JP2006346694A - Method for controlling electric current in non-consumable electrode arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically control a welding electric current Iw to be a proper value while manually adjusting a welding speed and a feed speed of a filler wire 4 to make a weld quality uniform corresponding to a temperature rise of a base material due to the progress of a welding process in non-consumable electrode arc welding manually carried out using the filler wire 4. <P>SOLUTION: In a method for controlling an welding current in non-consumable electrode arc welding carried out by manually feeding the filler wire 4 to a molten pool, wire voltage Vw between the filler wire 4 and the base material 2 is detected, and a feed speed Fw of the filler wire 4 is calculated based on the wire voltage Vw, and the welding current Iw is automatically changed according to the feed speed Fw of the filler wire 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to non-consumable electrode arc welding that can suppress a change in welding quality due to an increase in base material temperature during welding in non-consumable electrode arc welding performed while manually feeding a filler wire to a molten pool. The present invention relates to a current control method.

  FIG. 6 is a block diagram of a non-consumable electrode arc welding apparatus using a filler wire. Non-consumable electrode arc welding includes TIG welding or plasma welding. The welding power source main circuit MC receives a commercial power source such as a three-phase 200V input, performs output control such as inverter control and chopper control according to an error amplification signal Ea described later, and outputs a welding current Iw. A non-consumable electrode 1 such as a tungsten electrode is attached to the tip of a welding torch 5, and an arc 3 is generated between the base material 2. The filler wire 4 is manually fed to the molten pool by a welding operator. The welding operator also operates the welding torch 5. Since the feeding of the filler wire 4 is manual, the feeding wire 4 and the stopping time are repeated as one cycle. Therefore, in order to increase the average feeding speed, it is necessary to shorten this repetition cycle (increase the frequency).

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current setting circuit IR outputs a current setting signal Ir having a desired value. The error amplification circuit EA amplifies an error between the current setting signal Ir and the current detection signal Id, and outputs an error amplification signal Ea. Thereby, a welding apparatus becomes a constant current characteristic normally used for non-consumable electrode arc welding.

  FIG. 7 shows the bead appearance shown in FIG. 7A, the welding current Iw shown in FIG. 5B, and the welding speed Ws shown in FIG. FIG. Welding starts from time t1, and welding ends at time t2. As shown in FIG. 5B, the welding current Iw is a predetermined constant value. As shown in FIG. 3A, the base metal temperature is low at the beginning of welding, but gradually increases as welding progresses. At this time, since the welding current Iw is a constant value, heat input becomes excessive as welding progresses, and welding quality such as penetration and bead appearance varies. In order to suppress this, the welding worker determines excess heat input from the molten pool shape or the like based on many years of experience, and speeds up the movement of the welding torch to suppress this. That is, the welding operator increases the welding speed Ws as the welding progresses, as shown in FIG. At the same time, the welding operator increases the feeding speed of the filler wire in order to keep the welding amount substantially constant. The change in the welding speed Ws and the change in the feeding speed of the filler wire are in a substantially proportional relationship.

  A large change in the penetration and bead appearance can be suppressed by the above-described manual operation of the welding speed and the feeding speed of the welding operator. However, as shown in FIG. 5A, the bead 2a formed on the base material 2 changes its solidification rate when the welding speed increases, and the pitch of the wave surface on the bead surface changes. Therefore, in order to further suppress the change in the welding quality, it is necessary to directly change the heat input as the welding progresses.

  In order to keep the welding quality more uniform corresponding to the change in the base metal temperature as the welding progresses, it is necessary to directly change the heat input as described above. Since the heat input is substantially proportional to the welding current Iw, by changing the welding current Iw as the welding progresses, the heat input can be directly changed to make the welding quality more uniform. There are the following two methods as the prior art that enables the welding operator to adjust the welding current Iw during welding. The first method is to provide a current adjusting knob on the welding torch. The welding operator adjusts the current adjustment knob to change the welding current Iw so that the welding quality becomes uniform from observation of the molten pool or the like while welding. Next, the second method uses a stepping current regulator. This stepping current adjuster can adjust the welding current Iw according to the stepping angle like an accelerator of a car. In this case as well, the welding operator adjusts the stepping angle while performing welding to change the welding current Iw.

JP-A-56-131072 Japanese Patent No. 3030953

  As described above, in non-consumable electrode arc welding using a filler wire, a welding operator observes the state of a molten pool, an arc, a base material, etc. during welding so that the welding quality becomes good and uniform. The welding speed (torch moving speed), the feeding speed of the filler wire (manual insertion pitch), and the welding current value are changed. As described above, the welding current value is adjusted with a current adjustment knob, a stepping current adjuster, or the like. However, if the welding worker advances welding while simultaneously performing the above four actions (observation and three operations), a heavy burden has been imposed on the welding worker. Further, since the three operations are performed simultaneously, it is difficult to always perform the best operation. For this reason, a certain amount of welding quality change is allowed, and the welding current value is often kept constant.

