An Optimized Welding Method for Stainless Steel Composite Plates

Abstract

This invention discloses an optimized welding method for stainless steel composite plates, wherein the stainless steel composite plate comprises a base layer and a stainless steel cladding layer, and a transition layer is provided at the interface between the base layer and the stainless steel cladding layer. The optimized welding method includes the following steps: machining a trapezoidal bevel on the welding section of the stainless steel composite plate corresponding to the position of the base layer; opening a V-shaped bevel on the welding section of the stainless steel composite plate corresponding to the positions of the transition layer and the stainless steel cladding layer; welding the stainless steel cladding layer using single tungsten inert gas (TIG) welding; welding the transition layer using single TIG welding; and welding the base layer using single TIG welding. This method reduces the amount of stainless steel welding materials used, lowers welding costs, and improves welding efficiency while effectively ensuring high joint strength. Furthermore, the method used in this invention has low equipment requirements, is simple to operate, and correspondingly has low requirements for assembly precision, making it highly applicable in engineering work sites.

Description

Technical Field

[0001] This invention relates to a welding method, and more particularly to a welding method for stainless steel composite plates. Background Technology

[0002] In engineering, a specific welding sequence is required for a few multi-layer, multi-pass welding scenarios of stainless steel composite plate components: cladding layer - transition layer - base material layer. If conventional welding processes are used (i.e., carbon steel welding materials for the carbon steel base material and stainless steel welding materials for the stainless steel cladding layer), the later carbon steel weld beads can easily incorporate a large amount of alloying elements into the stainless steel welding materials, resulting in overall hardening and embrittlement (the microstructure transforms into martensitic structure), significantly reducing the mechanical properties of the joint.

[0003] However, in some production conditions in engineering projects, this welding sequence must be adopted. For example, in the circumferential welding connection of small oil and gas pipelines, technicians can only use stainless steel welding materials for the entire weld seam to solve this problem. For example, the national standard "Technical Requirements for Welding of Stainless Steel Composite Plates" (GB / T 13148—2008) describes the welding of composite plates under this welding sequence. In this case, the welding of the base layer weld seam should use stainless steel welding wire with performance matching that of the composite layer.

[0004] However, this approach has several drawbacks. First, it significantly increases the amount of stainless steel filler metal used, which greatly increases welding costs and reduces welding efficiency. Second, the yield strength of the weld will also decrease, which will increase the risk of failure of the stainless steel composite plate joint under heavy loads.

[0005] In addition, Chinese patent document CN112122783A, published on December 25, 2020, entitled "A Laser Butt Welding Method for Carbon Steel-Nickel Alloy Composite Plate", proposes to achieve the connection of composite layers by using laser self-fusion or filler wire welding under the condition of limited construction space and the requirement to weld the composite layer first. However, it focuses on the problem that the composite plate cannot be welded on one side under this welding sequence, without paying attention to the performance changes of the mixed weld bead of nickel-based alloy and carbon steel.

[0006] In addition, Chinese patent document CN113042895B, published on April 26, 2022, entitled "A Welding Method for a Nickel-Steel Composite Structure", proposes to complete the connection of the composite layer by laser self-fusion welding when the composite layer is welded first, and then to weld the adjacent weld bead by cold metal transfer welding, thereby completing the connection of the nickel-based alloy composite plate under this welding sequence. However, it mainly addresses the problem of reduced corrosion resistance of the composite layer caused by element migration at the interface between the composite layer and the substrate layer, and does not solve the problem of reduced toughness of the mixed weld bead of nickel-based alloy and carbon steel.

[0007] In addition, the above methods all use laser autofusion or filler wire welding when welding composite plates. These welding methods have very high requirements for the assembly accuracy of components, making them difficult to apply in the field operation environment. Moreover, the equipment is expensive, the operation is cumbersome, and the maintenance is difficult. Summary of the Invention

[0008] The purpose of this invention is to provide an optimized welding method for stainless steel composite plates. This method, through a special bevel design and based on the common tungsten inert gas welding method, can significantly reduce the dilution rate of the first weld bead that directly contacts the transition layer in the welding sequence of composite layer-transition layer-substrate layer. This allows the microstructure of the first weld bead to be controlled to match the microstructure of the base material, thereby achieving a reliable connection of the composite plate.

