Tandem Submerged Arc Welding
A welding process using two wire electrodes guided sequentially under a layer of flux powder. It drastically increases deposition rates and welding speeds on thick-walled parts.
Submerged arc tandem welding basically means welding with two wires simultaneously in a powder bed. The two wires run one behind the other into the same weld zone, giving you solid deposition rates and allowing you to move faster than with a single wire. This process is for thick plates where you want to lay down a lot of material. If the parameters aren't right, you'll quickly have issues with the weld bead shape—the powder can shift or you'll get porosity and cracks. Set up both wires properly; the distance and power distribution between them need to harmonize, otherwise one side runs hot and the other cold. Make sure the powder completely covers the zone, then the arc burns cleanly under the powder. For thin sheets, you don't need the tandem process; a single wire is enough. Only when you really want to build up material does the effort with the second wire pay off.