JP2022029074A - Two-wire welding method - Google Patents

Abstract

To provide a two-wire welding method using a buried arc which stably maintains a molten state of a filler wire and can obtain good welding quality.SOLUTION: A two-wire welding method for applying a welding voltage Vw between a consumable electrode and a base material, generating an arc, forming a molten pool, and welding a filler wire while inserting the filler wire to a rear half part of the molten pool includes: converting the arc into a buried arc state; oscillating a welding voltage Vw at a high voltage value HVr and a low voltage value LVr; and oscillating feeding speed Fw of the filler wire at high feeding speed HFr and low feeding speed LFr in synchronization with oscillation of the welding voltage Vw. When the welding voltage Vw oscillates, a temperature of the molten pool changes, and accordingly the molten state of the filler wire can be stabilized by changing the feeding speed Fw of the filler wire.SELECTED DRAWING: Figure 3

Description

The present invention relates to a two-wire welding method in which a welding voltage is applied between a consumable electrode and a base metal to generate an arc to form a molten pool, and a filler wire is inserted into the latter half of the molten pool for welding. be.

A two-wire welding method (hereinafter referred to as welding wire) in which a welding voltage is applied between a consumable electrode (hereinafter referred to as a welding wire) to generate an arc to form a molten pool, and a filler wire is inserted into the molten pool to weld. (See Patent Document 1) has been conventionally known. In this two-wire welding method, since the molten metal of the filler wire is added to the molten metal of the welding wire, the amount of molten metal increases, and high welding and high speed welding become possible. In particular, when high-speed welding is performed by the two-wire welding method, it is important to contact the filler wire with the molten pool from behind the consumable electrode arc and feed the filler wire in order to prevent the humping bead. This is because when the filler wire is fed into the consumable electrode arc and melted, the molten pool is hardly cooled, and the filler wire cannot suppress the swelling of the latter half of the molten pool, thus suppressing the humping bead. This is because it has no effect. On the other hand, if the filler wire is brought into contact with the latter half of the molten pool of the arc generation part and fed to be melted by the heat of the molten pool, the molten pool is cooled and the latter half of the molten pool is cooled by the filler wire. The portion is suppressed and the formation of the humping bead can be suppressed. Therefore, in the two-wire welding method of the prior art, the filler wire is cooled by contacting the filler wire with the molten pool in a cold state without applying an electric current.

Japanese Unexamined Patent Publication No. 2010-167489

In the two-wire welding method, when the arc generated between the welding wire and the base metal is buried and put into an arc state, deep welding can be obtained and further high welding can be achieved. The buried arc state tends to become unstable due to a slight disturbance. By vibrating the welding voltage to a high voltage value and a low voltage value, it is possible to suppress the buried arc state from becoming unstable. However, when the welding voltage value changes, the amount of heat input to the base metal changes, so the temperature of the molten pool also changes. Since the filler wire is melted by the heat from the molten pool, there is a problem that the molten state of the filler wire becomes unstable when the temperature of the molten pool fluctuates.

Therefore, it is an object of the present invention to provide a two-wire welding method using a buried arc, which can stably maintain the molten state of the filler wire even when the welding voltage is vibrated.

In order to solve the above-mentioned problems, the invention of claim 1 is
In a two-wire welding method in which a welding voltage is applied between a consumable electrode and a base metal to generate an arc to form a molten pool, and a filler wire is inserted into the latter half of the molten pool for welding.
The arc is buried and put into an arc state.
The welding voltage is vibrated to a high voltage value and a low voltage value, and the feeding speed of the filler wire is vibrated to a high feeding speed and a low feeding speed in synchronization with the vibration of the welding voltage.
This is a two-wire welding method characterized by the above.

The invention of claim 2 is
As the amplitude of the welding voltage increases, the amplitude of the feeding speed of the filler wire increases.
The two-wire welding method according to claim 1, wherein the two-wire welding method is characterized in that.

