JP2023182081A - Welding management device for erw steel pipes, welding management system, welding management method for erw steel pipes, and method for manufacturing erw steel pipes - Google Patents

Abstract

To provide a welding management device for electric resistance welded (ERW) steel pipes, a welding management system, a welding management method for ERW steel pipes, and a method for manufacturing ERW steel pipes, which are configured to suppress occurrence of welding defects.SOLUTION: A welding management device for ERW steel pipes comprises: an edge temperature detection unit; an edge temperature difference calculation unit; a V convergence angle calculation unit; a post-weld discharge molten steel area calculation unit; and welding state determination unit that determines whether electric resistance welding conditions are good or bad.SELECTED DRAWING: Figure 1

Description

The present invention provides a welding management device for ERW steel pipes, which quantifies the temperature distribution at the open pipe edge immediately before ERW welding, and suppresses welding defects by combining the temperature distribution with constituent factors of the ERW welding phenomenon. The present invention relates to a welding management system, a welding management method for ERW steel pipes, and a method for manufacturing ERW steel pipes.

ERW steel pipes are produced by continuous bending of a steel plate or steel strip in the circumferential direction using roll forming, and the two ends are butted together to form a hollow tube with a circular cross section. It is manufactured by continuous electric resistance welding of both edges of the open tube.

During electric resistance welding, both edges are heated above the melting point by direct current using a contact tip or induced current by an induction coil, and immediately after that, the joints of both edges are abutted (upset) using a welding roll (squeeze roll). do. At that time, oxides (penetrators) generated during the melting and heating process of the steel plate or steel strip are caused to flow out to the inner and outer surfaces of the pipe using an upset, and are discharged into unnecessary parts called beads, thereby preventing the occurrence of welding defects. ing. After the electric resistance welding, the excess portion is removed from the tube using a cutting tool or the like.

In order to suppress welding defects, it is important to suppress the generation of penetrators and the aggregation of penetrators until welding as much as possible. For this purpose, it is necessary to adjust welding conditions so that the time from the melting heating process to the start of joining both edges does not become excessive. It is also important to discharge the penetrator smoothly into the bead during the upsetting process. To this end, it is necessary to reduce the deviation in the temperature distribution in the thickness direction of the edge portion until the start of welding, and to suppress failures in ejection of the penetrator due to solidification of the molten edge portion during upsetting.

As a method to solve the above problem, various techniques have been disclosed to prevent welding defects in the manufacture of ERW steel pipes. A welding management system for welding processes has been proposed.

Patent Document 1 detects the coordinates of the corner positions of the outer surface and inner surface of both edges of an open tube before abutment from a photographed image, calculates the temperature distribution of the outer surface and inner corner portions of both edges, and detects the coordinates. A welding temperature measurement method has been proposed in which the temperature of the edge at the detected coordinates is determined by comparing the detected coordinates with the calculated temperature distribution and the heating conditions of both edges are controlled.

Patent Document 2 acquires an image of electric resistance welding, acquires an image of a region including a V-convergence region where both edges of an open pipe before abutment converge in a V-shape, and detects the abutment of both edges in the image. The temperature of the region where the melted part starts to discharge to the surface inside the wall thickness is converted to the brightness level at either the geometric convergence point of both edges, and it is determined that the temperature is above the threshold value. An operational monitoring device for electric resistance welding has been proposed.

Japanese Patent Application Publication No. 11-33621 Patent No. 5549963

In Patent Document 1, since the temperature of the corners of the inner and outer surfaces of the joint end faces is measured, it is possible to monitor the influence of the lap state between both end faces before abutment, but it is Since there is no temperature data for the central part of the wall thickness, which is difficult to heat, there is a problem that sufficient weld characteristics cannot be obtained due to insufficient heating of the central part of the wall thickness.

In Patent Document 2, the acceptability of welding conditions is determined by setting a lower limit value for the temperature of the outer surface or inner surface at either the abutting part of both edges or the convergence point formed geometrically by both edges. However, similarly to Patent Document 1, there is a problem that sufficient welding characteristics cannot be obtained because there is no temperature data at the center of the wall thickness.

The present invention has been made in view of the above circumstances, and provides a welding management device for an ERW steel pipe, a welding management system, a welding management method for an ERW steel pipe, and a method for manufacturing an ERW steel pipe for suppressing weld defects. The purpose is to

In order to achieve the above object, the present inventors investigated the temperature distribution in the wall thickness direction of the end faces of both edges in electric resistance welding, and the angle (V convergence) formed geometrically by the straight lines formed by both edges at that time. We conducted extensive research on the influence of angle) on the morphology of the penetrator remaining in the weld after upsetting with a squeeze roll and on the properties of the weld. As a result, the following became clear.

Here, the flow of electric resistance welding will be explained using an example from heating to welding of electric resistance welding shown in FIG. 3.

Conventionally, in electric resistance welding, heating is performed using a high-frequency current using a direct current heating method or an induction heating method. At this time, a skin effect occurs in the initial stage of heating due to a heating phenomenon unique to high-frequency heating. Therefore, the temperature of the outer surface and inner surface of the edge portion becomes higher than that of the central portion of the wall thickness. This heat conduction at the edge portion causes heat to move toward the thick center portion. Next, as the heating process progresses, the distance between the end faces becomes closer, so a proximity effect occurs and the temperature increase rate at the center of the wall thickness increases. Then, while heating the extreme surface layer of the entire edge portion to the melting point, electric resistance welding is performed at the abutting portion 202 through upsetting with a squeeze roll. At this time, the molten metal at the edge is discharged to the outside of the tube together with the penetrators distributed on the surface, forming a weld bead 207.

