JP2022144100A - Arc-welding device and arc-welding method - Google Patents

Abstract

To provide an arc-welding device and an arc-welding method capable of suppressing abrupt variation of welding current at a rise and a fall by properly controlling a set voltage.SOLUTION: An arc-welding device which inserts a tip part of a welding wire to an inside space of a concave melting portion formed in base material and performs arc welding includes a power source part which controls a set voltage in order to change a welding current flowing in the welding wire and controls a change of the welding current when conversion between a rise and a fall in the welding current occurs.SELECTED DRAWING: Figure 4

Description

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

Arc welding is performed by bringing the tip of the welding wire held by the tip of the welding torch close to the groove provided in the base material, applying a voltage between the welding wire and the base material, and generating an arc. .

There is a technology that realizes one-pass welding of thick plates by feeding the welding wire at a higher speed and supplying a large current of 300 A or more compared to general arc welding. When the welding wire is fed at a high speed and supplied with a large current, a recessed molten portion is formed in the base metal, and the tip of the welding wire enters the inner space of the molten portion surrounded by the molten portion. In this way, the tip of the welding wire penetrates deeper than the surface of the base material, so that the melted portion penetrates to the back surface side in the thickness direction of the base material, enabling one-pass welding. Hereinafter, the inner space surrounded by the concave molten portion will be referred to as a buried space, and the arc generated between the tip of the welding wire entering the buried space and the base material or the molten portion will be referred to as a buried arc.

For example, Patent Document 1 discloses that in buried arc welding using a buried arc, the welding current flowing through the welding wire is periodically varied by periodically varying the set voltage in order to stably maintain the buried space. is disclosed.

JP 2017-144480 A

However, as in Patent Document 1, when the set voltage is changed in order to stably maintain the buried space, when the set voltage fluctuates in a rectangular wave shape, that is, when the set voltage fluctuates at the rise and fall, the set voltage fluctuates. If it is abrupt, the welding current that fluctuates along with it also abruptly fluctuates at the rise and fall. Thus, when the welding current suddenly rises or falls, there is a problem that the state of the molten portion becomes unstable or the arc becomes unstable.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide an arc welding apparatus capable of suppressing abrupt fluctuations in the welding current at the rising and falling edges by appropriately controlling the set voltage. and to provide an arc welding method.

The arc welding apparatus according to the present invention performs arc welding by inserting the tip of the welding wire into the inner space of a recessed molten portion formed in a base material, wherein the welding current flowing through the welding wire is A power supply section is provided for controlling a set voltage for variation and for controlling variations in the welding current as the welding current transitions between rising and falling.

In the present invention, the power supply section controls a set voltage for varying the welding current flowing through the welding wire, so that when the welding current changes from rising to falling or from falling to rising, the Suppresses sudden changes in welding current.

In the arc welding apparatus according to the present invention, the power supply unit alternately switches the set voltage between an upper limit value and a lower limit value, switches from the lower limit value to the upper limit value, or switches from the upper limit value to the lower limit value. Do it over the first hour.

In the present invention, the power supply unit switches the set voltage from the lower limit value to the upper limit value or from the upper limit value to the lower limit value over the first time. A rapid change in the welding current can be suppressed.

In the arc welding device according to the present invention, the set voltage changes at a constant rate during the first period of time.

In the present invention, the power supply unit changes the set voltage at a constant rate during the first time period, thereby suppressing sudden changes in the welding current.

In the arc welding device according to the present invention, the change in the set voltage in the first half of the first time is smaller than that in the second half of the first time.

In the present invention, the power supply unit changes the set voltage so that the change in the first half of the first time period is smaller than that in the second half of the first time period, thereby suppressing abrupt changes in the welding current. can.

In the arc welding apparatus according to the present invention, the power supply section maintains the set voltage at the upper and lower limits for a second period of time, and the first period of time is 5-15% of the second period of time.

In the present invention, the first time is 5 to 15% of the second time in which the set voltage is maintained at the upper and lower limits, so that the influence on arc welding is minimized. A rapid change in the welding current can be suppressed.

