JPS59202179A - Automatic arc welding method - Google Patents

Abstract

PURPOSE:To maintain always a torch angle in an optimum reference condition by oscillating an arc forward of a welding direction and turning a torch in such a way that the difference between the arc voltage during oscillation and the arc voltage during non-oscillation is made equal to a reference value. CONSTITUTION:The arc voltage waveform passed through a low-pass filter 12 and the arc voltage during non-oscillation are inputted to a differential amplifier 16 and the pulse-shaped arc voltage waveform only during the oscillation period is inputted to an integrator 17. The integrator 17 calculates the area of the pulse waveform which is stored in storage devices 18, 19. If a torch angle theta is not equal to the initial reference value, the output S from the device 18 attains the value different from a reference value S0 and the torch is corrected and driven to the reference torch angle by a torch angle correcting motor (theta motor) 21.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic arc welding method for a weld joint line that changes in a curved or curved manner.

The angle of the welding torch to the joint line directly affects the weld bead shape and is generally kept close to 90'. However, as shown in Figure 1 (a) and (b), it is difficult to automatically and continuously perform fillet welding or butt welding of corrugated members in which the joint line (1) changes in a bending manner. It is necessary to detect the inclination of the joint line (1) with some kind of detector and correct the angle of the welding torch (2) to a predetermined value, but no suitable detector has been developed, and for this reason, There were cases where welding had to be interrupted during welding.

The present invention was invented in view of this situation, and the weld joint line is not straight and there is a
The object of the present invention is to provide an automatic arc welding method that allows continuous and good welding to be maintained without interrupting welding when the welding changes in a bending or curved manner. .

The feature of the present invention is that the welding arc is periodically oscillated in the welding direction by placing the upper button on the welding joint line, and the inclination of the welding joint line in the welding direction is detected from the change in the arc voltage waveform. This is an automatic arc welding method that automatically controls the axis of the torch to always maintain a constant angle with respect to the weld joint line and to maintain a constant arc length. It can be widely applied not only to TIG welding in which the electrode is not consumed, but also to so-called consumable electrode type arc welding such as MIG welding, carbon dioxide gas arc welding, and submerged arc welding in which the wire is fed at a constant speed.

In the present invention, since the voltage waveform of the welding arc, that is, the arc characteristics, is used as a sensor for detecting the inclination of the weld joint line, the inclination at the arc generation point can be detected in real time, and the weld joint line itself can be detected. This method is not affected by the condition of the material surface and has excellent control responsiveness and stability.

Embodiments according to the present invention will be described below with reference to the drawings.

In the present invention, the arc must be oscillated periodically and with the same amplitude in order to detect the inclination of the weld joint line. The arc oscillation method is basically as shown in Figure 2 (a) and (
(b) Two letters can be cited. The figure (a) shows the torch (2
) itself parallel to the basic axis (3) and forward (W
, D) Mechanically oscillated, the same figure (B) shows the torch (2)
This is a method of deflecting the arc (4) forward without moving the arc.This can be done by applying an electromagnetic field or spraying a fluid such as shielding gas.Many examples of these methods have already been published. Well, it's not particularly new.

In Fig. 2, the amplitude of the welding oscillation, to is the arc length at the reference axis (3) of the torch, tp is the arc length at the time of oscillation, and the distance between the weld joint line (1) and the reference axis (3) is Set the intersection to 0
The point of intersection with the center axis of the arc during swinging is defined as point P, and this definition will be followed hereinafter.

The period and time of arc oscillation are determined in relation to the welding speed at that time in order to quickly detect the inclination of the joint line. For example, when the welding speed is 3001t/-, the joint line 1a
In order to detect at + pitch, the oscillation period needs to be 0.2 seconds or less and the frequency needs to be 5 Hz or more. In addition, the swing time of the arc (4) in one cycle (state of point P in Figure 2) must be selected so as not to damage the welding shape and bead shape. ), the swing time must be shortened to about 1/10 of one cycle. FIG. 3 shows the relationship between the arc swing period T, swing time t, and amplitude W, and these terms are defined as shown.

As is well known, the relationship between the arc voltage Va and the arc length t is a linear relationship as shown in FIG.

