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A STEEL LADLE WITH IMPROVED LINING PATTERN AND METHOD FOR
DESIGNING SUCH PATTERN
FIELD OF INVENTION
The present invention relates to improved lining pattern for steel ladles and
magnesia - carbon and alumina - magnesia - carbon refractories for use in
linings of steel-making vessels. More particularly the present invention relates to
an improved lining pattern for steel ladles used for refining operations e.g. VAD
and ladle furnaces and also to a novel brick composition for lining a converter
used for the smelting of molten steel and a method for such Design.
BACKGROUND ART
The magnesia-carbon bricks have a wide range of applications that include LD
converter wear lining, VAD / LF ladle slag areas, ladle bottom impact pads. The
variety of magnesia carbon bricks offered includes normal density magnesia-
carbon bricks, metal line magnesia-carbon bricks and slag line magnesia-carbon
bricks for steel ladles.
The lining of metallurgical vessels in particular for converters in the steel industry
vessels usually consists of basic refractory materials and is often subject to very
severe conditions due to the combined effect of very high temperatures, thermal
and mechanical stresses, and chemical attack. The principal basic materials
used are fired magnesia bricks (of high MgO content) subsequently impregnated
with tar or carbonaceous material, and tar bonded magnesia bricks (of high MgO
content), which may be subsequently tempered.

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Of these two materials, the first are bricks in which magnesia grains of high purity
form strong ceramic bonds by sintering at high temperature. They have great
mechanical strength but suffer in use from brittle fracture in layers mainly parallel
to the hot face of the brick, in spite of the impregnation with carbonaceous
material, and this damage may even occur in the course of the first heating-up of
the lining to its operational temperature.
When the second of the above-mentioned materials, i.e. tar-bonded unfired
magnesia bricks, are used, particular care has to be taken during the heating-up
period of a new lining, because of transient mechanical weakening of the brick in
a temperature range up to 500 degree Celsius when the tar undergoes a process
of thermal cracking. Moreover, the desired ceramic bonding of the magnesia
grains by sintering in situ is substantially delayed, which is thought to be due to
interference by the intergrannular deposits of carbon in the brick. For these
reasons, such bricks are subject to strong wear.
The average life of 300 T steel teeming ladle in SMS-II at BSL was 43 heats
before the introduction of Ladle Furnace (LF) which got drastically reduced to
around 20 heats as all heats were taken through LF, It became extremely difficult
to manage ladle availability in SMS-II with this short life span. The different types
of bricks used in different regions are:-
1. Bottom and Metal Zone - Mag-chrome bricks
2. Slag Zone - Mag-carbon bricks
The properties of these bricks are given in Table I and II. Study was conducted to
understand the wear profile of existing Mag-chrome lining with Magnesia -
carbon in. slag zone, A number of ladles were monitored and an average wear
profile was drawn. The existing lining pattern of 300 T steel ladle along with wear
profile is given in Figure 1.

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In Mag-Chrome bricks, the main constituents are MgO and Cr203. During use,
these two constituents combine together and Mag-chrome spinel is formed. Mag-
chrome spinel tends to decompose at high temperature in presence of iron and
its oxide gives magnesia-chromia solid solution. On cooling, the two recombines
to form spinel and hence thermal recycling is accompanied by material cycling
between spinel and solid solution configurations. Since, this involves a change in
density; the cyclic stress gives alternate compression and tension. This
phenomenon leads to formation of cracks parallel to hot face and peeling of
chunks from refractory lining.
In Magnesia-Carbon bricks, the wear of refractories starts with decarburisation
step close to hot face. The refractory lining is repeatedly exposed to air at high
temperature leading to removal of carbon by oxidation and generation of pores
on the surface. Slag penetrates into the pores giving rise to formation of a brittle
reaction zone. This reaction zone dissolves slowly in the metal / slag exposing to
fresh surface.
Poor and inconsistent life of Well Block is one of the major constraints for
uninterrupted operation of the Ladles. Well Block need to be changed frequently
during campaign of ladle and for that ladle is to be cooled down. It creates
operational inconvenience and severe thermal shock to the lining and in turn
affect the performance of lining. It was found that heavy corrosion and erosion in
slag zone and striking pad area (bottom and lower wall) and low and inconsistent
life of well block were the main reasons for declaring the ladle down, though,
other areas were generally found to be in good condition.
SUMMARY OF INVENTION
Accordingly, the present invention discloses an improved lining design of 300T
steel ladle and a novel composition of brick used in the lining for steel ladles
used for the refining operations e.g. CAD and ladle furnaces.

