JPH0241399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welding control method for electric resistance welded pipes, and in particular, to prevent welding defects caused by uneven temperature distribution on the welding surface to be butt welded, and to achieve high quality welding. This paper proposes a welding control method for electric resistance welded pipes that enables the production of sewn pipes.

ERW tubes are made by bending a metal band into a cylindrical shape so that both edges thereof face each other, and applying a squeeze roll to both edges while heating and melting them using high-frequency current from a contact chip (or high-frequency induction from a conductive coil). Continuous production is achieved by butt welding the edges together, with lateral pressure applied between the edges. In order to improve the welding quality of ERW pipes manufactured in this way, welding conditions, especially heat input control, are considered extremely important control items, and in the past, skilled workers were responsible for checking the color of the weld, the appearance of the weld bead, etc. etc., and set and adjust various conditions empirically. However, in recent years, automatic control systems have been increasingly attempted in place of the above-mentioned human monitoring method, which is subject to individual differences. One such method is to measure the seam temperature after welding with a non-contact thermometer such as a two-color thermometer or radiation thermometer, and then control the heat input to match this measured value with the target value. There is a way. However, in this method, the temperature to be measured is the seam, but the seam temperature cannot be said to directly represent the welding quality, and the control accuracy is insufficient.

As a result of repeated research to eliminate the above-mentioned drawbacks, the present applicant has found that the temperature measurement target position is not the seam but the edge of the metal strip before welding.
They discovered that welding quality could be more directly represented, and have already filed an application for this technology (Japanese Patent Application No. 154505-1983). However, this method selects the edge of the metal strip, especially the outer circumferential surface of the metal strip near the edge, as the temperature measurement target, but this part is not the part that will be directly butt-welded, and moreover, for example, the edge In reality, there are temperature variations as shown by the isothermal lines in FIG. 1 between the edge and the end surface, which is the part to be directly butt welded. Figure 1 shows the edge end face EF between the sliding contact point A (hereinafter referred to as the power feeding point) between the edge of the open pipe OP and the contact chip CT to the point O where both side edges meet (hereinafter referred to as the welding point V). FIG. 2 is a diagram showing the temperature distribution using isothermal lines. As is clear from Figure 1, the temperature at the edge part of the edge part is higher than the center part of the edge end face EF due to the skin effect of the high frequency current supplied to the edge part, and temperature control only in the vicinity of the edge part is insufficient. It turns out that it is difficult to reliably prevent defects.

The present invention has been made based on this knowledge, and its purpose is to obtain the temperature distribution in the thickness direction at the edge end face of a metal strip to be butt welded, and to detect the lowest temperature among the temperature distributions. By controlling welding conditions such as welding heat input so that when the butt point, that is, the welding V point, is reached at the part showing this lowest temperature, the temperature is higher than the predetermined lower limit temperature to prevent cold defects from occurring. The object of the present invention is to provide a welding control method that makes it possible to manufacture high-quality electric resistance welded pipes with few welding defects.

The welding control method for electric resistance welded pipes according to the present invention heats and melts the opposing end surfaces of an open pipe formed by bending continuously fed metal strips, and then butts and welds the fused end surfaces to form a continuous electric resistance welded pipe. In the manufacturing process,
The temperature distribution in the wall thickness direction of the opposing end surfaces to be butt welded is detected at a position between the power supply part and the welding point V, and if the lowest temperature in the temperature distribution is lower than a predetermined reference value, the lowest temperature The welding conditions are controlled so that the temperature becomes equal to or higher than a predetermined lower limit temperature when the part showing the welding point V reaches the welding point V.

First, the principle of the welding control method for electric resistance welded pipes according to the present invention (hereinafter referred to as the method of the present invention) will be explained below.

