Austenitic stainless steel welding wire for hydrogen conveying pipeline and preparation method and application of austenitic stainless steel welding wire

Abstract

The invention provides an austenitic stainless steel welding wire for a hydrogen conveying pipeline as well as a preparation method and application thereof, and relates to the technical field of stainless steel welding wires for hydrogen conveying pipelines of gas turbines. The size diameter of the austenitic stainless steel welding wire for the hydrogen conveying pipeline ranges from 0.8 mm to 2.0 mm, and the austenitic stainless steel welding wire for the hydrogen conveying pipeline comprises, by mass, less than or equal to 0.12% of C, 0.35%-0.50% of Si, 1.2%-5.8% of Mn, less than or equal to 0.03% of P, less than or equal to 0.03% of S, 17.8%-19.7% of Cr, 13.9%-15.8% of Ni, 1.80%-2.45% of Mo, 0.16%-0.24% of N, 0.01%-0.25% of Nb + V and the balance Fe and other inevitable impurities. The austenitic stainless steel welding wire for the hydrogen conveying pipeline is obtained by combining reasonable component design with a reasonable manufacturing process, the method is simple and easy to operate, green and environmentally friendly, low in cost, short in process and high in efficiency, the mechanical property and hydrogen embrittlement resistance are improved when the austenitic stainless steel welding wire is applied to stainless steel of the hydrogen conveying pipeline of a gas turbine, and industrial large-scale production and popularization are facilitated.

Description

Technical Field

[0001] This invention relates to the technical field of stainless steel welding wire for hydrogen transmission pipelines of gas turbines, and in particular to an austenitic stainless steel welding wire for hydrogen transmission pipelines, its preparation method, and its application. Background Technology

[0002] With the ever-increasing global demand for clean energy, the construction of hydrogen transportation infrastructure is crucial as hydrogen is an efficient and clean energy carrier. Hydrogen pipelines are a key mode of large-scale hydrogen transportation, and austenitic stainless steel, due to its excellent corrosion resistance, high strength, and toughness, is widely used in the manufacture of hydrogen pipelines. During the welding process of hydrogen pipelines, the performance of the welding wire directly affects the quality of the weld joint and the service performance of the pipeline.

[0003] Existing austenitic stainless steel welding wires present several problems when used for welding hydrogen pipelines. For example, in a hydrogen environment, welded joints are prone to hydrogen embrittlement, leading to a decrease in joint toughness and strength, which affects the safe operation of the pipeline. Furthermore, some welding wires exhibit poor welding process performance, such as excessive spatter and poor weld formation, reducing welding efficiency and quality.

[0004] Chinese patent CN116586819A discloses a welding wire steel and welding wire for welding low-pressure hydrogen pipelines and its preparation method. The composition has low nickel and chromium content, and the preparation process does not involve heat treatment of the wire rod, resulting in low mechanical properties and elongation of the welded joint.

[0005] Chinese patent CN118559281A discloses an austenitic stainless steel welding wire and its preparation method, which uses a high Mn content. This high Mn content easily leads to segregation during ingot solidification, resulting in an uneven microstructure. If subsequent hot working (such as rolling and forging) and heat treatment processes cannot effectively eliminate this segregation, it will affect the stability of the welding wire's performance and the quality of the weld. A higher Mn content may increase the material's deformation resistance, potentially leading to a stronger work hardening tendency and a higher risk of wire breakage when drawn into fine-diameter welding wires.

[0006] Chinese patent CN113798728A discloses an austenitic stainless steel welding wire, its preparation method, and its application. The distinctive feature of this welding wire's composition design is the absence of microalloying elements such as niobium (Nb) and vanadium (V). In traditional material design, elements such as Nb and V are often used to refine the microstructure by inhibiting grain growth and precipitation strengthening, effectively improving the material's strength under certain conditions.

[0007] Chinese patent CN102649202A discloses a stainless steel welding wire, which describes an austenitic stainless steel welding wire with a high content of copper (Cu: 2.5-4.0%). While the addition of copper offers some benefits, such as precipitation strengthening and corrosion resistance, the physical and metallurgical properties of copper differ significantly from those of the base ferroalloy. Excessive copper may increase the weld metal's susceptibility to hot cracking; furthermore, under certain conditions, copper precipitation can form a copper-rich phase, potentially leading to uneven composition in the weld and thus affecting its performance.

[0008] Therefore, developing a high-performance austenitic stainless steel welding wire suitable for welding hydrogen pipelines is of great practical significance. Summary of the Invention

[0009] To address the technical problems of high hydrogen embrittlement sensitivity and difficulty in balancing weld strength and plasticity in existing technologies, this invention proposes an austenitic stainless steel welding wire for hydrogen transportation pipelines, its preparation method, and its application. The technical solution is as follows:

[0010] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the welding wire is Φ0.8-2.0mm, and the chemical composition by mass percentage is: C≤0.12%, Si 0.35-0.50%, Mn 1.2-5.8%, P≤0.03%, S≤0.03%, Cr 17.8-19.7%, Ni 13.9-15.8%, Mo 1.80-2.45%, N 0.16-0.24%, Nb+V0.01-0.25%, with the balance being Fe and other unavoidable impurities.

