A coiled tubing butt-welding gas shielded solid wire and welding method

Abstract

The application relates to the technical field of welding materials, in particular to a continuous oil pipe butt welding gas protection solid core welding wire and a welding method; the chemical components of the solid core welding wire include the following: C: 0.08%-0.14%, Si: 0.2%-0.3%, Mn: 0.7%-1.0%, Ni: 0.15%-0.25%, Cu: 0.25%-0.35%, Cr: 0.5%-0.7%, Mo: 0.10%-0.15%, Nb: 0.02%-0.03%, Ti: 0.01%-0.02%, and the rest is Fe and inevitable impurities; by adopting low-carbon components, the fatigue performance of a weld is reduced, then the Mn, Ni, Mo, Cr and Cu systems are adopted, and i and Nb trace elements are added at the same time, so that the solid solution strengthening, fine-grain strengthening and precipitation strengthening methods can be comprehensively utilized to improve the strength of the weld, the hardenability of the weld metal is improved, the generation of bainite is promoted, the toughness and strength of the metal weld are improved, and therefore the fatigue resistance of a pipe-pipe butt welding joint is comprehensively improved.

Description

Technical Field

[0001] This application relates to the field of welding materials technology, and in particular to a gas-shielded solid welding wire for butt welding of continuous tubing and a welding method thereof. Background Technology

[0002] Coiled tubing (CT, also known as coiled tubing, flexible tubing, or ducted tubing) is a long tubing wound on a reel that can be continuously run into and pulled out of a well, as opposed to conventional tubing connected by a helix. Compared to conventional technology, coiled tubing is economical, practical, and highly efficient, and has gained widespread acceptance in the oil and gas industry. However, when coiled tubing is used in oil and gas wells, the combined effects of acidic media, cyclic plastic deformation, and internal and external pressures can lead to reduced plasticity. When the stress is far below the yield strength of the tubing, brittle fracture can occur, causing serious safety accidents and damaging the ecological environment. Therefore, coiled tubing is required to have high plasticity, high strength, and high low-cycle fatigue performance. Currently, high-grade coiled tubing CT90 has a higher carbon content than CT70 / 80, thus requiring a balance between its high strength, plasticity, and fatigue resistance.

[0003] The main production process of coiled tubing includes: 1) slitting and coiling of steel coils; 2) 45° oblique welding of steel strips to perform plate-to-plate butt welding; 3) grinding, cleaning, and non-destructive testing of the welding area; 4) coiling of steel plates into tubing, followed by straight seam welding using laser welding, high-frequency welding, etc.; 5) weld grinding, overall tube heat treatment, coiling; tube aging treatment; and 6) packaging and warehousing. In the production and application of coiled tubing, due to reasons such as defective tubing, transportation length limitations, tubing failure, or damage, it is necessary to cut off the defective parts of the coiled tubing and then connect them by welding, or to connect two sections of coiled tubing together. While coiled tubing is now hailed as a "universal" application, among the coiled tubing materials already in use, the tube body welds and tube-to-tube butt welds remain the weakest areas in terms of coiled tubing performance. Their performance directly affects the effectiveness of coiled tubing technology. Therefore, tube-to-tube butt welding of coiled tubing is an indispensable application technology in coiled tubing manufacturing and technological applications.

[0004] However, the welding wires currently used for butt welding of coiled tubing are mostly common carbon steel welding wires such as ER50-6, which have a mismatch in strength, toughness, and low-cycle fatigue performance, limiting the fatigue performance of the pipe joints. Therefore, how to provide a gas-shielded solid welding wire for butt welding of coiled tubing to improve the fatigue resistance of pipe-to-pipe butt welds is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] This application provides a gas-shielded solid welding wire and welding method for butt welding of coiled tubing, in order to solve the technical problem of mismatch in strength, toughness and low-cycle fatigue performance of the welding wire used in butt welding of coiled tubing in the prior art.

[0006] In a first aspect, this application provides a gas-shielded solid welding wire for continuous tubing butt welding. The chemical composition of the solid welding wire, by mass fraction, includes: C: 0.08%–0.14%, Si: 0.2%–0.3%, Mn: 0.7%–1.0%, Ni: 0.15%–0.25%, Cu: 0.25%–0.35%, Cr: 0.5%–0.7%, Mo: 0.10%–0.15%, Nb: 0.02%–0.03%, Ti: 0.01%–0.02%, with the remainder being Fe and unavoidable impurities.