In the arc welding apparatus according to the present invention, the first time is 8-12% of the second time.

In the present invention, the first time is 8 to 12% of the second time in which the set voltage is maintained at the upper and lower limits, so that the influence on arc welding is minimized. A rapid change in the welding current can be suppressed.

The arc welding method according to the present invention is an arc welding method in which arc welding is performed by inserting the tip of the welding wire into the inner space of a recessed molten portion formed in a base material, wherein the welding current flowing through the welding wire is A set voltage is controlled for variation to control variations in the welding current as the welding current transitions between rising and falling.

In the present invention, when the welding current changes from rising to falling or from falling to rising by controlling the set voltage for varying the welding current flowing through the welding wire, the welding current suddenly changes. is suppressed.

According to the present invention, by appropriately controlling the set voltage, it is possible to prevent the welding current, which fluctuates with the set voltage, from sharply fluctuating at the rising and falling edges.

1 is a schematic diagram showing one configuration of an arc welding apparatus according to Embodiment 1. FIG. 4 is a flowchart showing arc welding procedures in the arc welding apparatus according to Embodiment 1. FIG. FIG. 3 is a side cross-sectional view showing a base material to be welded; 4 is a graph showing a set voltage generated by a power supply and variations in welding current according to the set voltage; FIG. 2 is a schematic diagram showing a state of buried arc welding according to Embodiment 1; 9 is a graph showing a set voltage generated by a power supply section in the arc welding device according to Embodiment 2;

An arc welding apparatus and an arc welding method according to embodiments of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

(Embodiment 1)
FIG. 1 is a schematic diagram showing one configuration of an arc welding apparatus 100 according to Embodiment 1. FIG. An arc welding apparatus 100 according to Embodiment 1 is a so-called consumable electrode gas shielded arc welding apparatus, and is used for manual or semi-automatic arc welding. The arc welding apparatus 100 can perform both buried arc welding and open arc welding using a buried arc.

The arc welding device 100 includes a welding power source 1, a torch 2 and a wire feeding section 3.
Torch 2 has a contact tip and a nozzle (not shown). The contact tip is in the shape of a round bar having a small diameter hole penetrating its axis, and is made of a conductive material such as a copper alloy. 5) is supplied. Also, the contact tip comes into contact with the welding wire 5 passing therethrough and supplies the welding current I to the welding wire 5 . Further, the torch 2 has a cylindrical shape surrounding the contact tip and has a nozzle for injecting shield gas to the welded portion. The shield gas is for preventing oxidation of the base material 4 and welding wire 5 melted by the arc 7 . 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, has 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 that is spirally wound and stored in a pail pack, or a reel wire that is wound on a wire reel.

The wire feeder 3 has a feed roller that feeds the welding wire 5 to the torch 2 and a motor that rotates the feed roller. The wire feeding unit 3 rotates the feeding roller to pull out the welding wire 5 from the pail pack or wire reel, and feeds the pulled out welding wire 5 to the torch 2 at a predetermined speed. The feeding speed of the welding wire 5 is, for example, about 5 to 100 m/min for buried arc welding.

The welding power source 1 is connected to the contact tip of the torch 2 and the base material 4 via a power supply cable. and a control circuit 12 .

The power supply unit 11 is a power supply with constant voltage characteristics, and controls the voltage output to the contact tip of the torch 2 and the base material 4 to periodically increase and decrease the welding current I. The power supply unit 11 includes a power supply circuit 11a that outputs a PWM-controlled DC current, a voltage control circuit 11b, a current setting circuit 11d, a voltage detection unit 11e, and a current detection unit 11f.

The current setting circuit 11 d outputs a current setting signal Ir indicating the set current value of the welding current I to the voltage control circuit 11 b and the feeding speed control circuit 12 . A feeding speed control circuit 12 controls the feeding speed of the welding wire 5 based on the current setting signal Ir. During buried arc welding, the current setting circuit 11d outputs a current setting signal Ir indicating a set current value of 300 A or more, preferably a set current value of 300 A or more and 1000 A or less, more preferably a set current value of 500 A or more and 800 A or less. It is output to the control circuit 11b and the feeding speed control circuit 12. FIG.

