JP2023007638A - Welding management device of electric welded tube, welding management method of electric welded tube, manufacturing method of electric welded tube and welding management system of electric welded tube - Google Patents

Abstract

To provide a technique of improving measurement accuracy of a discharged molten steel quantity in electric-welding.SOLUTION: A welding management device 100 of an electric welded tube comprises: a prior-welding discharged molten steel area calculation unit 117 which calculates a first discharged molten steel area at a junction position on the basis of the first image information including the junction formed by converging both edge parts of an open pipe and molten steel discharged to the pipe outer surface before electric-welding; a post-welding discharged molten steel area calculation unit 118 which calculates a second discharged molten steel area occupied by the discharged molten steel at a position immediately below a roll center on the basis of the second image information including the molten steel discharged to the pipe outer surface and the position immediately below the roll center of a weld stand after the electric-welding; an upset-time discharged molten steel area calculation unit 119 which calculates an upset-time discharged molten steel area from a difference between the first discharged molten steel area and the second discharged molten steel area; and a welding state determination unit 120 which determines the quality of an electric-welding condition on the basis of the information including the upset-time discharged molten steel area.SELECTED DRAWING: Figure 1

Description

The present invention provides a welding control apparatus, an electric resistance welded steel pipe welding control method, an electric resistance welded steel pipe manufacturing method, and an electric resistance welded steel pipe manufacturing method for quantifying the discharge amount of molten steel formed during electric resistance welding of electric resistance welded steel pipes and suppressing welding defects. It relates to a welding management system for sewn steel pipes.

Electric resistance welded steel pipes are formed by continuously bending a steel plate or steel strip in the circumferential direction using roll forming, and then abutting both ends to form an open pipe with a circular cross section, which is then butted. Manufactured by continuous electric resistance welding of both edges of the open pipe.

During electric resistance welding, both the edges are heated to the melting point or higher by direct energization from a contact tip or an induced current from an induction coil, and immediately after that, the joints of both edges are abutted (upset) by squeeze rolls. At that time, the oxide (penetrator) generated during the melting and heating process of the steel plate or steel strip is forced to flow out to the inner and outer surfaces of the pipe by upset, and is discharged to the unnecessary part called the bead to suppress the occurrence of welding defects. ing. After electric resistance welding, the surplus portion is cut off from the pipe with a cutting tool or the like.

In order to prevent welding defects, the input power (heat input) and upset during welding are adjusted during pipe manufacturing. It remains in the seam weld and causes welding defects. If the upset is increased, welding defects do not occur, but the increase in wall thickness during electric resistance welding becomes excessive, causing the pipe to lose its thickness.

In addition, if the input power is insufficient, welding defects due to cold welding or non-welding will occur. circulates and welding defects occur.

Therefore, various techniques have been disclosed for suppressing welding defects in the manufacture of electric resistance welded steel pipes. For example, a welding management system for a welding process that visualizes electric resistance welding phenomena has been proposed.

Patent Document 1 describes a first V convergence point where both ends of a metal plate geometrically intersect and a second V convergence point where both ends of the metal plate meet, based on an image of an area including a V-shaped convergence portion. A welding management system has been proposed that adjusts the amount of heat input so that the distance to the convergence point and the V convergence angle at the first V convergence point are within the range of a relational expression set in advance.

Patent Document 2 acquires an image of electric resistance welding, a collision point detection unit that detects the collision points at both ends of the steel plate that converges in a V shape, and a circumferential direction both ends of the steel plate that converges in a V shape. Preliminarily set using the brightness level of the welded portion at which the molten portion inside the plate thickness of the steel plate begins to be discharged to the surface in either one of the V convergence point detection units that detect the V convergence point, which is the geometrical convergence point. There has been proposed a welding management system that converts the temperature conversion data into the temperature of the temperature measurement area and determines whether or not the temperature of the temperature measurement area is equal to or higher than a predetermined lower limit.

Patent Document 3 describes a geometric V convergence point, which is a geometric intersection of the extension lines of both ends of the metal plate before contact upstream of the abutting portions at both ends of the metal plate, and a butting point at which both ends of the metal plate start to contact. It has a step of detecting the distance from a certain V convergence point, and with respect to the input power at a certain managed point, the input power in the transition region from the second type welding state to the two-stage convergence type second type welding state. A welding management system that calculates the amount of deviation has been proposed.

Patent Document 4 proposes a welding method in which image analysis of electric resistance welding is performed, and the amount of heat input is increased when the variation in the circumferential direction of the outer edge line of the molten metal is smaller than a preset reference value. .

Japanese Patent No. 5079929 Japanese Patent No. 5549963 JP 2019-198877 A Japanese Patent No. 4532977

In Patent Document 1, the quality of the heat input amount is determined based on the distance between the first V convergence point and the second convergence point. Because of the lack of information on the upset, the penetrator emissions, which affect weld quality, cannot be controlled or taken into account. Therefore, there is a problem that welding defects cannot be completely suppressed.
Similarly, in Patent Document 2, since the information is on the V convergence point, there is no information on the squeeze roll upset, and the discharge of the penetrator cannot be considered.
The second type welding state and the second type welding state of the two-stage convergence type in Patent Document 3 are welding states that occur under certain combination conditions of heat input and welding speed. For example, the welding speed is sufficiently high. Since it is a welding state that is not seen in electric resistance welding, there is a problem that welding management has not been generalized.
In Patent Document 4, since the molten metal discharged by the upset of the squeeze roll flows out, the outer edge line of the molten metal changes, and thus the variation in the outer edge line of the molten metal in the circumferential direction is erroneously detected, and the heat input amount is set incorrectly. occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances. An object of the present invention is to provide a management method, a manufacturing method of an electric resistance welded steel pipe, and a welding management system for an electric resistance welded steel pipe.

In order to achieve the above object, the present inventors have conducted intensive research on a quantitative evaluation method for the amount of molten steel discharged with a penetrator on the outer surface of a pipe by a squeeze roll upset in electric resistance welding. As a result, the following facts were clarified.

