Thermal Cutting, Brazing, Soldering, and Related Processes
Core Concepts
Study oxyfuel cutting principles: the preheat flame brings steel to ignition temperature (about 1,000–1,200 °F) and the oxygen jet oxidizes and blows away metal. Know neutral, oxidizing, and carburizing flames and their uses; oxyfuel cutting works on steel but not on aluminum or stainless without a powder or plasma assist. Plasma cutting handles conductive metals; air-carbon-arc gouging removes metal for back gouging. Brazing and soldering differ by filler melting temperature (soldering below 840 °F/450 °C, brazing above) and rely on capillary action rather than fusion of the base metal. Know flux functions, filler alloys (bronze, silver, aluminum), and joint clearance.
Traps
Distractors confuse soldering and brazing temperature thresholds, or assume oxyfuel cuts stainless cleanly. Remember a neutral flame is used for most cutting and welding; an oxidizing flame is for brass brazing. Capillary action requires a small, uniform gap.
Worked Example / Rule of Thumb
Temperature rule: soldering filler melts below 840 °F (450 °C); brazing filler melts above 840 °F but below the base-metal melting point. For a strong brazed joint, keep clearance around 0.001–0.005 in. so capillary action draws filler in.