Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – By means introducing treating material
Patent
1998-06-10
2000-03-07
Kastler, Scott
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
By means introducing treating material
266268, C21C 546
Patent
active
060336218
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is directed to a lance head in a water-cooled oxygen lance for treating melts, especially for oxygen top-blowing onto steel melts in a converter, with at least one expansion nozzle which widens conically in the direction of the bath surface proceeding from a pipe portion having the narrowest nozzle cross section.
Oxygen lances are used in steel mills operating on the basic oxygen process. In such steel production processes, especially the LD process, as it is called, accompanying elements contained in the crude iron are removed by means of oxygen through oxidation. For this purpose, oxygen is blown onto the melt located in the converter via the-lance at high speeds of MACH 1.0 and greater.
In order for the lance head to operate in the desired manner with respect to the metallurgy of the steelmaking process, the required amount of oxygen must contact the metal melt in an optimum way via the nozzle outlet openings. The individual oxygen lance heads are designed according to specifications oriented to the particular steel mill. In particular, the converter capacity, converter dimensions, actual bath level, and the quantity and pressure of oxygen are taken into account.
DE 37 00 892 A1 discloses an oxygen lance conventionally used in steel mills for treating melts, especially for top-blowing oxygen onto the metal melts, in which is provided a plurality of gas outlet openings diverging relative to the principal axis of the lance and having the narrowest possible critical cross section, as it is called, wherein the critical cross section is adjoined in the direction of flow by a conically widening expansion nozzle.
Lances of this construction can provide only an erratic oxygen jet which disadvantageously results in unwanted steel spray and extensive dust development in the mouth region of the converter.
The object of the present invention is to provide an oxygen lance head of the generic type in which the oxygen jet makes better use of energy, improves the reaction conditions in the converter and reduces the environment burden.
This object is met by the invention through the characterizing features of claim 1. The additional claims show advantageous further developments of the invention.
The above stated object is obtained by a lance head of the invention. An annular chamber which expands in diameter radially outward is provided in this duct which can be guided virtually up to the mouth of the nozzle. As a result of this constructional shape, there is obtained a pulsing gas jet which exits the nozzle so as to be stably structured and impinges on the surface of the melt.
The nozzle is so constructed that speeds in the range of 1 to 3 Mach can be obtained at pressures of up to 15 bar. The oscillation frequency of the gas is adjustable within a range of 200 to 2000 Hz. The preferred frequency range is between 600 and 800 Hz.
As a result of the stable structure of the jet, oxygen quantities can be used with a high degree of energy utilization for blowing on or blowing in a metal melt for steel processing.
Due to the fact that the jet impinges on, the surface of the bath into a steady or smooth manner, the tendency of the molten bath to spray is eliminated and dust generation is reduced.
The stabilization of the gas jet is improved in that the construction of the annular duct is not smooth. For this purpose, the annular chamber is divided into a plurality of chamber segments divided by crosspieces or webs. The chamber segments have different radii, wherein chamber segments located opposite one another by pairs have the same radius.
In another embodiment, the outside walls of the chamber segments have radii which increase continuously in a curved manner.
In a particularly simple construction, disks are arranged in series such that the webs correspond to one another and chamber segments with different radii are arranged in the direction of flow.
The expansion part of the nozzle adjoining the annular chamber in the direction of flow can be partly cylindrical before opening coni
REFERENCES:
patent: 4702462 (1987-10-01), Fritz
patent: 4746103 (1988-05-01), Takashiba et al.
patent: 5746970 (1998-05-01), Bergman et al.
Kastler Scott
Mannesmann Aktiengesellschaft
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