EP1590104B1 - Method for milling thin and/or thick slabs made of steel materials into hot-rolled strip - Google Patents

Abstract

A method for rolling thin and/or thick slabs made of steel materials into hot-rolled strip, which were previously cast as thin or thick slabs in a continuous casting machine, heated to rolling temperature in a pusher furnace or in a walking-beam furnace, and rolled in a common rolling train, then cooled and wound into coils. The method is carried out in a continuous manner at maximum capacity of the roughing train according to the quality standard of the hot-rolled strip while roller wear is reduced due to the fact that the roughing train is formed inline by roughing stands and finishing stands into which thin slab sections or thick slab sections are introduced at a suitable point of the roughing train according to the thickness thereof.

Description

The invention relates to a method for rolling thin and / or thick slabs of steel materials to hot strip, which were previously cast as thin or thick slabs in a continuous casting, heated in a tunnel kiln or in a walking beam furnace to rolling temperature and rolled in a rolling mill, then cooled and wound up into wrap-arounds.

In general, in a rolling train only one and the same product, if necessary. With different dimensions, produced in hot strip with different widths or thicknesses. The efforts to increase the utilization of a rolling mill have been made since 2001 by the so-called "mixed rolling", i. realized by mixed rolling of significantly different strand thicknesses and strand widths, whereby the investment costs of a plant can be reduced, thereby resulting in lower costs for the rolling stock.

A method for operating a cast roll mill is known (WO 02/068137 A1), wherein a cast roll mill is defined by the coupling of the processes "slab casting" and "hot rolling" otherwise decoupled in the conventional steel sheet production. The casting rolling is based on a slab production line (continuous casting machine) and a rolling line, wherein a slab feeding device is provided, which is independent of the slab production line. To achieve full capacity several casting machines are required. A maximum possible production capacity is only possible with either a plant with two casting plants or a two-strand casting plant. Nevertheless, the rolling mill always rolls faster than the casting would work at full casting. Unused production gaps caused by set-up times of the casting machine (distributor, mold or segment change and maintenance). During breaks in the slab production line, stockpiled slabs can be fed into the rolling mill to complete the break. The stocked slabs can only come from a second continuous casting machine. When producing thin slabs on a thin slab production line and producing thick slabs on a thick slab production line, a separate continuous casting machine is required for each of thin slabs and thick slabs, which in turn increases the investment funds. Accordingly, the desired coupling of the continuous casting machine with a (finishing) rolling train can not be fully achieved economically by means of two separate continuous casting machines for thin slabs and thick slabs or via a two-strand continuous casting machine, because in turn the higher investment costs are reflected in the end product. However, particularly disadvantageous is the rolling of thick slabs in a separate roughing mill. Here, the hot strip is wound after rolling into coils, placed inside a coil box in a holding furnace and fed from there to the finishing train. This procedure results in higher production costs, time and energy losses and a reduction in the production volume. According to the state of the art, therefore, only a filling of pauses in the intervals occurring in continuous casting machines remains for a greater utilization of the plant. Only the specific shorter rolling times compared to the specifically larger casting times can be exploited for an increase in the rolling mill performance.

The object of the invention is to coordinate the continuous casting process and the rolling process even more effectively by means of largely continuous rolling (maximum utilization of the rolling mills) while at the same time taking account of product planning with the least investment, with energy savings and subsequent introduction of the process into existing rolling mills to increase the rolling performance.

The above object is achieved in that from a single thin slab continuous casting machine, which is arranged upstream of an existing rolling mill, continuously behind one another thin slab sections emerging from the tunnel kiln or introduced into the rolling mill thick slab sections, the emerge from the walking beam oven, or thin slab sections, directly in the thickness reducing Vorwalzgerüste or run through roughing or immediately before the first rolling stand of the finishing train and finish rolled in a lying with the roughing stands in a rolling mill finish rolling and only then wound into wound coils. As a result, apart from operational maintenance, there are no breaks caused by casting and / or rolling, and above all, optimal product planning can take place. In view of the product planning, the expected maintenance work can also be scheduled more efficiently. Casting and rolling processes as well as the plant technology can be matched to the desired end product right from the start. This achieves stable overall conditions during casting, rolling and maintenance. There are fewer geometric errors on the hot strip. The roller wear is reduced overall. In addition, cost savings are achieved through significantly higher production throughput. The result is a continuous flow of material in the continuous casting plant and the (previously separate) rolling mill until the output of a predetermined in the quality, quality and quantity of hot strip to the winding coil. By a subsequently built thin slab continuous casting machine also considerable investment costs are saved. The thick slab sections can also be retrofitted or brought from an already existing, remote casting machine for thick slab sections.

