Method for predicting roundness of steel pipe, method for controlling roundness of steel pipe, method for manufacturing steel pipe, method for generating model for predicting roundness of steel pipe, and device for predicting roundness of steel pipe

Abstract

The roundness prediction method for steel pipes involved in this invention includes the following steps: using a roundness prediction model obtained by learning through machine learning to predict the roundness of the steel pipe after the pipe expansion process. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more parameters selected from the operation parameters of the bending process, and one or more parameters selected from the operation parameters of the joint gap reduction process as input data, and the roundness information of the steel pipe after the pipe expansion process as output data.

Description

Technical Field

[0001] This invention relates to a method for predicting the roundness of steel pipes after the pipe expansion process in the manufacturing process of steel pipes using the bending method, a method for controlling the roundness of steel pipes, a manufacturing method for steel pipes, a method for generating a roundness prediction model for steel pipes, and a device for predicting the roundness of steel pipes. Background Technology

[0002] The manufacturing technology for large-diameter, thick-walled steel pipes used in pipelines and other applications has become widespread. The following manufacturing technology (so-called UOE steel pipe) is commonly used: Steel plates of specified length, width, and thickness are stamped into a U-shape, then stamped into an O-shape and welded together to form a pipe. The diameter is further increased (so-called pipe expansion) to improve roundness. However, the UOE steel pipe manufacturing process requires significant stamping pressure in the stamping of the steel plate into U- and O-shapes, necessitating the use of large-scale stamping machines.

[0003] To address this, a technique has been proposed to reduce stamping pressure during the manufacturing of steel pipes with large diameters and thick walls. Specifically, the following technique has been implemented: After bending the ends of a steel plate in the width direction (so-called end bending), a U-shaped cross-section is formed by multiple three-point bending stamping processes using a punch (hereinafter, sometimes referred to as a U-shaped forming body). Further, a joint gap reduction process is performed to reduce the joint gap of the U-shaped forming body, forming an open pipe. The butt joints are then welded to form a steel pipe. Finally, a pipe expander is inserted into the steel pipe to enlarge its inner diameter. Furthermore, the pipe expander uses a device comprising multiple pipe expander tools having curved surfaces obtained by dividing an arc into multiple parts. By bringing the curved surfaces of the expander tools into contact with the inner surface of the steel pipe, the steel pipe is expanded and its shape is adjusted.

[0004] In the bending process, increasing the number of three-point bending presses improves the roundness of the steel pipe after the expansion process, but it requires a longer time to form the pipe into a U-shaped cross-section. On the other hand, reducing the number of three-point bending presses results in a cross-sectional shape that is close to a polygon, making it difficult to achieve a perfect circle. Therefore, the number of three-point bending presses is determined empirically based on the pipe's dimensions (e.g., 5 to 13 times for a 1200mm diameter pipe). Many solutions have been proposed for setting the operating conditions of this bending process used to improve the roundness of the expanded steel pipe.

[0005] For example, Patent Document 1 describes a method for performing three-point bending stamping with as few times as possible, wherein multiple tube expanding tools arranged in the circumferential direction of the tube expanding device abut against an undeformed portion that has not been deformed by the three-point bending stamping to expand the tube.

[0006] In addition, Patent Document 2 describes a method in which the roundness of the steel pipe after the pipe expansion process is improved by making the radius of curvature of the outer circumferential surface of the punch used in the three-point bending stamping and the radius of curvature of the outer circumferential surface of the pipe expanding tool satisfy a specified relationship.

[0007] Furthermore, Patent Document 3 describes a method for efficiently manufacturing steel pipes with high roundness without requiring excessive pressing pressure during the bending process. The method involves providing a lightly processed section with minimal curvature compared to other areas, or an unprocessed section where bending is omitted, in at least a portion of the steel plate during three-point bending stamping. Additionally, Patent Document 3 describes that in the joint gap reduction process, the lightly processed or unprocessed sections are not constrained; instead, pressing pressure is applied to a portion separated from the center of the lightly processed or unprocessed section by a predetermined distance. Furthermore, an O-ring stamping device is typically used in the joint gap reduction process, which is usually performed after the bending process.

[0008] In contrast, Patent Document 4 describes a method (hereinafter referred to as the "closed-loop stamping method") whereby, after forming a non-circular preform (a U-shaped cross-section) by three-point bending stamping, instead of the usual O-ring stamping process, the non-circular preform is supported by two lower support rollers, and a pressing tool positioned above the preform, opposite to the lower support rollers, applies a pressing force from the outside of the non-circular preform, thereby reducing the seam gap. This method is characterized by simplifying the device structure by applying the pressing force from the outside of the non-circular preform using the pressing tool, eliminating the need for a mold based on the outer diameter of the steel pipe, as is required with O-ring stamping devices. Furthermore, Patent Document 4 describes a method where, in three-point bending stamping, a portion of the preform is intentionally given relatively less forming, and in the closed-loop stamping method used in the seam gap reduction process, a pressing force is applied to this region of the U-shaped cross-section preform.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2012-170977

[0012] Patent Document 2: Japanese Patent No. 5541432

[0013] Patent Document 3: Japanese Patent No. 6015997

[0014] Patent Document 4: Japanese Patent Application Publication No. 2012-250285 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] The method described in Patent Document 1 involves aligning the pressing position of the three-point bending stamping with the pressing position of the tube expanding tool, thereby improving the roundness of the steel pipe after the tube expanding process. However, the manufacturing process of the steel pipe includes at least several steps: bending, reducing the joint gap, welding, and tube expanding. Therefore, the method described in Patent Document 1 does not consider the influence of the operating conditions in other processes on the roundness of the steel pipe after the tube expanding process, and thus may not always be able to improve the roundness of the steel pipe after the tube expanding process.

[0017] The method described in Patent Document 2, like that described in Patent Document 1, improves the roundness of the steel pipe after the pipe-expanding process by ensuring that the radius of curvature of the outer circumferential surface of the punch used in the three-point bending stamping (an operating condition of the bending process) satisfies a prescribed relationship with the radius of curvature of the outer circumferential surface of the pipe-expanding tool (an operating condition of the pipe-expanding process). However, like the method described in Patent Document 1, the method in Patent Document 2 fails to account for the influence of processes other than the bending process, such as the process of reducing the joint gap.

[0018] The method described in Patent Document 3 improves the roundness of the steel pipe after the expansion process by changing the processing conditions of the three-point bending stamping in the bending process according to the position of the steel plate and setting them to conditions related to the forming conditions in the process of reducing the joint gap. However, in the method described in Patent Document 3, when there are deviations in the thickness and material of the steel plate used as the blank, there is a problem that the roundness of the steel pipe after the expansion process will also be deviated even under the same forming conditions.

[0019] The method described in Patent Document 4 also improves the roundness of the steel pipe after the expansion process by setting the forming conditions of the U-shaped cross-section in the bending process and the forming conditions in the process of reducing the joint gap as related conditions. However, in the method described in Patent Document 4, there is also a problem that when there are deviations in the thickness and material of the steel plate used as the blank, the roundness of the steel pipe after the expansion process will also be deviated even under the same forming conditions.

[0020] This invention addresses the aforementioned problems and aims to provide a method and apparatus for predicting the roundness of steel pipes, capable of accurately predicting the roundness of steel pipes after the expansion process in a multi-step steel pipe manufacturing process. Another objective of this invention is to provide a method for controlling the roundness of steel pipes, capable of accurately controlling the roundness of steel pipes after the expansion process in a multi-step steel pipe manufacturing process. Furthermore, this invention provides a method for manufacturing steel pipes, capable of producing steel pipes with the desired roundness with a high yield. Moreover, this invention provides a method for generating a roundness prediction model for steel pipes, capable of generating a high-precision roundness prediction model for predicting the roundness of steel pipes after the expansion process in a multi-step steel pipe manufacturing process.

[0021] Technical solutions for solving the problem

[0022] The roundness prediction method for steel pipes involved in this invention predicts the roundness of steel pipes after the pipe expansion process in the manufacturing process of steel pipes. The manufacturing process of steel pipes includes: a bending process, in which a steel plate is processed into a U-shaped cross-section by multiple pressing with a punch; a joint gap reduction process, in which the joint gap of the U-shaped cross-section is reduced to form an open pipe; a welding process, in which the ends of the open pipes are joined together; and the pipe expansion process, in which the inner diameter of the steel pipe formed by joining the ends is increased. The roundness prediction method for steel pipes includes the following steps: using a roundness prediction model obtained by learning using machine learning to predict the roundness of the steel pipe after the pipe expansion process. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more parameters selected from the operation parameters of the bending process, and one or more parameters selected from the operation parameters of the joint gap reduction process as input data, and the roundness information of the steel pipe after the pipe expansion process as output data.

[0023] Alternatively, the roundness prediction model may include one or more operating parameters selected from the operating parameters of the tube expansion process as input data.

[0024] Alternatively, the property information of the steel plate may include one or more parameters such as the yield stress of the steel plate, the representative plate thickness, and the plate thickness distribution information.

[0025] Alternatively, the operating parameters of the bending process may include the punching position information and punching reduction amount of the punch used in the bending process, as well as the number of punching operations performed in the bending process.

[0026] Alternatively, the manufacturing process of the steel pipe may include an end bending process that bends the end of the steel plate in the width direction before the bending process, and the roundness prediction model may include one or more parameters selected from the operating parameters of the end bending process as the input data.

[0027] The first aspect of the present invention relates to a steel pipe roundness control method comprising the following steps: using the steel pipe roundness prediction method of the present invention, before the bending process begins, using the actual parameters of the steel plate's property information and the set values ​​of the operating parameters in downstream processes including the bending process, the roundness of the steel pipe after the pipe expansion process is predicted, and the operating parameters of the bending process are reset to reduce the roundness of the steel pipe after the pipe expansion process.

[0028] The second aspect of the present invention relates to a steel pipe roundness control method comprising the following steps: using the steel pipe roundness prediction method of the present invention, after the bending process is completed and before the joint gap reduction process begins, the roundness of the steel pipe after the pipe expansion process is predicted using the actual data of the steel plate's property information, the actual data of the bending process's operating parameters, and the set values ​​of the operating parameters in downstream processes, including the joint gap reduction process; and the operating parameters of the joint gap reduction process are reset to reduce the roundness of the steel pipe after the pipe expansion process.

[0029] The roundness control method for steel pipes according to the third aspect of the present invention includes the following steps: using the roundness prediction method for steel pipes according to the present invention, before the start of a reset target process selected from the end bending process, pressure bending process, joint gap reduction process and pipe expansion process constituting the manufacturing process of the steel pipe, the roundness information of the steel pipe after the pipe expansion process is predicted, and based on the predicted roundness information of the steel pipe, at least one or more operating parameters selected from the operating parameters of the reset target process, or one or more operating parameters selected from the operating parameters of the forming process downstream of the reset target process, are reset.

