JP2560652Y2 - Laser welding equipment for inner peripheral surface of pipe - Google Patents

Description

[Detailed description of the invention] [Industrial applications]

The present invention relates to an apparatus for welding the inner peripheral surface of a tube such as a heat transfer tube in a steam generator of a nuclear power plant using a laser beam.

[Prior art]

FIG. 6 shows an outline of a heat transfer section of a steam generator used in a pressurized water nuclear power plant, and FIG. 7 shows a principle of a conventional heat transfer tube repair method. In FIG. 6, an inlet nozzle 2 through which high-temperature water from a reactor flows is provided at a lower portion of the steam generator body 1, and the high-temperature water passes through the inside of a U-shaped tubular heat transfer tube 4 attached to a tube sheet 3. And returns to the reactor from the outlet nozzle 5. The water supply is supplied from the water supply nozzle 6, descends, flows upward on the outer surface of the heat transfer tube 4, exchanges heat with the high-temperature water inside the heat transfer tube 4, and rises as steam 7;
It is sent to a steam turbine (not shown). The heat transfer tube 4 is supported at several places in the axial direction by a support plate 8. The heat transfer tube 4 may be damaged due to corrosion or vibration, particularly in the region of the support plate 8, and therefore needs to be repaired. One of the repair methods is a sleeve repair method shown in FIG. That is, the sleeve 10 is inserted so as to cover the damaged portion 9 of the heat transfer tube 4 from the inside, and the upper and lower portions of the sleeve 10 are fixed as indicated by reference numeral 11. When circumferential seal welding is used as the fixing means, the heat transfer tube 4
If the material is special, it is necessary to use a considerable amount of high-temperature brazing material, so that there is a problem that the metallurgical structure of the heat transfer tube changes in addition to the difficulty in construction. Therefore, in order to solve the above-mentioned problem, the same applicant as the present application has been conducting research and development on the repair of the sleeve by laser welding, and has described the invention "Laser welding on the inner peripheral surface of the pipe" described in JP-A-64-27788. Apparatus "and the invention" In-pipe welding method using laser "described in Japanese Patent Application Laid-Open No. 64-27789. An inner tube laser welding apparatus according to the former invention is provided with a flexible tube through which an optical fiber transmitting a welding laser beam is inserted and a distal end side inserted into a heat transfer tube, and a flexible tube provided at a distal end portion of the flexible tube. A position detector for detecting a relative position of the flexible tube with respect to the heat transfer tube, an inwardly expanding fixing means for fixing the flexible tube in the heat transfer tube, and a rotation driving means provided on the distal end side of the flexible tube relative to the fixing means A rotating cylinder connected to the rotation driving means and rotating with respect to the flexible tube, and mounted to be rotatable relative to the rotating cylinder and abutting on the inner wall of the heat transfer tube to hold the rotating tube concentrically with the heat transfer tube. A guide support means and a laser beam for welding provided in the rotating cylinder and emitted from the tip of the optical fiber are collected on the inner wall of the heat transfer tube. And a condensing and reflecting optical system for guiding a state. In this inner tube laser welding apparatus, the flexible tube inserted into the heat transfer tube is stopped at a predetermined work site by the position detector, and the flexible tube is fixed to the heat transfer tube by fixing means. At this time, the rotating cylinder is held concentrically with the heat transfer tube by the guide support means, and from this state, the welding laser beam is irradiated to the inner wall of the heat transfer tube via the condensing reflection optical system, and at the same time, the rotation driving means is used. The rotating cylinder is rotated, and the laser beam for welding is caused to scan the inner wall of the heat transfer tube in the circumferential direction. Further, in the in-pipe welding method using a laser according to the latter invention, a notch is alternately provided as a liquid gas flow path at a symmetric portion of a plurality of adjacent lenses to cool the condensing optical system, and the condensing optical system is cooled. A gas nozzle is installed in the vicinity of the emission hole that emits laser from the cylinder built in at the tip to prevent spatter and fumes from adhering and mixing, and the laser focused by the focusing optical system is emitted by the reflection mirror Fins that deflect radially from the hole and allow gas cooling on the back surface of the reflecting mirror are welded to the inner surface of the tube. According to this laser welding method, when the sleeve is inserted into the heat transfer tube and welding is performed from the inner surface of the tube, the laser irradiation in the axial direction is deflected in the radial direction by the condensing optical system for condensing the laser and the reflecting mirror. A welding portion outside the cylinder can be welded from an emission hole provided in a cylinder having a built-in condensing optical system and a reflecting mirror.
Further, the condenser optical system and the reflection mirror in the cylinder can be gas-cooled, and spatters and fumes from a welded portion are prevented from adhering and mixing into the cylinder.

