Submerged Arc Welding Process for Shipbuilding Ultra-Thick Plate Butt Joint

Abstract

The present invention relates to a submerged arc welding process for the butt welding of ultra-thick plates for ships, including the selection of welding consumables for the welding of ultra-thick crack arrestor plates, groove machining, groove splicing, anti-deformation treatment, tack welding, preheating before welding, control of welding process parameters and control of interpass temperature, post-weld residual deformation treatment and flaw detection, and finally heat preservation of the welding area and other processes. During the welding process, the ultra-thick crack arrestor plates adopt an X-type groove pattern with a small welding groove angle, greatly reducing the welding filling amount of the crack arrestor plates. Electromagnetic heating is used for preheating before welding, and the heat diffuses from the middle of the thick plate to the surface for heating, making the heating more uniform, effectively preventing local heating and improving the welding quality; by adopting standardized preheating techniques and process requirements, advanced welding process technical parameters and welding anti-deformation control techniques, the plates are turned over multiple times during the welding process, and at the same time, multi-layer and multi-pass welding is used for welding, ensuring the advantages of straightness and precision requirements after welding.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-thick plate welding processes, specifically to the submerged arc welding process for butt welding of marine ultra-thick plates. Background Art

[0002] With the continuous development of the trunk container shipping trade, a large number of ultra-large container ships such as 16,000 TEU and 24,000 TEU have been built. In the construction of such ultra-large ships, a large amount of crack arrest plates with a thickness of 70 - 95 mm are used in the main deck and hatch coaming areas of the ship. The upper yield strength ReH of the crack arrest plates is not less than 460 Mpa, and the tensile strength Rm is 570 - 720 Mpa. They have high strength and large rigidity, and the welding requirements are extremely high. There has always been a lack of standardized advanced welding processes and technologies in the industry; moreover, no standardized advanced process specifications have been formed for the corresponding welding groove types, welding process parameter flows, and welding quality control.

[0003] Currently, the common groove type for submerged arc welding of conventional thick plates in the shipbuilding industry is the X-type groove (2 / 3 of the plate thickness plus 1 / 3 of the plate thickness). Its groove angle is 60° on the upper side and 80° on the lower side. First, weld one side of the groove with a thickness of 2 / 3 of the plate. After welding, turn it over and back gouge, and then weld the 1 / 3 groove position. This welding method has the problems of a relatively large groove angle, relatively large welding filling amount and workload; it is difficult to control the welding angular deformation, and the flatness and accuracy after welding cannot meet the construction requirements; there is a lack of standardized and advanced preheating technology, the welding quality cannot be effectively guaranteed, the qualified rate is low, and the amount of rework is large; there is a lack of professional welding process technical specifications for ultra-thick plates (crack arrest steel), and it is impossible to apply to the welding defect control of such plates.

[0004] Therefore, in order to improve the welding quality of ultra-thick crack arrest steel plates, greatly reduce the welding filling amount, and ensure that the flatness and accuracy after welding meet the construction requirements, a submerged arc welding process for butt welding of marine ultra-thick plates is provided. Summary of the Invention

[0005] The object of the present invention is to provide a submerged arc welding process for butt welding of marine ultra-thick plates to solve the problems raised in the above background art. The present invention has the advantages of using a small groove, electromagnetic preheating technology before welding, standardized process requirements and welding reverse deformation control technology, and welding in a way of turning over multiple times and performing multi-layer and multi-pass welding, which greatly improves the welding quality, greatly reduces the welding filling amount, and ensures that the flatness and accuracy of the plate after welding meet the construction requirements.

[0006] To achieve the above object, the present invention provides the following technical solution: A submerged arc welding process for marine extra-thick plate splicing, comprising the following steps: (1) Welding material selection: The steel plate to be welded is an EH47BCA or EH40BCA crack arrest steel plate with a thickness of 70-95 mm. The yield strength ReH of the EH47BCA crack arrest steel plate is ≥460 Mpa, and the tensile strength Rm is within the range of 570-720 Mpa. The welding material matching is as follows: For CO2 shielded welding, the welding wire used is TWE-81K2 flux-cored wire with pure CO2 shielding gas (for tack welding). When using automatic submerged arc welding, the welding wire is TSW-E31 with the welding flux TF-250. The yield strength ReH of the EH40BCA crack arrest steel plate is ≥390 Mpa, and the tensile strength Rm is within the range of 510-650 Mpa. For CO2 shielded welding, the welding wire used is Supercored81-K2 flux-cored wire with pure CO2 shielding gas (for tack welding). The submerged arc welding wire is H14 with the welding flux Superflux55ULT.

[0007] (2) Cutting the groove at the butt weld of the crack arrest steel plate: The front groove angle is 50°±5°, the depth is 3 / 5 of the plate thickness including a root gap of 6±2 mm, and the back groove is 60°±5°. The small groove type angle greatly reduces the welding filling amount and workload, ensures the welding quality requirements of the extra-thick crack arrest steel plate, and can greatly reduce the welding filling amount of such special plates, ensuring that the subsequent flatness and accuracy after welding meet the construction requirements.