As mentioned above, in electric resistance welding, the temperature at the center of the wall thickness tends to be low because heating is delayed compared to the inner and outer surfaces of the edge portions. If the heating of the center of the wall thickness of the edge portion is insufficient, there is a problem that a sufficient amount of weld metal cannot be obtained to discharge penetrators generated at the center of the wall thickness to the weld bead 207 during the heating process. Therefore, in the heating process, it is necessary to bring about the proximity effect at the center of the wall thickness at an early stage to reduce the temperature deviation in the wall thickness direction. Measures such as controlling the roll position of the forming rolls are required to adjust the butt state.

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 together to form an open tube, and then both edges of the butted open tube are upset using a stand by electric resistance welding. A welding control device for ERW steel pipes manufactured,
Before electric resistance welding, based on an image of the temperature distribution on the surface of at least one open pipe edge and spatial coordinates converted from pixel information of the image of the temperature distribution,
a pre-ERW welding edge temperature detection unit that detects the outer surface temperature T ₀ of the open pipe edge surface, the inner surface temperature T _i , the temperature Tc of the center of the wall thickness, and the coordinates of the temperature measurement position;
an edge temperature difference calculation unit that calculates a temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface;
A V convergence angle θ formed by straight lines converging along the open tube edge portion is calculated based on image information of a region including a junction point formed by straight lines converging along both edge portions of the open tube. A calculation section,
Based on image information including molten steel discharged to the outer surface of the pipe on the downstream side of the position directly below the roll center of the welding stand after electric resistance welding in the welding direction, from the position directly below the roll center of the welding stand in the welding direction a post-weld discharged molten steel area calculation unit that calculates a molten steel area A discharged to the outer surface of the downstream pipe;
Based on the information on the temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface, the temperature Tc at the center of the wall thickness, the V convergence angle θ, and the discharged molten steel area A, a welding condition determination section that determines whether welding conditions are acceptable;
A welding control device for electric resistance welded steel pipes.
[2] In determining the acceptability of the electric resistance welding conditions based on the amount of molten steel discharged to the outer surface of the pipe on the downstream side from the position directly below the roll center of the welding stand after electric resistance welding with respect to the welding direction, any of the above In [1], the welding power is adjusted to obtain a predetermined outer surface temperature T ₀ , a predetermined inner surface temperature T _i , and a predetermined temperature Tc at the center of the wall thickness for the V convergence angle θ. The described welding control device for ERW steel pipes.
[3] The welding control device for electric resistance welded steel pipes according to [1] or [2],
an edge temperature distribution imaging device that images the temperature distribution on both edge surfaces of an open tube before electric resistance welding;
Before ERW welding, the joint point formed by straight lines converging along both edges of the open pipe, and after ERW welding, on the outside of the pipe downstream of the position directly below the roll center of the welding stand in the welding direction. a welding part photographing device for photographing discharged molten steel;
A welding management system for ERW steel pipes.
[4] A steel plate or steel strip is bent in the circumferential direction, both edges are brought together to form an open tube, and then both edges of the butted open tube are upset using a stand by electric resistance welding. A welding control method for ERW steel pipes to be manufactured, the method comprising:
Before electric resistance welding, the outer surface temperature T 0 of the open tube edge surface, the inner surface temperature T ₀ , and A pre-ERW welding edge temperature detection step of detecting the surface temperature T _i , the temperature Tc at the center of the wall thickness, and the coordinates of the temperature measurement position;
an edge temperature difference calculation step of calculating a temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface;
A V convergence angle θ formed by straight lines converging along the open tube edge portion is calculated based on image information of a region including a junction point formed by straight lines converging along both edge portions of the open tube. calculation process,
Based on image information including molten steel discharged to the outer surface of the pipe on the downstream side of the position directly below the roll center of the welding stand after electric resistance welding in the welding direction, from the position directly below the roll center of the welding stand in the welding direction a post-weld discharge molten steel area calculation step of calculating an area A of molten steel discharged to the outer surface of the pipe on the downstream side;
Based on the information on the temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface, the temperature Tc at the center of the wall thickness, the V convergence angle θ, and the discharged molten steel area A, a welding condition determination step for determining whether welding conditions are acceptable;
Welding management method for ERW steel pipes, including:
[5] A method of manufacturing an ERW steel pipe using the welding control method for an ERW steel pipe described in [4] above.

According to the present invention, an electric resistance welded steel pipe having excellent quality can be obtained by welding while measuring the temperature distribution in the wall thickness direction and welding conditions during electric resistance welding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a welding management device and a welding management system including the same, showing an example of an embodiment of the present invention. It is a flowchart which shows the processing procedure of the welding management system of this embodiment. It is a figure which shows an example of the form of electric resistance welding. It is an explanatory view of each part of a welding part image of electric resistance welding. The quality of the weld is determined based on the results of a flattening test under various conditions of the temperature Tc at the center of the wall thickness and the area A of discharged molten steel in electric resistance welding, and the upper and lower limits of the area of discharged molten steel at the temperature Tc of the center of each thickness are determined. FIG. 6 is a diagram for explaining an example of a method of setting Amax and Amin and deriving a function that passes through each upper and lower limit point. The quality of the weld is determined based on the results of a flattening test under various conditions of the temperature Tc at the center of the wall thickness and the area A of discharged molten steel in electric resistance welding, and the upper and lower limits of the area of discharged molten steel at the temperature Tc of the center of each thickness are determined. After setting Amax and Amin and deriving a function that passes through each upper and lower limit point, determine the upper and lower limits ΔTmax and ΔTmin of the temperature difference between the outer and inner surfaces of the pipe edge surface at the specified position to eliminate weld defects. FIG. 3 is a diagram for explaining an example of a derivation method. At each V convergence angle θ in electric resistance welding, the relationship between the temperature Tc at the center of the wall thickness and the area A of discharged molten steel is determined from the results of the flattening test under each condition of the temperature Tc at the center of the wall thickness and the area A of discharged molten steel. FIG. 3 is a diagram for explaining an example of a method for deriving a tolerance range under arbitrary welding conditions by deriving a distribution of a welding tolerance range from , and interpolating the distribution of the welding tolerance range at each V convergence angle θ. FIG. 7 is a diagram showing the results of deriving the allowable range of the temperature Tc at the center of the wall thickness at the designated position and the discharged molten steel area A when the V convergence angle θ is 5 degrees.

