Manual welding method for nickel-iron-chromium alloy thick-wall pipeline

Abstract

The invention discloses a manual welding method for a nickel-iron-chromium alloy thick-wall pipeline. The manual welding method comprises a material preparation procedure, a preparation procedure before welding, an internal and external forced cooling procedure, an assembly and back protection procedure, a welding procedure and a post-welding heat treatment procedure. The material preparation procedure specifically comprises the steps that welding materials, a welding machine, a heat treatment machine, a welding measuring instrument and argon are prepared, and the welding materials comprise welding wires and welding rods; the pre-welding preparation procedure specifically comprises the steps that a double-V-shaped groove is machined in a pipe section of the pipeline; the welding procedure specifically comprises the steps that multi-layer multi-pass welding is adopted, positioning welding is conducted in a bottoming groove through a manual argon tungsten-arc welding method, and the postweld heat treatment procedure specifically comprises the steps that the constant temperature is 1000 DEG C, the constant temperature time is 4.5 min / mm, the heating and cooling speed is 60-65 DEG C / h, and heat preservation materials below 450 DEG C are wrapped and air-cooled to the room temperature. The method is high in welding efficiency and good in process stability and reliability, qualified welding joints can be obtained, and the welding seam performance meets the requirements of operation working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, in particular to the technical field of manual welding methods for nickel-iron-chromium alloy thick-walled pipes.

Background Art

[0002] The English full name of SMAW is Shielded Metal Arc Welding. Shielded (with shielding, having an outer skin) Metal (metal, metallic) Arc (arc, arc light) Welding (welding). So, the literal translation of SMAW is shielded metal arc welding, which is also manual arc welding with coated electrodes, that is, the commonly referred to manual arc welding. Its working principle is a method of using a manual operation of the welding electrode for welding. Its disadvantage is that the welding fume is relatively large, and appropriate ventilation protection should be done.

[0003] The English full name of GTAW is Gas Tungsten Arc Welding. Gas (gas, gaseous) Tungsten (tungsten, tungsten's) Arc (arc, arc light) Welding (welding). The literal translation of GTAW is tungsten inert gas arc welding, that is, tungsten inert gas shielded welding, which is the commonly referred to argon arc welding. Its principle is to pass inert argon gas (pure Ar) around the arc welding for protection, isolating the air outside the welding area to prevent oxidation of the welding area. Its welding quality is good and the forming effect is beautiful. Its disadvantage is that the price of pure Ar is relatively expensive, and waste should be avoided.

[0004] In the prior art, for the welding of nickel-iron-chromium alloy thick-walled pipes, there are construction difficulties. Therefore, a new manual welding method is needed, combined with appropriate welding process parameters, to achieve the welding of nickel-iron-chromium alloy thick-walled pipes.

Summary of the Invention

[0005] The purpose of the present invention is to solve the problems in the prior art and propose a manual welding method for nickel-iron-chromium alloy thick-walled pipes, which can provide a welding process for nickel-iron-chromium alloy thick-walled pipes with high welding efficiency and weld performance meeting requirements.

[0006] To achieve the above purpose, the present invention proposes a manual welding method for nickel-iron-chromium alloy thick-walled pipes, including a material preparation process, a pre-welding preparation process, an internal and external forced cooling process, a jointing and back protection process, a welding process, and a post-weld heat treatment process;

[0007] The material preparation process specifically includes: preparing welding materials, a welding machine, a heat treatment machine, welding measuring instruments, and argon gas. The welding materials include welding wires and electrodes;

[0008] The pre-welding preparation process specifically includes machining a double V-shaped groove on the pipe section of the pipe, with a groove angle of 70 degrees;

[0009] The internal and external forced cooling process specifically includes: for the outer wall of the pipeline, a water circulation forced air cooling device is used for cooling, and for the inside of the pipeline, argon filling or compressed air cooling is adopted;

