JP2000343224A - Consumable electrode type arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely obtain the stability of welding without bringing about the remakable cost-up by giving a wire the mechanical movement different from shifting according to the welding velocity. SOLUTION: The mechanical movement 6 different from shifting of the wire 1 shifted at the fixed velocity in the welding direction in given to the wire. For example, in the case of giving the mechanical movement in the A direction, molten drip 2 is positively shifted to a welding material 5 side, and in the case of giving the mechanical movement in the B direction, the molten drip can not be made to shift to the welding material 5 side. Since only the mechanical movement is given to the wire, the running cost-up is not brought about, and since the independent control is executed from the electric factor, the degree of freedom to the welding condition is wide and the arc heat can be dispersed with the mechanical movement. In the case of forming a bead over the wide range, the mechanical movement is made to the movement having periodicity and thus, the extremely stable welding can be executed and the outward appearance of the bead becomes beautiful.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode type arc welding method, and more particularly to a consumable electrode type arc welding method for performing droplet transfer by repeating arc generation and short circuit generation.

[0002]

2. Description of the Related Art In a consumable electrode type arc welding method, a consumable electrode wire (hereinafter, referred to as a wire) is continuously fed toward an object to be welded while a welding voltage is applied between the wire and the object to be welded. Is generated, and the generated heat is used to melt and join the wire and the workpiece. At the time of welding, an Ar gas (in the case of MIG welding), a CO ₂ gas, or a mixed gas of CO ₂ and Ar (in the case of MAG welding) is used as a shielding gas in order to set the welding site to a predetermined atmosphere.

When a thin steel sheet is welded by such a consumable electrode type arc welding method, the welding is performed in a low current and low voltage range, so that arc generation and short-circuit generation are repeated and the transfer of droplets is accompanied. proceed.

FIG. 4 schematically shows a droplet transfer phenomenon. Figure 4
(A) to (f) show changes with time of droplet transfer.

(A): When a voltage is applied between the wire 1 and the workpiece 5, an arc 3 is generated. (b): The tip of the wire 1 is melted by the arc heat, and a droplet 2 is formed. (c): The droplet 2 grows. (d): When welding is performed in a low current / low voltage range, the droplet 2 comes into contact with the bead 4 or the workpiece 5 without detaching from the wire 1. At this point, arc 1 is extinguished. (e): The droplet 2 moves to the workpiece 5. At this time, the welding current sharply increases due to the contact short circuit. (f): The droplet 2 is detached from the wire 1 by receiving a strong electromagnetic pinch force due to a sudden increase in welding current.

[0006] Thereafter, the arc 1 is generated again, and the state returns to the state (a). Thereafter, the same phenomenon is repeated.

[0007] The stability of welding is greatly affected by the droplet transfer phenomenon, and if the droplet transfer stability is poor, the following various problems are caused.

1) When the arc time and the short-circuit time are long, the number of short-circuits is reduced, and the bead appearance deteriorates.

2) When the arc length is shortened rapidly, the short circuit is not released and is maintained for a long time. During this time, the heated wire explosively melts and causes an arc break, so that the welding speed cannot be increased.

3) A strong electromagnetic pinch force generated by a sudden rise of the current at the beginning of the short circuit causes the short circuit to be released before the droplet transfers to the work to be welded. The droplet at the tip hardly migrates to the work to be welded, and grows as large as when the number of short circuits is reduced. Therefore, a large current flows at the time of short circuit, large spatters are generated, and arc breakage easily occurs.

4) When the present invention is applied to an assembly line of an automobile or the like, a welding amount for filling a gap existing at a welding portion is usually required, and a wire feeding amount is required despite a small heat capacity of a workpiece. (Welding amount) needs to be increased, so if you try to heat the wire sufficiently, the heat input to the workpiece will also increase, causing burn-out, or conversely, if you do not heat the wire enough, the wire will melt. It rushes into the pond and breaks through the work to be welded, causing burnout. In addition, when the wire plunges into the molten pool, a large short circuit occurs, the wire is excessively heated, the tip of the wire blows off, and a large arc is generated.However, at this time, the heat input to the wire decreases, so the wire cools down. And the phenomenon that the wire again plunges into the molten pool is repeated, making the welding very unstable and failing to obtain good welded properties. In particular, if the length of the protruding portion of the wire is long, the time constant of the current becomes large, so that the current cannot flow immediately to open the short circuit, so that a large short circuit is likely to occur, and this tendency is remarkable. Become.

