Method and apparatus for manufacturing metal tubes

Abstract

This invention relates to a method and apparatus for manufacturing metal tubes, disclosing an intelligent rolling mill capable of automatically moving a forming tool disposed within the mill stand to a predetermined position to achieve the desired forming, thereby improving formability. A non-driven draft roll (BD) dedicated to bending forming is arranged in multiple mill stands. A dedicated drive roll (DR) stand is arranged at the front and rear sections of each draft roll (BD) stand. The drive roll (DR) is constructed by applying thrust to the center of the billet via upper and lower flat rolls, and has a thrust control unit and a drive speed control unit for applying and controlling the thrust required for the process throughout the multi-stage drive roll (DR) assembly. By applying thrust to the center of the material via upper and lower flat rolls in the drive roll (DR) stand and controlling the pressure, the roll reference diameter is clearly defined, and the billet is conveyed at a predetermined speed and thrust, ensuring the necessary thrust for various product outer diameters and wall thicknesses.

Description

Technical Field

[0001] This invention relates to a forming process that uses a forming roller capable of being used as a roller with a diameter ratio of several times to continuously form a metal strip from a sheet into a semi-circular or circular shape, and then welds the two ends of the metal strip together to form a welded tube. The invention also relates to an apparatus and method for manufacturing the welded tube, which, depending on the product size and the type of metal, can reliably apply the required forming force to the blank being formed, and can perform efficient and high-precision forming without material being pushed or pulled in the production line direction between the forming rollers. Background Technology

[0002] Previously, the inventor filed a PCT patent application (PCT / JP2021 / 014863) regarding a method for manufacturing metal tubes. This method enables automated operation of a tube rolling mill for manufacturing metal tubes. It proposes a manufacturing method (intelligent rolling mill) that can automatically move the position of the forming tool located in the mill stand to a predetermined position to achieve the desired forming when manufacturing conditions change, such as when the initial plate of the billet to be formed changes or when the size of the metal strip changes due to so-called dimensional changes.

[0003] Regarding a tube rolling mill that uses a dual-purpose roll (which needs to be positioned within the mill stand to be compatible with forming rolls within a certain range of diameters), the following tube rolling mill is envisioned: In order to automate the initial pass-through process, for example, a roll flower design is incorporated into the overall tube rolling mill using the dual-purpose forming roll, which is designed to perform edge bending forming followed by circular bending forming, and the structure of all forming rolls in this tube rolling mill is specific.

[0004] Regarding the forming process using the forming rolls of the tube rolling mill, the forming process of the entire ideal forming process from plate to tube of the blank having a certain ideal property is simulated and analyzed by, for example, using the three-dimensional elastoplastic deformation finite element method. For this forming process, the following correlation is captured: the correlation is between the deformation shape value (e.g., material cross-sectional shape) of the entire material from the entry into the guide frame EG to the cross-shaped roll die TH and the position information of each roll of the forming rolls from the entry into the guide frame EG to the cross-shaped roll die TH.

[0005] Thus, if the forming process from sheet to tube as a single piece, obtained from the forming simulation analysis of metal strips with a certain variety, size, and manufacturing history, is further supplemented with the correlation between the material cross-sectional shape and the roll position due to different dimensions, and this correlation is used as the deformation shape value of the formed material at a certain measurement position in the tube rolling mill (e.g., the edge position, width dimension, and height dimension of the cross-sectional shape), then in the operation within the envisioned range of applications, the ideal roll position of the forming rolls on the roll stand before and after the measurement position can be determined based on the above correlation.

[0006] In addition to differences in variety and size, there are also inherent characteristics of the metal strip, such as the characteristics of the material being formed, the dimensional errors of the metal strip used, its hot rolling history, material differences, and its deviation in the production line direction. It can be inferred that the actual forming process when forming the strip on a rolling mill with a specified structure is different from the ideal model of the forming process of the metal strip that takes into account the characteristics of the rolling mill.

[0007] Therefore, by measuring the difference between the actual operation and the ideal model as the deformation shape value of the metal strip in the forming process, a comparison and prediction operation is performed to predict the position adjustment of the forming roller based on the difference between the forming process and the ideal model. In order to achieve the inherent forming process of the metal strip in operation, the forming roller that needs to be corrected and its position adjusted can be selected.

[0008] In developing the aforementioned intelligent rolling mill, various experiments were conducted on the applicant's FFX rolling mill (Patent Document 1), which is capable of manufacturing metal tubes from large to small diameters at an outer diameter ratio of 1:3 without changing the rolls. This FFX rolling mill is characterized by employing an involute roll pass with continuously varying curvature, utilizing all rolls including the initial BD roll, and using line bending along the upper roll to form ideal roll pass profiles for various product outer diameters and wall thicknesses.

[0009] The upper and lower forming rollers move horizontally in accordance with the expansion and contraction of the plate width, or move up and down in accordance with the wall thickness and the through line. The upper roller of the first stage of blanking is constructed to oscillate relative to the blank to change the contact surface, and a structure is adopted to adjust the roller position for various product outer diameters and wall thicknesses.

[0010] The manufacturing method of intelligent rolling mills capable of automated operation is an indispensable and well-matched solution for FFX rolling mills, which employ roll position adjustments for various product outer diameters and wall thicknesses. Automated initial plate passing is also possible, and the individual characteristics of the formed materials can be easily addressed and automated.

[0011] Patent Document 1: Japanese Patent No. 4906986

[0012] In the aforementioned intelligent rolling mill, in order to improve the formability towards higher quality, such as improving the shape (forming area and forming curvature) and accuracy of edge bending, as well as the associated improvement in the joint accuracy and welding quality, a new problem was discovered in the process of studying the forming process using the three-dimensional elastoplastic deformation finite element method, caused by the bending forming of the billet and the feed drive in a combined roll that uses an involute roll profile and performs bending along the upper roll.

[0013] In the blanking BD forming section, if the edge bending forming (shape and accuracy) based on line bending forming cannot be reliably completed, even if the forming from a semi-circle to a roughly circular shape based on circular bending forming is completed in the multi-roll CL forming section as the next process, welding defects will occur due to poor mating shape between the edges.

[0014] In detail, in the first stage of blanking, the pinch point of the upper and lower rollers is set near the edge so that the blank is bent and shaped along a specific part of the upper roller.

[0015] In the second to fourth stages of blank forming, the previously bent edges are supported by side rollers, and clamping points are set further inward than the area formed by the upper and lower rollers in the previous stage, causing the blank to bend and form along a specific section of the inner rollers. Here, since the side rollers have the important function of adjusting the range of bending, the position adjustment of the side rollers within the machine base becomes extremely important. Furthermore, forming cannot be completed unless the necessary and sufficient forming load is generated on the side rollers.

[0016] A unified method and formula for calculating the loads (forming reaction forces) required for roll forming has not yet been established; only a few simplified formulas under specific conditions were proposed in the 1980s. In actual equipment, forming loads can be measured, for example, by placing force sensors on the bearings of the upper and lower horizontal rollers, but this is difficult in the case of side rollers. However, in the simulation analysis of the forming process, it is possible to accurately determine the forming loads generated on the forming rollers and the entry resistance experienced by the blank from the forming rollers.

[0017] The aforementioned new problems are as follows: the forming roller is multi-purpose, and the position where the forming roller holds the blank changes depending on the product size; the forming reaction force on the forming roller is greatest at the clamping point, and the feed diameter, which is consistent with the blank's travel speed and the roller's circumferential speed, is also located near the clamping point; the roller reference diameter used in the design of the driving motor and reducer may not be consistent with the feed diameter that varies according to the tube-making conditions, and in the case of a smaller feed diameter, it may be braked.

