JP2017144480A - Arc-welding method and arc-welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc-welding method that is capable of preventing a bead from being disturbed and drooping by suppressing waving of a molten metal in buried arc welding even when gas-shield arc welding is carried out by using a large current of 300 A or higher.SOLUTION: The arc-welding method of a consumable electrode type welds a base material 4 by feeding a welding wire 5 to the part of the base material 4 to be welded and supplying a welding current to the welding wire 5 to generate an arc 7 between the tip part of the welding wire 5 and the welded part. The welding wire 5 is fed at a speed at which the tip part enters a buried space surrounded by a recessed welding part 6 formed in the base material 4 by the arc 7 generated between the tip part and the part to be welded, and the welding current is varied so that the frequency of the welding current can be 10 Hz to 1000 Hz, an average current can be 300 Az or higher, and a current amplitude can be 50 A or higher.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a consumable electrode type arc welding method and an arc welding apparatus.

  One of the welding methods is a consumable electrode type gas shielded arc welding method (for example, Patent Document 1). The gas shielded arc welding method is a technique in which an arc is generated between the welding wire fed to the welded part of the base material and the base material, and the base material is welded by the heat of the arc. In order to prevent oxidation of the base metal, welding is performed while injecting an inert gas around the weld. If it is a thin plate of about 5 mm, the butt joint of the base material can be welded in one pass.

  However, when the thickness is 9 to 30 mm, the base material cannot be welded in one pass by the conventional gas shield arc welding method. For this reason, thick plates are welded by multilayer welding in which a plurality of welding operations are repeated. However, in multi-layer welding, an increase in the number of welding steps becomes a problem. In addition, the amount of heat input becomes large, and deformation of the base material and embrittlement of the welded part become problems.

JP 2007-229775 A

  As a result of intensive investigations to solve such a problem, the inventors of the present application, as compared with a general gas shielded arc welding method, feed a welding wire at a high speed and supply a large current, The knowledge that one-pass welding can be realized was obtained. Specifically, one-pass welding of a thick plate can be realized by feeding a welding wire at about 5 to 100 m / min and supplying a large current of 300 A or more. When the welding wire is fed at high speed and supplied with a large current, a concave melted portion is formed in the base material by the heat of the arc, and the tip of the welding wire enters a space surrounded by the melted portion. When the tip of the welding wire enters deeper than the surface of the base material, the melted portion penetrates to the back side in the thickness direction of the base material, and one-pass welding becomes possible. Hereinafter, a space surrounded by the concave melted portion is referred to as a buried space, and an arc generated between the tip of the welding wire that has entered the buried space and the base material or the melted portion is appropriately referred to as a buried arc.

  However, in the high-current gas shielded arc welding method, the molten metal of the base metal and the welding wire that are melted by the heat of the arc increases, and the molten metal undulates due to the arc. There was a problem that it was greatly disturbed periodically. For example, if a welding wire is fed at a speed of 30 m / min and a butt carbon dioxide gas welding with a welding current of 450 A, a welding voltage of 40 V, and a plate pressure of 12 mm is performed, the molten metal greatly undulates, and the meandering and sagging of the beads occur Was confirmed.

  The present invention has been made in view of such circumstances, and its purpose is to suppress undulation of molten metal in buried arc welding even when gas shielded arc welding is performed using a large current of 300 A or more, An object of the present invention is to provide an arc welding method and an arc welding apparatus capable of preventing the occurrence of bead disturbance and sagging.

  In the arc welding method according to the present invention, a welding wire is fed to a welded portion of a base material, and a welding current is supplied to the welding wire, whereby an arc is generated between the distal end portion of the welding wire and the welded portion. A consumable electrode type arc welding method for welding and welding the base material, wherein the space surrounded by a concave melted portion formed in the base material by an arc generated between the tip portion and the welded portion The welding wire is fed at a speed at which the tip enters, and the welding current is varied so that the frequency of the welding current is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more.

In the present invention, the tip of the welding wire enters the buried space surrounded by the concave melted portion, and a buried arc is generated. Specifically, the tip of the welding wire is surrounded by the melted portion, and by periodically changing the welding current, the position of the wire tip in the buried space can be moved up and down. An arc is generated between the bottom and the side. The base metal melted by the heat of the arc and the molten metal of the welding wire closes the buried space and tends to flow in the direction in which the tip of the welding wire is buried, but from the tip of the welding wire to the side of the molten part It is pushed back by the force of the arc applied to the surface, and is stabilized in a state where the tip is surrounded by the melted portion.
In addition, molten metal in buried arc welding may be greatly undulated, but by periodically varying the welding current at the frequency, average current, and current amplitude, the molten metal is finer at a higher frequency than a large waving cycle. It can be vibrated to suppress large undulations of the molten metal, and one-pass welding of a thick plate can be realized.

  In the arc welding method according to the present invention, a welding wire is fed to a welded portion of a base material, and a welding current is supplied to the welding wire, whereby an arc is generated between the distal end portion of the welding wire and the welded portion. A consumable electrode type arc welding method for welding and welding the base material, wherein the space surrounded by a concave melted portion formed in the base material by an arc generated between the tip portion and the welded portion A first state in which an arc is generated between the tip portion and the bottom of the molten portion by feeding the welding wire at a speed at which the tip portion enters, and periodically changing the welding current; and the tip And a second state in which an arc is generated between the portion and the side of the melted portion are periodically changed.

In the present invention, the tip of the welding wire enters the buried space surrounded by the concave melted portion, and a buried arc is generated. Specifically, the tip of the welding wire is surrounded by the melted portion, and by periodically changing the welding current, the position of the wire tip in the buried space can be moved up and down. An arc is generated between the bottom and the side. The base metal melted by the heat of the arc and the molten metal of the welding wire closes the buried space and tends to flow in the direction in which the tip of the welding wire is buried, but from the tip of the welding wire to the side of the molten part It is pushed back by the force of the arc applied to the surface, and is stabilized in a state where the tip is surrounded by the melted portion.
In addition, molten metal in buried arc welding may wavy greatly, but by periodically changing the welding current, the first state where the arc flies to the bottom of the concave melted part and the arc to the side of the melted part. It is possible to periodically change the second state in which the metal flies, suppress the undulation of the molten metal, and realize one-pass welding of the thick plate.

  The arc welding method according to the present invention varies the first state and the second state at a frequency of 10 Hz to 1000 Hz.

  In the present invention, by fluctuating the first state and the second state at a frequency of 10 Hz or more and 1000 Hz or less, the molten metal is finely vibrated at a higher frequency than a large undulation cycle, and the large undulation of the molten metal is suppressed. Can do.

  In the arc welding method according to the present invention, the first state includes a droplet transfer form of drop transfer, and the second state includes a liquid column and an arc formed at the tip of the welding wire in a pendulum shape. Includes moving droplet transfer forms.

  In the present invention, by periodically changing the welding current, it is possible to periodically change the drop transition in which the arc flies to the bottom of the concave melted portion and the pendulum transition, and the undulation of the molten metal can be performed. Can be suppressed.

  In the arc welding method according to the present invention, the first state includes a droplet transfer mode of drop transfer, and the second state includes a droplet transfer mode of rotation transfer.

  In the present invention, by periodically changing the welding current, the drop transition in which the arc flies to the bottom of the concave melted portion and the rotating transition in which the arc flies to the side of the melted portion are periodically fluctuated. And the undulation of the molten metal can be suppressed.

