FIELD OF THE INVENTION:
The present invention relates to an soaking pit cover directed to avoid limitations and
complexities encountered in the existing refractory lined soaking pit covers. In particular,
the present invention is directed to the development of self-flow castable based lining for
soaking pit covers which would avoid the problems associated with the presently available
refractory used in the cover structures obtained of alumino-silicate type having alumina
content 42%. Advantageously, the self-flow castable based lining in the soaking pit cover of
the invention would be durable and would not have any problems of opening of joints
between bricks within few days due to high pressure of the furnace and the thermal shocks
experienced by the pit cover during operation and use. The self flow castable lining for
soaking pit cover require very little maintenance and at the same time achieve enhanced life
and longer pit availability, with no leakage from roof or side wall due to the joint free
castable lining of cover. This is also directed to minimize the chances of air infiltration in the
pit reducing the chances of skull formation of ingot /blooms. Specific energy consumption in
the soaking pit can be brought down from 0.44 to 0.426 Kcal/T involving the monolithic
castable self flow lining of the present invention which further helps in achieving an energy
saving of 3% and reduction in consumption of refractory from 0.6 ton to 0.1 ton per cover
due to reduced pit cover repairs. Peripheral plate burning is also reduced drastically owing
to elimination of flame leakage.
BCKGROUND ART:
It is well known in the art of refractory lining of furnaces that the types of refractories used
in the cover structure of soaking pits, are of alumino-silicate type having Alumina content of
42%. The bricks are of typical shapes and are hanged from the mechanical roof structure.
The adjacent bricks in such conventional arrangement are interlocked with tung and groove.
The typical properties of the conventional type of cover refractories have typical chemical
composition and physical properties that do not favor casting in insulating layers but are
obtained in the shape of small bricks. The joints between the bricks are opened within a few
days of use due to high pressure of the furnace and thermal shock. As a result the hot air
through joints damages the metallic hanger holding the bricks and weakens the refractory
structure. The end plate cutting owing to vicinity of the pit wall gets damage at an early
period. The conventional brick lining of the soaking pit cover thus needing frequent repair
and consequent loss of pit availability and thus the reducing the productivity.

There was therefore a persistent need to develop a self flow castable monolithic refractory
lining for the soaking pit cover such that the limitations and problems of the conventional
brick lining as described earlier could be eliminated and the productivity could be improved
by providing the typical properties of said castable lining and also consuming less energy
and repair time for lining damages.
OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore directed to developing the self flow
castable based refractory lining for the soaking pit cover such that the cast layer of joint
free monolithic lining of desired thickness comprising material composition and properties to
favor prevention of flame leakage from roof as well as side wall and thereby drastically
reducing the occurrences of peripheral plate burning.
Another object of the self flow castable based refractory lining for the soaking pit cover is
directed to minimize the chances of air infiltration in the pit by providing a joint free
monolithic lining and thus reducing the percentage of skull formation of ingots or blooms.
A further object of the self flow castable based refractory lining for the soaking pit cover is
directed to casting of said self flow castable wherein the refractory material is cast on to the
cover structure to which MS hangers are welded on to the supporting beams preferably 150
mm apart and two sets of SS 304 anchors are hanged there from each of said hangers such
as to form a network of suspended anchors, thereby giving the cast layer of castable after
natural curing and proper preheating, a longer working life with reduced requirement of
repair.
A further object of the self flow castable based refractory lining for the soaking pit cover is
directed to minimize the extent and frequency of the repair of lining due to damage during
operation.
A further object of the self flow castable based joint free refractory lining for the soaking pit
cover is directed to reduce the specific energy consumption from 0.44 to 0.426 Gcal/T i.e. a
power saving of about 3%, advantageously by eliminating leakage/heat loss from roof or
side walls.

