Oxy-fuelwelding (commonly called oxyacetylene welding, oxywelding, or gas welding in the U.S.) and oxy-fuel cutting are processes thatuse fuel gases and oxygen to weld and cut metals, respectively. Frenchengineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylenewelding in 1903. Pure oxygen, instead of air, is used to increase the flametemperature to allow localized melting of the workpiece material (e.g. steel)in a room environment. A common propane/air flame burns at about 2,250 K (1,980°C; 3,590 °F), a propane/oxygen flame burns at about 2,526 K (2,253 °C; 4,087°F), an oxyhydrogen flame burns at 2,800 °C (5,070 °F), and an acetylene/oxygenflame burns at about 3,773 K (3,500 °C; 6,332 °F).

Oxy-fuel is one of the oldest weldingprocesses, besides forge welding. In recent decades it has been obsolesced inmost all industrial uses due to various arc welding methods offering moreconsistent mechanical weld properties and faster application. Gas welding isstill used for metal-based artwork and in smaller home based shops, as well assituations where accessing electricity (e.g., via an extension cord or portablegenerator) would present difficulties.

In oxy-fuel welding, a welding torch is usedto weld metals. Welding metal results when two pieces are heated to atemperature that produces a shared pool of molten metal. The molten pool isgenerally supplied with additional metal called filler. Filler material dependsupon the metals to be welded.

In oxy-fuel cutting, a torch is used to heatmetal to its kindling temperature. A stream of oxygen is then trained on themetal, burning it into a metal oxide that flows out of the kerf as slag.

Torches that do not mix fuel with oxygen(combining, instead, atmospheric air) are not considered oxy-fuel torches andcan typically be identified by a single tank (oxy-fuel cutting requires twoisolated supplies, fuel and oxygen). Most metals cannot be melted with asingle-tank torch. Consequently, single-tank torches are typically suitable forsoldering and brazing but not for welding.