An automated welding method for stainless steel composite plates

Abstract

This invention discloses an automated 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. The method includes the following steps: machining a first trapezoidal bevel on the welding cross-section of the stainless steel composite plate corresponding to the position of the substrate layer; machining a second trapezoidal bevel on the welding cross-section of the stainless steel composite plate corresponding to the position of the transition layer, wherein the first trapezoidal bevel and the second trapezoidal bevel form a first single-sided step; not machining a bevel on the welding cross-section of the stainless steel composite plate corresponding to the position of the stainless steel cladding layer, wherein the second trapezoidal bevel forms a second single-sided step on the stainless steel cladding layer; performing zero-gap self-fusion welding of the stainless steel cladding layer using laser welding; performing filler welding of the transition layer using laser welding with a stainless steel welding wire matched to the stainless steel cladding layer; and performing filler welding of the substrate layer using tungsten inert gas welding with a welding wire matched to the substrate layer.

Description

Technical Field

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

[0002] When connecting stainless steel composite plates, multi-layer and multi-pass welding should be used, that is, the joint weld should be divided into a cladding stainless steel weld, a transition stainless steel weld, and a base carbon steel weld, and welded separately to ensure the corrosion resistance of the cladding weld and the overall strength and toughness of the joint.

[0003] When using this welding method, it is important to control the dilution rate of critical weld beads. For example, in the welding sequence of cladding layer-transition layer-base layer (which can only be used in the closed welding of small composite plate components due to limited operating space), the carbon steel weld bead adjacent to the transition layer is easily martensitized by alloying elements such as Cr and Ni that have melted into the stainless steel, which in turn worsens the joint's plasticity and toughness.

[0004] Currently, in the closed welding of small stainless steel composite plate components, due to limited operating space, it is necessary to adopt single-sided welding starting from the cladding layer. In this case, if mixed welding materials are used for filler (i.e., carbon steel welding materials are used for filler in carbon steel welds, and stainless steel welding materials are used for filler in transition and cladding layers), the joint weld will become significantly embrittled.

[0005] The existing approach to this problem is to fill the entire weld seam with stainless steel welding wire. However, this solution significantly increases the amount of stainless steel welding material used, increases welding costs and reduces welding efficiency. More importantly, it reduces the structural strength of the entire welded joint, posing a potential threat to the long-term stable service of the composite plate component.

[0006] Furthermore, Chinese patent document CN 112122783A, published on December 25, 2020, entitled "A Laser Butt Welding Method for Carbon Steel-Nickel Alloy Composite Plates," discloses that a laser welding self-fusion or filler wire welding method is used to achieve the connection of composite plates in a cladding-transition-base layer welding sequence. However, the main problem it solves is the inability to connect composite plate components under closed welding conditions, and it does not focus on and control the microstructure of the joint.

[0007] Chinese patent document CN114888410A, published on August 12, 2022, entitled "A Welding Process for Reverse Welding of Duplex Stainless Steel Composite Plates," discloses a method of welding the base layer after the transition layer and cladding layer welds to ensure the corrosion resistance of the cladding layer and the overall bending performance of the weld. However, the welding method in this invention is not a single-sided welding starting from the cladding layer, and therefore cannot be applied to the closed welding conditions of composite plate components in actual engineering.

[0008] Unlike the existing technical solutions mentioned above, the inventors adopted a completely new design and aimed to provide an automated welding method for stainless steel composite plates. This method can avoid martensitization of carbon steel weld beads by specially designing the bevel and comprehensively utilizing laser welding and arc welding methods, matching optimized process parameters, and using mixed welding materials for filling. This achieves a reliable connection of stainless steel composite plates in the cladding-transition-base layer welding sequence. Summary of the Invention

[0009] One of the objectives of this invention is to provide an automated welding method for stainless steel composite plates. This method, through the design of a special bevel and the combined use of laser welding and tungsten inert gas welding, avoids the martensitization of the carbon steel weld bead structure under the premise of applying mixed welding materials, and achieves a reliable connection of stainless steel composite plates in the welding sequence of cladding layer-transition layer-base layer.

[0010] To achieve the above objectives, this invention provides an automated 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 automated welding method includes the following steps:

[0011] A first trapezoidal bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the base material layer; a second trapezoidal bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the transition layer, the first trapezoidal bevel and the second trapezoidal bevel forming a first single-sided step; no bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the stainless steel composite layer, the second trapezoidal bevel forming a second single-sided step on the stainless steel composite layer.

[0012] Laser welding was used to perform autofusion welding on the stainless steel composite layer;

[0013] Using stainless steel welding wire that matches the stainless steel cladding layer, laser welding is used to filler wire welding the transition layer;

[0014] Using welding wire that matches the substrate layer, tungsten inert gas (TIG) welding is used to filler wire weld the substrate layer.

