JP2012096276A - Ac pulse arc welding method, ac pulse arc welding device, and ac pulse arc welding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC pulse arc welding method, welding device and welding system which can adequately adjust heat input to a workpiece to be welded.SOLUTION: One cycle of welding is repeated which consists of: a reverse polarity period, in which a first predetermined number of reverse polarity pulses, including a peak period Tpp in which a peak current Ipp is turned on; and a forward polarity period, in which a second predetermined number of forward polarity pulses, including a peak period Tpn in which a peak current Ipn is turned on in forward polarity and a base period Tbn in which a base current Ibn is turned on in forward polarity, in reverse polarity and a base period Tbp in which a base current Ibp is turned on in reverse polarity, are repeated. The peak period Tpn is shorter than the peak period Tpp. The absolute value of the peak current Ipn is smaller than the absolute value of the peak current Ipp.

Description

  The present invention relates to an AC pulse arc welding method, an AC pulse arc welding apparatus, and an AC pulse arc welding system.

In the conventional AC pulse arc welding equipment, a regular wave shape called penetration control or a scale-shaped bead is formed by combining an AC pulse with a positive polarity (EN) as the base current and a reverse polarity (EP) as the peak current. Some have created bead appearances (for example, Patent Document 1 and Patent Document 2).
FIG. 5 shows a welding current waveform of conventional AC pulse arc welding. As can be seen from the figure, the pulse current Ipp and the base current Ibp are output in the reverse polarity state of the welding current. Thereafter, the polarity is switched to the positive polarity, and the base current Ibn is output. This series of waveform patterns is periodically repeated. In FIG. 5, this period is Tf.
In the conventional AC pulse arc welding, the base material is adjusted by changing the positive current ratio by adjusting the base current Ibn in the positive polarity state (Ten in FIG. 5) and the base period Tbn (the time during which the base current Ibn flows). The heat input to (work) can be adjusted.

Japanese Patent Laid-Open No. 10-328837 JP 2010-75983 A

Originally, AC welding has the main purpose of controlling penetration into the workpiece by adjusting the heat input to the workpiece in the reverse polarity (EP) state and the melting of the welding wire in the positive polarity (EN) state. It is said.
In AC pulse arc welding equipment, peak pulse current (EP pulse current) flows in the reverse polarity state, and base current (EN base current) flows in the positive polarity state.
If the material of the welding wire or workpiece is sensitive to heat input in a positive polarity state such as aluminum, that is, if the material has a low melting point, the heat input to the workpiece can be adjusted by adjusting the positive polarity ratio.
However, when stainless steel or iron is not very sensitive to heat input in the positive state, that is, when the material has a high melting point, there is a problem that heat input to the workpiece cannot be adjusted appropriately. .
The present invention has been made in view of such problems, and for a stainless steel or iron welding wire or workpiece, the number of pulses of the reverse polarity pulse current group and the number of pulses of the positive pulse current group are adjusted, Furthermore, the time to flow the peak current with the positive polarity is shorter than the time to flow the peak current with the reverse polarity, and the absolute value of the peak current with the positive polarity is smaller than the absolute value of the peak current with the reverse polarity. An object of the present invention is to provide an AC pulse arc welding method, a welding apparatus, and a welding system capable of appropriately adjusting heat input.

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 method in which welding is performed by alternately applying a positive current and a reverse polarity current between a consumable electrode and a welding object. A reverse polarity period in which a reverse polarity pulse including a first peak period in which a peak current is passed and a first base period in which a first base current is passed with a reverse polarity is repeated for a first predetermined number of times; A positive polarity period in which a positive polarity pulse including a second peak period in which a second peak current is passed and a second base period in which a second base current is passed with a positive polarity is repeated a second predetermined number of times. Welding is repeated as one cycle, and the second peak period is shorter than the first peak period, and the absolute value of the second peak current is smaller than the absolute value of the first peak current. It is characterized by that.

