Laser cutting classification

Laser cutting can use auxiliary gases to help remove molten or vaporized materials, or no auxiliary gases. According to the different auxiliary gases used, laser cutting can be divided into four categories: gasification cutting, melt cutting, oxidation assist cutting and controlled fracture cutting. 1) Gasification cutting. The high energy density laser beam is used to heat the workpiece, so that the surface temperature of the material rises rapidly, and the boiling point of the material is reached in a very short time, which is enough to avoid melting caused by heat conduction, the material begins to vaporize, and some materials are vaporized into steam and disappear. The steam is ejected at a high speed, and at the same time as the vapor is ejected, part of the material is blown off the auxiliary gas stream from the bottom of the slit as a spout, and a slit is formed in the material. Some materials that cannot be melted, such as wood, carbon materials, and certain plastics, are cut by this method. Laser gasification cutting is often used for cutting very thin metal and non-metallic materials. 2) Melt cutting. The metal material is melted by laser beam heating. When the power density of the incident laser beam exceeds a certain value, the inside of the material begins to evaporate after the beam is irradiated to form a hole. As the workpiece moves, the small holes traverse in the direction of the cutting to form a slit. The laser beam continues to illuminate along the leading edge of the slit, and the molten material is continuously or pulsatingly blown away from the slit. Laser melt cutting is mainly used for the cutting of some non-oxidizable materials or active metals, such as stainless steel, titanium, aluminum and their alloys. 3) Oxidation and flux cutting. A laser is used as a preheating heat source, and oxygen or other reactive gas is used as a cutting gas. On the one hand, the injected gas acts on the cutting metal to cause an oxidation reaction to release a large amount of heat of oxidation; on the other hand, the molten oxide and the melt are blown out from the reaction zone to form a slit in the metal. The basic principles of oxidative fluxing cutting can be explained as follows: 1 With oxygen or other reactive gas, the surface of the material is quickly heated to the ignition temperature under laser irradiation, and the combustion reaction with oxygen is intense. Under this heat, a small hole filled with steam is formed inside the material. 2 The combustion material is transferred into slag to control the burning rate of oxygen and metal. The higher the oxygen flow rate, the faster the combustion chemical reaction and the removal of slag. The higher the oxygen flow rate, the better, because too fast a flow rate will result in rapid cooling of the reaction product (i.e., metal oxide) at the exit of the slit, which is detrimental to the quality of the cut. 3 There are two heat sources in the oxidation assisted cutting process, namely laser irradiation and thermal energy generated by the chemical reaction between oxygen and metal. 4 In the oxidation assisted cutting process with two heat sources, if the burning speed of oxygen is higher than the moving speed of the laser beam, the slit appears wide and rough. If the laser beam moves faster than the oxygen, the resulting slit is narrow. smooth. 4) Control fracture cutting. For brittle materials that are easily damaged by heat, a high-energy-density laser beam is used to scan the surface of the brittle material, so that the material is evaporated to a small groove by heat, and then a certain pressure is applied to perform high-speed, controllable cutting by laser beam heating. The brittle material will crack along the small groove. The principle of this cutting process is mainly that the laser beam heats a local area of ​​the brittle material, causing a large thermal gradient and severe mechanical deformation in the area, resulting in cracks in the material. Controlling the fracture is a steep temperature distribution generated by laser engraving, which generates local thermal stress in the brittle material, causing the material to crack along the small groove. It should be noted that this controlled fracture cutting is not suitable for cutting acute and angular slits. Cutting a large closed shape is also not easy to succeed