A method for preventing cracks in thick-walled stainless steel clad steel plate welding

Abstract

This invention provides a method for preventing cracking during welding of thick-walled stainless steel composite plates, specifically including: controlling deformation of the composite plate caused by rust removal, correcting deformation of the composite plate, controlling crack prevention during welding, and controlling welding quality. Compared to shot blasting, sandblasting can control the longitudinal deformation of the composite plate within 20mm. After leveling the steel plate with a multi-roller leveling machine, a counterweight pressure method is used to correct the deformation at warped positions to a flatness of 5mm / m. A method of cooling, inspecting, and confirming no cracks in each weld pass before proceeding to the next weld pass is adopted, using a transition layer and cladding layer, to detect welding defects early and improve the welding pass rate. Analysis and summary suggest that a suitable construction scheme for large composite plate storage tanks, strengthening rust removal and deformation prevention stress during on-site composite plate construction, improving welding management, and increasing post-weld inspection and control are effective means to improve the welding pass rate, accelerate construction progress, and reduce construction costs.

Description

Technical Field

[0001] This invention relates to the field of thick-walled stainless steel composite steel plate technology, and specifically to a crack-resistant welding method for thick-walled stainless steel composite steel plates. Background Technology

[0002] As the scale of downstream propylene processing products grows larger, the storage tanks used to store these products are also becoming increasingly larger. Construction and design units are seeking ways to ensure safe operation while reducing construction costs, with material costs accounting for a significant proportion of construction expenses. Therefore, many tanks on the market have been converted from stainless steel plates to stainless steel composite plates. These composite plates are divided into explosion-produced composite stainless steel plates and hot-rolled stainless steel composite plates. The biggest problem with composite plates is the difference in the coefficients of thermal expansion and contraction between the two materials. This leads to stress in the composite plate under the same temperature changes, increasing the probability of cracks during welding. This results in frequent rework of non-destructive testing, severely impacting the weld pass rate and causing high testing and repair costs. To reduce material costs for tank construction and overcome the high construction costs caused by weld cracks in composite plates, reducing stress in the composite plate, improving welding processes, and preventing and controlling weld cracks are key. Welding of composite steel plates is the most difficult part of on-site construction and is the most critical step in the manufacturing quality of large composite plate storage tanks, determining the overall quality of the tank. Summary of the Invention

[0003] To address the aforementioned problems, this invention discloses a method for preventing cracking in thick-walled stainless steel composite plates.

[0004] The specific plan is as follows:

[0005] A method for preventing cracking in thick-walled stainless steel composite steel plates during welding is characterized by comprising: controlling deformation of the composite plate caused by rust removal, correcting deformation of the composite steel plate, controlling cracking during welding of the composite steel plate, and controlling welding quality.

[0006] As a further improvement of the present invention, the rust removal causing deformation control of the composite plate includes: the bottom annular edge plate and wall plate of the butyl acrylate tank AB are composite plate structures, the bottom edge plate has 30 pieces with a size of 2000*9400mm, the wall plate has 168 pieces with a size of 2400*11820mm, the thickness ranges from 3+10mm to 3+26mm, the inner side of the tank wall is stainless steel, the outer wall is carbon steel, rust removal is performed on one side, and the stainless steel side is protected from carburization.

[0007] As a further improvement to this invention, to ensure rust removal quality and prevent pollution, a centralized off-site rust removal and primer anti-corrosion treatment is adopted, requiring a rust removal grade of Sa2.5. Two composite steel plates are bonded together with their stainless steel sides, and one side is first sandblasted to achieve the required surface roughness, with no visible oil, grease, or dirt, and no oxide scale, rust, coatings, or foreign impurities, leaving no trace of contaminants. After this effect, a primer is applied. Once the paint film dries, a crane is used to flip the two steel plates over for sandblasting and anti-corrosion treatment. This method allows for simple and smooth rust removal and painting of the steel plates, and it has been found that sandblasting achieves good results without causing serious deformation of the steel plates. Compared with shot blasting, sandblasting can control the deformation of the composite steel plate within 20mm in the longitudinal direction.

