When manufacturing and fabricating metal materials, precision and efficiency are key factors. Because of the need for precision and efficiency, fiber laser cutting machines are indispensable tools in various industries. These machines offer unparalleled accuracy and speed in cutting a wide range of metals. However, achieving the best results requires careful consideration of the choice of cutting assist gas.

The gas used in fiber laser cutting plays a crucial role in the cutting process. The gas selection influences cut quality, speed, and material compatibility. Oxygen, nitrogen, and compressed air are among the most common gasses used. Each of these offer advantages depending on the material being cut and the desired outcome.

In this blog we talk about the significance of selecting the right assist gas for your fiber laser cutting machine.

Reactive vs. Non-Reactive Gas

To cut metal with a high-quality edge, an assist gas blows through a cutting nozzle on the fiber laser head. Then the molten material pushes out of the hot spot where the laser light is hitting the material. This area is known as the kerf. Choosing the right assist gas can improve the edge quality and can increase the cutting speeds substantially for certain materials.

Before choosing the right gas, you have to understand the difference between a reactive and non-reactive gas. The primary consideration is that a reactive gas can change the properties of the metal that is being cut. Reactive gasses are generally used when cut-edge quality is not important, such as when mild steel material continues to another step of the process within 24 hours. Non-reactive gas is used when the cut edge does matter. If the metal is going to a laser welder in the next step of production for example.

Additionally, the gas acts as a positive pressure within the head to protect the laser optics and lens from molten material spatter. This provides a longer life with reduced maintenance for the fiber laser.

Quick Highlights

Connects to an existing shop air setup with a booster and provides high-quality cuts through aluminum with higher speeds than N2 or O2 in thinner materials.

Produces the best edge quality for economical price in most applications with aluminum, mild steels, galvanized steels, and UHSS automotive steels, especially in thinner gauges.

Helps in cutting thicker steel, as the reactive nature adds heat to the cut. Speed is limited by the chemical reaction compared to N2, and the edge quality is affected.

The most expensive gas most processors might use. The main reason for argon use is for metals that chemically react to cutting with nitrogen.

What Assist Gas To Use In Fiber Laser Cutting?

There are a variety of combinations and types of assist gas to use. Ultimately, the application will drive what assist gasses you invest in. However, the table below shows the most common recommendations for gasses and their uses.

Compressed Air

Compressed air is the simplest assist gas option. Shop compressors typically run between 75 to 175 psi. Depending on the application, this means you may need a pressure booster. A .06” or 16 gauge mild steel typically is cut best in the 150 to 200 psi range, for example. The air will also need to be used through a filter to ensure no contaminants are getting to the optics.

Compressed air when used as an assist gas is a blend of other gasses including nitrogen and oxygen. Due to this content of oxygen, compressed air is considered to be reactive. However, it is less reactive than just oxygen. Compressed air is a great choice for high-quality cuts through aluminum. Depending on application requirements, compressed air can be used with other metals too.

Nitrogen

Nitrogen is generally considered the assist gas to go with for high-quality cuts. With most materials, aside from exotics like titanium, nitrogen is considered non-reactive. This means no major chemical changes occur in the cut edge, and the material removal is simply by the pressure of the gas jet pushing the metal out of the cut. Due to a colder process, nitrogen assist gas cutting results in a very high-quality edge for a wide range of materials with a thin heat-affected zone.

Nitrogen is often used on parts that need to be stored before being used or processed further. This is due to oxygen and air cutting introducing oxides around the cut edge with prolonged storage.

Oxygen

One of the first assist gasses used was oxygen due to its high reactivity. The extra heat from using oxygen as an assist gas allows lower-powered lasers to cut through thicker material. Additionally, oxygen typically runs at a lower flow rate and pressure than nitrogen. This results in lower gas consumption and lower operating costs.

Although, this has negative effects as well. Often material is limited in speed and gas pressure if cut quality is important. As a result, the chemical reaction increases with increased gas pressure and flow rate. This leads to added heat that increases the melt of a cut edge. This is undesirable for high-quality cutting.

Oxygen-cut materials typically have oxides formed along the cutting edge. The oxides interfere with attempts to paint the material if not immediately fed into the painting process.

Certain materials such as stainless steel can additionally form blackened dross when cut with oxygen. Other metals can easily be cut by oxygen with said lower gas usage but the edge may not be as clean as with other assist gasses.

Argon

Argon is the most expensive and rarely used by most fabrication operations. Materials that use nitrogen can typically be cut with argon for a similarly high-quality cut edge. The main reason to use argon over nitrogen is if you are manufacturing from metals that are still chemically reactive to nitrogen. Most commonly, argon is used for titanium. At the temperature a fiber laser cutting raises the metal to, titanium is chemically reactive to a nitrogen atmosphere.

Even though argon cuts similarly to nitrogen, two differences limit widespread use. Argon has a higher specific heat than other assist gasses we have talked about. This means that while nitrogen is said to cool as a cut is made and oxygen adds heat to a cut, argon removes heat from a cut even faster than nitrogen.

The heat-affected zone is narrow. This can lead to a narrow HAZ being brittle as it is heated and cooled which leads to premature cracking. Conversely, this same property is used on some steel where a slightly hardened edge is desirable.

Gas TypeReactiveRecommended UsePrice
Compressed AirYesAluminum and parts going quickly to finishing processes$
OxygenYesLow edge quality applications$$
NitrogenNoHigh edge quality applications$$$
ArgonNoFor titanium metals$$$$

Conclusion

Whether you need a fiber laser cutting machine for high-level manufacturing or one-off prototyping, Moore Machine Tools is the premier provider of custom fiber laser solutions. Not only do we work with your application and budget in mind, but we also include installation and training with every purchase. Contact us today and one of our knowledgeable team members will help you determine the most suitable solution for your manufacturing needs.