JP2001205327A - Surface property discriminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for detecting and discriminating minute change in surface property like an oxidized film. SOLUTION: This device is a device for discriminating the change of the inside surface property of a steel tube 12 and provided with an image pickup unit 13 for imaging the inside surface of the steel tube 12, a driving device 14 for driving the image pickup unit 13, a drive controller 15 for controlling the driving device 14 and adjusting the relative positions of the image pickup unit 13 and the steel tube 12, an image processor 16 in which the picture imaged with the image pickup unit 13 is inputted and with which a surface property discriminating value for discriminating the change of the surface property is obtained by processing the picture and a surface property discriminator 17 for connecting the surface property discriminating value inputted from the image processor 16 to the relative position information inputted from the drive controller 15. The picture processing in the image processor 16 is for determining a feature value from the gray level histogram of the picture and determining the surface property discriminating value by comparing the determined feature value with a preset threshold value. In this way, the change in the surface property caused by the oxidized film which is generated on the inside surface of the steel tube is also accurately discriminated over the entire length of the steel tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for automatically detecting and discriminating a change in surface properties such as an oxide film formed on the surface of a metal material.

[0002]

2. Description of the Related Art An oxide film or scale is formed on the surface of a metal material such as a steel product or a semi-finished product in a manufacturing / processing step, which may adversely affect the quality. Such a problem will be described below using a steel pipe material for oil country tubular goods as an example.

[0003] Since steel pipe material for oil country tubular goods is used for a long time in a poor environment and cannot be easily maintained once installed, quality requirements for its inner surface properties are very severe. For example, if it is used without removing the oxide film or scale mainly generated in the rolling process of steel pipe material production, the valve will be clogged due to corrosion due to rust or scale peeling, causing severe damage to the oil recovery equipment and profitability. This is because it causes deterioration.

[0004] Therefore, the steel pipe material manufacturer, after rolling and forming,
We apply shot blasting using granular metal powder and apply rust preventive oil, etc., to prevent the above problems.

[0005]

However, in the shot blasting process, for example, it is difficult to formulate the blasting time because the blasting time varies depending on various factors such as the material and dimensions of the target material and the manufacturing conditions in the upper process. Therefore, if perfection is required in terms of quality, the actual blast time must be naturally extremely long (first problem), and an increase in shot blast cost (increase in cost) and an increase in production volume. It has the effect of lowering.

[0006] Further, since the residual state of the oxide film or scale depends on a visual inspection by an inspector after shot blasting, the inspection becomes qualitative due to individual differences or the like (second problem). It is difficult to standardize or maintain that level.

[0007] In addition, since the inspection is limited to inspection of only the end of the tube due to visual observation (third problem), quality assurance over the entire length is hindered. Note that these problems can be solved if there is a device for determining the removal state of the oxide film or the scale. In other words, by using such a device, it is possible to quantitatively grasp the removal state and to obtain an appropriate shot blast time, and eliminate the adverse effects such as individual differences and the like, so that it is impossible to visually check the central portion of the tube. This is because an inspection can also be performed.

As a method for determining the removal state of such an oxide film or scale, see, for example, JP-A-60-169.
No. 580 is disclosed. JP-A-60-1695
In the technique disclosed in No. 80, as shown in FIG. 11, a scanning image signal of a strip 2 is obtained by a scanning photoelectric converter 1,
From the scanned image signal, the remaining scale state index calculation circuit 3
Then, the remaining scale state of the strip 2 is calculated, and the remaining scale pattern determining circuit 4 determines the remaining scale pattern based on the remaining scale state index, and displays the remaining scale pattern on the display 5. In FIG. 11, reference numeral 6 denotes a lamp, and reference numeral 7 denotes a black plate for sharpening a side edge of the strip.

However, Japanese Patent Application Laid-Open No. Sho 60-169580
However, since the pattern is used to determine the pattern of the remaining scale state by measuring shape information caused by unevenness, it cannot be applied to the determination of minute objects such as an oxide film, and several mm
Only the scale having the uneven pattern of the size can be determined.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a device capable of automatically detecting and discriminating even a minute change in surface properties such as an oxide film. The purpose is.