[Problems to be solved by the invention]

In particular, for the heat transfer tubes of a steam generator used in a nuclear power plant, since the materials used are carefully selected and the quality control is also strictly performed, the sleeve inserted in such a heat transfer tube is laser-welded. In such a case, the laser welding apparatus is required to have various functions as described below. (1) A function that allows good outgassing and allows the welding device to be centered at the center of the sleeve. (2) A function capable of sufficiently cooling the gas, reducing the deterioration due to fumes and spatter generated from the welded portion, and deflecting the laser beam from the axial direction to the radial direction. (3) A function that enables multi-pass welding in the circumferential direction. (4) Function to monitor welding speed. (5) A function that can set the welding device at a predetermined position and hold it at that position. (6) Function to determine the welding start position by remote control. However, the above-described laser welding apparatus and method of the prior art can perform some of the above functions, but cannot perform all of them, so that they are not always satisfactory and have been improved. Accordingly, an object of the present invention is to provide a laser welding apparatus for an inner peripheral surface of a pipe, which can perform all of the functions described above.

[Means for Solving the Problems]

In order to achieve this object, laser welding which is inserted into a working pipe prior to the start of welding, stops at a predetermined working position in the working pipe, and performs laser welding on the inner peripheral surface of the working pipe with a laser beam. According to the present invention, the device is a conduit cable section including a tube through which an optical fiber for transmitting the laser beam is inserted and a distal end is inserted into the working tube; and the apparatus is connected to the conduit cable section;
An inflatable welding device holding portion that engages with the inner peripheral surface of the working tube when expanded to hold the welding device in the working tube; and that the laser beam emitted from the tip of the optical fiber is applied to the working tube. A rotatable condensing and reflecting optical system that guides the condensing and reflecting optical system to the welding portion; a rotation driving section including a hollow output shaft that can rotationally drive the condensing and reflecting optical system; and is mounted so as to be relatively rotatable with respect to the hollow output shaft. A centering mechanism of the laser welding device, comprising: an engaging portion that engages with the inner wall of the working tube and is displaceable in a radial direction; and a centering mechanism portion of the laser welding device; In order to stop at the predetermined working position, a position detector that issues a signal indicating the position of the predetermined portion when passing through the predetermined portion of the working tube, and during the welding, the condensing reflection optical system in the working tube Controls circumferential and axial position And a circumferential position detecting unit and an axial position detecting unit, which are respectively disposed so as to be driven by the output shaft of the rotation driving unit and are electrically connected to the rotation driving unit. The position detection unit in the circumferential direction includes an encoder including a hollow rotor connected to the output shaft, and the position detection unit in the axial direction moves in the axial direction when the output shaft rotates. A positioning and control unit comprising: a contact operating member screwed to the output shaft; and a pair of contacts disposed at upstream and downstream limit points with respect to the axial movement of the contact operating member; And scavenging means for removing metal vapor generated at the time of welding; and cooling means for cooling the converging / reflecting optical system at the time of welding.

