Kuiqing Guo

The bottom brick is a critical component of float glass furnace tin baths, serving under harsh conditions including high temperature, tin penetration, hydrogen diffusion and alkali attack. Traditional flint clay-based bottom bricks suffer from high porosity and insufficient service performance. In this study, a high-performance low-cement castable was developed by introducing mullite aggregates to partially replace flint clay. The effects of mullite particle size and addition content on sintering behavior, mechanical properties, thermal shock resistance, refractoriness under load and hydrogen diffusion were systematically investigated. The results demonstrate that, compared with the existing tin bath bottom bricks applied in float glass furnaces, the introduction of 18 wt% mullite with a particle size of 5–3 mm can significantly increase the bulk density, reduce the apparent porosity, enhance the mechanical strength at both room temperature and high temperature, and achieve a higher refractoriness under load and lower hydrogen diffusion capacity. Accordingly, a novel tin bath bottom brick with excellent comprehensive properties for float glass furnaces was successfully developed.

To meet the stringent industrial service requirements of magnesia–chrome refractory bricks, this study adopts a technical approach that synergistically combines precise component ratio optimization with a vacuum-pressure MgSO₄ salt impregnation process to investigate the performance optimization of magnesia–chrome bricks. Samples were prepared by controlled formulation mixing, pressing at 250 MPa, drying at 110 °C, and firing at 1750 °C. Phase composition, microstructure, and physical–mechanical properties were characterized by XRD, SEM, and standard refractory test methods. The optimal additions of chromite powder and Cr₂O₃ micro-powder were determined to be 3 wt.% and 2 wt.%, respectively, which reacted with periclase to form a secondary composite spinel, creating a dense spinel bridge network that connected adjacent grains. Furthermore, when the proportion of sintered magnesia powder (MgO > 97 wt.%) was increased to 11 wt.%, the material achieved efficient densification facilitated by enhancing sintering performance. Based on this optimized formulation, and due to the high elemental compatibility between MgSO₄ and the magnesia–chrome brick matrix as well as the excellent permeability of the solution, the MgSO₄ vacuum-pressure salt impregnation process was subsequently applied. The salt solution filled the open pores and microcracks of the material, forming a crystalline salt micro-pillar reinforcing phase. Consequently, the apparent porosity of the material decreased to 10.98%, the bulk density increased to 3.23 g/cm³, and the cold compressive strength and cold modulus of rupture reached as high as 113.52 MPa and 24.91 MPa, respectively. This study innovatively establishes a new pathway for enhancing the mechanical properties of magnesia–chrome refractory bricks through the synergistic design of component ratio optimization and salt impregnation process. The prepared magnesia–chrome refractory bricks exhibit both excellent mechanical properties and volume stability.