JPS6045034B2 - DC TIG weaving welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to increase the speed of TIG welding and improve the performance of the welding process by directing the TIG arc forward in the welding direction and sweeping it in a direction crossing the welding direction by a simple means. This paper aims to improve joint quality, and in particular relates to a method for high-speed welding of extremely thick plates in one pass for each layer.

Compared to MIG welding and CO2 gas arc welding, TIG welding is less likely to cause oxidation and nitridation of the weld metal, and can be applied to all-position welding.For these reasons, TIG welding is not widely used in various structures. It has been increasing rapidly in recent years.

On the other hand, the TIG welding method has lower welding efficiency than the other two methods, and there is a long-awaited need for the development of a means that can improve the welding speed. However, in TIG welding, 3 arcs are mainly generated on the molten metal, and preheating of the unwelded base metal relies exclusively on heat conduction, so if the welding speed is increased too much, there may be a problem with the base metal due to insufficient preheating. There is a problem in that poor compatibility (wettability) causes poor fusion between the weld metal and the base metal.

In addition, in the TlG welding method using a DC power source, the arc is extremely sensitive to fluctuations in the surrounding magnetic field due to magnetization or changes in shape of the welded material, and welding may become impossible due to magnetic blowing, etc. be. Or, even if it does not reach that point, the TIG arc itself tends to generate an arc between itself and the high temperature part, that is, the arc tends to swing in the direction of the welded bead, so the preheating of the unwelded base metal becomes even more scarce,
The defective fusion becomes more and more noticeable. The present inventors have been paying attention to these problems for some time, and when welding by connecting a DC power source not only to the non-consumable electrode but also to the filler metal,
When the filler metal is ahead of the non-consumable electrode in the direction of welding progress, the current direction flowing through the filler metal and the non-consumable electrode is the same, and the filler metal is behind the non-consumable electrode in the direction of welding progress. At some point, a DC TIG welding method was developed in which the direction of the current flowing through the filler metal and the non-consumable electrode is reversed, and the magnetic field formed by these directs the arc forward in the welding direction.

However, the present inventors were not satisfied with these results and proceeded with research aiming at a more stable and high-performance direct flow TIG welding method. In other words, the developed method was essentially an effective method; It seemed necessary to establish countermeasures against blowholes. In addition, since the developed method is not the so-called hot wire method itself, the filler metal itself is not heated, and if the tip of the filler metal comes off the molten pool for some reason, it will then fall onto the solidified bead. There was also the problem that the welding material had to be fed, making it impossible to continue welding. One way to solve these problems is to sweep the arc, but the conventional arc sweeping method has the following drawbacks.

1. In the method of mechanically weeping by attaching a weaver around the welding head, in addition to the weaver mentioned above,
Equipment such as the motor and slide base increases the size of the entire device, making it inconvenient to carry and difficult to apply to narrow spaces.

Second, the above mechanical methods usually require that the relative distance between the arc point and the tip of the filler metal be maintained.

Therefore, the welding torch and the filler metal guide are fixed integrally on the slide base provided on the weaver, but it is difficult to avoid fluctuations in the relative distance due to vibrations during weaving, and in some cases the filler metal guide It may not be possible to maintain the correct insertion position into the molten pool. 1 Another method is to attach an electromagnetic magnet to create a magnetic field near the arc, but in order to make this magnetic field more effective, it is necessary to place the electromagnetic magnet as close to the arc point as possible.

However, when welding thick steel plates, the magnetism flows toward the steel plate with higher magnetic permeability, and the tip of the electromagnetic magnet must be exposed to the inside of the groove, so the heat resistance of the electromagnetic magnet must be significantly improved. However, there are limits to this improvement, and even if water cooling is used in combination. Even if this is done, the device becomes larger and there is a problem similar to that in case 1. Because of this situation, it is necessary to consider weeping methods other than those described above, and various studies have been conducted on the essence of TIG arc.