EMBODIMENT OF THE INVENTION Hereinafter, a welding management device, a welding management system including the same, and a welding management method for electric resistance welded steel pipes, which are one embodiment of the present invention, will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are denoted by the same reference numerals.

First, with reference to FIG. 1, a flow of processing targeted by this embodiment and a schematic configuration of a welding management apparatus including a welding management system will be described. FIG. 1 is a diagram for explaining a welding management device and a welding management system including the same, showing one example of an embodiment of the present invention. After the steel plate (or steel strip) is continuously formed into a cylindrical shape by roll forming, while proceeding in the welding direction 4 in the figure, the stability of the cylindrical shape is ensured by the fin pass rolls 2, and both edges are The open tube 1 is formed while centering the butt positions of the parts. Thereafter, a high frequency current is supplied from the high frequency oscillator 3 to both edges of the open tube 1 through the pair of contact tips 31a and 31b, and the edges are heated until they melt. It is also possible to use an induction heating work coil instead of the contact tips 31a, 31b.

Next, the open tube 1 passes through a welding stand 40 surrounded by a roll group consisting of squeeze rolls 41a, 41b and top rolls 42a, 42b, and both edges are pressed together, and molten steel is applied to the outer surface (the outer periphery of the tubular steel plate). It is welded (erw welding) while being discharged to the surface).

The edge temperature distribution imaging device 10 is a thermometer capable of measuring temperature distribution in a two-dimensional image, such as a thermography device, and is a thermometer that can measure the temperature distribution in a two-dimensional image, for example, by measuring the flesh of the edge portion of the open tube 1 located between the contact tips 31a, 31b and the welding stand 40. It is installed so that the entire thickness can be photographed, and the heated surface from the outer surface to the inner surface is photographed at least at one of the opposing edges. At this time, the thermometer may be any thermometer that can measure temperature distribution, such as a radiation thermometer or a two-color thermometer. The edge temperature distribution photographing device 10 also includes adjusters such as a zoom lens and an exposure adjuster for adjusting the optical system. It is preferable to ensure a resolution of 500 μm/pixel or less with a photographic field of view of 100 mm×40 mm. More preferably, it is 100 μm/pixel or less, and in this case, the number of pixels of the camera is preferably 1920×1080 or more. If the resolution is high, such as more than 500 μm/pixel, the edge temperature detection accuracy may deteriorate significantly.

The welding part photographing device 11 is installed to be able to photograph the downstream and upstream sides of the welding direction 4 with respect to the squeeze roll center of the welding stand 40 using, for example, a camera. (part) is heated, melted, and pressed together. The position of the welding part photographing device 11 is adjusted so that the photographed image taken by this welding part photographing device 11 includes a joining point (V convergence point), which will be described later, and the roll center of the squeeze roll. At this time, the camera may be for capturing color images or monochrome images. The welding part photographing device 11 also includes adjusters such as a zoom lens and an exposure adjuster for adjusting the optical system. It is preferable to ensure a resolution of 100 μm/pixel or less with a photographic field of view of 100 mm×40 mm. More preferably, it is 50 μm/pixel or less, and in this case, the number of pixels of the camera is preferably 1920×1080 or more. If the resolution is greater than 100 μm/pixel, the detection accuracy of molten steel may deteriorate significantly.
In addition, the welding speed of electric resistance welding may exceed 100 m/min, and in order to photograph any shooting point more than once within a field of view of 100 mm, the frame speed must be set to 20 fps or more. It is preferable to set it to . If the frame speed is less than 20 fps, there will be areas in the welded portion of the electric resistance welded pipe where image analysis of welding cannot be performed, and welding defects may be overlooked.

The welding management device 1000 uses an edge temperature distribution imaging data input unit 100 and a welded area imaging data input unit 110 to acquire images of the welded portion captured by the edge temperature distribution imaging device 10 and the welded portion imaging device 11, respectively. The welding management device 1000 is composed of a general-purpose computer such as a workstation or a personal computer, and has arithmetic processing functions such as a CPU, an image processing function such as a GPU, and various memory functions such as ROM and RAM as examples of a storage unit 1403 described later. It also has outputs such as a recording medium such as a hard disk connected to a data communication terminal, a graphic display device, and an alarm device. In the welding management device 1000, the temperature distribution processing unit 121 uses a memory that stores a processing program, etc., a CPU that executes the processing program, etc. Detection of temperature distribution in the wall thickness direction from the outer surface to the inner surface of the edge portion, converting the coordinates (position) of the space where the temperature distribution is imaged by the coordinate space calculation section 123, and detecting the temperature distribution from the outer surface of the heated edge by the data processing section 124. Extracting the temperature distribution at a specified position in the pipe longitudinal direction in the temperature distribution up to the inner surface, and calculating the temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface at the specified position using the edge temperature difference calculation unit 125. A series of processes such as , etc. are performed. In parallel, in the welding image processing section 131, the tube edge image detection section 132 detects red-hot edges at both ends around the V convergence point, the V convergence angle calculation section 133 calculates the V convergence angle θ and the V convergence point, and welding. A series of processes are performed, such as detection of the position where both edges of the pipe actually join by the point detection unit 134, and calculation of the area A of discharged molten steel discharged to the outer surface of the pipe downstream from the welding stand by the post-weld discharge molten steel area calculation unit 135. It will be done. Further, the welding state determination unit 1401 performs welding determination, the output unit 1402 outputs the determination results, and performs welding management processing.

