Abstract
For more than 20 years, the sidewalls and bottom of steel ladles have been lined with carbon-bonded magnesia (MgO-C) and magnesia-alumina bricks (MAC). The alumina raw materials react with magnesia forming a spinel, which decreases open porosity and slag infiltration. The amount, grain size, and chemistry of the added spinel impact the properties of spinel-containing MgO-C. Corrosion tests have been performed in a steel casting simulator at 1580 °C using 18CrNiMo7-6 steel and Fe-rich slag as corrosion medium. Digital light microscopy and SEM/ EDS (scanning electron microscope with energy dispersive spectroscopy) were used to evaluate the corrosion mechanisms. The metal casting simulator test showed that the addition of CaO-MgO-Al2O3 aggregates results in the highest corrosion resistance against molten steel and synthetic basic slag compared to alumina-rich spinel aggregates.
Highlights
MgO-C exhibits excellent slag penetration resistance due to the non-wetting property of carbon.The combination of this good corrosion resistance with the high thermal shock resistance, low thermal expansion, high thermal conductivity, and high toughness makes it a superior refractory material for the slag line of steel ladles [1]
Since the CA-phases containing in spinel-binder CMA 72 are able to interact with MgO in a different way compared to AR78, it is expected that thermal different way compared to AR78, it is expected that thermal treatment will lead to different phases depending on the added spinel raw material [17]
The aim of this work was to identify the influence of AR78 and CMA 72 on the corrosion mechanism of MgO-C, determined by a laboratory corrosion test in a metal casting simulator with steel 18CrNiMo7-6 and synthetic slag at 1580 ◦ C for 30 min
Summary
MgO-C exhibits excellent slag penetration resistance due to the non-wetting property of carbon. The combination of this good corrosion resistance with the high thermal shock resistance, low thermal expansion, high thermal conductivity, and high toughness makes it a superior refractory material for the slag line of steel ladles [1]. Poor high-temperature strength and the oxidation of carbon at operation temperature limit the service life of MgO-C refractories. Lee and Zhang summarized the corrosion mechanisms of MgO-C [2]. The first decomposition step is the oxidization of the carbon component by surrounding oxygen and/or FeO (from the slag).
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