JPH09168819A - Manufacture of welded steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely weld butted end parts with high accuracy by controlling a welding torch for a laser beam so as to be accurately situated on a weld line at the time of manufacturing a welded steel tube, after welding the butted end parts of a tubular formed body by electric resistance welding, by removing the weld bead generated at the time of welding, next, remelting the weld line by the electric resistance welding by a laser beam and also welding it. SOLUTION: On both sides of the weld line 19 of the tubular formed body 1 welded by electric resistance welding, marking lines 21 are impressed by a marking mechanism 22, the position of the butted end part of the tubular formed body 1 is detected with a 1st charge coupled device(CCD) camera 16 which is provided on the upstream side of the converged point of V of the tubular formed body 1, in this way, the position of the marking mechanism 22 is controlled at equal distances from the weld line 19. And, the marking lines 21 are detected with the 2nd CCD camera 17 which is provided adjacently to the position of the welding torch 18 and, in this way, the welding torch 18 is controlled so as to be situated in the center position of the marking lines 21, that is, on the weld line 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a steel strip is continuously formed into a tubular shape, and its butt ends are electric resistance welded.
The present invention relates to a method for manufacturing a welded steel pipe in which an electric resistance welded portion is remelted by a high-density energy beam and then welded.

[0002]

2. Description of the Related Art As one of welded steel pipes, a steel strip is formed into a tubular shape, the obtained tubular formed body is continuously moved in a certain direction, and its butt end is preheated by electric resistance heating or high frequency induction heating. After that, there is known a method for producing a laser-welded steel pipe in which a butt end is continuously melted by a high-density energy beam, that is, a laser beam, which is irradiated from above, and this is welded.

Laser welding is a method of converging a laser beam into a beam having a small diameter of 1.0 mm or less, irradiating a portion to be welded with the laser beam having such a small diameter, melting and welding the welded portion. It has the advantages of low heat input, deep penetration, low distortion, and high-speed welding.

However, as described above, since the laser beam to be irradiated has an extremely small diameter, even if the irradiation position of the laser beam is slightly deviated from the abutting end portion of the tubular molded body, welding failure occurs. The allowable deviation of the irradiation position that does not cause welding defects is only ± 0.2 mm.

When welding the abutting ends of the tubular molded body that move continuously in a certain direction by the above-mentioned laser beam, rotation about the axis of the tubular molded body and the abutting end of the tubular molded body By waving, etc.
In many cases, the irradiation position of the laser beam with respect to the abutting end portion deviates beyond the above allowable amount.

In order to prevent the above-mentioned problems, Japanese Patent Publication No.
No. 24946 discloses a method of causing a laser beam irradiation head to follow the laser by an electric copying mechanism using a seam sensor such as a CCD and performing laser welding, and JP-A-6-668. Discloses a method in which a laser beam irradiation head is moved along with a mechanical copying mechanism to perform laser welding.

FIG. 2 is a schematic view showing an example of a conventional method of performing laser welding by causing an irradiation head of a laser beam to follow an electric tracing mechanism. As shown in the drawings, the strip steel is formed into a tubular shape by a forming device (not shown) to form a tubular formed body 1, which continuously moves in the arrow direction. On the upstream side of the V-converging point 3 where the butt welded portions of such a continuously moving tubular molded body 1 meet, each of the butt ends is provided with a power supply 4 for supplying a high-frequency current. Has been. Reference numeral 2 is a power supply for supplying a high frequency current to the power supply terminal 4.

The high-frequency current supplied to the tubular molded body 1 by the power supply 4 is concentrated on the abutting end of the tubular molded body 1 due to the skin effect. As a result, the abutting ends of the tubular molded body 1 are preheated by the high-frequency current flowing therethrough, and then abutted by the pair of squeeze rolls 5 provided in the vicinity of the V convergence point 3.

In the vicinity of the squeeze roll 5, a welding torch 11 for irradiating a laser beam and welding the laser beam from above is provided toward the abutting end of the tubular molded body 1, and more than the welding torch 11. On the upstream side, a CCD (ITV) camera 6 as a detection mechanism for detecting the abutting end of the tubular molded body 1 is provided close to the upstream side.

