JP2006026669A - Method for controlling welding current in non-consumable electrode type gas shielded arc welding, and power unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a welding current in non-consumable electrode type gas shielded arc welding, a method easy to operate and capable of keeping all current values within the range of rated current, and also to provide a power unit. <P>SOLUTION: With a first period Tu and a second period Td fixed that are alternately repeated as well as an average current value Iw and a current amplitude Iy, a current on the plus or increasing end of the amplitude Iy is supplied in the first period Tu, while a current on the minus or decreasing end of the amplitude Iy is supplied in the second period Td. In addition, the average current value in the first and the second period Tu, Td is controlled to be the average current value Iw. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a welding current control method and a power supply device when performing non-consumable electrode type gas shielded arc welding.

FIG. 5 is a connection diagram of a power supply device in conventional direct current non-consumable electrode type gas shielded arc welding.
In the figure, a main circuit section 1 surrounded by a one-dot chain line includes an input rectifier section 2, a switching section 3, a high-frequency transformer section 4, a secondary rectifier section 5, a current detector 6, a DC reactor 7, and a coupling coil. 8. The positive terminal of the main circuit portion 1 is connected to the welding base material 10, and the negative terminal is connected to the welding torch 9.

  A control unit 11 surrounded by a one-dot chain line includes a switching control unit 12 and an overall control unit 13. Connected to the overall control unit 13 are a set value input unit 15, a torch switch (start switch) 16, an electromagnetic valve 14 for controlling shield gas, and a current detector 6. Note that the set value input unit 15 is provided with a selection switch for selecting self-holding or not self-holding (not shown).

Next, the operation of the power supply apparatus in conventional non-consumable electrode type gas shielded arc welding will be described.
When the torch switch 16 is closed, AC supplied from the primary side input power (commercial AC power) is converted to DC by the input rectifier unit 2, then converted to high frequency AC by the switching unit 3, and welded by the high frequency transformer 4. Is converted to a voltage suitable for The high-frequency alternating current output from the high-frequency transformer 4 is converted into direct current again by the secondary rectifier unit 5, and then flows in the order of the direct current reactor 7, the welding base material 10, the welding torch 9, and the coupling coil 8. An arc (not shown) is generated between the welding torch 9.

  The overall control unit 13 compares the current value input to the set value input unit 15 with the current value detected by the current detector 6, amplifies the difference, and inputs the amplified difference to the switching control unit 12. Based on this signal, the switching control unit 12 drives the switching unit 3 so that the current flowing through the welded portion becomes substantially equal to the input current value.

FIG. 6 is a diagram showing a typical output current waveform of a power supply device in non-consumable electrode type gas shielded arc welding.
When the power supply device outputs a DC pulse current (hereinafter referred to as “pulse power supply”), as shown in FIG. 5A, Ip, Ib and Tp input to the set value input unit 15, Depending on the value of Tb, the peak current (duration Tp) of the current value Ip and the base current (duration Tb) of the current value Ib are alternately output.

In the case of pulse welding, the current (average current) having a current value I determined by the following formulas 1 and 2 is simply referred to as current.
I = (Ip · Tp + Ib · Tb) / T0 (Formula 1)
T0 = Tp + Tb (Formula 2)

  When the power supply device outputs a direct current, a current having a current value I input to the set value input unit 15 is output as shown in FIG. Hereinafter, a gas shielded arc welding power source that outputs a current whose current value does not change periodically is referred to as a “DC power source” and is distinguished from a pulse power source. The external connection diagrams of the pulse power supply and the DC power supply are the same, and the pulse power supply has a function of a DC power supply.

FIGS. 7A and 7B are timing charts during welding in the case of a DC power source. FIG. 7A shows a case without self-holding and FIG. 7B shows a case with self-holding.
As will be described later, the usage mode of the open / close signal of the torch switch 16 is different between “with self-holding” and “without self-holding”, and with self-holding, there are a plurality of such as changing the current value during welding. Used when control is required.

