A method for controlling the reverse deformation of 9Ni steel B-type bulkhead butt-jointed compression beam welding

Abstract

A method for controlling the reverse deformation of welding of a compression beam for butt joint of a 9Ni steel B-type cabin bulkhead. When the steel plates are butt jointed, 50×50 wooden squares are used to raise the two sides of the plates so that the plate butt joint forms an obtuse angle. The plate surface angle is between 170° and 179.9°. The plate edge is beveled using a planer. The bevels are symmetrically opened with a gap of 0‑2mm and a bevel angle of 50°‑80°. After the butt joint is turned over after automatic submerged arc welding, the back buckle is polished, and PT flaw detection is performed. After passing the test, the back is filled and covered for the second time, and the butt welding work is completed. After butt jointing, a clamp, a hand hoist and a supporting device are used to stabilize the plate. When the plate is pressed with a beam and a frame is installed, the deformation of the plate after welding can be reduced. The present invention can realize the reverse deformation control of the 9Ni material of the B-type cabin subassembly of an LNG ship, ensure the stability and integrity of the B-type cabin subassembly structure, and improve the operating safety and reliability of LNG ships.

Description

Technical Field

[0001] The invention belongs to the field of ship construction and design, and in particular relates to a method for controlling reverse deformation of 9Ni steel B-type bulkhead butt-jointed compression beam welding. Background Art

[0002] The construction of LNG-B tank is an important and complex engineering project. In the welding process of 9Ni steel, deformation is common. In order to ensure the chemical properties of the material, pyrotechnic correction work should be avoided after welding, which brings challenges to the quality and progress of the project. The present invention aims to propose a welding anti-deformation control method suitable for LNG-B tank according to the characteristics of 9Ni steel, so as to control and reduce welding deformation.

[0003] At present, more and more LNG storage tanks are being built in the world. In recent years, the international community has started welding and manufacturing 9Ni steel cryogenic storage tank ships. 9Ni steel is a ferritic low-temperature steel with high strength and good toughness. According to the alloy composition, 9Ni steel is a medium alloy steel, and the design temperature of equipment manufacturing is positioned in the range of -165 to -196℃. The strength and toughness of 9Ni steel, low carbon content, ultra-low Ps content, and the addition of Ni and Nb elements significantly improve the low-temperature toughness of the material, ensuring that the chemical properties of the material have both high strength and toughness. However, due to its large thermal deformation coefficient, large welding deformation is prone to occur during the welding process.

[0004] In the welding process, nickel-based alloy welding materials need to be selected, welding process measures need to be optimized, and anti-deformation measures need to be used in the actual welding process to avoid welding cold and hot cracks, and to prevent the decrease of low-temperature toughness after welding. In particular, the control of interlayer temperature and line energy during welding is crucial to the intrinsic quality of the welded joint. Therefore, it is very necessary to study the application of anti-deformation control of 9Ni steel welding in LNG-B type tank group.

[0005] After the wall panels are welded, they are laid flat on the tire frame. To ensure that the wall panels do not deform after the pressure beam is welded, the tire sealing method is adopted. The wall panels and the tire frame are welded by the conventional tire sealing method. However, when transporting the wall panels, they need to be separated by cutting discs, and the root cutting should be left to avoid causing damage of more than 0.3mm to the parent material. After separation, grinding operations are still required, and 100% PT flaw detection is required. This practice not only wastes manpower, but also fails to meet the production schedule requirements. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a method for controlling the reverse deformation of welding of a 9Ni steel B-type bulkhead butt-jointed compression beam, and the technical solution adopted is:

[0007] A method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams, the specific operation method is as follows:

[0008] S1: Select two 9Ni steel wall panels, place them horizontally on the frame, use a planer to bevel the joints of the two wall panels, bevel symmetrically, with a gap of 0-2mm and a bevel angle of 50°-80°; place a 50×50mm wooden square under the wall panels, close to the joints, so that the two wall panels form a concave angle of 170°-179.9° at the joints.

