A welding method for stainless steel composite plates

Abstract

This invention discloses a welding method for stainless steel composite plates, the stainless steel composite plates comprising a base layer and a stainless steel cladding layer, wherein a transition layer is provided at the interface between the base layer and the stainless steel cladding layer; wherein the welding method comprises the following steps: machining a composite bevel on the welding cross-section of the stainless steel composite plate corresponding to the position of the base layer, the composite bevel comprising a vertically inclined portion, a transition arc, a horizontally inclined portion, and a horizontal portion arranged sequentially; opening a rectangular bevel on the welding cross-section of the stainless steel composite plate corresponding to the position of the transition layer; 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; performing self-fusion welding of the stainless steel cladding layer using laser welding; using carbon steel welding wire matched to the base layer, performing filler wire welding of the transition layer using laser welding; and welding the base layer using hot-wire pulsed tungsten inert gas welding.

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] Stainless steel composite plates are composite structural materials made of stainless steel and low alloy structural steel through rolling, explosive bonding and other methods. They are gradually being promoted and applied in industry due to their good mechanical properties and corrosion resistance.

[0003] Because the physicochemical properties of the two component metals differ significantly, stainless steel composite plates require multi-layer, multi-pass welding for connection. A transition layer is added to achieve a compositional transition between the stainless steel weld of the cladding layer and the carbon steel weld of the base layer, thus preventing a decrease in the corrosion resistance of the cladding layer weld (forward welding sequence: base layer-transition layer-cladding layer) or a deterioration in the mechanical properties of the base layer weld (forward welding sequence: cladding layer-transition layer-base layer). Generally, regardless of the welding sequence, stainless steel welding materials are used for the cladding layer and transition layer welds. Although the filling area of ​​the transition layer and cladding layer stainless steel welds is smaller than that of the base layer carbon steel welds, and the amount of welding material used is relatively less, the consumption remains substantial when the project volume and the corresponding weld length increase. Summary of the Invention

[0004] One of the objectives of this invention is to provide a welding method for stainless steel composite plates. This method can use carbon steel welding materials as a transition layer to complete the compositional transition from stainless steel to carbon steel, thereby achieving a reliable connection of stainless steel composite plates without the need for stainless steel welding materials, reducing the welding cost of stainless steel composite plates, and generating considerable economic benefits.

[0005] To achieve the above objectives, the present invention provides a welding method for a stainless steel composite plate, 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; wherein the welding method includes the following steps:

[0006] A composite bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the base material layer. The composite bevel includes, in sequence, a vertical inclined portion, a transition arc, a horizontal inclined portion, and a horizontal portion. A rectangular bevel is opened on the welding section of the stainless steel composite plate at the position corresponding to the transition layer. No bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the stainless steel composite layer.

[0007] Laser welding was used to perform autofusion welding on the stainless steel composite layer;

[0008] Using carbon steel welding wire that matches the base layer, laser welding is used to filler wire welding the transition layer;

[0009] The substrate layer is welded using hot-wire pulse oscillation tungsten inert gas welding.

[0010] In this invention, the inventors, through a special design of the bevel and a specific welding method, can use carbon steel welding materials as a transition layer to complete the compositional transition from stainless steel to carbon steel, thus achieving a reliable connection of stainless steel composite plates without the need for stainless steel welding materials. Furthermore, using carbon steel welding materials to fill the transition layer weld allows the transition layer weld to maintain a good austenitic + ferrite structure with good ductility and toughness.

[0011] Furthermore, in the welding method for stainless steel composite plates described in this invention, the width w1 / 2 of the single side of the rectangular groove should be controlled within the range of the laser spot radius of laser welding -0.5mm.