  In the case of no self-holding, as shown in FIG. 6A, the value of the main current Iw that is a current for performing welding, the value of the preflow time Tg1 in which the shield gas flows before welding, and the oxidation of the welded portion are prevented. Therefore, the value of the postflow time Tg <b> 2 for flowing the shield gas after the end of welding is input to the set value input unit 15.

Next, the operation of the control device 11 when there is no self-holding will be described.
The controller 11 monitors the opening and closing of the torch switch 16, and immediately opens the solenoid valve 14 as soon as the torch switch 16 is closed (on), and the main current Iw until the torch switch 16 is opened (off) after the preflow time Tg1 has elapsed. Is output to the weld. Then, as soon as the torch switch 16 is opened, the supply of the main current Iw is stopped, and the solenoid valve 14 is closed after the postflow time Tg2.

  In the case of self-holding, as shown in FIG. 4B, as shown in FIG. 4B, the preflow time Tg1, the postflow time Tg2, the main current value Iw, the start current Is current value Is, the crater current Ic current value Ic, and the upslope time Tu. Each value of the down slope time Td is input to the set value input unit 15.

Next, the operation of the control device 11 when there is self-holding will be described.
The control device 11 monitors the opening and closing of the torch switch 16, and immediately opens the solenoid valve 14 when the torch switch 16 is closed, and outputs a start current of the current value Is until the torch switch 16 is opened after the preflow time Tg1 has elapsed. . When the torch switch 16 is opened, the current is increased to the main current Iw during the up slope time Tu, and then the main current Iw is output until the torch switch 16 is opened. Next, when the torch switch 16 is closed, the current is reduced to the current value Ic during the down slope time Td. Next, when the torch switch 16 is opened, the supply of crater current is stopped, and the electromagnetic valve 14 is closed after the postflow time Tg2 has elapsed.

  In the case of a pulse power supply, it is necessary to input current values Ip and Ib and durations Tp and Tb with respect to the main current value Iw, start current value Is and crater current value Ic, respectively. The same as in the case of a DC power supply.

By the way, in the case of a pulse power supply, four values must be set in order to determine one type of current value (for example, the main current value Iw), so that even a skilled worker takes time for setting. .
Therefore, with one current setting device (in this case, a current setting device for setting the main current value Iw), the current value Ip of the peak current, the current value Ib of the base current, the current value Is of the start current, and the crater current There is a non-consumable electrode-type gas shielded arc welding power source that can set the current value Ic (Patent Document 1).
In Patent Document 1, by providing a current compensator, the current value Ib of the base current does not become smaller than the minimum value Imin of the rated current, and the current value Ip of the peak current is the maximum value Imax of the rated current. I try not to be bigger than that.

In addition, when the pulse frequency shown in FIG. 6A is set to a low frequency pulse (0.1 to several Hz), the base material is melted during the pulse period, and solidification is promoted during the base period to prevent the molten metal from being melted off. This makes it easy to weld all positions of pipes and joints with different thicknesses. Further, when the medium frequency pulse (several tens to several hundreds of Hz) is used, the arc rigidity and concentration can be improved, so that it is easy to perform small-current welding and high-speed welding in which the arc is likely to fluctuate.
Therefore, there is a technique in which a low-frequency pulse and an intermediate-frequency pulse are combined, and the heat input control action of the low-frequency pulse and the arc concentration improvement action of the intermediate-frequency pulse are used at the same time (Patent Document 2).

Japanese Patent Publication No. 5-56236 Japanese Patent No. 2935434

In Patent Document 1, when the main current value Iw in which the current value Ib of the base current is less than the minimum value Imin is selected, the current value Ib of the base current never falls below the minimum value Imin, but the current value of the base current Since Ib becomes larger than the original value, the current value supplied to the welded portion becomes larger than the value set by the current setting device. Therefore, in such a case, trial welding is performed, and the set value of the current setting device is reduced so that the current value supplied to the welded portion becomes a desired current value. When the main current value Iw in which the peak current value Ip exceeds the maximum value Imax is selected, the peak current value Ip does not exceed the maximum value Imax, but the peak current value Ip is the original value. Therefore, the current value supplied to the welded portion is smaller than the value set by the current setting device. Therefore, in such a case, trial welding is performed, and the set value of the current setting device is increased so that the current value supplied to the welded portion becomes a desired current value.
That is, when the main current value Iw where the current value Ib of the base current is less than the minimum value Imin is selected or when the main current value Iw where the current value Ip of the peak current exceeds the maximum value Imax is selected, Setting was troublesome.

