JPH10277638A - Steel pipe welding method and steel pipe for welding - Google Patents

Abstract

(57) [Problem] To provide a welding method for steel pipes that can prevent welding defects due to poor fusion of a molten metal and an additive and enable sound welding when welding in an upward or vertical position. provide. SOLUTION: In a butt welding method of a steel pipe using a laser beam by a filler wire supply method, before welding, a groove for fitting a filler wire is provided on a butt end face of the steel pipe, and a filler wire is fitted into the groove. Butt ends are welded from outside of steel pipe. Alternatively, before welding, a foil ring having the same composition as the filler wire is attached to one or both end surfaces of the butt of the steel pipes in advance, and the end faces are butted and welded from outside the steel pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a steel pipe used in a pipeline and a steel pipe for welding.

[0002]

2. Description of the Related Art A conventional method is disclosed in Japanese Patent Application Laid-Open No. 61-5679.
As disclosed in Japanese Patent Application Publication No. 1 (1999) -123, a method of adjusting a distance between butted materials to be welded and supplying a filler wire with the adjusted gap as a guide is used. Further, in the method disclosed in JP-A-61-119392,
In order to stably supply the filler wire to the groove, a method of temporarily fixing the filler wire to the groove of the material to be welded is adopted.

[0003]

However, in the conventional method disclosed in Japanese Patent Application Laid-Open No. 61-56791, it is necessary to precisely match the material to be welded to the space for introducing the filler wire. It is technically necessary, and stable welding cannot be achieved unless the butt accuracy can be ensured. Furthermore, in addition to the need for a filler wire feeder at the work site and a device for controlling the butting interval of the materials to be welded, inexpensive methods such as the need for repair and adjustment of various devices are required. is not. Further, when welding a steel pipe for a pipeline on a field, it is necessary to rotationally scan the welding head around the steel pipe because the steel pipe to be welded cannot be rotated. In this case, in welding in the upward or vertical position, as shown in FIGS. 2A and 2B, the molten filler wire 11 falls freely due to gravity, so that fusion failure with the molten metal occurs. However, it may cause problems such as a lack of welding flame. In addition, the method disclosed in Japanese Patent Application Laid-Open No. 61-119392 requires not only a filler wire supply device but also a temporary fixing and a main welding as in the above-mentioned Japanese Patent Application Laid-Open No. 61-56791. Problems such as complicated processes.

Accordingly, the present invention makes it possible to add a filler wire or the same component to a joint without the need for a filler wire supply device, and to achieve sound welding free of welding defects such as solidification cracks and blowholes. To provide a method for joining steel pipes to each other. FIG. 2 (c)
As can be seen from (d), even in an upward or vertical welding, which was difficult with the conventional filler wire supply method, free fall of the molten filler wire due to gravity was not observed. An object of the present invention is to provide a method for joining steel pipes, which enables sound welding while preventing the occurrence of welding defects due to poor fusion of a metal and an additive.

[0005]

The gist of the present invention is as follows. In the butt welding method of a steel pipe using a laser beam by a filler wire supply method, a groove for fitting a filler fire is provided in advance at a butt end face of the steel pipe before laser beam irradiation, and a filler wire is fitted into the groove. Further, in the method for welding a steel pipe, characterized in that the end face is welded from the outside of the butt steel pipe, and the butt welding method for a steel pipe using a laser beam by a filler wire supply method, the butt welding of the steel pipe is performed before the laser beam irradiation. This is a method for welding steel pipes, comprising attaching a foil ring having the same composition as that of the filler wire to one end face or both end faces, and then welding the end faces from the outside of the butt steel pipe.

