An X52 steel grade pipe for pure hydrogen environment and its welding method

Abstract

This application discloses an X52 steel grade pipe for pure hydrogen environments and its welding method, relating to the field of hydrogen energy transportation welding materials technology, aiming to solve the problem of poor fracture toughness of X52 steel grade pipes for pure hydrogen environments. The X52 steel grade pipe for pure hydrogen environments includes: a first sub-pipe, a welding section, and a second sub-pipe; the first and second sub-pipes are connected by the welding section; along a first direction, the welding section includes: a first sub-welded section and a second sub-welded section connected to the first sub-welded section; the first direction is perpendicular to the extension direction of the X52 steel grade pipe for pure hydrogen environments; based on the mass of the welding section, the mass percentages of C, P, and S in the first sub-welded section are all greater than or equal to the mass percentages of C, P, and S in the second sub-welded section; it can be applied to hydrogen transportation pipelines.

Description

Technical Field

[0001] This application relates to the field of welding materials for hydrogen energy transportation, and more particularly to an X52 steel grade pipe for use in a pure hydrogen environment and its welding method. Background Technology

[0002] Hydrogen energy is a key clean energy source for promoting energy transition and achieving the "dual carbon" goal. Pipeline hydrogen transportation has become the mainstream method for large-scale hydrogen transportation due to its advantages such as large capacity, low cost and continuous stability.

[0003] Welding, as a core process for pipeline connections, directly impacts pipeline safety. However, the high-pressure, pure hydrogen environment places extremely stringent requirements on welded joints. Hydrogen molecules are small and highly permeable, easily penetrating the weld and heat-affected zone, causing hydrogen embrittlement. This leads to a decrease in the material's toughness and plasticity, increasing the risk of hydrogen-induced cracking and brittle fracture under the combined effects of residual stress and pressure. Therefore, in addition to meeting conventional strength requirements, the ring welded joints of hydrogen transportation pipelines must also possess high fracture toughness. Summary of the Invention

[0004] The purpose of this application is to provide an X52 steel grade pipe for use in a pure hydrogen environment and a welding method thereof. To achieve the above objective, this application adopts the following technical solution: In a first aspect, this application provides an X52 steel grade pipe for use in a pure hydrogen environment. The X52 steel grade pipe for use in a pure hydrogen environment includes: a first sub-pipe, a welded section, and a second sub-pipe; the first sub-pipe and the second sub-pipe are connected by the welded section; along a first direction, the welded section includes: a first sub-welded section and a second sub-welded section connected to the first sub-welded section; the first direction is perpendicular to the extension direction of the X52 steel grade pipe for use in a pure hydrogen environment; based on the mass of the welded section, the mass percentages of C, P, and S in the first sub-welded section are all greater than or equal to the mass percentages of C, P, and S in the second sub-welded section.

[0005] In the X52 steel grade pipe for pure hydrogen environment provided in this application embodiment, since C is an alloying element that can expand the austenite region, it can reduce the austenite phase transformation temperature and promote the formation of fine and high-toughness phase transformation structure, which has a positive effect on improving the toughness of the weld and heat-affected zone. P and S, as harmful impurity elements in steel, are prone to segregation at grain boundaries, reducing grain boundary bonding force and exacerbating the risk of hydrogen-induced intergranular cracking. Based on this, in the configuration of the X52 steel grade pipe for pure hydrogen environment connected by a first sub-pipe and a second sub-pipe through a weld, the weld 103 is divided into a first sub-weld 31 and a second sub-weld along the first direction Y (perpendicular to the extension direction of the X52 steel grade pipe for pure hydrogen environment), thereby establishing a structural layer along the wall thickness direction. Therefore, along the first direction, having a higher C content in the first sub-weld section than in the second sub-weld section allows the first sub-weld section to achieve higher hardenability and fine-grain strengthening during welding or heat treatment, forming a high-strength microstructure. Meanwhile, the second sub-weld section, with its relatively lower C content, has a more flexible microstructure, prioritizing plastic deformation capacity and crack propagation toughness, forming a regional gradient distribution. This effectively inhibits crack initiation from high-stress areas and its propagation inwards when the welded section is subjected to external loads, thereby improving the overall fracture resistance of X52 steel grade pipes used in pure hydrogen environments under high-pressure pure hydrogen conditions. P and S, as harmful impurity elements in steel, tend to segregate at grain boundaries, reducing grain boundary bonding and exacerbating the risk of hydrogen-induced intergranular cracking. If P and S are evenly distributed throughout the weld, the grain boundary bonding of the entire weld area is weakened, and the overall cracking sensitivity increases. Controlling P and S to a lower level in the second sub-weld can significantly reduce the degree of grain boundary weakening in critical sensitive areas, improve the ability to resist hydrogen-induced intergranular cracking and stress corrosion cracking, and further improve the overall fracture resistance of X52 steel grade pipelines used in pure hydrogen environments under high-pressure pure hydrogen environments, meeting the mechanical property requirements of hydrogen transmission pipelines for circumferential welds and ensuring weld quality.

[0006] In some embodiments, the first sub-welded portion comprises the following components by mass percentage: C 0.06%~0.15%, Si 0.45%~0.75%, Mn 0.9%~1.40%, P≤0.025%, S≤0.035%, Cr≤0.15%, Mo≤0.15%, Ni≤0.15%, Ti 0.002%~0.01%, V ≤0.03%, Cu 0.07%~0.09%, Co 0.001%~0.003%, Al 0.002%~0.004%, Nb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities.

