JPH01293976A - Pulse arc discharging device - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of an arc length and to uniformize the welding quality by detecting the fluctuation in welding arc lengths by an arc voltage, holding the mean current of a pulse arc discharging constant based on the detection value and controlling the effective current as well. CONSTITUTION:A voltage detector 6, welding voltage setter 8 and comparator 7 are arranged on a pulse arc welding power source 1 and a reversing circuit 12 is provided between a pulse width setter 11 and base current setter 10. When the extension length of a welding wire 2 is changed, the voltage VF between a torch 3 and base metal 5 is increased and a pulse width tau is reduced by the setter 11. In this case, the reverse signal of a differential voltage VO-VF is inputted to a base current setter 10, and the pulse width tau variation and that of a base current IE are repeatedly converged. The arc discharging effective current value can be controlled at the optimum value with holding the mean current value constant, so an arc length la fluctuation is prevented and the welding quality is uniformized.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a consumable electrode type pulse arc discharge device, particularly for a welding torch, etc. This invention relates to a pulse arc discharge device that can prevent the above.

[Prior Art] Fig. 7 shows a conventional pulse arc discharge device as shown in Japanese Patent Application Laid-Open No. 57-19184, in which (1) is a pulse arc welding power source, (2 is ) is a consumable electrode wire (hereinafter referred to as welding wire), (3) is a welding torch, (4) is an arc discharge, (5) is a base metal, and (6) is a welding torch (3) and a base metal (5). (7) is a voltage detector that detects the voltage between (V, ) and a predetermined welding voltage (VO) and outputs a difference voltage (Vo-vF). (8) is a welding voltage setting device to set the above welding voltage (VO), (9) is a pulse peak value (■,)
(11) is the pulse width setting device to set the pulse width (τ), (EX) is the welding wire (2) is the protrusion length, (℃8) is the arc length,
(IlX) is the distance between the welding torch (3) and the base metal (5). In addition to the above, the pulsed arc welding power source (1) includes other components such as a pulse waveform shaping section, but these are omitted for the sake of simplifying the explanation.

A conventional pulse arc discharge device is configured as described above,
Welding wire (2) by pulsed arc welding power source (1)
A DC base current (IB) and a pulse current (pulse peak value (Ip), pulse width (τ)) shown in Fig. 8 (a) and (b) were superimposed between the base metal (5) and the base metal (5). A current is applied to maintain a pulsed arc discharge (4) between the welding wire (2) and the base metal (5) to perform welding. Further, the welding wire (2) is continuously fed to the base metal (5) side, and the fed welding wire (2) is connected to the pulsed arc discharge (4).
It melts and transfers to the base metal (5) as a welding filler material. Note that the feeding speed of the welding wire (2) is generally proportional to the pulse period.

By the way, in the conventional pulse arc discharge device, during welding, the welding torch (3) fluctuates in the vertical direction and the base material (5)
Distance 1 between welding torch (3) and base metal (5) due to distortion of
In order to prevent the arc length (1,) from changing accordingly when 111(J!x) changes, the following feedback control is performed.

In other words, the voltage detector (6) detects the momentary voltage (V, )
This voltage (V, ) and the welding voltage (VO) set by the welding voltage setting device (8) are detected by the comparator (7).
are compared. This comparator (7) outputs a differential voltage (ν.-
VF) signal is output and input manually to the pulse width setting device (]1). The pulse width setting device (11) sets the control pulse amount (
After making Δτ) a function of the voltage difference (VOVF), the pulse width (τ) is calculated to be (τ.±Δτ). For example, the shielding gas is 602 gas, the feeding speed (v8) of the welding wire (2) is 7 m/min, and the pulse peak value (■,) is 50 OA.

When the base current (■!l) is 60A, the distance between the welding torch (3) and the base metal (5) (
ft,) fluctuates, and the protrusion length (E,) is 15.8 m.
When changing from m to 20.4 mm, if the pulse width (τ) is changed from 4.0 ms to 3.8 ms, the arc length is almost the same as when the protrusion length (E,) is 15.8 mm. (U,) is obtained.

