Plateau on-site welding method for high-strength bridge steel and welding material used in plateau on-site welding method

Abstract

The invention discloses a plateau field welding method for high-strength bridge steel, which comprises the following steps: taking carbon dioxide as a protective gas, and adopting a solid welding wire with the following components in continuous backing weld, filling weld and cosmetic weld: C is more than 0.02% and less than 0.04%, Mn is more than 1.10% and less than 1.30%, Si is more than or equal to 0.2% and less than or equal to 0.40%, Cr is more than 0.50% and less than 0.60%, Ni is more than 0.40% and less than 0.50%, Cu is more than 0.30% and less than 0.40%, Mo is more than 0.05% and less than 0.20%, P is less than or equal to 0.01%, S is less than or equal to 0.005%, and V is less than or equal to 0.04%. The balance is Fe and inevitable impurities; the welding parameters are set as follows: the welding voltage is larger than or equal to 26 V and smaller than or equal to 28 V, the welding current is larger than or equal to 260 A and smaller than or equal to 280 A, the welding speed is larger than or equal to 25 cm / min and smaller than 30 cm / min, the welding heat input is larger than or equal to 12 kJ / cm and smaller than or equal to 15 kJ / cm, and the shielding gas flow is larger than or equal to 15 L / min and smaller than or equal to 20 L / min. According to the method, the construction cost of the high-strength railway bridge is greatly reduced, and the performance of the welding seam obtained through welding is well matched with that of high-strength base metal.

Description

Technical Field

[0001] This invention belongs to the field of metal processing technology, specifically relating to a welding method, and more particularly to a high-strength bridge steel high-altitude field welding method and the welding materials used in this method. Background Technology

[0002] In high-altitude regions, such as the Qinghai-Tibet Plateau, due to the fragile ecological environment and the presence of permafrost and seasonal permafrost, railways often utilize viaducts. High-strength weathering steel of the 500MPa grade, with a tensile strength exceeding 630MPa, a yield strength exceeding 500MPa, and an elongation after fracture of not less than 18%, is an advanced high-strength steel material for railway bridges. Its excellent performance could play a crucial role in constructing long-span bridges in plateau regions; however, welding issues have become a major obstacle to its application. The primary reason is that the weld performance under ordinary welding materials and processes is difficult to match with the high-strength bridge steel base material.

[0003] To address the aforementioned technical problems, the inventors developed a new formula for solid welding wire and a welding process for high-strength weathering steel used in railway bridges using this solid welding wire, as described in the published Chinese invention patent application "A Welding Material and a Welding Method for High-Strength Weathering Steel for Railway Bridges" (Publication No. CN119216723A, Publication Date December 31, 2024). Through strict process control, the weld performance was matched with the base material, effectively solving the welding problem of high-strength weathering steel. This welding process uses 80% argon + 20% carbon dioxide as the welding shielding gas. Industrial high-purity argon is generally prepared using air separation or metal smelting tail gas recovery methods and transported in high-pressure liquid form using cryogenic tank trucks. In 2024-2025, the ex-factory price of liquid argon in the Chinese market was approximately RMB 1000-3000 / ton, while the cost of long-distance inter-provincial transportation could reach RMB 0.8-1.2 / ton·km. my country's high-altitude regions are far from industrial argon production areas, and the transportation distance of thousands of kilometers significantly increases the cost of welding methods using high-purity argon as the primary shielding gas (such as the method described in CN119216723A). Therefore, it is necessary to improve existing high-strength steel welding processes and develop a low-cost welding method applicable in high-cost environments (such as high-altitude railway bridge construction sites), along with new welding materials suitable for this method. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a high-strength bridge steel welding method for high-altitude field applications and the welding materials used in this method. Compared to the method in CN119216723A, the welding method of this invention significantly reduces costs. Furthermore, when welding 500MPa grade high-strength weathering steel using this method, the weld metal exhibits a tensile strength exceeding 630MPa and a yield strength exceeding 550MPa, while the weld joint achieves a tensile strength exceeding 630MPa and a yield strength exceeding 520MPa. The weld's yield strength and tensile strength both surpass the performance standards of the base material, achieving a good match with the base material's properties and laying the foundation for the long-term stable service of the welded joint. In addition, the weld exhibits excellent low-temperature impact resistance and corrosion resistance, fully meeting the requirements for long-term service of railway bridges at high altitudes.

