JP4793161B2 - Quality inspection method and apparatus for butt welds - Google Patents

Description

  The present technology relates to a quality inspection method and apparatus for a butt weld. In particular, the present invention relates to a quality inspection method and apparatus for a butt welded portion in which the quality of a welded portion is inspected after removing a raised portion caused by welding in a process of butt welding a steel strip or the like by a flash butt method or the like.

  Conventionally, in the cold rolling process and pickling process, the steel strip is continuously supplied to the process, so the equipment that connects the preceding coil and the succeeding coil by welding without stopping the line with a looper or the like, specifically flash In general, a welding machine such as a butt, seam welding, spot welding, or the like and an auxiliary device such as a build-up cutting means are provided. This build-up is caused by the molten metal protruding from the cross-section as it is pressed in the longitudinal direction of the plate in a state where the steel band butt portion is melted during welding. It is common to cut into a flat shape with a cutting tool such as a cutting tool or a grindstone.

  By the way, the quality determination of the welding between coils by these welding machines is important in preventing troubles such as fracture of the welded portion of the coil in the subsequent process. This is because, in general, the connected steel strip also passes through the same line, pinch roll, rolling roll, and the like as the base material, so that the welded portion needs to have the same shape as the base material as much as possible.

  For the quality judgment of welded parts, the steel strip is temporarily stopped after the build-up cutting, and a visual inspection that observes the front and back surfaces of the welded part, a hammer test that confirms the strength of the welded part using a hammer, and an automatic inspection As a method, a method of discriminating based on welding power and welding time as disclosed in Patent Document 1, an ultrasonic probe is embedded in a welding electrode as disclosed in Patent Document 2. Various methods such as a method for determining the quality of a welding state based on the transmission intensity of ultrasonic waves, a method for determining the quality of a welding state based on a surface temperature measured immediately after welding, as disclosed in Patent Document 3. A method has been proposed.

  In addition, as another conventional technique, a plurality of methods for measuring the shape of the welded portion after the swell removal after welding and determining the quality of the welded portion based on the measured shape are proposed. That is, Patent Document 4 proposes a method for determining pass / fail according to the magnitude of the fluctuation component of the differential waveform of the welded portion shape after removal of the bulge detected by the optical cutting method. Based on the welded part shape detected by the two-dimensional distance meter from the front and back surfaces of the welded part and the plate thickness information of the preceding and succeeding materials, a method for calculating the amount of misalignment of the butt and the remaining bead is proposed. ing.

JP-A-50-83245 JP-A-52-150760 JP 56-99082 A JP-A-1-209307 JP-A-5-154510

  However, the above visual inspection and hammer test cannot be performed in a welding machine in which welding electrodes are complicated, and it is necessary to stop the steel strip for a while after moving the steel strip to a position where the weld is exposed downstream of the welding machine. As a result, production efficiency is lowered, and the quality inspection is dependent on the subjectivity of the worker, so that there are problems of lack of reproducibility and objectivity.

  In the method of Patent Document 1, it is necessary to grasp in advance the ideal welding energy efficiency for each steel type and thickness of the steel strip to be welded, and even in actual operation, it is necessary to switch the discriminating factor for each of these factors. There has been a problem that it becomes complicated and a change in welding efficiency due to contamination and deterioration of the welded part and the welding machine affects the correlation between welding energy and welded part quality.

  In addition, the method of Patent Document 2 is costly because an ultrasonic probe is embedded for each electrode, and the determination is made based on the difference between the time when the transmitted wave becomes minimum and the time when the energization ends. Since the influence factor is not only the size of the weld estimated from the ultrasonic attenuation, there is a problem that the reliability of discrimination is questionable.

  In addition, the method of Patent Document 3 is evaluated based on the maximum temperature of the surface and its variation, so that not only a welding failure due to a misunderstanding or the like cannot be accurately detected, but also when the field of view of the radiation thermometer is deviated from the welding line. There is a problem that it is difficult to perform highly reliable detection because it is greatly affected by the change in emissivity due to errors and the state of scale adhesion on the surface.