Next, this principle will be explained in detail with reference to FIG. 10.

Figure 10 is an enlarged view of the welded part, and in the figure (V,)
is the voltage between the welding torch (3) and the base metal (5), (V
w) is the feeding speed during continuous feeding of welding wire (2), (E
X) is the protrusion length of the welding wire (2) from the power supply part of the welding torch (3) to the arc tip, and (Q,) is the Joule heating of the welding wire (2) from the power supply part to the arc tip by the pulsed current waveform. The amount of heat generated, (1) is the effective current of the pulse current waveform (I=Mo(IP2+τ+IB" (T-
τ))), (R) is the resistance value per unit length of the welding wire (2), (Q, ) is the amount of heat heated by the welding wire (2) by the arc discharge (4), and (kl) is the resistance value per unit length of the welding wire (2). The proportionality constant determined by the welding wire diameter and material, (T) is the average current (I =
-r (Ip・T +■B(at T-))), (Q2) is the amount of heat that heats the base material (5) by arc discharge (4),
(k2) is a proportionality constant determined by the gas, the shape of the base material, and the material.

As shown in Figure 10, the amount of heat entering the welding wire (2) (
Qw) is Qw = QJ + Ql, and the amount of heat (q, ) is
QJ=12-R-Ex/v w, and further heat quantity (Ql)
is calculated by Q + = + · d. Also welding wire (2)
The amount of melting is proportional to the amount of heat (Q8) entering the welding wire (2), creating a molten lump at the tip of the wire, and this molten lump is transferred to the base metal (5) by the pulsed current.

From this, the arc length (j2.) is the welding wire (2.
) is determined at the point where the feeding speed (v8) and the amount of the molten mass transferred to the base material (5) side are balanced. In other words, the condition for the arc length (J2.) to be constant is to maintain the value of the amount of heat (qw) at a constant value in the following formula % formula % (1).

As explained in Fig. 9, when welding with Ex = 15.8 mm, the pulse width (τ) is 4.0 ms, and welding can be performed with almost the optimal arc length (j2.), and the effective current in that case (1) is 263A, average current (T) is 177A
It is. Also, when the protrusion length (EX) changes from 15.8 mm to 20.4 mm, the pulse width (τ
), the arc length (42,) becomes E
Arc length (Il,) when x = 15.8mm
The pulse width (τ) is reduced to 3.6 mS to maintain
T) becomes 1668, and the amount of heat (ow) is kept at a constant value.

[Invention or problem to be solved]

In the conventional pulsed arc discharge device as described above, in order to prevent changes in the arc length 1) due to changes in the protrusion length (EX) of the welding wire (2), the arc length is controlled by the pulse width (τ). Therefore, the average current (1) changes as well as the effective current (1). When the average current (T) changes, the amount of heat (Q2) used to heat the base material (5) by the arc discharge (4) changes, and as a result, as shown in Figures 11 (a) and (b), Base material (5
), the welding cross-sectional area changes, and when the welding cross-sectional area of the base metal (5) is narrow, there is a problem that the welding strength becomes weak.

This invention was made to solve these problems, and it is possible to prevent fluctuations in the arc length even if the welding torch changes, and to make the cross-sectional area of the base metal approximately constant. The purpose of the present invention is to obtain a pulse arc discharge device that can perform the following steps.

(Means for Solving the Problems) A pulse arc discharge device according to the present invention has a base current that maintains an arc having a substantially constant peak value between a base metal and a welding wire, and a base current that maintains an arc having a substantially constant peak value. In a pulsed arc discharge device that supplies a pulsed current that is superimposed on the base current, there is also a detector that detects fluctuations in arc length using arc voltage, and an average of the pulsed arc discharge based on the output from this detector. A control device is provided for controlling the effective current of pulsed arc discharge while keeping the current value substantially constant.