Here, an example of a welded portion image of electric resistance welding shown in FIG. 3 will be described. FIG. 3 is a diagram showing an example of a welded portion image of electric resistance welding.
Conventionally, in electric resistance welding, heating is performed using a high-frequency current by a direct heating method or an induction heating method. At this time, both edge portions (both edge end faces) 202a and 202b of the open pipe are connected to the electric circuit until both edge portions (both edge end faces) 202a and 202b of the open pipe are joined at the V convergence point 204 shown in the welded portion image 20 of FIG. induced current flows. Due to the magnetic field generated from this induced current, an electromagnetic force perpendicular to the abutting surfaces of the edge portions 202a and 202b acts on the edge portions 202a and 202b of the open tube.
Both edges 202a and 202b of the open tube are locally heated to the melting point or higher by the induced current.

At this time, part of the molten steel 203a generated at both edge portions 202a and 202b (discharged molten steel 203a before welding) is discharged to the inner and outer surfaces of the pipe by electromagnetic force, and new surfaces are newly formed at both edge portions 202a and 202b. As it is generated, heating and discharging are repeated until the V convergence point 204 . Here, the nascent surface refers to a surface where the molten steel inside the surface at one moment breaks through the surface at the next moment and is exposed on the surface. The V convergence point 204 can be a geometrical intersection of parallel straight lines formed by both edges 202a and 202b of the open tube (see La and Lb in FIG. 4), but depending on the combination of heat input and welding speed is the downstream side of the V convergence point 204 (welding stand (welding stand) side where both the edge portions 202a and 202b are pressed against each other, reference numeral 205 side) without joining the both edge portions 202a and 202b on the V convergence point 204. In some cases, both edges 202a and 202b are physically joined together.

This phenomenon is caused by the fact that the molten steel at the end faces is discharged to the inner and outer surfaces of the pipe by electromagnetic force, with respect to the speed at which both edges 202a and 202b of the open pipe approach each other when the steel plate or steel strip advances toward the welding stand. This occurs under conditions slower than the speed at which a new surface is generated and the edges separate from each other. Specifically, the discharged molten steel (discharged molten steel) on the end face generated before welding is caused by the electromagnetic force of the current flowing on the end face, which causes the heating of electric resistance welding, to the inner and outer surfaces of the pipe. and pushed out. Since the bulk (molten steel volume) of the discharged molten steel disappears at the end faces, the distance between the end faces increases unless the end faces approach each other along the manufacturing process.

Therefore, when the points where the V convergence point 204 and the edges 202a and 202b are physically joined are the same, the V convergence point is the point where the V convergence point 204 and the edges 202a and 202b are physically joined. If the points do not match, the point where they are physically joined is the position where the maximum amount of molten steel is discharged from both edges 202a, 202b of the open pipe before welding.
The molten steel ejected onto the inner and outer surfaces of the pipe prior to welding remains around the bead during subsequent welding and is mixed with the molten steel ejected by the weld stand upset. In the welding stand, the penetrator generated on the joint surfaces of both edge portions 202a and 202b of the open pipe is physically discharged to the inner and outer surfaces of the pipe by upset. In order to suppress weld defects after welding, it is necessary to sufficiently discharge the penetrator by the above-mentioned upset, and as an indicator of the amount of discharge, the amount of discharged molten steel, which is the discharge medium of the penetrator, is an important control item. Become.

The amount of molten steel discharged from the welding stand can be controlled by adjusting the heat input and upset amount in operation, and the amount of molten steel discharged increases by increasing the heat input or increasing the upset amount. The amount of molten steel discharged from the welding stand is calculated from the amount of molten steel 203b discharged to the inner and outer surfaces of the pipe around the bead at 205 directly below the roll center of the welding stand where the discharge of molten steel from the welding stand is completed. Direct observation of the welding phenomenon using, for example, a high-speed camera revealed that it can be determined from the difference in the amount of molten steel discharged to the outside. It was also found that the amount of molten steel around the bead does not increase after passing the position 205 directly below the roll center of the welding stand.

The present invention is based on the above findings, and the gist thereof is as follows.
[1] A steel plate or steel strip is bent in the circumferential direction, both edges are butted to form an open pipe, and then both edges of the butted open pipe are upset using a welding stand. A welding management device for electric resistance welded steel pipes manufactured by welding,
Before electric resistance welding, based on the first image information including the joint formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe, the discharged molten steel occupied at the joint position. a pre-welding discharged molten steel area calculation unit for calculating the discharged molten steel area;
After electric resistance welding, the second discharged molten steel area occupied by the discharged molten steel at the position directly below the roll center is calculated based on the second image information including the position directly below the roll center of the welding stand and the molten steel discharged to the outer surface of the pipe. A post-welding discharged molten steel area calculation unit to calculate,
a molten steel discharge area calculation unit for calculating the discharged molten steel area during upset from the difference between the first discharged molten steel area and the second discharged molten steel area;
a welding state determination unit that determines whether an electric resistance welding condition is good or bad based on the information including the discharged molten steel area at the time of upset;
A welding management device for electric resistance welded steel pipes.
[2] the joining point included in the first image information;
The distance from the position directly below the roll center included in the second image information is
The welding management device for an electric resistance welded steel pipe according to [1], wherein the outer diameter of the steel pipe on the exit side of the welding stand is 30% or less in the pipe axial direction.
[3] The junction is
In the first image information for calculating the first discharged molten steel area, the point where both edges of the open pipe are joined in electric resistance welding, or the first image for calculating the first discharged molten steel area The electric resistance welded steel pipe welding management device according to the above [1] or [2], wherein the information is a V convergence point that is an intersection of straight lines approximated from both edge portions of the open pipe before electric resistance welding.
[4] The information including the discharged molten steel area at the time of upset is
The discharged molten steel area S at the time of upset,
pipe thickness t;
a coefficient A(r) set based on the upset amount r of the welding stand;
Welding management of the electric resistance welded steel pipe according to any one of [1] to [3], which has an emission parameter S×A(r)/t obtained from the S, the t, and the A(r). Device.
[5] A steel plate or steel strip is bent in the circumferential direction, both edges are butted to form an open pipe, and then both edges of the butted open pipe are upset using a welding stand. A welding control method for electric resistance welded steel pipes manufactured by welding,
Before electric resistance welding, the molten steel discharge area at the joint position based on the first image information including the joint formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe. A pre-welding discharged molten steel area calculation step for calculating the first discharged molten steel area;
After electric resistance welding, based on the second image information including the position directly below the roll center of the welding stand and the molten steel discharged to the outer surface of the pipe, the second discharged molten steel area, which is the discharged molten steel area at the position directly below the roll center A post-welding discharged molten steel area calculation step of calculating
a discharge molten steel area calculation step of calculating the discharged molten steel area during upset from the difference between the first discharged molten steel area and the second discharged molten steel area;
a judgment step of judging whether the electric resistance welding conditions are good or bad based on the discharged molten steel area at the time of upset;
Welding management method for electric resistance welded steel pipe.
[6] A steel plate or steel strip is bent in the circumferential direction, both edges are butted to form an open pipe, and then both edges of the butted open pipe are upset using a welding stand. A method for manufacturing an electric resistance welded steel pipe manufactured by welding,
A method for manufacturing an electric resistance welded steel pipe, wherein welding is controlled by the welding control method for an electric resistance welded steel pipe according to the above [5] during the electric resistance welding.
[7] A welding management device for an electric resistance welded steel pipe according to any one of [1] to [4];
Before electric resistance welding, the joint formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe are photographed, and after electric resistance welding, the position directly below the roll center of the welding stand, and a welding part imaging device for imaging the molten steel discharged to the outer surface of the pipe;
A welding management system for electric resistance welded steel pipes.

