JPH05104257A - Squeeze quantity measuring and calculating method and control method for resistance welded tube - Google Patents

Abstract

PURPOSE:To continuously measure, calculate and control the squeeze quantity during welding by picture-processing an image of a seam convergence part photographed by an image pickup device, obtaining the distance from a V convergence point to the squeeze roll center and an apex angle and calculating the squeeze quantity. CONSTITUTION:In resistance welded tube manufacturing equipment, the seam convergence part 3 is photographed by the image pickup device 7 using an optical lens 6, etc., from above a seam weld zone. This image is inputted to an image analyzer 9 as an analog picture signal, picture processing is performed by utilizing the luminance difference of a picture and the distance L from the V convergence point to the squeeze roll center and the apex angle theta are calculated. The calculated result is inputted to a signal converter 15 having a comparator 14, compared with the preset squeeze quantity and calculated and converted into a control signal to control the squeeze quantity. This control signal is inputted to a squeeze quantity control system 17 to control the squeeze quantity. Accordingly, the squeeze quantity of the resistance welded tube can be measured, calculated and controlled with high accuracy and high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the squeeze amount of an electric resistance welded pipe continuously rolled and welded from a metal strip and a control method therefor.

[0002]

2. Description of the Related Art In recent years, with the development of forming and welding techniques, various electric resistance welded pipes such as carbon steel pipes, stainless steel pipes, Ti pipes and superalloy pipes have been manufactured. It has come to be used in a wide variety of fields such as pipes and structural pipes. The environmental conditions under which these electric resistance welded pipes are used are becoming more and more severe year by year, and the quality requirements for welded parts tend to be stricter, and the prevention of welding defects has become an important issue.

Generally, in the production of an electric resistance welded pipe in which a metal strip is continuously roll-formed and welded, the amount of squeeze after high frequency heating and melting has a great influence on the occurrence of welding defects, and a welding defect called a penetrator. Control the amount generated. Therefore, it is important for quality control of the electric resistance welded portion to continuously measure the squeeze amount with high accuracy during welding and set and control the squeeze amount within an appropriate condition range.

The conventional setting of the squeeze amount in the electric resistance welding is performed by a method of measuring the difference in the outer peripheral length of the pipe before and after the squeeze roll with a tape measure in a welded state. However, in the squeeze roll, the pipe is subjected to a contraction process like a circumferential drawing, but this drawing amount of the circumferential length does not all act on the squeeze out, but due to the deformation of the base material part other than the vicinity of the abutting part. Is also absorbed. It is difficult to set an appropriate squeeze amount, because the distribution of the amount of reduction of the circumferential length to the vicinity of the abutting part and to the base metal part changes depending on the pipe outer diameter, material strength, etc. In addition, this method cannot monitor the amount of squeeze during welding,
There is also a problem that the measurement takes a long time. As another method for automatically measuring the amount of squeeze (upset), Japanese Patent Laid-Open No. Sho 5
6-4009, JP-A-55-48483, JP-A-52-
Methods such as Japanese Patent No. 153848 have been proposed.

As shown in FIGS. 3 (a) and 3 (b), the method according to Japanese Patent Laid-Open No. 56-4009 discloses a gap G1 between rolls of the final fin pass rolls 18, 18 and squeeze rolls 4, 4. The inter-gap G2 was measured, and the measured values and the roll hole type specifications W ₁ and h of both rolls 18 and 4 were measured.
₁ , (H ₁ = 2 · h ₁ + G ₁ ), W ₂ , h ₂ , (H ₂ =
Based on 2 · h ₂ + G ₂ ), the horizontal and vertical diameters of the pipe before and after the squeeze roll 4 are calculated, and the squeeze amount is obtained from the difference in outer peripheral length before and after the squeeze roll.

The method according to Japanese Patent Laid-Open No. 55-48483 uses a formula for determining the springback amount after measuring the pipe outer peripheral length on the inlet side of the squeeze roll by measuring the lateral diameter and edge width (edge spacing) of the open pipe. The outer peripheral length of the squeeze roll on the outlet side is calculated by measuring the lateral diameter of the welded pipe, and the squeeze amount is obtained from the difference in the outer peripheral lengths of the pipes.

In the method disclosed in Japanese Patent Laid-Open No. 52-153848, the distance x between the welding point and the squeeze roll center and the radius Rb of the valley portion of the squeeze roll in FIG.
.DELTA.Rc is calculated from and the difference between the perimeter Lp of the ellipse p at the welding point position and the perimeter Lq of the circle q at the squeeze roll center position shown in FIG. Calculate the squeeze amount from the difference.

