JP3398128B2 - Laser welding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser for joining two pipes by heating and melting the joints by irradiating the abutting portions of the two pipes whose end faces are butted against each other with laser light. Regarding the welding method.

[0002]

2. Description of the Related Art FIG. 11 shows a butt portion 5 of two pipes 2 having a V-shaped groove formed by a conventional multi-torch automatic MAG (Metal Active Gas) welding apparatus.
12 (a) is a diagram showing a butt portion 5 before welding, and FIG. 12 (b) is a diagram showing a welded portion 30 after welding. When welding the butt portion 5 formed with a V-shaped groove that is open to the outside,
Attach the two torches 1a, 1b to the outer peripheral surface 31 of the tube 2
Placed on the outside of the tube 2 with the torch 1 facing each other.
Welding is carried out while moving a and 1b around the pipe axis 4 along the outer circumference of the pipe 2 in the same rotation direction.

FIG. 13 is a diagram showing a method of welding the abutting portion 7 of two pipes 2 having an X-shaped groove by an automatic MAG welding device which is a multi-torch type of another prior art. 14 (a) is a diagram showing the butted portion 7 before welding, and FIG. 14 (b) is a diagram showing the welded portion 32 after welding. When welding the butt portion 7 formed with the X-shaped groove facing the outside and opening, the two torches 1c, 1d
Is placed outside the tube 2 with its electrode portion 3 facing the outer peripheral surface 31 of the tube 2, and one torch 1e is placed inside the tube 2 with the inner peripheral surface 33 of the tube 2 facing. The torches 1c to 1e are welded while moving around the tube axis 4 along the outer circumference and the inner circumference of the tube 2 in the same rotation direction.

FIG. 15 is a diagram showing a method of welding the abutting portion 9 by still another conventional plasma arc welding method, and FIG. 16 (a) is a diagram showing the abutting portion 9 before welding. FIG. 16B shows the welded portion 3 after welding.
FIG. In the plasma arc welding method, it is difficult to move the welding rod 11 along the outer circumference of the pipe 2 while fixing the pipe 2 to weld the abutting portion 9 over the entire circumference, that is, so-called “all-position welding”, It is necessary to perform welding with the tip 12 of the welding rod 11 held substantially vertically downward (downward in FIG. 15). That is, the upper half of the abutting portion 9 of the two pipes 2 arranged substantially horizontally, the welding rod 11 a arranged outside the pipe 2, the outer peripheral surface 31 around the pipe axis 4.
Along the inner peripheral surface 33 around the pipe axis 4 and the welding rod 11b disposed inside the pipe 2 in the lower half of the butted portion 9 in the two directions. Welding.

FIG. 17 is a view showing a method of welding the abutting portions 13 of two pipes 2 by still another conventional one-pass electron beam welding method, and FIG. 18 (a) is a welding method before welding. It is a figure which shows the part 13, FIG.18 (b)
FIG. 6 is a diagram showing a welded portion 35 after welding. When welding the abutting portion 13 by the 1-pass electron beam welding method (EBW: Electron-Beam Welding), the welding atmosphere of the abutting portion 13 is evacuated, and the electron beam emission hole is provided inside the tube 2 so that the electron beam emitting hole is provided. One electron gun 14 facing the inner peripheral surface 33 irradiates one electron beam 15 toward the inner peripheral surface 33 of the abutting portion 13 while moving around the tube axis 4 along the inner peripheral surface 33. The butt portion 13
Are completely melted in the thickness direction of the tubes 2, and the tubes 2 are joined.

FIG. 19 shows a butt portion 17 of two pipes 2 according to still another conventional one-pass laser welding method.
Fig. 20 (a) is a diagram showing a butt portion 17 before welding, and Fig. 20 (b) is a diagram showing a welded portion 36 after welding. When welding the abutting portion 17 by the one-pass laser welding method, one laser output head 18 provided inside the tube 2 and having a laser emission port facing the inner peripheral surface of the tube 2 has an inner circumference around the tube axis 4. By irradiating one laser 19 toward the inner peripheral surface 33 of the abutting portion 17 while moving along the surface 33, the abutting portion 17 is completely melted in the thickness direction of the pipe 2, and each of the pipes 2 To join.

[0007]

The above-described welding method using the automatic MAG welding apparatus has the advantage that the automatic MAG welding apparatus is inexpensive, but as shown in FIGS. 12 (b) and 14 (b). In addition, since the beads 6 and 8 form a multi-layered structure, it is necessary to use a plurality of torches 1 at the same time, as shown in FIGS. 11 and 13, in order to efficiently perform welding at high speed. However, this MAG welding method has a problem that the welding speed is basically low, and even if a multi-torch is used, the total construction time until completion of welding is long. Further, there is a problem that the configuration of the automatic MAG welding apparatus becomes complicated and the maintenance cost increases due to the multi-torch type.

The plasma arc welding method described above has the advantage that the apparatus is relatively inexpensive, but the welding speed is slow, and the amount of metal melted in one welding operation (one pass) is small. Therefore, in the case of welding the thick-walled pipes 2 to each other, as shown in FIG. 16B, first, the abutting portion 20 is welded to form the bead 10a, and then the groove portion 21a is welded to the bead 10a. There is a problem in that a three-pass construction is required in which the bead 10c is formed by forming the bead 10c by forming the groove 10b and then welding the groove portion 21b, and there is a problem that it takes a long time to complete welding.

