JP2003220469A - Narrow gap welding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a narrow gap welding apparatus capable of monitoring welding conditions to the last layer by using a common CCD camera without growing the apparatus in size and lowering the productivity. <P>SOLUTION: A CCD camera 1, a welding torch 13, and a wire torch 14 are arranged to a fitting plate 16 for drawing up in a line. By intrusion of the welding torch 13 and the wire torch 14 into a narrow gap G with an outer sheath 8 by passing through a shielding box 15, the image light of the welding part in the narrow gap G is reflected in the vertical direction which is inclined to 30-70° by the prism on the point of the outer sheath 8, and the image light is introduced in a refraction index distribution-type rod lense. After the strong ultraviolet ray emerges from the upper edge and is reduced by the shielding filter in the lense box 4, the image light is focused on the light receiving surface of the CCD camera 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention welds base metals together by an arc generated in a narrow groove formed in a base metal such as a steel plate of a thick plate and monitors the welded portion with an image pickup device. The present invention relates to a welding device for narrow groove.

[0002]

2. Description of the Related Art Main piping of power generation boilers and pressure vessels such as nuclear reactor pressure vessels (RPV) have a thickness of 30 mm to 15 mm.
It is made by welding a large number of 0 mm thick planks. For example, the main piping that forms part of the power generation boiler is composed of a main steam pipe, a high-temperature reheat steam pipe, a low-temperature reheat steam pipe, a main water supply pipe, etc. It is a diameter pipe. The main pipe is a pipe for sending high-temperature, high-pressure steam heated by the coil from the boiler to the turbine, and returning the steam that has worked in the turbine to the boiler coil again.

As described above, since the main pipe itself is exposed to high temperature and high pressure, the expansion and contraction amount at the time of starting and stopping the boiler is large and stress concentrates on the welded joint. Therefore, high quality welding is required for the welded portion of the main pipe. In reality, the groove width is 5 to 5 in order to suppress the heat input to the base material, reduce welding distortion and thermal influence, and perform welding efficiently.
The tip arc welding method with a narrow opening of 12 mm is used. More specifically, when stainless steel or high alloy steel is used as the base material, non-consumable electrode type GTA (Gas Tangsten Arc) welding method is used, and when low alloy or mild steel is used as the base material, consumable electrode is used. The GMA (Gas Metal Arc) welding method is often used.

FIG. 7 is an explanatory view for specifically explaining the narrow groove GTA welding method according to the conventional example. A narrow groove G having a width of 5 to 12 mm is machined between the base materials 17a and 17b arranged to face each other, and a long welding torch 13 having a thickness smaller than the groove width is inserted together with the wire torch 14. A tungsten electrode 18 is attached to the tip of the welding torch 13,
This tungsten electrode 18 is used as a negative electrode and the base materials 17a and 17b.
Is used as a positive electrode, and an arc AC is generated between them, and an inert (argon) shielding gas is blown to the welding portion from an outlet (not shown) at the tip of the welding torch 13 to shield the welding portion from the air. There is. The addition wire 21 is fed to the welded portion through the wire torch 14, and the base materials 17a and 17b are joined by filling the narrow groove G with the molten welding metal.

The addition wire 21 is wound on a wire reel 26 and guided by a wire feeder 25 to a welding portion via a conduit cable 27 and a wire torch 14. Further, since the welded portion cannot be completely shielded from the air entrained from the periphery of the welding torch 13 only by the shielding gas blown from the tip of the welding torch 13, the shielding box 15 is provided above the welding torch 13 outside the narrow groove G. The shielding gas is provided in the narrow groove G direction from here, and the entire inside of the narrow groove G is kept in an inert gas atmosphere. A welding device (not shown) including these respective components is transferred at a constant speed in the arrow direction along the narrow groove G direction by a transfer device (not shown) such as a carriage.