The advantageous product planning can be designed such that, within a rolling campaign, a percentage of thin slabs and a respective supplementary percentage of thick slabs are fed and rolled continuously successively to the common rolling train, wherein the respective number of thin or thick slabs is determined depending on the respective quality standard of the hot strip to be produced, a reduction of the rolling wear and a maximum production throughput.

Other features are that the thin slabs are primarily out of the continuous casting immediately out through the tunnel kiln with open roughing in the rolling mill and finish rolled. The casting of thin slabs is closest to the casting speed of the rolling speed.

Another improvement is that the slab sections are taken from an intermediate storage for thick and / or thin slabs upstream of the walking beam furnace, thermally prepared and rolled in the finish rolling line on the common rolling line. In the event that the slabs come from a remote continuous caster for slabs, even a uniform heating can not be waived.

It is further advantageous that the walking beam furnace is charged depending on the thick slabs, which are sorted by widths and thicknesses. This increases the flexibility of the process and also supports product planning.

The product planning can also be supported by other features that the thick slabs are poured and stored depending on the required widths and / or thicknesses.

In the product planning occurring special cases as well as during production unpredictable operating conditions can be considered according to an embodiment in that outside of the full rolling program a Walzlinie occurring thick slabs for average dimensions of the hot strip market cast and stored. This creates an additional option for product planning, which currently does not constitute a requirement, but represents an average of the hot-rolled strip market and can easily be integrated into the production process. Thus basically two types of storage are initially created: a planned supply and a supply for unpredictable operating conditions.

• eine Gruppe für eine geplante Produktion, um eine Dünnbrammen-Produktion entsprechend der Walzbedingungen optimal zu gestalten,
• eine Gruppe zur Kompensation von nicht planbaren Betriebszuständen, um Walzbedingungen in Verbindung mit der Dünnbrammen-Produktion optimal zu gestalten.

It is also advantageous that the thick or thin slabs are sorted in the interim storage by latitudes, grades and / or quality groups. This saves on feeding time into the tunnel kiln or in the walking beam furnace and also supports product planning. Thus, for example, groups can be formed as follows:

• a group for a planned production in order to optimally design a thin slab production according to the rolling conditions,
• a group to compensate for unpredictable operating conditions in order to optimize rolling conditions in connection with thin slab production.

In order to assist in tuning the rolling stock thickness to the stitching plans, it is envisaged that an intermediate product will be introduced in a downstream finishing train which has been cast and / or rolled in thickness and width as an approximately thin slab or slab. Smaller differences in thickness can also be detected by adjusting the pass plans in the rough rolling mills or the finishing train or vice versa on the slab thickness.

A further vote slab thickness / roll tapping can be done by the casting profile in the width and / or in the thickness is dimensioned by the continuous casting molds for optimum design of the intermediate product. This allows the intermediate product to be adjusted before the finishing train.

An independent alternative is that the continuous casting machine and the rolling mill are operated in the CSP process.

Likewise, another independent alternative is that the continuous casting machine with liquid core reduction (LCR) is operated.

A further adaptation of thin slabs and thick slabs to the roll tapping can be further made in that the thin slab is fed between two roughing stands in front of the finishing train, into which a thicker slab is introduced as a transitional slab. This case can occur if, for individual reasons, the thin slab can not be fed into the rolling mill at the optimum location. The feed is then removed before the finishing train. The thickness of the thin slab can be increased, with the pass schedules of the roughing stands being adjusted. Thus, for example, two roughing stands can be driven in tandem arrangement for a thick slab of 70 mm and / or roughing stands can be opened as described.

