A high heat input submerged arc welding method for thick bridge steel plates

Abstract

The present invention discloses a high-heat-input submerged arc welding method for thick bridge steel plates. The method comprises the following steps: designing a weld groove based on the thickness and mechanical properties of the bridge steel plates to be welded, and adjusting the welding heat input by adjusting the welding current, arc voltage, and welding speed. Using selected submerged arc welding wire and flux, the method achieves high-heat-input submerged arc welding for single-pass, multi-layer welding of each layer of bridge steel with a thickness of 25 to 100 mm. The mechanical properties of the 50 to 165 kJ / cm high-heat-input submerged arc welded joints meet the requirements of bridge industry manufacturing specifications. The joints have a tensile strength of 516 MPa or higher, fracture locations are located within the base material, there are no cracks after 180° lateral bending, and the impact energy absorption at -40°C of 65 J or higher at the center of the surface weld and 1 mm outside the fusion line. The method achieves high heat input, a wide range of plate thickness adaptability, fast deposition speed, a wide range of deposition adjustment, high overall welding efficiency, and ease of implementation. The welds are aesthetically pleasing, the weld joints have excellent mechanical properties, and strong engineering practicality.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge steel welding, and relates to a high heat input submerged arc welding method for thick bridge steel plates, and specifically relates to a 50-165 kJ / cm high heat input submerged arc welding method for bridge steel with a thickness of 25-100 mm and a tensile strength of 510-645 MPa. Background Art

[0002] With the rapid development of land transportation, the construction of large-span, wide-deck, high-load-bearing, and highly seismic-resistant steel bridges is increasing. This has led to a significant increase in demand for high-performance bridge steels, characterized by high strength and toughness, low yield-to-strength ratio, thick plates, and excellent weldability. During the construction of steel bridges, approximately 80% of the steel structure requires welding, and welding man-hours account for 30-40% of the total construction time. Therefore, efficient and high-quality bridge steel welding methods are crucial for improving the construction quality of steel bridges and shortening production cycles.

[0003] Existing high-efficiency welding methods, such as twin-wire submerged arc welding, three-wire submerged arc welding, gas-electric vertical welding, and electroslag welding, primarily increase the amount of wire melt per unit time by increasing welding process parameters (i.e., welding current and arc voltage), significantly improving welding deposition speed. These methods offer advantages such as high heat input and high welding efficiency, and are widely used in shipbuilding, marine engineering, and other fields. Compared to ship plate steel, bridge steel has higher mechanical property requirements, specifically lower low-temperature impact temperatures and higher standard values ​​for low-temperature impact absorbed energy of welded joints compared to the same grade of base metal. Furthermore, additional requirements are imposed on yield ratios and crack sensitivity indices. Under the influence of welding thermal cycles, grain growth in conventional bridge steel joints is prone to occur, significantly reducing the low-temperature impact toughness and strength of the joints. Therefore, it is often necessary to reduce the heat input during welding to prevent grain growth and achieve welded joints with good mechanical properties. Consequently, conventional bridge steel has low welding efficiency and is not suitable for high-heat-input welding.

[0004] In recent years, with the advancement of oxide metallurgy for steel plates, many domestic steel mills have developed a variety of bridge steels that can be welded with high heat input. Chinese invention patent publication number "CN101318254B," entitled "A Submerged Arc Welding Method for Thick Plates of High-Strength Bridge Steel," discloses a submerged arc butt welding process for high-strength bridge steel. Using a double-sided V-shaped asymmetric groove with a 60° groove angle and a 6mm blunt edge, this method achieves a heat input of 32 to 35 kJ / cm2 for bridge steel with a tensile strength of 570 to 650 MPa. This addresses the current issue of post-weld heat treatment and root cleaning required for submerged arc butt welding of long-span bridge structures. The Chinese invention patents with publication number "CN113182652B" and patent name "Submerged Arc Welding Process for Thick-Gauge TMCP State High-Strength and Low-Yield Ratio Bridge Steel" and the Chinese invention patent application with publication number "CN114734127A" and patent name "A Submerged Arc Welding Process for 485MPa-Grade Thick-Gauge Weathering-Resistant Bridge Steel" both disclose submerged arc welding process methods for bridge steel. Under heat input conditions of 25 to 42 kJ / cm, they solve the problem of achieving a balance between low-temperature toughness, strength, and cold bending performance for thick-gauge bridge steel welded joints, achieving welded joints with a low-temperature impact energy of >60J at -40°C. The above-mentioned disclosed technologies all have process disadvantages such as low welding heat input (all less than 50 kJ / cm), a narrow plate thickness adaptability range (36 to 65 mm), and the need for multi-layer and multi-pass welding. Accordingly, the welding efficiency is relatively low.

[0005] The publication numbers are “CN112139242B”, “CN102851589B”, “CN108359903B”, “CN102766748B” and “CN104004962B”, and the corresponding names are “A steel for high heat input welding and a method for improving the toughness of its heat-affected zone”, “A steel with low yield ratio capable of ultra-high heat input welding for low-temperature structures and a method for manufacturing the same”, “A low-alloy high-strength steel and a method for toughening the heat-affected zone of its high heat input welding”, “A method for producing a low-temperature steel plate capable of high heat input welding” and “A normalizing method for high heat input welding of marine engineering steel”. The Chinese invention patents entitled "Steel Plate and Its Manufacturing Method," as well as the Chinese invention patent applications with publication numbers "CN114672733A," "CN104451389A," and "CN114807557A," with corresponding titles such as "690MPa-grade steel plate capable of high heat input welding and its production method," "A 100mm thick E36 marine engineering steel plate resistant to high line energy welding," and "Low yield ratio steel plate suitable for high heat input welding and its production method," disclose the development of steel plates with excellent low-temperature toughness and high heat input weldability through composition design, steel smelting, and rolling control. Although these technologies increase the weldable heat input of bridge steel (between 50 and 200 kJ / cm) and achieve a low-temperature impact energy of >50J at -40°C in the coarse-grained zone of the joint, the corresponding welding process conditions are not disclosed, and the application mainly involves ship plate steel. Secondly, the welding heat input described is mainly the heat input during welding heat simulation, and its action process is significantly different from the actual welding thermal cycle. Therefore, the low-temperature impact performance data obtained by the above technology does not have a universal rule, and its process effect has little guiding significance for high heat input welding of bridge steel. Summary of the Invention

[0006] The purpose of the present invention is to address the technical problems of existing bridge steel thick plate welding such as low heat input, narrow plate thickness adaptation range, and low welding efficiency, and to propose a submerged arc welding method with low implementation cost, large heat input, wide plate thickness adaptation range, and high welding efficiency, so as to achieve high-efficiency, high-quality, large heat input welding of bridge steel thick plates and obtain welded joints with good mechanical properties.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions to achieve it.

