JPS6133769A - Penetration welding method - Google Patents

Abstract

PURPOSE:To form automatically and stably satisfactory penetration beads with high efficiency by converting the fluctuation of welding current to a digital signal, measuring the fluctuation, comparing the value with the preset limit value and controlling welding speed. CONSTITUTION:The instantaneous value WI of the current under welding is read in WIread. The value WI is compared with the preset lower limit value WIth of the current amplitude and the number of times when the value WI is smaller than the value WIth within a specified period is counted (Count up N). The count value N and the preset occurrence frequency limit value NL are counted upon lapse of the specified time (time out). The welding speed is decreased when the value N is larger and the welding speed is increased conversely when the value is smaller.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses a non-conducting backing material on the back side of the groove in plate joint welding of steel plates to stabilize a good uranami bead in single-sided welding. Welding method k [? It is something to do.

[Conventional technology]

In addition to bridges A, plate joints for steel I are commonly used.

Because grooves such as V and

The applicant has conducted research on this point and has developed a method for stably and efficiently forming a good uranami bead by welding the tip of the ■-shaped C face with an inexpensive backing material.
The application was filed as No. 75.

In this method, several welding power sources are connected to the welding torch, the anode is connected to the workpiece, and shielding gas is ejected from the shielding gas nozzle that fits the welding parts 1 to 2 externally, and is installed behind the welding torch. Control gas is ejected from a control gas nozzle toward the molten oil wetting area to push the molten pool forward and form it in a concave shape.

[Problem that the invention seeks to solve]

In the method developed above, the total length of the weld line is approximately 20 mm.
When the welding time is 0 s or less, an extremely well-shaped uranami bead can be obtained over a wide range of welding conditions, but as the welding length becomes longer, it is difficult to obtain a uranami bead with a good shape due to the accuracy of the groove shape. I understand.

[Means for solving problems]

The present invention was made to solve the above-mentioned problems, and its feature is to convert the fluctuation of welding current during welding into a digital signal, measure it, and compare it with a preset threshold value (ThresholdValue). It is necessary to control the welding speed so that the welding current is appropriate.

〔Example〕

The present invention will be explained below based on FIGS. 1 to 8. 1 and 2 are diagrams for explaining the method of the present invention. FIG. 1 is a front sectional view seen from the front in the welding direction, and FIG.
FIG.

A wire 26 is supplied from a wire reel to the welding torch 40 via the wire oscillator 1 to the device 27 in a bent state by a supply roller 28 .

In order to isolate the arc 30 from the surrounding air during welding, a first nozzle 3 into which the welding 1-ch 40 is fitted, and a second nozzle 4 into which the first nozzle 3 is fitted are provided. A shielding material 18 such as asbestos is provided at the lower end of the nozzle 1 so as to come into contact with the workpiece 25 to be welded.

Further, a control nozzle 5 is provided in the gap between the first nozzle 3 and the second nozzle 4 so as to be located at the rear in the direction in which the welding torch 40 moves.

During welding, the workpiece 25 is spaced at an appropriate root interval (10
IIIl+! A backing material 32 made of glass or the like is inserted directly under the back surface of the groove with a stopper 33 made of copper. The welding torch 40 is connected to the negative side of the welding power source, and the object to be welded 25 is connected to the positive side of the welding power source in a so-called rod-shaped configuration.

During welding, shielding gas (30%^r+
At the same time, an inexpensive shielding gas (100% C02) is injected from the second nozzle 4 to isolate the arc 30 from the surrounding air.

Since the wire 26 is given a torsional rotation surface by the oscillation device 27, the tip of the wire is supplied while rotating, and the arc 30 rotates on the surface of the molten pool 31. A control gas (70%
＾r+3Q%Co2) is ejected.

As a result, the molten pool 31 is pushed forward J and the molten pool 31 is formed into a concave shape by the dynamic pressure of this gas.

Furthermore, since this control gas has a high Ar composition, it also plays a role in improving the condition of the arc 30.

When welding is performed in this manner, the arc 30 ignited within the welding tip is generated not only at the bottom of the groove but also distributed to the side walls, and furthermore, the wire 26 rotates on the surface of the molten pool 31. As a result, arc heat is dispersed, and since the arc heat does not concentrate directly under the groove, the backing material 32 is not melted out, and a good Uranami bead is formed.

Now, in this welding, welding current and welding voltage.

If the welding speed is constant and the groove width has good dimensional precision, an uranami bead can be formed very well, but due to the dynamic characteristics of the current and voltage during welding and fluctuations in the groove width, It is difficult to satisfy this requirement, and if the weld length is extremely long (more than 200 degrees), it is difficult to properly form the uranami bead.

Figure 3 shows a welding current of 450A, a voltage of 35V, and a wire diameter of 1.
6#, groove width 10INR, welding speed 2F3c
m/min, 32cm/min, 20Ci/1
This shows a welding current waveform when welding is performed with n.

