High-performance thick-wall electro-gas welding method and device based on liquid nitrogen rapid cooling assistance

Abstract

The invention belongs to the technical field of welding, and discloses a thick-wall electro-gas welding high-performance welding method and device based on liquid nitrogen rapid cooling assistance. According to the method, to-be-welded thick plates with the thickness larger than 30 mm are assembled to form a welding groove, then electro-gas welding is adopted for welding the welding groove, and the welding groove is formed; in the welding process, local rapid cooling is conducted on the welded face in a liquid nitrogen cooling mode, meanwhile, cooling is conducted on the back face of the welded face in a water cooling mode, and therefore the cooling speed of a heat affected zone of a welded joint is increased under the assistance of liquid nitrogen rapid cooling. In the electro-gas welding process, the mode that liquid nitrogen cooling of the welding face is matched with water cooling of the back face of the welding face is adopted for cooling, the cooling speed of the welding heat affected zone can be increased under the assistance of quick cooling of liquid nitrogen, the cooling speed of the welding heat affected zone is increased to the maximum degree under the combined action of the liquid nitrogen and the back face, the high-temperature standing time is shortened, and the welding quality is improved. The width of a welding heat affected zone is reduced, so that the embrittlement problem of a coarse grain heat affected zone of a welding joint is avoided, and the toughness of the welding joint is improved.

Description

Technical Field

[0001] The present application belongs to the field of welding technology, and more specifically, relates to a high-performance welding method and device for thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling. Background Art

[0002] In recent years, as the exploitation of offshore oil and gas resources in my country has gradually developed towards harsh conditions such as low temperature and deep water, the thickness of steel used in offshore platform jackets has become increasingly larger, which has put forward higher requirements on welding efficiency and the quality of welded joints. At present, electric-gas vertical welding (EGW), as an efficient high-wire energy welding technology, is gradually replacing the traditional multi-pass welding process for wide and thick plates. The maximum wire energy of single-wire electric-gas vertical welding can reach 350kJ / cm, which can achieve single-pass forming of 40mm thick plates. In the face of thicker plates, the wire energy of double-wire electric-gas vertical welding can reach 750kJ / cm, which can achieve single-pass forming of up to 85mm thick plates. However, excessive heat input will inevitably lead to embrittlement of the heat-affected zone of the weld, reducing the overall toughness of the welded joint.

[0003] In order to improve the toughness of the welded joint, CN116890180A discloses a high-strength steel thick plate welded joint groove and double-wire gas-electric vertical welding method, which reduces the cross-sectional area of ​​the groove by reducing the angle of the groove, thereby weakening the heat input of the gas-electric vertical welding, but the reduction of the groove angle is limited by the swing amplitude space of the welding gun, and when the plate thickness increases, the heat input will increase rapidly. CN217832376U discloses a gas-electric vertical welding water-cooled slider device to increase the cooling effect, which increases the cooling effect by setting a water-cooled slider device, but the main function of the slider is to force the welded joint to form, and the function of water cooling is mainly to prevent the slider from melting, and it can only take away part of the heat in the welded joint area, and cannot achieve cooling of the heat-affected zone. Therefore, at present, gas-electric vertical welding is mostly used in some occasions with low performance requirements. Faced with the more severe low-temperature marine environment, the embrittlement problem of the coarse-grained heat-affected zone of the welded joint has seriously restricted its application. Summary of the invention

[0004] In response to the defects of the prior art, the present application provides a high-performance welding method and device for thick-walled gas-electric vertical welding assisted by liquid nitrogen rapid cooling, aiming to solve the problem of excessive heat input in existing gas-electric vertical welding, resulting in poor toughness of the welded joint.

[0005] According to one aspect of the present application, a high-performance welding method for thick-walled gas-electric vertical welding assisted by liquid nitrogen rapid cooling is provided, specifically: thick plates to be welded with a thickness greater than 30 mm are assembled to form a welding groove, and then the welding groove is welded by gas-electric vertical welding. During the welding process, the welding surface is locally cooled rapidly by liquid nitrogen cooling, and the back of the welding surface is cooled by water cooling, thereby improving the cooling rate of the heat-affected zone of the weld joint with the assistance of liquid nitrogen rapid cooling.