Here, in the present invention, the position directly below the roll center is not only strictly the position directly below the roll center, but also up to 10% or less of the outer diameter of the steel pipe downstream from the position directly below the roll center in the pipe axial direction. It may be any position within the area.

Further, in the present invention, the pipe thickness may be the target thickness of the steel pipe to be manufactured.

ADVANTAGE OF THE INVENTION According to this invention, the measurement accuracy of the discharged molten steel amount at the time of electric resistance welding can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the welding management apparatus and welding management system which show one example of the form for implementing this invention. 4 is a flow chart showing a processing procedure of the welding management device according to the embodiment; It is a figure which shows an example of the welding part image of electric resistance welding. It is explanatory drawing of each part of the welding part image of electric resistance welding. FIG. 5 is a diagram for explaining an example of a method of deriving a V convergence point when a welded portion image of electric resistance welding is binarized; FIG. 4 is a diagram for explaining an example of a method of deriving the discharged molten steel width and the discharged molten steel area before welding in image analysis of a welded portion of electric resistance welding; FIG. 4 is a diagram for explaining an example of a method of deriving the discharged molten steel width and the discharged molten steel area after welding in image analysis of a welded portion of electric resistance welding; FIG. 10 is a diagram for explaining an example of a method of deriving an area of discharged molten steel by upset of a squeeze roll in image analysis of a welded portion of electric resistance welding; FIG. 10 is a diagram for explaining an example of a method of dividing time for one revolution of a squeeze roll when deriving a discharged molten steel area due to an upset of the squeeze roll in image analysis of a welded portion of electric resistance welding; FIG. 4 is a diagram for explaining an example of a method of setting a threshold for determining whether the discharged molten steel area S×A(r)/t is good or bad;

A welding management device and a welding management system according to an embodiment of the present invention will be described in detail below with reference to the drawings. It should be noted that the present invention is not limited by this embodiment. Moreover, in the description of the drawings, the same parts are denoted by the same reference numerals.

First, with reference to FIG. 1, the flow of processing targeted by the present embodiment and the schematic configuration of a welding management system and a welding management device included in the system will be described. FIG. 1 is a diagram for explaining a welding management device and a welding management system showing one example of a form for carrying out the present invention.

The steel plate (or steel strip) is subjected to bending in the circumferential direction and continuously formed into a cylindrical shape by roll forming. While the stability of the cylindrical shape is ensured, the open tube 1 is formed while the abutting positions of both edge portions are centered. Thereafter, both edges of the open tube 1 are supplied with high-frequency current from the high-frequency oscillator 3 via a pair of contact tips 31a and 31b (or using an induction heating work coil (not shown)) to melt. heated until

Next, the open pipe 1 passes through a welding stand 40 surrounded by a group of rolls consisting of squeeze rolls 41a, 41b and top rolls 42a, 42b, and is pressure-welded at both edges so that the molten steel is applied to the outer surface (outer periphery of the tubular steel plate). surface) and welded (electric resistance welding).

Before electric resistance welding, the welded portion photographing device 10 photographs a junction formed by convergence of both edges of an open pipe and molten steel discharged to the outer surface of the pipe. After the electric resistance welding, the welded part photographing device 10 photographs the position directly below the roll center of the welding stand 40 and the molten steel discharged to the outer surface of the pipe. In the present embodiment, the position directly below the roll center is not limited to the position directly below the roll center, but may be up to 10% or less of the outer diameter of the steel pipe downstream from the position directly below the roll center in the pipe axial direction. It may be any position within the region.

The welded part photographing device 10 uses, for example, a camera and is installed so as to be able to photograph the upstream side of the welding stand 40, and photographs how both edges (welded parts) of the open pipe 1 are heated, melted, and pressed. The position of the weld imaging device 10 is adjusted so that a joint point (V convergence point) described later and the roll center of the squeeze roll are included in the captured image captured by the weld imaging device 10 . At this time, the camera may be either for color image capturing or for monochrome image capturing. The weld imaging device 10 also includes adjusters (not shown) such as a zoom lens and an exposure adjuster for adjusting the optical system. It is preferable that the field of view is 100 mm×40 mm or more and the resolution is as high as 100 μm/pixel or more. More preferably, it is 50 μm/pixel or more, and at this time, the number of pixels of the camera is preferably 1920×1080 or more. If the resolution is as low as less than 100 μm/pixel, the detection accuracy of molten steel may be remarkably deteriorated. In addition, the welding speed of electric resistance welding may exceed 100 m / min. It is preferable to set above. If the frame speed is less than 20 fps, there will be a region in the welded portion of the electric resistance welded pipe where image analysis of the weld cannot be performed, and there is a possibility that the weld defect will be overlooked.

