JPH0426949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high-speed rotating arc pulse fillet welding method, and particularly to prevention of burn-through when a welded member is extremely thin.

[Prior Art] Conventionally, welding of fillet joints made of extremely thin welded members with a thickness of about 3 mm or less, such as the joining of base plates of steel pipe drums, has generally been performed using a low welding current. This is because when the welding current is increased, the welded member at the bead side end becomes thinner, so that the welded member at the bead side end is damaged by burn-through due to the thermal influence of the arc.

To give an example of conventional welding conditions of this type, when welding a fillet joint of a 1.2 mm thick steel plate,
Welding current I = 100 ~ by carbon dioxide arc welding
The work was carried out under conditions of 120A and welding speed V = 25 to 30cm/min.

[Problems to be Solved by the Invention] However, when welding with a low welding current, the melting speed decreases, so it is necessary to slow down the welding speed, which significantly reduces the efficiency of welding work. Significantly reduces the efficiency of welding work. In order to improve the efficiency of welding work, it is desirable to increase the welding current, but when the welding member is extremely thin as described above, there is a problem of burn-through of the welding member.

In addition, because the welding current is suppressed for the bead formed in conventional thin plate fillet welding, there are problems such as excessive penetration, so-called convex beads, and undercuts. There was a problem in that it was difficult to obtain a bead of equal length because it was heated by mechanical copying using a roller or the like.

This invention was made in view of such problems, and even when the welding member is extremely thin, it is possible to use a high current without causing burn-through.
It is an object of the present invention to provide a high-speed rotating arc pulse fillet welding method that can form a flat bead with an even better leg length.

[Means for Solving the Problems] In the present invention, arc welding is performed while rotating the arc at high speed by rotating the welding wire around a rotation axis directed toward the groove route, and an arc sensor method is used. While tracing the groove, the output of the welding power source is pulsed in synchronization with the rotation so that the welding current increases as the wire approaches the center of the groove due to the rotation and decreases as the wire approaches the edge of the groove. The above problem is solved by superimposing the .

According to a preferred embodiment of the present invention, the synchronization of the rotation and the pulses is performed by controlling the speed of the rotation. Further, the groove tracing using the arc sensor method of the rotary axis oriented toward the groove root is performed by the following steps (a) to (d).

(a) Detecting the arc voltage or welding current with respect to the rotational angular position of the rotating arc, and (b) detecting the detected voltage or current in the range of 5° or more and 180° or less left and right around the front end position C _f of the rotation. The integrated value S _L in the rotation angle range (-φ ₀ to ₀ ) to the left from the position C _f and the rotation angle range to the right from the position C _f ( Find the integral value S _R at φ ₀ ~ 0), (c) calculate the value △S corresponding to the difference between the integral values S _L and S _R , (d) so that this difference △S becomes zero. The welding torch position is adjusted in the width direction of the groove.

Furthermore, downward welding is preferably performed by inclining the weld joint so that the front side of the weld joint is lower in the welding direction.

[Operation] According to the present invention, a high-speed rotating arc is employed as the arc, and the distance of this rotating arc from the groove edge changes regularly depending on its rotational position. Focusing on this point, the present invention performs groove copying using the arc sensor method, and the welding current decreases as the arc approaches the groove edge, and the welding current decreases as the arc approaches the center of the groove. A pulse is superimposed on the welding power supply output in synchronization with the rotation of the arc so that the pulse increases. In this case, even with high welding current,
Since the welding current decreases when the arc approaches the groove edge, burn-through of the welding member at the bead side end can be prevented. Furthermore, since the welding current increases when the arc approaches the center of the groove, welding efficiency can be improved. Furthermore, the bead becomes wider due to the rotation of the arc, and in conjunction with groove tracing using the arc sensor method, a flat bead with equal leg length can be formed.

[Example] The applicant may, for example, apply for Japanese Patent Application No. 60-88732
-249667), proposed a high-speed rotating arc fillet welding method that is optimal for fillet welding of thick plates. According to this kind of high-speed rotating arc fillet welding method, the physical effects of the arc are dispersed, and the advantages include peripheral dispersion of penetration, formation of a flat bead (curved bead), or improvement of wire melting speed due to rotating centrifugal force. is obtained. Furthermore, the rotation of the arc imparts a force to the bead to deflect it toward the standing plate, which has the effect of preventing the bead from sagging due to gravity.

The present invention is applicable to fillet welding of thin plates by performing this type of high-speed rotating arc fillet welding method while superimposing pulses on the output of the welding power source.