In addition, the current setting circuit 11d has a frequency for periodically varying the welding voltage V and the welding current I between the base material 4 and the welding wire 5, the amplitude of the periodically varying welding current I, and the periodically varying welding current I. An average current and the like of the current I are determined, and a set voltage is generated so that the welding current I has a target frequency, current amplitude, and average current. The current setting circuit 11d is a circuit that outputs an output voltage setting signal Er indicating the set voltage to the voltage control circuit 11b.

The voltage detector 11e detects the welding voltage V and outputs a voltage value signal Vd indicating the detected voltage value to the voltage control circuit 11b.

The current detection unit 11f detects, for example, a welding current I supplied from the welding power source 1 to the welding wire 5 via the torch 2 and flowing through the arc 7, and outputs a current value signal Id indicating the detected current value to a current setting circuit. 11d.

The voltage control circuit 11b is a circuit that operates with constant voltage characteristics and controls the operation of the power supply circuit 11a so that the power supply circuit 11a outputs a voltage corresponding to the output voltage setting signal Er. The voltage control circuit 11b electronically controls the electrical resistance R and the reactor L existing in the power supply path of the welding power source 1 to achieve constant voltage characteristics.

Further, the voltage control circuit 11b generates a difference signal Ei based on the voltage value signal Vd output from the voltage detection unit 11e and the current setting signal Ir and the output voltage setting signal Er output from the current setting circuit 11d. It calculates and outputs the calculated difference signal Ei to the power supply circuit 11a. The difference signal Ei is a signal indicating the difference between the detected current value and the current value to be output from the power supply circuit 11a.

The power supply circuit 11a includes an AC-DC converter that converts commercial alternating current, an inverter circuit that converts the converted direct current into a desired alternating current by switching, a rectifier circuit that rectifies the converted alternating current, and the like. The power supply circuit 11 a PWM-controls the inverter according to the differential signal Ei output from the voltage control circuit 11 b so that the differential signal Ei becomes smaller, and outputs a voltage to the welding wire 5 . As a result, a periodically fluctuating welding voltage V is applied between the base material 4 and the welding wire 5, and a periodically fluctuating welding current I is applied.

The welding power source 1 is configured to receive an output instruction signal from the outside via a control communication line (not shown). supply of The output instruction signal is, for example, a signal output from the torch 2 side to the welding power source 1 when a hand-operated switch provided on the torch 2 side is operated.

FIG. 2 is a flow chart showing the procedure of arc welding in the arc welding apparatus 100 according to this embodiment, and FIG. 3 is a side sectional view showing the base material 4 to be welded.
Below, for example, a solid wire with a diameter of 1.4 mm is used as the welding wire 5, carbon dioxide gas is used as the shielding gas, and buried arc welding is performed with a welding current of 500 A and a welding voltage of 42 V. do. Also, the set voltage is varied by ±10 V and a period of 11 ms.

First, a pair of base materials 4 to be joined are prepared, and welding conditions including voltage and current, welding mode, etc. are set (step S11). For example, 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, which are the parts to be welded, are butted against each other and arranged at predetermined welding operation positions. If necessary, the first base material 41 and the second base material 42 may be provided with grooves of any shape such as a Y shape and a square shape. The first and second base materials 41 and 42 are steel plates such as mild steel, carbon steel for machine structural use, and alloy steel for machine structural use.

After the various settings have been made, the welding power source 1 determines whether or not the voltage output start condition is satisfied by determining whether or not the output instruction signal has been input (step S12). If it is determined that the voltage output start condition is not satisfied because the output instruction signal has not been input (step S12: NO), the welding power source 1 repeats this determination until the output instruction signal is input.

If it is determined that the voltage output start condition is satisfied (step S12: YES), the feed speed control circuit 12 of the welding power source 1 sends a feed instruction signal instructing the feeding of the welding wire 5 to the wire feeding section 3. to feed the welding wire 5 at a speed corresponding to the current setting signal Ir (step S13).

