High-efficiency active agent for duplex stainless steel, preparation method and application thereof

Abstract

The application belongs to the field of active agents for welding, and provides a high-efficiency active agent for duplex stainless steel and a preparation method and application thereof. The active agent is composed of the following raw materials in percentage by weight: SiO2 powder 40-55%; TiO2 powder 30-40%; MnO2 powder 1-10%; NiO powder 1-10%; B2O3 powder 1-10%; MgO powder 1-10%, and the sum of the percentages of the raw materials is 100%. The problems of shallow weld penetration and low welding efficiency in the traditional welding method are solved, the weld structure and mechanical properties are improved, the arc is contracted and the molten pool flow state is changed, so that the penetration of TIG welding is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of welding activators, and specifically relates to a high-efficiency activator for duplex stainless steel, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Duplex stainless steel is a ferro-based corrosion-resistant alloy with excellent mechanical properties. Its microstructure consists of two phases, ferrite and austenite, with a near 1:1 ratio. Due to this well-balanced two-phase microstructure, duplex stainless steel combines the advantages of both ferrite and austenite. Comparisons with other major stainless steels reveal that duplex stainless steel exhibits better corrosion resistance and toughness than ferritic stainless steel, and better mechanical strength and stress corrosion resistance than austenitic stainless steel. Therefore, duplex stainless steel is a functional, integrated material with high strength and excellent corrosion resistance, and has been widely used in recent years in papermaking, construction, structural materials, nuclear reactors, petrochemical industries, and underwater engineering.

[0004] TIG welding (Tungsten Inert Gas Welding), also known as non-consumable electrode inert gas shielded arc welding, is the most commonly used welding method for welding 0.5-4.0 mm thick stainless steel. However, TIG welding suffers from insufficient weld penetration. Currently, activators are generally used to improve the weld penetration. For example, the welding method disclosed in ZL201910601454.7 has a weld penetration of 8 mm. Patent CN108637529A discloses an activator for tungsten inert gas welding of austenitic stainless steel, comprising the following components by weight percentage: 34-36% SiO2 powder, 25-27% TiO2 powder, 12-14% Cr2O3 powder, 7-9% NiO powder, 3-5% MnO powder, 7-9% CuO powder, and 5-7% B2O3 powder. However, it does not address the welding of duplex stainless steel, and the maximum weld penetration and joint performance need further improvement. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a highly efficient activator for duplex stainless steel, its preparation method, and its application. This solves the problems of shallow weld penetration and low welding efficiency in traditional welding methods, improves weld microstructure and mechanical properties, and causes arc contraction and changes in the flow state of the molten pool, thereby effectively increasing the penetration depth of TIG welding.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a highly efficient activator for duplex stainless steel, comprising the following raw materials in weight percentages: 40-55% SiO2 powder; 30-40% TiO2 powder; 1-10% MnO2 powder; 1-10% NiO powder; 1-10% B2O3 powder; and 1-10% MgO powder, wherein the sum of the percentages of each raw material is 100%.

[0008] In some embodiments, the raw materials are composed of the following weight percentages: 47%-55% SiO2 powder, 35%-40% TiO2 powder, 1%-4% MnO2 powder, 1%-4% NiO powder, 1%-4% B2O3 powder and 1%-6% MgO powder, the sum of the percentages of each raw material being 100%.

[0009] In some embodiments, the raw materials are composed of the following weight percentages: 40%-47% SiO2 powder, 30%-35% TiO2 powder, 4%-10% MnO2 powder, 4%-10% NiO powder, 4%-10% B2O3 powder and 6%-10% MgO powder, the sum of the percentages of each raw material being 100%.

[0010] In some effective embodiments, the high-efficiency activator for duplex stainless steel preferably comprises, by weight percentage: 47% SiO2 powder, 35% TiO2 powder, 4% MnO2 powder, 4% NiO powder, 4% B2O3 powder, and 6% MgO powder.

[0011] In some embodiments, the particle size of the SiO2 powder, TiO2 powder, MnO2 powder, NiO powder, B2O3 powder and MgO powder is less than 5 μm, and the purity is 99.9%.

