Dispensing – Molten metal dispensing
Patent
1990-02-12
1991-10-29
Kastler, S.
Dispensing
Molten metal dispensing
266280, 501104, C04B 3548
Patent
active
050608312
DESCRIPTION:
BRIEF SUMMARY
The object of the present invention is a new material for covering a casting shroud. More particularly, it concerns casting shrouds for killed steels or ferro-alloys with aluminum or containing it.
Following the reducing steel smelting operations and iron-into-steel conversion, the metal contains non-negligible amounts of dissolved oxygen. This oxygen is quite pernicious, notably during casting operations and in general working of the metal.
In order to suppress this dissolved oxygen, calming agents are employed. Among the latter, silicon, carbon, magnesium and aluminum can be cited. It is primarily this latter metal, alloyed or not, that is used to kill or calm steels, the results of which are the best.
Nevertheless, during casting operations, for reasons and under conditions that are still poorly known, fine particles of alumina accumulate in the casting shrouds, e.g., such as the nozzles, capable of causing an almost total blockage and a definite problem in the normal development of the casting systems.
In order to alleviate these difficulties, an initial solution consists in frequently changing the casting elements where alumina accumulates. This solution is expensive and considerably shortens the service life of the casting nozzles, notably those which convey the metal emerging from the distributor in the case of continuous casting.
In order to increase the service life of the nozzles, another solution consists in reducing the amount of aluminum to be added as much as possible. This palliative method is however not satisfactory.
At the beginning of the 1980's, studies conducted by Emilio Marino and Aldo Ramacciotti led to the French patent published under No. 2,529,540. It is indicated in this document that it is possible to avoid any accumulation of alumina in the nozzles, since these latter are produced from lime, if necessary, with some additive elements. These elements, the sum of which is between 3% and 25% by wt., are designed to promote the growth of the grains.
This technique, which definitely gives good results with regard to the accumulation of alumina grains, has a major shortcoming, that of the necessary precautions in the storage and transport of these nozzles. In effect, such a refractory material, comprised for the most part, even up to 100%, of unhydrated lime, is extremely reactive with respect to humidity, which results in a loss of mechanical property when such a casting element has been subjected to moisture.
This is why a new research approach has been developed, according to which the parts of the casting elements in contact with the molten metal are covered with a mineral layer that forms eutectics having a low melting point with alumina. These eutectics are washed and entrained with the alumina by the flowing of the molten metal.
This technique certainly constitutes a substantial improvement as compared with the existing techniques; however, it replaces the accumulation of alumina with an erosion of the alumina anti-accumulation layer, which reduces the service life of the casting elements.
Use of composite material of the SiAlON type offers a significant advance (cf. D. B. Hoggard, G. I. Rancoule, L. C. Myers, H. K. Park, and M. K. Fishler, "Development of a liner to reduce alumina buildup in graphitized alumina submerged pouring nozzles used in the continuous casting of steel", published at the second international conference on refractory materials, "Refractories '87, TOKYO, Japan, November 10-13, 1987"), but not a decisive one.
This is why one of the purposes of the present invention is to furnish a material for covering the pouring elements to avoid alumina accumulation.
Another purpose of the present invention is to furnish casting elements in which the accumulation of alumina is difficult, even impossible.
Another purpose of the present invention is, finally, to furnish a casting process for ferro-alloys killed with aluminum or with one of its alloys, such as the aluminum/magnesium alloys utilizing the said casting elements.
These purposes and others that will appear bel
REFERENCES:
patent: 4691844 (1987-09-01), Ishino et al.
patent: 4849383 (1989-07-01), Tanemura et al.
Patent Abstracts of Japan, vol. 12, No. 343, 9-14-88, (M-714)(3190).
Patent Abstracts of Japan, vol. 12, No. 381, 10-12-88 (M-752)(3228).
Fishler Mark K.
Rancoule Gilbert
Kastler S.
Vesuvius Crucible Company
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