Laser cutting in sheet metal processing is to use a focused high-power-density laser beam to irradiate the workpiece so that the irradiated material is rapidly melted, vaporized, ablated, or reaches the ignition point, and at the same time, the molten material is blown away by the high-speed airflow coaxial with the beam. To realize the cutting of the workpiece. Laser cutting is one of the thermal cutting methods.
Laser cutting in sheet metal processing can be divided into four categories: laser vaporization cutting, laser melting cutting, laser oxygen cutting, and laser scribing and controlled fracture.
1) Laser vaporization cutting
The laser beam with high energy density is used to heat the workpiece so that the temperature rises rapidly and reaches the boiling point of the material in a very short time, and the material begins to vaporize to form steam. These vapors are ejected at a high speed, and at the same time as the vapors are ejected, cuts are formed on the material. The heat of the vaporization of materials is generally very large, so laser vaporization cutting requires a lot of power and power density. Laser vaporization cutting is mostly used for cutting extremely thin metal materials and non-metal materials (such as paper, cloth, wood, plastic, rubber, etc.).
2) Laser melting cutting
During laser melting and cutting, the metal material is melted by laser heating, and then a non-oxidizing gas (Ar, He, N, etc.) is sprayed through a nozzle coaxial with the beam, and the liquid metal is discharged by the strong pressure of the gas to form a cut. Laser fusion cutting does not need to completely vaporize the metal, and the energy required is only 1/10 of that of vaporization cutting. Laser melting cutting is mainly used in the cutting of materials that are not easily oxidized or active metals, such as stainless steel, titanium, aluminum, and alloys.
3) Laser oxygen cutting
The principle of laser oxygen cutting is similar to that of oxyacetylene cutting. It uses a laser as a preheating heat source and active gas such as oxygen as cutting gas. On the one hand, the blown gas interacts with the cutting metal to undergo an oxidation reaction, releasing a large amount of oxidation heat; on the other hand, the molten oxide and melt are blown out from the reaction zone to form a cut in the metal. Because the oxidation reaction in the cutting process generates a lot of heat, the energy required for laser oxygen cutting is only 1/2 of that of fusion cutting, and the cutting speed is much higher than that of laser vaporization cutting and fusion cutting. Laser oxygen cutting is mainly used for easily oxidized metal materials such as carbon steel, titanium steel, and heat-treated steel.
4) Laser scribing and controlled fracture
Laser scribing is to scan the surface of the brittle material with a high-energy-density laser so that the material is heated and evaporated to form a small groove, and then a certain pressure is applied, and the brittle material will crack along the small groove. The lasers used for laser scribing are generally Q-switched lasers and CO2 lasers. Controlled fracture is to use the steep temperature distribution generated during laser grooving to generate local thermal stress in the brittle material so that the material is broken along the small groove.
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