[0015] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, the bottom width w1 / 2 of the second single-sided step is greater than or equal to the laser spot radius of the laser welding.

[0016] In this implementation, the bottom width w1 / 2 of the second single-sided step is greater than or equal to the laser spot radius of the laser welding, which can ensure that the composite layer weld is successfully welded and formed without melting the base carbon steel.

[0017] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, the top width w2 / 2 of the second single-sided step is ≤1.5mm.

[0018] In this implementation, by controlling the top width of the second single-sided step, i.e. the single-sided width of the top of the transition layer weld groove, to ≤1.5mm, the amount of excessive stainless steel weld melted into the base carbon steel weld can be reduced.

[0019] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, the width w3 of the first single-sided step is greater than or equal to (5 + 0.1b1), where b1 represents the distance between the surface of the substrate layer and its interface with the stainless steel composite layer.

[0020] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, the single-sided angle α of the first trapezoidal bevel is ≥ (1.5b1)°, where b1 represents the distance between the surface of the substrate layer and its interface with the stainless steel composite layer.

[0021] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, the distance b3 between the first single-sided step and the interface of the stainless steel composite layer is 1-2 mm.

[0022] In this embodiment, the feasibility of using tungsten inert gas welding (TIG) to perform filler wire welding on the substrate layer can be further guaranteed.

[0023] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, in the step of performing self-fusion welding of the stainless steel composite layer using laser welding, the diameter of the laser spot used is ≤1mm.

[0024] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, in the step of performing autofusion welding of the stainless steel composite layer using laser welding: the laser power is controlled to be 4.0-5.0KW, the welding speed is 3.0-3.5m / min, and the positive defocusing amount is 0-5mm.

[0025] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, the laser spot diameter used in the step of using laser welding to perform filler wire welding on the transition layer is ≤1mm.

[0026] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, in the step of using laser welding to perform filler wire welding on the transition layer: the laser power is controlled to be 5.0-6.0KW, the welding speed is 3.0-4.0m / min, the positive defocusing amount is 10-15mm, the wire feeding speed is 2.0-2.5m / min, and the wire feeding angle is 45-60°.

[0027] In this embodiment, the above welding process, combined with a specially designed bevel at the transition layer weld position, can control the top width of the transition layer weld to less than 3mm, thereby reducing the amount of stainless steel weld elements molten into the subsequent carbon steel weld.

[0028] Furthermore, in the automated welding method for stainless steel composite plates described in this invention, in the step of using tungsten inert gas welding to perform filler wire welding on the substrate layer: the welding voltage is controlled at 13.0-15.0V, the welding current at 180-220A, the welding speed at 160-180mm / min, the wire feed speed at 2.0-2.6m / min, and the oscillation width at 1-4mm.

[0029] In this embodiment, the welding process can effectively reduce the penetration depth while ensuring good weld formation. At the same time, with the already obtained narrow transition layer weld, the dilution rate of the carbon steel weld, especially the carbon steel weld bead in direct contact with the transition layer weld, can be controlled below 4.0%, thereby avoiding the formation of martensitic structure in the carbon steel weld.

[0030] The automated welding method for stainless steel composite plates described in this invention has the following advantages and beneficial effects compared to the prior art:

[0031] The automated welding method for stainless steel composite plates described in this invention can effectively avoid the formation of hard and brittle structures, improve the reliability of joint connections, and significantly reduce the amount of stainless steel welding materials used, thereby reducing welding costs while improving joint strength and welding efficiency.

[0032] In the automated welding method for stainless steel composite plates described in this invention, since the methods used are all automated welding technologies and parameterized welding processes, the dependence on the welding qualifications and experience of the welders is relatively small, thus it has good scalability.

[0033] In the automated welding method for stainless steel composite plates described in this invention, the problem of hard and brittle martensite structure generated by excessive dilution of carbon steel welds in stainless steel composite plate components where welding begins with the composite layer can be effectively solved, thereby obtaining a reliable welded joint. Attached Figure Description

[0034] Figure 1 The diagram illustrates the bevel used in the automated welding method for the stainless steel composite plate described in this invention.

[0035] Figure 2 The image shows the morphology of the welded joint of the composite plate prepared by the automated welding method of Embodiment 1 of the present invention after being etched with nitric acid alcohol.

[0036] Figure 3The image shows a metallographic photograph of the transition layer / carbon steel weld joint of a composite plate prepared by the automated welding method of Embodiment 1 of the present invention after etching with nitric acid alcohol. Detailed Implementation

[0037] The automated 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.

