A method for manufacturing high-frequency straight seam welded pipes for dense-phase / supercritical CO2 transport and a high-frequency straight seam welded pipe prepared by the method.

Abstract

This invention belongs to the field of steel pipe manufacturing technology, specifically relating to a method for manufacturing high-frequency straight seam welded pipes for dense-phase / supercritical CO2 transportation and the high-frequency straight seam welded pipes prepared using this method. It aims to solve the problem of the lack of stable and safe CO2 transportation pipelines suitable for long-distance, high-capacity dense-phase / supercritical CO2 transportation in existing technologies. The invention includes: pipe rolling, using an FFX rolling mill to roll milled steel strips into pipe blanks; high-frequency welding, performing high-frequency welding on the weld points of the pipe blanks using a double-electrode elastic floating contact welding process; and heat treatment. This invention can overcome the low-temperature crack initiation and crack arrest toughness defects in the application of high-frequency welded pipes for dense-phase / supercritical CO2 transportation.

Description

Technical Field

[0001] This invention belongs to the field of steel pipe manufacturing technology, specifically relating to a method for manufacturing high-frequency straight seam welded pipes for dense phase / supercritical CO2 transportation and the high-frequency straight seam welded pipes prepared using this method. Background Technology

[0002] With industrialization and urbanization, human activities have had an increasingly significant impact on the atmospheric environment, making greenhouse gas emissions a global concern, with CO2 showing the fastest growth. According to relevant reports, China's cumulative CO2 emissions are projected to reach 400 billion tons by 2060, making China the world's largest CO2 emitter. Under the national "dual carbon" goals and pathways, CO2 transport is a crucial link in the industrialization and commercial application of carbon dioxide capture, utilization, and storage (CCUS).

[0003] To achieve the goal of carbon neutrality by 2060, CCUS (carbon dioxide capture, utilization and storage) technology will be increasingly valued. Pipeline transportation is a key link in the implementation of this technology to meet the needs of long-distance and large-volume CO2 transportation.

[0004] Currently, the main methods of CO2 transportation include tank truck transportation, ship transportation, and pipeline transportation. Among them, pipeline transportation is the most cost-effective way to transport CO2 over long distances, with its cost being about 35% of that of tank truck transportation.

[0005] When CO2 is in a supercritical or dense phase, it has the density of a liquid, the viscosity and compressibility of a gas, making it most efficient for pipeline transportation.

[0006] For long-distance pipeline transportation of CO2, dense phase / supercritical transport is often used. This is because dense phase / supercritical CO2 has the characteristics of low viscosity and high density, resulting in low friction and low energy consumption during pipeline transportation, thus achieving higher economy and larger-scale transportation capacity.

[0007] Currently, long-distance dense-phase / supercritical CO2 pipelines are still in their initial stage. Most of the CO2 pipelines that have been built use gas-phase or liquid-phase transportation, mainly for oil fields to use their own generated CO2 for oil displacement. These pipelines are relatively short and cannot be adapted to the phase changes of long-distance dense-phase / supercritical CO2 transportation. Summary of the Invention

[0008] To address the lack of stable and safe CO2 transportation pipelines suitable for long-distance, high-capacity dense-phase / supercritical CO2 transportation in existing technologies, this invention provides a method for manufacturing high-frequency straight seam welded pipes for dense-phase / supercritical CO2 transportation and the high-frequency straight seam welded pipes prepared using this method.

[0009] The technical solution of the present invention includes:

[0010] A method for manufacturing high-frequency straight seam welded pipes for dense-phase / supercritical CO2 transport, characterized by comprising the following steps:

[0011] (1) Loading milling plate, cutting and blanking high-grade thick-walled steel strips according to the set dimensions, wherein the chemical composition of the steel strip is C≤0.07%, Mn≤1.40%, carbon equivalent≤0.60%, and the balance is iron;

[0012] (2) Pipe rolling: The sheared steel strip is rolled into a tube blank using an FFX rolling mill;

[0013] (3) High-frequency welding: The welding points of the tube blank are subjected to high-frequency welding using a double-electrode elastic floating contact welding process.

