JP2011149699A - Method and device for determining surface quality of steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for determining the surface quality of a steel plate that can accurately determine the surface quality of a steel plate over the total length of the steel plate. <P>SOLUTION: The method of determining surface quality of a steel plate includes: a plate width measurement/edge photographing step of measuring plate width of a steel plate under conveyance and photographing both the end edge sections in the width direction of the surface of the steel plate using a camera; a step of calculating the amount of turn-around of the seam for processing the photographed image, detecting an edge in the direction of the plate width and a seam flaw, and calculating distance between the detected seam flaw and the edge; an effective plate width calculation step of calculating effective plate width as a final product, based on the calculated amount of turn-around of the seam and the measured plate width; and a surface quality determination step of determining whether the surface quality of the steel plate is appropriate, based on the effective plate width. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and apparatus for determining the surface quality of a steel plate, which can accurately determine the surface quality of the steel plate over the entire length of the steel plate.

  A linear wrinkle called a seam wrinkle parallel to the rolling direction tends to occur at both width edge portions of a steel plate, particularly a stainless steel plate. The seam wrinkle generation mechanism is based on the fact that wrinkles generated on the side surface of the slab, wrinkles generated on the edge of the steel plate in the rolling process, uneven wrinkles, etc. It is known that the material wraps around the surface portion and remains.

  In particular, since hot rolling of a stainless steel plate is likely to generate seam wrinkles, various contrivances have been made in manufacturing processes that suppress the occurrence of seam wrinkles (for example, Non-Patent Document 1, Patent Documents 1, 2, and 3). However, with these methods, it has been difficult to completely prevent the occurrence of seam wrinkles.

  FIG. 2 is a diagram schematically illustrating seam wrinkles and seam wraparound amounts. As shown in FIG. 2, a plurality of seam ridges are often generated in parallel with the rolling direction. Among them, the seam ridge farthest from the edge is important for quality assurance. The distance D from the edge to the seam ridge is usually referred to as a seam wrap-around amount.

  When the plate width is W, and the seam wrapping amounts at the workpiece side and the drive side edge are D1 and D2, respectively, W ′ = W−D1−D2 is less than the plate width lower limit value Wa in the product warranty over the entire length of the steel plate. It is important not to manage.

  On the other hand, various methods have been adopted for inspecting the surface flaw of a stainless steel plate (for example, Patent Documents 4 and 5), but none of them describes the detection of seam flaws. This is because seam wrinkles occur in the vicinity of the edge, so that it is difficult to detect it by entering the edge dead zone of the inspection apparatus.

  That is, in the conventional surface inspection apparatus, the area within about 10 mm from the edge of the steel sheet is often over-detected due to the meandering of the steel sheet, ear defects, surface contamination, etc. This is because even if a seam wrinkle occurs, it cannot be detected.

  For the above reasons, conventionally, the extra width of the steel sheet has been made large in order to prevent the seam wrinkles from entering the product guarantee width of the steel sheet. In addition, the inspector stopped the line at several positions in the conveying direction of the steel sheet and manually measured the amount of seam wrapping to confirm that no seam wrinkles occurred within the product guarantee width.

"Iron and Steel" Vol.82 No.1 p.58-62 (1996)

JP 2000-312904 A JP 2001-179309 A JP 2006-150404 A JP-A-9-89802 JP 2008-145373 A

  However, in the conventional method in which the above-described margin of the product is large, there is a problem in production efficiency that the yield is reduced.

  In addition, in the method in which the inspector inspects and measures at several positions in the conveyance direction of the steel plate, the plate width and seam wrapping amount of the steel plate vary depending on the conveyance direction position of the steel plate, so quality assurance over the entire length of the steel plate is not always sufficient. It was. Furthermore, this inspector's manual method needs to stop the line at the time of measurement, which hinders productivity, and the inspector's personality is required to recognize low-contrast seams and measure the distance from the plate edge. Since the difference inevitably occurs, there is a problem that the objective surface quality cannot be judged.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the surface quality determination method and apparatus of a steel plate which can determine the surface quality of a steel plate correctly over the full length of a steel plate.

  The above problems are solved by the following invention.

  [1] A plate width measurement / edge photographing step of measuring the plate width of the steel plate being conveyed, and photographing both edge portions in the width direction of the surface of the steel plate with a camera, image processing of the photographed image, Effective as a final product based on the seam wrap amount calculation step that detects edges and seam wrinkles in the width direction and calculates the distance between the detected seam heel and the edge, and the calculated seam wrap amount and the measured plate width A method for determining the surface quality of a steel sheet, comprising: an effective sheet width calculating step for calculating a sheet width; and a surface quality determination step for determining whether or not the surface quality of the steel sheet is good based on the effective sheet width. .