  In addition, the method of Patent Document 4 calculates the welded shape after bulge removal by the optical cutting method, so there is an advantage that a wider measurement range can be taken compared to the temperature method etc., but the steel strip surface detected by the optical cutting method Since the waveform of the waveform includes minute fluctuations (high-frequency components) due to the influence of scattering or the like even in the mother plate part, the minute fluctuation components are also emphasized by the differential operation, and the S / N for detecting defective welds is reduced. There was a problem of doing.

  Further, in the method of Patent Document 5, since the bead residue is defined as the difference between the distance value of the base plate portion and the highest point in the measurement range, the cutting edge that is the most defective factor of welding failure to the plate breakage. The case where the level difference of the part cannot be detected directly, or the deformation such as the bending of the butt part is mistakenly detected as a level difference, and the plate breakage does not occur if welding and cutting are normal even if there is a mistake There was also a problem that the amount of mistaking was not the main factor for the quality of the weld. Furthermore, the two-dimensional rangefinder used in this method generally measures the reflectance change of the target surface within the scanning range of the laser beam while automatically correcting the gain, but generally the cut part after bead cutting is very Therefore, there is a problem that the shape of the welded portion including the cutting surface cannot be correctly measured with a normal two-dimensional distance meter because the mirror surface is strong and the reflectance is greatly different from that of the surrounding base plate. In addition, this may occur when there is a mistake in the plate to be abutted, etc., because one of the mother plates is sinking, the cutting tool blade will not be applied, and the opposite side will have an excessively protruding mother plate part. There has also been a problem that the detection performance of poor welding such as scraping and thinning is not sufficient.

  The present invention has been made to solve the above-described conventional problems, and improves the reliability of welding defects due to misalignment of the base plate, which is difficult to identify by the conventional distance meter method and optical cutting shape measurement, and the conventional visual inspection. The problem is to eliminate the inspector dependency that has been a problem in observation and hammering tests, and to improve reproducibility and objectivity.

  The present invention uses a device configuration of the light cutting method to detect a number of reflected light intensity distributions focusing on reflectance information on the surface of an object continuously along the weld line, The quality of the welded part is determined based on the proper reflection characteristics.

  In order to realize this, slit light extending in a direction substantially orthogonal to the bead portion immediately after the welding bead cutting (including light that is apparently considered as slit light by high-speed scanning of the laser spot light). , The diffuse reflected light (diffuse reflected light) is captured as an image, and the position and brightness of the reflected light are detected. This is because the cutting band immediately after bead cutting is in a mirror state, so the reflected light has a strong specular reflection component, most of it is in the regular reflection direction, the diffuse reflection component is small, and the amount of light is small. This is because the base material part (raw material part) that is not a welded part has a random surface state and thus has a strong diffuse reflection component and an increased amount of diffuse reflected light. Therefore, as with the light cutting method, when the slit light is irradiated in an oblique direction with a predetermined incident angle with respect to the steel sheet and observed (imaged) from the diffuse reflection direction with an imaging device such as a camera, the brightness of the reflected image of the slit light The distribution is bright at the base material portion (raw material portion) and dark at the cutting portion, and the difference can be clearly identified.

  Then, by collecting a large number of diffuse reflection lights of the slit light along the welding line and arranging the respective luminance signals as an image, if there is a high luminance area inside the weld bead cutting part, It is possible to combine a determination method in conformity with the point of interest in the conventional visual inspection, such as the uncut material caused by the misunderstanding.

The present invention has been made on the basis of the above research results, and in a method for inspecting the quality of a welded portion after removing a raised portion after butt welding, slit light in a direction substantially orthogonal to the weld line is used. , irradiated by scanning the weld line direction, the diffuse reflection light intensity distribution reflected by the welded portion of the slit light, respectively detected at a plurality of positions of the weld line direction, of the detected diffuse reflection light intensity distribution at the plurality of positions For each, a range surrounded by a position that is less than or equal to the first predetermined intensity is set, and within the range, a process for detecting the presence or absence of an isolated region that is greater than or equal to the second predetermined intensity and greater than or equal to the predetermined width is performed by welding. The above-described problem is solved by continuously performing a plurality of positions in the line direction and determining that there is a welding defect when there are a predetermined number or more of the isolated regions continuously .

