Vol. 26 No. 1 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. 1 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. 1 2024 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Kuts V.V., Oleshitsky A.V., Grechukhin A.N., Grigorov I.Y. Investigation of changes in geometrical parameters of GMAW surfaced specimens under the infl uence of longitudinal magnetic fi eld on electric arc....................................... 6 Saprykina N.А., Chebodaeva V.V., Saprykin A.А., Sharkeev Y.P., Ibragimov E.А., Guseva T.S. Optimization of selective laser melting modes of powder composition of the AlSiMg system................................................................. 22 Gubin D.S., Kisel’ A.G. Features of calculating the cutting temperature during high-speed milling of aluminum alloys without the use of cutting fl uid............................................................................................................................................. 38 EQUIPMENT. INSTRUMENTS Borisov M.A., Lobanov D.V., Zvorygin A.S., Skeeba V.Y. Adaptation of the CNC system of the machine to the conditions of combined processing...................................................................................................................................... 55 Nosenko V.A., Bagaiskov Y.S., Mirocedi A.E., GorbunovA.S. Elastic hones for polishing tooth profi les of heat-treated spur wheels for special applications..................................................................................................................................... 66 Podgornyj Y.I., Skeeba V.Y., Martynova T.G., Lobanov D.V., Martyushev N.V., Papko S.S., Rozhnov E.E., Yulusov I.S. Synthesis of the heddle drive mechanism....................................................................................................... 80 MATERIAL SCIENCE Ragazin A.A., Aryshenskii V.Y., Konovalov S.V., Aryshenskii E.V., Bakhtegareev I.D. Study of the eff ect of hafnium and erbium content on the formation of microstructure in aluminium alloy 1590 cast into a copper chill mold............................................................................................................................................................................ 99 Zorin I.A., Aryshenskii E.V., Drits A.M., Konovalov S.V. Study of evolution of microstructure and mechanical properties in aluminum alloy 1570 with the addition of 0.5 % hafnium........................................................................... 113 Karlina Y.I., Kononenko R.V., Ivantsivsky V.V., Popov M.A., Deryugin F.F., Byankin V.E. Relationship between microstructure and impact toughness of weld metals in pipe high-strength low-alloy steels (research review)..................... 129 Patil N.G., Saraf A.R., Kulkarni A.P Semi empirical modeling of cutting temperature and surface roughness in turning of engineering materials with TiAlN coated carbide tool................................................................................. 155 Sawant D., Bulakh R., Jatti V., Chinchanikar S., Mishra A., Sefene E.M. Investigation on the electrical discharge machining of cryogenic treated beryllium copper (BeCu) alloys........................................................................................ 175 Karlina A.I., Kondratiev V.V., Sysoev I.A., Kolosov A.D., Konstantinova M.V., Guseva E.A. Study of the eff ect of a combined modifi er from silicon production waste on the properties of gray cast iron................................................. 194 EDITORIALMATERIALS 212 FOUNDERS MATERIALS 223 CONTENTS
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 Study of the eff ect of a combined modifi er from silicon production waste on the properties of gray cast iron Antonina Karlina 1, a, *, Viktor Kondratiev 2, b, Ivan Sysoev 3, c, Aleksandr Kolosov 4, d, Marina Konstantinova 3, e, Elena Guseva 3, f 1 National Research Moscow State University of Civil Engineering, 26 Yaroslavskoe Shosse, Moscow, 129337, Russian Federation 2 A.P. Vinogradov Institute of Geochemistry of the Siberian Branch of the Russian Academy of Sciences, 1A Favorsky str., Irkutsk, 664033, Russian Federation 3 Irkutsk National Research Technical University, 83 Lermontova str., Irkutsk, 664074, Russian Federation 4 JSC Eurosibenergo, 22 Rabochaya str., Irkutsk, 664007, Russian Federation a https://orcid.org/0000-0003-3287-3298, karlinat@mail.com; b https://orcid.org/0000-0002-7437-2291, imz@mail.ru; c https://orcid.org/0000-0002-8561-5383, iwansys@mail.ru; d https://orcid.org/0000-0002-2330-1813, akolosov.irk@gmail.com; e https://orcid.org/0000-0002-8533-0214, mavikonst@mail.ru; f https://orcid.org/0000-0002-8719-7728, el.guseva@rambler.