JPS6149774A - Outside surface welding method of weld pipe - Google Patents

Abstract

PURPOSE:To execute welding with a high accuracy by deriving exactly a groove center position extending over the overall length of a seaming part, and controlling a weld position by a welding torch based on the groove center position. CONSTITUTION:A groove shape image 14 by a slit light 13 projected vertically toward a groove surface of a seaming part of a weld pipe 11 from a light source 12, and in a state orthogonal to the longitudinal direction of a groove part is brought to image pickup by an image pickup machine 15 and transferred to an arithmetic unit 18 through a memory 17. The arithmetic unit 18 converts its groove shape image 16 to a coordinate, an inclination value of each very small section of the groove shape converted to a coordinate is derived, a position of a groove end point of the groove shape is derived by comparing said inclination value with a reference inclination value of each reference shape, and a groove center position from the position of the right and the left groove end points of the groove shape is derived and transferred to a servo-mechanism part 19. The servo-mechanism 19 controls a welding torch 20 based on said groove center position.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a method for welding the outer surface of a welded pipe.

[Background Art] Conventionally, a method of detecting the groove center position of a seam part of a material to be welded and controlling the welding position by a welding torch based on the groove center position is disclosed in, for example, Japanese Patent Laid-Open No. 181478/1983. A method has been proposed.

This method, which has already been proposed, predetermines a single symmetrical standard groove shape, images the actual groove shape of the seam of the welded material to be actually welded, and It is possible to determine the groove center position of the material to be welded by obtaining groove information such as the groove tip point of the tip shape and comparing this groove information with information on the reference groove shape.

However, the conventional method described above is limited to a single reference groove shape and a symmetrical shape, so the groove shape may be asymmetrical due to tack beads being applied to the sutured portion, etc. Or, if the groove shape changes along the weld line, it becomes difficult or impossible to accurately determine the groove center position of the welded material, resulting in off-seams, etc. where the actual welding position deviates from the groove center position. There is a risk of welding defects.

[Purpose of the Invention] An object of the present invention is to provide a method for welding the outer surface of a welded pipe, which makes it possible to accurately determine the groove center position over the entire length of the seam and to perform welding with high precision.

[Structure of the Invention] In order to achieve the above object, the method for welding the outer surface of a welded pipe according to the present invention classifies the groove shape of the seam part of the welded pipe into a plurality of reference shapes in advance, and In addition to determining the standard slope value of the point, the actual groove shape of the seam of the welded pipe to be actually welded is imaged, the imaged groove shape is converted into coordinates, and the 8 of the coordinated groove shape is By determining the #4 value of the minute section and comparing this inclination value with the reference inclination value of each of the reference shapes, the position of the groove tip point of the groove shape is determined,
The groove center position is determined from the positions of the left and right groove tip points of the groove shape, and the welding position by the welding torch is controlled based on the groove center position.

C Detailed Description of the Invention] FIG. 1 is a perspective view showing an example of a welding apparatus used for carrying out the present invention, in which 11 is a welded pipe as a material to be welded, 12
is a light source, 13 is a slit light projected from the light source 12, 1
4 is a groove shape image obtained by the slit light 13; 15 is an imager for capturing the groove shape image 14; 16 is a field of view of the imager 15;
Reference numeral 17 designates a memory for storing the groove shape image 14 captured by the image pickup device 15, 18 a calculation device which will be described in detail later, 19 a servo mechanism section, and 20 a welding torch.

Here, the groove shape of the sutured portion of the welded pipe 11 to which the temporary bead is applied can be classified into four types of standard shapes A to D shown in FIGS. 2(A) to 2(D).

The reference shape A is a normal groove shape, and the slope of the groove tip point during the groove processing remains as it is. In the reference shape B, the slope of the groove tip point has changed to a larger value than the slope at the time of groove processing due to rework welding. In the reference shape C, the slope of the groove point has changed to a smaller value due to rework welding. The standard shape is such that the tack bead protrudes from the groove. That is, the arithmetic device 18 predetermines the four types of reference shapes A-D, and calculates the slope values αA to αD of the opening points of these reference shapes A-D.
has been established. Note that the slope of the reference shape AC is negative, the slope of the reference shape is positive, and there is a relationship αB>αA>αC.

FIG. 3 shows a left-right asymmetrical groove shape, and this groove shape is formed by a combination of the reference shapes A-D.

FIG. 4 is a flowchart showing the control procedure of the present invention, and FIG. 5 is a flowchart showing the calculation procedure of the calculation device 18.

That is, in the practice of the present invention, the slit beam 13 is projected vertically from the light source 12 toward the groove of the sutured portion of the welded pipe 11 and substantially perpendicular to the longitudinal direction of the groove. The tip shape image 14 is captured by an image pickup device 15 arranged at a certain angle (for example, 60 degrees) and a distance from the slit light 13, and as shown in FIG. The image is captured within the screen 21 as an image 14A. The image 14A on the image screen 21 is transmitted to the arithmetic unit 18 via the memory 17.

The arithmetic unit 18 coordinates the image 14A in a coordinate system having an origin at an appropriate position within the image screen 21, that is, captures the image 14A in a state in which it is binarized into XY coordinates as shown in FIG. In the figure, al, bl are the left and right end points of the groove shape, a2. b2 is the left and right starting point of the image 14A.

The arithmetic unit 18 first determines one of the bevel points a1 based on the binarized image.

Therefore, the calculation device 18 first calculates the slope (fiS(xi)) of each minute section DELTA in the X direction starting from one starting point a2 of the binarized image using the following equation (1).

