Welding method for low-temperature nickel steel

Abstract

The invention belongs to the technical field of welding, and provides a low-temperature nickel steel welding method which comprises the following steps: obtaining a target welding wire and a target liner; a single-face groove is formed in the to-be-welded side of the to-be-welded base metal; the to-be-welded base metal and the target liner are assembled to form a welding groove, and the groove gap of the welding groove is made to be the preset distance; obtaining the length of a welding seam to determine a welding sequence; the welding working condition is adjusted according to the plate thickness and the welding position of the to-be-welded base metal; and the welding groove is welded, and the thickness of the weld joint bottom layer is controlled to be the preset thickness. According to the welding method, by selecting the specially-made target welding wire and the target liner, the influence of phosphorus, sulfur, carbon and other harmful elements in the target welding wire and the target liner on a welding seam can be reduced, and bottoming cracks are reduced; by strictly controlling the welding sequence, the welding working condition and the thickness of the bottoming layer in the welding process, the welding stress in the welding process is reduced, bottoming cracks are further reduced, the welding quality and the first-pass yield of welding are improved, and the repair cost is reduced.

Description

Technical Field

[0001] The present application relates to the field of welding technology, and in particular to a welding method for low-temperature nickel steel. Background Art

[0002] VLEC (Very Large Ethylene Carrier) is an ultra-large fully refrigerated liquefied ethylene carrier, whose main function is to safely and efficiently transport cryogenic liquefied gases such as liquefied ethylene. The design of the cargo tank of a VLEC has extremely high technical requirements, especially its cargo containment system. The minimum design temperature of the cargo in the cargo tank reaches -104°C, which means that the main barrier structure of the cargo containment system must be made of materials that can maintain good performance in low temperature environments. Nickel alloy X12Ni5 low-temperature steel is widely regarded as an excellent material for manufacturing liquid tanks. This steel has excellent low-temperature toughness and weldability, and can maintain the integrity and stability of the structure at extremely low temperatures.

[0003] The independent liquid tanks of VLEC ships currently under construction generally adopt the TYPE B structural design. The structure is complex, and the capacity of a single liquid tank is as high as more than 20,000 cubic meters, which makes its welding technology difficult and requires high welding skills of workers. At present, the welding method of VLEC ship liquid tanks adopts single-sided welding with flux-cored wire and double-sided forming. This technology, combined with the use of ceramic liner, can complete welding under one-side construction, greatly simplifying the construction process, not only reducing the welding process, but also reducing the dependence on the welder's operating skills, which is expected to improve construction efficiency, reduce construction intensity and construction costs.

[0004] However, in the actual welding process, the base weld is prone to cracks, and the appearance of cracks directly leads to increased construction difficulty. After the base cracks are found, rework operations are required, which not only increases the extra workload, but may also lead to further deterioration in welding quality, thereby reducing the weld qualification rate, increasing the rework cost, and affecting the construction progress and quality of the entire liquid tank. Summary of the invention

[0005] The purpose of the present application is to provide a welding method for low-temperature nickel steel, which is used to solve the problem that when welding low-temperature nickel steel used to build liquid tanks in the prior art, the base weld is prone to base cracks.

[0006] To achieve the above-mentioned and other related purposes, the present application provides a low-temperature nickel steel welding method, comprising the following steps:

[0007] obtaining a target welding wire and a target backing pad;

[0008] A single-sided groove is formed on the side to be welded of the parent material to be welded;

[0009] Form the base metal to be welded and the target backing to form a welding groove, and make the groove gap of the welding groove a preset distance;

[0010] Obtain the length of the weld seam and determine the welding sequence according to the length of the weld seam;

[0011] Adjust the welding conditions according to the plate thickness and welding position of the base metal to be welded;

[0012] Weld the welding groove according to the determined welding sequence, and control the thickness of the root pass of the weld seam to be a preset thickness.

[0013] Optionally, the target welding wire is a flux-cored wire, and the composition of the target welding wire includes at least carbon, silicon, manganese, sulfur, phosphorus, chromium, nickel, molybdenum, copper and iron;

[0014] In the composition of the target welding wire, the sum of the content of phosphorus and the content of sulfur does not exceed 0.015%, the content of carbon does not exceed 0.12%, and the content of silicon does not exceed 0.4%.

[0015] Optionally, the material of the target backing includes the following components by mass percentage: kaolin 85% - 90%, quartz stone 5% - 8%, cryolite 2% - 3%, zirconia 1% - 1.5%, titanium dioxide 0.2% - 0.6%;

[0016] After pressure-forming the material of the target backing, sinter it at a temperature of 1000°C - 1350°C to form the target backing;

[0017] In the target backing, the sum of the content of phosphorus and the content of sulfur does not exceed 0.035%.

