Analysis of the Use of Rare-Earth Metals in Ferrous Metallurgy in Russia and the World

The current state of production of rare-earth metals (REMs) in Russia and in the world is analyzed. Data on REM production in different countries of the world and on new foreign REM production and processing projects are given. The balance of production, export, and import of raw materials and products with REMs in Russia, including scandium and yttrium, is presented. The maximum volume of REM consumption in Russia is calculated considering imported products with REMs. These data are compared with other countries, including the former Soviet Union. Much attention is paid to REM use in metallurgy. Data on REM influence on cast iron and steel properties are given. Data on the used forms of REMs are given for their use in Russian ferrous metallurgy. The structure of REM consumption by branches of ferrous and nonferrous metallurgy is investigated. The structure of REM consumption for steel alloying by types and areas of its application is studied by the example of two enterprises (one of them specializes in mass production and the other, in special steels). The peculiarities of REM consumption development in Russia’s ferrous metallurgy are investigated, the consumption volume is calculated, data on the import of raw materials with REMs for metallurgy is presented, and information on the producers of REM ferroalloys in Russia is given. The line of ferrous metallurgy products with REMs is analyzed. REM consumption in metallurgy of Russia and foreign countries is compared. The reasons for insufficient REM consumption in Russian metallurgy are considered, the change in production volumes of certain types of steel and cast iron is estimated, and recommendations on growth of REM consumption in metallurgy are developed.


INTRODUCTION
Rare-earth metals (REMs) include the elements of group III(B) of Mendeleev's periodic table: Sc, Y, La, and lanthanides (Ce-Lu). REMs belong to so-called rare metals, a group of elements historically established in the beginning of the 20th century, when they were just beginning to be used (rarely consumed), which includes four other groups in addition to REMs, i.e., trace, refractory, light, and radioactive elements [1]. Currently, there is confusion with the terms "rare" and "rare-earth" metals, and it is often even possible to find expressions such as "rare and rareearth metals." REMs are used in various industries (radio electronics, instrumentation, machinery industry, and metallurgy and chemical, glass, and ceramic industries, etc.). They are used in the production of perma-nent magnets, catalysts for oil cracking, rubber synthesis, luminophores, powders for polishing lenses, and microchips. REM consumption in the world is increasing due to development of the "green" energy industry. Scopes of REM application and existing technologies for their processing were discussed in [2,3]. In 2018, global REM production amounted to 201000 tons [4], of which 174000 tons were produced in China, which is not only the main supplier but also the main consumer of REMs. In 2019, world REM production was already 210000 tons (oxide equivalent) [5], taking into account such countries as China, United States, Burma, Australia, India, Russia, Madagascar, Thailand, Brazil, Vietnam, and Burundi (listed in descending order of production volume).
China's attempts to manage prices on the global REM market caused a surge of interest in REMs, export was limited in 2011-2012, and REM prices rose sharply. This led to the development of projects and even government programs of other countries for the extraction and processing of REMs [6,7], including Russia [8]. There was a sharp increase in the number of scientific publications on REMs. The problems of using secondary resources with REMs were discussed [6,[9][10][11]. Implementation of such projects proved to be a difficult task. After several years, prices returned to their previous level [12]. In 2012, REM production was resumed at Mountain Pass (Molycorp) (5000-6000 tons per year). The concentrate was supplied to the Estonian Silmet plant. This project was not profitable, and production was halted in 2015. In 2016, Molycorp avoided bankruptcy by changing its ownership and was renamed to Neo Performance Materials. Production of rare-earth ore resumed in Mountain Pass in 2018, and 26 000 tons of bastnaesite have been already produced in 2019, making the United States the largest producer of REM concentrates outside China [5]. In 2013, Indian Rare Earth Ltd (IREL) commissioned a monazite processing plant in Orissa. The production volume is about 2000 tons of REMs per year. Australian company Lynas postponed its plans to develop the new Duncan deposit in 2013 due to low prices for its products. The new processing plant in Malaysia (22000 tons per year since 2014) has not yet reached its design capacity. Lynas started making profits between 2018 and 2019. Today, it is the only company with a full REM production cycle outside China. Brazilian company CBMM started producing REMs of 1000 tons per year in 2015. More details about REM projects in other countries were described in [13]. As a result of these projects, China's share in REM production fell from 97% in 2010 [10] to 63% in 2019 [5]. However, these data do not consider illegal products and China's high share in foreign projects, including ownership and sales of products.