[0012] In this implementation, a rectangular bevel and horizontal extensions are made on both sides at the transition layer weld location. When the two stainless steel composite plates undergo laser filler wire welding of the transition layer, the laser heat source melts the rectangular bevel, the horizontal extensions on both sides, and part of the composite layer, ultimately forming the transition layer weld. The bevel width of the transition layer weld is greater than or equal to the laser spot diameter, which ensures the smooth completion of laser self-fusion welding of the composite layer weld without melting the carbon steel substrate. Simultaneously, by setting an upper limit of 0.5mm for the single-side width w1 / 2 of the rectangular bevel, the final width of the transition layer weld can be controlled, which helps control the low dilution rate of the substrate layer weld, especially the carbon steel weld bead in contact with the transition layer.

[0013] Furthermore, in the welding method for stainless steel composite plates described in this invention, the thickness b3 of the rectangular bevel is 0.05-0.5 mm.

[0014] In this implementation, the thickness b3 of the rectangular groove, i.e., the distance between the weld step of the base layer and the interface between the base layer and the stainless steel cladding layer, can be controlled within a certain range and should be as small as possible. However, if b3 is too small, the base layer weld, especially several weld passes in the first layer, will require very shallow penetration to avoid melting through the base layer to the stainless steel cladding layer. Therefore, the range of b3 can be limited to 0.05mm ≤ b3 ≤ 0.5mm.

[0015] Furthermore, in the welding method for stainless steel composite plates described in this invention, the width w2 of the horizontal portion of the composite bevel is 0.5-1mm.

[0016] Furthermore, to reduce the infiltration of carbon steel components into the transition layer weld, a horizontal section should be provided between the horizontal inclined portion of the composite bevel of the substrate layer and the rectangular bevel of the transition layer. The width of this horizontal section on one side is w2, and its distance from the interface between the substrate layer and the composite material layer is also b3. Considering the relatively small design value of b3, to reduce the welding difficulty of the subsequent substrate layer weld, the width w2 of the horizontal section of the composite bevel of the substrate layer should not be too large, and should be controlled between 0.5mm ≤ w2 ≤ 1mm. In this embodiment, by setting the horizontal section w2 within the range of 0.5mm-1mm, the welding difficulty of the subsequent substrate layer weld can be minimized while reducing the infiltration of carbon steel components into the transition layer.

[0017] Furthermore, in the welding method for stainless steel composite plates described in this invention, the angle α2 between the vertically inclined portion and the vertical direction is ≥ (1.5b1)°, where b1 represents the distance between the surface of the substrate layer and its interface with the stainless steel composite layer, and its unit parameter is mm.

[0018] In this implementation, controlling the angle α2 between the vertical tilt and the vertical direction to be ≥ (1.5b1)° facilitates the subsequent hot wire pulse oscillation tungsten inert gas welding operation.

[0019] Furthermore, in the welding method for stainless steel composite plates described in this invention, the angle α1 between the horizontally inclined portion and the horizontal direction is ≥5°.

[0020] This configuration helps to prevent the substrate material from melting into the stainless steel composite material.

[0021] Furthermore, in the welding method for stainless steel composite plates described in this invention, the extension width w3 of the horizontal inclined portion is ≥ (5 + 0.1b1), where b1 represents the distance between the surface of the substrate layer and its interface with the stainless steel composite layer, and its unit parameter is mm.

[0022] In this implementation, controlling the extension width w3 of the horizontally inclined portion to be greater than or equal to (5+0.1b1) can prevent the substrate layer from melting through to the stainless steel composite layer.

[0023] Furthermore, in the welding method for stainless steel composite plates described in this invention, the radius r of the transition arc is greater than or equal to 0.2w3, where w3 represents the extension width of the horizontal inclined portion, and its unit parameter is mm.

[0024] For embodiments where a smaller rectangular bevel thickness b3 is intentionally designed (e.g., the embodiment described above where b3 is 0.05-0.5 mm), since this embodiment would greatly limit the heat input during carbon steel weld welding, in order to avoid non-fusion welding defects during base layer weld welding, it is preferable to control the radius r of the transition arc to be ≥ 0.2w3.

