JP7222810B2 - Arc welding device and arc welding method - Google Patents

Description

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

One of the welding methods is a consumable electrode gas shielded arc welding method. Gas-shielded arc welding is a technique in which an arc is generated between the welding wire fed to the base material and the base material, and the heat of the arc is used to weld the base material. In order to prevent oxidation, welding is performed while injecting an inert gas around the weld. If it is a thin plate of about 5 mm, the butt joint of the base material can be welded in one pass.

In addition, there is a technology that realizes one-pass welding of 9 to 30 mm thick plates by feeding the welding wire at a higher speed and supplying a larger current than in the general gas shielded arc welding method. Specifically, by feeding the welding wire at about 5 to 100 m/min and supplying a large current of 300 A or more, one-pass welding of thick plates can be achieved. When the welding wire is fed at high speed and supplied with a large current, the heat of the arc forms a recessed molten portion in the base metal, and the tip of the welding wire enters the space surrounded by the molten portion. As the tip of the welding wire penetrates deeper than the surface of the base material, the melted portion penetrates to the back side of the base material in the thickness direction, thereby enabling one-pass welding. Hereinafter, the space surrounded by the concave molten portion is called 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 is appropriately called a buried arc. Welding performed by buried arc is called buried arc welding. On the other hand, an arc in which no recessed melted portion is formed or a normal arc in which the welding wire tip does not enter the recessed melted portion is called an open arc.

Patent Literature 1 discloses a consumable electrode type arc welding apparatus capable of obtaining a stable arc even when the projection length of the welding wire fluctuates.
In general consumable electrode arc welding with constant voltage characteristic control and similar characteristics, the welding current changes when the wire projection length changes, resulting in changes in penetration depth and arc conditions. is often a problem. However, the protruding length here refers to the distance from the contact tip to the base metal surface, and the length of the welding wire that exists as an individual during welding (the length from the tip of the contact tip to the arc generation point) It does not refer to In order to solve this problem, there is a technique for maintaining the welding current at the set value by automatically adjusting the wire feed speed that correlates with the welding current.
However, although the welding current can be maintained at the set value only by adjusting the wire feed speed, the appropriate arc length cannot be maintained at a constant level, resulting in unstable welding. In the arc welding apparatus according to Patent Literature 1, the arc length can be kept constant by automatically adjusting the feed speed and the set voltage at the same time.

JP-A-5-205451

However, in the arc welding apparatus described in Patent Document 1, the characteristics of buried arc welding and open arc welding are not considered.
Compared to a normal open arc, a buried arc requires more precise control of the arc length, that is, the wire tip position, for the following reasons.
First, when the wire tip position rises above the top of the melted portion, there is no buried arc.
Secondly, in the buried arc, which is characterized by obtaining deep penetration by generating the arc at a deep position of the molten part, a change in the wire tip position greatly affects the penetration depth.
Third, especially when a rotating or pendulum transition is used to stabilize the buried arc, the deeper wire tip position reduces the stability of the buried arc because it is less likely to support the side walls of the melted portion.

In addition, compared to a normal open arc, the buried arc requires a smaller voltage change amount to change the wire tip position, and when the control technology of Patent Document 1 is used, the feed used in a normal open arc is reduced. If the amount of change in feed speed/the amount of change in set voltage is used as it is, the effect of the latter is large, and the wire tip position cannot be maintained constant.

As described above, if the buried arc is controlled in the same manner as the open arc, the wire tip position with respect to the melted portion fluctuates. In buried arcs, there is a technical problem that such variations in wire tip position lead to destabilization of the buried arc.

An object of the present invention is to realize a stable buried arc state by maintaining a constant position of the tip of the wire with respect to the molten portion in buried arc welding even when the length of protrusion of the welding wire fluctuates. The object is to provide an arc welding apparatus and an arc welding method capable of

The arc welding apparatus according to this aspect is a consumable electrode type arc welding apparatus including a power supply unit that supplies a welding current to a welding wire fed to a base material, and a concave shape formed in the base material by an arc. A first mode in which the base material is welded by allowing the tip of the welding wire to enter the space surrounded by the melted portion of the a mode setting circuit for selecting a second mode in which the base material is welded without advancing; a feeding speed control circuit for controlling the feeding speed of the welding wire so that the feeding speed of the welding wire becomes slow when the length becomes short; and a voltage control circuit for controlling the output voltage of the power supply unit so that the output voltage of the power supply unit decreases when the output voltage of the power supply unit increases and the projection length of the welding wire decreases. The amount of change in the output voltage with respect to the amount of change in the feed speed according to the length of protrusion of the welding wire is smaller when the first mode is set than when the second mode is set.