  In the arc welding method according to the present invention, the first state includes a liquid column formed at the tip of the welding wire and a droplet transfer form in which the arc swings in a pendulum shape, and the second state includes a rotating rotor. Includes droplet transfer mode of ting transfer.

  In the present invention, by periodically varying the welding current, the pendulum transition in which the arc flies to the bottom of the concave melted portion and the rotating transition in which the arc flies to the side of the melted portion are periodically fluctuated. And the undulation of the molten metal can be suppressed.

  In the arc welding method according to the present invention, the welding current is varied so that the frequency of the welding current is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more.

  According to the welding conditions of 10 Hz or more and 1000 Hz or less, an average current of 300 A or more, and a current amplitude of 50 A or more, it is possible to effectively suppress the undulation of the molten metal and realize one-pass welding of a thick plate.

  In the arc welding method according to the present invention, the frequency of the welding current is 50 Hz to 300 Hz, the average current is 300 A to 1000 A, and the current amplitude is 100 A to 500 A.

  According to the welding conditions in which the frequency of the welding current is 50 Hz to 300 Hz, the average current is 300 A to 1000 A, and the current amplitude is 100 A to 500 A, it is possible to more effectively suppress molten metal waving and one-pass welding of a thick plate Can be realized.

  An arc welding apparatus according to the present invention includes a wire feeding portion that feeds a welding wire to a welded portion of a base material, and a power supply portion that supplies a welding current to the welding wire, and the welding current is supplied to the welding wire. A consumable electrode type arc welding apparatus for generating an arc between a tip portion and a welded portion of the welding wire by welding to weld the base material, wherein the wire feeding portion includes the tip portion and The welding wire is fed at a speed at which the tip portion enters a space surrounded by a concave melted portion formed in the base material by an arc generated between the welded portions, and the power supply unit The welding current is varied so that the frequency of the current is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more.

  In this invention, the front-end | tip part of a welding wire enters into the buried space surrounded by the concave fusion | melting part, and a buried arc generate | occur | produces. As described above, the tip of the welding wire is surrounded by the molten portion, and the molten metal may be greatly undulated, but the welding current is periodically changed at the frequency, the average current, and the current amplitude. Thus, the molten metal can be finely vibrated at a frequency higher than a large waving cycle, and the large undulation of the molten metal can be suppressed, and one-pass welding of a thick plate can be realized.

  An arc welding apparatus according to the present invention includes a wire feeding portion that feeds a welding wire to a welded portion of a base material, and a power supply portion that supplies a welding current to the welding wire, and the welding current is supplied to the welding wire. A consumable electrode type arc welding apparatus for generating an arc between a tip portion and a welded portion of the welding wire by welding to weld the base material, wherein the wire feeding portion includes the tip portion and The welding wire is fed at a speed at which the tip portion enters a space surrounded by a concave melted portion formed in the base material by an arc generated between the welded portions, and the power supply unit The first state in which an arc is generated between the tip and the bottom of the melted portion and the second state in which an arc is generated between the tip and the side of the melted portion are periodically changed. Fluctuate periodically .

  In the present invention, the tip of the welding wire enters the buried space surrounded by the concave melted portion, and a buried arc is generated. As described above, the tip of the welding wire is surrounded by the melted portion, and the molten metal may be greatly undulated, but by periodically changing the welding current, an arc is formed at the bottom of the concave melted portion. It is possible to periodically change the first state in which the arc flies and the second state in which the arc flies to the side of the molten portion, thereby suppressing the undulation of the molten metal, and realizing one-pass welding of the thick plate.

  According to the present invention, even when gas shielded arc welding is performed using a large current of 300 A or more, the undulation of molten metal in buried arc welding can be suppressed, and the occurrence of bead turbulence and sagging can be prevented. .

It is a schematic diagram which shows one structure of the arc welding apparatus which concerns on this Embodiment 1. FIG. It is a flowchart which shows the procedure of the arc welding method which concerns on this Embodiment 1. FIG. It is a sectional side view which shows the base material of welding object. It is a graph which shows the fluctuation | variation of a welding voltage and a welding current. It is a schematic diagram which shows the arc welding method which concerns on this Embodiment 1. FIG. It is a graph which shows the experimental result regarding stabilization of a buried space and a bead shape with a photograph. It is a table | surface which shows the experimental result regarding stabilization of a buried space and a bead shape with a schematic diagram. It is a graph which shows the conditions of the welding current and voltage which implement | achieve a buried arc. It is a conceptual diagram which shows the relationship between the wire diameter and wire protrusion length, and the conditions of the welding current and voltage which implement | achieve a buried arc. It is a graph which shows an example of the conditions of the welding current and voltage which implement | achieve a buried arc in the case of wire diameter 1.6mm and the protrusion length of a welding wire 25mm. It is a graph which shows each droplet transfer form of drop transfer, pendulum transfer, and rotating transfer. It is a conceptual diagram which shows the relationship between the welding current when a wire diameter is 1.2 mm and wire protrusion length is 25 mm, and the droplet transfer form of a welding wire. It is a conceptual diagram which shows the relationship between a wire diameter and a wire protrusion length, and the droplet transfer form of a welding wire. It is a conceptual diagram which shows the relationship between a welding current when a wire diameter is 1.4 mm and wire protrusion length is 25 mm, and the droplet transfer form of a welding wire.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is a schematic diagram showing one configuration of an arc welding apparatus according to the first embodiment. The arc welding apparatus according to the first embodiment is a consumable electrode type gas shielded arc welding machine capable of butt welding a base material 4 having a thickness of 9 to 30 mm in one pass, and includes a welding power source 1 and a torch 2. And a wire feeding unit 3.

  The torch 2 is made of a conductive material such as a copper alloy, and has a cylindrical shape that guides the welding wire 5 to the welded portion of the base material 4 and supplies the welding current Iw necessary for generating the arc 7 (see FIG. 5). Contact chip. The contact tip contacts the welding wire 5 that is inserted through the contact tip, and supplies the welding current Iw to the welding wire 5. The torch 2 has a hollow cylindrical shape surrounding the contact tip, and has a nozzle for injecting a shielding gas to the welded portion. The shielding gas is for preventing the base material 4 and the welding wire 5 melted by the arc 7 from being oxidized. The shield gas is, for example, carbon dioxide, a mixed gas of carbon dioxide and argon, an inert gas such as argon, or the like.

  The welding wire 5 is, for example, a solid wire, and has a diameter of 0.9 mm to 1.6 mm and functions as a consumable electrode. The welding wire 5 is, for example, a pack wire housed in a pail pack in a spirally wound state, or a reel wire wound around a wire reel.

  The wire feeding unit 3 includes a feeding roller that feeds the welding wire 5 to the torch 2 and a motor that rotates the feeding roller. The wire feeding unit 3 rotates the feeding roller to pull out the welding wire 5 from the wire reel and supplies the drawn welding wire 5 to the torch 2. Note that the feeding method of the welding wire 5 is an example, and is not particularly limited.

