JP2701656B2 - Back bead control method in single side welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a back bead in single-side welding for stably forming a back bead in high-speed rotary arc welding.

[0002]

2. Description of the Related Art A back bead control method for forming a stable back bead in single-side welding such as initial layer welding by arc welding is disclosed in, for example, Japanese Patent Application Laid-Open No. 64-15278. The outline of the back bead control method disclosed in the publication is shown in FIGS. In the figure, 1, 2,
Is a base material to be welded, for example with a narrow groove 3 for a weld joint. Reference numeral 4 denotes an insulating backing material such as a ceramic, which is provided with a groove 5 for forming a back bead, and a conductive material 6 such as an aluminum foil is adhered to the center of the groove surface. The insulating backing material 4 is adhered to the back surfaces of the base materials 1 and 2 so as to cover the lower part of the narrow groove 3. 7 is a conductive material 6
This is a voltmeter for detecting the voltage Vd between the first and second base materials 1 and 2. Reference numeral 10 denotes an electrode wire, 11 denotes an arc, 12 denotes a weld bead, 13 denotes a molten pool, 14 denotes a back bead, 18 denotes a welding torch, and includes an electrode nozzle 20 and an electrode tip 21.
This back bead control method uses an insulating backing material during the first layer welding of the narrow groove 3 by generating an arc 11 from the tip of the electrode wire 10 continuously fed in a shield gas atmosphere. Since the conductive material 6 on 4 contacts the arc 11 and generates a voltage Vd between the conductive material 6 and the base materials 1 and 2, the voltage Vd is detected by a voltmeter 7;
The width of the back bead 14 is to be controlled uniformly by controlling the welding parameters, for example, the welding speed, so that the detected voltage Vd coincides with a preset reference value. That is, the welding speed is increased if the detected voltage Vd is smaller than the reference value, and the welding speed is decreased if the detected voltage Vd is larger than the reference value. The conductive material 6 has such a property that it melts when it comes into contact with the arc 11 or the molten metal. Further, the reason why a ceramic material is used as the insulating backing material 4 is that the back bead is excellent in moldability, peelability from the back bead, and handleability.

The above voltage Vd is equal to the arc 11
There is a correlation with the relative distance 1 between the point of occurrence of and the tip position of the molten pool 13. That is, when the welding speed is low as shown in FIG.
Is generated, insufficient penetration occurs, and the arc heat is not sufficiently transmitted to the back side, so that the back bead 14 does not come out well. Further, since the arc 11 is not in contact with the conductive material 6, no signal of Vd is output. That is, Vd = 0. On the other hand, when the welding speed is too high as shown in FIG. 9 (c), the back bead 14 becomes too large or the back bead width becomes extremely large or small because the arc 11 precedes the tip of the molten pool 13. And Vd also increases. When the welding speed is appropriate, the arc 11 is generated near the tip of the molten pool 13 as shown in FIG.
Satisfactorily appears, and Vd shows a moderately clear value.

However, as shown in FIG. 10, the tip 15 of the molten pool 13 swings irregularly back and forth in the welding direction. Such rocking of the molten pool tip is also related to the material and state of the backing material 4, and the rocking state fluctuates irregularly due to the wettability of the molten steel to the backing material 4. As shown in FIG. 9 (b), the position of the arc at which a good back bead is obtained is determined by melting pool 1.
3, the arc length is largely changed by a slight swing of the molten pool tip even if the welding speed is appropriate. When the torch height is controlled in this state (controlling the height of the welding torch 18 from the back surface of the base material so that the welding current is constant), the welding torch 18 often moves up and down, and an arc is generated. Because of instability, it was customary not to control the torch height during the first layer welding where the back bead was formed.

[0005]

As described above, in the conventional back bead control method, the arc becomes unstable under the control of the torch height because the tip of the molten pool oscillates. It was difficult. If the base material and backing material are flat, back bead control is possible without controlling the torch height, but in practice the base material is often curved or inclined, so the first layer Torch height control is often required from the time of welding. Further, since the conventional back bead control method detects the voltage Vd between the conductive material of the insulating backing material and the base material generated by contact with the arc as described above, and controls the welding speed. In addition to the need for a special backing material with aluminum foil, etc., the aluminum foil may be melted by sputtering, or the aluminum foil may peel off and come into contact with the base material. A voltage signal cannot be obtained. In addition, there is a problem that it is difficult to handle the backing material because the aluminum foil needs to be insulated. On the other hand, a general backing method, for example, a back bead control method using a backing metal such as a flux and a copper plate is known (Japanese Patent Application Laid-Open No. Sho 64).
-15280 and JP-A-61-180677) show that the voltage Vd between the backing metal and the base material during welding is also reduced by these control methods.
Since the voltage Vd is not generated unless the arc reliably reaches the backing metal, the present invention can be applied only to a method in which a back bead is formed by keyhole welding. In the end, whatever the backing material, the method of detecting the voltage Vd between the base material and the base material as described above has poor controllability and cannot sufficiently cope with a change in groove accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to obtain a simple and controllable back bead control method using a normal backing method and a high-speed rotating arc welding method. With the goal.

