OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 Fig. 6. The structure of plasma torch elements after gradual uneven wear of the nozzle and electrode under conditions of inaccuracy in the manufacture of consumable elements: a, b – macrostructure of the electrode and nozzle, c–e – microstructure of individual sections of the electrode; f–h – microstructure of nozzle sections chamber, if the water pressure at the plasma torch inlet is not observed, leads to partial squeezing of gas and plasma into the electrode hole and its erosion, which can be observed during visual inspection (Figure 2, l, m). Increasing the resistance to water flow at the outlet of the plasma torch also made it possible to level out this defect in operation, even in the presence of inaccuracies in the manufacture of the nozzle or untimely starting arcing off, which can be seen from the absence of damage in the upper part of the working electrodes in Figures 5 and 6. Conclusion The process of plasma cutting with reverse polarity current is quite complex and non-uniform in time and on a large number of different factors. The conducted studies show that, similarly to a number of previously conducted studies on direct polarity plasma torches and on smaller thicknesses of cut sheet metal [11, 16, 20 and others] the main of the most dangerous factors for fatal failure of working elements of plasma torches under conditions of cutting thick sheet metal of titanium and aluminum alloys with the reverse polarity current are failure to maintain the gap in the discharge chamber and low gas pressure in the system. This can cause double arcing during cutting and short circuit between electrode and nozzle through the molten metal. Maintaining the minimum gap and gas pressure above 2.5–3.0 atmospheres can significantly reduce the risk of fatal failure of nozzles and electrodes. The use of water injection technology into the working zone allows improving the quality of the cut and the duration of operation of the consumables, which is also described in [17, 18], but can lead to some increase in electrode wear due to insufficient resistance to the water flow at the outlet of the plasma torch. Misalignment of the conical part of the nozzle and the hole at
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