JP2009103662A - Laser welding evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser welding evaluation method simplified in procedures necessary to determine weld quality at welded portions, ensuring a constant determination accuracy without depending on skills of surveyors. <P>SOLUTION: The laser welding evaluation method includes a cutting step S101 of cutting out a test piece 15 from a metal material to make a cross section of welded portion a measuring surface 22; a disposing step S103 of preparing an imaging stage 11 having a scale 16 disposed on an imaging surface 11a, and of disposing multiple test pieces 15 to bring the measuring surface 22 into contact with the imaging surface 11a; an imaging step S104 of taking an image of the test pieces along with the scale 16 using an imaging means 12; a calculating step S105 of calculating a physical amount of measuring items from images of measured surfaces of the test pieces; and an evaluation step S106 of evaluating the weld quality at the welded portions by comparing the physical amount with an evaluation criteria. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser welding evaluation method for evaluating the welding quality of a welded part in laser welding.

  Laser welding is known in which a workpiece such as a metal material is irradiated with a laser beam having a high energy density such as a YAG laser, and a weld is formed on the workpiece. In laser welding, it is desirable that the cross-section shape of the melted portion be uniform in order to stabilize the molten state of the welded portion and ensure sufficient strength in the welded portion. For example, Patent Document 1 describes a technique for calculating optimal laser beam control parameters (laser output and scanning speed) using data on material properties of a workpiece and a desired cross-sectional shape. If welding is performed using the control parameters calculated in this way, the cross-sectional shape of the welded portion can be formed into a desired shape.

On the other hand, even if welding is performed with the same control parameters, the cross-sectional shape of the melted part may not be formed in a desired shape due to a failure of the welding apparatus or the like. In order to grasp such a situation, for example, as described in Patent Document 2, after performing laser welding on a workpiece, a cross section of a welded part is cut out as a specimen, and this cross section is observed. There are inspection methods for evaluating the quality of the welded state, such as the throat thickness and leg length of the joining material.
JP 2007-260743 A JP 2007-57485 A

  However, the conventional method of evaluating the welding quality by observing the weld cross section has a problem that the work process becomes complicated as the number of test pieces to be inspected increases. In the conventional method, generally, a specimen is cut out from a welded part, and the specimen is fixed to an imaging stage so that the upper surface is a cross section of the welded part, and this upper surface is used as a measurement surface by an imaging means such as a microscope. The measurement surface was imaged from above. The range that can be imaged at a time with a microscope is small, and only one specimen can be observed at a time. In addition, it is necessary to fix the specimen on the imaging stage every time a new specimen is observed in order to keep the measurement plane horizontal so that the focal lengths at any position on the measurement plane are the same. there were. Thus, the work process has become complicated as the number of specimens to be inspected increases.

  Further, the conventional method has a problem that the work efficiency depends on the skill of the inspector. For example, when cutting a specimen from a weld, the number of inspection steps is affected by the processing accuracy of the specimen. When the processing accuracy of the specimen is high, the thickness of the specimen fixed on the imaging stage is constant, so the process of adjusting the focal length between the microscope and the measurement surface every time the specimen on the imaging stage is replaced. It becomes unnecessary. On the other hand, when the processing accuracy of the specimen is low, the distance between the measurement surface and the microscope varies for each specimen, so that it is necessary to adjust the focal length of the microscope for each specimen. As described above, the number of inspection work steps is affected by the skill of the inspector's processing technique and the work efficiency depends on the skill of the inspector.

  In the conventional method, the measurement surface is imaged for each specimen and the cross section of the weld is observed. Therefore, the distance between the microscope and the measurement surface and the focal length of the microscope depend on the size and thickness of the specimen. It may be different every time. Conventionally, a scale serving as a reference for an actual dimension is imaged together with a specimen, and based on this scale, various actual dimensions of a cross-sectional shape are calculated from a captured image of a measurement surface, and the quality of a welded state is evaluated. However, if the distance between the microscope and the measurement surface changes for each specimen, the size of the scale in the captured image will also differ for each specimen, so the accuracy of judging the quality of the welded part is not uniform. there were.

  The present invention has been made in order to solve the above-described problems. The present invention simplifies the procedure required to determine the weld quality of the welded portion, and ensures a certain determination accuracy without depending on the skill of the inspector. An object of the present invention is to provide a laser welding evaluation method that can be used.

  The laser welding evaluation method according to the present invention is a laser welding evaluation method for evaluating the welding quality of a welded portion of a metal material in laser welding, wherein a specimen is taken from a metal material so that a cross section of the welded portion becomes a measurement surface. A cutout step to cut out and an imaging stage having a scale arranged on the imaging surface are prepared, and a plurality of specimens are arranged on the imaging surface so that the measurement surface faces and contacts the imaging surface of the imaging stage Steps, imaging steps for imaging specimens arranged on the imaging surface using an imaging means together with a scale, and scales as a common reference, each image relating to the welding quality of the welded portion from the measurement surface image of each specimen The method includes a calculation step for calculating a physical quantity of a measurement item, and an evaluation step for evaluating the welding quality of the welded part by comparing the physical quantity with a predetermined evaluation criterion.

  In this laser welding evaluation method, a plurality of specimens are arranged on the imaging surface of the imaging stage so that the measurement surface of each specimen faces and contacts the imaging surface of the imaging stage. The image is picked up using the image pickup means together with the scale arranged on the surface. With such a configuration, it is not necessary to fix the specimen to the imaging stage, and the measurement surface of a plurality of specimens can be imaged at the same time, so even if the number of specimens to be inspected increases, the work process Is not complicated, and the procedure required to determine the welding quality of the welded portion can be simplified. In addition, since the measurement surface of the specimen placed so as to face and contact the imaging surface of the imaging stage is imaged by the imaging means, the distance between the imaging means and the measurement surface of the specimen is the processing accuracy of the specimen. Therefore, the measurement surface can be imaged with a certain accuracy without depending on the skill of the inspector. Furthermore, since the physical quantity of each measurement item related to the welding quality of the welded part is calculated from an image obtained by simultaneously imaging the measurement surfaces of a plurality of specimens using the scale as a common reference, the accuracy of determining the welded quality of the welded part is Can be made uniform between the specimens.

  Moreover, it is preferable that the laser welding evaluation method of the present invention further includes an etching step for performing metal etching on the measurement surface of the specimen between the cutting step and the placement step. Thereby, in the measurement surface of the specimen, the surface roughness of the welded portion and other portions will be different, and the contrast of both colors will be further increased, so that the welded portion can be more clearly identified, In the calculation step, each measurement item related to the welding quality of the welded portion can be accurately calculated.

  According to the laser welding evaluation method of the present invention, it is not necessary to fix the specimen to the imaging stage, and since the measurement surface of a plurality of specimens can be imaged simultaneously, the number of specimens to be inspected increases. However, the work process is not complicated, and the procedure required to determine the welding quality of the welded portion can be simplified. In addition, since the distance between the imaging means and the measurement surface of the specimen is always constant regardless of the processing accuracy of the specimen, the measurement surface can be imaged with a constant accuracy without depending on the skill of the inspector. . Furthermore, since the physical quantity of each measurement item related to the welding quality of the welded part is calculated from an image obtained by simultaneously imaging the measurement surfaces of a plurality of specimens using the scale as a common reference, the accuracy of determining the welded quality of the welded part is Can be made uniform between the specimens.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a laser weld evaluation method according to the invention will be described with reference to the drawings.

  In FIG. 1, the structure of the laser welded part evaluation system 10 for implementing the laser welded part evaluation method which concerns on this embodiment is shown. As shown in FIG. 1, the laser weld evaluation system 10 includes an imaging stage 11 in which specimens 15a, 15b, 15c and a scale 16 are arranged on an imaging surface 11a, and an imaging surface 11a from the lower side of the imaging stage 11. The physical quantity of each measurement item related to the welding quality of the welded portion is determined from the image of the imaging unit (imaging means) 12 and the measurement surfaces 22a, 22b, and 22c of the specimens 15a, 15b, and 15c captured by the imaging unit 12. A measurement item calculation unit 13 to be calculated, and a quality evaluation unit 14 to evaluate the welding quality of the welded part by comparing the physical quantity of the measurement item calculated by the measurement item calculation unit 13 with a predetermined evaluation criterion.

