JP2733624B2 - Pulse arc welding method and pulse arc welding apparatus using this method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improved pulse arc welding method and a pulse arc welding apparatus using the method.

[Prior art] In this type of welding method, a phenomenon in which a welding wire melts and shifts to a base metal occurs discontinuously at a critical current value, so that it is suitable for a base metal having a small thickness. In order to perform a proper welding, it is customary to carry out welding by applying a welding current in which a pulse current is superimposed on a base current equal to or less than a critical current.

FIG. 7 is a block diagram showing the configuration of such a pulse arc welding apparatus. 101 is a transformer for stepping down the AC voltage input to the terminals TIN, TIN, and 102 is an AC stepped down by the transformer 101. Rectifier circuit 103 for rectification, according to a control signal from drive circuit 107, terminal from rectifier circuit 102
A switching circuit for controlling a welding current supplied to a welded part (not shown) as a load through TOUT; a current detection circuit for detecting a current level signal corresponding to the welding current;
Is an arc current error amplification circuit that calculates an error between the setting signal from the arc current setting circuit 105 and the current level signal detected by the current detection circuit 104 and outputs a control signal to the drive circuit 107. The feedback control is performed so that the welding current to be supplied always corresponds to the pulse arc current reference waveform obtained by superimposing the pulse current on the base current set by the arc current setting circuit 105, so that stable welding is performed. Have been.

However, in such a pulse arc welding apparatus, the optimal current level in the normal welding state is uniquely determined by the arc current setting circuit 105.
When welding is performed using an aluminum wire, a copper alloy wire, or the like having higher conductivity than iron, stainless steel, and the like, sufficient heat cannot be applied to the welding wire, and arc starting cannot be performed.

Also, if the arc length is shortened due to the shape of the base material during welding, or if the welding wire and the base material are short-circuited, the arc re-enters due to the high conductivity of the welding wire. Heat was not obtained, and welding defects occurred.

[Problems to be Solved by the Invention] The present invention proposed in view of the above-mentioned circumstances, when a wire having high conductivity such as aluminum is used, an arc is generated at the time of arc start or short-circuit with a base material. It is an object of the present invention to provide a pulsed arc welding method capable of performing a stable welding by immediately shifting to an arc state even when the welding is stopped.

Another object of the present invention, which is proposed at the same time, is to provide a pulse arc welding apparatus capable of performing stable welding by using the above-described pulse arc welding method.

[Means for Solving the Problems] The present invention according to claim 1, proposed to achieve the above object, supplies a pulsed arc welding current, in which a pulse current is superimposed on a predetermined base current, to a portion to be welded. When a short circuit occurs in the process of performing pulse arc welding, a first rising portion that rises sharply from the zero level and a first rising portion when the value at the first rising portion reaches a predetermined reference value. A current having a waveform constituted by a second rising portion increasing at a gentler slope than the portion is supplied to the portion to be welded, and when an arc is generated, the current is immediately switched to a pulse arc welding current for normal pulse arc welding. ing.

According to a second aspect of the present invention, the reference level of the first rising portion is set to an average value level of the pulse arc welding current.

According to a third aspect of the present invention, there is provided an arc / short circuit discriminating means for discriminating when an arc has occurred and when a short circuit has occurred continuously for a predetermined time, and outputting a discrimination signal. A pulse arc current control unit that generates a pulse arc current reference waveform that defines a welding current; and a short-circuit current control unit that generates a short-circuit current reference waveform that specifies a conduction current when a short circuit occurs. While outputting an arc current reference waveform, when a short circuit occurs, the short-circuit current control section switches and outputs the short-circuit current reference waveform, and performs conduction control based on these reference waveforms. A first rising portion where the short-circuit current reference waveform generated in the portion rises sharply from the zero level, and a value at the first rising portion reaches a predetermined reference value. In filtration, it is formed of a second rising portion which increases in a gradual slope than the first rising portion.

According to a fourth aspect of the present invention, the short-circuit current reference waveform is generated by a charge / discharge output of a capacitor.

According to a fifth aspect of the present invention, the short-circuit current reference waveform is generated by an output of a linear circuit.

