JP2857448B2 - Hot wire TIG welding method, hot wire TIG welding apparatus, and contact detector between wire and base metal - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to hot wire TIG welding, and more particularly to a hot wire TIG welding method and a welding apparatus for heating and melting a wire by applying a current to the wire in a pulsed manner. .

[Conventional technology]

FIG. 9 shows a configuration of a welding apparatus generally used conventionally as a hot wire TIG welding method.

Tungsten electrode 2 and base metal 3 in TIG welding torch 1
Is connected to an arc power supply 4 for DC welding, and the arc 5 is used in an argon shielding gas with the tungsten electrode 2 as a negative electrode.
To form The welding wire 6 for welding is a wire feeder 7
Through the conduit 8 and the contact tip 9 connected to the conduit 8 to be guided to the arc forming portion to make contact with the base material 3. The contact tip 9 and the wire heating power source 10 are connected, and a direct current or an alternating current is supplied to the additional wire 6 to generate Joule heat, thereby increasing the melting speed of the additional wire 6. The addition wire 6 is inserted from outside the gas shield nozzle 11 at the tip of the TIG torch 1.

The addition wire 6 is a cold wire that is not electrically heated.
In the case of TIG welding, it can be said that the wire heating power supply 10 in FIG. 9 is excluded.

By the way, at the time of cold wire TIG welding, as shown in FIG. 10, the additional wire 6 is separated from the tungsten electrode 2 forming the arc 5 by about 3 mm and almost in parallel with the molten pool 12.
When the TIG torch 13 is configured to feed toward
The entire size of the torch including the wire feeding section is very compact.

However, in this case, since the tip of the wire 6 is in contact with the base material (melt pool) 3 in the conventional method,
Becomes equal to the base material potential, so that when the distance between the tungsten electrode 2 and the base material 3 happens to be slightly longer such as 5 mm, the arc 5 crawls from the base material 3 along the wire 6 and exits from the shortest wire portion. As a result, the melting stability of the arc 5 and the wire 6 is significantly impaired, and the melting operation cannot be performed. The same applies to the case of hot wire TIG welding. In particular, when the arc 5 comes out of the wire 6 and the melting of the wire remarkably progresses and the wire is continued to be melted, the arc current is supplied to the wire heating power supply 10. Flow and adversely affect the wire heating power supply 10.

Therefore, conventionally, in order to avoid such a state, the wire 6 is separated from the tungsten electrode 1 as much as possible and the tip of the wire is inserted into the molten pool 12 on the base material 3. For this reason, for example, the wire insertion angle θ shown in FIG. 9 must be 60 degrees or less, so that the wire 6 is inserted from the outside of the gas shield nozzle 11 of the torch 1, and eventually the portion around the torch is It was getting bigger. Usually, the wire 6 is inserted from a diagonal lateral direction of the arc torch through a wire guide or a wire contact tip 9 which moves integrally with the arc torch.
There is also a problem that if the arc length changes, the insertion position of the tip of the wire tends to change. Even when such a TIG torch is mounted on a process robot, the periphery of the torch is often large and it is difficult to insert the torch. For these reasons, most of the current arc welding robots are occupied by non-consumable electrode arc welding, and TIG arc welding robots are rarely used.

The present inventors have previously proposed a method for solving this problem (Japanese Patent Application Laid-Open No. 63-180376). In the present invention, the tip of the wire 6 and the molten pool 12 on the base material 2 are made to repeat contact and separation periodically, and as shown in FIG. During the contact period, that is, the contact detection signal is enabled only during the contact period. When the wire 6 comes into contact with the base material 3, the arc conduction is stopped. When the hot wire is to be welded in order to increase the wire melting rate, energization is started when the wire comes into contact with the base material, and the wire is heated and melted to separate from the base material.

In this manner, the wire is connected to the tungsten electrode 2
The arc is no longer generated from the wire 6 even if the wire 6 is immediately adjacent to the wire, and the wire 6 can be inserted and welded almost in parallel with the tungsten electrode 2.