  The imaging stage 11 is a plate member made of a transparent material such as glass or transparent plastic. The imaging stage 11 is provided with an imaging surface 11a on the upper surface, and a scale 16 with a scale of length is arranged on the imaging surface 11a.

  The specimens 15a, 15b, and 15c are welded to a metal material after laser welding is performed on the metal material while changing control parameters such as laser output, oscillation method, welding speed, and thickness of the metal material to be welded. It is cut out from the metal material so that the cross section of the part becomes the measurement surfaces 22a, 22b, 22c. FIG. 2 shows an example of how to cut out the specimens 15a, 15b, and 15c.

  As shown in FIG. 2, in this embodiment, the welding part 21 when performing lap welding between the upper plate 21a and the lower plate 21b of the metal material is illustrated. The upper plate 21a and the lower plate 21b of the metal material are made of, for example, a material that is encased in each system such as austenite and ferrite in stainless steel, and 5000 series, 6000 series, and 7000 series in aluminum alloys.

  The specimens 15a, 15b, and 15c are cut out from the welded portion 21 of the metal material so that one surface thereof becomes the measurement surfaces 22a, 22b, and 22c that are cross sections of the welded portion. The specimens 15a, 15b, and 15c are cut out with a size of 20 mm square, for example. Thereafter, the specimens 15a, 15b, and 15c are subjected to metal etching on the measurement surfaces 22a, 22b, and 22c. When the measurement surfaces 22a, 22b, and 22c are etched, the surface of the measurement surface is dissolved and removed by the action of the etching solution. At this time, since the material of the welded portion of the measurement surface is changed by laser welding and the etching rate is different from that of the other portions, the surfaces of the measurement surfaces 22a, 22b, and 22c after etching are the welded portions. The surface roughness is different in other parts. In metal etching, for example, a mixed solution of 90% ethanol and 10% nitric acid can be used as an etchant. The etching time is about 5 seconds, for example.

  Returning to FIG. 1, when the laser welding evaluation method according to the present embodiment is performed, the specimens 15 a, 15 b, and 15 c face each of the measurement surfaces 22 a, 22 b, and 22 c on the imaging surface 11 a of the imaging stage 11. Then, it is disposed on the imaging surface 11a of the imaging stage 11 so as to come into contact with each other. That is, the specimens 15a, 15b, and 15c are placed on the imaging surface 11a of the imaging stage 11 with the measurement surfaces 22a, 22b, and 22c facing downward. FIG. 1 shows a state in which three specimens 15a, 15b, and 15c are arranged on the imaging stage 11, but the number of specimens placed on the imaging stage 11 is as follows. Depending on the size of the imaging stage 11 and the specimen, the number may be more or less than three.

  The imaging unit 12 is disposed below the imaging stage 11 and is installed so that the imaging surface 11a of the upper imaging stage 11 can be imaged. The imaging unit 12 is positioned in advance so that the focal length matches the imaging surface 11 a of the imaging stage 11. The imaging unit 12 includes a light emitting unit, a light receiving unit, and a scanning unit (not shown). While the scanning unit moves in a uniaxial direction, the light emitting unit irradiates the imaging surface 11a with light and reflects the reflected light from the imaging surface 11a. Detection is performed by the light receiving unit, and image data of the imaging surface is acquired. Specifically, the imaging unit 12 is a carriage of an image scanner, a light emitting unit is a light source such as a white fluorescent lamp or a light emitting diode, a light receiving unit is a linear image sensor such as a CCD or CMOS, and a scanning unit is a linear unit. Drive means such as a motor for moving the carriage in a direction perpendicular to the sensor array of the image sensor. Irradiation light applied to the imaging surface 11a from the light emitting unit of the imaging unit 12 may be white light as in a normal image scanner, or visible light having an arbitrary wavelength such as a short wavelength visible light having a wavelength of about 400 nm. You may select suitably.

  The imaging unit 12 may specifically be a digital camera. In this case, the imaging unit 12 is fixed at one place and configured to capture the entire imaging surface 11a of the imaging stage at a time. In contrast to the present embodiment, the imaging unit 12 may be fixed at one place, and the imaging stage 11 may be moved to acquire image data of the entire imaging surface.

  When the measurement item calculation unit 13 receives the image data captured by the imaging unit 12, the measurement item calculation unit 13 identifies a cross section of the weld from the image data, and uses the scale scale in the same image data as a common reference, A physical quantity of a predetermined measurement item is calculated. When the quality evaluation unit 14 receives the measurement item data from the measurement item calculation unit 13, the quality evaluation unit 14 evaluates the welding quality of the welded portions of the specimens 15a, 15b, and 15c. The measurement item calculation unit 13 and the quality evaluation unit 14 are physically realized by a computer system including a CPU, a memory, a communication interface, a storage unit such as a hard disk, a display unit such as a display, and the like. Specific processing in the measurement item calculation unit 13 and the quality evaluation unit 14 will be described later.

  Next, the laser weld evaluation method according to this embodiment will be described. FIG. 4 shows a flowchart of the laser weld evaluation method.

  First, the specimens 15a, 15b, and 15c are cut out from the welded part 21 of the metal material so that the cross section of the welded part becomes the measurement surfaces 22a, 22b, and 22c of the specimen (S101: cutting step). The step of cutting the specimens 15a, 15b, and 15c may be performed manually by an inspector using a cutting machine or the like, or may be automatically performed by a control unit such as a computer. Thereafter, metal etching is performed on the measurement surfaces 22a, 22b, and 22c of the specimen (S102: etching step).

  Next, the cut specimens 15 a, 15 b, and 15 c are on the imaging surface of the imaging stage 11 so that the measurement surfaces 22 a, 22 b, and 22 c of the specimen face the imaging surface 11 a of the imaging stage 11. (S103: placement step). Specifically, for example, as shown in FIG. 1, the specimens 15a, 15b, and 15c are arranged on the imaging surface 11a with the measurement surfaces 22a, 22b, and 22c facing downward. Then, the specimens 15a, 15b, and 15c arranged on the imaging surface 11a are imaged by the imaging unit 12 together with the scale 16 that is also arranged on the imaging surface 11a (S104: imaging step).

  Next, each measurement item related to the welding quality of the welded part 21 from the images of the measurement surfaces 22a, 22b, and 22c of each specimen using the scale 16 imaged by the imaging unit 12 by the measurement item calculation unit 13 as a common reference. Is calculated (S105: calculation step). Specifically, the measurement item calculation unit 13 first receives the image data from the imaging unit 12, and extracts the measurement surfaces 22a, 22b, and 22c of the specimens 15a, 15b, and 15c from the image data. In order to extract the measurement surfaces 22a, 22b, and 22c, for example, a method of automatically detecting the difference in colors in the image using image processing software, a display device that displays image data, and a pointing device are used. A method of inputting a measurement point by the inspector may be appropriately selected. Next, the number of pixels on the scale of the image data is measured to calculate the actual length per pixel. And the measurement item of measurement surface 22a, 22b, 22c is measured by the number of pixels, is converted into actual length, and a measurement item is calculated. FIG. 3 shows an example of measurement items. As shown in FIG. 3, in the present embodiment, the measurement items are the area S of the weld cross section, the contour length L of the weld cross section, the width B of the weld cross section at the boundary between the upper plate 21a and the lower plate 21b, And the depth D of the weld section.

Then, the quality evaluation unit 14 compares the measurement item calculated by the measurement item calculation unit 13 with a predetermined evaluation criterion, and evaluates the welding quality of the welded portion (S105: evaluation step). Specifically, the quality evaluation unit 14 provides the following evaluation criteria, for example. The following examples are evaluation criteria in the case of lap welding in which the thicknesses of the upper plate 21a and the lower plate 21b of the metal material are 0.8 mm and 1.5 mm, respectively.
-Area S: 10% or less difference from normal product
・ Outline length L: Difference from normal product is 10% or less
・ Width B: 0.8mm or more
-Depth D: 1.2 mm or more.
Note that the “normal product” used in the above evaluation criteria refers to the case where laser welding is performed with the laser welding control parameters (laser output, oscillation method, welding speed, etc.) set when the specimen is created. This refers to the cross-sectional shape that should be realized.

