Core barrel welding method

Abstract

A kind of core containment plate welding method.The steps are:1) assembly top / bottom / annular plate: set up multiple outer buttress and inner buttress, adjustable pad is arranged on each buttress for adjusting level.Outer buttress is used to support top / bottom / annular plate and outer support tool, inner buttress is used to support inner support tool, top / bottom / annular plate is sequentially assembled by fixed distance sleeve;2) M plate is assembled in the gap between inner support tool and annular plate, gap and offset of M plate longitudinal seam are ensured by matching;3) positioning welding of containment plate assembly and bottoming welding of top / bottom / annular plate and M plate ring seam are carried out by manual welding;4) inner support tool is removed and laser welding deformation prevention tool is installed, M plate longitudinal seam is welded by laser welding;5) inner support tool is reinstalled, welding of remaining weld is completed by manual welding;6) heat treatment tool is installed, post-welding dimensional stabilization heat treatment is carried out.Compared with traditional manual welding method, the efficiency of the present application is improved by about 10 times, the weld quality is excellent, the labor cost is saved, and the product manufacturing cycle is shortened.

Description

Technical Field

[0001] This invention belongs to the field of reactor core cladding welding technology, and specifically relates to a reactor core cladding welding method. Background Technology

[0002] For the core shroud, a key component of the reactor internals, domestic research and manufacturing of laser welding processes are currently limited to plates up to 16mm thick. However, research and manufacturing of laser welding processes for 20mm thick core shrouds remain a blank area both domestically and internationally. Traditional processes for welding the longitudinal seams of the core shroud still employ a combination of hot-wire TIG welding and manual TIG welding. The hot-wire TIG welding process generally includes three steps: manual TIG welding, root cleaning of the outer longitudinal weld seam, and hot-wire TIG welding. The welding process plus root cleaning takes approximately 50 working days, resulting in long equipment downtime and low production efficiency. Given the widespread adoption of intelligent manufacturing in the manufacturing industry, there is a need to develop more efficient and reliable welding methods. Traditional manual welding methods result in low welding efficiency and unstable weld performance. Summary of the Invention

[0003] In view of the technical problems existing in the background art, the core cladding welding method provided by the present invention is about 10 times more efficient than the traditional manual welding method, saving labor costs and shortening the product manufacturing cycle.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A method for welding reactor core shrouds, comprising the following steps:

[0006] Step 1: Assemble the top / bottom / ring plates: Set up multiple outer and inner supports, each with adjustable pads for leveling. The outer supports are used to support the top / bottom / ring plates and the outer support fixtures, while the inner supports are used to support the inner support fixtures. Assemble the top / bottom / ring plates sequentially using spaced sleeves.

[0007] Step 2: Assemble the M plate in the gap between the inner support fixture and the ring plate, and ensure the gap and misalignment of the longitudinal seam of the M plate through fitting.

[0008] Step 3: Perform the positioning welding of the enclosure assembly and the root pass welding of the circumferential seam between the top / bottom / ring plate and the M plate using manual welding;

[0009] Step 4: Remove the internal support fixture and install the laser welding anti-deformation fixture, and use laser welding to weld the longitudinal seam of the M plate;

[0010] Step 5: Reinstall the internal support fixture and complete the remaining welds by hand welding;

[0011] Step 6: Install heat treatment fixtures and perform post-weld dimensional stabilization heat treatment.

[0012] Preferably, the decomposition steps of step 1 are as follows:

[0013] Step 1.1: Arrange one external support block in each of the four quadrants to support the top / bottom / ring plates and the external support fixture; staggered by 45° from the external support blocks, arrange one internal support block in each of the four directions to support the internal support fixture. Adjustable pads are provided on both the external and internal support blocks for leveling the workpiece;

[0014] Step 1.2: With the top plate facing downwards, hoist it onto the outer support pier. The through holes on the top plate should be offset from the outer support pier. Adjust the adjustable pads to ensure the top plate is level as required. Adjust the inner support fixture using the adjusting bolts to make the ring plate concentric with the inner support fixture.

[0015] Step 1.3: Hoist the bottom roller plate to the outer support pier, and adjust the gap between the roller plate and the ring plate to be uniform by using wedge blocks;

[0016] Step 1.4: Install the screw on the top plate. Based on the distance between the first ring plate and the top plate, install equidistant sleeves on the outside of the screw to install the first ring plate.

