JPH04187380A - Keyhole type one-side welding method - Google Patents

Abstract

PURPOSE:To perform high efficiency one-side welding at high speed by calculating an arc length at a rear point of the rotating position of an arc by detected values of the arc voltage and a welding current at the point and controlling the welding current so that the obtained arc length becomes equal to a set value. CONSTITUTION:When one-side welding is performed while forming a keyhole 8, the arc 3 rotates at high spied in front of a molten pool 7. A vibrational phenomenon to vibrate to the molten pool side is shown at the rear point Cr of the rotating position of the arc. When a root gap (a) is small or the root face (b) is large, the arc length at the Cr point becomes short and the back bead width is reduced. Since the arc length becomes short, the welding current at the Cr point increases and the arc voltage decreases. Accordingly, a state of a back bead can be detected by detecting the arc voltage and the welding current I at the Cr point. Consequently, it is not necessary to provide a special sensor and high efficiency one-side welding can be realized at high speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a keyhole type single-sided welding method using a high-speed rotating arc welding method, and more specifically to a back bead shape that is about to change due to fluctuations in the groove condition. The present invention relates to a keyhole type single-sided welding method in which stable control is performed based on information from an arc sensor, that is, welding current and arc voltage.

[Prior Art] In the conventional arc welding method in which single-sided welding is performed while forming a keyhole directly under the arc, a backing method is generally used to control the back bead shape, and the backing material is also A method is used to control welding conditions such as welding current, arc voltage, welding speed, etc. by installing an optical sensor to detect the welding process.
No. 787). Alternatively, if such a sensor is not provided, there is also a method of determining a correlation between the arc voltage or welding current and the width of the back bead in advance, and controlling the width of the back bead based on this correlation. (Unexamined Japanese Patent Publication No. 61-13
No. 7676, JP-A-61-180677).

[Issue 8 to be solved by the invention] However, the control method using the optical sensor described above requires a backing device that moves the backing material and the optical sensor in synchronization with the welding torch, and such a backing device is complicated. , and its installation may be difficult.

On the other hand, in the method of controlling the back bead width from the correlation with the arc voltage or welding current, it is necessary to understand all the correlations depending on the welding conditions, groove shape, plate thickness, and other various conditions. It is difficult to determine the factors of variation in the groove condition (fluctuations in the groove condition, e.g., root gap and root face, which often occur in actual single-sided welding), and - when there are variations in the groove condition (variations in the groove condition, e.g. root gap and root face, often occur in actual single-sided welding), a stable back bead cannot be achieved. control of the shape becomes more difficult.

In general, it is necessary to keep the groove condition uniform in order to produce a good back bead, but in reality, the root gap and root face often change.

Therefore, the inventors of the present invention endeavored to develop a technique that allows the shape of the back bead to be controlled without using a special sensor even if there are fluctuations in the groove condition. As a result, it was found that the problem could be solved by further developing the technology disclosed in Japanese Patent Application Laid-Open No. 62-248571, which was filed by the present applicant. In other words, this patent publication describes a high-speed rotating arc welding method that uses the arc itself rotating at high speed as a sensor and performs groove tracing control using this arc sensor. It was found that the change in the arc length at the rear point C of the rotational position of the arc corresponds to the change in the back bead shape due to the change in the groove condition.

The present invention was made based on such knowledge, and
Keyhole type single-sided welding that achieves high-speed, highly efficient single-sided welding and allows stable control of the back bead shape regardless of fluctuating groove conditions based solely on arc sensor information without using a special sensor. The purpose is to provide a method.

[Means for Solving the Problems] In order to achieve the above object, the keyhole type single-sided welding method according to the present invention is an arc welding method in which single-sided welding is performed while forming a keyhole directly under the arc. The welding method is used, and the torch height (the sum of the wire protrusion length and the arc length) is kept constant using the known ACC control method (a method of controlling the torch height so that the welding current is constant). Meanwhile, the arc length at a point C rearward of the arc rotation position is calculated from the detected values of the arc voltage and welding current at the point C, and the welding current is controlled so that the obtained arc length is equal to the set value. That is.

In addition, as the detected values of the arc voltage and welding current at this point C, we will use the values obtained by integrating and averaging a predetermined phase angle φ around this point C, and furthermore, we will use the values obtained by integrating and averaging the arc voltage and welding current at point C. When changing the welding current so that becomes equal to the set value, the wire feeding speed is also changed so that the torch height (the sum of the wire protrusion length and the arc length) becomes constant, and at the same time the welded cross-sectional area remains constant. The welding speed is also changed so that

[Function] The function of the present invention will be explained with reference to FIGS. 1, 2, and 3. FIG. 1 is a cross-sectional side view showing the keyhole type single-sided welding method of the present invention, and FIGS. 2 and 3 are a plan view and a cross-sectional front view of FIG. 1, respectively.

