A low-hydrogen flux-cored wire based on two-dimensional MXene surface self-assembly modification, a preparation method and application thereof

Abstract

This invention discloses a low-hydrogen flux-cored welding wire based on two-dimensional MXene surface self-assembly modification, its preparation method, and its application, belonging to the field of welding materials technology. The low-hydrogen flux-cored welding wire comprises a steel strip outer sheath and a flux core filled within it, the flux core being composed of metal alloy powder and modified composite flux core powder. Its preparation method includes: preparing a two-dimensional MXene colloidal dispersion using a chemical etching method; cationically modifying the insulating slag-forming powder; mixing the two and electrostatically self-assembling and coating them; after drying, mixing with the metal alloy powder; filling the steel strip; and rolling and drawing into shape. This invention constructs a three-dimensional continuous conductive network within the flux core through the MXene layer, improving arc stability; simultaneously, the MXene shell forms a physically water-blocking labyrinth, endowing the welding wire with ultra-low hydrogen characteristics; the active titanium released by the decomposition of MXene at high welding temperatures can refine the weld grains and improve mechanical properties. This welding wire can be widely used in automated gas-shielded welding processes for high-strength steel.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a low-hydrogen flux-cored welding wire based on two-dimensional MXene surface self-assembly modification, its preparation method, and its application. Background Technology

[0002] Flux-cored welding wires are widely used in heavy steel structures, shipbuilding, bridge construction, and energy pipelines due to their advantages such as high deposition efficiency, good welding process performance, and ease of automation. With the increasingly stringent welding quality requirements of high-end equipment manufacturing, improving arc stability and suppressing the diffusible hydrogen content in the weld metal have become the core challenges in the development of flux-cored welding wire technology.

[0003] In existing technologies, a large amount of insulating slag-forming agents (such as rutile, calcium fluoride, feldspar, quartz, etc.) must be added to the flux core of flux-cored welding wire to achieve functions such as droplet transfer, slag formation, deoxidation, and alloying. However, traditional flux-cored systems have the following problems and shortcomings.

[0004] First, there is insufficient arc stability. Conventional slag-forming powders are mostly insulators at room temperature. During the arc initiation and droplet transition stages, the insulating powder causes drastic fluctuations in contact resistance, leading to arc interruption or large particle spatter, reducing the connectivity of effective active sites, and severely affecting the continuity of automated welding.

[0005] Secondly, it is highly hygroscopic and prone to hydrogen absorption. Traditional slag-forming powders have strong hygroscopic properties and easily absorb ambient moisture during storage. Hydrogen decomposed under high-temperature electric arcs enters the molten pool, easily causing hydrogen-induced delayed cracking (cold cracking) in high-strength steel, severely restricting its application in high-strength steel welding.

[0006] Furthermore, microscopic modification and molding are difficult. Existing technologies typically employ copper plating on the outer sheath or the addition of alkali metal arc stabilizers, which only partially compensate at the macroscopic or spatial arc level, failing to fundamentally alter the insulating and hydrophilic defects of the slag-forming powder at the microscopic physical level. The lack of molding designs for practical flux-cored powder engineering applications makes it difficult to directly adapt theoretical improvements to existing flux-cored welding wire production processes.

[0007] Therefore, developing a micro-modified composite flux core material that is structurally stable, highly conductive, moisture-resistant, and environmentally friendly is of great significance for promoting the practical engineering application of high-quality welding technology. Summary of the Invention

[0008] In view of the above, it is necessary to provide a low-hydrogen flux-cored welding wire based on two-dimensional MXene surface self-assembly modification, its preparation method and application. This welding wire achieves a comprehensive improvement in arc ignition success rate, arc stability, moisture resistance and mechanical properties of deposited metal by constructing a microscopic three-dimensional conductive network and a physical water-blocking layer.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0010] A method for preparing a low-hydrogen flux-cored wire based on two-dimensional MXene surface self-assembly modification includes the following steps.

[0011] S1. A two-dimensional MXene colloidal dispersion with a negative surface charge was prepared by chemical etching.

[0012] S2. The insulating slag-forming powder is dispersed in an aqueous solution containing cationic polyelectrolytes for surface modification to obtain a positively charged insulating slag-forming powder suspension.