[0007] Optionally, the unavoidable impurities, by mass fraction, include: P ≤ 0.015% and S ≤ 0.015%.

[0008] Optionally, by volume fraction, the cladding metal microstructure after welding with the solid welding wire comprises: lath bainite: 90%–95%, acicular ferrite: 5%–10%.

[0009] Secondly, this application provides a welding method for gas-shielded solid wire for butt welding of continuous tubing, the method comprising:

[0010] Pre-treat the ends of the coiled tubing;

[0011] The pipe end of the continuous tubing is installed on a special tooling fixture and cooling water is introduced. Then, 5G all-position welding is performed using the solid welding wire described in the first aspect to obtain the welded continuous tubing.

[0012] The butt weld of the coiled tubing is ground to achieve the butt welding of the coiled tubing.

[0013] Optionally, the pretreatment of the coiled tubing end includes the following steps:

[0014] The end of the coiled tubing to be connected is beveled to obtain a pipe end with a single-sided blunt-edged V-shaped bevel.

[0015] The pipe end with a single-sided blunt-edged V-shaped bevel is ground and rust-removed to obtain the pipe end of a continuous tubing.

[0016] Optionally, the beveling angle is 30°±5°, and the blunt edge width of the single-sided V-shaped beveling with blunt edge is ≤0.5mm.

[0017] Optionally, the depth of the grinding and rust removal is ≤100mm.

[0018] Optionally, the 5G all-position welding includes performing G all-position welding under argon atmosphere conditions using a double-layer, double-pass welding method combined with a low heat input for the bottom layer.

[0019] Optionally, the grinding includes weld seam height repair grinding and longitudinal grinding. The weld seam height repair grinding is performed by angle grinding, and the longitudinal grinding is performed by sandpaper grinding.

[0020] Optionally, the special tooling fixture includes a fixing device, a hollow cooling copper ring, and a cooling water pipe. The pipe end passes through the hollow cooling copper ring, and the cooling water pipe is connected to the hollow cooling copper ring. The fixing device is located outside the hollow cooling copper ring so that the steel pipe to be welded is in the same straightness through the combined action of the fixing device and the hollow cooling copper ring.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art:

[0022] This application provides a gas-shielded solid welding wire for continuous tubing butt welding. By using a low-carbon composition, the carbon equivalent and cold cracking sensitivity of the weld metal are reduced, and the plasticity of the weld metal is improved. At the same time, a certain carbon content can ensure the weld strength, thereby reducing the fatigue performance of the weld. Furthermore, a Mn, Ni, Mo, Cr, Cu system is used, and trace elements i and Nb are added. Utilizing the above composite composition system, solid solution strengthening, grain refinement strengthening, and precipitation strengthening methods can be comprehensively used to improve the strength of the weld. The addition of alloying elements can avoid the formation of proeutectoid ferrite, which is beneficial to improving the hardenability of the weld metal, promoting the formation of bainite, and improving the toughness and strength of the metal weld, thereby comprehensively improving the fatigue resistance of the pipe-to-pipe butt weld joint. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the metallographic structure formed by the cladding of solid welding wire provided in the embodiments of this application;

[0026] Figure 2 A schematic flowchart of the welding method provided in the embodiments of this application;

[0027] Figure 3 A detailed flowchart illustrating the welding method provided in the embodiments of this application;

[0028] Figure 4 This is a schematic diagram of the structure of the special tooling fixture provided in the embodiments of this application.

[0029] Among them, 1-fixed device, 2-hollow cooling copper ring, 3-cooling water pipe;

[0030] Figure 5 This is a schematic diagram of a single-sided V-shaped bevel with a blunt edge provided in an embodiment of this application;

[0031] Figure 6 The solid welding wire and welding method provided in the embodiments of this application result in a welded continuous tubing;

[0032] Figure 7 The welded continuous tubing obtained by the ER80S gas shielded welding wire and welding method provided in the embodiments of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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, 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.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] The creative thinking behind this application is:

[0036] Currently, the welding wires used for butt welding of coiled tubing are mostly common carbon steel welding wires such as ER50-6. There is a mismatch in strength, toughness, and low-cycle fatigue performance, which limits the fatigue performance of the pipe joint. At the same time, the pipe butt welding method has a great influence on the performance of the connected pipe. The bevel angle, centering accuracy, welding parameters, cooling method, protection method, and weld formation affect the joint strength, ductility, toughness, and low-cycle fatigue performance.

