JP6777969B2 - Arc welding method and arc welding equipment - Google Patents

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 method in which an arc is generated between the welding wire fed to the welded portion of the base metal and the base metal, and the base metal is welded by the heat of the arc, and the temperature becomes particularly high. Welding is performed while injecting an inert gas around the welded portion in order to prevent oxidation of the base metal. If it is a thin plate of about 5 mm, the butt joint of the base material can be welded in one pass.

However, in the case of a thick plate of 9 to 30 mm, the base metal cannot be welded in one pass by the conventional gas shielded arc welding method. Therefore, the thick plate is welded by multi-layer welding in which the welding operation is repeated a plurality of times. However, in multi-layer welding, an increase in welding man-hours becomes a problem. In addition, the amount of heat input becomes large, and deformation of the base metal and embrittlement of the welded portion become problems.

JP-A-2007-229775

As a result of diligent studies to solve such a problem, the inventors of the present application feed the welding wire at a higher speed than the general gas shielded arc welding method and supply a large current to the thick plate. We obtained the finding that 1-pass welding can be realized. 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 a large current is supplied, a concave molten portion is formed in the base metal by the heat of the arc, and the tip portion of the welding wire enters the space surrounded by the molten portion. When the tip end portion of the welding wire penetrates deeper than the surface surface of the base metal, the molten portion penetrates to the back surface side in the thickness direction of the base metal, and one-pass welding becomes possible. Hereinafter, the space surrounded by the concave molten portion is referred to as a buried space, and the arc generated between the tip of the welding wire that has entered the buried space and the base metal or the molten portion is appropriately referred to as a buried arc.

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

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

In the arc welding method according to the present invention, a welding wire is supplied to a welded portion of a base metal, and a welding current is supplied to the welding wire to generate an arc between the tip of the welding wire and the welded portion. It is a consumable electrode type arc welding method in which the base metal is generated and welded, and the space surrounded by the concave melted portion formed in the base metal by the arc generated between the tip portion and the welded portion is described. The welding wire is fed at a speed at which the tip portion enters, and the welding current is varied so that the frequency of the welding current is 10 Hz or more and 1000 Hz or less, 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 molten portion, and a buried arc is generated. Specifically, the tip of the welding wire is surrounded by the molten portion, and by periodically changing the welding current, the position of the wire tip in the buried space can be moved up and down, and the tip and the molten portion can be moved up and down. An arc is generated between the bottom and sides of the wire. The base metal melted by the heat of the arc and the molten metal of the welding wire close the buried space and try 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 wire and stabilizes with the tip surrounded by the molten part.
Further, the molten metal in buried arc welding may undulate greatly, but by periodically fluctuating the welding current with the frequency, average current and current amplitude, the molten metal is finely undulated at a higher frequency than the large undulating period. It can be vibrated to suppress large waviness of molten metal, and one-pass welding of thick plates can be realized.

In the arc welding method according to the present invention, a welding wire is supplied to a welded portion of a base metal, and a welding current is supplied to the welding wire to generate an arc between the tip of the welding wire and the welded portion. It is a consumable electrode type arc welding method in which the base metal is generated and welded, and the space surrounded by the concave melted portion formed in the base metal by the arc generated between the tip portion and the welded portion is described. The first state in which an arc is generated between the tip and the bottom of the molten portion by feeding the welding wire at the speed at which the tip enters and periodically fluctuating the welding current, and the tip. The second state in which an arc is generated is periodically changed between the portion and the side portion of the molten portion.

In the present invention, the tip of the welding wire enters the buried space surrounded by the concave molten portion, and a buried arc is generated. Specifically, the tip of the welding wire is surrounded by the molten portion, and by periodically changing the welding current, the position of the wire tip in the buried space can be moved up and down, and the tip and the molten portion can be moved up and down. An arc is generated between the bottom and sides of the wire. The base metal melted by the heat of the arc and the molten metal of the welding wire close the buried space and try 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 wire and stabilizes with the tip surrounded by the molten part.
Further, the molten metal in buried arc welding may undulate greatly, but by periodically fluctuating the welding current, the arc flies to the bottom of the concave molten portion and the arc to the side of the fused portion. The second state in which the current flies can be changed periodically, the waviness of the molten metal can be suppressed, and one-pass welding of a thick plate can be realized.

In the arc welding method according to the present invention, the first state and the second state are varied at a frequency of 10 Hz or more and 1000 Hz or less.

In the present invention, by varying the first state and the second state at a frequency of 10 Hz or more and 1000 Hz or less, the molten metal is slightly vibrated at a frequency higher than a large waviness period, and large waviness of the molten metal is suppressed. Can be done.

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

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 molten portion and the pendulum transition, thereby causing the molten metal to undulate. It can be suppressed.

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

In the present invention, by periodically fluctuating the welding current, the drop transition in which the arc flies to the bottom of the concave molten portion and the rotating transition in which the arc flies to the side of the molten portion fluctuates periodically. It is possible to suppress the waviness of the molten metal.

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 transition form in which the arc swings like a pendulum, and the second state is a rotation. Includes a droplet transfer form of welding transfer.

In the present invention, by periodically fluctuating the welding current, the pendulum transition in which the arc flies to the bottom of the concave molten portion and the rotating transition in which the arc flies to the side of the molten portion fluctuates periodically. It is possible to suppress the waviness of the molten metal.

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 or more and 1000 Hz or less, the average current is 300 A or more, and the current amplitude is 50 A or more.

