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Many laser cutting applications rely on non-reactive (inert) gases as the assist gas. Nitrogen would be the typical choice for cutting stainless steels, aluminium and its alloys.
Cutting with non-reactive gases is often referred to as clean cutting or high-pressure cutting. Here, the material is melted solely by the laser power and blown out of the cut kerf by the kinetic energy of the gas jet. Unlike cutting with oxygen, the melt-shear removal process is the only process as inert gases do not react with the molten metal and no additional heat is generated. Therefore much higher laser power and gas pressures are required – also because the molten steel has quite a high viscosity compared with liquid iron oxide.
With nitrogen cutting, increasing the nitrogen pressure will result in faster cutting speeds. This speed gain is limited by the cooling effect of high-pressure gas flows. For mild steel and stainless steel thick sheets, the ideal pressure lies in the region between 10 and 15 bar. Higher figures are possible with the most powerful lasers available.
Meeting your nitrogen purity challenges
The nitrogen purity is important if a clean cut edge is required, for example when cutting stainless steel or aluminium metals. Even small percentages of oxygen contamination will result in yellowing of the cut edge in stainless steel as a result of oxidation. Also, more dross may be formed and this is difficult to remove.
The oxygen content in nitrogen becomes even more critical when very thick sections of stainless steel are being cut. Due to the lower cutting speeds, the material is able to react with the oxygen for longer. Hence a minimum nitrogen purity of 99.995% is often required.
Linde offers a complete range of products and services, uniting our in-depth laser cutting know-how with our long-standing experience in the delivery of fully integrated laser solutions.
Our spectrum of services extends from process consulting through gas storage and supply technologies to all-round technical support. The result is a state-of-the-art, all-inclusive supply and service package tailored to your specific needs, including specialised gas delivery systems to support the high volume and pressure requirements of laser cutting with nitrogen.