JPH05261535A - Method for controlling consumable electrode ac arc welding machine - Google Patents

Abstract

PURPOSE:To smoothly carry out arc starting and transfer to stationary welding by employing only reverse polarity at the time of generating an arc, increasing a ratio of straight polarity so as to attain a polarity ratio at the stationary time in order and also, increasing the wire feed speed to a target value according to the polarity ratio changing with lapse of time. CONSTITUTION:When a welding starting signal TS is inputted to an arithmetic and control part 13, the arithmetic and control part 13 commands the output of the no-load voltage at the EN ratio 0% and simultaneously, commands feed starting of a wire 9 toward base metals 11 at the slowdown wire feed speed for starting regardless of setting on a welding current setting device 18 to a motor driving circuit 14. When the wire 9 comes into contact with the base metals 11 and a welding current flows, a welding current detection part 17 detects it and the arithmetic and control part 13 changes over the wire feed rate to the proper one at the time of EN ratio 0%. After this, the EN ratio of the welding output is increased to attain the specified EN ratio. At this time, the proper wire feed rate is also controlled simultaneously with the change of the EN ratio of the welding output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies an AC voltage between a welding wire, which is a consumable electrode, and a base material, which is an object to be welded. The present invention relates to a control method of a consumable electrode type AC arc welding machine for welding.

[0002]

2. Description of the Related Art Conventionally, in a consumable electrode type arc welding method in which an arc is generated between a welding wire which is a consumable electrode that is automatically fed and a base material which is an object to be welded, usually the base material side is This is done only with the EP (rod plus) polarity that makes the wire negative and the wire side becomes positive, but recently, the EP polarity and the base material side are positive, and the wire side is negative EN.
A consumable electrode type AC arc welding method, in which (bar minus) polarity is arbitrarily time-divided and outputted, and the heat input amount to the base metal and the wire melting amount are controlled to control the welding bead shape, is being put to practical use.

In this consumable electrode type AC arc welding, the arc is extinguished every time the polarity of the welding arc is reversed, and the arc is regenerated. Therefore, it is necessary to stably generate the rearc. In particular, since the molten state is not stabilized at the time of starting the arc and immediately after the start of welding, there is a high probability that the re-arc will fail.

On the other hand, since the base metal temperature does not rise at the start of melting, if the arc is started with the EP / EN ratio at the time of steady welding, the bead width and the penetration at the arc start portion are different from those of the steady welding portion and a welding defect occurs. There is a risk of becoming.

Japanese Patent Publication No. 3-49665
At the time of arc start, it has an EP characteristic with deep melting,
After that, a solution was presented for both the problem of insufficient penetration at the time of arc start and the problem of re-arc failure at the time of arc start by the arc welder that shifts to the EP / EN ratio in the steady state.

The control according to Japanese Patent Publication No. 3-94665 will be described below. FIG. 4 is a control timing diagram at the time of arc start in the conventional consumable electrode type arc welding machine. Figure 4
At time t ₀ , a welding start signal TS for starting welding is input to the welding machine. The welding machine outputs the no-load voltage with the EN ratio close to 0% by the control method of Japanese Patent Publication No. 3-49665, and starts feeding the wire to the base metal at the slowdown speed Fs. The time when the tip of the wire comes into contact with the base material and a welding arc occurs is t ₁ . The welding machine detects that the output current has become “present”, and at this time t ₁
Which is the ratio of EN during steady welding with the passage of time from
_The EN ratio is gradually increased toward _X, and reaches the EN ratio during steady welding EN _X at time t ₂ . At this time, the wire feeding speed is the slowdown speed Fs at time t _0.
In the control, the feeding is started and the wire feeding speed Fx is switched to the steady wire feeding speed Fx at time t ₁ when the output current is detected to be “present”.

[0007]

However, in this high ratio EP arc start method, although the above two problems have been solved, the arc length at the arc start is shorter than that at the steady state. There were problems such as a large amount of spatter generation, arc instability, and insufficient penetration. That is, as shown in FIG. 5, the proper wire feeding speed with respect to the EN ratio differs depending on the EN ratio.
Although the EN ratio is changing every moment between time t ₁ and time t ₂ as shown in (4), if the wire feeding speed F _X is switched to an appropriate wire feeding speed F _X only for the EN ratio EN _{X in the} steady state, The proper arc length could not be maintained, resulting in a large amount of spatter generation, arc instability, and insufficient penetration. In order to solve this problem, a method of gradually approaching the wire feeding speed to a value at the time of steady welding with a delay circuit composed of a capacitor, a resistor, etc. can be considered, but it is not general because it is not related to the EN ratio.

