Arc voltage has an important effect on the weld bead shape and the depth of penetration; the precise effect being dependent on the joint preparation. Bead on plate welds and square edge close butt welds have increased bead width and dilution as the arc voltage increases, although the depth of penetration is relatively unaffected (Fig.1a). In a prepared V-butt joint, increasing the arc voltage may lead to lack of fusion in the root as the wide arc will not reach the bottom of the root. Reducing the voltage, in this case, will increase the depth of penetration as the narrow arc column is more easily able to reach the bottom of the preparation (Fig.1b).
Increasing arc voltage lengthens the arc so that weld bead width, reinforcement and flux consumption are increased as is the risk of arc blow. When alloying the weld metal from the flux, arc length and hence arc voltage must be carefully controlled as at high arc voltages more flux is melted allowing more alloying elements to enter the weld metal thereby affecting weld metal composition.