1, vaporized cutting.

Under high power density laser beam heating, the temperature of the material surface rises to the boiling point at a rate that is sufficient to avoid melting due to heat conduction, so that part of the material is vaporized to vapor and part of the material is discharged as a discharge from the bottom of the slit Auxiliary gas flow blown away. Some non-meltable materials, such as wood, carbon materials and certain plastics are cut by this vaporization cutting method.

Vaporization cutting process, the steam carry away melt particles and erosion debris, the formation of holes. About 40% of the material is evaporated during the vaporization process, and 60% of the material is jet-stream-driven.

2, melt cutting.

When the incident laser beam power density exceeds a certain value, the beam irradiation point inside the material began to evaporate, the formation of holes. Once this pinhole is formed, it will absorb all the energy of the incident beam as a blackbody. The aperture is surrounded by a molten metal wall, and then an airstream coaxial with the beam carries the molten material around the aperture. As the workpiece moves, the holes move in synchronization with the cutting direction to form a slit. The laser beam continues to illuminate the front edge of the seam, and the molten material is blown away from the seam continuously or pulsatile.

3, oxidation melt cutting.

Melting and cutting generally use inert gas, if replaced by oxygen or other reactive gases, the material is ignited under the laser beam, and the fierce chemical reaction with oxygen to produce another heat source, known as the oxidative melting cut. Specific description is as follows:

(1) The surface of the material is quickly heated to the ignition temperature under the irradiation of the laser beam, and then the combustion reaction with oxygen occurs intensely to release a large amount of heat. Under the action of this heat, a steam-filled hole is formed inside the material, and the periphery of the hole is surrounded by a molten metal wall.

(2) The conversion of combustion material into slag controls the combustion rate of oxygen and metal, and the speed at which oxygen diffuses through the slag to the front of the ignition also has a great influence on the combustion rate. The higher the oxygen flow rate, the faster the chemical reaction and slag removal. Of course, the higher the oxygen flow rate, the better, since the fast flow rate leads to rapid cooling of the reaction product at the kerf exit, ie the metal oxide, which is also disadvantageous for the cut quality.

(3) Obviously, there are two heat sources in the process of oxidative melting and cutting, that is, the energy of laser irradiation and the heat generated by chemical reaction between oxygen and metal. It is estimated that when cutting steel, the heat released by the oxidation reaction accounts for about 60% of the total energy required for cutting.

Obviously, the use of oxygen as an auxiliary gas results in a higher cutting speed compared to inert gases.

(4) In oxidative melt cutting with two heat sources, the kerf is wide and rough if the burning rate of oxygen is higher than the moving speed of the laser beam. If the laser beam moves faster than the rate of oxygen combustion, the resulting kerf is narrow and smooth.

4, control fracture cutting.

For brittle materials easily damaged by heat, high-speed, controlled cutting by laser beam heating is called controlled fracture cutting. The main content of this cutting process is that the laser beam heats a small area of brittle material, causing a large thermal gradient and severe mechanical deformation in the area, resulting in the formation of cracks in the material. As long as an equalized heating gradient is maintained, the laser beam can direct the crack in any desired direction.

It should be noted that this control of fracture cutting is not suitable for cutting acute angle and corner kerf. Cutting large closed shape is not easy to succeed. Control fracture Cutting speed, do not need too high power, otherwise it will cause the workpiece surface melting, sabotage cutting edges. The main control parameters are laser power and spot size.