In the figure, 1 is a welding torch, 2 is a welding wire, 3 is an arc, 4 and 5 are members to be welded, 6 is a groove, 7 is a molten pool, and 8
is the keyhole, 9 is the weld bead, and 10 is the back and one dot.

As shown in the figure, when single-sided welding is performed while forming the keyhole 8 using the high-speed rotating arc welding method, the arc 3 is always in front of the molten pool 7 and rotates at high speed. At the forward point Cr of rotation, the arc 3 swings toward the groove 6, as shown by the broken line, and at the rear point C, the arc 3 exhibits a vibration phenomenon in which it swings toward the molten pool 7. At this time, the shape of the back bead 10 is influenced by the condition of the groove 6 as described above, and the shape of the back bead 10 is affected by the size of the root gap a and the root face b.
The shape of changes. That is, variations in the condition of the groove 6 cause the molten pool 7 to narrow or widen the keyhole 8.

For example, if the root gap a is small or the root face b is large, the molten pool 7 advances in the direction of narrowing the keyhole 8, as shown by the broken line 11 in FIG. becomes shorter.

"Then, the arc length becomes smaller or no longer formed. As the arc length becomes shorter, the welding current at point C increases and the arc voltage decreases. Conversely, the root gap a If the root face b is large or the root face b is small, the molten pool 7 will conversely retreat in the direction of widening the keyhole 8, as shown by the broken line 12 in FIG. 1, resulting in a phenomenon opposite to the above.

Therefore, the state of the back bead can be detected by detecting the arc voltage E (voltage between the welding tip and the base metal) and the welding current I at point C.

Figure 4 shows the rotational position of the arc with respect to the welding direction (C,
Figure 5f shows the definitions of R, C, L).
The relationship between the rotational position of the arc and the arc voltage E due to variations in the groove condition is shown in the figure. In the figure, A indicates that the groove condition is appropriate, and B indicates that the root gap is small or the root face is large. Therefore, if the back bead is insufficient, C has a large root gap or a small root face, so the back bead is too large, exceeding 8. In other words, when the back bead is insufficient B compared to the proper state A, C The arc voltage E at point C decreases, and conversely, if the back bead becomes too large C, the arc voltage E at point C increases.

Next, in the control method of the present invention, the arc voltage E and welding current I at point C are first detected. However, in this case, in order to detect changes in the arc length, the ACC control method is used to increase the It is necessary to control the welding length (the sum of the wire protrusion length and the arc length) at a constant level.This is to avoid being affected by unevenness, waviness, etc. of the workpiece to be welded.Arc voltage E and welding current As shown in Fig. 4, the detection of I is integrated and averaged over a predetermined phase angle φ (in order to remove noise components).The phase angle φ is 5@ or more than 90''.
It is as follows. Next, calculate the arc length from these detected values, change the welding current so that the calculated value is equal to the set value, and furthermore, the torch height (the sum of the wire protrusion length and the arc length) becomes constant. The wire feeding speed is changed in this way, and at the same time, the welding speed is also changed so that the welded cross-sectional area becomes constant, that is, the ratio of the wire feeding speed to the welding speed becomes constant.

Further, the present invention can be implemented without using the conventional backing method. Note that since the purpose of the conventional arc sensor is groove tracing control, control is performed only based on information about the Cr point.

[Embodiment] FIG. 6 is a block diagram showing an embodiment of an apparatus for carrying out the keyhole type single-sided welding method of the present invention.

To rotate the arc 3 at the tip of the welding wire 2, there are an eccentric tip method (Japanese Patent Publication No. 63-39346) and an eccentric rotation mechanism method (Japanese Patent Publication No. 62-104684). Here, we will use the latter eccentric rotation method. It is shown in the mechanical formula. That is,
The upper part of the welding torch 1 is supported by a self-aligning ball bearing 21, and an eccentric rotation mechanism (gear mechanism) 22 is provided at the middle part via a self-aligning ball bearing (not shown). It rotates at high speed to perform motion. As a result, the tip of the welding wire 2 fed to the center of the welding torch 1 performs a circular motion, and the arc 3 rotates at high speed. - The rotational position of the welding wire 2 or the arc 3 (see FIG. 4) is detected by an encoder 24 attached to the motor 23.

A welding power source 25 is connected between the welding torch 1 and one of the members to be welded 4. Arc voltage E and welding current I of arc 3 are detected by arc voltage detector 26 and welding current detector 27, respectively, and differential amplifier 28.2, respectively.
The data is inputted to the CPU 30 via 9.

, 31 and 32 are an arc voltage reference value setter and a welding current reference value setter, respectively, and an arc voltage detector 26 and a differential amplifier 28 . The arc voltage and welding current waveform signals from the welding current detector 27 and the differential amplifier 29 and the rotational position signal from the encoder 24 are obtained, and the CPU 30
Groove tracing control 33 and AC using a well-known arc sensor
Torch height control 34 is performed using C control. The control circuit for this groove tracing and the torch height control circuit are not shown. However, here, in order to detect the change in the arc length at point C, in other words, it is necessary to control the height of the tip of the welding wire 2 to be constant due to the unevenness, waviness, etc. of the members 4 and 5 to be welded, so the ACC control method is used. The torch height is controlled to be constant.