[0010] The butt welding and back protection process specifically includes: cleaning the welding groove and its adjacent areas with thermal influence using alcohol or acetone solvent; adjusting the pipeline welding fixing frame, using stainless steel pipes to spot weld at both ends of the pipeline or passing through the inner walls of two pipe segments for pipe segment butt welding, and then carrying out back protection plugging or local back protection; using a local back protection device to carry out local back protection following the welding process or using stainless steel sheets to plug both ends of the butt welded pipe segments, with exhaust holes left at the upper end of the plug, argon filling holes left on one side, and plugging at the groove;

[0011] The welding process specifically includes: multi-layer and multi-pass welding is adopted, and manual tungsten inert gas arc welding is used to directly carry out positioning welding in the root groove. The welding process parameters during welding are:

[0012]

[0013] The post-weld heat treatment process specifically includes: the constant temperature is 1000 °C, the constant temperature time is 4.5 min / mm, the heating and cooling rate is 60 - 65 °C / h, and it is air-cooled to room temperature with heat preservation material covering below 450 °C.

[0014] Preferably, the welding wire is ERNiCrFe-6 φ2.4mm, and the welding electrodes are ENiCrFe-7 φ3.2 and φ4.0mm; the number of welding machines is 2, and the welding machines have been calibrated and are within the validity period. The welding machines have high-frequency arc starting and functions of advancing and lagging of the shielding gas; the attached instruments of the heat treatment machine have been calibrated and are within the validity period; the welding measuring instruments include welding inspection rulers, vernier calipers, temperature and humidity meters, thermometers, stopwatches, argon pressure gauges, anemometers, and oxygen content measuring instruments, and all the welding measuring instruments have been calibrated and are within the validity period; the argon gas is liquid argon.

[0015] Preferably, the present invention further includes a non-destructive inspection and integral pipe stress testing process, and a mechanical property test process;

[0016] The non-destructive inspection and integral pipe stress testing process specifically includes: carrying out penetrant testing on the surface of the welded joint, i.e., the weld and 20 mm on each side, carrying out RT and UT testing on the inside of the weld, and carrying out stress testing on the entire complete welded joint;

[0017] The mechanical property test process specifically includes: taking the welded joint with the weld as the center, and then conducting room-temperature transverse tensile test, high-temperature transverse tensile test, transverse side bend test, room-temperature impact test, metallographic structure test, hardness test, δ-ferrite measurement, grain size measurement, intergranular corrosion test, chemical analysis test, and sampling stress test.

[0018] The method for obtaining the specimen for the room-temperature transverse tensile test is: taking samples with the full thickness in the wall thickness direction of the pipeline, covering the entire wall thickness; the high-temperature tensile temperature for the high-temperature transverse tensile test is 650 °C; the specimen for the room-temperature impact test has a V-notch, and the V-notch angle is 45 ± 2 degrees. The size of the specimen for the room-temperature impact test is thickness × width × length = 10 × 10 × 55 mm; the width of the specimen for the metallographic structure test is 15 mm, the length includes the base metal, heat-affected zone, and weld zone along the weld, and the thickness is the full thickness of the base metal; the sampling part for the chemical analysis test is the inner surface of the welded joint. Taking 30 mm along the longitudinal direction of the weld and 50 mm along the transverse direction of the weld with the weld as the center, and the specimen thickness is 15 mm, that is, 50 × 30 × 15 mm; the size of the specimen for the intergranular corrosion test is 100 mm in length perpendicular to the weld, 15 mm in width along the weld, and the specimen thickness is 3 mm.

[0019] The beneficial effects of the present invention: The present invention has high welding efficiency, good process stability and reliability, can obtain qualified welded joints, and the weld performance meets the requirements of the operating conditions.

[0020] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the drawings.