[0008] As a further improvement of the present invention, the deformation correction of the composite steel plate includes: the stainless steel composite plate is a strong metallurgical bond between carbon steel and stainless steel, combining the characteristics of both materials. It has the strength required for the base material, but because the coefficients of thermal expansion and contraction of stainless steel and carbon steel are different (difference of 1.5 times), although the deformation of the composite plate after sandblasting is smaller than that after shot blasting, there is still some deformation. The shrinkage of the stainless steel surface is greater than that of the carbon steel surface, causing the stainless steel surface to warp. There is still a certain gap for the requirements of direct beveling and assembly of steel plates. Therefore, the deformation must be further corrected to meet the assembly quality requirements. A multi-roller leveling machine is used to straighten the composite steel plate. The upper and lower rollers need to be wrapped with aluminum plates to prevent carburization. The leveling machine has many rollers for straightening the steel plate, so a large straightening force is not required. The steel plate can be effectively leveled by repeatedly passing it between the rollers.

[0009] As a further improvement to the present invention, the specific steps are as follows:

[0010] (1) Two composite steel plates with their stainless steel sides facing each other are placed together. Adjust the roller spacing, put in the two steel plates, then adjust the upper roller to flatten the steel plates, and then start the leveling machine to run and press them over slowly.

[0011] (2) After being pressed by the leveling machine, a large part of the steel plate can be leveled. Repeat the operation several times until the flatness of the steel plate basically meets the standard requirements. Finally, deal with the right-angled local warping of the steel plate.

[0012] (3) For the right-angle local warping of the composite steel plate, the heavy pressure method is used. First, the composite steel plate is flipped onto the hardened cement on which the stainless steel plate is laid. Then, a 5-10mm slanted wooden board is placed under the warped part of the composite steel plate. Then, a 20-ton counterweight is used to press on the warped part of the composite steel plate, i.e. the carbon steel side, for 10-20 seconds. This can correct the deformation of the warped part to a flatness of 5mm / m.

[0013] As a further improvement of the present invention, the composite steel plate welding crack prevention control specifically includes: tank wall composite steel plate blanking and fabrication, tank wall composite steel plate assembly and tank wall composite steel plate welding.

[0014] As a further improvement of the present invention, the fabrication of the composite steel plate for the tank wall specifically includes: making a layout template according to the design layout drawing at a 1:1 scale; placing the non-standard-length composite steel plate on the mold; marking and dividing the dimensions on the steel plate; after checking and verifying that there are no errors, cutting is carried out using an automatic plasma cutting machine; during the cutting process, stationary personnel walk on the cutting steel plate to ensure cutting accuracy; the steel plate on the upper side of the weld seam is processed with an outer V-shaped beveling machine; after processing, the plasma cutting flash is polished with an angle grinder to produce a metallic luster; after polishing, the finished steel plate must be marked and placed on a wooden block, and measures should be taken to prevent moisture, dampness, and deformation.

[0015] As a further improvement of the present invention, the tank wall composite steel plate assembly specifically includes:

[0016] (1) First, the prefabricated wall panels should be inspected again. They can only be assembled after there are no obvious deformations, scratches, cracks, or bulges. If the stainless steel plates are bent too much during cutting, they should be corrected again to release the deformation stress generated during cutting.

[0017] (2) In accordance with the requirements of the inverted installation method, draw the outline of the wall panel on the base plate and install the positioning plate. The top of the wall panel is fixed with a plate (stainless steel plate) and spot welded. Then, measure the roundness and plumbness of the assembly with a steel ruler. After it is suitable, use a grinder to grind the oxide layer of the weld again.

[0018] (3) After grinding is completed, check that the misalignment of the circumferential weld is less than or equal to 1.5 mm before starting to weld the circumferential peak, and then install the top plate.

