JP5043557B2 - Arc termination control method for two-electrode arc welding - Google Patents

Description

  The present invention forms a good weld bead in two-electrode arc welding where a consumable electrode and a non-consumable electrode arc are generated using a welding torch having a consumable electrode and a non-consumable electrode disposed within a shield gas nozzle. The present invention relates to an arc termination control method for two-electrode arc welding.

  Two-electrode arc welding that simultaneously generates a consumable electrode arc while feeding a wire as a consumable electrode, and generates a non-consumable electrode arc surrounding the consumable electrode arc using a plasma gas such as Ar, for example. It has been proposed (see, for example, Patent Document 1). This technique of supplying heat to the weld base and supplying molten wire from both consumable and non-consumable electrode arcs is suitable for high efficiency welding where welding is performed at a relatively fast welding speed.

  However, in high-efficiency welding, the faster the welding speed, the more difficult it is to end the welding process appropriately. Inadequate termination will result in defects at the end of the weld bead. Such defects cause a decrease in weld strength. For example, if the molten pool generated during welding solidifies in a concave shape due to the dynamic pressure of the non-consumable electrode arc, it becomes a defect.

  For the welding method using only the consumable electrode arc, several termination processes have been proposed (see, for example, Patent Documents 2 and 3). However, these termination processes are not considered at all when a non-consumable electrode arc is used. For this reason, just applying these to two-electrode arc welding is not sufficient to eliminate the above-mentioned problems.

JP 63-168283 A JP 59-7480 A Japanese Patent Laid-Open No. 9-192832

  The present invention has been conceived under the circumstances described above, and an object thereof is to provide a two-electrode arc welding end control method capable of forming a good weld bead.

The arc termination control method of two-electrode arc welding provided by the present invention uses a welding torch having a consumable electrode and a non-consumable electrode disposed in a shield gas nozzle for discharging a shield gas, and uses a consumable electrode arc and a non-consumable electrode arc. An arc termination control method of two-electrode arc welding for welding by generating a consumable electrode arc, after a steady welding process in which the welding torch is moved in the welding forward direction while generating a consumable electrode arc and a non-consumable electrode arc The welding forward direction component of the welding torch moving speed is less than 0, the consumable electrode feed speed for feeding the consumable electrode, the consumable electrode arc current for generating the consumable electrode arc, and the non- The non-consumable electrode arc current for generating the consumable electrode arc is smaller than the magnitude in the above-mentioned steady welding process. Performs welding end pretreatment that, in the welding end pretreatment, the non-consumable electrode arc current is 0, is characterized by a value greater than 0 the consumable electrode arc current.

According to such a structure, a molten wire is supplied to the part which was a molten pool at the time of completion | finish of regular welding. Thereby, it can prevent that a molten pool solidifies with the concave shape. Therefore, it is possible to form a weld bead having a good shape, and the welding strength can be increased. Moreover, it can prevent that a molten pool becomes dented too much by the dynamic pressure of a non-consumable electrode arc.

  In a preferred embodiment of the present invention, in the welding end pretreatment, the flow rate of at least one of the shielding gas or the plasma gas for generating the non-consumable electrode arc is set higher than the amount in the steady welding treatment. Reduce. According to such a configuration, in the case of high-efficiency welding with a relatively high welding speed, the molten wire can be appropriately supplied to the molten pool even if the molten pool has a long shape.

  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 termination 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 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 and a welding end signal Cr is sent from the welding end circuit CR 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 and a welding end signal Cr is sent from the welding end circuit CR 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 , a reference example of the arc end control method of the two- electrode arc welding will be described below with reference to FIG. The two-electrode arc welding of this reference example is classified into high-efficiency welding in which the feeding speed of the wire W in the steady welding process is, for example, about 12.5 to 15 m / min.

  When the welding start signal St is in the high state, the steady welding is generally performed after a transitional welding start process. In the steady welding process, the wire feed speed Fw is set to the steady wire feed speed Fwn, the GMA arc welding voltage Vwa is set to the steady GMA arc welding voltage Vwan, and the plasma arc welding voltage Vwb is set to the steady plasma arc welding voltage Vwbn. Is done. The center gas Gc is supplied at a steady center gas flow rate Gcn, the plasma gas Gp is supplied at a steady plasma gas flow rate Gpn, and the shield gas Gs is supplied at a steady shield gas flow rate Gsn. The welding torch B is moved by, for example, a robot (not shown). At this time, the torch moving speed Ft is set to the steady torch moving speed Ftn. During the steady welding process, the GMA arc welding current Iwa flows with the magnitude of the steady GMA arc welding current Iwan, and the plasma arc welding current Iwb flows with the magnitude of the steady plasma arc welding current Iwbn. This means that the GMA arc 6a and the plasma arc 6b are generated with the set strength.

  In the steady welding process, the welding target portion of the welding base material P is melted by the heat supplied from the GMA arc 6a and the plasma arc 6b. The melted wire W is supplied to the melted portion. Thereby, what is called a molten pool is formed. Due to the dynamic pressure of the plasma arc 6b and the gas pressure of the shield gas Gs, the molten pool has a partially recessed shape. Due to the movement of the welding torch B, the molten pool moves to a region where the dynamic pressure of the plasma arc 6b and the gas pressure of the shield gas Gs do not reach. Then, when the surface tension of the molten pool acts, the concave shape of the molten pool is eliminated. As a result, the weld bead formed by solidifying the molten pool generally has a convex shape. Thereby, a weld bead is formed in the path along which the welding torch B has moved.