[0017] Repeat steps 1.1-1.4 to complete the installation of the second / third layer ring plate and the bottom plate. When installing the bottom plate, the bevel should face upwards.

[0018] Step 1.5: Assemble the outer support fixture to the bottom roller plate, assemble the top roller plate to the outer support fixture, and adjust and lock it; use a pressure plate to fix the top plate to prevent movement when assembling the M plate.

[0019] Preferably, the decomposition steps of step 2 are as follows:

[0020] Step 2.1: Install two M plates at 90° / 270° positions, hoist them between the ring plate and the inner support, and make sure the gap between the ring plate and the inner support matches the profile of the M plate. Adjust the inner support fixture to make the M plate and the ring plate fit tightly together, and make the end face of the M plate flush with the bevel of the top plate.

[0021] Step 2.2: Based on the internal cavity opening dimensions after assembling the two M-plates at 90° / 270° orientations, assemble the other two M-plates;

[0022] Step 2.3: Install the two M-plates at 90° / 270° orientations according to the requirements of Step 2.1, ensuring that the longitudinal joint gap of the M-plates is ≤0.15mm and the misalignment is ≤0.15mm.

[0023] Preferably, the decomposition steps of step 3 are as follows:

[0024] Step 3.1: For the four longitudinal seams of the M plates, use manual argon arc welding for self-fusion positioning welding. For the internal support fixture, 3-4 spot welds are evenly distributed between each layer of support plates, and each section is about 20mm long.

[0025] Step 3.2: Perform single-sided tack welding on all ring plates and M plate circumferential seams. The welding method is shielded metal arc welding. The tack welding is performed on the upward side. The welding position is flat welding / horizontal corner welding. Each weld section has 2 to 3 tack welding sections, and each section is about 10mm long.

[0026] The tack welding sequence follows these principles: 1) 5-layer top / bottom / ring plate sequence: First, perform tack welding on the top / bottom plates, then perform tack welding on the two ring plates near the top / bottom plates, and finally perform tack welding on the middle ring plates; 2) Interlayer sequence: First, perform tack welding near the longitudinal seams of the 4 M plates to ensure the gap and misalignment of the longitudinal seams of the M plates, and then perform tack welding on the remaining welds according to the principle of symmetrical distribution.

[0027] Step 3.3: Hoist the internal support fixture, and flip the fixture and product together 180° in the air;

[0028] Step 3.4: Perform root pass welding on the other side of the tack weld, following the same sequence as in Step 3.2. For fillet welds, perform root pass welding to 1 / 2 weld leg size. For bevel welds, weld to 1 / 3 of the depth. Perform VT / PT inspection after welding.

[0029] Step 3.5: Hoist the internal support fixture, and flip the fixture and product together 180° in the air;

[0030] Step 3.6: Perform root pass welding on the tack weld side, with the same requirements as in Step 3.4.

[0031] Preferably, the decomposition steps of step 4 are as follows:

[0032] Step 4.1: Remove the inner support fixture, hoist the workpiece and the outer support together onto the roller frame used by the laser welding machine, assemble the laser welding inner support fixture, readjust and check the longitudinal seam gap and misalignment.

[0033] Step 4.2: Use manual argon arc welding to weld the longitudinal seam of the M plate into an arc-extinguishing plate, and perform VT inspection after welding;

[0034] Step 4.3: Perform tack welding for the longitudinal seams of the M-plate using laser welding. The tack welding sequence should follow these principles: each longitudinal seam should be tack welded in three sections, each section being 150-200mm. First, perform tack welding on the middle sections of the four longitudinal seams, and then perform tack welding on both ends of the four longitudinal seams.

[0035] Step 4.4: Perform deep penetration laser welding of the longitudinal seams of the M-plates. The deep penetration laser welding follows these principles: each longitudinal seam is divided into three segments. First, weld the middle segments of the two symmetrical longitudinal seams of the M-plates, then weld the middle segments of the other two longitudinal seams. Then, weld the ends using the same symmetrical welding principle.

[0036] Step 4.5: Perform VT / PT inspection on the inner and outer surfaces of the laser welded longitudinal seam of the M plate.