[0011]

In order to achieve the above-mentioned object, a surface texture discriminating apparatus according to the present invention controls the relative position between an image pickup device and a metal material by a drive control device on the front or back surface of the metal material. While taking images with the imaging device,
In the image processing apparatus, a characteristic value is obtained from a density histogram of an image captured by the imaging apparatus, and the obtained characteristic value is compared with a preset threshold to obtain a surface property determination value. The relative position information input from the control device is linked by a surface property classifier. By doing so, even a minute change in surface properties such as an oxide film can be accurately determined.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface texture discriminating apparatus according to the present invention is a device for discriminating a change in surface texture generated on a front surface or a back surface of a metal material, and is an imaging device for imaging the front surface or the back surface of the metal material. And a driving device that drives at least one of the imaging device and the metal material, a drive control device that controls the driving device and adjusts a relative position between the imaging device and the metal material, and an image captured by the imaging device. An image processing apparatus that receives an image, obtains a surface texture determination value for processing the image to determine a change in surface texture, a surface texture determination value input from the image processing apparatus, and an image processing apparatus input from the drive control apparatus. A surface texture classifier that associates relative position information with each other, the image processing in the image processing apparatus obtains a feature value from a density histogram of an image, and determines the obtained feature value with a predetermined threshold. And requests a surface property determination value and compare.

In the surface texture determining apparatus according to the present invention, instead of measuring shape information due to unevenness, a characteristic value is obtained from a density histogram of an image, and the obtained characteristic value is compared with a preset threshold to compare the surface value. Since the property discrimination value is obtained and the change in the surface property is discriminated from the surface property discrimination value, even a minute change in the surface property such as an oxide film can be accurately discriminated.

In the image processing in the image processing device in the surface texture determining apparatus according to the present invention, density histograms of an image are obtained for each of a plurality of colors, and a characteristic value for each color is obtained from these density histograms. Alternatively, the obtained characteristic value for each color may be compared with a threshold value set for each color in advance to obtain a surface texture determination value for each color, and the final surface texture determination value may be obtained from these surface texture determination values. . In the case where the final surface texture discrimination value is determined based on the surface texture discrimination value for each color as described above, better discrimination accuracy can be obtained.

The surface texture discrimination value obtained by the image processing device in the surface texture discrimination device according to the present invention is, for example, Sa
Adopt a level. The Sa level will be described below. As a method for evaluating the surface properties of steel materials, ISO (Inte
rnational Organization for Standard)
8501 (visual evaluation of surface cleanliness) and ISO 8502
(Evaluation test of surface cleanliness) are provided.

The above can be applied to a surface finished for painting by a method such as blasting for hot (or cold) rolled steel, finishing with hand tools and power tools, and flame treatment, and is visually clean. ISO 8501 is normally used, except when testing for soluble salts and other invisible stains on the surface should be considered.

According to ISO 8501, the degree of surface cleanliness is expressed in terms of rust and finish grade, and the rust is represented by A (the surface of steel is mostly covered with a hard mill scale,
The rust, if any, is very slight. ), B (rust on the surface of steel is starting to rust, and mill scale is starting to peel off), C (mill scale on the surface of steel is already rusted or can be scraped off.) Pitting is only slightly visible to the naked eye) and D (mill scale on the surface of the steel is already rusted and considerable pitting is visible to the naked eye). .

The finishing grade is represented by “Sa (base adjustment by blast processing)”, “St (base adjustment by hand tool and power tool)”, “Fl ( The number following the letter indicates the degree to which the mill scale, rust and old paint are removed. In the base adjustment by blasting, Sa1 (light blasting), Sa2 (sufficient blasting), Sa21 / 2 (further blasting), Sa3 (blasting to obtain visually clean steel material) Process), and is displayed, for example, as BSa2.

[0019]

FIG. 1 shows a surface texture discriminating apparatus according to the present invention.
A description will be given based on the embodiment shown in FIGS. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a surface texture determining device according to the present invention. FIG. 2 is an explanatory diagram showing an embodiment of an imaging device which is a component of the surface texture determining device according to the present invention. (A)
Fig. 3 shows an image processing apparatus as a component of the surface texture determining apparatus according to the present invention. Fig. 3 shows an image processing apparatus provided outside the apparatus. FIG. 4 is a flowchart showing an example of the operation of an image processing apparatus which is a component of the surface texture determining apparatus according to the present invention, and FIG. 5 is a component of the surface texture determining apparatus according to the present invention. FIG. 6 is a diagram showing an example of a density histogram of an image, FIG. 7 is an explanatory diagram of a feature value, and FIGS. 8 to 10 are a feature value and a surface property discrimination value. It is a figure which shows an example of the relationship of.

