JPH03193279A - Welding input control method and device for resistance welded steel tube - Google Patents

Abstract

PURPOSE:To fix the welding efficiency and to improve the welding quality of a resistance welded steel tube by measuring the welding current and voltage close to welding, operating impedance at the time of welding to obtain the welding efficiency, monitoring its changing state and controlling welding input based on the change of the welding efficiency. CONSTITUTION:The current I flowing to a work coil 2 is detected by a current detector 5. In addition, the voltage V is detected by a voltage detector 6 and an impedance value is operated by a computing element 7. The welding efficiency is then obtained from the impedance value by a computing element 8. Further, the rate of change of the welding efficiency is obtained from the welding efficiency and a welding efficiency set value given from a welding efficiency setter 9. Based on this rate of change of the welding efficiency, the oscillating tube plate voltage control variable of a high-frequency power source 1 is then obtained to control the oscillating tube plate voltage of the high-frequency power source 1. By this method, the welding input to an open pipe 2 can be controlled to a fixed value.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a welding input control method and apparatus for electric resistance welded steel pipes.

<Conventional technology and its problems> As is well known, ERW steel pipes are produced by forming the material to be welded, such as copper strip or skelp, into a cylindrical shape using a forming machine, and then applying a high-frequency current to both edges to electrically After heating and melting, it is pressurized with a squeeze roll to form a tube.

Setting the welding conditions of the electric resistance welding device used in this case is as follows:
Conventionally, an operator measures the plate voltage E, plate current 12 of the oscillation tube of a high-frequency power supply, uses the output and efficiency of the oscillation tube calculated from these measured values as a target, and determines the material, dimensions, etc. of the tube. Depending on the situation, the appearance of the weld or the weld bead was visually monitored, but this required considerable experience and skill, and of course there were individual differences between workers. , electric resistance sewing wJ under constant welding conditions
The tubes were difficult to manufacture.

Therefore, in order to resolve this situation, for example,
As described in Publication No. 5-26955, welding current is detected by attaching a welding current detection element such as a Hall effect element or a coil to a hole provided in a conductor lead structure, and welding conditions are monitored. Alternatively, there is a method of comparing the welding current with a set value and applying it to a welding high-frequency power source to manufacture an electric resistance welded steel pipe under constant welding conditions.

However, in the above-mentioned welding current detection device of Japanese Patent Publication No. 55-26955, the current detection electric circuit connected to the current detection element is close to a high frequency large current circuit formed by a conductor lead structure, etc. The electric circuit is ti
This method has the disadvantage that it is easily affected by noise due to t1 lead, and the reliability of the detection results is extremely low.

In order to eliminate such drawbacks, as already disclosed by the present applicant in Japanese Unexamined Patent Publication No. 63-165083, a signal from an optical Faraday element attached to a conductive lead structure is transmitted from the conductive lead structure via an optical fiber. We have proposed a system in which the welding current is detected using a welding current detector located at a distant location.

However, although this method is fully applicable to the resistance method, there is a problem in that it cannot be applied to the induction method.

That is, in the case of the induction method, as shown in FIG. In order to prevent part of the current induced on the outer surface 3b from circulating through the inner surface 3C of the tube and becoming a reactive current, an invider 4 such as a ferrite core is inserted inside the oven pipe 3 to reduce the impedance on the inner surface. By increasing the current, the reactive current is prevented from decreasing.

Therefore, when attempting to measure the welding current flowing through the work coil 2 using the method described in the above-mentioned special σn No. 165083/1983, since reactive current is also included, it is accurately measured as a current that can contribute to true welding. It is impossible.

The present invention has been made to solve the above-mentioned problems, and aims to provide a method and apparatus for controlling welding input 1IiIJ of electric resistance sewing tiIJvt, which can be applied not only to the induction method but also to the resistance method. purpose.

