785MPa-grade high-toughness laser-arc hybrid welding solid welding wire and design method thereof

Abstract

The invention relates to the technical field of welding wires, in particular to a 785MPa-grade high-toughness laser-arc hybrid welding solid welding wire and a design method thereof.The 785MPa-grade high-toughness laser-arc hybrid welding solid welding wire is characterized in that 3.5%-5.5% of Ni and 0.5%-0.8% of Mo are added into welding wire alloy, and a large number of autocatalytic nucleation is induced to be generated, so that deposited metal forms an interlaced lath bainite structure; the contents of key alloy elements such as C, Mn, Ni and Mo are cooperatively regulated and controlled, so that the structure embrittlement tendency caused by steep rising and falling heat circulation in the laser-electric arc hybrid welding process is effectively controlled, a fine grain structure mainly comprising interlaced lath bainite is obtained, structure refinement is effectively achieved in deposited metal, and the welding quality is improved. Therefore, the alloy still has excellent impact toughness (KV2 reaches 91-100 J) in a low-temperature environment of-50 DEG C, the technical problem that high-strength laser-arc hybrid welding deposited metal is insufficient in toughness under extreme working conditions is solved, the safety of a welding structure is improved, the service life of the welding structure is prolonged, and upgrading of a maritime work equipment construction process is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of welding wires, and in particular to a 785MPa-grade high-strength and toughness laser-arc composite welding solid welding wire and a design method thereof. Background Art

[0002] Laser-arc hybrid welding (LAHW) is a trending high-precision welding technology in the offshore industry. Its development holds significant significance for upgrading my country's offshore equipment construction processes. However, the characteristic "sharp ramp" and "sudden drop" thermal cycle of LHW precludes direct use of existing gas-shielded welding wires. Norway's Kleven shipyard used a constant-strength gas-shielded welding wire to perform LHW welding of 420 MPa-grade marine high-strength steel. Mechanical property testing showed that the impact absorption energy at -30°C decreased from 210-240 J to 20-40 J, and the crack opening displacement decreased to 0.13-0.19 mm. Shipbuilding powerhouses such as the United States and Japan have also conducted LHW tests on HSLA, HLES, and NS series hull structural steels of varying strength grades using existing gas-shielded welding wires. The results demonstrate poor strength-toughness matching between the deposited metals. Furthermore, as strength increases, the weld metal hardens more significantly, indicating significant technical risks associated with directly using existing gas-shielded welding wires for LHW.

[0003] Laser-arc hybrid welding is a relatively new welding technology, but current research on hybrid welding primarily focuses on process development, while research on laser-arc hybrid welding materials suitable for different strength steel plates is seriously lagging. Publication No. CN113441871B discloses a flux-cored wire for laser-arc hybrid welding, with a deposited metal yield strength below 500 MPa. Publication No. CN113001059B describes a 440 MPa-grade high-strength steel welding wire and laser-arc hybrid welding process, with a good match between weld metal strength and toughness. However, these two composite wires, designed for lower-strength steel plates, cannot meet the current demand for lighter weight and higher toughness in offshore equipment. 10CrNi5MoV steel, a 785 MPa-grade high-strength and tough offshore steel, is widely used in the new generation of offshore equipment. Laser-arc hybrid welding is a key process for the construction and upgrading of next-generation offshore equipment. However, the lack of high-performance hybrid welding materials suitable for 10CrNi5MoV steel has severely hampered the transition to high-efficiency, low-stress construction, hindering the development of my country's marine resources.

[0004] Publication No. CN119589198A describes a welding wire and laser-arc hybrid welding process for 780MPa-grade wheel steel. The chemical composition and weight percentage of the welding wire are as follows: C 0.06%-0.08%, Si 0.30%-0.80%, Mn 1.80%-2.0%, Ni 1.5%-2.0%, Cu 0.20%-0.50%, Mo 0.20%-0.50%, Nb 0.04%-0.07%, Ti 0.06%-0.10%, V 0.03%-0.07%, RE 0.015%-0.10%, S ≤ 0.010%, P ≤ 0.010%, with the balance being Fe and unavoidable impurities. However, the weld zone microstructure of this technical solution is primarily composed of acicular ferrite, bainite, and a small amount of proeutectoid ferrite, and its yield strength and toughness cannot meet the requirements for offshore equipment.

