JPS608143B2 - Welding heat input control method in ERW pipe manufacturing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling welding heat input to within an appropriate range based on bead shape detection results obtained by optical cutting in the manufacture of electric resistance welded pipes.

In the production of lightning pipes, it is necessary to maintain welding heat input within an appropriate range in order to obtain good weld quality.

Conventionally, in the manufacture of open-seam pipes, the welding temperature near the welding point was measured, and based on the measurement results, the voltage of the high-frequency oscillator for electric resistance welding was controlled to maintain the welding heat input within an appropriate predetermined tolerance range. A welding heat input control method is known.

However, this method of controlling the heat input of lacquer bushes has the following problems.

In other words, in order to accurately measure the welding temperature, the neck is placed near the welding point. It is used as a localization layer. For this reason, as the heat input after melting increases, high temperature molten steel is discharged to the bead portion, and the tendency to measure the temperature of molten steel becomes stronger, and the measured value becomes saturated. Therefore, although proper heat input control can be performed in a low heat input range, accurate heat input control cannot be performed in a high heat input range. It becomes difficult to prevent welding defects (venerators) due to oxide inclusions that occur in high heat input castles with excessive heat input. Therefore, the present inventors conducted research to determine the above-mentioned problems in the conventional welding heat input control method, and as a result, the following findings were obtained.

■ The relationship between welding heat input and welding temperature is as shown in Figure 1 A, which shows an example.
(Common to 2, E, and He), the predetermined allowable heat input range (range between the two lines a and b in the figure) in which proper welding can be performed is close to the saturation region of the welding temperature, and the welding temperature is The temperature changes very little.

Therefore, appropriate heat input control is difficult depending on the welding temperature measurement results. ■(ee) The amount of overhang at the bead tip (definition will be described later) and the heat input in the weld bead in the cross-sectional shape measurement results of the weld bead before bead cutting obtained by the optical sectioning method described later are shown in Figure 1. As shown in Figure 2, there is a relationship in which the amount of overhang increases in response to an increase in heat input in a high heat input region (Fig. 2A shows an example of a bead shape with an overhang.

{o' The curvature of the bead tip (definition will be described later) by the same optical cutting method and the welding heat input are defined as the increase in heat input centered on the appropriate heat input area, as shown in Fig. There is a relationship in which the curvature 1/p correspondingly decreases (an example of the bead shape when heat input is appropriate is shown in Figure 2). However, as shown in Figure 1-2, the amount of dent at the bead tip (definition will be described later) due to the same light cutting method and the welding heat input are the amount of dent as the heat input increases in the region of insufficient heat input. (An example of the bead shape when there is insufficient heat input is shown in Figure 2 C. (to be described later) and welding heat input have a relationship in which the amount of variation in height increases in response to an increase in heat input centering on a region where the heat input is appropriate, as shown in FIG. 1E.

N Amount of variation in the circumferential width of the lower end of the weld bead (hereinafter referred to as "lower end width") by the same optical cutting method (definition will be given later)
As shown in FIG. 1, there is a relationship between the welding heat input and the welding heat input such that the lower end width increases as the heat input increases in the high heat input region. ■ Therefore, the amount of variation in the height of the weld bead before bead cutting, the amount of variation in the width of the lower end, the amount of concavity at the tip, and the amount of curvature of the weld bead before bead cutting, which change in response to increases and decreases in welding heat input, are obtained using the optical cutting method. , and at least 1 of the overhang amount
By controlling the voltage of the high-frequency oscillator that determines the welding heat input based on the two detection results, it is possible to shape the tip of the bead, for example, with a predetermined curvature or a predetermined amount of overhang. It is possible to manufacture thunder welded tubes while maintaining welding heat input within an appropriate range without measuring temperature.

This invention was made based on the above-mentioned findings from ■ to ■, and the amount of variation in height, the amount of variation in lower end width, and the amount of variation in the tip of a weld bead before bead cutting obtained by optical cutting method. Based on the detection result of at least one of the amount of dent, the curvature of the tip, and the amount of overhang of the tip, the voltage of the high-frequency oscillator for open seam welding that determines the welding heat input is controlled to keep the welding heat input within an appropriate range. This method is particularly featured as a method for controlling welding heat input in the manufacture of open seam pipes.

The present invention will be explained below by way of examples with reference to the drawings.

