JPS6040676A - Method for controlling output of welding power source accompanying short-circuiting - Google Patents

Abstract

PURPOSE:To decrease generation of spatter and deterioration of a weld zone and to improve welding quality and working efficiency in arc welding which accompanies short circuit transfer by controlling the peak current value of a welding wire during short-circuiting according to the function for the feed rate of the welding wire. CONSTITUTION:The current of a welding wire is decreased down to ISS during the time TSS when an arc period shifts into a short circuit period. Peak current ISP is supplied to the welding wire upon lapse of said period. The peak current ISP is controlled to the current meeting the function f(WFR) corresponding to the feed rate of the welding wire WFR, by which the generation of spatter is decreased and the transfer from the short circuit to the arc regeneration is smoothly accomplished in the stage of the transfer from the short circuit to the arc of the welding wire. The necking of the droplet just prior to the arc regeneration is further detected and the output of the welding power source is decreased down to IRA by stopping the supply of the current ISP and thereafter the arc period is started.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for controlling the output of a bath contact power source in arc welding involving a short circuit in which short circuits and arc generation are repeated.

Conventional Art In an arc welding method that involves a short-circuit transition in which a welding wire using a consumable electrode is fed to the base metal at a predetermined speed, short circuits and arc generation are alternated between the welding wire and the base metal. When a constant voltage DC power source is used as the welding power source, the welding current reaches its maximum at the moment when the arc is generated, and the energy at this time blows away the droplets at the tip of the welding wire, causing spatter. If a large amount of this type of spatter is generated, it will cause a decrease in welding efficiency such as a decrease in welding efficiency and the need to remove spatter adhering to the welded steel plate. Nitrogen from the atmosphere gets mixed into the weld metal, which obstructs the flow of shielding gas.
There are problems such as deterioration of the mechanical performance of the welded part, or in order to prevent this, it is necessary to frequently interrupt bath contact in order to remove all the spatter in the nozzle.

A method has been proposed in which the flow is reduced to 'RA' and the energy at the time of completion of droplet transfer is set to the minimum required for arc regeneration in order to suppress the generation of spatter.

According to this control method, a certain degree of effect in reducing spatter can be obtained compared to the case where constant voltage DC power supply sound is used.

However, after the droplets are short-circuited, the amount of spatter changes depending on the magnitude of the peak current IsP that is required to be passed through the welding wire to terminate the short-circuit, and there is a problem that the welding itself tends to become unstable. The inventors of the present invention have discovered this.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems in short-circuit transition welding, and provides a method for controlling the output of a welding power source that can effectively prevent the generation of spatter during short-circuit transition. The purpose is to

Summary of the Invention The present inventor has proposed a method for reducing spatter according to the above-mentioned proposal, in which a peak current ■sP for terminating the short circuit of droplets is
As a result of various experiments focusing on the fact that the spatter reduction rate varies depending on the size of the That is, the short circuit peak current IsP is output, and the constriction of the droplet, which is a sign of the end of the short circuit, is detected as a change in the stain resistance due to the unfixed voltage, and the welding current is decreased based on the detected signal. When the peak current sP is high, the current IRA at the time of arc re-occurrence is also high, and the amount of spatter generated increases. Conversely, short circuit peak current ■sP
When the amount of spatter is low, the amount of spatter generated can be suppressed, but the time TsP required to constrict the droplet becomes longer, and during that time the welding wire is fed, and even the unmelted part of the welding wire enters the molten pool, resulting in welding. There may be cases where the wire is welded to the base metal and the arc is re-generated.

As a result of the above observation, the inventor of the present invention has determined that in order to minimize the amount of spatter and to perform stable welding in which short circuits and arc generation are regularly repeated, the welding wire feed speed WFR must be adjusted to a minimum. It has been found that it is advantageous to change the short circuit peak current IsP accordingly.

According to the invention, therefore, in an arc welding process with short-circuit transition, the peak current value 'Sl) of the welding wire during a short-circuit is controlled as a function of the welding wire feed speed.

Example An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, a welding wire 1 using a consumable electrode is applied to a base metal 5 through welding holes 1 to 4 at a predetermined speed WFR by a feed roller 3 driven by a wire feed motor 2. will be sent. Note that shielding gas is emitted from the welding torch 4 so as to surround the welding part, similar to a known one.

The wire feeding motor 2 is controlled by a speed control circuit 7 which receives as input the setting value of a speed setting device 6 for wire feeding.

The rotational speed of the wire feed motor 2 is detected by a speed detector 8, and its detection signal is applied to a function generator 9. The function generator 9 is a welding wire 1117 detected by the speed detector 8.
) In order to obtain the optimum peak current ■sP for the feeding speed piWFR (m/min), a function f(WFR) that changes as shown, for example, by the dotted line in FIG. 3 is output.

The relationship between this feeding speed WFR and the function f(WFR) is
The current 151) is determined as follows through experiments and the like in order to suppress the generation of spatter during a short circuit and to achieve smooth welding.

