FIELD OF THE INVENTION
The present invention relates to a ladle cover and, in particular, to a system of thermal
insulation of ladle covers for effective energy efficient ladle heating and maintenance.
Importantly, the ladle cover with effective thermal insulation of the invention is directed
to favour attaining high ladle temperature during heating and proper retaining ladle
temperature. The thermal insulation system for ladle cover of the invention would also
favour improving the ladle insulation life and thus availability of ladle heating stand and
reducing the cost of ladle cover insulation.
BACKGROUND ART
It is well known that ladle is used in steel making process to receive molten steel from a
steel making unit/converter and subsequently teeming in Ingot moulds. Subsequently,
the ladle is moved to inspection and maintenance section where a sliding nozzle is
scrubbed or replaced with a new sliding nozzle. Importantly, the ladle is required to be
moved to a pre-heating station where the ladle is pre-heated such as by means of the
burner to raise its temperature at a desired level to minimize loss of liquid steel
temperature which is required to be received from a steel making unit /converter.
It is thus an extremely important requisite in steel making process that the ladle pre-
heating be carried out effectively. In particular, it is experienced that inefficient heating
leads to skull formation, reduction of refractory life and also unwanted loss of liquid steel
temperature after tapping. Importantly, high ladle bottom temperature of more than
about 1000°C is essential for tapping of steel in it.
The above requirement of ladle makes it extremely important that ladle more
importantly the ladle covers are effectively insulated so that the same is adapted to
prevent heat loss through the ladle cover and help in attaining high ladle temperature
during heating and adapted to further retain such required ladle temperature for
effective functioning and use of the ladle.
Usually, it is common in the art to provide for ladle covers which are insulated fully
either by ceramic fibre or refractory casting. Fully ceramic fibre insulation in ladle covers
are found to be prone to mechanical damage in the periphery due to slag / metal
deposition at the top of the ladle. Ceramic fibre insulation is lighter in weight than any
other type of insulation but mechanical abrasion strength of it is very less. Moreover, full
refractory casted insulated covers are found to be too heavy and require higher torque
for its movement apart from having a very short life span.

It is thus found that while the ladle covers are required to be functionally efficient in
favour of attaining high ladle temperature during heating and also retaining ladle
temperature, the conventional insulation means involving either the ceramic fibre
insulation or the refractory casting insulation for ladle cover suffer from inherent
problems of mechanical damage due to slag / metal deposition at the top of the ladle
with very less mechanical abrasion strength if obtained solely of ceramic fibre or if
obtained from refractory casting is too heavy to facilitate its movement and also suffer
from very short life span. It is, therefore, a need in the art to advance the art of
insulation of ladle cover which could meet the functional requirements of ladle cover
such at attaining high ladle temperature during heating, retaining ladle temperature and
at the same time would have good mechanical abrasion properties and light weight for
effective movement and also of desired life span.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide for a thermal insulation
system in ladle covers and the like for effective ladle heating which would facilitate
attaining high ladle temperature during heating and retaining ladle temperature and also
favour improving the life of the ladle for effective performance and importantly would not
suffer from mechanical damage / abrasion or complexities by way of being too heavy for
its movements for the desired purpose of ladle heating.
Another object of the present invention is directed to an effective ladle cover insulation
with improved life of the ladle cover insulation which would enable attaining high ladle
temperature during heating and also retaining the ladle heating temperature.
Another object of the present invention is directed to the development of the thermal
insulation of ladle cover which would favour improving the life and ladle insulation
system and thereby favour improving the ladle heating stand and reducing the cost of
ladle cover insulation.
Yet another object of the present invention is directed to development of thermal
insulation system for ladle cover which would favour effective heating of the ladle and
make it thermal energy efficient and favour reduction of skull formation and also
reduction of refractory consumption.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a ladle
cover thermal insulation system comprising a selective combination of ceramic fibre and
refractory castings insulations wherein the central portion of the ladle cover is insulated
with ceramic fibre and the outer annular ring of the cover is insulated by refractory
castings.
In the above disclosed ladle cover thermal insulation system the said ceramic fibre based
insulation in the central portion is secured with respect to the inner surface of the ladle
cover by anchor means. Preferably, the said ceramic fibre based insulation in the central
portion is secured with respect to the inner surface of the ladle cover by stainless steel
anchors welded vertically on the inner surface of the ladle cover. According to a further
preferred aspect, the anchor means/stainless steel rods are welded spaced apart from
one another preferably about 100mm apart in the central portion of the cover to hold the
ceramic fibre.
Importantly, the ladle cover thermal insulation system of the invention is adapted to
prevent heat loss through the cover and achieve higher ladle temperature of > 1000°C.
In accordance with an aspect of the invention , the ladle cover thermal insulation system
comprises a selective combination of ceramic fibre and refractory castings insulations
wherein the central portion of the ladle cover is insulated with ceramic fibre blanket and
the outer annular ring of the cover is insulated by refractory castings preferably Alumina
castables.
It is thus possible by way of the above disclosed thermal insulation system of ladle
covers for ladle heating and the like in accordance with the invention to achieve effective
ladle cover insulation which would effectively and advantageously prevent heat losses
through the ladle cover. In particular, the ladle cover thermal insulation of the invention
is directed to attain the desired high ladle temperature during heating and also retaining
the desired ladle temperature.
The characteristic of high mechanical abrasion strength further provide for improved life
in the ladle cover insulation system, which in turn favours in improving the availability of
ladle heating stand.

