Submerged arc welding wire and preparation method and application thereof

Abstract

The application provides a submerged arc welding wire and a preparation method and application thereof, and belongs to the technical field of special welding materials. The Si-Ni-Mo-Cu-Sn alloy system is used to improve the corrosion of the base body and the grain boundary; by controlling the range of Cs and Tg, using fine-grain strengthening and induced nucleation technology, the low-temperature toughness of the weld metal can be significantly improved. The experimental results show that the average annual corrosion rate of the weld of the submerged arc welding wire is 0.55-0.68 mm / a, the corrosion step of the base material and the weld is 8-20 mu m, and the impact absorption energy KV2 of the deposited metal at 20 DEG C is not less than 80 J.

Description

Technical Field

[0001] This invention relates to the field of special welding materials technology, and in particular to a submerged arc welding wire, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of my country's industrial economy, the demand for petroleum energy, known as the "lifeblood of industry," has surged, becoming a major energy consumer in my country. As petroleum demand continues to increase, the application of storage tanks has also grown, leading to increasingly prominent safety issues due to corrosion from various harmful media during operation. While crude oil itself does not corrode metals, it contains large amounts of inorganic salts, sulfides, nitrides, organic acids, oxygen, sulfur dioxide, and water. After long-term storage, crude oil precipitates, forming a highly acidic, high-Cl- content on the bottom plate of the storage tank. - The presence of sedimentary water significantly shortens the normal service life of oil tanks. Furthermore, if corrosion perforates the tank and causes crude oil leakage, it can lead to major fires and explosions, disrupting normal production and potentially causing environmental pollution. The structure of crude oil storage tanks is primarily achieved through welding, but the welded joints exhibit significant inhomogeneity in microstructure and composition, resulting in lower corrosion resistance compared to the base material. Therefore, the development of corrosion-resistant welding materials for crude oil storage tanks that simultaneously offer good weldability and corrosion resistance has attracted considerable attention.

[0003] Currently, the submerged arc welding wire (SAW) used with 12MnNiVR steel in the crude oil storage tank field, such as H08A, has the following main components: C≤0.10%, Mn0.30~0.60%, Si≤0.03%, Cu≤0.20%. This is a conventional welding wire and lacks corrosion resistance. Using the IMO standard "Guideline for the Inspection of Corrosion-Resistant Steels for Cargo Tanks of Crude Oil Tankers," under accelerated corrosion simulation conditions of pH=0.85 and 10% NaCl aqueous solution, its average annual corrosion rate is 2.1 mm / a, with corrosion steps between the base metal and the weld exceeding 30 μm. This far exceeds the standard of an average annual corrosion rate of 1 mm / a and a corrosion step not exceeding 30 μm. Therefore, how to improve the corrosion resistance of SAW wire while ensuring its low-temperature toughness has become a pressing problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a submerged arc welding wire, its preparation method, and its application. The submerged arc welding wire provided by this invention possesses excellent corrosion resistance and low-temperature toughness.

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

[0006] This invention provides a submerged arc welding wire, the chemical composition of which, by mass percentage, includes C 0.03-0.06%, Si 0.20-0.40%, Mn 1.00-1.40%, P ≤0.012%, S ≤0.005%, Ni 0.1-0.6%, Mo 0.10-0.30%, Cu 0.20-0.40%, Ti 0.02-0.06%, Ce 0.01-0.05%, Mg ≤0.005%, Sn 0.01-0.03%, and the balance Fe;

[0007] The contents of C, Si, Mn, Cu, Ni, Mo, Sn and Ti satisfy the following conditions: 1.2≤Cs≤1.8, 3.0≤Tg≤3.8, Cs=(2[Si]+1[Ni]+3[Mo]+5[Cu]+25[Sn]-10[C]) / (5[C]+[Mn]+2[Mo]+[Ni]), Tg=(2[Mn]+6[Ni]+3[Mo]+20[Ti]+40[Ce]) / (2[Si]+70[Sn]).

[0008] Preferably, the chemical composition, by mass percentage, includes C 0.035–0.055%, Si 0.30–0.40%, Mn 1.10–1.30%, P ≤0.012%, S ≤0.005%, Ni 0.15–0.5%, Mo 0.15–0.25%, Cu 0.25–0.35%, Ti 0.04–0.05%, Ce 0.02–0.04%, Mg ≤0.003%, Sn 0.02–0.025%, and the balance Fe.

