Welding method suitable for q500qe bridge steel plate

Abstract

The application discloses a welding method for Q500qE bridge steel plate, which comprises the following steps: groove processing, pretreatment and welding. The welding method adopts single-electric double-fine-wire submerged arc welding, the welding current is 330-580 A, the arc voltage is 28-32 V, the welding speed is 360-500 mm / min, the welding heat input is 15.4-29.9 kJ / cm, and the welding wire contains the following components: C 0.04-0.09%, Mn 1.4-1.7%, Si 0.15-0.28%, Mo 0.2-0.4%, Ni 2.2-2.9%, Ti 0.05-0.15%, B 0.002-0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, and the rest is Fe and impurities. The CTOD value of the weld metal and the coarse grain zone of the welding heat affected zone at-20 DEG C is greater than or equal to 0.28 mm.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a welding method suitable for Q500qE bridge steel plates. Background Technology

[0002] With economic development and technological progress, long-span steel structure bridges have been widely used and developed rapidly. In the future, bridge construction will continue to develop towards longer spans and diversification. Bridge structural steel will develop towards high performance, long life, lightweight, and intelligent features. Traditional bridge decks can no longer meet the design and construction requirements of long-span and diversified steel structure bridges.

[0003] The new generation of high-performance bridge steel, Q500qE, possesses excellent mechanical properties and is widely used in the construction of long-span, heavy-load bridges. However, the coarse-grained heat-affected zone (CGHAZ) of Q500qE bridge steel is prone to embrittlement after welding. Since bridge steel requires welding for connection in practical applications, and high heat input is typically used to improve welding efficiency, this increased heat input further deteriorates the properties of the CGHAZ, exacerbating the brittle fracture problem of Q500qE bridge steel. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a welding method suitable for Q500qE bridge steel plates, enabling the welding of Q500qE bridge steel plates to achieve high welding efficiency under relatively low heat input conditions, and producing welded joints with excellent strength, toughness, and low-temperature fracture toughness.

[0005] To achieve the above-mentioned objective, one embodiment of the present invention provides a welding method suitable for Q500qE bridge steel plates, used for welding Q500qE bridge steel plates, wherein the steel plate has a C content ≤0.09wt% and a carbon equivalent Ceq ≤0.44%.

[0006] The welding method includes sequential steps of beveling, pretreatment, and welding:

[0007] In the beveling process, the beveling is performed on the end of the steel plate to be welded.

[0008] In the pretreatment step, the bevel surface of the steel plate is cleaned and polished;

[0009] In the welding step, single-electric double-fine-wire submerged arc welding is used to weld the ends of steel plates of the same thickness to form a welded joint at the bevel. The welding current is controlled at 330-580A, the arc voltage at 28-32V, the welding speed at 360-500mm / min, and the welding heat input at 15.4-29.9kJ / cm. The chemical composition of the welding wire used, by mass percentage, includes: C 0.04-0.09%, Mn 1.4-1.7%, Si 0.15-0.28%, Mo 0.2-0.4%, Ni 2.2-2.9%, Ti 0.05-0.15%, B 0.002-0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, with the remainder being Fe and unavoidable impurities.

[0010] As a further improvement of one embodiment of the present invention, in the welding step, the flux used for submerged arc welding is a high-alkaline non-alloy sintered flux.

[0011] As a further improvement of one embodiment of the present invention, the flux used is OK Flux 10.62 flux.

[0012] As a further improvement of one embodiment of the present invention, the flux is preheated at 300-350°C for at least 2 hours before welding.

[0013] As a further improvement of one embodiment of the present invention, in the beveling process, the beveling form is a double U-shaped beveling, the beveling angle is 20°±3°, the blunt edge of the beveling is 0~1mm, and the root gap is 0~2mm.

[0014] As a further improvement of one embodiment of the present invention, the welding step employs multi-pass continuous welding, and the interpass temperature is controlled to be ≤220℃.