Description of the Drawings

[0021] Figure 1 is the pipe section division diagram of a manual welding method for nickel-iron-chromium alloy thick-walled pipelines of the present invention;

[0022] Figure 2 is the schematic diagram of the pipe groove size of a manual welding method for nickel-iron-chromium alloy thick-walled pipelines of the present invention;

[0023] Figure 3 is the schematic diagram of the inter-pass temperature measurement of a manual welding method for nickel-iron-chromium alloy thick-walled pipelines of the present invention;

[0024] Figure 4 is the sampling position diagram of the welded joint of a manual welding method for nickel-iron-chromium alloy thick-walled pipelines of the present invention;

[0025] Figure 5 is the room-temperature transverse tensile specimen diagram of a manual welding method for nickel-iron-chromium alloy thick-walled pipelines of the present invention;

[0026] Figure 6It is a high-temperature transverse tensile specimen diagram of a manual welding method for a nickel-iron-chromium alloy thick-walled pipe according to the present invention;

[0027] Figure 7 It is a transverse side bending specimen diagram of a manual welding method for a nickel-iron-chromium alloy thick-walled pipe according to the present invention;

[0028] Figure 8 It is a room-temperature impact specimen diagram of a manual welding method for a nickel-iron-chromium alloy thick-walled pipe according to the present invention.

[0029] Figure 1 In it: the upper part is the post-weld heat treatment part, the left part is the ESAB welding part, the right part is the Lincoln welding part, and the lower part is the part without post-weld heat treatment; Figure 3 In it: 1 - measuring point; Figure 4 In it: ③, ⑥, ⑨, are the clock positioning marks when the specimen is horizontally fixed and welded; Figure 5 In it: the total length of the specimen is suitable for the testing machine used, L - the length of the side parallel to the tensile surface, which is greater than or equal to the maximum width hk + 60 of the weld after machining, with the unit of mm; Figure 6 In it: the unmarked roughness is 1.6, and the shape and size of the convex part of the specimen can be designed according to the structure of the extensometer by itself; Figure 7 In it: B - the width of the specimen (at this time, it is the thickness direction of the specimen); Figure 8 In it: the upper left is taken from the heat-affected zone, the lower left is taken from the weld metal, the middle is the V-notch diagram, 2 - heat-affected zone, 3 - weld metal, 4 - impact specimen, 5 - weld zone, 6 - fusion line + 3mm.

Specific Embodiment

[0030] Refer to Figures 1 - 8 , the present invention includes a material preparation process, a pre-weld preparation process, an internal and external forced cooling process, a jointing and back protection process, a welding process, and a post-weld heat treatment process;

[0031] The material preparation process specifically includes: preparing welding materials, a welding machine, a heat treatment machine, welding measuring instruments, and argon. The welding materials include welding wires and electrodes;

[0032] The pre-weld preparation process specifically includes machining a double V-groove on the pipe section of the pipe, with the groove angle being 70 degrees;

[0033] The internal and external forced cooling process specifically includes: using a water circulation forced air cooling device for the outer wall of the pipe, and using argon filling or compressed air cooling for the inside of the pipe;

[0034] The pipe alignment and back protection process specifically includes: cleaning the welding groove and its adjacent thermally affected areas with alcohol or acetone solvent; adjusting the pipe welding fixing frame, using stainless steel pipes to spot-weld at both ends of the pipe or passing through the inner walls of two pipe segments for pipe segment alignment, and then performing back protection plugging or local back protection; using a local back protection device to perform local back protection following the welding process or using stainless steel sheets to plug both ends of the aligned pipe segments, leaving an exhaust hole at the upper end of the plug and an argon filling hole on one side, and plugging the groove.

[0035] The welding process specifically includes: welding is carried out by multi-layer and multi-pass welding. The positioning welding is directly carried out in the backing groove by the manual tungsten inert gas arc welding method. The welding process parameters during welding are:

[0036]

[0037] The post-weld heat treatment process specifically includes: the constant temperature is 1000 °C, the constant temperature time is 4.5 min / mm, the heating and cooling rate is 60 - 65 °C / h, and it is covered with heat insulation material and air-cooled to room temperature below 450 °C.