[0005] Publication number: CN118664176A An X80 pipeline steel welding wire and its laser-arc hybrid welding process, the chemical composition of the welding wire includes: 0.05-0.07% C, 0.50-0.70% Si, 1.10-1.30% Mn, 1.05-1.20% Ni, 0.20-0.30% Mo, 0.02-0.04% Ti, 0.0005-0.0020% B, S≤0.006%, P≤0.006%, the balance is Fe and unavoidable impurities. However, the design idea of ​​the scheme to improve the strength and toughness of the welded joint by increasing the content of acicular ferrite is significantly different from the present invention. After welding, the joint of the welding wire has an impact absorption energy of ≥100J at -20℃, and the tensile strength of the welded joint is σ b ≥726MPa, it can be found that the yield strength of the deposited metal is far lower than 785MPa, and the low-temperature toughness is insufficient, which cannot meet the current requirements of new marine engineering equipment for the welding performance of high-strength steel.

[0006] Therefore, it is urgent to design a high-strength and toughness laser-arc composite welding solid wire to solve the problem of lack of high-strength steel and high-performance laser-arc composite welding materials in the process of transformation of the new generation of marine engineering equipment to high-efficiency and low-stress construction. Summary of the Invention

[0007] In view of this, the present invention aims to propose a 785MPa-grade high-strength and toughness laser-arc composite welding solid welding wire to solve the problem of lack of high-performance laser-arc composite welding materials supporting high-strength steel in the construction process of the new generation of marine engineering equipment.

[0008] The present invention is based on the 785MPa grade 10CrNi5MoV steel composition system, and in view of the "steep rise and fall" thermal cycle characteristics of laser-arc hybrid welding, the matching laser-arc hybrid welding wire is designed with a composition. Lath bainite is used as the matrix structure of the deposited metal, and the content of strong hardenability elements such as C and Mn is strictly controlled to avoid the formation of martensite structure under rapid cooling conditions and prevent toughness deterioration. At the same time, based on the influence of alloying elements on the bainite phase transformation point, the present invention innovatively proposes to induce autocatalytic nucleation in the composite welding deposited metal through the synergistic effect of Ni and Mo (see Figure 1 ), thereby obtaining a complexly oriented interwoven bainite structure, and with the help of the fine grain strengthening effect, the strength and toughness of the deposited metal are simultaneously improved.

[0009] This is an original technological breakthrough in the design of high-strength welding wire. It no longer relies on traditional empirical proportions, but instead conducts purposeful organizational design through an in-depth understanding of the organizational evolution mechanism of alloying elements. It reflects the transformation of material design from "experience-oriented" to "mechanism-oriented". Traditional high-strength welding materials are prone to reduced toughness in low-temperature environments. The present invention regulates the bainite structure to significantly improve low-temperature toughness while ensuring high strength, solving key technical problems in the industry.

[0010] The specific principle is: the deposited metal is a typical cast structure and cannot be subjected to hot deformation treatment like steel plates, which makes it difficult to achieve effective refinement of the deposited metal. The increase in its strength is often accompanied by a loss of toughness. The present invention is based on the influence of alloying elements on the transformation behavior of bainite. By regulating the content of elements such as Ni and Mo, the nucleation behavior of bainite laths is regulated, inducing a large amount of autocatalytic nucleation to form an interwoven lath bainite structure, which is different from the traditional parallel lath bainite structure.

[0011] From a crystallographic perspective, high-angle grain boundaries can effectively hinder crack propagation. By inducing autocatalytic nucleation and increasing the complexity of bainite lath orientation in the deposited metal structure, this refines the effective grain size of the deposited metal and increases the proportion of high-angle grain boundaries in the structure, thereby improving its ability to hinder crack propagation. Based on the design concept of this invention, the deposited metal is effectively refined, thereby simultaneously improving strength and toughness through grain refinement.

[0012] The technical solution of the present invention is achieved as follows:

[0013] One object of the present invention is to disclose a design method for a 785MPa-grade high-strength and toughness solid welding wire for laser-arc hybrid welding, in which 3.5-5.5% Ni and 0.5-0.8% Mo are added to the welding wire composition to induce a large amount of autocatalytic nucleation, so that the deposited metal forms an interwoven lamellar bainite structure.