[0015] As a further improvement of one embodiment of the present invention, the tensile strength Rm of the steel plate is ≥630MPa, and the tensile strength Rm of the welding wire is ≥630MPa.

[0016] As a further improvement of one embodiment of the present invention, the thickness of the steel plate is 20-50 mm, and the diameter of the welding wire is 2 mm.

[0017] As a further improvement of one embodiment of the present invention, the weld microstructure of the welded joint after cooling to room temperature is a composite phase microstructure of acicular ferrite and bainite.

[0018] As a further improvement of one embodiment of the present invention, the tensile strength Rm of the welded joint is greater than 630 MPa, the impact energy KV2 of the welded joint at -40℃ is greater than 150 J, the crack tip opening displacement CTOD characteristic value of the weld metal and the coarse grain zone of the heat-affected zone at -20℃ is greater than 0.28 mm, and the welded joint is free from cracks when cold-bent at 180° at room temperature, wherein the bending mandrel diameter D = 40 mm.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) By designing the multi-element alloy composition of the welding wire and adopting the Ni-Mo-Ti-B alloy system, combined with the welding process of single-electric double fine wire submerged arc welding, on the one hand, the current density through the cross section of the welding wire can be large and the arc can be more concentrated during welding, thereby improving the deposition efficiency of the welding wire and the welding efficiency. This makes Q500qE bridge steel suitable for lower welding heat input, avoiding the deterioration of the performance of the coarse-grained heat-affected zone of Q500qE bridge steel after welding due to high heat input welding, and the weld joint can obtain a larger penetration depth under lower welding heat input conditions. On the other hand, by improving the welding thermal cycle and reducing the overheating degree of the molten pool, the proportion of heat conducted by the steel plate base material can be reduced, the fusion ratio can be reduced, thereby improving the microstructure of the weld metal, increasing the content of acicular ferrite, refining the microstructure of the weld formed after welding, and improving the strength and toughness of the weld joint. In summary, the welding efficiency is improved, and the weld joint has excellent strength, toughness and low-temperature fracture toughness, achieving a dual improvement in welding quality and welding efficiency.

[0021] (2) The welding method of the present invention for Q500qE bridge steel plates, through the comprehensive design of the steel plate base material, welding wire material, groove form and welding process, can not only have high welding efficiency under low heat input conditions, but also the welded joint has excellent strength and toughness and low temperature fracture toughness. After welding Q500qE bridge steel plates and cooling to room temperature, the weld joint formed by the weld is mainly composed of acicular ferrite and also contains bainite composite phase structure. The MA component in the coarse grains of the heat-affected zone is small and uniformly distributed, which refines the microstructure of the weld formed after welding, thereby making the welded joint have excellent strength and toughness to match Q500qE bridge steel plates.

[0022] (3) The tensile strength Rm of the welded joint is greater than 630 MPa, the impact energy KV2 of the welded joint at -40℃ is greater than 150 J, the crack tip opening displacement CTOD characteristic value of the weld metal and the coarse grain zone at -20℃ is greater than 0.28 mm, the welded joint has no cracks when cold bent at 180° at room temperature, and the bending mandrel diameter D = 40 mm. The welded joint has excellent comprehensive mechanical properties, the weld and the weld heat-affected zone have excellent low-temperature impact toughness, the welded joint has high impact toughness reserve and safety margin, the strength and toughness of the welded joint have a high matching with the strength and toughness of the steel plate, and the heat treatment process after welding is eliminated, which simplifies the production process, reduces the production cost, and improves the production efficiency, which can meet the requirements of high efficiency and high quality of bridge steel plates for welding. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection is not limited to the description.

[0024] One embodiment of the present invention provides a welding method for Q500qE bridge steel plates, which is applicable to welding Q500qE bridge steel plates.

[0025] Q500qE bridge steel plate refers to bridge structural steel plate with a yield strength of 500MPa or higher and a steel plate quality grade of E. Furthermore, the carbon content in this steel plate is ≤0.09wt%, and the carbon equivalent Ceq is ≤0.44%.

