In laser cutting, the laser beam heats up the material to its evaporation point. The beam penetrates the material and creates a cut. The steam and molten material must be pushed out of the cutting groove to ensure quick cutting and an even groove that is free of slag. This is done by blowing process gas through a narrow nozzle around the beam towards the cutting groove. Two types of gas are primarily used:
- Oxygen at a slightly elevated pressure (1 to 3 bar). The oxygen speeds things up by way of the oxidisation process caused by the high temperature of the material being cut. The disadvantage is the oxidisation of cutting surfaces.
- Nitrogen can be blown into the cutting groove at high pressure (15 bar). The nitrogen pushes out plasma and molten material from the cutting groove and protects the hot surfaces from oxidisation. The result is an extremely high-quality cut, but this is at the expense of more laser energy or a lower cutting speed.