[0009] Preferably, the chemical composition, by mass percentage, includes C 0.040–0.045%, Si 0.35–0.40%, Mn 1.20–1.25%, P ≤0.012%, S ≤0.005%, Ni 0.20–0.25%, Mo 0.20–0.25%, Cu 0.30–0.35%, Ti 0.04–0.05%, Ce 0.03–0.04%, Mg 0.001–0.003%, Sn 0.02–0.025%, and the balance Fe.

[0010] Preferably, 1.3≤Cs≤1.6 and 3.0≤Tg≤3.6.

[0011] The present invention also provides a method for preparing the submerged arc welding wire described in the above technical solution, comprising the following steps:

[0012] (1) The alloy raw materials are successively smelted, cast, forged and hot rolled to obtain wire rod;

[0013] (2) The wire rod obtained in step (1) is subjected to coarse drawing, fine drawing and copper plating in sequence to obtain submerged arc welding wire.

[0014] Preferably, step (1) includes heat preservation after casting and before forging.

[0015] Preferably, the insulation temperature is 1180–1220°C, and the insulation time is 2 hours.

[0016] Preferably, the hot rolling temperature in step (1) is 1180-1220°C, and the total deformation of the hot rolling is 60-80%.

[0017] Preferably, the hot rolling temperature is 1200°C.

[0018] The present invention also provides the application of the submerged arc welding wire described in the above technical solution or the submerged arc welding wire prepared by the preparation method described in the above technical solution in the bottom plate of crude oil storage tank.

[0019] This invention provides a submerged arc welding wire, the chemical composition of which, by mass percentage, includes C 0.03-0.06%, Si 0.20-0.40%, Mn 1.00-1.40%, P ≤0.012%, S ≤0.005%, Ni 0.1-0.6%, Mo 0.10-0.30%, Cu 0.20-0.40%, Ti 0.02-0.06%, Ce 0.01-0.05%, Mg ≤0.005%, and Sn. The content of C, Si, Mn, Cu, Ni, Mo, Sn, and Ti is 0.01-0.03% and the balance is Fe; the contents of C, Si, Mn, Cu, Ni, Mo, Sn, and Ti satisfy the following conditions: 1.2≤Cs≤1.8, 3.0≤Tg≤3.8, where Cs=(2[Si]+1[Ni]+3[Mo]+5[Cu]+25[Sn]-10[C]) / (5[C]+[Mn]+2[Mo]+[Ni]), and Tg=(2[Mn]+6[Ni]+3[Mo]+20[Ti]+40[Ce]) / (2[Si]+70[Sn]). This invention uses a Si-Ni-Mo-Cu-Sn alloy system to improve the corrosion resistance of the matrix and grain boundaries; by controlling the range of Cs and Tg, and employing fine-grain strengthening and induced nucleation techniques, the low-temperature toughness of the weld metal can be significantly improved. Experimental results show that the average annual corrosion rate of the submerged arc welding wire provided by the present invention is 0.55 to 0.68 mm / a, the corrosion step between the base metal and the weld is 8 to 22 μm, and the impact absorption energy KV2 of the deposited metal at -20℃ is not less than 80 J. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the weld metal samples after welding wire in Examples 1-10 and Comparative Examples 1-3.

[0021] Figure 2 This is a schematic diagram of the corrosion performance test of the weld metal deposited after welding of Examples 1-10 and Comparative Examples 1-3.

[0022] Figure 3 This is a macroscopic corrosion diagram of the corrosion pad from Example 1;

[0023] Figure 4 The image shows the macroscopic corrosion of the corrosion plate in Comparative Example 1.

[0024] Figure 5 The microstructure of the weld metal in Example 1;

[0025] Figure 6 The microstructure of the weld metal in Comparative Example 1 is shown.

