JPH028625Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a welding control device for ERW steel pipes, and particularly to a welding control device for ERW steel pipes that controls the amount of welding input by measuring the welding temperature of the ERW steel pipe and providing feedback on the deviation from the target temperature. This invention relates to improvements in welding control devices. Conventionally, as a method for evaluating and controlling welding conditions,
Some of this is due to welding temperature. That is, this method:
This method takes advantage of the fact that the temperature of the molten bead (hereinafter referred to as the weld bead) in the weld increases or decreases proportionally depending on the amount of heating power used during welding, and a radiation thermometer or two-color thermometer is placed near the weld. Then, the welding power to be input (referred to as welding input amount) is corrected by measuring the surface temperature of the weld bead and feeding back the deviation between the measured temperature and a preset target temperature. control is performed. However, such conventional methods suffer from fluctuations in the cooling rate due to changes in the melting point of the welding material and the shape of the weld bead, fluctuations in the ratio of melting amount to welding power, fluctuations in the thickness of the tube forming plate, fluctuations in the butt shape,
There was a problem in that it was difficult to properly evaluate the welding condition due to fluctuations in pipe manufacturing speed. In other words, among these fluctuation factors, fluctuations in the thickness of pipe forming plates, fluctuations in butt shape, fluctuations in pipe manufacturing speed, etc. can be predicted to some extent by the amount of change in measured temperature, but fluctuations in cooling rate and melting amount can be predicted to some extent. It is often difficult to predict fluctuations, etc., and as a result, the measured welding temperature and the amount of welding input do not correspond linearly, and there are cases where it is impossible to control the welding input appropriately. It is. The present invention was developed in view of these conventional problems, and it is possible to accurately grasp the state of fluctuations in the temperature of the weld zone caused by changes in the shape of the weld bead, which has been difficult to predict up until now. It is possible to properly evaluate and control the welding condition, and furthermore, it can be developed to appropriately adjust the butt shape in order to obtain the optimal bead shape. The purpose is to provide a control device. The present invention provides a welding control device for an ERW steel pipe, which controls the amount of welding input by measuring the welding temperature of the ERW steel pipe and feeding back the deviation from the target temperature. Temperature measuring means for measuring the temperature of the welding zone immediately after welding at at least two or more points in the welding direction, and determination for understanding the cooling pattern immediately after welding from the difference in temperature measured at each point. The above object is achieved by providing a control means for correcting the welding input amount in accordance with the cooling pattern. In this invention, the welding quality of ERW steel pipes is affected not only by the surface temperature of the weld bead, but also by fluctuations in the melting amount ratio, bead shape, etc.; This was done by focusing on the fact that this can be understood as a change in the cooling pattern after welding at different locations in different directions. In the present invention, based on this knowledge, the temperature is measured at two or more temperature measurement points, the cooling pattern is determined from the measured temperature difference, and based on this cooling pattern including information such as bead shape, etc. Since the welding input is controlled by the welding input, stable and high-quality welding can be performed at all times. Hereinafter, the principle of the device of the present invention will be explained first. The surface temperature distribution of the weld bead after welding indicates the temperature of the molten steel at the welding position, and the bead surface temperature remains approximately constant until the molten steel solidifies. This is thought to be due to the generation of solidification heat. The heat applied during welding is then cooled down by radiation and conduction, so as the ERW steel pipe is transported on the line and moves away from the current welding position, the temperature gradually decreases. A phenomenon occurs in which the temperature decreases. As a result of the inventors' tests, the cooling pattern of this ERW steel pipe has a certain regularity depending on the amount of welding input (heating amount) during welding, the amount of welded steel, the shape of the weld bead formed by pressure welding, etc. It was found that there was a change in Figure 1 shows the surface temperature distribution after welding as the temperature measurement position P changes. In the figure, A is a normal bead shape and the optimal welding input is supplied, B is a normal If excessive welding input is supplied to the bead shape, resulting in a so-called overheating state, if C is similarly underheated due to insufficient welding input being supplied, then D has the same welding input as A. Each case is shown in which the bead shape changes in the supplied state. Further, M indicates an example of the installation position of a thermometer used for actual welding control. The reason why it is slightly shifted from the welding position W is that the welding position W shows the temperature of the molten steel regardless of the amount of welding input, so there is no difference. As is clear from the figure, the temperature at this position M is around 1400°C in the proper state of A, and in the overheated state of B, heat is accumulated over a wide range, so cooling is slow and reaches around 1480°C. On the other hand, in the underheated state of C, it cools down quickly to around 1320°C. Further, when the bead shape changes while the proper welding input of D is supplied, the measured value at position M becomes 1480° C., which is almost the same as the overheated state of C. As can be seen from this example, with a normal bead shape, it is possible to judge the quality of welding by simply measuring the temperature at the M position, but if the bead shape changes, it may not be possible to distinguish it from overheating, for example. A situation arises. However, as in the present invention, in addition to measurements at the M position, measurements are taken at the N position at the same time, and by managing the temperature difference, it is possible to determine whether it is a fluctuation in the heat state or a fluctuation in the bead shape. It can be determined whether or not. That is, when the measurement results at the M position and the N position are compared, the results are as shown in Table 1.

