Study on preformed and in situ spinel containing alumina castable for steel ladle: Effect of fume silica content

Abstract

In the present study, the effect of fume silica content on preformed and in situ spinel containing alumina spinel castable was studied by varying fume silica content at 1 and 4 wt.%. Spinel content for preformed alumina spinel castables varied from 10 to 30 wt.% and MgO content for in situ alumina spinel castables varied from 2.8 to 8.4 wt.%, respectively, and the distribution coefficient (q value) was maintained at .21 and .29 as per Dinger and Funk model. Different castable compositions were processed as per conventional processing technique and further evaluated for densification and strength studies after heat treatment at 110, 1000, and 1550 • C. Fired samples at 1550 • C were further evaluated for the hot modulus of rupture study at 1400 • C and phase analysis study of the matrix phase. Also, the fired samples were studied for microstructural evaluation. K E Y W O R D Salumina spinel castable, calcium hexa-aluminate (CA 6 ), fume silica content, preformed and in situ spinel 1

Alumina‐spinel castable for steel ladles: An overview

“…96 XRD plots of preformed spinel castable (10-and 20-wt.% spinel) and in situ spinel castable (2.8-and 5.6-wt.% MgO) fired at 1550 • C are shown in Figures 6 and 7, respectively, confirming the previous context. 96 The presence of free periclase (minor) phase in the in situ spinel containing composition is the major difference between the phase content of the in situ and preformed spinel containing castables. The presence of CA 6 improves thermal shock, creep resistance, and the hot strength properties of the castables as a result of toughening mechanisms like crack deflection and crack bridging.…”

“…68 Phase analysis study also confirmed the formation of the hibonite (CA 6 ) phase for 1-wt.% fume silica addition in preformed and in situ spinelbased castables. 96 XRD plots of preformed spinel castable (10-and 20-wt.% spinel) and in situ spinel castable (2.8-and 5.6-wt.% MgO) fired at 1550 • C are shown in Figures 6 and 7, respectively, confirming the previous context. 96 The presence of free periclase (minor) phase in the in situ spinel containing composition is the major difference between the phase content of the in situ and preformed spinel containing castables.…”

“…CA 6 crystals are formed in the matrix region for preformed spinel composition in Figure 5A because free alumina is present in the matrix as there is no spinel formation reaction, whereas, for in situ spinel castable, CA 6 crystals are found both in the matrix region as well as at the edges of tabular alumina grains in Figure 5B as enough amount of fine alumina is not present in the matrix due to spinel formation in the matrix region 68 . Phase analysis study also confirmed the formation of the hibonite (CA 6 ) phase for 1‐wt.% fume silica addition in preformed and in situ spinel‐based castables 96 . XRD plots of preformed spinel castable (10‐ and 20‐wt.% spinel) and in situ spinel castable (2.8‐ and 5.6‐wt.% MgO) fired at 1550°C are shown in Figures 6 and 7, respectively, confirming the previous context 96 .…”

“…Microstructural analysis of the fractured surface of preformed and in situ-based alumina-spinel castable at 1550 • C was carried out by Kumar et al 96 Nonuniform shaped grains with rounded morphology for 4wt.% fume silica content; however, 1-wt.% fume silica batch showed needle-like morphology for calcium hexaaluminate (CA 6 ). This CA 6 phase was responsible for better hot strength properties of preformed and in situ spinel castables with 10-and 2.8-wt.% spinel and MgO addition, respectively.…”

“…Microstructural analysis of the fractured surface of preformed and in situ–based alumina‐spinel castable at 1550°C was carried out by Kumar et al 96 . Nonuniform shaped grains with rounded morphology for 4‐wt.% fume silica content; however, 1‐wt.% fume silica batch showed needle‐like morphology for calcium hexa‐aluminate (CA 6 ).…”