Which auxiliary gas should I use for fiber laser cutting machine?

by FORSUN CNC mechanic

As a general processing method in modern manufacturing, laser cutting machine has broken the traditional processing method and is widely used in various industries with a brand-new cutting method, especially fiber laser cutting machine, which has developed rapidly in recent years. Users who know the fiber laser cutting machine should know that auxiliary gas must be used in the cutting process. So many people are more concerned about the choice of “gas”. Today I will share with you the gas used in fiber laser cutting.

Why add auxiliary gas during processing for the fiber laser machine?

Before figuring out how to choose an auxiliary gas, you need to understand why the auxiliary gas is used and the role of the auxiliary gas. Experience summary: In addition to blowing away the slag in the coaxial slit, the auxiliary gas can be used to cool the surface of the processed object, reduce the heat-affected zone, cool the focusing lens, and prevent smoke and dust from entering the lens mount. Contaminate the lens, causing the lens to overheat; in addition, some cutting gas can also protect the substrate. The choice of gas pressure and type has a great influence on the cutting process, and the choice of auxiliary gas type has a certain influence on cutting performance, including cutting speed and cutting thickness.

Why do you need to add auxiliary gas when the fiber laser cutting machine cuts metal materials? There are four reasons.

The first is to cause the auxiliary gas to chemically react with the metal material to increase the strength of the capacity.

The second is to help the equipment blow off the slag in the cutting area and clean the cutting seams.

The third is to reduce the size of the heat-affected zone by cooling the adjacent area of the slit.

The fourth is to protect the focusing lens and prevent combustion products from polluting the optical lens.

Which auxiliary gas should I use for the fiber laser cutting machines?

The auxiliary gases that can be used by the laser cutting machine are mainly air, nitrogen, oxygen, and argon. Below we will introduce the uses and characteristics of different auxiliary gases.

Compressed air

Compressed air is the simplest auxiliary gas option and can be connected to existing workshop air installations.

Most shop compressors operate between 75-175 psi, so depending on the application, a booster may be required.

For example, 1.5 mm/0.060 inch/16 ga mild steel may cut best in the range of 150-200 psi. Before entering the head, the air needs to be cleaned to remove any oil or moisture to avoid contaminating the optical components, so a filter is needed to ensure that the air is clean.

As an auxiliary gas, compressed air is a mixture of other gases (including nitrogen and oxygen). Due to its oxygen content, compressed air is considered a reactive cutting gas for metal processing. However, its reactivity is not as good as the oxygen assist gas. Compressed air can cut aluminum with high quality, and the speed is slightly higher than when cutting nitrogen or oxygen in a thinner material thickness. Depending on the application requirements, compressed air can be used with many other metals.

Nitrogen

In most cases, nitrogen is considered to be the best edge quality for auxiliary gas generation.

For most purposes, except for some special materials (such as titanium), nitrogen is considered a non-reactive or inert auxiliary gas. This means that during the cutting process, nitrogen does not react with any component of the metal.

This means that there is no major chemical difference at the cutting edge, and the mechanism of material removal is simply the pressure of the gas jet pushing the molten metal out of the cut. Since this is a relatively cold process, nitrogen-assisted gas cutting can provide very high-quality edges for a variety of materials with very thin heat-affected zones.

Nitrogen is most suitable for aluminum, mild steel, galvanized steel, and UHSS automotive steel.

This auxiliary gas is usually used for parts that need to be stored for a period of time before use because oxygen and air cutting will introduce oxides around the cutting edge during long-term storage.

Oxygen

Oxygen is one of the first auxiliary gases used because it is reactive when cutting. When processing steel, oxygen will burn off the carbon in the steel in the cut. The incision generates additional heat, allowing earlier, lower-power lasers to cut thicker materials. Although, this same reactivity will also have some negative effects.

If good edge quality is required, the material is usually limited by speed and air pressure. As a result, the chemical reaction increases as the gas pressure and flow rate increase. This leads to an increase in heat, which increases the melting of the edges.

For high-quality edges, this is not always desirable.

Compared with nitrogen cutting, the flow rate and pressure of oxygen cutting are often lower. This leads to lower gas consumption and lower operating costs. However, in some cases, the cutting speed will be slightly slower.

Oxygen cutting materials usually also form oxides on the cutting edges. If it is not sent to the coating line immediately, the oxide will interfere with attempts to paint the material.

Certain materials (such as stainless steel) will form blackened scum “icicles” when cut with oxygen. When a lower gas usage rate is required, oxygen assist gas can be used to cut many metals. However, it is important to note that the edges may not be clean.

Argon

Argon is the rarest and most expensive gas encountered by most processors. Materials that are well cut with nitrogen can also use argon with similar high-quality edges. The main reason for using the more expensive argon is to cut metals that are still chemically reactive in pure nitrogen.

Most commonly, argon is used to process titanium. At the temperature that the laser cutter raises the metal to, titanium is chemically reactive even in a pure nitrogen atmosphere. This is the main reason for choosing argon instead of nitrogen.

Although argon is inert and the cutting method is similar to nitrogen, there are two differences that may limit wider use. Argon has higher specific heat than the other auxiliary gases in this list. This means that although nitrogen is said to cool the cutting while cutting, and oxygen is said to add heat to the cutting, argon removes heat from the cutting even faster than nitrogen. The heat-affected zone is very narrow, but for certain materials, such as martensitic steel. This can cause the narrow heat-affected zone to be very brittle, just like heating and quenching, which can lead to premature cracking. In contrast, this same characteristic is used in some steel formulations, where slightly hardened edges are required.

Summary

Compressed air connects to the existing workshop air device through a supercharger, and provides high-quality aluminum cutting in thinner materials at a faster rate than N2 or O2.

Nitrogen-In most applications of aluminum, mild steel, galvanized steel, and UHSS automotive steel, it produces the best edge quality at an economical price, especially in thinner specifications.

Oxygen helps to cut thicker steel because reactivity increases the heat of cutting. Compared with N2, the speed is limited by the chemical reaction, and the edge quality is affected.

Argon gas-the most expensive gas that most processors may use. The main reason for using argon is the metal used to chemically react with nitrogen for cutting.