[0014] (4) Heat treatment: The pipe body after welding is subjected to heat treatment. The heat treatment temperature is controlled at 980℃~1100℃ and the cooling rate is controlled at 5~10℃ / s.

[0015] As an alternative technical solution, in step (2), during the rough forming stage, by adjusting the roll parameters of the rough forming stand of the FFX mill, and utilizing the characteristics of the involute of the rolls, a bending moment is applied to the outermost edge of the strip, changing the edge to a small-scale reverse curve, and the overall steel strip becomes "W" shaped.

[0016] As an alternative technical solution, adjusting the roll parameters of the roughing stand of the FFX rolling mill includes increasing the downward pressure of the upper roll in the edge bending roll and correspondingly expanding the spacing of the side rolls to increase the bending forming amount of the strip edge portion during strip winding.

[0017] As an alternative technical solution, adjusting the roll parameters of the roughing stand of the FFX mill also includes reducing the amount of roll wrapping and forming, thereby reducing the elongation of the steel strip edge in the length direction.

[0018] As an optional technical solution, in step (2), during the precision forming stage, the diameter reduction of the precision forming frame is increased, and the width of the working plate after milling is increased, so that the edge has a local thickening effect, and the elongation of the material end face in all directions of the circumference is balanced.

[0019] As an alternative technical solution, the diameter reduction of the precision forming frame is increased by 0.3%.

[0020] As an optional technical solution, in step (3), the dual-electrode elastic floating contact welding includes two electrodes arranged in parallel, each electrode is compressed with a spring, and a fixing device that can move to compress and lock the spring compression amount is provided at the rear end of the spring. The pressure applied to the electrode welding foot is adjusted by adjusting the spring compression amount.

[0021] As an alternative technical solution, the dual electrodes are positioned across both sides of the weld seam to be welded.

[0022] As an alternative technical solution, in step (3), the overall input power during high-frequency welding is increased to more than 115% of the standard heat input power.

[0023] Adjust the speed of each drive motor to minimize the need for the strip to be pushed into shape.

[0024] The drive motor uses a smaller torque, while the torque of the pull-out frame and sizing frame is appropriately increased to allow the strip to bear a certain tension and improve the strip's resistance to edge waves.

[0025] A high-frequency straight seam welded pipe, characterized in that: the high-frequency straight seam welded pipe is prepared by the processing method described in claim 1.

[0026] The beneficial effects of this invention are:

[0027] (1) By adjusting the technical parameters of different rolling rolls in the roughing and finishing processes of the FFX mill, this invention can reasonably control the changes in yield and tensile strength of the coil during the forming process, and effectively solve the performance stability and safety problems of long-distance, high-capacity CO2 conveying pipelines.

[0028] (2) When the high-frequency straight seam welded pipe of the present invention is welded at high frequency, a double-electrode elastic floating contact welding method is adopted, which improves the range of welding power and welding speed, ensures the stability of welding output power, and reduces production costs.

[0029] (3) When the high-frequency straight seam welded pipe of the present invention is welded at high frequency, the welding status can be monitored by high-speed camera, and the welding heat output, welding speed, extrusion amount and other parameters can be precisely controlled to ensure that the welding is in the best state, reduce the generation of welding defects, and improve the low temperature toughness of the weld.

[0030] In summary, the manufacturing method of high-strength, thick-walled, high-frequency straight seam welded pipe of the present invention can overcome the low-temperature crack initiation and crack arrest toughness defects in the application of high-frequency welded pipes for dense phase / supercritical CO2 transportation. Attached Figure Description

[0031] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0032] Figure 1 This is a schematic diagram of the dual-electrode structure of the elastic floating contact welding of the present invention.

[0033] Figure 2 This is a schematic diagram illustrating the working principle of the FFX mill rough forming plate edge bending roll of the present invention.

[0034] Figure 3(a) is a schematic diagram of the existing working principle of the roughing stand rolls of the FFX rolling mill.