According to 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 waviness 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 or more and 300 Hz or less, the average current is 300 A or more and 1000 A or less, and the current amplitude is 100 A or more and 500 A or less.

According to the welding conditions where the frequency of the welding current is 50Hz or more and 300Hz or less, the average current is 300A or more and 1000A or less, and the current amplitude is 100A or more and 500A or less, the waviness of the molten metal is suppressed more effectively and the thick plate is welded in one pass. Can be realized.

The arc welding apparatus according to the present invention includes a wire feeding unit that supplies a welding wire to a portion to be welded of a base metal and a power supply unit that supplies a welding current to the welding wire, and applies a welding current to the welding wire. A consumable electrode type arc welding device that generates an arc between the tip of the welding wire and the welded portion by supplying the weld wire to weld the base metal, and the wire feeding portion is the tip portion and the welding portion. The welding wire is fed at a speed at which the tip portion enters the space surrounded by the concave molten portion formed in the base metal by the arc generated between the welded portions, and the power supply portion supplies the welding current. The welding current is varied so that the frequency of 10 Hz or more and 1000 Hz or less, 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 molten portion, and a buried arc is generated. As described above, the tip of the welding wire is surrounded by the molten portion, and the molten metal may undulate greatly, but the welding current is periodically changed by the frequency, the average current, and the current amplitude. As a result, the molten metal can be slightly vibrated at a frequency higher than the large waviness period, the large waviness of the molten metal can be suppressed, and one-pass welding of a thick plate can be realized.

The arc welding apparatus according to the present invention includes a wire feeding unit that supplies a welding wire to a portion to be welded of a base metal and a power supply unit that supplies a welding current to the welding wire, and applies a welding current to the welding wire. A consumable electrode type arc welding device that generates an arc between the tip of the welding wire and the welded portion by supplying the weld wire to weld the base metal, and the wire feeding portion is the tip portion and the welding portion. The welding wire is fed at a speed at which the tip portion enters the space surrounded by the concave molten portion formed in the base metal by the arc generated between the welded portions, and the power supply portion supplies the welding current. The first state in which an arc is generated between the tip portion and the bottom portion of the molten portion and the second state in which an arc is generated between the tip portion and the side portion of the molten portion are obtained by periodically changing the above. It fluctuates periodically.

In the present invention, the tip of the welding wire enters the buried space surrounded by the concave molten portion, and a buried arc is generated. As described above, the tip of the welding wire is surrounded by the molten portion, and the molten metal may undulate greatly. However, by periodically changing the welding current, an arc is formed at the bottom of the concave molten portion. The first state in which the metal flies and the second state in which the arc flies to the side of the molten portion can be periodically changed to suppress the waviness of the molten metal, and one-pass welding of a thick plate can be realized.

According to the present invention, even when gas shielded arc welding is performed using a large current of 300 A or more, it is possible to suppress waviness of molten metal in buried arc welding and prevent bead turbulence and sagging. ..

It is a schematic diagram which shows one structure of the arc welding apparatus which concerns on this Embodiment 1. It is a flowchart which shows the procedure of the arc welding method which concerns on this Embodiment 1. It is a side sectional view which shows the base material to be welded. It is a graph which shows the fluctuation of welding voltage and welding current. It is a schematic diagram which shows the arc welding method which concerns on this Embodiment 1. It is a chart which shows the experimental result about the stabilization of a buried space and a bead shape by a photograph. It is a chart which shows the experimental result about the stabilization of a buried space and a bead shape in a schematic diagram. It is a graph which shows the condition of the welding current and voltage which realizes a buried arc. It is a conceptual diagram which shows the relationship between the wire diameter and the wire protrusion length, and the welding current and voltage conditions which realize a buried arc. It is a graph which shows an example of the conditions of the welding current and the voltage which realizes the buried arc when the wire diameter is 1.6 mm, and the protrusion length of a welding wire is 25 mm. It is a chart which shows each droplet transfer form of a drop transfer, a pendulum transfer, and a rotating transfer. It is a conceptual diagram which shows 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 form of a welding wire. It is a conceptual diagram which shows the relationship between the wire diameter and the wire protrusion length, and the droplet transfer form of a welding wire. It is a conceptual diagram which shows the relationship between the welding current when the wire diameter is 1.4mm, and the wire protrusion length is 25mm, and the droplet transfer form of a welding wire.

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments thereof.
(Embodiment 1)
FIG. 1 is a schematic view showing a 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 welder capable of butt-welding a base metal 4 having a plate thickness of 9 to 30 mm in one pass, and is a welding power source 1 and a torch 2. And a wire feeding unit 3 is provided.

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 required for generating the arc 7 (see FIG. 5). Has a contact tip. The contact tip comes into contact with the welding wire 5 that penetrates the inside thereof, and supplies the welding current Iw to the welding wire 5. Further, the torch 2 has a hollow cylindrical shape surrounding the contact tip, and has a nozzle for injecting a shield gas to the welded portion. The shield gas is for preventing oxidation of the base metal 4 and the welding wire 5 melted by the arc 7. The shield gas is, for example, carbon dioxide gas, a mixed gas of carbon dioxide gas and argon gas, an inert gas such as argon, or the like.

The welding wire 5 is, for example, a solid wire having a diameter of 0.9 mm or more and 1.6 mm or less, 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 has 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 pulls out the welding wire 5 from the wire reel by rotating the feeding roller, and supplies the drawn welding wire 5 to the torch 2. The feeding method of the welding wire 5 is an example, and is not particularly limited.

