In-situ metallurgical submerged arc welding method for hydrogen storage / transportation material bypass high-nickel cold wire feeding

Abstract

The invention discloses an in-situ metallurgical submerged-arc welding method for hydrogen storage / transportation material bypass high-nickel cold wires, and relates to the field of submerged-arc welding. The problem that hydrogen embrittlement and hydrogen induced cracking are prone to occurring in a hydrogen conveying pipe welding joint is solved. The frame body is fixed to a sliding plate of a submerged arc welding gun, the wire feeding wheel set is installed on the frame body and inputs high-nickel cold wires into a stable area of a molten pool in a stepless speed change mode, the Hall sensor detects the wire feeding speed in real time and feeds back speed signals to the servo driver of the wire feeding wheel set, and therefore closed-loop control over the wire feeding speed is achieved. According to the submerged-arc welding method, in the welding process, the bypass high-nickel cold wire is introduced, quantitative regulation and control over the nickel element content in a weld joint and accurate control over heat input of the weld joint are achieved by adjusting the wire feeding speed of the bypass high-nickel cold wire, and then the hydrogen embrittlement resistance of the weld joint is improved. The method is used for hydrogen storage / transportation material welding.

Description

Technical Field

[0001] This invention relates to the field of submerged arc welding, specifically to an in-situ metallurgical submerged arc welding method for hydrogen storage / transport materials using a bypass feeding of high-nickel cold wire. It is used for multi-wire submerged arc welding of high-pressure vessels such as hydrogen storage tanks and hydrogen transport pipes, and particularly provides a welding method that adjusts the heat input and alloy composition of the molten pool by bypassing and varying the speed of the high-nickel cold wire feeding. Background Technology

[0002] Against the backdrop of a global energy structure transitioning towards cleaner and lower-carbon energy sources, hydrogen energy, with its abundant resources, high energy density, and environmental friendliness, is considered a key pillar in building a future sustainable energy system. In the hydrogen energy industry chain, large-scale, long-distance, and low-cost hydrogen transportation is a crucial link connecting hydrogen production and consumption. High-pressure gaseous pipeline hydrogen transportation, due to its technological maturity and economic viability, is considered the primary mode of onshore hydrogen transportation for the present and foreseeable future.

[0003] Multi-wire submerged arc welding, with its high efficiency and high deposition rate, has been widely used in the manufacturing of long-distance oil and gas pipelines. However, the welded joint is the weakest point in the entire pipeline transportation system. This is because the high heat input and multiple thermal cycles of traditional multi-wire submerged arc welding lead to a large microstructure gradient, coarsened grains, high dislocation density, and hard and brittle phases (martensite and bainite) in the weld and heat-affected zone. These conditions provide "traps" for the local enrichment of hydrogen, thus inducing hydrogen embrittlement.

[0004] X65MH pipeline steel, with its excellent strength-toughness ratio, good weldability, and economy, is considered one of the candidate materials for future high-pressure hydrogen pipelines. However, during hydrogen transportation, hydrogen atoms easily penetrate the interior of X65MH pipeline steel and accumulate in stress concentration areas or specific microstructural defects, leading to deterioration of the material's mechanical properties and delayed fracture at stress levels below the yield strength. In other words, X65MH pipeline steel suffers from hydrogen-induced cracking, which poses a serious challenge to the service safety of hydrogen pipelines.

[0005] Nickel, as an important alloying element, plays a multifaceted and positive role in improving the low-temperature toughness and resistance to hydrogen embrittlement in metals. Numerous studies have shown that adding an appropriate amount of nickel to weld metal can significantly improve its impact toughness at low temperatures. Nickel may introduce moderately energetic "beneficial" hydrogen traps by forming specific precipitates with other elements in steel or by altering grain boundary properties. This changes the diffusion behavior of hydrogen in steel, reduces hydrogen enrichment in stress concentration zones such as crack tips, and delays the occurrence of hydrogen embrittlement.

[0006] Currently, the main way to achieve weld metallization in industry is by using pre-customized welding materials containing specific alloy compositions. However, this traditional method has obvious limitations: on the one hand, customizing various specifications of special welding wires for different service requirements has a long development cycle and high production costs; on the other hand, it lacks online "metallurgical flexibility" in the process, and cannot make real-time and precise adjustments to the alloy composition during welding.

[0007] To address the aforementioned research gaps, an in-situ metallurgical process for bypassing high-Ni cold wire (Ni content > 70wt%) during multi-wire submerged arc welding of hydrogen pipelines has been invented. This process aims to reduce the cost of pre-set welding wire for alloying control, dynamically adjust the wire feeding speed and position, and achieve quantitative adjustment of weld alloying. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of hydrogen embrittlement and hydrogen-induced cracking in existing multi-wire submerged arc welding of hydrogen transport pipe joints. Furthermore, it provides an in-situ metallurgical submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials.