In this welding method, one-pass one-pass multi-layer welding is performed, and a layer having a thickness of one layer is 2 to 4 mm is formed. Therefore, when the base materials 17a and 17b become thicker, the welding work is performed. It becomes a long continuous welding for several hours. In addition, the tungsten electrode 18 is formed in the narrow groove G so that one of the base materials 17a, 17
When approaching the b side, the wall surface on the approaching side abnormally melts, and fusion failure occurs on the wall surface on the opposite side. As described above, it is very important to adjust the position of the tungsten electrode 18 in the narrow groove G, and in order to ensure high welding quality, it is necessary to monitor the arc welding condition in the narrow groove G. . For this reason, the labor burden on the welder is very large, and the CCD (Charge Coupled Device) camera is used to remotely control the welding conditions in the narrow groove G, and the welded portion is captured by the CCD camera. The image of the above was analyzed by an image processing device to automatically control the position of the tungsten electrode 18 and automatically adjust the welding conditions.

FIGS. 8A and 8B are explanatory views showing a welding state in a narrow groove using a welding device, FIG. 8A shows a case of pipe welding, and FIG. 8B shows a case of longitudinal member welding. The welding condition monitoring device is composed of a CCD camera 1 for photographing the welded portion, a monitoring television 22, a signal cable 23 for transmitting a video signal, and an image processing device (not shown) connected as necessary. In addition,
For details of the welding status monitoring device, see, for example, Japanese Patent Laid-Open No.
185810 or JP-A-7-299565.

Since the CCD camera 1 having a normal size does not enter the narrow groove G, the welded portion in the narrow groove G is monitored from diagonally above the narrow groove G. In addition, recently the diameter is 7 mm.
Although there is a special ultra-fine CCD camera on the market, it is necessary to directly receive the radiant heat from the weld inside the narrow groove G or to preheat the base metal to 100 to 250 ° C depending on the base material. Therefore, in order to arrange the CCD camera in the narrow groove G, a high temperature heat resistance of about 200 ° C. is a necessary condition. Further, since spatter and agglomerated particles scattered from the welded portion are exposed, the housing, particularly the lens, may be damaged. If countermeasures against splashing are taken to prevent such damage, the CCD camera 1 is installed in the narrow groove G. Very difficult to place.

There are a wide variety of inspection items for monitoring the welding condition, such as the left and right positions of the tungsten electrode 18, the arc length, the degree of melting of the wall surface of the base metal, and the contact position of the addition wire 21 with the molten pool. In order to check these matters as accurately as possible, it is necessary to view the weld from the horizontal direction. However, as described above, in the case of narrow groove welding, the CCD camera 1 has to be arranged outside the narrow groove G. Therefore, when the welding portion is to be expected, the pipe welding shown in FIG. In this case, if the position of the CCD camera 1 is slightly separated from the welding torch 13 according to the diameter of the base metal 17c, the welded portion can be visually recognized from the horizontal direction. Will always have a predetermined viewing angle with respect to the horizontal direction even if the CCD camera 1 is separated from the welding torch 13.

[0010]

As mentioned above, in the prior art, in order to check the weld as accurately as possible,
In the case of long material welding, use the CCD camera 1 as the welding torch 13.
Must be placed quite a distance from. As described above, since the distance between the CCD camera 1 and the welding torch 13 must be set large, the following problems occur.

That is, since the target monitored by the CCD camera 1 becomes far, the CCD camera 1 is likely to be affected by the mechanical vibration applied to the monitoring of the welded portion. Therefore, in order to improve the monitoring accuracy, it is necessary to increase the rigidity of the mounting jig for mounting the CCD camera 1. Therefore, the entire welding condition monitoring device becomes large and the welding torch 13 is introduced into the narrow groove G. The workability at the time of setup work is impaired, the work time is increased, the accuracy of the work is reduced, and the difficulty of the optical axis alignment work is increased. Further, in order to accurately recognize the target with the CCD camera 1, it is necessary to increase the magnification of the image, and for that purpose, a lens having a large aperture must be used. Further, since the shielding box 15 is arranged near the surface of the base material 17, when the welding portion reaches near the final layer, the shielding box 15 blocks the field of view of the welding portion, making it impossible to monitor. Occurs.

It is an object of the present invention to use a normal CCD camera to monitor the welding condition up to the final layer without increasing the size of the device, and for narrow gaps without lowering workability. It is to provide a welding device.