[0035] Figure 3(b) is a schematic diagram of the working principle of the roughing stand rolls of the FFX mill of the present invention.

[0036] Figure 4 This is a schematic diagram of three welding states in high-frequency welding.

[0037] Figure 5 This is a schematic diagram of the welding state under different combined input power for high-frequency welding.

[0038] Figure 6 This is a metallographic diagram of the HFW steel pipe body in Embodiment 2 of the present invention.

[0039] Figure 7 This is a metallographic diagram of the weld seam of the HFW steel pipe in Embodiment 2 of the present invention.

[0040] Figure 8 This is a diagram showing the distribution of transverse yield strength of the HFW steel pipe body according to an embodiment of the present invention.

[0041] Figure 9 This is a distribution diagram of the transverse tensile strength of the HFW steel pipe body in Embodiment 2 of the present invention.

[0042] Figure 10 This is a tensile strength distribution diagram of the HFW steel pipe weld seam in Embodiment 2 of the present invention.

[0043] Figure 11 This is a scatter plot of the impact energy of the HFW steel pipe weld in Embodiment 2 of the present invention.

[0044] Figure 12 This is the transverse Charpy impact ductile-brittle transition curve of the HFW steel pipe body in Embodiment 2 of the present invention.

[0045] Figure 13 This is the Charpy impact ductile-brittle transition curve of the HFW steel pipe weld in Embodiment 2 of the present invention.

[0046] Figure 14 This is a production process diagram of the method for manufacturing high-frequency straight seam welded pipes for dense phase / supercritical CO2 transportation according to the present invention.

[0047] Figure label:

[0048] 1-Welding electrode, 2-Welding electrode, 3-Spring, 4-Fixing device, 5-Upper roller, 6-Side roller. Detailed Implementation

[0049] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0050] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] This invention provides a method for manufacturing a high-frequency straight seam welded pipe for dense phase / supercritical CO2 transport and a high-frequency straight seam welded pipe prepared by the method.

[0052] like Figure 14 The diagram shown is a production process diagram of the high-frequency straight seam welded pipe manufacturing method for dense phase / supercritical CO2 transportation according to the present invention.

[0053] This includes uncoiling and leveling, shearing and welding, looping, milling, forming, high-frequency welding, online flaw detection, medium-frequency heat treatment, air / water cooling, sizing and straightening, online marking, pipe cutting to length, mechanical end finishing, hydrostatic testing, ultrasonic weld flaw detection, pipe end flaw detection, finished product inspection and warehousing, and marking and delivery.

[0054] like Figure 1 The diagram shows a schematic of the dual-electrode structure of the elastic floating contact welding of the present invention.

[0055] It includes electrodes 1 and 2 arranged side by side, with springs 3 fitted on each of electrodes 1 and 2. The front end of the spring 3 is connected to the electrode, and the rear end is connected to the fixing device 4. The fixing device 4 can move along the electrode rod and be fastened. By compressing the spring 3, a set welding pressure is applied to electrodes 1 and 2 respectively.

[0056] This invention relates to a novel dual-electrode high-frequency contact welding device that employs a dual-spring floating mechanism, replacing the conventional single-electrode pneumatic system. This allows for two welding feet, inner and outer, on each side of the plate edge during welding. The contact between the welding feet and the plate edge is primarily controlled by springs on the welding foot support side. By setting the length of the compression springs, the required pressure between the welding foot electrode and the steel pipe surface can be precisely obtained. Based on the characteristic curve of spring length versus welding foot pressure, and combined with the actual working conditions on site, the optimal compression of the inner and outer springs is set. This effectively ensures safe operation under conditions of plate edge fluctuation before and after welding, while reducing arcing and short circuits caused by poor contact in a single electrode, thereby improving the stability of the equipment during continuous on-site operation.

[0057] like Figure 2 The diagram shown illustrates the working principle of the FFX mill rough forming plate edge bending roll of this invention.