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. 1 pp. 194–211 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2024-26.1-194-211 ART I CLE I NFO Article history: Received: 12 December 2023 Revised: 10 January 2024 Accepted: 22 January 2024 Available online: 15 March 2024 Keywords: Modifi ers Grey cast iron Nanostructures Silicon dioxide Morphology Oxides Crystallization Plate Compacted Vermicular graphite ABSTRACT Introduction. During the metallurgical production of silicon, waste is generated that accumulates in dumps, harming the environment. Disposal and recycling of solid waste from silicon production is especially important because it contains important chemical compounds (silicon dioxide, silicon carbide, carbon nanotubes) that can be used in other industries, which will bring greater economic value. Considering the possibilities for extracting these useful components from silicon production waste, it is necessary to bring processing technologies to the stage of widespread practical application. Therefore, the development of a special waste processing technology to obtain a useful product in the form of a composition of silicon dioxide and silicon carbide remains an urgent problem. The purpose of the work is to study the formation of the morphological form of graphite when adding nano-modifi ers from silicon production waste. Methods. The work examined specimens of gray cast iron after modifi cation with a combined modifi er obtained from silicon production waste. The research methods are mechanical tests for statistical tension, analysis of the chemical composition and metallographic studies. Results and Discussion. It is revealed that the mechanical properties of gray cast iron increased by 30–50 % after modifi cation with a combined modifi er, compared with witness specimens. The morphology of graphite is an important parameter aff ecting the properties of cast iron. It is established that during the modifi cation process the morphology of graphite changes from lamellar to vermicular. Specimens of gray cast iron with vermicular form of graphite have high strength values compared to specimens of gray cast iron with lamellar form of graphite. The presented results confi rm the prospects of the developed approach aimed at obtaining new classes of modifi ers and products made of gray cast iron with a high complex of mechanical properties. For citation: Karlina A.I., Kondratiev V.V., Sysoev I.A., Kolosov A.D., Konstantinova M.V., Guseva E.A. Study of the eff ect of a combined modifi er from silicon production waste on the properties of gray cast iron. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2024, vol. 26, no. 1, pp. 194–211. DOI: 10.17212/1994-6309-2024-26.1-194-211. (In Russian). ______ * Corresponding author Karlina Antonina I., Ph.D. (Engineering), Research Associate National Research Moscow State Construction University, Yaroslavskoe shosse, 26, 129337, Moscow, Russia Tel: +7 950 120-19-50, e-mail: karlinat@mail.ru Introduction A large amount of waste is generated during the operation of steel plants around the world. Typically, this solid waste is partially recycled, but a signifi cant amount remains, causing damage to the environment. In all technological processes for the production of metallic silicon, material losses of varying degrees and quality occur. In Russia, at silicon production plants, a lot of unprocessed metallurgical slag remains in