[0038] The working process of the present invention:

[0039] A manual welding method for nickel-iron-chromium alloy thick-walled pipes according to the present invention is described in conjunction with the accompanying drawings during the working process.

[0040] Welding method: GTAW + SMAW;

[0041] Welding position: 5G.

[0042] Welding materials: welding wire: ERNiCrFe-6 φ2.4mm; welding electrode: ENiCrFe-7 φ3.2, φ4.0mm.

[0043] The pipe segment is evenly divided into 4 parts, namely A (0 → 3 o'clock), B (3 → 6 o'clock), C (6 → 9 o'clock), D (9 → 12 o'clock); it is divided into two regions in the thickness direction of the pipe wall. The two regions are bounded by the thickness center line. The region close to the inner wall is numbered 1, and the region close to the outer wall is numbered 2, as shown in the appendix. Figure 1 The mechanical property tests are sampled separately according to the above-mentioned zoning.

[0044] 1. Welding and heat treatment process: Prerequisite confirmation Table 1.

[0045] Table 1 Prerequisites

[0046]

[0047] 2. Pre-weld preheating

[0048] There is no requirement for preheating before welding this time, but internal and external forced cooling measures are adopted. For external wall cooling, a water circulation forced air cooling device is used, and for internal cooling, argon filling (when using manual tungsten inert gas arc welding) and compressed air cooling (when using manual shielded metal arc welding) measures are adopted.

[0049] 3. Alignment and back protection

[0050] Clean the welding groove and its adjacent areas affected by heat with solvents such as alcohol or acetone.

[0051] The base metal shall not be in contact with carbon steel or other alloy steels to prevent iron ion pollution. Stainless steel materials or other special welding joint inspection tools that prevent iron ion pollution shall be used to measure the groove and weld dimensions.

[0052] Adjust the pipeline welding fixed frame (5G welding position), use stainless steel pipes to fix at both ends of the pipeline or pass through the inner walls of two pipe sections, perform pipe section alignment, and then carry out back protection plugging or local back protection.

[0053] Use a local back protection device to carry out local back protection following the welding process or use stainless steel sheets to plug both ends of the aligned pipe sections. There shall be exhaust holes at the upper end of the plug, and argon filling holes may be provided on one side, and the groove shall be plugged.

[0054] 4. Welding process parameters

[0055] The positioning welding process is the same as the formal welding. After confirming that the argon filling effect meets the requirements, use the manual tungsten inert gas arc welding (GTAW) method to directly carry out positioning welding in the backing groove.

[0056] Arrange two welders to carry out symmetric welding.

[0057] Specifically, it shall be implemented in accordance with the appendix "Welding Process Qualification Plan".

[0058] 5. Interpass temperature control

[0059] Multi-layer and multi-pass welding is adopted for welding. When using manual shielded metal arc welding, try not to swing or swing slightly. It is planned to measure the interpass temperature 50 mm from the arc stop of the previous weld at the starting point of the next pass.

[0060] For each part, Zone 1, the maximum interpass temperature is 100 - 110 °C; for each part, Zone 2, the maximum interpass temperature is 140 - 150 °C.

[0061] During the filling and capping welding stages at 1 / 3 of the pipe wall thickness from the outer wall, measure the interpass temperature at 5 mm, 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, etc. before the starting point of the next pass, and also measure the interpass temperature before and after the external wall forced cooling measures are turned on, respectively, to form multiple groups of comparison data.

[0062] 6. Post-weld heat treatment parameters

[0063] After welding is completed, draw lines at the welding positions at 3, 6, 9, and 12 o'clock and make steel stamp marks. Immediately carry out post-weld heat treatment. The specific process parameters are shown in Table 2.