The present invention is also a butt-welding part quality inspection device for inspecting the quality of a welded part after removing a raised part after butt welding, and a light source for irradiating slit light in a substantially orthogonal direction with respect to a welding line When, of the slit light, light receiving means for respectively detecting the intensity distribution of the diffuse reflected light at a plurality of positions of the weld line direction, for each of the intensity distributions of the plurality of diffuse reflected light receiving optical, and following a first predetermined intensity An isolated area detecting means for detecting the presence or absence of an isolated area having a second predetermined intensity or more and a predetermined width or more within the range, and an isolated area detected by the isolated area detecting means. The present invention provides a quality inspection device for a butt-welded portion, comprising: a determination unit that determines a welding failure when a predetermined number of regions are continuously present.

  In the present invention, since welding failure is detected by paying attention to the optical reflection characteristics in the region including the weld line after the weld bulge is removed, the mother board that is difficult to identify by the conventional distance meter method or optical cutting shape measurement. It is possible to increase the certainty of poor welding due to misunderstanding. In addition, since these inspections are automatically performed by numerical indexes, there is no inspector dependency which has been a problem in conventional visual observation and hammering tests, and excellent reproducibility and objectivity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing an example of a configuration of a quality inspection device for a butt weld to which the method according to the present invention is applied. In FIG. 1, 1 is a measuring head, 2 is an image processing device, 3 is a display device, and 30 is an object to be measured (here, a steel strip).

  The measurement head 1 collects a light-cut image of a welded portion, and examples of its configuration include a laser light source (hereinafter also simply referred to as a light source) 10, a light source lens 11, a camera (imaging means) 12, and a light receiving lens 13. The measurement conditions such as the wavelength of the light source and the incident angle, which are configured by the mirror 14 and the like, may be applied mutatis mutandis as disclosed in Japanese Patent Application Laid-Open No. 2004-117053 filed by the present inventors. Assuming that the incident angle α of the light from the light source 10 and the angle β of the optical axis of the camera (imaging means) 12 are (α + β) under the condition of receiving diffusely reflected light except for the angle of receiving regularly reflected light. 90 ° is preferred. Further, as the light source 10, scan light that scans spot light focused in a dot shape at high speed in a fan shape or in parallel with a reflection mirror or the like may be used. Preferably, the light emitted from the light source is linearly focused. If a cylindrical light source is used and a slit light source in which these light source and lens are integrated is used, the structure is simplified. In addition, it is preferable that the short side width | variety of the slit light 10S is small enough compared with the level | step difference of welding. Here, when a method of scanning a point light source is employed, it is necessary to turn on the light source 10 for a period of at least one scanning period and to set the imaging period (exposure time) of the camera 12 to be equal to or longer than that period. .

  Note that the positional relationship among the light source 10, the imaging means 12, and the welded portion is as shown in FIG. 2, and the slit light 10S emitted from the light source 10 is in the direction of the weld line of the welded portion 30W (for example, in the direction of conveying the steel plate in the continuous line). (Corresponding to the width direction, which is the orthogonal direction), the positional relationship is such that the light is irradiated in a substantially orthogonal direction.

  In consideration of the operating environment of the apparatus, the measuring head 1 can have a sealed structure except for the openings 16 and 17 that do not block the optical path, and the apparatus can be protected from the heat of welding by cooling means such as air cooling (not shown). desirable. Furthermore, since the measuring head 1 collects light-cut images of the welded portion at a plurality of locations along the weld line, the measuring head 1 faces the butt welded portion in the width direction of the steel strip 3 while facing the butt welded portion with a substantially constant gap. It is desirable to be able to move.

  The image processing device 2 controls the operation of the measuring head 1 and also obtains a three-dimensional shape and luminance distribution image of the welded portion 30W from the light cut image group collected by the measuring head 1 at each position of the welded portion 30W. For example, as shown in FIG. 1, the light source power supply 4, the camera power supply 5, the image data conversion circuit 6, the image processing circuit 7, the image composition circuit 8, the determination circuit 9, etc. Can do.

  Among these, the light source power source 4 and the camera power source 5 supply predetermined driving power to the light source 10 and the camera 12, respectively, and a known power source circuit having a voltage and capacity corresponding to the device may be used.

