JP5120073B2 - AC pulse arc welding apparatus and control method - Google Patents

Description

  The present invention relates to an AC pulse arc welding apparatus and a control method thereof.

Conventional AC pulse arc welding equipment performs penetration control and scale shape creation by combining AC and DC pulses with a base current of positive polarity (EN) and a peak current of reverse polarity (EP) ( For example, Patent Document 1).
FIG. 4 shows a welding current waveform of conventional AC pulse arc welding. As can be seen from the figure, the welding current is output with a pulse current 101 and a base current 102 in a reverse polarity state. And it switches to positive polarity, the base current 103 is output, and this is repeated periodically.
Japanese Patent Laid-Open No. 10-328837

Originally, AC welding is mainly intended to control the penetration of the workpiece by adjusting the heat input to the workpiece in the reverse polarity (EP) state and the melting of the wire in the positive polarity (EN) state. .
However, in the conventional AC pulse arc welding apparatus, the peak pulse current (EP pulse current) flows in the reverse polarity state, and the base current (EN base current) flows in the positive polarity state. If the welding wire material is sensitive to heat input, that is, the melting point is low, the penetration control can be performed, but it is not very sensitive to heat input in the positive state like stainless steel or iron, that is, For welding wire materials having a high melting point, there is a problem that sufficient penetration control cannot be performed.
In addition, in the experiments conducted by the present applicant, when performing pulse arc welding by outputting a pulse current only during positive polarity in order to control penetration into stainless steel or iron, huge droplets grow on the tip of the wire. As a result, poor welding occurred.
The present invention has been made in view of such problems, and an object of the present invention is to provide a welding apparatus and a control method for performing sufficient penetration control on a stainless steel or iron welding wire.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 is an AC pulse arc welding apparatus for welding an iron or stainless steel thin plate by alternately applying a positive current and a reverse polarity current between a consumable electrode and a welding object. The first step of outputting the pulse current is performed by switching to the second step, the second step of generating the short circuit by outputting the base current is performed, and then the third step of outputting the pulse current by switching to the positive polarity is performed. The control means for executing the fourth step of outputting the base current is provided.
The invention according to claim 2 is characterized in that the kind of the shielding gas is an argon ratio of 80% to 98%.
According to a third aspect of the present invention, there is provided a control method for an AC pulse arc welding apparatus for welding a thin plate of iron or stainless steel by alternately applying a positive current and a reverse polarity current between a consumable electrode and a welding target. The first step of outputting the pulse current by switching to the reverse polarity is executed, the second step of generating the short circuit by outputting the base current, and then the third step of outputting the pulse current by switching to the positive polarity And the fourth step of outputting the base current is executed.
The invention according to claim 4 is characterized in that the kind of the shielding gas is an argon ratio of 80% to 98%.

According to the present invention, when a thin plate of stainless steel or iron is to be welded, the peak current of the pulse is generated even in the positive polarity (EN) state, so that sufficient penetration control can be performed. That is, the penetration can be made shallow by the effect of positive polarity (EN) that suppresses heat input to the workpiece by melting only the wire. In addition, the pulse current and base current are output only once in the positive polarity (EN) state, and the pulse current is output immediately after switching to the reverse polarity (EP). Will not grow.
In addition, since the pulse current (EP pulse current) is output in the reverse polarity (EP) state, the base current (EP base current) is output and short-circuited immediately, so that the droplet transfer at the wire tip can be performed. Therefore, stable welding can be performed by preventing welding defects (for example, undercut defects, defects in which the upper plate is chipped) generated at a large peak current with reverse polarity (EP).

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

FIG. 1 is a circuit diagram of an arc welding apparatus of the present invention.
In the figure, reference numeral 10 denotes a control CPU device which gives commands to an inverter 3 and an EP / EN switching device 9 which will be described later. Further, information on the welding voltage and the welding current is obtained from the voltage detection sensor 7 and the current detection sensor 8, respectively.
Reference numeral 1 denotes a three-phase AC power source. The three-phase alternating current output from the three-phase alternating current power source 1 becomes a direct current by the converter 2 and is converted into a high-frequency current by the inverter 3. The inverter 3 operates according to a command from the control CPU device 10. Further, the high frequency current converted by the inverter 3 is converted into a current and voltage by the transformer 4, converted to a direct current by the converter 5, and further smoothed by the reactor 6.
Reference numeral 9 denotes an EP / EN switching device to which a current smoothed by the reactor 6 is input, and a current is passed between the welding wire 13 and the workpiece 12 so as to have reverse polarity (EP) or positive polarity (EN). Here, the reverse polarity (EP) is a state in which the welding wire 13 is positive and the workpiece 12 is negative, and the positive polarity (EN) is a state in which the welding wire 13 is negative and the workpiece 12 is positive.
The welding wire 13 (consumable electrode) is fed by the wire feeding device 14.

  The welding current is controlled by the inverter 3 controlling the output current based on a command from the control CPU device 10. Further, switching between reverse polarity (EP) and positive polarity (EN) is performed by the EP / EN switching device 9 reversing the direction in which the current flows in accordance with a command from the control CPU device 10.

