EP0297067A1

EP0297067A1 - Metallurgical nozzle

Info

Publication number: EP0297067A1
Application number: EP88850208A
Authority: EP
Inventors: Göran Runsten
Original assignee: Hoganas AB
Current assignee: Hoganas AB
Priority date: 1987-06-23
Filing date: 1988-06-14
Publication date: 1988-12-28
Also published as: SE8702601L; FI883051A; NO882760D0; NO882760L; FI883051A0; SE8702601D0

Abstract

Nozzle intended for injecting gas into molten metal, characterized by an elongate body (9) of refractory material containing a plurality of through-going capillaries (11), and a metal sleeve (13) surrounding said body (9);
injection lance containing such nozzle; and
the use of the nozzle for injecting gas into molten metal.

Description

TECHNICAL AREA

The present invention relates to a metallurgical nozzle intended for injection of a gas into molten metal, devices containing such nozzles, such as injection lances, ladles, tundishes or the like, and the use of the nozzle.

BACKGROUND ART

Metallurgical nozzles for injection of gases into molten metal, for example molten iron or steel, usually consists of tubular members of metal or of a refractory ceramic material. The gas to be injected thus flows through a cylindrical passage having a substantially circular cross-section out into the surrounding molten metal. Such metallurgical nozzles of a conventional type are encumbered with several problems, among which the following can be mentioned.
The nozzle often is subjected to clogging depending on melting at the opening of the nozzle or sputtering of molten metal. Moreover, considerable difficulties arise with such nozzles of a conventional type with regard to varying the gas flow in that instabilities in the gas flow arise, so called back-attack. When using the nozzle for providing mixing of the molten metal the gas consumption is uneconomically high in order that the desired mixing shall be obtained.

SUMMARY OF THE INVENTION

The invention will in the following be further described in connection with the use of the nozzle in metallurgical lances for injection of gas, but it should be observed that the use of the nozzle in no way is limited to merely utilization in such metallurgical lances.
The object of the present invention is to provide a nozzle whereby the drawbacks associated with the prior art nozzles, for example as mentioned above, are eliminated or substantially reduced.
These and other objects of the invention are provided by means of a nozzle intended for the injection of gas into molten metal, said nozzle being characterized by an elongate body of refractory material containing a plurality of through-going capillaries extending in the longitudinal direction of the body and being essentially mutually parallel, and a metal sleeve surrounding said body.
In a preferred embodiment of this nozzle said body is conically tapering towards one end thereof, whereby it cannot be ejected from the sleeve in the direction of said one end. The elongate body is suitably made of a ceramic material.
The capillaries arranged in the body have preferably a cross-dimension of about 0.1 to 1 mm and are suitably substantially circular in cross-section. The elongate body also has a substantially circular cross-sectional shape.
According to a particular aspect of the invention there is provided a metallurgical injection lance intended for injection of gas into molten metal, said lance comprising a central tube and a surrounding envelope of a refractory material and at least one nozzle through which the gas can be supplied into the melt via the central tube. The lance is characterized in that the nozzle is designed in a manner described above.
The invention also covers the use of the nozzle as described above for the injection of gas into molten metal.
Finally the invention covers containers intended for molten metal, which containers include at least one nozzle of the design as described above, said nozzle being positioned so that gas can be injected through same, optionally together with solid materials in pulverulant form, into the molten metal. As examples of such containers there may be mentioned ladles, tundishes, ladle furnaces, heat-maintaining furnaces, shute furnaces and the like. Such supply of gas is particularly important when providing for effective mixing of the melt. The nozzle or nozzles can be positioned at one side of the container below the level of the melt in the bottom of the container.
The invention will in the following be further illustrated by specific example of a preferred embodiment in conjunction with the appended drawing. In the drawing:

Fig. 1 shows a diagramatic longitudinal section through the front end of a metallurgical lance according to the invention;
Fig. 2 shows a section taken along line II-II i Fig. 1;
Fig. 3 shows enlarged a longitudinal section through a nozzle designed in accordance with the invention; and
Fig. 4 shows a section taken along line IV-IV of Fig. 3.