[0014] Another object of the present invention is to disclose a 785MPa-grade high-strength and toughness laser-arc composite welding solid welding wire and a design method thereof. Based on the above-mentioned design method of a 785MPa-grade high-strength and toughness laser-arc composite welding solid welding wire, the chemical composition mass percentage of the welding wire is C: 0.02~0.05%, Si: 0.20~0.40%, Mn: 0.9~1.3%, Ni: 3.5~5.5%, Mo: 0.5~0.8%, Ti: 0.02~0.05%, V: 0.03~0.07%, S≤0.010%, P≤0.015%, and the rest is Fe.

[0015] Furthermore, the welding wire diameter ranges from 1.0 to 1.6 mm.

[0016] Furthermore, the welding steel plate has a thickness ranging from 10 to 100 mm and is made of 10CrNi5MoV steel.

[0017] Furthermore, the diameter of the welding wire is 1.2 mm, and the steel plate is 10CrNi5MoV steel with a thickness of 40 mm.

[0018] Furthermore, the welding wire adopts the following welding process when laser-arc hybrid welding: laser power 1.5~3.0kW, wire spacing 2~3mm, defocus amount +2~+3mm, welding voltage 15~18V, current 130~160A, welding speed 35~60cm / min, gas flow 15~25L / min, and shielding gas is a mixed gas of 95% Ar+5%CO2 by volume.

[0019] Furthermore, the welding wire adopts a laser-arc hybrid welding process, and defect-free welding is achieved at room temperature without preheating or postheating.

[0020] Furthermore, the chemical composition percentages of the welding wire are C: 0.027%, Si: 0.316%, Mn: 0.96%, Ni: 4.22%, Mo: 0.627%, Ti: 0.04%, V: 0.048%, Cu: 0, S: 0.0057%, P: 0.0054%, and Fe balance.

[0021] Furthermore, the chemical composition of the welding wire is as follows in percentage by mass: C: 0.036%, Si: 0.323%, Mn: 1.07%, Ni: 4.91%, Mo: 0.77%, Ti: 0.03%, V: 0.051%, Cu: 0, S: 0.0053%, P: 0.0051%, and Fe as the balance.

[0022] Furthermore, the yield strength R of the deposited metal of the welding wire p0.2 :805~827MPa, KV2:91~100J at -50℃; tensile strength of welded joint R m:918~933MPa.

[0023] Compared with the prior art, the 785MPa-grade high-strength and toughness laser-arc hybrid welding solid wire and its design method of the present invention have the following advantages:

[0024] 1. The high-strength and toughness laser-arc hybrid welding solid welding wire proposed in the present invention can significantly improve the strength and toughness of the laser-arc hybrid welding deposited metal without increasing the complexity of welding through precise design of alloy composition and directional optimization of the deposited metal structure characteristics. It can also achieve high-quality welding without the need for preheating or post-heat treatment, greatly reducing the construction difficulty and overall cost. It is particularly suitable for large-scale construction scenarios such as marine engineering that have strict requirements on the strength and toughness matching of laser-arc hybrid welding joints.

[0025] 2. The present invention effectively controls the tendency of structural embrittlement caused by the "steep rise and fall" thermal cycle during laser-arc hybrid welding by synergistically regulating the content of key alloying elements such as C, Mn, Ni, and Mo, thereby obtaining a fine-grained structure dominated by interwoven lath bainite. This effectively achieves structural refinement in the deposited metal, thereby maintaining excellent impact toughness (KV2 of 91 to 100 J) even at a low temperature of -50°C. This solves the technical problem of insufficient toughness of the deposited metal in laser-arc hybrid welding under extreme working conditions, thereby improving the safety and service life of the welded structure.

[0026] 3. The present invention adopts a systematic material design concept and process control method to achieve the coordinated optimization of the chemical composition, metallurgical behavior and welding process performance of the welding wire. It not only meets the performance requirements of laser-arc hybrid welding materials for 785MPa-grade high-strength steel (such as 10CrNi5MoV steel), but also provides a replicable and scalable technical path for the research and development of new high-strength and toughness welding materials. It has broad adaptability and promotion value, and contributes to the overall improvement of the welding technology level in the high-end manufacturing field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 Schematic diagram of bainite nucleation mode and typical organization;

[0029] Figure 2 The deposited metal morphology is shown in Figure 2. (a) The deposited metal morphology of Example 1, (b) The deposited metal morphology of Comparative Example 4;

[0030] Figure 3 This is the typical narrow gap laser-arc hybrid welding weld morphology of Example 1. DETAILED DESCRIPTION

[0031] In order to make the technical means, objectives and effects of the present invention easier to understand, embodiments of the present invention are described in detail below with reference to specific figures.

