JP5161005B2 - Gas control method for arc welding - Google Patents

Description

  The present invention relates to a gas control method for arc welding that can optimize the afterflow period of shield gas in arc welding.

  In non-consumable electrode type arc welding (hereinafter simply referred to as arc welding) such as TIG welding and plasma arc welding, it is necessary to shield the welded portion from the atmosphere with a shielding gas during welding. If this shielding state is incomplete, the molten pool and the non-consumable electrode (hereinafter simply referred to as an electrode) are oxidized, resulting in a defective weld bead and the electrode being damaged. For this reason, the discharge of the shield gas is started before a predetermined period (preflow period) in which the welding current is supplied, and the discharge of the shield gas is continued for a predetermined period (afterflow period) even after the stop of the supply of the welding current. Hereinafter, this sequence will be described.

  FIG. 6 is a typical welding current waveform diagram of TIG welding. FIG. 4A shows a gas control signal Gc for controlling the discharge / stop of the shield gas, and FIG. 4B shows the welding current Iw. Hereinafter, a description will be given with reference to FIG.

  When the torch switch is turned on and a torch switch signal (not shown) is input to the welding power source, discharge of the shield gas from the nozzle at the tip of the welding torch is started as shown in FIG. As shown in FIG. 6A, when the preflow period Tp elapses, the initial current Is is supplied as shown in FIG. Here, when the torch switch is turned off, the welding current Iw increases from the initial current Is to the main current Im during the up slope period Tu, and then the main current Im is energized. Here, when the torch switch is turned on again, during the down slope period Td, the welding current Iw decreases from the current current Im to the crater current Ic, and thereafter the crater current Ic is energized. Here, when the torch switch is turned off again, energization of the crater current Ic ends. However, as shown in FIG. 5A, the release of the shield gas continues during the afterflow period Ta.

  The above is the case with the crater mode, but a general tig welding power source is also equipped with a crater-free mode and a crater repetition mode. In the crater-free mode, there is no initial current Is and crater current Ic, and only this current Im is energized. In the crater repetition mode, when the crater current Ic is energized, when the torch switch is turned off, the current Im returns to energization again. When the torch switch is turned on, the crater current Ic is energized, and thereafter, the current Im and the crater current Ic are repeated in conjunction with the torch switch being turned on / off. When energization is terminated, the torch is separated from the base material to forcibly extinguish the arc.

  When welding is performed, the welding operator determines the main current Im, the initial current Is, the crater current Ic, the upslope period Tu, and the like according to the welding conditions such as the joint conditions, the material to be welded, and the plate thickness. It is necessary to set the down slope period Td, the preflow period Tp, and the afterflow period Ta (hereinafter referred to as parameters) to appropriate values. Setting many of these parameters to appropriate values according to various welding conditions requires many years of experience and troublesome work. In order to cope with this problem, a conventional technique has been proposed in which other parameters are automatically set according to a predetermined relationship with the current Im if the current Im is set (for example, Patent Document 1). 2).

Japanese Patent No. 3004889 JP 2006-26663 A

    As described above, when the main current Im is set, parameters such as the initial current Is, the crater current Ic, the up-slope period Tu, the down-slope period Td, the preflow period Tp, and the afterflow period Ta are set in advance. It can be automatically set to an appropriate value depending on the relationship. Accordingly, the afterflow period Ta can be automatically set based on the current Im so that the electrode and the molten pool are not oxidized.

    However, when the current Im is determined, the afterflow period Ta is fixed to a predetermined value. Therefore, when the welding time is short, the electrode and the molten pool are sufficiently cooled, and there is no risk of oxidation. The gas was to be released. On the contrary, when the welding time is long, the discharge of the shield gas is stopped before the electrode and the molten pool are sufficiently cooled, so that the electrode and the molten pool are oxidized.

  Therefore, in the present invention, the arc welding can be performed appropriately regardless of whether the welding time is short or long, and there is no wasteful release of shielding gas, and arc welding that can prevent oxidation of the electrode and the molten pool. An object of the present invention is to provide a gas control method.

