JP2008229704A - Arc start control method for two-electrode arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arc start control method for two-electrode arc welding, a method that makes quick transfer possible to a regular welding condition and that also makes formation of superior weld bead possible. <P>SOLUTION: The method includes: a step in which a wire W is made to approach a welding base material P at a slowed-down feeding speed Fw1, with a GMA arc welding voltage Vwa applied; a step in which the length of a GMA arc 6a is gradually made longer, after the wire W is brought into contact with the welding base material P, while the wire W is fed at a feeding speed Fw2 of an arc growing period, by gradually increasing the GMA arc welding voltage Vwa following the generation of the GMA arc 6a; and a step in which, after a plasma arc 6b is generated by a non-consumable electrode arc welding voltage Vwb, the feeding speed Fw is made a regular feeding speed Fw3 and in which regular welding is started by making the GMA arc welding voltage Vwa to be a voltage in the regular welding condition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a welding torch having a consumable electrode and a non-consumable electrode disposed in a shield gas nozzle to generate a consumable electrode arc and a non-consumable electrode arc, and quickly shifts to a steady welding state in two-electrode arc welding. In addition, the present invention relates to an arc start control method of two-electrode arc welding for forming a good weld bead.

  FIG. 3 shows a welding apparatus used for conventional two-electrode arc welding. A welding apparatus X shown in the figure includes a welding torch Y, a GMA arc welding power source PSM, and a plasma arc welding power source PSP. The welding torch Y has a structure in which a plasma nozzle 93, a plasma electrode 92, and a contact tip 91 are arranged on a concentric axis in a shield nozzle 94. A wire W as a consumable electrode is fed from a through hole provided in the contact chip 91. The contact chip 91 and the wire W are electrically connected to each other. The wire W is fed by a feed roller 95 using the motor M as a drive source. The welding torch Y is moved with respect to the welding base material P while being normally held by a robot (not shown).

  The GMA arc welding power source PSM is a power source for causing a GMA arc welding current Iwa to flow by applying a GMA arc welding voltage Vwa between the wire W and the welding base material P. A voltage setting signal Vr is sent from the voltage setting circuit VR to the GMA arc welding power source PSM. Further, a welding start signal St is sent from the welding start circuit ST to the GMA arc welding power source PSM. A feed control signal Fc is sent to the motor M from the GMA arc welding power source PSM. When the GMA arc welding voltage Vwa is applied from the GMA arc welding power source PSM, the wire W is set to the + side.

  The plasma arc welding power source PSP applies the plasma arc welding voltage Vwb between the plasma electrode 92 and the welding base material P, thereby converting the center gas Gc and the plasma gas Gp into plasma and flowing the plasma arc welding current Iwb. Is the power source. A welding start signal St is sent from the welding start circuit ST to the plasma arc welding power source PSP. In the steady welding state, when the plasma arc welding voltage Vwb is applied from the plasma arc welding power source PSP, the plasma electrode 92 is set to the + side.

  FIG. 4 is a timing chart showing an arc start control method of two-electrode arc welding using the welding apparatus Y. When the welding start signal St becomes High level at time tp1, as shown in FIG. 5 (Gp1), feeding of the wire W is started in a state where the feeding speed Fw is set to a very slow slow-down feeding speed. . At the same time, the consumable electrode arc welding voltage Vwa is set to a no-load voltage, and a high frequency discharge high voltage having a frequency of about several MHz and a voltage of about several kV is applied as the plasma arc welding voltage Vwb.

  Next, when the wire W contacts the welding base material P at the slow-down feed speed at time tp2, the GMA arc welding voltage Vwa takes a short-circuit voltage value of about several volts, and the GMA arc welding current Iwa flows. Then, the feeding speed Fw is set to the speed in steady welding.

  At time tp3, the wire W heated by Joule heat generated by energization during the short-circuit period from time tp2 to tp3 bends and melts. Thereby, the GMA arc 96a is generated while generating a large amount of sputtering. When the GMA arc 96a is generated, the GMA arc welding voltage Vwa is controlled at a constant voltage from the short-circuit voltage to the arc voltage indicated by the voltage setting signal Vr. Further, the GMA arc welding current Iwa decreases to a steady welding current value. The GMA arc 96a at this time is in a state where the arc length is shorter than in the steady welding state.

