Flux-cored wire for deep-sea wet FCAW and manufacturing method

Abstract

In a flux-cored wire and manufacturing method dedicated to deep-sea wet FCAW, the flux-cored wire comprises an outer layer steel band and an inner layer flux core, the material of the outer layer steel band is stainless steel, the material comprises carbon, chromium, nickel, titanium, niobium, molybdenum, copper, silicon, and aluminum, and the remainder is an iron element; the composition of the inner layer flux core is as follows, comprising 30%-50% of a gas generating agent, 20%-30% of a flux forming agent, 15%-25% of a heat generating agent, and 5%-25% of a metal powder; the components of the gas generating agent are sodium bicarbonate, calcium carbonate, and alkaline copper carbonate, wherein the mass percentage of sodium bicarbonate in the gas generating agent is 10%-30%, the share of calcium carbonate is 60%-70%, and the share of alkaline copper carbonate is 10%-30%.

Description

Technology Field

[0001] The present invention relates to the design and manufacture of flux-cored wires dedicated to deep-sea wet FCAW, and belongs to the field of wire technology. Background Technology

[0002] As the consumption of energy resources continues to increase, users have begun exploring the vast natural resources found in the ocean. This raises higher demands on the construction of offshore process structures. Underwater welding serves as a critical means for constructing and maintaining these structures, and its welding quality directly determines their reliability. Underwater welding technology plays an indispensable role, whether in the construction and installation of offshore oil and gas extraction platforms or in the maintenance and laying of seabed pipelines. Unlike onshore welding, structural materials in underwater welding are subjected to additional loads beyond operating loads, including those caused by storms, waves, tidal currents, seawater corrosion, and gravel and sand abrasion. Therefore, improving the quality of underwater welding and optimizing the welding process is a critical issue that currently needs to be addressed.

[0003] Underwater welding can be classified into dry welding, local dry welding, and wet welding based on the relationship between the welding zone and water resources. Underwater dry welding is a method of welding a workpiece by completely isolating it from water through a dry atmospheric or high-pressure air chamber; however, because this method is very expensive, research on underwater dry arc welding is currently more focused on the exploration and optimization of high-pressure dry processes. Local dry welding underwater proceeds with the workpiece welding process by isolating the arc from water through the construction of a fine air chamber, and research is currently heavily concentrated on the process and structure. Underwater wet welding is a method of welding in which the workpiece and welding torch are placed directly underwater; both arc combustion and droplet transitional occur within bubbles generated by water decomposition and gas generation from flux-cored wire, and these bubbles isolate the welding zone from the water environment, ensuring the progress of the welding process. Although underwater wet welding has advantages that are not comparable to the other two methods, such as simple operation, flexible welding positioning, and low construction costs, its drawbacks are also very distinct. Specifically, the presence of welding bubbles makes the welding process unstable, and water jets continuously penetrate the welding area, affecting the stability of the welding arc and causing arc extinction; the special cooling conditions underwater can cause wet welding to result in poor weld joint form and significant residual welding stress; and hydrogen generated by water decomposition easily causes the weld joint to produce a large amount of air holes and hydrogen, leading to delayed cracking.Depending on the welding materials, underwater wet welding is subdivided into underwater wet electrode arc welding and underwater wet flux-cored wire welding, or underwater FCAW (Flux-cored arc welding). In underwater wet electrode arc welding, the welding area is completely exposed underwater, and the welder dives directly to perform welding on the workpiece using a specialized underwater welding electrode. Early research on underwater wet electrode arc welding mainly focused on adjusting the quality of weld joints by improving coating components, whereas current research has concentrated on the impact of various material property parameters, such as water depth, waterproof coating layer, and electrode polarity, on process and performance. The manufacturing process of wet underwater welding electrodes must follow the following design principles. Specifically, to enable the welding electrode to weld smoothly using an upward welding method, a relatively large amount of iron must be added to the coating to ensure relatively excellent electrical conductivity, while simultaneously improving productivity; In order to reduce the solubility of hydrogen in the molten bath, a relatively large amount of oxygen must be added during the welding rod coating.

