|Title of Invention
LADLE BRICK SYNERGISTIC COMPOSITIONS"
|A ladle brick composition adapted to form MgAI2O4 spinel in-situ at high temperature comprising AI2O3 70-90% by wt. SiO2 4-8% by wt. MgO 5-25% by wt. CaO 0.5-1.0% by wt. Fe2O3 1.5-2.0% by wt. and TiO2 2-3% by wt. and a process for manufacturing such ladle bricks. The ladle bricks of the invention are directed to avoid problems of physical erosion/thermal spalling and slag corrosion known to exist in conventional ladle bricks. The brick of the invention is useful on panel forming in the bottom striking zone and side walls of steel ladles and would provide for extended lining life of the ladle walls.
|The present invention relates to alumina-magnesia-carbon ladle bricks and in particular to alumina-magnesia-carbon ladle bricks for application in a steel ladle/ :
It is generally known, that the working lining of metal zone of steel ladles routed through BOF-LF-CC is made of high alumina bricks because they are inexpensive and perform reasonably well due to their compatibility with the grade of steels made in the steel melting shop. The average life obtained is in the range 25-30 heats. It is however experienced that high alumina ladle bricks typically fail due to physical erosion/thermal spalling and slag corrosion and also penetration of metal/slag occurs through the bricks joints.
Other than high alumina bricks it is also known to use in the bottom and metal zone of steel ladles Doloma bricks, Mag-chrome bricks and Alumina-spinel castables. However, such known variety of bricks also suffer from inherent disadvantages like Doloma bricks which need protection against hydration, Mag-chrome bricks which have low thermal spalling resistance and problems of sticking with slag and slag dumping problem while Alumina-spinel castables suffer from huge investment costs in inr astructure development and demands high degree of shop discipline.
, It is thus the basic objective of the present invention to provide for ladle bricks which would avoid the problems of physical errosion/thermal spalling and slag corrosion known to exist in use of presently available ladle bricks discussed above.
Another object of the present invention is to provide for improved quality of steel ladle bricks for use on panel form in the bottom striking zone and sidewall of steel ladles which would provide for extended lining life of the ladle walls.
Another object of the present invention is to provide for simple and cost-effective process of manufacture of ladle bricks which would avoid the problems of the ladle bricks presently available in the art.
Thus according to an aspect of the present invention there is provided ladle brick
composition adapted to form MgAl2O4 spinel in-situ at high temperature comprising :
AI2O3 70-90% by wt.
SiO2 4-8% by wt.
MgO 5-25% by wt.
CaO 0.5-1.0% by wt!
Fe2O3 1.5-2.0% by wt. and
TiO2 2-3% by wt.
The above disclosed alumina-magnesia-carbon brick composition of the invention provide for required formation of Mg AI2O4 spinel in-situ in the hot face of the bricks which leads to continuous expansion and thereby prevents metal/slag penetration in between the brick joints.
In accordance with a preferred aspect the ladle brick composition adapted to form MgAI2O4 spinel-in-situ in accordance with the present invention comprise :
In accordance with yet another aspect of the present invention there is provided a process for manufacture of improved ladle bricks comprising: providing AI2O3 aggregate in amount of 60-80% by wt., MgO bearing material in amount of 5-25% by wt., carbon bearing material in amount of 2-10% by wt., and binder in amount of 5-10% by wt. selectively mixing the above ingredients with said binder to thereby produce the ladle bricks adapted to form MgAI2O3 spinel-in-situ.
The resin bonded alumina magnesia carbon ladle brick composition of the invention selectively includes carbon to make these bricks more resistant to slag attack and thermal spalling while MgO in the composition help in the formation of alumina-magnesia spinel (MgAI2O4) in the hot face at around 1260°C which has a larger crystalline structure than the parent grains and hence maintain tight brick joints. This prevents metal/slag penetration through the brick joints. The lining life is thereby increased to about 50-60 heats from the existing level of 25-30 heats.
In accordance a preferred aspect of the present invention there is provided a process for manufacture of improved ladle bricks adapted to form MgAI2O3 spinel in situ comprising :
i) providing a selective mix of AI2O3 aggregate and mixing the same with resin binder for about 3 to 4 mins. adding thereto the mix of (i) above source of carbon and magnesia bearing material and subjecting to further mixing with resin binder for another 5 minutes, press-forming the mix into bricks and further, and curing at temperature of 150-200°C for a period of 24 to 48 hours.