The metallurgical injection lance shown in Figs. 1 and 2 generally designated 1 largely consists of a central metal tube 3 surrounded by an outer tube or envelope 5 of a refractory material, for example a ceramic material. The two tubes 3, 5 are closed at their lower ends.
At the lower part of the injection lance 1 a number of laterally directed nozzles 7 are arranged through which communication is obtained between the interior of tube 3 and the outer phase of envelope 5. In the embodiment shown on the drawing the number of nozzles 7 are three and the nozzles are evenly distributed around the injection lance, as is clear from Fig. 2.
In Figs. 3 and 4 the design of such nozzle 7 is shown more in detail. The nozzle consists of an elongate body 9 of ceramic material. The central part 9 of the nozzle is designed with a circular cross-section and has a conical taper in the direction towards the outer end, which is diagramatically shown by angle α in Fig. 3. The taper of the embodiment shown is of the order 1°. The elongate body 9 is penetrated in the longitudinal direction by mutually parallel passages or capillaries 11 which connect the central metal tube 3 with the environment. In the embodiment shown the number of capillaries 11 are eight, but this number can vary within wide limits depending on gas flow, nozzle size, number of nozzles etc.
The elongate central body 9 is surrounded by a metal sleeve 13 closely engaging the outer surface of body 9. At the inner end this metal sleeve 13 is provided with external threads 15 enabling anchoring of the sleeve in the central metal tube 3 by engagement with a corresponding thread in the wall of metal tube 3. Metal sleeve 13 has a taper corresponding to that of the elongate body.
The materials used in the injection lance as regards metal tube 3 and the refractory envelope 5 are wholly conventional in character. Thus, steel can be used as a construction material in metal tube 3, whereas envelope 5 suitably is made of a refractory ceramic material. Also the material of the body 9 of the sleeve suitably consists of a ceramic material, for example selected among oxides, carbides and nitrides. Conceivable materials are also composit materials of different types. As example of materials of the former type there may be mentioned alumina of high density, and the latter type of materials may consist of a metal ceramic, such as zirconia in combination with molybdenum, or graphitized mixed oxides, for example based on alumina and zirconia.
The cross-dimension of the capillaries or passages 11 may be selected within relatively wide limits, and the preferred range is about 0.1 to 1 mm, particularly about 0.2 to 0.5 mm. The surrounding metal sleeve 13 can be made of any suitable heat-conductive material, for example copper, brass, steel or the like. The number of capillaries 11 is not critical but it is preferred that body 9 contains a plurality of evenly distributed capillaries 11, i.e. at least three and preferably up to ten or tens of capillaries.
With regard to the dimension of the nozzle itself the diameter thereof is preferably within the range 5 to 50 mm, particularly the order of 10 to 20 mm.
According to another aspect of the invention several nozzles can be arranged together in a plug, preferably by anchorage thereof through use of the threaded rear end of its metal sleeve. Such plug containing several nozzles can then be arranged in the container of interest in a conventional manner for enabling supply of gas into molten metal present in the container.
Although the invention has been illustrated in detail in connection to the use of the nozzle in metallurgical injection lances it should be noted that the invention is also applicable in connection with other applications. Thus, the invention can be applied to all types of containers for molten metals where it is desirable to add gas to the molten metal, for example for mixing, providing changes in the molten metal, for example decarborization with supply of oxygen-containing gas etc.
The nozzle device according to the invention as described above involves several important advantages compared to the conventional prior art. Among such advantages the following may be mentioned:

a. Variation of gas flow can be performed within wide limits, which is not possible with nozzles of a conventional construction.
b. Substantially reduced sputtering of molten metal into the nozzle will be obtained.
c. The errosion around the nozzle opening is substantially reduced.
d. Thanks to the high effectivity gas consumption is substantially reduced and smaller gas bubbles are obtained.
e. The nozzle construction according to the invention results in substantally reduced risk for back-attack.

Claims

1. Nozzle intended for injecting gas into molten metal, characterized by an elongate body (9) of refractory material containing a plurality of longitudinally extending through-going capillaries (11), and a metal sleeve (13) surrounding said body (9).

2. Nozzle according to claim 1, characterized in that said body (9) has a taper directed towards one end thereof whereby it cannot be pushed out of the sleeve (13) in the direction of said one end.

3. Nozzle according to claim 1 or 2, characterized in that the elongate body (9) is made of a ceramic material.

4. Nozzle according to claims 1, 2 or 3, characterized in that the capillaries (11) have a cross-section dimension of about 0.1 to 1 mm.

5. The use of the nozzle according to any of claim 1-4 for injecting gas into molten metal.

6. Container for molten metal, characterized by containing at least one nozzle according to any of claims 1-4 positioned in such a way as to enable injection of gas into the molten metal therethrough.

7. Container according to claim 6, characterized in that it is a ladle, tundish or similar device.

8. Injection lance (1) for injection of a gas into molten metal, comprising a central tube (3) and a surrounding envelope (5) of a refractory material, and at least one nozzle (7) through which the gas can be supplied to the molten metal through the central tube (3), characterized in that the nozzle comprises an elongate body (9) of refractory material containing a plurality of longitudinally extending through-going capillaries (11) establishing connection between the interior of the central tube (3) and the surrounding molten metal, said elongate body (9) being surrounded by a metal sleeve (13).

9. Injection lance according to claim 8, characterized in that said body (9) has a taper directed towards the outer end thereof whereby it cannot be pushed out of the sleeve (13) in the direction of said end.

10. Injection lance according to claim 8 or 9, characterized in that the elongate body (9) is made of a ceramic material.

11. Injection lance according to any of claims 8 to 10, characterized in that the capillaries (11) have a cross-section dimension of about 0.1 to 1 mm.

12. Injection lance according to any of claims 8 to 11, characerized in that said body (9) has in cross-section essentially circular shape.