Vol. 26 No. 3 2024 3 EDITORIAL COUNCIL EDITORIAL BOARD EDITOR-IN-CHIEF: Anatoliy A. Bataev, D.Sc. (Engineering), Professor, Rector, Novosibirsk State Technical University, Novosibirsk, Russian Federation DEPUTIES EDITOR-IN-CHIEF: Vladimir V. Ivancivsky, D.Sc. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Vadim Y. Skeeba, Ph.D. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Editor of the English translation: Elena A. Lozhkina, Ph.D. (Engineering), Department of Material Science in Mechanical Engineering, Novosibirsk State Technical University, Novosibirsk, Russian Federation The journal is issued since 1999 Publication frequency – 4 numbers a year Data on the journal are published in «Ulrich's Periodical Directory» Journal “Obrabotka Metallov” (“Metal Working and Material Science”) has been Indexed in Clarivate Analytics Services. Novosibirsk State Technical University, Prospekt K. Marksa, 20, Novosibirsk, 630073, Russia Tel.: +7 (383) 346-17-75 http://journals.nstu.ru/obrabotka_metallov E-mail: metal_working@mail.ru; metal_working@corp.nstu.ru Journal “Obrabotka Metallov – Metal Working and Material Science” is indexed in the world's largest abstracting bibliographic and scientometric databases Web of Science and Scopus. Journal “Obrabotka Metallov” (“Metal Working & Material Science”) has entered into an electronic licensing relationship with EBSCO Publishing, the world's leading aggregator of full text journals, magazines and eBooks. The full text of JOURNAL can be found in the EBSCOhost™ databases.
OBRABOTKAMETALLOV Vol. 26 No. 3 2024 4 EDITORIAL COUNCIL EDITORIAL COUNCIL CHAIRMAN: Nikolai V. Pustovoy, D.Sc. (Engineering), Professor, President, Novosibirsk State Technical University, Novosibirsk, Russian Federation MEMBERS: The Federative Republic of Brazil: Alberto Moreira Jorge Junior, Dr.-Ing., Full Professor; Federal University of São Carlos, São Carlos The Federal Republic of Germany: Moniko Greif, Dr.-Ing., Professor, Hochschule RheinMain University of Applied Sciences, Russelsheim Florian Nürnberger, Dr.-Ing., Chief Engineer and Head of the Department “Technology of Materials”, Leibniz Universität Hannover, Garbsen; Thomas Hassel, Dr.-Ing., Head of Underwater Technology Center Hanover, Leibniz Universität Hannover, Garbsen The Spain: Andrey L. Chuvilin, Ph.D. (Physics and Mathematics), Ikerbasque Research Professor, Head of Electron Microscopy Laboratory “CIC nanoGUNE”, San Sebastian The Republic of Belarus: Fyodor I. Panteleenko, D.Sc. (Engineering), Professor, First Vice-Rector, Corresponding Member of National Academy of Sciences of Belarus, Belarusian National Technical University, Minsk The Ukraine: Sergiy V. Kovalevskyy, D.Sc. (Engineering), Professor, Vice Rector for Research and Academic Aff airs, Donbass State Engineering Academy, Kramatorsk The Russian Federation: Vladimir G. Atapin, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Victor P. Balkov, Deputy general director, Research and Development Tooling Institute “VNIIINSTRUMENT”, Moscow; Vladimir A. Bataev, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Vladimir G. Burov, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Dmitry V. Lobanov, D.Sc. (Engineering), Associate Professor, I.N. Ulianov Chuvash State University, Cheboksary; Aleksey V. Makarov, D.Sc. (Engineering), Corresponding Member of RAS, Head of division, Head of laboratory (Laboratory of Mechanical Properties) M.N. Miheev Institute of Metal Physics, Russian Academy of Sciences (Ural Branch), Yekaterinburg; Aleksandr G. Ovcharenko, D.Sc. (Engineering), Professor, Biysk Technological Institute, Biysk; Yuriy N. Saraev, D.Sc. (Engineering), Professor, V.P. Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, Yakutsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary
Vol. 26 No. 3 2024 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Sukhov A.V., Sundukov S.K., Fatyukhin D.S. Assembly of threaded and adhesive-threaded joints with the application of ultrasonic vibrations...................................................................................................................................... 6 Baraboshkin K.A., Adigamov R.R., Yusupov V.S., Kozhevnikova I.A., Karlina A.I. Thermomechanical rolling in well casing production (research review)......................................................................................................................... 24 Dwivedi R., Somatkar A., Chinchanikar S. Modeling and optimization of roller burnishing of Al6061-T6 process for minimum surface roughness, better microhardness and roundness................................................................................ 