The invention of claim 3 is
The amplitude is changed so that the average value of the feeding speeds of the filler wires is constant.
The two-wire welding method according to claim 2, wherein the two-wire welding method is characterized in that.

According to the present invention, in the two-wire welding method using a buried arc, the molten state of the filler wire can be stably maintained even if the welding voltage is vibrated.

It is a schematic diagram of the welded part which shows the 2 wire welding method which concerns on embodiment of this invention. It is a block diagram of the welding apparatus for carrying out the two-wire welding method which concerns on embodiment of this invention. It is a timing chart of each signal in the welding apparatus of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of a welded portion showing a two-wire welding method according to an embodiment of the present invention. The figure is a side view of the welded portion, and the welding is proceeding to the left as shown by the arrow. Hereinafter, description will be made with reference to the figure.

The welding wire 1 is supplied from the welding torch 4, and an arc 3 is generated between the tip of the welding wire and the base metal 2. The welding wire 1 is fed at a constant speed. Here, the advance angle of the welding torch 4 is 0 °, and the welding wire 1 is fed vertically to the base metal 2. A molten pool 2a is formed in the base metal 2 by this arc 3. The center line indicating the feeding direction of the welding wire 1 is indicated by a alternate long and short dash line, and the point where this center line intersects the surface of the base metal 2 is the welding target position a.

The arc 3 is in a buried arc state. The buried arc state is a state in which the tip of the welding wire 1 has entered the inside of the molten region which is a recess due to the arc force. Therefore, the arc 3 is also generated inside the recess. In order to maintain a stable buried arc state, the welding current Iw set by the welding wire feed rate setting signal Wr in FIG. 2 is a large current value of at least 300 A or more, and the welding voltage setting signal Vr in FIG. 2 is used. It is necessary to set the set welding voltage Vw to an appropriate value that causes a buried arc state. When welding is performed in a buried arc state, it is possible to form a deeply melted melted portion with less spatter generation.

A high setting value and a low setting value are provided for the welding voltage setting signal Vr in FIG. 2, and the welding voltage Vw is vibrated to a high voltage value and a low voltage value by switching between both values. In this way, the arc length vibrates and the buried arc state is stabilized. The vibration frequency is in the range of 10 to 1000 Hz. The voltage amplitude is set so that the amplitude of the welding current is 50 A or more.

The filler wire 6 is fed in the filler wire guide 7 and is inserted into the insertion position b in the latter half of the molten pool 2a in a contact state. The feed rate of the filler wire 6 vibrates to a high feed rate and a low feed rate in synchronization with the vibration of the welding voltage. The average feeding speed of the filler wire 6 is about 10 to 20% of the feeding speed of the welding wire 1.

The distance between the welding target position a and the insertion position b is the wire-to-wire distance Lw (mm). The insertion position b of the filler wire 6 is a peripheral edge portion outside the recess of the molten pool 2a. When the distance Lw between the wires is smaller than the appropriate value, a short circuit occurs between the welding wire 1 and the molten pool 2a, and the arc state becomes unstable. Therefore, the distance Lw between the wires is adjusted to be equal to or larger than the value at which the short circuit does not occur. On the other hand, the distance Lw between the wires is adjusted to be less than a value at which the filler wire 6 can be melted by the heat from the molten pool 2a.

During welding, the shape of the molten pool 2a fluctuates, so that the insertion position b of the filler wire 6 deviates from the proper position, and the buried arc state may become unstable. When it is determined that the buried arc state has become unstable, the insertion position b of the filler wire 6 is automatically moved backward. The buried arc state becomes unstable when the insertion position b of the filler wire 6 enters the recess of the molten pool 2a. Therefore, the unstable state can be eliminated by moving the insertion position b backward.

The instability of the buried arc state can be determined by the occurrence of a short circuit between the welding wire 1 and the molten pool 2a. Further, the instability of the buried arc state can be determined by the fact that the short circuit between the welding wire 1 and the molten pool 2a occurs more than the reference number of times per unit time.

