Butt weld

A butt weld joins two plates or sections end to end in the same plane, the dominant joint type for ship hull shell, deck, and bulkhead plating. The edges are prepared with a square, single-V, double-V, or X bevel depending on thickness, then filled with weld metal across a root, fill, and cap sequence. Class rules treat full-penetration butt welds in primary structure as equal-strength to the parent plate, so weld metal yield and toughness must match the H36-grade base. Inspection is by radiographic or ultrasonic testing on the long seams; partial-penetration butts are restricted to non-critical connections.