DE102009037278A1 - Apparatus and method for producing a thin hot strip - Google Patents

Abstract

The invention relates to an apparatus for producing a thin hot strip (1) by casting rolls in an endless process, with a casting machine (2), in which first a thin slab (3) is cast, with at least one rolling mill downstream of the casting machine (2) ( 4, 5) in which the thin slab (3) is rolled using the primary heat of casting, and a number in the conveying direction (F) of the belt (1) in a rear region (6) arranged finish rolling stands (7), in which the strip (1) can be rolled with work rolls (8) to a final thickness. In order to improve the production of a thin hot strip in the endless process, the invention provides that the work rolls (8) of the finish rolling stands (7) have a low-wear roll surface. Furthermore, the invention relates to a method for producing a thin hot strip (1) by casting rolls in an endless process.

Description

The The invention relates to a device for producing a thin one Hot strip by casting rolls in an endless process, with a casting machine in which a thin slab is poured is downstream with at least one of the casting machine Rolling mill in which the thin slab is under use the primary heat of the casting process is rolled, and with a number in the conveying direction of the tape in one rear area arranged finish rolling stands in which the strip can be rolled with work rolls to a final thickness. Furthermore, the invention relates to a method for manufacturing a thin hot strip by casting rolls in one Endless process.

Attachments of this type are as Dünnbrammen- / Dünnband-Gießwalzanlagen known as CSP equipment. They allow one efficient production of hot strip when the rigid connection of Continuous casting plant and rolling mill and their temperature control is dominated by the entire system.

In the EP 0 286 862 A1 and the EP 0 771 596 B1 is described the endless rolling out of the casting heat out. 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 reveal the EP 0 415 987 B2 and the EP 0 889 762 B1 ,

A alternative technology is the rolling of single slabs or single bands. In the discontinuous rolling of tapes, the casting and rollers decoupled. The casting speed is in the Usually very low and the rolling speed is independent of it at a high level in the way that the temperature for the last forming is above the minimum temperature.

The Production of thin hot strip is for many Applications interesting. The disadvantage here is that at the rolling creates a high work roll wear, the work roll intermediate change especially in the conveying direction of the strip rear scaffolding of a rolling mill necessary power. So far, mostly so-called IC rolls are used there. This are rollers with a classic roll material with high carbide content and interdendritically arranged graphite. These rollers are distinguished through a uniform wear and are process-reliable. Under thermal stress they are relative insensitive; cracks create an orientation on the graphite.

Of the However, wear of these rollers is altogether relative high. This is accompanied by limited rolling times.

As a general rule Also known are work rolls in rolling mills, the one have special low-wear roller surface, in particular by a layer of low-wear material is formed. Such rolls are known as HSS rolls or semi-HSS rolls or known as PM rolls.

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

at the PM rolls are those that are made by the HIP process are made (hot isostatic pressing). This is powdered shell material compressed under high pressure. The HIP procedure is a Roll core conventionally prefabricated (ductile iron or forged). Then connect the HSS shell material with the core. For this we use the core as well as the powdery one Shell material in special HIP systems at very high, all-sided acting gas pressure and high temperature (about 1,100 ° C) over its Flow limit heated and compressed.

Such However, rolls have not hitherto been used for finish rolling, but only in the front area of a rolling stand squadron used. The reason for this is that these rollers are very are sensitive, d. H. with rolled ends or due to other disturbances it comes to surface eruptions or heat cracks and thus to an early failure of the roller, what its Use in the finishing stand basically uneconomical or even impossible.

Of the Invention is therefore based on the object, a device and a method for producing a thin hot strip according to the to upgrade the above-mentioned type so that they increased performance and higher profitability can be achieved.

These Task is according to the invention device technology solved by the fact that the work rolls of the finishing mills have a low-wear roller surface. This is achieved in particular by the fact that the roll surface a layer of low-wear material is formed.

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

The low-wear layer can also be made of a metal-ceramic composite material exist (so-called "cermets").

According to one Embodiment of the invention are the work rolls as HSS rolls or semi-HSS rolls (high speed steel rolls).

there advantageously have all work rolls of at least a rolling mill a low-wear roller surface on.