[0026] Figure 7 This is a scanning electron microscope image of the weld metal in Example 1. Detailed Implementation

[0027] This invention provides a submerged arc welding wire, the chemical composition of which, by mass percentage, includes C 0.03-0.06%, Si 0.20-0.40%, Mn 1.00-1.40%, P ≤0.012%, S ≤0.005%, Ni 0.1-0.6%, Mo 0.10-0.30%, Cu 0.20-0.40%, Ti 0.02-0.06%, Ce 0.01-0.05%, Mg ≤0.005%, Sn 0.01-0.03%, and the balance Fe;

[0028] The contents of C, Si, Mn, Cu, Ni, Mo, Sn and Ti satisfy the following conditions: 1.2≤Cs≤1.8, 3.0≤Tg≤3.8, Cs=(2[Si]+1[Ni]+3[Mo]+5[Cu]+25[Sn]-10[C]) / (5[C]+[Mn]+2[Mo]+[Ni]), Tg=(2[Mn]+6[Ni]+3[Mo]+20[Ti]+40[Ce]) / (2[Si]+70[Sn]).

[0029] The submerged arc welding wire provided by this invention comprises 0.03-0.06% C by mass percentage, preferably 0.035-0.055%, and more preferably 0.040-0.045%. In this invention, carbon is the most important element for improving the strength of low-alloy steel welds; carbon can be dissolved in the weld metal, improving the stability of austenite, expanding the austenite phase region, lowering the austenite-ferrite transformation temperature, and refining the grains, thereby improving the strength of the weld. However, it also reduces the corrosion resistance of the weld, so the carbon content is limited to the range of 0.03-0.06%.

[0030] The submerged arc welding wire provided by this invention, by weight percentage, further includes 0.20-0.40% Si, preferably 0.30-0.40%, and more preferably 0.35-0.40%. In this invention, silicon is a strong deoxidizer, and it mainly exists in the weld in the form of solid solution and oxide inclusions. Silicon is a ferrite-forming element, and the ferrite content increases accordingly with the increase of silicon content. Furthermore, silicon oxides exhibit strong corrosivity under acidic conditions, which can improve the corrosion resistance of the weld. However, excessive addition of silicon can impair toughness, and the flux also has a Si transition. Therefore, it is necessary to control the silicon content within the range of 0.20-0.40%.

[0031] The submerged arc welding wire provided by this invention, by mass percentage, further includes 1.00–1.40% Mn, preferably 1.10–1.30%, and more preferably 1.20–1.25%. In this invention, manganese is an important deoxidizing and desulfurizing element, which can both improve the strength of the weld metal and reduce the tendency for welding hot cracking. Simultaneously, manganese is one of the few elements that can improve both weld strength and weld toughness. Mn can improve austenite stability, lower the phase transformation temperature, refine grains, and thus affect weld toughness. However, when the manganese content in the weld metal is too high, it has a significant impact on the large-sized brittle microstructure MA, resulting in reduced toughness. Therefore, the manganese content is limited to the range of 1.00–1.40%.

[0032] The submerged arc welding wire provided by this invention, by weight percentage, also includes P ≤ 0.012%. In this invention, phosphorus has a detrimental effect on the toughness of the weld metal; excessive content can easily cause cracks in the weld, and its content should be minimized.

[0033] The submerged arc welding wire provided by this invention, by weight percentage, also includes S ≤ 0.005%. In this invention, sulfur has a detrimental effect on the toughness of the weld metal; excessive content can easily cause cracks in the weld, and its content should be minimized.

[0034] The submerged arc welding wire provided by this invention, by mass percentage, further includes 0.1-0.6% Ni, preferably 0.40-0.5%, and more preferably 0.40-0.45%. In this invention, the main function of Ni is to improve the low-temperature toughness of the weld metal and enhance the uniform corrosion resistance of the matrix. Simultaneously, its solid solution strengthening effect is utilized to improve the strength of the weld metal. The mechanism by which Ni improves low-temperature toughness is through toughening the ferrite matrix and increasing stacking fault energy, thereby reducing its brittle transition temperature. Furthermore, Ni is an austenite stabilizing element, and its appropriate addition lowers the austenite phase transformation temperature. When Ni and Sn coexist, excessively high Ni content can easily lead to hot cracking; therefore, the Ni content in the welding wire composition is limited to the range of 0.1-0.6%.

[0035] The submerged arc welding wire provided by this invention, by weight percentage, further includes 0.10–0.30% Mo, preferably 0.15–0.25%, and more preferably 0.20–0.25%. In this invention, Mo is relatively stable during welding and has a high transition coefficient. Adding an appropriate amount of Mo can effectively refine the grain size and improve strength and toughness. Mo can shift the self-corrosion potential of the weld to a positive value and can segregate at the austenite grain boundaries, often existing in the weld in the form of molybdates, which improves the uniform corrosion of the matrix and reduces the tendency of preferential corrosion at the austenite grain boundaries. However, the Mo content should be controlled to avoid increasing the hardness. Therefore, the content in the welding wire composition is limited to the range of 0.10–0.30%.

