JP4780570B2 - Arc welding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to an arc welding method. More specifically, in the invention of this application, in the groove arc welding construction, by periodically changing the wire feed speed, the arc generation point (welding wire tip) of the welding wire is swung in the vertical direction. The present invention relates to a high-efficiency and high-quality welding method characterized by freely controlling the arc heat density distribution on a base metal groove surface by controlling the phase difference between oscillation and welding current characteristics. .
[0002]
[Prior art and its problems]
Conventionally, in arc welding, in order to prevent welding defects such as poor fusion at the narrow gap portion (groove bottom) of V, K, ladle, etc. and narrow groove welded joints, a sufficient arc has entered the groove bottom. It is known that it is necessary to administer heat. However, if a high heat input arc welding method is used to sufficiently melt the bottom of the groove, metallological characteristic deterioration and welding deformation at the welded joint due to heat during welding become problems. In order to solve these problems, it is essential to appropriately control the distribution and concentration of arc heat within the groove.
[0003]
However, although various attempts have been made in the past, it is not easy to freely control the arc heat distribution, and it is still possible to perform high-quality and high-quality welding with this control. It was a big issue.
[0004]
[Means for Solving the Problems]
Therefore, in order to solve the problems as described above, the invention of this application firstly, while continuously supplying a welding wire as a consumable electrode into the groove of the material to be welded, an arc current is supplied. A consumable electrode type arc welding method in which arc welding is performed from the bottom of the groove to a desired height as the welding wire is consumed due to the charging of the welding wire, and the feed speed and arc current characteristics of the welding wire into the groove periodically varied respectively, the distal end of the welding wire, urchin by you staying near the bottom of the groove, is characterized by arc welding by setting a phase difference to both periods.
[0005]
Then, relates to the aforementioned first aspect, the invention of this application, as the second, varying the electrical quantity characterized by performing DC arc welding, as the third, the polarity of the welding wire is changed and performing AC arc welding, and the fourth is characterized by performing arc welding by changing the current waveform.
[0006]
That is, as described above, in the invention of this application, the feeding speed of the consumable electrode wire is periodically varied, and the arc generation point (wire tip) of the welding wire is swung in the arc axis direction. By coordinating the welding pulse current with this oscillation, the arc heat input point (solution wire tip) behavior range and moving speed are controlled, and heat energy is appropriately input to the groove bottom while the heat density of the groove surface is increased. The consumable electrode arc welding method can arbitrarily form the distribution.
[0007]
In this welding method, since the heat density distribution in the groove can be appropriately controlled, it is possible to perform a structure-preserving type welding construction that does not impair the characteristics of the base material that avoids excessive heat input. Further, it is effective for consumable electrode welding (MIG, MAG, CO ₂ , SAW) of a super-groove with a groove width of 10 mm or less, which is conventionally difficult to perform. Further, since the melting region and the heat-affected zone at the time of welding can be minimized, the effect is great in reducing deformation and residual stress.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The invention of this application has the features as described above. Hereinafter, embodiments of the present invention will be described in detail.
First, FIG. 1 illustrates a welding apparatus that can be used in the method of the present invention. In the apparatus shown in FIG. 1, a welding torch (2) connected to a welding power source (1) and a wire feed for feeding a welding wire (3) as a consumable electrode via the welding torch (2). And a welding wire (3) whose welding speed is periodically changed by a feeding device (7) to form, for example, a cleavage joint (7). In the groove 4), the arc heat input point (wire tip) can swing in the axial direction of the generated arc (5), that is, in the vertical direction in FIG.
[0009]
In the conventional welding method, the feeding speed of the welding wire (3) is kept constant, but in the welding method of the present invention, the feeding speed of the welding wire (3) is not constant but periodically. Will fluctuate.
In addition, the code | symbol 6 in FIG. 1 shows a molten metal, Z shows the position (distance from a groove bottom part) of a wire end.
[0010]
Further, as a comparison with the conventional method, for example, FIG. 2 (a) exemplifies a DC pulse arc in the conventional method in which the wire feeding speed is constant. The end rises from A1 to A2. When the arc current is decreased after reaching A2, the amount of melting of the wire decreases and the wire end decreases to A3. However, since the arc current decreases at the groove bottom, the amount of heat input becomes relatively small, which is in an unsuitable state for ensuring melting of the bottom.
[0011]
On the other hand, in the DC pulse welding that increases or decreases the feeding speed of the welding wire in FIG. 2B exemplifying the method of the present invention, the periodic change of the feeding speed of the welding wire and the phase difference at the time of pulse generation are controlled. Thus, a large current can be obtained when the wire end is at the groove bottom. This facilitates ensuring the melting of the groove bottom.
The arc generation position of the wire end at the groove of the welded material can be controlled by changes in the welding power source characteristics, welding arc current / voltage waveform, wire polarity, etc., but with respect to the welding wire feed speed, When these conditions are set in coordination, the heat input distribution can be controlled freely and effectively.
[0012]
And by controlling the phase difference at the time of changing the feeding speed of the welding wire and the arc current characteristic, it is possible to ensure melting of the material to be welded as the base material at the groove bottom.
For this optimization, it is considered that the optimum phase difference differs depending on the setting of the fluctuation period (frequency) of the welding wire feeding speed and arc current characteristics, for example, the fluctuation period (frequency) of the DC pulse current.
[0013]
Therefore, for example, the following example can be referred to for how to consider these periods (frequency).
