JPS61108472A - Arc welding method - Google Patents

Abstract

PURPOSE:To improve the stability of an arc by discriminating the contact state between a wire and a material to be welded and an arc generating state of the time of starting an arc, and shifting a lower speed than a wire feed speed to a set speed. CONSTITUTION:When a welding start switch 7 is turned on, a timer circuit 14 is operated, and by a control signal of the timer circuit 14, a wire feed speed switching circuit 10 inputs a set value of a low speed wire feed setting part 11 to a wire feed motor driving circuit 5 for another prescribed time (the time which has been set by a timer). After the prescribed time has elapsed, a set value of a welding condition wire feed setting part 12 is inputted automatically to the wire feed motor driving circuit 5 by the wire feed speed switching circuit 10. The prescribed time in this case is determined by the required for the time when a wire 2 contacts to a material to be welded 8, and an arc is generated, and the time required for the time when the wire 2 is fed for a short time through an interval extending from the tip of a welding chip to the material to be welded 8 by an inching operation in a welding work.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is an arc welding method in which welding is performed while continuously feeding a wire as a consumable electrode, which requires arc starting and stabilization. This invention relates to an arc welding method suitable for welding such as automatic welding work or high-speed welding work.

<Conventional technology> In the conventional arc welding method using a wire as a consumable electrode, in order to stabilize the arc starting, the output voltage at the time of arc starting, the ball diameter of the wire tip, and the wire feeding speed are controlled. Furthermore, arc start-up compensation is performed, such as by reducing the DC inductance value inside the arc welding machine power supply at the time of arc start-up, thereby accelerating the rise speed of the welding current.

In this case, when controlling the wire feed speed at arc startup, the wire is fed at a lower wire speed than the set wire feed speed determined by the welding conditions, so that the wire and the workpiece come into contact and the welding current flows. A method of shifting from a low wire feeding speed to a set wire feeding speed at the time of starting or after a predetermined time, or by feeding the wire at a wire feeding speed lower than the set wire feeding speed determined by the welding conditions. A method is used in which wire feeding is stopped when the material to be welded contacts and welding current begins to flow, and then the wire feeding speed is shifted to the set wire feeding speed when an arc is generated.

In this conventional control method, when an arc is generated immediately after contact between the wire and the material to be welded, or when the contact state (short circuit state) between the wire and the material to be welded continues, the wire is fed at a low speed in consideration of the arc starting phenomenon. Because there is no control to shift from the feeding speed to the set wire feeding speed, arc instability occurs due to the wire curling up when the arc starts, and welding defects occur when the cut wire fuses to the welding start point of the welded material. It was not practical because of problems such as

<Problems to be Solved by the Invention> An object of the present invention is to determine the contact state between the wire and the workpiece to be welded and the arc generation state at the time of starting the arc, and set the wire feeding speed from a speed lower than the wire feeding speed. It is an object of the present invention to provide an arc welding method in which the stability of the arc at the time of arc startup is improved by shifting to the wire feeding speed, and the drawbacks of the prior art are eliminated.

Means for Solving Problems> The present invention, in a welding method using a consumable electrode, determines the contact or arc generation state between the wire serving as the consumable electrode and the workpiece at the time of starting an arc, and This is an arc welding method characterized by setting the wire feeding speed to a constant value lower than the wire feeding speed determined by the welding conditions in the state, and setting the wire feeding speed to the wire feeding speed determined by the welding conditions in the arc generation state.

By controlling the wire speed according to the condition between the wire and the material to be welded at the time of starting the arc, it is possible to prevent the wire from curling up at the time of starting the arc and the fused wire at the welding start point of the material to be welded to be fused. There is no.

<Example> FIG. 1 shows an arc welding machine implementing the present invention.

