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D. Gregurek et al.
(a) Dissolution reaction occurring at the immediate brick hot face: The driving
force here is the lower activity of the refractory oxides like MgO in the slag.
The dissolution process, at least in a closed system, will continue until the liquid
slag has reached saturation. However, in practice the point of saturation is never
reached and dissolution continues until the entire refractory has been consumed.
(b) Dissolution and chemical reaction within the refractory microstructure: Infiltrating slag will dissolve magnesia especially from the fine particles in the brick
according to the respective phase equilibrium. This will not directly contribute
to corrosive wear which takes place at the immediate refractory hot face. Nevertheless, it will contribute to wear by preparing hot erosion due to a loss of
brick bonding.
(c) Kinetics of slag infiltration: Kinetics of slag infiltration causing processes mentioned above depend on several parameters like temperature, viscosity, pore size
distribution, and wetting angle.
On microscopic scale, several zones can be distinguished at the brick hot face
(Fig. 2):
– Adhering slag coating, frequently covering the immediate brick hot face;
– Reaction zone, below the slag coating showing severe dissolution of the magnesia.
Frequently relics of chromite precipitations after magnesia dissolution can be
observed;
– Adjacent to the reaction zone infiltrated and corroded brick microstructure.
In the infiltrated brick microstructure, due to corrosion of the coarse magnesia grains and matrix fines, the main reaction products are (Ca)–Mg–silicates,
namely monticellite (CaMgSiO 4 ), and forsterite (Mg 2 SiO 4 ), as well as Na–Mg–
Fe–Al–silicate. Two minor compounds, (Ca)–Mg–(Fe)–silicate of olivine type and
Na–Ca–Ba–silicate glassy phase, can also be detected.
Fig. 2 Magnesia-chromite brick. Mineralogical investigation. Left: slag coating covering the immediate brick hot face. Reaction zone (R). Infiltrated and corroded brick microstructure (I) Corroded
magnesia (MgO). Right: detail of the reaction zone. In contact with slag severe corrosion of magnesia (MgO) frequently with relics of primary and secondary chromite precipitations (Cr) after the
corrosion of the magnesia. Forsterite (Fo). Lead oxide (PbO)
D. Gregurek et al.
(a) Dissolution reaction occurring at the immediate brick hot face: The driving
force here is the lower activity of the refractory oxides like MgO in the slag.
The dissolution process, at least in a closed system, will continue until the liquid
slag has reached saturation. However, in practice the point of saturation is never
reached and dissolution continues until the entire refractory has been consumed.
(b) Dissolution and chemical reaction within the refractory microstructure: Infiltrating slag will dissolve magnesia especially from the fine particles in the brick
according to the respective phase equilibrium. This will not directly contribute
to corrosive wear which takes place at the immediate refractory hot face. Nevertheless, it will contribute to wear by preparing hot erosion due to a loss of
brick bonding.
(c) Kinetics of slag infiltration: Kinetics of slag infiltration causing processes mentioned above depend on several parameters like temperature, viscosity, pore size
distribution, and wetting angle.
On microscopic scale, several zones can be distinguished at the brick hot face
(Fig. 2):
– Adhering slag coating, frequently covering the immediate brick hot face;
– Reaction zone, below the slag coating showing severe dissolution of the magnesia.
Frequently relics of chromite precipitations after magnesia dissolution can be
observed;
– Adjacent to the reaction zone infiltrated and corroded brick microstructure.
In the infiltrated brick microstructure, due to corrosion of the coarse magnesia grains and matrix fines, the main reaction products are (Ca)–Mg–silicates,
namely monticellite (CaMgSiO 4 ), and forsterite (Mg 2 SiO 4 ), as well as Na–Mg–
Fe–Al–silicate. Two minor compounds, (Ca)–Mg–(Fe)–silicate of olivine type and
Na–Ca–Ba–silicate glassy phase, can also be detected.
Fig. 2 Magnesia-chromite brick. Mineralogical investigation. Left: slag coating covering the immediate brick hot face. Reaction zone (R). Infiltrated and corroded brick microstructure (I) Corroded
magnesia (MgO). Right: detail of the reaction zone. In contact with slag severe corrosion of magnesia (MgO) frequently with relics of primary and secondary chromite precipitations (Cr) after the
corrosion of the magnesia. Forsterite (Fo). Lead oxide (PbO)