Casting roller for a double-roller continuous casting machine

The invention relates to a casting roller (1), for a double-roller continuous casting machine, in particular for the casting of a steel strip, comprising a cylinder sleeve (2) which may rotate about a fixed axle (5). Intermediate rings (7b, 7c, 7d) rotating with the cylinder sleeve (2) are arranged between the cylinder sleeve (2) and the axle (5), which are provided with radial pressure means (9), acting on the cylinder sleeve (2). The above comprise a pressure chamber (10), pressurized with a fluid pressure medium and acting on a pressure ring (24) fixed to the inner wall of the cylinder sleeve (2), which may be deformed in the radial direction by inductive heating or radiated heat. The external profile of the casting roller (1) may be globally altered or local fine adjustments made by pressurizing the pressure chamber (10) with the pressure medium, or by heating the pressure ring (24).

BACKGROUND OF THE INVENTION

The invention concerns a casting roll for a twin-roll casting machine, especially for casting steel strip, with a cylinder sleeve, which rotates on a stationary axle.

Casting machines of this type work in such a way that, during the operation, the molten metal present in the mold space flows through the casting gap between the counterrotating casting rolls and is shaped into a metal strip.

Due to the high thermal load, the casting sleeves experience convex deformation, which results in a concave profile of the cast strip. This can result in diminished strip quality, especially since the cooling of the strip also causes transverse shrinkage of the strip. For this reason, the casting rolls are concavely shaped in the cold state, so that thermal expansion of the casting rolls produces a parallel or slightly convex shape of the strip, which allows noncritical transverse contraction during cooling of the strip and guarantees the accuracy to gage of the strip.

However, a disadvantage of casting rolls of this type is that, due to their concave shape, they can be used only for a certain influx of molten metal and thus heat input into the casting rolls. If the production parameters and thus the amount of molten metal flowing into the mold are changed, a different heat input and thus different thermal deformation of the casting rolls are obtained, which can result in the cast strip no longer being accurate to gage. The result of all this is that the casting rolls need to have different geometries for different production parameters.

Another disadvantage of concave casting rolls arises during the starting up of the casting machines without a dummy bar. Since in this case the casting gap cannot be completely closed when the casting rolls are run together, liquid steel then leaks out at the bottom, which makes a controlled start-up more difficult.

SUMMARY OF THE INVENTION

The objective of the invention is to avoid these disadvantages and to create a casting roll of the type described above, whose outer contour can be adjusted globally or locally by means that are simple in design and that can be easily and sensitively controlled.

In accordance with the invention, this objective is achieved by installing one or more intermediate rings and/or supporting rings between the cylinder sleeve and the axle. These rings are provided with pressure means that act on the cylinder sleeve. The pressure means are preferably nonrotatably connected with the cylinder sleeve and have a pressure chamber bordering on the inside wall of the cylinder sleeve. A fluid pressure medium can be admitted into the pressure chamber through supply channels in the axle and in the intermediate ring.

When the fluid pressure medium is admitted into the pressure chamber, uniform radial pressure is exerted on the cylinder sleeve. This causes expansion of the cylinder sleeve. Suitable positioning of the intermediate ring or rings along the axle and suitable admission of pressure medium into the pressure chambers make it possible at all times to achieve sensitive adjustment of the profile of the casting sleeve and thus the profile of the strip during the casting process. Accordingly, this makes it possible to compensate for changes in the process parameters without production interruptions. Starting up with or without a dummy bar is also considerably simplified, since it is now possible to bring the conventionally concave form of the casting roll into a cylindrical form, which guarantees complete closing of the casting gap when the casting rolls are run together. This allows a controlled start-up, because molten steel cannot flow out towards the bottom.

To ensure that pressure acts uniformly on the cylinder sleeve, the invention provides that the pressure chamber is annular and completely encircles the intermediate ring.

It is advantageous for the end face of the intermediate ring to abut the inside wall of the cylinder sleeve and for the intermediate ring to have a cavity that forms the pressure chamber. The cavity is bounded at its end face by a flexible seal, which is installed in the cavity and rests against the inside wall of the cylinder sleeve.

In another design in accordance with the invention, a circumferential intermediate gap is present between the intermediate ring and the inside wall of the cylinder sleeve and is spanned by a metal seal that bounds the pressure chamber.

In another variant of the invention, the intermediate ring abuts the inside wall of the cylinder sleeve and has a cavity that forms the pressure chamber, which is bounded on its end face by the inside wall of the cylinder sleeve and is surrounded by one or more outer seals installed in the cylinder sleeve.

It is advantageous for the intermediate ring to be rotatably positioned on the stationary axle and to be provided with one or more seals that seal the transition between the supply channels in the axle and in the intermediate ring.

