JPH116891A - Laser marking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion and unify the depth of thermal effect part by eliminating a double marking location in a display part and reducing laser light irradiation residence time. SOLUTION: By controlling the driving of a galvanomirror 13 with a computer and scanning a laser light in X-Y axes directions, letters are marked on a clad 1. The laser light is fixed in the Y axis direction in turn and scanned in the X axis direction and linear scanning lines x1, x2... are marked in parallel in the Y axis direction with a specific interval to mark letters. The scanning lines x1, x2... constituting the letters do not overlap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser marking method for marking a bar code, a character, a symbol or the like on a surface of a cladding tube of a nuclear fuel rod by using a laser beam.

[0002]

2. Description of the Related Art In fuel rods of a fuel assembly used in nuclear power generation, cladding tubes of the fuel rods are identified and managed so that individual fuel rods can be tracked in each process of manufacturing, transporting, storing, and using the fuel rods. It is required to be able to do it. As means for identifying fuel rods, marking of bar codes, characters, symbols, and the like on the surface of the cladding tube using a laser beam has been performed. As an example of such a conventional technique, there is one disclosed in Japanese Patent No. 2585781. According to this laser marking method, the cladding tube of the fuel rod before inserting the fuel pellet is inserted and held in the marking chamber, and the laser beam is irradiated in an atmosphere gas composed of a mixed gas of argon gas and oxygen gas. Then, the galvanomirror in the chamber is driven to roll the laser beam or scan in the X and Y axes to mark the surface of the cladding tube with characters or symbols by engraving. For example, as shown in FIG. 5, a display unit 2 such as a character or a symbol is displayed on the obtained cladding tube 1, and the display unit 2 is read and identified by a laser beam in each step.

[0003]

By the way, in the display unit 2 engraved by such a laser marking method, for example, as shown in FIGS. 6A and 6B, for example, "A", "8", etc. Intersection 3 between the lines that make up each character
Is a double stamped point. Similarly, when the laser beam is rolled and painted in a coil shape as shown in FIG. 7 for marking, the intersection 3 which is a double marking portion is similarly generated. Since such a double-marked portion has a longer heat retention time due to laser light irradiation on the cladding tube 1, the surface of the cladding tube 1 receives more laser light irradiation than necessary, and local corrosion is likely to occur, Further, there is a disadvantage that the strength of the cladding tube is reduced because the heat-affected zone depth is partially increased.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a laser marking method which eliminates double engraved portions during laser marking to prevent corrosion and a decrease in strength of a cladding tube.

[0005]

A laser marking method according to the present invention is a marking method for marking a display portion using a laser beam on a cladding tube of a nuclear fuel rod, wherein the marking lines are formed so that lines constituting the display portion do not overlap each other. It is characterized by doing so. By marking the display of characters and symbols with engraved lines that do not overlap each other,
Since there is no double engraved part and the heat input residence time by laser beam irradiation is shortened, corrosion of the cladding tube is prevented, and a display part having a uniform heat affected zone depth can be engraved. The engraved lines that constitute the display unit may be substantially parallel to each other, or may be configured so that only the outer contour lines are hollow.

[0006]

FIG. 1 is a block diagram showing an embodiment of the present invention.
2 will be described, and the same members as those described above will be denoted by the same reference numerals and description thereof will be omitted. FIG. 1 is a schematic configuration diagram of a laser marking device according to an embodiment, and FIG.
3A and 3B are characters engraved on the cladding tube by the laser marking method according to the embodiment, where FIG. 3A is an overall view and FIG. 3B is a partially enlarged view. In the laser marking device 10 shown in FIG. 1, the cladding tube 1 is inserted and held in a marking chamber 11 (hereinafter, sometimes referred to as a chamber). A laser oscillator 12 is provided outside the chamber 11, and a laser beam L oscillated from the laser oscillator 12 is provided.
A galvanomirror 13 is disposed on the optical path as a reflecting mirror for directing the laser light L into the chamber 11.
For the engraving display, the galvanomirror 13 operates a known driving means 14 by computer control (not shown) so that the laser beam L can be scanned on the surface of the cladding tube 1 in the X-axis and Y-axis directions. . Galvano mirror 13
A condenser lens 15 for condensing laser light on the surface of the cladding tube in the chamber is provided between the chamber and the chamber 11. An atmosphere gas introduction path 16 is formed in the marking chamber 11, and a mixed gas of an argon gas and an oxygen gas is introduced into the chamber 11 as an atmosphere gas.

A laser marking method performed by using such a laser marking device 10 will be described.
For example, as shown in FIGS. 2A and 2B, the character "8"
Is printed, the galvanomirror 13 is driven and controlled by a computer, and the laser beam is fixed on the surface of the cladding tube, for example, in the X-axis direction, and is moved only in the Y-axis direction to engrave a scanning line x1 of a predetermined distance. I do. Next, the laser beam is moved in the X-axis direction more than the width of the engraved scanning line x1, is engraved while being moved only in the Y-axis direction again, and engraving of the scanning line x2 is performed for a required distance. By repeating such operations, FIG.
It is possible to print a striped engraved character "8" as shown in FIG. According to such a printing method, there is no intersection 3 in the stamp, there is no double stamped portion, the corrosion hardly occurs and the heat affected zone does not partially increase in thickness, so the strength is partially reduced. Nothing to do.

As described above, according to the present embodiment, the intersection 3 is eliminated in the engraving of the cladding tube surface by the laser beam, and the double engraved portion is eliminated. Printing is possible, so that corrosion can be prevented, and marking with a uniform heat affected zone depth can be achieved.

FIG. 3 shows a second embodiment of the laser marking method. In the example shown in FIGS. 3A and 3B, the laser beam is fixed in the Y-axis direction and Can be created by the parallel scanning lines y1, y2,.

FIG. 4 shows a third embodiment of the laser marking method. In the example shown in FIGS. 4 (a) and 4 (b), a galvano laser beam scans in the X-axis and Y-axis directions. By driving and controlling the mirror 13 by a computer,
The outer (and inner) contour lines 8a, 8b of the character "8" are stamped as one continuous line, and then the scan substantially parallel inward along these outer (and inner) contour lines 8a, 8b. The lines z1, z2,... Are marked with laser light as one continuous line. In this case, by increasing the number of scanning lines zi as one continuous line outside the contour line 8a, a thick character can be formed. The inner parallel scanning line z
It is not necessary to engrave 1, z2..., And in that case, laser marking may be performed only by engraving the outer (and inner) outlines 8a and 8b.

[0011]

As described above, in the laser marking method according to the present invention, since there is no double engraved portion by the laser light on the display section on the cladding surface, the laser light irradiation residence time can be shortened and clear engraving can be achieved. Therefore, it is possible to prevent the corrosion and to achieve the marking with the uniform depth of the heat affected zone.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser marking device used for a laser marking method according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing characters marked according to the first embodiment, wherein FIG. 2A is an overall view and FIG. 2B is a partially enlarged view.

FIGS. 3A and 3B are diagrams showing marked characters according to the second embodiment, wherein FIG. 3A is an overall view and FIG. 3B is a partially enlarged view.

FIGS. 4A and 4B are diagrams showing characters marked according to the third embodiment, wherein FIG. 4A is an overall view and FIG. 4B is a partially enlarged view.

FIG. 5 is a partial side view showing the cladding tube on which characters and symbols are engraved.

6 (a) and 6 (b) are diagrams showing conventional engraved characters engraved on the cladding tube surface by laser marking.

FIG. 7 is a diagram showing a conventional stamp engraved on a surface of a cladding tube by rolling.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cladding tube 10 laser marking device 12 laser oscillator 13 galvanometer mirror 14 drive device

Claims (1)

[Claims] 1. A marking method for engraving a display unit using a laser beam on a cladding tube of a nuclear fuel rod, wherein the lines constituting the display unit are engraved so as not to overlap with each other.