Development and research of new technologies for precision plasma cutting of metals

Plasma torches of Russian origin concede to import metal-cutting plasma facilities by several parameters, in particular energy efficiency, quality of cut, degree of automation. To increase efficiency and safety of domestic electro-plasma technologies itь is necessary to perfect methods of analysis of known design solutions to provide new developments. The results of the plasma torch­es design widely used in metallurgical and machine-building technologies for air-plasma cutting of metals presented. It was noted that productivity, cutting quality and reliability of plasma equipment should be chosen as the main criteria of efficiency for plasma cutting technology. It was shown that special attention should be paid to improving the gas-vortex stabilizing method for the plasma forming gas, which ensures the efficiency of both the plasma torch and the plasma cutting process as a whole. Results of studies of a complex system for arranging the flow of plasma-forming gas through the channels of the gas-air path in the plasma torch and the subsequent creation of new systems for stabilizing the arc discharge of metal cutting DC plasma torches with high technological capabilities presented. The study was carried out by the methods of numerical simulation of gas-dynamic and thermo-physical pro­cesses for various designs of plasma torches. Optimized designs of plasma torches with various variants of gas-vortex stabilization systems were elaborated. A series of elaborated torches, which includes a single-stream plasma torches ПМВР-5 for precision cutting of medium thickness metals, as well as two-stream plasma torches ПМВР-9 for cutting metals of small and medium thicknesses presented. The last plasma torches use the technology of narrow-jet or compressed plasma and have no domestic analogues. A meth­odology of metal-cutting plasma torches designing by gas-dynamic, thermo-physical and acoustic criteria was elaborated. The results of experimental studies  showed that the use of new ПМВР-5 plasma torches allows to obtain precision cuts corresponding to the 1st and 2nd quality classes according to GOST 14792-80 on steels of the 09Г2С type of medium thickness. It was also shown that the use of new plasma torches makes it possible to perform precision finishing plasma cutting on low-carbon steels of medium thickness (without additional mechanical processing of the cutting edge) in the production technologies of welded joints.