[0037] Therefore, how to provide a gas-shielded solid welding wire and welding method for continuous tubing butt welding to improve the fatigue performance of pipe-to-pipe butt welds is a technical problem that urgently needs to be solved.

[0038] This application provides a gas-shielded solid welding wire for continuous tubing butt welding. The chemical composition of the solid welding wire, by mass fraction, includes: C: 0.08%–0.14%, Si: 0.2%–0.3%, Mn: 0.7%–1.0%, Ni: 0.15%–0.25%, Cu: 0.25%–0.35%, Cr: 0.5%–0.7%, Mo: 0.10%–0.15%, Nb: 0.02%–0.03%, Ti: 0.01%–0.02%, with the remainder being Fe and unavoidable impurities.

[0039] In this embodiment, the specific mass fraction of C is controlled, and a low-carbon composition design is adopted to reduce the carbon equivalent and cold cracking sensitivity of the weld metal, thereby improving the plasticity of the weld metal. At the same time, the carbon content can ensure the weld strength. Since the low-cycle fatigue performance is greatly affected by the strength, controlling the specific mass fraction of C can reduce the metal fatigue performance of the weld.

[0040] By controlling the specific mass fractions of Mn, Ni, Mo, Cr, and Cu, and combining them with trace elements such as Ti and Nb, solid solution strengthening, grain refinement strengthening, and precipitation strengthening can be achieved using Mn, Ni, Mo, Cr, Cu, Ti, and Nb, thereby improving the strength of the weld. The addition of alloying elements can prevent the formation of proeutectoid ferrite. Since proeutectoid ferrite has poor plasticity and low strength, these alloying elements can effectively improve the strength and plasticity of the weld. At the same time, these alloying elements are beneficial to improving the hardenability of the weld metal, promoting the formation of bainite, and improving the toughness and strength of the metal weld, thus comprehensively improving the fatigue resistance of the pipe-to-pipe butt weld joint.

[0041] In some alternative implementations, the unavoidable impurities, by mass fraction, include: P ≤ 0.015% and S ≤ 0.015%.

[0042] In this embodiment of the application, the content of harmful elements P and S is controlled. Since harmful elements can deteriorate the performance of welds, and S is prone to hot cracking and P is prone to cold cracking, they also have an adverse effect on the plasticity of welds.

[0043] like Figure 1 As shown, in some optional embodiments, the cladding metal microstructure after welding with the solid welding wire, by volume fraction, comprises: lath bainite: 90%–95%, acicular ferrite: 5%–10%.

[0044] In this embodiment of the application, controlling the specific volume fraction of lath bainite and acicular ferrite in the cladding metal structure can indicate the composition of the metallographic structure formed by the solid welding wire cladding. Lath bainite can effectively improve the toughness and strength of the metal weld, thereby improving the fatigue resistance of the weld joint.

[0045] like Figure 2 As shown, based on a general inventive concept, this application provides a welding method for gas-shielded solid welding wire for butt welding of continuous tubing, the method comprising:

[0046] S1. Pre-treat the ends of the coiled tubing;

[0047] S2. Install the pipe end of the continuous tubing on a special tooling fixture and pass cooling water through it. Then, use the solid welding wire to perform 5G all-position welding to obtain a welded continuous tubing.

[0048] S3. Grind the butt weld of the coiled tubing to achieve butt welding of the coiled tubing.

[0049] In this embodiment, the pipe end of the coiled tubing to be processed is pre-treated to make the pipe end surface clean and rough. Then, a special tooling fixture is used to make the pipe end in the same straightness, thereby ensuring the welding stability of the metal weld. Then, the specific welding method is controlled as 5G all-position welding, which can make the weld fill. Finally, the weld is polished to make it smoother and more stable, thereby obtaining a stable coiled tubing after welding.

[0050] This method is based on the above-mentioned solid welding wire. The specific composition of the solid welding wire can be referred to in the above embodiments. Since this method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0051] like Figure 3 As shown, in some optional embodiments, the pretreatment of the coiled tubing end includes the following steps:

[0052] S101. The end of the coiled tubing to be connected is beveled to obtain a pipe end with a single-sided blunt V-shaped bevel;

[0053] S102. Grind and remove rust from the pipe end with a single-sided blunt-edged V-shaped bevel to obtain the pipe end of a continuous tubing.

[0054] In this embodiment, by beveling and then grinding to remove rust, a single-sided blunt-edged V-shaped bevel is used to ensure that the pipe end can be stably clamped on a special tooling fixture during subsequent welding, so that stable welding can be performed, thereby forming a weld and obtaining a metal weld with the expected microstructure.