[0012] This invention uses SiO2 powder, TiO2 powder, MnO2 powder, NiO powder, B2O3 powder, and MgO powder as activator components. It comprehensively considers the effects of each individual activator component on increasing weld penetration depth, changes in the metallographic microstructure of the joint, as well as the requirements for the alloy system and the estimation of alloy loss. Among these, SiO2, MnO2, NiO, B2O3, and TiO2 have significant effects on improving weld penetration depth and aspect ratio. B2O3, SiO2, NiO, MnO2, and TiO2 can refine the weld. The addition of SiO2, NiO, and MgO to the weld grains helps to reduce the dendritic orientation of the fusion line. SiO2 can improve the solidification mode of the joint, while TiO2 can replenish the burn-off of trace elements in the joint and reduce the negative impact of impurity elements. At the same time, substances such as SiO2, NiO, and MnO2 in the activator will cause the arc to contract, resulting in a higher arc energy density and increased arc force. This increases the molten volume of the molten pool under the arc, thereby increasing the weld depth and reducing the weld width, thus improving the depth-to-width ratio of the joint.

[0013] A second aspect of the present invention provides a method for preparing a highly efficient activator for duplex stainless steel, comprising:

[0014] SiO2, TiO2, MnO2, NiO, B2O3 and MgO powders were dried and ground to a particle size of less than 5μm, and then sealed and stored in a drying oven.

[0015] When using, combine the ingredients according to the above proportions to obtain the final product.

[0016] More specifically, including:

[0017] (1) Place SiO2, TiO2, MnO2, NiO, B2O3 and MgO powders into a drying oven at room temperature and dry for 1 hour to remove the water of crystallization from the activator powder;

[0018] (2) The SiO2 powder, TiO2 powder, MnO2 powder, NiO powder, B2O3 powder and MgO powder are fully ground to have an independent particle size of less than 5μm and a purity of 99.9%;

[0019] (3) The fully ground SiO2 powder, TiO2 powder, MnO2 powder, NiO powder, B2O3 powder and MgO powder are classified, sealed and stored in a drying oven;

[0020] (4) When using, mix according to the ratio to obtain a high-efficiency activator for duplex stainless steel.

[0021] The present invention does not impose any special limitation on the mixing method; any mixing method known to those skilled in the art can be used, such as stirring.

[0022] A third aspect of the present invention provides the application of the above-mentioned highly efficient activator for duplex stainless steel in the field of welding.

[0023] A fourth aspect of the present invention provides a method for welding duplex stainless steel, comprising:

[0024] Pre-treatment of duplex stainless steel sheets to be welded;

[0025] The above-mentioned surfactant and organic solvent are mixed evenly to obtain an surfactant solution;

[0026] The solvent solution is applied to the area to be welded on the duplex stainless steel sheet. After standing, the organic solvent is allowed to evaporate completely, and then the sheet is welded to obtain the desired product.

[0027] More specifically, including:

[0028] S1. Grind and wash the duplex stainless steel sheet to be welded, and clean the oil, rust, moisture and other debris within a 25mm range on both sides of the area to be welded until the metal luster is exposed.

[0029] S2, mix the surfactant and organic solvent thoroughly and stir to prepare a viscous solution;

[0030] S3. Apply the viscous solution prepared with the above-mentioned activator evenly to the area to be soldered by brushing or spraying. The coating thickness should be sufficient to cover the metal surface.

[0031] S4. After coating as described above, let stand for 2-3 minutes to allow the polar organic solvent to evaporate naturally or to dry using a hot air gun or other equipment before welding.

[0032] In this invention, a highly efficient activator for duplex stainless steel is prepared into a viscous liquid using an organic solvent and coated onto the surface of the stainless steel to be welded. Welding is then carried out after the polar organic solvent has evaporated.

[0033] This invention does not impose any special limitations on the mixing operation; any mixing method known to those skilled in the art for the use of highly efficient surfactants and organic solvents for duplex stainless steel can be employed. This invention does not limit the amount of the organic solvent used; it is recommended to use acetone or alcohol in a 1:2.15 ratio to form a paste or viscous consistency for later use.

[0034] In this invention, the duplex stainless steel preferably includes the steps of sanding or grinding with an angle grinder, followed by washing with acetone or ethanol before coating. This invention does not impose any particular limitation on the specific operations of sanding or grinding with an angle grinder, or washing with acetone or ethanol; any operation method well-known to those skilled in the art can be used.