In FIG. 1 to FIG. 5, reference numeral 11 relates to the present invention which is arranged immediately after the shot blasting equipment, for example, in order to determine, on-line, a change in surface properties generated on the inner surface of the steel pipe 12 after shot blasting. This is a surface texture determination device, which is configured as follows.

Reference numeral 13 denotes an imaging device for imaging the inner surface of the steel pipe 12, as shown in FIG. 2, a CCD camera 13a for imaging the inner surface, and a ring illumination for irradiating the imaging area of the CCD camera 13a for inner imaging. 13b and steel pipe 12
Is provided with a tube end detector (not shown) for detecting the tip position of the tube.

The CCD camera 13a for imaging the inner surface may be housed in the imaging device 13 as shown in FIG. 2A, or may be stored in the imaging device 13 as shown in FIG.
A condensing lens 13c may be arranged in the inside, and may be arranged outside the imaging device 13 via an optical fiber. In FIG. 2, 13d is a reflecting mirror, and 13e is a measuring glass window.

Reference numeral 14 denotes a driving device for moving the above-mentioned imaging device 13 in the axial direction of the steel pipe 12 or rotating it in the circumferential direction. The driving device 14 is connected to the imaging device 13 via an arm 14a, for example. Figure 2 (a) inside
In the case of (1), a cable for transmitting an image signal is housed, and in the case of FIG. 2 (b), an optical fiber cable is housed. In FIG. 2, neither the cable nor the optical fiber cable is shown.

FIG. 5 shows an example of a guide structure of the imaging device 13 driven by the driving device 14.
When the inspection is performed over the entire length of the steel pipe 12 that reaches several meters, the arm 14a is structurally unstable when the arm 14a is cantilevered. Therefore, in the embodiment shown in FIG. Before and after the gantry 13f, for example, the bearing ball 1
The copying ball 13h is attached so as to be freely rotatable by 3g, and by copying the inner surface of the steel pipe 12 by using the copying ball 13h, a change in the distance from the inner surface of the steel pipe 12 due to bending of the arm 14a or the like is suppressed, and the image is displayed. The figure shows that the imaging accuracy is stabilized.

It is needless to say that the embodiment is not limited to the embodiment shown in FIG. 5 as long as the change in the distance from the inner surface of the steel pipe 12 due to the bending of the arm 14a or the like can be suppressed. For example,
The number of the copying balls 13h may be two each before and after, or one of the front and rear may be two and the other one may be one. Note that a tire-shaped roller may be used instead of the copying ball 13h. However, when the relative operation between the imaging device 13 and the steel pipe 12 is both in the axial direction and the circumferential direction of the steel pipe 12, it is preferable. Absent.

Reference numeral 15 denotes a drive control device which controls the drive device 14 and adjusts the relative positions of the image pickup device 13 and the steel pipe 12. The start and end of the measurement are detected by the image pickup device 13. The determination is made based on a signal from a tube end detector (not shown). The drive control device 15 may, for example, increase the moving speed to reduce the time before the start of the measurement, set the movement during the measurement to a predetermined speed, or reach the pipe end position at the end of the measurement. The measurement is terminated by the signal of the tube end detector, the detection device is returned to the standby position, or the imaging device 13 is rotated at the start of the measurement, and the rotation is stopped at the end of the measurement.

Reference numeral 16 denotes an image processing device which receives an inner surface image of the steel pipe 12 imaged by the imaging CCD camera 13a, processes these images and calculates a surface property discrimination value, and is shown in FIGS. 3 and 4. So, analog signal is A
An image input unit 16a for obtaining a digital image by performing a / D conversion;
From the digital image input from the image input unit 16a, density histograms for each of the three primary colors, for example, red (thick solid line), blue (thin solid line), and green (thin broken line) as shown in FIG. Processing unit 16b for calculating a characteristic value from the density histogram of the image processing unit 16;
b) comparing the feature value input from b with a threshold value prepared as a table in advance to obtain a surface property determination value for determining the state of the imaged inner surface of the steel pipe, and outputting the determined value to the outside; 16c. FIG. 6 is a density histogram of three primary colors when the finish grade representing the surface cleanliness by the blast processing is Sa1.