  The image data conversion circuit 6 is image input means for converting the luminance information (voltage) of the reflection intensity received by each pixel of the camera 12 into a numerical string corresponding to each two-dimensional pixel position.

  The image processing circuit 7 includes a luminance distribution calculation unit 7A and a luminance data memory 7B. The luminance distribution calculation unit 7A receives the image data taken from the image data conversion circuit 6, and the slit light 10S is reflected on the surface of the inspection object (3), and the diffused reflected light intensity (luminance) distribution data observed is observed. Calculate and store in the luminance data memory 7B. Although the specific calculation method of reflected light intensity distribution data is not specifically limited, For example, what is necessary is just to utilize the method disclosed by Unexamined-Japanese-Patent No. 2003-322513. Specifically, the diffuse reflected light of the slit light is picked up by a two-dimensional image pickup means such as a CCD camera to obtain a two-dimensional light cut image as shown in FIG. The pixel at the lower left corner of the two-dimensional mesh in FIG. 3 is X = X1, Y = Y1, the X axis in the width direction and the Y axis in the weld line direction, and the coordinates of each pixel are X = Xi (i = 1, 2). ,..., M), Y = Yj (j = 1, 2,..., N), the luminance of the pixel is I (Xi, Yj), and the luminance distribution in the Y direction at each coordinate position in the image X direction. Of these, the maximum value (maximum luminance) may be calculated.

  The image composition circuit 8 generates a luminance distribution image by connecting the luminance distributions of the slit light 10S output from the image data conversion circuit 6 and stored in the luminance data memory 7B. Can be configured.

  The determination circuit 9 determines whether or not the welding point is good based on the luminance distribution image data stored in the image synthesis circuit 8. For example, as shown in FIG. 4, a cutting position search circuit 91, an uncut portion detection circuit 92, an uncut portion generation area counting circuit 93, and a cutting defect discrimination circuit 94. Any of these may be configured by a logical operation element such as a comparison circuit, or may be configured by a computer having a program operation function corresponding thereto.

  The cutting position search circuit 91 calculates a region range of the bead peripheral portion (periphery portion of the bead cutting region end) based on the luminance change of the luminance distribution data. In the luminance distribution data at each measurement position measured by scanning in the welding line direction, the boundary part of the area where the luminance is reduced near the center is calculated as the bead cutting part. The calculation is performed using a search method in the horizontal direction.

  The uncut portion detection circuit 92 determines whether or not a plurality of brightness reduction regions lower than a predetermined luminance are generated in the region range of the peripheral portion of the bead (or whether there is a region higher than the predetermined luminance). ) Is detected. If it is normal, there is one luminance decrease region. However, if there are a plurality of regions, an abnormal candidate for an uncut portion (in a region higher than a predetermined luminance, there is no normal state, but there are one or more Abnormal). The detection method can be realized by, for example, counting whether or not a threshold having a predetermined luminance is crossed.

  The uncut portion generation area counting circuit 93 counts the output of the uncut portion detection circuit 92 along the weld line, and advances the count when uncut occurs in N consecutive measurements. N should be determined by matching with operational knowledge and results, but in the examples described later, N = 3.

  The cutting failure determination circuit 94 outputs a failure signal if the output of the uncut portion generation area counting circuit 92 exceeds a threshold value T. This threshold value T should also be determined by matching with the operation results, but T = 1 in the examples described later.

  Then, the display device 3 alerts the operator with a screen, sound, etc. according to the output of the cutting failure determination circuit 94, or fails in an external operation management device (business computer, etc.) via a signal line (not shown). Information is transmitted, and can be constituted by a known alarm device, CRT device, communication device, or the like.

  Hereinafter, the operation of the determination circuit 9 according to the present invention will be described with reference to the drawings.

  An example of the luminance distribution obtained as a result of processing the light section image detected by the measuring head 1 at a certain location of the welded portion 30W by the image processing circuit 7 is as shown in FIG. In FIG. 5, the horizontal axis is the coordinate direction substantially orthogonal to the weld line, the vertical axis is the relative value of luminance, and is the luminance distribution measured at an arbitrary position in the weld line direction. In the example of FIG. 5, welding was performed so as to intentionally cause undulation in one of the steel strips to be abutted and partially generate a butt defect, and measurement was performed after removing the swell. At this time, due to the undulation, an uncut defect occurred near the center of the plate width on the measurement surface side in this measurement example. As a result, as shown in FIG. 5A, the reflection luminance in the vicinity of the central portion was increased to approximately the same level as that of the surrounding base material portion. This is because an uncut region is generated at the site to be cut, and the surface property of this region is not in a mirror state but in a diffuse state. Therefore, the diffuse reflection component of this reflected light is captured. Because it is.