The above-described 1-pass electron beam welding method has an advantage that welding can be performed at high speed and low strain, but as shown in FIG. There is a problem that the end face 23 of each tube 2 of the butted portion 17 needs to be machined strictly, and the gap tolerance of the groove becomes small. Further, since it is necessary to make the welding atmosphere a vacuum, a vacuum chamber is required, which increases the size and complexity of the entire apparatus. Therefore,
The device becomes expensive. Further, there is a problem that the welding finish is easily affected by the external environment, and there is a waiting time for construction to evacuate the inside of the vacuum chamber.

The one-pass laser welding method has an advantage that it can be welded at a high speed and a low strain, and further, because the welding atmosphere of the abutting portion 17 does not need to be a vacuum, a vacuum chamber is not required and the apparatus can be downsized. It has the advantage of However, as shown in FIG. 20B, the formed bead 22 becomes thick. That is, since the amount of molten metal is larger than that in the electron beam welding method, there is a problem that it is difficult to perform stable welding in all positions.
In particular, when welding the upper half of the abutting portion 17 of each of the pipes 2 arranged substantially horizontally, the stable welding operation may be hindered by the sagging of the molten metal due to gravity. Further, since it is necessary to completely melt the tube 2 in the thickness direction using one laser beam, the output energy of the laser beam becomes large. Therefore, in order to generate a high-power laser beam, an extremely high-power laser oscillator is required, which causes a problem that the entire apparatus becomes expensive and maintenance cost increases.

Therefore, an object of the present invention is to weld the abutting portions of two pipes whose end faces are butted against each other at high speed and with high efficiency, and to make the apparatus compact and simple, and to prevent the influence of the external environment. It is to provide a laser welding method capable of performing stable welding without receiving it.

[0012]

The present invention according to claim 1 is arranged so that it is arranged substantially horizontally and the end faces thereof abut each other.
The butt section of the tube is heated and melted by irradiating the butt section with laser light in parallel from both the inner peripheral surface side and the outer peripheral surface side toward the inner peripheral surface and the outer peripheral surface of the butt section. However, in the laser welding method of joining two pipes, the irradiation position of the laser beam irradiated to the vertically facing surface of the inner peripheral surface and the outer peripheral surface of the butted portion is set along the circumferential direction of the pipe. The irradiation position of the laser light which is moved in one direction and which is irradiated to the vertically facing surface of the inner peripheral surface and the outer peripheral surface of the abutting portion is the irradiation position of the laser light irradiated to the vertically facing surface. By moving in the same direction along the circumferential direction of the pipe, the irradiation position of the laser light for irradiating the surface facing vertically upward, the irradiation position of the laser light for irradiating the surface facing vertically downward. Characterized by being preceded by A laser welding method for.

According to the present invention, the abutting portions of the two tubes arranged substantially horizontally and having their end faces abutting each other are irradiated with laser light from both the inner peripheral surface side and the outer peripheral surface side. The butt portion is heated and melted, and the two pipes are joined. That is, since a plurality of laser beams are radiated to the abutting portion from both sides of the inner peripheral surface and the outer peripheral surface, respectively, the laser light is radiated from either the inner peripheral surface side or the outer peripheral surface side. The butt does not have to be completely melted in the direction of the tube thickness. Therefore, as compared with the conventional one-pass laser welding method, the amount of metal to be melted is reduced by the laser light emitted from the inner peripheral surface side or the outer peripheral surface side. Compared to the case where the amount is large, the influence of the external environment on the welded portion is small, and stable welding is possible. Further, since the inner peripheral surface side and the outer peripheral surface side of the abutting portion are configured to be welded in parallel,
Compared with the prior art, the work efficiency is prevented from lowering and high quality welding is realized. Further, since it is not necessary to melt the entire thickness of the tube with the laser light on either the inner peripheral surface side or the outer peripheral surface side, it is possible to use laser light having a relatively low laser output. Therefore, the laser generation source for generating this laser light may be an existing laser generation source that generates low-power laser light, and thus a welding apparatus can be provided at low cost.

[0014]

In the first region of the upper half of the abutting portion of the two pipes arranged substantially horizontally, the inner peripheral surface faces vertically downward and the outer peripheral surface vertically vertically. When welding the first region, the irradiation position of the first laser light, which is irradiated from the inner peripheral surface side toward the inner peripheral surface, moves to one side along the circumferential direction of the pipe, and The irradiation position of the second laser light irradiated from the surface side toward the outer peripheral surface follows the irradiation position of the first laser light on the inner peripheral surface side and moves in the same rotation direction along the circumferential direction of the pipe. To do.

In the second region of the lower half of the butted portion, the outer peripheral surface faces vertically downward and the inner peripheral surface faces vertically upward. When welding the second region, the irradiation position of the second laser beam irradiated from the outer peripheral surface side toward the outer peripheral surface precedes, moves to one side along the circumferential direction of the pipe, and the inner peripheral surface The irradiation position of the first laser light irradiated from the side toward the inner peripheral surface is
Following the irradiation position of the second laser beam on the outer peripheral surface side, the tube moves in the same rotation direction along the circumferential direction of the tube.