[0006] Compared with the prior art, the above technical scheme conceived by the present application uses liquid nitrogen cooling to quickly cool the weld joint on the welding surface locally, which can effectively increase the cooling rate of the heat affected zone of the weld joint and avoid the embrittlement problem of the coarse-grained heat affected zone of the weld joint.

[0007] As a further preferred embodiment, when the wall thickness of the thick plate to be welded is less than 50 mm, the welding groove is a single-sided V-shaped groove, and indirect water cooling is used to cool the back of the welding surface; when the wall thickness of the thick plate to be welded is greater than or equal to 50 mm, the welding groove is an X-shaped groove, and when welding the first side, direct water cooling is used to cool the back of the welding surface, and when welding the other side, indirect water cooling is used to cool the back of the welding surface.

[0008] As further preferred, the flow rate of liquid nitrogen is 0.1 L / min to 0.2 L / min.

[0009] According to another aspect of the present application, a high-performance welding device for thick-walled gas-electric vertical welding assisted by liquid nitrogen rapid cooling is provided, which is used to perform the above method. The welding device includes a welding gun, a back water-cooling component and a front water-cooling component, wherein the welding gun is used to weld the welding groove by gas-electric vertical welding; the back water-cooling component is arranged on the back of the welding surface of the thick plate to be welded, and is used to water-cool the back of the welding surface; the front water-cooling component is arranged on the welding surface of the thick plate to be welded and moves with the welding gun, and the front water-cooling component includes a water-cooling slider and a protective gas channel, a cooling water channel and a liquid nitrogen injection channel arranged inside the water-cooling slider, the protective gas channel is used to provide protective gas during the welding process; the cooling water channel is used to pass cooling water during the welding process to cool the water-cooling slider to prevent it from melting so as to force the weld to form; the liquid nitrogen injection channel is used to spray liquid nitrogen on the welding joint during the welding process to achieve local rapid cooling of the heat-affected zone of the welding joint.

[0010] As a further preference, the protective gas channel is arranged at the center of the water-cooled slider, the first water inlet and the first water outlet of the cooling water channel are respectively arranged on both sides of the protective gas channel, and there are two liquid nitrogen injection channels, which are respectively arranged on both sides of the first water inlet and the first water outlet.

[0011] As a further preferred embodiment, a first liquid nitrogen injector and a second liquid nitrogen injector are respectively fixed inside the two liquid nitrogen injection channels, and the center lines of the first liquid nitrogen injector and the second liquid nitrogen injector are respectively 1 mm to 2 mm away from the outside of the weld fusion line, and the ends of the first liquid nitrogen injector and the second liquid nitrogen injector are 1 mm to 3 mm away from the welding surface of the thick plate to be welded.

[0012] As a further preferred embodiment, when the wall thickness of the thick plate to be welded is less than 50 mm, the back water cooling assembly includes a back water cooling pad and a water cooling pipe arranged inside the back water cooling pad, the back water cooling pad is arranged at the root of the welding groove along the length direction of the thick plate to be welded and is close to the thick plate to be welded, and the water cooling pipe is distributed in a serpentine shape inside the back water cooling pad.

[0013] As further preferred, the water inlet of the water cooling pipe is arranged at the bottom of the back water cooling pad, and the water outlet of the water cooling pipe is arranged at the top of the back water cooling pad.

[0014] As a further preference, the width of the back water cooling pad is more than 3 times the maximum groove width of the welding groove.

[0015] As a further preferred embodiment, when the wall thickness of the thick plate to be welded is greater than or equal to 50 mm, when welding the first side, the back water cooling assembly includes a cooling water pipe, and during welding, the cooling water pipe moves synchronously with the front water cooling assembly to spray water to the root of the groove to be welded; when welding the other side, the back water cooling assembly includes a back water cooling pad and a water cooling pipe arranged inside the back water cooling pad, the back water cooling pad is arranged at the root of the groove to be welded along the length direction of the thick plate to be welded and is close to the thick plate to be welded, and the water cooling pipe is distributed in a serpentine shape inside the back water cooling pad.

