EP2464469A2

EP2464469A2 - Device and method for producing a thin hot-rolled strip

Info

Publication number: EP2464469A2
Application number: EP10747585A
Authority: EP
Inventors: Jürgen Seidel; Ernst Windhaus; Markus Reifferscheid; Jürgen Müller
Original assignee: SMS Siemag AG
Current assignee: SMS Siemag AG
Priority date: 2009-08-12
Filing date: 2010-08-11
Publication date: 2012-06-20
Also published as: JP2013501625A; DE102009037278A1; WO2011018217A2; RU2012108837A; US20120175076A1; WO2011018217A3; KR20120041241A; TW201105438A; CN102574174A

Abstract

The invention relates to a device for producing a thin hot-rolled strip (1) by casting and rolling in a continuous process, comprising a casting machine (2) in which initially a thin slab (3) is cast, downstream of the casting machine (2) at least one rolling train (4, 5) in which the thin slab (3) is rolled using the primary heat of the casting process, and further comprising a number of finishing roll stands (7) arranged in a rear region (6) in the conveying direction (F) of the strip (1). The strip (1) can be rolled to a final thickness in the finishing roll stands using work rolls (8). In order to improve the production of a thin hot-rolled strip in the continuous process, according to the invention the work rolls (8) of the finishing roll stands (7) have a low-wear roll surface. The invention further relates to a method for producing a thin hot-rolled strip (1) by casting and rolling in a continuous process.

Description

Apparatus and method for producing a thin hot strip

The invention relates to an apparatus for producing a thin Warmban- by casting rolls in a continuous process, with a casting machine, in which a thin slab is cast, with at least one of the casting machine downstream rolling mill, in which the thin slab rolled using the primary heat of the casting process and with a number of finishing mills arranged in a rear region in the conveying direction of the strip, in which the strip can be rolled with work rolls to a final thickness. Furthermore, the invention relates to a method for producing a thin hot strip by casting rolls in an endless process.

Plants of this type are known as thin slab / thin strip caster under the name CSP plants. They enable efficient production of hot strip, if the rigid connection of continuous casting plant and rolling train and their temperature control is dominated by the entire plant. EP 0 286 862 A1 and EP 0 771 596 B1 describe endless rolling out of the casting heat. Here, the casting and rolling processes are directly coupled. A separation of the endless belt with a pair of scissors is done just before the reel. Similar processes for the continuous production of strip steel in the coupling of casting and rolling plant are disclosed in EP 0 415 987 B2 and EP 0 889 762 B1

An alternative technology is the rolling of single slabs or single strips. In the discontinuous rolling of tapes, the casting

BESTATIGUNGSKOPIE and rollers decoupled. The casting speed is usually very low and the rolling speed is independent of a high level in such a way that the temperature for the last transformation is above the minimum temperature. The production of thin hot strip is interesting for many applications. A disadvantage, however, is that during rolling a high work roll wear occurs, the work roll intermediate change makes necessary, especially in the direction of conveyance of the belt rear stands of a rolling mill. So far, mostly so-called IC rolls are used there. These are wafers with a classic roll material with a high carbide content and interdendritically arranged graphite. These rollers are characterized by uniform wear and are process reliable. Under thermal stress, they are relatively unsusceptible; cracks create an orientation on the graphite.

The wear of these rollers, however, is relatively high overall. This is accompanied by limited rolling times.

Also generally known are work rolls in rolling mills, which have a special low-wear roll surface, which is formed in particular by a layer of low-wear material. Such rolls are known as HSS rolls or semi-HSS rolls or as PM rolls.

The term HSS stands for high-speed steel and a material that has a relatively low carbide content. After casting, a re-esterification takes place with subsequent hardening and tempering.

The PM rolls are those made by the HIP process (hot isostatic pressing). Here, powdery shell material is pressed together under high pressure. In the HIP process, a roll core is conventionally prefabricated (nodular cast iron or forged). Then the HSS shell material is connected to the core. For this purpose, the core as well as the powdery shell material in special HIP systems are heated above its yield point at a very high, all-round gas pressure and high temperature (about 1100 ^° C.) and thereby compressed. However, such rolls are not yet used for finish rolling, but only in the front of a rolling stand squadron. The reason for this is that these rolls are very sensitive, ie in the case of rolled strip ends or as a result of other disturbances surface breaks or heat cracks and thus early failure of the roll occur, which makes their use in the finishing rolling mill fundamentally uneconomical or even impossible.

The invention is therefore based on the object, a device and a method for producing a thin hot strip according to the above-mentioned type so that they can be achieved increased efficiency and higher efficiency.

This object is achieved according to the invention device technology in that the work rolls of the finishing mills have a low-wear roller surface. This is achieved in particular by forming the surface of the roll by means of a layer of low-wear material.

The low-wear layer can consist of powder metallurgical material in a conventional manner. In this case, the low-wear layer is preferably made by the hot isostatic pressing (HIP) method.

