JPS5815228B2 - High frequency electric resistance welding phenomenon monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for monitoring welding phenomena during high-frequency electric resistance welding of flat plates, curved plates, etc.

Conventionally, when setting welding conditions in high-frequency electric resistance welding, the operator uses the anode current and voltage of the oscillation tube as indicators to determine the tube material,
This has been done by visually monitoring the appearance of sparks in the welding area or the appearance of the weld bead, depending on the size and other factors.

This requires considerable experience and skill, and there are of course individual differences between workers, and it is also physically tiring for each worker, so it is important to carry out electric resistance welding under constant welding conditions. The disadvantage was that it was difficult.

Therefore, in order to overcome the drawbacks of the prior art described above, the present inventors developed welding conditions (welding current, welding speed, power supply position, upset amount) for a large number of ERW tubes with different dimensions (outer diameter, thickness). We used a high-speed camera to observe the series of welding phenomena of heating, melting, and pressurization that occur on both strip edges between the power supply position and the center of the squeeze roll when the butt angle (butt angle) was varied. We studied the basic phenomena of

The results were presented in October 1976 by the Iron and Steel Institute (Lecture No. 23).
2233), and the Welding Society of Japan (lecture number 40) in November of the same year.
8409), we have found that there are three types of welding phenomena, as shown in Figure 1, which are broadly classified as completely different from conventional common sense.

Here, FIG. 1 is a schematic diagram showing a welding phenomenon, where a is a diagram showing a first type welding phenomenon, b is a diagram showing a second type welding phenomenon, C is a diagram showing a third type welding phenomenon, and P is a welding object, ■ is the well-known V convergence point, W is the welding point, G is the molten steel, M and N are the strip edges,
X and Y represent contact tips, and S represents a squeeze roll.

The characteristic of the three types of welding phenomena is that the welding point W repeats approximately periodic movement with respect to the V convergence point V (fixed position) formed by the strip edges M and N of the workpiece P to be welded.

As the welding phenomenon changes from the first type to the third type, the period of fluctuation of the welding point becomes longer and the amplitude of the fluctuation (movement distance) also becomes longer.

For reference, to give a specific example, in each of the welding phenomena shown in Fig. 1 a - c, the welding point W is less than 3 m sec in the first type welding phenomenon in a, and 3 m sec in the second type welding phenomenon in b.
5eC to less than 25m5eC, 2 for type 3 welding phenomenon of C
The fluctuations are repeated approximately periodically in an extremely short period of about 5 m sec to 1000 m sec.

Furthermore, such periodic fluctuations still occur even if welding conditions such as welding heat input and welding speed are set constant and there is no vibration due to roll eccentricity, etc. This is a basic phenomenon of welding.

It was also concluded that the above-mentioned fluctuation in the welding point W is the main factor that affects the color of the weld, the shape of the weld bead, and even the instability of the quality of the weld.

Incidentally, the positional fluctuation of the welding point W is a periodic fluctuation of the welding current circuit shape formed by X→V→W→V→Y in the workpiece P shown in FIG.

From an electrical circuit perspective, this is nothing but periodic fluctuations in load impedance.

In general, high-frequency electric resistance welding machines use a self-oscillation method, so due to periodic fluctuations in load impedance,
The oscillation frequency, the high frequency voltage, and the phase difference of the current always change periodically.

Furthermore, since the relationship between frequency and period is period=1/frequency, the high frequency oscillation period (hereinafter simply referred to as "oscillation period") also undergoes similar periodic fluctuations.

That is, by measuring one of the three welding characteristics (hereinafter referred to as "high-frequency welding characteristics") consisting of the period, frequency, or phase difference, it is possible to detect fluctuations in the welding current circuit shape, and therefore, The type of welding phenomenon can be accurately known.

In other words, the welding phenomenon changes from type 1 to type 3.

As the welding point increases, the fluctuation amplitude (traveling distance) of the welding point becomes longer, but the fluctuation amplitude of the oscillation period, that is, the dispersion, increases accordingly.

The present invention has been made based on the above findings, and its purpose is to provide a method for quantifying welding phenomena, and to obtain a weld bead with a uniform quality and a good external shape. That is.

The gist is a welding electrical characteristic measuring device that measures any one of the oscillation period, oscillation frequency, or phase difference of the voltage or current of a welding current circuit that high-frequency welds the ends of metal plates, and a time series from this device. This is a high-frequency electric resistance welding phenomenon monitoring device that includes a welding electrical characteristic variation calculation device that calculates the variation in welding electrical measurement signals sent to the machine over a certain period of time and obtains a welding phenomenon quantification value.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention.

1 is a welding electrical characteristic measuring device.

The welding electrical characteristic measuring device 1 measures either the voltage or current oscillation period, the oscillation frequency, or the phase difference between the voltage and current of a welding current circuit that high-frequency welds the ends of metal plates 2. be.

FIG. 3 shows an example of the welding electrical characteristic measuring device 1 for determining the oscillation period T and the oscillation frequency F.

Preset counter A counts the number of peaks in voltage V or current I, and resets itself when the number reaches a, and also provides a reset signal to integration counter B.

The integration counter B receives the reference signal (frequency f) from the time when the preset counter A starts counting.

), outputs the count number at the time the reset signal is sent from preset counter A, and resets itself.

The reference frequency oscillator C has a constant frequency f.

oscillates a signal.

Therefore, the oscillation period T is taken as the output, and the oscillation frequency f
When you want to extract Δ, converter E converts Δ into seconds (for example, 2 m
sec).

3 is a welding electrical property variation calculation device that calculates the welding electrical property measurement signals of any one of the oscillation period, oscillation frequency, and phase difference between voltage and current sent in time series from the welding electrical property measuring device 1 at regular intervals. This method calculates the variation and obtains a numerical value that quantifies the welding phenomenon.

