The cutting gas used is crucial to the cutting result.

Oxygen generally yields good cutting performance in carbon steels and low alloyed steels. However, oxygen reacts with the base metal, and the cut edge covers with an oxide layer. These are the reasons why we use nitrogen more and more often to cut high-alloy steels whenever sufficient laser power is available.

We also use nitrogen to increasingly for parts that are subsequently powder coat. Any oxides on the cut edge decrease the bond between the coating and the material. And may therefore result in corrosion problems.

The change from oxygen to nitrogen as a cutting gas requires additional changes in the set-up of the machine. The following rules of thumb apply to cutting pressure:

Recent developments in the laser industry have led to cutting lasers with output powers of up to 8kW. So more and more businesses are changing over to nitrogen for cutting stainless steels and other high-alloy materials. As there are no exothermic reactions supporting the laser process, cutting gas pressure increases with increasing material thickness.

As the focusing lens is an integral part of the gas chamber, its strength limits gas pressure, which may not exceed 12 bar (175 psi) in older machines, depending on lens material and dimensions. Modern cutting machines, however, normally with thicker cutting lenses allowing considerably higher cutting gas pressures of 20 bar and higher. Which are required for cutting thick section stainless steel.

The following section deals with common materials and their specifi c cutting parameters.

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