JPH0324303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a two-electrode rotating arc welding method.

[Prior art and its problems]

Conventionally, when fillet welding a vertical plate and a horizontal plate in one pass in a downward position, there is a two-electrode fillet arc welding method as a means for increasing the vertical leg length and the horizontal leg length.

In the above two-electrode fillet arc welding method, a leading electrode and a trailing electrode are intentionally provided at a predetermined interval in the welding direction, a leading arc is generated between the leading electrode and the fillet weld, a lower layer bead is formed, and the trailing electrode is A single electrode corner using one electrode consists of generating a trailing arc between the electrode and the lower bead to form an upper bead on the lower bead, and supplying shielding gas to the fillet weld. Vertical leg length and horizontal leg length can be increased compared to flesh arc welding.

However, in the conventional method described above, the welding speed is slow, and both bead surfaces protrude in a chevron shape, so extra weld metal is required to obtain the desired leg length.
Sometimes, since the surface of the lower bead is not smoothed, there is a problem that the lower bead and the upper bead may not be reliably welded together.

[Purpose of the invention]

Therefore, an object of the present invention is to achieve a high welding speed and
Another object of the present invention is to provide a two-electrode rotating arc fillet welding method that can smooth the lower and upper layer bead surfaces.

[Summary of the invention]

In this invention, a leading nozzle is directed toward a fillet weld formed by a vertical plate and a horizontal plate, a leading electrode is deviated from a central axis of the leading nozzle, and a shielding gas is directed toward the fillet weld. the leading nozzle is rotated to generate a leading arc between the leading electrode and the fillet welding part to form a lower bead; A trailing nozzle is provided at a distance from the trailing nozzle, the trailing nozzle is directed toward the lower bead, and a trailing electrode is deviated from the central axis of the trailing nozzle and supplied together with a shielding gas toward the lower bead; While rotating the trailing nozzle, a trailing arc is generated between the trailing electrode and the lower layer bead to form an upper layer bead on the lower layer bead, and in this way, the vertical plate and the horizontal plate and fillet welded under the following conditions, the rotation speed of the preceding arc (N _L ): 3N _p ~ 120
Hz, Rotation diameter of the preceding arc ( _DL ): 1 to 6 mm, Rotation speed of the trailing arc ( _NT ): _3Np to 120
Hz, rotational diameter of the trailing arc (D _T ): (W _L −8
mm) and 1 mm, whichever is larger (W _L + 6 mm), the distance between the leading electrode and the trailing electrode: a leading crater caused by the leading arc and a trailing crater caused by the trailing arc. Provided that N _p is the rotational speed of the arc at which the ratio (l ₁ /l ₂ ) of the vertical leg length ( _l 1 ) and horizontal leg length (l ₂ ) is maximum, W _L : the lower bead It is characterized by satisfying the width of .

[Structure of the Invention] The inventors of the present application first proposed a rotating arc fillet welding method for fillet welding a vertical plate and a horizontal plate so that the bead surface is smoothed in a patent application published in 1983.
-106901 (hereinafter referred to as the prior invention). The prior invention will be explained below.

The welding electrode is passed through the nozzle, deviated from the center axis of the nozzle, and directed perpendicularly to the groove of the workpiece, and an arc is generated between the tip of the welding electrode and the groove to move the workpiece. welding along the groove, rotating the nozzle to cause the arc to perform a circular motion corresponding to the deflection, and supplying shielding gas towards the groove; Arc welding methods are already known. This method has the advantage that since a wide arc with a constant width is obtained, welding can be performed with high efficiency without causing deep penetration locally.

The above-mentioned prior invention applies the above-mentioned rotating arc welding method to fillet welding, and the rotational speed (N) of the arc is changed from _3Np to 120Hz (7200 rotations/min).
and the rotating diameter (D) of the arc is 1.
It is characterized by being limited to a range of 6 mm to 6 mm.

In the above-mentioned prior invention, the reason why the rotational speed (N) of the arc is limited to the range from _3Np to 120Hz is as follows.
It is as follows.