[0032] It should be noted that all terms used in the present invention to indicate direction and position, such as "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "low", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection status between various components in a specific state. They are only for the convenience of describing the present invention, and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0033] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical connections; direct connections or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0034] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0035] The present invention discloses a design method for a 785MPa-grade high-strength and toughness laser-arc hybrid welding solid welding wire, which is characterized in that 3.5-5.5% Ni and 0.5-0.8% Mo are added to the welding wire alloy to induce a large amount of autocatalytic nucleation, so that the deposited metal forms an interwoven lamellar bainite structure.

[0036] The synergistic addition of Ni and Mo modifies the phase transformation behavior of the deposited metal, inducing an autocatalytic nucleation mechanism that promotes the nucleation and growth of bainite during cooling, contributing to the formation of an interwoven lamellar bainite structure. This structure exhibits a high dislocation density and a high proportion of high-angle grain boundaries, characterized by a fine, uniform, and multi-directional interlaced distribution. This structure effectively hinders crack propagation and improves crack resistance. Furthermore, this structure inhibits the formation of brittle martensite, enhancing the toughness of the welded joint at low temperatures. Ni significantly enhances low-temperature toughness, expands the austenite region, and promotes bainite formation. Mo, by combining with carbon to form nanoprecipitates, regulates the bainite transformation temperature, further refines the structure, and enhances strength. The yield strength of the deposited metal reaches 805–827 MPa, and the tensile strength of the welded joint reaches 918–933 MPa. At -50°C, the impact energy absorbed reaches 91–100 J, meeting the requirements of extreme environments such as marine engineering.

[0037] The present invention innovatively proposes to induce autocatalytic nucleation in the deposited metal through the synergistic effect of Ni and Mo, thereby obtaining an interwoven lamellar bainite structure with excellent mechanical properties. This is an original technological breakthrough in the design of high-strength welding wire. It no longer relies on traditional empirical proportions, but instead conducts purposeful organizational design through an in-depth understanding of the organizational evolution mechanism of alloying elements, reflecting the transformation of material design from "experience-oriented" to "mechanism-oriented". Traditional high-strength welding materials are prone to reduced toughness in low-temperature environments. The present invention regulates the bainite structure to significantly improve low-temperature toughness while ensuring high strength, solving key technical problems in the industry.

[0038] The present invention discloses a 785MPa-grade high-strength and toughness laser-arc composite welding solid welding wire and a design method thereof, comprising the following chemical composition (wt.%): C: 0.02-0.05%, Si: 0.20-0.40%, Mn: 0.9-1.3%, Ni: 3.5-5.5%, Mo: 0.5-0.8%, Ti: 0.02-0.05%, V: 0.03-0.07%, S≤0.010%, P≤0.015%, and the remainder is Fe.

[0039] The various alloying elements in the welding wire are designed with different contents based on the analysis of their functions. The final composition of the welding wire is determined after a large number of welding wire trials.

[0040] Carbon, an interstitial atom, can produce a strong solid solution strengthening effect. However, while increasing strength, it also causes lattice distortion, leading to stress concentration, which can easily induce crack initiation and deteriorate toughness. Furthermore, given the rapid cooling and heating thermal cycles characteristic of hybrid welding, increased carbon content can easily lead to the formation of martensite in the deposited metal, further reducing toughness. To ensure good overall mechanical properties, a lower limit of 0.02% and an upper limit of 0.05% are established.

[0041] The Si element can combine with the O element to form SiO2, thereby playing a deoxidation role. At the same time, it can also improve the wettability of the molten metal, which has an important influence on the weld formation during narrow gap welding. However, the Si content in the deposited metal cannot be too high to avoid increasing the crack sensitivity of the deposited metal. Therefore, the Si content is controlled at 0.20-0.40%.

[0042] Mn effectively strengthens the weld metal by solid solution. In theory, every 0.1% increase in Mn increases yield strength by 20-30 MPa. It also acts as a deoxidizer during welding, combining with oxygen to form MnO. However, excessive Mn content can reduce weldability, promote martensite formation, and reduce toughness. The Mn content should be controlled between 0.9 and 1.3%.

[0043] Nickel is a typical element that expands the austenite phase. It is generally believed that nickel can improve the low-temperature toughness of steel materials by increasing the retained austenite content or reducing the resistance to dislocation motion. However, numerous studies have shown that excessive nickel content in high-strength steel deposits can lead to the formation of large, aggregated bainite, which degrades toughness. Taking into account the effects of nickel on low-temperature toughness and the bainite transformation point in current alloy systems, and based on previous research, its content is controlled between 3.5% and 5.5%.