[0004] Chemical materials: Potassium / sodium water glass is selected and used as an adhesive, and plastic powder is spray-coated onto the surface of the welding rod to serve as a waterproof layer. A special underwater welding rod patented in the United States features a tube-shaped sleeve made of synthetic resin covering the outer surface of the coated welding rod; when in use, gas is injected between the outer surface of the welding rod coating and the sleeve to align water in a straight line around the arc; another is the 7018S underwater welding rod, which has a thin layer of aluminum powder applied to the coating; when underwater welding is performed, the aluminum powder generates a large amount of gas under high temperature to effectively align water in a straight line, protecting the metal of the weld joint from harmful substances penetrating. The particle size of the aluminum powder is close to 0.0254 µm, making the welding rod highly resistant to moisture. According to the results of moisture resistance tests conducted by the U.S. Navy, the hydrogen content in the metal of the weld joint obtained under conditions of 100% humidity for 20 consecutive days remained at a low value of 0.00023% (2.3 ppm), and the impact energy at -30°C reached 100 J; therefore, the 7018S underwater welding electrode can be applied to the underwater welding of high-strength steel materials. The 7018S underwater welding electrode is a U.S. product from the 1990s; it corresponds to a 490 MPa class low-hydrogen welding electrode for both AC and DC applications, and due to its excellent resistance to moisture absorption, it enables underwater welding of all positions. Stephen Liu et al. of the United States added Mn, Ti, B, and rare earth elements to the welding electrode coating to improve welding performance during the welding process and refine the microstructure of the weld joint. The former Soviet Union's special underwater welding rod is the EP-55 underwater welding rod, which is still applied to the underwater welding of general structural steel, and its mechanical performance is equivalent to China's T202 underwater welding rod.Models of dedicated underwater welding rods that have already been researched and manufactured in China include TS202, TS203, TSH-1, TS208, and TS306, with a maximum working depth typically of 30m. In this regard, the T202 titanium calcium type welding rod utilizes a DC power source and features a waterproof outer layer paint coating, enabling welding across all locations. There are three types of welding rod diameters: Φ3.2, Φ4.0, and Φ5.0mm. The metal of the weld joint has a σb ≥ 410MPa. The chemical composition (%) of the weld joint metal is C ≤ 0.12, Mn 0.30~0.60, Si ≤ 0.25, S ≤ 0.035, and P ≤ 0.04. Its joint strength σb corresponds to that of the J422 welding rod, and the cold bending angle is typically around 90°. TS208 recently Luoyang(. ) Ship Materials Research Institute and Shanghai Jinhu( This is a welding rod specifically designed for underwater applications, successfully researched and manufactured jointly by Underwater Engineering Co., Ltd. The main technical indicators of the TS208 welding rod are as follows. Mechanical performance is σb≥530MPa and δ≥14% under conditions of water depth ≤30m; process performance is stable in the welding arc combustion under seawater underwater welding conditions, with minimal spatter, good weld joint forming, excellent restriking performance, and no defects such as air holes or cracks in the weld joint. TS306 is a welding rod utilizing a nickel-iron alloy core wire and a double coating layer for waterproofing and gas prevention. The outer layer is coated with a flux-forming agent and a waterproofing agent to provide very strong sealing properties, ensuring the welding quality of the molten metal; the inner layer is coated with an alloying agent and a deoxidizing agent to ensure arc stability, weld joint plasticity, and alloy composition. It can be used for full-position welding of steel and cast iron pipes in wet or underwater structures. This is an ideal waterproof welding rod with a tensile strength of σb > 490 MPa and an elongation of δ ≥ 25%. This welding rod can be used for both AC and DC, but DC is more preferable. In addition, there is a dedicated high-efficiency underwater welding rod that is still in the experimental research stage, which is a thick gravity welding rod researched by Japan and the former Soviet Union. This rod uses magnetism to fix a support and completes the welding by moving the welding rod while clamping it.

[0005] The difference that distinguishes underwater wet FCAW from this is that it uses flux-cored wire; the outer layer of the wire is a steel band and the inner layer is a flux core. During welding, the internal flux core decomposes to generate gas and flux. The gas is advantageous for maintaining bubbles and arc stability, while the flux is beneficial for protecting the molten pool. By preventing direct contact between the molten pool and the water environment, it reduces the cooling rate of the weld joint, thereby improving the performance of the weld joint. Regarding welding materials, the most commonly used method currently is underwater manual coated electrode welding. However, this requires divers to perform the welding work while submerged, and each underwater welder has a very limited working time, which decreases as the water depth increases. Furthermore, because the electrode length is limited and must be replaced frequently during the welding process, the underwater construction time is extended, resulting in very low productivity and difficulty in guaranteeing quality. The gas in solid wire protects the weld; for example, GMA welding (Gas-Protected Arc Welding) faces problems with arc instability when the depth exceeds approximately 80m, mainly manifesting as arc breaking and metal particle spatter. Compared to solid wire, using flux-cored wire offers more significant advantages for deep-sea welding, as the matching of metal and weld material powders is more effective in terms of heat output, and the added welding paste effectively improves arc ionization conditions and promotes the stability of metal transitions. Of course, its welding efficiency has been significantly improved compared to manual welding.The technology and principles of underwater flux-cored wire welding were all first created by scholars of the former Soviet Union, and Patton Welding Institute (Ukraine) was a pioneer in this regard, conducting research on underwater welding and cutting of flux-cored wire as early as the 1960s. Using rutile flux-cored wire PPS-AN1, welding was performed on general low-carbon steel at all locations, and the tensile strength of the joint obtained reached 450 MPa. This figure is sufficiently high if the metal of the weld joint is not an alloy and does not contain carbon elements. According to the results of long-term application of flux-cored wire PPS-AN1, it can provide a weld joint of sufficient strength for low-carbon steel with a yield strength of 350 MPa, but the joint plasticity cannot meet the requirements of the AWS D3.6 standard for Class B joints.