At the boundary between the first region and the second region, the irradiation positions of the following first and second laser beams pass the irradiation positions of the preceding first and second laser beams. And precede.

As described above, by controlling the movement of the irradiation position of each of the first and second laser beams, the first keyhole formed by the preceding laser beam and the second keyhole formed by the following laser beam. Communicates with the keyhole. Therefore, a problem such as formation of pores at the butted portion does not occur. Further, since the metal in the vertically upper region of the thickness of the abutting portion is preheated by the preceding laser beam and then melted by the following laser beam, the temperature of the molten metal in the vertically upper region is high and It takes a long time for the molten metal in the side region to harden. Therefore, the bubbles in the welded portion can escape before the molten metal is hardened, so that blowholes can be prevented. Further, since the molten metal in the vertically lower region of the abutting portion hardens relatively quickly, it is possible to prevent the molten metal from sagging due to gravity in the vertically lower region. Further, the following laser light may be emitted with an advancing angle of about 30 ° or less. By irradiating with the advancing angle, the bubbles in the molten metal formed by the following laser light can escape into the keyhole formed by the same light, so that the blowhole can be prevented. As described above, since welding can be performed while repairing defects, a high quality welded joint can be obtained.

According to a second aspect of the present invention, the laser output of each laser beam irradiated toward the inner peripheral surface and the outer peripheral surface of the butted portion is kept constant, and the irradiation position of each laser beam is maintained. By controlling the moving speed in one direction along the circumferential direction of the pipe, the bead on the inner peripheral surface side of the butted portion, and the overlap amount in the thickness direction of the pipe with the bead on the outer peripheral surface side, over substantially the entire circumference. It is characterized by being held constant.

According to the present invention, the overlapping amount in the thickness direction of the pipe between the bead on the inner peripheral surface side and the bead on the outer peripheral surface side of the butted portion is kept substantially constant over the entire circumference of the pipe. ,
The strength and stress of the weld are almost uniform over the entire circumference of the pipe. Therefore, distortion of the weld and the pipe is reduced. Further, since the laser output of the laser light is held constant, it is not necessary to use a variable laser output source of the laser output as the laser light source, and the structure of the welding apparatus is simplified.

According to a third aspect of the present invention, the moving speed of the irradiation position of each laser beam irradiated toward the inner peripheral surface and the outer peripheral surface of the butted portion in one direction along the circumferential direction of the tube is constant. By controlling the laser output of each laser light in a state of being held at, the overlapping amount in the thickness direction of the pipe with the bead on the inner peripheral surface side of the abutting portion and the bead on the outer peripheral surface side is substantially over the entire circumference. It is characterized by being held constant.

According to the present invention, since the overlapping amount of the bead on the inner peripheral surface side and the bead on the outer peripheral surface side of the abutting portion in the thickness direction of the pipe is maintained substantially constant over the entire circumference of the pipe, welding is performed. The strength and stress of the part is almost uniform over the entire circumference of the tube. Therefore, the distortion of the welded portion and the pipe after the completion of welding is reduced. Moreover, since the moving speed of each laser light in the circumferential direction of the tube is kept constant, the structure of the moving mechanism of the laser output head for emitting the laser light can be simplified.

According to a fourth aspect of the present invention, each laser light emitted toward the inner peripheral surface and the outer peripheral surface of the abutting portion is obtained by dispersing the laser light output from one laser light source. It is characterized by being obtained.

According to the present invention, each laser beam is obtained by dispersing one laser beam obtained from one laser source. Therefore, the welding device only needs to have one laser source, the number of devices can be reduced, and the welding device can be provided at a low price.

According to a fifth aspect of the present invention, after welding the abutting portions, toward the bead formed on the inner peripheral surface side of the abutting portions or on both the inner peripheral surface side and the outer peripheral surface side,
It is characterized by irradiating a laser beam whose output energy is lower than that during welding.

According to the present invention, the bead formed on the inner peripheral surface side of the abutting portion or on both the inner peripheral surface and the outer peripheral surface has a lower output energy than that at the time of welding, for example, defocused laser light. Are irradiated, which partially melts and smoothes the surface of the bead. Therefore, the flow resistance of the fluid flowing in the pipe is reduced as much as possible, and the pressure loss is reduced. Further, by smoothing the bead surface formed on the outer peripheral surface side, it is possible to improve the appearance quality when the quality is poor.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION First, a laser welding apparatus 51 of one embodiment for realizing the laser welding method of the present invention will be described. FIG. 1 is a diagram showing a laser welding device 51.
The laser welding device 51 includes a pipe fixing mechanism 56 that fixes the two steel pipes 52 and 53, and a first laser output head 57 that is arranged on the inner peripheral surface 60 side of the abutting portion 54 of the two steel pipes 52 and 53. A second laser output head 58 disposed on the outer peripheral surface 62 side of the butting portion 54, and a laser oscillator 59.
And a laser light guide fiber cable 65 that connects the laser oscillator 59 to the first and second laser output heads 57 and 58.

