JP2022185474A - Square steel tube manufacturing management device, square steel manufacturing management method, square steel tube manufacturing method, and square steel tube manufacturing management system - Google Patents

Abstract

To provide a square steel tube manufacturing management device, a square steel tube manufacturing management method, a square steel tube manufacturing method, and a square steel tube manufacturing management system capable of accurately acquiring a desired corner curvature radius R.SOLUTION: A square steel tube manufacturing management device 12 for manufacturing a square steel tube by square-molding a stock steel tube via a square-molding stand comprises: a peripheral length change rate calculation unit 126 that calculates a peripheral length change rate rn from a difference between the peripheral length of the stock steel tube to be square-molded from a tube surface to a position 3t/8-5t/8 (t: thickness) in a thickness direction and the peripheral length of the tube surface of the square-molded steel tube to the position 3t/8-5t/8 in the thickness direction; and a square-molding stand state determination unit 127 that determines the state of the square-molding stand 9 on the basis of the peripheral length change rate rn.SELECTED DRAWING: Figure 5

Description

In the method of manufacturing a square steel pipe from a steel pipe, the present invention adjusts the forming conditions for the corner forming while measuring the amount of deformation of the steel pipe before and after the corner forming in order to obtain a square steel pipe having a target corner curvature radius R. related to manufacturing technology.

As one method of manufacturing square steel pipes, a steel plate is formed into a cylindrical shape by roll forming, both width ends are welded, and then formed into a cylindrical steel pipe in a subsequent sizing process. There is a method in which a cylindrical steel pipe is gradually formed into a square steel pipe by a square forming stand. The cross-sectional shape of the square steel pipe differs depending on the intended product. For example, in square steel pipes for construction, corners on the outer surface of square steel pipes manufactured by the method of obtaining roll-formed square steel pipes by roll forming by cold forming, welding, and square forming (BCR method) is defined as (2.5±0.5) times the thickness t. The wall thickness of the square steel pipe manufactured by the BCR method ranges from 6 mm to 28 mm, and even square steel pipes having the same outer size have different curvature radii at the corners depending on the wall thickness.

The square forming stand consists of a forming machine with a pair of four rolls arranged on the top, bottom, left and right. In the corner forming, the flat plate portion of the square steel pipe is formed by contact with the rolls, and the corners do not come into contact with the rolls. It is formed by bending deformation due to free deformation. Since it is difficult to precisely adjust the free deformation of the corners, it is necessary to finely adjust the roll position of the corner forming stand in order to obtain the desired corner dimensions of the final product. Therefore, it is difficult to standardize the adjustment method, and the curvature radius R of the corner may exceed or fall short of the specified range.

In order to address such a corner dimension problem, in Patent Document 1, a profile measuring device is used to measure cross-sectional shapes of a cylindrical section before corner forming, a section at the output side of each corner forming stand, and a section immediately after corner forming is completed. , a forming apparatus is disclosed that analyzes each measurement to calculate the proper pass schedule for each corner forming.

Japanese Patent No. 4779227

However, as in Patent Document 1, measuring the profile of the outer shape, analyzing the measured values, and optimizing the pass schedule for forming each corner improves the dimensional accuracy of the shape of the square steel pipe. In square steel pipes with different outer ratios, the amount of improvement in dimensional accuracy may not be sufficient.

The present invention has been made in view of such circumstances, and a manufacturing control apparatus for a square steel pipe, a manufacturing control method for a square steel pipe, and a manufacturing method for a square steel pipe that enable obtaining a desired corner curvature radius R with high accuracy. and to provide a manufacturing management system for square steel pipes.

The present inventors have earnestly studied how to improve the dimensional accuracy of the corner curvature radius R of a square steel pipe. As a result, we found the following.

In corner forming, in which a square steel pipe is obtained from a cylindrical steel pipe by roll forming, the radius of curvature R of the corner portion decreases and the arc length of the outer surface increases due to bending deformation of the corner portion. The arc length of the outer surface of the flat plate portion decreases while the radius of curvature increases due to bending back deformation. In addition, except for the final stand of the angle forming stand, the outer circumference is reduced due to drawing deformation in the pipe circumferential direction. Therefore, the outer circumference shows the result of the strain balance of bending deformation and circumferential drawing deformation. As a result, even when focusing on the outer peripheral length, the corners of the square steel pipe could not have the desired dimensions. In this regard, as a result of diligent studies by the present inventors, it was found that if the change in the circumferential length at or near the center of the wall thickness of the pipe is evaluated instead of the outer shape (peripheral length), the effect of drawing deformation in the circumferential direction can be evaluated. It was found that only the The inventors of the present invention have clarified that the amount of change in the corner curvature radius R is greatly affected by the amount of change in the circumferential length at the central portion of the thickness. It has been found that the desired corner curvature radius R can be obtained with high accuracy by controlling the amount of change.