Means for Solving the Problems> The present invention, when manufacturing an ERW steel pipe using a high frequency ERW welding device, measures the welding current and voltage immediately before welding, and calculates the impedance during welding from these measured values. , a step of calculating the welding efficiency using this impedance performance X1tr and monitoring its change state, and a step of controlling the welding input based on the change in the welding efficiency. This is a welding input control method for ERW steel pipes.

The apparatus also includes a device for manufacturing an ERW steel pipe using a high-frequency ERW welding device, which includes a current detector for detecting a welding current immediately before welding, a voltage detector for measuring a voltage immediately before welding, and the current detector. and an impedance calculation means for calculating impedance during welding from the measured value of the voltage detector, and a welding efficiency change calculation means for calculating the welding efficiency using the calculation signal from the impedance calculation means and monitoring the state of change thereof. This is a welding input control device for electric resistance welded steel pipes, comprising a welding input control means for controlling a welding input based on the degree of change in welding efficiency determined by the welding efficiency change calculating means.

As a result of intensive studies on detecting welding current using the induction method, the inventors of the present invention have determined that the welding current can be improved by capturing the change in the characteristics of the impeder, which affects the welding efficiency within the load impedance, as an impedance change. They have discovered that changes in efficiency can be measured, and have completed the present invention.

Now, to explain the principle of the present invention, if the conventional induction method shown in FIG. 2 is expressed as an impedance circuit, it will become as shown in FIG. ．． The outer surface 2b of the oven pipe, which is composed of a resistor R3 and electromagnetically coupled to the work coil 2, has a reactance Lx and a resistor R8, and in parallel to the outer surface 2b, the inner surface 2c has a reactance Ls, a resistor R, and a reactance of the V-shape 2a. L4. Resistor R4 is connected,
Furthermore, the reactance Ls and resistance R of the impeder 4 are expressed as being electromagnetically coupled to the reactance of the inner surface 2C.

The equivalent circuit seen from these high-frequency power sources 1 is as shown in the axis of Fig. 3, assuming that the equivalent reactance is R1, and the equivalent resistance is R1. Therefore, the equivalent impedance Z,
is expressed by the following formula (1).

Z, -R, +jωL, ・-(1) Now, the voltage applied across this equivalent impedance Z, is ■
, if the flowing current is ■, then the equivalent impedance is 2. can also be expressed by the following equation (2).

Z, -V/I ・−・−・・−
(2) Therefore, by measuring the voltage (2) and current I at the work coil 2, the impedance can be calculated.

Furthermore, according to experiments conducted by the inventors, the relationship between impedance Z and welding efficiency η has the characteristics shown in FIG. 4. Therefore, if impedance Z can be calculated as described above, welding efficiency η can be found.

Therefore, the welding efficiency η, which is determined by the material, size, etc. of the workpiece to be welded, is set in advance, and the degree of change Δη of the difference from the determined actual welding efficiency η is determined using the following equation (3).

Δη-(η-η3)/η, (3) Then, by using this efficiency change amount ΔI as a parameter, the control amount ΔE of the plate voltage E of the oscillation tube of the high-frequency power supply is expressed by the following equation (4). You can ask for it.

ΔEF−−k・Δη ・・−・−・・−・・−・−
(4) By performing such a procedure, the welding input can always be controlled to be constant.

Note that FIG. 5 shows an example of the relationship between the degree of efficiency change Δη and the high frequency power supply oscillation tube plate voltage control amount ΔE.

<Example> Below, an example of the present invention will be described in detail with reference to FIG. In the drawings, the same members as in the conventional example are given the same reference numerals.

In the figure, 5 is a current detector that measures the welding current flowing through the work coil 2, and 6 is a voltage detector that measures the voltage applied to both ends of the work coil 2.

7 is an impedance calculator which inputs the current measurement value detected by the current detector 5 and the voltage measurement value detected by the voltage detector 6 and calculates the impedance value during welding. have the ability.

8 is a welding efficiency change calculator, which inputs the impedance value calculated by the impedance calculator 7;
It has a function of inputting a preset impedance value to the impedance setting device 9 and calculating a change in welding efficiency.