  Further, immediately after the generation of the GMA arc 96a, as shown in the figure (Gp2), the plasma arc 96b is generated and the plasma arc welding current Iwb is energized. At this time, the plasma arc welding voltage Vwb decreases from the no-load voltage to the arc voltage. When the plasma arc 96b is generated, the length of the GMA arc 96a tends to increase rapidly. When an appropriate time elapses from time tp3, the length of the GMA arc 96a falls within a length that balances the feed rate Fw and the plasma arc welding voltage Vwb, as shown in FIG. As a result, the two-electrode arc welding by the welding apparatus X completes the transition to the steady welding state.

  However, the arc start control method of the two-electrode arc welding described above has the following problems.

  First, there is a problem that the time until the transition to the steady welding state becomes long. That is, after the GMA arc 96a is generated, the GMA arc welding voltage Vwa and the feeding speed Fw are set to the same magnitude as in the steady welding state. For this reason, until the GMA arc 96a is in a steady state, the GMA arc welding voltage Vwa and the feeding speed Fw are not properly balanced and become a transient state. In this transient state, the length of the GMA arc 96a tends to become unstable. Until the length of the GMA arc 96a has converged to the length of the steady welding state, a considerable amount of time may be spent after the time tp3.

  Second, it is difficult to make the weld bead good at the welding start location of the weld base material P. That is, at least when a predetermined time has elapsed since time tp3, the welding torch Y is started to move by the robot, and a good weld bead is formed. However, even during the period from the generation of the GMA arc 96a to the transition to the steady welding state, the droplets of the wire W adhere to the welding base material P and welding by the plasma arc 96b is performed. The weld bead formed in this transient state has a problem that the shape is disordered and the penetration depth becomes unstable as compared with the weld bead formed in the steady welding state.

JP 63-168283 A

  The present invention has been conceived under the circumstances described above, and is an arc start control method for two-electrode arc welding capable of quickly transitioning to a steady welding state and forming a good weld bead. The issue is to provide

  An arc start control method for two-electrode arc welding provided by the present invention generates a consumable electrode arc and a non-consumable electrode arc using a welding torch having a consumable electrode and a non-consumable electrode disposed in a shield gas nozzle. An arc start control method for two-electrode arc welding in which welding is performed by the first step, wherein a consumable electrode arc welding voltage is applied between the consumable electrode and the welding base material, and the first stage is slower than a steady speed in a steady welding state A second stage speed that is faster than the first stage speed and slower than the steady speed after contacting the consumable electrode with the welding base material at a speed; While the consumable electrode is fed toward the welding base material, the consumable electrode arc welding voltage is set to a steady welding state after the consumable electrode arc is generated. The step of gradually increasing the length of the consumable electrode arc by gradually increasing the voltage from a voltage lower than the voltage at the non-consumable electrode arc welding voltage applied between the non-consumable electrode and the welding base material After the non-consumable electrode arc is generated by the step of starting steady welding by setting the feed rate of the consumable electrode to the steady speed and the consumable electrode arc welding voltage to a voltage in a steady welding state; It is characterized by having.

  According to such a configuration, the transition to the steady welding state can be performed quickly. The reason is to stably generate and grow the consumable electrode arc and the non-consumable electrode arc. First, after the consumable electrode arc is generated, the consumable electrode arc welding voltage is gradually increased while feeding the consumable electrode at a constant speed. Thereby, the length of the said consumable electrode arc can be lengthened gradually. For this reason, it is possible to prevent an unstable state in which the length of the consumable electrode arc becomes excessively long or short. Next, by growing the consumable electrode arc in a stable state, the consumable electrode arc can be reliably grown to a length suitable for generating the non-consumable electrode arc. Thereby, the said non-consumable electrode arc can be generated reliably. The steady welding state can be reliably reached by setting the consumable electrode feed speed and the consumable electrode arc welding voltage to predetermined values. As described above, since the generation and growth of the consumable electrode arc and the non-consumable electrode arc are performed in a properly controlled state, it is not necessary to spend a considerable time until the unstable state is settled to the steady state. Therefore, the transition to the steady welding state can be performed quickly.

  In a preferred embodiment of the present invention, at least after the consumable electrode arc is generated, the welding torch is moved in the welding direction with respect to the welding base material, and at least after the consumable electrode arc is generated. And controlling at least one of the moving speed of the welding torch and the feeding speed of the consumable electrode so that the ratio of the moving speed of the welding torch and the feeding speed of the consumable electrode becomes a ratio in a steady welding state. To do.