  The luminance signal as shown in FIG. 5 is collected at each location where the measuring head 1 moves along the welding line and is output at each position. When the data is input to the image composition circuit 8, the luminance signal as shown in FIG. A brightness distribution image is generated. FIG. 6 shows the luminance distribution of FIG. 5 arranged in one line in the horizontal direction in order from top to bottom (or from bottom to top). Here, the bright portion in FIG. 6 indicates that the luminance is high, and the dark portion indicates that the luminance is low. It should be noted that the luminance distribution data of FIG. 5 is output every time the measurement head 1 moves along the welding line without being synthesized by the image synthesis circuit 8 and is output to the determination circuit 9. It may be.

  Next, among the operations of the determination circuit 9, the operation of the cutting position search circuit 91 will be described with reference to FIG. 7 (luminance distribution data) and FIG. 8 (flow diagram).

  First, (1) the average luminance value M of the entire luminance distribution data illustrated in FIG. 7 is calculated (step S1 in FIG. 8).

  Then, (2) the barycentric position of the pixel range in which the luminance is less than the average value M obtained in (1) (or the average value of the pixels below the average value) is calculated, and the coordinate point is set to A (step S2). . This point A is a starting point for the luminance change search, and is a point for searching for the changing point by moving the coordinates from here to the left and right in the figure.

  Then, (3) the minimum luminance is obtained while the luminance is lower than the average value M obtained in (1) of the luminance distribution, and the luminance value is set to V (step S3).

  On the other hand, with respect to the point A obtained in (2), (4) the maximum luminance in the left region is obtained and the luminance value is set to L (step S4), and (5) the maximum luminance in the right region. And the luminance value is R (step S5).

  Based on these V, L, and R, a luminance threshold TL for calculating the left change point and a luminance threshold TR for calculating the right change point are obtained, and the change point is determined based on these values.

  (6) For example, TL = (V + L) / 2 is set, and the coordinate point where the luminance value corresponding to each coordinate has finally exceeded TL is moved to the left side from the point A, and is set as the luminance change point PL (step S6).

  (7) Similarly, TR = (V + R) / 2, for example, and the coordinate point where the luminance value corresponding to each coordinate has finally exceeded TR is defined as the luminance change point PR by moving to the right from the point A.

  Then, the range of PL and PR is set as the region range (cutting range) of the bead peripheral portion, and the uncut portion detection circuit 92 detects whether or not there is an uncut portion in this region range.

  Thereafter, in the uncut portion detection circuit 92, the region (width) exceeding the threshold for detecting the uncut portion within the region range set by the cutting position search circuit 91 is equal to or greater than a predetermined value. It is detected whether or not there is a place. As a specific detection method, for example, it is detected whether or not the luminance of each address in the luminance distribution exceeds the luminance threshold value for detecting an uncut portion, and if it exceeds, the count value is incremented. Reset the value to 0 (zero). When the count value is equal to or greater than a predetermined value, it is determined that there is an uncut portion, and an uncut portion presence signal (for example, a value “1”) is output to the uncut portion generation area counting circuit 93. If it is not determined that there is an uncut portion, an uncut portion signal (for example, a value “2”) is output.

  Then, the uncut portion generation area counting circuit 93 counts up the input of the signal indicating that there is an uncut portion from the uncut portion detection circuit 92 and sets it as the first count value. It is also checked whether or not the first count value is continuously incremented by a predetermined value or more (for example, N = 3 corresponds to the predetermined value here in the above-mentioned “continuous N measurements”). . Then, when the first count value is incremented and matches the predetermined value, the second count value is incremented. Conversely, if the predetermined value is not reached, the first count value is reset to 0 (zero). Further, the second count value is incremented when the first count value is incremented and the condition that the second count value matches the predetermined value is met.

