The amount of defocus is an important parameter that affects the cutting quality in the process of laser cutting. In anaerobic cutting of stainless steel plates, the amount of slag is reduced by blowing off the molten residue with auxiliary gas. The cutting quality is very important. Therefore, it is necessary to set the focus position It is set inside the steel plate to expand the width of the slit to increase the flow of auxiliary gas.
The selection of defocus amount has a great influence on the cutting quality of stainless steel plate:
[1] When the focus position is moderate, the slit material melts, but the material near the cutting edge does not melt, and the slag is blown away, forming a slag-free, smooth slit.
[2] When the focus position is at the back, the energy absorbed by the unit area of the lower part of the cutting material decreases, and the cutting energy is weakened, resulting in the incomplete melting of the material and being blown away by the auxiliary gas, so that the incompletely melted material adheres to the lower surface of the cutting plate.
[3] When the focus position is advanced, the average energy absorbed per unit area in the lower half of the cutting material increases, causing the cut material and the material near the cutting edge to melt and flow like a liquid. At this time, due to the auxiliary air pressure and The cutting speed remains unchanged, and the molten material adheres to the lower surface of the material in a spherical shape and forms a slag.
In actual production, it is required that the focus of laser cutting stainless steel plate be selected on or below the surface of the material. This is because the width of the upper part of the cutting groove is enlarged, the fluidity of gas and melt is improved, and the smooth range of the cross section is expanded to improve the cutting quality.
During the cutting process, the focus position is not fixed for steel plates of different thicknesses. When the focus position is taken on or above the surface of the steel plate, due to the low average power density and insufficient energy in the lower part of the steel plate, slag is easily generated on the lower surface. Therefore, when laser cutting stainless steel plates, the focus position should be selected inside the material. To improve the fluidity of gas and molten metal, ensure sufficient energy density in the lower part, and expand the range of smooth surfaces.