Reference numeral 10 denotes a welding input control circuit, which has a function of controlling the plate voltage of the oscillation tube of the high frequency power source 1 based on the welding efficiency change signal from the welding efficiency change calculator 8.

11 is an equipment abnormality determination device, and a welding efficiency change calculator 8
The welding efficiency change signal from the welding efficiency change width is checked by comparing it with the welding efficiency change range setting value of the setting device 12, and if the setting value is exceeded and it is determined that there is an abnormality in the equipment, an abnormality signal is output to the display device 13. It has a function to display Note that 14 is a squeeze roll.

The operation of the welding input control device configured as described above will be explained below.

■ The current ■ flowing through the work coil 2 is detected by the current detector 5, the voltage V is detected by the voltage detector 6, and the impedance value Z is calculated by the impedance calculator 7 using the above formula (2). .

■ Next, in the welding efficiency calculator 8, the impedance 4t17. is calculated using the characteristics shown in FIG. Find the welding efficiency η from

(2) Further, using this welding efficiency η and the welding efficiency set value η given from the welding efficiency setting device 9, the degree of change Δη of the welding efficiency is determined from the above equation (3).

■ Then, using this degree of change in welding efficiency Δη, calculate the oscillation tube plate voltage control amount E of the high-frequency power source l based on the function expressed by equation (4) above ■ This oscillation tube plate voltage control amount Using ΔE, the plate voltage E of the oscillation tube of the high frequency power supply l.

control.

Thereby, the welding input to the oven pipe 2 can be controlled to be constant.

Note that when the welding efficiency change degree Δη changes more than the value Δη preset from the setting device 13, the equipment abnormality determination unit 11 determines that there is an abnormality in the welding equipment such as an invider, and the display 12, an abnormal signal is output and displayed.

Further, in the above embodiments, an induction method using an impeder has been described, but the present invention is not limited thereto, and it goes without saying that it can also be applied to a resistance method.

<Effects of the Invention> As explained above, according to the present invention, the change in welding efficiency is detected as a parameter, so the welding input can be always controlled to be constant, thereby improving the welding quality of ERW steel pipes. It is possible to contribute to the improvement of

[Brief explanation of drawings]

FIG. 1 is a configuration diagram schematically showing an embodiment of the present invention, and FIG.
The figure is a perspective view schematically showing a conventional example, FIG. 3(a),
(b) is an impedance circuit diagram of an induction type welding mechanism, Figure 4 is a characteristic diagram showing the relationship between impedance and welding efficiency, and Figure 5 is an example of the relationship between the degree of change in welding efficiency and the plate voltage control amount. FIG. 1...High frequency power supply, 2...Work coil,
3...Open pipe, 4...Impeder,
5... Current detector, 6... Voltage detector,
7... Impedance calculator, 8... Welding efficiency calculator, 9... Welding efficiency setting device, 10... Welding input control circuit. 11...Equipment abnormality determination device, 12...Setting device, 1
3...Display device, 14...Squeeze roll.

Claims (1)

[Claims] 1. When manufacturing an ERW steel pipe using a high frequency ERW welding device, a step of measuring the welding current and voltage immediately before welding and calculating the impedance during welding from these measured values. , a step of calculating a welding efficiency using the impedance calculation value and monitoring its change state, and a step of controlling a welding input based on the change in the welding efficiency. Welding input control method. 2. A device for manufacturing ERW steel pipes using high-frequency ERW welding equipment, comprising: a current detector that detects the welding current immediately before welding; a voltage detector that measures the voltage immediately before welding; and the current detector. impedance calculation means for calculating impedance during welding from the measured value of the voltage detector; welding efficiency change calculation means for calculating welding efficiency using a calculation signal from the impedance calculation means and monitoring the state of change; A welding input control device for electric resistance welded steel pipes, comprising: a welding input control means for controlling a welding input based on a degree of change in welding efficiency determined by a welding efficiency change calculation means.