[0018] Optionally, making the groove gap of the welding groove a preset distance includes the following steps:

[0019] Obtain the plate thickness of the base metal to be welded;

[0020] When the plate thickness of the base metal to be welded is 6mm - 8mm, control the groove gap to be 4mm - 5mm;

[0021] When the plate thickness of the base metal to be welded is 9mm - 15mm, control the groove gap to be 5mm - 6mm;

[0022] When the plate thickness of the base metal to be welded is 16mm - 25mm, control the groove gap to be 6mm - 8mm.

[0023] Optionally, the step of determining the welding sequence according to the length of the weld seam includes: when the length of the weld seam is 1500 mm to 5000 mm, dividing the weld seam into a plurality of first welding segments, and welding the plurality of first welding segments by using the segmented backstep welding method.

[0024] Optionally, the step of determining the welding sequence according to the length of the weld seam includes: when the length of the weld seam is greater than 5000 mm, dividing the weld seam into a plurality of second welding segments, and welding the plurality of second welding segments by using the symmetric welding method centered on the midpoint.

[0025] Optionally, the welding position is a flat butt joint; the steps of adjusting the welding conditions include:

[0026] When the plate thickness of the base metal to be welded is 6 mm to 8 mm, controlling the welding current of the root pass welding to be 150 A to 160 A, the welding voltage to be 24 V to 25 V, and the welding speed to be 14 cm / min to 15 cm / min;

[0027] When the plate thickness of the base metal to be welded is 9 mm to 15 mm, controlling the welding current of the root pass welding to be 160 A to 170 A, the welding voltage to be 25 V to 26 V, and the welding speed to be 15 cm / min to 16 cm / min;

[0028] When the plate thickness of the base metal to be welded is 16 mm to 25 mm, controlling the welding current of the root pass welding to be 170 A to 180 A, the welding voltage to be 26 V to 27 V, and the welding speed to be 16 cm / min to 18 cm / min;

[0029] Controlling the interpass temperature during the welding process to not exceed 150°C.

[0030] Optionally, the welding position is a horizontal butt joint; the steps of adjusting the welding conditions include:

[0031] When the plate thickness of the base metal to be welded is 6 mm to 8 mm, controlling the welding current of the root pass welding to be 140 A to 150 A, the welding voltage to be 21 V to 22 V, and the welding speed to be 10 cm / min to 12 cm / min;

[0032] When the plate thickness of the base metal to be welded is 9 mm to 15 mm, controlling the welding current of the root pass welding to be 150 A to 160 A, the welding voltage to be 22 V to 23 V, and the welding speed to be 12 cm / min to 14 cm / min;

[0033] When the plate thickness of the base metal to be welded is 16 mm to 25 mm, controlling the welding current of the root pass welding to be 160 A to 170 A, the welding voltage to be 23 V to 24 V, and the welding speed to be 14 cm / min to 16 cm / min;

[0034] Control the interlayer temperature during welding to not exceed 100°C.

[0035] Optionally, the welding position is a vertical butt joint; the steps of adjusting the welding conditions include:

[0036] When the thickness of the base metal to be welded is 6 mm to 8 mm, control the welding current for the root pass to be 130 A to 140 A, the welding voltage to be 18 V to 19 V, and the welding speed to be 7 cm / min to 8 cm / min;

[0037] When the thickness of the base metal to be welded is 9 mm to 15 mm, control the welding current for the root pass to be 140 A to 150 A, the welding voltage to be 19 V to 20 V, and the welding speed to be 8 cm / min to 9 cm / min;

[0038] When the thickness of the base metal to be welded is 16 mm to 25 mm, control the welding current for the root pass to be 150 A to 160 A, the welding voltage to be 20 V to 21 V, and the welding speed to be 9 cm / min to 10 cm / min;

[0039] Control the interlayer temperature during welding to not exceed 150°C.

[0040] Optionally, the steps of controlling the thickness of the weld root pass to be a preset thickness include:

[0041] When the welding position is a flat butt joint and the thickness of the base metal to be welded is 6 mm to 8 mm, the thickness of the root pass is 3 mm to 3.5 mm; when the thickness of the base metal to be welded is 9 mm to 15 mm, the thickness of the root pass is 3.5 mm to 4 mm; when the thickness of the base metal to be welded is 16 mm to 25 mm, the thickness of the root pass is 4.5 mm to 5 mm;

[0042] When the welding position is a horizontal butt joint and the thickness of the base metal to be welded is 6 mm to 8 mm, the thickness of the root pass is 3 mm to 3.5 mm; when the thickness of the base metal to be welded is 9 mm to 15 mm, the thickness of the root pass is 3.5 mm to 4 mm; when the thickness of the base metal to be welded is 16 mm to 25 mm, the thickness of the root pass is 3.5 mm to 4 mm;

[0043] When the welding position is a vertical butt joint and the thickness of the base metal to be welded is 6 mm to 8 mm, the thickness of the root pass is 4 mm to 4.5 mm; when the thickness of the base metal to be welded is 9 mm to 15 mm, the thickness of the root pass is 4.5 mm to 5 mm; when the thickness of the base metal to be welded is 16 mm to 25 mm, the thickness of the root pass is 5.5 mm to 6 mm.