[0008] (3) Groove splicing: Splice two steel plates with X-type butt grooves. The upper groove angle of the groove is 50°±5°, the lower groove angle is 60°±5°, and the root gap of the groove is 0-1 mm. Clean the impurities in the groove and the area within 20 mm on both sides close to the groove.

[0009] (4) Anti-deformation treatment of the crack arrest steel plate: Assemble and position the crack arrest steel plate. In the free state, add an anti-deformation of -1° to -2° when assembling the plate pieces.

[0010] (5) Tack welding: Perform tack welding in the groove. The length of each tack weld is not less than 50 mm; the welding material for tack welding is the same as that for the formal welding. Preheating is required before tack welding, and flame heating or electromagnetic heating can be used. The preheating temperature is 125℃-150℃.

[0011] (6) Preheating before welding: The main weld is preheated by electromagnetic heating. The preheating temperature is 125℃-150℃, and the temperature measurement point is at a position 75 mm away from the weld. The thick plate is heated diffusely from the middle to the surface, and the heating is more uniform. It effectively prevents local heating and brings subsequent welding problems.

[0012] The power saving effect of using electromagnetic heating can reach at least 30%, and the highest can reach more than 70%.

[0013] (7) Welding process parameters: First, weld the groove surface at 50° ± 5°. The welding current is 650A - 730A, the welding voltage is 26V - 30V, the welding speed is 460mm / min. The welding thickness without root is about 21mm - 25mm, and the welding angular deformation is about +4°. The remaining weld with a plate thickness of 15mm - 30mm is welded last after the reverse side welding is completed, then turn it over. After turning over, use carbon arc air gouging to back gouge it to a depth of 30mm - 48mm. After grinding to show metallic luster, start welding the turned-over side;

[0014] Welding current for the turned-over side: 700A - 800A, welding voltage: 28V - 32V, welding speed: 460mm / min. After all welding of the turned-over side is completed, the angular deformation of its weld is about +2°;

[0015] Turn it over again and weld the remaining weld with a thickness of 15mm - 30mm on the front side. The welding current is 700A - 800A, the welding voltage is 28V - 32V, and the welding speed is 460mm / min until the weld is completed. During the welding process, strictly control the process parameters. After all welding is completed, the angular deformation of its weld is about 0°.

[0016] (8) Welding interlayer temperature control: During the welding process, the welding interlayer temperature is higher than the preheating temperature. The welding interlayer temperature is controlled at 125°C - 250°C. If the temperature drops rapidly during the welding process, heating blocks can be placed on one side of the weld during the welding process, and the heating blocks continuously heat and keep the welding area warm.

[0017] Preferably, during the welding process, a starting and stopping arc plate is used. The starting and stopping arc lengths are not less than 100mm. If there is an arc extinguishing or welding through phenomenon during the process, use carbon arc air gouging to process the arc extinguishing place, and the gouging length is not less than 100mm. When re - starting the arc, the wire alignment position should be 20mm behind the processed position. There are instantaneous changes in current and voltage during arc starting and stopping, which are likely to cause defects. Using a starting and stopping arc plate can avoid generating defects and damaging the workpiece.

[0018] More preferably, the welding adopts the multi - layer and multi - pass welding method, and the slag of the previous weld pass must be completely removed.

[0019] More preferably, deformation control is carried out during the welding process, including the following steps:

[0020] (1) Use the welding parameters during welding to control the weld pass thickness and the generated angular deformation. Through empirical estimation and calculation, determine the steel plate turning - over time to adjust and control the angular deformation, and continuously adjust using the welding parameters and weld angular deformation during subsequent welding, finally obtaining a flat submerged arc automatic welding weld and crack - stopping steel plates;

[0021] (2) Develop a control plan for anti-deformation: In the free state, the anti-deformation of the plate assembly is -1° to -2°. Continuously weld until the weld bead thickness reaches about 21 mm to 25 mm. When the deformation is 3° to 4°, turn over the workpiece.

[0022] (3) After turning over, perform root cleaning. The maximum root cleaning depth of the 95 mm plate reaches 48 mm, and the deformation is -3° to -4°. After welding this side, turn over again and weld the remaining welds until welding is completed.

[0023] More preferably, when there is a difference between the welding deformation and the control plan, strengthen or weaken the weld deformation degree by controlling the welding current and the welding heat input; turn over twice during the whole welding process. When the deformation exceeds the control plan, increase the number of turnovers to control the deformation of the plate seam.

[0024] More preferably, when using iron weights and jigs as fixing measures during the welding process, it is necessary to monitor the welding deformation at the steel plate joint in real time and adjust it in time.

