METHOD FOR DETECTING SHAPE OF BUTT JOINT OF WELDED STEEL PIPE, AND QUALITY CONTROL METHOD AND APPARATUS FOR WELDED STEEL PIPES USING THE SHAPE DETECTING METHOD

• US 20190323828A1
• Filed: 07/14/2017
• Published: 10/24/2019
• Est. Priority Date: 12/20/2016
• Status: Active Grant

• Current Assignee: Nippon Steel Nisshin Co., Ltd. (Nippon Steel Corporation)
• Original Assignee: Nippon Steel Nisshin Co., Ltd. (Nippon Steel Corporation)
• Inventors: HIRAMOTO, Takafumi, KINO, Yasuyuki, EHARA, Teruo
• Granted Patent: US 10,704,897 B2
• Time in Patent Office: Days
• CPC Class Codes: B21C 37/08 Making tubes with welded or soldered seams with helically arranged seams B21C37/122
• CPC Class Codes: B21C 51/00 Measuring, gauging, indicating, counting, or marking devices specially adapted for use in the production or manipulation of material in accordance with subclasses B21B - B21F
• CPC Class Codes: B23K 31/00 Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups making tubes or profiled bars involving operations other than soldering or welding B21C37/04, B21C37/08
• CPC Class Codes: B23K 31/003 relating to controlling of welding distortion
• CPC Class Codes: G01B 11/03 by measuring coordinates of points
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50

Abstract

The present invention provides a method for detecting a shape of a butt joint of a welded steel pipe. A specific detection range including a butt joint of a welded steel pipe is scanned with a non-contact means to obtain geometric coordinate data. Coordinates of a start point and an end point of the specific detection range, a first selected point located between the start point and the butt joint, and a second selected point located between the butt joint and the end point are selected from the geometric coordinate data. A first approximate circle including the start point, the end point, and the first selected point, and a second approximate circle including the start point, the end point, and the second selected point are calculated. A deviation between the first and the second approximate circles is used as an index representing the shape of the butt joint.

Claims

1. A method for detecting a shape of a butt joint of a welded steel pipe based on geometric coordinate data of a specific detection range including the butt joint, the geometric coordinate data being obtained by scanning the specific detection range using a non-contact means and being projected on a two-dimensional plane, the method comprising:

selecting, from the geometric coordinate data, coordinates of a start point and an end point of the specific detection range, a first selected point located between the start point and the butt joint, and a second selected point located between the butt joint and the end point;

calculating a first approximate circle that includes the start point, the end point, and the first selected point, and a second approximate circle that includes the start point, the end point, and the second selected point; and

averaging the first approximate circle and the second approximate circle so as to calculate an imaginary circle, calculating, as a difference value, a maximum deviation of the first approximate circle or the second approximate circle from the imaginary circle in a thickness direction of the welded steel pipe within the specific detection range, and using the difference value as an index representing the shape of the butt joint.

4. A quality control method for welded steel pipes using the method for detecting a shape of a butt joint of a welded steel pipe according to claim 1, the quality control method comprising comparing the difference value with a predetermined threshold value so as to judge whether the shape of the butt joint of the welded steel pipe is acceptable or not.

2. A method for detecting a shape of a butt joint of a welded steel pipe based on geometric coordinate data of a specific detection range including the butt joint, the geometric coordinate data being obtained by scanning the specific detection range using a non-contact means and being projected on a two-dimensional plane, the method comprising:

selecting, from the geometric coordinate data, coordinates of a start point and an end point of the specific detection range, a first selected point located between the start point and the butt joint, and a second selected point located between the butt joint and the end point;

calculating a first approximate circle that includes the start point, the end point, and the first selected point, and a second approximate circle that includes the start point, the end point, and the second selected point; and

calculating a distance between a center of the first approximate circle and a center of the second approximate circle, and using the distance as an index representing the shape of the butt joint.

3. The method for detecting a shape of a butt joint of a welded steel pipe according to claim 2, wherein, instead of the distance between the center of the first approximate circle and the center of the second approximate circle, a differential distance in an X-axis direction between the center of the first approximate circle and the center of the second approximate circle and a differential distance in a Z-axis direction between the center and the center are used as indices representing the shape of the butt joint.