The present invention solves the above-mentioned conventional problems, and controls a consumable electrode type AC arc welding machine capable of eliminating welding defects such as a large amount of spatter at the time of arc start, arc instability, and insufficient penetration. It is intended to provide a method.

[0009]

In order to solve the above-mentioned problems, a control method for a consumable electrode type AC arc welding machine according to the present invention comprises:
Control of a consumable electrode type AC arc welding machine that performs arc welding by applying an AC voltage between a welding wire that is a consumable electrode and a base material that is a workpiece, and reverses the polarity of the AC voltage by time division. In the method, when the arc at the start of welding is generated, the consumable electrode side has only the opposite polarity, and after the arc occurs,
Increase the ratio of positive polarity where the consumable electrode side becomes negative over time so that the polarity ratio becomes steady during steady welding,
In addition, the feed rate of the consumable electrode is controlled so that the feed rate during steady welding is gradually increased with the feed rate during steady welding as a target value in accordance with the polarity ratio that changes with the passage of time.

[0010]

With the above structure, when the arc at the start of welding occurs, the consumable electrode side has a positive polarity only, and after the arc occurs, the consumable electrode side becomes negative with the passage of time so that the polarity ratio during steady welding is sequentially achieved. The ratio of the positive polarity is increased and the feed rate of the consumable electrode is gradually increased with the feed rate during steady welding as the target value according to the polarity rate that changes with the passage of time. Starting and a smooth transition to steady welding are possible, and welding defects such as a large amount of spatter at the start of arc and insufficient penetration are prevented, and stable welding starts.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a consumable electrode type AC arc welding machine in one embodiment of the present invention. In FIG. 1, a welding power source input terminal 1 is connected to a primary inverter unit 2, and the primary inverter unit 2 is a secondary inverter unit 4 that controls an output polarity via a welding transformer 3.
It is connected to the. The secondary inverter unit 4 is connected via a reactor 5 to one output terminal 6a of a welding power source, and the other output terminal 6b is connected to a welding transformer 3 via a welding current detector 7. One output terminal 6a of this welding power source is connected to the other output terminal 6b through a contact tip 8 for energization, a welding wire 9, a welding arc 10 and a base material 11, and is connected to the wire 9 which is a consumable electrode and a cover electrode. An AC voltage is applied to the base material 11 which is a welded product, and the polarity of this AC voltage is time-divided and inverted to perform arc welding.
The wire 9 is fed to the base material 11 by a wire feeding motor 12.

On the other hand, the operation control section 13 to which the welding start signal TS for starting welding is inputted is connected to the wire feeding motor 12 via the motor driving circuit 14, and the wire feeding motor via the motor driving circuit 14. Controls 12 wire feed rates. In addition, the arithmetic control unit 13 is operated via the secondary inverter control unit 15
Connected to the secondary inverter unit 4 and connected to the secondary inverter control unit 15
The secondary inverter unit 4 is controlled via. Further, the arithmetic control unit 13 is connected to the primary inverter unit 2 via the primary inverter control unit 16 and controls the primary inverter unit 2 via the primary inverter control unit 16. Further, the welding current detector 7 is connected to the arithmetic control unit 13 via the welding current detection unit 17, and the welding current detection output is output from the welding current detection unit 17 to the arithmetic control unit 13. Further, the arithmetic control unit 13 is connected to the welding current setting device 18, the welding voltage setting device 19 and the EN ratio setting device 20, respectively.

The operation of the above arrangement will be described below. First, the welding start signal TS for starting welding is calculated by the calculation control unit 13
Input to the secondary inverter control unit, the arithmetic control unit 13 confirms that there is no output current from the welding current detection unit 17.
15 EN ratio 0% regardless of the setting of EN ratio setting device 20
That the primary inverter control unit
Command 16 to output unloaded voltage. At the same time, regardless of the setting of the welding current setting device 18, the motor drive circuit 14 is instructed of the slow down wire feeding speed FS for smooth arc start. As a result, the wire feeding motor 12 rotates at the slow down wire feeding speed of FS, and as a result, the wire 9 is fed toward the base material 11 and the wire 9 comes into contact with the base material 11, which causes the welding current to flow. It flows to generate a welding arc 10.

