Plasma arc welding process for main shield corrugated plate of enclosure system

Abstract

The present invention relates to a plasma arc welding process for the main shielding corrugated plate of an enclosure system, and belongs to the field of welding technology. The technical solution is: from the first corrugation cycle welding to the last corrugation, welding is carried out in sequence according to the bottom straight segment C1 of the first corrugation, the bottom corrugated segment C2, the middle corrugated segment C3, the top corrugated segment C4, the middle corrugated segment C5 and the bottom corrugated segment C6, and the bottom straight segment C1 of the next corrugation, and segmented welding is carried out according to the welding specifications of each segment; the welding gun angle changes at a constant acceleration when transitioning between segments; when welding is extinguished, the welding current linearly decays to the extinguishing current within a certain extinguishing time, and then the welding gun movement and the arc stop at the same time to complete the welding. The positive effects of the present invention: each corrugation is divided into six sections and welded separately, the parameters between the sections change linearly and evenly, the welding process is stable and reliable, the weld quality meets the actual production requirements, it is suitable for automated welding equipment, and can greatly improve the welding production efficiency.

Description

Technical Field

[0001] The invention relates to a plasma arc welding process for a main shield corrugated plate of an enclosure system, in particular to a plasma arc welding process for a main shield corrugated plate of a Mark III enclosure system, and belongs to the technical field of welds. Background Art

[0002] The MARK III membrane cargo containment system is a key component of the membrane-type LNG carrier's cargo tank. It is primarily composed of a primary screen, a secondary shield, and an insulation layer. The primary shield's rectangular corrugated plates are welded together from 1.2mm-thick 304L stainless steel, directly contacting the liquefied natural gas. The welding quality requirements are extremely stringent, and this is one of the key manufacturing technologies for the MARK III membrane cargo containment system. Currently, the primary shield corrugated plates of the MARK III membrane cargo containment system are primarily welded using manual or semi-automatic TIG welding, which presents numerous issues, including unreliable weld quality, low welding production efficiency, high labor costs, and a hazardous working environment.

[0003] The paper "Research on Welding of Corrugated Plates of MARK III Type LNG Membrane Tanks" published in "Jiangsu Shipbuilding" Vol. 38, No. 4, 2021, studied the welding control and inspection of the corrugated plates of the main screen wall of the MARK III type LNG membrane tank, and summarized and analyzed the essentials of the welding process. Since the manual TIG welding method was used for the experiment, the welder needs to adjust the welding process parameters in real time. The patent application with application number CN202110778378.4, "A Smart Welding Machine for the Inner Wall of the Fuel Tank of an LNG Ship", discloses a mechanical device including a smart welding machine, a laser sensor, a 3D visual tracking system, etc., which mainly solves problems such as the stability and accuracy of the welding gun position and trajectory during the welding process, and does not improve the specific welding process. The development of a stable and reliable process suitable for automatic welding equipment has become one of the urgent problems that need to be solved in this industry. Summary of the Invention

[0004] The purpose of the present invention is to provide a plasma arc welding process for the main shielding corrugated plate of the enclosure system, in which each corrugation is divided into six sections and welded separately. The parameters between the sections change linearly and evenly. The welding process is stable and reliable, the weld quality meets the actual production requirements, is suitable for automated welding equipment, can greatly improve the welding production efficiency, and solve the above-mentioned technical problems existing in the existing technology.

[0005] The technical solution of the present invention is:

[0006] A plasma arc welding process for the main shield corrugated plate of an enclosure system is provided. The process divides a corrugation of the corrugated plate to be welded into six sections, namely, a bottom straight section C1, a bottom corrugated section C2, a middle corrugated section C3, a top corrugated section C4, a middle corrugated section C5 and a bottom corrugated section C6. The corrugated plate is plasma welded. Before welding, the welding gun working angle α2 is 55°-85°, the arc height d1 is 0.5-1.5mm, and the welding gun pointing position d2 is 0-1.5mm. The special feature of the process is that after starting welding, the arc is turned on and the welding gun starts to move at the set welding speed at the same time. The arc starting current is 0. After the arc is started, the welding current increases linearly to the welding current, and the welding is carried out from the first corrugation cycle to the last corrugation. The welding is carried out in sequence according to the bottom straight segment C1 of the first corrugation, the bottom corrugation segment C2, the middle corrugation segment C3, the top corrugation segment C4, the middle corrugation segment C5 and the bottom corrugation segment C6, and the bottom straight segment C1 of the next corrugation. The welding is carried out in sections according to the welding specifications of each section. When transitioning between sections, the welding gun angle changes with a constant acceleration. When the welding arc is closed, the welding current linearly decays to the arc closing current within a certain arc closing time, and then the welding gun movement and the arc stop at the same time to complete the welding.

