FIELD OF THE INVENTION:
The present invention relates to the development of a self-flow high alumina castable based
monolithic lining of desired characteristic for bull nose portion of reheating furnaces directed
to achieving reduced heat loss and refractory failure. The self-flow castable type refractory
lining of the present invention is concerned specifically with the bull nose lining
configuration of reheating furnaces. The new high alumina self flow castable monolithic
lining results in less heat loss and reduced the requirement of maintenance/repairs favoring
lower repair and manpower costs, saving energy and consumption of refractory materials,
improving the furnace availability for production and hence improving efficiency and
productivity in reheating furnace operation, making the invention capable for wide industrial
application in steel making and allied industry.
BACKGROUND ART:
It is well known in the field of steel rolling mills, that heat treatment furnaces of various
capacities are used for heat treatment of blooms/billets for subsequent rolling into different
shapes in successive steps/stages. Operating temperature of these furnaces are in the
range of 1200-1300°C. The furnace walls are conventionally lined with fireclay-based
refractory in both walls and roof to prevent heat loss and damage to furnace shell due to
over heating. These furnaces for the purpose of heat treatment are usually divided into
three sections/zones e.g. Pre-heating zone, heating zone and soaking zone. Each such zone
is connected to the other next zone by a connecting portion which is termed as 'Bull Nose'
and is normally of U-shape, resembling the nose of a bull in appearance as the name
suggests. This portion is also lined with fireclay bricks fabricated to desired shapes to
maintain the semi-circular contour of bull nose portion. Because of the typical shape of
blocks, the blocks in the bull nose portion are frequently subjected to cracking due to
thermal shock generated by cyclic heating and cooling of furnace. Shaped blocks of
refractory so cracked often fall from the rooftop and lead to shut down of the furnaces. Such
phenomena often causes interruption in furnace operation and production, requiring
frequent overhauling and repair/replacement of the furnace lining leading to reduced
through put and efficiency.
There had been therefore a persistent need to over come the limitations and disadvantages
of the conventional shaped blocks of refractory for bull nose portion in heat
treatment/reheating furnaces by adopting preferably a monolithic castable lining that would
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eliminate the problems of cracking of blocks and frequent furnace shut down and would
improve the operational efficiency of these furnaces.
OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore directed to obtaining a self flow
castable based monolithic refractory lining free of any joint, for the bull nose portion of the
reheating furnaces adapted to reduce refractory failure and heat loss to eliminate the
problem of frequent cracking and furnace shut down with conventional refractory lining.
A further object of the present invention is directed to a high alumina self flow monolithic
castable refractory lining of bull nose of reheating furnace to increase the furnace
availability and improve the production at less cost of operation saving heat loss/energy and
use of refractory materials.
A still further object of the self flow castable monolithic refractory lining for the bull nose of
reheating furnace is directed to reduce the requirement of maintenance/repair of refractory
lining of reheating furnace, particularly due to failure at bull nose portion and reduce
manpower requirement.
A still further object of the self flow castable monolithic refractory lining for the bull nose of
reheating furnace is directed to enhance the life of the refractory lining such that the
existing bull nose lining life of 3-4 months is extended up to about 2 years by adopting the
self flow castable lining of the invention, enabling ceaseless operation of the reheating
furnace without any interruption.
A still further object of the high alumina self flow castable monolithic refractory lining for the
bull nose of reheating furnace which could be configured to favored shape for improved
energy utilization and having anchor means selectively disposed for holding said monolithic
self flow castable based lining on semi-circular contour at roof of furnace.
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SUMMARY OF THE INVENTION:
Thus according to the basic aspect of the present invention there is provided a self flow
castable based monolithic lining of bull nose of reheating furnaces adapted to reduce
refractory failure and heat loss comprising:
high alumina self flow castable and metallic anchors adapted for holding the monolithic
structure in semicircular contour of roof of the furnace.
According to a further object of the present invention directed to said self flow castable
based monolithic lining wherein
said high alumina self flowing castables comprise :
AI2O3 - atleast 80%;
CaO - about 0.8%; and
FeO - about 1.0%, and
said metallic anchors comprise metallic SS anchors having particular configuration.
