JPS60223662A - Arc welding method - Google Patents

Abstract

PURPOSE:To generate substantially no spatters in a wide welding condition range from low to large current by superposing respectively optimum pulse currents in the stage of a short circuit and in the stage of an arc on the base current substantially smaller than said currents by detection signals for the short circuit and the arc so that the short circuit is forcibly executed. CONSTITUTION:The voltage transformed 3 to a prescribed voltage and rectified 4 to DC is outputted and is passed to an electrode 7c to generate an arc 7d between the electrode 7c and a base metal 7a. The electrode 7c is fed at a constant speed by feed rollers 7a for driving 8 said electrode. The voltage value set in a reference signal generating circuit 11 and the value detected by an arc voltage detecting circuit 9 are compared in a discriminating circuit 10 by which the short circuit is discriminated. The signal from the circuit 13 is thereafter stopped at the same instant when the signal of the arc state from the circuit 10 is applied. The pulse current for the short circuit is passed in the instantaneous short-circuit state at the tip of the electrode to prevent generation of spatters.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an arc welding method in which welding is performed by feeding a consumable electrode at a constant rate, and in particular to an arc welding method suitable for significantly reducing spatter generated during welding. Regarding welding methods.

[Background of the invention]

In the arc welding method in which welding is performed by feeding a consumable electrode at a constant speed, a circuit consisting of a current 1 with constant DC voltage characteristics and a DC reactor 2 as shown in Figure 1 has been put into practical use. ing. When welding is performed using a circuit configured in this manner, the welding phenomenon varies depending on the magnitude of the welding current. That is, in a region where the welding current value is relatively low, a so-called short-circuit transfer phenomenon is observed in which the molten metal at the tip of the consumable electrode contacts and transfers to the base metal. Figure 2 shows the changes in welding current and arc voltage when short circuits and arcs are repeated. In the figure, the line KPR indicates the external characteristic curve of the power source, L,,L,.

L2 has different arc lengths. e Arc characteristics for Ll * L2. is the case when the arc length is zero. When a short circuit begins, the current rapidly increases from 1 to 2, and when the short circuit is broken at 2, an arc voltage of 3 is generated, and the arc length immediately increases to become L2 and the arc voltage shifts to 3'. However, since the electrode is constantly being fed, the arc length gradually becomes shorter and changes from 3' to 4 to 5, and at 5 the arc length is shorted again.

When the welding phenomenon at this time is observed using a high-speed camera, spatter is most noticeable at the moment when an arc becomes a short circuit and at the moment when a short circuit becomes an arc. Of these, spatter that occurs when a short circuit occurs from an arc can be removed by setting the inductance of the DC reactor shown in Figure 1 to an appropriate value.
It can be reduced by controlling the rate of rise of the current from 1 to 2 in the figure. For this purpose, various methods have been considered and implemented. For example, a method has been considered in which a secondary control winding is provided in the reactor and an appropriate inductance is selected according to the welding conditions. Also, methods are being considered to control the rise of current when a short circuit occurs and the fall of current when an arc occurs from a short circuit. These methods are effective in reducing spatter that occurs when a short circuit occurs from the aforementioned arc. However, at the moment when an arc occurs from a short circuit, as shown in Figure 2, in the conventional method, the current value is always high in principle, so the arc force generated by this high current is strong, and the degree of rapid thermal expansion of the arc column is high. Since there is a lot of , spatter occurs.

For this reason, it has not yet been possible to significantly reduce spatter generated during welding.

1-k ++ Ayu-Ring In the case of a well-developed area, the arc is strong and pushes up the molten metal at the end of the electrode, as shown in Shin 3, so it is difficult to short-circuit, and therefore the droplet becomes larger. In addition, one-sided melting is severe, and many large spatters occur. Therefore, in this current range, conventional methods have been used to actively lower the arc voltage and use the hidden arc method to trap the generated spatter in the molten pool and prevent it from coming out, or to reduce the inductance of the power supply circuit. Methods have been considered to reduce current fluctuations in the event of a short circuit by making the wire very thick (SOO μH or more), but none of these methods have led to a significant reduction in spatter.

[Object of the Invention] The present invention has been made in view of the above-mentioned matters, and its purpose is to achieve a stable arc with almost no spatter in a wide welding current range from low current range to large current range. The object of the present invention is to provide a new arc welding method that provides the following.

[Summary of the invention]

The present invention detects a short circuit state and an arc state in an arc welding method in which welding is performed by feeding a consumable electrode at a constant speed, and uses this detection signal to set an optimal pulse current to a base current that is sufficiently smaller than the pulse current. By controlling the welding current so that it becomes the base current when the welding current changes to an arc, it prevents spatter that occurs when a short circuit becomes an arc. Superimposing an optimal first arc pulse current and a second arc pulse current smaller than the first arc pulse current on a base current sufficiently smaller than the first pulse current in order to stabilize the arc. to force a short circuit and detect the arc voltage,
By comparing this detection signal with the set value and controlling the current value during the arc period according to the difference, the arc voltage is kept almost constant, and spatter can be prevented from occurring in a wide range of welding conditions from low current to large current. It is characterized by being able to obtain a stable arc even though it is almost eliminated.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4 to 7.

