Welding materials for high heat input submerged arc welding of bridge steel, their preparation methods and applications

Abstract

This invention discloses a welding material for high heat input submerged arc welding of bridge steel, its preparation method, and its application. The welding material includes a solid submerged arc welding wire and a matching sintered submerged arc welding flux. The chemical composition of the welding wire steel used to prepare the submerged arc welding wire includes: C 0.05-0.1%, Si 0.05-0.1%, Mn 1.3-1.5%, Ni 1.2-1.4%, Nb 0.03-0.05%, Cr 0.1-0.16%, Mo 0.1-0.3%, Ti 0.05-0.13%, Al 0.002-0.01%, B 0.005-0.008%, P≤0.01%, S≤0.005%, N≤0.005%, with the balance being Fe and unavoidable impurities. The submerged arc welding flux comprises: CaO≤5%, CaF2 20-24%, MgO... The chemical composition of the welding material for high heat input submerged arc welding of bridge steel described in this invention is simple, the preparation method is simple, and the implementation cost is low. Using this submerged arc welding wire and the submerged arc welding flux, 50-100 kJ / cm high heat input submerged arc welding of Q370qE and Q420qE bridge steels exhibits good arc stability, slag fluidity, flux slag removal, and high-temperature stability of the weld metal. The welding deposition rate is fast, and the mechanical properties of the weld metal are good.

Description

Technical Field

[0001] This invention relates to a welding material for high heat input submerged arc welding of bridge steel, its preparation method and application, specifically to a solid submerged arc welding wire and a matching sintered submerged arc welding flux for submerged arc welding of two types of bridge steel, Q370qE and Q420qE, with a heat input of 50-100kJ / cm, as well as the preparation method of the submerged arc welding wire and the submerged arc welding flux, belonging to the field of welding material technology. Background Technology

[0002] With the development of the bridge manufacturing industry, the number of steel bridge structures has increased. In recent years, in order to improve the welding production efficiency of bridge steel structures, major domestic steel mills have successively developed bridge steel that can be welded with high heat input through composition design, metallurgical rolling, and welding thermal simulation tests, with an allowable welding heat input >50kJ / cm. However, the engineering application of domestically produced bridge steel that can be welded with high heat input is limited by factors such as the substandard welding performance of domestically produced bridge steel welding materials (welding materials for submerged arc welding include welding wire and flux) at high heat input (specifically, after welding heat input >35kJ / cm, the low-temperature impact toughness of the weld decreases significantly and is lower than the manufacturing specification requirements), and the high price of imported welding materials on the market.

[0003] In the welding process of bridge steel structures, the commonly used welding methods are gas metal arc welding (GMAW) and submerged arc welding (SAW). Among them, SAW has high welding deposition efficiency and large heat input. Domestic bridge manufacturing enterprises currently have SAW equipment with a maximum heat input of 50-100 kJ / cm, creating an urgent need for welding wires and fluxes suitable for high heat input SAW. Currently, commercially available mature high heat input SAW wires and fluxes are heavily reliant on imports and are mainly used in shipbuilding, typically in the three-wire SAW (FCB method) for ship plates. However, the mechanical performance requirements for welded joints in bridge structures are generally higher than those for ship structures (e.g., for Grade E steel, bridge manufacturing specifications require an impact test temperature of -40℃, while shipbuilding specifications only require -20℃). Therefore, existing high heat input SAW wires and fluxes for ship plate steel are not suitable for high heat input SAW welding of bridge steel. In addition, since submerged arc welding flux is made by sintering or melting a mixture of various ore particles (or powders), and the same type of ore from different origins often has significant quality differences, the design of submerged arc welding flux with high heat input for bridge steel is very difficult.

[0004] To address the aforementioned technical challenges, welding materials engineers have conducted some beneficial research and development on welding wires and fluxes capable of high heat input in submerged arc welding.

[0005] Chinese invention patent application CN 115815762A, entitled "A 500MPa Multi-Wire Submerged Arc Welding Electrode and Welding Wire Capable of Welding with a High Heat Input of 100-200kJ / cm and Welding Wire," promotes the nucleation of acicular ferrite by generating composite oxide inclusions of Si, Mn, Ti, and Ce, thereby improving weld toughness. Under heat input conditions of 100-200kJ / cm and an alkaline sintering flux based on Fe powder-MgO-SiO2-CaF2-Al2O3, although the above-mentioned welding wire can produce weld metal with good mechanical properties, its high carbon equivalent results in poor compatibility with commonly used Q345qE and Q370qE bridge steels. Furthermore, the yield strength ratio of the weld metal in the embodiment is close to the upper limit of 0.85 specified in bridge structural steel standards. In addition, the composition design of this welding wire is complex, requiring the quantitative addition of rare earth elements, which increases the production cost.

[0006] Chinese invention patent publication number "CN 114378480B" entitled "High Heat Input Submerged Arc Welding Wire Steel Rod and its Preparation Method, High Heat Input Submerged Arc Welding Wire, High Heat Input Welding Method" discloses a high heat input welding wire steel rod with excellent plasticity and toughness by controlling the formation of magnesium inclusions in the welding wire steel rod through composition design and smelting control. It also achieves high heat input submerged arc welding with a single-pass penetration thickness >40mm and a weld metal with good mechanical properties by using magnesium-containing flux. However, the welding wire steel composition design in this patent technology is complex, requiring the addition of magnesium alloy cored wire to control the magnesium inclusion content, thus increasing the difficulty and cost of welding wire steel smelting and rolling. Furthermore, the patent disclosure provides limited information on key flux technologies for high heat input submerged arc welding applications. Furthermore, for most bridge structure manufacturing, the application of 300kJ / cm heat input welding for plates thicker than 40mm is relatively rare. The design margin of this patented technology is too high, and its application will inevitably significantly increase welding production costs.