[0018] In other words, if the BD machine base is responsible for both forming and thrust, the stability of the thrust will be sacrificed. That is, it is recognized that the push and pull of the thrust between the BD machine bases under the feed diameter that varies according to the product size, as well as the forming reaction force (= thrust variation) generated during operation due to the management of the roller position, can be observed.

[0019] Unstable thrust can also affect forming. For example, when strong pressure is applied to the thinnest part of the roll to compensate for insufficient thrust, serpentine or slip marks may occur due to the sawing of the material between the machine bases.

[0020] Furthermore, since the thickness of the formed metal strip (coil) is not always uniform from top to bottom, and the BD rollers are position-controlled, if the thickness of the coil changes, the forming reaction force and thrust will also change because the roller position does not follow. However, since the BD rollers clamp the left and right ends of the coil in the width direction, if there is a difference in thickness between the left and right sides of the coil when the rollers are pressure-controlled, the upper roller unit will tilt slightly, so position management is the only option.

[0021] In summary, it is important to recognize that even for automated operations, corrective predictions can be made based on the comparison between the simulation results of the forming process and the position information of the forming blank, and the position control of the rollers can be made freely and accurately. The premise of the forming process analysis is still that the traveling speed of the blank is constant. If the blank is pushed or pulled between the driven blanking BD1 to BD4, the required thrust may not be guaranteed, hindering the bending forming along the line.

[0022] Based on the above understanding, and regarding the reproducibility of the simulation results of the forming process, an in-depth study was conducted on both the line bending forming method and its forming device.

[0023] The inventors noted that in the blanking BD section, in order to accurately set the clamping points of the upper and lower rollers and reliably perform inline bending forming, it is important that the forming rollers do not participate in generating the thrust on the blank, so that the blank can pass through multiple stages of BD while obtaining a constant speed and thrust. Based on this, the inventors studied the results of the driving method and noted that sufficient thrust needs to be provided before and after the blanking rollers BD to pass through the BD.

[0024] Therefore, the results of the study on the setting of the drive roller stand dedicated to driving revealed that by using upper and lower flat rollers with a clearly defined roller reference diameter for the drive roller DR, the billet can pass through the forming hole of the blanking roller BD under stable and necessary thrust through the drive roller DR configured in the front and rear sections of the blanking roller BD.

[0025] Furthermore, based on research into the configuration method of the machine base, the following situation was recognized, and the present invention was completed: that is, by configuring drive rollers DR in the front and rear sections of the blanking roller BD and setting them to be dedicated to driving, and setting the BD roller machine base to be undriven and dedicated to forming, when the flat roller in the DR machine base applies thrust to the center of the material through pressure control, the roller reference diameter is clear and the blank is transported at a constant speed and thrust. As shown in the simulation results of the forming process, the required thrust can be ensured for various product outer diameters and wall thicknesses. Through accurate roller position control in the BD roller machine base, the blank can accurately pass through the required roller pass and reliably perform pinch and line bending forming, thus improving the formability of the BD roller machine base assembly. Summary of the Invention

[0026] This invention relates to a manufacturing apparatus for welded pipes, comprising a forming mill used in the billet-opening process. In this process, a forming roll is used to perform line bending forming, employing a portion of an involute curve in the upper roll pass and bending the billet along the outer or inner region of the billet's width direction from the clamping point where the billet is held by the upper and lower rolls. A multi-purpose forming roll with a roll pattern designed to accommodate rolls with diameter ratios ranging from several times is used in multiple mill stands. Bending is performed from both ends of the billet by an edge bending forming method.

[0027] The manufacturing apparatus has a dedicated non-drive blanking roll BD for bending and forming arranged in multiple machine bases, wherein a dedicated drive roll DR machine base is arranged in the front and rear sections of each BD machine base. The drive roll DR is composed of a structure that applies a thrust to the center of the blank through upper and lower flat rolls, and has a thrust control unit and a drive speed control unit for applying and controlling the thrust required for the process in the multi-stage drive roll DR as a whole.

[0028] Furthermore, in the above-mentioned roughing roll mill, the thrust control unit of the present invention includes a fluid pressure device for applying load to the upper roll of each drive roll and a load control unit.

[0029] Furthermore, in the above-mentioned billet rolling mill, the upper and lower flat rolls of the drive roll have a shape that matches the flatness of the central part of the billet being formed.

[0030] Furthermore, the present invention provides a welding pipe manufacturing apparatus comprising a pipe rolling mill: a multi-roll mill is disposed downstream of the aforementioned billet rolling mill; the multi-roll mill has a non-driven, multi-stage four-roll or three-roll combined multi-roll mill stand that bears the forming of the lower part of the billet in a circular bending forming manner; and a finishing rolling mill is disposed downstream of the multi-roll mill; the finishing rolling mill has a driven, multi-stage finishing rolling mill stand disposed in the clamping process and forming the billet into a substantially circular shape.

[0031] The manufacturing apparatus has a thrust distribution control unit, which distributes the thrust required for each step of forming the billet into a round tube to the multi-stage drive roll group of the roughing roll mill and the multi-stage finishing roll group of the finishing roll mill, so that the drive rolls and finishing rolls apply thrust to the formed tube blank and control it.

[0032] Furthermore, the present invention is a welding pipe manufacturing apparatus in which the thrust distribution control unit is an arithmetic unit that operates the thrust control unit and drive speed control unit of the drive roll group, the position control unit that controls the position of the finishing roll in the machine base, and the drive speed control unit of the finishing roll according to the thrust distribution information.

[0033] This invention discloses a method for manufacturing welded pipes. In the billet-forming process, a billet-forming mill is used. This process employs a forming roll that uses a portion of an involute curve in the upper roll pass to perform line bending, bending the billet along the outer or inner side of the width direction of the billet starting from the clamping point where the billet is held by the upper and lower rolls. A multi-purpose forming roll with a roll pattern designed to accommodate multiple diameter ratios of the multi-purpose roll is used in multiple machine stands. Bending is performed from both ends of the billet using an edge bending forming method.

[0034] The billet rolling mill has a dedicated non-drive billet roll (BD) for bending and forming arranged in multiple stands. Each BD stand has a dedicated drive roll (DR) stand at the front and rear sections. The drive roll (DR) is constructed by applying thrust to the center of the billet via upper and lower flat rolls. It has a thrust control unit and a drive speed control unit for applying and controlling the thrust required for the process within the multi-stage drive roll (DR) assembly.

[0035] The manufacturing method obtains the thrust information required for edge bending forming of the blanking process corresponding to the blank being formed from the results of forming simulation analysis of the forming process based on the differences in variety and size within the applicable range. The thrust is applied to the blank being formed in the drive roller DR as a whole. The forming process is a forming process in which a blanking roll mill with a specific structure and operation sequence of the forming roll mill is envisioned, and the blank being formed is gradually formed into a semi-circular tube.

[0036] Furthermore, the present invention provides a method for manufacturing a welded pipe, which utilizes a pipe rolling mill in the following steps: a blanking process, a circular bending process to form a cylindrical shape by center bending, and a precision roll forming process to adjust the end face shape of the prepared butt joint edge portion of the pipe blank to form the desired circular shape. In the blanking process, a forming roll with an involute curve in the upper roll pass is used to perform line bending forming, bending along the outer or inner region of the billet's width direction from the clamping point where the billet is held by the upper and lower rolls. A multi-purpose forming roll with a roll pattern design that utilizes a multi-diameter ratio of several times is used in multiple machine stands. Bending is performed from both ends of the billet by an edge bending forming method.

[0037] The tube rolling mill includes a billet rolling mill with a dedicated non-drive billet roll (BD) for bending and forming arranged in multiple stands. Each BD stand has a dedicated drive roll (DR) stand at its front and rear sections. The drive roll (DR) is constructed by applying thrust to the center of the billet via upper and lower flat rolls. It has a thrust control unit and a drive speed control unit for applying and controlling the thrust required for the process within the multi-stage drive roll (DR) assembly.

