JPH06317539A - Laser irradiation device - Google Patents

Abstract

PURPOSE:To provide an efficient method for melting and removing flaws by making laser scanning by using a mirror in the direction of width and also employing a Fourier lens for a constant focal length. CONSTITUTION:Relating to a flaw removal device wherein a flaw part is, while interlocked with a surface flaw examination device, irradiated with a laser so that the flaw part is melted-cut and removed, a function wherein a surface flaw is detected by the surface flaw examination device and the position in the direction of width of the flaw part is detected and then a laser scanning mirror is rotated and controlled, in accordance with width the direction of the flaw part, and at the same time, a Fourier lens 17 is arranged in a laser scanning light path so that the variation in light path length due to laser scanning is corrected, is provided, so that the flaw part is tracked in the direction of line advancement, and laser is poured when the flaw part reaches the position. Therefore irradiation rage of the laser length becomes constant, enabling efficiently melting and removing flaws.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser irradiation apparatus for repairing a flaw on a metal strip.

[0002]

2. Description of the Related Art In recent years, as a partial surface ablation treatment of a traveling billet by a laser, a laser machining head which moves in a direction perpendicular to a traveling direction of a metal billet and a machining head in this machining head are disclosed in Japanese Patent Application Laid-Open No. 4-274892. Defects such as cracks on the surface of the metal billet by spraying oxygen gas or a mixed gas containing oxygen integrated into the laser processing head and the beam scanning optical system and scanning width adjusting device using a vibrating mirror etc. There is known a method and an apparatus for melting and removing.

[0003]

When a defect such as a crack on the surface of a metal billet as in the above-mentioned Japanese Patent Laid-Open No. 4-274892 is irradiated with a laser beam to be melted and melted away, a processing head is used. Although the scanning width adjustment by the beam scanning optical system by the vibrating mirror etc. built in is shown, the mechanism that corrects the optimum laser irradiation in the width direction of the flaw part is not clear, so the effective flaw There is a problem that it is not melted and removed. In order to solve such a problem, the present invention provides an efficient method for melting and removing defects by fixing the focal length by scanning a laser with a mirror in the width direction and adopting a Fourier lens. It is a thing.

[0004]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the gist of the invention is to irradiate a laser on a flaw portion in association with a surface flaw inspection device to melt the flaw portion. In a flaw removing device for fusing, surface flaws are detected by a surface flaw inspection device, a width direction position of the flaw portion is detected, and a laser scanning mirror is rotationally controlled in accordance with the width direction of the flaw portion. Along with this, a Fourier lens is arranged in the laser scanning optical path to have a function of correcting the change in optical path length due to laser scanning, and the flaw is tracked in the line advancing direction, and the flaw reaches the laser irradiation position. A laser irradiation device is characterized by irradiating a laser at a timing.

[0005]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a process diagram showing melting and fusing of a metal strip according to the present invention. In FIG. 1, the hot rolled coil 1 is unwound, continuously welded by a welding machine 2, and then pickled in a pickling tank 4 through a loop car 3 and the hot rolled coil 1 is a surface flaw inspection device. The flaw position is detected by 5, and the number of rotations of the bridle roll that conveys the hot-rolled coil 1 is calculated by the tracking device for the flaw portion by the pulse transmitter to calculate the conveyed amount of the hot-rolled coil 1 that has been conveyed. When the signal processing device detects a flaw on the surface of the hot-rolled coil, the flaw on the hot-rolled coil 1 is surely removed by melting the surface of the hot-rolled coil 1 by the laser irradiation position 6 and then cooled through the loop car 7. After being cold-rolled by the hot-rolling mill 8, it is wound as a cold-rolled coil 9.

FIG. 2 is a schematic view of a flaw melting / melting process according to the present invention. As shown in FIG. 2, the rewound hot-rolled coil 1 detects the flaw position by the surface flaw inspection device 5, and the flaw tracking device 10 detects the flaw position by the flaw detection signal and corresponds to the line speed. The defect position is transmitted to the laser emission control device 11, and the laser emission from the laser oscillator 12 is performed by the signal from the laser emission control device 11. On the other hand, the surface flaw inspection device 5 detects the position of the flaw in the width direction, and the flaw tracking device 10 transmits the flaw to the rotary mirror control device 13 and the rotary mirror drive motor 14 drives the target mirror to irradiate the flaw on the flaw. Be seen.