In Fig. 4, 3 is a transformer, 4 is a rectifier, 5 is a current limiting element that controls the output current, 6 is a drive circuit for 5, 7 is a welding part, 7a is a base material, 7b is an arc, 7c is a consumable electrode, 7d is a power feeding chip, 7e is a feeding roller that feeds the consumable electrode, 8 is a consumable electrode feeding motor, 9 is an arc voltage detection circuit, 1o detects short circuits and arcs by comparison with the signal of the reference signal generation circuit 11. 12 is a delay circuit for short-circuit pulse current, 13 is a short-circuit pulse current signal generation circuit, 14 is a first delay circuit for arc pulse current, 15 is a first arc pulse current signal generation circuit, and 16 is arc voltage. 17 is a circuit that compares the signal of the reference signal generating circuit 18 with the signal obtained in 16, 19 is a base current signal generating circuit, 2o is a current wire feeding control device, 21 is a second This is a delay circuit for arc pulse current.

Next, the operation of the above embodiment will be explained. When the transformer 3 transforms the normal voltage from 200 V to 60 to 80 V, the rectifier 4 rectifies it to direct current, and outputs the voltage, the current limiting element 5. Electricity is applied to the electrode 7C through the power supply chip 7d, and the electrode 7c and the base material 7
An arc 7d is generated between a and a. At this time, the electrode 7c is fed at a constant speed by a feed roller 7e driven by a feed motor 8. In this case, when transitioning from an arc to a short circuit, there is a sudden change from several tens of volts to around zero volts as shown in FIG. By comparing the value detected in step 9 with the value detected in step 9, it can be determined that a short circuit has occurred.

When determining a short circuit, the determination circuit 10 activates the short circuit pulse current signal generation circuit 13 through the delay circuit 12. At this time, the delay circuit 12 applies a signal to the short circuit pulse current signal generation circuit 13 after a preset delay time after the signal from the discrimination circuit 10 is applied. When the signal from the delay circuit 12 is applied, the short circuit pulse current signal generation circuit 13 outputs a preset waveform signal to the drive circuit 6,
A short circuit pulse current is output from the current limiting element 5. Further, the signal from the short-circuit pulse signal circuit 13 to the drive circuit 6 stops instantaneously when the arc state signal from the discrimination circuit 10 is applied. As a result, it was possible to prevent spatter from occurring due to the flow of a short-circuit pulse current during an instantaneous short-circuit of approximately 0.5 ms or less, which does not transfer by just momentarily touching the molten pool at the tip of the electrode, and at the same time, it was sufficiently short-circuited. Since a short circuit pulse current flows afterwards, it is possible to prevent spatter that occurs when the arc changes to a short circuit.

Further, when the determination circuit 10 determines the arc state, a signal from the arc pulse current signal generation circuit 10 is applied through the first arc pulse delay circuit 14, and after a preset delay time, the arc pulse current signal generation circuit 1
Apply a signal to 5.

Similarly, a signal of the second arc pulse current is applied to the arc pulse current signal generation circuit 15 after the time set by the delay circuit 21. When the signals from the delay circuits 14 and 21 are applied, the arc pulse current signal generation circuit 15 outputs a preset waveform signal to the drive circuit 6, and the current limiting element 5
A large arc current is output from the arc valve. The above short circuit pulse current and arc pulse current are generated by the base current signal generation circuit 1.
The pulse current output by the signal from 9 is superimposed on the base current, which is much larger than the pulse current.

Further, the average voltage during the arcing period is detected by the detection circuit 16,
The signal from the reference signal generation circuit 18 is compared with the comparison circuit 17, and according to the difference, the arc pulse current signal generation circuit 15
For example, the first arc pulse current width, which is set in advance, is changed. In this case, when the voltage va detected by the detection circuit 16 becomes higher than the set voltage Vs of the reference signal generation circuit 18 (V s < V a ), the pulse current width is controlled to be shorter than the set value. do. As a result,
The amount of electrode melting during the arc period decreases and the arc voltage becomes lower and equal to the set value. As a result of the above, the power supply chip 7d
Even if the distance between the base metal 7a and the base metal 7a changes, stable short-circuit transition welding can always be performed.