[0038] The tube rolling mill is configured with a multi-roll mill downstream of the billet rolling mill. The multi-roll mill has a non-driven, multi-stage four-roll or three-roll multi-roll stand that bears the forming of the lower part of the tube blank in a circular bending manner. Further downstream of the multi-roll mill is a finishing rolling mill. The finishing rolling mill has a driven, multi-stage finishing rolling mill stand located in the clamping process and forming the tube blank into a generally circular shape. The finishing rolling mill has a position control unit and a drive speed control unit for the finishing rolls within the stand, which control the position of the finishing rolls.

[0039] The manufacturing method obtains the thrust information required for each forming process corresponding to the blank based on the results of forming simulation analysis of the forming process according to the differences in variety and size within the applicable range. The thrust is applied to the blank in the drive roll DR machine base group and the finishing roll FP machine base group. The forming process is a tube rolling mill with a specific structure and operation sequence of the above-mentioned forming roll base, and the blank is gradually formed into a circular tube.

[0040] Based on the analysis of the above forming process, the required thrust in the billet rolling mill and the required thrust in the finishing rolling mill are determined, and the driving force allocated to each drive roll and each finishing roll is determined.

[0041] In the preform forming section, the forming roller does not need to consider its own driving force, and can adopt an outer diameter and roller die shape that are more specifically designed for forming, ignoring the roller reference diameter used for driving. In addition, since the material's entry resistance when passing through such a forming roller die can be analyzed, the thrust required during actual forming can be determined in advance.

[0042] The thrust information obtained in this way, required for forming and tube making, can be used effectively because the drive roller is driven by the center of the forming slab and thrust is applied by the flat upper and lower rollers.

[0043] Regarding the drive rollers, their flatness and wide contact area facilitate the generation of thrust, and their well-defined roller reference diameter, which can be standardized across all drive roller stands, makes speed synchronization easy. For example, the rollers are load (pressure) controlled by hydraulic cylinders, ensuring a constant thrust even with variations in the thickness of the formed blank.

[0044] As a device, since the diameter of the drive roller is small, the drive torque and reduction ratio can also be small, and the specifications of the reducer can be standardized, thus improving maintainability and reducing maintenance costs.

[0045] In the blanking machine stand, since there is no drive spindle, the design freedom of the forming machine stand is increased, and since the roller diameter can be reduced, the machine stand interval is shortened, resulting in the advantage of improved plate permeability of the formed slab. Attached Figure Description

[0046] Figure 1 This is an explanatory diagram illustrating edge bending forming, showing an involute groove on the roller surface and a clamping point where the blank to be formed is held by upper and lower rollers. Edge bending is achieved by bending from this clamping point along the outer or inner side of the blank's width direction using the upper roller.

[0047] Figure 2A This is an explanatory diagram showing the combined rollers used for the blanking processes BD1 to BD4, which also serve as forming rollers for edge bending. It shows how the roller spacing is increased or decreased, or the roller position is raised or lowered, relative to the width of the blank being formed.

[0048] Figure 2B This is an explanatory diagram showing the combined rollers used in the blanking processes BD1 to BD4 for edge bending, and in the circular bending processes CL1 to CL4 for forming a semi-circle into a roughly circular shape. It shows how the roller spacing is increased or decreased, or the roller position is raised or lowered, relative to the width of the blank being formed.

[0049] Figure 3 It is based on the target and Figures 4 to 15The results of the forming process simulation analysis of the billet rolling mill, multi-roll rolling mill with the same roll stand configuration, finishing rolling mill, and clamping rolling mill in the embodiment shown are illustrated in a three-dimensional diagram as a view of the positional relationship between the formed slab and the forming rolls, viewed from above along the through line direction.

[0050] Figure 4 This is a front view of the billet rolling mill and multi-roll rolling mill of an embodiment of the present invention, viewed from the operating side (WS). The slab being formed passes from left to right in the figure.

[0051] Figure 5 From Figure 4 The diagram shows the left side of the billet mill stand BD1 as observed from the upstream side.

[0052] Figure 6 From Figure 4 The diagram shows the right side of the multi-roller mill base CL1 viewed from the downstream side.

[0053] Figure 7 This is a three-dimensional diagram showing the drive roller frame.

[0054] Figure 8 yes Figure 4 The illustrated diagram shows a perspective view of the rolling mill in the embodiment shown.

[0055] Figure 9 This is a perspective illustration of a rolling mill configured with a pull-out track platform, which is used to laterally pull out the upper and lower roll units housing the upper and lower rolls from the roughing roll stand toward the operating side.

[0056] Figure 10 This is a perspective illustration of a rolling mill in which the upper and lower roll units, which house the upper and lower rolls, are pulled out as a whole from the roughing roll mill stand, with a pull-out track table for laterally pulling out to the operating side.

[0057] Figure 11A This is a three-dimensional diagram illustrating the upper and lower roller units of the roughing roll mill base BD1.

[0058] Figure 11B This is a three-dimensional diagram showing the upper and lower rollers of the roughing roll mill base BD1.

[0059] Figure 12 This is a three-dimensional diagram showing the upper and lower roller units of the roughing roller mill base BD4.

[0060] Figure 13 This is a three-dimensional illustration of the upper frame that houses the upper roller of the blanking roller mill base BD2.

[0061] Figure 14 This is a three-dimensional illustration of the lower frame that houses the lower roller of the blanking roller mill base BD2.

[0062] Figure 15 This is a three-dimensional illustration of the lower frame that houses the lower roller of the blanking roller mill base BD4. Detailed Implementation

[0063] Based on the simulation analysis results of a tube rolling mill having the same roll stand configuration as the roughing roll mill in the embodiment, the positional relationship between the formed slab and the forming rolls is determined by an overhead view along the through-line direction. Figure 3 The three-dimensional illustration shows the forming process from a plate to a round tube and the roller structure.

[0064] The roughing roll mill for edge bending is composed of four-stage roughing rolls BD1 to BD4 dedicated to forming. Five-stage drive rolls DR1 to DR5 dedicated to driving are arranged before and after the four-stage roughing rolls, thus forming a mill with a stand arranged in the order of DR1, BD1, DR2, BD2, DR3, BD3, DR4, BD4, DR5.

[0065] The roughing roll mill consists of a non-drive forming roll set that can achieve a diameter ratio of several times, but it can be said to have a structure that basically incorporates a drive roll set that is driven by upper and lower flat rolls that clamp the center of the slab to be formed and apply thrust.

[0066] The next section, which involves circular bending forming into a semi-circular shape, is a multi-roll mill equipped with four stages of multi-rolls, CL1 to CL4. The multi-rolls consist of a set of non-drive forming rolls that can be used for multiple purposes.

[0067] Furthermore, the finishing roll section, which is used to form a circular shape, is composed of finishing roll rolling mechanism consisting of finishing rolls FP1 to FP3 with a drive-type three-stage four-roll structure.

[0068] The finishing mill stands FPI, FP2, and FP3 are respectively composed of an upper finishing roll with an end face shape for adjusting the edge portion of the blank for preparation and joining, a side roll for forming the desired round tube shape, and a lower roll. This is a part where bending and deep drawing are combined.

[0069] In addition, in the case of a two-roll precision rolling mill, the upper and lower rolls are divided into two parts, with the upper roll being a precision rolling mill.

[0070] The final clamping section consists of a non-driven primary clamping roller SQ base, which welds the edge faces together.

[0071] The forming process from metal strip to metal tube is analyzed by simulation analysis based on the elastoplastic deformation of the pre-set roll pattern when using the forming roll specified in the above-mentioned tube rolling mill.