[0007] Chinese invention patent publication number "CN 1200791C" entitled "High Heat Input Submerged Arc Welding Joint, Method for Manufacturing the Joint, and Welding Wire and Flux Used" discloses a welding wire containing 0.03-0.15% C, 0.10-1.0% Si, 0.70-2.50% Mn, 0.003-0.03% Ti, and ≤0.005% N. It achieves a weld metal with a grain boundary ferrite area of ​​<15% under a heat input of 150 kJ / cm. Simultaneously, under a heat input of 150 kJ / cm, a weld metal containing one or more of the following components—0.10-0.50% Mo, 0.01-0.20% Nb, and 0.05-1.00% Ni—with a ratio of 0.6 ≤ B / N ≤ 1.2, also achieves a weld metal with a grain boundary ferrite area of ​​<10%. The implementation of this patented technology is complex and difficult. In the example, only the impact energy of the weld metal at 0℃ and -20℃ is given for 490MPa grade steel plates. Moreover, most of the test values ​​are close to the lower limit of the ship plate steel specification, and the toughness margin is small. It is not suitable for high heat input welding of E grade bridge structural steel. Summary of the Invention

[0008] To address the problems and shortcomings of existing technologies, the purpose of this invention is to provide a welding consumable for high heat input submerged arc welding of bridge steel, its preparation method, and its application. Specifically, it includes a solid submerged arc welding wire and a matching sintered submerged arc welding flux. The submerged arc welding wire, combined with the flux, can be used for submerged arc welding of bridge steel with a maximum heat input of 100 kJ / cm. For two types of bridge steel, Q370qE and Q420qE, using the aforementioned submerged arc welding wire and the aforementioned flux for 50–100 kJ / cm heat input submerged arc welding, the weld metal exhibits a tensile strength of 542–594 MPa, a yield strength of 408–476 MPa, a yield-to-tensile ratio of 0.75–0.80, an elongation of 20–24.5%, and an impact energy of 115–165 J at -40℃. The submerged arc welding wire and the aforementioned flux have simple chemical compositions, are easy to prepare, and produce weld metals with excellent mechanical properties.

[0009] To achieve the above-mentioned objectives, the present invention employs the following welding material technical solution.

[0010] A welding material for high heat input submerged arc welding of bridge steel includes a solid submerged arc welding wire and a matching sintered submerged arc welding flux. The chemical composition of the welding wire steel used to prepare the submerged arc welding wire, by mass percentage, includes: C 0.05-0.1%, Si 0.05-0.1%, Mn 1.3-1.5%, Ni 1.2-1.4%, Nb 0.03-0.05%, Cr 0.1-0.16%, Mo 0.1-0.3%, Ti 0.05-0.13%, Al 0.002-0.01%, B 0.005-0.008%, P≤0.01%, S≤0.005%, N≤0.005%, with the balance being Fe and unavoidable impurities.

[0011] Meanwhile, the submerged arc welding flux used with the submerged arc welding wire comprises, by mass percentage: CaO ≤ 5%, CaF2 20–24%, MgO 24–32%, Al2O3 14–20%, SiO2 6–11%, TiO2 10–18%, B2O3 0.6–1.5%, BaO ≤ 5%, and MnO 1.5–2.5%.

[0012] The functions and mechanisms of each component in the above-mentioned submerged arc welding wire technical solution are explained as follows:

[0013] Carbon (C) is a fundamental element for improving the strength of weld metal. Increasing the C content expands the austenitic region of the weld metal, increases hardenability, and enhances strength and hardness. However, excessive C reduces the weld metal's ductility and toughness and increases its susceptibility to cold cracking. Using a C content of 0.05–0.1% achieves a balance between appropriate weld metal strength and reduced hardenability and cold cracking susceptibility, resulting in good low-temperature toughness.

[0014] Si is an important element for removing oxygen during welding metallurgy. Increasing the Si content leads to a corresponding increase in grain boundary ferrite and side strip ferrite in the weld metal, resulting in a decrease in the low-temperature toughness and elongation of the weld metal. Especially under high heat input welding conditions, Si can cause the formation of coarse MA islands, severely affecting the low-temperature toughness of the weld heat-affected zone. Therefore, the Si content should be controlled between 0.05% and 0.1%.

[0015] Manganese (Mn) is an important element for oxygen and sulfur removal in welding metallurgy. Mn can effectively improve the strength of weld metal and reduce the susceptibility to hot cracking through sulfur removal. However, when the Mn content is too high, it easily undergoes conjugate segregation with elements such as phosphorus (P) and sulfur (S), significantly reducing the low-temperature toughness of the weld metal. Furthermore, due to the relatively high element loss in the weld pool caused by large heat inputs, the Mn content is controlled between 1.3% and 1.5%.

[0016] Ni has the effects of toughening the ferrite matrix and solid solution strengthening. Adding Ni can simultaneously improve the strength and low-temperature toughness of the weld metal. However, excessive Ni content will increase the difficulty of drawing the welding wire and reduce the resistance of the weld metal to hot cracking. In view of the low-temperature toughness requirements of the weld metal of Grade E bridge steel, the element loss during the high heat input submerged arc welding process is fully considered, and the Ni content is controlled at 1.2% to 1.4%.

[0017] Nitrogen (Nb) is a microalloying element that primarily pins austenite grain boundaries by forming high-temperature stable NbC and NbN dispersed particles, thereby inhibiting austenite grain growth and providing a grain refinement strengthening effect on the weld. This can improve the low-temperature toughness of the weld metal. However, excessively high Nb content can lead to the precipitation of brittle phases in welds with high heat input. Therefore, the Nb content is controlled at 0.03–0.05%.

[0018] Cr is a ferrite-forming element. Adding trace amounts of Cr can simultaneously improve the strength and low-temperature toughness of weld metal. However, excessive Cr will significantly increase the ductile-brittle transition temperature of weld metal. Therefore, the Cr content should be controlled at 0.1-0.16%.

[0019] Mo is also a ferrite-forming element, which can lower the austenite transformation temperature during weld metal cooling, inhibit the formation of grain boundary ferrite, promote the transformation of acicular ferrite, improve the creep resistance of the ferrite phase, and enhance the resistance to temper brittleness and low-temperature toughness of the weld metal. Therefore, the Mo content is controlled at 0.1–0.3%.

[0020] During welding metallurgy, Ti can form dispersed oxides and nitrides, which can effectively inhibit austenite growth and promote acicular ferrite nucleation, thereby enhancing the low-temperature toughness of the weld metal. To obtain weld metal with good low-temperature toughness, and considering the Ti burn-off during high heat input submerged arc welding, the Ti content is controlled at 0.05–0.13%.

[0021] Al has a strong affinity for oxygen, and the small-sized Al2O3 formed helps in the nucleation of acicular ferrite. When the Al content is too high, the Al2O3 formed is larger and affects the beneficial effects of Ti, reducing the low-temperature toughness of the weld. Therefore, the Al content should be controlled at 0.002-0.01%.

[0022] Boron (B) exhibits grain boundary segregation properties, reducing the austenite interface energy and inhibiting the formation of brittle grain boundary structures. Simultaneously, B combines with nitrogen (N) to form dispersed BN particles, promoting intragranular ferrite formation and refining the weld microstructure. Therefore, adding trace amounts of B helps improve the low-temperature toughness of the weld metal. However, excessive B can affect the ductility of the weld metal; therefore, the B content is controlled at 0.005–0.008%.

[0023] P, S, and N are impurity elements in welding wire steel. When their content is high, the low-temperature toughness of the weld metal will decrease significantly. Among them, the effects of P and S are particularly prominent. During welding, the upper limit of impurity elements is usually controlled, specifically requiring P ≤ 0.01%, S ≤ 0.005%, and N ≤ 0.005%.

