EP0640413B1 - A rolling arrangement - Google Patents

Description

The invention relates to a rolling device with a roll stand and an upstream descaling device.

From DE-C - 41 34 599 it is known, for the purpose of avoiding surface defects on the rolling stock, such as peeling points or ablations, of coolant on the feed side of the rolling stock in an area that extends as close as possible in front of the roll gap over the entire width of the rolling stock to spray the rolling stock and onto the jackets of the work rolls. This is intended to achieve a strong cooling in a very thin outer zone of the rolling stock, so that the cooling is not critical for the subsequent deformation.

The device provided for carrying out the cooling process according to DE-C - 41 34 599 has spray nozzles which are arranged at a greater distance from the rolls of the roll stand and by means of which coolant is sprayed obliquely against the surface of the rolling stock in the direction of the roll gap, so that part of the coolant jet hits the surface of the rolling stock and part of the surface of the roll. Here, however, there is a risk of scaling flaking, the entry of which into the roll gap can no longer be prevented, which can lead to surface defects.

From EP-A-0 241 919 and US-A-5,001,915 it is known for the hot rolling of rolling stock to remove the scale of the rolling stock by spraying cooling water, the cooling water by means of nozzles which are located across the rolling stock extending cooling beams are provided, is sprayed against the movement of the rolling stock on the surfaces of the rolling stock.

A particular problem arises in the case of rolling devices which are integrated in a continuous caster for on-line rolling of a cast strand, etc. especially in the first roll stand seen in the casting direction, which is arranged before or just after the solidification front of the cast strand. Such a rolling device can because of the relatively high temperatures of the cast strand at the outlet from the cooling chamber enclosing the secondary cooling zone of the strand guide, the low deformation speeds due to the relatively low feed rate (= casting speed) of the rolling stock, i.e. the cast strand, and because of the low deformation resistance of the cast structure of the cast strand be built easily and inexpensively, since only relatively low rolling forces occur. Only a relatively low drive power is required, so that the energy consumption is low in relation to the degree of deformation.

It has been shown, however, that the scale must be completely removed in front of such a rolling stand integrated into a continuous caster in order to achieve a perfect surface, although there is a problem that only a small amount of liquid should be used to remove the scale in order to remove the scale To keep the energy content of the cast strand as high as possible, which runs counter to the requirement for complete scale removal. This is especially true when only a thin cast strand, such as a ribbon-like strand with a thickness in a range between 20 and 80 mm, is cast.

According to EP-A-0 241 919, a descaling device is provided for the online rolling of a cast strand, as is known from rolling mill technology - for example presented by US-A-5,001,915. However, it has been found that, in order to achieve effective descaling, large quantities of water must be sprayed onto the cast strand, which leads to a relatively high temperature drop in the cast strand, in particular its surface areas, so that the descaling process known from rolling mill technology is suitable for the descaling of on-line rolled cast strands, especially because of the very low rolling speed (= casting speed), cannot be achieved without disadvantages.

The invention therefore has as its object to provide a rolling device with a roll stand and a pre-descaling device which meets the diverging requirements - namely perfect surface quality through complete scaling removal and as little liquid application as possible.

• daß die Entzunderungseinrichtung eine unmittelbar vor den Walzen des Walzgerüstes angeordnete Rotor-Entzunderungseinrichtung aufweist,
• wobei die aus der Rotor-Entzunderungseinrichtung austretenden und auf dem Walzgut auftreffenden Flüssigkeitsstrahlen gegen die Walzrichtung gerichtet sind, und die an der Auftreffstelle des Flüssigkeitsstrahles auf der Walzgutoberfläche auftreffende Flüssigkeit nach dem Auftreffen eine Strömungsresultierende aufweist, die - projiziert auf die Walzrichtung - eine Komponente entgegengesetzt zur Walzrichtung aufweist.

According to the invention, this object is achieved by

• that the descaling device has a rotor descaling device arranged directly in front of the rolls of the roll stand,
• wherein the liquid jets emerging from the rotor descaling device and impinging on the rolling stock are directed against the rolling direction, and the liquid impinging on the surface of the rolling stock at the point of impact of the liquid jet has a flow result after the impact, which - projected onto the rolling direction - has a component opposite to it Has rolling direction.