In Russia, within the subprogram Development of the Industry of Rare and Rare Earth Metals of the state program "Development of Industry and Increasing its Competitiveness in 2013-2018, 40 research and development projects were carried out on the basis of public-private partnership. As part of this, new REM materials and technologies were obtained. Currently, the Ministry of Industry and Trade of the Russian Federation has developed a draft of the Strategy of Industrial Development of Rare and Rare-Earth Metals of the Russian Federation for the Period until 2035. At the same time, the strategy implementation plan is provided within the rare and rare-earth metals product line of the road map for development of the high-tech sector in the Russian Federation Technologies of New Materials and Substances developed to implement the Agreement of Intent of July 10, 2019, between the Government of the Russian Federation and the State Atomic Energy Corporation Rosatom.
Ferrous metallurgy is one of the main consumers of rare metals [14]. The Central Research Institute for Ferrous Metallurgy together with industrial enter-prises developed the Interindustry Program of Studies on Manufacturing of New Types of Metallurgy Products Using Rare and Rare-Earth Metals for 2020-2035. Its main goal is to develop production and import substitution of high quality metal alloys and steels using rare metals (RMs) with a significant increase in the share of quality steels, including structural, corrosion-resistant, tool, stainless, and heatresistant steels and alloys for aerospace, instrumentation, machine tool industry, chemical and heavy engineering, medical industry, etc.
In order to implement the mentioned programs, it is important to estimate the amount of REMs consumed in ferrous metallurgy, the types of produced REM alloys, and the forms of consumed REMs as well as to evaluate the prospects and development options of the production of cast iron and steel with REMs.

REM PRODUCTION AND CONSUMPTION IN RUSSIA
In Russia, REM ores are produced in the Murmansk oblast. The only significant source of REMs is the Lovozero deposit (1.12% REM in ore). Loparite concentrate is produced at the Lovozero Mining and Processing Plant and then processed at the Solikamsk Magnesium Plant (SMP) using chlorine technology to obtain REM bulk carbonate concentrate. With a production capacity of 3600 tons per year, 2595.7 tons of REM (oxide equivalent) were produced in 2018, of which 2549.8 tons were exported [4]. The rest of the SMP bulk concentrate was processed by the Laboratory of Innovative Technologies (Group of Companies Skygrad) located near Moscow on an automated cascade of centrifugal extractors of their own design [15,16]. Pilot production with a capacity of 140 tons per year was launched in 2018 in the city of Korolev. The company produces cerium oxide, cerium carbonate, lanthanum oxide, neodymium oxide, solution of lanthanum, medium-heavy REM carbonate, neodymium metal, and samarium metal. The company plans to implement a project on REM extraction from phosphogypsum (up to 50000 tons at the initial stage and further up to 300000 tons per year in terms of raw materials) and to set up a separation plant in the town of Peresvet with production of up to 2000 tons per year in terms of raw materials in order to produce yttrium oxide and medium REM oxides, such as samarium, gadolinium, europium, and dysprosium, along with light REMs. A small amount (up to 70 tons) of SMP bulk concentrate is periodically processed at the Chepetsky Mechanical Plant to produce REM oxide concentrate and polishing powders. Nitric-acid technology of loparite concentrate processing is also tested at the pilot plant there.
Apatite-nepheline ore deposits (0.24-0.42% REM) are developed to produce apatite concentrates and further phosphate fertilizers. REMs are almost never extracted. They remain largely in phosphogyp-sum, a bulk waste material, and are also partially concentrated in the resulting phosphoric acid and fertilizers. Therefore, the amount of REMs lost annually to unprocessed raw materials in Russia is comparable to half of the global production (122000 tons). Only in 2016 did PAO Acron launch production of REMs from apatite concentrate with a capacity of up to 200 tons per year at the Olenii Ruchei deposit [17]. The manufactured products include oxides of lanthanum, cerium, didymium (a mixture of neodymium and praseodymium), neodymium, carbonate concentrates of lanthanum, carbonate concentrates of REMs, light REMs, and medium-heavy REMs as well as a REM nitric-acid solution. The plant for extraction from wet-process phosphoric acid and group separation of REMz with the capacity of 12 tons per year created by OAO PhosAgro-Cherepovets is currently suspended [2]. In 2016, OAO Uralchem launched a pilot plant to extract REMs from phosphogypsum.