[0008] A high-heat-input submerged arc welding method for thick bridge steel plates is disclosed. The method is applicable to bridge steel plates with a thickness of 25 to 100 mm, a lower yield strength of 360 to 510 MPa, a tensile strength of 510 to 645 MPa, an elongation after fracture of 18 to 27%, a yield strength ratio of 0.72 to 0.85, and an impact absorption energy of 300 J or greater at -40°C. The method can achieve a high-heat-input submerged arc welding heat input of 50 to 165 kJ / cm. The method specifically comprises the following steps:

[0009] Step 1, welding groove design and welding heat input setting: When the thickness of the bridge steel plate is 25-30mm, the designed welding groove is Y-shaped, the groove angle is 60-85°, the groove blunt edge is 10-13mm, and the welding heat input is set to 50-80kJ / cm by adjusting the welding current, arc voltage and welding speed; when the thickness of the bridge steel plate is 30-50mm, the designed welding groove is double-sided V-shaped with blunt edge, the groove angle is 45-100°, the groove is 10-13mm, and the welding heat input is set to 50-80kJ / cm; The blunt edge of the groove is 10 to 15 mm, and the welding heat input set by adjusting the welding current, arc voltage and welding speed is 80 to 120 kJ / cm; when the thickness of the bridge steel plate is 50 to 100 mm, the designed welding groove form is a double-sided U-shape, the groove angle is 40 to 52 degrees, the blunt edge of the groove is 16 to 20 mm, and the groove root radius is 5 to 8 mm. The welding heat input set by adjusting the welding current, arc voltage and welding speed is 120 to 165 kJ / cm;

[0010] Step 2: Welding material selection and pretreatment: Based on the mechanical properties of the bridge steel and the set welding heat input, submerged arc welding wire and flux are selected. The welding wire diameter is 4.0-5.5 mm. The flux is dried at 350-400°C for 2-3 hours before welding.

[0011] Step 3, single-pass multi-layer submerged arc welding per layer: When the thickness of the bridge steel plate is 25-30 mm, first, perform one layer of filling welding and one layer of cap welding in sequence in the front groove of the bridge steel workpiece to be welded, and control the interlayer temperature of the weld seam between 100-200°C. Then, turn the bridge steel workpiece to be welded over, and perform carbon planing or mechanical processing to clean the back of the groove to a depth of 5-10 mm. Finally, perform one layer of cap welding at the cleaned position on the back of the groove.

[0012] When the bridge steel plate is 30-50 mm thick, firstly, 0-1 layers of filling welding and 1 layer of cover welding are performed in the front groove of the bridge steel workpiece to be welded, then the bridge steel workpiece to be welded is turned over, and 0-1 layers of filling welding and 1 layer of cover welding are performed in the back groove thereof. During this process, the interlayer temperature of the groove weld on the same side, the front groove cover layer weld, and the first layer weld of the back groove is controlled to be between 100 and 200°C;

[0013] When the bridge steel plate is 50-100 mm thick, the bridge steel workpiece to be welded is first preheated to 100-200° C., and then 1-5 layers of filling welding and 1 layer of cover welding are sequentially performed on the front groove. Then, the bridge steel workpiece to be welded is turned over, and 1-5 layers of filling welding and 1 layer of cover welding are sequentially performed on the back groove. During this process, the interlayer temperature of the groove weld on the same side, the front groove cover layer weld, and the first layer weld of the back groove is controlled between 100-200° C.

[0014] Step ④, post-weld treatment of weldment: After the welding of the bridge steel workpiece is completed, immediately cover the surface of the weldment with insulation cotton to keep it warm and cool slowly, and control the cooling rate of the weldment between 100 and 150℃ / h.

[0015] Furthermore, when the welding heat input is 50-80 kJ / cm, the submerged arc welding method is a single-wire submerged arc welding method or a double-wire submerged arc welding method; when the single-wire submerged arc welding method is adopted, the welding current adjusted in step ① is 700-1000 A, the arc voltage is 35-45 V, and the welding speed is 290-335 mm / min. In addition, the dry stickout is set to 35-38 mm; when the double-wire submerged arc welding method is adopted, when adjusting the welding current and arc voltage in step ①, it is necessary to first set the current type on the front welding wire and the rear welding wire. Then, the welding current and arc voltage on the front welding wire and the rear welding wire, as well as the inclination angle of the front welding wire and the rear welding wire are adjusted respectively. The front welding wire is powered by direct current, the welding current is 700-950A, the arc voltage is 27-35V, and the inclination angle of the front welding wire is 0-15°. The rear welding wire is powered by alternating current, the welding current is 600-780A, the arc voltage is 32-40V, and the inclination angle of the rear welding wire is 0-30°. The welding speed is 460-550mm / min. In addition, the dry extension length is set to 35-38mm and the wire spacing is set to 25-35mm.

[0016] Furthermore, when the welding heat input is greater than 80 kJ / cm, the submerged arc welding method is a double-wire submerged arc welding method. When adjusting the welding current and arc voltage in step ①, it is necessary to first set the current type on the front welding wire and the rear welding wire, and then adjust the welding current and arc voltage on the front welding wire and the rear welding wire, as well as the inclination angles of the front welding wire and the rear welding wire respectively. The front welding wire is powered by direct current, the welding current is 900-1600A, the arc voltage is 34-42V, and the inclination angle of the front welding wire is 0-15°. The rear welding wire is powered by alternating current, the welding current is 800-1250A, the arc voltage is 38-45V, and the inclination angle of the rear welding wire is 0-20°. In addition, the dry extension is set to 39-45 mm and the wire spacing is 30-40 mm.

[0017] Further, in the above step ①, when the welding groove is Y-shaped, To design the groove angle; when the welding groove form is a double-sided V-shaped with blunt edges, the double-sided V-shaped groove with blunt edges is a symmetrical double-sided V-shaped groove with blunt edges, and according to To design the groove angle; when the welding groove is in the form of a double-sided U-shape, the double-sided U-shape is a symmetrical double-sided U-shape, and according to To design the groove angle.