Under such torch height control, when the rotational position signal from the encoder 24 is input to the CPU 30, '-Ee
The r integrator 35 and the lcr integrator 36 integrate the arc voltage and welding current waveform signals for each revolution of the arc 3 within a range of phase angle φ centered on point C, as shown in FIG. , integral value S of arc voltage, integral value S of welding current
seek.

ECr lcr And each average value of this integral value 5Eer ''' Ier, that is, E and I, is calculated by p calculation unit 3.
7, input cr cr cr, and solve the following 6 equations to obtain p.

Referring to Figure 7, E and! Detected value and er
The arc length g at point Cr can be calculated from the following equation using the wire feeding speed Vr detected by the control circuit 42.

C "E -V +V ... (1)
cr a L V L -a L I a -b v r / Ia
”' (2) V −V +X, Q
...(3) a o
crV 繻cI 10d river (4
)OCT X-el+f...(
5) Cr 2 ... (6) v r -g I a 10 h L I a where, V: Electric voltage drop between both ends at the protruding part of the welding wire ■a: Voltage drop of mini arc L: Wire protrusion Long ■ = Average value of welding current (value obtained by averaging the welding current detected by ammeter 27) vf: Wire feeding speed Determined experimentally depending on the type.

The arc length I obtained from the above 6 formulas is confusing. cro to the standard arc length p in the set proper state A The welding current I is changed so that it becomes equal.

That is, when g > g, g - cr
Decrease the welding current I until cro crp and ' crero
akuI
When , the melt becomes I -1.
er er.

Increase electrical connection work. Comparator 38 and p
A setting device 39 is provided. The output of the comparator rO 38 is fed back to the CPU 30 to control the welding current 1 (40), the wire feed speed v, (42), and the welding speed 1/(41). In 22, when changing the welding current I, the wire feeding speed Vr is also changed so that the wire protrusion length is constant in equation (6),
In addition, the welding current reference value in the torch height control (ACC) is used to always control the torch height to a constant value. Also, when changing the welding current I, welding cross-sectional area (
Welding speed V so that S-vr/v) is constant
Also change it.

[Effects of the Invention] As described above, according to the present invention, in keyhole type single-sided welding, the back bead shape can be controlled by the groove shape state.
This has been made possible by applying a high-speed rotating arc welding method and controlling the arc length at the rear point C of the arc rotation position to a constant value based only on information from the arc sensor. There is no need to provide one, and high-speed, high-efficiency single-sided welding can be achieved. In addition, the shape of the back bead according to the present invention is always properly adjusted to variations in the groove condition, so it is extremely stable and has many effects.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional side view showing the keyhole type single-sided welding method of the present invention, Figs. 2 and 3 are a plan view and a cross-sectional front view of Fig. 1, respectively, and Fig. 4 is rotation of the arc with respect to the welding direction. Fig. 5 is an arc voltage waveform diagram showing the relationship between the rotational position of the arc and the arc voltage due to variations in the groove condition, and Fig. 6 shows an example of the apparatus for carrying out the method of the present invention. The block diagram shown in FIG. 7 is an explanatory diagram used to calculate the arc length. 1... Welding torch 2... Welding wire 3... Arc 4.5... Part to be welded 6... Groove 7... Molten pool 8... Keyhole 9... Welding bead 10...Back bead 23...Motor 24...Encoder 26...Arc voltage detector 27...Welding current detector 28.29...Differential amplifier 30...CPU 35... E Integrator r 36...I Integrator r 37...p Arithmetic unit r 38...Comparator 39...g Setter rO Agent Patent attorney Muneharu Sasaki

Claims (4)

[Claims] (1) In the arc welding method that performs single-sided welding while forming a keyhole directly under the arc, a high-speed rotating arc welding method is used, and the torch height (sum of wire protrusion length and arc length) is kept constant using the ACC control method. At the same time, the arc length at the rear point C_r of the rotational position of the arc is calculated from the detected values of the arc voltage and welding current at the point C_r, and the arc length obtained is A keyhole single-sided welding method characterized by stably controlling the shape of the back bead by controlling the welding current so that the length is equal to a set value. (2) When calculating the arc length at the C_r point, use values obtained by integrating and averaging a predetermined phase angle φ around the C_r point as the detected values of the arc voltage and welding current at the C_r point. The keyhole type single-sided welding method according to claim 1. (3) When controlling the welding current so that the arc length at the point C_r obtained by calculation is equal to the set value, the torch height (sum of wire protrusion length and arc length) is kept constant. 3. The keyhole type single-sided welding method according to claim 1, wherein the wire feeding speed is also changed. (4) When changing the welding current so that the arc length at the C_r point becomes equal to a set value, the welding speed is also changed so that the welded cross-sectional area becomes constant. Keyhole single-sided welding method described.