In this aspect, when the welding wire projection length fluctuates, the welding current can be maintained by changing the feeding speed of the welding wire (see FIG. 5). Also, by varying the feeding speed and varying the output voltage of the power source, the arc length can be maintained (see FIGS. 7 and 8).
Not only for open arcs but also for buried arcs, basically, the welding current and arc length can be kept constant by varying the feeding speed of the welding wire and the output voltage. However, in the buried arc, the change in arc length is relatively gradual (see Fig. 9), and when the output voltage is varied in the same way as in the open arc, the wire tip position with respect to the recessed molten portion changes, and the buried arc destabilize.
Therefore, in this aspect, the amount of change in the output voltage with respect to the amount of change in the feed speed according to the protrusion length of the welding wire is higher when the first mode is set (buried arc) than when the second mode is set (open arc). controlled to be smaller than
By varying the output voltage in this manner, the welding current and arc length can be kept constant when the protrusion length varies in both buried arc welding and open arc welding. In other words, the arc can be stably maintained even if the welding wire protrusion length changes.

The arc welding apparatus according to this aspect includes the amount of change in the output voltage with respect to the amount of change in the feed speed when the first mode is set, and the output voltage with respect to the amount of change in the feed speed when the second mode is set. The larger the diameter of the welding wire, the larger the difference from the amount of change in .

In this aspect, the arc can be stably maintained regardless of the wire diameter.

The arc welding apparatus according to this aspect includes a power supply unit that supplies a welding current to the welding wire fed to the base material, and the welding wire is placed in a space surrounded by a recessed molten portion formed in the base material by the arc. is a consumable electrode type arc welding device that welds the base material by entering the tip of the welding wire, and when the protrusion length of the welding wire increases, the feeding speed of the welding wire increases, and the welding A feeding speed control circuit for controlling the feeding speed of the welding wire so that the feeding speed of the welding wire is slowed down when the wire projection length becomes short; voltage control for controlling the output voltage of the power supply unit so that the output voltage of the power supply unit increases when the welding wire is extended, and the output voltage of the power supply unit decreases when the protrusion length of the welding wire decreases. and a circuit, wherein the amount of change in the output voltage with respect to the amount of change in the feed speed according to the protruding length of the welding wire is set so that the melted portion is maintained.

In this mode, similarly to the above mode, even in buried arc welding, when the protrusion length fluctuates, the welding current and the arc length can be kept constant. In other words, the arc can be stably maintained even if the welding wire protrusion length changes.

In the arc welding apparatus according to this aspect, the power supply unit has a constant voltage characteristic, and the voltage control circuit periodically varies the set voltage of the power supply unit to vary the welding current, thereby controlling the welding current. A first state in which the tip portion of the wire deeply enters the space and a second state in which the tip portion shallowly enters the space are periodically changed.

In the present invention, the tip of the welding wire enters the buried space surrounded by the recessed molten portion and a buried arc is generated. Specifically, the tip of the welding wire is surrounded by the melted portion, and by periodically varying the welding current, the wire tip position in the buried space can be moved up and down. An arc occurs between the bottom and sides of the .
In the first state, the tip of the welding wire penetrates deeply into the buried space, and deep penetration is obtained by the arc irradiating the bottom of the molten portion.
The base material and the molten metal of the welding wire melted by the heat of the arc tend to flow in the direction in which the buried space is closed and the tip of the welding wire is buried, but in the second state, the tip of the welding wire enters the buried space shallowly, and the molten portion is supported by the arc force applied to the sides of the molten portion, so the buried space is maintained in a stable state.

In the arc welding apparatus according to this aspect, the voltage control circuit changes the value of the changing set voltage on the low voltage side when the protrusion length of the welding wire changes.

According to this aspect, by varying the value on the low voltage side of the varying output voltage, the buried arc can be stabilized compared to the case of varying the high voltage side.

In the arc welding apparatus according to this aspect, the voltage control circuit changes the value of the changing set voltage on the high voltage side when the protrusion length of the welding wire changes.

According to this aspect, by varying the value on the high voltage side of the varying output voltage, it is possible to form a buried arc that is more resistant to magnetic blow than when the low voltage side is varied.