As the characteristic value calculated from the density histogram, for example, as shown in FIG. 7, any two of various parameters such as a peak pixel density Xp, a peak frequency Yp, and a 10% width Xw are used. Is used. It should be noted that other than these, any parameter that can be extracted from the density histogram, for example, a ratio of 20% width, 30% width,. It is.

Further, from the density histogram for each of the three primary colors of each captured image as shown in FIG.
The characteristic value for each primary color is calculated, and the characteristic value for each of the three primary colors is compared with a threshold value prepared in advance as a table to determine the surface texture discriminating value for each of the three primary colors. For example, a majority decision method or a specific effective primary color priority method as described below is employed.

(Majority decision method) A red surface texture discrimination value j (color
1) After obtaining the green surface texture discrimination value j (color2) and the blue surface texture discrimination value j (color3), the surface texture discrimination value obtained by the following classification is used as the final surface texture discrimination value J. . However, the finishing grade Sa (ISO 8501) representing the surface cleanliness by the blast treatment is Sa1 (light blast treatment), Sa2 (sufficient blast treatment), and Sa3 (blast treatment for obtaining a visually clean steel material). .

When each of the red, green, and blue surface texture discrimination values j (color1), j (color2), and j (color3) is, for example, Sa1, the red surface texture discrimination value j (colo)
r1) is adopted as the final surface property discrimination value J. Red and green surface texture discrimination values j (color1), j (co
lor2) is, for example, Sa1, and the blue surface property determination value j (co
When lor3) is Sa2, the red surface texture determination value j (color1) is adopted as the final surface texture determination value J. The red surface texture discrimination value j (color1) is Sa2, and the green and blue surface texture discrimination values j (color2) and j (color3).
Is a green surface property discrimination value j (colo
r2) is adopted as the final surface property discrimination value J.

(Specific Effective Primary Color Priority Method) For example, the relationship between the peak pixel density Xp and the peak frequency Yp as shown in FIG. 8 (FIG. 8) is calculated from the density histogram for the red color of the captured image. Then, it is determined whether each of the calculated values falls within an area defined by a threshold value (shown by a straight line in FIG. 8) previously determined based on the finishing grade Sa representing the surface cleanliness, and the surface of each image is checked. Determine the property discrimination value.

By the way, Sa of the finish grade Sa described above is used.
Since the criteria such as 1, Sa2,... Are based on human sensory judgments in the first place, when a relational diagram as shown in FIG. 8 is actually created, judgment based on visual observation using images and feature values are used. There are cases where the judgment is different. Therefore, in order to avoid such a difference, the secondary determination is performed only for the surface texture determination value near the threshold value using a different color (for example, green or blue) in the same manner as described above, and the final surface texture is determined. Find the discriminant value. By doing so, the accuracy of the surface property judgment value existing near the threshold value as judgment data is also improved. Note that the secondary determination does not adopt the same feature value as the temporary determination, and if the temporary determination is a relationship between the peak pixel density Xp and the peak frequency Yp as shown in FIG.
It is desirable to obtain the relationship between the pixel density Xp of the peak and the 10% width Xw as shown in FIG. 9 or the relationship between the 10% width Xw and the peak frequency Yp as shown in FIG.

Reference numeral 17 denotes a surface texture discriminator for linking the final surface texture discrimination value input from the image processing device 16 and the relative position information between the steel pipe 12 and the imaging device 13 input from the drive control device 15. And outputs the surface property discrimination value for each relative position to the display 18 and the host computer 19. As a value to be output to the display 18 or the host computer 19, a value obtained by averaging measured values for each relative position may be adopted.

Although not shown in the present embodiment, as the tube end detector, a detector that determines the output of a commercially available displacement meter such as a laser type using a threshold value, a limit switch, or the like is used. In this embodiment, the final surface property discrimination value is obtained from the density histogram of three primary colors. However, it is needless to say that the surface property discrimination value may be obtained from the density histogram of one color.