[0019] (4) After the first stainless steel plate has completed the above steps (1), (2), and (3), lift the first plate;

[0020] (5) Start assembling the composite steel plate cladding according to the requirements of steps (1) and (2). Since the thickness of each strip of the cladding increases by more than 2mm from top to bottom, the circumferential weld seam of the assembly should be aligned with the inner wall of the tank as a reference, ensuring that the misalignment is not greater than 0.1 times the plate thickness and not greater than 1.5mm. After checking that the longitudinal weld seam, circumferential weld seam misalignment, cladding roundness, and plumbness of the assembled strip meet the specifications, the next step of composite plate welding can be carried out.

[0021] As a further improvement of the present invention, the welding of the composite steel plate of the tank wall specifically includes:

[0022] Basic requirements for welding

[0023] (1) In accordance with the basic requirements for tank construction, a sufficient number of welders shall be provided for each plate, and the welding shall be carried out by shielded metal arc welding and symmetrical welding.

[0024] (2) Weld the longitudinal weld first, then weld the circumferential weld. After welding the longitudinal weld of two adjacent rings of wall plates, weld the circumferential weld between them. When using an asymmetrical bevel, weld the larger bevel side first, then weld the smaller bevel side.

[0025] (3) Carbon arc gouging is used for root cleaning of welds.

[0026] Based on the statistical analysis of the crack detection results table of welders, the reasons for the appearance of cracks in the composite steel plate welding are as follows: (1) Excessive welding line energy, which damages the original properties of the base layer and the cladding steel plate, resulting in cracks caused by the mixing of the transition layer. (2) Thorough beveling treatment, with impurities cleaned within 20mm on both sides of the beveling. (3) Inadequate control of the welding construction sequence, resulting in the cladding, transition layer and cladding not being strictly doped. (4) Stress concentration after cracks appear, requiring rework to pass inspection.

[0027] The difficulty in welding lies in weld cracks. During production cuts and rework, cracks were found to appear in the transition layer or at the junction of the transition layer and the base layer. Therefore, it is necessary to control the factors that cause cracks, specifically:

[0028] (1) Develop a new welding process for butt welds of composite plates. On site, bevels are used for all butt welds. First, make the outer bevel, then weld the base layer, and then carbon gouge the inner bevel. The two bevel welding methods are similar.

[0029] (2) Welding parameters are strictly applied according to the welding process. After each weld pass is completed, the transition layer and cladding layer are cooled first. Then, after confirming that there are no cracks by penetrant testing, the weld pass is cleaned. Then, the next weld pass is welded. The penetrant testing is performed again. The above process is repeated until the welding is completed.

[0030] (3) Before welding the transition layer and the cladding layer, the root must be thoroughly cleaned and the slag and iron powder in the weld bead must be removed to eliminate the conditions for cracking before welding the transition layer and the cladding layer.

[0031] (4) The joint positions of each weld bead are staggered by 100mm and the T-shaped joints are also staggered;

[0032] (5) After the circumferential weld is completed, the weld is then subjected to X-ray inspection according to the design requirements. All T-joints and longitudinal and circumferential welds are inspected.

[0033] As a further improvement of the present invention, the welding quality control specifically includes: before welding, the wall panel installation must ensure assembly quality, and the misalignment should be within the specified range; the on-site material cutting bevels should be uniform, and the weld gaps should be uniform in width, with special attention paid to protecting the T-joint position to ensure a smooth and regular bevel; and rust and impurities should be thoroughly ground off; during welding, a 15cm gap should be left at both ends of the transition layer and cladding layer of the longitudinal seam, and the transition layer and cladding layer should be welded for the T-joint after the circumferential weld is completed, and the effect of the transition layer and cladding layer weld should be checked using non-destructive testing methods, and the welding speed and welding line energy should be strictly controlled; after welding is completed, X-ray inspection should be carried out in a timely manner, and the unqualified weld positions should be inspected and repaired in a timely manner.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) By changing the rust removal of composite steel plates, sandblasting can control the rust removal and corrosion prevention deformation of composite steel plates within 20mm in the longitudinal direction.

