Vaporized cutting refers to the removal of processed materials mainly by vaporizing the materials.
In the process of vaporization and cutting, the temperature of the workpiece surface rises rapidly to vaporization temperature under the action of the focused laser beam, the material is vaporized in a large amount, and the high-pressure vapor formed is ejected outward at supersonic speed. At the same time, a “hole” is formed in the laser action area, and the laser beam is reflected multiple times in the hole to rapidly increase the absorption rate of the material to the laser.
In the process of high-pressure steam jetting at high speed, the molten material in the slit of the cnc fiber laser cutting machine is blown away from the slit at the same time until the workpiece is cut off. The internal vaporization cutting is mainly carried out by vaporizing the material, so the required power density is very high, generally, it should be more than 10-octave watts per square centimeter.
Vaporized cutting is a method often used for fiber laser cutting some low-ignition-point materials (such as wood, carbon, and certain plastics) and refractory materials (such as ceramics, etc.). When cutting materials with pulsed lasers, vaporized cutting methods are often used.
Reactive melting cutting
In melting laser cutting, if the auxiliary airflow not only blows away the melt in the slit, but also can react with the workpiece to increase the heat source during the cutting process, this kind of cutting is called reaction melting cutting. Usually the gas that can react with the workpiece is oxygen or a mixed gas containing oxygen.
When the surface temperature of the workpiece reaches the ignition temperature, a strong combustion exothermic reaction will occur, which can greatly improve the fiber laser cutting ability of the fiber cutting machine. For mild steel and stainless steel, the energy provided by the combustion exothermic reaction is 60%. For active metals such as titanium, the energy provided by combustion is about 90%.
Therefore, compared with laser vaporization and general melting cutting, reactive melting cutting requires a lower laser power density, which is only 1/20 of vaporization cutting and 1/2 of melting cutting. However, in reactive melting cutting, the internal combustion reaction will cause some chemical changes on the surface of the material, which will affect the performance of the workpiece.
In the laser cutting process, if an auxiliary blowing system coaxial with the laser beam is added, the removal of the molten material during the cutting process is not only by the vaporization of the material itself, but mainly by the blowing action of the high-speed auxiliary airflow to remove the molten material. Continuously blowing away from the slit, this laser cutting process is called melting cutting of fiber optic laser cutter.
During the melting and cutting process, the temperature of the workpiece no longer needs to be heated above the vaporization temperature, so the required laser power density can be greatly reduced. According to the latent heat ratio of material melting and vaporization, the fiber laser power required for melting and cutting is only 1/10 of the vaporization cutting method.
This method of laser cutting machine is mainly used for semiconductor materials. A laser beam with a high power density is used to scribe shallow grooves on the surface of the semiconductor material. Since this groove weakens the bonding force of the semiconductor material, it can be broken by mechanical or vibration methods. The quality of laser scribing is measured by the size of surface debris and heat-affected zone.
This is a new type of fiber laser metal cutting machine processing method, which was proposed with the emergence of high-power excimer lasers in the ultraviolet band in recent years. Its basic principle: the energy of ultraviolet photons is similar to the binding energy of many organic materials. Using such high-energy photons to hit the binding bonds of organic materials and break them, to achieve the purpose of laser cutting. This new technology has broad application prospects, especially in the electronics industry.
Thermal stress cutting
When the brittle material is heated by the laser beam of the fiber laser tube cutting machine, the surface of the brittle material is prone to large stress, so that it can be broken neatly and quickly through the stress points heated by the laser. This cutting process is called laser thermal stress cutting. The mechanism of thermal stress cutting is that the laser beam heats a certain area of the brittle material to produce an obvious temperature gradient.
The higher surface temperature of the workpiece will cause expansion, and the lower temperature of the inner layer of the workpiece will hinder the expansion. As a result, tensile stress is generated on the surface of the workpiece, and the inner layer generates radial compression stress. When these two stresses exceed the fracture limit strength of the workpiece itself, cracks will appear on the workpiece, causing the workpiece to break along the crack. The speed of thermal stress cutting-strand is on the order of m/s. This cutting method is suitable for cutting glass, ceramics and other materials.