[0006] Underwater flux-cored wire welding has developed slowly for nearly 40 years. The main reasons for this are as follows: First, prior to the 1980s, the development of flux-cored wire itself was relatively slow and not widely applied, and it was only after the 1980s that it was gradually applied in some industries; second, the development capacity of marine resources was weak, and existing underwater welding was mainly used for offshore processes, ship maintenance, and welding of secondary structural parts, while welding of critical parts was intentionally designed to be carried out on land. Since the productivity and quality requirements for underwater welding are not high, manual welding with coated welding rods can satisfy these requirements. However, as the development of marine resources, particularly oil and natural gas resources, continues to progress in depth around the world, large-scale construction of offshore processes has already begun. Underwater welding is being used increasingly frequently because it can reduce the complexity of structural design for these processes and shorten construction cycles, thereby placing increasingly higher demands on the efficiency and quality of underwater welding. China's underwater wet welding materials have lagged behind those of developed Western countries, and therefore, how to rapidly improve the technological level and innovation capabilities of Chinese underwater wet welding materials has become a difficult task that researchers must tackle.

[0007] The present invention was designed primarily with such a welding process in mind. In shallow water environments, the water pressure above the workpiece is relatively low, so the bubble space becomes relatively large, resulting in a relatively stable welding process and relatively high welding quality. However, in deep-sea environments, the bubbles are violently compressed due to the very high water pressure above, and water jets continuously penetrate the welding area, affecting the stability of arc combustion and weld transfer. Consequently, arc extinction occurs frequently, further limiting the application of wet welding in deep-sea environments. Currently, there is relatively little research on wet FCAW in deep-sea environments and the optimization of its processes, and research is mainly focused on wet flux-cored wire welding in water depths of 80m or less. The most critical component of flux-cored wire is the internal flux core. The flux cores used in current research are mostly rutile-type flux cores, to which suitable fluxing agents composed of appropriate amounts of iron, SiO2, and Al2O3 are added. While such flux-cored wires are relatively suitable for shallow operating environments, in deep-sea environments, they cannot compensate for the bubble compression caused by the high pressure formed by the gases generated by the flux core. This results in weld instability and frequent arc breaking, severely impacting weld quality. At the same time, under deep-sea conditions, seawater is highly corrosive; since this affects the service life of weld joints and poses risks due to corrosion, it imposes specific requirements regarding the anti-corrosion properties of the weld joints. Therefore, applying the underwater wet FCAW process to deep-sea environments to obtain welded joints of relatively high quality, increasing bubble size and improving bubble stability during deep-sea welding operations, and enhancing the corrosion resistance of the welded joints is the most important problem currently faced. Therefore, it is necessary to develop and research a flux-cored wire specifically for deep-sea wet FCAW. The problem to be solved

[0008] In order to overcome the shortcomings of conventional technology and solve the problems existing in the deep-sea wet FCAW, the present invention creates a flux-cored wire specifically for deep-sea wet welding. When welding in deep sea, the flux core inside the wire can generate more gas, some of which is ionized and enters the plasma to maintain the arc and ensure its stable combustion, while the remaining part enters the bubble to maintain and even increase the bubble size, thereby overcoming the compression function that the high pressure of the deep sea exerts on the bubble, improving welding stability, and improving the forming of the weld joint. At the same time, using this wire significantly improves the anti-corrosion capability of the weld joint, extends the service life of the weld joint in the deep-sea environment, and reduces the risk of accidents and maintenance costs of marine structures. means of solving the problem

[0009] The technical solution of the present invention is as follows.

[0010] The present invention achieves different efficacy by designing the composition of the outer steel band and the inner flux core of the flux-cored wire, respectively. First, regarding the outer steel band, the present invention considers the use of stainless steel with good anti-corrosion properties instead of conventional low-carbon steel. The reason stainless steel possesses such excellent performance is that it contains a higher content of beneficial alloying elements compared to general low-carbon steel. Below, the beneficial effects of various alloying elements and the design content of the present invention are explained in detail.