As a result, the non-consumable electrodes used in TIG welding are generally thicker (e.g. 4Tr$t) to reduce electrode wear.
φ), the current density is smaller than that of MIG welding (usually about 1 Tnmφ), so the pinch effect is small. For this reason, TIG arc has extremely flexible properties, as it has less rigidity than MIG welding (which mainly uses active gas and metal plasma). It was found to be extremely large compared to that of So T.I.
In order to take advantage of the nature of the G-arc, in the method proposed above, a plurality of filler metals are prepared, a non-consumable electrode is sandwiched between the non-consumable electrodes on both sides of the welding center line, or on one side of the welding center line. The magnetic field is changed according to a constant or variable rhythm by making the current flowing through the filler metals placed before and after the welding direction when viewed from above into a pulsating current, thereby directing the magnetic field toward the front in the welding direction. We succeeded in making the TIG arc sweep in the direction perpendicular to the welding line while maintaining that state. In other words, this method requires only a pulsating current to be passed through the filler metal, so there is no need to make the structure around the torch larger or more complicated, and it is a weeping welding method that can be applied to the neck area. I can say it.
Incidentally, Japanese Patent Publication No. 45-39931 is known as a similar technique to the MIG welding method. This technology uses a wire-shaped current carrying conductor in addition to the consumable electrode, feeds the conductor from behind the consumable electrode, and adjusts the flow direction of each direct current flowing through the consumable electrode and the conductor. This directs the arc forward in the direction of welding progress.
As mentioned earlier, the MIG arc has much less flexibility than the TIG arc, so directing it forward itself is not as easy as described in the publication. Accordingly, various difficulties were also expected in making the arc sweep by the pulsating flow application method employed in the present invention. In other words, in the case of MIG welding, as mentioned above, the arc has great rigidity, so if you want to sweep the arc, the current supplied to the filler metal must be increased, and the filler metal is supplied to the molten pool. Sweeping is extremely unstable, as it may melt before it reaches the final stage. The configuration and effects of the present invention will be described in more detail below, but the embodiments described below and in the claims are not intended to limit the present invention, and various modifications can be made.

1 to 3 are explanatory diagrams showing the concept of arc column deflection in the present invention, where FIG. 1 is a front view seen from the welding progress direction, FIG. 2 is a plan view, and FIG. 3 is a side view. The welding direction is indicated by W.

The filler metals 6 and 6'' are located behind the shield cup 5 and are arranged on both sides of the welding center line with the non-consumable electrode 2 in between, so as to be oriented toward both groove surfaces 1a and 1b of the base metal 1. While being fed in the direction of the arrow Y, its tip is immersed in the molten pool 7. Beads 4 are sequentially formed at the rear of the molten pool 7. This figure shows the case of welding with direct current positive polarity. Since the base material 1 is used as an anode and the non-consumable electrode 2 is used as a cathode, in order to satisfy the above-mentioned conditions of the present invention, direct current to the filler metals 6, 6'' is applied to the filler metals 6, 6''. is used as an anode, and the base material 1 is used as a cathode. That is, the directions of current in the electrode 2 and the filler metals 6, 6'' are reversed, and magnetic fields are generated around each in directions that repel each other. As a result, the highly flexible arc column 3 is
The arc is deflected in the direction away from the filler metals 6 and 6'' to preheat the base metal 1. Reference photos 1A, No. B, and C show the arc deflection when the DC power source is connected according to Figures 1 to 3. In the photo, the tungsten electrode is energized at 200A.
, 15V1 When the current is applied to the filler metals 6 and 6'', when (4) are both zero, when B and C conduct a current of 5160A, 6■ only to either one of the filler metals 6 and 6''. , B, and C, arc deflection can be seen. In other words, when the current applied to the filler metals 6 and 6'' is zero (normal TIG arc welding conditions), there is no arc deflection, and the higher the current value applied to the filler metal, the greater the arc deflection angle. By the way, the amount of current applied to the non-consumable electrode was 200 A in the case of the reference photo, but if the value is too large, the current density will increase, and the rigidity of the arc will increase, causing the deflection and Generally, it is desirable to set the current value to 500 A or less, as this may interfere with the weeping described later.Although the current to the electrode is normally carried out with a steady current, it is of course possible to adjust it so that it becomes a pulsed arc. It is possible, and the characteristics of the TIG arc itself do not limit the present invention.Next, regarding the current value to be applied to the filler metal, the general M
In cases such as IG-TIG combined welding or plasma MIG welding, it is necessary to set the setting at a low value to avoid a situation where an arc is generated from the filler metal or a hot wire situation. It is desirable that the voltage at the wire protrusion in the material be lower than the TIG arc voltage and the current to be 200 A or less; under welding conditions exceeding these, the magnetic field is too strong and the highly flexible TI
The G arc may blow out or even be extinguished.

