Laser cutting is to use the high power density of the laser beam to focus the laser on a very small spot, heat the material rapidly, make it vaporize to form a cavity after reaching the boiling point, and then move the laser beam to create a slit on the surface of the material to complete the process. Cutting of processed objects.
Laser cutting is one of the thermal cutting methods, which can be divided into four types: laser gasification cutting, laser melting cutting, laser oxygen-assisted melting cutting and controlled fracture cutting.
Compared with other cutting methods, laser cutting is generally characterized by fast cutting speed and high quality. Specifically summarized in the following aspects:
(1) The cutting quality is good. Due to the small laser spot, high energy density and fast cutting speed, laser cutting can obtain better cutting quality.
(2) The laser gas cutting incision is narrow, the two sides of the incision are parallel and the perpendicularity to the surface is good.
(3) The cutting surface is smooth and beautiful, and it can even be used as the last processing procedure without machining, and the parts can be used directly.
(4) After the material is laser-cut, the width of the heat-affected zone is very small, the performance of the material near the cutting seam is almost unaffected, and the workpiece deformation is small and the cutting precision is high. The cutting speed of laser cutting and other cutting methods is shown in the table below, and the cutting material is low carbon steel plate.
(5) The cutting speed is fast, for example: 2500W laser cutting 1mm thick cold-rolled carbon steel plate, the cutting speed can reach 16-19m/min.
(6) Non-contact cutting, the nozzle has no contact with the workpiece during laser cutting, and there is no tool wear.
1. Laser cutting accounts for 39% of the laser equipment market
Although the laser market has grown in 2019, the growth rate began to slow compared with the previous two years. The sales revenue of laser equipment (including imports) in all fields was 65.8 billion yuan, an increase of 8.8% year-on-year. Affected by the uncertain global economic trend, it is estimated that the overall sales revenue of China's laser equipment market in 2020 will be 64.5 billion yuan, which will show the first negative growth in the past ten years, but its prospects are still broad and the absolute amount is not small.
In the industrial laser equipment market, laser cutting is the most widely used, accounting for 39%, marking and welding ranked second and third, accounting for 19% and 12% respectively.
2. Advance in the direction of high power, high precision and large format
In recent years, the technology of domestic laser cutting machine has made a breakthrough development, and it is advancing in the direction of high power, high precision and large format. Under the background of China's intelligent manufacturing, the industrial field has shown a trend of transformation from traditional processing to high-end manufacturing, and the market scale of China's laser cutting field will maintain a trend of rapid development.
3. Application of compressed air in the field of laser cutting
Laser cutting machines can meet the cutting requirements of various materials and complex shapes. In addition to the need for high-energy lasers, auxiliary gas is an indispensable material to complete the cutting process. The auxiliary gases used for laser cutting are mainly oxygen (O2), nitrogen (N2) and compressed air (Compressed Air). Compressed air is more readily available than oxygen and nitrogen, and it is very cheap compared to oxygen and nitrogen, and it is very common to use compressed air as an auxiliary gas for cutting.
The quality of compressed air has a very direct impact on the quality of metal laser cutting, and the size and stability of the gas pressure will affect the cutting effect. The selection of the size of the air compressor supporting the laser cutting machine as the auxiliary gas should mainly be determined according to the design auxiliary gas pressure and nozzle size of the laser cutting head used by the laser cutting machine, so that the best air compressor can be obtained. Match with laser cutting machine.
Comparison of laser cutting with different assist gases
During laser cutting, different cutting gases are selected according to the material of the cutting plate. The choice of cutting gas and its pressure has a great influence on the quality of laser cutting.
The auxiliary gases commonly used in laser cutting are oxygen (O2), nitrogen (N2), compressed air (Compressed Air), and sometimes argon (Ar). According to the gas pressure, it can be divided into high pressure gas and low pressure gas.