[0036] The submerged arc welding wire provided by this invention, by weight percentage, further includes 0.20-0.40% Cu, preferably 0.25-0.35%, and more preferably 0.30-0.35%. In this invention, Cu is an important element for improving the corrosion resistance of the weld. Its mechanism of action can be divided into two parts: first, when galvanic corrosion occurs, Cu can passivate the anodic reaction and significantly slow down the corrosion rate; second, the enrichment of Cu effectively hinders the reaction between the matrix and the corrosive medium, reducing the corrosion rate. However, excessive addition of Cu can easily cause welding cracks, so the Cu content is controlled within the range of 0.20-0.40%.

[0037] The submerged arc welding wire provided by the present invention further comprises 0.02-0.06% Ti by mass percentage, preferably 0.04-0.05%. In the present invention, Ti is a carbon and nitrogen element that easily forms compounds at grain boundaries, which plays a certain pinning role on austenite grain boundaries, thereby refining the grains; at the same time, Ti combines with oxygen to form inclusions, and an appropriate amount of Ti is beneficial to promoting AF nucleation.

[0038] The submerged arc welding wire provided by this invention, by mass percentage, further includes 0.01-0.05% Ce, preferably 0.02-0.04%, and more preferably 0.03-0.035%. In this invention, Ce mainly plays three roles: First, it improves the composition of inclusions, forming inclusions rich in Ce, S, O, and Al elements with lower mismatch with acicular ferrite, thus becoming nucleation sites for acicular ferrite and increasing the acicular ferrite content; second, it refines the size of inclusions. During the oxide metallurgical process in the molten pool reaction, Ce-rich oxides combine with larger inclusions to form large inclusions, which float to the surface and are discharged from the molten pool, thereby refining the size of inclusions, reducing the possibility of larger diameter inclusions becoming crack initiations, and improving toughness; third, it refines the weld microstructure and improves toughness.

[0039] The gas-shielded welding wire provided by this invention, by weight percentage, also contains Mg ≤ 0.003%. In this invention, Mg can improve the welding pool reaction and the transition of alloying elements. At the same time, the addition of Mg can also improve the welding process, such as weld formation.

[0040] The submerged arc welding wire provided by this invention, by weight percentage, further includes 0.01-0.03% Sn, preferably 0.02-0.025%. In this invention, Sn tends to agglomerate at columnar grain boundaries, affecting the low-temperature toughness of the weld, and the effect on low-temperature toughness is quite significant; however, Sn can significantly improve the corrosion resistance of the matrix under acidic conditions. The mechanism is mainly that under acidic aqueous solution conditions, Sn precipitates on the matrix surface and is oxidized to SnO2 to protect the matrix, thus appropriately improving corrosion resistance. Excessive addition can easily damage toughness, so the Sn content is controlled within the range of 0.01-0.03%.

[0041] The submerged arc welding wire provided by this invention, by weight percentage, also includes the balance Fe. In this invention, Fe is a matrix element.

[0042] In this invention, the contents of C, Si, Mn, Cu, Ni, Mo, Sn, and Ti satisfy the following conditions: 1.2≤Cs≤1.8, 3.0≤Tg≤3.8, where Cs=(2[Si]+1[Ni]+3[Mo]+5[Cu]+25[Sn]-10[C]) / (5[C]+[Mn]+2[Mo]+[Ni]), and Tg=(2[Mn]+6[Ni]+3[Mo]+20[Ti]+40[Ce]) / (2[Si]+70[Sn]), preferably 1.3≤Cs≤1.6, 3.0≤Tg≤3.6.