[0018] Furthermore, in the above step ③, when the thickness of the bridge steel plate is 25-30 mm or 30-50 mm, before performing high heat input submerged arc welding in the front groove of the bridge steel workpiece to be welded, a layer of small welding heat input bottom welding of 8-14 kJ / cm is first performed in the front groove of the bridge steel workpiece to be welded by gas shielded welding method, and the corresponding set bottom welding current is 180-300 A, the arc voltage is 21-32 V, and the welding speed is 285-410 mm / min; when the thickness of the bridge steel plate is 30-50 mm or 50-100 mm, after the bridge steel workpiece to be welded is turned over, the back groove of the bridge steel workpiece to be welded is first carbon planed or mechanically processed to clean the root, and the root cleaning depth is 2-8 mm, and then high heat input submerged arc welding is performed at the cleaned root of the back groove.

[0019] Furthermore, in the above step ④, after the bridge steel workpiece is welded, it is first subjected to a post-heat treatment at 200-300°C for 1.5-2h, and then insulation cotton is laid on the surface of the weldment for insulation and slow cooling.

[0020] Furthermore, when the thickness of the bridge steel plate is 30 mm, the designed welding groove is Y-shaped, the groove angle is 60°, the groove blunt edge is 10 mm, and the double-wire submerged arc welding method is adopted. The front welding wire is set to be DC, the welding current is 780A, the arc voltage is 29V, the front welding wire inclination is 0°, the rear welding wire is set to be AC, the welding current is 690A, the arc voltage is 35V, the rear welding wire inclination is 10°, the welding speed is 520 mm / min, the dry extension is 36 mm, and the wire spacing is 30 mm. During welding, first perform one layer of filling welding and one layer of cover welding in the front groove of the bridge steel workpiece to be welded, and control the interlayer temperature. The temperature is 150℃, and then the bridge steel workpiece to be welded is turned over and the back side of the groove is carbon planed and cleaned to a depth of 8mm. Then, a layer of cover welding is performed on the cleaned part of the back side of the groove. At the same time, by detecting the actual welding current and arc voltage on the front welding wire and the rear welding wire, as well as the welding speed, the actual welding heat input is obtained to be 52-57kJ / cm. Immediately after welding, thermal insulation cotton is laid on the surface of the weldment for insulation and slow cooling. The obtained high heat input submerged arc welding joint has a tensile strength of 550MPa, the fracture position is located at the base material, there is no crack in 180° side bending, and the -40℃ impact absorption energy at the center of the surface weld and 1mm outside the fusion line is ≥167J.

[0021] Furthermore, when the thickness of the bridge steel plate is 30 mm, the designed welding groove is a symmetrical double-sided V-shaped with a blunt edge, a groove angle of 90°, and a blunt edge of 10 mm. A double-wire submerged arc welding method is adopted, and the front welding wire is set to be DC, the welding current is 970 A, the arc voltage is 37 V, and the front welding wire inclination is 5°. The rear welding wire is set to be AC, the welding current is 920 A, the arc voltage is 41 V, and the rear welding wire inclination is 15°. The welding speed is 450 mm / min, the dry extension length is 40 mm, and the wire spacing is 35 mm. During welding, a small welding heat input of 10 kJ / cm is firstly performed in the front groove of the bridge steel workpiece to be welded using a consumable electrode gas shielding method. Bottom welding, and then a layer of cover welding is carried out in the front groove of the bridge steel workpiece to be welded, and then the bridge steel workpiece to be welded is turned over and another layer of cover welding is carried out in its reverse groove. During the process, the interlayer temperature is controlled at 150°C. At the same time, by detecting the actual welding current and arc voltage on the front welding wire and the rear welding wire, as well as the welding speed, the actual welding heat input is obtained to be 95-102kJ / cm. Immediately after welding, thermal insulation cotton is laid on the surface of the weldment for insulation and slow cooling; the obtained high heat input submerged arc welding joint has a tensile strength of 542MPa, the fracture position is located at the base material, there is no crack in 180° side bending, and the -40°C impact absorption energy at the center of the surface weld and 1mm outside the fusion line is ≥143J.

[0022] Furthermore, when the thickness of the bridge steel plate is 50 mm, the designed welding groove is a symmetrical double-sided U-shape, the groove angle is 46°, the groove blunt edge is 16 mm, and the groove root radius is 6 mm. A double-wire submerged arc welding method is adopted, and the front welding wire is set to be DC, the welding current is 1400 A, the arc voltage is 40 V, and the front welding wire inclination is 5°. The rear welding wire is set to be AC, the welding current is 1100 A, the arc voltage is 42 V, and the rear welding wire inclination is 20°. The welding speed is 430 mm / min, the dry extension length is 43 mm, and the wire spacing is 38 mm. Before welding begins, the bridge steel workpiece to be welded is preheated to 150°C, and then one layer of filling welding and one layer of covering are performed in sequence in the front groove of the bridge steel workpiece to be welded. Welding is performed, and then the bridge steel workpiece to be welded is turned over and one layer of filling welding and one layer of cap welding are performed in sequence in the reverse groove. During the welding process, the interlayer temperature is controlled at 150°C, and the actual welding current and arc voltage on the front welding wire and the rear welding wire, as well as the welding speed, are detected, and the actual welding heat input is obtained to be 143-152 kJ / cm; after welding, the weldment is first subjected to a post-heat treatment at 200-300°C for 1.5-2h, and then insulation cotton is laid on the surface of the weldment for insulation and slow cooling; the obtained high heat input submerged arc welding joint has a tensile strength of 533 MPa, the fracture position is located at the base material, there is no crack in 180° side bending, and the -40°C impact absorption energy at the center of the surface weld and 1mm outside the fusion line is ≥76J.

[0023] Compared with the prior art, the main significant advantages and beneficial effects of the present invention are:

[0024] 1. For bridge steel with a thickness of 25 to 100 mm, high heat input submerged arc welding can be achieved by designing the welding groove and adjusting the welding process parameters to set the welding heat input. The developed submerged arc welding method has the advantages of high welding efficiency, strong adaptability to plate thickness, and low implementation cost.

[0025] 2. Compared with the existing bridge steel welding method, the welding heat input of the present invention is large and the adjustment range is wide, which can be increased from 50kJ / cm to 165kJ / cm. Accordingly, it has the technical advantages of fast welding deposition speed, strong deposition amount adjustment ability and high deposition efficiency.

