Corrosion-resistant welding wire for marine building structure high-strength steel and preparation method of corrosion-resistant welding wire

Abstract

The invention relates to a corrosion-resistant welding wire for marine building structure high-strength steel and a preparation method of the corrosion-resistant welding wire, belongs to the technical field of welding materials, and solves the problems that in the prior art, a marine building structure high-strength steel welding material is insufficient in corrosion resistance and poor in obdurability matching under the high-temperature, high-humidity and high-salt marine atmospheric environment. The welding wire comprises the following chemical components in percentage by mass: 0.05 to 0.10 percent of C, 0.4 to 0.6 percent of Si, 1.80 to 2.00 percent of Mn, 3.5 to 4.0 percent of Ni, 0.60 to 0.80 percent of Cr, 0.30 to 0.50 percent of Mo, 0.01 to 0.03 percent of Sn, 0.60 to 1.0 percent of Cu, less than or equal to 0.008 percent of P, less than or equal to 0.008 percent of S, less than or equal to 0.005 percent of O, less than or equal to 0.005 percent of N, less than or equal to 0.001 percent of H and the balance of Fe and inevitable impurities. By controlling the mass ratio of Cu to Sn to be 20-100 and the equivalent ratio of chromium to nickel to be 19%-37%, the yield strength of deposited metal of the welding wire is larger than or equal to 700 MPa, the tensile strength is larger than or equal to 800 MPa, the impact absorption energy at the temperature of-40 DEG C is 60-150 J, and the corrosion weight loss rate is smaller than or equal to 1.52 g / m < 2 > / h. The welding wire is particularly suitable for welding high-strength steel with the tensile strength not lower than 700 MPa for a marine building structure.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a corrosion-resistant welding wire for high-strength steel marine structural engineering and its preparation method. Background Technology

[0002] Welding materials are crucial components in the fabrication of marine engineering structures, and their performance directly affects the mechanical integrity and long-term service durability of welded joints. In the marine atmospheric environment, structural steel and its welded joints face severe corrosion challenges from high temperatures, high humidity, and high salt spray, placing extremely high demands on the strength, toughness, and corrosion resistance of welding materials.

[0003] Currently, welding materials for weathering steel used in marine environments mostly employ systems with nickel (Ni) as the primary alloying element. These welding materials improve low-temperature toughness by introducing nickel into the weld metal to meet certain mechanical performance requirements. However, existing welding material formulations often focus on optimizing individual properties, lacking sufficient synergistic control of composition. This results in the weld metal often failing to achieve an ideal balance in terms of strength and toughness matching, particularly in corrosion resistance comparable to the base metal, thus failing to fully meet the comprehensive performance requirements of next-generation high-performance marine structural steel for welded joints.

[0004] Existing welding materials have technical limitations when dealing with harsh marine environments, such as insufficient matching of the strength and toughness of the deposited metal and incomplete matching of corrosion resistance with high-performance base materials. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a corrosion-resistant welding wire for high-strength steel marine structures and its preparation method, so as to at least solve one of the problems of existing welding wires being unable to simultaneously achieve strength, toughness and corrosion resistance in harsh marine environments, resulting in insufficient overall performance of welded joints.

[0006] On one hand, embodiments of the present invention provide a corrosion-resistant welding wire for high-strength steel in marine construction structures, wherein the chemical composition of the welding wire, by mass percentage, comprises:

[0007] C: 0.05–0.10%, Si: 0.4–0.6%, Mn: 1.80–2.00%, Ni: 3.5–4.0%, Cr: 0.60–0.80%, Mo: 0.30–0.50%, Sn: 0.01–0.03%, Cu: 0.60–1.0%, P: ≤0.008%, S: ≤0.008%, O: ≤0.005%, N: ≤0.005%, H: ≤0.001%, balance Fe and unavoidable impurities.

[0008] Furthermore, the chromium-nickel equivalent ratio of the welding wire is controlled within the range of 19% to 37%; the chromium-nickel equivalent ratio is calculated as the ratio of chromium equivalent to nickel equivalent, expressed as a percentage of the mass of each element, where:

[0009] The chromium equivalent is Cr + Mo + 1.5Si;

[0010] The nickel equivalent is Ni+30C+0.5Mn.

[0011] Furthermore, the chromium-nickel equivalent ratio is preferably 25% to 32%.

[0012] Furthermore, the mass ratio of Cu to Sn in the welding wire, Cu / Sn, is controlled within the range of 20 to 100.

[0013] Furthermore, the Cu / Sn mass ratio is preferably 30 to 50.

[0014] Furthermore, the weld metal of the welding wire has a yield strength ≥700MPa and a tensile strength ≥800MPa.

[0015] Furthermore, the weld metal of the welding wire absorbs 60-150 J of energy at low-temperature impact at -40°C.

[0016] Furthermore, the corrosion weight loss rate of the weld metal in 2% NaCl solution is not higher than 1.52 g·m⁻²·h⁻¹.