[0009] To achieve the above objectives, the present invention provides an optimized welding method for stainless steel composite plates, wherein the stainless steel composite plate comprises a substrate layer and a stainless steel cladding layer, and a transition layer is provided at the interface between the substrate layer and the stainless steel cladding layer; the optimized welding method includes the following steps:

[0010] A trapezoidal bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the base material layer; a V-shaped bevel is opened on the welding section of the stainless steel composite plate at the position corresponding to the transition layer and the stainless steel composite layer.

[0011] The stainless steel composite layer was welded using single tungsten inert gas welding.

[0012] The transition layer was welded using single tungsten inert gas welding;

[0013] The substrate layer was welded using single tungsten inert gas welding.

[0014] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, the angle between the inclined portion and the vertical direction of the trapezoidal bevel is consistent with the angle between the inclined portion and the vertical direction of the V-shaped bevel.

[0015] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, the angle between the inclined portion of the V-groove and the vertical direction, as well as the angle between the inclined portion of the trapezoidal groove and the vertical direction, are both α, with a value range of 15-25°.

[0016] In this implementation, in order to balance the operability of the tungsten inert gas welding torch and the amount and efficiency of bevel filling, the angle between the inclined part and the vertical direction of the trapezoidal bevel and the angle α between the inclined part and the vertical direction of the V-shaped bevel can be controlled between 15-25°.

[0017] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, the distance b3 between the step plane of the trapezoidal bevel and the interface between the substrate layer and the stainless steel composite layer is 1-1.5 mm.

[0018] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, the single-side width w1 of the trapezoidal bevel step is ≥ 1.5((b2+b3)×tanα+w2 / 2), where b2 represents the distance between the surface of the stainless steel composite layer and its interface with the substrate layer, with the unit parameter being mm, α represents the angle between the inclined part of the trapezoidal bevel and the vertical direction, and w2 represents the assembly gap.

[0019] In this implementation, the distance b3 between the step plane of the bevel and the interface between the substrate layer and the stainless steel cladding layer can be controlled to be between 1 and 1.5 mm. The single-sided width w1 of the bevel step is ≥ 1.5 ((b2+b3)×tanα+w2 / 2), which ensures that the ratio of the width of the first weld bead in direct contact with the transition layer to its weld width is less than 40%, which helps to control the low dilution rate of each weld bead in this layer. In addition, the step design of this bevel not only achieves a low dilution rate but also provides good flatness of the surface to be welded, which will be beneficial to obtaining good weld formation.

[0020] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, the assembly gap w2 is 1-3 mm.

[0021] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, in the step of welding the stainless steel composite layer using single tungsten inert gas welding: a solid stainless steel welding wire matching the stainless steel composite layer is used, pure argon gas (purity not less than 99%) is used for protection, the welding voltage is controlled at 9.0-11V, the welding current at 60-90A, the welding speed at 75-100mm / min, and the wire feed speed at 0.6-0.9m / min.

[0022] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, in the step of welding the transition layer using single tungsten inert gas welding: a solid stainless steel welding wire matching the stainless steel composite layer is used, pure argon gas (purity not less than 99%) is used for protection, the welding voltage is controlled at 10-13V, the welding current at 100-130A, the welding speed at 80-110mm / min, and the wire feed speed at 0.5-0.8m / min.

[0023] In this implementation, the welding process ensures good weld formation of the transition layer weld, and the flat surface to be welded will facilitate the formation control of the first weld bead in contact with the transition layer.

[0024] Furthermore, in the step of welding the substrate layer using single tungsten inert gas welding in the optimized welding method for stainless steel composite plates described in this invention:

[0025] First, weld the first weld bead that contacts the transition layer: This layer is welded in two evenly divided passes, with argon + CO2 mixture as the shielding gas and flux-cored welding wire that matches the base layer.