FIG. 5 shows an example of current and voltage waveforms according to this embodiment. Point A is the moment of transition from arc to short circuit, and point B is the moment of transition from short circuit to arc. When a short circuit occurs at point A, the discrimination circuit 10 detects it, and the delay circuit 12 outputs a signal from the short circuit pulse current signal generation circuit 13 with a delay of TDll, and the current limiting element 5 causes a short circuit pulse current of Ips to flow. Since this short circuit pulse current is output until the signal from the discrimination circuit 10 is applied, the width t ps of I Pg varies depending on the state of the short circuit. In FIG. 6(a), the short-circuit time is relatively short, and the discriminating circuit 10
Figure (b) shows the set value I p when a signal from
The case where the voltage is applied after reaching S is shown. Further, when detecting a state from a short circuit to an arc at point B, the delay circuit 14 delays the TDA and causes the arc pulse current signal generation circuit 15 to
The first arc pulse current IPA flows through the current-limiting element 5 as a result of the eight signal cycles. As a result of the above, a low base current is passed to maintain the arc for a while from the moment the short circuit turns into an arc, so it is possible to prevent spatter from occurring when the short circuit changes to an arc. On the other hand, during the arc period, a certain amount of molten metal is generated at the tip of the electrode, and the first
An arc pulse current IPA of 1 is applied for a set time, and then a second attenuated pulse current smaller than the arc pulse current of node 1 is applied. At this time, while the first arc pulse I pA is flowing, a certain amount of molten metal is generated at the electrode tip and a molten pool is generated in the base metal, but the molten metal at the electrode tip is pushed up by the arc force and easily No short circuit. Next, by superimposing a second attenuated pulse current smaller than the first arc pulse current on the base current, the arc force gradually weakens, causing the molten metal to fall toward the base metal, and the second arc pulse This gives the arc rigidity, making it stable without moving around irregularly. Second
In the case where the arc pulse of
As shown in a), the arc voltage during the base current period becomes very unstable, and in the worst case, arc breakage occurs. However, when the second attenuated arc pulse is superimposed, the arc voltage becomes very stable as shown in FIG. 7(b), and the voltage gradually decreases, resulting in a short circuit at the 0 point. Since the short circuit is forcibly performed in this way, it is possible to perform short circuit transition welding in a high current range without generating spatter, which was impossible with conventional methods.

〔Effect of the invention〕

According to the method of the present invention, as described below, short circuits and arcs are detected, and by using this signal, the optimal pulse current is superimposed on the base current, which is sufficiently higher than the pulse current, for short circuits and arcs, thereby forcing a short circuit. Therefore, it is possible to obtain a stable arc with almost no spatter occurring under a wide range of welding conditions from low current to high current. Therefore, droplets are transferred regularly to obtain a good bead, and since no spatter is generated, there is no need for post-treatment after welding, and high-speed welding is possible, so work efficiency is significantly improved.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional arc welding power source, Figures 2 and 3
The figures show an explanation of the operation and phenomena of a conventional arc welding power source 1' - Fig. 4 is an example according to the method of the present invention, Fig. 5 is a waveform diagram according to the example, and Figs. 6 and 7 are examples FIG. 5... Current limiting element, 6... Drive circuit, 9... Arc voltage detection circuit, 10... Discrimination circuit, 12, 14, 21
... Delay circuit, 13... Short circuit pulse current signal generation circuit, 15... Arc pulse current signal generation circuit, 16.
...Arc voltage averaging circuit, 17...Comparison circuit, 19
... Base current signal generation circuit, 20 ... Electrode wire feeding control circuit. Agent Patent Attorney Akio Takahashi No. 1, No. 2, No. 3, No. 4, No. 5, Figure No. 7 (L) (b)

Claims (1)

[Claims] 1. In the arc welding method in which welding is performed by feeding a consumable electrode at a constant speed, a short circuit state and an arc state are detected, and the detection signal is used to determine the short circuit pulse current during the short circuit time and the short circuit pulse current during the arc period. and a second arc pulse current smaller than the first arc pulse current are superimposed on a base current sufficiently smaller than the first arc pulse current. Arc welding characterized in that the arc voltage is kept almost constant by detecting the arc voltage, comparing this detection signal with a set value, and controlling the current value during the arc period according to the difference. Law. 2. The arc welding method according to claim 1, wherein the second arc pulse current has a damped pitch waveform. 3. The arc welding method according to 1 and 2, in which the detected arc voltage is an average value during the arcing period. 4. Claim 1, wherein the detected arc voltage is an average value during the first arc pulse current period
5. The arc welding method according to claims 1 and 2, wherein the detected arc voltage is an average value during the second arc pulse current period. Law. 6. The current value during the arc period is controlled by changing the peak value of the first arc pulse current. The arc welding method according to paragraphs 4 and 5. 7. The arc welding method according to claims 3, 4, and 5, characterized in that the current value during the arc period is controlled by changing the pulse width of the first arc pulse current. 8. The arc welding method according to claims 3, 4, and 5, characterized in that the current value during the arc period is controlled by changing the peak value of the second arc pulse current. 9. 6. The arc welding method according to claim 3, wherein the current value during the arc period is controlled by changing the pulse width of the second arc pulse current. 10. Claims 3, 4 and 4, characterized in that the current value during the arcing period is controlled by changing the ratio (duty) between the pulse time and rest time of the second arc pulse current. The arc welding method described in Section 5.