One-side welding (FCB)

One-side welding by the FCB (flux copper backing) process is single-pass submerged-arc welding of a butt seam from the top side only, the joint backed by a layer of bonded flux pressed up against the plate underside by a water-cooled copper bar. Kobe Steel developed FCB in 1964 to weld ship-panel butt seams in one pass without turning the plate, the key to fast panel-line throughput. Modern FCB runs three wires in tandem and welds plate of roughly 8 to 40 mm in a single layer, forming a sound back bead supported by the flux. Sister one-side SAW processes are RF (resin-backed flux) and FAB; all are class-approved for hull butt joints.