Back Bead Width Control in One Side SAW using Flux Copper Backing : Correlation between Back Bead Width and the Voltage as measured between Base Plate and Copper Backing (Report 1)

概要

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A back bead width control system has been proposed to stabilize the process of one side FCB SAW in which a stationary copper backing plate covered with a flux layer of several milimeters thickness is used as backing. When a stable welding process is maintained under an adequate welding condition, a signal voltage between the backing copper plate and the plate being welded is detected. The polarity and phase of the detected voltage having a few volts level well correspond to those of the arc voltage in case of AC current welding. In a stable FCB SAW process, the back side bead is usually formed by a key-hole action of the arc. The reason is probably that the arc penetrates the welding groove and the flux layer, then it contacts the copper plate and is reflected to the welding plate. A correlation between the detected voltage level and the back side bead width is recognized. A similar phenomenon is observed in a key-hole welding using a transfer type plasma arc. In order to maintain a constant back bead width the detected voltage is compared with a reference voltage, and then the welding current is controlled by the difference between the above voltages.
1987-10-01