When the rotational speed (N) of the arc is less than 3N _p ,
Since the rotational speed of the arc is slow, it is difficult for the molten metal to spread to the periphery, and the bead surface cannot be sufficiently smoothed. On the other hand, the rotational speed (N) of the arc is
When the temperature exceeds _3Np , the molten metal spreads to the periphery and the bead surface is smoothed, but when the arc production speed (N) exceeds 120Hz, the amount of spatter increases and good fillet welding cannot be performed. . For this reason, in the prior invention, the rotational speed (N) of the arc was limited to a range of _3Np to 120Hz.

FIG. 1 shows the relationship between the arc rotation speed (N) and the ratio of the maximum bead protrusion height (Δl) to the average value of the vertical leg length (l ₁ ) and horizontal leg length (l ₂ ).
As is clear from FIG. 1, it can be seen that when the rotational speed (N) of the arc is 3N _p or more, the surface of the bead becomes smooth.

The vertical leg length (l ₁ ) indicates the width of the bead 3 on the vertical plate 1 side, as shown in FIG. 3, and the horizontal leg length (l ₂ ) indicates the width of the bead 3 on the horizontal plate 2 side, as shown in The width of the side bead 3 is shown.

Further, FIG. 2 shows the relationship between the rotational speed (N) of the arc and the amount of spatter. As is clear from FIG. 2, it can be seen that the amount of spatter increases rapidly when the rotational speed (N) of the arc exceeds 120 Hz.

Next, the reason why the rotating diameter (D) of the arc is limited to a range of 1 to 6 mm in the above-mentioned prior invention will be explained.

If the rotational diameter (D) of the arc is less than 1 mm, sufficient penetration cannot be obtained and the function of rotating arc welding cannot be fully demonstrated. Furthermore, in the rotating arc fillet welding method, groove tracing is performed as follows. That is, a fluctuation value of either the welding current or the welding voltage is detected, and the detected fluctuation value is integrated over equal ranges to the left and right, centering on the forwardmost point of the welding electrode in the welding direction, and, The nozzle is moved in the width direction of the bead so that the difference between the left and right integral values becomes zero. Hereinafter, this method will be referred to as groove copying using an arc sensor, but if the rotating diameter (D) of the arc is less than 1 mm, even if the center of rotation of the arc deviates from the normal position, the difference between the left and right integral values will be This is not noticeable and the groove cannot be accurately traced using the arc sensor.

On the other hand, if the arc rotation diameter (D) exceeds 6 mm,
The arc is too close to vertical plate 1 and horizontal plate 2,
In particular, undercuts are likely to occur on the vertical plate 1 side. For this reason, in the prior invention described above, the rotating diameter (D) of the arc is limited to a range of 1 to 6 mm.

This invention applies the above-described prior invention to two-electrode fillet welding.

FIG. 4 shows the vertical plate 1 by the method of the present invention.
FIG. 2 is a perspective view showing a state in which the horizontal plate 2 and the horizontal plate 2 are fillet welded. In FIG. 4, the rotational speed of the preceding electrode 5A inserted into the preceding nozzle 4A for forming the lower layer bead 3A, that is, the rotational speed ( _NL ) of the preceding arc, is determined for the same reason as in the prior invention described above. Therefore, it is limited to the range of _3Np to 120Hz.
As a result, the surface of the lower layer bead 3A is smoothed. The rotational diameter (D _L ) of the preceding arc is 1 to 1 for the same reason as in the above-mentioned prior invention.
Limited to a range of 6mm. As a result, sufficient penetration can be obtained, the groove can be traced with high precision by the arc sensor, and undercuts that tend to occur on the vertical plate 1 side can be prevented. The reason for smoothing the surface of the lower bead 3A is
This prevents unnecessary consumption of weld metal, improves the weldability between the lower layer bead 3A and the upper layer bead formed by the trailing electrode, which will be described later, and further improves the accuracy of the groove tracing by the arc sensor of the trailing electrode. This is so that you can do it well.