The present invention is based on the above findings, and has the following features.
[1] A manufacturing control device used for manufacturing a square steel pipe by square forming a material steel pipe with a square forming stand,
Circumferential length at a position 3t/8 to 5t/8 (t: wall thickness) from the pipe surface in the thickness direction of the material steel pipe before corner forming, and wall thickness from the pipe surface after corner forming. a circumferential length change rate calculation unit that calculates a circumferential length change rate from the difference in the circumferential length at positions in the direction of 3t/8 to 5t/8;
A manufacturing control device for square steel pipes, comprising: a square forming stand state determination unit that determines a state of the square forming stand based on the circumferential length change rate.
[2] The production control device for square steel pipes according to [1], further comprising an output unit that outputs a determination result by the square forming stand state determination unit.
[3] Manufacture of the square steel pipe according to [1] or [2], further comprising a roll position adjustment unit that adjusts the roll position of the angle forming stand based on the determination by the angle forming stand state determination unit. management device.
[4] A manufacturing control method for manufacturing a square steel pipe by square forming a material steel pipe with a square forming stand, comprising:
Circumferential length at a position (t: wall thickness) in the thickness direction of 3t/8 to 5t/8 from the pipe surface of the material steel pipe before corner forming, and wall thickness from the pipe surface after corner forming. a circumferential length change rate calculation step of calculating a circumferential length change rate from the difference in the circumferential length at positions in the direction of 3t/8 to 5t/8;
and a corner forming stand state determining step for determining the state of the angle forming stand based on the perimeter length change rate.
[5] A method for manufacturing a square steel pipe by forming a raw material steel pipe into a square steel pipe using a square forming stand, comprising:
A method for manufacturing a square shaped steel pipe, comprising a corner forming step of performing corner forming with a corner forming stand whose state has been determined in the step of determining state of a corner forming stand according to the above [4].
[6] Equipped with a square steel pipe manufacturing control device according to any one of [1] to [3] above,
Furthermore, as an external profile meter, at least
a first external profile meter for measuring the shape of the material steel pipe before corner forming;
a second profile profiler for measuring the shape after corner forming;
A manufacturing management system for square steel pipes.
[7] The production management system for square steel pipes according to [6], further comprising a display device for displaying the determination result of the state of the square forming stand by the square forming stand state determination unit.

According to the present invention, it is possible to obtain a desired corner curvature radius R with high accuracy.

FIG. 1 is a schematic diagram showing an example of equipment for manufacturing an electric resistance welded steel pipe. FIG. 2 is a schematic diagram showing the forming process of the square steel pipe. FIG. 3 is a schematic diagram showing a cross section of a square steel pipe. FIG. 4 shows an outline of the manufacturing control system for square steel pipes of the present invention. FIG. 5 is a diagram for explaining the configuration of a manufacturing control system for square steel pipes. FIG. 6 is a diagram showing a flow for explaining the processing performed by the manufacturing control device for square steel pipes. FIG. 7 is a diagram for explaining an example of a method for measuring an outer profile of corner molding. FIG. 8 is a diagram for explaining a method of calculating the _radius of curvature ri of the thickness central portion.

The present invention will be described based on the drawings.

Before describing the square steel pipe manufacturing method, the square steel pipe manufacturing control apparatus, and the manufacturing control system of the present invention, a related art square steel pipe manufacturing method will be described. First, a method of manufacturing an electric resistance welded steel pipe used to obtain a square steel pipe will be described with reference to FIG. FIG. 1 is a schematic diagram showing an example of equipment for manufacturing an electric resistance welded steel pipe. A steel strip 1, which is a raw material for an electric resistance welded steel pipe, is subjected to entry-side straightening by, for example, a leveler 2, and then intermediately formed by a cage roll group 3 consisting of a plurality of rolls to form an open pipe, which is then formed of a plurality of rolls. Fin pass roll group 4 is used for finish forming. After the finish forming, the width end portions of the steel strip 1 are electric resistance welded by a welder 6 while pressure welding is performed by squeeze rolls 5 to form an electric resistance welded steel pipe 7 . The steel strip 1 may be, for example, a carbon steel hot-rolled steel plate. Further, in the present invention, the equipment for manufacturing the electric resistance welded steel pipe 7 is not limited to the pipe-making process shown in FIG.