[0035] The present invention does not have a particular limitation on the coating thickness, but it is preferable to be able to completely coat the stainless steel surface, and more preferably the coating thickness is 0.3-1mm.

[0036] The present invention does not have any particular limitation on the coating method. Any coating method known to those skilled in the art can be used, such as brushing or spraying.

[0037] In some embodiments, the welding process parameters are as follows: welding current 175-180A, welding speed 70-95mm / min, arc voltage 13-14V, argon flow rate of welding torch 15-18L / min, argon flow rate of back shielding 20-24L / min, tungsten electrode diameter 3.2mm, coating thickness 0.3-1mm, assembly gap 0.2-1mm, misalignment 0.2-0.3mm, and plate flatness less than 2mm.

[0038] Beneficial effects of the present invention

[0039] (1) The activator provided by this invention is composed entirely of oxides, is non-toxic and harmless, does not contain precious metals, and is low in cost, with a cost of no more than 170 yuan per kilogram. This invention mainly solves the problem of shallow penetration and low efficiency of single-pass welds in traditional TIG welding plates. The use of A-TIG welding can retain the advantages of high welding quality and beautiful forming of TIG welding, while significantly increasing the welding penetration and improving production efficiency. Moreover, the high-efficiency activator for duplex stainless steel in this invention can refine the weld grains, effectively hinder dislocation movement, improve the mechanical properties of the joint, and help improve welding production efficiency and reduce welding production costs. It can achieve 17.5mm single-sided welding with double-sided forming.

[0040] (2) The high-efficiency activator for duplex stainless steel of the present invention has stable welding quality. The activator coating layer is not easy to fall off during the welding process. The activator slag shell after welding is easy to clean. After welding, the joint is subjected to 100% radiographic testing and 100% penetrant testing according to AWSD 1.6-2007 standard. The joint is qualified by radiographic and penetrant testing. There are no defects such as cracks, incomplete penetration, incomplete fusion, and undercut. The weld is silvery white and has a beautiful shape.

[0041] (3) The high-efficiency activator for duplex stainless steel of the present invention does not require expensive welding equipment during welding. Compared with other welding methods, A-TIG requires simple equipment, is easy to operate and maintain, and is suitable for various welding positions. Currently, the A-TIG welding method has been widely used in energy production, aerospace, automotive industry, power machinery and other fields, such as nuclear reactors, automobile wheel hubs and pressure vessels. Under the same parameters, the grains and microstructure of duplex stainless steel welded using the activator of the present invention are significantly refined, the area of ​​grain boundaries increases, and the appearance of more grain boundaries effectively hinders the movement of dislocations, playing a role in grain boundary strengthening. More δ-ferrite precipitated in the joint. Compared to traditional argon arc welding, the ferrite content in the activator-welded joint increased from 44.35% to 57.67%. Furthermore, δ-ferrite has higher mechanical strength than austenite, which can improve the mechanical properties of the welded joint. However, more δ-ferrite in the joint is not necessarily better; there is a range. Excessive δ-ferrite will form more σ-phase, consuming a large amount of Cr and causing joint embrittlement. For duplex stainless steel, the δ-ferrite content is generally controlled between 40% and 60%. The ferrite content in the joint of this invention is 57.67%, which is within the specified range. Therefore, applying the activator of this invention does not deteriorate the joint.

[0042] (4) The material targeted by this invention is S32101 duplex stainless steel instead of 321 austenitic stainless steel. The maximum melting depth can reach 17.5mm, which is higher than the maximum melting depth of CN108637529A of 16mm, resulting in higher joint performance.

[0043] (5) Compared to MnO, MnO2 has a higher oxygen content, which is more conducive to promoting molten pool flow. The oxygen atoms in the oxide have good electron affinity and surface activity, which will cause the surface tension temperature gradient of the molten pool to change from negative to positive (better than fluorides), causing Marangoni convection reversal, increasing the convection velocity, increasing the penetration ability of the electric arc, and improving the heat transfer efficiency at the bottom of the molten pool. In addition, this duplex steel has 50% ferrite and 50% austenite. Manganese can ensure that austenite and ferrite reach the appropriate balance and reduce the nickel content. The addition of MgO helps to weaken the dendrite orientation of the fusion line. Compared with austenitic stainless steel, duplex stainless steel itself has a higher Cr content of 21.00-23.00% (austenitic stainless steel is 16.00-18.00%). Cr is a ferrite-forming element. In order to ensure that the ratio of ferrite and austenite is close to equilibrium, the activator of this invention does not add Cr2O3. Cu is an austenite-forming element, which is not conducive to the formation of ferrite. By controlling the content of Cu, Cr and Mn, the austenite and ferrite can be ensured to reach the corresponding equilibrium. Attached Figure Description