[0026] To complete the welding of other weld passes of the base layer: the shielding gas is pure argon (purity not less than 99%), and the welding wire is solid carbon steel welding wire that matches the base layer.

[0027] In this implementation, the overlap rate between each weld and the transition layer weld can be controlled to 50%.

[0028] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, when welding the first weld bead of the substrate layer: the welding voltage is controlled at 14-15.5V, the welding current at 140-160A, the welding speed at 120-140mm / min, and the wire feeding speed at 2.5-2.8m / min.

[0029] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, when welding other weld passes of the substrate layer: the welding voltage is controlled at 14-16V, the welding current at 250-280A, the welding speed at 150-180mm / min, and the wire feed speed at 2.6-3.0m / min.

[0030] Furthermore, in the optimized welding method for stainless steel composite plates described in this invention, when welding the first weld bead: the distance between the center of the welding torch and the edge of the trapezoidal bevel step in the width direction is controlled as (w1+(b2+b3)tanα+w2 / 2) / 2, where b2 is the distance between the surface of the stainless steel composite layer and its interface with the substrate layer, b3 is the distance between the step plane of the trapezoidal bevel and the interface between the substrate layer and the stainless steel composite layer, w1 is the single-side width of the trapezoidal bevel step, w2 is the assembly gap, and the unit parameter is mm. α represents the angle between the inclined part of the trapezoidal bevel and the vertical direction.

[0031] In this implementation, the dilution level of the base layer weld bead relative to the composite layer weld bead can be kept below 4.0%, thereby ensuring that the weld bead does not produce martensite and still retains good ductility and toughness.

[0032] The optimized welding method for stainless steel composite plates described in this invention has the following advantages and beneficial effects compared to existing technologies:

[0033] The welding method described in this invention can significantly reduce the dilution rate of the first weld bead that is in direct contact with the transition layer in the composite layer-transition layer-substrate layer welding sequence, thereby controlling the microstructure of the weld bead to be the same as that of the base material, and achieving a reliable connection of the composite plate.

[0034] Furthermore, in a preferred embodiment of the present invention, the use of mixed welding materials reduces the amount of stainless steel welding materials used, lowers welding costs, and improves welding efficiency compared to the prior art, while effectively ensuring the high strength of the joint.

[0035] In addition, the method used in this invention has low equipment requirements, is simple to operate, and has correspondingly low requirements for assembly accuracy, making it highly applicable in engineering work sites. Attached Figure Description

[0036] Figure 1 The diagram schematically illustrates the bevel used in the optimized welding method for the stainless steel composite plate described in this invention.

[0037] Figure 2 The cross-sectional morphology of the welded joint prepared by the optimized welding method of Embodiment 1 of the present invention is shown.

[0038] Figure 3 The image shows a microstructure of the first weld interface between the transition layer and the carbon steel substrate layer in a welded joint prepared using the optimized welding method of Embodiment 1 of the present invention. Detailed Implementation

[0039] The optimized welding method for stainless steel composite plates described in this invention will be further explained and described below with reference to specific embodiments and accompanying drawings. However, this explanation and description do not constitute an undue limitation on the technical solution of this invention.

[0040] Figure 1 It shows two spliced ​​stainless steel composite panels, A and B. Figure 1 The dashed line O in the figure represents the splicing seam. The stainless steel composite plate includes a carbon steel substrate layer 1 and a stainless steel composite layer 2, with a transition layer at the interface between the carbon steel substrate layer 1 and the stainless steel composite layer 2. Figure 1 The designation "b1" indicates the distance between the surface of the carbon steel substrate layer and its interface with the stainless steel cladding layer, while the designation "b2" indicates the distance between the surface of the stainless steel cladding layer and its interface with the carbon steel substrate layer.

[0041] In one specific embodiment, a stainless steel composite plate with the grade SUS304 / Q235 can be used, that is, the base material is Q235 and the stainless steel composite layer is SUS304. The thickness of the stainless steel composite plate is 10mm, wherein b1 is 8mm and b2 is 2mm.