[Problems to be solved by the invention]

However, according to the present invention, although the arc 5 can be formed stably, it is necessary to cause the wire 6 to be blown every time. At the time of hot wire welding, spatter occurs due to the blow and adheres to the tungsten electrode 2 on the immediate side. It happened. This spatter is very fine and does not adhere to the base material 3, but gradually accumulates on the tungsten electrode 2. If the electrode contamination gradually increases in this way, it becomes difficult to perform welding, so that a new problem of increasing the frequency of replacement of the tungsten electrode 2 has arisen.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the object of the present invention is to provide a method for hot wire welding in which the wire is heated and melted at each wire energizing cycle to form a weld metal and separate the wire tip from the base material. It is another object of the present invention to provide a welding method and a welding apparatus which drastically reduce the generation of spatters when separating from the third member.

Another object of the present invention is to provide an apparatus for detecting whether a wire is in contact with a base material in hot wire TIG welding in which a wire is heated with a pulse current while repeating contact and separation between the wire and the base material. It is in the thing.

[Means for solving the problem]

In order to achieve such an object, the present invention provides a method of starting heating of a wire after the wire comes into contact with a base material, and stopping the current supply of the wire before the tip of the wire separates from the base material. The tip is separated from the base material.

Furthermore, in order to achieve the above object, the present invention uses a detector that discriminates whether a wire is in contact with a base material from a wire voltage and a wire current, and measures a period in which the wire is in contact with the base material every time. Then, the average time is obtained, the wire energization is started at the start of the next contact, and the control is performed such that the wire energization is stopped after a lapse of a time slightly shorter than the average time from the start of the contact.

[Action]

Spatter occurs when the wire is heated and melted by the current flowing through the wire, and when the tip is narrowed and separated from the base material, the constricted part overheats and evaporates explosively, and an arc is generated from the separated part And the gas expands rapidly. According to the present invention, since the current supply is stopped before overheating and explosive evaporation, there is no explosive evaporation, and no arc is generated from the separation portion.

(Example of the invention)

FIG. 1 is a view showing an embodiment of a hot wire TIG welding apparatus according to the present invention, in which 14 is an arc power supply circuit section, 15 is a wire power supply circuit section, 16 is a wire feed control circuit, and 17 is associated with them. The hot wire TIG welding power source 18 is constructed by integrating these components. The output terminal on the secondary side of the hot wire TIG welding power source 18 is connected to the tungsten electrode 2 in the TIG torch 13, the contact tip 9 for energizing the wire, and the base material 3, respectively. Is connected to the wire feeding device 7. The wire current is a current detector 44 consisting of a Hall element.
And the output terminal voltage of the wire power supply circuit unit 15 is also detected and input to the control circuit unit 17.

FIG. 2 is a diagram for explaining output waveforms and the like in the embodiment of FIG. In the hot wire TIG welding power source 18, a slightly lower continuous current called a start current is supplied to the arc 5 in a period immediately after the arc start. When the melting of the base material 3 proceeds and the molten pool 12 is sufficiently formed,
When the wire feeding is started and the wire 6 comes into contact with the base metal 3 (the molten pool 12), the current control during welding is switched as shown in FIG. That is, after the wire 6 is welded to the base material 3, the heating of the wire is started, and before the tip of the wire is separated from the base material 3, the feeding of the wire is stopped. And the arc is regenerated after separation.

FIG. 3 is a block diagram for explaining a main circuit configuration inside the control circuit 17 of FIG. When the contact detection circuit 19 detects that the wire 6 has come into contact with the base material 3, the output signal Tu is sent to the arc conduction command circuit 20 and the output signal Ta is requested to immediately stop the arc conduction. At the same time, the output signal Tu is sent to the wire formation permission period signal forming circuit 21,
The output signal Tp there requests the wire conduction command circuit 22 to conduct the wire for a certain period. Next, when the contact detection circuit 19 detects that the wire 6 has separated from the base material 3, the arc energization command circuit 20 instructs the arc energization to be restarted immediately by the output signal Ta. Generally, the control is performed in this manner to obtain the waveform of the energizing current as shown in FIG. In addition,
Here, the circuit related to ON-OFF control of the arc current and the wire current is shown. There are other arc current cells and a circuit for externally instructing and controlling the wire current value, but they are omitted.

