The influence of plasma gas on changes in chemical composition and structures during the cutting process

Cutting is usually one of initial and basic operations of the manufacturing process of welded structures and realization constructions elements. Thermal cutting, in particular plasma arc cutting is often used to prepare elements. The plasma arc cutting process involves melting and ejecting the liquid metal from the cutting gap with a highly concentrated plasma electric arc which is generated between the non-consuable electrode and the workpiece. The paper presents the results of research on the influence of plasma gas on structural changes and chemical compositions changes resulting unalloyed steel cutting by air plasma arc. It was shown that in the air plasma arc cutting process the amorphous layer with a very high nitrogen content (about 1.6%) and a hardness of 750 HV 0.2 was used. This high nitriding effect is due to the diffusion of nitrogen from the plasma gas. As a result of the interaction of air plasma arc gases on the liquid metal, the cutting surface is carburized (about 0.5%). The alloy components are also burnt according to the theory of selective oxidation of chemical elements. The material structure after the air plasma cutting process shows the structures between the structure formed after oxygen cutting processs and nitrogen plasma cutting process. The process of argon-hydrogen plasma cutting has the least influence on the cut material.

Comparison of laser beam, oxygen and plasma arc cutting methods in terms of their advantages and disadvantages in cutting structural steels

The laser beam, plasma arc, and oxygen cutting methods are widely used in metal cutting processes. These methods are quite different from each other in terms of initial setup cost and cutting success. A powered laser beam is used in laser beam cutting, plasma is used in plasma arc cutting, flammable gas - oxygen mixture is used in the oxygen cutting method. In this study, the cutting success of these methods was investigated on tensile specimens. Microstructure, hardness (HV 0.1), surface roughness, and strengths were investigated after the cutting process. The tensile test implemented with tensile samples cut from the same material by these three methods, it was observed that the strength values of the samples changed by about 8% in tensile strength depending on the cutting process. The hardness of the cut surfaces in plasma arc cutting increased from 150 HV to 230 HV for S235JR material. For this reason, it is difficult to perform machining operations after plasma cutting. The hardness value reached after laser beam cutting is 185 HV. Plasma arc cutting is more cost-effective than laser beam cutting. 1-3° vertical inclination (conicity) occurs on the cut surface in plasma arc cutting, while this inclination almost does not occur in laser cutting. In plasma cutting benches, cutting is done with oxygen, and in cutting with oxygen, the taper is seen in a small amount.

Experimental Study of the Effect of Plasma Cutting on the Tensile Strength of Materials "Fe"

The cutting process in plasma cutting begins with the formation of a pilot arc between the electrode and the workpiece as a result of the electrical ionization reaction of the highly conductive cutting gas. The gas is heated by the pilot arc until its temperature rises very high then the gas will be ionized and become a conductor of electricity. When the gas stream leaves the nozzle, the gas expands rapidly carrying the molten metal so that the cutting process continues. This plasma temperature can reach 33,000°C, approximately 10 times the temperature produced by the reaction of oxygen and acetylene. If this is related to the mechanical properties of the material, where the material has been heated it will result in changes in the mechanical properties of the material in the heating area/around the cutting plane. Tensile testing is the most widely used type of test because it is able to provide representative information on the mechanical behavior of the material. Seeing an incident like this, it is necessary to test the Effect of Plasma Cutting on the Tensile Strength of 'Fe' Materials through a tensile test. Several studies have shown that torch height, amperage and cutting speed can affect material properties. The best tool parameter settings are obtained at a travel speed of 500 mm/min, 75 amperes and a torch-material distance of 3 mm so that these settings are used as a reference in this study. In analyzing the data, the authors compare the results of plasma cutting testing with conventional cutting, in order to know the changes in mechanical properties that occur.

Effect of Steel-Cutting Technology on Fatigue Strength of Steel Structures: Tests and Analyses

This paper presents the results of comparative fatigue tests carried out on steel S355J2N specimens cut out using different cutting methods, i.e., plasma cutting, water jet cutting, and oxyacetylene cutting. All the specimens were subjected to cyclic loading from which appropriate S-N curves were obtained. Furthermore, face-of-cut hardness and roughness measurements were carried out to determine the effect of the cutting method on the fatigue strength of the tested steel. The fatigue strength results were compared with the standard S-N fatigue curves. The fatigue strength of the specimens cut out with oxyacetylene was found to be higher than that of the specimens cut out with plasma even though the surface roughness after cutting with plasma was smaller than in the case of the other cutting technology. This was due to the significant effect of material hardening in the heat-affected zones. The test results indicate that, in comparison with the effect of the cutting technology, the surface condition of the specimens has a relatively small effect on their fatigue strength.

Experimental study of mild steel cutting process by using the plasma arc method

Purpose: In this study, plasma arc cutting (PAC) is an industrial process widely used for cutting various away types of metals in several operating conditions. Design/methodology/approach: It is carried out a systematic or an authoritative inquiry to discover and examine the fact, the plasma cutting process is to establish the accuracy and the quality of the cut in this current paper assessed a good away to better the cutting process. Findings: It found that the effect of parameters on the cutting quality than on the results performed to accomplish by statistical analysis. Research limitations/implications: The objective of the present work paper is to achieve cutting parameters, thus the quality of the cutting process depends upon the plasma gas pressure, scanning speed, cutting power, and cutting height. Practical implications: The product of the plasma cutting process experimentally has been the quality of the cutting equipment that was installed to monitor kerf width quality by exam the edge roughness, kerf width, and the size of the heat-affected zone (HAZ). Originality/value: The results reveal that were technically possessed of including all the relevant characteristics, then a quality control for the cutting and describe the consequence of the process parameters.

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.