Choosing an auxiliary gas for laser cutting: oxygen, nitrogen, or compressed air?

The assist gas is one of the most important—and at the same time most underappreciated—elements of the laser cutting process. It is responsible not only for removing molten material from the kerf, but also affects the course of the thermal reaction, edge quality, cutting speed, and the scope of subsequent machining of the workpiece.

The choice between oxygen, nitrogen, and compressed air should take into account the type and thickness of the material, edge quality requirements, planned post-cutting processes, and the total cost of producing the part. There is no single gas that is ideal for every production scenario—which is why this guide shows you how to select an assist gas for a specific fiber laser cutter and the actual operating conditions at your facility.

What role does the auxiliary gas play during laser cutting?

In a fiber laser cutting machine, the laser beam heats and melts the material along the cutting path, while the assist gas delivered through the nozzle removes the molten metal from the processing zone and maintains a stable cutting process. Depending on the type of gas, it can either actively participate in the cutting process or protect the material’s surface from oxidation.

For this reason, changing the gas has a direct impact on the performance and cost-effectiveness of laser cutting. Among other things, it affects:

• cutting speed,
• the appearance and structure of the edges,
• the amount of deposits or oxides formed,
• the ability to weld or paint the part directly,
• gas and energy consumption,
• the cost of producing a single item,
• the range of materials and thicknesses that can be effectively machined.

Therefore, the choice of gas should not be considered solely in terms of its purchase price. The total cost of the process is key—cutting time, gas consumption, system setup, and the scope of any additional processing.

Oxy-fuel laser cutting

Oxygen is primarily used in the laser cutting of carbon steel and structural steel. It does not merely serve to mechanically remove molten material—it reacts with the heated metal, triggering an oxidation reaction that provides additional thermal energy. As a result, oxygen aids in the laser cutting of steel, especially at greater thicknesses, and allows for a stable process at a lower gas pressure than is the case with nitrogen.

The Main Advantages of Oxy-Fuel Cutting

• additional energy from the oxidation reaction,
• efficient cutting of carbon steel,
• the ability to cut heavy plate with a laser,
• lower gas consumption by volume than in high-pressure processes,
• a stable process when the parameters are set correctly.

What do you need to keep in mind?

The edge produced using oxygen is covered with a layer of oxides. If the part is to be powder-coated, welded, or plated afterward, the surface often needs to be cleaned further. The chemical reaction also affects the appearance of the cut itself, so the choice of gas should be based on the requirements for the finished part. Oxygen works best primarily with carbon steel—it is not, however, the standard choice for high-quality cutting of stainless steel or aluminium, where oxidation of the cut edge degrades its properties and appearance.

Laser cutting with nitrogen

Nitrogen is an inert gas under cutting conditions. Its role is to intensively remove molten metal from the kerf and to limit contact between the heated surface and oxygen in the surrounding atmosphere. The result is a bright, unoxidized edge, which is why nitrogen is the primary gas used in laser cutting of stainless steel and aluminium, as well as in any application where post-processing surface cleanliness is critical. It can also be used for carbon steel when the goal is to minimize the oxide layer.

The Main Advantages of Nitrogen Cutting

• an edge without the typical oxide layer formed during oxy-fuel cutting,
• good quality of the cut surface,
• limiting the preparation of a workpiece for further processing,
• favorable conditions for subsequent welding, painting, or coating,
• High cutting speed for thin and medium-thickness steel plates with an appropriately powerful laser source.

In many applications, a part produced using nitrogen can proceed directly to the next stage of production. The reduction in grinding and edge cleaning can be so significant that it offsets the higher cost of the gas itself.

Restrictions and Requirements

Nitrogen is typically supplied at high pressure and in large quantities, which requires a system with sufficient productivity, proper gas storage or production, and stable supply parameters. The cost of nitrogen cutting depends, among other factors, on the thickness and type of material, the nozzle diameter, the required pressure, the cutting time, the number of cuts, and the method of gas delivery and price. For large-scale production, it is worth analyzing not only the price of gas from cylinders or tanks but also the cost-effectiveness of a nitrogen generator—though this depends on the facility’s actual demand, the required gas purity, and the nature of production. The proper selection of the laser source power is also of great importance here, as it determines the actual cutting speed when using nitrogen.