Furthermore, it is proposed that a thin slab or a thick slab, each with a thickness of 30 mm to 60 mm is introduced into the finishing train as a transfer slab.

For such a case is still provided that the thin slab is introduced with increased thickness with increasing distance between two roughing stands.

In the drawings, embodiments of the invention are shown, which are explained in more detail below.

Fig. 1

eine perspektivische Ansicht der Gieß-Walz-Anlage,

Fig. 2

eine perspektivische Ansicht des Zwischenlagers für sortierte Brammen

undShow it:

Fig. 1

a perspective view of the casting-rolling plant,

Fig. 2

a perspective view of the intermediate storage for sorted slabs

and

In a first process section, continuous casting takes place in a continuous casting machine 1 of thin slabs 2 or thick slabs 3 of steel materials (C steels, alloyed steels and the like). As thin slabs 2, slab cross-sections 2a with a thickness of about 30 mm to 70 mm are required. The thick slab 3 has a slab cross-section 3a with a thickness of about 70 mm to 300 mm. A transfer slab 16, described below, in front of a plurality of roughing stands 4c of a rolling train 4 has the thickness 9 of a thin slab 2 of approximately 30 mm and can therefore be fed directly into a finishing train 12.

The thin slab 2 and the thick slab 3 made of steel materials are rolled after casting in the continuous casting machine 1 in a common rolling mill 4 to hot strip 4a and wound into wound coils 18. The thin slab 2 and the thick slab 3 are uniform in temperature after continuous casting for thermal preparation of the rolling operation in a tunnel kiln 5 or a walking beam furnace 6 and heated to the ramming temperature of the first rolling stand 4b or 4c and then introduced into the rolling line 4.

The process is basically as follows: From a single thin slab continuous casting 1, which is upstream of an existing mill 4 by new construction or already exists, are continuously successively thin slab sections 2 b, which are led out of the tunnel kiln 5 or transversely in the Rolling mill 4 introduced thick slab sections 3b, which emerge from the walking beam furnace 6, or thin slab sections 2b, directly in the thickness 9 reducing roughing 4c or by advancing roughing stands 4c or immediately before the first rolling stand of the finishing train 12 introduced and in the with the roughing stands 4c finished finish rolling line 12 lying in a rolling line 4 and only after winding in laminar cooling devices to wound coils 18 wound.

The method according to the invention further provides that, within a rolling campaign, a percentage of thin slabs 2 and a respective supplementary percentage of thick slabs 3 are fed and rolled continuously consecutively-practically without pauses, apart from the maintenance-related downtimes - of the common rolling train 4. The respective number of thin slabs 2 and thick slabs 3 is determined as a function of the respective quality standard and the quality 10 of the hot strip 4 a to be produced, a reduction of the roller wear and a maximum production throughput. Such a ratio is e.g. 1/3 thin slabs 2 to 2/3 thick slabs 3. Such mixed rolling, in the second stage of the process, i. The rolling of different Brammendikken usually leads to disturbances in the rolling process. These disturbances can be further intensified by changing widths and steel grades. There are also increased geometry errors on the hot strip 4a. Particularly noteworthy is the increased roller wear. The faults can only be significantly reduced by sophisticated product planning.

Contributes to this, e.g. in that the thin slabs 2 are primarily rolled and discharged from the continuous casting machine 1 directly guided and rolled by the tunnel kiln 5 with open roughing stands 4c in the finishing train 4 and.

The thick slabs 3 are cast either on a remote continuous casting machine with a modified casting 15 of a continuous casting mold 14 or preferably due to a forward-looking planning in an independent, if necessary. Remotely located continuous casting and are from a Hubbalkenofen 6 upstream intermediate storage 7 for thick slabs 3rd or thin slabs 2, thermally prepared and transported in the direction of arrow 17 (general transport direction) and rolled in the common finishing train 4. The walking beam furnace 6 is depending on the thick slabs 3, which are sorted by widths 8 and thicknesses 9, charged. It has already been taken into account that the thick slabs 3 have been poured 9 and brought into the intermediate storage 7 as a function of the widths 8 and / or thicknesses required for the end product.