[0026] 3. Under the same welding heat input conditions, the weld of the present invention is stable and beautiful, and the obtained bridge steel high heat input welded joint has better low-temperature impact resistance and tensile performance, and the joint softening is not obvious. The submerged arc welded joint at a heat input of 165kJ / cm has a tensile strength of 516MPa, a fracture position at the base material, no cracks in 180° side bending, and the -40°C impact absorption energy at the center of the surface weld and 1mm outside the fusion line is ≥65J. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Flowchart of an embodiment of the present invention.

[0028] Figure 2 Schematic diagram of the Y-shaped groove in an embodiment of the present invention.

[0029] Figure 3 Schematic diagram of a double-sided V-groove with blunt edges in an embodiment of the present invention, taking a symmetrical double-sided V-groove with blunt edges as an example.

[0030] Figure 4 Schematic diagram of a double-sided U-shaped groove in an embodiment of the present invention, taking a symmetrical double-sided U-shaped groove as an example.

[0031] Figure 5 This is a schematic diagram of double-wire submerged arc welding in an embodiment of the present invention.

[0032] Figure 6 This is a macroscopic photograph of the cross section of the weld with the Y-shaped groove of the present invention.

[0033] Figure 7 This is a macroscopic photograph of the cross section of the weld with a blunt-edged symmetrical double-sided V-groove according to the present invention.

[0034] Figure 8 This is a macroscopic photograph of the cross section of the weld with the symmetrical double-sided U-groove of the present invention.

[0035] In the figure: 1, bridge steel to be welded, 2, front welding wire, 3, rear welding wire, 4, front contact nozzle, 5, rear contact nozzle; δ, bridge steel plate thickness, α, groove angle, p, blunt edge thickness, R, groove root radius, V w , welding speed, β1, front wire inclination angle, β2, rear wire inclination angle, d, wire spacing, h, dry extension length. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. However, the protection scope of the present invention is not limited to the following embodiments. Any technical solutions obtained by equivalent replacement or equivalent transformation are within the protection scope of the present invention.

[0037] The high heat input submerged arc welding method for thick bridge steel plates of the present invention is applicable to bridge steels with a plate thickness of 25 to 100 mm, a lower yield strength of 360 to 510 MPa, a tensile strength of 510 to 645 MPa, an elongation after fracture of 18 to 27%, a yield strength ratio of 0.72 to 0.85, and an impact absorption energy of ≥300 J at -40°C. The specific implementation process is as follows: Figure 1 shown.

[0038] Before welding, firstly, according to the thickness of the bridge steel 1 to be welded, the welding groove (including the welding groove form and groove size) is designed, and the groove of the bridge steel 1 to be welded is processed, and then the welding current, arc voltage and welding speed V are adjusted. w To set the welding heat input E accordingly.

[0039] Specifically, when the bridge steel plate thickness δ is 25-30 mm, the welding groove is set to be Y-shaped (schematic diagram as shown in FIG. Figure 2 (as shown), the appropriate welding heat input E is 50-80 kJ / cm. Accordingly, the groove angle α is determined using Expression (1) based on the groove root edge p and the welding heat input E. When the groove root edge p is 10-13 mm and the welding heat input E is 50-80 kJ / cm, Expression (1) yields an appropriate groove angle α of 60-85°.

[0040]

[0041] When the bridge steel plate thickness δ is 30-50 mm, the welding groove is set to be a double-sided V-shaped groove with blunt edges (the schematic diagram of the double-sided V-shaped groove with blunt edges is as shown in FIG. Figure 3(as shown), the appropriate welding heat input E is 80-120 kJ / cm. Accordingly, the groove angle α is determined using Expression (2) based on the groove blunt edge p and the welding heat input E, where k is the number of weld layers on one side of the groove. When the groove blunt edge p is 10-15 mm, the welding heat input E is 80-120 kJ / cm, and k is 1-2, Expression (2) yields an appropriate groove angle α of 45-100°.

[0042]

[0043] When the bridge steel plate thickness δ is 50-100 mm, the welding groove is set to a double-sided U-shaped groove (the schematic diagram of the double-sided symmetrical U-shaped groove is as shown in FIG. Figure 4 (as shown), the appropriate welding heat input E is 120-165 kJ / cm. Accordingly, the groove angle α is determined using Expression (3) based on the groove blunt edge p and the welding heat input E, where k is the number of weld layers on one side of the groove. When the groove blunt edge p is 16-20 mm, the groove root radius R is 5-8 mm, the welding heat input E is 120-165 kJ / cm, and k is 2-5, Expression (3) yields an appropriate groove angle α of 40-52°.

[0044]

[0045] According to the aforementioned groove design method, two correspondingly processed pieces of bridge steel (1) to be welded are butt-welded to form corresponding grooves. Arc-starting and arc-extinguishing plates are added, each 1 to 5 mm thicker than the blunt edge (p) of the groove. If the two pieces of bridge steel (1) to be welded have different thicknesses, the groove design is based on the thickness of the thinner piece.

[0046] After the bridge steel workpieces to be welded are welded, submerged arc welding wire and flux are selected according to the mechanical properties of the bridge steel 1 to be welded and the designed welding heat input E. The diameter of the welding wire is 4.0 to 5.5 mm, and the flux is dried and pre-treated at 350 to 400°C for 2 to 3 hours before welding.

[0047] When the bridge steel plate thickness δ is 25-30 mm, the submerged arc welding method can be a single-wire submerged arc welding method or a double-wire submerged arc welding method. Before welding, the welding current, arc voltage and welding speed V are adjusted. w To set the welding heat input E, the appropriate welding heat input E is 50-80 kJ / cm. When the submerged arc welding method is a single-wire submerged arc welding method, the corresponding settings are welding current 700-1000 A, arc voltage 35-45 V, welding speed V wis 290-335 mm / min, and the dry extension h is set to 35-38 mm. When the submerged arc welding method is a double-wire submerged arc welding method (such as Figure 5 As shown), in the process of adjusting the welding current and arc voltage, it is necessary to first set the current type on the front welding wire 2 and the rear welding wire 3, and then adjust the welding current and arc voltage on the front welding wire 2 and the rear welding wire 3 respectively, and set the inclination angles of the front welding wire 2 and the rear welding wire 3. The current type includes direct current and alternating current. The specific settings are that the front welding wire 2 is powered by direct current, the welding current is 700-950A, the arc voltage is 27-35V, the front welding wire inclination angle β1 is 0-15°, the rear welding wire 3 is powered by alternating current, the welding current is 600-780A, the arc voltage is 32-40V, the rear welding wire inclination angle β2 is 0-30°, and the welding speed V w The speed is 460-550 mm / min, the extension length h is 35-38 mm, and the wire spacing d is set to 25-35 mm. At this time, the double-wire submerged arc welding method is a double-wire eutectic pool submerged arc welding method.

