JP2515460B2 - ERW welded pipe manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electric resistance welded pipe in which a metal strip is continuously roll-formed and welded, and more particularly to a method for measuring a butt shape of a welded pipe seam converged portion.

[0002]

2. Description of the Related Art In recent years, along with the development of forming and welding techniques, various electric resistance welded pipes such as carbon steel pipes, stainless steel pipes, Ti pipes, superalloy pipes, etc. have been manufactured. , Pipes, structural pipes and so on. The 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 butt shape of the seam convergence portion, particularly the butt angles of both edge surfaces have a great influence on the welding quality. For example, if there is a bad butt angle, the power supply distance between the inner and outer surfaces of the pipe changes, causing an abnormal heating pattern, which also has a significant adverse effect on squeezeout of oxides, unwelding, cold welding, and welding defects called penetrators. Cause of. Therefore, it is not important for quality control of the electric resistance welded part to measure the butt shape of the seam converged portion with high accuracy and set / control the forming conditions.

In the conventional butt-shape measurement in electric resistance welding, test welding is performed before main welding, a welding bite sample 18 is sampled as shown in FIG. A method of qualitatively classifying the butt shapes from the heating pattern 20 on the fracture surface -A ', such as I-type, V-type, and inverted V-type as shown in FIG.

[0005]

However, in order to set an I-shaped butt shape having good welding quality by this method, a long stop time is required because roll adjustment and butt shape inspection must be repeated. There was a big problem that it impaired sexuality. Moreover, the setting accuracy was low. Therefore, there is a strong demand for the development of a new measurement method and a control method therefor capable of highly accurate and highly efficient butt shape measurement.

The present invention has been made to eliminate such drawbacks of the conventional method, and it is possible to detect the butt shape of the seam convergent portion with high accuracy and high efficiency, and to control the butt shape during welding. The purpose is to prevent the occurrence of welding defects and improve the productivity.

[0007]

Means and Actions for Solving the Problems The inventors of the present invention conducted a variety of experiments using a video camera and an image analysis device and studied a method for measuring the butt shape of the seam convergent portion. A pair of image pickup devices are installed on the inner and outer surfaces of the pipe so as to face the seam convergent position of the pipe, and the image pickup device images the pipe outer surface side seam converging portion and the pipe inner surface side seam converging portion, and synchronizes the outer surface side and the inner surface side. The images are alternately analyzed to find the coordinates of the seam convergence points on the inner and outer surfaces of the pipe, and the difference between the seam convergence point on the outer surface of the pipe and the seam convergence point on the inner surface of the pipe is calculated to find the butt shape. It has been found that can be detected with high accuracy and high efficiency. Furthermore, the difference between this calculation result and the preset target value is calculated,
It was found that the butt shape can be controlled with high accuracy by converting this into a control signal and adjusting the amount of reduction of the head roll or the like.

Hereinafter, an example in which the present invention is applied to the production of an electric resistance welded steel pipe will be described in detail with reference to the drawings. In FIG. 1, both edges 1 and 1 of the metal strip converge in a V shape and are heated by the high frequency current supplied from the contact shoes 2 and 2.
After being melted, they are joined at the seam convergence point 3 and pressed by the squeeze rolls 4 and 4 to perform welding. In this electric resistance welded pipe manufacturing facility, the image pickup devices 6 and 6 having a pair of optical lens systems facing the inner and outer surfaces of the roll-formed pipe in the vicinity of the seam convergence portion are arranged, and the seam convergence point 3 is set from the inside and outside surface of the pipe. Include the same field of view so that you can shoot. At this time, the imaging devices 6 and 6 may be moved and tilted in the tube axis direction as long as the field of view includes a seam convergence point. In that case, 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 image capturing devices 6 and 6 having an optical lens system is shown, but a method of transmitting the image by a fiberscope, a reflecting mirror, or the like can also be applied. , Does not impose any particular restrictions.

When the seam converging portion is imaged by the above method,
An image as shown in FIG. 4 is obtained on the two monitors 8, 8. FIG. 4 (a) shows an I-shaped butt, FIG. 4 (b) shows a V-shaped butt, and FIG. 4 (c) shows an inverted V-shaped butt. In both cases, the metal strip edges 1 on the inner and outer surfaces are shown by diagonal lines. , 1 are heated by a high frequency current to have high brightness. The images thus obtained are input from the image pickup devices 6 and 6 of FIG. 1 to the image recording devices 7 and 7 as analog video signals and recorded.
The recorded two series of video signals are video switcher 9
Are alternately input to the image analysis device 10 via.

An analog signal input to the image analysis device 10 is converted into a digital signal by an analog / digital converter (A / D converter) 11 and temporarily stored in the image memory 12. Reference numeral 13 denotes an arithmetic circuit (CPU), which is an image memory 12
The image signal is captured and the image is analyzed by using the brightness difference of the image. The detection of the butt shape by the image analysis device 10 is performed by obtaining the positions of the seam convergence points 3 and 3 on the outer surface of the tube and the inner surface of the tube, and calculating the position difference in the axial direction between the seam convergence points of the outer surface of the tube and the inner surface of the tube. Done. This method will be described in detail with reference to FIG.

In FIG. 5, two straight lines X set on the contact shoe side of the seam convergence point 3 for the image on the outer surface of the tube.
The coordinates a, b, c, d of the intersection of 1, X2 and the edge are detected by the brightness difference, and the coordinates of the intersection of the line segment ac and the line segment bd (seam convergence point 3) are calculated to obtain the seam convergence. The distance A between the squeeze roll centers 21 from the point 3 is calculated. Similarly, for the image on the inner surface of the tube, the coordinates a ', b', c ', d'of the intersections of the straight lines X1, X2 and the edge are similarly detected,
The coordinates of the intersection of the line segment a'c 'and the line segment b'd' (seam convergence point 3 ') are calculated and the distance A'between the seam convergence point 3'and the squeeze roll center 21 is calculated. Next, squeeze roll center 2 from the seam convergence point 3 on the outer surface
The difference A-A 'between the distance A between 1 and the distance A'between the squeeze roll centers 21 from the inner surface seam convergence point 3'is calculated.

