KR20120041241A - Device and method for producing a thin hot-rolled strip - Google Patents

Abstract

The present invention is directed to an apparatus for producing a thin hot rolled strip (1) through casting and rolling in a continuous process, comprising: a casting machine (2) on which a thin slab (3) is cast, and disposed behind the casting machine (2). Thin slab 3 is disposed in the rear region 6 in the conveying direction F of the strip 1 and at least one rolling train 4 and 5 which are rolled under the conditions that the primary row of the casting process is used. And internally the strip 1 comprises a plurality of finishing roll stands 7 which can be rolled to the final thickness by the work rolls 8. In order to improve the production of thin hot rolled strips in a continuous process, according to the invention, the working rolls 8 of the finishing roll stands 7 comprise a low wear roll surface. The invention also relates to a method for producing a thin hot rolled strip 1 through casting and rolling in a continuous process.

Description

Thin hot rolled strip manufacturing apparatus and its method {DEVICE AND METHOD FOR PRODUCING A THIN HOT-ROLLED STRIP}

The present invention relates to an apparatus for producing a thin hot rolled strip through casting and rolling in a continuous process, comprising: a casting machine in which a thin slab is cast therein, and a thin slab disposed in the rear of the casting machine, wherein the thin slab is formed in the primary row of the casting process. said apparatus comprising at least one rolling train which is rolled under conditions in which primary heat is used, and a plurality of finishing roll stands disposed in the rear region in the conveying direction of the strip and in which the strip can be rolled to a final thickness by working rolls It is about. The invention also relates to a method for producing thin hot rolled strips through casting and rolling in a continuous process.

This type of system is known as thin slab / thin strip cast rolling system under the name CSP system. The system allows for the efficient production of hot rolled strips if the solid connection of the continuous casting system and the rolling train and the corresponding temperature control are well managed by the whole system.

EP 0 286 862 A1 and EP 0 771 596 B1 describe a continuous rolling process consisting of casting heat. The casting and rolling processes here are connected directly. Cutting of the continuous strip using a shear is made just before the winder.

Similar methods for the continuous production of strip steels under the condition of connecting casting and rolling systems are disclosed in EP 0 415 987 B2 and EP 0 889 762 B1.

An alternative technique is the rolling of individual slabs or individual strips. In the case of rolling the strip discontinuously, the casting process and the rolling process are separated. The casting speed is generally very low and the rolling speed is adjusted to a high level in such a way that the temperature for the final forming exceeds the minimum temperature, regardless of the casting speed.

The manufacture of thin hot rolled strips is advantageous for numerous applications. In this connection, however, high work roll wear occurs during rolling, which has the disadvantage of requiring an intermediate work roll exchange, especially in the stands of the rolling sequence arranged rearward in the conveying direction of the strip. So far, so-called IC rolls have been mostly used in the stands of rolling trains. Such rolls include conventional roll materials containing high carbide ratios and graphite arranged between dendritic tissues. The rolls are characterized by uniform wear and have high process reliability. And the rolls are relatively insensitive to thermal loads. In other words, orientation occurs in the graphite upon cracking.

However, the wear of the rolls is relatively high overall. And with this the rolling time is limited.

In addition, work rolls in roll stands are also generally known which comprise a roll surface which is formed in particular by a layer of low wear material and which is particularly low wear. Rolls of this type are known as HSS rolls or semi-HSS rolls or PM rolls.

The name HSS refers to high-speed steel and refers to materials containing relatively low carbide proportions. After casting, re-austenitization takes place, followed by curing and annealing.

The PM roll is a roll manufactured according to the HIP (hot isostatic pressing) method. In this regard the powdered shell material is compressed under high pressure conditions. In the HIP method, the roll core is prefabricated in a conventional manner (spherical graphite casting or forging). Then the combination of core and HSS shell material is achieved. To this end, the core and powdered shell materials are heated and compressed under conditions where a very high gas pressure is applied in all directions in a special HIP system and the temperature is above the corresponding yield point (about 1,100 ° C).

However, the rolls have not been used for finishing rolling up to now but only in the front region of the roll stand train. The reason is that the roll is very sensitive, that is to say the case of rolling strip ends or another obstacle, which leads to surface breakage or thermal cracking and thus to early failure of the roll, This is because the use of these rolls inside the roll stand is basically uneconomical or even impossible.

It is therefore an object of the present invention to improve the apparatus and method in order to achieve increased performance capability and higher economics in the apparatus and method for producing thin hot rolled strips according to the aforementioned types.

This object is achieved in accordance with the present invention through the working rolls of the finishing roll stands in terms of device technology comprising a low wear roll surface. This is particularly achieved by the roll surface being formed by a low wear material layer.

The low wear layer can here be composed of a powder metallurgy material in a known manner. In this case the low wear layer is preferably produced by the so-called HIP method (hot isostatic pressurization method).

The low wear layer may also be composed of a metal-ceramic composite material (so-called “Cermet”).

According to an embodiment of the invention the working rolls are formed as HSS rolls (high speed steel rolls) or semi-HSS rolls.