[0044] As described above, compared with the prior art, the welding method of the low-temperature nickel alloy steel provided by the present application has at least the following beneficial effects:

[0045] In the welding method of the low-temperature nickel steel provided by the present application, by selecting special target welding wires and target backing pads, the influence of harmful elements such as phosphorus, sulfur, and carbon in the target welding wires and target backing pads on the weld can be reduced, and the generation of root cracks can be reduced; by strictly controlling the welding sequence, welding conditions, and the thickness of the root pass during the welding process, it helps to reduce the welding stress during the welding process, further reduce the generation of root cracks, improve the welding quality and the first-pass welding qualification rate, reduce the rework cost, and improve the production efficiency and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0047] Figure 1 It shows a schematic flow chart of a welding method for low-temperature nickel steel provided by an embodiment of the present application.

[0048] Figure 2 It shows a schematic structural diagram of a welding groove formed by an embodiment of the present application.

[0049] Figure 3 It shows a schematic structural diagram of root cracks generated in the prior art provided by an embodiment of the present application.

[0050] Figure 4 It shows a schematic principle diagram of a segmented backstep welding method provided by an optional embodiment of the present application.

[0051] Figure 5 It shows a schematic principle diagram of a center-symmetric welding method provided by an optional embodiment of the present application.

[0052] Figure 6 It shows a schematic structural diagram of the front side of the root pass of the weld after welding provided by an optional embodiment of the present application.

[0053] Schematic illustration of reference numerals:

[0054] 11. Base metal to be welded; 12. Target backing pad; 13. Welding groove. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] To make the technical objectives, technical solutions, and technical effects of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. The components of the embodiments of this application usually described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0056] Therefore, the following detailed description of the embodiments of this application is not intended to limit the scope of this application that is claimed, but merely represents the selected embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0057] In the description of this application, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of this application.

[0058] In the description of this application, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. In addition, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of this application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0059] This embodiment provides a welding method for low-temperature nickel steel. Referring to Figure 1 and Figure 2 , it includes steps S1 to S6, specifically including:

[0060] S1. Obtain a target welding wire and a target backing 12;

[0061] S2. Form a single-sided groove on the side to be welded of the base metal 11 to be welded;

[0062] S3. Assemble the base metal 11 to be welded and the target backing 12 to form a welding groove 13, and make the groove gap of the welding groove 13 be a preset distance;

[0063] S4. Obtain the length of the weld seam, and determine the welding sequence according to the length of the weld seam;

[0064] S5. Adjust the welding conditions according to the plate thickness and welding position of the base metal 11 to be welded;

[0065] S6. Weld the welding groove 13 according to the determined welding sequence, and control the thickness of the weld root pass to be a preset thickness.

[0066] In the prior art, during the welding of cryogenic nickel steel used for building liquid tanks, welding cracks are extremely likely to appear in the weld root pass. Referring to Figure 3 , generally, the extension direction of the root pass crack is longitudinal, that is, the root pass crack extends along the length direction of the weld seam, and the root pass crack is located at the center of the weld seam and extends along the length direction of the weld seam. Figure 3 Shows the root pass crack that appears during the welding of X12Ni5 cryogenic nickel steel. The length of the root pass crack in the weld seam is generally between 2 mm and 10 mm, and it has a sharp notch and a large aspect ratio. The longitudinal cracks generated in the root pass weld with a ceramic backing are generally solidification cracks (crystalline cracks) in hot cracks. During the solidification and crystallization process of the weld seam, the metal that crystallizes first is relatively pure, and the later crystallized part has more impurities, which are enriched at the grain boundaries. The eutectics formed by these impurities all have lower melting points. The low-melting eutectics are excluded to the central part where the columnar crystals meet, forming a high-temperature liquid film. At this time, the root pass weld cools and shrinks rapidly and is subjected to tensile stress. The liquid film in the weld seam may be pulled apart under the action of the tensile stress, and there is no excess liquid metal in the surrounding area to fill the pulled position at this time, resulting in a finally left cracked trace, that is, a solidification root pass crack is formed.

[0067] In this embodiment, by selecting a special target welding wire and the target backing 12, the influence of harmful elements such as phosphorus, sulfur, and carbon on the weld seam can be reduced, and the generation of root pass cracks can be reduced; by controlling the groove gap, welding conditions, and welding sequence, and controlling the thickness of the root pass, the probability of root pass cracks occurring can be further reduced, and the generation of root pass cracks can be reduced. It can be seen that the welding method of this embodiment can effectively reduce or avoid root pass cracks in the weld root pass, improve the first-pass welding qualification rate, reduce the repair cost, and significantly improve the production efficiency and quality.