Until recently, Hydrometallurgical Plant (OOO Intermix Met, Lermontov) was the main producer of compounds and alloys with scandium. In 2013, it launched a pilot plant to produce scandium concentrate at AO Dalur (Atomredmetzoloto Uranuim Holding). For this purpose, the project for the associated extraction of scandium from the productive solutions of the uranium mining enterprise was implemented [18]. The same Hydrometallurgical Plant at PAO VSMPO-AVISMA created a production plant for scandium extraction from titanium tetrachloride production wastes in 2015. OOO Intermix Met produced Sc 2 O 3 , ScF 3 , ScCl 3 , Al-Sc-alloy, and metal scandium from the obtained concentrates. At the end of 2017, the plant was shut down, a year later it was put back into operation. At present, the plant has changed owners, is undergoing reorganization, and the prospects for scandium production at the plant are uncertain. The project at AO Dalur is being developed separately. In 2017, the pilot plant started to produce scandium oxide. In 2016, the Urals Aluminium Smelter launched a pilot plant and produced a pilot batch of 99% Sc 2 O 3 from red mud. Due to problems with product sales, the project was suspended in 2018. The project of the Chinese company Shewu Technology Group Corp. to process red mud with the extraction of Sc 2 O 3 at the Bogoslovsk Aluminium Smelter as well as the project to process titanium dioxide waste from Crimea TITAN with production of scandium [19] were not implemented. The volume of imported Sc 2 O 3 and Y 2 O 3 is about 15 tons.
With about 20% of the world's REM reserves, Russia mines and processes only about 1% [20]. Foreign sources estimate the share of Russia's reserves to be lower: 10% [5] and 13.6% [21]. Figure 1 shows the balance of production and consumption of REMs in Russia in 2018 and summarizes the above data. The bulk of REMs produced in Russia is represented by the bulk concentrate of REM carbonates. Only 5.6% of produced REMs are separated with production of individual "light" REM compounds, while "heavy" REM compounds are not produced, i.e., the recently created REM separation facilities (with a capacity of about 350 tons per year) are only half loaded. Up to   95% of REMs produced in Russia are shipped abroad, where they are separated. As a result of imports, Russia annually receives about 1000 tons of REM oxides (separated and partially separated) and about 100 tons of REM per year in the form of metals and alloys. It can be stated that the manufacturing of highly-processed REM products is underdeveloped in Russia, semi-finished products are exported, and processed products, including separated REM, are imported. According to our calculations, Russia consumes 1230 tons of REM annually to produce electronics components, oil refining catalysts, permanent magnets, glass, optical components, polishing powders, refractory ceramics, alloys, and modifiers. As part of similar imported products, about 2000 tons of REM is supplied annually. Let us compare these figures with the world leaders of the REM industry. In 1990, the Soviet Union produced 8500 tons of REMs in its products and exported 14% of them [22], including 20-25% of individual REMs, and domestic consumption did not exceed 6000 tons [23]. In 1990, the United States mined 22 713 tons, imported 4990 tons of REM mixtures, 151 tons of REM oxides, 1363 tons of metallic REM, 199 tons of Sc and Y, and 93 tons of ferrocerium, exported 1730 tons of cerium compounds, 241 tons of Sc and Y, and 18 tons of ferrocerium, and apparent consumption was 30000 tons [24]. The total world production at that time was 53000 tons of REMs [25]. In 2008, the United States consumed 20 663 tons of REMs, Japan, 34330 tons, and the EU countries, 2013 tons [26]. In 2009, China consumed 70000 tons of REMs [27]. In 2019, the United States consumed 13000 tons of REMs [5] and 600 tons of yttrium oxide [13]. Japan consumed 20175 tons of REMs in 2016, while China consumed about 60% of world produc-tion [28]. As can be seen, a decrease in REM consumption is typical not only for Russia. This indicates that China is developing not only the mining and production of REMs, but also the production of consumer products with REMs. For example, the share of Chinese plants, including foreign plants, in the production of neodymium magnets reaches 80% [7]. Therefore, the REM problem is not in the absence of raw materials or technologies for their processing, but in the organization of sales of domestic products with REMs on the domestic market (import substitution), insufficient REM separation capacities, a low level of REM consumption, and the absence or weak development of industries producing consumer products with REMs.
Without addressing these problems, considering the monopolization of the world market with Chinese products, it makes no sense to increase capacities for REM production from ores (Tomtor [29], Zashikhinskoe, Katuginskoe, Lovozero deposits, etc.). All these projects are currently relevant only from the point of view of niobium supply to domestic ferrous metallurgy [14]. In the current state of production in Russia, the maximum domestic consumption of REMs may reach 3200 tons per year, provided that the import of corresponding goods with REMs is substituted. At the same time, this is still several times less than REM consumption than we had 30 years ago.