[0037] Preferably, the decomposition steps of step 5 are as follows:

[0038] Step 5.1: Remove the laser welding internal support fixture and reinstall the original internal support fixture;

[0039] Step 5.2: Use shielded metal arc welding to weld the fillet welds between the top / bottom / ring plates and the M plate. Weld the bevel welds between the top / bottom plates and the M plate to 2 / 3 of their length. Weld the fillet welds on the outer side of the longitudinal seam of the M plate to 1 / 2 of their length, meeting the weld leg size requirements. Perform VT / PT inspection on all the above welds.

[0040] Step 5.3: Use shielded metal arc welding to weld the bevel welds between the top / bottom plate and the M plate, and weld the outer corner welds of the longitudinal seams of the M plate. Perform VT / PT inspection on all the above welds.

[0041] Preferably, the decomposition steps of step 6 are as follows:

[0042] Step 6.1: Welding thermocouple fixing fixture and heat treatment fixture support;

[0043] Step 6.2: Install heat treatment fixtures and perform dimensional stabilization treatment at 400±20℃;

[0044] Step 6.3: Remove the heat treatment fixtures and dismantle the temporary accessories.

[0045] This patent can achieve the following beneficial effects:

[0046] This invention develops a laser welding process for 20mm thick reactor core shrouds, resulting in stable weld formation and excellent weld joint performance. There are currently no relevant technologies, either domestically or internationally, for welding 20mm thick reactor core shrouds in nuclear power systems. This invention solves the problem of laser welding of 20mm thick reactor core shrouds and its engineering application. In terms of welding efficiency, it is approximately 10 times more efficient than traditional manual welding methods, saving labor costs and shortening the product manufacturing cycle. Regarding welding quality, the weld formation is stable, and the weld joint performance is excellent. The use of laser welding with self-fusion eliminates the need for procurement and acceptance of welding materials, further reducing production costs. Attached Figure Description

[0047] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0048] Figure 1 This is a diagram showing the arrangement of the outer and inner supports of the present invention.

[0049] Figure 2 This is an assembly effect diagram of the top plate of the present invention;

[0050] Figure 3 This is an assembly effect diagram of the internal support tooling of the present invention;

[0051] Figure 4 This is an assembly effect diagram of all the ring plates and inner support fixtures of this invention;

[0052] Figure 5 This is a diagram showing the hoisting and assembly of the M-plate of the present invention (the scaffolding for the welding station of the enclosure panel assembly has been installed).

[0053] Figure 6 This is a diagram showing the positioning welding marks of the present invention;

[0054] Figure 7 This is a diagram showing the sequence of interlayer positioning welds in this invention;

[0055] Figure 8 This is a diagram showing the interlayer sequence of fillet welds in this invention;

[0056] Figure 9 This is a temperature-time curve for the heat treatment of this invention.

[0057] In the diagram: ring plate 101, inner support 102, wedge block 103, M plate 104, adjusting bolt 105, pressure plate 106, outer support 107, inner support 108, screw 109, adjustable pad 110; " / " represents "and". Detailed Implementation

[0058] Example 1:

[0059] Preferred solutions include Figure 1-8 As shown, a method for welding a reactor core shroud includes the following steps:

[0060] Tooling preparation: integral welding fixture for core shroud, laser welding inner support for core shroud, heat treatment fixture for shroud assembly, welding scaffold for shroud assembly, M-plate lifting lugs, arc extinguishing plate for longitudinal seam of M-plate, support block for heat treatment fixture of shroud, vernier calipers, inner diameter measuring rod, straight edge, and level.

[0061] Step 1: Assemble the top / bottom / ring plates: Set up multiple outer and inner supports, each with adjustable pads for leveling. The outer supports are used to support the top / bottom / ring plates and the outer support fixtures, while the inner supports are used to support the inner support fixtures. Assemble the top / bottom / ring plates sequentially using spaced sleeves.

[0062] Step 1.1: Arrange one external support block in each of the four quadrants to support the top / bottom / ring plates and the external support fixture; offset by 45° from the external support blocks in each of the four quadrants, arrange one internal support block for supporting the internal support fixture. The support blocks are 700mm high for easy observation and operation from below. Adjustable pads are provided on both the external and internal support blocks for leveling the workpiece. Adjust the measuring surface of the internal support fixture to be perpendicular to the platform (≤0.10mm), and use pressure plates to tighten and fix it.

