The dissertation is dedicated to upgrading the efficiency and extending the technological capabilities of plasma arc cutting. The review of the known results of research of Plasmatrons for cutting revealed that the limiting factor in increasing their performance capability are low energy characteristics, i.e. operational life, thermal efficiency, effective efficiency in heating of materials and high power consumption. The most potentially productive Plasmatrons solving the problem of plasma arc cutting technologies are those equipped with hollow “cold” and “hot” cylindrical cathodes. Nevertheless, they also need to improve the energy characteristics, which require significant theoretical research and experimental studies. Searching the ways to solve these problems has revealed some design decisions and conditions, which contribute to increasing the operational life and efficiency of Plasmatrons with hollow “cold” and “hot” cylindrical cathodes operating on oxygen-containing gases due to the forced distribution in the cathode
binding of the arc. This allowed us to create a new class of Plasmatrons for cutting metals up to 400 mm in thickness with a capacity of 40 to 300 kW. In this case, the specific erosion of the copper hollow cathode with an arc current of 700 A was (10^-9 – 10^-10) kg / Kl, which is substantially lower than the known data. For the first time, a sectioned Plasmatron with a hollow electrode has been developed for cutting metals of a large thickness (more than 100 mm), where are available the thermionic inserts (made of Tungsten), which are protected from the erosion of the working gas (air) with low pressure argon, that contributes to the formation of a diffuse arc binding and the increase of the arc current above 800 A. It has been established that the developed Plasmatron with the hollow "cold" electrode during cutting the metal on the reverse polarity increases the electrode operational life more than twice, and the productivity by 20-40%. Taking into account own research data and results of researches of other authors it has been established that the thermal efficiency of the cutting Plasmatron depends on the distance of the nozzle to the metal being cut, the polarity of combustion, the length of the nozzle channel and the flow of plasma gas. Energy costs per linear meter of cutting for Plasmatrons with the hollow and thermochemical electrodes are almost identical and go up with increasing of the metal cutting thickness. An engineering design procedure was developed for the cutting Plasmatrons, equipped with the hollow “cold” and “hot” cylindrical cathodes and operating on oxygen-containing gases, which have a long operational life. The Plasmatrons of such construction type were industrially tested at PrJSC "Severodonetsk Azot Association" in Severodonetsk and at LLC "BUDDETAL" in Kramatorsk. They were used when cutting steels (st. 3, st. 20, steel 45, 09Г2С, 17ГС) in thickness up to 400 mm; high-alloy steels (12Х18Н10Т, 17Х23Н18, 20Х13, 10Х17Н13М3Т) in thickness up to 150 mm; non-ferrous metals and alloys (Aluminum, Copper, Brass, Bronze) and Titanium in thickness up to 100 mm; for cutting round steel bar (40ХН2МА) up to 300 mm thick, forgings (steel 45) up to 200 mm thick; high-pressure pipes with wall thickness of 40-50 mm (12H18N10T, 12Х1МФ).