[0013] S3. The two-dimensional MXene colloidal dispersion obtained in step S1 is added dropwise to the suspension in step S2 for electrostatic self-assembly coating. During this process, the two-dimensional MXene nanosheets in the two-dimensional MXene colloidal dispersion are spontaneously adsorbed onto the surface of the positively charged insulating slag-forming powder due to electrostatic attraction, forming a uniform and dense coating layer. The dry weight of the two-dimensional MXene is controlled to be 0.2wt%-3.0wt% of the total mass of the insulating slag-forming powder. After washing and vacuum freeze-drying, a modified composite core powder with a core-shell structure is obtained.

[0014] S4. The modified composite flux-cored powder processed in step S3 is mixed with metal alloy powder, filled into a steel strip, and then rolled and drawn to obtain the low-hydrogen flux-cored welding wire.

[0015] It should be noted that the "two-dimensional MXene" mentioned in this invention refers to two-dimensional transition metal carbide / nitride nanosheets obtained by MAX phase etching and exfoliation. Specifically, using Ti3AlC2 MAX phase powder as a precursor, the Al atomic layer is selectively removed by chemical etching to obtain the chemical formula Ti3C2T X (T) X Two-dimensional MXene materials, representing surface functional groups such as -OH, -O, and -F, etc., are used. When dispersed in water after preparation, this material exists as a uniformly dispersed monolayer colloidal state, referred to as a "two-dimensional MXene colloidal dispersion." When the nanosheets in this dispersion electrostatically self-assemble and coat the surface of slag-forming particles, and then dry, they form a coating layer attached to the particle surface, referred to as a "two-dimensional MXene nanosheet." The aforementioned "two-dimensional MXene colloidal dispersion" and "two-dimensional MXene nanosheet" are different forms of the same nanomaterial at different process stages, with identical material properties.

[0016] In this invention, further, in step S1, the chemical etching method involves etching the MAX phase precursor Ti3AlC2 in a mixed solution containing lithium fluoride and hydrochloric acid; the etching reaction temperature is 0-5℃, the reaction time is 12-36 hours, and a single-layer or few-layer two-dimensional MXene colloidal dispersion is obtained after ultrasonic peeling.

[0017] In this invention, further, in step S2, the cationic polyelectrolyte is a polydimethyldiallylammonium chloride (PDDA) solution with a mass concentration of 0.5wt%-2wt%.

[0018] In this invention, further, in step S4, the mass ratio of the modified composite core powder to the metal alloy powder is (2-4):(6-8), and the filling rate of the mixed powder in the steel strip is 16%-18%.

[0019] The present invention also proposes a low-hydrogen flux-cored welding wire prepared by the above-described method, comprising: a steel strip outer sheath and a flux core filled therein; the flux core is composed of metal alloy powder and modified composite flux core powder; the modified composite flux core powder has a core-shell structure, wherein the insulating slag-forming powder is the core and the two-dimensional MXene nanosheets are the shell; after the welding wire is rolled and drawn, the modified composite flux core powder is in a compressed state, and the two-dimensional MXene nanosheets on its surface are in contact with each other, forming a three-dimensional continuous conductive network inside the flux core.

[0020] In this invention, the insulating slag-forming powder is further selected from one or more of rutile, calcium fluoride, and feldspar.

[0021] In this invention, the insulating slag-forming powder is further composed of rutile, calcium fluoride and feldspar mixed in a weight ratio of 4:3:3.

[0022] In this invention, the metal alloy powder further includes iron powder, manganese powder, and silicon powder.

[0023] The present invention also proposes an application of the aforementioned low-hydrogen flux-cored welding wire in automated gas-shielded welding, wherein the welding wire is used to reduce welding spatter and / or suppress diffuse hydrogen in the deposited metal.

[0024] Furthermore, in this invention, the low-hydrogen flux-cored wire reduces the welding spatter rate to below 3% and keeps the diffusible hydrogen content of the deposited metal below 0.03 mL / g.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] 1. This invention constructs a dense two-dimensional MXene coating layer on the surface of insulating slag-forming powder using electrostatic self-assembly technology. After rolling and drawing, the MXene layers on the powder particles come into contact with each other, forming a three-dimensional continuous conductive network inside the flux core. This network provides a low-resistance electronic transmission channel for welding current, fundamentally eliminating the drastic fluctuations in contact resistance caused by the accumulation of insulating slag-forming powder particles in traditional flux-cored welding wires. Welding test results show that the arc ignition success rate of the welding wire of this invention reaches 100%, the voltage / current variation coefficient is reduced by more than 60% compared with the unmodified welding wire, and the spatter rate is controlled below 3%.