[0013]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a welding condition monitoring means which extends downward from an image pickup device arranged above a base metal in the vicinity of a welding torch and is narrowly opened. An image of a welded portion, which is provided with a small-diameter and vertically-long photoconductor fitted in the tip, a sheath body provided so as to surround the photoconductor and protecting the photoconductor, and a sheath body provided below the sheath body. And a light reflecting means for reflecting light toward the light guide portion of the photoconductor, and preferably, the sheath body has a double structure of an inner sheath body and an outer sheath body, and a gap between them. It has a transfer means for causing a cooling fluid to flow therethrough and integrally transferring the welding torch, the gas releasing means, and the welding status monitoring means. The imaging device is a CCD camera, the photoconductor is a gradient index rod lens or an optical fiber, and the photoconductor and CC
A light-shielding filter for dimming ultraviolet rays may be provided in the optical path between the D camera and the D-camera so as to freely appear. Further, the image processing device may be connected to the CCD camera.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a view showing a welding state in a narrow groove using a welding device according to a first embodiment of the present invention, (a) is a front view of the welding device, and (b) is a side view thereof. is there. In the figure, 4 is a lens box which is connected to the CCD camera 1 and stores an eyepiece lens and a light blocking filter, and 16 is a C
An attachment plate for attaching the CD camera 1, the welding torch 13, and the wire torch 14 to the welding device, and 19 is a welding bead formed at the bottom of the narrow groove G by the completion of welding. It should be noted that the same or like parts as those of the conventional example are designated by the same reference numerals, and duplicate description will be omitted.

The CCD camera 1, the welding torch 13, and the wire torch 14 are mounted on a mounting plate 16 so as to be aligned in a straight line, and the welding torch 13 and the wire torch 14 penetrate the shield box 15 together with the outer sheath body 8 to form a narrow space. It is fitted in the groove G. With the above configuration, when the welding device moves, C
The CD camera 1, the welding torch 13, and the wire torch 14 move integrally. Welding progresses and welding bead 19
Even when it comes close to the surface of the base material 17, the shielding box 15 must keep a position that does not separate from the surface of the base material 17.

FIG. 2 is a structural view showing a lower structure of the welding condition monitoring device in a sectional shape, and FIGS. 3, 4, and 5 are respectively taken along cutting lines II, II-II, and III-III of FIG. FIG. In these drawings, 2 is a special light-shielding filter for dimming the intense ultraviolet rays generated from the arc AC, 3 is an eyepiece lens, 5 is a gradient index rod lens arranged along the optical axis of the eyepiece lens 3. , 6 is a cylindrical inner sheath that houses the gradient index rod lens 5, 7 is a gap, 8 is a cylindrical outer sheath that covers the outside of the inner sheath 6 through the gap 7,
Reference numeral 9 denotes an objective lens attached to the tip of the inner sheath body 1,
0 is a protective glass that protects the tip of the outer sheath body 8 from spatters and agglomerated particles generated from the welded portion, 11 is a prism that tilts the visual field of the gradient index rod lens 5 by 30 to 70 °, and 12 is shielded by the gap 7. A cooling gas inlet provided in the lens box 4 for allowing a cooling gas having the same composition as the gas to flow into the gap 7, and a fitting 28 for fitting the protective glass 10 to the outer sheath body 8.

The gradient index rod lens is composed of a cylindrical optical glass body in which the refractive index is distributed in a parabolic shape from the central axis toward the outer peripheral surface, and even if both end surfaces are flat, Since it has an optical property equivalent to that of a curved lens, it is preferably used for transmitting an object image over a predetermined distance.
For example, a gradient index rod lens 5 with a diameter of 2 mm or less
Is housed in an inner sheath body 6 which is a protective metal tube made of stainless steel or copper, and an objective lens 9 is attached to the tip thereof.

In the lens box 4 arranged between the gradient index rod lens 5 and the CCD camera 1, from the bottom, the eyepiece 3 for adjusting the focus and the intense ultraviolet rays generated from the arc AC are emitted. A light blocking filter 2 for reducing the light is arranged. There are no particular restrictions on the order of arrangement of the light blocking filter 2 and the eyepiece lens 3. The light-shielding filter 2 can be slid laterally by a drive mechanism (not shown), and the light-shielding filter 2 is brought out into the optical path during welding work.
At other times, retract the light blocking filter 2 from the optical path,
The CCD camera 1 confirms the condition of the welded portion before the welding operation and visually confirms the appearance of the weld bead 19 after the welding operation.