5. A quality control method for welded steel pipes using the method for detecting a shape of a butt joint of a welded steel pipe according to claim 2, the quality control method comprising comparing the distance between the center of the first approximate circle and the center of the second approximate circle, with a predetermined threshold value, so as to judge whether the shape of the butt joint of the welded steel pipe is acceptable or not.

6. A quality control method for welded steel pipes using the method for detecting a shape of a butt joint of a welded steel pipe according to claim 3, the quality control method comprising comparing the differential distance in the X-axis direction between the center of the first approximate circle and the center of the second approximate circle and the differential distance in the Z-axis direction between the center and the center, with respective predetermined threshold values, so as to judge whether the shape of the butt joint of the welded steel pipe is acceptable or not.

7. A quality control apparatus for welded steel pipes, the apparatus comprising:

a non-contact means comprising;

a light projecting unit configured to irradiate a specific detection range including a butt joint of a welded steel pipe with a fan-shaped light beam or to scan the specific detection range with a spot light beam; and

a data output unit configured to receive light reflected from the specific detection range irradiated or scanned with the light beam from the light projecting unit and to output, based on the reflected light, geometric coordinate data representing changes in position and shape of the butt joint; and

an arithmetic processor comprising;

an approximate circle calculating/processing unit configured to select, from the geometric coordinate data obtained by the non-contact means, coordinates of a start point and an end point of the specific detection range, a first selected point located between the start point and the butt joint, and a second selected point located between the butt joint and the end point, to calculate a first approximate circle that includes the start point, the end point, and the first selected point, and a second approximate circle that includes the start point, the end point, and the second selected point, and to average the first approximate circle and the second approximate circle so as to calculate an imaginary circle and calculate, as a difference value, a maximum deviation of the first approximate circle or the second approximate circle from the imaginary circle in a thickness direction of the welded steel pipe; and

a judgment processing unit configured to compare the difference value calculated by the approximate circle calculating/processing unit, with a predetermined threshold value, so as to judge whether the shape of the butt joint of the welded steel pipe is acceptable or not.

8. A quality control apparatus for welded steel pipes, the apparatus comprising:

a non-contact means comprising;

a light projecting unit configured to irradiate a specific detection range including a butt joint of a welded steel pipe with a fan-shaped light beam or to scan the specific detection range with a spot light beam; and

a data output unit configured to receive light reflected from the specific detection range irradiated or scanned with the light beam from the light projecting unit and to output, based on the reflected light, geometric coordinate data representing changes in position and shape of the butt joint; and

an arithmetic processor comprising;

an approximate circle calculating/processing unit configured to select, from the geometric coordinate data obtained by the non-contact means, coordinates of a start point and an end point of the specific detection range, a first selected point located between the start point and the butt joint, and a second selected point located between the butt joint and the end point, to calculate a first approximate circle that includes the start point, the end point, and the first selected point, and a second approximate circle that includes the start point, the end point, and the second selected point, and to calculate a distance between a center of the first approximate circle and a center of the second approximate circle; and

a judgment processing unit configured to compare the distance calculated by the approximate circle calculating/processing unit, with a predetermined threshold value, so as to judge whether the shape of the butt joint of the welded steel pipe is acceptable or not.

9. The quality control apparatus for welded steel pipes according to claim 8, wherein

the approximate circle calculating/processing unit calculates a differential distance in an X-axis direction between the center of the first approximate circle and the center of the second approximate circle and a differential distance in a Z-axis direction between the center and the center, instead of the distance between the center of the first approximate circle and the center of the second approximate circle, and

the judgment processing unit compares the differential distance in the X-axis direction between the center of the first approximate circle and the center of the second approximate circle and the differential distance in the Z-axis direction between the center and the center, calculated by the approximate circle calculating/processing unit, with respective predetermined threshold values, so as to judge whether the shape of the butt joint of the welded steel pipe is acceptable or not.