[0011] Chromium: can improve the hardenability and wear resistance of steel; can improve the electrode potential of steel by generating a passive film to inhibit anodic reactions, and can improve the seawater corrosion resistance and phase oxidation performance of steel;

[0012] Titanium: Improves the strength and toughness of steel by refining the grain structure. In the case of stainless steel, titanium eliminates or reduces intergranular corrosion, and when used in combination with other elements, it can enhance the steel's ability to resist air and seawater corrosion;

[0013] Nickel: It can improve the hardenability of steel by enhancing its strength and toughness. At high content levels, it can significantly alter certain physical properties of steel and alloys, thereby improving the corrosion resistance of steel. Nickel not only enables steel to withstand acids but also resists alkali corrosion, and it possesses the ability to withstand corrosion from both air and salts. However, the effect of nickel on the antiseptic properties of stainless steel is fully manifested only when it is matched with chromium; this is because low-carbon nickel steel must acquire a pure austenitic structure and reach a nickel content of 24%; Since nickel content must be at least 27% to significantly alter the corrosion resistance of the steel in some media, nickel cannot constitute stainless steel alone. Adding 9% nickel to a steel containing 18% chromium allows the steel to acquire a single austenite structure at room temperature, thereby significantly improving the corrosion resistance of the steel to non-oxidizing media (e.g., dilute sulfuric acid, hydrochloric acid, phosphoric acid, etc.).

[0014] Carbon: Carbon, which exhibits duality in stainless steel, determines the performance and structure of the stainless steel to a significant extent based on its content and distribution pattern; on one hand, carbon stabilizes austenite elements to a very large degree—approximately 30 times that of nickel—and high-carbon (martensite) stainless steel can sufficiently undergo quenching strengthening to significantly improve its strength in terms of mechanical performance; on the other hand, the affinity between carbon and chromium is very strong, and chromium, which accounts for 17 times the carbon content in stainless steel, combines with it to form chromium carbide. As the carbon content in the steel increases, the amount of chromium forming carbides with carbon increases, significantly reducing the corrosion resistance of the steel. Therefore, when examined from two aspects—strength and corrosion resistance—the functions of carbon in stainless steel are conflicting. In the course of actual application, to achieve the purpose of corrosion resistance, the carbon content of stainless steel is typically relatively low, around 0.1%; furthermore, to further enhance the corrosion resistance of steel, particularly its resistance to intergranular corrosion, ultra-low carbon stainless steel is typically used, with a carbon content of 0.03% and even reaching further levels;

[0015] Niobium: Niobium is a strong carbide-forming element with a much stronger affinity for carbon than chromium. When niobium is added to steel, the carbon in the steel first forms carbides with niobium and does not form carbides with chromium, ensuring that intergranular corrosion does not occur near grain boundaries due to a lack of chromium. Therefore, niobium often fixes carbon in steel, enhancing the stainless steel's ability to resist intergranular corrosion and improving the steel's weldability. The functional mechanism of niobium is nearly identical to that of titanium, and the amounts added to both must be determined by the carbon content; typically, the amount added for titanium is five times the carbon content, while for niobium it is eight times the carbon content.

[0016] Molybdenum and Copper: They can improve the corrosion resistance of some stainless steels to certain media, and molybdenum and copper can enhance the corrosion resistance of stainless steel against corrosive media such as sulfuric acid and acetic acid. Molybdenum can also significantly improve corrosion resistance to chlorine-containing ions (e.g., hydrochloric acid) and organic acids.

[0017] Silicon and aluminum: Can enhance the antioxidant capacity of stainless steel.

[0018] Likewise, the component design for the wire flux core is carried out.

[0019] The present invention examines a flux-cored wire to enable it to release a large amount of gas during deep-sea welding, thereby maintaining and further increasing the size of the arc bubbles. At the same time, because the cooling function of water jets is very intense in deep-sea environments—whether for the wire, the arc, or the melting tank—some heat-generating agent must be added to accelerate the melting of the wire and further promote gas generation and flux formation. Based on this, the composition of the flux-cored wire designed to correspond to the function of each element in the present invention is as follows.

[0020] Flux-cored wire specifically designed for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux core, and

[0021] The material of the outer steel band is stainless steel, and the material is characterized by mass percentage, carbon content <= 0.025%, chromium content: 17.5%-20.5%, nickel content: 8.5%-10.5%, titanium content: 0.13%-0.15%, niobium content: 0.2%-0.25%, molybdenum content: 1.5%-2.5%, copper content: 1.5%-2.5%, silicon content: 0.7%-1.2%, aluminum content: 0.7%-1.2%, and the remainder is iron element;

[0022] The composition of the inner layer flux core (characterized by mass percentage) is gas generator: 30%-50%, flux-forming agent: 20%-30%, heat-generating agent: 15%-25%, metal powder: 5%-25%; where the components of the gas generator are sodium bicarbonate, calcium carbonate, and alkaline copper carbonate, where the mass percentage of sodium bicarbonate in the gas generator is 10%-30%, the share of calcium carbonate is 60%-70%, and the share of alkaline copper carbonate is 10%-30%.

[0023] The chemical formulas for three types of gas-generating agents that decompose upon receiving heat to produce gas are as follows.

