Non-metallic Inclusions in Different Ferroalloys and Their Effect on the Steel Quality: A Review

Ferroalloys have become increasingly important due to their indispensable role in steelmaking. In addition, the demand for improved steel qualities has increased considerably, which in turn highlights the quality of ferroalloys. This is due to the fact that the impurities in ferroalloys directly and significantly influence the quality of steel products. To gain a better understanding of the main trace elements and inclusions in ferroalloys (such as FeSi, FeMn, SiMn, FeTi, FeCr, FeMo, FeNb, FeV, FeB, some complex ferroalloys) and their behaviours in steel melt after the additions of these ferroalloys, information from a large number of previous results on this topic was extensively reviewed in this work. The applications of different ferroalloys and their production trends were discussed. In addition, the effects of some trace element impurities from ferroalloys on the inclusion characteristics in steel were also discussed. The possible harmful inclusions in different ferroalloys were identified. Overall, the results showed that the inclusions present in ferroalloys had the following influence on the final steel cleanliness: (1) MnO, MnS and MnO–SiO2–MnS inclusions from FeMn and SiMn alloys have a temporary influence on the steel quality; (2) the effect of large size SiO2 inclusions (up to 200 μm) in FeSi and FeMo alloys on the steel cleanliness is not fully understood. The effect of Al, Ca contents should be considered before the addition of FeSi alloys. In addition, Al2O3 inclusions and relatively high Al content are commonly found in FeTi, FeNb and FeV alloys due to their production process. This information should be paid more attention to when these ferroalloys are added to steel; (3) except for the existing inclusions in these alloys, the Ti-rich, Nb-rich, V-rich carbides and nitrides, which have important effects on the steel properties also should be studied further; and (4) specific alloys containing REM oxides, Cr–C–N, Cr–Mn–O, Al2O3, Al–Ti–O, TiS and Ti(C, N) have not been studied enough to enable a judgement on their influence on the steel cleanliness. Finally, some suggestions were given for further studies for the development of ferroalloy productions.

Development of composition and process of obtaining multicomponent ferroalloys

The main product of ferroalloy plants is standard ferroalloys. They often do not have all the necessary service characteristics and are not very suitable for metal processing in a ladle. The developing progressive technology of steelmaking is forced to adapt to the existing range of ferroalloys, the standards for which have not been updated for 50 years or more. In addition, in recent years, the sources and markets of ferroalloy raw materials have changed, and their quality and content of leading elements have decreased. This makes it difficult or excludes the possibility of obtaining ferroalloys according to existing standards. In this regard, the production of more efficient ferroalloys of a new generation is required, suitable for progressive processes in the developing areas of ferrous and non-ferrous metallurgy 795 and smelted from non-traditional types of domestic ore raw materials. These include complex or multicomponent ferroalloys containing, in addition to iron, two or more functional elements. Complex ferroalloys should be created in the most favorable combinations of component. It contributes to the necessary effective impact on the iron-carbon melt with a high degree of assimilation of useful elements in it. The creation of scientific foundations for the formation of new compositions of multicomponent ferroalloys with high consumer properties, and the development of physicochemical processes for obtaining these alloys from unconventional ore raw materials contributes to solving the problems of developing compositions of effective new generation ferroalloys and expanding the ore base of ferroalloy production. When using the developed method of designing the composition of complex ferroalloys using unconventional raw materials, melting technologies were developed; various alloys of the systems were obtained and applied on a laboratory and industrial scale: Fe – Si – Cr, Fe – Si – B, Fe – Si – Ba – Ca, Fe – Si – Al – Nb, Fe – Si – Ca – Mg, Fe – Si – V – Ca – Mn, Fe – Si – Al.

Crystallization temperatures of complex ferroalloys

Thermo-gravimetric method was used to determine the temperature of crystallization onset of alloys of the Fe – Ni – Cr – C – Si system depending on concentration of chromium and nickel. It was shown that complex ferroalloys containing 0.2 – 21.0 % Ni (at Cr = 25 – 28 %); 0.5 – 45.0 % Cr (at Ni = 10 – 11 %); 2.0 % C and 0.3 % Si, iron, and impurities belong to the category of low-melting alloys and have rational values (1320 – 1400 °C) of crystallization temperatures in terms of their use for steel processing in the ladle. An increase of the chromium content to more than 45 % in these alloys is accompanied by an intense increase of their temperatures of the crystallization onset.

Manufacturing and Application of Complex Ferroalloys

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Prediction of melting time of complex ferroalloys by physical and chemical modeling

The purpose of this work is to implement a new approach to the description of the duration of melting (dissolution) of complex new generation ferroalloys during the deoxidation and doping of a metal melt. This approach is aimed at developing a methodology and criteria for the quantification and accounting of the micro-heterogeneity of multicomponent metal melts and their prediction on such important for steelmaking production characteristics as the melting time of ferroalloys, the description of the inter-mine interaction, which allows a deeper understanding of the process. deoxidation and refining of steel. In the work, the approach developed in the Institute of Ferrous Metallurgy of the National Academy of Sciences of Ukraine to solve problems of modeling of non-conformities that relate the composition, structure and properties of melts is used in the work. It is based on the original concept of physicochemical modeling of the processes of interatomic interaction in melts and solutions, developed by E.V. Prihodko. According to it, metal melts are considered as chemically unified systems. Changing their composition affects the complex of physicochemical properties due to changes in the parameters of their electronic structure. The method of calculation of criteria (∆Zy and d), characterizing the degree of difference between the electronic and structural state of the melt, as a chemically unified system, from the mechanical mixture of their initial components and the parameter was used to evaluate and account for the influence of the micron homogeneity of the structure of the metal melts of ferroalloy production. ρl, which takes into account the cluster spin in metal melts. Using these criteria and the available experimental data, analytical dependences were obtained to calculate the melting time of complex (ma-manganese, vanadium, niobium and boromatic) ferroalloys of the new generation. This will allow them to evaluate their effectiveness of application, which is associated with the highest assimilation of the main elements that affect

Deoxidizing and modifying properties of alkaline earth metals within ferroalumosilicocalcium and ferrosilicobarium alloys

Modification of alloys, in particular, by calcium and barium, is one of the promising directions for obtaining alloys with a fine crystalline structure. Complex ferroalloys – ferroalumosilicocalcium and ferrosilicobarium – were developed in the Chemical and Metallurgical Institute after Zh. Abishev. It was shown, that modification of steel by silicon-aluminum complex alloys containing chemically active elements – calcium and barium, should become one of the most effective methods to improve the quality of machine-building metal products.The chemical compositions of the smelted ferroaluminosiliconcalcium and ferrosilicobarium presented. The melting range of the nonmetallic compound formed during the deoxidation of steel by complex alloy containing calcium determined. Results of mechanical tests of the specimens of steel, modified by a complex alloy containing barium considered. A comparison of microstructure of the current production route steel and deoxidized with the complex alloys was carried out.In the course of metallographic studies of experimental steel specimens, a modifying influence on the morphology of nonmetallic inclusions by calcium and barium, supplied in a complex with aluminum and silicon alloys, was established.Metal processing by complex alloys such as ferrosilicoaluminum with calcium (FASC) and ferrosilicobarium (FSAB) indicates the possibility of achieving a higher degree of refining from oxide nonmetallic inclusions and a more even distribution of them in the ingot.The results of the industrial heats also indicated a possibility of improving of quality of casting through the decreasing of hot thermal cracks and gas-shrinkage defects, cleaner grain boundaries, a significant reduction in the number and size of carbide inclusions.