In the arc welding apparatus according to this aspect, the voltage control circuit varies the average value of the varying set voltage when the welding wire protrusion length varies.

According to this aspect, by varying the average value of the varying output voltage, it is possible to form a buried arc that is resistant to magnetic blow to some extent and has high stability.

The arc welding method according to this aspect is a consumable electrode type arc welding method that supplies a welding current to a welding wire that is fed to a base metal, and is surrounded by a recessed molten portion formed in the base metal by an arc. A first mode in which the base material is welded by allowing the tip of the welding wire to enter the space where the base material is welded, or the tip of the welding wire is not formed without forming the concave melted portion or entering the tip of the welding wire into the melted portion. selecting a second mode for welding the base material; and when the welding wire protruding length is increased, the welding wire feeding speed is increased, and when the welding wire protruding length is decreased. a step of controlling the feeding speed of the welding wire so that the feeding speed of the welding wire becomes slow; and a step of controlling the output voltage so that the output voltage becomes smaller when the protrusion length becomes shorter, wherein the change in the output voltage with respect to the amount of change in the feed speed according to the protrusion length of the welding wire. The amount is smaller when the first mode is set than when the second mode is set.

In this mode, similarly to the above mode, even in buried arc welding, when the protrusion length fluctuates, the welding current and the arc length can be kept constant. In other words, the arc can be stably maintained even if the welding wire protrusion length changes.

In the arc welding method according to this aspect, a welding current is supplied to a welding wire that is fed to a base metal, and the tip of the welding wire is moved into a space surrounded by a recessed molten portion formed in the base metal by an arc. In the consumable electrode type arc welding method in which the base material is welded by advancing the welding wire, when the welding wire protruding length increases, the welding wire feeding speed increases, and the welding wire protruding length increases. a step of controlling the feed speed of the welding wire so that the feeding speed of the welding wire is slowed when the welding wire is shortened; and controlling the output voltage so that the output voltage becomes smaller when the welding wire projection length becomes shorter, and the amount of change in the feed speed according to the welding wire projection length. is set such that the melted portion is maintained.

In this mode, similarly to the above mode, even in buried arc welding, when the protrusion length fluctuates, the welding current and the arc length can be kept constant. In other words, the arc can be stably maintained even if the welding wire protrusion length changes.

According to the above, in buried arc welding, even when the welding wire protrusion length fluctuates, the position of the wire tip portion with respect to the molten portion can be kept constant, and a stable buried arc state can be realized. .

1 is a schematic diagram showing one configuration of an arc welding apparatus according to Embodiment 1. FIG. 4 is a flow chart showing the procedure of the arc welding method according to Embodiment 1. FIG. FIG. 3 is a side cross-sectional view showing a base material to be welded; It is a schematic diagram which shows a buried arc state. FIG. 7 is an explanatory diagram showing a method of maintaining the welding current by varying the feeding speed of the welding wire when the protrusion length of the welding wire varies. FIG. 4 is a schematic diagram showing changes in arc length when the welding wire feeding speed is varied and the welding current is maintained. FIG. 4 is an explanatory diagram showing a method of maintaining the arc length by varying the welding wire feeding speed and varying the set voltage. FIG. 4 is a schematic diagram showing that the arc length is maintained by varying the welding wire feeding speed and varying the set voltage. FIG. 4 is a schematic diagram showing fluctuations in arc length when the wire tip position fluctuates in buried arc welding. 7 is a graph showing correction amounts of set voltages; 4 is a graph showing fluctuations in set voltage and welding current; FIG. 5 is a schematic diagram showing an arc welding method according to Embodiment 2; 9 is a graph showing a control method of set voltage according to the second embodiment;

A specific example of an arc welding apparatus and an arc welding method according to an embodiment of the present invention will be described 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.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be specifically described based on the drawings showing its embodiments.
(Embodiment 1)
<Arc welding equipment>
FIG. 1 is a schematic diagram showing one configuration of an arc welding apparatus according to this embodiment. The arc welding apparatus according to this embodiment is a consumable electrode type gas shielded arc welding machine capable of butt-welding a base material 4 having a thickness of 9 to 30 mm in one pass. A wire feeder 3 is provided. The arc welding apparatus according to this embodiment is a semi-automatic welding machine, and can perform both buried arc welding and open arc welding.

