KR20120102740A - Method for hot-rolling a slab and hot-rolling mill - Google Patents

Abstract

The present invention relates to a method for hot rolling a slab (1), in particular a steel slab, wherein the slab (1) is subjected to two or more molding steps at various temperature conditions in the hot rolling mill (2), and the slab ( 1) is cooled between two stages of this type of molding. In order to prevent premature formation of the ferrite form during hot rolling, according to the invention, the cooling of the slab 1 is such that the side end regions 3, 4 of the slab 1 have a central area 5 of the slab 1. Cooling with a lower cooling efficiency. The invention also relates to a hot rolling mill 2 for hot rolling a slab.

Description

Slab hot rolling method and hot rolling mill {METHOD FOR HOT-ROLLING A SLAB AND HOT-ROLLING MILL}

The present invention relates to a method for hot rolling a slab, in particular a steel slab, wherein the slab is treated in two or more forming steps at various temperature conditions in a hot rolling mill, the slab being subjected to two forming steps of this type. Is cooled. The invention also relates to a hot rolling mill for hot rolling a slab.

Hot rolling processes of slabs are well known in the art. In this case, as a preferred method, a multi-phase hot-rolling process is used, while a special method is a thermomechanical rolling process (TM method).

Typical applications of the method are in the production of hot rolled steel strips or steel sheets of microalloy steel material.

The goal in this case is the high homogeneity of the material made from the hot rolled slab, ie the material properties must be spatially constant within the material. To achieve this, as high a temperature uniformity as possible is provided internally of the slab during the hot rolling process, that is to say internally of the intermediate slab and consequently to provide uniform properties in the final product.

If individual rolling operation steps are carried out (as is typical for a thermomechanical rolling process) during hot rolling, pauses are inserted between the individual rolling steps, in which the slab is uniformly lower in new temperature. Cooled to As soon as the target temperature is reached, subsequent rolling steps are started. In this case, from the technical point of view, the intermediate slab preferably has a uniform temperature.

During the waiting time the side regions of the slab cool faster than the core of the slab. The result is the edge of the cold state. Such low temperature edges can be problematic in subsequent rolling passes. As a result, the properties of the final product may deteriorate. Since the waiting time between the rolling steps increases with the slab thickness, this problem is particularly often identified when the middle slab is thick.

It is therefore an object of the present invention to improve the method and the rolling mill in such a way that the aforementioned disadvantages are avoided in the method and corresponding rolling mill of the first mentioned type. A further object is therefore to be able to maintain the high quality of the intermediate slab and the final product. Another object is to enable the hot rolling process to be carried out under optimum conditions after the first slab cooling.

The solution of the above object according to the invention is characterized in that, according to the method, active cooling of the slab is achieved in such a way that the side end regions of the slab are cooled with a lower cooling efficiency than the center region of the slab.

Cooling of the slab is preferably effected by the function of the cooling medium, with the side end regions of the slab being at least partially shielded from the cooling medium.

Cooling of the slab can take place in the intermediate cooling structure or in the cooling zone.

Control of the active cooling in some cases ensures that undesirable conversion from the austenite form to the ferrite form is not achieved during the active cooling step.

The hot rolling process of the slab in this case is preferably a multiphase rolling process, in particular a thermomechanical rolling process.

A hot rolling mill proposed for hot rolling a slab comprises two or more hot rolling roll stands, between which there are one or more cooling stations in between the hot rolling roll stands or in front of the rough rolling stand where the slab can be cooled. Is placed. The hot rolling mill allows the cooling station to vary the cooling efficiency provided to the slab in such a way that the cooling of the slab is such that the side end regions of the slab are cooled with a lower cooling efficiency than the center area of the slab. It characterized in that it comprises a means for.

The means are cover members formed in accordance with a preferred embodiment so as to cover the side end regions of the slab for protection from the cooling medium.