In order to solve the above-described problem, the first invention
Welding with a welding current including at least this current while discharging shield gas to the weld,
In the gas control method of arc welding in which energization of the welding current is stopped at the end of welding and the shielding gas is continuously discharged only after a predetermined afterflow period after the energization is stopped.
The afterflow period is set by a predetermined period setting function with the current value and the energization time of the welding current as inputs.
This is a gas control method for arc welding characterized by the above.

The period setting function is a function for setting the afterflow period with an integrated value of the welding current as an input.
An arc welding gas control method according to the first aspect of the present invention.

  According to the first aspect, the afterflow period is set to an appropriate value by a predetermined period setting function using the current value and the energization time as inputs. For this reason, in the case of welding with a short energization time, the afterflow period is shortened, and wasteful release of shield gas can be prevented. Moreover, in the case of welding with a long energization time, the afterflow period becomes long, and oxidation of the electrode and the molten pool can be prevented. Therefore, in the first invention, both resource saving (shield gas) and high quality can be realized.

  According to the second invention, in addition to the effect of the first invention, the input of the period setting function can be unified with the integrated value of the welding current, so that the structure of the function can be simplified. For this reason, the man-hour for setting the period setting function in advance can be reduced.

  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 a gas control method for arc welding according to Embodiment 1 of the present invention. 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 as input, performs output control by inverter control according to a drive signal Dv described later, and outputs a welding current Iw. An arc 3 is generated between the non-consumable electrode 1 such as tungsten mounted on the welding torch 4 and the base material 2, and a welding current Iw is passed through the arc 3. A shielding gas 5 such as argon gas or helium gas is discharged so as to shield the arc 3 from the atmosphere. The release / stop control of the shield gas 5 is performed by opening and closing a gas electromagnetic valve GB provided in the middle of the gas pipe 7 connecting the gas cylinder 6 and the welding torch 4.

  The current setting circuit IMR outputs a predetermined current setting signal Imr. The initial current setting circuit ISR outputs a predetermined initial current setting signal Isr. The crater current setting circuit ICR outputs a predetermined crater current setting signal Icr. The up slope period setting circuit TUR outputs a predetermined up slope period setting signal Tur. The down slope period setting circuit TDR outputs a predetermined down slope period setting signal Tdr. The preflow period setting circuit TPR outputs a predetermined preflow period setting signal Tpr.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The energization time measurement circuit TW receives this current detection signal Id as input, measures the time during which the welding current Iw is energized, and outputs the energization time measurement signal Tw when energization is completed. The afterflow period calculation circuit TAR receives the current setting signal Imr and the energization time measurement signal Tw, and outputs an afterflow period setting signal Tar using a predetermined period setting function. This period setting function will be described later with reference to FIG.

  The torch switch TS is provided in the hand portion of the welding torch 4 and outputs a torch switch signal Ts corresponding to ON / OFF. The sequence control circuit SC includes the main current setting signal Imr, the initial current setting signal Isr, the crater current setting signal Icr, the up-slope period setting signal Tur, the down-slope period setting signal Tdr, A sequence described later in FIG. 3 by changing the torch switch signal Ts in conjunction with the on / off operation of the torch switch TS with the preflow period setting signal Tpr, the afterflow period setting signal Tar and the torch switch signal Ts as inputs. The control is performed, the start signal On and the current setting signal Ir are output, and the gas control signal Gc for opening / closing the gas solenoid valve GB is output.

  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. The drive circuit DV receives the current error amplification signal Ei and the activation signal On as described above. When the activation signal On is at a high level, the drive circuit DV performs pulse width modulation control based on the current error amplification signal Ei and outputs the drive signal Dv. To do. With these circuit blocks, the welding current Iw described above with reference to FIG. 6 is energized, and the shielding gas is discharged. At this time, the afterflow period Ta is automatically set to an appropriate value by a predetermined period setting function with the current setting signal Imr and the energization time measurement signal Tw as inputs.