REM USE IN METALLURGY
One of the most important areas of application of REMs is metallurgy. According to [30], metallurgy accounted for 19% of the world's REM consumption in 2016 and ranked second after permanent magnets (22.5%). Other sources in different years estimate the share of metallurgy in global REM consumption from 7-10 [6,9,21,31] to 16-20% [25, 32-34]. It is possible that this difference is because the production of accumulators and hydrogen storage tanks is included in the section of REM alloys. In the United States, the share of metallurgy in the final consumption of REMs varies: it was 15% in 2016 [13] and 5% in 2019 [5]. In the European Union, metallurgy consumed 12% of REMs in 2010 [6,35]. According to our calculations, in Russia, metallurgy consumes only 120 tons of REMs, i.e., 10% of the total volume. The distribution of REMs in Russian metallurgy in 2018-2019 is shown in Fig. 2. The overwhelming amount of REMs (86%) finds application in ferrous metallurgy. REM additives are used in production of cast iron to improve its quality (structure modification and cleaning from harmful impurities). Additives of 0.02% cerium make it possible to obtain high strength cast iron the properties of which are close to mild steel. This type of iron is 20-25% cheaper than cast steel and 3-4 times cheaper than forge steel [2]. Yttrium cast iron (0.1% Y) has four times higher wear resistance compared to grey cast iron. Iron's share in REM consumption in metallurgy  is about 50%. Another 36% is used in steel production as an additive for its deoxidation, degassing, and desulfurization.
The remaining REMs are consumed in nonferrous metallurgy. Neodymium and yttrium are used to produce magnesium alloys. Such alloys have high heat resistance, increased creep resistance, higher corrosion resistance, and good technological and casting properties in comparison to ordinary alloys. They are used in aviation and astronautics. Aluminum alloys with 0.2% scandium have good weldability and high mechanical properties. Therefore, they are used in components of structures for space and aviation purposes. A small amount of REMs are used in production of nickel-based heat resistant alloys that withstand aggressive media and high temperatures. In addition, REMs are used for alloying titanium alloys, aluminum alloys of the electrotechnical industry, copper-based alloys, precision alloys, etc.
A similar hierarchy of consumption in the European and world metallurgy was described in [9]: cast iron, high-strength low-alloy steel (for automotive industry), stainless high-alloy steel, special microalloyed steels and superalloys, magnesium alloys, and aluminum alloys. The consumption structure by elements in metallurgy in the world is as follows: 52% Ce; 26% La; 17% Nd; and 4% Pr [25]; in Russia, cerium and lanthanum account for about 90%.

REM USE IN IRON AND STEEL PRODUCTION
REMs, while having high density (6.76 g/cm 3 for cerium) and boiling temperature (3200°C for cerium), have relatively low melting temperature (804°C for cerium) as well as complete miscibility in iron melt and relatively low vapor pressure. This allows them to remain in the melt for a long time. When introduced into cast iron and steel, REMs interact with the gaseous elements dissolved in them (H, N, C, O, S), As, P, and nonferrous metals (Pb, Sb, Bi, Sn). REMs influence the surface tension of liquid metal and contribute to the reduction of adsorption of harmful impurities during steel crystallization, thus increasing the purity of grain boundaries and plasticity of the metal. However, low solubility of REMs in solid iron at high concentration can lead to their separation along the grain boundaries in the form of eutectics with melting temperature below the rolling temperature. REMs have a modifying effect, contribute to the crushing of metal crystals, and influence the structure, morphology, and distribution of admixtures and impurities in steel. In [36] the influence of REM on properties of different types of steel was considered in detail.
Most often REMs are used in foundries of machinery, mechanical and repair, pipe-rolling, and metallurgical plants as well as at road and railway transport plants for iron and steel processing. Modification of cast iron with REMs (3-5 kg/ton) makes it possible to obtain spherical graphite in its structure, thus improving its service properties. Modification with cerium improves strength, hardness, and wear resistance due to carbide grinding. The addition of alloys containing Y, La, or Ce in an amount of 0.3-0.5% leads to the regeneration of the cast iron structure with a predominance of isolated small carbide inclusions. The wear resistance and the machinability with a cutting tool improve.
The optimum REM content for steel is 0.02-0.05% and the number of added REMs is between 0.5 and 3.0 kg/ton. As a result of microalloying, technological and service properties of steel improve (hot ductility, weldability, heat resistance, adhesion to slag, the form of nonmetallic inclusions, structural heterogeneity, and mechanical properties). The data obtained from two Russian ferrous metallurgical enterprises for 2017-2019 for the analysis of consumption structure by steel types were obtained by the Central Research Institute for Ferrous Metallurgy. The first enterprise (Fig. 3) specializes in mass steel production. It produces more than 10 million tons of steel per year, of which only 31000 tons are REM-added. The most mass-produced steel with REMs is the steel for pipe billets and rail steel is in the second place.
