JPS5832578A - Arc welding method - Google Patents

Abstract

PURPOSE:To obtain stable penetration beads even during position welding while copying the groove by the arc per se in multilayer weaving welding by copying the groove by interrupting the arc control in a sub-section around the detecting central position of each weaving thereby changing welding current. CONSTITUTION:The position of a torch 2 in the groove width (X-axis) direction of base materials 1 for welding is detected with a meter 23, and is operated in a circuit 26 including analog memories 24, 25 which store right and left end positions Xl, Xr at every inversion of weaving. Said position is converted to the central position (Xl+Xr)/2 signal of every half period of weaving and is superposed with the position signal in the X-axis direction of each half period by a comparator 27. The position signal in the X-axis in every half period normalized by P'11 in the central position of the preceeding half period respectively before the previous one, for example, between the points D1-A2 is produced in the output of the circuit 27. Here, with the zero point P'11 as a center, peak current IP is flowed only in the specified sub-section DELTAX, and the control for arc length is interrupted.

Description

[Detailed Description of the Invention] The present invention relates to an arc welding method in which multi-layer weaving welding is performed by tracing the groove by the arc itself, and in particular relates to improvements to the first layer welding in order to obtain a stable and good Uranami bead shape even during posture welding. It is something.

Bevel Iil changes every moment during welding! Since the torch position is automatically detected and tracing is controlled in response to two-dimensional deviations in °C, welding is performed by groove tracing using the arc itself, without the need for a separate sensor such as a contact or non-contact type. The arc welding method used is known, for example, from Japanese Unexamined Patent Publication No. 19445/1983. The method disclosed in this publication provides a torch movement mechanism that compensates arc characteristics for changes in wire protrusion length or arc length in consumable electrode arc welding and non-consumable electrode arc welding with a constant wire feeding speed. In addition, a DC power source is used as the welding power source, and in the case of a non-consumable electrode, the entire torch is controlled to move in the axial direction by the torch moving mechanism so as to maintain the set arc voltage, and in the case of a consumable electrode, the torch is moved at a constant speed. The torch is controlled to move in the axial direction so that the protruding length of the consumable electrode wire fed from the lower end of the torch is kept constant, so the torch is moved along the bevel line of the base material.
The direction change point of the reciprocating oscillation is set to By setting the point at which the displacement or position in the direction of the torch axis reaches a predetermined value, the arc constantly reciprocates within the groove due to the inclination of the groove surface, performing a tracing operation, and stops from the loop F of the weld joint. Arc welding is achieved by keeping the height from the base metal surface to the toe constant. In addition, in this case, if there is a variation in the groove gap in the welding direction, the weld cross-sectional area changes every half cycle of the reciprocating oscillation, but the change in the interval distance for each half cycle is checked over time. By doing this, it is possible to obtain (m) corresponding to the above-mentioned weld cross-sectional area for each period.Also, by dividing the above-mentioned interval distance change k (for each; 1"J period + U:), the distance between the upper ends can be obtained Corresponding signals can be obtained for each half cycle, and the set values of welding conditions such as welding current, arc voltage, welding speed, etc. are determined separately based on these signals of the previous half cycle. Correction control can be carried out using each of the above methods, and thereby a proper initial layer Uranami bead can always be formed in the case of a predetermined yukagi and one-sided welding.

However, in the gamma welding method described above, which achieves groove tracing by actively weaving the torch and detecting the axial position of the torch near the groove wall, the torch remains in a downward position. In this case, the initial layer Uranami can be formed stably and well, but when the torch changes from a vertical position to an upward position, for example, when the torch changes from a vertical position to an upward position, as in the case of full circumferential welding 1 during butt bath welding of steel pipes, the torch If the welding conditions are not adjusted according to the position, the uranami bead may be insufficient, or the back side of the uranami bead may become slightly depressed and dented, especially near the upward position, making it necessary to perform back welding. , causing various problems.

