Complex Alloying of Low carbon Steel by Mineral Concentrates Under Electroslag Remelting Procedia Engineering 165 ( 2016 ) 1496 – 1502 1877 7058 © 2016 Published by Elsevier Ltd This is an open access[.]
Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 165 (2016) 1496 – 1502 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development” Complex alloying of low-carbon steel by mineral concentrates under electroslag remelting Evgeniy Kuzmichev a,*, Hosen Ri b, Sergey Nikolenko c, Denis Balakhonov a a Far Eastern State Transport University, Serysheva str 47, Khabarovsk, 68002, Russia b Pacific State University 136, Tikhookeanskaya str 136, Khabarovsk, 680035, Russia c Far Eastern Branch of Russian Academy of Sciences, Tikhookeanskaya str 153, Khabarovsk, 680035, Russia Abstract The paper considers the issues of complex utilization of mineral raw materials of the Far Eastern region to produce complex alloyed steels by electroslag remelting (ESR) The authors show the possibility of simultaneous use of different mineral concentrates containing tungsten, zirconium and titan for complex alloying of the remelted low-carbon steel The alloys obtained as result of series of experiments are studied from the point of view of their composition and structure © by Elsevier Ltd This is an open access article under the CC BY-NC-ND license 2016Published The Authors Published by Elsevier Ltd © 2016 (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground Peer-review under scientific committee of the 15th International scientific conference “Underground Urbanisation as a Urbanisation as aresponsibility Prerequisite of forthe Sustainable Development Prerequisite for Sustainable Development Keywords: mineral raw materials, electroslag remelting (ESR), complex alloying Introduction Multipurpose use and complex utilization of mineral raw materials without their deep technological processing is a topical and perspective research field of nowadays It is of especial current importance for the Russian Far East as the region is rich in minerals Research work in this field has resulted in profound experience of using mineral raw materials for production of alloying welding-surfacing materials and metal alloyed with such valuable alloying elements as tungsten, zirconiumium, titanium, boron, etc However, despite the results achieved, many issues * Corresponding author Tel.: +7-962-220-50-80 E-mail address: e_kuzmichev@mail.ru 1877-7058 © 2016 Published by Elsevier Ltd This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development doi:10.1016/j.proeng.2016.11.885 Evgeniy Kuzmichev et al / Procedia Engineering 165 (2016) 1496 – 1502 1497 remain insufficiently explored and require advanced consideration Complex alloying of metal during ESR using mineral raw materials is one of such issues [1 – 4] Complex alloying technology is applied in metallurgy to produce the most part of structural and tool alloyed steels This process involves using ferroalloys, pure alloying elements or any other adding materials as sources of alloying elements, whose production is costly and environmentally hazardous This makes the industrial technology of complex alloying labor intensive, costly and ecologically harmful In this case using low degree processed mineral raw materials as a source of alloying elements (mineral concentrates and ores) is regarded as more promising [5, 6, 7] Use of mineral raw materials without their deep technological processing will exclude labor extensive and environmentally harmful stages of production, which will simplify technology, cut production costs and improve environmental safety [8 – 10] In this case ESR is an advantageous technology for alloyed metal production ESR ensures production of high quality metal as the production process excludes the interaction of metal with the atmospheric gases and materials the casting mould is made of Slag bath serves as active refining environment, assimilates non-metal inclusions and makes alloying metal possible [11 – 15] Therefore, the major purpose of this research is studying complex alloying of metal under ESR using minerals containing oxides of alloying elements The research is intended to resolve the following tasks: to study possibilities for complex alloying with elements contained in two mineral concentrates and having low and high degrees of activity – tungsten and zirconium to study possibilities for complex alloying with elements contained in three mineral concentrates – tungsten, zirconium and titanium (one of them is an intermediate-level activity element) to study the possibilities for complex alloying by the elements contained in mineral concentrate and standard ferroalloy – tungsten and chrome 1498 Evgeniy Kuzmichev et al / Procedia Engineering 165 (2016) 1496 – 1502 Methodology of the experiment and materials Setting forth the problem of producing alloyed steels under sustainable development conditions Studying and analyzing data on producing alloyed steels using mineral associations Principles of selecting mineral associations for alloying steels Preliminary experimental research in deoxidizer selection Analysis of the experimental data Hypothesis on the possibility of complex alloying using mineral ssociations Development of the composition of charge ESR (Electroslag remelting) using the developed composition of charge Research of the composition, structure and properties of alloyed steel Conclusions Fig Methodology chart for alloyed steels production