[0058] By increasing the downward pressure of the upper roller 5 and increasing the lateral displacement of the two side rollers 6, the bending and forming amount of the strip edge portion during steel strip winding is increased.

[0059] Press down the upper roller of the edge bending machine and correspondingly widen the gap between the side rollers to increase the bending amount of the W structure of the material. By increasing the W bending amount, the elongation of the central part of the strip at the exit of the bending machine increases, allowing the edge of the strip to withstand a certain amount of compressive deformation, thereby improving the edge resistance of the strip.

[0060] Figure 3(a) shows a schematic diagram of the existing working principle of the vertical roll side roll of the roughing stand of the FFX rolling mill. The existing rolls have a large amount of roll forming during rolling, resulting in a heavy rolling burden.

[0061] Figure 3(b) shows a schematic diagram of the working principle of the FFX mill roughing stand rolls of the present invention. The present invention reduces the amount of roll forming, thereby reducing the elongation in the length direction of the strip edge caused by roll forming deformation.

[0062] like Figure 4 The diagram shows three welding states in high-frequency welding, including Class 1 welding, Class 2 welding, and Class 2′ welding.

[0063] To improve weld toughness, high-frequency welded steel pipes must ensure sufficient oxide removal from the plate edges while they are in a molten state. The welding condition of high-frequency welded steel pipes can reflect the on-site forming and welding situation in real time. A good welding condition ensures effective removal of oxide inclusions from the weld. The welding condition is determined by a combination of factors, including electrical power input, welding speed, plate wall thickness, opening angle, extrusion amount, and others. Currently, there are three main welding conditions: Class 1, Class 2, and Class 3. In actual production, Class 2 welding is primarily used.

[0064] This invention has discovered a novel 2′ type welding state. Due to its relatively high welding speed, wide range of electrical input power, and welding advantages, the 2′ type can effectively improve the removal of oxide inclusions in the weld and reduce the defect rate in the weld.

[0065] By debugging production process parameters on-site and using high-speed cameras to collect images during the welding process, the principles behind the generation of Class 2 and Class 2′ welding states were understood.

[0066] like Figure 5 The diagram shows the welding state under different combined input powers in high-frequency welding.

[0067] 1) As the overall input power increases, the V0 crosspoint, marked in red, moves upstream of the weld (red dashed line);

[0068] 2) At SPLmax (standard heat input power), it is generally defined as a Class 1 welding condition;

[0069] 3) Under the power of SPLmax(1+5%), the welding point W moves downstream, and the approach speed of the strip edge is close to the electromagnetic repulsion speed of the molten steel point, forming a certain point gap, which is a type 2 welding state.

[0070] 4) At SPLmax(1+10%) power, V1 is clearly separated from V0 and W point, the molten region is lengthened, the electromagnetic force gradually disappears, resulting in abnormal oxide removal and a tendency for defects to increase, corresponding to the transition state.

[0071] 5) At SPLmax(1+15%) and higher power, points V0 and V1 are completely separated. The gap before the weld point remains stable, and a double V-shaped region appears, which is a type 2′ weld.

[0072] Example

[0073] Example 1:

[0074] The forming welding and heat treatment processes used in this embodiment are shown in the table below:

[0075] Table 1 Process Parameters

[0076] Example 2:

[0077] The forming welding and heat treatment processes used in this embodiment are shown in the table below:

[0078] Table 2 Process Parameters

[0079] like Figure 6 The image shown is a metallographic diagram of the HFW steel pipe body according to Embodiment 2 of the present invention.

[0080] like Figure 7 The image shown is a metallographic diagram of the weld seam of the HFW steel pipe in Embodiment 2 of the present invention.

[0081] like Figure 8 The figure shown is a distribution diagram of the transverse yield strength of the HFW steel pipe body according to an embodiment of the present invention.

[0082] like Figure 9 The figure shown is a distribution diagram of the transverse tensile strength of the HFW steel pipe body in Embodiment 2 of the present invention.

[0083] like Figure 10 The figure shown is a distribution diagram of the tensile strength of the weld seam of the HFW steel pipe in Embodiment 2 of the present invention.