[0025] More preferably, if post-weld residual deformation occurs after welding, thermomechanical treatment can be used to adjust the EH40BAC / EH47BCA steel plate. The area of the EH40BAC / EH47BCA steel plate subjected to thermomechanical treatment needs to be subjected to MT inspection.

[0026] More preferably, after welding, cover the welding area with heat-insulating cotton for slow cooling until room temperature, and finally perform non-destructive testing on the weld.

[0027] More preferably, the submerged arc welding flux must be baked before use. The baking temperature is 300°C to 350°C, and the baking time is 1 to 2 hours.

[0028] More preferably, after welding, recycle the flux, clean the welding slag and dust, and observe the particle size of the flux to obtain the recycled flux. The recycled flux must be mixed with 40%-50% of new flux and used repeatedly.

[0029] During the splicing process of the hull plates, using the conventional welding method, 23.1 Kg of welding materials are required per meter of weld, the cost of welding materials per meter is 924 yuan, the labor cost per meter is 450 yuan, and the comprehensive cost per meter of weld is 1374 yuan; when changing to the submerged arc welding process for splicing super-thick ship plates in this application, 18.9 Kg of welding materials are required per meter of weld, the cost of welding materials per meter is 756 yuan, the labor cost per meter is 300 yuan, and the comprehensive cost per meter of weld is 1056 yuan. For 6 24,000 TEU container ships, a total of 852 meters of welds are spliced, saving a total of 271,000 yuan in welding comprehensive costs. After calculation, the welding materials are saved by about 18% compared with the original.

[0030] After adopting the submerged arc welding process for shipbuilding ultra-thick plate splicing in this application, the welding angular deformation of the hull splicing plate is controllable, and there is no requirement for thermal straightening;

[0031] Moreover, the qualified rate of non-destructive testing for the welds of a total of 852 meters spliced on 6 24,000 TEU container ships is 99.92%, verifying the effectiveness of the welding process in this application.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: In the submerged arc welding process for shipbuilding ultra-thick plate splicing, the ultra-thick crack arrestor plate adopts an X-shaped groove type and has a small welding groove angle, greatly reducing the welding filling amount of the crack arrestor plate. Electromagnetic heating is used for preheating before welding, and the heat diffuses from the middle of the thick plate to the surface for heating, making the heating more uniform, effectively preventing local heating, and improving the welding quality; By adopting standardized preheating techniques and process requirements, advanced welding process technical parameters, and welding reverse deformation control techniques, the plates are turned over multiple times during the welding process, and at the same time, multi-layer and multi-pass welding is used for welding, ensuring the advantages of flatness and precision requirements after welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the weld structure of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Embodiment 1:

[0036] Please refer to the attached Figure 1 , a submerged arc welding process for shipbuilding ultra-thick plate splicing, including the following steps: (1) Welding material selection: The steel plate to be welded is an EH47BCA crack arrestor plate or an EH40BCA crack arrestor plate with a thickness of 70 mm. The thicknesses of the two spliced crack arrestor plates are represented by t and t1 respectively, and the thickness difference between the two spliced steel plates is represented by a, a = t - t1, a < 4 mm.

[0037] The yield strength ReH of the EH47BCA crack arrestor plate ≥ 460 Mpa, and the tensile strength Rm is within the range of 570 - 720 Mpa;

[0038] The welding material matching is as follows: For the welding material used in CO2 shielded welding, TWE-81K2 flux-cored wire is selected and matched with pure CO2 shielding gas (for tack welding). When using submerged arc automatic welding, the welding wire is TSW-E31 and is matched with the welding flux TF-250;

[0039] The yield strength ReH of the EH40BCA crack arrest steel plate is ≥390 Mpa, and the tensile strength Rm is within the range of 510 - 650 Mpa;

[0040] The welding material matching is as follows: For CO2 shielded arc welding, the welding consumables are Supercored81-K2 flux cored wire with pure CO2 shielding gas (for tack welding). For submerged arc automatic welding, the welding wire is H14 with the flux Superflux55ULT;

[0041] The welding materials comply with AWS specifications: AWSA5.23ENi1K. The quality grade of the classification society is: 5YQ460MH5, and the wire brand is; TSW-E31; The diameter of the wire is 5mm, and the wire is used for root pass, filling, and capping of the weld. During the welding process, the dry elongation of the wire is 20 - 30mm; The flux with the brand TF-250 is selected, and the flux complies with AWS specifications: AWSA5.23F8P5-ECG.

[0042] The submerged arc welding flux must be baked before use, with a baking temperature of 300℃ - 350℃ and a baking time of 1 hour.

[0043] (2) Cutting the groove at the butt weld of the crack arrest steel plate: The groove processed by an automatic or semi-automatic gas cutting machine has a smooth and flat surface. The front groove angle is 50°, the depth is 3 / 5 of the plate thickness including a root gap of 6mm. The root gap is represented by p, p = 6mm, and the back groove is 60°.