The wear-resistant layer can also consist of a metal-ceramic composite material (so-called "cermets"). According to one embodiment of the invention, the work rolls are designed as HSS rolls or semi-HSS rolls (high-speed steel rolls). Advantageously, all work rolls of the at least one rolling train have a low-wear roll surface.

The method for producing a thin hot strip by casting rolls in an endless process is characterized in that the work rolls of the finish rolling stands are those with a low-wear roll surface, in particular those with a layer of low-wear material.

In order to ensure a secure rolling process and a long service life of the rolls, it is preferably provided that the roll gap between the work rolls is raised at least in the area of the finish rolling stands before the strip enters, and the roll gap is moved to the setpoint after the strip has entered. The drive-up of the roll gap is preferably carried out to a value at which a damage-free for the work roll rolling is possible at a certain thickness to be rolled.

Accordingly, it can also be provided that, at least in the area of the finish rolling stands, before the strip leaves the roll gap, the roll gap is raised from the desired value to a larger value.

It is advantageously provided that the strip is rolled in the finish rolling stands to a finished strip thickness between 0.5 mm and 1.5 mm.

The basic idea of the invention specifically focuses on the fact that - what is previously unknown and uncommon - for the finish rolling of a thin hot strip by casting rollers in a continuous process wear-resistant work rolls are used, which are indeed known as such, but due to the high roll load at Prefabricated rolls could not be used so far. This is supported or made possible by the described procedural measures, which ensure that even during the finish rolling process, there is no excessive load on the work rolls.

When inventively provided endless rolling interference can be avoided, which makes the use of work rolls with low-wear roll surface in the finish rolling possible. Here takes place a long time (of several hours) continuous rolling without threading and unthreading on the rolling mill. At the head or the end, the special measures mentioned, such as opening the scaffolding or rolling to larger, definite end thicknesses to be rolled, can be taken in order to keep the work roll load in the finishing stand low. The output losses are relatively small, since these loss lengths are low in comparison to the total band length of endlessly rolled bands. Under the conditions of continuous rolling using low-wear work rolls (in particular HSS rolls, PM rolls), the economic production of thin strip is particularly advantageous. There are fewer roll changes and thus less casting interruptions. Thus, rolling programs or casting sequences can be extended, with better belt contours, because the work roll wear is now lower in the rear stands.

The productivity of the entire system can be increased by extending the rolling programs or casting sequences.

In the drawings, embodiments of the invention are shown. Show it:

1 is a schematic view of a cast roll mill according to a first embodiment of the invention with roughing line and finishing train; and Fig. 2 is a casting rolling in an alternative to Fig. 1 embodiment of the invention with a compact rolling mill.

In Fig. 1, an apparatus for producing a thin hot strip 1 is outlined. The strip is produced by casting rolls in an endless process. For this purpose, a casting machine 2 is provided, in which initially a thin slab 3 is poured. In the conveying direction F of the slab or the strip, a rolling train 4, 5 is connected downstream. In the rolling train 4, 5, the thin slab 3 is gradually rolled by using the primary heat of the casting process to the finished strip. In this case, a roughing 4 and a finishing train 5 are provided. The finishing train 5 has a number of finish rolling stands 7, which are arranged in a rear region 6 of the rolling train 4, 5 viewed in the conveying direction F. The strip 1 is here rolled to the final thickness, which is preferably in the range between 0.5 mm and 1, 5 mm. The rolling of the strip in the finish rolling stands 7 takes place with work rolls 8 supported by support rolls.

It is essential that the work rolls 8 of the finishing stands 7 have a low-wear roll surface. In particular, the roll surface is formed by a layer of low-wear material. Although rolls of this type are - as stated above - known as such in the prior art. However, they have never been used for finish rolling a strip 1.

For the rollers with a wear-resistant surface which are used, reference is made to the article by M. Andersson et al., "Introduction of enhanced indefinite chill and high-speed steel rolls in European hot strip mills" in "Ironmaking and Steelmaking", 2004, Vol. No. 5, page 383 et seq., And EP 1 365 869 B1 (in particular paragraph [0014]). The HIP method is explained in more detail in the article by Ch. Willems et al. "PM-HIP Solutions for Tools and Molds" in "Stahl", 1998, Issue 6, pages 38 to 40.

Metal-ceramic composites, also referred to as cermets, are used as wear-resistant materials in a large number of components due to the combination of high hardness and fracture toughness, which is also utilized in the present case.

Preferably, use of the low-wear work rolls can be provided in all the structures of the hot strip mill, ie also in the roughing train 4 (the latter measure is already known as such in the prior art).

The process sequence is such that rolled-up strip ends or general faults and thus damage to the work rolls are avoided by the following measures:

Threading with an open nip or threading the tape head can be carried out with product dimensions that are sure to be produced (thicker finished strip). Only after the threading of the strip into the finishing stand is the thickness of the roll gap then set to a critical thickness to be produced, preferably to a value below 1, 5 mm.

