Welding method for optimizing welding seam structure of nickel-based alloy composite plate

Abstract

The invention discloses a welding method for optimizing a welding seam structure of a nickel-based alloy composite board. The nickel-based alloy composite board comprises a base material layer and a nickel-based alloy composite material layer, and a transition layer is arranged at the bonding interface of the base material layer and the nickel-based alloy composite material layer; the welding method comprises the steps that a trapezoidal groove is machined in the position, corresponding to the base material layer, of the welding section of the nickel-based alloy composite board; a U-shaped groove is machined in the position, corresponding to the transition layer, of the welding section of the nickel base alloy; a groove is not machined in the position, corresponding to the nickel-based alloy composite material layer, of the welding section of the nickel-based alloy composite plate, and a truncated edge is reserved; welding the nickel-based alloy composite material layer by adopting single tungsten electrode argon arc welding; welding the transition layer by adopting single tungsten electrode argon arc welding; and welding the base material layer by adopting single tungsten electrode argon arc welding.

Description

Technical Field

[0001] The invention relates to a welding method, in particular to a welding method for a composite plate. Background Art

[0002] Nickel-based alloy clad plate is a metal composite structural material with both corrosion resistance and good mechanical properties. Since its parent material has two component metals, its connection process requires multi-layer and multi-pass welding, that is, the clad plate weld is divided into three layers: the nickel-based alloy weld of the clad material layer, the transition layer weld, and the carbon steel weld of the base material layer.

[0003] In the manufacturing conditions of some composite plate components, due to limited operating space, the welding sequence of composite layer-transition layer-base material layer must be adopted. Since the content of Cr and Ni alloy elements in nickel-based alloys is very high, if conventional welding processes are used in this welding sequence, the carbon steel weld adjacent to the transition layer can easily melt into excessive alloy elements and produce martensite structure, which will correspondingly become hard and brittle, greatly reducing the mechanical properties of the joint.

[0004] At present, the existing technology has adopted a solution to this problem that occurs during the welding process of bimetallic composite plates, which is to use corrosion-resistant alloy welding materials for the entire weld. For example, the national standard "Technical Requirements for Welding of Stainless Steel Composite Plates" (GB / T 13148-2008) explains the welding of composite plates under this welding sequence. At this time, the welding of the base material layer weld should use corrosion-resistant alloy welding wires with performance matching that of the composite layer.

[0005] However, there are several disadvantages to using this method for nickel-based alloy composite plates. First, the material cost of nickel-based alloys is often several times that of stainless steel. After significantly increasing the amount of nickel-based alloy filler metal, the welding efficiency will be reduced while the welding cost will be greatly increased; second, the yield strength of nickel-based alloys is lower than that of carbon steel. If nickel-based alloy welding materials are used to fill the entire weld, the yield strength of the joint will also decrease, increasing the risk of failure of the nickel-based alloy composite plate joint when subjected to large loads.

[0006] In addition, a Chinese patent document with publication number CN112122783A, publication date December 25, 2020, and titled "A method for laser butt welding of carbon steel-nickel alloy composite plates" proposes using laser self-melting or wire welding to achieve the connection of composite layers under conditions where construction space is limited and the composite layer must be welded first. However, it focuses on the problem that the composite plate cannot be welded on one side under this welding sequence, and does not pay attention to the performance changes of the mixed weld of nickel-based alloy and carbon steel.

[0007] In addition, a Chinese patent document with publication number CN113042895B, publication date April 26, 2022, and titled “A welding method for a nickel-steel composite structure” proposes that when the composite layer is welded first, laser autogenous welding is also used to complete the connection of the composite layer, and then cold metal transition welding is used to weld the adjacent welds, thereby completing the connection of the nickel-based alloy composite plate under this welding sequence. However, it mainly targets the problem of decreased corrosion resistance of the composite layer caused by element migration at the interface between the composite layer and the substrate layer, and also does not solve the problem of decreased toughness of the mixed weld of nickel-based alloy and carbon steel.

[0008] In addition, the above methods all use laser self-melting or wire-filling welding when welding composite plates. Such welding methods require very high assembly accuracy of components, and the equipment is expensive, the operation is cumbersome, and the maintenance is difficult. Summary of the invention

[0009] The object of the present invention is to provide a welding method for optimizing the weld structure of a nickel-based alloy composite plate. The method is based on the welding sequence of composite layer-transition layer-base material layer, adopts the common tungsten inert gas arc welding method, and through the groove design, can effectively reduce the excessive melting of alloying elements of the nickel-based alloy into the first layer weld of the base material layer, thereby effectively controlling the dilution rate of the layer weld, improving the microstructure, and realizing reliable connection of the composite plate.