[0036] (2) After the steel plate is leveled by a multi-roller leveling machine, the deformation of the raised position is corrected to a flatness of 5mm / m by the counterweight pressure method.

[0037] (3) To control the welding process and welding process, we strictly implemented the welding process and adopted the method of cooling, inspecting and welding the transition layer and cladding layer in each weld bead until no cracks were found before welding the next weld bead. This method can detect welding defects in advance and improve the welding qualification rate. The welding qualification rate increased from 86.61% to 98%.

[0038] (4) Analyze and summarize a suitable construction plan for large composite plate storage tanks. Strengthening rust removal and stress prevention during on-site composite plate construction, improving welding management, and increasing post-weld inspection and control are effective means to improve the welding qualification rate, accelerate the construction progress, and reduce construction costs. Attached Figure Description

[0039] Figure 1 This is a diagram showing the welding process parameters in this invention. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0041] This embodiment describes two 25,000 m³ butyl acrylate tanks (940-TK-3101AB) for a raw material and product tank farm project. The basic structure is a 45 m diameter tank with a 24 m height. The tank top features a bidirectional meridian outer mesh shell with a mid-surface curvature radius of 45 m. The skin plate is 6 mm thick stainless steel, and the bottom edge plate is a 3+18 mm S30403+Q345R composite plate. The thickest part of the tank wall is a 3+26 mm S30403+Q345R composite plate. This project uses hot-rolled stainless steel composite plates. The total installation weight of the storage tanks is 1479 tons, and the installation weight of the composite steel plates is 828 tons.

[0042] Currently, there are relatively few large vertical cylindrical storage tanks used in project sites with composite panel equipment. Furthermore, compared to equipment manufacturing at a factory, on-site tank manufacturing and installation face challenges due to poor infrastructure, insufficient construction conditions, and stringent environmental pollution prevention requirements, making tank fabrication and installation significantly more difficult. Measures need to be taken to provide the necessary conditions for project installation and strengthen process control.

[0043] Based on the statistics of the first three wall panels of the first composite steel plate welded on site, the results of X-ray crack detection by the welders are shown in Table 1.

[0044] Table 1. Results of X-ray Crack Detection in Welders

[0045]

[0046]

[0047] Statistical analysis suggests the following are the main causes of crack formation:

[0048] (1) The bevel is unreasonable, the material is not cleaned and ground, the steel plate is severely deformed, the assembly gap and misalignment are not appropriate, which is obvious at the T-joint; (2) The longitudinal transition layer and the cladding layer of the wall panel are welded in one go, which makes it difficult to clean impurities in the subsequent ring peak welding connection; (3) The welder does not strictly control the welding process, and the welding level is uneven, which leads to cracks; (4) The line energy is too high when welding the base layer, the carbon steel molten pool of the base layer melts the cladding layer, which leads to slag inclusion in the cladding layer welding. When welding the transition layer, the line energy increases, which causes the base layer to affect the material of the cladding layer. The carbon content of the transition layer and the cladding layer increases, which leads to cracks when welding the transition layer and the cladding layer weld.

[0049] In response to the above-mentioned possible causes of crack formation, the following recommendations are made:

[0050] (1) Take into account the deformation of the composite plate bevel and formulate measures for rust removal, deformation prevention control and steel plate correction; (2) When welding the longitudinal seam, leave 15cm at each end without welding the transition layer and the cladding layer. After the base layer of the circumferential seam is welded, clean it and then weld the transition layer and cladding layer; (3) When welding the transition layer and cladding layer, perform a penetration test (PT) on each weld pass before welding the next weld pass; (4) Formulate a welding process instruction manual so that welders can strictly follow the welding process and use the smaller welding line energy and slower welding speed as much as possible; (5) Welders who do not comply with the welding process and have a low welding pass rate will be eliminated.