The rotor descaling device works primarily by mechanically removing the scale. This removal is promoted by quenching the scale by the liquid jets, which breaks up the scale skin. A mechanical scale breaker, such as a bending device, can advantageously be provided in front of the rotor descaling device to assist in breaking up the scale skin.

Rotor descaling devices are known per se, for example from DE-A-31 25 146 for descaling hot steel blocks. Here, a spray bar extending across the entire width of the steel block to its surface and parallel is set in rotation about an axis directed perpendicular to its longitudinal extent.

It has been shown that when using a rotor descaling device according to the invention, it is possible to find sufficient length with much smaller amounts of water than with conventional descaling systems, such as those e.g. are known from the aforementioned DE-C - 41 34 599, US-A - 5,001,915 and EP-A - 0 241 919, so that the rolling stock, e.g. a cast strand, only a very small proportion of its heat content is removed. This also enables very thin rolling stock with a very high energy content to be fed to the roll stand. By arranging the descaling device directly in front of the rolls of the roll stand, it is also possible to effectively minimize post-scaling to an extent that is no longer disruptive.

Preferably, the planes placed through the axis of the liquid jets and parallel to an axis of one of the rolls of the roll stand always form an acute angle with the rolling direction placed at the point of impact of the liquid jet on the surface of the rolling stock, the tip of which is opposite to the rolling direction

According to a preferred embodiment, which enables a particularly simple design of the descaling device, the rotor axis (s) of the rotor descaling device is / are arranged inclined with respect to the surface of the rolling stock, the angle of inclination of the rotor axis advantageously being opposite a straight line perpendicular to the surface of the rolling stock is greater than the angle that the axis of a liquid jet forms with the rotor axis.

A particularly short arrangement of the descaling device in front of the rolls of the roll stand can be achieved if a portion of the spray area generated by the liquid jets of the rotor descaling device is shielded from the surface of the rolling stock.

Here, according to a robust and inexpensive embodiment, a cover plate with a liquid drainage channel, which extends across the surface of the rolling stock, is expediently provided to shield the partial area.

The cover plate, seen in plan view, advantageously covers a spray area directed against the roll gap of the roll stand.

In order to do justice to the particularly cramped space conditions just in front of the rolls of the roll stand, especially for thin rolling stock, the cover is expediently provided with a rolling stock catching or rolling stock guide device directed against the rolling direction for the safe introduction of the rolling stock start into the roll gap. wherein the catching or guiding device is advantageously formed by a sheet metal plate extending parallel to one of the axes of the rolls of the roll stand, in which at least one recess is provided for the passage of the liquid jets emerging from the rotor descaling device.

Here, the recess is also advantageously designed in the form of a part of a circular ring.

A particularly important embodiment is characterized in that the roll stand is designed for rolling a cast strand, in particular a thin strand, the roll stand advantageously being integrated into a continuous casting installation.

The rolling device according to the invention allows the rotor descaling device to be arranged within the roll stand of the roll stand.

For particularly wide cast strands, the rotor descaling device expediently has two or more rotor heads arranged approximately parallel to the axes of the rolls of the roll stand.

In order to remove scaling which accidentally gets into the vicinity of the roll gap, according to a preferred embodiment, a transverse spraying device is provided in the immediate feed region of the rolls of the roll stand, preferably in the case of the presence of a spraying area cover plate, the transverse spraying device between the cover plate and the surface of the rolling stock is provided.

The invention is explained in more detail below with reference to the drawing using two exemplary embodiments, FIG. 1 illustrating a continuous casting installation with an integrated rolling device in a schematic illustration in a side view. FIG. 2 shows a detail II of FIG. 1 on an enlarged scale according to a first embodiment. FIG. 3 illustrates a second embodiment in a representation analogous to FIG. 2. FIG. 4 is a view along line IV-IV of FIG. 3.

A cooled continuous casting mold, which is designated by 1, is fed with liquid steel 2, which is fed from an intermediate vessel 3. The cast strand 4 which forms in the mold 1 and has a liquid core and initially only a thin strand shell is diverted into the horizontal strand guide 7 via an arcuate strand support device 5 which is provided with closely adjacent support rollers 6. The arcuate strand support device 5 and the first part of the horizontal strand guide 7 are surrounded by a cooling chamber 8, which contains the secondary cooling zone.