[0042] In some embodiments, the optimized welding method for stainless steel composite plates may include the steps of:

[0043] 100: Processing is performed at the welding position of the two spliced ​​stainless steel composite plates A and B as follows. Figure 1The bevel shown is described above. Specifically, a trapezoidal bevel is machined on the welded section of the stainless steel composite plate at the position corresponding to the carbon steel substrate layer. This trapezoidal bevel includes a sequentially arranged inclined portion 7 and a step 8 of the trapezoidal bevel, wherein the width of one side of the step 8 of the trapezoidal bevel is represented by w1. In some more specific embodiments, the width of one side of the step 8 of the trapezoidal bevel, w1, is ≥ 1.5((b2+b3)×tanα+w2 / 2).

[0044] The distance between the plane of step 8 of the trapezoidal bevel and the interface between the substrate layer and the stainless steel composite layer is... Figure 1 The distance b3 is represented by "b3". In some more specific embodiments, the distance b3 between the step 8 plane of the trapezoidal bevel and the interface between the substrate layer and the stainless steel composite layer can be controlled between 1 and 1.5 mm.

[0045] By controlling the single-side width w1 of the trapezoidal bevel step and the distance b3 between the step plane of the trapezoidal bevel and the interface between the substrate layer and the stainless steel cladding layer, it can be ensured that the ratio of the width of the first weld bead in direct contact with the transition layer to its weld width is less than 40%, which will help control the low dilution rate of each weld bead in this layer. In addition, the step design of this bevel not only achieves a low dilution rate but also ensures good flatness of the surface to be welded, which will be beneficial to obtaining good weld formation.

[0046] A V-shaped bevel is made on the welding section of the stainless steel composite plate at the positions corresponding to the transition layer and the stainless steel cladding layer. This V-shaped bevel has an inclined portion 9. The angles between the inclined portion 7 of the trapezoidal bevel and the vertical direction, as well as the angles between the inclined portion 9 of the V-shaped bevel and the vertical direction, are both α. In some more specific embodiments, the value of α can be in the range of 15-25° to improve the operability of the tungsten inert gas welding torch and the bevel filling amount and filling efficiency.

[0047] Assembly gap at Figure 1 The assembly clearance w2 is indicated by "w2". In some more specific implementations, the assembly clearance w2 can be 1-3 mm.

[0048] 200: The stainless steel cladding layer 2 is welded using single tungsten inert gas (TIG) welding to obtain the cladding layer weld 3. The shielding gas used for welding is pure argon gas with a purity of not less than 99%. Solid stainless steel welding wire that matches the stainless steel cladding layer is used for welding. The welding process parameters can be controlled as follows: welding voltage is controlled at 9.0-11V, welding current is controlled at 60-90A, welding speed is controlled at 75-100mm / min, and wire feed speed is controlled at 0.6-0.9m / min.

[0049] 300: The transition layer is welded using single tungsten inert gas (TIG) welding to obtain transition layer weld 4. The shielding gas used during welding is pure argon gas with a purity of not less than 99%, and the welding material is solid stainless steel welding wire that matches the stainless steel cladding layer. The welding process parameters can be controlled as follows: welding voltage is 10-13V, welding current is 100-130A, welding speed is 80-110mm / min, and wire feed speed is 0.5-0.8m / min.

[0050] By adopting the above welding process, it is possible to ensure that the transition layer weld has good weld formation, and the flat surface to be welded will be conducive to the formation control of the first weld bead in contact with the transition layer.

[0051] 400: Welding the base layer using single tungsten inert gas (TIG) welding: First, weld the first weld pass 5, which contacts the transition layer. This pass is applied in two evenly spaced passes. The shielding gas is an argon + CO2 mixture, such as 78% Ar + 18% CO2. The welding material is a flux-cored wire compatible with the carbon steel base layer. Then, complete the welding of the other weld passes 6 of the base layer: The shielding gas is pure argon with a purity of not less than 99%, and the welding wire is a solid carbon steel wire compatible with the base layer.