Next, the power supply unit 11 of the welding power source 1 detects the welding voltage V and the welding current I with the voltage detection unit 11e and the current detection unit 11f (step S14), and detects the detected welding voltage V and welding current I and the welding power source. The output of the power supply unit 11 is PWM-controlled so that the external characteristics of No. 1 match the set welding conditions (step S15). For example, the power supply unit 11 has external characteristics such that the decrease in welding voltage V with respect to an increase in welding current I of 100 A is 2 V or more and 20 V or less.

That is, the power supply unit 11 adjusts the set voltage so that the frequency, current amplitude, and average current of the detected welding current I match the set welding conditions in the constant voltage characteristic, and the welding current I rises and falls periodically. PWM control is performed by generating and outputting

Furthermore, in the arc welding apparatus 100 according to the present embodiment, by appropriately controlling the set voltage, in the welding current I that periodically fluctuates up and down, the welding current I can to control abrupt changes in A detailed description will be given below.

FIG. 4 is a graph showing the set voltage generated by the power supply unit 11 and the variation of the welding current I according to the set voltage. The horizontal axis of each graph shown in FIG. 4 represents time, and the vertical axis of each graph shown in FIGS. 4A and 4B represents the set voltage and the welding current I, respectively.

In the arc welding apparatus 100 according to the present embodiment, the power supply unit 11 having constant voltage characteristics periodically increases and decreases the set voltage as shown in FIG. 4A. For example, the set voltage may be periodically increased and decreased at a frequency of 10 Hz to 1000 Hz, preferably 50 Hz to 300 Hz, more preferably 80 Hz to 200 Hz.

As shown in FIG. 4A, the set voltage is alternately switched between an upper limit value (+10V) and a lower limit value (-10V). That is, the lower limit value is switched to the upper limit value or the upper limit value is switched to the lower limit value every half cycle. The upward switching from the lower limit value to the upper limit value and the downward switching from the upper limit value to the lower limit value are performed over a first period of time. That is, in the case of upward switching, the set voltage continues to rise gradually from the lower limit value to the upper limit value linearly at a constant rate during the first time period. Further, in the case of downward switching, the set voltage continues to decrease linearly from the upper limit value to the lower limit value gradually at a constant rate during the first time period. In other words, the rising and falling edges at the set voltage are oblique to the horizontal axis.

After switching up, the set voltage is maintained at the upper limit for a second time and then switched to the lower limit. After the downward switch, the set voltage is maintained at the lower limit for a second time and then switched to the upper limit.

As described above, the fluctuation period of the set voltage is 11 ms, the first time is 0.5 ms, and the second time is 5 ms. That is, upward switching and downward switching are performed over 10% of the second time during which the upper limit value or the lower limit value is maintained.

When the set voltage is periodically increased and decreased in this manner, the welding current I is also periodically increased and decreased as shown in FIG. 4B. As described above, in the arc welding apparatus 100 of the present embodiment, control is performed such that the set voltage is switched upward and downward over a predetermined period of time. That is, control is performed so that the set voltage is not suddenly switched upward and downward, that is, the rising edge and the falling edge of the set voltage are not vertical.

As a result, the welding current I, which fluctuates up and down, is moderately controlled by suppressing abrupt changes at the extreme values. That is, at a minimum portion (see P1 in FIG. 4) where the welding current I finishes downward and then turns upward, and a maximum portion (see P2 in FIG. 4) where the welding current I finishes upward and turns downward. , the welding current I gradually changes along a curved line.