Here, the welding management processing procedure performed by the welding management apparatus 1000 will be described with reference to the flowchart of FIG. 2. FIG. 2 is a flowchart showing the processing procedure of the welding management device of this embodiment. In the flowchart of FIG. 2, for example, the start occurs at the timing when the operator inputs an instruction to start the welding management process to the edge temperature distribution imaging data input unit 100 and the welding area imaging data input unit 110, and steps S1 and S6 start. Processing proceeds in parallel.

In the process of step S1, the pre-ERW welding edge temperature detecting unit 122 detects a signal from the edge temperature distribution photographing device 10 to at least one of both edges of the open pipe 1 heated by high-frequency heating in a section until welding. acquires two-dimensional temperature distribution data over the entire thickness of the edge portion before welding. Here, two-dimensional temperature distribution data on the joint surface of the edge portion, that is, in the pipe longitudinal direction and wall thickness direction, is extracted from the captured temperature distribution data. 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, a plurality of coordinate standard points are detected from the two-dimensional temperature distribution data captured in the process of step S1 or the image captured by the CCD camera attached to the edge temperature distribution imaging device 10. , the coordinate space calculation unit 123 performs spatial coordinate conversion from pixels to units of length. The coordinate standard points referred to herein are preferably markers whose coordinate positions or distances between each standard point are obvious in advance, but this is not a limitation. By detecting the distance between two arbitrary standard points and inputting the real spatial distance of the distance between the standard points, the coordinate space calculation unit 123 performs spatial coordinate transformation in the image of temperature distribution data. At the same time, the origin of the two-dimensional coordinates is set at an arbitrary position in the image of the temperature distribution data. Further, the arithmetic expressions necessary for coordinate transformation from pixels to units of length may be derived in advance. Thereby, the process of step S2 is completed, and the welding management process proceeds to the process of step S3.

In the process of step S3, the data processing unit 124 extracts the temperature distribution in the wall thickness direction of the pipe edge portion at an arbitrary longitudinal position of the pipe together with coordinate values from the temperature distribution data after the above-described spatial coordinate conversion process. The data processing unit 124 extracts a range including a region in the longitudinal direction of ±0.5 mm with respect to the specified longitudinal position of the pipe, and extracts a region of the entire thickness of the pipe edge portion. Corners corresponding to the outer and inner surfaces of the pipe edge are heated significantly due to the skin effect peculiar to high-frequency heating. Therefore, in the temperature distribution in the wall thickness direction, the temperature is high mainly at the corners of the outer surface and inner surface of the tube edge portion. To determine the full thickness region, the distance between the peaks at the outer and inner surface positions of the tube edge in the temperature distribution in the wall thickness direction is taken as the tube wall thickness detected from the temperature distribution, and the tube wall thickness that was input in advance is compared with the tube wall thickness detected from the temperature distribution. If the error is 3% or less, the temperature distribution in the wall thickness direction is extracted from the peak apex of the temperature distribution around the outer surface of the tube edge portion as the origin to the peak apex of the temperature distribution around the tube edge portion.
If the error exceeds 3%, it is determined that an appropriate temperature distribution is not obtained, and the field of view adjustment of the edge temperature distribution photographing device 10 (the image photographed by the CCD camera attached to the edge temperature distribution photographing device 10) is performed. , a plurality of coordinate standard points are detected, and the coordinate space calculation unit 123 performs spatial coordinate transformation from pixels to units of length).The process from step S1 is performed again, and the error is 3. Repeat until it is below %. Thereby, the process of step S3 is completed, and the welding management process proceeds to the process of step S4.

In the process of step S4, the data processing unit 124 extracts the temperature at the center position between the temperature peaks at the outer surface and inner surface positions of the pipe edge portion using the extracted temperature distribution data in the wall thickness direction, This is defined as the temperature Tc of the central portion of the wall thickness. At the same time, the temperatures at the peak apex positions of the temperature distribution around the outer surface and inner surface positions of the pipe edge portion are extracted as the outer surface temperature T _o and the inner surface temperature T _i , respectively.
Thereby, the process of step S4 is completed, and the welding management process proceeds to the process of step S5.

In the process of step S5, the edge temperature difference calculation unit 125 calculates the temperature difference ΔT using the extracted outer surface temperature T _o and inner surface temperature T _i of the pipe edge portion. Here, the above-mentioned temperature difference ΔT is calculated by subtracting the outer surface temperature T _o from the inner surface temperature T _i and is stored with the positive or negative sign attached to the difference value. Thereby, the process of step S5 is completed, and the welding management process proceeds to the process of step S9.

In the process of step S6, which is performed in parallel with steps S1 to S5, the welding image processing unit analyzes the tube edge portion, which is heated red-hot by high-frequency heating, based on the image taken by the welding portion photographing device 11. A tube edge image detection unit 132 of 131 performs edge detection. Here, a differential method is used as the edge detection method, but the method is not limited to this. This will be explained in detail with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing an example of a form of electric resistance welding, and FIG. 4 is an explanatory diagram of each part of a welded part image of electric resistance welding.
First, an edge detection image 20 of the welding part is obtained from changes in brightness around the heating part 201 using a captured image. Specifically, by a gradient method using a first-order differential, the boundary between a molten steel part with high brightness and a part other than molten steel parts with low brightness is determined as a position where the extreme value of the brightness change is shown.
In this edge detection image 20 of the welded part, image processing is performed in the vertical direction from the opening 205 where both edges are not joined, and the position where the edge is first detected is set as a point on each edge. . This process is repeated at several points along the entire length of the opening 205 in the longitudinal direction, and a straight line is obtained by approximating the end faces of both edges of the open pipe using the least squares method from the plurality of points detected on each edge. Approximate La and Lb. Here, the opening 205 is an area sandwiched between the heating parts 201 on both edges, and the positions included in the opening 205 may be manually specified in advance before detecting points on each edge. However, it is not limited to this. 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 V convergence angle calculation unit 133 calculates and extracts the V convergence angle θ using the straight lines La and Lb calculated by detecting both edges of the open pipe described above. The V convergence angle θ in the edge detection image of the weld is an angle formed by two straight lines La and Lb, and is an acute angle on the opening 205 side. Thereby, the process of step S7 is completed, and the welding management process proceeds to the process of step S8.