The present invention described in claim 6 is configured so that the slope of the short-circuit current reference waveform can be arbitrarily variably set from outside.

[Operation] According to the present invention as set forth in claim 1, when a short circuit occurs in the process of conducting a pulse arc welding by applying a pulse arc welding current in which a pulse current is superimposed on a predetermined base current, the first At the rising portion, the current is increased steeply to rapidly apply heat to the welding wire to promote melting of the wire. When the current level at the first rising portion reaches a predetermined reference value, the first current is increased. In the second rising portion, which increases at a gentler slope than the rising portion, the spatter is prevented and sufficient heat is applied to the welding wire to easily generate an arc. And
Immediately after the arc is generated, the current is switched to the pulse arc welding current at the time of ordinary pulse arc welding, and the operation is shifted to pulse arc welding.

According to the second aspect of the present invention, since the reference level of the first rising portion is set to the average value level of the pulse arc welding current, the conduction current rises sharply from the zero level to the reference level when a short circuit occurs. Even though, the melting of the wire is promoted, but the generation of spatter is prevented.

According to the third aspect of the present invention, at the time of normal welding, the occurrence of an arc is determined by the arc / short circuit determination means,
On the basis of the pulse arc current reference waveform of the pulse arc current control unit, a welding current in which a pulse current is superimposed on a predetermined base current is supplied to a portion to be welded to perform pulse arc welding.

However, when the welding is started or when the arc is stopped due to the short-circuit between the welding wire and the base material, the arc / short-circuit determining means determines the short-circuit current and switches to the short-circuit current control section, based on the short-circuit current reference waveform. An electric current according to claim 1 or 2 is applied to the welded portion. When an arc is generated, the arc / short circuit discriminating means discriminates the pulse arc current and immediately switches to the pulse arc current control section, and applies a pulse arc welding current based on the pulse arc current reference waveform to perform pulse arc welding.

In the present invention according to claim 4, the short-circuit current reference waveform is:
Generated by the charge and discharge output of the capacitor.

According to the fifth aspect of the present invention, the short-circuit current reference waveform is:
Generated by the output of the linear circuit.

Further, according to the present invention, since the inclination of the short-circuit current reference waveform can be arbitrarily set variably from the outside, it is possible to perform energization control according to welding conditions.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 illustrates a pulse arc welding control method according to the present invention. When an arc is generated and welding is performed normally, a pulse current having a peak value of level I2 is previously added to a base current of level I1. Welding is performed by applying a pulse arc welding current superimposed every predetermined T period.
When a short circuit occurs during this welding process (including at the start of welding), the current is temporarily reduced to zero level, and then sharply rises to a current level of level I3 at the first rising portion (FIG. 1). I section), then enter the second rising section (see II section in FIG. 2), and
The energizing current is increased at a gentler slope than the rising portion of the current. Then, at the same time when the arc is generated, the waveform is switched to the original pulse arc current waveform (see the part III in FIG. 3), and thereafter, the pulse arc welding is continued again.

In such a pulse arc welding method, at the same time when a short circuit occurs, heat is rapidly applied to the welding wire at the first rising portion I to promote melting of the wire, and the second rising portion II
Therefore, since the generation of an arc is promoted while preventing the generation of a spatter, the spatter is prevented from being generated as in a case where a large current is immediately applied to generate an arc, and the safety is ensured in a short time. An arc can be generated.

Next, FIG. 2 is a block diagram showing the configuration of the pulse arc welding apparatus of the present invention.
Indicates an arc / short circuit discriminating means, B indicates a pulse arc current control unit, and C indicates a short circuit current control unit.

The output current control of this pulse arc welding apparatus is performed by pulse width modulation control (hereinafter referred to as PWM control) using an inverter circuit 3 which operates by receiving a supply of a smoothed DC power by rectifying an AC power supply by a rectifier circuit 1 and a smoothing capacitor 2. The output of the inverter circuit 3 is supplied to the welding portion D via the transformer 4 and the rectifier circuit 5. The welding part D is provided with a DC reactor 6 and a shunt 7. The output voltage of the DC reactor 6 is applied to an arc / short circuit discriminating circuit 8 of an arc / short circuit discriminating means A, and the generation of an arc in the welded portion is performed. The state is monitored, and a current level signal corresponding to the energizing current detected by one of the shunts 7 is a feedback signal to the pulse arc current control unit B and the short-circuit current control unit C.