The second enterprise (Fig. 4) specializes in the production of forged products. It produces 0.2 million tons of steel per year, of which only 2000 tons are REM added. Therefore, the share of steel produced with the addition of REMs does not exceed 1% of total production. The following special steels stand out in terms of REM consumption: high-strength structural steels (0.005-0.050% Ce, 0.015-0.030% Y, and 0.05% La), corrosion-resistant steels, stainless steels (0.01-0.08% Ce  and 0.05% Y), steels for production of corrosion-resistant pipe billets (0.03% Ce), and heat-resistant steels (0.01-0.20% Ce). Scandium should be discussed separately. Introduction of scandium microadditives reduces the content of N, C, O, P, and S in 01X18T and 05X18H10T steels and has a positive effect on the structure and properties. Scandium, being a surface-active element in relation to Fe-Cr-Ni melts, has a complex effect on them, i.e., refining, modifying, and alloying [37]. Additives of scandium help to slow down grain growth in steels during heating, increase their high-temperature ductility and corrosion resistance, as well as the resistance of ferritic class steels against 475-degree brittleness. Currently, no industrial iron-based alloys with scandium additives are produced in Russia. The use of metal or pressed mixture of pure metals as an alloying scandium additive is hindered due to its high cost. In this regard, the Central Research Institute for Ferrous Metallurgy is studying the problem of obtaining scandium-containing alloys based on iron and nickel with sufficiently low temperatures of melting and dissolving in liquid steel.

REM FORMS USED IN FERROUS METALLURGY
Alloys obtained by electrolysis (mischmetal, ferrocerium, and ferrocerium with magnesium FCM-5) are still common forms of REM additives in cast iron and steel. Mischmetal is an alloy of light REMs in their natural ratio. Sometimes a mixture of lanthanum and cerium oxides is used for its production after separation of neodymium and heavier REMs from them. Such alloys are usually more expensive than ferroalloys. They are characterized by low and unstable absorption of REMs, pyrophoric, require hermetic containers for storing, special methods of grinding, as well as special methods and devices for introduction into liquid metal. Their use is justified historically (these are the first and most accessible alloys with REMs) as well as for a number of special steels and alloys, in which the amount of impurities, including iron, is strictly regulated, e.g., for heat-resistant nickel-based alloys.
Pure REMs in the form of metals (yttrium, lanthanum, cerium, and neodymium) are used in the production of special steels and nonferrous metals. The content of individual REMs in them is regulated. The differences in the effect of individual REMs on the properties of cast iron and steel are unexplored. REMs differ in physical properties, i.e., density, melting and boiling point (scandium, yttrium, and REMs of the cerium and yttrium group), and atomic radius. Metal yttrium and yttrium alloys are used in the production of cast iron and steel for the manufacture of parts operating under heavy loads, low temperatures, and abrasive wear. A more effective effect of yttrium compared to cerium for the production of spheroidal graphite cast iron was shown. Yttrium and scandium can be used in iron-based alloys for nuclear reactors. In them, yttrium is bound by boron and is concentrated in the grain volume. Therefore, the helium produced from boron does not weaken the grain boundaries, preventing embrittlement. Yttrium is used in heating element alloys, superalloys, and high-temperature superconductors as well as for the production of wearresistant and corrosion-resistant cutting tools. In metallurgy, it was observed that individual REMs have a more pronounced effect than bulk REMs. For example, in castings made of high strength cast iron using metallic lanthanum, finer graphite inclusions were obtained, and shrinkage of castings during curing was reduced in comparison to bulk REMs. When modifying steel, sometimes cerium is used instead of mischmetal. Nickel alloys with REMs (Ni-Ce) are used for alloying stainless steel, martensite-ageing steel, steel for castings, etc. The use of praseodymium was described for changing the structure of low-carbon steel in [38]. According to the data of the Central Research Institute for Ferrous Metallurgy, the additive of silicon-based alloys with samarium or gadolinium in the Cr-Ni-Mo steel contributes to the crushing of the cast structure, reducing the zone of column crystals, and increasing the strength and plastic properties of steel, the values of impact toughness, and cold resistance. Data on properties of individual REMs when they are added to different alloys were given in [39].
