JPH03155479A - Welding control method for resistance welded tube - Google Patents

Abstract

PURPOSE:To maintain weld zone quality at a high level by picking up an image of a bead shape of a weld zone cross section to obtain a shape parameter, correction-calculating a target value of the peak temperature or heating width by the shape parameter as a set value and controlling the welding heat gain based on it. CONSTITUTION:A bead shape meter 12 is arranged just after a squeeze roll 4 and an image of a cross-sectional shape of a welding seam part 11 is picked up. A picture signal of the welding seam part 11 whose image is picked up by the bead shape meter 12 is inputted to a picture processing circuit 13 where the bead cross-sectional shape is extracted to obtain the bead shape. A controller 8 correction-culculates the target value of the peak temperature or heating width of the welding seam part 11 by using this shape parameter. This correction value is anew made to the set value of the peak temperature or heating width and an electric current of a power unit 6 is controlled and the welding heat gain to be applied to the seam of an open pipe by a high-frequency induction coil 5 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a welding control method for electric resistance welded pipes that takes into account the butt shape and upset amount.

[Prior Art] For example, conventional electric resistance welded steel pipes are made by continuously forming a thin steel plate into a cylindrical shape using a group of forming rolls (roll forming), and then generating an electric current at the joint of the open pipe using a resistance method or an induction method. It is manufactured continuously by pressurizing and joining the seams with a pair of right and left squeeze rolls.

The quality of the welded part is determined by the amount of current generated at this time or the amount of welding heat input.

Conventionally, welding has been controlled using the peak temperature or heating width of the welded portion as a target value.

FIG. 3 is a conceptual diagram showing such a conventional welding control method. That is, a roll forming section 3 consisting of a group of forming rolls 2 while uncoiling a thin steel plate 1 as a raw material.
Gradually form it into a cylindrical shape. A high frequency induction coil 5 is provided in front of a pair of left and right squeeze rolls 4 arranged to press and join the oven pipe 10a after molding.
A predetermined high-frequency current is passed through the high-frequency induction coil 5 from the power supply 6 to heat the seam of the oven pipe 10a, and the seam is immediately pressed and joined with the squeeze roll 4. Immediately after the squeeze roll 4, a linear array thermometer 7 is arranged in the bead width direction above the weld seam 11 of the ERW steel pipe 10b, and it measures the temperature distribution in the width direction of the weld seam 11 and the heating width in a non-contact manner. It is designed to be measured using a method. Then, the peak temperature or heating width in the measured temperature distribution is detected, the detected value is input to the control device 8, and the detected value is used as the set temperature width given as the target value of the peak temperature in the control device 8. For example 1100℃~1200℃
Or, the width of the part where the temperature distribution near the seam exceeds a predetermined temperature given as a target value for the heating width, for example, 5 degrees for a pipe size of 271° and 3φ, so that it falls within a prescribed target value. The current of the power supply device 6 is feedback-controlled. This controls the amount of welding heat input added to the joint of the open pipe 10a. The weld seam 11 is then removed by a bead cutter (not shown).

[Problem to be solved by the invention] It is well known that the three major factors that determine the welding quality of electric resistance welded pipes are (1) welding heat input, (2) butt shape, and (3) amount of absethe/soot (pressure welding force). Are known. In order to ensure this welding quality, these factors must be controlled in the most suitable state.

The conventional welding control method for electric resistance welded pipes is to detect the peak temperature or heating width of the welded part as described above, and then add the temperature to the seam of the open pipe so that the detected value falls within a preset target value. This was to control the amount of welding heat input.

However, even if the butt shape and upset amount after roll recombination are set to the same outer diameter as the previous one, variations in strength within the same coil or between coils cannot be reproduced due to changes in material or dimensions. This is extremely difficult, and if the butt shape or upset amount changes, there is a possibility that welding quality will deteriorate.

Therefore, an object of the present invention is to provide a welding control method for an electric resistance welded pipe that takes into consideration the butt shape and the amount of upset in order to ensure the quality of the welded portion.

[Means for Solving the Problem] In order to achieve the above object, the welding control method for an ERW pipe according to the present invention detects the peak temperature or heating width of the welded portion of the ERW pipe as described above. , when controlling the amount of welding heat input added to the seam of open pipes so that the detected value of the peak temperature or heating width falls within a predetermined target value, the control further parameterizing the seam shape of the cross section of the welded part. This system images the seam shape of the welded part, processes the obtained image to obtain shape parameters, corrects and calculates the target value of the peak temperature or heating width using the shape parameters, and calculates this correction value. The welding heat input is controlled by setting the value as a new set value.