According to these methods, the amount of squeeze can be automatically measured during welding, but the principle of measurement is the same as that for measuring the difference in pipe outer peripheral length before and after squeezing, which is generally performed conventionally. There is a problem that it is difficult to set an appropriate squeeze amount when the pipe outer diameter, material strength, etc. change.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the drawbacks of the conventional method. The seam of an electric resistance welded pipe is obtained by using an image pickup device installed above the seam weld. An image of the converging portion is photographed, the image is image-processed by an image analysis device, the distance L between the squeeze roll centers and the apex angle θ are obtained from the V converging point, and the squeeze amount is calculated to continuously perform the welding. It is an object of the present invention to provide a method for measuring, calculating and controlling the squeeze amount with high accuracy and efficiency.

[0010]

Means and Actions for Solving the Problems The present inventors have obtained the following findings as a result of various experiments using a video camera and an image analysis device. The occurrence of welding defects
As shown in FIG. 5, there is a deep relationship with the metal flow rising angle of the welded portion HAZ. There are many welding defects when the squeeze amount is insufficient when the metal flow rising angle is 50 degrees or less and when the offset occurs when the squeeze amount is 80 degrees or more. Therefore, in order to prevent welding defects, the metal flow rising angle should be 50-
It has been found that it is sufficient to set and control the proper range of 80 degrees.

As shown in FIG. 6, the rising angle of the metal flow is calculated from the distance L from the V convergence point to the squeeze roll center and the apex angle θ, regardless of the outer diameter and strength of the pipe, by the equation SQ _c = 2Ltan θ / 2. There is a correlation with the squeeze amount SQ _c calculated geometrically, and this squeeze amount SQ _c
We found that _c can be controlled with high precision using the index.

The present invention will be described in detail below with reference to the drawings. In FIG. 1, both edges 1, 1 of the metal strip are converged in a V shape and are heated and melted by a high frequency current supplied from the contact shoes 2, 2 and abutted at a seam convergence point 3 to squeeze rolls 4, 4. It is pressurized and welded. In this electric resistance welded pipe manufacturing facility, an image pickup device 7 using an optical lens 6 and the like is arranged so that the seam convergent portion can be photographed from above the seam welded portion. At this time, the optical lens 6
The imaging device 7 may be moved in the axial direction of the tube 5 and the imaging device may be tilted in the axial direction of the tube 5 for imaging. In that case, the angle of the image is corrected. In the case of FIG. 1, an example in which the image of the seam converging portion is directly captured by the optical lens 6 and the imaging device 7 is shown, but a method of transmitting the image by a fiberscope, a reflecting mirror, or the like can also be applied, and is particularly limited. Not something to do. Further, the image pickup device is preferably a CCD (solid-state image pickup device) camera in which high frequency noise is hard to enter, and it is preferable to select a high shutter speed as a photographing condition in order to obtain a still image of the V converging portion. When the seam converging portion is imaged during welding by this method, both edges 1 and 1 of the metal strip are heated by the high frequency current on the monitor 8 of the imaging device, and an image with high brightness on both edges 1 and 1 of the metal strip is obtained.

The image thus obtained is the image pickup device 7 of FIG.
Is input to the image analysis device 9 as an analog video signal. The video signal may be input to the image analysis device 9 after recording on the recording device 10 such as a video deck or a magneto-optical disk recorder. The analog video signal input to the image analysis device 9 is converted into a digital video signal by an analog / digital converter (A / D converter) 11 and temporarily stored in the image memory 12. 13 is an arithmetic circuit (CPU),
The image signal of the image memory 12 is taken in and the image analysis is performed by utilizing the difference in brightness of the image. The image analysis method is as follows. First, straight lines X ₁ -X ₂ and X ₃ -X ₄ set at arbitrary positions as shown in FIG.
The coordinates a, b, c, d of the intersection of
The coordinates of the intersection (V convergence point) are estimated from c and bd, and the squeeze roll center distance L and the apex angle θ are calculated from the V convergence point. Next, using these values, the squeeze amount S
Calculate Q _c = 2 Ltan θ / 2. The distance L between the squeeze roll centers and the apex angle θ from the V convergence point may be detected by a method other than the above, and there is no particular limitation.

Subsequently, the calculation result is input to the signal conversion device 15 having the comparison circuit 14 of FIG. 1, compared with the preset squeeze amount, calculated, and converted into a control signal for controlling the squeeze amount. This control signal is input to the squeeze amount control system 17 to control the squeeze amount. According to the above method, the squeeze amount of the electric resistance welded pipe can be measured and calculated with high accuracy and efficiency.

