This piece of 0.05” thick S.S. was cut with 400W of power using 80 PSI oxygen at a speed of 215 inches per minute (IPM).

This piece of 0.05” thick S.S. was cut with 400W of power using 250 PSI nitrogen at a speed of 25 inches per minute (IPM). Notice the clean, non-oxidized edge.

When cutting stainless with oxygen assist, the oxygen reacts exothermically with the steel, adding energy to the cut process and increasing speeds. The downside is that this reaction coats the cut edge with a blackened oxide layer. If these cut parts are slated for the welding booth, then the oxide layer must be mechanically removed to assure proper weldability. Photo 1 shows a section of 304 stainless steel that was cut with 400 watts of CO₂ power and 80 PSI of oxygen assist. Note that the cut edge is oxidized with some underside dross present.

The presence of high-pressure nitrogen adds little, if any, exothermic energy but the higher gas jet pressure does add mechanical energy, which serves to blow the molten metal through the cut kerf before it cools enough to stick and form dross on the bottom edge of the cut face. Photo 2 shows the same 304 stainless material after cutting with high-pressure nitrogen.

At a power level of 400 watts with a nitrogen assist pressure of 250 PSI, the edge is clean and shiny (not oxidized) and exhibits little, if any, dross. Cut speeds are substantially slower when using nitrogen – 25 IPM versus 215 IPM with oxygen in this example – however the slower cut speed is overcome by removing the time and cost of post-processing oxidized parts. Additionally, the cooling effect of nitrogen on the stainless steel reduces the heat-affected zone (HAZ) and the possibility of fracturing when stressed.