[0044] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0045] Figure 1 Macroscopic morphology of cross-section of duplex stainless steel flat joint;

[0046] Figure 2 Schematic diagram of Marangoni convection;

[0047] Figure 3 The bar chart shows the room temperature tensile strength of the S32101 duplex stainless steel welded according to the present invention; wherein, C2 is the S32101 duplex stainless steel welded in Example 1, C5 is the S32101 duplex stainless steel welded in Comparative Example 2, and TIG-S32101 is the S32101 duplex stainless steel welded in Comparative Example 1.

[0048] Figure 4 This is a hardness distribution diagram of the S32101 duplex stainless steel welded according to the present invention; C2 is the S32101 duplex stainless steel welded in Example 1, C5 is the S32101 duplex stainless steel welded in Comparative Example 2, and TIG-S32101 is the S32101 duplex stainless steel welded in Comparative Example 1.

[0049] Figure 5 The image shows the morphology of a bent S32101 duplex stainless steel specimen welded in Example 1.

[0050] Figure 6 The diagram shows the δ-ferrite content in the S32101 duplex stainless steel joint welded in Example 1.

[0051] Figure 7 The image shows the microstructure of the S32101 duplex stainless steel welded in Example 1.

[0052] Figure 8 The image shows the microstructure of the S32101 duplex stainless steel welded in Comparative Example 1.

[0053] Figure 9 The image shows the microstructure of the welded S32101 duplex stainless steel in Comparative Example 2. Detailed Implementation

[0054] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0055] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0056] Example 1

[0057] A high-efficiency activator for duplex stainless steel comprises, by mass percentage: 47% SiO2 powder, 35% TiO2 powder, 4% MnO2 powder, 4% NiO powder, 4% B2O3 powder, and 6% MgO powder. The SiO2, TiO2, MnO2, NiO, B2O3, and MgO powders are thoroughly ground to an independent particle size of less than 5 μm, and all have a purity of 99.9%. The thoroughly ground activator powders are then classified, sealed, and stored in a drying oven. In use, according to the specified proportions, weigh the raw materials using an electronic balance with an accuracy of 0.01 mg. Pour all the prepared ingredients into a beaker, then weigh an appropriate amount of alcohol using a graduated cylinder and add it to the beaker. While adding the alcohol, continuously stir the activator. Mix the alcohol and activator thoroughly at a ratio of 1:2.15 to create a viscous solution. Grind and wash the duplex stainless steel sheet to be welded, cleaning oil, rust, moisture, and other impurities from within a 25mm radius on both sides of the welding area until a metallic luster is exposed. Then, use a brush to evenly apply the activator to the left and right sides of the welding area, with a coating thickness of 0.3-1mm, for 10mm on each side. Welding can be performed after the alcohol has evaporated. When welding 22mm thick S32101 duplex stainless steel using the activator from Example 1 for A-TIG welding, the weld penetration depth reached 17.5mm.

[0058] Welding was performed on 6.35mm thick S32101 duplex stainless steel. The welding parameters were: welding current 180A, welding speed 80mm / min, arc voltage 13V, argon flow rate 15L / min (welding torch) / 20L / min (back shield), tungsten electrode diameter 3.2mm, coating thickness 0.3-1mm, assembly gap 0.2mm, misalignment 0.2mm, and plate flatness less than 2mm. The specimens were air-cooled, cut, inlaid, polished, and etched. The weld penetration and width were measured to determine the relationship between the activator and the weld penetration and width. The microstructure and mechanical properties of the alloy were also analyzed. Figures 1-7 As shown.