[0027] 2. In this invention, MXene nanosheets tightly coat the surface of hydrophilic slag-forming particles in a "core-shell" structure, forming a dense physical barrier layer. Mechanistically, this layered structure prolongs the diffusion path of water molecules, creating a "physical maze effect," thereby effectively inhibiting the penetration of environmental moisture into the slag-forming powder. After 72 hours of exposure to high temperature and humidity (30℃ / 80%RH), the diffusible hydrogen content of the weld metal deposited by the welding wire of this invention remains below 0.03 mL / g (i.e., 3 mL / 100g), far lower than the diffusible hydrogen level of the unmodified welding wire under the same conditions, demonstrating excellent environmental stability.

[0028] 3. The two-dimensional MXene (Ti3C2T) used in this invention X During the high-temperature welding range (approximately 400-600℃), in-situ structural decomposition occurs, releasing highly active titanium. Mechanistically, this active titanium combines with oxygen in the molten pool to achieve deep deoxidation, reducing oxide inclusions; simultaneously, it reacts with carbon to generate nanoscale TiC particles in situ. These nanoscale TiC particles can serve as heterogeneous nucleation sites for acicular ferrite, promoting the refinement of the weld microstructure. EBSD microstructural analysis shows that the proportion of acicular ferrite in the weld metal of this invention is significantly increased, and the yield strength, tensile strength, and -40℃ low-temperature impact toughness are all superior to those of unmodified welding wire and physically mixed welding wire, achieving a synergistic improvement in both strength and toughness. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation process of the low-hydrogen flux-cored welding wire in an embodiment of the present invention.

[0030] Figure 2 These are microstructure characterization diagrams of different samples in the embodiments of the present invention; wherein, Figure 2 Image a is a transmission electron microscope (TEM) image of the modified composite core powder. Figure 2 b is the corresponding energy dispersive spectroscopy (EDS) surface scan elemental distribution map.

[0031] Figure 3 Here is a scanning electron microscope cross-sectional image of the flux-cored welding wire prepared in an embodiment of the present invention; wherein, Figure 3 a represents the overall cross-sectional morphology. Figure 3 b and Figure 3 c is a magnified view of a portion of the image.

[0032] Figure 4 The MXene powder (Ti3C2T) in the embodiments of the present invention X Thermogravimetric analysis curves.

[0033] Figure 5 This is a comparison diagram of the arc characteristics of different samples in the embodiments of the present invention; wherein, Figure 5 a-5c shows the voltage / current waveform: Figure 5 a is a voltage / current waveform diagram of the welding wire in an embodiment of the present invention. Figure 5 b is the voltage / current waveform diagram of a traditional welding wire. Figure 5 c represents the voltage / current waveform of the physically hybrid welding wire; Figure 5 d is a bar chart comparing the voltage / current variation coefficient and the splashing rate.

[0034] Figure 6 This is a comparison chart of the diffusible hydrogen content of different samples under different environmental exposure times in embodiments of the present invention.

[0035] Figure 7 This is an electron backscatter diffraction (EBSD) characterization diagram of the microstructure of the fused metal in an embodiment of the present invention. Detailed Implementation

[0036] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] The main preparation process of this invention is as follows: Figure 1 As shown.

[0038] Raw materials and reagents: The chemical reagents used in the embodiments of this invention (lithium fluoride, hydrochloric acid, polydimethyldiallylammonium chloride, etc.) are all analytical grade; the purity of the Ti3AlC2 MAX phase powder used is ≥98%, and the particle size is <38μm; the low carbon steel strip used is commercially available SPCC cold-rolled steel strip, with a width of 12mm and a thickness of 0.8mm; the purity of the protective gas argon is ≥99.99%.

[0039] In this invention, "MXene" refers to a two-dimensional transition metal carbide / nitride nanomaterial obtained by MAX phase etching and exfoliation. In the form of a dispersion liquid, it is called "MXene colloidal dispersion"; in the form of a dry powder, it is called "MXene powder"; when it is coated onto the surface of slag-forming particles through electrostatic self-assembly, it is called "two-dimensional MXene nanosheets".

