metaljoining

Metal joining refers to the processes used to connect metal components to form assemblies. It encompasses methods that rely on metallurgical bonding (fusion or diffusion), mechanical engagement, or adhesive bonding. The choice of method depends on materials, geometry, service conditions, and required joint performance.

Fusion welding uses heat to melt base metals and, often, a filler metal to form a joint on solidification. Common processes include arc welding (shielded metal arc, MIG, and TIG), plasma welding, laser welding, and electron-beam welding. Fusion welding can produce very strong joints but generates a heat-affected zone and residual stresses, which can cause distortion or changes in material properties.

Resistance welding joins parts by electrical resistance and pressure, such as spot, seam, and projection welding. Solid-state or friction-based methods, including friction stir welding and ultrasonic welding, weld without melting the base metals and can reduce distortion or be effective with dissimilar metals or thin sections.

Brazing and soldering join metals with a liquid filler metal while the base metals do not melt. Brazing typically uses filler alloys above 450 C; soldering uses lower temperatures. Joint strength depends on surface preparation, fit-up, and capillary action, with braze alloys offering good high-temperature capabilities.

Adhesive bonding and mechanical fastening provide hybrid or alternative joints. Structural adhesives can distribute loads over broad areas and resist corrosion, while bolts, rivets, and screws enable disassembly and repair, often used in combination with other joining methods.

Key considerations include material compatibility, corrosion, fatigue, thermal expansion, joint design, surface preparation, and quality control. Standards and testing (ISO, ASTM, and nondestructive testing methods) guide acceptance. Applications span aerospace, automotive, construction, shipbuilding, electronics, and consumer products.