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

FIG. 1 is a schematic configuration diagram showing an example of a welding device used in an embodiment of the present invention.

In the figure, a base plate 2 having a convex cross section is fitted to the end of a steel pipe drum 1, and a groove 3 of a fillet joint is formed on the inner peripheral surface of the end of the steel pipe drum 1. The steel tube drum 1 and the base plate 2 are supported at an inclined angle from a support 4, and are rotated in the CW direction via a shaft 6 by rotational drive of a support rotation motor 5.
A rotating arc torch (welding torch) 7 rotates a welding wire 9 around the rotation axis 0 by a wire rotation motor (not shown) housed in a torch head 8.
While rotating in the CW direction, welding proceeds in the welding direction Z along the groove 3 as the support 4 rotates. In this case, since the steel pipe drum 1 and the base plate 2 are inclined as described above, the torch 7 performs downward welding.

In addition, the rotating arc torch 7 is operated in the groove width direction, which is a direction perpendicular to the root of the groove 3 (in the direction perpendicular to the paper surface,
It is supported by both moving mechanisms 10 and 11: an X-axis tracing mechanism 10 that corrects the torch position in the direction (hereinafter referred to as the X-axis direction), and a Y-axis tracing mechanism 11 that corrects the torch position in the height direction of the torch 7. The welding current and voltage to this torch 7 are supplied from the main welding power source 12 via the cable terminal 13, but the main welding power source 12 is connected in parallel with an auxiliary power source 14 for pulses so that pulses are superimposed on its output. It is connected to the.
This pulse auxiliary power supply 14 is regularly supplied with a switching circuit 15 using, for example, a thyristor stack.
Outputs pulse current by turning it ON and OFF.

Note that 16 is an arm that supports the torch head 8.

FIG. 2 is a view of the welded part when performing high-speed rotating arc welding with the above-mentioned device, viewed from above in the rotation axis 0 direction, and C _f , C _r , R, and L each indicate the rotational position of the wire 9. , C _f is the position of the wire 9 in the front with respect to the welding direction Z, C _r is the position of the wire 9 in the rear with respect to the welding direction Z, and R is the position of the wire 9 on the right side in the clockwise direction toward the welding direction. , L indicates the position of the wire 9 on the left side in the counterclockwise direction toward the welding direction.

CW is the rotation direction of wire 9, 3R is the right groove edge,
3L indicates the left groove edge, and φ indicates the rotation angle of the wire 9 with respect to the welding direction Z. It is assumed that the straight line connecting the position C _f to the intersection of the rotation axis 0 and the groove 3 to the position _r coincides with the route A by groove tracing using the arc sensor method. That is, it is assumed that the rotation axis 0 is oriented toward the route A.

The pulses are superimposed by the pulse auxiliary power supply 14 in synchronization with the rotation of the wire 9 so that the welding current is maximum at the positions C _f and _Cr and is minimum at the positions R and L. In other words, as the wire 9 approaches the groove edges 3R, 3L, the welding current decreases, and conversely, the wire 9 approaches the groove edges 3R, 3L.
The pulses are superimposed so that the welding current increases as it moves away from the groove and approaches the center of the groove. The rotation of the wire and the pulses may be synchronized by controlling the speed of the wire rotation, for example.

FIG. 3 shows a welding current waveform graph when the above pulse superimposition is performed. In FIG. 3, the vertical axis represents the welding current I, and the horizontal axis represents the rotational position of the wire 9, which changes with time t. When the pulses are superimposed in this way, even if a high welding current is used near the positions C _f and _Cr , the welding current will be low near the positions R and L where the arc approaches the groove edges 3R and 3L.
Burn-through of the base material near the groove edges 3R and 3L can be prevented. Therefore, even when the welding member is extremely thin, it is possible to increase the welding current (average value) and improve the efficiency of the welding operation. For example, if the steel pipe drum 1 and base plate 2 are steel plates with a thickness of 1.2 mm, welding current I = 180 ~ 220 A, welding speed V = 60 ~ 80 cm/sec
It can be performed under the following conditions, and work efficiency is greatly improved compared to conventional thin plate fillet welding. In addition, by employing high-speed rotating arc welding, it is possible to form a flat, equilateral long bead. Furthermore, as shown in FIG.
Since the flow is forward, the curvature of the bead becomes more pronounced, and the shape of the formed bead becomes more ideal.