[0052] Using this implementation method, the overlap rate between each weld and the transition layer weld can be controlled to 50%.

[0053] In some more specific embodiments, when welding the first weld bead 5: the welding voltage is controlled at 14-15.5V, the welding current at 140-160A, the welding speed at 120-140mm / min, and the wire feed speed at 2.5-2.8m / min.

[0054] Furthermore, in some more specific embodiments, when welding the first layer of weld 5: the distance in the width direction between the center of the welding torch and the edge of the trapezoidal bevel step can be controlled as (w1+(b2+b3)tanα+w2 / 2) / 2.

[0055] In some more specific embodiments, when welding other weld passes of the carbon steel substrate layer: the welding voltage can be controlled at 14-16V, the welding current at 250-280A, the welding speed at 150-180mm / min, and the wire feed speed at 2.6-3.0m / min.

[0056] In this embodiment, the dilution level of the carbon steel substrate layer weld bead relative to the stainless steel cladding layer weld bead can be further reduced to less than 4.0%, thereby further ensuring that the weld bead microstructure does not produce martensite and still retains good ductility and toughness.

[0057] To further demonstrate the technical effects of the preferred embodiments of this invention, Table 1 lists the characteristic parameters of the bevel used in the preferred embodiments 1-5 of this invention.

[0058] Table 1.

[0059] Example Bevel angle α (°) <![CDATA[b3(mm)]]> <![CDATA[w1(mm)]]> <![CDATA[w2(mm)]]> Example 1 15 1 3 2 Example 2 18 1 3 2 Example 3 25 1.2 4 1 Example 4 15 1.5 2.5 1.5 Example 5 20 1 4 3

[0060] Table 2 lists the welding process parameters used in the step of forming the stainless steel composite layer weld in the preferred embodiments 1-5 of the present invention.

[0061] Table 2.

[0062]

[0063] Table 3 lists the welding process parameters used in the step of forming the transition layer weld in the preferred embodiments 1-5 of the present invention.

[0064] Table 3.

[0065]

[0066]

[0067] Table 4 lists the welding process parameters used in the step of forming the first weld bead of the carbon steel substrate layer in the preferred embodiments 1-5 of the present invention.

[0068] Table 4.

[0069]

[0070] Table 5 lists the welding process parameters used in the steps of forming other weld passes in the carbon steel substrate layer in the preferred embodiments 1-5 of the present invention.

[0071] Table 5.

[0072]

[0073] Furthermore, to demonstrate the effectiveness of the preferred embodiment, Table 6 lists the Cr content of each base material layer and weld in the welded joint of the stainless steel composite plate obtained by welding according to Embodiment 1 of the present invention. Calculations show that the dilution rate of the first carbon steel weld bead 5, which is in direct contact with the transition layer, is 2.4%. Therefore, the formation of martensitic structure in the carbon steel base material layer weld can be avoided.

[0074] Table 6.

[0075]

[0076] Figure 2 The cross-sectional morphology of the optimized joint prepared by the optimized welding method of Embodiment 1 of the present invention is shown.

[0077] from Figure 2 As can be seen, the welded joint is well bonded and there are no welding defects.

[0078] Figure 3 The image shows a microstructure on both sides of the first weld interface of the transition layer / carbon steel substrate layer in a welded joint prepared by the optimized welding method of Embodiment 1 of the present invention.

[0079] from Figure 3 It can be seen that the transition layer weld still maintains the parent phase austenite structure, which cannot be corroded by nitric acid alcohol. At the same time, the structure of the first layer weld of the carbon steel base layer still maintains the parent phase ferrite structure of the welding material itself. The joint structure transition is good and the connection is reliable.

