Effect of CaCO₃ addition on the performance of lightweight Al₂O₃‐MgAl₂O₄ refractories with gradient density

Abstract

In this study, to improve the comprehensive performance of lightweight Al 2 O 3 -MgAl 2 O 4 refractories with gradient density, CaCO 3 was added in the matrix to develop platelet structures by adding different amounts (1, 2, 3, and 4 wt%).The effect of CaCO 3 addition on the phase composition, microstructure, and properties of lightweight refractories was investigated. The results showed that CaO⋅6Al 2 O 3 and Ca 2 Mg 2 Al 28 O 46 formed. Meanwhile, platelet structure is distributed at the junction between aggregate and matrix. With the increase of CaCO 3 content, although there were no apparent changes in apparent porosity and bulk density, both the compressive strength and refractoriness under load improved significantly. Furthermore, the results of three-point bending tests showed thermal shock resistance was improved in terms of the value of residual strength ratio from 14.2% to 22.5% for specimens before and after 4 wt% CaCO 3 addition. The findings showed that the introduction of CaCO 3 is feasible and effective for performance improvements of lightweight refractories.

Properties and microstructures of porous corundum‐spinel aggregates fabricated via the Kirkendall effect

“…Al 2 O 3 -MgO refractory castables have been extensively used for working lining of steel ladles because of their excellent slag resistance, high thermal shock stability, and good chemical stability. [1][2][3][4][5] The high bulk density and thermal conductivity of traditional Al 2 O 3 -MgO refractory castables are attributed to the use of dense tabular alumina aggregates during their preparation, which results in high energy consumption and considerable heat loss. [6][7][8][9][10] To overcome these disadvantages, lightweight refractories can be used as working lining because they can increase ther-mal efficiency and decrease energy consumption while maintaining the slag resistance and mechanical properties of the refractories.…”

“…Al 2 O 3 –MgO refractory castables have been extensively used for working lining of steel ladles because of their excellent slag resistance, high thermal shock stability, and good chemical stability 1–5 . The high bulk density and thermal conductivity of traditional Al 2 O 3 –MgO refractory castables are attributed to the use of dense tabular alumina aggregates during their preparation, which results in high energy consumption and considerable heat loss 6–10 .…”

Evaluation of fracture behavior of lightweight magnesia‐based refractories via wedge splitting test along with acoustic emission detection

“…To mitigate the heat loss, microporous aggregates were used to prepare the lightweight refractories for working linings, instead of dense aggregates. [8][9][10][11][12][13][14] The previous study indicated that lightweight magnesia-based refractories have higher strengths and lower thermal conductivity than dense refractories. 15 Mechanical properties and fracture behavior of lightweight magnesia-based refractories have been widely studied.…”

“…Conventional magnesia‐based refractories prepared by sintered or fused dense aggregates as raw materials, have high thermal conductivity and bulk density, leading to excessive heat loss through refractory lining. To mitigate the heat loss, microporous aggregates were used to prepare the lightweight refractories for working linings, instead of dense aggregates 8–14 . The previous study indicated that lightweight magnesia‐based refractories have higher strengths and lower thermal conductivity than dense refractories 15 …”