[0055] like Figure 5 As shown, in some optional embodiments, the beveling angle is 30°±5°, and the blunt edge width of the single-sided blunt edge V-shaped bevel is ≤0.5mm.

[0056] In this embodiment, the specific beveling angle and blunt edge width are controlled so that the pipe end can be stably clamped on the special tooling fixture during subsequent welding, enabling stable welding to be performed.

[0057] In some alternative implementations, the depth of the grinding and rust removal is ≤100mm.

[0058] In this embodiment of the application, controlling the specific depth of grinding and rust removal can ensure that impurities at the pipe end are thoroughly removed, while also obtaining a suitable rough surface, so that the solid welding wire can form a stable weld at the joint during the cladding stage.

[0059] In some alternative implementations, the 5G all-position welding includes performing G all-position welding under an argon atmosphere using a double-layer, double-pass welding method combined with a low heat input for the bottom layer.

[0060] In this embodiment of the application, the specific method of controlling 5G all-position welding can be achieved by using double-layer double-pass welding combined with a small heat input for the bottom layer, so that single-sided welding can be formed on both sides. At the same time, the heat input is increased by filling the weld bead, thereby ensuring that the weld can fill the end of the pipe to be welded and obtain a metal weld that meets the expected microstructure.

[0061] In some optional embodiments, the grinding includes weld excess height grinding and longitudinal grinding. The weld excess height grinding is performed by angle grinding, and the longitudinal grinding is performed by abrasive cloth grinding.

[0062] In this embodiment, the specific grinding method can be controlled by using angle grinding to grind the weld horizontally, and then using sandpaper grinding to grind it vertically, thereby making the weld smoother.

[0063] like Figure 4 As shown, in some optional embodiments, the special tooling fixture includes a fixing device 1, a hollow cooling copper ring 2, and a cooling water pipe 3. The pipe end passes through the hollow cooling copper ring 2, and the cooling water pipe 3 is connected to the hollow cooling copper ring 2. The fixing device 1 is located outside the hollow cooling copper ring 2 so that the steel pipe to be welded is in the same straightness through the combined action of the fixing device 1 and the hollow cooling copper ring 2.

[0064] In this embodiment of the application, a specific special tooling fixture is defined, which allows cooling water to circulate through the cooling water pipe 3 in the hollow part of the hollow cooling copper ring 2. The copper ring and cooling water are used to cool the steel pipe, accelerate the cooling speed of the heat-affected zone of the pipe, and avoid the phenomenon of hardness reduction in the heat-affected zone of the pipe.

[0065] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0066] Example 1

[0067] A gas-shielded solid welding wire for continuous tubing butt welding, the chemical composition of the solid welding wire by mass fraction includes: C: 0.1%, Si: 0.27%, Mn: 0.81%, Ni: 0.18%, Cu: 0.45%, Cr: 0.68%, Mo: 0.13%, Nb: 0.024%, Ti: 0.012%, P: 0.006%, and S: 0.004%, with the remainder being Fe and unavoidable impurities.

[0068] like Figure 1 As shown, by volume fraction, the cladding metal microstructure after solid wire welding includes: lath bainite: 90%–95%, acicular ferrite: 5%–10%.

[0069] With CT90 steel grade The specification continuous tubing is a sample.

[0070] like Figure 2 As shown, a welding method for gas-shielded solid wire for butt welding of continuous tubing includes:

[0071] Step 1: Use a steel pipe beveling machine to process a single-sided V-shaped bevel with a blunt edge at the end of the connected continuous tubing. The bevel angle is 30±5° and the blunt edge width is 0.5mm.

[0072] Step 2: Use a hand grinder to remove rust and oil stains within 10mm of the inner and outer walls of the tube to expose the metallic luster. Use a hand angle grinder to grind the oil stains at the bevel to expose the metallic luster.

[0073] Step 3: Pass the connecting pipe to be connected through the hollow cooling copper ring, ensuring that the two pipes are on the same horizontal line, maintain a 1mm gap between the two pipe joints, press the copper ring tightly, and use a fixing device to fix the copper ring and the connecting pipe.

[0074] Step 4, pipe-to-pipe butt welding: Before welding, circulating cooling water is introduced through the cooling water pipe. Solid core welding wire with the above chemical composition and a diameter of 2.0 mm is used. Manual argon arc welding is adopted. The pipe V-shaped bevel is welded once, and double-layer double-pass welding is performed. The shielding gas flow rate is 8L / min, the argon purity is 99.7%, the current for the root pass is 80A, and the welding speed is 20cm / min. The current for the fill and cover passes is 100A, and the welding speed is 15cm / min.