[0024]

[0025]

[0026]

[0027] Preferably, the solvent-forming agent comprises two types, namely rutile and fluorite, and the mass ratio of the two is 1:1.

[0028] Preferably, the heat generating agent comprises Al-NaF and a silicon carbon exothermic agent, and the Al-NaF mixed material undergoes two relatively strong heat dissipation reactions during the heating process, occurring within temperature ranges of 300°C to 500°C and 800°C to 1150°C, respectively. The heat dissipation reaction at low temperatures (300°C to 500°C) is caused by decomposition within the corresponding temperature range or local oxidation of NaF, while the heat dissipation reaction at high temperatures (800°C to 1150°C) is caused by intense oxidation of Al. The silicon carbon exothermic agent is manufactured by mixing silicon iron powder and carbon increaser powder and then performing ball pressing; it is added at the preliminary stage of rotary furnace and electric furnace smelting to provide heat and accelerate flux formation. The components of the silicon carbon exothermic agent ensure its exothermic effect, and the raw materials used have a distinct eco-friendly effect. In the heat generating agent, the mass proportion of Al-NaF is 60% to 70%, and the remainder is the silicon carbon exothermic agent.

[0029] Preferably, the metal powder comprises the following elements, namely iron, copper, aluminum, tungsten, magnesium, and manganese, wherein iron, copper, and aluminum each account for 25%-30%, and tungsten, magnesium, and manganese each account for 5%-10%, characterized by mass percentage.

[0030] Since the operating conditions of the welding corresponding to the present invention are not only underwater but also deep ocean conditions, and the operating conditions are more complex and the welding process more unstable, the requirements for the compositional design of the welding rod must be correspondingly higher.

[0031] Preferably, all components of the inner layer flux core are added in powder form, and to improve the performance of the welding material, the present invention requires that the particle size of each component be such that the gas generator, flux forming agent, and metal powder are 60-80 mesh and the heat generating agent is 80-100 mesh, as follows.

[0032] Preferably, other parameters of the deep-sea wet FCAW flux-cored wire designed in the present invention are as follows, such that the overall diameter of the flux-cored wire is 2mm-2.5mm, and furthermore, preferably 2.2mm.

[0033] Preferably, the flux-cored filling rate in the flux-cored wire is 35%-40% and is characterized by mass percentage. Since the protective effect of the self-protecting flux-cored wire is entirely derived from the flux-cored, the proportion of flux-cored installed is 35-40%.

[0034] Preferably, the outer layer steel band has a width of 8.5 mm and a thickness of 0.4 mm.

[0035] The manufacturing method for producing the above-described flux-cored wire dedicated to deep-sea wet FCAW includes the following steps.

[0036] (1) Each component of the inner layer flux core with the corresponding proportions applied comprises a gas generator, a solvent-forming agent, a heat-generating agent, and a metal powder, and, as required, is ground to the corresponding particle size, and each component is placed in a powder mixer for 6 hours and mixed uniformly;

[0037] (2) The outer steel band is wound into a U shape and filled with welding paste powder, and the filling rate of the flux-cored wire is 35%-40%;

[0038] 3) The flux-cored steel band is gradually drawn through a wire drawing mold until the wire reaches the required wire diameter, which is 2-2.5 mm. Effects of the invention

[0039] The beneficial effects of the present invention are as follows.

[0040] (1) The present invention rationally designs the components of the steel band of the flux-cored wire and considers the use of stainless steel. During the welding process, the stainless steel metal enters the molten tank as a major part of the volume and fuses with the metal in the molten tank. After cooling, it forms a welded joint, thereby greatly improving the corrosion resistance ability in deep marine environments, greatly extending the service life of marine welded structural materials, and greatly reducing the maintenance costs of the equipment.

[0041] (2) The present invention rationally designs the components of the flux core of the flux-cored wire, and mainly includes a gas generator, a flux-forming agent, a heat-generating agent, and metal powder. Since a large amount of gas generator is added, the volume of the welding bubble can be maintained and even expanded when welding is performed in deep sea, making the welding process more stable and the forming of the weld joint better. At the same time, by adding a heat-generating agent, the melting of the wire can be further accelerated, the progress of the gas generation and flux-forming processes can be promoted, and the protective function of the welding process can be enhanced. By including metal powder, the electrical and thermal conductivity of the flux core is improved, and the effective heat input of the welding is enhanced, which is particularly significant in situations where heat dissipation is rapidly accelerated in deep sea environments.

[0042] In summary, the flux-cored wire designed for deep-sea wet FCAW according to the present invention is suitable for welding in deep-sea environments, ensuring that welding performed under deep-sea conditions can result in weld joints with excellent mechanical performance, good corrosion resistance, and a longer service life. Specific details for implementing the invention

[0043] The present invention will be further explained below through examples, but is not limited to the following.