[0017] Furthermore, this invention also proposes a method for preparing corrosion-resistant welding wire for high-strength steel marine structural engineering, which includes the following steps:

[0018] S1. The raw materials are proportioned according to the stated mass percentage, and steel ingots are obtained through vacuum melting and casting;

[0019] S2. The steel ingot is hot-rolled to produce wire rod;

[0020] S3. The wire rod is drawn to reduce its diameter and then subjected to intermediate annealing to produce welding wire;

[0021] By controlling the final rolling temperature and the cooling rate of the hot-rolled wire rod, the wire rod obtains a uniform metallographic structure, thereby achieving a uniform distribution of Sn and Cu elements in the matrix and avoiding Sn element segregation.

[0022] Furthermore, the final rolling temperature of the hot rolling is 850–950°C; and / or, the final step of the drawing and diameter reduction is to process the welding wire diameter to 1.0 mm–1.6 mm.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1) By controlling the Ni content to 3.5-4.0% and synergistically controlling the Cr / Ni equivalent ratio to 19%-37%, this invention leverages the improving effect of Ni on low-temperature toughness and the strengthening effect of Cr, Mo, and other elements to ensure that the weld metal achieves a yield strength of ≥700MPa and a tensile strength of ≥800MPa while maintaining a high impact toughness of 60-150J at -40℃. This overcomes the common problem of balancing strength and toughness in high-strength steel welding.

[0025] 2) This invention introduces trace amounts of Sn (0.01–0.03%) and synergistically designs it with Cu. By controlling the Cu / Sn mass ratio at 20–100 (preferably 30–50), Sn forms a dense SnO2-MG composite corrosion product layer in the later stages of corrosion, which, together with Cu, increases the surface corrosion potential and passivates the anodic reaction. This reduces the corrosion weight loss rate of the deposited metal in 2% NaCl solution to 1.52 g / m³. 2 With a corrosion resistance of less than / h, its corrosion resistance is comparable to that of high-grade base materials such as Q420NS.

[0026] 3) This invention promotes the formation of an ideal microstructure in the weld metal, primarily composed of ferrite and lath bainite, by precisely controlling the equivalent ratios of C, Si, Mn, and Cr / Ni (19%–37%). For example… Figure 1 and Figure 2 As shown, the microstructure is dominated by acicular ferrite / lamellar bainite, significantly reducing the formation of granular bainite with poor toughness. This microstructure, with its high-density dislocations and fine-grained structure, not only provides a strong and tough match for the deposited metal, but its uniformity also lays the microstructural foundation for excellent corrosion resistance. Furthermore, this compositional system improves weldability, resulting in a stable weld pool, less spatter, and easier attainment of well-formed, defect-free, high-quality welds.

[0027] 4) The welding wire composition system of this invention is specifically designed for high-strength steel used in marine engineering structures with a tensile strength of not less than 700 MPa. The strength, toughness, and corrosion resistance of its deposited metal are well matched with this type of high-end base material, solving the problem that welded joints in marine engineering often become weak links in structural performance.

[0028] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0029] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0030] Figure 1 This is a metallographic microstructure diagram of the weld metal in Embodiment 1 of the present invention.

[0031] Figure 2 This is a transmission electron microscope image of the weld metal in Embodiment 1 of the present invention.

[0032] Figure 3 This is a corrosion morphology diagram of the weld metal in Embodiment 1 of the present invention. Detailed Implementation

[0033] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0034] The welding of high-strength steel for existing marine structures often results in weak points in corrosion at the weld joints due to insufficient corrosion resistance of the weld metal. Conventional 3Ni steel welding wires struggle to achieve corrosion resistance comparable to high-grade base materials such as Q420NS while maintaining high strength and good low-temperature toughness.

[0035] On one hand, a specific embodiment of the present invention discloses a corrosion-resistant welding wire for high-strength steel marine construction structures. The chemical composition of the welding wire, by mass percentage, includes: C: 0.05-0.10%, Si: 0.4-0.6%, Mn: 1.80-2.00%, Ni: 3.5-4.0%, Cr: 0.60-0.80%, Mo: 0.30-0.50%, Sn: 0.01-0.03%, Cu: 0.60-1.0%, P: ≤0.008%, S: ≤0.008%, O: ≤0.005%, N: ≤0.005%, H: ≤0.001%, with the balance being Fe and unavoidable impurities.

[0036] Through precise welding wire composition design, the synergistic effect of various alloying elements ensures that the deposited metal achieves the required comprehensive performance.

[0037] Furthermore, the chromium-nickel equivalent ratio of the welding wire is controlled within the range of 19% to 37% (e.g., 19%, 20%, 25%, 28%, 30%, 32%, 35%, 37%); the chromium-nickel equivalent ratio is calculated as the ratio of chromium equivalent to nickel equivalent in terms of the mass percentage of each element, wherein: the chromium equivalent is Cr+Mo+1.5Si; and the nickel equivalent is Ni+30C+0.5Mn.

