A high corrosion resistance low hydrogen flux cored wire for offshore welded pipe and a preparation method thereof

Abstract

This invention discloses a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes and its preparation method. The flux-cored welding wire comprises a low-carbon steel strip outer sheath and flux powder. The flux powder comprises the following components by mass percentage: rutile, iron powder, nickel powder, molybdenum powder, chromium powder, ferromanganese, silicon powder, calcium fluoride, rare earth oxides, Ti-B composite refining agent, nano-TiN particles, and graphite. This invention is the first to employ a ternary synergistic system composed of rare earth oxides, nano-TiN, and a Ti-B composite refining agent. Through a progressive mechanism of rare earth purifying the molten pool, nano-TiN providing heterogeneous nucleation cores, and Ti-B promoting the formation of acicular ferrite, deep purification and ultra-refinement of the weld microstructure are achieved. The welding wire prepared by this invention is suitable for high-reliability welding of marine engineering welded pipes, subsea pipelines, and offshore platform steel structures.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes and its preparation method. Background Technology

[0002] With the continuous expansion of global offshore oil and gas resource development and the rapid development of the offshore wind power industry, high-strength pipeline steel of API X70, X80, and even X100 grades is increasingly widely used in marine engineering. Marine engineering structures are exposed to high concentrations of chloride ions (Cl-) for extended periods during service. - It operates in harsh corrosive environments (with concentrations reaching over 19,000 mg / L), and is simultaneously subjected to the coupled effects of multiple factors, including alternating wave loads, low temperatures (below 0°C in some sea areas during winter), and static stress caused by the structure's own weight. These service conditions make the welded joints highly susceptible to the following failure modes: 1) Pitting and crevice corrosion: Chloride ions destroy the passivation film on the weld surface, causing localized corrosion and accelerating crack initiation; 2) Low-temperature brittle fracture: The weld microstructure has insufficient toughness reserve under low-temperature conditions, and the impact absorption energy is significantly reduced; 3) Corrosion fatigue: The synergistic effect of corrosive media and alternating stress significantly accelerates the growth rate of fatigue cracks, greatly shortening the service life of the structure.

[0003] Currently, while existing flux-cored welding wires for marine engineering meet the basic requirements of API standards in terms of conventional mechanical properties (such as tensile strength and yield strength), they still suffer from the following common technical defects: the weld metal has limited corrosion resistance in seawater and acidic media containing H2S, and its pitting potential is low, making it difficult to meet long-life design requirements; the deposited metal has a high diffusible hydrogen content (usually >5mL / 100g), which significantly increases the susceptibility to hydrogen-induced cold cracking under thick plate multi-layer multi-pass welding conditions; the volume fraction of acicular ferrite (AF) in the weld microstructure is insufficient, resulting in an unsatisfactory match between strength and toughness; the slag-gas-forming system in the flux-cored wire formulation has limited purification effects on the molten pool, such as deoxidation, desulfurization, and degassing, and the content of impurity elements and inclusions is high; under long-term corrosion-fatigue coupled conditions, the fatigue life of the weld metal decreases significantly, becoming a weak link in the safe service of the structure. Summary of the Invention

[0004] To address the above problems, this invention provides a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes and its preparation method.

[0005] The technical solution of this invention is as follows: a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes, comprising a low-carbon steel strip outer sheath and flux powder filled within the outer sheath. The flux powder comprises the following components by mass percentage: rutile 18%–24%; iron powder 22%–28%; nickel powder 3%–5%; molybdenum powder 1.0%–2.5%; chromium powder 2.5%–4.5%; manganese powder 6%–10%; silicon powder 1%–3%; calcium fluoride 4%–8%; rare earth oxides 0.3%–1.2%; Ti-B composite refining agent 0.2%–0.8%; nano-TiN particles 0.2%–0.6%; graphite 0.3%–0.8%; and the balance being iron powder. The sum of the mass percentages of the above components is 100%.

[0006] The core powder comprises the following components by mass percentage: rutile 21.0%; iron powder 25.0%; nickel powder 4.0%; molybdenum powder 1.8%; chromium powder 3.5%; manganese powder 8.0%; silicon powder 2.0%; calcium fluoride 6.0%; rare earth oxides 0.8%; Ti-B composite refining agent 0.5%; TiN nanoparticles 0.4%; graphite 0.5%; and the remainder is iron, with the sum of the masses of all components being 100%.