[0044] Example 1:

[0045] The flux-cored wire for deep-sea wet FCAW comprises an outer steel band and an inner flux-core; the outer steel band is stainless steel, characterized by mass percentages, with a carbon content of 0.025%, a chromium content of 18%, a nickel content of 9.0%, a titanium content of 0.14%, a niobium content of 0.22%, a molybdenum content of 2.0%, a copper content of 2.0%, a silicon content of 1.0%, an aluminum content of 1.0%, and the remainder being iron elements; the outer steel band has a width of 8.5 mm and a thickness of 0.4 mm.

[0046] The composition of the inner layer flux core above consists of 40% gas generator, 25% flux-forming agent, 20% heat-generating agent, and 15% metal powder, characterized by mass percentage; the gas generator comprises 20% sodium bicarbonate, 60% calcium carbonate, and 20% alkaline copper carbonate; the flux-forming agent comprises two types, namely rutile and fluorite, with a ratio of 1:1, characterized by mass percentage; the heat-generating agent comprises 65% Al-NaF and 35% silicon carbon exothermic agent; among the metal powders, iron, aluminum, and copper each account for 25%, tungsten accounts for 5%, and magnesium and manganese each account for 10%; the gas generator, flux-forming agent, and metal powder are 70 mesh, and the heat-generating agent is 90 mesh; The diameter of the flux-cored wire is 2.2 mm, and the flux-cored filling rate within the flux-cored wire is 35%.

[0047] Example 2:

[0048] The flux-cored wire for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux core; the outer layer steel band corresponds to Example 1; the composition of the inner layer flux core is 30% gas generator, 25% solvent-forming agent, 20% heat-generating agent, and 25% metal powder; the composition of the gas generator corresponds to Example 1; the composition of the solvent-forming agent corresponds to Example 1; the composition of the heat-generating agent corresponds to Example 1; the composition of the metal powder corresponds to Example 1; the particle size of the flux core corresponds to Example 1; and the diameter of the flux-cored wire corresponds to the filling rate of the flux core as in Example 1.

[0049] Example 3:

[0050] The flux-cored wire dedicated to deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux core; the outer layer steel band corresponds to Example 1; the composition of the inner layer flux core is 50% gas generator, 25% solvent-forming agent, 20% heat-generating agent, and 5% metal powder; the composition of the gas generator corresponds to Example 1; the composition of the solvent-forming agent corresponds to Example 1; the composition of the heat-generating agent corresponds to Example 1; the composition of the metal powder corresponds to Example 1; the particle size of the flux core corresponds to Example 1; and the diameter of the flux-cored wire corresponds to the filling rate of the flux core as in Example 1.

[0051] Example 4:

[0052] The flux-cored wire dedicated to deep-sea wet FCAW comprises an outer steel band and an inner flux core, the material of the outer steel band is stainless steel, and the material, characterized by mass percentage, comprises carbon with a content of 0.024%, chromium with a content of 17.5%, nickel with a content of 8.5%, titanium with a content of 0.13%, niobium with a content of 0.2%, molybdenum with a content of 1.5%, copper with a content of 1.5%, silicon with a content of 0.7%, and aluminum with a content of 0.7%, with the remainder being iron elements; the composition of the inner flux core (characterized by mass percentage) comprises 45% gas generator, 20% solvent-forming agent, 15% heat-generating agent, and 20% metal powder; Here, the components of the gas generator are sodium bicarbonate, calcium carbonate, and alkaline copper carbonate, and here, the mass percentage of sodium bicarbonate in the gas generator is 15%, the share of calcium carbonate is 70%, and the share of alkaline copper carbonate is 15%.

[0053] Example 5:

[0054] The flux-cored wire dedicated to deep-sea wet FCAW comprises an outer steel band and an inner flux core, wherein the material of the outer steel band is stainless steel, and the material, characterized by mass percentage, comprises carbon with a content of 0.025%, chromium with a content of 20.5%, nickel with a content of 10.5%, titanium with a content of 0.15%, niobium with a content of 0.25%, molybdenum with a content of 2.5%, copper with a content of 2.5%, silicon with a content of 1.2%, and aluminum with a content of 1.2%, and the remainder is iron element; the composition of the inner flux core (characterized by mass percentage) comprises 30% gas generator, 30% solvent-forming agent, 25% heat-generating agent, and 15% metal powder; Here, the components of the gas generator are sodium bicarbonate, calcium carbonate, and alkaline copper carbonate, and here, the mass percentage of sodium bicarbonate in the gas generator is 30%, the share of calcium carbonate is 60%, and the share of alkaline copper carbonate is 10%.

[0055] Example 6:

[0056] The flux-cored wire for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux-core, and its composition is as described in Example 5, the only difference being that the composition of the gas generator is sodium bicarbonate, calcium carbonate, and alkaline copper carbonate, wherein the mass percentage of sodium bicarbonate in the gas generator is 10%, the share of calcium carbonate is 60%, and the share of alkaline copper carbonate is 30%.