[0072] like Figure 4The simulation analysis results are illustrated in a three-dimensional image. For a metal strip of a certain size and material, all forming rolls in the tube rolling mill, except for the guide roll EG and the drive roll DR, are used to analyze the relationship between the deformation state of the billet from the metal strip to the metal tube and the position of the forming rolls in contact with the billet, and to analyze the forming process.

[0073] When using 3D CAD data and 3D elastoplastic FEM (finite element method) analysis, in the case of the forming process in which the forming blank is gradually deformed elastoplastically by the forming rollers at a constant speed instead of being driven by rotation, and the forming blank enters the cavity formed by the various forming rollers and is subjected to entry resistance, it is possible to grasp the forming reaction force and entry resistance borne by all forming rollers.

[0074] Therefore, in the above analysis, the existence of drive rollers DR1 to DR5 is ignored in the billet forming section, and the finishing rollers FP1 to FP3 are not driven by rotation in the finishing forming section. In any forming section, the forming reaction force borne by the forming rollers and the entry resistance of the die during the elastic-plastic deformation of the formed billet can be determined.

[0075] Based on the results, the forming load and necessary thrust of each forming roller can be determined, and the thrust required for each forming section can be calculated. Furthermore, by analyzing the forming process for different product sizes and materials, the thrust that should be applied to various formed blanks can be calculated.

[0076] In the three-dimensional illustration viewed from above along the direction of travel of the formed blank, the five-stage drive rolls DR1 to DR5 and the three-stage finishing rolls FP1 to FP3 apply thrust to the formed tube blank during the forming process from plate to tube.

[0077] Based on the above forming process analysis, it is possible to determine the thrust required for the process from welding to forming a round tube in the clamping process, identify the thrust required in the billet rolling mill and the finishing rolling mill, and determine the driving force allocated to each drive roll and each finishing roll.

[0078] In the blank forming section, since the forming roller does not need to consider the driving force it generates, it is possible to analyze the entry resistance of the blank when passing through the forming roller with an outer diameter and roller die shape that are more specifically designed for forming, ignoring the reference diameter of the roller used for driving. Therefore, it is possible to know in advance the thrust required during actual forming.

[0079] The thrust information obtained in this way, required for forming and tube making, can be effectively used because the drive roller is driven by the central part of the forming slab in the width direction, which is sandwiched between flat upper and lower rollers, and thus applies thrust.

[0080] Regarding the drive rollers, their flatness and wide contact area facilitate the generation of thrust, and their well-defined roller reference diameter, which can be standardized across all drive units, makes speed synchronization easy. For example, the rollers are load (pressure) controlled by hydraulic cylinders, ensuring a constant thrust even with variations in the thickness of the formed blank.

[0081] The drive roller is basically a flat roller. Figure 2A The central portion of the blank being formed, held by the blanking rollers, is slightly pushed by the lower roller in the width direction to promote bending along the line near the two edges of the blank. Therefore, the upper and lower flat rollers of the drive rollers DR2 to DR4 can be shaped to match the flatness of the central portion of the blank being formed. In this case, the aforementioned effect is also the same.

[0082] As a device, since the diameter of the drive roller is small, the drive torque and reduction ratio can also be small, and the specifications of the reducer can be standardized, thus improving maintainability and reducing maintenance costs.

[0083] In the blanking machine stand, since there is no drive spindle, the design freedom of the forming machine stand is increased, and since the roller diameter can be reduced, the machine stand interval is shortened, resulting in the advantage of improved plate permeability of the formed slab.

[0084] In the thrust control unit for applying and controlling the thrust required for the blanking process in the multi-stage drive roller DR assembly, any known method of conveying metal strip by rollers can be used. For example, if an electric motor is used in the drive, the required speed can be indicated by the drive speed control unit of the electric motor, and then the thrust can be adjusted by adjusting the position of the upper and lower rollers, or by adjusting the position of the lower roller and then appropriately adjusting the position of the upper roller. The position adjustment of the upper and lower rollers can be achieved using known mechanical mechanisms.

[0085] In addition, it can be equipped with a fluid pressure device, air compressor, hydraulic cylinder, etc., that applies a load to the upper roller after the position of the upper and lower drive rollers is adjusted, and a PLC, microcomputer or computer can be used to operate the valve to make each fluid pressure device generate the required pressure, or to indicate the operation.

[0086] The manufacturing apparatus and method of the present invention are characterized in that, when manufacturing a metal tube, the thrust information required for forming is obtained based on the analysis results of the forming process of each step in forming the blank from a plate shape into a round tube, and the thrust required for each step is allocated to the multi-stage drive roll group of the roughing roll mill and the multi-stage finishing roll group of the finishing roll mill, so that the drive roll and the finishing roll apply thrust to the blank and are controlled.

[0087] Therefore, the thrust distribution control unit needs to have a thrust control unit for driving the roll assembly, a drive speed control unit, a position control unit for controlling the position of the finishing rolls within the mill stand, and a drive speed control unit for the finishing rolls.

[0088] In particular, since the three-stage finishing rolls FP1 to FP3 mentioned above are not used interchangeably, the four rolls, including the upper roll, side roll, and lower roll, which contain the finishing rolls, will be replaced with rolls corresponding to the product size. Therefore, they will make full circumferential contact with the tube blank being formed, making it most suitable for applying thrust. The position adjustment control of each roll and the adjustment of the roll driving force (e.g., control of the drive speed) become important for controlling the formability and the application of thrust.

[0089] That is, by replacing the roller with one that corresponds to the product size and adjusting the end face shape of the edge to be joined to form the required round tube shape, it is possible to control the roller position within the machine base by, for example, using a position adjustment mechanism such as a jack connected to the roller shaft support, and to apply a specified pressing force to set the thrust, so that the roller drive motor maintains a specified speed and generates a specified thrust on the three-stage finishing roll.

[0090] Based on the thrust information required for tube forming, the thrust distribution required for each process can be set to the drive roll group and the finishing roll group by operating the PLC or microcomputer used to control the jacks and motors of each machine base. However, in cases where the distribution method differs due to differences in product size and variety, in order to make the operation easier or to achieve automation, it is preferable to use a computing device that controls all or all of the PLC or microcomputer of each machine base or according to the forming part for thrust distribution control.

[0091] For example, as a thrust distribution control using a computing device, a computing device may be used, which includes: a storage core for calculating and storing the thrust distribution to the drive roll group and the finishing roll group; a drive speed control core for each drive roll; an indicator core for instructing a fluid pressure device that applies a load to the upper roll of the drive roll to generate the required load; a position control core for performing position control of the finishing rolls in each stand; and a power control core for controlling the drive speed of the finishing rolls.

[0092] In order to automate the operation of the tube rolling mill, the following steps must be performed beforehand.

[0093] For metal strips of various sizes (plate width, wall thickness) within the range of the forming rolls envisioned in this rolling mill, or for various metal strips of different sizes and qualities based on their size and the material, purpose, specifications, etc. of the metal strips, analyze their respective forming processes.

[0094] During the forming process using roller forming, the state of the tube blank directly below the forming roller is assumed. However, it is impossible to measure the deformation morphology of the tube blank directly below the forming roller. The deformation morphology of the tube blank is at least one of the following: outer circumferential surface shape, inner circumferential surface shape, vertical cross-sectional shape, outer circumferential length, and forming load in each stand of the forming roller stand.

[0095] Based on the analysis results of the various forming processes, the deformation morphology values ​​of the tube blank near each forming roller stand in all forming roller stands (e.g., the upstream or downstream side closest to the stand) or the deformation morphology values ​​of the tube blank near forming tools such as forming holes in each stand, as well as the position information of the forming rollers in each stand, can be obtained.