[0007] The filling rate of the core powder is 18wt%-25wt%.

[0008] The rare earth oxide is selected from one or more of CeO2, La2O3 or Y2O3.

[0009] The Ti-B composite refining agent includes ferrotitanium powder and ferroboronium powder.

[0010] A method for preparing a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes, comprising: Step 1: Weigh the following components according to their mass percentages: rutile 18%–24%; iron powder 22%–28%; nickel powder 3%–5%; molybdenum powder 1.0%–2.5%; chromium powder 2.5%–4.5%; manganese powder 6%–10%; silicon powder 1%–3%; calcium fluoride 4%–8%; rare earth oxides 0.3%–1.2%; Ti-B composite refining agent 0.2%–0.8%; nano-TiN particles 0.2%–0.6%; graphite 0.3%–0.8%; the balance is iron powder. The sum of the mass percentages of the above components is 100%. Step 2: Place the core powder weighed in Step 1 into a ball mill jar and use stainless steel grinding balls for ball milling; Step 3: The ball-milled core powder from Step 2 is uniformly mixed and placed in a tube furnace with argon gas continuously introduced. The furnace temperature is set to 150℃ and the drying time is 1 hour. The dried core powder is then placed in a powder mixer for thorough mixing, with a mixing time of 2 hours. Step 4: Roll the low-carbon cold-rolled steel on a wire drawing machine, wrap the flux core powder prepared in step 3 inside the low-carbon cold-rolled steel, close the alloy strip through a die, and then reduce the diameter of the coarse welding wire to 1.6mm. Step 5: Perform electrochemical copper plating on the surface of the flux-cored wire drawn to the finished diameter, with the copper plating layer thickness controlled within the range of 0.3 to 0.5 μm; Step 6: Wind the copper-plated finished flux-cored welding wire into a coil according to the specified coil weight, place it in an aluminum-plastic composite vacuum packaging bag, evacuate to below -0.095MPa, fill with high-purity argon gas, and seal for storage.

[0011] In step 2, Milling balls with diameters of 5 mm, 10 mm, and 20 mm were selected. The milling speed was 300 r / min, and the milling time was 2 to 3 hours. The resulting powder particle size was 15 to 45 µm.

[0012] This invention, for the first time, employs a ternary synergistic system composed of rare earth oxides, nano-TiN, and a Ti-B composite refining agent. Through a progressive mechanism involving rare earth purification of the molten pool, nano-TiN providing a heterogeneous nucleation core, and Ti-B promoting the formation of acicular ferrite, deep purification and ultra-refinement of the weld microstructure are achieved. The ultra-low hydrogen synergistic system of calcium fluoride, rare earth oxides, and graphite effectively controls the hydrogen content. This invention provides a novel flux-cored welding wire that combines high tensile strength, excellent low-temperature toughness, ultra-low diffusible hydrogen content, and excellent seawater corrosion resistance, possessing significant engineering and economic value for ensuring the safety of marine engineering structures and extending their service life. Attached Figure Description

[0013] Figure 1 This is a metallographic schematic diagram of the weld structure in this invention. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0015] This invention provides a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes, comprising a low-carbon steel strip outer sheath and flux powder filled within the outer sheath. The flux powder comprises the following components by mass percentage: rutile 18%–24%; iron powder 22%–28%; nickel powder 3%–5%; molybdenum powder 1.0%–2.5%; chromium powder 2.5%–4.5%; manganese powder 6%–10%; silicon powder 1%–3%; calcium fluoride 4%–8%; rare earth oxides 0.3%–1.2%; Ti-B composite refining agent 0.2%–0.8%; nano-TiN particles 0.2%–0.6%; graphite 0.3%–0.8%; and the remainder being iron powder, with the sum of the mass of all components being 100%.

[0016] The functions and design principles of each component are as follows: Rutile: Its main component is TiO2. It acts as a slag-forming agent and arc stabilizer, reducing slag viscosity and improving weld formation. Compared with conventional flux-cored welding wire, this invention optimizes the slag-gas-forming system within the rutile content range, forming a reasonable slag-gas balance with graphite, significantly reducing welding spatter rate (by about 25%) and improving arc stability.