[0007] The welding specifications for each section are as follows:

[0008] The bottom straight section C1 of the corrugated plate: the welding peak current is 80-100A, the base current is 20-40A, the welding speed is 300-400mm / min, the ion gas flow rate is 0.2-0.4L / min, the duty cycle is 40%-50%, the pulse frequency is 3.5Hz-5Hz, and the travel angle α1 is 90°-100°;

[0009] Bottom corrugated section C2: welding peak current is 75-95A, base current is 15-25A, welding speed is 180-260mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4Hz, and travel angle α1 is 90°-98°;

[0010] Middle corrugated section C3: welding peak current is 75-95A, base current is 15-30A, welding speed is 200-300mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-95°;

[0011] Top corrugated section C4: welding peak current is 75-95A, base current is 15-25A, welding speed is 200-300mm / min, ion gas flow rate is 0.15-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-98°;

[0012] Middle corrugated section C5: welding peak current is 75-95A, base current is 15-30A, welding speed is 200-300mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-95°;

[0013] Bottom corrugated section C6: welding peak current is 75-95A, base current is 15-25A, welding speed is 180-260mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4Hz, and travel angle α1 is 90°-98°.

[0014] The acceleration of the welding gun angle change during the transition between the sections is:

[0015] Between C1 and C2: 20-40° / S 2 ,

[0016] Between C2 and C3: (-30)-(-45°) / S 2 ,

[0017] Between C3 and C4: (-20)-(-30°) / S 2 ,

[0018] Between C4 and C5: 20-30° / S 2 ,

[0019] Between C5 and C6: 30-45° / S 2 ,

[0020] Between C6 and C1: (-20)-(-40°) / S 2 .

[0021] The arc starting current is 20-40A, the arc starting time is 0.5-3s, the arc ending current is 20-40A, and the arc ending time is 1-5s.

[0022] The positive effects of the present invention are: each corrugation is divided into six sections and welded separately, the parameters between each section change linearly and evenly, the welding process is stable and reliable, the weld quality meets the actual production requirements, it is suitable for automated welding equipment, and can greatly improve welding production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the corrugation segments of the corrugated plate of the present invention;

[0024] Figure 2 This is a schematic diagram of the travel angle of the gun of the present invention;

[0025] Figure 3 This is a schematic diagram of the relative positions of the welding gun and the test plate of the present invention;

[0026] Figure 4 This is a photo of the weld in Example 1 of the present invention;

[0027] Figure 5 This is a typical cross-sectional photo of the weld in Example 1 of the present invention;

[0028] Figure 6 This is a photo of the weld in Example 2 of the present invention;

[0029] Figure 7 This is a typical cross-sectional photo of the weld in Example 2 of the present invention;

[0030] Figure 8 This is a photo of the weld in Example 3 of the present invention;

[0031] Figure 9 This is a typical cross-sectional photo of the weld in Example 3 of the present invention;

[0032] In the figure: C1: bottom straight section; C2: bottom corrugated section; C3: middle corrugated section; C4: top corrugated section; C5: middle corrugated section; C6: bottom corrugated section; the travel angle α1 is the angle between the welding gun axis and the welding direction; the working angle α2 is the angle between the welding gun axis and the workpiece surface; d1 is the plasma arc height, that is, the distance between the nozzle and the workpiece surface; d2 is the pointing position of the welding gun (pointing to the upper plate is "+", pointing to the bottom plate is "-"). Implementation Method

[0033] The present invention will be further described below through embodiments with reference to the accompanying drawings.

[0034] A plasma arc welding process for a main shield corrugated plate of an enclosure system, wherein one corrugation of the corrugated plate is divided into six segments, namely, a bottom straight segment C1, a bottom corrugated segment C2, a middle corrugated segment C3, a top corrugated segment C4, a middle corrugated segment C5, and a bottom corrugated segment C6. The corrugated plate is plasma welded. Before welding begins, the welding gun working angle α2 is 55°-85°, the arc height d1 is 0.5-1.5 mm, and the welding gun pointing position d2 is 0-1.5 mm.