[0068] In step S1 of this embodiment, the target welding wire is a flux-cored welding wire, and the composition of the target welding wire at least includes carbon, silicon, manganese, sulfur, phosphorus, chromium, nickel, molybdenum, copper, and iron; and, in the composition of the target welding wire, the sum of the content of phosphorus and the content of sulfur does not exceed 0.015%, and the content of carbon does not exceed 0.12%, and the content of silicon does not exceed 0.4%.

[0069] Among the components of the target welding wire, carbon, sulfur, and phosphorus are the impurity elements that have the greatest impact on solidification cracks. In particular, phosphorus is extremely difficult to be discharged or reduced through the welding metallurgical reaction via the slag and basically remains entirely in the molten pool, thereby increasing the phosphorus content in the weld. Carbon can exacerbate the harmful effects of phosphorus and sulfur elements and is the main element affecting crystallization cracks in low-temperature nickel steel. By strictly controlling the contents of phosphorus, sulfur, and carbon, the generation of root pass cracks can be effectively reduced.

[0070] Manganese is provided in the components of the target welding wire. Manganese has a desulfurization effect, can replace iron sulfide with manganese sulfide, and change the film-like iron sulfide into spherical distribution, thereby improving the crack resistance of the weld. Refined grain element molybdenum is also provided in the components of the target welding wire, which helps to reduce the generation of root pass cracks.

[0071] Silicon is also provided in the components of the target welding wire. Silicon is a sulfur phase-forming element and is beneficial to eliminating crystallization cracks. However, when the content of silicon exceeds 0.4%, silicate inclusions are easily formed, reducing the mechanical properties of the weld. Therefore, by controlling the content of silicon, it helps to reduce the generation of root pass cracks while ensuring the mechanical properties of the weld.

[0072] Chromium and copper are also provided in the components of the target welding wire. The chromium element can increase the high-temperature oxidation resistance of the weld, help improve the mechanical properties of the weld, and also maintain good plasticity and toughness. The copper element helps to improve the corrosion resistance of the weld and can improve the strength and toughness of the weld.

[0073] In an alternative embodiment, the components of the target welding wire include the following components by mass percentage: 0.03% of carbon, 0.73 of silicon, 3.7% of manganese, 0.003% of sulfur, 0.011% of phosphorus, 18.8% of chromium, 13.7% of nickel, 2.4% of molybdenum, copper with a content less than 0.03%, and the remaining mass percentage of iron.

[0074] In step S1 of this embodiment, the sum of the phosphorus content and the sulfur content of the target backing 12 does not exceed 0.035%. Among the components of the target backing 12, carbon, sulfur, and phosphorus are the impurity elements that have the greatest impact on solidification cracks. By controlling the phosphorus content and the sulfur content in the target backing 12, the generation of root pass cracks can be effectively reduced. It should be noted that in this embodiment, "content" means mass ratio.

[0075] In an alternative embodiment, the material of the target gasket 12 comprises components in the following mass percentages: kaolin 85% - 90%, quartzite 5% - 8%, cryolite 2% - 3%, zirconia 1% - 1.5%, and titanium dioxide 0.2% - 0.6%. After subjecting the above material of the target substrate to pressure molding, sintering is performed at a temperature of 1000°C - 1350°C to form the target gasket 12. By selecting high-purity kaolin, quartzite, etc., the material uniformity and high quality are ensured, and the contents of phosphorus and sulfur elements are controlled from the source. During the molding process, the pressure and temperature are strictly controlled to reduce impurity elements such as phosphorus and sulfur. During the sintering process, by adjusting the sintering temperature and time, the release and volatilization of impurity elements such as phosphorus and sulfur are controlled, thereby effectively reducing the contents of phosphorus and sulfur in the target gasket 12 and reducing the occurrence of backing cracks.

[0076] In step S2, the base metal to be welded 11 can be, for example, low-temperature nickel steel X12Ni5. The plate thickness of the base metal to be welded 11 can be, for example, 6 mm - 25 mm. The root face value and the groove angle of the single-sided groove of the base metal to be welded 11 can be set according to actual needs.

[0077] In an alternative embodiment, in step S2, after forming a single-sided groove on the side of the base metal to be welded 11 to be welded, the following steps can further be included: cleaning the base metal to be welded 11. Optionally, the single-sided groove of the base metal to be welded 11 and the outer surface within 30 mm from the single-sided groove can be cleaned to remove oil stains, rust, scale, and other substances harmful to welding; further, a grinding wheel abrasive disc can be used for grinding and cleaning.

[0078] In step S3, the two base metals to be welded 11 are aligned to form a welding groove 13, and the target gasket 12 is placed below the welding groove 13 to complete the assembly of the base metal to be welded 11 and the target gasket 12.

