JPH0394977A - Method and equipment for pulse arc welding - Google Patents

Abstract

PURPOSE:To perform stable welding by immediately changing over to a pulse arc welding current at the time of usual pulse arc welding when an arc is generated. CONSTITUTION:When the arc is generated and welding is performed normally, the pulse arc current obtained by superimposing a pulse current of a crest value of a level 12 on a base current of a level 11 for every predetermined specified period T is applied to perform welding. In the process of welding, when a short circuit is generated, the applied current is once lowered up to a zero level and then, it is allowed to rise sharply up to a current level of a level 13 at a first rising part I and then, the applied current is increased at an inclination gentler than the first rising part I at a second rising part II. The moment the arc is generated, the changeover is then executed to an original pulse arc current waveform and afterward, pulse arc welding is again performed continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved pulse arc welding method and a pulse arc welding apparatus using this method. [Conventional technology This kind of f81j! In this method, the phenomenon in which the welding wire melts and transfers to the base metal occurs discontinuously at the critical current value, so in order to be able to perform good welding even on base metals with small plate thickness, Usually, welding is carried out by applying a welding t4 current in which a pulse current is superimposed on a base current below the critical current.

FIG. 7 shows a block diagram of the configuration of such a pulse arc welding device, and 101 is a terminal TIN.
, a transformer that steps down the AC voltage input to the TIN,
102 is a rectifier circuit that rectifies the AC voltage stepped down by the transformer 101; 103 is a welding current that is supplied from the rectifier circuit 102 to a welded part (not shown) as a load through a terminal TOUT in accordance with a control signal from the drive circuit 107; 104 is a current detection circuit that detects a current level signal corresponding to the welding current; 106 is a setting signal from arc t-current setting circuit 105 and t-current detection circuit 104;
This is an arc current error amplification circuit that calculates the error with the t current level signal detected by the t current level signal and outputs a control signal to the drive circuit 107. Feedback control is performed so that the waveform always corresponds to the pulsed arc current reference waveform, which is a pulsed current superimposed on the base current, in order to perform stable welding.However, in such pulsed arc welding equipment,
Since the arc current setting circuit 105 uniquely determines the optimal current level under normal welding conditions, it is difficult to use wires such as iron or stainless steel; When performing welding, it has been difficult to apply sufficient heat to the welding wire, making it impossible to start the arc.

In addition, if the arc length becomes short due to the shape of the base metal during welding, or if there is a short circuit between the welding wire and the base metal, the arc will shift again due to the high conductivity of the welding wire. It was not possible to generate enough heat to do this, resulting in poor welding.

[Problems to be Solved by the Invention] The present invention, proposed in view of the above circumstances, solves the problem of arc starting or short circuit with the base material when using a wire with high conductivity such as aluminum. An object of the present invention is to provide a pulsed arc welding method that can immediately switch to an arc state and perform stable welding even when the arc is stopped.

Another object of the present invention, proposed at the same time, is to provide a pulse arc welding device that can perform stable welding by using the pulse arc welding method described above.

[Means for Solving the Problems] The present invention as set forth in claim 1 proposed to achieve the above object applies a pulsed arc welding current in which a pulsed current is superimposed on a predetermined base flow to a welded part. When a short circuit occurs in the process of pulse arc welding by applying current, there is a first rising part that rises steeply from the zero level, and when the value at this first rising part reaches a predetermined reference value, the first rising part rises sharply from the zero level. A waveform current consisting of a second rising part that increases with a gentler slope than the rising part is applied to the part to be welded, and when an arc occurs, the current is immediately switched to the normal pulsed arc welding current for pulsed arc Pa welding. is being used.

In the present invention as set forth in claim 2, the reference level of the first rising portion is set to the average value level of the pulsed arc welding current.

