JPH02255283A - Method for controlling welding of seam welded pipe - Google Patents

Abstract

PURPOSE:To execute welding control with high adaptability to a disturbance, such as change in the electrical load of a weld zone by regulating a welding voltage in accordance with the result of the detection of the current value passed in a high-frequency oscillation circuit and the result of the detection of a welding temp. CONSTITUTION:The plate current of an oscillating tube 9 is detected by an ammeter 15. The deviation between a target heat input quantity and a thermometer output is inputted to an integrating element and the deviation between the output thereof and the thermometer output obtd. by multiplying the welding current and a feedback gain is inputted to an AVR 6 to generate a voltage. An SCR 7 rectifies the voltage. A boosting transformer 8 is inputted with this voltage and generates a plate voltage by a transmission element of first order lag. The plate voltage is inputted to an oscillation circuit 40a and generates the welding current. While the welding current is inputted to the weld zone 50, the welding current is fed back to the AVR 6. The weld zone 50 generates a temp. and a thermometer 11 generates the above-mentioned thermometer output by the transmission element of first order lag. The time when the welding temp. is restored to the target range after the change of the material is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling welding heat input in high frequency electric resistance welding.

[Prior art]

In the field of manufacturing welded pipes, high-frequency electric resistance welding is generally used for pipes called electric resistance welded pipes as a welding method with a high welding speed.

FIG. 3 is a schematic diagram showing an example of a welding pipe manufacturing process using a method of manufacturing an electric resistance welded pipe, for example, a high frequency induction welding method.

First, the abutting surfaces 2 of the strip plate 1, which is formed into a tubular shape by a group of forming rolls (not shown) and conveyed in the direction of the arrow, are abutted by the squeeze rolls 3, forming a wedge shape with the abutting portion as the apex. A high frequency voltage is applied to a work coil 4 disposed on the upstream side of the squeeze roll 3 in the conveyance direction and surrounding the strip 1, and an induced current generated by the current flows along the wedge-shaped abutment surface 2. This high-frequency induced current heats the abutting surface 2, and the apex of the tree shape,
That is, the welding point reaches the welding temperature and is welded under pressure by the squeeze roll 3.

In such electric resistance welding, if appropriate welding heat input is not ensured, welding quality will deteriorate. Therefore, various attempts have been made in the past, one of which is the so-called temperature feed bank concept, which measures the temperature of the weld zone and controls the welding heat input so that the welding temperature is maintained within a certain range. These methods have been proposed, for example, in JP-A-58-25882 and JP-A-57-195587.

Figure 4 is a typical circuit diagram of a high frequency electric resistance welding device.
Power supply section 20. Boosting section 309 oscillating section 40. It is roughly divided into a welding section 50 and a temperature measuring section 60. In the power supply section 20,
After the AC voltage applied from the AC power supply 5 is voltage-adjusted by the AVR 6, it is rectified by the SCR 7 and applied to the step-up transformer 8 of the step-up section 30.

The AC voltage boosted by the step-up transformer 8 is converted into a DC voltage by the rectifier 9, and is applied to the oscillation tube 10 of the oscillation section 40. In the oscillating section 40, the DC voltage is converted back into an AC voltage, and a high frequency current is generated in the work coil 4 of the welding section 50 through the coil lla of the CT lance 11.

The temperature measurement unit 60 measures the temperature at the welding point of the ERW pipe 1 with a thermometer 1.
2, and based on this measurement result, AVR6
voltage is adjusted to control the welding temperature.

FIG. 5 is a block diagram showing an embodiment of temperature feedback for controlling welding temperature. The deviation between the target heat input amount, that is, the target welding temperature, and the actual thermometer output is input to the compensation element 21, and the output is input to AVI? 6
generates voltage ■1 by the characteristic 22 of multiplying the gain by . The SCR 7 generates a voltage v2 which is obtained by rectifying the voltage 1 according to the characteristic 23 of multiplying the gain by 2, and upon inputting this voltage, the step-up transformer 8 generates a plate voltage Ep through the primary delayed transmission element 24. The plate voltage Ep is input to the oscillation circuit 40a of the oscillation section 40, and the oscillation circuit 40a generates the welding current I according to the characteristic 25 of multiplying the gain by 3. When this welding current I is input, the welding part 50 generates a temperature T based on the characteristic 26 of multiplying the gain by 4. Then, the thermometer 11 receives the temperature T and generates the thermometer output through the first-order delay transmission element 27.

[Problem to be solved by the invention]

By the way, in order to maintain stable welding quality, the most direct and effective method is to keep the welding temperature constant; It varies depending on the shape, impeder efficiency change, etc.). In order to control this constant, temperature feedback has been attempted as described above, but when measuring the welding temperature, the output signal of the thermometer contains noise due to the influence of the atmosphere near the welding part. It was inevitable that I would put it away.

Therefore, if you try to improve the connectivity of a closed-loop system with temperature feedback, the noise contained in the thermometer's output signal will become a disturbance, making it impossible to achieve stable control, so you will have no choice but to sacrifice connectivity. It was necessary to perform controlled controls.

The present invention has been made in view of the above circumstances, and the present inventor has discovered the facts in steel pipe manufacturing equipment that performs high-frequency ERW welding, that is, in controlling the welding temperature of ERW pipes,
Based on the fact that the dynamic characteristics of the control system are controlled by the transformer in the step-up section and the thermometer, we inherited the idea of temperature feedback, which is the most direct and effective means, and developed this system. The purpose of the present invention is to provide a welding control method for electric resistance welded pipes that can improve coordination.