As can be seen, the welding current constantly fluctuates during welding, and its amplitude increases as the welding speed increases. In that case, the welding result is 26mm when the welding speed is appropriate.
cm/1ain (in the case of Fig. 3(a)), a proper Uranami beat ub as shown in Fig. 4 (al) is formed, but
Fast welding speed of 32cIR/min (3rd city)>
In this case, the amount of welding is insufficient and the welding condition as shown in No. 4 Doichi is likely to occur.
(Fig. 3 (C)) shows that failure of molten G injection is likely to occur and the situation as shown in Fig. 4 (C) is likely to occur.
.

Therefore, in order to always form a proper Uranami bead, it is necessary to measure the fluctuations in the welding current during welding and increase or decrease the welding speed as appropriate so that the welding current becomes appropriate.

Next, control of this welding current will be explained with reference to FIGS. 5 and 6.

First, the instantaneous value Wl of the current during welding is read using WIread. This is done through the amplifier A-p as shown in Figure 6.
The data is digitized by a D converter and input to the computer CPU. This reading is performed every 25 to 100 microseconds, but since one amplitude of the welding current waveform is about 3 milliseconds, the culm is measured 30 to 120 times during one amplitude.

The instant 1ifiWI of the first lever is the lower limit IWIth of the current amplitude (threshold 1ii T threshold
Value) within a certain time (0,5 to 1
．． 5 seconds), count how many times the instantaneous value Wl is smaller than the lower limit value W I th (Count up
N).

After a certain period of time (time 01lt), the above 71
Compare the count value N with the preset frequency limit value N1, and if the count value N is large, reduce the welding speed, and conversely reduce the welding speed to 11.
If the numerical value N is small, increase the welding speed.

The output frequency limit value N[ is determined in relation to the lower limit value W I th, and an appropriate value is selected through experiments. Further, the increase or decrease in the welding speed can be appropriately selected in relation to a certain time period, but it is preferable to increase or decrease the welding speed by one command at about 1 cIR/sin.

In the above example, the darkness value was set as the lower limit of the current amplitude, but it may also be set as the upper limit of the current amplitude, or it may be set at the upper and lower limits as a so-called zone control [Cole method % formula % Figure 7 shows ■ Groove 10a * Welding current 360A to 380A
, shows the case where the welding speed is controlled by setting the lower limit value WItl+ of the welding current to 260Δ at a voltage of 33V to 34V, and Fig. 8 shows the case where welding is carried out under the same conditions as Fig. 7 at a constant welding speed of 20ca+/m1n. -b's.

When the welding speed was controlled, the welding current had a nearly constant waveform as shown in Figure 7, and the Uranami bead was also good, but when the welding speed was kept constant, the welding current fluctuated as shown in Figure 8. As a result, melting occurred.

Figure 9 shows the case where the groove width was temporarily increased from 9M to 12# under the same conditions as Figure 7, and welding was carried out while controlling the welding speed. 9Jll
This figure shows the case where welding is performed with the amount reduced to .

As can be seen from this, due to changes in the groove width, the waveform of the welding current is likely to be disturbed, the Z value is more frequently cut off, and the welding speed fluctuates rapidly.

In addition, in the first embodiment, the molten pool is pushed forward using a control gas in type 1 narrow gap gas shield metal welding, but the present invention is not limited to this. It can also be applied to V-shaped, single-shaped grooves, etc., and there is no need to use a control gas at the groove. Of course, it can also be used for submerged arc welding.

〔Effect of the invention〕

As explained above, according to the present invention, fluctuations in welding current during welding are converted into digital signals, measured, and compared with a preset threshold value to control the welding speed so that the welding current is appropriate. Therefore, even if the groove precision is poor, a good Uranami bead can be automatically and stably formed with high efficiency, making complete automation possible.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams for explaining the method of the present invention. Figure 1 is a front sectional view seen from the front in the welding direction, Figure 2 is a side view of Figure 1, and Figure 3 is a welding current. 450A, voltage 35
■, wire diameter 1.6m, groove width 10s+m, welding speed 26 car/1llin, 32cm/l
A graph showing the welding current and current waveform when welding at 1 inch and 20 cm/1 ain, Fig. 4 is an explanatory diagram showing the state of the back plate bead, Fig. 5 is a flow chart showing an embodiment of the method of the present invention, Fig. 6 is an explanatory diagram of the data input section, Fig. 7 is an explanatory diagram showing the welding state when the welding speed is controlled, Fig. 8 is an explanatory diagram of the welding state when the welding speed is kept constant, FIG. 9 is an explanatory diagram showing a case in which welding is performed while controlling the welding speed by increasing the development width by 1-12 times, and FIG. 10 is an explanatory diagram showing a case in which welding is performed by decreasing the groove width. 3...First nozzle 4...Second nozzle 5...
・Control nozzle 18... Shield material 25...
Object to be welded 26... Wire 27... Wire A7
Oscillating device 28... Supply roller 30...
・Arc 31... Molten pool 32... Backing material 33.
...Welding torch ub...Uranami bead A11)...Amplifier A/D...Converter C
PU...computer

Claims (1)

[Claims] 1. In plate joint welding in which an electrically nonconducting backing material is provided on the back side of the groove and one side is welded to form a back wave, the fluctuations in the welding current during welding are converted into digital signals and measured, and this is set in advance. The Uranami welding method is characterized in that the welding speed is controlled so that the welding current is appropriate in comparison with a threshold value.