In an alternative variant of the pressure means of the invention, the invention provides that the pressure means have a co-rotating pressure ring, which is fixed on the inside wall of the cylinder sleeve, rests circumferentially on the intermediate ring and can be expanded in the radial direction by inductive heating. When the pressure ring is heated, it is more or less expanded, and consequently the cylinder sleeve is expanded. In this way, here too it is always possible to adjust the casting roll profile and thus the strip profile as well during the casting process.

It is advantageous for the pressure ring to be provided with thermal insulation.

In the case of casting rolls with several intermediate rings, it is advantageous if they can be moved along the stationary axle.

It is also advantageous if the contact surfaces between the intermediate rings and the inside wall of the cylinder sleeve lie on a common surface.

DETAILED DESCRIPTION OF THE INVENTION

The casting roll1inFIG. 1has a cylinder sleeve2with supporting rings at its end faces, which, together with the cylinder sleeve2, can be rotated on a stationary axle5supported on bearings6. Three intermediate rings7aare installed inside the casting roll1and serve the purpose of adjusting the outer profile of the casting roll1. The intermediate rings7are positioned on the stationary axle5with spacers8, which are mounted on the supporting rings3and4.

The intermediate rings7arotate together with the cylinder sleeve2. This co-rotation is effected by the spacers8and the supporting rings3and4.

AsFIG. 4shows, the intermediate rings are provided with pressure means9with a pressure chamber10, which has an annular design and encircles the intermediate ring7aaround its entire circumference. A fluid pressure medium, such as hydraulic oil or the like, can be admitted into the pressure chamber10through supply channels11,12in the axle5and in the intermediate ring7a.High-viscosity pressure media can be used to apply the necessary pressures. The transition between the supply channels11and12is sealed with sealing elements13installed in the intermediate ring7a.The end faces of the intermediate rings7aabut the inside wall14of an annular projection15of the cylinder sleeve2, and the intermediate rings7ahave an annular groove16, which forms the pressure chamber10and is bounded at its end face by a flexible seal17inserted in the annular groove16. The intermediate rings7aalso have a shoulder18, which interacts with the spacers8and serves as a positioning aid.

The casting roll inFIG. 2differs from the casting roll inFIG. 1essentially by the fact that its intermediate rings7b,7c,and7dhave designs that are different from that of the intermediate rings7a.

InFIG. 5, which shows the intermediate ring7b,a circumferential intermediate gap19is present between the intermediate ring7band the inside wall14of the cylinder sleeve2and is spanned by a metal seal20that bounds the pressure chamber10. The metal seal20is inserted in annular grooves21a,21bin the intermediate ring7band the cylinder sleeve2, respectively. It is secured there by an annular flange22, which is mounted on the side of the intermediate ring7b.The intermediate ring7bis also positioned relative to the cylinder sleeve2by the metal seal20, so that the shoulder18that would otherwise be present, as in the case of the intermediate ring7a,can be eliminated.

The intermediate ring7cshown inFIG. 6differs from the intermediate ring7aonly in that the flexible seal17is not present, and that the end face of the pressure chamber10is bounded by the inside wall14of the cylinder sleeve2and is surrounded by seals23installed in the cylinder sleeve2. In intermediate rings7aand7c,the annular groove16is designed with a rectangular cross section. However, it is immediately possible in accordance with the invention to design the annular groove16with a semicircular cross section. It is also immediately possible to provide several partial annular grooves distributed along the circumference instead of a fully circumferential annular groove.

The intermediate ring7dinFIG. 7differs from the intermediate rings7a,7b,and7cin that it is mounted in a stationary way on the stationary axle and does not rotate with the cylinder sleeve. A pressure ring24, which is mounted in a stationary way and rotates with the cylinder sleeve, is provided on the inside wall14of the cylinder sleeve2and can be expanded in the radial direction by inductive heating. The pressure ring24replaces the pressure chamber10of the intermediate rings7a,7b,and7c,which can be pressurized by a pressure medium. The cylinder sleeve2is expanded by this pressure ring24. To further intensify this effect, the pressure ring24is provided with insulation25, which thermally insulates it from the cylinder sleeve2and the intermediate ring7d.The pressure ring24can be heated not only inductively from the stationary axle5, but also by radiant heat, but in this case, no insulation is provided between the pressure ring and the intermediate ring.

The casting roll inFIG. 3differs from the casting rolls inFIGS. 1 and 2in that its intermediate rings7a′ are not seated directly on the stationary axle5, but rather are supported on a coaxial support cylinder26, which is nonrotatably joined in the middle with the cylinder sleeve2by means of clamping rings27and can rotate on the stationary axle5together with the cylinder sleeve2and the intermediate rings7a′. Bearings28for the support cylinder26are provided on the axle5. To position the intermediate rings7a′, the inside wall14of the cylinder sleeve2is provided with projections29, and the intermediate rings7a′ are installed by being stopped against the projections29. As a result, the intermediate rings7a′ have different diameters, starting from the center. The central arrangement of the support cylinder26relative to the cylinder sleeve results in the further advantage that, with a possible wedge shape of the strip to be produced, equalization can be ensured by decreasing or increasing the casting gap on one side, as necessary.