[0048] When the bridge steel plate thickness δ is 30-100 mm, the submerged arc welding method can be a double-wire submerged arc welding method or a three-wire submerged arc welding method. Similarly, before welding, the welding current, arc voltage and welding speed V are adjusted. w To set the welding heat input E, the appropriate welding heat input E is 80 to 165 kJ / cm. When the submerged arc welding method is a double-wire submerged arc welding method (such as Figure 5 As shown), in the process of adjusting the welding current and arc voltage, it is necessary to first set the current type on the front welding wire 2 and the rear welding wire 3, and then adjust the welding current and arc voltage on the front welding wire 2 and the rear welding wire 3 respectively, and set the inclination angles of the front welding wire 2 and the rear welding wire 3. The current type includes direct current and alternating current. The specific settings are that the front welding wire 2 is powered by direct current, the welding current is 900-1600A, the arc voltage is 34-42V, the front welding wire inclination angle β1 is 0-15°, the rear welding wire 3 is powered by alternating current, the welding current is 800-1250A, the arc voltage is 38-45V, the rear welding wire inclination angle β2 is 0-20°, and the welding speed V w The speed is 430-500 mm / min, the stickout length h is 39-45 mm, and the wire spacing d is 30-40 mm. In this case, the double-wire submerged arc welding method is a double-wire eutectic pool submerged arc welding method. When the submerged arc welding method is a three-wire submerged arc welding method, the welding current and arc voltage set for each welding wire are correspondingly reduced, thereby reducing the output power requirement of a single submerged arc welding power source.

[0049] After the high heat input submerged arc welding of the bridge steel begins, the front groove is welded first, then the bridge steel workpiece to be welded is turned over, and then the back groove is welded. Specifically, when the bridge steel plate thickness δ is 25-30mm, first, one layer of filling welding and one layer of cap welding are sequentially performed in the front groove of the bridge steel workpiece to be welded, and the interlayer temperature is controlled between 100-200°C; then the bridge steel workpiece to be welded is turned over, and the back of the groove is carbon planed or machined to a root cleaning depth of 5-10mm; finally, one layer of cap welding is performed at the root cleaning on the back of the groove, completing the high heat input submerged arc welding of the bridge steel 1.

[0050] When the thickness δ of the bridge steel plate is 30-50 mm, first, 0-1 layers of filling welds and 1 layer of cover welds are performed in the front groove of the bridge steel workpiece to be welded; then, the bridge steel workpiece to be welded is turned over, and 0-1 layers of filling welds and 1 layer of cover welds are performed in the back groove of the bridge steel workpiece to be welded. During this process, the interlayer temperature of the groove welds on the same side (i.e., the filling layer welds and cover layer welds of the front groove or the back groove), as well as the front groove cover layer welds and the first layer welds of the back groove (when there is a filling layer weld, the first layer weld is the filling layer weld; when there is no filling layer weld, the first layer weld is the cover layer weld) is controlled to be between 100 and 200°C.

[0051] When the bridge steel plate thickness δ is 50-100mm, the bridge steel workpiece to be welded is first preheated to 100-200°C, and then 1-5 layers of filling welds and 1 layer of cover weld are sequentially performed in the front groove of the bridge steel workpiece to be welded; then the bridge steel workpiece to be welded is turned over, and 1-5 layers of filling welds and 1 layer of cover weld are sequentially performed in the back groove of the bridge steel workpiece to be welded. In this process, the interlayer temperature of the groove welds on the same side (i.e., the filling layer welds and filling layer welds of the front groove or the back groove, and the filling layer welds and cover layer welds of the front groove or the back groove), as well as the front groove cover layer welds and the first layer of filling welds of the back groove are controlled to be between 100-200°C.

[0052] In addition, when the thickness δ of the bridge steel plate is 25-30 mm or 30-50 mm, before performing high heat input submerged arc welding in the front groove of the bridge steel workpiece to be welded, a gas shielded welding method can be used to perform a layer of small welding heat input E of 8-14 kJ / cm in the front groove of the bridge steel workpiece to be welded. The correspondingly set backing welding current is 180-300 A, the arc voltage is 21-32 V, and the welding speed V is 100-150. w It is 285~410mm / min; when the thickness δ of the bridge steel plate is 30~50mm or 50~100mm, after the bridge steel workpiece to be welded is turned over, the back groove of the bridge steel workpiece to be welded can be carbon planed or mechanically processed to clean the root, the root cleaning depth is 2~8mm, and then the back groove of the bridge steel workpiece to be welded can be subjected to high heat input submerged arc welding.

[0053] After welding the bridge steel workpiece, immediately cover it with insulation cotton for slow cooling. Alternatively, heat treatment can be performed at 200-300°C for 1.5-2 hours, followed by covering the weldment with insulation cotton for slow cooling. During the slow cooling process, control the weldment cooling rate between 100-150°C / h.

[0054] The high-heat-input submerged arc welding method, with single-pass, multi-layer welding per layer, efficiently and cost-effectively achieves high-heat-input welding of thick bridge steel plates, resulting in welded joints with excellent low-temperature impact toughness and minimal joint softening. Under the following conditions: bridge steel plate thickness δ of 25 to 100 mm, lower yield strength of 360 to 510 MPa, tensile strength of 510 to 645 MPa, elongation at break of 18 to 27%, yield strength ratio of 0.72 to 0.85, and -40°C impact energy absorption of 300 J or greater, the welded joints exhibit excellent comprehensive mechanical properties after high-heat-input submerged arc welding at a maximum temperature of 165 kJ / cm. These properties include: joint tensile strength of 510 MPa or greater, fracture location within the base metal, 180° lateral bend of the joint meeting requirements, and -40°C impact energy absorption of 65 J or greater at the center of the surface weld and 1 mm beyond the fusion line.

[0055] The following examples illustrate the application of the twin-wire submerged arc welding method of the present invention for different bridge steel plate thicknesses, specifically explaining the parameter selection for the high-heat-input submerged arc welding method for bridge steel. For all examples, the bridge steel 1 to be welded had a lower yield strength of 455 MPa, a tensile strength of 520 MPa, an elongation of 24%, a yield strength ratio of 0.82, and an impact energy absorption of ≥300 J at -40°C. The submerged arc welding wire was JKD-C2NiK-W with a diameter of 5.0 mm, and the flux was JKD-B101q-W.