[0024] The functions and mechanisms of each component in the above-mentioned submerged arc welding flux technical solution are explained as follows:

[0025] In welding fluxes, CaO primarily functions to form slag and increase basicity. It also enhances the flux's resistance to high currents and improves slag removal, while reducing the content of sulfur (S) and phosphorus (P) impurities, thus improving the mechanical properties of the weld. However, excessive CaO content can lead to an excessively high melting point, resulting in poor weld formation and increased susceptibility to moisture absorption.

[0026] In welding fluxes, CaF2 primarily functions to form slag, remove oxygen and hydrogen, and also lower the flux melting point, increase flux basicity, enhance slag fluidity, and inhibit porosity. However, excessively high CaF2 content can lead to decreased arc stability and poor weld formation.

[0027] In welding fluxes, MgO primarily functions as a slag-forming agent and increases basicity. It also raises the flux melting point, reduces diffusible hydrogen, and improves the impact toughness of the weld metal. However, excessive MgO content can lead to an excessively high flux melting point, resulting in decreased slag removal and poorer weld formation.

[0028] Al2O3 mainly functions as a slag-forming agent and viscosity adjuster in fluxes. It also increases the flux melting point, resulting in a smoother weld surface and reduced undercut. However, excessively high Al2O3 content can lead to increased weld reinforcement, more porosity, poor weld formation, and difficulty in slag removal.

[0029] In flux, SiO2 primarily functions as a slag-forming agent and a reducer for basicity. It also adjusts the melting point and viscosity of the slag, thereby improving slag removal performance. When the SiO2 content is low, a higher CaF2 content can reduce porosity. However, excessively high SiO2 content results in high slag viscosity, leading to poor weld formation and severe metallite loss. It also significantly reduces flux basicity, thus decreasing the low-temperature impact toughness of the weld.

[0030] In welding flux, TiO2 primarily functions to remove oxygen and form slag in the weld. During welding, it reacts with oxygen in the weld and introduces Ti into the weld, thereby improving weld quality and welding process performance. Furthermore, Ti can combine with boron (B) to refine the weld grains, increasing weld strength and toughness. However, excessively high Ti content can decrease flux basicity, conversely reducing weld toughness.

[0031] In flux, B2O3 primarily functions to regulate weld composition and properties. By introducing a portion of B into the weld and combining with Ti to form TiN / BN, it can refine weld grains and enhance weld toughness. However, excessively high B content leads to excessive B transition, which in turn reduces the mechanical properties of the weld.

[0032] BaO mainly plays a role in stabilizing the electric arc and removing oxygen and hydrogen in flux, and can also improve slag removal performance. However, when the content is too high, it will reduce the stability of the electric arc.

[0033] In welding flux, MnO primarily functions as a slag-forming agent and removes oxygen and sulfur. When Mn transitions into the weld, it can also improve weld strength and impact toughness. Furthermore, MnO helps improve arc stability and welding speed. However, excessively high content leads to poor weld formation and a decrease in overall mechanical properties.

[0034] Furthermore, preferably, the chemical composition of the welding wire steel, by mass percentage, further includes: 9≤30C+5Mn+6Cr+6Mo+2Ni≤13, 45≤300C+10Si+15Mn+5Ni+15Cr+20Mo+1500B≤66; simultaneously, the volume content of Ti inclusions in the welding wire steel is 3.56×10⁻⁶. 5 ~4.45×10 5 pcs / mm 3 The welding wire steel has a tensile strength of 535–586 MPa, a yield strength of 392–463 MPa, a reduction of area of ​​83–88%, and a yield strength ratio of 0.73–0.79.

[0035] Preferably, the method for preparing the submerged arc welding wire provided by the present invention includes smelting and rolling of welding wire steel and drawing of welding wire.

[0036] (1) The welding wire steel smelting and rolling process includes the following steps in sequence:

[0037] ① KR method hot metal desulfurization pretreatment: Before pretreatment, the hot metal temperature is controlled at ≥1400℃, and the chemical composition of the hot metal by mass percentage includes: C 3.4~4.0%, Si 0.3~0.5%, S≤0.05%, P≤0.08%, with the remainder being Fe and other unavoidable impurities; after pretreatment, the hot metal temperature is controlled at ≥1320℃, and the S content in the hot metal is ≤0.003%;

[0038] ② Converter smelting: The tapping temperature of the converter is ≥1600℃, and calcium aluminate synthetic slag is used for slag making. The main components of the synthetic slag by mass percentage are: 40%≤CaO≤50%, 30%≤Al2O3≤40%, 5%≤CaF2≤15%, and the rest are unavoidable impurities.

[0039] ③ Refining: It includes two steps: LF refining and RH vacuum refining. The LF refining time is 40-45 min, the argon blowing time is 20-25 min, and the flow rate is 250-280 L / min. The vacuum degree during RH vacuum refining is ≤3 kPa, the holding time before breaking the vacuum is 10-15 min, and the oxygen content is ≥0.004%.

[0040] ④ Continuous casting: The superheat of molten steel during casting is 20-30℃, and the billet casting speed is constant at 2.0-2.4m / min;

[0041] ⑤ Temperature-controlled rolling: After heating the steel billet obtained from continuous casting to 1050-1100℃, it is descaled by high-pressure water with a pressure ≥20MPa, and then rolling begins at 950-1000℃. The finishing rolling start temperature is controlled to ≤870℃ and the final rolling diameter is 6.3-6.5mm.

[0042] ⑥ Controlled cooling: The Stellmore controlled cooling process is used to keep the temperature of the temperature-controlled rolled welding wire rods warm and cool them slowly. The speed of the cooling line roller is 0.14m / s, the cooling rate is ≤0.5℃ / s, and the wire drawing temperature is 870~900℃.

[0043] (2) The drawing of the welding wire is carried out by drawing the welding wire steel as raw material multiple times to form the submerged arc welding wire used for high heat input submerged arc welding of bridge steel. Specifically, when the target welding wire diameter is 5.0 mm, the welding wire steel needs to be drawn 4 times with a compression rate of 0.05 to 0.1 and a speed of 0.8 to 1.1 m / s to finally obtain the diameter of the submerged arc welding wire of 4.9 to 5.1 mm; when the target welding wire diameter is 4.0 mm, the welding wire steel needs to be drawn 6 times with a compression rate of 0.1 to 0.12 and a speed of 0.8 to 2.0 m / s to finally obtain the diameter of the submerged arc welding wire of 3.9 to 4.1 mm.

[0044] The submerged arc welding flux used with the submerged arc welding wire is prepared by the following steps in sequence:

[0045] ①Ingredients: Wollastonite, fluorite, calcined magnesia, bauxite, quartz, rutile titanium dioxide, borax, barite, and manganese ore are used as raw materials. The raw materials are selected, crushed, ground, weighed, and batched in sequence according to the components of the submerged arc welding flux to obtain flux raw material powder.