[0057] Example 7:

[0058] The flux-cored wire for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux-core, and its composition is as described in Example 1, the only difference being that the gas generator, solvent-forming agent, and metal powder are 60 mesh and the heat-generating agent is 80 mesh.

[0059] Example 8:

[0060] The flux-cored wire for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux-core, and its composition is as described in Example 1, the only difference being that the gas generator, solvent-forming agent, and metal powder are 80 mesh and the heat-generating agent is 100 mesh.

[0061] Example 9:

[0062] The flux-cored wire for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux-core, and its composition is as described in Example 1, the only difference being that the diameter of the flux-cored wire is 2 mm.

[0063] Example 10:

[0064] The flux-cored wire for deep-sea wet FCAW comprises an outer layer steel band and an inner layer flux core, and its composition is as described in Example 1, the only difference being that the diameter of the flux-cored wire is 2.5 mm and the flux-cored filling rate within the flux-cored wire is 40%.

[0065] Example 11:

[0066] The manufacturing method for producing a flux-cored wire for deep-sea wet FCAW described in Example 1 includes the following steps.

[0067] (1) Each component of the inner layer flux core with the corresponding proportions applied comprises a gas generator, a solvent-forming agent, a heat-generating agent, and a metal powder, and, as required, is ground to the corresponding particle size, and each component is placed in a powder mixer for 6 hours and mixed uniformly;

[0068] (2) The outer steel band is wound into a U shape and filled with welding paste powder, and the filling rate of the flux-cored wire is 35%;

[0069] 3) The flux-cored steel band is gradually drawn through a wire drawing mold until the wire reaches the required wire diameter, which is 2.2 mm.

[0070] Comparative Example 1:

[0071] The flux-cored wire for deep-sea wet FCAW comprises an outer steel band and an inner flux core; the outer steel band is low-carbon steel with a carbon content of 0.04%; the composition of the flux core is consistent with Example 1; the particle size of the flux core is consistent with Example 1; and the diameter of the flux-cored wire and the filling rate of the flux core are consistent with Example 1.

[0072] Comparison Example 2:

[0073] The flux-cored wire for deep-sea wet FCAW comprises an outer steel band and an inner flux core; the outer steel band corresponds to Example 1; the composition of the flux core does not include a gas generator, but consists of 50% solvent-forming agent, 30% heat-generating agent, and 20% metal powder; the composition of the solvent-forming agent corresponds to Example 1; the composition of the heat-generating agent corresponds to Example 1; the composition of the metal powder corresponds to Example 1; the particle size of the flux core corresponds to Example 1; and the diameter of the flux-cored wire and the filling rate of the flux core correspond to Example 1.

[0074] All of the above wires are manufactured according to the following procedures.

[0075] 1. Each component of the flux core to which the corresponding proportions have been applied comprises a gas generator (not added), a solvent-forming agent, a heat-generating agent, and a metal powder, and, if required, is ground to the corresponding particle size, and each component is placed in a powder mixer for 6 hours and mixed uniformly;

[0076] 2. Wrap the steel band into a U-shape and fill it with welding paste powder;

[0077] 3. The filled flux-cored steel band is gradually drawn through a wire drawing mold until the wire reaches the required wire diameter.

[0078] Experimental Example

[0079] The present invention conducted deep-water wet FCAW welding experiments using a flux-cored wire specifically produced for deep-sea wet FCAW as described above, the workpiece being welded was AH36 steel plate for ships and offshore processes, and the welding parameters were as listed in Table 1.

[0080] Table 1 Welding Parameter Batch Table

[0081]

[0082] Performance tests including the following performances, namely seawater corrosion resistance (3.5% NaCl solution immersion test), tensile strength, maximum elongation, and 0°C impact toughness, are conducted on welded joints with stable cut sections after welding. The results obtained by measuring performance for each example are as shown in Table 2.

[0083] Table 2 Performance comparison by wire

[0084]

[0085] According to the results measured in the experiment, the performance of the unwelded workpiece is 0.58 mm / a for seawater corrosion resistance, 540 MPa for tensile strength, 23% for maximum elongation, and 31.0 J for impact toughness at 0°C. As can be seen from the control results, after replacing the outer layer steel band with ordinary low-carbon steel, its corrosion rate increases significantly and its anti-corrosion properties in the marine environment decrease, thereby shortening the service life of marine structural materials and repair welds.

