Mild steel and low-alloy steel

Oxygen-cutting with CO2 lasers is the most common method for cutting flat stock mild steels and low-alloy steels. Hollow profiles and tubular structures, such as those used in the car industry are often cut with Nd:YAG lasers manipulated by robots.

Today, plates with a thickness of up to 25mm (1 in), we can cut those easily with laser powers of up to 6kW. We often position the focal point close to the upper surface of the workpiece. Table 1 contains a guideline for the most important parameters, Fig. 10 surveys the gas consumption. Regarding the cutting tables in this brochure as guidelines. Deviations may occur, depending on type of laser, beam delivery system, nozzle arrangements and focus conditions. This applies particularly to the cutting of profiles. Here, cutting speed is often much lower than indicate in the cutting tables, because the motion system (i.e. robot) cannot follow the contours quickly enough.

We can use a lens with a focal length of 127mm (5 in) may when cutting sheets of plate material of up to 6mm (1/4 in). And we should use a 190mm (7.5 in) lens for material thicknesses over 6mm (1/4 in).

Laser power of at least 3kW or higher is required when cutting plates with thicknesses of up to 12–25mm (0.5–1.0 in). Cutting oxygen pressure is generally under 1 bar (14.7 psi), and the nozzle diameter is larger, 2–3mm (0.08–0.12 in). The focus point may situates 1–3mm (0.04– 0.12 in) above the upper surface of the workpiece.

Purity of oxygen forms an important parameter when cutting mild steels and low-alloy steels.

The cutting speed can increase by using higher purity oxygen (99.9%–99.95%) rather than standard oxygen purity (99.5%).

Cutting speed can increase by 10–30%, depending on material thickness and types of steel. Although the productivity gain depends largely on the nature of the parts. The positive effect is greater when cutting larger parts with simple geometry than when cutting complicated shapes. Where cutting speed is limited by the capacity of the mechanical steering system rather than the cutting process itself.

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