JPS6335357B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric resistance welding tube welding device, and particularly to welding heat input control.

In ERW tube welding, for example, high frequency ERW tube welding, a high frequency current is induced in the V-shape portion of the end face of a tube formed and butt welded, and welding is performed by resistance heat generation. In this case, welding temperature is an important factor that determines the quality of welding, and various control methods have been proposed. For example, there is a high frequency heat input adjustment method using welding current measurement, as disclosed in Japanese Patent Laid-Open No. 50-45753, and a method of detecting welding temperature with a temperature sensor to control heat input.

However, according to experiments conducted by the present inventors, heat input control using welding current measurement does not reflect disturbances such as changes in the thickness of the heated object as changes in the welding current, and therefore does not have the ability to adjust the welding temperature. I understood. In addition, although heat input control using temperature measurement is preferable in principle, there are problems with disturbances in the measurement conditions and the responsiveness of the temperature measuring device itself, so
It was unsuitable for this class of high-speed welding.

The purpose of the present invention is to stabilize the quality of welded seams by incorporating changes in plate thickness into heat input control using welding current measurement, and to also make it possible to detect local defects in welded seams from changes in welding current. To provide ERW pipe welding equipment.

In the present invention, heat input is controlled by adding plate thickness correction to the feed rate of the electric resistance welded pipe, and the plate thickness is detected from the thickness measurement of the strip plate or the temperature of the seam after welding.

FIG. 1 shows the basic configuration of the present invention. In order to enhance the welding effect, an impeder 2 with a cooling pipe 2a inside is inserted into the tube material 1 formed into a tubular shape, and while the tube material 1 is moved in the direction of the arrow, its V
The opposing edges of the letter-shaped seam portion 1a are pressed together by two squeeze rollers 3a and 3b, and tuned by a variable voltage high frequency oscillation circuit 4 including a voltage adjustment circuit 4a such as a thyristor and an oscillation circuit 4b using a vacuum tube or the like. A high frequency current is passed through the seam portion 1a by a heating material 6, such as an induction coil or a contactor, through a circuit 5, and welding is performed using the proximity effect and the skin effect. Note that 4c is a booster circuit, and 4d is a rectifier circuit.

In the voltage adjustment circuit 4a, the AC output voltage _Eac is controlled by the control device 7, and the output current iω of the oscillation circuit 4 is controlled using the output voltage _Eac as a manipulated variable.
The output current iω of the oscillator circuit 4 is detected by a current detector 8 that constitutes a current transformer together with the heating material 6, for example, and this detected current iω is set by a setting device 9 as the amount of heat input and the amount of heat set according to the tube material feeding speed. A feedback loop is constructed to compare the signals and generate a control signal for the control device 7.
Among the factors that change the welding temperature, this feedback loop includes power supply fluctuations, performance deterioration in oscillators such as vacuum tubes, impeder core deterioration and falling out,
It is possible to correct electrical fluctuation factors such as changes in the contact point of the contact tip and mechanical fluctuation factors such as changes in the V-shave angle.

Note that the control amount of the above feedback loop is not limited to the oscillator output current iω, but also the AC output voltage.
A similar control function can be provided by controlling E _ac , DC voltage E _p or AC voltage e _HF .

In such heat input control, in this configuration, the detected value of the feed speed S _p of the tube material 1 and the welding temperature θ
The feed rate is determined in the computing unit 10 that receives the detected value as input.
A plate thickness correction calculation is performed for S _p , and the calculation result is passed through a function generator 11 having a speed-heat input function characteristic to set the output of the setting device 9. Reference numeral 12 denotes a feed rate detector composed of, for example, a tachometer generator.
The temperature detector 13 is used to detect changes in plate thickness by detecting welding temperature, and this will appear as a change in welding temperature if the plate thickness changes at the same feed rate and heat input. Further, the temperature detector 13 does not directly measure the welding temperature, but measures the welding temperature at a position past the atmosphere that is inconvenient for temperature measurement, such as sparks, scale, steam, and water at the welding part. This is based on the fact that the plate thickness changes very gradually (JIS standards allow a value of ±10%, making the tip and rear ends of the band coil thinner), which is a characteristic unique to ERW pipes. This is based on the fact that detecting the material temperature due to residual heat from the heat used in welding provides better measurement conditions than directly measuring the temperature of the weld zone.

On the other hand, the arithmetic unit 14 calculates the current detected by the current detector 8.
Input iω and the detected speed S _p of the speed detector 12,
A local defect in welding is determined based on the instantaneous abnormality of the detected current iω, and the location of the defect is detected based on the detection speed S _p , and a defective product sorting signal is generated. Causes of abnormality in current iω include, for example, instantaneous power failure, instantaneous overvoltage, V
These phenomena occur due to sheave short circuits, etc., and these phenomena result in deterioration of welding quality (overheating, cold welding), and the position signal and sorting signal are calculated by the computing unit 14.

By providing the computing unit 10 in this way, among the factors that change the welding temperature, changes in pipe manufacturing speed (during acceleration/deceleration or steady speed changes) are controlled by the detected speed S _p , and the heat input is controlled by the detected speed S p. Changes in plate thickness are controlled by heat input by correcting the detection speed S _p based on the detected temperature θ. In addition, by providing the computing unit 14, among the factors that change the welding temperature, instantaneous change factors such as the above-mentioned V-shave short circuit can be detected by detecting the position on the pipe from the integral of the detected speed S _p up to the point of change of the detected current iω. Then, control is performed to remove the welded portion or remove the electric resistance welded pipe as a defective product.