  According to such a configuration, a good weld bead can be formed. That is, when the consumable electrode arc is generated, the welding torch is moving in the welding direction. For this reason, the droplets of the consumable electrode do not unduly concentrate and adhere to one place of the welding base material. In addition, in the entire period from the occurrence of the consumable electrode arc to the steady welding state, the ratio between the moving speed of the welding torch and the feeding speed of the consumable electrode is the same as that in the steady welding state. Controlled. For this reason, the weld bead formed by this welding has an appearance, a cross-sectional shape, and a penetration depth very close to a steady welding state immediately after the start point. Therefore, a good weld bead can be formed.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

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

  FIG. 1 shows an example of a welding apparatus used in an arc start control method for two-electrode arc welding according to the present invention. The welding apparatus A of this embodiment includes a welding torch B, a GMA arc welding power source (consumable electrode arc welding power source) PSM, and a plasma arc welding power source (non-consumable electrode arc welding power source) PSP. The welding torch B has a structure in which a plasma nozzle 3, a plasma electrode (non-consumable electrode) 2, and a contact tip 1 are arranged on a concentric axis in a shield gas nozzle 4. From the gap between the shield gas nozzle 4 and the plasma nozzle 3, for example, a shield gas Gs such as Ar is supplied. A plasma gas Gp such as Ar is supplied between the plasma nozzle 3 and the plasma electrode 2. A center gas Gc such as Ar is supplied between the plasma electrode 2 and the contact chip 1.

  A wire W as a consumable electrode is fed from a through hole provided in the contact chip 1. The contact chip 1 is electrically connected to the wire W. The wire W is fed by a feed roller 5 using the motor M as a drive source. The plasma electrode 2 is made of, for example, Cu or a Cu alloy, and is indirectly water-cooled by cooling water passing through a path outside the figure. The plasma nozzle 3 is made of, for example, Cu or a Cu alloy, and is directly water-cooled by forming a channel through which cooling water passes. The welding torch B is normally moved with respect to the welding base material P while being held by a robot (not shown).

  The GMA arc welding power source PSM is a power source for flowing a GMA arc welding current Iwa by applying a GMA arc welding voltage Vwa between the wire W and the welding base material P via the contact tip 1. A voltage setting signal Vr is sent from the voltage setting circuit VR to the GMA arc welding power source PSM. Further, a welding start signal St is sent from the welding start circuit ST to the GMA arc welding power source PSM. A feed control signal Fc is sent to the motor M from the GMA arc welding power source PSM. When the GMA arc welding voltage Vwa is applied from the GMA arc welding power source PSM, the wire W is set to the + side.

  The plasma arc welding power source PSP is a power source for causing a plasma arc welding current Iwb to flow by applying a plasma arc welding voltage Vwb between the plasma electrode 2 and the welding base material P. A welding start signal St is sent from the welding start circuit ST to the plasma arc welding power source PSP. When the plasma arc welding voltage Vwb is applied from the plasma arc welding power source PSP, the plasma electrode 2 is set to the + side.

  Next, an example of the arc start control method of the two-electrode arc welding according to the present invention will be described below with reference to FIG. The two-electrode arc welding according to the present embodiment is classified into high-efficiency welding with a welding speed in a steady welding state of, for example, about 12.5 to 15 m / min.

  First, when the welding start signal St becomes a high level at time t1, the wire W is fed in a state where the feeding speed Fw is set to the slow-down feeding speed (first stage speed) Fw1 as shown in FIG. To start. This slow-down feed speed Fw1 is much slower than the feed speed Fw in the steady welding state. Further, a GMA arc welding voltage Vwa and a plasma arc welding voltage Vwb are applied. The magnitude of each voltage is a no-load voltage.

  Next, at time t2, the wire W comes into contact with the welding base material P as shown in FIG. Then, a GMA arc welding current Iwa flows between the wire W and the welding base material P. Thereby, Joule heat starts to be generated in the wire W. Further, at time t2, the feeding speed Fw is increased from the slow-down feeding speed Fw1 to the arc growth period feeding speed (second stage speed) Fw2. The arc growth period feeding speed Fw2 is a speed slower than the steady feeding speed Fw3 in the steady welding state. Further, at time t2, the welding torch B is started to move with respect to the welding base material P by a robot (not shown). The arc growth period moving speed Ft2 at this time is such that the ratio of the arc growth period moving speed Ft2 and the arc growth period feeding speed Fw2 is the steady moving speed Ft3, where the moving speed Ft in the steady welding state is the steady moving speed Ft3. It is controlled to be equal to the ratio with the steady feeding speed Fw3.

  Immediately after the wire W comes into contact with the welding base material P, the wire W is melted by Joule heat, and the tip portion is scattered. As a result, a GMA arc 6a is generated at time t3 as shown in FIG. When the GMA arc 6a is generated, the GMA arc welding voltage Vwa is slightly reduced, and the GMA arc welding current Iwa is significantly reduced. The speed at which the gap between the wire W and the welding base material P opens is generally the difference between the speed at which the wire W melts and the feed rate Fw2 during the arc growth period.

