JPS63243850A - Method for detecting sliver defect of rolled plate material - Google Patents

Abstract

PURPOSE:To detect a sliver defect generated at the time of hot rolling continuously without contacting by projecting laser light on the plate surface of a rolled plate material in a specific direction, finding maximum pattern width from the diffraction pattern of the reflected laser light, and comparing it with a reference value. CONSTITUTION:The plate surface of the rolled plate material 2 is irradiated with the laser light 6 in the direction which crosses the rolling direction of the plate material 2 at right angles and slants by a specific angle from the perpendicular to the plate surface. The diffraction pattern of the laser light reflected by the plate surface, on the other hand, is drawn on a screen 8 and the light quantity distribution in the pattern width direction at the maximum width part is found from the diffraction pattern on the screen 8. Then the maximum pattern width is determined from the obtained light quantity distribution curve and compared with the reference value to decide whether or not there is the sliver defect.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for detecting sliver defects in rolled plate materials, and in particular, a method for detecting sliver defects that occur during hot rolling of metal sheet materials without contact. The present invention relates to a detection method suitable for use online.

(Background Art) During hot rolling of metal sheets such as aluminum sheets, due to lack of oil, etc., scratches similar to fasteners, or so-called sliver defects, occur on the surface of the sheet in the rolling direction, which impairs the quality of the rolled sheet. It is desirable to know the occurrence of such sliver defects in the rolling process as early as possible in order to reduce the occurrence of such defects.

For this reason, conventionally, detection of sliver defects in such rolled plate materials has been carried out off-line by etching cut plates cut from successive rolled plate materials with a NaOH solution, and then visually inspecting the cut plates. This is done by.

However, with such conventional methods for detecting sliver defects, (a) it is not possible to inspect the temporary full length of the rolled plate material, (b) it takes a lot of man-hours, and (c) it takes a long time to obtain the results. Therefore, there were inherent problems such as (d) there being a risk of producing a large number of defective boards, and (d) differences in judgment depending on the inspector (judgment error).

On the other hand, in recent years, a method has been revealed that uses laser light to detect scratches and abnormalities on an object to be inspected, or to identify objects. This change can be detected from the output of a detector as it changes due to scratches or foreign matter. Although this laser light etch method can detect small defects on the board surface,
Sliver defects, which are understood as the properties of the entire surface, are affected by the surface properties of the rolled plate material, making it difficult to distinguish between normal parts and defective parts.

(Solving Section B) The present invention has been made against the background of the above, and its purpose is to continuously remove sliver defects that occur during hot rolling, etc., in a non-contact manner. Another object of the present invention is to provide a method for detecting sliver defects in rolled plate materials, which allows online inspection of sliver defects in real time. be.

(Solution Means) In order to achieve such an object, the present invention provides, with respect to the plate surface of a rolled plate material, from a direction perpendicular to the rolling direction of the plate material and a direction inclined at a predetermined angle from a perpendicular to the plate surface. While irradiating the laser beam, a diffraction pattern of the laser beam reflected from the plate surface is drawn on a screen, and the light intensity distribution in the width direction of the pattern at the maximum width portion is determined from the diffraction pattern of the screen. The gist of this invention is a method for detecting sliver defects in rolled plate materials, which is characterized by determining the maximum pattern width from a distribution curve, and determining the presence or absence of sliver defects by comparing the maximum pattern width with a reference value. be.

(Specific configuration/example) By the way, when a rolled metal plate with uniform directionality is irradiated with a coherent laser beam in a direction perpendicular to the rolling grains, a diffraction pattern is formed in the direction perpendicular to the rolling grains. However, the pattern width of this diffraction pattern changes depending on the condition of the rolling stitches. Therefore, sliver defects in rolled metal sheets are caused by scratches perpendicular to the rolling grains.
The above-mentioned diffraction pattern width is wider for a plate with sliver defects than for a plate without sliver defects. The present invention has been made in view of this fact, and attempts to detect sliver defects by measuring the maximum width of a diffraction pattern from a rolled metal plate in real time.

Here, FIG. 1 shows a conceptual diagram of a system for obtaining a desired diffraction pattern. In this case, the rolled plate 2 is generally continuously run in the rolling direction (longitudinal direction), and the rolled plate 2 is moved in a direction perpendicular to the rolling direction of the rolled plate 2 and perpendicular to the plate surface. A laser beam 6 is irradiated from a laser transmitter 4 from a direction inclined at a predetermined angle (α) from .

Then, the reflection of the irradiated laser beam 6 from the plate surface is projected onto the screen 8 as a diffraction pattern. Furthermore, the diffraction pattern 10 projected onto the screen 8 has a maximum pattern width at approximately the center in the longitudinal direction, but this maximum pattern width changes depending on the presence or absence of sliver defects. .

In addition, in such a diffraction pattern acquisition system, the method of irradiating (projecting) the laser beam 6 is as shown in FIG. 2(a), by fixing the laser transmitter 4 and
There is no problem even if the laser beam 6 is simply irradiated to one point on the plate surface of the rolled plate 2. Since sliver defects generally appear over the entire width of the rolled sheet 2, it is possible to determine the degree of sliver defects even if they are detected at one position in the width direction of the sheet. .

However, as shown in FIG. 2Cb) and (c), the laser beam 6 emitted from the laser transmitter 4 is
If the laser beam 6 is scanned in the width direction of the rolled plate 2 by scanning in the width direction of the rolled plate 2, or by moving the laser transmitter 4 itself in the width direction of the plate, A diffraction pattern at the position can be obtained. Note that the angle (α) of the laser beam projected onto the rolled plate 2 with respect to the perpendicular line of the rolled plate 2 is usually 10.
The light is projected at an angle of about 40° to 40°.

