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.

Ladle furnace slag disintegrates into fine powder during cooling due to phase transformations of di-calcium silicate. This creates an adverse impact on working conditions and the environment by dust generation. In this paper, a short overview on different studies to overcome the disintegration problem is provided. An attempt was also made to study the effects of several different additives and their mixtures on disintegration of slag. Phase equilibria calculations were carried out for some additives using FactSage ® to understand the phase changes in the slag. Based on the phase equilibria calculations and literature data, initial laboratory experiments were conducted at 1650°C with different additives such as boric acid, aluminium and fly ash. Slag samples were analysed with XRF and XRD for chemical and phase analysis before and after treatment. The disintegration of slag can be prevented either by addition of 0.5 wt% or more of boric acid or 9 wt% of aluminium or 6 wt% of fly ash or 4-8 wt% fly ash along with 0.125-0.25 wt% of boric acid in slag. Based on the optimised conditions, industrial trials were conducted.

Recycling ladle furnace (LF) slag helps in sustainable steel making and reduces steel production costs. This paper focuses on recycling Si/Mn/Al-killed LF slag as a replacement for CaO-Al 2 O 3 -based synthetic slag for treating high carbon Si/Mn-killed steels. Characterization of different types of LF slag was carried out to identify chemical composition and mineralogical phases. Industrial trials were carried out by recycling LF slag along with lime and calcined bauxite as additives. The effect of recycled LF slag on the kinetics of desulphurization and other process parameters was studied and compared with regular practice. It was observed that LF slag can be recycled successfully as a replacement for CaO-Al 2 O 3 -based synthetic slag at an industrial scale.

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