  Therefore, in the present invention, in non-consumable electrode arc welding using a filler wire, the welding operator manually adjusts the welding speed and the feeding speed while observing the molten pool during welding, and the welding current is adjusted. Provided is a current control method for non-consumable electrode arc welding in which adjustment can be automated.

In order to solve the above-described problem, the first invention is a current control method for non-consumable electrode arc welding performed while manually feeding a filler wire to a molten pool.
The wire voltage between the filler wire and the base metal is detected, the feeding speed of the filler wire is calculated based on the wire voltage, and the welding current value is automatically set according to the feeding speed of the filler wire. The current control method for non-consumable electrode arc welding is characterized in that

  According to a second aspect of the present invention, there is provided a current control method for non-consumable electrode arc welding, wherein the feeding speed of the filler wire according to the first aspect of the invention is calculated from the ripple frequency of the wire voltage.

  According to a third aspect of the present invention, the current control for non-consumable electrode arc welding according to the first or second aspect is characterized in that the change in the welding current is prohibited during a predetermined initial period from the start of welding. Is the method.

  According to the first aspect of the invention, the feeding speed of the filler wire is calculated based on the wire voltage, and the welding current value is changed in accordance with the change in the feeding speed, so that the welding quality associated with the progress of welding can be improved. Variation can be suppressed and uniform. Furthermore, since the change in the welding current value is automatically performed, there is no burden on the welding operator.

  According to the second aspect of the invention, the feeding speed can be calculated from the ripple frequency of the wire voltage, and the above effect is achieved.

  According to the third aspect of the present invention, during the initial period from the start of welding, it is possible to prohibit an unnecessary change in the welding current in a transient state by prohibiting a change in the welding current according to the feeding speed. For this reason, said effect can be show | played, without the welding state in an initial period becoming unstable.

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

[Embodiment 1]
FIG. 1 is a block diagram of a welding apparatus for carrying out a current control method for non-consumable electrode arc welding according to Embodiment 1 of the present invention. In the figure, the same blocks as those in FIG. 6 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 6 will be described.

  The voltage detection circuit VD detects a wire voltage Vw between the filler wire 4 and the base material 2 and outputs a voltage detection signal Vd. Since the filler wire 4 is a conductive material, the wire voltage Vw is a value that is substantially proportional to the distance between the tip of the filler wire 4 and the base material 2. Therefore, each time the welding operator inserts the filler wire 4, the distance between the wire tip and the base material changes periodically. A ripple is superimposed on the wire voltage Vw. That is, the ripple frequency Fw [Hz] of the wire voltage Vw is synchronized with the insertion pitch of the filler wire 4. Here, since the insertion length per one insertion of the filler wire 4 performed by the welding operator can be considered to be substantially constant, as a result, the ripple frequency Fw of the wire voltage Vw is the feeding speed of the filler wire 4. It is approximately proportional to The ripple frequency detection circuit FW receives the voltage detection signal Vd, detects the ripple frequency, and outputs a ripple frequency signal Fw.

  The current increase / decrease value calculation circuit DIR receives the ripple frequency signal Fw and outputs a current increase / decrease value signal ΔIr according to a predetermined relationship. This predetermined relationship is that when the value of the ripple frequency signal Fw increases, the value of the current increase / decrease value signal ΔIr is a negative value and its absolute value increases. This predetermined relationship will be described later with reference to FIGS. The adder circuit AD adds the current setting signal Ir and the current increase / decrease value signal ΔIr and outputs a current control setting signal Icr. The subsequent steps are the same as in FIG.

  The welding operator changes the welding speed while observing the molten pool and the like, and changes the feeding speed of the filler wire 4 substantially in proportion thereto. Then, the change in the feeding speed is detected by the ripple frequency Fw of the wire voltage Vw. Subsequently, the current increase / decrease value signal ΔIr is changed according to the ripple frequency Fw to automatically change the welding current Iw. This eliminates the need for the welding operator to adjust the current during welding, reducing the burden. Furthermore, since the welding current value Iw is automatically adjusted in conjunction with the welding progress state (feeding speed), good and uniform welding quality can be obtained. In the above description, the feeding speed is detected by the ripple frequency Fw. However, a roll may be provided in the feeding path of the filler wire 4 and the rotational speed of the roll may be detected.

  FIG. 2 is an example of a relationship diagram between the ripple frequency Fw and the current increase / decrease value ΔIr in the current increase / decrease value calculation circuit DIR. The ripple frequency Fw on the horizontal axis changes in the range of 0 to 2 Hz, and the current increase / decrease value ΔIr on the vertical axis changes in the range of 0 to −15 A. For example, as indicated by point P1, ΔIr = −4A when Fw = 1 Hz, and is −4A from the current value set by the current setting signal Ir. Further, as indicated by point P2, when Fw = 2 Hz, ΔIr = −15A, which is −15A from the current value set by the current setting signal Ir. Since the relationship between Fw and ΔIr in the figure varies depending on the material of the base material, the plate thickness, the joint, and the like, it is determined in advance for each of these welding conditions.