According to experiments, it is recognized that the short circuit peak current 'SP with respect to the welding wire feeding speed WFR has a critical tendency as shown by the solid line in FIG. 3. In other words, in the region below the critical threshold, the short-circuit peak current is too low, and the time TsP required to constrict the droplet is not long, and the welding wire becomes welded to the base metal, resulting in stable welding. do not. On the other hand, welding is not possible in the region above the criticality, and the maximum permissible value of the peak current sP is based on the power capacity of the welding power source that supplies power to the welding wire.
The higher the SP, the greater the capacity for sputtering. Therefore, the function 15P: f (WFR) determined by short-circuit peak current l5Pt - welding wire feeding speed is set in the region above the critical axis with a certain margin for stable welding, and in order to suppress the generation of welding as much as possible. It is set to be as close as possible to the critical value shown by the solid line in the M3 diagram.

Furthermore, if the peak current IsP is set to a high level, not only will spatter occur more, but also the peak current IsP will be applied and the IsP will increase at the reed where the constriction of the droplet, which is a sign of the end of the short circuit, will be detected. The holding time TSP becomes shorter, but in order for short circuits and arc generation to occur regularly, the holding time TSP depends on the diameter of the welding wire.
It is also experimentally known that approximately 3 m5eC is optimal, and it is preferable that the above function is determined taking this fact into account.

Therefore, in this invention, the type of welding wire,
Peak current sP and wire feed m degree w depending on wire diameter etc.
Depending on the critical tendency with FR, the above function [(WFR) is expressed by a quadratic function shown by the dotted line in FIG. 3, which is slightly more elegant than the critical value shown by the solid line.

Note that instead of a quadratic function, a linear function may be approximated to the extent that there is no problem in practical use, as shown by the dotted line in FIG.

In FIG. 2, the output signal f(WFR) of the function generator 9 is applied to the welding power source 10 to control the current 'SP of the welding wire 1 according to E(WFR).

11 is a voltage detector that detects the arc voltage between the welding wire 1 and the base metal 5; and 12 is a current detector that detects the current of the welding wire 1. The current in the welding wire detected by the current detector 12 is fed back to the welding power source 10, and is controlled so that the current in the welding wire 1 at the time of short circuit corresponds to the function f(WFR).

In the above-mentioned welding apparatus, when the short-circuit period starts from the arc period, the power source 10 reduces the current of the welding wire 1 to ■ss for a time Tss, as shown in FIG. is controlled by a timer, etc.), and a peak current Isp is supplied to the welding wire 1 from the welding power source 10. This peak current "SP" is controlled to correspond to the function f (WFR) corresponding to the feeding speed WFR of the welding wire 1, and there is little spatter generation even during the transition from a short circuit of the welding wire to an arc. Short circuit →
The transition to early playback is also performed smoothly. Peak current I S l) by detecting the constriction of the droplet just before arc regeneration
After the supply of the welding power source is stopped and the output of the welding power source is reduced to tIRA, the arcing period begins.

Effects As detailed above, in arc welding involving short-circuit transition, the present invention changes the peak current at the time of a short circuit between the welding wire and the base metal in accordance with the welding wire feeding speed. Therefore, even if the wire feeding speed is set to an arbitrary value, spatter generation can be reduced and the welding wire droplet constriction generation time ('I''SP) can be controlled to be optimal. It also prevents the interruption of welding work due to welding due to the penetration of the welding wire A, etc., and reduces the reduction in welding efficiency due to welding and the deterioration of the mechanical performance of the welded part.
The quality of welded parts and work efficiency can be improved.

The currents shown in Figures 1, 3, and 4 are merely examples, and the magnitude, rate of impoverishment, etc. should be set as desired.

[Brief explanation of drawings]

Fig. 1 is a graph showing an example of the change in current of the welding wire during welding involving short-circuit transition, Fig. 2 is a block diagram showing an example of a control device applied to the present invention, and Fig. Fourth
The figure is a graph showing an example of a function for welding wire feeding speed. 1... Welding wire, 2... Wire feeding motor, 4...
... Welding torch, 5... Base metal, 6... Speed setting g translation 7... Speed i'[ilJ control circuit, 8... Speed detector, 9... Function generator, 10... ... Welding power source, Ts I) ... Short circuit peak current period, IS l)
...Peak current during short circuit Patent applicant Kobe Steel, Ltd.

Claims (1)

[Claims] (1) In addition to reversing short circuits and arcing between the welding wire and the base metal, the welding current is lowered immediately after the short circuit, and then increased to the short circuit peak current to prevent the constriction of the droplet, which is a sign of the end of the short circuit. In welding that detects and reduces the welding current and then regenerates the arc, the output of the welding power source is controlled so that the short circuit peak current is a function of the welding wire feeding speed. A method for controlling the output of a welding power source.