[0007]

In order to achieve the above object, a method for controlling a back bead in single-sided welding according to the present invention comprises applying a backing material to a back side of a base material and rotating a high-speed rotating arc from a front side of the base material. In the method of forming a back bead by welding on one side by welding, if the torch height control is necessary, the integral value Scr of the arc voltage or welding current at the arc rotation position Cr at the rear of the welding progress direction is made constant. In addition to controlling the torch height, the torch height at that time is detected, and the welding speed is controlled so that the torch height is kept constant. On the other hand, when the torch height control is unnecessary, the torch height is kept constant, and the welding speed is adjusted so that the integrated value Scr of the arc voltage or welding current at the arc rotation position Cr behind the welding progress direction is constant. Is controlled.

[0008]

[Function] Since high-speed rotating arc welding is performed while rotating the arc, even if the center position of the rotating arc is near the tip of the molten pool where a good back bead is obtained, the above-mentioned Cr point is higher than that of the molten pool tip. Since it is located rearward, the arc at the point Cr is always on the molten pool irrespective of the swing of the molten pool tip, and the arc length at the Cr point changes due to the swing of the molten pool tip. Therefore, the arc voltage or the welding current at the point Cr changes due to the change in the arc length. The arc voltage is integrated, and the torch height is constantly controlled so that the integrated value Scr is constant. If controlled, the back bead can be controlled without the arc becoming unstable. When it is not necessary to control the torch height, it is only necessary to control the welding speed so that the arc voltage at the Cr point or the integrated value Scr of the welding current becomes constant while keeping the torch height constant. Is fine. Since the control uses the arc voltage or the welding current at the Cr point as described above, an ordinary backing method may be used.

[0009]

FIG. 1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is a front sectional view of a first layer welded portion, and FIG. 3 is a plan view thereof. The same components as those in the conventional example shown in FIGS. In this embodiment, an ordinary backing material 4 is adhered to the back sides of the base materials 1 and 2. As the backing material 4, for example, an insulating material such as ceramics, a combination of a backing tape such as a glass tape and a backing metal, a combination of a flux and a backing metal, or a solid backing method such as a solid backing method. It may be used in. Such a normal backing material 4 is brought into close contact with, for example, the lower part of the narrow groove 3. Reference numeral 5 denotes a back bead forming groove provided on the backing material 4.

Next, welding is performed by a known high-speed rotating arc welding method. Here, the rotating arc welding method is a method of welding while giving a circular motion to the arc, and the method of rotating the arc is a method using an eccentric electrode tip 21 as shown in FIG. -39346),
There is a method of precessing the electrode nozzle 20 with the upper part as a fulcrum (Japanese Patent Laid-Open No. 62-104684), but any method may be used. The electrode nozzle 20 is rotated by a motor 22 via a gear mechanism 23 to rotate the arc 11 at a predetermined radius. The rotation speed of the arc 11 is 10H
z or more. Usually, it is about 50 Hz to 100 Hz.
The rotating diameter of the arc 11 can be changed in accordance with the groove width even during welding by changing the amount of eccentricity using, for example, a double eccentric ring (Japanese Patent Application No. 2-284478).
issue).

Under such high-speed rotating arc welding, groove tracking control and torch height control (arc length control) are generally performed by an arc sensor (Japanese Patent Laid-Open No. 57-91).
877). Here, the groove tracking control is a control method for correcting a displacement of the electrode wire 10 with respect to the center in the groove width direction (X axis), and detects an arc voltage or a welding current for each rotation of the arc. From these waveforms, a predetermined angle φ centered on the arc rotation position Cf point ahead of the welding progress direction.
And corrects the displacement of the electrode wire 10 so that the two integrated values coincide with each other.
For this reason, the electrode nozzle 20 is supported on the body via an X-axis feed mechanism (not shown). What is torch height control?
This is a control method in which the torch height (Y axis), that is, the sum of the wire protrusion length and the arc length is kept constant, and a predetermined area of the welding current is integrated around the Cf point for each rotation of the arc,
The torch height is controlled so that the integrated value matches the reference value. For this reason, the electrode nozzle 20 is supported via a Y-axis feed mechanism (not shown). In FIG. 1, 24 is a feed roller for the electrode wire 10, 25 is an encoder for detecting the arc rotation position (Cf, R, Cr, L), 26 is a welding power source, and 27 is an arc voltage. Is an ammeter for detecting the welding current, and 29 is a torch height detector such as a potentiometer for detecting the torch height h.

When high-speed rotary arc welding is performed under the groove tracking control and the torch height control using the arc sensor as described above, FIG. Thus, regardless of the swing of the tip 15 of the molten pool 13, the arc 11 at the Cr point always
Above, the arc length changes due to the swing of the molten pool tip 15. For example, even when the welding speed v is proper, if the molten pool tip 15 retreats from the proper position P to the position P1, the arc length at the point Cr at that time becomes longer, so that the arc voltage at the point Cr becomes large. The welding current is small. Conversely, if the molten pool tip 15 advances to the position P2, the arc length at the point Cr becomes shorter, the arc voltage at the point Cr becomes smaller, and the welding current becomes larger. The present invention intends to control the back bead 14 by utilizing the fact that the arc voltage or the welding current at the Cr point changes due to the swing of the molten pool tip 15, as described above.