[Action]

A typical case where the working pipe is a heat transfer pipe of a steam generator will be described. In the heat transfer pipe to be laser-welded, a sleeve is already provided by the laser welding of the present invention so as to cross a welded portion which needs to be welded due to damage. It is inserted by a tool separate from the device, and the position of the sleeve is known. Such a weld is usually likely to occur at a position where the heat transfer tube passes through the tube support plate. As the laser welding device is inserted into this heat transfer tube, the position detector of the positioning and control unit, which is an eddy current coil, sequentially detects the positions of predetermined portions of the heat transfer tube corresponding to the plurality of tube support plates. It emits a signal and also detects the end of the sleeve and emits a signal. Since the position of the sleeve is known, the detection signal at the end of the sleeve can be identified based on, for example, the number of detection signals from the tube support plate. Is set to a predetermined work position in the heat transfer tube by remote control. In this state, when the inner-spread type welding device holding portion is operated, the holding portion expands radially outward in the heat transfer tube and engages with the inner peripheral surface thereof. Thus, the laser welding device is held concentrically with the heat transfer tube under the action of the centering mechanism, and is fixed at the predetermined working position. Next, a laser oscillator, which can be installed outside the steam generator, is operated to emit a laser beam from the converging / reflecting optical system toward the welding portion, and the rotational driving portion and the circumferential position of the positioning / control portion are controlled. The detection unit and the axial position detection unit, the scavenging unit, and the cooling unit are operated. When the rotation drive unit is operated, its output shaft is rotated, and the condensing and emitting optical system is also rotated, so that laser welding is performed on the welded portion in the circumferential direction. At that time, in the circumferential position detection unit consisting of the encoder and the rotor, the encoder transmits a pulse for each constant rotation angle of the rotor rotated by the output shaft, to detect the rotation speed of the output shaft, The rotation speed of the condensing / reflecting optical system driven from the output shaft, that is, the welding speed, can be monitored. Also, in the axial position detection unit consisting of the contact operating member and the pair of contacts, when the output shaft rotates, the contact operating member moves up and down in the axial direction according to the rotation direction, abuts on the contact, and outputs. Detect the shaft rotation limit. Therefore, the welding speed can be monitored from the signals of the position detectors in the circumferential direction and the axial direction, and the welding start position can be set by remote control, so that the rotation angle of the output shaft can be accurately grasped. Further, during the welding process as described above, the scavenging means and the cooling means are operated to remove the metal vapor generated at the time of welding and to cool the condensing reflection optical system.

