To develop new ferroalloys of a rational composition, data on their physical and chemical characteristics are needed. One of the main characteristics of th

The authors studied the physicochemical characteristics of new complex alloys containing, %: 11 – 30 Nb, 23 – 28 Si, 3 – 10 Al and 3 – 4 Ti. It was shown that complex alloys have the most favorable values of density and crystallization temperatures compared to standard ferroniobium (60 wt. % Nb). Complex alloys with a low concentration of niobium have acceptable crystallization temperatures and optimal density values (5740 – 6560 kg/m³). This allows the pieces of ferroalloy to be completely in the liquid steel when it is released into the ladle, and to be constantly in motion, which increases absorption of the leading components. When the niobium concentration increases to 30 %, phase composition of the alloy changes: a decrease in the proportion of the low-temperature FeSi phase with low density values and an increase in the proportion of the high-density ternary compound NbFeSi₂ with a crystallization temperature of ~1713 °C. An increase in Nb concentration from 11 to 17 % leads to a decrease in the crystallization temperature, and a further increase to 30 % Nb, on the contrary, is accompanied by an increase in the liquidus and solidus temperatures to 1700 and 1610 °C, respectively, which is consistent with liquidus line in phase diagram of the Fe – Nb system with a minimum in Nb concentration range ~18 %. The best characteristics, both from the point of view of obtaining ferroalloys and use for alloying steel, belong to an alloy containing, wt. %: 17.1 Nb, 24.6 Si, 7.6 Al and 3 Ti. This alloy is characterized by the temperature of crystallization onset (1550 °C) below the liquid steel bath temperature and belongs to the category of low-melting alloys. It has optimal density values – 6390 kg/m³, which has a positive effect on the performance characteristics of niobium ferroalloys.

The study addresses the need to enhance steel properties through improved deoxidation processes, a critical stage in steel production. Traditional deoxidizers such as ferrosilicon, ferromanganese, and aluminum effectively remove oxygen but often lead to the formation of undesirable non-metallic inclusions, negatively impacting steel's mechanical properties. This research investigates the efficacy of complex Fe-Si-Mn-Al alloys as innovative deoxidizers, offering potential advantages in uniform inclusion distribution and mechanical property optimization. Semi-industrial and synthetic complex alloys were produced using high-ash coal, substandard manganese ores, and other materials, followed by metallographic and SEM analyses of deoxidized steel samples. The results highlight significant variations in microstructure, inclusion morphology, and hardness. Steel treated with complex alloys exhibited enhanced uniformity of inclusions and superior mechanical properties, including bainitic and martensitic structures with higher hardness values (up to 46.50 HRc). Compared to traditional deoxidizers, these alloys reduced the presence of detrimental inclusions like manganese sulfides and enhanced the distribution of oxides and nitrides. While martensitic structures offered high strength, challenges like brittleness were noted. This research underscores the potential of complex alloys to revolutionize steel deoxidation, providing pathways for producing high-strength, durable materials suitable for advanced industrial applications.

For development of new ferroalloys and their application, it is necessary to know their physical and chemical characteristics. The most important characteristics of the alloy, on which assimilation and distribution of the main elements of ferroalloys in the iron-carbon melt depend, are their time of melting and dissolution. Using a mathematical model for calculating the melting time, developed by the employees of the Ural Federal University and the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences, the authors studied the duration of melting of complex nickel-containing ferroalloys in liquid steel. The program allows one to calculate the temperature of a piece of ferroalloy, thickness of the frozen steel crust, size of the alloy piece and duration of the melting periods depending on physicochemical and thermophysical characteristics of the ferroalloys. The melting mechanism of ferroalloys determines the time of their melting in liquid steel. This work contains mathematical modeling of melting of complex nickel ferroalloys containing %: ~10 Ni; 0.5 – 55.0 Cr; ~0.2 C; ~0.2 Si, in iron-carbon melt. It was found that all the alloys under consideration belong to the group of low-melting ferroalloys and process of their melting proceeds in three periods. With an increase in the initial diameter of ferroalloy piece from 3 to 100 mm, the melting time increases by 250 – 300 times. It is shown that an increase in Cr content up to 37 % in complex alloy leads to a decrease in the melting time, and with a further increase in the Cr content to 55 %, an increase in the melting time occurs. A decrease in temperature of liquid steel bath from 1700 to 1520 °С is accompanied by an increase in the duration of melting of complex ferroalloys by 7 – 8 times. In general, the considered complex nickel ferroalloys are characterized by a much faster melting process in liquid steel compared to standard ferrochrome and ferronickel.

This study evaluates the effects of semi-industrial and synthetic Fe–Si–Mn–Al deoxidizers on the microstructure, non-metallic inclusions, and hardness of St3 steel. Seven complex alloys with different Fe, Si, Mn, and Al contents were produced and compared with conventional FeSi–FeMn–Al deoxidizers. The steel samples were examined by optical microscopy and Rockwell hardness testing. Depending on the deoxidizer composition, ferrite–pearlite, bainitic, martensitic, and structurally heterogeneous regions were observed. The measured hardness ranged from 26 to 47 HRC. Porosity and dendritic heterogeneity remained in several samples. The results demonstrate that the composition of an Fe-Si-Mn-Al deoxidizer is associated with differences in optically observed microstructural characteristics and reported hardness. These findings provide an experimental basis for selecting complex deoxidizer compositions for further steelmaking studies.

Термогравиметрическим методом определены температуры начала кристаллизации сплавов системы Fe – Ni – Cr – С – Si в зависимости от концентрации хрома и никеля. Комплексные ферросплавы содержат 0,2 – 21,0 % Ni (при Cr = 25 ÷ 28 %) и 0,5 – 45,0 % Cr (при Ni = 10 ÷ 11 %); примерно 2,0 % С и 0,3 % Si; остальное железо и примеси. Эти ферросплавы относятся к категории легкоплавких сплавов и обладают рациональными (1320 – 1400 °С) температурами кристаллизации с точки зрения применения для обработки стали в ковше. Повышение до 45 % содержания хрома в таких сплавах сопровождается интенсивным ростом температур начала кристаллизации.