[0005] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0006] A high-strength bridge steel field welding method for high-altitude areas, using carbon dioxide as the shielding gas, includes the following welding process parameters:

[0007] 1) Solid welding wire with the following composition is used in continuous root pass, fill pass, and cover pass welding:

[0008] C: 0.02% < C < 0.04%,

[0009] Mn: 1.10%<Mn<1.30%,

[0010] Si: 0.2% ≤ Si ≤ 0.40%,

[0011] Cr: 0.50%<Cr<0.60%,

[0012] Ni: 0.40%<Ni<0.50%,

[0013] Cu: 0.30%<Cu<0.40%,

[0014] Mo: 0.05%<Mo<0.20%, and

[0015] P≤0.01%, S≤0.005%, V≤0.04%, balance being Fe and unavoidable impurities;

[0016] 2) Setting welding parameters

[0017] Welding voltage ≤ 26V ≤ 28V

[0018] Welding current ≤ 260A ≤ 280A

[0019] 25cm / min ≤ welding speed < 30cm / min

[0020] 12kJ / cm≤welding heat input≤15kJ / cm, and

[0021] 15L / min ≤ Protective gas flow rate ≤ 20L / min;

[0022] 3) Setting temperature parameters

[0023] (1) Preheating parameters of the base material

[0024] For steel plates with a thickness ≤32mm, no preheating is required; for steel plates with a thickness ≤60mm and a thickness between 32mm and 60mm, preheating is required to 100-120℃.

[0025] (2) Inter-track temperature control

[0026] When the temperature of each weld seam is ≤150℃, proceed with the welding of the next weld seam.

[0027] Preferably, when the steel plate thickness is 32mm < 60mm, the base material within 100mm of the weld is preheated to 100℃~110℃.

[0028] Preferably, the weld temperature is measured using an infrared thermometer.

[0029] Preferably, the welding process parameters further include:

[0030] 4) Beveling form of the base material

[0031] The steel plate thickness is ≤16mm, and a single V-shaped bevel is used. The bevel angle between the two steel plates is 60°, and a 2mm blunt edge is left.

[0032] For steel plates with a thickness of 16mm < 32mm, a double V-shaped bevel is used, with the bevels of the two steel plates at an angle of 60°, leaving a 2mm blunt edge.

[0033] For steel plates with a thickness of 32mm < 60mm, a double U-shaped bevel is used, with a 2mm blunt edge.

[0034] Preferably, the welding parameters can be adjusted according to the thickness of the steel plate to be welded as follows:

[0035] (1) For steel plate thickness ≤ 16mm, the welding parameters for root pass, fill pass and cover pass remain unchanged, including: 26V≤ welding voltage < 27V, 260A≤ welding current < 270A, 25cm / min≤ welding speed < 30cm / min, 12kJ / cm≤ welding heat input ≤ 15kJ / cm, 15L / min≤ shielding gas flow rate ≤ 20L / min;

[0036] (2) 16mm < steel plate thickness ≤ 60mm, the welding parameters for root pass and cover pass are set as follows: 26V ≤ welding voltage < 27V, 260A ≤ welding current < 270A, 25cm / min ≤ welding speed < 30cm / min, 12kJ / cm ≤ welding heat input ≤ 15kJ / cm, 15L / min ≤ shielding gas flow rate ≤ 20L / min; the welding parameters for fill pass are set as follows: 27V ≤ welding voltage ≤ 28V, 270A ≤ welding current ≤ 280A, 25cm / min ≤ welding speed < 30cm / min, 12kJ / cm ≤ welding heat input ≤ 15kJ / cm, 15L / min ≤ shielding gas flow rate ≤ 20L / min.

[0037] As a preferred embodiment, the present invention provides a high-altitude field welding method for high-strength bridge steel with a thickness ≤16mm, using carbon dioxide as the shielding gas and employing the aforementioned solid welding wire, comprising the following specific process steps:

[0038] I. The butt joint adopts a single V-shaped bevel, with the bevel angle between the two steel plates being 60°, leaving a 2mm blunt edge, and removing the floating rust within 30mm of the weld to expose the metallic luster;

[0039] II. Adjusting welding process parameters

[0040] 26V≤Welding voltage<27V, 260A≤Welding current<270A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min;

[0041] III. Using the solid welding wire described in this invention, after completing the first pass with the parameters adjusted in step II, clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and proceed with the next weld when the weld temperature is ≤150℃.

[0042] IV. Repeat step III to continuously complete the root pass, fill pass, and cover pass welding until the weld is 0-2 mm above the base material surface, and allow it to cool naturally.

[0043] As another preferred embodiment, the present invention provides a high-altitude field welding method for high-strength bridge steel with a thickness of 16mm < ≤ 60mm, using carbon dioxide as the shielding gas and employing the aforementioned solid welding wire, comprising the following specific process steps:

[0044] (i) Based on the thickness of the steel plate to be welded, bevel the butt joint, remove the loose rust within 30mm of the weld, and expose the metallic luster; wherein:

[0045] For steel plates with a thickness of 16mm < 32mm, a double V-shaped bevel is used, with the bevels of the two steel plates at an angle of 60°, leaving a 2mm blunt edge.

[0046] For steel plates with a thickness of 32mm < 60mm, a double U-shaped bevel is used, with a 2mm blunt edge left.

