation for the tungsten electrode 2. Rotate the electrode around this center by Ф1 = 15-25° (as shown). Figure 6 (as shown); When welding the cover layer, the position of the welding gun should be shifted to the left or right on the premise of meeting the overlap and sidewall fusion requirements. The tungsten electrode 2 does not need to be rotated. The tungsten electrode 2 swing angle is Ф1=18-30°.

[0047] In some embodiments, the cleaning method and requirements between layers are as follows: After each layer or pass of welding is completed, observe whether the weld protection is good. If oxidation is found on the weld surface, use a grinding wheel or other mechanical methods to remove the oxide film. At the same time, before welding the next layer or pass, the weld surface and the groove need to be cleaned with alcohol or acetone to remove water, oil and other contaminants before subsequent welding can be carried out.

[0048] In some embodiments, the interlayer temperature control method and requirements are as follows: after each layer or pass of welding is completed, the temperature of the weld can be reduced to ≤100°C by spraying or wiping cooling water on the weld surface and the surrounding pipe before subsequent welding can be carried out. The chloride ion content in the cooling water is required to be ≤25mg / L.

[0049] In some embodiments, the specific steps of post-weld heat treatment are as follows: the workpiece containing the weld is placed in the heat treatment furnace at room temperature and placed stably in the effective heating zone of the heat treatment furnace. The support height must be ≥500mm to prevent deformation during heat treatment. The workpiece is heated to 500-600℃ at a rate of ≤100℃ / hour and held at that temperature for 1 hour. The purpose of this slow heating rate and holding at 500-600℃ is to reduce the generation of thermal stress.

[0050] Furthermore, the specific steps of post-weld heat treatment also include: after the heat treatment is completed, heating to 980-1010℃ at a rate of ≥120℃ / hour and holding for 3 hours. The purpose of this rapid heating step is to reduce the generation of precipitated strengthening phases to reduce internal stress. The purpose of holding at 980-1010℃ for 3 hours is to eliminate residual stress generated during the welding process. After the heat treatment is completed at 980-1010℃, the heat treatment furnace door is opened and the furnace is cooled to room temperature in the air.

[0051] Furthermore, the required travel speeds of the roller frame 4 and the welding carriage 9 are set as follows: The welding carriage 9 moves along the track 7 via a gear meshing with the rack 6 on the track 7. A welding head 10 is connected to the welding carriage 9, and a welding torch 1 is mounted on the welding head 10. The roller frame 4 is driven by a motor, which in turn drives the rollers 8 on the roller frame 4 to rotate. After the rollers 8 rotate, the pipe placed on the rollers 8 rotates in the opposite direction to the direction of the rollers 8 due to friction. By setting the travel speed of the welding carriage 9 and the rotation speed of the rollers 8 to be the same, and at 80-120 mm / min, and by setting the rotation directions of the welding carriage 9 and the rollers 8 to be the same, while the rotation directions of the welding carriage 9 and the HT700P pipe 3 are opposite, the welding torch 1 is made relatively stationary with respect to the center of the pipe. At this time, the welding torch 1 can be fixed at any position between -10° and 5° from the vertical center line of the pipe.

[0052] The welding process parameters (current, voltage, wire feed speed) for mechanical tungsten inert gas welding (GTAW) are set as shown in Table 1.

[0053]

[0054]

[0055] Table 1: Welding Process Specification Parameters

[0056] This welding process for HT700P nickel-based alloy pipe addresses common problems such as hot cracking, poor fusion, and inclusions in HT700P nickel-based alloys by controlling factors such as welding material selection, bevel preparation, interpass temperature, and welding parameters. This ensures the formation of welded joints with excellent mechanical properties and aesthetically pleasing results, representing a unique welding process specifically for large-diameter HT700P nickel-based pipes. Furthermore, by setting the traveling speed of the welding carriage 9 and the rotation speed of the rollers 8 to be the same, and with the welding carriage 9 and rollers rotating in the same direction (i.e., the welding carriage 9 and the HT700P pipe 3 rotating in opposite directions), the welding torch 1 is relatively stationary relative to the center of the HT700P pipe 3, achieving flat welding. This minimizes the movement of the welding torch 1 within the bevel, stabilizing the welding process and ensuring weld quality. By controlling the heating rate, holding temperature and time, and cooling rate during heat treatment, thermal stress is reduced, residual welding stress is eliminated, and workpiece failure during heat treatment is avoided, while simultaneously ensuring the workpiece meets the required performance for operating conditions.

