Figure 6:
Optimum working area for steel sheets thicker than 1
mm
In comparison to the previous case, it was not possible to increase
the speed more than
3,000 mm/min. From this speed on, the cuts present pittings and areas where the
complete thickness of the sheet had not been cut. In the
same way as the previous case,
figure 7 shows how the kerf size varies for the different levels of power and speed
values.
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Figure 7: Kerf values at a pressure of 4 bars and -1.5 focal position
Once again, the kerf values range around 0.21 mm (spot size).
For the sheets thicker
than 1 mm, values higher than those obtained in the thinner sheets can be observed. In
the same way that has occurred in previous experiments, the kerf increases as the power
increases and decreases as the speed increases.
Figures 8 and 9 show microphotographs in which the cutting edge of DP750 and
ZstE260+ZE can be observed.
In
the case of Dual Phase, grain growth is present on the edge. In the case of
ZstE260+ZE, a recristallized and tempered zone is present. In both cases,
the thinner the
sheet, the thicker the HAZ, since laser cutting of this family of sheets requires higher
heat contribution.
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