Plastic and nonmetallic article shaping or treating: processes – Furnace lining formation or repair
Patent
1995-12-08
1997-11-11
Kastler, Scott
Plastic and nonmetallic article shaping or treating: processes
Furnace lining formation or repair
266280, 266286, 266DIG1, B22D 4102
Patent
active
056860293
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for manufacturing fireproof crucibles for steel-processing ladles, in which aluminum deoxidation is carried out in order to quench liquid steel.
BACKGROUND OF THE INVENTION
Crucibles that are of fire-proof bauxite and which are produced according to such known procedures form a highly sintered surface layer on their hot side during operation; this surface layer is based on the metallurgical process of aluminum deoxidation that is used to produce completely killed steels, of the kind that are required, in particular, for continuous slab casting. The underlying chemical reaction is:
The metallic aluminum is present in the liquid steel, whereas the silicon dioxide originates from the fire-proof bauxite mass. The layer that contains the high alumina (Al.sub.2 O.sub.3), which is referred to as "furring" in professional circles, and an extremely hard sintered layer that is located behind it, are formed on the hot side of the bauxite lining.
A disadvantage connected with crucibles that are manufactured and stressed in this way is the furring, Which increases with every charge and which leads to constantly diminishing capacity of the steel-processing ladle. If the lower limiting volume of the steel ladle is reached, all of the fire-proof crucible must be broken out, a task that is rendered extremely difficult because of the hardness of the sinter. For a considerable time, unsuccessful attempts have been made to remove the furring on the inner side of the crucibles by using pick-type tools; such attempts have been unsuccessful because when the sinter is broken off, the crucible becomes brittle, at least, and as a rule it disintegrates completely.
SUMMARY OF THE INVENTION
It is the task of the present invention to create a procedure of the type discussed above, that uses the formation of the high-alumina layer and the highly sintered layer that is located behind it on the inside of the crucibles to simplify the reestablishment of the fire-proof lining when the limit of use is reached.
This problem has been solved by a procedure of the type described, using the distinguishing features.
It is essential for the present invention that the furring on the outer safety crucible, with the highly sintered layer, makes it possible to break out the expendable crucible without becoming damaged itself. There is no sintering of the fire-proof material of the expendable crucible with that of the safety crucible, so that the sintered layer of the safety crucibles forms a boundary layer, and it is possible to work as far as this when breaking out the expendable crucible.
It is not necessary to determine the precise number of charges that have to be processed in order to form the safety crucible with sufficient furring. In some instances, it is necessary to keep track of the occurrence of the furring, in which case one can assume that 10 to 50 charges should be completed with the first crucible prior to the introduction of the expendable crucible.
It is a particular advantage if the ceramic of the expendable crucible and, accordingly, the fire-proof substance that is used for this, is such that, during operation, there is no complete sintering through the thickness of the wall of the expendable crucible. The expendable crucible adjacent to the furring of the outer safety crucible has a boundary layer that is of significantly less strength than the adjacent, sintered boundary layer of the safety crucible, which means that a subsequent scaling or breaking off of the inner expendable crucible is made easier and that damage to the safety crucible is all but precluded. Thus, the the reestablishment of the inner layer that forms the expendable crucible can be carried out several times until, for safety reasons, the first lining, which is to say the safety crucible, has to be broken out and replaced by a new one.
A fireproof substance that has an identical or similar raw materials base and an identical or similar binding system as that used for the safety crucible can be used for the expendab
REFERENCES:
patent: 3944193 (1976-03-01), Imai et al.
patent: 4799652 (1989-01-01), Daussan et al.
patent: 5330690 (1994-07-01), Eitel
patent: 5511762 (1996-04-01), Connors, Jr. et al.
Baxley Esq. Charles E.
Chemikalien-Gesellschaft Hans Lungmuss m.b.H.
Kastler Scott
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