That is, in Fig. 1, (1a) and (1b) are a pair of F14 pipes as base materials, (2) is a welding electrode placed in the groove formed in the butt part of both steel pipes, and (3) is this welding electrode. A welding arc is generated between the electrode (2) and the base metal by a constant current power source using a torch that holds the electrode (2). Now, in the groove at the upper part of one arm in Fig. 1, the torch (6) is stacked from point kA to the right side in the drawing along one inclined groove surface (4), but in this case, In order to keep the arc voltage constant, the torch (3) is raised and lowered according to changes in the vertical height from the groove bottom (5) to each welding point.
The distance between the electrode (2) held at the base metal and the base material is controlled to be always constant. The vertical displacement ffi of the torch (6) is A
Between points B, O, and D, the groove changes depending on the surface shape, and the height position on the other inclined groove surface (6) is the same as the height position of the torch (3) at point A. Torch (3)
At point D, which is reached, the direction of the swing is reversed. In Fig. 1, the height position at point A is indicated by the height H) from the bottom surface (5).
It goes without saying that it may also be expressed as the height from I) (H).In other words, for weaving reversal control, the above (H) is given as the V constant value, and the horizontal The amount of displacement of the torch (3) is set at
('H), or by reversing the direction every time the torch (3) reaches the set value (Hl)'.
By controlling the reversal of cB movement direction, groove copying is achieved. In this way, the first layer <P't) is formed, and the uranami bead (W) is formed. When such welding passes around the butt needle of the steel pipe and reaches the lower part of the steel pipe, the torch (6
) is welded from the bottom of the groove in an upward position, and is formed by weaving welding in an upward position. There is a depression as shown in (S).The depression (S) may occur over a part of the front and rear posture ranges, with the lower part of the yaws in between, and the groove width of the depression (S) The center position in the direction almost coincides with the center position of the welding layer (Pl) or the center position of the weaving.

An object of the present invention is to provide an arc welding method that enables the formation of a stable and good Uranami bead even during posture welding while achieving groove tracing by the arc itself.

That is, in the arc welding method of the present invention, the arc length is maintained constant by moving the torch toward and away from the base metal so as to maintain the arc voltage constant while reciprocating the torch in the width direction in the welding progress direction. The direction of the oscillation is changed each time the axial displacement or position of the torch due to the approach and separation reaches a predetermined value, and multilayer lie-one welding is performed by tracing the groove by the arc. In the welding method, the weaving center position is detected every half cycle of weaving, and the weaving center position detected in the previous half cycle is set as the center and the above-mentioned weaving center position is detected over a preset small section within each half cycle. The welding current is changed over this small section while cutting off the welding length control. The welding current in the section is made larger than the welding current in other than the small section.

In this way, in the present invention, a pulsed current with an amplitude of 1.6 times the orientation of the torch is superimposed on a low-level welding current at the weaving center position. Compensation for the shape of the initial wave bead due to changes in the orientation of the torch during multiple welding is achieved by superimposing the pulsed current in the small section, and the degree of compensation depends on the width of the small section and the pulsed current. This can be achieved by adjusting the settings with the amplitude value.

The present invention will be described below based on embodiments and together with the drawings.

FIG. 2 is a block diagram showing an example of a control system for carrying out the present invention, in which (1) shows the welding base material, (2) shows the welding electrode, 6) shows the torch, and σ) shows the torch (6). The torch lifting mechanism (14) is a torch lateral movement mechanism that allows the torch to perform lateral movement for weaving and bevel copying, and the lifting motor (8) (hereinafter referred to as the Y-axis motor) is used for each.
and a lateral movement motor (15) (hereinafter referred to as the X-axis motor). )-chi (3) is raised and lowered by the arc voltage detector θ)b- detection signal and the arc voltage reference setter (
10) The deviation from the reference arc -5 pressure is measured using a differential amplifier (
11), and provides this deviation signal to a Y-axis motor controller (12) K via a pg switch (20), and the controller (12) controls the Y-axis motor so that the deviation is always zero. However, it can be achieved by controlling the ) - Torch moving mechanism (14) Along with the horizontal movement of the torch (3) by the VC, the torch (
6) The arc points at the tip are M, B, 0, D in Figure 1.
It passes through each point in order and moves along the cross-sectional shape of the groove, and moves up and down accordingly. Changes in the amount of vertical movement of the torch (3) are measured using a l tensile meter (1
3) (hereinafter referred to as Y-axis potentiometer) detects a voltage signal that changes over time, and this voltage signal is set to the above-mentioned (H) or (H') by the inversion position reference setting device (18). The corresponding setting value is compared with the comparator (19), and the output of this Y-axis potentiometer (13) exceeds the value corresponding to the torch position of the reversal position A and D in Fig. 1. At this time, a swing reversal signal is input from the comparator (19) to the X-axis motor controller (17), thereby reversing the direction of rotation of the X1lk motor (15).

