Modification of oxide inclusions in calcium-treated Al-killed high sulphur steels

Abstract

A study has been carried out to understand the modification of alumina inclusions in an Al-Killed high sulphur steel with calcium treatment in 150 tonne steel ladle. To avoid abnormalities during casting, inclusions chemistry needs to be controlled so that these inclusions are in liquid phase during continuous casting of steel. For calcium treatment to be effective, general practice is to desulphurise the steel so as to reach sulphur levels below 0.010% to prevent formation of solid CaS inclusions that are harmful to steel quality and final properties. To avoid this additional desulphurising step which involves cost and is time consuming, the authors have developed a new approach of calcium treatment of steel at an industrial scale. This approach involves treating the liquid steel with calcium treatment at low aluminium levels which enables formation of liquid calcium aluminate inclusions (C 12 A 7 ) in the melt and then addition of sufficient aluminium for achieving grade requirement (i.e.

Application of Raman Spectroscopy for Characterizing Synthetic Non-Metallic Inclusions Consisting of Calcium Sulphide and Oxides

“…Although calcium treatment plays a role in modifying high melting point inclusions, with low Al 2 O 3 activity in the inclusions, elemental sulphur can react with calcium to form CaS inclusions. They are solid at casting temperatures and can be very detrimental to the steel quality [7,8]. For example, studies conducted by researchers [7][8][9] have demonstrated that CaS can be found in steel samples from billet [8] and hot-rolled plates [7].…”

“…They are solid at casting temperatures and can be very detrimental to the steel quality [7,8]. For example, studies conducted by researchers [7][8][9] have demonstrated that CaS can be found in steel samples from billet [8] and hot-rolled plates [7]. Additionally, Abdelaziz et al in 2009 [9] suggested that the formation of CaS may be largely associated with the addition of Ca to liquid steel.…”

“…The amount of calcium aluminate phases, such as C12A7, CA, C3A, and calcium sulphides, generally depends on the calcium and sulphur contents, the activity of the aluminum, and the temperature of the molten steel [6]. Therefore, the study of calcium aluminate and sulphide inclusions has received much attention, with various characterization techniques, such as SEM-EDS (scanning electron microscopy-energy dispersive X-ray spectroscopy [7,8], confocal scanning laser microscopy (CSLM) [10], and others [3], used to understand the transformation and control measures for inclusions. Using Raman spectroscopy presents a potential characterization technique for inclusion studies.…”

Transformation of Inclusions in a Complicated‐Deoxidized Heavy Rail Steels During Heating

“…[2,5] Extensive studies have been performed on the characterization and control of inclusions in steels, involving the formation, modification, and removal of inclusions. [6][7][8][9][10][11][12][13][14][15] However, little attention was paid to study the variation of inclusions in solid steels during heating and rolling so far. [16][17][18][19] Significant variation in the composition of inclusions from the molten steel of continuous casting tundish to continuous casting products was reported.…”

Estimation of Activity Interaction Parameters in Fe-S-j Systems

“…The content of sulphur in steels is normally required to be extremely low. “Inclusion engineering” [ 3 ] could be one of the ways to reduce the harmful effects of sulphur [ 4 ] with a relatively low cost. However, implementation of this technique needs to well understand the basic thermodynamics behavior of sulphur in iron-based melts.…”