In addition, a hot wire situation occurs, and in order to ensure short-circuit contact with the molten pool, it is necessary to increase the wire feeding speed, resulting in inconveniences such as excessive weld metal. Next, regarding the weeping of the arc column, in the present invention, a means is adopted in which the current flowing to the filler metal is made into a pulsating flow, and the form of this pulsating current is exemplified as shown in Fig. 4. .

Figure 4 shows the pulsating flow pattern in the filler metal on the left side A-C.
The weeping situation formed by these pulsating flows is shown on the right. First, in A, the time when the filler metal 6 is energized and the time when 7 is not energized corresponds to the time when the filler metal 6'' is not energized and when it is energized, n is the energization time time interval, and T1 is the de-energization time time interval. , and Ah indicates the current when energized.
On the right side of the figure, the upper figure shows the state where the energization of the filler metal 6 is off, and the lower figure shows the state where the energization of the melt metal 6'' is off.
In both cases, the arc 3 is directed in the direction of welding progress, but in the former case it is deflected to the left of the drawing, and in the latter it is deflected to the right of the drawing, and by repeating this alternately, it intersects the weld line. Weeping in the direction is completed. Also B(7)j
In the illustrated example, when a relatively large current Ah is applied to the filler metal 6 and when a relatively small current N is applied, this corresponds to when a relatively small current A1 is applied to the filler metal 6 and when a relatively large current Ah is applied. A weeping pattern similar to that obtained by alternately turning on and off can be obtained. Furthermore, the dashed line in the pattern showing each pulsating flow in B is a case where the amount of current is varied on an even smaller order, and more fine weeping management can be performed. The pulsating flow pattern C is still another embodiment, which is a compromise between the concepts of A and B.
In each of the above examples, the filler metals 6 and 6'' were fed continuously, but when these were fed intermittently in alternation, the filler metals 6 and 6'' Since the contact and separation of the ponds 7 occur alternately, a weeping pattern similar to the on-off described in A above is exhibited. In any case, as described above, by selecting various values of Ah, Al, Th, and n, the weeping width (weeping angle) and the weeping puff cycle can be freely adjusted, and the weeping progress or amplitude at both ends Each behavior can also be freely adjusted by changing the current value. Therefore, even when welding extremely thick plates, disturbances in the magnetic field due to the base metal can be suppressed as much as possible, and since large-scale equipment is not used, sufficient weeping can be provided even to the deep parts of the development. , and 1 layer is 1
It can be said that one of the significant effects of the present invention is that a Wiebig pattern sufficient for bus welding can be easily obtained. In addition, in general single-sided back welding, if an abnormality is encountered along the weld line, such as a variation in the development root gap, misalignment, or error in the root face, the TIG arc current value will be changed in response to these. However, the temperature and shape of the arc, as well as the size of the molten pool, change accordingly.