[0015]

EXAMPLE An electric resistance welded steel pipe was manufactured using the apparatus shown in FIG. Table 1 shows the chemical composition of the steel strip, and Table 2 shows the pipe forming conditions. For metal bands, API standards with different strength levels, 5LX
-X52 and 5LX-X70 are used, and the pipe-making sizes are different in outer diameter, 216.3 mmφ x 9.5 mmt and 406.
There were 2 levels of 4 mmφ × 9.5 mmt. Experiment No. in Table 2 1
4 to 4 are examples of the present invention, the target squeeze amount S by the method of FIG.
It was automatically controlled by setting Q _o to 4.0 mm. Experiment No. 4 to 8 are comparative examples, in which temporary welding was performed before main welding, and the difference in outer peripheral length before and after squeezing was set to 6.7 mm, which was 70% of the plate thickness. For other welding conditions, see Experiment No. Apex angle = 5.
5 to 6.0 °, pipe making speed = 25m / min, welding heat input = 4
Under the standard condition of 50 kVA, a pipe having a length of 60 m under each condition was produced.

Experiment No. The measurement of the squeeze amount of 1 to 4 is a three-plate CCD (solid-state image sensor) with a high-speed shutter that is not easily affected by high frequency noise as the image pickup device 6.
Using a camera, the shooting conditions are shutter speed = 1/100
Recording is performed for 00 seconds at a shooting speed of 30 frames / second, the captured image is recorded on an optical disc, and images at 1-second intervals are input to the image signal processing device 10 in real time, and luminance measurement measures the squeeze roll center from the V convergence point. The distance L and the apex angle θ are calculated, and the squeeze amount SQ _c = 2Ltan θ / 2
Was calculated.

[0017]

[Table 1]

[0018]

[Table 2]

After pipe forming, these electric resistance welded steel pipes are welded at 10 m intervals in the longitudinal direction, from 5 locations at right angles to the pipe axis (C
Direction) Welded portion microscopic sample for microscopic observation for each (total:
5 pieces / condition) were collected and the rising angle of the metal flow was measured. Also, from the same position, C with a 2 mm V notch in the weld
Ten Charpy test pieces in each direction were produced (total: 50 pieces / condition) and tested at + 100 ° C. to cause ductile fracture. Next, the fracture surface of this Charpy test piece was observed with a stereoscopic microscope of 10 to 50 times, and the area ratio of welding defects was measured. As a result, as shown in Table 2 and FIG. 7, the metal flow rising angle and the welding defect area ratio show that the method according to the present invention reduces the standard deviation (σ) of the metal flow rising angle and reduces the welding defects. It turns out that it shows a great effect.

[0020]

According to the present invention, the squeeze amount during welding can be measured with high accuracy and high efficiency, and by setting and controlling the squeeze amount using this measuring technique, the metal flow angle can be kept constant. Can be controlled to an appropriate value, and highly efficient production of ERW pipes with few welding defects becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus arrangement of the method of the present invention.

FIG. 2 is a schematic view showing an image analysis method of the present invention.

FIG. 3 is a schematic diagram showing a conventional squeeze amount measuring method.

FIG. 4 is a schematic view showing a conventional squeeze amount measuring method.

FIG. 5 is a diagram showing a relationship between a metal flow rising angle and a welding defect area ratio.

FIG. 6 is a diagram showing a relationship between an estimated squeeze amount and a metal flow rising angle.

FIG. 7 is a diagram showing measurement results of a metal flow rising angle and a welding defect area ratio in an example.

[Explanation of symbols]

1 Metal Band Edge 2 Contact Shoe 3 Seam Convergence Point 4 Squeeze Roll 5 Tube 6 Optical Lens System 7 Imaging Device 8 Monitor 9 Image Analysis Device 10 Recording Device 11 A / D Converter 12 Image Memory 13 Arithmetic Circuit 14 Comparison Circuit 15 Signal Conversion Device 16 Squeeze amount setting circuit 17 Squeeze amount control system 18 Fin pass roll LV Convergence point to squeeze roll center distance θ Apex angle SQ _c Squeeze amount measured value SQ _o Squeeze amount set value

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Okuda 3434 Shimada, Hikari City, Yamaguchi Prefecture, Nippon Steel Works, Ltd., Hikari Steel Works (72) Inventor, Kuniomi Sakata 3434 Shimada, Hikari City, Yamaguchi Prefecture, Japan (72) Inventor Kiyoshi Matsui 3434 Shimada, Hikari City, Yamaguchi Prefecture Nippon Steel Works, Ltd. Hikari Steel Co., Ltd.

Claims (2)

[Claims] 1. In the production of an electric resistance welded pipe in which a metal strip is continuously roll-formed and welded, an image of a seam converging portion is taken by an imaging device installed above the seam welding portion, and the image is analyzed. Then, the distance L between the V convergence points and the apex angle θ are calculated from the squeeze roll center, and the squeeze amount is calculated by the calculation formula SQ _c = 2Ltan θ / 2. Calculation method. 2. The electric resistance welded pipe manufacturing method, wherein the squeeze amount SQ _c obtained by the method of claim 1 is compared with a preset squeeze amount SQ _o to control the squeeze amount. Control method of squeeze amount.