[0025] Furthermore, in the 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 laser power is controlled to be 5.0-6.0KW, the welding speed is 3.5-4.0m / min, and the positive defocusing amount is 0-5mm.

[0026] Furthermore, in the 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.

[0027] Furthermore, in the 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 diameter of the laser spot used is ≤1mm.

[0028] Furthermore, in the 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 6.0-8.0KW, the welding speed is 5.0-6.0m / min, the positive defocusing amount is 10-15mm, the wire feeding speed is 0.2-0.5m / min, and the wire feeding angle is 45-60°.

[0029] In this implementation, by using a specially designed bevel, the transition layer weld will melt down part of the stainless steel composite layer weld, ultimately ensuring that the carbon steel component (including carbon steel base metal and carbon steel welding wire) melted into the transition layer weld does not exceed 25%, so that the transition layer weld can still maintain a tough parent phase austenite + ferrite structure.

[0030] Furthermore, in the welding method for stainless steel composite plates described in this invention, in the step of welding the substrate layer using hot-wire pulse oscillation tungsten inert gas welding: the welding voltage is controlled at 13.0-15.0V, the peak current is 180-220A, the base current is 70-120A, the duty cycle is 40-70%, the pulse frequency is 3-8Hz, the hot-wire current is 60-80A, the welding speed is 150-180mm / min, the wire feed speed is 2.2-2.6m / min, and the oscillation width is 1-2mm.

[0031] In this implementation, when filling the base layer weld using hot-wire pulsed tungsten inert gas welding, the penetration depth and dilution rate can be further reduced by adding oscillation. This welding method, combined with a specially designed bevel, ensures that the dilution rate of the base layer weld, especially the carbon steel weld bead in direct contact with the transition layer weld, is controlled below 4.0% without completely penetrating the base layer weld step.

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

[0033] The welding method described in this invention can use carbon steel welding materials as a transition layer to complete the compositional transition from stainless steel to carbon steel, thereby achieving a reliable connection of stainless steel composite plates without the need for stainless steel welding materials, reducing the welding cost of stainless steel composite plates and generating considerable economic benefits. Attached Figure Description

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

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

[0036] Figure 3 The image shows a metallographic photograph of the weld joint of a stainless steel composite plate prepared by the welding method of Embodiment 1 of the present invention, after being etched by nitric acid alcohol, at the weld joint section of the transition layer / carbon steel substrate layer. Detailed Implementation

[0037] The welding method of the stainless steel composite plate of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings. However, such explanation and description do not constitute an improper limitation on the technical solution of the present invention.

[0038] The purpose of this invention is to provide a welding method for stainless steel composite plates. 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.

[0039] 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 b2 is 2mm and b1 is 8mm.

[0040] In some embodiments, the 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 bevel shown is described. Specifically, a composite bevel is machined on the weld section of the stainless steel composite plate at the position corresponding to the substrate layer. This composite bevel includes a vertically inclined portion 6, a transition arc 7, a horizontally inclined portion 8, and a horizontal portion 9 arranged sequentially. The width of the horizontal portion 9 (on one side) is... Figure 1 The designation is "w2"; a rectangular bevel 10 is made on the welding section of the stainless steel composite plate corresponding to the position of the transition layer, and the width of one side of the rectangular bevel is w1 / 2; no bevel is processed on the welding section of the stainless steel composite plate corresponding to the position of the stainless steel cladding layer, that is, the welding surface of the stainless steel cladding 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 carbon steel welding wire that matches the base layer, laser welding is used to filler wire welding the transition layer to form transition layer weld 4, i.e. Figure 1 The area circled by the gray dashed line. In this step, during laser filler wire welding, the laser heat source melts the rectangular groove, the horizontal extensions on both sides, and the downward melting part of the composite material layer, ultimately forming the transition layer weld 4.