[0079] In an alternative embodiment, performing step S3 to make the groove gap of the welding groove 13 be a preset distance includes the following steps: obtaining the plate thickness of the base material 11 to be welded; when the plate thickness of the base material 11 to be welded is 6 mm to 8 mm, controlling the groove gap to be 4 mm to 5 mm; when the plate thickness of the base material 11 to be welded is 9 mm to 15 mm, controlling the groove gap to be 5 mm to 6 mm; when the plate thickness of the base material 11 to be welded is 16 mm to 25 mm, controlling the groove gap to be 6 mm to 8 mm. In other words, the value of the preset distance is determined according to the plate thickness of the base material 11 to be welded. When the plate thicknesses of the base material 11 to be welded are 6 mm to 8 mm, 9 mm to 15 mm, and 16 mm to 25 mm respectively, the preset distances are 4 mm to 5 mm, 5 mm to 6 mm, and 6 mm to 8 mm respectively. Further, when the plate thickness of the base material 11 to be welded is 8 mm to 9 mm, the preset distance can be 5 mm, and when the plate thickness of the base material 11 to be welded is 15 mm to 16 mm, the preset distance can be 6 mm. According to the plate thickness of the base material 11 to be welded, strictly controlling the value of the groove gap can improve the weld quality, reduce the probability of root crack generation, and reduce the occurrence of root cracks.

[0080] In step S4, according to the obtained length of the weld, the welding sequence during the welding process is determined. When the length of the weld is small, welding can be directly performed along the welding direction. When the length of the weld is large, a segmented welding method can be used for welding. During the welding process, due to shrinkage and tensile stress during the solidification of the molten pool, the liquid film will be more likely to be pulled apart. By setting a reasonable welding sequence, the welding stress can be effectively reduced, the welding quality can be improved, and the generation of root cracks can be reduced.

[0081] In an alternative embodiment, performing step S4 to determine the welding sequence according to the length of the weld includes: when the length of the weld is 1500 mm to 5000 mm, dividing the weld into several first weld segments, and using the segmented backstep welding method to weld the several first weld segments; optionally, the length of each first weld segment is 600 mm to 700 mm. Among them, the segmented backstep welding method is a welding process in which the welding direction of each first weld segment is opposite to the growth direction of the entire weld; further, among the several first weld segments, for two consecutive first weld segments, the first weld segment located downstream in the welding direction can be welded first, and then the first weld segment located upstream in the welding direction can be welded. Figure 4 The schematic diagram of the principle of the segmented backstep welding method adopted by this application is shown. Figure 4 In it, the lower black lines represent two consecutive first weld segments, the welding direction is from left to right, the first weld segment marked ① is welded first, and then the first weld segment marked ② is welded.

[0082] In an alternative embodiment, when performing step S4, the step of determining the welding seam sequence according to the length of the welding seam includes: when the length of the welding seam is greater than 5000 mm, dividing the welding seam into a plurality of second welding segments, and welding the plurality of second welding segments by means of center-symmetric welding; optionally, the length of the second welding segment is 600 mm to 700 mm. Among them, center-symmetric welding is to first weld the second welding segment located in the middle position among three consecutive second welding segments, and then weld the second welding segments located at both ends; further, for three consecutive second welding segments, the second welding segment located in the middle position can be welded first, then the second welding segment located at the upstream end in the welding direction, and finally the second welding segment located at the downstream end in the welding direction. Figure 5 The schematic diagram of the principle of the center-symmetric welding method adopted in the present application is shown. Figure 5 In the figure, the black line below means three consecutive second welding segments, and the welding direction is from left to right. First, weld the second welding segment where label ① is located, then weld the second welding segment where label ② is located. Finally, weld the second welding segment where label ③ is located.

[0083] In step S5, corresponding to different welding positions and the base material 11 to be welded with different plate thicknesses, there are corresponding welding conditions. If the welding speed is too slow, the current or voltage is too large, thermal cracks will be caused. If the welding speed is too fast, the current or voltage is too small, the welding seam quality will be reduced. By setting appropriate welding conditions, it helps to reduce the generation of root cracks and improve the welding quality.

[0084] In an alternative embodiment, when the welding position is a flat butt joint, the steps of adjusting the welding conditions in step S5 include: when the plate thickness of the base material 11 to be welded is 6 mm to 8 mm, controlling the welding current of the root pass welding to be 150 A to 160 A, the welding voltage to be 24 V to 25 V, and the welding speed to be 14 cm / min to 15 cm / min; when the plate thickness of the base material 11 to be welded is 9 mm to 15 mm, controlling the welding current of the root pass welding to be 160 A to 170 A, the welding voltage to be 25 V to 26 V, and the welding speed to be 15 cm / min to 16 cm / min; when the plate thickness of the base material 11 to be welded is 16 mm to 25 mm, controlling the welding current of the root pass welding to be 170 A to 180 A, the welding voltage to be 26 V to 27 V, and the welding speed to be 16 cm / min to 18 cm / min; controlling the interpass temperature during the welding process to not exceed 150 °C. In addition, during the welding process, the welding slag between layers should be cleaned in time, and when there are no defects in the welding, the next layer should be welded in time.