[0017] Iron powder (22%–28%, plus the balance iron powder): used as filler metal and matrix component to improve deposition efficiency. The balance iron powder is used to balance the components to 100%.

[0018] Nickel powder: It introduces Ni into the weld, expanding the austenite region, lowering the phase transformation temperature, and significantly improving the low-temperature toughness of the weld metal. Simultaneously, Ni works synergistically with Cr and Mo to improve corrosion resistance while suppressing the upward shift of the low-temperature brittle transition temperature.

[0019] Molybdenum powder: A transition element, Mo strengthens weld metal through solid solution and enhances its high-temperature strength and resistance to temper brittleness. Mo synergistically forms a dense passivation film with Cr, improving pitting corrosion resistance; simultaneously, Mo inhibits the precipitation of proeutectoid ferrite at grain boundaries and promotes the formation of acicular ferrite.

[0020] Chromium powder: Cr, a transition element, is a key alloying element for improving the seawater corrosion resistance of weld metal. Cr forms a Cr-rich passivation film on the weld surface, significantly increasing the pitting potential. The Cr content in conventional 690MPa grade flux-cored welding wire is typically 1.0%–2.0%. This invention increases the Cr content to 2.5%–4.5%, which significantly improves corrosion resistance. To avoid the decrease in toughness and increased sensitivity to welding cracks caused by high Cr, this invention achieves a coordinated balance of strength, toughness, and corrosion resistance by combining 3%–5% Ni and 1.0%–2.5% Mo, as well as the grain refinement effect of Ti-B composite refining agents and nano-TiN particles.

[0021] Manganese powder: A transition element (Mn), it acts as a deoxidizer and desulfurizer, purifying the weld metal and providing solid solution strengthening. Mn and Si work together to deoxidize, reducing the oxygen content of the weld metal and minimizing inclusions.

[0022] Silicon powder: A transitional element, Si acts as a deoxidizer in synergy with Mn, while simultaneously improving the fluidity of the molten pool and the surface formation of the weld.

[0023] Calcium fluoride: used as a slag-forming agent and hydrogen remover. At high welding temperatures, CaF2 decomposes to produce fluorides, which combine with hydrogen in the molten pool to form HF gas that escapes, significantly reducing the diffusible hydrogen content in the deposited metal. The CaF2 content in conventional flux-cored welding wire is typically 1%–3%. This invention increases it to 4%–8%, reducing the diffusible hydrogen content from the conventional 6.8 mL / 100 g to below 3.2 mL / 100 g. However, excessively high CaF2 content leads to decreased arc stability and increased spatter. This invention achieves a balance between hydrogen reduction and process performance by controlling it at 4%–8% and synergistically optimizing arc characteristics with rutile and graphite.

[0024] Rare earth oxides: selected from one or more of CeO2, La2O3, or Y2O3. Rare earth elements possess strong chemical reactivity, enabling them to deeply purify the molten pool. They combine with impurity elements such as S and P to form high-melting-point compounds that float to the surface and are removed, reducing inclusion content. Simultaneously, rare earths can refine grains and improve inclusion morphology (spheroidization, dispersed distribution). Conventional flux-cored welding wires typically contain less than 0.2% rare earth oxides or none at all. This invention uses a higher content of 0.3% to 1.2%, which significantly improves weld purity and microstructure uniformity.

[0025] Ti-B composite refining agent: The Ti-B composite refining agent refers to a composite alloy powder containing titanium and boron elements. It can be a mechanical mixture of ferrotitanium powder and ferroboron powder, or a titanium-boron compound powder such as TiB2, wherein the mass ratio of Ti to B is controlled within the range of (8-12):1. Ti-B composite refining agent is a commonly used microalloying method in the field to promote the nucleation of acicular ferrite, but in this invention, it is combined with nano-TiN particles and rare earth oxides in a ternary synergistic formulation. Ti combines with N and O in the molten pool to form TiN and TiO. x Fine inclusions act as nucleation sites for acicular ferrite; boron segregates towards austenite grain boundaries, lowering grain boundary energy and inhibiting the precipitation of proeutectoid ferrite, thereby promoting the nucleation of acicular ferrite within the grains. The synergy between Ti-B and nano-TiN can increase the volume fraction of acicular ferrite to over 65%.