FIG. 2 is a schematic diagram showing a forming process of a related art square steel pipe. As shown in FIG. 2 , the electric resistance welded steel pipe 7 is reduced in diameter in a cylindrical shape by a group of sizing rolls (sizing stand) 8 consisting of a plurality of rolls, and then a group of corner forming rolls (a corner forming stand) consisting of a plurality of rolls. 9, the square steel pipe 10 is formed into shapes such as R1, R2, and R3 in sequence. The number of stands of the sizing roll group 8 and the angle forming roll group 9 is not particularly limited. Further, the caliber curvature of the sizing roll group 8 or the angle forming roll group 9 is preferably one condition.

An example of a square steel pipe obtained by such a manufacturing method will be described with reference to FIG.
FIG. 3 is a cross-sectional view showing a cross-section perpendicular to the axial direction of the square steel pipe 10. As shown in FIG. The square steel pipe 10 has a plurality of flat plate portions and corner portions alternately formed in the pipe circumferential direction. Here, the case where the cross section is substantially square, that is, the case where the side length H of the flat plate portion has the same vertical diameter and horizontal diameter will be described as an example, but the present invention is not limited to this. A cross section of the square steel pipe 10 perpendicular to the pipe axis direction may be substantially rectangular. Also, the case where the seam portion is formed at the central position of the flat plate portion in the pipe circumferential direction will be described as an example, but the present invention is not limited to this.

As shown in FIG. 3, when the welded portion (seam portion) of the steel pipe is set to 0° as a reference position, and the positions of 45°, 135°, 225°, and 315° are set to the centers of the corners, the radius of curvature of the corners is As shown in FIG. 3, is the radius of curvature at the intersection of a line (L) starting from the center of the tube and forming an angle of 45° with the adjacent sides and the outside of the corners. The radius of curvature of the corners is the radius of a sector whose center angle is 65°, which is determined by a line drawn toward the connection point (A, A') between the flat plate portion and the arc portion with the center on the above L. and In addition, as a method of calculating the radius of curvature, for example, the curvature using the law of sine from the measurement result of the distance relationship of 3 points (the intersection point on the outside of the corner and the 2 points that are the connection points between the flat plate portion and the arc portion) There are a method of calculating the radius and a method of measuring the radius of curvature from a radial gauge that well matches the corners within the three points, but the method is not limited to this.

As a technique for obtaining the square steel pipe as described above, the present invention makes it possible to obtain a desired corner portion curvature radius R with high accuracy.

The inventors of the present invention have taken as an example a steel pipe having a corner portion curvature radius R of 2.0 to 4.0 times the wall thickness t, and have earnestly studied a manufacturing method for obtaining such a steel pipe with high accuracy. perfected the invention. Specifically, while using the same roll set of the square forming stand, the rate of change in the peripheral length at or near the center of the wall thickness during square forming is controlled. However, it was found that a steel pipe having a corner curvature radius R of 2.0 to 4.0 times the wall thickness t can be obtained with high accuracy.
For example, in order to obtain a square steel pipe in which the corner curvature radius R of the outer surface of the square steel pipe is 2.0 times or more and 3.0 times or less as large as the wall thickness by the BCR method, the cylindrical steel pipe (raw material steel pipe) before and after corner forming must be It has been found that it is sufficient to adjust the circumferential length and control the circumferential length change rate of the thickness central portion in the corner forming to 3 to 6%. In addition, in order to obtain a square steel pipe having a corner portion curvature radius R of 3.0 times or more and 4.0 times or less as large as the wall thickness, it is necessary to control the peripheral length change rate at the central portion of the wall thickness to 0.5 to 3%. I found out that I should.
At this time, if the circumferential length change rate is controlled to be less than 0.5%, the shape of the flat plate portion cannot be made parallel, and there is a possibility that the target cross-sectional dimension of the square steel pipe cannot be obtained. Also, if the circumferential length change rate exceeds 6%, the radius of curvature of the corners of the square steel pipe becomes small, but problems such as cracking on the outer surface of the corners may occur. Moreover, it is preferable to control the rate of change in the circumference of each corner forming stand except the final stand to 0.1% or more and 3% or less. If it is less than 0.1%, the effect of elastic recovery after molding becomes large, and molding cannot be performed as intended. Molding with a content of more than 3% may cause a shape defect because the flat plate portion becomes an inward concave shape. In this way, the inventors have found that the desired corner radius of curvature can be obtained with high accuracy by adjusting the roll position of the corner forming stand based on the circumferential length change rate at or near the center of the thickness. . It was also found that the vicinity of the thickness central portion should be a region from the thickness central portion (t/2 position) to t/8 in the thickness direction (radial direction) toward the outer surface and the inner surface side. Specifically, when adjusting the roll position of the corner forming stand based on the circumferential length change rate at a position that is more than t / 8 in the thickness direction (radial direction) from the thickness center to the outer surface and inner surface side, It has been found that the thicker the square steel pipe, the less accurately the desired radius of curvature of the corners can be obtained. Preferably, the adjustment of the roll position is performed based on the rate of change in the peripheral length of the thickness central portion.