  The invention according to claim 2 changes the ratio of positive current and reverse polarity current by changing at least one of the first predetermined number of times and the second predetermined number of times, It is characterized by adjusting heat input.

  According to a third aspect of the present invention, at least one of the peak current value, the peak period, the base current value, and the base period is changed in accordance with the change of the first predetermined number of times or the second predetermined number of times. It is characterized by changing.

  According to a fourth aspect of the present invention, there is provided an AC pulse arc welding apparatus that performs welding by alternately applying a positive current and a reverse polarity current between a consumable electrode and a welding object, and the first polarity is reversed. A reverse polarity period in which a reverse polarity pulse including a first peak period in which a peak current is passed and a first base period in which a first base current is passed with a reverse polarity is repeated for a first predetermined number of times; A positive polarity period in which a positive polarity pulse including a second peak period in which a second peak current is passed and a second base period in which a second base current is passed with a positive polarity is repeated a second predetermined number of times. Welding is repeated as one cycle, and the second peak period is shorter than the first peak period, and the absolute value of the second peak current is smaller than the absolute value of the first peak current. It is characterized by that.

  The invention according to claim 5 changes the ratio of positive current and reverse polarity current by changing at least one of the first predetermined number of times and the second predetermined number of times, It is characterized by adjusting heat input.

  According to a sixth aspect of the present invention, at least one of the peak current value, the peak period, the base current value, and the base period is changed in accordance with the change of the first predetermined number of times or the second predetermined number of times. It is characterized by changing.

  The invention according to claim 7 is the peak current value, the peak period, the base current value, the base period, the first predetermined number of times, the second predetermined number of times, the ratio of the positive current, and the inverse At least one of the polar current ratios is displayed outside.

  According to an eighth aspect of the present invention, there is provided the AC pulse arc welding apparatus according to any one of the fourth to seventh aspects, and a robot that moves the tip of the consumable electrode relative to the welding object. It is provided with.

According to the present invention, when a material having a high melting point such as stainless steel or iron is to be welded, the peak current conduction time in the positive polarity (EN) state is longer than the peak current conduction time in the reverse polarity (EP) state. By shortening and making the absolute value of the peak current value in the positive polarity (EN) state smaller than the absolute value of the peak current value in the reverse polarity (EP) state, the number of positive polarity (EN) pulses is increased. Even so, the enlargement of the droplets at the tip of the welding wire is suppressed, the directivity of the arc can be ensured, and stable welding becomes possible.
Furthermore, by changing the number of pulses of reverse polarity (EP) and the number of pulses of positive polarity (EN) in various ways, the ratio of positive current and reverse polarity current can be changed to adjust the heat input in detail. Is possible.
Information such as peak current value, base current value, peak current period, base current period, number of pulses, positive current ratio, and reverse polarity current ratio in the positive polarity (EN) state and the reverse polarity (EP) state, respectively. By displaying, the operator can easily set or confirm parameters related to welding.

It is a schematic diagram which concerns on the alternating current pulse arc welding apparatus of this invention. (A) is a welding current waveform of AC pulse arc welding according to the present invention, and (b) is a welding voltage waveform. It is a macro photograph of the welding section which shows the amount of penetration to a base material. (A) has one reverse polarity (EP) pulse and one positive (EN) pulse; (b) has three reverse polarity (EP) pulses and positive (EN) pulses. (C) is the case where the number of reverse polarity (EP) pulses is one and the number of positive polarity (EN) pulses is three. It is a schematic diagram which concerns on the alternating current pulse arc welding system of this invention. It is a welding current waveform which concerns on the conventional alternating current pulse arc welding apparatus.

