JP2701667B2 - Arc Start Bead Meeting Method - 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 associating arc start beads for connecting the starting ends of welding beads by rotary arc welding.

[0002]

2. Description of the Related Art In known rotary arc welding, the rotational positions (Cf, R, Cr) of an arc rotating at a high speed with a predetermined radius are known.
, L), the arc voltage and the welding current waveform at predetermined angles are detected at the left and right, respectively, around the forward point Cf in the welding advancing direction, and control is performed so that the integrated values of the left and right become equal. A groove copying control of a copying arc sensor method is performed (Japanese Patent Laid-Open No. 62-248571).

[0003] Such a rotary arc welding method is widely used for butt welding, fillet welding, and the like. For example, the same applies to circumferential welding of a narrow groove of a pipe. However, in the case of pipes, in order to achieve high-efficiency welding, generally two welding machines, ie, a leading welding machine (hereinafter, referred to as a first welding machine) and a succeeding welding machine (hereinafter, referred to as a second welding machine) are used. The left and right halves are to be welded.

That is, as schematically shown in FIG. 7, the first welding machine 1 is started from the “top” (point A) of the pipe 10,
Welding is performed in the direction of arrow a to “ground” (point B), and the left half circumference is welded. Similarly, the right half of the circumference is welded by the second welding machine 2, but the first welding machine 1 and the second welding machine 2 cannot be started simultaneously from the same point A. Start arc from point A,
After returning the second welding machine 2 to the point A in the direction c with a delay,
The welding is started by a method such as an arc start in the direction b. In this way, the left and right weld beads (not shown) are connected by “heaven” and “ground”, respectively. In the figure,
Reference numerals 3 and 4 respectively denote a first electrode nozzle and a second electrode nozzle for rotary arc welding. Reference numerals 5 and 6 denote a first welding wire and a second welding wire, respectively. The circumferential guide rails 9 are wheels of each of the welding machines 1 and 2 running on the guide rail 8.

By the way, conventionally, when connecting the right and left welding beads with “top”, the wire rotation position of the rotating arc is set at the Cf point in front of the welding traveling direction in order to activate the arc sensor from the start. Was. 8 to 1
FIG. 0 shows an outline of a conventional arc start bead associating method.

FIG. 8 is a schematic plan view of a bead meeting portion, and FIG. 9 is a sectional side view thereof. FIG. 10 is a sectional front view of the bead meeting portion. In the first welding machine 1, Cf at a position shifted leftward from the point A by the rotation diameter D of the rotating arc.
The first welding wire 5 is set at the point, and when it is confirmed that an arc has been generated at the point Cf, the first welding machine 1 is started to form the first welding bead 11 on the left side. After that, the second welding wire 6 of the second welding machine 2 is set to the Cf point shifted rightward by the rotating diameter D of the rotating arc from the point A, and an arc is generated. Start and form the second weld bead 12 on the right. Therefore, the start end 11a of the first weld bead 11 and the start end 12a of the second weld bead 12 are fused with each other, and the left and right weld beads 11, 12 can be connected at the point A.

[0007]

However, if the set positions of the first and second welding wires 5 and 6 at the time of the arc start are both set at the Cf point, the welding machine starts immediately after the arc is generated and confirmed. Since the fusion portion between the start end 11a of the first weld bead 11 and the start end 12a of the second weld bead 12 is shortened, and since the bead start end 11a of the first welder is cooled at the time of arc start of the second welder, As shown in FIG. 9, there is a problem that the penetration does not become uniform at the junction 13 between the left and right weld beads 11, 12. In particular, the back bead may not be connected in the first layer reverse wave welding, and a welding defect such as poor fusion may occur in the joint portion 13.

Further, if the shift amount of the welding wire is corrected in advance in consideration of the deviation of the bead starting end, the above-mentioned problem can be solved, but the calculation of the shift amount requires too many factors and is extremely troublesome.

Further, the front bead shape of the bead association portion 13 becomes convex as shown in FIG.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to make the penetration at the junction of the arc start bead uniform by a simple method and improve the quality thereof. Another object of the present invention is to improve the convex shape of the bead meeting portion.

[0011]

According to the present invention, in a first welding step, an arc start position of a rotating arc is set to a rear point Cr in a welding advancing direction, thereby forming a first welding bead and then a second welding bead. In the process, the arc start position of the rotating arc is also set to the rear point Cr in the welding traveling direction, and the position is aligned with the start end of the first welding bead. Immediately after the welding current is instantaneously increased to a large current with the arc start and energized and fused with the start end of the first welding bead, immediately reduced and energized, and then returned to the normal welding current, The object has been solved by using an arc start bead associating method in which the second weld bead is connected to the first weld bead. The method of controlling or energizing the welding current in the second welding step as described above may be applied to the first welding step.

Further, according to the present invention, the arc start position of the rotating arc in the first welding step is set to the forward point Cf in the welding traveling direction in the same manner as in the prior art, and only the arc starting position of the rotating arc in the second welding step is set as described above. Similarly, it is set as the rear point Cr in the welding progress direction and at the position of the start end of the first welding bead. The method of controlling the welding current is the same as described above.