The pulse arc current control unit B includes a pulse arc current waveform setting circuit 9b, a frequency setting circuit 9c, and a pulse arc current error amplifier circuit 9a, and outputs a pulse waveform having a repetition frequency set by the frequency setting circuit 9c. In addition to the current waveform setting circuit 9b, a pulse arc current reference waveform in which the pulse current is superimposed on the base current is generated, and this reference waveform and the current level signal from the shunt 7 are added to the pulse arc current error amplification circuit 9a, Feedback control is performed so that the current flowing through the welded portion always becomes a current based on the pulsed arc current reference waveform.

On the other hand, the short-circuit current control unit C
a, short-circuit current waveform generation circuit 10b and dI / dt mutation point setting circuit
The short-circuit current reference waveform is generated by adding the mutation level signal set by the dI / dt mutation point setting circuit 10c to the short-circuit current waveform generation circuit 10b, and the reference waveform and the current level from the shunt 7 are provided. In addition to the short-circuit current error amplifier 10a, feedback control is performed so that the current flowing through the welded portion always becomes a current based on the short-circuit current reference waveform.

In the present embodiment, the peak value of the pulse current of the pulse arc current waveform setting circuit 9b is determined by the welding current setting device 11, and the mutation level of the dI / dt mutation point setting circuit 10c is linked.

The welding current setter 11 simultaneously sends a setting signal to the wire feed control circuit 17 to regulate the speed at which the wire feed motor 16 is driven.

In the arc / short circuit discriminating circuit 8 constituting the arc / short circuit discriminating means A, the welding voltage supplied to the welding portion D via the reactor 6 is taken out.
And the voltage when short-circuited, and the welding wire 14
A determination signal is output according to the difference between the voltage value when an arc is generated apart from the power supply and when a short circuit occurs continuously for a predetermined period of time and when an arc is generated.

The inverter circuit 3 switches the DC current supplied to the transformer 4 by the control output from the PWM control circuit 12, and the PWM control circuit 12 receives the discrimination signal output from the short circuit / arc discrimination circuit 8 and performs a switching operation. The current waveform switching circuit 13 selectively controls the control signal of the pulse arc current error amplifier 9a of the pulse arc current control unit B when an arc occurs and the control signal of the short circuit current error amplifier 10a of the short circuit current control unit C when a short circuit occurs. Is being entered.

In FIG. 2, error amplifiers 9a and 10a are provided in each of the pulse arc current control section B and the short-circuit current control section C, and control signals output from these sections are switched by the current waveform switching circuit 13 to perform PWM control. Although it is configured to output to the circuit 12, it is not limited to such a configuration.For example, the current waveform switching circuit 13 switches and outputs the reference waveforms from the pulse arc current waveform setting circuit 9b and the short-circuit current waveform setting circuit 10b. It is also possible to adopt a configuration in which the switched reference waveform and the current level signal from the shunt 7 are received by the error amplifier circuit and a control signal is output to the PWM control circuit 12.

Next, FIG. 3 shows a specific circuit example of such a short-circuit current control circuit section C. The variation level signal set by the welding current setter 11 is supplied to the comparator CMP via the amplifier AMP1. Input to the non-inverting input terminal. The charge / discharge output of the time constant circuit CR is input to the inverting input terminal of the comparator CMP via the amplifier AMP2. Here, the time constant circuit CR has a configuration in which a parallel circuit composed of a capacitor C1 and a Zener diode ZD is connected to two resistors R1 and R2, and one of the two resistors R2 can be connected and disconnected by a contact SW1. Have been. The capacitor C1 is provided with a contact SW2 and a resistor R3. The contact SW2 is closed when an arc is generated to discharge the electric charge charged in the capacitor C1 (corresponding to claim 4).