By contrast, in the casting roll inFIG. 1, the intermediate rings7ahave the same diameter, so that their contact surfaces with the inside wall14of the cylinder sleeve2lie on a common surface.

The casting rolls of the invention in accordance withFIGS. 1,2, and3offer individual, multiple operational and positioning possibilities for the intermediate rings7a,7a′,7b,7c,and7dfor the profile adjustment of the cylinder sleeve2in the axial direction of the casting roll.

The intermediate rings7a,7a′,7b,7c,and7dproduce negligible supporting forces on the stationary axle of the casting roll. The relative motion between the rotating cylinder sleeve2and the stationary axle5occurs with extremely low sealing frictional forces.

In addition, the casting roll of the invention is characterized by the fact that it guarantees simple assembly and disassembly, especially of the cylinder sleeve2.

It is also distinguished by a small structural space in regard to other elements that are to be installed inside the cylinder sleeve2, such as vibrators, magnetic elements, or the like.

In regard to the casting roll of the invention, the invention also takes into account the fact that, due to the different dimensional stability of the cylinder element2and the intermediate rings7a,7a′,7b,7c,and7d,the latter experience less deformation than the cylinder sleeve2. This can be influenced by a suitable choice of materials for these parts.

In regard to the expansion of the cylinder sleeve2by means of the intermediate rings7a,7a′,7b,7c,and7d,naturally, the thermal expansion of the cylinder sleeve2is also taken into consideration.

FIG. 8shows another enlarged sectional view of the terminal bearing of the cylinder sleeve2of a supporting ring4, which is also designed as an intermediate ring in accordance with the invention. For this purpose, in a given supporting ring4, pressure means9′ that act on the cylinder sleeve2are provided. It is advantageous for these pressure means9′ to be installed at an angle towards the cylinder sleeve, for example, an angle of about 30°from the horizontal, so that it does not act on the sleeve2radially, but rather at the corresponding angle. The pressure means9′ have a pressure chamber10, which again are connected to a source of pressure medium by supply channels11.

The surface of the cylinder sleeve can be caused to vibrate by pulsation of the pressure medium in at least one intermediate ring or by a vibrator installed on at least one intermediate ring, so that heat dissipation can be influenced or increased.

FIGS. 9 and 10show a variant of the pressure means59by which the cylinder sleeve2can be expanded. Preferably, in analogy to the embodiment shown inFIG. 1, several pressure means59of this type are installed along the cylinder sleeve2, which make it possible for this sleeve2to be uniformly expanded at least over a portion of its total length.

The pressure means59have an expansion ring51, between the axle and which a pressure chamber55is formed, which is connected to a pressure medium supply54and is laterally sealed by suitable sealing means52,53. The expansion ring51is surrounded by a spiral bush56, which has a spiral design and an axis coaxial to the axis of the axle5and which, during an expansion, expands accordingly. This spiral bush56forms the inner ring of an encapsulated roller bearing57, which on the outer side is likewise formed by a spiral bush56′ of this type. Segments58′ that form a ring are also present between the spiral bush56′ and the cylinder sleeve2. The outer surfaces of these segments58abut the inside of the sleeve2.

The expansion ring51radially expanded by the pressure medium, for example, a hydraulic oil, expands the inner spiral bush56, which in turn expands the outer spiral bush56′ via the rollers, and the outer spiral bush56′ then expands the cylinder sleeve2via the ring58. These pressure means59result in the advantage that, with the expansion ring51acted on by a pressure medium and with the spiral bush56surrounding the expansion ring51, no rotating parts are present, so that a seal with greater operational reliability is possible.

FIG. 11shows a top view of part of the ring that consists of segments58. These segments58mesh together by corresponding peaks and congruent recesses.

Another variant is shown inFIGS. 12,13, and14, which illustrate pressure means69designed similarly to the pressure means ofFIGS. 9 and 10. In this case, an expansion ring71that surrounds the axle5, a roller bearing57with spiral bushes76,76′ as the inner and outer rings, and a ring78are also provided.

As shown inFIG. 14, the ring78is divided by a slot81. This ring78and with it the inner spiral bushes can be more or less compressed for assembly by means of a fastening device80and thus changed in diameter. For this purpose, the fastening device consists of pins82,83, which are fastened to the ring78on both sides of the slot and are surrounded by a flexible ring element84. One of the pins83has a cam83′. The ring78can be compressed or loosened by turning this cam83′.

For different roll diameters of the casting machine, one or more such rings78with at least one slot82may be provided between the outer spiral bush76′ and the inner side of the cylinder sleeve5.