The prism 11 arranged under the gradient index rod lens 5 guides the image light of the welded portion to the gradient index rod lens 5 with an inclination of 30 to 70 °. The protective glass 10 prevents spatter and agglomerated particles generated from the welded portion from adhering to the prism 11 or the like and causing stains or damages.

As shown in FIGS. 2 and 3, for example, the outer diameter is 4
Four caulking protrusions projecting inward are formed at upper and lower two places of the outer sheath body 8 of mm or less, and are supported and fixed to the outer peripheral portion of the inner sheath body 6. In this way, the sheath body that protects the gradient index rod lens 5 has a double structure, and in the gap 7 between them,
A cooling gas having the same composition as the shielding gas introduced into the lens box 4 from the cooling gas inlet 12 flows down.
Due to the cooling action of this cooling gas, the temperature rise of the outer sheath body 8 is suppressed to about 60 ° C. or less, and the gradient index rod lens 5
Protects against high temperature environment.

The image light of the welded portion in the narrow groove G is transmitted through the protective glass 10, is reflected by the prism 11 in the vertically upward direction inclined by 30 to 70 °, is condensed by the objective lens 9, and is of a refractive index distribution type. The light is guided into the rod lens 5, is emitted from the upper end of the rod lens 5, is condensed by the eyepiece lens 3, and intense ultraviolet rays are reduced by the light shielding filter 2, and then is imaged on the light receiving surface of the CCD camera 1. The image of the welded portion is converted into image data by the CCD camera 1, transmitted to the monitor television 22 via the signal cable 23, and reproduced as a projected image on the screen.

In this way, the condition of the welded portion in the narrow groove G is reproduced on the screen of the monitor TV 22 regardless of its position, so that the welder uses the monitor TV 22 to weld the welded portion in the narrow groove G. It is possible to perform the welding operation smoothly by appropriately operating the welding device while remotely monitoring the situation. It is also possible to connect the image processing device to the CCD camera 1 and analyze the image of the welded portion by image processing to automatically adjust the position of the tungsten electrode 18, the welding condition and the like.

As described above, in this embodiment, the welding condition monitoring device enters the narrow groove G only at the outer sheath body 8 portion, so that the width of the narrow groove G is 10 mm or less. Can be easily fitted inside the outer sheath body 8 and the shielding box 1
Since it can be arranged near the welding torch 13 through 5
Since the state of the arc AC can be monitored from the first layer to the last layer with a clear image, and the welding condition monitoring device can be downsized, the optical axis can be easily aligned and the welding torch 13 can be installed in the narrow groove G. There is no loss of workability. Further, the gradient index rod lens 5 is provided with a double sheath body, that is, an inner sheath body 6.
Since the outer sheath body 8 is covered with the outer sheath body 8 and a cooling gas having the same component as the shielding gas is made to flow through the gap 7 to cool the gap 7, the temperature rise of the outer sheath body 8 can be suppressed to about 60 ° C. or less. In the present embodiment, the case where the present invention is applied to the narrow groove GTA welding has been described, but the present invention is not limited to this and can be applied to the narrow groove GMA welding or the narrow groove laser welding.

FIG. 6 is a view showing a welding state in a narrow groove using a welding device according to a second embodiment of the present invention, (a) is a front view of the welding device, and (b) is the same. It is a side view. In the figure, reference numeral 29 is a vertical moving body which is attached to a mounting plate 16 so as to be vertically movable and to which the CCD camera 1 and the wire torch 14 are fixed. In this embodiment, the welding torch 13 has a narrow groove G.
The tungsten electrode 18, which is located above the base metal 17 and does not enter the inside, enters the narrow groove G and projects long from the welding torch 13. Also, the inner sheath body 6
An optical fiber is used instead of the gradient index rod lens for the optical material housed inside.

Since the welding portion is shielded by the shielding gas flowing from the welding torch 13 into the narrow groove G, the welding torch 13 needs to be installed on the upper side of the base metal 17 and has a length of about 40 mm or more. It cannot be installed in deep grooves. It is necessary to shorten the protrusion length of the tungsten electrode 18 as the welding progresses and the welding bead 19 becomes multi-layered, and the welded portion approaches the surface of the base material 17, but the vertical moving body 29 is raised and the CCD is raised accordingly. The camera 1 and the wire torch 14 are moved upward.