The present invention according to claim 3 includes an arc/short circuit discriminating means for discriminating between an arc occurrence and a case where a short circuit continues for a predetermined period of time and outputs a discrimination signal; It is equipped with a pulsed arc current control section that generates a pulsed arc current reference waveform that defines the welding current, and a short-circuit current control section that generates a short-circuit current reference waveform that defines the energizing current when a short circuit occurs. While outputting a pulse arc current reference waveform, when a short circuit occurs, the output is switched to the short circuit current reference waveform of the short circuit TL flow control section, and energization control is performed based on these reference waveforms. The short-circuit current reference waveform generated in the current control section has a first rising portion that rises steeply from the zero level, and when the value at this first rising portion reaches a predetermined reference value, the short-circuit current reference waveform rises from the first rising portion. The second rising portion increases with a gentle slope.

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

The present invention according to claim 5 is characterized in that the short-circuit electromechanical reference waveform is
The configuration is such that it is generated using the output of a linear circuit.

Further, in the present invention as set forth in claim 6, the slope of the short-circuit current reference waveform can be arbitrarily and variably set from the outside.

[Function] In the present invention as set forth in claim 1, if a short circuit occurs during pulse arc welding by applying a pulse arc contracting current in which a pulse 'R flow is superimposed on a predetermined base current, At the first rising part, the applied current is increased steeply to rapidly apply heat to the welding wire to promote melting of the wire, and when the applied current level at this first rising part reaches a predetermined reference value, In the second rising portion, which increases at a gentler slope than the first rising portion, spatter is prevented and sufficient heat is applied to the welding wire to easily generate an arc. and,
Immediately after an arc occurs, the current is switched to the pulsed arc welding current used in normal pulsed arc welding, and the process shifts to pulsed arc welding.

In the present invention as set forth in claim 2, the reference level of the first rising portion is set to the average value level of the pulsed arc welding current, so that when a short circuit occurs, the conducting current increases sharply from the zero level to the reference level. However, although wire melting is promoted, spatter generation is prevented.

In the present invention as set forth in claim 3, during normal welding, the occurrence of an arc is determined by the arc/short circuit determining means, and the pulse is set to a predetermined base current based on the pulsed arc current reference waveform of the pulsed arc current control section. T? Pulse arc welding is performed by applying a welding current superimposed with A to the part to be welded.

However, at the start of welding or when the welding wire and the base metal are short-circuited and the generation of arc stops, the arc/short-circuit discrimination means makes a determination, switches to the short-circuit current control section, and uses the short-circuit current reference waveform to The current according to claim 1 or 2 is applied to the part to be welded. When an arc occurs, it is determined by the arc/short circuit discriminating means, and the pulse arc current control section is immediately switched to apply a pulse arc welding current based on the pulse arc current reference waveform to perform pulse arc welding.

In the present invention as set forth in claim 4, the short-circuit current reference waveform is generated by the charging/discharging output of the capacitor.

In the present invention as set forth in claim 5, the short circuit current reference waveform is generated by the output of the linear circuit.

Further, in the present invention as set forth in claim 6, since the slope of the short-circuit current reference waveform can be arbitrarily variably set from the outside, it is possible to perform energization control according to welding conditions.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 explains the pulsed arc welding control method of the present invention. When an arc is generated and welding is performed normally, a pulsed current with a peak value of level I2 is applied to the base t flow of level 11. Welding is performed by applying superimposed pulsed arc welding currents at predetermined intervals T. When a short circuit occurs during this welding process (including at the start of welding), the tt flow is once lowered to zero level, and then the tt flow is level 3 at the first rising part.
Raise it steeply to the flow level (see section I in Figure 1)
, then enters the second rising part (see part ■ in the same figure)
, the slope is gentler than the first rising part! increasing the current. Then, as soon as the arc is generated, switch to the original pulsed arc current waveform (see part ■ in the same diagram), and then start pulsed arc welding again! ! Do it under control. In such a pulsed arc welding method, at the same time 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 at the second rising portion ■, the generation of spatter is prevented. This feature prevents the occurrence of splatter that would occur when a large current is immediately applied to generate an arc, making it possible to generate an arc safely in a short period of time. becomes.

Next, FIG. 2 shows a block diagram of the configuration of the pulse arc welding apparatus of the present invention.
Reference numeral denotes an arc/short-circuit discrimination means, B a pulse arc t-flow control section, and C a short-circuit 1-flow control section.