Therefore, as shown in Fig. 2, when the weld joint line (1) and the direction of welding progress are parallel, the arc voltage waveform caused by the fluctuation will be as shown in Fig. 5, voltage waveform / (43i (b)). .

The voltage waveforms (a) and (b) in Figure 5 are respectively similar to those in Figure 2 (
b) It corresponds to 1. Chivalry). Voltage waveform in Figure 5 (A)
In the case of , the arc length does not change, so the arc voltage becomes a constant value Vao, and the voltage waveform (in the case of →, the arc length increases from to to Lp during the swing time t, so the arc length increases only during the Kt period as shown in the figure) A pulsed voltage waveform Vap is obtained.

Next, voltage waveforms (a) and (b) in FIG. 6 show a case where the weld joint line (1) and the welding direction (W, D) are not parallel. The voltage waveforms (a) and (b) in the same figure correspond to (6) and (b) according to the arc swinging method in FIG. 2, and for simplicity, only the axis of the arc is shown. In the voltage waveforms (a), ←) of Fig. 6, if the arc length at the reference axis of the torch (2) is to, which is the same as in Fig. 2, then the arc length during swinging is t;, t; h' are each shorter than in the case of Fig. 2 due to the influence of the slope of the joint line.

Therefore, the arc voltage waveform accompanying the fluctuation in this case is
The voltage waveforms (a) and (b) in FIG. 7 will be obtained.

At this time, the difference between the arc voltage during oscillation and the arc voltage at the torch reference axis is vapl-V in the case of voltage waveform (A).
ao' ((0), vap for voltage waveform (b))
-Va.

(<ΔV), and the voltage difference (0 in (6), (
When (b), △VO) becomes smaller.

Therefore, if this voltage difference is (6), 0. In case (b), when the welding torch (2) is rotated from A to B as shown in Fig. 8 (a) and (b) so that △VOK is equal, the arc due to the torch swing The voltage waveforms are
As shown in the voltage waveforms (a) and (b) of FIG. 5, the angle φ between the torch axis and the weld joint line (1) can be automatically returned to the reference state shown in FIG. 2. In this case, the torch (2
) is rotated to the reference state, as a matter of course, equal to the inclination angle of the joint line (1) with respect to the welding direction (W, D).

As described above, the arc is periodically oscillated forward in the welding direction with the same amplitude, and the difference between the arc voltage Vap during oscillation and the arc voltage vaO during non-oscillation, that is, at the torch reference axis, is constantly measured. By rotating the welding torch (2) so that the difference is equal to a predetermined reference setting value, the torch angle (φ ) can always be maintained at an optimal reference state. In addition, in the embodiment, the arc voltage difference Vap-v
The cross-sectional area of the arc voltage waveform during oscillation, indicated by diagonal lines in Fig. 7, is calculated, and this value is used as the predetermined standard setting. It may also be controlled to be equal to the value SO, but in practice this method has better control stability since unnecessary noise components such as power supply ripple are superimposed on the arc voltage waveform. . Also, the above control is rocking! It is not necessary to perform the torch angle control every FrI+1 cycle, and when the oscillation frequency is high, the same torch angle control as above may be performed by calculating the average value over a plurality of oscillation cycles.

The method of controlling the torch angle in the present invention is based on the premise that the arc length on the torch reference axis is kept constant during the non-swinging period. Keeping the arc length constant is a basic prerequisite for welding, apart from torch angle control, in order to obtain good welding results.

Next, a method of controlling the arc length in an inclined joint line according to the present invention will be explained using FIGS. 9 and 10.

FIG. 9 shows the case where the arc is swung in a deflective manner in the inclined weld joint line (1). welding torch (
2) moves in the welding progress direction (W, D) from the position (2-1) and reaches the position (2-2), the arc voltage waveform due to the swinging of the arc changes as shown in Fig. 10 ( 2-1) to (
2-2). In other words, the arc voltage decreases overall due to the influence of the slope of the weld joint line (1), and looking at the value when the arc is not swinging, the arc voltage decreases from arc length to to t'
The arc voltage decreases from VaO to VaO'. Therefore, the arc voltage difference VaO-・
If Vao' (-ΔVO) is calculated and the welding torch is moved by Δt in the axial direction (Y-axis in Figure 9) so that this value becomes zero, the state (2-3) will be reached and the arc The voltage returns to the original (2-1) state. In this case, the direction of movement of the torch (Y-axis) is not limited to the direction of the torch axis shown in FIG. 9, and may be a direction having an arbitrary angle thereto.