In the process of step S8, the post-weld discharged molten steel area calculation unit 135 calculates the area A of molten steel discharged to the outer surface of the pipe after the welding stand (SQ stand) 40. Here, the position after the SQ stand 40 indicates a position downstream from the position 204 directly below the roll center of the SQ stand in the welding direction, and the position is specified in advance. The specification method includes a method of directly specifying the coordinate position and a method of detecting the coordinate position of a marker indicating the position 204 directly below the roll center of the SQ stand, but is not limited to this method. Using the image captured by the welding part photographing device 11, the discharged molten steel downstream of the position 204 directly below the roll center of the SQ stand is defined as the discharged molten steel 203 after the SQ stand. The area of pixels occupied by the discharged molten steel 203 after this SQ stand is detected as the area of molten steel discharged to the outer surface of the tube, and a group of pixels having a brightness greater than a predetermined threshold is determined to be the area of molten steel. The area of the detected molten steel discharged onto the outside surface of the pipe is processed using 50 images in the same field of view, the average value of the detected molten steel area is calculated, and that value is used to determine the area of molten steel discharged onto the outside surface of the pipe. Let the area be A. It is preferable that the image group subjected to the averaging process is equal to or more than one period of rotation of the SQ roll. 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 welding state determination unit 1401 calculates and detects the temperature Tc of the central part of the wall thickness at the specified position, which is calculated or detected after the processes of steps 5 and 8 are completed, and the temperature Tc of the pipe edge surface at the specified position. The quality of the welding conditions is determined based on the temperature difference ΔT between the outer surface and the inner surface, the V convergence angle θ, and the discharged molten steel area A after the welding stand. Specifically, using steel pipes obtained under various welding conditions, an offline evaluation test of the welded part is performed, and the characteristics of the obtained welded part and the above specifications calculated and detected by the welding management device 1000 are evaluated. The temperature Tc at the center of the pipe wall thickness at the position, the temperature difference ΔT between the outer and inner surfaces of the pipe edge surface at the specified position, the V convergence angle θ, and the discharged molten steel area A after the welding stand. Clarify the relationship in advance and determine the upper and lower limits of the allowable temperature difference ΔT between the wall thickness central portion Tc at the specified position and the outer and inner surfaces of the pipe edge surface at the specified position so that the desired quality of the welded part can be obtained. Set.

The setting of the above-mentioned allowable range is carried out for each of the above-mentioned V convergence angles θ, and the method thereof is shown below. When welding is performed at a certain V convergence angle θ, the boundary of the allowable range that treats the wall thickness center Tc at the specified position and the area A of discharged molten steel after passing through the welding stand as parameters is The upper and lower limits of the allowable range are determined using the subsequent area A of discharged molten steel and the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the specified position. Off-line evaluation tests for welds include a flattening test, an ultrasonic flaw detection test to detect oxides in the weld, and a Charpy impact test in which test pieces are cut from the weld. Select a test method.

An example of how to set the upper and lower limits of the allowable range of the temperature difference ΔT between the discharged molten steel area A and the outer and inner surfaces of the pipe edge surface at the specified position will be described below with reference to FIGS. 5, 6, and 7. However, this is not the case. Figure 5 shows the quality of the welded part determined from the results of a flattening test under various conditions of the temperature Tc at the center of the wall thickness and the area A of discharged molten steel in electric resistance welding, and the discharged molten steel at the temperature Tc of the center of each wall thickness. FIG. 6 is a diagram for explaining an example of a method of setting upper and lower limits Amax and Amin of area and deriving a function that passes through each upper and lower limit point. First, the area A of discharged molten steel after passing through a welding stand detected under various welding conditions is made to correspond to the characteristics desired for the welded portion of the steel pipe that was being welded at the time of detection. Here, the flatness ratio of the welded part measured by a flattening test is used as the desired characteristic for the welded part of the steel pipe. Here, the flattening ratio can be calculated based on the flattening test method described in JIS G3478:2015, and H/D (outer diameter D of the pipe, when cracks start to occur in the welded part in the flattening test) It is determined as the distance H) between the flat plates. The smaller the flattening ratio H/D, the greater the strength of the weld, which is an index showing that the weld has excellent characteristics. Furthermore, the upper limit of the flattening ratio is determined depending on the type of steel pipe.

First, the relationship between the discharged molten steel area A, the thickness central portion Tc at the specified position, and the flattening ratio H/D at an arbitrary V convergence angle θ is clarified. In order to perform electric resistance welding with the arbitrary V convergence angle θ constant, electric resistance welding is performed without changing the fin width of the fin pass roll used for forming or the roll position of the squeeze roll. When performing electric resistance welding, the edge temperature distribution photographing device 10 measures the temperature difference ΔT between the wall thickness center Tc at the specified position and the outer surface and inner surface of the pipe edge surface at the specified position, and the welding part photographing device 11, the V convergence angle θ and the discharged molten steel area A are calculated. Then, electric resistance welding is performed with the welding power adjusted, and the flattening test described above is performed on the obtained tube to measure the flattening ratio H/D.