[0010] In order to achieve the above object, the present invention provides a welding method for optimizing the weld structure of a nickel-based alloy composite plate, wherein the nickel-based alloy composite plate comprises a substrate layer and a nickel-based alloy composite layer, and a transition layer is provided at the bonding interface between the substrate layer and the nickel-based alloy composite layer; the welding method comprises the steps of:

[0011] A trapezoidal groove is processed at the position corresponding to the base material layer on the welding section of the nickel-based alloy composite plate; a U-shaped groove is processed at the position corresponding to the transition layer on the welding section of the nickel-based alloy; no groove is processed at the position corresponding to the nickel-based alloy composite material layer on the welding section of the nickel-based alloy composite plate, and a blunt edge is retained;

[0012] The nickel-based alloy composite layer is welded by single tungsten-arc argon welding;

[0013] The transition layer is welded by single tungsten-arc argon welding;

[0014] The base material layer is welded by single tungsten inert gas arc welding.

[0015] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, the angle α between the inclined portion of the trapezoidal groove and the vertical direction is 15-25°.

[0016] In this embodiment, in order to take into account both the operability and the filling efficiency of the argon arc welding torch, the angle α between the inclined portion of the trapezoidal groove and the vertical direction can be controlled to be between 15° and 25°.

[0017] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, the single-side width of the step of the trapezoidal groove w1≥2(w2+2r) / 3, where w2 represents the assembly gap, r represents the radius of the transition arc of the U-shaped groove, and the unit parameters are all mm.

[0018] In this embodiment, the single-side width of the step of the trapezoidal groove can be controlled to be w1≥2(w2+2r) / 3, so as to ensure that the ratio of the width of the first layer weld of the subsequent base material layer in direct contact with the transition layer to its melt width is less than 35%, which will help to control the low dilution rate of each weld in this layer.

[0019] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, the distance b4 between the step of the trapezoidal groove and the bonding interface between the substrate layer and the nickel-based alloy composite layer is 0.5-1.5 mm.

[0020] In this embodiment, in order to coordinate the shaping control of the first layer of the weld bead of the substrate layer, a step may be processed in the weld of the substrate layer. In order to ensure that the weld bead of this layer is in direct contact with the parent material of the composite material layer during welding, the distance b4 between the step of the trapezoidal groove and the bonding interface between the substrate layer and the nickel-based alloy composite material layer may be controlled to be between 0.5 and 1.5 mm.

[0021] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, the thickness b3 of the blunt edge is 0.5-2 mm.

[0022] In this embodiment, in order to facilitate the single-sided welding and double-sided forming of the nickel-based alloy weld of the composite layer, the position corresponding to the nickel-based alloy composite layer on the welding section of the nickel-based alloy composite plate may not be processed with a groove, but a blunt edge may be retained. The blunt edge thickness b3 may be controlled within the range of 0.5-2 mm.

[0023] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, the assembly gap w2 is 1-3 mm.

[0024] In this embodiment, the welding construction can be facilitated by controlling the assembly gap w2 to be between 1-3 mm.

[0025] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, the radius of the transition arc of the U-shaped groove r = (b2-b3) / 2, where b2 represents the distance from the surface of the nickel-based alloy composite layer to the bonding interface between it and the substrate layer, and b3 is the thickness of the blunt edge, and the unit parameters are all mm.

[0026] In this embodiment, due to the poor fluidity of the molten pool of nickel-based alloys, in order to ensure good forming and avoid unfused defects at the bottom of the molten pool, the bottom position of the transition layer weld can be processed into a U-shaped groove, and the radius of the transition arc of the U-shaped groove is controlled to be r = (b2-b3) / 2.

[0027] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, in the step of welding the nickel-based alloy composite layer by single tungsten electrode argon arc welding: the shielding gas adopts pure argon gas (purity not less than 99%), and a nickel-based alloy solid welding wire matching the nickel-based alloy composite layer is used, the welding voltage is controlled to be 10-13V, the welding current is 80-110A, the welding speed is 80-110mm / min, and the wire feeding speed is 0.3-0.8m / min.