  The welding power source 1 is connected to the contact tip of the torch 2 and the base material 4 through a power supply cable, and supplies a power source 11 that supplies a welding current Iw, and a feed rate control unit that controls the feed rate of the welding wire 5. 12. The power supply unit 11 and the feed speed control unit 12 may be configured separately. The power supply unit 11 is a power supply having a constant voltage characteristic, and includes a power supply circuit 11a that outputs a PWM-controlled DC current, an output voltage setting circuit 11b, a frequency setting circuit 11c, a current amplitude setting circuit 11d, an average current setting circuit 11e, a voltage A detection unit 11f, a current detection unit 11g, and a comparison circuit 11h are provided.

  The voltage detection unit 11f detects the welding voltage Vw and outputs a voltage value signal Ed indicating the detected voltage value to the comparison circuit 11h.

  The current detector 11g detects, for example, a welding current Iw that is supplied from the welding power source 1 to the welding wire 5 via the torch 2 and flows through the arc 7, and outputs a current value signal Id indicating the detected current value to an output voltage setting circuit. To 11b.

  The frequency setting circuit 11c outputs a frequency setting signal for setting a frequency for periodically changing the welding voltage Vw and the welding current Iw between the base material 4 and the welding wire 5 to the output voltage setting circuit 11b. When performing the arc welding method according to the first embodiment, the frequency setting circuit 11c is a frequency setting signal indicating a frequency of 10 Hz to 1000 Hz, preferably a frequency of 50 Hz to 300 Hz, more preferably a frequency of 80 Hz to 200 Hz. Is output.

  The current amplitude setting circuit 11d outputs an amplitude setting signal for setting the amplitude of the periodically changing welding current Iw to the output voltage setting circuit 11b. When performing the arc welding method according to the first embodiment, the current amplitude setting circuit 11d exhibits a current amplitude of 50 A or more, preferably a current amplitude of 100 A or more and 500 A or less, more preferably a current amplitude of 200 A or more and 400 A or less. Outputs amplitude setting signal.

  The average current setting circuit 11e outputs an average current setting signal for setting the average current of the welding current Iw that varies periodically to the output voltage setting circuit 11b and the feed speed control unit 12. When carrying out the arc welding method according to the first embodiment, the average current setting circuit 11e has an average current of 300A or more, preferably an average current of 300A to 1000A, more preferably an average current of 500A to 800A. An average current setting signal indicating is output.

  Based on the current value signal Id, the frequency setting signal, the amplitude setting signal, and the average current setting signal output from each unit, the output voltage setting circuit 11b makes the welding current Iw have the target frequency, current amplitude, and average current. For example, an output voltage setting signal Ecr indicating a target voltage having an arbitrary waveform such as a rectangular wave shape or a triangular wave shape is generated, and the generated output voltage setting signal Ecr is output to the comparison circuit 11h.

  The comparison circuit 11h compares the voltage value signal Ed output from the voltage detection unit 11f with the output voltage setting signal Ecr output from the output voltage setting circuit 11b, and sends a difference signal Ev indicating the difference to the power supply circuit 11a. Output.

  The power supply circuit 11a includes an AC-DC converter that performs AC / DC conversion on commercial AC, an inverter circuit that converts AC / DC converted DC into required AC, a rectifier circuit that rectifies the converted AC, and the like. The power supply circuit 11a performs PWM control of the inverter according to the difference signal Ev output from the comparison circuit 11h, and outputs a voltage to the welding wire 5. As a result, a welding voltage Vw that varies periodically is applied between the base material 4 and the welding wire 5, and the welding current Iw is energized. The welding power source 1 is configured such that an output instruction signal is input from the outside via a control communication line (not shown), and the power source unit 11 is welded to the power circuit 11a using the output instruction signal as a trigger. Supply of the current Iw is started. The output instruction signal is output from the welding robot to the welding power source 1, for example. In the case of a manual welding machine, the output instruction signal is output from the torch 2 side to the welding power source 1 when a hand operation switch provided on the torch 2 side is operated.

The power supply unit 11 of the welding power supply 1 has a constant voltage characteristic. For example, the power supply unit 11 has an external characteristic in which a decrease in welding voltage with respect to an increase in welding current of 100 A is 4 V or more and 20 V or less. By setting the external characteristics of the power supply unit 11 in this way, it becomes easy to maintain a buried arc state.
When the decrease in the welding voltage is less than 4 V, the welding voltage fluctuation is small with respect to the arc length fluctuation due to the disturbance factor, and the welding current largely fluctuates. As a result, the melted portion 6 swings greatly, and it becomes difficult to maintain the state of the buried arc. By setting the decrease in the welding voltage to 4 V or more, the perturbation of the melted portion 6 is suppressed and it becomes easy to maintain the buried arc state.
In addition, when the arc length is shortened due to a disturbance factor, the value of the welding current is increased, the melting rate of the welding wire 5 is increased, and the arc length is increased. On the other hand, when the arc length becomes longer due to disturbance factors, the value of the welding current decreases, the melting rate of the welding wire 5 decreases, and the arc length becomes shorter (arc length self-control action). When the decrease in the welding voltage exceeds 20 V, the variation in the welding current is small with respect to the variation in the arc length due to a disturbance factor, so that the self-control action of the arc length is small. As a result, it becomes difficult to maintain the state of the buried arc. By making the decrease in the welding voltage 20 V or less, the self-control action of the arc length is maintained, and it becomes easy to maintain the buried arc state.
The voltage drop is preferably 5 V or more. The voltage drop is preferably 15 V or less.

FIG. 2 is a flowchart showing the procedure of the arc welding method according to the first embodiment, and FIG. 3 is a side sectional view showing the base material 4 to be welded. First, a pair of base materials 4 to be joined by welding are arranged in an arc welding apparatus, and various settings of the welding power source 1 are performed (step S11). Specifically, as shown in FIG. 3, a plate-like first base material 41 and a second base material 42 are prepared, and end surfaces 41 a and 42 a which are welded portions are abutted and arranged at predetermined welding work positions. . If necessary, the first base material 41 and the second base material 42 may be provided with a groove having an arbitrary shape such as a Y shape or a cross shape. The first and second base materials 41 and 42 are steel plates such as mild steel, carbon steel for machine structure, alloy steel for machine structure, and the thickness is 9 mm or more and 30 mm or less.
And the welding power source 1 sets the welding conditions of the welding current Iw within the range of the frequency of 10 Hz or more and 1000 Hz or less, the average current of 300 A or more, and the current amplitude of 50 A or more.

  The welding current Iw may all be set by the welding operator, or the welding power source 1 accepts the execution of the welding method according to the first embodiment at the operation unit and automatically sets all the conditions. You may comprise so that it may be performed. Also, the welding power source 1 accepts some welding conditions such as average current at the operation unit, determines the remaining welding conditions that match the accepted some welding conditions, and performs the condition setting semi-automatically. It may be configured.

  After various settings are made, the welding power source 1 determines whether or not the output start condition of the welding current Iw is satisfied (step S12). Specifically, the welding power source 1 determines whether or not a welding output instruction signal is input. When it is determined that the output instruction signal is not input and the output start condition of the welding current Iw is not satisfied (step S12: NO), the welding power source 1 stands by in the input waiting state for the output instruction signal.

  When it determines with satisfy | filling the output start condition of the welding current Iw (step S12: YES), the feed speed control part 12 of the welding power supply 1 sends the feed instruction signal which instruct | indicates the feed of a wire to the wire feed part 3. The welding wire 5 is fed at a predetermined speed (step S13). The feeding speed of the welding wire 5 is set within a range of about 5 to 100 m / min, for example. The feeding speed control unit 12 determines the feeding speed according to the average current setting signal output from the average current setting circuit 11e. Note that the feeding speed of the welding wire 5 may be a constant speed or may be periodically changed. Moreover, you may comprise so that a welding operator may set the feed speed of a wire directly.