[0046] ② Stirring: First, dry stir the prepared flux raw material powder for 20-30 minutes using a dry stirrer to obtain a uniformly stirred dry flux powder; then, transfer the dry flux powder into a wet stirrer and add 20-22% water glass by weight of the total dry flux powder, followed by 30-40 minutes of wet stirring to obtain a uniformly stirred, thick paste-like wet flux material.

[0047] ③ Granulation and drying: The wet flux material is fed into a granulator for granulation, and then the prepared wet flux granules are sent into a drying oven for drying at 200-250℃ for 30-45 minutes to obtain dry flux granules;

[0048] ④ Screening and sintering: The dried flux particles after drying and dehydration are vibrated and screened through a vibrating screen to control the particle size. Then, the dry flux particles are sintered in a furnace at 850-900℃ for 40 minutes. After cooling and screening again, the submerged arc flux is obtained.

[0049] Preferably, the submerged arc welding flux has a pH of 2.2 to 2.7 and a particle size of 10 to 30 mesh.

[0050] Preferably, the submerged arc welding wire, when used with the submerged arc welding flux, is suitable for submerged arc welding of two types of bridge steel, Q370qE and Q420qE, with a heat input of 50-100 kJ / cm. The weld metal has a tensile strength of 542-594 MPa, a yield strength of 408-476 MPa, a yield ratio of 0.75-0.80, an elongation of 20-24.5%, and an impact energy of 115-165 J at -40℃. In this case, the plate thickness that can be welded through in a single pass is 15-25 mm.

[0051] Preferably, before submerged arc welding with a heat input of 50-100 kJ / cm, the submerged arc welding flux needs to be dried at 350-400°C for 2-3 hours.

[0052] Compared with the prior art, the main significant advantages and beneficial effects of the present invention are:

[0053] (1) This invention, through a reasonable design of the welding wire alloy composition, generates a large number of Ti-containing inclusions inside the welding wire steel. This improves the high-temperature stability of the weld metal, hinders austenite growth, promotes acicular ferrite nucleation, and inhibits the formation of brittle phases during high heat input submerged arc welding. Simultaneously, through the reasonable design of the flux composition, the arc exhibits good stability, the slag exhibits good fluidity, the flux exhibits good slag removal properties, and the weld exhibits good formability. Overall, using the submerged arc welding wire and the submerged arc flux described in this invention for high heat input submerged arc welding results in good welding processability and stable joint mechanical properties.

[0054] (2) For two types of bridge steel, Q370qE and Q420qE, using the submerged arc welding wire described in this invention and the submerged arc welding flux for 50-100kJ / cm heat input double-wire submerged arc welding, weld metal with tensile strength of 542-594MPa, yield strength of 408-476MPa, yield ratio of 0.75-0.80, elongation of 20-24.5%, and impact energy of 115-165J at -40℃ can be obtained. The mechanical properties of the weld metal meet the requirements of the "Railway Steel Bridge Manufacturing Specification Q / CR9211-2015". Among them, when welding with a heat input of 100kJ / cm, the plate thickness that can be penetrated in a single pass is 20-25mm. For 30mm thick bridge steel, only one pass is required on each side. The welding deposition speed is fast and the welding efficiency is high.

[0055] (3) The submerged arc welding wire of the present invention for high heat input submerged arc welding of bridge steel has a simple composition system. The smelting, rolling and cooling processes of the welding wire steel used to prepare the submerged arc welding wire are simple and the production cost is low. The wire drawing preparation method is simple, easy to implement and has a low wire breakage rate.

[0056] (4) The submerged arc welding flux of the present invention for high heat input submerged arc welding of bridge steel is a sintered flux with simple composition, appropriate acidity and alkalinity and particle size, good moisture resistance, good slag removal properties and good low-temperature toughness of weld metal during high heat input submerged arc welding; the preparation process of the submerged arc welding flux is simple and easy to implement, with low production cost and convenient use, and can be widely used for high heat input submerged arc welding of bridge steel. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the welding bevel.

[0058] Figure 2 The macroscopic part of the submerged arc welding head has a heat input of 52kJ / cm.

[0059] Figure 3 Macroscopic view of submerged arc welding joint with a heat input of 100 kJ / cm.

[0060] Figure 4 The microstructure of submerged arc weld with a heat input of 52 kJ / cm is shown.

[0061] Figure 5 Microstructure of submerged arc weld with a heat input of 100 kJ / cm.

[0062] Figure 6 Microscopic morphology of the fracture surface at the center of a submerged arc weld with a heat input of 52 kJ / cm.

[0063] Figure 7 Microscopic morphology of the fracture surface at the center of a submerged arc weld with a heat input of 100 kJ / cm. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, the scope of protection of this invention is not limited to the following embodiments. All technical solutions obtained by equivalent transformations or other means are within the scope of protection of this invention.

[0065] This invention provides a welding material for high heat input submerged arc welding of bridge steel, comprising a solid submerged arc welding wire and a matching sintered submerged arc welding flux. The preparation method of the submerged arc welding wire includes, in sequence, the smelting and rolling of welding wire steel and the drawing of welding wire. The chemical composition of the welding wire steel used to prepare the submerged arc welding wire, by mass percentage, includes: C 0.05-0.1%, Si 0.05-0.1%, Mn 1.3-1.5%, Ni 1.2-1.4%, Nb 0.03-0.05%, Cr 0.1-0.16%, Mo 0.1-0.3%, Ti 0.05-0.13%, Al 0.002-0.01%, B 0.005-0.008%, P≤0.01%, S≤0.005%, N≤0.005%, with the balance being Fe and unavoidable impurities.

[0066] Taking into account the strength and toughness requirements of bridge steel weld metal and the burn-off problem of welding elements under high heat input, the chemical composition and content of the welding wire steel are rationally designed, and the content of impurity elements is strictly controlled to ensure that the submerged arc welding wire prepared from the welding wire steel has a low carbon equivalent and crack sensitivity index. Therefore, the chemical composition of the welding wire steel, by mass percentage, must also meet the following requirements: 9≤30C+5Mn+6Cr+6Mo+2Ni≤13, 45≤300C+10Si+15Mn+5Ni+15Cr+20Mo+1500B≤66.