S (xi) = [Y (xi + DELTA)
−Y (xi)]/DELTA (1) Here, Y (xi) is the Y coordinate corresponding to the xi coordinate.

Next, the calculation device 18 calculates the slope value S (xi
), the shape of the minute section becomes the reference shape A-
It is determined whether the shape corresponds to either C or the reference shape. That is,
If S (xi) is negative, it is determined that the groove shape corresponds to one of the standard shapes A to C, and if S (xi) is positive, it is determined that the groove shape corresponds to the standard shape.

For a minute section whose groove shape is determined to correspond to one of standard shapes A to C, the shape corresponds to standard shape B or standard shape A. It is sequentially determined whether the shape corresponds to the reference shape C or the reference shape C, and the position of the opening point a1 is determined.

First, the arithmetic unit 18 compares S (xi) with the reference slope value αB, and when the condition of l S (Xi) l≧aB−=(2) is satisfied, the arithmetic unit 18 determines that the shape corresponds to the reference shape B. At the same time, the xi is detected as one of the groove tip points a1 of the groove shape, and the edge points a1 are stored.

When the arithmetic unit 18 satisfies the condition of the above equation (2),
Compare S (xi) with the reference slope value αA.

When the condition of I S (Xi) I ≧aA=(3) is satisfied, the shape is determined to be equivalent to the reference shape A, and at the same time, the xi is set as the groove tip point a of one of the groove shapes.
1, and the end point a1 is stored.

When the arithmetic unit 18 does not satisfy the condition of the above equation (3),
S (xi) is compared with the reference slope value αC, and when the condition of I S (xi) I ≧ac-(4) is satisfied, the shape is determined to be equivalent to the reference shape C, and at the same time xi is one groove tip point a of the groove shape
1, and the end point al is stored.

In addition, the calculation device 18 calculates, for a minute section whose groove shape is determined to correspond to the reference shape as described above,
S (xi) is compared with the reference slope value αD, and when the condition of I S (Xi) I≧a D ”-・- (5) is satisfied, XI is determined as one of the groove edges of the groove shape. It is detected as point a1, and the end point al is stored.

When the detection of one end point a1 of the groove shape is completed in this way, the calculation device 18 detects the other end point b1. That is, the calculation device 18 calculates the slope value of each minute section starting from the other starting point b2 of the binarized image in the same way as detecting the one end point a1, and calculates the sign of the calculated slope value and the reference slope values αA to αD. The other end point b1 is detected by comparison with .

When the calculation device 18 completes the detection of both end points a1 and bl of the groove shape, the calculation device 18 determines their average value [al+bl]/2 as the groove center position. The arithmetic device 18 further outputs a control signal to the servo mechanism section 19 to make the difference between the current torch position and the groove center position zero based on the groove center position information. and controls the welding position by the welding device 20.

Note that even if the groove shape is asymmetrical as shown in FIG. 3, the left and right shapes and their groove tip points a1 and bl can be determined independently, and their edge points a1
, bl can be used to determine the groove center position based on the end points a1 and bl, such as by determining the average value [a1+b 11 /2].

Figures 8 (A) and (B) show the groove center position determined by applying the present invention to samples A and B, which have two or more types of groove shapes in the sutured portion, and the actual groove shape. FIG. 3 is a diagram showing the difference from the center position. According to FIG. 8 (A>, (B)), the groove center position of the welded material with different groove shapes is ±0.5 mm.
It is recognized that it can be detected with high accuracy. Therefore, according to the present invention, it is possible to obtain a welded part of stable quality without defects such as off-seams.

[Effects of the Invention] As described above, the method for welding the outer surface of a welded pipe according to the present invention has the following effects:
The groove shape of the seam of the welded pipe is classified in advance into multiple reference shapes, and the reference slope value of the groove tip point of each reference shape is determined, and the actual groove shape of the seam of the welded pipe to be actually welded is determined. By imaging the imaged groove shape, converting the imaged groove shape into coordinates, determining the slope value of each minute section of the coordinated groove shape, and comparing this slope value with the reference slope value of each of the reference shapes. , find the position of the groove point of the groove shape, find the groove center position from the positions of the left and right groove points of the groove shape, and control the welding position by the welding torch based on the groove center position. This is how it was done. Therefore, it is possible to accurately determine the groove center position over the entire length of the seam, perform welding with high precision, and obtain a high-quality weld.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a welding device used in carrying out the present invention, Figs. 2 (A) to (D) are schematic diagrams showing each of the reference groove shapes classified into a plurality of types, and Fig. 3 4 is a flowchart showing the control procedure of the present invention, 5 is a flowchart showing the calculation procedure of the arithmetic device, and fJIB is a schematic diagram showing the image captured by the imaging device. , Fig. 7 is a schematic diagram showing the groove shape converted into coordinates, and Fig. 8 (A
), CB) are diagrams showing the detection results of the groove center position according to the present invention. DESCRIPTION OF SYMBOLS 11... Welding pipe, 15... Image pickup device, 18... Arithmetic device, 19... Servo mechanism part, 20... Welding torch. Agent Patent Attorney Osamu Shiokawa■

Claims (1)

[Claims] (1) The groove shape of the seam of the welded pipe is classified in advance into multiple reference shapes, and the reference slope value of the groove tip point of each reference shape is determined. Image the groove shape, convert the imaged groove shape into coordinates, determine the slope value of each minute section of the coordinated groove shape, and compare this slope value with the reference slope value of each of the reference shapes. By doing so, the position of the groove point of the groove shape is determined, the groove center position is determined from the positions of the left and right groove points of the groove shape, and the welding position by the welding torch is determined based on the groove center position. Control the external welding method of welded pipes.