The output current control of this pulse arc welding device is AC 1!
The source is rectifier circuit 1 and smoothing capacitor 2! 1. The output of the inverter circuit 83 is controlled by a pulse width modulation control (hereinafter referred to as PWM control) using an inverter circuit 3 that operates on the supply of smoothed DC power, and the output of the inverter circuit 83 is controlled by the transformer 4 and the rectifier circuit. 5 to the welding part D. This welding part D is provided with a DC reactor 6 and a shunt 7, and the output voltage of the DC reactor 6 is applied to the arc/short circuit discriminating circuit 8 of the arc/short circuit discriminating means 8 to detect the arc in the welded part. We are monitoring the occurrence status, and one of the flow dividers 7
A current level signal corresponding to the detected current is a feedback signal to the pulse arc K flow control section B and the short circuit xi control section C.

The pulsed arc current control section B includes a pulsed arc current waveform setting circuit 9b, a frequency setting circuit 9C, and a pulsed arc current error amplification circuit 9a, and controls a pulsed waveform having a repetition frequency set by the frequency F1 stage constant circuit 9C. In addition to the pulsed arc current waveform setting circuit 9b, a pulsed arc current reference waveform is generated by superimposing the pulsed current on the base current, and this reference waveform and the current level signal from the shunt 7 are applied to the pulsed arc current error amplification circuit 9a. Feedback control is performed so that the current flowing to the part to be welded is always a current based on the pulse arc electric current reference waveform.

On the other hand, the short-circuit current control section C includes the short-circuit current error amplification circuit I
O a+ Short circuit current waveform generation circuit 10b and d I
/dt mutation point setting circuit 10c, dI/
dtThe mutation level signal set by the mutation point setting circuit 10c is applied to the short circuit current waveform generating circuit 10b to generate a short circuit 'r4.
Generate a current reference waveform, add this base 4 waveform and the current level signal from the shunt 7 to the short-circuit current error amplifier 10a,
Feedback control is performed so that the current applied to the part to be welded is always based on the short-circuit current reference waveform.

In this embodiment, the welding current setter 11 determines the peak value of the pulse current of the pulse current waveform setting circuit 9b, and also links the variation level of the dI/dt variation point setting circuit 10c. .

Further, the welding current setting device 1l simultaneously sends a q constant signal to the wire feed control circuit 17 to specify the speed at which the wire feed motor 16 is driven.

The arc/short circuit discriminating circuit 8 constituting the arc/short circuit discriminating means 8 extracts the welding voltage supplied to the welding part D via the reactor 6, and the welding wire 14
Depending on the difference between the voltage 110 when the welding wire 14 is short-circuited with the welding base metal 15 and the voltage value when the welding wire 14 is separated from the welding base metal 15 and an arc is generated, the voltage is maintained for a predetermined period of time after the arc is generated. A determination signal is output depending on whether a short circuit occurs or not.

The inverter circuit 3 switches the direct current flowing through the transformer 4 based on the control output from the PWM control circuit l2, and the PWM control circuit n12 performs switching operation in response to the discrimination signal output from the short circuit/arc discrimination circuit 8. When an arc occurs, the pulse arc current error amplifier 9a of the pulse arc current control section B is controlled by the current waveform switching circuit 13.
In addition, at the time of a short circuit, the control signal of the short circuit current control section C's short circuit error amplifier 10a is selectively inputted.

In the above-mentioned FIG. 2, error amplifiers 'a9a and 10a are provided in each of the pulse arc electric control unit B and the short-circuit current control unit C, and the control signals outputted from these are sent to the current waveform switching circuit 13. Although the configuration is such that the current waveform switching circuit 13 outputs the pulse arc current waveform setting circuit 9b, the configuration is not limited to this configuration.
and the reference waveform from the short-circuit current waveform setting circuit 10b are switched and output, and the switched reference waveform and the current level signal from the shunt 7 are received by an error amplifier circuit to generate a control signal P.
It is also possible to configure the output to the WM control circuit l2.