[0075] Step 5: Use an angle grinder to grind the weld seam excess height until it is flush with the pipe body base material. The grinding direction is parallel to the pipe body axis to avoid circumferential grinding marks. After grinding, use 80-grit sandpaper to grind the weld seam smooth along the longitudinal direction of the pipe body. After grinding, visual inspection should show no obvious grinding marks.

[0076] The special tooling fixture includes a fixing device 1, a hollow cooling copper ring 2, and a cooling water pipe 3. The pipe end is inserted into the hollow cooling copper ring 2, and the cooling water pipe 3 is connected to the hollow cooling copper ring 2. The fixing device 1 is located outside the hollow cooling copper ring 2, so that the steel pipe to be welded is in the same straightness through the combined action of the fixing device 1 and the hollow cooling copper ring 2.

[0077] Example 2

[0078] Comparing Example 2 with Example 1, the difference between Example 2 and Example 1 is as follows:

[0079] The chemical composition of the solid welding wire, by mass fraction, includes: C: 0.08%, Si: 0.2%, Mn: 0.7%, Ni: 0.15%, Cu: 0.25%, Cr: 0.5%, Mo: 0.10%, Nb: 0.02%, Ti: 0.01%, P≤0.015% and S≤0.015%, with the remainder being Fe and unavoidable impurities.

[0080] Example 3

[0081] Comparing Example 3 with Example 1, the difference between Example 3 and Example 1 is as follows:

[0082] The chemical composition of the solid welding wire, by mass fraction, includes: C: 0.14%, Si: 0.3%, Mn: 1.0%, Ni: 0.25%, Cu: 0.35%, Cr: 0.7%, Mo: 0.15%, Nb: 0.03%, Ti: 0.02%, P≤0.015% and S≤0.015%, with the remainder being Fe and unavoidable impurities.

[0083] Comparative Example 1

[0084] Comparative Example 1 and Example 1 will be compared. The difference between Comparative Example 1 and Example 1 is as follows:

[0085] Replace the solid wire with ER80S welding wire.

[0086] Relevant experimental and effect data:

[0087] The weld obtained in Example 1 was observed using a metallographic microscope, such as... Figure 1As shown, the microstructure of the cladding metal can be observed to be lath bainite and a small amount of acicular ferrite. The impact and tensile properties were tested according to the standards GB / T 2652-2008 "Tension Test Method for Welds and Deposited Metals" and GB / T 2650-2008 "Impact Test Method for Welded Joints". The results are shown in Table 1.

[0088] Table 1. Performance of the cladding metal from gas-shielded welding wire

[0089] Yield strength (MPa) Tensile strength (MPa) Elongation (%) 0℃ impact energy 628 698 23.5 273,303,297 / 291

[0090] According to SY / T 7495-2020 "Maintenance and Inspection Standard for Coiled Tubing", a special bending fatigue testing machine and tensile testing machine for coiled tubing fatigue testing were used to test the CT90 steel grade of the solid welding wire and ER80S welding wire in this application. Low-cycle fatigue and tensile tests were conducted on the butt welded joints of coiled tubing. The low-cycle fatigue test conditions were a bending radius of 1219 mm and an internal pressure of 35 MPa. The tensile test data are shown in Table 2, and the low-cycle fatigue test data are shown in Table 3.

[0091] Table 2 Tensile Properties of Pipe Fittings

[0092]

[0093] Table 3 Low-cycle fatigue performance of pipe fittings

[0094]

[0095] As shown in Tables 2 and 3, the original pipe had an average tensile strength of 730 MPa and an average low-cycle fatigue failure rate of 372 cycles. The pipe joint welded using the solid welding wire and welding method described in this application had an average tensile strength of 741 MPa and an average low-cycle fatigue failure rate of 305 cycles. Compared to the original pipe joint, the tensile strength did not decrease, and the low-cycle fatigue life was 82% of that of the original pipe. Fatigue fracture occurred in the heat-affected zone. The results are as follows... Figure 6 As shown.

[0096] The pipe joints welded using the welding method of ER80S gas-shielded welding wire and the solid core welding wire of this application had an average tensile strength of 694 MPa and an average low-cycle fatigue failure count of 155 cycles. Compared to the original pipe joint, the tensile strength was significantly reduced, and the low-cycle fatigue life was only 41% of the original pipe. Fatigue fracture occurred in the weld seam. The results are as follows: Figure 7 As shown.

