December 9, 2021

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Auxiliary Gas Guide: The Best Choice for CNC Laser Cutting Machine

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Auxiliary Gas Guide

As an efficient and precise metal processing equipment, Jeesun CNC laser cutter machine is widely used for cutting work of a variety of metal materials. During laser cutting, different kinds of cutting gases and auxiliary gases are used. The choice of gas type and its pressure have a great impact on the quality of laser cutting. In the actual application, it is quite necessary to consider what kind of gas to use according to the different materials and thicknesses.

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1.Types of auxiliary gas

The auxiliary gases commonly used in metal laser cutting are oxygen (O2), nitrogen (N) and compressed air, sometimes argon (Ar) is also used. According to the gas pressure, the auxiliary gases can be divided into high pressure gas and low pressure gas.

2 .The role of auxiliary gas

(1). To reacts with materials to increase cutting speed. For example, oxygen can be used to achieve combustion effects.

(2). To blow away the residual slag to achieve a good cutting effect. In this case, air is mainly used because no additional cost is required;

(3). To improve the quality of cutting surface, it can effectively achieve the effect of smooth and clean cutting surface, no burr and no dross.

(4). To protect the lens from slag sticking to the lens and affect the cutting quality.

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3 .Selection of auxiliary gas

different kinds of laser cutting processes are selected in terms of the material to be cut and combining with the power of CNC laser cutting machine, the choice of auxiliary gas is also different. The characteristics, uses and scope of different types of auxiliary gases are as follows:

(1). Oxygen (O2) is mainly used for cutting carbon steel. The heat generated from chemical reaction of oxygen and iron promotes the endothermic melting of metals, which can greatly improve the cutting efficiency, realizing the cutting of thicker materials, and significantly improving the processing capacity of laser cutting machines. At the same time, due to the presence of oxygen, a significant oxide film will be generated on the end face of the cut, and the material around the cut surface will have a quenching effect, which will increase the hardness of this part of the material and cause a certain impact on subsequent processing. Oxygen-cut material has black or dark yellow end faces. Generally, carbon steel plates are cut by oxygen, low-pressure drilling, and low-pressure cutting.

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(2) Nitrogen (N): When nitrogen is used as the auxiliary gas for cutting, nitrogen will form a protective atmosphere around the molten metal to prevent the material from being oxidized and the formation of an oxide film to achieve non-oxidative cutting. at the same time, however, as nitrogen does not have a chemical reaction with the metal, there is no heat of reaction, the cutting ability is not as good as oxygen, and the nitrogen consumption of nitrogen cutting is several times greater than oxygen, and the cutting cost is higher than oxygen cutting. The non-oxidized cutting surface has the characteristics of direct welding, smearing, strong corrosion resistance, etc., and the cut end surface is white. Generally, nitrogen is used to cut stainless steel, galvanized sheet, aluminum and aluminum alloy sheet, brass, etc., and perforate with low pressure and cut with high pressure. When cutting with nitrogen, the change of gas flow has a great impact on the cutting performance. Under the condition that the pressure of cutting gas is well guaranteed, it must be ensured that the gas flow is sufficient.

(3). Compressed Air: Compressed air can be directly provided by an air compressor, which is easier to obtain than oxygen and nitrogen, and the price is very cheap. Although the air contains only about 20% oxygen, the cutting efficiency is far less than that of oxygen cutting, but the cutting ability is close to that of nitrogen, and the air cutting efficiency is slightly higher than that of nitrogen cutting. The end face of air cut is yellow. When there is no strict requirement on the color of the material cut surface, compressed air instead of nitrogen is the most economical and practical choice.

(4). Argon (Ar): As an inert gas, Ar can prevent oxidation and nitridation during laser cutting, and can also be used in welding. However, the price of argon is higher than that of nitrogen. Generally, it is not cost-effective to use argon for general laser cutting. Argon cutting is mainly used for titanium and titanium alloys. The end face of the cut made by argon gas turned white.

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4. Economic comparison between compressed air laser cutting and nitrogen laser cutting

Take the Chinese market as an example, at present, the liquid nitrogen on the market is about 1,400 RMB/T, and the liquid nitrogen for laser cutting requires a Dewar tank, which is generally 120 kg per can and the price is more than 3 RMB/ kg. For the time being, it is calculated at 1400 RMB/T. 120 × 1.4 = 168 RMB. The specific gravity of nitrogen in the standard state is 1.25 kg / m3, so the maximum amount of liquid nitrogen in a tank of a Dewar tank is about 120 / 1.25 = 96Nm3, which is converted into a nitrogen cost of 168/96 = 1.75 RMB/Nm3. If the air compressor provides 16bar of compressed air, it can provide 1.27 m3 per minute. The full load input power of this type of air compressor is 13.4 kW. The industrial electricity cost is calculated at 1.0 RMB/ kW·h, and the air cost per m3 is 13.4 × 1.0 / (1.27 × 60) = 0.176 RMB/ m3 according to the actual consumption of 0.5 m3 of gas per minute. The laser cutting machine works 8 hours per day. Compared with nitrogen cutting, air cutting can save costs (1.75-0.176) × 8 × 60 × 0.5 = 378 RMB per day. If the laser cutting machine works for 300 days a year, the cost of gas consumption can be saved in a year is 378 × 300 = 113400 RMB. Obviously, it is very economical and practical to use compressed air to replace nitrogen cutting. The cost of gas saved in one year is enough to buy 3 high-quality integrated air compressors.

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