[0044] Mo has a significant influence on the bainite transformation point and combines with carbon to form nanoscale M2C-type precipitations, enhancing strength. Taking into account the Ni and Mn contents in the current alloy system, the Mo content is optimized to promote autocatalytic nucleation of bainite in the weld metal, with the Mo content controlled at 0.5-0.8%.

[0045] V is a strong carbide-forming element that tends to form MX-type carbides with C and N, playing a strengthening role in the deposited metal. At the same time, V also has the effect of solid solution strengthening, which can effectively improve the strength. By adding an appropriate amount of V, the strength loss caused by the reduction of C content can be compensated. The V content is controlled at 0.03-0.07%.

[0046] Ti easily combines with oxygen in the deposited metal to form small oxides. These oxides provide nucleation sites for bainite laths within the grains, inducing intragranular nucleation. This further increases the complexity of the weld metal's microstructure, increases the proportion of high-angle grain boundaries, and improves the structure's resistance to cracking. However, excessive Ti content can reduce the wire's processability. Based on previous test data, the Ti content is controlled within a range of 0.02 to 0.05%.

[0047] S and P are harmful elements and their content should be reduced as much as possible. Considering the smelting cost of welding wire, the upper limit of control is 0.01%.

[0048] Carbon is an interstitial atom that produces a strong solid solution strengthening effect. C content must be strictly controlled to ensure excellent overall mechanical properties. Si combines with oxygen to form SiO2, which acts as a deoxidizer and improves wettability of the droplet, facilitating weld formation during narrow-gap laser-arc hybrid welding. Manganese provides effective solid solution strengthening and acts as a deoxidizer during welding. Ni expands the austenite phase, reducing resistance to dislocation motion and improving low-temperature toughness. Mo has a significant influence on the bainite transformation point, combining with carbon to form nanoscale precipitates that enhance strength. Furthermore, Mo can regulate the bainite transformation point in the deposited metal and promote autocatalytic nucleation. Ti readily combines with oxygen to form small oxides, providing nucleation sites for bainite laths within the grain, further refining the microstructure, increasing the proportion of high-angle grain boundaries, and enhancing crack resistance. V is a strong carbide-forming element that forms MX-type carbides with carbon and nitrogen, strengthening the deposited metal while also providing solid solution strengthening.

[0049] The yield strength Rp0.2 of the deposited metal of the welding wire of the present invention reaches 805~827MPa, and the -50℃ KV2 impact absorption energy reaches 91~100J, showing a good match between strength and toughness. It can achieve defect-free welding at room temperature without preheating or postheating, reducing welding costs and process complexity. It is particularly suitable for application scenarios such as marine engineering that require high-efficiency, low-stress construction and have high requirements for the strength and toughness of the deposited metal.

[0050] This setting achieves the goals of high strength and good toughness by precisely controlling the alloy composition, while simplifying the welding process and improving production efficiency and economic benefits.

[0051] Specifically, the welding wire diameter ranges from 1.0 to 1.6 mm.

[0052] Welding wires of different diameters are suitable for different welding currents and speeds, thus meeting the requirements of various weld thicknesses and joint types. Thinner wires (such as 1.0mm) are suitable for thin plate welding and provide more precise control, while thicker wires (such as 1.6mm) are more suitable for thick plate welding and can withstand higher welding currents, improving welding efficiency.

[0053] This setting maximizes welding speed while ensuring welding quality by selecting the appropriate wire diameter. This is especially true when using thicker diameter wires, significantly improving work efficiency without sacrificing welding quality. It helps achieve ideal penetration depth, weld width, and weld shape, ensuring that the weld joint has excellent mechanical properties and appearance quality.

[0054] Specifically, the thickness of the welding steel plate ranges from 10 to 100 mm, and the material is 10CrNi5MoV steel.

[0055] 10CrNi5MoV steel is a high-strength steel. When welding this level of steel, it is necessary to match it with welding materials that also have high strength. The welding wire provided by the present invention can ensure a good strength match between the weld joint and the parent material, meeting the high-strength requirements of structural parts. For steel plates with a thickness between 10 and 100 mm, the traditional welding method has low welding efficiency and large deformation. By combining laser-arc hybrid welding with narrow gap welding grooves and using high-performance supporting welding materials, efficient, low-stress, and high-quality welding can be achieved.