[0051] This invention provides a method for preventing cracking in thick-walled stainless steel composite plates during welding, specifically including: controlling deformation of the composite plate caused by rust removal, correcting deformation of the composite plate, controlling cracking during welding of the composite plate, and controlling welding quality.

[0052] In this embodiment, the control of rust removal leading to composite plate deformation includes: the bottom annular edge plate and wall plate of the butyl acrylate tank AB are composite plate structures, with 30 bottom edge plates measuring 2000*9400mm and 168 wall plates measuring 2400*11820mm, with thicknesses ranging from 3+10mm to 3+26mm. The inner side of the tank wall is made of stainless steel, and the outer wall is made of carbon steel. Rust is removed on one side only, and the stainless steel side is protected from carburization.

[0053] In this embodiment, to ensure rust removal quality and prevent contamination, a centralized off-site rust removal and primer anti-corrosion treatment is adopted, with a rust removal grade requirement of Sa2.5. Two composite steel plates are bonded together with their stainless steel sides facing each other. One side is first sandblasted to achieve the required surface roughness, with no visible oil, grease, or dirt, and no oxide scale, rust, coatings, or foreign impurities. After achieving this effect, no residual traces of contaminants are left. Then, a primer is applied. After the paint film dries, a crane is used to flip the two steel plates over for sandblasting and anti-corrosion treatment. This method allows for simple and smooth rust removal and painting of the steel plates, and it has been found that sandblasting achieves good results without causing serious deformation of the steel plates. Compared with shot blasting, sandblasting can control the deformation of the composite steel plate within 20mm in the longitudinal direction.

[0054] In this embodiment, the deformation correction of the composite steel plate includes: the stainless steel composite plate is a strong metallurgical bond between carbon steel and stainless steel, combining the characteristics of both materials. It has the strength required for the base material, but because the coefficients of thermal expansion and contraction of stainless steel and carbon steel are different (difference of 1.5 times), although the deformation of the composite plate after sandblasting is smaller than that after shot blasting, there is still some deformation. The stainless steel surface shrinks more than the carbon steel surface, causing the stainless steel surface to warp. This is not enough for the requirements of direct beveling and assembly of the steel plate. Therefore, further deformation correction is necessary to meet the assembly quality requirements. A multi-roller leveling machine is used to straighten the composite steel plate. The upper and lower rollers need to be wrapped with aluminum plates to prevent carburization. Since there are many rollers used to straighten the steel plate, a large straightening force is not required. Passing the plate through the rollers several times can effectively level the steel plate.

[0055] In this embodiment, the specific steps are as follows:

[0056] (1) Two composite steel plates with their stainless steel sides facing each other are placed together. Adjust the roller spacing, put in the two steel plates, then adjust the upper roller to flatten the steel plates, and then start the leveling machine to run and press them over slowly.

[0057] (2) After being pressed by the leveling machine, a large part of the steel plate can be leveled. Repeat the operation several times until the flatness of the steel plate basically meets the standard requirements. Finally, deal with the right-angled local warping of the steel plate.

[0058] (3) For the right-angle local warping of the composite steel plate, the heavy pressure method is used. First, the composite steel plate is flipped onto the hardened cement on which the stainless steel plate is laid. Then, a 5-10mm slanted wooden board is placed under the warped part of the composite steel plate. Then, a 20-ton counterweight is used to press on the warped part of the composite steel plate, i.e. the carbon steel side, for 10-20 seconds. This can correct the deformation of the warped part to a flatness of 5mm / m.

[0059] In this embodiment, the crack prevention control of the composite steel plate welding specifically includes: material preparation of the tank wall composite steel plate, assembly of the tank wall composite steel plate, and welding of the tank wall composite steel plate.