FIG. 5 is a schematic diagram showing the state of buried arc welding according to the first embodiment. For example, a welding current I having an average current of 300 A or more is supplied to the welding wire 5, and the welding wire 5 is fed at about 5 to 100 m/min. At this time, the base material 4 melted by the heat of the arc 7 generated between the tip portion 5a of the welding wire 5 and the welded portion and a recessed molten portion 6 made of the molten metal of the welding wire 5 are formed in the base material 4, The tip 5a of the welding wire 5 enters the buried space 6a surrounded by the melted portion 6. As shown in FIG. When the power supply unit 11 periodically raises and lowers the welding current I (set voltage), the welding wire 5 penetrates deeply into the buried space 6a, and an arc 7 is generated between the tip 5a of the welding wire 5 and the bottom 61 of the melted portion 6. A first state (see FIG. 5A) occurs, and a second state (see FIG. 5B) in which the welding wire 5 shallowly enters the buried space 6a and an arc 7 is generated between the tip 5a and the side 62 of the melted portion 6. occurs periodically.

In the first state, the tip portion 5a of the welding wire 5 penetrates deeply into the buried space 6a, and the arc 7 irradiating the bottom portion 61 of the molten portion 6 provides deep penetration. In the second state, the tip portion 5a of the welding wire 5 shallowly enters the buried space 6a, and the molten portion 6 is supported by the force of the arc 7 applied to the side portion 62 of the molten portion 6. As shown in FIG.
As described above, by periodically raising and lowering the welding current I, the first state and the second state are cyclically repeated, so that the buried space 6a can be stably maintained.

Returning to the description of FIG. Next, the power supply unit 11 of the welding power source 1 determines whether or not to stop outputting the welding current I (step S16). Such determination is made based on whether or not the input of the output instruction signal continues. When the input of the output instruction signal continues, the power supply unit 11 determines not to stop the voltage output (step S16: NO), and the process returns to step S13. When the input of the output instruction signal does not continue, the power supply unit 11 determines to stop outputting the voltage (step S16: YES), and the process returns to step S12.

As described above, in buried arc welding, in order to stably maintain the buried space 6a, control is performed to periodically increase and decrease the welding current I by periodically increasing and decreasing the set voltage. However, if the set voltage fluctuates in the form of a rectangular wave and the set voltage fluctuates abruptly at the rise and fall, the welding current I, which fluctuates up and down accordingly, also sharply rises and falls. fluctuates to In the case of a sudden rise (increase) in the welding current I, the force received from the arc 7 changes rapidly in the region where the arc 7 is formed in the molten portion 6, so the state of the molten portion 6 becomes unstable. On the other hand, when the welding current I falls sharply, the rigidity of the arc 7 is momentarily lost and the arc 7 fluctuates, resulting in instability.

On the other hand, in the arc welding apparatus 100 of the present embodiment, as described above, when the set voltage is periodically raised and lowered, the set voltage is not suddenly switched upward and downward. Direction switching and downward switching are performed over a predetermined period of time. As a result, the welding current I, which fluctuates up and down, is restrained from abrupt changes at the extremities, and gentle fluctuations can be obtained. Therefore, when the welding current I rises abruptly, the state of the molten portion 6 becomes unstable, and when the welding current I falls abruptly, the arc 7 becomes unstable. can be prevented. Furthermore, since the sudden change in the welding current I is suppressed, it is possible to reduce the noise generated when the welding current I suddenly changes.

In the above description, the case where the first time required for upward switching and downward switching is 10% of the second time during which the upper limit value or lower limit value of the set voltage is maintained has been described as an example. It is not limited.

If the first time is less than 5% of the second time, the current change at the rise/fall of the welding current I is not sufficiently suppressed, the above-mentioned problems cannot be solved, and the effect of stabilizing the buried arc is obtained. can't When the first time exceeds 15% with respect to the second time, the buried arc becomes less stable than when the set voltage is varied in a square. Therefore, the first time may be 5%-15% of the second time, and within this range the effect on the stability of the buried arc is negligible.

Further, as the first time becomes 5% or more of the second time, the effect of stabilizing the buried arc is obtained. On the other hand, when the first time exceeds 12% of the second time, the amount of change in current is generally smaller than when control is not performed for upward switching and downward switching of the set voltage in this embodiment. Therefore, the originally intended buried arc stabilization effect begins to decrease. Therefore, it is more desirable that the first time is 8%-12% of the second time.

