Metallurgical apparatus – Process
Patent
1990-11-20
1993-02-23
Kastler, Scott
Metallurgical apparatus
Process
266280, 266275, B22D 4102
Patent
active
051887940
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for covering a metallurgical vessel such as a tundish or casting ladle with a purifying lining.
A purifying lining is understood to mean a lining which is capable of reducing contamination of molten metal with impurities such as oxides.
In order to limit oxidation of molten metal, a current practice consists in employing means such as casting tubes interposed between the casting, ladle and the tundish and covering powders placed or the surface of the molten metal.
However, these means do not make it possible to reduce contamination of the metal bath completely.
It is already known to make use of linings for metallurgical vessels, in particular for tundishes, which are obtained by spraying a composition in the form of aqueous slurry containing refractory particles such as SiO.sub.2, Al.sub.2 O.sub.3, MgO or a mixture of these latter, and an organic or inorganic binder. These particles sinter under the action of heat of the molten metal as this latter is poured into the vessel, thus ensuring cohesion of the lining. However, linings of this type do not have a purifying function in regard to the molten metal and some of them even have a contaminating effect.
There is also known a lining obtained by application of burnt dolomite consisting essentially of CaO and of MgO in the form of grains mixed with a binder such as a thermosetting resin, for example.
Linings obtained by application of raw dolomite or calcium carbonate are also known.
After application of these linings, these latter are subjected to heating which decomposes the carbonate and/or the binder. There thus remains a porous layer consisting essentially of CaO and/or of MgO having a density of less than 1.
Linings of this type have purifying properties with respect to molten metal. These properties are mainly based on the avidity of CaO for oxides which contaminate the metal such as Al.sub.2 O.sub.3, FeO, Fe.sub.2 O.sub.3, while producing compounds which are more readily fusible than the constituents and which migrate towards the slag.
However, these linings are subject to a disadvantage in that they have very low mechanical strength, with the result that they do not resist the abrasion caused by the molten metal.
In order, to overcome these disadvantages, the present applicants have performed the following two tests:
In a first test, the applicants applied within a tundish an aqueous mixture comprising approximately 98% raw dolomite and 2% sodium silicate as binder.
After spraying, the lining was burnt right through up to approximately 900.degree. C. so as to release CO.sub.2 from the dolomite.
The burnt lining thus formed had a porous structure whose mechanical strength was insufficient to withstand the abrasion produced by the molten metal.
In a second test, the present applicants poured the aforementioned mixture into the space located between the internal wall of the tundish and a wall forming a mold.
After drying at 180.degree. C., it was found that the lining had no internal mechanical strength and was destroyed at the time of withdrawing the wall which forms a mold, with the result that this mode of operation is of no interest from an industrial standpoint.
The present applicants have continued their researches in order to discover an industrially acceptable solution which makes it possible to obtain a purifying lining from raw dolomite or calcite.
The aim of the present invention is precisely to propose a method and a composition for the formation of a purifying lining of this type, and a lining obtained by application of this method.
The invention is thus directed to a method and a composition for lining the internal wall of a metallurgical vessel so as to form a purifying lining having a base of at least one oxide of an alkaline-earth metal.
In accordance with the invention, this method is characterized by the following steps : containing at least one simple or multiple carbonate of alkaline-earth metal to which there has been added a certain proportion of granular refractory material, and constitu
Daussan Andre
Daussan Gerard
Daussan Jean-Charles
Daussan et Compagnie
Kastler Scott
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