Automatic welding method for steel corner area of main screen wall of cargo wall system of LNG transport ship

Abstract

The invention discloses an automatic welding method for a steel corner area of a main screen wall of a cargo wall system of an LNG (Liquefied Natural Gas) transport ship, and solves a series of inherent limitations that the steel corner area of the main screen wall is low in production efficiency, highly depends on the argon arc welding operation level of welding workers, is poor in manual welding quality stability, is high in post-welding repair cost and the like when lap welding of corrugated plates is completed by using manual argon arc welding. In addition, the problems that automatic welding equipment cannot be directly assembled in the limited included angle position space of any two faces in the cabin, the positions of adjacent included angles in the cabin interfere with the overall dimension of the automatic welding equipment, the automatic welding equipment abuts against and collides with a steel corner body and bolts on the steel corner due to a traditional automatic welding machine assembling method, and the welding efficiency is high are solved. And a cable connected with a welding gun on the automatic welding equipment scrapes a corrugated plate at the position of an adjacent included angle, and a series of problems that the automatic welding of the steel corner area of the main screen wall cannot be directly realized by using the traditional automatic welding equipment are solved.

Description

Technical Field

[0001] This invention belongs to the field of marine shipbuilding and design, and specifically relates to an automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier. Background Technology

[0002] Currently, in the field of marine shipbuilding, the construction technology of LNG carriers generally adopts the Mark III membrane-type cargo containment system technology of France's GTT. The industry has achieved automatic welding of the same type of ultra-thin plates between adjacent 1.2mm 304L stainless steel corrugated plates of the main screen wall of the cargo containment system. However, in the steel corner area of ​​the main screen wall of the cargo containment system, it is necessary to overlap and weld the 1.2mm 304L stainless steel corrugated plate onto the 8mm 304L stainless steel. Moreover, this area is the angle between any two surfaces in the hold. The space at the angle is limited and cannot be directly installed with automatic welding equipment. The adjacent angle position interferes with the outer dimensions of the automatic welding equipment. The traditional automatic welding machine assembly method will cause the automatic welding equipment to bump and knock against the steel corner body and the bolts on the steel corner. It will also cause the cable connecting the welding gun on the automatic welding equipment to scratch the corrugated plate at the adjacent angle position, resulting in damage to the surface of the corrugated plate, which in turn leads to manual cutting and repair work. In addition, the angles of the steel corners of the main screen wall are not uniform. Depending on the specific location of the steel corners inside the cabin, there are a total of 4 angles: 90°, 135°, 108.4°, and 161.6°. The automatic welding equipment cannot effectively accommodate the automatic welding operation with inconsistent welding areas.

[0003] Shipbuilding companies using GTT's Mark III membrane-type cargo containment system technology in the LNG carrier construction field typically employ manual TIG welding to complete the corrugated plate lap welding in the steel corner areas of the main shield wall of the cargo containment system. Manual TIG welding suffers from low production efficiency in these areas, high dependence on the welder's skill level, poor weld quality stability in the corrugated plate lap welding, significant high production costs due to labor and post-weld rework, and long construction cycles for LNG carrier cargo containment systems. Automatic welding, on the other hand, meets the GTT M1303 testing standard, with a first-pass yield consistently above 99%. Therefore, the industry urgently needs to upgrade the welding process in the steel corner areas of the main shield wall from manual welding to automated welding production, primarily through technological upgrades, methodological innovation, and tooling development. This invention provides an automated welding method for the steel corner areas of the main shield wall in LNG carrier cargo containment systems, overcoming existing limitations and problems. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an automatic welding method for the steel corner areas of the main shield wall of an LNG carrier cargo containment system. The method aims to achieve automatic welding of the steel corner areas of the main shield wall and at limited angles between any two surfaces within the cargo hold. The technical solution adopted is as follows: An automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier requires an adjustable angle support component. The adjustable angle support component has a side support plate and a bottom support plate. The edges of the side support plate and the bottom support plate are joined to form an included angle. An angle measuring scale is fixed at the included angle. An automatic welding track is fixed on the bottom support plate. The angle measuring ruler is arc-shaped as a whole, consisting of an arc-shaped sleeve and an arc-shaped inner ruler inserted into the sleeve. The arc-shaped inner ruler extends and retracts inside the sleeve and is fixed by locking bolts. Locking devices are fixed to the back of the side support plate and the bottom support plate. The locking devices are connected to the steel corner bolts on the steel corner, which fixes the adjustable angle support component to the steel corner. Multiple adjustable angle support components are used simultaneously and continuously fixed on the steel corner. During connection, the angle measuring scale is adjusted so that the included angle between the side support plate and the bottom support plate is the same as the angle of the current corner connector. The locking piece on the back of the bottom support plate is rotated to adjust the level of the bottom support plate to 100mm±2mm. The automatic welding tracks on the multiple bottom support plates are connected end to end to form a complete automatic welding track. The edge of the corrugated plate rests on the steel corner to form a weld bead. The automatic welding equipment travels along the automatic welding track to weld the weld bead. After welding, the adjustable angle support components are removed. After the weld has cooled, the grinding workers use an electric grinder to polish the oxide layer of the weld. After grinding, a vacuum cleaner is used to thoroughly clean the work area.