The calculation of the variation is performed at a fixed time interval tc seconds (for example, 30
0m5ec) every m (for example, 15
The purpose is to find the dispersion of the n (for example, 75) measured values within the most recent fixed time tb seconds (for example, 159 m5 ec) among the measured values of 0).When using the standard deviation as the amount to find the dispersion, use the following formula. Calculate by

However, it is assumed that Xi: oscillation period measurement value and Δ are given as a time series signal every second.

i=1.2.3,...X: Average value, calculated every tc seconds.

Y: Standard deviation, calculated every tc seconds.

n: Number of measured values for variation calculation (n = tb/Δt)
.

In addition, the deviation (Xi
-X) or the difference (range) between the maximum and minimum values of the n measured values may be used.

The welding phenomenon quantification numerical value increases as the welding phenomenon changes from the first type to the third type.

The present invention configured as described above is capable of measuring the oscillation period, oscillation frequency, or phase difference between the voltage or current of the welding current circuit that performs high-frequency welding at the end of the metal plate 2 using the welding electrical characteristic measuring device 1. and transmits the welding electrical measurement signal to the welding electrical characteristic variation calculation device 3.

The welding electrical property variation calculation device 3 calculates the variation of welding electrical property measurement signals sent in time series at regular time intervals.

The welding phenomenon is monitored using the values calculated in this way, and the welding phenomenon is further quantified into continuous values based on the calculated values.

By setting the quantified value of this welding phenomenon to a predetermined value commensurate with the welding phenomenon to be achieved, the quality of the welded part is the same even if there are slight changes in the dimensions, material, etc. of the workpiece during welding. are obtained continuously.

4 is a low frequency removal filter, which is provided as necessary.

The low frequency removal filter 4 is placed between the welding electrical property measuring device 1 and the welding electrical property variation calculating device 3, and reduces the number of digits of numerical values handled by removing the DC component from the welding electrical property measurement signal, thereby calculating the variation. This is an attempt to simplify the .

Furthermore, if one is prepared to calculate a large number of digits of variation, the low frequency removal filter 4 is not necessary.

5 is a time setting device, which sets the variation calculation time width to the welding conditions (
If you want to change it depending on the speed, joint angle, etc.), you instruct the variation calculation device 3.

6 is a conversion calculation device.

The conversion calculation device converts welding phenomena into numerical values (welding phenomenon quantification numerical values) when the operator monitors or controls the display.
It is necessary to convert the information into the type of welding phenomenon using a conversion table or by mental calculation, but this is automatically done to reduce the burden on the operator, and is provided as necessary.

Further, 7 is a display/recording device, which is comprised of a device for displaying and recording welding phenomenon measurement values and other necessary signals.

The welding machine operator can know the type of welding phenomenon by looking at the displayed value, and if the welding phenomenon is not desired, he can monitor and control the welding phenomenon by adjusting the heat input amount or other operations. .

FIG. 4 is a graph showing the relationship between welding phenomenon quantification values and welding phenomena using the above method based on welding experiment data, and the horizontal axis is the type of welding phenomenon visually determined from photographs of welding points. There is a range from ■ to 3.

The vertical axis is the welding phenomenon quantification value obtained by the above method with a variation calculation time width of 150 msec.

In the welding experiment, the oscillation period of the welding secondary current was set to 2 msec.
The measurement was carried out at each time, and the variation was calculated using the method of calculating the standard deviation according to equations (1) and (2).

The plotted points in FIG. 4 are distributed around the one-dot chain line drawn in the center, suggesting that the welding phenomenon can be measured by obtaining the welding phenomenon quantification value on the vertical axis.

However, the measurement error is approximately ±0.5 on the horizontal axis.

As is clear from the above explanation, by using the device of the present invention, an operator can visually monitor the color of the weld, the appearance shape of the weld bead, etc., or qualitatively monitor it using a high-speed camera, high-speed video television, etc. Physical fatigue is reduced because the type of welding phenomenon can be determined by quantitatively monitoring display fluctuations or periodic fluctuation patterns without relying on physical observation.

Furthermore, by recording and storing welding characteristic values as data, it is effective for managing the quality of welded parts, etc.

Furthermore, the welding heat input, etc. can be adjusted manually or automatically in a short time without requiring special operator skill, and the rise time etc. at the initial stage of energization can be shortened, resulting in good work efficiency.

Furthermore, the welding phenomenon can be kept stable, thereby significantly improving the yield, and also significantly reducing problems such as flattening defects, UST defects, and water pressure defects during water pressure tests.

This dramatically improves the reliability of electric resistance welding, and is extremely valuable in contributing to the development of the industry.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a welding phenomenon, where a shows a first type welding phenomenon, b shows a second type welding phenomenon, and C shows a third type welding phenomenon. 2 and 3 are block diagrams showing the configuration of the apparatus of the present invention, and FIG. 4 is a graph showing the relationship between welding phenomenon quantification values and welding phenomena. 1: Welding electrical property measuring device, 2: Metal plate, 3: Welding electrical property variation calculation device.

Claims (1)

[Claims] 1. A welding electrical characteristic measuring device that measures any one of the oscillation period, oscillation frequency, or phase difference of the voltage or current of a welding current circuit for high-frequency welding the ends of metal plates, and a device that measures the voltage or current of a welding current circuit for high-frequency welding. 1. A high-frequency electric resistance welding phenomenon monitoring device comprising a welding electrical characteristic variation calculation device that calculates the variation of received welding electrical measurement signals at fixed time intervals and obtains a welding phenomenon quantification value.