[0038] This invention aims to automate the welding process on stainless steel composite plates. Figure 1 The image shows two spliced ​​stainless steel composite panels, A and B. Figure 1 The dashed line O in the figure represents the seam. This stainless steel composite panel includes a carbon steel substrate layer 1, a stainless steel cladding layer 2, and a transition layer located between the carbon steel substrate layer 1 and the stainless steel cladding layer 2 (the transition layer is an atomic diffusion layer between the substrate layer and the cladding layer, which is difficult to see from the macroscopic structure and therefore is not shown separately in the figure). Figure 1 The designation “b3” indicates the distance between the interface between the first single-sided step and the stainless steel composite layer; “b1” indicates the distance between the surface of the carbon steel substrate layer and its interface with the stainless steel composite layer; and “b2” indicates the distance between the surface of the stainless steel composite layer and its interface with the carbon steel substrate layer.

[0039] In a specific example, a stainless steel composite plate with the grade SUS304 / Q235 and a thickness of 10mm can be used. The stainless steel composite layer is SUS304, the carbon steel base layer is Q235, the thickness of b2 is 2mm, and the thickness of b1 is 8mm.

[0040] In some embodiments, the automated welding method for stainless steel composite plates includes the steps of:

[0041] 100: Processing is performed at the welding position of the two spliced ​​stainless steel composite plates A and B as follows. Figure 1 The bevels are shown. A first trapezoidal bevel 6 is machined on the welding section of the stainless steel composite plate corresponding to the base material layer; a second trapezoidal bevel 8 is machined on the welding section of the stainless steel composite plate corresponding to the transition layer. The first trapezoidal bevel 6 and the second trapezoidal bevel 8 form a first single-sided step 7, and the second trapezoidal bevel forms a second single-sided step 9 on the stainless steel composite layer; no bevel is machined on the welding section of the stainless steel composite plate corresponding to the stainless steel composite layer, meaning the welding surface 10 of the stainless steel composite layer is a vertical plane.

[0042] 200: Laser welding is used to perform autofusion welding on the stainless steel composite layer to form the composite layer weld 3.

[0043] 300: Using stainless steel welding wire compatible with the stainless steel cladding layer, laser welding is used to perform filler welding on the transition layer to form transition layer weld 4. Figure 3 The “w2” indicates the width of the top of the transition layer weld.

[0044] 400: Using carbon steel welding wire that matches the carbon steel base layer, tungsten inert gas welding is used to filler wire welding of the carbon steel base layer to form the base layer weld 5.

[0045] Preferably, in some embodiments, the bottom width w1 / 2 of the second single-sided step is greater than or equal to the laser spot radius of the laser welding, that is, the total bottom width w1 of the two second single-sided steps formed by the two spliced ​​stainless steel composite plates A and B is greater than or equal to the laser spot diameter of the laser welding. This setting can ensure that the composite layer weld is successfully welded and formed without melting the base carbon steel.

[0046] Preferably, in some embodiments, the top width w2 / 2 of the second single-sided step is ≤1.5mm, that is, the total top width w2 of the two second single-sided steps formed by the two spliced ​​stainless steel composite plates A and B is ≤3mm. This design can reduce the amount of stainless steel weld seam fused into the base carbon steel weld seam.

[0047] In addition, in some embodiments, in order to further improve the operability of tungsten inert gas welding for filler wire welding of the substrate layer, the width w3 of the first single-sided step can be controlled to be greater than or equal to (5+0.1b1), and the angle α of the first trapezoidal bevel can be controlled to be greater than or equal to (1.5b1)°, where b1 represents the distance between the surface of the substrate layer and its interface with the stainless steel composite layer; the distance b3 between the first single-sided step and the interface with the stainless steel composite layer is 1-2 mm.

[0048] Furthermore, in some preferred embodiments, in step 200, the laser spot diameter is ≤1mm; the laser power is controlled to be 4.0-5.0KW, the welding speed is 3.0-3.5m / min, and the positive defocusing amount is 0-5mm.

[0049] In step 300: the filler wire can be stainless steel welding wire ER309L with performance not lower than that of stainless steel cladding layer, the laser spot diameter is ≤1mm; the laser power is controlled at 5.0-6.0KW, the welding speed is 3.0-4.0m / min, the positive defocusing amount is 10-15mm, the wire feeding speed is 2.0-2.5m / min, and the wire feeding angle is 45-60°.

[0050] In this embodiment, the above welding process, combined with a specially designed bevel at the transition layer weld position, can control the top width of the transition layer weld to less than 3mm, thereby further reducing the amount of stainless steel weld elements molten into the subsequent carbon steel weld.

[0051] In step 400: ER50-6 carbon steel welding wire, which is compatible with the base material, can be used for welding. The welding voltage is controlled at 13.0-15.0V, the welding current at 180-220A, the welding speed at 160-180mm / min, the wire feed speed at 2.0-2.6m / min, and the swivel width at 1-4mm.