[0009] The technical solution of this invention is:

[0010] This invention first provides a bypass speed-controlled high-nickel cold wire feeding device, including a frame 1 fixed on the slide plate of a submerged arc welding torch, a wire feeding wheel assembly 2, and a Hall sensor. The wire feeding wheel assembly 2 is mounted on the frame 1 and is used to feed high-nickel cold wire into the stable zone of the molten pool in a stepless speed-controlled manner, in addition to the main welding wire, thereby regulating the chemical element composition in the weld and improving the resistance to hydrogen embrittlement. The Hall sensor mounted on the wire feeding wheel assembly 2 detects the wire feeding speed in real time and feeds the speed signal back to the servo driver of the wire feeding wheel assembly 2 to achieve closed-loop control of the wire feeding speed.

[0011] Furthermore, the wire feeding wheel assembly 2 is driven by a servo motor to achieve stepless speed feeding.

[0012] Furthermore, it also includes a guide nozzle, which is installed at the lower part of the frame 1 and is used to adjust the feeding of the high-nickel cold wire in a two-dimensional space in both the circumferential and radial directions.

[0013] Preferably, the input angle adjustment range of the guide nozzle is: circumferential wire feeding angle of 40-70°, and radial wire feeding angle of 4-15mm from the center of the molten pool.

[0014] This invention also provides an in-situ metallurgical submerged arc welding method for hydrogen storage / transport materials with bypass feeding of high-nickel cold wire. This submerged arc welding method introduces a bypass high-nickel cold wire during the welding process. By adjusting the wire feeding speed of the bypass cold wire, the nickel content in the weld and the heat input of the weld can be quantitatively controlled, thereby improving the weld's resistance to hydrogen embrittlement. Specifically, it includes the following steps:

[0015] First, multiple continuously and automatically fed main welding wires are used for submerged arc welding to form a common molten pool; Secondly, 4-15 mm behind the last main welding wire arc and from the center of the molten pool, the high-nickel cold wire is fed into the molten pool stabilization zone in a non-consumable electrode manner. Furthermore, the feed speed of the high-nickel cold wire is infinitely adjustable to ensure that the content of the deposited metal reaches 1.0-2.2 wt%. Finally, the welded samples were electrochemically charged with hydrogen and their impact toughness was measured to verify and optimize the nickel content and wire feed speed.

[0016] Furthermore, the high-nickel cold wire is fed in at a position 4-15mm behind the arc of the last main welding wire.

[0017] Preferably, the circumferential angle at which the high-nickel cold wire is fed into the stabilization zone of the molten pool is 45-60°.

[0018] Preferably, the feeding speed of the high-nickel cold wire is steplessly adjustable within the range of 1-15 m / min.

[0019] Furthermore, multiple continuously and automatically fed main welding wires couple all the electric arcs to form a molten pool on the workpiece.

[0020] Preferably, the main welding wire is a low-hydrogen welding wire, the flux is a sintered flux, the bevel is X-type, V-type or double U-type, the bevel angle is 60-70°, and the blunt edge height is 0.8-3mm.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention achieves dynamic balance of molten pool heat input and precise control of weld nickel content through bypass variable speed feeding of high-nickel cold wire, specifically manifested in:

[0023] (1) Nickel, as an austenite stabilizing element, can significantly alter the phase composition and hydrogen diffusion behavior of the weld when added to welding materials. On the one hand, nickel reduces the solubility and diffusion coefficient of hydrogen in the weld by increasing the proportion of austenite phase (especially under high cooling rate welding conditions). On the other hand, by adding high-nickel cold wire, the introduction of nickel can refine the grains and increase the grain boundary area, thereby suppressing the local enrichment of hydrogen by forming high-density hydrogen traps (such as dislocations and precipitation phase interfaces).

[0024] (2) The present invention adds cold wire into the molten pool, which can neutralize the heat input and improve the microstructure of the weld metal by different nickel content, increase the number of hydrogen traps, and thus effectively solve the industry problem of metal hydrogen embrittlement and efficiency in hydrogen energy storage / transport.

[0025] 2. This invention enables dynamic adjustment of the nickel content in the weld, specifically in the following ways:

[0026] This invention adds a high-nickel (>50wt%) cold wire feeding device to the side of the main welding wires (2-6 wires). The cold wire diameter is 0.8-2.4mm, and it is directly fed into the molten pool via a non-consumable electrode method. Nickel melts into the weld to form an austenitic structure, which inhibits hydrogen diffusion and improves toughness. Variable speed wire feeding adjusts the microstructure and precipitate type in the weld joint, thereby controlling the resistance to hydrogen embrittlement and improving its low-temperature impact toughness and resistance to hydrogen damage.

[0027] For example, for X65MH steel, when the bypass wire feeding speed is 3m-6m / min, the nickel content in the cladding metal is 1.0-2.2wt%, and the hydrogen embrittlement resistance is best at this time.

