JPS63256272A - All position automatic arc welding method - Google Patents

Abstract

PURPOSE:To prevent the incomplete penetration at the toe and central part of a bead by synchronizing the oscillation of a welding torch with the travel of a torch oscillating device to stop a travel device till it starts traveling and attains the other end of the oscillation width from the vicinity of its center. CONSTITUTION:The welding torch is oscillated with a simple pattern and in synchronization with this oscillating period, the travel and stoppage of the torch oscillating device are repeated alternately. Or, the welding torch is oscillated and changed in a rectangular wave shape and a curved wave shape at the high speed and low speed. The torch movement from one end to the other end of a groove is accompanied by the travel of the travel device and the travel of the travel device is stopped in the vicinity of the central part of the oscillation width and it is moved by only the torch oscillation. By this method, the incomplete penetration at the toe and central part of the bead is prevented and the automatic welding of a joint such as a horizontally fixed pipe, etc., is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for automatically welding a joint that requires all-position welding of a metal structure by arc welding.

[Conventional technology]

Various automatic arc welding methods for all-position welding have already been developed. These are equipped with consumable electrodes or non-consumable electrodes, and various types of welding torches have been invented and devised, including those that swing or those that do not swing. These are devices in which a traveling device equipped with a welding torch and a welding torch swinging device travels at a constant speed. Moreover,
Since this is an automatic welding machine, this running speed is as accurate as possible (we are pursuing measures to maintain a constant speed).

In this way, in addition to the weaving pattern that is devised by simply swinging the torch, there are also methods that change the welding current, or a combination of these.

[Problems to be solved by the present invention]

By the way, when a welding torch swinging device is mounted on the traveling device, the weaving pattern of the welding torch is determined by a combination of the swinging pattern of the torch swinging device and the traveling speed.

Weaving of the welding torch is very important when performing multi-layer welding using all-position welding. In particular, welding is carried out at a low current in order to prevent molten metal from dripping when facing upward or in a room position.

As a result, the penetration depth becomes shallow, and both ends of the torch oscillation,
Particularly, there is a risk of melting into the groove surface and causing defects.

Therefore, as stated in the conventional Japanese Patent Publication No. 50-233'66r arc welding method, the welding current is periodically increased at both ends of the torch oscillation, and at the same time, the wire feeding speed is changed according to the height of the welding current. A method has been proposed in which the welding speed is periodically varied in phase with the wire feeding speed. This is a method in which the welding current, wire feeding speed, and welding speed, that is, the vehicle traveling speed, are simply synchronized and periodically changed. This method prevents significant convex beads when welding in an upward or vertical position, and is an old technique. However, in welding methods such as self-shielded arc welding where penetration is shallow, poor penetration may occur at the center of the bead when the torch swings from one end to the other. This is CO2 welding, M
This is a phenomenon that occurs when the torch movement speed is fast even in AG-type welding. In addition to this method, a swinging device having a complicated mechanism has been developed so that the torch swings in a swinging pattern as shown in FIG. However, these methods require a complicated electrical control device or have a complicated mechanical structure, which may cause failures at welding sites, making them unsuitable. In particular, when mechanically drawing a swinging pattern using a torch swinging device, the i!
It is difficult to draw a perfect weaving pattern.

For example, if you want to stop the welding torch for about 0.5 to 3 seconds at both ends of the weaving, the torch cannot be stopped with a combination of a device that runs at a constant speed and a simple swing pattern.
It was necessary to combine a torch swing pattern in the opposite direction to the traveling direction as shown in Figure 2. This also has to be synchronized with the traveling speed, so it is not possible to freely select the traveling speed, or to synchronize with the traveling speed,
There were problems such as a complicated torch swing mechanism.

Moreover, with this kind of equipment, the penetration on both sides of the groove is thick (
If this is done, the shape of the weld penetration will be deep at both ends (and shallow at the center), which tends to cause poor penetration at the center of the bead.

