JPH0369623B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an arc welding method using a consumable wire electrode (hereinafter simply referred to as wire). [Prior art] An arc welding method in which a wire is continuously fed toward a workpiece to be welded (hereinafter referred to as the base metal), and a welding voltage is applied between the wire and the base metal to generate a welding arc to perform welding. When stopping welding, the wire feeding is first braked to stop the welding, and then the welding voltage is cut off. At this time, even if the wire feeding drive was stopped, the inertia of the feeding motor would cause the wire to be fed out a small length, which would plunge into the molten pool formed on the surface of the base material and be welded. . In order to prevent this welding of the wire to the base metal, the welding voltage is conventionally cut off at a temperature of 0.2 to
This is performed with a delay of 0.5 (seconds) to melt the protruding extra wire (hereinafter referred to as the first conventional technique). In this first conventional technology, depending on the wire feeding speed, the welding voltage, and the characteristics of the wire feeding motor,
It was necessary to adjust the delay time from when the welding voltage was cut off to when the wire feed was stopped. Therefore, when a large number of base metals are sequentially welded using an automatic arc welding device, the first conventional technique requires (1) the time required for one process from welding one base metal to welding the next base metal; Welding is likely to occur when characteristics change, such as when the delay time for cutting off the welding voltage is shortened in order to shorten the delay time, or when the wire feed motor stops slowly. When the torch is moved to the next base material or the base material is moved to the next process,
This method has disadvantages in that the base metal is pulled by the wire, damaging the welding equipment and equipment disposed around it, and causing welding defects such as deformation and breakage of the base metal. The invention of claim 1 of JP-A No. 57-17381 (hereinafter referred to as the second prior art), when stopping welding, after stopping wire feeding, cutting off the welding voltage and extinguishing the welding arc, By applying a welding voltage again between the wire and the base material for a predetermined period of time, the protruding wire is melted, making welding less likely to occur than in the first prior art. In this second conventional technique, (1) the welding voltage is applied again every time welding is stopped, regardless of whether welding has occurred, so it is not possible to shorten the time for one process, and (2) the welding voltage is applied when welding is stopped. If welding occurs when the welding voltage is cut off and the wire cannot be melted when the welding voltage is applied again, equipment damage or welding defects similar to the first conventional technique will occur.(3) When applying this welding voltage If wire melting occurs near the torch, the molten metal will weld to the hole in the contact tip (the hole that guides the wire) after the welding voltage is cut off, blocking this hole and causing damage to the base metal and wire (actually However, since the distance between the tip and the tip of the contact tip is too wide, the welding arc does not ignite even when a welding voltage is applied, resulting in a situation where the wire cannot be fed. The invention of claim 2 of the same Japanese Patent Application Laid-open No. 57-17381 (hereinafter referred to as the third prior art) is mainly concerned with releasing welding, and when welding is stopped,
After the wire feeding is stopped, the welding voltage is cut off, the welding arc is extinguished, the short circuit between the wire and the base metal is inspected, and the welding voltage is turned off between the wire and the base metal only in case of a short circuit, that is, welding. This is a method in which the welded wire is fused and cut by applying it again for a predetermined period of time. This third conventional technique can immediately move the torch to the next base material or move the base material to the next process when welding is stopped and there is no welding. Don't waste time comparing. However, this third prior art has the following problems: (1) When the wire melts when applying the welding voltage again near the torch, and when the wire cannot be cut off once the welding is canceled, the second (2) Repeated release of the welding described above may cause a short circuit due to interference between the wire and the base metal, such as interference between the welding power source and surrounding equipment, jigs, and the base metal. In the event of an accident, the above-mentioned welding must be permanently released, and frequent operation of the welding power source has the disadvantage of causing damage and damage to the area around the torch. [Problems to be Solved by the Invention] It is an object of the present invention to prevent the molten metal from welding into the hole of the contact tip after cutting off the welding voltage when cutting the wire, and to prevent the molten metal from welding into the hole of the contact tip even if the welding is repeatedly released. An object of the present invention is to provide an arc welding method that automatically releases welding between a wire and a base material without causing damage to a welding power source. [Configuration for Solving the Problems] The arc welding method of the present invention includes the following steps when stopping welding:
a first step of cutting off the welding voltage and extinguishing the welding arc after stopping feeding the wire electrode;
A second method detects welding of the wire electrode by inspecting the presence or absence of a short circuit between the workpiece and the wire electrode.
If welding of the wire electrode is detected in the step and the second step, welding voltage is applied between the workpiece and the wire electrode to release the welding, and the feeding of the wire electrode is changed from normal welding. a third step in which the welding is performed at low speed, and the feeding of the wire electrode is stopped after a predetermined period of time has elapsed, and the welding voltage is cut off;
A fourth method detects welding of the wire electrode by detecting the presence or absence of a short circuit between the workpiece and the wire electrode.