In such a configuration, the arc / short circuit detection circuit 8
Detects short circuit and outputs a short circuit judgment signal, the contact SW2
Is opened, and the capacitor C1 starts charging.

However, at this time, since the terminal voltage of the capacitor C1 has not reached the variation point level specified by the welding current setting unit 11, the output of the comparator CMP becomes the “H” level, and the contact SW1 is closed. Therefore, the time constant of the time constant circuit CR is small, and the capacitor C1 is charged with a steep rising characteristic (see the portion (I) in FIG. 4).

Then, when the terminal voltage of the capacitor C1 increases and reaches the variation point level Vt specified by the welding current setter 11, the output of the comparator CMP becomes the "L" level and the contact SW1 is opened. The time constant of the constant circuit CR increases, and the capacitor C1 is charged with a gradual rising characteristic (see the part (II) in FIG. 4).

As a result, a neck is generated at the tip of the welding wire 14, and when the arc is regenerated, the contact SW2 is closed, so that the capacitor C1 is discharged instantaneously (see the part (III) in FIG. 4).
The terminal voltage of the capacitor C1 is output to the short-circuit current error amplifier circuit 10a via the amplifier AMP2, and the difference between the terminal voltage of the capacitor C1 and the current level signal transmitted from the shunt 7 is converted to the PWM control circuit 12 via the current waveform switching circuit 13. , And the feedback control is performed so that the conduction current always becomes a current level according to the terminal voltage of the capacitor C1 (short-circuit current reference waveform).

The curve shown by the broken line in FIG. 4 shows the short-circuit current reference waveform when no arc occurs, and the maximum value VPMAX is determined by the Zener diode provided in the time constant circuit CR.
It is set by the Zener voltage VZD of ZD and the gain of AMP2.

FIGS. 3a and 3b show another example of the short-circuit current waveform generating circuit 10b, in which the slope of the short-circuit current reference waveform is arbitrarily set externally by changing the value of the resistor R1 of the time constant circuit CR. This is a possible configuration (corresponding to claim 6), and the same portions are denoted by the same reference numerals and description thereof will be omitted.

Next, FIG. 4 shows a short-circuit current reference waveform generated by the short-circuit current waveform generating circuit 10b, and FIG. 5 shows a waveform of the welding current corresponding to FIG. In these figures, large Ip and small Ip indicate the peak value when the welding current is large and small,
Small indicates the variation point of the welding current, and (I) indicates
(II) respectively corresponds to

According to experiments by the present inventors, when such control is performed, the dI / dt of the first rising portion is given as an example.
Good results were obtained by setting (part in FIG. 5) 100 to 200 A / ms and dI / dt of the second rising portion (part in FIG. 5) 25 to 50 A / ms. Also, the mutation point It shortens the short circuit time,
In addition, in order to suppress the amount of spatter generated during arc regeneration, it is desirable to set the welding current to an average value (corresponding to claim 2).

In the above embodiment, the short-circuit current waveform generating circuit 10b using the charging and discharging of the capacitor C1 is shown. However, in the present invention, the reference waveform may be generated using the output characteristics of the linear circuit. The figure shows an example of the configuration (corresponding to claim 5).

Also in this embodiment, the threshold value Vt of the comparator CMP that defines the variation point It is set so as to correspond to about the average value of the welding current, and the additional value provided on the inverting input side of the inverting amplifier AMP connected to the feedback capacitor Cf. The output waveform Vo of the linear amplifier AMPl is changed through the connection and disconnection of the resistor R '. The contacts SW3 provided at both ends of the feedback capacitor Cf are closed when an arc is generated, and are opened when a short circuit continues for a predetermined time. The contact SW4 is opened and closed by the output signal of the comparator CMP. The contact SW4 is closed at the time of "H" level, and the contact SW4 is opened at the time of "L" level.

With such a configuration, when the short circuit is determined, the output of the comparator CMP is at the “H” level, so that the contact S
W4 is closed, and at the same time, the contact SW3 is opened when the short circuit is determined. As a result, the capacitor Cf is connected to the two resistors R and R '.
And the charging current flows into the inverting amplifier AMP. Thus, when the output of the linear amplifier AMPl reaches the transition point level Vt, the comparator CMP outputs the "L" level, so that the contact SW4 is opened and the charging speed of the capacitor C is reduced. Then, when an arc is generated between the welding wire 14 and the base material 15, the contact SW3 is closed and the output waveform of the linear amplifier AMPl instantly becomes zero.