[0035] After starting welding, the arc is opened and the welding gun starts to move at the set welding speed at the same time. After a certain arc starting time, the arc current increases linearly to the welding current, and then the welding specifications of the bottom straight segment C1 of the first corrugation of the corrugated plate, the bottom corrugated segment C2, the middle corrugated segment C3, the top corrugated segment C4, the middle corrugated segment C5 and the bottom corrugated segment C6, and the bottom straight segment C1 of the lower corrugation of the corrugated plate are sequentially performed in a segmented cycle, and so on. When transitioning between each segment, the welding gun angle changes at a constant acceleration; when the welding arc is closed, the welding current linearly decays to the arc closing current within a certain arc closing time, and then the welding gun movement and the arc stop at the same time to complete the welding.

[0036] The welding specifications for each section are as follows:

[0037] Corrugated plate bottom straight section C1: welding peak current is 80-100A, base current is 20-40A, welding speed is 300-400mm / min, ion gas flow is 0.2-0.4L / min, duty cycle is 40%-50%, pulse frequency is 3.5Hz-5Hz, and travel angle α1 is 90°-100°

[0038] Bottom corrugated section C2: welding peak current is 75-95A, base current is 15-25A, welding speed is 180-260mm / min, ion gas flow is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4Hz, and travel angle α1 is 90°-98°

[0039] Middle corrugated section C3: welding peak current is 75-95A, base current is 15-30A, welding speed is 200-300mm / min, ion gas flow is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-95°

[0040] Top corrugated section C4: welding peak current is 75-95A, base current is 15-25A, welding speed is 200-300mm / min, ion gas flow rate is 0.15-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-98°

[0041] Middle corrugated section C5: welding peak current is 75-95A, base current is 15-30A, welding speed is 200-300mm / min, ion gas flow is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-95°

[0042] Bottom corrugated section C6: welding peak current is 75-95A, base current is 15-25A, welding speed is 180-260mm / min, ion gas flow is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4Hz, and travel angle α1 is 90°-98°

[0043] The acceleration of the welding gun angle change during the transition between the sections is:

[0044] Between C1 and C2: 20-40° / S 2 ,

[0045] Between C2 and C3: (-30)-(-45°) / S 2 ,

[0046] Between C3 and C4: (-20)-(-30°) / S 2 ,

[0047] Between C4 and C5: 20-30° / S 2 ,

[0048] Between C5 and C6: 30-45° / S 2 ,

[0049] Between C6 and C1: (-20)-(-40°) / S 2 .

[0050] The arc starting current is 20-40A, the arc starting time is 0.5-3s, the arc ending current is 20-40A, and the arc ending time is 1-5s.

[0051] As a preferred embodiment, the implementation is as follows: Example

[0052] Plasma welding was used to weld lap welds of 1.2 mm stainless steel corrugated plates. The welding gun working angle α2 was 80°, the arc height d1 was 1 mm, and the welding gun pointing position d2 was 1 mm. Pulse welding was used, with an arc starting current of 30 A and a current rise time of 2 s. The parameters for each section are as follows:

[0053] The bottom straight section C1 of the corrugated plate: the welding peak current is 90A, the base current is 30A, the welding speed is 350mm / min, the ion gas flow rate is 0.3L / min, the duty cycle is 44%, the pulse frequency is 4Hz, and the travel angle α1 is 95°;

[0054] Bottom corrugated section C2: welding peak current is 80A, base current is 18A, welding speed is 210mm / min, ion gas flow rate is 0.16L / min, duty cycle is 38%, pulse frequency is 3.2Hz, and travel angle α1 is 93°;

[0055] Middle corrugated section C3: welding peak current is 82A, base current is 20A, welding speed is 260mm / min, ion gas flow rate is 0.18L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 92°;

[0056] Top corrugated section C4: welding peak current is 85A, base current is 20A, welding speed is 280mm / min, ion gas flow rate is 0.2L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 93°;

[0057] Middle corrugated section C5: welding peak current is 82A, base current is 20A, welding speed is 260mm / min, ion gas flow rate is 0.18L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 92°;

[0058] Bottom corrugated section C6: welding peak current is 80A, base current is 18A, welding speed is 210mm / min, ion gas flow rate is 0.16L / min, duty cycle is 40%, pulse frequency is 3.2Hz, and travel angle α1 is 93°;

[0059] The accelerations of the welding gun angle changes during the transition between the segments are:

[0060] Between C1 and C2 segments: 20° / S 2 ,

[0061] Between C2 and C3 segments: (-30°) / S 2 ,

[0062] Between C3 and C4 segments: (-20°) / S 2 ,

[0063] Between C4 and C5: 20° / S 2 ,

[0064] Between C5 and C6: 30° / S 2 ,

[0065] Between C6 and C1: (-20°) / S 2 .