[0085] In an optional embodiment, the welding position is horizontal butt joint, and the step of adjusting the welding conditions in step S5 includes: when the plate thickness of the base material 11 to be welded is 6mm~8mm, the welding current of the base welding is controlled to be 140A~150A, the welding voltage is 21V~22V, and the welding speed is 10cm / min~12cm / min; when the plate thickness of the base material 11 to be welded is 9mm~15mm, the welding current of the base welding is controlled to be 150A~160A, the welding voltage is 22V~23V, and the welding speed is 12cm / min~14cm / min; when the plate thickness of the base material 11 to be welded is 16mm~25mm, the welding current of the base welding is controlled to be 160A~170A, the welding voltage is 23V~24V, and the welding speed is 14cm / min~16cm / min; the interlayer temperature during the welding process is controlled not to exceed 100℃. Due to the fast cooling speed of the horizontal butt weld, the temperature gradient generated in the heat-affected zone of the weld is large, which makes welding cracks more likely to occur. Therefore, the interlayer temperature during the welding process needs to be controlled to no more than 100°C to reduce the occurrence of base cracks.

[0086] In an optional embodiment, the welding position is vertical butt joint, and the step of adjusting the welding condition in step S5 includes: when the plate thickness of the base material 11 to be welded is 6mm-8mm, the welding current of the base welding is controlled to be 130A-140A, the welding voltage is 18V-19V, and the welding speed is 7cm / min-8cm / min; when the plate thickness of the base material 11 to be welded is 9mm-15mm, the welding current of the base welding is controlled to be 140A-150A, the welding voltage is 19V-20V, and the welding speed is 8cm / min-9cm / min; when the plate thickness of the base material 11 to be welded is 16mm-25mm, the welding current of the base welding is controlled to be 150A-160A, the welding voltage is 20V-21V, and the welding speed is 9cm / min-10cm / min; the interlayer temperature during welding is controlled to be no more than 150°C. After the base layer welding is completed, the welding slag between the layers is cleaned up in time, and when there is no defect in the welding, the next layer is welded in time.

[0087] In step S6, according to the determined welding sequence and the adjusted welding conditions, the welding groove 13 is welded using the welding equipment and the target welding wire. During the welding process, the thickness of the weld base layer is controlled to be a preset thickness. Among them, the current polarity of the welding equipment is reverse direct current, and the value of the preset thickness can be specifically set according to the welding position and the plate thickness of the base material 11 to be welded. By strictly controlling the thickness of the weld base layer during the welding process, it is helpful to improve the welding quality and reduce the occurrence of base cracks.

[0088] In an alternative embodiment, the welding position is a flat butt joint. When performing step S6, the steps of controlling the thickness of the root pass of the weld seam to a preset thickness include: when the plate thickness of the base metal 11 to be welded is 6 mm to 8 mm, the thickness of the root pass is 3 mm to 3.5 mm; when the plate thickness of the base metal 11 to be welded is 9 mm to 15 mm, the thickness of the root pass is 3.5 mm to 4 mm; when the plate thickness of the base metal 11 to be welded is 16 mm to 25 mm, the thickness of the root pass is 4.5 mm to 5 mm. That is, when the plate thicknesses of the base metal 11 to be welded are 6 mm to 8 mm, 9 mm to 15 mm, and 16 mm to 25 mm respectively, the corresponding preset thicknesses are 3 mm to 3.5 mm, 3.5 mm to 4 mm, and 4.5 mm to 5 mm respectively. When the plate thickness of the base metal 11 to be welded is 8 mm to 9 mm, the preset thickness is 3.5 mm; when the plate thickness of the base metal 11 to be welded is 15 mm to 16 mm, the preset thickness is 4 mm to 4.5 mm.

[0089] In an alternative embodiment, the welding position is a transverse butt joint. When performing step S6, the steps of controlling the thickness of the root pass of the weld seam to a preset thickness include: when the plate thickness of the base metal 11 to be welded is 6 mm to 8 mm, the thickness of the root pass is 3 mm to 3.5 mm; when the plate thickness of the base metal 11 to be welded is 9 mm to 15 mm, the thickness of the root pass is 3.5 mm to 4 mm; when the plate thickness of the base metal 11 to be welded is 16 mm to 25 mm, the thickness of the root pass is 3.5 mm to 4 mm. That is, when the plate thicknesses of the base metal 11 to be welded are 6 mm to 8 mm and 9 mm to 25 mm respectively, the corresponding preset thicknesses are 3 mm to 3.5 mm and 3.5 mm to 4 mm respectively. When the plate thickness of the base metal 11 to be welded is 8 mm to 9 mm, the preset thickness is 3.5 mm.