As mentioned above, in the torch angle control method of the present invention, it is assumed that the arc length is kept constant when not swinging, so in actual control, the arc length control shown in Fig. 9 is performed. , After confirming that the arc voltage difference △VO in the non-oscillating state has become zero, select the order to perform the torch angle control operations shown in Fig. 8 (a) and (b). Stable control results without malfunction can be obtained.

Next, an example of one control circuit will be explained with reference to FIG.

The control circuit of FIG. 11 uses the area (S) of the arc voltage waveform at the time of oscillation in FIG. 7 to control the torch angle (θ).
A method of calculating is adopted. FIG. 12 is a schematic diagram of a welding device driven by the control circuit.

The detected arc voltage waveform (Va 11) is filtered by a low-pass filter (2) to remove high-frequency noise such as power supply ripple superimposed on the waveform, and then first passed through a switch (S
l) After the arc voltage component only during the period when the shear arc is not oscillated passes through the smoothing circuit (to) and is averaged, it is inputted to the positive terminal of the differential amplifier Q4 as Vao. On the other hand, the switch (S2) is momentarily closed only during the first non-oscillation period in the main control operation, and remains open after storing the memory (c) K reference arc voltage (vaoo). Therefore, the movement of the torch height motor (Y motor, 15) driven by the output voltage of the differential amplifier α4 is controlled so that the arc voltage when not swinging is always equal to Vaoo. Tsumashi, welding cart (c) K in Fig. 12
The attached Y motor 06 is driven, and the welding torch (2
) in the Y-axis direction to keep its arc length constant.

Next, control of the torch angle (θ motor) will be explained. The arc voltage waveform that has passed through the low-pass filter (a) and the smoothed non-swinging arc voltage (vaoo
) is input to the differential amplifier 0, so that a pulsed arc voltage waveform only during the swing period is input to the integrator α force. Therefore, the integrator αη calculates the area of the pulse waveform (the area of the shaded part in FIG. 7). The operating period of the integrator αη is determined by a synchronous pulse generator that is connected to the oscillating device (A) and distinguishes between the oscillating period and the non-oscillating period of the arc.
The operation starts in the set pulse field that occurs when the oscillation starts,
The integrated voltage is reset to zero level by the set pulse (A) generated at the end of the swing.

The timing of this set and reset is not limited to one swing number, but is also performed for a plurality of swing numbers. The waveform area calculated by the integrator σ is stored in the memory (to) and (In).The memory (2) stores the first integrator output (So) applied to the switch (S3). remember,
hold this. The output of the memory (I→ is the integrator 07) is repeatedly corrected and stored. Therefore, if the torch angle (θ) is not equal to the initial reference value, the memory 0
The barrel output (S) is different from the standard value (So),
The torch angle is corrected and driven to a reference torch angle by a torch angle correction motor (θ motor, 21). The switch (S4) is designed to be closed only when the output of the differential amplifier 04 is at zero level, that is, when the arc length during non-swinging is the reference value. Operates only when the Y-motor) is stopped. In other words, after the arc length is controlled to be constant, the welding trolley (c) K attached θ motor Q]) in Fig. 12 is set so that the angle of the arc with respect to the weld joint line is 90°. 2) Move the other end along the arcuate rail 4 to control the angle (φ) of the torch (2). Further, according to the control method of the present invention, it is also possible to detect the end of the welding member and automatically terminate welding. That is, in FIG. 13(A), the welding torch (2) is placed at the welding end M (the end of the stiffener +811
), the arc voltage (Vap in FIG. 5, (b)) when the arc swings forward becomes abnormally high. Incidentally, in (Fig. 16, part c), the arc voltage is abnormally reduced due to the influence between the walls. Therefore, by using these logics, that is, abnormal change information, it is possible to automatically detect the end of a member.

