FIELD OF THE INVENTION
The present invention relates to improved Magnesia carbon bricks for steel ladles and
method of its manufacture. More particularly, the present invention relates to resin bonded
magnesia carbon bricks with improved ageing characteristics and compaction adapted to
ensure enhanced thermo-mechanical properties. Importantly, the method of production of
the magnesia bricks according to the invention involves addition of a polyhydric alcohol and
preferably furfuryl alcohol in selective amounts depending on mix composition, used to
control the ageing behaviour of the mix by increasing the wettability of graphite and
maintaining desired optimum volatile matter contents in the mix before pressing for better
compaction avoiding occurrence of crack and or lamination due to drying even when
ambient temperature is high such as in summer. During mixing, a particular sequence of
addition and mixing time is followed to obtain optimum coating of graphite particles on resin
coated magnesia grains for desired controlled polymerization of resin. Advantageously also,
the addition of alumina rich spinel in selective proportion is made in order to achieve
improved thermo mechanical properties. Such bricks with alumina rich spinel addition
become expansible when exposed to high temperature, as excess alumina of alumina rich
spinel react with fine magnesia present to form spinel. The associated expansion during this
spinel formation favours sealing of the pores caused due to burning of carbon and, also
sealing the brick joints thus preventing the metal penetration through the joints. Presence
of alumina rich spinel in magnesia carbon bricks according to the invention, also improves
hot strength of the bricks by formation of additional ceramic bonding due to spinel
formation. Additionally the presence of alumina rich spinel helps to improve corrosion and
thermal shock resistance of the bricks during service due to vacant positions in spinel
structure, its lower thermal expansion coefficient and modulus of elasticity. The magnesia
carbon bricks of the present invention are thus having the prospects of wide scale
application in ladle lining for improving lining life.
BACKGROUND ART
It is well known in the art of resin bonded magnesia carbon brick manufacturing, the raw
materials like MgO of different quality and size fractions, graphite, antioxidant and additives
are mixed in required proportion with phenol formaldehyde resin. During mixing a particular
sequence of addition and mixing time is followed to obtain optimum coating of magnesia

grains and graphite flakes by resin and additives. The mix is left for ageing for 16-24 hours
depending upon the quality of resin, ambient temperature and shop logistics. The purpose
of ageing is to allow time i) for wetting of graphite and magnesia particles by resin in order
to develop a resin coating on these particles and ii) formation of darbon-carbon chain by
slow polymerisation reaction of resin so that during pressing a good bonding is developed
between these particles. During this period due to polymerisation reaction water is
released, which evaporates out. Also some part of volatile matter of fesin is lost during this
period. These processes during ageing are time-temperature dependent phenomena.
During summer, due to rise in ambient temperature the mix has a ter dency of drying due to
loss of excessive volatile matter. The optimum volatile matter content in the mix for
pressing is 1.0-1.2%. If the volatile matter content after ageing is on higher side, the brick
has a tendency to crack and or laminate and, on the other hand if it is on lower side the
compaction is poor and green bulk density is lowered affecting the overall brick quality.
It has also been observed in conventional lining practice with existing Magnesia Carbon
i
bricks that the Carbon of Magnesia carbon bricks gets coked and is subsequently burnt
during service. This burning off of carbon creates pores in the bricks which compensates the
expansion caused due to conversion of Aluminium (added as antioxidant) to Alumina. Thus
the bricks do not show any expansible characteristics at high temperature, and so the brick
joints created during laying of bricks in ladle do not get sealed causing metal penetration
during service. This results to structural disintegration of the bricks.
There has therefore been a need in the art to developing a magnesia carbon bricks with on
one hand improved ageing behaviour by enhancing wettability property of graphite utilized
to control rate of polymerization of resin, and on the other hand developing selective
composition of compounds/additives with optimized pre-pressing volatile matter contents
and their mixing sequence/timings favoring desired compaction durinc brick manufacturing
adapted to favor in-service high temperature chemical reactions with tiricks having alumina
rich spinel with expansible/sealing property and thermo-mechanicall strength properties
ensuring enhanced life of lining.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to a res n bonded Magnesia
Carbon bricks composition and its method of manufacture involving selective mixing

