STUDY ON THE PHENOMENA OF THE CONTROLLABILITY OF ARCAPPEARANCE IN THE CONSUMABLE ELECTRODE PULSE CURRENT ARC WELDING PROCESS AND ITS PRACTICAL APPLICATION

It has been well-known that the metal transfer and the heat input can be controlled in consumable electrode pulse current are welding process. But we have discovered further another controllable characteristic of this process during our experiments. In the case of pulse-spray transfer even though the average arc current and voltage are kept constant, the visible are appearance can be varied by altering the other operating variables. Keeping the average arc energy unchanged, three different typical visible are appearannees, i.e, the bunch type, bell type and cone type, can be obtained. Each type of these arc appearances offers it's special thermal and mechanical features, and so brings about distinct technological characteristics. During the pulse current cycle, the varied process of the size and the shape of the luminous region of the are has been observed by the high-speed photography. The lumineus region of the arc in the duration of the pulse current period grows gradually from a thin linear shape to a bunch shape and finally to a cone shape and remains so continucusly if the pulse current time is enough. We call the time necessary for this growing process the dynamic time of the luminous region of the pulse current arc (t_d). The resulting visible appearance of the pulse current arc depends on the relationship between t_d and t_d (pulse current time). The effects of the pulse current magnitude, the pulse current wave form and the shielded gas composition on the t_d have been examined. The dissimilarity of the technological features of these different visible arc appearances as well as its reasons have also been discussed. The controllability of the arc appearances is of help to extend the application field of the cosumable electrode shielded gas arc welding process. It can be utilized successfully in several practical applications, such as in the welding of thin platcs, one-side welding without backings, narrow gap welding process, positional welding processes and so on.