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Therefore, such as disclosed herein, there is a steel ladle with an improved lining
pattern comprising of alumina-magnesia-carbon bricks in the metal zone of ladle;
magnesia-carbon bricks in the slag zone of the ladle and also 2/3rd magnesia-
chrome and 1/3rd alumina-magnesia-carbon bricks in striking zone of bottom.
Also disclosed, herein, a Alumina-magnesia-carbon brick composition for lining a
steel ladle consisting essentially of, in weight percent, about 28% (Min) MgO,
about 55% (Min) Al203, about 10% (Max) Si02, about 8% (Min) LOI, about 6%
(Max) AP and about 2.85 (Min) BD g/cm3.
Another primary object of this invention is to reduce corrosion and erosion in the
refractory lining in slag zone and striking pad area (bottom and lower wall) by
using improved quality of bricks and optimum lining pattern.
Another object of this invention is to improve the life of well blocks and housing
blocks by using better quality material so that their life matches with the life of the
refractories of other regions.
Another exemplary object of this invention is to reduce the number of joints in the
lining and formation of tight joints. The overall object of this invention is to
optimize the ladle-lining pattern for LD-CC route to get higher lining life and
improve the availability of steel ladles.
As per another object of the present invention there is provision for an improved
ladle bricks, which is simple, easy having readily available components, and
have an enhanced performance and is long lasting compared to other available
bricks.

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Another exemplary embodiment of the present invention is to provide a method
for designing improved lining pattern for steel ladles used for refining operations
e.g. VAD and ladle furnaces
Another object of the present invention is to reduce heat loss from AMC and
Mag-Chrome linings by application of additional insulation with 5mm mill board /
ceramic paper with brick / castable safety lining to reduce heat loss which help
for smooth operation with marginal additional cost.
These together with other objects of the invention, along with the various features
of novelty, which characterize the invention, are pointed out with particularity in
the claims annexed to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and the specific objects
attained by its uses, reference should be made to the accompanying drawings
and descriptive matter in which there is illustrated preferred embodiments of the
invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 is a diagram showing the steel ladle with existing lining pattern and with
the wear profile (prior art);
FIG. 2 is a diagram showing the steel ladle with improved lining pattern according
to the present invention;
FIG. 3 is the top view of the steel ladle with improved lining pattern according to
the present invention.
DETAILED DESCRIPTION
The advent of steel making from open hearth era to LD converters and from ingot
casting with higher tapping temperature, increased holding time and more
stringent process parameters, has called for superior refractories to take care of

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availability of steel making units and ladles. Steel ladle has now become a part
and parcel of steel making process. Requirement of refractories for steel ladle
has drastically changed after introduction of Ladle Furnace (LF). With recent
progress and diversification of technology, the high demand for refractories as a
material for quality production, for equipment reliability and cost has increased
many fold.
The wear of lining is dependent on operational practices apart from refractories
quality. While higher tapping temperatures and holding time adversely affect the
life of ladle, optimum preheating time, less turn around time between successive
heats are beneficial. Alloy additions, its quantity and chemistry of slag etc, may
contribute in different ways. Weightage on the factors varies with operational
practices in the plants. Selection for refractories for lining steel ladles, thus,
needs to be optimized accordingly. From refractories point of view, the wear is
dependent on (i) design of lining, (ii) shape of refractories, (iii) quality of bricks
and (iv) repair practices.
Operational parameters, from LD tapping to concast, were recorded and the
parameters were considered while selecting refractories for ladle lining.
Operating parameters are given in Table III.
Properties of Alumina-magnesia-carbon (AMC) are given in Table IV. Special test
for repeated PLC was done for AMC bricks to understand its expansile nature
during operation. Used Mag-Chrome, MgO-C and AMC bricks were examined for
the physical appearance. XRD and optical microscopy of samples were done to
identify different phases. A detail study was conducted to understand the wear
mechanism in existing and modified lining.
Physical properties of AMC bricks are much superior to mag-chrome bricks.
These bricks are resin-bonded containing carbon and have low porosity.
Repeated PLC of AMC bricks show that it has continuous expansion and the rate