[0056] Example 1

[0057] Figure 6 The figure shows a macroscopic photograph of the cross section of the weld in the Y-shaped groove of the present invention, where the thickness δ of the bridge steel plate is 30 mm. Before welding, according to expression (1), two pieces of bridge steel 1 to be welded are processed and welded together to form a Y-shaped groove bridge steel workpiece with a groove angle α of 60° and a groove blunt edge p of 10 mm. In addition, an arc starting plate and an arc extinguishing plate with a thickness of 13 mm are spot welded at both ends of the bridge steel workpiece to be welded. Then, a double-wire submerged arc welding method is adopted, and the front welding wire 2 is set to pass direct current, the welding current is 780A, the arc voltage is 29V, the front welding wire inclination angle β1 is 0°, the rear welding wire 3 is set to pass alternating current, the welding current is 690A, the arc voltage is 35V, the rear welding wire inclination angle β2 is 10°, and the welding speed V w The speed is 520mm / min, the dry elongation h is 36mm, and the wire spacing d is 30mm.

[0058] During welding, first perform one layer of filling welding and one layer of cap welding in the front groove of the bridge steel workpiece to be welded, and control the inter-layer temperature at 150℃. Then turn the bridge steel workpiece over and perform a carbon planer to clean the back of the groove to a depth of 8mm. Then perform one layer of cap welding on the back of the groove. Immediately after welding, cover the surface with insulation cotton to keep it warm and cool slowly. During the welding process, the actual welding current and arc voltage on the front welding wire 2 and the rear welding wire 3, as well as the welding speed V w , and the actual welding heat input is 52~57kJ / cm.

[0059] Finally, after the mechanical properties test of the welded joint, the tensile strength of the high heat input submerged arc welded joint was 550MPa, the fracture position was located at the base material, the joint had good 180° side bending and no cracks appeared, and the -40°C impact absorption energy at the center of the joint surface weld and 1mm outside the fusion line was ≥167J. All performance data met the requirements of the "QCR9211-2015 Railway Steel Bridge Manufacturing Specifications".

[0060] Example 2

[0061] Figure 7 This is a macroscopic photograph of the cross section of the weld with a blunt-edge symmetrical double-sided V-shaped groove according to the present invention. At this time, the thickness δ of the bridge steel plate is 30 mm. Before welding, according to expression (2), two pieces of bridge steel 1 to be welded are processed and assembled and welded into a bridge steel workpiece to be welded with a blunt-edge symmetrical double-sided V-shaped groove having a groove angle α of 90° and a groove blunt edge p of 10 mm. In addition, an arc starting plate and an arc extinguishing plate with a thickness of 13 mm are fixed at both ends of the bridge steel workpiece to be welded. Then, a double-wire submerged arc welding method is adopted, and it is set that the front welding wire 2 is passed through direct current, the welding current is 970A, the arc voltage is 37V, the front welding wire inclination angle β1 is 5°, the rear welding wire 3 is passed through alternating current, the welding current is 920A, the arc voltage is 41V, the rear welding wire inclination angle β2 is 15°, and the welding speed V w The speed is 450mm / min, the dry elongation h is 40mm, and the wire spacing d is 35mm.

[0062] During welding, a layer of 10kJ / cm2 low welding heat input E-base welding is first performed in the front groove of the bridge steel workpiece to be welded using the metallurgical electrode gas shielding method. Then, a layer of cover welding is performed in the front groove of the bridge steel workpiece to be welded. Then, the bridge steel workpiece to be welded is turned over and another layer of cover welding is performed in its reverse groove. During the process, the interlayer temperature is controlled at 150°C. At the same time, the actual welding current and arc voltage on the front welding wire 2 and the rear welding wire 3, as well as the welding speed V w The actual welding heat input is 95-102 kJ / cm; immediately after welding, the surface is covered with insulation cotton for insulation and slow cooling.

[0063] Finally, after the mechanical properties test of the welded joint, the tensile strength of the high heat input submerged arc welded joint was 542MPa, the fracture position was located at the base material, the joint had good 180° side bending and no cracks appeared, and the -40°C impact absorption energy at the center of the joint surface weld and 1mm outside the fusion line was ≥143J. All performance data met the requirements of the "QCR9211-2015 Railway Steel Bridge Manufacturing Specifications".

[0064] Example 3

[0065] Figure 8 This is a macroscopic photograph of the cross section of the weld in the case of a double-sided symmetrical U-shaped groove according to the present invention. At this time, the thickness δ of the bridge steel plate is 50 mm. Before welding, according to expression (three), the two pieces of bridge steel 1 to be welded are processed and welded together to form a double-sided symmetrical U-shaped groove bridge steel workpiece with a groove angle α of 46° and a groove blunt edge p of 16 mm. In addition, an arc starting plate and an arc extinguishing plate with a thickness of 20 mm are fixed at both ends of the bridge steel workpiece to be welded. Then, a double-wire submerged arc welding method is adopted, and it is set that the front welding wire 2 is passed through direct current, the welding current is 1400A, the arc voltage is 40V, the front welding wire inclination angle β1 is 5°, the rear welding wire 3 is passed through alternating current, the welding current is 1100A, the arc voltage is 42V, the rear welding wire inclination angle β2 is 20°, and the welding speed V w The speed is 430mm / min, the dry elongation h is 43mm, and the wire spacing d is 38mm.

[0066] Before welding begins, the bridge steel workpiece is preheated to 150°C. Then, one layer of filling weld and one layer of cap weld are performed in sequence on the front groove of the bridge steel workpiece. Then, the bridge steel workpiece is turned over and one layer of filling weld and one layer of cap weld are performed in sequence on the back groove of the bridge steel workpiece. During the welding process, the interpass temperature is controlled at 150°C. At the same time, the actual welding current and arc voltage on the front welding wire 2 and the rear welding wire 3, as well as the welding speed V w The actual welding heat input is 143-152 kJ / cm. After welding, the weldment is first subjected to post-heat treatment at 200-300°C for 1.5-2 hours, and then covered with insulation cotton to keep it warm and cool slowly.

[0067] Finally, after the mechanical properties test of the welded joint, the tensile strength of the high heat input submerged arc welded joint was 533MPa, the fracture position was located at the base material, the joint had good 180° side bending and no cracks appeared, and the -40°C impact absorption energy at the center of the joint surface weld and 1mm outside the fusion line was ≥76J. All performance data met the requirements of the "QCR9211-2015 Railway Steel Bridge Manufacturing Specifications".