[0028] 3. If the anti-hydrogen embrittlement effect is found to be poor in subsequent experiments after the addition of an external cold wire, the wire feed speed can be adjusted to continuously optimize the anti-hydrogen embrittlement effect. Experimental comparisons show that adding a high-nickel cold wire to the submerged arc welding pool can reduce the hydrogen embrittlement sensitivity of the X65MH pipeline steel welded joint and the cladding metal. Therefore, nickel plays a suppressive role in hydrogen embrittlement sensitivity.

[0029] As an austenite stabilizing element, nickel promotes the formation of residual austenite in the weld. Its addition to the welding material can significantly change the phase composition and hydrogen diffusion behavior of the weld. Its content increases from <5% in the absence of nickel to 12%. Its face-centered cubic structure can effectively reduce hydrogen solubility and diffusion coefficient.

[0030] In addition, the addition of nickel refines the grains (the average grain size is reduced from 15 μm to 8 μm), increases the grain boundary area, and forms high-density dislocations and precipitates (such as Ni-Ti composite precipitates), which act as hydrogen traps to suppress the local enrichment of hydrogen.

[0031] 4. This invention uses X65MH pipeline steel as the base material and proposes a technology of "multi-wire submerged arc welding + bypass cold wire feeding (cold wire grade is ERNiCr-3)". The cold wire is directly fed into the molten pool to adjust the heat input. Moreover, the welding wire does not pass through the arc, so the loss of its alloy elements is low. By controlling the amount of cold wire fed, the nickel content in the weld area can be adjusted in situ and flexibly, and the microstructure of the welded joint is customized.

[0032] By measuring the different nickel content in the weld, the influence of the weld joint's impact toughness and resistance to hydrogen embrittlement is obtained. This method combines the high efficiency of multi-wire submerged arc welding with the precise alloying capability of bypass cold wire, avoiding the complexity and high cost of specially customized welding wires of various specifications to obtain welds with different nickel contents, and providing a new approach for high-performance hydrogen pipeline welding.

[0033] 5. The core of the bypass cold wire feeding technology of this invention, particularly its application in multi-wire submerged arc welding, lies in feeding one or more non-energized "cold" filler metal wires into the molten pool maintained by the main welding arc (group) in a specific manner. The melting of the cold wire relies primarily on the overheating of the molten pool, rather than direct heating by the arc. The introduction of this process brings multiple benefits:

[0034] (1) It can significantly increase the overall deposition rate of metal without significantly increasing (or even adjusting) the welding heat input.

[0035] (2) The addition of cold wire will absorb some of the heat of the molten pool, which helps to control the temperature of the molten pool, slows down the cooling rate or changes the temperature gradient, thus having a beneficial effect on the evolution of the microstructure of the weld and hydrogen embrittlement.

[0036] (3) Since the cold wire does not pass through the electric arc, the loss of its alloying elements is very low, which greatly facilitates the precise control of the chemical composition of the weld. In particular, for some alloying elements that are easily burned in the electric arc or react in complex ways with the flux, adding them in the form of a cold wire can achieve higher yield and more controllable composition.

[0037] (4) The addition of cold wire can significantly change the dilution rate of the base metal in the weld metal. It is also an effective means when it is necessary to obtain a special weld with a large difference in composition from the base metal.

[0038] 6. This invention employs a three-pronged approach: "bypass cold wire precision nickel addition + low heat input grain refinement + closed-loop control," fundamentally weakening hydrogen diffusion, enrichment, and crack initiation driving forces in the weld, thereby solving the problem of hydrogen-induced cracking. Specifically, this is reflected in:

[0039] (1) Reduce hydrogen diffusion and enrichment in the weld: By using a bypass cold wire, the nickel content in the weld is stably controlled at 1.3-1.48 wt%. In this range, nickel exists as a face-centered cubic austenite stabilizing element, which can significantly reduce the solubility and diffusion coefficient of hydrogen. Nickel promotes fine grain structure, increases grain boundary area, and forms "hydrogen traps" such as high-density dislocations and Ni-Ti composite precipitation phases, so that hydrogen atoms are uniformly dispersed and local enrichment is avoided to prevent crack initiation.

[0040] (2) Refining the microstructure of the heat-affected zone without increasing heat input: The cold wire is fed directly into the molten pool in a "non-consumable electrode" manner to absorb the overheating of the molten pool, offset the high heat input of multi-wire submerged arc welding, reduce the width of the coarse grain zone and the proportion of hardened phase (martensite / bainite), and reduce the sensitivity to hydrogen-induced cracking. In addition, by using a 0-18m stepless speed change, the nickel content and cooling rate can be adjusted online to avoid the fixed high dilution rate and high heat input caused by a one-time high-nickel main welding wire.