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

[0045] Preferably, in some embodiments, the width w1 / 2 of a single side of the rectangular bevel should be controlled within the range of the laser spot radius of laser welding - 0.5 mm. That is, the total width w1 of the two rectangular bevels formed by the two spliced ​​stainless steel composite plates A and B should be controlled within the range of the laser spot diameter of laser welding - 1 mm. This design can achieve a smaller width of transition layer weld while ensuring the smooth completion of laser self-fusion welding of the stainless steel composite layer weld and without melting the carbon steel substrate.

[0046] Preferably, in some embodiments, the thickness b3 of the rectangular bevel can be limited to the range of 0.05mm ≤ b3 ≤ 0.5mm.

[0047] Preferably, in some embodiments, the angle α2 between the vertically inclined portion 6 and the vertical direction is ≥ (1.5b1)°, where b1 represents the distance from the surface of the substrate layer to its interface with the stainless steel cladding layer, with the unit parameter being mm. In this embodiment, controlling the angle α2 facilitates the subsequent hot-wire pulse oscillating tungsten inert gas welding operation.

[0048] Preferably, in some embodiments, the angle α1 between the horizontally inclined portion 8 and the horizontal direction is ≥5°, and the extension width w3 of the horizontally inclined portion 8 is ≥(5+0.1b1). In this embodiment, it is possible to avoid melting through the carbon steel substrate to the stainless steel composite substrate.

[0049] Preferably, in some embodiments, the radius r of the transition arc 7 is ≥ 0.2w3, where w3 represents the extension width of the horizontal inclined portion 8, and its unit parameter is mm.

[0050] Preferably, in some embodiments, in step 200, laser autofusion welding is used for welding, the laser spot diameter is ≤1mm, and a composite layer weld 3 is formed. The laser power can be controlled to be 5.0-6.0KW, the welding speed to be 3.5-4.0m / min, and the positive defocusing amount to be 0-5mm.

[0051] In step 300, laser filler wire welding is used to weld the transition layer weld 4. The filler metal can be ER50-6. The laser spot diameter is ≤1mm, the laser power is controlled at 6.0-8.0KW, the welding speed is 5.0-6.0m / min, the positive defocusing amount is 10-15mm, the wire feeding speed is 0.2-0.5m / min, and the wire feeding angle is 45-60°.

[0052] By employing this preferred embodiment and in conjunction with a specially designed bevel, the transition layer weld will melt down part of the composite layer weld, ultimately ensuring that the proportion of carbon steel components (including carbon steel base metal and carbon steel welding wire) melted into the transition layer weld does not exceed 25%.

[0053] In step 400, carbon steel weld wire ER50-6, which is matched with the base material, is used to weld the carbon steel weld 5. The welding method is hot-wire pulse tungsten inert gas welding, and the welding voltage is controlled at 13.0-15.0V, peak current at 180-220A, base current at 70-120A, duty cycle at 40-70%, pulse frequency at 3-8Hz, hot wire current at 60-80A, welding speed at 150-180mm / min, wire feed speed at 2.2-2.6m / min, and swing width at 1-2mm.

[0054] In this embodiment, when hot-wire pulse oscillating tungsten inert gas welding is used to fill the base layer weld, the special bevel design of this invention can ensure that the dilution rate of the carbon steel weld, especially the carbon steel weld bead that is in direct contact with the transition layer weld, is controlled below 4.0% without fully penetrating the carbon steel weld step.

[0055] 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.

[0056] Table 1.

[0057]

[0058] 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.

[0059] Table 2.

[0060]

[0061]

[0062] 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.

[0063] Table 3.

[0064]

[0065] 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.

[0066] Table 4.

[0067]

[0068] 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 transition layer weld bead relative to the composite layer weld bead is 82.10%, and the dilution rate of the carbon steel weld bead in direct contact with the transition layer relative to the composite layer weld bead is 3.25% (less than 4.0%). Therefore, the formation of martensitic structure in the carbon steel weld bead can be avoided.

