FIELD OF THE INVENTION
The present invention relates to improved refractory lining system for steel ladles
involving 70-90% alumina quality refractory material (Low Cement Castable) and in
particular to, application of said castable/monolithic refractory mass as safety lining
in steel ladles involving multi segmented metallic former. More specifically, the
present invention is directed to providing monolithic safety lining by low cement
castable involving a metallic former having similar contour to steel ladle shell
preferably of 165t capacity so that it can hold the load during application of about
lOt refractory mass and leaves a side wall gap of about 70mm. Importantly, the
former is made to rest on monolithic safety bottom and can be dismantled after the
application of castable without any shape distortion for future use. The metallic
former is composed of small pieces/segments provided with metallic hooks/handle
favouring ease of handling/fitting. The metallic former thus can be fitted and
dismantled manually even if the crane facility is not available. This refractory lining
pattern can be advantageously applied to steel carrying units like BF hot metal
ladles, mixer ladles or transfer ladles with higher campaign life.
BACKGROUND OF THE INVENTION
The steel ladle having 165T capacity (150t metal) used in steel melting shop at the
applicants' plants is conventionally lined with magnesia carbon refractory material
(MgO-C) to hold / treat liquid steel. This wear refractory brick lining is backed up by
two layers of 30% alumina (IS-6) safety bricks of 40mm thick so that if there is any
failure in wear lining in the existing lining pattern. These back up safety bricks are
provided to arrest metal through and avert any unwanted accident. An insulation
layer of 10mm thickness is also provided in between these safety bricks to arrest
heat loss. After each campaign life of steel ladle, these safety bricks (~ 6T) are
wasted during dismantling of worn out refractory. This increases overall cost of
refractory and extra time (about 10 -12 hrs) for laying in each campaign. Moreover,
these safety layers are not at all reliable owing to quality (30% AI203) and weak
brick joints. As a result, red spots and metal leakage are observed in ladle shell
towards the ladle maturing time. The full potential of working lining refractories also
could not be extracted apprehending possible metal through/penetration. Existing
lining design thus suffered from low quality safety bricks with innumerable weak
joints. As a result, any metal / slag penetration caused red hot of shell / metal
through with a loss of 150t liquid steel.
There has been therefore a continuing need in the art to developing an improved
refractory lining pattern for steel ladles which would eliminate the problems and
limitations of the prior art.
The present invention is an attempt to providing for an improved refractory lining
system for steel ladles involving refractory safety lining, especially with improved
castable monolithic safety refractory lining cast with a segmented metal former
favouring on one hand higher strength and enhanced campaign life avoiding joints
responsible for accidents due to metal through/penetration and resultant metal loss
and on the other hand faster and easy relining/relaying of castable monolithic
refractory safety lining at the end of campaign life increasing ladle availability.
OBJECTS OF THE INVENTION
The basic object of the present invention is directed to providing an improved
refractory lining system for steel ladles involving a castable monolithic refractory
lining with improved strength using metallic former as safety lining at the back of
work lining ensuring enhanced campaign life.
A further object of the present invention is directed to providing an improved
refractory lining system involving a castable monolithic refractory safety lining with
improved strength using metallic former which would be free of any joint and thus
avoiding any accidental metal through/penetration and consequent metal loss.
A still further object of the present invention is directed to providing an improved
refractory lining system involving a castable monolithic refractory safety lining in
steel ladles with improved strength using metallic former wherein the said metal
former is segmented into pieces with ease of handling and assembly as well as
dismantling manually even if the crane facility is not available.
A still further object of the present invention is directed to providing an improved
refractory lining system involving a castable monolithic refractory safety lining with
improved strength using metallic former wherein application of monolithic safety
lining by low cement castable would be provided with said segmented metallic
former which when assembled provide similar contour of steel ladle shell so that it
can hold the load during application of refractory mass and leaves required side wall
gap.
A still further object of the present invention is directed to providing an improved
refractory lining system for steel ladles involving a castable monolithic refractory
safety lining with improved strength using metallic former wherein if there is any
leakage or failure of the work lining during circulation of steel ladle, the monolithic
refractory would ensure the strength to withstand as a safety working lining.
A still further object of the present invention is directed to providing an improved
refractory lining system for steel ladles involving a castable monolithic refractory
safety lining that ensure strong permanent safety lining with no joints, reduce overall
ladle relining time resulting in increase of ladle availability and enhance ladle
reliability.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to providing a refractory lining
system for steel ladles comprising reduced thickness of work lining comprising
magnesia carbon refractory bricks;
a monolithic refractory safety lining with shell wall as backup of said work lining
comprising 70-90% alumina quality refractory material (Low Cement Castable);
a resin bonded MgO based backfill mass as intermediate layer between said work
lining and the monolithic safety lining;
ceramic fiber insulation of desired thickness on side and bottom laid with ladle shell
to arrest heat loss from lining.