  [2] In the method for determining the surface quality of a steel sheet according to [1] above, in the seam wrap-around amount calculating step, a one-dimensional luminance profile in the sheet width direction is obtained from the image and then averaged in the conveying direction. After obtaining a three-dimensional luminance average profile, applying shading correction, detecting seam wrinkles with a predetermined threshold, and calculating the distance between the seam wrinkles farthest from the edge among the detected seam wrinkles A method for judging the surface quality of steel sheets.

  [3] In the method for determining the surface quality of a steel sheet according to [1] or [2] above, in the effective plate width calculating step, the workpiece side seam wrap amount D1, the drive side seam wrap amount D2, and the plate width measurement. The effective plate width W ′ = W−D1−D2 is obtained from the value W, and in the surface quality determination step, W ′ and the plate width allowable lower limit value Wa are compared, and (1) W ′ ≧ Wa over the entire length of the steel plate. (2) If only W ′ <Wa near the leading edge of the steel sheet, the part is removed and judged as acceptable. (3) W except for the vicinity of the leading edge of the steel sheet. '<Wa when there is a place where it is Wa, it is judged as rejected, characterized in that the steel sheet surface quality judgment method.

  [4] A sheet width meter for measuring the sheet width of the steel sheet being transported, a camera for photographing both end edges in the width direction of the surface of the steel sheet, and the distance between the sheet edge and the seam ridge at both ends from the camera photographed image An image processing apparatus that calculates the amount of seam wrapping, and a pass / fail determination apparatus that determines the quality of the surface quality of the steel sheet based on the calculated seam wrapping amount and the measured sheet width. Surface quality judgment device.

  The present invention measures the plate width of the steel plate at a plurality of positions in the conveyance direction of the steel plate, photographs the width edge portion of the steel plate with a camera, and calculates the distance between the plate edge portion and the seam collar from the camera image. Since the quality of the surface quality is determined based on the plate width at these multiple positions and the distance between the seam collar portion and the edge portion of both width edge portions, the number of measurement points in the conveyance direction of the steel plate can be easily increased. The surface quality can be determined over substantially the entire length of the steel sheet. This is particularly effective when the plate width and seam wrapping amount greatly vary in the transport direction.

  In addition, since it is possible to objectively measure the amount of seam wrap and determine the surface quality based on a certain standard, individual differences by the measurer can be eliminated, and highly reliable surface quality determination can be performed.

  Moreover, since it became possible to perform highly reliable determination over the entire length of the steel plate, it became possible to avoid taking the extra width of the steel plate more than necessary and to improve the yield.

  Furthermore, since the surface quality can be determined without stopping the steel plate being conveyed, there is an effect that productivity can be improved.

It is a flowchart which shows an example of the process sequence of the surface quality determination method of the steel plate which concerns on this invention. It is a figure which illustrates a seam wrinkle and the amount of seam wraparound typically. It is a figure which illustrates typically the effective board width which is an evaluation value in the present invention. It is a flowchart which shows the example of a calculation procedure of seam wraparound amount. It is a figure which illustrates the example of calculation of the seam wraparound amount typically. It is a flowchart which shows the example of surface quality determination of this invention. It is a flowchart which shows the example of effective board width calculation of this invention. It is a figure which shows typically the structural example of the surface quality determination apparatus of the steel plate which concerns on this invention. It is a figure which shows typically the apparatus arrangement example of the surface quality determination apparatus of the steel plate which concerns on this invention. It is a figure which shows typically the example of arrangement | positioning of the illumination in this invention, and a camera. It is a figure which shows typically the measurement equipment arrangement | positioning in a present Example.

  FIG. 1 is a flowchart showing an example of a processing procedure of a surface quality determination method for a steel sheet according to the present invention. Hereinafter, the details of the method for determining the surface quality of a steel sheet according to the present invention will be sequentially described with reference to FIG.

  First, the plate width W (x) at a position x from the front end in the conveyance direction of the steel plate is measured with a plate width meter, and both width edge portions of the steel plate surface at the position x are photographed with a camera (Step.01 plate width). Measurement and edge photography). As the plate width meter, a known optical plate width meter can be used. Further, for imaging of the edge portion, a general-purpose illumination and camera may be used to collect an image of the steel plate including the plate edge portion, and a line sensor camera or an area sensor camera can be used as the camera.

  In a line where the plate width varies greatly, two cameras in the plate width direction may be preset to the assumed left and right plate edge portions, respectively, and an image may be collected. The sheet width measurement position of the steel sheet and the camera photographing position in the conveying direction may be performed at positions close to each other.

  Next, each edge image is subjected to image processing to calculate a seam wrapping amount D1 (x) on the workpiece side and a seam wrapping amount D2 (x) on the drive side (Step.02 seam wrapping amount calculation). Specific image processing contents are shown below.

(1) The edge position Pe in the plate width direction in the image is determined.
(2) Detect seam 疵.
(3) The position Ps in the image of the seam seam farthest from the plate edge among the detected seam seams is determined.
(4) Multiply the difference between the plate edge position Pe and the innermost seam 疵 position Ps by the resolution in the plate width direction of the camera to obtain the distance (seam wrap amount) D from the plate edge to the innermost seam 疵.
(5) For each of the left and right plate edges, seam wrap amounts D1 and D2 are obtained in the above (1) to (4), respectively.

  Next, using the plate width W (x) measured at Step.01 and the seam wraparound amounts D1 (x) and D2 (x) calculated at Step.02, the effective plate represented by the following equation (1) The width W ′ (x) is calculated (Step. 03 effective plate width calculation) (see FIG. 3).

  Seams are harmful defects and should not be included in the final product. Accordingly, the seam wrinkle portion is cut by a trimming device in a lower process, and the above W ′ (x) indicates that the plate width after trimming is at most W ′ (x) or less.

  Finally, the surface quality of the steel sheet is determined based on the value of W ′ (x) over the entire length of the steel sheet (Step 04 surface quality determination). Since the sheet width and the seam wrapping amount of the steel sheet vary depending on each position in the transport direction, it is desirable to evaluate the value of W ′ (x) at as many positions as possible in the transport direction. In Step 04, it is determined whether or not the value of W ′ (x) satisfies a predetermined acceptance criterion over the entire length of the steel plate.

  Next, an example of a specific procedure and contents of image processing in Step.02 seam wraparound amount calculation will be described with reference to FIGS. FIG. 4 is a flowchart illustrating an example of a calculation procedure of the seam wraparound amount. FIG. 5 is a diagram schematically illustrating an example of calculating the seam wraparound amount.

  First, in the width edge image of the steel plate surface, the one-dimensional luminance profile in the plate width direction is averaged along the conveying direction to obtain the one-dimensional luminance average profile in the conveying direction (Step 21). Although the seam wrinkle depends on the generation process, generally, the seam wrinkle is usually a very thin wrinkle of 0.1 mm or less, so that the image contrast is generally lowered and the S / N is also lowered.

  Therefore, it is effective to average the luminance along the conveyance direction as described above by utilizing the characteristic that the seam ridge is a linear ridge parallel to the conveyance direction. FIG. 5 shows an example in which a low-contrast seam wrinkle is revealed by luminance averaging. Although two seam wrinkles with low contrast are barely recognized near the edge in the image shown on the left of the figure, from the one-dimensional luminance profile in the plate width direction as shown in Figures (a) to (c), It is difficult to separate and extract seams from ground noise.

  However, by integrating and averaging each one-dimensional luminance profile along the vertical direction (conveying direction) of the image, as shown in FIG. The heel part can be recognized.

Next, shading correction is applied to the one-dimensional luminance average profile to remove illumination unevenness (Step 22). By shading correction, spatially low frequency luminance fluctuations such as illumination unevenness are reduced, and high frequency luminance fluctuation parts such as seams are emphasized. As a result, as shown in FIG. 5 (e), the seam ridge can be extracted separately from the ground noise.
Next, the plate edge position Pe is obtained from the one-dimensional luminance average profile before or after shading correction (Step 23). Since the plate edge is also parallel to the transport direction, it is preferable to use the one-dimensional luminance average profile for detection of the plate edge. As a method for recognizing the plate edge position, for example, in a one-dimensional luminance average profile before shading correction, an intermediate luminance between the outside of the plate and the inside of the plate is used as a threshold value, and a portion exceeding this value is recognized as a plate edge. Further, the one-dimensional luminance average profile after shading correction may be recognized by performing a predetermined threshold process.
Next, the one-dimensional luminance average profile after shading correction is binarized by a preset threshold value to extract the seam ridge, and the position Ps of the seam ridge farthest from the plate edge is obtained (Step 24). (See FIG. 5 (e)).

  Finally, the seam wraparound amount D is calculated by the following equation (2) (Step 25).

Here, Res is the resolution in the plate width direction of the camera, the unit of Pe and Ps is the number of pixels, and the unit of Res is mm / pixel.

