JPS59153577A - Consumable electrode type arc welding device - Google Patents

Abstract

PURPOSE:To perform surely arc starting by selecting start current according to welding conditions, setting the period of the start current and performing arc welding in accordance with the same. CONSTITUTION:The diameter of a wire electrode optimum for objects to be welded is selected with a wire diameter selector 14, and the optimum welding current value meeting a wire feed speed is set with a welding current setter 16 and both are outputted respectively to a start current selector 18. The selector 18 selects the optimum start current from plural start current setters 20-24. The generation of short-circuiting by the welding current is detected with a short-circuiting detector 28. A start current period setter 30 sets the optimum period when the start current is conducted by the output signals from the selector 18 and the detector 28. Arc starting is performed in accordance with the set period and the current is changed over to a stationary state by using a start current control circuit 32, then welding is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a consumable electrode type arc welding device, in particular, a welding device that generates an arc between the workpiece and the wire electrode while feeding the wire electrode toward the workpiece. The present invention relates to a device for performing

Conventionally, this type of consumable electrode type arc welding apparatus was started in the following manner.

That is, a DC voltage is applied between the wire electrode wound on a reel and the workpiece, and the wire electrode is fed toward the workpiece at a constant speed by a feeding device. When the tip of the wire electrode 10 comes into contact with the surface of the workpiece 12 as shown in FIG. 1(5), a start current flows from the wire electrode 10 toward the workpiece 12. In this way, the starting current is passed at the time of starting by generating a minute arc in the gap between the tip of the wire electrode 10 and the workpiece 12, and this minute arc melts the tip of the wire electrode 10 by a predetermined amount, thereby melting the tip of the wire electrode 10 to a desired amount. This is to generate an arc having an arc length of from the entire end face of the wire electrode 10.

In the conventional device, this starting current rises at a predetermined rising speed regardless of welding conditions such as wire diameter and welding current, so it is controlled so that it flows by a predetermined value after a predetermined period ( ·Ta.

For example, as shown in FIG. 2, if the wire electrode 10 comes into contact with the surface of the workpiece 12 at time TO, the current starts flowing so that the start current The rising curve of was set in advance. Assuming that the time until the arc is generated is short, as shown by the broken line curve in FIG. occurs. When the short-circuit state changes to an arc state, the current gradually decreases. When the current decreases to I2 at time T6I, the welding current is switched to a steady state, and thereafter the welding current I2 is controlled to flow at a constant level. If the arc occurs in a very short time like this, the current at the time the arc occurs is small, so there are few slats at the start.

However, in the conventional device, in order to reliably generate an arc, a predetermined margin is taken into consideration from time To to T1.
Since the control was such that an excessive short-circuit current flows during this period, even if the tip of the wire electrode 10 comes into contact with the surface of the workpiece 12, as shown in FIG. 1 (5), an arc will immediately occur. If the arc start is delayed instead, the arc is generated at time T1. In this case, no arc is generated between the object to be welded 12 and the tip of the wire electrode 10, and the current is very large as shown in ) in FIG.
The wire breaks due to I□ and an arc is generated due to the fuse action, resulting in large spacks or a large flameout of the wire electrode 10.The current flows at a predetermined value regardless of the welding conditions. Therefore, if a wire electrode 10 with a different wire diameter is used or the welding current is changed, there is a drawback that a reliable arc start cannot be performed and a gutter occurs. In other words, the optimum value for ≠ Li = sister electric g is determined depending on the wire diameter. For example, as the wire diameter increases, the starting current must be increased, and similarly for welding current, it is necessary to increase the welding current. Then, it is necessary to increase the start current, but similarly, if the start is delayed, an excessive start current will further increase spatter at the start part, promote arc creep, and cause the electrode wire 10 to There was a drawback that a burnback phenomenon in which the tip for sending out (not shown) was welded frequently occurred, and a reliable arc start could not be performed.

For this reason, attempts have been made to control the starting current according to the welding conditions, but in the conventional → no-starting control method, the starting current changes in a similar shape to the characteristic curve shown in Figure 2. As a result, when the peak value of the starting current is set small, an arc is generated only from a part of the tip of the wire electrode 10, and an arc is not generated from the entire end face of the wire electrode 12, resulting in an unstable arc and the arc disappearing. The drawback was that it was easy.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a consumable electrode type arc welding device that can perform a reliable arc start according to welding conditions.

In order to achieve the above object, the present invention provides a consumable electrode type arc that welds the workpiece by generating an arc between the workpiece and the wire electrode while feeding the wire electrode toward the workpiece. In a welding device, a start current selector selects a predetermined limited start current according to welding conditions, a start current period setting device sets the start current period according to welding conditions, and a start current period setting device selects a predetermined limited start current according to welding conditions; The present invention is characterized in that it includes a start current control circuit that supplies a limited start current to the workpiece and the wire electrode for a predetermined period.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows a preferred embodiment of the consumable electrode type arc welding apparatus according to the present invention.

