Development of Equipment and Technology for Precision Air-Plasma Cutting of Plate Steel

Abstract

Abstract: This work studies the structure of cutting seams obtained after cutting steel 09G2S with a new PMVR-5.3 narrow-jet plasma torch which has a number of design features in the gas dynamic stabilization system (GDS) of plasma arc. To increase the efficiency of the GDS in the PMVR-5.3 plasma torch, a symmetrical input of plasma-forming gas (PFG) into the flow division system and a gas-dynamic flow stabilizer using two (forming and stabilizing) swirlers with a variable number of swirl channels were used. It is shown that the achieved advantage in the GDS efficiency makes it possible to obtain a high cutting quality on steel 09G2S with a thickness of 40 mm at high productivity and lower energy costs. Analytical methods have proven a high precision degree of cutting with the new torch—a small cut width, no melting and rounding of the upper edge, as well as a grate in the lower part of the cut and splashes in its upper part, almost zero angular deviation, minimal surface microtopography values and width of the thermal impact zone. A metallographic analysis and a hardness measurement detected three subzones in the thermal impact zone with significant structural changes in two of them. Several factors are noted influencing the revealed structuring changes as well as the changes in the elemental composition of the cutting seam surface layer revealed during the X-ray spectral analysis. Attention is drawn to the surface microtopography after plasma cutting. This topography is commensurate by all quality indicators with the postmilling machining of the surface and corresponds to the second class of surface cleanliness. It is proven that the new narrow-jet plasma torch allows performing a high-quality cutting of plate steel with thicknesses up to 40 mm or more. However, the welding of blanks without pre-machining can be carried out at a cut thickness of no more than 20 mm. © 2022, Allerton Press, Inc.