JPH0327305B2 - - Google Patents

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. [Prior Art] 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 running speed is an automatic welding machine, we are pursuing measures to maintain a constant speed as accurately as possible. 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 Invention] 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 multilayer welding in all positions. In particular, welding is carried out at a low current in order to prevent molten metal from dripping when in an upward or vertical 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 Japanese Patent Publication No. 50-23366 ``Arc Welding Method'', the welding current was raised periodically at both ends of the torch oscillation, and at the same time the wire feeding speed was changed according to the height of the welding current. A method has been proposed in which the welding speed is periodically changed in phase with the feed speed. This is a method in which the welding current, wire feeding speed, and welding speed, that is, the truck running speed, are simply synchronized and periodically changed. This method is an excellent technique as it can prevent the formation of a significant convex bead when welding in an upward or vertical position. 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 phenomenon occurs even in CO ₂ welding and MAG welding when the torch movement speed is fast. 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. Particularly when drawing a swinging pattern mechanically using a torch swinging device, it is difficult to draw a weaving pattern that is truly suitable for forming a weld bead due to the above-mentioned traveling speed. 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 running direction as shown in FIG. Since this also has to be synchronized with the traveling speed, there are problems such as it is not possible to freely select the traveling speed, or the torch swinging mechanism becomes complicated because it is synchronized with the traveling speed. Moreover, if such a device is used to increase the penetration on both sides of the bead, the shape of the 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 the problem] The inventors have created a torch swinging mechanism that is as simple as possible, yet does not cause poor penetration at both ends of the weaving of the torch or at the center of the bead.
He invented and applied for a method to form a flat weld bead with stability in all positions (Japanese Patent Application No. 60-196978), but the present invention makes the patented technology even more effective and makes it even more specific. It has become. In other words, 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, and the swinging width is This is an all-position automatic arc welding method characterized by stopping the travel of the traveling device from near the center to 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. The welding torch oscillation pattern is the third
As shown in the figure, the way of swinging the torch is changed to parallel movement a.
and pendulum type b, linear c, circular arc d,
Can be applied in combination with triangular shape e and trapezoidal shape f. [Operation] By carrying out the method of the present invention, the weaving pattern of the welding torch tip relative to the joint groove can draw a very complicated 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 achieve sufficient penetration over a relatively long period of time. This is also an important technique because it draws the molten metal to one side of the groove, preventing it from dripping and creating a convex bead. The traveling device is added to the movement of the torch from one end of the groove to the other, and the molten metal moves quickly so that it does not get stuck in the center of the groove. However, if it moves to the other end all at once, there may be insufficient penetration at the center of the swing width. Therefore, the traveling device stops traveling near the center of the swing width, and is moved only by swinging the torch. As a result, it is possible to obtain a delicate weaving pattern that is well-balanced to prevent molten metal from dripping and to obtain sufficient penetration in the case of poor penetration in the center of the bead. In particular, self-shielded arc welding has a shallow penetration depth and tends to form a convex bead. Therefore, in order to ensure melting on the groove surface and make the bead flat, it is necessary to
It requires a long stopping time of 0.5 to 3 seconds compared to other welding methods, and the balance between the speed, penetration depth, and amount of molten metal when swinging from one end of the weaving to the other is important. . Automation of self-shielded arc welding has been considered extremely difficult because conventional automatic machines have not been able to provide such long downtimes or produce such delicate weaving patterns. In the present invention, this delicate and complex weaving pattern can be obtained using a very simple device, and a flat weld bead with sufficient penetration without dripping of molten metal can be obtained in all welding positions. In addition, when CO ₂ welding or MAG welding is performed using this method, not only a good bead shape is obtained in all-position welding, but also there is an advantage that spatter is less likely to occur. 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 the weaving, it overlaps with the following molten pool, creating an unstable state, and the wire tip and molten metal It is thought that this may cause spatter. In the method of the present invention, welding is performed by constantly attracting the molten pool to the tip of the wire, so the arc can be sustained without becoming particularly unstable even at the turning point of the weaving, which reduces the occurrence of spatter. Conceivable. In the case of automatic welding machines, reducing spatter 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 mm and a plate thickness of 30 mm was performed by self-shielded arc welding.
The groove shape is a 60 degree V-bevel, and the root spacing is 2 mm. The torch is a combination of the pendulum type shown in Figure 3b and the linear vibration type shown in c. The welding conditions are shown in Table 1.

[Table] Figure 4 shows the laminated state of this welding. The bead shape was uniform over the entire line, and good automatic welding was possible with no defects. Example 2 Using mild steel plates with a thickness of 12 mm, butt vertical advancement welding was performed using CO ₂ welding. The groove shape was a 50 degree V-groove, the root spacing was 5 mm, and single-sided welding was performed using a tape-shaped refractory backing material. Electrode wire is 1.2
mmφ solid wire (Si-Mn system) was used.
The torch oscillation is a parallel movement type in Figure 3, and the first layer is e.
The second layer has a triangular shape, the second layer has a trapezoidal shape of f, and the third layer has a linear shape of c. The welding conditions are shown in Table 2.

[Table] As a result, there was no poor penetration, and the welding results were sound with good Uranami bead and surface bead. Example 3 Using steel plates with a thickness of 12.7 mm, upward butt welding was performed using CO ₂ welding. The groove shape is a 45 degree V groove,
One-sided welding was performed using a tape-shaped refractory backing material with a root spacing of 5 mm. Electrode wire is 1.2
mmφ solid wire (Si-Mn system) was used.
The torch oscillation is a combination of the pendulum type shown in Fig. 3b and the linear vibration shown in c. In addition, in the torch oscillation, consideration was given to providing a stopping time at the center of the oscillation in the first layer so that the Uranami bead would have 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.

[Table] As a result, a sound welding result was obtained with no penetration defects and good uranami bead and surface bead. Example 4 MAG welding (A-CO ₂ ) using a steel plate with a thickness of 25 mm
Butt welding was performed. The groove shape is the X groove shown in Figure 5, and the groove angle is 50 degrees, respectively.
The root face is 0mm. This was welded in upward and downward positions. Electrode wire is 1.2mmφ
A solid wire (Si-Mn type) 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.

〔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 cycle to achieve the weaving of the torch necessary for all-position multilayer welding. Patterns can be drawn freely, and as a result, even in an upward or vertical position, the bead does not sag and become a convex bead, forming a flat bead.
This prevents poor penetration at the bead toe and center, and enables automatic welding of joints whose posture changes continuously, such as horizontally fixed pipes.
In addition, it significantly reduced spatter during MAG welding and CO ₂ welding, and was highly effective in terms of maintenance as an automatic welding machine.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the method of the present invention, in which FIG. 1a is a diagram illustrating the change over time in the swinging speed of the torch, FIG. 1b is a diagram illustrating the change over time in the traveling speed of the traveling device, and FIG. Figure 2 is a diagram explaining the synthesis of weaving patterns by the conventional method, and Figure 2a,
b, c are swing patterns of the torch alone, d, e, f
is a diagram illustrating a change in running speed of the traveling device over time, and g, h, and i are a weaving pattern obtained by combining them. Fig. 3 is a diagram for explaining the torch oscillation method that can be applied to the present invention, Fig. 4 is a diagram for explaining the weld bead lamination situation in Example 1, and Fig. 5 is a diagram for explaining the groove shape in Example 4 and its It is a figure explaining a lamination situation.

Claims (1)

[Claims] 1 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.