  Next, from time t3 to time t4, the GMA arc welding voltage Vwa is gradually increased in a state where the feed rate Fw is set to the feed rate Fw2 during the arc growth period. In this embodiment, the GMA arc welding voltage Vwa is increased linearly. Along with this, the GMA arc welding current Iwa increases. As a result, the Joule heat generated in the wire W and the heat from the GMA arc 6a gradually increase. Since the feeding speed Fw is constant at the arc growth period feeding speed Fw2, the gap between the wire W and the welding base material P is increased by the increase of Joule heat and heat from the GMA arc 6a. As a result, the length of the GMA arc 6a is gradually increased as shown in FIG. This means that the plasma atmosphere space generated between the wire W and the weld base material P is expanded.

  By expanding the plasma atmosphere space between the wire W and the welding base material P, a plasma arc 6b is induced between the plasma electrode 2 to which the plasma arc welding voltage Vwb is applied and the welding base material P. Thus, at time t4, a plasma arc 6b is generated as shown in FIG. When the plasma arc 6b is generated, the plasma arc welding current Iwb starts to flow, and the plasma arc welding voltage Vwb decreases.

  Then, the feeding speed Fw and the moving speed Ft are gradually increased from time t4 to time t5. Specifically, the feeding speed Fw is linearly increased so as to become the steady feeding speed Fw3 at time t5. Further, the moving speed Ft is linearly increased so as to become the steady moving speed Ft3 at time t5. In other words, the ratio between the feeding speed Fw and the moving speed Ft is kept equal to the ratio between the steady feeding speed Fw3 and the steady moving speed Ft3 also between the time t4 and the time t5.

  On the other hand, in this embodiment, the GMA arc welding voltage Vwa at time t4 is set to a value slightly higher than the value in the steady welding state. Therefore, the length of the GMA arc 6a at time t4 is longer than the length in the steady welding state. This is to make it easier to generate the plasma arc 6b. From time t4 to time t5, the GMA arc welding voltage Vwa is gradually reduced to a value in the steady welding state at time t5. Thereby, the length of the GMA arc 6a becomes the length of the steady welding state as shown in FIG.

  After time t5, the feed speed Fw is a steady feed speed Fw3, the movement speed Ft is a steady movement speed Ft3, and the GMA arc welding voltage Vwa and the plasma arc welding voltage Vwb are values that should be in a steady welding state. keep. Thereby, after time t5, welding base material P with welding torch B is realized in a steady state.

  Next, the effect | action of the arc start control method of the two-electrode arc welding of this embodiment is demonstrated.

  According to this embodiment, the transition to the steady welding state can be performed quickly. The reason is that the GMA arc 6a and the plasma arc 6b are stably generated and grown. First, during the period from time t3 to time t4, the GMA arc welding voltage Vwa is gradually increased with the feeding speed Fw being the arc growth period feeding speed Fw2. Thereby, the length of the GMA arc 6a can be gradually increased according to the magnitude of the GMA arc welding voltage Vwa. That is, it is possible to prevent an unstable state in which the length of the GMA arc 6a becomes excessively long or short between time t3 and time t4. Next, by growing the GMA arc 6a in a stable state, the GMA arc 6a can be reliably grown to a length suitable for generating the plasma arc 6b at time t4. Thereby, plasma arc 6b can be generated reliably at time t4. Then, by gradually increasing the feeding speed Fw and the moving speed Ft from time t4 to time t5, the steady welding state can be reliably reached at time t5. As described above, since the generation and growth of the GMA arc 6a and the plasma arc 6b from the time t3 to the time t5 are performed in a properly controlled state, it takes a considerable time until the unstable state is converged to the steady state. There is no need. Therefore, the transition to the steady welding state can be performed quickly. In particular, in high-efficiency welding in which the welding speed in the steady welding state reaches 12.5 to 15 m / min, the shorter the time required for shifting to the steady welding state, the better for improving the efficiency of the welding operation.

  Moreover, according to this embodiment, a favorable weld bead can be formed. The reason is to control the ratio of the moving speed Ft and the feeding speed Fw to be constant. In the present embodiment, the movement of the welding torch B is started when the wire W contacts the welding base material P at time t2. For this reason, when the GMA arc 6a is generated at time t3, the welding torch B is in a state of moving in the welding direction. Thereby, the droplet of the wire W does not unduly concentrate and adhere to one place of the welding base material P. In addition, after the movement of the welding torch B is started at time t2, the ratio between the moving speed Ft and the feeding speed Fw is the entire period from time t3, time t4, time t5 to the steady welding state. The ratio is controlled to be the same as the ratio of the steady moving speed Ft3 and the steady feeding speed Fw3 in the steady welding state. For this reason, the weld bead formed by this welding has an appearance, a cross-sectional shape, and a penetration depth very close to a steady welding state immediately after the start point. Therefore, according to this embodiment, a good weld bead can be formed.