The set forth tasks were solved in accordance with the methodology presented in Fig.1 A number of ceramic alloying fluxes has been developed on the basis of mineral raw materials Principles of sustainable development that imply complex utilization of mineral raw materials in their mining area under environmentally sound conditions have been the guiding principle in this development process The composition of the raw materials used is as follows: fluorite concentrate, wt %: CaF2 – 90.0; SiO2 – 2.9; CaCO3 – 2.9; S 0.10; P 0.01; other 4.2; scheelite concentrate, wt %: WO3 – 60.05, CaO – 24.11, SiO2 – 3.11, Fe2O3 – 4.13, P2O5 – 4.62, Cu – 0.08, CO2 – 0.34, Al2O3 – 0.26, K2O – 0.08, MgO – 1.65, S – 0.61, TiO2 – 0.2, FO – 0.61, NaO2 – 0.15; zirconium concentrate, wt %: 1499 Evgeniy Kuzmichev et al / Procedia Engineering 165 (2016) 1496 – 1502 ZrO2 – 52; SiO2 – 45.4; Al2O3 – 1.9; CaO – 0.4; other – 0.3; rutile concentrate, wt %: TiO2 – 94, Al2O3 – 0.6, Fe2O3 – 2, SiO2 – 1.5, ZrO2 – 0.78, P2O5 – 0.07, SO3 – 0.05 Carbon in its graphite form was chosen as reducer of alloying elements on the basis of preliminary experiments When such strong carbide-forming elements as titanium, zirconium and tungsten contained in mineral raw material are reduced with carbon, this creates precondition for formation of carbide phases Compositions of experimental fluxes are presented in Table The fluxes were produced in accordance with standard technologies After the components were dosed in accordance with the calculated formulation, dry furnace charge mixture was being mixed for an hour in a mixer of tumbling barrel type Fluxes were prepared as follows: after mixing the charge with liquid glass, damp raw mass was rubbed through a fine sieve (1.5 mm holes) and further dried the temperature of 150 200 °С for 1.5 hour After being dried, the flux was bolted through a sieve (30 holes per cm2) and was tempered at 450 °С for three hours Taking into consideration high hygroscopicity of ceramic fluxes, they were heat treated at 380…400 °С before use Experiments were conducted in ESR plant Low carbon welding wire Sv-08A (diameter mm, GOST 2246-70) was used as electrode core wire Remelting was conducted at the voltage of 40…45 V and the current of 300…400 А Table Composition of experimental fluxes, wt % Flux Scheelite Zirconium concentrate Fluorite Graphite Ferrochromium FХ200 Rutile concentrate F1 19 19 42 20 - - F2 10 10 40 30 10 - F3 60 - 20 10 - 10 The ingots produced were cut into samples The elemental composition of samples was studied with X-ray spectrometer "Spetroscan MAKS-GV" Studying structure under microscopic analysis was performed with metallographic microscope ЕС МЕТАМ РВ-21 (magnification х1000) and hardware-and-software complex for metallographic analysis “SpectrMet-5.6” Specific features of the materials produced were studied with scanning electron microscope Carl Zeiss EVO 40HV as a unit with energy dispersive spectroscopy Oxford Instruments INCA ENERGY X-Sight 350 Phase composition was studied with X-ray diffractometer "DRON-7" in Сu КD-emission Results and discussions Remelting experimental fluxes resulted in the corresponding alloys Their chemical compositions are presented in Table Table Chemical composition of experimental alloys, wt % Alloy W Mn Cr Si C S P Zr Ti A1 2.8 0.38 0.06 1.7 0.0046 0.147 1.07 - A2 2.43 0.34 0.05 1.53 2.02 0.03 0.03 0.37 4.44 A3 10.4 0.158 1.34 0.178 0.95 0.035 0.105 - - Alloy A1 was alloyed by tungsten and zirconium that have significantly different isobaric potentials Zirconium’s high activity influenced its transition into alloy Its content in built-up metal is 2.6 times less than the content of tungsten while their contents in the charge were approximately equal In addition to sensitivity to oxygen, zirconium and tungsten’s transfer into alloy is evidently influenced by silicon as the content of silicon dioxide in zirconium concentrate is considerable (45.4 wt %) As silicon has a lower sensitivity to oxygen, its more intensive reduction causes deficit of reductor in respect of zirconium and tungsten which decreases their transition into alloy 1500 Evgeniy Kuzmichev et al / Procedia Engineering 165 (2016) 1496 – 1502 Microstructure of alloy A1 is the one of hypereutectoid steel with developed carbide phase and consists of finedispersed pearlite grains disposed in intercrystalline space and partially inside the cementite grains Microroentgen spectral analysis showed that tungsten is mainly concentrated in inclusions of 1…4 micron (Fig 2) and, in a lesser concentration, in alloy matrix The most part of zirconium is contained in uniformly distributed regular-shaped inclusions (Fig 3) X-ray phase analysis of the alloy showed presence of zirconiumium carbides ZrC, and compound tungsten and iron based carbides Fe3W3C Fig Alloy A1 backscattered electron image and spectrum in point Fig Alloy A1 backscattered electron image and spectrum in point The experiment ascertained the possibility of complex alloying of steel with tungsten of low activity and zirconium of high activity, which provides us with the reason to consider alloying with intermediate-level activity elements possible The assumption found its confirmation in the chemical analysis of Alloy A2 The experiment showed the possibility of complex alloying with elements contained in the form of oxides as constituents of concentrates and having different isobaric potentials Comparison of this data with the data of the previous experiment