[0030] The method for manufacturing steel pipes according to the present invention includes the step of manufacturing steel pipes using the roundness control method of the present invention.

[0031] The method for generating a roundness prediction model for steel pipes involved in this invention generates a roundness prediction model for steel pipes after the pipe expansion process in the manufacturing process of steel pipes. The manufacturing process of the steel pipe includes: a bending process, in which a steel plate is processed into a U-shaped cross-section by multiple pressing with a punch; a joint gap reduction process, in which the joint gap of the U-shaped cross-section is reduced to form an open pipe; a welding process, in which the ends of the open pipes are joined together; and the pipe expansion process, in which the inner diameter of the steel pipe formed by joining the ends is increased. The method for generating the roundness prediction model for the steel pipe includes the following steps: Multiple learning data sets are obtained, and a roundness prediction model is generated by machine learning using the obtained learning data sets. The multiple learning data sets are one or more actual data sets selected from the attribute information of the steel plate, one or more actual data sets selected from the actual operation data of the bending process, and one or more actual data sets selected from the actual operation data of the joint gap reduction process as input actual data. The actual roundness data of the steel pipe after the pipe expansion process in the steel pipe manufacturing process using the input actual data is used as output actual data.

[0032] Alternatively, the machine learning described herein may be selected from neural networks, decision tree learning, random forests, and support vector regression.

[0033] The roundness prediction device for steel pipes involved in this invention predicts the roundness of steel pipes after the pipe expansion process in the manufacturing process of steel pipes. The manufacturing process includes: a bending process, in which a steel plate is processed into a U-shaped cross-section by multiple pressing with a punch; a joint gap reduction process, in which the joint gap of the U-shaped cross-section is reduced to form an open pipe; a welding process, in which the ends of the open pipe are joined together; and the pipe expansion process, in which the inner diameter of the steel pipe formed by joining the ends is increased. The roundness prediction device for steel pipes includes: an operation parameter acquisition unit, which acquires one or more parameters selected from the attribute information of the steel plate, and one or more parameters selected from the operation parameters of the bending process. The system includes an operation parameter acquisition unit, which takes one or more operation parameters selected from the operation parameters of the joint gap reduction process, and a roundness prediction unit. The operation parameter acquisition unit inputs the operation parameters obtained by the operation parameter acquisition unit into a roundness prediction model obtained by learning using machine learning, thereby predicting the roundness information of the steel pipe after the pipe expansion process. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more operation parameters selected from the operation parameters of the bending process, and one or more operation parameters selected from the operation parameters of the joint gap reduction process as input data, and outputs the roundness information of the steel pipe after the pipe expansion process.

[0034] Alternatively, a terminal device may be provided, comprising: an input unit for acquiring input information based on user operations; and a display unit for displaying the roundness information, wherein the operation parameter acquisition unit updates part or all of the acquired operation parameters based on the input information acquired by the input unit, and the display unit displays the roundness information of the steel pipe predicted by the roundness prediction unit using the updated operation parameters.

[0035] Invention Effects

[0036] According to the steel pipe roundness prediction method and apparatus of the present invention, the roundness of the steel pipe after the expansion process in the manufacturing process of a steel pipe consisting of multiple processes can be predicted with high accuracy. Furthermore, according to the steel pipe roundness control method of the present invention, the roundness of the steel pipe after the expansion process in the manufacturing process of a steel pipe consisting of multiple processes can be controlled with high accuracy. Additionally, according to the steel pipe manufacturing method of the present invention, steel pipes with the desired roundness can be manufactured with a high yield. Moreover, according to the steel pipe roundness prediction model generation method of the present invention, a steel pipe roundness prediction model that accurately predicts the roundness of the steel pipe after the expansion process in the manufacturing process of a steel pipe consisting of multiple processes can be generated. Attached Figure Description

[0037] Figure 1 This is a diagram illustrating the manufacturing process of a steel pipe as one embodiment of the present invention.

[0038] Figure 2 This diagram illustrates an example of the process of forming a U-shaped cross-section using a bending device.

[0039] Figure 3 This diagram illustrates an example of the process of forming a U-shaped cross-section using a bending device.

[0040] Figure 4 This is a diagram showing an example of the structure of an O-ring stamping device.

[0041] Figure 5 This is a diagram illustrating a structural example of a closed stamping device.

[0042] Figure 6 This is a diagram showing an example of the structure of a tube expander.

[0043] Figure 7 This is a diagram illustrating the structure of a device for measuring the outer diameter shape of a steel pipe.

[0044] Figure 8 This is a diagram illustrating a method for generating a roundness prediction model as an embodiment of the present invention.

[0045] Figure 9 This is a diagram illustrating an example of the relationship between the amount of stamping work and the roundness of the steel pipe after the expansion process, depending on the changes in the operating conditions of the bending process.

[0046] Figure 10 This is a diagram illustrating the position and amount of each press.

[0047] Figure 11 This is a flowchart illustrating a roundness control method as an embodiment of the present invention.

[0048] Figure 12 This is a three-dimensional diagram showing the overall structure of the C-shaped stamping device.

[0049] Figure 13 This is a cross-sectional view showing the structure of the stamping mechanism.

[0050] Figure 14 This is a diagram illustrating a method for generating a roundness prediction model as another embodiment of the present invention.

[0051] Figure 15 This is a diagram illustrating a method for controlling the roundness of a steel pipe as one embodiment of the present invention.

[0052] Figure 16This is a diagram showing the structure of a roundness prediction device for steel pipes as one embodiment of the present invention. Detailed Implementation

[0053] [Steel pipe manufacturing process]

[0054] Figure 1 This is a diagram illustrating the manufacturing process of a steel pipe as one embodiment of the present invention. (See diagram for details.) Figure 1 As shown, in the steel pipe manufacturing process according to one embodiment of the present invention, the steel plate used as the billet is a thick steel plate manufactured by a thick plate rolling process, which is a preceding process in the steel pipe manufacturing process. Here, the thick steel plate is represented by a yield stress of 245–1050 MPa, a tensile strength of 415–1145 MPa, a plate thickness of 6.4–50.8 mm, a plate width of 1200–4500 mm, and a length of 10–18 m. Furthermore, the width end of the thick steel plate is pre-ground into a chamfered shape called a bevel. This is to prevent overheating of the outer surface corner of the width end during the subsequent welding process, thereby stabilizing the weld strength. Additionally, the width of the thick steel plate affects the outer diameter after being formed into a steel pipe, and is therefore adjusted to a specified range considering the deformation history in subsequent processes.

[0055] In the manufacturing process of steel pipes, an end-bending process is sometimes performed to bend the ends of the steel plate in the width direction. This end-bending process utilizes a C-shaped stamping device to perform end-bending processing (also known as edge curling) on ​​the ends of the steel plate in the width direction. The C-shaped stamping device has a pair of upper and lower dies and a pair of upper and lower clamping members that hold the center of the steel plate in the width direction. Since the length of the die is shorter than the length of the steel plate, the end-bending process is performed repeatedly while feeding the steel plate sequentially in the length direction. This end-bending process is performed on both ends of the steel plate in the width direction. Because it is difficult to apply bending moment to the ends in the width direction during three-point bending stamping, the end-bending process is a process in which bending deformation is applied in advance using dies. This improves the roundness of the steel pipe as the final product. Examples of operational parameters used to determine the processing conditions include the length of the die contact between the end of the steel plate and the center in the width direction (i.e., the end-bending width), the clamping force, the feed rate of the steel plate during repeated end-bending processing in the length direction, the feed direction, and the number of feeds.

[0056] The subsequent bending process involves using a bending device to perform multiple three-point bending presses with a punch, shaping the steel sheet into a U-shaped cross-section. The subsequent seam reduction process typically uses an O-ring press to reduce the seam gap of the U-shaped cross-section, forming an open tube. However, the closed-circuit stamping method described in Patent Document 4 can be used instead of the O-ring press. The subsequent welding process involves binding the seam gaps formed at the ends of the open tube together by contacting the ends with each other. Thus, the formed body becomes a steel pipe with joined ends. The subsequent pipe expansion process uses a pipe expansion device including multiple pipe expansion tools with curved surfaces obtained by dividing an arc into multiple parts, expanding the steel pipe by bringing the curved surfaces of the expansion tools against the inner surface of the steel pipe. The steel pipe manufactured in this way is inspected to determine whether its material, appearance, dimensions, and other qualities meet the specified specifications, and then shipped as a product. In addition, in this embodiment, the inspection process includes a roundness measurement process for measuring the roundness of the steel pipe.

[0057] In this embodiment, among the series of manufacturing processes that involve forming a steel plate into an open pipe and then expanding it after welding, the end bending process, the press bending process, the joint gap reduction process, and the pipe expansion process are referred to as "forming processing processes." These processes are common to each other as processes that impart plastic deformation to the steel plate to control the size and shape of the steel pipe. Hereinafter, each process of the steel pipe manufacturing process will be described in detail with reference to the accompanying drawings.

[0058] <End bending process>

[0059] use Figure 12 , Figure 13 A detailed description is provided of the C-shaped stamping device for end bending. Figure 12 This is a three-dimensional diagram showing the overall structure of the C-shaped stamping device. For example... Figure 12 As shown, the C-shaped stamping device 30 includes: a conveying mechanism 31 for conveying a steel plate S along its length; a stamping mechanism 32A for bending one end Sc in the width direction to a predetermined curvature, with the downstream side of the steel plate S in the conveying direction as the front; a stamping mechanism 32B for bending the other end Sd in the width direction to a predetermined curvature; and a spacing adjustment mechanism (not shown) for adjusting the spacing between the left and right stamping mechanisms 32A and 32B according to the width of the steel plate S to be bent at the end. The conveying mechanism 31 consists of a plurality of rotary-driven conveying rollers 31a respectively arranged in front of and behind the stamping mechanisms 32A and 32B. Additionally, the reference numeral Sa in the figure indicates the front end (front end in the length direction) of the steel plate S.

[0060] Figure 13(a) shows a cross-section in the width direction of a stamping mechanism 32A that performs bending processing on one width-direction end Sc of the steel plate S, viewed from the upstream side of the conveying direction towards the downstream side of the conveying direction. Furthermore, stamping mechanisms 32A and 32B are symmetrical and have the same structure. Stamping mechanisms 32A and 32B include: an upper die 33 and a lower die 34 arranged opposite each other in the vertical direction as a pair of dies; and a hydraulic cylinder 36, which serves as a die-moving unit, pushes the lower die 34 together with a tool holder 35 (moving it towards the upper die 33) and closes the die with a predetermined stamping force. Additionally, stamping mechanisms 32A and 32B sometimes include a clamping mechanism 37 that holds the steel plate S inside the width direction of the upper die 33 and the lower die 34. The lengths of the upper die 33 and the lower die 34 in the length direction of the steel plate S are generally shorter than the length of the steel plate S. In this case, while utilizing the conveying mechanism 31 (see reference...) Figure 12 The steel plate S is fed intermittently along its length while undergoing multiple end bending processes.