The square steel pipe manufacturing method of the present invention completed based on the above knowledge is a square steel pipe manufacturing method for manufacturing a square steel pipe by square forming a material steel pipe such as an electric resistance welded steel pipe 7 with a square forming stand, comprising: This is a method of manufacturing a square shaped steel pipe, including a corner forming step of performing corner forming with a corner forming stand whose state has been determined in a step of determining the state of a corner forming stand in the manufacturing control method described later.
The above manufacturing control method is based on the perimeter at a position (t: wall thickness) in the thickness direction of 3 t/8 to 5 t/8 from the pipe surface of the material steel pipe before corner forming, and after corner forming A peripheral length change rate calculation step for calculating the peripheral length change rate from the difference in the peripheral length at the position of 3 t / 8 to 5 t / 8 in the thickness direction from the pipe surface, and based on the peripheral length change rate, the state of the angle forming stand and a corner forming stand condition determination step for determining the . A method for manufacturing a square steel pipe of the present invention is a method for manufacturing a square steel pipe formed by a square forming stand whose state is determined by this manufacturing control method, and includes a step of determining the state of the square forming stand after the step of calculating the circumferential length change rate. and a corner forming step of performing corner forming with the corner forming stand whose state has been determined in .

4 and 5 are diagrams for explaining the outline of the configuration of the production control system 20 for square steel pipes of the present invention and the production control device 12 included in the system.
The manufacturing control device 12 that constitutes the square steel pipe manufacturing control system 20 of the present invention uses a square forming stand 9 to process a material steel pipe (which may be a steel pipe subjected to square forming), which is the above-described electric resistance welded steel pipe 7 . A manufacturing control device used to manufacture a square steel pipe 10 by corner forming, and is a position 3 t/8 to 5 t/8 in the thickness direction from the pipe surface of the raw steel pipe before corner forming (t: thickness ) and the difference in the circumferential length at positions 3 t/8 to 5 t/8 in the wall thickness direction from the pipe surface after corner forming, the circumferential length change rate r _n is calculated by the circumferential length change rate calculation unit 126 and a corner forming stand state determining unit 127 for determining the state of the corner forming stand 9 based on the circumference change rate _rn .

The manufacturing control device 12 also includes an input unit 121, a control unit 122 for controlling the adjustment of the roll position of the angle forming stand 9 based on the circumference change rate _rn , information on the roll position position and the circumference change rate _rn . etc., may be provided.
Further, the control unit 122 includes an outer diameter distribution calculation unit 123, a pre-square forming circumference calculation unit 124, a post-square forming circumference calculation unit 125, the above-mentioned circumference length change rate calculation unit 126, a corner forming stand state determination unit 127, An output section 128 and a roll position adjustment section 129 may be provided. Each of these functions will be described later.

The manufacturing control device 12 is composed of a general-purpose computer such as a workstation or a personal computer, and has an arithmetic processing function by a CPU or the like, an image processing function by a GPU or the like, and various memory functions such as ROM and RAM as an example of the storage unit 130. In addition, it may have a recording medium such as a hard disk connected via a data communication terminal.

The production control system 20 has the production control device 12 described above, and may further have an external profile meter 11 for measuring the shape of the material steel pipe. The outer profile meter 11 has a first outer profile meter 111 for measuring the shape of the material steel pipe before corner forming, and a second outer profile meter 112 for measuring the shape after corner forming. It's okay. Further, the manufacturing control system 20 may have a display device 15 for displaying the judgment result of the state of the corner forming stand by the corner forming stand state judging section 127 . The display device 15 can be a display device or the like that allows a user to visually recognize information.
Moreover, the manufacturing control system 20 may have an output device such as an alarm device.
Further, the manufacturing control system 20 may have a roll position adjusting device 16 that adjusts the roll position of the corner forming stand 9 based on instructions from the roll position adjusting section 129 of the manufacturing control device 12 .

Next, the thickness center portion of the steel pipe before and after forming by the corner forming stand 9 or the vicinity of the thickness center portion (thickness direction 3 t / 8 to 5 t / 8 position (t: thickness), (hereinafter referred to as the thickness center portion etc.))), and determine the state of the corner forming stand to determine whether or not the roll position needs to be adjusted. explain. FIG. 6 shows a flow for calculating the perimeter change rate of the wall thickness central portion of the square steel pipe.