Next, a specific example of the surface quality determination in Step.04 will be described based on FIG.
First, an effective plate width W ′ (x) is measured at a position in the conveyance direction x (0 ≦ x ≦ L) for a steel plate having a conveyance direction length L (Step 41). In the case of a steel plate with L = 700 m, for example, x is measured at a 2 m pitch.
Next, the value of W ′ (x) over the entire length of the steel sheet is compared with the sheet width lower limit value Wa, and the pass / fail of the steel sheet is determined as follows (Step. 42).

(1) When W ′ (x) ≧ Wa is satisfied over the entire length
⇒ Judge that the steel plate is acceptable.

(2) When there is a part where W '(x) <Wa only at the tail end of the steel sheet, otherwise W' (x) ≥ Wa
⇒Remove the part where W '(x) <Wa (failed part) and pass the rest.

(3) When there is a place where W '(x) <Wa other than the leading edge of the steel plate
⇒ Judge that the steel sheet is rejected.

  The above Wa is the product guarantee width of each steel sheet plus trim margin, etc.If the effective sheet width W '(x) is less than this, the product guarantee width will not be met, or there will be seams in the product. It means that there is a fear of being included. Therefore, (3) determines that the steel sheet is rejected when such a defective portion is present except at the leading end of the steel sheet.

  In the above description, for the sake of convenience of explanation, the surface quality determination method for one side of the steel plate has been described. However, in practice, the above method is preferably applied to both sides of the steel plate.

  FIG. 7 shows a method of calculating the effective plate width W ′ (x) when determining the surface quality of both surfaces of the steel plate. That is, the workpiece-side seam wrap amount D1t (x) and the drive-side seam wrap amount D2t (x) on the steel plate front surface, and the workpiece-side seam wrap amount D1b (x) and the drive-side seam wrap amount D2b (x) on the steel plate back surface Are measured respectively (Step 51). Then, at each position x in the transport direction, the effective plate width W ′ (x) is obtained by the following equation (3) (Step 52).

Here, Max {D1t (x), D1b (x)} means the larger value of D1t (x) and D1b (x).

  By such processing, for example, it is possible to make an appropriate determination even when the amount of seam wrap around the front side is large on the work side and the back side is large on the drive side.

  FIG. 8 is a diagram schematically showing a configuration example of the steel sheet surface quality determination device according to the present invention. Hereinafter, based on FIG. 8, the detail of the surface quality determination apparatus of the steel plate which concerns on this invention is demonstrated.

  In FIG. 8, the illumination 2a, the camera 3a, and the image treatment device 5a detect a seam wrinkle on the front surface of the steel plate 1 and calculate the distance from the edge. The camera 3a may be configured to capture the entire width with one camera, but may be configured with two cameras that capture both ends of the steel plate as shown in FIG. In the line where the plate width varies greatly, the positions in the width direction of the cameras at both ends may be preset by sliding in the plate width direction according to the expected plate width of the steel plate.

  As the illumination 2a, a linear light source that linearly illuminates the entire plate width as shown in FIG. 9 is suitable, but is not limited to this. For example, two surfaces that locally illuminate both ends of a steel plate You may comprise by a light source. In addition, if the camera can shoot with sufficient sensitivity, illumination can be omitted.

  As the camera 3a, an area sensor camera or a line sensor camera can be used. The visual field of the camera is set so as to cover the edge portion of the steel plate 1 and the expected seam wrinkle generation range (for example, within 30 mm from the edge). The surface edge part of the steel plate conveyed by the camera is photographed at a constant time interval or at a constant distance interval in synchronization with the steel plate conveyance distance. The frequency of photographing is preferably determined depending on the variation of the plate width of the steel plate and the variation degree of the seam wrinkle occurrence position. For example, the photographing is performed every time the steel plate moves 2 m. As an arrangement of the illumination and the camera, an optical arrangement that avoids regular reflection is appropriate. For example, as shown in FIG.

  The image processing device 5a calculates the distance between the plate edge and the seam wrinkles at both ends from the image taken by the camera 3a. The specific calculation method is as described above (see FIGS. 4 and 5).

  On the other hand, the illumination 2b, the camera 3b, and the image treatment device 5b detect seam wrinkles on the back surface and calculate the distance from the edge, and the functions and configurations are the same as those of the above-described front surface.

  The plate width meter 4 measures the plate width of a steel plate, and a known optical plate width meter can be used. The sheet width measurement position of the steel sheet and the camera photographing position in the conveying direction may be performed at positions close to each other.