  The arc start control method for two-electrode arc welding according to the present invention is not limited to the above-described embodiment. The specific configuration of the arc start control method for two-electrode arc welding according to the present invention can be varied in design in various ways.

  When the consumable electrode arc is grown in the arc start control method according to the present invention, the consumable electrode arc welding voltage is not limited to a linear increase pattern. For example, it may be increased non-linearly or divided in fine steps. Good. When the feed rate of the consumable electrode and the moving speed of the welding torch are increased after the non-consumable electrode arc is generated, the pattern is not limited to a linear increase pattern. For example, it is increased nonlinearly or increased in fine steps. May be. Alternatively, the time from time t4 to time t5 in FIG. 2 may be set to an extremely short time, and the feeding speed Fw and the moving speed Ft may be instantaneously shifted to the steady feeding speed Fw3 and the steady moving speed Ft3.

  In order to control the ratio between the feed speed of the non-consumable electrode and the moving speed of the welding torch to be the ratio in the steady welding state, for example, one is changed according to a given pattern while the other is followed. The specific control form of both is not limited.

It is a system configuration figure showing a welding device used for an example of an arc start control method of two-electrode arc welding concerning the present invention. It is a timing chart which shows an example of the arc start control method of the two-electrode arc welding which concerns on this invention. It is a system block diagram which shows the welding apparatus used for an example of the arc start control method of the conventional 2 electrode arc welding. It is a timing chart which shows an example of the arc start control method of the conventional 2 electrode arc welding.

Explanation of symbols

A Welding device B Welding torch Fc Feeding control signal Fw Feeding speed Fw1 Slow-down feeding speed (first stage speed)
Fw2 Arc growth period feeding speed (second stage speed)
Fw3 steady feeding speed (steady speed)
Ft Movement speed Ft2 Arc growth period movement speed Ft3 Steady movement speed Iwa GMA arc welding current (consumable electrode arc welding current)
Iwb Plasma arc welding current (non-consumable electrode arc welding current)
P Welding base material PSM GMA arc welding power source (consumable electrode arc welding power source)
PSP plasma arc welding power source (non-consumable electrode arc welding power source)
ST Welding start circuit St Welding start signal Vwa GMA arc welding voltage (consumable electrode arc welding voltage)
Vwb Plasma arc welding voltage (non-consumable electrode arc welding voltage)
W wire (consumable electrode)
1 Contact chip 2 Plasma electrode (non-consumable electrode)
3 Plasma nozzle 4 Shield nozzle 5 Feed roller 6a GMA arc (consumable electrode arc)
6b Plasma arc (non-consumable electrode arc)

Claims (2)

An arc start control method for two-electrode arc welding in which welding is performed by generating a consumable electrode arc and a non-consumable electrode arc using a welding torch having a consumable electrode and a non-consumable electrode disposed in a shield gas nozzle,
A step of bringing the consumable electrode closer to the welding base material at a first stage speed slower than a steady speed in a steady welding state with a consumable electrode arc welding voltage applied between the consumable electrode and the welding base material. When,
After the consumable electrode is brought into contact with the welding base material, the consumable electrode is fed toward the welding base material at a second stage speed that is faster than the first stage speed and slower than the steady speed. Gradually increasing the length of the consumable electrode arc by gradually increasing the consumable electrode arc welding voltage from a voltage lower than the voltage in the steady welding state after the consumable electrode arc is generated;
After the non-consumable electrode arc is generated by the non-consumable electrode arc welding voltage applied between the non-consumable electrode and the welding base material, the supply speed of the consumable electrode is set to the steady speed, and the consumable electrode arc And a step of starting steady welding by setting the welding voltage to a voltage in a steady welding state. At least after the consumable electrode arc is generated, the welding torch is moved in the welding direction with respect to the welding base material, and
At least after the occurrence of the consumable electrode arc, the moving speed of the welding torch and the consumption of the consumable electrode are adjusted so that the ratio of the moving speed of the welding torch and the feeding speed of the consumable electrode becomes a ratio in a steady welding state. The arc start control method for two-electrode arc welding according to claim 1, wherein at least one of the electrode feed speeds is controlled.

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