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 the dumps [1, 2]. Storage of this solid waste requires many square kilometers of land. Waste is collected in the form of wet or dry powders [1–7]. It is estimated [1, 2, 6, 7] that more than 100,000 tons of waste are generated annually during the production of metallic silicon [7]. Despite signifi cant eff orts to reduce its harmful eff ects on the environment, there is no way to prevent contamination of soil and groundwater. Currently, work is being carried out in the Russian Federation on the use of industrial waste as modifying additives in various industries: construction [4–6], metallurgy [1, 2, 7]. Modifi cation is one of the most important metallurgical treatments applied to molten iron immediately before casting to promote solidifi cation without excessive eutectic undercooling, which promotes the formation of carbides, usually with undesirable graphite morphology. Gray iron (lamellar graphite) continues to be the most produced metal material in the global foundry industry, although its rate has slowed due to its replacement by higher-performing malleable irons or lighter-weight aluminum-based alloys. It is well known [8–21] that the crystallization of graphite is signifi cantly infl uenced by the presence of molten impurities in the melt in which it grows, even when these minor elements are present in quantities of less than 0.1 %. It can have a positive eff ect, promoting nucleation and spheroidization, or a negative eff ect, causing graphite degeneration. The main source of these elements is charge materials such as scrap steel, pig iron and pig iron return. A three-stage model of the nucleation of lamellar graphite in gray cast iron was proposed in 2,000 with the formation of oxide-sulfi de graphite [8–14]. A large series of research programs have defi ned the following model [8–21]: (1) Small oxide regions (0.1–3 μm, typically < 2 μm) are formed in the melt; (2) Complex compounds (Mn,X)S (from 1 to 10 μm, usually < 5 μm) nucleate on these microinclusions, where X = Ca, Ba, Sr, Zr, Mg, P, Ti, La, Ce, etc.; (3) Graphite nucleates on the sides of (Mn,X)S compounds due to the low crystallographic mismatch of graphite [8, 9]. The role of complex sulfi des (Mn,X)S in the formation of graphite in gray cast irons is confi rmed by other representative research works [10–15]. Recently [16, 17] it was discovered that oxygen is mainly present in the fi rst microcompound, which is visible as the core of the (Mn,X)S particle, and, in any case, also at the sulfi de-graphite interface, formed into a thin (nano-sized) layer and including O, Si, Al, Ca, Ba, Sr, La and Mg. The presence of this oxide-based layer is hypothesized to increase the ability of (Mn,X) S compounds to nucleate graphite due to their better crystallographic compatibility: this is illustrated by the use of a hexagonal system compared to a cubic system for sulfi de and the low mismatch found for the face (0001) graphite. The smaller the mismatch between two substances (δ), the stronger the nucleation potential between it: the highest nucleation capacity is achieved at δ < 6 % (LaS, CeS, SrMnS), the average nucleation capacity is achieved at δ = 6 % to 12 % (BaS , CaS), and weak nucleation ability is detected at δ > 12 % (MnS, MgS) [18, 19]. The results of research on the morphological characteristics of graphite lead to adjustments to national standards [22–25]. The works [1, 2, 7] show the possibility of using silicon production waste as modifi ers in the production of cast iron. Two modifi ers were developed [7], obtained after fl otation processing of waste in the form of silicon dioxide and nanotubes [1, 7]. The use of modifi ers obtained from silicon production waste not only improves the mechanical properties of gray cast iron, but also aff ects the morphology of graphite [26–34]. The morphology of graphite is a very important parameter aff ecting the properties of cast iron. The room temperature morphology of graphite in cast Fe-C-Si alloys is primarily the result of nucleation from a liquid melt and growth of graphite crystals followed by diff usive growth of carbon in the solid state. The chemical complexity of iron melts and the temporary nature of nucleation and local segregation caused by the chemical composition of the alloy, melt processing and casting conditions are the main determining factors. The interaction between these variables can result in a wide variety of graphite forms, including lamellar/ fl ake (LG), compacted/vermicular (CG), spheroidal/nodular (SG), and other graphite forms (TG) [9, 10, 14, 15, 26–9], as well as some degenerate morphologies such as pointed, blasted or massive graphite (CHG). Although nodular cast iron was discovered in the late 1930s [8–12], the mechanism, by which graphite changes its shape, remains unclear [8–21, 26–30]. Compacted graphite (CG) iron is a new engineering material containing graphite, worm-shaped (vermicular) with rounded edges in a (ferrite-pearlite) matrix.