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of expansion after the first cycle comes down slowly. This residual expansion is
due to in-situ formation of MgO-AbCb spinel in the bricks during use. This in-situ
expansion ensures tight joints and reduces the wear of lining due to penetration
of metal and sag through joints.
In alumina-magnesia-carbon system, alumina and magnesia react to form spinel
during use. The formation of spinel leads to an expansion in the brick volume and
when it happens in lining already installed, the lining comes under compression.
This can give a tight joint in the lining of ladle furnace. It is observed, however,
that molten metal penetrates in the gaps between bricks at some places during
early campaign. As the brick expands during use, the molten metal is squeezed
out. Very thin layer seems to get oxidized and reacts with the brick surface
leading to ceramic welding of the two bricks. This behavior indicates that (i) the
molten metal wets the refractory surface and spreads readily over it and (ii) the
metal layer gets oxidized and adheres to refractory surface very strongly. Thus, it
protects against decarburisation of lining and is expected to have a good
corrosion resistance.
In order to estimate comparison, heat loss between AMC and Mag-chrome
bricks, shell temperature were measured at various stages of operation. It was
observed that the shell temperatures at various stages in both the cases are in
the same range. The thermal conductivity of the AMC is 1.5 times higher than the
Mag-chrome bricks. However due to low wear rate, the remaining thickness is
always more than mag-chrome lining and fireclay safety has predominant
weightage on flow of heat flux and thus there is no significant difference in the
heat loss for the AMC and mag-chrome brick linings. Application of additional
insulation with 5mm mill board / ceramic paper will reduce the heat loss through
both type of linings which may help for smooth operation with marginal additional
cost.

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Initially, a panel trial was conducted. In this trial the rate of erosion of AMC bricks
was 2.5 mm per heat whereas it was 5.0 mm per heat for mag-chrome bricks. No
structural spalling was observed in AMC bricks and the surface was very smooth
after use. Based on wear rate, it was inferred that the AMC lining should give
2-2.5 times more life (50-60) than mag-chrome bricks. A series of trials were
conducted and the final optimized lining pattern is given in Fig. 2. The types of
bricks used in different regions are as follows: -
Bottom : Combination of AMC and Mag-Chrome bricks
Metal Zone : Alumina-magnesia-carbon bricks (AMC)
Slag Zone : Mag-Carbon bricks.
Moreover, to reduce the heat loss from AMC and Mag-Chrome linings, additional
insulation with 5mm mill board / ceramic paper with brick / castable safety lining
is made for smooth operation with marginal additional cost.
The bottom lining pattern consists of 2/3rd mag-chrome and 1/3rd AMC bricks in
striking pad area.
RESULTS
1. Physical properties of Alumina - Magnesia - Carbon (AMC) bricks are
much superior to mag-chrome bricks. These bricks are resin-bonded containing
carbon and have low porosity. Repeated PLC of AMC bricks show that it has
continuous expansion.
2. AMC bricks have continuous expansion at high temperature due to in-situ
spinel formation. This continuous expansion provided tight joints in the lining
during use.

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3. Heat loss from AMC and Mag-Chrome linings are in the same range.
However, application of additional insulation with 5 mm mill board / ceramic
paper with brick / castable safety lining will reduce heat loss which helps for
smooth operation with marginal additional cost.
4. The modified lining pattern consists of 2/3rd mag-chrome and 1/3rd AMC
bricks in striking zone of bottom, AMC in metal zone and MgO-C bricks in the
slag zone.
5. Modified lining pattern can give a straight life of 45-50 heats and another
40 - 50 heats may be taken after one bottom repair.
Table 1 - Properties of Mag-chrome bricks :-

Chemical :-
MgO (%), min 70
Cr203(%) 7-12
Physical:
Apparent Porosity (%), max 20
Cold Crushing Strength (kg/cm2), min 350
Refractoriness Under Load (ta °C), min 1580
Thermal Spalling (cycle), min (At 1300°C/water quenching) - 5
Size Tolerance whichever is greater +1.5% or 1mm

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Table II - Properties of MgO-C bricks :-

Properties SAIL 023 Low Cost
Chemical:
MgO (%), Min. 90 88
AI2O3, (%), Max 4 4
CaO(%), Max 2 3
Si02 (%), Max. 1 1.5
Fe203(%), Max 0.7 1.0
Total carbon 9-11 10
Physical:
A. P. (%), Max 3.5 4.5
B.D. (g/cm3), Min 2.92 2.92
CCS (kg/cm2), min 450 400
HMOR (kg/cm2), at 1400°C/% hr, 110 80
min
Size Tolerance (Max) ± 1% or 1mm ± 1% or 1mm
- whichever is whichever is
greater greater