[0011] The following are the roles that each element plays in the welding wire:

[0012] C is an element that strongly stabilizes austenite and expands the austenite region. It can play a significant strengthening role in steel. However, if the C content is too high, a large number of intergranular carbides will precipitate at the grain boundaries, which will seriously affect its intergranular corrosion resistance and hydrogen embrittlement resistance.

[0013] Si: It can be used as an alloying element, but it also has harmful effects. In the steelmaking process, Si acts as a reducing agent and deoxidizer, which has a good deoxidizing effect, can improve welding processability and weld metal toughness, and also has a certain solid solution strengthening effect, which can improve the strength of the material; however, on the other hand, excessive Si content will increase the tendency of weld cracking.

[0014] Mn: To expand the austenitic phase region, Mn can increase the solubility of N in austenitic stainless steel and also has a certain solid solution strengthening effect. In addition, the addition of Mn can reduce the harmful effects of impurities such as S and P, and improve the resistance of austenitic stainless steel to crystallization cracking.

[0015] P and S: These are harmful elements in alloys. These two elements tend to segregate near grain boundaries, which can easily lead to welding hot cracks and reduce the toughness of the material. Their content needs to be strictly controlled.

[0016] Cr: is a key element determining the corrosion resistance of stainless steel. Cr can also combine with elements such as nitrogen (N) and carbon (C) to form Cr₂N and Cr₂. 23 Nitrides and carbides such as C6 can increase the strength of steel, but reduce its plasticity and toughness.

[0017] Ni is an austenite-stabilizing element. Increasing the nickel content can improve the stability of austenite, and studies have shown that it can enhance the resistance of austenitic stainless steel to hydrogen embrittlement.

[0018] Mo exhibits significant solid solution strengthening effects in austenitic stainless steels, while also significantly enhancing their resistance to pitting corrosion.

[0019] Nitrogen (N) is an extremely strong austenite-forming element that can stabilize austenite structures. At the same time, nitrogen can dissolve in austenite to increase the strength and hardness of steel.

[0020] Nb and V: Commonly used microalloying elements in austenitic stainless steel. Nb has a stronger grain strengthening effect, while V has a stronger precipitation strengthening effect.

[0021] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0022] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0023] S2, billet forging: hot forging of the densely crystalline steel ingot of S1 to obtain a 50×50mm billet;

[0024] S3, Hot-rolled wire rod: The square billet of S2 is hot-rolled to obtain hot-rolled wire rod with a diameter of 7.0-8.0mm;

[0025] S4. Continuous cold drawing and annealing: The hot-rolled wire rod of S3 is continuously cold-drawn and annealed to obtain austenitic stainless steel welding wire for hydrogen pipelines.

[0026] Optionally, the hot forging temperature in S2 is 1100-1150℃, the holding time is 120-200min, the forging ratio is 3-6, and the final forging temperature is maintained at ≥950℃ during the forging process.

[0027] Optionally, the hot rolling temperature in S3 is 1080-1150℃, the holding time is 90-130min, the rolling process adopts a multi-pass small reduction process, the total reduction is 60-80%, the single-pass reduction is controlled at 10-20%, and the final rolling temperature is controlled not lower than 950℃.

[0028] Optionally, in S4, continuous cold drawing and annealing are performed. The hot-rolled wire rod adopts a multi-pass drawing process, first rough drawing to an intermediate size of Φ2.2mm, and then fine drawing to the final target size of Φ0.8-2.0mm. The reduction rate per pass is controlled at 15-30%. During the drawing process, when the total reduction rate reaches a certain level and the material hardens severely and cannot continue drawing, intermediate annealing is required. The annealing temperature is between 1050-1100℃.

[0029] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method is described. The welding process of the austenitic stainless steel welding wire is as follows: tungsten inert gas (TIG) welding is used, with a welding current of 125-160A, a welding voltage of 12-16V, DC positive polarity, a welding speed of 1-2mm / s, and argon gas with a purity of not less than 99.99%. The flow rate of the shielding gas is controlled at 13-18L / min during the welding process.

[0030] Optionally, the microstructure of the weld metal formed by welding the hydrogen transmission pipeline of the gas turbine to the hydrogen transmission pipeline using austenitic stainless steel welding wire consists of an austenitic phase with a volume fraction of more than 95%, a ferrite phase with a volume fraction of no more than 5%, and a carbide phase with a volume fraction of no more than 0.5%. The austenitic phase is equiaxed or dendritic, with a grain size of 10-50 μm; the δ-ferrite phase is discontinuously distributed in a worm-like or skeletal pattern, with a size of 1-10 μm; and the carbide phase is mainly M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.1-0.5 μm.