Therefore, it is necessary to change the melting rate of the filler metal, and the TI
The current value of the G arc and the feed rate of the filler metal had to be synchronized. However, this adjustment is extremely complicated;
It is extremely advantageous that the above-mentioned abnormality can be dealt with simply by changing the amount of current applied to the filler metal as in the present invention. Some examples of such measures will be explained below. ``1) For example, the above-mentioned Figure 4B
What if the root face suddenly becomes thicker when welding a pattern? Considering L, the back bead in that part will be difficult to come out as it is. Therefore, if you adjust the current values shown by Ah and A1 to be even larger,
Arc The forward deflection angle of the column increases, and the arc directly hits the groove root surface of the unwelded part in the front.
act. As a result, the root portion is sufficiently melted and the back bead is sufficiently formed. )) In the same case, if the time period for energizing the filler metal is lengthened, the time that the arc is directed forward becomes longer and sufficient penetration can still be obtained.

(3) Regarding the above Yanghe, there is a method of combining measures (1) and (2).

(4) In the same case as above, change to the pattern shown in FIG. 4C, for example, and increase Ah further to 5 if necessary.

(5) In the above (4), there is a method of using the means of (2) in combination. (6) The above (4) and (5) may be combined.

(7) With various other minor adjustments made in accordance with these,
Several further aspects are possible. The above is a case where the filler material is supplied from the rear of the non-consumable electrode with positive DC polarity, and by adding pulsating current to this, it was possible to easily obtain a subtle weeping pattern. When the filler metal is added from the front of the non-consumable electrodes, the directions of current application may be the same.

Furthermore, in the case of DC reverse polarity, the direction of current flow to the non-consumable electrode and the filler material may be considered to be opposite to the above-mentioned case of positive polarity, and the same results can be obtained in either case. Also, when feeding filler metal from before and after the non-consumable electrode, these methods may be used. In each of the above explanations, the case where the filler metals 6,6'' are arranged almost symmetrically on both sides of the welding center line has been explained, but as already mentioned, the filler metals 6,6'' are placed on one side of the welding center line and from the two non-consumable electrodes. A similar effect can be obtained by placing the welding at the front and back in the direction of welding.Figure 5 is a plan view showing an example of this method, and the symbols in the figure have the same meanings as before. The current direction is the same for the electrode 2 and the filler metal 6, and the current direction for the filler metal 6'' is the same. does the opposite. First, in state A, only the energization to the filler metal 6'' is stopped, so the arc column 3
is drawn toward the filler metal 6 side (front right). On the contrary, D
Understand that since only the current to the filler metal 6 is stopped, the arc column 3 is repelled to the left and forward by the magnetic field of the filler metal 6'', and that A and D are both ends of the weeping. On the other hand, B shows the case where both the filler metals 6, 6'' are energized, and the arc column 3 shows the state B, which is the balanced state of A and D, and C shows the case where both the filler metals 6, 6'' are energized. '', the magnetic field disappears and the arc column 3 is directed directly under the non-consumable electrode 2. Therefore, if a pulsating flow pattern as shown in Fig. 6 is given, weeping The pattern will look like A-+B-+D-+B-+A in Fig. 5, and if a pulsating flow pattern as shown in Fig. 7 is given, the weeping pattern will be A-+C in Fig. 5. 〉D→C→A・・・・・・
Both of these can satisfy the requirements for a meritorious invention. If the non-energizing time b shown in the seventh equation is substantially zero, the pattern A1)→A will be obtained. Next, examples of the present invention will be described.

Example 1 Under the conditions shown in Table 1, downward welding and upward welding of pipes according to the method of the present invention were studied.

Reference photos 2a and 2b show the bead cross-sectional macrostructure of the welded part in the downward and upward positions, respectively, and reference photos 3a and 3b show the side bends in the downward and upward positions, respectively. Note that the groove shape is as shown in FIG. The present invention is constructed as described above, and its effects are summarized as follows. 1. A plurality of filler metals are placed before and/or after the non-consumable electrode, which directs the arc forward in the direction of welding progress. can be swept in a direction perpendicular to the weld line.