The welding power supply 1 is connected to the contact tip of the torch 2 and the base material 4 via a power supply cable, and is a power supply unit 11 that supplies a welding current Iw and a feed rate control unit that controls the feed rate of the welding wire 5. 12 and. The power supply unit 11 and the feed rate control unit 12 may be formed separately. The power supply unit 11 is a power supply having a constant voltage characteristic, and is 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, and a voltage. It includes a detection unit 11f, a current detection unit 11g, and a comparison circuit 11h.

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.

For example, the current detection unit 11g detects the welding current Iw that is supplied from the welding power supply 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 the output voltage setting circuit. Output 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 metal 4 and the welding wire 5 to the output voltage setting circuit 11b. When the arc welding method according to the first embodiment is carried out, the frequency setting circuit 11c is a frequency setting signal indicating a frequency of 10 Hz or more and 1000 Hz or less, preferably a frequency of 50 Hz or more and 300 Hz or less, and more preferably a frequency of 80 Hz or more and 200 Hz or less. Is output.

The current amplitude setting circuit 11d outputs an amplitude setting signal for setting the amplitude of the welding current Iw, which fluctuates periodically, to the output voltage setting circuit 11b. When the arc welding method according to the first embodiment is carried out, the current amplitude setting circuit 11d exhibits a current amplitude of 50 A or more, preferably 100 A or more and 500 A or less, and more preferably 200 A or more and 400 A or less. Outputs the 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, which fluctuates periodically, to the output voltage setting circuit 11b and the feed rate control unit 12. When the arc welding method according to the first embodiment is carried out, the average current setting circuit 11e has an average current of 300 A or more, preferably an average current of 300 A or more and 1000 A or less, more preferably an average current of 500 A or more and 800 A or less. Outputs the average current setting signal indicating.

The output voltage setting circuit 11b sets the welding current Iw to the target frequency, current amplitude, and average current based on the current value signal Id, frequency setting signal, amplitude setting signal, and average current setting signal output from each part. In addition, for example, an output voltage setting signal Ecr indicating a target voltage of 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 transmits the difference signal Ev indicating the difference to the power supply circuit 11a. Output.

The power supply circuit 11a includes an AC-DC converter that converts commercial AC to AC / DC, an inverter circuit that converts AC / DC converted DC into required AC by switching, a rectifier circuit that rectifies the converted AC, and the like. The power supply circuit 11a PWM-controls 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 fluctuates periodically is applied between the base metal 4 and the welding wire 5, and the welding current Iw is energized. The welding power supply 1 is configured so that an output instruction signal is input from the outside via a control communication line (not shown), and the power supply unit 11 is welded to the power supply circuit 11a by using the output instruction signal as a trigger. The 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. Further, in the case of a manual welding machine, the output instruction signal is output from the torch 2 side to the welding power supply 1 when the 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 that the 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 the buried arc state.
When the decrease in the welding voltage is less than 4 V, the fluctuation in the welding voltage is small with respect to the fluctuation in the arc length due to the disturbance factor, and the welding current fluctuates greatly. As a result, the molten portion 6 sways greatly, making it difficult to maintain the state of the buried arc. By setting the lowering of the welding voltage to 4 V or more, the pulsation of the molten portion 6 is suppressed, and it becomes easy to maintain the buried arc state.
Further, when the arc length is shortened due to a disturbance factor, the value of the welding current increases, the melting speed of the welding wire 5 increases, and the arc length becomes long. On the other hand, when the arc length becomes long due to a disturbance factor, the value of the welding current decreases, the melting speed of the welding wire 5 decreases, and the arc length becomes short (self-control action of the arc length). When the decrease in the welding voltage exceeds 20 V, the fluctuation of the welding current is small with respect to the fluctuation of the arc length due to the 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 reducing the welding voltage to 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. Further, 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 a 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-shaped first base material 41 and a second base material 42 are prepared, and the end faces 41a and 42a to be welded are abutted and arranged at a predetermined welding work position. .. If necessary, the first base material 41 and the second base material 42 may be provided with grooves having an arbitrary shape such as a Y shape or a re shape. The first and second base materials 41 and 42 are steel plates such as mild steel, carbon steel for machine structure, and alloy steel for machine structure, and have a thickness of 9 mm or more and 30 mm or less.
Then, 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 be set entirely by the welding operator, or the welding power source 1 accepts the implementation of the welding method according to the first embodiment at the operation unit and automatically sets all the conditions. It may be configured to do so. In addition, the welding power supply 1 accepts some welding conditions such as the average current at the operation unit, determines the remaining welding conditions that meet some of the accepted welding conditions, and sets the conditions semi-automatically. It may be configured.

After various settings are made, the welding power supply 1 determines whether or not the output start condition of the welding current Iw is satisfied (step S12). Specifically, the welding power supply 1 determines whether or not a welding output instruction signal has been 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 supply 1 stands by in the input waiting state of the output instruction signal.

When it is determined that the output start condition of the welding current Iw is satisfied (step S12: YES), the feeding speed control unit 12 of the welding power supply 1 sends a feeding instruction signal instructing the wire feeding to the wire feeding unit 3. The welding wire 5 is fed at a predetermined speed (step S13). The feeding speed of the welding wire 5 is set, for example, in the range of about 5 to 100 m / min. The feed rate control unit 12 determines the feed rate according to the average current setting signal output from the average current setting circuit 11e. The feeding speed of the welding wire 5 may be a constant speed or may be changed periodically. Further, the welding operator may be configured to directly set the feeding speed of the wire.