[0041] (3) Real-time closed-loop control ensures process stability: "Hall sensor + servo motor closed-loop system" ensures wire feeding speed accuracy of ±0.1m / min, avoids nickel content deviation due to wire feeding fluctuation, and thus ensures the consistency of weld hydrogen trap density and toughness. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the welding experimental system of the present invention; in the figure, (a) represents a physical diagram of the experimental device, and (d) represents a schematic diagram of the submerged arc experimental system.

[0043] Figure 2 This is a schematic diagram of the welding process parameters, welding sequence, and bevel morphology design of the present invention; in the figure, (a) represents the welding voltage; (b) represents the welding current; and (c) represents the welding sequence, welding position, and bevel size.

[0044] Figure 3 This is a schematic diagram of the electrochemical hydrogen charging experimental apparatus for impact samples. In the figure, (a) represents the physical diagram of the experimental system, (b) represents the sampling position of the notch, and (c) represents the schematic diagram of the electrochemical hydrogen charging experimental apparatus.

[0045] Figure 4 This is a line graph showing the relationship between room temperature impact energy and hydrogen charging time for welded joints after welding with different cold wire feed speeds and nickel content of deposited metal wires.

[0046] Figure 5 This is a line graph showing the average impact toughness loss rate of welded joints after welding with different nickel content of deposited metal under different cold wire feeding speeds. One is without cold wire feeding (i.e., the nickel content in the weld is 0%), and the other is with a wire feeding speed of 4m / min (the nickel content in the weld is 1.48wt%). The two are compared.

[0047] Figure 6 This is a schematic diagram of the overall structure of the submerged arc welding experimental platform of the present invention; in the figure: 1, frame, 2, wire feeding wheel group.

[0048] Figure 7 These are SEM morphology comparison images of the fracture surfaces of impact test specimens. Detailed Implementation

[0049] Specific implementation method one: Combining Figure 1 and Figure 6This embodiment describes a bypass speed-controlled high-nickel cold wire feeding device, which includes a frame 1 fixed on the slide plate of a submerged arc welding torch, a wire feeding wheel assembly 2, and a Hall sensor. The wire feeding wheel assembly 2 is mounted on the frame 1 and is used to feed high-nickel cold wire into the stable zone of the molten pool in a stepless speed-controlled manner, in addition to the main welding wire, thereby regulating the chemical element composition in the weld and improving the resistance to hydrogen embrittlement. The Hall sensor mounted on the wire feeding wheel assembly 2 detects the wire feeding speed in real time and feeds the speed signal back to the servo driver of the wire feeding wheel assembly 2 to achieve closed-loop control of the wire feeding speed.

[0050] The cold wire feeding device in this embodiment is mainly driven by a servo motor to drive the wire feeding wheel assembly, and equipped with a Hall sensor to monitor the wire feeding speed in real time, feeding back to the PLC controller to achieve closed-loop control. The wire feeding speed adjustment logic is based on the steel grade (e.g., X70 steel requires 8% Ni, X80 steel requires 10% Ni) and the welding material composition, and calculates the cold wire feeding speed using the formula VNi=k·(Ctarget-Cbase)·Qmelt, where VNi is the cold wire speed, Ctarget is the target Ni content, Cbase is the base material Ni content, and Qmelt is the molten pool metal content.

[0051] The high-nickel cold wire feeding device in this embodiment can precisely control the nickel content of the weld: by using a servo driver (to drive the wire feeding wheel group 2 to feed the wire in a stepless speed change manner) + Hall sensor closed-loop system, the wire feeding speed is stabilized within the accuracy of ±0.1m / min, so that the high-nickel cold wire enters the molten pool at a repeatable and programmable rate, thereby locking the Ni content of the weld in the optimal hydrogen embrittlement resistance range of 1.3–1.48wt%.

[0052] This implementation method can also achieve online adjustment of heat input and cooling rate: the high-nickel cold wire is fed in a stepless speed regulation manner, which can increase or decrease the amount of overheat absorption of the molten pool in real time. Without changing the energy of the main welding wire, the heat input and cooling gradient can be finely adjusted, thereby reducing the formation of coarse grain region and hard and brittle phase, and reducing the sensitivity to hydrogen-induced cracking.

[0053] In addition, closed-loop control avoids nickel content deviation and molten pool temperature disturbance caused by wire feeding fluctuations, ensuring that the hydrogen trap density, grain size and impact toughness of the entire weld are uniform and consistent, making the hydrogen embrittlement resistance predictable and repeatable.

[0054] The stable zone of the molten pool refers to the area within the molten pool during welding where the temperature is relatively low, the flow is relatively stable, and it is not directly affected by the electric arc. This zone is usually located at the rear of the molten pool, near the tail end, where the temperature and flow state are relatively stable, making it suitable for adding filler metal (such as cold wire) to achieve uniform melting and alloying.