The means is also a cooling bar for discharging the cooling medium on the slab, the jetting jet width of the cooling medium can be adjusted over the width of the slab.

The cooling station is preferably an intermediate cooling structure or a cooling zone.

In addition, according to the invention, during hot rolling, active intermediate cooling is performed, which is configured such that the side regions (edges) of the slab are not cooled. Thus, after the active cooling process and after the compensation time, regardless of whether cooling takes place either actively or passively (in air), a slab exhibiting a more uniform temperature distribution than the slab cooled in the conventional manner is obtained. do.

The hot rolling mill is characterized in that the cooling process is controlled by a connected temperature calculation device, as the case may be, so that the lowering of the ferrite precipitation temperature can be prevented so that undesirable formation of the ferrite form is optionally eliminated.

Finally, the hot rolling mill is characterized in that the cooling width is adjusted to the corresponding cooling width by an electric or mechanical device.

In the drawings embodiments of the invention are shown.
1 is a side view schematically showing a hot rolling mill in which only two hot rolling roll stands are shown with a cooling station interposed therebetween.
FIG. 2 is a schematic cross-sectional view cut along the cutting line AB according to FIG. 1 for a half of the upper part of the cooling station.
FIG. 3 is a schematic cross-sectional view cut along the cutting line AB according to FIG. 1 for the upper half of the cooling station as an alternative solution.

1 shows a hot rolling mill 2 in which the slab 1 can be rolled inside. A number of hot rolled roll stands 8, 9 are provided for this purpose, only two of which are shown in FIG. 1. The slab is conveyed in the rolling direction W during rolling, where it is rolled in a known manner. The slab is treated by a thermomechanical process during rolling.

The slab 1 is thereby reduced in thickness in the first hot rolling roll stand 8. At the rear of the stand 8 the slab 1 is cooled, for which the slab is guided through a cooling station 7, which in this case is formed as an intermediate cooling structure.

Then, at the rear of the cooling station 7, the slab 1 is again rolled in the hot rolling roll stand 9, more precisely at a lower temperature condition than in the roll stand 8.

The cooling of the slab 1 in the cooling station 7 takes place via the injection of the cooling medium 6 in the form of water in this case. For this purpose a known cooling bar 12 is provided.

The method by which the slab 1 is cooled according to the first embodiment can be seen from FIG. 2. The slab 1 is thus conveyed under the jet jet of the cooling medium 6 in the transport direction W under the cooling bar (from below the cooling medium is injected from the cooling bar into the slab as well (this is shown ), Thereby cooling the slab 1. In order to reduce cooling in the side end regions 3 and 4 of the slab 1, cover plates 10 and 11 are provided, these cover plates having a sufficiently large side region in the slab in the direction of the double arrow, with a cooling medium 6. ) Is moved in the direction of the slab center so that it is not in direct contact with it. In contrast, the central region 5 of the slab is provided with the complete cooling efficiency of the cooling medium.

By selecting the position of the cover plates 10 and 11, it is possible to influence to what extent the side regions 3, 4 of the slab 1 should be protected, thereby making a choice of the mentioned parameters. Through this, a uniform temperature distribution can be ensured throughout the width of the slab 1. The width and position of the slab can be known from the final centering process of the slab in front of the cooling station 7 and can be transferred from Level-2. The setting or positioning of the cover plates 10 and 11 is made correspondingly.

Nevertheless, a relatively fast and therefore economical hot rolling production is possible because of the rapid cooling process of the slab 1 by means of active cooling in the cooling station 7, whereby it is possible in the stand 9. This is because subsequent further hot rolling process of can be started immediately.

Another embodiment of the inventive concept is shown in FIG. 3. Accordingly, a cooling bar 12 is used that covers a sufficient width of the slab 1. However, slide plates 10 'and 11' are also provided on the cooling bar 12. These slide plates cover the edge region of the cooling bar 12 and in particular the nozzles located in the edge region, so that the width of the cooling jet jet can be adjusted somewhat larger. For this purpose the slide plates 10 ', 11' are correspondingly displaced in the direction of the double arrow. The effect is the same as in the solution according to Fig. The side end regions 3, 4 of the slab 1 are fed with less cooling medium, whereas the central region 5 is provided with maximum cooling efficiency.