[0016] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art: 1. In the process of gas-electric vertical welding, the present application adopts liquid nitrogen cooling on the welding surface and water cooling on the back of the welding surface to reduce the temperature. With the assistance of liquid nitrogen rapid cooling, the cooling rate of the welding heat affected zone can be increased. Under the combined effect of the two, the cooling rate of the welding heat affected zone can be accelerated to the greatest extent, the high temperature residence time can be reduced, and the width of the welding heat affected zone can be reduced, thereby avoiding the embrittlement problem of the coarse-grained heat affected zone of the welded joint, improving the toughness of the welded joint, and making it more adaptable to the demanding low-temperature marine environment; 2. At the same time, the present application optimizes the shape of the groove and the specific method of water cooling on the back of the welding surface according to the wall thickness, which can further increase the cooling speed, thereby further improving the toughness of the welded joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a top view of the high-performance welding process of thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling of a 40 mm thick plate provided in Example 1 of the present application; Figure 2 It is a cross-sectional view of the groove of the high-performance welding process of thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling of a 40 mm thick plate provided in Example 1 of the present application; Figure 3 It is a top view of the high-performance welding process of thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling of an 80 mm thick plate provided in Example 2 of the present application; Figure 4 It is a cross-sectional view of the groove of the high-performance welding process of thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling of an 80 mm thick plate provided in Example 1 of the present application; Figure 5 is the CTOD test curve of the welded joint and the welded joint without cooling in Example 1 of the present application; Figure 6 It is the CTOD test curve of the welded joint and the uncooled welded joint in Example 2 of the present application.

[0018] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-thick plate to be welded, 2-back water-cooling pad, 3-water-cooling pipe, 4-water-cooling slider, 5-first liquid nitrogen injector, 6-first water inlet, 7-protective gas channel, 8-first water outlet, 9-second liquid nitrogen injector, 10-second water inlet, 11-second water outlet, 12-cooling water channel, 13-liquid nitrogen injection channel, 14-liquid nitrogen, 15-cooling water pipe, 16-cooling water, 17-welding gun. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] like Figures 1 to 4 As shown, the present application provides a high-performance welding method for thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling, specifically: a thick plate 1 to be welded with a thickness greater than 30 mm is assembled to form a welding groove, the welding groove preferably adopts a single-sided V-shaped groove or an X-shaped groove, and then the welding groove is welded by gas-electric vertical welding; During the welding process, the welding surface of the thick plate 1 to be welded is locally and rapidly cooled by liquid nitrogen cooling. Liquid nitrogen has a fast cooling speed and can quickly absorb a large amount of heat and quickly take away the heat from the weld joint area, thereby achieving rapid cooling of the heat-affected zone and avoiding the embrittlement problem of the coarse-grained heat-affected zone of the weld joint, thereby making the welded product more suitable for the demanding low-temperature marine environment. At the same time, liquid nitrogen also has the advantage of no residual pollution and will not have adverse effects on the weld joint. At the same time, the back side of the welding surface of the thick plate 1 to be welded is cooled by indirect water cooling or direct water cooling, so as to increase the cooling speed of the heat affected zone of the weld joint in combination with liquid nitrogen rapid cooling.

[0021] The present application adopts liquid nitrogen cooling to perform local rapid cooling on the welding surface of the thick plate to be welded, which can effectively increase the cooling rate of the welding heat affected zone and avoid the embrittlement problem of the coarse-grained heat affected zone of the weld joint.

[0022] Furthermore, when the wall thickness of the thick plate 1 to be welded is less than 50 mm, the welding groove is a single-sided V-shaped groove, and the back of the welding surface of the thick plate 1 to be welded is water-cooled by indirect water cooling; when the wall thickness of the thick plate 1 to be welded is greater than or equal to 50 mm, the welding groove is an X-shaped groove, and when welding the first side, direct water cooling is used to cool the back of the welding surface, and when welding the other side, indirect water cooling is used to cool the back of the welding surface.