[0007] In some embodiments, the second sub-welded portion comprises the following components by mass percentage: C 0.04%~0.09%, Si 0.30%~0.60%, Mn 1.00%~1.30%, P≤0.01%, S≤0.006%, Cr 0.10%~0.50%, Mo≤0.01%, Ni 0.10%~0.50%, Ti 0.01%~0.02%, V 0.005%~0.015%, B%≤0.002%, with the balance being Fe and other unavoidable impurities.

[0008] In some embodiments, the second sub-weld portion includes a filling portion and a cover portion. The filling portion is disposed between the first sub-tube and the second sub-tube and contacts the first sub-weld portion. The cover portion is disposed on the side of the filling portion away from the first sub-weld portion and at least partially covers the surfaces of the first sub-tube and the second sub-tube away from the first sub-weld portion.

[0009] In some embodiments, the filling portion includes: at least one filling sub-part stacked along a first direction; the dimension of each filling sub-part along the first direction is less than or equal to 3 mm.

[0010] In some embodiments, the vertical distance from the cover surface to the first sub-tube along the first direction is less than or equal to 2 mm.

[0011] Secondly, this application provides a welding method for an X52 steel grade pipe used in a pure hydrogen environment. The welding method for the X52 steel grade pipe used in a pure hydrogen environment includes: providing a first sub-pipe; the first sub-pipe includes a first weld joint. Providing a second sub-pipe; the second sub-pipe includes a second weld joint. The first weld joint and the second weld joint are arranged opposite to each other, and the first sub-pipe and the second sub-pipe are connected by welding to form a welded portion; along a first direction, the welded portion includes: a first sub-welded portion and a second sub-welded portion connected to the first sub-welded portion; the first direction is perpendicular to the extension direction of the X52 steel grade pipe used in a pure hydrogen environment; based on the mass of the welded portion, the mass percentages of C, P, and S in the first sub-welded portion are all greater than or equal to the mass percentages of C, P, and S in the second sub-welded portion.

[0012] In some embodiments, forming a welded portion includes: performing a first welding operation on a portion of a first weld joint and a second weld joint using a welding wire to form a first sub-welded portion; and performing a second welding operation on another portion of the first weld joint and the second weld joint using a welding electrode to form a second sub-welded portion. The welding wire, by weight, comprises the following components in percentage weight: C 0.06%~0.15%, Si 0.45%~0.75%, Mn 0.9%~1.40%, P≤0.025%, S≤0.035%, Cr≤0.15%, Mo≤0.15%, Ni≤0.15%, Ti 0.002%~0.01%, V ≤0.03%, Cu 0.07%~0.09%, Co 0.001%~0.003%, Al 0.002%~0.004%, Nb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities. The welding electrode, by weight, comprises the following components in percentage weight: C 0.04%~0.09%, Si 0.30%~0.60%, Mn 1.00%~1.30%, P≤0.01%, S≤0.006%, Cr 0.10%~0.50%, Mo≤0.01%, Ni 0.10%~0.50%, Ti 0.01%~0.02%, V 0.005%~0.015%, B%≤0.002%, balance being Fe and other unavoidable impurities.

[0013] In some embodiments, the first welding is performed using a tungsten electrode under inert gas protection; the current range for the first welding is 95A to 110A; the voltage range for the first welding is 10V to 14V; and the welding speed for the first welding is 6cm / min to 8cm / min.

[0014] In some embodiments, the second welding is performed by arc welding; the current range for the second welding is 105A~115A; the voltage range for the second welding is 20V~24V; and the welding speed ranges from 9 cm / min to 12 cm / min.

[0015] In some embodiments, before setting the first weld joint and the second weld joint opposite to each other, the method further includes: preheating the first weld joint and the second weld joint; the preheating temperature range is 60°C to 100°C. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of an X52 steel grade pipe for a pure hydrogen environment is provided for some embodiments of this application; Figure 2 A flowchart illustrating a welding method for X52 steel grade pipes used in a pure hydrogen environment, provided for some embodiments of this application; Figure 3 This is a schematic diagram of the X52 steel grade pipe for a pure hydrogen environment provided in Embodiment 1 of this application before its fabrication. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0021] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0022] Currently, the existing welding process system for long-distance pipelines is mainly established around the needs of oil and gas transportation. Its process selection, material matching and parameter optimization are all aimed at meeting the service conditions of natural gas. However, it has failed to be designed for the characteristics of hydrogen, making it difficult to guarantee the fracture toughness of its ring weld joint in a high-pressure pure hydrogen environment.

[0023] Based on this, embodiments of this application provide an X52 steel grade pipe 100 for use in a pure hydrogen environment. For example... Figure 1As shown, the X52 steel grade pipe 100 for a pure hydrogen environment includes: a first sub-pipe 101, a welded section 103, and a second sub-pipe 102. The first sub-pipe 101 and the second sub-pipe 102 are connected by the welded section 103.

[0024] Along the first direction Y, the welding part 103 includes: a first sub-welding part 31 and a second sub-welding part 32 connected to the first sub-welding part 31; the first direction Y is perpendicular to the extension direction of the X52 steel grade pipe 100 for a pure hydrogen environment.

