Schematic view of the setup used in experiments for remote-fusion cutting. The diameter dS of the spot depends on the working distance z, the diameter of the focal spot d foc, and the focal length of collimation and objective lens. A cross jet protects the optics.
Typical process schema. From left to right, the cutting velocity and laser intensity are increased with a constant increment. Phases 1 through 6 indicate different cutting (1, 3, 5) and welding (2, 4, 6) processes, respectively. The given values illustrate a representative sample for t = 1.8 mm and P = 8 kW (Ref. 20 ).
Cutting speed v vs. average laser power density for different thicknesses of the press-hardened steel 22MnB5. Each dot stands for the actual cutting result. Two areas can be distinguished: subprocess A with a pushing melt ejection arises for low velocities and a medium laser power intensity, while subprocess B (see black bordered area) shows a dragging melt ejection at a higher speed (Ref. 20 ).
Cross-section of a laser-fusion cut into a 22MnB5 sheet of 1 mm thickness (P = 8 kW, v = 5 m/min, dS = 770 μm). The molten material resting in the kerf solidified in a circular cross-section due to surface tension. The dark vertical lines (see arrows) define the area of austenitization. Superimposed the kerf cross-section is the Vickers hardness measurement (red curve) (Ref. 20 ).
Snapshots taken of the melt ejection for subprocess A (a) and subprocess B (b). Positive and negative ejection is seen from one and the same steel of thickness t = 1.8 mm at a laser power of P = 8 kW. In (a) v = 3 m/min, dS = 770 μm, while in (b) v = 14 m/min, and dS = 560 μm (Ref. 20 ).
Angle of melt ejection vs. cutting speed. t = 1.8 mm, P = 8 kW, dS = 770 μm. Effective melt ejection is observed for the range 3 ≤ v ≤ 11 m/min only (Ref. 20 ).
Cross-sections for the three cutting ranges ①, ③, and ⑤, as defined in Chap. III. 1. (a) ①: Cutting without directional melt disposal; (b) ③: Subprocess A: pushing melt ejection at low velocities; (c) ⑤: Subprocess B: dragging melt ejection at high velocities. Please again note the regime of austenitization (Ref. 20 ).
Longitudinal sections for subprocess A for similar parameters P and v, but different thicknesses: (a) t = 1.4 mm, (b) t = 1.8 mm, (c) t = 2.2 mm. The spot diameter dS increases with sheet thickness (Ref. 20 ).
Longitudinal sections for subprocess B for similar parameters P, v, and dS , but different thicknesses: (a) t = 1.4 mm, (b) t = 1.8 mm, (c) t = 2.2 mm (Ref. 20 ).
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