Silicon based ferroalloys, such as FS30RZM30, are obtained in electric furnaces from REM concentrate using carbon, silicon, and aluminum as a reducing  agent. In terms of costs, they are the most economical alloys suitable for large tonnage production. Employees of the Central Research Institute for Ferrous Metallurgy developed technologies for producing several grades and alloys with REMs containing both individual REMs and their mixtures. These technologies are characterized by significant savings of raw materials and energy resources [40,41]. Such alloys are better absorbed by steel and are cheaper in comparison to mixtures. They are used in production of cast iron and steel, both as alloys with REMs of the cerium group (STSEMISH) and with REMs of the yttrium group (SIITMISH). They are not oxidized during storage and increase stability of properties of end products. The content of REMs is 15-30%. However, these ferroalloys are often not suitable for processing special alloys and steels due to their high silicon content. In [42], it was noted that 90% of all mold steel is smelted in electric arcs and induction furnaces with acidic lining. Under the condition of repeated remelting of waste (sprue and risers), silicon concentration gradually increases in the alloys. Nonmetallic inclusions rich in silicon contaminate the metal and are distributed by lines at the grain boundary, thus worsening steel characteristics. Silicon-based ferroalloys, such as FS30RZM30, were produced by the Kluchevsky Ferroalloy Plant (about 130 tons per year REM equivalent in 1970s). Today, their production and consumption in Russia has significantly decreased (no more than 10% of all forms of REMs in metallurgy). In addition to the Kluchevsky Ferroalloy Plant, such alloys are smelted in Russia by the Central Research Institute for Ferrous Metallurgy, OOO Spetsferrosplav, and OAO NIIM. Previously, the use of alloys with REMs was limited by the imperfection and complexity of the method of their introduction into the melt, which led to the instability of the properties of metal products [43]. Today, the method of alloy modification during casting in a ladle has become widely spread in metallurgical enterprises due to development of devices for the introduction of modifiers of fines; at the same time, their consumption has significantly decreased.
In the case of out-of-furnace treatment of steel, deoxidation, refining, and modification are combined with microalloying and carried out in a casting ladle [44]. One of the following methods is used to introduce REMs into steel: additive to the jet when metal is tapped from the furnace into the ladle, modification in the mold, or introduction of a modifier in the form of a flux cored wire directly into the ladle [45]. The most universal and effective modifiers are in the fused form. Modifiers in the form of a mechanical mixture of different components are used in cored wire fillers [46]. Complex modifiers, along with REMs, contain B, Mg, Al, Si, Ca, Cu, Zr, V, etc. Alloys and fused modifiers have no pyro effect and are absorbed 2-3 times better in comparison to mischmetal and pure metals.
Silicon-free nickel-based complex alloys (SFCAs) containing 5-30% Al, 5-15% Ca, 10-30% REMs, V, Mo, B, Nb, and N are used in special electrometallurgy, in electroslag remelting, casting, and heating [42], except for foundry production (up to 3 kg/ton). They favorably influence casting properties, structure, and characteristics of steel, and they have exceptional deoxidizing and refining capability. Such alloys are produced by the out-of-furnace calcium-thermal method at AO Rosredmet and OOO Complex technologies. The base grade of SFCAs (AKTSe) has 20% REMs, 57% nickel, 20% aluminum, and 3% calcium. In addition to the SFCA base grade, there are alloys modified with vanadium (AKCeF), titanium (AKCeT), niobium (AKCeB), and titanium and niobium (AKCeTB). The proposed iron-based SFCAs are AKCeZH and KTSeZH. SFCAs, simultaneously with deep deoxidation, refinement, and modification of the structure, provide microalloying, which leads to 2-3 times higher mechanical and operational characteristics, especially plasticity, impact toughness, cold resistance, and fatigue resistance [44]. In some cases, limitations on aluminum content are so severe that the use of such SFCAs is unacceptable. For the same reason, the use of ferroalloys, such as FS30RZM30, calcium metal, obtained using aluminum as a reducing agent, is sometimes restricted.
Manufacturers of SFCAs usually indicate limited use and the worse characteristics of ferroalloys, such as FS30RZM30, and complex modifiers with silicon because of their high silicon content [42,44]. However, complex modifiers with REMs based on ferrosilicon with alkaline-earth metals as well as based on calcium silicon or silicon with REMs (REM silicides) are now the most common. Complex modifiers, such as Fe-Si-Mg-REM, can be produced either in induction furnaces by alloying magnesium with ferrosilicon and other components or directly at ferroalloy plants by dissolving rotating magnesium ingots in liquid primary ferrosilicon. In Russia, they are obtained in induction furnaces. The disadvantage of the technology for obtaining modifiers by alloying magnesium with ferroalloys is the repeated melting of silicon and ferrosilicon. REMs play an important role in the composition of the modifier for the production of high strength cast irons with spherical and especially vermicular graphite. The modifiers of Sferomag and Sferomaks series with the following chemical composition are used to process cast iron in the ladle: 4.7-7.5% Mg; 0.3-5.0% Ca; 0.5-3.2% REM; 1.8-3.0% Ba; 45-55% Si; <1.5% Al; and the rest, Fe. The use of similar modifiers on the basis of barium and strontium alloys is limited in Russia, while in the United States such alloys are produced on a large scale by the carbon-thermal method in ore-thermal furnaces [47]. Insteel series modifiers containing 7-12% REMs, which are alloys, e.g., SiCaBaRZM and SiCaBaRZMAl, are used for steel processing [45]. They make it possible to increase corrosion resistance of steel for pipe billets, effectively clean the melt from nonmetallic inclusions, reduce the amount of dis- solved gases, improve the technological properties of products, and reduce the pouring temperature by increasing its fluidity, which reduces the development of hot thermal cracks [45,48,49]. Alloys and modifiers in Russia are produced by OOO NPP Technology, OAO NIIM, and OOO Complex Technologies. Production of alloys with REMs for ferrous metallurgy is also associated (was associated) with OOO NKM Nord, OOO NPO BKL, and AO Siberian Chemical Plant.