A still further aspect of the present invention directed to a self flow castable based
monolithic lining of bull nose of reheating furnace wherein said high alumina self flowing
castables are selectively obtained to provide for a physical constitution comprising:
B.D after drying at 110°C/24 hrs. - about 2.95 gm/cc
CCS -at 110°C/24 hrs. - about 550 kg/cm2
-at 800°C/2 hrs. - about 350 kg/cm2
-at 1400°C/2 hrs. - about 800 kg/cm2
PLC at 1400°C in(%) after 1 hr. - ± 0.5
HMOR at 1400°C in kg/cm2, 30 minutes - about 60
Of fired Sample at 1500°C
Water requirement - 5%, max.
Free flow - 100, min.
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Advantageously, according to an aspect of said self flow castable based monolithic lining of
the invention comprising insulating castable of a thickness of about 50mm on top of the
monolithic lining of bull nose adapted to reduce heat loss through the bull nose.
Another important aspect of the present invention is directed to a method of producing self
flow castable monolithic lining for bull nose of reheating furnace comprising:
providing the selective high alumina Self flow alumina castable in a format alongwith
anchors for construction of lining of bull nose portion of reheating furnace adapted to
improve the lining life and reduce heat loss.
The method of producing self flow castable monolithic lining according to the invention
involves said selective high alumina Self flow alumina castable comprise said castable
composition containing at least 80% alumina;
said format with SS anchors comprise metallic SS anchors at desired locations for casting of
said self flow castables to obtain desired contour of bull nose at roof top of reheating
furnace;
said SS anchors of selective configuration adapted for holding in position said monolithic
castable lining structure in semicircular contour of bull nose providing longer service life of
lining free of any crack with reduced heat loss and being energy efficient.
A still further aspect of said method of producing self flow castable monolithic lining
according to the invention, wherein said self flow castable used comprise :
Chemical composition (wt%):
AI2O3 - atleast 80%
CaO - about 0.8%
FeO - about 1.0%
Such as to provide for the following Physical Characteristics:
B.D after drying at 110°C/24 hrs. - about 2.95gm/cc;
CCS -at 110°C/24 hrs.- about 550 kg/cm2;
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-at 800°C/2 hrs. - about 350 kg/cm2;
-at 1400°C/2 hrs. - about 800 kg/cm2;
PLC at 1400°C in(%) after 1 hr. - ± 0.5;
HMOR at 1400°C in kg/cm2, 30 minutes - about 60;
Of fired Sample at 1500°C
Water requirement - 5%, max.
Free flow - 100, min.
Importantly, according to the method of producing self flow castable monolithic lining of the
present invention wherein said monolithic castable lining is configured with preferred
semicircular contour for longer service life free of any defect/crack, on continuous operation
of the reheat furnace.
Also said method of producing self flow castable monolithic lining of the present invention
wherein insulating castable lining of thickness of about 50mm thickness is provided on top
of said monolithic castable lining adapted to provide desired energy saving by reduction of
heat loss and fuel consumption.
The present invention and its objective and advantages are described in greater details with
reference to the following accompanying non-limiting figures and examples.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure 1: is the illustration of the format with anchors before casting of the bull nose lining
structure.
Figure 2: is the illustration of the monolithic bull nose lining configuration as cast with high
alumina self flow castable, according to the present invention.
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DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES:
The present invention is directed to replace the conventional fireclay based shaped blocks of
refractory lining at the bull nose portion of reheating furnace with high alumina self flow
castable monolithic refractory lining free of any joint maintaining preferred semicircular
contour and resistant to cracking due to thermal shock arising due to repeated cooling and
heating cycles in the heat treatment furnaces. The objective of the invention is to develop
high alumina self flow castable based lining design for bull nose portion of reheating
furnaces to reduce refractory failure and prevent heat loss through roof top of the furnace
because of cracked blocks or gaps in between blocks, as experienced in conventional
refractory lining configuration. The self flow castable monolithic lining of the bull nose
portion is capable of increasing the life of lining by 5-6 times than conventional lining
applications and thus improve the productivity significantly. The lining accoding to the
present invention also reduces maintenance and repair of refractory lining due to
occurances of cracking or other damages commonly experienced. The refractory
consumption and inventory is also reduced by virtue of longer service life achieved. Because
of the enhanced availability and increased life of lining, 30 days of extra availability of
furnace is ensured. The monolithic refractory lining eliminates the problem of cracking and
saves energy consumption. The improved condition of lining of bull nose portion configured
to desired shape help achieving reduction in fuel consumption up to 5%.