FIG. 4 shows an integration region of the arc voltage or the welding current at the point Cr, and integrates the area of the arc voltage or the welding current at a predetermined angle θ at the point Cr. This integral value is defined as Scr. Is not more than 180 °, preferably 0 ° <θ ≦ 90 °. The arc voltage or welding current may use data obtained during high-speed rotating arc welding. FIG. 4 also shows an arc voltage or welding current integration region centered on the Cf point during the groove tracing control.

FIG. 5 is a block diagram showing an embodiment of the back bead control system according to the present invention, in which the torch height is controlled by using a welding current at the point Cr. The same applies to the case of arc voltage. The welding current is detected by the ammeter 28 for each rotation of the arc, or the arc voltage is detected by the voltmeter 27. These detection signals are output to the low-pass filter 3
The noise is removed through 0 and sent to the respective Scr integrators 31 to determine the value of Scr. Further, the comparator 32 compares the Scr from the integrator 31 with the reference value S0 from the setting unit 33, and drives the Y-axis feed mechanism 34 so that the difference becomes zero, so that the difference from the back of the base materials 1 and 2 Control the torch height.
At this time, the torch height h, that is, the torch height h1 at point P1 or the torch height h2 at point P2 due to the oscillation of the molten pool tip 15 is detected by the torch height detector 29, and the comparator 35 sets the setting device 36. Compared to the standard torch height h0,
The welding speed control device 37 of the welding machine truck 38 is controlled so that the difference becomes zero. That is, if the detected torch height h is larger than the reference value h0, the welding speed v is increased, and if the detected torch height h is smaller than the reference value h0, the welding speed v is decreased.
By controlling the welding speed corresponding to the swing of the molten pool tip 15, the back bead 14 can be formed favorably.

Next, the flatness and the like of the base material are well exhibited.
When the torch height control is not required, welding is performed with the torch height kept constant at the reference value h0 from the beginning. In this case, it is only necessary to control the welding speed v so that the integral value Scr at the Cr point becomes constant.

[0016]

The present invention has the following effects because it has been configured as described above. (1) Since the arc voltage or welding current at the point Cr behind the arc rotation position is detected, the arc is less affected by the swing of the tip of the molten pool and the controllability is good. Therefore, stable control of the torch height is possible for any shape of base material or groove, and the back bead can be formed favorably. (2) Since a normal backing material can be used, there is no trouble as in the conventional method, and the backing is simple. (3) Since data obtained at the time of high-speed rotation arc welding can be used, the control system becomes the same system and can be simplified.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

FIG. 2 is a front sectional view of a first-layer welded portion.

FIG. 3 is a plan view of a first-layer welded portion.

FIG. 4 is an explanatory diagram showing an integration area at a point Cr behind the arc rotation position.

FIG. 5 is a block diagram of a back bead control system of the present invention.

FIG. 6 is an explanatory diagram showing a conventional back bead control method.

FIG. 7 is a front sectional view of a conventional first-layer welded portion.

FIG. 8 is a plan view of a conventional first-layer welded portion.

FIG. 9 is an explanatory diagram showing a relative positional relationship between an arc and a molten pool in a conventional method.

FIG. 10 is an explanatory diagram showing that the arc length changes due to the swing of the molten pool tip.

[Explanation of symbols]

 Reference numerals 1 and 2 Base material 3 Narrow groove 4 Backing material 10 Electrode wire 11 Arc 12 Weld bead 13 Weld pool 14 Back bead 15 Weld pool tip 18 Welding torch 20 Electrode nozzle 21 Electrode tip 22 Motor 23 Gear mechanism 24 Feeding roller 25 Encoder 26 Welding power supply 27 Voltmeter 28 Ammeter 29 Torch height detector 30 Low pass filter 31 Scr integrator 32 Comparator 33 S0 setting unit 34 Y axis feed mechanism 35 Comparator 36 h0 setting device 37 Welding speed control device 38 Welding machine Cart

Claims (2)

(57) [Claims] 1. A backing method is applied to a back side of a base material, and one side is welded from a front side of the base material by high-speed rotating arc welding.
In the method of forming the back bead, when it is necessary to control the torch height, the torch height is adjusted so that the integral value Scr of the arc voltage or welding current at the arc rotation position Cr behind the welding progress direction is constant. A method of controlling a back bead in single-sided welding, comprising controlling and detecting a torch height at that time, and controlling a welding speed so that the torch height is constant. 2. Using a backing method on the back side of the base material, performing one-side welding from the front side of the base material by high-speed rotating arc welding,
In the method of forming the back bead, when it is not necessary to control the torch height, the torch height is kept constant, and the integrated value of the arc voltage or welding current at the arc rotation position Cr behind the welding progress direction. S
A method for controlling a back bead in single-sided welding, wherein the welding speed is controlled so that cr is constant.