When butt welding the edges of an open pipe OP with temperature variations in the thickness direction as shown in Figure 1 on the edge end face using a squeeze roll, in order to prevent cold defects from occurring in the welded part. For example, the temperature of the edge end surface is measured at point B, an intermediate point between A and O, and the temperature pattern in the thickness direction at the measurement point is determined to detect the lowest temperature, and the part showing this lowest temperature is the weld V. When this point is reached, the heat input to the edge, the welding speed, etc. may be controlled so that the temperature is equal to or higher than the lower limit to prevent cold defects from occurring. That is, it is assumed that the temperature distribution in the thickness direction of the edge end face EF measured at point B in FIG. 1 is as shown in FIG. The graph in Figure 2 shows the temperature on the horizontal axis and the position in the thickness direction of the edge end face on the vertical axis.As is clear from this graph, the temperature at the edge near the inner and outer peripheral surfaces is expensive, but
It is shown that the temperature decreases toward the center in the thickness direction, and reaches the lowest temperature t approximately at the center. In this case, the part showing the lowest temperature t is the weld V
When point O is reached, it is sufficient that the temperature is equal to or higher than the lowest temperature that does not cause cold defects. Incidentally, the rise in temperature of a certain portion of the edge end surface during the process from the power supply point A to the measurement point B to the welding point O can generally be expressed as shown in FIG. In the graph of FIG. 3, the horizontal axis shows the position of the lowest temperature of the open pipe OP from the power supply point A to the welding point O, and the vertical axis shows the temperature. The solid line F in the graph shows the temperature increase curve, and the dashed-dotted line shows the lower limit temperature T required at the welding point O to prevent cold defects from occurring. Therefore, as is clear from the graph, the open pipe OP at weld V point O
In order for the temperature _{of the} edge end surface of
Operate the temperature control element in the following cases to weld V point O
It is necessary to control so that the lower limit value T ₀ or more is reached. The temperature rise curve F is usually expressed as F=f(H, V, D) as a function of welding heat input H, welding speed V, and wall thickness D, so the lowest temperature is welding heat input H,
In other words, it can be controlled by changing the current value or the welding speed V.

The specific configuration of the apparatus for carrying out the method of the present invention will be explained below. FIG. 4 is a schematic diagram showing the overall configuration of an apparatus for carrying out the method of the present invention, and FIG. 5 is a block diagram showing the configuration of main parts of the temperature pattern measuring apparatus. It is curved into a cylindrical shape with edges facing each other, and both edges are connected to a contact chip CT (or induction coil).
While sliding in contact with the squeeze roll SR, the heated and melted edges are butt welded together and sent out as an ERW tube R in the direction of the white arrow for the subsequent process. There is. Reference numeral 1 denotes a temperature pattern measuring device which detects the temperature distribution in the thickness direction of one edge end face EF at a suitable position midway between the power feeding point A and the welding point O through an image guide 6, and measures the temperature distribution based on this. Find the lowest temperature and compare it with a preset standard value. If the lowest temperature is lower than the standard value, at least the lower limit value T ₀ is determined when the part showing the lowest temperature reaches the welding V point O. A command signal is issued to the high frequency power supply control circuit 8 so that (not shown) to set and control welding conditions such as setting the motor rotation speed.

Next, the configuration of the temperature pattern measuring device 1 will be explained based on FIG. 5. The objective side terminal of the image guide 6 is from the power feeding point A to the V point O in the open pipe OP.
It is arranged so that at least the entire one-sided edge end face EF in the middle between the two ends can be included in the field of view over the entire surface in the thickness direction. The other end of the image guide 6 faces the lens 7, and is connected to the imaging devices 11, 12,
Reference numeral 13 is configured to image the field of view of the portion of the image guide 6 facing the objective side end via this lens 7.

