JPS6339346B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention prevents poor fusion at corners and high-temperature cracking in the case of large currents, stabilizes the arc, ensures sufficient penetration at corners, and provides excellent quality without defects. The present invention relates to a narrow gap arc welding method that can form welds with high efficiency.

In order to streamline multi-layer build-up welding of thick plates, a narrow-gap arc welding method is known in which the gap is narrower than before.

A problem with the narrow gap arc welding method described above is insufficient penetration in the corners, and various methods have been studied to solve this insufficient penetration.

For example, as shown in Fig. 1, a curved groove with a radius of about 100 mm is formed in a narrow gap 2 provided between the base materials 1 and 1' to be welded using a bending roll provided near the feed roll. There is a known method in which the wire 3 is inserted through the contact tube 4, a multilayer solution is applied using two electrodes in tandem, and the leading wire is used to aim at one corner, and the trailing wire is used to aim at the opposite corner. There is. However, in the above method,
Since the curved surface of the wire becomes unstable in direction, it has been difficult to perform stable welding.

Therefore, as shown in FIG. 2, welding is carried out while the tip of the wire 3 inserted into the narrow gap 2 is vibrated in the left-right direction, or the third method is used.
As shown in the figure, a method has been developed in which the wire 3 is rotated back and forth at a constant period.

However, with the method of vibrating the tip of the wire in the left-right direction as shown in Figure 2,
It is only possible to give low-speed vibrations of about 0.5 to 1 Hz, and on top of that, the arc becomes unstable due to the influence of the surrounding magnetic field, and it is difficult to accurately target the vibrations at both corners of the groove. This tends to cause phenomena such as droplets not being transferred to the spray and, therefore, stable welding being impossible.

In addition, in the method shown in Figure 3, in which the wire is rotated back and forth at a constant cycle, the tip of the wire receives an impact when the wire is reversed, causing spatter where droplets are scattered, making the arc unstable. easy to become,
For this reason, the number of rotations of the wire is at most 1.5 to 6.
The limit is around Hz, 10Hz at most, and a large-scale drive mechanism is required to reverse the wire.

As mentioned above, in the method of vibrating the wire in the left-right direction or the method of rotating the wire back and forth at a constant cycle, the upper limit of the vibration or rotation frequency is 10 Hz at maximum, so there is a risk of increased penetration in the corners and damage to the bead surface. The effect of increasing bending and wire melting rate is low;
Therefore, there has been a problem in that it is not possible to form defect-free welded parts of excellent quality with high efficiency.

From the above-mentioned viewpoints, this invention provides a narrow gap arc welding method that can stabilize the arc, achieve sufficient penetration in the corners, and form defect-free, high-quality welds with high efficiency. A narrow gap arc welding method in which a nozzle is inserted into a narrow gap formed between base materials, and a solution is applied while supplying a sealing gas by a wire supplied through the nozzle, The wire is supplied offset from the central axis of the nozzle, and the nozzle is continuously rotated in one direction at a high speed of more than 10 Hz, thereby causing an arc generated from the tip of the wire to be applied in one direction. This method is characterized by welding while performing high-speed circular motion.

Next, the present invention will be explained with reference to examples and drawings.

FIG. 4 shows a schematic perspective view of an example of a wire rotation device used in the method of the present invention. In the drawing, reference numeral 5 denotes a nozzle having a height sufficient to be inserted into the narrow groove 2 formed between the base materials 1 and 1', and a tip 6 is provided on the tip surface 5a of the nozzle 5.
is attached at an eccentric position with respect to the axis of the nozzle 5, and a wire feed port 7 is provided on the rear end surface 5b of the nozzle 5 at the same eccentric position as the attachment position of the tip 6. From feed port 7 to tip 6
A wire 3 is inserted through the nozzle 5 toward the tip 6, and its tip protrudes from the tip 6. 8 is a feed roller for the wire 3, and 9 is a motor for rotating the feed roller.

An annular rack 10 is provided on the outer periphery of the upper part of the nozzle 5.
is mounted insulated from the nozzle 5, and a gear disc 11 driven and rotated by a motor 12 is meshed with the annular rack 10.

The nozzle 5 having the above structure is slidably supported by a nozzle receiving pipe 13 fitted to the outer peripheral surface of its upper portion, and the nozzle receiving pipe 13 is connected to a welding cart 15 by a support rod 14. It also serves as a current-carrying part.

With the device having the above structure, the nozzle 5 is inserted into the narrow gap 2, and while the shielding gas is blown into the narrow gap 2, the nozzle 5 is moved in one direction by the motor 12.
Welding is performed while continuously rotating at a high speed of over 10Hz.

As a result, the arc generated from the tip of the wire 3 undergoes high-speed circular motion in one direction. Due to the centrifugal force generated by such high-speed circular motion in one direction of the arc, the molten metal 16 at the tip of the wire 3 is deflected toward the outer circumference, as shown in a schematic front view in FIG. It becomes easier to approach the side walls of the base materials 1, 1'. Furthermore, in the schematic plan view of FIG. 6, under the influence of the high-speed circular motion of the arc 17 in one direction, as shown by arrow a, the molten pool 18 directly under the arc also rotates as shown by arrow b. Flows outward.