[0028] In this embodiment, by adopting the above process, it is possible to ensure that the weld bead on the composite material layer side has a sufficiently good welding formation under the premise of single-sided operation on the substrate layer side.

[0029] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, in the step of welding the transition layer using single tungsten electrode argon arc welding: the shielding gas uses pure argon (purity not less than 99%), and a nickel-based alloy solid welding wire matching the nickel-based alloy composite layer is used, the welding voltage is controlled to be 9-13V, the welding current is 80-130A, the welding speed is 100-120mm / min, and the wire feeding speed is 0.6-1.0m / min.

[0030] In this embodiment, the above process can ensure that the transition layer weld is well fused with the composite layer weld and the parent material, and the surface has good welding forming. The flat surface to be welded will be beneficial to the forming control of the subsequent substrate layer carbon steel weld, especially the first layer weld of the substrate layer.

[0031] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, in the step of welding the substrate layer by single tungsten electrode argon arc welding:

[0032] First, the first weld of the base material layer in direct contact with the transition layer is welded: the shielding gas is argon + CO2 mixed gas, and the flux-cored wire matching the base material layer is used;

[0033] Complete the welding of other welds of the base material layer: the shielding gas adopts pure argon gas (purity not less than 99%), and uses a carbon steel solid welding wire that matches the base material layer.

[0034] Further, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, when welding the first layer of the weld of the substrate layer: it is divided into three passes, and the welding order is to weld the welds on both sides first, and then weld the middle weld. When the welds on both sides are welded, the distance between the center of the welding gun and the step edge of the trapezoidal groove in the width direction is controlled to be (w1+2((w2+2r) / 3) / 2 during each welding, wherein w1 represents the single-side width of the step of the trapezoidal groove, w2 represents the assembly gap, and r represents the radius of the transition arc of the U-shaped groove, and the unit parameters are all mm. In this embodiment, the overlap rate of each weld and the transition layer weld can be controlled to be 33%.

[0035] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, when welding the first layer of the weld of the substrate layer: the welding voltage is controlled to be 14-16V, the welding current is 150-180A, the welding speed is 120-150mm / min, and the wire feeding speed is 2.7-3.0m / min.

[0036] In this embodiment, the transition layer weld obtained by the groove design and the aforementioned weld optimization process can ensure that the dilution level of the carbon steel weld layer relative to the composite material layer weld is less than 3.0%, thereby preventing the structure of the weld layer from being transformed into martensite as a whole and still maintaining good plasticity and toughness.

[0037] Furthermore, in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention, when welding other welds of the substrate layer: the welding voltage is controlled to be 14-16V, the welding current is 250-280A, the welding speed is 150-180mm / min, and the wire feeding speed is 2.6-3.0m / min.

[0038] The welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention has the following advantages and beneficial effects compared with the prior art:

[0039] The welding method of the present invention can effectively control the dilution rate level of the first layer of carbon steel weld that is in direct contact with the transition layer weld, avoid the hard-brittle transition of the entire structure, and achieve reliable connection of the composite plate joint.

[0040] In addition, compared with the prior art solution that requires the use of all-nickel-based alloy welding materials in this welding scenario, the welding method described in the present invention improves the structural strength of the joint, greatly reduces the welding cost, improves the welding efficiency, and improves the economic benefits.

[0041] In addition, the welding method of the present invention requires simple equipment, low assembly precision, convenient operation, and good scalability on engineering sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The groove schematic diagram used in the welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention is schematically shown.

[0043] Figure 2 The microstructure photograph of the first layer weld interface of the transition layer / carbon steel substrate layer in the weld joint using the optimized nickel-based alloy composite plate weld structure of Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0044] The welding method for optimizing the weld structure of the nickel-based alloy composite plate described in the present invention will be further explained and illustrated in conjunction with specific embodiments and drawings of the specification. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0045] Figure 1 Shows two spliced ​​nickel-based alloy composite plates A and B. Figure 1 The dotted line O in the figure represents a joint. The nickel-based alloy composite plate comprises a carbon steel substrate layer 1 and a nickel-based alloy composite material layer 2, and a transition layer is provided at the bonding interface between the carbon steel substrate layer 1 and the nickel-based alloy composite material layer 2. Figure 1 The symbol "b1" represents the distance between the surface of the carbon steel substrate layer and the bonding interface between it and the nickel-based alloy composite layer, and the symbol "b2" represents the distance between the surface of the nickel-based alloy composite layer and the bonding interface between it and the carbon steel substrate layer.