According to the data from [9], REMs in the form of mischmetal and silicides of REMs, such as FS30RZM30, are mainly used in world metallurgy. However, foundry production in Europe and North America increasingly consume ferrosilicon magnesium (FeSiMg) containing less REMs. REMs are being replaced by alkaline-earth metals. The following forms of REMs used in metallurgy are listed: cast iron and steel (mischmetal, REM silicides, and cerium), high-strength low-alloy steel (mischmetal and cerium), stainless high-alloy steel (Ce and Y), special microalloy steels and superalloys (La, Gd, Y, Ce, Nd, and Pr), magnesium alloys (Y, Nd, Gd, and Pr), and aluminum alloys (Y, Ce, La, and La).

ANALYSIS OF THE CURRENT STATE OF REM CONSUMPTION IN FERROUS METALLURGY
The structure of REM consumption by form, according to our estimations, is as follows: 80-90% in the form of complex modifiers and 10-20% in the form of mischmetal, pure REMs, and ferroalloys, such as FS30RZM30. Almost all raw materials with REMs for metallurgy are imported from abroad ( Table 1). The main part of mischmetals, ferroalloys with REMs, lanthanum, and cerium (about 90 t) is consumed to obtain complex modifiers. The rest is used directly for alloying cast iron, steel, and nonferrous metal alloys.
Since silicon-based complex modifiers are mainly used, the question of replacing mischmetal for their production with FS30RZM30 alloys is not fundamental from the metallurgical point of view. The problem is in the cost of materials with REMs. Ferroalloys with REMs of domestic production often cost as much and even more than imported mischmetal. Similarly, the cost of domestic concentrates and oxides of REMs is not lower than the cost of imported alloys and metals with REMs. Due to the cheapness and wider availability, domestic metallurgy is focused on imported mischmetal, pure REMs, and modifiers prepared from them. The domestic REM market is small, characterized by many users with low volumes of consumption of various products, and few manufacturers, which are not motivated to compete and reduce the cost of their products. That is why the problem of expanding the domestic raw materials market with REMs for metallurgy remains an urgent one. Obviously, the organization of large tonnage production of REM alloys using electric furnace methods should lead to a decrease in their cost as compared to the production of modifiers from mischmetal and pure REMs.
REM consumption in Russia's metallurgy has increased significantly in recent years. In 1991, it was 790 tons and in 1998, 13 tons [23]. In 2011, only 15 tons of REMs were imported (10 tons of ferrocerium and 5 tons of lanthanum), while some metals were produced in Russia from imported REM fluorides (20 tons) [50]. According to the Russian Ministry of Industry and Trade, REM consumption in metallurgy was 110 tons in 2018 [51]. According to our calculations, REM consumption in metallurgy in 2019 was already about 120 tons, of which just over 100 tons was consumed in ferrous metallurgy. Despite significant growth in REM consumption in Russia's metallurgy, the domestic market remains small, and it has not reached the levels of 1991. The total REM consumption per year also significantly increased in Russia, tons per year: 3000 in 1991; 480 in 1998 [23], 300 in 2000 [50], 400 in 2005 [27], 600 in 2010 [50], 1200 in 2018 [51], and 1230 in 2019. However, this is significantly less than the declared 2000-3000 tons even under the inertia scenario of the development of the  [53]. According to [30], REM consumption in metallurgy in 2016 amounted to 30000 tons (oxide equivalent), including China, 23000 tons, Japan and Southeast Asia, 3000 tons, United States, 2000 tons, and other countries, 2000 tons. In 2010, 1000 tons of REMs were used in metallurgy in the European Union countries [6]. In the United States, metallurgy consumed about 650 tons in 2019 and, judging by export, even more pure REMs and their alloys are produced (import of REM alloys in 2019 amounted to 310 tons and pure REM metals, 590 tons; export volumes were 1400 and 100 tons, respectively) [5]. For comparison of REM consumption in metallurgy of different countries, we considered steel production and REM consumption in the entire metallurgy (Table 2).