[0031] Optionally, the weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength ≥450MPa, an elongation after fracture ≥25%, and a hydrogen embrittlement sensitivity ≤8%.

[0032] Optionally, in the application of the austenitic stainless steel welding wire for hydrogen transmission pipelines according to claim 8, the material of the gas turbine hydrogen transmission pipeline welded by the austenitic stainless steel welding wire for hydrogen transmission pipelines includes 304L, 316L, etc.

[0033] Technical principle of the invention:

[0034] This invention significantly improves the stability of the austenitic phase, inhibits hydrogen-induced martensitic transformation, and reduces hydrogen trapping sites and local stress concentration by adjusting key austenitizing elements (high Ni equivalent: Ni 13.9-15.8%, high N 0.16-0.24%), thereby enhancing the material's resistance to hydrogen-induced cracking. Mo strengthens grain boundaries, further hindering hydrogen diffusion and crack propagation. N and Mn (1.2-5.8%), as strong austenite stabilizing elements and solid solution strengthening elements, can further improve the strength-toughness balance of weld metal while increasing strength. Microalloying carbide-forming elements (Nb+V) (total 0.01-0.25%) can form fine and stable carbonitrides, pinning grain boundaries, inhibiting grain growth during welding thermal cycling, while increasing recrystallization temperature, refining the weld solidification structure, and improving its performance.

[0035] The above technical solution has at least the following advantages compared with the existing technology:

[0036] The above-mentioned solution proposes an austenitic stainless steel welding wire for hydrogen transportation pipelines, its preparation method, and its application, which can solve the technical problems of high hydrogen embrittlement sensitivity and difficulty in balancing weld strength and plasticity in the prior art.

[0037] This invention ensures that austenitic stainless steel welding wire has good weldability and that the weld metal composition meets the requirements by designing alloy composition and using supporting processes such as vacuum induction smelting, purification, forging, rolling and drawing, and controlling process parameters in each process. It can be used to weld austenitic stainless steel pipes for hydrogen transportation pipelines, including 304L and 316L.

[0038] This invention, through electroslag remelting and other methods, can effectively remove impurity elements and gas content, significantly improve the solidification structure of steel ingots, reduce component segregation, and improve metal purity and uniformity.

[0039] This invention, through forging, can break up coarse cast dendritic structures, refine grains, eliminate microscopic defects, and improve the density and mechanical properties of materials.

[0040] This invention, through hot rolling, can further optimize the microstructure, forming uniform and fine equiaxed crystals, providing a good microstructure basis for subsequent drawing.

[0041] This invention processes the material to the target diameter (e.g., Φ0.8-2.0mm) through solution treatment followed by multiple drawing and annealing processes, while controlling the work hardening process to give the welding wire high strength, good plasticity and stable wire feeding performance, ultimately ensuring that the weld metal has excellent resistance to hydrogen embrittlement and mechanical properties.

[0042] The welding process of the austenitic stainless steel welding wire for hydrogen transportation pipelines prepared by this invention is as follows: tungsten inert gas (TIG) welding is used, with a welding current of 125–160 A, a welding voltage of 12–16 V, DC positive polarity, a welding speed of 1–2 mm / s, and argon gas with a purity of not less than 99.99%. The flow rate of the shielding gas is controlled at 13–18 L / min during the welding process.

[0043] The weld metal formed by welding austenitic stainless steel welding wire for hydrogen pipelines to gas turbine hydrogen pipelines prepared by the present invention has a tensile strength ≥450MPa, an elongation after fracture ≥25%, and a hydrogen embrittlement sensitivity ≤8%.

[0044] In summary, compared with other traditional methods, the method of this invention obtains austenitic stainless steel welding wire for hydrogen transportation pipelines through reasonable component design and reasonable manufacturing process; the method is simple to operate, environmentally friendly, low in cost, short in process, and high in efficiency, which is conducive to large-scale industrial production and promotion. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a stress-strain curve of a welded joint using austenitic stainless steel welding wire for hydrogen transport pipelines, according to Embodiment 1 of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0048] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0049] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0050] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0051] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0052] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the welding wire is Φ0.8-2.0mm, and the chemical composition by mass percentage is: C≤0.12%, Si 0.35-0.50%, Mn 1.2-5.8%, P≤0.03%, S≤0.03%, Cr 17.8-19.7%, Ni 13.9-15.8%, Mo 1.80-2.45%, N 0.16-0.24%, Nb+V0.01-0.25%, with the balance being Fe and other unavoidable impurities.

[0053] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0054] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0055] S2, billet forging: hot forging of the densely crystalline steel ingot of S1 to obtain a 50×50mm billet;

[0056] S3, Hot-rolled wire rod: The square billet of S2 is hot-rolled to obtain hot-rolled wire rod with a diameter of 7.0-8.0mm;

[0057] S4. Continuous cold drawing and annealing: The hot-rolled wire rod of S3 is continuously cold-drawn and annealed to obtain austenitic stainless steel welding wire for hydrogen pipelines.

