Oxy-Fuel Cutting Principle

The effectiveness of oxy-fuel cutting relies on a specific set of material properties. The metal’s ignition temperature must be below its melting point. If the metal melts before it oxidizes, the oxygen jet will simply blow away molten metal rather than sustaining the cutting reaction. This is a primary reason the process is highly effective for plain carbon steels but not for cast iron (high carbon content) or aluminum. Secondly, the oxide (slag) formed must have a lower melting point than the base metal. This allows the high-pressure oxygen stream to effectively blow the molten slag out of the cut, known as the kerf, exposing fresh metal to continue the reaction. The process is self-sustaining as the exothermic oxidation of iron generates significant heat, which helps maintain the kindling temperature along the cut path.

This method is not suitable for non-ferrous metals like aluminum and copper, or for stainless steels. These materials form highly refractory and tenacious oxides (e.g., aluminum oxide, chromium oxide) with melting points much higher than the base metal. These oxides form a protective layer that prevents the oxygen jet from reaching the underlying metal, thus inhibiting the cutting process.