[0060] In this embodiment, the fabrication of the composite steel plate for the tank wall specifically includes: making a layout template according to the design layout drawing at a 1:1 scale; placing the non-standard-length composite steel plate on the template; marking and dividing the dimensions on the steel plate; after checking and verifying that there are no errors, cutting is carried out using an automatic plasma cutting machine; during the cutting process, stationary personnel walk on the cutting steel plate to ensure cutting accuracy; the steel plate above the weld seam is processed with an outer V-shaped beveling machine; after processing, an angle grinder is used to polish the plasma cutting burrs to a metallic luster; after polishing, the finished steel plate must be marked and placed on a wooden block, while taking measures to prevent moisture, dampness, and deformation.

[0061] In this embodiment, the composite steel plate assembly for the tank wall specifically includes:

[0062] (1) First, the prefabricated wall panels should be inspected again. They can only be assembled after there are no obvious deformations, scratches, cracks, or bulges. If the stainless steel plates are bent too much during cutting, they should be corrected again to release the deformation stress generated during cutting.

[0063] (2) In accordance with the requirements of the inverted installation method, draw the outline of the wall panel on the base plate and install the positioning plate. The top of the wall panel is fixed with a plate (stainless steel plate) and spot welded. Then, measure the roundness and plumbness of the assembly with a steel ruler. After it is suitable, use a grinder to grind the oxide layer of the weld again.

[0064] (3) After grinding is completed, check that the misalignment of the circumferential weld is less than or equal to 1.5 mm before starting to weld the circumferential peak, and then install the top plate.

[0065] (4) After the first stainless steel plate has completed the above steps (1), (2), and (3), lift the first plate;

[0066] (5) Start assembling the composite steel plate cladding according to the requirements of steps (1) and (2). Since the thickness of each strip of the cladding increases by more than 2mm from top to bottom, the circumferential weld seam of the assembly should be aligned with the inner wall of the tank as a reference, ensuring that the misalignment is not greater than 0.1 times the plate thickness and not greater than 1.5mm. After checking that the longitudinal weld seam, circumferential weld seam misalignment, cladding roundness, and plumbness of the assembled strip meet the specifications, the next step of composite plate welding can be carried out.

[0067] In this embodiment, the welding of the composite steel plate of the tank wall specifically includes:

[0068] Basic requirements for welding

[0069] (1) In accordance with the basic requirements for tank construction, a sufficient number of welders shall be provided for each plate, and the welding shall be carried out by shielded metal arc welding and symmetrical welding.

[0070] (2) Weld the longitudinal weld first, then weld the circumferential weld. After welding the longitudinal weld of two adjacent rings of wall plates, weld the circumferential weld between them. When using an asymmetrical bevel, weld the larger bevel side first, then weld the smaller bevel side.

[0071] (3) Carbon arc gouging is used for root cleaning of welds.

[0072] Based on the statistical analysis of the crack detection results table of welders, the reasons for the appearance of cracks in the composite steel plate welding are as follows: (1) Excessive welding line energy, which damages the original properties of the base layer and the cladding steel plate, resulting in cracks caused by the mixing of the transition layer. (2) Thorough beveling treatment, with impurities cleaned within 20mm on both sides of the beveling. (3) Inadequate control of the welding construction sequence, resulting in the cladding, transition layer and cladding not being strictly doped. (4) Stress concentration after cracks appear, requiring rework to pass inspection.

[0073] The difficulty in welding lies in weld cracks. During production cuts and rework, cracks were found to appear in the transition layer or at the junction of the transition layer and the base layer. Therefore, it is necessary to control the factors that cause cracks, specifically:

[0074] (1) A new welding process was developed for butt welds of composite plates. On-site, all welds will use beveling. First, the outer beveling is made; after welding the base layer, the inner beveling is carbon-gouged. The two beveling welding methods are similar. Welding process parameters are as follows: Figure 1 .

[0075] (2) Welding parameters are strictly applied according to the welding process. After each weld pass is completed, the transition layer and cladding layer are cooled first. Then, after confirming that there are no cracks by penetrant testing, the weld pass is cleaned. Then, the next weld pass is welded. The penetrant testing is performed again. The above process is repeated until the welding is completed.