Further, in the present embodiment, the apparatus is arranged so that online determination is possible immediately after the shot blasting equipment. However, the apparatus may be installed so as to perform offline determination after the equipment at the subsequent stage of the shot blasting equipment. .

Still further, the apparatus of the present invention is installed at the preceding stage of the shot blast equipment to determine the state before descaling,
It may be used to calculate an optimal descale time, or may be applied to a base material or other rust due to other processing.

Further, in this embodiment, the driving device 14
Although the imaging device 13 is shown to move, the imaging device 13 may be fixed, and the steel pipe 12 may be moved and rotated.

[0039]

As described above, in the surface texture determining apparatus according to the present invention, the characteristic value is obtained from the density histogram of the image, and the obtained characteristic value is compared with a preset threshold to obtain the surface texture determining value. Since the change in the surface texture is determined from the surface texture determination value, even a minute change in the surface texture such as an oxide film generated on the inner surface of the steel pipe can be accurately determined over the entire length of the steel pipe. This can greatly contribute to saving blast time and abrasive material.

Then, a density histogram of the image is obtained for each of a plurality of colors, a characteristic value for each color is obtained from these density histograms, and the obtained characteristic value for each color is set in advance to a threshold value set for each color. Calculate the surface property discrimination value for each color by comparing with
When the final surface property discrimination value is determined from these surface property discrimination values and discrimination is performed, better discrimination accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a surface texture determining apparatus according to the present invention.

FIGS. 2A and 2B are explanatory views showing an embodiment of an imaging device which is a component of the surface texture determination device according to the present invention, wherein FIG. 2A shows an imaging camera housed in the device, and FIG. Is provided outside the apparatus.

FIG. 3 is a block diagram showing a schematic configuration of an embodiment of an image processing apparatus which is a component of the surface texture determining apparatus according to the present invention.

FIG. 4 is a flowchart showing an example of the operation of an image processing apparatus which is a component of the surface texture determining apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a guide configuration of an imaging device which is a component of the surface texture determination device according to the present invention;
(A) is a side view, (b) is a front view.

FIG. 6 is a diagram illustrating an example of a density histogram of an image.

FIG. 7 is an explanatory diagram of a feature value.

FIG. 8 is a diagram illustrating an example of a relationship between a characteristic value and a surface property determination value, and is a diagram illustrating a relationship between a peak pixel density and a peak frequency.

FIG. 9 is a diagram illustrating an example of a relationship between a characteristic value and a surface property determination value, and is a diagram illustrating a relationship between a peak pixel density and a 10% width.

FIG. 10 is a diagram illustrating an example of a relationship between a characteristic value and a surface property determination value, and is a diagram illustrating a relationship between a 10% width and a peak frequency.

FIG. 11 is a diagram illustrating a technique disclosed in Japanese Patent Application Laid-Open No. Sho 60-169580.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Surface texture discrimination device 12 Steel pipe 13 Imaging device 14 Drive device 15 Drive control device 16 Image processing device 17 Surface texture discriminator

Claims (2)

[Claims] An apparatus for determining a change in surface properties generated on a front surface or a back surface of a metal material, wherein the imaging device captures an image of the front surface or the back surface of the metal material, and at least one of the imaging device and the metal material. A driving device for driving one,
A drive control device that controls the drive device and adjusts a relative position between the imaging device and the metal material; and a surface texture determination that receives an image captured by the imaging device, processes the image, and determines a change in surface texture. An image processing device for obtaining a value, a surface texture discriminator for associating a surface texture discrimination value input from the image processing device with relative position information input from the drive control device, and an image in the image processing device. A surface texture discriminating apparatus characterized in that the processing is to calculate a feature value from a density histogram of an image, and to compare the obtained feature value with a preset threshold to obtain a surface texture discrimination value. 2. The image processing in the image processing apparatus comprises the steps of: obtaining a density histogram of an image for each of a plurality of colors; obtaining a characteristic value for each color from these density histograms; 2. The method according to claim 1, wherein a surface property discrimination value for each color is obtained by comparing with a threshold value previously set for each color, and a final surface property discrimination value is obtained from the surface property discrimination values. Surface property determination device.