The torch 2 is made of a conductive material such as a copper alloy, guides the welding wire 5 to the portion to be welded of the base material 4, and supplies the welding current I required to generate the arc 7 (see FIGS. 4, 8, etc.). It has a cylindrical contact tip that feeds. The contact tip comes into contact with the welding wire 5 passing therethrough and supplies the welding current I to the welding wire 5 . The torch 2 has a hollow cylindrical shape surrounding the contact tip, and has a nozzle for injecting a shielding gas to the welded portion. The 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. In the case of buried arc welding, the feeding speed of the welding wire 5 is, for example, about 5 to 100 m/min. For open arc welding, for example, about 1 to 22 m/min. It should be noted that the feeding method of the welding wire 5 is merely an example, and is not particularly limited.

The welding power source 1 is connected to the contact tip of the torch 2 and the base material 4 via a power supply cable. 12. Note that the power supply unit 11 and the feeding speed control circuit 12 may be configured separately. The power supply unit 11 is a power supply with constant voltage characteristics, and includes a power supply circuit 11a that outputs a PWM-controlled DC current, a voltage control circuit 11b, a mode setting circuit 11c, a current setting circuit 11d, a voltage detection unit 11e, and a current detection unit. 11f.

The mode setting circuit 11c sets the first mode (see FIG. 4) for welding the base material 4 by inserting the tip 5a of the welding wire 5 into the space 6a surrounded by the recessed molten portion 6 formed in the base material 4 by the arc 7. , FIG. 9, etc.), or a second mode (see FIG. 8) in which the base material 4 is welded without forming the concave molten portion 6 or without allowing the tip portion 5a of the welding wire 5 to enter the molten portion 6. This circuit selects and outputs a mode setting signal indicating the selected mode to the voltage control circuit 11b and the current setting circuit 11d.
The mode setting circuit 11c may be configured to manually select the mode, or may be configured to automatically determine and select the mode based on the set current, voltage, and feeding speed. good.

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 . When the mode setting circuit 11c selects the first mode, that is, when buried arc welding is selected, the current setting circuit 11d sets a current value of 300 A or more, preferably a current value of 300 A or more and 1000 A or less, More preferably, a current setting signal Ir indicating a set current value of 500 A or more and 800 A or less is output to the voltage control circuit 11b and the feeding speed control circuit 12. FIG. When the mode setting circuit 11c selects the second mode, that is, when open arc welding is selected, the current setting circuit 11d outputs a current setting signal Ir indicating a set current value of 300 A, for example, to the voltage control circuit 11b. and output to the feeding speed control circuit 12 .
The current setting circuit 11d is a circuit that outputs an output voltage setting signal Er indicating the set voltage of the welding power source 1 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 the voltage control circuit 11b. and output to the feeding speed control circuit 12 .

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.
The voltage control circuit 11b receives the voltage value signal Vd output from the voltage detection unit 11e, the current value signal Id output from the current detection unit 11f, the current setting signal Ir output from the current setting circuit 11d, and the output voltage A difference signal Ei is calculated based on the setting signal Er, and the calculated difference signal Ei is output 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 predetermined welding voltage V is applied between the base material 4 and the welding wire 5, and a 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). The supply of current I is started. 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.

<Control of feeding speed and set voltage>
FIG. 2 is a flow chart showing the procedure of the arc welding method according to this embodiment, and FIG. 3 is a side sectional view showing the base material 4 to be welded. First, a pair of base materials 4 to be joined by welding are placed in an arc welding apparatus, and various settings such as a welding mode are performed (step S11). Specifically, as shown in FIG. 3, plate-shaped first base material 41 and second base material 42 are prepared, and end faces 41a and 42a, which are portions 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 conditions for starting output of the welding current I are satisfied (step S12). Specifically, welding power source 1 determines whether or not a welding output instruction signal is input. When it is determined that the output start condition of the welding current I is not satisfied because the output instruction signal has not been input (step S12: NO), the welding power source 1 waits for the input of the output instruction signal.

If it is determined that the output start condition of the welding current I is satisfied (step S12: YES), the feed speed control circuit 12 of the welding power source 1 sends a feed instruction signal for instructing wire feeding to the wire feed 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).

When the first mode is set, the power supply unit 11 supplies a large current of 300 A or more to the welding wire 5 to realize a buried arc. When the second mode is set, the power supply unit 11 supplies a welding current I of less than 300A to the welding wire 5 to achieve an open arc.

FIG. 4 is a schematic diagram showing a buried arc state. When a large 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, the heat of the arc 7 generated between the tip 5a of the welding wire 5 and the welded part A recessed molten portion 6 composed of the molten base material 4 and the molten metal of the welding wire 5 is formed in the base material 4, and the tip portion 5a of the welding wire 5 enters the buried space 6a. When the tip 5a of the welding wire 5 penetrates deeply into the buried space 6a, the arc 7 irradiates the bottom 61 of the recessed molten portion 6, resulting in deep penetration.

Next, the voltage control circuit 11b determines whether or not the protrusion length has changed (step S16). The voltage control circuit 11b detects variations in the protrusion length, for example, based on the welding current I detected by the current detection section 11f. The length of projection here refers to the distance from the contact tip to the surface of the base material 4, and is the length of the welding wire 5 that exists as an individual during welding (the length of the arc generated from the tip of the contact tip). It does not refer to the length to a point).

If it is determined that the protrusion length has changed (step S16: YES), the feed speed control circuit 12 changes the feed speed of the welding wire 5 according to the amount of change in the protrusion length (step S17). Specifically, when the welding current I detected by the current detector 11f becomes smaller than the current value set by the current setting circuit 11d, the feed speed control circuit 12 detects the detected welding current I. and the set current value, the feeding speed of the welding wire 5 is increased. When the welding current I detected by the current detector 11f becomes larger than the current value set by the current setting circuit 11d, the feed speed control circuit 12 controls the detected welding current I and the set welding current I. The feeding speed of the welding wire 5 is decreased according to the difference from the current value.

FIG. 5 is an explanatory diagram showing a method of maintaining the welding current I by varying the feeding speed of the welding wire 5 when the protrusion length of the welding wire 5 fluctuates, and FIG. 6 shows the feeding of the welding wire 5. FIG. 5 is a schematic diagram showing changes in arc length when the speed is varied and the welding current I is maintained. In FIG. 5, the horizontal axis indicates current (A) and the vertical axis indicates voltage (v).
First, consider the case of general external characteristic control, open arc welding. As the projection length increases, the resistance value of the welding wire 5 increases, the welding current I decreases, and the welding voltage increases (from state A to state B in FIG. 1). In general, since there is a correlation between the arc length and the welding voltage, an increase in the welding voltage means an increase in the arc length at the same wire feed speed. As the feeding speed of the welding wire 5 is increased from this state, the welding current I rises and finally matches the set current (from state B to state C in FIG. 1). However, in this case, although the feeding speed of the welding wire 5 is higher in state C than in state A, the welding current I and the welding voltage are the same, and the output is required to obtain the same arc length. becomes insufficient. Therefore, in state C, the arc length becomes shorter than in state A.

Therefore, when the welding current I is increased from the state B, the power supply unit 11 performs control to simultaneously increase not only the feeding speed of the welding wire 5 but also the set voltage.

FIG. 7 is an explanatory diagram showing a method for maintaining the arc length by varying the feeding speed of the welding wire 5 and the set voltage, and FIG. It is a schematic diagram which shows that an arc length is maintained by making it fluctuate. In FIG. 7, the horizontal axis indicates current (A) and the vertical axis indicates voltage (v).
The power supply unit 11 raises the set voltage from the voltage VA to the voltage VC' when the projection length of the welding wire 5 is increased and the feeding speed of the welding wire 5 is increased. By increasing the set voltage, the arc length can be kept constant as shown in state C' in FIG. Comparing state C shown in FIG. 6 with state C' shown in FIG. 8, state C' shown in FIG. 8 has a higher set voltage and a lower welding wire 5 feed speed. Therefore, between state C in FIG. 6 and state C' in FIG. 8, the latter has a longer arc length.
At this time, the larger the amount of change in the set voltage with respect to the amount of change in the feeding speed, the longer the arc length. A and state C') can have the same arc length.

The method for maintaining the welding current I and the arc length in the second mode, that is, open arc welding, has been described above. can be done.
However, in buried arc welding, even if the wire tip position fluctuates, the arc length is less likely to fluctuate.

FIG. 9 is a schematic diagram showing fluctuations in arc length when the wire tip position fluctuates in buried arc welding. As shown in FIG. 9, in a buried arc that pushes down the molten metal surface by arc force, when the wire tip position changes, the position of the molten metal surface also changes in the same direction (broken line in FIG. 9). Therefore, in the buried arc, even if the wire tip position changes, the arc length does not easily change, that is, the amount of voltage change becomes small. In other words, compared to an open arc, the amount of change in set voltage required to change the wire tip position is smaller. Therefore, if the correction amount parameter of the set voltage with respect to the amount of change in the feeding speed of the welding wire 5 adjusted using the open arc is applied as it is to the buried arc, the voltage change becomes excessive, and the wire tip position is kept at a fixed position. cannot hold. For example, when the protrusion is extended, both the feeding speed and the set voltage are tried to be increased, but the effect of the set voltage becomes excessive and the wire tip position is pulled up. If the protrusion length becomes shorter, the wire tip position becomes deeper.

Based on the characteristics of the buried arc described above, the power supply section 11 controls the fluctuation of the set voltage as follows.

First, the voltage control circuit 11b selects a correction amount for the set voltage of the welding wire 5 according to the welding mode and wire diameter (step S18). The correction amount is a parameter that indicates the ratio of the amount of change in the output voltage to the amount of change in the feeding speed of the welding wire 5 . The correction amount in the first mode is smaller than the correction amount in the second mode.

FIG. 10 is a graph showing the correction amount of the set voltage. The horizontal axis indicates the set current (A), and the vertical axis indicates the amount of correction of the set voltage (V·(m/min)). As a specific correction amount, the appropriate range for buried arc welding with wire diameters of φ1.2, φ1.4, and φ1.6 (solid wire), the shield gas being CO2, and the appropriate range for normal open arc welding. 10A, 10B, and 10C together with . That is, in Embodiment 1, a value suitable for buried arcs lower than open arcs is used as the correction amount parameter indicating the amount of change in the set voltage with respect to the amount of change in the feeding speed of the welding wire 5 . That is, the amount of change in the set voltage with respect to the amount of change in the feeding speed according to the protruding length of the welding wire 5 is set so that the concave molten portion 6 is maintained. By setting the correction amount parameter in this way, it becomes possible to keep the set current and the wire tip position constant even in the buried arc.
Note that, as shown in FIGS. 10A, 10B, and 10C, the difference between the correction amount in the first mode and the correction amount in the second mode is set to increase as the wire diameter increases. .

Returning to FIG. 2, the voltage control circuit 11b having selected the correction amount in step S18 changes the set voltage according to the amount of change in the protrusion length and the correction amount selected in step S18 (step S19). Specifically, the voltage control circuit 11b controls the set voltage so that the set voltage increases when the feeding speed of the welding wire 5 increases according to the amount of variation in the protrusion length. The voltage control circuit 11b controls the set voltage so that the set voltage becomes smaller when the feeding speed of the welding wire 5 decreases according to the amount of variation in the protrusion length.

Next, the power supply unit 11 of the welding power source 1 determines whether or not to stop outputting the welding current I (step S20). Specifically, welding power source 1 determines whether or not the input of the output instruction signal continues. If the input of the output instruction signal continues and it is determined not to stop the output of the welding current I (step S20: NO), the power supply unit 11 returns the process to step S13 and continues the output of the welding current I.

When determining to stop outputting the welding current I (step S20: YES), the power supply unit 11 returns the process to step S12.

(Example)
An example of the arc welding method according to the first embodiment will be described.
Wire diameter φ1.4, solid wire, shielding gas CO2, wire feed speed 15.9 m/min, set current 500 A, set voltage 42.5 V, when performing buried arc welding, the amount of change in wire feed speed is set to 0.7 V (m/min). When the arc welding method according to Embodiment 1 is performed under such conditions, even if the projecting length of the welding wire 5 is changed to 25 mm ± 10 mm, the wire tip position is kept constant while maintaining the set current. It was possible to perform buried arc welding effectively.

As described above, in the arc welding apparatus and the arc welding method according to the first embodiment, even when the protrusion length of the welding wire 5 fluctuates in buried arc welding, the position of the wire tip with respect to the molten portion 6 can be kept constant to achieve a stable buried arc condition.
In both buried arc welding and open arc welding, the welding current I and the arc length can be kept constant when the protrusion length varies. In other words, the arc can be stably maintained even if the welding wire 5 protrudes in length.

Also, the arc 7 can be stably maintained regardless of the wire diameter.

(Embodiment 2)
The arc welding apparatus and the arc welding method according to the second embodiment differ from the first embodiment in that the welding current I is periodically varied and the set voltage control method. Since other configurations and effects are the same as those of the first embodiment, corresponding portions are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 11 is a graph showing changes in the set voltage and the welding current I. FIG. The horizontal axis of each graph shown in FIG. 11 represents time, and the vertical axis of each graph shown in FIGS. current I.