[Function] In this invention, the variation in the arc length is detected by the detector, and based on the output value from the detector, the control device controls the pulse arc discharge while keeping the average current value of the pulse arc discharge almost constant. The effective current of is controlled.

Therefore, even if the welding torch changes, it is possible to prevent changes in the arc length, and moreover, the amount of arc heat that depends on the average current value is kept almost constant, and the cross-sectional area of the weld penetration of the base metal is kept almost constant. It becomes possible to do so.

(Embodiment) FIG. 1 shows an embodiment of the present invention, and in the figure, the same reference numerals as in FIGS. 7 to 11 indicate the same or corresponding parts. (12) is an inversion circuit for inverting the signal, and the difference voltage (Vo VF) is the pulse width setting device (11).
The signal is input to the inverting circuit (12). And the output (V
F-VO) is input to a base current setter (10).

FIG. 2 shows the amount of pulse width change (Δ
τ) and the amount of change in base current (ΔIB), in which (13) is the characteristic line in the above embodiment.

Figure 3 shows the pulse peak value (IP) of the pulse current at 50
0A, pulse period 15m5, and average current (T)
Or base current (I) when pulse width (τ) is constant
The characteristics of the effective current (1) for B) and the transient state when the arc length control of this example is performed are respectively shown. Effective current characteristics with respect to base current (■,), (15)
is a similar effective current characteristic when the average current (■) is 18OA. In addition, (16) is the effective current characteristic when the pulse l1m (τ) is 4 ms, and (17) is the effective current characteristic when the pulse width (τ) is 3.5 m.
The effective current characteristic at s, (18) is when the pulse width (τ) is 3 m
This is the effective current characteristic at s. Also, (19) is V, =Vo
It is a virtual line that screams, and also a broken line A-+B-+C-+D
→EF-4G→H→I→J→→L→M→N→0→P
is the transient characteristic from the A state to the P state under this arc length control.

FIGS. 4(a) and 4(b) show cross-sectional views of the weld bead when welding is performed at the above points A and P, respectively.

In the pulse arc discharge device configured as described above, for example, the position of the welding torch (3) changes, and the protrusion length (EX) of the welding wire (2) changes from 15.8 mm to 20 mm.
．． Consider the case where the distance changes to 4 mm. Ex=15.
In the case of 8 mm, there is point A in Figure 3, the effective current (1) at that time is 2fi3A, and the pulse width (τ) is 4ms.

The average current (T) is 1778.

The protrusion length (EX) of welding wire (2) is 20.4m
m, the welding torch (3
) and the base material (5) increases, and the pulse width (τ) increases to 3 by inputting the differential voltage (VO-VF) to the pulse width setting device (11). .6m5 (point B)
It shrinks to. At the same time, the inverted signal (vr vo) of the differential voltage (Vo-VF) is manually input to the base current setting device (10), so the base current (■a) is 72A (point C).
become. Then, the voltage (V,) becomes the welding voltage (VO)
Furthermore, the pulse width (τ) is 3.3 m5
(point D), and the pulse width change amount (Δτ) is 0.3 m.
When the current is reduced to s, the base current (I8) becomes 81A, which is the point E. When the base current (IB) becomes 81A, the voltage (V, ) becomes higher than the welding voltage (vo), and the pulse width (τ) further decreases to 3.1m5 (point F).
When the pulse width change amount (Δτ) is reduced by 0.2 ms, the base current (IB) becomes 87A. In this way, the pulse width (
By repeating the decrease in τ) and the increase in the base current (IB), P
converges at a point. That is, at point P, the pulse width (τ) is 3 ms, the effective current (1) is 24 OA, and the average current (T)
is approximately 1778.

In the above explanation, the protrusion length (EX
) changes from 15.8mm to 20.4mm A-+B-40-4D-4E→F→G→H→■→
J→N→L-4M-4N→0→P has been explained step by step, but it goes from point A to point P immediately. Also, here we have explained the case where the protrusion length (Ex) becomes long, but
Even when the length is shortened, the transient state opposite to the above is repeated and the length immediately moves from point P to point A.