【Example】

Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts. FIG. 1 shows a laser welding apparatus according to a preferred embodiment of the present invention inserted into a U-shaped heat transfer tube (working tube) 4 used in a steam generator as shown in FIG. The welding device is continuous along lines AA and BB. In a use state, a portion shown on the upper side in FIG. 1 is an upper portion of the welding device, and a first portion below the welding device. The lower part shown on the lower side of the figure is located. Therefore, in the following description, “upper” or “upper” means the left side in FIG. 1, and “lower” or “lower” means the first side in FIG.
Represents the right side in the figure. The laser welding apparatus shown in FIG. 1 generally includes a conduit cable section 21, a welding apparatus holding section 22, a positioning / control section 23, a rotation driving section 24, a converging / reflecting optical system 25,
And an alignment mechanism 26. The conduit cable section 21 incorporates an optical fiber 27 for transmitting a laser beam such as a YAG laser and various signal lines, and also has a function as a gas pipeline.
Preferably a flexible tube 21a and a micro tube 30
Consists of In FIG. 1, the inwardly expanding welding device holding portion 22 located on the left side of the conduit cable portion 21 is a tubular flexible holding bag 28 attached to a block 29 attached to a long casing 51.
Having. The holding bag 28 is in flow communication with the microtube 30, and when the pressurized gas flows into the holding bag 28 through the microtube 30, the holding bag 28 expands or expands radially outward, and It engages with the inner peripheral surface of the heat tube 4. Thereby, the welding device is positioned in the heat transfer tube 4. When the pressurized gas is discharged through the microtube 30, the holding bag 28 is reduced in diameter, and the holding of the welding device is released. In the figure, the positioning / control unit 23 disposed on the left side of the welding device holding unit 22 includes an eddy current coil unit (position detector) 31 mounted on the long casing 51 and an axial position detection unit 32.
And a circumferential position detector 33. Fifth
The figure shows the positioning / control section 23 in a simplified cross section. In FIGS. 1 and 5, an eddy current coil portion 31 is formed by winding an eddy current coil 31b in an insulating holder 31a mounted on a long casing 51 in a circumferential direction of a welding device, and electromagnetically surrounding the eddy current coil 31b. When the condition changes in the axial direction of the welding device, the electric output changes. The eddy current coil part 31 utilizes such a property, and for example, the eddy current coil 31 when the welding device passes across the tube support plate 8 is used.
Based on the change in the output of b, the number of the tube support plate that the welding device has passed or the position of the tube support plate is macroscopically detected. The eddy current coil section 31
The same operation is performed when the welding device passes through the upper and lower ends of the sleeve (working pipe) 10 so that the positional relationship of the welding device with respect to the sleeve 10 can be known. Next, the axial position detection unit 32 of the positioning / control unit 23
A contact holder or contact operating member 35 which is screwed into a male screw portion 34a of a motor shaft (output shaft) 34 described later and which moves up and down (left and right in FIGS. 1 and 5) by rotation of the motor shaft 34. (As its name implies, it holds a contact 35a, which is a moving contact that moves with the contact holder 35) and an upstream and downstream limit point for the axial movement of the moving contact 35a. The two switch contacts 36 fixed to the long casing 51 at the upper and lower limit points
(A pair of contacts). Since the contact holder 35 is prevented from rotating by known means, when the motor shaft 34 rotates in a manner described later, the contact holder 35 moves up and down in accordance with the rotation direction. The moving contact held by the holder contacts the switch contact 36. As a result, an electric signal is transmitted, and the clockwise or counterclockwise rotation limit of the motor shaft 34 can be detected. Since the vertical movement of the condensing / reflecting optical system 25 is caused by the rotational drive of the motor shaft 34 as described later, the axial position detecting unit 32 defines the condensing point of the laser, that is, the upper limit and the lower limit of the welding portion 53. be able to. The circumferential position detection unit 33 of the positioning / control unit 23 includes a hollow shaft encoder 38 having a hollow rotation 37 and attached to a long casing 51. The hollow rotor 37 is fixed to the motor shaft 34 by a key 37a as shown in the figure, and emits a pulse every time the motor shaft 34 rotates a predetermined angle, as is well known. Based on this pulse, the motor shaft 34