The pipe fixing mechanism 56 holds the abutting portions 54 of the two steel pipes 52, 53 whose end faces 55 are abutted against each other from the outer peripheral surface 62 side, and fixes the abutting portions 54, and the steel pipes 56 are fixed to each other. This is a member for positioning the steel pipes 52, 53 so that the pipe axes 64 of the pipes 52, 53 are coaxial.

The first laser output head 57 is arranged on the inner peripheral surface 60 side of the abutting portion 54 with the laser emission port 87 facing the inner peripheral surface 60 of the abutting portion 54, and is attached to each steel pipe 52, 53. It is movably provided along the inner peripheral surface 60 about the common tube axis 64. The first laser output head 57 emits the first laser light 61 from the laser emission port 87 toward the inner peripheral surface 60 of the abutting portion 54.

The second laser output head 58 is arranged on the outer peripheral surface 62 side of the abutting portion 54 with the laser emission port 87 facing the outer peripheral surface 62 of the abutting portion 54, and is common to the steel pipes 52 and 53. Outer peripheral surface 6 around the axis 64
2 is provided so as to be movable in the same direction as the first laser output head 57. This second laser output head 5
8 emits the second laser light 63 from the laser emission port 87 toward the outer peripheral surface 62 of the abutting portion 54.

The laser oscillator 59 includes a housing 68,
A laser beam 6 is stored inside the housing 68.
Laser source 66 that outputs 9 and this laser source 6
It is configured to include a spectroscopic means 67 such as a half mirror that disperses one laser beam 69 output in 6 into two first and second laser beams 61 and 63. This spectroscopic means 67
First and second laser light 61, 63 split by
Through the laser guiding fiber 65, the first and second
It is input to the laser output heads 57 and 58. In this way, the two first and second laser beams 61 and 63 are obtained by splitting the one laser beam 69 output from the one laser generation source 66, so that the laser welding device 5
1 need only have one laser source 66. Therefore, the number of devices can be reduced, and the laser welding device 51 can be provided at a low price. Also,
Laser light 69 output by the laser source 66
A pulsed laser such as a YAG laser or a continuous wave laser such as a carbon dioxide laser is used as the laser.

Next, the first and second laser output heads 5
7, 58 will be described in detail. This first and second
As the laser output heads 57 and 58, a straight cylindrical laser output head 71 shown in FIG. 2 or a refraction cylindrical laser output head 72 shown in FIG. 3 is used. 2 and 3, members having the same function are designated by the same reference numerals.

As shown in FIG. 2, the straight cylinder type laser output head 71 has an output head housing 73 having both ends open and one end (upper part in FIG. 2) to which a laser light guide fiber cable 65 is connected. A tapered welding nozzle 76 provided on the other end side (downward in FIG. 2) of the output head housing 73, a wavelength selection mirror 77, a recollimator lens 74, and a condenser lens provided inside the output head housing 73. 75, a hollow bent portion 84 bent outward from the opening 83 of the side wall of the output head housing 73, and a welding portion observing device 78 such as a CCD camera provided at the end of the bent portion 84. Composed.

The laser light 85 output from the laser oscillator 59 (see FIG. 1) is emitted from the laser light guide fiber cable 65.
The light is incident on the inside of the output head housing 73 through the optical fiber 79 inside. Laser light 85 emitted from the optical fiber 79
Is transmitted through the wavelength selective transmission mirror 77, its width is kept constant by the recollimator lens 74, is condensed by the condenser lens 75, and is emitted from the laser emission port 87 at the tip of the welding nozzle 76. Visible light 81 incident on the inside of the output head housing 73 from the welded portion is reflected by the wavelength selection mirror 77 toward the opening 83 side, and the bent portion 84.
Is received by. The visible light 81 incident on the bent portion 84 is
By the inclined wall 86 of the bent portion 84, the welding portion observation device 78
After being reflected to the side and collected, the welding portion observation device 78
Is received by. Further, as shown by the arrow 82, a shield gas such as an inert gas is introduced into the welding nozzle 76 and is led out from the laser emission port 87.

As shown in FIG. 3, the refracting cylindrical laser output head 72 has an output head housing 92 having first to third openings 89 to 91 facing the T-shaped three directions and an output. The tapered welding nozzle 76 provided on the first opening 89 side of the head housing 92, the wavelength selection mirror 77, and the recollimator lens 74 provided inside the output head housing 73.
And a condensing lens 75 and a welding portion observing device 78 such as a CCD camera provided on the second opening 90 side of the output head housing 92. The laser light guide fiber cable 65 is connected to the third opening 91 side of the output head housing 92.

The laser light 85 output from the laser oscillator 59 passes through the optical fiber 79 in the laser light guide fiber cable 65 and enters the output head housing 73. The width of the laser beam 85 is kept constant by the recollimating lens 74. The laser beam 85 that has passed through the recollimator lens 74 is reflected toward the first opening 89 side by the wavelength selection mirror 77, and the condensing lens 75.
After being collected by the laser beam, the laser beam is emitted from the laser emission port 87 at the tip of the welding nozzle 76. The visible light 81 entering the inside of the output head housing 73 from the welded portion is the wavelength selection mirror 7
The light is reflected toward the second opening 90 side by 7 and is condensed by the condenser lens 88, and then enters the welding portion observation device 78. Further, as shown by the arrow 82, a shield gas such as an inert gas is introduced into the welding nozzle 76 and is led out from the laser emission port 87.

