Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reexamination Certificate
2002-03-01
2003-09-16
Elve, M. Alexandra (Department: 1725)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S429000, C164S442000, C164S448000
Reexamination Certificate
active
06619375
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a casting roll for a thin strip casting plant, in particular for the continuous casting of thin strips of steel, comprising an essentially cylindrical core, a mantle of copper or a copper alloy optionally being provided with at least one outside layer, an internal cooling system as well as an adjusting means for adjusting the outline of the casting roll in its front-end regions.
A casting roll of this kind is known f.i. from EP-A-0 664 173. Casting rolls of this kind are used for continuously casting refractory metals such as steel. Here, two casting rolls of this kind are arranged parallel to each other and turned in opposite directions around their respective axes. The metal melt is cast into a slit defined between the casting rolls and is cooled and solidified when in contact with the surfaces of the casting rolls provided with an internal cooling system and when passing through the slit, so that the metal emerges from the casting slit in the form of an essentially solidified strip. The thickness of the strip is determined by the width of the casting slit and the width of the strip is determined by the length of the casting slit, which is limited at its ends by sealing surfaces adjacent to the fronts of the casting rolls.
Here, the problem of curvatures of the surfaces of the casting rolls arises, that is, a deviation of the surfaces of the casting rolls from the desired strictly cylindrical or slightly crowned form. The reason for this is to be seen in thermally caused deformations of the mantles of the casting rolls subject to very high temperatures.
In order to reduce the crown of the rolls, which occurs in continuous casting, and/or to control the crown of the rolls, it is known (JP-A-60-27446) to provide conically tapered pistons in the casting rolls. These conically tapered pistons are lodged in a displaceable manner in two piston sliding spaces arranged at the opposite ends of the casting roll, respectively, so that by displacing the conically tapered piston in the axial direction, the outer circumferential surface of the casting roll is deformed by the wedge-like effect of the conically tapered piston. However, it can not be avoided here that the pistons, seen depending on the position in the piston sliding spaces at different sites in the longitudinal direction of the casting roll, exercise forces on the casting roll, i.e. the mantle of the casting roll, whereby it is very difficult—if it is possible at all—to exactly level out the crown of the roll.
Especially in the front-end regions of the casting rolls, the high specific heat flows, which occur in the solidification process when thin-strip-casting, result in specific thermal strains and stresses, whereby here, higher strip thicknesses result than in the center region of a cast strip. Instead of the required concave profile, the strip has a profile of a locally substantially convex form. It is true that attempts have been made to remedy this by way of a precompensation, namely by forming a concave casting-roll profile, but this was helpful only to a limited extent, due to the dependence on the generally set strip thickness, the casting rate, the height of the bath level and other parameters having an influence on the solidification and heat elimination, such as quality of the steel, temperature of the melt, etc.
From the above EP-A-0 664 173 it is known to support the front-end regions of the casting-roll mantle by means of ring-shaped hollow supporting bodies at the core and to conduct hot water through the hollow spaces of the ring-shaped hollow bodies, so that thermal strains caused hereby are transferred to the mantle and deform it, giving it the desired profile. However, a construction of this kind results in that the casting roll becomes very complex, given that it is necessary to provide two different water cycles, namely on the one hand the hot-water cycle for levelling out the thermally caused deformations and on the other hand a cooling-water cycle for eliminating the heat released by the metal which is solidifying. Accordingly, a casting roll of this kind is expensive, and it involves many risks with respect to the rough casting operations in a steel mill.
The inventions has as its objects to avoid these disadvantages and difficulties and to develop a casting roll of the above kind by means of which thermal crowns may be reduced and/or completely levelled out with the aid of constructively simple means. In particular, the casting roll should be robust enough for continuous operation and little susceptible to trouble. Furthermore, building the construction should be cheap, and the construction should ensure a simple operation.
In the case of a casting roll of the above kind, this object is achieved with the adjusting means having in each front-end region of the casting roll a supporting disk adjustable in the longitudinal direction of the casting roll and engaging a ring radially surrounding the supporting disk and abutting the mantle from the inside in its front-end regions, which ring is fixedly attached with regard to the core in the longitudinal direction of the casting roll.
For a casting roll, a supporting disk as such is known from U.S. Pat. No. 5,613,546, but this supporting disk directly engages the mantle of the casting roll and does not provide for levelling out thermal crowns but for centering the mantle with regard to the core.
According to a preferred embodiment, the ring is sealed against the mantle as well as the core by means of a gasket. Hereby, an absolute impermeability of the internal cooling system of the casting roll is ensured. In a construction according to JP-A-60-27446, f.i., such an impermeability is not a matter of course. In this known construction, the conically tapered pistons are provided within the core and, on the outside, surrounded by the cooling system for the mantle. Hereby, a widening of the mantle by means of the pistons results in a radial displacement of the supply and discharge ducts of the internal cooling system of the mantle.
In its outer circumferential surface, the supporting disk is preferably furnished with a frustoconical surface abutting a counter-frustoconical surface provided at the ring in its inner circumferential surface.
An embodiment which is constructively easy to build and safe in operation is characterized in that for the adjustment of the supporting disk in the longitudinal direction of the casting roll, a plurality of bolts distributed close to the outer circumference of the supporting disk is provided, by the aid of which bolts the supporting disk is adjustable against the core, wherein preferably the bolts are screwed into blind holes arranged at the core. Here, the setting of the supporting disks is effected before beginning to cast.
A further preferred embodiment is characterized in that the supporting disk is adjustable by means of a ring nut against the core in the longitudinal direction of the casting roll.
In order to be able to effect an adjustment during the strip-casting, according to another preferred embodiment the supporting disk is hydraulically adjustable against the core in the longitudinal direction of the casting roll.
Suitably, the ring extends up to a maximum of 75 mm from the front-end region in the longitudinal direction of the casting roll to its center, preferably up to 50 mm, in particular up to 35 mm.
Preferably, the mantle has a thickness less than or equal to 50 mm in its front-end regions, where contact with the ring occurs.
REFERENCES:
patent: 5207265 (1993-05-01), Hasegawa et al.
patent: 5613546 (1997-03-01), Delassus et al.
patent: 5638891 (1997-06-01), Fukase et al.
patent: 5839501 (1998-11-01), Delassus et al.
patent: 3839110 (1989-06-01), None
patent: 3836886 (1990-05-01), None
patent: 4203964 (1992-08-01), None
patent: 0427574 (1991-05-01), None
patent: 0664173 (1995-07-01), None
patent: 60-27446 (1985-02-01), None
patent: 60-127007 (1985-07-01), None
Hohenbichler Gerald
Reiter Thomas
Schertler Armin
Staudinger Günther
Dickstein , Shapiro, Morin & Oshinsky, LLP
Elve M. Alexandra
McHenry Kevin
Voest-Alpine Industriean-lagenbau GmbH
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