[0057] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A welding process for nickel-based alloy pipe HT700P, characterized in that, Includes the following steps: Preparation of bevel: For mechanical tungsten electrode (2) argon arc welding, the bevel is processed into a U-shape, and the bevel gap is 0-1.0 mm, the blunt edge platform length is 0.5-1.5 mm, and the blunt edge thickness is 1.5-3.0 mm; Pre-welding cleaning and assembly preparation: Clean the bevel and its inner and outer walls with alcohol or acetone to remove water, oil and other contaminants. Assemble the two HT700P pipes (3) to be welded together. The assembly gap is 0-1.0mm and the assembly misalignment is 0-0.5mm. After assembly, fix it by manual tungsten inert gas (2) argon arc welding. The assembly positioning welding current is 90-140A and the voltage is 9-14V. Material preparation before welding: When using mechanical argon arc welding, select AWS ERNiCrCoMo-1 nickel-based alloy coiled welding wire with a diameter of φ1.0mm; Equipment setup before welding: Before welding, fix the rail (7) to the pipe with the support leg (5), adjust the height of the support leg (5), and adjust the distance between the support leg (5) and the edge of the bevel; Preheating temperature: No preheating is required before each layer of welding, but when the room temperature is low, below 5℃, the area on both sides of the weld joint of not less than 150mm needs to be preheated to 15-20℃. Argon protection setup on the back: Before welding the first to fourth layers, the HT700P pipe (3) is protected with 100% argon gas with a flow rate of 10-25 L / min, and the sides of the bevel are sealed. After argon gas is passed for a certain period of time, an oxygen content analyzer is used for testing. Welding can only be carried out when the reading reaches below 0.1%. During welding: Place the tungsten electrode (2) in the bevel of the welding gun (1), adjust the position and angle of the welding gun (1) and the tungsten electrode (2), start the welding power supply to form an arc for 5-10 seconds, and then start the roller frame (4). After the welding carriage (9) moves 365°, stop welding so that the overlap length between the arc start position and the arc end position is 10-20mm, and the arc start positions between each layer or each pass are staggered by ≥20mm; Welding pass setting requirements: When welding 1-2 layers, no weld pass is required. When welding the filler layer from the 3rd layer to the cover layer, each layer needs to be welded in passes. If the pressure amount of the 2nd pass can be ≥5mm, then each layer is welded in 2 passes, provided that the sidewall fusion is good. If the pressure amount of the 2nd pass is <5mm, then each layer needs to be welded in 3 passes to ensure that the pressure amount is ≥5mm so that the interpass fusion is good. The cover layer welding can be carried out in 4-5 passes, with the overlap between weld passes being ≥5mm, and ensuring that the two sides of the cover weld cover the bevel edge by ≥5mm. Non-destructive testing: After the first layer of welding is completed, penetrant testing is performed and the results are satisfactory before proceeding with subsequent welding; after the cover layer welding is completed, radiographic testing, ultrasonic testing, and penetrant testing are performed, and post-weld heat treatment is carried out after the results are satisfactory. Post-weld heat treatment: The HT700P is subjected to stress-relieving heat treatment after welding.

2. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, In the pre-welding cleaning and assembly preparation steps, the welding wire used for spot welding is AWS ERNiCrCoMo-1 nickel-based alloy rod welding wire. The shielding gas used in the welding torch (1) is 100% argon, with a flow rate of 8-12 L / min.

3. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, In the pre-welding equipment arrangement steps, the distance from the center of the rack (6) on the track (7) to the edge of the bevel in the circumferential direction is the same, and the center of the track (7) coincides with the center of the HT700P pipe (3) as much as possible.

4. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, During welding, the shielding gas used in the welding torch (1) is 100% Ar with a flow rate of 8-20 L / min.

5. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, Tungsten electrode (2) position requirements: When welding the first layer, place the tungsten electrode (2) in the welding gun (1) in the groove, align the tungsten electrode (2) with the center of the groove, and keep the tungsten electrode (2) 5-15mm away from the root of the groove. When welding, the tip of the tungsten electrode (2) should not be shaken relative to the center line of the groove or the shaking angle Ф1≤6°. When welding the second layer, place the tungsten electrode (2) in the bevel of the welding torch (1), align the tungsten electrode (2) with the center of the weld, and keep the tungsten electrode (2) 5-15mm away from the surface of the weld. When welding, the tip of the tungsten electrode (2) is rocked relative to the center line of the bevel at an angle of Ф1 = 15-25°. When welding the filler layer in two passes, if welding the left side, shift the welding torch (1) to the left to the center of the weld center line and the edge of the bevel, and rotate the tungsten electrode (2) to the left at an angle of Ф2 = 15-30° as the center of the rocking of the tungsten electrode (2), with a rocking angle of Ф1 = 15-25°. If welding the right side, shift the welding torch (1) to the right to the center of the weld centerline and the edge of the bevel, and rotate the tungsten electrode (2) to the right by Ф2 = 15-30° as the center of the tungsten electrode (2) rocking, and rock the tungsten electrode (2) at an angle of Ф1 = 15-25°. When welding the filler layer in three passes, it can be divided into three passes: left-side welding, middle welding, and right-side welding, and the welding is carried out in sequence. When welding the left side, the welding gun (1) is shifted to the left to the center of the weld center line and the edge of the groove, and the tungsten electrode (2) is rotated to the left by Ф2 = 15-30° as the center of the tungsten electrode (2) and the shaking angle is Ф1 = 15-25°. When welding the middle, the tungsten electrode (2) in the welding gun (1) is placed in the groove, so that the tungsten electrode (2) is aligned with the center of the weld and the tungsten electrode (2) is 5-15mm away from the weld surface. When welding, the tip of the tungsten electrode (2) is shaken relative to the center line of the groove by Ф1 = 18-30°. If welding the right side, the welding gun (1) is shifted to the right to the center of the weld center line and the edge of the groove, and the tungsten electrode (2) is rotated to the right by Ф2 = 15-30° as the center of the tungsten electrode (2) and the shaking angle is Ф1 = 15-25°. When welding the cover layer, the position of the welding torch (1) is shifted to the left or right on the premise of satisfying the overlap and sidewall fusion. The tungsten electrode (2) does not need to be rotated. The tungsten electrode (2) is rocked at an angle of Ф1 = 18-30°.

6. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, Cleaning methods and requirements between layers: After each layer or pass of welding is completed, observe whether the weld protection is good. If oxidation is found on the weld surface, use a grinding wheel or other mechanical methods to remove the oxide film. At the same time, before welding the next layer or pass, the weld surface and the inside of the groove need to be cleaned with alcohol or acetone to remove water, oil and other contaminants before subsequent welding can be carried out.

7. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, Interlayer temperature control methods and requirements: After each layer or pass of welding is completed, the temperature of the weld can be reduced to ≤100℃ by spraying or wiping cooling water on the weld surface and surrounding pipes before subsequent welding can be carried out. The chloride ion content in the cooling water is required to be ≤25mg / L.

8. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, The specific steps for post-weld heat treatment are as follows: Place the workpiece containing the weld into the heat treatment furnace at room temperature and place it stably in the effective heating zone of the heat treatment furnace. The support height must be ≥500mm to prevent deformation during heat treatment. Heat to 500-600℃ at a rate of ≤100℃ / hour and hold for 1 hour. The purpose of this slow heating rate and holding at 500-600℃ is to reduce the generation of thermal stress.

9. The welding process for a nickel-based alloy tube HT700P according to claim 8, characterized in that, The specific steps of post-weld heat treatment also include: after the heat treatment is completed, heating to 980-1010℃ at a rate of ≥120℃ / hour and holding for 3 hours. The purpose of this rapid heating is to reduce the generation of precipitation strengthening phase to reduce internal stress. The purpose of holding at 980-1010℃ for 3 hours is to eliminate residual stress generated during the welding process. After the heat treatment is completed at 980-1010℃, the heat treatment furnace door is opened and the furnace is cooled to room temperature in the air.

10. The welding process for a nickel-based alloy tube HT700P according to claim 1, characterized in that, Setting the required travel speed of the roller frame (4) and the welding carriage (9): The welding carriage (9) is driven by a gear meshing with the rack (6) on the track (7) to enable the carriage to travel along the track (7). The welding carriage (9) is connected to a welding head, and the welding head (10) is equipped with a welding torch (1). The roller frame (4) is driven by a motor, which drives the roller (8) on the roller frame (4) to rotate. After the roller (8) rotates, the pipe placed on the roller (8) rotates in the opposite direction to the roller (8) due to friction. By setting the walking speed of the welding carriage (9) and the rotation speed of the roller (8) to be the same and 80-120 mm / min, and by setting the rotation direction of the welding carriage (9) and the roller (8) to be the same, and the rotation direction of the welding carriage (9) and the pipe to be opposite, the welding gun (1) and the center of the pipe are relatively stationary. At this time, the welding gun (1) can be fixed at any position between -10° and 5° from the vertical center line of the pipe.

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