After the cast strand 4 exits the cooling chamber 8, the cast strand (which has a thickness of approximately 60 mm) becomes a rolling device 9 (in which it is reduced to approximately 40 mm thickness), which is formed by a roll stand 10 and an upstream descaling device 11 , forwarded. After the rolling device 9, a separating device 12 is provided for separating the solidified and deformed cast strand 4 in slabs 13. If the cast strand 4 is processed into thin strip, the separation takes place according to the desired coil weight. The separated slabs 13 (thin slabs when casting a thin strand) are fed to a roller hearth furnace, not shown, in which the thin slabs are kept at the rolling temperature or, if appropriate, heated to this temperature, the roller hearth furnace also taking over the function of buffering the thin slabs for malfunctions. Rolling out to thin strip then takes place in a multi-stand finishing train, also not shown.

As can be seen from FIG. 2, the descaling device 11 is arranged directly in front of the work rolls 14 of the roll stand 10, etc. in the area between the side walls 15 of the roller stand 16. The descaling device 11 is designed as a rotor descaling device, the number of rotor heads 17 of the rotor descaling device 11 being selected according to the width of the cast strand 4. If several rotor heads 17 are provided, these are arranged side by side in a plane parallel to the axes 18 of the work rolls 14 of the roll stand 10 (cf. FIG. 4).

Each rotor head 17 has at least one rotating spray arm 19, which is preferably designed as a double spray arm 19 and extends radially and at the ends of which spray nozzles 20 are arranged. Instead of the spray arm 19, a rotating plate can also be provided, on the circumference of which spray nozzles are arranged. The axes 22 of the liquid jets 21 emerging from the spray nozzles 20 form an acute angle α with the rotor axis 23 of the associated rotor head 17. As can be seen from Fig. 2, the rotor axes 23 of the rotor heads 17 are arranged inclined relative to the surface 24 of the rolling stock (= surface 24 of the cast strand 4), the angle of inclination β of the axes of rotation 23 of the rotor heads 17 being greater than the angle α relative to the vertical , which include the axes 22 of the liquid jets 21 with the rotor axis 23 of the rotor heads 17. This ensures that the planes placed in each case by the axis 22 of the liquid jets 21 and parallel to one of the axes 18 of the work rolls 14 of the roll stand 10 always coincide with the rolling direction 26 placed on the surface 24 of the cast strand 4 at the point of impact 25 of the liquid jet 21 Include an acute angle, the tip of which is opposite to the rolling direction 26.

This has the effect that the liquid impinging on the impact point 25 of the liquid jet 21 on the surface 24 of the cast strand 4 has a flow resultant after the impact, which, projected onto the rolling direction 26, has a component opposite to the rolling direction 26, whereby the direction of flight of the flaking off Tinder is oriented opposite to the rolling direction.

To avoid spray water, the liquid jets 21 enter a housing 28 covering the surface 24 of the cast strand 4 in the region of the descaling device 11 immediately after exiting the spray nozzles 20 through an opening 27. This housing 28 is provided with a shielding wall 29 opposite the roll gap 30 formed by the work rolls 14, so that almost no spray water can be whirled against the roll gap 30.

In the immediate feed area of the work rolls 14 of the roll stand 10, a transverse spray 31 is also provided, which makes it possible to remove any scale particles that may be swirling around. The cross-spray 31 further reduces post-scaling due to reheating, which could possibly occur due to the very small amount of liquid that is applied by the rotor descaling device 11

According to the embodiment shown in FIG. 3, the rotor heads 17 are arranged with rotor axes 23 arranged perpendicular to the surface 24 of the cast strand 4, as a result of which the liquid jets 21 extend over a partial area 32 of the liquid jets 21 Formed impact circle 33 would be directed against the roll gap 30. In order to prevent the liquid jets 21 from striking the surface 24 of the cast strand 4 in this region 32, a shield is provided in this region 32, which is formed by a cover plate 34 extending transversely across the surface 24 of the cast strand 4. This cover plate 34 has a liquid drainage channel 35 which drains off the liquid collecting on this cover plate 34.