[0023] Furthermore, the groove angle is 30°~50°, the root is reserved for a blunt edge of 3mm~5mm, and the gap is reserved for 2mm~3mm during assembly. The welding current is 320A~480 A, the welding voltage is 36V~44 V, the welding speed is 2.9 cm / min~3.6 cm / min, the welding gun swing amplitude range is 10 mm~15 mm, the dwell time on both sides is 0.4s, the heat input range is 240kJ / cm~353kJ / cm, and the heat input range is 240 kJ / cm~353 kJ / cm. The diameter of the gas-electric vertical welding wire is 1.6mm, the wire dry extension length is 30mm~35mm, the shielding gas during welding is 100% CO2, and the gas flow rate is 30L / min~35L / min.

[0024] Furthermore, the liquid nitrogen flow rate is 0.1L / min to 0.2L / min. If the flow rate is too low, the cooling effect of the welding heat affected zone will be poor. If the flow rate is too high, the welding cost will be too high on the one hand, and on the other hand, brittle structures such as lath martensite / bainite will be produced in the heat affected zone.

[0025] According to another aspect of the present application, a high-performance thick-wall gas-electric vertical welding device assisted by liquid nitrogen rapid cooling is provided for executing the above method, wherein the welding device comprises a welding gun 17, a back water-cooling assembly and a front water-cooling assembly, wherein the welding gun 17 is used to weld the welding groove by gas-electric vertical welding; the back water-cooling assembly is arranged on the back of the welding surface of the thick plate 1 to be welded, and is used to water-cool the back of the welding surface; the front water-cooling assembly is arranged on the welding surface of the thick plate 1 to be welded and moves with the welding gun 17, the front water-cooling assembly comprises a water-cooling slider 4 and a protective gas channel 7, a cooling water channel 12 and a liquid nitrogen injection channel 13 arranged inside the water-cooling slider 4, the protective gas channel 7 is used to provide protective gas during the welding process; the cooling water channel 12 is used to pass cooling water during the welding process to cool the water-cooling slider 4 to prevent the water-cooling slider 4 from being melted due to excessive temperature; the liquid nitrogen injection channel 13 is used to spray liquid nitrogen onto the welding joint during the welding process to achieve local rapid cooling.

[0026] Furthermore, when the water-cooled slider 4 is installed, its center line is strictly ensured to be aligned with the center line of the groove to be welded, and the shielding gas channel 7 is set at the center of the water-cooled slider 4; the first water inlet 6 and the first water outlet 8 of the cooling water channel 12 are respectively set on both sides of the shielding gas channel 7, and the first water inlet 6 and the first water outlet 8 are connected to the first constant temperature circulating cooling water tank during operation to realize the circulation of cooling water; there are two liquid nitrogen injection channels 13, which are respectively set on both sides of the first water inlet 6 and the first water outlet 8, facing the position of the coarse grain heat affected zone on both sides of the weld, and a liquid nitrogen injector is fixed inside the liquid nitrogen injection channel 13 to realize liquid nitrogen injection cooling, and the center line of the liquid nitrogen injector should always be 1mm to 2mm away from the outside of the weld fusion line to ensure that the liquid nitrogen 14 effectively acts on the position of the coarse grain heat affected zone. More preferably, the distance between the end of the liquid nitrogen injector and the thick plate 1 to be welded should be between 1mm and 3mm.

[0027] Further, when the wall thickness of the thick plate 1 to be welded is less than 50 mm, Figure 1 , 2 As shown, the back water cooling assembly includes a back water cooling pad 2 and a water cooling pipe 3 arranged inside the back water cooling pad 2. The back water cooling pad 2 is installed at the root of the groove to be welded along the length direction of the thick plate 1 to be welded and is close to the back of the welding surface of the thick plate 1 to be welded. The water cooling pipe 3 is distributed in a serpentine shape inside the back water cooling pad 2. The second water inlet 10 of the water cooling pipe 3 is arranged at the bottom of the back water cooling pad 2, and the second water outlet 11 of the water cooling pipe 3 is arranged at the top of the back water cooling pad 2. When working, the second water inlet 10 and the second water outlet 11 are connected to the No. 2 constant temperature circulating cooling water tank to realize the circulation of cooling water. The temperature of the No. 1 constant temperature circulating cooling water tank and the No. 2 constant temperature circulating cooling water tank is set to 20℃~30℃.

