Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – By means introducing treating material
Patent
1997-04-24
1998-12-29
Kastler, Scott
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
By means introducing treating material
266209, 222603, C21C 710
Patent
active
058536582
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention refers to a gas purging device for a snorkel or blowpipe of a degassing vessel, the latter being lined with a refractory material.
From the DE 39 11 881 C1 a sintered gas purging plug is known, which is embedded into the side wall of an evacuation vessel in the region of the steel melt. Here, it is a discrete gas purging element.
The development of gas purging elements for degassing vessels is described in "Radex-Rundschau, No. 4, 1990, 365". It is mentioned there that in a typical installation the purging is effected with six to twelve tubes within the inlet blowpipe of the vacuum vessel, each having a diameter of 3 or 4 mm.
A RH method is described in "Radex-Rundschau, No. 4, 1992, 171", wherein, in the inlet blowpipe, argon is injected through steel tubes of 3 to 4 mm thickness.
In the RH (Ruhrstahl-Heraeus) method, the liquid steel is transported from a pouring ladle along an ascension pipe into the evacuation vessel with the aid of a conveying gas, in particular argon, which is fed into the ascension pipe above the level of the steel melt, by the increase of volume thereof within the ascension pipe and further by the difference in pressure between the external air pressure and the low pressure within the evacuation vessel. The steel being sucked into the evacuation vessel is atomized resulting in a great increase of surface and thus a good degassing. Simultaneously introduced oxygen being supplied from the slag, among others, during the whole treatment time, leads to the formation of carbon monoxide gassing out in the vacuum vessel, the desired decarbonization being achieved thereby.
It has been attempted to optimize the decarbonization to the lowest possible values by additionally blowing-in oxygen.
A fast decarbonization process is achieved in particular by a high circulation speed of the melt and thus an increase of the conveying gas flow, and by an increase of the blowpipe diameter of the vacuum installation.
In the EP 0 297 850 A1, a method and a device for degassing a molten metal in a RH process are described. For that, several channels are arranged in the inlet blowpipe at the periphery, which are divided into two groups, a group of which being supplied with high pressure gas and a group being supplied with low pressure gas. In this way the supplied flows of gas infiltrate into the molten metal being fed through the blowpipe with different depth to facilitate an uniform gassing of the molten metal over the blowpipe cross section.
The object of the invention is to optimize known gas purging devices for degassing vessels, in particular a decreased and more uniform wear behaviour of the refractory ceramic lining being intended.
The invention is based on the knowledge that this objective can be achieved by an "all around purging" of the steel being conducted through the blowpipe (the submerged nozzle) with an adequate treating gas, if the following parameters are taken into accountL: veil. in the immediate region of the wall of the blowpipe.
The channels of the gas purging device should extend with a small distance between each other over the whole periphery and preferably over at least part of the height (for example 10 to 50%) of the refractory lining of the blowpipe.
An uniform, quasi "continuous" gas supply with fine distribution over the whole periphery of the blowpipe is required.
Accordingly, the invention in its most general embodiment refers to a gas purging device for a blowpipe of a degassing vessel, being lined with a refractory material, the gas purging device having a plurality of channels which run, distributed over the periphery of the blowpipe, through the refractory lining in radial direction with regard to the central longitudinal axis M of the blowpipe, and are connectable at the outside to at least one gas supply pipe, characterized in that the channels the blowpipe, ascends directly adjacent to the inner wall thereof.
Such a design results in the following advantages: An uniform flow of liquid steel up to the inside of the vacuum vessel is achieved.
REFERENCES:
patent: 5011531 (1991-04-01), Takahashi et al.
Radex Rundschau, No. 4, "Development of Purge Elements for Degassing Units" pp. 365-376, Dec. 1990.
Aichinger Klaus
Niehues Heinrich
A. Earley John F.
A. Earley III John F.
Kastler Scott
Veitsch-Radex Aktiengesellschaft fur Feuerfeste Erzeugnisse
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