As a common processing method in modern manufacturing industry, laser cutting machine breaks the traditional processing method and is widely used in all walks of life with a new cutting method. So, today we will talk about the cutting process of fiber laser cutting machine Why do you need to add auxiliary gas and how to use the auxiliary gas reasonably.
Laser cutting is the use of a focused high-power-density laser beam to irradiate the workpiece, so that the irradiated material is rapidly melted, gasified, ablated or reached the ignition point, and at the same time the molten material is blown away by the high-speed airflow coaxial with the beam, so as to achieve the workpiece cut open. Laser cutting is one of the thermal cutting methods. In addition to blowing away the slag in the coaxial slit, the use of auxiliary gas can also cool the surface of the processed object, reduce the heat-affected zone, cool the focusing lens, and prevent smoke from entering the lens seat to contaminate the lens and cause the lens to overheat; in addition, some cutting Gas can also play a role in protecting the base metal. The choice of gas pressure and type has a greater impact on the cutting process, and the type of auxiliary gas selected will have a certain impact on cutting performance, including cutting speed and cutting thickness.
The auxiliary gases that can be used by laser cutting machines mainly include air, nitrogen, oxygen and argon. Below we will introduce the uses and characteristics of different auxiliary gases. The pressure and flow rate of each laser cutting machine manufacturer are different, which are inseparable from the size of the cutting nozzle and the thickness of the cutting material. Generally, the required pressure is 0.3-0.8Mpa, and the cutting nozzle is generally 0.02-0.05Mpa. The flow rate is different according to the thickness of the cutting material. For example, when cutting 22mm carbon steel, the flow rate of some manufacturers must reach 10M3/h (including the protective oxygen for double-layer cutting nozzles).
Oxygen is mainly used for carbon steel cutting and perforation of stainless steel and aluminum thick plates. It mainly reacts with the cutting metal and releases a large amount of oxidation heat. In addition, the gas at a certain pressure will blow away oxides and slag, forming cuts in the metal. Since the oxidation reaction in the cutting process generates a lot of heat, cutting does not require too high power. The disadvantage is that the cutting speed of the thin plate is slow, and it is easy to burn when cutting sharp corners.
Nitrogen is considered the best edge quality production assist gas in most cases. For most purposes, nitrogen is considered a non-reactive or inert assist gas, with the exception of some exotic materials such as titanium. This means that the nitrogen will not react with any component of the metal during the cutting process. This means that there are no major chemical differences at the cut edge and the mechanism of material removal is simply the pressure of the gas jet pushing the molten metal out of the cut. Because it is a cooler process, nitrogen-assisted gas cutting can provide very high-quality edges on a variety of materials with very thin heat-affected zones. Therefore, nitrogen plays a very important role in thermal processing. However, there are still some problems in applying it to welding or cutting process. During thermal processing, the heat loss and mass loss of oxygen are the main energy losses. As the nitrogen flow rate increases, the temperature decreases with a concomitant decrease in the oxygen uptake, which means that the rate of temperature change during thermal processing generally increases.
The main applicable plates are stainless steel, electroplated steel plate, brass, aluminum, aluminum alloy, etc. The function is to prevent oxidation reaction and blow off the melt.
Nitrogen works best on aluminum, mild steel, galvanized steel, and automotive steel.
Argon is the rarest and most expensive gas used by most processors, and materials that cut well with nitrogen can also use argon with similar high quality edges. Argon is an inert gas, which is used to prevent oxidation and nitriding in laser cutting machine cutting, and is also used in welding. Compared with other processing gases, it has a high price and correspondingly increases the cost.
The main suitable materials for argon are titanium and titanium alloys.
Air is a mixture of nitrogen, oxygen and other gases. The collection method is relatively simple. Compressed by an air compressor into the air storage tank, extracted after filtration, cooling, and drying, the cost is relatively low, although the air contains about 20% oxygen, so the air can make up for the lack of oxygen and nitrogen to a certain extent. According to our current experiments, taking a 3000w fiber laser cutting machine as an example, it only needs the air at the outlet pressure of the air compressor to reach 1.2Mpa to realize high-quality cutting of carbon steel below 2mm, stainless steel below 10mm, and aluminum plate below 5mm. However, if the metal is cut with oxygen, a small amount of oxide film will appear on the cutting surface, but it can be used as a measure to prevent the coating film from falling off.
For choosing which auxiliary gas is suitable, we have to consider the actual situation, such as cutting material, cutting thickness, production budget and other conditions. Many gases can be used in general, the key point is to consider the cutting cost and the requirements for the product, such as cutting stainless steel materials, when there are no high requirements for the quality or surface quality of the product, for example, painting and other processes are required in the later stage of cutting the product In the processing process, 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 protective gas, such as craft products.
Compressed air for high quality cutting of aluminum; nitrogen for best edge quality of aluminum, mild steel, galvanized steel and automotive steel; oxygen for cutting thicker steel; argon for cutting in nitrogen A metal that undergoes a chemical reaction.
