Views: 33 Author: Site Editor Publish Time: 08-17-2021 Origin: Site
Nowadays, laser cutting machines are no longer a problem for cutting steel plates below 10mm thickness. But if you need to cut thicker stainless steel plates, traditional laser cutting methods may not have the advantage. To cut high-quality thick plate stainless steel, we need to master certain cutting skills. Today, Leapion Laser will give you an analysis from the following points.
In the actual cutting process of the metal laser cutting machine, the thickness of the plate that can be cut through is limited, which is closely related to the inability of the cutting front iron to burn stably. For the combustion process to continue, the temperature at the top of the slit must reach the ignition point. The energy released by the iron-oxygen combustion reaction alone cannot actually ensure the continuous combustion process.
On the one hand, because the cutting seam is continuously cooled by the oxygen stream sprayed from the nozzle, the temperature of the cutting front is reduced;
On the other hand, the ferrous oxide layer formed by combustion covers the surface of the workpiece and hinders the diffusion of oxygen. When the concentration of oxygen decreases to a certain level, the combustion process will be extinguished.
When cutting thick plates with a metal laser cutting machine, the decrease in oxygen purity is also an important factor affecting the quality of the cut.
In order to keep the cutting stable, it is required that the purity and pressure of the cutting oxygen flow in the thickness direction of the plate be kept basically constant. In the traditional laser cutting process, common cone nozzles are often used, which can meet the requirements for use in thin plate cutting. However, when cutting thick plates, as the air supply pressure increases, shock waves are easily formed in the nozzle flow field. The shock waves have many harms to the cutting process, reducing the purity of the oxygen flow and affecting the quality of the cut.
The diameter of the nozzle determines the shape of the gas flow entering the incision, the gas diffusion area, and the gas flow rate, which affects the stability of the melt removal and cutting. The air flow into the incision is large, the speed is fast, and the position of the workpiece in the air flow is appropriate, the stronger the jetting ability to remove the molten material. The thicker the stainless steel, the larger the nozzle should be used, the larger the proportional valve setting, and the larger the flow rate, can the pressure be ensured and the normal section effect can be cut.
Single and double-layer nozzles: Generally speaking, double-layer nozzles are used for oxidative cutting (the auxiliary gas is oxygen), and single-layer nozzles are used for fusion cutting (the auxiliary gas is nitrogen). However, some lasers have special instructions, whether to use a single layer or a double layer. In this case, follow the laser instructions.
In order to ensure the cutting effect and protect the nozzle from damage, it is necessary to do a coaxial test before cutting to ensure that the nozzle is coaxial with the laser output beam. Test method: Attach the transparent tape to the nozzle outlet end surface, adjust the laser output power for drilling, observe whether there is a center hole and the position of the center hole on the transparent tape, adjust the adjustment screw on the handle of the lens cavity synchronously, until the laser is on The hole punched in the scotch tape coincides with the center of the nozzle.
Various auxiliary gases are often used in stainless steel laser cutting processing, such as oxygen, nitrogen, air, etc. Different gas types are used, and the effect of cutting sections is different. Oxygen is a black section, air is light yellow, and nitrogen can keep the original color of stainless steel from being oxidized. Nitrogen is the preferred auxiliary gas for stainless steel cutting.
Recommended oxygen and nitrogen purity:
1) Oxygen
Advantages: high cutting speed, able to cut thick sheets
Purity recommendation: ≥99.999%
2) Nitrogen
Advantages: avoid oxidation of the cutting edge, so the workpiece does not need to be reworked
Purity recommendation: ≥99.995%
The focus is different, and the thickness, material, and quality that can be cut are also different. Different materials and thicknesses need to be adjusted to different focus. Before cutting, the actual zero focus is measured, and the test and analysis of the cutting process parameters can be carried out with the zero focus as the benchmark. The negative defocus is the main process selection direction for stainless steel cutting.
The effect of frequency change on stainless steel thick plate cutting: the frequency is reduced from 500-200Hz, the cutting section effect becomes finer, and the layering gradually improves. When the frequency is set to 100Hz, it cannot be cut and the blue light is reversed. Through frequency change, find the best frequency range. In order to ensure the best cutting section, the number of pulses must be perfectly matched with the energy of a single pulse.
The effect of duty cycle change on stainless steel thick plate cutting: duty cycle 53% is the critical value. If you continue to decrease the duty cycle, there will be traces of incomplete cutting on the lower surface, the duty cycle will increase to 60%, and the section will become rough and layered. Obviously, the cut surface is yellow.
The pulse duty cycle refers to the proportion of the beam irradiation time in each pulse. The frequency is the number of times the peak power occurs in a pulse, and the duty cycle is the ratio of the peak power to the trough power in a pulse.
With the increasing economic development, the application fields of stainless steel medium and heavy plates are becoming more and more extensive. We can learn the above 5 process skills, so as to better use laser cutting machines to cut stainless steel plates and improve the production efficiency and benefits of enterprises. For more professional questions about laser cutting machines, welcome to consult Leapion Laser.