[0038] This invention reveals that the chromium-nickel equivalent ratio is a key parameter for coordinating the strength, toughness, and corrosion resistance of the deposited metal. When this ratio is below 19%, the system exhibits an excessive austenitizing tendency, which easily leads to the formation of granular bainite structures that are detrimental to toughness during cooling. Conversely, when the ratio is above 37%, the ferrititizing effect is excessive, resulting in insufficient strength and the potential precipitation of harmful carbides.

[0039] Controlling this ratio within the range of 19% to 37% plays a crucial role in precisely regulating the solid-state phase transformation process of the weld metal. This promotes the formation of an ideal mixed microstructure dominated by ferrite and lath bainite, while effectively suppressing the formation of large amounts of granular bainite. By obtaining this optimized microstructure, the weld metal simultaneously possesses the high strength of the lath bainite phase, the good toughness of the ferrite phase, and the overall uniform corrosion resistance, thus achieving a high-performance balance on a macroscopic level.

[0040] Preferably, the chromium-nickel equivalent ratio is 25% to 32%.

[0041] When the chromium-nickel equivalent ratio is 25%–32%, the ratio of ferrite to lath bainite reaches its optimal state, resulting in the finest and most uniform microstructure. At this ratio, the yield strength, low-temperature impact toughness, and corrosion resistance of the deposited metal are optimally synergistically achieved, realizing the best balance between high strength, high toughness, and excellent corrosion resistance.

[0042] The welding wire of this invention achieves a balance of high strength, high toughness, and excellent corrosion resistance in the deposited metal through the synergistic effect of the aforementioned key alloying elements. The composition design and mechanism of action of each element are as follows:

[0043] Carbon (C): Carbon is an important strengthening element in steel, significantly improving the strength of the weld metal through solid solution strengthening and dispersion strengthening. In this invention, the C content is controlled between 0.05% and 0.10%. Appropriate amounts of C can synergistically work with elements such as Ni, Cr, and Mo to improve the hardenability of the material and promote the formation of fine strengthening structures. However, excessively high C content increases the susceptibility to welding cracks and may also form harmful carbides with elements such as Cr, reducing toughness and corrosion resistance; excessively low content cannot meet the high strength requirements, therefore, its content range must be strictly controlled.

[0044] Silicon (Si): In welding wire, silicon primarily functions as a deoxidizer and a solid solution strengthener. During welding, Si combines with oxygen to form stable oxides, reducing the oxygen content in the weld and preventing defects such as porosity. Simultaneously, Si dissolves in ferrite, increasing the strength and hardness of the deposited metal. This invention controls the Si content to 0.4–0.6%, a range that ensures good deoxidation and strengthening effects without causing a decrease in material toughness or deterioration in welding processability due to excessive content.

[0045] Manganese (Mn): Manganese is an important strengthening and deoxidizing element. Mn can significantly improve the hardenability of steel, promote the formation of high-strength bainitic structure, and improve the strength and toughness of weld metal through solid solution strengthening. In addition, Mn can combine with sulfur to form MnS, reducing the harmful effects of sulfur on materials and improving hot working properties. In this invention, the Mn content is controlled at 1.80-2.00%. This content can fully exert its strengthening and microstructure-improving effects, synergistically achieving the high strength requirements of weld metal with other elements, while avoiding a decrease in toughness due to excessive addition.

[0046] Nickel (Ni): Nickel is the core element ensuring toughness in this invention. Its addition significantly improves the low-temperature toughness of the weld metal, effectively compensating for the toughness loss caused by the addition of elements such as Cr and Mo. Simultaneously, Ni improves the hardenability of the material, facilitating the formation of fine bainitic structures during welding cooling, thus contributing to strength while improving toughness. Given that Ni is a valuable alloying element, to control costs, its content is optimized to the range of 3.5% to 4.0% in this invention.

[0047] Chromium (Cr): Chromium is one of the main alloying elements in this invention. It can form an infinite solid solution in steel, resulting in significant solid solution strengthening. Simultaneously, chromium is a key element for improving corrosion resistance, promoting the rapid formation of a stable protective rust layer in the early stages of corrosion, thereby effectively reducing the corrosion rate in later stages. However, excessively high chromium content can combine with carbon to precipitate network carbides (such as Cr) at grain boundaries. 23 The presence of Cr (C6) not only impairs the low-temperature toughness of the material but can also become the initiation point for pitting corrosion, thus adversely affecting its corrosion resistance. Therefore, this invention strictly controls the Cr content to 0.60%–0.80% to balance its strengthening effect, contribution to corrosion resistance, and potential harm to toughness.

[0048] Molybdenum (Mo): Molybdenum significantly improves the strength, hardness, and toughness of weld metal, while enhancing the corrosion resistance and heat resistance of the material. Through solid solution strengthening and grain refinement, Mo synergistically enhances the strength, toughness, and corrosion resistance of the material with elements such as Cr and Ni. Furthermore, Mo improves the hardenability of steel and promotes the formation of a uniform and fine-grained strengthened microstructure. In this invention, the Mo content is controlled at 0.30–0.50%. This content allows for full utilization of its synergistic effect with other elements, improving the overall performance of the weld metal and avoiding increased costs and deteriorated welding processability due to excessively high content.

[0049] Copper (Cu): Copper is a key corrosion-resistant element in this invention. The addition of Cu can passivate the anodic reaction during the corrosion process and promote the formation of a denser, more protective internal rust layer, thereby significantly improving corrosion resistance in chloride ion environments. However, it should be noted that excessive Cu can increase the hot cracking susceptibility of the weld metal. Therefore, this invention controls its content between 0.60% and 1.0% to maximize its corrosion resistance benefits and mitigate process risks.

[0050] Tin (Sn): As a key trace element for corrosion resistance, tin plays a crucial role in long-term corrosion protection. During corrosion, Sn combines with oxygen to form SnO2, and further combines with iron corrosion products (such as α-FeOOH) to form a stable graphite (SnO2-MG) complex. This complex layer provides an excellent barrier against the penetration of corrosive media. However, excessively high Sn content can easily lead to the formation of coarse oxide inclusions at grain boundaries, deteriorating mechanical properties and toughness. Therefore, its content is strictly limited to 0.01%–0.03%.

[0051] In particular, this invention achieves a significant improvement in corrosion resistance by introducing Sn and precisely controlling the Cu / Sn content ratio within the range of 20–100 (preferably 30–50). Cu and Sn produce a synergistic effect during corrosion, jointly increasing the surface corrosion potential of the deposited metal and promoting the formation of a denser and more stable composite corrosion product layer. This specific elemental ratio is far more effective than adding Cu or Sn alone, and cannot be achieved through simple superposition.

[0052] Simultaneously, this invention proposes a synergistic control strategy for the Cr / Ni equivalent ratio, controlling it within the range of 19% to 37%, preferably 25% to 32%. This design aims to finely regulate the microstructure of the weld metal. By balancing the synergistic effects of Cr (primarily contributing to corrosion resistance and strength) and Ni (primarily contributing to toughness and microstructure refinement), it effectively promotes the formation of acicular ferrite and lath bainite, while suppressing granular bainite structures that are detrimental to toughness. This synergistic control mechanism based on the equivalent ratio is key to achieving a synergistic improvement in the high strength, high toughness, and excellent corrosion resistance of the weld metal.

[0053] Phosphorus (P): Phosphorus is a harmful impurity element in welding wire. P tends to segregate at grain boundaries, leading to increased cold brittleness of the material, significantly reducing the low-temperature toughness of the weld metal and the crack resistance of the weld joint, and also adversely affecting corrosion resistance. Therefore, this invention strictly controls the P content to ≤0.008% to reduce its harmful effects and ensure the comprehensive performance of the deposited metal.

[0054] Sulfur (S): Sulfur is another harmful impurity element. S combines with Fe to form FeS. FeS has a low melting point and easily precipitates at grain boundaries, leading to increased hot brittleness of the material, reduced weldability and high-temperature performance, and also impaired corrosion resistance. This invention strictly controls the S content to ≤0.008% to avoid its negative impact on material properties.

[0055] Oxygen (O): Oxygen forms oxide inclusions in weld metal, which disrupt the continuity of the metal, reduce the toughness, strength, and corrosion resistance of the material, and increase the probability of weld porosity. Therefore, this invention strictly controls the O content to ≤0.005%, and reduces the introduction of oxygen by optimizing the smelting and welding processes to ensure the purity of the deposited metal.

[0056] Nitrogen (N): Nitrogen can play a certain role in solid solution strengthening in steel, but excessive content will lead to a decrease in the toughness of the material, and may also form nitride inclusions, affecting the corrosion resistance of welded joints. This invention controls the N content to ≤0.005% to balance its strengthening effect and its adverse effects on toughness and corrosion resistance.

[0057] Hydrogen (H): Hydrogen is one of the main factors leading to cold cracking in welding, and it also reduces the toughness and corrosion resistance of materials. This invention strictly controls the H content to ≤0.001%, and reduces the introduction of hydrogen by adopting processes such as vacuum smelting and welding material drying, thereby reducing the risk of welding cracks and ensuring the safe service of welded joints.