The acceptance / rejection determination device 6 calculates the effective plate width W ′ from the outputs of the image processing device 5a, the image processing device 5b, and the plate width meter 4 over the entire length of the steel plate 1, and the quality of the surface quality of the steel plate is determined by the method described above. Is determined.
The image processing device 5a and the image processing device 5b can be configured by a single computer equipped with an image processing board. In addition, the pass / fail determination device 6 and the image processing devices 5a and 5b can be shared by the same computer.

  An embodiment in which the present invention is applied to a pickling line for a stainless steel sheet will be described. FIG. 11 is a diagram schematically showing the arrangement of measuring devices in the present example. A plate width meter composed of an illumination and a camera was installed before the exit side coiler of the pickling line, and the plate width of the steel plate was measured over the entire length at a 2 m pitch. Two imaging devices composed of linear illumination and a CCD line sensor camera are installed in the plate width direction near the upstream position of this plate width meter, and plate edge portion images are collected over the entire length at a pitch of 2 m. . The plate width meter measurement position and the edge portion photographing position in the steel plate conveyance direction were controlled to be exactly the same position by tracking the steel plate conveyance. In addition, the arrangement of the illumination and the camera was set to an angle shown in FIG.

  The calculation of the amount of seam wrapping was performed according to the procedure shown in FIG. 4 described above, and the determination of the surface quality was performed according to the procedure shown in FIGS. 6 and 7 described above. In order to investigate the effect of the present invention, the steel sheet whose surface quality is determined according to the present invention is sent to another inspection line, the line is stopped at 10 locations in the steel sheet conveying direction, and the amount of seam wrapping by the inspector's manual work is reduced. Measurements were made.

  As a result, it was confirmed that the measurement result according to the present invention coincided with the measurement result by the inspector with the standard deviation σ = 0.3 mm. As a result, it was proved that the seam wrap-around amount can be detected with high accuracy over the entire length of the steel sheet without stopping the line by the method of the present invention. In addition, there is a case in which the effective plate width W ′ is minimized at the 10 intermediate positions where the stop measurement is performed on the inspection line, and surface quality defects that are overlooked in the conventional judgment method are also detected by the method according to the present invention. It was also confirmed that it could be detected.

DESCRIPTION OF SYMBOLS 1 Steel plate 2a, b Illumination 3a, b Camera 4 Plate width meter 5a, b Image processing device 6 Pass / fail judgment device

Claims (4)

While measuring the plate width of the steel plate being conveyed, and shooting the width direction both ends edge portion of the surface of the steel plate with a camera, a plate width measurement and edge shooting step,
A seam wrap amount calculating step that performs image processing on the captured image, detects edges and seam wrinkles in the plate width direction, and calculates a distance between the detected seam wrinkles and the edges;
An effective plate width calculation step for calculating an effective plate width as a final product based on the calculated seam wraparound amount and the measured plate width;
A method for determining the surface quality of a steel sheet, comprising: a surface quality determination step for determining whether the surface quality of the steel sheet is good or bad based on the effective plate width. In the surface quality judgment method of the steel plate according to claim 1,
In the seam wraparound amount calculating step,
After obtaining a one-dimensional luminance profile in the plate width direction from the image, obtaining a one-dimensional luminance average profile by averaging in the transport direction, further performing shading correction, and detecting seam wrinkles with a predetermined threshold value, A method for determining the surface quality of a steel sheet, comprising calculating a distance between the edge of the detected seam seam and the edge farthest from the edge. In the surface quality judgment method of the steel plate according to claim 1 or claim 2,
In the effective plate width calculating step,
The effective plate width W ′ = W−D1−D2 is obtained from the workpiece side seam wrap amount D1, the drive side seam wrap amount D2, and the plate width measurement value W.
In the surface quality determination step,
Compare W 'and the sheet width allowable lower limit Wa. (1) If W'≥Wa over the entire length of the steel sheet, determine that it is acceptable. (2) If only W'<Wa near the leading edge of the steel sheet. The surface of the steel sheet, characterized in that it is determined that the part is removed and that it is determined to be acceptable. (3) If there is a part where W ′ <Wa other than the vicinity of the tail end of the steel sheet, it is determined that the part is rejected. Quality judgment method. A board width meter that measures the sheet width of the steel sheet being conveyed,
A camera for photographing both edge portions in the width direction of the surface of the steel sheet;
An image processing device that calculates a seam wrapping amount that is a distance between a plate edge and a seam ridge at both ends from the camera image;
An apparatus for determining the surface quality of a steel sheet, comprising: a pass / fail determination apparatus that determines the quality of the surface quality of the steel sheet based on the calculated amount of seam wrap and the measured plate width.