[0064] Table 2 Post-weld heat treatment process parameters

[0065] Item Process Parameter Remarks Constant Temperature 1000℃ Constant Temperature Time 4.5min / mm Heating / Cooling Rate Heating / Cooling Rate: 60 - 65°C / h; Insulated with heat preservation material and air-cooled to room temperature below 450°C Others -

[0066] 7. Nondestructive inspection and integral pipe stress test

[0067] After welding is completed, conduct penetrant testing on the surface of the welded joint (weld seam and 20 mm on each side), and conduct RT and UT testing on the inside of the weld seam to verify the quality of the welded joint.

[0068] Conduct stress testing on the entire complete welded joint and record the data.

[0069] According to the aforementioned requirements, divide the pipe section into 4 parts from A to D, and conduct post-weld heat treatment on two of them.

[0070] 8. Mechanical property test

[0071] Take samples from the mechanical property specimens of the welded joint in a total of eight regions in four parts respectively. The sampling positions are shown in the appendix Figure 4 . Take samples with the weld seam as the center, and conduct room temperature tensile test, high temperature tensile test, transverse bending test, room temperature impact test, macrostructure metallography, microstructure metallography, hardness test, δ-ferrite measurement, grain size measurement, intergranular corrosion test, chemical analysis (weld seam and base metal) test, and sampling stress test.

[0072] 8.1 Room temperature transverse tensile test

[0073] Take samples of the full thickness in the wall thickness direction, covering the entire wall thickness. The sampling positions are shown in the appendix Figure 4 As shown, take 2 samples in each region, that is, take 4 samples at each location. The sample size is shown in the appendix Figure 5 , where W = 25 mm, S = 22 mm, L = hK + 60 mm, and the total length of the sample is 250 mm.

[0074] When taking samples for the room temperature transverse tensile test, the distance from the welding positions at 6 o'clock and 12 o'clock should be ≥ 2 cm.

[0075] The sample numbers are A1-TT-1 to A1-TT-2, A2-TT-1 to A2-TT-2 from the inside to the outside of the pipe wall, and so on.

[0076] 8.2 High temperature transverse tensile test

[0077] Take 4 high temperature transverse tensile samples in each of the eight regions adjacent to the room temperature tensile test. Take samples evenly in the thickness direction of each region. See the appendix for details Figure 4Among them, two are for high-temperature short-time tensile tests, another one is for high-temperature creep tensile test, and the remaining one is for standby. The high-temperature tensile temperature is 650°C. The specimen dimensions are shown in the appendix Figure 6 :

[0078] The specimen numbers from the inside to the outside of the pipe wall are A1-TT-3 to A1-TT-6; A2-TT-3 to A2-TT-6, and so on.

[0079] 8.3 Transverse side bend test

[0080] The face bend and root bend tests are replaced by transverse side bend tests. Two transverse side bend specimens are taken from each area, that is, a total of 4 specimens for each part and 16 specimens for the entire pipe section. The sampling locations are shown in the appendix Figure 4 as shown, covering the entire thickness direction.

[0081] The specimen width B = 45mm, thickness t = 10mm, and length L = 200mm. For details, see the appendix Figure 7 :

[0082] The specimen numbers from the outside to the inside of the pipe wall are A1-BT-1 to A1-BT-2, A2-BT-1 to A2-BT-2, and so on.

[0083] 8.4 Room temperature impact test

[0084] The sampling locations of the room temperature impact specimens in the weld zone and heat affected zone are shown in the appendix Figure 4 as shown. For the impact specimens in the weld zone and heat affected zone, starting from the outside of the pipe wall, the surface of the first group of specimens is located 1mm from the inner surface of the base metal (zone 1), the second group is located on the inner wall side near the boundary of the two zones (zone 1), and the axis of the third group of specimens is located at t / 4 from the surface of the base metal (zone 2). Each group (including the weld zone and heat affected zone) has a total of 6 specimens, and a total of 18 specimens for each part.

[0085] The specimens are notched in a V shape, and the room temperature impact test is carried out according to the "Metallic materials - Charpy pendulum impact test method" (GB / T 229-2020). The specimen dimensions are thickness × width × length of 10 × 10 × 55mm.