[0058] Based on the above-mentioned composition and equivalence ratio control, including fully utilizing the stabilizing effect of Ni austenite to effectively reduce the ductile-brittle transition temperature and suppress brittle transformation at low temperatures, obtaining a favorable microstructure through chromium-nickel equivalence ratio control, and avoiding the damage to toughness caused by inclusions and harmful gases, the weld metal of the welding wire described in this invention exhibits excellent mechanical properties: yield strength ≥700MPa (e.g., 720MPa, 730MPa, 740MPa, 750MPa, 760MPa, 770MPa, 780MPa), and tensile strength ≥800MPa (e.g., 810MPa, 820MPa, 830MPa, 840MPa, 850MPa, 860MPa). This high strength level is mainly achieved through solid solution strengthening of C, Mn, and Si, and the combined effect of Ni, Cr, and Mo to improve hardenability, promoting the formation of a fine lath bainite / ferrite mixed structure in the weld metal.

[0059] Meanwhile, the weld metal of the welding wire absorbs 60-150J of low-temperature impact energy at -40℃ (e.g., 60J, 70J, 80J, 90J, 100J, 110J, 120J, 130J, 140J, 150J), exhibiting excellent low-temperature toughness.

[0060] Considering the long-term durability of the welding wire in harsh marine environments, its corrosion resistance is crucial. The corrosion weight loss rate of the deposited metal of the welding wire in a 2% NaCl solution is no higher than 1.52 g·m³. -2 ·h -1 (e.g., 1.52 g·m) -2 ·h -1 1.65 g·m -2 ·h -1 1.68 g·m -2 ·h -1 1.71 g·m -2 ·h -1 1.74 g·m -2 ·h -1 ).

[0061] Furthermore, the mass ratio of Cu to Sn in the welding wire, Cu / Sn, is controlled within the range of 20–100 (e.g., 20, 40, 50, 60, 80, 100). Cu can increase the corrosion potential of steel, passivate the anodic reaction in galvanic corrosion, and promote the formation of a dense internal rust layer; while the addition of trace amounts of Sn (0.01–0.03%) can form SnO2 with oxygen in the later stage of corrosion, and further form SnO2-MG complex with iron corrosion products (such as α-FeOOH), which has an excellent barrier effect against corrosive media.

[0062] Preferably, the Cu / Sn mass ratio is 30 to 50, at which point the synergistic corrosion resistance effect of Cu and Sn is optimal, resulting in a significant increase in the surface corrosion potential of the deposited metal and a minimum corrosion rate.

[0063] Furthermore, the welding wire is suitable for welding high-strength steel used in marine construction structures with a tensile strength of not less than 700 MPa. The strength, toughness, and corrosion resistance of its deposited metal are well-matched with high-grade marine platform steel base materials such as Q420NS, ensuring the consistency of performance between the welded joint and the base material in harsh marine environments, thereby guaranteeing the safe service life of the overall structure.

[0064] Compared with existing technologies, the welding wire provided in this embodiment achieves a balance of high strength, high toughness and excellent corrosion resistance through a unique compositional synergistic design, including precise control of key elements, optimization of the Cu / Sn ratio and reasonable setting of the chromium-nickel equivalent ratio, thus solving a key technical problem in the welding of high-strength steel for marine building structures.

[0065] The welding wire of this invention is a solid welding wire suitable for gas shielded welding, particularly welding processes protected by an argon-rich gas mixture (e.g., 80% Ar + 20% CO2). This welding wire can be produced through conventional vacuum smelting, rolling into wire rods, and multi-pass drawing to reduce its diameter to the desired diameter (e.g., ...). It is prepared using a process called [process name missing]. The surface of the welding wire usually needs to be copper-plated to improve its conductivity and rust resistance.

[0066] In one specific embodiment, the present invention provides a method for preparing corrosion-resistant welding wire for high-strength steel in marine structural engineering, comprising the following steps:

[0067] S1. The raw materials are proportioned according to the stated mass percentage, and steel ingots are obtained through vacuum melting and casting;

[0068] S2. The steel ingot is hot-rolled to produce wire rod;

[0069] S3. The wire rod is drawn to reduce its diameter and then subjected to intermediate annealing to produce welding wire;

[0070] By controlling the final rolling temperature and the cooling rate of the hot-rolled wire rod, the wire rod obtains a uniform metallographic structure, thereby achieving a uniform distribution of Sn and Cu elements in the matrix and avoiding Sn element segregation.

[0071] Furthermore, the final rolling temperature of the hot rolling is 850–950°C; and / or, the final step of the drawing and diameter reduction is to process the welding wire diameter to 1.0 mm–1.6 mm.

[0072] Specifically, in S1, after the raw materials are proportioned, vacuum induction melting is used for melting and casting. The vacuum level is controlled below 1 Pa. Vacuum melting can effectively control the gas content (especially O, N, and H) and reduce the loss of beneficial alloying elements (such as Mn and Cr). Welding wire for marine environments requires extremely high purity; even trace amounts of gas and impurities can significantly deteriorate the low-temperature toughness and corrosion resistance of the weld metal. This invention, through vacuum melting, stably controls the O, N, and H contents to ultra-low levels of ≤0.005%, ≤0.005%, and ≤0.001%, respectively, laying the foundation for obtaining high-strength and high-toughness weld metal.

[0073] Specifically, in S2, the final rolling temperature of hot rolling is controlled within the range of 850–950℃. This temperature range is chosen based on the following considerations: if the final rolling temperature is higher than 950℃, it will lead to coarse austenite grains, forming a coarse unbalanced structure during subsequent cooling, which is not conducive to subsequent drawing; while if it is lower than 850℃, it may enter the two-phase region for rolling, resulting in uneven structure and severe work hardening.

[0074] Preferably, controlling the final rolling temperature at 880–920°C ensures sufficient austenite recrystallization and yields fine and uniform original austenite grains.

[0075] Specifically, the wire rod is subjected to slow cooling treatment, for example, by placing it in an insulated pit or slow cooling hood, controlling the cooling rate at 10-30°C / hour until the temperature drops below 500°C. Sn has a strong tendency to segregate in steel; if cooling is too rapid (e.g., air cooling or wind cooling), Sn will accumulate at grain boundaries, severely deteriorating the steel's thermoplasticity and the drawing properties of the welding wire, and potentially leading to hot cracking during welding. The aforementioned slow cooling process provides sufficient diffusion time for Sn and Cu atoms, allowing them to achieve a uniform and dispersed solid solution distribution in the ferrite / pearlite matrix, thereby eliminating the adverse effects of Sn and enabling Cu to fully exert its positive role in improving resistance to marine atmospheric corrosion.

[0076] Specifically, in S3, the drawing reduction process employs multi-pass continuous drawing, with the reduction rate per pass controlled between 10% and 15%. An intermediate annealing is performed after each cumulative reduction reaches 50% to 60%. The intermediate annealing temperature is 750–850℃, with a holding time of 1–2 hours, followed by furnace cooling. This process eliminates work hardening, restores the material's plasticity and toughness, and ensures the welding wire can be smoothly drawn to its final size without breakage. Finally, the welding wire diameter is machined to a commonly used specification of 1.0 mm to 1.6 mm. This diameter range balances welding process stability (smooth wire feeding) and deposition efficiency, making it suitable for automated welding equipment.

[0077] On the other hand, a specific embodiment of the present invention discloses a welding joint.

[0078] The base material of the welded joint is high-strength low-alloy steel with a yield strength of not less than 690 MPa, such as marine engineering steel conforming to GB / T1591 standard. This base material is welded using the aforementioned corrosion-resistant welding wire, and the welded joint exhibits corrosion resistance comparable to that of the base material in a marine atmospheric environment.

[0079] Specifically, the welded joint can be prepared using conventional welding processes such as gas metal arc welding (GMAW). As a typical but non-limiting embodiment, an argon-rich gas mixture (e.g., 80% Ar + 20% CO2) is recommended as the protective medium. Those skilled in the art can make adaptive adjustments within the conventional welding process parameter window according to specific working conditions and equipment conditions. Exemplary process parameter ranges can be set as follows: welding current 160–200 A, arc voltage 22–26 V, and welding speed 30–40 cm / min. Under such optimized welding specifications, the corrosion-resistant welding wire of the present invention can reliably produce high-quality welded joints with aesthetically pleasing weld formation and free from macroscopic defects such as porosity and slag inclusions.

[0080] Compared with existing technologies, the welded joint obtained in this embodiment, due to the use of corrosion-resistant welding wire with specific composition designed according to this invention, not only achieves good matching with the high-strength base material in terms of mechanical properties (tensile strength ≥800MPa, Charpy V-notch impact absorption energy ≥60J at -40℃), but more importantly, its corrosion resistance in harsh marine environments is comparable to that of the base material. This characteristic ensures that the weld area no longer constitutes a weak point in corrosion protection in the high-temperature, high-humidity, and high-salt-spray marine atmospheric environment, thereby significantly improving the overall durability and long-term service safety of marine structures.

[0081] Specifically, the corrosion weight loss rate of the weld metal in a 2% NaCl aqueous solution in a simulated marine atmospheric environment does not exceed 1.52 g·m⁻¹. -2 ·h -1 It exhibits excellent resistance to uniform corrosion. This demonstrates its superior corrosion resistance, ensuring that the welded joint can achieve long-term corrosion protection in a marine atmospheric environment in sync with the base material, thus solving the key technical problem of premature failure of welded structures due to insufficient corrosion resistance of the weld metal.

[0082] The present invention will be described in more detail below through specific embodiments. These embodiments are merely descriptions of the best implementation of the invention and do not limit the scope of the invention in any way.

[0083] Examples 1-5 and Comparative Examples 1-2: Preparation of Welding Wire

[0084] The welding wires of Examples 1-5 and Comparative Examples 1-2 of this invention were all prepared using the following process:

[0085] First, steel ingots with precisely controlled composition are smelted in a vacuum induction furnace, and then hot-rolled into steel ingots with a diameter of [missing information]. The wire rod is finally reduced to a diameter of [diameter value missing] through multiple drawing passes. Welding wire.