[0084] like Figure 11 The figure shown is a scatter plot of the impact energy of the weld seam of the HFW steel pipe in Embodiment 2 of the present invention.

[0085] like Figure 12 The figure shows the transverse Charpy impact ductile-brittle transition curve of the HFW steel pipe body in Embodiment 2 of the present invention.

[0086] like Figure 13 The figure shows the Charpy impact ductile-brittle transition curve of the HFW steel pipe weld in Embodiment 2 of the present invention.

[0087] In the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0088] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0089] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0090] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a high-frequency straight seam welded pipe for dense phase / supercritical CO2 transport, characterized in that, Includes the following steps: (1) Milling plate for feeding: Mill the high-grade thick-walled steel strip according to the set dimensions. The chemical composition of the steel strip is C≤0.07%, Mn≤1.40%, carbon equivalent≤0.60%, and the balance is iron. (2) Tube rolling: The milled steel strip is rolled into a tube blank using an FFX rolling mill; (3) High-frequency welding: The welding points of the tube blank are subjected to high-frequency welding using a double-electrode elastic floating contact welding process. (4) Heat treatment: The welded pipe seam is heat treated. The heat treatment temperature is controlled at 980℃~1100℃ and the cooling rate is controlled at 5~10℃ / s.

2. The method for manufacturing high-frequency straight seam welded pipe for dense phase / supercritical CO2 transportation as described in claim 1, characterized in that: In step (2), during the rough forming stage, by adjusting the roll parameters of the rough forming stand of the FFX mill, and utilizing the characteristics of the involute of the rolls, a bending moment is applied to the outermost edge of the strip, changing the edge to a small-scale reverse curve, and the overall strip becomes "W" shaped.

3. The method for manufacturing high-frequency straight seam welded pipe for dense phase / supercritical CO2 transportation as described in claim 2, characterized in that: The adjustment of the roll parameters of the roughing stand of the FFX mill includes increasing the downward pressure of the upper roll in the edge bending roll and correspondingly expanding the spacing of the side rolls to increase the bending forming amount of the strip edge portion during strip winding.

4. The method for manufacturing high-frequency straight seam welded pipe for dense phase / supercritical CO2 transportation as described in claim 3, characterized in that: The adjustment of the roll parameters of the roughing stand of the FFX mill also includes reducing the amount of roll wrapping and reducing the elongation of the steel strip edge in the length direction.

5. The method for manufacturing high-frequency straight seam welded pipe for dense phase / supercritical CO2 transportation as described in claim 1, characterized in that: In step (2), during the precision forming stage, the diameter reduction of the precision forming frame is increased, and the width of the working plate after milling is increased, so that the edge has a local thickening effect and the elongation of the material end face in all directions of the circumference is balanced.

6. The method for manufacturing a high-frequency straight seam welded pipe for dense phase / supercritical CO2 transport as described in claim 5, characterized in that: The diameter reduction of the precision forming frame is increased by 0.3%.

7. The method for manufacturing high-frequency straight seam welded pipe for dense phase / supercritical CO2 transportation as described in claim 1, characterized in that: In step (3), the dual-electrode elastic floating contact welding includes two electrodes arranged in parallel. Each of the two electrodes is compressed with a spring, and a fixing device that can move to compress and lock the spring compression amount is provided at the rear end of the spring. The pressure applied to the electrode welding foot is adjusted by adjusting the spring compression amount.

8. The method for manufacturing a high-frequency straight seam welded pipe for dense-phase / supercritical CO2 transport as described in claim 7, characterized in that: The dual electrodes are positioned across both sides of the weld seam to be welded.

9. The method for manufacturing a high-frequency straight seam welded pipe for dense phase / supercritical CO2 transport as described in claim 1, characterized in that: In step (3), the overall input power during high-frequency welding is increased to more than 115% of the standard heat input power.

10. A high-frequency straight seam welded pipe, characterized in that: The high-frequency straight seam welded pipe is manufactured using the processing method described in claim 1.

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