[0052] In this embodiment, the welding process can effectively reduce the penetration depth while ensuring good weld formation. At the same time, with the already obtained narrow transition layer weld, the dilution rate of the carbon steel weld, especially the carbon steel weld bead in direct contact with the transition layer weld, can be controlled below 4.0%, thereby avoiding the formation of martensitic structure in the carbon steel weld.

[0053] To further illustrate 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.

[0054] Table 1.

[0055]

[0056]

[0057] Table 2 lists the welding process parameters used in step 200 of forming the composite layer weld in preferred embodiments 1-5 of the present invention.

[0058] Table 2.

[0059]

[0060] Table 3 lists the welding process parameters used in step 300 of forming the transition layer weld in preferred embodiments 1-5 of the present invention.

[0061] Table 3.

[0062]

[0063] Table 4 lists the welding process parameters used in step 400 of forming the substrate layer weld in preferred embodiments 1-5 of the present invention.

[0064] Table 4.

[0065]

[0066]

[0067] In addition, to demonstrate the implementation effect of the preferred embodiment, Table 5 lists the Cr content of each layer of base material and weld in the joint of the stainless steel composite plate obtained by welding according to Embodiment 1 of the present invention. By calculation, it can be found that the dilution rate of the carbon steel weld bead in contact with the transition layer relative to the stainless steel cladding weld bead is only 2.64%, which is less than 4.0%, thus avoiding the formation of martensitic structure in the carbon steel weld bead.

[0068] Table 5.

[0069]

[0070] Figure 2 The image shows the morphology of the welded joint of the composite plate prepared by the automated welding method of Embodiment 1 of the present invention after being etched with nitric acid alcohol.

[0071] from Figure 2 As can be seen, the welded joint is well bonded, and it can be seen that due to the application of the method of the present invention, the width of the transition layer weld is effectively controlled, which helps to reduce the dilution rate of carbon steel weld.

[0072] Figure 3 The image shows a metallographic photograph of the transition layer / carbon steel weld joint of a composite plate prepared by the automated welding method of Embodiment 1 of the present invention after etching with nitric acid alcohol.

[0073] from Figure 3 It can be seen that the transition layer weld was not corroded, indicating that it still maintains the austenitic structure of the base material. The carbon steel weld bead immediately adjacent to the transition layer has a ferrite + pearlite structure and no martensite structure. This means that the weld bead in this layer has not undergone significant hardening.

[0074] 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.

[0075] 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 automated welding method for stainless steel composite plates, the stainless steel composite plates 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; Its features are, The automated welding method includes the following steps: A first trapezoidal bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the base layer; a second trapezoidal bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the transition layer, the first and second trapezoidal bevels forming a first single-sided step; no bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the stainless steel cladding layer, the second trapezoidal bevel forming a second single-sided step on the stainless steel cladding layer; the bottom width w1 / 2 of the second single-sided step is greater than or equal to the laser spot radius of laser welding; the top width w2 / 2 of the second single-sided step is less than or equal to 1.5 mm; the width w3 of the first single-sided step is greater than or equal to (5 + 0.1b1), where b1 represents the distance from the surface of the base layer to its interface with the stainless steel cladding layer; the distance b3 between the first single-sided step and the interface with the stainless steel cladding layer is maintained at 1-2 mm. Laser welding was used to perform autofusion welding on the stainless steel composite layer; Using stainless steel welding wire that matches the stainless steel cladding layer, laser welding is used to filler wire welding the transition layer; Using welding wire that matches the substrate layer, tungsten inert gas (TIG) welding is used to filler wire weld the substrate layer.

2. The automated welding method for stainless steel composite plates as described in claim 1, characterized in that, The angle α of the first trapezoidal bevel is ≥ (1.5b1)°, where b1 represents the distance between the surface of the substrate layer and its interface with the stainless steel composite layer.

3. The automated welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of performing self-fusion welding on stainless steel composite layers using laser welding, the diameter of the laser spot used is ≤1mm.

4. The automated welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of performing autofusion welding on stainless steel composite layers using laser welding: the laser power is controlled at 4.0-5.0KW, the welding speed is 3.0-3.5m / min, and the positive defocusing amount is 0-5mm.

5. The automated welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of using laser welding to perform filler wire welding on the transition layer, the diameter of the laser spot used is ≤1mm.

6. The automated welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of using laser welding to perform filler wire welding on the transition layer: the laser power is controlled at 5.0-6.0KW, the welding speed is 3.0-4.0m / min, the positive defocusing amount is 10-15mm, the wire feeding speed is 2.0-2.5m / min, and the wire feeding angle is 45-60°.

7. The automated welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of using tungsten inert gas welding to perform filler wire welding on the substrate layer: control the welding voltage to be 13.0-15.0V, the welding current to be 180-220A, the welding speed to be 160-180mm / min, the wire feed speed to be 2.0-2.6m / min, and the wire width to be 1-4mm.

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