As is clear from the above description, the automatic arc welding method according to the present invention enables excellent welding even when the weld joint line changes in a curved or curved manner.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are explanatory diagrams when the weld joint line is bent, Figures 2 (a) and (b) are explanatory diagrams of the arc oscillation force method in the present invention, and Figure 6 is the swing period of the arc T・
An explanatory diagram showing the relationship between swing time t and amplitude W, Figure 4 is a characteristic diagram showing the relationship between arc voltage (Va) and arc length (t), and Figure 5 is a weld joint line and welding direction. Explanatory diagram of the arc voltage waveform when and are not parallel, Figure 6 (a) and (b)
is an explanatory diagram when the weld joint line and the welding direction are not parallel, and FIG. 7 is an explanatory diagram of the arc voltage waveform in the case of FIG. 6.
8(a) and 8(b) are explanatory diagrams of the welding torch turning method, FIG. 9 is an explanatory diagram of the welding torch control method of the present invention, and FIG. 10 is an explanatory diagram of the arc voltage waveform in FIG. 9. , 1st
FIG. 1 is a control circuit for carrying out a method according to an embodiment of the present invention, FIG. 12 is a schematic diagram of a welding device driven by the control circuit of FIG. 11, and FIGS. 13 (a) and (b). FIG. 2 is an explanatory diagram for explaining a method of detecting the end of a welded member. (1)...Welding joint wire, (2)...Welding torch, (
3)... Reference axis, (4)... Arc. Agent Patent attorney Sanro Kimura Procedural amendment (voluntary) Commissioner of the Patent Office ao a 58□12n
2? 's1, Indication of the case Patent application No. 1987-760902, Title of the invention Automatic arc welding method 3, Person making the amendment Relationship to the case Patent applicant name (412) Nippon Kokan Co., Ltd. 4, Agent 6, Contents of Supplement 1F in Column 7 of “Claims” of the specification subject to amendment (Amendment) (1) While swinging the welding arc in the direction of welding progress, the arc voltage waveform ( Va) is detected, and the difference △■ between the peak value of the arc voltage ffap) during the period in which the arc is oscillated and the arc voltage (dog 0) during the most recent period in which the arc is oscillated is calculated as 1 of the oscillation. The welding torch is rotated so that △V becomes equal to a predetermined standard setting value, and the angle between the welding torch and the welding joint line is automatically controlled so that it is always constant. (2) The arc voltage waveform (Va) is detected while the welding arc is oscillated in the welding progress direction, and the arc voltage (Vao) during the period when the arc is not oscillated is determined in advance. The welding torch is moved in the height direction so that the values are equal to the standard set value, and the distance between the electrode tip and the weld joint line is automatically controlled to be constant, and the arc voltage during the period when the arc is oscillated. The difference △V between the peak value (Vao) and the arc voltage (Vao) during the period when the arc is not oscillated is determined in one period or multiple periods of oscillation, and △■ is equal to the predetermined reference setting value. An automatic arc welding method characterized by automatically controlling the welding torch so that the angle between the welding torch and the weld joint line is always constant. (3) Detect the arc voltage waveform (Va) while swinging the welding arc in the welding progress direction, and determine the peak value (Vap) of the arc voltage during the period when the arc is swinging. Arc voltage (Vao) during the period when the arc is not oscillated
Find the difference △■ in one cycle or multiple cycles of oscillation,
The welding torch is rotated so that △V is equal to a predetermined reference setting value, and the angle between the welding torch and the weld joint line is automatically controlled so that it is always constant. Automatic arc welding method characterized by terminating welding. (4) Detect the arc voltage waveform (Va) while swinging the welding arc in the welding progress direction, and compare the arc voltage waveform during the swinging period with the arc voltage (Va) during the non-swinging period.
ao), determine the area of the waveform in one cycle or multiple cycles of oscillation by time integration, rotate the welding torch so that this value is equal to a predetermined reference setting value, and then perform the welding process with the welding torch. An automatic arc welding method characterized by automatic control so that the angle formed with the joint line is always constant. (5) Detect the arc voltage waveform (V a ) while swinging the welding arc in the welding progress direction, detect the arc voltage (Vao) during the period when the arc is not swinging, and check that this value is a predetermined value. The welding torch is moved in the height direction so that it is equal to the reference setting value, and the distance between the electrode tip and the weld joint line (arc length) is automatically controlled to be constant, and the arc is oscillated. The arc voltage waveform of the period is based on the arc voltage (Vao) of the non-oscillating period, and the area of the waveform is determined by time integration for one period or multiple periods of the oscillation, and this value is the predetermined reference setting value. An automatic arc welding method characterized by automatically controlling the welding torch so that the angle between the welding torch and the weld joint line is always constant. (6) Detect the arc voltage waveform (Va) while swinging the welding arc in the welding progress direction, and compare the arc voltage waveform during the swinging period with the arc voltage (Va) during the swinging period.
Based on o), determine the area of the waveform in one cycle or multiple cycles of oscillation by time integration, rotate the welding torch so that this value is equal to a predetermined reference setting value, and then perform the welding process with the welding torch. This is an automatic arc welding method that automatically controls the angle with the joint line to always be constant. 444