[0061] In the end bending process, the lower die 34, which is in contact with the outer surfaces of the width-direction ends Sc and Sd of the steel plate S to be end bent, has a pressing surface 34a opposite to the upper die 33. The upper die 33 has a convex curved forming surface 33a opposite to the pressing surface 34a and having a radius of curvature corresponding to the inner diameter of the steel pipe to be manufactured. The pressing surface 34a has a concave curved surface that approaches the upper die 33 as it moves outward in the width direction. However, although the pressing surface 34a of the lower die 34 is concave, it can be an inclined plane as long as it approaches the upper die 33 as it moves outward in the width direction. The curved surface shapes of the upper die 33 and the lower die 34 are sometimes designed appropriately based on the thickness of the steel plate S, the outer diameter of the steel pipe, etc., and are appropriately selected according to the material being processed.

[0062] Figure 13 (b) is related to Figure 13 (a) A cross-section of the stamping mechanism 32A at the same location in the width direction, but showing the state in which the lower die 34 is pushed up by the hydraulic cylinder 36 and the die is closed. The lower die 34 is pushed up by the hydraulic cylinder 36, and the width direction end Sc of the steel plate S is bent into a shape along the arc-shaped forming surface 33a of the upper die 33. The width of the end bending forming (end bending processing width) varies depending on the width of the steel plate S, but is generally about 100 to 400 mm.

[0063] <Bending Process>

[0064] Figure 2This diagram illustrates an example of a process for forming a U-shaped cross-section using a bending device. In the diagram, reference numeral 1 indicates a die positioned within the transport path of the steel plate S. The die 1 consists of a pair of left and right rod-shaped members 1a and 1b that support the steel plate S at two points along its transport direction, and their spacing ΔD can be adjusted according to the size of the steel tube to be formed. Reference numeral 2 indicates a punch that can move towards and away from the die 1. The punch 2 includes: a punch tip 2a with a downwardly convex processing surface that directly contacts the steel plate S and presses it into a concave shape; and a punch support body 2b connected to the back of the punch tip 2a and supporting it. Typically, the maximum width of the punch tip 2a is equal to the width (thickness) of the punch support body 2b.

[0065] When bending the steel plate S using the bending device constructed with the above structure, the steel plate S is placed on the die 1, and the steel plate S is intermittently fed at a specified feed rate while following the specified procedure. Figure 3 The technique shown involves using punch 2 to perform three-point bending and stamping successively from both ends of the steel plate S towards the center along its width. Additionally, Figure 3 This diagram illustrates the process of bending and feeding a steel plate S, which has undergone pre-processed end bending, from top to bottom in the left column (processing the first half (a) to (e)) and then from top to bottom in the middle column (processing the second half (f) to (i)), thereby forming the molded body S1 as shown in the right column diagram ((j)). Furthermore, in Figure 3 In the diagram, the arrows marking the steel plate S and punch 2 indicate the direction of movement of the steel plate S and punch 2 in each process. Furthermore, in the U-shaped cross-section formed body S1 after processing based on this process, the gap between the ends is referred to as the "joint gap".

[0066] Here, the operational parameters that determine the operating conditions in the bending process include the number of stampings, stamping position information, stamping reduction, lower die interval, and punch curvature.

[0067] The number of stamping cycles refers to the total number of times the steel plate is pressed in the width direction using three-point bending stamping. The more stamping cycles, the smoother the U-shaped cross-section becomes, and the more roundness of the steel pipe after the expansion process is improved.

[0068] The pressing position information refers to the position of the steel plate pressed by the punch in the width direction. Specifically, it can be determined by the distance from one end of the steel plate in the width direction or by a distance based on the center of the steel plate in the width direction. The pressing position information is preferably processed as data associated with the number of pressings (in the order of the first pressing to the Nth pressing).

[0069] The so-called stamping reduction refers to the amount of pressure applied by the punch 2 at each pressing position. The stamping reduction is determined by... Figure 2 Using the line connecting the uppermost point of the punch die 1 as a reference, the amount by which the lower end face of the punch tip 2a protrudes downward from this reference is defined. At this time, the pressing amount of the punch tip 2a can be set to a different value for each press; therefore, it is preferable to process the number of presses and the pressing amount as related data. Thus, when the number of presses is set to N, the number of presses, the press position information, and the pressing amount are used as a dataset, and the operating conditions in the bending process are determined using 1 to N datasets. These datasets are used because, in the bending process, by locally changing the press position and the punch pressing amount, the overall cross-sectional shape changes in the open tube state, affecting the roundness of the steel pipe after the expansion process. However, it is not necessary to use all N datasets as input variables for the roundness prediction model described later. Alternatively, conditions that have a significant impact on the roundness of the steel pipe after the expansion process can be selected, such as using the initial (first) or final (Nth) stamping position information and stamping reduction amount of the bending process to generate a roundness prediction model.

[0070] The so-called lower mold spacing refers to Figure 2 The spacing between the pair of left and right rod-shaped members 1a and 1b shown is represented by the parameter ΔD in the figure. If the lower die spacing increases, the curvature of the local steel plate will change even for the same stamping reduction, thus affecting the roundness of the steel pipe after the tube expansion process. Therefore, it is preferable to use the lower die spacing, which is set according to the size of the steel pipe to be formed, as an operating parameter in the bending process. In addition, in cases where the lower die spacing is changed each time the punch is pressed in, it can also be used as an operating parameter as data related to the number of stampings.

[0071] The term "punch curvature" refers to the curvature of the tip of the punch used for pressing. A greater punch curvature results in a greater local curvature imparted to the steel plate during three-point bending, thus significantly impacting the roundness of the steel pipe after the expansion process. However, it is difficult to change the punch curvature for each press when forming a steel plate. It is preferable to use the punch curvature, set according to the dimensions of the steel pipe to be formed, as an operating parameter in the bending process.

[0072] <Seam Gap Reduction Process>

[0073] The seam gap reduction process is a process that reduces the seam gap of a U-shaped cross-section molded body formed by a bending process. Bending and compressive forces are applied to bring the ends of the U-shaped cross-section molded body closer together. However, even when bending or compressive forces are applied to the U-shaped cross-section molded body, the seam gap will widen due to springback when the load is removed. Therefore, strong bending or compressive forces are applied in advance to anticipate springback, resulting in a deformation that flattens the U-shaped cross-section molded body longitudinally as a whole.

[0074] Figure 4 This describes the structure of an O-ring stamping device typically used in the process of reducing joint gaps. For example... Figure 4 As shown in (a), the O-shaped stamping device uses an upper die 3 and a lower die 4 to apply compressive deformation to the U-shaped cross-section forming body S1 in the longitudinal direction. At this time, the surfaces of the upper die 3 and the lower die 4 that contact the U-shaped cross-section forming body S1 are processed into curved shapes. By bringing the upper die 3 and the lower die 4 closer together, the lower part of the U-shaped cross-section forming body S1 is constrained along the curved surface of the lower die 4. Furthermore, the upper part of the forming body S1, including the ends, is subjected to bending and compressive forces by the upper die 3, thereby causing the ends to approach each other along the curved surface of the upper die 3. As a result, the gap between the circumferentially opposite ends temporarily decreases. Then, by releasing the pressure applied by the die, the gap widens due to springback. Figure 4 (b) The final joint gap G of the open pipe S2 shown is determined. At this time, the so-called O-shaped stamping reduction is a value obtained by subtracting the distance between the uppermost point of the inner tangent surface of the upper die 3 and the lowermost point of the inner tangent surface of the lower die 4 when the die is pressed in from the outer diameter of the target steel pipe. In addition, their ratio is sometimes used and called the O-shaped stamping reduction rate.

[0075] In addition to the O-ring pressing reduction amount, other operational parameters used to determine the operating conditions in the process of reducing the joint gap include the O-ring pressing position and the O-ring pressing die R.

[0076] The O-shaped stamping reduction position refers to the angle formed by the line connecting the end of the seam gap of the U-shaped cross-section of the formed body S1 to the center position in the width direction and the vertical line. Furthermore, the O-shaped stamping die R refers to the curvature of the area in the upper die 3 and lower die 4 that abuts against the formed body S1. Here, the greater the O-shaped stamping reduction in the O-shaped stamping device, the greater the curvature near the 3 o'clock and 9 o'clock positions of the formed body S1, thereby reducing the final roundness of the steel pipe.

[0077] On the other hand, when using a closed-circuit stamping method instead of an O-ring stamping device, as a device for forming an open tube S2 from a formed body S1, the following applies: Figure 5 The closed stamping device shown. For example... Figure 5As shown, the closed stamping device includes lower tools 10a and 10b. The lower tools 10a and 10b are spaced apart from each other and each has a drive mechanism capable of reversing the rotation direction. Furthermore, the lower tools 10a and 10b are supported by spring units 11a and 11b, etc. An upper tool 13 equipped with a punch 12 is disposed opposite to the lower tools 10a and 10b. A pressing force is applied from the outside to the U-shaped cross-section of the formed body S1 via the punch 12.

[0078] At this point, the U-shaped cross-section forming body S1 is formed into an open tube S2 through two steps. In the first step, the forming body S1 is positioned by the rotatable lower tools 10a and 10b, as roughly represented by a dashed line, so that the area R1, located on the right side of the seam gap G, which is to be subjected to bending deformation, is near the 3 o'clock position on a clock face. Then, a pressing force is applied using the punch 12, and after the pressing force is applied, the load on the punch 12 is removed. Next, as the second step, similarly to the first step, the pressing position is positioned so that the area R2, located on the left side of the seam gap G, which is to be subjected to bending deformation, is near the 9 o'clock position on a clock face. Then, a pressing force is applied using the punch 12, and after the pressing force is applied, the load on the punch 12 is removed, thereby forming the open tube S2.

[0079] Here, the stamping position in the first and second steps refers to the angle of the line connecting the center of the butt joint gap G and the center of the steel plate in the width direction. Figure 5 (The angle between the dashed line and the plumb line). Additionally, the pressing force in the first and second steps refers to the pressing force exerted by the punch 12 on the molded body S1.