[0063] Step 1.2: With the top plate facing downwards, hoist it onto the outer support pier. The through holes on the top plate should be offset from the outer support pier. Adjust the adjustable pads to make the top plate level within 0.25mm. Adjust the inner support fixture using the adjusting bolts to make the ring plate concentric with the inner support fixture.

[0064] Step 1.3: Hoist the bottom roller plate to the outer support pier, and adjust the gap between the roller plate and the ring plate to be uniform by using wedge blocks;

[0065] Step 1.4: Install the screw at the φ21 through hole on the top plate. Based on the distance between the first ring plate and the top plate, install equidistant sleeves on the outside of the screw to install the first ring plate.

[0066] Repeat steps 1.1-1.4 to complete the installation of the second / third layer ring plate and bottom plate. When installing the bottom plate, the bevel should face upwards, and the deviation between the ring plate and the inner cavity should be ≤0.10mm.

[0067] Step 1.5: Assemble the outer support fixture to the bottom roller plate, assemble the top roller plate to the outer support fixture, and adjust and lock it; use a pressure plate to fix the top plate to prevent movement when assembling the M plate.

[0068] Step 2: Assemble the M plate in the gap between the inner support fixture and the ring plate, and ensure the gap and misalignment of the longitudinal seam of the M plate through fitting.

[0069] Step 2.1: Install two M-plates at 90° / 270° azimuth. Using the lifting lugs welded to the ends of the M-plates, hoist them between the ring plate and the inner support. The gap profile between the ring plate and the inner support should match the profile of the M-plate. Take care to prevent collisions during hoisting. If necessary, grind the ring plate to ensure proper installation of the M-plates. Adjust the inner support fixture to ensure the M-plates are tightly fitted to the ring plate, and the end face of the M-plate is flush with the bevel of the top plate.

[0070] Step 2.2: Based on the internal cavity opening dimensions after assembling the two M-plates at 90° / 270° orientations, assemble the other two M-plates;

[0071] Step 2.3: Install the two M-plates at 90° / 270° orientations as required in Step 2.1. Grind them if necessary to ensure that the longitudinal gap of the M-plates is ≤0.15mm and the misalignment is ≤0.15mm.

[0072] Step 3: Use manual welding to perform positioning welding of the enclosure assembly and root welding of the circumferential seam between the top / bottom / ring plate and the M plate.

[0073] Step 3.1: For the four longitudinal seams of the M plates, use manual argon arc welding for self-fusion positioning welding. For the internal support fixture, 3-4 spot welds are evenly distributed between each layer of support plates, and each section is about 20mm long.

[0074] Step 3.2: Perform single-sided tack welding on all ring plates and M plate circumferential seams. The welding method is shielded metal arc welding. The tack welding is performed on the upward side. The welding position is flat welding / horizontal corner welding. Each weld section has 2 to 3 tack welding sections, and each section is about 10mm long.

[0075] The tack welding sequence follows these principles: 1) 5-layer top / bottom / ring plate sequence: First, perform tack welding on the top / bottom plates, then perform tack welding on the two ring plates near the top / bottom plates, and finally perform tack welding on the middle ring plates; 2) Interlayer sequence: First, perform tack welding near the longitudinal seams of the 4 M plates to ensure the gap and misalignment of the longitudinal seams of the M plates, and then perform tack welding on the remaining welds according to the principle of symmetrical distribution.

[0076] Specifically, the tack welding sequence between the ring plates is as follows: Figure 7 As shown.

[0077] 1) Weld welds numbered 1 to 4 in sequence according to ⑥⑦⑧⑨⑩. Depending on the situation, 2 or 4 welders may be arranged to weld in sequence.

[0078] 2) Weld welds numbered 5 to 8 in the order of ⑥⑦⑧⑨⑩. Depending on the situation, 2 or 4 welders may be arranged to weld in sequence.

[0079] ...

[0080] 3) Weld welds numbered 44 to 48 in the order of ⑥⑦⑧⑨⑩. Depending on the situation, 2 or 4 welders may be arranged to weld in sequence.