If welding of the wire electrode is detected in the fourth step, a fifth step of updating a counter indicating the number of executions of the third step, and checking the value of the counter, and the third step If the predetermined number of times (≧2) has not been executed, the third
a sixth step of returning to step 1 and stopping the operation of the welding device after the welding has been performed a predetermined number of times;
If welding of the wire electrode is not detected in the second and fourth steps, a seventh step starts the next welding process.

[Effect]

After the welding of the wire electrode is released, the wire electrode is not moved away from the workpiece but is advanced (feeded) toward the workpiece, that is, the tip of the wire electrode moves away from the contact tip, so that the molten metal of the wire electrode flows into the contact. No welding to the chip holes,
Furthermore, the wire electrode tip and the object to be welded are fused and cut without being welded again. Furthermore, since the welding release operation is repeated a predetermined number of times at most, damage to the welding power source does not occur. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an arc welding apparatus to which the arc welding method of the present invention is applied. Main control device 1
is the core (consisting of CPU, ROM, RAM, etc.) for implementing the arc welding method of the present invention. In addition, from an input device (not shown), a command as to whether or not to perform a welding release operation, the number of welding release operations,
The welding voltage, wire feeding speed, etc. at the time of completion of welding are input to the main controller 1. The wire feed control device 2 is controlled by a command signal S ₁ from the main control device 1 and controls the wire feed motor 3 . Wire feed motor 3
A wire feed roller 4 is connected to its output shaft, and the wire 5 held by the wire feed roller 4 is fed toward the base material 6. The off-delay circuit 8 starts a delay operation when the command signal S ₁ from the main controller 1 becomes low level, and outputs a low level signal S ₂ to the welding power source 7 after a predetermined delay time T ₁ has elapsed. The input end of the short circuit detection circuit 9 is connected to the output side of the welding power source 7, and the output end thereof is connected to the main controller 1. Figure 2 shows welding power source 7.
2 is a circuit diagram of an embodiment of the short circuit detection circuit 9. FIG. The welding power source 7 is a DC power source E ₁ and a switch SW (thyristor or relay contact) connected in series to this.
Consisting of The auxiliary power source E ₂ is connected in parallel with the DC power source E ₁ so as to have opposite polarity, and the resistor R ₁ is connected in series with this. Diode D, resistor R ₂ ,
A series circuit of capacitor C is connected to auxiliary power supply E ₂ and resistor R ₁
connected in parallel to the series circuit. with resistance R ₃
A series circuit of R ₄ is connected in parallel to capacitor C,
The base of the transistor TR is connected to the connection point between the resistors R ₃ and R ₄ . When the wire 5 and the base material 6 are separated, the output of the auxiliary power supply E ₂ charges the capacitor C via the resistor R ₁ , the diode D, and the resistor R ₂ and then turns on the transistor TR, so the short circuit detection circuit 9 The output S ₃ of the short circuit detection circuit 9 becomes low level, and if they are in close contact, the voltage drop across the resistor R ₁ is large and the transistor TR is off, so the output S ₃ of the short circuit detection circuit 9
becomes high level. Next, the operation of the arc welding apparatus of this embodiment will be explained. (1) At the start of welding When the command signal _S1 of the main control device 1 becomes high level, the wire feed control device 2 is started and the off-delay circuit 8 is started at the same time. Therefore, the wire feed motor 3 is started, the wire feed roller 4 rotates, the wire 5 is fed toward the base material 6, and the off-delay circuit 8
A high level output signal _S2 is input to the welding power source 7, and a welding voltage is applied from the welding power source 7 to the wire 5 and the base metal 6, so an arc 10 is generated and welding is started. (2) When welding is stopped The operation when welding is stopped will be explained with reference to the flowchart in Figure 3. When the command signal _S1 of the main control device 1 becomes low level, the wire feeding control device 2 immediately stops, and the rotation of the wire feeding motor 3 and therefore the feeding of the wire 5 is stopped (step 101). . After a delay time _T1 has elapsed since the command signal _S1 became low level, the output signal _S2 of the off-delay circuit 8 becomes low level, which is input to the welding power source 7 and the welding voltage is cut off (step 102). Next, a short circuit between the wire 5 and the base material 10 is detected by the short circuit detection circuit 9.