A further aspect of the present invention is directed to a refractory lining system for
steel ladles wherein said ceramic fibre insulation comprising 5 to 6 mm preferably
about 5mm thick ceramic fiber laid with shell wall upto metal zone from bottom and
10 to 12 mm preferably about 10mm ceramic fibre laid with shell bottom, to arrest
heat loss from the lining.
A still further aspect of the present invention is directed to a refractory lining system
for steel ladles, wherein said backfill mass comprises dry refractory mass introduced
between safety lining and work layer to take care of expansion of work layer.
A still further aspect of the present invention is directed to said refractory lining
system for steel ladles wherein said work layer of refractory is thinner comprising
one layer of 185mm MgO-C bricks on side wall up to metal zone to keep the metal
holding capacity same or higher.
Yet another aspect of the present invention is directed to a refractory lining system
for steel ladles, wherein said 70-90% alumina quality refractory material (Low
Cement Castable) comprises

A still further aspect of the present invention is directed to a metallic former adapted
for casting monolithic safety linings for ladles and the like comprising: plurality of
releasable connected metallic segments constituting on assembling formers adapted
to support castings of monolithic safety lining having cooperative contour to the ladle
shell/structure to be safety lined.
Said metallic former further comprises metallic hooks / handles means adapted to
handle manually.
A further aspect of the present invention is directed to low cement castable wherein
stainless steel anchors were fixed on ladle shell to hold the heavy load/structure of
monolithic refractory mass and arrest them from free falling during dismantling of
wearout refractory lining.
A further aspect of the present invention is directed to said metallic former wherein
said metallic former is adapted to rest on monolithic safety bottom and can be
dismantled after application of castables without any shape distortion for subsequent
application and use.
A still further aspect of the present invention is directed to said metallic former
having a configuration enabling generation of monolithic safety lining free of any
joints and adapted to avoid any metal /slag penetration.
Another aspect of the present invention is directed to a process for the developing of
refractory lining system using the metallic former as described above comprise the
steps of:
(i) assembling the segmented metallic former as per the contour of the
ladle;
(ii) providing castables in said former to provide for a monolithic safety
lining;
(Mi) providing work lining comprising magnesia carbon refractory bricks;
(iv) providing a combination of backfill mass and safety bricks preferably
30% alumina (IS-6) as intermediate layer between said work lining
(upto metal zone) and the monolithic inner lining;and
(v) providing ceramic fiber insulation of desired thickness on side (upto
metal zone) and bottom laid with ladle shell to arrest heat loss from
lining.
A still further aspect of the present invention is directed to said process comprising
covering ceramic fibre paper with polythene sheet such that moisture pick up does
not take place during casting of the refractory on the metallic former.
Yet another aspect of the present invention is directed to said process wherein
thinner work layer of refractory is provided to maintain the desired holding capacity
and dry refractory mass introduced between the safety lining and work layer to take
care of expansion of work layer.
The various other objects and advantages are described hereunder in greater details
with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: is the schematic illustration of the existing lining pattern in steel ladles.
Figure 2: is the schematic illustration of the modified lining pattern with monolithic
safety lining according to the present invention.
Figure 3: is the photographic image showing the Angle & Rib connections in the
segmented metallic former during fabrication used for the monolithic castable safety
lining according to the present invention.
Figure 4: is the photographic image showing complete piece of segmented metallic
former for safety lining of steel ladle according to the present invention.
Figure 5: is the schematic half sectional view of metallic former for application of
castable in steel ladle, wherein each of the five segments/rings contains eight
segments.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention is directed to providing an improved refractory lining system
for steel ladles comprising monolithic refractory safety lining with enhanced
campaign life and in particular to providing segmented metallic former for faster and
easy laying of such castable low cement monolithic refractory safety lining adapted
to avoid metal through/penetration through metal shell of ladle.
It has been already discussed herein before that the steel ladles having 165T
capacity (150t metal) used in steel melting shop is conventionally lined with
magnesia carbon refractory material (MgO-C) to hold / treat liquid steel. This wear
refractory brick lining is backed up by two layers of 30% alumina (IS-6) safety bricks
of 40mm thick so that if there is any failure in wear lining, these back up safety
bricks can arrest metal through and avert any unwanted accident. There is also
provided 10mm insulation layer in between these safety bricks to arrest heat loss.