Next, the power supply unit 11 of the welding power supply 1 detects the welding voltage Vw and the welding current Iw by 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 conditions and the welding current Iw fluctuates periodically (step S15). That is, the welding power supply 1 outputs by periodically fluctuating the target voltage so that the welding current Iw periodically fluctuates at a frequency of 10 Hz or more and 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 supply 1 determines whether or not to stop the output of the welding current Iw (step S16). Specifically, the welding power supply 1 determines whether or not the input of the output instruction signal is continuous. When the input of the output instruction signal is continued 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 is determined that the output of the welding current Iw is stopped (step S16: YES), the power supply unit 11 returns the process to step S12.

FIG. 4 is a graph showing fluctuations in welding voltage Vw and welding current Iw, and FIG. 5 is a schematic view showing an arc welding method according to the first embodiment. The horizontal axis of each graph shown in FIG. 4 indicates time, and the vertical axis of each graph shown in FIGS. 4A to 4C is the set voltage of the welding power source 1, the welding voltage Vw between the base metal 4 and the welding wire 5, and the arc. It is a 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 or more and 1000 Hz or less, the average current is 300 A or more, and the current amplitude is 50 A or more. .. Specifically, the welding power supply 1 having a constant voltage characteristic sets a target voltage so that the welding current Iw fluctuates in this way, and the target voltage is periodically fluctuated. The same applies to the control of the welding current Iw below. By periodically fluctuating the welding current I with a constant voltage characteristic, the molten portion 6 of the buried arc can be stabilized more effectively.
Preferably, the power supply unit 11 controls the welding current Iw so that the frequency of the welding current Iw is 50 Hz or more and 300 Hz or less, the average current is 300 A or more and 1000 A or less, and the current amplitude is 100 A or more and 500 A or less.

More preferably, as shown in FIG. 4C, the power supply unit 11 has a welding current Iw so that the frequency of the welding power supply 1 is 80 Hz or more and 200 Hz or less, the current amplitude is 200 A or more and 400 A or less, and the average current is 500 A or more and 800 A or less. 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 metal 4 having a plate pressure of 12 mm under the welding conditions of the welding current Iw, for example, if 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 feeding rate are set in this way, the set voltage becomes a rectangular wavy voltage having a frequency of 100 Hz and a voltage amplitude of 30 V, for example, as shown in FIG. 4A, and is between the welding wire 5 and the base metal 4. A welding voltage Vw as shown in FIG. 4B is applied to, and a welding current Iw as shown in FIG. 4C flows. The welding power supply 1 controls the set voltage at a frequency of 100 Hz so that, for example, the current amplitude of the welding current Iw is 240 A and the average current is 530 A. Further, the welding power source 1 controls the feeding of the welding wire 5 at a speed of about 40 m / min. The welding voltage Vw fluctuates in the range of 41 V or more and 27 or less, but the fluctuation range of the welding voltage Vw changes due to the influence of various impedances. The current waveform shown in FIG. 4C is an example and is not particularly limited. For example, the current waveform may have 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 molten metal of the base metal 4 and the welding wire 5 melted by the heat of the arc 7 generated between the tip portion 5a of the welding wire 5 and the welded portion. The molten portion 6 of is formed in the base metal 4. Then, when the state of the arc 7 was photographed with a high-speed camera, as shown in the left figure of FIG. 5, the first state in which the arc 7 was generated between the tip portion 5a of the welding wire 5 and the bottom portion 61 of the molten portion 6 and the first state. It was confirmed that it periodically fluctuates from the second state in which the arc 7 is generated between the tip portion 5a and the side portion 62 of the molten portion 6.

Specifically, the first state in which the arc 7 flies from the tip portion 5a of the welding wire 5 to the bottom portion 61 of the molten portion 6, and the first state in which the arc 7 flies from the tip portion 5a of the welding wire 5 to the side portion 62 of the molten portion 6. Repeat the two states. In the first state, for example, the droplet transfer form of the welding wire 5 is a drop transfer state. In the second state, for example, the droplet transfer form of the welding wire 5 is a rotating transition state. The drop transition is an example of a droplet transition from the tip 5a of the welding wire 5 to the bottom 61 of the molten portion 6, and the rotating transition is from the tip 5a of the welding wire 5 to the side 62 of the molten portion 6. This is an example of a form in which droplets are transferred. In the molten metal, the buried space 6a is closed and the tip portion 5a of the welding wire 5 tries to flow in the buried direction, but in the second state, the arc 7 flies to the side portion 62 of the molten portion 6 and the molten portion 6 The molten metal of No. 5 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 figure of FIG. 5, as a result of the droplets transferred from the tip portion 5a of the welding wire 5 melted by the large current, the tip portion 5a of the welding wire 5 is shortened.
By varying the first and second states at 10 Hz or higher, preferably 50 Hz or higher and 300 Hz or lower, more preferably 80 Hz or higher and 200 Hz or lower, the molten metal can be slightly vibrated at a frequency higher than a large wavy period. It can suppress the waviness of molten metal.