[0076] (3) Before welding the transition layer and the cladding layer, the root must be thoroughly cleaned and the slag and iron powder in the weld bead must be removed to eliminate the conditions for cracking before welding the transition layer and the cladding layer.

[0077] (4) The joint positions of each weld bead are staggered by 100mm and the T-shaped joints are also staggered;

[0078] (5) After the circumferential weld is completed, the weld is then subjected to X-ray inspection according to the design requirements. All T-joints and longitudinal and circumferential welds are inspected.

[0079] In this embodiment, the welding quality control specifically includes: before welding, the wall panel installation must ensure assembly quality, and the misalignment should be within the specified range; the on-site material cutting bevels should be uniform, and the weld gaps should be uniform in width, with special attention paid to protecting the T-joint position to ensure a smooth and regular bevel; and rust and impurities should be thoroughly ground off; during welding, a 15cm gap should be left at both ends of the transition layer and cladding layer of the longitudinal seam, and the transition layer and cladding layer should be welded for the T-joint after the circumferential weld is completed, and the effect of the transition layer and cladding layer weld should be checked using non-destructive testing methods, and the welding speed and welding heat should be strictly controlled; after welding is completed, X-ray inspection should be carried out in a timely manner, and the unqualified weld positions should be inspected and repaired in a timely manner.

[0080] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A method for preventing cracking in thick-walled stainless steel composite steel plates, characterized in that, Specifically, it includes: Rust removal leading to deformation control of composite plates, deformation correction of composite steel plates, crack prevention control in composite steel plate welding, and welding quality control; The control of rust removal leading to composite plate deformation includes: to ensure rust removal quality and prevent pollution, off-site centralized rust removal and primer anti-corrosion treatment is adopted, with the rust removal grade required to reach Sa2.5 level; two composite steel plates are bonded together with their stainless steel sides, and one side is first sandblasted to remove rust, achieving the required surface roughness, with no visible oil, grease, or dirt on the surface, and no oxide scale, rust, coatings, or foreign impurities, and no residual traces of contaminants. After the effect of the paint film drying, the two steel plates are flipped over using a crane for sandblasting rust removal and anti-corrosion treatment. This method allows for simple and smooth rust removal and painting of steel plates, and it has been found that the sandblasting effect is good and does not cause serious deformation of the steel plates; The deformation correction of the composite steel plate includes the following specific steps: (1) Two composite steel plates with their stainless steel sides facing each other are placed together. Adjust the roller spacing, put in the two steel plates, then adjust the upper roller to flatten the steel plates, and then start the leveling machine to run and press them over slowly. (2) After being pressed by the leveling machine, a large part of the steel plate can be leveled. Repeat the operation several times until the flatness of the steel plate basically meets the standard requirements. Finally, deal with the right-angled local warping of the steel plate. (3) For the right-angle local warping of the composite steel plate, the heavy pressure method is adopted. First, the composite steel plate is flipped onto the hardened cement on which the stainless steel plate is laid. Then, a 5-10mm inclined wooden board is placed under the warped position of the composite steel plate. Then, a 20-ton counterweight is used to press on the warped position of the composite steel plate, that is, the carbon steel side, for 10-20 seconds. The deformation of the warped position can be corrected to a flatness of 5mm / m. The crack prevention control for the composite steel plate welding includes: fabrication of the tank wall composite steel plate, assembly of the tank wall composite steel plate, and welding of the tank wall composite steel plate; the assembly of the tank wall composite steel plate specifically includes: (1) First, the prefabricated wall panels should be inspected again. They can only be assembled after there are no obvious deformations, scratches, cracks, or bulges. If the stainless steel plates are bent too much during cutting, they should be corrected again to release the deformation stress generated during cutting. (2) According to the requirements of the inverted assembly method, draw the outline of the wall panel on the base plate and make the positioning plate. Fix the top edge of the wall panel with spot welding. Then measure the assembly roundness and plumbness with a steel ruler. After it is suitable, use a grinder to grind the oxide layer of the weld again. (3) After grinding is completed, check that the misalignment of the circumferential weld is less than or equal to 1.5 mm before starting to weld the circumferential peak, and then make the top plate; (4) After the first ring of stainless steel plates has completed the above steps (1), (2), and (3), lift the first ring of plates; (5) Start assembling the composite steel plate cladding according to the requirements of steps (1) and (2). Since the thickness of each ring of the cladding increases by more than 2mm from top to bottom, the circumferential weld seam of the assembly should be aligned with the inner wall of the tank as a reference, and the misalignment should not be greater than 0.1 times the plate thickness and not greater than 1.5mm. After checking that the longitudinal weld seam, circumferential weld seam misalignment, cladding roundness, and plumbness of the assembled plate meet the specifications, the next step of composite plate welding can be carried out.