FIG. 4 is an enlarged cross-sectional view of the groove 3 shown in FIG. 1 in the groove width direction, and shows a comparison of the bead shapes formed by the present invention and the conventional method. In the figure,
Solid line a represents a bead formed by the method of the present invention;
Dashed line b is a bead formed by a conventional method. As shown in the figure, according to the method of the present invention, the conventional convex shape is eliminated, and it is possible to form a flat bead of equal leg length.

In the above embodiment, it is assumed that the rotation axis 0 coincides with the route A by groove tracing using the arc sensor method. However, as for groove tracing using the arc sensor method, for example, the applicant It is advisable to use the ``Group profile control method for high-speed rotating arc fillet welding'' proposed in No. 94905 (Japanese Unexamined Patent Publication No. 62-248571). Here, this type of groove tracing control method will be explained.

When the rotation axis 0 coincides with the groove route A as shown in FIG. 3, the current waveform is symmetrical about the position C _f as shown in FIG. 4. However, if the rotational axis 0 deviates from the root A of the groove, the current waveform becomes asymmetrical with respect to the position C _f . This asymmetry is due to arc characteristics in which the welding current I and arc voltage E change depending on the distance between the groove edge and the wire, but the details of this arc characteristic can be found in the above-mentioned Japanese Patent Application No. 61-94905. I am familiar with

By detecting and correcting the asymmetric waveform of the welding current I or arc voltage E, the amount of deviation in the X-axis direction can be corrected. That is, the waveform is divided left and right with respect to the welding direction centering on point _Cf , each divided waveform is taken out within a certain angle _φ0 from point _Cf , and the area (integral) of the waveform created between this angle _φ0 is value)
By determining S _L and S _R and correcting the torch 7 in the X-axis direction so that the areas S _L and S _R become equal, the rotation axis 0 can be made to coincide with the root A of the groove.

Note that if the angle φ ₀ is less than 5°, the waveform will be more susceptible to noise, so the waveform range should be from 5° to
Set to 180°.

By performing tracing control to correct the position of the torch 7 in the X-axis direction as described above, the rotation axis 0 can always be directed to the route A even if the groove width changes. By the way, in the Y-axis direction (vertical direction), by integrating the waveform of the welding current I or arc voltage E during one rotation of the torch 7, and comparing and correcting the reference value, You can modify the position of the direction. That is, by using the same method as in the X-axis direction, find the value S corresponding to the sum of the areas S _L and S _R , compare this sum S of areas with the reference value S ₀ , and calculate the difference S - The height of the welding torch is controlled so that S ₀ becomes zero. The reference value S ₀ is set in advance as the above-mentioned area sum S when the welding torch height is at an appropriate value. Further, the value of the sum of the areas S is the value of one revolution of the arc or an integral number n times, that is, S= _o〓 ⁿ⁼¹ (S _L +S _R ). The maximum value of this integer n is generally not more than the number of revolutions per second of the arc.

As described above, automatic tracing for correcting the position of the torch 7 in the X-axis direction and the Y-axis direction can be performed.

FIG. 5 shows an example of a control block diagram used in an embodiment of the present invention.

In addition, in this control block diagram, to simplify the explanation, the area created by the waveform is controlled in the X-axis direction,
Although the same S _L and S _R are used for Y-axis direction control, they are not necessarily limited to integral values at the same rotation angle φ ₀ .