FIG. 6 is a chart showing the experimental results regarding the stabilization of the buried space 6a and the bead shape with photographs, and FIG. 7 is a chart showing the experimental results regarding the stabilization of the buried space 6a and the bead shape in a schematic diagram. Under the welding conditions that the wire diameter is 1.4 mm, the protrusion 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. After changing, the thick plate was buried and arc welded.
The upper figures of FIGS. 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. The middle figures of FIGS. 6 and 7 show the bead shape when welding is performed under the conditions of the welding current frequency of 10 Hz and the amplitude of 50 A, and the lower figures 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, by vibrating the welding current under welding conditions with a frequency of 10 Hz or higher and a current amplitude of 50 A or higher, a better bead shape can be obtained as compared with 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.
Further, according to the operating principle of suppressing the waviness of the molten metal by vibrating the molten metal at a high frequency, even if the frequency of the welding current is 10 Hz or higher, the waviness of the molten metal is similarly suppressed and the buried space 6a is stabilized. It is expected that it can be made. Further, since the waviness of the molten metal can be sufficiently suppressed with a current amplitude of 50 A, it is expected that the waviness of the molten metal can be suppressed even with a current amplitude of 50 A or more. In fact, when welding was performed under welding conditions with 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. 6 and 7. The wire diameter, the protrusion 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 welding current frequency is 10 Hz or more. And if the current amplitude is 50 A, a good bead shape can be obtained in the same manner. In particular, when 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>
The welding conditions for realizing the buried arc will be described below.
In arc welding, the position of the tip portion 5a of the welding wire 5 is generally located above the base metal 4, and an arc is generated between the tip portion 5a of the welding wire 5 and the base metal 4 in that state. The arc generated in such a state is called a non-buried arc. In the non-buried arc, the distance between the tip portion 5a of the welding wire 5 and the surface of the molten metal formed on the surface of the base metal 4 is called the arc length, and this arc length increases as the welding voltage decreases. It is known to be shorter. In normal arc welding, when the welding voltage is lowered and the arc length is shortened, the distance between the molten metal and the tip portion 5a of the welding wire 5 becomes closer, and finally the arc length becomes 0 and the welding wire 5 and the welding wire 5 A short circuit occurs with the base metal 4, making it difficult to maintain the arc.

However, in high current welding, the molten metal is pushed away by the arc pressure, so that short circuits are less likely to occur even if the voltage is lowered. As a result, even if the tip portion 5a of the welding wire 5 is located deeper than the surface of the base metal 4 or the molten metal, the space formed by the molten metal being pushed away by the arc pressure, that is, the presence of the buried space 6a No short circuit occurs 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 where the arc pressure becomes strong. Specifically, a welding current of 300 A or more is required (for example, Satoshi Asai, "Higher efficiency of factory welding-Examples of heavy electrical equipment welding-", The Japan Welding Engineering Society Welding Information Center, WE-COM Magazine No. 16, April 2015). The voltage value at which the buried arc can be realized 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 portion 5a of the welding wire 5 is set to the base metal 4 or the melting. A buried arc can be realized by setting the voltage so low that it can be lowered to a position lower than the metal surface.

FIG. 8 is a graph showing the welding current and voltage conditions for realizing the buried arc. The horizontal axis shows the welding current, and the vertical axis shows the welding voltage. The white area shows the welding current and voltage that can realize the 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, and conversely, when the welding voltage is too low, the output is insufficient and it becomes difficult to maintain the arc. .. In the intermediate region, there is a range in which the arc 7 is generated in the buried space 6a and becomes a buried arc.

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 becomes larger or the protruding length of the welding wire 5 becomes shorter, the range of welding current and voltage that can realize the buried arc is as shown in reference numerals Arc3, Aec2, and Arc1. In order, it shifts to the lower voltage region side for the same current.

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 protrusion length of the welding wire 5 is 25 mm. The horizontal axis of FIG. 10 shows the welding current, and the vertical axis shows the welding voltage. The black circle plot shows the boundary between the unburied 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 and becomes a buried arc when the welding voltage is decreased at the welding current indicated by the black circle plot. Further, the black circle plot on the lower polygonal line becomes a buried arc when the welding voltage is increased and becomes a non-buried arc when the welding voltage is decreased at the welding current indicated by the black circle plot. In short, if the welding voltage is high with respect to the welding current, normal arc welding, that is, non-buried arc welding is performed, and conversely, if the welding voltage is too low, the output is insufficient and it becomes difficult to maintain the arc. In the intermediate region, there is a range in which the arc 7 is generated in the buried space 6a and becomes a buried arc.

As described above, the welding current for realizing the buried arc is 300 A or more, and when the tip portion 5a of the welding wire 5 approaches the molten metal, a current capable of generating an arc pressure to push the molten metal away is generated. The value. Further, the welding voltage for realizing the buried arc is a voltage value capable of lowering the position of the tip portion 5a of the welding wire 5 to a position lower than the base material 4 or the surface of the molten metal.
As the specific welding current and voltage, the welding current and voltage may be appropriately determined in consideration of the tendency shown in FIGS. 8 and 9 while referring to the range of the welding current and voltage shown in FIG.

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

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 shielded arc welding is performed using a large current of 300 A or more. As a result, the waviness of the molten metal can be suppressed, and the bead can be prevented from being disturbed and dripping.
Further, in order to suppress the waviness of the molten metal more effectively, it is necessary to keep the arc length constant. In the case of general constant current pulse welding, the self-control action of the arc length cannot be obtained, so it is necessary to perform some control to guarantee a constant arc length. Since the arc welding apparatus according to the first embodiment has a constant voltage characteristic and a self-control action of the arc length can be obtained, the arc length is kept constant and the waviness of the molten metal can be suppressed more effectively.