The image of the abutting end of the tubular molded body 1 taken by the CCD camera 6 is processed by the image processing circuit 7, and the position of the abutting end is detected.
The position signal of the butt ends detected in this way is sent to the drive circuit 9 via the control circuit 8 and the drive circuit 9
Sends a drive signal for the welding torch 11 to the drive device 10. The position of the welding torch 11 is controlled by the operation of the drive device 10 so that the welding torch 11 is located at the butt end of the tubular molded body 1 to be welded (hereinafter,
Prior art).

According to the prior art, the welding torch 11 is controlled by the CCD camera 6 as a detection mechanism so as to be positioned at the butt end of the tubular molded body 1 to be welded. The ends can be laser-welded with high precision without any deviation.

On the other hand, as a method for manufacturing a welded steel pipe using a high-density energy beam, that is, a laser beam, the butt ends of tubular molded bodies that continuously move in a certain direction are electric resistance welded by electric resistance heating or high frequency induction heating. Then, in order to remove the oxide called penetrator generated during high frequency induction heating, which remains in the electric resistance welded portion, a method of remelting and welding the electric resistance welded portion by a laser beam is known. .

[0013]

In the case of the above-described method of remelting and welding the electric resistance welded portion by the laser beam after the electric resistance welding, the welding bead produced by the electric resistance welding is removed by a bite or the like. It is necessary to.
As described above, after the tubular formed body is electric resistance welded, the generated welding bead is removed by a bite, and then the electric resistance welded portion is remelted by a laser beam and, in the case of a method of welding, welding by a bite, etc. In order to remove the beads, a distance of a predetermined length is required from the electric resistance welding position to the fusion welding position by the laser beam.

Therefore, according to the method of the prior art, even if the position of the welding torch for irradiating the laser beam is controlled by picking up an image of the electric resistance welded end of the tubular molded body with a CCD camera as a detection mechanism, the CCD is used. After the image is taken by the camera, the welding line often changes in the circumferential direction of the pipe due to twist or rotation occurring in the pipe before welding with the welding torch. As a result, even if the position of the welding torch that irradiates the laser beam is controlled by the method of the prior art, it is inevitable that the irradiation of the laser beam deviates from the welding line and a welding defect occurs.

Therefore, an object of the present invention is to solve the above-mentioned problems, to weld a tubular molded body by electric resistance welding, then cut and remove the welding beads generated at the time of welding with a bite, etc. The position of the welding torch can be controlled so that the welding torch is properly positioned on the welding line even when irradiating with a density energy beam, that is, a laser beam and remelting, and welding is performed. It is an object of the present invention to provide a method capable of accurately and accurately welding end portions.

[0016]

DISCLOSURE OF THE INVENTION According to the present invention, a steel strip is continuously formed into a tubular shape, and the tubular formed body is formed on the upstream side of a V-converging point at which a butt end of the formed tubular body first contacts. The butt ends of the body are heated by electric resistance heating or high-frequency induction heating to melt the same, and the first squeeze roll is used for abutting to perform electric resistance welding, and then,
After removing the welding bead generated in the electric resistance welded portion, the electric resistance welded portion is remelted by the high-density energy beam emitted from the welding torch on the downstream side of the electric resistance welded portion, and the second squeeze roll is also used. In the method for producing a welded steel pipe, which is abutted with each other to weld the welded pipe, one is formed on each of both sides of the welding line of the electric resistance welded tubular formed body, with the welding line interposed therebetween.
Two marking lines are marked by a pair of marking mechanisms, and a first detection mechanism provided on the upstream side of the V convergence point of the tubular molded body detects and detects the abutting end position of the tubular molded body. The position of the pair of marking mechanisms is controlled so as to be equidistant from the welding line, and the position of the welding torch for irradiating the high-density energy beam Is detected by the second detection mechanism provided on the upstream side of the two marking lines, and the two marking lines marked by the pair of marking mechanisms are detected, and the center position of the detected two marking lines is traced. And controlling the welding torch, which irradiates the high-density energy beam, so as to be positioned on the center position of the two marking lines, that is, on the welding line. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing one embodiment of the method of the present invention. As shown in the drawing, a tubular molded body 1 molded into a tubular shape by a molding device (not shown) and continuously moving in the direction of the arrow has a butt end to which V is first contacted.
On the upstream side of the converging point 3, there is provided a power supply 4 which is in contact with each of the butt ends and supplies a high frequency current to the butt ends. Reference numeral 2 is a power supply for supplying a high frequency current to the power supply terminal 4. The high-frequency current passed through the tubular molded body 1 by the power supply 4 is concentrated on the abutting end of the tubular molded body 1 due to the skin effect. As a result, the butted end portion of the tubular molded body 1 is heated and melted in the vicinity of the V convergence point 3.