[0044] (3) Groove splicing: Splice two steel plates with X-shaped butt grooves. The upper groove angle of the groove is 50°, the lower groove angle is 60°, and the root gap of the groove is 0 - 1mm. The root gap is the gap between the welding joints, represented by b, b = 0 - 1mm. With back gouging, full penetration can be achieved. After the groove is spliced, clean the impurities in the groove and within the area 20mm on both sides close to the groove.

[0045] (4) Anti-deformation treatment of the crack arrest steel plate: Assemble and position the crack arrest steel plate. In the free state, add a -1° anti-deformation when assembling the plate pieces;

[0046] The deformation control during the welding process includes the following steps:

[0047] First, control the bead thickness and the angular deformation that has occurred using the welding parameters during welding. Through empirical estimation and calculation, determine the timing of turning the steel plate to adjust and control the angular deformation, and continuously adjust using the welding parameters and weld angular deformation during subsequent welding until a flat submerged arc automatic welding seam and crack arrest steel plate are finally obtained;

[0048] Secondly, formulate a control plan for anti-deformation: In the free state, the anti-deformation of the plate assembly is -1° to -2°. Continuously weld until the weld bead thickness reaches about 21 mm to 25 mm, and turn over when the deformation is 3° to 4°.

[0049] Thirdly, after turning over, carry out root cleaning. The maximum root cleaning depth of the 70 mm plate reaches 34 mm, and the deformation is 3° to 4°. After welding this side, turn over again and weld the remaining welds until welding is completed.

[0050] (5) Tack welding: Tack welding is carried out to fix the position of the steel plate welding joint. Tack welding is carried out inside the groove, and the length of each tack weld is 60 mm; The start and end of the tack weld are processed smoothly to avoid incomplete penetration.

[0051] The welding materials for tack welding are the same as those for formal welding. Preheating is required before tack welding. Preheating is an effective measure to prevent cold cracks, hot cracks and hardened structures in the heat-affected zone. It slows down the cooling rate during welding, reduces the shrinkage stress. At the same time, preheating can also remove factors such as oil and moisture that affect the weld quality, promote the escape of hydrogen in the weld and prevent cracks in the weld.

[0052] Flame heating can be used for preheating. Flame heating is generally gas flame heating. Gas flame heating uses the oxygen-acetylene flame used in ordinary gas welding to control the local heating temperature of the flame. Stop preheating when the preheating temperature of the heated part reaches 125°C to 150°C.

[0053] (6) Preheating before welding: The main weld is preheated by electromagnetic heating. Electromagnetic heating uses alternating current to generate an alternating magnetic field, causing eddy currents to be generated inside the crack arrest plate in the covered area. The crack arrest plate heats up rapidly. Stop heating when the preheating temperature of the main weld reaches 125°C to 150°C. The temperature measurement point is at a position 75 mm away from the weld.

[0054] (7) Welding process parameters: First, weld the 50° groove surface. The welding current is 650 A to 730 A, preferably 650 A. The welding voltage is 26 V to 30 V, preferably 26 V. The welding thickness without root retention is about 20 mm to 21 mm, and the welding angular deformation is about +4°. The remaining 15 mm to 16 mm thick weld is welded last after the reverse side welding is completed, and then turn over. After turning over, use carbon arc air gouging to back gouge it to a depth of 30 mm to 34 mm. Start welding the reverse side after grinding to show metallic luster.

[0055] Welding current for the reverse side: 700 A; Welding voltage: 28 V; Welding speed: 460 mm / min. After all welding on the reverse side is completed, the angular deformation of the weld is about +2°.

[0056] Turn over again and weld the remaining welds with a thickness of 15 mm to 16 mm on the front side. The welding current is 700 A to 800 A, the welding voltage is 28 V to 32 V, and the welding speed is 460 mm / min until the welding of the welds is completed. During the welding process, strictly control the process parameters. After all welding is completed, the angular deformation of the weld is about 0°.

[0057] When there is a difference between the welding deformation and the control plan, strengthen or weaken the degree of weld deformation by controlling the magnitude of the welding current and the magnitude of the welding heat input; turn over twice during the entire welding process. When the deformation exceeds the control plan, increase the number of turnovers to control the deformation of the plate seam.

[0058] During the welding process, use a strike-off and arc-extinguishing plate. The length of striking off and arc extinguishing is 100 mm. If there is an arc extinguishing or burn-through phenomenon during the process, use carbon arc air gouging to process the arc extinguishing place. The gouging length is not less than 100 mm. When re-striking the arc, the alignment position of the welding wire should be 20 mm behind the processed position.

[0059] Submerged arc welding adopts the welding method of multi-layer and multi-pass welding. The slag of the previous weld pass must be completely removed.

[0060] (8) Control of interpass temperature: During the welding process, the interpass temperature is higher than the preheating temperature. The interpass temperature is controlled at 125 °C to 250 °C. If the temperature drops rapidly during the welding process, heating blocks can be placed on one side of the weld during the welding process, and the heating blocks continuously heat and keep warm the welding area.