[0059] Example 2

[0060] A high-efficiency activator for duplex stainless steel comprises, by mass percentage: 55% SiO2 powder, 35% TiO2 powder, 2% MnO2 powder, 2% NiO powder, 2% B2O3 powder, and 4% MgO powder. The SiO2, TiO2, MnO2, NiO, B2O3, and MgO powders are thoroughly ground to an independent particle size of less than 5 μm, and all have a purity of 99.9%. The thoroughly ground activator powders are then classified, sealed, and stored in a drying oven. In use, according to the specified proportions, weigh the raw materials using an electronic balance with an accuracy of 0.01 mg. Pour all the prepared ingredients into a beaker, then weigh an appropriate amount of alcohol using a graduated cylinder and add it to the beaker. While adding the alcohol, continuously stir the activator. Mix the alcohol and activator thoroughly at a ratio of 1:2.15 to form a viscous solution. Grind and wash the duplex stainless steel sheet to be welded, cleaning oil, rust, moisture, and other impurities within a 25mm radius on both sides of the welding area until a metallic luster is exposed. Then, use a brush to evenly apply the activator to the left and right sides of the welding area for 10mm, with a coating thickness of 0.3-1mm. Welding can be performed after the alcohol has evaporated. When welding 22mm thick S32101 duplex stainless steel using the activator from Example 2 for A-TIG welding, the weld penetration depth reached 16.9mm.

[0061] The activator of Example 2 was used to weld 6.35mm thick S32101 duplex stainless steel. The tensile strength of the weld joint was measured to be 720.86MPa and the joint strength coefficient was 100.12%.

[0062] As can be seen from Example 2, the tensile strength of the high-efficiency activator joint for duplex stainless steel provided by the present invention reaches 720.86 MPa and fractures in the base material, with a joint strength coefficient of 100.12%. This demonstrates that by reasonably adjusting the dosage of each component in the activator, the activator can still effectively solve the problems of shallow weld penetration and low efficiency in traditional TIG welding of plates. Therefore, parameter adjustments within this range fall within the protection scope of the present invention.

[0063] Comparative Example 1

[0064] Welding was performed on 6.35mm thick S32101 duplex stainless steel. The only difference from Example 1 was that no activator was added; it was a conventional TIG weld. The specimens were air-cooled, cut, inlaid, polished, and etched. The weld penetration and width were measured to determine the relationship between the activator and the weld penetration and width. The microstructure of the alloy was also analyzed. Figure 8 As shown.

[0065] Comparative Example 2

[0066] Welding was performed on 6.35mm thick S32101 duplex stainless steel. The only difference from Example 1 was the use of activator ZL201910601454.7, authorized by Nanjing University of Technology. After welding, the specimens were air-cooled, cut, inlaid, polished, and etched. The weld penetration and width were measured to determine the relationship between the activator and the weld penetration and width. The microstructure of the alloy was also analyzed. Figure 9 As shown.

[0067] from Figures 7 to 9 The weld microstructure consists of austenite and ferrite, with banded γ-phase surrounded by a continuous δ-phase matrix. A small amount of Widmanstätten-like austenite also exists, growing at a certain angle into the ferrite grains. During weld cooling, austenite first nucleates at the ferrite boundaries, due to the higher free energy at these locations. Quantitative metallographic analysis revealed that the volume fractions of austenite and ferrite were 42.33% and 57.67%, respectively. Compared to welds without activator, welds coated with activator exhibit refined grains and increased grain boundary area. The presence of more grain boundaries effectively hinders dislocation movement, resulting in grain boundary strengthening. Furthermore, the entry of Si and Ti elements into the joint has a certain effect on improving the performance of stainless steel. Silicon is a ferrite-forming element, and increasing Si content can promote ferrite formation. Increased ferrite content can improve the elastic limit, yield point, and tensile strength of stainless steel, thus improving its performance. Secondly, titanium has the best affinity for carbon. In the weld, carbon preferentially combines with titanium to form titanium carbide (TiC), which is dispersed in austenite and hinders austenite grain growth. At the same time, TiC can also prevent the formation of chromium carbide and reduce chromium consumption at grain boundaries.

[0068] Table 1. Comparison of mechanical properties of welds in the embodiments and comparative examples.