Next, the roll position of the roll used for forming, which is located upstream of the squeeze roll, is changed to change the outer diameter curvature around the end of the open tube, and the butt angle of both edges in electric resistance welding is adjusted. . The butt angle shown here is the angle formed by the opposing end surfaces of both edges when looking at the open tube from the front.
Rolls used for forming that changes the roll position include edge forming and fin pass rolls, but are not limited to these. When the abutting angle of both edges is changed, electric resistance welding is performed with the welding power adjusted in the same manner as above, and the flattening test is performed on the obtained tube to measure the flattening ratio H/D. When changing the butt angle of both edges in ERW welding, when the cross section of the open tube is viewed from the front, the width of the opening of the open tube is wider on the outside surface side (V-shaped butt), the proximity effect Due to the difference, the outer surface temperature T ₀ becomes smaller than the inner surface temperature T _i , and the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the specified position becomes positive. Conversely, when the width of the opening of an open tube is narrower on the outer surface side (inverted V-shaped butt), the outer surface temperature T ₀ becomes larger than the inner surface temperature T _i due to the difference in proximity effect. , the temperature difference ΔT between the outer surface and the inner surface of the tube edge surface at the specified position becomes negative.
In the repeated electric resistance welding as described above, the flattening ratio H/D was measured in the electric resistance welded steel pipe having the combination of the wall thickness center Tc at the specified position and the discharged molten steel area A, as shown in FIG. Plot. Here, when the welding part property is 〇, it is less than or equal to the target flatness H/D, that is, it satisfies the target welding part strength, and when the welding part property is ×, it is more than the target flatness H/D, that is, The target strength of the welded part is not met. In each coordinate data, the boundaries of the upper and lower limits of the discharged molten steel area A at the thickness center portion Tc of each specified position are determined under the conditions that the desired flattening ratio can be satisfied. The boundaries of the upper and lower limits of the discharged molten steel area A at each Tc are a data group in which the weld characteristics are × for three or more consecutive plots in the increasing direction and decreasing direction of the discharged molten steel area A under a constant Tc condition, respectively. For the region of The area of discharged molten steel with the minimum value for which the properties of adjacent welds are 〇 is taken as the area.
Then, the permissible range of the discharged molten steel area A is determined using a calculation method such as the least squares method for the upper limit Amax and the lower limit Amin of the discharged molten steel area A at the wall thickness central portion Tc of each designated position. Here, there is no specification as to how to give the boundary, but in order to reduce the calculation cost, it is also possible to calculate the boundary by linear approximation. If the above discharged molten steel area is less than Amin, insufficient molten steel will be discharged to the outside due to the pressure of the squeeze roll during welding, and oxides will remain in the welded part, resulting in a worsening of the flattening ratio. In addition, if the discharged molten steel area exceeds Amax, the edge part will be overheated during welding, and the generation and growth of oxides on the edge part surface will become noticeable, resulting in a worsening of the flattening ratio. The allowable range of A is Amin to Amax.

Next, with respect to the coordinate data in which the upper and lower limits of the discharged molten steel area A are determined as described above, among the combinations of the discharged molten steel area A at the wall thickness center portion Tc of each designated position that exists within the tolerance range, The upper and lower boundaries of the thickness center portion Tc at the specified position in each discharged molten steel area A are determined. Figure 6 shows the quality of the welded part determined based on the results of flattening tests under various conditions of the temperature Tc at the center of the wall thickness and the area A of the discharged molten steel during electric resistance welding. After setting the upper and lower limits Amax and Amin of the area and deriving a function that passes through each upper and lower limit point, set the upper and lower limits of the temperature difference between the outer and inner surfaces of the pipe edge surface at the specified position to eliminate weld defects. FIG. 6 is a diagram for explaining an example of a method for deriving ΔTmax and ΔTmin. In order to find the upper and lower limits of the wall thickness center Tc, the boundaries are derived based on the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the specified position calculated at each point as shown in FIG. I do. Here, the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the designated position at each point is divided into data groups at regular intervals, such as 0°C or more and less than 10°C, -10°C or more and less than 0°C. I do. For example, ΔT1 in FIG. 6 is -200°C or more and less than -150°C, ΔT2 is -150°C or more and less than -100°C, and ΔT4 is 250°C or more and less than 300°C. The data in the data groups classified as above all satisfy the desired welding zone characteristics within the range of Amin to Amax, and extract the data group with the maximum value ΔTmax and minimum value ΔTmin of the temperature difference ΔT, and specify the data group. A boundary that satisfies the range of the maximum temperature difference ΔTmax and the minimum value ΔTmin is determined from the graph of the wall thickness center portion Tc of the position and the discharged molten steel area A. The boundary line is determined using a calculation method such as the method of least squares. Here, there is no specification as to how to give the boundary, but in order to reduce the calculation cost, it is also possible to calculate the boundary by linear approximation. As mentioned above, by applying the temperature difference ΔT between the outer and inner surfaces of the pipe edge surface to the boundary of the discharged molten steel area A obtained in Fig. 5, it is possible to It is possible to remove the level of × mixed in the welding area, and it is possible to eliminate the conditions where the welding part characteristics become ×. Furthermore, from a technical standpoint, if the wall thickness central portion Tc at the designated position is less than the lower limit ΔTmin, overheating on the outside surface of the tube becomes significant, and the area of molten steel discharged to the outside surface of the tube is overestimated. Therefore, even though the central part of the wall thickness is not sufficiently heated, image analysis using the welding part imaging device 11 incorrectly determines that the area of molten steel discharged to the outside is acceptable. As a result, the desired flatness of the welded area cannot be met. In addition, if the thickness center portion Tc at the specified position exceeds the upper limit ΔTmax, the outer surface of the edge portion will not be heated sufficiently, and during upset by the squeeze roll, the molten portion near the outer surface of the edge portion will solidify early, and the outer surface Since the path for discharging the molten steel to the outside is blocked, the molten steel containing oxides cannot be sufficiently discharged, resulting in a problem that the desired flatness cannot be obtained.