(Embodiment 2)
FIG. 6 is a graph showing the set voltage generated by the power supply section 11 in the arc welding device 100 according to the second embodiment. The horizontal axis of the graph shown in FIG. 6 indicates time, and the vertical axis indicates set voltage. Also in the arc welding apparatus 100 of the second embodiment, in buried arc welding, in order to stably maintain the buried space 6a, the set voltage is periodically raised and lowered, thereby periodically raising and lowering the welding current I. Control is performed.

The set voltage is alternately switched between an upper limit value (+10V) and a lower limit value (-10V). That is, the lower limit value is switched to the upper limit value or the upper limit value is switched to the lower limit value every half cycle. The upward switching from the lower limit value to the upper limit value and the downward switching from the upper limit value to the lower limit value are performed over a first period of time. That is, in the case of upward switching, the set voltage continues to rise gradually from the lower limit value to the upper limit value in a downward convex curve during the first time period. In the case of downward switching, the set voltage continues to drop gradually from the upper limit value to the lower limit value in an upwardly convex curve during the first time period. In both cases of upward switching and downward switching, the change in the set voltage in the first half of the first time is smaller than that in the second half of the first time.

After switching up, the set voltage is maintained at the upper limit for a second time and then switched to the lower limit. After the downward switch, the set voltage is maintained at the lower limit for a second time and then switched to the upper limit. As in the first embodiment, the first time required for upward switching and downward switching is 10% of the second time during which the upper limit value or the lower limit value is maintained.

When the set voltage is periodically increased and decreased in this way, the welding current I is also periodically increased and decreased accordingly. As described above, in the arc welding apparatus 100 of the present embodiment, the upward switching and downward switching of the set voltage takes a predetermined time so that the upward switching and downward switching of the set voltage do not occur suddenly. done. As a result, the welding current I, which fluctuates up and down, is restrained from abrupt changes at the extremities, and is gently fluctuated (see FIG. 4).

In the above description, the case where both the switching of the set voltage from the lower limit value to the upper limit value and the switching of the set voltage from the upper limit value to the lower limit value are performed over the first time period has been described as an example. It is not limited to this. Only one of the switching of the set voltage from the lower limit value to the upper limit value and the switching of the set voltage from the upper limit value to the lower limit value may be performed over the first time.

In the above description, it has been described that the set voltage is controlled to suppress abrupt changes in the extreme values of the welding current I that fluctuates up and down, but the present invention is not limited to this. For example, when the welding current I rises or falls, the rate of change of the welding current I may be limited to suppress rapid changes in the extreme values of the welding current I.

The disclosed embodiments 1 and 2 should be considered as examples in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the meaning described above, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. At least part of the embodiments described above may be combined arbitrarily.

4 Base Material 5 Welding Wire 5a Tip Part 6 Melting Portion 11 Power Supply Part 100 Arc Welding Device

Claims (7)

In an arc welding apparatus that performs arc welding by inserting the tip of a welding wire into the inner space of a recessed molten portion formed in the base material,
An arc welding apparatus comprising a power supply unit that controls a set voltage in order to vary the welding current flowing through the welding wire, and that controls variations in the welding current when the welding current changes between rising and falling. The power supply unit
alternately switching the set voltage between an upper limit value and a lower limit value;
Switching from the lower limit value to the upper limit value or from the upper limit value to the lower limit value is performed over the first time
The arc welding device according to claim 1. The arc welding device according to claim 2, wherein the set voltage changes at a constant rate during the first time period. The arc welding device according to claim 2, wherein a change in the set voltage in the first half of the first time is smaller than that in the second half of the first time. the power supply unit maintains the set voltage at the upper limit value and the lower limit value for a second time;
The arc welding apparatus according to any one of claims 2 to 4, wherein said first time is 5-15% of said second time. The arc welding apparatus of claim 5, wherein said first time is 8-12% of said second time. In the arc welding method in which arc welding is performed by inserting the tip of the welding wire into the inner space of the recessed molten portion formed in the base material,
An arc welding method comprising: controlling a set voltage in order to vary the welding current flowing through the welding wire; and controlling the variation of the welding current when the welding current changes between rising and falling.

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