[0081] Step 3.3: Hoist the internal support fixture, and flip the fixture and product together 180° in the air;

[0082] Step 3.4: Perform root pass welding on the other side of the tack weld, following the same sequence as in Step 3.2. For fillet welds, perform root pass welding to 1 / 2 weld leg size. For bevel welds, weld to 1 / 3 of the depth. Perform VT / PT inspection after welding.

[0083] Step 3.5: Hoist the internal support fixture, and flip the fixture and product together 180° in the air;

[0084] Step 3.6: Perform root pass welding on the tack weld side, with the same requirements as in Step 3.4.

[0085] Specifically, the tack welding sequence between the ring plates is as follows: Figure 7 As shown.

[0086] 1) Weld the first weld in the order of ①②③④⑤, and arrange 2 or 4 welders to perform the welding in sequence as needed;

[0087] 2) Weld the root pass in the order of ①②③④⑤ for welds numbered 5 to 8. Depending on the situation, 2 or 4 welders may be assigned to perform the welding in sequence.

[0088] ...

[0089] 3) Weld the root pass in the order of ①②③④⑤ for welds numbered 44 to 48. Depending on the situation, 2 or 4 welders may be assigned to perform the welding in sequence.

[0090] 4) Weld the root pass in the order of ⑥⑦⑧⑨⑩ for welds numbered 1 to 4. Depending on the situation, 2 or 4 welders may be assigned to perform the welding in sequence.

[0091] 5) Weld the root pass in the order of ⑥⑦⑧⑨⑩ for welds numbered 5 to 8. Depending on the situation, 2 or 4 welders may be assigned to perform the welding in sequence.

[0092] ...

[0093] 6) Weld the first weld in the order of ⑥⑦⑧⑨⑩ for welds numbered 1 to 4. Depending on the situation, 2 or 4 welders may be arranged to perform the welding in sequence.

[0094] Step 4: Remove the internal support fixture and install the laser welding anti-deformation fixture, and use laser welding to weld the longitudinal seam of the M plate;

[0095] Step 4.1: Remove the inner support fixture, hoist the workpiece and the outer support together onto the roller frame used by the laser welding machine, assemble the laser welding inner support fixture, readjust and check the longitudinal seam gap and misalignment; check all bolts and support blocks, and tighten them again if they are loose.

[0096] Step 4.2: Use manual argon arc welding to weld the longitudinal seam of the M plate into an arc-extinguishing plate, and perform VT inspection after welding;

[0097] Step 4.3: Perform tack welding for the longitudinal seams of the M plate using laser welding, with an I-groove. The laser welding tack welding sequence follows these principles: each longitudinal seam undergoes three tack welding segments, each segment being 150-200mm. First, perform tack welding on the middle segments of the four longitudinal seams, then perform tack welding on both ends of the four longitudinal seams;

[0098] The workpiece is in a horizontal position. After welds No. 1 and No. 4 are completed, the cylinder is rotated to weld welds No. 2 and No. 3.

[0099] Step 4.4: Perform deep penetration laser welding of the longitudinal seams of the M-plates. The deep penetration laser welding follows these principles: each longitudinal seam is divided into three segments. First, weld the middle segments of the two symmetrical longitudinal seams of the M-plates, then weld the middle segments of the other two longitudinal seams. Then, weld the ends using the same symmetrical welding principle.

[0100] Step 4.5: Perform VT / PT inspection on the inner and outer surfaces of the laser welded longitudinal seam of the M plate.

[0101] Step 5: Reinstall the internal support fixture and complete the remaining welds by hand welding.

[0102] Step 5.1: Remove the laser welding internal support fixture and reinstall the original internal support fixture;

[0103] Step 5.2: Use shielded metal arc welding to weld the fillet welds between the top / bottom / ring plates and the M plate. Weld the bevel welds between the top / bottom plates and the M plate to 2 / 3 of their length. Weld the fillet welds on the outer side of the longitudinal seam of the M plate to 1 / 2 of their length, meeting the weld leg size requirements. Perform VT / PT inspection on all the above welds.

[0104] Step 5.3: Use shielded metal arc welding to weld the bevel welds between the top / bottom plate and the M plate, and weld the outer corner welds of the longitudinal seams of the M plate. Perform VT / PT inspection on all the above welds.