[0028] Furthermore, the width W of the back water cooling pad 2 is the maximum groove width W 1 More than 3 times of W, that is, W ≥ 3W 1 , to ensure the water cooling effect on the back.

[0029] Further, when the wall thickness of the thick plate 1 to be welded is greater than or equal to 50 mm, Figure 3 , 4 As shown, when welding the first side, the back water cooling assembly includes a cooling water pipe 15, which moves synchronously with the front water cooling assembly during welding, and is used to spray cooling water 16 to the root of the groove to be welded, thereby cooling the back of the welding surface by direct water cooling. When welding the other side, the back water cooling assembly includes a back water cooling pad 2 and a water cooling pipe 3 arranged inside the back water cooling pad 2. The back water cooling pad 2 is arranged at the root of the groove to be welded along the length direction of the thick plate 1 to be welded and is close to the thick plate 1 to be welded. The water cooling pipe 3 is distributed in a serpentine shape inside the back water cooling pad 2.

[0030] The existing gas-electric vertical welding technology without external cooling source only limits the heat input by limiting the cross-sectional area of ​​the groove, or relies on the action of the water-cooled slider to accelerate the cooling of the weld, and the effect is very weak. This application uses an external cooling source. During welding, the back of the welding surface is cooled as a whole through a large-area water-cooled pad or by directly spraying water on the root of the weld joint. The welding surface is acted on the coarse-grained heat-affected zone by liquid nitrogen, causing local temperature field distortion. Under the combined effect of the two, the cooling rate of the welding heat-affected zone is accelerated to the greatest extent, its high-temperature residence time is reduced, the width of the welding heat-affected zone is reduced, and the toughness of the welded joint is improved.

[0031] The technical solution provided by this application is further described below based on specific embodiments.

[0032] Example 1 This embodiment takes a 40 mm thick high-strength steel plate as an example to provide a high-performance welding method for thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling. The specific steps are as follows: S1 prepares the thick plate to be welded 1 and assembles it. The welding groove form adopts a single-sided V-shaped groove with a groove angle of 35° and a 3 mm blunt edge reserved at the root. When assembling, a gap of 2 mm is reserved. After the assembly is completed, Figure 1 As shown; S2 installs the back water cooling pad 2, the width of the back water cooling pad 2 is 200 mm, it is installed at the root of the groove and fits with the thick plate 1 to be welded, a serpentine water cooling channel 3 is arranged inside it, and the second water inlet 10 and the second water outlet 11 are connected to the second constant temperature circulating cooling water tank through water pipes respectively; S3 installs a water-cooled slider 4, the middle of the water-cooled slider 4 is a protective gas channel 7, and the two sides are a first water inlet 6 and a first water outlet 8 for cooling water. A cooling water channel 12 is provided inside the water-cooled slider 4, and the first water inlet 6 and the first water outlet 8 are respectively connected to a constant temperature circulating cooling water tank No. 1 through water pipes; S4 performs bottom filling and installs the first liquid nitrogen injector 5 and the second liquid nitrogen injector 9. The welding power source model used is YD-600KH. The temperature of the No. 1 and No. 2 constant temperature circulating cooling water tanks is set to 20°C; the No. 2 constant temperature circulating cooling water tank is turned on, and circulating water is passed into the back water cooling pad 2; the No. 1 constant temperature circulating cooling water tank is turned on, and circulating water is passed into the water cooling slider 4; then the bottom is welded and filled until the liquid nitrogen injection channel 13 at the bottom of the water cooling slider 4 is flush with the bottom of the thick plate 1 to be welded; after stopping welding, the first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 are respectively installed at a distance of 1 mm from the fusion line on both sides of the weld, and the end faces thereof are adjusted to be 2 mm away from the surface of the test plate to ensure that the liquid nitrogen effectively acts on the coarse grain heat affected zone; S5 starts the first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 and performs gas-electric vertical welding. The welding parameters are set as follows: welding current is 450 A, welding voltage is 43 V, welding speed is 3.5 cm / min, welding gun swing amplitude range is 12 mm, dwell time on both sides is 0.4 s, gas-electric vertical welding wire diameter is 1.6 mm, wire dry extension length is 30 mm, and shielding gas is 100% CO during welding. 2 , gas flow rate is 30 L / min; Start the first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 and keep their liquid nitrogen output speed at 0.1 L / min; officially start welding. During the welding process, the back water-cooling pad 2 continuously cools the thick plate 1 to be welded as a whole. At the same time, the water-cooling slider 4 moves upward and drives the first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 to move upward synchronously. The first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 continuously spray liquid nitrogen on the coarse-grained heat-affected zone to locally and quickly cool it until the welding is completed.

