Fabrication and Properties of Lightweight Microporous Magnesia-based Refractories Using Low-grade Magnesite via One-step Sintering Method

doi:10.19691/j.cnki.1004-4493.2025.01.001

China's Refractories ›› 2025, Vol. 34 ›› Issue (1): 1-11.DOI: 10.19691/j.cnki.1004-4493.2025.01.001

Fabrication and Properties of Lightweight Microporous Magnesia-based Refractories Using Low-grade Magnesite via One-step Sintering Method

LI Zilong¹, HUANG Ao^{1, 2}, ZOU Yongshun^{1, 2*}, LIU Yangxi¹, GU Huazhi^{1, 2}, FU Lyuping^{1, 2}

1 The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
2 Joint International Research Laboratory of Refractories and Metallurgy, Wuhan 430081, China

Online:2025-03-15 Published:2025-03-27
Contact: *e-mail: yongshun_zou@wust.edu.cn
About author:Li Zilong, born in 2002, is a postgraduate of Faculty of Materials, Wuhan University of Science and Technology. He has won the first-class academic scholarship and the second-class academic scholarship. His main research direction is the fabrication and properties of porous magnesia-based refractories.

Abstract

Abstract: Traditional magnesia-based refractories face challenges such as high thermal conductivity and poor slag penetration resistance, which contradict the energy efficiency requirements of modern metallurgy. In this study, microporous magnesia was prepared using low-grade magnesite via the one-step sintering method. The microstructure and properties of microporous magnesia prepared by high-silicon and high-calcium magnesites calcined at various temperatures were compared. The pore structure and phase evolution were analyzed, the effect of which on the properties of lightweight magnesia-based dry vibration mix was discussed. The results indicated that within high-silicon magnesite, SiO₂ initially reacted with MgO to form Mg₂SiO₄, which gradually reacted with CaO impurities as the temperature increased transforming into a MgO-CaO-SiO₂ ternary liquid phase and uniformly permeated along the grain boundaries. Due to the bridging effect of strip-like CaO in high-calcium magnesite, the reorganization and sintering of MgO grains at high temperatures were inhibited, resulting in the presence of a significant number of elongated pores within the magnesia after calcination at various temperatures, which was detrimental to the mechanical properties and slag resistance. The microporous MgO prepared by high-silicon magnesite at 1 700 °C exhibited the superior physical properties. The microporous MgO aggregates had a stronger interlocking force with the matrix, resulting in a greater bonding strength. Moreover, the micropores not only effectively reduced the thermal conductivity but also facilitated the supersaturated precipitation of molten slag, hindering further penetration. Compared to the dry vibration mix prepared by fused MgO, the lightweight magnesia-based dry vibration mix prepared with the high-silicon magnesite exhibited higher mechanical strength (~40% increase) and thermal insulation performance (0.870 W · (m · K)^-1 at 1 000 °C), and improved slag resistance.

Key words: microporous magnesia, lightweight dry vibration mix, slag resistance, magnesite, thermal conductivity

LI Zilong, HUANG Ao, ZOU Yongshun, LIU Yangxi, GU Huazhi, FU Lyuping. Fabrication and Properties of Lightweight Microporous Magnesia-based Refractories Using Low-grade Magnesite via One-step Sintering Method[J]. China's Refractories, 2025, 34(1): 1-11.

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Fabrication and Properties of Lightweight Microporous Magnesia-based Refractories Using Low-grade Magnesite via One-step Sintering Method

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