Figure 7 shows the temperature Tc at the center of the wall thickness and the discharged molten steel from the results of the flattening test under each condition of the temperature Tc at the center of the wall thickness and the area A of discharged molten steel at each V convergence angle θ in electric resistance welding. To explain an example of a method of deriving a tolerance range for welding from the relationship of area A, interpolating the distribution of the tolerance range for welding at each V convergence angle θ, and deriving the tolerance range under arbitrary welding conditions. It is a diagram. Regarding the derivation of the permissible range of the combination of the discharge molten steel area A and the wall thickness center portion Tc at the specified position based on the above-mentioned flattening ratio H/D, change the V convergence angle θ and repeat the same process. Then, a welding tolerance range 2000 shown in FIG. 7 is determined. Here, the pitch of the V convergence angle θ is not particularly specified, but under normal operating conditions, it is preferable to derive the allowable range by dividing the maximum and minimum values of the preset V convergence angle θ into 5 or more divisions. . Furthermore, for the condition of the V convergence angle θ for which the allowable range has not been directly determined as described above, processing is performed such as interpolating and approximating the allowable range of the V convergence angle θ for which the allowable range has been determined before and after the condition. The results obtained through this process can be recorded in the storage unit 1403. 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 output unit 1402 outputs the quality determination of the welding conditions obtained in step S9 to the outside. Since it is necessary for the operator to recognize the determination result in order to output it to the outside, it is preferable to output it to a graphic device, an alarm device, etc. provided in the welding management device 1000. Thereby, the process of step S10 is completed, and the series of welding management processes is ended.

The welding management device for electric resistance welded steel pipes has been described above as an embodiment of the present invention.
Further, the present invention also provides a welding management system having the above-described welding management device.
In addition, the welding management system having the above-mentioned welding management device can be used when manufacturing ERW steel pipes, and specifically, the manufacturing method of ERW steel pipes is continuous in the circumferential direction with respect to the steel plate or steel strip. It is manufactured by ERW welding, in which both edges are butted together to form an open tube, and then both edges of the abutted open tube are continuously upset using a welding stand. During welding, welding management is performed by the processing performed by the welding system described above. The welding control method for electric resistance welded steel pipes is also carried out by the method explained above. Furthermore, an ERW steel pipe can be manufactured using the above-described welding management method for an ERW steel pipe.

As described above, according to the present invention, it is possible to suppress welding defects by accurately measuring the heating distribution and abutting state of the end face during electric resistance welding and by also taking into account the amount of discharged molten steel after welding.

Further, regarding the embodiments of the present invention described above, these embodiments are merely examples for implementing the present invention. Therefore, the present invention is not limited to the embodiments described above, and all other embodiments, examples, operational techniques, etc. made by those skilled in the art are included in the present invention as long as they do not depart from the spirit thereof. included in the category of

First, in order to derive the allowable range of welding conditions for various ERW welded pipes with a pipe thickness of 5 mm and a steel pipe outer diameter of φ90 mm, we set the V convergence angle θ to 3 to 7 degrees, and the temperature at the center of the edge wall thickness. Set the position at which Tc is to be measured to be 6 mm away from just below the axis of the squeeze roll on the welding stand upstream, adjust the edge bend forming during forming, and adjust the difference value ΔT between the inner and outer surfaces of the tube at the same position by -300°C to +300°C. Electric resistance welding was performed at a temperature of 40 m/min and a welding speed of 40 m/min. The V convergence angle θ was adjusted by changing the fin roll width of the fin pass roll. In addition, in order to adjust the temperature difference ΔT between the inner and outer surfaces of the tube, the roll position of the fin pass roll was changed, and the bending deformation especially around the edge portion was adjusted.

In various types of electric resistance welding, a two-color thermometer camera was used while changing the welding power, the frame rate was 20 fps, the number of pixels in the pipe longitudinal direction was 1920 pixels, the number of pixels in the pipe thickness direction was 1080 pixels, and the number of pixels in the pipe longitudinal direction was 20 fps. A two-dimensional image of the temperature distribution before welding was obtained with a directional field of view of 50 mm. In addition, images before and after the welded part during welding were acquired using a CCD camera in various electric resistance welding operations at a frame rate of 20 fps, a pixel count in the tube longitudinal direction of 1920 pixels, and a field of view in the tube longitudinal direction of 60 mm. From these acquired images, the temperature Tc of the center wall thickness at the designated position of each frame, the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the designated position, the V convergence angle θ, and the welding The discharged molten steel area A after passing through the stand was extracted, and the average values of Tc, ΔT, and A for one rotation of the squeeze roll were calculated when the V convergence angle θ was fixed at a predetermined value. The obtained steel pipe was cut to a length of 100 mm, a flattening test was performed on the welded part based on JIS G3478:2015, the steel pipe was sandwiched between two flat plates, and the difference between the two flat plates when a crack occurred in the welded part was measured. The distance H between the plates was measured, and the flattening ratio H/D was calculated by dividing the distance H between the flat plates by the initial outer diameter D of the steel pipe. If the flattening ratio H/D was 2/3 or less, it was considered to be a pass. For these series of operations, the allowable range of welding conditions was derived for the V convergence angle from 3° to 7° at 1° intervals.

As a representative example, FIG. 8 shows the result of deriving the allowable range of the temperature Tc at the center of the wall thickness at the specified position and the discharged molten steel area A when the V convergence angle θ is 5 degrees. Regarding the upper and lower limits of the allowable range of the temperature Tc at the center of the wall thickness at each specified position and the area A of discharged molten steel, A linear approximation was performed for each of the lower limit values using the least squares method. Similarly, the upper and lower limits of the discharged molten steel area A at the temperature Tc of the central portion of the wall thickness at each fixed designated position were linearly approximated using the least squares method. Here, the upper limit (ΔTmax) of the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface at the specified position was 250°C, and the lower limit (ΔTmin) was -80°C.

Table 1 shows the temperature Tc at the center of the wall thickness, the temperature difference ΔT between the inner and outer surfaces, the V convergence angle θ, the area A of discharged molten steel, and the acceptance rate of the flattening ratio of the steel pipes of the invention example and the comparative example. In the invention example, the roll position is set up so that the temperature difference ΔT between the outer surface and the inner surface of the pipe edge surface is about +100°C and the V convergence angle is about 5°, and the temperature Tc at the center of the edge wall thickness is Welding power was adjusted so that the discharged molten steel area satisfied 1400°C ± 10°C and 3.2 ± 0.2 mm ² . On the other hand, in the comparative example, welding control during electric resistance welding was not performed, the welding power was adjusted, and the state of discharged molten steel was checked only visually.