  An example processed in this way is shown below. Here, the transition of the data output by the uncut portion detection circuit 92 and the uncut portion generation area counting circuit 93 for each measurement position in this measurement example is the uncut portion ( The output corresponds to the generation / disappearance of part (b). In the measurement example of FIG. 9, the output of the uncut portion generation region counting circuit 93 is 2, and it was correctly determined that the welding was defective.

  Next, for comparison, measurement using the apparatus of the present embodiment was performed on the butt weld after the second bead cutting, which was determined by a skilled worker to be good welding. The luminance distribution image output from the image synthesis circuit 8 according to this measurement example is as shown in FIG. In the measurement example of FIG. 10, the output of the uncut portion occurrence area counting circuit 93 was 0, and the butt weld of FIG. 10 was correctly determined to be harmless.

  In the above description, the uncut portion is determined for the entire plate width. However, when the notching operation is performed to cut off both ends of the plate width of the welded portion according to the configuration of the rolling line, both ends of the plate width known in advance are known. May be excluded from inspection. In addition, since the light source, camera, and other devices of this inspection apparatus can be used for measurement based on light cutting shape measurement, it is more reliable if the inspection according to the present invention and the inspection with the conventional cutting step shape are used in combination. High inspection is possible.

  Further, the configuration after the image processing circuit 7 described in the above embodiment may be realized by a computer program and implemented by a CPU, a memory, or the like, following a computer application apparatus performed in recent years. The light source 10 is not limited to a laser.

1 is a block diagram including a partial cross-sectional view illustrating an example of a configuration of an embodiment of the present invention. The perspective view which extracts and shows the principal part similarly The figure which shows the example of the light section image which was similarly imaged with the camera The figure which similarly shows an example of the detailed structure of a determination circuit The figure which shows the example of the data of the luminance distribution measured with respect to the welding part which the cutting defect generate | occur | produced by the butt part curvature similarly The figure which shows the example of the image data which similarly accumulated the brightness distribution data in the weld line direction The figure explaining operation of a cutting position search circuit similarly Similarly, a flowchart showing the processing procedure of the operation of the cutting position search circuit The graph explaining the operation of the measurement example of the present invention The figure which shows the example of the image data which accumulate | stored luminance distribution data in the weld line direction with respect to a normal weld part

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Measuring head 2 ... Image processing apparatus 3 ... Display apparatus 4 ... Light source power supply 5 ... Camera power supply 6 ... Image data conversion circuit 7 ... Image processing circuit 8 ... Image composition circuit 9 ... Determination circuit 10 ... Laser light source 10S ... Slit light 12 ... Camera 30 ... Object to be measured 30W ... Butt weld

Claims (2)

In the method of inspecting the quality of the welded part after removing the raised part after butt welding,
Slit light in a direction substantially perpendicular to the weld line is scanned and irradiated in the weld line direction,
Diffuse reflected light intensity distribution reflected at the welded portion of the slit light is detected at each of a plurality of positions in the welding line direction,
For each of the diffuse reflected light intensity distributions detected at the plurality of positions, a range surrounded by a position that is equal to or lower than the first predetermined intensity is set.
Within that range, the process of detecting the presence or absence of an isolated region that is greater than or equal to the second predetermined intensity and greater than or equal to the predetermined width is continuously performed for a plurality of positions in the weld line direction,
A quality inspection method for a butt-welded portion, wherein a defective weld is determined when a predetermined number or more of the isolated regions are continuously present . A quality inspection device for a butt weld that inspects the quality of the weld after removing the raised portion after butt welding,
A light source that irradiates slit light in a substantially orthogonal direction with respect to the welding line;
Light receiving means for each detection of said slit light, the intensity distribution of diffuse reflected light at a plurality of positions of the weld line direction,
For each of the received intensity distributions of the plurality of diffusely reflected lights, a range surrounded by a position that is equal to or lower than the first predetermined intensity is set, and the second predetermined intensity or higher and the predetermined width or higher are set within the range. An isolated region detecting means for detecting the presence or absence of an isolated region;
A determination unit that determines a welding failure when there are a predetermined number or more of isolated regions continuously detected by the isolated region detection unit;
An apparatus for inspecting the quality of a butt weld, characterized by comprising: