Patent Application
20120132389
The invention relates to a casting nozzle for a horizontal strip casting facility, in particular for casting steel strip. Such casting facilities require liquid steel to be applied upon a cooled continuous belt from the nozzle which forms a casting channel.
Such a casting nozzle is known from “Direct Strip Casting” (DSC)—an Option for the Production of New Steel Grades”—steel research 74 (2003) No. 11/12 p. 724-731.
In this known arrangement, liquid steel flows from a distributor via a horizontally aligned feed channel into the casting nozzle which has in cross section a narrow rectangular channel surrounded by refractory material and configured as hollow block with bottom, top, and two side walls.
A web made of refractory material is arranged in the outflow region, as viewed in flow direction, first on the upper side and then on the underside of the casting nozzle channel transversely to the flow direction, and extends into the channel. Both webs form a weir in order to keep back possible small slurry residues and oxides in the melt to act in a manner of a siphon. The transfer of the liquid steel onto the cooled continuous belt is implemented in sliding manner along a slant in the outflow region.
As a result of surface tension and mass flow, the steel stream undergoes a contraction in the outflow region of the casting nozzle. This effect causes an irregular distribution of the melt in transverse direction on the continuous belt and thus to inadequate edge fill of the cast steel strip.
It is an object of the invention to so improve the known casting nozzle as to attain a more even distribution of the melt also in transverse direction, when contacting the continuous belt.
Starting from the preamble of the main claim, the stated object is solved by the features of the characterizing part. Advantageous refinements are the subject matter of sub-claims.
The casting nozzle in accordance with the invention is characterized in that the clear cross section of the hollow block, as viewed in flow direction, decreases in the outflow region uniformly in direction of the outflow, and the end face of the bottom is constructed towards the surface of the continuous belt in such a manner that the melt contacts the continuous belt perpendicularly. For that purpose, the end face of the bottom may be configured perpendicular or be provided with an undercut.
The slanted profile results in a reduction of the clear cross section of the hollow block to a minimum value that still ensures the necessary throughput at the outflow and causes a backup of melt which pushes the melt stream in opposition to the action of the surface tension also to the marginal zones.
The cross sectional reduction is realized preferably by a decrease of the clear vertical distance. An ascent of the bottom in relation to the top has been proven as a beneficial variation.
The reduction in distance can be realized in a particularly simple manner when implemented linear. The desired effect can easily be realized when the surface of the bottom ascends linearly up to the outflow edge, as viewed in flow direction.
The hollow block may be made of one piece or of multiple parts from separate elements. When multiple parts are involved, the hollow block may be made of separate bottom element with a single-part hood comprised of top and two side walls or of a separate top element, a separate bottom element and two separate side elements.
For the sake of simplicity, only the bottom element is provided with the slanted run-on surface according to the invention. This has the advantage of a simple exchange in the event the bottom element should wear off faster than the top element or the side elements.
Also the rectangular or undercut arrangement of the end face of the bottom element of the casting nozzle in relation to the surface of the continuous belt results in a better melt distribution upon the continuous belt. The outflowing melt thus contacts the continuous belt nearly perpendicular and generates an additional transverse momentum. The height from the outflow edge to the continuous belt should hereby amount to preferably 30 mm.
Preferably, the ascent of the slanted run-on surface of the bottom element is linear, resembling a ramp. The extent of the ascent in flow direction should amount to at least 30 mm, preferably at >50 mm.
In order to be able to influence the outflowing melt early on in terms of a uniform distribution in transverse direction, for example by gas jets or inductors, it is helpful to extend the bottom element, as viewed in flow direction, beyond the top element. This overhang should be at least 10 mm. Such an overhang permits manipulation of the outflowing melt already in the region of the casting nozzle instead of only on the continuous belt.
It is proposed for this case to provide the marginal zones of the overhang of the bottom element with descending slanted surfaces, respectively, as viewed in flow direction. As a result, the melt stream, as viewed in transverse direction, is deflected to the marginal zones to also promote a better distribution of the melt.
To facilitate production of the separate bottom element, it is of advantage to provide the outflow edge with a chamfer. This chamfer reduces wear of the highly strained outflow edge at the same time.
An exemplary embodiment of the casting nozzle according to the invention is described in greater detail.
It is shown in:
As is known in the state of the art, the bottom element 3 includes a web which projects into the channel 6 and extends transversely to the flow direction and which forms a so-called lower weir 7.
Placed upstream of the casting nozzle 1 is a feed channel 8 which is connected to a distributor, not shown here.
In the shown embodiment, a web projects at the top element 9 of the feed channel 8 into the clear cross section and extends transversely to the flow direction to form a so-called upper weir 10. Both weirs 7, 10 interact together like a siphon and should, if need be, keep back slurry residue and oxides left in the melt.
Both weirs 7, 10 may be arranged in the casting nozzle 1 and in the feed channel 8, or, as shown here, the upper weir 10 in the feed channel 8 and the lower weir 7 in the casting nozzle 1.
The feed channel 8 is surrounded by a frame 22 of metal which has an end configured in the form of a tongue to be able to clamp the adjacent casting nozzle 1.
In accordance with the invention, the surface of the bottom 3 has a slanted run-on surface 11 having a linear ascent and extending up to the outflow edge 12. In order for the outflowing melt 13 to contact the continuous belt substantially perpendicular, the outflow, unlike the state of the art, is not provided with a slant but the end face 21 of the bottom element 3 extends at a right angle in relation to the surface of the continuous belt 14.
Illustration of the type of cooling of the continuous belt 14 is omitted here. Only the front deflection roller 15 of the revolving belt and the two side boundaries 16, 17 of the continuous belt 14 are depicted.
The slanted run-on surface 11 has an extent 18, as viewed in flow direction, of at least 30 mm, preferably >50 mm.
In this exemplary embodiment, the start of the slanted run-on surface 11 is provided in immediate proximity of the lower weir 7. To reduce wear of the slanted run-of surface 12, the latter is provided with a chamfer 23. To generate a certain transverse momentum onto the melt, the height 19 from the lower edge of the chamfer 23 to the surface of the continuous belt 14 is preferably 30 mm.
In order to be able to manipulate early on the melt outflowing from the casting nozzle in terms of attaining a uniform distribution in transverse direction, the end face 21 of the bottom element 3 has an overhang 20 in relation to the end face 26 of the top element 2.
As a result, parts of the outflowing melt 13 is deflected in the marginal zones and accelerated, as indicated by the depicted arrows.
In projection, each of the slanted surfaces 24, 25 defines a triangle defined by a first corner being formed by the start of the slanted run-on surface 11, a second corner being formed by the outflow edge 12, and a third corner being formed by the end face of the respective side element 4, 5.
The illustration in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 012 984.7 | Mar 2009 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2010/000213 | 2/15/2010 | WO | 00 | 11/18/2011 |