  In Patent Document 2, it is possible to form various current waveforms. However, when the main current value Iw in which the current value Ip of the peak current exceeds the maximum value Imax is selected, or the current value Ib of the base current is There is no detailed description of the case where the main current value Iw that is less than the minimum value Imin is selected.

  An object of the present invention is to provide a welding current control method and a power supply apparatus in non-consumable electrode type gas shielded arc welding which can be easily operated and can keep all current values within the range of rated current.

  In order to achieve the above object, the first means of the present invention provides a method for controlling welding current in non-consumable electrode type gas shielded arc welding in which a current having an input current value is supplied to a weld. The first and second periods, the average current value, and the amplitude of the current are determined in advance, and the first period indicates the current on the plus side or the increase side of the amplitude in the second period. Supplies the current on the minus side or the decrease side of the amplitude, and controls the average value of the current values in the first period and the second period to be the average current value. And

  According to a second means of the present invention, there is provided a power supply apparatus for non-consumable electrode type gas shielded arc welding in which a current having an input current value is supplied to the welded portion. A main current value and current amplitude setting means, a calculation means, and a determination means are provided, and the welding current is controlled by the welding current control method described in the first means.

  Since the current supplied to the welded portion matches the set value and all the current values can be within the rated current range, the operation is easy.

Hereinafter, the present invention will be described based on the illustrated embodiments.
FIG. 1 is a connection diagram of a power supply device in non-consumable electrode type gas shielded arc welding according to the present invention, and the same or the same function as in FIG.
The switch 20 is a switch for selecting whether to perform pulse welding using a pulse current or DC welding, and is connected to the overall control unit 13. The overall control unit 13 outputs, via the switching control unit 12, a pulse current when pulse welding is selected, and a direct current when the other (no pulse) is selected.

  The set value input unit 15 is provided with first period setting means, second period setting means, and main current value and current amplitude setting means.

  The calculation / determination means 21 is connected to the overall control unit 13.

Next, the operation of the present invention will be described in the case of a direct current.
Prior to processing, the set value input unit 15 sets the first period Tu, the second period Td, the average current value Iw, and the current amplitude Iy. The average current value is a current value corresponding to the above main current, and hence is referred to as a current value Iw. Here, Tu = Td.

FIG. 2 is a current waveform diagram during main welding according to the present invention.
First, the current configuration will be described. The maximum value of the rated current of this power supply device is Imax, and the minimum value is Imin.

As shown in the figure, the welding current increases from the current value In to the current value Iq (where Iq = In + Iy) in the period Tu that is the first period, and in the period Td that is the second period following the period Tu. The current value Iq decreases to the current value In. The period Tu and the period Td are alternately repeated.
In this way, it is possible to obtain a welded portion having a wider bead width and shallow penetration than in the case of direct current (current is constant at Iw). Also, the arc becomes a so-called soft arc.

By the way, when setting the average current value Iw and the current amplitude Iy, the current value Iq may exceed the maximum value of the rated current, or the current value In may be less than the minimum value Imin of the rated current.
Therefore, when the average current value Iw and the current amplitude Iy are set, the calculation / determination means 21 immediately adds 1 / 2Iy to the set average current value Iw. If Iw + 1 / 2Iy> Imax, the calculation / determination means 21 is set. The current width Iy is canceled to set the current value Iq = Imax, and the current value In is changed to In = Iw− (Imax−Iw).
Further, 1/2 Iy is subtracted from the set Iw, and when Iw−1 / 2Iy <Imin, the set current width Iy is canceled to obtain the current value In = Imin, and the current value Iq is set to Iq = Iw + Change to (Iw-Imin).
As a result, the average current Iw does not change, and the current value does not deviate from the rated current range of the power supply device.