[0080] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0081] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. An optimized welding method for stainless steel composite plates, the stainless steel composite plate comprising a substrate layer and a stainless steel cladding layer, wherein a transition layer is provided at the interface between the substrate layer and the stainless steel cladding layer; characterized in that, The optimized welding method includes the following steps: A trapezoidal bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the base material layer; a V-shaped bevel is opened on the welding section of the stainless steel composite plate at the position corresponding to the transition layer and the stainless steel composite layer. The stainless steel composite layer was welded using single tungsten inert gas welding. The transition layer was welded using single tungsten inert gas welding; The substrate layer was welded using single tungsten inert gas welding.

2. The optimized welding method for stainless steel composite plates as described in claim 1, characterized in that, The angle between the inclined part and the vertical direction of the trapezoidal bevel is the same as the angle between the inclined part and the vertical direction of the V-shaped bevel.

3. The optimized welding method for stainless steel composite plates as described in claim 2, characterized in that, The angle between the inclined part of the V-shaped bevel and the vertical direction, as well as the angle between the inclined part of the trapezoidal bevel and the vertical direction, are both α, with a value range of 15-25°.

4. The optimized welding method for stainless steel composite plates as described in claim 1, characterized in that, The distance b3 between the stepped plane of the trapezoidal bevel and the interface between the substrate layer and the stainless steel composite layer is 1-1.5mm.

5. The optimized welding method for stainless steel composite plates as described in claim 4, characterized in that, The single-side width w1 of the trapezoidal bevel step is ≥ 1.5((b2+b3)×tanα+w2 / 2), where b2 represents the distance between the surface of the stainless steel composite layer and its interface with the substrate layer, with the unit parameter being mm, α represents the angle between the inclined part of the trapezoidal bevel and the vertical direction, and w2 represents the assembly gap.

6. The optimized welding method for stainless steel composite plates as described in claim 1, characterized in that, The assembly clearance w2 is 1-3mm.

7. The optimized welding method for stainless steel composite plates as described in claim 1, characterized in that, In the steps of welding stainless steel cladding layers using single tungsten inert gas welding: use solid stainless steel welding wire that matches the stainless steel cladding layer, use pure argon gas for protection, control the welding voltage to be 9.0-11V, the welding current to be 60-90A, the welding speed to be 75-100mm / min, and the wire feed speed to be 0.6-0.9m / min.

8. The optimized welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of welding the transition layer using single tungsten inert gas welding: use solid stainless steel welding wire that matches the stainless steel cladding layer, use pure argon gas for protection, control the welding voltage to be 10-13V, the welding current to be 100-130A, the welding speed to be 80-110mm / min, and the wire feed speed to be 0.5-0.8m / min.

9. The optimized welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of welding the substrate layer using single tungsten inert gas welding: First, weld the first weld bead that contacts the transition layer: This layer is welded in two evenly divided passes, with argon + CO2 mixture as the shielding gas and flux-cored welding wire that matches the base layer. Complete the welding of other weld passes of the base layer: use pure argon as the shielding gas and solid carbon steel welding wire that matches the base layer.

10. The optimized welding method for stainless steel composite plates as described in claim 9, characterized in that, When welding the first weld bead: control the welding voltage to be 14-15.5V, the welding current to be 140-160A, the welding speed to be 120-140mm / min, and the wire feed speed to be 2.5-2.8m / min.

11. The optimized welding method for stainless steel composite plates as described in claim 9, characterized in that, When welding other passes of the substrate layer: control the welding voltage to 14-16V, the welding current to 250-280A, the welding speed to 150-180mm / min, and the wire feed speed to 2.6-3.0m / min.

12. The optimized welding method for stainless steel composite plates as described in claim 9, characterized in that, When welding the first layer of weld: During each weld, the distance between the center of the welding torch and the edge of the trapezoidal bevel step in the width direction is controlled as (w1+(b2+b3)tanα+w2 / 2) / 2, where b2 is the distance between the surface of the stainless steel cladding layer and its interface with the base material layer, b3 is the distance between the step plane of the trapezoidal bevel and the interface between the base material layer and the stainless steel cladding layer, w1 is the single-side width of the trapezoidal bevel step, w2 is the assembly clearance, and the unit parameter is mm. α represents the angle between the inclined part of the trapezoidal bevel and the vertical direction.

Images