In order to solve the above problems,
Conventionally, various studies have been made. For example, JP-A-9-
In the 94667 publication, a wire guide portion made of a nonconductive material having heat resistance of the same hole diameter as the wire feed portion is attached to the tip of the contact chip, and the wire is heated to some extent by Joule heat even during arc generation, Japanese Patent Application Laid-Open No. 7-116839 discloses a method of preventing a wire from rushing into a molten pool, by suppressing the occurrence of spatter by reducing the output current at the time of a short circuit, and further controlling the output current at the time of arc transfer. A method for preventing the occurrence of poor welding is disclosed in JP-A-6-170538 and JP-A-7-130130, by switching and controlling the external characteristics of a welding power supply device at high speed to prevent arcing and short-circuiting. A method for stabilizing the repetition cycle of occurrence has been proposed. Further, Japanese Patent Application Laid-Open No. 7-116839 proposes a method for accurately determining an arc state and a short-circuit state necessary for ensuring the stability of welding.

[0013]

However, the method described in the above patent publication has the following problems.

In the method described in JP-A-9-94667,
By making the distance between the contact tip (current-carrying part) and the workpiece longer than the normal length, the amount of heat input to the workpiece is reduced and the Joule heat generated by the wire protrusion is increased, thereby reducing the heat generated at the arc generator. Although it is possible to suppress, in the actual line there are various combinations of plate thicknesses, it is not always advantageous to increase the Joule heat at the wire protrusion and suppress the amount of heat generated by the arc,
Conversely, it may have an adverse effect. Further, since such a special contact chip is used as a consumable item, a remarkable increase in cost is caused.

In the methods described in JP-A-7-116839, JP-A-6-170538, and JP-A-7-1130, the stability of welding is controlled by controlling the power supply output. Is due to errors and fluctuations in gaps and target positions.
It may not always be possible to control effectively. Further, in order to realize this method, it is necessary to accurately determine the arc state and the short-circuit state by a method as described in Japanese Patent Application Laid-Open No. 7-116839. It is difficult to make an accurate determination at high speed according to the situation.

The present invention has been made in order to solve such a problem. In a consumable electrode type arc welding method for performing droplet transfer by repeating arc generation and short circuit generation,
An object of the present invention is to provide a consumable electrode type arc welding method that can reliably attain welding stability without significantly increasing the cost.

[0017]

An object of the present invention is to provide a consumable electrode type arc welding method in which an arc and a short circuit are repeatedly generated between a wire and an object to be welded so as to transfer a droplet. The problem is solved by a consumable electrode type arc welding method that imparts a mechanical movement different from the moving movement.

FIG. 1 schematically shows the principle of the method of the present invention.
Usually, the wire 1 moves at a constant welding speed in the welding direction, but performs a mechanical movement 6 different from the movement, for example,
If applied in the direction A or B in Fig. 1, droplets will be applied in the direction A.
2 can be positively transferred to the bead 4, that is, the workpiece 5 side. In the case of the direction B, the droplet 2 can be prevented from being transferred to the workpiece 5 side, and the transfer of the droplet can be controlled.

According to the method of the present invention, since only the mechanical movement is imparted to the wire, the running cost is not significantly increased unlike the use of the special tip. In addition, since the welding phenomenon other than the droplet transfer is controlled independently of the electrical factors complicatedly entangled with each other, the degree of freedom with respect to the welding conditions is wide, and the welding stability can be ensured. Further, since the arc heat can be dispersed by mechanically moving the wire, it is also effective in preventing welding defects such as burnout.