[0055] This invention employs an in-situ metallurgical process of bypassing high-Ni cold wire (Ni content > 70wt%) during multi-wire submerged arc welding of hydrogen pipelines. The aim is to reduce the cost of alloying control of pre-set welding wire, dynamically adjust the wire feeding speed and position, and achieve quantitative adjustment of weld metal alloying, thereby improving the weld metal's resistance to hydrogen embrittlement.

[0056] Specific Implementation Method Two: Combining Figure 1 and Figure 6 In this embodiment, the wire feeding wheel assembly 2 is driven by a servo motor to achieve stepless speed control for wire feeding. This configuration allows for the stepless and stable feeding of high-nickel cold wire into the molten pool's stable zone according to a set wire feeding accuracy and speed curve. This provides precisely controllable nickel content and manageable heat input to the weld, ultimately suppressing hydrogen embrittlement and hydrogen-induced cracking. Other components and connections are the same as in Specific Embodiment One.

[0057] Specific implementation method three: Combining Figure 1 and Figure 6 This embodiment further includes a guide nozzle, which is installed at the lower part of the frame 1 and is used to adjust the feeding of the high-nickel cold wire in a two-dimensional space in both the circumferential and radial directions. This configuration facilitates precise locking of the cold wire outlet position in the two-dimensional space, ensuring that the high-nickel cold wire avoids the main arc and accurately inserts into the stable region of the molten pool, thereby guaranteeing uniform melting of nickel and suppressing hydrogen embrittlement. Other components and connections are the same as in specific embodiments one or two.

[0058] As a preferred embodiment, the guide nozzle can be implemented using a ball joint universal joint, with the outlet end of the guide nozzle made into a ball head that mates with a ball socket. Loosening the locking nut allows for continuous rotation in any direction (circumferential or radial) from ±15° to ±20°, and locking it in place. The structure is compact, the angle is continuously adjustable, and it is easy to implement.

[0059] Specific implementation method four: Combination Figure 1 and Figure 6 This embodiment describes the input angle adjustment range of the guide nozzle as follows: the circumferential wire feeding angle is 40-70°, and the radial wire feeding angle is 4-15mm from the center of the molten pool.

[0060] This setup ensures that the high-nickel cold wire is always inserted into the stable zone of the molten pool at the most suitable angle and position, preventing burn-out of the main arc while ensuring sufficient melting. This allows for precise control of the nickel content in the weld and suppression of hydrogen embrittlement. Other components and connections are the same as in specific implementation methods one, two, or three.

[0061] In this embodiment, the circumferential wire feed angle refers to the angle between the cold wire and the longitudinal direction (welding direction) of the weld. The radial wire feed angle refers to the swing angle of the cold wire tip in the "radial direction of the molten pool".

[0062] Specific Implementation Method Five: Combining Figures 1 to 3 This embodiment describes an in-situ submerged arc welding method. During the welding process, a bypass high-nickel cold wire is introduced. By adjusting the wire feed speed of the bypass cold wire, the nickel content in the weld and the heat input of the weld are quantitatively controlled, thereby improving the weld's resistance to hydrogen embrittlement. The specific steps include:

[0063] First, multiple continuously and automatically fed main welding wires are used for submerged arc welding to form a common molten pool; Secondly, 4-15mm behind the last main welding wire arc and from the center of the molten pool, a high-nickel cold wire is fed into the stable zone of the molten pool in a non-consumable electrode manner to achieve in-situ metallurgy of the weld metal. Furthermore, the feed speed of the high-nickel cold wire is infinitely adjustable to ensure that the content of the deposited metal reaches 1.0-2.2 wt%. Finally, the welded samples were electrochemically charged with hydrogen and their impact toughness was measured to verify and optimize the nickel content and wire feed speed.

[0064] This invention combines the high efficiency of multi-wire submerged arc welding with the precise alloying capability of bypass-feeding high-nickel cold wire, applying it to the welding of X65MH hydrogen pipeline steel. By controlling the feed rate of the high-nickel cold wire, the nickel content in the weld region can be adjusted in situ and flexibly, thereby customizing and optimizing the weld microstructure to obtain welded joints with both excellent low-temperature impact toughness and superior resistance to hydrogen embrittlement. This method avoids the complexity and high cost of customizing multiple specifications of nickel-based main welding wires to obtain welds with different nickel contents, providing a promising new approach for high-performance hydrogen pipeline welding. Compared to adding nickel to the main welding wire or flux, bypass-feeding of nickel with cold wire minimizes nickel evaporation in the high-temperature arc plasma and chemical reactions with the flux, thus ensuring efficient and stable nickel production.

[0065] In practical applications, this embodiment can also be used to feed high-nickel welding wire with a nickel content of 70% or more.