[0026] Nano-TiN particles: Titanium nitride particles with a particle size of 50–200 nm are directly added to the flux core as an external heterogeneous nucleation core. Nano-TiN and acicular ferrite share a body-centered cubic structure with a lattice mismatch of only about 4.7% and low interfacial energy, which can efficiently promote the nucleation of acicular ferrite. Simultaneously, nano-TiN can pin austenite grain boundaries, inhibiting grain coarsening. Conventional flux-cored wires do not add nano-TiN particles; this invention is the first to introduce them into flux-cored wires for marine welded pipes, forming a ternary synergistic system with Ti-B composite refining agents and rare earth oxides, achieving deep purification and ultra-refinement of the weld microstructure.

[0027] Graphite: As a gas generator and deoxidizer, it produces a CO / CO2 protective atmosphere when burned, isolating the air and reducing the dissolution of nitrogen and hydrogen; at the same time, C can adjust the carbon content of the weld metal to ensure strength.

[0028] The outer sheath is made of low-carbon cold-rolled steel strip; the filling rate of the core powder is 18wt%-25wt%.

[0029] This invention also provides a method for preparing a high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes, the specific implementation steps of which are as follows: Step 1: Weigh the following components according to their mass percentages: rutile 18%–24%; iron powder 22%–28%; nickel powder 3%–5%; molybdenum powder 1.0%–2.5%; chromium powder 2.5%–4.5%; manganese powder 6%–10%; silicon powder 1%–3%; calcium fluoride 4%–8%; rare earth oxides 0.3%–1.2%; Ti-B composite refining agent 0.2%–0.8%; nano-TiN particles 0.2%–0.6%; graphite 0.3%–0.8%; the balance is iron powder. The sum of the mass percentages of the above components is 100%. Step 2: Place the core powder weighed in Step 1 into a ball mill jar, select stainless steel grinding balls with diameters of 5mm, 10mm, and 20mm, mill at a speed of 200~300r / min, and mill for 2~3 hours. The resulting powder particle size is 15~45µm.

[0030] Graded ball milling process description: One of the process innovations of this invention is the use of three different diameter grinding balls for graded ball milling. Large-diameter grinding balls (20mm) primarily provide impact crushing, breaking down larger particles; medium-diameter grinding balls (10mm) provide grinding, refining medium-sized particles; and small-diameter grinding balls (5mm) provide fine grinding and uniform mixing, resulting in a more concentrated powder particle size distribution. The synergistic effect of the three types of grinding balls allows for efficient refining of the powder to 15-45μm within a short time (2-3 hours), with a uniform particle size distribution, avoiding the "over-grinding" or "under-grinding" phenomena caused by grinding balls of a single particle size. If only a single grinding ball is used, either the particle size distribution will be too wide, or a longer ball milling time will be required, increasing energy consumption and the risk of impurity introduction.

[0031] Step 3: The core powder from step 2, which was ball-milled, is uniformly mixed and placed in a tube furnace with argon gas continuously introduced. The furnace temperature is set to 150℃~180℃ and the drying time is 1h~1.5h. The dried core powder is then placed in a powder mixer for thorough mixing, with a mixing time of 1h~2h. Argon-protected low-temperature drying instructions: Drying with argon gas at 150℃~180℃ removes adsorbed moisture from the powder surface while preventing oxidation or agglomeration of the core powder (especially nano-TiN particles and rare earth oxides) at high temperatures. Drying temperatures below 200℃ prevent premature decomposition or moisture absorption by components such as CaF2.

[0032] Step 4: Roll the low-carbon cold-rolled steel on a wire drawing machine, wrap the flux-cored powder prepared in step 3 inside the low-carbon cold-rolled steel, close the alloy strip through a die, reduce the diameter of the coarse welding wire to 1.6 mm, and remove impurities from the surface of the welding wire; the filling rate of the flux-cored powder is 18wt%-25wt%.

[0033] Step 5: Perform electrochemical copper plating on the surface of the flux-cored welding wire drawn to the finished diameter. The thickness of the copper plating layer is controlled within the range of 0.3 to 0.5 μm to improve the conductivity, rust prevention and wire feeding smoothness of the welding wire.

