KR20160118175A - Welding jig for laser welding of spacer grids for a nuclear fuel assembly - Google Patents

Abstract

The present invention relates to a laser welding method of a spacer grid for a nuclear fuel assembly, and is a laser welding method of the spacer grid for a nuclear fuel assembly in which laser welding is performed by welding jig provided with a plurality of reference markers, comprising: (S10) a first step of extracting image information based on a position coordinate of the reference markers; (S20) a second step of correcting the position coordinate of the reference markers in the image information extracted in the first step (S10); and (S30) a third step of performing laser welding on a welding point based on the position coordinate of the corrected reference markers.

Description

Technical Field [0001] The present invention relates to a welding fixture for laser welding of a support grid for a nuclear fuel assembly,

The present invention relates to a welding fixture for laser welding a support grid for nuclear fuel assemblies.

The support grid for the nuclear fuel assemblies constitutes the skeleton together with the fuel rod, the measuring tube, and the guide tube, and the grid plates having the springs and dimples stamped thereon are assembled in a lattice form so that the intersections are welded, do.

On the other hand, the support lattice plates are formed such that incisions are formed at right angles to each other so as to be assembled, and the intersections of the plates crossing the lattice plates are assembled by inserting the incisions of the support lattice plates.

1, the laser welding operation is performed in the welding chamber together with the welding fixture to be supported by the support grid itself 10, and the welding fixture is provided on the four outer sides of the supporting grid itself A retention strap 20 and an upper press plate 30 and a lower press plate 40 which are assembled with the retention strap 20 and are fixed to the upper press plate 30 and the lower press plate 40 The through holes 31 and 41 are formed at positions corresponding to the intersections of the support gratings so that the laser beams are irradiated to the intersections of the support gratings through the through holes 31 and 41 so that welding can be performed.

The upper pressing plate 30 and the lower pressing plate 40 are formed with fixing holes 32 and 42 so that the welding jig is assembled through the welding rotary plate and the fixing holes 32 and 42 provided in the welding chamber . Such a welding jig has a constant clearance and firmly fixes the support grid 10 to be welded to prevent weld failure.

2, the welding rotary plate comprises a first welding rotary plate 51 and a second welding rotary plate 52. One side of the first welding rotary plate 51 is supported by a support member 53, (A) on the horizontal axis by the driving unit 54. [

The second welding rotary plate 52 is rotatably driven on the vertical axis of the first welding rotary plate 51 (reference B).

A laser welding device 70 is provided on the upper part of the welding rotary table, and the laser welding device 70 is provided to be capable of linear motion on the x-axis, the y-axis and the z-axis.

Therefore, the support grid itself, which is fixedly seated on the welding rotary plate together with the welding jig, is welded on the welding portion by the rotational motion in the biaxial direction and the linear motion of the laser welding device 70 in the three axial directions.

The laser welding apparatus of the prior art can obtain accurate image information about the welding point so that accurate welding operation can be performed by grasping the precise position of the welding point, thereby correcting the positional deviation between the laser beam irradiation position and the welding point, .

For example, Japanese Patent Application Laid-Open No. 10-0922159 (Publication Date: October 21, 2009) and Japanese Patent Laid-Open Publication No. 58-168488 (Publication Date: And corrects positional deviation between the laser beam irradiation position and the welding point.

3 (a), the position (WP) of each weld point should be accurately formed at the intersection of the support grid itself, but due to the clearance, tolerance, or assembly pressure of the welded grid itself Position deviation occurs.

Therefore, as shown in FIG. 3 (b), the positional deviation XG (YG) is corrected from the image information about the deviation between the position WP of the welding point and the intersection of the support grid itself, .

Specifically, the position coordinates of the respective welding points of the support grid itself are programmed into the NC control apparatus, and the laser welding apparatus 70 is controlled with the position coordinates programmed for each welding point to perform rough positioning, The welding operation is performed by performing image correction on the laser welding apparatus 70 with respect to the positional deviation XG (YG) by obtaining the image information in the state where the alignment is completed (i.e., the state shown in FIG. 3B).

However, in such a conventional laser welding operation, after the laser welding apparatus 70 is driven up to the approximate position, image information about the welded portion is obtained, positional deviation is extracted, and the welding position of the laser welding apparatus 70 is finely corrected By performing the welding operation, the position control of the laser welding apparatus 70 for one welding portion proceeds in two steps. Therefore, there is a problem in that it takes much time to complete the welding work for the support grid having many welded joints with many intersections.

Registered Patent No. 10-0922159 (Date of Notification: 2009.10.21)

Registration No. 10-0922161 (Date of Notification: 2009.10.21)

Japanese Patent Application Laid-Open No. 58-168488 (published on Apr. 10, 1983)

The present invention aims to provide a welding fixture capable of shortening the welding operation time and improving the productivity in the laser welding method of the conventional support grids for nuclear fuel assemblies.