The Process for producing a thin hot strip by Casting rolls in an endless process is characterized that as work rolls of finishing mills such with a low-wear roller surface used be wear-resistant, especially those with a layer Material.

there is to ensure a safe rolling process and a long service life of the rollers preferably provided that at least in the area of the finishing mills before the arrival of the band the roll gap between the work rolls ascended and after entry of the strip of the nip is moved to the setpoint. Driving up the Rolling gap is preferably carried out to a value at which a for the work roll damage-free rolling in a safe to be rolled thickness is possible.

Corresponding can also be provided that, at least in the field of finishing mills before the strip exits the nip from the set point to a greater value is ascended.

With Advantage is provided that the tape in the finishing mills rolled to a finished strip thickness between 0.5 mm and 1.5 mm.

Of the The basic idea of the invention specifically focuses on what - what hitherto unknown and uncommon - for the finish rolling of a thin hot strip by casting rolls used in an endless process wear-resistant work rolls which are already known as such, but as a result of the high roller load during finish rolling not yet used could become.

supports or this is made possible by the procedural described Measures to ensure that it is also during the finish rolling process no excessive strain on the work rolls comes.

At the According to the invention provided endless rollers Rolling faults are avoided, leading to the use of work rolls with low-wear roller surface also in the finish rolling area makes possible. Here one finds over a longer one Time (of several hours) continuous rolling without threading and unthreading held at the rolling mill. At the head or the end can the special measures mentioned, such as opening scaffolding or rolling on larger, safe to be rolled end thicknesses, taken to the work roll load low in the finishing stand. The output losses are relatively small, since these loss lengths in comparison to the total band length of the endless rolled bands are low.

Under the conditions of continuous rolling using low-wear Work rolls (especially HSS rolls, PM rolls) is the economic one Production of thin strip particularly advantageous. Find it fewer roll changes and therefore less casting interruptions instead of. Thus, rolling programs or casting sequences lengthened, with better band contours, because the work roll wear now in the rear Scaffolding is lower.

The Productivity of the whole plant can be increased by an extension the rolling programs or casting sequences are increased.

In the drawing embodiments of the invention are illustrated. Show it:

1 schematically a casting mill according to a first embodiment of the invention with roughing and finishing mill; and

2 a cast rolling mill in one too 1 alternative embodiment of the invention with compact rolling mill.

In 1 is a device for producing a thin hot strip 1 outlined. The strip is produced by casting rolls in an endless process. For this is a casting machine 2 provided, in the first a thin slab 3 is poured. In the conveying direction F of the slab or the strip is a rolling train 4 . 5 downstream. In the rolling mill 4 . 5 becomes the thin slab 3 gradually rolled to the finished strip using the primary heat of the casting process. This is a rough road 4 and a finishing train 5 intended. The finishing train 5 has a number of finishing mills 7 which is in a rear area seen in the conveying direction F. 6 the rolling mill 4 . 5 are arranged. The ribbon 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 finishing stands 7 carried out with supported by backup rolls work Whale Zen 8th ,

Here it is essential that the work rolls 8th the finishing mills 7 have a low-wear roller 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 to finish a strip 1 used.

For the used rollers with wear-resistant surface is on the contribution of 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. 5, page 383 ff , and on the EP 1 365 869 B1 (in particular paragraph [0014]).

The HIP procedure 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 known as cermets, are due to the combination of high hardness and fracture toughness in a variety used by components as wear-resistant materials, which is also exploited here.

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

The procedure is such that rolled strip ends or general disturbances 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.

It continues to be an endless rolling practice for a multitude provided by coils for the long filet part of the tape.

Also the unthreading of the tape can again with a larger one Final thickness or open nip done.

In the 2 The device shown differs from that according to FIG 1 essentially only in that here a compact rolling mill 4 is provided. However, this also has a rear F in the conveying direction 6 in which the work rolls 8th 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 are various known devices of the device for producing the thin hot strip, however are not primary to the invention.