FIG. 2 is a block diagram of a welding device for carrying out the two-wire welding method according to the embodiment of the present invention described above in FIG. The figure shows the case where the consumable electrode type arc welding is DC carbon dioxide arc welding, mag welding or MIG welding. Hereinafter, each block will be described with reference to the figure.

The power main circuit PM receives a commercial power source such as 3-phase 200V (not shown) as an input, and controls the output by inverter control according to the drive signal Dv described later, and weld voltage Vw and welding current Iw for generating arc 3. Is output. Although not shown, the power supply main circuit PM is a primary rectifier circuit that rectifies a commercial power supply, a capacitor that smoothes the rectified direct current, and an inverter circuit that converts the smoothed direct current into high-frequency alternating current according to the above drive signal Dv. It is equipped with a high-frequency transformer that steps down the high-frequency alternating current to an appropriate voltage value to generate an arc 3, a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current.

The welding wire 1 is fed in the welding torch 4 by the rotation of the welding wire feeding roll 5 coupled to the welding wire feeding motor WM, and is fed from the power supply main circuit PM described above via a feeding chip (not shown). The power is supplied and an arc 3 is generated between the base material 2 and the base metal 2. A welding voltage Vw is applied between the welding wire 1 and the base metal 2, and a welding current Iw is energized.

The filler wire 6 is fed in the filler wire guide 7 by the rotation of the filler wire feeding roll 8 coupled to the filler wire feeding motor FM, and is inserted into the molten pool 2a formed by the arc 3. The filler wire 6 is inserted into the insertion position b described above in FIG. 1 in a state of being in contact with the molten pool 2a.

The moving mechanism 9 is a motor for moving the insertion position b of the filler wire 6 backward by a predetermined distance each time the buried arc state determination signal Ad reaches the high level for a short time by inputting the buried arc state determination signal Ad described later. It is a mechanism including. Therefore, each time the buried arc state determination signal Ad reaches the High level for a short time, the distance Lw between the wires increases by a predetermined distance. As the above mechanism, a mechanism for converting the rotary motion of the motor into a linear motion by a slide crank mechanism, a mechanism for converting the rotary motion of the motor into a swing motion by a crank and a swing wheel, and the like have been conventionally used. .. The above predetermined distance is, for example, 1 mm.

The welding voltage detection circuit VD detects the above welding voltage Vw and outputs a welding voltage detection signal Vd.

The welding voltage setting circuit VR has a predetermined high voltage setting value HVr during a predetermined high voltage period HT, and a predetermined low voltage setting value LVr during a predetermined low voltage period LT. Is output. The welding wire feeding speed setting circuit WR outputs a predetermined welding wire feeding speed setting signal Wr. The feeding speed of the welding wire 1 is set by the welding wire feeding speed setting signal Wr, and the value of the welding current Iw is determined. The values of the welding voltage setting signal Vr and the welding wire feeding speed setting signal Wr are set so as to be in a stable buried arc state as described above in FIG.

The voltage error amplification circuit EV amplifies the error between the above-mentioned welding voltage setting signal Vr and the above-mentioned welding voltage detection signal Vd, and outputs a voltage error amplification signal Ev.

The drive circuit DV receives the voltage error amplification signal Ev as an input, performs PWM modulation control based on this signal, and based on the result, drives the drive signal Dv for driving the inverter circuit in the power supply main circuit PM. Is output. With this circuit, the welding device becomes a power source with constant voltage characteristics.

The welding wire feeding control circuit WC sends a welding wire feeding control signal Wc for feeding the welding wire 1 at a feeding speed corresponding to the value of the welding wire feeding speed setting signal Wr. Output to the feed motor WM.