Means for Solving Problem C] The welding control method for an ERW pipe according to the present invention detects the welding temperature and adjusts the welding voltage applied to a high frequency oscillation circuit to control the welding temperature to a target temperature. In the welding control method of an electric resistance welded pipe for welding a sewn pipe, a current flowing through the high frequency oscillation circuit is detected, and the welding voltage is adjusted based on the detection result of this and the detection result of the welding temperature. It is characterized by

[Effect]

The electric resistance welded tube is welded by adjusting the voltage applied to the high frequency oscillation circuit based on the detection result of the current value passed through the high frequency oscillation circuit and the detection result of the welding temperature.

(Example) Hereinafter, the present invention will be specifically explained based on drawings showing examples thereof. Fig. 1 is a circuit diagram showing the configuration of an apparatus for carrying out the welding control method for an electric resistance welded pipe according to the present invention; The figure is a block diagram showing the control contents, and the configuration of the device is approximately the same as the conventional example shown in FIG. is an ammeter that detects the welding current flowing through the oscillating section 5, and is designed to detect the plate current of the oscillating tube 10.

Next, to explain the control contents using Fig. 2, the deviation between the target heat input amount and the thermometer output is input to the integral element 31 to make the steady deviation zero, and the output and characteristic 28 are The deviation between the welding current (2) multiplied by the feed bank gain G1 and the thermometer output multiplied by the feedback gain G2 according to characteristic 29 is input to the AVR 6. By inputting this, the AVR6 has a voltage of 1 due to the characteristic 22 of multiplying the gain by 1.
occurs.

SCR7 has a voltage ■, due to the characteristic 23 that multiplies the gain by 2.
Rectified voltage (2) is generated, and upon inputting this voltage, the step-up transformer 8 generates a plate voltage Ep through its primary transmission element 24.The plate voltage Ep is manually inputted to the oscillation circuit 40a of the oscillation section 40, The oscillation circuit 40a generates a welding current (■) according to the characteristic 25 in which the gain is multiplied by 3.This welding current I is input to the welding section 50, while the above-mentioned characteristic 28
This is the AVR6 feed bank. Welding part 50
generates the temperature T by the characteristic 26 of multiplying the gain by 4. Then, the thermometer 11 receives the temperature T and generates the thermometer output through the first-order delay transmission element 27.

It is desirable to use the entire current that actually flows near the end face of the heated part of the ERW tube as the welding current (■), but since it is difficult to measure, as shown in this example, the plate of the oscillation tube 10 is In addition to the current, it may be represented by the current at point A or B in the oscillation circuit 40a, or it may be replaced by a signal that can represent the load fluctuation of the welding part in some way (for example, a fluctuation in the oscillation frequency). can.

Figure 6 + al (b) is a graph showing the temporal changes in welding temperature and welding voltage (control voltage) during welding of a small diameter ERW tube mill, respectively; An example of control by feedback is also shown in Fig. 6 (bl
1 shows an example of control by feedback with addition of welding current according to the method of the present invention, and in both cases, the material is changed at point a. In the figure, the thick line indicates the welding temperature, the thin line indicates the welding voltage, and the broken line in FIG. 6 (bl) indicates the welding current.

First, in the conventional example, after changing the material, it took about 1.5 seconds for the welding temperature to recover within the target temperature range. On the other hand, in the method of the present invention, the recovery time is shortened to less than 1 second, and it can be seen that the continuity is greatly improved.

〔effect〕

As described above, in the method of the present invention, by adding the welding current as a feedbank signal to the conventional control method of independent feedback of only the temperature signal, it is possible to eliminate the influence of disturbances applied when measuring temperature with a thermometer. Stable control can be performed, and since the welding current signal is a signal before being integrated by a thermometer, it is stable against disturbances such as changes in the electrical load of the welding part due to changes in the material of the welded material etc. It is possible to improve coordination without impairing the

As a result, the present invention has excellent effects such as reducing welding defects and improving welding quality and pipe manufacturing yield.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a device implementing the welding control method for electric resistance welded pipes according to the present invention, Fig. 2 is a block diagram showing the control contents, and Fig. 3 is a schematic diagram showing an example of the welding pipe manufacturing process. , Fig. 4 is a circuit diagram of a conventional high-frequency electric resistance welding device, Fig. 5 is a block diagram showing conventional control contents, and Fig. 6 shows welding temperature, welding voltage, and welding during welding of a small diameter electric resistance welding pipe mill. It is a graph showing temporal changes in current. 1... ERW pipe 4... Work coil 6... AV
I? 7...SCR8...Step-up transformer 9...
・Oscillator tube 12...Thermometer 15...Ammeter 40
...Oscillating part 40a...High frequency oscillation circuit patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono Diagram (b)

Claims (1)

[Claims] 1. To detect welding temperature and control it to a target temperature,
A welding control method for an ERW pipe in which the welding voltage applied to a high frequency oscillation circuit is adjusted to weld the ERW pipe includes detecting a current flowing through the high frequency oscillation circuit, and combining the detection result with the welding temperature. A method for controlling welding of an electric resistance welded pipe, characterized in that the welding voltage is adjusted based on a detection result.