[0046] In a specific embodiment, a nickel-based alloy composite plate with the grade of Incoloy825 / X52 can be used, that is, the base material is X52, and the nickel-based alloy composite material is Incoloy825. The thickness of the nickel-based alloy composite plate is 13 mm, wherein b1 of the nickel-based alloy composite plate is 10 mm, and b2 is 3 mm.

[0047] In some embodiments, an optimized welding method for nickel-based alloy clad plates may include the steps of:

[0048] 100: Processing at the welding position of two spliced ​​nickel-based alloy composite plates A and B as follows Figure 1 The groove shown. Wherein, a trapezoidal groove is processed at a position corresponding to the carbon steel substrate layer on the welding cross section of the nickel-based alloy composite plate, and the trapezoidal groove includes an inclined portion 7 and a step 8 of the trapezoidal groove arranged in sequence, wherein the single-side width of the step 8 of the trapezoidal groove is represented by w1. In some more specific embodiments, the single-side width w1 of the step 8 of the trapezoidal groove is ≥2(w2+2r) / 3.

[0049] By controlling the single-side width w1 of the step of the trapezoidal groove, it can be ensured that the ratio of the width of the first layer of weld bead of the subsequent base material layer in direct contact with the transition layer to its molten width is less than 35%, which will help control the low dilution rate of each weld bead in this layer.

[0050] The distance between the plane of the step 8 of the trapezoidal groove and the bonding interface between the substrate layer and the nickel-based alloy composite layer is Figure 1 In some more specific embodiments, the distance b4 between the plane of the step 8 of the trapezoidal groove and the bonding interface between the substrate layer and the nickel-based alloy composite layer can be controlled to be between 0.5 and 1.5 mm.

[0051] By controlling the distance between the step 8 plane of the trapezoidal groove and the bonding interface between the substrate layer and the nickel-based alloy clad layer, the first layer of the weld bead of the substrate layer can be formed in coordination with the formation of the first layer of the weld bead and the direct contact of the weld bead with the clad layer parent material can be ensured during welding.

[0052] In some more specific embodiments, the angle α between the inclined portion of the trapezoidal groove and the vertical direction can be controlled to be between 15° and 25°, which will help to balance the operability and filling efficiency of the argon arc welding torch.

[0053] A U-shaped groove is formed at the position corresponding to the transition layer and the nickel-based alloy composite material layer on the welding section of the nickel-based alloy composite plate, and the U-shaped groove has a transition arc 9, and r represents the radius of the transition arc of the U-shaped groove. In some more specific embodiments, due to the poor fluidity of the molten pool of the nickel-based alloy, in order to ensure good forming and avoid the defect of unfused bottom of the molten pool, the radius of the transition arc of the U-shaped groove can be controlled to r=(b2-b3) / 2.

[0054] The position corresponding to the nickel-based alloy composite material layer on the welding section of the nickel-based alloy composite plate is not processed with a groove, and a blunt edge of 10 is retained. The thickness of the blunt edge is Figure 1 In some more specific embodiments, the blunt edge thickness b3 can be controlled within the range of 0.5-2 mm, which can facilitate single-sided welding and double-sided forming of the nickel-based alloy weld of the composite material layer.

[0055] Assembly clearance Figure 1 In some more specific embodiments, the assembly gap w2 may be 1-3 mm, which may facilitate welding construction.

[0056] 200: The nickel-based alloy composite layer 2 is welded by single tungsten electrode argon arc welding to obtain a composite layer weld 3. The welding shielding gas adopts pure argon gas with a purity of not less than 99%, and the welding uses a nickel-based alloy solid welding wire that matches the nickel-based alloy composite layer; the welding process parameters can be controlled as follows: the welding voltage is controlled to be 10-13V, the welding current is 80-110A, the welding speed is 80-110mm / min, and the wire feeding speed is 0.3-0.8m / min.

[0057] By adopting the above welding process, it is possible to ensure that the weld bead on the surface of the composite material layer has a sufficiently good welding formation under the premise of single-sided operation on the substrate layer side.

[0058] 300: The transition layer is welded by single tungsten electrode argon arc welding to obtain a transition layer weld 4. During welding, the shielding gas is pure argon gas with a purity of not less than 99%, and the welding material is a nickel-based alloy solid welding wire that matches the nickel-based alloy composite layer; the welding process parameters can be controlled as follows: welding voltage is 9-13V, welding current is 80-130A, welding speed is 100-120mm / min, and wire feeding speed is 0.6-1.0m / min.