However, since various disturbances actually occur with respect to the wire melting, the control circuit of FIG. 3 including the corresponding control will be described in further detail. The wire voltage Vw and the wire current Iw are detected and input to the contact detection circuit 19 to form a contact signal Tu which becomes H when the wire 6 is separated from the base material 3 and becomes L when the wire is in contact with the base material. I do. This contact signal Tu
The signal forming circuit 21 forms and outputs a signal Tp which is H during the period during which the wire conduction is permitted and L during the period during which the wire conduction is not permitted. This signal
In the steady state, the period in which Tp is H is formed so as to be slightly shorter than the period in which the wire is in contact with the base material. Therefore, the wire is separated from the base material after the current supply to the wire is completed. However, changes in wire speed and other changes can also cause the wires to break apart during wire contact. When the wire separates from the base material while the wire is energized, the wire current sharply decreases.Therefore, the wire energization prohibition period setting circuit 23 uses the wire current differential output Iw from the wire current differentiating circuit 24 based on the wire current Immediately after the start of a rapid decrease, the output Ti is set to L for a certain period of time to stop the supply of the wire current. This suppresses the occurrence of spatter when the wire is blown and separated during the current supply period.

On the other hand, the fusing force circuit 25 monitors the contact signal Tu, and when the contact is continued for a certain period (15 ms in this embodiment) or more, sets the output signal Fu to H and requests that the wire current be continuously supplied. . As a result, the wire is overheated and fusing occurs, and the wire is separated from the base material. Also at the time of this wire separation, the energization inhibition period setting circuit 23 operates to suppress the occurrence of spatter.

When the wire current Iw becomes equal to or more than a predetermined current (500 A in the present embodiment), the overcurrent protection circuit 26 sets the output OVC to L, suspends power supply immediately, and prevents the power control element inside the wire heating power supply from being destroyed. The external control signal Sc controls the start and end of energization by an external switch or the like. The wire energization command circuit 22 aggregates these signals and generates a wire power supply circuit.
15 as a drive signal Tw.

FIG. 4 illustrates details of the configuration of the contact detection circuit 19. The output terminal voltage Vw of the wire power supply circuit unit 15 is a voltage between the base material 3 and the contact tip 9 of the wire, that is, the voltage between the wire extension and the voltage including the voltage drop in the cable on the way. This output terminal is connected to a pull-up circuit 27 for applying a voltage via a high resistance. Therefore, the output voltage a1 of the pull-up circuit is 0 V when the wire tip is not in contact with the wire and the wire tip is in contact with the base material, and the wire 6 tip is separated from the base material 3 and is in the arc plasma. Normally a plasma potential of -4 to -8 V when floating, and a pull-up voltage of -12 when the wire tip is out of the plasma.
Become V

In the comparison circuit (1) 28, when the output voltage a1 of the pull-up circuit 27 is on the 0V side from the threshold voltage -3.5V, it is determined that the wire is in contact with the base material, and the output a2 is set to H.
To When the wire current is supplied, the output voltage b1 of the pull-up circuit 27 is a voltage on the minus side from -3.5V, and the output terminal voltage Vw of the wire heating unit is on the minus side from -4V. Do not judge. Therefore, the wire current Iw is detected, and the output a3 is set to L when the wire current is 30 A or more by the comparison circuit (2) 29, and it is determined that the wire 6 is still in contact at this time. Actually a signal extension circuit
The output signal a4 is inverted to H at 30 and the signal end time is extended by 0.3 ms. During this 0.3 ms, the wire current is 0
The state becomes A, and thereafter, the wire contact state is determined based on the output signal a2 of the comparison circuit (1) 28. If the wire current Iw is 30 A or less and the output terminal voltage Vw is -3.5 V or more when the wire 6 starts to be energized after the wire 6 starts to contact, for example, the cable through which the wire heating current flows is considerably long and the voltage drop occurs. There are times when it can no longer be ignored. In this case, even though the wires are in contact, it is determined that the wires are separated.

As a countermeasure, when the output signal a2 changes from L to H, the output a5 is set to H for 10 μs by the pulse forming circuit 31. When a4 is L and a5 is H in the discrimination / extension circuit 32, the output a6 is set to H for 0.3 ms. And When the power supply to the wire is stopped, a2 normally changes from L to H and a pulse is output again at the output a5. However, since the signal a4 is still H due to the operation of the signal extension circuit 30, the output a5 is output.
Remains at L. The output signal thus formed
The a2, a4, and a6 are collected by the NOR circuit 33, and when the output Tu is L, it is determined that the wire is in contact with the base material.