In other words, the edge of the slab can be protected by a withdrawal "moving-out drawer" (as in the cooling zone) during the active cooling process (see the solution according to FIG. 2), or always with only the cooling bars controlled The spray pattern of these cooling bars can be protected, in particular, by being adapted for a particular slab width (see solution according to FIG. 3).

Of course, other technical variations of the concept according to the invention are also possible.

Thus, the problem that the edge of the moving slab 1 is in a low temperature state is prevented, that is, the slab has a uniform temperature across the cross section.

1: slab
2: hot rolling mill
3: side end area of slab
4: side end area of slab
5: center area of slab
6: cooling medium
7: cooling station (middle cooling structure)
8: hot rolled roll stand
9: hot rolled roll stand
10: means for covering
10 ': means for covering
11: Means for Covering
11 ': means for covering
12: cooling bar
W: rolling direction

Claims (12)

A method for hot rolling a slab (1), in particular a steel slab, wherein the slab (1) is subjected to two or more molding steps at various temperature conditions in the hot rolling mill (2), the slab (1) being subjected to two times In the hot rolling method, which is actively cooled between forming steps of this type,
The cooling of the slab (1) is characterized in that the side end regions (3, 4) of the slab (1) are made to be cooled with a lower cooling efficiency than the central region (5) of the slab (1). The cooling of the slab 1 is effected by the function of the cooling medium 6, wherein the lateral end regions 3, 4 of the slab 1 are at least partially shielded from the cooling medium 6. Hot rolling method characterized in that. The hot rolling method according to claim 1, wherein the slab (1) is cooled in an intermediate cooling structure (7). The hot rolling method according to claim 1, wherein the slab (1) is cooled in a cooling zone. The hot rolling method according to any one of claims 1 to 4, wherein the hot rolling process of the slab (1) is a multiphase rolling process, in particular a thermomechanical rolling process. As a hot rolling mill 2 for hot rolling a slab 1, in particular a steel slab, the hot rolling mill 2 comprises at least two hot rolling roll stands 8, 9, and the hot rolling roll stands In the hot rolling mill, between or in front of the rough rolling stand, one or more cooling stations 7 are arranged in which the slab 1 can be cooled.
The cooling station 7 is provided in such a way that the side end regions 3, 4 of the slab 1 are cooled in a lower cooling efficiency than the central region 5 of the slab 1. Hot rolling mill, characterized in that it comprises means (10, 11; 10 ', 11', 12) for allowing the cooling efficiency provided to the slab (1) to vary over the width of the slab (1). The hot rolling mill according to claim 6, wherein the means (10, 11) are cover members formed to cover the lateral end regions (3, 4) of the slab (1) for protection from the cooling medium (6). . The device (10) according to claim 6, wherein the means (10 ', 11', 12) are cooling bars (12) for discharging the cooling medium (6) on the slab (1), wherein the jet jet width of the cooling medium (6) is slab. Hot rolling mill characterized in that it can be adjusted (10 ', 11') over the width of (1). The hot rolling mill according to any one of claims 6 to 8, characterized in that the cooling station (7) is an intermediate cooling structure. The hot rolling mill according to any one of claims 6 to 8, characterized in that the cooling station (7) is a cooling zone. The control according to any one of claims 6 to 10, wherein the cooling process is optionally controlled by means of a connected temperature calculation device, whereby lowering of the ferrite precipitation temperature is prevented so that undesirable formation of ferrite forms is optionally eliminated. Hot rolling mill, characterized in that. The hot rolling mill according to any one of claims 6 to 11, wherein the cooling width is adjusted to the corresponding cooling width by an electric or mechanical device.

Images