Electric heating – Metal heating – By arc
Patent
1990-10-26
1995-04-11
Shaw, Clifford C.
Electric heating
Metal heating
By arc
B23K 909
Patent
active
054060524
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pulsed arc welding system and more particularly, to pulsed arc welding system designed to achieve regularity and controllability during the fusion and separation of an electrical discharge electrode, so that high-quality welding performance is attained.
BACKGROUND ART
One example of the related prior art is found in the pulsed arc welding system disclosed in Japanese Patent Application Laid Open No. 19177-1982 and another such example is found in the short circuiting transfer arc welding system disclosed in Japanese Patent No. 54585-1987.
The pulsed arc welding system in Japanese Patent Application Laid Open No. 19177-1982 performs a welding process by executing the following procedures. First, the system generates a pulsed arc electric current between a consumable welding wire electrode (hereinafter simply referred to as the "wire electrode") and the base metal. Then the system fuses the base metal and the wire electrode by applying the heat generated by a pulsed arc of electric current. Next, the system cuts off the tip of the molten wire electrode by applying the electromagnetic pinching force of such a pulsed arc electric current to the tip of the wire electrode. Finally, the system intermittently transfers molten globules of the wire electrode to the base metal (this transfer is called "spraying transfer". The advantage of this system are as follows. First, the system is capable of performing a welding process with a pulsed electric current in an area where this welding has an average electric current lower than that of a direct current arc welding system. Second, the system can perform the welding process to a thinner base metal. Third, the system can attain the spraying transfer thereby eliminating the spatter which would otherwise occur in the course of welding.
Also, the short circuiting transfer arc welding system disclosed in Japanese Patent No. 54585 performs a similar welding process. The welding system periodically generates an arc of electric current between the wire electrode and the base metal. The heat generated by this are of electric current melts, the base metal and the wire electrode. Subsequently, the welding system transfers the molten globule formed on the tip of the wire electrode to the base metal by a short circuiting transfer. Consequently, this system is capable of securing a stable welding state by periodically generating an arc of electrical current, and then transferring the molten globule by short circuit transfer.
However, in order to achieve high-quality welding by the pulsed arc welding process, it is necessary to eliminate the spatter which tends to occur in the molten globule during the welding process. In addition, it is necessary to prevent the occurrence of undercuts (i.e., defects in the shape of the welding beads) and to form separated molten globules which are approximately identical size.
In order to eliminate the spatter, it is necessary to prevent the wire electrode and the base metal from touching each other (i.e., short circuiting). In order to prevent the occurrence of undercuts, it is necessary to shorten the arc length. Both of these requirements can be satisfied if the molten globules are formed into fine particles when they are separated from the wire electrode during the spraying transfer. Moreover, in order to create separated molten globules that are substantially the same size, the same pulse form should be repeated periodically in the waveform of the pulsed arc electric current.
The operation of conventional pulsed arc welding systems are shown in FIG. 54. In FIG. 54, .tau. expresses the pulse width, I.sub.B expresses the base electric current, and I.sub.f represents the pulsed peak electric current.
FIG. 54(a) illustrates the operation of a conventional welding system in an atmosphere comprising 100 percent CO.sub.2 gas. In this atmosphere, the width .tau. of the pulsed arc is narrow in relation to the molten globule on the wire electrode. FIG. 54(b) illustrates the operation of a conventiona
REFERENCES:
patent: 4438317 (1984-03-01), Ueguri et al.
patent: 4485293 (1984-11-01), Tabata et al.
patent: 4497997 (1985-02-01), Bodewig
patent: 4546234 (1985-10-01), Ogasawara et al.
patent: 4553018 (1985-11-01), Kondo et al.
Welding Journal, Aug. 1985, Study of Metal Transfer in Pulsed GMA Welding, by S. Ueguri, K. Hara and H. Komura, pp. 242-s through 250-s.
Katou Yoshiaki
Mizuno Masanori
Nagano Osamu
Tabata Yoichiro
Ueda Yoshihiro
Mitsubishi Denki & Kabushiki Kaisha
Shaw Clifford C.
Turner Richard C.
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