[0005] Furthermore, the automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier is further improved by using angle measuring scales for 90°, 135°, 108.4° and 161.6°.

[0006] Furthermore, in the above-mentioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier, the locking component is a hollow cylinder with nuts fixed at both ends. Connecting bolts are fixed to the back of the side support plate and the bottom support plate. The connecting bolts are connected to the nuts at one end of the cylinder, and the steel corner bolts are connected to the nuts at the other end of the cylinder.

[0007] Rotate the cylinder, and the connecting bolts and steel corner bolts move forward or backward simultaneously to connect or disconnect the adjustable angle support component from the steel corner.

[0008] Furthermore, in the above-mentioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier, an arc-extinguishing magnetic sensor is installed at the end of the automatic welding track.

[0009] Furthermore, in the above-mentioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier, before operation, the surface of the boundary corrugated plate is checked for damage and the welding area is cleaned with acetone, requiring that there be no oil or dust.

[0010] Furthermore, in the above-mentioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier, the steel corner is made of 8mm stainless steel plate.

[0011] The above-mentioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier is further improved by having the edge of the corrugated plate overlap the steel corner to form a weld bead, requiring the parallelism between the bottom support plate and the weld bead to reach 185±8mm.

[0012] Furthermore, in the aforementioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier, the thickness of the corrugated plate is 1.2 mm.

[0013] Furthermore, the above-mentioned automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier is further improved by having an angle scale on the surface of the arc-shaped inner ruler and the arc-shaped sleeve being made of transparent material.

[0014] The beneficial effects of this invention are: 1. This invention innovatively utilizes automated welding equipment positioned at the steel corner workstation and employs matching tooling. This allows for the lap welding of 1.2mm thick 304L stainless steel corrugated plates onto 8mm thick 304L stainless steel using automated welding equipment. The automated welding equipment can freely operate along the weld path in the steel corner area of ​​the main shield wall, completely replacing the industry-standard Argon Arc Welding method used in this area. This solves problems such as low production efficiency, poor weld quality stability, and high post-weld repair costs associated with manual welding. It also fundamentally addresses the dependence on welding workers during the construction of the main shield wall steel corner area of ​​the cargo containment system, and the issue of the weld quality being highly dependent on the welding workers' Argon Arc Welding skills. Consequently, it reduces the construction cost of LNG carriers by lowering labor costs and the cost of configuring Argon Arc Welding equipment, while improving the construction efficiency of the LNG carrier cargo containment system and ensuring the completion of various milestones and production schedules.

[0015] 2. Fully utilize the narrow area of ​​the main shield wall's steel corner region, and leverage the space above and to the sides of this area to resolve the interference between the angle between any two adjacent surfaces within the cabin and the external dimensions of the automatic welding equipment. Without altering the external dimensions of the automatic welding equipment, ensure that it can freely operate along the weld path within the main shield wall's steel corner region. This maximizes the sharing of automatic welding equipment between the main shield wall's steel corner region and other planar areas. By sharing plasma automatic welding equipment within the cabin, the cost of purchasing new equipment for technological upgrades can be reduced, minimizing the equipment investment costs following technological innovations in the construction of LNG carrier cargo containment systems.

[0016] 3. By fully utilizing the main screen wall's steel corner area and the bolts on the steel corners, and by designing and using quick-locking devices fixed to the steel corner bolts, adjustable angle supports can be fixed in any steel corner area of ​​the main screen wall at 90°, 135°, 108.4°, and 161.6°. The working space for the automatic welding equipment is constructed by utilizing the space above and to the side of the main screen wall's steel corner area. This avoids the problem of the automatic welding equipment bumping or hitting the steel corner body and the bolts on the steel corners, and also enables the automatic welding equipment to operate stably and continuously in the narrow area of ​​the main screen wall's steel corner area.

[0017] 4. The adjustable angle support and automatic welding equipment track designed for automatic welding equipment are compatible with steel corners of various angles within the cabin. This compatible adjustable angle support and track can be adjusted arbitrarily at four angles: 90°, 135°, 108.4°, and 161.6°, depending on the specific location of the steel corner within the cabin. This allows the automatic welding equipment to use a single track for operation in steel corner areas of different angles on the main screen wall, reducing the time and labor costs associated with finding matching tracks, installing different tracks, and storing different tracks due to changes in the angle of the steel corners within the cabin.