[0086] The first group:

[0087] The impact specimen numbers for the weld zone near the inner surface in zone 1 are A1-TOP-1 to A1-TOP-3, and so on;

[0088] The impact specimen numbers for the heat affected zone near the inner surface in zone 1 are A1-TOP-4 to A1-TOP-6, and so on.

[0089] The second group:

[0090] The impact specimen numbers for the weld zone at the midline in zone 1 are A1-TOP-7 to A1-TOP-9, and so on.

[0091] The impact specimen numbers in the middle heat-affected zone of Zone 1 are A1-TOP-10 to A1-TOP-12, and so on.

[0092] The third group:

[0093] The impact specimen numbers in the weld zone of Zone 2 are A2-TOP-13 to A-TOP-15, and so on.

[0094] The impact specimen numbers in the heat-affected zone of Zone 2 are A2-TOP-16 to A2-TOP-18, and so on.

[0095] 8.5 Metallographic structure test

[0096] The sampling positions for macro and micro metallographic specimens are as shown in the appendix. Figure 4 One specimen is taken from each part. Dimensions: width is 15 mm, length along the transverse direction of the weld is 50 mm (including the base metal, heat-affected zone, and weld zone), and thickness is the full thickness of the base metal. The macro and micro metallographic specimens are divided into 2 segments in the thickness direction of the base metal according to the regional boundary, that is, 1 segment for each region, and a total of 16 pieces for the whole pipe.

[0097] 8.6 δ-ferrite content determination

[0098] During the micro metallographic test, the δ-ferrite content is determined. There shall be no δ-ferrite in the metallographic structure of the weld metal of a single austenitic steel.

[0099] 8.7 Hardness

[0100] The hardness test is carried out on the macro metallographic specimen, and data is provided synchronously with the segmentation of the macro metallographic specimen. Each set of data includes the hardness data of the base metal on both sides, the heat-affected zone on both sides, and the weld zone.

[0101] The hardness measurement points in each group are evenly distributed in a horizontal straight line on the cross-section of the relevant area. 3 points are measured on each side of the base metal, 3 points are measured on each side of the heat-affected zone, and 6 points are measured in the weld zone, for a total of 18 points.

[0102] 8.8 Chemical analysis

[0103] The sampling position is the inner surface of the welded joint. Taking the weld as the center, cut 30 mm along the longitudinal direction of the weld and 50 mm along the transverse direction of the weld. The thickness of the specimen is 15 mm, that is, 50×30×15 mm.

[0104] The chemical analysis data includes the weld and the base metal.

[0105] 8.9 Grain size determination

[0106] The grain size determination is carried out on the micro metallographic specimen.

[0107] 8.10 Intergranular corrosion test

[0108] The sampling location is as attached Figure 4 As shown. The specimen size is a length of 100 mm perpendicular to the weld, a width of 15 mm along the weld, and a thickness of 3 mm for the specimen.

[0109] Welding Procedure Qualification Scheme (Table 1)

[0110]

[0111] When calculating the thickness of the weld metal, the reinforcement of the weld is not considered.

[0112] Welding Procedure Qualification Scheme (Table 2)

[0113]

[0114] This welding procedure qualification scheme also completely replaces the welding procedure qualification task sheet.