[0097] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0098] (1) The gas-shielded solid welding wire for continuous tubing butt welding provided in this application adopts a low-carbon system, and then adopts the Mn, Ni, Mo, Cr, Cu system, and adds some Ti and Nb trace elements. It comprehensively utilizes solid solution strengthening, fine grain strengthening, precipitation strengthening and other methods to improve strength, and avoids the generation of proeutectoid ferrite. It is beneficial to improve the hardenability of weld metal, promote the formation of bainite, improve the toughness and strength of metal weld, and thus comprehensively improve the fatigue resistance of pipe-to-pipe butt weld joints.

[0099] (2) The welding method of gas-shielded solid wire for butt welding of continuous tubing provided in this application embodiment, through the design of special tooling fixtures, the hollow cooling copper ring 2 can cooperate with the fixing device 1 to fix the butt pipe and maintain the straightness of the pipe opening during use. Each hollow cooling copper ring 2 is connected to the water inlet pipe and the water outlet pipe. Cooling circulating water can be circulated inside the hollow cooling copper ring 2. During the welding process, the cooling circulating water plays the role of cooling the heat-affected zone of the butt pipe, avoiding grain coarsening in the heat-affected zone and a decrease in strength and low-cycle fatigue performance.

[0100] (3) The welding method of gas-shielded solid welding wire for butt welding of coiled tubing provided in this application embodiment, together with special solid welding wire and specially designed tooling fixtures, ensures the strength, high toughness and high and low cycle fatigue performance of the weld joint of the coiled tubing, and can be mainly used for on-site repair welding of coiled tubing in production and use.

[0101] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0102] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0103] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A gas-shielded solid welding wire for butt welding of continuous tubing, characterized in that, The chemical composition of the solid welding wire, by mass fraction, is as follows: C: 0.08%–0.14%, Si: 0.2%–0.3%, Mn: 0.7%–1.0%, Ni: 0.15%–0.25%, Cu: 0.25%–0.35%, Cr: 0.5%–0.7%, Mo: 0.10%–0.15%, Nb: 0.02%–0.03%, Ti: 0.01%–0.02%, with the remainder being Fe and unavoidable impurities; By volume fraction, the cladding metal microstructure after welding with the solid welding wire comprises: lath bainite: 90%–95%, acicular ferrite: 5%–10%.

2. The solid welding wire according to claim 1, characterized in that, The unavoidable impurities, by mass fraction, include: P ≤ 0.015% and S ≤ 0.015%.

3. A welding method for gas-shielded solid wire for butt welding of continuous tubing, characterized in that, The method includes: Pre-treat the ends of the coiled tubing; The end of the continuous tubing is installed on a special tooling fixture and cooling water is introduced. Then, 5G all-position welding is performed using the solid welding wire as described in any one of claims 1-2 to obtain the welded continuous tubing. The butt weld of the coiled tubing is ground to achieve butt welding of the coiled tubing. The special tooling fixture includes a fixing device (1), a hollow cooling copper ring (2), and a cooling water pipe (3). The pipe end is inserted into the hollow cooling copper ring (2), and the cooling water pipe (3) is connected to the hollow cooling copper ring (2). The fixing device (1) is located outside the hollow cooling copper ring (2) so that the steel pipe to be welded is in the same straightness through the combined action of the fixing device (1) and the hollow cooling copper ring (2).

4. The method according to claim 3, characterized in that, The pretreatment of the coiled tubing ends includes the following steps: The end of the coiled tubing to be connected is beveled to obtain a pipe end with a single-sided blunt-edged V-shaped bevel. The pipe end with a single-sided blunt-edged V-shaped bevel is ground and rust-removed to obtain the pipe end of a continuous tubing.

5. The method according to claim 4, characterized in that, The beveling angle is 30°±5°, and the blunt edge width of the single-sided V-shaped beveling with blunt edge is ≤0.5mm.

6. The method according to claim 4, characterized in that, The depth of the grinding and rust removal is ≤100mm.

7. The method according to claim 3, characterized in that, The 5G all-position welding includes 5G all-position welding under argon atmosphere conditions using a double-layer, double-pass welding method combined with a low heat input for the bottom layer.

8. The method according to claim 3, characterized in that, The grinding includes weld seam height repair grinding and longitudinal grinding. The weld seam height repair grinding is performed by angle grinding, and the longitudinal grinding is performed by sandpaper grinding.

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