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

HAZ
Figure 8: Micrographs of cut edges for DP 750.
 
 
 
 
 
 
 
 
 
Figure 9: Micrographs of cut edges ZStE260 + ZE.
 
 
 
4. CONCLUSIONS 
Some useful conclusions can be drawn from this study: 
• Firstly, as regards thickness, 0.7 and 0.8 mm sheets resulting good quality cuts at 
a large range of speeds varying from 2,000 mm/min to 7,000 mm/min. 
Furthermore, 200W is a level of power sufficient to work up to a speed of 4,000 
mm/min. 
Sheet top surface 
HAZ 
HAZ + Burr 
12/15

---

• If a higher speed is required, the power should be increased to 300W, to allow 
working with speeds of up to 8,000mm/min. The risk of the appearance of 
pittings is higher as the speed is increased. The power should be increased to 
avoid this effect, as long as the pressure and the focal position are maintained. 
• As regards gas pressure, it has been established that it is possible to work in the 
whole range of speeds mentioned previously with a value of 6 bars. Once the 
correct value has been established, small variations in pressure do not determine 
the quality and capacity of the cut to the same extent as modifying the power 
and/or speed. 
• The main restriction in sheets thicker than 1 mm has been the cutting speed. 
Good quality cuts have been achieved less than 3,000 mm/min with a minimum 
power of 300W. With respect to gas pressure, the best results have been 
obtained with values of 4 bars. This is due to the fact that the oxygen flow 
should be reduced as the thickness of the sheets becomes greater to avoid the 
exothermal reaction in the cutting area being too violent and damaging the area. 
In all the experiments, both in the case of the thin and the thick sheets, the optimum 
focal position has been established near the under surface of the sheet. On the contrary, 
in the experiments where the laser beam has been focused on the surface of the sheet 
and even above the sheet, the results have been worse. 
As regards the properties of the material, the appearance of burrs in the Zinc coated 
sheets has been observed. This is due to this material's lower melting point. In the rest 
of the sheets, the HAZ varied depending on the composition, the most affected being 
the 
ZStE260P.
This study demonstrates that high strength steel cutting is perfectly viable, when it is 
subjected to the same type of considerations as normal steel.