In order to accomplish the above object, a welding fixture for laser welding a support grid for a nuclear fuel assembly according to the present invention is a welding fixture for laser welding by assembling a support grid, And a plurality of fiducial markers capable of image recognition.

Preferably, the fiducial markers are disposed between at least a plurality of through holes.

Preferably, the fiducial marker comprises a pin body having a circular plane to be assembled to a welding jig body; And a pin head having a diameter smaller than that of the pin body and assembled to the upper portion of the pin body.

More preferably, the pin body and the pin head have at least different brightness levels on the upper surface.

More preferably, the pin head is semi-spherical.

According to the welding fixture of the present invention, image information can be extracted based on a plurality of reference markers capable of image recognition, and laser welding can be performed at an accurate position.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a view showing a support grid itself and a welding fixture,
FIG. 2 is a view showing a main configuration of a general laser welding apparatus,
3 (a) and 3 (b) are diagrams showing the positional correction for the welding point in the prior art laser welding apparatus,
4 is a configuration diagram of a laser welding apparatus for a laser welding method according to the present invention,
5 is a plan view of a welding fixture according to the present invention,
6 (a) and 6 (b) are a plan view and a side view showing a preferred embodiment of a reference marker of a welding fixture according to the present invention,
7 is a flow chart showing a laser welding method of a support grid according to the present invention,
FIG. 8 is a view for explaining the alignment process of the support grid in the laser welding method of the support grid according to the present invention,
9 is a view for explaining the welding process of the crossing point of the support grid in the laser welding method of the support grid according to the present invention,
10 is a view for explaining the welding process of the sleeve in the laser welding method of the support grid according to the present invention,
11 is a photograph showing a sleeve welding portion in a laser welding method of a support grid according to the present invention.

The specific structure or functional description presented in the embodiment of the present invention is merely illustrative for the purpose of illustrating an embodiment according to the concept of the present invention, and embodiments according to the concept of the present invention can be implemented in various forms. And should not be construed as limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

It is to be understood, however, that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It will be further understood that the terms " comprises ", or "having ", and the like in the specification are intended to specify the presence of stated features, integers, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 4, the laser welding apparatus includes a laser welding module 110 in which welding is performed to generate a laser beam, and an image is photographed on a welding part, an image processing unit 120 in which image processing is performed on the photographed image, A control unit for receiving the image data transmitted from the image processing unit 120 and controlling the rotation driving of the laser welding module 110 and the welding rotary plate 130, 140).

The laser welding module 110 includes a laser generating unit 111 for generating a laser beam, an image capturing unit 112 disposed perpendicularly to the laser generating unit 111, And a beam splitter 113 which is guided to the welding point, and preferably further includes a driving unit 114 for linear driving in three axial directions.

Although not shown, the laser welding module 110 may be provided with a known aiming optics for focusing and irradiating the laser beam to the welding spot.

The laser welding module 110 can be moved in three axial directions by the driving unit 114. For example, the laser welding module 110 determines the position of the welding spot by horizontally moving on a plane, The focusing with respect to the welding point can be made with the aiming optics.

The image processing unit 120 processes the image signal transmitted from the image capturing unit 112 to detect a welding position, and extracts a peak value by an FFT-based cross-correlation algorithm based on a standard image. Thereby extracting position information of the welding point and the like.

The welding rotating plate 130 is placed on the supporting grid 10 assembled by the welding jig 200 and rotatably drives the supporting grid 10 according to the welding position.

The welding rotary plate 130 is rotatably supported by the support member 131 so that the vertical rotary axis and the horizontal axial rotary motion can be performed.

In this embodiment, the welding position is moved by the horizontal movement of the laser welding module 110. However, in another embodiment, when the laser welding module is fixed and the supporting grid 10 is placed in the seating position The support member may move horizontally to move the welding position.

Particularly, the welding jig 200 is characterized in that a reference marker is provided together with a through hole through which the laser passes.

As illustrated in FIG. 5, the welding jig 200 may be formed with a plurality of through holes 230 corresponding to the positions of the intersection points CP of the support grid to perform a welding operation such as the intersection CP of the support grid And a plurality of fiducial markers 210 and 220 are provided on the welding fixture 200 with a predetermined pattern.

In this embodiment, the reference markers 210 and 220 are divided into a first reference marker 210 used for aligning a welding fixture or an intersection welding of a support grid, and a second reference marker 220 used for welding a sleeve. .