[0061] When using weights and jigs as fixing measures during the welding process, it is necessary to monitor the welding deformation at the steel plate joint in real time and adjust it in time.

[0062] If post-weld residual deformation occurs after the welding is completed, thermal forming can be used to adjust the EH40BAC / EH47BCA steel plate. The areas of the EH40BAC / EH47BCA steel plate that have been adjusted by thermal forming need to be subjected to MT inspection.

[0063] After the welding is completed, cover the welding area with heat insulation cotton for slow cooling until room temperature, and finally perform non-destructive testing on the weld.

[0064] After the welding is completed, recycle the welding flux, clean the welding slag and dust, and observe the particle size of the welding flux to obtain the recycled welding flux. The recycled welding flux must be mixed with 40% to 50% of new welding flux and baked again before being used repeatedly.

[0065] Example 2:

[0066] The difference between Example 2 and Example 1 is that in Example 2,

[0067] (1) The steel plate to be welded is an EH47BCA crack arrest steel plate or an EH40BCA crack arrest steel plate with a thickness of 80 mm;

[0068] (2) Cutting the groove at the butt weld of the crack arrest steel plate: The groove processed by an automatic or semi-automatic gas cutting machine has a smooth and flat surface. The front groove angle is 52°, the depth is 3 / 5 of the plate thickness including a root gap of 6 mm. The root gap is represented by p, p = 6 mm, and the back groove is 62°.

[0069] (3) Groove splicing: Splice two steel plates with X-shaped butt grooves. The upper groove angle of the groove is 52°, the lower groove angle is 62°, and the root gap of the groove is 0 - 1 mm. The root gap is the gap between the welding joints, represented by b, b = 0 - 1 mm. With back gouging, full penetration can be achieved. After the groove is spliced, clean the impurities in the groove and within a 20-mm area on both sides close to the groove.

[0070] (4) Anti-deformation treatment for the crack arrest steel plate: Assemble and position the crack arrest steel plate. In the free state, add an anti-deformation of ~2° when assembling the plates.

[0071] The deformation control during welding includes the following steps:

[0072] First, control the bead thickness and the angular deformation that has occurred using the welding parameters during welding. Through empirical estimation and calculation, determine the timing of flipping the steel plate to adjust and control the angular deformation, and continuously adjust using the welding parameters and weld angular deformation during subsequent welding until a flat submerged arc automatic welding seam and crack arrest steel plate are obtained.

[0073] Second, formulate a control plan for anti-deformation: In the free state, the anti-deformation during plate assembly is 1° - 2°. Continue welding until the bead thickness reaches approximately 21 mm - 23 mm and the deformation is 3° - 4°, then flip the plate.

[0074] Third, perform back gouging after flipping. The maximum back gouging depth for an 80-mm plate reaches 38 mm, and the deformation is 3° - 4°. After welding this side, flip the plate again and weld the remaining welds until welding is completed.

[0075] (5) Tack welding: Tack welding is carried out to fix the positions of the steel plate welding joints. Perform tack welding within the groove, and the length of each tack weld is 70 mm. Electromagnetic heating can be used for preheating, and stop preheating when the preheating temperature of the heated part reaches 125°C - 150°C.

[0076] (6) Pre-welding preheating: The main body weld is preheated by electromagnetic heating. Electromagnetic heating uses alternating current to generate an alternating magnetic field, causing eddy currents to be generated inside the crack arrest plate in the covered area. The crack arrest plate quickly heats up. The preheating temperature of the main body weld is stopped at 125°C to 150°C, and the temperature measurement point is at a position 75 mm away from the weld.

[0077] (7) Welding process parameters: First, weld the 52° bevel surface. The welding current is 650 A to 730 A, preferably 650 A. The welding voltage is 26 V to 30 V, preferably 26 V. The welding speed is 460 mm / min. The welding thickness without root retention is about 21 mm to 23 mm, and the welding angular deformation is about +4°. The remaining 19 mm to 21 mm thick weld is welded last after the reverse side welding is completed. Then, turn it over. After turning over, use carbon arc air gouging to back gouge it to a depth of 34 mm to 38 mm. After grinding to show a metallic luster, start welding the reverse side.

[0078] Welding current for the reverse side: 750 A; welding voltage: 30 V; welding speed: 460 mm / min. After all welding on the reverse side is completed, the angular deformation of the weld is about +2°.

[0079] Turn it over again and weld the remaining 19 mm to 21 mm thick weld on the front side. The welding current is 700 A to 800 A, preferably 750 A. The welding voltage is 28 V to 32 V, preferably 30 V. The welding speed is 460 mm / min until the weld is completed. During the welding process, strictly control the process parameters. After all welding is completed, the angular deformation of the weld is about 0°.

[0080] When there is a difference between the welding deformation and the control scheme, strengthen or weaken the weld deformation degree by controlling the magnitude of the welding current and the magnitude of the welding heat input; turn over twice during the entire welding process. When the deformation exceeds the control scheme, increase the number of turnovers to control the deformation of the plate seam.