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 In foreign literature the names compacted, vermicular, worm-shaped [22, 23, 25] can be found. In the domestic literature the term vermicular is used [24]. The intermediate graphite (CG) morphology provided an advantageous combination of the mechanical properties of ductile iron and the physical properties of gray cast iron. The purpose of this work is to identify the formation of the morphological form of graphite with the introduction of a combined modifi er from silicon production waste. The objectives of the work are: 1) to conduct research to assess the modifying eff ect of a combined modifi er obtained from silicon production waste in the smelting of gray cast iron; 2) to determine the eff ect of the combined modifi er on the nucleation of vermicular graphite; 3) to analyze the eff ects of compression/expansion during the crystallization of cast iron when using a combined modifi er. Experimental technique Experimental cast iron (type SCh15) was smelted in an electric induction furnace (15 kg; 8,000 Hz) using cast iron scrap, FeSi and carbonaceous material. The melt, heated to 1,500 °C and held in the oven for 5 minutes, was released into a pouring ladle at a temperature of 1,480 °C and poured into a sand mold made of furan resin at a temperature of 1470 °C. Cylindrical rods were produced (30 mm in diameter and 100 mm in height). A combined modifi er based on silicon dioxide and silicon carbide was added to the bottom of the mold cavity (additive from 0.5 to 1.5 wt. %, grain size less than 1.0 mm). Research included: determination of the chemical composition of cast iron; determination of specimens’ hardness using the Brinell method; tensile testing of specimens; study of the macro- and microstructure of gray cast iron. The combined modifi er was obtained from cyclone dust waste by fl otation treatment [1, 7, 32, 33]. The appearance of the modifi er is shown in fi gure 1, and the composition of the crystalline phase in Table 1 and fi gure 2. Compacting the modifi er was carried out from the resulting mechanical mixtures either by tableting using a press, or a product was obtained manually globulated using paraffi n. When analyzing the convex shape factor, the diff erence between the real and convex perimeter of the graphite particles is fi rst determined and then the resulting value is divided by the ratio of the square root of the convex perimeter to the real perimeter of the measured particle. The roundness shape factor is commonly used to defi ne the diff erent morphologies of graphite in cast iron, from fl ake to vermicular to nodular graphite, including various subclasses for each type of graphite. The graphite roundness shape factor (RSF) is considered (according to the international standard ISO 945-4-2019) to be a characteristic of the representative morphology of graphite in cast irons. The international standard ISO 16112:2017 “Compacted graphite cast irons – Classifi cation” [25] defi nes some of the graphite morphologies that may be present in this type of cast iron. In this RSF standard, a b Fig. 1. The appearance of the combined modifi er: formed out of silicon production waste (a); electronic photography of the structure (b)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 Ta b l e 1 The composition of the crystal phase of the combined modifi er according to XRD results No. Phase Content (%) 1 SiO2 (Quartz) 50 2 SiC (Moissanite) 35 3 SiO2 (Cristobalite) 10 4 C (Graphite) 5 Fig. 2. Diff raction pattern of the combined modifi er nodular graphite (ISO Form VI) was defi ned using RSF = 0.625–1.0, with intermediate forms of graphite (ISO Forms IV and V) with RSF = 0.525–0.625 and vermicular graphite (ISO Form III) with RSF < 0.525. In our case, the graphite roundness shape factor (RSF) was in the range of 0.425–0.519. Results and discussion The chemical composition of specimens of gray cast iron and with modifi cation is presented in Table 2. It can be seen that the use of the modifi er does not signifi cantly change the chemical composition of gray cast iron, with the exception of a slight increase in silicon by 0.1 %. It is known that for gray cast iron the main indicators of mechanical properties are the minimum value of tensile strength and hardness. Table 3 presents the results of mechanical tests of witness cast iron and specimens after modifi cation. It can be seen that with the same chemical composition, the use of a modifi er increases the mechanical properties of the casting. The study of the macro- and microstructure of gray cast iron was carried out in accordance with GOST 3443-87 using optical and electron microscopy, which made it possible to identify the peculiarities of the infl uence of modifi ers. Figs. 3, 4 present the results of optical and electron microscopy. Typically, the eutectic solidifi cation unit is represented by austenite and plate-shaped graphite (fi gure 3). In all cases, a predominantly lamellar structure of Gf1 type graphite is observed according to GOST 3443-87. Foundry practices can infl uence the nucleation and growth of graphite fl akes such that size and type improve
