Published on: 25 September 2025

Assist gas

We use assist gases when laser cutting sheet metal and tubes. Various assist gases are available. Their suitability depends on the type of material to be laser cut. In this blog post, we explain which assist gases we use to cut metal parts and why some gases are more suitable for particular situations than others.

Laser cutting with oxygen

Oxygen is also known as an active gas, because a chemical reaction occurs when it is used as an assist gas. After laser cutting with oxygen, an oxide layer always remains on the surface of the cut material. Before the product can be sprayed or welded, this layer must first be removed, which can be seen as a disadvantage. However, the benefit of using oxygen as an assist gas is that a relatively smooth cutting surface is created.

Laser cutting with nitrogen

As well as oxygen, nitrogen can be used as an assist gas for laser cutting. Using nitrogen as an assist gas is also referred to as cutting with an inert gas. Inert gases prevent undesirable chemical reactions, in contrast to oxygen, for example. This means the material is not affected, and little or no contamination remains on the cut surface. However, cutting with nitrogen results in a rougher cut surface and a higher risk of burr forming.

Choosing the right assist gas

Not every material can be cut with both oxygen and nitrogen. The suitability of each gas depends on the thickness of the material, cut quality and production process. The table below shows which assist gases can be used to cut our materials.

	Nitrogen	Oxygen
Stainless steel	✔	❌
Aluminium
Without film 2 mm	✔	✔
Without film 2,5 mm	✔	✔
Without film 3 mm	✔	✔
Without film 4 mm	✔	✔
Other types	✔	❌
Steel
Sendzimir	✔	❌
Zincor	✔	❌
Steel up to 3 mm (except RAEX)	✔	❌
S235JR Pickled and oiled 4, 5, 6 & 8 mm	✔	✔
S355MC Pickled and oiled 4, 5, 6 & 8 mm	✔	✔
S420MC Pickled and oiled 4, 5, 6 & 8 mm	✔	✔
S235JR Pickled and oiled 10 mm and thicker	❌	✔
S355MC Pickled and oiled 10 mm and thicker	❌	✔
S420MC Pickled and oiled 10 mm and thicker	❌	✔
235JR Rolled blue	❌	✔
S355MC Rolled blue	❌	✔
S700MC Rolled blue	❌	✔
CorTen A	❌	✔
Wear resistant steel RAEX 400	❌	✔

Sophia® chooses the right assist gas for you

In our production facility, your products are laser cut to size using fibre laser cutting. Our online software Sophia® automatically selects the correct method and the most suitable assist gas for your specific situation. You can influence the choice of assist gas in some cases if desired.