The imaging device 11 has its optical axis aligned with the lens 7, and between the two, a half mirror 20 and an optical filter 21 are arranged in this order from the lens 7 side to the optical axis.
They are arranged at a 45° angle. A part of the light that passes through the image guide 6 and passes through the lens 7 is reflected by the half mirror 20 and is further reflected by the plane boundary 23 arranged parallel to the reflection surface, and the optical axis of the light is directed to the light from the imaging device 11. Imaging device 13 parallel to the axis
It is designed to reach. The light transmitted through the half mirror 20 reaches the optical filter 21, which is an interference filter whose transmission wavelength component has a peak wavelength of λ ₁ , and the light transmitted through this reaches the imaging device 11 and passes through the optical filter 21. The light that is not transmitted is reflected by the incident surface, and an optical filter 22 is disposed in parallel to the optical filter 21 in the reflected optical path. The optical filter 22 is an interference filter whose reflection wavelength component has a peak wavelength of λ ₂ (λ ₁ <λ ₂ ), and the light reflected by it is transmitted to the imaging device 11,
13 optical axes and an imaging device 12 whose optical axes are parallel to each other.
It is designed to reach.

The imaging device 13 is provided to capture the shape of the welded surface of the open pipe OP, and is a normal color or monochrome television camera using a vidicon or the like as an imaging tube. On the other hand, the imaging devices 11 and 12 are provided to obtain information for performing a two-color temperature calculation as described later, and use photoelectric conversion elements such as image disectors capable of random scanning.

As described above, each of the imaging devices 11, 12, and 13 captures light of different wavelength components incident through different optical paths, but the imaging fields of view are adjusted in advance so that they are all the same. .

Now, the imaging devices 11 and 12 each consist of camera head sections 110 and 120 and their control units 111 and 121, for example, Hamamatsu Television Co., Ltd.
A random access camera C1181 made by Manufacturer Co., Ltd. is used.
The control units 111 and 121 are connected to a common arithmetic unit 3.

The arithmetic device 3 generates an X deflection signal for scanning in the X direction (horizontal direction) and a Y deflection signal for scanning in the Y direction (vertical direction), and provides the scanning signal generating section 31 to the camera control unit; Signal processing unit 32 that receives video signals VD1 and VD2 generated by control units 111 and 121, respectively
It consists of.

Video signals VD1 and VD2 are adjusted so that both imaging devices have the same field of view, and a common
Since the deflection signal and Y deflection signal are given,
This is an electrical conversion signal corresponding to the energy of light emitted from the same position in the imaging field whose main components are wavelengths λ ₁ and λ ₂ , respectively.

Such video signals VD1 and VD2 are passed through the integrator 3
The integral values are input to 201 and 3202, and each integral value is input to the A/D for each main scan in the X direction or Y direction.
(analog/digital) converter 321, and 3
22, the data is converted into digital data and taken into the arithmetic unit 323. The calculation unit 323 performs the following two-color temperature calculation based on the data taken in from the A/D converters 321 and 322. That is, the level of the video signals VD1 and VD2 at a certain point in time is determined by the edge end surface EF position (X,
The data ε ₁ corresponds to the values of radiant energy corresponding to the wavelengths λ ₁ and λ ₂ of Y), and are obtained by A/D conversion.
(X, Y) and ε ₂ (X, Y) have values corresponding to the above-mentioned radiant energy. Therefore, by performing a two-color temperature calculation using this data, the temperature T(X, Y) [°K] at the position (X, Y) can be obtained. That is, the energy ratio of both and the temperature T
(X, Y) can be practically linearly approximated if the wavelengths λ ₁ and λ ₂ are appropriately selected.
3, the following two color temperature calculation formulas (1) are executed sequentially.

T(X, Y)=αε ₁ (X, Y)/ε ₂ (X, Y)+
β...(1) However, α and β are constants determined by λ ₁ and λ _2. The values of λ ₁ and λ ₂ are based on the spectroscopy of the photoelectric conversion elements used as the camera head sections 110 and 120 that constitute the imaging devices 11 and 12. Sensitivity characteristics and open pipe
It is appropriately selected depending on the temperature of the edge end face of the OP. In the apparatus used in the present invention, wavelengths from the visible range to the near infrared are used as λ ₁ and λ ₂ , so there is no problem of conduction loss caused by the image guide 6, and the influence of a poor surrounding atmosphere can be avoided.

The calculation unit 323 performs the two-color temperature calculation as described above once for each integration of the integrators 3201 and 3202. That is, one calculation is performed for each main scan, and the average temperature of the main scan line area is determined. While outputting this temperature to the image meseri 41,
While the temperature measurement is performed for one screen with the tube traveling direction as the main scanning direction, the calculations are successively compared to find the lowest temperature for that screen, and this is output to the high frequency power supply control circuit 8.