Also some of the secondary benefits derived from the application of high alumina self flow
castable monolithic lining of bull nose of reheating furnace is achieved by way of
improvement of furnace yield because of favored less skull formation, effected by
eliminating crack/gap on lining allowing air to enter and oxidize ingot/bloom surface leading
to skull formation. The advantages of the high alumina castable linining for the bull nose of
reheat furnace can be better understood and illustrated with the help of the following
Example I.
Example I:
According to an embodiment for the high alumina self flow castable monolithic lining on the
bull nose of the reheating furnace, the chemical composition and the physical characteristics
of the castable lining are obtained as given by the following specification:
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Chemical Characteristics (wt%):
AI2O3 - at least 80%
CaO - about 0.8%
FeO - about 1.0%
Physical Characteristics:
B.D after drying at 110°C/24 hrs. - about 2.95gm/cc;
CCS -at 110°C/24 hrs. - about 550 kg/cm2;
-at 800°C/2 hrs. - about 350 kg/cm2;
-at 1400°C/2 hrs. - about 800 kg/cm2;
PLC at 1400°C in(%) after 1 hr. - ± 0.5;
HMOR at 1400°C in kg/cm2, 30 minutes - about 60;
Of fired Sample at 1500°C
Water requirement - 5%, max.;
Free flow - 100, min.;
The above characteristics of high alumina (80% by wt.) self flow based castable was applied
to form bull nose lining on to the format providing desired U-shap contour with selectively
located SS anchor for favored holding of the monolithic castable lining, up to a insulating
thickness of 50mm in order to achieve favored reduction of heat loss and higher energy
efficiency in the operation of the reheat furnace. The SS anchors helped to hold the cast
refractory lining of above characteristics in position providing crack free longer operational
life of lining with uninterrupted and extended furnace availability and thus improving
productivity. Moreover, the selective thickness of insulating lining of the self flow type
castable refractory help achieving improved fuel economy by way of reducing less heat loss
from rooftop of the reheat furnace and reducing fuel consumption up to 5%.
Reference is now invited to accompanying Figure 1, wherein the arrangement of a format
alongwith specially configured SS metallic anchors in selective numbers are illustrated prior
to casting of bull nose monolithic lining according to the invention. The SS anchors, specially
configured provided in the format in which the self flow castable is cast to obtain the desired
8

bull nose lining with preferred semicircular contour, wherein the anchors help holding the
monolithic castable such that longer service life of up to 2 years of the lining is achieved,
without any interruption or frequent maintenance in absence of any crack formation due to
heating and cooling cycles and thus improving the productivity and energy efficiency of the
reheating furnace.
Attention is next invited to accompanying Figure 2, that illustrates the bull nose lining
having self flow castable based monolithic semicircular contoured structure at the roof top
of the furnace. The desired contour is obtained with the help of format of casting. The lining
so obtained is free of any joint and while in service at operating temperature range of 1200-
1300°C, on selective heating and cooling of batches of ingots and blooms do not develop
any crack on the lining with enhanced life of up to 2 years, that is 5-6 times higher than
conventional shaped block lining. Moreover, the insulating lining of about 50mm thickness
on the top of the castable lining provides for energy efficiency and less heat loss during
operation and a resultant higher yield of the reheating furnace operations.
It is thus possible by way of this invention to obtain high alumina self flow type castable
based lining for the Bull Nose portion of reheating/HT furnace in still rolling mills adapted to
provide longer lining life and increased availability of furnace coupled with a host of benefit
attributes that include:
a. 5-6 times increase in Bull Nose lining life;
b. Reduction in refractory inventory and associated costs.
c. Improvement of furnace availability of more than 30 additional days per year;
d. Reduction in energy consumption by way of reducing heat loss from furnace top by
eliminating crack/gap and reducing fuel consumption by about 5% because of
improved lining condition of furnace .
e. Improvement of furnace yield due to favored less skull formation, which is usually
caused by oxidation of ingot/bloom surface on air entry when cracks occur with
conventional fire clay lining with shaped block for bull nose.
f. Reduction in maintenance/repair time and furnace shut down.
g. Reduction in requirement of maintenance/service crew.
h. Improved furnace efficiency and productivity and less cost of production.
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WE CLAIM:
1. A self flow castable based monolithic lining of bull nose of reheating furnaces
adapted to reduce refractory failure and heat loss comprising:
high alumina self flow castable and metallic anchors adapted for holding the
monolithic structure in semicircular contour of roof of the furnace.
