A welding wire for submerged arc welding of hydrogen-resistant pipeline steel, a manufacturing method and a welding process

Abstract

This invention belongs to the field of pipeline steel welding technology, and specifically relates to a welding wire, its manufacturing method, and welding process for submerged arc welding of hydrogen-resistant pipeline steel. The welding wire for submerged arc welding of hydrogen-resistant pipeline steel has the following chemical composition by mass percentage: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the remainder being Fe. The chemical composition of the welding wire of this invention is strictly controlled by the amount of P and S added, and the amount of Mn added is reduced. By adding Mo and Ni alloys, it has good purity and hydrogen corrosion resistance while meeting the requirements of strength and hardness. It is suitable for submerged arc welding of hydrogen-resistant pipeline steel with steel grades below L360 / X52. After double-sided welding, the tensile strength of the weld is 550~600MPa, the hardness of the weld is less than 200HV10, and the impact toughness of the welded joint at -20℃ is >100J.

Description

Technical Field

[0001] This invention belongs to the field of pipeline steel welding technology, and specifically relates to a welding wire, manufacturing method and welding process suitable for submerged arc welding of hydrogen-resistant pipeline steel with steel grade below L360 / X52. Background Technology

[0002] Pipeline transportation is an essential method for large-scale, long-distance hydrogen transport. Compared to the economical radius of 150km for long-haul trailers, pipeline hydrogen transport can easily achieve distances exceeding 200km, and the transport capacity of liquid hydrogen is also far less than that of pipeline hydrogen transport. Generally, a pure hydrogen pipeline can achieve a transport capacity of 100 tons / day, efficiently and quickly meeting the needs of downstream hydrogen industries. Hydrogen, as a gas with extremely small molecules, is colorless and odorless. Compared to natural gas, it has a lower density and a higher diffusion coefficient. Prolonged contact with hydrogen in ordinary pipe materials can cause it to penetrate into the internal defects of the metal structure, making it difficult for the hydrogen to diffuse out. This leads to reduced plasticity and strength in the metal material, resulting in cracking, severe degradation of mechanical properties, and brittle fracture—a phenomenon known as "hydrogen embrittlement."

[0003] Conventional straight-seam and spiral-seam submerged arc welded steel pipes, due to their high content of elements such as C, Mn, S, P, and Cr, are highly susceptible to hydrogen embrittlement. Furthermore, under excessively high pressure, the hydrogen embrittlement and hydrogen-induced cracking of the required high-strength materials become even more pronounced. Therefore, lower-grade steel pipes are preferred for transporting hydrogen. Currently, in the welding process of these steel pipes, high-alloy-content welding wires such as H08Mn2Si and H08A are often used, coupled with SJ101 and SJ301 fluxes. However, the use of these welding materials presents problems such as low requirements for alloy composition and P / S content control, and excessively high strength. Direct application to the welding of hydrogen-resistant pipeline steel increases the hydrogen embrittlement sensitivity of the weld seam. It also causes segregation and inclusion phenomena in the weld seam, thus seriously affecting the safety of hydrogen transportation pipelines.

[0004] Chinese invention patent CN 114346522 A, which discloses "a stainless steel submerged arc welding wire flux and welding process for hydrogen energy that can use AC power," mainly focuses on the hydrogen storage and transportation requirements in ultra-low temperature environments below -100℃. This invention primarily targets L316 stainless steel, employing a high Ni, Cr, Mo alloy design. The welding process requires multi-layer welding with low heat input per wire. Strict temperature control between layers is necessary to effectively manage the microstructure, resulting in a relatively limited process window. Welding low-alloy pipeline steel using this invention's welding process is highly prone to weld hot cracking, making it unsuitable for welding pipeline steel grades below L360 / X52. Furthermore, there are currently no precedents for applying such high-alloy welding materials to pipeline steel grades below L360 / X52 on the market. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a welding wire, manufacturing method, and welding process for submerged arc welding of hydrogen-resistant pipeline steel. For hydrogen-resistant pipeline steel of grades L360 / X52 and below, after submerged arc welding, the weld has moderate tensile strength, excellent impact toughness, and HIC and SSCC corrosion resistance consistent with the corresponding hydrogen-resistant base material, ensuring the strength and toughness of the pipeline steel and the safety of hydrogen resource transportation in the pipeline after welding.

[0006] The technical solution of the present invention is: a welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel, wherein the chemical composition of the welding wire by mass percentage is: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the remainder being Fe.

[0007] The welding wire is used for submerged arc welding of hydrogen-resistant pipeline steel with steel grades below L360 / X52. The weld tensile strength is 550~600MPa, the weld hardness is less than 200HV10, and the impact toughness of the welded joint at -20℃ is >100J.

