JPH0712541B2 - High speed rotating arc automatic welding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-speed rotary arc automatic welding method, and more particularly to smoothing of beads.

[Conventional technology]

Conventionally, for example, in fillet welding of a standing plate erected on a lower plate, welding is performed along a joint in a downward horizontal posture to weld a corner portion.

[Problems to be solved by the invention]

In fillet welding in the downward horizontal posture as described above, due to the influence of gravity, as shown in FIG. 8, a bead 4 is likely to be generated, in which the vertical plate leg length l ₁ and the lower plate leg length l ₂ are different. There was a problem that it could not be smoothed.

In addition, depending on the welding conditions, there is a problem that an undercut is likely to occur on the standing plate.

The present invention has been made to solve the above problems, and an object of the present invention is to propose a high-speed rotating arc automatic welding method capable of smoothing beads and forming beads with good penetration at high speed. Is.

[Means for solving problems]

A high-speed rotary arc automatic welding method according to the present invention is a welding method in which an arc is rotated at a high speed by rotating an electrode nozzle. It is characterized in that the bead smoothness represented by the area ratio is equal to or higher than the limit rotational speed Ncr (Hz) at which the bead smoothness starts to become greater than when the arc rotational speed is zero.

[Action]

In the present invention, since the molten pool is easily spread to the peripheral portion by rotating the arc at a high speed, the bead shape is flattened and the penetration is secured by smoothing the bead.

〔Example〕

FIG. 1 is a perspective view showing an embodiment of the present invention, in which 1 is a lower plate, 2 is a standing plate standing on the lower plate 1, 3 is an electrode rotating at a high speed, and 4 is a bead formed. is there.

During this welding, the arc is rotated at a high speed because the bead surface is smoothed by the high speed rotation of the arc, the penetration of the groove side wall is increased, and good welding can be performed at a high speed.

The bead smoothing effect due to the arc rotation differs depending on the arc rotation speed N (Hz) and the welding speed. As shown in FIG. 2, the cross-sectional area of the convex portion of the bead 4 is S, the cross-sectional area of the bead 7 is S _0, and the area ratio S / S ₀ of the convex portion of the bead is used to determine the smoothness of the bead (1- S / S ₀ ) × 100 (%), welding current V is 300A and welding speed V is 25cm / min, 50cm / min and 75cm /
FIG. 3 shows the result of examining the relationship between the rotational speed N (Hz) of the arc and the smoothness of the bead as min. In FIG. 3, a
When the welding speed v is 25 cm / min and the arc rotating diameter D is 4 mm, b is the welding speed v is 50 cm / min and the arc rotating diameter is
In the case of 4 mm, c indicates the case where the welding speed v is 75 cm / min and the rotating diameter of the arc is 2 mm. As shown in FIG. 3, the bead smoothness is smaller in the range where the arc rotation speed is low than in the conventional case where there is no rotation, but when the arc rotation speed is gradually increased, the bead smoothness also increases and the bead smoothness increases. The bead smoothness is higher than that when there is no. The bead smoothness approaches a substantially constant value when the arc rotation speed exceeds a certain rotation speed.

Therefore, as shown in Fig. 4, the smoothness of the bead However, the arc rotation speed Ncr (Hz), which is the limit at which the arc rotation speed N starts to become greater than the value at zero, is obtained for each welding condition, and the arc rotation speed N is the limit rotation according to each welding condition. By setting the speed to Ncr (Hz), the bead smoothing effect due to the rotating arc can be obtained.

Further, as shown in FIG. 4, the rotation speed N of the arc is set to be equal to or higher than the rotation speed N _CRM (Hz) at which the smoothness of the bead starts to reach its maximum, so that the smoothing effect of the bead by the rotation arc is maximized. You can

Table 1 shows the values of the above limit rotation speed Ncr (Hz) and the rotation speed Ncr _M (Hz) at which the bead smoothness starts to reach the maximum.

Table 1 shows the case where the welding current is 300A. As is clear from Table 1, the bead can be smoothed even when the welding speed v is high.

As described above, the arc rotation speed N is set to the limit rotation speed Ncr (H
z) With the above values, the bead can be smoothed, so that the bead 4 formed is flatter than the bead 4a when the arc is not rotating, as shown in Fig. 5, and the penetration in the width direction is increased. Can be achieved.

Further, when the arc rotation speed N increases, the wire welding speed MR also increases in proportion to the rotation speed N, as shown in FIG. 6, for example. That is, fillet welding becomes highly efficient. Fig. 6 shows the results of investigating changes in the melting rate MR of the wire in MAG welding with a wire diameter of 1.2 mm and a welding current of 300 A, with the arc rotation diameter being 6 mm and the arc rotation speed N being varied.
In FIG. 6, the horizontal axis represents the arc rotation speed N (Hz), and the vertical axis represents the wire melting speed MR (g / min).

In the above embodiment, the case of fillet welding has been described, but in the case of butt welding the plate 5 and the like as shown in FIG. 7 (a), or the narrow groove as shown in FIG. 7 (b). The same can be applied to the case of welding.

〔The invention's effect〕

As described above, according to the present invention, by rotating the arc at a high speed above a certain speed, the bead can be smoothed and good penetration can be secured.

Further, since the wire melting speed is increased by the high speed rotation of the arc, the efficiency of welding can be improved and the speed of welding can be increased.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is an explanatory view of the bead shape in the above embodiment, FIGS. 3 and 4 are characteristic diagrams of arc rotation speed and bead smoothness, and FIG. FIG. 5 is a cross-sectional view of the bead formed by the above embodiment, FIG. 6 is a characteristic diagram of arc rotation speed and wire melting speed, and FIG.
FIGS. 8A and 8B are explanatory views showing another embodiment, respectively.
The figure is a cross-sectional view showing a bead shape according to a conventional example. 1 ... Lower plate, 2 ... Standing plate, 3 ... Electrode, 4 ... Bead.

Claims (2)

[Claims] 1. A welding method in which an arc is rotated at a high speed by rotating an electrode nozzle, wherein a rotating speed N (Hz) of the arc is represented by a ratio of a cross-sectional area of a bead smooth portion to a total cross-sectional area of the bead. A high-speed rotating arc automatic welding method, characterized in that the smoothness is set to a rotational speed Ncr (Hz) or more, which is a limit at which the rotational speed of the arc starts to become greater than that when the rotational speed is zero. 2. The lower limit of the arc rotation speed N (Hz) is Ncr (H
z) or more and the rotational speed Ncr _M (Hz) or more at which the smoothness of the bead starts to reach its maximum, and the method for automatic high-speed rotating arc welding according to claim 1.