  The quality evaluation unit 14 determines whether or not each measurement item satisfies the evaluation criteria, and determines that the weld quality of the specimen is “normal” when all the evaluation criteria are satisfied. In other cases, it is determined that the welding quality of the specimen is “abnormal”.

  In the laser welding evaluation method of the present embodiment, the imaging stage 11 is imaged so that the measurement surfaces 22a, 22b, and 22c of the specimens 15a, 15b, and 15c face and come into contact with the imaging surface 11a of the imaging stage 11. The image is picked up using the image pickup unit 12 together with the scale 16 that is arranged on the surface 11 a and is similarly arranged on the image pickup surface 11 a of the image pickup stage 11. With such a configuration, it is not necessary to fix the specimens 15a, 15b, and 15c to the imaging stage 11, and it is possible to simultaneously image the measurement surfaces 22a, 22b, and 22c of the plurality of specimens 15a, 15b, and 15c. Therefore, even if the number of specimens to be inspected increases, the work process does not become complicated, and the procedure required to determine the welding quality of the welded portion can be simplified.

  In addition, since the imaging unit 12 images the measurement surfaces 22a, 22b, and 22c of the specimen arranged so as to face and contact the imaging surface 11a of the imaging stage 11, the imaging unit 12 and the measurement surface 22a of the specimen are used. Since the distances from 22b and 22c are always constant regardless of the processing accuracy of the specimen, the measurement surface can be imaged with constant accuracy without depending on the skill of the inspector. Furthermore, since the physical quantity of each measurement item related to the welding quality of the welded part 21 is calculated from images obtained by simultaneously imaging the measurement surfaces 22a, 22b, and 22c of a plurality of specimens using the scale 16 as a common reference, the weld quality of the welded part is calculated. Can be made uniform among a plurality of specimens.

  Further, in the etching step S102, by performing metal etching on the measurement surfaces 22a, 22b, and 22c of the specimen, the surface roughness of the welded portion 21 and other portions on the measurement surfaces 22a, 22b, and 22c of the specimen is different. As a result, the contrast between the two colors is further increased, so that the welded portion 21 can be more clearly identified, and each measurement item related to the weld quality of the welded portion can be accurately calculated in the calculation step S105. .

  As described above, the laser welding evaluation method according to the present invention has been described with reference to the preferred embodiment, but the present invention is not limited to the above embodiment.

It is a figure which shows the structure of the laser welding part evaluation system for enforcing the laser welding part evaluation method which concerns on one Embodiment of this invention. It is a figure which shows an example of the process of cutting out a test piece from a welding part. It is a figure which shows the measurement item which concerns on the cross section of the welding part calculated in a calculation step. It is a flowchart of the laser welding part evaluation method which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Imaging stage, 12 ... Imaging unit (imaging means), 13 ... Measurement item calculation part, 14 ... Quality evaluation part, 15a, 15b, 15c ... Specimen, 16 ... Scale, 22 ... Measurement surface, S101 ... Extraction step , S102 ... placement step, S103 ... imaging step, S104 ... calculation step, S105 ... evaluation step.

Claims (2)

A laser welding evaluation method for evaluating the welding quality of a welded portion of a metal material in laser welding,
A cutting step of cutting a specimen from the metal material so that a cross section of the weld becomes a measurement surface;
An arrangement step of preparing an imaging stage having a scale arranged on the imaging surface, and arranging the plurality of specimens on the imaging surface such that the measurement surface faces and contacts the imaging surface of the imaging stage. When,
An imaging step of imaging the specimen placed on the imaging surface using an imaging means together with the scale;
A calculation step for calculating a physical quantity of each measurement item related to the weld quality of the weld from the image of the measurement surface of each specimen, using the scale as a common reference,
An evaluation step for comparing the physical quantity with a predetermined evaluation criterion to evaluate the weld quality of the weld,
A laser welding evaluation method comprising: The laser welding evaluation method according to claim 1, further comprising an etching step of performing metal etching on the measurement surface of the specimen between the cutting step and the arranging step.

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