Silicomanganese (SiMn) as an alloy supplies silicon and manganese to the steelmaking industry.
It is produced through carbothermic reduction in a submerged arc furnace. The slag and metal
are typically tapped through a single-level tap hole at 50 K (50 C) below the process temperature
of 1873 K to 1923 K (1600 C to 1650 C). In one tapblock refractory design configuration,
the tap hole is installed as a carbon tapblock and rebuilt during the life of the lining
using carbon-based cold ramming paste. The carbon tapblock lasts for a number of years and
ramming paste only for months. The purpose of the study presented here was to determine to
what extent chemical reactions between carbon-based refractory and slag or metal in the tap
hole of a SiMn furnace can contribute to wear of tap-hole refractory. The results of the study
are reported in two parts. In Part I, the results of thermodynamic calculations of the potential
for chemical reaction between carbon-based refractory material and slag or metal are reported.
The results were tested experimentally using pure graphite and synthetic SiMn slag (produced
from pure oxides). The paper also reports the composition, microstructure, and phases of
industrial SiMn slag, and commercially available carbon block and cold ramming paste
refractory materials. These compositions were used in predicted equilibria of refractory–slag
reactions. Thermodynamic calculations suggest that reaction between SiMn slag and carbonbased
tap-hole refractory is possible, and experiments with nominally pure materials support
this. However, practical refractory materials are by no means pure materials, and contain
secondary phases and porosity which can be expected to affect reaction with slag. Such reactions
are examined in Part II.