JP6754935B2 - Arc welding control method - Google Patents

Description

The present invention is short-circuit arc welding in which welding is performed by repeating a short-circuit period and an arc period, when an arc is generated between a welding wire as a consumable electrode and a base metal to be welded to perform welding output. It relates to an arc welding control method and an arc welding apparatus for improving the arc start performance of the above.

In the consumable electrode type arc welding, various measures have been taken because spatter and arc instability are particularly likely to occur at the time of arc start in an unsteady state.

FIG. 6 is a diagram illustrating the operation of a welding power supply device that performs arc start control of conventional short-circuit arc welding. FIG. 6A shows a wire feeding rate waveform, FIG. 6B shows a welding voltage waveform, and FIG. 6C shows a welding current waveform.

At the timing of the wire feeding start time t1 shown in FIG. 6, the wire feeding speed of the main welding set by the welding condition setting unit (not shown) is stored in the storage unit (not shown). The initial short-circuit current is sent to the wire feeding unit (not shown) together with the peak current, peak current output time, and slowdown speed, and the welding wire starts feeding. The contact between the welding wire and the base metal is detected by the short-circuit / arc detection unit (not shown), and the wire feeding speed shown in FIG. 6 changes from the main welding transition start time t2 to the main welding wire feeding speed WF1. And migrate. Hereinafter, this series of operations will be referred to as arc start control.

The wire feeding speed or welding current for this welding is used with various changes because the conditions differ depending on the product requirements to be welded, such as the joint shape and plate thickness of the base metal, bead width, and tact time.

In the above-mentioned conventional arc start control, a method is known in which an initial short circuit current is supplied at the time of the first short circuit of the arc start to start welding.

In addition, the moment when a capacitor is connected between the output terminals of the welding power supply to the initial short-circuit current, the capacitor is charged and contacted before the welding wire and the base metal come into contact after turning on the SW that starts and ends welding. It is known that adjusting the heat input state by impulse start, which gives an impulse current to the initial short-circuit current by discharging the capacitor charged in, is effective in improving the arc startability (for example, patent). Reference 1).

Further, as a control parameter for adjusting the heat input state of the arc start control, a method of adjusting the tip shape of the welding wire by the welding end mode is also known. Generally, a low current is supplied for a certain period of time to the welding end mode of mild steel welding, and a base end is used to generate a ball at the tip of the welding wire and end, and a high peak current is supplied for a certain period of time to stainless steel welding. A pulse termination is used to sharpen the tip of the weld wire by removing the molten metal at the tip.

In any case, in the conventional arc start control, a fixed value predetermined by the base metal material and the diameter of the welding wire is used for the initial short-circuit current.

Japanese Unexamined Patent Publication No. 4-59177

In the conventional arc start control of short-circuit arc welding in which the initial short-circuit current is a fixed value, when the wire feeding speed of main welding is set to be high, a long-circuit short circuit occurs due to insufficient heat input, and short-circuit opening is not performed and spattering occurs. Occurs. Further, when the wire feeding speed of the main welding is set to be low, an arc burns up due to excessive heat input and the arc becomes unstable, so that a bead having a non-uniform width is formed.

In arc start control, where the initial short-circuit current is a fixed value when changing whether or not impulse start is used, if impulse start is switched as a control parameter, arc burn-up occurs due to excessive heat input to the welding wire. Since the arc becomes unstable, a bead with a uniform width may not be formed.

Also, when using the base end or pulse end of the welding end mode, the arc start control in which the initial short-circuit current is a fixed value can be changed after the welding end in the base end and pulse end when the welding end mode is changed as a control parameter. Since the tip shape of the welding wire is different, a short circuit may occur for a long time due to insufficient heat input, and spatter may occur without opening. Further, there is a problem that a bead having a non-uniform width may be formed because the arc becomes unstable due to the occurrence of burning due to excessive heat input.

In this way, in the conventional arc welding start control of short-circuit arc welding in which the initial short-circuit current is a fixed value, for example, the wire feeding speed, the welding current, the method at the end of welding, the heat input state of the wire tip, and the wire tip Depending on the shape, a short circuit occurs for a long time due to insufficient heat input, the short circuit is not opened, and spatter occurs. In addition, there is a problem that beads having a non-uniform width are formed because the arc becomes unstable due to the occurrence of burning due to excessive heat input.

Further, the arc welding control method of the present invention for solving the above problems is an arc welding control method in which short-circuit arc welding is performed by repeating a short-circuit period and an arc period, and is an initial stage for opening a short circuit at the time of arc start. the output time of the peak current or peak current of short-circuit current, which change according to the change of the control parameter for adjusting the heat input state,
The control parameter is an impulse start.
The peak current of the initial short-circuit current or the output time of the peak current at the time of arc start is changed according to the presence or absence of impulse start of arc start.