In the arc welding method according to the present embodiment, the power supply unit 11 having constant voltage characteristics periodically varies the set voltage as shown in FIG. 11A. When performing the arc welding method according to the second embodiment, the set voltage may be periodically varied at a frequency of 10 Hz or more and 1000 Hz or less, preferably 50 Hz or more and 300 Hz or less, more preferably 80 Hz or more and 200 Hz or less. . The amplitude of the welding current I is 50A or more, preferably 100A or more and 500A or less, more preferably 200A or more and 400A or less. The average value of the welding current I is preferably 300A or more and 1000A or less, more preferably 500A or more and 800A or less.
By periodically varying the set voltage in this way, the welding voltage V and the welding current I are periodically varied as shown in FIGS. 4B and 4C.

FIG. 12 is a schematic diagram showing the arc welding method according to the second embodiment. When a welding current I having an average current of 300 A or more is supplied in the first mode, the base material 4 and the molten metal of the welding wire 5 are melted by the heat of the arc 7 generated between the tip 5a of the welding wire 5 and the welded portion. is formed in the base material 4, and the tip 5a of the welding wire 5 enters the buried space 6a. When the state of the arc 7 was photographed with a high-speed camera, when the welding current I was periodically varied, the welding wire 5 penetrated deeply into the buried space 6a, and the tip of the welding wire 5 was removed, as shown in the left diagram of FIG. A first state in which an arc 7 is generated between the portion 5a and the bottom portion 61 of the melted portion 6, and a welding wire 5 shallowly enters the buried space 6a and an arc 7 is generated between the tip portion 5a and a side portion 62 of the melted portion 6. It was confirmed that the second state periodically fluctuated.

In this way, the tip 5a of the welding wire 5 enters the buried space 6a and is surrounded by the recessed molten portion 6, and by periodically varying the welding current I, the tip 5a in the buried space 6a The position of 5a can be moved up and down.
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 irradiated to the side portion 62 of the molten portion 6, so that the buried space 6a is maintained in a stable state.
Therefore, by periodically varying the welding current I, the buried space 6a can be stably maintained.

FIG. 13 is a graph showing the control method of the set voltage according to the second embodiment. When the set voltage fluctuates periodically as described above, the voltage control circuit 11b, when the protrusion length of the welding wire 5 fluctuates, for example, as shown in FIG. Vary the side value.

In addition, as shown in FIG. 13B, the voltage control circuit 11b may change the value of the changing set voltage on the high voltage side when the protrusion length of the welding wire 5 changes.

Furthermore, as shown in FIG. 13C, the voltage control circuit 11b may vary the average value of the varying set voltage when the protrusion length of the welding wire 5 varies.

In the arc welding apparatus and the arc welding method according to the second embodiment, the welding current I is periodically varied, and the first state in which the wire tip deeply enters the buried space 6a and the second state in which the wire tip is pulled up. and are periodically repeated, deep penetration can be obtained while maintaining the buried space 6a in a stable state.

Further, as shown in FIG. 13A, by varying the low voltage side value of the varying set voltage, the buried arc can be stabilized compared to the case of varying the high voltage side value.

Furthermore, as shown in FIG. 13B, by varying the value on the high voltage side of the varying set voltage, it is possible to form a buried arc that is more resistant to magnetic blow than when the value on the low voltage side is varied. If the value on the low voltage side is changed, the magnetic blow may become stronger or weaker, resulting in unstable behavior. By varying the value of the set voltage on the high voltage side, the behavior against the magnetic blow is stabilized, and the weakness to the magnetic blow is eliminated.

Furthermore, as shown in FIG. 13C, by varying the average value of the varying set voltage, it is possible to form a buried arc that is somewhat resistant to magnetic blow and has high stability.

