JP2019005790A - Non-consumable electrode arc welding control method - Google Patents

Abstract

To suppress occurrence of arc interruption in non-consumable electrode arc welding.SOLUTION: A non-consumable electrode arc welding control method according to which a welding current Iw is electrically conducted and a welding voltage Vw is applied between a non-consumable electrode which is attached to a welding torch and a base material to generate arc, thereby performing welding. In this method, when the welding voltage Vw during generation of arc becomes a reference voltage value or more and a rate of increase of the welding voltage Vw becomes a reference rate of increase or more, the welding torch is moved so that a stand-off Lw, which is a distance between a tip of the electrode and the base material, becomes short. The state that the stand-oof Lw is so made as to be short is continued until the welding voltage Vw becomes less than a second reference voltage value. Thus, an omen state of arc interruption is discriminated and the stand-off Lw is so made as to be short, and therefore, occurrence of arc interruption can be suppressed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a non-consumable electrode arc welding control method in which a welding current is applied between a non-consumable electrode attached to a welding torch and a base material, an arc is generated by applying a welding voltage, and welding is performed. .

  Non-consumable electrode arc welding includes TIG welding, plasma arc welding, and the like. In non-consumable electrode arc welding, a non-consumable electrode such as a tungsten electrode is used as an electrode, and welding is performed by generating an arc between the electrode and the base material in a state shielded from the atmosphere by a shielding gas such as argon gas. Do. DC non-consumable electrode arc welding is used for steel, stainless steel, etc., and AC non-consumable electrode arc welding is used for aluminum or the like.

  In non-consumable electrode arc welding, it is common to ignite an arc by applying a high frequency high voltage between an electrode and a base material from a high frequency generation circuit at the start of welding. The high frequency high voltage is about several MHz several kV. Once the arc is ignited, the application of the high frequency high voltage is stopped. That is, no high frequency high voltage is applied during arc generation. When an arc break occurs for a predetermined period (about 100 ms) or more during welding, a high frequency high voltage is applied to ignite the arc again. In AC non-consumable electrode arc welding, since the arc is extinguished once when the polarity is switched, a high frequency high voltage is applied when the polarity is switched (see Patent Document 1). When switching the polarity, a high DC voltage may be applied for a short time instead of the high frequency high voltage.

Japanese Patent Laid-Open No. 1-154870

  When arc breakage occurs during welding, welding quality such as penetration depth and bead appearance deteriorates. Arc breaks are likely to occur when the welding current is a small current value, the surface condition of the base material is poor, the shield condition is poor, and the like. Therefore, it is important to suppress the occurrence of arc breaks in order to perform high-quality welding.

  Accordingly, an object of the present invention is to provide a non-consumable electrode arc welding control method capable of suppressing the occurrence of arc breaks.

In order to solve the above-described problems, the invention of claim 1
In a non-consumable electrode arc welding control method for welding by applying a welding current between a non-consumable electrode attached to a welding torch and a base material and applying a welding voltage to generate an arc,
When the welding voltage during arc generation is equal to or higher than the reference voltage value and the rate of increase of the welding voltage is equal to or higher than the reference rate of increase, the standoff that is the distance between the tip of the electrode and the base material is short. Moving the welding torch so that
This is a non-consumable electrode arc welding control method.

The invention of claim 2 holds the state in which the stand-off is shortened for a predetermined period.
The non-consumable electrode arc welding control method according to claim 1.

The invention of claim 3 maintains the state in which the stand-off is shortened until the welding voltage becomes less than a second reference voltage value.
The non-consumable electrode arc welding control method according to claim 1.

Invention of Claim 4 changes the said reference voltage value according to the setting value of the said welding current,
It is a non-consumable electrode arc welding control method of any one of Claims 1-3 characterized by the above-mentioned.

  According to the present invention, it is possible to determine the precursor state of arc breakage and move the welding torch so that the standoff, which is the distance between the tip of the electrode and the base material, is shortened. Can do.

It is a block diagram of the welding apparatus for enforcing the non-consumable electrode arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus mentioned above in FIG. It is a block diagram of the welding apparatus for enforcing the non-consumable electrode arc welding control method which concerns on Embodiment 2 of this invention.