In the first embodiment, the case where the period in which the welding current Iw and the welding voltage Vw are large and the period in which the welding voltage Vw is small are substantially the same has been described, but the ratio of each period may be changed. By changing the ratio of the period, it is possible to adjust the width of the vertical position fluctuation of the tip portion 5a of the welding wire 5 while suppressing the waviness of the molten metal. For example, by increasing the ratio of the period in which the welding current Iw and the welding voltage Vw are large, the ratio at which the tip portion 5a of the welding wire 5 is held higher than the bottom portion 61 of the molten portion 6 increases. 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 have different welding conditions such as a welding current Iw from the first embodiment, the differences will be mainly described below. Since other configurations and actions and effects are the same as those in the first embodiment, the corresponding parts are designated by the same reference numerals and detailed description thereof will be omitted.

First, the droplet transfer form in buried arc welding and its characteristics 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 modes. The center row shows a schematic diagram showing an image obtained by photographing the molten portion 6 in each droplet transition form every 0.4 msec using a high-speed camera. In buried arc welding, there are multiple droplet transfer forms. The plurality of droplet transfer forms include, for example, three types of droplet transfer forms shown in FIG. 11, that is, drop transfer, pendulum transfer, and rotating transfer. The drop transition and the rotating transition are general names, but the pendulum transition is a coined word by the inventor.

These droplet transfer forms are comprehensively influenced by various factors including the welding current, the wire protrusion 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. It is determined, but it is particularly strongly affected by welding current. The wire protrusion length is the distance between the tip of the contact tip and the base material 4. When the welding current is relatively small, a drop transition is exhibited, and as the welding current rises, the droplet transition mode shifts to a pendulum transition and a rotating transition.

The drop transition is a droplet transition mode in which the tip 5a of the welding wire 5 melts and the droplets are granularly separated from the welding wire 5, and an arc is formed between the tip 5a of the welding wire 5 and the bottom 61 of the molten portion 6. 7 occurs. That is, in the drop transition, the arc 7 faces downward, that is, in the extension direction of the welding wire 5.
In the pendulum transition, the liquid column and the arc 7 formed at the tip portion 5a of the welding wire 5 swing in a pendulum shape on the same plane, and the plane as a whole is slightly centered on the protrusion direction of the welding wire 5. It is a characteristic droplet transfer form that rotates little by little.
In the rotating transition, an arc 7 is generated between the tip portion 5a of the welding wire 5 and the side portion 62 of the molten portion 6, and the liquid column formed at the tip portion 5a of the welding wire 5 and the molten portion 6 in which the arc 7 is concave. It is a droplet transfer form that continues to rotate while facing the side portion 62 of the wire.

As an example, the welding current and droplet transfer under the conditions that 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 YGW12, and the feeding speed of the welding wire 5 is 30 m / min. The relationship with the form 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 form of the welding wire 5. The thick line arrow indicates the welding current, and the thin line arrow indicates the range of the welding current in each droplet transition form. The relationship between the welding current shown in FIG. 12 and the droplet transfer form is under the above-mentioned conditions such as wire diameter and wire protrusion length, and is merely an example.
When the welding current is in the 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 drop transition and the pendulum transition are mixed.
When the welding current is in the current range of 550 A or more and less than 600 A, the welding transition form of the 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 modes of the pendulum transition and the rotating transition are mixed.
When the welding current is in the current range of 700 A or more, the droplet transition form of the rotating transition becomes dominant.

In the buried arc welding, a buried space 6a, that is, a space surrounded by a concave molten portion 6 is formed in the molten metal, but in the molten metal, the buried space 6a is always closed and the tip portion 5a of the welding wire 5a is formed. Try to flow in the direction of being buried. However, the molten portion 6 is supported by the force of the arc radiated from the tip portion 5a of the welding wire 5 to the side portion 62 of the molten portion 6, and the buried space 6a is held in a stable state. When the buried space 6a cannot be fully supported by the arc 7, the opening of the buried space 6a is narrowed and finally contacts the welding wire 5 to cause a short circuit. A short circuit will significantly destabilize the weld condition. For example, in a situation where drop migration is dominant, the arc 7 cannot sufficiently support the side portion 62 of the molten portion 6, and the short circuit may cause welding to become unstable.
On the other hand, in the rotating transition, the arc 7 is irradiated to the side portion 62 of the concave molten portion 6, and the opening of the buried space 6a can be supported to stabilize the buried space 6a.
Further, even in the pendulum transition, since the arc 7 is irradiated to the side portion 62 of the molten portion 6 at regular intervals, a similar effect of stabilizing the buried space 6a can be obtained as in the rotating transition. In the drop transition, the arc 7 is irradiated downward, that is, the bottom portion 61 of the molten portion 6 is irradiated, so that the above stabilizing effect cannot be obtained.
On the other hand, in the rotating transition, the buried space 6a can be stabilized, but since the arc 7 is not irradiated to the bottom 61 of the buried space 6a, the penetration of the base metal 4 into 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 irradiates the bottom portion 61 of the molten portion 6, the penetration of the welding current per unit output becomes relatively deep. Even in the pendulum transition, since the arc 7 is irradiated to the bottom 61 of the molten portion 6 at regular intervals, a relatively deep penetration can be obtained as in the drop transition.

Considering the above, it can be seen that although the drop transition and the rotating transition exhibit regular droplet transition, it is not possible to achieve both stabilization of the buried space 6a and deep penetration. Further, in the pendulum transition, it is considered that the stabilization of the buried space 6a and the deep penetration can be achieved at the same time, but since the liquid column and the arc 7 behave irregularly, stable welding cannot always be realized. ..
That is, regardless of which of the three solution transfer forms is used, it is not possible to achieve both stabilization of the buried space 6a and deep penetration with only the single droplet transfer form. Further, as described above, since the droplet transfer form changes depending on the current range of the welding current, it is difficult to use only a specific droplet transfer form for general purposes.