[0009] Grind the groove, remove pollutants on both sides of the groove, and use submerged arc automatic welding machine for welding. The welding parameters are as follows: current 310A-320A, voltage 29V-30V, and welding speed 50-55cm / min. After welding, the two wall panels form a convex angle at the joint. Turn over the welded wall panels, place the two wall panels on the tire frame in a free state, back-fasten and grind the wall panels, remove pollutants on both sides of the back-fastening, perform 100% PT inspection, and use submerged arc automatic welding machine for cover welding. After welding, the two wall panels are butt-jointed to form a 180° right angle.

[0010] S2: Remove the wooden planks under the siding, and use multiple sets of lever hoists and multiple lockers to fix the docked siding to the frame. Multiple sets of lever hoists and multiple lockers are arranged at equal intervals on the edge of the siding, and multiple hydraulic jacks are arranged under the siding. One end of the lever hoist is hooked to the edge of the siding, and the other end is fixed to the frame. The locker clamps the siding and the frame.

[0011] The butt-jointed wall panels are welded with a transversely arranged frame FR and a longitudinally arranged flat iron FB. The flat iron FB pressure beam angle joints are welded by a double-sided submerged arc trolley simultaneously in the same direction from the middle to both ends in a segmented back-welding method. The welding machine current is adjusted to 280A-300A, the voltage to 26V-37V, and the welding speed to 38-50cm / min. The frame FR is welded by manual arc welding, and the welding parameters are: current 100A-125A, voltage 22V-23V, and welding speed 4.5-4.9cm / min.

[0012] The above-mentioned 9Ni steel B-type cabin bulkhead butt compression beam welding reverse deformation control method, further, the locking device has a U-shaped ring, the locking bolt passes through a free end of the U-shaped ring, and is threadedly connected to the free end of the U-shaped ring, the edge of the wall panel is inserted into the U-shaped ring, one end of the U-shaped ring is located below the tire frame, and the other end is located above the wall panel, tighten the locking bolt, and the locking bolt and the U-shaped ring clamp the wall panel and the tire frame.

[0013] The above-mentioned 9Ni steel B-type cabin bulkhead butt-jointed compression beam welding reverse deformation control method further selects a 16×3470×5492-sized wall panel and a 16×3470×8808-sized wall panel, and butt-joins the two wall panels.

[0014] The above-mentioned 9Ni steel B-type cabin bulkhead butt compression beam welding reverse deformation control method, further, the welding material needs to be preheated before welding, the submerged arc welding flux baking temperature is 300°C, the baking time is 2-4 hours; the manual welding rod baking temperature is 300°C, and the baking time is 1 hour.

[0015] The above-mentioned 9Ni steel B-type cabin bulkhead butt-jointed compression beam welding reverse deformation control method further has a wooden square size of 50×50cm.

[0016] The above-mentioned method for controlling the reverse deformation of the welding of the compression beam of the 9Ni steel B-type cabin bulkhead butt joint further requires 100% UT+10% X-ray film inspection of the butt joint after the wall panels are butt jointed.

[0017] The above-mentioned method for controlling reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams, further comprises the step of providing a spacing between adjacent tire frames of 1 meter.

[0018] The above-mentioned method for controlling reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams further comprises a stainless steel gasket disposed between the locking bolt and the wall plate.

[0019] The above-mentioned method for controlling the reverse deformation of the welding of the compression beam of the 9Ni steel B-type bulkhead is further characterized in that 18 sets of lever hoists and 32 lockers are used for the butted wall panels.

[0020] The above-mentioned method for controlling the reverse deformation of the welding of the compression beam of the 9Ni steel B-type bulkhead is further characterized in that 24 5-ton hydraulic jacks are arranged under the butt-jointed wall panels.

[0021] According to the structural characteristics of the B-type cabin, the present invention designs a tooling device suitable for the fixed point to achieve the tire sealing effect. In addition, the present invention allows the fixed point to be adjusted at any time according to the actual situation on site, which is highly flexible. After the tire is separated, there is no need to perform a complicated plate repair process, which saves time and reduces the labor burden, thereby minimizing the cost. The rigid fixation is removed after all the welds on the welded components cool to room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the application of anti-deformation before welding of the wall panel butt seam;

[0023] Figure 2 This is a schematic diagram of the wall plate deformation after submerged arc automatic welding is completed;

[0024] Figure 3 Schematic diagram of grinding the back buckle after turning over the wall panel;

[0025] Figure 4 This is a schematic diagram of submerged arc automatic welding on the back of the wall panel;