[0026] Specifically, the carbon equivalent of the steel plate

[0027] Ceq=[C]+[Mn] / 6+([Cr]+[Mo]+[V]) / 5+([Ni]+[Cu]) / 15;

[0028] Where [C], [Mn], [Cr], [Mo], [V], [Ni], and [Cu] represent the mass percentage of the corresponding elements in the steel plate.

[0029] The welding method applicable to the aforementioned Q500qE bridge steel plates specifically includes the following sequential steps: beveling, pretreatment, and welding. Each step is described in detail below.

[0030] (1) Beveling process

[0031] Two Q500qE bridge steel plates of the same thickness were taken for welding, and the ends of the steel plates to be welded were beveled.

[0032] The thickness of the steel plate is preferably 20-50 mm.

[0033] The preferred bevel type is a double U-shaped bevel with a bevel angle of 20°±3°, a blunt edge of 0-1mm, and a root gap of 0-2mm.

[0034] By designing the bevel type, bevel angle, blunt edge, and root gap, the amount of weld metal can be reduced, the deformation of the welded steel plate can be reduced, the fusion ratio can be lowered, and the dilution rate of the base metal of the steel plate on the weld metal can be reduced.

[0035] (2) Pretreatment steps

[0036] The bevel surface of the steel plate is cleaned and ground. The bevel surface includes the outer circumferential surface of the steel plate end to be welded where the bevel is located. In this way, the oxide scale, loose rust, oil, and moisture on the bevel surface are removed, thereby avoiding the appearance of micro-cracks in the final weld joint, which would affect the welding performance and improve the welding safety.

[0037] (3) Welding steps

[0038] Single-wire double-fine-wire submerged arc welding is used to weld the ends of steel plates of the same thickness to form a welded joint at the bevel. The welding current is controlled at 330-580A, the arc voltage at 28-32V, the welding speed at 360-500mm / min, and the welding heat input at 15.4-29.9kJ / cm.

[0039] The chemical composition of the welding wire used, by mass percentage, includes: C 0.04-0.09%, Mn 1.4-1.7%, Si 0.15-0.28%, Mo 0.2-0.4%, Ni 2.2-2.9%, Ti 0.05-0.15%, B 0.002-0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, with the remainder being Fe and unavoidable impurities.

[0040] By designing the multi-element alloy composition of the welding wire, adopting the Ni-Mo-Ti-B alloy system, and using a single-electric double-fine-wire submerged arc welding process, the following advantages are achieved: First, the current density passing through the welding wire cross-section is increased, and the arc is more concentrated, thereby improving the deposition efficiency of the welding wire and the overall welding efficiency. This allows Q500qE bridge steel to be used with lower welding heat input, avoiding the performance degradation of the coarse-grained heat-affected zone after welding due to high heat input. Furthermore, the weld joint achieves greater penetration depth under lower welding heat input conditions. Second, by improving the welding thermal cycle and reducing the overheating of the molten pool, the proportion of heat conducted through the base steel plate is reduced, decreasing the fusion ratio. This improves the microstructure of the weld metal, increases the content of acicular ferrite, refines the microstructure of the weld after welding, and enhances the strength and toughness of the weld joint. In summary, this approach improves welding efficiency, and the weld joint exhibits excellent strength, toughness, and low-temperature fracture toughness, achieving a dual improvement in welding quality and efficiency.

[0041] In this embodiment, the steel plate does not need to be preheated before welding.

[0042] Preferably, the tensile strength Rm of the steel plate is ≥630MPa, and the tensile strength Rm of the welding wire is ≥630MPa. This ensures that the strength and toughness of the weld metal formed by welding have better compatibility with the base steel material, as well as consistency in mechanical properties, thereby extending the service life of the steel plate.

[0043] Preferably, the flux used in submerged arc welding is a high-alkalinity non-alloy sintered flux. By using a high-alkalinity sintered flux, the transfer of alloying elements into the weld can be avoided, improving welding performance, facilitating slag removal, and resulting in a smooth and aesthetically pleasing weld bead. When applied to thick plate welding, it exhibits excellent impact strength and welding efficiency, and can smoothly transition with the sidewall, making it suitable for narrow-gap welding.