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

FIG. 1 is a schematic view showing a configuration of an AC pulse arc welding apparatus of the present invention.
In the figure, reference numeral 10 denotes a control unit which gives commands to an inverter 3 and an EP / EN switching unit 9 which will be described later, and controls their operations. Further, the control unit 10 obtains values of the welding voltage and the welding current 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 is converted into direct current by the converter 2 and further converted into high frequency current by the inverter 3. The inverter 3 controls the output waveform in accordance with a command from the control unit 10. The high frequency current converted by the inverter 3 is converted into a direct current by the converter 5 after the current and voltage are changed by the transformer 4, and further smoothed by the reactor 6.
The current smoothed by the reactor 6 is input to the EP / EN switching unit 9. The EP / EN switching unit 9 switches the polarity so as to be reverse polarity (EP) or positive polarity (EN) when a current is passed between the welding wire 22 and the workpiece W. A current is supplied to the welding wire 22 via a power supply device (contact tip) in the welding torch 21.
The reverse polarity (EP) means that the welding wire 22 is positive (plus) and the workpiece W is negative (minus), and the positive polarity (EN) means that the welding wire 13 is negative (minus) and the workpiece W is negative. Means a positive (plus) state.
The welding wire 22 (consumable electrode) is fed toward the workpiece W by the wire feeding device 23. Although omitted in FIG. 1, the shield gas is supplied to the welding torch during the actual welding operation, and is ejected from the tip of the welding torch toward the workpiece W.
In this embodiment, iron or stainless steel is assumed as the workpiece W.

  The welding current is controlled by the inverter 3 controlling the output current based on a command output from the control unit 10. Further, switching between the reverse polarity (EP) and the positive polarity (EN) is performed by the EP / EN switching unit 9 reversing the direction in which the current flows based on a command output from the control unit 10. Since the switching method between the reverse polarity (EP) and the positive polarity (EN) is a known technique, a detailed description thereof will be omitted.

In the present embodiment, a portion surrounded by a broken line in FIG. The welding power source 15 is connected to an external controller 30, and the external controller 30 gives a command to the welding power source 15 and monitors the welding state output from the welding power source 15.
When welding is performed, the external controller 30 gives a welding voltage and welding current command to the welding power source 15. The welding voltage and welding current commands given by the external controller 30 to the welding power source 15 are rough values such as the average voltage value during welding and the absolute value of the current value. -A welding current and a welding voltage are given between workpiece | work, and this is appropriately controlled per microsecond-ms, and the tip part of welding wire 22 is melted and welding is performed.

The welding power source 15 includes a storage unit 11. The storage unit 11 is configured by a rewritable nonvolatile memory, for example, and stores various parameters related to welding. The welding power source 15 further includes an operation unit 12a and a display unit 12b. The operation unit 12a includes a plurality of keys and switches, and the display unit 12b is realized by a liquid crystal panel or the like.
Information such as the welding voltage during the welding operation, the command value of the welding current, the detection value by the voltage detection sensor 7 and the current detection sensor 8 can be displayed on the display unit 12b. It is also possible to read out the content of the parameter designated by the operator by key operation from the storage unit 11 and display it on the display unit 12b, or to change the content of the parameter. Alternatively, the operation unit 12a and the display unit 12b may be configured by a touch panel so that both are integrated.

Next, the welding current control of the present invention will be described.
FIG. 2 shows a welding current and a welding voltage by the AC pulse arc welding apparatus of the present invention. FIG. 2A shows a welding current waveform detected by the current detection sensor 8, and FIG. 2B shows a welding voltage waveform detected by the voltage detection sensor 7. Hereinafter, the pulse arc welding according to the present invention will be described with reference to FIG.

During Tep, which is the period of the reverse polarity (EP) state, the reverse polarity (EP) peak current Ipp is output during the reverse polarity (EP) peak period Tpp, and the reverse polarity during the reverse polarity (EP) base period Tbp. (EP) The base current Ibp is output. The peak period refers to the time during which the peak current is applied, and the base period refers to the time during which the base current is applied.
The peak current Ipp and the base current Ibp are set to one reverse polarity (EP) pulse, and a predetermined number Np of reverse polarity (EP) pulses are output during the reverse polarity (EP) period. Although three reverse polarity (EP) pulses are output in FIG. 2, the number of pulses can be changed as will be described later.