[0043] The corrosion types occurring at welded joints in the inner bottom plate of corrosion-resistant crude oil storage tanks in actual service environments can be classified into four types: uniform corrosion of the substrate, electrochemical corrosion, microbial corrosion, and pitting corrosion. Uniform corrosion, electrochemical corrosion, and pitting corrosion are the key factors determining the corrosion rate of the welded joint. This invention mainly considers two aspects to improve the corrosion resistance of welded joints: using a Cu-Mo-Ni element system to ensure uniform corrosion of the matrix and adding trace amounts of Sn to reduce the corrosion rate of preferential corrosion zones (such as crystal planes <1,1,1> and grain boundaries). Both are indispensable. However, the addition of large amounts of fine-graining elements Mn, Ni, and Mo will increase the number of grains, the ratio of grain boundaries to interfaces, and the <1,1,1> crystal plane, thus disrupting the overall corrosion resistance balance. The elemental ratio of C, Si, Mn, Ni, Mo, Cu, and Sn is adjusted to satisfy the following relationship: Cs = (2[Si] + 1[Ni] + 3[Mo] + 5[Cu] + 25[Sn] - 10[C]) / (5[C] + [Mn] + 2[Mo] + [Ni]), and 1.2 ≤ Cs ≤ 1.8.

[0044] To ensure the corrosion resistance of the weld seam of the bottom plate of a corrosion-resistant crude oil storage tank, a large amount of corrosion-resistant elements, such as Si, Mo, Ni, Cu, and trace amounts of harmful elements, are often added to the welding wire to improve corrosion resistance. However, the addition of alloying elements will also reduce the low-temperature impact toughness of the weld seam. This invention employs grain refinement and inclusion heterogeneous nucleation techniques to obtain a refined microstructure dominated by acicular ferrite, thereby ensuring weld toughness. Mn, Ni, and Mo are important grain-refining elements, which refine grains by lowering the phase transformation temperature. Ni can also increase stacking fault energy, thus greatly improving the low-temperature toughness of the weld. The addition of Ti is mainly to obtain Ti-rich oxide inclusions, which have a low mismatch with acicular ferrite and become heterogeneous nucleation sites. Si is a ferrite element. Sn mainly accumulates at grain boundaries, causing grain boundary brittleness. By adjusting the ratio of Si, Mn, Mo, Ni, Ti, and Sn, the following conditions are met: Tg = (2[Mn] + 6[Ni] + 3[Mo] + 20[Ti] + 40[Ce]) / (2[Si] + 70[Sn]), and 3.0 ≤ Tg ≤ 3.8. In the oxide metallurgical process during the molten pool reaction, Ce-rich oxides combine with larger inclusions to form large inclusions. These large inclusions float to the surface and are removed from the molten pool, thus refining the inclusion size and reducing the likelihood of larger diameter inclusions becoming crack initiators, thereby improving toughness. In the weld metal, inclusions with a size of 0.6–1.8 μm have an 80% probability of becoming acicular ferrite nucleation sites, further refining the weld microstructure and improving toughness. Adjusting the mix proportions can help increase the effective inclusion size, thereby obtaining a large area of ​​AF microstructure, refining the microstructure, and improving toughness.

[0045] The weld metal obtained by the welding wire of this invention under typical heat input (25-45 kJ / cm) utilizes a Si-Ni-Mo-Cu-Sn alloy system to improve the corrosion resistance of the matrix and grain boundaries. Under accelerated corrosion simulation environment of pH=0.85 and 10% NaCl aqueous solution, the average annual corrosion rate is 0.68 mm / a. The base metal and weld are continuous and smooth, without corrosion steps, meeting the corrosion standards. Fine-grain strengthening and induced nucleation techniques are employed to refine the grains and enhance toughness. The microstructure in the service state is austenitic grain boundaries. The microstructure contains a small amount of blocky ferrite and fine acicular ferrite within the grains. The matrix contains dispersed submicron-sized composite oxide inclusions of Si, Mn, Ti, Ce, Al, etc. The inclusions have an increased probability of becoming nucleation sites for acicular ferrite, resulting in a higher proportion of intragranular acicular ferrite by area in the complex alloy system. The acicular ferrite microstructure is very fine, and the ferrite laths grow radially with large-angle grain boundaries between the laths, which has a strong resistance to crack propagation and can significantly improve the low-temperature toughness of the weld metal.

[0046] The welding wire of this invention is applicable to submerged arc welding of large corrosion-resistant crude oil storage tanks. Its corrosion resistance is 1 to 2 times that of conventional single-wire submerged arc welding wire. It also has a wide range of adjustable welding parameters, stable welding process performance under typical heat input (25 to 45 kJ / cm), good molten pool fluidity, beautiful deposited metal formation, and excellent crack resistance.