[0008] A method for preparing a welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel, comprising the following steps: S1: The welding wire raw material is deoxidized and alloyed in a vacuum induction furnace and then smelted into molten iron. The chemical composition of the molten iron by mass percentage is: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the remainder being Fe; S2: The molten iron from step S1 is cast into a 150×150mm continuous casting billet, and the continuous casting billet is rolled into Ф6.5mm wire rod using a fully continuous, twist-free 28-stand rolling mill. S3: The wire rod produced in step S2 is repeatedly bent at a speed of 5~8m / s to make the wire rods form an angle of 120° to achieve elastic deformation, and the rust on the wire rod is removed. S4: The welding wire rod processed in step S3 is cleaned with a high-pressure water cleaning machine and polished with a 400-mesh coarse abrasive belt and a 1200-mesh fine abrasive belt to remove the oxide scale and dents from the wire surface. S5: The welding wire rod processed in step S4 is passed through an air-sealed tubular channel and a concentrated H2SO4 electrolyte at a temperature of 50°C (160~190g / l) is added to pickle away the oil and oxides adhering to the surface of the wire. S6: The welding wire coil processed in step S5 is cleaned by a reciprocating trough-type 10~15KHZ ultrasonic cleaning device to remove residual molten metal and micro-materials in the pits on the surface of the welding wire coil, and the surface treatment is dried by a dryer. S7: After the welding wire rod processed in step S6 is uniformly coated with a layer of borax film on its surface in a borosilicate treatment tank, it is drawn in a straight-pull manner through a variable diameter drawing process of Ф6.5mm→Ф5.8mm→Ф5.1mm→Ф4.5mm→Ф4.0mm→Ф3.2mm to produce a bare welding wire with a diameter of 4.0 mm or 3.2 mm. S8: The welding wire processed in step S7 is laid out, and during this process, it undergoes mechanical degreasing, hot water washing, pre-degreasing, electrolytic alkaline washing, water washing, electrolytic acid washing, water washing and activation neutralization. Then, the welding wire is passed through an electroplating solution with a concentration ratio of ρ(H2SO4):ρ(CuSO4) of 2:1 at a speed of 1.4 m / s to complete the copper plating treatment. S9: The copper-plated solder wire processed in step S8 is washed with water, neutralized and passivated, washed with water, washed with hot water and dried before being wound up; S10: After adjusting the diameter and warp distance of the welding wire processed in step S9, the finished welding wire that meets the usage requirements is finely wound. After acceptance, packaging, labeling, and warehousing, the finished product is put into storage.

[0009] In step S2, the continuously cast square billet is rolled in three stages using a fully continuous, twist-free 28-stand rolling mill. The specific steps are as follows: S21: Temperature controlled at 1060±20℃, rolled into a round billet bar of Ф50±0.5mm by double-wire roughing at 0.35m / s; S22: The billet is pre-rolled into a round bar with a diameter of Ф27.6±4mm by single-line pre-finishing rolling at a temperature controlled at 980±20℃ and a speed of 8.6 m / s. S23: The wire rod is rolled into Ф6.5mm wire rod by a single wire finishing mill at 83 m / s under a temperature control of 860±20℃.

[0010] A welding process for submerged arc welding of hydrogen-resistant pipeline steel, using the welding wire described above, includes the following steps: S01: Prepare welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel. The welding wire is solid and has diameters of Ф4.0 mm and Ф3.2 mm respectively. S02: Prepare a flux suitable for submerged arc welding wire used in hydrogen-resistant pipeline steel. The chemical composition of the flux, by mass percentage, is as follows: HJ431 fused welding powder 20-30%, CaF2: 10-15%, MgO: 5-10%, Al2O3: 8-15%, BaCO3: 3-7%, TiO2: 3-5%, Re: 1-0.05%, S≤0.015%, P≤0.020%. S03: The submerged arc welding of the hydrogen-resistant pipeline steel adopts double-wire inner and outer single-sided submerged arc welding. The groove type of the hydrogen-resistant pipeline steel is an X-type symmetrical groove or a Y-type symmetrical groove. The welding sequence is to first submerge the inner surface and then submerge the outer surface. The distance between the front and rear welding wires on the inner and outer surfaces is 10~15mm. The angle of the front wire is 0~5° and the angle of the rear wire is 10~15°. The wire extension length is 28~35mm.