[0047] (ii) Preheating of base material

[0048] For steel plate thicknesses between 16mm and 32mm, no preheating is required; for steel plate thicknesses between 32mm and 60mm, preheat the steel plate within a 100mm radius of the weld to 100℃~110℃.

[0049] (iii) Root pass welding

[0050] (iii)-1. Adjust welding process parameters

[0051] 26V≤Welding voltage<27V, 260A≤Welding current<270A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min;

[0052] (iii)-2. Using the solid welding wire described in this invention, after completing the first pass under the parameters adjusted in step (iii)-1, clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and proceed with the next weld when the weld temperature is ≤150℃.

[0053] (iii)-3. Repeat step (iii)-2 until the root pass is completed;

[0054] (iv) Filler weld

[0055] (iv)-1 Adjust welding process parameters

[0056] 27V≤Welding voltage≤28V, 270A≤Welding current≤280A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min;

[0057] (iv)-2 When the temperature of the last weld after step (iii) is ≤150℃, weld the first pass of the filler weld under the welding parameters adjusted in step (iv)-1, clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and when the weld temperature is ≤150℃, proceed to the next weld.

[0058] (iv)-3 Repeat step (iv)-2 until the filler weld is complete;

[0059] (v) Cover weld

[0060] (v)-1 Adjust welding process parameters

[0061] 26V≤Welding voltage<27V, 260A≤Welding current<270A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min;

[0062] (v)-2 The temperature of the last weld after step (iv) is ≤150℃. After the first weld of the cover weld is completed under the parameters adjusted in step (v)-1, proceed to the next weld.

[0063] (v)-3 Repeat step (v)-2 until the weld is 0-2 mm above the surface of the base material, and allow it to cool naturally.

[0064] The number of weld passes for the root pass, fill pass, and cover pass is conventional and can be easily determined by those skilled in the art based on the actual situation.

[0065] In this specification, "using carbon dioxide as the shielding gas" means that the shielding gas used during welding is pure (100%) carbon dioxide, and does not contain any other inert or non-inert gases except for unavoidable impurities.

[0066] This invention also provides a welding material for the high-altitude field welding method of the aforementioned high-strength bridge steel, wherein the welding material is a solid welding wire with a copper-plated surface; based on the total mass of the solid welding wire, the composition of the solid welding wire is as follows:

[0067] C: 0.02% < C < 0.04%,

[0068] Mn: 1.10%<Mn<1.30%,

[0069] Si: 0.2% ≤ Si < 0.45%,

[0070] Cr: 0.50%<Cr<0.60%,

[0071] Ni: 0.40%<Ni<0.50%,

[0072] Cu: 0.30%<Cu<0.40%,

[0073] Mo: 0.05%<Mo<0.20%, and

[0074] P≤0.01%, S≤0.005%, V≤0.04%, with the balance being Fe and unavoidable impurities.

[0075] Preferably, based on the total mass of the solid welding wire, the composition of the solid welding wire is as follows:

[0076] C: 0.03% ≤ C < 0.04%,

[0077] Mn: 1.15%≤Mn<1.30%,

[0078] Si: 0.3% ≤ Si ≤ 0.40%,

[0079] Cr: 0.50%<Cr<0.60%,

[0080] Ni: 0.40%<Ni<0.50%,

[0081] Cu: 0.30%<Cu<0.40%,

[0082] Mo: 0.10% ≤ Mo < 0.20%, and

[0083] P≤0.01%, S≤0.005%, V≤0.04%, with the balance being Fe and unavoidable impurities.

[0084] More preferably, based on the total mass of the solid welding wire, the composition of the solid welding wire is as follows:

[0085] C: 0.03% ≤ C < 0.04%,

[0086] Mn: 1.15%≤Mn≤1.20%,

[0087] Si: 0.35%≤Si≤0.40%,

[0088] Cr: 0.55%≤Cr<0.60%,

[0089] Ni: 0.40%<Ni<0.50%,

[0090] Cu: 0.35%≤Cu<0.40%,

[0091] Mo: 0.10% ≤ Mo ≤ 0.15%, and

[0092] P≤0.01%, S≤0.005%, V≤0.04%, with the balance being Fe and unavoidable impurities.

[0093] Preferably, based on the total mass of the solid welding wire, the sum of the mass percentages M of the three elements Cr, Ni, and Cu is in the range of 1.20% ≤ M < 1.50%.

[0094] Preferably, the atmospheric corrosion resistance index I of the solid welding wire, calculated according to its chemical composition, is 6.5% to 7.2%; wherein the atmospheric corrosion resistance index I is calculated using formula (1):

[0095] I=26.01×(%Cu)+3.88×(%Ni)+1.20×(%Cr)+1.49×(%Si)+17.28×(%P)-7.29×(%Cu)×(%Ni)-9.10×(%Ni)×(%P)-33.39×(%Cu)2 (1).

[0096] In the above formula (1), (% element) is the mass percentage of the element in the solid welding wire.