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

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

Although the welding current Iw in the small current period has been described as the drop transition current region and the welding current Iw in the large current period has been described as the pendulum transition or rotating transition current region, the welding current Iw in the small current period and the large current period has been described. The current range is not limited to this.
Specifically, at least one of a current range of 300 A or more and less than 450 A, a current range of 450 A or more and less than 550 A, a current range of 550 A or more and less than 600 A, a current range of 600 A or more and less than 700 A, and a current range of 700 A or more. It is preferable to periodically change the welding current between the two current ranges so that the arc 7 irradiates the bottom 61 and the side 62 of the molten portion 6. The fluctuation cycle of the welding current is preferably set in the range of 10 Hz or more and 1000 Hz or less, preferably in the range of 50 Hz or more and 300 Hz or less. 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 preferably 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 fluctuates the welding current so that the welding current Iw in the small current period is in the current range of 300 A or more and less than 450 A, and the welding current Iw in the large current period is in the current range of 550 A or more and less than 600 A. It is good to let it. In this case, the drop transition and the droplet transition modes of the pendulum transition are periodically switched, and the first state in which the arc 7 is generated between the tip 5a of the welding wire 5 and the bottom 61 of the molten portion 6, and the tip 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, the arc welding apparatus periodically fluctuates the welding current so that the welding current Iw in the small current period is in the current range of 300 A or more and less than 450 A, and the welding current Iw in the large current period is in the current range of 700 A or more. good. In this case, the droplet transition form of the drop transition and the rotating transition 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, the arc welding apparatus periodically fluctuates the welding current so that the welding current Iw in the small current period is in the current range of 550 A or more and less than 600 A, and the welding current Iw in the large current period is in the current range of 700 A or more. good. In this case, the droplet transfer form of the pendulum transition and the rotating transition 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.

Furthermore, the welding current may be changed periodically by using a current region in which the two droplet transfer forms coexist.
For example, the arc welding apparatus periodically fluctuates the welding current so that the welding current Iw in the small current period is in the current range of 450 A or more and less than 550 A, and the welding current Iw in the large current period is in the current range of 700 A or more. Is also good. In this case, the state in which the drop transition and the pendulum transition are mixed and the rotating transition are periodically switched.
Further, the arc welding apparatus periodically fluctuates the welding current so that the welding current Iw in the small current period is in the current range of 300 A or more and less than 450 A, and the welding current Iw in the large current period is in the current range of 600 A or more and less than 700 A. You may let me. In this case, the drop transition and the mixed state of the pendulum transition and the rotating transition are periodically switched.

The above-mentioned welding conditions are an example, and the range of the welding current is not limited to the above-mentioned numerical range in terms of the material of the welding wire 5, the wire system, the protrusion length, and the feeding speed of the welding wire 5. .. Hereinafter, various conditions that enable mutual transition of the drop transition, the pendulum transition, and the droplet transition form of the rotating transition in the buried arc will be described.

As the material of the welding wire 5, in addition to YGW12, solid wires such as YGW11, YGW15, YGW17, YGW18, and YGW19 can be used. However, a flux cored wire, a metal cored wire, or another new wire 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. The longer the protrusion length, the shallower the penetration, so it is better to keep it at 35 mm at the longest. On the other hand, when the protruding length is shortened, the tip of the tip approaches the molten pool and the tip is consumed more severely. This tendency is particularly remarkable because of high current welding, and if it is less than 10 mm, frequent tip replacement is required.
Further, the protruding length of the welding wire 5 affects the transition current of the transition form (see FIG. 13). 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 more and 1.6 mm or less, for example. The wire diameter can be basically any wire diameter by appropriately changing the welding conditions, and is not particularly limited, but is 0.9 mm in consideration of general availability. ~ 1.6 mm is realistic. Further, the wire diameter affects the transition current of the droplet transition form (see FIG. 13). From this point of view, when the extremely thick welding wire 5 or the thin welding wire 5 is used, the transition region of the droplet transfer form is greatly expanded, and it becomes difficult to use an arbitrary 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 appropriately determined 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 protrusion length and the droplet transfer form of the welding wire 5. The horizontal axis represents the welding current, and the vertical axis represents the length of the protrusion of the welding wire 5 and the size of the wire system. The transition current of the droplet transition form is strongly influenced by the wire diameter and the protrusion length. FIG. 13 shows the influence of the protrusion length and the wire diameter of the welding wire 5 on the transition current of the droplet transition form. As shown in FIG. 13, the larger the wire diameter or the shorter the protruding length, the more the transition current shifts toward the high current region as a whole. This is due to the difference in the resistance heat generation of the welding wire 5, and when the wire diameter becomes large or the protrusion length becomes short, the resistance of the wire decreases, and the amount of heat input to the welding wire 5 due to the resistance heat generation decreases. Therefore, in order to reproduce the same droplet transition phenomenon, it is necessary to increase the welding current by that amount to increase the heat input, so that the transition current shifts to the high current side as a whole.

As an example, the change in 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 form of the welding wire 5. 14 is the same as in FIG. 11, under the conditions that the wire protrusion length is 25 mm, the diameter of the welding wire 5 is 1.4 mm, the material of the welding wire 5 is YGW 12, and the feeding speed of the welding wire 5 is 30 m / min. It shows the relationship between the welding current and the droplet transfer form, 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 FIGS. 11 and 14, the transition current of the droplet transition form shifts to the high current side as a whole.