[0011] In step S02, the HJ431 smelting welding powder contains SiO2 ≤ 40%, MnO + Al2O3 ≤ 35%, and CaO + MgO ≤ 15%; the CaF2 is added in the form of fluorite mineral powder, with a CaF2 content of not less than 95% and P ≤ 0.003%; the MgO is added in the form of fused magnesia, with an MgO content of not less than 97%, S ≤ 0.003%, and P ≤ 0.05%; the Al2O3 is added in the form of bauxite, with an Al2O3 content of not less than 84% and S and P ≤ 0.03%; the BaCO3 is added in the form of barium carbonate, with a content of not less than 70%; the TiO2 is added in the form of natural rutile, with a TiO2 content of more than 58%; and the Re alloy is added in the form of rare earth ferrosilicon alloy, with a Re content of more than 30% and a Si content of more than 45%.

[0012] The HJ431 welding powder has a particle size of 80-100 mesh; the fluorite mineral powder has a particle size of 100 mesh or more; the fused magnesia has a particle size of 80-100 mesh; the bauxite has a particle size of 80-100 mesh; the SiO2 has a particle size of 80-100 mesh; the natural rutile has a particle size of 100 mesh or more; and the rare earth ferrosilicon has a particle size of 80-120 mesh. When the required chemical composition of the sintering flux is added in the form of HJ431 fused welding powder, fluorite, fused magnesia, bauxite, barium carbonate, rutile, and rare earth ferrosilicon, the mineral composition and alloy weight percentage in the sintering flux are: HJ431 fused welding powder 20-30%, fluorite 12-18%, fused magnesia 8-12%, bauxite 10-22%, barium carbonate 5-12%, rutile 8-15%, and rare earth ferrosilicon 0.2-1%.

[0013] In step S03, the thickness of the hydrogen-resistant pipeline steel is 9-14 mm. The X-shaped symmetrical bevel has an outer surface bevel angle of 60-70°, an inner surface bevel angle of 60-70°, a blunt edge of 5-6 mm, a gap size of 1-2 mm, and a misalignment of 0-3 mm. The Y-shaped symmetrical bevel has an outer surface bevel angle of 60-70°, a bevel depth of 6-7 mm, a blunt edge of 5-6 mm, a gap size of 1-2 mm, and a misalignment of 0-3 mm.

[0014] In step S03, the submerged arc welding process on the inner surface is as follows: the pre-welding wire uses DC positive polarity, with a wire diameter of Ф4.0 mm, a welding speed of 1.2 m / min, a current of 600–750 A, and a voltage of 30–32 V; the post-welding wire uses AC polarity, with a wire diameter of Ф3.2 mm, a current of 400–600 A, and a voltage of 33–36 V. The submerged arc welding process on the outer surface is as follows: the pre-welding wire uses DC positive polarity, with a wire diameter of Ф4.0 mm, a welding speed of 1.2 m / min, a current of 700–800 A, and a voltage of 30–32 V; the post-welding wire uses AC polarity, with a wire diameter of Ф4.0 mm, a current of 500–700 A, and a voltage of 33–36 V.

[0015] The technical effects of this invention are as follows: 1. The chemical composition of the welding wire of this invention strictly controls the amount of P and S added, reduces the amount of Mn added, and adds Mo and Ni alloys to achieve good purity and hydrogen corrosion resistance while meeting strength and hardness requirements. Combined with appropriate special flux, it is suitable for submerged arc welding of hydrogen-resistant pipeline steel of steel grades below L360 / X52. After double-sided welding, the weld tensile strength is 550~600MPa, the weld hardness is less than 200HV10, and the impact toughness of the welded joint at -20℃ is >100J; 2. The welded metal R... t0.5 =300~420MPa, R m =460~580MPa, impact toughness A at -20℃ kv With a hydrogen content of ≥27J and a diffusible hydrogen content of ≤3mL / 100g, the hydrogen resistance of the steel pipe is effectively improved. Detailed Implementation

[0016] Example 1 A welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel, wherein the chemical composition of the welding wire by mass percentage is: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the remainder being Fe.

[0017] The chemical composition of the welding wire of this invention is strictly controlled in terms of the amount of P and S added, and the amount of Mn added is reduced. By adding Mo and Ni alloys, it can achieve good purity and hydrogen corrosion resistance while meeting the requirements of strength and hardness. It is suitable for submerged arc welding of hydrogen-resistant pipeline steel with steel grades below L360 / X52.

