JPH0332434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for continuously detecting and tracking a weld line after welding a welded steel pipe.

In a welded steel pipe manufacturing line, the welded steel pipes are then subjected to induction heating for seam annealing to correct distortion in the welded portion or to a process for detecting weld defects. In each of these steps, the position of the weld line must be accurately known. If the steel pipe were fed as welded, the weld line would be very easy to identify and there would be no problem, but in reality, steel pipes often twist to the left or right on the feed line, and are pulled. This makes it difficult to automate subsequent processes.

Conventionally, workers have performed visual confirmation, or detection and tracking have been performed using ultrasonic waves, eddy currents, or the like. Furthermore, a method has been proposed in which calculations are performed based on conditions such as the welding process, and the amount of twist is estimated according to the distance from the welding head to the desired position. They were often unsatisfied with aspects such as personnel costs, work efficiency, equipment prices, and accuracy. Therefore, sufficient quality control was not carried out, and this became a bottleneck in the welded steel pipe manufacturing line.

An object of the present invention is to provide a method and apparatus for reliably detecting and tracking a weld line after welding (hereinafter simply referred to as a weld line for simplicity) with a simple configuration.

This object is achieved by a method and a device for detecting and tracking weld lines in welded steel pipes as defined in the claims.

The method and device according to the present invention eliminate the drawbacks of conventional devices and enable highly accurate detection and tracking with a simple configuration. As a result, subsequent steps can be carried out quickly and reliably, which is extremely advantageous in terms of quality control. Further, since fluorescent light is detected, the influence of ambient light can be ignored, and the advantage is that the S/N ratio of the detection signal can be improved.

The invention will now be described in detail with reference to the accompanying drawings, which illustrate examples.

FIG. 1 shows a configuration diagram in which the present invention is applied to a schematically illustrated steel pipe production line. A steel strip 1, which is a material for an electric resistance welded pipe, passes through a slitting and side trimming step A, reaches an entry step B, and then passes through a squeeze roll 2 through a forming step C, which forms the steel strip into a tubular shape. An electric welding machine 3 is disposed upstream of the squeeze roll 2 or in alignment with the squeeze roll. As is well known, the installation position of the electric welding machine 3 differs depending on whether the welding machine is a high frequency type or a low frequency type.

A wire drawing device 4 is disposed a short distance l ₁ downstream from the electric welding machine 3 . This line drawing device 4 is used to draw a fluorescent paint line or a broken line at a position offset by an angle θ (see FIG. 2) toward the valley in the circumferential direction from the weld line located directly above FIG. 1 at the time of welding. This is the device. This line is drawn because the steel moves at a certain speed.
For example, paint may be sprayed continuously. Although the distance l ₁ is relatively large for convenience of illustration, it is possible to reduce errors by making it as small as possible to the extent that it does not hinder work or the arrangement of various devices. In this way, the welded steel pipe P that is electrically welded and sent in the direction of arrow 7 has the following characteristics:
A line made of fluorescent paint is reliably drawn at a position offset from the weld line by an angle θ toward the valley side in the circumferential direction.

At an appropriate position on the downstream side of the welded steel pipe P,
A device 5 for reading the lines of fluorescent paint drawn by the previous process is provided. The reader 5 includes an irradiation source for exciting the fluorescent paint and a fluorescent detector. Therefore, it is equipped with an ultraviolet irradiation device and a filter that selectively passes fluorescent light.
It can be formed using a CCD camera or the like.

This reading device 5 is connected to other process equipment 6 such as an induction heating device for post-annealing or an inspection (flaw detection) device for detecting various welding defects.
It is placed at close range l ₂ of . The magnitude and sign of l ₂ are selected depending on the control method.

For example, if the reading device 5 detects the fluorescent light F at the center as shown in FIG. 3, the weld line will be located at a position offset by an angle θ toward the mountain side in the circumferential direction. Therefore, by moving the device 6 in the circumferential direction as shown by the arrow 8 in accordance with the output indicating the detected position of the reading device 5, it is possible to always perform the inspection or processing process of the weld line in the optimum condition. . In the example in Figure 3, the weld line is δ from the center to the right.
Since the angle δ is very small, the reading device 5 is located at almost the same position as the drawing device 4 in FIG. Needless to say, this can be dealt with by shifting it as shown by arrow 9.

Such control is performed by a control device that receives the output of the reader 5, determines the position on the circumference of the steel pipe of the line that emits fluorescent light, and determines that the weld line is located at an angle θ from that position toward the mountain side in the circumferential direction. It is carried out by. Furthermore, in order to make the device 6 follow the welding line, the position of the angle θ from the position of the line that emits fluorescent light to the circumferential mountain side is used as a reference, and the device 6 is positioned based on the deviation between this reference and the current position of the device 6. Just control it.

In addition, in the present invention, the line is drawn with fluorescent paint and the fluorescent light is detected by generating fluorescent light of an appropriate wavelength, making it possible to read the position of the line without being affected by ambient light. This is because. As a result, the S/N ratio is improved, a clearer output signal can be obtained than in conventional methods using ultrasonic waves or eddy currents, and detection accuracy is significantly improved.

It will be clear that the individual elements for carrying out the method according to the invention, such as the drawing device 4, the reading device 5 and the device for tracking the device 6, can be constructed using conventional techniques.

Although the present invention has been disclosed based on examples showing typical configurations of the present invention, it will be obvious that many modifications and changes can be made within the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the configuration when the present invention is applied to a pipe production line. FIG. 2 is a view taken along the -' arrow in FIG. FIG. 3 is a view taken along the -' arrow in FIG.
The correspondence of main reference numerals in the figure is as follows. 1: Steel strip, 2: Squeeze roll, 3: Electric welding machine, 4: Wire drawing device, 5: Reading device, 6: Device.

Claims (1)

[Claims] 1. A method for detecting and tracking a weld line after welding steel pipes in a welded steel pipe production line, comprising: a predetermined angle θ from the welding position to the valley side in the circumferential direction at close range of a welding machine on the steel pipe production line; drawing a line of fluorescent paint parallel to the weld line after welding at a position, reading the fluorescent paint drawn in the previous process at a desired position downstream of the steel pipe manufacturing line, and processing the read signal to form a circle. The method described above includes the following steps: determining the position of the weld line after welding at the angle θ toward the circumferential mountain side, and generating a corresponding signal. 2. In a device for detecting and tracking the weld line after welding of steel pipes on a welded steel pipe manufacturing line, welding is carried out at a position offset by a predetermined angle θ from the welding position toward the valley side in the circumferential direction at close range of the welding machine on the steel pipe manufacturing line. a line drawing device 4 for drawing a line of fluorescent paint parallel to the subsequent weld line; a reading device 5 for exciting the fluorescent paint and detecting the generated fluorescence at a desired position downstream of the steel pipe production line; , and Receiving the output signal of the reading device 5, calculating the position of the welding line after welding, which is located at the angle θ from the line of the fluorescent paint toward the mountain side in the circumferential direction, and outputting a control output according to the calculated value. and a control device that generates.