[0086] S1. Proportion the raw materials according to the mass percentages shown in Table 1, and use a vacuum induction furnace for melting and casting. During the melting process, the vacuum degree is controlled below 1.0 Pa.

[0087] S2. Heat the above steel ingot to 1150℃ and hold for 2 hours, then perform multiple hot rolling passes to finally produce a steel ingot with a diameter of [missing information]. The wire rod is produced by controlling the final rolling temperature of hot rolling at 880℃~920℃. After rolling, the wire rod is placed in a slow cooling pit and slowly cooled to below 500℃ at a cooling rate of 15~25℃ / hour.

[0088] S3. After surface pretreatment of the wire rod, perform multi-pass drawing to reduce its diameter. When the cumulative diameter reduction reaches approximately 55%, perform intermediate annealing at 800℃ for 1.5 hours. Finally, reduce the wire diameter to...

[0089] The specific chemical composition (mass percentage) of each embodiment and comparative example is shown in Table 1.

[0090] Table 1. Chemical composition (wt%) of welding wires used in the examples and comparative examples

[0091] C Si Mn Ni Cr Mo Sn Cu Cu / Sn ratio Chromium-nickel equivalent ratio Example 1 0.06 0.5 1.8 3.8 0.7 0.4 0.02 0.8 40 0.28 Example 2 0.06 0.5 1.8 3.8 0.7 0.4 0.01 1 100 0.28 Example 3 0.06 0.5 1.8 3.8 0.7 0.4 0.03 0.6 20 0.28 Example 4 0.05 0.6 1.8 3.5 0.8 0.5 0.02 0.8 40 0.37 Example 5 0.1 0.4 2 4 0.6 0.3 0.02 0.8 40 0.19 Comparative Example 1 0.06 0.5 1.8 3.8 0.7 0.4 0.01 0.5 - 0.28 Comparative Example 2 0.06 0.5 1.8 3.8 0.5 0.4 0.02 0.8 40 0.25

[0092] Note 1: Chromium-nickel equivalent ratio = Chromium equivalent (Cr + Mo + 1.5Si) / Nickel equivalent (Ni + 30C + 0.5Mn).

[0093] Note 2: In Table 1, "-" indicates that the element was not added or the proportion is not applicable. P, S, O, N, H: The content was strictly controlled in all examples, with O≤0.005%, N≤0.005%, H≤0.001%, and Fe as the balance.

[0094] Characterization Testing and Result Analysis

[0095] The prepared welding wire was used for welding test plates. The base material of the test plates was Q690D high-strength low-alloy steel plate conforming to GB / T1591 standard, with a thickness of 20mm. The welding equipment was a Fronius TPS450 welding machine, and the welding parameters were uniformly set as follows: current 180A, voltage 24V, welding speed 36cm / min, shielding gas 80%Ar+20%CO2, and DC welding mode. After welding, the mechanical properties and corrosion resistance of the weld metal were tested according to the relevant national standards GB / T 2652 and GB / T 4334, respectively.

[0096] The weld metals of Examples 1-5 and Comparative Examples 1-2 of this invention were subjected to performance tests, including mechanical property tests on yield strength (R). p0.2 ), tensile strength (R) m The Charpy V-notch impact absorption energy (KV2) at -40℃ was measured. For corrosion resistance testing, the sample was immersed in a 2% NaCl solution (mass fraction) at (35±1)℃ with continuous ventilation (air flow rate 1.5 L / min) for 72 hours to simulate a marine atmospheric environment. The corrosion weight loss rate was measured in grams per square meter per hour (g·m²). -2 ·h -1 The test results are summarized in Table 2.

[0097] Table 2. Performance of deposited metal in examples and comparative examples

[0098]

[0099] As can be seen from Table 2, the weld metals of Examples 1-5 of this invention all exhibit excellent comprehensive properties: their yield strength is in the range of 732-775 MPa, their tensile strength is in the range of 840-856 MPa, their impact absorption energy at -40℃ is as high as 97-144 J, and their corrosion weight loss rate is controlled at 1.52-1.74 g·m⁻¹. -2 ·h -1 The performance is at a relatively low level. It fully meets the requirements for high strength, high toughness, and excellent resistance to marine corrosion.

[0100] In contrast, the performance of Comparative Examples 1 and 2 is significantly inferior. Comparative Example 1, which did not contain Sn, exhibited acceptable mechanical properties, but its corrosion weight loss rate reached 1.88 g·m⁻¹. -2 ·h -1 The corrosion resistance deteriorated significantly; in Comparative Example 2, the Cr content was lower than the range specified in this invention, and the chromium-nickel equivalent ratio deviated from the preferred value, resulting in a corrosion weight loss rate as high as 1.89 g·m³. -2 ·h -1 Its corrosion resistance does not meet the requirements.

