Improved properties of in-situ MgAl2O4-TiO2 dense layer reinforced low-carbon MgO-based refractories

Abstract

With the increasing severity in the service environment of secondary refining furnaces, traditional refractories cannot meet the high requirements. MgO-based fired refractories are subject to the thermal shock effect and slag penetration which are detrimental to their performance. In this study, low-carbon MgO-based refractories are reinforced by an in-situ MgAl2O4(MA)-TiO2 dense layer with the addition of low-cost self-prepared titanium carbonitride [Ti(C, N)]. The influence of the addition of as-prepared Ti(C, N) on the properties of low-carbon MgO-based refractories was investigated. The reinforced refractories had no cracks after 190 thermal shock cycles, demonstrating the highest hot modulus of rupture (HMOR) with excellent thermal shock resistance (TSR). After 2.5 h of rotary immersion in a steel slag, the corrosion depth of the composites was only 26.3% of that of commercial MgO-CaO refractories. Based on the thermodynamic analysis, the Ti(C, N) reinforcement mechanism for the low-carbon MgO-based refractories was studied. A MA-TiO2 dense layer formed during the oxidation process of the composites which enhanced the oxidation resistance. The volume expansion caused by the partial oxidation of Ti(C, N) prevents the penetration of the molten slag to refractories and Ti(C, N) powders forming a protective layer to further effectively protect the composites from slag corrosion owing to its high surface area. In addition, 3CaO·2TiO2 formed by the reaction between the steel slag and Ti(C, N) further increased the slag corrosion resistance (SCR) of the composites. This research offers a new idea for the material selection for secondary refining furnaces to achieve a green and effective steel-making production route and enriches the understanding of the phase behaviour in the Mg-Al-Ti-C-O-N system under high temperatures.