Abstract

Basic oxygen furnace (BOF) is the most popular process selection for oxygen steelmaking and is a relatively cheap conversion process for refining iron into steel. MgO-C is the widely accepted refractory used as working lining. BOF is the most important steel making application in terms of refractory tonnage and the new demands on low carbon steel have been increasing the oxygen volume flow and new process operation. Combination of top and bottom blowing are often used to lower operating costs through better stirring action in the steel bath. MgO-C bricks are been exposed to severe oxidation and corrosion by gases and slags, erosion due to higher emulsion agitation and thermal shock. Also normal thermal cycling due to tap to tap operation can affect the behavior of MgO-C bricks even if any other exceptional interference occurs.

Considering the complex heterogeneous microstructure of MgO-C bricks and the fact that their mechanical properties are strongly affected by in situ transformations during curing and heating process, measurements of the elastic modulus evolution with temperature may provide important information for the understanding the role of different additives and microstructure modification as well as for the development of novel products.

This work presents the evaluation of physical properties, cold and hot mechanical resistance, as well as in situ hot elastic modulus (E) measurements in the temperature range of 30 to 1400°C for antioxidants (Al, Si or Al-Mg alloy) containing MgO-C bricks in a reducing atmosphere. Cured and fired samples were evaluated throughout 1 or 2 heating-cooling cycles compared to the additive-free composition. A comparative evaluation of microstructures during thermal cycling is presented and discussed and linked to BOF operational conditions.