[0033] After welding, the fracture toughness test of the welded joint was carried out according to GB 21143-2014. The sampling location was the heat affected zone, the test temperature was -20°C, and compared with the welded joint without cooling. The test curve is as follows: Figure 5 As shown. The CTOD values ​​without cooling were calculated by the formula to be 0.015 mm and 0.016 mm, and the CTOD values ​​of Example 1 after cooling were 0.368 mm and 1.032 mm, and the fracture toughness was greatly improved.

[0034] Example 2 This embodiment takes a 80 mm thick high-strength steel plate as an example to provide a high-performance welding method for thick-wall gas-electric vertical welding assisted by liquid nitrogen rapid cooling. The specific steps are as follows: S1 prepares the thick plate to be welded 1 and assembles it. The welding groove adopts X-shaped groove, the groove angle of the welding surface is 30°, the groove depth of the welding surface is 45mm, the blunt edge is reserved 3mm, and the groove angle of the back of the welding surface is 35°. When assembling, a gap of 2mm is reserved. Figure 3 As shown; S2 installs a cooling water pipe 15, which directly acts on the root of the X-shaped groove by spraying water. During welding, its upward movement speed is consistent with the water-cooling slider 4 on the welding surface; S3 and S4 are the same as in Example 1; S5 starts the first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 and performs gas-electric vertical welding on the welding surface. The welding parameters are set as follows: welding current is 460 A, welding voltage is 44 V, welding speed is 3.3 cm / min, and the other parameters are consistent with implementation 1.

[0035] In S6, the back water-cooling pad 2 is used to indirectly cool the welded side, and the water-cooling slider 4 is moved to the unwelded side. The first liquid nitrogen injector 5 and the second liquid nitrogen injector 9 are started to perform gas-electric vertical welding on the other side. S3 and S4 are repeated to set the welding parameters: the welding current is 420 A, the welding voltage is 41 V, the welding speed is 3.4 cm / min, and the other parameters are consistent with implementation 1.

[0036] After welding, the fracture toughness test of the welded joint was carried out according to GB 21143-2014. The sampling location was the heat affected zone, the test temperature was -20°C, and compared with the welded joint without cooling. The test curve is as follows: Figure 6 As shown. The CTOD values ​​without cooling were calculated by the formula to be 0.021 mm and 0.072 mm, and the CTOD values ​​of Example 2 after cooling were 0.421 mm and 0.694 mm, and the fracture toughness was greatly improved.

[0037] The above results show that the combination of the welding process parameters and the cooling method developed in this application can significantly improve the fracture toughness of the heat-affected zone of the gas-electrode vertical welding joint.

[0038] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0039] In addition, references throughout this specification to "one embodiment"; "one embodiment", "an example" or similar language indicate that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment"; "in one embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0040] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A high-performance thick-wall gas-electric vertical welding method based on liquid nitrogen rapid cooling assistance, characterized in that: Specifically, thick plates (1) to be welded with a thickness greater than 30 mm are assembled to form a welding groove, and then the welding groove is welded by gas-electric vertical welding. During the welding process, the welding surface is locally cooled rapidly by liquid nitrogen cooling, and the back of the welding surface is cooled by water cooling, thereby increasing the cooling speed of the heat-affected zone of the weld joint with the assistance of liquid nitrogen rapid cooling.