[0025] Based on the mass of the welding part 103, the mass percentage of C, P, and S in the first sub-welding part 31 is greater than or equal to the mass percentage of C, P, and S in the second sub-welding part 32.

[0026] Here, the first sub-tube 101 can be the same or different.

[0027] Understandably, since C is an alloying element that can expand the austenite region, it can lower the austenite phase transformation temperature and promote the formation of fine and high-toughness phase transformation structures, which has a positive effect on improving the toughness of the welded part 103 and the heat-affected zone. P and S, as harmful impurity elements in steel, are prone to segregation at grain boundaries, reducing grain boundary bonding and exacerbating the risk of hydrogen-induced intergranular cracking. Based on this, in the configuration of the X52 steel grade pipe 100 used in a pure hydrogen environment, which is connected to the second sub-pipe 102 via the welded part 103 through the first sub-pipe 101, the welded part 103 is divided into the first sub-welded part 31 and the second sub-welded part 32 along the first direction Y (perpendicular to the extension direction of the X52 steel grade pipe used in a pure hydrogen environment), thereby establishing a structural layer along the wall thickness direction.

[0028] Therefore, by having a higher C content in the first sub-welded part 31 than in the second sub-welded part 32 along the first direction Y, the first sub-welded part 31 can achieve higher hardenability and fine grain strengthening effect during welding or heat treatment, forming a high-strength microstructure. Meanwhile, the second sub-welded part 32, with a relatively lower C content, has a more flexible microstructure, prioritizing plastic deformation capacity and crack propagation toughness, forming a regional gradient distribution. This enables the welded part 103 to effectively suppress crack initiation from the high-stress area and propagation inward when subjected to external loads, thereby improving the overall fracture resistance of the X52 steel grade pipe 100 used in a pure hydrogen environment under high-pressure pure hydrogen conditions.

[0029] P and S, as harmful impurity elements in steel, tend to agglomerate at grain boundaries, reducing grain boundary bonding and exacerbating the risk of hydrogen-induced intergranular cracking. If P and S are evenly distributed throughout the weld, the grain boundary bonding of the entire weld area will be weakened, and the overall cracking sensitivity will increase. Controlling P and S to a lower level in the second sub-weld 32 can significantly reduce the degree of grain boundary weakening in critical sensitive areas, improve the ability to resist hydrogen-induced intergranular cracking and stress corrosion cracking, and further improve the overall fracture resistance of X52 steel grade pipe 100 used in pure hydrogen environment under high pressure pure hydrogen environment, meet the mechanical property requirements of hydrogen transmission pipeline for circumferential welds, and ensure weld quality.

[0030] Here, the inspection of weld 103 can be RT radiographic testing or phased-array ultrasonic testing. For example, the qualification standard for RT radiographic testing and phased-array ultrasonic testing is Level II or above, and the first sub-weld 31 is not allowed to have any lack of fusion.

[0031] In some embodiments, the first sub-welded portion 31 comprises the following components by mass percentage: C 0.06%~0.15%, Si 0.45%~0.75%, Mn 0.9%~1.40%, P≤0.025%, S≤0.035%, Cr≤0.15%, Mo≤0.15%, Ni≤0.15%, Ti 0.002%~0.01%, V ≤0.03%, Cu 0.07%~0.09%, Co 0.001%~0.003%, Al 0.002%~0.004%, Nb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities.

[0032] For example, the mass percentage of C can be 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, or 0.15%, etc., and there is no limitation here.

[0033] For example, the mass percentage of Si can be 0.45%, 0.55%, 0.60%, 0.65%, 0.70%, or 0.75%, etc., and there is no limitation here.

[0034] For example, the mass percentage of Mn can be 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, or 1.4%, etc., and there is no limitation here.

[0035] For example, the mass percentage of P can be 0.025%, 0.024%, 0.023%, 0.022%, 0.021%, or 0.020%, etc., and there is no limitation here.

[0036] For example, the mass percentage of S can be 0.035%, 0.034%, 0.033%, 0.032%, 0.031%, or 0.030%, etc., and there is no limitation here.

[0037] For example, the mass percentage of Cr can be 0.15%, 0.14%, 0.13%, 0.12%, 0.11%, or 0.10%, etc., and there is no limitation here.

[0038] For example, the mass percentage of Mo can be 0.15%, 0.14%, 0.13%, 0.12%, 0.11%, or 0.10%, etc., and there is no limitation here.

[0039] For example, the mass percentage of Ni can be 0.15%, 0.14%, 0.13%, 0.12%, 0.11%, or 0.10%, etc., and there is no limitation here.

[0040] For example, the mass percentage of Ti can be 0.002%, 0.004%, 0.006%, 0.008%, 0.009%, or 0.01%, etc., and there is no limitation here.

[0041] For example, the mass percentage of V can be 0.03%, 0.025%, 0.02%, 0.015%, 0.01%, or 0.005%, etc., and there is no limitation here.

[0042] For example, the mass percentage of Cu can be 0.07%, 0.075%, 0.08%, 0.085%, 0.087%, or 0.09%, etc., and there is no limitation here.

[0043] For example, the mass percentage of Co can be 0.001%, 0.0015%, 0.002%, 0.0025%, 0.0027%, or 0.003%, etc., and there is no limitation here.

[0044] For example, the mass percentage of Al can be 0.002%, 0.0025%, 0.003%, 0.0035%, 0.0037%, or 0.004%, etc., and there is no limitation here.