The process shown in the flowchart starts, for example, at the timing when the operator inputs an instruction to start the manufacturing control process to the input unit 121, and the process proceeds to step S1.

In the process of step S1, the control unit 122 causes the roll position adjusting device 16 to measure the current position of each roll of the corner forming stand 9, and records it as numerical data in the storage unit 130 of the manufacturing control device 12. The manufacturing control apparatus 12 has a processor that performs calculation processing, and the storage unit 130 has a storage medium such as a memory for recording data. Thereby, the process of step S1 is completed, and the process proceeds to step S2.

In the process of step S2, the controller 122 causes the external profile meter 11 to measure the profile of the cross section of the steel pipe.
First, the control unit 122 causes the first external profile meter 111 to measure the profile of the steel pipe cross section before corner forming.
Here, in the angle forming stand 9 shown in FIG. 4, in the angle forming direction (steel pipe advancing direction), the first roll (roll for forming the steel pipe into the shape of R1) and the second roll (roll for forming the steel pipe into the shape of R2) are used in this order. roll to shape the steel pipe), third roll (roll to shape the steel pipe into the shape of R3), and fourth roll (roll to further shape the steel pipe after the third roll). It may be before being formed by the first roll, may be before being formed by the second roll, may be before being formed by the third roll, or may be before being formed by the fourth roll. It's okay.

Further, when the profile of the steel pipe cross section before corner forming is measured by the first external profile meter 111, and the calculation of the external curvature radius r _i ' distribution, which will be described later, is performed, the process of this step is performed again, The control unit 122 causes the second external profile meter 112 to measure the profile of the cross section of the steel pipe after corner forming.

In measuring the profile after corner forming, the axial measurement position of the steel pipe may be within a range of up to 3 m in the longitudinal direction of the profile measurement position before corner forming. is more preferable.
Here, "after corner forming" is not particularly limited as long as it is a stage after before corner forming. It may refer to any stage after roll forming. Further, if "before corner forming" refers to before the steel pipe is formed by the second roll, "after corner forming" may be at any stage after the steel pipe is formed by the second roll. Further, if "before corner forming" refers to before the steel pipe is formed by the third roll, "after corner forming" may refer to any stage after forming by the third roll. Further, if "before corner forming" refers to before the steel pipe is formed by the fourth roll, then "after corner forming" may mean after being formed by the fourth roll.

The measured data before and after the angle formation is recorded in the storage unit 130, and the numerical values measured in the PC are converted into XY biaxial coordinates (horizontal direction-vertical direction).
Here, the measurement of the steel pipe cross-sectional profile of only two data before and after corner forming is described, but three or more data may be measured. data and post-corner data.
In terms of measurement accuracy, simplification of the manufacturing control device 12 and the manufacturing control system 20, and initial cost, it is preferable to use the first roll entry side before corner forming, and the fourth roll exit side after corner formation. is. More preferably, before corner forming, it is possible to more accurately measure the rate of change in the peripheral length of the central portion of the thickness due to bending deformation of the corner during corner forming and drawing deformation in the circumferential direction. , the entrance side of the first roll, and after corner forming, the exit side of the third roll and the exit side of the fourth roll.

Here, the profile measurement performed in this step will be described in more detail with reference to FIG.

FIG. 7 is a diagram for explaining an example of a method for measuring the outer profile of corner forming. 11 is a diagram showing 11. FIG.

As a method for measuring the outer shape of the entire circumference of the steel pipe at each position by the outer profile meter 11 installed on the entrance side of the first corner forming stand, between the corner forming stands, and on the exit side of the final corner forming stand, Any method may be used as long as it is a method capable of continuously measuring axial vertical cross sections in the circumferential direction.

For example, as shown in FIG. 7, by arranging a plurality of optical two-dimensional displacement gauges as an outer profile meter 11 in the circumferential direction of the pipe, the outer shape of the steel pipe can be measured seamlessly. Moreover, it is preferable that there are 360 or more points for measuring the outer shape of the steel pipe in the circumferential direction of the pipe. If the number of measurement points is less than 360, the measurement resolution may deteriorate and the shape measurement error may increase. At this time, the plurality of outer profile meters 11 are arranged at the same longitudinal position so that the outer shape of the steel pipe can be measured in the pipe circumferential direction with high precision, and positioned so that the cross-sectional center of the steel pipe is the origin of the measurement coordinates. make adjustments.