  Next, the power supply unit 11 of the welding power source 1 detects the welding voltage Vw and the welding current Iw with the voltage detection unit 11f and the current detection unit 11g (step S14), and the frequency, current amplitude, and average of the detected welding current Iw. A target voltage is generated and the welding voltage is PWM controlled so that the current matches the set welding condition and the welding current Iw periodically varies (step S15). In other words, the welding power source 1 outputs the target voltage periodically varying so that the welding current Iw periodically varies at a frequency of 10 Hz to less than 1000 Hz, an average current of 300 A or more, and a current amplitude of 50 A or more in the constant voltage characteristic. To control.

  Next, the power supply unit 11 of the welding power source 1 determines whether or not to stop the output of the welding current Iw (step S16). Specifically, the welding power source 1 determines whether or not the input of the output instruction signal is continued. When the input of the output instruction signal continues and it is determined that the output of the welding current Iw is not stopped (step S16: NO), the power supply unit 11 returns the process to step S13 and continues the output of the welding current Iw.

  When it determines with stopping the output of the welding current Iw (step S16: YES), the power supply part 11 returns a process to step S12.

  FIG. 4 is a graph showing fluctuations in the welding voltage Vw and the welding current Iw, and FIG. 5 is a schematic diagram showing the arc welding method according to the first embodiment. The horizontal axis of each graph shown in FIG. 4 represents time, and the vertical axis of each graph shown in FIGS. 4A to 4C represents the set voltage of the welding power source 1, the welding voltage Vw between the base material 4 and the welding wire 5, and the arc, respectively. 7, the welding current Iw flowing through 7.

In the arc welding method according to the first embodiment, the power supply unit 11 controls the welding current Iw so that the frequency of the welding current Iw is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more. . Specifically, the welding power source 1 having a constant voltage characteristic sets the target voltage so that the welding current Iw varies in this way, and periodically varies the target voltage. The same applies to the control of the welding current Iw below. By periodically varying the welding current I with constant voltage characteristics, the melted portion 6 of the buried arc can be more effectively stabilized.
Preferably, the power supply unit 11 controls the welding current Iw so that the frequency of the welding current Iw is 50 Hz to 300 Hz, the average current is 300 A to 1000 A, and the current amplitude is 100 A to 500 A.

  More preferably, as shown in FIG. 4C, the power supply unit 11 has a welding current Iw such that the frequency of the welding power source 1 is 80 Hz to 200 Hz, the current amplitude is 200 A to 400 A, and the average current is 500 A to 800 A. To control. In FIG. 4C, the frequency of the welding current is about 100 Hz, the current amplitude is about 240 A, and the average current is about 530 A. When welding the base material 4 having a plate pressure of 12 mm under the welding conditions of the welding current Iw, for example, when the diameter of the welding wire 5 is 1.2 mm, the welding wire 5 may be fed at a speed of about 40 m / min. . Hereinafter, the diameter of the welding wire 5 is appropriately referred to as a wire diameter. When the welding current Iw and the wire feed speed are set in this way, the set voltage becomes a rectangular wave voltage having a frequency of 100 Hz and a voltage amplitude of 30 V, as shown in FIG. 4A, for example, and between the welding wire 5 and the base material 4 4B is applied with a welding voltage Vw as shown in FIG. 4B, and a welding current Iw as shown in FIG. 4C flows. For example, the welding power source 1 controls the set voltage at a frequency of 100 Hz so that the current amplitude of the welding current Iw is 240A and the average current is 530A. Further, the welding power source 1 controls the feeding of the welding wire 5 at a speed of about 40 m / min. In addition, although the welding voltage Vw is fluctuate | varied in the range of 41V or more and 27 or less, the fluctuation | variation range of the welding voltage Vw changes with the influence of various impedances. Moreover, the current waveform shown in FIG. 4C is an example, and is not particularly limited. For example, the current waveform may be a substantially rectangular wave shape or a triangular wave shape.

  When the welding current Iw is periodically changed under such welding conditions, a concave shape made of the base metal 4 melted by the heat of the arc 7 generated between the tip 5a of the welding wire 5 and the welded portion and the molten metal of the welding wire 5 is obtained. The molten portion 6 is formed in the base material 4. And when the state of the arc 7 was photographed with a high-speed camera, as shown in the left diagram of FIG. 5, a first state in which the arc 7 is generated between the tip portion 5 a of the welding wire 5 and the bottom portion 61 of the molten portion 6, It was confirmed that the second state in which the arc 7 is generated between the front end portion 5a and the side portion 62 of the melted portion 6 varies periodically.

Specifically, a first state in which the arc 7 flies from the tip 5a of the welding wire 5 to the bottom 61 of the melting portion 6 and a first state in which the arc 7 flies from the tip 5a of the welding wire 5 to the side 62 of the melting portion 6 is performed. Repeat 2 states. The first state is, for example, a state in which the droplet transfer form of the welding wire 5 is drop transfer. The second state is, for example, a state in which the droplet transfer form of the welding wire 5 is rotating. The drop transition is an example of a mode in which droplets migrate from the tip 5a of the welding wire 5 to the bottom 61 of the melted part 6, and the rotating transition from the tip 5a of the welding wire 5 to the side part 62 of the melted part 6. It is an example of the form which moves to a droplet. The molten metal closes the buried space 6a and tends to flow in the direction in which the tip 5a of the welding wire 5 is buried, but in the second state, the arc 7 jumps to the side portion 62 of the molten portion 6 and the molten portion 6 The molten metal is pushed back in the direction away from the welding wire 5, and the buried space 6a is stabilized in a concave state. In the right diagram of FIG. 5, the tip 5a of the welding wire 5 is shortened as a result of the transfer of the droplets at the tip 5a of the welding wire 5 melted by a large current.
By changing the first state and the second state at 10 Hz or more, preferably 50 Hz or more and 300 Hz or less, more preferably 80 Hz or more and 200 Hz or less, the molten metal can be slightly vibrated at a higher frequency than a large waving cycle. And the undulation of the molten metal is suppressed.

FIG. 6 is a chart showing experimental results related to stabilization of the buried space 6a and the bead shape, and FIG. 7 is a chart showing experimental results related to stabilization of the buried space 6a and the bead shape. Under the welding conditions where the wire diameter is 1.4 mm, the protruding length of the welding wire 5 is 18 mm, the feeding speed of the welding wire 5 is 17.5 m / min, and the average welding current is 530 A, the frequency and amplitude of the welding current are adjusted. It was changed and buried arc welding of thick plates was performed.
6 and 7 show the experimental results when the frequency of the welding current is 0 Hz and the amplitude is 0 A, that is, the appearance and shape of the bead when welding is performed without vibrating the welding current. 6 and 7 show the bead shape when welding is performed under the conditions of a welding current frequency of 10 Hz and an amplitude of 50 A, and the lower diagrams of FIGS. 6 and 7 show the welding current frequency of 50 Hz and the amplitude. Shows the appearance and shape of the bead when welding is performed under the condition of 100A.