FIG. 3 is an explanatory diagram of a welding heat input control device for welded steel pipes for implementing the present invention.

As shown in the figure, a plate material 1 is formed into a tubular shape, high frequency power from a high frequency oscillator 2 is supplied to the plate material 1 through a contact tip 2a to heat the side edge of the plate material 1, and the plate material 1 is rolled by a squeeze roll (not shown). The raw pipe 1' obtained by welding the butt portions under pressure advances in the direction of arrow a, and while the bead 3 at the top is maintained at a predetermined temperature, it is cut with a cutter (not shown). be dropped. A single-wavelength slit light 5 is irradiated from a cylindrical lens 4 provided directly above the raw tube 1' to the pea 3 and its surrounding area (welded part) of the raw tube 1' immediately after welding. 6
It is a ladder light generating device/layer, from which, for example, 4416
The He-Cd laser beam of wavelength A is transmitted to the optical fiber 7.
A cylindrical lens 41 is supplied through the cylindrical lens 41 to form a slit light 5, which is e.g.
The beam is irradiated obliquely at an angle of 0o and along the circumference of the pipe onto the welded part of the raw pipe 1'.

In this way, the light cutting profile 3' (reflected light from) corresponding to the cross-sectional shape of the welded part generated by the irradiation of the single-wavelength slit light 5 on the welded part of the Thai tube 1' is generated in the welded part 1'. In addition, it passes through a narrow-band interference filter 8 whose center band passes through the wavelength of the slit light 5, and the influence of ambient light and incandescent light generated from the bead 3 immediately after welding is removed, and the image is received by an ITV camera 9. The optical cutting profile reception signal from the ITV camera 9 is sent to the frame memory 10, where an image (shape) corresponding to the profile is stored.
Data is stored. Frame ends with blind QI.
An example of a received signal (image) of a photocutting profile of a bead with an overhang is shown in FIG. As shown in Figure 2A, when both sides of the bead tip sag, these sagging bead parts block the slit light irradiated from above, resulting in a discontinuous profile as shown in Figure 4. is formed. Reference numeral 11 denotes a sampling line selection signal for time-sequentially generating the required number of vertical scanning signals and horizontal scanning signals for sampling the image data stored in the frame memory 1 in sampling coordinates consisting of orthogonal X and Y axes. The generating circuit 12 is a maximum brightness that detects the maximum brightness on the vertical or horizontal scanning signal in the sampling coordinates of the image (shape) data in frame memory 0 sampled by the vertical or horizontal scanning signal for each scanning signal. A detection circuit 13 determines the coordinate on the vertical or horizontal scanning signal (Y coordinate in the case of a vertical scanning signal, X coordinate in the case of a horizontal scanning signal) that gives the maximum luminance based on the detection output from the maximum luminance detection circuit 12. ) for each scanning signal one-dimensionally, 14 is a one-dimensional memory 13
A shape index calculator 15 calculates the bead shape, that is, the amount of variation in height, the amount of variation in lower end width, the amount of depression, the amount of overhang, and the curvature based on the stored data. Based on the output of the high frequency oscillator 2, the AVR of the high frequency oscillator 2
(Automatic voltage regulator) This is an arithmetic unit that controls the voltage of 16.

17 is a CRT for monitoring images of the ITV camera 9 and frame memory 10;

FIG. 5 shows a flowchart of an example of processing of a light-cut profile image reception signal performed by such a configuration.