[0018] The chemical composition of the welding wire in this invention is based on the C-Mn-Ni-Mo alloy system, and the selection principles for each chemical component are as follows: (1) As the main strengthening element in the weld structure, C plays an important role in the tensile properties of the weld. However, as the carbon content increases, the hardness will increase, and when it reaches a certain level, it will change the structure and produce a multiphase structure. Considering that C will be burned off during the welding process, C is controlled at 0.03-0.06%. (2) The content of Mn has a great influence on the mechanical properties of weld metal. Generally, with the increase of Mn content, the yield strength and tensile strength of weld metal increase linearly. In addition, Mn can significantly reduce the brittle transition temperature and improve the impact toughness of weld. In order to ensure that the weld has appropriate strength, the amount of Mn added in this project should not be too high. Therefore, the Mn content is controlled at 0.4-1.2%. (3) Si has a significant impact on the microstructure and properties of welds. It mainly plays a deoxidizing role in weld metals. Especially when Mn and Si are present at the same time, as the Mn-Si content increases, the phase transformation temperature of continuous cooling gradually decreases and the microstructure becomes finer. However, at the same time, because Si can significantly increase the phase transformation temperature of pearlite, relatively coarse carbides are formed during the welding process. This will affect both the corrosion performance and the impact toughness of the weld. Therefore, the Si content should be between 0.10% and 0.30%. (4) As a ferrite stabilizing element, Mo can promote AF nucleation in the weld and is beneficial to the improvement of weld impact toughness. However, on the other hand, Mo has a great influence on weld strength. As the content increases, the weld strength increases linearly. However, excessive Mo content can easily cause weld embrittlement during high heat input welding and has an adverse effect on the low temperature toughness of the weld. Therefore, the Mo content in the welding wire is limited to 0.10-0.25%. (5) Ni: Ni acts as a strengthening component in weld metal, and can achieve strengthening effect through grain refinement and solid solution strengthening. As the best toughening component at low temperature, Ni can significantly improve the low temperature toughness of weld metal. In order to give full play to the beneficial role of Ni, while increasing its content, it is necessary to reduce the C content and strictly limit the S and P content. In order to obtain high strength and low temperature toughness, the Ni content in the welding wire of the present invention is controlled at 0.5-1.5%; (6) P and S are impurity elements. S is infinitely miscible with iron in the liquid state and easily forms a fusible eutectic Fe+FeS distributed in austenite, causing hot brittleness in the weld and resulting in a sharp decrease in the weld's plasticity and toughness. P is prevalent in the form of phosphides, which promotes hydrogen evolution corrosion. However, phosphorus can also improve the corrosion resistance of steel. Increasing its content will cause cold brittleness and deteriorate the toughness of steel. Therefore, its content is controlled at P≤0.010% and S≤0.005%.

[0019] The welding wire is used for submerged arc welding of hydrogen-resistant pipeline steel with steel grades below L360 / X52. The weld tensile strength is 550~600MPa, the weld hardness is less than 200HV10, and the impact toughness of the welded joint at -20℃ is >100J.

[0020] A method for preparing a welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel, comprising the following steps: S1: The welding wire raw material is deoxidized and alloyed in a vacuum induction furnace and then smelted into molten iron. The chemical composition of the molten iron by mass percentage is: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the remainder being Fe; S2: The molten iron from step S1 is cast into a 150×150mm continuous casting billet, and the continuous casting billet is rolled into Ф6.5mm wire rod using a fully continuous, twist-free 28-stand rolling mill. S3: The wire rod produced in step S2 is repeatedly bent at a speed of 5~8m / s to make the wire rods form an angle of 120° to achieve elastic deformation, and the rust on the wire rod is removed. S4: The welding wire rod processed in step S3 is cleaned with a high-pressure water cleaning machine and polished with a 400-mesh coarse abrasive belt and a 1200-mesh fine abrasive belt to remove the oxide scale and dents from the wire surface. S5: The welding wire rod processed in step S4 is passed through an air-sealed tubular channel and a concentrated H2SO4 electrolyte at a temperature of 50°C (160~190g / l) is added to pickle away the oil and oxides adhering to the surface of the wire. S6: The welding wire coil processed in step S5 is cleaned by a reciprocating trough-type 10~15KHZ ultrasonic cleaning device to remove residual molten metal and micro-materials in the pits on the surface of the welding wire coil, and the surface treatment is dried by a dryer. S7: After the welding wire rod processed in step S6 is uniformly coated with a layer of borax film on its surface in a borosilicate treatment tank, it is drawn in a straight-pull manner through a variable diameter drawing process of Ф6.5mm→Ф5.8mm→Ф5.1mm→Ф4.5mm→Ф4.0mm→Ф3.2mm to produce a bare welding wire with a diameter of 4.0 mm or 3.2 mm. S8: The welding wire processed in step S7 is laid out, and during this process, it undergoes mechanical degreasing, hot water washing, pre-degreasing, electrolytic alkaline washing, water washing, electrolytic acid washing, water washing and activation neutralization. Then, the welding wire is passed through an electroplating solution with a concentration ratio of ρ(H2SO4):ρ(CuSO4) of 2:1 at a speed of 1.4 m / s to complete the copper plating treatment. S9: The copper-plated solder wire processed in step S8 is washed with water, neutralized and passivated, washed with water, washed with hot water and dried before being wound up; S10: After adjusting the relaxation diameter and warp distance of the welding wire processed in step S9 according to the technical requirements of GB / T8110 standard, the finished welding wire that meets the usage requirements is finely wound. After acceptance, packaging and labeling, the finished product is put into the warehouse.