It is also possible that outside the full rolling program of a rolling line 4 occurring thick slabs 3 are poured and stored for average dimensions of the hot strip market. The proportion of thick slabs 3 is produced earlier by a period of several days than intended for the casting of the thin slabs 2. This period makes it possible to produce all the required widths 8 and thicknesses 9 without special application losses on a thick slab casting machine 1. The intermediate storage 7 in front of the walking beam furnace 6 contains thicker slabs 3, which are intended for the planned rolling program and also the transition slabs 16, with which disturbances or short-term changes of the rolling program, can be absorbed as a kind of "fuses".

The thick slabs 3 or the thin slabs in the intermediate storage 7 are sorted according to widths 8, thicknesses 9, grades 10 and / or quality groups 11 (see FIG. 2). When processing the planned rolling program, the casting machine 1 pours the thin slabs 2 with the required width 8 and thickness 9. Due to the direct charging of the thin slabs 2, the casting machine 1 receives the priority for thin slabs 2. The lifting beam furnace 6 for the thick slabs 3 has the second priority.

The finishing train 4 basically decides at what time the hot dies 3 are introduced into the rolling line 4.

The walking beam furnace 6 is driven as a function of the width 8, the thickness 9 and the quality 10 of a thin slab 2, whereby an optimal strip geometry occurs with the least possible roller wear. The types of storage in the intermediate storage 7 allow such flexibility.

In the downstream finishing train 12, an intermediate product 13 is introduced at a position (see Fig. 1) which has been poured and rolled in the thickness 9 and the width 8 as a thin slab 2 or as a thick slab 3. For appropriate specifications for the device, eg. As the casting profile 15, or effects on the stitch plans applied. For example. For example, the continuous casting mold 14 can influence the casting profile 15 in the width 8 and / or in the thickness 9 for an optimum design for a transitional slab 16. The continuous casting machine 1 and the rolling train 4 can be operated in the CSP process. The respective continuous casting machine can also be operated with liquid core reduction (LCR). According to further proposals, the thin slab 2 can be introduced into a roughing stand 4c of the rolling train 4 into which the thick slab 3 can be introduced as a transfer slab 16 as well.

As a transfer slab 16, a thin slab 2 or a thick slab 3, each having a thickness 9 of 30 mm to 60 mm is fed immediately before the finishing train 12. A thin slab 2 is introduced with the same thickness 9 in front of the last roughing stand 4c. The transitional slab 16 may be a thin slab 2 with and without deviation from the base thickness, or a reduced thick slab 3 that is run into the roughing stands 4c. It can also form a reduced thin slab 2 for the roughing stands 4c.

In the event that a thin slab 2 for special reasons can not be introduced at the optimum locations of the rolling train 4, it is provided that the thin slabs 2 of increased thickness 9 are introduced with increasing distance to the finishing train 12 before a roughing stand 4c , The thickness 9 of the thin slab 2 is further increased and the stitch plans of the roughing stands 4c are adjusted. For example, two roughing stands 4c are rolled in tandem for a thick slab 3 having the thickness 9 of 70 mm and / or the roughing stands 4c are opened.

The intermediate storage 7 may also consist of two bearings for thick slabs 9, for example, which are each sorted by quality groups 11 and width classes. One group is for product planning and one group is for unpredictable operating conditions.

