JPS6257768A - All position automatic arc welding method - Google Patents

Abstract

PURPOSE:To perform the arc welding to form a flat bead by stabilizing all positions without incomplete penetration at both end parts in weaving of a torch by changing the traveling speed of a torch rocking device with synchronizing with the rocking period of a welding torch. CONSTITUTION:A welding torch is rocked in a simple pattern as shown in the figure and the traveling of the torch rocking device is varied in rectangular waveform at high and low speeds or successively simultaneously with the rocking period thereof, or the traveling and stoppage are repeated alternately. The weaving pattern at the welding torch top for the joint groove can thus draw extremely complicated locus. Consequently, the torch is quickly swung at the place where the drop of the welding metal comes into problem like overhead position and vertical position. The weaving pattern that sufficient penetration is obtainable can be obtd. as well by spending time comparatively on the both end parts causing incomplete penetration.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for automatically welding joints that require all-position welding, such as circumferential joints of fixed pipes, by arc welding.

(Prior Art) Various automatic arc welding methods for circumferential joints of fixed pipes have already been developed. These welding torches are equipped with consumable or non-consumable electrodes, and various types of welding torches have been invented, including those that oscillate and those that do not oscillate.

These are devices in which a traveling device carrying a welding torch and a welding torch oscillating device travels at a constant speed.

Furthermore, measures are being taken to maintain this traveling speed as accurately as possible at a constant speed in response to changes in the welding posture due to fixed tube welding.

(Problems to be Solved by the 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. . When welding horizontal fixed pipes, the welding position changes continuously from an upward position to a vertical position and then to a downward position. Weaving of the welding torch is very important when performing multi-layer welding using such all-position welding. That is, in the upward or vertical position, welding is performed with low heat input to prevent molten metal from dripping. Therefore, the penetration depth becomes shallow, and there is a risk of poor penetration occurring at both ends of the torch swing, especially at the groove surface. Therefore,
Conventionally, a current variation method is used in which the welding current is increased at both ends of the torch oscillation, and a complicated mechanism is used in which the torch oscillates to draw an oscillation 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. When mechanically drawing a swinging pattern on bamboo using a torch swinging device, it is difficult to draw a weaving pattern that is truly appropriate for forming a weld bead due to the above-mentioned running speed. For example, in self-shielded arc welding, the penetration is shallow, so weaving ends at 0.
It is necessary to stop the welding torch for about 5 to 3 seconds. On the other hand, since conventional automatic machines travel at a constant speed, it is not possible to stop the torch with a simple swing pattern, and it is necessary to combine a torch swing pattern in the opposite direction to the running direction as shown in Figure 2. did not become. This also has to be synchronized with the running speed, so you cannot freely select the running speed.
Another problem is that the torch swing mechanism becomes complicated in order to synchronize it with the traveling speed. Therefore, automation of self-shielded arc welding is considered extremely difficult, and its practical application has not yet been achieved.

(Means for Solving the Problem) The inventors have created a torch swinging mechanism that is as simple as possible, yet does not cause insufficient penetration at both ends of the weaving of the torch, and forms a flat weld bead in all positions in a stable manner. invented a method. That is, this is an automatic arc welding method characterized by changing the running speed of a torch swinging device in synchronization with the swinging period of a welding torch. The welding torch is oscillated in a simple pattern as shown in Fig. 1, and in synchronization with the oscillation period, the torch oscillation device runs at high speed, low speed, in a rectangular wave pattern,
Alternatively, the speed may be changed continuously, or running and stopping may be repeated alternately.

(Function) 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.

This allows the torch to be swung quickly in areas where dripping of weld metal is a problem, such as in an upward or vertical position, and to create a weaving pattern that takes a relatively long time to achieve sufficient penetration at both ends where poor penetration occurs. Obtainable.

Especially in self-shielded arc welding with shallow penetration depth,
The stopping time at both ends of the weaving is 0.5 to 3 seconds, which is longer than other welding methods. Conventional automatic machines cannot therefore provide this long downtime, making it extremely difficult to automate self-shielded arc welding. In the present invention, this stopping time can be freely selected, and a trajectory close to the weaving pattern of a skilled welder can be obtained with a very simple device, so that sufficient welding without dripping of molten metal can be achieved for all welding positions. A flat, flat weld bead is obtained. This has made it possible to automate multilayer welding in all positions.

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

Example 1 An outer surface butt joint 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 a 600V groove, and the root spacing is 2 gourds. The welding conditions are shown in Table 1.

Table 1 The laminated state of this welding is shown in Figure 3. The bead shape was uniform over all positions, and good automatic welding was possible with no defects.

Example 2 Internal butt joint for a horizontal fixed pipe with an inner diameter of 1500 m and a plate thickness of 20 mm? :Consumable electrode type arc welding with 20%Ar+80%CO2 gas shield (wire: 51-Mn system 1.
2 vranX) was performed. The groove shape was 6o0v, a backing metal was used, and the root spacing was 5WIIl. Table 2 shows the welding conditions.

Table 2 The laminated state of this welding is shown in Figure 4. The bead shape was uniform over all positions, with no defects, and good automatic welding was possible.

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

[Brief explanation of drawings]

Figure 1 (a), (b), (c), (d), (e
), (f), (g), (h), (i) are explanatory diagrams for obtaining the entire welding torch weaving pattern according to the present invention, Fig. 2 (a), (b), ((ri, (d), ( e)
. (f), (g), (middle), and (i) are explanatory diagrams of weaving patterns according to the conventional method, and FIGS. 3 and 4 are diagrams of laminated beads welded according to the present invention. 1, 1c 1"...Welding torch swing pattern 2, 2'
, 2"... Traveling device running pattern
2...Low speed running time a, a4 a"...Weaving pattern 4, 4', 4"...Welding torch swing pattern s, s/, 5//...Travel pattern 6 at constant speed , 6', 6"...Conventional method weaving pattern V>Vt,,■...Constant running speed LXfAIL ("A)
) Egyo Hayatei (-倦) Figure 3 Figure 4 Contents continued from page 1 ■Inventor Tsugube Kikuno Sagamihara Calligraphy Hashimoto 5-≦Inside the Art Center

Claims (1)

[Claims] In arc welding, an all-position automatic arc welding method is characterized in that the traveling speed of a torch swinging device is changed in synchronization with the swinging cycle of a welding torch.