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 Ta b l e 2 Chemical composition of cast iron of experimental smelters No. 1 and 2 (wt. %) Element C Si Mn P S Cr Ni Smelting without modifi er 3.55 2.10 0.6 0.086 0.052 0.05 0.06 Smelting with modifi er 3.49 2.51 0.5 0.098 0.055 0.01 0.06 Cast iron grade SCh15 (GOST 1412-85) 3.5–3.7 2.0–2.4 0.5–0.8 ≤0.2 ≤0.15 – – Ta b l e 3 Test results of a combined modifi er from silicon production waste Specimen Modifi er consumption (wt. %) Hardness, HB σu (MPa) Compliance with cast iron grade исходный – 195; 201; 193 139; 143; 147 SCh1510, SCH1515 No. 1 0.5 196; 200; 198 155; 151; 149 SCH1510, SCH1515 No. 2 1.0 205; 208; 209 165; 174; 177 SCH1520 No. 3 1.5 255; 260; 258 305; 310; 312 SCH1530 a b Fig. 3. Lamellar rectilinear form of graphite on the surface of unmodifi ed cast iron specimens: optical (a) and electron (b) microscopy a b Fig. 4. The vermicular graphite shape of the surface of cast iron specimens after modifi cation: optical (a) and electronic (b) microscopy
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 mechanical properties. The amount and size of graphite, morphology and distribution of graphite fl akes are critical in determining the mechanical behavior [26–34]. Lamellar graphite of the Gf1 type in our studies has a random orientation. As shown in fi gure 2, b, the morphology of vermicular graphite type Gf5 was observed using optical and electron microscopy. Figure 4 shows a large amount of vermicular graphite with uneven distribution. The ends of vermicular graphite are relatively smooth, round and blunt in shape, while the outer edge has a wavy, uneven shape. It is obvious that the graphite structures are thin and dispersed. Vermicular graphite makes up approximately 50 % of the volume, and several other graphite phases can be seen throughout the fi eld of view. Vermicular graphite inside the eutectic cluster (fi gure 4, b) is a continuous structure with a hemispherical end. The ends of vermicular graphite between the eutectic clusters are not nested into each other and represent full-fl edged and independent particles of the eutectic cluster. Figure 4, b shows metallographic photographs of the core of a gray cast iron casting. The graphite morphology is fi ne vermicular graphite about 100–200 μm in length and only a small amount of spherical graphite. According to the requirements of regulatory documents, it is necessary to calculate each graphite morphology over the cross section of the specimen. The percentage of vermicular graphite on the surface and core of the casting is 93 % and 51 %, respectively. The matrix structure of the casting is pearlitic; a small amount of ferrite precipitates around the graphite. It was found that specially shaped graphite existed in the matrix in addition to vermicular graphite and spherical graphite, as shown in fi gure 4, b. This type of graphite morphology is presented in the form of spherical graphite with a small tail, which was called tadpole graphite (distorted graphite) in [18]. Most of the distorted graphite head has an irregular spherical shape, with a diameter of about 20–50 μm, and a tail length of about 30–120 μm. Interestingly, the graphite tail in some areas is separated from the parent body of spherical graphite. The morphology of distorted graphite is between spheroidal graphite and vermicular graphite, which is not yet fully developed. When analyzing the results (Table 2, 3), it is clear that the combined modifi er demonstrates good modifying properties. The modifi ed specimens showed higher mechanical properties compared to the witness sample. Previously, in [7, 32, 33], we compared modifi ers consisting of silicon dioxide with the standard modifi er FS75, which showed an increase in the positive eff ect on the structure and properties. From the theory and practice of foundry production it is known that the eff ectiveness of modifi cation in the smelting of gray cast iron is checked when processing cast iron with a low carbon equivalent. This study shows that the combined modifi er has a positive eff ect on the mechanical properties of gray cast iron. On specimens without modifi cation (fi gure 3), we see that graphite has a morphological shape in the form of plates. Vermicular graphite (fi gure 4) is a transitional form between fl ake graphite and spherical graphite [8–19], and its roundness factor (RSF) ranges from 0.3 to 0.6. The roundness coeffi cient was calculated according to the formulas [23, 25]. The morphology of graphite plays an important role in the mechanical properties of gray cast irons. According to the theory of cast iron crystallization, the fi nal shape of graphite is uncontrollable at the nucleation stage and depends on the growth stage. The diff erences in graphite morphology are due to diff erent growth rates in all directions. The direction of growth depends mainly on the chemical composition [17–21]. The diff erences in the growth behavior