Welding management device 100 acquires an image of a welded portion captured by welded portion imaging device 10 through input unit 110 . The welding management apparatus 100 is composed of a general-purpose computer such as a work station or a personal computer, and has an arithmetic processing function such as a CPU, an image processing function such as a GPU, and various memory functions such as ROM and RAM as an example of the storage unit 121 described later. In addition, it has a recording medium such as a hard disk connected by a data communication terminal, and outputs such as a graphic display device and an alarm device. The welding management device 100 uses a memory that stores processing programs and a CPU that executes the processing programs to detect molten steel before and after welding by the image processing unit 111, and to calculate the discharge molten steel area at the V convergence point and the position of the welding stand. Furthermore, welding determination by the welding state determination unit 120, output of determination results by the output unit 122, and the like are performed, and welding management processing is executed.

Specifically, the welding management device 100 performs a continuous bending process in the circumferential direction on a steel plate or steel strip, butts both ends to form a substantially tubular open pipe having a circular cross section, and then butts the open pipe. A welding management device for an electric resistance welded steel pipe manufactured by electric resistance welding that continuously upsets both edges of an open pipe using a welding stand, wherein both edges of the open pipe are controlled before electric resistance welding Calculate the first discharged molten steel area occupied by the discharged molten steel at the joint position based on the first image information including the joint formed by convergence and the molten steel discharged to the outer surface of the pipe Discharged molten steel area before welding Based on the calculation unit 117 and the second image information including the position directly below the roll center of the welding stand and the molten steel discharged to the outer surface of the pipe after electric resistance welding, the discharged molten steel at the position directly below the roll center is the second image information. A discharged molten steel area calculation unit 118 after welding that calculates the second discharged molten steel area, a discharged molten steel area calculation unit 119 that calculates the discharged molten steel area at the time of upset from the difference between the first discharged molten steel area and the second discharged molten steel area, and a welding state determination unit 120 that determines whether the electric resistance welding conditions are good or bad based on information including the discharged molten steel area due to the upset.

Welding management apparatus 100 may also include output unit 122 that outputs the determination result of welding state determination unit 120 .

In addition, the welding management device 100 has an image processing unit 111 that performs processing for calculating the discharged molten steel area corresponding to the discharged molten steel amount in the upset. A calculation unit 113, a junction detection unit 114, a molten steel edge detection unit 115, and a molten steel area calculation unit 116 may be provided. Each of these functions will be described later.

Further, the welding management system 11 includes the welding management device 100 and the weld imaging device 10 described above.

Here, a welding management processing procedure by the welding management device 100 will be described with reference to the flowchart of FIG. 2 . FIG. 2 is a flow chart showing a processing procedure of the welding management device of this embodiment. In the flowchart of FIG. 2, for example, the operation starts when the operator inputs an instruction to start the welding management process to the input unit 110, and the process proceeds to step S1.

In the process of step S1, the image processing unit 111 of the welding management device 100 acquires an image of the welded portion (first image information) from the welded portion imaging device 10 of the welding management system 11, and performs monochrome processing or binarization processing. I do. Here, the first image information includes the image information of the joint point formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe before electric resistance welding. , the first image information is used to calculate a first discharged molten steel area, which will be described later.

Then, the pipe edge detection unit 112 of the image processing unit 111 detects from the processed welded portion image 20 the edges of the edges on the joint surface side at the heating units 201 of both edge portions, which are hotter than the surroundings due to the heating of the open pipe 1 . Perform detection processing. Specifically, the pipe edge detection unit 112 performs edge detection by differential processing from the welded portion image 20 illustrated in FIG. An edge extraction image 21 is obtained by extracting both edge portions (edge end surfaces) 202a and 202b. For extraction of both edge portions 202a and 202b, image processing is performed in the vertical direction from the opening 206 where both edge portions 202a and 202b are not joined to each other, and the position where the edges are detected first is extracted as both edge portions 202a and 202b. , 202b. Thereby, the process of step S1 is completed, and the welding management process proceeds to the process of step S2.

In the process of step S2, the V convergence point calculation unit 113 of the image processing unit 111 calculates straight lines La and Lb that approximate both edge end faces 202a and 202b detected in the edge extraction image 21 (see FIG. 6). Specifically, the V convergence point calculation unit 113 calculates a straight line passing through arbitrary points in the end faces 202a and 202b of both edges by the method of least squares. Then, the V convergence point calculator 113 finds the intersection of the two straight lines La and Lb, and sets this as the V convergence point 204 .

At this time, the V convergence point calculation unit 113 sets the coordinate space for the edge extraction image 21 and performs conversion processing from the number of pixels of the image to the length unit. Here, a two-axis coordinate system of XY with the lower left end of the edge extraction image 21 as the origin is used, and the length is treated as millimeters, but it is not limited to this. In the conversion process from the number of pixels to the length unit, the number of pixels per 100 mm is detected by photographing a standard sample such as a gauge in the same field of view in advance, and the conversion process from the number of pixels to the length is performed. After the conversion process, the coordinate position of the V convergence point is calculated. Thereby, the process of step S2 is completed, and the welding management process proceeds to the processes of steps S3 and S4.

In the processes of steps S3 and S4, it is determined whether or not the V convergence point 204 and the point where the open pipe both edge end faces 202a and 202b actually physically join (hereinafter referred to as joining point 207) match. The joining point 207 is a point where both edge portions 202a and 202b of the open pipe are joined in electric resistance welding in the first image information, or both edges of the open pipe before electric resistance welding in the first image information. This is the V convergence point 204, which is the intersection point of the straight lines approximated by the portions 202a and 202b.

Here, the joining point detection unit 114 of the image processing unit 111 detects the position of the joining point 207 . The junction detection unit 114 detects the presence or absence of an opening 206 downstream of the position of the V convergence point 204 (the welding stand side, reference numeral 205 side). It is determined that both edge end faces 202a and 202b are joined. On the other hand, as shown in FIG. 5, if there is an opening 206 on the downstream side (welding stand side) of the position of the V convergence point 204, both edge end surfaces 202a and 202b must be joined at the V convergence point. be judged.