[0097] Preferably, the cross-sectional diameter of the solid welding wire is 1.2 mm.

[0098] The solid welding wire of the present invention is prepared by conventional methods in the art, and the main processes include: melting, casting, forging, rolling, wire rod pretreatment, wire drawing, copper plating, etc.

[0099] In this specification, unless otherwise expressly specified, a numerical range expressed in terms of two endpoints, such as preheating the steel plate to 100℃~120℃, includes both endpoints; that is, the range of the preheating temperature T of the steel plate is 100℃≤T≤120℃.

[0100] Unless otherwise specified in this specification, "high-strength bridge steel" can be used interchangeably with "500MPa grade high-strength weathering steel for railway bridges". Both refer to high-strength weathering steel with a tensile strength of 630MPa or above, a yield strength of 500MPa or above, and an elongation after fracture of not less than 18%.

[0101] Those skilled in the art will readily understand that the welding method described in this invention can be used not only for on-site welding of high-strength bridge steel in high-altitude areas, but also for on-site and / or on-site welding of high-strength bridge steel in high-altitude areas, as well as in non-high-altitude areas (such as plains).

[0102] The ex-factory price of industrial-grade carbon dioxide is generally between 200 and 400 yuan per ton; compared with high-purity argon, carbon dioxide has a significant cost advantage. However, carbon dioxide is more chemically reactive than argon, which can adversely affect weld performance. The welding method provided in this application, by controlling welding parameters and designing the chemical composition of welding materials, successfully achieved on-site welding of high-strength bridge steel using 100% carbon dioxide as the shielding gas, breaking through the technical bottleneck of high-strength weathering steel welding. The weld metal obtained by the welding method of this application has a tensile strength of over 630 MPa and a yield strength of over 550 MPa; the corresponding welded joint has a tensile strength of over 630 MPa and a yield strength of over 520 MPa. The weld metal and welded joint exhibit superior performance to the base metal in terms of yield strength and tensile strength, achieving a good match with the base metal performance and laying the foundation for the long-term stable service of the welded joint. The impact energy absorbed by the weld at -40℃ reaches over 100 J (KV2). Simultaneously, the impact energy absorbed at -60℃ reaches over 54 J (KV2). It is evident that the weld obtained by the welding method of this application has excellent resistance to low-temperature impact, which is of great significance for ensuring the safety of railway bridge steel structures under low-temperature environment conditions.

[0103] High-strength weathering steel for 500MPa grade railway bridges has an atmospheric corrosion resistance index (I) of 6.5. The composition of the weld is determined by both the welding material and the fused portion of the base metal. The melting of the base metal is primarily influenced by the welding process. Therefore, the corrosion resistance of the weld is a result of the combined effects of the welding material and the welding process. The weld welded using the method of this invention has an atmospheric corrosion resistance index (I) of 6.9, a 6% improvement over the base metal. Compared to the corrosion resistance of the base metal, this method appropriately enhances the corrosion resistance of the weld while achieving a reasonable match with the base metal's properties, resulting in the optimal effect of comparable corrosion resistance between the weld and the base metal. Attached Figure Description

[0104] The present invention will now be further described with reference to the accompanying drawings.

[0105] Figure 1 This is a schematic diagram of the bevel and weld of the two steel plates welded in Example 4. The steel plate thickness is 16mm, the bevel is V-shaped, and the included angle between the bevels of the two steel plates is 60°.

[0106] Figure 2 This is a schematic diagram of the bevel and weld of the two steel plates to be welded in Example 5. The steel plate thickness is 60mm, and the bevel is a double U-shape.

[0107] Figure 3 This is a schematic diagram of the bevel and weld of the steel plate to be welded in Example 6. The bevel is a double V-shape, the steel plate thickness is 32mm, and the included angle between the bevels of the two steel plates is 60°.

[0108] Figures 1-3 In the attached figures, the meanings of the reference numerals are as follows:

[0109] 10: Welded steel plate, 20: Weld seam, 30: Blunt edge. Detailed Implementation

[0110] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0111] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products.

[0112] Examples 1-3: A solid welding wire

[0113] The chemical compositions of the solid welding wires in Examples 1-3 are shown in Table 1:

[0114] Table 1. Chemical composition of solid welding wires in Examples 1-3

[0115] Example 1 Example 2 Example 3 C(％) 0.030 0.035 0.038 Mn(%) 1.20 1.18 1.15 Si (%) 0.39 0.37 0.36 Cr(％) 0.57 0.55 0.56 Ni (%) 0.46 0.44 0.43 Cu (%) 0.36 0.37 0.35 Mo (%) 0.13 0.15 0.14 V(％) 0.004 0.004 0.004 P(％) 0.005 0.005 0.005 S(％) 0.003 0.003 0.003 Fe (%) margin margin margin

[0116] Prepared by the following method:

[0117] (1) Smelting: Steel is smelted in an electric furnace according to the designed composition;

[0118] (2) Casting ingots: The molten steel is poured into steel ingots;

[0119] (3) Forging: Forging the cast steel ingot;

[0120] (4) Rolling: The forged steel billet is rolled to form a steel wire rod with a cross-sectional diameter of 8mm;

[0121] (5) Wire rod pretreatment: Remove the oxide scale from the steel wire rod and clean it;

[0122] (6) Wire drawing: The wire drawing process is carried out on an automated production line to form a solid welding wire with a cross-sectional diameter of 1.2mm;

[0123] (7) Copper plating: Copper plating is performed on the welding wire in an automated production line;

[0124] (8) Packaging: The finished welding wire is wound and packaged on an automated production line.