Next, welding current control according to the welding apparatus of the present invention will be described. In this embodiment, the workpiece to be welded is stainless steel with a plate thickness of 1 mm, and the material of the welding wire is stainless steel.
FIG. 2 shows a welding current / voltage waveform according to the AC pulse arc welding apparatus of the present invention. FIG. 2A shows the welding current waveform, and FIG. 2B shows the welding voltage waveform, which are data detected by the current detection sensor 8 and the voltage detection sensor 7, respectively. Moreover, FIG. 3 has shown the state of the droplet of the welding wire front-end | tip. The welding conditions are as described in the figure.
The following description will be made separately for each of the periods A to D shown in FIG. 2, but the EP base current 19 is opposite to the base current and EP pulse current 16 that are output in the reverse polarity (EP) state. The pulse current output in the polarity (EP) state is shown. The EN base current 15 is the base current output in the positive polarity (EN) state, and the EN pulse current 18 is the positive polarity ( The pulse current output in the state of (EN) is shown.

(1) Period A
A command is given from the control CPU device 10 to the EP / EN switching device 9 to switch to the reverse polarity (EP) and output an EP pulse current 16. When the welding current is switched from the EN base current 15 output before the period A to the EP pulse current 16, the droplets at the tip of the welding wire are constricted as shown in FIG. 3A.

(2) Period B
When the EP base current 19 is output, a short circuit occurs at a portion 17 so that the droplet at the tip of the welding wire smoothly moves to the molten pool as shown in FIG. 3B.
Here, when the output time or the current value of the EP pulse current 16 is increased, the droplet detachment from the welding wire tip occurs and no short circuit occurs. Therefore, since spatter due to a short circuit does not occur, it is generally preferable to increase the output time or current value of the EP pulse current 16. However, when the object to be welded is a thin plate as in this embodiment, the output time of the EP pulse current 16 or the current value is limited to prevent welding failure such as burnout, and the reverse polarity (EP) state is maintained. Sometimes, a short circuit is generated to transfer the droplets.

(3) Period C
When the short circuit is released and an arc is generated, a command is given from the control CPU device 10 to the EP / EN switching device 9 to switch from reverse polarity (EP) to positive polarity (EN), and an EN pulse current 18 is output. The EN pulse current 18 rapidly melts the tip of the welding wire and forms droplets at the tip of the welding wire as shown in FIG. 3C.
The welding apparatus according to the present invention is different from the conventional AC pulse arc welding apparatus in this period. That is, when switching from the reverse polarity (EP) to the positive polarity (EN) state, the base current is conventionally output, but in the present invention, the pulse current (EN pulse current 18) is output.
During this period, a pulse current (EN pulse current 18) is output when switching from reverse polarity (EP) to positive polarity (EN), so heat input to the work is suppressed (reduces). ), Even if it is iron or stainless steel, the amount of penetration can be suppressed sufficiently.

(4) Period D
When the EN base current 15 is output, a droplet formed on the tip of the welding wire grows as shown in FIG. 3D.
(5) Thereafter, welding is performed by repeating the cycle (periods A to D).

  As described above, according to this embodiment, it is possible to prevent welding defects and perform stable welding on a stainless steel or iron thin plate.

  In addition, not only the said Example but a workpiece | work can be implemented similarly if it is a thin plate about 1.5 mm or less. Furthermore, the material of the workpiece may be iron instead of stainless steel. Moreover, the kind of shielding gas should just be 80 to 98% of argon ratios.

The circuit diagram of the arc welding apparatus which shows 1st Example of this invention (A) Welding current waveform (b) Welding voltage waveform according to the welding apparatus of the present invention Explanatory drawing showing the state of the droplet at the tip of the welding wire Welding current waveform related to conventional AC pulse arc welding equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2 Converter to convert from alternating current to direct current 3 Inverter to convert to high frequency 4 Transformer 5 Converter to convert from alternating current to direct current 6 Reactor to smooth current 7 Voltage detection sensor 8 Current detection sensor 9 EP / EN Switching device 10 CPU device for control 11 Power feeding device 12 to welding wire 12 Work piece 13 Welding wire (consumable electrode)
14 Welding wire feeder 15 EN base current 16 EP pulse current 18 EN pulse current 19 EP base current

Claims (4)

In the AC pulse arc welding apparatus for welding a thin plate of iron or stainless steel by alternately applying a positive current and a reverse polarity current between the consumable electrode and the welding object,
The first step of outputting the pulse current by switching to the reverse polarity is executed, the second step of generating the short circuit by outputting the base current, and then the third step of outputting the pulse current by switching to the positive polarity. An AC pulse arc welding apparatus comprising control means for executing and executing a fourth step of outputting a base current. 2. The AC pulse arc welding apparatus according to claim 1, wherein the shielding gas has an argon ratio of 80% to 98%. In the control method of the AC pulse arc welding apparatus for welding a thin plate of iron or stainless steel by alternately applying a positive current and a reverse polarity current between the consumable electrode and the welding object,
Execute the first step of switching to reverse polarity and outputting pulse current,
Execute a second step of generating a short circuit by outputting a base current;
After that, execute the third step of switching to positive polarity and outputting the pulse current,
A control method for an AC pulse arc welding apparatus, wherein a fourth step of outputting a base current is executed. 4. The control method for an AC pulse arc welding apparatus according to claim 3, wherein the type of the shielding gas is an argon ratio of 80% to 98%.

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