It is only special on an induction furnace 9 and on a holding furnace 10 pointed out that is operated conventionally. Furthermore, be a cooling section 11 mentioned, behind which is a reel 12 for winding the finished tape into a coil 13 located.

The used work rolls 8th in the finishing stands 7 are, as already partially mentioned above, 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 form of the work rolls or - associated - the desired band contour determined. Especially disturbing are a high band edge drop (edge-drop) or beads by z. B. high edge wear.

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

Just thin ribbons cause high wear. The wear effect during rolling becomes especially clear a width. In conventional hot strip mills is here also the risk of Bandendenverwalzungen or other Walzunfehlern high.

Therefore offers this technology, namely the Dünnbandwalzung in an endless thin slab plant with the use of low-wear Work rolls (even in the last frame) special. The Endless technology avoids rolling defects and low-wear Rollers improve the quality of the product and leave an extension of the rolling program length too.

The combination of direct use (casting with subsequent rolling at low energy input) and the extension of the casting sequences make the explained technology particularly economical.

LIST OF REFERENCE NUMBERS

1

hot strip (Tape)

2

casting machine

3

thin slab

4

rolling train

5

rolling train

6

rear Area

7

Finishing stand

8th

Stripper

9

induction furnace

10

holding furnace

11

cooling section

12

reel

13

coil

F

conveying direction

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0286862 A1 [0003]
• EP 0771596 B1 [0003]
• - EP 0415987 B2 [0004]
• EP 0889762 B1 [0004]
• - EP 1365869 B1 [0033]

Cited non-patent literature

• 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. 5, page 383 et seq. [0033]
• - Ch. Willems et al. "PM-HIP Solutions for Tools and Molds" in "Stahl", 1998, Issue 6, pages 38 to 40 [0034]

Claims (12)

Device 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 belt ( 1 ) in a rear area ( 6 ) arranged finish rolling stands ( 7 ), in which the band ( 1 ) with work rolls ( 8th ) can be rolled to a final thickness, characterized in that the work rolls ( 8th ) of the finishing mills ( 7 ) have a low-wear roller surface. Device according to claim 1, characterized in that that the roll surface wear by a layer wear Material is formed. Device according to claim 2, characterized in that that the wear-resistant layer of powder metallurgy Material exists. Device according to claim 3, characterized in that that the wear-resistant layer of powder metallurgy Material by the HIP process (hot isostatic pressing process) is made. Device according to claim 2, characterized in that that the low-wear layer of a metal-ceramic composite material consists. Device according to Claim 1 or 2, characterized that the work rolls as HSS rolls or semi-HSS rolls (High Speed Steel rollers) are executed. Device according to one of claims 1 to 6, characterized in that all work rolls ( 8th ) of the at least one rolling train ( 4 . 5 ) have a low-wear roller surface. Method for producing a thin hot strip ( 1 ) by casting rolls in an endless process, in which first in a casting machine ( 2 ) a thin slab ( 3 ), which are then deposited in at least one rolling mill ( 4 . 5 ) is rolled using the primary heat of the casting process and wherein the strip ( 1 ) in a conveying direction (F) of the strip ( 1 ) rear area ( 6 ) in a number of finishing stands ( 7 ) with work rolls ( 8th ) is rolled to a final thickness, characterized in that as working rolls ( 8th ) of the finishing mills ( 7 ) are used with a low-wear roller surface, in particular those with a layer of low-wear material. A method according to claim 8, characterized in that at least in the field of finishing mills ( 7 ) before the band ( 1 ) the nip between the work rolls ( 8th ) and after the arrival of the band ( 1 ) the roll gap is moved to the setpoint. A method according to claim 9, characterized in that the roll gap is raised to a value in which a for the work roll ( 8th ) damage-free rolling is possible with a sure to be rolled thickness. Method according to one of claims 8 to 10, characterized in that at least in the field of finishing mills ( 7 ) before leaving the band ( 1 ) the roll gap is raised from the setpoint to a greater value. Method according to one of claims 8 to 11, characterized in that the band ( 1 ) in the finishing stands ( 7 ) is rolled to a finished strip thickness between 0.5 mm and 1.5 mm.

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