The first reference marker 210 includes an alignment reference marker 210a disposed at four corners of the welding fixture 200 according to the position and a reference marker 210b for aligning the welding fixture 200 And an intersection welding reference marker 210b arranged in a line with an interval.

6A, the first reference marker 210 has a first pin body 211 having a circular plane to be assembled on the upper portion of the body of the welding jig, and a second pin body 211 having a smaller size than the first pin body 211 And a first pin head 212 having a diameter and being assembled on top of the first pin body 211. [

The first pin body 211 is provided with a first fixing protrusion 211a protruding vertically from the lower portion thereof and the first fixing protrusion 211a is assembled to the upper portion of the body of the welding fixture.

6 (b), the second fiducial marker 220 includes a second pin body 221 having a circular plane to be assembled on the upper portion of the body of the welding jig, And a second pin head 222 having a small diameter and being assembled on top of the second pin body 221. In particular, the second pin head 222 is semi-spherical.

The first and second fiducial markers 210 and 220 commonly have first and second pin heads 212 and 222 having diameters smaller than that of the first and second pin bodies 211 and 221, For example, the surfaces of the first and second fin bodies 211 and 221 are matte black and the first and second pin heads 212 and 212 The first and second pin heads 212 and 222 have a large lightness difference from the first and second pin bodies 211 and 221 so that the reference markers using image information processing It can be effective for position coordinate extraction.

In particular, the second fiducial markers 220 used for sleeve welding have a semicircular second pin head 222, so that even when the support grids are rotated on the horizontal axis to perform laser welding, It is effective to extract the position coordinates of

These reference markers are recognized as image information for the welds and used as reference points for the welds, and the specific welding process will be described with reference to the related drawings.

In this embodiment, the reference marker is separately attached to the body of the welding fixture. Alternatively, the reference marker may be a mark (pattern) formed directly on the surface of the body of the welding fixture. Preferably, It may be provided by machining a circular pattern on the body surface of the welding jig.

4, the control unit 140 receives image information about the welding point or the like transmitted from the image processing unit 120 and controls the rotation driving of the driving unit 114 or the welding rotary plate 130, 10). ≪ / RTI > In particular, the control unit 140 stores the position coordinates of the welding jig 200 with respect to the reference marker and the relative coordinates of the welding point with reference to the reference marker.

The control unit 140 extracts the image information for the welded portion from the position coordinates of the reference markers and corrects the positional coordinates with respect to the reference markers in the image information so that the welding operation for the correct welding point can be performed.

7 is a flow chart showing a laser welding method of a support grid according to the present invention.

Referring to FIG. 7, a method of laser welding a support grid according to the present invention includes a first step (S12) of extracting image information based on a position coordinate of a reference marker; A second step S20 of correcting the position coordinates of the reference marker in the image information extracted in the first step S12; And a third step (S30) of performing laser welding on the welding point based on the position coordinates of the corrected reference markers.

Preferably, the method may further include a fourth step (S40) of performing laser welding on the next welding point according to a predetermined pattern based on the welding point where welding is completed.

For example, in the present invention, it can be understood that a certain pattern is laser welded while moving horizontally by a set pitch interval in the case of welding to the intersection of the support grid, and in the case of welding to the sleeve, It is understood that laser welding is carried out while horizontally moving by a predetermined pitch interval while being rotated by a predetermined angle (for example, 45 degrees) with respect to the horizontal axis.

The controller 140 extracts image information based on the reference marker of the welding fixture 200. The control unit 140 controls the driving unit 114 to move the reference marker The laser welding module 110 is positioned and the image information is obtained through the camera 112 and the image processing unit 120 at the corresponding positions.

Preferably, the first step may further include a step (S11) of extracting image information of the position coordinates of two reference markers before the welding operation and aligning the support grids.

8, the position coordinates of two alignment reference markers 210a 'are extracted and calculated from the four corners of the welding fixture 200. At this time, the positions of the two alignment reference markers 210a' The rotation angle [theta] for aligning the welding jig 200 from the coordinates can be obtained. Therefore, the welding jig 200 can be accurately aligned by rotating the welding rotary plate by the rotation angle? So that the welding reference markers 210a are positioned at the aligned coordinates.

Alignment of the welding fixture 200 may be performed in a procedure requiring confirmation of the alignment state of the welding fixture at the beginning of welding or during the welding process.

Next, the second step S20 is a process of extracting image information based on the position coordinates of the reference markers necessary for welding, and then correcting the position coordinates by reflecting the positional deviation with respect to the reference markers in the image information.

In the third step S30, laser welding is performed on the welding point based on the position coordinates of the corrected reference markers. Laser welding is performed for each welding point based on the position coordinates.

In a fourth step S40, laser welding is performed to the next welding point according to a predetermined pattern on the basis of the welding point at which the welding is completed. As a result, Laser welding is performed on the intersections of the support grids while moving horizontally, and in the case of welding to the sleeve, the support grids are rotated about the horizontal axis by a predetermined angle (for example, 45 degrees) Laser welding can be performed while moving by a set pitch interval.

More specifically, referring to FIG. 9, a description will be made of a welding process for the intersection of the support grid. In this embodiment, a plurality of reference markers for welding an intersection point are disposed at the center of the welding fixture 200 in the longitudinal direction. The control unit 140 moves the laser welding module 110 to the stored position coordinates of the reference marker 210b at the bottom of the intersection welding to process the image information about the area, And performs position coordinate correction of the fiducial marker 210b. This corrects the positional coordinates of the fiducial markers 210b for intersection welding due to the tolerance generated when the welding jig 200 is loaded on the welding rotary 130.

Next, the control unit 140 performs laser welding on the welding point according to the relative coordinate r from the corrected intersection welding reference marker 210b to the stored intersection point.

Thereafter, laser welding is performed for the intersections while horizontally moving in the horizontal direction by a predetermined pitch (d) with respect to the same welding point.

10, the supporting grid will be described with reference to FIG. 10. In this embodiment, the support grid includes a first sleeve 11 at the center and a guide tube assembled with the guide tube, The second sleeve 12 is laser welded to the support grid. The welding jig 200 corresponds to the first and second sleeves 11 and 202 and the brackets 201 and 202 fastened to the respective sleeves by bolts are fixed to the upper portion of the second sleeve 12.

In this embodiment, the process of welding the first sleeve 11 and the second sleeve 12 to the support grid is the same, and therefore, the first sleeve 11 will be described in the following description.

A pair of second reference markers 221 and 222 are disposed facing each other with respect to the first sleeve 11 as a center.

The welding of the first sleeve 11 is performed by rotating the position of the welding jig 200 with respect to the second reference markers 221 of the two reference markers 221 and 222 And laser welding is performed to the welding point of the sleeve according to the relative coordinates of the welding point of the second reference marker 221 and the sleeve. In this embodiment, the sleeve is laser welded at the four welding points of the support grid, so that after laser welding of the sleeve by the relative coordinates of the first reference marker 221 and the sleeve, The welding can be performed while rotating the welding wire 90 by 90 degrees.

The second fiducial markers 221 and 222 arranged to face each other in this embodiment function as fiducial markers for a rotation angle of 180 degrees. Accordingly, even if the fiducial mark 200 is rotated at an arbitrary rotation angle, It is possible to extract image information for the marker.

FIG. 11 is a photograph showing a sleeve welded portion. The welded portion of the first sleeve 11, which is assembled with the support grating, protrudes from the upper surface of the welding jig. Thus, when the support grating is laid down by 45 degrees with respect to the horizontal axis, .

In the present invention, the pin head of the second fiducial marker 221 has a semicircular shape so that the positional coordinates of the fiducial markers can be easily extracted in a state where the welding fixture is rotated at an arbitrary angle other than the plane.

The laser welding method of the support grid according to the present invention is characterized in that in comparison with the conventional technique in which image information is extracted at each welding point to perform positional coordinates and laser welding is performed at the corrected positional coordinates, The positional coordinates of the reference marker are corrected and welded to relative coordinates up to the welding point based on the reference markers, and the remaining welding points are horizontally The welding operation time can be remarkably shortened by performing laser welding on the welding spot while moving or rotating the supporting grid by a predetermined angle.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be apparent to those of ordinary skill in the art.

110: laser welding module 111: laser generator
112: image capturing unit 113: beam splitter
114: driving unit 120: image processing unit
130: welding rotary plate 140:
200: welding fixture 210: first reference marker
210a: fiducial markers for alignment 210b: fiducial markers for intersection welding
220: second reference marker 230: through hole

Claims (5)

A welding fixture for laser welding by assembling support grids,
A welding fixture for laser welding a support grid for nuclear fuel assemblies, comprising a plurality of reference markers capable of image recognition, wherein a plurality of through holes are formed so that the laser can penetrate through the welding sites. The welding fixture for laser welding a support grid for nuclear fuel assemblies according to claim 1, wherein the fiducial markers are disposed between at least a plurality of through holes. 2. The apparatus of claim 1, wherein the fiducial markers
A pin body having a circular plane to be assembled to a welding jig body;
And a pin head having a diameter smaller than that of the pin body and assembled to the upper portion of the pin body. 4. The welding fixture for laser welding a support grid for a fuel assembly according to claim 3, wherein the pin body and the pin head have at least a different surface brightness. The welding fixture for laser welding a support grid for a nuclear fuel assembly according to claim 3, wherein the pin head is semi-spherical.

Images