A first squeeze roll 13 for pressing the tubular compact 1 from both side surfaces thereof is provided near the V convergence point 3, and the tubular compact 1 is pressurized by the first squeeze roll 13 and electrically charged. Sewn and welded.

In the vicinity of the first squeeze roll 13, a first CC for picking up an image of the abutting end position is provided as a detection mechanism for detecting the abutting end position of the tubular molded body 1.
A D (ITV) camera 16 is provided.

On the downstream side of the first squeeze roll 13, there is provided a cutting tool 15 for cutting and removing the welding bead generated at the time of electric resistance welding, and the welding bead is cut and removed by the cutting tool 15.

A welding torch 1 for irradiating a laser beam 20 from above and remelting it toward the welding line 19 which is electric resistance welded is provided on the downstream side of the installation position of the cutting tool 15.
8 and a second squeeze roll 14 that applies pressure to the tubular formed body 1 that has been electric resistance welded from both side surfaces thereof.

Between the first CCD camera 16 and the bite 15, two extremely shallow marking lines 21 having a depth of several μm are provided on both sides of the welding line 19 of the tubular body 1 welded by electric resistance welding. A pair of marking mechanisms 22 for marking are provided. The pair of marking mechanisms 22 may be a torch that emits a low-power laser beam, or a mechanical cutting mechanism such as a cutting tool. The distance between the pair of marking mechanisms 22 is constant, and the marking mechanism 22 can be moved in the direction orthogonal to the welding line 19 by the second drive device 24.

On the upstream side close to the installation position of the welding torch 18, a pair of marking mechanisms 22 are provided on both sides of the welding line 19 of the tubular body 1 electro-welded to sandwich the welding line 19. As a second detection mechanism for detecting the marking line 21, a second CCD (I
A TV) camera 17 is provided.

The weld bead of the tubular body 1 which has been electric resistance welded is removed and flattened by the cutting tool 15. In this way, the tubular molded body 1 in which the welding beads have been removed and flattened
The electric resistance welded portion is melted by the high-density energy beam, that is, the laser beam 20 emitted from the welding torch 18 provided on the downstream side of the installation position of the cutting tool 15, and a molten pool penetrating the entire wall thickness is formed therein. Formed and second
The squeeze roll 14 applies a slight pressure to weld.

The image of the butt end of the tubular molded body 1 taken by the first CCD camera 16 is processed by the first image processing circuit 25, and the position of the butt end is detected. The position signal of the butt ends detected in this way is sent to the first drive circuit 27 via the first control circuit 26, and the first drive circuit 27 outputs the first drive signal of the pair of marking mechanisms 22 to the first drive circuit 27. Send to the driving device 23.
By the operation of the first drive device 23, the positions of the pair of marking mechanisms 22 are controlled so as to be equidistant from the welding line 19 of the tubular molded body 1.

The images of the two marking lines 21 on both sides sandwiching the welding line 19 of the electric resistance welded tubular molded body 1 taken by the second CCD camera 17 are the second image processing circuit 28. The position of the two marking lines 21 and the distance between them are detected.
The position signal of the marking line 21 detected in this way is sent to the second drive circuit 30 via the second control circuit 29, and the second drive circuit 30 outputs the drive signal of the welding torch 18 to the second drive device 24. Send to. Due to the operation of the second drive device 24, the welding torch 18 moves the two marking lines 2
It is controlled so as to be located at the central position of 1, that is, on the welding line 19 of the tubular molded body 1.

