Among laser cutting methods, there are four main cutting methods: vaporization cutting, melting cutting, oxygen-assisted melting cutting and controlled fracture cutting. This article uses the melting cutting method to make the material at the laser spot reach the melting point, and at the same time blows or removes it with the help of auxiliary gas The molten material around the hole and the scanning path are set to complete the entire test process. Laser material processing systems mainly include lasers, optical path shaping and transmission systems, motion trajectory control and operating systems, among which lasers are the most important. The laser consists of three parts: the laser medium, the pump source and the optical resonant cavity. The laser medium is the core part of the laser and is used to achieve particle number inversion. It produces a material system that produces stimulated radiation; the pump source is used to realize particle number inversion. A device that inverts the excitation energy; the optical resonator not only provides the conditions required to form laser oscillation, but also controls the output power, mode, beam divergence angle, etc.
Laser cutting technology principles and characteristics
With the increase in the types of new lasers, lasers currently mainly used in the field of mechanical manufacturing engineering include CO2 lasers, Nd:YAG lasers, femtosecond pulse lasers, fiber lasers, etc. Among them, CO2 laser is a gas laser, which has the characteristics of large laser output power, wide spectral line range, good monochromaticity of gas laser, good uniformity of working material and flexible excitation method; Nd:YAG laser is a solid laser, also known as YAG laser. Lasers have the characteristics of compact structure, coupling with optical fibers, and short output laser wavelength; femtosecond pulse lasers, also known as ultrafast and ultrashort lasers, have the characteristics of extremely short action time, high peak power density, and small heat-affected zone. ; Fiber laser has the characteristics of good heat dissipation performance, wide tunable range, high conversion efficiency, and maintenance-free. This article uses fiber laser to complete the laser ring cutting and hole making test, which can achieve higher conversion rate and better heat dissipation performance. At the same time, our school’s laboratory has fiber laser cutting equipment. The wide application of laser cutting benefits from the good laser cutting characteristics. Compared with conventional cutting methods such as mechanical cutting, flame cutting, and plasma cutting, laser cutting has non-contact processing, good cutting quality, high cutting efficiency, and saves materials. It has the characteristics of wide adaptability and flexibility, low noise, small vibration, and no pollution.
Interaction between laser and material
The interaction process between laser and material
When laser energy acts on material, the essence of the physical process is the interaction between the electromagnetic field and the material structure. After absorbing the energy, the temperature will continue to rise, so with the Different heating processes will occur over time .
(1) Impact strengthening process When the laser pulse energy is high enough and the action time is short enough to meet the corresponding initial conditions, the laser beam will generate compressive stress on the material surface, forming a surface strengthening process.
(2) Heat absorption process When the metal surface is irradiated by a laser beam, in addition to part of the scattered or reflected energy, most of the photons will vibrate through interaction with the metal lattice and be converted into heat energy. During the heat absorption process, the energy conversion efficiency is related to parameters such as material properties, laser wavelength, and whether it is polarized.
(3) Surface melting process: After the material surface absorbs heat energy, the temperature rises. When the melting point of the material is reached, the surface of the material will begin to melt to form a molten pool, and the thermal influence will spread to the interior, causing the molten pool to continue to expand toward the interior.
(4) Vaporization process When the laser beam has high enough intensity and density, vaporization and plasma radiation phenomena begin to appear on the material surface. After continuous irradiation of the laser beam, the surface of the melted molten pool will vaporize, begin to generate plasma, and form surface ablation.
(5) Composite process: After the vaporization process is completed, the vaporization and plasma sputtering and reverse radiation on the surface of the material will shield the incident light. If certain conditions are met and the irradiation continues, the shielding effect will gradually decay and form an automatic Fresnel Er absorption, that is, self-sustaining adjustment state, forming a compound process.