[0125] Example 4 Welding of a high-strength bridge steel

[0126] This embodiment describes a method for welding a parallel butt joint of high-strength weathering steel for 500MPa grade railway bridges. The steel plate thickness is 16mm, and the solid welding wire from Embodiment 2 is used. Carbon dioxide is used as the shielding gas, and gas-shielded welding is performed according to the following process and steps:

[0127] I. Press the steel plate butt joint according to... Figure 1 The cut is a single V-groove, with the angle between the grooves of the two steel plates being 60°, leaving a 2mm blunt edge, and the groove depth is 14mm. Remove the loose rust within 30mm of the weld to expose the metallic luster.

[0128] II. Adjust welding parameters:

[0129] Welding voltage 26V; welding current 260A; welding heat input 14kJ / cm; shielding gas flow rate 18L / min; welding speed controlled at 28cm / min.

[0130] III. Without preheating the base material, directly use the solid welding wire of Example 2 and complete the first weld according to the welding machine process parameters adjusted in step II; clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and proceed with the next weld when the weld temperature is ≤150℃.

[0131] IV. Repeat step III until the weld is 0-2 mm above the surface of the base material, then allow it to cool naturally.

[0132] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 2.

[0133] Example 5 Welding of a high-strength bridge steel

[0134] This embodiment describes a method for welding a parallel butt joint of high-strength weathering steel for railway bridges with a strength of 500MPa. The steel plate thickness is 60mm. Solid welding wire from Embodiment 1 is used, with carbon dioxide as the shielding gas. Gas-shielded welding is performed according to the following process and steps:

[0135] I. Press the steel plate butt joint according to... Figure 2 The design includes a double U-shaped bevel, with the bevels of the two steel plates forming a 10° angle, leaving a 2mm blunt edge, and a bevel depth of 29mm. Remove any loose rust within 30mm of the weld seam to expose the metallic luster.

[0136] II. Preheat the base steel plate within 100mm of the weld to 100℃.

[0137] III. Adjust welding parameters and perform root pass welding:

[0138] Welding voltage: 26V; welding current: 260A; welding heat input: 14kJ / cm; shielding gas flow rate: 18L / min; welding speed: 28cm / min. Using the solid welding wire from Example 2, five passes were welded for the root pass according to the adjusted welding parameters. After each pass, the surface oxide scale was cleaned, and the weld temperature was measured using an infrared thermometer. The next pass was performed only when the weld temperature was ≤150℃.

[0139] IV. Adjust welding parameters and perform filler welding:

[0140] Welding voltage: 27V; welding current: 260A; welding heat input: 14.5kJ / cm; shielding gas flow rate: 18L / min; welding speed: 28cm / min. Complete the filler weld according to the adjusted welding parameters; after each weld, clean the surface oxide scale, measure the weld temperature using an infrared thermometer, and proceed to the next weld when the weld temperature is ≤150℃, until the weld is 5mm from the surface.

[0141] V. Adjust welding parameters for cover welding.

[0142] Welding voltage: 26V; welding current: 260A; welding heat input: 14kJ / cm; shielding gas flow rate: 18L / min; welding speed: 28cm / min. Complete the cover pass welding according to the adjusted welding parameters; after each pass, clean the surface oxide scale, measure the weld temperature using an infrared thermometer, and proceed to the next pass when the weld temperature is ≤150℃; continue until the weld is 0-2mm higher than the base material surface, then allow it to cool naturally.

[0143] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 2.

[0144] Example 6 Welding of a high-strength bridge steel

[0145] This embodiment describes a method for welding a parallel butt joint of high-strength weathering steel for railway bridges with a strength of 500MPa. The steel plate thickness is 32mm. Solid welding wire from Embodiment 3 is used, with carbon dioxide as the shielding gas. Gas-shielded welding is performed according to the following process and steps:

[0146] I. Press the steel plate butt joint according to... Figure 3 The design includes a double V-groove, with the angle between the grooves of the two steel plates at 60° and a groove depth of 15mm, leaving a 2mm blunt edge. Remove any loose rust within 30mm of the weld seam to expose the metallic luster.