[0047] The welding wire of the present invention exhibits the following corrosion and mechanical properties of the deposited metal under typical heat input (25-45 kJ / cm): average annual corrosion rate of weld: 0.55-0.68 mm / a, corrosion step between base metal and weld: 8-20 μm, impact absorption energy at 20℃ - 20℃ KV2: 90.2-172.2 J.

[0048] The welding wire alloy system of this invention is reasonably controlled, and its wire rod smelting, rolling and welding wire drawing processes are easy to implement, with stable quality, making it suitable for large-scale promotion and application.

[0049] The present invention also provides a method for preparing the submerged arc welding wire described in the above technical solution, comprising the following steps:

[0050] (1) The alloy raw materials are successively smelted, cast, forged and hot rolled to obtain wire rod;

[0051] (2) The wire rod obtained in step (1) is subjected to coarse drawing, fine drawing and copper plating in sequence to obtain submerged arc welding wire.

[0052] This invention involves sequentially melting, casting, forging, and hot rolling alloy raw materials to obtain wire rod.

[0053] The present invention does not have any special limitation on the source of the alloy raw materials; commercially available products known to those skilled in the art that meet the composition requirements can be used.

[0054] The present invention does not impose any special limitations on the smelting and casting operations; operations familiar to those skilled in the art can be used.

[0055] After casting is completed, the present invention preferably removes the riser and grinds the surface of the cast ingot in sequence.

[0056] The present invention does not have any special limitations on the removal of risers and grinding of ingot surfaces; any operations known to those skilled in the art can be used.

[0057] In this invention, the process of casting followed by forging preferably includes heat preservation; the heat preservation temperature is preferably 1180-1220℃, more preferably 1200℃; and the heat preservation time is preferably 2 hours.

[0058] In this invention, the deformation of the forging is preferably 80%.

[0059] After forging, the present invention preferably grinds the forged product. The present invention does not have specific limitations on the grinding operation; any operation well known to those skilled in the art can be used.

[0060] In this invention, the hot rolling temperature is preferably 1180-1220°C, more preferably 1200°C; the total deformation of the hot rolling is preferably 60-80%.

[0061] After hot rolling, the present invention preferably subjectes the hot-rolled product to pickling and borax treatment sequentially to obtain wire rod. The present invention does not impose any particular limitations on the pickling and borax treatment operations; operations well-known to those skilled in the art can be used.

[0062] After obtaining the wire rod, the present invention performs coarse drawing, fine drawing and copper plating on the wire rod in sequence to obtain submerged arc welding wire.

[0063] After the fine drawing is completed, the product obtained by the fine drawing is preferably acid-washed. The acid-washing operation is not particularly limited in the present invention; any operation well known to those skilled in the art can be used.

[0064] In this invention, the copper plating method is preferably chemical copper plating; the copper plating thickness is preferably 0.19–0.23 μm. This invention does not impose any special limitations on the copper plating operation; any operation well-known to those skilled in the art can be used.

[0065] The preparation process provided by this invention is simple and suitable for industrial production.

[0066] The present invention also provides the application of the submerged arc welding wire described in the above technical solution or the submerged arc welding wire prepared by the preparation method described in the above technical solution in the bottom plate of crude oil storage tank.

[0067] The present invention does not impose any special limitations on the application of the submerged arc welding wire in the bottom plate of crude oil storage tanks; any operation familiar to those skilled in the art can be used.

[0068] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0069] Examples 1-10

[0070] The chemical composition of submerged arc welding wire is shown in Table 1.

[0071] Comparative Examples 1-3

[0072] The chemical composition of the welding wire is shown in Table 1.

[0073] Table 1. Chemical composition (wt%) of welding wires in Examples 1-10 and Comparative Examples 1-3

[0074]

[0075]

[0076] The preparation methods of the welding wires in Examples 1-10 and Comparative Examples 1-3 are as follows:

[0077] Steel for welding wire was smelted in a 75kg vacuum induction furnace. Steel billets were prepared according to the alloy composition of the welding wire. The billets were filled into the vacuum smelting furnace, evacuated to a vacuum, and protected with argon gas. The furnace was heated to a high temperature until the billets melted into molten steel. A measured amount of Ce alloy blocks was added, and the furnace temperature was adjusted. The billets were then cast into cylindrical steel ingots with a diameter of φ150mm × 170mm. The risers were removed from the ingots, the surface was polished, and the furnace was heated to 1200℃ and held for 2 hours. The ingots were then removed, forged into square billets with a cross-section of 5mm × 50mm and a length of approximately 1500mm. The forged square billets were polished, heated to 1200℃ in the furnace, rolled, and drawn into φ6.5mm wire rods. The wire rods underwent pickling, borax treatment, rough drawing, fine drawing, pickling, and copper plating to finally produce φ4mm submerged arc welding wire. The copper plating thickness was 0.19mm.