[0080] <Welding Process>

[0081] Then, the open pipe S2 is joined together with the end faces of the joint gap and welded using a welding machine (joining unit) to form a steel pipe. For example, a welding machine consisting of three welding mechanisms—a temporary attachment welding machine, an inner surface welding machine, and an outer surface welding machine—is used. In these welding machines, the temporary attachment welding machine uses rollers to continuously press the mating surfaces together in an appropriate positional relationship, welding the pressed portion along the entire length of the pipe axis. Next, the temporarily attached pipe is welded from the inner surface of the mating portion by the inner surface welding machine (submerged arc welding), and further welded from the outer surface of the mating portion by the outer surface welding machine (submerged arc welding).

[0082] <Pipe Expanding Process>

[0083] For steel pipes welded together at the joint gap, a pipe expander is inserted inside the steel pipe to increase the diameter of the steel pipe (the so-called pipe expander). Figure 6Figures (a) to (c) are structural examples of pipe expanding devices. Figure 6 As shown in (a), the pipe expanding device includes multiple expanding molds 16 along the circumferential direction of the conical outer peripheral surface 17, each having a curved surface obtained by dividing a circular arc into multiple parts. When expanding a steel pipe using the pipe expanding device, as... Figure 6 As shown in (b) and (c), firstly, the expanding mold 16 is aligned with the expanding start position by moving the steel pipe P using the steel pipe moving device, and the pull rod 18 is retracted from the expanding start position, thereby performing the first expanding process. As a result, the expanding mold 16, which slides in contact with the conical outer peripheral surface 17, is displaced radially by a wedge action, expanding the steel pipe P. Then, the unevenness of the cross-sectional shape of the steel pipe P decreases, and the cross-sectional shape of the steel pipe P approaches a perfect circle. Next, the pull rod 18 is advanced to the expanding start position, and the expanding mold 16 is restored to its original position in the axial direction using the release mechanism. The steel pipe P is then moved further by an amount corresponding to the distance (axial length) between the expanding mold 16 and the expanding mold 16. Then, the above actions are repeated after aligning the expanding mold 16 with the new expanding position. Thus, the first expanding process can be performed each time along the entire length of the steel pipe P by the distance between the expanding mold 16.

[0084] At this point, operational parameters that determine the operating conditions of the pipe expansion process include the expansion ratio, the number of expansion mold pieces, and the diameter of the expansion mold. The expansion ratio refers to the ratio of the difference between the outer diameter after expansion and the outer diameter before expansion to the outer diameter before expansion. The outer diameter before and after expansion can be calculated by measuring the circumference of the steel pipe. The expansion ratio can be adjusted by the stroke of the expansion mold in the radial direction. The number of expansion mold pieces refers to the number of pieces that abut against the steel pipe in the circumferential direction during expansion. The diameter of the expansion mold refers to the curvature of the portion of each expansion mold that abuts against the steel pipe.

[0085] Among the operational parameters that allow for easy adjustment of the roundness after the pipe-expanding process, the expansion ratio is crucial. When the expansion ratio increases, the curvature of the area in contact with the expansion mold throughout the entire circumference is uniformly imparted according to the expansion mold's radius (R), thereby improving roundness. In this case, the more expansion mold pieces there are, the better the local curvature variations in the circumferential direction of the steel pipe can be suppressed, resulting in better roundness after the expansion process. However, if the expansion ratio is too large, the compressive yield strength of the steel pipe product may decrease due to the Bauschinger effect. When the steel pipe is used for pipeline applications, high compressive stress acts in the circumferential direction, requiring a high compressive yield strength from the steel pipe material itself; increasing the expansion ratio beyond this is inappropriate. Therefore, in practice, the expansion ratio is set such that the roundness of the steel pipe converges to a specified value at an expansion ratio lower than the pre-set upper limit.

[0086] <Roundness Measurement Procedure>

[0087] In the final inspection step of the steel pipe manufacturing process, the steel pipe undergoes quality inspection, and its roundness is measured. The roundness measured in this step is an index indicating the degree to which the outer diameter shape of the steel pipe deviates from a perfect circle. Generally, the closer the roundness is to 0, the closer the cross-sectional shape of the steel pipe is to a perfect circle. Roundness is calculated based on the outer diameter information of the steel pipe measured by a roundness measuring machine. For example, if the pipe is divided circumferentially at any point along its length and the outer diameters at the corresponding positions are measured, and the maximum and minimum diameters are set as Dmax and Dmin respectively, the roundness can be defined by Dmax-Dmin. In this case, the more divisions, the more easily small irregularities in the steel pipe after the expansion process can be quantified, which is preferable. Specifically, using 4 to 36,000 divisions is preferable. More preferably, 360 or more divisions are preferred.

[0088] Furthermore, the position along the length of the steel pipe for which roundness is to be measured can be arbitrarily chosen. Roundness can be measured near the ends of the steel pipe along its length, or it can be measured at the center of the steel pipe along its length. Alternatively, multiple roundness measurement positions can be selected along the length of the steel pipe, and the roundness at each position can be measured; the average of the roundness measured at multiple positions along the length can also be calculated. However, roundness does not necessarily have to be based on the difference between the maximum and minimum diameters. It can also be defined as follows: based on a graph representing the outer diameter shape of the steel pipe using a continuous line graph, an equivalent assumed circle (diameter) with the same area as the inner area of ​​the curve is calculated, and the area deviating from the outer diameter shape of the steel pipe is represented as an image using this assumed circle as a reference. For example, the following method can be used as a means of measuring the outer diameter shape of the steel pipe.

[0089] (a) such as Figure 7 As shown in (a), using an apparatus having an arm 20 capable of rotating 360 degrees about the approximate central axis of the steel pipe P, displacement gauges 21a and 21b mounted at the front end of the arm 20, and a rotation angle detector 22 for detecting the rotation angle of the rotation axis of the arm 20, the distance between the rotation center of the arm 20 and a measuring point on the outer periphery of the steel pipe P is measured using displacement gauges 21a and 21b for each minute angular unit of rotation of the arm 20, and the outer diameter shape of the steel pipe P is determined based on the measured value.

[0090] (b) such as Figure 7As shown in (b), a device is used that includes a rotating arm 25 that rotates about the central axis of the steel pipe P, a frame (not shown) provided at the end of the rotating arm 25 so as to be movable in the radial direction of the steel pipe P, a pair of pressing rollers 26a and 26b that abut against the outer and inner surfaces of the end of the steel pipe P and rotate with the rotation of the rotating arm 25, and a pair of pressing cylinders fixed relative to the frame to press the pressing rollers 26a and 26b against the outer and inner surfaces of the steel pipe P. The outer diameter shape of the steel pipe is determined based on the amount of radial movement of the frame and the pressing position of each pressing cylinder against the pressing rollers 26a and 26b.

[0091] In this embodiment, the roundness prediction result of the roundness prediction model described later can be verified by comparing it with the measured roundness value obtained in the above-described inspection process. Therefore, the prediction accuracy of the roundness prediction model described later can also be improved by adding the actual value of its prediction error to the prediction result of the roundness prediction model.

[0092] [Method for generating roundness prediction models]

[0093] Figure 8 This diagram illustrates a method for generating a roundness prediction model as an embodiment of the present invention. The roundness prediction model generation unit 100 in the diagram collects actual data on the properties of the steel plate as a blank, actual data on the operation of the bending process, actual data on the operation of the joint gap reduction process, and actual data on the roundness of the steel pipe after the pipe expansion process, and generates a roundness prediction model M through machine learning.

[0094] Actual data on the properties of the steel plate is sent from the host computer 110 to the roundness prediction model generation unit 100. However, the properties of the steel plate can also be measured before forming begins in the bending process, and the results can be input from a terminal or the like, thereby sending the data to the roundness prediction model generation unit 100. Furthermore, actual operational data from the bending process, actual operational data from the joint gap reduction process, and actual roundness data after the tube expansion process are each sent to the roundness prediction model generation unit 100, linked as data for each object material determined by manufacturing number, product number, etc., and stored in the database 100a. Moreover, actual operational data from the tube expansion process can also be added to the database 100a. Various types of data that can be collected as actual data can be used as the actual operational data stored in the database 100a. This is because even information not used in the actual data when generating the roundness prediction model M through machine learning can be effectively utilized when regenerating the roundness prediction model M later, without the need to re-accumulate data.

[0095] Figure 14This diagram illustrates another embodiment of the method for generating a roundness prediction model. It is an example of a manufacturing process that includes an end-bending process as a forming process for steel pipes, preceding the bending process, where actual operational data for each manufacturing process is obtained and stored in the database of the roundness prediction model generation unit.

[0096] The number of actual data points accumulated in database 100a as described above is at least 10, preferably at least 100, and more preferably at least 1000. This is because the more data points used as the basis for the machine learning model, the higher the accuracy of the roundness prediction after the tube expansion process. In this embodiment, using the database 100a created in this way, the machine learning unit 100b generates a roundness prediction model M through machine learning. This machine learning uses at least one or more actual data points selected from the attribute information of the steel plate, one or more actual data points selected from the operational data of the bending process, and one or more actual data points selected from the operational data of the joint gap reduction process as input actual data. The actual data of the roundness of the steel pipe after the tube expansion process in the manufacturing process of the steel pipe using the input actual data is used as output actual data. In addition, one or more actual data points selected from the operational data of the tube expansion process can be added to the input actual data as needed. Moreover, if an end bending process is performed before the bending process, one or more actual data points selected from the operational data of the end bending process can be added to the input actual data.

[0097] Machine learning methods can employ well-known learning approaches. Examples include neural networks and other known machine learning methods. Other methods include decision tree learning, random forests, and support vector regression. Additionally, combined models can be used. Furthermore, the roundness prediction model M can generate a machine learning model that, instead of using the roundness value as the output data, determines whether the roundness falls within a predetermined acceptable range and uses the data obtained by binarizing the result into pass / fail as the output data. In this case, classification models such as k-neighborhood regression or logistic regression can be used. Furthermore, the aforementioned database 100a can continuously accumulate operational data and can periodically (e.g., once a month) update the roundness prediction model M. This improves the prediction accuracy of the roundness prediction model M.

[0098] The roundness prediction model M for the steel pipe after the expansion process, generated as described above, has the following characteristics. Specifically, the properties of the steel plate, such as yield stress and plate thickness, are subject to certain deviations during the manufacturing of the steel plate as a blank. These deviations affect the curvature of the steel plate and its curvature after load removal during the three-point bending stamping process of the bending operation. Therefore, by using these steel plate properties as input parameters for the roundness prediction model M, the influence of yield stress and plate thickness on roundness can be taken into account. Furthermore, the joint gap reduction process also involves applying bending or compressive forces using molds, etc. Since the curvature of the steel plate after load removal is altered based on yield stress and plate thickness, these properties are also used as input parameters for the roundness prediction model M.