[0026] Figure 5Schematic diagram of the extensive use of clamps, lever hoists and supports for the siding;

[0027] Figure 6 This is a schematic diagram of submerged arc automatic welding of flat iron FB pressure beam;

[0028] Figure 7 This is a schematic diagram of the welding sequence for frame installation. The circle numbers in the figure represent the welding sequence, and → represents the welding direction;

[0029] Figure 8 The completed schematic diagram after welding is provided for the team;

[0030] Among them, 1- wall panel, 2- tire frame, 3- locking device, 4- lever hoist, 5- stainless steel gasket, 6- hydraulic jack, 7- submerged arc welding machine, 8- wooden square, 9- butt joint. DETAILED DESCRIPTION

[0031] The present invention will be further described in conjunction with the accompanying drawings.

[0032] 9Ni steel is used as the material to make the B-type cabin. The specific operation steps of the B-type cabin panel docking and pressure beam are as follows:

[0033] Preparation work before welding: material inspection and pretreatment of the 9Ni arriving plates of type B cabin group are carried out. According to the drawings, 16×3470×5492 wall panels, 1 sheet, and 16×3470×8808 wall panels are selected. A planer is used to bevel the joints of the two plates. The bevels are symmetrically opened with a gap of 0-2mm and a bevel angle of 60°.

[0034] like Figure 1 As shown, for anti-deformation control, the siding panel is placed horizontally on the frame, and then about 4.5 meters are measured on both sides from the joint position of the two panels, and 50×50 wooden squares are placed under the panels to make the joint form an obtuse angle of 178.7°.

[0035] like Figure 2 As shown, the groove is polished, pollutants on both sides of the groove are removed, and the submerged arc automatic welding of the joint seam is carried out according to the welding process requirements. The welding machine current is adjusted to 316A and the voltage is adjusted to 30V for welding. After the wall panel is welded, the angle between the two plates is deformed to 180.8°.

[0036] like Figure 3 As shown, the wall panels are turned over, back-fastened, polished, and the contaminants on both sides of the back-fastening are removed. A 100% PT flaw detection is performed to ensure that no cold cracks are generated in the welds after the back-fastening. The two wall panels are placed on the tire frame in a free state, and the angle between the two panels is 179.4°.

[0037] like Figure 4As shown in the figure, referring to the welding process specification, the wall panel is turned over and the cover is welded with a submerged arc automatic welding machine. After welding, the angle between the two plates is 180°. After the panel butt joint work is completed, the butt joint needs 100% UT+10% X-ray film inspection and completion inspection.

[0038] like Figure 5 As shown, each panel edge is equipped with 3 sets of 2-ton lever hoists to firmly connect the siding and the tire frame, and 9 sets of lever hoists are used for each panel. At the same time, lockers are installed on the tire frame points on the outside of the panel edge to make the white steel pads on the top of the tire frame fit tightly with the siding. Since the tire frame spacing is 1 meter, 16 lockers are used for each panel. The hydraulic jacks should be evenly arranged under the siding. By adjusting the jacks, the flatness of the upper surface of the siding can be ensured to be within the tolerance range of ±5mm. 12 5-ton hydraulic jacks are required for each panel to ensure that the siding is fixed and the tire sealing effect is achieved. When transporting the siding, follow the above steps in reverse order to carry out the tire lifting work, saving time and effort.

[0039] like Figure 6 As shown in the figure, after the preparation work is completed, the double-sided submerged arc trolley is used to weld the angle joint of the flat iron FB pressure beam from the middle to both ends in the same direction at the same time. The welding machine current is adjusted to 285A, the voltage is 28V, and the welding speed is 40cm / min. In this way, the residual stresses generated by the two symmetrical welds can offset each other, and the continuous welds can be artificially turned into intermittent welds, which can minimize the residual stress inside the workpiece. Secondly, for minor components, such as the short angle joints of the reinforcing rib plate and the elbow plate, submerged arc automatic welding is not suitable, and manual arc welding is used. During the welding process, the welding machine current is adjusted to 110A, the voltage is 22V, and the welding speed is maintained at 4.5cm / min.

