Processing method for butt welding of CT130 steel-grade coiled tubing

Abstract

The invention belongs to the technical field of coiled tubing machining and manufacturing, and particularly relates to a machining method for butt welding of CT130 steel-grade coiled tubing. A machining method for butt welding of CT130 steel-grade coiled tubing comprises the steps that after dirt, impurities and burrs at the pipe end of the coiled tubing are removed, beveling is conducted; pipe openings in the two ends of the coiled tubing are assembled; performing circumferential weld butt welding on pipe orifices at the two ends of the grouped coiled tubing by adopting an argon tungsten-arc welding method; carrying out heat treatment on the butt-welded weld zone by adopting a self-fluxing welding treatment mode; the surface of the weld joint subjected to heat treatment is ground so that the weld joint can be flush with the coiled tubing end base material; and the ground welding seam and the two sides of the ground welding seam are subjected to rolling diameter reduction, and machining is completed. According to the method, the welding seam is subjected to self-fluxing welding, the welding seam area is subjected to heat treatment through electric arc heat, the strength and plasticity of the butt-welded joint of the CT130 coiled tubing can be effectively improved, and the good low-cycle bending fatigue performance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of coiled tubing processing and manufacturing, and particularly relates to a processing method for butt welding of CT130 steel grade coiled tubing. Background Art

[0002] Coiled tubing operation technology is a new oil and gas field development operation technology that has emerged in recent years. With the development of coiled tubing operation technology and the increasingly harsh operating conditions, ultra-high strength coiled tubing has become the main direction of coiled tubing development. In order to meet the development needs of coiled tubing operation technology, coiled tubing manufacturers have developed CT130 steel grade coiled tubing and applied it on site. During the operation process, the coiled tubing needs to withstand loads such as tension, compression, torsion, repeated bending and low-cycle fatigue, and the pipe body is very prone to deformation, bending, scratches and other damage. In order to ensure the safety of the operation, the damaged pipe section is usually cut off at the oil field site, and then repaired by butt welding.

[0003] However, the existing technology for the butt welding process of CT130 steel grade coiled tubing is still imperfect. SY / T7495-2020 "Maintenance and Inspection of Coiled Tubing" and other relevant technical documents only regulate the butt welding process of CT110 steel grade and below coiled tubing. The yield strength of CT130 coiled tubing is above 896MPa and the tensile strength is above 931MPa. It is an ultra-high strength pipe. With the increase of strength, the weld area is prone to high strength and hardness during butt welding, and plasticity is difficult to ensure. Problems such as this make the welded joint prone to strain concentration when subjected to bending fatigue loads, resulting in a decrease in joint fatigue life and affecting operational safety. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a processing method for CT130 steel grade coiled tubing butt welding, which can effectively improve the strength and plasticity of the CT130 coiled tubing butt welding joint and obtain good low-cycle bending fatigue performance.

[0005] The technical solution of the present invention is: a processing method for butt welding of CT130 steel grade coiled tubing, comprising the following steps: S1: Remove dirt, impurities and burrs from the end of the coiled tubing and then bevel it; S2: Assemble the ends of the coiled tubing; S3: Use tungsten inert gas arc welding to perform girth welding on both ends of the coiled tubing after teaming; S4: heat treating the weld area after the butt welding in step S3 by using an autogenous welding method; S5: Grind the weld surface after heat treatment to make it flush with the parent material of the coiled tubing end; S6: Perform roll compressing and reducing the diameter on the welded seam after grinding in step S5 and its two sides to complete the processing.

[0006] In step S1, the groove is a V-shaped groove with a groove angle of 37° ± 0.5°, and a root face of 1 - 1.5 mm is reserved.

[0007] In step S2, the gap for butt joint of pipe ends is 2.0 - 2.2 mm. The requirement for the straightness of pipe end butt joint is as follows: Use a 300 mm straightedge to select 4 points at intervals of 90° along the circumference of the pipe end for straightness inspection. Keep the straightedge parallel to the axis of one pipe section and close to the pipe body. When the other pipe end fits with the edge of the straightedge and there is no gap observed visually, it is qualified.

[0008] In step S3, for the tungsten inert gas arc welding method, the welding process is divided into backing welding, filling welding, and capping welding. Among them, CHW-90C welding wire is used for backing welding and filling welding, the thickness of the weld bead is controlled within 1 mm, and the heat input is controlled within 9.5 - 10 KJ / cm; JM-120 welding wire is used for capping welding, the weld bead is divided into two layers, the heat input is controlled within 8.5 - 9.5 KJ / cm, and the thickness of the capping weld layer is controlled within 1.2 mm.