The filler wire feeding speed setting circuit FR receives the above voltage setting signal Vr as an input, and when the voltage setting signal Vr is the high voltage setting value HVr, it becomes the predetermined high feeding speed setting value HFr, and the voltage setting signal Vr becomes. When the low voltage set value LVr is set, the filler wire feed rate setting signal Fr that becomes the predetermined low feed rate set value LFr is output. The larger the amplitude of the high voltage set value HVr and the low voltage set value LVr of the voltage setting signal Vr, the more the amplitude of the high feed rate set value HFr and the low feed rate set value LFr of the filler wire feed rate setting signal Fr. To increase. At this time, the amplitude of the filler wire feeding speed setting signal Fr is changed so that the average value of the filler wire feeding speed setting signal Fr becomes constant.

The filler wire feed control circuit FC provides the filler wire feed control signal Fc for feeding the filler wire 6 at the filler wire feed rate Fw corresponding to the value of the filler wire feed rate setting signal Fr. Output to the filler wire feed motor FM.

The short-circuit discrimination circuit SD receives the above welding voltage detection signal Vd as an input, and when this value is equal to or less than the short-circuit discrimination value (about 10V), it determines that the welding wire 1 and the molten pool 2a are in a short-circuited state and is at a high level. The short-circuit determination signal Sd is output.

The buried arc state determination circuit AD receives the above short-circuit identification signal Sd and the above welding voltage detection signal Vd as inputs, selects one from the following 1) to 3) and performs processing, and the buried arc state determination signal Ad. Is output.
1) Every time the short-circuit discrimination signal Sd reaches the high level, the buried arc state discrimination signal Ad, which becomes the high level for a short time, is output. The state in which a short circuit occurs is a sign that the buried arc state becomes unstable.
2) The number of times the short-circuit discrimination signal Sd changes to the High level is detected for each unit time, and when the number of short-circuits exceeds a predetermined reference number, the buried arc state discrimination signal Ad which becomes the High level for a short time is output. For example, the unit time is 100 ms, and the reference number of times is three times. A state in which the number of short circuits per unit time exceeds the reference number is a sign that the buried arc state becomes unstable.
3) When the fluctuation range of the welding voltage detection signal Vd becomes equal to or larger than the reference value, the buried arc state determination signal Ad, which becomes the High level for a short time, is output. A state in which the fluctuation range of the welding voltage exceeds the reference value is a sign that the buried arc state becomes unstable.

FIG. 3 is a timing chart of each signal in the welding apparatus of FIG. FIG. 3A shows a time change of the voltage setting signal Vr, FIG. 2B shows a time change of the welding voltage Vw, FIG. 3C shows a time change of the welding current Iw, and FIG. ) Indicates the time change of the filler wire feeding speed setting signal Fr, and FIG. 3E shows the time change of the filler wire feeding speed Fw. Hereinafter, the operation of each signal will be described with reference to the figure.

In the figure, the feeding speed of the welding wire (not shown) is a predetermined value set by the welding wire feeding speed setting signal Wr of FIG.

As shown in FIG. 3A, the voltage setting signal Vr becomes a predetermined high voltage set value HVr during the predetermined high voltage period HT at times t1 to t2, and becomes a predetermined low voltage at times t2 to t3. During the period LT, the low voltage set value LVr is set in advance. In response to this, as shown in FIG. 3B, the welding voltage Vw increases from time t1 with a slope to a high voltage value, and decreases from time t2 with a slope to a low voltage value. .. Therefore, the welding voltage Vw oscillates between a high voltage value and a low voltage value. As shown in FIG. 3C, the welding current Iw increases from time t1 with a slope to a high current value, and decreases from time t2 with a slope to a low current value. Since the welding voltage Vw oscillates, the welding current Iw oscillates to a high current value and a low current value.

