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The Laser User Magazine
Issue 053 - Winter 2008
Energy input from oxidation in laser-oxygen cutting of mild steel
Author: John Powell, Dirk Petring, Vasant Kumar, Saeed Al-Mashikhi, Alexander Kaplan, Katy Voisey
One of the mainstays of modern industry involves the use of a laser in conjunction with an oxygen jet to profile mild or carbon steel. The laser-oxygen cutting process was invented in 1967 in the UK by Peter Houldcroft and is nowadays used to profile mild steel up to 25 mm thick.
Laser-oxygen cutting uses a focused laser beam to heat up mild steel to a temperature at which it will ignite and burn in a stream of high purity oxygen. In principle the process is similar toflame cutting, which involves using an oxygen/fuel gas flame to pre-heat the metal to the required ignition temperature whilst simultaneously feeding a jet of high purity oxygen centrally into the cut zone. In both forms of cutting the reaction of iron and oxygen provides energy to the cutting process and also generates a low viscosity, oxidized melt which is easily removed from the cut zone by the mechanical action of the oxygen jet. Both processes produce a macroscopically smooth cut edge which is generally covered in microscopic parallel grooves or striations.
The industrial application of laser-oxygen cutting is dominated by the CO2 laser but there are some applications where Nd:YAG or fibre lasers are preferred – usually to exploit fibre optic beam delivery or when fine detail is to be cut. In all cases of laser-oxygen cutting of mild steel, the basic phenomena are similar: a laser, acting co-axially with an oxygen jet initiates and propagates an exothermic reaction between oxygen and iron.