JP3976841B2 - Laser marking method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser marking method for marking a display portion such as a bar code, a character, or a symbol on a surface of a cladding tube of a nuclear fuel rod using a laser beam.
[0002]
[Prior art]
Fuel rods for fuel assemblies used in nuclear power generation are required to be able to identify and manage fuel rod cladding so that individual fuel rods can be tracked in each process such as manufacturing, transportation, storage, and use of fuel rods. Yes. As a means for identifying a fuel rod, a laser beam is used to mark a bar code, a character, a symbol or the like on the surface of the cladding tube.
An example of such a prior art is 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 galvanometer mirror in the chamber is driven to roll the laser beam or scan in the X and Y axis directions to mark the surface of the cladding tube with characters, symbols, and the like by imprinting.
For example, as shown in FIG. 5, a display unit 2 such as characters and symbols is displayed on the obtained cladding tube 1, and this is read and identified by a laser beam in each step.
[0003]
[Problems to be solved by the invention]
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. The intersection 3 is a double-engraved place. Similarly, when the laser beam is rolled and painted and engraved in the shape of a coil as shown in FIG.
Since such a double-engraved portion has a long heat input residence time due to laser beam irradiation on the cladding tube 1, the surface of the cladding tube 1 is subject to excessive laser beam irradiation and local corrosion is likely to occur. Moreover, since the depth of the heat affected zone is partially increased, there is a disadvantage that the strength of the cladding tube is lowered.
[0004]
In view of such problems, an object of the present invention is to provide a laser marking method in which double marking portions are eliminated during laser marking to prevent corrosion and strength reduction of the cladding tube.
[0005]
[Means for Solving the Problems]
The laser marking method according to the present invention is a marking method in which a display portion is engraved on a cladding tube of a nuclear fuel rod using a laser beam. The outer contour line, the inner contour line, the outer contour line, and the inner contour line of the display portion . by stamping the substantially parallel scan lines located between the contour line along the contour, respectively, wherein the display unit, respectively, as the outer and inner contour and the scanning lines do not overlap each other one constituting the It is characterized in that it is engraved as a continuous line of books .
By marking the display part of characters, symbols, etc. with the inner and outer contour lines and scanning lines that are engraved so as not to overlap each other, the double engraving location is eliminated and the heat input residence time due to laser light irradiation is shortened It is possible to prevent the pipe from being corroded and to mark the display portion having a uniform heat affected zone depth.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
First , a laser marking apparatus used in a laser marking method according to an embodiment of the present invention and a reference example of a laser marking method using the laser marking apparatus will be described with reference to FIGS. 1 and 2. The description will be omitted using reference numerals. Figure 1 is a schematic configuration diagram of a record over The marking device, Fig 2 is a character that has been imprinted on the cladding tube in Reference Example Les chromatography The marking method is (a) overall view is, (b) is a partial 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 disposed outside the chamber 11, and a galvanometer mirror 13 is disposed on the optical path of the laser light L emitted from the laser oscillator 12 as a reflection mirror for directing the laser light L into the chamber 11. In order to display the marking, the galvanometer mirror 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-Y axis direction. ing. A condensing lens 15 is provided between the galvanometer mirror 13 and the chamber 11 for condensing the laser light on the surface of the cladding tube in the chamber.
An atmosphere gas introduction path 16 is formed in the marking chamber 11 so that a mixed gas of argon gas and oxygen gas is introduced into the chamber 11 as the atmosphere gas.
[0007]
A laser marking method performed using such a laser marking apparatus 10 will be described.
For example, as shown in FIGS. 2A and 2B, when printing the character “8”, the galvano mirror 13 is driven and controlled by a computer, and the laser light is fixed on the surface of the cladding tube, for example, in the X-axis direction. In addition, the scanning line x1 of a predetermined distance is marked by moving only in the Y-axis direction. Next, the laser beam is moved in the X-axis direction more than the width of the imprinted scanning line x1, and is imprinted while moving again only in the Y-axis direction, and the scanning line x2 is imprinted by a required distance. By repeating such an operation, a striped engraved character “8” as shown in FIG. 2A can be printed.
According to such a printing method, there is no intersection 3 in the marking, there is no double marking, and the strength is partially reduced because corrosion does not easily occur and the heat-affected zone does not partially thicken. I don't have to.
[0008]
According to the laser marking method as described above, there is no intersection 3 in the marking by the laser beam on the surface of the cladding tube, and there is no double marking part, so the laser beam irradiation residence time can be shortened and clear printing is possible. Therefore, it is possible to prevent the corrosion and to achieve the marking with the uniform heat affected zone depth.
[0009]
FIG. 3 shows another reference example of the laser marking method. In the example shown in FIGS. 3A and 3B, parallel scanning lines in the X-axis direction with the laser light fixed in the Y-axis direction are shown. A similar stamped character can be created by y1, y2,.
[0010]
Next, FIG. 4 shows a laser marking method according to an embodiment of the present invention. In the example shown in FIGS. 4A and 4B, the laser beam is scanned in the X-axis and Y-axis directions. By driving and controlling the galvanometer mirror 13 with a computer, the outer (and inner) contour lines 8a and 8b of the character “8” are engraved as one continuous line, and then the outer (and inner) contour lines are engraved. The scanning lines z1, z2,... Substantially parallel to the inside along 8a and 8b are imprinted with a laser beam as one continuous line. In this case, the character can be formed thick by increasing the scanning line zi as one continuous line outside the outline 8a.
[0011]
【The invention's effect】
As described above, the laser marking method according to the present invention includes a scanning line that is positioned between the outer contour line, the inner contour line, and the outer and inner contour lines of the display unit and substantially parallel to the contour line. Are engraved as a single continuous line so that the outer and inner contour lines and the scanning lines constituting the display portion do not overlap each other, so that the laser light is applied to the display portion on the surface of the cladding tube. Since there are no double markings due to, the laser beam irradiation residence time can be shortened and clear marking is possible, so that corrosion can be prevented, and marking with a uniform heat affected zone depth can be achieved. And a display part can be formed thickly by marking the substantially parallel scanning line in alignment with the said outline between the outside and inside outline .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a laser marking device used in a laser marking method according to an embodiment of the present invention.
2A and 2B are diagrams showing marked characters according to a reference example of a laser marking method, in which FIG. 2A is an overall view and FIG. 2B is a partially enlarged view.
3A and 3B are diagrams showing marked characters according to another reference example of the laser marking method, in which FIG. 3A is an overall view and FIG. 3B is a partially enlarged view.
4A and 4B are diagrams showing marked characters according to an embodiment of the present invention, in which FIG. 4A is an overall view and FIG. 4B is a partially enlarged view.
FIG. 5 is a partial side view showing a cladding tube engraved with characters and symbols.
FIGS. 6A and 6B are diagrams showing conventional engraved characters imprinted on the surface of a cladding tube by laser marking. FIGS.
FIG. 7 is a diagram showing a conventional inscription stamped on the surface of a cladding tube by rolling.
[Explanation of symbols]
1 cladding tube 10 laser marking device 12 laser oscillator 13 galvanometer mirror 14 driving device
8a, 8b outline

Claims (1)

In a marking method in which a display portion is engraved on a cladding tube of a nuclear fuel rod using a laser beam, the outer contour line and an inner contour line of the display portion are positioned between the outer contour line and the inner contour line. By imprinting substantially parallel scanning lines along the contour lines, the outer and inner contour lines constituting the display unit and the scanning lines are imprinted as one continuous line so as not to overlap each other. A laser marking method characterized by the above .

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