[0147] II. Adjust welding parameters and perform root pass welding:

[0148] Welding voltage: 26V; welding current: 260A; welding heat input: 14kJ / cm; shielding gas flow rate: 18L / min; welding speed: 28cm / min. Using the solid welding wire from Example 2, five passes were welded for the root pass according to the adjusted welding parameters. After each pass, the surface oxide scale was cleaned, and the weld temperature was measured using an infrared thermometer. The next pass was performed only when the weld temperature was ≤150℃.

[0149] IV. Adjust welding parameters and perform filler welding:

[0150] Welding voltage: 27V; welding current: 260A; welding heat input: 14.5kJ / cm; shielding gas flow rate: 18L / min; welding speed: 28cm / min. Complete the filler weld according to the adjusted welding parameters; after each weld, clean the surface oxide scale, measure the weld temperature using an infrared thermometer, and proceed to the next weld when the weld temperature is ≤150℃, until the weld is 5mm from the surface.

[0151] V. Adjust welding parameters for cover welding.

[0152] Welding voltage: 26V; welding current: 260A; welding heat input: 14kJ / cm; shielding gas flow rate: 18L / min; welding speed: 28cm / min. Complete the cover pass welding according to the adjusted welding parameters; after each pass, clean the surface oxide scale, measure the weld temperature using an infrared thermometer, and proceed to the next pass when the weld temperature is ≤150℃; continue until the weld is 0-2mm higher than the base material surface, then allow it to cool naturally.

[0153] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 2.

[0154] Table 2. Test results of deposited metal and welded joint performance in Examples 4-6

[0155]

[0156] a: This test item was not conducted.

[0157] Comparative Example 1: Welding of a High-Strength Bridge Steel

[0158] This comparative example uses solid welding wire with the chemical composition shown in Table 3, and carbon dioxide as the shielding gas, to perform parallel butt joint welding on 500MPa grade high-strength weathering steel for railway bridges with a steel plate thickness of 16mm. Except for the difference in the solid welding wire, the other processes and steps are the same as in Example 4.

[0159] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 4.

[0160] Comparative Example 2: Welding of a High-Strength Bridge Steel

[0161] This comparative example uses solid welding wire with the chemical composition shown in Table 3, and carbon dioxide as the shielding gas, to perform parallel butt joint welding on 500MPa grade high-strength weathering steel for railway bridges with a steel plate thickness of 60mm. Except for the solid welding wire, the other processes and steps are the same as in Example 5.

[0162] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 4.

[0163] Comparative Example 3: Welding of a High-Strength Bridge Steel

[0164] This comparative example uses solid welding wire with the chemical composition shown in Table 3, and carbon dioxide as the shielding gas, to perform parallel butt joint welding on 500MPa grade high-strength weathering steel for railway bridges with a steel plate thickness of 32mm. Except for the solid welding wire, the other processes and steps are the same as in Example 6.

[0165] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 4.

[0166] Comparative Example 4: Welding of a High-Strength Bridge Steel

[0167] This comparative example uses solid welding wire from Example 1, with carbon dioxide as the shielding gas, and follows the process and steps to perform parallel butt joint welding on 500MPa grade high-strength weathering steel for railway bridges with a steel plate thickness of 16mm:

[0168] I. Press the steel plate butt joint according to... Figure 1 The cut is a single V-groove, with the angle between the grooves of the two steel plates being 60°, leaving a 2mm blunt edge, and the groove depth is 14mm. Remove the loose rust within 30mm of the weld to expose the metallic luster.

[0169] II. Adjust welding parameters:

[0170] Welding voltage 26V; welding current 260A; shielding gas carbon dioxide, gas flow rate 18L / min; welding speed controlled at 33cm / min; welding heat input 13kJ / cm.

[0171] III. Without preheating the base material, directly use the solid welding wire of Example 1 and complete the first weld according to the welding machine process parameters adjusted in step II; clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and proceed with the next weld when the weld temperature is ≤150℃.

[0172] IV. Repeat step III until the weld is 0-2 mm above the surface of the base material, then allow it to cool naturally.

[0173] After the welded test plate cooled, samples were taken for testing of the deposited metal and joint performance. The results are shown in Table 4.

[0174] Table 3. Chemical composition of the solid welding wires used in Comparative Examples 1-3

[0175] Comparative Example 1 Comparative Example 2 Comparative Example 3 C(％) 0.02 0.04 0.08 Mn(%) 1.10 1.30 1.60 Si (%) 0.18 0.45 0.60 Cr(％) 0.40 0.50 0.60 Ni (%) 0.30 0.40 0.60 Cu (%) 0.30 0.42 0.45 Mo (%) 0.05 0.15 0.20 P(％) 0.005 0.005 0.005 S(％) 0.003 0.003 0.003 V(％) 0.005 0.005 0.005 Fe (%) margin margin margin

[0176] Table 4. Test results of weld deposited metal and welded joint properties in Comparative Examples 1–4

[0177]

[0178] a: This test item was not conducted.