The conventional refractory lining pattern is schematically illustrated in
accompanying Figure 1. After each campaign life of steel ladle, these safety bricks
(~ 6T) are wasted during dismantling of worn out refractory. This wastage increases
overall cost of refractory and extra time (about 10 -12 hrs) for laying in each
campaign. Moreover, these safety layers are not at all reliable owing to quality (30%
AI203) and weak brick joints. As a result, red spots and metal leakage are observed
in ladle shell towards the ladle maturing time. The full potential of working lining
refractories also could not be extracted due to fear of metal through / penetration.
The present invention thus attempts to avoid the limitations and disadvantages of
the existing art by providing a modified and improved refractory lining pattern for
steel ladles with increased campaign life and eliminate accidental metal
leak/penetration due to failure of lining.
Accompanying Figure 2 schematically illustrates the modified lining pattern for steel
ladles according to the present invention.
The present invention undertakes to replace the IS-6 quality safety brick layers
adjacent to side wall of ladle with 70-90% alumina quality refractory material (Low
Cement Castable). The material has higher strengths and other refractory properties
retained at high temperature also. The comparative physical properties of IS-6 vis-a-
vis LC-70 are presented in the following Table-I.
The refractory lining for steel ladles according to the invention is carried out in two
ways are:
1. Development of comprehensive refractory lining system and
2. Providing segmented metallic former for monolithic back-up layer of steel
ladles in steel plants.
1. Comprehensive refractory lining system is developed by way of the present
invention based on study of the existing lining pattern and its performance, and
introduction of monolithic safety lining with good quality castable keeping insulation
with ladle shell to arrest heat loss. Anchors are fixed with ladle shell to hold the
monolithic structure. Ceramic fibre papers are covered by polythene sheet so that
moisture pick up does not take place during casting. The casting of monolithic safety
lining is done with the help of metallic former. Thinner work layer of refractory is
designed to keep the metal holding capacity same or higher. Dry refractory mass is
introduced between safety lining and work layer to take care of expansion of work
layer.
2. Application of monolithic back up layer or safety lining by castable has been
provided with a former having similar contour to steel ladle shell so that it can hold
the load during application of about lot refractory mass and leaves a required side
wall gap. The former should rest on monolithic safety bottom and can be dismantled
after the application of castable without any shape distortion for future use. As
calculated the total metallic former weighs about 2t and handling of single former is
not possible due to shop logistics, hence this metallic former has been designed into
5 segments and each divided into 8 pieces i.e. total of 40 pieces constituted the
complete former for easy handling/fitting as well as dismantling.
Advantageously, in the present lining pattern developed according to the present
invention, if there is any leakage or failure of the work lining during circulation of
steel ladle, this monolithic refractory safety lining ensure enough strength to
withstand as a safety working lining. The monolithic structure also eliminates weak
joints and hence metal/slag penetration is totally restricted. The ceramic fibre of
5mm thick upto metal zone from bottom has been laid with shell to arrest heat loss
from the lining. Bottom of ladle is also provided with 10mm ceramic fibre with shell
(unlike existing lining where insulation is put in between the safety).
Application of monolithic safety lining by low cement castable is implemented with a
metal former having similar contour to 165t steel ladle shell so that it can hold the
load during application of about lOt refractory mass and leaves a side wall gap of
desired thickness. The invented metal former is made to rest on monolithic safety
bottom and can be dismantled after the application of castable without any shape
distortion for future use. As calculated the total metallic former (5mm thick) weighs
about 2.0t and handling of single former is not possible due to shop logistics. And
hence according to another advantageous aspect of the present invention, this
metallic former has been designed into 5 segments/rings and each ring is further
divided into 8 pieces i.e. a total of 40 pieces for ease of handling/fitting as well as
dismantling. The fabrication details of segmented structure of metal former wherein
metallic angles / ribs have been provided to each parts of metallic former are
illustrated in the accompanying Figure 3 & 4.
Thus, this type of metallic former is disclosed for the first time for use in 165t steel
ladle. This former not only simplify monolithic application of low cement castable
ensuring at least 10 campaigns safety lining life compared to 1 campaign with
present bricks, but eliminate the problem of metal through/penetration. The metallic
former according to the present invention can be fitted and dismantled manually
even if the crane facility is not available. Each of these pieces has been additionally
provided metallic hooks/handle. Accompanying Figure 5 schematically illustrate half
sectional view of the complete metal former structure segmented into 5 pieces of
approximately 800 mm height and each segments divided into 8 pieces, thus
covering the inside of the steel ladle.