[0021] In step S2, the continuously cast square billet is rolled in three stages using a fully continuous, twist-free 28-stand rolling mill. The specific steps are as follows: S21: Temperature controlled at 1060±20℃, rolled into a round billet bar of Ф50±0.5mm by double-wire roughing at 0.35m / s; S22: The billet is pre-rolled into a round bar with a diameter of Ф27.6±4mm by single-line pre-finishing rolling at a temperature controlled at 980±20℃ and a speed of 8.6 m / s. S23: The wire rod is rolled into Ф6.5mm wire rod by a single wire finishing mill at 83 m / s under a temperature control of 860±20℃.

[0022] Example 2 A welding process for submerged arc welding of hydrogen-resistant pipeline steel, using the welding wire described above, includes the following steps: S01: Prepare welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel. The welding wire is solid and has diameters of Ф4.0 mm and Ф3.2 mm respectively. S02: Prepare a flux suitable for submerged arc welding wire used in hydrogen-resistant pipeline steel. The chemical composition of the flux, by mass percentage, is as follows: HJ431 fused welding powder 20-30%, CaF2: 10-15%, MgO: 5-10%, Al2O3: 8-15%, BaCO3: 3-7%, TiO2: 3-5%, Re: 1-0.05%, S≤0.015%, P≤0.020%. S03: The submerged arc welding of the hydrogen-resistant pipeline steel adopts double-wire inner and outer single-sided submerged arc welding. The groove type of the hydrogen-resistant pipeline steel is an X-type symmetrical groove or a Y-type symmetrical groove. The welding sequence is to first submerge the inner surface and then submerge the outer surface. The distance between the front and rear welding wires on the inner and outer surfaces is 10~15mm. The angle of the front wire is 0~5° and the angle of the rear wire is 10~15°. The wire extension length is 28~35mm.

[0023] In step S02, the HJ431 smelting welding powder contains SiO2 ≤ 40%, MnO + Al2O3 ≤ 35%, and CaO + MgO ≤ 15%; the CaF2 is added in the form of fluorite mineral powder, with a CaF2 content of not less than 95% and P ≤ 0.003%; the MgO is added in the form of fused magnesia, with an MgO content of not less than 97%, S ≤ 0.003%, and P ≤ 0.05%; the Al2O3 is added in the form of bauxite, with an Al2O3 content of not less than 84% and S and P ≤ 0.03%; the BaCO3 is added in the form of barium carbonate, with a content of not less than 70%; the TiO2 is added in the form of natural rutile, with a TiO2 content of more than 58%; and the Re alloy is added in the form of rare earth ferrosilicon alloy, with a Re content of more than 30% and a Si content of more than 45%.

[0024] The HJ431 welding powder has a particle size of 80-100 mesh; the fluorite mineral powder has a particle size of 100 mesh or more; the fused magnesia has a particle size of 80-100 mesh; the bauxite has a particle size of 80-100 mesh; the natural rutile has a particle size of 100 mesh or more; and the rare earth ferrosilicon has a particle size of 80-120 mesh. When the required chemical composition of the sintering flux is added in the form of HJ431 fused welding powder, fluorite, fused magnesia, bauxite, barium carbonate, rutile, and rare earth ferrosilicon, the mineral composition and alloy weight percentage in the sintering flux are as follows: HJ431 fused welding powder 20-30%, fluorite 12-18%, fused magnesia 8-12%, bauxite 10-22%, barium carbonate 5-12%, rutile 8-15%, and rare earth ferrosilicon 0.2-1%.

[0025] In step S03, the thickness of the hydrogen-resistant pipeline steel is 9-14 mm. The X-shaped symmetrical bevel has an outer surface bevel angle of 60-70°, an inner surface bevel angle of 60-70°, a blunt edge of 5-6 mm, a gap size of 1-2 mm, and a misalignment of 0-3 mm. The Y-shaped symmetrical bevel has an outer surface bevel angle of 60-70°, a bevel depth of 6-7 mm, a blunt edge of 5-6 mm, a gap size of 1-2 mm, and a misalignment of 0-3 mm.

[0026] In step S03, the submerged arc welding process on the inner surface is as follows: the pre-welding wire uses DC positive polarity, with a wire diameter of Ф4.0 mm, a welding speed of 1.2 m / min, a current of 600–750 A, and a voltage of 30–32 V; the post-welding wire uses AC polarity, with a wire diameter of Ф3.2 mm, a current of 400–600 A, and a voltage of 33–36 V. The submerged arc welding process on the outer surface is as follows: the pre-welding wire uses DC positive polarity, with a wire diameter of Ф4.0 mm, a welding speed of 1.2 m / min, a current of 700–800 A, and a voltage of 30–32 V; the post-welding wire uses AC polarity, with a wire diameter of Ф4.0 mm, a current of 500–700 A, and a voltage of 33–36 V.