As shown in FIG. 6 (a), the match determination is A-
If A ′ = 0, I type butt matching, as shown in FIG.
If A '<0, V-shaped butt, A- as shown in FIG.
If A '> 0, it becomes an inverted V-shaped butt, and the magnitude of this absolute value indicates the strength of the V-shaped butt or the inverted V-shaped butt. The seam convergence point position may be obtained by a method other than the above. Further, the butt determination is performed by comparing the distance between the squeeze roll centers from the seam convergence point on the inner and outer surfaces, but another method may be used as long as the relative position difference of the seam convergence point is known, and there is no particular limitation.

Further, the above calculation result is the comparison circuit 15 of FIG.
Is input to the signal processing device 14 having the above, and is compared and calculated with the target value input from the matching setting circuit 16 in advance. The calculation result is input to the signal converter 17 and converted into a head roll reduction amount control signal to adjust the head roll reduction amount. The butt shape is controlled by adjusting the amount of head roll reduction by the above method.

In the above-mentioned method, the control signal is input to the head roll pressure reduction control system to control the butt shape, but this control signal is input to the seam guide roll pressure reduction control system or edge cutting angle control. The butt shape may be controlled. According to the above method, the butt shape can be measured and controlled with high accuracy and high 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 making conditions. The steel strip used was API standard 5LX-X70 class, and the pipe-making size was 406.4 mmφ × 9.5 mmt. Experiment No. Reference numeral 1 is an example of the present invention, and the butt shape during welding was automatically controlled to be I-shaped by the method of FIG. Experiment No. Reference numeral 2 is a comparative example, and the butt shape was set to I-shape before welding by the conventional method shown in FIG.

Other welding conditions are the same as those in Experiment No. 1, Experiment No.
2 Both Apex angle = 5 °, Pipe forming speed = 25m / min
The welding heat input = 450 kVA and the squeeze amount = 6.5 mm were set as standard conditions, and a pipe having a length of 100 m was manufactured.
Experiment No. A three-plate CCD camera, which is not easily affected by high-frequency noise, was used as the image pickup device No. 1, and an analog optical disk with a high image search speed was used as the recording device. The cycle time for measuring and controlling the butt shape was 2 seconds, and the butt shape was automatically controlled by adjusting the head roll reduction amount.

After welding, 2 mm from the ERW steel pipe to the weld
A total of 100 Charpy test pieces with V notches were produced and tested at + 100 ° C. for 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. The results are shown in Table 2, and it can be seen that the method according to the present invention can significantly reduce the butt adjustment time and has an extremely large effect of preventing welding defects.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the present invention, the butt shape of the seam convergent portion can be measured with high accuracy and high efficiency, and by controlling the butt shape using this measuring technique, electric welding with few welding defects can be performed. Highly efficient production of welded pipes is possible.

[Brief description of drawings]

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

FIG. 2 is a schematic view showing a conventional butt shape detection method.

FIG. 3 is a schematic diagram showing conventional butt shape pattern classification.

FIG. 4 is a schematic diagram showing a monitor image taken by the method of the present invention.

FIG. 5 is a schematic view showing the principle of butt shape detection of the method of the present invention.

FIG. 6 is a schematic diagram showing a method for determining a butt shape according to the method of the present invention.

[Explanation of symbols]

1 outer edge of metal strip 1'inner edge of metal strip 2 contact shoe 3 outer seam convergence point 3'inner seam convergence point 4 squeeze roll 5 head roll 6 imager 7 image recorder 8 monitor 9 video switcher 10 Image analysis device 11 A / D converter 12 Image memory 13 Arithmetic circuit 14 Signal processing device 15 Comparison circuit 16 Butt setting circuit 17 Signal conversion device 18 Welding bite sample 19 Press 20 Heating pattern 21 Squeeze roll center X1, X2 Edge coordinates Auxiliary lines a and b indicating the position to be detected Intersection point between the auxiliary line X1 and both outer surface edges c, d Intersection point between the auxiliary line X2 and both outer surface edges a ', b'Intersection point between the auxiliary line X1 and both inner surface edges c' , D'Intersection point of auxiliary line X2 and both edges on the inner surface side A Squeeze row from seam convergence point on the outer surface side Squeeze roll center distance from the seam converging point of the center distance A 'inner surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Okuda 3434 Shimada, Hitsu-shi, Yamaguchi Pref., Nippon Steel Co., Ltd., Hikari Works, Ltd. Inside the Hikari Steel Works

Claims (1)

(57) [Claims] 1. A method for manufacturing an electric resistance welded pipe in which a metal strip is continuously roll-formed and welded, wherein an image pickup device for taking an image of a seam convergence portion of the roll-formed pipe from inside and outside surfaces of the pipe is provided with a seam convergence portion. Installed opposite to each other, images of the pipe outer surface side seam converging part and the pipe inner surface side seam converging part are taken by the image pickup device, and the images are analyzed to analyze the pipe outer surface side seam convergence point and the pipe inner surface side seam convergence. The coordinates of the points are obtained, the difference between the relative positions in the pipe axis direction of the outer surface side seam convergence point and the inner surface side seam convergence point is calculated, and the difference between the difference in the relative position in the pipe axis direction and the preset target value is calculated. A method of manufacturing an electric resistance welded pipe, which is calculated and controls the butt shape according to the value of the difference.