METHOD FOR DETERMINING REFRACTORY
SPECIMEN HEAT RESISTANCE
and T. Volkov-Husoviæ
Translated from Novye Ogneupory, No. 4, pp. 55 – 58, April 2008.
Original article submitted February 21, 2007.
The most important properties governing the operation of refractories are refractoriness, service temperature
and heat resistance. The heat resistance of specimens based on Al
is determined by a standard laboratory
procedure with cooling in water (JUS.B.D.8.319). In order to analyze possible worsening of specimen
property indices before, during and after rapid water cooling a Pro Plus Program control system is used. This
program has also been used for analyzing the nature of grain size distribution. Simultaneously mechanical
properties such as strength, dynamic elasticity modulus, determined from data for measuring resonance
frequency and ultrasonic (US) velocity, are determined. The correlation between worsening property indices,
US velocity, strength and heat resistance is studied in this work. The results obtained are used for a model
predicting refractory specimen heat resistance.
The lining of furnaces for firing high-temperature
ceramics is subject to the action of rapid temperature oscilla-
tions (thermal shock) and stresses promoting formation of
crack growth. In the majority of cases substructural break-
down gives rise to gradual spalling of lining refractories and
their subsequent breakdown up to the necessity of stopping
the furnace for lining replacement. This work requires
considerable economic expenditure, caused by stopping the
furnace for repair and delays in replacing refractories,
particularly in steel casting production. Depending on heat
resistance refractories are used in different service
conditions. In choosing refractories a duel approach is used.
Consideration is given to: 1) material properties [1 – 4] and
2) heat transfer conditions [5 – 7]. As an alternative infor
mation about heat resistance may be obtained by experiment.
One of these tests, well known due to its simplicity, involves
rapid cooling of specimens taken from a furnace into water,
molten metal, oil, or molten salt that is at low temperature.
In order to check the heat resistance of refractories it is
normal to use rapid cooling in water. Rapid thermal cooling
of refractories leads to crack nucleation and (or) their
propagation leading to loss of strength. Since crack forma
tion has a marked effect on US velocity in a material and its
Young’s modulus, a change in these indices may be used for
monitoring during a study of the level of damage under the
action of thermal shock. The aim of this work involves using
non-destructive testing methods for determining the heat
resistance of refractories and revealing their advantages for
the possibility of predicting the behavior of refractories with
thermal shock. Specimen damage was studied by the Pro
Plus Program method that is the most fitting method for
determining the level of surface failure in specimens with
thermal shock. Dependences will be provided in this work
between changes in mechanical properties (strength and
dynamic elasticity modulus) and the behavior of specimens
during thermal shock. Results presented in this work are part
of a study of a group of refractories based on Al
only concern refractories containing 78% Al
directly from the manufacturer. These refractories have been
studied previously when a number of physical properties
were evaluated from thermal shock characteristic data
[8 – 16]. Specimens are presented in Fig. 1 before and after
thermal shock with rapid cooling in water (JUS.B.D.8.319).
Photographs of specimens were obtained before and after
rapid cooling in water. Before studying the failure surface
thin films of chalk were applied in order to obtain high
contrast in determining differences in the surfaces of speci
Refractories and Industrial Ceramics Vol. 49, No. 3, 2008
1083-4877/08/4903-0197 © 2008 Springer Science+Business Media, Inc.
Belgrade University, Faculty of Technology and Metallurgy,