[0101] like Figure 1 As shown in the metallographic diagram, the deposited metal of Example 1 exhibits a mixed microstructure of ferrite and lath bainite. The lath bainite regions exhibit a fine lath morphology with directional lath arrangement; ferrite is distributed within them. This optimized mixed microstructure, obtained by controlling the chromium-nickel equivalence ratio, is the core microscopic basis for achieving high strength, while simultaneously avoiding the damage to toughness caused by a large amount of granular bainite.

[0102] Figure 2 (Transmission electron microscopy image) further reveals the fine substructure of the lath bainitic region: high-density dislocations exist within the laths, and the lath width is controlled at the submicron level. This refined substructure effectively coordinates microscopic deformation and is key to ensuring that the deposited metal possesses both high strength and excellent low-temperature toughness.

[0103] Figure 3 (Scanning electron microscopy corrosion morphology image) shows that the corrosion products in the weld zone consist of needle-like or clustered α-FeOOH (goethite), with fine and interlocked crystals forming a continuous and dense protective rust layer. This rust layer effectively blocks the intrusion of corrosive media such as Cl-, thus exhibiting an extremely low corrosion weight loss rate on a macroscopic scale.

[0104] In summary, the welding wire of this invention, through precise compositional synergistic design, achieves a balance between high strength (yield strength ≥ 700 MPa, tensile strength ≥ 800 MPa) and high toughness (impact energy ≥ 60 J at -40℃) in its deposited metal. Furthermore, the dense corrosion product rust layer formed by the synergistic effect of Cu / Sn ensures excellent resistance to marine corrosion (corrosion weight loss rate ≤ 1.52 g·m³). -2 ·h -1 Ultimately, multi-performance synergy optimization was achieved, fully meeting the welding requirements of high-strength steel for marine building structures.

[0105] 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 changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A corrosion-resistant welding wire for high-strength steel marine structural engineering, characterized in that, The chemical composition of the welding wire, by mass percentage, includes: C: 0.05–0.10%, Si: 0.4–0.6%, Mn: 1.80–2.00%, Ni: 3.5–4.0%, Cr: 0.60–0.80%, Mo: 0.30–0.50%, Sn: 0.01–0.03%, Cu: 0.60–1.0%, P: ≤0.008%, S: ≤0.008%, O: ≤0.005%, N: ≤0.005%, H: ≤0.001%, balance Fe and unavoidable impurities.

2. The corrosion-resistant welding wire according to claim 1, characterized in that, The chromium-nickel equivalent ratio of the welding wire is controlled within the range of 19% to 37%; the chromium-nickel equivalent ratio is calculated as the ratio of chromium equivalent to nickel equivalent, expressed as a percentage of the mass of each element, where: The chromium equivalent is Cr + Mo + 1.5Si; The nickel equivalent is Ni+30C+0.5Mn.

3. The corrosion-resistant welding wire according to claim 2, characterized in that, The preferred chromium-nickel equivalent ratio is 25% to 32%.

4. The corrosion-resistant welding wire according to claim 1, characterized in that, The mass ratio of Cu to Sn in the welding wire, Cu / Sn, is controlled within the range of 20 to 100.

5. The corrosion-resistant welding wire according to claim 4, characterized in that, The preferred Cu / Sn mass ratio is 30 to 50.

6. The corrosion-resistant welding wire according to any one of claims 1-5, characterized in that, The weld metal of the welding wire has a yield strength ≥700MPa and a tensile strength ≥800MPa.

7. The corrosion-resistant welding wire according to any one of claims 1-5, characterized in that, The weld metal of the welding wire absorbs 60-150 J of energy at low-temperature impact at -40°C.

8. The corrosion-resistant welding wire according to any one of claims 1-5, characterized in that, The corrosion weight loss rate of the weld metal in 2% NaCl solution is no higher than 1.52 g·m⁻¹. -2 ·h -1 .

9. A method for preparing corrosion-resistant welding wire for high-strength steel marine structural engineering, used to prepare the corrosion-resistant welding wire according to any one of claims 1-8, characterized in that, Includes the following steps: S1. The raw materials are proportioned according to the stated mass percentage, and steel ingots are obtained through vacuum melting and casting; S2. The steel ingot is hot-rolled to produce wire rod; S3. The wire rod is drawn to reduce its diameter and then subjected to intermediate annealing to produce welding wire; By controlling the final rolling temperature and the cooling rate of the hot-rolled wire rod, the wire rod obtains a uniform metallographic structure, thereby achieving a uniform distribution of Sn and Cu elements in the matrix and avoiding Sn element segregation.

10. The preparation method according to claim 9, characterized in that, The final rolling temperature of the hot rolling is 850–950°C; and / or, the final step of the drawing and diameter reduction is to process the welding wire diameter to 1.0 mm–1.6 mm.

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