Next, the laser welding method of the present invention will be described with reference to FIGS. 4 is a simplified diagram for explaining the laser welding method of the present invention, FIG. 5 is a diagram showing a welded portion 126 after welding is completed, and FIG. 6 is a perspective view showing a state during welding. FIG. 7 is an enlarged view showing a region 93 surrounded by a virtual line in FIG. First to join 2
The steel pipes 52, 53 are arranged substantially horizontally with their pipe axes 64 being coaxial with each other.
5 to each other, and each steel pipe 5 by the pipe fixing mechanism 56.
Fix 2, 53.

Next, the first laser output head 5 provided inside the abutting portion 54 of the two steel pipes 52, 53.
The first laser light 61 is irradiated toward the inner peripheral surface 60 while moving the tube 7 in one rotation direction (direction of arrow 100) along the inner peripheral surface 60 with the tube axis 64 as the central axis. In parallel with this, the second laser output head 58 provided on the outside 99 of the abutting portion 54 is attached to the outer peripheral surface 6 with the tube axis 64 as the central axis.
The second laser light 63 is emitted toward the outer peripheral surface 62 while moving in the same rotation direction (direction of the arrow 101) as the first laser output head 57 along 2. In this way, the two laser output heads 57 and 58 irradiate the abutting portion 54 with the first and second laser beams 61 and 63, whereby the abutting portion 54 is heated and melted over the entire circumference, and the two abutting portions 54 are heated. Steel pipes 52 and 53 are joined together. In this way, since the inner peripheral surface 60 side and the outer peripheral surface 62 side of the abutting portion 54 are welded in parallel, a decrease in work efficiency can be prevented as compared with the prior art.

More specifically, the abutting portion 54
In the first region 102 of the upper half, the inner peripheral surface 60 faces vertically downward and the outer peripheral surface 62 faces vertically upward. This first area 1
When welding 02, the irradiation position of the first laser beam 61 irradiated from the inside 98 toward the inner peripheral surface 60 precedes,
The irradiation position of the second laser light 63, which moves to one side (clockwise when viewed from FIG. 5) along the inner peripheral surface 60 and is irradiated from the outer 99 toward the outer peripheral surface 62, is the position of the first laser light 61. Following the movement of the irradiation position, the first movement is performed along the outer peripheral surface 62 in the same rotation direction (clockwise as viewed from FIG. 5).
And controlling the movement of the second laser output heads 57, 58.

In the second region 103 in the lower half of the butting portion 54, the outer peripheral surface 62 faces vertically downward, and the inner peripheral surface 6
0 faces vertically above. When welding the second region 103, the irradiation position of the second laser light 63 irradiated from the outside 99 toward the outer peripheral surface 62 precedes one side along the outer peripheral surface 62 (as viewed from FIG. 5). (Clockwise) and move inside 98
The irradiation position of the first laser light 61 irradiated from the inner peripheral surface 60 to the inner peripheral surface 60 follows the movement of the irradiation position of the second laser light 63 on the outer peripheral surface 62, and rotates the same along the inner peripheral surface 60. The first and second laser output heads 57 and 58 are controlled so as to move in the direction (clockwise as viewed in FIG. 5).

At the first boundary position 104 that divides the first area 102 and the second area 103, the second laser light 63 overtakes the irradiation position of the first laser light 61 and precedes, and the second boundary position. At 105, the irradiation position of the first laser light 61 overtakes and precedes the irradiation position of the second laser light,
The first and second laser output heads 57 and 58 are controlled.

Further, as shown in FIGS. 6 and 7, the first laser beam 61 and the second laser beam 63 do not completely melt the abutting portion 54 in the thickness direction by only one of the laser beams. Is irradiated. That is, the first laser beam 61 is irradiated so that the focal point 112 thereof is arranged so as to slightly project from the thickness direction center line 114 of the steel pipe 52 toward the outer peripheral surface 62 side (upper side in FIG. 7).
The focus 113 of the second laser light 63 is slightly closer to the inner peripheral surface 60 side than the center line 114 in the thickness direction of the steel pipe 52 (see FIG. 7).
Is irradiated so as to be arranged so as to project downward (below). Therefore, as the first and second laser beams 61 and 63, laser beams having a relatively low laser output can be used. Therefore, the laser light source 66 (see FIG. 1) is
An existing laser light source that generates low-power laser light may be used. Thereby, the laser welding device 51 can be provided at low cost.

Further, as described above, each laser beam 61, 6
Butt portion 54 is not completely melted in the thickness direction by only one of the three laser beams, so that each of the first and second laser beams 61, 63 is different from the conventional one-pass laser welding method. The amount of metal to be melted in each case decreases. Therefore, the amount of hanging down of the molten metal due to gravity is reduced. As a result, compared to the case where the amount of sagging is large as in the conventional technique, the influence of the external environment on the welded portion is less, and stable welding is possible.