Claims (6)

[Claims] (1) While swinging the welding arc in the direction of welding progress,
Detects the arc voltage waveform (Va) and fluctuates the difference ΔV between the peak value of the arc voltage (Vap) during the period when the arc is oscillated and the arc voltage (Vao) during the period when the arc is not oscillated. The welding torch is rotated so that ΔV is equal to a predetermined reference setting value, and the angle between the welding torch and the weld joint line is automatically controlled so that it is always constant. Characteristic automatic arc welding method. (2) While swinging the welding arc in the direction of welding progress,
The arc voltage waveform (Va) is detected, and the welding torch is moved in the height direction so that the arc voltage (Va o ) during the period when the arc is not oscillated is equal to a predetermined reference setting value, and the electrode tip is The distance between the arc and the weld joint line is automatically controlled to be constant, and the peak value (vap) of the arc voltage during the period when one arc is oscillated, and the arc voltage during the period when the arc is not oscillated (Vao) ) difference △
Stop V in one or more cycles of oscillation, and rotate the welding torch so that △V becomes equal to the predetermined reference setting value, so that the angle between the welding torch and the weld joint line is always constant. An automatic arc welding method characterized by automatic control. (3) While swinging the welding arc in the direction of welding progress,
Detects the arc voltage waveform (Va) and fluctuates the difference ΔV between the peak value of the arc voltage (Vap) during the period when the arc is oscillated and the arc voltage (VaO) during the period when the arc is not oscillated. The welding torch is rotated so that ΔV is equal to a predetermined reference setting value, and the angle between the welding torch and the weld joint line is automatically controlled so that it is always constant. and an automatic arc welding method characterized by detecting the end of the welding member and terminating the welding by comparing the arc voltage difference ΔV with a reference value. (4) While swinging the welding arc in the direction of welding progress,
The arc voltage waveform (Va) is detected, and the area of the waveform is calculated by time integration based on the arc voltage waveform during the period when the arc is oscillating, with reference to the arc voltage (vaO) during the non-oscillating period. The welding torch is rotated so that this value is determined in one cycle or multiple cycles and becomes equal to a predetermined reference setting value, and automatic control is performed so that the angle between the welding torch and the weld joint line is always constant. Characteristic automatic arc welding method. (5) While tilting the welding arc in the direction of welding progress,
Detects the arc voltage waveform (Va), detects the arc voltage (Vao) during the period when the arc is not oscillating, and moves the welding torch in the height direction so that this value becomes equal to a predetermined reference setting value. Then, the distance between the electrode tip and the weld joint line (arc length) is automatically controlled to be constant, and the arc voltage waveform during the period when the arc is oscillating is changed to ), the area of the waveform is determined by time integration for one cycle or multiple cycles of oscillation, and the welding torch is rotated so that this value is equal to the predetermined reference setting value, and the welding torch and welding joint are An automatic arc welding method that automatically controls the angle between the wire and the wire to be always constant. (6) While swinging the welding arc in the direction of welding progress,
Detect the arc voltage waveform (Va), and convert the arc voltage waveform during the period in which the arc is oscillating to the arc voltage (Va) during the oscillation period.
vaO), the area of the waveform is calculated by time integration,
The welding torch is rotated so that this value is equal to a predetermined standard setting value, and the angle between the welding torch and the weld joint line is always constant. 1. An automatic arc welding method characterized in that the end of the welding member is detected and welding is completed by controlling the arc voltage waveform during the oscillation period and comparing the time integral value of the arc voltage waveform with a reference value.