There is also provided an endless rolling practice for a plurality of coils for the long fillet portion of the belt.

Also, the unthreading of the tape can be done again with a larger final thickness or open nip.

The device shown in Fig. 2 differs from that of FIG. 1 essentially only in that here a compact rolling mill 4 is provided. However, this also has a downstream in the conveying direction F ren part 6, in which the work rolls 8 are provided with low-wear roller surface. In this plant, an endless rolling process or alternatively a batch operation can be run.

In the figures, various known devices of the device for producing the thin hot strip are shown, which are not primary for the invention.

It is only particularly pointed to an induction furnace 9 and a holding furnace 10, which is operated conventionally. Furthermore, a cooling section 11 may be mentioned, behind which there is a reel 12 for winding the finished strip to form a coil 13.

As already mentioned above, the work rolls 8 used in the finishing stands 7 are known as such under the designations HSS rolls, semi-HSS rolls, PM-HIP rolls or cermet rolls. Other sheath materials are also possible which are wear-resistant but generally sensitive.

The rolling program length is usually determined by the depth of wear or shape of the work rolls or - associated - the desired band contour. Particularly disturbing are a high band edge drop (edge drop) or beads by z. B. high edge wear.

Furthermore, the roll and strip surface quality significantly influences the rolling program length. Not only high roughness, but also impressions on the roll surface by z. B. banded band ends, are relevant.

Especially with thin ribbons creates a high degree of wear. The wear effect when rolling a width becomes particularly clear. In conventional warm Bandstraßen here is also the risk of Bandendenverwalzungen or other Walzunfehlern high.

Therefore, this technology, namely the thin strip rolling in an endless thin slab plant with the use of low-wear work rolls (also in the last framework) is particularly suitable. The endless technology avoids rolling defects and the low-wear rollers improve the quality of the product and allow lengthening of the rolling program length.

The combination of direct feed (casting followed by low power energy rolling) and extension of the casting sequences make the described technology particularly economical.

LIST OF REFERENCE NUMBERS

1 hot strip (band)

2 casting machine

3 thin slab

4 rolling mill

5 rolling mill

6 rear area

7 finishing mill

8 stripper

9 induction furnace

10 holding furnace

11 cooling section

12 reel

13 coil

F conveying direction

Claims

claims:

1. An apparatus for producing a thin hot strip (1) by casting rolls in an endless process, with a casting machine (2), in which a

Thin slab (3) is cast, with at least one of the casting machine (2) downstream rolling mill (4, 5), in which the thin slab (3) is rolled using the primary heat of the casting process, and with a number in the conveying direction (F) of the band (1) finish rolling stands (7) arranged in a rear area (6), in which the strip (1) can be rolled to a final thickness with work rolls (8), characterized in that the work rolls (8) of the finish rolling stands (7) have a low-wear

Have roll surface.

2. Apparatus according to claim 1,

characterized,

the roll surface is formed by a layer of low-wear material.

3. Apparatus according to claim 2,

characterized,

that the low-wear layer consists of powder metallurgical material.

4. Apparatus according to claim 3, characterized,

that the low-wear layer of powder metallurgical material is produced by the HIP process (hot isostatic pressing process).

5. Apparatus according to claim 2,

characterized,

that the low-wear layer consists of a metal-ceramic composite material.

6. Apparatus according to claim 1 or 2,

characterized,

that the work rolls are designed as HSS rolls or semi-HSS rolls (high speed steel rolls).

7. Device according to one of claims 1 to 6,

characterized,

all working rolls (8) of the at least one rolling train (4, 5) have a low-wear roll surface.

8. A method for producing a thin hot strip (1) by casting rolls in an endless process, in the first in a casting machine

(2) a thin slab (3) is cast, which is then rolled in at least one rolling train (4, 5) using the primary heat of the casting process and wherein the belt (1) in a conveying direction (F) of the belt (1) rolled in a number of finishing stands (7) with work rolls (8) to a final thickness, characterized in that in that the working rolls (8) of the finish rolling stands (7) are those with a low-wear roll surface, in particular those with a layer of low-wear material.

9. The method according to claim 8,

characterized,

that, at least in the area of the finishing stands (7), the roll gap between the work rolls (8) is raised before the strip (1) enters and the roll gap is moved to the desired value after the strip (1) has entered.

10. The method according to claim 9,

characterized,

in that the roll gap is raised to a value at which a roller which is damage-free for the work roll (8) is wound safely

Thickness is possible.

11. The method according to any one of claims 8 to 10,

characterized,

in that, at least in the area of the finishing stands (7), before the strip (1) leaves the roll gap, the roll gap is raised from the desired value to a larger value.

12. The method according to any one of claims 8 to 11,

characterized,

that the strip (1) is rolled in the finish rolling stands (7) to a finished strip thickness between 0.5 mm and 1, 5 mm.