Automatic percussion welding

PERCUSSION welding is not new. Early work goes back beyond the beginning of the century, but little application has been made of it and only a meager amount of literature is available. However, this method has a real field of usefulness as the application described in this paper will show. The original Vang process wherein a capacitor charged to a high potential, often to several thousand volts, is discharged across the gap between parts as they approach each other under a propelling force, is a good general description of the method used. The arc so produced heats the abutting surfaces before they collide so that a very thin layer of metal is brought to welding temperature. The propelling force, while continuing to act, brings the parts together percussively and the weld is made. Little metal is heated and little heat penetrates the adjoining metal; therefore, the heat balance problem is greatly minimized and different metals weld together with little trouble. There is, however, the problem of protecting personnel from high voltage. Also, the two surfaces being welded must be insulated electrically from each other. This excludes the use of this process for joining the ends of the same piece of metal, as in making a ring.