[Table] As is clear from this table, when the bead shape changes while an appropriate welding input is supplied, M
In the case of a normal bead shape, the temperature would have dropped to 1400℃ at the position, but it only dropped to 1480℃, so it is hard to distinguish it from an overheat condition, but at the N position, if it was an overheat condition, the temperature would drop from 1480℃ to 1400℃. It can be seen that the temperature that was supposed to drop to 1,460 degrees Celsius is clearly distinguishable. In other words, if the cause was overheating, there would have been a temperature drop of 80°C from the M position to the N position, but if the cause was an abnormality in the bead shape, the temperature drop would have been only 20°C. Not descending. Therefore, as in the present invention, if the temperature at two locations of the ERW steel pipe after welding is measured and the temperature difference is managed to determine the cooling pattern, the bead shape can be determined. It becomes possible to evaluate and control the welding state taking into account the changing state. FIG. 2 shows an embodiment of the present invention. This embodiment is a welding control device for an ERW steel pipe that controls the amount of welding input by measuring the welding temperature of the ERW steel pipe 10 and feeding back the deviation from the target temperature. Temperature measuring instruments 12 and 14 for measuring the temperature of the weld zone immediately after welding No. 10 at at least two points M and N in the welding direction, respectively, and the temperature Tm measured at each point M and N. , Tn, a calculator 16 for calculating the difference _T1 between the temperatures, Tn, a determiner 18 for determining the cooling pattern after welding from the temperature difference _T1 , and a determining unit 18 for correcting the welding input amount according to the cooling pattern. controller 2
0. The temperature measuring instruments 12 and 14 use two-color thermometers as sensors, and the information is guided to photoelectric conversion elements 26 and 28 through optical fibers 22 and 24, and the temperature is measured by replacing the height of the temperature with the strength of an electric signal. Those that do are adopted. The arithmetic unit 16, determination unit 18, and controller 20 are
In reality, one control device 30 is configured to incorporate a program that performs the above functions. In this case, the determiner 18 compares and determines which of several pre-stored cooling patterns the temperature difference T ₁ obtained as a result of measurement is closest to. Further, the controller 20
The welding input at the welding part W is controlled while the difference between the measured temperature and the target temperature is corrected by a coefficient corresponding to this cooling pattern and fed back. Next, the operation of this embodiment will be explained. Using this example device, a small diameter ERW steel pipe mill was used.
An example of making a 48.6φ pipe is shown below. Two temperature measuring instruments 12 and 14 were arranged to measure a position M at 80 mm and a position N at 120 mm after the welding point. Note that the pipe forming speed v is constant. In the steady state, the plate voltage Ep is controlled as the plate thickness t of the steel pipe changes, and the weld bead temperature is constant and maintained at an appropriate level of heating (Third
Figure _S1 area). When the relay part Q of the ERW steel pipe 10 arrives, the temperature Tm at point M suddenly changes from 1400℃ to 1480℃.
It changed to ℃. In this case, if there was no observation at N, it would only be measured as a change in the heating state, but because the temperature Tn was measured at the same time at the N point, the temperature rise from 1300℃ to 1460℃ at the N point was measured. It is recognized that the temperature difference after the above Q point is 20
℃ only, and could be interpreted as a change in bead shape. As a result, feedback control was performed that took this change in bead shape into consideration, and an appropriate welding input could be supplied to maintain an optimal welding condition. In the above embodiment, two temperature measuring means are used.
Although a color thermometer, an optical fiber, and a photoelectric conversion element were used, the temperature measuring means in the present invention is not limited to these measuring means; for example, a conventionally known radiation thermometer may be used. You can also do this. As explained above, according to the present invention, it is possible to evaluate and control the welding condition while taking into account changes in the bead shape, which were difficult to predict in the past. An excellent effect can be obtained in that the welding process can be performed on the welding process. Furthermore, since the bead shape can be grasped, it is possible to maintain a proper bead shape by adjusting the butt shape.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the cooling temperature distribution state at each position after welding to explain the principle of the present invention, and Fig. 2 shows an embodiment of the welding control device for electric resistance welded steel pipes according to the present invention. Figures 3A to 3D, which are schematic perspective views including some block diagrams, show the temperature at the M and N positions, the plate voltage of the welding device, the plate thickness of the ERW steel pipe, and the pipe manufacturing speed over time. FIG. 10...Erw steel pipe, 12, 14...Temperature measuring device, 16...Calculator, 18...Judgment device, 20...
controller.

Claims (1)

[Scope of Claim for Utility Model Registration] An electric resistance welded steel pipe welding control device that measures the welding temperature of the electric resistance welded steel pipe and controls the welding input amount by feeding back the deviation from the target temperature, A temperature measuring means for measuring the temperature of a welded part of a sewn steel pipe immediately after welding at at least two points in the welding direction, and determining a cooling pattern immediately after welding from the difference in temperature measured at each point. 1. A welding control device for electric resistance welded steel pipes, comprising: a determination means for correcting a welding input amount according to the cooling pattern; and a control means for correcting a welding input amount according to the cooling pattern.