OBRABOTKAMETALLOV Vol. 26 No. 4 2024 TECHNOLOGY particularly for titanium alloys with relatively low thermal conductivity. This makes it diffi cult to avoid edge oxidation due to insuffi cient metal removal from the kerf and excessive melting of the surface. However, increasing the power of the plasma arc source and cutting at a slightly higher current (around 400 A) could allow for acceptable quality cuts on titanium alloy plates up to 100 mm thick, even when using air as the plasma-generating gas. Conclusion The conducted studies demonstrate that it is possible to obtain 100 mm thick blanks from sheet rolled aluminum, copper and titanium alloys using the reverse polarity plasma cutting. The best surface quality of the cut is observed in the Al-6Mg aluminum alloy and Cu-9 Al-2 Mn bronze. These alloys exhibit only minor changes in mechanical properties and surface layer structure, as well as minimal geometric distortions in the cut. The zone with reduced magnesium content in the aluminum alloy does not exceed 0.5 mm from the cut surface, while in bronze, there is virtually no change in chemical composition. Both alloys show the presence of oxygen only on the cut surface without the formation of an oxide layer. In contrast, the quality of the Ti-5Al-5Mo-5V titanium alloy cut is signifi cantly lower. Due to the higher melting temperature, achieving full penetration of the plate is more challenging, and signifi cant edge distortion can be observed in the lower part of the plate. A substantial oxide layer forms on the surface, within which microcracks develop during cooling. This necessitates the requirement for shot blasting post-processing of the titanium alloy after cutting when air is used as the plasma-forming gas, or alternatively, replacing air with nitrogen. It is also noteworthy that in the upper part of the cut zone, where metal displacement from the kerf is more effi cient, the oxide layer is relatively thin. Cutting in air with additional water injection for the titanium alloy can also be employed but would likely require higher arc power and gas pressure. a b c d Fig. 11. Microhardness (a), change in oxygen content (b) in the surface layers of titanium alloy Ti-5Al-5Mo-5V and the results of X-ray analysis of the base metal (c) and the cut surface (d)
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