2. The welding method according to claim 1, characterized in that When the wall thickness of the thick plate (1) to be welded is less than 50 mm, the welding groove is a single-sided V-shaped groove, and the back of the welding surface is cooled by indirect water cooling; when the wall thickness of the thick plate (1) to be welded is greater than or equal to 50 mm, the welding groove is an X-shaped groove, and when welding the first side, the back of the welding surface is cooled by direct water cooling, and when welding the other side, the back of the welding surface is cooled by indirect water cooling.

3. The welding method according to claim 1, characterized in that The flow rate of liquid nitrogen is 0.1L / min~0.2L / min.

4. A high-performance thick-wall gas-electric vertical welding device based on liquid nitrogen rapid cooling assistance, used to perform the method as claimed in any one of claims 1 to 3, characterized in that: The welding device comprises a welding gun (17), a back water cooling assembly and a front water cooling assembly, wherein the welding gun (17) is used to weld the welding groove by gas-electric vertical welding; the back water cooling assembly is arranged on the back of the welding surface of the thick plate (1) to be welded, and is used to water cool the back of the welding surface; the front water cooling assembly is arranged on the welding surface of the thick plate (1) to be welded and moves with the welding gun (17), and the front water cooling assembly comprises a water cooling slider (4) and a protective gas channel (7), a cooling water channel (12) and a liquid nitrogen injection channel (13) arranged inside the water cooling slider (4), wherein the protective gas channel (7) is used to provide protective gas during the welding process; the cooling water channel (12) is used to pass cooling water during the welding process to cool the water cooling slider (4) to prevent it from melting so as to force the weld to form; and the liquid nitrogen injection channel (13) is used to spray liquid nitrogen on the weld joint during the welding process to achieve local rapid cooling of the heat-affected zone of the weld joint.

5. The welding device according to claim 4, characterized in that The protective gas channel (7) is arranged at the center of the water-cooled slider (4); the first water inlet (6) and the first water outlet (8) of the cooling water channel (12) are respectively arranged on both sides of the protective gas channel (7); and there are two liquid nitrogen injection channels (13), which are respectively arranged on both sides of the first water inlet (6) and the first water outlet (8).

6. The welding device according to claim 5, characterized in that A first liquid nitrogen injector (5) and a second liquid nitrogen injector (9) are respectively fixed inside the two liquid nitrogen injection channels (13); the center lines of the first liquid nitrogen injector (5) and the second liquid nitrogen injector (9) are respectively 1 mm to 2 mm away from the outside of the weld fusion line; and the distance between the ends of the first liquid nitrogen injector (5) and the second liquid nitrogen injector (9) and the welding surface of the thick plate (1) to be welded is 1 mm to 3 mm.

7. The welding device according to claim 4, characterized in that: When the wall thickness of the thick plate (1) to be welded is less than 50 mm, the back water cooling assembly comprises a back water cooling pad (2) and a water cooling pipe (3) arranged inside the back water cooling pad (2); the back water cooling pad (2) is arranged at the root of the weld groove along the length direction of the thick plate (1) to be welded and is close to the thick plate (1) to be welded; and the water cooling pipe (3) is distributed in a serpentine shape inside the back water cooling pad (2).

8. The welding device according to claim 7, characterized in that The water inlet of the water cooling pipe (3) is arranged at the bottom of the back water cooling pad (2), and the water outlet of the water cooling pipe (3) is arranged at the top of the back water cooling pad (2).

9. The welding device according to claim 7, characterized in that: The width of the back water cooling pad (2) is more than three times the maximum groove width of the welding groove.

10. The welding device according to claim 4, characterized in that: When the wall thickness of the thick plate (1) to be welded is greater than or equal to 50 mm, when welding the first side, the back water cooling assembly comprises a cooling water pipe (15), and during welding, the cooling water pipe (15) moves synchronously with the front water cooling assembly to spray water to the root of the groove to be welded; when welding the other side, the back water cooling assembly comprises a back water cooling pad (2) and a water cooling pipe (3) arranged inside the back water cooling pad (2), the back water cooling pad (2) is arranged at the root of the groove to be welded along the length direction of the thick plate (1) to be welded and is close to the thick plate (1) to be welded, and the water cooling pipe (3) is distributed in a serpentine shape inside the back water cooling pad (2).

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