The Role of Chromite flour in Chrome-Magnesium Bricks
Chromite flour (i.e., crushed chromite) is more than just a filler in chrome-magnesium bricks; it plays several key roles:
Improving High-Temperature Structural Strength: After adding Chromite flour, MgO undergoes a solid-phase reaction with Cr₂O₃, Fe₂O₃, and other minerals at high temperatures, forming composite spinels (such as MgCr₂O₄ and MgFe₂O₄). significantly improving the brick’s high-temperature strength, creep resistance, and refraction under load.
Enhancing Thermal Shock Resistance: The addition of chromium ore modulates the thermal expansion properties of the entire material system. The spinel phase and microcracks effectively absorb and distribute thermal stress, thereby enhancing the brick’s thermal shock resistance and making it more durable in environments with large temperature fluctuations.
Improved resistance to slag erosion: Chrome-magnesia bricks are commonly used in steelmaking furnaces (such as open-hearth furnaces, electric furnaces, and converters), refining furnaces (such as AOD and VOD furnaces), and cement rotary kilns, all of which are subject to corrosion from both acidic and alkaline slags.
Resistance to alkaline slag: The MgO in the bricks inherently resists alkaline slag.
Resistance to acidic slag: Cr₂O₃ provides excellent resistance to acidic slag (especially high-SiO₂ slag). More importantly, when slag erodes, a dense layer of highly viscous magnesium chromate spinel forms on the brick surface, effectively preventing further slag penetration and erosion, effectively providing a protective “slag against slag” effect.
Buffering thermal stress: The thermal expansion coefficient of chromite flour differs from that of magnesia particles. During firing and cooling, tiny cracks or pores form at the interface between the two. These microcracks effectively buffer stresses caused by rapid temperature fluctuations during service, preventing major cracking in the brick.