[0058] Specifically, in S2, the hot forging temperature is 1100-1150℃, the holding time is 120-200min, the forging ratio is 3-6, and the final forging temperature is maintained at ≥950℃ during the forging process.

[0059] Specifically, in S3, the hot rolling temperature is 1080-1150℃, the holding time is 90-130min, the rolling process adopts a multi-pass small reduction process, the total reduction is 60-80%, the single-pass reduction is controlled at 10-20%, and the final rolling temperature is controlled not lower than 950℃.

[0060] Specifically, in S4, continuous cold drawing and annealing are performed. Hot-rolled wire rods are drawn using a multi-pass drawing process. First, they are rough drawn to an intermediate size of Φ2.2mm, and then fine drawn to the final target size of Φ0.8-2.0mm. The reduction rate per pass is controlled at 15-30%. During the drawing process, when the total reduction rate reaches a certain level and the material hardens severely and cannot be drawn further, intermediate annealing is required. The annealing temperature is between 1050-1100℃.

[0061] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method is described. The welding process of the austenitic stainless steel welding wire is as follows: tungsten inert gas (TIG) welding is used, with a welding current of 125-160A, a welding voltage of 12-16V, DC positive polarity, a welding speed of 1-2mm / s, and argon gas with a purity of not less than 99.99%. The flow rate of the shielding gas is controlled at 13-18L / min during the welding process.

[0062] Specifically, the microstructure of the weld metal formed by welding the hydrogen transmission pipeline of the gas turbine to the hydrogen transmission pipeline using austenitic stainless steel welding wire consists of austenitic phase with a volume fraction of more than 95%, ferrite phase with a volume fraction of no more than 5%, and carbide phase with a volume fraction of no more than 0.5%. The austenitic phase is equiaxed or dendritic, with a grain size of 10-50 μm; the δ-ferrite phase is discontinuously distributed in a worm-like or skeletal pattern, with a size of 1-10 μm; and the carbide phase is mainly M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.1-0.5 μm.

[0063] Specifically, the weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength ≥450MPa, an elongation after fracture ≥25%, and a hydrogen embrittlement sensitivity ≤8%.

[0064] In particular, the application of the austenitic stainless steel welding wire for hydrogen transmission pipelines according to claim 8 is characterized in that the material of the gas turbine hydrogen transmission pipeline welded by the austenitic stainless steel welding wire for hydrogen transmission pipelines includes 304L, 316L, etc.

[0065] Example 1

[0066] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the austenitic stainless steel welding wire for hydrogen transportation pipelines is Φ2.0mm, and the chemical composition by mass percentage is: C 0.018%, Si 0.35%, Mn 1.85%, P 0.020%, S 0.010%, Cr 19.5%, Ni 14.2%, Mo 1.9%, N 0.18%, Nb 0.02%, V 0.07%, with the balance being Fe and other unavoidable impurities.

[0067] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0068] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0069] S2, billet forging: The densely crystalline steel ingot of S1 is hot forged at a temperature of 1100℃ and a holding time of 120min. The forging ratio is 4.5. During the forging process, the final forging temperature is maintained at ≥950℃ to obtain a 50×50mm billet.

[0070] S3, Hot Rolling of Wire Rod: The square billet of S2 is hot rolled at a temperature of 1080℃ and a holding time of 100min. The rolling is carried out at a final rolling temperature of ≥950℃. The hot rolling adopts a multi-pass small reduction method, with a total reduction of 65% and a single pass reduction controlled at 10%, to obtain a Φ7.0mm hot rolled wire rod.

[0071] S4. Continuous cold drawing and annealing treatment: The hot-rolled wire rod of S3 is first roughly drawn to Φ2.2mm, then heated to 1050℃ for solution annealing treatment, and finally finely drawn to the final target Φ2.0mm to obtain austenitic stainless steel welding wire for hydrogen transportation pipelines.

[0072] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method, with the following welding parameters: tungsten inert gas (TIG) welding is used, the welding current is 135A, the welding voltage is 14V, DC positive polarity is used, the welding speed is 1.3mm / s, the shielding gas is argon gas with a purity of 99.995%, and the shielding gas flow rate is controlled at 15L / min during the welding process.

[0073] The microstructure of the weld metal formed by welding the hydrogen transport pipeline to the 316L stainless steel pipe of the gas turbine hydrogen transport pipeline using austenitic stainless steel welding wire consists of 96% austenite phase, 3% ferrite phase, and 0.4% carbide phase by volume. The austenite phase is equidendritic with a grain size of 25 μm; the δ-ferrite phase is discontinuously distributed in a worm-like pattern with a size of 3-4 μm; and the carbide phase is mainly composed of M... 23 C6 type, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.2-0.3 μm.