Preferably all working rolls of at least one rolling train comprise a low wear roll surface.

A method for producing thin hot rolled strips through casting and rolling in a continuous process is that a work roll comprising a low wear roll surface, in particular a work roll comprising a low wear material layer, is used as the work roll of the finishing roll stand. It features.

Here, in order to ensure a high service life of the roll mill and the roll, it is preferred that the gap between rolls of the work rolls is openly moved before the inflow of the strip, at least in the region of the finishing roll stands, and the gap between the rolls after the inflow of the strip is a set value. Is moved to. The open movement of the gap between rolls is here preferably made of a value at which a rolling process can be made that does not cause damage to the work roll under conditions of thickness to be reliably rolled.

Correspondingly, also, at least in the region of the finishing roll stands, the gap between rolls is moved openly from the set value to a larger value before the outflow of the strip.

Preferably the strip is rolled to a final strip thickness between 0.5 mm and 1.5 mm inside the finishing roll stands.

The basic idea of the present invention is, although known per se, for finishing rolls of thin hot rolled strips through casting and rolling in a continuous process (as point so far known and not used), high rolls in finish rolling The aim is to ensure that the low wear work rolls that have not been available so far due to the load are used.

This is aided or made possible by the described method technology measures which ensure that the finishing roll process does not cause excessive load on the work rolls.

Rolling disturbances in the continuous casting provided according to the invention can be avoided, which makes it possible to use work rolls comprising a low wear roll surface even in the finishing rolling zone. Disclosed herein is a rolling process which lasts for a longer time (of several hours) without withdrawal and withdrawal in the rolling train. At the tip or end, the aforementioned special measures can be taken such as opening the stands or rolling to a thicker final thickness to be surely rolled, so as to keep the work roll load low in the finishing stand. The yield loss here is relatively small because the loss length is short compared to the total strip length of the strip being continuously rolled.

Economical production of thin strips is particularly advantageous under the conditions of continuous rolling using low wear work rolls (especially HSS rolls, PM rolls). A small number of roll changes and thus a small number of casting stops are initiated. The strip profile can thus be improved at the same time as the rolling program and the casting sequence are respectively extended, because according to the invention there is less work roll wear even in the rear stands.

The productivity of the overall system can be increased by extending each of the rolling program and the casting sequence.

Embodiments of the invention are shown in the drawings.
1 is a schematic diagram illustrating a casting and rolling system according to a first embodiment of the present invention comprising a rough rolling sequence and a finishing rolling sequence.
FIG. 2 is a schematic diagram illustrating a casting and rolling system according to an embodiment of the present invention, including a compact rolling sequence replaced with FIG. 1.

1 shows an apparatus for producing a thin hot rolled strip 1. Strip production takes place through casting and rolling in a continuous process. A casting machine 2 is provided for this purpose, in which the thin slab 3 is first cast inside. The rolling trains 4 and 5 are arranged at the rear in the conveying direction F of the slab or strip. Inside the rolling train rows 4 and 5, the thin slab 3 is gradually rolled into a strip finished product under conditions where the primary heat of the casting process is used. In this connection a rough rolling sequence 4 and a finishing rolling sequence 5 are provided. The finishing rolling train 5 includes a plurality of finishing roll stands 7 disposed in the rear region of the rolling train rows 4 and 5 when viewed in the conveying direction F. The strip 1 here is preferably rolled to a final thickness in the range between 0.5 mm and 1.5 mm. The rolling of the strip in the finishing roll stands 7 is effected by working rolls 8 supported by supporting rolls.

The important point here is that the working rolls 8 of the finishing roll stands 7 comprise a low wear roll surface. In particular, the roll surface is formed by a low wear material layer.

Rolls of this type have never been used for finishing rolling of the strip 1, although they are known per se in the prior art (as described above).

For the rolls used, including wear-resistant surfaces, the article "Ironmaking and Steelmaking," published by M. Andersson (Anderson) et al., 2004, Vol. 31, pp. 383 p. Reference is made to the introduction of enhanced indefinite chill and high speed steel rolls in European hot strip mills "and EP 1 365 869 B1 (particularly paragraph).

The HIP method is described in more detail in the paper "PM-HIP Solutions for Tools and Molds", published by Ch, Willems et al. In Steel, 1998, vol. 6, pages 38-40.

Metal-ceramic composite materials, also referred to as cermets, are used as wear resistant materials in many components based on a combination of high hardness and fracture toughness, which are also utilized herein.

Preferably the use of low abrasion work rolls in all stands of the hot rolling strip rolling train can be provided, and also in the rough rolling train 4 (the measures provided for the rough rolling train are already known per se in the prior art. Known).

In this case the process sequence is such that damage to the rolled strip end or general disturbance and consequent damage to the work roll is prevented by the following measures.

The entry in the condition that the gap between the rolls is open, or the entry of the strip tip can be made under the condition that the product dimension (the thicker final strip) is reliably produced. Then, after the strip is drawn into the finishing roll stand, the thickness of the inter-roll gap is adjusted to the target thickness to be produced decisively, preferably to a value of less than 1.5 mm.