In the above disclosed process of the invention the AI2O3 aggregate is used in amounts of 60-80% by wt, MgO bearing material in amount of 5-25% by wt. carbon bearing material in amount of 2 to 10% by wt. and binder in an amount of 5-10% by wt.
The carbon bearing material used in the process can be selected from graphite of natural sources.
The magnesia bearing material used can be selected from purer grade of nature, or sea water magnesia and the binder used can be selected from phenol-formaldehyde resin.
In accordance with a preferred aspect of the invention, the process of manufacture the alumina-magnesia carbon ladle bricks comprise:
providing a selective mix of coarse 2-3 mm, medium 1-2 mm and fine 0-1 mm AI2O3 aggregate, and
i) mixing of coarse AI2O3 fraction having size ranging from 1 to 3 mm in amount of 70 to 80% by wt. with binder in amount of 2.5 to 5% for a period of 3 to 4 mins.
ii) adding the fine Al2O3 fractions having size ranging from 0 to 1 mm in amount of 20 to 30% by wt. to the mix of (i) above and selectively mixing of graphite
and magnesia bearing material in amounts of 2 to 10% by wt. and 5 to 25%
by wt. respectively with binder in amounts of 2.5 to 5% by wt. and subjecting
the same to mixing ; iii) press forming of bricks therefrom the mix of step (ii) above in pressure
ranging from 800 to 1000 Kg/Cm2, and finally, iv) curing the bricks in the temperature range of 150 - 200°C for a period of 24 to
In the above disclosed process of the invention the raw materials/ingredients used are crushed, grinded and screened to generate different size fractions. These different size fractions are used in varied proportions to get maximum compactness of the material when it is formed in shapes for ultimate use as lining material for steel ladle.
Importantly, the selective amount of MgO in the brick matrix of the invention provides for control of the thermal expansion of the brick during its end use in the steel teeming ladle.
Importantly, the process of the invention involves optimisation of granulometry and composition to achieve desired characteristics of ladle bricks by selecting proper 'size fractions and quality of coarse, medium and fine fractions of alumina and magnesia bearing material and preferably by way of
i) selection of purer grades of carbon and magnesia bearing material;
ii) mixing of fines separately;
iii) dry mixing of coarse and medium together in a mixer for about 2 to 3 minutes;
iv) addition of the liquid binder as per requirement and mixing for 3 to 4 minutes;
v) forming of brick by pressing the mix at a specific pressure of about 800 to
1000 preferably 1000 kg/cm2 in a press ; vi) heat treatment of bricks at a particular temperature for a certain period of
The details of the invention its objects and advantages will be further apparent from the ensuing description made in relation to the following non-limiting exemplary embodiments of the invention.
To determine the end properties of the brick of the invention with composition specification as discussed above the same was obtained and tested and a comparative study of its properties vis-a-vis conventional high alumina ladle bricks was made and the results are provided hereunder in TABLE -1
Further, the continuous expansion characteristics of the Alumina-magnesia-carbon bricks of the invention was evaluated and the same is represented in accompanying Figure 1.
It is thus possible by way of the present invention to provide a process for making spalling resistant and continuous expansion type refractory brick by in-situ spinel formation on the working surface.
The ladle bricks produced in accordance with the present invention can be used as a lining material in the metal zone and bottom of steel teeming ladle. Such ladle bricks used in steel ladles provide for improvement in life of ladle lining to about 50 to 60 heats from the existing level of 25 to 30 heats. This would provide for simplicity and importantly cost-effectiveness in the manufacture of steel.
The ladle brick composition according to the invention is a synergistic composition which does not result in the mere aggregation of the properties of the individual compounds.
1. A ladle brick synergistic composition adapted to form MgAI204 spinel in-situ at high
temperature comprising :
Al2O3 70-90% by wt.
SiO2 4-8% by wt.
MgO 5-25% by wt.
CaO 0.5-1.0% by wt.
Fe2O3 1.5-2.0% by wt. and
TiO2 2-3% by wt.
2. A ladle brick composition as claimed in claim 1 comprising preferably,
3. A ladle brick synergistic composition adapted to form MgAI2O4 spinel in-situ at high
temperature substantially as hereindescribed and illustrated with reference to the
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|STEEL AUTHORITY OF INDIA LIMITED
|ISPAT BHAWAN, LODI ROAD, NEW DELHI-11003, INDIA.
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date