52 Ilinykh A.S., Pikalov A.S., Miloradovich V.K., Galay M.S. Experimental studies of rail grinding modes using a new high-speed electric drive...................................................................................................................................................... 66 Karlina Yu.I., Konyukhov V.Yu., Oparina T.A. Assessment of the possibility of resistance butt welding of pipes made of heat-resistant steel 0.15C-5Cr-Mo................................................................................................................................... 79 Gimadeev M.R., Stelmakov V.A., Shelenok E.A. Product life cycle: machining processes monitoring and vibroacoustic signals fi lterings.................................................................................................................................................................... 94 EQUIPMENT. INSTRUMENTS Zakovorotny V.L., Gvindjiliya V.E., Kislov K.V. Information properties of frequency characteristics of dynamic cutting systems in the diagnosis of tool wear....................................................................................................................... 114 Ablyaz T.R., Blokhin V.B., Shlykov E.S., Muratov K.R., Osinnikov I.V. Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products....................................................... 135 Sidorov E.A., GrinenkoA.V., ChumaevskyA.V., Panfi lovA.O., Knyazhev E.O., NikolaevaA.V., CheremnovA.M., Rubtsov V.E., Utyaganova V.R., Osipovich K.S., Kolubaev E.A. Patterns of reverse-polarity plasma torches wear during cutting of thick rolled sheets..................................................................................................................................... 149 MATERIAL SCIENCE Semin V.O., Panfi lov A.O., Utyaganova V.R., Vorontsov A.V., Zykova A.P. Corrosion properties of CuAl9Mn2/ER 321 composites formed by dual-wire-feed electron beam additive manufacturing................................ 163 Dewangan R., Sharma B.P., Sharma S.S. Investigation of hardness behavior in aluminum matrix composites reinforced with coconut shell ash and red mud using Taguchi analysis............................................................................ 179 Saprykina N.А., Saprykin A.А., Sharkeev Y.P., Ibragimov E.А. The eff ect of technological parameters on the microstructure and properties of the AlSiMg alloy obtained by selective laser melting......................................................... 192 Burdilov A.A., Dovzhenko G.D., Bataev I.A., Bataev A.A. Methods of synchrotron radiation monochromatization (research review).................................................................................................................................................................. 208 Burkov A.A., Dvornik M.A., Kulik M.A., Bytsura A.Yu. Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution..................................................................................................................................................................... 234 Pugacheva N.B., Bykova T.M., Sirosh V.A., MakarovA.V. Structural features and tribological properties of multilayer high-temperature plasma coatings........................................................................................................................................ 250 Sharma B.P., Dewangan R., Sharma S.S. Characterizing the mechanical behavior of eco-friendly hybrid polymer composites with jute and Sida cordifolia fi bers.................................................................................................................... 267 Kornienko E.E., Gulyaev I.P., Smirnov A.I., Plotnikova N.V., Kuzmin V.I., Golovakhin V., Tambovtsev A.S., Tyryshkin P.A., Sergachev D.V. Fine structure features of Ni-Al coatings obtained by high velocity atmospheric plasma spraying.................................................................................................................................................................... 286 EDITORIALMATERIALS 298 FOUNDERS MATERIALS 307 CONTENTS
OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 Patterns of reverse-polarity plasma torches wear during cutting of thick rolled sheets Evgeny Sidorov 1, a, *, Artem Grinenko 2, b, Andrey Chumaevsky 1, c, Alexander Panfilov 1, d, Evgeny Knyazhev 1, e, Alexandra Nikolaeva 1, f, Andrey Cheremnov 1, g, Valery Rubtsov 1, h, Veronika Utyaganova 1, i, Ksenia Osipovich 1, j, Evgeniy Kolubaev 1, k 1 Institute of Strength Physics and Materials Sciences SB RAS, 2/4, pr. Akademicheskii, Tomsk, 634055, Russian Federation 2 ITS-Siberia LLC, Krasnoyarsk, 16a Severnoe shosse, 660118, Russian Federation а https://orcid.org/0009-0009-2665-7514, eas@ispms.ru; b https://orcid.org/0009-0002-9511-1303, giga2011@yandex.ru; c https://orcid.org/0000-0002-1983-4385, tch7av@gmail.com; d https://orcid.org/0000-0001-8648-0743, alexpl@ispms.ru; e https://orcid.org/0000-0002-1984-9720, clothoid@ispms.tsc.ru; f https://orcid.org/0000-0001-8708-8540, nikolaeva@ispms.tsc.ru; g https://orcid.org/0000-0003-2225-8232, amc@ispms.tsc.ru; h https://orcid.org/0000-0003-0348-1869, rvy@ispms.tsc.ru; i https://orcid.org/0000-0002-2303-8015, veronika_ru@ispms.ru; j https://orcid.org/0000-0001-9534-775X, osipovich_k@ispms.ru; k https://orcid.org/0000-0001-7288-3656, eak@ispms.tsc.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2024 vol. 26 no. 3 pp. 149–162 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2024-26.3-149-162 ART I CLE I NFO Article history: Received: 16 June 2024 Revised: 22 June 2024 Accepted: 04 July 2024 Available online: 15 September 2024 Keywords: Plasma cutting Macrostructure Wear Nozzle Electrode Heat affected zone Metal melting Cutting parameters Funding The results were obtained in the framework of the Integrated Project “Establishment of production of high-tech equipment for adaptive high-precision plasma heavy cutting of non-ferrous metals for the metallurgical, aerospace and transport industries of the Russian Federation” (Agreement No. 075-11-2022-012 dated April 06, 2022) implemented by the ISPMS SB RAS at the financial support of the Ministry of Education and Science of the Russian Federation as part of Decree of the Government of the Russian Federation No. 218 dated April 09, 2010. Acknowledgements Research was partially conducted at core facility “Structure, mechanical and physical properties of materials” and center “Nanotech” ISPMS RAS. ABSTRACT The introduction describes the features of the process of plasma cutting of various metals and alloys using reverse-polarity plasma torches with and the features of cutting thick sheets. The purpose of the work is to study the wear process of plasma torches operating on reverse polarity current when cutting thick rolled sheets of aluminum and titanium alloys. Research methods include optical and scanning electron microscopy, filming of the cutting process and visual inspection of plasma torch elements after receiving specimens. Results and discussion. The section shows the appearance of the main working elements of the plasma torch after cutting in various modes, which led to both stable and gradual wear and to catastrophic failure of the plasma torch. The results of structural studies of the main characteristic zones of nozzles and electrodes after cutting are presented. The studies carried out made it possible to establish the main reasons for the failure of the working elements reverse-polarity plasma torches. The causes of catastrophic failure of plasma torches include failure to maintain the gap between the nozzle and the electrode and melting of the channel of gas supply into the discharge chamber. The wear of nozzles and electrodes in a stable mode can be intensified due to abnormal operation of the starting arc, the presence of manufacturing inaccuracies and excess gas pressure. In conclusion, the main conclusions based on the results of the research are formulated. The process of wear of electrodes, nozzles and body elements of plasma torches during operation at high electric arc power values is described. For citation: Sidorov E.A., GrinenkoA.V., ChumaevskyA.V., PanfilovA.O., Knyazhev E.O., NikolaevaA.V., CheremnovA.M., Rubtsov V.E., Utyaganova V.R., Osipovich K.S., Kolubaev E.A. Patterns of reverse-polarity plasma torches wear during cutting of thick rolled sheets. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2024, vol. 26, no. 3, pp. 149–162. DOI: 10.17212/1994-6309-2024-26.3-149-162. (In Russian). ______ * Corresponding author Sidorov Evgeny A., Ph.D., Student, Engineer Institute of Strength Physics and Materials Sciences SB RAS, 2/4, pr. Akademicheskii, 634055, Tomsk, Russian Federation Tеl.: +7 382 228–68–63, e-mail: eas@ispms.ru
OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 Introduction Plasma cutting of various metals and alloys has advantages for industrial applications related to high productivity, cutting quality and the ability to cut hot-rolled plates [1–3]. The plasma cutting is an effective method for obtaining workpieces from steels [4], aluminum [5], copper [6], titanium [7] alloys. When cutting, it is possible both to form a clear cut at an angle of 90 degrees to the surface of the sheet, and to form the necessary cutting edges for further welding of structures [8]. Mainly, equipment operating on direct polarity current [9, 10], which has limitations for cutting hot-rolled plates, is used for plasma cutting. The use of plasma cutting technology with reverse polarity current makes it possible to increase the productivity of the process [11–14], especially in the production of large capacity workpieces. Actually in the literature there is quite a small amount of data on cutting of non-ferrous metal and alloy sheets with a thickness of about 30–100 mm [15–18]. At the same time, plasma cutting of thick plates has difficulties associated with high values of plasma arc current and its intensive impact on the working elements of the plasma torch. In addition to studies aimed at establishing the influence of cutting process parameters on the surface quality and structural-phase changes in the impact of the plasma jet on the material [12, 16], it is necessary to carry out work in the field of changing the state of the plasma torch during cutting. This is especially relevant from the point of view of economic efficiency of plasma cutting with reverse polarity current, since it is characterized by a lower degree of wear of plasma torch elements during operation [11]. Plasma cutting with reverse polarity current, despite the long operating time, is a promising method for obtaining workpieces from thick plates in industry. Plasma cutting with reverse polarity current is the most relevant for obtaining workpieces from thick sheet metal. This is due to the lower current values at the same thickness of the cut plates in comparison with cutting with direct polarity current. The systems with a hollow anode used for cutting with reverse polarity current allow obtaining lower current density on its surface in comparison with thermochemical cathodes for cutting with direct polarity current, which also contributes to the increase of plasma torch life. For these reasons, plasma cutting with reverse polarity current for thick plates is more relevant both in terms of process efficiency and from the point of view of equipment reliability and durability. In this direction, the development of modern design solutions and the development of domestic plasma cutting equipment with a number of advantages in comparison with existing analogues are currently required. At present time, within the framework of the joint project of ISPMS SB RAS and “ITS-Siberia” modern equipment for plasma cutting of thick rolled non-ferrous metals and alloys of large thicknesses with a reverse polarity current is being developed. The purpose of this work is to identify the main regularities of the process of failure of working elements of plasma torches of the developed design depending on various factors in the cutting process. Materials and methods The studies were carried out at the manufacturing area of “ITS–Siberia” and on experimental equipment at ISPMS SB RAS. Cutting was carried out on a plasma torch with reverse polarity, developed in the course of a joint scientific and technical project. The scheme of the plasma cutting process is shown in Figure 1, a. The plates 1 were cut by a plasma jet 2 formed in the environment of a protective and plasma-forming gas 3 due to the burning of the starting arc 4 at the start of the process and the working arc 5 during cutting. The supply of protective and plasma-forming gas 6 to the cutting zone is performed at fixed pressure from the compressor. Nozzle 7 is fixed by a nut 8 and serves to form a dense jet of gas and plasma 9 formed by swirl ring 10 and arcing. Additionally, the plasma torch of the developed design provides for the introduction of water 11 into the cutting zone through the hole in the working electrode 14. This allows increasing the quality of the cut and reducing the wear of the nozzle and electrode [19, 20]. Protection against overheating of the nozzle and electrode is also provided by a constant flow of water 12 through channels in the body 13. Water supply in the plasma torch is arranged in such a way that the flow 13 first washes the nozzle, then the electrode, and then is carried partially to the exit of the plasma torch and into the inner cavity of the nozzle and then by the flow 11 into the working zone. Current is supplied to the electrode through a copper
OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 solenoid 15, additionally forming a magnetic field to focus the plasma flow and electric arc. The inner body of the plasma torch 16 with water and air supply channels is made of fluoroplastic, and the outer body 17 is made of steel. The working electrode 14 (Figure 1, b) and nozzle 7 (Figure 1, c) are made of M1 copper. Operation of the plasma torch in the standard mode is associated with the formation of a plasma jet around the plasma-forming arc (Figure 1, d). Water supply to the cutting zone leads to the formation of “water mist” 18 (Figure 1, d). The presence of water mist during cutting accelerates the process of material cooling and makes it possible to cut aluminum alloys without a protective atmosphere in the form of nitrogen, since the oxidation of the edge is minimal and the quality of the cut is high enough [19, 20]. The main difficulties in cutting arose at the start of the process, when the starting arc is ignited and then the working arc 19 with the plasma column is formed (Figure 1, e). In this case, if the process is normal, the plasma column is formed, the arc is short-circuited between the sheet and the electrode, and the plasma jet is turned off (Figure 1, d). If there are problems at the start, the effect of external arcing can be realized (Figure 1, f), when the ignition of the working arc does not support the formation of a plasma jet. Cutting was carried out according to the modes typical for aluminum and titanium alloy plates 60–100 mm thick. The development and optimization of cutting modes for hot-rolled non-ferrous metal plates was carried out earlier in [13–16]. The current of the electric arc ranged from 300 to 370A, the voltage from 300 to 400 V, the height of the plasma torch above the surface of the plate during the cutting process was from 16 to 25 mm. The gas pressure was from 2.0 to 4.0 bar, the water pressure in the system before entering the plasma torch cooling circuit was 6 bar, the gap between the nozzle and the electrode was from 0.5 to 2.0 mm. Cutting speed was from 250 to 3,000 mm/min. Air was used as a plasma-forming gas. The main Fig. 1. The operational scheme of the reverse-polarity plasma torch (a), the appearance of the working electrode (b) and nozzle (c), the cutting process under normal conditions (d), the start of the cutting process (e), the process of external arc burning (f) and cutting with excess speed (g): 1 – plate; 2 – plasma jet; 3 – gas flow; 4 – starting arc; 5 – working arc; 6 – flow of plasma-forming and protective gas; 7 – nozzle; 8 – external nut; 9 – vortex flows of gas and plasma; 10 – swirl ring; 11 – water supply to the hollow electrode; 12 – supply of cooling water to the plasma torch body; 13 – water cooling channels; 14 – electrode; 15 – solenoid; 16 – inner casing made of fluoroplastic; 17 – outer steel casing; 18 – “water mist”; 19 – arc burning at the moment of starting; 20 – external arc burning
OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 purpose of the work was to describe the characteristic wear patterns of nozzles and electrodes of the plasma torch during operation and to identify the causes of its occurrence. After obtaining experimental samples of worn-out plasma torch nozzles and electrodes, specimens for structural studies were cut out of it using the electrical discharge machining (DK7750 machine). Structural studies were carried out on an optical microscope Altami MET 1C, laser scanning microscope Olympus LEXT 4100 and scanning electron microscope Zeiss LEO EVO 50. Results and discussion Plasma cutting of hot-rolled products at currents of more than 300 A results in significant damage to consumables (Figure 2). The most significant damage occurs during the starting of process during operation of the starting arc, after that the main mechanism of nozzle and electrode wear is erosion during interaction with the gas-plasma flow. At the initial stage of the process, the accuracy of the interface between the nozzle and the electrode is of particular importance, the gap in which for a plasma torch of this design should be about 1.0–1.5 mm. Fig. 2. The appearance of nozzles (a, c, e, g, i, k) and electrodes (b, d, f, h, j, l) before testing (a, b), when tested in the condition of non-observance of the gap between the nozzle and electrode (c, d), when testing with melting of the gas supply holes in the swirl ring (e, f), when testing without turning off the starting arc (g, h) and with insufficiently precise manufacturing of the nozzle (i, j) under conditions of low gas pressure, and when tested in optimal cutting conditions without defects (k, l)
OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 With a small gap, the risk of prolonged double arcing during the operation stage or short circuit to the discharge chamber when arcing increases, which can lead to catastrophic failure of the working elements (Figure 2, c, d). One of the reasons for the plasma torch failure can be the melting of holes in the swirl ring, leading to a sharp increase in temperature in the cavity between the electrode and the nozzle due to the lack of heat removal by the gas flow (Figure 2, e, f). As a result, the metal of the nozzle and electrode melts sharply and the nozzle hole is blocked. The process of gradual wear of the nozzle and electrode material is mainly associated with hightemperature erosion during the interaction of copper with the plasma and gas flow (Figure 2, g–l). This process can be further complicated by the operation of the starting arc during cutting (Figure 2, g, h) or by inaccuracy in the manufacture of plasma torch elements (Figure 2, i, k). With an average operating time per failure of more than 250–300 starts of consumable elements (nozzle and electrode) in the process of cutting hot-rolled plate (up to 100 mm) products, untimely starting arcing off or inaccuracies in manufacturing can reduce this parameter to 100–150 starts. The processes of catastrophic failure of plasma torch lead to its abrupt failure even after one start. The reason is mainly insufficient clearance between nozzle and electrode. The temperature in the zone of the discharge chamber rises so high in a short time that the metal begins to melt and boil, leaving a characteristic structure on the surface in the form of a melting zone with a large number of pores (2 in Figure 3). Moreover, there are practically no traces of oxides or erosion products on the electrode surface, and the thin melting zone 2 passes into the base metal 1 (Figure 3, a, c–e). The inner surface of the nozzle has traces of oxidation, metal boiling and erosion (Figure 3, b, f–h). The metal entering the nozzle channel quickly crystallizes and plugs it. The Fig. 3. The structure of plasma torch elements after a catastrophic failure of the nozzle and electrode with insufficient clearance between it: a, b – macrostructure of the electrode and nozzle, c–e – microstructure of individual sections of the electrode; f–h – microstructure of nozzle sections
OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 pores in the melted material are mainly spherical 3 or irregularly shaped 4 (Figure 3). On the plasma torch of the developed design, gas pressure less than 2 bar increased the risk of formation of this phenomenon. Increasing the pressure above 2.5-3.0 bar and setting the gap between the nozzle and the electrode not less than 1.0-1.5 mm practically canceled the risk of failure of the plasma torch as a result of double arc formation or short circuit in the discharge chamber. The second type of catastrophic failure of plasma torches of this design is melting of channels in the swirl ring (Figure 4). In this case, during operation, due to the fairly close location of the junction of the swirl ring and nozzle to the discharge zone (Figure 4, b), its partial fusion may occur. During operation, the distortion of the elements in this area gradually accumulates under the action of the starting arc to such an extent that the gas supply holes are partially blocked, which causes the temperature of the nozzle and electrode to rise sharply. Then, as in the previous case, it suddenly melts, boils and plugs the nozzle hole. At the same time, on the surface of both the electrode and the nozzle there are signs of erosion and oxidation during operation. This phenomenon occurs partly for design reasons, and partly due to insufficient clearance between the electrode and the nozzle during assembly. It is possible to reduce the risk of this process by adjusting this clearance at a level of 1.0–1.5 mm. During plasma cutting, ignition of the starting arc between the electrode and the nozzle forms the initial plasma flow into the cutting zone, after which it is switched to the working arc and cutting in the normal mode. If the starting arc is not switched off in time during operation, it is possible to increase the intensity of wear of working elements of the plasma torch and formation of deposits on the electrode surface (Figure 5). According to the data of scanning electron microscopy, the composition of deposits (5, 6 in Figure 5) Fig. 4. The structure of plasma torch elements after a catastrophic failure of the nozzle and electrode due to clogging of the gas supply channels in the swirl ring: a, b – macrostructure of the electrode and nozzle, c–e – microstructure of individual sections of the electrode; f–h – microstructure of nozzle sections
OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 includes impurities that were part of the water, copper and oxygen. There is also a significant amount of oxygen on the nozzle surface. Nozzle and electrode wear accelerates in comparison with wear in normal mode, but in this case, the consumables withstood up to 150 starts when cutting hot-rolled products. Separately, we can emphasize the influence of nozzle and electrode manufacturing accuracy on the wear of working elements. When operating in normal mode without a significant excess of wear intensity of the working elements of the plasma torch, deviation from the nominal position of the nozzle hole causes its uneven wear (Figure 6). In the case presented in Figure 6, when manufacturing the nozzle, the misalignment of the nozzle outlet and conical nozzle cavity of the order of 0.4-0.5 mm was allowed. This caused the initial deviation of the arc and plasma column during cutting from the vertical orientation and more significant wear at an angle to the vertical axis, which with the time of operation increased and led to even more significant changes in the shape of the nozzle. The irregularity of electrode wear is also evident. Timely starting arcing off, control and observance of the gap between the nozzle and electrode, gas pressure in the system and water supply lead to a small risk of catastrophic wear of consumables and formation of deposits on the electrode surface. However, uneven wear leads to deviation of the plasma jet from its nominal position and, as a consequence, to insufficient cut quality after 100–150 starts. For this reason, the alignment of the hole at the outlet and in the conical part in the nozzle of the plasma torch should be at a high enough level to ensure the accuracy of the cut during operation of the plasma torch. Cutting of specimens in the standard mode is characterized by the minimum intensity of wear of consumable elements, which is shown in Figure 2, l, k. Increasing the gas (air) pressure in the system from 2.0–2.5 to 3.0–3.5 bar increases the service life of consumable elements of the plasma torch by more than two times and reduces the risk of double arcing during operation. Increasing the pressure in the discharge Fig. 5. The structure of the plasma torch elements after the gradual failure of the nozzle and electrode during constant operation of the starting arc: a, b – macrostructure of the electrode and nozzle; c–e – microstructure of individual sections of the electrode; f–h – microstructure of nozzle sections
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
OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 its outlet leads to a faster failure of both the nozzle itself and the working electrode due to uneven wear. In addition, increased wear of the working elements of the plasma torch can ensure untimely starting arcing off when switching to the operating mode. In normal operation, the wear of the working elements of the plasma torch developed during the implementation of the joint project of ITS Siberia and ISPMS SB RAS when cutting aluminum and titanium alloy sheets up to 100 mm thick with a reverse polarity current, although quite intense in comparison with cutting sheet metal of smaller thicknesses, currently allows for more than 250–300 starts with different cutting lengths. References 1. Wen J., He L., Zhou T., Tian P., Zhou T., Feng Z. Modeling of the polycrystalline cutting of austenitic stainless steel based on dislocation density theory and study of burr formation mechanism. Journal of Mechanical Science and Technology, 2023, vol. 37 (6), pp. 2855–2870. DOI: 10.1007/s12206-023-0512-8. 2. Akkurt A. The effect of cutting process on surface microstructure and hardness of pure and Al 6061 aluminium alloy. Engineering Science and Technology, an International Journal, 2015, vol. 18 (3), pp. 303–308. DOI: 10.1016/j. jestch.2014.07.004. 3. Levichev N., Tomás García A., Dewil R., Duflou J.R. A virtual sensing approach for quality and productivity optimization in laser flame cutting. The International Journal of Advanced Manufacturing Technology, 2022, vol. 121, pp. 6799–6810. DOI: 10.1007/s00170-022-09750-8. 4. He G.-J., Gu L., Zhu Y.-M., Chen J.-P., Zhao W.-S., Rajurkar K.P. Electrical arc contour cutting based on a compound arc breaking mechanism. Advances in Manufacturing, 2022, vol. 10 (4), pp. 583–595. DOI: 10.1007/ s40436-022-00406-0. 