Instrucciones para la preparación de los trabajos a presentar en el XV congreso Nacional de Ingeniería Mecánica

HAZ + Burr 
Figure 5: Micrographs of cut edges for ZStE260+Z100. Top: 300W. Bottom: 400W. 
 
3.2.- Steel sheets with a thickness greater than 1 mm: DP750,GXE450B and 
ZStE260+ZE 
In this group, the energy to cut the sheets of DP750, GXE450B and ZStE260+ZE is 
higher. This result was expected, as these sheets are thicker than the previous ones. 
Figure 
6
 shows how at the same cutting speed, in comparison, a higher power is 
required. 
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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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Sheet top surface