As described above, by controlling the movement of the first and second laser output heads 57 and 58 and the irradiation depth of the first and second laser beams 61 and 63, the butt portion 54 is vertically upward in the thickness direction. The side region 107 is preheated by the preceding laser light 61 and then melted by the following laser light 62. Therefore, the temperature of the molten metal in the vertically upper region 107 is high, and this region 107
It takes a long time for the molten metal to harden. By this, the generated bubbles can escape from the region 107 to the outside by the time the molten metal is hardened, so that blowholes can be prevented. Also, the butting part 5
The vertically lower region 108 of No. 4 is heated only by the preceding laser light 61, so that the molten metal hardens relatively quickly. Therefore, it is possible to prevent the molten metal from hanging down in this region 108. As described above, since welding can be performed while repairing defects, a high quality welded joint can be obtained.

Further, as shown in FIGS. 6 and 7, the first keyhole 105 formed by the preceding first laser beam 61 and the second keyhole formed by the second laser beam 62 following the first keyhole 105. It is preferable to control the moving speeds of the first and second laser output heads 57 and 58 so that 106 and 100 are always in communication. As a result, a defect such as formation of pores in the welded portion 126 does not occur.

At this time, the overlapping amount in the thickness direction of the steel pipe 52 between the first bead 109 on the inner peripheral surface 60 side of the welded portion 126 and the second bead 110 on the outer peripheral surface 62 side is substantially constant over the entire circumference of the pipe. Is preferably held at. Thus, the overlapping portion 1 of the first and second beads 109, 110
By making the overlapping amount of 15 substantially constant, the strength and stress of the welded portion 126 become substantially uniform over the entire circumference of the steel pipe 52, and the welded portion 111 and the welded steel pipe 52,
The 53 strain is reduced compared to prior art welding methods.

The first and second beads 109,
As a method of keeping the overlapping amount of 110 almost constant,
Laser light 6 emitted from the laser output heads 57 and 58
There is a method of controlling the moving speed of the irradiation positions of the laser beams 61 and 63 while keeping the laser outputs of 1 and 63 constant. That is, the moving speed of the laser output heads 57 and 58 is controlled while the laser output is constant. In this method, since the laser outputs of the first and second laser beams 61 and 63 are kept constant, it is not necessary to use a variable energy type laser oscillator as the laser oscillator 59 (see FIG. 1), and the laser welding apparatus is not required. The configuration of 51 is simplified.

Further, the first and second beads 109,
As another method of keeping the overlapping amount of 110 substantially constant, a state where the moving speed of the irradiation positions of the laser beams 61 and 63 is kept constant, that is, a state where the moving speeds of the laser output heads 57 and 58 are kept constant Then, the laser light 61, 63
There is a method of controlling the laser output of. With this method, the structure of the moving mechanism for moving the laser output heads 57 and 58 can be simplified.

As described above, the laser output head 5
7 and 58 are equipped with the weld observation device 78, the condition of the weld 126 can be monitored during the welding operation, and the occurrence of defects can be immediately detected.

Further, it is preferable that the first bead 109 formed on the inner peripheral surface side of the abutting portion 5 is irradiated with a laser beam having a lower output energy than that at the time of welding, for example, a defocused laser beam. That is, it is preferable that the inner peripheral portion of the abutting portion 5 or both surfaces of the inner peripheral portion and the outer peripheral portion thereof be welded by makeup. This causes the bead surface to partially melt and become smooth. Therefore, the flow resistance of the fluid in the pipe is reduced as much as possible, and the pressure loss is reduced. Further, by smoothing the bead surface formed on the outer peripheral surface side, it is possible to improve the appearance quality when the quality is poor.

FIG. 8 is a block diagram showing the control system of the laser welding apparatus 51. In addition to the above-described mechanical structure, the laser welding device 51 includes a control unit 123 that controls the laser welding device 51, first and second laser output heads 57,
Position detection means 118 for detecting the angular position of the tube 58 around the tube axis 64, and the first and second laser output heads 57, 5
No. 8 laser emission port 87 (see FIGS. 2 and 3) and the objective distance detecting means 119 for detecting the distance between the inner peripheral surface 60 or the outer peripheral surface 62 of the abutting portion 54, and the processing conditions of the preceding laser output head. And a second processing condition database 121 in which a plurality of following laser output head processing conditions are stored.
And a third processing condition database 122 in which information for calculating the penetration depth of the melted portion by the laser output head that moves in advance is stored.

That is, the control section 123 receives the penetration depth information observed by the welding section observing device 78, the angular position information detected by the position detecting means 118, and the objective distance information detected by the objective distance detecting means 119. Based on the first to third processing condition databases 120-1
The optimum processing conditions are selected from 22 and the first and second laser output heads 5 are selected based on the selected processing conditions.
7, 58 and the laser oscillator 59 are controlled.

Next, the control method of the control unit 123 will be described with reference to FIGS. 9 and 10. FIG. 9 is a flowchart showing a method of controlling the laser output head (the first or second laser output head 57, 58 which emits the laser beam substantially vertically upward) by the control unit 123, and FIG. 7 is a flowchart showing a method for controlling a laser output head (first or second laser output heads 57 and 58 that emits laser light substantially vertically downward) followed by a control unit 123.