As can be seen from the experimental results shown in FIGS. 6 and 7, a good bead shape can be obtained by oscillating the welding current under welding conditions with a frequency of 10 Hz or more and a current amplitude of 50 A or more compared to the case of a frequency of 0 Hz. I understand. Such a good bead shape indicates that the buried space 6a is stabilized by vibrating the welding current at a frequency of 10 Hz, and the occurrence of a short circuit is suppressed.
Also, by virtue of the operating principle of suppressing molten metal undulation by vibrating the molten metal at a high frequency, even if the frequency of the welding current is 10 Hz or higher, the molten metal undulation is similarly suppressed to stabilize the buried space 6a. It is expected that Moreover, since the undulation of the molten metal can be sufficiently suppressed with a current amplitude of 50 A, it is expected that the undulation of the molten metal can be suppressed even with a current amplitude of 50 A or more. Actually, when welding was performed under the welding conditions of a melting current frequency of 50 Hz and a welding current of 100 A or more, a better bead shape was obtained as shown in FIGS. The wire diameter, the protruding length of the welding wire 5, the feeding speed, and the average current are not particularly limited as long as the buried arc described below can be realized, and the frequency of the welding current is 10 Hz or more. If the current amplitude is 50 A, a good bead shape can be obtained in the same manner. In particular, if the frequency is 50 Hz and the current amplitude is 100 A or more, a better bead shape can be obtained.

<Welding conditions for buried arc>
Hereinafter, the welding conditions for realizing the buried arc will be described.
In arc welding, generally, the position of the tip 5a of the welding wire 5 is located above the base metal 4 and an arc is generated between the tip 5a of the welding wire 5 and the base 4 in this state. An arc generated in such a state is called a non-buried arc. In a non-buried arc, the distance between the tip 5a of the welding wire 5 and the surface of the molten metal formed on the surface of the base material 4 is referred to as the arc length. This arc length decreases as the welding voltage decreases. It is known to be shortened. In normal arc welding, when the arc voltage is shortened by lowering the welding voltage, the distance between the molten metal and the tip 5a of the welding wire 5 is reduced, and eventually the arc length becomes zero and the welding wire 5 A short circuit occurs between the base material 4 and it becomes difficult to maintain the arc.

  However, in high current welding, since the molten metal is pushed away by the arc pressure, short-circuiting is less likely to occur even if the voltage is lowered. As a result, even if the tip 5a of the welding wire 5 is positioned deeper than the base material 4 or the molten metal surface, the presence of the space 6a formed by the molten metal being pushed away by the arc pressure, that is, the buried space 6a. A short circuit does not occur and the arc can be maintained. This is the buried arc phenomenon.

  That is, a buried arc can be realized by generating an arc under a low voltage condition in a high current region in which the arc pressure is increased. Specifically, a welding current of 300 A or more is necessary (for example, Tomo Asai, “Increasing efficiency of factory welding-case of heavy electrical equipment welding”, Japan Welding Association, Welding Information Center, WE-COM Magazine. No. 16, April 2015). The voltage value capable of realizing the buried arc varies depending on the welding current, the wire diameter, and the protruding length of the welding wire 5, but as described above, the position of the tip 5a of the welding wire 5 is changed to the base material 4 or the molten metal. By setting the voltage low enough to be lowered to a position lower than the metal surface, a buried arc can be realized.

  FIG. 8 is a graph showing the welding current and voltage conditions for realizing a buried arc. The horizontal axis indicates the welding current, and the vertical axis indicates the welding voltage. The open area indicates the welding current and voltage that can achieve a buried arc. As shown in FIG. 8, when the welding voltage is high with respect to the welding current, normal arc welding, that is, non-buried arc welding is performed. Conversely, when the welding voltage is too low, the output is insufficient and it becomes difficult to maintain the arc. . In the middle region, there is a range that becomes a buried arc in which the arc 7 is generated in the buried space 6a.

  Further, the range of welding conditions for realizing the buried arc is affected by the wire diameter and the protruding length of the welding wire 5 as described above.

  FIG. 9 is a conceptual diagram showing the relationship between the wire diameter and the wire protrusion length, and the welding current and voltage conditions for realizing the buried arc. As shown in FIG. 9, as the wire diameter increases or the protruding length of the welding wire 5 decreases, the range of the welding current and voltage that can realize a buried arc is as shown by reference numerals Arc3, Aec2, and Arc1. Shifting to the lower voltage region side for the same current in order.

  FIG. 10 is a graph showing an example of welding current and voltage conditions for realizing a buried arc when the wire diameter is 1.6 mm and the welding wire 5 has a protruding length of 25 mm. In FIG. 10, the horizontal axis indicates the welding current, and the vertical axis indicates the welding voltage. The black circle plot shows the boundary between the non-buried arc and the buried arc. In FIG. 10, the black circle plot on the upper polygonal line becomes a non-buried arc when the welding voltage is increased in the welding current indicated by the black circle plot, and becomes a buried arc when the welding voltage is decreased. Further, the black circle plot on the lower polygonal line becomes a buried arc when the welding voltage is increased in the welding current indicated by the black circle plot, and becomes a non-buried arc when the welding voltage is decreased. In short, when the welding voltage is high with respect to the welding current, normal arc welding, that is, non-buried arc welding is performed, and conversely, when the welding voltage is too low, the output is insufficient and it is difficult to maintain the arc. In the middle region, there is a range that becomes a buried arc in which the arc 7 is generated in the buried space 6a.

As described above, the welding current that realizes the buried arc is 300 A or more, and when the tip 5a of the welding wire 5 approaches the molten metal, an electric current that can generate an arc pressure that pushes the molten metal away. Value. Further, the welding voltage that realizes the buried arc is a voltage value that can lower the position of the tip 5a of the welding wire 5 to a position lower than the base material 4 or the molten metal surface.
The specific welding current and voltage may be determined as appropriate in consideration of the tendency shown in FIGS. 8 and 9 with reference to the range of the welding current and voltage shown in FIG.

<Welding conditions that can stabilize buried space and suppress undulation of molten metal>
Other suitable welding conditions that stabilize the buried space 6a and can suppress the undulation of the molten metal will be described.
Such suitable welding conditions are, for example, a frequency of welding current of 20 Hz to 600 Hz, an amplitude of 50 A to 500 A, and an average current of 300 A to 1000 A.
Further, the frequency of the welding current may be 40 Hz to 380 Hz, the amplitude may be 100 A to 500 A, and the average current may be 300 A to 1000 A.
Furthermore, the frequency of the welding current may be 60 Hz or more and 280 Hz or less, the amplitude may be 100 A or more and 500 A or less, and the average current may be 300 A or more and 900 A or less.
Furthermore, the frequency of the welding current may be 60 Hz to 180 Hz, the amplitude may be 150 A to 500 A, and the average current may be 300 A to 800 A.

As described above, according to the arc welding method and the arc welding apparatus according to the first embodiment, the welding current Iw is periodically changed even when gas shield arc welding is performed using a large current of 300 A or more. As a result, the undulation of the molten metal can be suppressed, and the occurrence of bead disturbance and sagging can be prevented.
Moreover, in order to suppress the undulation of molten metal more effectively, it is necessary to keep the arc length constant. In the case of general constant current pulse welding, since the self-control action of the arc length cannot be obtained, it is necessary to perform some control for assuring a constant arc length. Since the arc welding apparatus according to the first embodiment has constant voltage characteristics and a self-control action of the arc length is obtained, the arc length is kept constant, and the undulation of the molten metal can be more effectively suppressed.