FIG. 5 is a block diagram showing the internal configuration of the wire energizing period signal forming circuit 21. The contact detection signal Tu is L when the wire is in contact with the base material, and is H when the wire is separated. The time proportional signal circuit (1) receives the contact detection signal Tu as an input, and the output signal b1 of the output signal b1 becomes 0V when Tu is H, and the voltage increases in proportion to the elapsed time when Tu becomes L.

The signal delay circuit (1) 35 receives the contact detection signal Tu as an input, and the output signal b2 of the signal delay circuit H2 is H when Tu is H and before it elapses to L before a certain period (1 ms in this embodiment), and thereafter L.
Becomes The time proportional signal circuit (2) 36 receives the output signal b2 of the signal delay circuit (1) 35 as an input, and
In this case, an output signal b3 is generated in which the voltage increases in proportion to the elapsed time when the voltage becomes 0 V and L. The slope at which this voltage rises is equal to or slower than the time proportional signal circuit (1) 34. Next, the output b4 of the sample period signal circuit 37
Is always H, and becomes L only for a certain period (0.1 ms in this embodiment) from when the wire 6 is separated from the base material 3, that is, when the input signal Tu changes from L to H. In this way, the sample and hold circuit 37 separates the wire from the base material, that is, when the signal Tu is L
A certain period of time from the point when it changes to H (0.1 ms in this embodiment)
During this period, the output b3 of the time proportional signal circuit (2) 36 is sampled and then held, and a voltage b5 corresponding to each contact time is output. The output signal b7 of the averaging time circuit 38 is the same as the sample period signal b4. It is L for a certain period (0.3 ms in this embodiment) from L to H, and H for other periods.

As shown in detail in FIG. 6, the averaging correction circuit 39 is a charging / discharging circuit including a resistor R, a capacitor C, an analog switch Sa, and an amplifier Am. The analog switch Sa is turned on, and the output voltage b5 of the sample-and-hold circuit 37 is connected to the capacitor C via the resistor R. In this way, a voltage b7 corresponding to the average of the contact time obtained while taking in the contact time for each time and correcting the average of the previous contact time is output. The energization permission signal circuit 40 compares the output voltage b1 of the time proportional signal circuit (1) 34 with the output voltage b6 of the averaging correction circuit 39, and sets the output Tp to H only when b1> b6. Permit wire energization.
The wire energization permission period signal forming circuit 21 is constituted by such a circuit, and functions so that the wire 6 is separated from the base material 3 after the wire energization is completed. The difference between the contact time and the energization permission period is determined by the delay time in the signal delay circuit (1) 35 and the time proportional signal circuit (1) 36 and the time proportional signal circuit (2) 36
The weight of the average of the contact times measured each time is adjusted by the averaging time b7.

Since the hot wire TIG welding apparatus 18 according to the present invention is configured as described above, the wire energization is suspended before the wire tip is separated from the base material 3, and the wire 6 is stopped during the wire energization suspension.
The tip could be separated from the base material 3 and almost no spatter occurred.

A hot wire TIG welding apparatus 18 according to the embodiment of FIG.
Is a power supply in which the arc power supply circuit unit 14 and the wire power supply circuit unit 17 are integrated into two separate power supplies. FIG. 7 shows another embodiment of the present invention, in which the output of one TIG arc power supply 41 is divided and used as a wire heating power supply. In other words, the negative output terminal of the TIG arc power supply having a normal drooping characteristic is connected to the contact tip 9 that energizes the wire through the tungsten electrode 2 and the transistor 42 that switches a large current, and the positive output terminal is connected to the base material 2. . The control circuit 43 functions in principle substantially the same as the circuit of FIG. 3, and turns on / off the transistor 42 based on the contact signal Tu.

FIG. 8 shows a current waveform in this device. Wire 6
Detects that the transistor 42 has contacted the base material 3, the transistor 42
To ON. Then, the current of the power supply 41 is short-circuited by the wire 6 so to speak, most of the current flows through the wire 6, and the arc 5 is extinguished. When the wire is heated in this manner and the transistor 42 is turned off after an appropriate time elapses and the wire energization is stopped, the arc is regenerated and the current of the power supply 41 flows through the arc. After the suspension of the current supply to the wire, the wire 6 separates from the base material 3. During this time,
An arc may occur between the wire 6 and the tungsten electrode 2 which are in contact with the base material 3 and have a base material potential,
Since the period is as short as about 1 ms, it does not hinder the welding operation. Also, according to the present embodiment, spatters hardly occur. Although the power supply can be constructed at a lower cost than the dual power supply system shown in FIG. 1, the wire current becomes almost the same as the arc current because of the use of the power supply with the drooping characteristic. Case).