[0045] For example, the mass percentage of Nb can be 0.001%, 0.0015%, 0.002%, 0.0025%, 0.0027%, or 0.003%, etc., and there is no limitation here.

[0046] In some embodiments, the second sub-welded portion 32 comprises the following components by mass percentage: C 0.04%~0.09%, Si 0.30%~0.60%, Mn 1.00%~1.30%, P≤0.01%, S≤0.006%, Cr 0.10%~0.50%, Mo≤0.01%, Ni 0.10%~0.50%, Ti 0.01%~0.02%, V 0.005%~0.015%, B%≤0.002%, with the balance being Fe and other unavoidable impurities.

[0047] For example, the mass percentage of C can be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, or 0.09%, etc., and there is no limitation here.

[0048] For example, the mass percentage of Si can be 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, or 0.60%, etc., and there is no limitation here.

[0049] For example, the mass percentage of Mn can be 1.00%, 1.05%, 1.1%, 1.2%, 1.25%, or 1.3%, etc., and there is no limitation here.

[0050] For example, the mass percentage of P can be 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, or 0.005%, etc., and there is no limitation here.

[0051] For example, the mass percentage of S can be 0.006%, 0.005%, 0.004%, 0.003%, 0.002%, or 0.001%, etc., and there is no limitation here.

[0052] For example, the mass percentage of Cr can be 0.10%, 0.20%, 0.30%, 0.40%, 0.45%, or 0.50%, etc., and there is no limitation here.

[0053] For example, the mass percentage of Mo can be 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, or 0.005%, etc., and there is no limitation here.

[0054] For example, the mass percentage of Ni can be 0.10%, 0.20%, 0.30%, 0.40%, 0.15%, or 0.50%, etc., and there is no limitation here.

[0055] For example, the mass percentage of Ti can be 0.01%, 0.012%, 0.014%, 0.016%, 0.018%, or 0.20%, etc., and there is no limitation here.

[0056] For example, the mass percentage of V can be 0.005%, 0.007%, 0.009%, 0.011%, 0.013%, or 0.015%, etc., and there is no limitation here.

[0057] For example, the mass percentage of B can be 0.002%, 0.0017%, 0.0015%, 0.0013%, 0.0011%, or 0.001%, etc., and there is no limitation here.

[0058] Understandably, C, Mn, Ni, and Cu are all elements that expand the austenite region, which can lower the austenite transformation temperature and help obtain a fine and highly tough transformation structure. However, C and Mn are prone to segregation and forming hardened structures, so their contents need to be controlled. In the first sub-welded part 31, the contents of C and Mn are controlled at 0.06%~0.15% and 0.9~1.40%, respectively; in the second sub-welded part 32, they are controlled at 0.04%~0.09% and 1.00~1.30%, respectively.

[0059] Ni is beneficial to the low-temperature toughness of the weld and can improve the hot brittleness caused by Cu. The Ni content in the first sub-welding part 31 is controlled at ≤0.15%, and the Cu content is controlled at 0.07%~0.09%; the Ni content in the second sub-welding part 32 is controlled at 0.10%~0.50%.

[0060] P and S are unavoidable harmful elements in welding materials, which are prone to segregation and formation of inclusions and other defects, so they must be strictly limited. In the first sub-welding part 31, P ≤ 0.025% and S ≤ 0.035% are required; in the second sub-welding part 32, P ≤ 0.01% and S ≤ 0.006% are required.

[0061] Cr, Mo, Si, and Al are all ferrite stabilizing elements, which will shrink the austenite stabilization region. Cr can improve corrosion resistance, but it will worsen weldability. In the first sub-weld part 31, the Cr content is controlled at ≤0.15%, and in the second sub-weld part 32, the Cr content is controlled at 0.10%~0.50%.

[0062] Mo can promote the formation of acicular ferrite with good toughness. The Mo content in the first sub-weld part 31 is ≤0.15%, and the Mo content in the second sub-weld part 32 is ≤0.01%. Al is a strong deoxidizing element. Too much Al will form large-sized oxide inclusions. The Al content in the first sub-weld part 31 is controlled at 0.002%~0.004%.

[0063] Higher Si content will worsen weldability, so the Si content in the first sub-welding part 31 is limited to 0.45%~0.75%, and the Si content in the second sub-welding part 32 is controlled at 0.30%~0.60%.

[0064] Nb, Ti, and V, as microalloying elements, can form carbides to refine grains and simultaneously fix N, mitigating its adverse effects on toughness. In the first sub-welding section 31, their contents are controlled as follows: Nb 0.001%~0.003%, Ti 0.002%~0.01%, V ≤0.03%. In the second sub-welding section 32, the contents are controlled as follows: Ti 0.01%~0.02%, V 0.005%~0.015%. In summary, controlling the content of the aforementioned components can make the microstructure of the welded part 103 more uniform and the stress distribution more reasonable, further improving the overall fracture resistance of the X52 steel grade pipe 100 used in a pure hydrogen environment under high pressure pure hydrogen conditions.

[0065] In some embodiments, the second sub-welding portion 32 includes a filling portion 321 and a cover portion 322. The filling portion 321 is disposed between the first sub-tube 101 and the second sub-tube 102 and contacts the first sub-welding portion 31. The cover portion 322 is disposed on the side of the filling portion 321 away from the first sub-welding portion 31 and at least partially covers the surfaces of the first sub-tube 101 and the second sub-tube 102 away from the first sub-welding portion 31.