Since the peak current of the initial short-circuit current and the output time of the peak current that open the short-circuit at the start of the arc are optimized, the short-circuit for a long time caused by insufficient heat input at the start of the arc is eliminated, and the arc burns due to excessive heat input. Since it does not occur, spatter can be reduced and beads having a uniform width can be formed.

The figure which shows the schematic structure of the welding power supply device in Embodiment 1. (A) A diagram showing a time change of the wire feeding speed in the first embodiment, (b) a diagram showing a time change of the welding voltage in the first embodiment, and (c) a high wire feeding speed in the first embodiment. The figure which shows the time change of the welding current at the time (WF1), (d) the figure which shows the time change of the welding current when the wire feeding speed is low (WF2) in Embodiment 1. (A) The figure occupying the relationship between the wire feeding speed and the peak value of the short-circuit initial current in the first embodiment, and (b) the relationship between the wire feeding speed and the peak value output time of the short-circuit initial current in the first embodiment. Figure shown (A) A diagram showing a time change of the wire feeding speed in the second embodiment, (b) a diagram showing a time change of the welding voltage in the second embodiment, and (c) a welding without an impulse start in the second embodiment. The figure which shows the time change of the electric current, (d) the figure which shows the time change of the welding current at the time of impulse start in the second embodiment. (A) A diagram showing a time change of the wire feeding speed in the third embodiment, (b) a diagram showing a time change of the welding voltage in the third embodiment, and (c) a base end in the welding end mode in the third embodiment. The figure which shows the time change of the welding current when is selected, (d) the figure which shows the time change of the welding current when pulse end is selected as the welding end mode in Embodiment 3. (A) A diagram showing the time change of the wire feeding speed in the conventional arc start characteristic, (b) A diagram showing the time change of the welding voltage in the conventional arc start characteristic, (c) A diagram showing the time change of the welding current in the conventional arc start characteristic. Diagram showing time change

(Embodiment 1)
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.

FIG. 1 is a diagram showing a schematic configuration of a welding power supply device according to the first embodiment. FIG. 2A is a diagram showing a time change of the wire feeding speed. FIG. 2B is a diagram showing a time change of the welding voltage. FIG. 2C is a diagram showing a time change of the welding current when the wire feeding speed is high (WF1). FIG. 2D is a diagram showing the time change of the welding current when the wire feeding speed is low (WF2).

The welding power supply device inputs the primary rectifying unit 2 that rectifies the AC power input from the input power supply 1, the switching unit 3 that controls the welding output, and the output of the switching unit 3 and converts them into power suitable for welding. It includes a transformer 4, a secondary rectifying unit 5 that rectifies the secondary output of the transformer 4, a reactor 6 that smoothes the output of the secondary rectifying unit 5, and a driving unit 7 that drives the switching unit 3.

Further, a short circuit or an arc is detected from the welding voltage detection unit 9 that detects the welding voltage, the welding current detection unit 8 that detects the welding current, and the current and voltage acquired by the welding voltage detection unit 9 and the welding current detection unit 8. It includes a short-circuit / arc detection unit 10, an impulse start circuit 11 that assists arc start control, and an impulse start detection unit 12 that detects the presence / absence and characteristics of impulse start.

Furthermore, the welding condition setting unit 13 for setting the welding conditions such as the welding current, the welding voltage, the wire feeding speed, the shield gas type, the welding wire type, and the welding wire diameter, and the information set by the welding condition setting unit 13 It includes a storage unit 14 in which various parameters such as a peak current of the short-circuit initial current and a pulse parameter related to the peak current output time are stored.

The drive unit 7 controls the switching unit 3 to control the welding output.

Further, the welding wire 19 is fed by a wire feeding motor controlled by the wire feeding unit 20. Electric power for welding is supplied to the welding wire 19 via a tip 16 provided on the torch 15, and an arc 17 is generated between the welding wire 19 and the base metal 18 to perform welding.

The operation of the welding power supply device of the present invention configured as described above and performing short-circuit arc welding by repeating a short-circuit period and an arc period will be described with reference to FIGS. 1, 2, and 3. The welding condition setting unit 13 sets an arbitrary shield gas, welding wire type, welding wire diameter, welding current, or wire feeding speed setting value, which is stored in advance in the storage unit 14 and corresponds to the setting. The peak current of the short-circuit initial current for opening the short-circuit at the start and the output time of the peak current are selected or changed according to the set value, and the command value is output to the drive unit 7. In FIG. 1, when the welding start SW (not shown) is turned on, a wire feeding command is output to the wire feeding unit 20 based on the conditions output by the storage unit 14.

In the arc start, the short circuit between the welding wire 19 and the base metal 18 is opened at the start of welding to generate the arc 17 first, in other words, the first short circuit at the start of welding is short-circuited to open the arc. This is the operation process of starting the arc to be generated.