[0040] Example 1: Preparation of a two-dimensional MXene colloidal dispersion with a negative surface charge.

[0041] Weigh 2.0 g of lithium fluoride (LiF) and dissolve it in 40 mL of 9 mol / L hydrochloric acid solution. Mix the solution in an ice bath with stirring. Slowly add 2.0 g of Ti3AlC2 MAX phase powder in portions and react at a constant temperature for 24 h with continuous magnetic stirring. Repeatedly centrifuge and wash the reaction product until the pH of the supernatant reaches approximately 6. Add deionized water and sonicate under argon protection in an ice bath for 1 h. Then centrifuge to remove any unremoved precipitate. The supernatant is the monolayer / few-layer two-dimensional MXene (Ti3C2T). X The colloidal dispersion was then subjected to vacuum freeze-drying to obtain two-dimensional MXene (Ti3C2T). X )powder.

[0042] Example 2: Preparation of modified composite core powder.

[0043] (1) Pretreatment of insulating slag powder: weigh rutile (TiO2), calcium fluoride (CaF2) and feldspar in a weight ratio of 4:3:3, prepare 100g of slag powder, and disperse it in 500mL of 1wt% polydimethyldiallylammonium chloride (PDDA) aqueous solution.

[0044] (2) Cationic modification: Stir mechanically at room temperature for 2 hours, filter and rinse repeatedly with deionized water to remove free PDDA, and then resuspend the positively charged powder in 500 mL of deionized water.

[0045] (3) Electrostatic self-assembly: The negatively charged MXene colloidal dispersion obtained in Example 1 was slowly added dropwise to the above suspension (the dry weight of the two-dimensional MXene nanosheets was controlled to be 1% of the total mass of the slag-forming powder), and the mixture was stirred continuously until the liquid phase was completely clear. During this process, the MXene nanosheets in the MXene colloidal dispersion were uniformly coated on the surface of the slag-forming particles through electrostatic interaction, thus forming a continuous nanosheet shell structure.

[0046] (4) Crosslinking, curing and drying: The self-assembled product is filtered and placed at -50℃ for vacuum freeze drying for 24 hours to obtain the modified composite core powder with core-shell structure.

[0047] For comparative studies, the following control powder was also prepared in this embodiment.

[0048] Control group 1 (unmodified raw powder): Insulating slag-forming powder (a mixture of rutile, calcium fluoride and feldspar) mixed in a weight ratio of 4:3:3 was used directly without any surface modification.

[0049] Control group 2 (physically mixed powder): MXene powder obtained by vacuum freeze-drying the MXene colloidal dispersion prepared in Example 1 was physically dry-mixed with the same insulating slag-forming powder (rutile, calcium fluoride, and feldspar mixed in a weight ratio of 4:3:3). The dry weight percentage of the two-dimensional MXene nanosheets was also 1% of the total mass of the slag-forming powder. This control powder was not modified with PDDA or subjected to electrostatic self-assembly.

[0050] Example 3: Preparation of low-hydrogen flux-cored welding wire.

[0051] The modified composite flux-cored wire prepared in Example 2 was mixed with metal alloy powder at a mass ratio of 3:7 in a three-dimensional mixer until homogeneous. The metal alloy powder consisted of the following components by weight percentage: 1.5%-2.5% manganese powder, 0.5%-1.2% silicon powder, 0.5%-1.5% nickel powder, 0.1%-0.4% molybdenum powder, with the balance being iron powder and unavoidable impurities. A low-carbon steel strip was rolled into a U-shaped groove, and the mixed powder was quantitatively filled in (filling rate controlled at 17%). Through a closed die and a multi-pass drawing micro-shrinking process, the wire was drawn to a diameter of 1.2 mm, thus obtaining a low-hydrogen flux-cored wire modified based on the self-assembly of two-dimensional MXene nanosheets.

[0052] Conventional welding wire (control group 1) and physically mixed welding wire (control group 2) were prepared using the same process with the control powder.

[0053] Example 4: Microscopic morphology and phase characterization.