[0056] Compared with traditional welding methods, this setting, laser-arc hybrid welding technology combined with the welding wire of the present invention can significantly improve welding efficiency without sacrificing welding quality. It is particularly suitable for welding medium and thick plates, thereby shortening the manufacturing cycle and reducing production costs.

[0057] Preferably, the welding wire has a diameter of 1.2 mm and the steel plate is 10CrNi5MoV steel with a thickness of 40 mm.

[0058] The 1.2mm diameter welding wire can achieve relatively ideal droplet transfer characteristics during laser-arc hybrid welding, improve the stability of the welding process, avoid the formation of defects such as welding porosity and lack of fusion defects, and improve welding quality.

[0059] Specifically, the laser-arc hybrid welding specifications are: laser power 1.5~3.0kW, filament spacing 2~3mm, defocus amount +2~+3mm, welding voltage 15~18V, current 130~160A, welding speed 35~60cm / min, gas flow 15~25L / min, and the shielding gas is a mixed gas of 95% Ar+5% CO2 by volume.

[0060] Laser power is controlled within the 1.5-3.0 kW range. Combined with appropriate arc parameters (voltage of 15-18 V and current of 130-160 A), this ensures good penetration depth and width in 40 mm thick steel plates while avoiding excessive heat input that could degrade the heat-affected zone. A 2-3 mm inter-wire spacing creates a synergistic effect between the laser and arc, enhancing melt pool stability, improving weld quality, and increasing deposition efficiency. A 95% Ar + 5% CO2 shielding gas mixture reduces inclusions in the deposited metal while providing a certain degree of oxidizing properties to stabilize the arc morphology, reduce spatter, and enhance weld surface quality. A defocus of +2-3 mm (i.e., the focus is positioned above the workpiece) combined with laser oscillation helps expand the laser active area, avoid lack of fusion defects, slow the cooling rate, inhibit the formation of brittle hard structures (such as martensite), and promote the formation of bainite, thereby improving joint toughness. A welding speed of 35-60 cm / min allows for flexible production adjustments while ensuring penetration, meeting efficient manufacturing requirements.

[0061] This parameter combination has been systematically optimized to achieve a uniform and dense weld structure, high joint strength (Rm can reach over 900 MPa), and excellent low-temperature impact toughness of the deposited metal (KV2 at -50°C reaches over 90J), meeting the requirements of harsh environments such as marine engineering. The welding process is stable, spatter is minimal, the weld formation is beautiful, and repeatability is good, making it suitable for industrial continuous production.

[0062] Specifically, the welding wire adopts a laser-arc hybrid welding process, and defect-free welding is achieved at room temperature without preheating or postheating.

[0063] Welding without preheating is often prone to cold cracking, especially in high-strength quenched and tempered steels. This process significantly improves crack resistance and achieves crack-free welding by optimizing the wire alloy system and manipulating the deposited metal structure (for example, by predominantly interwoven bainite to reduce internal stress). This process eliminates preheating and postheating steps, simplifies on-site welding operations, and reduces the need for auxiliary equipment and energy, making it particularly suitable for field or offshore operations.

[0064] This setting eliminates the need for supporting equipment such as preheating furnaces, insulation blankets, temperature measuring devices, and their energy consumption, reduces manual operation time, and significantly reduces welding manufacturing costs. The preheating and post-heating processes are often time-consuming. Canceling these steps can shorten the welding cycle and speed up project progress. It is particularly suitable for large-scale industrial production and on-site emergency repair operations. It is easier to realize the automation and robot integration of the welding process, and improve the consistency of welding quality and the level of production intelligence.

[0065] Specifically, the chemical composition of the welding wire is as follows: C: 0.027%, Si: 0.316%, Mn: 0.96%, Ni: 4.22%, Mo: 0.627%, Ti: 0.04%, V: 0.048%, Cu: 0, S: 0.0057%, P: 0.0054%, and Fe balance.

[0066] The wire yield strength R p0.2 The tensile strength Rm of the welded joint is 805 MPa, the elongation after fracture A is 21%, the cross-sectional shrinkage Z is 70%, the impact absorption energy KV2 at -50°C is 100 J, and the tensile strength Rm of the welded joint is 918 MPa.

[0067] This setup can provide sufficient strength to meet the needs of high-strength welding and is suitable for applications in extreme environments such as marine engineering.