[0086] At the same time, the ratio of wire welding paste powder has a very significant effect on the performance of the weld joint, particularly the ratio of the gas generator. As described in Example 1, when it is 40%, the obtained weld joint has excellent overall performance. When the ratio is lowered to 30% or raised to 50%, the performance is slightly lower than that of Example 1, although the difference is not large. However, all are much higher than the base metal, which explains that the component ratio of the flux core designed in the present invention is relatively reasonable. When a gas generator is not added, that is, when its ratio is set to 0, the performance of the obtained weld joint deteriorates significantly. As described in Comparative Example 2, since the outer layer steel band of the wire is still stainless steel, the change in terms of corrosion resistance is not significant; however, its strength, plasticity, and toughness all show a distinct downward trend compared to the previous example and are all lower than the base metal. Upon examining the cause, it is as follows: since a gas generator is not added, gas is not replenished in the weld bubbles when welding in a deep-sea environment. At deep water depths, the bubble volume contracts significantly under high pressure, and a large amount of seawater enters the welding area, causing arc breaking to occur frequently. At the same time, this also severely affects droplet transitional, causing the quality of the weld joint to deteriorate significantly. As can be seen from this, the addition of a gas generator plays a very active role in improving weld quality under conditions where deep-sea welding is performed.

[0087] In summary, the deep-sea wet FCAW flux-cored wire designed by the present invention is suitable for welding in a high-pressure marine environment with relatively strong corrosiveness, and can obtain high-quality welded joints with strong corrosion resistance and excellent mechanical performance.

Claims

Claim 1 In a flux-cored wire dedicated to deep-sea wet FCAW, the wire comprises an outer steel band and an inner flux core, wherein the material of the outer steel band is stainless steel, and the material is characterized by mass percentage, carbon content <= 0.025%, chromium content: 17.5%-20.5%, nickel content: 8.5%-10.5%, titanium content: 0.13%-0.15%, niobium content: 0.2%-0.25%, molybdenum content: 1.5%-2.5%, copper content: 1.5%-2.5%, silicon content: 0.7%-1.2%, aluminum content: 0.7%-1.2%, and the remainder is iron element; the composition of the inner flux core is characterized by mass percentage, gas generator: 30%-50%, solvent forming agent: 20%-30%, heat generating agent: A flux-cored wire for deep-sea wet FCAW, characterized by having 15%-25%, metal powder: 5%-25%; wherein, the components of the gas generator are sodium bicarbonate, calcium carbonate, and alkaline copper carbonate, wherein the mass percentage of sodium bicarbonate in the gas generator is 10%-30%, the share of calcium carbonate is 60%-70%, and the share of alkaline copper carbonate is 10%-30%. Claim 2 A flux-cored wire for deep-sea wet FCAW according to claim 1, characterized in that the solvent-forming agent comprises two types, namely rutile and fluorite, and the mass ratio of the two is 1:

1. Claim 3 A flux-cored wire for deep-sea wet FCAW according to claim 1, wherein the heat generating agent comprises Al-NaF and a silicon carbon heating agent, the silicon carbon heating agent is manufactured by mixing silicon iron powder and carbon increaser powder and then performing ball pressing, and the mass fraction occupied by Al-NaF is 60%-70% and the remainder is the silicon carbon heating agent. Claim 4 A flux-cored wire for deep-sea wet FCAW according to claim 1, characterized in that the metal powder comprises the following elements, namely iron, copper, aluminum, tungsten, magnesium, and manganese, wherein iron, copper, and aluminum each account for 25%-30%, and tungsten, magnesium, and manganese each account for 5%-10%, characterized by mass percentage. Claim 5 A flux-cored wire for deep-sea wet FCAW according to claim 1, characterized in that all components of the inner layer flux-cored are added in powder form, the gas generator, solvent-forming agent, and metal powder are 60-80 mesh, and the heat-generating agent is 80-100 mesh. Claim 6 A flux-cored wire for deep-sea wet FCAW according to claim 1, characterized in that the total diameter of the flux-cored wire is 2mm-2.5mm. Claim 7 A flux-cored wire for deep-sea wet FCAW according to claim 6, characterized in that the total diameter of the flux-cored wire is 2.2 mm. Claim 8 A flux-cored wire for deep-sea wet FCAW according to claim 1, characterized by a flux-cored filling rate of 35%-40% within the flux-cored wire and characterized by a mass percentage. Claim 9 Flux-cored wire for deep-sea wet FCAW according to claim 1, characterized in that the outer layer steel band has a width of 8.5 mm and a thickness of 0.4 mm. Claim 10 A manufacturing method for producing a flux-cored wire dedicated to deep-sea wet FCAW according to any one of claims 1 to 9, comprising the following steps: (1) each component of the inner layer flux core to which the corresponding proportion is applied comprises a gas generator, a solvent forming agent, a heat generating agent, and a metal powder, and, as required, grinds each component to the corresponding particle size, and places each component into a powder mixer for 6 hours to ensure uniform mixing; (2) winding an outer layer steel band into a U shape and filling it with welding paste powder; (3) gradually drawing the wire from the filled flux core steel band through a wire drawing mold until it reaches the required wire diameter; characterized by comprising the following steps.

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