[0090] In an alternative embodiment, the welding position is a vertical butt joint. When performing step S6, the steps of controlling the thickness of the root pass of the weld seam to a preset thickness include: when the plate thickness of the base metal 11 to be welded is 6 mm to 8 mm, the thickness of the root pass is 4 mm to 4.5 mm; when the plate thickness of the base metal 11 to be welded is 9 mm to 15 mm, the thickness of the root pass is 4.5 mm to 5 mm; when the plate thickness of the base metal 11 to be welded is 16 mm to 25 mm, the thickness of the root pass is 5.5 mm to 6 mm. That is, when the plate thicknesses of the base metal 11 to be welded are 6 mm to 8 mm, 9 mm to 15 mm, and 16 mm to 25 mm respectively, the corresponding preset thicknesses are 4 mm to 4.5 mm, 4.5 mm to 5 mm, and 5.5 mm to 6 mm respectively. When the plate thickness of the base metal 11 to be welded is 8 mm to 9 mm, the preset thickness is 4.5 mm; when the plate thickness of the base metal 11 to be welded is 15 mm to 16 mm, the preset thickness is 5 mm to 5.5 mm.

[0091] In this embodiment, according to the determined welding sequence, the root pass welding is carried out on the welding groove 13 under the adjusted welding conditions by using the welding setup to form the root layer of the weld. Optionally, in step S6 of this embodiment, the welding of the welding groove 13 may further include the following steps: after the root layer is welded, the working conditions of the welding equipment are adjusted, and the filler pass welding and capping welding are carried out on the welding groove 13 to form the filler layer and the capping layer. Further, the shielding gas used during the welding process of the welding equipment is carbon dioxide.

[0092] In an alternative embodiment, the base metal 11 to be welded is a low-temperature nickel steel. After the welding of the base metal 11 to be welded is completed by using the welding method of this embodiment, the following steps are further included: non-destructive testing is carried out on the weld to judge the quality of the weld. Specifically, the weld obtained by welding can be respectively subjected to penetrant testing, ultrasonic testing, and radiographic testing. Figure 6 The structure of the front side of the root layer of the weld obtained by using the welding method of the present application is shown. The results show that the formed weld after welding is in good shape, the overall appearance is flat and smooth, and the test results can all meet the qualified grades of penetrant testing, ultrasonic testing, and radiographic testing.

[0093] In summary, for the welding method of low-temperature nickel steel provided in this embodiment, by selecting the special target welding wire and the target backing 12, the influence of harmful elements such as phosphorus, sulfur, and carbon therein on the weld can be reduced, and the generation of root cracks can be reduced; the target welding wire is provided with components such as manganese, silicon, chromium, and copper, which can improve the crack resistance of the weld, enhance the high-temperature oxidation resistance and corrosion resistance of the weld, improve the plasticity, toughness, and strength of the weld, and reduce the generation of root cracks while ensuring the mechanical properties of the weld; by strictly controlling the welding sequence, welding conditions, and the thickness of the root layer during the welding process, it helps to reduce the welding stress during the welding process, further reduce the generation of root cracks, and improve the welding quality. The welding method of this embodiment effectively improves the root cracks in welding, increases the first-pass welding qualification rate, reduces the repair cost, and significantly improves the production efficiency and product quality.

[0094] The above embodiments are only illustrative of the principles and effects of the present application and are not used to limit the present application. Any person familiar with this technology can modify, change, or combine the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present application should still be covered by the claims of the present application.

Claims

1. A welding method for low temperature nickel steel, characterized in that: The following steps are involved: obtaining a target welding wire and a target backing pad; A single-sided groove is formed on the side to be welded of the parent material to be welded; Assembling the base material to be welded and the target backing to form a welding groove, and making the groove gap of the welding groove a preset distance; Obtaining the length of the weld, and determining the welding sequence according to the length of the weld; Adjust the welding conditions according to the plate thickness and welding position of the base material to be welded; According to the determined welding sequence, the welding groove is welded, and the thickness of the weld base layer is controlled to be a preset thickness.

2. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The target welding wire is a flux-cored welding wire, and the components of the target welding wire at least include carbon, silicon, manganese, sulfur, phosphorus, chromium, nickel, molybdenum, copper and iron; In the composition of the target welding wire, the sum of the phosphorus content and the sulfur content does not exceed 0.015%, the carbon content does not exceed 0.12%, and the silicon content does not exceed 0.4%.

3. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The target liner is made of the following components in percentage by mass: 85% to 90% kaolin, 5% to 8% quartz, 2% to 3% cryolite, 1% to 1.5% zirconium oxide, and 0.2% to 0.6% titanium dioxide; After press-forming the material of the target liner, sintering at a temperature of 1000° C. to 1350° C. to form the target liner; In the target gasket, the sum of the phosphorus content and the sulfur content does not exceed 0.035%.

4. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The groove gap of the welding groove is set to a preset distance, comprising the following steps: Obtaining the plate thickness of the base material to be welded; When the thickness of the base material to be welded is 6 mm to 8 mm, the groove gap is controlled to be 4 mm to 5 mm; When the thickness of the base material to be welded is 9 mm to 15 mm, the groove gap is controlled to be 5 mm to 6 mm; When the plate thickness of the base material to be welded is 16 mm to 25 mm, the groove gap is controlled to be 6 mm to 8 mm.

5. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The step of determining the welding sequence according to the length of the weld includes: when the length of the weld is 1500 mm to 5000 mm, dividing the weld into a plurality of first weld sections, and welding the plurality of first weld sections by using a segmented back-welding method.

6. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The step of determining the welding sequence according to the length of the weld includes: when the length of the weld is greater than 5000 mm, dividing the weld into a plurality of second weld segments, and welding the plurality of second weld segments by means of symmetrical welding.

7. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The welding position is flat butt joint; The steps to adjust the welding conditions include: When the thickness of the base material to be welded is 6 mm to 8 mm, the welding current of the base welding is controlled to be 150 A to 160 A, the welding voltage is 24 V to 25 V, and the welding speed is 14 cm / min to 15 cm / min; When the thickness of the base material to be welded is 9 mm to 15 mm, the welding current of the base welding is controlled to be 160 A to 170 A, the welding voltage is 25 V to 26 V, and the welding speed is 15 cm / min to 16 cm / min; When the thickness of the base material to be welded is 16 mm to 25 mm, the welding current of the base welding is controlled to be 170 A to 180 A, the welding voltage is 26 V to 27 V, and the welding speed is 16 cm / min to 18 cm / min; The interlayer temperature during welding was controlled to not exceed 150°C.

8. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The welding position is horizontal butt joint; The steps to adjust the welding conditions include: When the thickness of the base material to be welded is 6 mm to 8 mm, the welding current of the base welding is controlled to be 140 A to 150 A, the welding voltage is 21 V to 22 V, and the welding speed is 10 cm / min to 12 cm / min; When the thickness of the base material to be welded is 9 mm to 15 mm, the welding current of the base welding is controlled to be 150 A to 160 A, the welding voltage is 22 V to 23 V, and the welding speed is 12 cm / min to 14 cm / min; When the thickness of the base material to be welded is 16 mm to 25 mm, the welding current of the base welding is controlled to be 160 A to 170 A, the welding voltage is 23 V to 24 V, and the welding speed is 14 cm / min to 16 cm / min; The interlayer temperature during welding was controlled to not exceed 100°C.

9. The welding method of low temperature nickel alloy steel according to claim 1, characterized in that: The welding position is vertical butt joint; The steps to adjust the welding conditions include: When the thickness of the base material to be welded is 6 mm to 8 mm, the welding current of the base welding is controlled to be 130 A to 140 A, the welding voltage is 18 V to 19 V, and the welding speed is 7 cm / min to 8 cm / min; When the thickness of the base material to be welded is 9 mm to 15 mm, the welding current of the base welding is controlled to be 140 A to 150 A, the welding voltage is 19 V to 20 V, and the welding speed is 8 cm / min to 9 cm / min; When the thickness of the base material to be welded is 16 mm to 25 mm, the welding current of the base welding is controlled to be 150 A to 160 A, the welding voltage is 20 V to 21 V, and the welding speed is 9 cm / min to 10 cm / min; The interlayer temperature during welding was controlled to not exceed 150°C.

10. The welding method of low temperature nickel alloy steel according to claim 9, characterized in that: The steps of controlling the thickness of the weld base layer to a preset thickness include: When the welding position is flat butt, when the plate thickness of the base material to be welded is 6mm-8mm, the thickness of the base layer is 3mm-3.5mm; when the plate thickness of the base material to be welded is 9mm-15mm, the thickness of the base layer is 3.5mm-4mm; when the plate thickness of the base material to be welded is 16mm-25mm, the thickness of the base layer is 4.5mm-5mm; When the welding position is horizontal butt joint, when the plate thickness of the base material to be welded is 6mm-8mm, the thickness of the base layer is 3mm-3.5mm; when the plate thickness of the base material to be welded is 9mm-15mm, the thickness of the base layer is 3.5mm-4mm; when the plate thickness of the base material to be welded is 16mm-25mm, the thickness of the base layer is 3.5mm-4mm; When the welding position is vertical butt welding, when the plate thickness of the parent material to be welded is 6mm~8mm, the thickness of the base layer is 4mm~4.5mm, when the plate thickness of the parent material to be welded is 9mm~15mm, the thickness of the base layer is 4.5mm~5mm, and when the plate thickness of the parent material to be welded is 16mm~25mm, the thickness of the base layer is 5.5mm~6mm.

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