[Means for solving problems]

The inventors have developed a method that uses a torch swinging mechanism as simple as possible to form a flat weld bead that does not cause poor weld penetration at both ends of the weaving of the torch or at the center of the bead, and that stabilizes the entire posture. Invented and applied for (patent application filed in 1989)
0-196978), but the present invention makes the technology of that patent more effective and further embodies it.

In other words, the swinging of the welding l-ch and the running of the torch swinging device are synchronized, and when the torch swinging starts moving from one end to the other, the traveling device equipped with the welding l-ch swinging device runs. This is an all-position automatic arc welding method characterized by stopping the travel of the traveling device from near the center of the swing width until reaching the other end. The welding torch is oscillated in a simple pattern as shown in Fig. 1, and the torch oscillating device is alternately run and stopped in synchronization with this oscillation cycle, or the welding torch is oscillated in a rectangular wave pattern at high and low speeds, or in synchronization with this oscillation cycle. It changes in a curved wave shape. As shown in Figure 3, the welding torch oscillation pattern is divided into parallel movement type (al) and pendulum type (
The Nill type of bl can be used in combination with linear shape (C1, circular arc shape (dl, triangular shape +8), and trapezoid shape (fl).

[Effect]

By implementing the method of the present invention, the weaving pattern of the welding torch tip relative to the joint groove can draw a very complex trajectory despite the simple device.

As a result, in the upward or vertical position, the welding torch is stopped at both ends of the groove where poor penetration occurs, or is moved very slowly to obtain sufficient penetration over a relatively long period of time. This also attracts the molten metal to one side of the groove, which is an important technique to prevent the molten metal from dripping and creating a convex bead. The running of the traveling device is added to the torch movement from one end of the groove to the other, and the molten metal moves quickly so that it does not reach the center of the groove. Penetration may be insufficient.Therefore, the running device is stopped near the center of the swing width, and the movement is performed only by swinging the torch.This will prevent the molten metal from penetrating poorly at the center of the bead. It is possible to obtain a delicate weaving pattern that is well-balanced to prevent the material from dripping while still achieving sufficient blending.

In particular, self-shielded arc welding has a shallow penetration depth (
, and the bead tends to become convex. Therefore, in order to ensure penetration on the groove surface and make the bead flat, a long stopping time is required compared to other welding methods, 0°5 to 3 seconds at both ends of the weaving. The balance between speed, penetration depth, and amount of molten metal when swinging from one end to the other is important. Automating self-shielded arc welding has been considered extremely difficult because conventional automatic machines cannot overcome this long downtime and cannot produce this delicate weaving pattern. In the present invention, this delicate and complicated weaving pattern can be easily
The weld bead was obtained using conventional equipment, and a flat, well-penetrated weld bead with no dripping of molten metal was obtained for all welding positions.

In addition, when performing CO2 welding or MAGi welding using this method, in addition to providing good results in the bead shape of all-position welding,
There is an advantage that the occurrence of spatter is reduced. This is because when a conventional traveling device runs at a constant speed, the wire tip tends to precede the molten pool, and at the turning point of weaving, it overlaps with the following molten pool, creating an unstable state, causing the wire tip and molten metal to come into contact with each other. , spacks are thought to occur. In the method of the present invention, welding is carried out by constantly attracting the molten pool to the tip of the wire, so the arc can be sustained without falling into an especially unstable situation even at the turning point of weaving, which reduces the occurrence of spatter. Conceivable. In the case of automatic welding machines, this reduction in spack is a very important matter in terms of maintenance of the torch and the traveling mechanism.

(Example〕 Examples according to the present invention are shown below.

Example 1 A butt joint on the outer surface of a horizontal fixed pipe with an outer diameter of 1100 m and a plate thickness of 30 mm was made by self-shielded arc welding.

The groove shape is 60 degrees, and the root spacing is 2 cranes. The torch is a combination of the pendulum type shown in FIG. 3(b) and the linear vibration type shown in FIG. 3(C). The welding conditions are shown in Table 1.

Table 1 The laminated state of this welding is shown in Fig. 4. The bead shape was uniform over the entire line and there were no defects (good automatic welding was achieved).