The functions of the auxiliary gas for laser cutting mainly include: supporting combustion and heat dissipation, blowing off the melting stains produced by cutting in time, preventing the cutting melting stains from rebounding upward into the nozzle, and protecting the focusing lens. Depending on the material to be cut, combined with the power of the laser cutting machine, different laser cutting processes are selected, and the selection of auxiliary gas is also different. The characteristics, uses and scope of application of different types of auxiliary gases are as follows:
(1) Oxygen (O2) is mainly used for cutting carbon steel materials. The chemical reaction heat of oxygen and iron promotes the endothermic melting of the metal, which can greatly improve the cutting efficiency, realize the cutting of thicker materials, and significantly improve the processing capacity of the laser cutting machine. However, at the same time, due to the presence of oxygen, an obvious oxide film will be produced on the end face of the incision, and it will have a quenching effect on the material around the cutting surface, improve the hardness of this part of the material, and have a certain impact on subsequent processing. The cut end face of the oxygen-cut material is black or dark yellow. Generally, carbon steel plates are cut by oxygen, punched at low pressure, and cut at low pressure.
(2) Nitrogen (N2) When nitrogen is used as an auxiliary gas for cutting, nitrogen will form a protective atmosphere around the molten metal to prevent the material from being oxidized, avoid the formation of an oxide film, and achieve non-oxidative cutting. But at the same time, because nitrogen does not chemically react with metal, there is no reaction heat, the cutting ability is not as good as oxygen, and the nitrogen consumption of nitrogen cutting is several times larger than that of oxygen, and the cutting cost is higher than that of oxygen cutting. The non-oxidation cutting surface has the characteristics of direct welding, smearing, strong corrosion resistance, etc., and the end surface of the incision is white. Generally, nitrogen gas is used to cut stainless steel, galvanized sheet, aluminum and aluminum alloy sheet, brass and other materials, punched with low pressure, and cut with high pressure. During nitrogen cutting, the change of gas flow has a great influence on the cutting. In the case of ensuring the cutting gas pressure, it is necessary to ensure that the gas flow is sufficient.
(3) Compressed air (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 only contains 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 efficiency of air cutting is slightly higher than that of nitrogen cutting. The cut ends of the air cut are yellowed. When there is no strict requirement on the surface color of the material incision, it is the most economical and practical choice to use compressed air instead of nitrogen for cutting.
(4) Argon (Ar) Argon is an inert gas, which can prevent oxidation and nitridation in laser cutting, and can also be used in welding. However, the price of argon gas is higher than that of nitrogen gas. Generally, it is not cost-effective to use argon gas for ordinary laser cutting. Argon gas cutting is mainly used for titanium and titanium alloys, etc. The end face of the incision in argon gas cutting is white.
At present, the liquid nitrogen on the market is about 1400 yuan / ton, and the liquid nitrogen used for laser cutting needs to use a Dewar tank, generally a 120kg can, and the price of 1kg is more than 3 yuan, and it is calculated at 1400 yuan / ton.
120x1.4=168 yuan, the specific gravity of nitrogen in the standard state is 1.25kg/m³, so the maximum usage of a can of liquid nitrogen in a Dewar tank is about: 120/1.25=96Nm³, converted into nitrogen cost per Nm³: 168/ 96=1.75 yuan/Nm³
If a domestic brand air compressor is used to provide 16bar of compressed air, providing 1.27m³ per minute, the full load input power of this type of air compressor is 13.4kW.
The industrial electricity cost is calculated at 1.0 yuan/kWh, then the air cost per m³ is: 13.4x1.0/(1.27x60) = 0.176 yuan/m³, according to the actual consumption of 0.5m³ gas per minute, the laser cutting machine works 8 hours a day, The daily cost savings of air cutting compared to nitrogen cutting is: (1.75-0.176) x8x60x0.5=378 yuan. If the laser cutting machine works 300 days a year, the gas cost that can be saved in one year is: 378x300=113,400 yuan. It can be seen that the use of compressed air instead of nitrogen cutting is very economical and practical.
In recent years, the technology of domestic laser cutting machine has made a breakthrough development, and it is advancing in the direction of high power, high precision and large format. Under the background of China's intelligent manufacturing, the industrial field has shown a trend of transformation from traditional processing to high-end manufacturing. The market scale of China's laser cutting field will always maintain a trend of rapid development, which will bring great benefits to laser air compressors. Market growth space.