[0068] Specifically, the chemical composition of the welding wire is as follows: C: 0.036%, Si: 0.323%, Mn: 1.07%, Ni: 4.91%, Mo: 0.77%, Ti: 0.03%, V: 0.051%, Cu: 0, S: 0.0053%, P: 0.0051%, and Fe balance.

[0069] The wire yield strength R p0.2 The tensile strength Rm is 827 MPa, the elongation after fracture A is 20%, the cross-sectional shrinkage Z is 70%, the impact absorption energy KV2 at -50°C is 91J, and the tensile strength Rm of the welded joint is 933 MPa.

[0070] This setup has a reasonable organizational design and precise composition control. The welding wire can directly weld thick plates (such as 40mm) of 10CrNi5MoV steel at room temperature, achieving crack-free and defect-free welding, significantly simplifying the process flow, achieving high-speed welding, and obtaining a stable molten pool, good forming and uniform organization.

[0071] Specifically, the yield strength R of the deposited metal of the welding wire p0.2 :805~827MPa, KV2:91~100J at -50℃; tensile strength of welded joint Rm:918~933MPa.

[0072] Through precise composition design and microstructure control, a comprehensive performance match of high strength, high toughness and high plasticity is achieved, which is particularly suitable for laser-arc hybrid welding of thick plates of 785 MPa grade high-strength steel (such as 10CrNi5MoV steel).

[0073] Example 1

[0074] The chemical composition of the welding wire is:

[0075] C: 0.027%, Si: 0.316%, Mn: 0.96%, Ni: 4.22%, Mo: 0.627%, Ti: 0.04%, V: 0.048%, Cu: 0, S: 0.0057%, P: 0.0054%, Fe balance.

[0076] Example 2

[0077] The chemical composition of the welding wire is:

[0078] C: 0.036%, Si: 0.323%, Mn: 1.07%, Ni: 4.91%, Mo: 0.77%, Ti: 0.03%, V: 0.051%, Cu: 0, S: 0.0053%, P: 0.0051%, Fe balance.

[0079] Comparative Example 1

[0080] The chemical composition of the welding wire is:

[0081] C: 0.031%, Si: 0.308%, Mn: 1.19%, Ni: 6.11%, Mo: 0.411%, Ti: 0.021%, V: 0.054%, Cu: 0, S: 0.0053%, P: <0.005%, Fe balance.

[0082] Comparative Example 2

[0083] The chemical composition of the welding wire is:

[0084] C: 0.04%, Si: 0.55%, Mn: 1.52%, Ni: 3.17%, Mo: 0.32%, Ti: 0.047%, V: 0%, Cu: 0.4%, S: 0.0056%, P: <0.005%, Fe balance.

[0085] Comparative Example 3

[0086] The chemical composition of the welding wire is:

[0087] C: 0.06%, Si: 0.27%, Mn: 1.48%, Ni: 3.63%, Mo: 1.14%, Ti: 0.062%, V: 0.028%, Cu: 0, S: 0.0051%, P: 0.0053%, Fe balance.

[0088] Comparative Example 4

[0089] The chemical composition of the welding wire is:

[0090] C: 0.052%, Si: 0.303%, Mn: 1.23%, Ni: 3.69%, Mo: 1.13%, Ti: 0.024%, V: 0.061%, Cu: 0, S: <0.005%, P: <0.005%, Fe balance.

[0091] The present invention will be further described in detail with reference to examples, but the present invention is not limited to these examples.

[0092] The chemical composition of the welding wire used in the examples and comparative examples is shown in Table 1. The welding wire specification is φ1.2 mm, and the composition is shown in Table 2. The steel plate used in the test is 40 mm thick 10CrNi5MoV steel. The laser-arc hybrid welding process is shown in Table 2, and 95% Ar + 5% CO2 is used as the shielding gas.