sequence of components to obtain the final product adapted to ensure better compaction
and improved thermo mechanical properties.
Another object of the present invention is directed to said resin bonded Magnesia Carbon
bricks wherein polyhydric alcohol is selectively added to the mix to ncrease the wettability
of graphite to favor control polymerization of resin and maintain desired volatile matter
content.
A still further object of the present invention is directed to said resin bonded Magnesia
Carbon bricks wherein enhanced graphite coating on resin coated magnesia grain is utilized
to control excessive polymerization reaction of resin during age ng by restricting the
escaping of water formed due to polymerization, even when ambient temperature is high in
summer.
A still further object of the present invention is directed to said resin bonded Magnesia
Carbon bricks wherein enhanced graphite coating on resin coated magnesia grains is utilized
to reduce the loss of volatile matter of resin during ageing so that the volatile matter
content in the mix is maintained at optimum level in order to achieve desired ageing
behavior and compaction during pressing, avoiding the tendency of pricks to crack and or
laminate.
A still further object of the present invention is directed to said resin bonded Magnesia
Carbon bricks wherein excess alumina of added alumina rich spinel favor spinel formation at
high temperature in bricks during service with associated expansion in volume so as to seal
the pores caused due to carbon burning and also to seal the brick joints to thereby
reducing/preventing the metal penetration through joints or avoiding structural
disintegration of bricks.
A still further object of the present invention is directed to said resin bonded Magnesia
Carbon bricks wherein hot strength of bricks is further improved due to additional ceramic
bond formations during spinel formation by reaction between excess alumina of alumina rich
spinel and magnesia fines present in the brick composition.
A still further object of the present invention is directed to said resin bonded Magnesia
Carbon bricks wherein presence of alumina rich spinel in the bricks also contribute to
improving slag corrosion and thermal shock resistance of bricks due to vacant positions in
spinel structure, its lower thermal expansion coefficient and modulus of elasticity.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to Magnesia Carbon brick composition
for improved ageing characteristics, compaction and thermo-mechanical properties having
batch composition, comprising:
Magnesia (Coarse) in the range of 19-21% by weight;
Magnesia (Middle) in the range of 23-26% by weight;
Magnesia (Fine) in the range of 33-35% by weight;
Magnesia (microfine) in the range of 8-9 % by weight;
Graphite in the range of 7-8% by weight;
Aluminium Powder in the range of 1-2% by weight;
Alumina rich spinel in the range of 3-4% by weight;
Resin in the range of 3.8-4% by weight; and
Furfuryl Alcohol in the range of 0.4-0.5 % by weight.
Another aspect of the present invention is directed to Magnesia Carbon brick composition for
improved ageing characteristics, compaction and thermo-mechanical properties having said
batch composition, wherein said Magnesia comprises:

A further aspect of the present invention is directed to Magnesia Carton brick composition
for improved ageing characteristics, compaction and thermo-mechani:al properties having
said batch composition, wherein said Graphite comprises:


A still further aspect of the present invention is directed to Nagnesia Carbon brick
composition for improved ageing characteristics, compaction and thermo-mechanical
properties having said batch composition, wherein said Aluminium po vder comprises:

A still further aspect of the present invention is directed to Magnesia Carbon brick
composition for improved ageing characteristics, compaction and thermo-mechanical
properties having said batch composition, wherein said Alumina rich spinel preferably
alumina rich magnesia aluminate spinel comprises:

According to yet another aspect of the present invention directed to Magnesia Carbon brick
composition for improved ageing characteristics, compaction and thermo-mechanical

properties having said batch composition, wherein said Resin, preferably Phenol
Formaldehyde Resin(Resol type) comprises:

A still further aspect of the present invention is directed to Magnesia Carbon brick
composition for improved ageing characteristics, compaction and thermo-mechanical
properties having said batch composition, wherein said Furfuryl alcohol with Molecular
formula CsH602 comprises:

Importantly, properties of Magnesia Carbon bricks obtained of the Isaid magnesia carbon
brick composition comprises:

According to yet another aspect, the present invention is directed to a method for
production of Magnesia Carbon bricks with improved ageing character sties, compaction and
thermo-mechanical properties comprising selective mixing sequence and timings for
addition of ingredients, followed by ageing, screening, pressing, tempering and then
packing, wherein said selective mixing sequence comprises the steps of:

(i) Magnesia micro fines, alumina rich Spinel and Aluminium powder of desired
fineness mixed thoroughly and this pre-mix batch kept separately;
(ii) Coarse and middle fractions of Magnesia are added in tre mixer and mixed pre
for about 2 to 3 minutes preferably for about 2 minutes;
(iii) Adding 60 to 70% preferably about 70% of resin to the mix in the mixer and
mixed for about 3 to 4 minutes preferably about 3 minutes;
(iv) Graphite is then added to the mix and mixed for 4 to 6 mmutes preferably about
5 minutes.
(v) Furfuryl alcohol is next added to the mix followed by addi :ion of remaining 30 to
40 preferably about 30% resin, Magnesia fines and the piemix batch of step (i),
which are mixed for 10 to 15 minutes preferably about 12 Tiinutes;followed by
(vi) Discharge of the mix from mixer for ageing.
A still further aspect of the present invention is directed to a me:hod for production of
Magnesia Carbon bricks wherein the brick composition is preferably selected such as the
volatile matter content in the mix after ageing for pressing could be maintained optimum in
the range of 1.0 to 1.2 % for desired compaction.
A still further aspect of the present invention is directed to said me:hod for production of
Magnesia Carbon bricks wherein said brick composition is selectively srovided such that the
said resin is covered with graphite particles to hinder escaping of water such so as to
prevent/control excessive polymerization of resin.
A still further aspect of the present invention is directed to said me hod for production of
Magnesia Carbon bricks, wherein said alumina rich spinel addition favour sealing of pores
caused due to burning of carbon and sealing of brick joints in the I ning by expansion of
bricks, preventing metal penetration.
A still further aspect of the present invention is directed to said meqnoa for production of
Magnesia Carbon bricks comprising additional ceramic bond formation!; by reaction between
excess alumina of alumina rich spinel and magnesia present to form spinel at high
temperature during service, which helps to improve hot strength of bricks.
A still further aspect of the present invention is directed to said metiod for production of
Magnesia Carbon bricks comprising addition of alumina rich spinel addition to improve slag
corrosion and thermal shock resistance of bricks.

The present invention and its objects and advantages are described in greater details with
reference to the following accompanying non limiting illustrative drawing.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: is the schematic illustration of the process flow chart for the process of
manufacturing of the MgO-C bricks according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWING
The present invention relates to resin bonded magnesia carbon tricks with addition of
furfuryl alcohol and alumina rich spinel to ensure improved ageing cr aracteristics for better
compaction even when ambient temperature is high and enhanced thermo-mechanical
properties for steel ladles and method of its manufacture.
The objects and advantages of the present invention is better explained by way of the
following accompanying example.
Example 1:
According to an embodiment of the present invention the batch conposition of Magnesia
Carbon brick using different components in the mix are as follows:
Magnesia (Coarse) in the range of 19-21% by weight;
Magnesia (Middle) in the range of 23-26% by weight;
Magnesia (Fine) in the range of 33-35% by weight;
Magnesia (microfine) in the range of 8-9 % by weight;
Graphite in the range of 7-8% by weight;
Aluminium Powder in the range of 1-2% by weight;
Alumina rich spinel in the range of 3-4% by weight;
Resin in the range of 3.8-4% by weight (additional); and
Furfuryl Alcohol in the range of 0.4-0.5 % by weight (additional)

The details of the different raw material additives and binder used in the above composition
are as follows:


Alumina rich Magnesia Aluminate Spinel comprising:

Reference is now invited to the accompanying Figure 1 that illustrates schematically the
flow process chart for the production of Magnesia Carbon bricks according to the present
invention showing the sequence of steps involved comprising mix ng of the different
ingredients and additives as given above followed by ageing, screening, pressing, tempering
at 250°C and then packing. The mixing sequence for preparation of mix for production of
Magnesia Carbon in said process as illustrated in the accompanying Figure 1 is as follows:

(i) Magnesia micro fines, alumina rich Spinel and Aluminium powder of desired
fineness are mixed and kept separately;
(ii) Coarse and middle fractions of Magnesia are added in l:he mixer and mixed for
about 2 to 3 minutes preferably for about 2 minutes;
(iii) Adding 60 to 70 % preferably about 70% of resin to the mix in the mixer and
mixed for about 3 to 4 minutes preferably about 3 minutes;
(iv) Graphite is then added to the mix and mixed for 4 to 6 minutes preferably
about 5 minutes,
(v) Furfuryl alcohol is next added to the mix followed by addition of remaining 30
to 40 preferably about 30% resin, Magnesia fines and the premix batch of step
(i) which are mixed for 10 to 15 minutes preferably abcut 12 minutes;followed
by
(vi) discharge of mix from mixer for ageing.
The process for the production of Magnesia Carbon brick of the indention as illustrated in
the example above is adapted to providing improved ageing bene viour, compaction and
thermo-mechanical properties of bricks. To evaluate the properties to be achieved,
laboratory studies have been carried out with four different polyhydric alcohols to find
their effect on wettability of graphite in order to investigate and solve the problem
relating to drying during ageing. From such experimental studies, it has been found that
the furfuryl alcohol is the most effective in increasing wettab lity of graphite. This
graphite with improved wettability gets adhered better with the resin coating already
formed on magnesia grains. Thus the resin is ultimately covered to a great extent by
graphite particles, which prevents escaping of water, formed due to polymerisation
reaction of resin, slowing down the polymerisation of resin and prevents its excessive
polymerisation, especially required in summer when ambient temperature is high. Also
the graphite coating over resin helps to lower the loss of volatil 3 matter of resin. An
optimum polymerisation of resin with optimum volatile matter content in the mix for a
longer duration is maintained by these phenomena, which in turn retards the drying of
the mix during ageing period even when ambient temperature is high in summer time.
The amount of furfuryl alcohol addition then have been optimised by carrying out further
work on actual batch composition of magnesia-carbon brick using the necessary raw
materials, additives and resin to develop the preferred composition with desired range of
proportion for the individual components.

In case of the Magnesia Carbon bricks according to the present invention, sealing of
brick joints is achieved by making the bricks expansible. For th s, the effect of addition
of alumina rich magnesia-aluminate spinel in very fine size in magnesia carbon bricks
has been studied. From this study it has been found that such bricks, with alumina rich
spinel addition become expansible when exposed to high temperature. Spinel structure
is such that within its unit cell considerable octahedral and tstrahedral sites remain
vacant. Therefore, it forms solid solution with varying amount of Al203, MgO and other
oxides. Due to this characteristic, spinel can be made to have either excess MgO or Al203
in the form of solid solution. This excess alumina present in the added spinel reacts at
high temperature with micro fine magnesia present in the brick and forms spinel during
service in the ladle. Spinel formation is associated with an expansion of 7-8% by
volume. Such expansion resulted by spinel formation seals th<2 pores caused due to
burning of carbon and makes the brick expansible, which in turn seals the brick joints
eliminating possibility of the metal penetration through the joints.
It has been observed that hot strength of magnesia carbon brick is higher when metallic
aluminium is added as an antioxidant to prevent oxidation of graphite to a certain
extent. The metallic aluminium in bricks forms alumina upon oxidation, which in turn
forms aluminium carbide by reacting with carbon. Magnesia carbon brick as such does
not have any ceramic bonding as it is not pre-fired during manufacturing or before
putting it in service. However, because of the chemical reactions and subsequent
formations of aluminium carbide, ceramic bonding develops during service, which
contributes to high hot strength of this type of bricks. In the de/eloped Magnesia also
the formation of spinel at high temperature additionally contributes to ceramic bonding,
which helps to improve hot strength further.
Presence of alumina rich spinel improves corrosion resistance of refractory bricks as due
to vacant sites in its structure, spinel can trap the rapidly diffusing species such as
oxides of iron and manganese from the slag within its crystal structure forming complex
spinel, i.e., (Mg, Mn, Fe)0.(Fe, AI)203. Further, the lime of slag reacts with alumina of
alumina-rich spinel forming highly refractory hibonite (CaO.6 Al203). Depletion of MnO,
FeO and CaO makes the slag richer in silica and hence more vis:ous. This increase in
viscosity of slag reduces its ability to penetrate inside the brick. As a consequence of
these phenomena, presence of alumina rich spinel in the developed magnesia carbon