[0034] Step 6: Wind the copper-plated finished flux-cored welding wire into a coil according to the specified coil weight, place it in an aluminum-plastic composite vacuum packaging bag, evacuate to below -0.095MPa, fill with high-purity argon gas (purity ≥99.99%), and seal for storage. Example 1

[0035] First, a low-hydrogen, high-corrosion-resistant flux-cored welding wire for marine welded pipes is prepared. Then, this welding wire is used for welding marine engineering welded pipes, subsea oil and gas pipelines, and offshore platform steel structures. Specifically: Step 1: Weigh the following core powders by mass percentage: rutile 21.0%; iron powder 25.0%; nickel powder 4.0%; molybdenum powder 1.8%; chromium powder 3.5%; manganese powder 8.0%; silicon powder 2.0%; calcium fluoride 6.0%; rare earth oxides 0.8%; Ti-B composite refining agent 0.5%; nano TiN 0.4%; graphite 0.5%; and the remainder is iron. The sum of the mass of all components is 100%.

[0036] Step 2: Place the core powder weighed in Step 1 into a ball mill jar, select stainless steel grinding balls with diameters of 5mm, 10mm, and 20mm, mill at a speed of 300r / min for 2-3 hours, and obtain a powder particle size of 15-45µm.

[0037] Step 3: The ball-milled core powder from Step 2 is uniformly mixed and placed in a tube furnace with argon gas continuously introduced. The furnace temperature is set to 150℃ and the drying time is 1 hour. The dried core powder is then placed in a powder mixer for thorough mixing, with a mixing time of 2 hours. Step 4: Roll the low-carbon cold-rolled steel on a wire drawing machine, wrap the flux-cored powder prepared in step 3 inside the low-carbon cold-rolled steel, close the alloy strip through a die, reduce the diameter of the coarse welding wire to 1.6 mm, and remove impurities from the surface of the welding wire; the filling rate of the flux-cored powder is 18wt%-25wt%.

[0038] Step 5: Perform electrochemical copper plating on the surface of the flux-cored wire drawn to the finished diameter, with the copper plating layer thickness controlled within the range of 0.3 to 0.5 μm.

[0039] Step 6: Wind the copper-plated finished flux-cored welding wire into a coil according to the specified coil weight, place it in an aluminum-plastic composite vacuum packaging bag, evacuate to below -0.095MPa, fill with high-purity argon gas (purity ≥99.99%), and seal for storage.

[0040] In the application, API X80 pipeline steel plate with a thickness of 20mm was used. The bevel type was single V-shaped with an angle of 60° and a blunt edge of 2mm. Multi-layer and multi-pass welding was performed. The welding current was set to 260A, the arc voltage to 29V, the shielding gas to 100%Ar, the gas flow rate to 20L / min, and the welding speed to 350 mm / min.

[0041] The weld test results showed that, after mechanical property testing and microstructure observation, the tensile strength was 725 MPa, the yield strength was 640 MPa, and the diffusible hydrogen content was 3.2 mL / 100g.

[0042] The beneficial effects of this invention are as follows: A ternary synergistic grain refinement system of rare earth oxides, nano-TiN, and Ti-B: rare earth oxides purify the molten pool, reduce inclusion content, and improve their distribution; nano-TiN particles provide high-density heterogeneous nucleation sites; and Ti-B composite refiners inhibit grain boundary ferrite and promote intragranular acicular ferrite nucleation. The synergistic effect of these three components results in a smaller average effective grain size in the weld compared to conventional welding wire. Figure 1 As shown, the weld microstructure is mainly composed of acicular ferrite, and the volume of acicular ferrite is significantly increased compared to that in conventional methods, which results in a significant improvement in corrosion fatigue life.

[0043] The Cr, Ni and Mo corrosion resistance-toughness synergistic system: High Cr (2.5%~4.5%) provides the basis for corrosion resistance, but high Cr easily leads to a decrease in toughness and an increase in sensitivity to welding cracks; Ni (3%~5%) expands the austenite region and improves low-temperature toughness, offsetting the adverse effects of high Cr; Mo (1.0%~2.5%) strengthens through solid solution and improves resistance to temper brittleness, while synergistically improving the stability of the passivation film with Cr.

