JP2018202431A - Non-consumable electrode arc welding control method - Google Patents

Abstract

To suppress occurrence of arc interruption in non-consumable electrode arc welding.SOLUTION: In a non-consumable electrode arc welding control method, welding current Iw is conducted and welding voltage Vw is applied between a non-consumable electrode and a base material to generate an arc, thereby performing weldment. In this method, when the welding voltage Vw during arc generation becomes a reference voltage value or higher and a rate of increase of the welding voltage Vw becomes a reference rate of increase or higher, a high-frequency high voltage is applied between the electrode and the base material. Application of the high-frequency high voltage is performed until the welding voltage Vw becomes lower than a second reference voltage value. Consequently, an omen state of arc interruption is discriminated and the high-frequency high voltage is applied, 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 and a base material to generate an arc by applying a welding voltage and welding.

  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 has a small current value, when the distance between the electrode and the base material varies, when the surface state of the base material is poor, or when the shield state is poor. 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 the non-consumable electrode arc welding control method in which a welding current is applied between a non-consumable electrode and a base material and a welding voltage is applied to generate an arc and weld,
When the welding voltage during arc generation is equal to or higher than a reference voltage value and the increase rate of the welding voltage is equal to or higher than the reference increase rate, a high frequency high voltage is applied between the electrode and the base material.
This is a non-consumable electrode arc welding control method.

The invention of claim 2 applies the high frequency high voltage for a predetermined period.
The non-consumable electrode arc welding control method according to claim 1.

The invention of claim 3 applies the high frequency high voltage 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, since a precursor state of arc breakage is determined and a high frequency high voltage is applied, occurrence of arc breakage can be suppressed.

It is a block diagram of the welding power source for implementing 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 power supply mentioned above in FIG. It is a block diagram of the welding power supply 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 power source 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 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 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 welding power source in accordance with the current error amplification signal Ei, and a desired value of the welding current Iw is energized.

  The welding start circuit ST outputs a welding start signal St that becomes High level when starting welding. This welding start circuit ST corresponds to a torch switch attached to the welding torch 4 in the case of manual welding, and corresponds to a robot control device in the case of robot welding.

  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 the welding start signal St, the current energization determination signal Cd, and the arc interruption sign determination signal Ad as input, and at the following 1) or 2), the high frequency control circuit becomes a high level. The signal Hc is output.
1) When the welding start signal St is at a high level (startup) and the current energization determination signal Cd is at a low level (non-energization). This state is when the arc is ignited at the start of welding or when an arc break occurs during welding.
2) When the arc break precursor determination signal Ad is at a high level (when a precursor is determined). This state is when a precursor state of arc interruption is determined during arc generation.

  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.

  FIG. 2 is a timing chart of each signal in the welding power source 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. 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.

  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 high frequency generation circuit HF operates and a high frequency high voltage is applied between the electrode 1 and the base material 2. By application of the high frequency high voltage, the arc is induced to be formed at the shortest distance between the electrode 1 and the base material 2. As a result, the arc length is gradually shortened and returned to the normal value. As shown in FIG. 5B, the welding voltage Vw continues to increase for a while from time t3, then reverses from time t4 to decrease, and becomes less than the second reference voltage value Vt2 determined at time t5. Return 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 high frequency generation circuit HF stops its operation, so that the application of the high frequency high voltage stops. 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, a high frequency is generated between the electrode and the base material. Apply high voltage. Thereby, in this Embodiment, since the precursor state of arc interruption is discriminate | determined and a high frequency high voltage is applied, 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 power source 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 power source 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 precursor discriminating circuit Ad Arc break precursor 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 generation circuit Hf High frequency high voltage ID Current detection circuit Id Current detection Signal IR Current setting circuit Ir Current setting signal Iw Welding current PM Power supply main circuit ST Welding start circuit 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 voltage Setting signal VTSR Current setting interlocking reference voltage setting circuit Vw Contact voltage

Claims (4)

In the non-consumable electrode arc welding control method in which a welding current is applied between a non-consumable electrode and a base material and a welding voltage is applied to generate an arc and weld,
When the welding voltage during arc generation is equal to or higher than a reference voltage value and the increase rate of the welding voltage is equal to or higher than the reference increase rate, a high frequency high voltage is applied between the electrode and the base material.
A non-consumable electrode arc welding control method. Applying the high-frequency high voltage for a predetermined period;
The non-consumable electrode arc welding control method according to claim 1. Applying the high frequency high voltage 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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