There is no need to particularly define the shape of the groove for fitting the filler wire, and it is not necessary to particularly define the position of the groove in the thickness direction of the steel pipe or the number of grooves. At this time, the filler wire used should be thinner than the expected width of the molten cross section, and the depth of the groove for fitting the filler wire shall be shallower than half of the expected width of the molten cross section. The area is equal to or less than the cross-sectional area of the filler wire. This makes it possible to prevent the occurrence of welding defects without leaving the filler wire fitting groove after welding. Also, before actual welding, beveling is performed as pretreatment of the steel pipe, and it is possible to divert the groove used for filler wire fitting using the equipment used for beveling. There is no need to introduce processing equipment.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of the present laser steel pipe welding system. The laser oscillation device is a carbon dioxide laser oscillator 1, and a laser beam 5 oscillated from the laser oscillator is transmitted to a movable processing head 3 by a transmission optical system 2. The configuration of the transmission optical system is a plurality of reflection mirrors 8 and a beam duct 2 that protects the laser beam and ensures the safety of workers. The beam duct 2 may be manufactured according to the maximum diameter of the steel pipe 4 to be welded. For example, the length of one of these ducts is roughly the maximum diameter of the steel pipe, does not contact the steel pipe, and is a length that takes into account the size of the mobile processing head. The beam duct 2 is a bellows-shaped duct, which can be freely expanded and contracted, and this telescopic bellows duct is effective for a copying apparatus at a groove position to be described later.

Each reflecting mirror reflects the laser beam 5 at an angle of 90 degrees with respect to the optical axis. A pair of two reflecting mirrors for reflecting the laser beam at an angle of 90 degrees is provided as a set, and a bearing that freely rotates around the optical axis is attached between the mirror holders that hold the reflecting mirrors. It can be deflected to any angle in parallel planes. The movable processing head 3 includes a reflection mirror (BM), a condensing optical system, a focus position copying apparatus, a groove position copying apparatus, a welding nozzle, a processing head self-propelling apparatus, and a guide rail attached to the steel pipe 4. 7

[0009]

EXAMPLE Using this system, a steel pipe having a diameter of about 711 mm and a thickness of about 15 mm and meeting the API standards of the United States was welded. The laser oscillation device is a commercially available 25 kW carbon dioxide laser oscillator. The reflection mirror used in the transmission optical system is a mirror for a carbon dioxide gas laser obtained by applying gold plating to oxygen-free copper having a diameter of 100 mm. The beam duct is a stainless steel tube, and the bearing uses a ball bearing having an outer diameter of 150 mm specified by the JIS standard. The focusing optical system included in the movable processing head uses a parabolic mirror with a focal length of about 500 mm, and the laser emitting portion of the focusing optical system has a nozzle for supplying an assist gas for welding. The focal position copying apparatus includes a laser type distance sensor and a moving mechanism for keeping the distance between the steel tube and the light collecting optical system constant. The groove position copying apparatus has a calculation part for judging a groove part by image processing and a moving mechanism for accurately irradiating a laser to the groove part. These moving mechanisms are of a type in which power is externally supplied and driven by a motor. The movable processing head is moved around the steel pipe by a guide rail attached to the steel pipe, and the self-propelled device is driven by a motor and supplied with power from the outside, so that the speed and the moving distance can be controlled. The guide rail is manufactured in advance according to the size of the steel pipe.

The welding conditions are as follows: a laser output of 25 kW and a focal length of about 500 mm.
The scanning speed of the movable processing head was 2.0 m / min. As shown in FIG. 3A, a half-moon-shaped groove 10 having a width of 1.2 mm and a depth of 0.6 mm was formed in the center of the plate in the thickness direction at the butt groove as a welded portion of the material. A material end face was attached to the filler wire fitting groove 10 so as to sandwich the YGW 11 filler wire 11 having a diameter of 1.2 mm specified by JIS Z3312. As a result, FIG.
As shown in the schematic diagram of the X-ray inspection result of (a), the welding defect (for example, blowhole 19) generated in FIG.
A sound weld was obtained as shown in FIG. In addition, when the welding was carried out under the same conditions in the upright position and the upright position, the filler wire was fused to the molten metal without burn-through to the outside, and a sound welding result without any welding defects was obtained. Was.