  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 the non-consumable electrode arc welding control method according to Embodiment 1 of the present invention. This figure shows a case where the non-consumable electrode arc welding is DC TIG welding. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200V, performs output control such as inverter control according to a current error amplification signal Ei described later, and outputs a welding current Iw.

  The welding torch 4 is equipped with a non-consumable electrode 1 and supplies power to the electrode 1. The robot RM holds the welding torch 4 and moves the welding torch 4 along the taught welding line.

  The welding current Iw is energized through the welding torch 4, the electrode 1, the arc 3 and the base material 2, and a welding voltage Vw is applied between the electrode 1 and the base material 2. The distance in the axial direction of the electrode 1 between the tip of the electrode 1 and the base material 2 is the standoff Lw.

  The current setting circuit IR outputs a predetermined current setting signal Ir. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current error amplification circuit EI amplifies an error between the current setting signal Ir and the current detection signal Id and outputs a current error amplification signal Ei. Constant current control is performed by performing output control of the power supply main circuit PM according to the current error amplification signal Ei, and a welding current Iw having a desired value is energized.

  The current energization determining circuit CD receives the current detection signal Id, and when this value is equal to or greater than a threshold value (about 1 A), it determines that an arc has occurred and becomes a high level current energizing determination signal Cd. Is output.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd.

  The reference voltage setting circuit VTR outputs a predetermined reference voltage setting signal Vtr. The reference increase rate setting circuit DTR outputs a reference increase rate setting signal Dtr which is a predetermined positive value.

  The voltage differentiation circuit DV receives the voltage detection signal Vd as described above, differentiates the voltage detection signal Vd, and outputs a voltage differentiation signal Dv.

  The arc interruption sign determination circuit AD receives the current conduction determination signal Cd, the voltage detection signal Vd, the reference voltage setting signal Vtr, and the reference increase rate setting signal Dtr, and the current conduction determination signal Cd is High. The reference voltage value Vd is equal to or greater than the reference voltage value Vt determined by the reference voltage setting signal Vtr and the value of the voltage differential signal Dv is determined by the reference increase rate setting signal Dtr when the level (arc is generated). When the rate of increase is equal to or higher than Dt, the high level is output, and when a predetermined period has elapsed, the low level is output when the arc breakage symptom determination signal Ad is output. The timing for returning the arc-off sign determination signal Ad to the Low level may be a time point when the voltage detection signal Vd becomes less than a predetermined second reference voltage value Vt2. The second reference voltage value Vt2 is smaller than the reference voltage value Vt.

  The high frequency control circuit HC receives a welding start signal St and the above-described current energization determination signal Cd from the robot controller RC, which will be described later, the welding start signal St is at a high level (startup), and the current energization determination signal Cd. When is at the low level (non-energized), the high-frequency control signal Hc that is at the high level is output. The state in which the high frequency control signal Hc is at a high level is when the arc is ignited at the start of welding or when an arc break occurs during welding.

  The high frequency generation circuit HF has the same configuration as that of the prior art, and a detailed configuration is omitted. However, the high frequency generation circuit HF includes a high voltage transformer, a spark gap, a resonance capacitor, and the like. When Hc is at a high level, a high frequency high voltage Hf is output.

  The coupling coil CC is inserted into the energization path of the welding current Iw, and applies the high frequency high voltage Hf between the electrode 1 and the base material 2. The bypass capacitor C bypasses the high frequency high voltage so as not to be applied to the power supply main circuit PM.

The robot controller RC receives the current energization determination signal Cd and the arc break sign determination signal Ad, performs the following processing, and outputs a welding start signal St and an operation control signal Mc.
1) An operation control signal is output to a plurality of servo motors (not shown) of the robot RM, and the welding torch 4 is moved to the welding start position.
2) When the welding torch 4 reaches the welding start position, the welding start signal St is set to High level and output.
3) After that, when the current conduction determination signal Cd becomes High level, the welding torch 4 is moved along the weld line.
4) When the arc break sign determination signal Ad changes to a high level during welding, the welding torch 4 is moved in the axial direction of the electrode 1 so that the stand-off Lw is shorter than a predetermined teaching value by a predetermined value. Thereafter, when the arc break sign determination signal Ad changes to the Low level, the welding torch 4 is moved so that the standoff Lw returns to the teaching value.