[0027] Example 3 According to the welding wire and preparation method for submerged arc welding of hydrogen-resistant pipeline steel described in Example 1 above, the welding process described in Example 2 is adopted, and the specific details are as described in Examples 4, 5, 6, and 7. The comparative examples are Comparative Examples 1, 2, 3, and 4. The chemical elemental composition of the welding wire in Examples 4-7 and Comparative Examples 1-4 by weight percentage is shown in Table 3.

[0028] Table 3 Chemical elemental composition of welding wires in Examples 4-7 and Comparative Examples 1-4, by weight percentage (%) Serial Number C Mn Si Mo Ni P S Example 4 0.03 1.1 0.20 0.25 1.5 0.01 0.005 Example 5 0.05 0.9 0.15 0.20 0.85 0.009 0.003 Example 6 0.06 0.85 0.18 0.20 0.50 0.008 0.005 Example 7 0.04 1.2 0.26 0.10 1.0 0.006 0.005 Comparative Example 1 0.07 0.9 0.18 0.24 1.4 0.008 0.005 Comparative Example 2 0.05 1.3 0.18 0.22 0.90 0.008 0.005 Comparative Example 3 0.06 0.85 0.20 0.26 0.60 0.009 0.005 Comparative Example 4 0.04 1.2 0.26 0.10 1.8 0.006 0.005 Table 4 shows the different ways of using welding wire in Examples 4-7 and Comparative Examples 1-4.

[0029] Table 4. Welding wire usage parameters in Examples 4-7 and Comparative Examples 1-4 Project number Matching flux Diffused hydrogen content (mL / g) Slag removal properties Spreadability Degassing Example 4 The flux described in this invention is compatible with the welding wire used for submerged arc welding of hydrogen-resistant pipeline steel. 0.285 Automatic detachment Smooth and flat No dents were observed on the surface. Example 5 The flux described in this invention is compatible with the welding wire used for submerged arc welding of hydrogen-resistant pipeline steel. 0.266 Automatic detachment Smooth and flat No dents were observed on the surface. Example 6 The flux described in this invention is compatible with the welding wire used for submerged arc welding of hydrogen-resistant pipeline steel. 0.294 Automatic detachment Smooth and flat No dents were observed on the surface. Example 7 The flux described in this invention is compatible with the welding wire used for submerged arc welding of hydrogen-resistant pipeline steel. 0.268 Automatic detachment Smooth and flat No dents were observed on the surface. Comparative Example 1 SJ301 0.453 Sticky residue Weld undercut No dents were observed on the surface. Comparative Example 2 SJ101 0.336 Automatic detachment Irregular weld No dents were observed on the surface. Comparative Example 3 HJ431 0.276 Sticky residue Irregular weld Surface pitting Comparative Example 4 SJ101 0.369 Automatic detachment Irregular weld No dents were observed on the surface. The mechanical properties of the circumferential welds welded using welding wires from Examples 4-7 and Comparative Examples 1-4 are shown in Table 5.

[0030] Table 5. Welding wire testing results and mechanical and technological properties of circumferential welds in Examples 4-7 and Comparative Examples 1-4.

[0031] Referring to Tables 3 and 4, the weight percentages of certain components in the welding wires of Comparative Examples 1-4 exceed the scope covered by the technical solution of this invention. For example, in Comparative Example 1, the weight percentage of C is higher than the controlled weight percentage of C in the welding wire of this invention; in Comparative Example 2, the weight percentage of Mn is higher than the controlled weight percentage of Mn in the welding wire of this invention; in Comparative Example 3, the weight percentage of Mo is higher than the controlled weight percentage of Mo in the welding wire of this invention; and in Comparative Example 4, the weight percentage of Ni is higher than the controlled weight percentage of Ni in the welding wire of this invention. The usage methods of the welding wires in Comparative Examples 1-4 do not conform to the scope covered by the technical solution of this invention. For example, the welding flux used in Comparative Examples 1-4 is the conventional SJ301 and SJ101 welding wires and HJ431 smelted flux, respectively. As can be seen from Table 4, in Comparative Examples 1-4, at least one of the performance indicators is lower than the standard design requirements. For example, the post-weld process performance of all four comparative examples fails to meet the requirements, and except for Comparative Example 3, which meets the standard requirements for diffusible hydrogen content, the others do not meet the standard requirements.

