weld

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by coalescence. Most welds are formed by heating the workpieces above their melting points and allowing them to fuse, often with the addition of filler material. Some welds rely on pressure alone to create the bond, without melting the base metals. Welding differs from soldering and brazing in that it typically requires higher temperatures and often results in a single, continuous piece of material.

Common materials welded include steel, stainless steel, aluminum, titanium, and various alloys. Weld joints can be butt, fillet, lap, or corner configurations, and welding can be performed in different positions.

Manufacturing employs several process families. Arc welding uses an electric arc as the heat source; metal electrodes may be consumable (SMAW, GMAW/MIG, FCAW) or non-consumable (GTAW/TIG). Shielding gas or flux protects the weld pool. Resistance welding uses pressure and electric current, as in spot welding. Energy beam welding uses focused laser or electron beam energy, often in controlled atmospheres. Friction-based methods such as friction stir welding are used for some alloys.

Quality and safety are central concerns. Proper technique, material preparation, welding parameters, and post-weld treatment influence strength and integrity. Common defects include porosity, cracks, slag inclusions, and lack of fusion. Inspection methods include visual checks and nondestructive testing such as radiography or ultrasonics. Welding safety requires protective equipment to shield eyes and skin, ventilation to control fumes, and adherence to standards set by organizations such as AWS and ISO.