Next, FIG. 3 shows a specific circuit example of such a short-circuit %E'tfA control circuit section C, in which the variation level signal set by the welding t-flow setting device 1l is connected to the amplifier AMP.
The human power is applied to the non-inverting input terminal of the converter CMP through I. The charging/discharging output of the time constant circuit CR is input to the inverting input terminal of the converter CMP via the amplifier AMP2. Here, the time constant circuit CR includes two resistors Rl,
A parallel circuit consisting of a capacitor C1 and a Zener diode ZD is connected to R2, and one of the two resistors, R2, can be connected and disconnected by a contact SW1. Further, the capacitor C1 is provided with a contact SW2 and a resistor R3, and this contact SW2 is closed when an arc occurs, and the M.sub.C.sub.1 is charged in the capacitor C1. discharge the load (corresponding to claim 4).

In such a configuration, when the arc/short circuit detection circuit 8 detects a short circuit and outputs a short circuit determination signal, the contact SW2
is opened and capacitor C1 starts charging.

However, at this point, the terminal voltage of capacitor C1 is m
Since the variation point level specified by the contact current setting device I1 has not been reached, the output of the converter CMP is at the rHJ level and the contact SWI is closed, so the time constant of the time constant circuit CR is small. , capacitor C1 is charged with a steep rise characteristic (see part (I) in Figure 4). Then, when the terminal voltage of the capacitor C1 increases and reaches the variation point level Vt specified by the welding current setting device II, the output of the comparator CMP becomes the rLJ level and the contact SWI is formed, so that the time constant The time constant of circuit CR becomes large, and capacitor Cl is charged with a gradual rise characteristic (see part (II) of FIG. 4). As a result, a constriction occurs at the tip of the welding wire 14, and when the arc is regenerated, the contact SW2 is formed and the capacitor CI is instantly discharged (see part (m) in Fig. 4).
．． The terminal voltage of this capacitor C1 is the amplifier AM
1! is output to the short circuit current error amplification circuit 10a via P2 and transmitted from the shunt 7! The error with the current level signal is output to the PWM control circuit 12 via the current waveform switching circuit 13, and feedback control is performed so that the conducting current always has a current level corresponding to the terminal voltage of the capacitor C1 (short-circuit current reference waveform). will be carried out.

The curve shown by the broken line in Figure 4 shows the short-circuit current reference waveform when no arc occurs, and its maximum (
lIIV PMAX is set by the Zener voltage VZD of the Zener diode ZD provided in the time constant circuit CR and the gain of AMP2. 3a and 3b show other examples of the short-circuit current waveform generating circuit 10b, and both show the resistor R1 of the time constant circuit CR.
The inclination of the short-circuit current reference waveform can be arbitrarily set from the outside by changing the value of (corresponding to claim 6), and the same parts are given the same reference numerals and explanations will be omitted.

Next, FIG. 4 shows a short circuit current reference waveform generated by the short circuit current waveform generating circuit Job, and FIG. 5 shows a corresponding welding current waveform. In these figures, IP large, I
P small indicates the peak value when the welding current is large or small, It large and It small indicate the variation points of the welding current, respectively, (1) corresponds to ■, and (■) corresponds to ■, respectively.

According to experiments conducted by the present inventors, when performing such control, for example, the dl/d of the first rising portion
t (part ■ in Fig. 5) is 100 to 20 OA/ms.
d T/d t of the second rising part (■ part in Figure 5)
was set at 26 to 50 A/ms and good results were obtained. Furthermore, in order to shorten the short-circuit time and suppress the amount of spatter generated during arc regeneration, it is preferable that the variation point it is set to about the average value of the welding current (corresponding to claim 2). In the above embodiment, the short-circuit t-current waveform generation circuit Job was shown using the charging and discharging of the capacitor C1, but in the present invention, the reference waveform may be generated using the output characteristics of the linear circuit. Figure 6 shows an example of its configuration (corresponding to claim 5)
.

In this embodiment as well, the threshold +l! of the comparator CMP that defines the mutation point It! Ivt is set to approximately correspond to the average value of the welding current, and the output waveform Vo of the linear amplifier AMP/ is changing. Contacts SW3 provided at both ends of the feedback capacitor Cf are closed when an arc occurs, and are opened when the short circuit continues for a predetermined period of time. Contact SW4 is opened and closed by the output signal of converter CMP, and when it is at "H" level, contact SW4 is closed, and when it is at "L" level, contact SW4 is opened.