In FIG. 2, it is detected that the welding wire 19 starts to be fed at the timing of the wire feeding start time t1 and the welding wire 19 comes into contact with the base metal 18 at the timing of the main welding transition start time t2. Next, as shown in FIGS. 2 (c) and 2 (d), the arc corresponds to the condition set by the welding condition setting unit 13, and according to the wire feeding speed of the welding wire, specifically, the set value. Change the peak current and peak current time of the short-circuit initial current to open the short-circuit at the start.

Further, FIG. 3 shows changes in the peak current and the peak current output time of the short-circuit initial current with respect to the wire feeding speed. In FIG. 3, the relationship between the wire feeding speed, the initial short-circuit current peak value, and the peak current output time is proportional and is represented by a linear curve, but it does not necessarily have to be a linear curve. As an example, when the wire feeding speed (WF) is 3 m / min, the peak current is about 350 A, the peak current output time is about 2 msec, and when the wire feeding speed (WF) is 10 m / min, the peak current is about 500 A. The output time of the peak current is about 5 msec. When the wire feeding speed of the main welding is set to be low, the welding wire 19 tends to burn up, so that the heat input is reduced. Further, at a high setting, the welding wire tends to cause a short circuit for a long time, so that the heat input is increased.

According to the welding control method and the welding power supply device of the first embodiment, it is possible to suppress spatter generation caused by a long-time short circuit due to insufficient heat input to the welding wire 19 at the time of arc start, which occurs when the wire feeding speed is set to be high. At the same time, it is possible to suppress arc instability due to arc burning that occurs when the wire feeding speed is set to be low, and it is possible to form a bead with a uniform width.

(Embodiment 2)
The present embodiment will be described with reference to FIGS. 1 and 4. The same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The difference from the first embodiment is that the impulse start circuit 11 and the impulse start detection unit 12 are used. FIG. 4A is a diagram showing a time change of the wire feeding speed in the second embodiment. FIG. 4B is a diagram showing a time change of the welding voltage. FIG. 4C is a diagram showing a time change of the welding current when the impulse start is not performed. FIG. 4D is a diagram showing a time change of the welding current with an impulse start.

When an impulse start circuit is connected and impulse start is used to give an impulse current to the initial short-circuit current at the moment when the welding wire 19 contacts the base metal 18, the rise of the initial short-circuit current for opening the short-circuit at the time of arc start is steep. Therefore, an arc is likely to be generated, and the arc startability is improved. However, depending on the material of the base metal to be welded, the size of the welding wire diameter, and the like, excessive heat input to the welding wire 19 may cause arc burning and arc instability. Therefore, the impulse start detection unit 12 confirms the connection or validity (ON) of the impulse start circuit 11, and when the connection or validity (ON) is confirmed, the storage unit depends on the presence or absence of the impulse start at the start of welding. Stable arc start is possible by selecting, changing and outputting the peak current and peak current output time of the initial short-circuit current for opening the short circuit at the time of impulse start from 14.

The parameter values of peak current and peak current output time are, for example, peak current is around 400A and peak current output time is within 2msec with impulse start, and peak current is around 500A and peak current output time is within 5msec without impulse start. Is.

Further, in the state where the impulse start circuit 11 and the impulse start detection unit 12 are used as in the first embodiment, the peak current and the peak current short-circuit time of the initial short-circuit current are further changed from the storage unit 14 for each feeding speed of the welding wire. Select and output. As a result, it is possible to prevent arc instability due to arc burning that occurs when the wire feeding speed is set to be low, and to make the bead width uniform. In addition, it is possible to suppress spatter generation caused by a long-time short circuit due to insufficient heat input when the wire feeding speed is set high. The tendency of the peak current and the peak current output time of the pulse of the short-circuit initial current with respect to the wire feeding speed is the same operation as in FIG.

For example, impulse start is effective when welding a material such as aluminum or copper, which has a low resistance value and a high thermal conductivity, and therefore has a small heat input effect and is difficult to melt. However, on the contrary, a material having a high resistance value and a low thermal conductivity such as stainless steel may promote arc instability due to arc burning due to excessive heat input. Similarly, depending on the size of the wire diameter, the resistance value is high when the wire diameter is small, which may promote arc burning. The fine system has a wire diameter of, for example, 0.9 mm or less.

(Embodiment 3)
The present embodiment will be described with reference to FIGS. 1 and 5. The same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The difference from the first embodiment is a method of ending current that is selected in advance and output from the stored storage unit 14 when the welding start SW that starts and ends welding is turned off (t3).

FIG. 5A is a diagram showing a time change of the wire feeding speed in the third embodiment. (B) It is a figure which shows the time change of the welding voltage in Embodiment 3. (C) It is a figure which shows the time change of the welding current at the time of the base end current output in Embodiment 3. (D) It is a figure which shows the time change of the welding current at the time of the pulse end current output in Embodiment 3.

