JP5863281B2 - Arc welding method and arc welding apparatus - Google Patents

Description

  The present invention relates to an arc welding method and an arc welding apparatus.

  In arc welding, it is necessary to appropriately set welding conditions such as a welding current, a welding voltage, and a welding speed (torch moving speed) according to the thickness of the workpiece and the required welding quality. However, it is not easy to set the welding current, the welding voltage, and the like appropriately, and it is often difficult unless a skilled worker is employed.

  For example, in consumable electrode type arc welding, there is a correlation between the welding current and the welding voltage. Therefore, using this correlation, a welding voltage corresponding to the welding current is set in advance. Control) is known (for example, Patent Document 1). In the central adjustment, the welding voltage is automatically set when the worker inputs the welding current, so that even a less experienced worker can easily set the welding conditions.

JP-A-6-238445

  In the above-described method for setting welding conditions by means of a single adjustment, the current value can be set according to the workpiece, but the voltage value is uniquely determined based on the correlation with the current value. It is not always possible to obtain a voltage value suitable for. For example, when the workpiece is a thick plate (for example, 4 mm or more), there is little problem even if the voltage value is somewhat large. However, when the workpiece is a thin plate (for example, less than 4 mm), the workpiece is perforated by arc heat (so-called Therefore, there is a possibility that an appropriate voltage value cannot be set by the above-described setting method based on the single adjustment.

  By the way, in arc welding (in particular, MIG welding or MAG welding), a so-called constant voltage characteristic that controls a current value so that the welding voltage is constant may be employed. When arc welding is performed using constant voltage characteristics, the current value increases when the wire feed rate is increased, and the current value decreases when the wire feed rate is decreased. At this time, if the wire feed speed is appropriate, an arc A is generated between the wire P and the workpiece W as shown in FIG. 6 (FIG. 6A), and the tip of the wire P is melted by the arc heat. Then, a droplet B is generated (FIG. 6B), and the droplet grows by sending out the wire P (FIGS. 6C and 6D). When the droplet reaches a predetermined size, it is short-circuited to the surface of the workpiece (FIG. 6E), and then the droplet B leaves the wire and adheres to the surface of the workpiece as a weld metal B ′ (FIG. 6F). ).

  On the other hand, if the wire feed speed is too high, as shown in FIG. 7, the droplet B at the tip of the wire P approaches the workpiece W without sufficiently growing (FIGS. 7B to 7D), and finally The tip of the wire P directly contacts the workpiece W (FIG. 7E). A control unit (not shown) that detects this causes the voltage P to suddenly rise to melt the wire P rapidly, so that spatter B ″ is generated and the molten metal is scattered around (FIG. 7 ( f)). For this reason, the metal welded to the workpiece W is reduced, and there is a possibility that a hole is formed in the workpiece W.

  As described above, it is necessary to set the wire feed speed appropriately. However, at present, since the wire feed speed at which the welding wire does not come into contact with the workpiece is searched for, it takes a lot of labor to set the welding conditions. At the same time, the reliability of the set welding conditions was not high.

  The present invention has been made in view of the above circumstances, and even when arc welding is performed on a thin plate, appropriate welding conditions (particularly, voltage value and wire feed speed) that do not cause drilling can be easily obtained. It is intended to be able to be set to.

  The present invention made to achieve the above object is an arc welding method using a consumable electrode type arc welding apparatus having constant voltage characteristics, and acquires a set value of a welding voltage based on a plate thickness of a workpiece. A step of obtaining a temporary setting value of the wire feed speed, a step of performing arc welding on the workpiece using an arc welding apparatus in which the setting value of the welding voltage and the temporary setting value of the wire feed speed are input; And a step of correcting the wire feed speed based on the bending state of the welding wire during the arc welding.

  As described above, by acquiring the set value of the welding voltage according to the plate thickness of the workpiece, it is possible to generate an arc with an appropriate length according to the plate thickness of the workpiece. Can prevent perforation. Further, in the arc welding method of the present invention, after setting the welding voltage and the wire feed speed, the wire feed speed is corrected while arc welding is performed on the work, thereby keeping the distance between the tip of the welding wire and the work properly. be able to. At this time, if the distance between the welding wire and the workpiece can be directly confirmed, the wire feed speed may be corrected based on the distance. However, during arc welding of the workpiece, the distance between the welding wire and the workpiece is correct. Since the arc is always generated, it is very difficult to directly check the distance between the tip of the welding wire and the workpiece.