  FIG. 3 is a relationship diagram between the ripple frequency Fw and the current increase / decrease value ΔIr, which is different from FIG. 2 described above. In the figure, the horizontal axis represents the ripple frequency deviation ΔFw, and the vertical axis represents the current increase / decrease value ΔIr. This ripple frequency deviation ΔFw is defined as ΔFw = Fw−Fwt by a predetermined reference ripple frequency Fwt. However, when ΔFw <0, ΔFw = 0. The reference ripple frequency Fwt is a value determined in advance for each type of workpiece. Thereby, when the ripple frequency Fw during welding becomes more than the reference ripple frequency Fwt, it is determined that the heat input to the base material has been exceeded, and the welding current value Iw is decreased.

  There is also a method of automatically setting the reference ripple frequency Fwt to the ripple frequency Fw when a predetermined time has elapsed from the start of welding. During the predetermined time until the reference ripple frequency Fwt is set, increase / decrease of the welding current is prohibited. In this way, it is not necessary to set the reference ripple frequency Fwt beforehand through experiments or the like.

  FIG. 4 shows the bead appearance shown in FIG. 4A and the welding shown in FIG. 4B when the non-consumable electrode arc welding is performed by the current control method for non-consumable electrode arc welding according to Embodiment 1 described above. It is a time change figure of electric current Iw, welding speed Ws shown in the figure (C), and ripple frequency Fw shown in the figure (D). This figure corresponds to FIG. 7 described above. Welding is started at time t1, and as the welding progresses, the base material temperature rises and heat input is exceeded. The welding operator judges that the heat input has been exceeded from observation of the molten pool and the like, and increases the welding speed and the feeding speed as shown in FIG. As the feeding speed increases, the ripple frequency Fw of the wire voltage increases as shown in FIG. In response to this, the negative value of the current increase / decrease value ΔIr increases, and the welding current value Iw gradually decreases as shown in FIG. For this reason, the degree of increase in the welding speed and the feeding speed is suppressed to be smaller than that in FIG. As a result, as shown in FIG. 5A, the weld quality such as the pitch of the wave on the bead surface, penetration, and bead appearance becomes substantially uniform and good.

[Implementation default 2]
FIG. 5 is a time variation diagram of welding speed Ws and ripple frequency Fw showing a current control method of non-consumable electrode arc welding according to Embodiment 2 of the present invention. In FIG. 4, the welding speed Ws shown in FIG. 4C and the ripple frequency Fw shown in FIG. Since the welding state is in a transient state during the initial period Ts after the start of welding, it is not necessary to change the welding current Iw according to the ripple frequency Fw during the initial period Ts. This is because during the initial period Ts, the welding operator does not change the welding speed and the feeding speed by judging that the heat input has been exceeded, but operates to quickly bring the transient state into the steady state. It is. Therefore, during the predetermined initial period Ts, a change in the welding current due to the ripple frequency Fw is prohibited to prevent the welding current from changing unnecessarily.

It is a block diagram of the welding apparatus for enforcing the electric current control method of the non-consumable electrode arc welding which concerns on Embodiment 1 of this invention. FIG. 5 is a relationship diagram between a ripple frequency Fw and a current increase / decrease value ΔIr according to the first embodiment. FIG. 6 is a relationship diagram between a ripple frequency deviation ΔFw and a current increase / decrease value ΔIr according to the first embodiment. It is a time change figure of a bead appearance when welding is performed by Embodiment 1, welding current Iw, welding speed Ws, and ripple frequency Fw. It is a time change figure of welding speed Ws and ripple frequency Fw which shows the electric current control method of non-consumable electrode arc welding concerning Embodiment 2. FIG. It is a block diagram of the non-consumable electrode arc welding apparatus of a prior art. It is a time change figure of a bead appearance, welding current Iw, and welding speed Ws when welding is performed by a conventional technique.

Explanation of symbols

1 Non-consumable electrode 2 Base material 2a Bead 3 Arc 4 Filler wire 5 Welding torch DIR Current increase / decrease value calculation circuit EA Error amplification circuit Ea Error amplification signal FW Ripple frequency detection circuit Fw Ripple frequency (signal)
Icr current control setting signal ID current detection circuit Id current detection signal IR current setting circuit Ir current setting signal Iw welding current MC welding power supply main circuit Ts initial period VD voltage detection circuit Vd voltage detection signal Vw wire voltage Ws welding speed ΔFw ripple frequency deviation ΔIr Current increase / decrease value (signal)

Claims (3)

In the current control method of non-consumable electrode arc welding performed while manually feeding the filler wire to the molten pool,
The wire voltage between the filler wire and the base metal is detected, the feeding speed of the filler wire is calculated based on the wire voltage, and the welding current value is automatically set according to the feeding speed of the filler wire. A current control method for non-consumable electrode arc welding, characterized in that:   2. A current control method for non-consumable electrode arc welding, wherein a feeding speed of the filler wire according to claim 1 is calculated by a ripple frequency of the wire voltage. 3. The current control method for non-consumable electrode arc welding according to claim 1, wherein the change of the welding current is prohibited during a predetermined initial period from the start of welding.

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