A still further object of the self flow castable based joint free refractory lining for the soaking
pit cover is directed to obtaining said joint free lining by casting of the self flow castable
based lining material after preparing into a mixer by thorough mixing of a batch of 250 kg
of castable taken with requisite quantity of water and rotating the whole batch mix for five
minutes, prior to unloading in small trays and pouring into the format of pit cover.
A further object of the self flow castable based refractory lining for the soaking pit cover is
directed to pouring said castable in the cover from a mixer so as to obtain the insulation
layer of a preferred thickness after natural curing , comprising a 25 mm ceramic fibre
insulation cover with 40 mm insulation castable has been laid.
A further object of the self flow castable based refractory lining for the soaking pit cover is
directed to increased pit availability due to reduced/ minor repairs and thus reducing the
refractory consumption in pit cover reduced from 0.6 to 0.1 ton/cover.
SUMMARY OF THE INVENTION:
The basic aspect of the present invention is directed to a soaking pit cover comprising:
mechanical roof structure having supporting beams ;
hanger means disposed from said mechanical structure;
a network of suspended anchors held with respect to said hanger;
a self -flow castable composition laid on the format of said cover; and
a ceramic fibre insulation with insulation castables.
A further aspect of the present invention directed to a soaking pit cover wherein said self
flow castable composition comprises :
AI2O3 : preferably about 78%; and
CaO: preferably about 0.8%.
A still further aspect of the present invention directed to a soaking pit cover wherein the
said self-flow castable is selectively provided for a physical characteristics comprising :
Water requirement (%):preferably about 6
Flow (%) min: preferably about 100

B.D., gm/cc at 1100C/24 Hrs: preferably about 2.9
CCS kg/cm2 at 110°C/24 Hrs: preferably about 360
1400°C/3 Hrs: preferably about 1200
PLCR at 1400°C/lHr(%):preferably +/- 0.1
HMOR at 1400°C/l/2hr (fired at 1400°C/3 hrs): preferably 50.
A further aspect of the present invention directed to a soaking pit cover wherein MS hangers
are welded to the mechanical structure at a distance of preferably about 150mm.
A still further aspect of the present invention directed to a soaking pit cover wherein from
each individual hanger, two sets of anchors are hanged to thereby obtain the network of
suspended anchors.
Another important aspect of the present invention directed to a process for the manufacture
of said soaking pit cover comprising:
providing mechanical roof structure having supporting beams ;
providing hanger means disposed from said mechanical structure;
providing a network of suspended anchors held with respect to said hanger;
providing a self -flow castable composition laid on the format of said cover; and
providing a ceramic fibre insulation with insulation castables.
A further aspect of the present invention directed to a process for the manufacture of a
soaking pit cover comprising:
welding the MS hangers from supporting beams at a distance of about 150mm;
hanging two sets of anchors from each individual hanger to form the network of
suspended anchors;
covering the entire surface of shutter (dome structure) with polyethene sheet and
greasing with shutter release agent and installing the anchors properly;
providing the mixer to the casting side and coating the anchors with tar properly;
placing the cover on the dome adjusting desired roof thickness;
pouring self-flow castable in the mixer alongwith mixing requisite quantity of water
in the mixer and rotating the batch for a desired period to obtain uniformity of the
mix;

unloading the batch and pouring into the format of pit cover and subjecting to
natural curing; and
laying a layer of ceramic fibre insulation cover with insulation castables.
A still further aspect of the present invention directed to a process for the manufacture of a
soaking pit wherein the layer thickness of ceramic fibre insulation cover is of preferably
about 25mm and the insulation castable is of preferably about 40 mm.
The present invention and its objects and advantages are described and illustrated in
greater details with particular reference to the accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES:
Figure1: is the illustration of the sectional view of the cast refractory structure of the pit
cover comprising the MS hangers welded to supporting beam and a network of suspended
SS 304 anchors, to support said layer of castable lining.
Figure 2: is the illustration of the graphical plot of the heating schedule of the monolithic
refractory castable, comprising natural curing followed by preheating, prior to placing into
operation.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES:
The types of refractories used conventionally in the cover structure of soaking pits, are of
alumino-silicate type having Alumina content of 42%. These are bricks of typical shapes
and are hanged from the mechanical roof structure. The adjacent bricks in such
conventional arrangement are interlocked with tung and groove. The typical properties of
the conventional type of cover refractories have typical chemical composition and physical
properties that do not favor casting in insulating layers but are obtained in the shape of
small bricks. The joints between the bricks are opened within a few days of use due to high
pressure of the furnace and thermal shock. As a result the hot air through joints damages
the metallic hanger holding the bricks and weakens the refractory structure. The end plate
cutting owing to vicinity of the pit wall gets damage at an early period. The conventional