  In this embodiment, the case of a direct current has been described. However, as shown in FIG. 3, the present invention can be applied to a peak current Ip or a base current in pulse welding. 3A shows a case where the present invention is applied to the peak current Ip, FIG. 3B shows a case where the present invention is applied to the base current Ib, and FIG. 3C shows a case where the present invention is applied to the peak current Ip and the base current Ib. Since the control can be easily performed from the above description, the detailed description is omitted.

  Although the case where the current waveform is a triangular wave within the range of the amplitude Iy has been described above, the present invention may be a rectangular wave as shown in FIG. 4A shows a case where the present invention is applied to the peak current Ip in pulse welding, FIG. 4B shows a case where the present invention is applied to the base current Ib, and FIG. 4C shows a case where the present invention is applied to the peak current Ip and the base current Ib. It is. Since the control can be easily performed from the above description, the detailed description is omitted.

In the above description, the period Tu = Td, but the period Tu ≠ Td may be used.
Even when the period Tu ≠ Td, the average current Iw can be easily obtained by calculation.

It is a connection diagram of a non-consumable electrode type gas shielded arc welding power source according to the present invention. It is an electric current waveform figure at the time of the main welding which concerns on this invention. It is an electric current waveform figure at the time of the main welding which concerns on this invention. It is an electric current waveform figure at the time of the main welding which concerns on this invention. It is a connection diagram of a conventional direct current non-consumable electrode type gas shielded arc welding power source. It is a figure which shows the typical output current waveform of a gas shielded arc welding power supply. It is a timing chart at the time of welding in the case of DC power supply.

Explanation of symbols

Tu First period Td Second period Iw Average current value Iy Amplitude

Claims (7)

In the control method of the welding current in the non-consumable electrode type gas shielded arc welding in which the current of the input current value is supplied to the welded portion,
First and second periods that are alternately repeated, an average current value, and an amplitude of a current are determined. In the first period, a current on the plus side or an increase side of the amplitude is set as the second period. In the period, the current on the negative side or the decrease side of the amplitude is supplied, and the average value of the current values in the first period and the second period is controlled to be the average current value. A method for controlling a welding current in non-consumable electrode type gas shielded arc welding.   The control of the welding current in the non-consumable electrode type gas shielded arc welding according to claim 1, wherein the current waveform within the amplitude is changed to a triangular wave by gradual rising and falling of the current within the amplitude. Method.   2. The non-consumable electrode according to claim 1, wherein the current waveform in the amplitude is a rectangular wave by making the rise and fall of the current in the amplitude steep and constant at the end of the amplitude. Method for controlling welding current in gas-type gas shielded arc welding.   When the maximum value of the amplitude exceeds the maximum value of a rated current, the maximum value of the amplitude is set to the maximum value, and the amplitude is reduced so that the main current value is maintained. Item 2. A method for controlling a welding current in the non-consumable electrode type gas shielded arc welding according to Item 1.   When the minimum value of the amplitude is less than the minimum value of the rated current, the minimum value of the amplitude is set to the minimum value, and the amplitude is reduced so that the main current value is maintained. The control method of the welding current in the non-consumable electrode type gas shielded arc welding according to claim 1.   2. The method for controlling a welding current in non-consumable electrode type gas shielded arc welding according to claim 1, wherein the first and second periods are a part of a pulse period and / or a base period in pulse welding. In the power supply device in the non-consumable electrode type gas shielded arc welding that supplies the current of the input current value to the weld,
The first and second period setting means, main current value and current amplitude setting means, and calculation / determination means are provided, and the welding current is controlled by the welding current control method according to claim 1. A power supply apparatus for non-consumable electrode type gas shielded arc welding characterized by controlling.

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