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.
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 too, 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.
Which auxiliary gas should you use for the fiber laser machine?
In the above content, many gases can be used in common use. It is important to consider cutting costs and product requirements, such as cutting stainless steel materials. When the product quality or surface quality is not very high, such as cutting the product, it needs to go through processing procedures such as painting. Air can be used as the cutting gas, which can reduce a lot of costs. When the cut product is the final product and there is no follow-up process, it is necessary to use a protective gas, such as a processed product. Therefore, in the cutting process, the gas must be selected according to the characteristics of the product.
Compressed air for high-quality cutting aluminum; nitrogen for the best edge quality of aluminum, low-carbon steel, galvanized steel, and automotive steel; oxygen for cutting thicker steel; argon for cutting in nitrogen Reactive metal.
Application of auxiliary gas:
- Compressed air: widely used in the processing of sheet metal cabinets, cabinets, and other products.
- Nitrogen production: processing some parts of the decoration industry, aerospace, and other parts.
The laser cutting machine uses different auxiliary gases to cut different materials. The pressure and required flow rate of the auxiliary gas vary with the thickness of the cutting material.
What is the gas consumption of my fiber laser machine?
Before, during, and after installing the fiber laser machine, we always receive a lot of questions about gas consumption when cutting metal. Below we provide some background information and tips on the correct supply and use of auxiliary gas.
The laser-quality nitrogen and oxygen used to cut metal must first be supplied to the machine at the correct pressure. How much gas the machine ultimately consumes depends on many factors, such as:
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Nozzle diameter used in cutting
The larger the hole in the cutting nozzle, the more liters of gas per unit time required to maintain the same pressure. If the nozzle diameter is doubled, the gas consumption will increase exponentially, so the gas consumption will increase by 4 times.
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Gas pressure used in cutting
Higher pressures usually result in cleaner cut notches, but this also consumes more gas.
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Speed of cutting material
During the cutting process, the auxiliary gas is continuously blown out through the nozzle. At slower speeds, the process takes longer, and each linear meter of cutting material will consume more gas.
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Material type and material thickness
Obviously, thicker materials cut more slowly, but the gas pressure must also vary with the thickness of the material. Generally speaking:
The oxygen pressure decreases as the material (steel) become thicker
Nitrogen pressure increases as the material become thicker (stainless steel)
The power of the laser source and the type/brand of the laser source
Depending on the power of the laser source and the characteristics of the laser beam itself, the machine will be able to pierce the material faster or slower and then cut it. Due to higher speeds and less gas consumption, heavier laser sources are cheaper to use in practice.
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Parameter settings such as focus height, dynamic control, etc.
The fine-tuning of the parameters also have a significant impact on the final gas consumption. For example, the difference in focus setting is 0.1 mm. Has caused a speed difference of 15% or more. In addition, the operator can consciously select variables such as very clean cutting notches, high speed, wide and narrow notches, cooling points, and automatic speed adjustment, which means that gas consumption varies greatly.
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Gas loss from the device itself
The installation of high-pressure tanks, packaging, piping and pressure-reducing valves can also cause a large amount of gas loss. When the machine is turned off, the supply line must be depressurized. The longer the supply line and the larger the diameter must be, the greater the gas loss.
The choice between 300 bar or 200 bar packing is also very different. The final 18-20 bar will always remain in the tank. By choosing a package with a filling pressure of 300 bar, the efficiency of the package will be significantly improved, and ultimately less gas will be lost.
How to solve the problem of burnt and residue of metal fiber laser cutting machine?
How to prevent the influence of oxidation reaction heat is the main idea to solve the problem of carbon steel punching burnout. This method can be used for laser cutting. At the end of oxygen blanking, the auxiliary gas is used to delay the release of air or nitrogen from the power switch. This method can handle sheet metal punches of 1/6 thickness.
Low-frequency pulse cutting conditions and peak output power conditions have the characteristics of reducing heat output, which can optimize cutting conditions. This working condition is a single pulse laser beam with high peak output, high energy intensity, and low frequency, which can reduce the accumulation of molten metal on the surface of the material and the heat output.
In short, the way to deal with this phenomenon is to increase the working pressure of the auxiliary gas and set the maximum output and low-frequency pulse standards. When using auxiliary gas in the air, it will not burn like nitrogen and will not produce bottom dross.
The fiber laser cutting machine uses a fiber laser, which has a lot of heat. Under the action of this laser, effective cutting can be achieved. The speed and accuracy are very high, which is why so many people are willing to choose. If you have any questions about purchasing a fiber laser machine, please consult us.
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