4 is an image composition device, and 5 is a video display device consisting of a CRT. The image synthesizing device 4 uses a video signal obtained from the imaging device 13 (composed of a camera head section 130 and a control unit 131 like the imaging devices 11 and 12) to display the video on the video display device 5 in the form shown in FIG. This is combined with the temperature pattern calculation result by the calculation unit 323 of the calculation device 3.

The raster of the video display device 5 is 3 as shown in FIG.
The first area is the image display area 5 on the upper left side excluding about 1/4 on the right side and about 1/4 on the bottom side of the raster.
1, the image of the edge end face EF near the temperature measurement point is
Display is based on a video signal from the imaging device 13.

Next, the area on the right side is a Y-direction distribution display section 52 that displays the temperature distribution in the thickness direction of the edge end face EF within the imaging field of the open pipe OP as dots, and also displays a vertical line serving as a scale indicating the level.

Two vertical lines X shown in the video display section 51
=X ₁ and X ₌ The dot shown in the section 52 has the Y coordinate of the dot position X=X ₁ ~
Typical temperatures between X ₂ are shown. This representative temperature is calculated by A/D converting the integrated values of the video signals VD1 and VD2 obtained by scanning between X=X ₁ and X ₂ on the Y coordinate as ε ₁ and ε ₂ respectively (1 ) The two color temperatures are calculated using the formula.

Next, the lower area displays the temperature distribution in the axial length direction (pipe traveling direction) at the center in the wall thickness direction within the imaging field of view of the edge end face EF of the open pipe OP, as well as a horizontal line that serves as a scale to indicate the level. This is an X-direction distribution display section 53 that represents.

Two horizontal lines Y shown in the video display section 51
= _Y1 and Y= _Y2 are cursor lines indicating the upper and lower limits (the left and right limits are the left and right limits of the video display unit 51) of the area to be sampled for the temperature distribution shown on the X-direction distribution display unit 53, The dot shown in the display section 53 is Y=Y ₁ at the X coordinate of the dot position.
Representative temperatures between ~ _Y2 are shown. This representative temperature is the same as that in the display section 52 described above.

Note that the video signals VD1 and VD2 between X = X ₁ and _{X 2} (or between Y = Y ₁ and _{Y 2} ) were sampled at multiple positions per main scan without using the integrators 3201 and 3202. The data may be integrated by the calculating section and two color temperature calculations may be performed using both integrated values.

The image synthesizing device 4 is capable of displaying images in the form described above, and has the following configuration, for example. Now, the scanning signal generating section 31
As shown in the figure, the area between X=X ₁ and X=X ₂ is
A deflection signal with the main scanning direction as the X direction and the sub-scanning direction as the Y direction, and the area between Y=Y ₁ and Y=Y ₂ ,
It is assumed that the deflection signal is set to alternately generate a deflection signal in which the main scanning direction is the Y direction and the sub-scanning direction is the X direction. The signal processing unit 32 integrates the video signals VD1 and VD2 for each scan in the main scanning direction based on the deflection signal generated by the scanning signal generation unit 31, and converts both integrated values into A/D converters to obtain the data described in (1) above. By calculating the formula, a representative temperature is obtained for each scan. 41 is a digital image memory allocated to the display sections 52 and 53, and the calculation section 323 writes the Y (or X) coordinate value of the scanning line while the main scanning direction is the X (or Y) direction. including vertical (or horizontal)
The temperature value calculated for scanning is given to the image memory 41 as an address and as a write horizontal (or vertical) address, and data for dot display is written to the corresponding address. The vertical or horizontal lines that serve as temperature scales in the display units 52 and 53 are displayed at addresses corresponding to the pixels in the image memory 41 that are to be displayed, using data separately given to the calculation unit 323. The data required for this purpose is written. Therefore, when changing the range of the temperature scale, it is necessary to add a calculation to the write horizontal (vertical) address based on the calculated temperature value to perform a necessary shift according to the data for displaying the scale. Furthermore, if a color display is to be performed, the data to be written to the image memory 41 for the line display of the scale and the data to be written to the image memory 41 for the dot display of the calculation results may be made different.