[0099] Furthermore, since the bending process involves repeatedly imparting discontinuous curvature along the width of the steel plate, a localized curvature distribution is created along the width of the steel plate. Subsequently, when a combined deformation of compression and bending is applied, as in the joint gap reduction process, similar to how the bending moment acting on a so-called "curved beam" varies depending on the beam's curvature, the bending moment applied in the joint gap reduction process will also be locally distributed based on the localized curvature distribution of the steel plate imparted in the bending process. Therefore, the operating conditions of the bending process influence the curvature distribution along the width of the steel plate after the joint gap reduction process. In this respect, it is meaningful to use the operating parameters of both the bending and joint gap reduction processes as input parameters for the roundness prediction model M.

[0100] For example, Figure 9 The results were obtained by measuring the roundness of the steel pipe after the pipe expansion process (with the same operating conditions set) when manufacturing a steel pipe with an outer diameter of 30 inches and a thickness of 44.5 mm and the number of stampings set to 9 in the bending process. Figure 9 The results are shown by setting other operating conditions in the bending process to constant and changing the amount of pressure applied during the final (9th) press (final pass pressure) by three levels.

[0101] like Figure 9 As shown, there exists an optimal value for the stamping amount used in the joint gap reduction process to make the roundness of the steel pipe after the expansion process close to 0. However, this optimal value varies depending on the operating conditions of the bending process. That is, it can be seen that in order to reduce the roundness of the steel pipe after the expansion process, the operating conditions of the joint gap reduction process need to be changed according to the operating conditions of the bending process. It is impossible to set appropriate operating conditions simply by considering the operating conditions of the bending process and the joint gap reduction process as independent parameters affecting the roundness of the steel pipe after the expansion process. The parameters used for machine learning will be explained below.

[0102] <Steel plate property information>

[0103] As the property information of the steel sheet that becomes the billet, any parameter that affects the roundness of the steel pipe after the expansion process can be used, such as the steel sheet's yield stress, tensile strength, longitudinal modulus of elasticity, sheet thickness, thickness distribution within the sheet surface, yield stress distribution in the thickness direction, degree of Bauschinger effect, and surface roughness. In particular, factors affecting the deformation state and springback of the steel sheet caused by the three-point bending stamping in the bending process, and factors affecting the deformation state and springback of the steel sheet caused by the compression / bending processing in the joint gap reduction process, are preferred as indicators.

[0104] The yield stress, thickness distribution, and thickness of the steel plate directly affect the stress and strain state during three-point bending stamping. Tensile strength, as a parameter reflecting the work hardening state during bending, influences the stress state during bending deformation. The Bauschinger effect affects the yield stress and subsequent work hardening behavior when the load caused by bending deformation reverses, thus impacting the stress state during bending deformation. Furthermore, the longitudinal modulus of elasticity of the steel plate affects the springback behavior after bending. Moreover, the thickness distribution within the plate surface influences the distribution of bending curvature during the pressing process, and surface roughness affects the friction state between the die and the steel plate in the process of reducing the butt joint gap, thereby affecting the roundness of the steel pipe after the expansion process.

[0105] Among these attributes, yield stress, representative plate thickness, plate thickness distribution information, and representative plate width are particularly preferred. This is because these are measurements taken during the quality inspection process of the steel plate manufacturing process, specifically the thick plate rolling process, which affects the deformation behavior in the bending and joint gap reduction processes, and also influences the roundness of the steel pipe after the tube expansion process. Furthermore, this is because these are attribute information with deviations for each steel plate used as a billet.

[0106] Yield strength is information obtained through tensile testing of small test pieces used for quality assurance, collected from thick steel plates used as blanks. It can be used as a representative value within the plane of the steel plate. Representative thickness, on the other hand, refers to the thickness representing the thickness within the plane of the steel plate. This can be the thickness at the center of the steel plate's width direction at any point along its length, or the average thickness along its length. Furthermore, the average thickness of the entire steel plate within its plane can be calculated and used as the representative thickness. Thickness distribution information refers to information representing the thickness distribution along the width direction of the steel plate. A representative example is the convexity of the steel plate. Convexity represents the difference in thickness between the center of the steel plate's width direction and a point separated from the edge of the steel plate by a specified distance (e.g., 100mm, 150mm, etc.) along its width direction. However, the thickness distribution information is not limited to this; the coefficients of an approximation obtained by using a function of quadratic or higher to approximate the thickness distribution along the width direction can also be used as the thickness distribution information. Such representative plate thickness and thickness distribution information can be obtained from data measured by a plate thickness gauge during the rolling process of the thick plate rolling process, or from data measured during the inspection process of the thick steel plate.

[0107] Furthermore, the so-called representative plate width is a representative value related to the width of the steel plate used as the blank. When there are deviations in the width of the thick steel plate used as the blank, or when the ends are ground during beveling, the width of the steel plate may vary, affecting the deviation in the outer diameter accuracy of the finished steel pipe. The representative plate width can be the width at any position along the length of the steel plate, or it can be the average width along the length. In this case, it is preferable to measure the width of the steel plate before the bending process and use its value.

[0108] <Operating parameters for end bending process>

[0109] When the operating parameters of the end bending process are used as input to the roundness prediction model, parameters that determine the shape formed by the forming surface 33a of the upper die 33 and the shape formed by the pressing surface 34a of the lower die 34 used in the C-shaped stamping apparatus 30 can be used as operating parameters. Alternatively, the end bending processing width (the width for performing end bending), the feed rate of the steel sheet, the feed direction and number of feeds, the pushing force (C-shaped stamping pressure), and the holding force of the clamping mechanism 37 can also be used as operating parameters. This is because these are factors that can affect the deformation of the end of the steel sheet in the width direction during the end bending process.

[0110] Regarding the shape of the forming surface 33a of the upper mold 33, there are cases where a shape formed by continuous arcs with multiple radii of curvature is given, and cases where a shape formed by an involute curve or the like is given. Parameters for determining the cross-sectional shape of the geometry can be used. For example, in the case where the cross-sectional shape is formed by a parabolic shape, the cross-sectional shape can be determined by using the coefficients of the first and second terms of the quadratic equation representing the parabola passing through the origin. Therefore, such coefficients can be used as operating parameters for the end bending process.

[0111] On the other hand, if multiple molds are kept and used appropriately, based on the outer diameter, wall thickness and steel type of the steel pipe to be manufactured, as the shape formed by the forming surface 33a of the upper mold 33, and the molds are appropriately replaced, the mold management number used to determine the mold used in the end bending process can also be used as the operation parameter of the end bending process.

[0112] <Operating parameters for bending process>

[0113] In this embodiment, the operating parameters of the bending process are used as input to the roundness prediction model. As operating parameters for the bending process, various parameters that affect the local bending curvature of the steel sheet and its width distribution, such as the number of punches, punching position information, punching reduction, lower die interval, and punch curvature described above, can be used. Particularly preferred are all information including the punching position information, punching reduction, and the number of punches performed in the bending process. Examples of this "including all information" include... Figure 10 The method shown. Figure 10 (a) and (b) show examples of the pressing position and pressing amount when the punch was pressed 16 times and 10 times respectively for steel plates of the same width. In this case, the pressing position is information indicating the distance from the end of the steel plate in the width direction, which serves as the reference point, and is used as the pressing position information. On the other hand, corresponding to each pressing position, the pressing amount is recorded; thus, the "number of pressings," "pressing position," and "pressing amount" can be considered as a set of data. Figure 10 In the examples shown in (a) and (b), the operating parameters of the bending process are determined by 16 sets and 10 sets of data when the number of stamping cycles is 16 and 10, respectively.

[0114] In this embodiment, such a dataset is used as input to the roundness prediction model in the following form. For example, as input to the roundness prediction model, the stamping position and stamping amount when stamping is performed at one end of the steel plate and at the position closest to the end, and the stamping position and stamping amount when stamping is performed at the other end of the steel plate and at the position closest to the end, can be used. In three-point bending stamping, when the stamping amount at one end of the steel plate is increased, Figure 2 The curvature increases at approximately the 1 o'clock and 11 o'clock positions of the steel pipe shown, resulting in a transversely elongated shape as a U-shaped cross-section. Furthermore, the closer these stamping positions are to the ends of the steel plate, the lower the joint gap, again resulting in a transversely elongated shape as a U-shaped cross-section. Consequently, even after forming an open pipe and undergoing welding and expansion processes, the steel pipe retains a transversely elongated shape, affecting its roundness. Moreover, the curvature of the punch during stamping, the overall number of stamping operations, and the spacing of the lower die during stamping also affect the roundness of the formed steel pipe.

[0115] On the other hand, as input to the roundness prediction model, by using all the stamping reduction position information and stamping reduction amount data along with the number of stamping operations, the prediction accuracy of the roundness prediction model can be further improved. For example, based on the assumed maximum number of stamping operations, the stamping reduction position and stamping reduction amount data are stored according to the number of stamping operations when stamping is performed. Furthermore, the stamping reduction position and stamping reduction amount are 0 in stamping processes where no stamping is performed. For example, in... Figure 10 In the examples shown in (a) and (b), assuming a maximum number of stamping operations of 16, when the number of stamping operations is 10, the data from the 11th to 16th stamping operations are treated as 0 and used as input to the roundness prediction model. In this case, the number of stamping operations, the stamping position, and the stamping reduction amount are the actual operational data for the bending process, information needed to control the bending device, and therefore the set values ​​set by the host computer can be used. However, if a measuring device is available to measure the stamping position and reduction amount of the punch, the measurement results can also be used as actual operational data.

[0116] <Operating parameters for reducing seam gaps>

[0117] In this embodiment, the operating parameters of the joint gap reduction process are used as inputs to the roundness prediction model. As the joint gap reduction process, when using an O-ring punch, the O-ring punch reduction amount, O-ring punch reduction position, and O-ring punch die R can be used. On the other hand, when using a closed punching method, the closed punch reduction position and closed punch pressing force from the above steps are used. In particular, when using an O-ring punch, the O-ring punch reduction amount is preferred. This is because when the O-ring punch reduction amount is increased, the area between the point constrained / pressed by the upper die and the point constrained by the lower die, mainly near the 3 o'clock and 9 o'clock positions of the steel pipe, is unconstrained, and bending and compression deformations concentrate, thus increasing the curvature of this area and affecting the final roundness. At this time, as actual operating data in the joint gap reduction process, the O-ring punch reduction amount, O-ring punch reduction position, and O-ring punch die R are information needed to control the O-ring punch, and the set values ​​set by the host computer can be used. However, if a measuring device (such as a laser rangefinder) is available to measure the amount and position of the O-ring press, the measurement results can also be used as actual operational data.