[0066] Furthermore, this embodiment does not specifically limit whether the compositions of the multiple main welding wires are the same, or the number of main welding wires. However, as a preferred embodiment, the number of main welding wires can be three, and the composition of each main welding wire is different. In addition, the composition of the first welding wire (also often called the arc-starting welding wire or the root pass welding wire) may sometimes differ from that of other subsequent filler welding wires. For pipe welding, especially root pass welding, controlling the penetration depth is crucial. The composition and diameter of the first welding wire affect the characteristics of the weld pool and its penetration ability. Selecting welding wires with appropriate melting characteristics and alloying elements can ensure penetration of the base metal while avoiding problems such as burn-through, and forming a weld bead of a specific shape, laying a good foundation for subsequent filler welds.

[0067] For example:

[0068] First wire: DC: Welding wire current: 900-980A, voltage: 30-32V, welding speed: 1.0-1.35m / min;

[0069] Second wire: AC: Welding current: 700-750A, voltage: 32-37V, welding speed: 1.0-1.35m / min;

[0070] Third wire: AC: Welding current: 500-550A, voltage: 36-40V, welding speed: 1.0-1.35m / min

[0071] Step 13: Adjust the spacing between the welding wires:

[0072] Adjust the distance between each pair of welding wires to 6-8mm; the phase angles are: 0° for the first wire, 90° for the second wire, and 180° for the third wire.

[0073] It facilitates the formation of weld beads of a specific shape, laying a good foundation for the filling of subsequent weld beads.

[0074] This implementation method, based on in-situ metallurgical theory, utilizes bypass cold wire feeding technology, which has shown promising application prospects in GMAW, GMTW, and laser welding. However, for multi-wire submerged arc welding with more concentrated energy, multi-arc coupling, and more complex molten pool dynamics, there is no precedent for the application of bypass cold wire feeding technology. Moreover, this method of using bypass alloyed welding wire to quantitatively adjust the Ni content in the weld, thereby refining the grains by inducing acicular ferrite formation through Ni alloying, is proposed for the first time. This avoids the need to add Ni to the main welding wire in existing technologies, which requires a time-consuming and labor-intensive smelting process. In such cases, the designed main welding wire composition may not be suitable, necessitating re-smelting, which is also time-consuming, labor-intensive, and costly.

[0075] Specific Implementation Method Six: Combination Figures 1 to 3 In this embodiment, the high-nickel cold wire is fed in 4-15 mm behind the last main welding wire arc. This placement avoids the high-temperature zone of the arc, as this position is outside the main arc plasma beam, significantly reducing nickel evaporation, oxidation, and violent reactions with the flux, ensuring a high nickel yield. Furthermore, entering the molten pool stable zone 4-15 mm from this point is a stable flow zone at the tail end of the molten pool, where the temperature is still above the nickel melting point. The cold wire can then rapidly and uniformly melt using the residual heat of the molten pool, avoiding incomplete fusion or inclusions. Additionally, the cold wire absorbs heat in this region, allowing for localized fine-tuning of the molten pool temperature, reducing overall heat input, thereby refining the grains, reducing embrittlement in coarse-grained areas, and further suppressing hydrogen embrittlement. Other components and connections are the same as in any of the specific embodiments one through five.

[0076] Specific implementation method seven: Combining Figures 1 to 3In this embodiment, the circumferential angle at which the high-nickel cold wire is fed into the stable zone of the molten pool is 45-60°. This setting avoids the direct arc zone, and by inserting it at an angle, the end of the cold wire is positioned behind and to the side of the main arc tail flame, avoiding direct arc burning, significantly reducing nickel burn-off and oxidation, and improving yield. This angle precisely cuts into the eddy current zone at the tail of the molten pool, allowing the molten pool flow to quickly entrain and uniformly dilute the cold wire, preventing it from "floating" or developing incomplete fusion defects. If the angle of the cold wire is less than 45°, it is prone to colliding with the arc or flux flow, leading to spatter and arc instability; when it is greater than 60°, it may touch unmelted base material, causing cold wire vibration or insufficient fusion. Other components and connections are the same as in any of the specific embodiments one to six.

[0077] Specific implementation method eight: Combination Figures 1 to 3 In this embodiment, the feed speed of the high-nickel cold wire is infinitely adjustable within the range of 1-15 m / min. This setting facilitates precise control of the nickel content of the weld. A faster cold wire speed removes more heat from the molten pool, reducing the effective heat input by 5-15% without lowering the main welding wire current and voltage, thus refining the grains and reducing the width of the coarse-grained region. Conversely, a slower speed increases heat input when increased penetration or compensation for low-temperature environments is needed, preventing incomplete fusion. If changes in bevel gap, flux thickness fluctuations, or base metal temperature differences occur, real-time compensation can be achieved simply by adjusting the wire feed speed online. Other components and connections are the same as in any of the specific embodiments one through seven.

