Refractory castables containing alumina-magnesia/self-forming spinel
(MgAl2O4) are used in impact pads of steel ladles in steelmaking
processes. In order to understand the wear mechanisms of refractory materials, several
recipes were tested from a corrosion, slag resistance and thermal shock point of view. The
results show that the corrosion is extremely limited at the slag/refractory interface for
all cases. Nevertheless, for higher cement alumina content castables, the formation of
cracks is observed in refractory castables into which slag can penetrate. The slag reacts
with the alumina to form a new phase such as hibonite (CA6) and calcium dialuminate (CA2).
The volumetric change of these reactions involving CA2 and CA6 lead to the apparition of
macro-cracks. Thus, the penetration of slag and steel are increased, causing hot
mechanical properties to degrade. For lower cement alumina castables, the formation of
micro-cracks is avoided by controlling volume expansion. Thus, the slag deposit reacts
with alumina grains and the matrix at the slag/refractory interface to produce a
monomineral layer of hibonite. In this way, the monomineral layer acts as a barrier and
limits the penetration of slag and steel into the refractory lining. Thus, to increase the
lifetime of refractory castables containing alumina-magnesia/self-forming spinel, it is
advised to control volume expansion in order to avoid the formation of cracks and limit
the penetration of secondary metallurgy steel ladle slag.