That is, as an example, the frame memory 1 shown in FIG.
The image (shape) signal stored as 0 is a vertical scanning signal from the sampling line selection signal generation circuit 11 (in FIG. 6A, one signal xs of the required number of signals sequentially generated along the X axis The maximum brightness detection circuit 12 detects the coordinate on the Y axis that gives the maximum brightness for each (see Figure 6 (b); the coordinate corresponding to xs is ys), and this detection result is
Based on the memory data obtained in this way, the shape index calculator 14 detects the presence or absence of a dent at the tip of the bead, and if there is a dent, the calculation is performed. A detected value corresponding to the amount of dent in the container 15 is output. As shown in FIG. 4, if there is no dent, sampling is performed based on x* which gives the coordinates P*(x*, y*) of the highest point obtained by the shape index calculator 14 by sampling the vertical scanning signal. inputting a horizontal scanning signal from the line selection signal generation circuit 11 to the frame memory 10;
The image signal described herein is scanned, and for each horizontal scanning signal, the bright part of the image, which is binarized based on the received level of reflected light from the light cutting profile in the image signal, is detected by the maximum brightness detection circuit 12 of x*. If there is an overhang, at least one of the horizontal scanning signals cannot detect a bright area (image signal), so the shape index calculator 14 detects that there is an overhang. The amount of overhang is calculated as described later in
A detected value corresponding to this is output to the calculator 15. When there is no overhang, that is, when each horizontal scanning signal detects a head, the shape index calculator 14 calculates the curvature of the bead tip from the data from the one-dimensional memory 13 based on the vertical scanning signal as described later. Calculate this and use the calculator 15
Output to. Next, an example of a specific method for calculating the recess, overhang, and curvature of the bead tip will be described.

A Calculation of concavity■ Figure 7 shows the image (shape) in the frame memory 10.
As shown in the diagram showing an example of the signal, as the vertical scanning signal line is moved to the right from xo to xN, the y coordinate increases,
After passing through the maximum y coordinate (ya), the y coordinate decreases, passing through the minimum y coordinate (yb), the y coordinate increases again, and the increase reaches the maximum y coordinate (yc, but smaller than secretion). , and decreases again to end the scan.

■ Therefore, if there are two peaks (monme, yc) with at least one dip (yb) in between as the vertical scanning signal moves to the right, it is determined that there is a depression, and ya, yb, yc Based on , the amount of depression y is calculated using the following formula.

y=k {max(monme, yc)-yb} (k: constant) or ynik {1/2 (snake ten yc) one yb} ■ Also, x.

As the vertical scanning signal is shifted to the right until xN, the y-coordinate increases, passes the maximum y-coordinate, and then decreases until xN without increasing again, it is determined that there is no dent. In this case, the bead highest point P*(x*,y*)
The coordinates of are detected and stored. B Overhang calculation ■ As shown in Figure 8, x
Divide the image into two by =x* and set the overhang (amount) on the left O
L, detect and calculate the right overhang (amount) OR.

Although only OL will be described here, OR can be performed in the same way. ■ Along the horizontal scanning signal $, x.

It is detected whether there is a binarized bright point between mix x mix x*.・SF Kusa Usui Ura Hiragaki , S: Detected value This makes y.

When scanning from to yN, if there is an overhang, ls = 1 will be divided into two as shown in Figure 9 (if there is no overhang, ls = 1 will continue from y to y*) . At this time, OL is calculated using the following equation. OL
:teaNiteza'If there is no hang) (If there is an overhang) k: Constant (same constant as the concavity calculation) ■ Calculate OR in the same way.

■Finally, the overhang amount of 0 is calculated using the following equation.

0=max(OL,OR) or 0=1/2(OL+O
R〉C Curvature calculation ■ Bead highest point P* (x*, y
The area including the coordinates of *) is scanned at equal intervals using a vertical scanning signal.

■ As shown in Figure 10, the three adjacent coordinates obtained in this way are (xn-,, y-river,), (xn, yn)
, (xn+, yn+,), the curvature 1/p is approximated and calculated using the following formula.

k,, k2: constant (k2 is the same constant as k in the concavity calculation)
The curvature 1/p is obtained as the average value of a plurality of pn.

As described above, the amount of concavity, amount of overhang, and curvature of the bead tip are calculated, and the calculator 15 calculates
Based on these calculation results, for example, if a dent is detected, the calculation is performed according to the amount of the dent, and if an overhang is detected, the calculation is performed according to the amount of overhang (and the curvature if necessary). If no depression or overhang is detected, the AVR 16 is controlled according to the curvature, and the bead tip shape becomes a predetermined curvature or overhang amount, that is, appropriate heat input for lacquer twill. Therefore, good weld quality can be obtained. In addition, in the shape index calculator 14, the above-mentioned dents, overhangs,
In parallel with the calculation of the curvature, or independently as necessary, the amount of variation in the height and/or the amount of variation in the lower end width of the weld bead is calculated.