For 100 samples of 100 mm length cut out from the obtained electric resistance welded steel pipes, a flattening test of the welded portion was performed based on JIS G3478:2015, and the flattening ratio H/D was measured. The pass rate of flattening ratio H/D is determined by the number of steel pipes that satisfy 2/3 or less, and if the pass rate is 95% or more, it is judged that electric resistance welding has been properly performed. Invention example steel pipe No. The pass rate for No. 1 was 100%, and the electric resistance welding was properly performed, whereas steel pipe No. In No. 2, the pass rate was 92%, and the specified electric resistance welding could not be performed.

1 Open pipe 2 Fin pass roll 3 High frequency oscillator 4 Welding direction 10 Edge temperature distribution imaging device 11 Welding area imaging device 20 Edge detection image of welding area 31a, 31b Contact tip 40 Welding stand 41a, 41b Squeeze roll 42a, 42b Top roll 100 Edge temperature distribution photography data input unit 110 Welding part photography data input unit 121 Temperature distribution processing unit 122 Edge temperature detection unit before ERW welding 123 Coordinate space calculation unit 124 Data processing unit 125 Edge temperature difference calculation unit 131 Welding image processing unit 132 Pipe edge image detection section 133 V convergence angle calculation section 134 Junction point detection section 135 Discharged molten steel area calculation section after welding 201 Heating section 202 Abutting section 202a, 202b Open pipe both edge end faces 203 Discharged molten steel after welding stand 204 Discharged molten steel of welding stand Position directly below the roll center 205 Opening θ V convergence angle 207 Weld bead 1000 Welding management device 1001 Welding management system 1401 Welding state determination section 1402 Output section 1403 Memory section La, Lb Straight line approximating both edge end faces of open pipe 2000 Tolerance range

Claims (5)

An electric current manufactured by bending a steel plate or steel strip in the circumferential direction, then butting both edges to form an open tube, and then using a stand to upset both edges of the butted open tube. A welding control device for sewn steel pipes,
Before electric resistance welding, based on an image of the temperature distribution on the surface of at least one open pipe edge and spatial coordinates converted from pixel information of the image of the temperature distribution,
a pre-ERW welding edge temperature detection unit that detects the outer surface temperature T ₀ of the open pipe edge surface, the inner surface temperature T _i , the temperature Tc of the center of the wall thickness, and the coordinates of the temperature measurement position;
an edge temperature difference calculation unit that calculates a temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface;
A V convergence angle θ formed by straight lines converging along the open tube edge portion is calculated based on image information of a region including a junction point formed by straight lines converging along both edge portions of the open tube. A calculation section,
Based on image information including molten steel discharged to the outer surface of the pipe on the downstream side of the position directly below the roll center of the welding stand after electric resistance welding in the welding direction, from the position directly below the roll center of the welding stand in the welding direction a post-weld discharged molten steel area calculation unit that calculates a molten steel area A discharged to the outer surface of the downstream pipe;
Based on the information on the temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface, the temperature Tc at the center of the wall thickness, the V convergence angle θ, and the discharged molten steel area A, a welding condition determination section that determines whether welding conditions are acceptable;
A welding control device for electric resistance welded steel pipes. In determining the acceptability of the electric resistance welding conditions based on the amount of molten steel discharged to the outer surface of the pipe on the downstream side from the position directly below the roll center of the welding stand after electric resistance welding with respect to the welding direction, the arbitrary V convergence angle The welding power according to claim 1, wherein the welding power is adjusted to obtain a predetermined outer surface temperature T ₀ , a predetermined inner surface temperature T _i , and a predetermined temperature Tc at the center of the wall thickness with respect to θ. Welding control device for sewn steel pipes. The welding management device for electric resistance welded steel pipes according to claim 1 or 2;
an edge temperature distribution imaging device that images the temperature distribution on both edge surfaces of an open tube before electric resistance welding;
Before ERW welding, the joint point formed by straight lines converging along both edges of the open pipe, and after ERW welding, on the outside of the pipe downstream of the position directly below the roll center of the welding stand in the welding direction. a welding part photographing device for photographing discharged molten steel;
A welding management system for ERW steel pipes. An electric current manufactured by bending a steel plate or steel strip in the circumferential direction, then butting both edges to form an open tube, and then using a stand to upset both edges of the butted open tube. A welding management method for a sewn steel pipe, the method comprising:
Before electric resistance welding, the outer surface temperature T 0 of the open tube edge surface, the inner surface temperature T ₀ , and A pre-ERW welding edge temperature detection step of detecting the surface temperature T _i , the temperature Tc at the center of the wall thickness, and the coordinates of the temperature measurement position;
an edge temperature difference calculation step of calculating a temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface;
A V convergence angle θ formed by straight lines converging along the open tube edge portion is calculated based on image information of a region including a junction point formed by straight lines converging along both edge portions of the open tube. calculation process,
Based on image information including molten steel discharged to the outer surface of the pipe on the downstream side of the position directly below the roll center of the welding stand after electric resistance welding in the welding direction, from the position directly below the roll center of the welding stand in the welding direction a post-weld discharge molten steel area calculation step of calculating an area A of molten steel discharged to the outer surface of the pipe on the downstream side;
Based on the information on the temperature difference ΔT between the outer surface and the inner surface of the open pipe edge surface, the temperature Tc at the center of the wall thickness, the V convergence angle θ, and the discharged molten steel area A, a welding condition determination step for determining whether welding conditions are acceptable;
Welding management method for ERW steel pipes, including: A method of manufacturing an ERW steel pipe using the welding management method for an ERW steel pipe according to claim 4.

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