[0067] To obtain the welding wire steel, the present invention provides a method for preparing submerged arc welding wire, wherein the smelting and rolling scheme for the welding wire steel includes six steps in sequence: KR method hot metal desulfurization pretreatment, converter smelting, refining, continuous casting, temperature-controlled rolling, and controlled cooling. The specific implementation methods for each step are as follows:

[0068] ① KR method hot metal desulfurization pretreatment: Before pretreatment, the hot metal temperature is controlled at ≥1400℃, and the chemical composition of the hot metal by mass percentage includes: C 3.4~4.0%, Si 0.3~0.5%, S≤0.05%, P≤0.08%, with the remainder being Fe and other unavoidable impurities; after pretreatment, the hot metal temperature is controlled at ≥1320℃, and the S content in the hot metal is ≤0.003%;

[0069] ② Converter smelting: The tapping temperature of the converter is ≥1600℃, and calcium aluminate synthetic slag is used for slag making. The main components of the synthetic slag by mass percentage are: 40%≤CaO≤50%, 30%≤Al2O3≤40%, 5%≤CaF2≤15%, and the rest are unavoidable impurities.

[0070] ③ Refining: It includes two steps: LF refining and RH vacuum refining. The LF refining time is 40-45 min, the argon blowing time is 20-25 min, and the flow rate is 250-280 L / min. The vacuum degree during RH vacuum refining is ≤3 kPa, the holding time before breaking the vacuum is 10-15 min, and the oxygen content is ≥0.004%.

[0071] ④ Continuous casting: The superheat of molten steel during casting is 20-30℃, and the billet casting speed is constant at 2.0-2.4m / min;

[0072] ⑤ Temperature-controlled rolling: After heating the steel billet obtained from continuous casting to 1050-1100℃, it is descaled by high-pressure water with a pressure ≥20MPa, and then rolling begins at 950-1000℃. The finishing rolling start temperature is controlled to ≤870℃ and the final rolling diameter is 6.3-6.5mm.

[0073] ⑥ Controlled cooling: The Stellmore controlled cooling process is used to keep the temperature of the temperature-controlled rolled welding wire rods warm and cool them slowly. The speed of the cooling line roller is 0.14m / s, the cooling rate is ≤0.5℃ / s, and the wire drawing temperature is 870~900℃.

[0074] The above-described method for preparing welding wire steel effectively controls the composition and content of molten iron, as well as the residual amount of impurity elements, resulting in a weld wire steel volume content of 3.56 × 10⁻⁶. 5 ~4.45×10 5 pcs / mm 3 The Ti-containing inclusions hinder austenite growth and suppress the formation of brittle phases in the weld metal. Simultaneously, the Ti-containing inclusions and boron compounds act as nucleation sites, promoting the nucleation of acicular ferrite during weld metal cooling, thereby improving the low-temperature toughness of the weld metal. Furthermore, controlled rolling and cooling of the welding wire steel shortens the pearlite transformation time, reduces the formation of network cementite, and improves the microstructure uniformity of the welding wire steel, facilitating subsequent wire drawing. Finally, the welding wire steel with a tensile strength of 535–586 MPa, a yield strength of 392–463 MPa, a reduction of area of ​​83–88%, and a yield strength ratio of 0.73–0.79 is produced.

[0075] In the method for preparing the solid submerged arc welding wire, during the wire drawing process, the welding wire steel is used as raw material, and through multiple drawing operations, the submerged arc welding wire for high heat input submerged arc welding of bridge steel is formed. Specifically, when the target welding wire diameter is 5.0 mm, the welding wire steel needs to be drawn four times with a compression rate of 0.05–0.1 and a speed of 0.8–1.1 m / s, ultimately obtaining a submerged arc welding wire with a diameter of 4.9–5.1 mm; when the target welding wire diameter is 4.0 mm, the welding wire steel needs to be drawn six times with a compression rate of 0.1–0.12 and a speed of 0.8–2.0 m / s, ultimately obtaining a submerged arc welding wire with a diameter of 3.9–4.1 mm. The submerged arc welding wire made using this welding wire steel is suitable for submerged arc welding of bridge steel with a heat input of 50–100 kJ / cm.

[0076] For submerged arc welding, the flux and its compatibility with the welding wire significantly affect weld formation and joint mechanical properties, especially low-temperature impact toughness. In bridge steel structure manufacturing, the low-temperature impact test temperature of the welded joint is the same as that of the bridge steel base material itself; for example, for Grade E bridge steel, both the base material and the welded joint have an impact test temperature of -40℃. However, in the shipbuilding steel structure manufacturing industry, the impact test temperature of the welded joint is higher than that of the ship plate steel base material itself. For example, for Grade E ship plate steel, the impact test temperature of the base material is -40℃, while the impact test temperature of the welded joint is -20℃. This means that the impact toughness requirement for ship plate steel welded joints is lower than that of the base material itself. Therefore, in general, the mechanical property requirements for bridge steel welded joints are higher than those for ship plate steel. Accordingly, the submerged arc welding wire and flux used for ship plate steel are not suitable for bridge steel of the same grade.

[0077] To achieve the aforementioned objectives, this invention provides a technical solution for submerged arc welding (SAW) flux used in high-heat-input submerged arc welding of bridge steel. Through a rationally designed flux formulation, the SAW flux exhibits excellent slag removal and O, S, and P impurity removal characteristics during high-heat-input SAW, resulting in good weld formation and excellent mechanical properties in the weld metal. Specifically, the SAW flux comprises the following components by mass percentage: CaO ≤ 5%, CaF2 20–24%, MgO 24–32%, Al2O3 14–20%, SiO2 6–11%, TiO2 10–18%, B2O3 0.6–1.5%, BaO ≤ 5%, and MnO 1.5–2.5%.

[0078] The submerged arc welding flux for high heat input submerged arc welding of bridge steel described in this invention is a sintered flux. To obtain the submerged arc welding flux, this invention also provides a preparation method for the submerged arc welding flux, which sequentially includes the following steps: batching, stirring, granulation, drying, screening, and sintering. The specific technical implementation method is as follows:

[0079] ①Ingredients: Wollastonite, fluorite, calcined magnesia, bauxite, quartz, rutile titanium dioxide, borax, barite, and manganese ore are used as raw materials. The raw materials are selected, crushed, ground, weighed, and batched in sequence according to the components of the submerged arc welding flux to obtain flux raw material powder.

[0080] ② Stirring: First, dry stir the prepared flux raw material powder for 20-30 minutes using a dry stirrer to obtain a uniformly stirred dry flux powder; then, transfer the dry flux powder into a wet stirrer and add 20-22% water glass by weight of the total dry flux powder, followed by 30-40 minutes of wet stirring to obtain a uniformly stirred, thick paste-like wet flux material.

[0081] ③ Granulation and drying: The wet flux material is fed into a granulator for granulation, and then the prepared wet flux granules are sent into a drying oven for drying at 200-250℃ for 30-45 minutes to obtain dry flux granules;

[0082] ④ Screening and sintering: The dried flux particles after drying and dehydration are vibrated and screened through a vibrating screen to control the particle size. Then, the dry flux particles are sintered in a furnace at 850-900℃ for 40 minutes. After cooling and screening again, the submerged arc flux is obtained.

