welds

Welds are joints formed by fusing materials at the joint boundary, typically metals or thermoplastics, through heat with or without pressure and often with filler metal. Welding aims to create a continuous, structurally sound connection that distributes loads across the joint. It differs from brazing and soldering, which join parts without full metallurgical fusion.

Common weld configurations include butt welds (edges joined in a line), fillet welds (an angled triangular weld, usually in T-, lap-, or corner joints), corner welds, lap welds, plug welds, and slot welds. Welds can be produced by various processes that fall into categories such as fusion welding, solid-state welding, and resistance welding.

Fusion welding processes rely on melting the base metals and sometimes a filler metal. Examples include shielded metal arc welding (SMAW), gas metal arc welding (GMAW/MIG), gas tungsten arc welding (GTAW/TIG), and submerged arc welding (SAW), as well as oxyfuel welding in some cases. Solid-state welding joins parts without melting, using pressure and heat, including friction and diffusion methods. Resistance welding uses electrical resistance to generate heat, such as spot and seam welding.

Weld quality depends on joint design, material cleanliness, proper process parameters, and control of heat input. Common defects include porosity, lack of fusion, cracks, and undercut, which can compromise strength and durability. Inspection methods range from visual examination to nondestructive testing, including radiography, ultrasonics, magnetic particle, and dye penetrant testing.

Standards and safety guidance from organizations such as AWS, ISO, and regional codes govern practices, materials, and qualification of welders. Welds enable the fabrication of a wide range of structures and components across construction, aerospace, automotive, piping, and manufacturing industries.