Brazing

Brazing is a metal-joining process in which a filler metal is melted and drawn into the joint by capillary action, while the base metals remain solid. The filler alloy has a melting point above 450°C (842°F), which distinguishes brazing from soldering. Brazed joints can join dissimilar metals and produce strong, leak-tight connections when properly performed.

The brazing process typically involves fit-up of clean parts, application of a flux to prevent oxide formation, and heating with a torch, furnace, or induction equipment until the filler metal flows into the joint. The assembly is then cooled to form a metallurgical bond between the base metals and the filler. Flux residues are usually cleaned after brazing to prevent corrosion or staining.

Filler metals come in silver-, copper-, aluminum-, and nickel-based alloys, designed for compatibility with the base metals and the service environment. Silver-based fillers often provide high strength and good corrosion resistance; copper-based fillers are common for nonferrous metals and steels; aluminum-based fillers require specialized fluxes and conditions; nickel-based fillers are used for high-temperature applications. The choice of filler, flux, and heating method depends on the metals being joined, required joint properties, and operating conditions.

Joint design emphasizes capillary action, proper fit-up, and appropriate gap clearances to ensure complete fill and strength. Common joint configurations include butt, lap, and fillet joints. Post-braze cleaning is often necessary to remove flux residues and to ensure long-term performance.

Applications span HVAC and plumbing, aerospace, automotive, electronics, and jewelry. Brazing offers strong joints with minimal distortion and the ability to join dissimilar metals under controlled conditions.