[0074] The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength of 458 MPa, an elongation after fracture of 35%, and a hydrogen embrittlement sensitivity of 6%.

[0075] Example 2

[0076] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the austenitic stainless steel welding wire for hydrogen transportation pipelines is Φ1.2mm, and the chemical composition by mass percentage is: C 0.015%, Si 0.42%, Mn 3.40%, P 0.015%, S 0.015%, Cr 18.4%, Ni 15.5%, Mo 2.2%, N 0.20%, V 0.10%, with the balance being Fe and other unavoidable impurities.

[0077] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0078] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0079] S2, billet forging: The densely crystalline steel ingot of S1 is hot forged at a temperature of 1120℃ and a holding time of 150min. The forging ratio is 5.0. During the forging process, the final forging temperature is maintained at ≥950℃ to obtain a 50×50mm billet.

[0080] S3, Hot Rolling of Wire Rod: The square billet of S2 is hot rolled at a temperature of 1100℃ and a holding time of 110min. The rolling is carried out at a final rolling temperature of ≥950℃. The hot rolling adopts multiple passes with small reductions, the total reduction is 70%, and the single pass reduction is controlled at about 15%, to obtain a hot-rolled wire rod with a diameter of Φ7.0mm.

[0081] S4. Continuous cold drawing and annealing: The S3 hot-rolled wire rod is first rough-drawn to Φ2.2mm, then heated to 1060℃ for solution annealing, and finally fine-drawn through multiple passes to the final target Φ1.8mm to obtain austenitic stainless steel welding wire for hydrogen transportation pipelines. During the drawing process, when the material hardens to the point that drawing cannot continue, intermediate annealing at 1060℃ is required.

[0082] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method, with the following welding parameters: tungsten inert gas (TIG) welding is used, the welding current is 140A, the welding voltage is 14V, DC positive polarity is used, the welding speed is 1.5mm / s, the shielding gas is argon gas with a purity of 99.995%, and the shielding gas flow rate is controlled at 16L / min during the welding process.

[0083] The microstructure of the weld metal formed by welding the hydrogen transport pipeline to the 316L stainless steel pipe of the gas turbine hydrogen transport pipeline using austenitic stainless steel welding wire consists of 97% austenite phase, 2.5% ferrite phase, and 0.2% carbide phase by volume. The austenite phase is equidendritic with a grain size of 30 μm; the δ-ferrite phase is discontinuously distributed in a worm-like pattern with a size of 3-4 μm; and the carbide phase is mainly composed of M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.1-0.2 μm.

[0084] The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength of 465 MPa, an elongation after fracture of 32%, and a hydrogen embrittlement sensitivity of 5%.

[0085] Example 3

[0086] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the austenitic stainless steel welding wire for hydrogen transportation pipelines is Φ0.8mm, and the chemical composition by mass percentage is: C 0.010%, Si 0.32%, Mn 5.50%, P 0.005%, S 0.015%, Cr 18.9%, Ni 14.1%, Mo 2.4%, N 0.24%, Nb 0.05%, V 0.12%, with the balance being Fe and other unavoidable impurities.

[0087] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0088] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0089] S2, billet forging: The densely crystalline steel ingot of S1 is hot forged at a temperature of 1140℃ and a holding time of 180min. The forging ratio is 5. During the forging process, the final forging temperature is maintained at ≥950℃ to obtain a 50×50mm billet.

[0090] S3, Hot Rolled Wire Rod: The S2 square billet is hot rolled at a temperature of 1130℃ and a holding time of 120min. The final rolling temperature is ≥950℃. The hot rolling adopts a multi-pass small reduction method, with a total reduction of 75% and a single pass reduction controlled at about 18%, to obtain a Φ8.0mm hot rolled wire rod.

[0091] S4. Continuous cold drawing and annealing: The S3 hot-rolled wire rod is first rough-drawn to Φ2.2mm, then heated to 1080℃ for solution annealing, and finally fine-drawn through multiple passes to the final target Φ0.8mm to obtain austenitic stainless steel welding wire for hydrogen transportation pipelines. During the drawing process, when the material hardens to the point that drawing cannot continue, intermediate annealing at 1080℃ is required.

[0092] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method, with the following welding parameters: tungsten inert gas (TIG) welding is used, the welding current is 150A, the welding voltage is 15V, DC positive polarity is used, the welding speed is 1.7mm / s, the shielding gas is argon gas with a purity of 99.996%, and the shielding gas flow rate is controlled at 18L / min during the welding process.

[0093] The microstructure of the weld metal formed by welding the hydrogen transport pipeline to the 316L stainless steel pipe of the gas turbine hydrogen transport pipeline using austenitic stainless steel welding wire consists of 98% austenite phase, 1.5% ferrite phase, and 0.1% carbide phase by volume. The austenite phase is equidendritic with a grain size of 40 μm; the δ-ferrite phase is discontinuously distributed in a worm-like pattern with a size of 3-4 μm; and the carbide phase is mainly composed of M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.15-0.20 μm.