As described above, the wire diameter and the overhang length of the welding wire 5 can be appropriately determined with reference to FIG. 12 or 14 in consideration of the tendency shown in FIG.

The welding power source 1 that carries out 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 supply 1 may receive and store the welding conditions at the operation unit, or may store the welding conditions in advance. The welding power source 1 controls the feeding of the welding wire 5 based on the set welding conditions, and periodically fluctuates 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 the mixture thereof are used. It fluctuates periodically between the two states, the waviness of the molten metal can be suppressed, and the buried space 6a can be stabilized and deep penetration can be realized.

It should be noted that the arc 7 is not necessarily applied to the side portion 62 of the molten portion 6 during a large current period. When the current period is switched at a high frequency, the droplet transition mode transitions transiently. Therefore, for example, even during the current region where the pendulum transition or the rotating transition occurs in the original steady state, that is, during the large current period, it is not always necessary. The droplet transition form may not transition to the pendulum transition or the rotating transition, and then the pendulum transition or the rotating transition may be exhibited with a slight delay after the small current period.
Similarly, even during high current periods, drop transitions may occur or the arc 7 may irradiate the bottom 61 of the molten portion 6.

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

Further, during the large current period and the small current period, the welding current does not need to be held at a constant current value, and the current waveform of the welding current that fluctuates periodically is limited to a specific waveform such as a rectangular wave. It's not something. For example, the current waveform of the welding current may be a triangular wave. The large current period is a period in which the welding current is large on average, and the small current period is a period in which the welding current is small on average.

Furthermore, in the second embodiment, an example in which the droplet transition form is changed by periodically changing the current range of the welding current has been described, but the change in the welding current is accompanied by the transition of the above-mentioned droplet transfer form. Even if it is not present, the force of the arc 7 fluctuates periodically in a large current period and a small current period, and a constant minute, relatively large frequency vibration is applied to the molten portion 6. As a result, a relatively small frequency or a sudden large sway of the buried space 6a is suppressed, so that this alone has a certain effect on the stabilization of the buried space 6a. Therefore, it is possible to realize a certain degree of stabilization of the buried space 6a by the present invention without necessarily accompanying the transition of the droplet transition form described above.

The embodiments disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims, not the above-mentioned meaning, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Welding power supply 2 Torch 3 Wire feeding part 4 Base material 5 Welding wire 5a Tip part 6 Melted part 6a Buried space 61 Bottom 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 Feeding speed control unit 41 1st base material 42 2nd 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)

By supplying a welding wire to the welded portion of the base metal and supplying a welding current to the welding wire, an arc is generated between the tip of the welding wire and the welded portion to weld the base metal. It is a consumable electrode type arc welding method.
The welding wire is fed at a feeding speed of 30 m / min or more.
The welding wire is fed at a speed at which the tip portion enters the space surrounded by the concave molten portion formed in the base metal by the 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 or more and 1000 Hz or less, the average current is 300 A or more, and the current amplitude is 50 A or more. By supplying a welding wire to the welded portion of the base metal and supplying a welding current to the welding wire, an arc is generated between the tip of the welding wire and the welded portion to weld the base metal. It is a consumable electrode type arc welding method.
The welding wire is fed at a feeding speed of 30 m / min or more.
The welding wire is fed at a speed at which the tip portion enters the space surrounded by the concave molten portion formed in the base metal by the arc generated between the tip portion and the welded portion.
By periodically changing the welding current, an arc is generated between the tip portion and the bottom portion of the molten portion, and a second state in which an arc is generated between the tip portion and the side portion of the molten portion. An 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 or more and 1000 Hz or less. 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 liquid column formed at the tip of the welding wire and a droplet transition form in which an arc swings like a pendulum. 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 of a rotating transition. The first state includes a droplet migration 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 or 3, wherein the second state includes a droplet transfer form of a rotating transition. 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 or more and 1000 Hz or less, 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 or more and 300 Hz or less, the average current is 300 A or more and 1000 A or less, and the current amplitude is 100 A or more and 500 A or less. A wire feeding unit that feeds a welding wire to a portion to be welded of a base metal and a power supply unit that supplies a welding current to the welding wire are provided, and the welding wire is supplied with a welding current to supply the welding wire. A consumable electrode type arc welding device that generates an arc between the tip and the welded portion and welds the base metal.
The wire feeding unit is
The welding wire is fed at a feeding speed of 30 m / min or more at which the tip portion enters the space surrounded by the concave molten portion formed in the base metal by the arc generated between the tip portion and the welded portion. Feed
The power supply unit
An arc welding device that fluctuates the welding current so that the frequency of the welding current is 10 Hz or more and 1000 Hz or less, the average current is 300 A or more, and the current amplitude is 50 A or more. A wire feeding unit that feeds a welding wire to a portion to be welded of a base metal and a power supply unit that supplies a welding current to the welding wire are provided, and the welding wire is supplied with a welding current to supply the welding wire. A consumable electrode type arc welding device that generates an arc between the tip and the welded portion and welds the base metal.
The wire feeding unit is
The welding wire is fed at a feeding speed of 30 m / min or more at which the tip portion enters the space surrounded by the concave molten portion formed in the base metal by the arc generated between the tip portion and the welded portion. Feed
The power supply unit
By periodically changing the welding current, an arc is generated between the tip portion and the bottom portion of the molten portion, and a second state in which an arc is generated between the tip portion and the side portion of the molten portion. An arc welding device that periodically changes the state.