In addition, although there is no particular specification for the position where the external profile meter 11 is installed, for example, on the entry side of the first corner forming stand, it is preferably at a position before preforming occurs, between the corner forming stands and On the output side of the final stand for forming corners, it is preferable that the formed steel pipe is at a position where the elastic recovery is sufficient, and it should be 0.5 to 2.0 m behind the bottom of each roll (downstream side of the stand). is preferred.

Moreover, it is preferable to install the external profile meter 11 on the entry side of the first corner forming stand and the exit side of the last corner forming stand. Preferably, it is also installed in a stand one stage upstream from the final stand. More preferably, an external profile meter 11 is installed between all the stands. In FIG. 5, among these plurality of external profile meters 11, the profile meter 11 for measuring the steel pipe shape before corner forming is designated as the first external profile meter 111, and the profile meter 11 for measuring the steel pipe shape after corner forming is designated as the second external profile meter 111. An external profile meter 112 is used.

As described above, the process of step S2 is completed, and the process proceeds to the process of step S3 (see FIG. 6 again).

In the process of step S3, the outer shape distribution calculation unit 123 of the control unit 122 determines, for example, from the biaxial coordinate data that the central portion of the width of the top surface of the steel pipe is the vertex, the vertex coordinates are (X ₀ , Y ₀ ), an arbitrary point is (X _i , Y _i ), the angle θ _i between the straight line L passing through the vertex and the center O of the steel pipe and the straight line L' passing through the arbitrary point and the center O of the steel pipe is calculated from a trigonometric function. Also, assuming an arc passing through an arbitrary point (X _i , Y _i ), its neighboring points (X _i−1 , Y _i−1 ), and points (X _i+1 , Y _i+1 ), the arc and the angle dθ _i forming the arc is calculated (see FIG. 8 ₎ . This processing is performed over one round in the circumferential direction of the tube, and the processing is performed over the entire circumference. This completes the processing of step S3, and proceeds to the processing of step S4.

In the process of step S4, if the control unit 122 has obtained the information of the circumference before corner shaping and the information of the circumference after corner shaping, which will be described later, the process proceeds to step S5. If the information on the perimeter after corner shaping has not been acquired, it is determined to return to the process of step S2.

Subsequently, in the process of step S5, the pre-corner forming peripheral length calculator 124 of the control unit 122 calculates any value from 3/8 times to 5/8 times the wall thickness t from the calculated curvature radius r _i ' of the arc. The radius of curvature r _i is used. Preferably, r _i =r _i ′−t/2 obtained by subtracting half the thickness is calculated as the radius of curvature of the arc. This process is performed for the entire circumference of the radius of curvature r _i ' of the arc formed by the arbitrary point calculated above and the points on both sides thereof. Here, the peripheral length _L0 of the central part of the wall thickness of the steel pipe at the position where the outer profile was measured before corner forming is calculated according to the formula (1). Note that the processing in step S5 may be performed simultaneously with the processing in steps S2 to S4 that are performed again.

Thereby, the process of step S5 is completed, and the process proceeds to step S6.

In the processing of step S6, the post-corner-forming circumference calculation unit 125 of the control unit 122 calculates the thickness from 3/8 times the wall thickness to 5/5 from the calculated curvature radius r _i ' of the arc, as in the processing in step S5. Use the radius of curvature r _i minus any eight times. Preferably, r _i =r _i ′−t/2 obtained by subtracting half the thickness is calculated as the radius of curvature of the arc.
This processing is performed for the entire circumference of the radius of curvature r _i ' of the arc formed by the calculated arbitrary point and the points on both sides thereof. Here, the peripheral length _Ln of the thickness central portion of the steel pipe at the position where the outer profile is measured is calculated according to Equation (2). Here, n indicates the corner forming stand number, for example, L1 indicates the circumference after corner forming in the _first corner forming stand (first roll).

As the corner forming progresses, a flat plate portion is formed, and the radius of curvature r _i ' of the arc becomes infinite, making it impossible to calculate r _i ×dθ _i . In that case, the length of the line segment connecting the points (X _i-1 , Y _i-1 ) and (X _i+1 , Y _i+1 ) is calculated, r _i ×dθ _i = {(X _i+1 −X _{i −1} ) ² +(Y _i+1 −Y _i−1 ) ² } ^1/2 . In view of this point, it is preferable to set in advance the upper limit value of the radius of curvature r _i ' of the arc that can employ the above formula (2). If this upper limit is exceeded, r _i ×dθ _i ={(X _i+1 −X _i−1 ) ² +(Y _i+1 −Y _i−1 ) ² } ^1/2 . The above upper limit is preferably 7000 mm. More preferably it is 5000 mm.