In the figure, a rotational position detector 17 detects the rotational angle φ of the wire 9 and provides it to a discriminator 18. The discriminator 18 compares this rotation angle φ with the pulse signal from the pulse signal generator 19 of the auxiliary pulse power source 14, and determines whether the welding current is maximum at positions C _f and _Cr and welding at positions R and L. The rotation speed of the wire rotation motor 21 is controlled via the rotation speed controller 20 so that the current becomes minimum, and the rotation of the wire 9 and pulse superimposition are synchronized. In addition, the current detector 22 detects the welding current I.
is detected, and this welding current I and the reference current setting device 23
The differential amplifier 24 calculates the difference I-I ₀ between the reference current I ₀ (average value of the welding current) set in advance.
This calculated value I-I ₀ is divided by a switch 25 into the left side (L side) and the right side (R side) with respect to the welding direction. The timing of division by switch 25 is determined by a command signal from switching logic circuit 26.
The switching logic circuit 26 is connected to the rotational position detector 17.
φ ₀ setting device ₂ that presets the rotation angle φ of the wire 9 detected by
The output φ ₀ (for example, 45°) of the wire 9 is compared and calculated, and the section where the rotation angle of the wire 9 is from -45° to 0° is defined as the L section, and the waveform of this section is output from the L side of the switch 25. and is integrated by an integrator 29. Similarly, the signal is output from the R side of the waveform switch 25 in the R section where the rotation angle is from 0° to 45°, and is integrated by the integrator 30. The n setter 28 is set with the number n of times these integrals are processed, and the integrators 29 and 30 perform waveform integration on n arc rotations outputted through the switching logic circuit 26, and The outputs S _L and S _R are output to the memory devices 31 and 32. The memory units 31 and 32 store and store the signals S _L and S _R input from the integrators 29 and 30 every n times.
S _L and S _R are output to a differential amplifier 33 and an adder 34 . The differential amplifier 33 calculates the difference S _L −S _R between these signals, inputs this value to the X-axis controller 35, and inputs the above-mentioned X
Drives the X-axis motor 36 of the axis moving mechanism 10 and calculates the difference S _L
-Set _R so that it becomes zero. On the other hand, the adder 34 adds the signals S _L and S _R , and the added value S _L +S _R is input to one input terminal of the differential amplifier 37 . Further, the memory 38 stores the initial value of S _L + S _R , that is, the value S ₀ corresponding to the appropriate welding torch height, and this value is input to the other input terminal of the differential amplifier 37, and the differential (S _L +S _R )-S ₀ is determined by the amplifier 37, and is applied to the Y-axis controller 39, which drives the Y-axis drive motor 40 of the Y-axis moving mechanism 11 to control the welding torch height.

In the above description, a case has been described in which groove tracing control is performed by detecting welding current, but groove tracing control can also be performed by detecting arc voltage in the same manner as in the above description.

Further, in the above embodiment, a shape consisting of the steel pipe drum 1 and the base plate 2 is shown as an example of a thin plate fillet joint, but the scope of application of the present invention is not limited to this joint shape.

[Effects of the Invention] As explained above, according to the present invention, it is possible to increase the welding current when the rotating arc is at the center of the groove and decrease it when it is at the edge of the groove. A high current can also be used for welding members, which improves the efficiency of welding work, and has the effect of forming a flat bead without welding the thin plate at the bead side end.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of a welding device used in an embodiment of the present invention, FIG. 2 is an explanatory diagram of a welded part by the device shown in FIG. 1, and FIG. 3 is an arc current waveform diagram.
FIG. 4 is an enlarged sectional view of the groove, and FIG. 5 is a block diagram of a control circuit used in one embodiment of the present invention. In the figure, 3 is a groove, 7 is a rotating arc torch (welding torch), 9 is a welding wire, 10 is an X-axis movement mechanism, 11 is a Y-axis movement mechanism, 12 is a main welding power source,
14 is an auxiliary power supply for pulses, 15 is a switching circuit, A
is the root of groove 3, 0 is the rotation axis, C _f , C _r , R,
L indicates the rotational position of the wire 9. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. Fillet welding performed while rotating the arc at high speed by rotating the welding wire around a rotational axis directed toward the groove route, while performing groove tracing using the arc sensor method. , characterized in that a pulse is superimposed on the welding current output in synchronization with the rotation so that the welding current increases as the wire approaches the center of the groove due to the rotation and decreases as the wire approaches the edge of the groove. High-speed rotating arc pulse fillet welding method. 2. The high-speed rotating arc pulse fillet welding method according to claim 1, wherein the synchronization with the rotation pulse is performed by controlling the speed of the rotation. 3. Groove tracing using an arc sensor method with the rotating shaft core oriented toward the groove root; (a) detecting the arc voltage or welding current with respect to the rotation angle position of the rotating arc; Integrate each constant rotation angle _{φ 0} in the range of 5° to 180° to the left and right around the front end position C _f in the rotation, and calculate the rotation angle range (−φ ₀ to 0) and the integral value S _R in the rotation angle range (0 to φ ₀ ) to the right from the position C _f , and ( _c ) calculate the difference between the integral values S _L and S _R. Claim 1 is characterized in that the welding is performed by calculating the corresponding value ΔS, and (d) correcting the welding torch position in the width direction of the groove so that this difference ΔS becomes zero. High speed rotating arc pulse fillet welding method described. 4. The high-speed rotating arc pulse fillet welding method according to claim 1, characterized in that downward welding is performed by tilting the weld joint so that the front side of the weld joint is lower in the welding direction.