of lamellar, spherical and vermicular graphite depend mainly on the exclusion of selective adsorption of surface-active atoms on the graphite surface [18]. During eutectic cluster growth, low melting point and low content compounds such as sulfur and phosphorus are typically thrown to the grain boundaries, and austenite does not surround the vermicular graphite during growth. As graphite solidifi es, it is able to change the direction of its growth at the solid-liquid interface. During the solidifi cation process of cast iron, the mode of graphite growth and the fi nal morphology depend on the thermodynamic conditions and chemical composition of the molten cast iron. According to works [8–19, 26–39], the mechanism of formation of graphite morphology in cast iron is as follows. When the molten iron is suffi ciently pure and free of surfactants (O, S or other impurities), the main growth direction of graphite is the normal of the basal plane (0001) (c direction), and the graphite will preferentially develop through spiral growth into a spherical shape, since it can occur with minimal activation energy [20, 21]. However, molten iron inevitably contains surfactants such as S and O, which have been found
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 [8–13] to be absorbed at graphite-iron interfaces and are likely to increase the undercooling required for growth, especially at the hexagonal facet plane. graphite lattice shapes. As a result, the direction of graphite growth changes to normal to the plane of the face (a-direction) and lamellar graphite is formed [1, 15-18]. Therefore, when producing compacted graphite cast iron, elements (Mg, La, Ce, etc.) are usually added to consume the surfactants around the graphite. As a result, graphite grows alternately in the a direction and then in the c direction, forming vermicular graphite [8–11]. In our case, compounds of silicon dioxide and silicon carbide perform the same roles, which leads to a change in the morphology of graphite in gray cast iron. It is important to note that for decades, graphite shapes in cast iron have been assessed by comparing microscopic images to stylized reference images, with a preferred magnifi cation of 100× [23–25]. Two different approaches to graphite classifi cation have been standardized by ISO and ASTM (see fi gure 5) and the domestic standard [24], which diff er in the number, name and examples of graphite particles depicted (fi gure 5). However, when analyzing foreign and domestic standards, all evaluation approaches subjectively change the shape of graphite from lamellar to nodular with some more or less degenerate shapes in between. In fi gure 5, we took the requirements for graphite morphology from each standard and combined them in one drawing. The domestic standard [24] contains more than 13 types of graphite morphology and is designated by the letters Г with the corresponding index. For example [22–25], the EN ISO 945-1 defi ned VI ISO and V ISO shapes can be considered similar to ASTM I ASTM and II ASTM shapes, although II ASTM are convex particles whereas V ISO shape appears more star-shaped. Both forms contain the desired round particles as well as less round particles that are not likely to aff ect the mechanical properties. IV ISO and III ASTM forms contain particles that are common in ductile iron, but the forms presented are diff erent. IV ISO and III ASTM forms are compacted particles that are desirable in ductile iron and may also be found in nodular cast iron. II ISO form is a stylized representation of degenerated graphite particles known as pointed or intercellular graphite, which is mainly formed from trace elements. Unlike its stylistic image, this form does not appear independently, but Fig. 5. Various standard approaches to graphite classifi cation: upper row: graphite types in accordance with EN ISO 945-1, middle row: graphite types in accordance with ASTM A247 – 16a. 9, lower row: graphite types in accordance with GOST 3443-77
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 only in combination with spherical or fl ake graphite. In contrast, V ASTM form is an actual microscopic image of degenerated graphite, which has a very diff erent appearance II ISO from. Although VI ASTM form shows an example of blasted graphite, EN ISO 945-1 does not provide reference pictures for these types of graphite degeneration. Both ASTM A247 and EN ISO 945-1 represent fl ake graphite (I ISO and VII ASTM) in the same way. In addition to stylistic illustrations, EN ISO 945-1 also contains actual microscopic examples of I ISO Forms and III–VI ISO. In GOST 3443-87, fl ake graphite is represented by Гф1–Гф4, vermicular Гф5, Гф6. According to the requirements of GOST 3443-77, during the analysis process, in the case of a pronounced mixed morphology of graphite, it is necessary to carry out a manual analysis of each structural component (lamellar, vermicular, spherical), which is associated with high labor intensity of the analysis and subjective interpretation of the results. In GOST 