Importantly, it is found by way of present invention that the selective thermal insulation
system of ladle cover for effective ladle heating in accordance with invention provides for
a selective and best combination for efficient heating and also prolonged life of the
insulation.
Importantly, as apparent from the disclosure above, the thermal insulation system for
ladle cover in accordance with the invention thus provides for a selective thermal
insulation combination comprising of the central portion of the ladle cover being
insulated with ceramic fibre and the outer annular ring of the cover being insulated by
refractory casting.
Preferably, the central portion insulation obtained from ceramic fibre is anchor welded
vertically on the inner surface of the ladle cover preferably, by means of stainless steel
of anchors.
The above thermal insulation system for ladle cover thus achieves the required insulation
and at the same time ensures a comparative lighter weight than totally refractory
insulated ladle covers available in the art. Moreover, the combination of the ceramic fibre
based central portion and the outer annular ring portion obtained of refractory casting
provides for a modified ladle cover which is less maintenance prone vis-a-vis
conventional ladle cover insulation obtained of either ceramic fibre and light weight
compared to ladle cover insulations solely obtained of refractory castings.
Advantageously, the thermal insulation system for ladle cover of the invention is adapted
to prevent mechanical damage to ceramic fibre especially at the periphery and impart
extra protection at the center. The thermal insulation system for ladle cover of the
invention apart from preventing heat loss and achieving higher ladle temperature are
also found to provide for higher life of ladle cover insulation which would make the use of
ladle cover cost effective, efficient and user friendly.
The details of the invention, its objects and advantages are explained hereunder in
greater detail in relation to non-limiting exemplary illustration as per the following
accompanying figures:
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1 : is an illustration of the ladle cover in accordance with the invention involving
the ceramic fibre based central portion and refracting casting at the periphery;

Figure 2: is an illustration of the modified ladle cover of the invention clearly illustrating
the selective combination of refractory casting and ceramic fibre
Reference is first invited to figure 1, which illustrates the thermal insulation system for
ladle covers and like in accordance with the present invention. As illustrated in the said
figure the ladle cover with the thermal insulation system is obtained of a selective
combination of thermal insulation involving the central portion (CP) of the ladle cover
(LC) insulated with ceramic fibre (CF) and the outer annular ring (AR) of the cover (LC)
obtained from refractory casting (RC).
Importantly, as further illustrated in the figure the ceramic fibre based central portion is
secured by means of stainless steel (SS) anchor welded vertically to the inner surface of
the ladle cover.
The above system of thermal insulation involving the combination of central portion of
ceramic fibre and annular ring peripheral region of refractory casting make the ladle
cover of the invention light weight and at the same time achieve effective ladle cover
insulation and required light and easily maneuverable weight of the ladle cover. Also the
insulation system of the ladle cover of the invention is found to be less maintenance
prone.
Reference is invited to accompanying figure 2 which illustrates further the thermal
insulation system of the ladle cover in accordance with the invention.
As further illustrated in the said figure the ladle cover (LC) as mentioned in relation to
figure 1 above comprises of the central portion obtained of a ceramic blanket (CB) and
outer annular ring portion obtained of alumina castables (AC). The ceramic blanket is
maintained in position and is secured with respect to the inner surface of the cover by
means of stainless steel rods (SSR) also shown in figure 2. The ladle cover as usual is
provided with burner port (BP) as further illustrated in the figure.
It is found that by way of the invention that the above selective combination of
refractory casting at the peripheral ring of the ladle cover and ceramic fibre at the
central part of the ladle cover favour achieving effective ladle cover insulation and less
damage prone and greater life span of the ladle cover insulation. A comparative study of
ladle cover tip surface temperature of a conventional ladle cover and the modified ladle
cover of the invention was carried out and the results are provided herewith in the Table
1.