[0093] Table 1 Chemical composition of the welding wire of the present invention (wt. %)

[0094]

[0095] Table 2 Test plate laser-arc hybrid welding specifications

[0096]

[0097] Table 3 Mechanical properties test results

[0098]

[0099] After mechanical property testing, it was found that both Example 1 and Example 2 have good strength-toughness matching. On the basis of the yield strength reaching 785 MPa, the -50 ℃ impact absorption energy reaches more than 90 J. Compared with Example 1, the yield strength of Comparative Example 1 is slightly lower, and the impact absorption energy is significantly reduced. This is because Comparative Example 1 continues to increase the Ni content to 6.11% on the basis of Example 1. Due to the metallurgical characteristics of the deposited metal, the toughness is reduced by continuously increasing the Ni content, which is consistent with the effect of Ni in the gas shielded welding deposited metal; Compared with the embodiment, Comparative Example 2 increases the Mn content to 1.52%, resulting in improved hardenability of the deposited metal and deterioration of toughness; at the same time, 0.4% Cu is added. Too much Cu in the deposited metal will reduce toughness and increase the tendency of welding cracks; Compared with the embodiment, Comparative Examples 3 and 4 significantly increase the content of C, Mn and Mo. These three elements can significantly improve the hardening tendency of the deposited metal. At the same time, laser-arc composite welding has a "steep rise and fall" thermal cycle characteristic, which leads to the appearance of hardened structure in the deposited metal and deterioration of toughness. As Figure 2 (a) shows the microstructure of the deposited metal of Example 1. It can be seen that interwoven lamellar bainite structure is generated, which effectively refines the deposited metal structure, proving that the bainite in the deposited metal of the welding wire of the present invention undergoes autocatalytic nucleation, achieving microstructure directional design; Figure 2 (b) shows the microstructure of the deposited metal of Comparative Example 4. The microstructure is a typical parallel lamellar bainite structure, and a large amount of polymerized bainite structure is generated, which has a deteriorating effect on toughness, resulting in deterioration of toughness.

[0100] Figure 3 The surface and cross-sectional morphologies of a typical laser-arc hybrid weld produced by the welding wire of Example 1 are shown. The deposited metal exhibits good spreadability and is free of defects. The crack resistance of the welding wire of Example 1 was tested using a window-type crack resistance test method. The results show that the deposited metal exhibits no cracks at room temperature without preheating or postheating.

[0101] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A design method for a 785MPa grade high strength and toughness laser-arc hybrid welding solid wire, characterized in that: Adding 3.5-5.5% Ni and 0.5-0.8% Mo to the welding wire alloy induces a large amount of autocatalytic nucleation, so that the deposited metal forms an interwoven lamellar bainite structure.

2. A 785MPa grade high strength and toughness laser-arc hybrid welding solid wire, characterized in that: Based on the design method of a 785MPa-grade high-strength and toughness laser-arc composite welding solid welding wire described in claim 1, the chemical composition mass percentage of the welding wire is C: 0.02~0.05%, Si: 0.20~0.40%, Mn: 0.9~1.3%, Ni: 3.5~5.5%, Mo: 0.5~0.8%, Ti: 0.02~0.05%, V: 0.03~0.07%, S≤0.010%, P≤0.015%, and the rest is Fe.

3. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: The diameter range of welding wire is 1.0~1.6mm.

4. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: The thickness of the welding steel plate ranges from 10 to 100 mm, and the material is 10CrNi5MoV steel.

5. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: The diameter of the welding wire is 1.2 mm, and the steel plate is 10CrNi5MoV steel with a thickness of 40 mm.

6. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: The welding wire adopts the laser-arc hybrid welding process: laser power 1.5~3.0kW, wire spacing 2~3mm, defocus amount +2~+3mm, welding voltage 15~18V, current 130~160A, welding speed 35~60cm / min, gas flow 15~25L / min, and the shielding gas is a mixed gas of 95%Ar+5%CO2 by volume.

7. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 6, characterized in that: The welding wire adopts laser-arc hybrid welding process, and can achieve defect-free welding at room temperature without preheating or postheating.

8. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: The chemical composition mass percentage of the welding wire is C: 0.027%, Si: 0.316%, Mn: 0.96%, Ni: 4.22%, Mo: 0.627%, Ti: 0.04%, V: 0.048%, Cu: 0, S: 0.0057%, P: 0.0054%, and Fe balance.

9. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: The chemical composition of the welding wire is C: 0.036%, Si: 0.323%, Mn: 1.07%, Ni: 4.91%, Mo: 0.77%, Ti: 0.03%, V: 0.051%, Cu: 0, S: 0.0053%, P: 0.0051%, Fe balance.

10. The 785MPa high-strength and toughness laser-arc hybrid welding solid wire according to claim 2, characterized in that: Yield strength R of deposited metal of welding wire p0.2 :805~827MPa, KV2:91~100J at -50℃; tensile strength of welded joint R m :918~933MPa.

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