In the figure, an arc welding power source 1 applies a predetermined voltage between a wire 2 fed through a wire feeding roller 4 and a workpiece 8 to be welded inside a welding torch 3 when a welding start switch 7 is turned on. This is a power source for generating arc 9 between wire 2 and material to be welded 8 to perform welding. The wire 2 is fed by controlling the rotation speed of the wire feed motor 6 according to the output of the wire feed motor drive circuit 5 which is activated when the welding start switch 7 is turned on. This is done by connected wire feed rollers 4. The output level of the wire feeding motor drive circuit 5 is
Welding It is determined by the setting value set by the conditional wire feeding setting section 12. In this case, the setting value set in the welding condition wire feeding section 12 is related to the welding current of the set welding condition, and when the set welding current is a large value, the setting value of the welding condition wire feeding section 12 ( The setting voltage value) is set high, the output level of the wire feed motor drive circuit 5 is increased, the rotational speed of the wire feed motor 6 is increased, and the feeding speed of the wire 2 is increased. Conversely, when the set welding current is a small value, the set voltage value of the welding condition wire feed section 12 is set low, the output level of the wire feed motor drive circuit 5 is lowered, and the rotation speed of the wire feed motor 6 is decreased. , and the feeding speed of the wire 2 is decreased.

In addition, in the example of experimenting with CO□ welding or MAG welding using flux-cored wire and solid wire, the set value set in the low-speed wire feed setting section 11 is set in the wire feed setting section 12 under each welding condition. Since the value is 115 times the set value, the low-speed wire feed section 11 and the welding condition wire feed setting section 12 can also be configured by resistance elements that are variable in conjunction with each other. The wire feed speed switching circuit 10 inputs the set value of the low speed wire feed setting section 11 to the wire feed motor drive circuit 5 using control signals from the reset circuit 13 and the timer circuit 14, or changes the welding condition wire feed. This circuit determines whether to input the setting value of the setting section 12. That is, when the welding start switch is turned off, the reset circuit 13 is activated, and the wire feed speed switching circuit 10 uses the control signal from the reset circuit 13 to cause the wire feed motor drive circuit 5 to switch to the low speed wire feed section 11. The configuration is such that the setting value is input. Since the reset circuit 13 is a circuit provided to feed the wire at a low speed at the start of welding, when the welding start switch is turned on, the wire feeding speed switching circuit 10 is controlled by the control signal of this reset circuit 13. The configuration is such that it is not possible.

Next, when the welding start switch 7 is turned on, the timer circuit 14 is activated, and the control signal from the timer circuit 14 causes the wire feeding speed switching circuit 10 to continue feeding the wire for a predetermined period of time (time set by the timer). The setting value of the low-speed wire feed setting section 11 is input to the motor drive circuit 5, and after a predetermined period of time, the wire feed speed switching circuit 10 automatically changes the welding condition wire feed setting to the wire feed motor drive circuit 5. The configuration is such that setting values for the section 12 are input. In this case, the predetermined time is the time required for the wire 2 to come into contact with the workpiece 8 to generate an arc, and for the welding tip (not shown) built into the welding torch 3 during the inching operation of the wire 2 during the welding operation. The time required for the wire 2 to be fed for a short time (the setting of the wire feeding speed set in the low-speed wire feeding setting section 11) Feeding by value takes a long time and has poor workability, so it is determined by the time required for short feeding (the latter time is rather the major determining factor).

It is set to about 1 second. However, this timer circuit 14
The timing of the control signal to the wire feed speed switching circuit 1o is also determined when the welding start switch 7 is turned on and the comparator 18, which detects the occurrence of an arc and stops the operation of the timer circuit 14, is activated. From that moment on, the timer circuit 14 for the wire feed speed switching circuit 10 is activated.
The control signal from the wire feed speed switching circuit 10 is invalidated, and the input from the wire feed speed switching circuit 10 to the wire feed motor drive circuit 5 is automatically switched to the setting value of the welding condition wire feed setting section 12. .