[0078] Specific Implementation Method Nine: Combining Figures 1 to 3 This embodiment describes a method where multiple continuously fed main welding wires couple all the arcs to form a single molten pool on the workpiece. This configuration achieves high deposition efficiency by creating a sufficiently large and stable shared molten pool in a single operation. This provides a "large-capacity, high-uniformity" process platform for the subsequent precise alloying and heat input fine-tuning of the bypass cold wire, thereby suppressing hydrogen-induced cracking while achieving efficient welding. Other components and connections are the same as in any of the specific embodiments one through eight.

[0079] Specific Implementation Method Ten: Combining Figures 1 to 3 In this embodiment, the main welding wire is a low-hydrogen type, the flux is a sintered flux, the bevel is X-type, V-type, or double U-type, the bevel angle is 60-70°, and the blunt edge height is 0.8-3mm. This configuration lays a reliable foundation for precise nickel addition via the bypass cold wire and for suppressing hydrogen-induced cracking. Other components and connections are the same as in any of the specific embodiments one through nine.

[0080] Combination Figures 1 to 7 Explanation of the working principle of this invention:

[0081] The welding experimental system of this invention mainly consists of a parameter acquisition system and a three-wire submerged arc welding device, such as... Figure 1 and Figure 7 As shown.

[0082] The three-wire submerged arc welding equipment mainly consists of a multi-wire submerged arc welding host, a moving platform, a workpiece clamping mechanism, a welding power supply system, a welding machine feeding device, a main control cabinet, an operating table, and a welding parameter acquisition system.

[0083] The experimental workpiece used in this invention is a pre-welded X65MH steel plate. Through microalloying design (addition of elements such as Nb, V, and Ti), X65MH steel plate has become the preferred material for high-pressure hydrogen pipelines due to its high strength, low hydrogen embrittlement sensitivity, excellent weldability, and economy. The chemical compositions of the base material and welding materials are shown in Table 1, and the chemical composition of the flux is shown in Table 2.

[0084] Table 1 Chemical composition of base metal and welding wire (mass fraction, %)

[0085]

[0086] Table 2 Chemical composition of flux SJ101MH (mass fraction, %)

[0087]

[0088] During the experiment, the welding process parameters and bevel structure of this invention are as follows:

[0089] Actual welding process parameters and bevel cross-sections collected by an arc analyzer, such as... Figure 2 As shown, considering the weld penetration, filler volume, and the influence of the alternating magnetic field generated by the arc of each wire, wire 1 is DC reverse polarity, while wires 2 and 3 are AC polarity. Each welding wire has a diameter of 4.0 mm, and the spacing between adjacent wires is 16 mm. To ensure stable arc combustion and avoid interference from the alternating magnetic field, the phase angle of the welding power supply is set to 0°, 90°, and 180° sequentially.

[0090] The bevel shape and welding sequence are consistent with actual production, and welding is performed on both sides.

[0091] Impact test specimens were prepared from the test plate according to GB / T 2650-2022 standard after cold working of one-wire / two-wire welding. The impact test specimens were then subjected to an electrochemical hydrogen charging test. Figure 4 As shown.

[0092] The test specimen was taken from the center of the weld with a V-notch, and the sampling location was 2 mm from the outer weld side of the test plate. The specimen size was 10 mm × 10 mm × 55 mm. Figure 3As shown in (b), the electrochemical hydrogen charging device mainly consists of a DC regulated power supply, a hydrogen charging reaction device, a hydrogen charging solution, and a data acquisition device, as follows: Figure 3 As shown in (a).

[0093] The hydrogen charging solution was 0.1 mol / L H2SO4, with 100 mg / L thiourea added as a poisoning agent to inhibit hydrogen leakage and ensure that the notch of the sample was completely submerged in the solution. Before hydrogen charging, the surface of the impact sample was ground and mechanically polished to remove the effects of surface work hardening, and then washed with water and degreased with ketone. The sample was connected to the negative terminal of a DC regulated power supply, and Pt was connected to the positive terminal. The hydrogen charging current density was 10 mA / cm2, and the hydrogen charging times were 0 h, 12 h, 24 h, 36 h, and 48 h. Immediately after hydrogen charging, room temperature impact tests were performed. The impact toughness (higher indicates better performance) and toughness loss rate (higher indicates worse performance) under different hydrogen charging times were calculated and analyzed. Subsequently, the fracture cross section was analyzed by SEM.

[0094] Actual experiments have shown that impact toughness can indirectly reflect resistance to hydrogen embrittlement; the higher the impact toughness, the better the resistance to hydrogen embrittlement.

[0095] After hydrogen charging tests were conducted on the impact specimens of the single-wire and double-wire welded joints at 0h, 12h, 24h, 36h and 48h respectively, room temperature impact tests were immediately performed. When Ni ≈ 0 wt% in the welding wire, the average room temperature impact energy of the welded joints were 230 J, 215 J, 216 J, 210 J and 201 J respectively; when Ni ≈ 1.48 wt% in the welding wire, the average room temperature impact energy of the welded joints were 237 J, 225 J, 228 J, 213 J and 213 J respectively.

[0096] from Figure 4 It can be seen that with the increase of hydrogen charging time, the impact toughness of both groups of samples gradually decreased, reaching the lowest value of 201J and 213J after 48h of hydrogen charging, respectively. A longitudinal comparison of the impact energy values ​​of the two groups of samples under the same hydrogen charging time shows that the room temperature impact toughness of the welded joint with Ni≈1.48wt% in the welding wire is significantly higher than that of the control sample under different hydrogen charging time conditions, and even reaches the plateau period (the dissolved H atoms in the notch reach saturation) at 36h and 48h, while the impact toughness of the control group continues to decrease.

[0097] from Figure 5 As can be seen, the average impact toughness loss rate of both increases with the increase of hydrogen charging time. In longitudinal comparison, when Ni ≈ 1.48 wt% in the welding wire, the impact toughness loss rate of the welded joint is significantly lower than that of the control group. The loss rates of both reach their highest values ​​at 48 h, which are 12.6% and 10.08%, respectively. This shows that when the Ni content in the welding wire increases, the impact toughness loss rate after hydrogen charging also decreases.

[0098] Analysis of the impact fracture morphology shows that, for example Figure 7 The image shows SEM images of the fracture surfaces of impact specimens from one-wire and two-wire welded joints prepared in air. A closer examination of the fractured specimens from the top view reveals numerous ductile dimples on the fracture surface of the welded joints. These dimples are characteristic features of ductile fracture, indicating the ductile fracture process, including void initiation, crack propagation, and merging. Therefore, the fracture mechanism of the welded joints prepared in air is ductile fracture.

[0099] Figure 7 In the figure, (a1)-(a3) represent the fracture morphology of the one-wire joint in the non-hydrogen-charged state, and (b1)-(b3) represent the fracture morphology of the one-wire joint after 24 hours of electrochemical hydrogen charging. The cleavage steps of the No. 1 sample after one-wire welding are more dense, and the secondary cracks are more significant and coarser, indicating that the main crack propagation process is accompanied by strong local brittle fracture.

[0100] Figure 7 In the figure, (c1)-(c3) represent the fracture morphology of the two-wire joint in the non-hydrogen-charged state, and (d1)-(d3) represent the fracture morphology of the two-wire joint after 24 hours of electrochemical hydrogen charging. The secondary crack of the No. 2 sample after two-wire welding is mainly limited to a local area and does not completely penetrate, indicating that the localization of brittle propagation during its fracture process is weak, and a large-scale hydrogen-induced embrittlement area is not formed, and the degree of embrittlement is relatively mild.

[0101] Therefore, after 48 hours of electrochemical hydrogen charging, the toughness of sample No. 2 was still better than that of sample No. 1.

[0102] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make other changes within the spirit of the invention and apply it to fields not mentioned in the invention. Of course, all such changes made in accordance with the spirit of the invention should be included within the scope of protection claimed by the invention.

Claims

1. An in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials, characterized in that: In this submerged arc welding method, a bypass high-nickel cold wire is introduced during the welding process. By adjusting the wire feeding speed of the bypass cold wire, the nickel content in the weld can be quantitatively controlled and the heat input of the weld can be precisely controlled, thereby improving the weld's resistance to hydrogen embrittlement.

2. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 1, characterized in that: During the welding process, multiple continuously and automatically fed main welding wires are used for submerged arc welding to form a common molten pool.

3. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 2, characterized in that: The process of forming a molten pool is as follows: multiple continuously fed main welding wires couple all the electric arcs on the workpiece to form a molten pool.

4. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 3, characterized in that: The high-nickel cold wire should be fed in 4-15mm behind the arc of the last main welding wire.

5. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 3, characterized in that: The high-nickel cold wire is fed into the molten pool stable zone in a non-consumable electrode manner, 4-15 mm behind the last main welding wire arc and at a distance from the center of the molten pool.

6. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 5, characterized in that: The main welding wire is a low-hydrogen type welding wire, the flux is a sintered flux, the bevel is X-type, V-type or double U-type, the bevel angle is 60-70°, and the blunt edge height is 0.8-3mm.

7. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 6, characterized in that: The feeding speed of the high-nickel cold wire is infinitely adjustable, so that the content in the deposited metal reaches 1.0-2.2wt%.

8. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 7, characterized in that: The feeding speed of the high-nickel cold wire is infinitely adjustable within the range of 1-15m / min.

9. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 8, characterized in that: The circumferential angle at which the high-nickel cold wire is fed into the stabilization zone of the molten pool is 45-60°.

10. The in-situ submerged arc welding method for bypassing high-nickel cold wire in hydrogen storage / transport materials according to claim 9, characterized in that: After welding, the welded samples were electrochemically charged with hydrogen and their impact toughness was measured to verify and optimize the nickel content and wire feed speed.

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