[0054] The modified powder prepared in Example 2 was observed using transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Figure 2 As shown in Figure a, it can be clearly observed that the surface of the slag-forming particles is tightly wrapped by two-dimensional MXene nanosheets. These nanosheets are derived from the MXene colloidal dispersion prepared in Example 1, and are fixed to the particle surface after electrostatic self-assembly. Figure 2 The EDS surface scan of b shows that the coating surface is rich in Ti and C elements, proving that the core-shell structure was successfully constructed by electrostatic self-assembly.

[0055] The cross-section of the welding wire prepared in Example 3 was observed using a scanning electron microscope (SEM). Figure 3 As shown. Figure 3 a represents the overall cross-sectional morphology. Figure 3b and Figure 3 c is a magnified view of a specific area; combined with Figure 3 a- Figure 3 The results showed that, under the stretched and compressed state, the two-dimensional MXene nanosheets on the surface of the powder particles were pressed and contacted with each other, forming a three-dimensional continuous conductive network that runs through the entire core.

[0056] The MXene powder obtained by vacuum freeze-drying of the MXene colloidal dispersion prepared in Example 1 was tested using a thermogravimetric analyzer (TGA). Figure 4 As shown in the figure. The results indicate that the MXene powder sample obtained after drying undergoes structural decomposition in the high-temperature welding range (approximately 400-600℃), releasing highly active titanium, which verifies the rationality of its functional timing sequence.

[0057] It should be noted that when the amount of two-dimensional MXene nanosheets (on a dry weight basis) is less than 0.2 wt%, it is difficult to form a continuous and complete coating layer on the surface of the slag-forming particles, the three-dimensional conductive network cannot be effectively constructed, and the improvement in arc stability is not significant. When the amount of two-dimensional MXene nanosheets is greater than 3.0 wt%, the flowability of the core powder decreases and the cost increases significantly, resulting in a lower overall cost-effectiveness. Therefore, this invention controls the amount of two-dimensional MXene nanosheets within the range of 0.2 wt% to 3.0 wt%.

[0058] Example 5: Comparison of arc stability and spatter rate tests.

[0059] The welding test adopted an automated CO2 gas shielded welding process with the following welding parameters: welding current 280A, arc voltage 30V, and welding speed 350mm / min.

[0060] Arc ignition success rate test: The arc ignition success rate of the welding wire in this embodiment of the invention reaches 100%, while the arc ignition success rate of control group 1 (traditional welding wire) is about 60%-70%, and that of control group 2 (physically mixed welding wire) is about 80%.

[0061] Voltage / current waveform analysis: such as Figure 5 As shown in a-5c, Figure 5 Figure a shows that the waveform of the welding wire in the embodiment of the present invention is extremely smooth and regular; Figure 5 Figure b shows that the waveform of control group 1 has a large number of irregular spikes and open circuits; Figure 5 c shows that the waveform stability of control group 2 has improved, but there are still obvious fluctuations.

[0062] Splash rate test: such as Figure 5 As shown in Figure d, the wire spatter rate in this embodiment of the invention is controlled at an extremely low level of ≤3%, which is significantly lower than that of control groups 1 and 2. Furthermore, the voltage / current variation coefficient of the welding wire of this invention is reduced by more than 60% compared to control groups 1 and 2.

[0063] The above results show that the microscopic three-dimensional conductive network constructed from two-dimensional MXene nanosheets fundamentally eliminates the resistance abrupt change caused by insulating powder and significantly improves arc stability.

[0064] Example 6: Diffusion hydrogen and environmental adaptability test.

[0065] The diffusible hydrogen content was determined according to the method in (GB / T 3965-2012 "Determination of diffusible hydrogen in welded metal").

[0066] The effects of exposure to high temperature and high humidity (30℃ / 80%RH) for 72 hours on the moisture absorption and hydrogen increase of different welding wires were investigated.

[0067] The results are as follows Figure 6 As shown, the diffusible hydrogen content of control group 1 (uncoated) welding wire spiked to over 10 mL / 100g after 72 hours of exposure due to the hydrophilicity of the slag-forming powder (highly prone to cold cracking). The diffusible hydrogen content of control group 2 (physically mixed) welding wire also increased. However, in the composite welding wire system of this invention, the layered shell structure formed by the two-dimensional MXene nanosheets acts like a "physical water-resistant maze," preventing the intrusion of air moisture. After 72 hours, the diffusible hydrogen content of the deposited metal remained below 0.03 mL / g (i.e., 3 mL / 100g). This demonstrates the material's excellent environmental stability.