Thereafter, a command is given from the control unit 10 to the EP / EN switching unit 9 to switch the polarity to positive polarity (EN).
During Ten which is the period of the positive polarity (EN) state, the positive polarity (EN) peak current Ipn is output during the positive polarity (EN) peak period Tpn, and the positive polarity during the positive polarity (EN) base period Tbn. (EN) The base current Ibn is output. Here, the positive polarity (EN) peak period Tpn is made shorter than the reverse polarity (EP) peak period Tpp, and the absolute value of the positive polarity (EN) peak current Ipn is made smaller than the reverse polarity (EP) peak current Ipp.

  The peak current Ipn and the base current Ibn are set to one positive (EN) pulse, and a predetermined number Nn of positive (EN) pulses are output during the positive (EN) period. In FIG. 2, three positive (EN) pulses are output, but the number of pulses can be changed as will be described later.

  Thereafter, a command is given from the control unit 10 to the EP / EN switching unit 9 to switch the polarity to the reverse polarity (EP) again. With such a cycle as one AC period (Tf in FIG. 2), welding is performed by repeating a series of cycles.

  FIG. 2 shows a case where the rising and falling edges of the reverse polarity (EP) peak current Ipp and the positive polarity (EN) peak current Ipn are steep and become a rectangular wave. However, one or both of rising and falling of the peak current may be made gentle so as to have a predetermined slope so that a trapezoidal wave is formed.

  In the positive polarity (EN) period Ten, the droplet at the wire tip tends to be enlarged, but the positive polarity (EN) peak period Tpn is shorter than the reverse polarity (EP) peak period Tpp, and the positive polarity (EN) peak. By making the absolute value of the current Ipn smaller than the absolute value of the reverse polarity (EP) peak current Ipp, enlargement of droplets at the tip of the welding wire can be suppressed. As a result, the directivity of the arc can be secured and stable welding can be achieved.

Reverse polarity (EP) peak period Tpp, reverse polarity (EP) peak current Ipp, reverse polarity (EP) base period Tbp, reverse polarity (EP) base current Ibp, positive polarity (EN) peak period Tpn, positive polarity (EN) For peak current Ipn, positive polarity (EN) base period Tbn, and positive polarity (EN) base current Ibn, experiments were performed in advance with appropriate values according to various welding voltages and welding current commands given from external controller 30. Database.
Also in this case, the positive polarity (EN) peak period Tpn is made shorter than the reverse polarity (EP) peak period Tpp, and the absolute value of the positive polarity (EN) peak current Ipn is made smaller than the reverse polarity (EP) peak current Ipp. Try to keep the conditions.
The accumulated data is stored as a parameter in the storage unit 11, and the values of the parameters corresponding to the welding voltage and welding current commands given from the external controller 30 are read out from the storage unit 11 during the actual welding operation. The peak period, base period, peak current, and base current are determined according to the content and welding is performed.

Further, the number of reverse polarity (EP) pulses (Np) and the number of positive polarity (EN) pulses (Nn) are also determined by setting values stored in advance in the storage unit 11 as parameters.
The parameters related to the peak period, the base period, the peak current, the base current, and the parameters related to the number of pulses can be changed by the operator by operating the operation unit 12a.

  Here, the ratio Ren of the positive polarity (EN) current when the reverse polarity (EP) peak current and the positive polarity (EN) peak current are rectangular waves as shown in FIG. 2 is defined by the following equation.

Ren represents the ratio of the welding current of the positive polarity (EN) period Ten to the average value of the absolute value of the welding current.
The control unit 10 can calculate Ren based on the current parameter setting and display it on the display unit 12b. Prior to the welding operation, the operator can check Ren while changing parameters related to the peak period, base period, peak current and base current, and parameters related to the number of pulses, and can appropriately adjust and set the parameters.
If the ratio of the reverse polarity (EP) current is Rep, Rep can be easily obtained by the following equation.

