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

parts (fig 
2
 left). The size of the HAZ, indicated as a distinct grey band (fig 
2
 right), was 
measured with a metallographic microscope. Heating measurements have also been 
carried out using an infrared camera. All the sheets were cleaned before cutting. 
 
Figure 2: Left. Section of the cut. Right. Top view of the cut and HAZ 
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3. DISCUSSION OF RESULTS
The behaviour of the steel sheets cut during the tests allows the results to be divided 
into two large groups, i.e. the steel sheets with a thickness of less than 1 mm (ZStE260P 
and ZStE260+Z100) and with a thickness greater than 1 mm (DP750,GXE450B and 
ZStE260+ZE).
Some differences in the parameters of optimum cuts have been found in each group, 
given the fact that the different chemical composition and coating of each sheet 
significantly influences the thermal behaviour influenced by the thickness and thermal 
characteristics of the different materials.
3.1.- Steel sheets with a thickness less than 1 mm: ZStE260P and ZStE260+Z100 
General consideration, without taking into account yet such exhaustive considerations 
as roughness measurements, rectangularity tolerances, etc., is that similar cutting speed 
and power values have been obtained in both sheets. At a constant assisting gas pressure 
of 6 bars, taking values –1 and –1.5 mm as focal point positions with respect to the top 
surface of ZStE260P and ZStE260+Z100 steels respectively, the optimum working 
region for these steel sheets can be observed in figure 3.
Figure 3: Optimum working area for steel sheets thinner than 1
 mm
 
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As can be seen, cutting speeds of over 7,000 mm/min were achieved, when competitive 
laser cuts are more than 3,000 mm/min. As regards cutting quality, figure 4 shows the 
kerfs of the different cuts. As was to be expected, the values are near to the spot size 
(0.21 mm). 
Spot size 
Figure 4: Kerf values at a pressure of 6 bars and -1 focal position 
As far as metallurgical analysis is concerned, the edges of the cut are shown in figure 5. 
Metallurgical structure corresponds to two cuts in ZstE260+Z100 performed at a cutting 
speed of 6000 m/min, 6 bar and –1 mm focal position. In the first one, beam power 
300W has been used whereas in the second one beam power has been 400W. Burr 
formation as well as thicker HAZ (40 microns) can be observed in the latter case. 
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Sheet top surface 
HAZ
,
Sheet top surface