  FIG. 2 is a timing chart of each signal in the welding apparatus described above with reference to FIG. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the current conduction determination signal Cd, D) shows the change over time of the arc break sign determination signal Ad, and (E) shows the change over time of the standoff Lw. This figure shows a case where the arc length becomes long due to a disturbance during the arc generation, and a sign of arc breakage is reached. Hereinafter, the operation of each signal will be described with reference to FIG.

  During the period before time t1, a stable arc is generated. During this period, the welding current Iw set by the current setting signal Ir is energized as shown in FIG. Further, as shown in FIG. 5B, the welding voltage Vw is a normal value proportional to the arc length. As shown in FIG. 5C, the current energization determination signal Cd is at a high level because the welding current Iw is energized. As shown in FIG. 4D, the arc break sign determination signal Ad is at a low level because the welding voltage Vw is a normal value. As shown in FIG. 5E, the standoff Lw has a predetermined teaching value. This teaching value is, for example, 4 mm.

  The arc length becomes longer due to the disturbance from time t1, and a sign of arc breakage is obtained. As the arc length increases, the welding voltage Vw gradually increases from time t1 and the rate of increase gradually increases as shown in FIG. At time t2, welding voltage Vw becomes equal to or higher than a predetermined reference voltage value Vt, and at time t3, the rate of increase in welding voltage Vw (voltage differential signal Dv) becomes equal to or higher than a predetermined reference rate of increase Dt. At time t3, the current conduction determination signal Cd shown in FIG. 5C is at a high level, the welding voltage Vw is equal to or higher than the reference voltage value Vt, and the rate of increase of the welding voltage Vw is equal to or higher than the reference rate of increase Dt. Therefore, as shown in FIG. 4D, the arc break sign determination signal Ad changes to the high level. In response to this, the robot controller RC moves the welding torch 4 so that the standoff Lw is shortened by a predetermined value. As a result, as shown in FIG. 5E, the standoff Lw has a slope from the teaching value at time t3 and is shortened by a predetermined value. The predetermined value is, for example, 1 to 2 mm.

  As the standoff Lw becomes shorter, the arc length also becomes shorter. For this reason, as shown in FIG. 5B, the welding voltage Vw continues to rise for a while from time t3, then reverses from time t4 to decrease, and the second reference voltage predetermined at time t5. It becomes less than the value Vt2 and returns to the normal value at time t6. As shown in FIG. 4D, the arc interruption sign determination signal Ad returns to the Low level at time t5 when the welding voltage Vw becomes less than the second reference voltage value Vt2. In response to this, the robot controller RC moves the welding torch 4 so that the standoff Lw becomes the original teaching value. As a result, as shown in FIG. 5E, the standoff Lw returns to the teaching value with a slope at time t5. The timing at which the arc-breaking sign determination signal Ad is returned to the low level may be a predetermined period after the high-level change at time t3. The predetermined period is, for example, 100 ms. As shown in FIG. 5A, the welding current Iw is controlled at a constant current, and thus remains constant throughout the entire period.

  The reference voltage value Vt is set to an intermediate value between the maximum value of the welding voltage Vw when the arc length is in the normal range and the no-load voltage value when the arc break occurs. Since the maximum value of the welding voltage Vw when the arc length is in the normal range is, for example, 40V and the no-load voltage value is, for example, 70V, the reference voltage value Vt = 50V is set, for example. The reference increase rate Dt is determined as an appropriate value by experiment so that a precursor state of arc breakage can be detected. For example, Dt = 5 V / ms is set. The second reference voltage value Vt2 is set to a value smaller than the reference voltage value Vt. For example, Vt2 = 45V is set.

  The reason that the precursor state of the arc breakage is determined based on the rate of increase of the welding voltage Vw in addition to the value of the welding voltage Vw is because there is a possibility that the precursor state may be determined later with only one of them. Furthermore, it is because it may be late to determine the precursor state with only one of them, and the arc break may not be prevented. By using both, it is possible to accurately and early determine the precursor state of the arc break. For this reason, generation | occurrence | production of arc interruption can be prevented more reliably.