The speed of the mechanical movement applied to the wire depends on the power output during welding, the welding speed, and the wire feeding speed, but it is desirable that the speed be at least higher than the welding speed.

As a method of imparting mechanical movement to the wire, translational movement accelerates the wire at the time of change between forward and backward movements, and droplets at the tip of the wire are liable to be spattered, so that uniform movement is possible. Rotary movement is preferred.

In the case of forming a bead over a long range, if the mechanical motion imparted to the wire is a motion having periodicity, extremely stable welding can be performed, and the bead appearance becomes more beautiful.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION A 0.8 mm thick alloyed hot-dip galvanized steel sheet is prepared by using a wire having a diameter of 0.9 mmφ with a gap between the steel sheet and wire of 10 mm, a wire feeding speed of 3.4 m / min, and a welding speed.
Welding was performed under the conditions of 50 cm / min, shielding gas Ar + 20% CO ₂ while changing the set voltage. At this time, the wire was given a constant-speed rotating motion with a rotating diameter of 2 mmφ and a frequency of 50 Hz. Then, the welding voltage region in which stable welding can be performed and welding voltage / current waveforms were investigated. As a comparison, a similar investigation was conducted for a conventional example in which a constant rotational motion was not applied to a wire.

FIG. 2 shows a welding voltage region in which stable welding can be performed. It can be seen that the proper range of the welding voltage of the invention example is much wider than that of the comparative example. Therefore,
According to the method of the present invention, stable and stable welding can be achieved even if there are errors or fluctuations in the gap or the target position in the actual line.

From FIG. 2, it can be seen that the method of the present invention is also effective against burn-through. This is due to the effect of the dispersion of the arc heat due to the movement of the wire in addition to the stability of welding. Because it is.

FIG. 3 shows an example of a welding voltage / current waveform. In the invention example, the waveform is stable at any set voltage, and it can be seen that stable welding is performed.

On the other hand, in the comparative example, the waveform is disturbed, the short circuit is irregularly generated, and the peak current at the time of the short circuit also varies. In particular, when the set voltage was as low as 13 V, the waveform was greatly disturbed, and welding was impossible.

[0028]

Since the present invention is constructed as described above, the consumable electrode type arc welding method for performing droplet transfer by repeating arc generation and short circuit generation without causing a remarkable increase in cost. In addition, it is possible to provide a consumable electrode type arc welding method in which welding stability can be achieved.

Therefore, according to the method of the present invention, it is possible to perform welding without occurrence of welding defects such as spatter and burnout.

[Brief description of the drawings]

FIG. 1 is a schematic view of the principle of the method of the present invention.

FIG. 2 is a diagram showing a welding voltage region in which stable welding can be performed.

FIG. 3 is a diagram illustrating an example of a welding voltage / current waveform.

FIG. 4 is a schematic diagram of a droplet transfer phenomenon.

[Explanation of symbols]

 1 Wire 2 Drop 3 Arc 4 Bead 5 Workpiece 6 Mechanical motion

Continuing from the front page (72) Inventor: Morinoaki Ono 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Makoto Kabazawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan In-house F term (reference) 4E001 AA03 BB08 BB09 DD02 DD04 DF04 DF09 EA03 4E082 AA03 AA04 AB01 BA01 BB01 BB02 CA01 DA01 EA01 EA02 EA11 EB11 EC03 EC13 EC16 ED01 ED04 EE01 EE02 EE03 EE04 EE06

Claims (3)

[Claims] 1. A consumable electrode type arc welding method in which a droplet is transferred by repeatedly generating an arc and a short circuit between a consumable electrode wire and a workpiece to be welded. A consumable electrode arc welding method that imparts different mechanical movements. 2. The consumable electrode type arc welding method according to claim 1, wherein the mechanical motion imparted to the consumable electrode wire is a rotational motion. 3. The consumable electrode type arc welding method according to claim 1, wherein the mechanical motion imparted to the consumable electrode wire is a motion having periodicity.