[0018] 5. Arranging automatic welding equipment tracks in the steel corner areas of the main screen wall provides a standing position and observation space for the automatic welding supervisor. This facilitates the supervisor's observation of the automatic rise and fall of the welding head, arc initiation and termination, and weld bead formation. During automatic welding, the supervisor can observe the weld bead shape and arc length changes in real time and adjust the welding torch position using a remote control. It also allows for monitoring the welding machine's welding posture selection, real-time welding position, and changes in welding torch height, speed, and angle at different positions on the controller monitoring page. Furthermore, it helps the automatic welding supervisor observe the deformation and shrinkage of the corrugated plate during the welding process. If abnormal welding shrinkage occurs, the supervisor can immediately observe and stop the automatic welding equipment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a steel corner structure; Figure 2 This is a schematic diagram illustrating the automatic welding process after the adjustable angle support component is connected to the steel corner. Figure 3 This is an enlarged schematic diagram of the angle measuring scale structure; Figure 4 This is a structural diagram of the locking component; Figure 5 This is a side view diagram of the angle measuring ruler structure; 1-Side support plate, 2-Bottom support plate, 3-Connecting bolt, 4-Steel corner bolt, 5-Angle measuring ruler, 6-Automatic welding track, 7-Arc sleeve, 8-Arc inner ruler, 9-Locking bolt, 10-Weld bead, 11-Corrugated plate, 12-Automatic welding equipment, 13-Locking component. Detailed Implementation

[0020] The invention will be further described with reference to the accompanying drawings.

[0021] An automatic welding method for the steel corner areas of the main wall of an LNG carrier cargo containment system requires adjustable angle support components, such as... Figure 2 As shown, the adjustable angle support component has a side support plate 1 and a bottom support plate 2. The edges of the side support plate and the bottom support plate are joined to form an angle. An angle measuring scale 5 is fixed at the angle. An automatic welding track 6 is fixed on the bottom support plate.

[0022] like Figure 3 , 5 As shown, the angle measuring scale is arc-shaped, comprising an arc-shaped sleeve 7 and an arc-shaped inner ruler 8 inserted inside the sleeve. The arc-shaped inner ruler can extend and retract within the sleeve and is fixed by a locking bolt 9. The surface of the arc-shaped inner ruler is provided with angle graduations, and the arc-shaped sleeve is made of transparent acrylic material.

[0023] Locking components 13 are fixed to the back of the side support plate and the bottom support plate. These locking components mate with steel corner bolts 4 on the steel corner, thus fixing the adjustable angle support component to the steel corner. For example... Figure 4 As shown, the main body of the locking component is a hollow cylinder with nuts fixed at both ends. Connecting bolts 3 are fixed to the back of the side support plate and the bottom support plate. The connecting bolts are connected to the nuts at one end of the cylinder, and the steel corner bolts are connected to the nuts at the other end of the cylinder.

[0024] Rotating the cylinder causes the connecting bolts and steel corner bolts to move forward or backward simultaneously, connecting or disconnecting the adjustable angle support component from the steel corner. The edge of the corrugated plate 11 rests on the steel corner, forming a weld bead 10.

[0025] When multiple adjustable angle support components are used simultaneously, the specific operation process is as follows: S1: According to the assembly drawings, connecting bolts are welded and fixed on the back of the side support plate and the bottom support plate. The positions of the connecting bolts and the steel corner bolts are corresponding. One end of the locking component is threaded to the connecting bolt, and the other end is threaded to the steel corner bolt.

[0026] S2: Adjust the included angle of the adjustable angle support according to the angle of the steel corner. The angle of the angle measuring scale on the adjustable angle support is equal to 90° and is fixed and locked by the locking screw. Make the included angle of the adjustable angle support component equal to the angle of the corner connector. At this time, the two surfaces of the side support plate, bottom support plate and corner connector are parallel. Then tighten the locking bolt on the angle measuring scale.

[0027] S3: Rotary locking component. The height of the adjustable angle support component decreases as the quick-locking component rotates. When its levelness reaches 100mm±2mm and its parallelism with the weld bead reaches 185±8mm, the rotation of the locking component stops.

[0028] S4: Install an arc-extinguishing magnetic sensor at the end of the automatic welding track and test the sensitivity of the arc-extinguishing magnetic sensor.

[0029] S5: The grounding wire of the automatic welding equipment is fixedly installed on the steel corner bolts of the adjacent workstation, and the connection of the grounding wire of the automatic welding equipment is confirmed to be firm and reliable.

[0030] S6: Use a tungsten gauge to adjust the tungsten electrode position, install the plasma welding torch vertically at 90°, and check the cleanliness of the contact tip.