[0179] In summary, this invention provides a welding method for high-strength weathering steel for 500MPa grade railway bridges, using 100% carbon dioxide as the shielding gas. This method overcomes the limitations of existing welding methods that use high-purity argon as the main shielding gas, significantly reducing the construction cost of railway bridges while ensuring that the weld performance matches the high-strength base material, thus guaranteeing the safety of the bridge during long-term service.

Claims

1. A high-strength bridge steel field welding method for high-altitude areas, using carbon dioxide as the shielding gas, and the welding process parameters include: 1) Solid welding wire with the following chemical composition is used in continuous root pass, fill pass, and cover pass welding: C: 0.02% < C < 0.04%, Mn: 1.10%<Mn<1.30%, Si: 0.2% ≤ Si ≤ 0.40%, Cr: 0.50%<Cr<0.60%, Ni: 0.40%<Ni<0.50%, Cu: 0.30%<Cu<0.40%, Mo: 0.05%<Mo<0.20%, and P≤0.01%, S≤0.005%, V≤0.04%, balance being Fe and unavoidable impurities; 2) Setting welding parameters Welding voltage ≤ 26V ≤ 28V Welding current ≤ 260A ≤ 280A 25cm / min ≤ welding speed < 30cm / min 12kJ / cm≤welding heat input≤15kJ / cm, and 15L / min ≤ Protective gas flow rate ≤ 20L / min; 3) Setting temperature parameters (1) Preheating parameters of the base material For steel plates with a thickness ≤32mm, no preheating is required; for steel plates with a thickness ≤60mm and a thickness between 32mm and 60mm, preheating is required to 100-120℃. (2) Inter-track temperature control When the temperature of each weld seam is ≤150℃, proceed with the welding of the next weld seam.

2. The high-altitude field welding method according to claim 1, characterized in that, When the steel plate thickness is 32mm < steel plate thickness ≤ 60mm, the base material within 100mm of the weld should be preheated to 100℃~110℃. Preferably, the weld temperature is measured using an infrared thermometer.

3. The high-altitude field welding method according to claim 1 or 2, characterized in that, The welding process parameters also include: 4) Beveling form of the base material The steel plate thickness is ≤16mm, and a single V-shaped bevel is used. The bevel angle between the two steel plates is 60°, and a 2mm blunt edge is left. For steel plates with a thickness of 16mm < 32mm, a double V-shaped bevel is used, with the bevels of the two steel plates at an angle of 60°, leaving a 2mm blunt edge. For steel plates with a thickness of 32mm < 60mm, a double U-shaped bevel is used, with a 2mm blunt edge.

4. The high-altitude field welding method according to any one of claims 1 to 3, characterized in that, The welding parameters can be adjusted according to the thickness of the steel plate to be welded as follows: (1) For steel plate thickness ≤ 16mm, the welding parameters for root pass, fill pass and cover pass remain unchanged, including: 26V≤ welding voltage < 27V, 260A≤ welding current < 270A, 25cm / min≤ welding speed < 30cm / min, 12kJ / cm≤ welding heat input ≤ 15kJ / cm, 15L / min≤ shielding gas flow rate ≤ 20L / min; (2) 16mm < steel plate thickness ≤ 60mm, the welding parameters for root pass and cover pass are set as follows: 26V ≤ welding voltage < 27V, 260A ≤ welding current < 270A, 25cm / min ≤ welding speed < 30cm / min, 12kJ / cm ≤ welding heat input ≤ 15kJ / cm, 15L / min ≤ shielding gas flow rate ≤ 20L / min; the welding parameters for fill pass are set as follows: 27V ≤ welding voltage ≤ 28V, 270A ≤ welding current ≤ 280A, 25cm / min ≤ welding speed < 30cm / min, 12kJ / cm ≤ welding heat input ≤ 15kJ / cm, 15L / min ≤ shielding gas flow rate ≤ 20L / min.

5. A high-altitude field welding method for high-strength bridge steel with a thickness ≤16mm, using carbon dioxide as the shielding gas and employing solid welding wire as defined in claim 1, comprising the following specific process steps: I. The butt joint adopts a single V-shaped bevel, with the bevel angle between the two steel plates being 60°, leaving a 2mm blunt edge, and removing the floating rust within 30mm of the weld to expose the metallic luster; II. Adjusting welding process parameters 26V≤Welding voltage<27V, 260A≤Welding current<270A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min; III. Using the solid welding wire described in this invention, after completing the first pass with the parameters adjusted in step II, clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and proceed with the next weld when the weld temperature is ≤150℃. IV. Repeat step III to continuously complete the root pass, fill pass, and cover pass welding until the weld is 0-2 mm above the base material surface, and allow it to cool naturally.