  Then, the distance (presence of contact | abutting) of a welding wire and a workpiece | work can be estimated by detecting the bending condition of a welding wire. That is, when the welding wire sent out from the wire supply unit comes into contact with the workpiece, the welding wire is continuously sent out thereafter, so that the bending of the welding wire increases. Therefore, the allowable range of bending of the welding wire when arc welding is performed in a normal state where the welding wire does not contact the workpiece is set, and the bending degree of the welding wire when arc welding is actually performed is set in advance. When the allowable range is exceeded, it can be determined that the welding wire is in contact with the workpiece. Therefore, arc welding is performed while gradually increasing the wire feed speed, and a state in which the welding wire is actually brought into contact with the workpiece is intentionally created, and the wire feed speed at this time is obtained as a limit value. By correcting the wire feed speed so as to be smaller, the contact between the welding wire and the workpiece in the subsequent arc welding can be prevented.

  The arc welding method as described above is a consumable electrode type arc welding apparatus having constant voltage characteristics, wherein a voltage control unit to which a set value of a welding voltage acquired based on a workpiece thickness is input, and wire feed A wire feed speed control unit for controlling the speed, and a detection unit for detecting the bending state of the welding wire during arc welding, and the wire feed speed control unit detects the welding wire detected by the detection unit. This can be realized by an arc welding apparatus having correction means for correcting the wire feed speed based on the degree of bending.

  As described above, according to the present invention, the welding voltage is set according to the plate thickness of the workpiece, and the wire feed speed is corrected according to the bending state of the welding wire when the arc welding is actually performed. Even when arc welding is performed on a thin plate, it is possible to easily set appropriate welding conditions that do not cause drilling of the workpiece.

1 is a block diagram of an arc welding apparatus according to an embodiment of the present invention. It is sectional drawing of the torch of the said arc welding apparatus. It is a block diagram of the control part of the said arc welding apparatus. It is a flowchart of the arc welding condition setting method which concerns on embodiment of this invention. It is a side view which shows the bending condition of the tube which covers a welding wire. (A)-(f) is a side view which shows the growth process of the droplet in normal arc welding. (A)-(f) is a side view which shows the process of the arc welding in case a wire feed rate is too quick.

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

  FIG. 1 shows an arc welding apparatus 1 according to an embodiment of the present invention. The arc welding apparatus 1 is a consumable electrode type that performs welding while melting the welding wire P, and particularly performs MIG welding or MAG welding. The arc welding apparatus 1 includes a torch 10, a wire supply unit 20 that supplies a welding wire P to the torch 10, a power supply 30 that applies a voltage between the workpiece W and the welding wire P, a voltage of the power supply 30, and a wire supply And a control unit 40 that controls the wire feed speed of the unit 20 and the welding speed (the moving speed of the torch 10) and provides constant voltage characteristics.

  The torch 10 is configured to hold the welding wire P passing through the inside in a bent state and to confirm the bending state of the welding wire P. Specifically, as shown in FIG. 2, it has a cylindrical holding part 11 and a tube 12 provided on the inner periphery of the holding part 11 and covering the outer periphery of the welding wire P. The tube 12 can be deformed flexibly and can be expanded and contracted, and can be configured, for example, by winding a wire rod in a spiral shape. The tube 12 is disposed approximately at the center of the inner periphery of the holding portion 11, both ends are fixed to the holding portion 11, and are connected to the inner peripheral surface of the holding portion 11 by an elastic member 13 such as a spring. As a result, the welding wire P disposed on the inner periphery of the tube 12 can freely change the degree of bending inside the holding portion 11. The holding unit 11 is provided with a detection unit (not shown), and the detection unit detects the bending state of the tube 12, that is, the bending state of the welding wire P.

  As shown in FIG. 3, the control unit 40 includes a voltage control unit 41 that controls the voltage of the power supply 30, a wire feed rate control unit 42 that controls the wire feed rate of the wire supply unit 20, and a welding speed, that is, the torch 10. A welding speed control unit (not shown) for controlling the moving speed of the welding machine. The wire feed speed control unit 42 includes temporary setting means 43 that acquires a temporary setting value of the wire feed speed, and correction means 44 that corrects the wire feed speed based on the bending state of the welding wire P detected by the detection unit. Have.

  Hereinafter, the setting method of the welding conditions in the arc welding performed using said arc welding apparatus 1 is demonstrated. In the present embodiment, for example, fillet welding is performed on a portion where two thin workpieces (steel plates) constituting a panel of an automobile body are overlapped (see FIG. 1). The plate thickness of each workpiece W is, for example, 4 mm or less, and specifically in the range of 0.6 to 3.2 mm.

In the arc welding method of this embodiment, as shown in FIG. 4, step S <b> 1 for obtaining a welding voltage setting value V based on the plate thickness of the workpiece W, and a wire feed rate based on the welding voltage setting value V are shown. a step S2 of acquiring a temporary set value C _0, perform arc welding on the workpiece, the welding wire is a step S3 to obtain the limit value C ₁ of the work feeding speed when in contact with the workpiece, said limit value Step S4 for correcting the wire feed speed based on C ₁ and obtaining the set value C ₂ of the wire feed speed, and obtaining the welding speed G (movement speed of the torch 10) based on the set value C ₂ of the wire feed speed. Step S5.