  In the first embodiment, the case where the period during which the welding current Iw and the welding voltage Vw are large and the period during which the welding voltage Vw is small is substantially the same, but the ratio of each period may be changed. By changing the ratio of the period, it is possible to adjust the range of fluctuation in the vertical position of the distal end portion 5a of the welding wire 5 while suppressing the undulation of the molten metal. For example, by increasing the ratio of the period during which the welding current Iw and the welding voltage Vw are large, the ratio at which the tip 5a of the welding wire 5 is held at a position higher than the bottom 61 of the melted part 6 is increased. As a result, the amount of heat input to the base material 4 can be increased and the bead moldability can be improved.

(Embodiment 2)
Since the arc welding method and the arc welding apparatus according to the second embodiment are different from the first embodiment in the welding conditions such as the welding current Iw, the following mainly describes the differences. Since other configurations and operational effects are the same as those of the first embodiment, the corresponding portions are denoted by the same reference numerals, and detailed description thereof is omitted.

First, the droplet transfer mode and its features in buried arc welding will be described.
FIG. 11 is a chart showing each droplet transfer mode of drop transfer, pendulum transfer, and rotating transfer. In FIG. 11, the left column shows welding conditions, and the right column shows a plurality of different droplet transfer forms. The middle row shows a schematic diagram showing an image obtained by photographing the molten portion 6 in each droplet transfer form every 0.4 msec using a high-speed camera. In buried arc welding, there are multiple droplet transfer modes. The plurality of droplet transfer modes include, for example, three types of droplet transfer modes shown in FIG. 11, that is, drop transfer, pendulum transfer, and rotating transfer. Drop transfer and rotating transfer are general names, but pendulum transfer is coined by the inventor.

  These droplet transfer modes are comprehensively influenced by various factors including the welding current, the wire protruding length, the diameter of the welding wire 5, the material of the welding wire 5, the feeding speed of the welding wire 5, and the like. Although determined, it is particularly strongly influenced by the welding current. The wire protrusion length is the distance between the tip of the contact chip and the base material 4. When the welding current is relatively small, a drop transition is exhibited, and the droplet transfer form transitions to a pendulum transition and a rotation transition as the welding current increases.

The drop transfer is a droplet transfer form in which the tip 5a of the welding wire 5 is melted and the droplets are separated from the welding wire 5 in a granular form, and an arc is generated between the tip 5a of the welding wire 5 and the bottom 61 of the melting part 6. 7 occurs. That is, in the drop transition, the arc 7 is downward, that is, the extending direction of the welding wire 5.
In the pendulum transfer, the liquid column and the arc 7 formed at the distal end portion 5a of the welding wire 5 swing in a pendulum shape on the same plane, and the plane as a whole is slightly set with the protruding direction of the welding wire 5 as the central axis. It is a characteristic droplet transfer form that rotates one by one.
In the rotation transition, an arc 7 is generated between the distal end portion 5a of the welding wire 5 and the side portion 62 of the molten portion 6, and the liquid column and the arc 7 formed at the distal end portion 5a of the welding wire 5 are concavely melted portion 6. This is a droplet transfer form that continues to rotate while facing the side 62 direction.

  As an example, welding current and droplet transfer mode under conditions where the wire protrusion length is 25 mm, the diameter of the welding wire 5 is 1.2 mm, the material of the welding wire 5 is YGW 12, and the feeding speed of the welding wire 5 is 30 cm / min. 12 is summarized in FIG.

FIG. 12 is a conceptual diagram showing the relationship between the welding current when the wire diameter is 1.2 mm and the wire protrusion length is 25 mm and the droplet transfer mode of the welding wire 5. The thick line arrows indicate the welding current, and the thin line arrows indicate the range of the welding current in each droplet transfer form. The relationship between the welding current and the droplet transfer form shown in FIG. 12 is only an example under the conditions such as the above-described wire diameter and wire protrusion length.
When the welding current is in a current range of 300 A or more and less than 450 A, the droplet transfer form of drop transfer becomes dominant.
When the welding current is in the current range of 450 A or more and less than 550 A, the droplet transfer forms of drop transfer and pendulum transfer are mixed.
In the case where the welding current is in a current range of 550 A or more and less than 600 A, the welding transition mode of pendulum transition becomes dominant.
When the welding current is in the current range of 600 A or more and less than 700 A, the welding transition forms of pendulum transition and rotating transition are mixed.
When the welding current is in a current region of 700 A or more, the droplet transfer form of the rotating transfer becomes dominant.

In buried arc welding, a buried space 6a, that is, a space surrounded by a concave molten portion 6 is formed in the molten metal. However, the buried space 6a is always closed in the molten metal, and the tip 5a of the welding wire 5 is closed. Tries to flow in the direction in which it is buried. However, the melted portion 6 is supported by the force of the arc irradiated from the tip 5a of the welding wire 5 to the side portion 62 of the melted portion 6, and the buried space 6a is held in a stable state. When the buried space 6a is not completely supported by the arc 7, the opening of the buried space 6a is narrowed and finally comes into contact with the welding wire 5 to cause a short circuit. When short-circuited, the welding state becomes extremely unstable. For example, in a situation where drop transition is dominant, the side portion 62 of the melted portion 6 cannot be sufficiently supported by the arc 7, and there is a possibility that the welding may become unstable due to the short circuit.
On the other hand, in the rotating transition, the arc 7 is irradiated to the side portion 62 of the concave melted portion 6, and the buried space 6a can be stabilized by supporting the opening of the buried space 6a.
In addition, since the arc 7 is irradiated to the side portion 62 of the melted portion 6 at regular intervals even when the pendulum moves, a similar effect of stabilizing the buried space 6a can be obtained as in the case of the rotating transition. In the drop transition, the arc 7 is directed downward, that is, the bottom 61 of the melted portion 6 is irradiated, so the above-described stabilization effect cannot be obtained.
On the other hand, although the buried space 6a can be stabilized in the rotation transition, since the arc 7 is not irradiated to the bottom 61 of the buried space 6a, the penetration of the base material 4 with respect to the output of the welding current tends to be relatively shallow. is there. On the other hand, in the drop transition, since the arc 7 is irradiated to the bottom 61 of the melted part 6, the penetration per unit output of the welding current becomes relatively deep. Since the arc 7 is irradiated to the bottom 61 of the melted part 6 at regular intervals even in the pendulum transition, a relatively deep penetration is obtained as in the drop transition.

Considering the above, it can be seen that the drop transfer and the rotating transfer exhibit regular droplet transfer, but it is impossible to achieve both stabilization of the buried space 6a and deep penetration. In addition, in the pendulum transfer, it is considered that both the stabilization of the buried space 6a and the deep penetration can be achieved. However, since the liquid column and the arc 7 behave irregularly, it is not always possible to realize stable welding. .
That is, even if any one of the three solution transfer modes is used, it is impossible to realize both stabilization of the buried space 6a and deep penetration only by a single droplet transfer mode. Further, as described above, since the droplet transfer mode changes depending on the current region of the welding current, it is difficult to use only a specific droplet transfer mode for general purposes.

  Next, an arc welding method according to the second embodiment based on the above circumstances will be described. In the second embodiment of the present invention, the stabilization of the buried space 6a and the deep penetration are realized by using these three droplet transfer modes in combination.