3443-87, lamellar graphite is represented by Гф1–Гф4, vermicular Гф5, Гф6. According to the requirements of GOST 3443-87, during the analysis process, in the case of a pronounced mixed morphology of graphite, it is necessary to carry out a manual analysis of each structural component (lamellar, vermicular, spherical), which is associated with high labor intensity of the analysis and subjective interpretation of the results. In [35–38], a new approach to the instrumental assessment of the morphological features of graphite during crystallization is presented based on thermal analysis combined with an assessment of expansion and contraction during cooling. Amechanical expansion/contraction system was used to evaluate the initial expansion of magnesium-treated cast irons, which was identifi ed as the main factor infl uencing the shrinkage sensitivity of cast irons with diff erent graphite morphologies [36]. It was found (fi gure 6) [39] that the formation of graphite led to an important event at the onset of solidifi cation, namely initial expansion in all cast irons containing graphite, due to the force generated by the formation of diff erent graphite morpholoFig. 6. The cooling curve of pre-eutectic cast iron with characteristic temperatures showing the solidifi cation intervals of the primary and eutectic phases and the correlation with the formation of shrinkage defects [39]
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 gies applied to the mold wall [35, 36]. Liquid iron begins to cool and shrink immediately after pouring. The density of the liquid increases and the specifi c volume decreases, which leads to shrinkage of the liquid. This shrinkage can be compensated for by risers. According to [39], in iron, solidifi cation then begins at the liquidus temperature (TL) with the formation of dendrites that grow inward from the walls of the cup until eutectic solidifi cation begins (zone 1 in fi gure 6). Dendritic shrinkage can continue even after solidifi cation has begun (TE_start), since the amount of eutectic formed is initially small (zone 2). As long as the supply channel is open and the permeability of the loose dendritic region is suffi ciently high, the shrinkage is compensated by the fl ow from the risers. After reaching maximum supercooling (TE_low), the rapid formation of eutectic shifts the emphasis of solidifi cation from the predominance of dendritic shrinkage (zones 1 and 2) to the predominance of graphitic expansion (zones 3 and 4). The expansion of graphite may or may not continue until the end of solidifi cation [39]. In zone 3, suffi cient expansion of the graphite compensates for the compression of the liquid and dendrites. In zone 4, when the amount of eutectic formed and therefore graphite decreases, there is a risk of micro-shrinkage (microporosity) as the expansion of graphite may become insuffi cient to compensate for the shrinkage. In principle, both LG and SG cast irons are close to eutectic in composition and should exhibit expansion during solidifi cation, hence should not be prone to cavity formation or shrinkage of porosity. Although this is true for gray cast iron, conventionally produced nodular iron is subject to shrinkage porosity. For nodular cast iron, the melting zone is much larger and its permeability is much less than that of fl ake graphite cast iron. This, according to [39], limits the fl ow from the riser and reduces the cooling rate. Due to the limited growth of graphite at the end of solidifi cation, austenite shrinkage predominates, which causes a decrease in the specifi c volume and leads to uncompensated shrinkage in the last solidifi cation zone. This eff ect and the signifi cant release of gas from the solidifying liquid lead to the formation of porosity. Experimental linear displacement analysis (LDA) and thermal analysis (TA) devices have been used by a number of researchers [7–21] to measure the amplitude of the expansion/contraction eff ects occurring during the solidifi cation of cast iron. An extensive literature review on various methods was provided in [35]. A setup for thermal analysis was previously presented by us in [7]. In addition to this, a stand was developed that includes two parallel molds for pouring specimens (mold sizes 200 mm and 30 mm), a cooling module (0.72 cm) and a deformation recording module. The high-speed interface simultaneously records temperature and linear displacement data. The results of preliminary experiments are shown in fi gure 7. The morphology of graphite has a marked infl uence on the initial expansion value: it increases from fl ake graphite (LG) through vermicular graphite (CG) to nodular graphite (NG), respectively. In the same way, sensitivity to shrinkage increases, and the connection between two parameters is obvious: initial expansion - level of shrinkage. These experiments also demonstrated the importance of accurately estimating contraction/expansion events and their relationship to cooling curve events, respectively. Several key parameters have been identifi ed that correlate