[0009] According to the processing method of butt welding of CT130 steel grade coiled tubing described in claim 1, it is characterized in that: In step S4, two layers are welded at the welded seam by self-fusion welding using argon arc welding, and the heat treatment of the welded seam area is carried out by arc heat. The welding current is 55 - 65 A, the welding voltage is 7 - 8 V, and the welding speed is 45 - 55 mm / min.

[0010] In step S6, during the roll compressing and reducing the diameter process, a diameter reducing roll pressing device is used to roll and reduce the diameter of the welded seam and its 20 mm range on both sides, so that the outer diameter of the welded seam and the base metal on both sides of the welded seam is reduced to 0.5 mm lower than the nominal wall thickness.

[0011] The diameter reducing roll pressing device includes a machine body. A vertical guide rail is provided inside the machine body. A roller frame is slidably connected to the guide rail. A first upper roller and a second upper roller are provided at the lower part of the roller frame. A handle is provided at the upper part of the roller frame. The handle passes through the machine body and is rotatably connected to the upper part of the machine body. A lower roller is provided below the inner side of the machine body.

[0012] The rotation axes of the first upper roller, the second upper roller, and the lower roller are arranged in parallel. The lower roller is located below the middle position of the first upper roller and the second upper roller.

[0013] When the diameter reducing roll pressing device is in use, first rotate the handle to adjust the position of the roller frame, so that the first upper roller, the second upper roller, and the lower roller clamp the outer wall of the coiled tubing at the welded seam, and then rotate the diameter reducing roll pressing device around the outer diameter of the pipe until the reduction amount of the outer diameter reaches the design requirement.

[0014] The technical effects of the present invention are as follows: 1. According to the principle of equal-strength matching, the welding wire CHW-90C with a tensile strength close to that of the base material of the coiled tubing is used for backing and filling welding to ensure good strength at the root of the weld; the welding wire JM-120 with a tensile strength close to the yield strength of the pipe body is used for capping welding to ensure the plasticity of the capping weld; 2. By using the self-fusion welding treatment method for the weld, the heat of the arc is used to heat-treat the weld area. After two self-fusion weldings, the weld structure will be significantly refined and the hardness will be significantly reduced, further improving the plasticity of the weld. When the butt welding joint undergoes fatigue bending deformation, good plastic deformation can occur in the weld area, reducing strain concentration and improving the fatigue performance of the welding joint; 3. By means of rolling and reducing the diameter, the outer diameter size of the welding joint area is reduced, the geometric accuracy of the outer diameter of the welding joint is improved, the out-of-roundness is reduced, and at the same time, local deformation strengthening is generated on the outer surface of the welding joint by rolling, and residual compressive stress is formed, further improving the anti-fatigue performance of the welding joint.

[0015] The following will be further described in conjunction with the drawings. Description of the Drawings

[0016] Figure 1 It is a flow chart of a processing method for butt welding of CT130 grade coiled tubing according to an embodiment of the present invention.

[0017] Figure 2 It is a structural schematic diagram of a diameter-reducing rolling device according to an embodiment of the present invention.

[0018] Reference numerals: 1 - fuselage; 2 - roller frame; 3 - handle; 4 - first upper roller; 5 - second upper roller; 6 - lower roller; 7 - guide rail. Detailed Embodiment Embodiment 1

[0019] As Figure 1 shown, a processing method for butt welding of CT130 grade coiled tubing includes the following steps: S1: Remove dirt, impurities and burrs at the ends of the coiled tubing and then bevel the ends; S2: Assemble the two ends of the coiled tubing; S3: Use the tungsten inert gas arc welding method to perform circumferential weld butt welding on the two ends of the assembled coiled tubing; S4: Use the self-fusion welding treatment method to heat-treat the weld area after the butt welding in step S3; S5: Grind the surface of the weld after heat treatment to make it flush with the base material at the ends of the coiled tubing; S6: Perform rolling and diameter reduction on the weld and its two sides after grinding in step S5 to complete the processing.

[0020] In step S1, the groove is a V-shaped groove, the groove angle is 37°±0.5°, and a blunt edge of 1-1.5 mm is retained.

[0021] In step S2, the gap between the pipe ends is 2.0-2.2 mm, and the straightness requirement of the pipe ends is as follows: a 300 mm ruler is used to select 4 points at 90° intervals along the circumference of the pipe ends for straightness inspection, and the ruler is parallel to the axis of the pipe section at one end and close to the pipe body. When the other end of the pipe ends fits the edge of the ruler and there is no gap visually observed, it is qualified.