[0094] The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength of 472 MPa, an elongation after fracture of 30%, and a hydrogen embrittlement sensitivity of 3%.

[0095] Example 4

[0096] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the austenitic stainless steel welding wire for hydrogen transportation pipelines is Φ1.2mm, and the chemical composition by mass percentage is: C 0.012%, Si 0.40%, Mn 4.50%, P 0.006%, S 0.045%, Cr 19.4%, Ni 14.5%, Mo 1.5%, N 0.20%, Nb 0.03%, V 0.15%, with the balance being Fe and other unavoidable impurities.

[0097] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0098] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0099] S2, billet forging: The densely crystalline steel ingot of S1 is hot forged at a temperature of 1130℃ and a holding time of 160min. The forging ratio is 5. During the forging process, the final forging temperature is maintained at ≥950℃ to obtain a 50×50mm billet.

[0100] S3, Hot Rolled Wire Rod: The S2 square billet is hot rolled at a temperature of 1120℃ and a holding time of 110min. The final rolling temperature is ≥950℃. The hot rolling adopts a multi-pass small reduction method, with a total reduction of 78% and a single pass reduction controlled at about 15%, to obtain a Φ8.0mm hot rolled wire rod.

[0101] S4. Continuous cold drawing and annealing: The S3 hot-rolled wire rod is first rough-drawn to Φ2.2mm, then heated to 1090℃ for solution annealing, and finally fine-drawn through multiple passes to the final target Φ1.2mm to obtain austenitic stainless steel welding wire for hydrogen transportation pipelines. During the drawing process, when the material hardens to the point that drawing cannot continue, intermediate annealing at 1090℃ is required.

[0102] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method, with the following welding parameters: tungsten inert gas (TIG) welding is used, the welding current is 155A, the welding voltage is 13V, DC positive polarity is used, the welding speed is 1.6mm / s, the shielding gas is argon gas with a purity of 99.993%, and the shielding gas flow rate is controlled at 14L / min during the welding process.

[0103] The microstructure of the weld metal formed by welding the hydrogen transport pipeline to the 316L stainless steel pipe of the gas turbine hydrogen transport pipeline using austenitic stainless steel welding wire consists of 97% austenite phase, 1.0% ferrite phase, and 0.1% carbide phase by volume. The austenite phase is equidendritic with a grain size of 35 μm; the δ-ferrite phase is discontinuously distributed in a worm-like pattern with a size of 3-5 μm; and the carbide phase is mainly composed of M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.15-0.25 μm.

[0104] The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength of 465 MPa, an elongation after fracture of 31%, and a hydrogen embrittlement sensitivity of 4%.

[0105] Example 5

[0106] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the austenitic stainless steel welding wire for hydrogen transportation pipelines is Φ0.9mm, and the chemical composition by mass percentage is: C 0.026%, Si 0.50%, Mn 3.80%, P 0.005%, S 0.004%, Cr 19.5%, Ni 15.1%, Mo 2.0%, N 0.20%, V 0.175%, with the balance being Fe and other unavoidable impurities.

[0107] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0108] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0109] S2, billet forging: The densely crystalline steel ingot of S1 is hot forged at a temperature of 1130℃ and a holding time of 150min. The forging ratio is 6. During the forging process, the final forging temperature is maintained at ≥950℃ to obtain a 50×50mm billet.

[0110] S3, Hot Rolled Wire Rod: The S2 square billet is hot rolled at a temperature of 1110℃ and a holding time of 110min. The rolling is carried out at a final rolling temperature of ≥950℃. The hot rolling adopts a multi-pass small reduction method, with a total reduction of 65% and a single pass reduction controlled at about 13%, to obtain a Φ8.0mm hot rolled wire rod.

[0111] S4. Continuous cold drawing and annealing: The S3 hot-rolled wire rod is first rough-drawn to Φ2.2mm, then heated to 1070℃ for solution annealing, and finally fine-drawn through multiple passes to the final target Φ0.9mm to obtain austenitic stainless steel welding wire for hydrogen pipelines. During the drawing process, when the material hardens to the point that drawing cannot continue, intermediate annealing at 1070℃ is required.

[0112] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method, with the following welding parameters: tungsten inert gas (TIG) welding is used, the welding current is 135A, the welding voltage is 14V, DC positive polarity is used, the welding speed is 1.9mm / s, the shielding gas is argon gas with a purity of 99.995%, and the shielding gas flow rate is controlled at 16L / min during the welding process.

[0113] The microstructure of the weld metal formed by welding the hydrogen transport pipeline to the 316L stainless steel pipe of the gas turbine hydrogen transport pipeline using austenitic stainless steel welding wire consists of 99% austenite phase, 1.0% ferrite phase, and 0.3% carbide phase by volume. The austenite phase is equidendritic with a grain size of 35 μm; the δ-ferrite phase is discontinuously distributed in a worm-like pattern with a size of 2.5-4.0 μm; and the carbide phase is mainly M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.3-0.4 μm.

[0114] The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength of 470 MPa, an elongation after fracture of 30%, and a hydrogen embrittlement sensitivity of 2.5%.

[0115] Example 6

[0116] An austenitic stainless steel welding wire for hydrogen transportation pipelines, wherein the diameter of the austenitic stainless steel welding wire for hydrogen transportation pipelines is Φ2.0mm, and the chemical composition by mass percentage is: C 0.016%, Si 0.38%, Mn 3.0%, P 0.007%, S 0.010%, Cr 17.9%, Ni 14.5%, Mo 2.3%, N 0.18%, Nb 0.01%, V 0.10%, with the balance being Fe and other unavoidable impurities.

[0117] A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines, comprising the following steps:

[0118] S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means.

[0119] S2, billet forging: The densely crystalline steel ingot of S1 is hot forged at a temperature of 1100℃ and a holding time of 130min. The forging ratio is 4. During the forging process, the final forging temperature is maintained at ≥950℃ to obtain a 50×50mm billet.

[0120] S3, Hot Rolled Wire Rod: The S2 square billet is hot rolled at a temperature of 1090℃ and a holding time of 100min. The final rolling temperature is ≥950℃. The hot rolling adopts a multi-pass small reduction method, with a total reduction of 65% and a single pass reduction controlled at about 13%, to obtain a Φ8.0mm hot rolled wire rod.

[0121] S4. Continuous cold drawing and annealing: The S3 hot-rolled wire rod is first rough-drawn to Φ2.2mm, then heated to 1060℃ for solution annealing, and finally fine-drawn through multiple passes to the final target Φ2.0mm to obtain austenitic stainless steel welding wire for hydrogen transportation pipelines. During the drawing process, when the material hardens to the point that drawing cannot continue, intermediate annealing at 1060℃ is required.

[0122] An application of austenitic stainless steel welding wire for hydrogen transportation pipelines prepared based on the above method, with the following welding parameters: tungsten inert gas (TIG) welding is used, the welding current is 130A, the welding voltage is 13V, DC positive polarity is used, the welding speed is 1.4mm / s, the shielding gas is argon gas with a purity of 99.995%, and the shielding gas flow rate is controlled at 14L / min during the welding process.

[0123] The microstructure of the weld metal formed by welding the hydrogen transport pipeline to the 316L stainless steel pipe of the gas turbine hydrogen transport pipeline using austenitic stainless steel welding wire consists of 97% austenite phase, 1.3% ferrite phase, and 0.15% carbide phase by volume. The austenite phase is equidendritic with a grain size of 32 μm; the δ-ferrite phase is discontinuously distributed in a worm-like pattern with a size of 3.5-4.5 μm; and the carbide phase is mainly M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.10-0.25 μm.

[0124] The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength of 461 MPa, an elongation after fracture of 28%, and a hydrogen embrittlement sensitivity of 4%.

[0125] The above-mentioned solution proposes an austenitic stainless steel welding wire for hydrogen transportation pipelines, its preparation method, and its application, which can solve the technical problems of high hydrogen embrittlement sensitivity and difficulty in balancing weld strength and plasticity in the prior art.

[0126] This invention ensures that austenitic stainless steel welding wire has good weldability and that the weld metal composition meets the requirements by designing alloy composition and using supporting processes such as vacuum induction smelting, purification, forging, rolling and drawing, and controlling process parameters in each process. It can be used to weld austenitic stainless steel pipes for hydrogen transportation pipelines, including 304L and 316L.

[0127] This invention, through electroslag remelting and other methods, can effectively remove impurity elements and gas content, significantly improve the solidification structure of steel ingots, reduce component segregation, and improve metal purity and uniformity.

[0128] This invention, through forging, can break up coarse cast dendritic structures, refine grains, eliminate microscopic defects, and improve the density and mechanical properties of materials.

[0129] The welding process of the austenitic stainless steel welding wire for hydrogen transportation pipelines prepared by this invention is as follows: tungsten inert gas (TIG) welding is used, with a welding current of 125–160 A, a welding voltage of 12–16 V, DC positive polarity, a welding speed of 1–2 mm / s, and argon gas with a purity of not less than 99.99%. The flow rate of the shielding gas is controlled at 13–18 L / min during the welding process.

[0130] This invention, through hot rolling, can further optimize the microstructure, forming uniform and fine equiaxed crystals, providing a good microstructure basis for subsequent drawing.

[0131] This invention processes the material to the target diameter (e.g., Φ0.8-2.0mm) through solution treatment followed by multiple drawing and annealing processes, while controlling the work hardening process to give the welding wire high strength, good plasticity and stable wire feeding performance, ultimately ensuring that the weld metal has excellent resistance to hydrogen embrittlement and mechanical properties.