In the first and second embodiments, when the set voltage is constant, an example in which it is periodically varied has been described, but other constant voltage characteristic control or buried arc stabilization control based on a similar arc control method The present invention can also be applied to

1 welding power source, 2 torches, 3 wire feeding section, 4 base material, 5 welding wire, 6 melting portion, 6a buried space, 11 power source section, 12 feeding speed control circuit, 11a power source circuit, 11b voltage control circuit, 11c Mode setting circuit, 11d current setting circuit

Claims (9)

A consumable electrode type arc welding device comprising a power supply unit that supplies a welding current to a welding wire that is fed to a base material,
A first mode in which the base material is welded by causing the tip of the welding wire to enter a space surrounded by a recessed molten portion formed in the base material by an arc, or a first mode in which the recessed molten portion is not formed or the a mode setting circuit that selects a second mode in which the base material is welded without allowing the tip of the welding wire to enter the molten portion;
When the welding wire protruding length increases, the welding wire feeding speed increases, and when the welding wire protruding length decreases, the welding wire feeding speed decreases. a feeding speed control circuit for controlling the feeding speed of the welding wire;
The power supply is configured such that the output voltage of the power supply unit increases when the welding wire protruding length increases, and the output voltage of the power supply unit decreases when the welding wire protruding length decreases. and a voltage control circuit that controls the output voltage of the
The arc welding apparatus, wherein the amount of change in the output voltage with respect to the amount of change in the feed speed according to the protrusion length of the welding wire is smaller when the first mode is set than when the second mode is set. The difference between the amount of change in the output voltage with respect to the amount of change in the feeding speed when the first mode is set and the amount of change in the output voltage with respect to the amount of change in the feeding speed when the second mode is set is The arc welding device according to claim 1, wherein the welding wire has a larger diameter. A power supply unit that supplies a welding current to the welding wire fed to the base metal is provided, and the leading end of the welding wire is caused to enter a space surrounded by a recessed molten portion formed in the base metal by an arc to cause the base metal to melt. A consumable electrode type arc welding device for welding materials,
When the welding wire protruding length increases, the welding wire feeding speed increases, and when the welding wire protruding length decreases, the welding wire feeding speed decreases. a feeding speed control circuit for controlling the feeding speed of the welding wire;
The power supply is configured such that the output voltage of the power supply unit increases when the welding wire protruding length increases, and the output voltage of the power supply unit decreases when the welding wire protruding length decreases. and a voltage control circuit that controls the output voltage of the
Arc welding equipment, wherein the amount of change in the output voltage with respect to the amount of change in the feed speed according to the protruding length of the welding wire is set such that the molten portion is maintained. The power supply unit has constant voltage characteristics,
The voltage control circuit is
By periodically varying the set voltage of the power supply unit, the welding current is varied so that the tip of the welding wire enters a first state deeply into the space and a second state enters the space shallowly. The arc welding apparatus according to any one of claims 1 to 3, wherein the and are periodically varied. The voltage control circuit is
The arc welding device according to claim 4, wherein when the welding wire protrusion length fluctuates, a value on the low voltage side of the fluctuating set voltage is fluctuated. The voltage control circuit is
The arc welding apparatus according to claim 4, wherein when the welding wire protrusion length varies, a value on the higher voltage side of the varying set voltage is varied. The voltage control circuit is
The arc welding device according to claim 4, wherein when the welding wire protrusion length varies, an average value of the varying set voltage is varied. A consumable electrode type arc welding method for supplying a welding current to a welding wire fed to a base material,
A first mode in which the base material is welded by causing the tip of the welding wire to enter a space surrounded by a recessed molten portion formed in the base material by an arc, or a first mode in which the recessed molten portion is not formed or the selecting a second mode for welding the base material without allowing the tip of the welding wire to enter the molten portion;
When the welding wire protruding length increases, the welding wire feeding speed increases, and when the welding wire protruding length decreases, the welding wire feeding speed decreases. controlling the feeding speed of the welding wire;
controlling the output voltage so that the output voltage increases when the welding wire protrusion length increases, and the output voltage decreases when the welding wire protrusion length decreases;
The arc welding method, wherein the amount of change in the output voltage with respect to the amount of change in the feed speed according to the protrusion length of the welding wire is smaller when the first mode is set than when the second mode is set. A welding current is supplied to a welding wire fed to a base material, and the base material is welded by causing the tip of the welding wire to enter a space surrounded by a concave molten portion formed in the base material by an arc. A consumable electrode type arc welding method,
When the welding wire protruding length increases, the welding wire feeding speed increases, and when the welding wire protruding length decreases, the welding wire feeding speed decreases. controlling the feeding speed of the welding wire;
controlling the output voltage so that the output voltage increases when the welding wire protrusion length increases, and the output voltage decreases when the welding wire protrusion length decreases;
The arc welding method, wherein the amount of change in the output voltage with respect to the amount of change in the feed speed according to the protruding length of the welding wire is set such that the molten portion is maintained.

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