That is, first, when the ratio (V _fr ) of the fluctuation (V ₆ ) of the periodic wire feed speed to the average wire feed speed (V _fav ) is constant, when the fluctuation frequency increases, the vertical swing width ( ΔZ) decreases rapidly, and the effect of controlling the heat density distribution cannot be obtained. For example, FIG. 3 illustrates the relationship between the wire feed speed fluctuation frequency (f) and the wire end swing amplitude (ΔZ) when the phase difference is −π / 4 in the case of a DC pulse current. When V _fr is 0.25 to 0.75, when the wire feed speed frequency (f) increases to 10 Hz, the vertical fluctuation width (ΔZ) of the wire end decreases rapidly, and at 10 Hz or more, it is averaged at the minimum level. I understand that.
[0014]
Thus, for example, if the inside of the groove is filled with a weld metal from the bottom of the groove to a height of about 10 mm under welding conditions assuming a welding heat input of ˜25 kJ / cm, the vertical fluctuation amount of the wire end is at least 5 mm. As mentioned above, it is considered that the target is a little over 10 mm and the heat input density distribution is given within this range. Accordingly, from FIG. 3, it is desirable that the wire feed speed fluctuation frequency (f) is 10 Hz or less.
[0015]
As for the pulse current, when the pulse frequency is increased, the melting rate of the wire is governed by the averaged current, and the fluctuation effect due to the pulse current at the wire end cannot be expected. For example, considering the welding conditions and the amount of vertical fluctuation of the wire end, it is desirable to use a pulse frequency of a current of 10 Hz or less as a guide.
[0016]
Therefore, the method of the present invention for controlling the phase difference between the welding wire feed speed and the arc current characteristic change will be described more specifically.
First, FIG. 4 exemplifies the welding current and the wire end position when the pulse voltage cycle is 0.4 seconds in the conventional welding method in which the wire feed speed is constant. The arc generation end (wire end) moves rapidly upward from the groove bottom, and sufficient heat cannot be applied to the groove bottom.
[0017]
On the other hand, FIG. 5 illustrates the interrelationship between the arc generation end (wire end) and the pulse current when the period of the pulse voltage is 0.4 seconds and the fluctuation period of the wire feed speed is also 0.4 seconds. It is. A phase difference of −π / 4 is an appropriate condition, and when a pulse current is applied, the wire end is present at the bottom of the groove and then moves most gently upward. Compared to the conventional method of FIG. It can be seen that heat can be administered to the bottom.
[0018]
Furthermore, FIG. 6 illustrates the case where the cycle of the pulse voltage is 0.2 seconds and the fluctuation cycle of the wire feed speed is 0.4 seconds, that is, the case where two pulses are generated in one cycle of the feed speed fluctuation. It is. It can be seen that when the phase difference is π / 2, the wire end stays near the bottom of the groove, and at this time, one pulse of heat input is effectively administered.
FIG. 7 illustrates a case where AC arc welding is performed instead of the above DC pulse arc welding. The AC cycle is 0.2 seconds and the wire feed rate fluctuation cycle is 0.4 seconds. In the case of an AC arc, the welded material can be effectively melted when the wire side has a positive polarity. In addition, since the melting degree becomes larger when the wire side has a negative polarity than when the polarity is positive, the wire end position changes in a complicated manner depending on the relative relationship between the periodic wire feed speed fluctuation and the wire melting speed fluctuation. In FIG. 7, when the phase difference is 0, it is appropriate, and when the wire end stops at the groove bottom, the wire side has a positive polarity (when the melting current is positive), and it is possible to ensure melting of the groove bottom. You can see that
[0019]
And from these things, it becomes possible to further freely control the heat density distribution on the base material groove surface by arbitrarily setting the welding current waveform (heat input).
According to the present invention as described above, the heat density distribution in the groove can be freely controlled, and the groove bottom portion in the groove having a groove width of 10 mm or less and in a groove having a groove width of 10 mm or less is usually used. Welding that can control melting and bead surface shape smoothing at the same time can be performed, and this makes it possible to perform a structure-preserving-type welding that does not cause excessive welding heat input and does not impair the properties of the base material.
[0020]
【The invention's effect】
As described above in detail, the invention of this application provides a welding system that can freely control the dispersion and concentration of arc heat on the groove surface of the base material. By controlling the heat input density distribution of the arc, it is possible to ensure the base material melting while suppressing excessive welding heat input. At the same time, since the heat density at the time of welding can be reduced, a structure-preserving type welding construction that does not impair the properties of the base material is expected.
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating the configuration of a welding apparatus.
FIG. 2 is a diagram showing a change in behavior of a wire end by a conventional method (a) and phase control (b) between a wire feed speed and a pulse current.
FIG. 3 is a diagram illustrating a relationship between a wire feed speed frequency and a wire up-and-down swing width.
FIG. 4 is a diagram showing a change in behavior of a wire end in the case of a conventional method with a constant wire feed speed as a specific example.
FIG. 5 is a diagram showing a change in behavior of a wire end as an example.
FIG. 6 is a diagram showing the behavior of a wire end as another embodiment.
FIG. 7 is a diagram showing the behavior of a wire end during AC pulse arc welding as an example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Welding power source 2 Welding torch 3 Welding wire 4 Material to be welded 5 Welding arc 6 Molten metal 7 Wire feeder

Claims (4)

Consumption of arc welding from the bottom of the groove to the desired height as the welding wire is consumed by supplying an arc current while continuously feeding the welding wire, which is a consumable electrode, into the groove of the workpiece. an electrode-type arc welding method, the feed rate and arc current characteristic of the welding wire GMA in to periodically change each distal end of the welding wire, dwell near the bottom of the groove Thus, an arc welding method characterized by arc welding with a phase difference set in both cycles.   2. The arc welding method according to claim 1, wherein direct current arc welding is performed by changing an electric quantity.   2. The arc welding method according to claim 1, wherein AC arc welding is performed by changing the polarity of the welding wire.   The arc welding method according to claim 1, wherein arc welding is performed by changing a current waveform.

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