  Therefore, Rep may be displayed on the display unit 12b instead of Ren or in parallel with Ren.

In addition to individually setting parameters related to peak period, base period, peak current and base current, and parameters related to the number of pulses, the peak period, base period, and peak current are set according to the number of pulses set by the operator. Alternatively, the welding power source 15 may automatically adjust parameters relating to the base current.
For example, every time the operator operates the parameter to increase the number of positive polarity (EN) pulses (Nn) by one, the control unit 10 automatically increases or reverses the reverse polarity (EP) peak period Tpp by a predetermined time. The absolute value of the polarity (EP) peak current Ipp is increased by a predetermined value, the positive polarity (EN) peak period Tpn is shortened by a predetermined time, or the absolute value of the positive polarity (EN) peak current Ipn is increased by a predetermined value. Or make it smaller.
By doing this, even inexperienced workers can realize appropriate welding conditions by changing the number of pulses without being aware of welding parameters such as peak period, base period, peak current and base current. be able to.

FIG. 3 is a macrograph of the weld cross section showing the change in penetration into the workpiece when the number of reverse polarity (EP) pulses Np and the number of positive polarity (EN) pulses Nn are changed.
In the example of FIG. 3, the workpiece is iron with a thickness of 2 mm, the material of the welding wire is iron, and the welding joint is a butt joint. Further, argon gas having an argon ratio of about 80 to 98% was used as the shielding gas.

FIG. 3A is a photograph showing the penetration into the workpiece when the number of reverse polarity (EP) pulses Np is one and the number of positive polarity (EN) pulses Nn is one.
FIG. 3B is a photograph when the number of reverse polarity (EP) pulses Np is three and the number of positive polarity (EN) pulses Nn is 1, that is, when the positive polarity (EN) current ratio (Ren) is reduced. It is. Compared to the penetration in FIG. 3A, the penetration into the workpiece is deeper.
FIG. 3 (c) is a photograph when the number of reverse polarity (EP) pulses Np is 1, and the number of positive polarity (EN) pulses Nn is 3, that is, when the positive polarity (EN) current ratio (Ren) is increased. It is. Compared to the penetration in FIG. 3A, the penetration into the workpiece is shallower.
In addition, although the workpiece | work was iron in the example of FIG. 3, the material of a workpiece | work may be stainless steel. Also, the plate thickness may be thicker than the example (2 mm) in FIG.

  As described above, according to the present invention, the peak period, the base period, the peak current, the base current, the number Np of reverse polarity (EP) pulses, and the positive polarity (EN) pulse are applied to a stainless steel or iron workpiece. By changing the number Nn in various ways, stable welding can be performed by changing the ratio Ren of positive current (EN) current and adjusting the amount of penetration of the welding wire into the workpiece.

  FIG. 4 is a schematic diagram showing an AC pulse arc welding system configured by combining the pulse arc welding apparatus described in Embodiment 1 with a robot 26 having a welding torch attached to the tip. The feeding device 23 is mounted on the robot 26 and feeds the welding wire built in the welding wire feeding unit 24 to the welding torch 21 at the tip of the robot. Although omitted in FIG. 1, the shield gas is supplied from the gas cylinder 25 to the welding torch 21 in FIG. 4.

Further, the external controller 30 in FIG. 1 functions as a robot controller in FIG. That is, welding can be performed by controlling the robot 26 to change the position and posture of the welding torch 21 at the tip in various ways and moving the tip of the welding torch so as to draw a desired welding line with respect to the workpiece W. Further, a welding command is given to the welding power source 15 and the welding status is monitored.
The robot controller 30 is connected to the teaching device 31. The teaching device 31 includes an operation unit 31a composed of a plurality of keys and switches, and a display unit 31b realized by a liquid crystal panel or the like.
In the first embodiment, information on welding is displayed and various parameters are displayed and changed by the operation unit 12a and the display unit 12b of the welding power source 15, but in this embodiment, the operation unit 31a and display of the teaching device 31 are displayed. A similar function can be realized by the unit 31b. That is, the robot controller 30 communicates with the control unit 10 of the welding power source 15, reads the values of the voltage sensor 7 and the current sensor 8 via the control unit 10, and reads and writes the contents of the storage unit 11. Can do.