[0118] <Operating parameters for the tube expansion process>

[0119] In addition to the aforementioned operating parameters, when using the operating parameters of the tube expansion process as input to the roundness prediction model, the tube expansion ratio can also be used as an operating parameter for the tube expansion process. A higher tube expansion ratio results in a more rounded steel pipe after the tube expansion process. However, from the perspective of compressive yield strength of the steel pipe product, the upper limit of the tube expansion ratio is limited; therefore, values ​​within this range are used. In this case, the tube expansion ratio is information needed to control the tube expansion device, and a set value set by the host computer can be used. Alternatively, after tube expansion, the average outer diameter of the entire circumference can be measured using a measuring device such as a shape gauge, and the average tube expansion ratio calculated based on the change between the outer diameter and the outer diameter calculated from the width of the steel plate before processing can be used as actual operating data. Furthermore, if a tube expansion ratio measuring device is available during the tube expansion process, its measurement results can also be used as actual operating data. In addition to the tube expansion ratio, the number of tube expansion die pieces and the diameter of the tube expansion die can also be used as operating parameters for the tube expansion process.

[0120] [Methods for predicting roundness after pipe expansion]

[0121] The roundness prediction method for steel pipes after the expansion process using the roundness prediction model generated as described above is used as follows. That is, by using this method, the appropriateness of the manufacturing conditions in each process of the steel pipe manufacturing process can be verified. The steel pipe manufacturing process includes: a bending process, which processes the pipe into a U-shaped cross-section by multiple pressing using a punch; a joint gap reduction process, which reduces the joint gap of the U-shaped cross-section to form an open pipe; a welding process, which joins the ends of the open pipe together; and a pipe expansion process, which expands the inner diameter of the steel pipe formed by joining the ends together. The operating conditions of the bending process and the joint gap reduction process have a complex influence on the roundness of the steel pipe after the expansion process, and the deviation of the property information of the steel plate in the upstream process also has an impact. Therefore, the influence of these factors on the roundness of the product can be quantitatively evaluated. Thus, the deviation of the roundness of the steel pipe product can be predicted based on the actual deviation of the property information of the steel plate used as the blank, thereby allowing for changes to the operating conditions of the bending process and the joint gap reduction process that take into account such blank deviations. That is, even if there are certain deviations in the properties of the billet, the operating conditions of the bending process and the joint gap reduction process can be optimized in advance so that the roundness of the steel pipe product converges within the specified range.

[0122] <Roundness Control Methods>

[0123] Next, a method for controlling the roundness of steel pipes after the expansion process using the roundness prediction model generated as described above will be explained. Midway through the manufacturing process of a steel pipe that undergoes numerous steps, the roundness of the steel pipe after the expansion process is predicted using actual operational data from upstream processes and pre-set operating condition values ​​from downstream processes. This allows it to determine whether the predicted roundness converges to the allowable roundness for the product. Consequently, the operating conditions in downstream processes can be reset as needed. Such an implementation will be illustrated below. Figure 11 .like Figure 11 As shown, this embodiment is an example in which, during the steel pipe manufacturing process, actual data related to the property information of the steel plate used as a blank is sent from the host computer 110, and the roundness of the steel pipe after the pipe expansion process is predicted before the bending process. At this time, setting values ​​for each process, including preset values ​​for the bending process, preset values ​​for the joint gap reduction process, and preset values ​​for the pipe expansion process as needed, are sent to the operation condition resetting unit 120. Furthermore, the host computer 110 sends the collected actual data on the steel plate's property information and the preset roundness target value for the target roundness of the steel pipe after the pipe expansion process to the operation condition resetting unit 120.

[0124] Based on this information, the roundness prediction model M is used online to predict the roundness of the steel pipe after the expansion process. Then, the predicted roundness (predicted roundness value) is compared with the target roundness (target roundness value). If the predicted roundness is less than the target roundness value, the steel pipe is manufactured without changing the set values ​​of the operating conditions for the bending process, the joint gap reduction process, and the expansion process. On the other hand, if the predicted roundness is greater than the target roundness value, the operating conditions for the bending process are reset. Specifically, the settings are reset to increase the number of punches in the bending process by one or two more times and shorten the interval between the punching positions. This improves the roundness of the steel pipe after the expansion process. Furthermore, the reset operating conditions for the bending process can be reused as input data for the roundness prediction model to predict roundness again, and the reset values ​​for the bending process operating conditions can be determined to confirm whether the predicted roundness is smaller than the target roundness value. Then, the reset operating conditions for the bending process are sent to the bending process operating condition control unit, and the operating conditions for the bending process are determined. By repeatedly performing the roundness determination in the operation condition reset unit 120, even if the roundness target value is set to a small value, the operation conditions for the bending process can be set appropriately, thus enabling the manufacture of steel pipes with better roundness.

[0125] Furthermore, the resetting of operating conditions as described above is not necessarily limited to the bending process. The operating conditions for the joint gap reduction process and the pipe expansion process can be reset, or a combination of these multiple processes' operating conditions can be reset. In this embodiment, the degree of freedom for setting the operating conditions for the joint gap reduction process and the pipe expansion process is lower than that for the bending process; therefore, the operating conditions for the bending process are reset. On the other hand, in the steel pipe manufacturing process, actual data of the steel plate's property information can be sent to the host computer 110, and after the bending process, before the joint gap reduction process, the roundness prediction of the steel pipe after the pipe expansion process can be performed. At this time, as the operating conditions for the bending process, the actual operating data is sent to the operating condition resetting unit 120. In addition, the setting values ​​for each process, including the preset values ​​for the joint gap reduction process and the preset values ​​for the pipe expansion process (depending on the situation), are sent to the operating condition resetting unit 120. Similarly, the host computer 110 sends the actual data of the collected steel plate attribute information and the pre-set roundness target value for the target roundness of the steel pipe after the expansion process to the operating condition resetting unit 120. Furthermore, a roundness prediction model is used online to predict the roundness of the steel pipe after the expansion process. Then, the predicted roundness is compared with the roundness target value. If the predicted roundness converges to the roundness target value, the steel pipe is manufactured without changing the setting value of the joint gap reduction process. On the other hand, if the predicted roundness does not converge to the roundness target value, the operating conditions for the joint gap reduction process are reset. Specifically, as the joint gap reduction process, multiple O-ring pressing reduction conditions are input into the created roundness prediction model, and other conditions are set as constant conditions, with the O-ring pressing reduction amount set to obtain the best roundness. The reset operating conditions for the joint gap reduction process are then sent to the operating condition control unit for the joint gap reduction process, and the operating conditions for the joint gap reduction process are determined. Furthermore, the following method can also be used: before the bending process, the operating conditions of the bending process can be reset by the above-mentioned roundness control, and after the bending process, the actual value of the operating conditions of the bending process can be used to reset the joint gap reduction process.

[0126] As described above, according to the roundness control method of this embodiment, a roundness prediction model is used that simultaneously considers the influence of the deviation of the steel plate's property information, the interaction between the bending process and the joint gap reduction process on roundness. Therefore, appropriate operating conditions can be set to ensure good roundness of the steel pipe after the expansion process, and steel pipes with high roundness can be manufactured.

[0127] Next, refer to Table 1 and Figure 15As an embodiment of the present invention, a roundness control method is described in the case where the roundness control method includes an end bending process of the steel plate before the bending process.

[0128] In this embodiment, firstly, a resetting target process is selected from among multiple forming processes constituting the steel pipe manufacturing process. Then, before the resetting target process begins, a roundness prediction model M is used to predict the roundness of the steel pipe after the expansion process. Next, at least one operating parameter selected from the operating parameters of the resetting target process, or at least one operating parameter selected from the operating parameters of the forming process downstream of the resetting target process, is reset to reduce the roundness of the steel pipe after the expansion process.

[0129] Here, the multiple forming processes constituting the manufacturing process of the steel pipe refer to the end bending process, pressure bending process, joint gap reduction process, and pipe expansion process, which plastically deform the steel plate to form the steel pipe into a specified shape. The target process is redefined by selecting any of these forming processes. Then, before performing the forming process in the selected target process, the roundness prediction model M of the steel pipe after the pipe expansion process is used to predict the roundness of the steel pipe. At this time, for forming processes upstream of the target process, since the forming of the steel plate has been completed, the actual data can be used as input to the roundness prediction model M when using the operating parameters of the upstream forming process. On the other hand, for forming processes downstream of the target process, since actual operating data cannot be collected, preset values ​​set in a host computer or similar device are used as input to the roundness prediction model M of the steel pipe. In this way, the roundness of the steel pipe after the pipe expansion process, which is related to the target material, can be predicted.

[0130] Then, it is determined whether the predicted roundness of the steel pipe after the expansion process converges to the roundness allowed for the product. Therefore, if the roundness of the steel pipe after the expansion process is smaller than the predicted value, the operating conditions in the target setting process and the forming process downstream of the target setting process can be reset. Here, the reset operating parameters can be either the operating parameters in the target setting process or the operating parameters in the forming process downstream of the target setting process. It is sufficient to select the operating parameters of the forming process suitable for changing the roundness of the steel pipe after the expansion process based on the difference between the predicted roundness and the roundness allowed for the product. Alternatively, both the operating parameters in the target setting process and the operating parameters in any forming process downstream of the target setting process can be reset. This is because when the difference between the predicted roundness and the roundness allowed for the product is large, the roundness of the steel pipe after the expansion process can be effectively changed.

[0131] Table 1 specifically illustrates the forming process selected as the process to be reset and the corresponding forming process whose operating parameters can be reset. Case 1 involves selecting the end-bending process as the process to be reset in the manufacturing process of a steel pipe, which includes an end-bending process. In this case, before the end-bending process begins, the roundness of the steel pipe after the expansion process is predicted using the set values ​​of the operating parameters from the forming processes including the pressure bending process and the joint gap reduction process. If the predicted roundness is large, any operating parameter from each forming process—end-bending, pressure bending, joint gap reduction, and expansion—can be reset. The operating parameters to be reset can be not only those from the end-bending process but also those from other forming processes. Furthermore, when the steel plate's property information is included as input to the roundness prediction model M, actual data, including measured values ​​related to the steel plate's property information, can be input before the end-bending process, which is the process to be reset, begins.