As shown in FIG. 3D, the filler wire feed rate setting signal Fr becomes a predetermined high feed rate set value HFr during the high voltage period HT at time t1 to t2, and is set in advance at time t2 to t3. During the low voltage period LT, the predetermined low filler wire feed rate set value LFr is obtained. In response to this, as shown in the figure (E), the filler wire feed rate Fw accelerates to a high feed rate with an inclination from time t1 and has an inclination from time t2 to provide a low feed rate. Decelerate to feed rate. Therefore, the filler wire feeding speed Fw vibrates to a high feeding speed and a low feeding speed in synchronization with the vibration of the welding voltage Vw.

According to the above-described embodiment, the welding voltage is vibrated to a high voltage value and a low voltage value, and the feeding speed of the filler wire is set to a high feeding speed and a low feeding speed in synchronization with the vibration of the welding voltage. Vibrate. By vibrating the welding voltage to a high voltage value and a low voltage value, the arc length vibrates and the buried arc state is stabilized. The vibration frequency is in the range of 10 to 1000 Hz. The amplitude of the welding voltage is preferably set so that the amplitude of the welding current is 50 A or more. When the welding voltage vibrates, the amount of heat input to the molten pool changes and the temperature of the molten pool changes. When the temperature of the molten pool changes, the molten state of the filler wire changes. Therefore, the molten state of the filler wire can be stabilized by changing the feeding speed of the filler wire in synchronization with the vibration of the welding voltage. As a result, good welding quality can be obtained.

Further, according to the present embodiment, it is preferable to increase the amplitude of the feeding speed of the filler wire as the amplitude of the welding voltage increases. As the amplitude of the welding voltage increases, the temperature change of the molten pool also increases. Therefore, as the amplitude of the welding voltage increases, the amplitude of the feeding speed of the filler wire also increases, so that the molten state of the filler wire can be further stabilized.

Further, according to the present embodiment, it is preferable to change the amplitude so that the average value of the feeding speeds of the filler wires is constant. When the amplitude of the feeding speed of the filler wire is changed according to the amplitude of the welding voltage, the amplitude is changed so that the average value of the feeding speed of the filler wire becomes constant. By doing so, the welding amount of the filler wire becomes constant, so that a good weld bead can be formed.

1 Welding wire (consumable electrode)
2 Base material 2a Molten pond 3 Arc 4 Welding torch 5 Welding wire feeding roll 6 Filler wire 7 Filler wire guide 8 Filler wire feeding roll 9 Moving mechanism a Welding aim position AD Buried arc state discriminating circuit Ad Buried arc state discriminating signal b Filler wire insertion position DV Drive circuit Dv Drive signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Filler wire feed control circuit Fc Filler wire feed control signal FM Filler wire feed motor FR Filler wire feed speed setting circuit Fr Filler wire feeding speed setting signal Fw Filler wire feeding speed HFr High feeding speed setting value HVr High voltage setting value Iw Welding current LFr Low feeding speed setting value LVr Low voltage setting value Lw Inter-wire distance PM Power supply main circuit SD Short-circuit discrimination circuit Sd Short-circuit discrimination signal VD Welding voltage detection circuit Vd Welding voltage detection signal VR Welding voltage setting circuit V Welding voltage setting signal Vw Welding voltage WC Welding wire feed control circuit Wc Welding wire feed control signal WM Welding wire feed motor WR Welding wire feeding speed setting circuit WR Welding wire feeding speed setting signal

Claims (3)

In a two-wire welding method in which a welding voltage is applied between a consumable electrode and a base metal to generate an arc to form a molten pool, and a filler wire is inserted into the latter half of the molten pool for welding.
The arc is buried and put into an arc state.
The welding voltage is vibrated to a high voltage value and a low voltage value, and the feeding speed of the filler wire is vibrated to a high feeding speed and a low feeding speed in synchronization with the vibration of the welding voltage.
A two-wire welding method characterized by this. As the amplitude of the welding voltage increases, the amplitude of the feeding speed of the filler wire increases.
The two-wire welding method according to claim 1. The amplitude is changed so that the average value of the feeding speeds of the filler wires is constant.
2. The two-wire welding method according to claim 2.

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