[0040] like Figure 7 As shown in the figure, the long straight weld of the frame FR is welded by two people using hand-operated arc welding from the middle to both ends in the same direction, and then a single person uses hand-operated arc welding for the secondary components such as the toggle plate and rib plate. The welding machine current is adjusted to 100A, the voltage is 22V, and the welding speed is maintained at 4.5cm / min. During the welding operation, the welding speed can be slowed down, the welding can be performed intermittently, and the concentrated overheating of the weld can be reduced, thereby avoiding deformation caused by stress concentration.

[0041] like Figure 8 As shown, the compression beam work is completed, the corner joints need 100% PT testing, and the team will immediately complete the work and inspect it.

[0042] The present invention can realize the reverse deformation control of the 9Ni material of the B-type tank substructure of the LNG ship, ensure the stability and integrity of the B-type tank substructure, and improve the operation safety and reliability of the LNG ship.

Claims

1. A method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams, characterized in that: The specific operation method is as follows: S1: Select two 9Ni steel sidings, place them horizontally on a tire frame, and use a planer to bevel the butt joints of the two sidings. The bevels are symmetrically cut with a gap of 0-2mm and a bevel angle of 50°-80°. Place a 50×50 mm wooden square under the sidings and near the butt joints, so that the two sidings form a concave angle of 170°-179.9° at the butt joints. Grind the groove, remove pollutants on both sides of the groove, and use a submerged arc automatic welding machine for welding. The welding parameters are: current 310A-320A, voltage 29V-30V, and welding speed 50-55cm / min. After welding, the two wall panels form a convex angle at the joint. Turn over the welded wall panels, place the two wall panels on the tire frame in a free state, back-fasten and grind the wall panels, remove pollutants on both sides of the back-fastening, perform 100% PT flaw detection, and use a submerged arc automatic welding machine for cover welding. After welding, the two wall panels are butt-jointed to form a 180° flat angle. S2: Remove the wooden planks under the wall panels, and use multiple sets of lever hoists and multiple lockers to fix the butted wall panels to the frame. Multiple sets of lever hoists and multiple lockers are arranged at equal intervals on the edge of the wall panels, and multiple hydraulic jacks are arranged under the wall panels. One end of the lever hoist is hooked to the edge of the wall panel, and the other end is fixed to the frame. The locker clamps the wall panel and the frame; The butt-jointed wall panels are welded with a transversely arranged frame FR and a longitudinally arranged flat iron FB. The flat iron FB pressure beam angle joints are welded by a double-sided submerged arc trolley simultaneously in the same direction from the middle to both ends in a segmented back-welding method. The welding machine current is adjusted to 280A-300A, the voltage to 26V-37V, and the welding speed to 38-50cm / min. The frame FR is welded by manual arc welding, and the welding parameters are: current 100A-125A, voltage 22V-23V, and welding speed 4.5-4.9cm / min.

2. The method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams according to claim 1 is characterized in that: The locker has a U-shaped ring, and the locking bolt passes through a free end of the U-shaped ring and is threadedly connected to the free end of the U-shaped ring. The edge of the siding is inserted into the U-shaped ring, one end of the U-shaped ring is located below the tire frame, and the other end is located above the siding. Tighten the locking bolt, and the locking bolt and the U-shaped ring clamp the siding and the tire frame.

3. The method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams according to claim 1 is characterized in that: The welding materials need to be preheated before welding. The baking temperature of submerged arc flux is 300℃ and the baking time is 2-4 hours; the baking temperature of manual welding rod is 300℃ and the baking time is 1 hour.

4. The method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams according to claim 1 is characterized in that: After the wall panels are butt-jointed, the joints need to be inspected with 100% UT+10% X-rays.

5. The method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams according to claim 1 is characterized in that: The distance between adjacent tire frames is 1 meter.

6. A method for controlling reverse deformation of 9Ni steel B-type bulkhead butt-jointed compression beam welding according to claim 2, characterized in that: A stainless steel gasket is arranged between the locking bolt and the wall plate.

7. The method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams according to claim 1 is characterized in that: The butted wall panels use 18 sets of lever hoists and 32 locks.

8. The method for controlling the reverse deformation of welding of 9Ni steel B-type bulkhead butt-jointed compression beams according to claim 1 is characterized in that: There are 24 5-ton hydraulic jacks installed under the docked wall panels.

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