Further, when the welding arc 10 is generated, the welding current "present" information is input from the welding current detector 17 via the welding current detector 7. As a result, the arithmetic control unit 13
Outputs a command to the secondary inverter control unit 15 so that the number of clocks is started and the EN ratio is sequentially set to the set value of the EN ratio setting unit 20. At the same time, the arithmetic and control unit 13 changes the EN
Based on the information indicating the ratio, as shown in FIG. 5, the wire feeding speed optimum for the momentary EN ratio is set to the motor drive circuit.
Command 14

FIG. 2 is a block diagram showing the configuration of the arithmetic control unit 13 of FIG. In FIG. 2, the arithmetic control unit 13 is provided with an arithmetic element unit 13a, a read-only storage unit 13b in which data is written in advance, and a timer unit 13c. In this storage unit 13b, in the case of each EN ratio, an appropriate wire feeding speed for the welding current is stored in advance as data. In addition, the timer unit 13c is in a countable state only when the welding start signal TS is on, and the count value is 0 when it is off.
Reset welding current detection signal A ₀ increases the clock value only when the welding output current is “present” (timer section
The clock circuit section and the like are omitted due to the increase in the number of clocks in 13c).

After the arc is generated, the timer section 13c increments the clock value from 0 and supplies the clock number data Tn to the arithmetic element section 13a. The arithmetic element unit 13a calculates Tn data and the input EN% from the EN ratio setting unit 20 according to the following equation, and outputs the EN ratio signal Cs to the secondary inverter control unit 15.

Cs = Tn (in the case of Tn <EN%) Cs = EN% (in the case of Tn ≧ EN%) At the same time, the calculation element unit 13 a stores the storage unit in accordance with the calculation result Cs and the value from the welding current setter 18. Appropriate wire feeding speed data is taken out from 13c and outputted to the motor drive circuit section 14 as a signal M. For example, as a result of the above equation, when the EN ratio is 10% and the welding current setting device 18 is instructing 100 A, the computing element unit 13a displays the wire feed speed data of 4.2 m / min in the storage unit 13b. Is output and output as an M signal.

Further, the control method of the consumable electrode type AC arc welding machine will be described with reference to the control timing chart of FIG.
When a welding start signal for starting welding is input to the welder at time t ₀ , the welder outputs a no-load voltage with an EN ratio of 0%. At the same time, the wire 9 is fed toward the base material 11 at the wire feeding speed of Fs. The wire 9 is in contact with the base material 11 flows welding output current, welder detects this proper F ₀ when the EN ratio 0% represented by the point a of FIG. 5
Switch to the wire feeding speed. After that, the EN ratio of the welding output is increased to reach the EN ratio of ENx at time t ₂ , but at this time, not only the EN ratio of the welding output is changed, but also the wire feeding speed is changed. Control is performed so that Fx is reached at time t ₂ while controlling the wire feeding speed to be appropriate for the EN ratio at that time. Specifically, in FIG. 5, the wire feeding speed is increased from the point a of the wire feeding speed F ₀ immediately after the arc occurrence to the point b → c with the lapse of time, and reaches the point x at the time t _2. Control to do so.

[0019]

As described above, according to the present invention, when the arc is generated, only the EP polarity is set, and the EN ratio at the time of steady welding is sequentially shifted, and the wire feeding speed is changed every moment.
Since the N ratio becomes an appropriate value, it is possible to smoothly start the arc and transition to smooth steady welding, and it is possible to prevent welding defects such as large spatter generation and insufficient penetration at the arc start, and stable welding start. It is something that can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a consumable electrode type AC arc welding machine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a calculation control unit 13 in FIG.

FIG. 3 is a control timing diagram at the time of arc start by the consumable electrode type AC arc welding machine of FIG. 1.

FIG. 4 is a control timing chart at the time of arc start in the conventional consumable electrode type arc welding machine.

FIG. 5 is a diagram showing a relationship between an appropriate wire feeding speed and an output current when the EN ratio is changed.

[Explanation of symbols]

 2 Primary inverter section 4 Secondary inverter section 7 Welding current detector 9 Wire 11 Base metal 12 Wire feeding motor 13 Calculation control section 13a Calculation element section 13b Storage section 13c Timer section 14 Motor drive circuit 15 Secondary inverter control section 16 Primary inverter controller 17 Welding current detector 18 Welding current setting device 19 Welding voltage setting device 20 EN Ratio setting device

Claims (1)

[Claims] 1. A consumable electrode type AC for performing arc welding by applying an AC voltage between a welding wire that is a consumable electrode and a base material that is a workpiece, and inverting the polarity of the AC voltage by time division. This is a control method for an arc welder, in which the consumable electrode side has a positive polarity when an arc occurs at the start of welding, and the consumable electrode side becomes negative with the passage of time so that the polarity ratio becomes constant during steady welding after the arc occurs. The ratio of the positive polarity is increased, and the feed rate of the consumable electrode is controlled to be sequentially increased with the feed rate during steady welding as a target value according to the polarity rate that changes with the passage of time. Control method for consumable electrode type AC arc welding machine.