On the other hand, the condition for activating the comparator 18 and invalidating the control signal from the timer circuit 14 to the wire feed speed switching circuit 10 is that the comparator 18 activates the arc welding power source 1 generated when the welding start switch 7 is turned on. This is when the welding current is flowing without being detected by the no-load voltage, and after the first arc voltage is generated at arc start-up. The specific circuit configuration is such that a welding current detector (for example, a shunt) 15 provided in the output circuit of the arc welding power source 1 detects the presence or absence of welding current, and when the welding current is flowing, the arc welding power source 1 detects the presence or absence of welding current. The welding current detection switch 17 inserted in the output circuit of the arc welding power source 1 is operated by the welding current detection switch drive circuit 16 which has a phase delay using the detected welding current as input, and the output voltage of the arc welding power source 1 is changed to the output voltage of the comparator 18. The arc voltage is detected as an input, and if an arc is generated, a control signal is immediately applied from the comparator 18 to the timer circuit 14 to disable the control signal from the timer circuit 14 to the wire feed speed switching circuit 10. This is a configuration that allows The reason why the welding current detection switch drive circuit 16 is provided with a phase delay is as follows.

An extremely short arc breakage of several tens of milliseconds (ms) that occurs during arc startup does not contribute to improving arc stability during arc startup, so a phase lag is introduced in order to improve the stability of the entire wire feeding system. ing.

With this configuration, the arc starting phenomenon between the wire 2 and the welded material 8 at the time of arc starting (the wire 2 and the welded material 8
is in contact or is generating an arc).
When in contact, the wire feed speed is kept low, and once an arc occurs, the wire feed speed can be changed to a wire feed speed that corresponds to the set welding conditions. This prevents arc instability due to wire curling up when the arc starts, and welding of the welded material. The problem of welding defects caused by the welding wire being fused to the starting point has been resolved.

FIG. 2 is a diagram illustrating the operation of the embodiment of FIG. 1.

In FIG. 2, A shows the moment the wire 2 contacts the welding material 8, B shows the moment an arc is generated between the wire 2 and the welding material 8, and C shows the state where the arc is cut. Fig. 2 shows a state where the wire 2 and the workpiece 8 are in contact immediately after the arc is started, and during the contact period AB, as shown in the operation of the welding current, in the case of a constant voltage type arc welding power source, there is a large short circuit. Although the current flows, the wire feeding speed is set at the low speed wire feeding setting section 1 from when the welding start switch 7 is turned on.
The low speed according to the setting value set in 1 is maintained. At B, where the contact eventually breaks and an arc occurs, the wire feeding speed becomes the set value set by the welding condition wire feeding setting section 12.

<Effects of the Invention> According to the present invention, the wire feeding speed can be controlled depending on the state (contact state or arc generation state) between the wire and the workpiece at the time of arc startup. Arc stability is greatly improved.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the arc welding machine of the present invention, and FIG.
FIG. 2 is an explanatory diagram of the operation of the embodiment of FIG. 1; 1... Arc welding power source, 2... Consumable electrode (wire)
. 3... Welding torch, 4... Wire feeding roller, 5...
... Wire feeding motor drive circuit, 6... Wire feeding motor, 7... Welding start switch, 8... Material to be welded,
9... Arc, 10... Wire feed speed switching circuit, 11... Low speed wire feed setting section, 12... Welding condition wire feed setting section, 13... Reset circuit, 14
...Timer circuit, 15...Welding current detector, 1,6
... Welding current detection switch drive circuit, 17... Welding current detection switch. 18... Comparator.

Claims (1)

[Claims] 1. In an arc welding method using a consumable electrode, the contact or arc generation state between the wire as the consumable electrode and the workpiece is determined at the time of starting the arc, and if the wire is in contact, the wire is not fed. An arc welding method characterized in that the feeding speed is set to a constant value lower than the wire feeding speed determined by the welding conditions, and in the state where an arc occurs, the wire feeding speed is set to the wire feeding speed determined by the welding conditions. 2. The arc welding method according to claim 1, wherein an arc welding current detection circuit is inserted in series as a method for determining the contact state or the arc generation state. 3. A patent claim characterized in that the ratio between the wire feeding speed in a contact state and the wire feeding speed in an arcing state is constant, and a resistance element is used that is interlocked and variable according to welding conditions. The arc welding method described in Scope 1.