5. Wei J., He W., Lin C., Zhang J., Chen J., Xiao J., Xu J. Optimizing process parameters of in-situ laser assisted cutting of glass–ceramic by applying hybrid machine learning models. Advanced Engineering Informatics, 2024, vol. 62, p. 102590. DOI: 10.1016/j.aei.2024.102590. 6. Shulyat’ev V.B., Gulov M.A., Karpov E.V., Malikov A.G., Boiko K.R. Laser cutting of aluminum alloys using pulsed radiation from a CO2 laser under conditions of an optical discharge in an argon jet. Bulletin of the Lebedev Physics Institute, 2023, vol. 50 (suppl. 10), pp. S1075–S1078. DOI: 10.3103/S1068335623220116. 7. Barsukov G.V., Selemenev M.F., Zhuravleva T.A., Kravchenko I.N., Selemeneva E.M., Barmina O.V. Influence of the parameters of chemical thermal treatment of copper slag particles on the quality of hydroabrasive cutting. Journal of Machinery Manufacture and Reliability, 2023, vol. 52 (7), pp. 679–686. DOI: 10.1134/S1052618823070075. 8. Boulos M.I., Fauchais P., Pfender E. Plasma torches for cutting, welding and PTA coating. Handbook of Thermal Plasmas. Cham, Springer, 2023. DOI: 10.1007/978-3-319-12183-3_47-2. 9. Sharma D.N., Kumar J.R. Optimization of dross formation rate in plasma arc cutting process by response surface method. Materials Today: Proceedings, 2020, vol. 32, pp. 354–357. DOI: 10.1016/j.matpr.2020.01.605. 10. Shchitsyn V.Yu., Yazovskikh V.M. Effect of polarity on the heat input into the nozzle of a plasma torch. Welding International, 2002, vol. 16 (6), pp. 485–487. DOI: 10.1080/09507110209549563. 11. Ilii S.M., Coteata M. Plasma arc cutting cost. International Journal of Material Forming, 2009, vol. 2 (suppl. 1), pp. 689–692. DOI: 10.1007/s12289-009-0588-4. 12. Gostimirović M., Rodic D., Sekulić M., Aleksic A. An experimental analysis of cutting quality in plasma arc machining. Advanced Technologies & Materials, 2020, vol. 45 (1), pp. 1–8. DOI: 10.24867/ATM-2020-1-001. 13. Grinenko A.V., Knyazhev E.O., Chumaevskii A.V., Nikolaeva A.V., Panfilov A.O., Cheremnov A.M., Zhukov L.L., Gusarova A.V., Sokolov P.S., Gurianov D.A., Rubtsov V.E., Kolubaev E.A. Structural features and morphology of surface layers of AA2024 and AA5056 aluminum alloys during plasma cutting. Russian Physics Journal, 2023, vol. 66, pp. 925–933. DOI: 10.1007/s11182-023-03025-9. 14. Chumaevskii A.V., Nikolaeva A.V., Grinenko A.V., Panfilov A.O., Knyazhev E.O., Cheremnov A.M., Utyaganova V.R., Beloborodov V.A., Sokolov P.S., Gurianov D.A., Kolubaev E.A. Structure formation in surface layers of aluminum and titanium alloys during plasma cutting. Physical Mesomechanics, 2023, vol. 26, pp. 711–721. DOI: 10.1134/S1029959923060103. 15. Rubtsov V.E., Panfilov A.O., Knyazhev E.O., Nikolaeva A.V., Cheremnov A.M., Gusarova A.V., Beloborodov V.A., Chumaevskii A.V., Ivanov A.N. Development of plasma cutting technique for C1220 copper, AA2024 aluminum alloy, and Ti-1,5Al-1,0Mn titanium alloy using a plasma torch with reverse polarity. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2022, vol. 24, no. 4, pp. 33–52. DOI: 10.17212/1994-6309-2022-24.4-33-52.
OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 16. Rubtsov V.E., Panfilov A.O., Knyazhev E.O., Nikolaeva A.V., Cheremnov A.M., Gusarova A.V., Beloborodov V.A., Chumaevskii A.V., Grinenko A.V., Kolubaev E.A. Influence of high-energy impact during plasma cutting on structure and properties of surface layers of aluminum and titanium alloys. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2023, vol. 25, no. 4, pp. 216–231. DOI: 10.17212/1994-6309-2023-25.4-216-231. (In Russian). 17. Matushkina I., Anakhov S., Pyckin Yu. Design of a new gas-dynamic stabilization system for a metalcutting plasma torch. Journal of Physics: Conference Series, 2021, vol. 2094, p. 042075. DOI: 10.1088/17426596/2094/4/042075. 18. Gariboldi E., Previtali B. High tolerance plasma arc cutting of commercially pure titanium. Journal of Materials Processing Technology, 2005, vol. 160 (1), pp. 77–89. DOI: 10.1016/j.jmatprotec.2004.04.366. 19. Cinar Z., Asmael M., Zeeshan Q. Developments in plasma arc cutting (PAC) of steel alloys: a review. Jurnal Kejuruteraan, 2018, vol. 30 (1), pp. 7–16. DOI: 10.17576/jkukm-2018-30(1)-02. 20. Kudrna L., Fries J., Merta M. Influences on plasma cutting quality on CNC machine. Multidisciplinary Aspects of Production Engineering, 2019, vol. 2, pp. 108–117. DOI: 10.2478/mape-2019-0011. Conflicts of Interest The authors declare no conflict of interest. 2024 The Authors. Published by Novosibirsk State Technical University. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0).
RkJQdWJsaXNoZXIy MTk0ODM1