  FIG. 2 is a diagram illustrating an example of a period setting function built in the above-described afterflow period calculation circuit TAR. In the figure, the horizontal axis represents the energization time measurement signal Tw (s), and the vertical axis represents the afterflow period setting signal Tar (s). The function L1 is when the current setting signal Imr = * 125A, the function L2 is when Imr = * 150A, and the function L3 is when Imr = * 175A. For example, when the current setting signal Imr = 150 A and the energization time measurement signal Tw = Tw1 (s), the function L2 is first selected, and Tar = Tar1 when Tw = Tw1 is calculated. The function is set to a predetermined current value interval over the entire range from the minimum value to the maximum value of the current. For example, when the value of the current setting signal Imr is an intermediate value between the functions L1 and L2, the value is calculated by proportional distribution from the values of the functions L1 and L2.

  FIG. 3 is a timing chart showing the sequence control in the above-described sequence control circuit SC. FIG. 4A shows the torch switch signal Ts, FIG. 4B shows the gas control signal Gc, FIG. 3C shows the start signal On, and FIG. 4D shows the current setting signal Ir. . This figure shows a case where the same welding current Iw as that in FIG. 6 is applied. Hereinafter, a description will be given with reference to FIG.

  At time t1, when the torch switch signal Ts becomes a high level (on state) as shown in FIG. 9A, the gas control signal Gc becomes a high level as shown in FIG. Since the valve GB is opened, the discharge of the shield gas 5 is started. When a period determined by the preflow period setting signal Tpr has elapsed at time t2, the current setting signal Ir changes from 0 to the value of the initial current setting signal Isr, as shown in FIG. As described above, since the activation signal On becomes the high level, the output of the welding power source is started, the initial current is applied, and an arc is generated.

  At time t3, when the torch switch signal Ts is at a low level (off state) as shown in FIG. 9A, the period (time t3) determined by the upslope period setting signal Tur as shown in FIG. During t4), the value gradually increases from the value of the initial current setting signal Isr to the value of the current setting signal Imr, and a welding current corresponding to this increases. During the period from time t4 to time t5, as shown in FIG. 6A, the torch switch signal Ts remains at the low level. Therefore, as shown in FIG. The value of the signal Imr remains as it is and this current flows.

  At time t5, when the torch switch signal Ts is at a high level (ON state) as shown in FIG. 9A, the period (time t5) determined by the down slope period setting signal Tdr as shown in FIG. The current setting signal Ir in .about.t6) gradually decreases from the value of the current setting signal Imr to the value of the crater current setting signal Icr, and a welding current corresponding to this becomes energized. During the period from time t6 to t7, as shown in FIG. 6A, the torch switch signal Ts remains at the high level, so that the current setting signal Ir is set to the crater current setting as shown in FIG. The value of the signal Icr remains as it is, and the crater current is energized.

  At time t7, when the torch switch signal Ts becomes low level (off state) as shown in FIG. 6A, the current setting signal Ir becomes 0 as shown in FIG. As shown in C), the energization is stopped because the activation signal On becomes the Low level. During the period determined by the afterflow period setting signal Tar at times t7 to t8, as shown in FIG. 5B, the gas control signal Gc maintains the high level, so the gas solenoid valve GB maintains the open state. The release of the shielding gas 5 continues. At time t8, as shown in FIG. 5B, the gas control signal Gc becomes the low level, so that the discharge of the shield gas 5 is stopped.

  According to the first embodiment described above, the value of the afterflow period setting signal Tar is set to an appropriate value by a predetermined period setting function with the current setting signal Imr and the energization time measurement signal Tw as inputs. For this reason, in the case of welding with a short energization time, the afterflow period is shortened, and wasteful release of shielding gas can be prevented. Moreover, in the case of welding with a long energization time, the afterflow period becomes long, and oxidation of the electrode and the molten pool can be prevented. Therefore, in Embodiment 1, resource saving and high quality can be realized without taking time and effort.