  For example, when periodically changing the magnitude of the welding current, the welding current Iw in the small current period is set as a current region exhibiting a drop transition, and the welding current Iw in the large current period is represented as a current region exhibiting a pendulum transition or a rotating transition. By doing so, it is possible to periodically repeat the drop transition and the pendulum transition or the rotation transition. When the droplet transfer form becomes a pendulum transfer or a rotation transfer during a large current period, the arc 7 is irradiated to the side part 62 of the concave melted part 6 and the buried space 6a can be stabilized. On the other hand, when the droplet transfer form becomes drop transfer in the small current period, the arc 7 is irradiated to the bottom 61 of the concave melted portion 6 to obtain deep penetration. By repeating these periodically, it becomes possible to achieve both stabilization of the buried space 6a and deep penetration.

Although the welding current Iw in the small current period is described as the current region of the drop transition and the welding current Iw in the large current period is described as the current region of the pendulum transition or the rotating transition, the welding current Iw in the small current period and the large current period is described. The current region is not limited to this.
Specifically, at least one of a current region of 300A to less than 450A, a current region of 450A to less than 550A, a current region of 550A to less than 600A, a current region of 600A to less than 700A, and a current region of 700A or more. It is preferable to periodically vary the welding current so that the arc 7 is irradiated to the bottom 61 and the side 62 of the melted portion 6 by periodically varying between the two current regions. The fluctuation period of the welding current may be set in the range of 10 Hz to 1000 Hz, preferably in the range of 50 Hz to 300 Hz. The diameter of the welding wire 5 is preferably set to 0.9 mm or more and 1.6 mm or less, and the feeding speed of the welding wire 5 is set to 30 m / min or more. The feeding speed of the welding wire 5 may be a constant feeding speed such as 30 m / min, 50 m / min, 60 m / min, or may be varied according to the magnitude of the welding current.

  For example, the arc welding apparatus periodically varies the welding current so that the welding current Iw in the small current period is in a current region of 300 A or more and less than 450 A, and the welding current Iw in the large current period is in a current region of 550 A or more and less than 600 A. Good to do. In this case, the droplet transfer mode of the drop transfer and the pendulum transfer is periodically switched, and the first state in which the arc 7 is generated between the tip portion 5a of the welding wire 5 and the bottom portion 61 of the molten portion 6, and the tip portion 5a and The second state in which the arc 7 is generated between the side portions 62 of the molten portion 6 is periodically repeated.

  Further, when the arc welding apparatus periodically varies the welding current so that the welding current Iw in the small current period is in a current region of 300 A or more and less than 450 A and the welding current Iw in the large current period is in a current region of 700 A or more. good. In this case, the droplet transfer mode of the drop transfer and the rotating transfer is periodically switched, and the first state in which the arc 7 is generated between the tip portion 5a of the welding wire 5 and the bottom portion 61 of the molten portion 6, and the tip portion 5a. And the 2nd state which the arc 7 generate | occur | produces between the side parts 62 of the fusion | melting part 6 is repeated periodically.

  Furthermore, when the arc welding apparatus periodically varies the welding current so that the welding current Iw in the small current period is in a current region of 550 A or more and less than 600 A and the welding current Iw in the large current period is in a current region of 700 A or more. good. In this case, the droplet transfer mode of the pendulum transfer and the rotating transfer is periodically switched, and the first state where the arc 7 is generated between the tip portion 5a of the welding wire 5 and the bottom portion 61 of the molten portion 6, and the tip portion 5a. And the 2nd state which the arc 7 generate | occur | produces between the side parts 62 of the fusion | melting part 6 is repeated periodically.

Furthermore, the welding current may be periodically changed using a current region in which two droplet transfer modes are mixed.
For example, the arc welding apparatus periodically varies the welding current so that the welding current Iw in the small current period is 450 A or more and less than 550 A, and the welding current Iw in the large current period is 700 A or more. Also good. In this case, the state where the drop transition and the pendulum transition are mixed and the rotating transition are periodically switched.
In addition, the arc welding apparatus periodically varies the welding current so that the welding current Iw in the small current period is in a current region of 300 A or more and less than 450 A, and the welding current Iw in the large current period is in a current region of 600 A or more and less than 700 A. You may let them. In this case, the drop transition and the state where the pendulum transition and the rotating transition are mixed are periodically switched.

  The above welding conditions are only examples, and the welding wire 5 material, wire system, protrusion length, and welding wire 5 feed speed are not limited to the above numerical range. . Hereinafter, various conditions that enable mutual transition of droplet transfer modes of drop transfer, pendulum transfer, and rotating transfer in a buried arc will be described.

  The material of the welding wire 5 may be a solid wire such as YGW11, YGW15, YGW17, YGW18, YGW19, etc. in addition to YGW12. However, a flux cored wire, a metal cored wire, and other new wires may be applied as the welding wire 5.

The protruding length of the welding wire 5 is preferably 10 mm or more and 35 mm or less. Since the penetration becomes shallower as the protruding length becomes longer, it is better to keep it at 35 mm at the longest. On the other hand, when the protruding length is shortened, the tip end approaches the molten pool, and the tip wear becomes intense. This tendency is particularly noticeable because of high current welding, and frequent tip replacement is required when the thickness is less than 10 mm.
Furthermore, the protruding length of the welding wire 5 affects the transition current in the transition form (see FIG. 13). Also from the viewpoint of the balance, there is an appropriate range for the protruding length, and about 10 to 35 mm is appropriate.

  The wire diameter is preferably 0.9 mm or greater and 1.6 mm or less, for example. The wire diameter can be basically adapted to any wire diameter by appropriately changing the welding conditions, and is not particularly limited. About 1.6 mm is realistic. Further, the wire diameter affects the transition current in the droplet transfer form (see FIG. 13). Also from this point of view, when an extremely thick welding wire 5 or a thin welding wire 5 is used, the transition region of the droplet transfer form widens greatly, and it becomes difficult to use any droplet transfer form. Therefore, about 0.9 to 1.6 mm is appropriate.

  Since the feeding speed of the welding wire 5 correlates with the welding current, it may be determined as appropriate so that the buried space 6a is formed according to the welding current.

  FIG. 13 is a conceptual diagram showing the relationship between the wire diameter and the wire protruding length and the droplet transfer form of the welding wire 5. The horizontal axis indicates the welding current, and the vertical axis indicates the length of the protruding length of the welding wire 5 and the size of the wire system. The transition current in the form of droplet transfer is strongly influenced by the wire diameter and protrusion length. FIG. 13 shows the influence of the protruding length of the welding wire 5 and the wire diameter on the transition current in the droplet transfer form. As shown in FIG. 13, as the wire diameter is larger or the protruding length is shorter, the transition current is shifted toward the high current region as a whole. This is due to the difference in resistance heat generation of the welding wire 5. When the wire diameter is increased or the protruding length is shortened, the resistance of the wire is decreased, and the amount of heat input to the welding wire 5 due to resistance heat generation is decreased. Therefore, in order to reproduce the same droplet transfer phenomenon, it is necessary to increase the heat input by increasing the welding current accordingly, so that the transition current is shifted to the high current side as a whole.

