The main process classification and description of laser cutting
1、Gasification laser cutting processing
Under the heating of a high-power density laser beam, the surface temperature of the material rises to the boiling point temperature so fast, enough to avoid the melting caused by heat conduction, so part of the material vaporizes into steam and disappears, and part of the material is ejected from the bottom of the slit. The auxiliary gas stream blows away. The temperature of laser cutting exceeds 11000°C, which is enough to vaporize any material, so when laser cutting. In addition to melting, gasification also plays an important role. The laser cutting process of some materials (such as carbon and certain ceramics) is purely a gasification process.
2、Melting laser cutting processing
When the power density of the incident laser beam exceeds a certain value, the inside of the material at the point where the beam is irradiated will evaporate, forming holes. Once this small hole is formed, it will act as a black body to absorb all the incident beam energy. The small hole is surrounded by a wall of molten metal, and then the auxiliary airflow coaxial with the beam takes away the molten material around the hole. As the workpiece moves, the small hole moves synchronously in the cutting direction to form a slit. The laser beam continues to irradiate along the front edge of this slit, and the molten material is continuously or pulsatingly blown away from the slit.
3、Oxidation melting laser cutting processing
Melting and cutting generally use inert gas. If it is replaced by oxygen or other active gases, the material is ignited under the irradiation of a laser beam, and a fierce chemical reaction occurs with oxygen to generate another heat source, which is called oxidative melting and cutting.
4、Controlled fracture laser cutting processing
For brittle materials that are easily damaged by heat, high-speed and controllable cutting is performed by laser beam heating, which is called controlled fracture cutting. The main content of this cutting process is: the laser beam heats a small area of the brittle material, causing a large thermal gradient and severe mechanical deformation in this area, leading to the formation of cracks in the material. As long as a uniform heating gradient is maintained, the laser beam can guide cracks in any desired direction.
CO2 laser cutting processing: Laser cutting is mainly CO2 laser cutting. CO2 laser cutting is to use a focusing mirror to focus the CO2 laser beam on the surface of the material to melt the material, and at the same time use the compressed gas coaxial with the laser beam to blow away the melted material, and Make the laser beam and the material move relative to each other along a certain track, thereby forming a slit of a certain shape. The obvious advantages of CO2 laser cutting technology over other methods are:
（1）The cutting quality is good. The incision width is narrow (generally 0.1-0.5mm), high accuracy (generally the hole center distance error is 0.1-0.4mm, the contour size error is 0.1-0.5mm), and the cut surface roughness is good (generally Ra is 12.5--25μm ), the cut seam generally does not need to be processed again and can be welded.
（2）The cutting speed is fast. For example, with 2KW laser power, the cutting speed of 8mm thick carbon steel is 1.6m/min; the cutting speed of 2mm thick stainless steel is 3.5m/min, the heat affected zone is small, and the deformation is minimal.
（3）Clean, safe and pollution-free. Greatly improve the working environment of operators. Of course, in terms of accuracy and incision surface roughness, CO2 laser cutting cannot exceed electrical machining; in terms of cutting thickness, it is difficult to reach the level of flame and plasma cutting. But the above significant advantages are enough to prove: CO2 laser cutting has and is replacing part of the traditional cutting process methods, especially the cutting of various non-metallic materials. It is an advanced processing method that develops rapidly and is widely used.
Since the 1990s, due to the development of my country's socialist market economy, competition among enterprises has been fierce. Each enterprise must correctly choose certain advanced manufacturing technologies according to its own conditions to improve product quality and production efficiency. Therefore, CO2 laser cutting processing technology has achieved rapid development in my country.