[0105] Step 6: Install heat treatment fixtures and perform post-weld dimensional stabilization heat treatment.

[0106] Step 6.1: Welding thermocouple fixing fixture and heat treatment fixture support;

[0107] Step 6.2: Install heat treatment fixtures and perform dimensional stabilization treatment at 400±20℃.

[0108] Using the welding method of this invention, the welding cycle for the longitudinal seams of the reactor core shroud, originally 50 days, is now reduced to 4 days, significantly shorter than the original target of 10 days, representing an efficiency improvement of 12.5 times. The method was piloted at a company, and the results were as follows:

[0109] I. Cost per unit before improvement:

[0110] Welding cost: 600 yuan / day × 20 days = 12000 yuan

[0111] Root cleaning cost: 1000 yuan / day × 30 days = 30000 yuan

[0112] Material cost: 200 yuan / kg × 80 kg + welding material acceptance fee of 10,000 yuan = 26,000 yuan

[0113] Total cost: 68,000 yuan

[0114] II. Cost Calculation per Unit After Improvement:

[0115] Welding cost: 1600 yuan / day × 4 days = 6400 yuan

[0116] Total cost: 6400 yuan

[0117] A single project saves 68,000 - 6,400 yuan = 61,600 yuan, reducing costs by 91%.

[0118] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for welding core shrouds, characterized in that... Includes the following steps: Step 1: Assemble the top / bottom / ring plates: Set up multiple outer and inner supports, each with adjustable pads for leveling; the outer supports are used to support the top / bottom / ring plates and the outer support fixtures, and the inner supports are used to support the inner support fixtures. Assemble the top / bottom / ring plates sequentially through spaced sleeves. Step 2: Assemble the M plate in the gap between the inner support fixture and the ring plate, and ensure the gap and misalignment of the longitudinal seam of the M plate through fitting. Step 3: Perform the positioning welding of the enclosure assembly and the root pass welding of the circumferential seam between the top / bottom / ring plate and the M plate using manual welding; Step 4: Remove the internal support fixture and install the laser welding anti-deformation fixture, and use laser welding to weld the longitudinal seam of the M plate; Step 5: Reinstall the internal support fixture and complete the remaining welds by hand welding; Step 6: Install heat treatment fixtures and perform post-weld dimensional stabilization heat treatment.

2. The method for welding the core shroud according to claim 1, characterized in that: The breakdown steps for step 1 are as follows: Step 1.1: Arrange one external support block in each of the four quadrants for supporting the top / bottom / ring plate and the external support fixture; staggered by 45° from the external support blocks, arrange one internal support block in each of the four directions for supporting the internal support fixture; adjustable pads are provided on both the external and internal support blocks for leveling the workpiece. Step 1.2: With the top plate facing downwards, hoist it onto the outer support pier. The through holes on the top plate should be offset from the outer support pier. Adjust the adjustable pads to ensure the top plate is level as required. Adjust the inner support fixture using the adjusting bolts to make the ring plate concentric with the inner support fixture. Step 1.3: Hoist the bottom roller plate to the outer support pier, and adjust the gap between the roller plate and the ring plate to be uniform by using wedge blocks; Step 1.4: Install the screw on the top plate. Based on the distance between the first ring plate and the top plate, install equidistant sleeves on the outside of the screw to install the first ring plate. Repeat steps 1.1-1.4 to complete the installation of the second / third layer ring plate and the bottom plate. When installing the bottom plate, the bevel should face upwards. Step 1.5: Assemble the outer support fixture to the bottom roller plate, assemble the top roller plate to the outer support fixture, and adjust and lock it; use a pressure plate to fix the top plate to prevent movement when assembling the M plate.

3. The method for welding the core shroud according to claim 1, characterized in that: The breakdown steps for step 2 are as follows: Step 2.1: Install two M plates at 90° / 270° positions, hoist them between the ring plate and the inner support, and make sure the gap between the ring plate and the inner support matches the profile of the M plate. Adjust the inner support fixture to make the M plate and the ring plate fit tightly together, and make the end face of the M plate flush with the bevel of the top plate. Step 2.2: Based on the internal cavity opening dimensions after assembling the two M-plates at 90° / 270° orientations, assemble the other two M-plates; Step 2.3: Install the two M-plates at 90° / 270° orientations according to the requirements of Step 2.1, ensuring that the longitudinal joint gap of the M-plates is ≤0.15mm and the misalignment is ≤0.15mm.