[0078] The welding wires of Examples 1-10 and Comparative Examples 1-3 were subjected to single-wire welding metal deposition tests according to the welding process parameters in Table 2. The welding heat input was 25-45 kJ / cm, alkaline sintering flux was used for welding, and the layer temperature was controlled not to exceed 160℃.

[0079] Table 2 Welding process parameters for deposited metal test

[0080]

[0081] After welding, the specimens underwent visual inspection. Ultrasonic testing was used to perform non-destructive testing on the weld metal. If the test was successful, impact test specimens and corrosion plates were taken from the welded metal. The specimen dimensions and test methods were performed according to GB / T 228 and MSC289. The impact test specimen was cut from the center of the weld metal, with its longitudinal axis perpendicular to the length of the weld metal, the notch face perpendicular to the surface of the weld metal, and the notch axis located at the center of the weld metal. The specimen dimensions were 10×10×55mm, and the impact test method was performed according to GB / T229. Figure 1 The diagram shows the structural sampling of the weld metal after welding in Examples 1-10 and Comparative Examples 1-3. After sampling, the surface of the ferrule was polished with 600-grit sandpaper, and the ferrule was fully immersed in a simulated environment (pH = 0.85, 10% NaCl aqueous solution) for 72 hours to simulate corrosion. Figure 2 The average annual corrosion rate was calculated according to Formula I. After the corrosion-resistant strips of the welded joint were fully immersed for 168 hours, the corrosion steps were observed under a 100x metallographic microscope. The macroscopic corrosion diagram of the corrosion-resistant strips in Example 1 is shown below. Figure 3 As shown, the macroscopic corrosion diagram of the corrosion-resistant pad in Comparative Example 1 is as follows. Figure 4 As shown.

[0082]

[0083] In Equation I: W represents weight loss (g), and S represents surface area (cm²). 2 D is the density (g / cm³). 3 ).

[0084] The corrosion and mechanical properties of the weld metal of Examples 1-10 and Comparative Examples 1-3 are shown in Table 3.

[0085] Table 3. Corrosion and mechanical properties of weld metal from Examples 1-10 and Comparative Examples 1-3

[0086]

[0087]

[0088] From Table 3, Figure 3 as well as Figure 4 It can be seen that the chemical composition of Examples 1 to 10 meets the requirements of the present invention. When Cs satisfies 1.3≤Cs≤1.6, the average annual corrosion rate of the weld is 0.55 to 0.68 mm / a, and the corrosion step between the base metal and the weld is 8 to 20 μm, which meets the corrosion requirements of the invention. When Tg satisfies 3.0≤Tg≤3.8, the impact absorption energy KV2 of the weld metal at -20℃ is not less than 80J. The chemical composition of Comparative Examples 1 to 3 does not meet the requirements of the invention, and the corrosivity or impact energy of the weld metal does not meet the standard, nor can the low-temperature impact toughness of the weld metal be guaranteed.

[0089] Metallographic specimens were taken from the impact specimens of the weld metal. Figure 5 The microstructure of the weld metal in Example 1 is shown. Figure 6 The microstructure of the weld metal in Comparative Example 1 is shown.

[0090] Combination Figure 5 As can be seen, the microstructure of the weld metal in the embodiment is mainly composed of acicular ferrite, with a small amount of grain boundary ferrite and granular bainite. The acicular ferrite has fine grains and large-angle grain boundaries, which can hinder crack propagation and improve impact toughness.

[0091] Combination Figure 6 It can be seen that the microstructure of the comparative weld metal is mainly composed of massive ferrite, a small amount of acicular ferrite and granular bainite.

[0092] The content of acicular ferrite in the weld metal of Examples 1-10 and Comparative Examples 1-3 was statistically analyzed, as shown in Table 4.

[0093] Table 4. Statistics on the proportion of acicular ferrite in the examples and comparative examples.