[0031] S7: Test the operation trajectory of the automatic welding equipment without arc ignition, and check the changes in the distance between the welding torch tip and the weld bead to be welded, as well as the stability of the cable connection.

[0032] S8: Open the protective gas valve and confirm the gas pressure. Use the plasma power supply gas flow display to confirm that the protective gas flow setting meets the requirements of the WPS welding process specification.

[0033] S9: Check the coolant level in the cooler, turn on the cooler power in sequence, and turn on the welding machine power and control device power after 2 minutes.

[0034] S10: Remotely activate the PILOT arc. The automatic welding equipment head is lowered and approaches the starting position of the weld bead through remote control. When the welding overlap distance is exceeded, the main arc welding is started.

[0035] S11: The automatic welding supervisor observes the weld bead formation shape and arc length changes in real time. If necessary, the automatic welding supervisor uses remote control to correct the welding torch trajectory deviation using the automatic welding equipment head.

[0036] S12: Another automatic welding supervisor monitors the welding posture selection, real-time welding position, welding torch height, speed, and angle changes at different positions on the controller monitoring page.

[0037] S13: Complete the automatic welding of the corrugated plate lap weld on the steel corner according to the drawings and plan, and wait for the protective gas flow indicator value to return to zero.

[0038] S14: The automatic welding supervisor shall turn off the power supply to the control device, the welding machine, and the protective gas valve.

[0039] S15: Disassemble the automatic welding equipment and its grounding wire on the adjacent steel corner bolts, and remove the arc-extinguishing magnetic sensor at the end of the automatic welding track.

[0040] S16: Remove the automatic welding track and adjustable angle support components.

[0041] S17: After the weld has cooled down, the grinding operator uses an electric grinder to polish the oxide layer of the weld. After grinding, a vacuum cleaner is used to thoroughly clean the work area.

Claims

1. An automatic welding method for the steel corner areas of the main shield wall of an LNG carrier cargo containment system, characterized in that, An adjustable angle support component is required. The adjustable angle support component has a side support plate and a bottom support plate. The edges of the side support plate and the bottom support plate are joined to form an angle. An angle measuring scale is fixed at the angle. An automatic welding track is fixed on the bottom support plate. The angle measuring ruler is arc-shaped as a whole, consisting of an arc-shaped sleeve and an arc-shaped inner ruler inserted into the sleeve. The arc-shaped inner ruler extends and retracts inside the sleeve and is fixed by locking bolts. Locking devices are fixed to the back of the side support plate and the bottom support plate. The locking devices are connected to the steel corner bolts on the steel corner, which fixes the adjustable angle support component to the steel corner. Multiple adjustable angle support components are used simultaneously and continuously fixed on the steel corner. During connection, the angle measuring scale is adjusted so that the included angle between the side support plate and the bottom support plate is the same as the angle of the current corner connector. The locking piece on the back of the bottom support plate is rotated to adjust the level of the bottom support plate to 100mm±2mm. The automatic welding tracks on the multiple bottom support plates are connected end to end to form a complete automatic welding track. The edge of the corrugated plate rests on the steel corner to form a weld bead. The automatic welding equipment travels along the automatic welding track to weld the weld bead. After welding, the adjustable angle support components are removed. After the weld has cooled, the grinding workers use an electric grinder to polish the oxide layer of the weld. After grinding, a vacuum cleaner is used to thoroughly clean the work area.

2. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, Angle measuring scales are available in 90°, 135°, 108.4°, and 161.6°.

3. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The main body of the locking component is a hollow cylinder with nuts fixed at both ends. Connecting bolts are fixed to the back of the side support plate and the bottom support plate. The connecting bolts are connected to the nuts at one end of the cylinder, and the steel corner bolts are connected to the nuts at the other end of the cylinder. Rotate the cylinder, and the connecting bolts and steel corner bolts move forward or backward simultaneously to connect or disconnect the adjustable angle support component from the steel corner.

4. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, An arc-extinguishing magnetic sensor is installed at the end of the automatic welding track.

5. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, Before operation, check the surface of the boundary corrugated plate for damage and clean the welding area with acetone, ensuring it is free of oil and dust.

6. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The steel corner pieces are made of 8mm stainless steel sheet.

7. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The corrugated plate edge rests on the steel corner to form a weld bead, requiring the bottom support plate to be 185±8mm parallel to the weld bead.

8. The automatic welding method for the steel corner area of ​​the main screen wall of the cargo containment system of an LNG carrier according to claim 1, characterized in that, The thickness of the corrugated sheet is 1.2mm.

9. The automatic welding method for the steel corner area of ​​the main shield wall of an LNG carrier cargo containment system according to claim 1, characterized in that, The curved inner ruler has angle markings on its surface, and the curved sleeve is made of transparent material.

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