[0068] It can be seen from the above embodiments that under different conditions of the thickness of the bridge steel plates to be welded, by designing the welding groove design and matching the setting of the welding heat input, the high heat input submerged arc weld of the thick bridge steel plate of the present invention is well formed, and the various mechanical properties data of the joint meet the requirements of industry specifications, indicating that the high heat input submerged arc welding method described in the present invention has good engineering practicality.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high heat input submerged arc welding method for thick bridge steel plates, wherein the applicable bridge steel plate thickness (δ) is 25 to 100 mm, the lower yield strength is 360 to 510 MPa, the tensile strength is 510 to 645 MPa, the elongation after fracture is 18 to 27%, the yield strength ratio is 0.72 to 0.85, the impact absorption energy at -40°C is ≥ 300 J, and the welding heat input (E) is 50 to 165 kJ / cm, characterized in that: The specific steps include: Step ①, welding groove design and welding heat input setting: When the bridge steel plate thickness (δ) is 25-30 mm, the designed welding groove form is Y-shaped, the groove angle (α) is 60-85°, and the groove blunt edge (p) is 10-13 mm. By adjusting the welding current, arc voltage and welding speed (V w ) sets the welding heat input (E) to 50-80 kJ / cm; when the bridge steel plate thickness (δ) is 30-50 mm, the designed welding groove is a double-sided V-shaped with blunt edges, the groove angle (α) is 45-100°, and the groove blunt edge (p) is 10-15 mm. By adjusting the welding current, arc voltage and welding speed (V w ) sets the welding heat input (E) to 80-120 kJ / cm; when the bridge steel plate thickness (δ) is 50-100 mm, the designed welding groove is a double-sided U-shaped, the groove angle (α) is 40-52°, the groove blunt edge (p) is 16-20 mm, and the groove root radius (R) is 5-8 mm. By adjusting the welding current, arc voltage and welding speed (V w ) Set the welding heat input (E) to 120-165 kJ / cm; Step 2: Welding material selection and pretreatment: Based on the mechanical properties of the bridge steel and the set welding heat input (E), submerged arc welding wire and flux are selected. The welding wire diameter is 4.0-5.5 mm. The flux is dried at 350-400°C for 2-3 hours before welding. Step ③, single-pass multi-layer submerged arc welding per layer: When the thickness (δ) of the bridge steel plate is 25-30 mm, first, one layer of filling welding and one layer of capping welding are sequentially performed in the front groove of the bridge steel workpiece to be welded, and the interlayer temperature of the weld is controlled between 100 and 200°C. Then, the bridge steel workpiece to be welded is turned over, and the back side of the groove is carbon planed or machined to a root cleaning depth of 5-10 mm. Finally, one layer of capping welding is performed at the root cleaning on the back side of the groove. When the thickness (δ) of the bridge steel plate is 30-50 mm, 0-1 layers of filling welding and 1 layer of cover welding are first performed in the front groove of the bridge steel workpiece to be welded, and then the bridge steel workpiece to be welded is turned over, and 0-1 layers of filling welding and 1 layer of cover welding are performed in the back groove thereof. During this process, the interlayer temperature of the groove weld on the same side, the front groove cover layer weld, and the first layer weld of the back groove is controlled to be between 100° C. and 200° C.; When the thickness (δ) of the bridge steel plate is 50-100 mm, the bridge steel workpiece to be welded is first preheated to 100-200° C., and then 1-5 layers of filling welding and 1 layer of cover welding are sequentially performed in the front groove. Then, the bridge steel workpiece to be welded is turned over, and 1-5 layers of filling welding and 1 layer of cover welding are sequentially performed in the back groove. During this process, the interlayer temperature of the groove weld on the same side, the front groove cover layer weld, and the first layer weld of the back groove is controlled between 100-200° C. Step ④, post-weld treatment of weldment: After the welding of the bridge steel workpiece is completed, immediately cover the surface of the weldment with insulation cotton to keep it warm and cool slowly, and control the cooling rate of the weldment between 100 and 150℃ / h.

2. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1, characterized in that: When the welding heat input (E) is 50-80 kJ / cm, the submerged arc welding method is a single-wire submerged arc welding method or a double-wire submerged arc welding method; when the single-wire submerged arc welding method is adopted, the welding current is adjusted to 700-1000 A, the arc voltage is adjusted to 35-45 V, and the welding speed (V w ) is 290~335mm / min, and the dry extension length (h) is also set to 35~38mm; when the double-wire submerged arc welding method is adopted, when adjusting the welding current and arc voltage in step ①, it is necessary to first set the current type on the front welding wire (2) and the rear welding wire (3), and then adjust the welding current and arc voltage on the front welding wire (2) and the rear welding wire (3), as well as the respective inclination angles of the front welding wire (2) and the rear welding wire (3), wherein the front welding wire (2) is supplied with direct current, the welding current is 700~950A, the arc voltage is 27~35V, the front welding wire inclination angle (β1) is 0~15°, the rear welding wire (3) is supplied with alternating current, the welding current is 600~780A, the arc voltage is 32~40V, the rear welding wire inclination angle (β2) is 0~30°, and the welding speed (V w ) is 460~550mm / min, and the dry extension (h) is set to 35~38mm and the wire spacing (d) is set to 25~35mm.

3. The high heat input submerged arc welding method for thick bridge steel plates according to claim 1, wherein: When the welding heat input (E) is greater than 80 kJ / cm, the submerged arc welding method is a double-wire submerged arc welding method. When adjusting the welding current and arc voltage in step ①, it is necessary to first set the current type on the front welding wire (2) and the rear welding wire (3), and then adjust the welding current and arc voltage on the front welding wire (2) and the rear welding wire (3), as well as the respective inclination angles of the front welding wire (2) and the rear welding wire (3), wherein the front welding wire (2) is supplied with direct current, the welding current is 900-1600A, the arc voltage is 34-42V, and the front welding wire inclination angle (β1) is 0-15°; the rear welding wire (3) is supplied with alternating current, the welding current is 800-1250A, the arc voltage is 38-45V, the rear welding wire inclination angle (β2) is 0-20°, and the welding speed (V w ) is 430~500mm / min, and the dry extension (h) is set to 39~45mm and the wire spacing (d) is set to 30~40mm.

4. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1, characterized in that: In step ①, when the welding groove is Y-shaped, follow To design the groove angle (α); when the welding groove form is a double-sided V-shaped groove with blunt edges, the double-sided V-shaped groove with blunt edges is a symmetrical double-sided V-shaped groove with blunt edges, and according to To design the groove angle (α); when the welding groove is a double-sided U-shaped, the double-sided U-shaped is a symmetrical double-sided U-shaped, and according to To design the groove angle (α).

5. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1, characterized in that: In step ③, when the thickness (δ) of the bridge steel plate is 25-30 mm or 30-50 mm, before performing high heat input submerged arc welding in the front groove of the bridge steel workpiece to be welded, a gas shielded welding method is first used to perform a layer of small welding heat input of 8-14 kJ / cm in the front groove of the bridge steel workpiece to be welded. The correspondingly set backing welding current is 180-300 A, the arc voltage is 21-32 V, and the welding speed (V w ) is 285~410mm / min; when the thickness of the bridge steel plate (δ) is 30~50mm or 50~100mm, after the bridge steel workpiece to be welded is turned over, the back groove of the bridge steel workpiece to be welded is first carbon planed or mechanically cleaned to a depth of 2~8mm, and then high heat input submerged arc welding is performed at the back groove root cleaning.

6. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1, characterized in that: In step ④, after the bridge steel workpiece is welded, it is first subjected to a post-heat treatment at 200-300°C for 1.5-2h, and then insulation cotton is laid on the surface of the weldment for insulation and slow cooling.

7. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1 or 2, characterized in that: When the bridge steel plate thickness (δ) is 30 mm, the designed welding groove is Y-shaped, the groove angle (α) is 60°, the groove blunt edge (p) is 10 mm, and a double-wire submerged arc welding method is adopted. The front welding wire (2) is set to pass direct current, the welding current is 780A, the arc voltage is 29V, the front welding wire inclination angle (β1) is 0°, the rear welding wire (3) is set to pass alternating current, the welding current is 690A, the arc voltage is 35V, the rear welding wire inclination angle (β2) is 10°, and the welding speed (V w ) is 520mm / min, the dry extension length (h) is 36mm, and the wire spacing (d) is 30mm; during welding, firstly, one layer of filling welding and one layer of cover welding are sequentially performed in the front groove of the bridge steel workpiece to be welded, and the interlayer temperature is controlled to be 150℃, then the bridge steel workpiece to be welded is turned over and the back side of the groove is carbon planed and the root cleaning depth is 8mm, then one layer of cover welding is performed at the root cleaning of the back side of the groove, and at the same time, the actual welding current and arc voltage on the front welding wire (2) and the rear welding wire (3), as well as the welding speed (V w ), the actual welding heat input (E) is 52-57 kJ / cm. Immediately after welding, the surface of the weldment is covered with insulation cotton for heat preservation and slow cooling; The obtained high heat input submerged arc welded joint has a tensile strength of 550MPa, a fracture position located at the base material, no cracks at 180° side bending, and an impact absorption energy of -40°C ≥167J at the center of the surface weld and 1mm outside the fusion line.

8. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1 or 3, characterized in that: When the thickness (δ) of the bridge steel plate is 30 mm, the designed welding groove is a symmetrical double-sided V-shaped groove with a blunt edge, the groove angle (α) is 90°, the groove blunt edge (p) is 10 mm, and a double-wire submerged arc welding method is adopted. The front welding wire (2) is set to be DC, the welding current is 970A, the arc voltage is 37V, the front welding wire inclination angle (β1) is 5°, the rear welding wire (3) is set to be AC, the welding current is 920A, the arc voltage is 41V, the rear welding wire inclination angle (β2) is 15°, and the welding speed (V w ) is 450mm / min, the dry extension length (h) is 40mm, and the wire spacing (d) is 35mm; during welding, a layer of 10kJ / cm small welding heat input (E) base welding is first performed in the front groove of the bridge steel workpiece to be welded using the consumable electrode gas shielding method, and then a layer of cover welding is performed in the front groove of the bridge steel workpiece to be welded, and then the bridge steel workpiece to be welded is turned over and another layer of cover welding is performed in its reverse groove. During the process, the interlayer temperature is controlled to be 150℃, and at the same time, the actual welding current and arc voltage on the front welding wire (2) and the rear welding wire (3), as well as the welding speed (V w ), the actual welding heat input (E) is 95-102 kJ / cm. Immediately after welding, the surface of the weldment is covered with insulation cotton for insulation and slow cooling; The obtained high heat input submerged arc welded joint has a tensile strength of 542MPa, a fracture position located at the base material, no cracks at 180° side bending, and an impact absorption energy of -40°C ≥143J at the center of the surface weld and 1mm outside the fusion line.

9. A high heat input submerged arc welding method for thick bridge steel plates as claimed in claim 1 or 3, characterized in that: When the thickness (δ) of the bridge steel plate is 50 mm, the designed welding groove is a symmetrical double-sided U-shaped groove, the groove angle (α) is 46°, the groove blunt edge (p) is 16 mm, and the groove root radius (R) is 6 mm. The double-wire submerged arc welding method is adopted, and the front welding wire (2) is set to pass direct current, the welding current is 1400 A, the arc voltage is 40 V, and the front welding wire inclination angle (β1) is 5°. The rear welding wire (3) is set to pass alternating current, the welding current is 1100 A, the arc voltage is 42 V, and the rear welding wire inclination angle (β2) is 20°. The welding speed (V w ) is 430mm / min, the dry extension length (h) is 43mm, and the wire spacing (d) is 38mm; before the start of welding, the bridge steel workpiece to be welded is preheated to 150℃, and then one layer of filling welding and one layer of cover welding are carried out in sequence in the front groove of the bridge steel workpiece to be welded, and then the bridge steel workpiece to be welded is turned over and one layer of filling welding and one layer of cover welding are carried out in sequence in the reverse groove. During the welding process, the interlayer temperature is controlled to be 150℃, and the actual welding current and arc voltage on the front welding wire (2) and the rear welding wire (3), as well as the welding speed (V w ), the actual welding heat input (E) is 143-152 kJ / cm; after welding, the weldment is first subjected to post-heat treatment at 200-300°C for 1.5-2 hours, and then the weldment surface is covered with insulation cotton for insulation and slow cooling; The obtained high heat input submerged arc welded joint has a tensile strength of 533MPa, a fracture position located at the base material, no cracks at 180° side bending, and an impact absorption energy of -40°C ≥76J at the center of the surface weld and 1mm outside the fusion line.

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