In FIG. 3, a wire diameter selector 14 is provided to select the optimum diameter of the wire electrode 10 for the workpiece 12 to be welded. Further, the welding current value has a substantially proportional relationship with the wire feeding speed; for example, as the wire feeding speed increases, the welding current value also increases.

For this reason, the apparatus of this embodiment is provided with four welding current setting devices 11' for setting the optimum welding current value in accordance with the wire feeding speed. In this embodiment, the wire diameter selector 14 and welding current setter 16 are configured so that they can be manually selected and set before the start of welding.

A start current selector 18 is provided to select a start current having a predetermined limited value in accordance with welding conditions such as the wire diameter and welding current, and this start current selector 18 is used to select the wire diameter. Based on the wire diameter and welding current value selected and set by the welding current setting device 14 and welding current setting device 16, a plurality of start current setting devices 20 to 20 are set in advance.
Starting current 110, I+ set at 24, respectively
1. Select the optimal starting current for welding conditions from among 11z.

Further, the welding current flowing through the electrode wire 10 is detected by a welding current detector 26, and the detection signal is supplied to a short circuit detector 28. The short circuit detector 28 detects the occurrence of a short circuit due to the supplied welding current.

A start current period setter 30 is provided to set a period during which a selected start current is applied according to the welding conditions, and the setter 30 is connected to the wire diameter selector 14 and the welding current setter 16, respectively. After a short circuit is detected by the short circuit detector 28 based on the selected and set wire diameter and welding current value, the optimum start current period is set for these welding conditions.

The start current value and short-circuit current period, which are selected and set according to the welding conditions, are determined in consideration of the following points.

In other words, if the starting current is set to a large value, large spatter that can cause the wire to break due to the fuse action will occur as in the conventional device, so the Nuttat current value will be reduced when the tip of the wire electrode 10 comes into contact with the surface of the workpiece 12. It must be set to the minimum value that will cause an arc to occur. In other words, if the starting current value is set smaller than this minimum value, the starting current will continue to flow with the electrode wire 10 and the workpiece being short-circuited without generating an arc, and the wire electrode 10 will be heated by resistance heating. This is because spatter will occur as in the conventional device. In addition, the starting current (limited to the minimum value) is unstable at the point when the arc begins to occur. Therefore, in order to stabilize this unstable arc without extinguishing it, the starting current During this period, a stable arc is generated over the entire tip of the wire electrode 10 by melting the tip of the wire electrode 10 and igniting it by an arc to a desired arc length, without generating large spatter. This is the required period (this must be set).

Furthermore, in this embodiment, a predetermined limited starting current is applied to the wire electrode 10 for a predetermined period at the time of arc start.
A start current control circuit 32 is provided to flow the current from the welding point to the workpiece 12 and then switch to steady state fogging.

In other words, the start current control circuit 32 has a comparator 34, and the current corresponding to the selected current selected by the start current selector 18 and the welding current detected by the welding current detector 26 are compared. The comparator 34 supplies a control current until the welding current value reaches the selected current value. Further, the start current control circuit 32 has a comparator 36, which includes a current corresponding to the welding current set by the welding current setting device 16 and a current corresponding to the welding current detected by the welding current detector 26. is supplied to the comparator 36f, and the comparator 36 flows the control current until the welding current reaches a preset welding current.

Further, the start current control circuit 32 is provided with a switch for switching between the arc start state and the steady state, and the switch 38 changes the control current from the comparator 34 to the start current at the time of arc start. Period setter 30
The control current from the comparator 36 is supplied to the control circuit 42 via the drive circuit 40 for a period set in , and during steady operation due to the subsequent switching action, the control current from the comparator 36 is supplied to the control circuit 42 via the drive circuit 40. is configured to do so.

In this embodiment, the control circuit 42 includes a transistor 44 and is configured to control the current flowing from the wire electrode 10 to the workpiece 12 by controlling the current flowing from the drive circuit 40 to the base of the transistor 44. ing.

The embodiment of the present invention has the above configuration, and its operation will be explained below.

First, before starting the arc, manually operate the wire diameter selector 14 to select the same wire diameter as the diameter of the wire electrode 10, and set the welding current value optimal for the wire feeding speed using the welding current setting device 16. do.

Next, the wire electrode 10 having a predetermined selected diameter is fed toward the workpiece 12 at a predetermined speed, and the tip of the wire electrode 10 is connected to the surface of the workpiece 12 as shown in the fourth position. , and a starting current flows. At the time of arc start, the start current selector 18 selects a plurality of start current setters 20 to 24 in advance based on the wire diameter and welding current value selected and set by the wire diameter selector 14 and the welding current setter 16, respectively. The optimum start current (for example, start current, .) for these welding conditions is selected from among the start currents 110 to 1□ set respectively in supply to. Short circuit detector 28 is welding current detector 2
The occurrence of a short circuit between the wire electrode 10 and the workpiece 12 is detected by the welding current detected at step 6, and a short circuit detection signal is supplied to the start current period setting device 30. Then, the comparator 34 compares the selected current from the start current selector 18 and the welding current from the welding current detector 26, and changes the control current to the switch 38 until the welding current becomes the same as the selected current.
Continue to supply. At arc start, switch 3
8 is switched to supply the control current from the comparator 34 to the control circuit 42 via the drive circuit 40, and the transistor 44 of the control circuit 42 operates as shown in FIG. At time T3, a start current 110 is passed from the wire electrode 10 to the workpiece 12.