Laser Cutting with Compressed Air

Compressed air can be a cost-effective alternative to oxygen and nitrogen. Since it consists mainly of nitrogen but also contains oxygen, it is not a completely inert gas—the process involves both the mechanical removal of liquid material and a limited oxidation reaction. This technology is used for cutting selected grades of steel, stainless steel, and aluminium, particularly for thinner and medium-thickness materials. The actual capabilities depend on the power of the laser source, the machine design, the productivity of the compressed air system, and the required part quality. We discuss this method in more detail in a separate article on compressed-air laser cutting (AirCut).

The Most Important Advantages of Compressed Air

• lower cost of the medium compared to purchasing nitrogen,
• reducing dependence on gas supplies,
• high cutting speed for thin materials,
• greater production flexibility,
• the option to use your own compressor system.

This solution is particularly interesting in mass production involving a large proportion of parts made from thinner steel plates, where slight edge oxidation does not pose a technical obstacle.

The quality of compressed air is crucial

The air supplied to the laser cutting head must be properly conditioned—it must not contain excess moisture, oil, or solid contaminants. A contaminated medium reduces process stability and poses a risk to the optical system components. A laser cutting system should therefore include the following properly selected components:

• compressor,
• dehumidifiers,
• filters,
• separators,
• buffer tanks,
• pipes and system components with sufficient capacity.

At STIGAL, we select and offer complete compressor systems, including all necessary equipment, tailored to a specific laser cutting machine and the actual operating conditions at the facility. As a result, the system ensures the proper air parameters and process stability from the very first day of operation.

Oxygen, Nitrogen, or Compressed Air—A Comparison

Each gas performs best under different conditions. Oxygen provides additional energy and enables efficient cutting of thicker steel; nitrogen produces a clean, non-oxidized edge; and compressed air helps reduce the cost of the cutting medium when cutting thinner materials. Thanks to STIGAL AirCut technology and the proper selection of parameters, air allows for very good edge quality — comparable in many applications to other gases, though with a different visual character: matte and darker, rather than shiny as with nitrogen cutting.

The Importance of Gas Parameters and Quality

Simply choosing the right type of gas does not guarantee a good result. It is equally important to select the appropriate set of process parameters:

• gas pressure and flow,
• the type and diameter of the nozzle,
• location of the fire,
• laser source power,
• cutting speed,
• breakdown parameters,
• the distance between the nozzle and the material.

Gas purity is also important—contaminants affect process stability, edge quality, and the durability of system components. In the case of compressed air, the effective removal of moisture, oil, and particulates is particularly important. Parameters should be selected as a complete technological package: simply increasing the gas pressure does not always improve the result and often leads only to greater consumption of the medium without a proportional improvement in quality.

Can a single laser cutter use different gases?

An industrial laser cutting machine for steel plates can be configured to work with several types of assist gases, allowing the technology to be tailored to the material, thickness, and quality requirements of a specific job. For example, the same metal-cutting laser can use:

• oxygen to selected carbon steel components,
• nitrogen for parts requiring a non-oxidized edge,
• Compressed air for cost-effective mass production.

This approach increases production flexibility, but requires a properly configured gas system and correctly developed process tables for each medium.

How do I choose a auxiliary gas for my own production?

It’s a good idea to start the gas selection process by analyzing the actual orders being filled at the plant. The most important questions are:

• What materials will be machined most often?
• What are the most common thicknesses used in production?
• Can the edge be oxidized?
• Will the parts be welded, painted, or coated?
• Is sanding performed after cutting?
• What percentage of production is mass production?
• What types of gas and compressor systems are available?
• Which is more important—maximum quality, speed, or minimum unit cost?

In many facilities, the best solution is not to choose a single gas, but to have the option of using several different gases depending on the task at hand. Our guides on the operating costs of laser cutters and on when to choose laser or plasma as a cutting technology can be helpful in this analysis.

Selection of Laser Cutting Technologies in STIGAL Machines

STIGAL designs and manufactures industrial fiber laser cutting machines and complete metal cutting systems tailored to actual production processes. When selecting a configuration, we analyze the types of materials, thickness range, expected productivity, edge finish requirements, and projected consumption of auxiliary gases. This allows us to select not only the appropriate laser power for metal cutting but also the gas system, compressed air system, and solutions that support stable production. Our product lineup includes both versatile fiber laser cutters and machines configured as laser cutters for steel plates with specific production profiles.

Frequently Asked Questions — Selecting Gas for Laser Cutting