In the above embodiment, the case where the inverted signal (VF Vo) of the differential voltage (vo VF) is input to the base current setting device (10) is shown, but as shown in FIG.
Even if VF) is input manually to the pulse peak value setter (9) to increase or decrease the pulse peak current value, the same effect as in the above embodiment can be expected.

In addition, in the above embodiment, the differential voltage (VO-Vr) is input to the pulse width setting device (11) to control the pulse width (τ), but instead of controlling the pulse width (τ), the pulse width Even if the frequency is controlled, the same effects as in the above embodiment can be expected.

Furthermore, in the above embodiment, as shown in FIG.
o VF), but if the effective value at point B is sampled and detected at the same time as the differential voltage (VOVF), and that value is maintained, the result will be as shown in Figure 6. As shown, the instantaneous shift from point A to point A can also be used to maintain a constant arc load instead of keeping the arc length (° C. 1) constant.

In the pulsed arc discharge device according to the present invention, the control device may be equipped with means for increasing or decreasing the base current value by controlling the pulse width or pulse frequency in accordance with fluctuations in the arc voltage, or in accordance with fluctuations in the arc voltage. It is preferable to use a device equipped with means for increasing or decreasing the pulse peak current value by controlling the pulse width or pulse frequency accordingly.

【Effect of the invention〕

As explained above, this invention controls the effective current of pulsed arc discharge while keeping the average current value of pulsed arc discharge almost constant in response to fluctuations in arc voltage, so even if the welding torch fluctuates. In addition, it is possible to prevent fluctuations in the arc length, and to make the penetration cross-sectional area during welding almost constant, improving welding reliability and achieving precise welding.

Further, the present invention uses, as a control device, a device equipped with means for increasing and decreasing the base current value according to fluctuations in the arc voltage, or a device equipped with a means for increasing and decreasing the pulse peak current value according to fluctuations in the arc voltage. Because
There are advantages such as the ability to configure the pulse arc discharge device according to the present invention by only slightly modifying the conventional device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a pulse arc discharge device according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between the amount of change in base current and the amount of change in pulse width, and Fig. 3 is the effective current characteristic with respect to base current. and a graph showing the transient characteristics when the arc length control of the present invention is performed, FIG.
a) and (b) are schematic diagrams showing the weld bead cross section of this invention, FIG. 5 is a diagram equivalent to FIG. 1 showing another embodiment of this invention, and FIG. 6 is a diagram showing the application of this invention to other controls. Fig. 3 shows the characteristics when
b) is a waveform diagram showing an example of a pulsed arc current waveform, Fig. 9 is a graph showing pulse width characteristics with respect to protrusion length in a conventional device, and Fig. 10 is a pulsed arc portion showing the division of Joule heating and arc heating. FIGS. 11(a) and 11(b) are diagrams corresponding to FIGS. 4(a) and (b) showing welding heat cross sections in the conventional device, respectively. (1)...Pulse arc welding power source, (2)...Welding wire, (3)...Welding torch, (4)...Arc discharge, (5)...Base metal, (6) ...Voltage detector, (
7)... Comparator, (8)... Welding voltage setting device, (9
)...Pulse peak value setting device, (10)...Heas current setting device, (11)...Pulse width setting device, (12)
... Inversion circuit, (Ex) ... Protrusion length, (υa
)...Arc length. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A pulsed arc discharge that supplies between a base metal and a welding wire a base current that has a nearly constant peak value and maintains an arc, and a pulsed current that has a nearly constant peak value and is superimposed on the base current. The device includes a detector that detects changes in arc length using arc voltage, and a control device that controls the effective current of pulsed arc discharge while keeping the average current value of pulsed arc discharge approximately constant based on the output from this detector. A pulse arc discharge device comprising: