JPS6146235B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an automatic uranami welding method.

Conventionally, Uranami welding in the gas shielded arc welding method uses CO ₂ + Ar, O ₂ + CO ₂ + in the shielding gas.
A mixed gas such as Ar is used, and a torch such as a delta oscillator or chestnut oscillator is made to perform complex operations in order to advance the arc point and form a uniform back bead.

However, mixed gas is difficult to control, and the complicated control of the torch makes the equipment large and expensive, making it difficult to handle such heavy and high-grade equipment for on-site welding of pipelines, steel construction, etc. There was a problem that made people avoid it because it was inconvenient.

The present invention solves the above problem by selecting appropriate welding conditions, using only CO ₂ as a shielding gas, and making it possible to perform back wave welding in a narrow gap by simply weaving the torch.

The present invention will be specifically described below based on Examples.

Welding targets structural members such as piping and steel frames.
The materials used for these structural members are carbon steel and low alloy steel.

The welding device used is a known welding device equipped with a solid wire supply device and a weaving oscillator mechanism that reciprocates the torch only in the direction perpendicular to the welding line, on a trolley that runs on rails arranged along the welding line. This is a carbon dioxide shielded arc welding device.

A solid wire with a diameter of 1.2 mm containing a deoxidizing agent such as Si or Mn is used.

The shape of the butt joint of the two members to be welded is a narrow groove with a bevel angle of 30° and a root gap of 3 to 4 mm.

Using the above-mentioned welding equipment and solid wire, welding was performed on the butt joints under conditions of a welding current of 100 to 110 A and a welding voltage of 18 to 20 V, varying the welding speed and weaving speed, and the back bead was examined.

Figure 1 shows an experimental example of uranami welding of low-alloy steel containing about 1% Cr.The vertical axis shows the welding speed, and the horizontal axis shows the weaving speed. It is a graph showing the range in which a substantially uniform back bead is formed for each case.

As can be seen from this graph, as the root gap widens, the amount of solid wire deposited must naturally increase, and the appropriate welding speed range shifts to the lower welding speed side.

However, if the welding speed is too slow, too much of the back bead will protrude, and in extreme cases, a burn-through phenomenon will occur. The lower limit of welding speed is 70mm/min.

Furthermore, if the weaving cycle is lowered at a constant welding speed, the amount of solid wire welded increases, resulting in the same phenomenon as when the welding speed is slowed down. Conversely, if the weaving cycle is increased, penetration will be insufficient, resulting in poor fusion, and the back bead will become disordered.

Even if the welding speed is set too high, penetration will be insufficient and the back bead will be disordered as described above.

To form a substantially uniform back bead for a V-groove with a root gap of 3 mm and a 30° angle, the welding speed is 110 to 200 mm/min, the weaving cycle is 36 to 76 cycles/min, and the welding speed is ₁₁₀ to 200 mm/min. It turns out that the condition is that the coordinates of the area shown in

Similarly, for a root gap of 4 mm and a V-groove of 30°, the welding speed is 70 to 170 mm/min, the weaving cycle is 22 to 76 cycles/min, and the coordinates surrounded by the dashed line L2 in Fig. ₂ are as follows. The condition is that it be shown in the area.

Combining the above points, the root gap is 3-4.
To form a substantially uniform back bead for a 30° V-groove, the relationship between welding speed and weaving cycle is as shown by the diagonal line in Figure 1, when the root gap is 3 mm.
The condition is that the appropriate coordinate area for the root gap and the appropriate coordinate area for the root gap of 4 mm overlap each other.

As mentioned above, the present invention involves back wave welding into a narrow gap, so even if inexpensive carbon dioxide gas is used as the shielding gas, the arc is stable, and the welding equipment can be a simple weaving torch, so it is easy to handle. Uranami welding can be performed easily and at low cost. Furthermore, since a substantially uniform back bead can be formed up to a root gap of 3 to 4 mm, high groove precision is not required. For example, it can be applied to back wave welding to a groove created by gas cutting, and has excellent effects. It is something that you have.

[Brief explanation of the drawing]

FIG. 1 is a graph showing appropriate ranges of welding speed and weaving speed.

Claims (1)

[Claims] 1. In carbon dioxide gas arc welding to a V-shaped groove with a root gap of 3 to 4 mm and a groove angle of approximately 30° on steel structural members such as pipeline pipes and steel frames, the torch weaving cycle and welding speed are as shown in the attached drawing. An automatic back wave welding method for a narrow gap, characterized in that the area is within the shaded area in FIG.