[0096] The analysis results of these various forming processes can be conceived as data on the correlation between the deformation morphology value of each metal strip with a certain size and quality, i.e., a certain metal strip, a tube blank under a certain ideal model, and the position of the forming roll.

[0097] Alternatively, it can be used as data relating the deformation morphology of the billet near the forming roll or the forming roll in a certain range and specific position on the tube rolling mill's passage line to the position information of the forming tool within the aforementioned specific frame.

[0098] As an analytical method for the forming process of forming a metal strip into a metal tube using a forming roller, simulation analysis can be performed based on the roller pattern and roller surface shape design envisioned during the design phase, using various known analytical methods. For example, in mechanical design, CAE analysis is indispensable, requiring the preparation of its model and simplified shape. Analysis methods can also be employed by appropriately combining shape data and various analytical methods using 3D CAD, and further, 3D elastoplastic FEM analysis can be incorporated to perform the above analyses. Analysis can also be performed by forming roller base or by forming part.

[0099] Through the above simulation analysis, we can obtain a variety of analysis results of forming processes, which can be used as data on the correlation between various tube blank deformation morphology values ​​and forming tool positions.

[0100] Although it can be further analyzed and utilized as numerical data, for example, when comparing the correlation value data based on an ideal model in a certain tube rolling mill with the correlation value data measured based on the actual operation model in the same rolling mill, in order to be recognized by humans or artificial intelligence, it is preferable to develop and adopt a program to transform the correlation value data into visual data, so that it can be converted into position information on specific coordinates, and then it can be visualized in two dimensions or three dimensions.

[0101] Considering the tube blank shape that can be measured by measuring sensors in actual tube rolling mill operations, the deformation shape value of the tube blank can be visualized by any one of the following factors, such as the outer circumferential shape, inner circumferential shape, vertical cross-sectional shape, outer circumferential length, forming load in each stand of the forming roll row, or various combinations of the aforementioned factors.

[0102] For example, as a value representing the deformation shape of the tube blank, any one or all of the following—the outer circumferential shape, the inner circumferential shape, and the vertical cross-sectional shape—can be quantified, visualized, or graphically represented on coordinates or in virtual space: the outer circumferential shape, the inner circumferential shape, and the height of the tube blank as presented on the center plane of the production line. The center plane of the production line is a vertical plane containing a line passing through the tube blank as a pre-defined direction of travel.

[0103] In the various stages of tube making, welding, and shaping, the measuring sensor that can measure the deformation morphology of the tube blank during the forming process can appropriately employ known measurement methods such as mechanical or magnetic measurement using various contact heads and proximity heads, and further combine non-contact optical scanning such as laser beams or cameras, and non-contact magnetic scanning.

[0104] As a method for measuring the width of the tube blank and its height as presented on the center plane of the production line, at two edge positions orthogonal to the horizontal plane of the production line, any of the aforementioned known methods can be used. The center plane of the production line is a vertical plane containing the aforementioned through line, which serves as the predetermined direction of travel for the tube blank. Furthermore, in measuring the forming load in each machine base, any known force sensor, such as a load cell for measuring the load on the roller shaft, can be used.

[0105] In tube manufacturing, to prevent scratches and dirt caused by scale peeling off due to bending, as is the case with hot-rolled steel, water-soluble lubricants are sprayed or atomized onto the tube blank and rolls on the required roll mill stand. However, due to the large amount of this solvent being sprayed or atomized, the tube blank can sometimes be covered or wetted by the water-soluble lubricant, making it impossible or difficult to measure the deformation morphology of the tube blank.

[0106] Therefore, for example, metal strips that have undergone pre-descaling treatment offline through chemical or mechanical descaling processes such as pickling can be used. Furthermore, tube forming can begin after mechanical descaling is performed on any one or a portion of the entire surface or predetermined outer and inner circumference surfaces of the pre-formed metal strip.

[0107] In this tube-making process, it is preferable not to use water-soluble lubricants, but to perform local lubrication by spraying a small amount of non-water-soluble lubricant onto the required parts of the metal strip or forming tool as needed.

[0108] The tube rolling mill of this invention can also be used for automated operation. The method is as follows: During the stroke of the object being analyzed, the deformation morphology of the tube blank during forming is measured using a measuring sensor. Then, using a computing unit, the inherent forming process of the tube blank during the stroke is envisioned and analyzed. The position information of the forming rollers required for this forming process is selected, and the position information of the forming rollers within the machine base that need adjustment is output. The computing unit compares the measured deformation morphology of the tube blank during forming with data in the storage unit to predict the forming process of the tube blank.

[0109] Example

[0110] Figure 4 The rolling mill shown is constructed as a single unit, consisting of the entry guide EG on the entry side, the four-stage roughing roll stands BD1-BD4, and the four-stage multi-roll stands CL1-CL4. All stands are mounted on a common base B and interconnected.

[0111] The front side of the production line where the formed blank travels from left to right in the diagram is called the operating side (WS), and the inner side is called the driving side (DS).

[0112] The billet rolling mill base has a portal frame 1 with a pair of column heads connected by beam components, which is erected along the production line direction on the operating side and the drive side. The beam components carrying lifting jacks 2 are connected between the operating side and the drive side at the same position by a crossbeam 3. A box-type lifting screw jack unit 4 for lifting the lower roller is fixedly arranged between the operating side and the drive side at the lower part of the portal frame 1.

[0113] Furthermore, the box-shaped upper and lower roller unit 5, formed by stacking the upper frame 5a and the lower frame 5b, is configured to be inserted and withdrawn horizontally from the operating side to the driving side. The upper frame 5a houses a pair of upper rollers that can expand and contract in the width direction of the billet, and the lower frame 5b, sandwiching the central lower roller, houses a pair of lower rollers that can expand and contract. When the upper and lower roller unit 5 is inserted into the portal frame 1, the lifting jack 2 at the top of the frame connects to the upper frame 5a, and the lower frame 5b is mounted and fixed on the lifting screw jack unit 4.

[0114] The drive roller mill base is not an independent base. The upstream drive roller mill base DR1 is a structure that clamps and supports the column 10, the portal frame 1 of the roughing roller mill base BD1, and the roller bearing seats 11a and 12a of the upper and lower flat rollers 11 and 12. A bridging component 14 of the drooping hydraulic unit 13 is connected between the top of the portal frame 1 of the column 10 and the BD1 base, so that the upper roller bearing seat 11a can be raised and lowered, and the lower roller bearing seat 12a is mounted and fixed on the lifting wedge unit 15.

[0115] The drive roller frames DR2, DR3, and DR4 are shell-like structures that share the portal frame 1 located on their upstream and downstream sides. The roller bearing seats 11a and 12a of the portal frame 1 and the upper and lower flat rollers 11 and 12 are clamped and supported, and the bridging component 14 of the hydraulic unit 13 that raises and lowers the upper roller bearing seat 11a is fixed to the top of the portal frame 1.

[0116] The downstream drive roller base DR5, like the upstream drive roller base DR1, is a shell-like structure that shares the column frame 6 of the BD4 base and the multi-roller CL1 base.

[0117] For the lifting wedge unit 15, via Figure 7 The structure is described as follows: a pair of wedge-shaped components 15b, 15b having an inclined surface rising towards the center are moved closer and further away on the beam component 15a via a transmission nut mechanism, thereby causing the lifting components 15c, 15c to climb onto the inclined surface, wherein a roller bearing seat 12a (lower frame 5b in BD) is mounted and fixed on the lifting components 15c, 15c.

[0118] like Figure 11B As shown, the upper and lower rollers 20 of the first-stage billet rolling mill base BD1 consist of a pair of upper rollers 21 and 22 (top rollers) that function as swing rollers to change the contact point with the billet, lower rollers 23 and 24 (side rollers) that clamp the upper rollers 21 and 22 and perform line bending near the two edges of the billet, and a lower central roller 25 (central roller) disposed between the pair of lower rollers 23 and 24 to push the center of the billet. Pushing the center of the billet is to promote bending near the two edges of the billet.

[0119] Figure 11A Although the interior is not shown, a pair of expanding and contracting yokes that can slide along a direction perpendicular to the production line are housed in the upper frame 5a. The bearing housing of the upper roller is built into the swing yoke and can be swingably held on the expanding and contracting yoke. The expanding and contracting yokes expand and contract along the width direction of the blank by a helical shaft 5c operated from the drive side. The worm wheel of the swing seat is a structure that engages with a worm shaft operated from the drive side and swings.

[0120] Within the lower frame 5b, a central lower roller is built into the center, and a pair of brackets that can slide along the width direction of the blank to be formed are housed on both sides of it, so that the lower roller is inclinedly supported in the expansion and contraction yoke, and expands and contracts along a direction perpendicular to the production line by means of a spiral shaft 5c operated from the drive side.

[0121] like Figure 13 , 14 As shown, the second-stage blanking roll base BD2 includes: a pair of upper rolls 31, 32 for forming the two inner edges of the blank compared to those formed by BD1; a pair of lower rolls 33, 34 for clamping the blank with the upper rolls 31, 32; and a lower central roll 35 disposed between the pair of lower rolls 33, 34 and pushing the center of the blank. The structure of the upper and lower frame housing these upper and lower rolls is the same as that of the first stage.

[0122] The third and fourth stage blanking roll stands BD3 and BD4 have: a pair of side rolls 53 and 54, which, while abutting and supporting the portion bent at the edge in the first two stages, control the bending along the line towards the upper rolls 51 and 52 used to form a portion further inward than the previous edge; and a wide lower central roll 55 for clamping the blank with the upper rolls 53 and 54.

[0123] In the upper frame 5a, a pair of upper rollers 51 and 52 expand and contract in the blank width direction by means of a transmission nut mechanism and a screw shaft operated from the drive side, moving towards and away from each other. The upper rollers 51 and 52 are axially supported on a nut component coaxially arranged with the screw shaft 5c.

[0124] like Figure 15 As shown, the lower frame 5b also causes the two sides of the pair of side rollers 53 and 54 to approach and move away (expansion and contraction movement) in the blank width direction via a transmission nut mechanism and a screw shaft operated from the drive side. The lower roller 55 is axially supported in the center of the lower frame and has a built-in screw shaft 5c. The shaft support bracket 56 of the side rollers 53 and 54 is mounted on a nut component coaxially arranged with the screw shaft 5c.

[0125] Following the initial blanking section BD is the intermediate formed circular bending section, which consists of four multi-roll mill stands CL1 to CL4.

[0126] The first-stage multi-roll mill base CL1 contains a pair of clustered side rolls 61 and 62 that abut against the end bending portion and the inner bending portion of the slab, and upper and lower center bending rolls 63 and 64 for bending the central portion of the slab (center bending).

[0127] The second-stage multi-roll mill stand CL2 consists of a pair of side rolls 71 and 72 that abut against the edge and inner curved portions of the slab and are used for further bending and forming of the lower part of the tube blank.

[0128] The third and fourth stage multi-roll mill stands CL3 and CL4 consist of a pair of side rolls 81, 82, 91, 92 and a lower roll 83, 93 for circular bending of the central part of the slab, which are roughly shaped into a round tube in the fourth stage.

[0129] like Figure 4 , Figure 8 As shown, the structure of the four-stage multi-roller frame is a structure in which the four-stage crossbeam frame 7 is supported by each other on the portal frame 6 erected between the operating side and the drive side, and can be raised and lowered freely relative to the front frame.

[0130] A lower roller 64 is freely installed in the center of the crossbeam base 7, which is set between the operating side and the drive side of each machine base. The bracket components 8 and 8 that support the cluster side rollers 61 and 62 on both sides of the lower roller 64 are slidably mounted on the crossbeam base 7. Through the transmission nut mechanism and the screw shaft operated from the drive side, the two sides of the pair of side rollers 61 and 62 are brought closer and further apart (expansion and contraction movement) in the direction of the blank width.

[0131] Each beam base 7 is raised and positioned by a pair of jacks 9, 9 placed on the base B below it, and the lower roller 64 is raised and positioned independently by another jack 9a.

[0132] The first-stage multi-roller frame CL1 has a built-in unit within the portal frame 6 that allows the yoke of the upper roller 62 to move freely up and down in a hydraulic cylinder.

[0133] The aforementioned initial forming section and intermediate forming section are always used within a predetermined diameter range without being replaced. For example... Figure 2A , Figure 2B As shown, for a slab, contact with the slab is achieved and forming is made possible by the oscillation of the upper roller, the horizontal movement in the width direction, the vertical movement in the up-down direction, the horizontal movement of the lower roller in the direction perpendicular to the production line, the horizontal movement of the side rollers in the direction perpendicular to the production line, and the vertical movement of the central roller in the up-down direction.

[0134] Therefore, the positions of each forming roller are moved in various ways within the machine base. Figure 2A This indicates the position of each forming roller when forming the maximum diameter (maximum plate width) within a predetermined diameter range. Figure 2B This indicates the roller position when forming the smallest diameter (smallest plate width).

[0135] Furthermore, the blanking roll shown in the figure represents a conventional roll that is driven, but in an embodiment where the roll is not driven, the overall diameter of the roll is reduced, and the lower roll and side roll are tilted in order to reduce the diameter of the upper roll.

[0136] In Figure 2, which illustrates the positional differences of the shared forming rollers accompanying the aforementioned product size variations, for example, if there are 13 different outer diameter dimensions and 12 different plate thickness dimensions, then there are 156 different size variations. Since it is impossible to form extremely small-diameter thick walls and large-diameter thin walls, even excluding these, there are at least a hundred and several dozen possible forming roller positions.

[0137] The later forming section consists of three-stage precision rolling mill stands FP1, FP2, and FP3, and clamping roll stand SQ.

[0138] The finishing roll stands FP1, FP2, and FP3 are each composed of an upper roll for adjusting the end face shape of the prepared edge portion of the tube blank, a side roll for forming the desired round tube shape, and a lower roll. Here, bending and drawing are combined, and the cross-sectional shape and edge end face shape of the tube blank are adjusted to achieve a shape finish suitable for welding. Therefore, when forming products of different sizes, forming rolls corresponding to the product size are replaced.

[0139] The base structure of the embodiment is not shown, but the roller structure uses... Figure 3 The structure shown is the same as that of the billet rolling mill base, with the upper roll, side roll, and lower roll arranged in a frame, which can be pulled out laterally on the operating side by stacking the frames.

[0140] The frame of the finishing mill is equipped with jacks for raising and lowering the upper roll, jacks for moving the side rolls horizontally, and jacks for raising and lowering the lower roll.

[0141] Taking a tube rolling mill with the above-mentioned forming roll structure as an example, the forming process from metal strip to metal tube when using the forming roll is analyzed using three-dimensional CAD data and three-dimensional elastoplastic FEM analysis method. That is, by using a simulation analysis method of three-dimensional elastoplastic deformation of metal strip under the condition of using the configuration of forming rolls based on a pre-set roll pattern and a planned die shape (here, a simulation analysis method formed by further adding various original analysis methods software developed by the inventor to the three-dimensional elastoplastic deformation analysis software based on the known three-dimensional elastoplastic deformation analysis method), the phased and continuous forming process from metal strip to metal tube when using the forming rolls in each of the 12 stages of the mill is analyzed according to each of the aforementioned forming steps, and is analyzed as a forming process of elastoplastic deformation of a continuous integral object from sheet to tube, and the forming process is analyzed as the correlation between the deformation state of the tube blank formed by the forming rolls of the tube rolling mill and the position of the forming rolls in contact with the tube blank.

[0142] Based on the analysis results, the forming load applied to each forming roller, the entry resistance value borne by the material, and the thrust required to pass through each forming section are calculated. According to the differences in product size, steel type, etc., the forming process is analyzed, and the thrust to be applied to various forming slabs is calculated.

[0143] Therefore, the required thrust in the roughing roll mill and the required thrust in the finishing roll mill were determined, and the driving force allocated to each drive roll and each finishing roll was determined.

[0144] Each drive roller can be controlled by a hydraulic cylinder for lifting to generate a specified thrust.

[0145] Because the outer diameter of the drive rolls is uniform and reduced, the BD rolls used as forming rolls are also reduced in diameter. Furthermore, each frame is an integrated structure with the units of the frame having built-in rolls in the through-line direction and in its transverse direction. Therefore, it has excellent rigidity and is most suitable for small and lightweight applications.

[0146] Compared to the previous structure where the forming roll also serves as the drive roll, the sizing roll mill with an integrated drive roll reduces the length in the production line direction by 19%, the width direction by 23%, the height direction by 14%, and the total weight of the mill base excluding the rolls by 42% for 5-inch mills with product diameters ranging from 42.7mm to 127mm.

[0147] Because the blanking roll is not driven, the diameter of the upper and lower rolls can be minimized, and the lower and side rolls can be configured at an angle. For various upper and lower rolls, the upper roll can be built into the upper frame, and the lower roll can be built into the lower frame. The upper and lower frames can be stacked to form a structure that is pulled out laterally in the horizontal direction. This shortens the maintenance time for roll changes and core taking, simplifies the cleaning of the rolls and machinery, and expands the manufacturing range by preparing and replacing roll units with different compatibility ranges.

[0148] The upper and lower rolls of the roughing roll are respectively arranged within a frame, and a helical shaft is used in the roll's expansion and contraction mechanism, thus the load becomes internal stress. When the vertical component of the forming load generated on the entire frame is measured using a force sensor or the like, the measured component can serve as a new parameter for evaluating the forming load generated in the roughing roll stand.

[0149] The aforementioned manufacturing apparatus, based on prior analysis of the forming process of the blank from a sheet to a round tube, obtains the thrust information required for forming. It then distributes the thrust required for each process to the multi-stage drive roll group of the roughing roll mill and the multi-stage finishing roll group of the finishing roll mill. In the case of thin-walled, small-diameter tubes within the applicable range, the thrust is sometimes evenly distributed between the drive roll group and the finishing roll group; in the case of thick-walled, large-diameter tubes, a 3:7 distribution is sometimes used. Therefore, the motor used is set to have a variable output range that matches the aforementioned distribution range.

[0150] In the FP1 to FP3 mill stands of the three-stage finishing mill rolls, a roll position adjustment mechanism using jacks is used to adjust the roll position within the mill stand, apply a specified pressing force to set the thrust, and use a variable frequency motor to drive the rolls to maintain a specified speed, thereby controlling the stable generation of thrust on the three-stage finishing mill roll group.

[0151] Industrial availability

[0152] The welding pipe manufacturing method of the present invention uses a forming roller that can be used as a roller with a diameter ratio within a range of several times. When continuously forming a metal strip from a plate into a semi-circular shape in the blank forming process, the method focuses on the thrust applied to the blank to be formed and divides it into a blank forming roller that undertakes the forming and a drive roller that applies the thrust. The rollers are set according to their functions, thereby providing a welding pipe manufacturing apparatus that can reliably apply the thrust required for forming the blank according to the differences in product size and metal type. It can achieve high-efficiency and high-precision forming without the material being pushed or pulled towards the production line between the forming rollers.

[0153] Explanation of reference numerals in the attached figures:

[0154] EG enters the guide;

[0155] BD1~BD4 roughing roll mill stands;

[0156] CL1~CL4 multi-roller mill bases;

[0157] B abutment;

[0158] WS operating side;

[0159] DS drive side;

[0160] 1. Portal frame;

[0161] 2. Lifting jacks;

[0162] 3. Crossbeam;

[0163] 4. Lifting screw jack unit;

[0164] 5. Upper and lower roller units;

[0165] 5a Upper frame;

[0166] 5b Lower frame;

[0167] 5c spiral shaft;

[0168] 6. Column frame;

[0169] 7. Crossbeam base;

[0170] 10 pillars;

[0171] 11, 12 flat rollers;

[0172] 11a and 12a roller bearing housings;

[0173] 13. Hydraulic unit;

[0174] 14. Bridging components;

[0175] 15. Wedge-shaped unit for lifting;

[0176] 15a Beam component;

[0177] 15b Wedge-shaped component;

[0178] 15c Lifting component;

[0179] 20 upper and lower rollers;

[0180] 21, 22, 31, 32, 51, 52 upper rollers;

[0181] 23, 24 lower roller;

[0182] 25, 55 lower central rollers;

[0183] 53 and 54 side rollers;

[0184] Cluster side rollers 61, 62, 71, 72, 81, 82, 91, 92;

[0185] 63, 64 Center bending rollers.

Claims

1. A manufacturing apparatus for a welded tube having a forming mill used in a billet-forming process, comprising a forming mill in the manufacturing line direction for continuously rolling a sheet-shaped billet into a semi-cylindrical shape and then into a cylindrical shape, and butt-welding the two ends of the billet in the width direction to obtain a welded tube. The manufacturing apparatus includes a forming mill used in the billet-opening process. The forming mill in the billet-opening process consists of a multi-stage billet-opening roll forming stand. The multi-stage billet-opening roll forming stand is used to bend the billet from a plate shape into a semi-cylindrical shape from both ends of the initial billet by edge bending. The blank forming machine base is constructed by combining a pair of upper and lower rollers and a lower central roller, or further, a pair of side rollers, and arranging the rollers within the machine base in a manner that allows for adjustable contact with the blank to be formed. The pair of upper and lower rollers and the lower central roller are dual-purpose forming rollers designed with a roll pattern that accommodates multiple diameters within a range. Furthermore, the pair of upper and lower rollers of the blank forming machine base are configured such that a portion of an involute curve is used in the upper roller die, and bending is performed along the region of the upper roller that bends the blank in the width direction from the clamping point where the blank is held by the upper and lower rollers. The manufacturing apparatus comprises multiple blank forming roll stands, all forming rolls of which are dedicated to forming without drive. Each of the multiple blank forming roll stands has a dedicated drive roll stand at its front and rear sections. The drive roll stand applies a thrust to the blank being formed by clamping the center of the blank with upper and lower rolls and driving it. The manufacturing apparatus utilizes a thrust control unit that controls the thrust of each drive roller and a drive speed control unit located on each drive roller. The overall thrust of the multiple drive rollers enables the formed billet to pass through the forming mill in the billet opening process.

2. The manufacturing apparatus for welded tubes according to claim 1, having a forming mill used in the billet-opening process, wherein, The thrust control unit has a load control unit that applies a load to the upper roller of the drive roller.

3. The manufacturing apparatus for welded tubes according to claim 1 or 2, having a forming mill used in the billet-opening process, wherein, Downstream of the forming mill used in the billet forming process described above, a forming mill used in the multi-roll forming process is arranged. The forming mill used in the multi-roll forming process has a non-driven, multi-stage four-roll or three-roll multi-roll mill stand that undertakes the forming of the lower part of the billet in a circular bending forming manner during the intermediate forming stage. The manufacturing apparatus further includes, downstream of the forming mill used in the multi-roll forming process, a forming mill used in the finishing rolling process. The forming mill in the finishing rolling process has a multi-stage finishing roll stand, which is located in the clamping process and holds the finishing rolls used to form the billet into a generally cylindrical shape in a drivable manner. The forming mill in the finishing rolling process also has a position control unit within the stand that controls the position of the finishing rolls and a drive speed control unit for the finishing rolls. The manufacturing apparatus has a thrust distribution control unit, which distributes all the thrust required by the forming mill in each process of continuously forming the billet from strip into a round tube to the multi-stage drive roll group of the forming mill used in the billet-opening process and the multi-stage finishing roll group of the forming mill used in the finishing rolling process, so that the drive roll group and the finishing roll group apply thrust to the billet and control it.