brick lining of the soaking pit cover thus needing frequent repair and consequent loss of pit
availability and thus the reducing the productivity. The Chemical Composition and the
physical properties of the conventional refractory brick lining are given in the following
Table I.
TABLE I:
SI No. Chemical Composition, Wt. % Values
1 AI2O3 42
2 SiO2 55
3 Fe2O3 2.0
SI No. Physical properties -
1 Bulk Density, gm/cc 2.15
2 Appparent Porosity 20
3 Cold Crushing Strength(kg/cm2) 300
4 Permanent Linear Change onReheating at 1500°C/2 hrs(%) 0.1-0.5
Reference is first invited to accompanying figure 1 that illustrates the self-flow
castable refractory according to the present invention, as a sectional view of the cast
refractory structure of the pit cover.
In order to convert an existing conventional brick type refractory lining to the self flow
castable lining of the present invention, the bare surface of the cover structure for soaking
pit has to be obtained, after dismantling total refractory; or alternatively lay fresh castable
layer on a new cover structure; Mild Steel (MS) hangers are welded at preferred gap of 150
mm on to the supporting beams of the cover structure. From each of such individual
hanger, two sets of SS 304 anchors were hanged. Thus a network of suspended anchors
was formed. Then the entire surface of shuttering (dome structure) was covered with
polythene sheet and greased with shutter release agent. All the anchors were installed and
coated with tar properly. The cover was placed on the dome carefully adjusting to ensure
7

the desired roof thickness. The mixer was brought to the casting side of the cover and 250
kgs of self flow castable refractory composition were poured in the mixer and requisite
quantity of water added to the material in the mixer. The whole batch charge was rotated in
the mixer for five minutes and thus completing the mixing when uniformity of the material
is obtained. The batch was then unloaded in trays and poured into the format/mold of the
pit cover. A total quantity of 6.5 T of self flow castable was required for one pit cover. The
monolithic lining was obtained after natural curing as a layer of 25mm ceramic fibre
insulation cover with 40mm castable insulation layer. The typical physico-chemical
characteristics/specification of self flow castable used for soaking pit roof casting in a
particular embodiment of the present invention, is as given in the accompanying Table II.
TABLE II :
SI No. Chemical Composition, Wt. % Values
1 AI2O3 78%
2 CaO 0.8%
SI No. Physical properties -
1 Water requirements(%) 6
2 Flow (%),min. 100
3 Bulk Density, gm/cc at1100°C/24 hrs
4 Cold Crushing Strengthkg/cm2 at 110°C/24 hrs& at 1400°C/3 hrs 3601200
5 Permanent Linear Change onReheating at 1400°C/l hr(%) ±0.1
6 Hot Modulus Of Rupture at1400°C/l/2 hr(fired at 1400°C/ 3 hrs) 50
8

Reference is now invited to figure 2, that illustrates the heating schedule for the self flow
castable of the present invention laid on the pit cover and was placed into operation for
longer periods than the conventional brick type lining. Such a cover runs properly with
minor repairs. The castable lining being joint free and monolithic in nature, leakage from
roof as well as the side walls has been eliminated. This has also minimized the chances of
air infiltration in the pit, which in turn reduces the percentage of skull formation of ingot or
blooms.
It is thus possible by way of this invention through proper selection of refractory materials
and additives for casting complicated semi-circular shapes for soaking pit cover. Specific
energy consumption in the soaking pit has come down from 0.44 to 0.426 Gcal/T. This has
also increased the pit availability because of reduced frequency of repair and hence
refractory consumption in pit cover has come down significantly such that the refractory
consumption in pit is reduced from 0.6 to 0.1 ton/cover with saving in maintenance man-
power .The monolithic lining of the present invention has eliminated flame leakage and
reduced the energy saving of about 3%, avoiding peripheral plate burning. The effective
sealing of pit has also effected reduction in skull formation of ingot/blooms.