[0026]

As described above, according to the first aspect of the present invention, the thin film which extends downward from the image pickup device arranged above the base material in the vicinity of the welding torch and fits into the narrow groove. Since it has a vertically long photoconductor, a sheath body that protects the photoconductor, and a light reflection means that reflects the image light of the welding portion toward the light guide portion of the photoconductor, a narrow and deep opening is provided. Even within the destination,
It is possible to monitor the welding condition up to the final layer with a clear image without increasing the size of the device, and workability is not degraded.

According to the second aspect of the invention, the sheath body has a double structure of the inner sheath body and the outer sheath body, and the cooling fluid is flown into the gap between them, so that the photoconductor is heated to a high temperature. It is possible to prevent exposure and dramatically improve the heat resistance of the welding condition monitoring means. According to the invention described in claim 3, since the welding torch, the gas releasing means and the welding status monitoring means are integrally transferred, the arc can be stably formed and the welded portion can be stably monitored. You can

According to the fourth aspect of the present invention, since a light-shielding filter for reducing ultraviolet rays is provided in the optical path between the photoconductor and the CCD camera so as to be freely exposed, the durability of the CCD camera is improved. You can According to the invention of claim 5,
Since the image processing device is connected to the CCD camera, the position of the tungsten electrode, welding conditions, etc. can be automatically adjusted.

[Brief description of drawings]

FIG. 1 is a front view (a) and a side view (b) of a welding apparatus showing a welding state in a narrow groove according to a first embodiment of the present invention.

FIG. 2 is a structural diagram showing a lower structure of a welding condition monitoring device in a sectional shape.

3 is a cross-sectional view taken along the line I-I of FIG.

4 is a cross-sectional view taken along the section line II-II of FIG.

5 is a cross-sectional view taken along the section line III-III in FIG.

FIG. 6 is a front view (a) and a side view (b) of a welding device showing a welding state in a narrow groove according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram for specifically explaining a narrow groove GTA welding method according to a conventional example.

FIG. 8 is an explanatory view (a) showing a welding state in a narrow groove of pipe welding using a welding device according to a conventional example and an explanatory view (b) showing a welding state in a narrow groove of longitudinal material welding. is there.

[Explanation of symbols]

1 CCD camera 2 Shading filter 3 eyepiece 4 lens box 5 Gradient Index Rod Lens 6 Inner sheath 8 Outer sheath 9 Objective lens 10 Protective glass 11 prism 13 welding torch 14 wire torch 15 Shield box 16 Mounting plate 17 (a, b) base material 18 Tungsten electrode 19 Weld beads 21 Additive wire 22 Surveillance TV AC arc G narrow groove

Claims (5)

[Claims] 1. A welding means for welding the base materials together by generating an arc between a base material having a narrow groove and a tungsten electrode protruding from a welding torch fitted in the narrow groove. Narrow groove welding including an inert gas discharge means for flowing an inert gas near the welded portion to shield the welded portion from the air, and a welding condition monitoring means for photographing and monitoring the welded portion with an imaging device. In the apparatus, the welding status monitoring means,
A small-diameter, vertically-long photoconductor that extends downward from the imaging device disposed above the base material near the welding torch and fits into the narrow groove, and surrounds the photoconductor. And a light reflecting means provided on the lower part of the sheath for reflecting the image light of the welding portion toward the light guide of the photoconductor. Narrow groove welding equipment characterized by the following. 2. The welding device for a narrow groove according to claim 1, wherein the sheath body has a double structure of an inner sheath body and an outer sheath body, and a cooling fluid is flown in a gap between them. . 3. The welding device for a narrow groove according to claim 1, further comprising a transfer means for integrally transferring the welding torch, the gas releasing means and the welding status monitoring means. 4. The image pickup device is a CCD camera, the photoconductor is a gradient index rod lens or an optical fiber, and a light blocking filter for reducing ultraviolet rays is provided in an optical path between the photoconductor and the CCD camera. The welding device for a narrow groove according to claim 1, wherein the welding device is provided so as to be freely movable. 5. The welding device for narrow groove according to claim 4, wherein an image processing device is connected to the CCD camera.