〔The invention's effect〕

According to the present invention, the additive wire can be inserted very close to the tungsten electrode and inserted into the molten pool.
The added wire can be fed from inside the shield nozzle, and the torch for hot wire TIG welding can be made smaller.

Also, compared to the conventional method, the insertion position of the wire tip can be considerably closer to the center axis of the arc, so the influence of the positional relationship between the welding progress direction and the wire insertion direction is reduced, and the The welding torch can now be operated freely with little regard for the relationship.

In addition, the present welding method itself does not energize the wire during the energization of the arc, so that even in the case of hot wire TIG welding, magnetic blowing of the arc, which is considered to deteriorate welding workability, does not occur.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a TIG welding apparatus according to an embodiment of the present invention, FIG. 2 is an output current waveform diagram thereof, and FIGS.
1 is a diagram illustrating a control circuit of the apparatus of the embodiment of FIG. 1, FIG. 7 is a schematic configuration diagram of a TIG welding apparatus according to another embodiment of the present invention, and FIG. FIG. 9 is a schematic diagram of a conventional TIG welding apparatus, and FIG.
FIG. 11 is an explanatory diagram of a conventional TIG torch, and FIG. 11 is an output current waveform diagram according to the conventional technology. DESCRIPTION OF SYMBOLS 1 ... TIG torch, 2 ... Tungsten electrode, 3 ... Base material, 5 ... Arc, 6 ... Addition wire, 14 ... Arc power supply circuit part, 15 ... Wire power supply circuit part, 16 ... Wire transmission Supply control circuit, 17 Control circuit section.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiro Tsunoda 1-2-10 Isogo, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Babkotsuk Hitachi, Ltd. Yokohama Plant (56) References JP-A-58-3784 (JP, A) JP-A-63-144872 (JP, A) JP-A-63-13672 (JP, A) JP-A-63-180376 (JP, A) Fully open JP-A-60-166469 (JP, U) (58) (Int.Cl. ⁶ , DB name) B23K 9 / 167,9 / 095,9 / 12

Claims (6)

(57) [Claims] 1. A power supply for a TIG arc, a torch for a TIG arc, an additional wire feeder, and a power supply for heating a wire, wherein the tip of the wire repeatedly contacts and separates from the base material at a frequency of 5 Hz or more. A hot wire TIG welding method that starts wire energization after contact with the material, and suspends wire energization before the wire tip separates from the base material. 2. A hot wire TIG welding apparatus equipped with a TIG arc power supply, a TIG arc torch, an additional wire feeder, and a wire heating power supply. Means for periodically repeating contact and separation with the pond; means for detecting whether or not the wire tip is in contact with the base material from the wire terminal voltage and wire current waveforms; A time-measuring means for measuring the period during which the wire is energized, and a wire energization permission period setting that determines the wire energization period so that the wire energization period is slightly shorter than the contact period during the next contact period based on the result of repeatedly measuring the contact time. Means, and a control signal output means for receiving a signal output from the wire energization permission period setting means and outputting a control signal to an output control means. Apparatus. 3. An arc current output control circuit is provided which enables arc conduction only while the wire is away from the base material and suspends arc conduction while the wire is in contact with the base material. The hot wire TIG according to claim 2, wherein
Welding equipment. 4. The hot wire according to claim 2, further comprising an arc current output control circuit operable to perform the arc energization only during a period in which the wire energization is suspended.
TIG welding equipment. 5. When the wire is in contact with the base material, 60
The hot wire TIG welding device according to claim 2, further comprising an arc current control device that sets a low arc current of A or less and sets a high arc current when the wire is separated from the base material. 6. A means for detecting that the wire has started to contact the base material since the wire voltage becomes −2 V to 0 V when the wire heating current is kept in a non-energized state; Means for starting wire energization within 0 to 1 ms after detecting the start; means for stopping energization of the wire current after a predetermined energization period has elapsed; and a wire current sharply decreasing before the predetermined energization period has elapsed. Means to stop the wire current supply as soon as it starts to work, means to judge that the wire is in contact with the base material while the wire current is flowing, and that the wire voltage has become -2 V or more after the wire supply is stopped. Means for detecting that the wire has been separated from the base material, a contact detector between the wire and the base material.