[0022] The tungsten inert gas welding method described in step S3 has a welding process divided into base welding, filling welding and cover welding, wherein the base welding and filling welding are welded with CHW-90C welding wire, the weld thickness is controlled within 1mm, and the heat input is controlled within 9.5~10KJ / cm; the cover weld is welded with JM-120 welding wire, the weld is divided into two passes, the heat input is controlled within 8.5~9.5KJ / cm, and the thickness of the cover weld layer is controlled within 1.2mm.

[0023] In step S4, two layers are welded at the weld by argon arc welding in a self-melting welding manner, and the weld area is heat treated by arc heat, with a welding current of 55-65A, a welding voltage of 7-8V, and a welding speed of 45-55mm / min.

[0024] In the rolling and reducing diameter process in step S6, a reducing rolling device is used to roll and reduce the diameter of the weld and the 20 mm range on both sides of the weld, so that the outer diameter of the weld and the parent material on both sides of the weld is reduced to less than the nominal wall thickness of 0.5 mm.

[0025] According to the principle of equal strength matching, the present invention adopts the welding wire CHW-90C, whose tensile strength is close to that of the coiled tubing parent material, and the tensile strength of the welding wire cladding metal is 896MPa, to perform base and filling welding to ensure good strength of the weld root; adopts the welding wire JM-120, whose tensile strength is close to the yield strength of the pipe body, and the tensile strength of the welding wire cladding metal is 830MPa, to perform cover welding to ensure the plasticity of the cover weld. At the same time, by adopting the self-melting welding treatment method for the weld, the weld area is heat-treated by arc heat. It is verified by experiments that after two self-melting weldings, the weld structure will be significantly refined, and the hardness will be significantly reduced, further improving the plasticity of the weld. As a result, when the butt weld joint is subjected to fatigue bending deformation, the weld area can produce good plastic deformation, reduce strain concentration, and improve the fatigue performance of the weld joint. By rolling the compression diameter, the outer diameter of the weld joint area is reduced, the geometric accuracy of the outer diameter of the weld joint is improved, and the out-of-roundness is reduced. At the same time, local deformation strengthening is produced on the outer surface of the weld joint through rolling, and residual compressive stress is formed, which further improves the fatigue resistance of the weld joint.

[0026] likeFigure 2 As shown in the figure, the described diameter-reducing rolling device includes a fuselage 1. Inside the fuselage 1, there is a vertical guide rail 7. A roller frame 2 is slidably connected to the guide rail 7. At the lower part of the roller frame 2, there are a first upper roller 4 and a second upper roller 5. At the upper part of the roller frame 2, there is a handle 3. The handle 3 passes through the fuselage 1 and is rotatably connected to the upper part of the fuselage 1. Below the inside of the fuselage 1, there is a lower roller 6.

[0027] The rotation axes of the first upper roller 4, the second upper roller 5 and the lower roller 6 are arranged in parallel. The lower roller 6 is located below the middle position between the first upper roller 4 and the second upper roller 5.

[0028] When the diameter-reducing rolling device is in use, first rotate the handle 3 to adjust the position of the roller frame 2, so that the first upper roller 4, the second upper roller 5 and the lower roller 6 clamp the outer wall weld of the coiled tubing. Then rotate the diameter-reducing rolling device around the outer diameter of the pipe until the reduction amount of the outer diameter reaches the design requirements.

[0029] By means of rolling and diameter reduction, the outer diameter size of the welded joint area is reduced, the geometric accuracy of the outer diameter of the welded joint is improved, the out-of-roundness is reduced. At the same time, local deformation strengthening is generated on the outer surface of the welded joint through rolling, and residual compressive stress is formed, further improving the anti-fatigue performance of the welded joint. Embodiment 2

[0030] Adopt a processing method for butt welding of CT130 grade coiled tubing as described in Embodiment 1. Taking the butt welding of CT130 grade φ50.8×4.8mm coiled tubing as an example, the specific steps include: S1. After removing dirt, impurities and burrs at the ends of the coiled tubing, bevel the ends. S2. Assemble the two ends of the coiled tubing. S3. Perform butt welding on the two ends of the coiled tubing. Tungsten inert gas welding is used. The welding process is divided into root pass, filling and capping welding. Among them, the root pass and filling welding are carried out using CHW-90C welding wire, the weld bead thickness is controlled within 1mm, and the heat input is controlled within 9.5 KJ / cm. The capping weld bead is welded using JM-120 welding wire. The weld bead is divided into two layers, and the heat input is controlled within 9 KJ / cm. In total, 4 layers and 5 passes are welded this time, including 1 layer of capping root pass, 2 layers of filling welds, and 1 layer of capping weld in two layers. S4. Weld two layers at the weld area by self-fusion using argon arc welding, with a welding current of 65A, a welding voltage of 7V, and a welding speed of 50mm / min. S5. Grind the weld surface to make it flush with the base metal. S6. Use a rolling device to perform rolling and diameter reduction on the weld and its two sides for 20mm, so that the outer diameters of the weld and the base metal on both sides of the weld are reduced to 0.5mm lower than the nominal wall thickness.

[0031] It can be seen from Table 1 that for the welded joints of the CT130 coiled tubing butt welding processed by the processing method of the present invention, the results show that good effects are obtained in terms of tensile strength, hardness, plasticity and fatigue times. The test results are all better than the standard requirements, improving the operation safety of the coiled tubing.

[0032] Table 1 Performance of the butt welded joint of CT130 grade φ50.8×4.8mm coiled tubing

[0033] As mentioned above, the above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A processing method for butt welding of CT130 grade coiled tubing, characterized in that: It includes the following steps: S1: Remove dirt, impurities and burrs at the ends of the coiled tubing and then bevel the ends; S2: Assemble the two ends of the coiled tubing; S3: Use the tungsten inert gas welding method to perform circumferential weld butt welding on the two ends of the assembled coiled tubing; S4: Use the self-fusion welding treatment method to perform heat treatment on the weld area after butt welding in step S3; S5: Grind the surface of the weld after heat treatment to make it flush with the base metal at the ends of the coiled tubing; S6: Perform rolling and reducing the diameter on the weld and its two sides after grinding in step S5 to complete the processing.

2. The processing method for butt welding of CT130 grade coiled tubing according to claim 1, characterized in that: The bevel in step S1 is a V-shaped bevel, the bevel angle is 37°±0.5°, and a root face of 1~1.5 mm is reserved.

3. The processing method for butt welding of CT130 grade coiled tubing according to claim 1, characterized in that: The gap for assembling the pipe ends in step S2 is 2.0~2.2 mm, and the flatness requirement for assembling the pipe ends is: Use a 300 mm straightedge to select 4 points at intervals of 90° along the circumference of the pipe end for flatness inspection. Keep the straightedge parallel to the axis of one end pipe section and close to the pipe body. When the other end pipe orifice fits with the edge of the straightedge and there is no gap visually observed, it is qualified.

4. The processing method for butt welding of CT130 grade coiled tubing according to claim 1, characterized in that: In the tungsten inert gas welding method in step S3, the welding process is divided into backing, filling and capping welding. Among them, CHW-90C welding wire is used for backing and filling welding, the weld bead thickness is controlled within 1 mm, and the heat input is controlled at 9.5~10 KJ / cm; The capping weld bead is welded with JM-120 welding wire, the weld bead is divided into two layers, the heat input is controlled within 8.5~9.5 KJ / cm, and the capping weld layer thickness is controlled within 1.2 mm.

5. The processing method for butt welding of CT130 grade coiled tubing according to claim 1, characterized in that: In step S4, two layers are welded at the weld area by self-fusion welding using argon arc welding, and the weld area is heat-treated using the arc heat. The welding current is 55~65 A, the welding voltage is 7~8 V, and the welding speed is 45~55 mm / min.

6. The processing method for butt welding of CT130 grade coiled tubing according to claim 1, characterized in that: In step S6, during the rolling and reducing the diameter process, a reducing rolling device is used to roll and reduce the diameter of the weld and its 20 mm range on both sides, so that the outer diameter of the weld and the base metal on both sides of the weld is reduced to 0.5 mm lower than the nominal wall thickness.

7. The processing method for butt welding of CT130 grade coiled tubing according to claim 6, characterized in that: The described diameter-reducing rolling device includes a fuselage (1). Inside the fuselage (1), there is a vertical guide rail (7). A roller frame (2) is slidably connected to the guide rail (7). Below the roller frame (2), there are a first upper roller (4) and a second upper roller (5). Above the roller frame (2), there is a handle (3). The handle (3) passes through the fuselage (1) and is rotatably connected to the upper part of the fuselage (1). Below the inside of the fuselage (1), there is a lower roller (6).

8. The processing method for butt welding of CT130 grade coiled tubing according to claim 7, characterized in that: the rotation axes of the first upper roller (4), the second upper roller (5) and the lower roller (6) are arranged in parallel, and the lower roller (6) is located below the middle position between the first upper roller (4) and the second upper roller (5).

9. The processing method for butt welding of CT130 grade coiled tubing according to claim 6, characterized in that: when the diameter-reducing rolling device is in use, first rotate the handle (3) to adjust the position of the roller frame (2) so that the first upper roller (4), the second upper roller (5) and the lower roller (6) clamp the outer wall weld of the coiled tubing, and then rotate the diameter-reducing rolling device around the outer diameter of the pipe until the outer diameter reduction reaches the design requirements.

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