The rotation angle can be accurately grasped. Therefore, by combining the above-described signal of the axial position detection unit 32 and the signal of the circumferential position detection unit 33, accurate positioning of the welding portion 53 can be achieved. Referring again to FIG. 1, the rotation drive unit 24 is disposed above the positioning / control unit 23 in the embodiment. The rotation drive unit 24 includes the hollow motor shaft 34 whose upper and lower limit points are supported by bearings 39, and an ultrasonic motor 40. As is well known, the ultrasonic motor 40 can switch between rotation and stop at a small rotation angle at a high speed, and a high output torque can be obtained even under such a condition. Since the required reducer is unnecessary,
The motor output torque can be used with high efficiency despite its small size. Each ultrasonic motor 40 has a set of a motor 69 and a stator 70.
In the embodiment, the cascade has a multi-stage structure in which four sets of the rotor 69 and the stator 70 are arranged in the axial direction in order to increase the output. 1 and 2C.
As can be seen from the drawing, the rotation of the motor shaft 34 can be transmitted to the lens case 42 because it is connected to the lens case 42 by the rotation transmission pin 41. However, with respect to the movement in the axial direction, since the rotation transmitting pin 41 is inserted through the long window formed along the axial direction in the lens case 42, the lens case 42 has the same axial length as the long window. It is independently movable with respect to the motor shaft 34 within a permissible range. That is, the lens case 42 is designed so that when the motor shaft 34 rotates, it can move up and down according to the direction of rotation. An optical fiber sheath 44 is inserted into the hollow rotor shaft 34, and the upper end of the optical fiber sheath 44 is supported above the motor shaft 34 via a bearing 43. The upper portion of the motor shaft 34 is provided with a lens holder 46 of an entrance side lens group 45 of a converging / reflecting optical system lens group to be described later.
The motor shaft 34 and the optical fiber sheath
As can be seen from the arrows in FIG. 1, the annular gaps between 44, which represent the flows of gases necessary to protect the tip of the welding device,
It is a flow path of the same gas. The converging / reflecting optical system 25 is added to the lens case 42 screwed to the upper end of the long casing 51 as indicated by reference numeral 47,
A lens group 48 held by the lens holder 46 in the lens case 42, and a reflection mirror 49 mounted in a mirror case 68 attached to the lens case 42 by a known means. Has an emission hole 50 formed therein. As described above, when the motor shaft rotates and the rotation is transmitted to the lens case, the lens case moves up and down according to the rotation direction of the motor shaft. Since the operation of the lens case 42 determines the welding line, the pitch of the threaded portion indicated by reference numeral 47 is determined so that appropriate welding can be obtained. The lens group 48 is a group of four lenses, and is designed so that the beams between the second and third lenses are substantially parallel to the axis of the condensing optical system 25. Since the two lenses 45 on the incident side are housed in the lens holder 46 above the motor shaft 34, they do not move in the axial direction even when the motor shaft 34 rotates, and the optical fiber 27 Optical relationship can be maintained. On the other hand, since the two lenses on the emission side are housed in the lens case 42, when the motor shaft 34 rotates, the two lenses rotate together with the lens case 42 and move in the axial direction to move the second and third lenses. Although the distance between the lenses changes, as described above, the beams between them are almost parallel, so that the optical influence on the output beam can be practically neglected. The reflection mirror 49 deflects the beam emitted from the lens group 48 in the radial direction toward the exit hole 50.