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2 Converter 3 Inverter 4 Transformer 5 Converter 6 Reactor 7 Voltage detection sensor 8 Current detection sensor 9 EP / EN switching part 10 Control part 11 Storage part 12a Operation part 12b Display part 15 Welding power supply 21 Welding torch 22 Welding wire (Consumable electrode)
23 Welding wire feeding device 24 Welding wire feeding unit 25 Gas cylinder 26 Robot 30 External controller (robot controller)
31 Teaching device 31a Operation unit 31b Display unit W Work Ipp Reverse polarity pulse current Ibp Reverse polarity base current Ipn Positive polarity pulse current Ibn Positive polarity base current Tpp Reverse polarity peak period Tbp Reverse polarity base period Tpn Positive polarity peak period Tbn Positive polarity base Period Temp Reverse polarity period Ten Positive polarity period Tf 1 AC cycle

Claims (8)

In the AC pulse arc welding method of performing welding by alternately applying a positive current and a reverse polarity current between the consumable electrode and the welding object,
Reverse polarity that repeats a reverse polarity pulse including a first peak period in which a first peak current is passed in reverse polarity and a first base period in which a first base current is passed in reverse polarity for a first predetermined number of times Period,
Positive polarity in which a positive pulse including a second peak period in which a second peak current is passed with positive polarity and a second base period in which a second base current is passed with positive polarity is repeated a second predetermined number of times Period,
, Welding is repeated in one cycle,
The second peak period is shorter than the first peak period;
An AC pulse arc welding method, wherein an absolute value of the second peak current is smaller than an absolute value of the first peak current.   The ratio of the positive current and the reverse polarity current is changed by changing at least one of the first predetermined number of times and the second predetermined number of times, and the heat input to the welding object is adjusted. The AC pulse arc welding method according to claim 1.   The at least one of the peak current value, the peak period, the base current value, and the base period is changed in accordance with the change of the first predetermined number of times or the second predetermined number of times. 2. The AC pulse arc welding method according to 2. In an AC pulse arc welding apparatus that performs welding by alternately applying a positive current and a reverse polarity current between a consumable electrode and a welding object,
Reverse polarity that repeats a reverse polarity pulse including a first peak period in which a first peak current is passed in reverse polarity and a first base period in which a first base current is passed in reverse polarity for a first predetermined number of times Period,
Positive polarity in which a positive pulse including a second peak period in which a second peak current is passed with positive polarity and a second base period in which a second base current is passed with positive polarity is repeated a second predetermined number of times Period,
, Welding is repeated in one cycle,
The second peak period is shorter than the first peak period;
An AC pulse arc welding apparatus, wherein an absolute value of the second peak current is smaller than an absolute value of the first peak current.   The ratio of the positive current and the reverse polarity current is changed by changing at least one of the first predetermined number of times and the second predetermined number of times, and the heat input to the welding object is adjusted. The AC pulse arc welding apparatus according to claim 4.   The at least one of the peak current value, the peak period, the base current value, and the base period is changed in accordance with the change of the first predetermined number of times or the second predetermined number of times. 5. The AC pulse arc welding apparatus according to 5.   At least one of the peak current value, the peak period, the base current value, the base period, the first predetermined number of times, the second predetermined number of times, the positive current ratio, and the reverse polarity current ratio 6. The AC pulse arc welding apparatus according to claim 5, wherein: AC pulse arc welding apparatus according to any one of claims 4 to 7,
An AC pulsed arc welding system comprising a robot that moves the tip of the consumable electrode relative to the welding object.