In addition, (16) is a setting device that provides a speed reference signal to the controller (17) in order to control the speed of the X-axis motor (15) to a desired value, (22) FiX-axis and Y-axis movement mechanism (14)
(7) and torch 6) in the direction of welding progress.The moving speed of this trolley (22) is [4].
It goes without saying that the speed of the bogie (not shown) is controlled to a set speed by a travel controller.

In the operation system in which the arc itself can follow the groove by this fixed completion length control 7, in this invention, the torch (
3) The 5' position in the X direction (groove width, direction) is detected by the X-axis potentiometer (26), and the x@
The output of the l tensiometer (23) is stored in the left end analysis memory (24) which stores the signal corresponding to the left end (Mu point side) position (Xt> for each reversal of weaving) and the right end (D
An arithmetic circuit (26) including a right edge analog memory (25) that stores a signal corresponding to the point type) position (Xr)K is calculated by K, and the weaving center position It (Xc) (= (Xt+Xr)
/2), and the weaving center position signal in the previous half cycle obtained in this way is converted into a signal corresponding to
is superimposed on the axial position signal and thus the comparator circuit (2
7), an X-axis direction position signal is generated for each half cycle, which is normalized by the weaving center position in the previous half cycle. The change in the position signal in the X-axis direction is as shown in Fig. 3 (Ji), and after a transverse movement of half a period of weaving from the point on one of the inclined groove surfaces (4) in Fig. 1, D on the other inclined groove surface (6)
It reaches point t, then reverses and reaches the point on the inclined groove surface (4), where it reverses again and does the same KD! , Muhata, Dlsmu4, D4, Mu5, Dr. . . , weaving is performed to achieve %A'. The weaving center position Jd is the pH point in the half cycle between the points DI'' and 12. is normalized, and its zero point is shown in Figure 3 (11).
P11').

In Figure 2, (28) is a tj window comparator, which has a comparison input for two different high and low voltage levels (
It produces a high level output for a signal input with a voltage level intermediate between Vu) and (Vj), and the voltage level of the signal input is (
A low level output is generated when the voltage is above (Vu) or below (vg).The comparison input (Vu) (Vl) is a setting signal that determines the width of the aforementioned small section, and is used by the current change section setter (29).
) is obtained by converting the set voltage fJ by the converter (30) to the upper and lower limits Ig corresponding to the subsection. In Fig. 3(a), this small section is shown as ``X'', and this ΔX
are associated with the voltage level CVI ) (Vu ) as described above.

Now, Dt-A whose zero point is the weaving center position ('1Pu) obtained in the half cycle of the previous M1-I)t.
The half-cycle X-axis direction position signal of a is sent to the window comparator (28) as a comparison input (Vj) corresponding to the small section width ΔXK.
(VLI), and sets the output of the window comparator (28) to a high level only when the voltage level corresponds to a small section of ΔX with PI3 in the center. The output of Wind Convalet # (2B) is 1Ill each at high level.
It directly controls the analysis switches (21) and (31) that are turned on when receiving the II input, and also controls other similar analysis switches (20) and (32) via inverters (33) and (34). It is designed to be controlled by That is, the analysis switches (21) and (31) are turned on when the output of the window comparator (28) is at a high level, and turned off when the output is at a low level. Further, the other analysis switches (20) and (32) are turned off when the output of the window comparator (28) is at a high level, and turned on when the output is at a low level. As described above, the analog switch (20) controls whether or not the output of the differential amplifier (11) is input to the Y-axis motor controller (12).
Analog switch (21) a Analog switch (20)
When the controller (12) is turned off, the controller (11) is reversibly turned on and the input of the controller (12) is grounded. Another analyzer switch (31) and (32) each has a pace current regulator (36).
) and the beater current regulator (37), and when the output of the window comparator (28) is at a low level, the corresponding rig switches (20) and (62) are turned on. When the constant arc length control is activated, the pace current (1) adjusted by the base current regulator (36) appears at the welding power source current adjustment output terminal (35), while the output of the window comparator (28) becomes high level in the ΔX interval, the analysis switch (21
) and (61) are turned on, constant arc length control is temporarily cut off, and the output terminal (35MC has a peak current of 1
Peak current adjusted by 111EII (37)
appears. This situation is shown in Figure 5(a) with K attached (
6). In other words, in each half cycle, a large beater current ( IP
) is passed as a welding current, and in other sections, a base current (work 1) is passed as a steady welding current.For example, when weaving with the torch in an upward position, welding is performed at approximately the center of the groove. This method performs timing control of pulsed bath welding current similar to pulsed TIG welding.