[0081] During the welding process, use a lead-in and lead-out arc plate. The lead-in and lead-out arc length is 130 mm. If there is an arc extinction or welding through phenomenon during the process, use carbon arc air gouging to process the arc extinction position, with a gouging length of 130 mm. When re-igniting the arc, the wire alignment position should be 20 mm behind the processed position.

[0082] When performing submerged arc welding, since the thickness of each weld bead can reach 6 - 10 mm, but the thermal effect of the next layer of weld can only reach 3 - 5 mm; the welding adopts a multi-layer and multi-pass welding method. The thermal effect of the next layer of weld can reach 6 - 10 mm. The subsequent weld bead reheats the previous weld bead and its heat-affected zone, causing phase transformation in the heated zone's microstructure and properties. The slag of the previous weld bead must be completely removed.

[0083] (8) Welding interlayer temperature control: During the welding process, the welding interlayer temperature is higher than the preheating temperature, and the welding interlayer temperature is controlled at 200 °C. If the temperature drops rapidly during the welding process, heating blocks can be placed on one side of the weld seam during the welding process, and the heating blocks continuously heat and keep the welding area warm.

[0084] Example 3:

[0085] The difference between Example 3 and Example 1 and Example 2 is that in Example 3,

[0086] (1) The steel plate to be welded is an EH47BCA crack arrestor steel plate or an EH40BCA crack arrestor steel plate with a thickness of 95 mm;

[0087] (2) Cutting the groove at the butt weld of the crack arrestor steel plate: The groove processed by an automatic or semi-automatic gas cutting machine has a smooth surface. The front groove angle is 50°, the depth is 3 / 5 of the plate thickness including a root gap of 6 mm. The root gap is represented by p, p = 6 mm, and the back groove is 60°.

[0088] (3) Groove splicing: Splice two steel plates with X-shaped butt grooves. The upper groove angle of the groove is 50°, and the lower groove angle is 60°. The root gap of the groove is 0 - 1 mm. The root gap is the gap between the welding joints, represented by b, b = 0 - 1 mm. With back gouging, full penetration can be achieved. After the groove is spliced, clean the impurities in the groove and the area within 20 mm on both sides close to the groove.

[0089] (4) Anti-deformation treatment for the crack arrestor steel plate: Assemble and position the crack arrestor steel plate. In the free state, when assembling the plate pieces, add an anti-deformation of ~2°;

[0090] The deformation control during the welding process includes the following steps:

[0091] First, control the bead thickness and the angular deformation that has occurred using the welding parameters during welding. Through empirical estimation and calculation, determine the timing of turning the steel plate to adjust and control the angular deformation, and continuously adjust using the welding parameters and the weld angular deformation during subsequent welding until a flat submerged arc automatic welding seam and crack arrestor steel plate are obtained;

[0092] Second, formulate a control plan for anti-deformation: In the free state, the anti-deformation during plate piece assembly is 1° - 2°. Continuously weld until the bead thickness reaches about 21 mm - 25 mm and the deformation amount is 3° - 4°, then turn over;

[0093] Third, perform back gouging after turning over. The maximum back gouging depth for a 95 mm plate reaches 48 mm, and the deformation amount is 3° - 4°. After welding this side, turn over again and weld the remaining weld seam until welding is completed.

[0094] (5) Tack welding: Tack welding is carried out to fix the position of the steel plate welding joint. Tack welding is carried out within the groove, and the length of each tack weld > 50 mm; Electromagnetic heating can be used for preheating, and the preheating stops when the preheating temperature of the heated part reaches 140°C.

[0095] (6) Preheating before welding: The main weld is preheated by electromagnetic heating. Electromagnetic heating uses alternating current to generate an alternating magnetic field, causing eddy currents to be generated inside the crack arrest plate in the covered area, and the crack arrest plate heats up rapidly. The preheating of the main weld stops when the temperature reaches 125°C - 150°C, and the temperature measurement point is at a position 75 mm away from the weld;

[0096] (7) Welding process parameters: First, weld the 50° groove surface. The welding current is 650 A - 730 A, preferably 650 A, the welding voltage is 26 V - 30 V, preferably 26 V, the welding speed is 460 mm / min, the welding thickness without root remaining is about 21 mm - 25 mm, the welding angular deformation is about +4°. The remaining 26 mm - 30 mm thick weld is welded last after the reverse side welding is completed, and then it is turned over. After turning over, carbon arc air gouging is used to back gouge it, with a depth of 38 - 48 mm. After grinding to show a clear metallic luster, start welding the reverse side;

[0097] Welding current for the reverse side: 700 A - 800 A, preferably 750 A, welding voltage: 28 V - 32 V, preferably 32 V; Welding speed: 460 mm / min. After all welding on the reverse side is completed, the angular deformation of its weld is about +2°;

[0098] Turn it over again and weld the remaining 26 mm - 30 mm thick weld on the front side. Welding current: 700 A - 800 A, preferably 750 A, welding voltage is 28 V - 32 V, preferably 30 V. Welding speed is 460 mm / min until the weld is completed. During the welding process, strictly control the process parameters. After all welding is completed, the angular deformation of its weld is about 0°.