FIG. 2 shows a concrete block configuration of the arithmetic units 10 and 14 in FIG. 1. The plate thickness calculator 15 of the calculator 10 receives the detected temperature θ from the temperature detector 13 as input, and calculates the plate thickness value from this detected temperature θ.
The plate thickness calculator 15 calculates the plate thickness value from the deviation of the actual detected temperature θ with respect to the welding temperature at the standard plate thickness from functional calculations and table data, while the feed rate and heat input of the tube material 1 are constant. Next, a standard plate thickness value is set in the plate thickness setter 16 of the calculator 10, and this set value and the calculated value of the plate thickness calculator 15 are compared to the comparator 17.
A comparison is input to the comparator 17, and the deviation (increase/decrease in thickness) between the standard plate thickness setting value and the calculated value is determined.
The output of this comparator 17 is used as a multiplier input of a multiplier 18, and the speed detection value from the feed speed detector 12 is given to the multiplicand input of the multiplier 18. The multiplication by this multiplier 18 is to convert the plate thickness increase/decrease into an increase/decrease in the feed speed S _p . For example, when the plate thickness increases more than the standard value, the current speed S _p is decelerated to be reduced by the ratio of the plate thickness increment. Find the quantity.

Next, the gain setter 19 of the arithmetic unit 10 amplifies the speed detection value _Sp of the feed speed detector 12 with a set gain to obtain a value proportional to the detection value _Sp . This gain setter 19 divides the detection level of the current speed S _p using, for example, a potentiometer, and adjusts the ratio with the output of the multiplier 18 . Next, the adder 20 adds or subtracts the output of the multiplier 18 and the output of the gain setter 19. Through this addition and subtraction, the detected value of the speed S _p is corrected by the speed correction amount of the calculator 18 that corresponds to the plate thickness correction amount. The addition/subtraction result of the adder 20 is the input of the function generator 11, that is, the plate thickness corrected speed S _p
output. Therefore, when welding a part where the plate thickness is thicker than the standard plate thickness, the detected speed S _p is assumed to be a faster value than the speed for the standard plate thickness, and the heat input is controlled in the direction of increasing, and the unit volume of the welded part is The welding temperature is controlled to be constant by keeping the amount of heat input per weld constant. Conversely, when welding parts where the plate thickness is thinner than the standard plate thickness, the welding temperature is controlled to be constant by controlling the amount of heat input to be lower.

Note that the plate thickness calculator 15 is not limited to calculating from the welding part temperature θ, but also uses light, ultrasonic waves, fluidics, X-rays, capacitance, magnetic quantity, etc. before forming the strip or after forming and welding. The plate thickness may be directly calculated using a well-known measuring device using

The discriminator 21 of the arithmetic unit 14 receives the oscillator output current iω detected by the current detector 8 as an input, detects the current iω, and extracts a signal whose detected signal exceeds a predetermined level. Filter 2 which receives this signal as input
2 extracts components of a predetermined frequency or higher. The discriminator 21 and the filter 22 obtain an abnormal welding temperature occurrence timing signal in which the current iω changes instantaneously due to a V-shave short circuit, etc., and this signal is amplified and waveform-shaped by an amplifier to provide a calculation command for the position calculator 24 and an error signal. Set the cutting command to the good product cutting command unit 25. The position calculator 24 integrates the speed S _p from the time of starting welding, and numerically outputs the integrated value when a calculation command is given as a welding defect location. In addition, the defective product cutting command device 25 amplifies the power of the cutting command signal and drives the cutting or marking device for the defective welding portion.

As explained above, the ERW pipe welding device according to the present invention detects the change in the thickness of the pipe material from the welding temperature or directly in heat input control by measuring the welding current,
Since the detected value of the pipe manufacturing speed is corrected according to this detected value and the heat input amount is set, it is possible to control the heat input including plate thickness correction, and further stabilize the quality of the welded seam. In particular, the plate thickness changes greatly at the beginning and end of the band coil, and this has a significant effect on improving welding quality in these areas. Furthermore, in the present invention, it is possible to detect local failures in welded seams by detecting when the level and rate of change of the oscillator output current exceed a predetermined value, making it easy to detect lot failures due to local welding failures. This also makes it easier to detect defective locations. Using this method not only improves the reliability of high-frequency electric resistance welded pipes and saves the operator's adjustment labor, but also enables the practical use of high-quality stainless steel pipes for chemical piping and aluminum oval pipes for radiators, which cannot currently be manufactured. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of an electric resistance welding pipe welding device according to the present invention, and FIG. 2 is a diagram showing the computing unit 1 in FIG. 1.
0.14 is a concrete block diagram. 1... ERW pipe, 4... Variable voltage high frequency oscillation circuit, 5
...tuned circuit, 8...oscillator output current detector, 10...
Arithmetic unit, 11...function generator, 12...speed detector,
13... Temperature detector, 14... Arithmetic unit, 17... Comparator, 18... Multiplier, 20... Adder, 21... Discriminator, 22... Filter, 24... Position computing unit, 25...
Defective product cutting command device.

Claims (1)

[Scope of Claims] 1. In ERW tube welding in which high-frequency current is induced in the end faces to be butt-welded and welding is performed by resistance heat generation, heat input is controlled by measuring the welding current according to the detected value of the feed speed of the ERW tube. and a control unit that corrects the detected value of the pipe material feed rate in accordance with a change in the plate thickness of the welded part calculated from the measured value of the welded part temperature or determined from the directly measured value of the plate thickness. Welding equipment. 2. A computing unit is provided that detects a welding defect by determining that the high-frequency current has exceeded a predetermined level and a predetermined rate of change, and calculates the position of the welding defect from an integral calculation of the feed rate of the ERW pipe. An electric resistance welding pipe welding device according to claim 1.