  When the regular welding is finished, the welding start signal St is in a low state at time t1, and the welding end signal Cr is in a high state. Then, a welding end preliminary process is performed from time t1 to time t2. Specifically, the wire feed speed Fw is set to the end wire feed speed Fwe, and the GMA arc welding voltage Vwa is set to the end GMA arc welding voltage Vwae. The end wire feed speed Fwe and the end GMA arc welding voltage Vwae are both smaller than the steady wire feed speed Fwn and the steady GMA arc welding voltage Vwan. As a result, the GMA arc welding current Iwa decreases to the end GMA arc welding current Iwae. This weakens the GMA arc 6a. On the other hand, the plasma arc welding voltage Vwb is set to zero. As a result, the plasma arc welding current Iwb becomes 0 and the plasma arc 6b disappears. Further, the supply of the center gas Gc and the plasma gas Gp is stopped. The flow rate of the shield gas Gs is reduced to the end shield gas flow rate Gse.

  In the welding end preliminary process, the molten wire is supplied at the end wire supply speed Fwe to the place where the welding torch B exists at the time t1 in the welding base material P. This portion is a portion that is a recessed weld pool at the final point of the steady welding process. This portion is a portion that is not completely subjected to the steady welding process, and may solidify in a concave shape. In the welding end pretreatment, an appropriate amount of molten wire is supplied to this portion.

  Then, after a predetermined time elapses, the welding end signal Cr is set to the low state at time t2. Then, the wire feed speed Fw and the GMA arc welding voltage Vwa are set to 0, and the supply of the shield gas Gs is stopped. Thereby, the welding by the welding apparatus A is completely complete | finished.

Next , the operation of the reference example of the arc end control method of two- electrode arc welding will be described.

According to the present reference example , the molten wire is supplied after time t1 to the portion that was a depressed molten pool at the end of steady welding. At this time, the dynamic pressure by the plasma arc 6b and the gas pressures of the center gas Gc and the plasma gas Gp do not act on this portion. Therefore, there is no possibility that not only a weld bead portion formed by steady welding but also an inappropriately recessed portion is formed until reaching the end of the weld bead. Therefore, a good weld bead can be formed over the entire region, and the welding strength can be improved.

  After time t1, by setting the flow rate of the shield gas Gs to the end shield gas flow rate Gse, it is possible to prevent an excessive gas pressure from being applied to the molten pool. Further, by continuing to supply the shielding gas Gs, it is possible to avoid that the end portion of the weld bead is unduly oxidized before solidification.

3 and 4 show another reference example and an embodiment of the present invention. In these figures, the Reference Example and the same or similar elements are denoted by the same reference numerals as the reference example.

FIG. 3 shows another reference example of the arc end control method of two- electrode arc welding. In this reference example , when the welding end signal Cr is in a high state, the plasma arc welding voltage Vwb is changed to the end plasma arc welding voltage Vwbe, the flow rates of the center gas Gc and the plasma gas Gp are the end center gas flow rate Gce and the end plasma gas flow rate. The point set in Gpe is different from the reference example described above. With this configuration, in the welding end preliminary process from time t1 to time t2, the plasma arc welding current Iwb flows at the magnitude of the end plasma arc welding current Iwbe, and the plasma arc 6b weakened from the steady state is generated. Is preserved.

According to such a reference example , in the welding end pretreatment, the molten wire is supplied in a state surrounded by the weakened plasma arc 6b. As a result, the molten wire reaches the welding base material P in a relatively high temperature state. In addition, there is little risk that the molten pool will solidify rapidly due to heat from the plasma arc 6b. Therefore, the molten wire and the molten portion of the weld base material P can be sufficiently mixed at the end of the weld bead.

FIG. 4 shows an example of an arc end control method of two-electrode arc welding according to the present invention. In this embodiment, when the welding end signal Cr is in a high state, the torch moving speed Ft is set to the end torch moving speed Fte, which is different from any of the reference examples described above. About points other than this, it is the same as that of the reference example mentioned above. As understood from this figure, the end torch moving speed Fte is a negative value. For this reason, the welding torch B moves in the opposite direction to the steady welding process from time t1 to time t2. The absolute value of the end torch moving speed Fte is significantly smaller than the steady torch moving speed Ftn.

  According to such an embodiment, when the molten pool formed at the end of the steady welding has a shape extending in the traveling direction of the welding torch B, the molten pool is prevented from solidifying while being recessed. Suitable for For example, this is the case when performing high-weld welding where the steady torch moving speed Ftn is significantly increased.

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

It is a system configuration figure showing an example of a welding device used for an arc end control method of two-electrode arc welding concerning the present invention. It is a timing chart which shows the reference example of the arc completion | finish control method of 2 electrode arc welding. It is a timing chart which shows the other reference example of the arc completion | finish control method of 2 electrode arc welding. It is a timing chart which shows an example of the arc end control method of 2 electrode arc welding concerning the present invention.

A Welding device B Welding torch CR Welding end circuit Cr Welding end signal Fc Feeding control signal Fw Feeding speed Ft Moving 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)

Arc termination of 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 for discharging a shield gas A control method,
After a steady welding process in which the welding torch is moved in the welding forward direction while generating a consumable electrode arc and a non-consumable electrode arc,
While making the welding forward direction component of the moving speed of the welding torch less than 0,
A consumable electrode feed speed for feeding the consumable electrode, a consumable electrode arc current for generating the consumable electrode arc, and a non-consumable electrode arc current for generating the non-consumable electrode arc are large in the steady welding process. It performs welding end pretreatment of smaller than of,
In the welding end preliminary process, the non-consumable electrode arc current is set to 0, and the consumable electrode arc current is set to a value exceeding 0 . In the welding end pretreatment, at least one of the flow rate of the plasma gas for generating the shielding gas or the non-consumable electrode arc is less than the amount in the steady welding process, according to claim 1 2 An arc end control method for electrode arc welding.

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