[0068] Example 7: Mechanical properties of welded metal and microstructure analysis of EBSD.

[0069] Mechanical property tests were conducted in accordance with GB / T 2652-2022 "Destructive Testing of Welds in Metallic Materials - Longitudinal Tensile Test of Weld Metal in Fusion Welded Joints" and GB / T 2650-2022 "Destructive Testing of Welds in Metallic Materials - Impact Test".

[0070] The microstructure of the weld metal deposited by the welding wire of this invention was characterized. For example... Figure 7 As shown in the EBSD microstructure diagram, the proportion of highly tough acicular ferrite is significantly increased in the system of this invention due to the in-situ generation of nano-TiC particles as nucleation sites.

[0071] Tensile and impact tests show that the yield strength, tensile strength and -40℃ impact toughness (absorbed energy) of the welding wire of the present invention are significantly better than those of control group 1 and control group 2, achieving a synergistic improvement in high strength and high toughness.

[0072] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a low-hydrogen flux-cored wire based on two-dimensional MXene surface self-assembly modification, characterized in that, Includes the following steps: S1. A two-dimensional MXene colloidal dispersion with a negative surface charge was prepared by chemical etching. S2. The insulating slag-forming powder is dispersed in an aqueous solution containing cationic polyelectrolytes for surface modification to obtain a positively charged insulating slag-forming powder suspension. S3. The two-dimensional MXene colloidal dispersion obtained in step S1 is added dropwise to the suspension in step S2 for electrostatic self-assembly coating. The dry weight of the two-dimensional MXene is controlled to be 0.2wt%-3.0wt% of the total mass of the insulating slag powder. After washing and vacuum freeze-drying, a modified composite core powder with a core-shell structure is obtained. S4. The modified composite flux-cored powder processed in step S3 is mixed with metal alloy powder, filled into a steel strip, and then rolled and drawn to obtain the low-hydrogen flux-cored welding wire.

2. The preparation method according to claim 1, characterized in that, In step S1, the chemical etching method involves etching the MAX phase precursor Ti3AlC2 in a mixed solution containing lithium fluoride and hydrochloric acid. The etching reaction temperature is 0-5℃, the reaction time is 12-36 hours, and a single layer or few layers of two-dimensional MXene are obtained after ultrasonic peeling.

3. The preparation method according to claim 1, characterized in that, In step S2, the cationic polyelectrolyte is a polydimethyldiallylammonium chloride (PDDA) solution with a mass concentration of 0.5wt%-2wt%.

4. The preparation method according to claim 1, characterized in that, In step S4, the mass ratio of the modified composite core powder to the metal alloy powder is (2-4):(6-8), and the filling rate of the mixed powder in the steel strip is 16%-18%.

5. A low-hydrogen flux-cored welding wire prepared by the method according to any one of claims 1-4, characterized in that, include: The steel strip has an outer sheath and a core filled inside it; the core is composed of metal alloy powder and modified composite core powder; the modified composite core powder has a core-shell structure, wherein the insulating slag-forming powder is the core and the two-dimensional MXene is the shell; after the welding wire is rolled and drawn, the modified composite core powder is in a compressed state, and the two-dimensional MXene layers on its surface are in contact with each other, forming a three-dimensional continuous conductive network inside the core.

6. The low-hydrogen flux-cored welding wire according to claim 5, characterized in that, The insulating slag-forming powder is selected from one or more of rutile, calcium fluoride, and feldspar.

7. The low-hydrogen flux-cored welding wire according to claim 6, characterized in that, The insulating slag-forming powder is composed of rutile, calcium fluoride and feldspar mixed in a weight ratio of 4:3:

3.

8. The low-hydrogen flux-cored welding wire according to claim 5, characterized in that, The metal alloy powder includes iron powder, manganese powder, and silicon powder.

9. The application of a low-hydrogen flux-cored welding wire according to any one of claims 5-8 in automated gas-shielded welding, characterized in that, The welding wire is used to reduce welding spatter and / or suppress diffuse hydrogen in the weld metal.

10. The application according to claim 9, characterized in that, The low-hydrogen flux-cored wire reduces the welding spatter rate to below 3% and keeps the diffusible hydrogen content of the deposited metal below 0.03 mL / g.

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