3 (b), 3 (c), and 3 (c) by a similar method.
A groove 1, such as a triangle, rectangle, or polygon, as shown in FIG.
Although the embodiment of No. 0 was adopted, sound welding without any welding defect could be obtained in any of the embodiments. Also, FIG.
As shown in FIG. 5, each end 1 of the opposed steel pipes 13, 14
A plurality of grooves 10 are provided in 5 and 16, and a wire 11 having a small diameter is provided.
As shown in FIG. 6, when the filler ring 12 in the form of a foil is supplied without performing groove processing on the groove portions at the end portions 15 and 16 of the steel pipes 13 and 14, as shown in FIG. No sound welding results were obtained.

When the laser welding system of the present invention is used for welding on a vessel laying an oil pipeline and for constructing a gas pipeline, the laser welding system is reduced by about 1 / compared to the conventional arc welding method.
Welding is completed in 10 actual welding times, so that not only high-speed construction can be performed, but also a high-quality joint having no welding defects such as blowholes and solidification cracks can be obtained in the welded portion.

[0013]

According to the present invention, in a steel pipe for a pipeline, in a steel pipe having a groove for a filler wire at an end face of a butt portion, an additive for adjusting a component such as a filler wire is embedded in the groove in advance. In addition, it is not necessary to install a filler wire supply device such as a wire torch or a wire guide in the processing head, and the welding operation is not interrupted by replacing the wire reel. In addition, by welding the steel pipe with a laser beam, the filler metal can be misaligned with the molten metal due to misalignment of the filler wire with respect to the welding line and free fall of the filler wire due to gravity in welding in an upward or vertical position. It is possible to prevent the occurrence of welding defects due to poor fusion of objects. Also, a filler wire supply device at the work site,
Since there is no need for a device for controlling the butting interval of the materials to be welded, there is no need to repair or adjust various devices, and the cost is low.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a laser system employed in the method of the present invention.

FIG. 2 is an explanatory view of welding in an upward posture and a vertical posture.

FIG. 3 is a conceptual diagram of a steel pipe groove showing an embodiment of a steel pipe welding method according to the present invention.

FIG. 4 is a conceptual diagram of a steel pipe groove portion showing another embodiment of FIG.

FIG. 5 is a conceptual view of a steel pipe groove portion showing still another embodiment in FIG. 3;

FIG. 6 is a conceptual diagram of a steel pipe groove showing another embodiment of the steel pipe welding method according to the present invention.

FIG. 7 is a view showing measurement of blowhole defects by X-ray inspection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1 'Laser oscillator 2 Transmission optical system and beam duct 3, 3' Moving work head 4 Steel pipe 5, 5 'Laser beam 6, 6' Condensing optical system 7 Guide rail 8 Reflecting mirror 9 Universal joint 10 Filler wire fitting groove 11 Filler wire 12 Filler ring 13 Leading steel pipe 14 Trailing steel pipe 15 Terminating part of leading steel pipe 16 Starting end of trailing steel pipe 17 Keyhole 18 Plasma 19 Blowhole

Claims (6)

[Claims] In a butt welding method of a steel pipe using a laser beam by a filler wire supply system, a groove for fitting a filler wire is provided in advance at a butt end face of the steel pipe before laser beam irradiation, and a filler wire is fitted into the groove. A method for welding a steel pipe for a pipeline, wherein the end faces are welded from the outside of the butt steel pipe after the joining. 2. A butt-welding method for a steel pipe using a laser beam by a filler wire supply method, wherein a foil-like ring having the same component as the filler wire on one end face or both end faces of the butt of the steel pipe before laser beam irradiation. A method for welding steel pipes for pipelines, wherein the end face is welded from the outside of the butt steel pipe after mounting. 3. A steel pipe for welding, comprising a groove for fitting a filler wire on a butt end face of the steel pipe for welding. 4. The steel pipe for welding according to claim 3, wherein the filler wire fitting groove extends in a circumferential direction of the steel pipe. 5. The steel pipe according to claim 3, wherein a plurality of grooves for fitting the filler wire are provided. 6. The steel pipe according to claim 3, wherein a filler wire is embedded in the groove for fitting the filler wire in advance.