6. A high-altitude field welding method for high-strength bridge steel with a thickness of 16mm < ≤ 60mm, using carbon dioxide as the shielding gas and employing solid welding wire as defined in claim 1, comprising the following specific process steps: (i) Based on the thickness of the steel plate to be welded, bevel the butt joint, remove the loose rust within 30mm of the weld, and expose the metallic luster; wherein: For steel plates with a thickness of 16mm < 32mm, a double V-shaped bevel is used, with the bevels of the two steel plates at an angle of 60°, leaving a 2mm blunt edge. For steel plates with a thickness of 32mm < 60mm, a double U-shaped bevel is used, with a 2mm blunt edge left. (ii) Preheating of base material For steel plate thicknesses between 16mm and 32mm, no preheating is required; for steel plate thicknesses between 32mm and 60mm, preheat the steel plate within a 100mm radius of the weld to 100℃~110℃. (iii) Root pass welding (iii)-1. Adjust welding process parameters 26V≤Welding voltage<27V, 260A≤Welding current<270A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min; (iii)-2. Using the solid welding wire described in this invention, after completing the first pass under the parameters adjusted in step (iii)-1, clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and proceed with the next weld when the weld temperature is ≤150℃. (iii)-3. Repeat step (iii)-2 until the root pass is completed; (iv) Filler weld (iv)-1 Adjust welding process parameters 27V≤Welding voltage≤28V, 270A≤Welding current≤280A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min; (iv)-2 When the temperature of the last weld after step (iii) is ≤150℃, weld the first pass of the filler weld under the welding parameters adjusted in step (iv)-1, clean the surface oxide scale, measure the weld temperature with an infrared thermometer, and when the weld temperature is ≤150℃, proceed to the next weld. (iv)-3 Repeat step (iv)-2 until the filler weld is complete; (v) Cover weld (v)-1 Adjust welding process parameters 26V≤Welding voltage<27V, 260A≤Welding current<270A, 25cm / min≤Welding speed<30cm / min, 12kJ / cm≤Welding heat input≤15kJ / cm, 15L / min≤Shielding gas flow rate≤20L / min; (v)-2 The temperature of the last weld after step (iv) is ≤150℃. After the first weld of the cover weld is completed under the parameters adjusted in step (v)-1, proceed to the next weld. (v)-3 Repeat step (v)-2 until the weld is 0-2 mm above the surface of the base material, and allow it to cool naturally.

7. A welding material for a high-altitude field welding method for high-strength bridge steel according to any one of claims 1 to 6, wherein the welding material is a copper-plated solid welding wire; based on the total mass of the solid welding wire, the composition of the solid welding wire is: C: 0.02% < C < 0.04%, Mn: 1.10%<Mn<1.30%, Si: 0.2% ≤ Si < 0.45%, Cr: 0.50%<Cr<0.60%, Ni: 0.40%<Ni<0.50%, Cu: 0.30%<Cu<0.40%, Mo: 0.05%<Mo<0.20%, and P≤0.01%, S≤0.005%, V≤0.04%, with the balance being Fe and unavoidable impurities.

8. The welding material according to claim 7, characterized in that, Based on the total mass of the solid welding wire, the composition of the solid welding wire is as follows: C: 0.03% ≤ C < 0.04%, Mn: 1.15%≤Mn<1.30%, Si: 0.3% ≤ Si ≤ 0.40%, Cr: 0.50%<Cr<0.60%, Ni: 0.40%<Ni<0.50%, Cu: 0.30%<Cu<0.40%, Mo: 0.10% ≤ Mo < 0.20%, and P≤0.01%, S≤0.005%, V≤0.04%, balance being Fe and unavoidable impurities; Preferably, based on the total mass of the solid welding wire, the composition of the solid welding wire is as follows: C: 0.03% ≤ C < 0.04%, Mn: 1.15%≤Mn≤1.20%, Si: 0.35%≤Si≤0.40%, Cr: 0.55%≤Cr<0.60%, Ni: 0.40%<Ni<0.50%, Cu: 0.35%≤Cu<0.40%, Mo: 0.10% ≤ Mo ≤ 0.15%, and P≤0.01%, S≤0.005%, V≤0.04%, with the balance being Fe and unavoidable impurities.

9. The welding material according to claim 7 or 8, characterized in that, Based on the total mass of the solid welding wire, the sum of the mass percentages M of the three elements Cr, Ni, and Cu ranges from 1.20% to M < 1.50%. Preferably, the atmospheric corrosion resistance index I of the solid welding wire, calculated according to its chemical composition, is 6.5% to 7.2%; wherein the atmospheric corrosion resistance index I is calculated using formula (1): I=26.01×(%Cu)+3.88×(%Ni)+1.20×(%Cr)+1.49×(%Si)+17.28×(%P)-7.29×(%Cu)×(%Ni)-9.10×(%Ni)×(%P)-33.39×(%Cu)2 (1).

10. The welding material according to any one of claims 7 to 9, characterized in that, The cross-sectional diameter of the solid welding wire is 1.2 mm.

Images