[0132] The weld metal formed by welding austenitic stainless steel welding wire for hydrogen pipelines to gas turbine hydrogen pipelines prepared by the present invention has a tensile strength ≥450MPa, an elongation after fracture ≥25%, and a hydrogen embrittlement sensitivity ≤8%.

[0133] In summary, compared with other traditional methods, the method of this invention obtains austenitic stainless steel welding wire for hydrogen transportation pipelines through reasonable component design and reasonable manufacturing process; the method is simple to operate, environmentally friendly, low in cost, short in process, and high in efficiency, which is conducive to large-scale industrial production and promotion.

[0134] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0135] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0136] It should be understood that, in various embodiments of the present invention, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0137] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An austenitic stainless steel welding wire for hydrogen transportation pipelines, characterized in that, The austenitic stainless steel welding wire used in the hydrogen transport pipeline has a diameter of Φ0.8-2.0mm and a chemical composition by mass percentage as follows: C≤0.12%, Si 0.35-0.50%, Mn1.2-5.8%, P≤0.03%, S≤0.03%, Cr 17.8-19.7%, Ni 13.9-15.8%, Mo 1.80-2.45%, N 0.16-0.24%, Nb+V 0.01-0.25%, with the balance being Fe and other unavoidable impurities.

2. A method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 1, characterized in that, The preparation method of the austenitic stainless steel welding wire for the hydrogen transportation pipeline is as follows: S1. Raw material smelting: Weigh the raw materials according to the composition of the austenitic stainless steel welding wire for hydrogen pipelines, and prepare steel ingots by vacuum smelting. Then, obtain steel ingots with dense crystalline structure by electroslag and other means. S2, billet forging: hot forging of the densely crystalline steel ingot of S1 to obtain a 50×50mm billet; S3, Hot-rolled wire rod: The square billet of S2 is hot-rolled to obtain hot-rolled wire rod with a diameter of 7.0-8.0mm; S4. Continuous cold drawing and annealing: The hot-rolled wire rod of S3 is continuously cold-drawn and annealed to obtain austenitic stainless steel welding wire for hydrogen pipelines.

3. The method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 2, characterized in that, In S2, the hot forging temperature is 1100-1150℃, the holding time is 120-200min, the forging ratio is 3-6, and the final forging temperature is maintained at ≥950℃ during the forging process.

4. The method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 2, characterized in that, In S3, the hot rolling temperature is 1080-1150℃, the holding time is 90-130min, the rolling process adopts a multi-pass small reduction process, the total reduction is 60-80%, the single-pass reduction is controlled at 10-20%, and the final rolling temperature is controlled not lower than 950℃.

5. The method for preparing austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 2, characterized in that, S4 hot-rolled wire rod adopts a multi-pass drawing process. It is first rough drawn to an intermediate size of Φ2.2mm, and then fine drawn to the final target size of Φ0.8-2.0mm. The reduction rate of surface area per pass is controlled at 15-30%. During the drawing process, when the total reduction rate reaches a certain level and the material hardens severely and cannot be drawn further, intermediate annealing is required. The annealing temperature is between 1050-1100℃.

6. An application of an austenitic stainless steel welding wire for hydrogen transportation pipelines prepared according to the method of claim 2, characterized in that, The welding process for austenitic stainless steel welding wire is as follows: using tungsten inert gas (TIG) welding, with a welding current of 125-160A, a welding voltage of 12-16V, DC positive polarity, a welding speed of 1-2mm / s, and argon gas with a purity of not less than 99.99%. The shielding gas flow rate is controlled at 13-18L / min during the welding process.

7. The application of the austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 6, characterized in that, The microstructure of the weld metal formed by welding the hydrogen transmission pipeline of the gas turbine to the hydrogen transmission pipeline using austenitic stainless steel welding wire consists of austenitic phase with a volume fraction of more than 95%, ferrite phase with a volume fraction of no more than 5%, and carbide phase with a volume fraction of no more than 0.5%. The austenitic phase is equiaxed or dendritic, with a grain size of 10–50 μm. The δ-ferrite phase is discontinuously distributed in a worm-like or skeletal pattern, with a size of 1–10 μm. The carbide phase is mainly composed of M... 23 Type C6, in granular or short rod-shaped form, precipitates along grain boundaries or phase boundaries, with a size of 0.1-0.5 μm.

8. The application of the austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 7, characterized in that, The weld metal formed by welding the hydrogen transmission pipeline of the gas turbine with austenitic stainless steel welding wire has a tensile strength ≥450MPa, an elongation after fracture ≥25%, and a hydrogen embrittlement sensitivity ≤8%.

9. The application of the austenitic stainless steel welding wire for hydrogen transportation pipelines according to claim 7, characterized in that, The hydrogen transmission pipelines for gas turbines are welded using austenitic stainless steel welding wire, and the materials include 304L and 316L.

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