Therefore, there is no need for a mechanical oscillator such as a weaver, an electromagnetic magnet, etc., and there is no need to place any load around the welding head, making the entire device compact. Therefore, it is easy to apply to narrow spaces. 2. Since the magnetic field from the filler metal that is extremely close to the arc point is used, an effective magnetic field can be obtained regardless of the thickness of the base metal, and regardless of the groove shape or groove gap, so the arc Weeping can be performed reliably.

3 Even if there are variations in the groove root gap, misalignment, or errors in the root face, the melting state of the groove root can be easily controlled.

Since the 4T1G arc is directed in the forward direction of the welding line and is swept, high-speed welding can be performed satisfactorily.

[Brief explanation of the drawing]

Figures 1 to 3 are explanatory diagrams showing the principle of the present invention, Figures 4, 6, and 7.
FIG. 5 is an explanatory diagram showing the waveform of the pulsating current, FIG. 5 is a plan view showing the arc deflection situation, and FIG. 8 is an explanatory diagram of the groove used in the example. 2...Non-consumable electrode, 6,6''...Filler material.

Claims (1)

[Claims] 1. A DC TIG welding method using a single non-consumable electrode and a plurality of filler metals, both of which are connected to a DC power source, wherein the filler metal is non-consumable. The electrodes are sandwiched and placed on both sides of the welding center line, or on one side of the welding center line, in front and behind the non-consumable electrode in the direction of welding progress, and the filler metal is fed into the molten pool. When the filler metal and the non-consumable electrode are located in front of the welding direction, the direction of the current flowing through the filler metal and the non-consumable electrode is the same; when the filler metal is behind the non-consumable electrode in the welding direction, the filler metal and the non-consumable electrode In addition to setting the direction of the current flowing through the non-consumable electrode in the opposite direction, the current flowing through the filler metal is made into a pulsating current, so that the arc intersects the weld line with the arc directed forward in the welding direction. A direct current TIG weaving welding method that is characterized by weaving in different directions. 2 In claim 1, the pulsating flow to the filler metal is defined as the pulsating flow to the filler metal, which is applied to each filler metal disposed on one side and the other side of the welding center line among a plurality of filler metals that are continuously fed. A welding method in which electricity is alternately turned on and off to the material. 3 In claim 1, the pulsating flow to the filler metal is arranged at the front side and rear side of the non-consumable electrode in the welding progress direction among the plurality of filler metals that are continuously fed. A welding method in which electricity is alternately turned on and off to each filler metal. 4 In claim 1, the pulsating flow to the filler metal is defined as the pulsating flow to the filler metal, which is applied to each filler metal disposed on one side and the other side of the welding center line among the plurality of filler metals that are continuously fed. A welding method in which the current applied to the material is alternately high and low, and low and high. 5 In claim 1, the pulsating flow to the filler metal is arranged at the front side and rear side of the non-consumable electrode in the welding direction of the plurality of filler metals that are continuously fed. A welding method in which the current value applied to each filler metal is repeated such that the current value is alternately high and low, and low and high. 6. The welding method according to claim 2 or 3, which is carried out by changing the value of the current applied to the filler metal on the energized side. 7 In claim 2, 3 or 6, on-
A welding method in which the off-switching time interval is varied. 8. The welding method according to claim 4 or 5, in which the time interval for switching the current value to each filler metal is changed. 9 In Claims 4, 5, or 8, one or both of the peak value of the current in the filler metal on the side where the current value is large and the base value of the current in the filler metal on the side where the current value is small. A welding method that is performed by changing the 10. The welding method according to claim 1, in which each filler metal is fed alternately to provide a pulsating flow to the filler metal. 11. A welding method according to claims 1 to 9 or 10, which is applied to circumferential butt lateral welding of pipe structures. 12 In claims 1 to 10 or 11,
A welding method in which the upper limit of the amount of current applied to the filler metal is 200A. 13
A welding method according to claims 1 to 11 or 12, in which the upper limit of the amount of current applied to the non-consumable electrode is 500A. 14 In claims 1 to 12 or 13,
A welding method in which the voltage applied to the filler metal is lower than the voltage applied to the non-consumable electrode.