JP2000079474A - Arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely control a distribution and concentration of arc heat in a groove surface of a base material and to satisfactorily melt the base material while preventing excessive welding heat input by periodically fluctuating a wire feeding speed and controlling a phase difference between the fluctuation and the time when an arc current characteristic is changed. SOLUTION: A high current is obtained when the end of a wire exists in a bottom part of a groove by suitably controlling a phase difference between a periodic change of a feeding speed of a welding wire and a phase difference at the time when a pulse is generated, and the bottom part of the groove is surely molten. In DC pulse welding wherein the feeding speed of the welding wire is increased and decreased, when deposited metal is embedded e.g. up to the height of 10 mm from the bottom part of the groove at a welding heat input of 25 KJ/cm, a vertical fluctuating quantity of the wire end is preferably 5-10 mm and a fluctuating period of the feeding speed of the wire is preferably 10 Hz or below. When a period of a pulse voltage is 0.4 sec and a period of the wire feeding speed is also 0.4 sec, the phase difference is preferably -π/4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding method. More specifically, in the invention of this application, in a groove arc welding operation, an arc generating point (weld wire tip) of a welding wire is swung up and down by periodically changing a wire feeding speed. The present invention relates to a high-efficiency and high-quality welding method characterized by freely controlling an arc heat density distribution on a base material groove by controlling a phase difference between rocking and welding current characteristics. .

[0002]

2. Description of the Related Art Conventionally, in arc welding, in order to prevent welding defects such as poor fusion at a narrow gap portion (groove bottom) of a V, K, R type or the like and a narrow groove welding joint. It is known that it is necessary to administer sufficient arc heat input to the groove bottom. However, if a large heat input arc welding method is used in order to sufficiently melt the groove bottom, the metallurgical properties of the welded joint and the deformation of the weld at the weld joint become a problem due to heat during welding. In order to solve these problems, it is essential to appropriately control the distribution and concentration of arc heat within the groove.

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 difficult to perform this control and perform high-efficiency and high-quality welding. This has been a major challenge for arc welding.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a first aspect of the present invention, in which, in arc welding using a consumable electrode system, wire feeding is performed at a groove of a material to be welded. The feed rate is fluctuated periodically,
There is provided a consumable electrode type arc welding method characterized in that welding is performed by controlling a phase difference between the fluctuation and a change in arc current characteristics.

[0005] The present invention relates to the first invention, as a second invention, a method of performing DC arc welding by changing an electric quantity as an arc current characteristic, and as a third invention, a method of performing an arc current characteristic as an arc current characteristic. As a fourth invention, a method of performing AC arc welding by changing the polarity of a welding wire is described as:
As a fifth invention, a method of performing arc welding by changing a current waveform as an arc current characteristic is provided, which provides a welding method in which a fluctuation period of a wire end position of a welding torch and a fluctuation period of an arc current characteristic are combined.

That is, as described above, in the invention of this application, the feeding speed of the consumable electrode wire is periodically changed,
The arc generating point (wire tip) of the welding wire is swung in the arc axis direction. By coordinating the welding pulse current with this swing, the arc heat input point (solution wire tip) behavior range and moving speed are controlled, and the heat energy of the arc surface at the groove surface is properly controlled while thermal energy is applied to the groove bottom. The consumable electrode type arc welding method is capable of arbitrarily forming the distribution.

[0007] In this welding method, the heat density distribution in the groove can be appropriately controlled, so that it is possible to carry out a structure-preserving type welding work that does not impair the properties of the base material while avoiding excessive heat input. Also,
It is effective for consumable electrode welding (MIG, MAG, CO ₂ , SAW) of a super narrow groove with a groove width of 10 mm or less, which is conventionally difficult to perform. In addition, since the melting area and the heat affected zone during welding can be minimized, the effect of reducing deformation and residual stress is great.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the above-mentioned features, and an embodiment of the invention will be described below in detail. First, FIG. 1 illustrates a welding device that can be used in the method of the present invention. In the apparatus of FIG. 1, a welding torch (2) connected to a welding power source (1) and the welding torch (2)
And a wire feeder (7) for feeding a welding wire (3) as a consumable electrode through the wire. The feed speed of the welding wire (3) is controlled by the feeder (7). Within the groove of the material to be welded (4), which is periodically fluctuated to form, for example, a narrow groove joint, the arc heat input point (wire tip) is set in the axial direction of the generated arc (5), 1 can be swung up and down.

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. It will fluctuate periodically. In addition, the code | symbol 6 in FIG. 1 has shown the molten metal, and Z has shown the position of the wire end (distance from the groove bottom).

Further, as a comparison with the conventional method,
For example, FIG. 2A illustrates a DC pulse arc in the conventional method in which the wire feeding speed is constant.
At the time of a large current, the wire melting amount increases, and the wire end rises from A1 to A2. If the arc current is reduced after reaching A2, the amount of melting of the wire decreases, and the wire end drops to A3. However, at the bottom of the groove, the amount of heat input becomes relatively small due to a decrease in the arc current, and the state becomes unsuitable for securing melting at the bottom.

On the other hand, FIG. 2 exemplifying the method of the present invention.
In DC pulse welding in which the feed speed of the welding wire is increased or decreased in (b), the wire end is at the groove bottom by controlling the periodic change in the feed speed of the welding wire and the phase difference at the time of pulse generation. Sometimes a large current can be provided. This facilitates the melting of the groove bottom.
The arc generation position of the wire end at the groove of the material to be welded can be controlled by changes in welding power supply characteristics, welding arc current / voltage waveform, wire polarity, etc., but with respect to the feeding speed of the welding wire, When these conditions are set in cooperation with each other, the heat input distribution can be freely and effectively controlled.

By controlling the feed wire feeding speed and the phase difference at the time of changing the arc current characteristics to the optimum values, it is possible to ensure the melting of the material to be welded as the base material at the groove bottom. it can. For this optimization, it is considered that the optimum phase difference differs depending on the setting of the fluctuation period (frequency) of the feeding speed of the welding wire and the arc current characteristics, for example, the fluctuation period (frequency) of the DC pulse current.

The following example can be referred to for how to consider these periods (frequency). That is, first, the average wire feeding speed (V _fav )
In the case where the ratio (V _fr ) of the fluctuation (V ₆ ) of the periodic wire feeding speed with respect to the temperature is constant, when the fluctuation frequency increases, the vertical swing width (ΔZ) of the wire end sharply decreases, and the heat density distribution control is performed. Effect cannot be obtained. For example, FIG. 3 shows a case where the phase difference is -π / 4 and the wire feeding speed fluctuation frequency (f) and the wire end swing amplitude (Δ
Z), the V _fr is _equal to 0.
At 25 to 0.75, the wire feed speed frequency (f)
Is increased to 10 Hz, the vertical swing width (Δ
It can be seen that Z) decreases sharply and is averaged at the minimum level above 10 Hz.

Thus, for example, the heat input of welding is about 25 kJ /
If the inside of the groove is to be filled with the weld metal from the bottom of the groove to about 10 mm in height under welding conditions that assume cm, the amount of vertical fluctuation of the wire end should be at least 5 mm or more and a maximum of just over 10 mm. It is considered to provide a heat input density distribution in this range. Then, from FIG. 3, it is desirable that the wire feeding speed fluctuation frequency (f) is set to 10 Hz or less as a standard.

As for the pulse current, if the pulse frequency is increased, the melting speed of the wire is governed by the averaged current, and the swing effect of the pulse current at the wire end cannot be expected. For example, in consideration of the above 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.

The method of the present invention for controlling the phase difference between the feeding speed of the welding wire and the change of the arc current characteristic will be described more specifically by way of example. First, FIG. 4 illustrates the welding current and the wire end position when the pulse voltage cycle is set to 0.4 second in the conventional welding method in which the wire feeding speed is constant. The arc generating end (wire end) moves rapidly upward from the groove bottom,
Not enough heat can be applied to the groove bottom.

On the other hand, the correlation between the arc generating end (wire end) and the pulse current when the pulse voltage cycle is 0.4 seconds and the wire feeding speed variation cycle is 0.4 seconds is illustrated. Is shown in FIG. When the phase difference is -π / 4, the appropriate condition is satisfied. When a pulse current is applied, the wire end is present at the bottom of the groove and moves most gently upward thereafter. It can be seen that heat can be applied to the bottom.

Further, when the period of the pulse voltage is 0.2 seconds and the fluctuation period of the wire feeding speed is 0.4 seconds,
That is, FIG. 6 illustrates a case where two pulses are generated in one cycle of the feeding speed fluctuation. When the phase difference is π / 2, the wire end stops near the groove bottom, and
It can be seen that the heat input of the pulse is effectively administered. FIG. 7 illustrates a case where AC arc welding is performed instead of the DC pulse arc welding described above. The cycle of AC is 0.
2 seconds, and the fluctuation period of the wire feeding speed is 0.4 seconds. In the case of an AC arc, the material to be welded can be effectively melted when the wire side has a positive polarity. When the wire side has a negative polarity, the melting rawness is larger than when the wire side has a positive polarity, so that the wire end position changes in a complicated manner due to the periodic relationship between the fluctuation in the wire feeding speed and the fluctuation in the melting speed of the wire. In FIG. 7, the case where the phase difference is set to 0 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 the melting of the groove bottom can be ensured. It turns out that it becomes.

From these facts, it is possible to more 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 controlled freely, and the bottom of the groove in a groove such as a V, L, K type or an ultra-narrow groove with a groove width of 10 mm or less can be obtained. Welding work that can simultaneously control the securing of melting and smoothing of the bead surface shape can be performed. This also enables a structure-preserving welding work that does not cause excessive welding heat input and does not impair the properties of the base material.

[0020]

As described in detail above, the invention of this application provides a welding system capable of freely controlling 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 secure the melting of the base material while suppressing excessive welding heat input. At the same time, the heat density during welding can be reduced,
We can expect a structure preserving type welding work that does not impair the properties of the base material.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating the configuration of a welding device.

FIG. 2 is a diagram showing a change in behavior of a wire end by a conventional method (a) and a phase control of a wire feeding speed and a pulse current (b).

FIG. 3 is a diagram illustrating a relationship between a wire feeding speed frequency and a wire vertical swing width;

FIG. 4 is a diagram showing, as a specific example, a behavior change of a wire end in a case of a conventional method in which a wire feeding speed is constant.

FIG. 5 is a diagram showing a behavior change of a wire end as an example.

FIG. 6 is a diagram showing a behavior of a wire end as another embodiment.

FIG. 7 is a diagram showing a behavior of a wire end during AC pulse arc welding as an example.

[Explanation of symbols]

 Reference Signs List 1 welding power source 2 welding torch 3 welding wire 4 material to be welded 5 welding arc 6 molten metal 7 wire feeding device

Continuing from the front page (72) Inventor Kazuo Hiraoka 1-2-1 Sengen, Tsukuba-shi, Ibaraki Prefectural Science and Technology Agency Metal Materials Research Laboratory (72) Inventor Terumi Nakamura 1-2-1 Sengen Tsukuba-shi, Ibaraki Science and Technology (72) Inventor Hideyuki Yamamoto 2-1-1, Tagawa, Yodogawa-ku, Osaka-shi, Osaka F-term (reference) 4E001 AA03 BB05 BB08 BB09 BB10 DE02 DE04 DF06 QA01

Claims (5)

[Claims] In an arc welding using a wire consumable electrode system, a wire feeding speed is periodically changed at a groove of a material to be welded, and a phase difference between the change and a change in an arc current characteristic is controlled. A consumable electrode type arc welding method characterized by welding. 2. The welding method according to claim 1, wherein DC arc welding is performed by changing an electric quantity as an arc current characteristic. 3. The welding method according to claim 1, wherein AC arc welding is performed by changing the polarity of the welding wire as an arc current characteristic. 4. The welding method according to claim 1, wherein the arc welding is performed by changing a current waveform as an arc current characteristic. 5. The welding method according to claim 1, wherein a variation cycle of the wire end position of the welding torch and a variation cycle of the arc current characteristic are combined.