Electric heating – Metal heating – By arc
Patent
1990-12-27
1994-01-25
Shaw, Clifford C.
Electric heating
Metal heating
By arc
21913033, B23K 909
Patent
active
052817911
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to welding apparatus utilizing a pulsed discharge, i.e., pulsed arc welding apparatus, and more particularly to a pulsed arc welding apparatus which control and correct a welding current waveform, wherein the welding current waveform for use in arc weld is supplied in accordance with the periodic repetition of a preset simulation arc length.
PRIOR ART
There are known welding apparatus such as an arc welding apparatus which uses the heat derived from the arc discharge caused to occur between a welding electrode and workpieces so as to weld the workpieces, and a pulsed arc welding apparatus which utilizes a pulsed discharge for the arc discharge. Particularly, some pulsed arc welding apparatus employs a group of pulsating currents comprising pulse trains.
As shown in FIGS. 47(a), (b), a conventional arc welding apparatus of the sort stated above is such that a pulsating current is repeatedly synchronously supplied as an arc current for arc welding purposes. FIG. 44 is shown a structure of such an arc welding apparatus. As shown in FIG. 44, the arc welding apparatus comprises an arc welding power supply 1 for supplying a welding current to a wire electrode 3 supported by a welding torch 2 and to workpieces 4b to be welded so as to have an arc 4a produced, a voltage detector 5 for detecting the arc voltage generated between the wire electrode 3 and the workpieces 4b, a current detector 6 for detecting the arc current, and an automatic welding evaluation unit 71. The automatic welding evaluation unit 71, comprises a voltage setting device 7a2, for setting a comparison voltage Va, a mean voltage converter 7a2 for receiving the arc voltage V detected and converting the arc voltage V to a mean voltage V, a comparator 7a3 for comparing the mean voltage V with the comparison voltage Va, a current setting device 7a4, for supplying a preset predetermined current from the arc welding power supply 1 to the arc 4a, an adder 7a5 for receiving an output signal .DELTA.V from the comparator 7a3 and correcting the output Io of the current setting device 7a4, and a comparator 7a6 for comparing an arc current I from the current detector 6 with the output Io of the adder 7a5 and for outputting a directive signal (ON, OFF) so as to make the arc welding power supply 1 supply the arc current I in line with the set current Io.
With this arrangement, the operation of the conventional apparatus will subsequently be described. When the arc welding voltage (hereinafter called the welding voltage) converted so as to supply an arc current waveform is applied across the gap between the wire electrode 3 and the workpieces 4b by a switching element forming the arc welding power supply 1, the arc 4a is produced between the wire electrode 3 and the workpieces 4b. The wire electrode 3 and the workpieces 4b are heated and melted by the heat thus generated at that time and the workpieces 4b are welded as the molten lump of the melted wire electrode 3 transfers to the workpiece side.
When disturbances resulting from the variation of the feed rate of the wire electrode, the deflection of the welding torch and the distortion of the workpiece and the like occur, however, the heat input supplied from the welding power supply changes as the disturbance causes the arc welding load to change. As a result, the gap (the arc length) between the welding electrode and the workpieces tends to become too wide or narrow in comparison with the locus of the regular arc length accompanied by the normal fusion.multidot.separation of the molten lump and hence the welding condition becomes unstable. For this reason, the electrode-to-workpiece arc voltages V detected by the voltage detector 5 are averaged by the mean voltage converter 7a2 and the mean arc voltage V and the comparison voltage Va set by the voltage setting device 7a1' are compared by the comparator 7a3. If the mean arc voltage V is greater than the comparison voltage Va (.DELTA.V<0), it is assumed longer than an imaginary mean arc length equivalent to
REFERENCES:
patent: 4201906 (1980-05-01), Puschner
patent: 4300035 (1981-11-01), Johansson
patent: 4438317 (1984-03-01), Ueguri et al.
patent: 4721843 (1988-01-01), Budai et al.
patent: 4794232 (1988-12-01), Kimbrough et al.
Ueguri et al., "Study of Metal Transfer in Pulsed GMA Welding", Welding Journal, Aug. 1985, pp. 242 et seq.
Katou Yoshiaki
Mizuno Masanori
Nagano Osamu
Tabata Yoichiro
Ueda Yoshihiro
Mitsubishi Denki K.K.
Shaw Clifford C.
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