At this time, regarding the determination of the presence or absence of the opening 206, the welded portion image 20 is used when pixels having brightness smaller than a predetermined threshold exist continuously in the welding direction on the downstream side of the V convergence point 204. is determined to be the presence of the opening 206 . Further, the downstream end of the opening 206 is the most downstream position downstream of the V convergence point 204 where the opening 206 is determined to exist, and this point is regarded as the junction point 207 to detect the coordinate data. Here, in order to reduce the load of calculation processing, the region for detecting the opening 206 can be set in advance within an arbitrary region on the downstream side of the position of the V convergence point 204 . As a result, the processing of step S4 is completed, and if the V convergence point 204 and the junction point 207 match, the welding management processing proceeds to step S5. Proceed to processing.

In the process of step S5, the molten steel edge detection unit 115 of the image processing unit 111 determines the coordinates of the same longitudinal position as the V convergence point 204 determined to match the joining point 207, and the molten steel discharged to the outer surface of the pipe before welding. The edge of the molten steel 203a is detected. Here, using the edge extraction image 21, the coordinate point of the V convergence point 204 is set as the starting point, and the coordinates of the edge detection point are calculated in the vertical direction of the image (the circumferential direction of the pipe). Similar detection processing is performed on the opposite side of the pipe in the circumferential direction, and both edges of the molten steel 203a discharged to the outer surface of the pipe centering on the V convergence point 204 are detected. Here, if the molten steel 203a is not discharged to the outer surface of the pipe before welding due to insufficient heat input, the edges of the heating portion 201 of both edge portions (both edge end surfaces) 202a and 202b are detected. Thereby, the process of step S5 is completed, and the welding management process proceeds to the process of step S7.

In the process of step S6, the molten steel edge detection unit 115 detects the edge of the molten steel 203a discharged to the outer surface of the pipe before welding at the same longitudinal position coordinates as the joint 207. Here, using the edge extraction image 21, the coordinate point of the joint point 207 is set as a starting point, and the coordinates of the edge detection point are calculated while proceeding in the vertical direction of the image (the circumferential direction of the pipe). Similar detection processing is performed on the opposite side of the pipe in the circumferential direction, and both edges of the molten steel 203a discharged to the outer surface of the pipe centering on the junction 207 are detected. Thereby, the process of step S6 is completed, and the welding management process proceeds to the process of step S7.

In the process of step S7, the pre-welding discharged molten steel area calculation unit 117 of the molten steel area calculation unit 116 calculates the first Based on the image information, the first discharged molten steel area is calculated (pre-welding discharged molten steel area calculation step). Specifically, the pre-welding discharged molten steel area calculation portion 117 is located in the same longitudinal direction as the junction 207 (or V convergence point 204) formed by converging the open pipe both edge portions 202a and 202b before electric resistance welding. The discharged molten steel area (first discharged molten steel area) before welding is calculated using the edge of the molten steel 203a discharged to the outer surface of the pipe detected at the coordinates of .

Here, as an example of image information (first image information) processing by the pre-welding discharged molten steel area calculation unit 117, description will be made using FIG. FIG. 6 is a diagram for explaining an example of a method of deriving the discharged molten steel width and the discharged molten steel area before welding in image analysis of a welded portion of electric resistance welding.

First, the pre-welding discharged molten steel area calculation unit 117 uses the edge extraction image 21 to calculate the widths Wa and Wb of the heating unit 201 on the upstream side of the V convergence point 204 (fin pass roll side, opposite side of the welding stand side). Calculate The widths Wa and Wb of the heating portion are obtained from the difference between the approximate straight lines La and Lb of the two edge end faces 202a and 202b at the same longitudinal position and the circumferential coordinates of the edge of the heating portion 201. FIG. It is preferable to use an average value of several positions for calculating the heating portion widths Wa and Wb.

Next, the pre-welding discharged molten steel area calculation unit 117 calculates the circumferential coordinates of both edges of the molten steel 203a discharged to the outer surface of the pipe detected at the same longitudinal coordinates as the V convergence point 204 (joint point 207). From the difference, the discharged molten steel width Ma before welding at one point in the welding management process is calculated. For this discharged molten steel width Ma, using the welding speed v and the frame speed f of the photographing, the discharged molten steel area Sai before welding at one point in the welding management process is defined as _{Sai =} Ma x v/f. By totaling the discharged molten steel area before welding at this one-point time for the entire time of the welding management process, the discharged molten steel area Sa before welding is calculated, and this is the discharged molten steel area before welding (first discharged molten steel area ). It is preferable that the total time of the welding management process is at least the time of one cycle of the squeeze rolls. Here, if the molten steel 203a is not discharged to the outer surface of the pipe before welding due to insufficient heat input, the discharged molten steel area Sa is calculated as the sum of the heated portion widths Wa and Wb as the discharged molten steel width Ma. In addition, when the V convergence point 204 and the junction point 207 do not match, the detection and calculation processing that was performed based on the V convergence point 204 in the above content is similarly performed in the electric resistance welding in the first image information. Processing is performed with reference to the point where the two edge portions 202a and 202b of the open tube actually join to each other. Thus, the calculation of the first discharged molten steel area by the pre-welding discharged molten steel area calculation unit 117 can be performed based on the area information (discharged molten steel area Sa before welding) in the image information (first image information).
Thereby, the process of step S7 is completed, and the welding management process proceeds to the process of step S8.

In the processing of step S8, the molten steel edge detection unit 115 detects the edge of the discharged molten steel at the position 205 directly below the roll center of the welding stand. Here, description will be made with reference to FIG.

First, the image processing unit 111 of the welding management device 100 acquires an image of the welded portion (second image information) from the welded portion imaging device 10 of the welding management system 11, and performs monochrome processing or binarization processing. Here, the second image information includes the position 205 directly below the roll center of the welding stand and the image information of the molten steel discharged to the outer surface of the pipe after electric resistance welding. Used to calculate the secondary molten steel area.

A position 205 directly below the roll center of the welding stand can be specified in advance by manual input through the input unit 110 based on either the welded portion image 20 or the edge extraction image 21 . In addition, there is a method of marking a position directly below the roll center of the welding stand and detecting the position of the welding roll center in image detection, but any method may be used.

Next, starting from the same longitudinal position as the welding stand roll center position 205 and the same circumferential coordinates as the V convergence point 204, the vertical direction of the image (the circumferential direction of the pipe) is directly below the welding stand roll center. , the edge of the discharged molten steel 203b is detected and the coordinates of the detection point are calculated. This is also performed on the opposite side in the circumferential direction, and both edges of the discharged molten steel 203b directly below the roll center of the welding stand are detected. Thereby, the process of step S8 is completed, and the welding management process proceeds to the process of step S9.

In the process of step S9, the post-welding discharged molten steel area calculation unit 118 of the molten steel area calculation unit 116 generates image information (second image information) including molten steel at a position directly below the roll center (in particular, molten steel discharged in the circumferential direction of the pipe). Based on, the second discharged molten steel area is calculated (post-welding molten steel discharged molten steel area calculation step). Specifically, the post-welding discharged molten steel area calculation unit 118 uses the edge of the discharged molten steel 203b at the preset position 205 directly below the roll center of the welding stand of the pipe after electric resistance welding to determine the area directly below the roll center of the welding stand. Calculate the discharged molten steel area (second discharged molten steel area).

Here, as an example of image information (second image information) processing by the post-welding discharged molten steel area calculation unit 118, a description will be given using FIG. FIG. 7 is a diagram for explaining an example of a method of deriving the discharged molten steel width and the discharged molten steel area after welding in image analysis of a welded portion of electric resistance welding.

First, the post-welding discharged molten steel area calculation unit 118 calculates the discharged molten steel 203b directly below the roll center of the welding stand from the difference in the circumferential direction coordinates of both edges of the discharged molten steel 203b. A molten steel width Mb is calculated. The post-welding discharged molten steel area calculation unit 118 calculates the discharged molten steel area immediately below the roll center of the welding stand at a point in time when the welding management process is performed by using the welding speed v and the frame speed f of the photographing with respect to the discharged molten steel width Mb. Let Sb _i be Sb _i =Mb×v/f. By summing the discharged molten steel area Sb _i at the position 205 directly below the roll center of the welding stand at this one-point time for the entire time of the welding management process, the discharged molten steel area Sb directly below the roll center of the welding stand is calculated. The discharged molten steel area (second discharged molten steel area) directly below the roll center of the welding stand. The total time for the welding control process is at least the time for one cycle of the squeeze rolls. Here, when the molten steel 203b discharged to the outer surface of the pipe directly below the roll center of the welding stand is not generated due to insufficient heat input or upset, the discharged molten steel area Sb is the sum of the heated part widths Wa and Wb. Calculate as Mb. If the V convergence point 204 and the junction point 207 do not match, the detection and calculation processing that was performed based on the V convergence point 204 in the above content is similarly applied to both edge portions of the open pipe in electric resistance welding. Processing is performed with reference to the point where 202a and 202b actually join.

In this way, the calculation of the second discharged molten steel area by the before-after-welding discharged molten steel area calculation unit 118 is based on the area information (discharged molten steel area Sb immediately below the roll center of the welding stand) in the image information (second image information). It can be carried out.
Thereby, the process of step S9 is completed, and the welding management process proceeds to the process of step S10.

In the process of step S10, the molten steel discharged molten steel area calculation unit 119 of the molten steel amount calculation unit 116 calculates the discharged molten steel area during upset from the difference between the first discharged molten steel area and the second discharged molten steel area. discharge molten steel area calculation process). Specifically, the upset molten steel area calculation unit 119 uses the discharged molten steel area Sa before welding calculated in steps 7 and 9 and the discharged molten steel area Sb at the position 205 directly below the roll center of the welding stand to calculate the upset. Calculate the discharged molten steel area S (discharged molten steel area at the time of upset).

Here, description will be made using FIG. 8 in which the V convergence point 204 and the junction point 207 are coincident. Since the discharged molten steel before welding is small, the discharged molten steel area Sa before welding also includes the area Sh where the heating part 201 is detected. Therefore, the value obtained by subtracting the area Sh where the heating part 201 is detected from the discharged molten steel area Sa before welding is defined as the substantial discharged molten steel area Sa' before welding. Next, the discharged molten steel area calculation unit 119 calculates the difference between the discharged molten steel area Sb immediately below the roll center of the welding stand and the substantially discharged molten steel area Sa′ before welding, which is the discharged molten steel area S due to the upset (discharged molten steel during upset). area).

Further, in the above calculation, regarding the discharged molten steel area Sa′ before welding and the discharged molten steel area Sb immediately below the roll center of the welding stand, each of the areas discharged from both edges of the open pipe is targeted for a nearby position or the same position. It is preferable to calculate the discharged molten steel area S by upset using the area of molten steel.
The neighborhood means that the distance between the joining point 207 included in the first image information and the position 205 directly below the roll center included in the second image information is 30% or less of the outer diameter of the steel pipe on the exit side of the welding stand in the pipe axial direction. pointing to something Most preferably they are identical and said distance is zero.

Reference is now made to FIG. FIG. 9 is a diagram for explaining an example of a time division method for one rotation of the squeeze roll when deriving the discharged molten steel area due to the upset of the squeeze roll in the image analysis of the welded portion of electric resistance welding.
As shown in FIG. 9, the above distance adjustment method preferably includes a time lag dt in the calculation of the discharged molten steel area Sa' before welding and the discharged molten steel area Sb immediately below the roll center of the welding stand. The time lag dt is calculated by dividing the distance L between the V convergence point 204 and the position 205 directly below the roll center of the welding stand by the welding speed v, and the time dt=L/v. Even when the time lag dt is provided, the processing time t required for calculating the discharged molten steel area Sa' before welding and the discharged molten steel area Sb immediately below the roll center of the welding stand is at least the time for one cycle of the squeeze roll.
Thereby, the process of step S10 is completed, and the welding management process proceeds to the process of step S11.

In the process of step S11, the welding state determination unit 120 determines whether the electric resistance welding conditions are good or bad based on the information including the discharged molten steel area at the time of upset (determination step). Specifically, the welding state determination unit 120 uses the calculated discharged molten steel area S at the time of upset to determine whether the welding is good or bad.

Here, using steel pipes obtained under various welding conditions in advance, evaluation tests of the welds were performed offline, and the relationship between the properties of the obtained welds and the discharged molten steel area by upset calculated by the welding management system. and set the upper and lower thresholds for the molten steel discharge area due to a good upset. Off-line evaluation tests for welds include flatness tests, ultrasonic flaw detection tests for detecting oxides in welds, and Charpy impact tests for cutting test pieces from welds. Choose a method. Further, the discharged molten steel area S due to the upset has a proportional relationship with the thickness of the pipe. In determining the threshold value by various offline evaluation methods, the discharged molten steel area S at the time of upset is divided by the pipe thickness t, and the generalized discharged molten steel area S/t can be used to apply to the conditions of steel pipes with different wall thicknesses. . Here, the pipe thickness t can be the target thickness of the steel pipe to be manufactured.
Also, the generalized discharged molten steel area S/t is multiplied by a coefficient A(r) that is a function of the welding upset amount r. The amount of upset r can be calculated, for example, from the amount of change in the circumferential length of the central portion of the wall thickness of the steel pipe before and after passing through the welding stand, but is not limited to this. Electric resistance welding is performed by changing only the welding upset amount r in advance, and the ratio S _r /S _r0 of the discharged molten steel area S _r0 under the condition of the reference upset amount r ₀ and the discharged molten steel area S _r at an arbitrary upset amount r is calculated. derive From the distribution of the ratio S _r /S _r0 and the amount of upset r, a coefficient A(r) expressed by an arbitrary functional expression relating to r is derived by the method of least squares or the like.

Here, FIG. 10 shows the flattening ratio when the flattening test of the weld is performed based on JIS G3478: 2015 and the discharged molten steel area (discharge parameter) S × A (r) / t by generalized upset. Show relationship. A flatness of 2D/3 or less (D: tube outer diameter) is regarded as acceptable, and a threshold value for determining whether the discharged molten steel area (discharge parameter) S×A(r)/t is acceptable is set. This threshold is used to determine the quality of welding, and if the discharged molten steel area S / t × A (r) at the time of upset calculated under certain welding conditions is within the acceptable determination range, the welding is determined to be good. If it is outside, it is judged as unsuitable. Note that the result obtained by this process can be recorded in the storage unit 121 . Thereby, the process of step S11 is completed, and the welding management process proceeds to the process of step S12.

In the processing of step S12, the output unit 122 outputs the quality determination of the welding conditions obtained in step S11 to the outside. Since it is necessary for the operator to recognize the judgment result in order to output it to the outside, it is preferable to output it to a graphic device, an alarm device, or the like provided in the welding management system 11 . As a result, the processing of step S12 is completed, and a series of welding management processing is ended.

The welding management device for electric resistance welded steel pipes has been described above as an embodiment of the present invention.
The present invention also provides a welding management method used in the welding management device described above, an electric resistance welded steel pipe manufacturing method including this welding management method, and a welding management system having the welding management device.
Specifically, the manufacturing method of an electric resistance welded steel pipe involves subjecting a steel plate or steel strip to a continuous bending process in the circumferential direction, abutting both edges to form an open pipe, and then bending both edges of the abutted open pipe. On the other hand, in a method for manufacturing an electric resistance welded steel pipe manufactured by electric resistance welding that is continuously upset using a welding stand, welding is performed by the above-described welding system (welding control method) during electric resistance welding. manage.

As described above, according to the present invention, the area of discharged molten steel during electric resistance welding can be measured with high accuracy, which makes it possible to measure the amount of discharged molten steel quantitatively and accurately, thereby suppressing welding defects. can do.

Further, the embodiments of the present invention described above are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and other embodiments, examples, operational techniques, etc. made by those skilled in the art are all within the scope of the spirit of the present invention. included in the category of

In order to derive the threshold for the generalized molten steel discharge area (discharge parameter) S/t × A (r) during upset, various electric resistance welded pipes with a pipe thickness of 2 to 13 mm and a steel pipe outer diameter of φ89.1 mm Electric resistance welding was performed with a welding power of 200 kW to 800 kW, a welding upset amount r of 10% to 50% of the pipe thickness t, and a welding speed of 50 m/min. A CCD camera was used in various types of electric resistance welding, with a frame rate of 2000 fps, 1920 pixels in the longitudinal direction of the pipe, and a field of view of 60 mm in the longitudinal direction of the pipe. A moving image analysis was performed on the obtained images in a period corresponding to one rotation of the welding roll, and the discharged molten steel area S/t was calculated. In addition, in various steel pipes, S _r /S _r0 is calculated with a standard upset amount of t × 0.25 mm as a reference condition, and from the relationship between the upset amount r and S _r /S _r0 , r is used as a function A ( r) is derived from the least squares method. In this embodiment, A(r)=0.03×r ² +0.7×r+2.0, but A(r) is not limited to a quadratic function of r. A function that minimizes the error of the least-squares method may be set at the stage of The obtained steel pipe was cut into a length of 100 mm, and a flattening test was performed on the welded portion based on JIS G3478:2015 to measure the flattening ratio. Acceptance judgment of oblateness was set to 2D/3 or less, and as a result of calculating the range of discharged molten steel area S×A(r)/t at that time, it was 200 or more and 560 or less. Next, a steel pipe having a thickness t of 4 mm and an outer diameter of φ89.1 mm was welded at a welding speed of 50 m/min.

In Examples 1 and 2, the welding power was 450 kW, and the upset amount was adjusted so that the discharged molten steel area S/t×A(r) obtained by image analysis of electric resistance welding was 200 or more and 560 or less.

In Examples 3 and 4, the upset amount is 1 mm (pipe thickness t x 0.25), and the discharge molten steel area S x A (r) / t obtained by image analysis of electric resistance welding is 200 or more and 560 or less. adjusted the welding power to

In Example 5, the amount of upset was adjusted so that the discharged molten steel area S×A(r)/t exceeded 560.

In Example 6, the upset amount is 1 mm (pipe thickness t x 0.25), and the welding power is adjusted so that the discharge molten steel area S x A (r) / t obtained by image analysis of electric resistance welding is less than 200. bottom.