Example 2 A YG-12 Tsuru mild steel plate was used for butt vertical advancement welding using CO2 welding. Bevel shape is 50 degrees ■Bevel,
One-sided welding was performed using a tape-shaped refractory backing material with a root spacing of 5 rhymes. As the electrode wire, a 1.2 meφ solid wire (Si--Mn type) was used. The torch oscillation is of the parallel movement type shown in Fig. 3(a), the first Pi has a triangular shape as shown in (e), the second layer has a trapezoidal shape as shown in (f), and the third layer has a linear shape as shown in (C). It is a combination.

The welding conditions are shown in Table 2.

Table 2 As a result, the welding result was sound, with no defects in the weld penetration and good uranami bead and surface bead.

Example 3 Using a 12.7 amO steel plate with a thickness of 12.7, upward butt welding was performed using CO2 melting. The groove shape is a 45 degree V groove,
Single-sided welding was performed using a tape-shaped refractory backing material with Roux I and spacing of 5. As the electrode wire, a solid wire (St--Mn type) with a diameter of 1.2 mm was used. The torch oscillation is a combination of the pendulum type shown in FIG. 3(b) and the linear vibration shown in FIG. 3(C). In addition, in the torch oscillation, a stopping time was provided for the first layer at the center of the oscillation to ensure that the Uranami bead had sufficient excess. In this case, the travel of the traveling device is controlled independently of the center stop of the torch, but stopping the travel before the torch comes to a center stop has a better effect on the Uranami shape.
As a result, a sound welding result was obtained with no poor penetration (and good uranami bead and surface bead).

Example 4 Plate width 25 mm) T+' for steel tffl, MAG? 8
Butt welding was performed at Jfi (A-C02). The groove shape is an X groove shown in FIG. 5, the groove angle is 50 degrees, and the root face is Q ma. This was welded in upward and downward positions. Electrode wires are 1 and 2
+nφ solid wire (Si-Mn system) was used. The same oscillation pattern as in Example 3 was used for the torch. The welding conditions are shown in Table 4. First welded upward, then gouged the root and welded downward.

Table 4 As a result, there was no metal lead in not only upward welding but also downward welding, making it possible to perform high quality and highly efficient welding.

〔Effect of the invention〕

As described above, the present invention uses a combination of a very simple torch oscillating device and a traveling device that changes the traveling speed in synchronization with the oscillating period to achieve the I-- required for all-position multilayer welding. The weaving pattern of the bead can be drawn freely (this allows the bead to form a flat bead without sagging and becoming a convex bead even in an upward or vertical position, and prevents welding at the bead toe and center. This prevents poor fitting and enables automatic welding of joints whose posture changes continuously, such as horizontally fixed pipes.

In addition, spatter was significantly reduced during MAG welding and CO2 welding, and it was highly effective in terms of maintenance as an automatic welding machine.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the method of the present invention, in which Fig. 1 (a) shows the change over time in the swinging speed of the torch, Fig. 1 (b) shows the change in the running speed of the traveling device over time, and (C1 is a diagram explaining the weaving pattern). Figure 2 is a diagram explaining the synthesis of weaving patterns by the conventional method. Changes in running speed over time, (gl (hl) (i) are diagrams explaining the weaving pattern obtained by combining them. Figure 3 is a diagram explaining the swinging force formula of the torch that can be applied to the present invention, and Figure 4 is a diagram explaining the weaving pattern by combining these. Figure 5 is a diagram illustrating the weld bead bond layer condition in Example 1, and Figure 5 is a diagram illustrating the groove shape and its contact layer status in Example 4. Applicant: Attorney at Shin Nippon Ristetsu Co., Ltd. Minoru Aoyagi Figure 1 Figure 2

Claims (1)

[Claims] In arc welding, the swinging of the welding torch and the running of the torch swinging device are synchronized, and when the torch swinging starts moving from one end to the other, the traveling device equipped with the torch swinging device starts running. An all-position automatic arc welding method characterized by stopping the travel of the traveling device from near the center of the swing width until reaching the other end.