As described above, as a welding end mode for adjusting the shape of the tip of the wire after the main welding end time t3, a method of base end and pulse end is known, and in base end and pulse end, the weld wire after welding end. The state of the tip of 19 is different, and when the base ends, a ball is formed at the tip of the welding wire as shown in FIG. 5C, and welding ends. As shown in FIG. 5D, the pulse ends when the tip of the welding wire has a conical pointed shape like the tip of a pencil.

In the welding condition setting unit 13, either the base end mode or the pulse end welding end mode is selected as a control parameter for adjusting the shape of the tip of the welding wire or the heat input state, and is stored in the storage unit 14. The initial short-circuit current at the next arc start is set by the welding end mode that is called from the storage unit 14 when the welding start SW is OFF (t3) and corresponds to the shape of the tip of the welding wire at the end of welding. Stable arc start is possible by changing the peak current and peak current output time of.

In other words, the peak current value or peak current value output time for opening the short circuit at the time of short circuit of the arc start is used as a control parameter for adjusting the shape of the tip of the welding wire or the heat input state at the end of the previous welding. By changing according to it, stable arc start becomes possible.

Here, the selection of either the base end or pulse end welding end mode may be automatically selected by setting other welding conditions (wire diameter, wire material, etc.), or may be individually selected by the operator. It may be the choice of.

The parameter values of the peak current and the peak current output time are, for example, about 400 A and about 3 msec at the end of the pulse, and about 500 A and within about 5 msec at the end of the base.

When pulse termination is selected, the peak current at the initial short-circuit current is set lower and the peak current output time is set shorter than when base termination is selected.
As a result, it is possible to prevent arc instability due to arc burning at the start of the next welding when the end of the pulse is selected, and to make the bead width uniform. In addition, it is possible to suppress spatter generation caused by a long-time short circuit due to insufficient heat input at the start of the next welding when the end of the base is selected.

Further, as in the first embodiment, the welding condition setting unit 13 sets the set value of the welding current or the welding wire feeding speed, which is stored in advance in the storage unit 14 to release the short circuit at the time of arc start. The peak current and peak current short-circuit time of the initial short-circuit current are selected or changed according to the set values, and the command value is output to the drive unit 7. As a result, it is possible to prevent arc instability due to arc burning that occurs when the wire feeding speed is set to be low, and to make the bead width uniform.

Further, it is possible to suppress spatter generation caused by a long-time short circuit due to insufficient heat input when the wire feeding speed is set to be high. The trends of the peak current and the peak current output time of the short-circuit initial current with respect to the wire feeding speed are the same as those in FIG.

As described above, according to the welding power supply device and the arc start control of the first, second, and third embodiments, the arc start is performed according to the control parameters for adjusting the wire feeding speed, the heat input state, and the tip shape of the wire. The peak current of the initial short circuit current and the output time of the peak current are optimized to open the short circuit at the time. As a result, a long-term short circuit caused by insufficient heat input at the start of the arc can be suppressed, and the occurrence of arc burning due to excessive heat input can be prevented. Therefore, the wire feeding speed, the base material material, and the weld wire diameter vary. Good arc start characteristics can be obtained under welding conditions. As a result, it is possible to prevent spatter from occurring and to form a stable bead with a uniform bead width.

According to the present invention, in consumable electrode type arc welding, good arc start characteristics can be obtained regardless of the wire feeding speed, the type of welding wire, the type of shield gas, the material of the base material, etc. Since it can be suppressed and arc instability due to arc burning can be suppressed, it is industrially useful as an arc welding control method and an arc welding apparatus for performing arc welding capable of welding with a uniform bead width.

1 Input power supply 2 Primary rectifying unit 3 Switching unit 4 Transformer 5 Secondary rectifying unit 6 Reactor 7 Drive unit 8 Welding current detection unit 9 Welding voltage detection unit 10 Short circuit / arc detection unit 11 Impulse start circuit 12 Impulse start detection unit 13 Welding Condition setting unit 14 Storage unit 15 Torch 16 Chip 17 Arc 18 Base material 19 Welding wire 20 Wire feeding unit t1 Wire feeding start time t2 Welding transition start time t3 Welding end time

Claims (1)

This is an arc welding control method in which short-circuit arc welding is performed by repeating a short-circuit period and an arc period, and the peak current of the initial short-circuit current or the output time of the peak current for opening the short-circuit at the arc start is adjusted to the heat input state. It is changed according to the control parameters.
The control parameter is an impulse start.
An arc welding control method that changes the peak current of the initial short-circuit current or the output time of the peak current to open a short circuit at the time of arc start according to the presence or absence of impulse start at the time of arc start.

Images