FIG. 3 is a schematic diagram of a laser irradiation apparatus according to the present invention in which a Fourier lens is arranged in the laser scanning optical path. As shown in FIG. 3, laser irradiation is performed from the laser oscillator 12, the laser optical path 16 changes its direction by the rotating mirror 15, and the Fourier lens 17 changes the optical path length by laser scanning of the hot rolled coil 1. It has a function to correct. That is, the flaw in the hot rolled coil 1 is detected, the flaw is tracked online, and when the flaw reaches the laser irradiation position, the rotary mirror drive motor 14
The rotation angle of the rotating mirror 15 is adjusted to irradiate the flaw with a laser beam, and the Fourier lens is used to keep the focal length constant. As a result, the change in the focal length due to the change in the optical path length in the width direction of the metal strip is corrected, the irradiation distance of the laser light to the flaw is always kept constant, and the melting / welding strength can be kept constant. It enables high-performance melting and fusing.

[0008]

[Example] After pickling the hot rolled coil in the black skin state unwound from the pay-off reel and removing the scale on the surface of the hot rolled coil, the surface flaw detector detects when the flaw surface can be clearly identified. At the same time as detecting the flaw, the position in the width direction of the flaw is measured and transmitted to the laser irradiation device. On the other hand, tracking is performed from the surface flaw detection device to the laser irradiation device according to the line speed, the position in the longitudinal direction is transmitted to the laser irradiation device, and the laser scanning mirror is rotated according to the width direction of the flaw portion. Therefore, for example, if the rotating mirror is rotated by 1 °, the laser light path after reflection is changed by 2 °. That is, a double angle change is performed. As a result, the position changes by only a change of 2 ° according to the distance to the metal strip, and the change in the optical path is always corrected by the Fourier lens so that the change in the optical path is always corrected by the focal length with respect to the flaw. Modify so that the laser irradiation is performed at. The constant focal length makes it possible to melt and ablate flaws and remove even flaws with a flaw width of 2 mm and a depression depth of 0.1 mm, then pickled and then cold-rolled metal strip. No surface defects were found on the plate.

As described above, by disposing the Fourier lens in the laser scanning optical path, the rotation of the rotating mirror in accordance with the width direction of the metal strip is simultaneously corrected by the Fourier lens so as to correct the change in the optical path length due to the laser scanning, and the laser is constantly laser-scanned. The irradiation distance of light is kept constant, and the efficiency of melting and fusing and the accuracy of flaws are improved. It should be noted that the above description is for the case of one laser irradiation head, but if a plurality of laser irradiation heads capable of individually irradiating in the width direction are arranged, it is possible to better cope with the width direction. Therefore, it becomes possible to perform high melting / melting removal.

[0010]

As described above, by adopting the Fourier lens according to the present invention, the irradiation distance of the laser light is made constant by the function of correcting the change in the optical path length due to the laser scanning, and the efficient melting of flaws It became possible to remove by melting.

[Brief description of drawings]

FIG. 1 is a process diagram showing melting and fusing of a metal strip according to the present invention,

FIG. 2 is a schematic view of a flaw melting / ablation process according to the present invention

FIG. 3 is a schematic view of a laser irradiation apparatus according to the present invention in which a Fourier lens is arranged in a laser scanning optical path.

[Explanation of symbols]

 1 Hot Rolled Coil 2 Welding Machine 3 Loop Car 4 Pickling Tank 5 Surface Defect Inspection Device 6 Laser Irradiation Position 7 Loop Car 8 Cold Rolling Machine 9 Cold Rolled Coil 10 Defect Tracking Device 11 Laser Transmission Control Device 12 Laser Transmitter 13 Rotation Mirror control device 14 Rotating mirror drive motor 15 Rotating mirror 16 Laser optical path 17 Fourier lens

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Claims (2)

[Claims] 1. A flaw removal device which irradiates a laser on a flaw portion in tandem with a surface flaw inspection device to melt and ablate the flaw portion, wherein the surface flaw inspection device detects the surface flaw and the flaw portion is detected. Function to detect the position in the width direction of the laser and control the rotation of the laser scanning mirror in accordance with the width direction of the flaw, and to arrange the Fourier lens in the laser scanning optical path to correct the change in optical path length due to laser scanning. And track the flaw in the line advancing direction,
A laser irradiating device which irradiates a laser at the timing when the flaw reaches the laser irradiation position. 2. The laser irradiation apparatus according to claim 1, comprising a plurality of laser irradiation heads capable of individually irradiating in the width direction.