[0066] Understandably, the filling portion 321 of the second sub-weld portion 32 can effectively fill the gap between the first sub-pipe 101 and the second sub-pipe 102, ensuring the tightness and integrity of the connection, while forming a good bond with the first sub-weld portion 31; the cover portion 322 plays a sealing and reinforcing role, by covering the surface of the first sub-pipe 101 and the second sub-pipe 102, further limiting the segregation and diffusion of harmful elements (such as C, P, S) in this area, reducing the risk of hydrogen-induced crack initiation, while improving the peel resistance and overall sealing performance of the weld portion 103, thereby enhancing the fracture toughness of the X52 steel grade pipe 100 used in a pure hydrogen environment under high pressure pure hydrogen environment.

[0067] In some embodiments, reference Figure 1 The filling portion 321 includes: at least one filling sub-portion 3211 stacked along the first direction Y; the dimension D of each filling sub-portion 3211 along the first direction Y is, that is, D is less than or equal to 3mm.

[0068] For example, D can be 3mm, 2.8mm, 2.6mm, 2.4mm, 2.2mm or 2mm, etc., and there is no limitation here.

[0069] In some embodiments, the vertical distance H1 from the cover surface 322 to the first sub-tube 101 along the first direction Y is less than or equal to 2 mm.

[0070] For example, H1 can be 2mm, 1.8mm, 1.6mm, 1.4mm, 1.2mm or 1mm, etc., and there is no limitation here.

[0071] In some other embodiments, the vertical distance H2 from the cover surface 322 to the second sub-tube 102 along the first direction Y is less than or equal to 2 mm.

[0072] For example, H2 can be 2mm, 1.8mm, 1.6mm, 1.4mm, 1.2mm or 1mm, etc., and there is no limitation here.

[0073] Understandably, setting the thickness D of each filler sub-part 3211 to no more than 3mm is beneficial for achieving uniform heating and cooling during welding or joining, reducing the temperature gradient and residual stress between layers, while suppressing the macroscopic segregation of elements such as C, P, and S between layers, and avoiding the formation of local hardened structures.

[0074] Furthermore, the vertical distances H1 and H2 from the cover surface 322 to the first sub-tube 101 and the second sub-tube 102 are both no more than 2mm, ensuring that the cover surface is in close contact with the surface of the sub-tubes, effectively sealing the edge of the connection area and reducing hydrogen permeation channels and stress concentration points.

[0075] Therefore, the above settings help to obtain a finer and more uniform weld structure, reduce the probability of hydrogen-induced crack initiation, and thus improve the fracture toughness and long-term service reliability of X52 steel grade pipes used in pure hydrogen environments under high pressure pure hydrogen environments.

[0076] Embodiments of this application provide a welding method for X52 grade steel pipes used in pure hydrogen environments. For example... Figure 2 As shown, the welding method for the X52 steel grade pipe used in a pure hydrogen environment includes: S1~S3.

[0077] S1: Provide a first sub-tube; the first sub-tube includes a first weld joint.

[0078] For example, the first sub-tube 101 is machined with a single-sided V-groove, see [reference]. Figure 3 The face angle 1 of the bevel is 30±1.5°, and the height of the blunt edge 2 (which can be understood as the dimension along the first direction Y) is 1.5mm~2.0mm.

[0079] S2: Provide a second sub-tube; the second sub-tube includes a second weld joint.

[0080] For example, the second sub-tube 102 is machined with a single-sided V-groove, see [reference]. Figure 3 The face angle 1 of the bevel is 30±1.5°, and the height of the blunt edge 2 (which can be understood as the dimension along the first direction Y) is 1.5mm~2.0mm.

[0081] S3: The first weld joint and the second weld joint are arranged opposite to each other, and the first sub-pipe and the second sub-pipe are connected by welding to form a welded part; along the first direction, the welded part includes: a first sub-welded part and a second sub-welded part connected to the first sub-welded part; the first direction is perpendicular to the extension direction of the X52 steel grade pipe used in a pure hydrogen environment; based on the mass of the welded part, the mass percentages of C, P, and S in the first sub-welded part are all greater than or equal to the mass percentages of C, P, and S in the second sub-welded part.

[0082] For example, the first weld joint 101A and the second weld joint 102A can be assembled by tack welding. After completion, the assembly bevel size is measured using a universal welding gauge. The assembly gap is 2.5 mm - 4.5 mm, the misalignment is no more than 1 / 8 of the wall thickness, and the local maximum within a continuous 50 mm length should not exceed 3 mm.

[0083] Understandably, by arranging (i.e. pairing) the first weld joint 101A of the first sub-pipe 101 and the second weld joint 102A of the second sub-pipe 102 opposite each other and welding them, a welded part with a compositional gradient can be formed along the extension direction perpendicular to the X52 steel grade pipeline used in a pure hydrogen environment. At the same time, the thermal cycling during the welding process helps to refine the grains and improve the uniformity of the microstructure, so that the welded part has a lower tendency to hydrogen-induced cracking in a high-pressure pure hydrogen environment, ultimately significantly improving the fracture toughness and service safety of the X52 steel grade pipeline used in a pure hydrogen environment.

[0084] In some embodiments, S3 forming the weld portion 103 includes: S3.1 to S3.2.