[0044] OK Flux 10.62 flux is preferred. By using OK Flux 10.62 flux, the weld metal formed by welding can be highly pure, and the weld microstructure is mainly composed of fine acicular ferrite, thereby ensuring that the weld metal has excellent strength, toughness and low-temperature fracture toughness.

[0045] Furthermore, OK Flux 10.62 flux should be preheated at 300–350°C for at least 2 hours before soldering to remove moisture absorbed by the flux and prevent cold cracking of the weld joint during soldering.

[0046] Preferably, the diameter of the welding wire is 2mm. Such a fine welding wire can ensure a large current density through the cross-section of the welding wire during welding, and the arc is more concentrated, thereby improving the deposition efficiency of the welding wire and enabling the welded joint to achieve a greater penetration depth under lower welding heat input conditions.

[0047] Furthermore, the welding process employs multi-pass continuous welding, with the specific number of passes controlled according to the thickness of the steel plate, the bevel type, and the welding heat input, while controlling the interpass temperature to ≤220℃.

[0048] Compared with the prior art, the welding method of the present invention for Q500qE bridge steel plates, through the comprehensive design of the steel plate base material, welding wire material, groove form and welding process, not only achieves high welding efficiency under low heat input conditions, but also produces welded joints with excellent strength, toughness and low-temperature fracture toughness. After welding Q500qE bridge steel plates and cooling to room temperature, the weld joint formed by the weld is mainly composed of acicular ferrite and also contains bainite composite phase structure. The MA component in the coarse grains of the heat-affected zone is small and uniformly distributed, which refines the microstructure of the weld formed after welding, thereby giving the welded joint excellent strength and toughness to match Q500qE bridge steel plates.

[0049] Specifically, the tensile strength Rm of the welded joint is greater than 630 MPa, the impact energy KV2 of the welded joint at -40℃ is greater than 150 J, the crack tip opening displacement CTOD characteristic value of the weld metal and the coarse-grained zone at -20℃ is greater than 0.28 mm, and the welded joint is free from cracks when cold-bent at 180° at room temperature, with a bending mandrel diameter D = 40 mm. The welded joint has excellent comprehensive mechanical properties, and the weld and the heat-affected zone have excellent low-temperature impact toughness. The welded joint has a high impact toughness reserve and safety margin. The strength and toughness of the welded joint are highly matched with the strength and toughness of the steel plate. Moreover, the heat treatment process after welding is eliminated, simplifying the production process, reducing production costs, and improving production efficiency, which can meet the requirements of high efficiency and high quality for bridge steel plates.

[0050] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

[0051] The following provides several embodiments of the present invention to further illustrate the technical solution of the present invention. Of course, these embodiments are only a preferred subset of the numerous variations contained in the present invention, and not all of them.

[0052] Example 1

[0053] The steel plate to be welded is a Q500qE bridge steel plate, and the C content in the steel plate is ≤0.09wt%, and the carbon equivalent Ceq is ≤0.44%.

[0054] The welding method involves the following steps:

[0055] (1) Beveling process

[0056] The aforementioned Q500qE bridge steel plate was used to prepare test specimens. The tensile strength of the steel plate Rm ≥ 630MPa, the thickness of the steel plate test specimens was 20mm, and the cross-sectional dimensions of the steel plate test specimens were 1000mm × 400mm.

[0057] Take two steel plate samples and perform beveling on the welding end of each steel plate sample to form a double U-shaped bevel. The bevel angle is 20°±3°, the blunt edge of the bevel is 0~1mm, and the root gap is 0~2mm.

[0058] (2) Pretreatment steps

[0059] The bevel surface of the steel plate sample is cleaned and polished until all oxide scale, loose rust, oil and moisture are removed.