[Function] The butt shape and upset a, together with the welding heat input, are one of the most important factors that determine the quality of the welded part of the ERW pipe.
The butt shape and amount of upset directly affect the bead shape of the weld. Therefore, first, the bead shape of the cross section of the weld is imaged using an appropriate method, the image is processed to determine the shape parameters, and then the target value of the peak temperature or heating width is corrected and calculated using the shape parameters, and the corrected value is calculated. If we decide to control the welding heat input using the set value again, even if the butt shape and upset amount change slightly due to material exchange, the welding input can be adjusted appropriately according to the butt shape and upset amount a. The amount of heat can be measured to ensure the quality of the welded part. Note that the shape parameters include, for example, the lower bead width, the center bead height, the maximum bead height,
bead cross-sectional area, etc. The target value of the peak temperature or heating width is corrected using one or more of these shape parameters.

[Example] FIG. 1 is a control block diagram to which the method of the present invention is applied,
In the figure, the same reference numerals as in FIG. 3 indicate the same parts.

As shown in FIG. 1, a bead shape meter 12 is placed immediately after the squeeze roll 4 to image the cross-sectional shape of the weld seam portion 11. As the bead shape meter 12, a shape detection device disclosed in, for example, Japanese Patent Publication No. 60-6755 by the present applicant can be used. This method uses a light cutting method, and the slit light of the laser beam is applied to the welding seam.
1 from diagonally above, and the reflected light is imaged by an ITV camera.

The image signal of the weld seam 11 captured by the bead shape meter 12 is input to the image processing circuit 13, where it is processed by a method such as binarization to extract the bead cross-sectional shape and obtain the bead shape 11a. .

FIG. 2 shows an example of the bead shape obtained in this manner. As shown in FIG. 2, the bead shape 11a after upsetting usually has a mountain-like shape with a somewhat concave center, and then from this bead shape 11a, for example, the lower width A of the bead Steel pipe surface 10c
width of the corner rising from the center), central bead height B (from the central concave portion 11b of the bead shape 11a to the steel pipe surface, 10
C), maximum bead height C (bead shape 11H
The height from the maximum top 11c to the surface 10c of the steel pipe), the bead cross-sectional area D (the area of the hatched part in the figure), etc. are determined as shape parameters.

Next, using this shape parameter, for example, the bead cross-sectional area, the control device 8 corrects and calculates a target value for the peak temperature or heating width of the weld seam portion 11.

Then, the current of the power supply device 6 is controlled by using this correction value as a new set value of the peak temperature or heating width, and the amount of welding heat input to be added to the joint of the open pipe by the high frequency induction coil 5 is controlled.

For example, in the case of peak temperature, the correction value is 1100℃~
The target value of 1200°C can be set to a value such as 1100°C to 1150°C that takes into account the butt shape and upset amount.

Therefore, the welding heat input amount is controlled so that the value detected by the seam temperature detector such as a linear array thermometer or the heating width detector 7 falls within the changed target value. In this way, the welding heat input is controlled using the corrected target value based on the shape parameter that takes into account the butt shape and the amount of upset, so even if the butt shape and upset ffi change slightly due to material exchange, the welding part It is possible to maintain high quality.

In the above embodiment, the induction method using the high-frequency induction coil 5 has been described, but the same applies to the resistance method using a contact tip.

[Effects of the Invention] As described above, according to the present invention, in addition to a system that feedback controls the peak temperature or heating width of the welded portion of an ERW pipe, a shape parameter is determined from the cross-sectional shape of the bead, and this shape parameter is used. We installed a control system that corrects the target value of the peak temperature or heating width of the weld zone, and used the correction value as the set value to appropriately control the welding heat input. This makes it possible to control pipe welding, maintains high quality welds even when changing materials, and helps improve productivity.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram applied to the ERW pipe welding control method of the present invention, Fig. 2 is a diagram showing an example of a seam shape in a cross section of a welded part, and Fig. 3 is a control block diagram of the conventional ERW pipe welding control method. It is a control block diagram. 5... High frequency induction coil 6... Power supply device 7... Seam temperature detector or heating width detector 8...
-Control device 10a...Oven pipe 10b...Erw tube 11...Weld seam portion 11a...Bead shape 12...Bead shape meter 13...Image processing circuit

Claims (1)

[Claims] Detecting the peak temperature or heating width of a welded part of an ERW pipe,
In an electric resistance welding pipe welding control method for controlling the amount of welding heat input added to a joint of an open pipe so that the detected value of the peak temperature or heating width falls within a predetermined target value, the bead shape of the cross section of the welded part is The welding heat input amount is controlled by capturing an image, processing the obtained image to obtain a shape parameter, correcting and calculating the target value of the peak temperature or heating width using the shape parameter, and using this correction value as a set value. Features: Welding control method for ERW pipes.