draws our attention to the following patterns of relationships Twofold decrease in the amount of scheelite and zirconium concentrate in the charge and additional injection of rutile concentrate decreased tungsten content insignificantly (1.15 times) whereas the zirconium content decreased considerably (2.89 times) In our Evgeniy Kuzmichev et al / Procedia Engineering 165 (2016) 1496 – 1502 1501 opinion in this case, as well as in the previous experiment, significant amount of silicon dioxide decreased the transition of zirconium, as the most active element, into alloy Another factor that contributed to significant differences in the amount of elements’ transitions into alloy is the increase in the amount of reductor towards the concentrates in the charge (the previous experiment obviously lacked reductor), which ensured more complete tungsten reduction and facilitated silicon reduction (its amount is comparable with the amount used in the previous experiment) Titanium demonstrates the highest degree of transition into alloy This can be explained by several reasons Firstly, the content of titanium in rutile concentrate and, correspondingly, in the flux charge is 1.6 and 1.8 times higher than the content of tungsten oxide and zirconium oxide Secondly, titanium’s intensive reduction is determined by its significant sensitivity to carbon (strong carbine forming capacity) that exceeds the sensitivity to carbon of both tungsten and zirconium This factor facilitated formation of titanium carbides and their presence was confirmed by both microroentgen and spectral, and roentgen-phase analyses Microstructure of Alloy A2 is of ledeburite class and has a structure characteristic of cast metal with the content of structurally free phase exceeding 60 % Formation of ledeburite under wt.% carbon content in the alloy was caused by alloying by tungsten which shifted eutectoid transformation point towards lesser concentrations of carbon The structure of alloy displays presence of regular shaped carbide inclusions of 1…4 μm, located both isolated and in clusters Microroentgen spectral analysis of the alloy determined that the most of titanium is contained in regular-shaped inclusions (Fig 4) These inclusions also display presence of carbon and tungsten And tungsten is lumped mostly along the edges of these inclusions The matrix, according to the data obtained by microroentgen spectral analysis, is a solid solution of carbon, silicon and tungsten in iron Fig Alloy A2 backscattered electron image and spectrum in point Analysis of A3 confirmed the possibility of complex alloying of metal with the flux of mineral concentrate and standard ferroalloy Chemical analysis confirmed the assumption that silicon dioxide influences the process of tungsten transition into alloy In this experiment we excluded the influence of silicon dioxide from zirconium concentrate This allowed us to increase the content of tungstem in the built-up metal four times with a lesser concentrate-reductor ratio The microstructure of the alloy, the fine-needled martensite, is hardening phase The martensite contains regularshaped inclusions – carbides In order to remove hardening structures and to convert the alloy to equilibrium state the sample was annealed After annealing the structure became homaxonic consisting of granular pearlite and carbide phase Thus, the research conducted established possibility of complex alloying of remelted steel with different combinations of alloying elements These elements are contained in the form of oxides in mineral raw materials and as a constituent of ferro-alloy Analysis of the microstructures of the alloys showed presence of solid phase 1502 Evgeniy Kuzmichev et al / Procedia Engineering 165 (2016) 1496 – 1502 constituents, carbides The results obtained give us reason for further research aimed at elaboration and production of alloyed construction and tool steels by the ERS method Conclusions The research conducted is the first experimentally proved substantiation of the possibility of complex alloying of low-carbon steel under ESR with the fluxes based on scheelite, zirconium and rutile concentrates as well as on ferrochromium Carbon reduction of titanium oxide, zirconium oxide and tungsten oxide allows ESR production of carbide steel References [1] Babenko E.G Osnovnye aspekty transportnogo mineralogicheskogo materialovedeniya [Major Aspects of Transport Mineralogical Material Science] / E.G Babenko, A.D Verkhoturov, V.G Grigorenko – Vladivistok: Dalnauka, 2004 – 234 p [2] Babenko E.G Teoreticheskie i tehnologicheskie osnovy povysheniya kachestva i svoistv splavov (pokrytiy) na baze legiruyushchih svarochno-naplavochnyh materialov s ispolzovaniem 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under conditions of global changes in nature environment]// Vestnik RAN 2004 Vol 84, Iss 12, pp 1082–1089 ... production of alloyed construction and tool steels by the ERS method Conclusions The research conducted is the first experimentally proved substantiation of the possibility of complex alloying of low- carbon. .. inclusions and makes alloying metal possible [11 – 15] Therefore, the major purpose of this research is studying complex alloying of metal under ESR using minerals containing oxides of alloying elements... ascertained the possibility of complex alloying of steel with tungsten of low activity and zirconium of high activity, which provides us with the reason to consider alloying with intermediate-level