[0069] Table 5.

[0070]

[0071] Figure 2The image shows the morphology of the welded joint of the composite plate prepared by the welding method of Embodiment 1 of the present invention after being etched by nitric acid alcohol.

[0072] from Figure 2 As can be seen from the data, the welded joint is well bonded, indicating that the method of the present invention can achieve the connection of stainless steel composite plates.

[0073] Figure 3 The image shows a metallographic photograph of the transition layer / carbon steel weld joint of the composite plate prepared by the welding method of Embodiment 1 of the present invention after etching with nitric acid alcohol.

[0074] from Figure 3 It can be seen that the transition layer weld cannot be corroded by nitric acid alcohol, indicating that it still retains the austenitic corrosion-resistant structure of the base material. The carbon steel weld bead adjacent to the transition layer is controlled to be ferrite + pearlite, and no martensite appears. This shows that the invention objective has been achieved, that is, the transition of the microstructure / composition from the transition layer of the stainless steel composite plate to the carbon steel weld is completed by using carbon steel welding materials, and the composite plate joint connection is reliable.

[0075] 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.

[0076] 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. A welding method for a stainless steel composite plate, 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 welding method includes the following steps: A composite bevel is machined on the welding section of the stainless steel composite plate at the position corresponding to the base material layer. The composite bevel includes a vertically inclined portion, a transition arc, a horizontally inclined portion, and a horizontal portion arranged sequentially. A rectangular bevel is opened on the welding section of the stainless steel composite plate at the position corresponding to the transition layer. 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 single-side width w1 / 2 of the rectangular bevel is greater than or equal to the laser spot radius of the laser welding and less than or equal to 0.5 mm. The thickness b3 of the rectangular bevel is 0.05-0.5 mm. The width w2 of the horizontal portion of the composite bevel is 0.5-1 mm. The extension width w3 of the horizontally inclined portion is greater than or equal to (5+0.1b1), where b1 represents the distance from the surface of the base material layer to its interface with the stainless steel cladding layer, and its unit parameter is mm. Laser welding was used to perform autofusion welding on the stainless steel composite layer; Using carbon steel welding wire that matches the base layer, laser welding is used to filler wire welding the transition layer; The substrate layer is welded using hot-wire pulse oscillation tungsten inert gas welding.

2. The welding method for stainless steel composite plates as described in claim 1, characterized in that, The angle α2 between the vertically inclined portion and the vertical direction is ≥ (1.5b1)°, where b1 represents the distance between the surface of the substrate layer and the interface between it and the stainless steel composite layer, and its unit parameter is mm.

3. The welding method for stainless steel composite plates as described in claim 1, characterized in that, The angle α1 between the horizontally inclined portion and the horizontal direction is ≥5°.

4. The welding method for stainless steel composite plates as described in claim 1, characterized in that, The radius r of the transition arc is greater than or equal to 0.2w3, where w3 represents the extended width of the horizontal inclined portion, and its unit parameter is mm.

5. The 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 5.0-6.0KW, the welding speed is 3.5-4.0m / min, and the positive defocusing amount is 0-5mm.

6. The 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.

7. The 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.

8. The 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 6.0-8.0KW, the welding speed is 5.0-6.0m / min, the positive defocusing amount is 10-15mm, the wire feeding speed is 0.2-0.5m / min, and the wire feeding angle is 45-60°.

9. The welding method for stainless steel composite plates as described in claim 1, characterized in that, In the step of welding the substrate layer using hot-wire pulse oscillation tungsten inert gas welding: the welding voltage is controlled at 13.0-15.0V, the peak current is 180-220A, the base current is 70-120A, the duty cycle is 40-70%, the pulse frequency is 3-8Hz, the hot wire current is 60-80A, the welding speed is 150-180mm / min, the wire feed speed is 2.2-2.6m / min, and the oscillation width is 1-2mm.

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