Effect of simultaneous addition of CaO–Al₂O₃ flux and CaSi on the modification of inclusions in aluminium‐killed steel

Abstract

This paper investigates the effect of CaO‐Al2O3 flux, used in conjunction with CaSi, on the formation of inclusions in aluminium‐killed steel. 50 kg scale experiments were carried out in an air induction furnace. The amounts of CaSi (1.25–2.5 kg/t) and fluxes (CaO:Al2O3 from 40:60 to 60:40) were varied in different experimental heats. The volume fraction and size of inclusion were determined through quantitative metallography. The change in the composition of inclusions was qualitatively studied through elemental x‐ray analysis by EPMA. The size of inclusions in general was found to be larger in the case of the simultaneous addition of CaSi with flux, compared to that obtained through CaSi alone. Larger inclusions lead to easier flotation resulting in lesser volume fraction. The inclusion content was lowest with flux containing 40% CaO and 60% Al2O3. Better globularisation of alumina inclusion was observed in the case of the simultaneous addition of flux with CaSi, compared to situations where CaSi alone is added. The present investigation has therefore identified the specific amount and composition of flux necessary for restricting the inclusion content as well as improving its globularisation.

Morphology Control for Al2O3 Inclusion Without Ca Treatment in High-Aluminum Steel

“…[8] showed significant negative values and they decreased by the order of CaOAEAl 2 O 3 (CA), C 3 A, and C 12 A 7 within the steelmaking-temperature ranges, expressing that it was possible to form lower melting point Ca-aluminates from the perspective of the thermodynamics. [41,42] Lind et al [10,39,43] investigated the mechanism and kinetics of reactions between solid CaO and Al 2 O 3 in the absence of molten steel at 1873 K (1600°C), proving that the chemical reaction between Al 2 O 3 and CaO was the rate-controlling step; even then, solid CaO and Al 2 O 3 could be completely liquidized to liquid Caaluminates within 2 to 3 min. Many investigations [44][45][46][47][48][49] have been carried out for the dissolution of Al 2 O 3 in slag, demonstrating that the dissolution rate of Al 2 O 3 particle decreased with increasing Al 2 O 3 content in slag due to that the driving force of Al 2 O 3 dissolution decreased.…”

Estudo Experimental Do Tratamento De Inclusões Com Cálcio Em Escala Laboratorial

“…O baixo rendimento do cálcio pode ser atribuído ao fato dos experimentos terem sido conduzidos sem a presença de escória. Das et al (10) afirmam que uma grande quantidade de CaSi deve ser usada para a modificação de inclusões quando for usado sem escória. Segundo os autores, a influência positiva da escória está relacionada ao fato da evaporação do cálcio ser minimizada pela escória.…”

Kinetics Study on the Modification Process of Al2O3 Inclusions in High-Carbon Hard Wire Steel by Magnesium Treatment

“…The alumina nonmetallic inclusions in hard wire steel have an important influence on the fatigue resistance of wire breaking or hard wire products during cold drawing, resulting in early fracture of steel in practical application [1][2][3]. The number, size, type and distribution of alumina inclusions are very important for the properties of hard wire steels [4][5][6][7][8]. The solubility of magnesium in molten steel is relatively high.…”