[0115] The above embodiments are illustrative of the present invention and not restrictive thereof. Any simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A manual welding method for nickel-iron-chromium alloy thick-walled pipes, characterized in that: It includes the material preparation process, pre-welding preparation process, internal and external forced cooling process, alignment and back protection process, welding process, and post-weld heat treatment process; The material preparation process specifically includes: preparing welding materials, welding machines, heat treatment machines, welding measuring instruments, and argon gas. The welding materials include welding wires and electrodes; The pre-welding preparation process specifically includes machining a double-V groove on the pipe section of the pipeline, with a groove angle of 70 degrees; The internal and external forced cooling process specifically includes: using a water circulation forced air cooling device for cooling the outer wall of the pipeline, and using argon filling or compressed air cooling inside the pipeline; The alignment and back protection process specifically includes: cleaning the welding groove and its adjacent areas with thermal influence using alcohol or acetone solvent; adjusting the pipeline welding fixing frame, using stainless steel pipes to spot-fix at both ends of the pipeline or passing through the inner walls of two pipe sections for pipe section alignment, and then performing back protection plugging or local back protection; using a local back protection device to perform local back protection following the welding process or using stainless steel sheets to plug both ends of the aligned pipe sections. An exhaust hole is left at the upper end of the plug, and an argon filling hole is left on one side for plugging at the groove; The welding process specifically includes: using multi-layer and multi-pass welding, directly performing positioning welding in the backing groove using the manual tungsten inert gas arc welding method. The welding process parameters during welding are: The post-weld heat treatment process specifically includes: a constant temperature of 1000 °C, a constant temperature time of 4.5 min / mm, a heating and cooling rate of 60 - 65 °C / h, and air cooling to room temperature with heat insulation materials wrapped below 450 °C.

2. The manual welding method for a thick-walled nickel-iron-chromium alloy pipe as described in claim 1, characterized in that: The welding wire is ERNiCrFe-6 φ2.4mm, and the electrodes are ENiCrFe-7 φ3.2 and φ4.0mm; the number of welding machines is 2, and the welding machines have been calibrated and are within the validity period. The welding machines have high-frequency arc ignition and functions of early and lagging protection gas; the auxiliary instruments of the heat treatment machine have been calibrated and are within the validity period; the welding measuring instruments include welding inspection rulers, vernier calipers, temperature and humidity meters, thermometers, stopwatches, argon pressure gauges, anemometers, and oxygen content measuring instruments, and all the welding measuring instruments have been calibrated and are within the validity period; the argon gas is liquid argon.

3. A manual welding method for a thick-walled nickel-iron-chromium alloy pipe as claimed in claim 1, characterized in that: It also includes the non-destructive inspection and integral pipe stress testing process, and the mechanical property test process; The non-destructive inspection and integral pipe stress testing process specifically includes: performing penetrant testing on the surface of the welded joint, i.e., the weld and 20 mm on each side, performing RT and UT testing on the inside of the weld, and performing stress testing on the entire complete welded joint; The mechanical property test process specifically includes: after cutting the welded joint with the weld as the center, performing room temperature transverse tensile test, high-temperature transverse tensile test, transverse bending test, room temperature impact test, metallographic structure test, hardness test, δ-ferrite determination, grain size determination, intergranular corrosion test, chemical analysis test, and sampling stress test.

4. A manual welding method for a nickel-iron-chromium alloy thick-walled pipe as described in claim 3, characterized in that: The method for obtaining specimens for the room-temperature transverse tensile test is as follows: full-thickness sampling is taken in the thickness direction of the pipe wall, covering the entire pipe wall thickness; the high-temperature tensile temperature for the high-temperature transverse tensile test is 650 °C; the specimens for the room-temperature impact test are notched with a V-notch, and the V-notch angle is 45 ± 2 degrees. The dimensions of the specimens for the room-temperature impact test are thickness × width × length = 10 × 10 × 55 mm; the width of the specimens for the metallographic structure test is 15 mm, the length includes the base metal, heat-affected zone, and weld zone along the weld, and the thickness is the full thickness of the base metal; the sampling location for the chemical analysis test is the inner surface of the welded joint. Taking the weld as the center, 30 mm is cut longitudinally along the weld, 50 mm is cut transversely across the weld, and the specimen thickness is 15 mm, that is, 50 × 30 × 15 mm; the dimensions of the specimens for the intergranular corrosion test are 100 mm in length perpendicular to the weld, 15 mm in width along the weld, and 3 mm in specimen thickness.

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