[0060] (3) Welding steps

[0061] The ends of steel plates of the same thickness are welded using single-electrode double-fine-wire submerged arc welding. Multiple passes of continuous welding are used to form a welded joint at the bevel. The steel plate does not require preheating before welding. The welding current is controlled at 350±20A, the arc voltage is 28~29V, the welding speed is 360mm / min, the welding heat input is 15.4kJ / cm, and the interpass temperature is controlled at ≤220℃.

[0062] The welding wire used has a diameter of 2mm, a tensile strength Rm≥630MPa, and a chemical composition by mass percentage including: C 0.04~0.09%, Mn 1.4~1.7%, Si 0.15~0.28%, Mo 0.2~0.4%, Ni 2.2~2.9%, Ti 0.05~0.15%, B 0.002~0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, with the remainder being Fe and unavoidable impurities.

[0063] The matching flux is a high-alkaline non-alloy sintered flux, specifically OK Flux 10.62 flux. Before welding, OKFlux 10.62 flux should be preheated at 300-350℃ for 2 hours.

[0064] After welding is completed and cooled to room temperature, samples are taken from the weld joint in a direction parallel to the weld seam, and the microstructure of the weld joint is observed using a metallographic microscope. In this embodiment, the weld seam microstructure of the weld joint is a composite phase microstructure of acicular ferrite and bainite, and the grain size is fine.

[0065] According to GB / T2653, a side bending test sample of the joint was taken. The welded joint was bent 180° at room temperature with a bending mandrel diameter D = 40mm. The welded joint surface showed no cracks, indicating that the welded joint had excellent cold bending performance.

[0066] Example 2

[0067] The steel plate to be welded is a Q500qE bridge steel plate, and the C content in the steel plate is ≤0.09wt%, and the carbon equivalent Ceq is ≤0.44%.

[0068] The welding method involves the following steps:

[0069] (1) Beveling process

[0070] The aforementioned Q500qE bridge steel plate was used to prepare test specimens. The tensile strength of the steel plate Rm ≥ 630MPa, the thickness of the steel plate test specimens was 32mm, and the cross-sectional dimensions of the steel plate test specimens were 1000mm × 400mm.

[0071] Take two steel plate samples and perform beveling on the welding end of each steel plate sample to form a double U-shaped bevel. The bevel angle is 20°±3°, the blunt edge of the bevel is 0~1mm, and the root gap is 0~2mm.

[0072] (2) Pretreatment steps

[0073] The bevel surface of the steel plate sample is cleaned and polished until all oxide scale, loose rust, oil and moisture are removed.

[0074] (3) Welding steps

[0075] The ends of steel plates of the same thickness are welded using single-electric double-fine-wire submerged arc welding. Multiple passes of continuous welding are used to form a welded joint at the bevel. The steel plate does not require preheating before welding. The welding current is controlled at 560±20A, the arc voltage is 31~32V, the welding speed is 500mm / min, the welding heat input is 21.5kJ / cm, and the interpass temperature is controlled at ≤220℃.

[0076] The welding wire used has a diameter of 2mm, a tensile strength Rm≥630MPa, and a chemical composition by mass percentage including: C 0.04~0.09%, Mn 1.4~1.7%, Si 0.15~0.28%, Mo 0.2~0.4%, Ni 2.2~2.9%, Ti 0.05~0.15%, B 0.002~0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, with the remainder being Fe and unavoidable impurities.

[0077] The matching flux is a high-alkaline non-alloy sintered flux, specifically OK Flux 10.62 flux. Before welding, OKFlux 10.62 flux should be preheated at 300-350℃ for 2.5 hours.

[0078] After welding is completed and cooled to room temperature, samples are taken from the weld joint in a direction parallel to the weld seam, and the microstructure of the weld joint is observed using a metallographic microscope. In this embodiment, the weld seam microstructure of the weld joint is a composite phase microstructure of acicular ferrite and bainite, and the grain size is fine.

[0079] According to GB / T2653, a side bending test sample of the joint was taken. The welded joint was bent 180° at room temperature with a bending mandrel diameter D = 40mm. The welded joint surface showed no cracks, indicating that the welded joint had excellent cold bending performance.