Since the lens is housed in the mirror case coupled to the lens, it rotates together with the two lenses on the emission side, and there is no change in the relative position between them. Further, as shown in FIG. 2A, since the cooling fins (cooling means) 52 are formed in the reflecting mirror 49 in the axial direction, the mirror cooling gas 58 can easily flow along the reflecting mirror 49, and can be efficiently cooled. is there. Further, in order to blow away metal vapor such as fumes and spatters generated during welding from the welding portion 53 between the heat transfer tube 4 and the sleeve 10, a mirror cooling gas flow path (between the outer lid 57 and the lens case 42) is provided. In addition to the cooling means 61, an assist gas flow path (scavenging means) 60 is defined, and the nozzle 55
It is designed so that fumes and the like are washed away in a direction away from the exit hole 50 by the assist gas 54 that exits, and do not enter the interior through the exit hole 50. Therefore, the welding equipment
It is advantageous to control the exit hole 50 (having a dimension close to the beam diameter) so as to be located as low as possible with respect to the welded portion 53 from the viewpoint of preventing intrusion of fumes and the like. For this reason, the angle of the reflection surface of the reflection mirror 49 is selected so as to emit an upward beam within a range that does not affect the penetration shape.
It is preferable that the beam is 95 to 110 ° and the beam is 5 to 20 ° upward from horizontal. Further, the condensing / reflecting optical system 25 includes a shielding plate 56 for shielding the above-described fumes and the like from the reflecting mirror 49 and the lens group 48. Since the outer lid 57 of the nozzle portion 55 is close to the welded portion 53 and becomes high temperature and is easily damaged, it is preferable that the outer lid 57 be formed of platinum which is rich in heat resistance, ductility and weldability. It is preferable to manufacture with tungsten which has high heat resistance because of fumes and the like. As described above, in the laser welding apparatus according to the present invention, the assist gas 54 for blowing off fumes and the like, the mirror cooling gas 58 for cooling the reflecting mirror 49, and the lens group 48
Lens cooling gas 59 is used to cool the pipes. However, if three separate pipelines are separately provided in the conduit cable section 21, the cross-sectional area of each pipeline is reduced, and the pipeline resistance is increased, which is preferable. For this reason, the gas is supplied to one portion of the upper portion of the motor shaft 34 near the upper portion of the motor shaft 34 by using a hollow portion having a large cross-sectional area by utilizing the hollow portion, and the remaining portions are divided into three systems. Since the lens cooling gas 59 does not require much, it is supplied from the gap of the bearing 43, and the assist gas 54 and the mirror cooling gas 58 are supplied to the lens case 42 as shown in FIG. 2B.
First, the assist gas flow channel 60 and the mirror cooling gas flow channel 61 are grooved to secure the flow rates. The flow distribution is adjusted such that the sectional area ratio of the assist gas flow channel 60 and the mirror cooling gas flow channel 61 is preferably 2 to 5: 1. In laser welding, since the variation in the distance between the reflecting surface of the reflecting mirror 49 and the welded portion 53 affects the penetration depth, it is necessary to keep this distance as constant as possible. Therefore, an alignment mechanism 26 is provided at the top or the tip of the welding device. The synchronizing mechanism 26 is a pantograph type having three link mechanisms 62 which are arranged at equal intervals in the circumferential direction. Each link mechanism 62 has a roller (engaging portion) 63 held at an adjacent end of the pair of links, and a compression coil spring disposed at a remote end of the pair of links.
By compressing the pair of links in the mutual direction by 64, the peripheral surface of the roller 63 comes into contact with the inner surface of the heat transfer tube 4. The center of the three rollers 63, that is, the center of the welding device, can be accurately aligned with the center of the heat transfer tube 4 because the heat transfer tube 4 is substantially circular. The alignment mechanism 26
In order to not disturb the flow of the assist gas 54, the lower end thereof is inclined upward as shown in FIG.
As will be understood from the drawing, in order to improve the escape of the assist gas 54, gas venting means, that is, a plurality of gas vent grooves 71 and gas vent holes 72 are formed alternately. Although the centering mechanism 26 shown in FIG. 1 is of a pantograph type, as shown in FIG. 3, FIG. 3A and FIG. 4), a multi-stage brush (engaging portion) 67 extending outward in the radial direction as shown in FIG.
May be in contact with the inner peripheral surface of the heat transfer tube 4 by a brush type.

