Powder cutting is oxygen cutting in which a suitable powder is injected into the cutting oxygen stream to assist the cutting action (definition from BS499:Part 1:1991 Section 7 No.72 008).
Oxygen cutting (also known as oxy-fuel cutting) is the thermal cutting of materials by chemical reaction with oxygen after the part has been raised to ignition temperature. Mild steels readily ignite in a stream of oxygen when they are heated to about 870°C. For stainless steels, the ignition temperature is over 1500°C. Furthermore, the oxides formed when cutting mild steel have lower melting points than the parent metal and this facilitates a clean cut. With stainless steel, however, the oxide has a higher melting point than the parent metal and hampers the cutting process. These barriers to cutting can be overcome by adding materials to the cutting gas stream which either remove the oxide film or raise the reaction temperature -
- Flux injection: flux is injected into the cutting gas stream which chemically removes the oxides of chromium
- Iron-rich powder injection: finely divided iron-rich powder is fed separately into the cutting zone in a gaseous medium; combustion of the iron powder increases the reaction temperature and the fluidity of oxidation products
The iron-rich powder injection technique has also been used for cutting copper, nickel and aluminium and their alloys, and for cutting cast irons.
The quality of the cut surface is, at best, equivalent to flame cut carbon steel; but with many materials, the cut quality is very poor.
Further information
FAQ: What is flame cutting?
Job knowledge for welders:
Oxyfuel cutting - process and fuel gases
Cutting processes - application of oxyfuel cutting
Questions and answers. Gas Welding and Cutting. 2nd Edition. P H M Bourbousson & K Leake. Publ: London; Newnes Technical; 1982. ISBN 0 408 01180 7.