[0066] After welding is completed, the arc extinguishing program is started, the arc extinguishing time is 2S, and the arc extinguishing current is 30A;

[0067] Typical photos of welds are as follows Figure 4 and Figure 5 As shown, the weld surface is uniform and smooth, and the weld penetration, weld width, weld thickness, etc. meet the relevant industry requirements.

[0068] Implementation Example 2:

[0069] Plasma welding was used to weld lap welds of 1.2 mm stainless steel corrugated plates. The welding gun working angle α2 was 75°, the arc height d1 was 1.2 mm, and the welding gun pointing position d2 was 0.8 mm. Pulse welding was used with an arc starting current of 40 A and a current rise time of 3 s. The parameters for each section are as follows:

[0070] The bottom straight section C1 of the corrugated plate: the welding peak current is 95A, the base current is 30A, the welding speed is 380mm / min, the ion gas is 0.3L / min, the duty cycle is 45%, the pulse frequency is 4Hz, and the travel angle α1 is 93°;

[0071] Bottom corrugated section C2: welding peak current is 83A, base current is 20A, welding speed is 220mm / min, ion gas is 0.18L / min, duty cycle is 40%, pulse frequency is 3.4Hz, and travel angle α1 is 96°;

[0072] Middle corrugated section C3: welding peak current is 85A, base current is 20A, welding speed is 260mm / min, ion gas is 0.18L / min, duty cycle is 38%, pulse frequency is 3.5Hz, and travel angle α1 is 91°;

[0073] Top corrugated section C4: welding peak current is 88A, base current is 18A, welding speed is 280mm / min, ion gas is 0.2L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 95°;

[0074] Middle corrugated section C5: welding peak current is 85A, base current is 20A, welding speed is 260mm / min, ion gas is 0.18L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 91°;

[0075] Bottom corrugated section C6: welding peak current is 80A, base current is 18A, welding speed is 210mm / min, ion gas is 0.18L / min, duty cycle is 40%, pulse frequency is 3.4Hz, and travel angle α1 is 96°;

[0076] The acceleration of the welding gun angle change during the transition between sections is:

[0077] Between C1 and C2 segments: 40° / S 2 ,

[0078] Between C2 and C3 segments: (-45°) / S 2 ,

[0079] Between C3 and C4 segments: (-30°) / S 2 ,

[0080] Between C4 and C5: 30° / S 2 ,

[0081] Between C5 and C6: 45° / S 2 ,

[0082] Between C6 and C1: (-40°) / S 2 .

[0083] After welding is completed, the arc extinguishing program is started, the arc extinguishing time is 3S, and the arc extinguishing current is 40A;

[0084] Typical photos of welds are as follows Figure 6 and Figure 7 As shown, the weld surface is uniform and smooth, and the weld penetration, weld width, weld thickness, etc. meet the relevant industry requirements. Example

[0085] Plasma welding was used to weld lap welds of 1.2 mm stainless steel corrugated plates. The welding gun working angle α2 was 85°, the arc height d1 was 0.8 mm, and the welding gun pointing position d2 was 1.2 mm. Pulse welding was used, with an arc starting current of 35 A and a current rise time of 4 s. The parameters for each section are as follows:

[0086] The bottom straight section C1 of the corrugated plate: the welding peak current is 88A, the base current is 30A, the welding speed is 350mm / min, the ion gas is 0.3L / min, the duty cycle is 45%, the pulse frequency is 4Hz, and the travel angle α1 is 98°;

[0087] Bottom corrugated section C2: welding peak current is 82A, base current is 20A, welding speed is 240mm / min, ion gas is 0.2L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 95°;

[0088] Middle corrugated section C3: welding peak current is 82A, base current is 20A, welding speed is 250mm / min, ion gas is 0.2L / min, duty cycle is 38%, pulse frequency is 3.5Hz, and travel angle α1 is 93°;

[0089] Top corrugated section C4: welding peak current is 85A, base current is 18A, welding speed is 280mm / min, ion gas is 0.2L / min, duty cycle is 42%, pulse frequency is 3.7Hz, and travel angle α1 is 95°;

[0090] Middle corrugated section C5: welding peak current is 82A, base current is 20A, welding speed is 250mm / min, ion gas is 0.2L / min, duty cycle is 38%, pulse frequency is 3.5Hz, and travel angle α1 is 93°;

[0091] Bottom corrugated section C6: welding peak current is 82A, base current is 20A, welding speed is 240mm / min, ion gas is 0.2L / min, duty cycle is 40%, pulse frequency is 3.5Hz, and travel angle α1 is 95°;

[0092] The acceleration of the welding gun angle change during the transition between the sections is:

[0093] Between C1 and C2 segments: 30° / S 2 ,

[0094] Between C2 and C3 segments: (-35°) / S 2 ,

[0095] Between C3 and C4 segments: (-25°) / S 2 ,

[0096] Between C4 and C5: 25° / S 2 ,

[0097] Between C5 and C6: 35° / S 2 ,

[0098] Between C6 and C1: (-30°) / S 2 .

[0099] After welding is completed, the arc extinguishing program is started, with an arc extinguishing time of 5 seconds and an arc extinguishing current of 35A.

[0100] Typical photos of welds are as follows Figure 8 and Figure 9 As shown, the weld surface is uniform and smooth, and the weld penetration, weld width, weld thickness, etc. meet the relevant industry requirements.

Claims

1. A plasma arc welding process for a primary shield corrugated plate of an enclosure system, wherein one corrugation of the corrugated plate to be welded is divided into six segments, namely, a bottom straight segment C1, a bottom corrugated segment C2, a middle corrugated segment C3, a top corrugated segment C4, a middle corrugated segment C5, and a bottom corrugated segment C6. The corrugated plate is plasma welded. Before welding begins, the welding gun working angle α2 is 55°-85°, the arc height d1 is 0.5-1.5 mm, and the welding gun pointing position d2 is 0-1.5 mm. The process is characterized by: After starting welding, the arc is turned on and the welding gun starts to move at the set welding speed. The arc starting current increases linearly to the welding current after the arc is started. The welding is carried out from the first corrugation cycle to the last corrugation, and the bottom straight segment C1 of the first corrugation, the bottom corrugation segment C2, the middle corrugation segment C3, the top corrugation segment C4, the middle corrugation segment C5 and the bottom corrugation segment C6, and the bottom straight segment C1 of the next corrugation are welded in sequence. The welding is carried out in sections according to the welding specifications of each section. The welding gun angle changes at a constant acceleration when transitioning between sections. When the welding arc is closed, the welding current linearly decays to the arc closing current within a certain arc closing time, and then the welding gun movement and the arc stop at the same time to complete the welding. The acceleration of the welding gun angle change when transitioning between sections is: Between C1 and C2: 20-40° / S 2 , Between C2 and C3: (-30)-(-45°) / S 2 , Between C3 and C4: (-20)-(-30°) / S 2 , Between C4 and C5: 20-30° / S 2 , Between C5 and C6: 30-45° / S 2 , Between C6 and C1: (-20)-(-40°) / S 2 .

2. The plasma arc welding process for the main shield corrugated plate of the enclosure system according to claim 1 is characterized in that The welding specifications for each section are as follows: The bottom straight section C1 of the corrugated plate: the welding peak current is 80-100A, the base current is 20-40A, the welding speed is 300-400mm / min, the ion gas flow rate is 0.2-0.4L / min, the duty cycle is 40%-50%, the pulse frequency is 3.5Hz-5Hz, and the travel angle α1 is 90°-100°; Bottom corrugated section C2: welding peak current is 75-95A, base current is 15-25A, welding speed is 180-260mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4Hz, and travel angle α1 is 90°-98°; Middle corrugated section C3: welding peak current is 75-95A, base current is 15-30A, welding speed is 200-300mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-95°; Top corrugated section C4: welding peak current is 75-95A, base current is 15-25A, welding speed is 200-300mm / min, ion gas flow rate is 0.15-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-98°; Middle corrugated section C5: welding peak current is 75-95A, base current is 15-30A, welding speed is 200-300mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4.5Hz, and travel angle α1 is 90°-95°; Bottom corrugated section C6: welding peak current is 75-95A, base current is 15-25A, welding speed is 180-260mm / min, ion gas flow rate is 0.1-0.3L / min, duty cycle is 35%-45%, pulse frequency is 3Hz-4Hz, and travel angle α1 is 90°-98°.

3. A plasma arc welding process for main shield corrugated plates of an enclosure system according to claim 1 or 2, characterized in that: The arc starting current is 20-40A, the arc starting time is 0.5-3s, the arc ending current is 20-40A, and the arc ending time is 1-5s.

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