[0080] Example 3

[0081] The steel plate to be welded is a Q500qE bridge steel plate, and the C content in the steel plate is ≤0.09wt%, and the carbon equivalent Ceq is ≤0.44%.

[0082] The welding method involves the following steps:

[0083] (1) Beveling process

[0084] The aforementioned Q500qE bridge steel plate was used to prepare the test specimen. The tensile strength of the steel plate Rm ≥ 630MPa, the thickness of the steel plate test specimen was 50mm, and the cross-sectional dimensions of the steel plate test specimen were 1000mm × 400mm.

[0085] Take two steel plate samples and perform beveling on the welding end of each steel plate sample to form a double U-shaped bevel. The bevel angle is 20°±3°, the blunt edge of the bevel is 0~1mm, and the root gap is 0~2mm.

[0086] (2) Pretreatment steps

[0087] The bevel surface of the steel plate sample is cleaned and polished until all oxide scale, loose rust, oil and moisture are removed.

[0088] (3) Welding steps

[0089] The ends of steel plates of the same thickness are welded using single-electric double-fine-wire submerged arc welding. Multiple passes of continuous welding are used to form a welded joint at the bevel. The steel plate does not require preheating before welding. The welding current is controlled at 560±20A, the arc voltage is 31~32V, the welding speed is 360mm / min, the welding heat input is 29.9kJ / cm, and the interpass temperature is controlled at ≤220℃.

[0090] The welding wire used has a diameter of 2mm, a tensile strength Rm≥630MPa, and a chemical composition by mass percentage including: C 0.04~0.09%, Mn 1.4~1.7%, Si 0.15~0.28%, Mo 0.2~0.4%, Ni 2.2~2.9%, Ti 0.05~0.15%, B 0.002~0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, with the remainder being Fe and unavoidable impurities.

[0091] The matching flux is a high-alkaline non-alloy sintered flux, specifically OK Flux 10.62 flux. Before welding, OKFlux 10.62 flux should be preheated at 300-350℃ for 2 hours.

[0092] After welding is completed and cooled to room temperature, samples are taken from the weld joint in a direction parallel to the weld seam, and the microstructure of the weld joint is observed using a metallographic microscope. In this embodiment, the weld seam microstructure of the weld joint is a composite phase microstructure of acicular ferrite and bainite, and the grain size is fine.

[0093] According to GB / T2653, a side bending test sample of the joint was taken. The welded joint was bent 180° at room temperature with a bending mandrel diameter D = 40mm. The welded joint surface showed no cracks, indicating that the welded joint had excellent cold bending performance.

[0094] The tensile properties, impact properties, and crack tip opening displacement (CTOD) characteristic values ​​at -20°C of the welded joints of Examples 1-3 above were further tested, as follows:

[0095] (1) In terms of tensile properties, the tensile properties of the welded joint after cooling to room temperature after welding were tested in accordance with GB / T2651. The tensile strength Rm of the welded joint is shown in Table 1. The tensile test was performed by sampling the welded joint and the tensile direction was parallel to the welding direction.

[0096] (2) Impact performance: The impact performance of the welded joint cooled to room temperature after welding was tested in accordance with GB / T2650. The results of the low-temperature impact performance test of each region of the welded joint at -40℃ are shown in Table 1. The impact energy kV2 at -40℃ was tested at the impact notch positions at the weld metal, at the fusion line FL, and at 1mm outside the fusion line (i.e., FL+1). Three sampling test results are shown for each test position.

[0097] (3) Referring to standard BS7448, the crack tip opening displacement CTOD characteristic value of the welded joint at -20℃ was measured by the three-point bending test. The notch positions were located in the weld metal and the coarse grain zone (CGHAZ) of the weld heat-affected zone. Three sampling test results were shown for each test position. The test results are shown in Table 2.