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Table III - Operating parameters of steel ladles in SMS-II, BSL-
Tapping Temperature +1680°C~60%
+1700°C~15%
+1720°C~10%
Average Ladle cycle time 200 - 240 minutes
Ladle additions in SRU Lime, Al, CaF2, CaSi, FeMn, Coke etc
Slag Analysis (%) Si02 CaO MgO FeO Al203 MnO
SRU in 3-5 40-47 5-10 4-5 32-35 1.2-3.2
SRU out 3-5 44^9 8-19 1-2 35-38 0.3-0.9
Table IV- Properties of Alumina-magnesia-carbon bricks:-

Properties AMC-I
Specification Test results
MgO (%), 14 min 16-16.5
Al203,(%), 75 min 75-76
Si02 (%), 3 max 2.7-2.9
LOI (%), 6 min 8.0-8.2
AP (%) 4 max 3-4
B.D. (g/cc) 2.9 min 2.95-3
Coked AP (%) - 12
Coked BD (g/cm3)
CCS (kg/cm2) - 2.95

450 min 520-740
HMOR (kg/cm2) 80 min 92-112
at1400°C/y2hr
Depth of Oxidation 6 max 3-4
1600°C/3hrs(mm)
PLCat1400°C/5hrs +0.3 min +1.1-+1.3
(Reducing) (%)
PLCat1400°C/2hrs - -
(Reducing) (%) after
1st cycle +0.73
2nd cycle +1.18
3rd cycle +1.33
4th cycle +1.53
5th cycle +1.66

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Although the foregoing description of the present invention has been shown and
described with reference to particular embodiments and applications, thereof, it
has been presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the particular embodiments
and applications disclosed. It will be apparent to those having ordinary skill in the
art that a number of changes, modifications, variations, or alterations to the
invention as described herein may be made, none of which depart from the spirit
or scope of the present invention. The particular embodiments and applications
were chosen and described to provide the best illustration of the principles of the
invention and its practical application to, thereby, enable one of ordinary skill in
the art to utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. All such changes,
modifications, variations, and alterations should, therefore, be seen as being
within the scope of the present invention as determined by the appended claims
when interpreted in accordance with the breadth to which they are fairly, legally,
and equitably entitled.

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We Claim-
1. A method for designing improved lining pattern for steel ladles used for
refining operations comprising of:-
providing alumina-magnesia-carbon bricks in the metal zone of
ladle;
providing magnesia-carbon bricks in the slag zone of the ladle;
providing 2/3rd magnesia-chrome and 1/3rd alumina-magnesia-
carbon bricks in striking zone of bottom.
2. A method for designing improved lining pattern for ladles as claimed in
claim 1, further comprising the step of inserting ceramic papers adjacent to the
shell to reduce the shell temperature.
3. A method for designing improved lining pattern for ladles as claimed in
claim 1, further comprising the step of placing firebrick split between shell and
working lining for additional insulation.
4. A steel ladle with an improved lining pattern comprising of :-
alumina-magnesia-carbon bricks in the metal zone of ladle;
magnesia-carbon bricks in the slag zone of the ladle and 2/3rd
magnesia-chrome and 1/3rd alumina-magnesia-carbon bricks in
striking zone of bottom.
5. A steel ladle with an improved lining pattern as claimed in claim 4, wherein
there is provided ceramic papers adjacent to the shell to reduce the shell
temperature.

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6. A steel ladle with an improved lining pattern as claimed in claim 4, wherein
there is provided firebrick splits between shell and working lining for additional
insulation.
7. The Alumina-Magnesia-Carbon bricks, wherein, the brick composition
consists essentially of, in weight percent, about 28% (Min) MgO, about 55%
(Min) Al203, about 10% (Max) Si02, about 8% (Min) LOI, about 6% (Max) AP and
about 2.85% (Min) BD g/cm3.
8. An improved lining pattern for a furnace as claimed in any of the preceding
claims.
9. A steel ladle with an improved lining pattern, substantially as herein
described with particular reference to accompanying drawings.
10. The Alumina-Magnesia-Carbon bricks, substantially as herein described
with particular reference to accompanying Tables.

To,
The Controller of Patents,
The Patent Office, Kolkata.

The present invention relates to improved lining pattern for steel ladles and
magnesia - carbon and alumina - magnesia - carbon refractories for use in
linings of steel-making vessels and a method for designing said improved lining
pattern for steel ladles used for refining operations comprising of providing
alumina-magnesia-carbon bricks in the metal zone of ladle, providing magnesia-
carbon bricks in the slag zone of the ladle, providing 2/3rd magnesia-chrome and
1/3rd alumina-magnesia-carbon bricks in striking zone of bottom.