It is thus possible by way of the present invention to providing an improved
refractory lining pattern for steel ladles comprising 70-90% alumina quality
refractory material (low cement castable) based monolithic safety lining at the back
of work lining adjacent to ladle shell along with ceramic fibre insulation to arrest heat
loss, to enhance campaign life and ensuring simple and faster laying of such castable
monolithic lining using a segmented metallic former thus reducing the downtime of
ladles due to relining at end of campaign life.
We Claim:
1. A refractory lining system for steel ladles comprising work lining with magnesia
carbon refractory bricks;
a monolithic refractory safety lining with shell wall as backup of said work lining
comprising 70-90% alumina quality refractory material (Low Cement Castable);
a combination of backfill mass and/or safety bricks preferably 30% alumina (IS-6) as
intermediate layer between said work lining and the monolithic safety lining;
ceramic fiber insulation of desired thickness on side and bottom laid with ladle shell
to arrest heat loss from lining.
2. A refractory lining system for steel ladles as claimed in claim 1, wherein said
ceramic fibre insulation comprising 5 to 6 mm preferably about 5mm thick ceramic
fiber laid with shell wall upto metal zone from bottom and 10 to 12 mm preferably
about 10mm ceramic fibre laid with shell bottom, to arrest heat loss from the lining.
3. A refractory lining system for steel ladles as claimed in anyone of claims 1 or 2,
wherein said backfill mass comprises dry refractory mass introduced between safety
lining and work layer to take care of expansion of work layer.
4. A refractory lining system for steel ladles as claimed in anyone of claims 1 to 3,
wherein said work layer of refractory thinner comprises one layer of IS 6 bricks on
side wall up to metal zone to keep the metal holding capacity same or higher.
5. A refractory lining pattern for steel ladles as claimed in anyone of claims 1 to 4,
wherein said 70-90% alumina quality refractory material (Low Cement Castable)
comprising
6. A metallic former adapted for casting monolithic safety linings for ladles and the
like comprising: plurality of releasably connected metallic segments constituting on
assembling formers adapted to support castings of monolithic safety lining having
cooperative contour to the ladle shell/structure to be safety lined.
7. A metallic former as claimed in claim 6 comprising anchor means adapted to hold
with respect to the ladle shell.
8. A metallic former as claimed in anyone of claims 6 to 7 wherein said metallic
former is adapted to rest on monolithic safety bottom and can be dismantled after
application of castables without any shape distortion for subsequent application and
use.
9. A metallic former as claimed in anyone of claims 6 to 8 having a configuration
enabling generation of monolithic safety lining free of any joints and adapted to
avoid any metal /slag penetration.
10. A process for the developing of refractory lining system using the metallic former
as claimed in anyone of claims 8 or 9 comprising:
(i) assembling the segmented metallic former as per the contour of the
ladle;
(ii) providing castables in said former to provide for a monolithic safety
lining;
(iii) providing work lining comprising magnesia carbon refractory bricks;
(iv) providing a combination of backfill mass and/or safety bricks
preferably 30% alumina (IS-6) as intermediate layer between said
work lining and the monolithic inner lining; and
(v) providing ceramic fiber insulation of desired thickness on side and
bottom laid with ladle shell to arrest heat loss from lining.
11. A process as claimed in claim 10 comprising covering ceramic fibre paper with
polythene sheet such that moisture pick up does not take place during casting of the
refractory on the metallic former.
12. A process as claimed in anyone of claims 10 to 11 wherein thinner work layer of
refractory is provided to maintain the desired holding capacity and dry refractory
mass introduced between the safety lining and work layer to take care of expansion
of work layer.

ABSTRACT

An improved refractory lining system for steel ladles is disclosed comprising 70-90%
alumina quality refractory material (Low Cement Castable) used for
castable/monolithic refractory safety lining, as backup of work lining, cast by means
of multi segmented metallic former. The metallic former having similar contour to
steel ladle shell preferably of 165t capacity is designed to hold the load during
application of about 10t refractory mass and leaves required side wall gap.
Importantly, the metallic former is made to rest on monolithic safety bottom and can
be dismantled after the application of castable without any shape distortion for future
use. The metallic former is fabricated with small pieces/segments provided with
metallic hooks/handle favouring fast and easy handling/fitting, which can be fitted
and dismantled manually even if crane facility is not available. This refractory lining
pattern can be advantageously applied to steel carrying units like BF hot metal
ladles, mixer ladles or transfer ladles with enhanced campaign life.