[0099] When there is a difference between the welding deformation and the control scheme, the degree of weld deformation is strengthened or weakened by controlling the magnitude of the welding current and the magnitude of the welding heat input; The whole welding process is turned over twice. When the deformation exceeds the control scheme, increase the number of turnovers to control the deformation of the plate seam.

[0100] During the welding process, use a strike-off and extinguishing arc plate. The strike-off and extinguishing arc length is 100 mm. If there is an arc extinguishing or burn-through phenomenon during the process, use carbon arc air gouging to process the arc extinguishing position, with a gouging length of 100 mm. When re-striking the arc, the alignment position of the welding wire should be 20 mm behind the processed position.

[0101] When performing submerged arc welding, the slag of the previous weld bead must be completely removed.

[0102] (8) Welding interlayer temperature control: During the welding process, the welding interlayer temperature is higher than the preheating temperature, and the welding interlayer temperature is controlled between 125°C and 250°C. If the temperature drops rapidly during the welding process, heating blocks can be placed on one side of the weld to continuously heat and keep the welding area warm.

[0103] When using iron weights and jigs as fixing measures during the welding process, it is necessary to monitor the welding deformation at the steel plate joints in real time and make timely adjustments.

[0104] If post-weld residual deformation occurs after welding, thermal straightening can be used to adjust the EH40BAC / EH47BCA steel plates. The areas of the EH40BAC / EH47BCA steel plates that have undergone thermal straightening need to be subjected to MT testing.

[0105] After welding is completed, the welding area is covered with heat-insulating cotton for slow cooling until room temperature, and finally non-destructive testing of the weld is carried out.

[0106] When using iron weights and jigs as fixing measures during the welding process, it is necessary to monitor the welding deformation at the steel plate joints in real time and make timely adjustments.

[0107] If post-weld residual deformation occurs after welding, thermal straightening can be used to adjust the EH40BAC / EH47BCA steel plates. The areas of the EH40BAC / EH47BCA steel plates that have undergone thermal straightening need to be subjected to MT testing.

[0108] After welding is completed, the welding area is covered with heat-insulating cotton for slow cooling until room temperature, and finally non-destructive testing of the weld is carried out.

[0109] A large amount of 70 - 95 mm ultra-thick crack arrestor steel plates are used in the main deck and hatch coaming areas of the hull. Especially for the welding in the torsion box and hatch coaming areas, the submerged arc welding process for splicing marine ultra-thick plates is adopted.

[0110] The above shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0111] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Submerged arc welding process for butt welding of ultra-thick ship plates, comprising the following steps: (1) Welding material selection: The steel plates to be welded are EH47BCA and EH40BCA crack arrest steel plates with a thickness of 70 - 95 mm. The yield strength ReH of the EH47BCA crack arrest steel plate is ≥ 460 Mpa, and the tensile strength Rm is in the range of 570 - 720 Mpa. The welding material matching is as follows: When performing tack welding, the welding material for CO2 shielded welding is TWE-81K2 flux cored wire with pure CO2 shielding gas, and the wire for submerged arc automatic welding is TSW-E31 with welding flux TF-250; For the EH40BCA crack arrest steel plate, the yield strength ReH is ≥ 390 Mpa, and the tensile strength Rm is in the range of 510 - 650 Mpa. When performing tack welding, the welding material for CO2 shielded welding is Supercored81-K2 flux cored wire with pure CO2 shielding gas, and the wire for submerged arc automatic welding is H14 with welding flux Superflux55ULT; (2) Cutting the groove at the butt weld of the crack arrest steel plate: The front groove angle is 50° ± 5°, the depth is 3 / 5 of the plate thickness including a root gap of 6 ± 2 mm, and the back groove is 60° ± 5°; (3) Groove splicing: Splice two steel plates with X-shaped butt grooves. The upper groove angle of the groove is 50° ± 5°, the lower groove angle is 60 ° ± 5 °, and the root gap of the groove is 0 - 1 mm. Clean the impurities in the groove and the area within 20 mm on both sides close to the groove; (4) Anti-deformation treatment of the crack arrest steel plate: Assemble and position the crack arrest steel plate. In the free state, add an anti-deformation of -1 ° to -2° when assembling the plate pieces; (5) Tack welding: Perform tack welding in the groove. The length of each tack weld is not less than 50 mm; The welding material for tack welding is the same as that for formal welding. Preheating is required before tack welding, and flame heating or electromagnetic heating can be used. The preheating temperature is 125℃ - 150℃; (6) Preheating before welding: The main weld is preheated by electromagnetic heating, and the preheating temperature is 125℃ - 150℃. The temperature measurement point is at a position 75 mm away from the weld; (7) Welding process parameters: First, weld the groove surface with an angle of 50° ± 5°. The welding current is 650A - 730A, the welding voltage is 26V - 30V, the welding speed is 460 mm / min, the welding thickness without root is about 21 mm - 25 mm, and the welding angular deformation is about +4°. The remaining 15 mm - 30 mm of the weld thickness is welded last after the reverse side welding is completed, and then it is turned over. After turning over, use carbon arc air gouging to back gouge it to a depth of 30 mm - 48 mm. After grinding to show a metallic luster, start welding the reverse side; Welding current for the reverse side: 700A - 800A, welding voltage: 28V - 32V, welding speed: 460 mm / min. After all the reverse side welding is completed, the angular deformation of the weld is about +2°; Turn over again and weld the remaining welds on the front side with a thickness of 15 mm to 30 mm. The welding current is 700 A to 800 A, the welding voltage is 28 V to 32 V, and the welding speed is 460 mm / min until the welding of the welds is completed. During the welding process, strictly control the process parameters. After all welding is completed, the angular deformation of the weld is about 0°; (8) Control of interpass temperature: During the welding process, the interpass temperature is higher than the preheating temperature, and the interpass temperature is controlled at 125 °C to 250 °C. If the temperature drops rapidly during the welding process, heating blocks can be placed on one side of the weld during the welding process, and the heating blocks continuously heat and keep the welding area warm.