From the viewpoint of measurement accuracy, the position in the thickness direction of the steel pipe whose circumference is measured in step S5 (position 3 t/8 to 5 t/8 in the thickness direction from the pipe surface), and the circumference is measured in step S6. The position in the thickness direction of the steel pipe (the position in the thickness direction from 3t/8 to 5t/8 from the pipe surface) is preferably the same.

Thereby, the process of step S6 is completed, and it progresses to the process of step S7.

In the process of step S7, the circumference length change rate calculation unit 126 of the control unit 122 determines the circumference length _Ln of the thickness central portion and the like at the position where the outer profile is measured, and the circumference length _L0 of the thickness central portion and the like. A peripheral length change rate r _n (see the following formula (3)) is calculated by dividing the difference by the peripheral length L ₀ of the central portion of the thickness. The output unit 128 of the control unit 122 outputs this circumferential length change rate r _n to the display device 15 such as a display device, and the circumferential length change rate r A process for displaying _n can be performed. Thereby, the process of step S7 is completed, and the process proceeds to step S8.

In the process of step S8, the corner forming stand state determination unit 127 of the control unit 122 determines the state of the corner forming stand. Specifically, the angle forming stand state determination unit 127 determines that the rate of change in the peripheral length r _n of the thickness central portion, etc. at the position where the outer profile is measured is the predetermined target corner after final forming. Determine whether the permissible range of the perimeter change rate (r _min or more, r _max or less) of the thickness center of each corner forming stand for obtaining the radius of curvature R is satisfied, and if it is satisfied, step The process of S8 is completed, the current roll position of each roll and _rn are stored in the storage unit 130 as performance data, and the process proceeds to step S10. If not, the process of step S8 is completed and the process proceeds to step S9.

In the process of step S<b>9 , the roll position adjusting section 129 of the control section 122 adjusts the roll position of the corner forming stand 9 based on the determination by the corner forming stand state determining section 127 . Specifically, the roll position adjustment unit 129 adjusts the thickness of the roll of the corner forming stand 9 existing between the position where the outer profile is measured and the position where the outer profile is measured on the upstream side. The amount of adjustment of each roll position is adjusted according to the amount of deviation from the median value of the permissible range of the perimeter change rate of the thickness center portion of each square forming stand in the perimeter change rate r _n of the thickness center portion etc. calculate. Regarding the adjustment amount, the adjustment amount of the roll position is calculated from the function of the roll position of each roll formulated by an approximate expression using the performance data stored in the storage unit 130 and the circumferential length change rate _rn . The roll position adjusting unit 129 causes the roll position adjusting device 16 to move the roll position of the corresponding corner forming stand according to the calculated roll position. At the start of step S9, the above-described formulas (approximate formulas) are readjusted based on the current roll position of each roll and the circumferential length change rate r _n stored as actual data in the storage unit 130 . Step S9 is completed by causing the roll position adjustment device 16 to move the roll position, and the process proceeds to step S1.

In the process of step S10, the output unit 128 causes the display device 15 to display the circumference change rate _rn . This completes the manufacturing management process.

As described above, in the embodiments of the present invention, the above-described manufacturing control device, manufacturing control method, manufacturing control system having the above-described manufacturing control device, and square steel pipe using a corner forming stand controlled by the above-described manufacturing control method is provided.

A hot-rolled steel sheet is continuously formed into an open tube with an elliptical cross-section by a group of cage rolls and a group of fin pass rolls, then the opposite end surfaces of the open tube are heated to the melting point or higher by high-frequency induction heating or high-frequency resistance heating, and squeeze rolls are used to form the open tube. It was pressure welded and used as a base pipe of an electric resistance welded steel pipe. The obtained electric resistance welded steel pipe was formed into a cylindrical shape by a group of sizing rolls of two stands, and then corner-formed by a group of corner-forming rolls of four stands to achieve a wall thickness of 9 mm and an outer diameter of 500 mm and a wall thickness of 28 mm and an outer diameter of 500 mm. of square steel pipes were obtained. In this embodiment, the outer shape refers to the vertical diameter and horizontal diameter of the square steel pipe in a cross-sectional view perpendicular to the pipe axis direction. The square steel pipe used in this example had a substantially square cross section and had the same vertical diameter and horizontal diameter.

These square steel pipes were formed using the same group of corner forming rolls so that the target corner curvature radius R of the outer surface was 2.5 times or 3.5 times the wall thickness, and the target corner curvature radius R The roll position of the square forming stand was adjusted in order to obtain a square steel pipe with an allowable dimensional error within ±0.5 times the wall thickness.