[Effect of the invention]

As described above, the laser welding apparatus for the inner peripheral surface of the pipe according to the present invention described in the claims for utility model registration includes a conduit cable section, a welding apparatus holding section, a condensing / reflecting optical system, a rotation driving section, and a centering apparatus. A mechanism unit, a positioning / control unit, a scavenging unit, and a cooling unit are provided. These components operate in the above-described manner, and (1) gas is easily released, and the welding device is located at the center of the sleeve. Centering function, (2) sufficient gas cooling, less deterioration due to fumes and spatters generated from the weld, and the ability to deflect the laser beam in the radial direction from the axial direction, and (3) multiple passes in the circumferential direction A function that enables welding, (4) a function that can monitor the welding speed, (5) a function that can set and maintain the welding device at a predetermined position, and (6) a remote control of a welding start position. it can It is capable of performing all of the capacity, as a working tube, particularly a device suitable for application to laser welding of the inner peripheral surface of the heat transfer tube of a steam generator of a nuclear power plant is provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a laser welding apparatus for an inner peripheral surface of a pipe according to the present invention, and FIG. 1A is a plan view of a centering mechanism in the laser welding apparatus of FIG. 1, FIG. 2A, FIG. 2B and FIG. Figure 2C shows the first
FIG. 3 is a sectional view taken along lines 2A-2A, 2B-2B, and 2C-2C of FIG. 3, and FIG.
3A is an end view of FIG. 3 viewed from the left side, and FIG.
FIG. 4 is a sectional view taken along line 3B-3B of FIG. 4, FIG. 4 is a partial sectional view showing another modified embodiment of the centering mechanism, and FIG. 5 is a positioning / control unit in the laser welding apparatus of FIG. FIG. 6 is a cross-sectional view schematically showing a heat generator of a steam generator used in a pressurized water nuclear power plant.
FIG. 7 is a sectional view showing the principle of a conventional heat transfer tube repairing method. In the figure, 4 ... work pipe (heat transfer pipe), 10 ... work pipe (sleeve), 21 ... conduit cable section, 22 ... welding apparatus holding section, 23 ... positioning / control section, 24 ... rotary drive Department, 25
… Focusing / reflecting optical system, 26… Centering mechanism section, 27… Optical fiber, 31… Position detector (eddy current coil section), 32… Axial position detection section, 33… Circumferential direction , The position detector, 34 ...
Hollow output shaft (motor shaft), 35: Contact operating member (contact holder), 35a: Moving contact, 36: Switch contact (paired contacts), 37: Hollow rotor, 38: Encoder, 52 ... …
Cooling means (cooling fins), 60 scavenging means (assist gas flow path), 61 cooling means (mirror cooling gas flow path), 63
... engagement part (roller), 66 ... engagement part (ball), 67 ... engagement part (brush), 71 ... gas release means (gas release groove),
72 ... Gas venting means (gas vent hole).

Continued on the front page (72) Inventor Yoshimasa Tsukamoto 1-1-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside the Mitsubishi Heavy Industries, Ltd. Kobe Shipyard (72) Inventor Isao Shirasu 1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo No.1-1, Mitsubishi Heavy Industries, Ltd., Kobe Shipyard

Claims (1)

(57) [Scope of request for utility model registration] (1) Inserting into a working pipe prior to the start of welding,
A laser welding device which stops at a predetermined working position in the working tube and performs laser welding with a laser beam on an inner peripheral surface of the working tube, wherein an optical fiber for transmitting the laser beam is inserted and a tip side is inserted. A conduit cable portion including a tube inserted into the working tube; and an inner expansion type connected to the conduit cable portion and engaged with an inner peripheral surface of the working tube when inflated to hold the welding device in the working tube. A rotatable condensing / reflecting optical system that guides the laser beam emitted from the tip of the optical fiber to the welding portion of the working tube in a condensed state, and rotationally drives the condensing / reflecting optical system A rotary drive unit including a possible hollow output shaft; an engagement unit mounted to be rotatable relative to the hollow output shaft and capable of engaging with the inner wall of the working tube and displacing in the radial direction; Having a step, a centering mechanism of the laser welding device, and a position of the predetermined portion when passing through a predetermined portion of the work tube so as to stop the laser welding device at the predetermined work position in the work tube. A position detector that emits a signal to inform the operator, and during welding, the output shaft of the rotary drive unit is driven by the output shaft of the rotary drive unit to control the circumferential and axial positions of the converging and reflecting optical system in the working tube. And a circumferential position detecting unit and an axial position detecting unit electrically connected to the rotation drive unit, and the circumferential position detecting unit is connected to the output shaft. A contact actuating member screwed to the output shaft in such a manner as to be movable in the axial direction when the output shaft rotates, the contact actuating member comprising an encoder including a hollow rotor. Regarding axial movement A positioning / control unit comprising a pair of contacts arranged at upstream and downstream limit points; scavenging means for removing metal vapor generated at the time of welding the work tube; and the condensing / reflecting optics at the time of welding A laser welding apparatus for an inner peripheral surface of a pipe, comprising: cooling means for cooling a system.