2. The submerged arc welding process for the butt welding of ultra-thick marine plates according to claim 1, characterized in that: During the welding process, a strike-off and run-off plate is used. The length of arc striking and arc extinguishing is not less than 100 mm. If there is an arc extinguishing or burn-through phenomenon during the process, carbon arc air gouging should be used to process the arc extinguishing position, and the gouging length is not less than 100 mm. When re-striking the arc, the wire alignment position should be 20 mm behind the processed position.

3. The submerged arc welding process for the butt welding of ultra-thick marine plates according to claim 1, characterized in that: The welding adopts the multi-layer and multi-pass welding method, and the slag of the previous weld pass must be completely removed.

4. The submerged arc welding process for marine super-thick plate splicing according to claim 1, characterized in that: During the welding process, deformation control is carried out, including the following steps: (1) Use the welding parameters during welding to control the weld bead thickness and the angular deformation that has occurred. Through empirical estimation and calculation, Determine the steel plate turning-over time to adjust and control the angular deformation, and continuously use the welding parameters and weld angular deformation for adjustment during subsequent welding to finally obtain a flat submerged arc automatic welding weld and crack-arresting steel plates; (2) Develop a control plan for reverse deformation: In the free state, the reverse deformation of the plate assembly is -1° to -2°. Continuously weld until the weld bead thickness reaches about 21 mm to 25 mm and the deformation is 3° to 4°, then turn over; (3) After turning over, carry out root cleaning. The maximum root cleaning depth of the 95 mm plate reaches 48 mm, and the deformation is -3° to -4°. After welding this side, turn over again and weld the remaining welds until the welding is completed.

5. The submerged arc welding process for shipbuilding ultra-thick plate splicing according to claim 4, characterized in that: When there is a difference between the welding deformation and the control plan, strengthen or weaken the weld deformation degree by controlling the magnitude of the welding current and the magnitude of the welding heat input; turn over twice during the entire welding process. When the deformation exceeds the control plan, increase the number of turnovers to control the deformation of the plate seam.

6. The submerged arc welding process for shipbuilding ultra-thick plate splicing according to claim 4, characterized in that: When using iron weights and jigs as fixing measures during the welding process, it is necessary to monitor the welding deformation at the steel plate joint in real time and adjust it in time.

7. The submerged arc welding process for butt welding of ultra-thick marine plates according to claim 4, characterized in that: If post-weld residual deformation occurs after the welding is completed, thermal straightening can be used to adjust the EH40BCA / EH47BCA steel plates. The areas of the EH40BCA / EH47BCA steel plates that have been adjusted by thermal straightening need to be subjected to MT inspection.

8. The submerged arc welding process for the butt welding of ultra-thick ship plates according to claim 4, characterized in that: After the welding is completed, cover the welding area with heat-insulating cotton for slow cooling until room temperature, and finally conduct non-destructive testing of the welds.

9. The submerged arc welding process for butt welding of ultra-thick ship plates according to claim 1, characterized in that: The submerged arc welding flux must be baked before use. The baking temperature is 300 °C to 350 °C, and the baking time is 1 to 2 hours.

10. The submerged arc welding process for marine extra-thick plate splicing according to claim 1, characterized in that: After the welding is completed, recycle the flux, clean the welding slag and dust, and observe the particle size of the flux to obtain the recycled flux. The recycled flux must be mixed with 40%-50% of new flux and used repeatedly.

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