[0044] The CaF2, rare earth oxides, and graphite ultra-low hydrogen synergistic system: CaF2 (4%–8%) actively removes hydrogen; rare earth oxides purify the molten pool and reduce hydrogen adsorption sites; graphite generates gas to isolate air and reduce hydrogen sources. The three work synergistically to control the diffusible hydrogen content to ≤4 mL / 100g, far lower than the >5 mL / 100g of conventional flux-cored welding wire.

[0045] A synergistic system for arc stabilization using rutile, graphite, and silicon powder: optimizing the slag-gas generation system to improve arc stability and droplet transfer mechanism.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes, comprising a low-carbon steel strip sheath and flux powder filled within the sheath, characterized in that, The core powder comprises the following components by weight percentage: rutile 18%–24%; iron powder 22%–28%; nickel powder 3%–5%; molybdenum powder 1.0%–2.5%; chromium powder 2.5%–4.5%; manganese powder 6%–10%; silicon powder 1%–3%; calcium fluoride 4%–8%; and rare earth oxides 0.3%–1.2%. Ti-B composite refining agent 0.2%–0.8%; nano TiN particles 0.2%–0.6%; graphite 0.3%–0.8%; balance iron powder, the sum of the mass percentages of the above components is 100%.

2. The high corrosion resistance, low hydrogen flux-cored welding wire for marine welded pipes according to claim 1, characterized in that, The core powder comprises the following components by mass percentage: rutile 21.0%; iron powder 25.0%; nickel powder 4.0%; molybdenum powder 1.8%; chromium powder 3.5%; manganese powder 8.0%; silicon powder 2.0%; calcium fluoride 6.0%; rare earth oxides 0.8%; Ti-B composite refining agent 0.5%; TiN nanoparticles 0.4%; graphite 0.5%; and the remainder is iron, with the sum of the masses of all components being 100%.

3. The high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes according to claim 1, characterized in that, The filling rate of the core powder is 18wt%-25wt%.

4. The high corrosion resistance, low hydrogen flux-cored welding wire for marine welded pipes according to claim 1, characterized in that, The rare earth oxide is selected from one or more of CeO2, La2O3 or Y2O3.

5. The high corrosion resistance, low hydrogen flux-cored welding wire for marine welded pipes according to claim 1, characterized in that, The Ti-B composite refining agent includes ferrotitanium powder and ferroboronium powder.

6. The method for preparing the high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes according to any one of claims 1-5, characterized in that, include: Step 1: Weigh the following components according to their mass percentages: rutile 18%–24%; iron powder 22%–28%; nickel powder 3%–5%; molybdenum powder 1.0%–2.5%; chromium powder 2.5%–4.5%; manganese powder 6%–10%; silicon powder 1%–3%; calcium fluoride 4%–8%; rare earth oxides 0.3%–1.2%; Ti-B composite refining agent 0.2%–0.8%; nano-TiN particles 0.2%–0.6%; graphite 0.3%–0.8%; balance iron powder, the sum of the mass percentages of the above components is 100%; Step 2: Place the core powder weighed in Step 1 into a ball mill jar and use stainless steel grinding balls for ball milling; Step 3: The ball-milled core powder from Step 2 is uniformly mixed and placed in a tube furnace with argon gas continuously introduced. The furnace temperature is set to 150℃ and the drying time is 1 hour. The dried core powder is then placed in a powder mixer for thorough mixing, with a mixing time of 2 hours. Step 4: Roll the low-carbon cold-rolled steel on a wire drawing machine, wrap the flux core powder prepared in step 3 inside the low-carbon cold-rolled steel, close the alloy strip through a die, and then reduce the diameter of the coarse welding wire to 1.6mm. Step 5: Perform electrochemical copper plating on the surface of the flux-cored wire drawn to the finished diameter, with the copper plating layer thickness controlled within the range of 0.3 to 0.5 μm; Step 6: Wind the copper-plated finished flux-cored welding wire into a coil according to the specified coil weight, place it in an aluminum-plastic composite vacuum packaging bag, evacuate to below -0.095MPa, fill with high-purity argon gas, and seal for storage.

7. The method for preparing high corrosion-resistant, low-hydrogen flux-cored welding wire for marine welded pipes according to claim 6, characterized in that, In step 2, Milling balls with diameters of 5 mm, 10 mm, and 20 mm were selected. The milling speed was 300 r / min, and the milling time was 2 to 3 hours. The resulting powder particle size was 15 to 45 µm.

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