[0094]

[0095]

[0096] As can be seen from Table 4, the content of acicular ferrite in the weld metal of the present invention is not less than 40%.

[0097] To analyze the reasons for the increased proportion of acicular ferrite, the metallographic sample of Example 1 was observed using SEM electron microscopy. Figure 7 As shown, Figure 7 This is a scanning electron microscope image of the weld metal in Example 1.

[0098] Combination Figure 7 Analysis revealed that the deposited metal inclusions in Example 1 were SiO2-MnO-Ce. x O y -TiO x Composite inclusions become nucleation sites for acicular ferrite, and it was found that the probability of inclusions with a size of 0.2 to 1.8 μm becoming nucleation sites is as high as 80%. The adjustment of the proportion of Si, Mn, Ce and Ti elements further refines the inclusion size, resulting in more effective inclusions and increased AF content, thereby improving the impact toughness of the weld.

[0099] The test results from the above embodiments and comparative examples show that the submerged arc welding solid wire of the present invention achieves the mechanical properties of the deposited metal under typical heat input (25-45 kJ / cm), that is, it obtains good strength and corrosion resistance, and also has excellent low-temperature impact toughness. The impact absorption energy Akv of the weld metal at -20℃ is 90.2-172.2 J. It can be applied to the production and welding manufacturing of large welded structural parts in industries such as petroleum and shipbuilding.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A submerged arc welding wire, the chemical composition of which, by mass percentage, is C 0.03~0.06%, Si 0.20~0.40%, Mn 1.00~1.40%, P≤0.012%, S≤0.005%, Ni 0.1~0.6%, Mo 0.10~0.30%, Cu 0.25~0.40%, Ti 0.02~0.06%, Ce 0.01~0.05%, Mg≤0.005%, Sn 0.01~0.03%, and the balance Fe; The contents of C, Si, Mn, Cu, Ni, Mo, Sn and Ti satisfy the following conditions: 1.3≤Cs≤1.6, 3.0≤Tg≤3.6, where Cs=(2[Si]+1[Ni]+3[Mo]+5[Cu]+25[Sn]-10[C]) / (5[C]+[Mn]+2[Mo]+[Ni]), and Tg=(2[Mn]+6[Ni]+3[Mo]+20[Ti]+40[Ce]) / (2[Si]+70[Sn]).

2. The submerged arc welding wire according to claim 1, characterized in that, The chemical composition, by mass percentage, is: C 0.035~0.055%, Si 0.30~0.40%, Mn 1.10~1.30%, P≤0.012%, S≤0.005%, Ni 0.15~0.5%, Mo 0.15~0.25%, Cu 0.25~0.35%, Ti 0.04~0.05%, Ce 0.02~0.04%, Mg≤0.003%, Sn 0.02~0.025%, and the balance Fe.

3. The submerged arc welding wire according to claim 2, characterized in that, The chemical composition, by mass percentage, is: C 0.040~0.045%, Si 0.35~0.40%, Mn 1.20~1.25%, P≤0.012%, S≤0.005%, Ni 0.20~0.25%, Mo 0.20~0.25%, Cu 0.30~0.35%, Ti 0.04~0.05%, Ce 0.03~0.04%, Mg 0.001~0.003%, Sn 0.02~0.025%, and the balance Fe.

4. A method for preparing the submerged arc welding wire according to any one of claims 1 to 3, comprising the following steps: (1) The alloy raw materials are successively smelted, cast, forged and hot rolled to obtain wire rod; (2) The wire rod obtained in step (1) is subjected to coarse drawing, fine drawing and copper plating in sequence to obtain submerged arc welding wire.

5. The preparation method according to claim 4, characterized in that, The process in step (1) includes heat preservation after casting and before forging.

6. The preparation method according to claim 5, characterized in that, The insulation temperature is 1180~1220℃, and the insulation time is 2h.

7. The preparation method according to claim 4, characterized in that, The hot rolling temperature in step (1) is 1180~1220℃, and the total deformation of the hot rolling is 60~80%.

8. The preparation method according to claim 7, characterized in that, The hot rolling temperature is 1200℃.

9. The application of the submerged arc welding wire according to any one of claims 1 to 3 or the submerged arc welding wire prepared by the preparation method according to any one of claims 4 to 8 in the bottom plate of crude oil storage tank.

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