bricks would additionally contribute positively towards slag corrbsion resistance of such
bricks.
Another positive contribution of alumina rich spinel addition in the developed magnesia
carbon bricks would be towards thermal shock resistance duu to the lower thermal
expansion co-efficient and modulus of elasticity of spinel.
The Magnesia Carbon bricks adapted to providing improved ageing characteristics,
compaction and thermo-mechanical properties as obtained using the
components/ingredients, their mixing in sequence following the process steps as
described in the above example found to have the following end properties:
AP (%) in the range of 3.6 - 4.9;
BD gm/cc in the range of 2.94 - 2.99;
CCS kg/cm2 in the range of 460 - 542;
Coke porosity (%) in the range of 9.5 - 10.5;
HMOR (kg/ cm2) in the range of 100 - 110;
PLC (%) in the range of 0.6 - 0.8;
It is thus possible by way of the present invention to developing a composition for
Magnesia Carbon bricks adapted to achieve improved ageing characteristics, compaction
and enhanced thermo mechanical properties in service. Moreover, the expansible
behaviour obtained due to presence of alumina rich magnesia-a uminate spinel in the
bricks produced according to the process of the invention and spinel formation in service
at high temperature favour on one hand ceramic bonding resulting in high hot strength
and on the other hand enable sealing of the pours due to carbcn burn off as well as
seals the brick joints reducing the chances of metal penetnition. The developed
Magnesia Carbon bricks further adapted to ensure corrosion resistance and thermal
shock resistance while in service and thus ensuring longer ladle lining life. The Magnesia
Carbon bricks according to the present invention thus ensure increased ladle availability
when used for ladle lining, improved productivity with reduction in overall refractory
consumption and cost and thus favouring large scale application of these bricks for lining
of steel ladles in iron and steel industry.

We Claim:
1. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition, comprising
Magnesia (Coarse) in the range of 19-21% by weight;
Magnesia (Middle) in the range of 23-26% by weight;
Magnesia (Fine) in the range of 33-35% by weight;
Magnesia (microfine) in the range of 8-9 % by weight;
Graphite in the range of 7-8% by weight;
Aluminium Powder in the range of 1-2% by weight;
Alumina rich spinel in the range of 3-4% by weight;
Resin in the range of 3.8-4% by weight ; and
Furfuryl Alcohol in the range of 0.4-0.5 % by weight.
2. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition as claimed in claim 1,
wherein said Magnesia comprising
MgO 97 % min.
Fe203 0.2% max.
Al203 0.12% max.
Si02 0.35% max.
CaO 2.4% max.
B203 0.03% max.
CaO : Si02 5 min.
Bulk sp. gravity 3.4 gm/cc min.
Av. Crystal size 100 micron min.
3. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition a$ claimed in claims 1,
wherein said Graphite comprises


4. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition as claimed in claims 1,
wherein said Aluminium powder comprises

5. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition as: claimed in claims 1,
wherein said Alumina rich spinel preferably alumina rich magnesia aluminate spinel
comprising

6. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition as claimed in claims 1,
wherein said Resin, preferably Phenol Formaldehyde Resin(Resol type) comprises


7. Magnesia Carbon brick composition for improved ageing characteristics, compaction
and thermo-mechanical properties having batch composition as claimed in claims 1,
wherein said Furfuryl alcohol with Molecular formula C5H6O2 ccrhprises

8. Magnesia Carbon bricks obtained of the magnesia carbon brick composition as
claimed in anyone of claims 1 to 7 comprising,

9. A method for production of Magnesia Carbon bricks with improved ageing
characteristics, compaction and thermo-mechanical properties as claimed in claim 8
comprising involving selective mixing sequence and timings for addition of
ingredients, followed by ageing, screening, pressing, tempering and then packing,
wherein said selective mixing sequence comprises the steps of
(i) Magnesia micro fines, alumina rich Spinel and Aluminium powder of
desired fineness mixed and kept separately;

(ii) Coarse and middle fractions of Magnesia are added in the mixer and
mixed for about 2 to 3 minutes preferably for about 2 minutes;
(iii) Adding 60 to 70 % preferably about 70% of resin is then added to the
mix in the mixer and mixed for about 3 to 4 minutes preferably about
3 minutes;
(iv) Graphite is then added to the mix and mixed for 4 to 5 minutes
preferably about 5 minutes,
(v) Furfuryl alcohol is next added to the mix followed by addition of
remaining 30 to 40 % preferably about 30% resin, Magnesia fines and
premix batch of step (i) which are mixed for 10 to 15 minutes
preferably about 12 minutes; followed by
(vi) discharge of mix from mixer for ageing.
10. A method for production of Magnesia Carbon bricks as claimed n claim 9 wherein the
brick composition is preferably selected such as the volatile matter content in the mix
after ageing for pressing could be maintained optimum in the range of 1.0 to 1.2 % for
desired compaction.
11. A method for production of Magnesia Carbon bricks as claimed in anyone of claims 9 or
10 wherein said brick composition is selectively provided such that the said resin is
covered with graphite particles to hinder escaping of water such so ias to prevent/control
excessive polymerization of resin.
12. A method for production of Magnesia Carbon bricks as claimed in anyone of claims 9 to
11, wherein said alumina rich spinel addition is carried out to favour sealing of pores
caused due to burning of carbon and brick joints preventing metal penetration.
13. A method for production of Magnesia Carbon bricks as claimed in anyone of claims 9 to
12 comprising formation of spinel at high temperature during service, contribute to
additional ceramic bonding which helps to improve hot strength of bricks.
14. A method for production of Magnesia Carbon bricks as claimed in anyone of claims 9 to
13 comprising addition of alumina rich spinel addition to improve slag corrosion
resistance and thermal shock resistance of bricks.

15. Magnesia Carbon brick composition and bricks with improved ageing characteristics,
compaction and thermo-mechanical properties obtained thereof and a method of its
manufacturing substantially as herein described with reference to the non limiting
illustrative drawing and example.

The present invention relates to resin bonded Magnesia carbon bricks composition with
improved ageing characteristics and compaction adapted to ensure enhanced thermomechanical
properties for steel ladles and method of its manufacture. Importantly, the said
method involves addition of selective polyhydric alcohol preferably furfuryl alcohol to control
the ageing behaviour of the mix by increasing the wettability of graphite and maintaining
desired optimum volatile matter content in the mix before pressing tor better compaction
even when ambient temperature is high. A particular mixing sequence and timing is
followed to obtain desired controlled polymerization of resin. The alumina rich spinel
addition makes the brick expansible during service, favoring sealing of the pores and also
sealing the brick joints preventing the metal penetration through the joints. The MgO-C
bricks of the invention provide improved hot strength of the bricks along with better slag
corrosion and thermal shock resistance to suit wide scale application in ladle lining with
improved lining life.