[Effects of the Invention] According to the pulse arc welding method of the present invention, the welding wire is rapidly heated by the first rising portion of the current that flows when a short circuit occurs to promote melting, and the second rising portion is gently heated. Since the occurrence of spatter is prevented by the rise in current and the occurrence of arc is promoted, the arc can be transferred safely in a short time, and stable welding can be performed.

According to the second aspect of the present invention, by setting the reference level of the first rising portion to the average value level of the pulse arc welding current, the arc can be safely transferred in a short time.

Further, according to the pulse arc welding apparatus of the present invention, stable welding can be performed by using the method of the present invention.

According to the present invention described in claims 4 and 5, the pulse arc welding apparatus of the present invention can be effectively implemented with a simple configuration.

Furthermore, according to the present invention, since the current waveform when a short circuit occurs can be easily changed with a simple configuration, the pulse arc welding apparatus can be set in accordance with the welding conditions. Can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a welding current waveform showing a welding method of the present invention, FIG. 2 is a block diagram showing a configuration of a welding apparatus of the present invention, and FIG. 3 is a short-circuit current of the short-circuit current control unit. FIG. 3a and FIG. 3b are circuit diagrams of another embodiment, FIG. 4 is a short-circuit current reference waveform diagram,
FIG. 5 is a corresponding welding current waveform diagram, FIG. 6 is a circuit diagram when a short-circuit current waveform generating circuit of the short-circuit current control unit is configured using a linear circuit, and FIG. 7 is a conventional pulse arc welding apparatus. It is a block diagram. [Explanation of Signs] I: First rising part II: Second rising part A: Arc / short circuit discriminating means B: Pulse arc current control unit C: Short circuit current control unit C1, Cf: Capacitor

Claims (6)

(57) [Claims] When a short circuit occurs, a current having a predetermined waveform is applied to a portion to be welded when a pulse arc welding current in which a pulse current is superimposed on a predetermined base current is applied to the portion to be welded. Arc welding method for promoting the generation of an arc by performing the first step, wherein when a short circuit occurs, the first step rises sharply from zero level.
When a value at the first rising portion reaches a predetermined reference level, a current having a waveform constituted by a second rising portion that increases at a gentler slope than the first rising portion is welded. A pulse arc welding method characterized in that a current is applied to a portion and an arc is generated, and when an arc is generated, the current is immediately switched to a pulse arc welding current for normal pulse arc welding. 2. The pulse arc welding method according to claim 1, wherein a reference level at the first rising portion is set to an average value level of the pulse arc welding current. 3. An arc / short circuit discriminating means for discriminating between a time when an arc is generated and a case where a short circuit occurs continuously for a predetermined time, and outputting a determination signal, and defining a welding current when the arc is generated. A pulse arc current control unit for generating a pulse arc current reference waveform for generating a short-circuit current reference waveform for defining an energizing current when a short-circuit occurs. A pulse arc welding apparatus that outputs a current reference waveform and, when a short circuit occurs, switches to and outputs a short-circuit current reference waveform of the short-circuit current control unit, and performs energization control based on these reference waveforms. A first rising portion in which the short-circuit current reference waveform generated by the short-circuit current control portion rises sharply from a zero level at the time of a short circuit; and a first rising portion. A pulse arc welding apparatus characterized in that when the value at the bend reaches a predetermined reference value, the pulse arc welding apparatus has a shape including a second rising portion that increases with a gentler slope than the first rising portion. 4. The pulse arc welding apparatus according to claim 3, wherein the short-circuit current reference waveform is generated by a charge / discharge output of a capacitor. 5. The pulse arc welding apparatus according to claim 3, wherein said short-circuit current reference waveform is generated by an output of a linear circuit. 6. The pulse arc welding apparatus according to claim 3, wherein the slope of the short-circuit current reference waveform can be arbitrarily variably set from outside.