As an example, the change of the transition current when the wire diameter changes is specifically shown.
FIG. 14 is a conceptual diagram showing the relationship between the welding current when the wire diameter is 1.4 mm and the wire protrusion length is 25 mm and the droplet transfer mode of the welding wire 5. FIG. 14 is similar to FIG. 11 in that the wire protruding length is 25 mm, the diameter of the welding wire 5 is 1.4 mm, the material of the welding wire 5 is YGW12, and the welding wire 5 feed speed is 30 cm / min. This shows the relationship between the current and the droplet transfer mode, and the welding conditions differ only in the wire diameter. Comparing the case where the wire diameter is 1.2 mm and the case where the wire diameter is 1.4 mm, as shown in FIG. 11 and FIG. 14, the transition current in the droplet transfer form transitions to the high current side as a whole.

  As described above, the wire diameter and the protruding length of the welding wire 5 can be appropriately determined in consideration of the tendency shown in FIG. 13 with reference to FIG. 12 or FIG.

  The welding power source 1 that implements the welding method sets the welding current, the frequency of the welding current, and the feeding speed of the welding wire 5 described in the welding method. The welding power source 1 may receive and store the welding conditions at the operation unit, or may store them in advance. The welding power source 1 controls the feeding of the welding wire 5 based on the set welding conditions, and periodically varies the welding current.

  As described above, in the arc welding method and the arc welding apparatus according to the second embodiment, when the welding current is changed under the above conditions, the drop transition, the pendulum transition, the rotating transition, and these two are mixed. It fluctuates periodically between the two states, the undulation of the molten metal can be suppressed, and stabilization of the buried space 6a and deep penetration can be realized.

Note that the side portion 62 of the melted portion 6 is not necessarily irradiated with the arc 7 during the large current period. When the current period is switched at a high frequency, the droplet transition form transitions transiently.For example, even in the current region where the pendulum transition or rotating transition occurs in the original steady state, that is, during the large current period, it is not always necessary. There is a case where the droplet transfer mode does not shift to the pendulum transfer or the rotation transfer, and then exhibits the pendulum transfer or the rotation transfer with a slight delay after the small current period.
Similarly, even during a high current period, a drop transition may be exhibited, or the arc 7 may be irradiated to the bottom 61 of the molten portion 6.

  Further, the small current period does not necessarily have to be a current region that constantly exhibits a drop transition, and the large current period does not necessarily have to be a current region that constantly exhibits a pendulum transition or a rotating transition. Since the transition of the droplet transfer form is transitional, there may be a case where the droplet transfer form is different temporarily or transiently even if it is not in the current region that constantly exhibits the corresponding droplet transfer form.

  Furthermore, the large current period and the small current period need not be in a state where the welding current is maintained at a constant current value, and the current waveform of the periodically varying welding current is limited to a specific waveform such as a rectangular wave. It is not something. For example, the current waveform of the welding current may be a triangular wave. The large current period is a period when the welding current is large on average, and the small current period is a period when the welding current is small on average.

  Furthermore, in the second embodiment, the example in which the droplet transfer mode is changed by periodically changing the current region of the welding current has been described. However, the transition of the droplet transfer mode is accompanied by the change in the welding current. Even if not, the force of the arc 7 periodically fluctuates between a large current period and a small current period, and a certain fine vibration having a relatively large frequency is applied to the melted portion 6. As a result, large peristalsis of the buried space 6a that occurs at a relatively low frequency or suddenly is suppressed, and this alone has a certain effect on stabilization of the buried space 6a. Therefore, the present invention can stabilize the buried space 6a to some extent without necessarily involving the transition of the droplet transfer form.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Welding power supply 2 Torch 3 Wire feeding part 4 Base material 5 Welding wire 5a Tip part 6 Melting part 6a Buried space 61 Bottom part 62 Side part 7 Arc 11 Power supply part 11a Power supply circuit 11b Output voltage setting circuit 11c Frequency setting circuit 11d Current amplitude Setting circuit 11e Average current setting circuit 11f Voltage detection unit 11g Current detection unit 11h Comparison circuit 12 Feed speed control unit 41 First base material 42 Second base material Vw Welding voltage Iw Welding current Ecr Output voltage setting signal Ed Voltage value signal Id Current value signal Ev Difference signal

Claims (10)

While feeding a welding wire to the welded portion of the base material and supplying a welding current to the welding wire, an arc is generated between the tip portion of the welding wire and the welded portion, and the base material is welded. A consumable electrode type arc welding method,
The welding wire is fed at a speed at which the tip portion enters a space surrounded by a concave melted portion formed in the base material by an arc generated between the tip portion and the welded portion,
An arc welding method in which the welding current is varied so that the frequency of the welding current is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more. While feeding a welding wire to the welded portion of the base material and supplying a welding current to the welding wire, an arc is generated between the tip portion of the welding wire and the welded portion, and the base material is welded. A consumable electrode type arc welding method,
The welding wire is fed at a speed at which the tip portion enters a space surrounded by a concave melted portion formed in the base material by an arc generated between the tip portion and the welded portion,
By periodically changing the welding current, a first state in which an arc is generated between the tip and the bottom of the melted portion, and a second in which an arc is generated between the tip and the side of the melted portion. Arc welding method that periodically changes the state. The arc welding method according to claim 2, wherein the first state and the second state are varied at a frequency of 10 Hz to 1000 Hz. The first state includes a droplet transfer form of drop transfer,
The arc welding method according to claim 2 or 3, wherein the second state includes a droplet transfer form in which a liquid column and an arc formed at the tip of the welding wire swing in a pendulum shape. The first state includes a droplet transfer form of drop transfer,
The arc welding method according to claim 2, wherein the second state includes a droplet transfer form of rotating transfer. The first state includes a droplet transfer form in which a liquid column and an arc formed at the tip of the welding wire swing in a pendulum shape,
The arc welding method according to claim 2, wherein the second state includes a droplet transfer form of rotating transfer. The arc according to any one of claims 2 to 6, wherein the welding current is varied so that the frequency of the welding current is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more. Welding method. The arc welding method according to claim 1 or 7, wherein the frequency of the welding current is 50 Hz to 300 Hz, the average current is 300 A to 1000 A, and the current amplitude is 100 A to 500 A. A wire feeding section for feeding a welding wire to a welded portion of the base material; and a power supply section for supplying a welding current to the welding wire, and supplying the welding current to the welding wire, An arc welding apparatus of a consumable electrode type that generates an arc between a tip portion and a welded portion and welds the base material,
The wire feeding unit is
The welding wire is fed at a speed at which the tip portion enters a space surrounded by a concave melted portion formed in the base material by an arc generated between the tip portion and the welded portion,
The power supply unit is
An arc welding apparatus that varies the welding current so that the frequency of the welding current is 10 Hz to 1000 Hz, the average current is 300 A or more, and the current amplitude is 50 A or more. A wire feeding section for feeding a welding wire to a welded portion of the base material; and a power supply section for supplying a welding current to the welding wire, and supplying the welding current to the welding wire, An arc welding apparatus of a consumable electrode type that generates an arc between a tip portion and a welded portion and welds the base material,
The wire feeding unit is
The welding wire is fed at a speed at which the tip portion enters a space surrounded by a concave melted portion formed in the base material by an arc generated between the tip portion and the welded portion,
The power supply unit is
By periodically changing the welding current, a first state in which an arc is generated between the tip and the bottom of the melted portion, and a second in which an arc is generated between the tip and the side of the melted portion. Arc welding equipment that periodically changes the state.