with the specifi c behavior of our inoculants as it relates to graphite release and shrinkage sensitivity of gray cast iron. These were: depth of eutectic supercooling, recalescence and maximum recalescence rate, temperature of the end of solidifi cation, maximum initial expansion and the total integral from the fi rst derivative of the compression curve to the end of pre-pearlite compression. Subcooling at the end of solidifi cation relative to the metastable (carbide) Fig. 7. The results of the study of the infl uence of graphite morphology on the initial expansion (compression curve) and the tendency to shrinkage (Гф1 – lamellar, Гф5 – vermicular)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 equilibrium temperature and expansion within the solidifi cation sequence appear to have a strong infl uence [39] on the susceptibility to macro- and micro-shrinkage in ductile iron castings. The work [34] states that molten cast iron usually contains double oxide fi lms (bifi lms). These silicate oxide fi lms provide a substrate on which oxysulfi des and graphite nuclei form. The presence of these double silicate fi lms explains the diversity of graphite morphology. Lamellar graphite grows along the fi lms, and spherical graphite grows when these fi lms are destroyed, for example, with the addition of magnesium. It was shown in [10–17, 35–39] that the appearance of the vermicular form of graphite was associated not only with the interaction of silicon with carbon monoxide, but also due to the interaction, in this case, of silicon monoxide with a graphite nucleus. As the temperature of the metal melt decreases, the surface activity of SiO decreases [10–12], its mobility decreases, and at the site of formation it dissolves in graphite, changing its morphology to vermicular [35–39]. In conclusion, we note that the components of the combined modifi er (silicon oxides and carbides) do not dissolve immediately when added to the melt; dissolution occurs slowly, which gives a preliminary inoculation eff ect that slowly fades and remains eff ective for several hours [8, 12–15, 26 , 28, 34–42]. At the same time, the behavior of SiC before modifi cation in gray cast iron melts has not been suffi ciently studied, but it is stated [31, 41, 42] that during the dissolution of SiC in the melt, graphite clusters form around SiC particles as a result of local supersaturation of the melt with Si and C. These graphite clusters, which are thermodynamically metastable over a period of time, play an important role in the pre-modifi cation eff ect of SiC in the melt and promote the formation of graphite and eutectic nucleation. Dissolution of the FeSi compound can also result in the formation of graphite clusters, but due to the higher dissolution rate these clusters remain stable only for short periods of time. Consequently, when SiC is dissolved, more graphite clusters are formed, which last longer than when FeSi is dissolved. The formation of many graphite clusters around the SiC particles reduces the carbon content in the rest of the melt, and therefore austenite nucleation occurs at higher temperatures. The use of modifi ers from silicon production waste to achieve the technological properties of gray cast iron together with other advanced technologies in mechanical engineering and metal processing [43–50] will make it possible to comprehensively solve high-tech, knowledge-intensive problems. Conclusions 1. Studies conducted to assess the modifying eff ect of a combined modifi er obtained from silicon production waste in the smelting of gray cast iron show its high effi ciency compared to classical modifi ers. It is established that the addition of a combined modifi er based on silicon oxide and carbide instead of the standard FeSi modifi er led to an increase in tensile strength and hardness by 35–50%, due to a change in the morphology of graphite from lamellar to vermicular. 2. It is shown that the proposed composition of the combined modifi er induces the nucleation of a large amount of vermicular graphite, and also increases the number of eutectic cells and reduced the tendency to form white cast iron. 3. It is shown that the analysis of compression/expansion eff ects during the crystallization process correlates well with the change in solidifi cation parameters in accordance with the characteristics of the molten cast iron, which depend on the melting procedure and the modifi ers used, the rigidity of the mold and thermal behavior (heat transfer parameters). References 1. Kondrat’ev V.V., Balanovskii A.E., Ivanov N.A., Ershov V.A., Kornyakov M.V. Evaluation of the eff ect of modifi er composition with nanostructured additives on grey cast iron properties. Metallurgist, 2014, vol. 58, pp. 377– 387. DOI: 10.1007/s11015-014-9919-x. 2. Kondrat’evV.V.,MekhninA.O., IvanovN.A., BogdanovYu.V., ErshovV.A. Issledovaniya i razrabotka retseptury nanomodifi tsirovannogo chuguna dlya nippelei anodov alyuminievykh elektrolizerov [Research and development of
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