Further, the diffraction pattern of the laser beam reflected from the plate surface of the rolled plate 2 is drawn (projected) on the screen 8, and as shown in FIG. The light is received by the camera 14 placed on the front side (on the side of the laser transmitter 4) or the camera 14 placed behind the screen 8 (on the side opposite to the laser transmitter 4), and its diffraction pattern image is analyzed. That's what happens. Note that the photoelectric element of this camera 14 is C.
An OD element, an image pickup tube, etc. are used.

Then, from the diffraction pattern received by the camera 14, the light amount distribution in the pattern width direction at the maximum width portion (the center portion in the longitudinal direction of the diffraction pattern) is determined, and a light amount distribution curve as shown in FIG. 4 is drawn. However, in this case, the peak light amount 16 of the diffraction pattern is kept constant. That is, it is adjusted so as to match the peak light intensity value of the diffraction pattern obtained from a rolled plate without sliver defects to be compared and contrasted. Note that this peak light amount 16 can be controlled by mechanical processing using a camera aperture, etc., or by AGC.
Through electrical processing using a circuit or the like, the peak light intensity of the diffraction pattern that is generated and measured is made constant.

In addition, for the diffraction pattern in which the peak light amount is constant, a threshold level 18 is set as shown in FIG. 4, and the pattern width is determined by measuring the light amount width above this threshold level. is required. Then, the maximum width of this pattern width within the field of view of the camera is measured and determined.

The maximum width of the diffraction pattern obtained in this way is compared with a predetermined reference value, that is, the maximum pattern width of the diffraction pattern obtained from the plate surface without sliver defects, to determine the presence or absence of sliver defects. It will be done.

In other words, if there is no sliver defect on the surface of the rolled plate 2 to be measured, the maximum width of the diffraction pattern should be substantially no different from the reference value, while on the other hand, if there is a sliver defect on the rolled plate 2, Depending on the degree of the sliver defect, a difference is caused between the maximum width of the diffraction pattern and the reference value, and when the difference is greater than a certain value, it is possible to determine that there is a sliver defect, by this,
The properties of the entire plate surface of the rolled plate 2 can be grasped.

Incidentally, FIGS. 5 and 6 show examples in which the inventors conducted measurements on hot-rolled aluminum plates, and FIGS. 5(a) and 6(a) As shown in FIG. 5(b) and FIG. 6(b), the light intensity distribution of the diffraction pattern of the aluminum rolled plate material without sliver defects and the pattern width in the rolling direction are different from those of aluminum with sliver defects. For hot rolled plate materials,
The pattern width at the threshold level is wide,
Compared to the pattern width obtained from a sheet surface without sliver defects in the rolling direction, it is recognized that the pattern width increases by a certain amount due to the occurrence of sliver defects.

Therefore, by mechanically reading a predetermined increase (difference) in pattern width, it is possible to determine the presence or absence of a sliver defect extremely easily, without requiring any skill. There is no possibility of judgment errors due to individual differences among examiners.

(Effects of the Invention) As is clear from the above description, according to the present invention, a laser beam is irradiated onto the plate surface of a rolled plate material from a predetermined direction, and the diffraction pattern of the reflected laser beam is The presence or absence of sliver defects is determined by determining the maximum pattern width and comparing it with a reference value, so it can be applied to rolled plate materials that are run without contact, and can be used continuously. As a result, it has become possible to inspect the presence or absence of sliver defects online in real time.

Moreover, according to the present invention, not only can the entire length of the board be inspected, but also the presence or absence of sliver defects can be determined based on the magnitude of the numerical difference from the reference value, so that errors in judgment by inspectors may occur. It also exhibits characteristics such as being able to do nothing.

Furthermore, since the presence or absence of sliver defects can be inspected in real time, this information can be fed back to control rolling conditions.
This makes it easy to find optimal rolling conditions, and it also has the advantage of being relatively inexpensive to manufacture as a measuring device.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an example of a system for obtaining a diffraction pattern, and FIGS. 2(a), (b), and (c) are explanatory diagrams showing different laser beam projection methods, respectively. FIGS. 3(a) and 3(b) are explanatory diagrams showing different examples of the light receiving method of the diffraction pattern, respectively.
The figure is a graph showing an example of a light intensity distribution curve of a diffraction pattern, and FIGS. 5(a) and (b) and FIGS. 6(a) and (b) show a plate material without a sliver defect and a sliver defect-free one, respectively. FIG. 5 shows a light amount distribution curve of each diffraction pattern, and FIG. 6 shows a change in pattern width with respect to the rolling direction. There is. 2: Rolled plate 4: Laser transmitter 6: Laser beam 8 Niscreen 10; Diffraction pattern 12: Vibrating mirror 14: Camera
16; Peak light intensity 18: Threshold level Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1 Figure 2 Figure 2 Figure 2 CC) Two, two, two, two! = Figure 3 (a) Figure 3 Figure 4 Han'11+ (Diffraction pattern width direction) Figure 5 (a) ↑ Figure 5 0≦ -, \°

Claims (1)

[Claims] A diffraction pattern of the laser beam reflected from the plate surface while irradiating the plate surface of the rolled plate material with laser light from a direction perpendicular to the rolling direction of the plate material and inclined at a predetermined angle from a perpendicular to the plate surface. Draw on the screen,
After determining the light intensity distribution in the pattern width direction at the maximum width part from the diffraction pattern of the screen, the maximum pattern width is determined from the obtained light intensity distribution curve, and the sliver defect is detected by comparing the maximum pattern width with a reference value. 1. A method for detecting sliver defects in rolled plate material, comprising determining the presence or absence of sliver defects.