A heat-transfer model of the melting electrode in gas metal are welding (GMAW) was used to compare the relative sensitivity of the process when welding with aluminum electrodes compared to that of steel electrodes. The aluminum model was verified with experiments for ER-1100 and ER-rpre electrodes. The dimensionless parameters in the model showed that conductive heat transfer dominates other effects in aluminum compared to steel, which causes the differences in sensitivity of the process to the input parameters (current, wire-feed speed, and/or voltage). If the steel and aluminum electrode extensions are compared at about the midpoint of the current range for electrodes of the same diameter (1.2 mm), the aluminum electrode is 28 times more sensitive to changes in the wire-feed speed than is the steel electrode. When welding with a 1.2- mm-diameter aluminum wire at 150 A, a 1% change in wire-feed speed causes an 8-mm change in the arc length. When welding with a 1.2 mm-diameter steel wire at 200 A, a 1% change in wire-feed speed causes a 0.5-mm change in the arc length. Similar sensitivity to changes in current is exhibited by aluminum. Dynamic analysis about the set points described above indicates the electrode extension in aluminum is many times more sensitive than steel to perturbations in wire-feed speed and current at low frequencies, but aluminum has a similar response to steel at high frequencies.
aluminum GMAW, arc length, electrode extension, process sensitivity, steel
Process Sensitivity of GMAW: Aluminum vs. Steel, Welding Journal
(Accessed December 1, 2022)