Therefore, the heat of the arc 17 is sufficiently applied to the side walls of the base metals 1 and 1', and the heat is transferred by convection of the molten pool 18, so that the base metal 1 is heated as shown in the explanatory diagram in FIG. , 1' increases, and the surface of the bead 19 becomes curved. As a result, there will be no insufficient penetration in the corners, the penetration will be uniform, and a defect-free welded part of excellent quality will be obtained. Such curvature of the bead surface and uniform penetration cannot be achieved unless the nozzle is continuously rotated in one direction at a high speed of at least 10 Hz, and as the nozzle rotation speed increases, the The effect will be noticeable.

Furthermore, as shown in the explanatory diagram in FIG.
Due to the centrifugal force generated by continuous high-speed rotation in one direction, the shape of the molten metal 16 at the tip of the wire 3 becomes elongated, and as a result, the area of the molten metal 16 that comes into contact with the arc 17 increases, causing it to flow into the wire 3. As the arc heat increases, detachment of the droplet 16a is promoted,
Therefore, the melting rate of the wire 3 increases. This increase in the melting speed of the wire 3 becomes more noticeable as the number of rotations of the nozzle 5 increases, and the melting speed of the wire 3 when the number of rotations of the nozzle 5 is set to 100Hz is higher than that when the nozzle 5 is not rotated. This will increase approximately 20%.

Therefore, the arc is stabilized, the penetration in the corners is sufficient, and it is possible to form defect-free and high-quality welds with high efficiency, and high-quality welds without high-temperature cracking can be achieved even at high currents. part is obtained.

On the other hand, in the case of the method of reciprocating vibration or reciprocating rotation of the wire 3 as shown in FIG. 2 or FIG. Since no centrifugal force is generated, the centrifugal force does not cause the arc to approach the side wall of the base material, rotate the molten pool directly under the arc, or increase the wire melting speed.
Therefore, there is insufficient penetration in the corners, the melting speed of the wire is slow, and it is not possible to form defect-free and high-quality welds with high efficiency.Moreover, the impact generated at the wire tip when the arc is reversed is As a result, spatter occurs frequently and the arc becomes unstable.

FIG. 9 shows an example of the chip shape,
In addition to the above-mentioned shape as shown in figure a, if the tip 6 is formed with a bend 6a as shown in figure b, the arc radius becomes wider and is suitable for a slightly wider groove. A desired arc radius can also be obtained by attaching the tip 6 to the nozzle tip surface 5a not eccentrically, but by attaching it to the axis of the nozzle 5 and forming a bend 6a in the tip 6.

Next, the present invention will be explained with reference to examples.

Example 1 A thick steel plate with a thickness of 100 mm was prepared with a groove pitch of 12 mm and a diameter of 1.2 mm.
Welding was carried out under the following conditions using Ar + 20% Co ₂ as a shielding gas, using a wire of 1 mm (Si-Mn material).

Chip shape Type shown in Figure 9a Rotation speed 20Hz Welding current 300A Welding voltage 30V Welding speed 30cm/min As a result, compared to the conventional method of reciprocating vibration or reciprocating rotation of the wire, insufficient penetration in the corners is eliminated. The welding speed was increased by approximately 1.3 times, and the number of passes was reduced from 30 passes for the same plate thickness using the conventional method to 25 passes, and the entire length of the weld was inspected by non-destructive testing. However, no defects were obtained.

Example 2 The same thick steel plates as in Example 1 were welded using the same wire and shielding gas as in Example 1 under the following conditions.

Chip shape Type shown in Figure 9a Rotation speed 80Hz Welding current 400A Welding voltage 35V Welding speed 45cm/min As a result, as in Example 1, there was no lack of penetration in the corner compared to the conventional method, and the number of passes was 25 Not only did it require only a single pass, but a defect-free weld was obtained over the entire length, and the welding speed was increased by about 1.5 times.

As explained above, according to the method of this invention,
When performing narrow gap arc welding on thick plates, etc., it is possible to form defect-free, high-quality welds with high efficiency without causing insufficient penetration in the corners, and even with high current, high-temperature cracking does not occur. Since the nozzle does not need to be reversed as in the conventional method, there is no need for a large-scale drive mechanism for reversing, and a simple device can be used, resulting in many industrial advantages. This will bring about a positive effect.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams showing an example of a conventional narrow gap arc welding method, FIG. 4 is a schematic perspective view showing an example of a device used in the method of the present invention, and FIG. 5 is a method of the present invention. A schematic front view showing an example, Fig. 6 is a schematic plan view thereof, Fig. 7 is an explanatory drawing showing the bead formation state, Fig. 8 is an explanatory drawing showing the droplet detachment state, and Fig. 9 is an explanatory drawing showing the chip shape. FIG. In the drawings, 1, 1'...base material to be welded, 2...narrow gap, 3...
... Wire, 4 ... Contact tube, 5 ... Nozzle, 6 ... Chip, 7 ... Wire feed port, 8 ...
...Wire feeding roller, 9...Motor, 10...Rack, 11...Gear disk, 12...Motor, 13...
... Nozzle receiving pipe, 14 ... Support rod, 15 ... Welding trolley, 16 ... Molten metal, 17 ... Arc, 1
8... Molten pool, 19... Bead.

Claims (1)

[Claims] 1. A narrow gap arc welding method in which a nozzle is inserted into a narrow gap formed between base materials, and welding is performed while supplying shielding gas with a wire supplied through the nozzle. In this method, the wire is supplied offset from the central axis of the nozzle, and the nozzle is continuously rotated in one direction at a high speed of more than 10 Hz, so that an arc generated from the tip of the wire is A narrow gap arc welding method characterized by welding while performing high-speed circular motion in one direction.