Importantly, it is found that the outer surface temperature of the ladle cover of the
invention is around 80°C to 90°C lower than that of conventional ladle covers indicating
lower heat loss through the ladle cover top. Such prevention of heat loss through the
ladle cover helps in achievement of ladle temperature higher than 1000°C.
Stainless steel rods are adapted for providing the extra protection of the ceramic fibre at
the central part of the ladle cover, thereby providing for the much required effective
combination of such ceramic fibre based central part and the peripheral ring of refractory
casting of the thermal insulation system for ladle cover of the invention. Advantageously,
the ladle cove insulation system in accordance with the invention can also be extended in
the other ladle cover of ladle heating system.
The thermal insulation system for ladle cover for ladle heating of the invention would
therefore provide for the much desired effective ladle cover insulation to make ladle
heating energy efficient favouring attaining high ladle temperature during heating and
also retaining ladle temperature. The ladle cover of the invention with the thermal
insulation system is found to have improved life of the ladle cover insulation and favour
higher availability of ladle heating stand with reduction of skull formation and the
refractory consumption. Advantageously also, thermal insulation system for ladle cover
of the insulation apart from achieving the above advantageous and selective thermal
insulation and efficient characteristic as a ladle cover is also found to favour for cost
effective and less maintenance prone ladle cover insulation for its wide scale and
effective application and use.

The characteristics of the conventional ceramic fiber and refractory castable materials used
for the ladle cover thermal insulation system according to the present invention are as
follows:
High-temperature insulation wool (HTIW), known as ceramic fiber wool until the 1990s, is
one of several types of synthetic mineral wool, generally defined as those resistant to
temperatures above 1000°C). The first variety, aluminium silicate fibre, developed in the
1950s, was referred to as refractory ceramic fibre.
Ceramic Fibre:
Physical properties:
Operating Temp : 1425°C (Maximum)
Porosity : 60% (Minimum)
Thermal Conductivity: 0.24 WMK at 1000°C
Density : 128 kg/M3
Chemical Analysis: (wt %)
% Al2O3 : 32 (Minimum)
% SiO2 : 55 (Maximum)
%ZrO2 : 13 (Minimum)
Others : Traces
Refractory castables are defined as:
"A packaged, dry mixture of hydraulic cement (generally calcium aluminate cement) and sp
ecially selected and proportioned refractoryaggregates which, when mixed with water, prod
uces refractory concrete or mortar."
Refractory casting:
Physical properties:
Density: 2.75 gm/cc (Minimum)
Cold Crushing Strength: 450 (Minimum) at 110°C
: 700 (Minimum) at 1200°C
HMOR (Hot Modulas of Rupture): 50kg/cm2 (Minimum) at 1450°C / 30 minutes
Operating Temp : 1600°C (Maximum)
Chemical Analysis: (wt %)
% Al2O3 : 72 (Minimum)
%'Fe2O3 : 1.3 (Maximum)
% CaO : 1.0 (Maximum)

WE CLAIM:
1. A ladle cover thermal insulation system comprising a selective combination of ceramic
fibre and refractory castings insulations wherein the central portion of the ladle cover is
insulated with ceramic fibre and the outer annular ring of the cover is insulated by
refractory castings, said selective combination enabling attaining high ladle temperature
during heating and also retaining ladle temperature.
2. A ladle cover thermal insulation system as claimed in claim 1 wherein the said ceramic
fibre based insulation in the central portion is secured with respect to the inner surface
of the ladle cover by anchor means.
3. A ladle cover thermal insulation system as claimed in claim 2 wherein the said ceramic
fibre based insulation in the central portion is secured with respect to the inner surface
of the ladle cover by stainless steel anchors welded vertically on the inner surface of the
ladle cover.
4. A ladle cover thermal insulation system as claimed in anyone of claims 2 to 3 wherein
the anchor means/stainless steel rods are welded spaced apart from one another
preferably about 100mm apart in the central portion of the cover to hold the ceramic
fibre.
5. A ladle cover thermal insulation system as claimed in anyone of claims 1 to 4 adapted
to prevent heat loss through the cover and achieve higher ladle temperature of at least
1000°C.
6. A ladle cover thermal insulation system as claimed in anyone of claims 1 to 5
comprising a selective combination of ceramic fibre and refractory castings insulations
wherein the central portion of the ladle cover is insulated with ceramic fibre blanket and
the outer annular ring of the cover is insulated by refractory castings comprising Alumina
castables.

ABSTRACT

A THERMAL INSULATION SYSTEM FOR LADLE COVER
A system of thermal insulation of ladle covers for effective energy efficient
ladle heating and maintenance. A ladle cover with the thermal insulation
system basically is obtained of a selective combination of thermal insulation
involving the central portion of the ladle cover insulated with ceramic fibre
and the outer annular ring of the cover obtained from refractory casting.
Importantly, the ladle cover with effective thermal insulation of the invention
is directed to favour attaining high ladle temperature during heating and
proper retaining ladle temperature. The thermal insulation system for ladle
cover of the invention would also favour improving the ladle insulation life
and thus availability of ladle heating stand and reducing the cost of ladle
cover insulation.