(1) Acquisition of welding voltage set value V (step S1)
First, a welding voltage set value V corresponding to the thickness t of the workpiece to be welded is acquired. Specifically, from a test or past data, a table showing the correlation between the workpiece plate thickness and the voltage value that does not cause drilling of the workpiece of that plate thickness should be acquired and welded. A set value V of the welding voltage corresponding to the plate thickness t of the workpiece W is obtained from the above table, and this set value V is input to the voltage control unit 41 of the arc welding apparatus 1. This step S1 is performed, for example, when the operator obtains the set value V of the welding voltage by looking at the table and inputs the set value V to the voltage control unit 41 by the operator's hand. Alternatively, the above table may be stored in advance in the voltage control unit 41, and the welding voltage set value V may be automatically set by the operator inputting the plate thickness t.

(2) Acquisition of temporary setting value C ₀ of wire feed speed (step S2)
Next, a temporary setting value C ₀ of the wire feed speed by the wire supply unit 20 is acquired. The temporary setting value C ₀ of the wire feed speed can be arbitrarily set, but is acquired based on, for example, the welding voltage setting value V acquired in the above step S1, and more specifically, automatically acquired by one-way adjustment. The Specifically, first, a table indicating a combination of a voltage value and a current value capable of maintaining the arc is acquired from a test or past data in advance, and this table is stored in the temporary setting unit 43 of the wire feed speed control unit 42. When the welding voltage set value V is transmitted from the voltage control unit 41 to the temporary setting means 43, the temporary setting means 43 acquires the current value I corresponding to the welding voltage set value V from the above table, and this current setting the wire feed speed based on the value I as a temporary set value C _0. Since performing gradually increased while the welding wire feed rate at the next step S3 from the temporary set value C _0, the temporary set value C ₀ is preferably set to a lower value. Therefore, for example, the wire feed speed corresponding to the value I ′ smaller than the current value I obtained by the single adjustment may be set as the temporary setting value C ₀ .

(3) execution of the arc welding (acquisition of the wire feed speed limits C ₁₎ (Step S3)
Next, arc welding is actually performed on the workpiece W using the arc welding apparatus 1 to which the setting value V of the welding voltage and the temporary setting value C ₀ of the wire feed speed are input. In the present embodiment, while gradually raising the wire feed speed from the temporary set value C _0, subjected to arc welding the workpiece W. Specifically, the voltage control unit 41 sets the voltage of the power source 30 to the set value V acquired in step S1, and the wire feed rate control unit 42 sets the wire feed rate by the wire supply unit 20 in step S2. in a state set to the provisional setpoint C ₀ acquired, to start arc welding to the work W. Then, arc welding is performed while gradually increasing the wire feed speed from the temporary setting value C ₀ , the tip of the welding wire P is brought into contact with the workpiece W (see FIG. 7E), and the wire feed at the moment of contact is made. to obtain the speed as a limit value C _1.

  At this time, whether or not the tip of the welding wire P is in contact with the workpiece W can be determined by the degree of bending of the welding wire P. Specifically, the tube 12 and the welding wire P are as shown by a solid line in FIG. 5 in a state where welding is performed while the tip of the welding wire P is normally fed without contacting the workpiece W (see FIG. 6). The bending state is shown (the welding wire P is not shown in FIG. 5). On the other hand, when the tip of the welding wire P comes into contact with the workpiece W, the welding wire P continues to be sent out from the wire supply unit 20 with the tip in contact with the workpiece W. Therefore, as shown by the dotted line in FIG. The deflection of the becomes larger. Therefore, first, an allowable range of the degree of bending of the tube 12 (welding wire P) when arc welding is performed in a normal state where the welding wire P does not contact the workpiece W is obtained from the test or past data. Then, the degree of bending of the tube 12 is detected at any time by a detection unit (not shown), and if the degree of bending exceeds the allowable range, it can be determined that the tip of the welding wire P has contacted the workpiece W. For example, as shown in FIG. 5, one or a plurality of (three in the illustrated example) markers 12a are provided on the outer periphery of the tube 12, and a detection unit (for example, a CCD camera or the like) determines whether or not the markers 12a are within a predetermined range. By detecting with a sensor), the bending state of the tube 12 can be confirmed.