In addition, the start current period setting device 30 is connected to the wire diameter selector 1.
Based on the wire diameter and welding current selected and set by 4 and welding current setting device 16, the optimum start current period for these welding conditions is set, and the time T4 at which the start current I10 stops flowing due to the short circuit detection signal. During this period, a switching holding signal is output to the switching device 38. Therefore, the fifth
As shown in the figure, a constant starting current 110 continues to flow from the wire electrode 10 to the workpiece 12 for a period t from time T3 to time T4.

Then, at time T4, the start current period setting device 30
A switching signal is output from the switch 38 to the switch 38, and the switch 38 switches to supply the control signal from the comparator 36 to the control circuit 42 via the drive circuit 40, thereby transitioning to a steady state.

The comparator 36 compares the welding current I2t set by the welding current setting device 16 with the welding current detector 26.
The welding current detected at is compared with the corresponding current, and the control current is supplied to the control circuit 42 via the drive circuit 40 until the welding current reaches the set welding current (2). Therefore, a predetermined welding current I2 continues to flow from the wire electrode 10 to the workpiece 12, and as shown in FIG. An arc with a predetermined arc length is generated.

In the diagram shown in FIG. 5, a wire electrode 10 and a workpiece 1
The time when the short-circuit condition with 2 is broken and the arc starts to occur is within the period from To to T4, but if the arc start is very good, that is, the arc starts to occur for a very short time. , it is usually time 'rO
An arc occurs between -'r3. The time from arc generation to T4 is the time required to stabilize the arc, and by burning the wire electrode 10 to a predetermined appropriate arc length, the steady arc after T4 can be immediately stabilized. can.

Furthermore, if the time until arc generation is delayed and the short-circuit state between the wire electrode 10 and the workpiece 12 continues after T3, the wire will break due to the fuse action and the arc will start at T3.
- T4, but unlike conventional arcs, the current at the time of arc generation is IIO, which is a sufficiently limited current value, so even if it breaks due to the fuse action, large spatter that would scatter the wire will not occur. At the same time, the burn-up of the arc does not become excessive, so the burnback phenomenon in which the tip and the electrode wire 1o are welded together can be prevented.

As described above, in this embodiment, the start current value and start current period are set according to the diameter of the wire electrode 10 and the welding current value, so that large spatter due to fuse action does not occur as in conventional devices. , it is possible to perform a reliable arc start according to the welding conditions without causing gas burnback.

In the embodiment described above, the start current selector 18 and the start current period setter 30 are configured to be selected and set depending on the conditions of both the wire diameter and welding current. , wire diameter, and welding current may be selected and set depending on one of the conditions.

As explained above, according to the present invention, there is provided a start current selector that selects a predetermined limited start current according to welding conditions, and a start current period setter that sets the start current period according to welding conditions. By including a start current control circuit that supplies a predetermined limited start current to the workpiece and the wire electrode for a predetermined period at the time of arc start, it is possible to perform a reliable arc start according to the welding conditions.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the wire electrode at arc start in a conventional consumable electrode type arc welding device, Fig. 2 is a characteristic curve diagram showing the current flowing through the wire electrode in a conventional consumable electrode type arc welding device, and Fig. 3 4 is a block circuit diagram showing a preferred embodiment of the consumable electrode type arc welding device according to the present invention, FIG. 4 is an explanatory diagram showing the wire electrode at the time of arc start in the device shown in FIG. FIG. 5 is a characteristic curve diagram showing the current flowing through the wire electrode in the device shown in FIG. The same members in each figure are given the same reference numerals, 10 is a wire electrode, 12 is a workpiece to be welded, 14 is a wire diameter selector, 16 is a welding current setting device, 18 is a start current selector, and 30 is a start current Period setter, 32 is a start current control circuit, 44
is a transistor. Agent Makoto Kuzuno - '$1 Amendment to figure procedure (spontaneous) Commissioner of the Japan Patent Office 1, Indication of case Patent Application No. 1982-27263 2
, Name of the invention: Consumable electrode type arc welding device 3, Person making the amendment Representative: Hitoshi Katayama Department 4, Agent 5: Detailed description of the invention in the specification to be amended. that's all

Claims (1)

[Claims] (1) In a consumable electrode type arc welding device that welds the workpiece by generating an arc between the workpiece and the wire electrode while feeding the wire electrode towards the workpiece, depending on the welding conditions, a start current selector for selecting a predetermined limited start current; a start current period setting device for setting the start current period according to welding conditions; and a start current period setting device for setting the start current period according to welding conditions; A consumable stick type arc welding device comprising a start current control circuit for supplying a workpiece to a welding object and a wire electrode. (2. In the device described in claim (1), one or both of the ear diameter and welding current are selected and set respectively from the start current selector and the start current period setting device t. A consumable electrode type arc welding device characterized by: