Full definition
Permanent metal joining process using localized fusion with or without filler material. Main types: arc welding (SMAW, MIG/GMAW, TIG/GTAW), resistance welding (spot, seam), oxy-acetylene, laser, and friction welding. Requires procedure qualification (WPS) and welder qualification (WPQ) per AWS D1.1 (structural), ASME IX (pressure vessels), or API 1104 (pipelines).