First, the control of the preceding laser output head will be described with reference to FIG. When the welding work is started in step s0, the process proceeds to step s1 and the position detecting means 1
18 detects the angular position of the laser output head preceded by
The objective distance detecting means 119 detects the distance between the preceding laser output head and the inner peripheral surface or the outer peripheral surface of the abutting portion 54. Next, in step s2, the first position detection unit 118 and the object distance detection unit 119 detect the first position based on the detection results.
Optimal processing conditions are selected from the processing condition database 120, and in step s3, laser light is emitted toward the abutting portion 54 based on the selected processing conditions.
Next, in step s4, the welded portion 126 in the middle of welding is observed by the welded portion observation device 78, and in step s5, the penetration depth of the molten metal is calculated from the third processing condition database 122 based on this observation result. And step s6
Then, the calculated penetration depth is output to the second processing condition database 121. After that, when the welding end portion is detected in step s7, the process proceeds to step s8, and welding end processing is performed. If the welding end portion is not detected in step s7, the process returns to step s1 and the above control is repeated.

Next, the control of the laser output head that follows will be described with reference to FIG. When the movement of the following laser output head is started at step t0, the process proceeds to step t1, where the position detecting means 118 detects the angular position of the following laser output head, and the objective distance detecting means 119 follows the following laser output head. The distance from the inner peripheral surface or the outer peripheral surface of the butting portion 54 is detected. Next, in step t2, the position detecting means 118 and the object distance detecting means 11 are detected.
Based on the detection result of No. 9, the optimum processing condition is selected from the second processing condition database 120 in which the penetration depth information of the metal melted by the preceding laser output head is input, and this is selected in step t3. Laser light is emitted toward the abutting portion 54 based on the processing conditions. Next, in step t4, the welded portion irradiated with the laser light is observed by the welded portion observation device 78. After that, when the welding end portion is detected in step t5, the process proceeds to step t6, the welding end process is performed, and the welding operation is ended in step t7. If the welding end portion is not detected in step t6, the process returns to step t1 and the above control is repeated.

As described above, in the laser welding method of the present invention, since the laser beams 61 and 63 are used as the heat source for melting the butt section 54, the butt section 54 is moved at a high speed in the thickness direction. It can be melted and thus the welding can be completed at high speed. Also,
Unlike the electron beam welding method, since it is not necessary to make the atmosphere of the welded portion vacuum, a vacuum chamber is not required, and the laser welding apparatus 51 can be miniaturized and simplified. Furthermore, since the waiting time for welding work until vacuuming is not required, the total working time of welding work can be shortened as compared with the electron beam welding method. In addition, since the bead 109.110 formed is larger than in the electron beam welding method, it is not necessary to strictly process the end face 55 of each steel pipe 52, 53, and the gap tolerance of the groove of this end face 55 is large. .

The above-described laser welding method of the present invention is preferably carried out, for example, in pipeline laying work, and can withstand large-diameter pipes and high-pressure transportation for transporting fluids such as large volumes of gas. It is particularly preferably implemented when connecting slab tubes for.

[0058]

According to the first aspect of the present invention, the abutting portion is irradiated with the laser light from both sides of the inner peripheral surface and the outer peripheral surface, respectively. Does not need to be completely melted in the thickness direction of the tube. Therefore, the amount of metal to be melted by the laser light on either one side is reduced, so that the amount of hanging down of the molten metal due to gravity is reduced, and it is possible to prevent the welding operation from being hindered. Further, since the inner peripheral surface side and the outer peripheral surface side of the abutting portion are welded in parallel, the work efficiency does not decrease as compared with the prior art. Further, since it is not necessary to completely melt the laser beam on either side in the thickness direction of the tube, a laser beam having a relatively low laser output can be used.

Further, according to the present invention, the first keyhole formed by the preceding laser beam and the second keyhole formed by the following laser beam communicate with each other,
Problems such as formation of pores at the butted portion do not occur. In addition, the metal in the vertically upper region of the thickness of the abutting portion, after being preheated by the preceding laser light,
Since it is melted by the following laser beam, the temperature of the molten metal in the vertically upper region is high, and the time until the molten metal in the vertically upper region is hardened becomes long. Therefore,
By the time the molten metal is hardened, the bubbles in the welded portion can escape, so blowholes can be prevented. Further, since the molten metal in the vertically lower region of the abutting portion hardens relatively quickly, it is possible to prevent the molten metal from sagging due to gravity in the vertically lower region.

According to the second aspect of the present invention, the overlap amount of the bead on the inner peripheral surface side and the bead on the outer peripheral surface side of the butted portion in the pipe thickness direction is substantially constant over the entire circumference of the pipe. Since the strength and the stress of the welded portion are substantially uniform over the entire circumference of the pipe, the distortion of the welded portion and the pipe is reduced. Further, since the laser output of the laser light is kept constant, it is not necessary to use a variable laser output source of laser output.

According to the third aspect of the present invention, the overlapping amount in the thickness direction of the pipe between the bead on the inner peripheral surface side and the bead on the outer peripheral surface side of the butted portion is kept substantially constant over the entire circumference of the pipe. As a result, the strength and stress of the weld become substantially uniform over the entire circumference of the pipe, and the distortion of the weld and the pipe after welding is completed is reduced. Further, since the moving speed of each laser beam is kept constant, the structure of the moving mechanism of the laser output head for emitting the laser beam can be simplified.

