Classification of Weld Discontinuities in Overhead Crane Girder Fabrication by Visual Detectability and Root Cause

Weld quality assurance in overhead crane girder fabrication is vulnerable when acceptance relies solely on surface evidence. This review develops a two-axis classification that links visual detectability to process-specific root causes of discontinuities in gas metal arc welding and submerged arc welding. Ten sources published from 2021 to 2025 were examined through comparative source analysis, conceptual synthesis, and typologization. The resulting taxonomy separates directly visible material-loss and profile conditions from surface-connected indications and visually unresolved internal discontinuities. Porosity and burn-through occupy different positions in this scheme. Porosity may remain hidden unless a pore intersects the surface, whereas burn-through produces immediate evidence after metal has been displaced. Their causal pathways also diverge across shielding, surface condition, flux condition, heat input, travel speed, electrode extension, plate thickness, and fit-up. The classification supports process control, inspection planning, traceable disposition, and qualified repair of continuous web-to-flange welds in crane girder production quality systems.