JPS6147635B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding method using, for example, a non-consumable electrode, and particularly to an arc welding method suitable for performing Uranami welding.

Generally, an arc welding device used in this type of arc welding method is constructed as shown in FIG. That is, 1 is a welding torch, 2 is a welding wire, 3 is a material to be welded, 4 is an arc starting switch, and 5
is the operator's fingertip, and 6 is the welding wire feed switch.

Now, when welding, welding torch 1
By pressing the arc starting switch 4 provided at the
An arc is generated between the welding wire and the welding current is applied, and the welding wire feed switch 6 is pressed with a fingertip to move the welding torch 1 along the welding line of the workpiece 3 while feeding the welding wire 2. It is designed to perform welding.

Next, Fig. 2 shows a welding procedure using the arc welding apparatus shown in Fig. 1, and shows a state in which a pair of welded materials 3, 3 with a groove formed at the butt part are butted and welded. So, Uranami bead 8
When welding the materials to be welded 3, 3, welding that requires the appearance of a Perform welding to fill this groove. Such Uranami are often used in welded products that require high quality, such as high-pressure boilers and nuclear power plants. In order to improve Uranami welding, it is important to control the groove shape of the butt part, the root gap, and the skill of the welder, and in particular, the control of the skill of the welder has been the most difficult problem to solve.
In addition, Uranami welding is performed in places such as space where there is no gravity.
Although this can be done relatively easily, it is currently difficult to prevent melting due to the influence of gravity.

That is, since it is necessary to bring out the uranami bead 8 in the above-mentioned first layer welding, the plate thickness at the bottom of the groove is made thin to reduce the heat capacity, so melting and separation are likely to occur in the uranami bead 8, which is affected by gravity. As a result, irregularities in the Uranami beads 8 or bead burn-through tend to occur, and the range of stable welding conditions is extremely narrow.

The method of the present invention was developed in view of the above-mentioned drawbacks, and an object of the present invention is to provide an arc welding method that can obtain stable back waves.

That is, in welding that requires uranami, the groove shape of the groove is such that the plate thickness at the bottom of the groove is thinner, and the surface tension, arc force, and gravity of the groove surface are reduced during welding. This was done by focusing on the fact that it is difficult to obtain a stable back wave due to the relationship between Specifically, when metal is melted by firing an arc within the groove, the molten metal comes out as a wave due to the arc force and gravity, but before this molten metal solidifies, it is caused by the surface tension described above. This method focuses on the phenomenon of molten metal being sucked up, and in order to solidify the molten metal quickly, the method of this invention uses a pulsating current of a predetermined frequency as the welding current, and feeds the welding wire during the period when the base current flows. This is to promote solidification of the welded portion of the material to be welded, thereby performing Uranami welding.

The method of this invention will be explained in detail below based on the drawings.

Fig. 3 is a time chart showing the arc welding method of the present invention, showing the relationship between welding current and welding wire feeding speed, with the vertical axis showing welding current value and welding wire feeding speed, and the horizontal axis showing time. There is.

In FIG. 3, I ₁ is a base current, I ₂ is a pulse current superimposed on the base current I ₁ , and the base current I ₁ and the pulse current constitute a pulsating current. _I3 is the peak current that is the sum of the base current _I1 and pulse current _I2 , _T1 is the time during which the peak current _I3 flows, and _T2 is the base current _I1.
The configuration is such that the wire feeding is stopped during the above T ₁ hour, and the welding wire 2 is fed at a speed W ₁ during the T ₂ hour, and the above peak current I ₃
During the period in which the welding wire 2 is flowing, the feeding of the welding wire 2 is stopped and the welding wire 2 is fed at the same time as the base current becomes the base current.

Now, when the arc starting switch 4 in the arc welding apparatus shown in FIG. 1 is pressed, a base current _I1 is generated. In this case, even if the user releases the arc starting switch 4, the base current is maintained as it is because the base current is self-maintained. In such a state, when the arc is aligned with the welding line of the materials to be welded 3, 3, and then the welding wire feed switch 6 is pressed, the peak current _I3 is first applied to the materials to be welded 3, 3.
After the groove welded portion of No. 3 is sufficiently melted, the base current becomes _I1 , the amount of heat generated decreases, and the molten pool begins to solidify. At the same time, feed the welding wire 2,
Before the weld metal is sucked up by surface tension,
The cooling effect caused by this melting of the welding wire 2 promotes solidification of the molten metal. Hereinafter, the welding process of Uranami welding is carried out while repeating the above-described melting and solidification.

Next, one embodiment of the present invention will be described. That is, in this embodiment, as shown in Fig. 4, the outer diameter is
Welded materials 3, 3 with a diameter of 318.5 mm and a thickness T of 10.3 mm were used, and the groove angle θ was made into a V shape of 60 degrees, and a mild steel welding wire 2 with a diameter of 1.2 mm and a tungsten electrode with a diameter of 3.2 mm were used. This is an example in which welding was performed at a welding speed of 60 mm/min.
mm, and the length l of the straight part is 1 mm.

Then, the peak current I ₃ mentioned above is 130A, the base current I ₁ is 50A, and the time T ₁ during which the peak current I ₃ flows is
The time T ₂ during which the base current I ₁ and the base current I 1 flow are set to 0.5 seconds, so that the currents I ₃ and I ₁ flow alternately at intervals of 0.5 seconds, and the feeding speed of the welding wire 2 is set to the peak current I The base current is set to be 0 mm/min during the period when I ₃ is flowing, that is, within the time T ₁ , and 850 mm/min during the period when the base current I ₁ is flowing, that is, during the time T ₂ . It was confirmed that good Uranami welding could be performed in Examples under such conditions.

As described above, according to the present invention, the welding current of the welding torch 1 is made into a pulsating current having a predetermined pulse amplitude, and the welding wire 2 is fed during only the period of the base current of the pulsating current to weld the workpiece. Since Uranami welding was carried out by promoting the solidification of the welded part and stopping the feeding of the welding wire during the period of peak current, the welded part of the welded materials 3 and 3 was periodically melted and solidified. In Uranami welding, which has a small heat capacity, the welding work progresses while
Alternatively, it has an excellent practical effect of preventing burn-through, etc., and making it possible to perform stable Uranami welding at all times.

[Brief explanation of the drawing]

Figure 1 is a front view of a general arc welding device;
Fig. 2 is a perspective view showing the welding state, Fig. 3 is a time chart of the arc welding method of the present invention, and Fig. 4 is a perspective view showing the welding state.
The figure is a sign for explaining one embodiment of the present invention. In the drawing, 1 is a welding torch, 2 is a welding wire, 3
is the material to be welded, I ₁ is the base current, and I ₃ is the peak current. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 The welding current of the welding torch is a pulsating current with a predetermined pulse amplitude, and the welding wire is fed during the period of only the base current of this pulsating current to promote solidification of the welded part of the welded material, and to increase the peak current. Arc welding is performed by stopping the feeding of the welding wire, melting the welded part of the material to be welded, and periodically repeating melting and solidification of the welded part of the material to be welded. Method.