4. The manufacturing apparatus for welded tubes according to claim 3, having a forming mill used in the billet-opening process, wherein, The thrust distribution control unit is a calculation unit that operates the thrust control unit and drive speed control unit of the drive roll group, the position control unit that controls the position of the finishing roll in the machine base, and the drive speed control unit of the finishing roll according to the thrust distribution information.

5. A method for manufacturing a welded pipe, comprising using a manufacturing apparatus for welded pipes having a forming mill in a billet-forming process, the manufacturing apparatus having a forming mill in the manufacturing line direction for continuously rolling a billet from a plate shape into a semi-cylindrical shape and then into a cylindrical shape, and butt-welding the two ends of the billet in the width direction to obtain a welded pipe. The manufacturing apparatus includes a forming mill used in the billet-opening process. The forming mill in the billet-opening process consists of a multi-stage billet-opening roll forming stand. The multi-stage billet-opening roll forming stand is used to bend the billet from a plate shape into a semi-cylindrical shape from both ends of the initial billet by edge bending. The blank forming machine base is constructed by combining a pair of upper and lower rollers and a lower central roller, or further, a pair of side rollers, and arranging the rollers within the machine base in a manner that allows for adjustable contact with the blank to be formed. The pair of upper and lower rollers and the lower central roller are dual-purpose forming rollers designed with a roll pattern that accommodates multiple diameters within a range. Furthermore, the pair of upper and lower rollers of the blank forming machine base are configured such that a portion of an involute curve is used in the upper roller die, and bending is performed along the region of the upper roller that bends the blank in the width direction from the clamping point where the blank is held by the upper and lower rollers. The manufacturing apparatus comprises multiple blank forming roll stands, all forming rolls of which are dedicated to forming without drive. Each of the multiple blank forming roll stands has a dedicated drive roll stand at its front and rear sections. The drive roll stand applies a thrust to the blank being formed by clamping the center of the blank with upper and lower rolls and driving it. The manufacturing apparatus utilizes a thrust control unit that controls the thrust and a drive speed control unit located on each drive roller. The overall thrust of the multiple drive rollers enables the formed billet to pass through the forming mill in the billet opening process. The thrust control unit includes a load control unit that applies a load to the upper roll of each drive roller. The manufacturing method includes: The analysis process uses a forming simulation analysis unit employing the three-dimensional elastoplastic deformation finite element method to simulate the forming process. The forming process is obtained by simulating the forming process in advance based on the differences in various characteristics such as size, material, and quality of the blank to be formed within the applicable range. The forming process is the process in the forming mill used for the billeting process, in which the blank with specific characteristics such as size, material, and quality enters the forming die formed by the billeting rolls in each mill stand and is elastoplastically deformed to continuously form a semi-circular tube from a strip. The calculation process, based on the analysis results, calculates the forming load applied to the forming rolls in each stand and the entry resistance value borne by the material, thereby obtaining in advance the thrust information required by the forming mill in the billet forming process corresponding to the characteristics of the billet being formed; and In the forming process, in order to apply and control the thrust required by the forming rollers in the blanking process by the multi-stage drive rollers as a whole, the thrust control unit and drive speed control unit of the drive roller group are operated based on the thrust information corresponding to the characteristics of the blank being formed.

6. A method for manufacturing a welded pipe, comprising a manufacturing apparatus for a forming mill having a billet forming process, a multi-roll forming process, and a finishing rolling process, wherein the manufacturing apparatus has a forming mill in the manufacturing line direction for continuously rolling a billet from a plate shape into a semi-cylindrical shape and then into a cylindrical shape, and butt-welding the two ends of the billet in the width direction to obtain a welded pipe. The manufacturing apparatus includes a forming mill used in the billet-opening process. The forming mill in the billet-opening process consists of a multi-stage billet-opening roll forming stand. The multi-stage billet-opening roll forming stand is used to bend the billet from a plate shape into a semi-cylindrical shape from both ends of the initial billet by edge bending. The blank forming machine base is constructed by combining a pair of upper and lower rollers and a lower central roller, or further, a pair of side rollers, and arranging the rollers within the machine base in a manner that allows for adjustable contact with the blank to be formed. The pair of upper and lower rollers and the lower central roller are dual-purpose forming rollers designed with a roll pattern that accommodates multiple diameters within a range. Furthermore, the pair of upper and lower rollers of the blank forming machine base are configured such that a portion of an involute curve is used in the upper roller die, and bending is performed along the region of the upper roller that bends the blank in the width direction from the clamping point where the blank is held by the upper and lower rollers. The manufacturing apparatus comprises multiple blank forming roll stands, all forming rolls of which are dedicated to forming without drive. Each of the multiple blank forming roll stands has a dedicated drive roll stand at its front and rear sections. The drive roll stand applies a thrust to the blank being formed by clamping the center of the blank with upper and lower rolls and driving it. The manufacturing apparatus is located downstream of the forming mill used in the billet forming process described above, with a forming mill used in the multi-roll forming process disposed thereon. The forming mill used in the multi-roll forming process has a non-driven, multi-stage four-roll or three-roll multi-roll mill stand that bears the forming of the lower part of the billet in a circular bending forming manner during the intermediate forming stage. The manufacturing apparatus further includes, downstream of the forming mill used in the multi-roll forming process, a forming mill used in the finishing rolling process. The forming mill in the finishing rolling process has a multi-stage finishing roll stand, which is located in the clamping process and holds the finishing rolls used to form the billet into a generally cylindrical shape in a drivable manner. The forming mill in the finishing rolling process also has a position control unit within the stand that controls the position of the finishing rolls and a drive speed control unit for the finishing rolls. The manufacturing apparatus has a thrust distribution control unit, which distributes all the thrust required by the forming mill in each step of continuously forming the billet from strip into a round tube to the multi-stage drive roll group of the forming mill used in the billet-opening step and the multi-stage finishing roll group of the forming mill used in the finishing rolling step, so that the drive roll group and the finishing roll group apply thrust to the billet and control it. The manufacturing method includes: The analysis process uses an analysis unit employing the three-dimensional elastoplastic deformation finite element method to simulate the forming process for each forming step. The forming process is obtained by simulating the forming process in advance based on the differences in various characteristics such as the size, material, and quality of the blank to be formed within the applicable range. The forming step is a forming process in which the blank with specific characteristics such as the size, material, and quality of the product enters the forming die formed by the blanking rolls, multi-rolls, and finishing rolls in each mill stand and is elastoplastically deformed to continuously form a strip into a semi-circular tube and then a circular tube. The calculation process, based on the analysis results, determines the forming load applied to the forming rolls in each mill stand and the entry resistance value borne by the material, thereby obtaining in advance the thrust information required by the forming mill in each forming process, corresponding to the characteristics of the blank to be formed; and In the thrust distribution process, during forming, a thrust distribution control unit is operated based on thrust information corresponding to the characteristics of the billet being formed. The thrust distribution control unit is used to distribute all the thrust required by the forming mill in the above-mentioned processes of continuously forming the billet from strip into a round tube to the multi-stage drive roll group of the forming mill used in the billet-opening process and the multi-stage finishing roll group of the forming mill used in the finishing rolling process.

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