With this configuration, when a short circuit is determined, the output of the converter CMP is rHJ level, so the contact SW4 is closed, and at the same time, when a short circuit is determined, the contact SW4 is closed.
W3 will be held. As a result, the capacitor Cf is charged by the output of the amplifier AMP set through a parallel circuit consisting of two resistors R and R', and the charging current flows into the inverting amplifier AMP. Thus, the linear amplifier AMPj
! When the output reaches the variation point level Vt, the converter CMP outputs an "L" level, so the contact SW4 is opened and the charging speed of the capacitor C is slowed down. Then, when an arc occurs between the welding wire 14 and the base metal 15,
Contact SW3 is closed and linear amplifier A. The output waveform of MP1 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 applied when a short circuit occurs. iI promotes melting and prevents the occurrence of spatter due to the gradual increase in current at the second rising part, and also promotes the generation of arc, making it possible to safely transfer the arc in a short time and perform stable welding. Can be done. 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 pulsed arc welding current, it is possible to safely shift the arc 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 described above. According to the present invention as described in claims 4 and 5, it becomes possible to effectively implement the pulse arc welding apparatus of the present invention with a simple configuration.

Furthermore, according to the present invention as set forth in claim 6, it is possible to easily change the current waveform when a short circuit occurs with a simple configuration, so that the pulse arc welding device can be set in accordance with the welding conditions. can be provided.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the welding method of the present invention with current waveforms, Fig. 2 is a block diagram showing the configuration of the welding device of the present invention, and Fig. 3 is a short circuit t of the short circuit current control section.
A detailed circuit diagram of the current waveform generation circuit, Figures 3a and 3b are circuit diagrams of another embodiment thereof, Figure 4 is a short circuit electric current reference waveform diagram, Figure 5 is a corresponding welding current waveform diagram, FIG. 6 is a circuit diagram of a short-circuit current waveform generating circuit of a short-circuit current control section configured using a linear circuit, and FIG. 7 is a configuration diagram of a conventional pulse arc welding device. [Description of symbols: First rising portion ■ Second rising portion A: Arc/short circuit determining means B: Pulse arc current controller C: Short circuit current controller CI, Cf...capacitor

Claims (6)

[Claims] (1) While performing welding by applying a pulsed arc welding current, which is a predetermined base current superimposed with a pulse current, to the welded part, when a short circuit occurs, a current with a predetermined waveform is applied to the welded part. This is a pulsed arc welding method that promotes arc generation by
When the value at this first rising portion reaches a predetermined reference level, a current with a waveform consisting of a rising portion and a second rising portion increasing at a gentler slope than the first rising portion is applied to the welded material. A pulsed arc welding method characterized in that when an arc is generated, the current is immediately switched to the pulsed arc welding current used in normal pulsed arc welding. (2) The pulsed arc welding method according to claim 1, wherein the reference level at the first rising portion is set to an average value level of the pulsed arc welding current. (3) Arc/short circuit discrimination means for discriminating between the occurrence of an arc and the occurrence of a short circuit that continues for a predetermined period of time and outputting a discrimination signal; A pulse arc current control section that generates a pulse arc current reference waveform, and a short circuit current control section that generates a short circuit current reference waveform for specifying the conduction current when a short circuit occurs, and when an arc occurs, the pulse arc current reference is The pulse arc welding device outputs a waveform, and when a short circuit occurs, switches the output to a short circuit current reference waveform of the short circuit current control section and performs energization control based on these reference waveforms, the pulse arc welding device comprising: The short-circuit current reference waveform generated in the current control section has a first rising part that rises steeply from the zero level at the time of the short circuit, and when the value at this first rising part reaches a predetermined reference value, the first rising part A pulse arc welding device characterized by having a shape including a second rising portion that increases at a gentler slope than the rising portion. (4) The pulse arc welding apparatus according to claim 3, wherein the short-circuit current reference waveform is generated by a charging/discharging output of a capacitor. (5) The pulse arc welding apparatus according to claim 3, wherein the short-circuit current reference waveform is generated by an output of a linear circuit. (6) Claim 3 characterized in that the slope of the short-circuit current reference waveform can be arbitrarily and variably set from the outside.
The pulse arc welding device described in .