Refractory nozzle

Abstract

A refractory nozzle is provided for arrangement in or on a wall of a metallurgical crucible, particularly for steel melts, having a discharge duct surrounding a flow passage, wherein the discharge duct has a surface delimiting the flow passage and an outer housing. In order to improve the known solutions of the prior art, one embodiment of the nozzle is characterized by the discharge duct having an upper part and a lower part with the lower part being fixed in or on the upper part, wherein the surface of the upper part delimiting the flow passage is made of a different material than the surface of the lower part delimiting the flow passage. In a second embodiment the nozzle is characterized by the discharge duct having an upper part and a lower part with the lower part being fixed on or in the upper part, wherein the diameter of the flow passage in the upper part is greater than the diameter in the lower part.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 10 / 191,906, filed Jul. 8, 2002, and the disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] The invention concerns a refractory nozzle for arrangement in or on a wall of a metallurgical crucible, particularly for steel melts, having a flow passage and a discharge duct surrounding the flow passage, wherein the discharge duct has a surface delimiting the flow passage and an external housing. Such devices are needed in the casting industry in order to make it possible for metal melts, particularly steel melts, to run out of melt crucibles. [0003] An arrangement of this type is known, for example, from British patent specification GB 2 157 210 A. Here, a so-called immersion nozzle is described, from which molten steel flows from an upper crucible into a lower melt crucible, wherein the nozzle or spout dips into the melt of the lower...

AI Technical Summary

Benefits of technology

[0005] An object of the present invention is to make available a nozzle which improves the known solutions of the prior art and ensures a nearly trouble-free running out of the molten metals into a further melt crucible.

[0009] It is particularly advantageous that the material defining the flow passage and the construction of the upper part is thermally highly insulating, at least at temperatures of about 1400° C. to 1650° C. (that is, at steel manufacturing temperatures), highly pure, chemically inert toward steel, and highly temperature-resistant, and that the material of the lower part delimiting the flow passage is a refractory ceramic. By “highly insulating” is understood a material with a coefficient of thermal conductivity of at most 1.5 Wm−1K−1, “highly pure” means a purity of >99% by weight, and “highly temperature-resistant” means materials with a melting point of >1800° C. This ensures that no heat is withdrawn from the melt and that it is not contaminated. On the other hand, such an apparatus has long term stability in relation to molten metals.

[0011] The material of the upper part delimiting the flow passage can also be made of a mixture essentially formed of aluminum oxide and graphite. Mullite, zirconium dioxide or calcium oxide can also be used as materials for the upper part. Advantageously, the housing can be made of metal, particularly of steel, ceramics or another refractory material, in order to ensure a high strength. A steel housing in particular prevents undesired gas penetration.

[0012] Expediently, the material of the lower part delimiting the flow passage is at least partially surrounded by a heater, in order to make possible a preheating of the nozzle and thereby to prevent thermal stresses or to promote an adhesion-free flow. The heater is advantageously made of at least one material selected from the group of molybdenum, carbon, nickel-chromium, iron-chromium-aluminum. Between heater and housing, a thermally highly insulating material is advantageously arranged, in order to avoid an escape of heat to the outside. It is advantageous if the diameter of the flow passage in the lower part is smaller than the diameter of the flow passage in the upper part, in order to achieve the advantages already described above with respect to the second embodiment of the invention.

Problems solved by technology

This can be desirable under certain circumstances, but in many cases it is disadvantageous, namely when properties of the melt are thereby influenced in an unfavorable and undesired manner.

Such a control process is relatively inexact and mechanically expensive.

Moreover, as a rule, it leads to the formation of turbulence within the metal flow, whereby an adhesion of the through-flowing metal takes place on the wall of the nozzle.

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