For the safe introduction of the rolling stock into the roll gap 30 - this is particularly important for thin strands - a catching and guiding device, which is shown in dash-dot lines in FIGS. 3 and 4, is provided according to a preferred embodiment, which is parallel to one another the axes 18 of the work rolls 14 of the roll stand 10 extending sheet metal plate 34 'is formed. This sheet metal plate 34 'is integrated with the cover plate 34 and has recesses 36 in the form of a part of a circular ring for the passage of the liquid jets 21 emerging from the spray nozzles 20.

The number of spray nozzles 20 per rotor head 17 can be selected depending on the amount of liquid required. The speed of the spray arms 19 is controlled as a function of the casting speed, that is to say as a function of the speed at which the casting strand 4 is drawn into the roll stand 10. The liquid is preferably sprayed at a pressure between 200 and 500 bar.

Claims (16)

1. A rolling arrangement (9) comprising a rolling stand (10) and a preceding descaling means (11), characterized in that

   • the descaling means (11) comprises a rotor descaling means arranged immediately in front of the rolls (14) of the rolling stand (10),

   • wherein the liquid jets (21) emerging from the rotor descaling means and impinging on the rolling stock (4) are directed opposite to the rolling direction (26).
2. A rolling arrangement according to claim 1, characterized in that the planes laid through the axis (22) of the liquid jets (21) and parallel to an axis (18) of one of the rolls (14) of the rolling stand (10) always enclose an acute angle with the rolling direction (26) laid on the surface (24) of the rolling stock (4) at the point of impact (25) of the liquid jet (21), the vertex of which angle is directed opposite to the rolling direction (26).
3. A rolling arrangement according to claim 1 or 2, characterized in that the rotor axis(es) (23) of the rotor descaling means (11) is/are arranged in a manner inclined relative to the surface (24) of the rolling stock (4) (Figs. 1, 2).
4. A rolling arrangement according to claim 3, characterized in that the angle of inclination (β) of the rotor axis (23) relative to a straight line oriented perpendicular to the surface (24) of the rolling stock (4) is larger than the angle (α) enclosed by the axis (22) of a liquid jet (21) with the rotor axis (23).
5. A rolling arrangement according to one of claims 1 to 4, characterized in that a partial region (32) of the spraying region (33) produced by the liquid jets (21) of the rotor descaling means (11) is shielded off relative to the surface (24) of the rolling stock (4) (Figs. 3, 4).
6. A rolling arrangement according to claim 5, characterized in that for shielding off said partial region (32) there is provided a cover sheet (34) including a liquid draining channel (35) and extending across the surface (24) of the rolling stock (4).
7. A rolling arrangement according to claim 5 or 6, characterized in that the cover sheet (34), viewed in ground section, covers a spraying region (32) directed against the rolling gap (30) of the rolling stand (10).
8. A rolling arrangement according to claim 7, characterized in that the cover sheet (34) is provided with a rolling stock capturing or guiding means (34') directed opposite to the rolling direction, for safely introducing the front end of the rolling stock into the rolling gap (30).
9. A rolling arrangement according to claim 8, characterized in that the capturing and guiding means (34') is comprised of a plate panel (34') extending parallel to one of the axes (18) of the rolls (14) of the rolling stand (10) and in which at least one recess (36) is provided for the passage of the liquid jets (21) emerging from the rotor descaling means (11).
10. A rolling arrangement according to claim 9, characterized in that the recess (36) is designed in the form of an annulus section.
11. A rolling arrangement according to one of claims 1 to 10, characterized in that the rolling stand (10) is adapted for the rolling of a cast strand (4), in particular of a thin strand.
12. A rolling arrangement according to claim 11, characterized in that the rolling stand (10) is integrated with a continuous casting plant.
13. A rolling arrangement according to one of claims 1 to 12, characterized in that the rotor descaling means (11) is disposed within the rolling housing (16) of the rolling stand (10).
14. A rolling arrangement according to one of claims 1 to 13, characterized in that the rotor descaling means (11) comprises two or several rotor heads (17) adjacently arranged approximately parallel to the axes (18) of the rolls (14) of the rolling stand (10).
15. A rolling arrangement according to one of claims 1 to 14, characterized in that a cross spraying means (31) is provided in the immediate region of entry of the rolls (14) of the rolling stand (10).
16. A rolling arrangement according to claim 15, characterized in that in case a spraying region cover sheet (34) is provided the cross spraying means (31) is provided between the cover sheet (34) and the surface (24) of the rolling stock (4).

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