[0085] S3.1: The first sub-welded part 31 is formed by first welding a portion of the first weld joint and the second weld joint using welding wire.

[0086] S3.2: A second welding is performed on another part of the first weld joint and the second weld joint using a welding rod to form a second sub-welded part 32. The welding wire, by weight, comprises the following components in percentage weight: C 0.06%~0.15%, Si 0.45%~0.75%, Mn 0.9%~1.40%, P≤0.025%, S≤0.035%, Cr≤0.15%, Mo≤0.15%, Ni≤0.15%, Ti 0.002%~0.01%, V ≤0.03%, Cu 0.07%~0.09%, Co 0.001%~0.003%, Al 0.002%~0.004%, Nb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities. The welding electrode, by weight, comprises the following components in percentage weight: C 0.04%~0.09%, Si 0.30%~0.60%, Mn 1.00%~1.30%, P≤0.01%, S≤0.006%, Cr0.10%~0.50%, Mo≤0.01%, Ni0.10%~0.50%, Ti0.01%~0.02%, V0.005%~0.015%, B%≤0.002%, balance being Fe and other unavoidable impurities.

[0087] Understandably, the above welding method achieves the compositional gradient setting of the welded part through step welding. S3.1 uses a welding wire with a specific composition for the first welding to form the first sub-welded part. The welding wire has a high C content (0.06%~0.15%), which is beneficial to expand the austenite region, refine the microstructure, and improve the strength and hardenability of the inner side of the welded part. At the same time, the P and S contents are controlled within a certain range (P≤0.025%, S≤0.035%) to ensure basic toughness.

[0088] S3.2 employs a second welding process using welding rods to form the second sub-welded section. This welding rod has a low carbon content (0.04%~0.09%) and stricter P and S content requirements (P≤0.01%, S≤0.006%). Appropriate amounts of microalloying elements such as Ni, Ti, V, and B are also added to further improve grain boundary quality and microstructure toughness. After the two welding steps, the first sub-welded section has a higher carbon content to ensure strength, while the second sub-welded section has lower C, P, and S contents to ensure plasticity and resistance to hydrogen embrittlement. This creates a reasonable strength-toughness gradient distribution along the first direction in the welded section, significantly reducing the risk of hydrogen-induced intergranular cracking under high-pressure pure hydrogen conditions and improving the overall fracture toughness of X52 steel grade pipes used in pure hydrogen environments.

[0089] In some embodiments, the first welding is performed using a tungsten electrode under inert gas protection; the current range for the first welding is 95A to 110A; the voltage range for the first welding is 10V to 14V; and the welding speed for the first welding is 6cm / min to 8cm / min.

[0090] For example, the inert gas can be argon, with a gas purity of ≥99.96% and a water content of ≤0.004%.

[0091] Understandably, the above settings are conducive to obtaining a stable molten pool and sufficient fusion, avoiding the generation of welding defects; tungsten inert gas protection can effectively isolate air, preventing elements such as C, P, and S from oxidizing and burning off at high temperatures or introducing impurities from the environment, thereby ensuring that the high C content in the first sub-welded part is stably retained, achieving the expected strength gradient design; at the same time, this parameter range helps to control the weld cooling rate, suppress the excessive generation of brittle hardening structures such as martensite, so that the first sub-welded part can obtain high strength while retaining a certain degree of toughness, thereby improving the fracture resistance of X52 steel grade pipes used in pure hydrogen environments under high pressure pure hydrogen environments.

[0092] In some embodiments, the second welding is performed by arc welding; the current range for the second welding is 105A~115A; the voltage range for the second welding is 20V~24V; and the welding speed ranges from 9 cm / min to 12 cm / min.

[0093] Understandably, the above settings, in the second welding process, help refine the microstructure of the second sub-weld, reduce the width of the heat-affected zone, and thus reduce the segregation of harmful elements such as C, P, and S in this area. Arc welding with these parameter ranges can achieve good penetration depth and fusion ratio, ensuring full bonding between the capping section and the filler section and the surface of the sub-pipe, improving the sealing and anti-peeling properties of the weld. Simultaneously, the faster cooling rate is conducive to the formation of fine acicular ferrite and other tough microstructures. Combined with the lower C, P, and S content in the welding electrode, this significantly improves the plasticity and hydrogen embrittlement resistance of the second sub-weld, thus forming a reasonable strength-toughness gradient with the first sub-weld, further enhancing the fracture toughness of X52 steel grade pipes used in pure hydrogen environments under high-pressure pure hydrogen conditions.

[0094] In some examples, the time interval between the end of the first weld and the start of the second weld is ≤15 minutes.

[0095] In some examples, the misalignment of the second weld, i.e., the continuous length of a local area not exceeding 3mm, does not exceed 50mm, and the cover section 322 is formed by paving welds.

[0096] In some embodiments, before setting the first weld joint and the second weld joint opposite to each other, the method further includes: preheating the first weld joint and the second weld joint; the preheating temperature range is 60°C to 100°C.

[0097] For example, a contact thermometer can be used for preheating temperature measurement.

[0098] Understandably, preheating can reduce the temperature gradient and cooling rate in the weld area, decrease the hardening tendency during welding, and thus inhibit the formation of brittle hardening structures such as martensite. At the same time, preheating helps promote the diffusion and escape of hydrogen, reduce the hydrogen content in the weld, and reduce the risk of hydrogen-induced crack initiation. In addition, this temperature range can improve the fusion between the base metal and the weld metal on both sides of the weld, reduce defects such as incomplete fusion and porosity, improve the density and overall quality of the weld, and thus enhance the fracture toughness of X52 steel grade pipes used in pure hydrogen environments under high pressure pure hydrogen conditions.