The external profile meter 11 was installed on the entry side of the first corner forming stand and the exit side of each corner forming stand, and was installed at a position 1.0 m behind the bottom of the roll (downstream side of the stand). In the manufacture of square steel pipes, square forming is performed using a corner forming stand that has been subjected to manufacturing control processing to adjust the roll position determined from the change rate of the circumference of the steel pipe such as the central part of the wall thickness by the external profile meter 11. As an example of the present invention, a comparative example was obtained by performing corner forming using a corner forming stand that was not subjected to manufacturing control processing. In addition, in the production of the square steel pipe, manufacturing control processing was performed to adjust the roll position obtained from the rate of change in the circumference of the steel pipe such as the central part of the wall thickness by the external profile meter 11. From the first corner forming stand to the final Perimeter change rate r _n (r ₁ ∼r ₄ ) were calculated as examples of the present invention, and comparative examples were obtained by calculating the circumferential length change rates r _n (r ₁ to r ₄ ) at other positions.
When calculating the circumferential length change rate of the thickness central portion from the external profile, geometric calculation was performed from data of 720 points in the circumferential direction.
A radial gauge was used to measure the radius of curvature of the corner outer surface of 100 square steel pipes thus obtained. Table 1 shows the measured maximum and minimum corner curvature radii R of square steel pipes. In the inventive examples, the error from the target radius of curvature of the outer surface of the corners could be suppressed to within ±0.5t (t: wall thickness) in all the square steel pipes. The radius error was greater than ±0.5t.

From the results shown in Table 1, all invention examples yield square steel pipes that satisfy the target curvature radius R of corner portions.

1 Steel strip 2 Leveler 3 Cage roll group 4 Fin pass roll group 5 Squeeze roll 6 Welding machine 7 Electric resistance welded steel pipe 8 Sizing roll group (sizing stand)
9 Corner forming roll group (corner forming stand)
10 square steel pipe 11 external profile meter 12 manufacturing control device 15 display device (display device)
16 roll position adjusting device 20 manufacturing management system 121 input unit 122 control unit 123 outer shape distribution calculation unit 124 pre-angle forming circumference calculation unit 125 post-angle forming circumference calculation unit 126 circumference change rate calculation unit 127 angle forming stand state determination unit 128 output section 129 roll position adjustment section 130 storage section

Claims (7)

A manufacturing control device used for manufacturing a square steel pipe by square forming a material steel pipe with a square forming stand,
Circumferential length at a position (t: wall thickness) in the thickness direction of 3t/8 to 5t/8 from the pipe surface of the material steel pipe before corner forming, and wall thickness from the pipe surface after corner forming. a circumferential length change rate calculation unit that calculates a circumferential length change rate from the difference in the circumferential length at positions in the direction of 3t/8 to 5t/8;
A manufacturing control device for square steel pipes, comprising: a square forming stand state determination unit that determines a state of the square forming stand based on the circumferential length change rate. 2. The square shaped steel pipe manufacturing control device according to claim 1, further comprising an output section for outputting a determination result by said square forming stand state determining section. 3. The square shaped steel pipe manufacturing control device according to claim 1, further comprising a roll position adjusting section for adjusting a roll position of said square forming stand based on the determination by said square forming stand state determining section. A manufacturing control method for manufacturing a square steel pipe by square forming a material steel pipe with a square forming stand, comprising:
Circumferential length at a position (t: wall thickness) in the thickness direction of 3t/8 to 5t/8 from the pipe surface of the material steel pipe before corner forming, and wall thickness from the pipe surface after corner forming. a circumferential length change rate calculation step of calculating a circumferential length change rate from the difference in the circumferential length at positions in the direction of 3t/8 to 5t/8;
and a corner forming stand state determining step for determining the state of the angle forming stand based on the perimeter length change rate. A square steel pipe manufacturing method for manufacturing a square steel pipe by square forming a material steel pipe with a square forming stand, comprising:
A method for manufacturing a square shaped steel pipe, comprising a corner forming step of performing corner forming with a corner forming stand whose state has been determined in the angle forming stand state determination step according to claim 4 . Equipped with a square steel pipe manufacturing control device according to any one of claims 1 to 3,
Furthermore, as an external profile meter, at least
a first external profile meter for measuring the shape of the material steel pipe before corner forming;
a second profile profiler for measuring the shape after corner forming;
A manufacturing management system for square steel pipes. 7. The manufacturing control system for square steel pipes according to claim 6, further comprising a display device for displaying the judgment result of the state of the square forming stand by the square forming stand state judging section.

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