[0013]

In the first welding machine used in the first welding step,
When the arc rotation is started with the wire rotation position set to the above-mentioned Cr point, the arc starts at the Cr point, so that the back lining of the first layer can be more preferably made than at the point A.

In the second welding step, the wire rotation position of the second welding machine is also set to the Cr point, and the starting position of the already formed first welding bead is automatically positioned using experimental values. By performing the arc start together, the second weld bead can be uniformly fused with the start end of the first weld bead. The back bead of the first layer can also be connected well at this bead meeting portion.

Further, at least at the time of the arc start in the second welding step, when a welding current is instantaneously increased to a large current and the current is applied, a keyhole is formed at the start end of the first weld bead, and a key hole is formed. The second weld bead can be completely fused. Immediately after this fusion, the current is instantaneously reduced to a low current to reduce the amount of molten metal and uniformly fuse. Therefore, the convex shape of the bead meeting portion can be reduced. After that, the welding current is returned to the normal welding current and the rotating arc welding is performed.

Next, when the wire rotation position of the first welding machine is set to the Cf point as in the conventional case, the starting end of the first welding bead is similarly set, and the wire rotation position of the second welding machine is the C r point. Since the position is automatically determined using the experimental value, the position can be aligned with the start end of the first weld bead, and the two beads can be satisfactorily associated with each other as described above. Also in this case, the method of controlling the welding current in the second welding step is the same as described above, and it is possible to prevent a convex bead at the bead association portion.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below by taking the case of circumferential welding of pipes as an example. FIG. 1 is an explanatory view showing an outline of a method of associating arc start beads according to one embodiment of the present invention, and is a schematic plan view of a bead associating portion. FIG. 2 is a cross-sectional side view of the bead meeting portion, FIG. 3 is a cross-sectional front view of the bead meeting portion, and FIG. 4 is an explanatory diagram showing a method of controlling a welding current. The arrangement of the first welding machine 1 and the second welding machine 2 is the same as the conventional one (see FIG. 7).

In this embodiment, a first welding step is first performed using a first welding machine. At this time, the wire rotation position of the rotary arc of the first welding machine is set to the rear point Cr in the welding advancing direction a, and the position is adjusted to the “top” of the pipe 10, that is, the point A. Then, the arc is started at this position to form the first weld bead 11. In addition, the groove tracking control of the arc sensor system is controlled using arc voltage and welding current waveforms at predetermined angles on the left and right, respectively, around the front point Cf as in the conventional case.

As described above, since the arc is started at the point Cr, even if the first welding machine is started immediately after the arc generation is confirmed, the first layer back bead 11b can be formed better than the point A. That is, in the experimental example, the arc is generated and the arc rotates and the truck runs for 100 to 400 ms. During this time, the arc stops at the Cr point, so that the first layer back bead immediately below the Cr point is easily formed.

After the first welding bead 11 is formed in this manner, in the second welding step, the wire rotation position of the rotating arc of the second welding machine is set to the rear point Cr in the welding advancing direction b. While being stopped at the Cr point, it is moved to the point A side, and is automatically adjusted to a position to be the starting end 11a of the already formed first welding bead 11 using experimental values. The arc was started at this position, and an example of the welding current Ia at that time was controlled as follows.

That is, as shown in FIG. 4, the welding current was instantaneously increased to 420 A at the start of the arc, and the welding current was increased to 0.15 seconds. Thereafter, the current decreased to 250 A, and the current was supplied for 0.15 seconds, and thereafter, the welding current was returned to the normal 400 A. As a result, the height h of the convex portion of the bead association portion 13 was 2.5 to 3.0 mm in the conventional case, whereas the height h was reduced by about 1/4 in the present embodiment.

First, the arc force is increased by the application of a large current, and a stable keyhole is formed at the starting end 11a of the first welding bead 11, so that the fusion with the starting end 11a is prevented. This is considered to be due to good performance, secondly, lowering of the arc force due to low-current application after fusion, and thirdly, reducing the wire melting rate.

By controlling the welding current at the time of the second welding as described above, the starting end 11a of the first welding bead 11 and the second welding bead 12 can be completely fused, and a good shape without a convex shape can be obtained. The bead meeting part 13 is obtained. Also, the first layer back bead 12b can be connected well to the first first layer back bead 11b. The groove following control of the second welding machine is also performed using the arc voltage and welding current waveforms at predetermined angles on the left and right, respectively, around the point Cf in the same manner as described above.

The positioning of the wire rotation position of the second welding machine is performed by adjusting the distance G (experimental value) between the rotation center axis 16 of the second welding wire 6 and the rotation center axis 15 of the first welding wire 5.
Is simply set at a position that is substantially separated by the rotation diameter D of the rotating arc.

Next, FIG. 5 is a schematic plan view of a bead meeting portion showing another embodiment of the present invention, and FIG. 6 is a sectional side view thereof. In this embodiment, the wire rotation position of the first welding machine is set to the forward point Cf in the welding advancing direction a as in the conventional case, and only the wire rotation position of the second welding machine is set to the welding advancing direction b in the same manner as described above.
At the rear end Cr of the first welding bead 11 and the position of the starting end 11a of the first welding bead 11. The method of controlling the welding current in the second welding step is the same as in the above embodiment.

When the wire rotation position of the first welding machine is set to the Cf point and the arc is started, the starting end 11a of the first welding bead 11 is obtained. Since the wire rotation position of the second welding machine is set to the Cr point as described above, an experimental value is used at a position where the second welding wire 6 is stopped at the Cr point and the starting end 11a of the first welding bead 11 is used. Align,
If the arc is started, both beads 1
1, 12 can be satisfactorily associated, and the fusion of the bead association portion 13 can be uniform.

Contrary to the above embodiment, when the wire rotation position of the first welding machine is set to the point Cr and the wire rotation position of the second welding machine is set to the point Cf, the start end 1 of the first welding bead 11 is set.
In the position 1a, the arc does not reach until the arc is generated and rotated, and the vehicle travels immediately, so that a sufficient amount of heat for forming the back bead cannot be obtained. Therefore, it is difficult to obtain a uniform weld bead.

It should be noted that the present invention is not limited to the case of circumferential welding of pipes using two first and second welding machines as in the above embodiment, and one welding machine may be used. ,
In addition, the present invention can be applied to any welded joint as long as the arc start bead is associated. Further, the control of the welding current shown in FIG. 4 is not limited to only the second welding step, and the same control may be performed in the first welding step. However, it goes without saying that this current control is always performed in the second welding step. Further, instead of or in addition to the welding current control, the wire feed speed may be controlled.

[0029]

As described above, according to the present invention, in both the first welding step and the second welding step, the arc start point of the rotating arc is set to the rear point Cr in the welding advancing direction. Since the welding is performed by aligning the Cr point with the starting end of the existing first welding bead and controlling the welding current as described above at the time of arc start, a bead having a good shape which does not become convex. An association portion is obtained, the fusion of the bead association portions can be made uniform, and the quality thereof can be improved. Also, the back bead can be satisfactorily associated with the first layer underside welding.

The same effect as described above can be obtained even when the arc start point in the first welding step is set to the front point Cf in the welding direction and the arc start point in the second welding step is set to the rear point Cr in the welding direction. Is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a bead meeting portion according to an embodiment of the present invention.

FIG. 2 is a cross-sectional side view of the bead meeting portion.

FIG. 3 is a sectional front view of the bead meeting portion.

FIG. 4 is a diagram showing a method for controlling a welding current in the embodiment.

FIG. 5 is a schematic plan view of a bead meeting portion according to another embodiment of the present invention.

FIG. 6 is a cross-sectional side view of the bead meeting portion of the embodiment of FIG. 5;

FIG. 7 is an explanatory view of a conventional pipe circumferential welding method.

FIG. 8 is a schematic plan view of a conventional bead meeting portion.

FIG. 9 is a cross-sectional side view of the bead meeting portion in FIG. 8;

FIG. 10 is a cross-sectional front view of a bead meeting portion in FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st welding machine 2 2nd welding machine 3 1st electrode nozzle 4 2nd electrode nozzle 5 1st welding wire 6 2nd welding wire 7 Groove 10 Pipe 11 1st welding bead 11a Start end of 1st welding bead 12th 2 weld bead 12a Start end of second weld bead 13 Bead joint

Claims (2)

(57) [Claims] 1. An arc start bead associating method for connecting start ends of first and second weld beads by rotary arc welding, wherein an arc start position of the rotary arc is set to a rear point Cr in a welding traveling direction. A first welding step of forming a first welding bead, and setting an arc start position of the rotating arc at a rear point Cr in the same welding progress direction, and aligning the position with a starting end of the first welding bead. A second welding step of welding in a direction opposite to the above, and connecting a second welding bead to the first welding bead. Further, at least at the time of starting the arc in the second welding step, the welding current is adjusted to the arc start. Immediately after energizing with a large current and fusing with the start end of the first welding bead, immediately energizing with a low current and then returning to the normal welding current , Arc start bead method association, characterized in that to reduce the protrusion of the bead meeting part. 2. An arc start bead associating method for connecting start ends of first and second weld beads by rotary arc welding, wherein an arc start position of the rotary arc is set to a forward point Cf in a welding advancing direction. A first welding step of forming a first weld bead, and setting an arc start position of the rotating arc at a rear point Cr in a welding traveling direction, and aligning the position with a start end of the first weld bead. And a second welding step of connecting the second welding bead to the first welding bead. Further, at least at the time of the arc start in the second welding step, the welding current is instantaneously changed to the arc start. Immediately after the high current is applied and fused with the start end of the first welding bead, the current is immediately reduced to a low current and the current is returned to the normal welding current. Arc start bead method association, characterized in that to reduce the protrusion of de meeting part.