[0059] By adopting the above welding process, it can be ensured that the transition layer weld is well fused with the composite layer weld and the parent material, and the surface has good welding forming. The flat welding surface will be conducive to the forming control of the subsequent base material layer carbon steel weld, especially the first layer weld of the base material layer.

[0060] 400: Single tungsten inert gas arc welding is used to weld the base material layer, where:

[0061] First, the first weld bead 5 in contact with the transition layer is welded: this layer is welded in three passes, and the welding sequence is to weld the two side welds first and then the middle weld. The shielding gas is argon + CO2 mixed gas, such as 78% Ar + 18% CO2, and the welding material is a flux-cored wire that matches the carbon steel substrate layer.

[0062] Then, the welding of other welds 6 of the base material layer is completed: the shielding gas is pure argon gas with a purity of not less than 99%, and the welding wire is a carbon steel solid welding wire matching the carbon steel base material layer.

[0063] In some more specific embodiments, when welding the first layer of weld bead 5 , the welding voltage can be controlled to be 14-16V, the welding current to be 150-180A, the welding speed to be 120-150mm / min, and the wire feeding speed to be 2.7-3.0m / min.

[0064] In addition, in some more specific embodiments, when welding the first layer of weld 5: the distance between the center of the welding gun and the step edge of the trapezoidal groove can be controlled to be (w1+2((w2+2r) / 3) / 2. In this embodiment, the overlap rate of each weld seam and the transition layer weld can be controlled to be 33%.

[0065] In the above-mentioned embodiment, the transition layer weld obtained by the groove design and the aforementioned weld optimization process can ensure that the dilution level of the carbon steel weld layer relative to the composite material layer weld is less than 3.0%, thereby preventing the structure of the weld layer from being transformed into martensite as a whole and still maintaining good plasticity and toughness.

[0066] In some more specific embodiments, when welding other welds 6 of the carbon steel substrate layer, the welding voltage can be controlled to be 14-16V, the welding current to be 250-280A, the welding speed to be 150-180mm / min, and the wire feeding speed to be 2.6-3.0m / min.

[0067] In order to further reflect the technical effects of the preferred implementation of this case, Table 1 lists the characteristic parameters of the grooves used in the preferred embodiments 1-5 of the present invention.

[0068] Table 1.

[0069]

[0070] Table 2 lists the welding process parameters used in the steps of forming the nickel-based alloy composite layer weld in preferred embodiments 1-5 of the present invention.

[0071] Table 2.

[0072]

[0073] Table 3 lists the welding process parameters used in the steps of forming the transition layer weld in preferred embodiments 1-5 of the present invention.

[0074] Table 3.

[0075]

[0076] Table 4 lists the welding process parameters used in the steps of forming the first weld bead of the carbon steel substrate layer in preferred embodiments 1-5 of the present invention.

[0077] Table 4.

[0078]

[0079] Table 5 lists the welding process parameters used in the steps of forming other welds of the carbon steel substrate layer in preferred embodiments 1-5 of the present invention.

[0080] Table 5.

[0081]

[0082] In addition, in order to prove the implementation effect of the preferred embodiment, Table 6 lists the Cr element content of each layer of the base material and the weld in the welded joint of the nickel-based alloy composite plate obtained by welding in Example 1 of the present invention, and the dilution rate of the first layer of carbon steel weld 5 directly in contact with the transition layer is calculated to be 1.81%. Therefore, the martensitic structure of the carbon steel base material layer weld can be avoided.

[0083] Table 6.

[0084]

[0085] Figure 2 The microstructure photograph of the first layer weld interface of the transition layer / carbon steel substrate layer in the weld joint using the optimized nickel-based alloy composite plate weld structure of Example 1 of the present invention is shown.

[0086] from Figure 2 It can be seen that the microstructure photos of both sides of the transition layer / base layer carbon steel first layer weld interface after corrosion by nitric acid alcohol solution in the optimized welded joint of the nickel-based alloy composite plate prepared by the method of the present invention. It can be seen that the transition layer weld is not corroded, which means that the weld structure of this layer is still retained as the full austenite corrosion-resistant structure of the parent phase, while the adjacent carbon steel weld is still maintained as a ferrite grain structure, indicating that the weld layer does not undergo martensite hardening and brittleness as a whole, which confirms that the weld structure is effectively optimized.