[0083] Acidity / alkalinity is a crucial indicator of flux properties, affecting slag removal and weld mechanical properties. Fluxes with a pH below 1.0 are considered acidic, while those above 1.0 are considered alkaline. Lower pH values ​​facilitate slag removal but result in poorer weld mechanical properties, particularly low-temperature impact toughness. Increasing the pH improves weld mechanical properties but hinders slag removal. Another important flux indicator is particle size. Excessively large particles reduce fluidity, slow melting, and increase the risk of porosity and cracks, leading to reduced weld strength. Conversely, excessively small particles result in significant welding spatter and uneven weld formation. For high-heat-input submerged arc welding applications on bridge steel, the aforementioned component design and preparation method yielded a submerged arc flux with a pH of 2.2–2.7 and a particle size of 10–30 mesh.

[0084] Regarding the submerged arc welding wire used for high heat input submerged arc welding of bridge steel, the following is based on serial number 1. # ~3 # Three embodiments and serial number 4 # ~6 # Three comparative examples (at least one component in each comparative example is not within the scope of this invention, examining the influence of the components on the mechanical properties of the welding wire steel, the welding process performance of the submerged arc welding wire, and the mechanical properties of the weld metal) further illustrate the implementation effect of the submerged arc welding wire technology. Example 1 is obtained using the described smelting and rolling method. # ~3 #Comparative Example 4 # ~6 # The welding wire steels were tested for chemical composition and mechanical properties, and the results are shown in Tables 1 and 2. The carbon equivalent (CEV) of the welding wire steels in the three examples were 0.42%, 0.42%, and 0.41%, respectively, and the crack sensitivity index (Pcm) was 0.18%, 0.20%, and 0.17%, respectively. The carbon equivalent (CEV) of the welding wire steels in the three comparative examples were 0.35%, 0.43%, and 0.47%, respectively, and the crack sensitivity index (Pcm) was 0.16%, 0.24%, and 0.22%, respectively.

[0085] Furthermore, testing was conducted in Example 1. # ~3 # The welding wire steel also contained a volume content of 3.56 × 10⁻⁶. 5 ~4.45×10 5 pcs / mm 3 Ti inclusions.

[0086] Table 1. Welding wire steel composition (wt%, balance Fe) for the examples and comparative examples

[0087]

[0088] Table 2 Mechanical properties of welding wire steel in the examples and comparative examples

[0089]

[0090] As can be seen from Tables 1 and 2, the mechanical properties of the welding wire steel changed to varying degrees after the composition of the welding wire steel was adjusted. (Comparative Example 4) # ~6 # At least one component in the welding wire steel is outside the scope of this invention. Accordingly, the carbon equivalent of the three comparative welding wire steels varies greatly, and comparative example 5... # and 6 # The crack sensitivity index of the welding wire steel was greater than 0.2%. Meanwhile, the mechanical properties of the three comparative welding wire steels also changed significantly, with all exhibiting low reduction of area, particularly comparative example 4. # The mechanical properties of the welding wire steel are close to the lower limit of the specification, with insufficient allowance; Comparative Example 5 # and 6 # The increased carbon equivalent of welding wire steel provides sufficient margin for mechanical properties, but reduces weldability and reduces the yield strength ratio to near the upper limit of 0.85.

[0091] Table 3. Welding wire drawing process of the examples and comparative examples (target welding wire diameter 4.0 mm)

[0092]

[0093] Table 4. Welding wire drawing process of the examples and comparative examples (target welding wire diameter 5.0 mm)

[0094]

[0095]

[0096] Using the wire drawing process parameters shown in Tables 3 and 4, Example 1 was tested. # ~3 # Comparative Example 4 # ~6 # Submerged arc welding wires with target diameters of 4.0 mm and 5.0 mm can be obtained by drawing welding wire steel, as shown in Example 11 in the table. # ~31 # and 12 # ~32 # The welding wire steel used corresponds to Example 1. # ~3 # Comparative Example 41 # ~61 # and 42 # ~62 # The ratio of welding wire steel used should be 4. # ~6 # .

[0097] Regarding the submerged arc welding flux used for high heat input submerged arc welding of bridge steel, three examples (numbered 7) were prepared using wollastonite, fluorite, calcined magnesia, bauxite, quartz, rutile titanium dioxide, borax, barite, and manganese ore as raw materials and the aforementioned submerged arc welding flux preparation method. # ~9 # ) and 3 comparative examples (serial number 10) # ~12 # The dry flux powder (with corresponding components shown in Table 5) was used to investigate the effects of acidic oxides, basic oxides, and fluorides on the welding process performance and mechanical properties of submerged arc welding flux, in order to further illustrate the implementation effect of the submerged arc welding flux technology.

[0098] Table 5. Flux composition of the examples and comparative examples (unit: kg)

[0099]

[0100] After the dry flux powder with the components shown in Table 5 is stirred evenly, in Example 7 # ~9 # Comparative Example 10 # ~12 #20 kg, 22 kg, 20 kg, 23 kg, 22 kg, and 26 kg of sodium silicate (modulus 2.4) were added to the dry flux powder, respectively, and wet-stirred for 35 min. Next, the thick paste-like wet flux material was granulated using a granulator, and then dried at 250°C for 40 min to obtain dry flux granules. After vibration screening and sintering in an 870°C furnace for 40 min, the final product obtained had a composition corresponding to Example 7. # ~9 # Comparative Example 10 # ~12 # The submerged arc welding flux has a particle size of 10-30 mesh. Accordingly, Example 7... # ~9 # The pH values ​​of the fluxes were 2.3, 2.7, and 2.2, respectively, while those of Comparative Example 10 were... # ~12 # The pH values ​​of the fluxes were 2.7, 3.3, and 2.9, respectively.

[0101] For 30mm thick Q370qE and Q420qE bridge steels, using the submerged arc welding wire of the present invention with a diameter of 5.0mm and the submerged arc welding flux of the present invention (see Table 6 for the combination), a heat input of 50-100kJ / cm was used for twin-wire submerged arc welding (the welding groove adopts the standard groove of the deposited metal test, see Table 6 for the standard groove). Figure 1 The corresponding welding process parameters are shown in Table 7. Specifically, the front wire is connected to a DC power supply with a welding current of 750–1040 A and an arc voltage of 28–32 V; the rear wire is connected to an AC power supply with a welding current of 670–880 A and an arc voltage of 35–43 V; and the welding speed is 42–52 cm / min. Furthermore, the submerged arc welding flux was dried at 350–400 °C for 2–3 hours before welding. During welding, the welding process performance of the submerged arc welding wire and the submerged arc welding flux was tested; after welding, the mechanical properties of the weld metal were tested, and the results are shown in Table 8.