(4) (acquired set value C ₂₎ Correction of the wire feed speed (step S4)
Thereafter, the wire feed speed is corrected by the correction means 44 of the wire feed speed control unit 42 based on the limit value C ₁ acquired in step S3. In the present embodiment, the wire feed speed is corrected to a value smaller than the limit value C ₁ obtained in step S3, and this value is obtained as the set value C ₂ for the wire feed speed. The wire feed rate is high it is possible to increase the torch feed rate, it is possible to increase the productivity, the set value C ₂ of the wire feed rate is preferably as fast as possible. Accordingly, setting values C ₂ of the wire feed speed is greater than the provisional setpoint C _0, and is preferably set slightly smaller than the limit value C _1, for example, about 70% to 90% of the limit value C ₁ Set to

(5) Setting of welding speed G (step S5)
The welding speed G is set based on the wire feed speed setting value C ₂ obtained above. Specifically, a table indicating the correlation between the current value and the welding speed when appropriate arc welding is performed is acquired from a test or past data in advance. And the table, and a current value corresponding to the set value C ₂ of the wire feed speed, to obtain a welding speed G corresponding to this current value. Thus, the setting of the welding conditions for arc welding performed on the workpiece W using the arc welding apparatus 1 (the setting value V of the welding voltage, the setting value C ₂ of the wire feed speed, and the welding speed G) is completed.

When the setting of the welding conditions is completed, arc welding to the workpiece W is performed again under these conditions. At this time, since the set value V of the welding voltage is set based on the thickness t of the workpiece, it is a value that does not cause the workpiece W to be perforated. Further, the hole set value C ₂ of the wire feed rate that is smaller than the limit value C _1, the welding wire can be prevented contact between the P and the workpiece W, the workpiece W becomes less weld metal by spatter scatter The situation where light occurs can be prevented. As described above, according to the present invention, both the voltage value and the wire feed speed (current value) can be set appropriately, and the punching of the workpiece can be reliably prevented.

The method for setting the welding conditions as described above is not limited to the initial setting, and can be applied to feedback control for correcting the wire feed speed while performing arc welding. That is, since the arc welding apparatus 1 has a constant voltage characteristic, the welding voltage for some reason is out of the set value V, the current value, i.e., the welding voltage by varying the wire feed speed from the set value C ₂ An attempt is made to maintain the set value V. When the workpiece W is a thin plate as in this embodiment, the welding voltage set value V is set to be small and the distance between the welding wire P and the workpiece W is small, so that the welding voltage is kept constant. For this reason, when the wire feed speed is increased, the welding wire P and the workpiece W are likely to contact each other. Therefore, the above welding condition setting method may be applied to correct the welding conditions during arc welding. Specifically, when the fact that the welding wire P and the workpiece W during the arc welding abuts detection unit detects and corrects to slow the set value C ₂ of the wire feed speed. Thereby, contact | abutting with the welding wire P and the workpiece | work W is avoided in subsequent arc welding, and the punching of the workpiece | work W can be prevented more reliably. The correction of the wire feed speed may be performed every time the welding wire P and the work W come into contact with each other, or may be performed when the welding wire P and the work W come into contact with each other a predetermined number of times.

  The welding condition setting method as described above may be performed on the sample workpiece W or may be performed on the workpiece W used as a product.

DESCRIPTION OF SYMBOLS 1 Arc welding apparatus 10 Torch 11 Holding part 12 Tube 13 Elastic member 20 Wire supply part 30 Power supply 40 Control part 41 Voltage control part 42 Wire feed speed control part 43 Temporary setting means 44 Correction means C ₀ Temporary setting value C of wire feed speed ₁ set value of the limit value C ₂ wire feed speed setting value G welding speed P welding wire V welding voltage wire feed speed W workpiece

Claims (2)

An arc welding method using a consumable electrode type arc welding apparatus having constant voltage characteristics,
A step of acquiring a set value of the welding voltage based on a thickness of the workpiece, a step of acquiring a temporary set value of the wire feed speed, and a set value of the welding voltage and the temporary set value of the wire feed speed are input. A step of performing arc welding on the workpiece using the arc welding apparatus, and detecting that the tip of the wire is in contact with the workpiece based on a bending state of the welding wire inside the torch while performing the arc welding , And a step of correcting the wire feed speed so that the wire feed speed becomes smaller than the moment when the tip of the wire comes into contact with the workpiece. A consumable electrode type arc welding apparatus having constant voltage characteristics,
A torch, a wire supply unit for supplying a welding wire to the torch, a voltage control unit to which a set value of a welding voltage acquired based on a plate thickness of the workpiece is input, and a wire feed rate of the wire supply unit is controlled. A wire feed speed control unit, and a detection unit for detecting the bending state of the welding wire inside the torch while performing arc welding,
The wire feed speed control unit detects that the tip of the wire is in contact with the workpiece based on the bending state of the welding wire detected by the detection unit, and the wire feed rate at the moment when the tip of the wire contacts the workpiece An arc welding apparatus having correction means for correcting the wire feed speed so as to be smaller than the above .

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