  According to the first embodiment described above, when the welding voltage during arc generation is equal to or higher than the reference voltage value and the increase rate of the welding voltage is equal to or higher than the reference increase rate, the welding torch is shortened so that the standoff is shortened. Move. Thereby, in this Embodiment, since the precursor state of arc interruption is discriminate | determined and standoff is shortened and arc length is shortened, generation | occurrence | production of arc interruption can be suppressed.

[Embodiment 2]
In the invention of the second embodiment, the reference voltage value for determining the precursor state of arc break is changed according to the set value of the welding current.

  FIG. 3 is a block diagram of a welding apparatus for carrying out the non-consumable electrode arc welding control method according to Embodiment 2 of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. This figure is obtained by replacing the reference voltage setting circuit VTR of FIG. 1 with a current setting interlocking reference voltage setting circuit VTSR. Hereinafter, this block will be described with reference to FIG.

  The current setting interlocking reference voltage setting circuit VTSR outputs a reference voltage setting signal Vtr calculated by a predetermined function having the current setting signal Ir as an input. As described above, the reference voltage setting signal Vtr is set to an intermediate value between the maximum value of the welding voltage Vw when the arc length is in the normal range and the no-load voltage value when the arc break occurs. The no-load voltage value is almost the same value regardless of the value of the welding current Iw. On the other hand, the maximum value of the welding voltage Vw when the arc length is in the normal range increases in proportion to the value of the welding current Iw. Therefore, if the reference voltage setting signal Vtr is set so as to increase as the current setting signal Ir increases, it is possible to determine the precursor state of the arc break earlier. As a result, arc breakage can be more reliably suppressed.

  The timing chart of each signal in the welding apparatus described above with reference to FIG. 3 is the same as FIG. However, the difference is that the reference voltage value Vt for discriminating the precursor state of the arc break changes in conjunction with the current setting signal Ir.

  In the above-described embodiment, the case where the non-consumable electrode arc welding is DC TIG welding has been described, but the same applies to AC TIG welding and DC / AC plasma arc welding.

1 (Non-consumable) Electrode 2 Base material 3 Arc 4 Welding torch AD Arc break sign discriminating circuit Ad Arc break sign discriminating signal C Bypass capacitor CC Coupling coil CD Current conducting discriminating circuit Cd Current conducting discriminating signal Dt Reference rise rate DTR Reference rise Rate setting circuit Dtr Reference rise rate setting signal DV Voltage differentiation circuit Dv Voltage differentiation signal EI Current error amplification circuit Ei Current error amplification signal HC High frequency control circuit Hc High frequency control signal Hf High frequency high voltage HF High frequency generation circuit ID Current detection circuit Id Current detection Signal IR Current setting circuit Ir Current setting signal Iw Welding current Lw Standoff Mc Operation control signal PM Power supply main circuit RC Robot controller RM Robot St Welding start signal VD Voltage detection circuit Vd Voltage detection signal Vt Reference voltage value Vt2 Second reference voltage Value VTR Reference voltage setting circuit Vtr Reference Pressure setting signal VTSR current setting interlocking reference voltage setting circuit Vw welding voltage

Claims (4)

In a non-consumable electrode arc welding control method for welding by applying a welding current between a non-consumable electrode attached to a welding torch and a base material and applying a welding voltage to generate an arc,
When the welding voltage during arc generation is equal to or higher than the reference voltage value and the rate of increase of the welding voltage is equal to or higher than the reference rate of increase, the standoff that is the distance between the tip of the electrode and the base material is short. Moving the welding torch so that
A non-consumable electrode arc welding control method. Holding the standoff short for a predetermined period of time;
The non-consumable electrode arc welding control method according to claim 1. Holding the standoff short until the welding voltage is less than a second reference voltage value,
The non-consumable electrode arc welding control method according to claim 1. Changing the reference voltage value according to a set value of the welding current;
The non-consumable electrode arc welding control method according to any one of claims 1 to 3.

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