In other words, the presence or absence of welding is detected (step
103), after a predetermined period of time has elapsed in order to prevent false detection of the presence or absence of welding due to transient phenomena at the time of disconnection of the circuit formed by the welding power source 7, wire 5, base metal 6 and the interconnection cable and arc. Welding is detected (step 103). If it is determined that there is no welding, control moves to the next step to move the base material 6 or the torch. If it is determined that welding has occurred, it is determined whether or not to perform a welding release operation (step 104). If not, all operations of the welding device are stopped (step 115). When executing the welding operation, first, the number of executions of the welding release operation is inputted from an input device (not shown) and set in a loop counter (this may be set in advance) (step 105). This value may be a fixed value, but it should be repeated within a range that does not cause any trouble to the welding power source 7 due to frequent application/cutoff of the welding voltage. Next, set command signal _S1 to high level and apply welding voltage (step
106), start feeding the wire 5 (step
107). The feeding speed of the wire 5 at this time is lower than that during normal welding. This is to keep the molten part of the wire 5 away from the torch in order to prevent the hole 11 of the contact chip from being blocked by solidification of molten metal if the wire 5 is fused near the torch, and also to prevent it from being fused. This is to prevent excessive stress from being applied to the base material 6 and the torch by the wire 5 when the wire 5 is fed. Next, wait for the time when the wire 5 will be fused (step
108). Note that this waiting time, the applied welding voltage and wire feeding speed described above are variable in this embodiment because the optimum values differ depending on the characteristics of the welding power source 7, the diameter of the wire 5, the quality of the base material 6, etc. There is.
If a predetermined period of time has elapsed, the command signal _S1 is set to low level to stop feeding the wire 5 (step 109), and the welding voltage is cut off (step 110). Next, in order to avoid erroneous detection of welding due to the above-mentioned transient phenomenon, welding is detected by the short circuit detection circuit 9 after a predetermined period of time has elapsed (step 111). If it is determined that there is no welding, that is, if the wire 5 has been fused, control moves to the next step as before. If welding is determined, the loop counter is decremented by 1 (step 112). Next, it is determined whether the loop counter is 0 or not (step 113), and
Otherwise, the process returns to step 106 and repeats the welding release operation described above. If the loop counter is 0, that is, the welding cannot be released even after repeating the welding release operation a predetermined number of times, the equipment, jigs, and base materials in and around the welding power source 7
In this case, an alarm is output (step 114),
Stop all operations of this welding equipment (step
115). This allows the operator to quickly and completely recover from a short circuit accident. [Effects of the Invention] As explained above, the present invention, after welding the wire electrode, advances the wire electrode toward the object to be welded and repeats the welding release operation a predetermined number of times at maximum, thereby releasing the wire welding and It is possible to prevent the molten metal of the wire electrode from being welded to the hole of the contact tip, and even in the event of a short-circuit accident, it is possible to perform a good welding operation without causing damage to the welding power source or the like.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing one embodiment of an arc welding device to which the arc welding method of the present invention is applied;
The figure is a circuit diagram of an embodiment of the welding power source 7 and short-circuit detection circuit 9 shown in FIG. 1, and FIG. 3 is a flowchart showing the operation when welding is stopped in the arc welding apparatus shown in FIG. 1. 1: Main control device, 2: Wire feeding control device,
3: wire feeding motor, 4: wire feeding roller,
5: wire, 6: base metal, 7: welding power source, 8: off-delay circuit, 9: short circuit detection circuit, 10: arc, 11: contact chip hole.

Claims (1)

[Claims] 1. In an arc welding method in which a welding voltage is applied between a workpiece and a consumable wire electrode supplied toward the workpiece to ignite a welding arc, when welding is stopped, the wire After stopping the feeding of the electrode, the first step is to cut off the welding voltage to extinguish the welding arc, and to check for short circuits between the wire electrodes of the workpiece to prevent welding of the wire electrodes. If welding of the wire electrode is detected in the second step, a welding voltage is applied between the workpiece and the wire electrode to release the welding, and the feeding of the wire electrode is stopped normally. The third step is to perform welding at a lower speed than when welding, stop feeding the wire electrode after a predetermined period of time, and cut off the welding voltage, and inspect the presence or absence of a short circuit between the workpiece and the wire electrode. , a fourth step of detecting welding of the wire electrode; a fifth step of updating a counter indicating the number of times the third step is executed when welding of the wire electrode is detected in the fourth step; a sixth step of detecting the value, and returning to the third step if the third step has not been performed a predetermined number of times (≧2), and stopping the operation of the welding device if the third step has been performed a predetermined number of times; and a seventh step of starting the next welding process if welding of the wire electrode is not detected in the second and fourth steps. 2. The arc welding method according to claim 1, wherein an alarm is issued when the operation of the welding device is stopped in the sixth step.