| Abstract [eng] |
Duplex stainless steel EN 1.4462 is difficult-to-cut meterial due to its low thermal conductivity and unbreakable chip, which causes various problems during precision machining. The main objective of this work is to investigate the machinability of this steel to ensure optimal cost for the best surface finish. This study investigated the effect of cutting speed (150-250 m/min), feed (0,05-0,15 mm/rev), depth of the cut (0,5-1,5mm) on the final product characteristics when emulsion cooling is used. The study found that the precision machining time can vary up to 3,45 times for selected cutting parameters, that the tendency of chips to break increases with increasing feed and cutting speed, that the hardness of the surface layers is mainly influenced by cutting speed and chip formation, it was also found that surface roughness up to 0,433 Ra can be archieved by turning and that the chip deformation coefficient decreases with inceasing of a feed and cutting speed. The results show that the most effective and efficient way to produce parts with a surface roughness tolerance of up to 0,8 Ra is by turning at a cutting speed of 200 m/min, a feed rate of 0,05 mm/rev, and a cutting depth of 1 mm. The study of surface layers affected by turning has shown that high temperatures can not only cause hardening but also thermal softening on surfaces. From this study it was found that different cutting regimes in precision machining can harden the surface from 6 HV to 46 HV, and the deformation and temperature during cutting affects layers from 0,15 mm to 0,45 mm. Thermal softening has been observed in 6 out of 9 samples, and the damaga caused can reduce the wear resistance of the final products, as it has been observed that in some cases the surface hardness is reduced by 20 HV, and the depth of the softened layer reaches 0,15 mm. |