The initial spacing between the two marking lines 21 marked by the pair of marking mechanisms 22 is narrowed by the upset amount at the time of electric resistance welding, and further, when the welding bead is cut by the cutting tool 15 or the pipe body is moved. The resulting rotation causes the tube to move circumferentially. However, according to the method of the present invention, as described above, after the welding bead is cut by the cutting tool 15, the positions of the two marking lines 21 are detected by the second CCD camera 17, whereby the position of the welding torch 18 is adjusted. It is controlled accurately.

As described above, according to the method of the present invention, the position immediately before the V convergence point before the butt end of the tubular molded body 1 is subjected to electric resistance welding is detected by the first CCD camera 16 and its position is determined. Marking lines 2 are formed on both sides of the welding line 19 of the tubular formed body 1 which is electric resistance welded so as to be centered.
Since 1 is marked, even if the pipe body rotates or the like after the upset or welding bead removal at the time of electric resistance welding, the welding line 19
The position of is recorded. Therefore, the marking line 21
By detecting the CCD camera 17 and guiding the welding torch 18 to the center of the marking line 21, the welding line 19 is accurately remelted by the laser beam 20 and welded regardless of the rotational displacement of the electric resistance welded portion. can do.

[0029]

As described above, according to the present invention,
Even when the tubular bead is welded by electric resistance welding, the welding beads generated during welding are cut and removed with a bite, and then the electric resistance welded portion is irradiated with a high-density energy beam, that is, a laser beam to remelt and weld. , The position of the welding torch can be controlled so that the welding torch is properly positioned on the welding line, and the butted end of the tubular molded body can be accurately and accurately welded, which is industrially useful. The effect is brought about.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of the method of the present invention.

FIG. 2 is a schematic view showing an example of a conventional laser welded steel pipe manufacturing method.

[Explanation of symbols]

 1 Tubular molded body 2 Power supply 3 V Convergence point 4 Power supply 5 Squeeze roll 6 CCD camera 7 Image processing circuit 8 Control circuit 9 Drive circuit 10 Drive device 11 Welding torch 12 Welding line 13 First squeeze roll 14 Second squeeze roll 15 bytes 16 First CCD camera 17 Second CCD camera 18 Welding torch 19 Welding line 20 Laser beam 21 Marking line 22 Marking mechanism 23 First driving device 24 Second driving device 25 First image processing circuit 26 First control circuit 27 First driving circuit 28 First image processing circuit 29 Second control circuit 30 Second drive circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B23K 37/08 B23K 37/08 E

Claims (1)

[Claims] 1. A steel strip is continuously formed into a tubular shape, and the butt end of the tubular formed body is electrically resistanceed at an upstream side of a V convergence point at which the butt end of the obtained tubular formed body first contacts. After heating by heating or high-frequency induction heating to melt it, the first squeeze roll abuts to perform electric resistance welding, and then the welding beads generated in the electric resistance welding portion are removed, and then the electric resistance welding portion On the downstream side of
In the method for producing a welded steel pipe, wherein the electric resistance welded portion is remelted by a high-density energy beam emitted from a welding torch and abutted by a second squeeze roll to weld the welded steel pipe, the electric resistance welded tubular molding Two marking lines are marked on each of both sides sandwiching the welding line of the body by a pair of marking mechanisms, and by a first detection mechanism provided on the upstream side of the V convergence point of the tubular molded body, Detecting the butt end position of the tubular molded body, controlling the position of the pair of marking mechanisms so as to be equidistant from the welding line, in accordance with the detected position of the butt end, and , Marked by the pair of marking mechanisms by a second detection mechanism provided on the upstream side of the welding torch that is close to the position of the welding torch that irradiates the high-density energy beam, and Of the marking lines are detected, and the welding torch for irradiating the high-density energy beam is positioned on the center positions of the two marking lines, that is, on the welding lines, following the detected center positions of the two marking lines. A method for manufacturing a welded steel pipe, which is characterized in that