2. A self flow castable based monolithic lining as claimed in claim 1 wherein
said high alumina self flowing castables comprise :
AI2O3 - atleast 80%;
CaO - about 0.8%; and
FeO - about 1.0%, and
said metallic anchors comprise metallic SS anchors.
3. A self flow castable based monolithic lining as claimed in anyone of claims 1 or 2
wherein said high alumina self flowing castables are selectively obtained to provide
fora physical constitution comprising:
B.D after drying at 110°C/24 hrs. - about 2.95gm/cc
CCS -at 110°C/24 hrs. - about 550 kg/cm2
-at 800°C/2 hrs. - about 350 kg/cm2
-at 1400°C/2 hrs. - about 800 kg/cm2
PLC at 1400°C in(%) after 1 hr. -±0.5
HMOR at 1400°C in kg/cm2, 30 minutes - about 60
Of fired Sample at 1500°C
Water requirement - 5%, max.
Free flow - 100, min.
4. A self flow castable based monolithic lining as claimed in anyone of claims 1 to 3
comprising insulating castable of a thickness of about 50mm on top of the monolithic
lining of bull nose adapted to reduce heat loss through the bull nose.
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5. A method of producing self flow castable monolithic lining for bull nose of reheating
furnace as claimed in claim 1, comprising:
providing the selective high alumina Self flow alumina castable in a format alongwith
anchors for construction of lining of bull nose portion of reheating furnace adapted to
improve the lining life and reduce heat loss.
6. A method of producing self flow castable monolithic lining as claimed in claim 5
wherein said selective high alumina Self flow alumina castable comprise said castable
composition containing at least 80% alumina;
said format with SS anchors comprise metallic SS anchors at desired locations for
casting of said self flow castables to obtain desired contour of bull nose at roof top of
reheating furnace;
said SS anchors of selective configuration adapted for holding in position said
monolithic castable lining structure in semicircular contour of bull nose providing
longer service life of lining free of any crack with reduced heat loss and being energy
efficient.
7. A method of producing self flow castable monolithic lining as claimed in anyone of
claims 5 or 6 wherein said self flow castable used comprise :
Chemical composition (wt%):
AI2O3 - atleast 80%
CaO - about 0.8%
FeO - about 1.0%;
Such as to provide for the following Physical Characteristics:
B.D after drying at 110°C/24 hrs. - about 2.95 gm/cc
CCS -at 110°C/24 hrs. - about 550 kg/cm2
-at 800°C/2 hrs. - about 350 kg/cm2
-at 1400°C/2 hrs. - about 800 kg/cm2
PLC at 1400°C in(%) after 1 hr. - ± 0.5
HMOR at 1400°C in kg/cm2, 30 minutes - about 60;
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Of fired Sample at 1500°C
Water requirement - 5%, max.
Free flow - 100, min.;
12
8. A method of producing self flow castable monolithic lining as claimed in anyone of
claims 5 to 7 wherein said monolithic castable lining is configured with preferred
semicircular contour for longer service life free of any defect/crack, on continuous
operation of the reheat furnace.
9. A method of producing self flow castable monolithic lining as claimed in anyone of
claims 5 to 8 wherein insulating castable lining of thickness of about 50mm is
provided on top of said monolithic castable lining adapted to provide desired energy
saving by reduction of heat loss and fuel consumption.
10. A self flow castable based monolithic lining of bull nose of reheating furnaces
adapted to reduce refractory failure and heat loss and its manner of manufacture
substantially as herindescribed and illustrated with reference to the accompanying
figures.

The invention relates to a self flow castable based monolithic lining of bull nose of reheating
furnaces adapted to reduce refractory failure and heat loss comprising high alumina self
flow castable and SS metallic anchors for holding the monolithic structure in semicircular
contour of roof of the furnace. The high alumina self flow castable based lining of the
invention comprise wt % of AI2O3 of at least 80% and provide desired physical
characteristics of the bull nose lining. The invention is also directed to a method of
producing said self flow castable monolithic lining with selective high alumina Self flow
alumina castable composition containing at least 80% alumina, in a format comprising
metallic SS anchors at desired locations to obtain desired contour of bull nose at roof top of reheating furnace, holding said monolithic castable lining structure in position in
semicircular contour of bull nose providing longer service life of lining free of any cracking with reduced heat loss and fuel consumption.