[0069] Example 1 722.15 100.3％ Example 2 720.86 100.12％ Comparative Example 1 713.53 99.1％ Comparative Example 2 717.26 99.62％

[0070] The mechanical properties of the joint were tested. The tensile properties of the welded joint are shown in Table 1 above. It can be seen that without the activator, the tensile strength of the welded joint is 713.53 MPa. With the activator of Example 1, the tensile strength of the A-TIG welded joint is 722.15 MPa, which significantly improves the mechanical properties of the welded joint.

[0071] As can be seen from Examples 1 and 2, the tensile strength of the duplex stainless steel joint with high-efficiency activator provided by the present invention reaches 722.15 MPa and fractures in the base material, with a joint strength coefficient of 100.3%. No cracks were generated on the outer surface after a 180° face and back bend. Furthermore, the weld hardness using the activator of the present invention is higher than that without the activator. The hardness of the weld without the activator is approximately 247.9 HV, while the hardness of the weld with the activator is approximately 265.75 HV. This is because after adding the activator, it enters the weld under the action of arc heat, increasing the types and content of weld alloy elements, hindering grain growth, increasing the nucleation rate, refining the grains, changing the solidification mode, and precipitating more δ-ferrite, thereby improving the weld hardness.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly efficient activator for duplex stainless steel, characterized in that, It is composed of the following raw materials in weight percentages: SiO2 powder 40-55%; TiO2 powder 30-40%; MnO2 powder 1-10%; NiO powder 1-10%; B2O3 powder 1-10%; MgO powder 1-10%, and the sum of the percentages of each raw material is 100%.

2. The high-efficiency activator for duplex stainless steel as described in claim 1, characterized in that, It is composed of the following raw materials in weight percentages: 47%-55% SiO2 powder, 35%-40% TiO2 powder, 1%-4% MnO2 powder, 1%-4% NiO powder, 1%-4% B2O3 powder and 1%-6% MgO powder, and the sum of the percentages of each raw material is 100%.

3. The high-efficiency activator for duplex stainless steel as described in claim 1, characterized in that, It is composed of the following raw materials in weight percentages: 40%-47% SiO2 powder, 30%-35% TiO2 powder, 4%-10% MnO2 powder, 4%-10% NiO powder, 4%-10% B2O3 powder and 6%-10% MgO powder, and the sum of the percentages of each raw material is 100%.

4. The high-efficiency activator for duplex stainless steel as described in claim 1, characterized in that, The high-efficiency activator for duplex stainless steel is composed of the following raw materials in weight percentages: 47% SiO2 powder, 35% TiO2 powder, 4% MnO2 powder, 4% NiO powder, 4% B2O3 powder and 6% MgO powder.

5. The high-efficiency activator for duplex stainless steel as described in claim 1, characterized in that, The particle size of the SiO2 powder, TiO2 powder, MnO2 powder, NiO powder, B2O3 powder and MgO powder is all less than 5μm, and the purity is 99.9%.

6. A method for preparing a highly efficient activator for duplex stainless steel, characterized in that, include: SiO2, TiO2, MnO2, NiO, B2O3 and MgO powders were dried and ground to a particle size of less than 5μm, and then sealed and stored in a drying oven. When used, the mixture is combined according to the proportions of any one of claims 1-5 to obtain the final product.

7. The application of the high-efficiency activator for duplex stainless steel according to any one of claims 1-5 in the field of welding.

8. A method for welding duplex stainless steel, characterized in that, include: Pre-treatment of duplex stainless steel sheets to be welded; The surfactant according to any one of claims 1-5 and the organic solvent are mixed evenly to obtain an surfactant solution; The activator solution is applied to the area to be welded on the duplex stainless steel sheet, left to stand to allow the organic solvent to evaporate completely, and then welded to obtain the final product.

9. The method for welding duplex stainless steel as described in claim 8, characterized in that, The organic solvent is acetone or alcohol; Alternatively, the area coated with the activator solution is the target welding area and extends outward from the boundary of the welding area by 5-10 mm.

10. The method for welding duplex stainless steel as described in claim 8, characterized in that, The welding process parameters are as follows: welding current 175-180A, welding speed 70-95mm / min, arc voltage 13-14V, argon flow rate of welding torch 15-18L / min, argon flow rate of back shielding 20-24L / min, tungsten electrode diameter 3.2mm, coating thickness 0.3-1mm, assembly gap 0.2-1mm, misalignment 0.2-0.3mm, and plate flatness less than 2mm.

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