Similarly, in each half cycle of one weaving, arc length control is interrupted only during a certain small section centered on the center position of the weaving detected in the previous half cycle, and at the center position of the weaving detected in the previous half cycle. A similar effect can be obtained by stopping weaving for a certain period of time, flowing a large peak current (IP) as a welding current only during this period, and flowing a steady welding current during the other periods.

In this case, the magnitude of the peak current (Ip) is set according to the orientation of the torch, and this setting may be continuously varied according to the angular position of the cart in the circumferential direction of the steel pipe, for example when welding the entire circumference of the steel pipe. .

As described above, in the present invention, even in weaving welding in a position such as an upward position of the torch, welding is performed near the weaving center, 1tt11. It is possible to effectively prevent the depression of the underwave bead surface and form a good initial layer of underwave by changing the arc, and in this case, the groove tracing by the arc itself is not hindered.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the shape of the initial weld layer and the movement of the torch in the cross section of a welded joint when weaving welding is performed by following the groove by the arc itself, and FIG. 2 is a control diagram for putting this invention into practice. A block diagram showing an example of the system, Figure 3 is a diagram explaining its operation, (1) is a diagram showing the displacement of the arc point in the X-axis direction over time, and (middle) is a diagram showing the change in welding current over time. The line is ['4. (1) (1a) (1b)--Bath base material (M pipe), (2)...Welding electrode, (3)...Torch, ■-
...Torch lifting mechanism, (8)...Y-axis motor, (9)
...Arc pressure detector, (10)...Arc voltage reference setter, (11)...Differential amplifier (12)...Y
Axis motor controller, (13)... Yldl tension meter, (14)... Torch fIti movement mechanism, (15
)...X-axis motor, (17)...X-axis motor controller, (18)...Reverse position reference setting device, (19)...
Comparator, (20) (21) (31) (32)
... Analog switch, (23) ... X-axis tenth meter, (24) (25) ... Analog memory, (
26)... Arithmetic circuit, (27)... Comparison circuit, (2
8)...Window comparator, (29)...Current change interval setter, (60)...Converter, (!13)
(34)...Inverter, (35)...Welding power source current regulator. Agent Patent Attorney Tadashi Sato Figure 1

Claims (3)

[Claims] (1) While swinging the torch back and forth in the width direction of the welding process, the torch is moved toward and away from the base metal so as to keep the arc voltage constant, and the arc length is kept constant, and the approach and separation is performed. In the arc welding method, the displacement or position of the torch in the axial direction becomes a predetermined value, and the direction of the oscillation is changed to perform multilayer weaving welding by tracing the groove by the arc. The weaving center position is detected every half cycle, and the weaving center position detected by the sum of the previous half cycles is set at the center Kl-, and the constant arc length control is interrupted over a preset small section within each half cycle. An arc welding method characterized by varying the welding current over a small section. (2) During welding (the welding current in the small section 11 is increased more than the welding current in other sections)
The arc welding method described in section. (3) In addition to interrupting the constant arc length control during the short period, the weaving center position detected in the previous half cycle is stopped for a preset period of time, and at the same time, the welding current is stopped during the welding period other than the stopped period. The arc welding method according to claim 1, wherein the welding current is increased.