[0098] Table 1

[0099]

[0100] Table 2

[0101]

[0102]

[0103] In summary, when Q500qE bridge steel plates are welded using the welding method of this invention, the weld microstructure of the weld joint after cooling to room temperature is a composite phase structure of acicular ferrite and bainite with fine grain size. The tensile strength Rm of the weld joint is >630MPa, the impact energy KV2 of the weld heat-affected zone at -40℃ is ≥150J, and the crack tip opening displacement CTOD characteristic value of both the weld metal and the coarse-grained zone of the weld heat-affected zone at -20℃ is ≥0.28mm. The weld joint exhibits no cracks when cold-bent at 180° at room temperature, with a bending mandrel diameter D = 40mm. The weld joint has excellent low-temperature fracture toughness, high toughness reserve and safety margin, and the strength and toughness of the weld joint are highly matched with those of the steel plate.

[0104] As can be seen from the above embodiments, the welding method of the present invention for welding Q500qE bridge steel plates not only has high welding efficiency under low heat input conditions, but also the welded joint has excellent low-temperature fracture toughness, high toughness reserve and safety margin. Moreover, the strength and toughness of the welded joint have a high degree of matching with the strength and toughness of the Q500qE bridge steel plate. In addition, the heat treatment process after welding is eliminated, simplifying the production process, reducing production costs and improving production efficiency.

[0105] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0106] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A welding method suitable for Q500qE bridge steel plates, characterized in that, Used for welding Q500qE bridge steel plates, wherein the steel plate has a C content ≤0.09wt% and a carbon equivalent Ceq ≤0.44%. The welding method includes sequential steps of beveling, pretreatment, and welding: In the beveling process, the beveling is performed on the end of the steel plate to be welded. In the pretreatment step, the bevel surface of the steel plate is cleaned and polished; In the welding step, single-electric double-fine-wire submerged arc welding is used to weld the ends of steel plates of the same thickness to form a welded joint at the bevel. The welding current is controlled at 330-580A, the arc voltage at 28-32V, the welding speed at 360-500mm / min, and the welding heat input at 15.4-29.9kJ / cm. The chemical composition of the welding wire used, by mass percentage, includes: C 0.04-0.09%, Mn 1.4-1.7%, Si 0.15-0.28%, Mo 0.2-0.4%, Ni 2.2-2.9%, Ti 0.05-0.15%, B 0.002-0.005%, Cu≤0.35%, S≤0.005%, P≤0.012%, with the remainder being Fe and unavoidable impurities.

2. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, In the welding process, the flux used for submerged arc welding is a high-alkaline non-alloy sintered flux.

3. The welding method for Q500qE bridge steel plates according to claim 2, characterized in that, The flux used is OK Flux 10.62 flux.

4. The welding method for Q500qE bridge steel plates according to claim 3, characterized in that, The flux is preheated at 300–350°C for at least 2 hours before welding.

5. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, In the beveling process, the beveling shape is a double U-shaped beveling, the beveling angle is 20°±3°, the blunt edge of the beveling is 0~1mm, and the root gap is 0~2mm.

6. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, The welding process employs multi-pass continuous welding, and the interpass temperature is controlled to be ≤220℃.

7. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, The tensile strength Rm of the steel plate is ≥630MPa, and the tensile strength Rm of the welding wire is ≥630MPa.

8. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, The thickness of the steel plate is 20-50 mm, and the diameter of the welding wire is 2 mm.

9. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, The weld microstructure of the welded joint after cooling to room temperature is a composite phase microstructure of acicular ferrite and bainite.

10. The welding method for Q500qE bridge steel plates according to claim 1, characterized in that, The tensile strength Rm of the welded joint is greater than 630 MPa, the impact energy KV2 of the welded joint at -40℃ is greater than 150 J, the crack tip opening displacement CTOD characteristic value of the weld metal and the coarse grain zone of the heat-affected zone at -20℃ is greater than 0.28 mm, and the welded joint is free from cracks when cold-bent at 180° at room temperature, with the bending mandrel diameter D = 40 mm.

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