In addition, continuous rolling practice is provided for numerous coils for long strip fillet part applications.

Further, withdrawal of the strip can again be made under conditions where the final thickness is thicker or the gap between rolls is open.

The device shown in FIG. 2 differs substantially from the device according to FIG. 1 in that a compact rolling train 4 is provided in this embodiment. However, the device also comprises a part 6 provided with working rolls 8 which are located rearward in the transport direction F and which comprise a low wear roll surface therein. In such a system, a continuous rolling process can be carried out or a batch mode of operation can be carried out in an alternative manner.

The figures also show various known units of the apparatus for producing thin hot rolled strips, but these units are not critical for the present invention.

However, only the induction furnace 9 and the insulation furnace 10 which operate only in the conventional manner are known here. And a cooling zone 11 in which a winder 12 for winding the strip finished product into the coil 13 is arranged behind it.

The work rolls 8 used in the finishing roll stands 7 are known per se in the name of HSS rolls, semi-HSS rolls, PM-HIP rolls or cermet rolls as already mentioned in part above. It is also possible to have other jacketing materials that are wear resistant but usually sensitive.

The rolling program period is usually determined by the wear depth or shape of the work rolls, or (in conjunction with) the desired strip profile. Particular obstacles are, for example, high bumps or high strip edge drop due to high edge wear.

In addition, roll surface quality and strip surface quality also significantly influence the rolling program period. In addition, high roughness, as well as squeezing caused by the roll surface, for example by rolled strip ends, is relevant.

In the case of very thin strips, high wear occurs. In particular, the wear effect is clearly observed when rolling a predetermined width. In this case, there is also a high risk of strip end rolling or other rolling errors in conventional hot rolling strip rolling columns.

Therefore, a thin strip rolling is provided, in particular in the technology herein, in other words in a continuous thin slab system (also used in the final stand) using low wear work rolls. Continuous technology prevents rolling errors, and low wear rolls improve product quality and allow for an extended rolling program period.

The combination of a direct application (implementation of the casting process followed by a rolling process in conditions of low energy supply) and the extension of the casting sequence make the above mentioned technology particularly economical.

1: hot rolled strip (strip)
2: casting machine
3: gourd slab
4: rolling column
5: rolling column
6: rear area
7: finishing roll stand
8: work roll
9: induction furnace
10: holding furnace
11: cooling zone
12: winder
13: coil
F: feed direction

Claims (12)

Apparatus for producing a thin hot rolled strip (1) through casting and rolling in a continuous process, comprising: a casting machine (2) in which a thin slab (3) is cast therein, and arranged behind and in the rear of the casting machine (2) The thin slab 3 is arranged in the rear region 6 in one or more rolling trains 4, 5, which are rolled under the conditions in which the primary row of the casting process is used, and in the conveying direction F of the strip 1. In the apparatus, in which the strip 1 comprises a plurality of finishing roll stands 7 which can be rolled to the final thickness by working rolls 8,
The work rolls (8) of the finishing roll stands (7) comprise a low wear roll surface. The apparatus of claim 1 wherein the roll surface is formed by a low wear material layer. The apparatus of claim 2 wherein the low wear layer is comprised of a powder metallurgy material. 4. An apparatus according to claim 3, wherein the low wear layer is made of powder metallurgy material by HIP method (hot isostatic pressurization). The device of claim 2, wherein the low wear layer is comprised of a metal-ceramic composite material. The apparatus according to claim 1 or 2, wherein the working roll is formed as an HSS roll (high speed steel roll) or a semi-HSS roll. Device according to one of the preceding claims, characterized in that every working roll (8) of at least one rolling train (4, 5) comprises a low wear roll surface. A method for producing a thin hot rolled strip (1) by casting and rolling in a continuous process, first of which a thin slab (3) is cast inside the casting machine (2), and then the thin slab is subjected to at least one rolling sequence (4). , 5) are rolled under the conditions in which the primary row of the casting process is used, and the strip 1 has a plurality of finishing roll stands in the region 6 located rearward in the conveying direction F of the strip 1 7) In the above method, which is rolled to the final thickness by working rolls 8 therein,
A work roll comprising a low wear roll surface, in particular a work roll comprising a layer of low-hair material, is used as work rolls (8) of the finishing roll stands (7). The roll-to-roll spacing between the work rolls 8 is moved openly and at least after the inflow of the strip 1 before the introduction of the strip 1 in at least the region of the finishing roll stands 7. The interval is shifted to a set value. 10. A method according to claim 9, characterized in that the gap between rolls is open-moved to a value at which a rolling process can be made that does not cause damage to the work rolls (8) under conditions of thickness to be reliably rolled. The roll-to-roll spacing according to any one of claims 8 to 10, wherein the gap between rolls is openly shifted from a set value to a larger value at least in the region of the finishing roll stands (7) before the outflow of the strip (1). How to. The method according to any one of claims 8 to 11, wherein the strip (1) is rolled to a final strip thickness between 0.5 mm and 1.5 mm in the finishing roll stands (7).

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