LIST OF REFERENCE NUMBERS

1

Continuous casting machine (for thin slabs)

2

thin slab

2a

thin slab cross section

2 B

thin slab section

3

thick slab

3a

thick slab cross section

3b

thick slab section

4

Rolling train (rolling line)

4a

hot strip

4b

Finishing stand

4c

roughing stands

5

tunnel kiln

6

walking beam furnace

7

Intermediate storage for thick, thin slab sections

8th

Width of a (thick) slab

9

Thickness of a (thick) slab

10

quality

11

quality group

12

Finishing mill

13

intermediate

14

continuous casting

15

Gießprofil

16

Übergangsbramme

17

arrow

18

winding coils

Claims (15)

1. Method of rolling thin and/or thick slabs (2; 3) of steel materials to form hot strip (4a), which was previously cast as thin or thick slabs (2; 3) in a continuous casting machine (1), heated in a tunnel furnace (5) or a walking beam furnace (6) to rolling temperature and rolled in a rolling train (4), subsequently cooled and wound to form wound coils (18), characterised in that the rolling train (4) comprises roughing stands (4c) and a finishing rolling train (12) and that - from a single thin slab continuous casting machine (1) which is to be or is arranged upstream of an existing rolling train (4) - continuously successive thin slab sections (2b) exiting from the tunnel furnace (5) or - introduced transversely into the rolling train (4) - thick slab sections (3b), which exit from the walking beam furnace (6), or thin slab sections (2b) are led directly into the roughing stands (4c), which reduce thickness (9), or through moved-apart roughing stands (4c) or to directly in front of the first roll stand of the finishing train (12) and are rolled to finished state in the finishing train (12), which lies in a rolling line (4) with the roughing stands (4c) and only then wound to form wound coils (18).
2. Method according to claim 1, characterised in that within a rolling campaign a percentage proportion of thin slabs (2) and a respective supplementary percentage proportion of thick slabs (2) are continuously fed in succession to the common rolling train (4) and rolled out, wherein the respective number of thick or thin slabs (2; 3) is fixed in dependence on the respective quality standard of the hot strip (4a) to be produced, a reduction of the roll wear and a maximum production throughput.
3. Method according to one of claims 1 and 2, characterised in that the thin slabs (2) preferentially exiting from the continuous casting machine (1) are directly led through the tunnel furnace (5), with opened roughing stands (4c), into the finishing train (4) and rolled to finished state.
4. Method according to one of claims 1 to 3, characterised in that the slabs (2; 3) are removed from an intermediate store (7), which is connected upstream of the walking beam furnace (6), for thick and/or thin slabs (2; 3), thermally pretreated and rolled out in the finishing train (4) lying on the rolling line (4).
5. Method according to claim 4, characterised in that the walking beam furnace (6) is charged in dependence on the thick slabs (3) classified according to width (8) and thickness (9).
6. Method according to claims 1 to 5, characterised in that the thick slabs (3) are cast and intermediately stored in dependence on the required widths (8) and/or thicknesses (9).
7. Method according to one of claims 1 to 6, characterised in that thick slabs (3) occurring outside the full rolling program of a rolling line (4) are cast for average dimensions of the hot strip market and intermediately stored.
8. Method according to claim 7, characterised in that the thick or thin slabs (3; 2) are classified in the intermediate store (7) according to widths (8), qualities (10) and/or quality groups (11).
9. Method according to one of claims 1 to 8, characterised in that an intermediate product (13), which in thickness (9) and width (8) was cast and/or subject to preliminary rolling as an approximately thin slab (2) or an approximately thick slab (3), is introduced into a downstream finishing train (12).
10. Method according to one of claims 1 to 9, characterised in that the cast profile (15) is dimensioned in width (8) and/or in thickness (9) by the continuous casting moulds (14) for an optimum shape of the intermediate product (15).
11. Method according to one of claims 1 to 10, characterised in that the continuous casting machine (1) and the rolling train (4) are operated in the CSP procedure.
12. Method according to one of claims 1 to 11, characterised in that the continuous casting machine (1) is operated with liquid core reduction (LCR).
13. Method according to one of claims 1 to 12, characterised in that the thin slab (2) is fed between two roughing stands (4c) of the finishing train (4), into which a thicker slab (3) is introduced as transition slab (16).
14. Method according to claim 13, characterised in that a thin slab (2) or a thick slab (3) each with a thickness (9) of 30 millimetres to 60 millimetres is introduced as transition slab (16) into the rolling line (4).
15. Method according to one of claims 1 to 14, characterised in that the thin slab (2) is introduced with increased thickness (9) in the case of reducing spacing between two roughing stands (4c).

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