Abstract
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.
Highlights
FERROALLOYS consist of one or more alloying elements that are bound to iron, which are used to provide the desired chemical elements into molten steel
These publications[1,2,9,10,11,12,13,14,15,16] have in general been more concerned about the production theories and technologies to produce ferroalloys, but few studies have focused on steel cleanliness related to ferroalloy additions
It is apparent that the impurities present in ferroalloys can have a marked effect on the quality of steels
Summary
FERROALLOYS consist of one or more alloying elements that are bound to iron, which are used to provide the desired chemical elements into molten steel. Several books and papers have been published and numerous conferences have been held focusing on ferroalloys These publications[1,2,9,10,11,12,13,14,15,16] have in general been more concerned about the production theories and technologies to produce ferroalloys, but few studies have focused on steel cleanliness related to ferroalloy additions. This work aims to provide a unified, comprehensive and combined overview of impurities present in different ferroalloys as well as how these impurities can influence the steel cleanliness It is the authors’ ambition that the results can be used for the determination of the requirements for ferroalloys and how to optimize the technological parameters (such as time and intensity of melt stirring, holding time before steel casting, etc.) during the production of high-quality alloyed steels
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