This comparison is rather arbitrary and does not consider the REM distribution for the production of different alloys, including batteries. However, in our opinion, it characterizes the level of production of such grades of cast iron and steel, which are subject to more stringent requirements in comparison to mass production. These are high-added-value metallurgical products. In terms of REM consumption in metallurgy in Russia, there is a sharp lag not only behind the world leaders (14-17 times) but also behind the world level (11 times). Russia's lagging behind the world leaders will be even more fatal, if we consider that severe climatic conditions, high intensity of use of metal products, relatively low metal stock, difficult mining conditions and geographical location of mineral deposits, and long service life of the already used metal should lead to even higher demand for quality steel.
The specific consumption of REMs in metallurgy in Russia decreased by five times compared to 1991. This can be explained by the decrease in production volumes and the high share of imported steel products with REMs. According to our data, the share of import in the consumption of corrosion-resistant stainless steels is 77.3%, tool high-speed steels, almost 100%, and machine steels (maraging, bearing, spring, high-strength, and rail steels), up to 70% for certain types. Consumer goods with REMs include cutting tools, tableware, and stainless-steel products, which are also largely imported. Therefore, when addressing the problem of import substitution and growth in production of special steels and alloys, as well as consumer goods based on them, the increase in REM consumption should be expected.
REM consumption for high strength cast iron production also has a growth potential. For example, Russia lags behind China and European countries in terms of consumption of pipes made of high strength cast iron [54]. The only plant in Russia that produces such pipes is the Lipetsk Metallurgical Plant Svobodnyi Sokol that consumes only 27000 tons of cast iron. In technologically developed countries, the share of steel and grey iron castings is decreasing, while production of spheroidal graphite castings is increasing by 2-3% annually. They are used not only for the production of pipes but also for parts of metallurgical equipment, machine tools, in heavy transport, and agricultural machinery [55]. According to [56], in Russia in the period from 2006 to 2012 the production of castings from high strength cast iron with spherical graphite increased by 12% (up to 900000 tons), and casting production in general decreased by 4.5 times since Soviet times; the number of foundries decreased from 3500 to 1250; ten research institutes in the field of foundry production were closed down.

CONCLUSIONS
In order to solve the problems of the REM industry in Russia, it is necessary to have an organizational and economic mechanism that would allow the domestic rare-earth industry to sell its products on the domestic market instead of imported products. After that, it will be necessary to increase REM separation capacities. The introduction of new REM production capacities makes no sense without the creation of new industries focused on their consumption, including metallurgy. Global REM production is 210000 tons (oxide equivalent). Non-Chinese REM mining and processing projects are being developed. Due to the organization of large-scale production of consumer goods with REMs, China remains the world leader in the industry: in mining and processing of REMs and in production of consumer goods with REMs. Different sources estimate the share of metallurgy in global REM consumption at 10-20%.
REM consumption in Russia is 1230 tons, of which 120 tons are consumed by metallurgy. In the metallurgy sector, ferrous metallurgy accounts for 86% of REM consumption (50% for cast iron and 36% for steel). REM is most often used in the production of high strength cast iron with spherical graphite. The most mass-produced steel with REMs is steel for pipe billets, with rail steel in second place. The share of steel with REMs does not exceed 1% of its total production volume.
In ferrous metallurgy, REMs are used in the form of their alloys (mischmetal and ferrocerium), pure metals (lanthanum, cerium, and yttrium), silicides in ferroalloys based on ferrosilicon, and complex modifiers based on silicon and without it.
Almost all raw materials with REMs for Russian metallurgy are imported (mischmetal, ferroalloys, and pure metals). The problem of import substitution in the domestic market of raw materials with REMs for metallurgy remains an urgent one. The organization of large tonnage production of alloys with REMs by the electric furnace method should lead to a decrease in their cost in comparison with the production of modifiers from mischmetals and pure REMs. The problem is the high cost of products with REMs made by domestic enterprises.
Despite a significant growth in REM consumption in metallurgy, the domestic market remains small. In terms of REM consumption in metallurgy in Russia, there is a big lag not only behind world leaders but also behind the global level. In addressing the problem of import substitution and growth in consumption of high strength cast iron, special steels and alloys, as well as consumer goods based on them, the growth REM consumption should be expected. In terms of the scale of REM use, domestic metallurgy does not meet modern requirements. If domestic metallurgy is brought to the world level, the demand for REM can increase by 5-10 times.