On the other hand, the video signal output from the imaging device 13 is input to the multiplexer 42 and signal separation circuit 43 of the image synthesis device 4. The signal separation circuit 43 extracts a vertical synchronization signal and a horizontal synchronization signal from the input video signal, reads them out, and sends them to the address generation circuit 4.
Output to 4. The read address generation circuit 44 reads data from the image memory 41 using a vertical synchronization signal, a horizontal synchronization signal, and a clock pulse (the period of which is determined by the number of pixels in the horizontal direction or the horizontal address of the image memory) input from an oscillation circuit (not shown). Create an address for the image memory 41
while issuing a selection control signal to the multiplexer 42. Image memory 41 at read address
The data read from is input to the multiplexer 42 via a D/A (digital/analog) converter 45.

Reference numeral 46 denotes a cursor display signal generation circuit, _which generates the above-mentioned X=X ₁ , , Y=Y ₁ , Y=Y ₂
This circuit generates a signal for displaying four straight lines, and the generated signal is input to the multiplexer 42.

The selection control signal given by the address generation circuit 44 to the multiplexer 42 is transmitted to the imaging device 13 during a period corresponding to the scanning of the display section 51 in the video display device 5.
The video signal output from the cursor display signal generation circuit 46 is selected, and the output from the display section 52, 53 is selected.
During the period corresponding to the scanning of the image memory 41 (during which the image memory 41 is in the read enable state)
The configuration is such that data to be read from is selected and the selected signal is sent to the video display device 5.
The image displayed on the video display device 5 in this way is as shown in FIG. It corresponds to this. Note that the temperature scales in FIGS. 2 and 6 are in opposite directions.

As described above, in the method of the present invention, the temperature distribution in the wall thickness direction of the opposing end surfaces of the open pipes to be welded together is detected at a position between the power supply part and the welding point V, and the lowest If the temperature is lower than the predetermined reference value, the welding conditions are controlled so that the temperature reaches the predetermined lower limit when the lowest temperature reaches the welding V point, so the edge of the open pipe is energized. The temperature at the center in the wall thickness direction caused by the skin effect and end face effect caused by the high frequency current generated by the welding process can be reliably raised above the lower limit temperature, reliably preventing welding defects and greatly improving the quality of the ERW pipe. , the present invention has excellent effects.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the state of temperature distribution on the edge end face of an open pipe using isothermal lines, Figure 2 is a graph showing an example of the temperature pattern at the temperature measurement point, and Figure 3
The figure is a graph showing the temperature transition of the edge end face of an open pipe, Figure 4 is a schematic diagram of the apparatus for carrying out the method of the present invention, Figure 5 is a block diagram of the temperature pattern measuring apparatus used in the method of the present invention, and Figure 6 7 is a display format diagram of a video display device, and FIG. 7 is a scanning method 1.
It is an explanatory diagram showing an example. OP...Open pipe, P...ERW pipe, CT...contact chip, SR...squeeze roll, EF...end face, 1...temperature pattern measuring device, 8...high frequency power supply control circuit, 9...high frequency power supply.

Claims (1)

[Claims] 1. In the process of continuously manufacturing electric resistance welded pipes by heating and melting the opposing end surfaces of an open pipe made by bending continuously fed metal strips and butt welding the molten end surfaces, the opposing end surfaces to be butt welded. The temperature distribution in the wall thickness direction is detected at a position between the power supply part and the welding V point, and if the lowest temperature in the temperature distribution is lower than a predetermined reference value, the part showing the lowest temperature is the welding V point. 1. A welding control method for an electric resistance welded pipe, characterized in that the welding conditions are controlled so that the temperature becomes equal to or higher than a predetermined lower limit temperature when the temperature reaches a predetermined lower limit temperature.