An example of the flowchart is shown in FIG. The amount of variation in the height of the weld bead is calculated as follows. That is,
In the frame memory 10, as shown in FIG.
The y-coordinate yh sampled by a specific vertical scanning signal xh corresponding to the vicinity of the circumferential center of the weld bead is
The shape index calculator 14 detects the data in time series via the one-dimensional memory 13. An example of the detection results is shown in FIG. 12. Then, the 12th
As shown in the figure, the width between the two upper and lower envelope lines (indicated by two-dot chain lines in the figure) of the time-series detection curve, that is, the amount of variation WH in the height of the weld bead is detected. Further, the variation amount WB of the lower end width of the weld bead is calculated as follows. That is, the shape index calculator 14 calculates the difference between adjacent stored data in the one-dimensional memory 13 based on the following formula (see FIG. 6A). △M=yi 10,1 yi (13i min N-1) Based on the data obtained in this way, the shape index calculator 1
4, the coordinates of both lower ends of the bead (xL, yL), (x
R, yR) (see FIG. 6A) is calculated based on the following formula.

△yshi>△y* △yyu<△y* (1 Mikumi L-1) △yR-. <1△y* △Mm>-△y*(Rmim3N-1) (However, △y*' is an appropriate constant) As a result, the shape index calculator 14 further calculates the lower end middle B of the bead. , B=kノ(xL-xR)20(yL
-yR)2 (k: constant).

The shape index calculator 14 detects B obtained in this manner in time series. Then, the shape index calculator 14 detects the amount of variation in the lower end width of the weld bead in the same manner as the detection of the amount of variation in height. In this way, the amount of variation WH in the height of the weld bead and the amount of variation W8 in the lower end width are determined, and based on these calculation results, the AVR 16 is controlled by the calculator 15 so as to provide an appropriate welding heat input. Ru. As explained above, in this invention, the temperature of the weld zone, which is difficult to accurately measure due to the welding heat input, can be measured extremely accurately by applying the measurement results of the bead shape. Welding heat input can be controlled to fall within an appropriate range.

[Brief explanation of drawings]

Figure 1A is a diagram showing the relationship between welding heat input and welding temperature.
Figure 1 shows the relationship between welding heat input and overhang amount, Figure 1 C shows the relationship between welding heat input and curvature, and Figure 1 2 shows the relationship between welding heat input and dent amount. Figure 1 (e) is a diagram showing the relationship between welding heat input and height variation, Figure 1 is a diagram showing the relationship between welding heat input and lower end width variation, and Figure 2 (a) is Diagram 2 showing an example of a bead shape with an overhang.
The figure shows an example of the bead shape when heat input is good,
Fig. 2' is a diagram showing an example of a bead shape when heat input is insufficient, Fig. 3 is an explanatory diagram of a welding heat input control device for a lock-stitch welded steel pipe for carrying out the present invention, and Fig. 4 is a diagram showing an example of a bead shape when heat input is insufficient. Figure 5 is a diagram showing an example of a received signal of a light-cut profile of a bead with a hang; Figure 5 is a flowchart of an example of processing of a light-cut profile received signal; Figure 6A is a diagram of a received signal of a bead's light-cut profile; Figure 6 shows an example of the detection mode by the maximum brightness detection circuit; Figure 7 shows an example of the detection mode by the maximum brightness detection circuit;
8 and 10 are images in the frame memory (
FIG. 9 is a diagram showing an example of an overhang detection signal, FIG. 11 is a diagram showing another example of a flowchart of an example of processing of a light cut profile image reception signal, and FIG. It is a figure which shows an example of the detection result of the fluctuation|variation amount of the height of a weld bead. In the drawings, 1'... element tube, 2... high frequency oscillator, 3... bead, 5... slit light, 9... ITV camera, 10...
Frame memory, 14... Shape index calculator, 15...
- Arithmetic unit, 16...AVR. Matsuri' Zuhatsu Figure 2 Figure 3 Figure 4. Figure 5 Figure 6 Ax A Figure 8 Figure 9 Figure 9

Claims (1)

[Claims] 1. At least one of the following: amount of variation in height, amount of variation in lower end width, amount of dent in the tip, curvature of the tip, and amount of overhang at the tip of the weld bead before bead cutting, obtained by the optical cutting method A method for controlling welding heat input in ERW pipe manufacturing, characterized by controlling the voltage of a high-frequency oscillator for ERW welding, which determines welding heat input, based on two detection results, to keep the welding heat input within an appropriate range. .