[0099] To make the objectives and technical solutions of this application clearer, further detailed descriptions are provided below with reference to embodiments. The specific examples described herein are merely illustrative of the invention and are not intended to limit the invention.

[0100] This embodiment 1 provides an X52 steel grade pipe for use in a pure hydrogen environment, referencing... Figure 1 This is for hydrogen transport pipelines; the welding method for X52 grade steel pipelines used in pure hydrogen environments includes the following steps: (1) Select a new type of X52 steel grade pipe with a specification of 610×14.3mm, which is a hydrogen-resistant pipe specially designed for pure hydrogen environment. The X52 steel grade pipe used in pure hydrogen environment has the following components by mass percentage: C 0.34%, Si 0.23%, Mn 1.36%, P 0.004%, S 0.0009%, Ni 0.02%, Cr 0.26%, Cu 0.01%, Nb 0.038%, V 0.018%, Ti 0.01%, Mo < 0.01%, Al 0.034%, N 0.004%, B 0.0002%, Ca 0.002%, V+Nb+Ti 0.065%, Pcm 0.127%.

[0101] (2) Cut the X52 steel grade pipe used in the pure hydrogen environment into two 250mm sub-pipes, and perform single-sided V-groove machining on the sub-pipes to form weld joints, refer to Figure 3 The bevel angle 1 is 30°-31°, and the height of the blunt edge is 1.0-1.5mm.

[0102] (3) The weld joints are assembled by tack welding, with an assembly gap of 3.0mm~4.0mm and a misalignment of less than or equal to 1.0mm.

[0103] (3) Place the weld joint to be welded on the 5G position welding support frame, and clean the inner and outer surfaces of the X52 steel grade pipe used in the pure hydrogen environment within 25mm on both sides of the bevel until it presents a metallic luster.

[0104] (4) Before welding, use flame heating to uniformly preheat the area within 75mm on both sides of the bevel. Use a contact thermometer to uniformly measure 4 points on the circumference 25mm away from the pipe opening. The preheating temperature is 60℃~100℃.

[0105] (6) The welding method of tungsten inert gas (TIG) welding is adopted, and the first welding is performed in a half-circle upward welding manner to form the first sub-welded part 31; the welding material is ER70S grade gas shielded welding wire with a diameter of 2.4mm. The welding process parameters are: welding current of 95A~110A, welding voltage of 10V~14V, welding speed of 6 cm / min~8cm / min, and shielding gas flow rate of 11L / min~13L / min. The welding wire contains the following mass percentages: C 0.07%, Si 0.64%, Mn 0.98%, P 0.018%, S 0.011%, Cr 0.020%, Mo 0.004%, Ni 0.010%, V 0.001%, Cu 0.060%, Nb < 0.001%, and the balance is Fe. The inert gas is Ar, the purity of Ar gas in the Ar container is ≥99.96%, and the water content of Ar gas is ≤0.004%.

[0106] (7) Thirteen minutes after the first welding is completed, a second welding is performed using shielded metal arc welding (SMAW), with the welding proceeding upwards in a half-circle motion (see reference). Figure 1 The first sub-welding part 321 and the cover part 322 are obtained by filling and covering in the first direction (Y) to form the second sub-welding part 32. Among them, the part of the filling part 321 near the first sub-welding part 31 is a single layer and a single pass, and the rest is a single layer and a double pass. The cover part 322 is a single layer and a double pass. The welding material is a low hydrogen welding rod with a diameter of 3.2 mm. The parameters of the second welding are: welding current 105A~115A, welding voltage 20 V~24V, welding speed 9cm / min~12cm / min. The welding rod contains the following mass percentages: C 0.08%, Si 0.41%, Mn 1.27%, P 0.005%, S 0.001%, Ni 0.05%, Mo <0.01%, V 0.01%, Ti 0.02%, B 0.0024%, and the balance is Fe. Furthermore, the temperature range between the first sub-welding part 31, the filling part 321, and the cover part 322 is controlled between 80℃ and 100℃, and a contact thermometer is used for temperature measurement; the dimension (which can be understood as the metal thickness) of each filling sub-part 3211 along the first direction does not exceed 3mm, and the cover part 322 adopts a panel welding method.

[0107] Non-destructive testing was performed on the welded part 103 (circumferential weld) after welding, including RT radiographic testing and phased array ultrasonic testing. The testing standard was SY / T 4109-2020, and the testing level was Class II or above. The first sub-welded part 31 had no fusion failure.

[0108] Impact toughness and fracture toughness under hydrogen environment were tested on the X52 steel grade pipe used in Example 1 for a pure hydrogen environment. Under low temperature conditions (-10℃), the average impact absorption energy of the three samples at the weld 103 and the inner and outer surfaces of the heat-affected zone was not less than 150J, and the single value was not less than 110J; the fracture toughness value K under 7.2MPa hydrogen pressure was also tested. JB0.2L The average value is not less than 95 MPa m 1 / 2 The single value is not less than 70MPa m 1 / 2 ， It has excellent fracture toughness.