[0132] Cases 2 and 3 can also be handled using the same considerations as in Case 1, selecting the target process for resetting and the operating parameters for resetting. On the other hand, Case 4 involves the tube expansion process as the target process for resetting. In this case, before the tube expansion process begins, the roundness prediction model M is used to predict the roundness of the steel pipe after the tube expansion process. In this case, as input to the roundness prediction model M, at least the actual operating data from the bending process and the joint gap reduction process can be used. Alternatively, actual data from the steel plate's property information and the actual operating data from the end bending process can also be used. Thus, the predicted roundness of the steel pipe after the tube expansion process is compared with the roundness allowed for the product, and if a reduction in roundness is desired, the operating parameters in the tube expansion process are reset. As the operating parameters for the tube expansion process to be reset, the tube expansion rate is preferably used. Furthermore, the amount of change in the reset tube expansion rate from the initial setting value can be set based on empirical insights. However, if the input of the roundness prediction model M includes the expansion rate of the expansion process, the value of the reset expansion rate can also be used as the input of the roundness prediction model M to re-predict the roundness of the steel pipe after the expansion process and determine whether the reset conditions are appropriate.

[0133] Table 1

[0134] (Table 1)

[0135]

[0136] ○: Molding process that allows for resetting operating parameters

[0137] Here, refer to Figure 15 A method for controlling the roundness of a steel pipe, which is one embodiment of the present invention, will be described. Figure 15The example shown illustrates a scenario where the joint gap reduction process is selected as the resetting target process, and the U-shaped forming body is transferred after the bending process is completed in order to perform the joint gap reduction process. In this case, the actual operation data from the bending process is sent to the operation condition resetting unit 120. The actual operation data can be sent via a network from the control computer of each forming process that controls each forming process. However, it can also be sent from the control computer of each forming process to the host computer 110, which oversees the overall steel pipe manufacturing process, and then from the host computer 110 to the operation condition resetting unit 120. Furthermore, as needed, actual data related to the steel plate's property information is sent from the host computer 110 to the operation condition resetting unit 120. Moreover, the actual operation data from the end bending process can also be sent as needed. Additionally, the setting values ​​for the operation parameters of the joint gap reduction process and the pipe expansion process, which are resetting target processes and forming processes downstream of the resetting target process, are sent from the control computer of each process to the operation condition resetting unit 120. However, if the setting values ​​of the operating parameters for the joint gap reduction process and the pipe expansion process are stored in the host computer 110, they can also be sent from the host computer 110 to the operating condition resetting unit 120. In addition, the host computer 110 sends the roundness target value determined according to the specifications of the steel pipe that will become the product to the operating condition resetting unit 120.

[0138] The operating condition resetting unit 120 uses the roundness prediction model M online to predict the roundness of the steel pipe after the expansion process based on this information, and compares the predicted roundness (roundness prediction value) with the target roundness (roundness target value). If the predicted roundness value is less than the target roundness value, the operating condition resetting unit 120 determines the operating conditions for the remaining forming processes without changing the set values ​​of the operating conditions for the bending process, the joint gap reduction process, and the expansion process, and manufactures the steel pipe. On the other hand, if the predicted roundness is greater than the target roundness value, the operating condition resetting unit 120 resets at least the operating conditions for the joint gap reduction process or the expansion process. Specifically, it can reset the O-ring reduction amount, etc., in the joint gap reduction process. Furthermore, it can reset the expansion rate in the expansion process. Moreover, it can reset either the O-ring reduction amount or the expansion rate.

[0139] Furthermore, the operating condition reset unit 120 can also reuse the reset operating parameters as input data to the roundness prediction model M to perform roundness prediction again, and confirm whether the predicted roundness is smaller than the roundness target value, thus determining the reset values ​​for the operating conditions of the joint gap reduction process and the pipe expansion process. The reset operating conditions for the joint gap reduction process and the pipe expansion process are sent to their respective control computers, becoming the operating conditions for the joint gap reduction process and the pipe expansion process. By repeatedly performing roundness determination in the operating condition reset unit 120, even if the roundness target value is set small, appropriate operating conditions for the joint gap reduction process and the pipe expansion process can be set, thus enabling the manufacture of steel pipes with better roundness. Moreover, after performing roundness control on the steel pipe after the pipe expansion process, in which the joint gap reduction process is the reset target process, the roundness control on the steel pipe formed into an open pipe and then welded can be performed again, in which the pipe expansion process is the reset target process. This is because, having obtained the actual operating data of the joint gap reduction process, the roundness prediction accuracy of the steel pipe is further improved.

[0140] As described above, according to the roundness control method of this invention, a roundness prediction model M that considers the influence of the interaction between the bending process and the joint gap reduction process on roundness is used. Therefore, appropriate operating conditions can be set to ensure good roundness of the steel pipe after the expansion process, and steel pipes with high roundness can be manufactured. In addition, high-precision roundness control that reflects the deviation of the property information of the steel plate as a billet can be achieved.

[0141] <Steel Pipe Roundness Prediction Device>

[0142] Next, refer to Figure 16 A roundness prediction device for steel pipes, which is one embodiment of the present invention, will be described.

[0143] Figure 16 This is a diagram showing the structure of a roundness prediction device for steel pipes, as an embodiment of the present invention. Figure 16 As shown, the roundness prediction device 160 for steel pipes according to one embodiment of the present invention includes an operation parameter acquisition unit 161, a storage unit 162, a roundness prediction unit 163, and an output unit 164.

[0144] The operation parameter acquisition unit 161, for example, has an interface capable of acquiring any roundness prediction model M generated by the machine learning unit from the roundness prediction model generation unit 100. For example, the operation parameter acquisition unit 161 preferably has a communication interface for acquiring the roundness prediction model M from the roundness prediction model generation unit 100. In this case, the operation parameter acquisition unit 161 may also receive the roundness prediction model M from the machine learning unit 100b using a prescribed communication protocol. Furthermore, the operation parameter acquisition unit 161 acquires the operating conditions of the forming equipment (the equipment performing the forming process) from the control computer or host computer provided with the equipment for each forming process, for example. For example, the operation parameter acquisition unit 161 preferably has a communication interface for acquiring the operating conditions. Additionally, the operation parameter acquisition unit 161 can acquire input information based on user operations. In this case, the roundness prediction device 160 for the steel pipe also has an input unit that includes one or more input interfaces that detect user input and acquire input information based on user operations. Examples of input units include physical keys, capacitive keys, touchscreens integrated with the output unit's display, and microphones that accept sound input, but these are not limited to these. For example, the input unit accepts input regarding the operating conditions of the roundness prediction model M obtained by the operation parameter acquisition unit 161 from the roundness prediction model generation unit 100.

[0145] Storage unit 162 includes at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or a combination of at least two of these. Storage unit 162 functions as, for example, a main storage device, an auxiliary storage device, or a cache memory. Storage unit 162 stores any information used in the operation of the roundness prediction device 160 for steel pipes. Storage unit 162 stores, for example, the roundness prediction model M obtained by the operation parameter acquisition unit 161 from the roundness prediction model generation unit 100, the operating conditions obtained by the operation parameter acquisition unit 161 from the host computer, and the roundness information predicted by the roundness prediction device 160 for steel pipes. Storage unit 162 may also store system programs and application programs, etc.

[0146] The roundness prediction unit 163 includes one or more processors. In this embodiment, the processor is a general-purpose processor or a dedicated processor for a specific process, but is not limited to these. The roundness prediction unit 163 is communicatively connected to each structural part constituting the roundness prediction device 160 of the steel pipe and controls the overall operation of the roundness prediction device 160 of the steel pipe. The roundness prediction unit 163 can be, for example, any general-purpose electronic device such as a PC (Personal Computer) or a smartphone. The roundness prediction unit 163 is not limited to these; it can also be one or multiple server devices that can communicate with each other, or other electronic devices dedicated to the roundness prediction device 160 of the steel pipe. The roundness prediction unit 163 uses the operating conditions obtained via the operating parameter acquisition unit 161 and the roundness prediction model M obtained from the roundness prediction model generation unit 100 to calculate the predicted value of the roundness information of the steel pipe.

[0147] Output unit 164 outputs the predicted value of the roundness information of the steel pipe calculated by roundness prediction unit 163 to a device for setting the operating conditions of the forming processing equipment. Output unit 164 may include one or more output interfaces that output information and notify the user. The output interface is, for example, a display. The display is, for example, an LCD or an organic EL display. Output unit 164 outputs data obtained by the operation of the roundness prediction device 160 of the steel pipe. Output unit 164 may also replace the roundness prediction device 160 of the steel pipe and be connected to the roundness prediction device 160 of the steel pipe as an external output device. As a connection method, any method such as USB, HDMI (registered trademark), or Bluetooth (registered trademark) can be used. For example, as output unit 164, a display that outputs information in the form of images, a speaker that outputs information in the form of sounds, etc., can be shown, but it is not limited to these. For example, output unit 164 prompts the user with the predicted value of the roundness information calculated by roundness prediction unit 163. The user can appropriately set the operating conditions of the forming processing equipment based on the predicted value of roundness prompted by output unit 164.

[0148] A more preferred embodiment of the roundness prediction device 160 for steel pipes after the expansion process described above is a terminal device such as a flat panel terminal. This terminal device includes an input unit 165 that acquires input information based on user operation, and a display unit 166 that displays the predicted value of the roundness information calculated by the roundness prediction unit 163. This involves acquiring user-operated input information from the input unit 165 and updating part or all of the operating parameters of the forming equipment already input into the roundness prediction device 160 for steel pipes based on the acquired input information. That is, for steel plates being processed in the forming equipment, if the roundness information of the steel pipe is predicted by the roundness prediction unit 163, the operator uses the terminal device to perform a correction operation on a portion of the operating parameters of the forming equipment already input into the operating parameter acquisition unit 161. At this time, the operating parameter acquisition unit 161 maintains the initial input data for the operating parameters of the forming equipment that were not corrected by the terminal device, and only changes the operating parameters that were corrected. Therefore, new input data for the roundness prediction model M is generated in the operation parameter acquisition unit 161, and the roundness prediction unit 163 calculates the predicted value of the roundness information based on the input data. Furthermore, the calculated predicted value of the roundness information is displayed on the display unit 166 of the terminal device via the output unit 164. Thus, the person in charge of the molding equipment operation or the factory manager can immediately confirm the predicted value of the roundness information when the operating parameters of the molding equipment are changed, and quickly adjust to appropriate operating conditions.

[0149] Example

[0150] In this embodiment, pipeline steel plates (API grade X60) with a thickness of 38.0–38.4 mm and a width of 2700–2720 mm are used. The steel pipes, after an expansion process, are manufactured by performing bending, joint gap reduction, welding, and expansion processes. During manufacturing, the operating conditions of the bending and joint gap reduction processes are arbitrarily changed (fine-tuned) to obtain steel pipes with various roundnesses. As actual data for the steel plate's properties, the average in-plane thickness of the steel plate is used as the representative thickness, and test data of yield stress obtained during the inspection process of the thick plate rolling process are further used. Furthermore, the bending process has a fixed number of pressing strokes of 9, with the first pressing position being 1120 mm from the center of the steel plate in the width direction, and pressing positions set at 224 mm intervals in the width direction of the steel plate. At this point, the stamping reduction at each position is based on 15.8mm, and is finely adjusted for each steel plate (range of 55.0 to 60.0mm).