On the other hand, the rotational speed of the trailing electrode 5B inserted into the trailing nozzle 4B for forming the upper layer bead 3B, that is, the rotational speed ( _NT ) of the leading arc, is determined for the same reason as in the prior invention described above. According to
Limited to the range of _3Np to 120Hz. The rotational diameter (D _T ) of the trailing arc has a lower limit of (W _L −8) mm or 1 mm, whichever is larger, and an upper limit of (W _L +6) mm. Here, (W _L ) is the width of the lower bead 3A due to the preceding arc.

The reason for limiting the rotation diameter (D _T ) of the trailing arc in this way is that if the rotation diameter (D _T ) of the trailing arc is less than the lower limit value, sufficient penetration cannot be ensured.
In addition, the arc sensor cannot accurately trace the groove. On the other hand, if the rotational diameter (D _T ) of the trailing arc exceeds the upper limit value, the trailing arc will come too close to the vertical plate 1 and the horizontal plate 2, and undercuts are likely to occur particularly on the vertical plate 1 side. Because it will be.

A gap is provided between the leading electrode 5A and the trailing electrode 5B so that the leading crater caused by the leading arc and the trailing crater caused by the trailing arc do not overlap. This is to prevent magnetic blowing and to not disturb the bead shape.

When the vertical plate 1 and the horizontal plate 2 are fillet welded in this manner, a lower bead 3A and an upper bead 3B with smoothed surfaces are formed, as shown in FIG. Note that the leading and trailing electrodes 5A and 5B in this invention may be either consumable or non-consumable.

〔Effect of the invention〕

As explained above, according to the present invention, welding can be performed with high efficiency, and the lower and upper layer beads are smoothed, so there is no need for extra weld metal, and the lower and upper beads are smoothed. Since the welding is reliable, very useful effects such as no welding defects are brought about.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the rotation speed of the arc and the amount of bead protrusion, FIG. 2 is a graph showing the relationship between the rotation speed of the arc and the amount of spatter, and FIG. 3 is a graph showing the relationship between the rotation speed of the arc and the amount of spatter. Cross-sectional view of the obtained bead,
FIG. 4 is a perspective view showing fillet welding performed by the method of the present invention, and FIG. 5 is a sectional view of a bead obtained by the method of the present invention. In the drawings: 1...Vertical plate, 2...Horizontal plate, 3...Bead,
3A...Lower layer bead, 3B...Upper layer bead, 4A
... Leading nozzle, 4B ... Trailing nozzle, 5A...
Leading electrode, 5B... trailing electrode.

Claims (1)

[Scope of Claims] 1. A leading nozzle is directed toward a fillet weld formed by a vertical plate and a horizontal plate, and a leading electrode is deviated from the center axis of the leading nozzle and directed toward the fillet weld. and supplying it together with a shielding gas, while rotating the preceding nozzle, generating a preceding arc between the preceding electrode and the fillet welding part to form a lower bead, downstream of the preceding nozzle in the direction of welding progress, providing a trailing nozzle spaced apart from the leading nozzle, and directing the trailing nozzle toward the lower bead;
A trailing electrode is deviated from the center axis of the trailing nozzle and supplied together with a shielding gas toward the lower bead, and while rotating the trailing nozzle, a trailing electrode is deviated from the center axis of the trailing nozzle and a trailing electrode is supplied between the trailing electrode and the lower bead while rotating the trailing nozzle. An arc is generated to form an upper layer bead on the lower layer bead, and the vertical plate and the horizontal plate are fillet welded in this way, under the following conditions, rotation speed of the preceding arc (N _L ): 3N _p ~120Hz Rotation diameter of the leading arc (D _L ): 1 ~ 6 mm, Rotation speed of the trailing arc (N _T ): 3N _p ~120
Hz, rotational diameter of the trailing arc (D _T ): (W _L −8
mm) and 1 mm, whichever is larger (W _L + 6 mm), the distance between the leading electrode and the trailing electrode: a leading crater caused by the leading arc and a trailing crater caused by the trailing arc. Provided that N _p is the rotational speed of the arc at which the ratio (l ₁ /l ₂ ) of the vertical leg length ( _l 1 ) and horizontal leg length (l ₂ ) is maximum, W _L : the lower bead A two-electrode rotating arc fillet welding method characterized by satisfying the width of .