[0109] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An X52 grade steel pipe for use in a pure hydrogen environment, characterized in that, include: First sub-tube, welding section, and second sub-tube; The first sub-tube and the second sub-tube are connected by the welded joint; Along the first direction, the welding portion includes: a first sub-welding portion and a second sub-welding portion connected to the first sub-welding portion; The first direction is perpendicular to the extension direction of the X52 steel grade pipe used in a pure hydrogen environment; Based on the mass of the welded part, the mass percentages of C, P, and S in the first sub-welded part are all greater than or equal to the mass percentages of C, P, and S in the second sub-welded part.

2. The X52 steel grade pipe for a pure hydrogen environment according to claim 1, characterized in that, Based on the mass of the first sub-welded part, the first sub-welded part comprises the following components by mass percentage: C 0.06%~0.15%, Si 0.45%~0.75%, Mn 0.9%~1.40%, P≤0.025%, S≤0.035%, Cr≤0.15%, Mo≤0.15%, Ni≤0.15%, Ti0.002%~0.01%, V≤0.03%, Cu 0.07%~0.09%, Co 0.001%~0.003%, Al 0.002%~0.004%, Nb0.001%~0.003%, with the balance being Fe and other unavoidable impurities.

3. The X52 steel grade pipe for a pure hydrogen environment according to claim 1, characterized in that, Based on the mass of the second sub-welded part, the second sub-welded part comprises the following components by mass percentage: C 0.04%~0.09%, Si 0.30%~0.60%, Mn 1.00%~1.30%, P≤0.01%, S≤0.006%, Cr 0.10%~0.50%, Mo≤0.01%, Ni 0.10%~0.50%, Ti 0.01%~0.02%, V 0.005%~0.015%, B%≤0.002%, with the balance being Fe and other unavoidable impurities.

4. The X52 steel grade pipe for a pure hydrogen environment according to claim 1, characterized in that, The second sub-welding part includes: A filling portion is disposed between the first sub-tube and the second sub-tube, and contacts the first sub-welding portion; The cover surface is located on the side of the filling portion away from the first sub-weld portion, and at least partially covers the surfaces of the first sub-tube and the second sub-tube away from the first sub-weld portion.

5. The X52 steel grade pipe for a pure hydrogen environment according to claim 4, characterized in that, The filling portion includes: at least one filling sub-part stacked along the first direction; each filling sub-part having a dimension of less than or equal to 3 mm along the first direction; and / or Along the first direction, the vertical distance from the cover surface to the first sub-tube is less than or equal to 2 mm.

6. A welding method for X52 grade steel pipes used in a pure hydrogen environment, characterized in that, include: A first sub-tube is provided; the first sub-tube includes a first weld joint; A second sub-tube is provided; the second sub-tube includes a second weld joint; The first weld joint and the second weld joint are arranged opposite to each other, and the first sub-pipe and the second sub-pipe are connected by welding to form a welded part; Along the first direction, the welding portion includes: a first sub-welding portion and a second sub-welding portion connected to the first sub-welding portion; The first direction is perpendicular to the extension direction of the X52 steel grade pipe for a pure hydrogen environment; based on the mass of the welded part, the mass percentages of C, P, and S in the first sub-welded part are all greater than or equal to the mass percentages of C, P, and S in the second sub-welded part.

7. The welding method for X52 steel grade pipes for pure hydrogen environments according to claim 6, characterized in that, The formation of the welded portion includes: A first sub-welded part is formed by first welding a portion of the first weld joint and the second weld joint using welding wire. A second welding process is performed on another part of the first weld joint and the second weld joint using welding rods to form a second sub-welded part; The welding wire, by weight, comprises the following components in the following weight percentages: C 0.06%~0.15%, Si 0.45%~0.75%, Mn 0.9%~1.40%, P≤0.025%, S≤0.035%, Cr≤0.15%, Mo≤0.15%, Ni≤0.15%, Ti 0.002%~0.01%, V ≤0.03%, Cu 0.07%~0.09%, Co 0.001%~0.003%, Al 0.002%~0.004%, Nb 0.001%~0.003%, with the balance being Fe and other unavoidable impurities; Based on the mass of the welding electrode, the welding electrode comprises the following components in the following mass percentages: C 0.04%~0.09%, Si 0.30%~0.60%, Mn 1.00%~1.30%, P≤0.01%, S≤0.006%, Cr 0.10%~0.50%, Mo≤0.01%, Ni 0.10%~0.50%, Ti 0.01%~0.02%, V 0.005%~0.015%, B%≤0.002%, with the balance being Fe and other unavoidable impurities.

8. The welding method for X52 steel grade pipes for pure hydrogen environments according to claim 7, characterized in that, The first welding was performed using a tungsten electrode under inert gas protection. The current range for the first welding is 95A~110A; the voltage range for the first welding is 10V~14V; and the welding speed for the first welding is 6cm / min~8cm / min.

9. The welding method for X52 steel grade pipes for pure hydrogen environments according to claim 7, characterized in that, The second welding was performed using electric arc welding; The current range for the second welding is 105A~115A; the voltage range for the second welding is 20V~24V; and the welding speed range for the second welding is 9 cm / min~12 cm / min.

10. The welding method for X52 steel grade pipes for pure hydrogen environments according to claim 6, characterized in that, Before setting the first weld joint and the second weld joint opposite each other, the method further includes: The first weld joint and the second weld joint are preheated; the preheating temperature range is 60℃~100℃.

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