[0087] It should be noted that the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0088] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A welding method for optimizing the weld structure of a nickel-based alloy composite plate, wherein the nickel-based alloy composite plate comprises a substrate layer and a nickel-based alloy composite layer, and a transition layer is provided at the bonding interface between the substrate layer and the nickel-based alloy composite layer; characterized in that: The welding method comprises the steps of: A trapezoidal groove is processed at the position corresponding to the base material layer on the welding section of the nickel-based alloy composite plate; a U-shaped groove is processed at the position corresponding to the transition layer on the welding section of the nickel-based alloy; no groove is processed at the position corresponding to the nickel-based alloy composite material layer on the welding section of the nickel-based alloy composite plate, and a blunt edge is retained; The nickel-based alloy composite layer is welded by single tungsten-arc argon welding; The transition layer is welded by single tungsten-arc argon welding; The base material layer is welded by single tungsten inert gas arc welding.

2. The welding method according to claim 1, characterized in that The angle α between the inclined portion of the trapezoidal groove and the vertical direction is 15-25°.

3. The welding method according to claim 1, characterized in that The single-side width of the step of the trapezoidal groove w1≥2(w2+2r) / 3, where w2 represents the assembly gap, and r represents the radius of the transition arc of the U-shaped groove, and the unit parameters are all mm.

4. The welding method according to claim 1, characterized in that: The distance b4 between the step of the trapezoidal groove and the bonding interface between the substrate layer and the nickel-based alloy composite layer is 0.5-1.5 mm.

5. The welding method according to claim 1, characterized in that: The thickness b3 of the blunt edge is 0.5-2 mm.

6. The welding method according to claim 1, characterized in that: The assembly gap w2 is 1-3mm.

7. The welding method according to claim 1, characterized in that: The radius of the transition arc of the U-shaped groove is r=(b2-b3) / 2, where b2 represents the distance from the surface of the nickel-based alloy composite layer to the bonding interface between it and the substrate layer, and b3 is the thickness of the blunt edge, and the unit parameters are all mm.

8. The welding method according to claim 1, characterized in that: In the step of welding the nickel-based alloy composite layer by single tungsten electrode argon arc welding: pure argon gas is used as the shielding gas, a nickel-based alloy solid welding wire matching the nickel-based alloy composite layer is used, the welding voltage is controlled to be 10-13V, the welding current is 80-110A, the welding speed is 80-110mm / min, and the wire feeding speed is 0.3-0.8m / min.

9. The welding method according to claim 1, characterized in that: In the step of welding the transition layer using single tungsten electrode argon arc welding: pure argon is used as the shielding gas, a nickel-based alloy solid welding wire matching the nickel-based alloy composite layer is used, the welding voltage is controlled to be 9-13V, the welding current is 80-130A, the welding speed is 100-120mm / min, and the wire feeding speed is 0.6-1.0m / min.

10. The welding method according to claim 1, characterized in that: In the steps of welding the base material layer by tungsten inert gas welding: First, the first weld of the base material layer in direct contact with the transition layer is welded: the shielding gas is argon + CO2 mixed gas, and the flux-cored wire matching the base material layer is used; Complete the welding of other welds of the base material layer: use pure argon as the shielding gas and use carbon steel solid welding wire that matches the base material layer.

11. The welding method according to claim 10, characterized in that: When welding the first weld of the base material layer: it is divided into three passes, and the welding order is to weld the two side welds first, and then the middle weld. When welding the two side welds, the distance between the center of the welding gun and the step edge of the trapezoidal groove in the width direction is controlled to be (w1+2((w2+2r) / 3) / 2 in each welding, where w1 represents the single-side width of the step of the trapezoidal groove, w2 represents the assembly gap, and r represents the radius of the transition arc of the U-shaped groove, and the unit parameters are all mm.

12. The welding method according to claim 10, characterized in that: When welding the first weld of the base material layer: control the welding voltage to 14-16V, the welding current to 150-180A, the welding speed to 120-150mm / min, and the wire feeding speed to 2.7-3.0m / min.

13. The welding method according to claim 10, characterized in that: When welding other welds of the base material layer: control the welding voltage to 14-16V, the welding current to 250-280A, the welding speed to 150-180mm / min, and the wire feeding speed to 2.6-3.0m / min.

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