In Comparative Example 1, the welding power and the amount of upset were adjusted without conducting welding control during electric resistance welding, and the state of discharged molten steel was confirmed only visually.

100 samples of 100 mm length cut out from the obtained electric resistance welded steel pipe were subjected to a flattening test of the weld zone based on JIS G3478:2015 to measure the flattening ratio. Table 1 shows the ratio of the number of steel pipes satisfying 2D/3 or less for the acceptance judgment of oblateness. It can be seen that in Examples 1 to 6, the oblateness of the steel pipes is improved.

1 Open Tube 2 Fin Pass Roll 3 High Frequency Oscillator 31a, 31b Contact Tip 40 Welding Stand 41a, 41b Squeeze Roll 42a, 42b Top Roll 10 Welding Photographing Device 11 Welding Management System 100 Welding Management Device 110 Input Part 111 Image Processing Part 112 Pipe edge detection unit 113 V convergence point calculation unit 114 Junction detection unit 115 Molten steel edge detection unit 116 Molten steel area calculation unit 117 Discharged molten steel area calculation unit before welding 118 Discharged molten steel area calculation unit after welding 119 Discharged molten steel area calculation unit during upset 120 Welding state determination unit 121 Storage unit 122 Output unit 20 Welded image 21 Edge extraction image of welded image 201 Heating unit 202a, 202b Both edge end surfaces of open pipe 203a Discharged molten steel before welding 203b Discharged molten steel immediately below the roll center of the welding stand 204 V convergence point 205 Position directly below the roll center of the welding stand 206 Opening 207 Junction point La, Lb Straight line approximating both edge end faces of the open pipe Wa, Wb Heated part width v Welding speed f Flame speed Ma Located on the V convergence point Discharged molten steel width before welding at one point Mb Discharged molten steel width directly below the roll center at one point on the V convergence point Sb _i Discharged molten steel area directly below the roll center at one point on the V convergence point _Sai One point on the V convergence point Area of discharged molten steel before welding Sa Discharged molten steel area before welding on V convergence point Sh Area formed by heated part on V convergence point Sa' Discharged molten steel area before welding on actual V convergence point Sb V convergence point Discharged molten steel area directly below the upper roll center S Area of molten steel discharged by upset LV Distance between the V convergence point and the position directly below the roll center of the welding stand t Processing time for welding control dt When calculating the discharged molten steel area directly below the roll center time lag of

Claims (7)

A steel plate or steel strip is bent in the circumferential direction, both edges are butted to form an open pipe, and then both edges of the butted open pipe are upset using a welding stand. A welding management device for an electric resistance welded steel pipe,
Before electric resistance welding, based on the first image information including the joint formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe, the discharged molten steel occupied at the joint position. a pre-welding discharged molten steel area calculation unit for calculating the discharged molten steel area;
After electric resistance welding, the second discharged molten steel area occupied by the discharged molten steel at the position directly below the roll center is calculated based on the second image information including the position directly below the roll center of the welding stand and the molten steel discharged to the outer surface of the pipe. A post-welding discharged molten steel area calculation unit to calculate,
a molten steel discharge area calculation unit for calculating the discharged molten steel area during upset from the difference between the first discharged molten steel area and the second discharged molten steel area;
a welding state determination unit that determines whether an electric resistance welding condition is good or bad based on the information including the discharged molten steel area at the time of upset;
A welding management device for electric resistance welded steel pipes. the joining point included in the first image information;
The distance from the position directly below the roll center included in the second image information is
2. The welding management device for an electric resistance welded steel pipe according to claim 1, wherein the outer diameter of the steel pipe on the delivery side of the welding stand is 30% or less in the pipe axial direction. The junction is
In the first image information for calculating the first discharged molten steel area, the point where both edges of the open pipe are joined in electric resistance welding, or the first image for calculating the first discharged molten steel area 3. The electric resistance welded steel pipe welding management device according to claim 1 or 2, wherein the information is a V convergence point which is an intersection of straight lines approximated from both edge portions of the open pipe before electric resistance welding. The information including the discharged molten steel area at the time of upset is
The discharged molten steel area S at the time of upset,
pipe thickness t;
a coefficient A(r) set based on the upset amount r of the welding stand;
The welding management device for electric resistance welded steel pipes according to any one of claims 1 to 3, having an emission parameter S×A(r)/t obtained from said S, said t, and said A(r). A steel plate or steel strip is bent in the circumferential direction, both edges are butted to form an open pipe, and then both edges of the butted open pipe are upset using a welding stand. A welding control method for an electric resistance welded steel pipe,
Before electric resistance welding, the molten steel discharge area at the joint position based on the first image information including the joint formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe. A pre-welding discharged molten steel area calculation step for calculating the first discharged molten steel area;
After electric resistance welding, based on the second image information including the position directly below the roll center of the welding stand and the molten steel discharged to the outer surface of the pipe, the second discharged molten steel area, which is the discharged molten steel area at the position directly below the roll center A post-welding discharged molten steel area calculation step of calculating
a discharge molten steel area calculation step of calculating the discharged molten steel area during upset from the difference between the first discharged molten steel area and the second discharged molten steel area;
a judgment step of judging whether the electric resistance welding conditions are good or bad based on the discharged molten steel area at the time of upset;
Welding management method for electric resistance welded steel pipe. A steel plate or steel strip is bent in the circumferential direction, both edges are butted to form an open pipe, and then both edges of the butted open pipe are upset using a welding stand. A method for manufacturing an electric resistance welded steel pipe,
A method for manufacturing an electric resistance welded steel pipe, wherein welding control is performed by the electric resistance welded steel pipe welding control method according to claim 5 during the electric resistance welding. a welding management device for an electric resistance welded steel pipe according to any one of claims 1 to 4;
Before electric resistance welding, the joint formed by converging both edges of the open pipe and the molten steel discharged to the outer surface of the pipe are photographed, and after electric resistance welding, the position directly below the roll center of the welding stand, and a welding part imaging device for imaging the molten steel discharged to the outer surface of the pipe;
A welding management system for electric resistance welded steel pipes.

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