[Embodiment 2]
FIG. 4 is a block diagram of a welding power source for carrying out the arc welding gas control method according to Embodiment 2 of the present invention. In the figure, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. In the figure, the energization time measurement circuit TW in FIG. 1 is replaced with a current integral value calculation circuit SI indicated by a broken line, and the afterflow period calculation circuit TAR in FIG. 1 is replaced by a second afterflow period calculation circuit TAR2 indicated by a broken line. doing. Hereinafter, these circuits will be described with reference to FIG.

  The current integration value calculation circuit SI receives the current detection signal Id, integrates the current detection signal Id from the start of energization to the end of energization, and outputs a current integration value signal Si. The second afterflow period calculation circuit TAR2 receives the current integrated value signal Si and outputs an afterflow period setting signal Tar using a predetermined current integrated value corresponding period setting function.

  FIG. 5 is a diagram illustrating an example of the current integration value corresponding period setting function described above. In the figure, the horizontal axis represents the current integration value signal Si (A · s), and the vertical axis represents the afterflow period setting signal Tar (s). The afterflow period setting signal Tar corresponding to the value of the current integrated value signal Si is calculated by the function L4 shown in FIG.

  The current integration value corresponding period setting function shown in the figure does not need to set a plurality of functions as in the case of the period setting function group described above with reference to FIG. Since a function is sufficient, the structure of the function becomes simple. The sequence control of the second embodiment is the same as that in FIG. 3 described above.

  According to the second embodiment described above, the function structure can be simplified by setting the input of the period setting function to the integral value of the welding current. For this reason, the time required for presetting the period setting function can be reduced.

  In the embodiment described above, the case of non-consumable electrode arc welding has been described, but the present invention can also be applied to consumable electrode arc welding.

It is a block diagram of the welding power supply for enforcing the gas control method of the arc welding which concerns on Embodiment 1 of this invention. It is a figure which illustrates the period setting function incorporated in the afterflow period calculation circuit TAR of FIG. 2 is a timing chart showing sequence control in the sequence control circuit SC of FIG. It is a block diagram of the welding power supply for enforcing the gas control method of the arc welding which concerns on Embodiment 2 of this invention. FIG. 5 is a diagram illustrating a current integration value corresponding period setting function built in the second afterflow period calculation circuit TAR2 of FIG. 4; It is a figure which shows the welding current waveform and the discharge | release period of shield gas in TIG welding of a prior art.

Explanation of symbols

1 Non-consumable electrode 2 Base material 3 Arc 4 Welding torch 5 Shield gas 6 Gas cylinder 7 Gas piping DV Drive circuit Dv Drive signal EI Current error amplification circuit Ei Current error amplification signal GB Gas solenoid valve Gc Gas control signal Ic Crater current ICR Crater current Setting circuit Icr Crater current setting signal ID Current detection circuit Id Current detection signal Im Main current IMR Main current setting circuit Imr Current setting signal Ir Current setting signal Is Initial current ISR Initial current setting circuit Isr Initial current setting signal Iw Welding current L1 L4 function On start signal PM power main circuit SC sequence control circuit SI current integral value calculation circuit Si current integral value signal Ta afterflow period TAR afterflow period calculation circuit Tar afterflow period setting signal TAR2 second afterflow period calculation circuit Td down Slope period T R Down slope period setting circuit Tdr Down slope period setting signal Tp Preflow period TPR Preflow period setting circuit Tpr Preflow period setting signal TS Torch switch signal Tu Torch switch signal Tu Up slope period TUR Up slope period setting circuit Tur Up slope period setting signal TW Energization Time measurement circuit Tw Energization time measurement signal

Claims (2)

Welding with a welding current including at least this current while discharging shield gas to the weld,
In the gas control method of arc welding in which energization of the welding current is stopped at the end of welding and the shielding gas is continuously discharged only after a predetermined afterflow period after the energization is stopped.
The afterflow period is set by a predetermined period setting function with the current value and the energization time of the welding current as inputs.
A gas control method for arc welding characterized by the above. The period setting function is a function for setting the afterflow period with an integrated value of the welding current as an input.
The gas control method for arc welding according to claim 1.

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