[0032] As can be seen from Tables 4 and 5, compared with Comparative Examples 1-4, the tensile strength of the welds welded using the welding wires in Examples 4-7 is 498-521 MPa, the impact toughness of the welds at -20℃ exceeds 100 J, and the average hardness is less than 200 HV. 10 Meanwhile, the slag shell can be automatically removed after welding with the special fluxes used with the welding wires, ensuring a smooth and aesthetically pleasing weld surface. Therefore, the welding wires in Examples 4-7, when used for welding hydrogen-resistant pipeline steel of grade L360 / X52 and below, exhibit high strength and toughness. The weld morphology is significantly improved compared to ordinary fluxes, and all performance characteristics are far superior to similar products currently available. This invention can meet the performance requirements of hydrogen-resistant pipeline steel pipes of grade L360 / X52 and below.

[0033] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A welding process for welding wire used in submerged arc welding of hydrogen-resistant pipeline steel, characterized in that: A welding wire for submerged arc welding of hydrogen-resistant pipeline steel is used. The chemical composition of the welding wire, by mass percentage, is: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the balance being Fe. The specific steps include: S01: Prepare welding wire suitable for submerged arc welding of hydrogen-resistant pipeline steel. The welding wire is solid and has diameters of Ф4.0 mm and Ф3.2 mm respectively. S02: Prepare a flux suitable for submerged arc welding wire used in hydrogen-resistant pipeline steel. The chemical composition of the flux, by mass percentage, is: HJ431 fused welding powder 20-30%, CaF2: 10-15%, MgO: 5-10%, Al2O3: 8-15%, BaCO3: 3-7%, TiO2: 3-5%, Re: 1-0.05%, S≤0.015%, P≤0.020%. In step S02, the HJ431 fused welding powder contains SiO2≤40%, MnO+Al2O3≤35%, CaO+MgO≤15%. The CaF2 is added in the form of fluorite mineral powder, with a CaF2 content of not less than 95% and P≤0.003%. The MgO is added in the form of fused magnesia, with an MgO content of not less than 97%, S≤0.003%, and P≤0.05%. The Al2O3 is added in the form of bauxite, with an Al2O3 content of not less than 84% and S and P ≤ 0.03%; the BaCO3 is added in the form of barium carbonate, with a content of not less than 70%; the TiO2 is added in the form of natural rutile, with a TiO2 content of more than 58%; the Re is added in the form of rare earth ferrosilicon alloy, with a Re content of more than 30% and a Si content of more than 45%. When the chemical composition required for sintering flux is added in the form of HJ431 smelted welding powder, fluorite, fused magnesia, bauxite, barium carbonate, rutile, and rare earth ferrosilicon, the mineral composition and alloy weight percentage in the sintering flux are as follows: HJ431 smelted welding powder 20-30%, fluorite 12-18%, fused magnesia 8-12%, bauxite 10-22%, barium carbonate 5-12%, rutile 8-15%, and rare earth ferrosilicon 0.2-1%. S03: The submerged arc welding of the hydrogen-resistant pipeline steel adopts double-wire inner and outer single-sided submerged arc welding. The groove type of the hydrogen-resistant pipeline steel is an X-type symmetrical groove or a Y-type symmetrical groove. The welding sequence is to first submerge the inner surface and then submerge the outer surface. The distance between the front and rear welding wires on the inner and outer surfaces is 10-15mm. The angle of the front wire is 0-5° and the angle of the rear wire is 10-15°. The wire extension length is 28-35mm.

2. The welding process for submerged arc welding wire for hydrogen-resistant pipeline steel according to claim 1, characterized in that: The welding wire is used for submerged arc welding of hydrogen-resistant pipeline steel with steel grades below L360 / X52. The weld tensile strength is 550~600MPa, the weld hardness is less than 200HV10, and the impact toughness of the welded joint at -20℃ is >100J.

3. The welding process for a welding wire used in submerged arc welding of hydrogen-resistant pipeline steel according to claim 1, characterized in that: The preparation of the welding wire for submerged arc welding of hydrogen-resistant pipeline steel includes the following steps: S1: The welding wire raw material is deoxidized and alloyed in a vacuum induction furnace and then smelted into molten iron. The chemical composition of the molten iron by mass percentage is: C: 0.03~0.06%, Mn: 0.8~1.2%, Si: 0.10~0.30%, P≤0.010%, S≤0.005%, Ni: 0.50~1.50%, Mo: 0.10~0.25%, with the remainder being Fe; S2: The molten iron from step S1 is cast into a 150×150mm continuous casting billet, and the continuous casting billet is rolled into Ф6.5mm wire rod using a fully continuous, twist-free 28-stand rolling mill. S3: The wire rod produced in step S2 is repeatedly bent at a speed of 5~8m / s to make the wire rods form an angle of 120° to achieve elastic deformation, and the rust on the wire rod is removed. S4: The welding wire rod processed in step S3 is cleaned with a high-pressure water cleaning machine and polished with a 400-mesh coarse abrasive belt and a 1200-mesh fine abrasive belt to remove the oxide scale and dents from the wire surface. S5: The welding wire rod processed in step S4 is passed through an air-sealed tubular channel and a concentrated H2SO4 electrolyte at a temperature of 50°C (160~190g / l) is added to pickle away the oil and oxides adhering to the surface of the wire. S6: The welding wire coil processed in step S5 is cleaned by a reciprocating trough-type 10~15KHZ ultrasonic cleaning device to remove residual molten metal and micro-materials in the pits on the surface of the welding wire coil, and the surface treatment is dried by a dryer. S7: After the welding wire rod processed in step S6 is uniformly coated with a layer of borax film on its surface in a borosilicate treatment tank, it is drawn in a straight-pull manner through a variable diameter drawing process of Ф6.5mm→Ф5.8mm→Ф5.1mm→Ф4.5mm→Ф4.0mm→Ф3.2mm to produce a bare welding wire with a diameter of 4.0 mm or 3.2 mm. S8: The welding wire processed in step S7 is laid out, and during this process, it undergoes mechanical degreasing, hot water washing, pre-degreasing, electrolytic alkaline washing, water washing, electrolytic acid washing, water washing and activation neutralization. Then, the welding wire is passed through an electroplating solution with a concentration ratio of ρ(H2SO4):ρ(CuSO4) of 2:1 at a speed of 1.4 m / s to complete the copper plating treatment. S9: The copper-plated solder wire processed in step S8 is washed with water, neutralized and passivated, washed with water, washed with hot water and dried before being wound up; S10: After adjusting the diameter and warp distance of the welding wire processed in step S9, the finished welding wire that meets the usage requirements is finely wound. After acceptance, packaging, labeling, and warehousing, the finished product is put into storage.

4. The welding process for a welding wire used in submerged arc welding of hydrogen-resistant pipeline steel according to claim 3, characterized in that: In step S2, the continuously cast square billet is rolled in three stages using a fully continuous, twist-free 28-stand rolling mill. The specific steps are as follows: S21: Temperature controlled at 1060±20℃, rolled into a round billet bar of Ф50±0.5mm by double-wire roughing at 0.35m / s; S22: The billet is pre-rolled into a round bar with a diameter of Ф27.6±4mm by single-line pre-finishing rolling at a temperature controlled at 980±20℃ and a speed of 8.6 m / s. S23: The wire rod is rolled into Ф6.5mm wire rod by a single wire finishing mill at 83 m / s under a temperature control of 860±20℃.

5. The welding process for a welding wire used in submerged arc welding of hydrogen-resistant pipeline steel according to claim 1, characterized in that: The HJ431 welding powder has a particle size of 80-100 mesh; the fluorite mineral powder has a particle size of 100 mesh or more; the fused magnesia has a particle size of 80-100 mesh; the bauxite has a particle size of 80-100 mesh; the natural rutile has a particle size of 100 mesh or more; and the rare earth ferrosilicon has a particle size of 80-120 mesh.

6. The welding process for a welding wire used in submerged arc welding of hydrogen-resistant pipeline steel according to claim 1, characterized in that: In step S03, the thickness of the hydrogen-resistant pipeline steel is 9-14 mm. The X-shaped symmetrical bevel has an outer surface bevel angle of 60-70°, an inner surface bevel angle of 60-70°, a blunt edge of 5-6 mm, a gap size of 1-2 mm, and a misalignment of 0-3 mm. The Y-shaped symmetrical bevel has an outer surface bevel angle of 60-70°, a bevel depth of 6-7 mm, a blunt edge of 5-6 mm, a gap size of 1-2 mm, and a misalignment of 0-3 mm.

7. The welding process for a welding wire used in submerged arc welding of hydrogen-resistant pipeline steel according to claim 1, characterized in that: In step S03, the submerged arc welding process on the inner surface is as follows: the pre-welding wire uses DC positive polarity, with a wire diameter of Ф4.0 mm, a welding speed of 1.2 m / min, a current of 600–750 A, and a voltage of 30–32 V; the post-welding wire uses AC polarity, with a wire diameter of Ф3.2 mm, a current of 400–600 A, and a voltage of 33–36 V. The submerged arc welding process on the outer surface is as follows: the pre-welding wire uses DC positive polarity, with a wire diameter of Ф4.0 mm, and a welding speed of 1.2 m / min. Current: 700~800A, voltage: 30~32V, the post-welding wire uses AC, the wire diameter is Ф4.0 mm, current: 500~700A, voltage: 33~36V.

Images