[0151] On the other hand, as a process to reduce the seam gap, an O-ring stamping device is used to maintain the U-shaped molded body with the open portion facing upwards in a U-shaped posture. An upper die with an arc surface having a radius R of 457.2 mm and a central angle θc of 60°, and a flat surface connected to the arc surface at an angle θd of 30°, and a lower die with a concave arc surface having a radius R of 502.9 mm are used. The operating conditions are arbitrarily set (fine-tuned) within a range of 1.0% to 3.0% relative to the outer diameter, where the distance between the vertices of the R portion of the die (the vertices of the R portion are the uppermost part of the arc surface for the upper die and the lowermost part for the lower die) is relative to the outer diameter. A roundness prediction model is generated during the stage of accumulating 100 actual data points obtained as described above into a database.

[0152] The roundness prediction model generated in this way is installed as an online model. Figure 11 The system shown describes a method for controlling the roundness of steel pipes, in which the bending process is designated as a resetting process. The target roundness value for the steel pipe is set to 10 mm. Before the resetting process, the roundness of the pipe after the expansion process is predicted. If the predicted roundness exceeds the target value, the process is reset to increase the number of presses in the bending process. As a result, the average roundness of 10 pipes manufactured previously was confirmed to be 11.2 mm, with a pass rate of 80%. In contrast, in this invention, the average roundness is reduced to 6.0 mm, and the pass rate reaches 90%.

[0153] Industrial availability

[0154] According to the present invention, a method and apparatus for predicting the roundness of a steel pipe can be provided, which can predict the roundness of the steel pipe after the expansion process in a steel pipe manufacturing process consisting of multiple processes with high accuracy. Furthermore, according to the present invention, a method for controlling the roundness of a steel pipe can be provided, which can control the roundness of the steel pipe after the expansion process in a steel pipe manufacturing process consisting of multiple processes with high accuracy. Additionally, according to the present invention, a method for manufacturing a steel pipe can be provided, which can manufacture steel pipes with the desired roundness with high yield. Moreover, according to the present invention, a method for generating a roundness prediction model for a steel pipe can be provided, which can generate a roundness prediction model that can predict the roundness of the steel pipe after the expansion process in a steel pipe manufacturing process consisting of multiple processes with high accuracy.

[0155] Label Explanation

[0156] 1. Stamping Die

[0157] 1a, 1b Rod-shaped components

[0158] 2 Punch

[0159] 2a Punch front end

[0160] 2b Punch support body

[0161] 3. Upper mold

[0162] 4. Lower mold

[0163] 10a, 10b Lower Tools

[0164] 11a, 11b Spring Units

[0165] 12 punches

[0166] 13. Upper tool

[0167] 16. Pipe Expanding Mold

[0168] 17. Conical outer circumference

[0169] 18 pull rods

[0170] 20 arms

[0171] 21a, 21b Displacement gauges

[0172] 22 Rotation Angle Detector

[0173] 25 Rotating Arm

[0174] 26a, 26b Pressing rollers

[0175] 30 C-shaped stamping device

[0176] 31 Conveying Mechanism

[0177] 31a Conveyor Roller

[0178] 32A and 32B stamping mechanisms

[0179] 33 Upper mold

[0180] 33a Molding surface

[0181] 34 Lower mold

[0182] 34a Pressing surface

[0183] 36 Hydraulic cylinders

[0184] 37 Clamping mechanism

[0185] 100 Roundness Prediction Model Generation Unit

[0186] 100a Database

[0187] 100b Machine Learning Department

[0188] 110 Host Computer

[0189] 120 Operating Condition Resetting Section

[0190] 160 steel pipe roundness prediction device

[0191] 161 Operation Parameter Acquisition Unit

[0192] 162 Storage Department

[0193] 163 Roundness Prediction Department

[0194] 164 Output Section

[0195] 165 Input Section

[0196] 166 Display Department

[0197] G joint gap

[0198] M-roundness prediction model

[0199] P steel pipe

[0200] R1 and R2 areas

[0201] S steel plate

[0202] S1 Molded Body

[0203] S2 Open Pipe

Claims

1. A method for controlling the roundness of steel pipes, comprising a method for predicting the roundness of steel pipes after the pipe expansion process in the manufacturing process. The manufacturing process of the steel pipe includes: The bending process involves using a punch to press the steel plate multiple times to form a U-shaped cross-section. The process of reducing the seam gap reduces the seam gap of the U-shaped cross-section forming body to create an open tube; the welding process joins the ends of the open tube together; and the tube expansion process increases the inner diameter of the steel tube formed by joining the ends together. The method for predicting the roundness of the steel pipe includes the following steps: A roundness prediction model obtained through machine learning is used to predict the roundness of the steel pipe after the expansion process. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more parameters selected from the operation parameters of the bending process, and one or more parameters selected from the operation parameters of the joint gap reduction process as input data, and the roundness information of the steel pipe after the expansion process as output data. The roundness control method for the steel pipe includes the following steps: using the roundness prediction method for the steel pipe, before the bending process begins, using the actual parameters of the steel plate's property information and the set values ​​of the operating parameters in downstream processes, including the bending process, to predict the roundness of the steel pipe after the pipe expansion process, and resetting the operating parameters of the bending process to reduce the roundness of the steel pipe after the pipe expansion process.

2. A method for controlling the roundness of steel pipes, which uses a method for predicting the roundness of steel pipes after the pipe expansion process in the manufacturing process. The manufacturing process of the steel pipe includes: The bending process involves using a punch to press the steel plate multiple times to form a U-shaped cross-section. The process of reducing the seam gap reduces the seam gap of the U-shaped cross-section forming body to create an open tube; the welding process joins the ends of the open tube together; and the tube expansion process increases the inner diameter of the steel tube formed by joining the ends together. The method for predicting the roundness of the steel pipe includes the following steps: A roundness prediction model obtained through machine learning is used to predict the roundness of the steel pipe after the expansion process. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more parameters selected from the operation parameters of the bending process, and one or more parameters selected from the operation parameters of the joint gap reduction process as input data, and the roundness information of the steel pipe after the expansion process as output data. The roundness control method for the steel pipe includes the following steps: using the roundness prediction method for the steel pipe, after the bending process is completed and before the joint gap reduction process begins, the roundness of the steel pipe after the pipe expansion process is predicted using the actual data of the steel plate's attribute information, the actual data of the bending process's operating parameters, and the set values ​​of the operating parameters in downstream processes, including the joint gap reduction process. The operating parameters of the joint gap reduction process are then reset to reduce the roundness of the steel pipe after the pipe expansion process.

3. A method for controlling the roundness of steel pipes, which uses a method for predicting the roundness of steel pipes after the pipe expansion process in the manufacturing process. The manufacturing process of the steel pipe includes: The bending process involves using a punch to press the steel plate multiple times to form a U-shaped cross-section. The process of reducing the seam gap reduces the seam gap of the U-shaped cross-section forming body to create an open tube; the welding process joins the ends of the open tube together; and the tube expansion process increases the inner diameter of the steel tube formed by joining the ends together. The method for predicting the roundness of the steel pipe includes the following steps: A roundness prediction model obtained through machine learning is used to predict the roundness of the steel pipe after the expansion process. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more parameters selected from the operation parameters of the bending process, and one or more parameters selected from the operation parameters of the joint gap reduction process as input data, and the roundness information of the steel pipe after the expansion process as output data. The roundness control method for the steel pipe includes the following steps: using the roundness prediction method for the steel pipe, before the start of the reset target process selected from the end bending process, pressure bending process, joint gap reduction process and pipe expansion process constituting the manufacturing process of the steel pipe, the roundness information of the steel pipe after the pipe expansion process is predicted, and based on the predicted roundness information of the steel pipe, at least one or more operating parameters selected from the operating parameters of the reset target process, or one or more operating parameters selected from the operating parameters of the forming process downstream of the reset target process, are reset.

4. The method for controlling the roundness of a steel pipe according to any one of claims 1 to 3, wherein, The roundness prediction model includes one or more operating parameters selected from the operating parameters of the tube expansion process as input data.

5. The method for controlling the roundness of a steel pipe according to any one of claims 1 to 3, wherein, The property information of the steel plate includes one or more parameters such as the yield stress of the steel plate, the representative plate thickness, and the plate thickness distribution.

6. The method for controlling the roundness of a steel pipe according to any one of claims 1 to 3, wherein, The operating parameters of the bending process include the punching position information and punching reduction amount of the punch used in the bending process, as well as the number of punching operations performed in the bending process.

7. The method for controlling the roundness of a steel pipe according to any one of claims 1 to 3, wherein, The manufacturing process of the steel pipe includes an end bending process that bends the end of the steel plate in the width direction before the bending process. The roundness prediction model includes one or more parameters selected from the operating parameters of the end bending process as the input data.

8. A method for manufacturing a steel pipe, comprising the step of manufacturing the steel pipe using the roundness control method of any one of claims 1 to 7.

9. A roundness prediction device for steel pipes, used to predict the roundness of steel pipes after the pipe expansion process in the manufacturing process of steel pipes, wherein the manufacturing process of steel pipes includes: The bending process involves using a punch to press the steel plate multiple times to form a U-shaped cross-section. The process includes a joint gap reduction step, which reduces the joint gap of the U-shaped cross-section forming body to form an open tube; a welding step, which joins the ends of the open tube together; and a tube expansion step, which expands the inner diameter of the steel tube formed by joining the ends together. The roundness prediction device for the steel tube includes: The operation parameter acquisition unit acquires one or more parameters selected from the attribute information of the steel plate, one or more operation parameters selected from the operation parameters of the bending process, and one or more operation parameters selected from the operation parameters of the joint gap reduction process; and The roundness prediction unit predicts the roundness information of the steel pipe after the pipe expansion process by inputting the operation parameters obtained by the operation parameter acquisition unit into the roundness prediction model obtained by learning using machine learning. The roundness prediction model includes one or more parameters selected from the attribute information of the steel plate, one or more operation parameters selected from the operation parameters of the bending process, and one or more operation parameters selected from the operation parameters of the joint gap reduction process as input data, and outputs the roundness information of the steel pipe after the pipe expansion process as output data.

10. The roundness prediction device for steel pipes according to claim 9, wherein, The roundness prediction device for the steel pipe includes a terminal device, which has: an input unit for acquiring input information based on user operations; and a display unit for displaying the roundness information. The operation parameter acquisition unit updates part or all of the acquired operation parameters based on the input information acquired by the input unit. The display unit shows the roundness information of the steel pipe predicted by the roundness prediction unit using the updated operating parameters.

Images