2. The anti-crack welding method for thick-walled stainless steel composite plates according to claim 1, characterized in that, The fabrication of the composite steel plate for the tank wall specifically includes: making a layout template according to the design layout drawing at a 1:1 scale; placing the non-standard-length composite steel plate on the template; marking and dividing the dimensions on the steel plate; after checking and verifying that there are no errors, cutting is carried out using an automatic plasma cutting machine. During the cutting process, personnel are prohibited from walking on the cutting steel plate to prevent vibration and ensure cutting accuracy; the steel plate above the weld seam is processed with an outer V-shaped beveling machine; after processing, the plasma-cut flash is polished with an angle grinder to achieve a metallic luster; after polishing, the finished steel plate must be marked and placed on a wooden block, while taking measures to prevent moisture, dampness, and deformation.

3. The anti-crack welding method for thick-walled stainless steel composite plates according to claim 2, characterized in that, The welding of the composite steel plates for the tank wall presents a challenge in weld cracking. During on-site repairs, cracks were found to appear in the transition layer or at the junction of the transition layer and the base layer. Therefore, it is necessary to control the factors that cause cracking, specifically including: (1) Develop a new welding process for butt welds of composite plates. On site, bevels are used. First, make the outer bevel. After welding the base layer, carbon gouge the inner bevel. The two bevel welding methods are the same. (2) Welding parameters are strictly applied according to the welding process. After each weld pass is completed, the transition layer and cladding layer are cooled first. Then, after confirming that there are no cracks by penetrant testing, the weld pass is cleaned. Then, the next weld pass is welded. The penetrant testing is performed again. The above process is repeated until the welding is completed. (3) Before welding the transition layer and the cladding layer, the root must be thoroughly cleaned and the slag and iron powder in the weld bead must be removed to eliminate the conditions for cracking. Then the transition layer and the cladding layer are welded. (4) The joint positions of each weld bead are staggered by 100mm and staggered by a T-shaped joint; (5) After the circumferential weld is completed, the weld is then inspected by X-ray according to the design requirements. All T-joints and longitudinal and circumferential welds are inspected.

4. The anti-crack welding method for thick-walled stainless steel composite plates according to claim 3, characterized in that, The welding quality control specifically includes: before welding, ensuring the assembly quality of the wall panel installation, and ensuring that the misalignment is within the specified range; ensuring uniform beveling and weld gap width during on-site material cutting, paying special attention to protecting the T-joint position and ensuring a smooth and regular beveling; and thoroughly grinding away rust and impurities; during welding, leaving 15cm at each end of the transition layer and cladding layer of the longitudinal seam, and welding the transition layer and cladding layer for the T-joint after the circumferential weld is completed, and using non-destructive testing methods to check the weld bead effect of the transition layer and cladding layer, and strictly controlling the welding speed and welding heat input; and promptly conducting X-ray inspection after welding, and promptly repairing any unqualified weld locations.

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