[0102] Table 6 Combinations of Submerged Arc Welding Wire and Flux

[0103] Combination number Test plate material grade Welding wire serial number Flux serial number C1 Q370qE <![CDATA[12 # (5mm in diameter) <![CDATA[7 # ]]> C2 Q420qE <![CDATA[22 # (5mm in diameter) <![CDATA[8 # ]]> C3 Q420qE <![CDATA[32 # (5mm in diameter) <![CDATA[9 # ]]> C4 Q370qE <![CDATA[12 # (5mm in diameter) <![CDATA[7 # ]]> C5 Q420qE <![CDATA[32 # (5mm in diameter) <![CDATA[9 # ]]> C6 Q370qE <![CDATA[42 # (5mm in diameter) <![CDATA[7 # ]]> C7 Q420qE <![CDATA[52 # (5mm in diameter) <![CDATA[8 # ]]> C8 Q420qE <![CDATA[62 # (5mm in diameter) <![CDATA[9 # ]]> C9 Q370qE <![CDATA[12 # (5mm in diameter) <![CDATA[10 # ]]> C10 Q420qE <![CDATA[62 # (5mm in diameter) <![CDATA[12 # ]]> C11 Q370qE <![CDATA[42 # (5mm in diameter) <![CDATA[11 # ]]>

[0104] Table 7. Process parameters for twin-wire submerged arc welding

[0105]

[0106] Table 8. Test results of welding process performance and mechanical properties of weld metal

[0107]

[0108]

[0109] According to the test results in Table 8, compared with combinations C1 to C5, the arc stability of combinations C6 to C8 is reduced because the steel composition of the comparative submerged arc welding wire used in these combinations is not within the scope of this invention. Among them, the weld metal strength of combination C6 is low and it is only suitable for Q370qE bridge steel. The weld metal strength of combinations C7 and C8 is improved, but the yield strength ratio exceeds 0.85 and the impact energy at -40℃ is lower than the specification requirements.

[0110] Compared to combinations C1 to C5, because the composition of the comparative submerged arc welding flux used in combinations C9 to C11 is not within the scope of this invention, the impact energy of the weld metal at -40°C is lower than the standard requirements, and the flux slag removal and arc stability are both reduced. When the composition of the comparative submerged arc welding wire steel used in combinations C10 and C11 is not within the scope of this invention, the weld metal strength is either too high or insufficient, and the yield strength ratio is greater than 0.85. In general, because the composition of the comparative submerged arc welding wire steel or the comparative submerged arc welding flux used in combinations C6 to C11 is not within the scope of this invention, the mechanical properties of the weld metal in combinations C6 to C11 all fail to meet the requirements for bridge steel structure manufacturing, and the welding process performance (mainly arc stability and flux slag removal) also decreases.

[0111] In summary, under heat input conditions of 50–100 kJ / cm, using the submerged arc welding wire and flux described in this invention for high heat input submerged arc welding of Q370qE and Q420qE bridge steels, the welding arc stability and flux slag removal properties are good. Weld metals with tensile strength of 542–594 MPa, yield strength of 408–476 MPa, yield-to-tensile ratio of 0.75–0.80, elongation of 20–24.5%, and impact energy of 115–165 J at -40℃ can be obtained. The mechanical properties of the weld metal meet the requirements of the "Railway Steel Bridge Manufacturing Specification Q / CR9211—2015".

[0112] Furthermore, this invention also applies to 30mm thick Q370qE bridge steel, using the above-mentioned 1 # Submerged arc welding wire and the above 7 # Submerged arc welding was performed using a dual-wire submerged arc welding process with heat inputs of 52 kJ / cm and 100 kJ / cm under V-groove and X-groove conditions, respectively. Macroscopic photographs of the welded joints are shown below. Figure 2 and Figure 3 As shown, the corresponding weld center microstructure is as follows: Figure 4 and Figure 5 As shown, the corresponding weld center fracture morphology is as follows: Figure 6 and Figure 7 As shown.

[0113] like Figure 2 and Figure 3As shown, with a heat input of 52 kJ / cm, a single pass can penetrate a plate thickness of approximately 15 mm. Therefore, a 30 mm thick bridge steel test plate only requires two passes on the front and one pass on the back. With a heat input of 100 kJ / cm, a single pass can penetrate a plate thickness of approximately 25 mm, requiring one pass on each side of the 30 mm thick bridge steel test plate. In general, the welding deposition speed is fast and the welding efficiency is high.

[0114] from Figure 4 and Figure 5 As can be seen, under both heat input conditions, the weld microstructure consists of elongated proeutectoid ferrite, a large amount of acicular ferrite, and pearlite. Figure 6 and Figure 7 As can be seen from the table, the fracture surface at the center of the submerged arc weld joint with a heat input of 52 kJ / cm mainly consists of dimples and quasi-cleavage plateaus, without obvious, parallel cleavage steps. The cleavage plateaus on the fracture surface at the center of the submerged arc weld joint with a heat input of 100 kJ / cm are more pronounced, but dimples exist between the plateaus. Table 9 shows the impact energy at -40℃ at the weld center. It can be seen from the table that the low-temperature toughness at the weld center with a heat input of 52 kJ / cm is better than that with a heat input of 100 kJ / cm. Meanwhile, because many dimples are distributed between the cleavage plateaus on the fracture surface at the weld center with a heat input of 100 kJ / cm, the low-temperature toughness at this location is still higher than the specification requirements.

[0115] Table 9 Results of impact toughness test at weld center

[0116]

[0117] Finally, there are many other specific methods and approaches to implement this invention, and the above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several equivalents, improvements, and modifications can be made without departing from the principle of this invention, and these equivalents, improvements, and modifications should also be considered within the scope of protection of this invention.

Claims

1. Welding consumables for high heat input submerged arc welding of bridge steel, characterized in that, include: (1) Solid submerged arc welding wire; (2) The sintered submerged arc welding flux used; The chemical composition of the welding wire steel used to prepare the solid submerged arc welding wire, by mass percentage, includes: C 0.05~0.1%, Si 0.05~0.1%, Mn 1.3~1.5%, Ni 1.2~1.4%, Nb 0.03~0.05%, Cr 0.1~0.16%, Mo 0.1~0.3%, Ti 0.05~0.13%, Al 0.002~0.01%, B 0.005~0.008%, P≤0.01%, S≤0.005%, N≤0.005%, with the balance being Fe and unavoidable impurities, simultaneously satisfying: 9≤30C+5Mn+6Cr+6Mo+2Ni≤13; 45≤300C+10Si+15Mn+5Ni+15Cr+20Mo+1500B≤66; The volume content of Ti inclusions in the welding wire steel is 3.56 × 10⁻⁶. 5 ~4.45×10 5 pcs / mm 3 The welding wire steel has a tensile strength of 535~586MPa, a yield strength of 392~463MPa, a reduction of area of ​​83~88%, and a yield strength ratio of 0.73~0.