According to the fourth aspect of the present invention, each laser beam can be obtained by dispersing one laser beam obtained from one laser source, so that the number of devices can be reduced. The laser welding device can be provided at a low price.

According to the present invention of claim 5, the surface of the bead formed on the inner peripheral surface side of the butted portion is partially melted and becomes smooth. Therefore, the flow resistance of the fluid flowing in the pipe is reduced as much as possible, and the pressure loss is reduced.

Further, by partially smoothing the surface of the bead formed on the outer peripheral surface side, it is possible to improve when the appearance quality is poor.

[Brief description of drawings]

FIG. 1 is a diagram showing a laser welding device 51.

FIG. 2 is a diagram showing a straight cylindrical laser output head 71.

FIG. 3 is a view showing a refracting cylindrical laser output head 72.

FIG. 4 is a diagram for explaining the laser welding method of the present invention.

FIG. 5 is a view showing a welded portion 126 after welding is completed.

FIG. 6 is a diagram showing a state during welding.

7 is an enlarged view showing a region 93 surrounded by a virtual line in FIG.

FIG. 8 is a block diagram showing a control system of a laser welding device 51.

FIG. 9 is a flow chart showing a method of controlling a preceding laser output head.

FIG. 10 is a flow chart illustrating a method of controlling a following laser output head.

FIG. 11 is a diagram showing a method of welding the abutting portions 5 of two pipes 2 having V-shaped grooves formed by an automatic MAG welding device.

12A is a diagram showing a butted portion 5 before welding, and FIG. 12B is a diagram showing a welded portion 30 after welding.

FIG. 13 is a diagram showing a method of welding the abutting portions 5 of two pipes 2 having an X-shaped groove formed by an automatic MAG welding device.

14A is a diagram showing a butted portion 7 before welding, and FIG. 14B is a diagram showing a welded portion 32 after welding.

FIG. 15 shows a butt portion 9 in the plasma arc welding method.
It is a figure which shows the method of welding.

16 (a) is a diagram showing a butted portion 9 before welding, and FIG. 16 (b) is a diagram showing a welded portion 34 after welding.

FIG. 17 is a diagram showing a method of welding the abutting portion 13 by a one-pass electron beam welding method.

18 (a) is a diagram showing a butted portion 13 before welding, and FIG. 18 (b) is a diagram showing a welded portion 35 after welding.

FIG. 19 shows an abutting portion 17 by a one-pass laser welding method.
It is a figure which shows the method of welding.

20A is a diagram showing a butted portion 17 before welding, and FIG. 20B is a diagram showing a welded portion 36 after welding.

[Explanation of symbols]

51 Laser welding equipment 52,53 steel pipe 54 Butt 55 Edge 56 tube fixing mechanism 57 First Laser Output Head 58 Second Laser Output Head 59 Laser oscillator 61 First laser light 63 Second laser light 109 1st bead 110 Second Bead 115 Overlap

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23K 26/00-26/42

Claims (5)

(57) [Claims] 1. An inner peripheral surface side and an outer peripheral surface are provided at a butting portion of two pipes which are arranged substantially horizontally and whose end surfaces are butted against each other.
From both sides to the inner and outer peripheral surfaces of the butted part
In the laser welding method in which the butt portions are heated and melted by irradiating the laser beams in parallel toward each other to join the two pipes to each other, the inner circumferential surface and the outer circumferential surface of the butt portions are vertically downward.
The irradiation position of the laser light irradiated on the surface facing the
Move in one direction along the circumferential direction and
Irradiation on the inner or outer surface of the part facing vertically upward
The irradiation position of the laser light to be generated on the surface facing vertically downward.
The circumference of the pipe is tracked according to the irradiation position of the irradiated laser light.
Move in the same direction along the direction and
The irradiation position of the laser light that illuminates the
A laser welding method, characterized in that the irradiation position of the laser light for irradiating the facing surface is set ahead . 2. One of the irradiation positions of each laser beam along the circumferential direction of the pipe in a state where the laser output of each laser beam irradiated toward the inner peripheral surface and the outer peripheral surface of the butted portion is kept constant. By controlling the moving speed in the direction, the overlapping amount in the thickness direction of the pipe between the bead on the inner peripheral surface side of the abutting portion and the bead on the outer peripheral surface side is kept substantially constant over the entire circumference. The laser welding method according to claim 1. 3. The moving speed in one direction along the circumferential direction of the tube of the irradiation position of each laser beam irradiated toward the inner peripheral surface and the outer peripheral surface of the butted portion is kept constant. By controlling the laser output of the laser light,
2. The laser welding method according to claim 1, wherein the overlapping amount of the bead on the inner peripheral surface side of the butted portion and the bead on the outer peripheral surface side in the thickness direction of the pipe is kept substantially constant over the entire circumference. 4. The laser light emitted toward the inner peripheral surface and the outer peripheral surface of the abutting portion is obtained by dispersing laser light output from one laser light generating source. The laser welding method according to claim 1. 5. After welding the butt portion, a laser beam having a lower output energy than that at the time of welding is directed toward a bead formed on the inner peripheral surface side of the butt portion or both the inner peripheral surface and the outer peripheral surface side. Irradiation is carried out.
The laser welding method according to any one of 4 to 4.