4. The method for welding the core shroud according to claim 1, characterized in that: The breakdown steps for step 3 are as follows: Step 3.1: For the four longitudinal seams of the M plates, perform self-fusion tack welding using manual argon arc welding. For the internal support fixture, place 3-4 spot welds evenly between each layer of support plates, with each section being 20mm in length. Step 3.2: Perform single-sided tack welding on all the circumferential seams between the ring plates and the M plate. The welding method is shielded metal arc welding. The tack welding is performed on the upward side. The welding position is flat welding / horizontal corner welding. Each weld section has 2 to 3 tack welding sections, and each section is 10mm long. The tack welding sequence follows these principles: 1) 5-layer top / bottom / ring plate sequence: First, perform tack welding on the top / bottom plates, then perform tack welding on the two ring plates near the top / bottom plates, and finally perform tack welding on the middle ring plates; 2) Interlayer sequence: First, perform tack welding near the longitudinal seams of the 4 M plates to ensure the gap and misalignment of the longitudinal seams of the M plates, and then perform tack welding on the remaining welds according to the principle of symmetrical distribution. Step 3.3: Hoist the internal support fixture, and flip the fixture and product together 180° in the air; Step 3.4: Perform root pass welding on the other side of the tack weld, following the same sequence as in Step 3.

2. For fillet welds, perform root pass welding to 1 / 2 weld leg size. For bevel welds, weld to 1 / 3 of the depth. Perform VT / PT inspection after welding. Step 3.5: Hoist the internal support fixture, and flip the fixture and product together 180° in the air; Step 3.6: Perform root pass welding on the tack weld side, with the same requirements as in Step 3.

4.

5. The method for welding the core shroud according to claim 1, characterized in that: The breakdown steps for step 4 are as follows: Step 4.1: Remove the inner support fixture, hoist the workpiece and the outer support together onto the roller frame used by the laser welding machine, assemble the laser welding inner support fixture, readjust and check the longitudinal seam gap and misalignment. Step 4.2: Use manual argon arc welding to weld the longitudinal seam of the M plate into an arc-extinguishing plate, and perform VT inspection after welding; Step 4.3: Perform tack welding for the longitudinal seams of the M plate using laser welding. The laser welding tack welding sequence follows these principles: each longitudinal seam is tack welded in three sections, each section being 150-200mm; first, perform tack welding on the middle section of the four longitudinal seams, and then perform tack welding on both ends of the four longitudinal seams. Step 4.4: Perform deep penetration laser welding of the longitudinal seam of the M plate. The deep penetration laser welding is performed according to the following principle: each longitudinal seam is divided into three sections; first, the middle section of the two symmetrical longitudinal seams of the M plate is welded, and then the middle section of the other two longitudinal seams of the M plate is welded; then the welding of both ends is performed in the same symmetrical welding principle. Step 4.5: Perform VT / PT inspection on the inner and outer surfaces of the laser welded longitudinal seam of the M plate.

6. The method for welding the core shroud according to claim 1, characterized in that: The breakdown steps for step 5 are as follows: Step 5.1: Remove the laser welding internal support fixture and reinstall the original internal support fixture; Step 5.2: Use shielded metal arc welding to weld the fillet welds between the top / bottom / ring plates and the M plate. Weld the bevel welds between the top / bottom plates and the M plate to 2 / 3 of their length. Weld the fillet welds on the outer side of the longitudinal seam of the M plate to 1 / 2 of their length, meeting the weld leg size requirements. Perform VT / PT inspection on all the above welds. Step 5.3: Use shielded metal arc welding to weld the bevel welds between the top / bottom plate and the M plate, and weld the outer corner welds of the longitudinal seams of the M plate. Perform VT / PT inspection on all the above welds.

7. The method for welding the core shroud according to claim 1, characterized in that: The breakdown steps for step 6 are as follows: Step 6.1: Welding thermocouple fixing fixture and heat treatment fixture support; Step 6.2: Install heat treatment fixtures and perform dimensional stabilization treatment at 400±20℃; Step 6.3: Remove the heat treatment fixtures and dismantle the temporary accessories.

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