79. The submerged arc welding flux used with the submerged arc welding wire comprises, by mass percentage: CaO ≤5%, CaF2 20~24%, MgO 24~32%, Al2O3 14~20%, SiO2 6~11%, TiO2 10~18%, B2O3 0.6~1.5%, BaO ≤5%, and MnO 1.5~2.5%.

2. The method for preparing welding materials for high heat input submerged arc welding of bridge steel according to claim 1, characterized in that, (1) Preparation of the solid submerged arc welding wire: including the smelting and rolling of welding wire steel and the drawing of welding wire; The smelting and rolling of the welding wire steel includes KR method hot metal desulfurization pretreatment, converter smelting, refining, continuous casting, temperature-controlled rolling and controlled cooling processes. The welding wire drawing process involves using the welding wire steel as raw material and preparing the submerged arc welding wire for high heat input submerged arc welding of bridge steel through multiple drawing processes. (2) Preparation of the submerged arc welding flux: including batching, stirring, granulation, drying, screening and sintering.

3. The method for preparing welding materials for high heat input submerged arc welding of bridge steel according to claim 2, characterized in that, The smelting and rolling of the welding wire steel specifically includes the following processes: ① KR method hot metal desulfurization pretreatment: Before pretreatment, the hot metal temperature is controlled at ≥1400℃, and the chemical composition of the hot metal by mass percentage includes: C 3.4~4.0%, Si 0.3~0.5%, S≤0.05%, P≤0.08%, with the remainder being Fe and other unavoidable impurities; after pretreatment, the hot metal temperature is controlled at ≥1320℃, and the S content in the hot metal is ≤0.003%. ② Converter smelting: The tapping temperature of the converter is ≥1600℃, and calcium aluminate synthetic slag is used for slag making. The main components of the synthetic slag by mass percentage are: 40%≤CaO≤50%, 30%≤Al2O3≤40%, 5%≤CaF2≤15%, and the rest are unavoidable impurities. ③ Refining: This includes two steps: LF refining and RH vacuum refining. The LF refining time is 40-45 min, and the argon blowing time is 20-25 min with a flow rate of 250-280 L / min. The vacuum degree during RH vacuum refining is ≤3 kPa, the holding time before breaking the vacuum is 10-15 min, and the oxygen content is ≥0.004%. ④ Continuous casting: The superheat of molten steel during casting is 20~30℃, and the billet casting speed is constant at 2.0~2.4m / min; ⑤ Temperature-controlled rolling: After heating the steel billet obtained from continuous casting to 1050~1100℃, it is descaled by high-pressure water with a pressure ≥20MPa, and then rolling begins at 950~1000℃. The finishing rolling start temperature is controlled to ≤870℃ and the final rolling diameter is 6.3~6.5mm. ⑥ Controlled cooling: The Stellmore controlled cooling process is used to keep the temperature of the temperature-controlled rolled welding wire steel warm and slow-cool it. The speed of the cooling line roller is 0.14m / s, the cooling rate is ≤0.5℃ / s, and the wire drawing temperature is 870~900℃.

4. The method for preparing welding materials for high heat input submerged arc welding of bridge steel according to claim 2, characterized in that: When drawing the solid submerged arc welding wire, using the welding wire steel as raw material, when the target welding wire diameter is 5.0 mm, the welding wire steel needs to be drawn four times with a compression rate of 0.05~0.1 and a speed of 0.8~1.1 m / s, finally obtaining a submerged arc welding wire with a diameter of 4.9~5.1 mm; when the target welding wire diameter is 4.0 mm, the welding wire steel needs to be drawn six times with a compression rate of 0.1~0.12 and a speed of 0.8~2.0 m / s, finally obtaining a submerged arc welding wire with a diameter of 3.9~4.1 mm.

5. The method for preparing welding materials for high heat input submerged arc welding of bridge steel according to claim 2, characterized in that, The preparation method of the submerged arc welding flux used with the submerged arc welding wire specifically includes the following steps: ①Ingredients: Wollastonite, fluorite, calcined magnesia, bauxite, quartz, rutile titanium dioxide, borax, barite, and manganese ore are used as raw materials. The raw materials are selected, crushed, ground, weighed, and batched in sequence according to the components of the submerged arc welding flux to obtain flux raw material powder. ② Stirring: First, dry stir the prepared flux raw material powder for 20-30 minutes using a dry stirrer to obtain a uniformly stirred dry flux powder; then, transfer the dry flux powder into a wet stirrer and add 20-22% water glass by weight of the total dry flux powder, followed by 30-40 minutes of wet stirring to obtain a uniformly stirred, thick paste-like wet flux material. ③ Granulation and drying: The wet flux material is fed into a granulator for granulation, and then the prepared wet flux granules are sent into a drying oven for drying at 200~250℃ for 30~45 minutes to obtain dry flux granules; ④ Screening and sintering: The dried flux particles after drying and dehydration are vibrated and screened through a vibrating screen to control the particle size of the dry flux particles. Then, the dry flux particles are sintered in a furnace at 850~900℃ for 40 minutes. After cooling and screening again, the submerged arc flux is obtained. The resulting submerged arc welding flux has a pH of 2.2~2.7 and a particle size of 10~30 mesh.

6. The application of the welding consumable for high heat input submerged arc welding of bridge steel according to claim 1, characterized in that: The submerged arc welding wire, used with the submerged arc welding flux, is employed for submerged arc welding of two types of bridge steel, Q370qE and Q420qE, with a heat input of 50~100kJ / cm. The weld metal exhibits a tensile strength of 542~594MPa, a yield strength of 408~476MPa, a yield-to-tensile ratio of 0.75~0.80, an elongation of 20~24.5%, and an impact energy of 115~165J at -40℃. The resulting weld metal's mechanical properties meet the requirements of the "Railway Steel Bridge Manufacturing Specification Q / CR9211—2015". At this point, the thickness of the plate that can be welded through in a single pass is 15~25mm.

7. The application according to claim 6, characterized in that: Before submerged arc welding with a heat input of 50~100kJ / cm, the submerged arc welding flux needs to be dried at 350~400℃ for 2~3 hours.

8. A method for high heat input submerged arc welding of bridge steel, characterized in that, Using the submerged arc welding wire of the welding material described in claim 1 and the submerged arc welding flux, high heat input submerged arc welding was performed on two types of bridge steel, Q370qE and Q420qE, and the mechanical properties of the resulting weld metal met the requirements of the "Railway Steel Bridge Manufacturing Specification Q / CR9211—2015".

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