WE CLAIM:
1. A soaking pit cover comprising:
mechanical roof structure having supporting beams ;
hanger means disposed from said mechanical structure;
a network of suspended anchors held with respect to said hanger;
a self -flow castable composition laid on the format of said cover; and
a ceramic fibre insulation with insulation castables.
2. A soaking pit cover as claimed in claim 1 wherein said self flow castable composition
comprises :
AI2O3 : preferably about 78%; and
CaO: preferably about 0.8%.
3. A soaking pit cover as claimed in anyone of claims 1 or 2 wherein the said self-flow
castable is selectively provided for a physical characteristic comprising :
Water requirement (%): preferably about 6
Flow (%) min: preferably about 100
B.D.,gm/cc at 1100C/24 Hrs: preferably about 2.9
CCS kg/cm2 at 110°C/24 Hrs: preferably about 360
1400°C/3 Hrs: preferably about 1200
PLCR at 1400°C/lHr(%):preferably +/- 0.1
HMOR at 1400°C/l/2hr (fired at 1400°C/3 hrs): preferably 50.
10

4. A soaking pit cover as claimed in anyone of claims 1 to 3 wherein MS hangers are
welded to the mechanical structure at a distance of preferably about 150mm.
5. A soaking pit cover as claimed in anyone of claims 1 to 4 wherein from each
individual hanger, two sets of anchors are hanged to thereby obtain the network of
suspended anchors.
6. A process for the manufacture of a soaking pit as claimed in anyone of claims 1 to 5
comprising:
providing mechanical roof structure having supporting beams ;
providing hanger means disposed from said mechanical structure;
providing a network of suspended anchors held with respect to said hanger;
providing a self-flow castable composition laid on the format of said cover; and
providing a ceramic fibre insulation with insulation castables.
7. A process for the manufacture of a soaking pit as claimed in claim 6 comprising:
welding the MS hangers from supporting beams at a distance of about 150mm;
hanging two sets of anchors from each individual hanger to form the network of
suspended anchors;
covering the entire surface of shutter (dome structure) with polyethene sheet and
greasing with shutter release agent and installing the anchors properly;
providing the mixer to the casting side and coating the anchors with tar properly;
placing the cover on the dome adjusting desired roof thickness;
11

pouring self-flow castable in the mixer alongwith mixing requisite quantity of water
in the mixer and rotating the batch for a desired period to obtain uniformity of the
mix;
unloading the batch and pouring into the format of pit cover and subjecting to
natural curing; and
laying a layer of ceramic fibre insulation cover with insulation castables.
8. A process for the manufacture of a soaking pit as claimed in anyone of claims 6 or 7
wherein the layer thickness of ceramic fibre insulation cover is preferably about
25mm and the insulation castable is of preferably about 40 mm.
9. A soaking pit cover and its process of manufacture substantially as hereindescribed
and illustrated with reference to the accompanying figures.
Dated this 27th day of March, 2007.

A soaking pit cover with self flow castable based refractory lining such as to eliminate the
problem of opening up of the joints among refractory bricks in the conventional lining. MS
hangers are welded to the supporting beams of pit cover structure with two SS 304 anchors
suspended from each of said hangers such as to form a network of suspended anchors. The
castable with prfered properties prepared in a mixer and brought to the side of cover. A
mix of 6.5T of self flow castable is required for one pit cover, poured in small batches,
ensuring the desired roof thickness. A layer of 25mm ceramic fibre insulation cover with
40mm castable insulation is laid and cured naturally. This monolithic lining require minor
repairs with enhanced life and longer pit availability, with no flame leakage, avoiding
peripheral plate burning and minimizing the chances of air infiltration and skull formation of
ingot/blooms. Specific energy consumption has come down from 0.44 to 0.426 Gcal/T, with
an energy saving of 3%. The lining reduced the consumption of refractory in pit from 0.6
ton to 0.1 ton per cover.